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Find video protocols related to scientific articles indexed in Pubmed.
Pyrene Degradation Accelerated by Constructed Consortium of Bacterium and Microalga: Effects of Degradation Products on the Microalgal Growth.
Environ. Sci. Technol.
PUBLISHED: 11-11-2014
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Abundant microbes including bacteria, fungi, or algae are capable of biodegrading polycyclic hydrocarbons (PAHs). However, pure cultures never occur in the contaminated environments. This study aimed to understand the general potential mechanisms of interactions between microbes under pollution stress by constructing a consortium of PAH-degrading microalga (Selenastrum capricornutum) and bacterium (Mycobacterium sp. strain A1-PYR). Bacteria alone could grow on the pyrene, whereas the growth of algae alone was substantially inhibited by the pyrene of 10 mg L(-1). In the mixing culture of algae and bacteria, the growth rate of algae was significantly increased from day 4 onward. Rapid bacterial degradation of pyrene might mitigate the toxicity of pyrene to algae. Phenolic acids, the bacterial degradation products of pyrene, could serve as the phytohormone for promoting algal growth in the coculture of algae and bacteria. In turn, bacterial growth was also enhanced by the algae presented in the mixing culture. Consequently, the fastest degradation of pyrene among all biodegradation systems was achieved by the consortium of algae and bacteria probably due to such interactions between the two species by virtue of degradation products. This study reveals that the consortium containing multiple microbial species is high potential for microbial remediation of pyrene-contaminated environments, and provides a new strategy to degrade the recalcitrant PAHs.
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Coupling solid-phase microextraction with ambient mass spectrometry using surface coated wooden-tip probe for rapid analysis of ultra trace perfluorinated compounds in complex samples.
Anal. Chem.
PUBLISHED: 10-29-2014
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Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified.
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Safety of pregnancy after surgical treatment for breast cancer: a meta-analysis.
Int. J. Gynecol. Cancer
PUBLISHED: 09-05-2014
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Because of the rising trend of delayed pregnancies, more and more women remain nulliparous at the diagnosis of breast cancer, and approximately 71% of them desire to conceive after breast cancer treatment. Advances in breast cancer screening have made early diagnosis of breast cancer possible, and many patients have the opportunity to be treated by surgery. In this study, we conducted a meta-analysis to evaluate the effect of pregnancy on patient survival and prognosis after surgical treatment for breast cancer.
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Presence of notched QRS on paced electrocardiographs as a predictor of poor response to cardiac resynchronization therapy.
Chin. Med. J.
PUBLISHED: 08-23-2014
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Cardiac resynchronization therapy (CRT) on patients with advanced and refractory heart failure has made remarkable progress. Clinically, notched QRS (nQRS) is commonly seen on electrocardiographs (ECGs) with bundle branch block morphology and on paced ECGs after implantation of a CRT device, which may reflect the heterogeneity of ventricular myocardial depolarization and electrical activity. The aim of this study was to determine whether patients with more nQRS myocardial segments on paced ECGs had a worse response to CRT than patients with fewer nQRS myocardial segments.
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Attention-dependent early cortical suppression contributes to crowding.
J. Neurosci.
PUBLISHED: 08-08-2014
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Crowding, the identification difficulty for a target in the presence of nearby flankers, is ubiquitous in spatial vision and is considered a bottleneck of object recognition and visual awareness. Despite its significance, the neural mechanisms of crowding are still unclear. Here, we performed event-related potential and fMRI experiments to measure the cortical interaction between the target and flankers in human subjects. We found that the magnitude of the crowding effect was closely associated with an early suppressive cortical interaction. The cortical suppression was reflected in the earliest event-related potential component (C1), which originated in V1, and in the BOLD signal in V1, but not other higher cortical areas. Intriguingly, spatial attention played a critical role in the manifestation of the suppression. These findings provide direct and converging evidence that attention-dependent V1 suppression contributes to crowding at a very early stage of visual processing.
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Bile acid signaling in metabolic disease and drug therapy.
Pharmacol. Rev.
PUBLISHED: 07-31-2014
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Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates hepatobiliary secretion of lipids, lipophilic metabolites, and xenobiotics. In the intestine, bile acids are essential for the absorption, transport, and metabolism of dietary fats and lipid-soluble vitamins. Extensive research in the last 2 decades has unveiled new functions of bile acids as signaling molecules and metabolic integrators. The bile acid-activated nuclear receptors farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, vitamin D receptor, and G protein-coupled bile acid receptor play critical roles in the regulation of lipid, glucose, and energy metabolism, inflammation, and drug metabolism and detoxification. Bile acid synthesis exhibits a strong diurnal rhythm, which is entrained by fasting and refeeding as well as nutrient status and plays an important role for maintaining metabolic homeostasis. Recent research revealed an interaction of liver bile acids and gut microbiota in the regulation of liver metabolism. Circadian disturbance and altered gut microbiota contribute to the pathogenesis of liver diseases, inflammatory bowel diseases, nonalcoholic fatty liver disease, diabetes, and obesity. Bile acids and their derivatives are potential therapeutic agents for treating metabolic diseases of the liver.
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Global versus local: double dissociation between MT+ and V3A in motion processing revealed using continuous theta burst transcranial magnetic stimulation.
Exp Brain Res
PUBLISHED: 07-08-2014
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The functional properties of motion selective areas in human visual cortex, including V3A, MT+, and intraparietal sulcus (IPS) are not fully understood. To examine the functional specialization of these areas for global and local motion processing, we used off-line, neuronavigated, continuous theta burst (cTBS) transcranial magnetic stimulation to temporarily alter neural activity within unilateral V3A, MT+, and IPS. A within-subjects design was employed and stimulation sessions were separated by at least 24 h. In each session, subjects were asked to discriminate the global motion directions of successively presented random dot kinematograms (RDKs) before and after cTBS. RDKs were presented at either 100 or 40 % coherence in either the left or right visual field. We found that V3A stimulation selectively impaired discrimination of 100 % coherent motion, while MT+ stimulation selectively impaired discrimination of 40 % coherent motion. IPS stimulation impaired discrimination of both motion stimuli. All cTBS effects were specific to stimuli presented contralaterally to the stimulation site and vertex stimulation had no effect. The double dissociation between the cTBS effects on MT+ and V3A indicates distinct roles for these two regions in motion processing. Judging the direction of 100 % coherent motion can rely on local motion processing because every dot moves in the same direction. However, judging the global direction of 40 % coherent motion requires global processing. Thus, our results suggest separate, parallel processing of local and global motion in V3A and MT+, respectively, with the outputs of these two areas being combined within the IPS.
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Fish oil and fenofibrate prevented phosphorylation-dependent hepatic sortilin 1 degradation in Western diet-fed mice.
J. Biol. Chem.
PUBLISHED: 07-01-2014
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Obesity and diabetes are associated with hepatic triglyceride overproduction and hypertriglyceridemia. Recent studies have found that the cellular trafficking receptor sortilin 1 (Sort1) inhibits hepatic apolipoprotein B secretion and reduces plasma lipid levels in mice, and its hepatic expression was negatively associated with plasma lipids in humans. This study investigated the regulation of hepatic Sort1 under diabetic conditions and by lipid-lowering fish oil and fenofibrate. Results showed that hepatic Sort1 protein, but not mRNA, was markedly lower in Western diet-fed mice. Knockdown of hepatic Sort1 increased plasma triglyceride in mice. Feeding mice a fish oil-enriched diet completely restored hepatic Sort1 levels in Western diet-fed mice. Fenofibrate also restored hepatic Sort1 protein levels in Western diet-fed wild type mice, but not in peroxisome proliferator-activated receptor ? (PPAR?) knock-out mice. PPAR? ligands did not induce Sort1 in hepatocytes in vitro. Instead, fish oil and fenofibrate reduced circulating and hepatic fatty acids in mice, and n-3 polyunsaturated fatty acids prevented palmitate inhibition of Sort1 protein in HepG2 cells. LC/MS/MS analysis revealed that Sort1 phosphorylation at serine 793 was increased in obese mice and in palmitate-treated HepG2 cells. Mutations that abolished phosphorylation at Ser-793 increased Sort1 stability and prevented palmitate inhibition of Sort1 ubiquitination and degradation in HepG2 cells. In summary, therapeutic strategies that prevent posttranslational hepatic Sort1 down-regulation in obesity and diabetes may be beneficial in improving dyslipidemia.
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In vivo tracing uptake and elimination of organic pesticides in fish muscle.
Environ. Sci. Technol.
PUBLISHED: 06-20-2014
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Bioconcentration factors (BCFs) measured in the laboratory are important for characterizing the bioaccumulative properties of chemicals entering the environment, especially the potential persistent organic pollutants (POPs), which can pose serious adverse effects on ecosystem and human health. Traditional lethal analysis methods are time-consuming and sacrifice too many experimental animals. In the present study, in vivo solid-phase microextraction (SPME) was introduced to trace the uptake and elimination processes of pesticides in living fish. BCFs and elimination kinetic coefficients of the pesticides were recorded therein. Moreover, the metabolism of fenthion was also traced with in vivo SPME. The method was time-efficient and laborsaving. Much fewer experimental animals were sacrificed during the tracing. In general, this study opened up an opportunity to measure BCFs cheaply in laboratories for the registering of emerging POPs and inspecting of suspected POPs, as well as demonstrated the potential application of in vivo SPME in the study of toxicokinetics of pollutants.
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A pedigree with pulmonary alveolar microlithiasis: a clinical case report and literature review.
Cell Biochem. Biophys.
PUBLISHED: 05-13-2014
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Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive disease characterized by the presence of innumerable calcium phosphate microliths in the alveoli. Clinical-radiological dissociation is an important hallmark of this disease. Most PAM patients are asymptomatic and pulmonary tissue changes are discovered incidentally. PAM is pathologically attributable to the formation and aggregation of calcium phosphate microliths in the alveoli after mutations in the SLC34A2 gene (the type IIb sodium-phosphate cotransporter gene) coding NaPi-IIb. In the clinical work, we discovered an inbred pedigree with PAM, which include four PAM siblings. We performed a sequence analysis of the SLC34A2 gene in all members of this PAM pedigree and found that a homozygous mutation c.575C > A (p.T192 K) in exon 6 was involved. To the best of our knowledge, this study was the first to discover nucleotide mutations in exon 6 in Asians.
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Cytoplasmic tyrosine phosphatase Shp2 coordinates hepatic regulation of bile acid and FGF15/19 signaling to repress bile acid synthesis.
Cell Metab.
PUBLISHED: 04-18-2014
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Bile acid (BA) biosynthesis is tightly controlled by intrahepatic negative feedback signaling elicited by BA binding to farnesoid X receptor (FXR) and also by enterohepatic communication involving ileal BA reabsorption and FGF15/19 secretion. However, how these pathways are coordinated is poorly understood. We show here that nonreceptor tyrosine phosphatase Shp2 is a critical player that couples and regulates the intrahepatic and enterohepatic signals for repression of BA synthesis. Ablating Shp2 in hepatocytes suppressed signal relay from FGFR4, receptor for FGF15/19, and attenuated BA activation of FXR signaling, resulting in elevation of systemic BA levels and chronic hepatobiliary disorders in mice. Acting immediately downstream of FGFR4, Shp2 associates with FRS2? and promotes the receptor activation and signal relay to several pathways. These results elucidate a molecular mechanism for the control of BA homeostasis by Shp2 through the orchestration of multiple signals in hepatocytes.
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Intrinsic debromination potential of polybrominated diphenyl ethers in different sediment slurries.
Environ. Sci. Technol.
PUBLISHED: 04-08-2014
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The fate of BDE-153 (BDE = brominated diphenyl ethers) in different mangrove, fresh water pond, and marine subsurface sediments collected from Hong Kong SAR was investigated. Under anaerobic conditions, all sediments showed good intrinsic abilities to reductively debrominate BDE-153, producing debromination products ranging from hexa- to mono-BDEs in 90 days. The half-lives of BDE-153 in eight different sediments varied from 7.6 to 165 days, with higher debromination in mangrove than marine and fresh water pond sediments. All sediments exhibited the preference in removing the bromine in para, followed by meta, and the lowest in ortho positions; however, fresh water pond sediments had relatively higher fractions of meta (BDE-99) and ortho substitution (BDE-118) of the three penta-BDE products. Mai Po mangrove and fresh water pond subsurface sediments were also capable of debrominating BDE-47 in 90 days of anaerobic incubation with half-lives of 76.2 and 56.9 days, respectively; but not BDE-209. BDE-47, -153, and -209 in Mai Po surface sediment were not transformed under 30 day aerobic incubation. This study demonstrated that the microbial-mediated debromination of BDE-47 and -153 occurred in natural subsurface sediments under anaerobic conditions although the rates and pathways varied among the sediment types.
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Complex effects of two presumably antagonistic endocrine disrupting compounds on the goldfish Carassius aumtus: a comprehensive study with multiple toxicological endpoints.
Aquat. Toxicol.
PUBLISHED: 04-05-2014
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We studied the effects of endocrine disrupting compounds nonylphenol (NP) and letrozole (LE) on the male goldfish Carassius aumtus. Exposure to NP (20 ?g l(-1)) alone caused a significant up-regulation in the expression of aromatase, estrogen receptors and vitellogenin (VTG) genes, an increase in hepatic and plasma VTG concentration, but no obvious testicular impairment. Exposure to LE (1 mg kg(-1)) alone resulted in a significant decline in aromatase activity, reduced levels of plasma 17?-estradiol (E2), and enhanced sperm maturation. Co-exposure with LE (1 mg kg(-1)) could only partially affect some of the estrogenic effects caused by NP (20 ?g l(-1)) (i.e. expression of hepatic and brain estrogen receptor genes, hepatic VTG concentration), but inhibit other estrogenic effects (i.e. brain and testicular aromatase activity, plasma E2). In addition, co-exposure resulted in impairment of liver mitochondria (i.e. detachment of ridges from the membrane, and uneven distribution of the cytoplasm with clusters of glycogen granules), but did not cause significant damage to the testes (i.e. the morphology, the spermatogonia and spermatozoa densities). Our results clearly showed that nonylphenol and letrozole co-exposure could induce profound effects on fish, and highlighted the importance of adopting multiple toxicological endpoints when evaluating the combined effects of endocrine disrupting compounds.
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Occurrence and distribution of phthalate esters in riverine sediments from the Pearl River Delta region, South China.
Mar. Pollut. Bull.
PUBLISHED: 03-20-2014
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Sixty-eight sediment samples collected from Dongjiang River, Xijiang River, Beijiang River and Zhujiang River in the Pearl River Delta (PRD) region, Southern China, were analyzed for 16 phthalate esters (PAEs). PAEs were detected in all riverine sediments analyzed, which indicate that PAEs are ubiquitous environmental contaminants. The ?16PAEs concentrations in riverine sediments in the PRD region ranged from 0.567 to 47.3 ?g g(-1) dry weight (dw), with the mean and median concentrations of 5.34 ?g g(-1) dw and 2.15 ?g g(-1) dw, respectively. Elevated PAEs concentrations in riverine sediments in the PRD region were found in the highly urbanized and industrialized areas. Of the 16 PAEs, diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs, with the mean and median concentrations of 1.12 ?g g(-1)dw, 0.420 ?g g(-1) dw and 3.72 ?g g(-1) dw, and 0.429 ?g g(-1) dw, 0.152 ?g g(-1) dw and 1.55 ?g g(-1) dw, respectively, and accounted for 94.2-99.7% of the ?16PAEs concentrations. Influenced by local sources and the properties of PAEs, a gradient trend of concentrations and a fractionation of composition from more to less industrialized and urbanized areas were discovered. As compared to the results from other studies, the riverine sediments in the PRD region were severely contaminated with PAEs. Information about PAEs contamination status and its effect on the aquatic organisms in the PRD region may deserve further attention.
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Bile acid signaling in lipid metabolism: Metabolomic and lipidomic analysis of lipid and bile acid markers linked to anti-obesity and anti-diabetes in mice.
Biochim. Biophys. Acta
PUBLISHED: 03-11-2014
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Bile acid synthesis is the major pathway for catabolism of cholesterol. Cholesterol 7?-hydroxylase (CYP7A1) is the rate-limiting enzyme in the bile acid biosynthetic pathway in the liver and plays an important role in regulating lipid, glucose and energy metabolism. Transgenic mice overexpressing CYP7A1 (CYP7A1-tg mice) were resistant to high-fat diet (HFD)-induced obesity, fatty liver, and diabetes. However the mechanism of resistance to HFD-induced obesity of CYP7A1-tg mice has not been determined. In this study, metabolomic and lipidomic profiles of CYP7A1-tg mice were analyzed to explore the metabolic alterations in CYP7A1-tg mice that govern the protection against obesity and insulin resistance by using ultra-performance liquid chromatography-coupled with electrospray ionization quadrupole time-of-flight mass spectrometry combined with multivariate analyses. Lipidomics analysis identified seven lipid markers including lysophosphatidylcholines, phosphatidylcholines, sphingomyelins and ceramides that were significantly decreased in serum of HFD-fed CYP7A1-tg mice. Metabolomics analysis identified 13 metabolites in bile acid synthesis including taurochenodeoxycholic acid, taurodeoxycholic acid, tauroursodeoxycholic acid, taurocholic acid, and tauro-?-muricholic acid (T-?-MCA) that differed between CYP7A1-tg and wild-type mice. Notably, T-?-MCA, an antagonist of the farnesoid X receptor (FXR) was significantly increased in intestine of CYP7A1-tg mice. This study suggests that reducing 12?-hydroxylated bile acids and increasing intestinal T-?-MCA may reduce high fat diet-induced increase of phospholipids, sphingomyelins and ceramides, and ameliorate diabetes and obesity. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.
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Overproduction of fatty acids in engineered Saccharomyces cerevisiae.
Biotechnol. Bioeng.
PUBLISHED: 03-09-2014
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The long hydrocarbon fatty acyl chain is energy rich, making it an ideal precursor for liquid transportation fuels and high-value oleo chemicals. As Saccharomyces cerevisiae has many advantages for industrial production compared to Escherichia coli. Here, we attempted to engineer Saccharomyces cerevisiae for overproduction of fatty acids. First, disruption of the beta-oxidation pathway, elimination of the acyl-CoA synthetases, overexpression of different thioesterases and acetyl-CoA carboxylase ACC1, and engineering the supply of precursor acetyl-CoA. The engineered strain XL122 produced more than 120 mg/L of fatty acids. In parallel, we inactivated ADH1, the dominant gene for ethanol production, to redirect the metabolic flux to fatty acids synthesis. The engineered strain DG005 produced about 140 mg/L fatty acids. Additionally, Acetyl-CoA carboxylase was identified as a critical bottleneck of fatty acids synthesis in S. cerevisiae with a cell-free system. However, overexpression of ACC1 has little effect on fatty acids biosynthesis. As it has been reported that phosphorylation of ACC1 may influent its activity, so phosphorylation sites of ACC1 were further identified. Although the regulatory mechanisms remain unclear, our results provide rationale for future studies to target this critical step. All these efforts, particularly the discovery of the limiting step are critical for developing a "cell factory" for the overproduction of fatty acids by using type I fatty acids synthase in yeast or other fungi.
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Fully automatic exposed and in-syringe dynamic single-drop microextraction with online agitation for the determination of polycyclic musks in surface waters of the Pearl River Estuary and South China Sea.
J Sep Sci
PUBLISHED: 02-25-2014
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An automatic exposed and in-syringe dynamic single-drop microextraction method (SDME) for the determination of five polycyclic musks in natural waters was developed using gas chromatography with mass spectrometry. Online agitation was first introduced to the automatic SDME with a magnetic mixer fixed to the bottom of the sample tray of the autosampler. A high enrichment factor (110 ?182) for the target analytes could be achieved after several parameters that affected the microextraction were optimized. The recoveries were between 84.9 and 119.5%, while the limit of detection ranged from 3.4 to 11 ng/L with relative standard deviation < 11.1% for the polycyclic musks. This new SDME mode is fully automatic with great convenience, high enrichment and good reproducibility, and no human intervention. The proposed method was, therefore, successfully applied to determine the polycyclic musks in 31 surface sea waters that were collected from the Pearl River Estuary and the South China Sea. Most polycyclic musks could be detected with the total concentrations ranging from 58.9 to 528.5 ng/L. By using spatial interpolation method of ordinary kriging, the most contaminated area was found near the cities of Dongguan and Guangzhou with local discharge via the major rivers.
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Primary clear cell adenocarcinoma of the colon presenting as a huge extracolic mass: A case report.
Oncol Lett
PUBLISHED: 01-28-2014
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A primary clear cell adenocarcinoma of the colon is a rare oncologic entity. The current study presents a case of such a tumor in the transverse colon of a 26-year-old male, and describes the computed tomography features of the neoplasm. The tumor appeared as an extensive extracolic mass, which displaced the loop of the small bowel and pancreas, and invaded the spleen. A laparotomy was performed and a huge mass measuring 12 cm maximally was revealed, arising from the transverse colon close to the left colonic flexure, with invasion of the spleen. The tumor and the spleen were resected concurrently. Histopathological examination of the excised mass revealed features of clear cell adenocarcinoma. A primary clear cell adenocarcinoma of the colon is a rare tumor, with only 13 cases reported in the English literature at present. The present case is reported here due to its rarity.
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In vitro reconstitution of mevalonate pathway and targeted engineering of farnesene overproduction in Escherichia coli.
Biotechnol. Bioeng.
PUBLISHED: 01-17-2014
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Approaches using metabolic engineering and synthetic biology to overproduce terpenoids, such as the precursors of taxol and artemisinin, in microbial systems have achieved initial success. However, due to the lack of steady-state kinetic information and incomplete understanding of the terpenoid biosynthetic pathway, it has been difficult to build a highly efficient, universal system. Here, we reconstituted the mevalonate pathway to produce farnesene (a precursor of new jet fuel) in vitro using purified protein components. The information from this in vitro reconstituted system guided us to rationally optimize farnesene production in E. coli by quantitatively overexpressing each component. Targeted proteomic assays and intermediate assays were used to determine the metabolic status of each mutant. Through targeted engineering, farnesene production could be increased predictably step by step, up to 1.1 g/L (? 2,000 fold) 96 h after induction at the shake-flask scale. The strategy developed to release the potential of the mevalonate pathway for terpenoid overproduction should also work in other multistep synthetic pathways.
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Role of CHD5 in human cancers: 10 years later.
Cancer Res.
PUBLISHED: 01-13-2014
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CHD5 was first identified because of its location on 1p36 in a region of frequent deletion in neuroblastomas. CHD5 (chromodomain-helicase-DNA-binding-5) is the fifth member of a family of chromatin remodeling proteins, and it probably functions by forming a nucleosome remodeling and deacetylation (NuRD) complex that regulates transcription of particular genes. CHD5 is preferentially expressed in the nervous system and testis. On the basis of its position, pattern of expression, and function in neuroblastoma cells and xenografts, CHD5 was identified as a tumor suppressor gene (TSG). Evidence soon emerged that CHD5 also functioned as a TSG in gliomas and a variety of other tumor types, including breast, colon, lung, ovary, and prostate cancers. Although one copy of CHD5 is deleted frequently, inactivating mutations of the remaining allele are rare. However, DNA methylation of the CHD5 promoter is found frequently, and this epigenetic mechanism leads to biallelic inactivation. Furthermore, low CHD5 expression is strongly associated with unfavorable clinical and biologic features as well as outcome in neuroblastomas and many other tumor types. Thus, based on its likely involvement as a TSG in neuroblastomas, gliomas, and many common adult tumors, CHD5 may play an important developmental role in many other tissues besides the nervous system and testis.
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Function and structure of human left fusiform cortex are closely associated with perceptual learning of faces.
Curr. Biol.
PUBLISHED: 01-09-2014
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Training can lead to long-lasting improvement in our perceptual ability, which is referred to as perceptual learning. Unraveling its neural mechanisms has proved difficult. With functional and structural magnetic resonance imaging (MRI), we addressed this issue by searching for the neural correlates of perceptual learning of face views over a long time course. Human subjects were trained to perform a face view discrimination task. Their behavioral performance and MRI signals were measured before, immediately after, and 1 month after training. We found that, across individual subjects, their behavioral learning effects correlated with the stability improvement of spatial activity pattern in the left fusiform cortex immediately after and 1 month after training. We also found that the thickness of the left fusiform cortex before training could predict subjects' behavioral learning effects. These findings, for the first time, not only suggest that, remarkably, the improved pattern stability contributes to the long-term mechanisms of perceptual learning, but also provide strong and converging evidence for the pivotal role of the left fusiform cortex in adaptive face processing.
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Metabolic engineering of Escherichia coli for production of fatty acid short-chain esters through combination of the fatty acid and 2-keto acid pathways.
Metab. Eng.
PUBLISHED: 01-08-2014
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Fatty acid short-chain esters (FASEs) are biodiesels that are renewable, nontoxic, and biodegradable biofuels. A novel approach for the biosynthesis of FASEs has been developed using metabolically-engineered E. coli through combination of the fatty acid and 2-keto acid pathways. Several genetic engineering strategies were also developed to increase fatty acyl-CoA availability to improve FASEs production. Fed-batch cultivation of the engineered E. coli resulted in a titer of 1008 mg/L FASEs. Since the fatty acid and 2-keto acid pathways are native microbial synthesis pathways, this strategy can be implemented in a variety of microorganisms to produce various FASEs from cheap and readily-available, renewable, raw materials such as sugars and cellulose in the future.
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Therapeutic targets for neuroblastomas.
Expert Opin. Ther. Targets
PUBLISHED: 01-06-2014
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Neuroblastoma (NB) is the most common and deadly solid tumor in children. Despite recent improvements, the long-term outlook for high-risk NB is still < 50%. Further, there is considerable short- and long-term toxicity. More effective, less toxic therapy is needed, and the development of targeted therapies offers great promise.
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Dynamical resonances accessible only by reagent vibrational excitation in the F + HD->HF + D reaction.
Science
PUBLISHED: 12-21-2013
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Experimental limitations in vibrational excitation efficiency have previously hindered investigation of how vibrational energy might mediate the role of dynamical resonances in bimolecular reactions. Here, we report on a high-resolution crossed-molecular-beam experiment on the vibrationally excited HD(v = 1) + F ? HF + D reaction, in which two broad peaks for backward-scattered HF(v = 2 and 3) products clearly emerge at collision energies of 0.21 kilocalories per mole (kcal/mol) and 0.62 kcal/mol from differential cross sections measured over a range of energies. We attribute these features to excited Feshbach resonances trapped in the peculiar HF(v = 4)-D vibrationally adiabatic potential in the postbarrier region. Quantum dynamics calculations on a highly accurate potential energy surface show that these resonance states correlate to the HD(v = 1) state in the entrance channel and therefore can only be accessed by the vibrationally excited HD reagent.
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Retinoic Acid-related Orphan Receptor ? Regulates Diurnal Rhythm and Fasting Induction of Sterol 12?-Hydroxylase in Bile Acid Synthesis.
J. Biol. Chem.
PUBLISHED: 11-13-2013
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Sterol 12?-hydroxylase (CYP8B1) is required for cholic acid synthesis and plays a critical role in intestinal cholesterol absorption and pathogenesis of cholesterol gallstone, dyslipidemia, and diabetes. In this study we investigated the underlying mechanism of fasting induction and circadian rhythm of CYP8B1 by a cholesterol-activated nuclear receptor and core clock gene retinoic acid-related orphan receptor ? (ROR?). Fasting stimulated, whereas restricted-feeding reduced expression of CYP8B1 mRNA and protein. However, fasting and feeding had little effect on the diurnal rhythm of ROR? mRNA expression, but fasting increased ROR? protein levels by cAMP-activated protein kinase A-mediated phosphorylation and stabilization of the protein. Adenovirus-mediated gene transduction of ROR? to mice strongly induced CYP8B1 expression, and increased liver cholesterol and 12?-hydroxylated bile acids in the bile acid pool and serum. A reporter assay identified a functional ROR? response element in the CYP8B1 promoter. ROR? recruited cAMP response element-binding protein-binding protein (CBP) to stimulate histone acetylation on the CYP8B1 gene promoter. In conclusion, ROR? is a key regulator of diurnal rhythm and fasting induction of CYP8B1, which regulates bile acid composition and serum and liver cholesterol levels. Antagonizing ROR? activity may be a therapeutic strategy for treating inflammatory diseases such as non-alcoholic fatty liver disease and type 2 diabetes.
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The Assembly of Multivalent Protein Ligands and Quantum Dots: A Multifaceted Investigation.
Langmuir
PUBLISHED: 10-09-2013
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The development of multivalent protein ligands for nanoparticles lags behind that of multidentate polymer and small molecule ligands, largely because of a lack of thorough understanding on the interaction between nanoparticles and multimeric proteins. Guided by protein crystal structures, we have harnessed recombinant technology to develop a collection of mCherry fused multimeric proteins with different spatial distribution of quantum dot (QD)-binding sequence, hexahistidine tag (histag). All the proteins can behave as ligands to assemble with ZnS-CdSe QDs through metal-affinity driven self-assembly. We have observed that protein shape and geometry greatly affect the stoichiometry and stability of their assemblies with QDs. We also demonstrate a peptide-induced structural transition of a nanobelt protein that pre-organizes the QD-binding sites and effects a more efficient assembly with QDs. This work reports the first multifaceted investigation on how multivalent proteins, in particular dimer, tetramers and linear multidentate proteins, assemble with QDs. It also manifests our capability of harnessing the structural and conformational information of proteins to design multivalent protein ligands for QD surface functionalization.
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CHD5 is required for spermiogenesis and chromatin condensation.
Mech. Dev.
PUBLISHED: 08-30-2013
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Haploid spermatids undergo extensive cellular, molecular and morphological changes to form spermatozoa during spermiogenesis. Abnormalities in these steps can lead to serious male fertility problems, from oligospermia to complete azoospermia. CHD5 is a chromatin-remodeling nuclear protein expressed almost exclusively in the brain and testis. Male Chd5 knockout (KO) mice have deregulated spermatogenesis, characterized by immature sloughing of spermatids, spermiation failure, disorganization of the spermatogenic cycle and abnormal head morphology in elongating spermatids. This results in the inappropriate placement and juxtaposition of germ cell types within the epithelium. Sperm that did enter the epididymis displayed irregular shaped sperm heads, and retained cytoplasmic components. These sperm also stained positively for acidic aniline, indicating improper removal of histones and lack of proper chromatin condensation. Electron microscopy showed that spermatids in the seminiferous tubules of Chd5 KO mice have extensive nuclear deformation, with irregular shaped heads of elongated spermatids, and lack the progression of chromatin condensation in an anterior-to-posterior direction. However, the mRNA expression levels of other important genes controlling spermatogenesis were not affected. Chd5 KO mice also showed decreased H4 hyperacetylation beginning at stage IX, step 9, which is vital for the histone-transition protein replacement in spermiogenesis. Our data indicate that CHD5 is required for normal spermiogenesis, especially for spermatid chromatin condensation.
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Saturated fatty acids activate ERK signaling to downregulate hepatic sortilin 1 in obese and diabetic mice.
J. Lipid Res.
PUBLISHED: 07-31-2013
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Hepatic VLDL overproduction is a characteristic feature of diabetes and an important contributor to diabetic dyslipidemia. Hepatic sortilin 1 (Sort1), a cellular trafficking receptor, is a novel regulator of plasma lipid metabolism and reduces plasma cholesterol and triglycerides by inhibiting hepatic apolipoprotein B production. Elevated circulating free fatty acids play key roles in hepatic VLDL overproduction and the development of dyslipidemia. This study investigated the regulation of hepatic Sort1 in obesity and diabetes and the potential implications in diabetic dyslipidemia. Results showed that hepatic Sort1 protein was markedly decreased in mouse models of type I and type II diabetes and in human individuals with obesity and liver steatosis, whereas increasing hepatic Sort1 expression reduced plasma cholesterol and triglycerides in mice. Mechanistic studies showed that the saturated fatty acid palmitate activated extracellular signal-regulated kinase (ERK) and inhibited Sort1 protein by mechanisms involving Sort1 protein ubiquitination and degradation. Consistently, hepatic ERK signaling was activated in diabetic mice, whereas blocking ERK signaling by an ERK inhibitor increased hepatic Sort1 protein in mice. These results suggest that increased saturated fatty acids downregulate liver Sort1 protein, which may contribute to the development of dyslipidemia in obesity and diabetes.
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Combined toxicity of polycyclic aromatic hydrocarbons and heavy metals to biochemical and antioxidant responses of free and immobilized Selenastrum capricornutum.
Environ. Toxicol. Chem.
PUBLISHED: 07-25-2013
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The aquatic environment often contains different groups of contaminants, but their combined toxicity on microalgae has seldom been reported. The present study compared the toxic effects of combined mixed polycyclic aromatic hydrocarbons (PAHs) and heavy metals on growth and antioxidant responses of free and immobilized microalga, Selenastrum capricornutum. Five PAHs-phenanthrene, fluorene, fluoranthene, pyrene, and benzo[a]pyrene-and four heavy metals at different concentrations-0.05 to 0.1?µg Cd(2+) ml(-1) , 0.05 to 1?µg Cu(2+) ml(-1) , 0.05 to 1?µg Zn(2+) ml(-1) , and 0.5 to 2.5?µg Ni(2+) ml(-1) -were examined. Results showed that the chlorophyll a content of free and immobilized S. capricornutum was not affected by PAHs but was significantly inhibited by heavy metals. Conversely, the antioxidant parameters, including the content of reduced glutathione (GSH) and the activities of superoxide dismutase and peroxidase, were significantly induced by both PAHs and metals. For the combined toxic effects of PAHs and heavy metals, cell growth and antioxidant responses varied with exposure time and contaminants and differed between free and immobilized cells. The effects of cocontaminants on the GSH content in free cells were mainly synergistic but changed to antagonistic in immobilized cells. The toxic effects of cocontamination on free cells were also more obvious than those on immobilized cells. These findings suggest that immobilization offers some protection to microalgal cells against toxic contaminants causing differences in the interaction and responses to combined toxicants between free and immobilized cells. Immobilized cells might be more suitable for treating wastewater containing toxic contaminants than free cells.
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Application of fully automatic hollow fiber liquid phase microextraction to assess the distribution of organophosphate esters in the Pearl River Estuaries.
Sci. Total Environ.
PUBLISHED: 07-17-2013
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Organophosphate esters (OPEs) are widespread organic pollutants that could be detected in various environmental matrices. In this study, a sample pretreatment method was developed for the determination of 9 OPEs by automatic hollow fiber-liquid phase microextraction (HF-LPME) coupled with gas chromatography-mass spectrometry (GC-MS). High sensitivity of OPEs could be achieved after optimization of several important parameters with the limits of detection (LODs) ranging from 2.6 to 120ngL(-1) for different individual OPEs, and the relative standard deviations (RSDs) ranged from 2.1% to 10.4%. Acceptable recoveries were observed and the proposed method was then successfully applied to determine OPEs in seawaters collected from 23 sampling sites of the Pearl River Estuaries in dry and wet seasons, respectively. All of the OPEs could be detected, except tris(2-ethylhexyl) phosphate (TEHP). The total concentrations of 9 OPEs in seawaters were ranging from 2.04 (Hemen) to 3.12 (Humen) ?gL(-1) in the dry season and from 1.08 (Hemen) to 2.50 (Jitimen) ?gL(-1) in the wet season. By using spatial interpolation method of ordinary kriging, the most polluted area of ?OPEs was found in Humen in the dry season, while it was Jitimen in the wet season. Moreover, the annual input of ?OPEs discharged via eight estuaries ranged from 384tons (Jitimen) to 1225tons (Modaomen), and the total annual input was 5694tons.
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Effects of low molecular-weight organic acids and dehydrogenase activity in rhizosphere sediments of mangrove plants on phytoremediation of polycyclic aromatic hydrocarbons.
Chemosphere
PUBLISHED: 05-17-2013
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This work evaluated the roles of the low-molecular-weight organic acids (LMWOAs) from root exudates and the dehydrogenase activity in the rhizosphere sediments of three mangrove plant species on the removal of mixed PAHs. The results showed that the concentrations of LMWOAs and dehydrogenase activity changed species-specifically with the levels of PAH contamination. In all plant species, the concentration of citric acid was the highest, followed by succinic acid. For these acids, succinic acid was positively related to the removal of all the PAHs except Chr. Positive correlations were also found between the removal percentages of 4-and 5-ring PAHs and all LMWOAs, except citric acid. LMWOAs enhanced dehydrogenase activity, which positively related to PAH removal percentages. These findings suggested that LMWOAs and dehydrogenase activity promoted the removal of PAHs. Among three mangrove plants, Bruguiera gymnorrhiza, the plant with the highest root biomass, dehydrogenase activity and concentrations of LMWOAs, was most efficient in removing PAHs.
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Metabolic engineering of fatty acyl-ACP reductase-dependent pathway to improve fatty alcohol production in Escherichia coli.
Metab. Eng.
PUBLISHED: 05-16-2013
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Fatty alcohols are important components of surfactants and cosmetic products. The production of fatty alcohols from sustainable resources using microbial fermentation could reduce dependence on fossil fuels and greenhouse gas emission. However, the industrialization of this process has been hampered by the current low yield and productivity of this synthetic pathway. As a result of metabolic engineering strategies, an Escherichia coli mutant containing Synechococcus elongatus fatty acyl-ACP reductase showed improved yield and productivity. Proteomics analysis and in vitro enzymatic assays showed that endogenous E. coli AdhP is a major contributor to the reduction of fatty aldehydes to fatty alcohols. Both in vitro and in vivo results clearly demonstrated that the activity and expression level of fatty acyl-CoA/ACP reductase is the rate-limiting step in the current protocol. In 2.5-L fed-batch fermentation with glycerol as the only carbon source, the most productive E. coli mutant produced 0.75g/L fatty alcohols (0.02g fatty alcohol/g glycerol) with a productivity of up to 0.06g/L/h. This investigation establishes a promising synthetic pathway for industrial microbial production of fatty alcohols.
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Applications of in vivo and in vitro solid-phase microextraction techniques in plant analysis: A review.
Anal. Chim. Acta
PUBLISHED: 05-04-2013
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As a very popular sample preparation technique, solid-phase microextraction (SPME) coupled with various analytical instrumentation, has been widely used for the determination of trace levels of different plant compounds, such as volatile organic compounds (VOCs) emitted from the different plant organs, and environmental contaminants in plants. In this review, recent applications of in vitro and in vivo SPME in plant analysis are discussed and summarized according to the different organs of plants, including fruits, flowers, leaves, stems, roots and seeds, and the whole plant as well. Future developments and applications of SPME in plant analysis, especially in vivo sampling approaches, are also prospected.
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Distribution and accumulation of polybrominated diphenyl ethers (PBDEs) in Hong Kong mangrove sediments.
Sci. Total Environ.
PUBLISHED: 03-28-2013
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Polybrominated diphenyl ethers (PBDEs) have been used extensively as brominated flame retardants in various polymers, and have become serious environmental contaminants, particularly in coastal sediments. Mangrove wetlands are important coastal ecosystems in tropical and subtropical regions, and mangrove sediments are often the pollutant sinks due to their close proximity with human activities. In Hong Kong, sediment samples collected from five mangrove swamps were found to be contaminated with PBDEs and the eight measured BDE congeners, including BDE-28, -47, -99, -100, -153, -154, -183 and -209 were detected in all mangrove sediments, indicating that these pollutants were widespread in Hong Kong mangrove wetlands. Among the five swamps, relatively high concentrations of PBDEs were recorded in Mai Po mangrove swamp in the northwestern Hong Kong, which is part of the RAMSAR site but is severely influenced by the pollution from the Pearl River Delta. The depth profile of PBDEs in sediment cores collected from Mai Po also showed the inputs of PBDEs in this mangrove swamp increased year by year. In all sediments, the concentrations of BDE-209 were 1-2 orders of magnitude higher than the other congeners in the same sediment. The concentrations of BDE-209 and ?PBDEs (defined as the sum of seven targeted BDE congeners except BDE-209) ranged from 1.53 to 75.9ngg(-1) and from 0.57 to 14.4ngg(-1), respectively. Among the targeted BDE congeners except BDE-209, slightly different composition was recorded among samples collected from different locations, with BDE-153 and -183 being the pre-dominated congeners. In all mangrove swamps, except Tai O in the southwest of Hong Kong, ?PBDEs concentrations showed a common trend of landward>seaward>mudflat. The concentrations of ?PBDEs were significantly correlated with total organic matter (TOM) content in sediments but not with the sediment particle sizes in each mangrove swamp.
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Regulation of cholesterol and bile acid homeostasis by the cholesterol 7?-hydroxylase/steroid response element-binding protein 2/microRNA-33a axis in mice.
Hepatology
PUBLISHED: 03-25-2013
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Bile acid synthesis not only produces physiological detergents required for intestinal nutrient absorption, but also plays a critical role in regulating hepatic and whole-body metabolic homeostasis. We recently reported that overexpression of cholesterol 7?-hydroxylase (CYP7A1) in the liver resulted in improved metabolic homeostasis in Cyp7a1 transgenic (Cyp7a1-tg) mice. This study further investigated the molecular links between bile acid metabolism and lipid homeostasis. Microarray gene profiling revealed that CYP7A1 overexpression led to marked activation of the steroid response element-binding protein 2 (SREBP2)-regulated cholesterol metabolic network and absence of bile acid repression of lipogenic gene expression in livers of Cyp7a1-tg mice. Interestingly, Cyp7a1-tg mice showed significantly elevated hepatic cholesterol synthesis rates, but reduced hepatic fatty acid synthesis rates, which was accompanied by increased (14) C-glucose-derived acetyl-coenzyme A incorporation into sterols for fecal excretion. Induction of SREBP2 also coinduces intronic microRNA-33a (miR-33a) in the SREBP2 gene in Cyp7a1-tg mice. Overexpression of miR-33a in the liver resulted in decreased bile acid pool, increased hepatic cholesterol content, and lowered serum cholesterol in mice. Conclusion: This study suggests that a CYP7A1/SREBP2/miR-33a axis plays a critical role in regulation of hepatic cholesterol, bile acid, and fatty acid synthesis. Antagonism of miR-33a may be a potential strategy to increase bile acid synthesis to maintain lipid homeostasis and prevent nonalcoholic fatty liver disease, diabetes, and obesity.
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True complete left bundle branch block morphology strongly predicts good response to cardiac resynchronization therapy.
Europace
PUBLISHED: 03-06-2013
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To determine whether patients with congestive heart failure and true left bundle branch block (LBBB) morphology have better response to cardiac resynchronization therapy (CRT) than do patients without true LBBB.
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Efficient auto-excision of a selectable marker gene from transgenic citrus by combining the Cre/loxP system and ipt selection.
Plant Cell Rep.
PUBLISHED: 02-06-2013
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A highly efficient Cre-mediated deletion system, offering a good alternative for producing marker-free transgenic plants that will relieve public concerns regarding GMOs, was first developed in citrus. The presence of marker genes in genetically modified crops raises public concerns regarding their safety. The removal of marker genes can prevent the risk of their flow into the environment and hasten the publics acceptance of transgenic products. In this study, a new construct based on the Cre/loxP site-recombination system was designed to delete marker genes from transgenic citrus. In the construct, the selectable marker gene isopentenyltransferase gene (ipt) from Agrobacterium tumefaciens and the Cre recombinase gene were flanked by two loxP recognition sites in the direct orientation. The green fluorescent protein (gfp) reporter gene for monitoring the transformation of foreign genes was located outside of the loxP sequences. Transformation and deletion efficiencies of the vector were investigated using nopaline synthase gene (NosP) and CaMV 35S promoters to drive expression of Cre. Analysis of GFP activity showed that 28.1 and 13.6 % transformation efficiencies could be obtained by NosP- and CaMV 35S-driven deletions, respectively. Molecular analysis demonstrated that 100 % deletion efficiency was observed in the transgenic plants. The complete excision of the marker gene was found in all deletion events driven by NosP and in 81.8 % of deletion events driven by CaMV 35S. The results showed that Cre/loxP-mediated excision was highly efficient and precise in citrus. This approach provides a reliable strategy for auto-deletion of selectable marker genes from transgenic citrus to produce marker-free transgenic plants.
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Mutation spectrum in a large cohort of unrelated Chinese patients with hypertrophic cardiomyopathy.
Am. J. Cardiol.
PUBLISHED: 01-31-2013
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Hypertrophic cardiomyopathy (HC) is a hereditary heterogeneous cardiovascular disorder. Existing data have been of predominantly Caucasian samples, and a large study is needed in Chinese population. The present study was intended to explore the genetic basis and clinical characteristics correlated with different genotypes in a large cohort of Chinese patients. Direct gene sequencing of ?-myosin heavy chain (MYH7), myosin binding protein-C (MYBPC3), and cardiac troponin T (TNNT2) was performed in 136 unrelated Chinese HC patients. Clinical evaluations were conducted. In total, 32 mutations were identified in 36 patients (27%), including 10 novel ones. Distribution of mutations was 56% (MYBPC3), 31% (MYH7), and 13% (TNNT2), respectively. Double mutations were identified in 3% patients. The occurrence of HC-associated sarcomeric mutations was associated with an earlier age of onset, increased left ventricular hypertrophy, a higher incidence of syncope, previous family history, and sudden cardiac death. No statistical difference was identified in patients carrying MYBPC3 and MYH7 mutations with regard to clinical characteristics and outcomes. Patients with double mutations were associated with malignant progression in the study. In conclusion, MYBPC3 is the most predominant gene in HC. Multiple mutations are common in MYH7, MYBPC3, and TNNT2. The present study suggests a large diversity of HC and a prognostic role of genotype.
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Microwave-assisted extraction combined with gel permeation chromatography and silica gel cleanup followed by gas chromatography-mass spectrometry for the determination of organophosphorus flame retardants and plasticizers in biological samples.
Anal. Chim. Acta
PUBLISHED: 01-24-2013
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An analytical method for the determination of 14 organophosphorus flame retardants (OPFRs), including halogenated OPFRs, non-halogenated OPFRs and triphenyl phosphine oxide (TPPO) in biological samples was developed using gas chromatography-mass spectrometry (GC/MS). Biological samples were extracted using microwave-assisted extraction (MAE) with hexane/acetone (1:1, v/v) as the solvent; then, a two-step clean-up technique, gel permeation chromatography (GPC) combined with solid phase extraction (SPE), was carried out before GC/MS analysis. Experimental results showed that the developed method efficiently removed the lipid compounds and co-extract interferences. Moreover, using the relatively "narrow" column (with an i.d. of 10 mm) significantly decreased the elution volume and, therefore, prevented the loss of the most volatile OPFRs, especially trimethyl phosphate (TMP) and triethyl phosphate (TEP). The method detection limits (MDLs) for OPFRs in the biological samples ranged from 0.006 to 0.021 ng g(-1) lw, and the recoveries were in the range of 70.3-111%, except for TMP (38.9-55.6%), with relative standard deviations (RSDs) of less than 14.1%. The developed method was applied to determine the amount of the target OPFRs in biological samples (i.e., fish and domestic birds) that were collected from the Pearl River Delta (PRD) region in southern China. Of the 14 OPFRs, tri-n-butyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP) and tributoxyethyl phosphate (TBEP) were present in all of the biological samples that were analyzed, and dominated by TnBP, TCEP and TBEP. The concentrations of OPFRs in the biological samples that were collected from the PRD region were higher than those reported in other locations.
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Nuclear receptors in bile acid metabolism.
Drug Metab. Rev.
PUBLISHED: 01-22-2013
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Bile acids are signaling molecules that activate nuclear receptors, such as farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, and vitamin D receptor, and play a critical role in the regulation of lipid, glucose, energy, and drug metabolism. These xenobiotic/endobiotic-sensing nuclear receptors regulate phase I oxidation, phase II conjugation, and phase III transport in bile acid and drug metabolism in the digestive system. Integration of bile acid metabolism with drug metabolism controls absorption, transport, and metabolism of nutrients and drugs to maintain metabolic homeostasis and also protects against liver injury, inflammation, and related metabolic diseases, such as nonalcoholic fatty liver disease, diabetes, and obesity. Bile-acid-based drugs targeting nuclear receptors are in clinical trials for treating cholestatic liver diseases and fatty liver disease.
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A two-level model for the analysis of syndrome of acute ischemic stroke: from diagnostic model to molecular mechanism.
Evid Based Complement Alternat Med
PUBLISHED: 01-10-2013
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Prompt and accurate diagnosis of acute ischemic stroke is critical to seek acute therapy. In traditional Chinese medicine (TCM) science, there is a comprehensive system of diagnosis and medical care of acute ischemic stroke. Here we introduce a two-level model for the analysis of TCM syndrome of acute ischemic stroke. Owing to the limitation of sample size and imbalance, we focused on the analysis of wind-phlegm collateral obstruction syndrome (Feng Tan Yu Zu Zheng). Firstly, a Support-Vector-Machine- (SVM-) based diagnostic model was set up through selection of core symptoms. After pairwise undersampling, we improved the performance of prediction and generated the core symptoms-based diagnostic model of wind-phlegm collateral obstruction syndrome. Next, Pathway Pattern-based method and MetaDrug platform were used to shed light on the molecular basis of the significance of core symptoms in three complementary aspects: symptom-gene-pathway multilayer correlation network, enriched pathways, and most relevant interaction network. The integration of diagnostic model and molecular mechanism analysis creates an interesting perspective for better understanding the syndrome. The two-level model would provide a new opportunity for the study of TCM syndromes.
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Heme oxygenase-1 regulates postnatal lung repair after hyperoxia: Role of ?-catenin/hnRNPK signaling.
Redox Biol
PUBLISHED: 01-01-2013
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In the newborn, alveolarization continues postnatally and can be disrupted by hyperoxia, leading to long-lasting consequences on lung function. We wanted to better understand the role of heme oxygenase (HO)-1, the inducible form of the rate-limiting enzyme in heme degradation, in neonatal hyperoxic lung injury and repair. Although it was not observed after 3 days of hyperoxia alone, when exposed to hyperoxia and allowed to recover in air (O2/air recovered), neonatal HO-1 knockout (KO) mice had enlarged alveolar spaces and increased lung apoptosis as well as decreased lung protein translation and dysregulated gene expression in the recovery phase of the injury. Associated with these changes, KO had sustained low levels of active ?-catenin and lesser lung nuclear heterogeneous nuclear ribonucleoprotein K (hnRNPK) protein levels, whereas lung nuclear hnRNPK was increased in transgenic mice over-expressing nuclear HO-1. Disruption of HO-1 may enhance hnRNPK-mediated inhibition of protein translation and subsequently impair the ?-catenin/hnRNPK regulated gene expression required for coordinated lung repair and regeneration.
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Hepatic cannabinoid receptor type 1 mediates alcohol-induced regulation of bile acid enzyme genes expression via CREBH.
PLoS ONE
PUBLISHED: 01-01-2013
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Bile acids concentration in liver is tightly regulated to prevent cell damage. Previous studies have demonstrated that deregulation of bile acid homeostasis can lead to cholestatic liver disease. Recently, we have shown that ER-bound transcription factor Crebh is a downstream effector of hepatic Cb1r signaling pathway. In this study, we have investigated the effect of alcohol exposure on hepatic bile acid homeostasis and elucidated the mediatory roles of Cb1r and Crebh in this process. We found that alcohol exposure or Cb1r-agonist 2-AG treatment increases hepatic bile acid synthesis and serum ALT, AST levels in vivo alongwith significant increase in Crebh gene expression and activation. Alcohol exposure activated Cb1r, Crebh, and perturbed bile acid homeostasis. Overexpression of Crebh increased the expression of key bile acid synthesis enzyme genes via direct binding of Crebh to their promoters, whereas Cb1r knockout and Crebh-knockdown mice were protected against alcohol-induced perturbation of bile acid homeostasis. Interestingly, insulin treatment protected against Cb1r-mediated Crebh-induced disruption of bile acid homeostasis. Furthermore, Crebh expression and activation was found to be markedly increased in insulin resistance conditions and Crebh knockdown in diabetic mice model (db/db) significantly reversed alcohol-induced disruption of bile acid homeostasis. Overall, our study demonstrates a novel regulatory mechanism of hepatic bile acid metabolism by alcohol via Cb1r-mediated activation of Crebh, and suggests that targeting Crebh can be of therapeutic potential in ameliorating alcohol-induced perturbation of bile acid homeostasis.
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Glucose and insulin induction of bile acid synthesis: mechanisms and implication in diabetes and obesity.
J. Biol. Chem.
PUBLISHED: 12-05-2011
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Bile acids facilitate postprandial absorption of nutrients. Bile acids also activate the farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5 and play a major role in regulating lipid, glucose, and energy metabolism. Transgenic expression of cholesterol 7?-hydroxylase (CYP7A1) prevented high fat diet-induced diabetes and obesity in mice. In this study, we investigated the nutrient effects on bile acid synthesis. Refeeding of a chow diet to fasted mice increased CYP7A1 expression, bile acid pool size, and serum bile acids in wild type and humanized CYP7A1-transgenic mice. Chromatin immunoprecipitation assays showed that glucose increased histone acetylation and decreased histone methylation on the CYP7A1 gene promoter. Refeeding also induced CYP7A1 in fxr-deficient mice, indicating that FXR signaling did not play a role in postprandial regulation of bile acid synthesis. In streptozocin-induced type I diabetic mice and genetically obese type II diabetic ob/ob mice, hyperglycemia increased histone acetylation status on the CYP7A1 gene promoter, leading to elevated basal Cyp7a1 expression and an enlarged bile acid pool with altered bile acid composition. However, refeeding did not further increase CYP7A1 expression in diabetic mice. In summary, this study demonstrates that glucose and insulin are major postprandial factors that induce CYP7A1 gene expression and bile acid synthesis. Glucose induces CYP7A1 gene expression mainly by epigenetic mechanisms. In diabetic mice, CYP7A1 chromatin is hyperacetylated, and fasting to refeeding response is impaired and may exacerbate metabolic disorders in diabetes.
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In vitro reconstitution and steady-state analysis of the fatty acid synthase from Escherichia coli.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 10-31-2011
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Microbial fatty acid derivatives are emerging as promising alternatives to fossil fuel derived transportation fuels. Among bacterial fatty acid synthases (FAS), the Escherichia coli FAS is perhaps the most well studied, but little is known about its steady-state kinetic behavior. Here we describe the reconstitution of E. coli FAS using purified protein components and report detailed kinetic analysis of this reconstituted system. When all ketosynthases are present at 1 ?M, the maximum rate of free fatty acid synthesis of the FAS exceeded 100 ?M/ min. The steady-state turnover frequency was not significantly inhibited at high concentrations of any substrate or cofactor. FAS activity was saturated with respect to most individual protein components when their concentrations exceeded 1 ?M. The exceptions were FabI and FabZ, which increased FAS activity up to concentrations of 10 ?M; FabH and FabF, which decreased FAS activity at concentrations higher than 1 ?M; and holo-ACP and TesA, which gave maximum FAS activity at 30 ?M concentrations. Analysis of the S36T mutant of the ACP revealed that the unusual dependence of FAS activity on holo-ACP concentration was due, at least in part, to the acyl-phosphopantetheine moiety. MALDI-TOF mass spectrometry analysis of the reaction mixture further revealed medium and long chain fatty acyl-ACP intermediates as predominant ACP species. We speculate that one or more of such intermediates are key allosteric regulators of FAS turnover. Our findings provide a new basis for assessing the scope and limitations of using E. coli as a biocatalyst for the production of diesel-like fuels.
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Curcumin differentially regulates endoplasmic reticulum stress through transcriptional corepressor SMILE (small heterodimer partner-interacting leucine zipper protein)-mediated inhibition of CREBH (cAMP responsive element-binding protein H).
J. Biol. Chem.
PUBLISHED: 10-12-2011
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Curcumin (diferuloylmethane), a major active component of turmeric (Curcuma longa), is a natural polyphenolic compound. Herein the effect of curcumin on endoplasmic reticulum (ER) stress responsive gene expression was investigated. We report that curcumin induces transcriptional corepressor small heterodimer partner-interacting leucine zipper protein (SMILE) gene expression through liver kinase B1 (LKB1)/adenosine monophosphate-activated kinase (AMPK) signaling pathway and represses ER stress-responsive gene transcription in an ER-bound transcription factor specific manner. cAMP responsive element-binding protein H (CREBH) and activating transcription factor 6 (ATF6) are both ER-bound bZIP family transcription factors that are activated upon ER stress. Of interest, we observed that both curcumin treatment and SMILE overexpression only represses CREBH-mediated transactivation of the target gene but not ATF6-mediated transactivation. Knockdown of endogenous SMILE significantly releases the inhibitory effect of curcumin on CREBH transactivation. Intrinsic repressive activity of SMILE is observed in the Gal4 fusion system, and the intrinsic repressive domain is mapped to the C terminus of SMILE spanning amino acid residues 203-269, corresponding to the basic region leucine zipper (bZIP) domain. In vivo interaction assay revealed that through its bZIP domain, SMILE interacts with CREBH and inhibits its transcriptional activity. Interestingly, we observed that SMILE does not interact with ATF6. Furthermore, competition between SMILE and the coactivator peroxisome proliferator-activated receptor ? (PGC-1?) on CREBH transactivation has been demonstrated in vitro and in vivo. Finally, chromatin immunoprecipitation assays revealed that curcumin decreases the binding of PGC-1? and CREBH on target gene promoter in a SMILE-dependent manner. Overall, for the first time we suggest a novel phenomenon that the curcumin/LKB1/AMPK/SMILE/PGC1? pathway differentially regulates ER stress-mediated gene transcription.
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Characteristics and assessment of phthalate esters in urban dusts in Guangzhou city, China.
Environ Monit Assess
PUBLISHED: 08-24-2011
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Phthalate esters (PAEs) were examined in indoor and outdoor dust samples from the subtropical city of Guangzhou, China. The ?(16)PAEs concentrations ranged from 121 to 3,223 ?g g(-1) dust, with the median concentration of 840 ?g g(-1) dust. Significantly higher concentrations of PAEs in dust samples were found in offices where electrical and electronic devices, carpet pads, and office furniture were widely used. Of the 16 PAEs, diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs in indoor and outdoor dust samples, and accounted for >96.8% and >93.1% of the ?(16)PAEs concentrations, respectively. The median daily inhalation exposure of ?(16)PAEs were 3.53 and 0.247 ?g kg(-1) body weight day(-1), and at the 95(th) percentile were 7.62 and 0.530 ?g kg(-1) body weight day(-1), up on the measured concentrations and estimated dust ingestion rates, respectively, for toddles and adults. The ubiquitous distribution of PAEs as noted in this study suggests the need for detailed assessment of PAEs concentrations using more sites and to further investigate the factors influencing PAEs exposure in China.
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Experimental and theoretical differential cross sections for a four-atom reaction: HD + OH ? H?O + D.
Science
PUBLISHED: 07-23-2011
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Quantum dynamical theories have progressed to the stage in which state-to-state differential cross sections can now be routinely computed with high accuracy for three-atom systems since the first such calculation was carried out more than 30 years ago for the H + H(2) system. For reactions beyond three atoms, however, highly accurate quantum dynamical calculations of differential cross sections have not been feasible. We have recently developed a quantum wave packet method to compute full-dimensional differential cross sections for four-atom reactions. Here, we report benchmark calculations carried out for the prototypical HD + OH ? H(2)O + D reaction on an accurate potential energy surface that yield differential cross sections in excellent agreement with those from a high-resolution, crossed-molecular beam experiment.
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Cannabinoid receptor type 1 (CB1R) signaling regulates hepatic gluconeogenesis via induction of endoplasmic reticulum-bound transcription factor cAMP-responsive element-binding protein H (CREBH) in primary hepatocytes.
J. Biol. Chem.
PUBLISHED: 06-21-2011
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Activated cannabinoid 1 receptor (CB1R) signaling has been implicated in the development of phenotypes associated with fatty liver, insulin resistance, and impaired suppression of hepatic glucose output. Endoplasmic reticulum stress-associated liver-specific transcription factor CREBH is emerging as a critical player in various hepatic metabolic pathways and regulates hepatic gluconeogenesis in diet-induced obese settings. In this study, we elucidated the critical role of CREBH in mediating CB1R signaling to regulate glucose homeostasis in primary rat and human hepatocytes. mRNA and protein levels and glucose production were analyzed in primary rat and human hepatocytes. ChIP assays were performed together with various transcriptional analyses using standard techniques. CB1R activation by 2-arachidonoylglycerol (2-AG) specifically induced CREBH gene expression via phosphorylation of the JNK signaling pathway and c-Jun binding to the AP-1 binding site in the CREBH gene promoter. 2-AG treatment significantly induced hepatic gluconeogenic gene expression and glucose production in primary hepatocytes, and we demonstrated that the CREBH binding site mutant significantly attenuated 2-AG-mediated activation of the gluconeogenic gene promoter. Endogenous knockdown of CREBH led to ablation of 2-AG-induced gluconeogenic gene expression and glucose production, and the CB1R antagonist AM251 or insulin exhibited repression of CREBH gene induction and subsequently inhibited gluconeogenesis in both rat and human primary hepatocytes. These results demonstrate a novel mechanism of action of activated CB1R signaling to induce hepatic gluconeogenesis via direct activation of CREBH, thereby contributing to a better understanding of the endocannabinoid signaling mechanism involved in regulating the hepatic glucose metabolism.
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Rhesus macaques develop metabolic syndrome with reversible vascular dysfunction responsive to pioglitazone.
Circulation
PUBLISHED: 06-20-2011
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The metabolic syndrome (MetS) is a constellation of clinical features that include central obesity, hypertension, atherogenic dyslipidemia, and insulin resistance. However, the concept remains controversial; it has been debated whether MetS represents nothing more than simultaneous co-occurrence of individual risk factors or whether there are common shared pathophysiological mechanisms that link the individual components.
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Bile Acid signaling in liver metabolism and diseases.
J Lipids
PUBLISHED: 06-10-2011
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Obesity, diabetes, and metabolic syndromes are increasingly recognized as health concerns worldwide. Overnutrition and insulin resistance are the major causes of diabetic hyperglycemia and hyperlipidemia in humans. Studies in the past decade provide evidence that bile acids are not just biological detergents facilitating gut nutrient absorption, but also important metabolic regulators of glucose and lipid homeostasis. Pharmacological alteration of bile acid metabolism or bile acid signaling pathways such as using bile acid receptor agonists or bile acid binding resins may be a promising therapeutic strategy for the treatment of obesity and diabetes. On the other hand, bile acid signaling is complex, and the molecular mechanisms mediating the bile acid effects are still not completely understood. This paper will summarize recent advances in our understanding of bile acid signaling in regulation of glucose and lipid metabolism, and the potentials of developing novel therapeutic strategies that target bile acid metabolism for the treatment of metabolic disorders.
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Aldo-keto reductase 1B7 is a target gene of FXR and regulates lipid and glucose homeostasis.
J. Lipid Res.
PUBLISHED: 06-05-2011
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Aldo-keto reductase 1B7 (AKR1B7) is proposed to play a role in detoxification of by-products of lipid peroxidation. In this article, we show that activation of the nuclear receptor farnesoid X receptor (FXR) induces AKR1B7 expression in the liver and intestine, and reduces the levels of malondialdehyde (MDA), the end product of lipid peroxidation, in the intestine but not in the liver. To determine whether AKR1B7 regulates MDA levels in vivo, we overexpressed AKR1B7 in the liver. Overexpression of AKR1B7 in the liver had no effect on hepatic or plasma MDA levels. Interestingly, hepatic expression of AKR1B7 significantly lowered plasma glucose levels in both wild-type and diabetic db/db mice, which was associated with reduced hepatic gluconeogenesis. Hepatic expression of AKR1B7 also significantly lowered hepatic triglyceride and cholesterol levels in db/db mice. These data reveal a novel function for AKR1B7 in lipid and glucose metabolism and suggest that AKR1B7 may not play a role in detoxification of lipid peroxides in the liver. AKR1B7 may be a therapeutic target for treatment of fatty liver disease associated with diabetes mellitus.
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The biosynthesis of the polyether antibiotic nanchangmycin is controlled by two pathway-specific transcriptional activators.
Arch. Microbiol.
PUBLISHED: 06-04-2011
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The nanchangmycin (NAN) produced by Streptomyces nanchangensis NS3226 is a polyether antibiotic resembling monensin in their gene clusters and the chemical structures. They can inhibit gram-positive bacteria and be a growth promoter for ruminants. Within the nanchangmycin gene cluster (nan), we identified that two SARP-family regulatory genes, nanR1 and nanR2, were both required to activate the transcription of all nan polyketide genes. Overexpression of NanR1 and NanR2 in wild-type increase NAN yields by at least three folds. Bioinformatic analysis of the immediate upstream DNA sequence of each nan gene and quantitative real-time RT-PCR analysis of the nan operons identified five putative SARP binding sites. Moreover, deletion of an AraC-family repressor gene nanR4 increased expression of NanR1 and R2 and led to a threefold increase in NAN production.
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Overexpression of cholesterol 7?-hydroxylase promotes hepatic bile acid synthesis and secretion and maintains cholesterol homeostasis.
Hepatology
PUBLISHED: 02-11-2011
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We reported previously that mice overexpressing cytochrome P450 7a1 (Cyp7a1; Cyp7a1-tg mice) are protected against high fat diet-induced hypercholesterolemia, obesity, and insulin resistance. Here, we investigated the underlying mechanism of bile acid signaling in maintaining cholesterol homeostasis in Cyp7a1-tg mice. Cyp7a1-tg mice had two-fold higher Cyp7a1 activity and bile acid pool than did wild-type mice. Gallbladder bile acid composition changed from predominantly cholic acid (57%) in wild-type to chenodeoxycholic acid (54%) in Cyp7a1-tg mice. Cyp7a1-tg mice had higher biliary and fecal cholesterol and bile acid secretion rates than did wild-type mice. Surprisingly, hepatic de novo cholesterol synthesis was markedly induced in Cyp7a1-tg mice but intestine fractional cholesterol absorption in Cyp7a1-tg mice remained the same as wild-type mice despite the presence of increased intestine bile acids. Interestingly, hepatic but not intestinal expression of several cholesterol (adenosine triphosphate-binding cassette G5/G8 [ABCG5/G8], scavenger receptor class B, member 1) and bile acid (ABCB11) transporters were significantly induced in Cyp7a1-tg mice. Treatment of mouse or human hepatocytes with a farnesoid X receptor (FXR) agonist GW4064 or bile acids induced hepatic Abcg5/g8 expression. A functional FXR binding site was identified in the Abcg5 gene promoter. Study of tissue-specific Fxr knockout mice demonstrated that loss of the Fxr gene in the liver attenuated bile acid induction of hepatic Abcg5/g8 and gallbladder cholesterol content, suggesting a role of FXR in the regulation of cholesterol transport.
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The precedence of topological change over top-down attention in masked priming.
J Vis
PUBLISHED: 01-01-2011
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Recent data indicate that unconscious masked priming can be mediated by top-down attentional set, so that priming effects of congruence between a masked prime and a subsequent probe vanish when the congruence ceases to be task relevant. Here, we show that, while the attentional set determines masked priming for color and orientation features, it does not fully determine priming based on the topological properties of stimuli. Specifically, across a series of different choice-RT tasks, we find that topological congruence between prime and probe stimuli affects RTs for the probes even when other stimulus information (e.g., color or orientation) is required for the response, whereas congruence priming effects of color or orientation occur only when these features are response relevant. Our results suggest that changes in topological properties take precedence over task-directed top-down attentional modulation in masked priming.
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Cortical dynamics underlying face completion in human visual system.
J. Neurosci.
PUBLISHED: 12-15-2010
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In natural images, visual objects are typically occluded by other objects. A remarkable ability of our visual system is to complete occluded objects effortlessly and see whole, uninterrupted objects. How object completion is implemented in the visual system is still largely unknown. In this study, using a backward masking paradigm, we combined psychophysics and functional magnetic resonance imaging to investigate the temporal evolvement of face completion at different levels of the visual processing hierarchy. Human subjects were presented with two kinds of stimuli that were designed to elicit or not elicit the percept of a completed face, although they were physically very similar. By contrasting subjects behavioral and blood oxygenation level-dependent (BOLD) responses to completed and noncompleted faces, we measured the psychophysical time course of the face completion and its underlying cortical dynamics. We found that face completion manifested its effect between 50 and 250 ms after stimulus onset. Relative to noncompleted faces, completed faces induced weaker BOLD response at early processing phases in retinotopic visual areas V1 and V2 and stronger BOLD response at late processing phases in occipital face area and fusiform face area. Attending away from the stimuli largely abolished these effects. These findings suggest that face completion consists of two synergetic phases: early suppression in lower visual areas and late enhancement in higher visual areas; moreover, attention is necessary to these neural events.
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Topological change disturbs object continuity in attentive tracking.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 11-29-2010
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The question of what is a perceptual object is one of the most central and also controversial issues in cognitive science. According to the topological approach to perceptual organization, the core intuitive notion of an object--the holistic identity preserved over shape-changing transformations--may be characterized precisely as topological invariance. Here we show that, across a series of multiple-object tracking tasks, performance was not disrupted when the moving items underwent massive featural changes. However, performance was significantly impaired when the items changed their topological properties of holes, demonstrating that topological invariance constrains what counts as an object in the first place. Consistent with previous findings, fMRI studies indicated that the anterior temporal lobe may be involved in the formation of object representation defined by topological constraints.
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Disrupted postnatal lung development in heme oxygenase-1 deficient mice.
Respir. Res.
PUBLISHED: 10-10-2010
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Heme oxygenase (HO) degrades cellular heme to carbon monoxide, iron and biliverdin. The HO-1 isoform is both inducible and cyto-protective during oxidative stress, inflammation and lung injury. However, little is known about its precise role and function in lung development. We hypothesized that HO-1 is required for mouse postnatal lung alveolar development and that vascular expression of HO-1 is essential and protective during postnatal alveolar development.
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Mechanism and stereospecificity of a fully saturating polyketide synthase module: nanchangmycin synthase module 2 and its dehydratase domain.
J. Am. Chem. Soc.
PUBLISHED: 10-08-2010
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Recombinant nanchangmycin synthase module 2 (NANS module 2), with the thioesterase domain from the 6-deoxyerythronolide B synthase (DEBS TE) appended to the C-terminus, was cloned and expressed in Escherichia coli. Incubation of NANS module 2+TE with (±)-2-methyl-3-keto-butyryl-N-acetylcysteamine thioester (1), the SNAC analog of the natural ACP-bound substrate, with methylmalonyl-CoA (MM-CoA) in the absence of NADPH gave 3,5,6-trimethyl-4-hydroxypyrone (2), identified by direct comparison with synthetic 2 by radio-TLC-phosphorimaging and LC-ESI(+)-MS-MS. The reaction showed k(cat) 0.5 ± 0.1 min(-1) and K(m)(1) 19 ± 5 mM at 0.5 mM MM-CoA and k(cat)(app) 0.26 ± 0.02 min(-1) and K(m)(MM-CoA) 0.11 ± 0.02 mM at 8 mM 1. Incubation in the presence of NADPH generated the fully saturated triketide chain elongation product as a 5:3 mixture of (2S,4R)-2,4-dimethyl-5-ketohexanoic acid (3a) and the diastereomeric (2S,4S)-3b. The structure and stereochemistry of each product was established by comparison with synthetic 3a and 3b by a combination of radio-TLC-phosphorimaging and LC-ESI(-)-MS-MS, as well as chiral capillary GC-MS analysis of the corresponding methyl esters 3a-Me and 3b-Me. The recombinant dehydratase domain from NANS module 2, NANS DH2, was shown to catalyze the formation of an (E)-double bond by syn-dehydration of the ACP-bound substrate anti-(2R,3R,4S,5R)-2,4-dimethyl-3,5-dihydroxyheptanoyl-ACP6 (4), generated in situ by incubation of (2S,3R)-2-methyl-3-hydroxypentanoyl-SNAC (5), methylmalonyl-CoA, and NADPH with the recombinant [KS6][AT6] didomain and ACP6 from DEBS module 6 along with the ketoreductase from the tylactone synthase module 1 (TYLS KR1). These results also indirectly establish the stereochemistry of the reactions catalyzed by the KR and enoylreductase (ER) domains of NANS module 2.
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Genetic engineering of Escherichia coli for biofuel production.
Annu. Rev. Genet.
PUBLISHED: 09-09-2010
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In order to mitigate climate change without adversely affecting global energy supply, there is growing interest in the possibility of producing transportation fuels from renewable sources via microbial fermentation. Central to this challenge is the design of biocatalysts that can efficiently convert cheap lignocellulosic raw materials into liquid fuels. Owing to the wealth of genetic and metabolic knowledge associated with Escherichia coli, this bacterium is the most convenient starting point for engineering microbial catalysts for biofuel production. Here, we review the range of liquid fuels that can be produced in E. coli and discuss the underlying biochemistry that enables these metabolic products. The fundamental and technological challenges encountered in the development of efficient fermentation processes for biofuel production are highlighted. The example of biodiesel is a particularly illustrative case study and is therefore discussed in detail.
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Effect of nutrients on the biodegradation of tributyltin (TBT) by alginate immobilized microalga, Chlorella vulgaris, in natural river water.
J. Hazard. Mater.
PUBLISHED: 08-19-2010
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The removal and degradation of tributyltin (TBT) by alginate immobilized Chlorella vulgaris has been evidenced in our previously published work. The present study was further to investigate the effect of spiked nutrient concentrations on the TBT removal capacity and degradation in the same alginate immobilized C. vulgaris. During the 14-d experiment, compared to the control (natural river water), the spiked nutrient groups (50% or 100% nutrients of the commercial Bristol medium as the reference, marked as 1/2N or 1N) showed more rapid cell proliferation of microalgae and higher TBT removal rate. Moreover, significantly more TBT was adsorbed onto the alginate matrix, but less TBT was taken up by the algal cells of the nutrient groups than that of the control. Mass balance data showed that TBT was lost as inorganic tin in the highest degree in 1N group, followed by 1/2N group and the least was in the control, but the relative abundance of the intermediate products of debutylation (dibutyltin and monobutyltin) were comparable among three groups. In conclusion, the addition of nutrients in contaminated water stimulated the growth and physiological activity of C. vulgaris immobilized in alginate beads and improved its TBT degradation efficiency.
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Multiplex RT-PCR for rapid detection and differentiation of class I and class II Newcastle disease viruses.
J. Virol. Methods
PUBLISHED: 07-27-2010
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A multiplex RT-PCR was developed for detection and differentiation of class I and class II strains of Newcastle disease virus (NDV). The method was shown to have high specificity and sensitivity. The results obtained from the multiplex RT-PCR for a total of 67 NDV field isolates obtained in 2009 were consistent with those obtained by nucleotide sequencing and phylogenetic analysis. A phylogenetic tree based on the partial sequences of the F gene revealed that the 67 field isolates of NDV could be divided into two classes. Twenty-seven NDV isolates were grouped into class I, and two genotypes were identified. Most of the class I isolates were determined to be of genotype 3, with the exception of isolate NDV09-034, which belonged to genotype 2. Forty class II NDV isolates were divided into three genotypes, namely genotype VII (27 isolates), genotype I (2 isolates) and genotype II (11 isolates). Isolates of genotypes I and II in class II were shown to be related to commercial vaccine strains used commonly in China. All isolates of genotype VII were predicted to be virulent, on the basis of the sequence motif at the cleavage site of the F gene. This genotype has become predominantly responsible for most outbreaks of ND in China in recent years. In conclusion, this multiplex RT-PCR provides a new assay for rapid detection and differentiation of both classes of NDV isolates.
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Effects of pyrene and fluoranthene on the degradation characteristics of phenanthrene in the cometabolism process by Sphingomonas sp. strain PheB4 isolated from mangrove sediments.
Mar. Pollut. Bull.
PUBLISHED: 07-15-2010
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Cometabolism has been suggested as an attractive approach to enhance the degradation rates of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs). However, the effects of these recalcitrant PAHs on the degradation characteristics of low-molecular-weight PAHs are largely unknown. This study was conducted to investigate the effects of pyrene (PYR) and fluoranthene (FLA) on the degradation characteristics of phenanthrene (PHE) in the cometabolism process by Sphingomonas sp. strain PheB4 isolated from mangrove sediments. Based on the kinetics and characteristics of PHE metabolites, it was proposed that the transformation of hydroxylated PHE into 1-hydroxy-2-naphthoic acid was a rate-limiting step in the degradation of PHE by strain PheB4. Compared to a single addition of PYR or FLA, the presence of a mixture of PYR and FLA decreased the degradation rate of PHE to a larger extent, which was likely because it could inhibit the production of 1-hydroxy-2-naphthoic acid more effectively.
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Transgenic expression of cholesterol 7alpha-hydroxylase in the liver prevents high-fat diet-induced obesity and insulin resistance in mice.
Hepatology
PUBLISHED: 07-13-2010
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Cholesterol 7alpha-hydroxylase (CYP7A1) is the rate-limiting enzyme in the bile acid biosynthetic pathway that converts cholesterol into bile acids in the liver. Recent studies have shown that bile acids may play an important role in maintaining lipid, glucose, and energy homeostasis. However, the role of CYP7A1 in the development of obesity and diabetes is currently unclear. In this study, we demonstrated that transgenic mice overexpressing Cyp7a1 in the liver [i.e., Cyp7a1 transgenic (Cyp7a1-tg) mice] were resistant to high-fat diet (HFD)-induced obesity, fatty liver, and insulin resistance. Cyp7a1-tg mice showed increased hepatic cholesterol catabolism and an increased bile acid pool. Cyp7a1-tg mice had increased secretion of hepatic very low density lipoprotein but maintained plasma triglyceride homeostasis. Gene expression analysis showed that the hepatic messenger RNA expression levels of several critical lipogenic and gluconeogenic genes were significantly decreased in HFD-fed Cyp7a1-tg mice. HFD-fed Cyp7a1-tg mice had increased whole body energy expenditure and induction of fatty acid oxidation genes in the brown adipose tissue. Conclusion: This study shows that Cyp7a1 plays a critical role in maintaining whole body lipid, glucose, and energy homeostasis. The induction of CYP7A1 expression with the expansion of the hydrophobic bile acid pool may be a potential therapeutic strategy for treating metabolic disorders such as fatty liver diseases, obesity, and diabetes in humans.
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Preparation and characterization of porous carbon material-coated solid-phase microextraction metal fibers.
J Chromatogr A
PUBLISHED: 07-08-2010
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Two kinds of porous carbon materials, including carbon aerogels (CAs), wormhole-like mesoporous carbons (WMCs), were synthesized and used as the coatings of solid-phase microextraction (SPME) fibers. By using stainless steel wire as the supporting core, six types of fibers were prepared with sol-gel method, direct coating method and direct coating plus sol-gel method. Headspace SPME experiments indicated that the extraction efficiencies of the CA fibers are better than those of the WMC fibers, although the surface area of WMCs is much higher than that of CAs. The sol-gel-CA fiber (CA-A) exhibited excellent extraction properties for non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene), while direct-coated CA fiber (CA-B) presented the best performance in extracting polar compounds (phenols). The two CA fibers showed wide linear ranges, low detection limits (0.008-0.047?gL(-1) for BTEX, 0.15-5.7?gL(-1) for phenols) and good repeatabilities (RSDs less than 4.6% for BTEX, and less than 9.5% for phenols) and satisfying reproducibilities between fibers (RSDs less than 5.2% for BTEX, and less than 9.9% for phenols). These fibers were successfully used for the analysis of water samples from the Pearl River, which demonstrated the applicability of the home-made CA fibers.
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Production of metabolites in the biodegradation of phenanthrene, fluoranthene and pyrene by the mixed culture of Mycobacterium sp. and Sphingomonas sp.
Bioresour. Technol.
PUBLISHED: 05-05-2010
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The effects of the mixed culture of Mycobacterium sp. strain A1-PYR and Sphingomonas sp. strain PheB4 on the degradation characteristics of single polycyclic aromatic hydrocarbon were investigated. In the mixed bacterial culture, phenanthrene, fluoranthene and pyrene were degraded by 100% at Day 3, 71.2% and 50% at Day 7, respectively. Compared to their respective pure cultures, the degradation of phenanthrene and fluoranthene decreased, but that of pyrene increased significantly. Based on GC-MS analysis, eight and six new metabolites were produced from the biodegradation of phenanthrene and fluoranthene, respectively, while only two new metabolites were formed from pyrene. To our knowledge, this is the first report that the mixed bacterial culture could increase the diversity of metabolites from PAH, but the diverse metabolite pattern was not necessarily beneficial to the degradation of the recalcitrant PAH. The enhancement on pyrene degradation was possibly attributed to the rapid growth of strain PheB4.
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A novel bile acid-activated vitamin D receptor signaling in human hepatocytes.
Mol. Endocrinol.
PUBLISHED: 04-06-2010
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Vitamin D receptor (VDR) is activated by natural ligands, 1alpha, 25-dihydroxy-vitamin D(3) [1alpha,25(OH)(2)-D(3)] and lithocholic acid (LCA). Our previous study shows that VDR is expressed in human hepatocytes, and VDR ligands inhibit bile acid synthesis and transcription of the gene encoding cholesterol 7alpha-hydroxylase (CYP7A1). Primary human hepatocytes were used to study LCA and 1alpha,25(OH)(2)-D(3) activation of VDR signaling. Confocal immunofluorescent microscopy imaging and immunoblot analysis showed that LCA and 1alpha, 25(OH)(2)-D(3) induced intracellular translocation of VDR from the cytosol to the nucleus and also plasma membrane where VDR colocalized with caveolin-1. VDR ligands induced tyrosine phosphorylation of c-Src and VDR and their interaction. Inhibition of c-Src abrogated VDR ligand-dependent inhibition of CYP7A1 mRNA expression. Kinase assays showed that VDR ligands specifically activated the c-Raf/MEK1/2/extracellular signal-regulated kinase (ERK) 1/2 pathway, which stimulates serine phosphorylation of VDR and hepatocyte nuclear factor-4alpha, and their interaction. Mammalian two-hybrid assays showed a VDR ligand-dependent interaction of nuclear receptor corepressor-1 and silencing mediator of retinoid and thyroid with VDR/retinoid X receptor-alpha (RXRalpha). Chromatin immunoprecipitation assays revealed that an ERK1/2 inhibitor reversed VDR ligand-induced recruitment of VDR, RXRalpha, and corepressors to human CYP7A1 promoter. In conclusion, VDR ligands activate membrane VDR signaling to activate the MEK1/2/ERK1/2 pathway, which stimulates nuclear VDR/RXRalpha recruitment of corepressors to inhibit CYP7A1 gene transcription in human hepatocytes. This membrane VDR-signaling pathway may be activated by bile acids to inhibit bile acid synthesis as a rapid response to protect hepatocytes from cholestatic liver injury.
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Determination of octylphenol and nonylphenol in aqueous sample using simultaneous derivatization and dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry.
J Chromatogr A
PUBLISHED: 04-03-2010
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A simple and fast sample preparation method for the determination of nonylphenol (NP) and octylphenol (OP) in aqueous samples by simultaneous derivatization and dispersive liquid-liquid microextraction (DLLME) was investigated using gas chromatography-mass spectrometry (GC/MS). In this method, a combined dispersant/derivatization catalyst (methanol/pyridine mixture) was firstly added to an aqueous sample, following which a derivatization reagent/extraction solvent (methyl chloroformate/chloroform) was rapidly injected to combine in situ derivatization and extraction in a single step. After centrifuging, the sedimented phase containing the analytes was injected into the GC port by autosampler for analysis. Several parameters, such as extraction solvent, dispersant solvent, amount of derivatization reagent, derivatization and extraction time, pH, and ionic strength were optimized to obtain higher sensitivity for the detection of NP and OP. Under the optimized conditions, good linearity was observed in the range of 0.1-1000 ?g L?¹ and 0.01-100 ?g L?¹ with the limits of detection (LOD) of 0.03 ?g L?¹ and 0.002 ?g L?¹ for NP and OP, respectively. Water samples collected from the Pearl River were analyzed with the proposed method, the concentrations of NP and OP were found to be 2.40 ± 0.16 ?g L?¹ and 0.037 ± 0.001 ?g L?¹, respectively. The relative recoveries of the water samples spiked with different concentrations of NP and OP were in the range of 88.3-106.7%. Compared with SPME and SPE, the proposed method can be successfully applied to the rapid and convenient determination of NP and OP in aqueous samples.
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Effects of metals on biosorption and biodegradation of mixed polycyclic aromatic hydrocarbons by a freshwater green alga Selenastrum capricornutum.
Bioresour. Technol.
PUBLISHED: 04-03-2010
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The effects of metals (cadmium, zinc, copper and nickel in a mixture) on biosorption and biodegradation of five mixed polycyclic aromatic hydrocarbons (PAHs), namely fluorene (FLU), phenanthrene (PHE), fluoranthrene (FLA), pyrene (PYR) and benzo[a]pyrene (BAP), by Selenastrum capricornutum were investigated. Exposure to metals significantly influenced the interactions between cells and PAHs and, such impact was PAH species dependent. For low molecular weight PAHs (FLU and PHE), both metal dosage and exposure time posed a significant, positive effect on their removal, with up to 99% of FLU and 89% of PHE were removed from the medium in seven days, which was mainly due to the cellular degradation induced by metal stress. For high molecular weight PAHs (FLA, PYR and BAP), the presence of metals did not affect the removal efficiency, but the uptake in the ethyl acetate-extractable fraction of the biomass was increased.
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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.