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Find video protocols related to scientific articles indexed in Pubmed.
[Prevention against and treatment of doxorubicin-induced acute cardiotoxicity by dexrazoxane and schisandrin B].
Yao Xue Xue Bao
PUBLISHED: 09-20-2014
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In this study, it is to compare the effectiveness of prevention against and treatment of doxorubicin (DOX) induced cardiotoxicity by dexrazoxane and schisandrin B (Sch B) in rats. Sprague-Dawley (SD) rats were randomly divided into the following 6 groups: normal saline group, DOX group, DOX+DEX group, DOX+Sch B (80 mg x kg(-1)) group, DOX+Sch B (40 mg x kg(-1)) group and DOX+Sch B (20 mg x kg(-1)) group. The results showed that Sch B could combat the increase of myocardial enzymes in peripheral blood, decrease of the enzyme activity of myocardial tissue antioxidant enzymes and disorders of systolic and diastolic function of heart in rats intravenously injected with doxorubicin (15 mg x kg(-1)). Sch B was better than DEX in protecting rat against DOX-induced the symptoms. Sch B could protect rat against DOX-induced acute cardiomyopathy and has clinical potential applications.
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A bridge between the aminoacylation and editing domains of leucyl-tRNA synthetase is crucial for its synthetic activity.
RNA
PUBLISHED: 07-22-2014
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Leucyl-tRNA synthetases (LeuRSs) catalyze the linkage of leucine with tRNA(Leu). LeuRS contains a catalysis domain (aminoacylation) and a CP1 domain (editing). CP1 is inserted 35 Å from the aminoacylation domain. Aminoacylation and editing require CP1 to swing to the coordinated conformation. The neck between the CP1 domain and the aminoacylation domain is defined as the CP1 hairpin. The location of the CP1 hairpin suggests a crucial role in the CP1 swing and domain-domain interaction. Here, the CP1 hairpin of Homo sapiens cytoplasmic LeuRS (hcLeuRS) was deleted or substituted by those from other representative species. Lack of a CP1 hairpin led to complete loss of aminoacylation, amino acid activation, and tRNA binding; however, the mutants retained post-transfer editing. Only the CP1 hairpin from Saccharomyces cerevisiae LeuRS (ScLeuRS) could partly rescue the hcLeuRS functions. Further site-directed mutagenesis indicated that the flexibility of small residues and the charge of polar residues in the CP1 hairpin are crucial for the function of LeuRS.
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A solution-phase bifunctional catalyst for lithium-oxygen batteries.
J. Am. Chem. Soc.
PUBLISHED: 06-12-2014
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A lithium-oxygen battery would deliver the highest energy density of a rechargeable battery, but the multiphase electrochemical reaction on the air cathode has difficulty proceeding when operated with only solid catalysts. We report here the organic-electrolyte-dissolved iron phthalocyanine (FePc) as a shuttle of (O2)(-) species and electrons between the surface of the electronic conductor and the insulator Li2O2 product of discharge. The Li2O2 is observed to grow and decompose without direct contact with carbon, which greatly enhances the electrochemical performance. Our results signal that the use of molecular shuttles that are catalytically active may prove to be enablers of a practical lithium-air rechargeable battery.
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The mRNA of human cytoplasmic arginyl-tRNA synthetase recruits prokaryotic ribosomes independently.
J. Biol. Chem.
PUBLISHED: 06-04-2014
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There are two isoforms of cytoplasmic arginyl-tRNA synthetase (hcArgRS) in human cells. The long form is a component of the multiple aminoacyl-tRNA synthetase complex, and the other is an N-terminal truncated form (NhcArgRS), free in the cytoplasm. It has been shown that the two forms of ArgRS arise from alternative translational initiation in a single mRNA. The short form is produced from the initiation at a downstream, in-frame AUG start codon. Interestingly, our data suggest that the alternative translational initiation of hcArgRS mRNA also takes place in Escherichia coli transformants. When the gene encoding full-length hcArgRS was overexpressed in E. coli, two forms of hcArgRS were observed. The N-terminal sequencing experiment identified that the short form was identical to the NhcArgRS in human cytoplasm. By constructing a bicistronic system, our data support that the mRNA encoding the N-terminal extension of hcArgRS has the capacity of independently recruiting E. coli ribosomes. Furthermore, two critical elements for recruiting prokaryotic ribosomes were identified, the “AGGA” core of the Shine-Dalgarno sequence and the “A-rich” sequence located just proximal to the alternative in-frame initiation site. Although the mechanisms of prokaryotic and eukaryotic translational initiation are distinct, they share some common features. The ability of the hcArgRS mRNA to recruit the prokaryotic ribosome may provide clues for shedding light on the mechanism of alternative translational initiation of hcArgRS mRNA in eukaryotic cells.
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Cold hardiness and biochemical response to low temperature of the unfed bush tick Haemaphysalis longicornis (Acari: Ixodidae).
Parasit Vectors
PUBLISHED: 05-05-2014
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The survival of overwintering ticks, is critical for their subsequent population dynamics in the spring, and consequent transmission of tick-borne diseases. Survival is largely influenced by the severity of the winter temperatures and their degree of cold hardiness at the overwintering stage. The bush tick Haemaphysalis longicornis, is widely distributed in China, and can transmit various pathogens that pose serious medical/veterinary problems. In the present study we investigated the effect of low temperature stress to tick survival, super-cooling point and body content of water, glycerol and total protein.
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The plateau zokors' learning and memory ability is related to the high expression levels of foxP2 in the brain.
Sheng Li Xue Bao
PUBLISHED: 04-30-2014
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Plateau zokor (Myospalax baileyi) is a subterranean mammal. Plateau zokor has high learning and memory ability, and can determine the location of blocking obstacles in their tunnels. Forkhead box p2 (FOXP2) is a transcription factor implicated in the neural control of orofacial coordination and sensory-motor integration, particularly with respect to learning, memory and vocalization. To explore the association of foxP2 with the high learning and memory ability of plateau zokor, the cDNA of foxP2 of plateau zokor was sequenced; by using plateau pika as control, the expression levels of foxP2 mRNA and FOXP2 protein in brain of plateau zokor were determined by real-time PCR and Western blot, respectively; and the location of FOXP2 protein in the brain of plateau zokor was determined by immunohistochemistry. The result showed that the cDNA sequence of plateau zokor foxP2 was similar to that of other mammals and the amino acid sequences showed a relatively high degree of conservation, with the exception of two particular amino acid substitutions [a Gln (Q)-to-His (H) change at position 231 and a Ser (S)-to-Ile (I) change at position 235]. Higher expression levels of foxP2 mRNA (3-fold higher) and FOXP2 protein (>2-fold higher) were detected in plateau zokor brain relative to plateau pika brain. In plateau zokor brain, FOXP2 protein was highly expressed in the cerebral cortex, thalamus and the striatum (a basal ganglia brain region). The results suggest that the high learning and memory ability of plateau zokor is related to the high expression levels of foxP2 in the brain.
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Evaluating time-reminder strategies before amber: common signal, green flashing and green countdown.
Accid Anal Prev
PUBLISHED: 04-08-2014
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The safety level of signalized intersection depends greatly on drivers' decision-making behaviors, which are significantly influenced by the time-reminder strategy before amber of the signal device. However, previous related studies are mainly based on the statistical results from the field data rather than explore the influence mechanism of the signal device on the signalized intersection's safety level. Therefore, this study aims to find out how these three typical signal devices with various time-reminder strategies, i.e., common signal device (CSD), green signal flashing device (GSFD), and green signal countdown device (GSCD), affect drivers' decision-making processes during the period from the end of the green phase to the onset of the red phase (i.e., G2R) and then evaluate their safety performance from the aspect of RLR violations. Firstly, an overall decision-making framework during G2R is presented to describe the driver-signal interaction and encloses four decision-making processes, which can be analyzed and modeled based on the field data collected from six signalized intersections in Changsha, China. Empirical analyses show that the time point of decision-making before amber under GSCD is the earliest and that under CSD is the latest, which can also be modeled and reproduced by back propagation neural network (BPNN). After that, five binary logistic regression models are developed to determine the safety effect during other various processes and results show that red-light-running (RLR) violations are not only dependent on the range of dilemma zones (DZ) but also substantially on stop and go decisions of those vehicles in DZ, both of which are the potential cause and direct factors to RLR violations and found to be significantly affected by the time-reminder strategy of the green signal device. Finally, although GSCD stimulates the drivers in DZ to choose to cross the intersection during amber, which produces a higher RLR risk compared with CSD and GSFD, the intersection with GSCD is verified to own the lowest RLR violations due to its greatly positive effect in cutting down the range of DZ.
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Gene cloning, expression and immunogenicity of the protective antigen subolesin in Dermacentor silvarum.
Korean J. Parasitol.
PUBLISHED: 02-19-2014
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Subolesin (4D8), the ortholog of insect akirins, is a highly conserved protective antigen and thus has the potential for development of a broad-spectrum vaccine against ticks and mosquitoes. To date, no protective antigens have been characterized nor tested as candidate vaccines against Dermacentor silvarum bites and transmission of associated pathogens. In this study, we cloned the open reading frame (ORF) of D. silvarum 4D8 cDNA (Ds4D8), which consisted of 498 bp encoding 165 amino acid residues. The results of sequence alignments and phylogenetic analysis demonstrated that D. silvarum 4D8 (Ds4D8) is highly conserved showing more than 81% identity of amino acid sequences with those of other hard ticks. Additionally, Ds4D8 containing restriction sites was ligated into the pET-32(a+) expression vector and the recombinant plasmid was transformed into Escherichia coli rosetta. The recombinant Ds4D8 (rDs4D8) was induced by isopropyl ?-D-thiogalactopyranoside (IPTG) and purified using Ni affinity chromatography. The SDS-PAGE results showed that the molecular weight of rDs4D8 was 40 kDa, which was consistent with the expected molecular mass considering 22 kDa histidine-tagged thioredoxin (TRX) protein from the expression vector. Western blot results showed that rabbit anti-D. silvarum serum recognized the expressed rDs4D8, suggesting an immune response against rDs4D8. These results provided the basis for developing a candidate vaccine against D. silvarum ticks and transmission of associated pathogens.
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Application of Auto-regressive Linear Model in Understanding the Effect of Climate on Malaria Vectors Dynamics in the Three Gorges Reservoir.
Biomed. Environ. Sci.
PUBLISHED: 02-13-2014
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It is important to understand the dynamics of malaria vectors in implementing malaria control strategies. Six villages were selected from different sections in the Three Gorges Reservoir for exploring the relationship between the climatic factors and its malaria vector density from 1997 to 2007 using the auto-regressive linear model regression method. The result indicated that both temperature and precipitation were better modeled as quadratic rather than linearly related to the density of Anopheles sinensis.
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Coexistence of bacterial leucyl-tRNA synthetases with archaeal tRNA binding domains that distinguish tRNA(Leu) in the archaeal mode.
Nucleic Acids Res.
PUBLISHED: 02-05-2014
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Leucyl-tRNA (transfer RNA) synthetase (LeuRS) is a multi-domain enzyme, which is divided into bacterial and archaeal/eukaryotic types. In general, one specific LeuRS, the domains of which are of the same type, exists in a single cell compartment. However, some species, such as the haloalkaliphile Natrialba magadii, encode two cytoplasmic LeuRSs, NmLeuRS1 and NmLeuRS2, which are the first examples of naturally occurring chimeric enzymes with different domains of bacterial and archaeal types. Furthermore, N. magadii encodes typical archaeal tRNA(Leu)s. The tRNA recognition mode, aminoacylation and translational quality control activities of these two LeuRSs are interesting questions to be addressed. Herein, active NmLeuRS1 and NmLeuRS2 were successfully purified after gene expression in Escherichia coli. Under the optimized aminoacylation conditions, we discovered that they distinguished cognate NmtRNA(Leu) in the archaeal mode, whereas the N-terminal region was of the bacterial type. However, NmLeuRS1 exhibited much higher aminoacylation and editing activity than NmLeuRS2, suggesting that NmLeuRS1 is more likely to generate Leu-tRNA(Leu) for protein biosynthesis. Moreover, using NmLeuRS1 as a model, we demonstrated misactivation of several non-cognate amino acids, and accuracy of protein synthesis was maintained mainly via post-transfer editing. This comprehensive study of the NmLeuRS/tRNA(Leu) system provides a detailed understanding of the coevolution of aminoacyl-tRNA synthetases and tRNA.
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Pachytene piRNAs instruct massive mRNA elimination during late spermiogenesis.
Cell Res.
PUBLISHED: 01-17-2014
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Spermatogenesis in mammals is characterized by two waves of piRNA expression: one corresponds to classic piRNAs responsible for silencing retrotransponsons and the second wave is predominantly derived from nontransposon intergenic regions in pachytene spermatocytes, but the function of these pachytene piRNAs is largely unknown. Here, we report the involvement of pachytene piRNAs in instructing massive mRNA elimination in mouse elongating spermatids (ES). We demonstrate that a piRNA-induced silencing complex (pi-RISC) containing murine PIWI (MIWI) and deadenylase CAF1 is selectively assembled in ES, which is responsible for inducing mRNA deadenylation and decay via a mechanism that resembles the action of miRNAs in somatic cells. Such a highly orchestrated program appears to take full advantage of the enormous repertoire of diversified targeting capacity of pachytene piRNAs derived from nontransposon intergenic regions. These findings suggest that pachytene piRNAs are responsible for inactivating vast cellular programs in preparation for sperm production from ES.
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Effects of MicroRNA-10b on lung cancer cell proliferation and invasive metastasis and the underlying mechanism.
Asian Pac J Trop Med
PUBLISHED: 01-15-2014
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To study the influence of MicroRNA-10b on proliferation and invasion of human low metastatic lung cancer cell 95-C and its mechanism.
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[Ecological behavior comparison between Anopheles pseudowillmori and A. willmori in villages with malaria outbreaks in Motuo County, Tibet Autonomous Region].
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi
PUBLISHED: 12-24-2013
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To understand the ecological behaviors of Anopheles pseudowillmori and A. willmori in medium or high altitude areas of Motuo County, Tibet Autonomous Region, and their transmission potential for malaria.
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Microscopic Insights into Extraction Mechanism of Copper(II) in Ammoniacal Solutions Studied by X-ray Absorption Spectroscopy and Density Functional Theory Calculation.
J Phys Chem A
PUBLISHED: 11-13-2013
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A microscopic investigation on the extraction process of copper(II) in ammoniacal solutions has been performed by X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation. The structural change of copper(II) species in ammoniacal solution has been derived from X-ray absorption near-edge spectroscopy (XANES) by principal component analysis and linear combination fitting. It was found that the coordination structure of the extracted copper complex in the organic phases is planar square and independent of the aqueous pH, whereas the geometries of copper(II) species in ammoniacal solutions changed from axially elongated octahedron to distorted planar square with increase of pH. The coordination geometry and structural parameters of copper(II) species were further obtained by extended X-ray absorption fine structure (EXAFS) fitting and DFT calculation with the B3LYP functional. These results reveal that the formation of tetracoordinated copper(II) ammine species can evidently inhibit the copper extraction reaction. Thus, the extraction mechanism of copper(II) in ammoniacal solutions has been elucidated in view of the microscopic structural aspects of copper species in both organic phase and ammoniacal solutions.
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Functional recoveries of sciatic nerve regeneration by combining chitosan-coated conduit and neurosphere cells induced from adipose-derived stem cells.
Biomaterials
PUBLISHED: 09-18-2013
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Suboptimal repair occurs in a peripheral nerve gap, which can be partially restored by bridging the gap with various biosynthetic conduits or cell-based therapy. In this study, we developed a combination of chitosan coating approach to induce neurosphere cells from human adipose-derived stem cells (ASCs) on chitosan-coated plate and then applied these cells to the interior of a chitosan-coated silicone tube to bridge a 10-mm gap in a rat sciatic nerve. Myelin sheath degeneration and glial scar formation were discovered in the nerve bridged by the silicone conduit. By using a single treatment of chitosan-coated conduit or neurosphere cell therapy, the nerve gap was partially recovered after 6 weeks of surgery. Substantial improvements in nerve regeneration were achieved by combining neurosphere cells and chitosan-coated conduit based on the increase of myelinated axons density and myelin thickness, gastrocnemius muscle weight and muscle fiber diameter, and step and stride lengths from gait analysis. High expressions of interleukin-1? and leukotriene B4 receptor 1 in the intra-neural scarring caused by using silicone conduits revealed that the inflammatory mechanism can be inhibited when the conduit is coated with chitosan. This study demonstrated that the chitosan-coated surface performs multiple functions that can be used to induce neurosphere cells from ASCs and to facilitate nerve regeneration in combination with a cells-assisted coated conduit.
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Aminoacylation and translational quality control strategy employed by leucyl-tRNA synthetase from a human pathogen with genetic code ambiguity.
Nucleic Acids Res.
PUBLISHED: 08-22-2013
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Aminoacyl-tRNA synthetases should ensure high accuracy in tRNA aminoacylation. However, the absence of significant structural differences between amino acids always poses a direct challenge for some aminoacyl-tRNA synthetases, such as leucyl-tRNA synthetase (LeuRS), which require editing function to remove mis-activated amino acids. In the cytoplasm of the human pathogen Candida albicans, the CUG codon is translated as both Ser and Leu by a uniquely evolved CatRNA(Ser)(CAG). Its cytoplasmic LeuRS (CaLeuRS) is a crucial component for CUG codon ambiguity and harbors only one CUG codon at position 919. Comparison of the activity of CaLeuRS-Ser(919) and CaLeuRS-Leu(919) revealed yeast LeuRSs have a relaxed tRNA recognition capacity. We also studied the mis-activation and editing of non-cognate amino acids by CaLeuRS. Interestingly, we found that CaLeuRS is naturally deficient in tRNA-dependent pre-transfer editing for non-cognate norvaline while displaying a weak tRNA-dependent pre-transfer editing capacity for non-cognate ?-amino butyric acid. We also demonstrated that post-transfer editing of CaLeuRS is not tRNA(Leu) species-specific. In addition, other eukaryotic but not archaeal or bacterial LeuRSs were found to recognize CatRNA(Ser)(CAG). Overall, we systematically studied the aminoacylation and editing properties of CaLeuRS and established a characteristic LeuRS model with naturally deficient tRNA-dependent pre-transfer editing, which increases LeuRS types with unique editing patterns.
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The tRNA recognition mechanism of the minimalist SPOUT methyltransferase, TrmL.
Nucleic Acids Res.
PUBLISHED: 06-26-2013
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Unlike other transfer RNAs (tRNA)-modifying enzymes from the SPOUT methyltransferase superfamily, the tRNA (Um34/Cm34) methyltransferase TrmL lacks the usual extension domain for tRNA binding and consists only of a SPOUT domain. Both the catalytic and tRNA recognition mechanisms of this enzyme remain elusive. By using tRNAs purified from an Escherichia coli strain with the TrmL gene deleted, we found that TrmL can independently catalyze the methyl transfer from S-adenosyl-L-methionine to and isoacceptors without the involvement of other tRNA-binding proteins. We have solved the crystal structures of TrmL in apo form and in complex with S-adenosyl-homocysteine and identified the cofactor binding site and a possible active site. Methyltransferase activity and tRNA-binding affinity of TrmL mutants were measured to identify residues important for tRNA binding of TrmL. Our results suggest that TrmL functions as a homodimer by using the conserved C-terminal half of the SPOUT domain for catalysis, whereas residues from the less-conserved N-terminal half of the other subunit participate in tRNA recognition.
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Differences of glycolysis in skeletal muscle and lactate metabolism in liver between plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzoniae).
Sheng Li Xue Bao
PUBLISHED: 06-22-2013
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The plateau pika (Ochotona curzoniae) and plateau zokor (Myospalax baileyi) are specialized native species of the Qinghai-Tibetan plateau. The goal of this study was to examine physiological differences in skeletal muscle glycolysis and hepatic lactate metabolism between these two species. The partial sequence of pyruvate carboxylase (PC) gene was cloned and sequenced. The mRNA expression levels of PC and lactate dehydrogenases (LDH-A, LDH-B) were determined by real-time PCR. The enzymatic activity of PC was measured using malic acid coupling method. The concentration of lactic acid (LD) and the specific activities of LDH in liver and skeletal muscle of two species were measured. The different isoenzymes of LDH were determined by native polyacrylamide gel electrophoresis (PAGE). The results showed that, (1) LDH-B mRNA level in skeletal muscle of plateau zokor was significantly higher than that of plateau pika (P < 0.01), but no differences was found at LDH-A mRNA levels between them (P > 0.05); (2) PC, LDH-A and LDH-B mRNA levels in liver of plateau pika were significantly higher than those of plateau zokor (P < 0.01); (3) The LDH activity and concentration of LD in skeletal muscle and liver, as well as the PC activity in liver of plateau pika were significantly higher than those of plateau zokor (P < 0.01); (4) The isoenzymatic spectrum of lactate dehydrogenase showed that the main LDH isoenzymes were LDH-A4, LDH-A3B and LDH-A2B2 in skeletal muscle of plateau pika, while the main LDH isoenzymes were LDH-AB3 and LDH-B4 in skeletal muscle of plateau zokor; the main isoenzymes were LDH-A3B, LDH-A2B2, LDH-AB3 and LDH-B4 in liver of plateau pika, while LDH-A4 was the only isoenzyme in liver of plateau zokor. These results indicate that the plateau pika gets most of its energy for sprint running through enhancing anaerobic glycolysis, producing more lactate in their skeletal muscle, and converting lactate into glucose and glycogen in the liver by enhancing gluconeogenesis. As a result, the plateau pika has a reduced dependence on oxygen in its hypoxic environment. In contrast, plateau zokor derives most of its energy used for digging activity by enhancing aerobic oxidation in their skeletal muscle, although they inhabit hypoxic underground burrows.
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Discovery of a potent benzoxaborole-based anti-pneumococcal agent targeting leucyl-tRNA synthetase.
Sci Rep
PUBLISHED: 06-04-2013
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Streptococcus pneumoniae causes bacterial pneumonia with high mortality and morbidity. The emergency of multidrug-resistant bacteria threatens the treatment of the disease. Leucyl-tRNA synthetase (LeuRS) plays an essential role in cellular translation and is an attractive drug target for antimicrobial development. Here we report the compound ZCL039, a benzoxaborole-based derivative of AN2690, as a potent anti-pneumococcal agent that inhibits S. pneumoniae LeuRS (SpLeuRS) activity. We show using kinetic, biochemical analyses combined with the crystal structure of ZCL039-AMP in complex with the separated SpLeuRS editing domain, that ZCL039 binds to the LeuRS editing active site which requires the presence of tRNA(Leu), and employs an uncompetitive inhibition mechanism. Further docking models establish that ZCL039 clashes with the eukaryal/archaeal specific insertion I4ae helix within editing domains. These findings demonstrate the potential of benzoxaboroles as effective LeuRS inhibitors for pneumococcus infection therapy, and provide future structure-guided drug design and optimization.
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Multilevel functional and structural defects induced by two pathogenic mitochondrial tRNA mutations.
Biochem. J.
PUBLISHED: 05-02-2013
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Point mutations in hmtRNAs (human mitochondrial tRNAs) can cause various disorders, such as CPEO (chronic progressive external ophthalmoplegia) and MM (mitochondrial myopathy). Mitochondrial tRNALeu, especially the UUR codon isoacceptor, is recognized as a hot spot for pathogenic mtDNA point mutations. Thus far, 40 mutations have been reported in hmtRNAsLeu. In the present paper, we describe the wide range of effects of two substitutions found in the T?C arms of two hmtRNAsLeu isoacceptors. The G52A substitution, corresponding to the pathogenic G12315A mutation in tRNALeu(CUN), and G3283A in tRNALeu(UUR) exhibited structural changes in the outer corner of the tRNA shape as shown by RNase probing. These mutations also induced reductions in aminoacylation, 3-end processing and base modification processes. The main effects of the A57G substitution, corresponding to mutations A12320G in tRNALeu(CUN) and A3288G in tRNALeu(UUR), were observed on the aminoacylation activity and binding to hmEF-Tu (human mitochondrial elongation factor Tu). These observations suggest that the wide range of effects may amplify the deleterious impact on mitochondrial protein synthesis in vivo. The findings also emphasize that an exact understanding of tRNA dysfunction is critical for the future development of therapies for mitochondrial diseases.
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The Yin and Yang of tRNA: proper binding of acceptor end determines the catalytic balance of editing and aminoacylation.
Nucleic Acids Res.
PUBLISHED: 04-12-2013
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Faithful translation of the genetic code depends on accurate coupling of amino acids with cognate transfer RNAs (tRNAs) catalyzed by aminoacyl-tRNA synthetases. The fidelity of leucyl-tRNA synthetase (LeuRS) depends mainly on proofreading at the pre- and post-transfer levels. During the catalytic cycle, the tRNA CCA-tail shuttles between the synthetic and editing domains to accomplish the aminoacylation and editing reactions. Previously, we showed that the Y330D mutation of Escherichia coli LeuRS, which blocks the entry of the tRNA CCA-tail into the connective polypeptide 1 domain, abolishes both tRNA-dependent pre- and post-transfer editing. In this study, we identified the counterpart substitutions, which constrain the tRNA acceptor stem binding within the synthetic active site. These mutations negatively impact the tRNA charging activity while retaining the capacity to activate the amino acid. Interestingly, the mutated LeuRSs exhibit increased global editing activity in the presence of a non-cognate amino acid. We used a reaction mimicking post-transfer editing to show that these mutations decrease post-transfer editing owing to reduced tRNA aminoacylation activity. This implied that the increased editing activity originates from tRNA-dependent pre-transfer editing. These results, together with our previous work, provide a comprehensive assessment of how intra-molecular translocation of the tRNA CCA-tail balances the aminoacylation and editing activities of LeuRS.
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A potential threat to malaria elimination: extensive deltamethrin and DDT resistance to Anopheles sinensis from the malaria-endemic areas in China.
Malar. J.
PUBLISHED: 04-04-2013
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Insecticide resistance in malaria vectors is a growing concern in many countries and requires immediate attention because of the limited chemical arsenal available for vector control. There is lack of systematic and standard monitoring data of malaria vector resistance in the endemic areas, which is essential for the ambitious goal of malaria elimination programme of China.
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Isolation of Liquiritigenin-4-Apiosyl-Glucoside and Liquiritin from the Root of Glycyrrhiza uralensis by High-Performance Centrifugal Partition Chromatography.
J Chromatogr Sci
PUBLISHED: 04-03-2013
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High-performance centrifugal partition chromatography (HPCPC) combined with ultraviolet detection was employed for the separation and purification of flavonoids from Glycyrrhiza. At the detection wavelength of 276 nm, two flavonoids, liquiritigenin-4-apiosyl-glucoside and liquiritin, were successfully separated by HPCPC with an optimized two-phase solvent system composed of ethyl acetate-ethanol-water (1:0.1:1, v/v/v). The purity of these compounds was 95.0 and 97.1%, respectively, as determined by high-performance liquid chromatography. Their structures were identified by electrospray ion source mass spectroscopy (ESI-MS(n)) in the negative ion mode.
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Human cytoplasmic ProX edits mischarged tRNAPro with amino acid but not tRNA specificity.
Biochem. J.
PUBLISHED: 03-30-2013
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aaRSs (aminoacyl-tRNA synthetases) are responsible for ensuring the fidelity of the genetic code translation by accurately linking a particular amino acid to its cognate tRNA isoacceptor. To ensure accuracy of protein biosynthesis, some aaRSs have evolved an editing process to remove mischarged tRNA. The hydrolysis of the mischarged tRNA usually occurs in an editing domain, which is inserted into or appended to the main body of the aaRS. In addition, autonomous, editing domain-homologous proteins can also trans-edit mischarged tRNA in concert or in compensating for the editing function of its corresponding aaRS. The freestanding ProX is a homologue of the editing domain of bacterial ProRS (prolyl-tRNA synthetase). In the present study, we cloned for the first time a gene encoding HsProX (human cytoplasmic ProX) and purified the expressed recombinant protein. The catalytic specificity of HsProX for non-cognate amino acids and identity elements on tRNAPro for editing were also investigated. We found that HsProX could deacylate mischarged Ala-tRNAPro, but not Cys-HstRNA(UGGPro), and specifically targeted the alanine moiety of Ala-tRNAPro. The importance of the CCA76 end of the tRNA for deacylation activity and key amino acid residues in HsProX for its editing function were also identified.
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Leucine-specific domain modulates the aminoacylation and proofreading functional cycle of bacterial leucyl-tRNA synthetase.
Nucleic Acids Res.
PUBLISHED: 03-21-2013
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The leucine-specific domain (LSD) is a compact well-ordered module that participates in positioning of the conserved KMSKS catalytic loop in most leucyl-tRNA synthetases (LeuRSs). However, the LeuRS from Mycoplasma mobile (MmLeuRS) has a tetrapeptide GKDG instead of the LSD. Here, we show that the tetrapeptide GKDG can confer tRNA charging and post-transfer editing activity when transplanted into an inactive Escherichia coli LeuRS (EcLeuRS) that has had its LSD deleted. Reciprocally, the LSD, together with the CP1-editing domain of EcLeuRS, can cooperate when inserted into the scaffold of the minimal MmLeuRS, and this generates an enzyme nearly as active as EcLeuRS. Further, we show that LSD participates in tRNA(Leu) recognition and favours the binding of tRNAs harbouring a large loop in the variable arm. Additional analysis established that the Lys598 in the LSD is the critical residue for tRNA binding. Conversion of Lys598 to Ala simultaneously reduces the tRNA-binding strength and aminoacylation and editing capacities, indicating that these factors are subtly connected and controlled at the level of the LSD. The present work provides a novel framework of co-evolution between LeuRS and its cognate tRNA through LSD.
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Interdomain communication modulates the tRNA-dependent pre-transfer editing of leucyl-tRNA synthetase.
Biochem. J.
PUBLISHED: 02-09-2013
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EcLeuRS [Escherichia coli LeuRS (leucyl-tRNA synthetase)] has evolved both tRNA-dependent pre- and post-transfer editing capabilities to ensure catalytic specificity. Both editing functions rely on the entry of the tRNA CCA tail into the editing domain of the LeuRS enzyme, which, according to X-ray crystal structural studies, leads to a dynamic disordered orientation of the interface between the synthetic and editing domains. The results of the present study show that this tRNA-triggered conformational rearrangement leads to interdomain communication between the editing and synthetic domains through their interface, and this communication mechanism modulates the activity of tRNA-dependent pre-transfer editing. Furthermore, tRNA-dependent editing reaction inhibits misactivating non-cognate amino acids from the synthetic active site. These results also suggested a novel quality control mechanism of EcLeuRS which is achieved through the co-ordination between the synthetic and editing domains.
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NHC-catalyzed hydroacylation of styrenes.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 01-25-2013
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New hydroacylation catalysts: Highly electron-rich N-heterocyclic carbenes (NHCs) facilitate the intermolecular hydroacylation of unstrained olefins. This unprecedented organocatalytic coupling joins simple and abundant aldehydes and styrenes to yield valuable ketone products. EWG=electron-withdrawing group, EDG=electron-donating group.
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piRNA-triggered MIWI ubiquitination and removal by APC/C in late spermatogenesis.
Dev. Cell
PUBLISHED: 01-19-2013
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The PIWI/PIWI-interacting RNA (piRNA) machinery has been well documented to maintain genome integrity by silencing transposons in animal germ cells. Recent studies have advanced our understanding of the biogenesis and function of this machinery; however, its metabolism has remained largely unexplored. Here, we show that murine PIWI (MIWI) is degraded through the APC/C-26S proteasome pathway and that piRNAs play an indispensable role in this process by enhancing MIWI interaction with an APC/C substrate-binding subunit. Interestingly, piRNA-triggered MIWI destruction occurs in late spermatids, which in turn leads to piRNA elimination, suggesting a feedforward mechanism for coordinated removal of the MIWI/piRNA machinery at a specific developmental stage. Importantly, the proper removal of MIWI/piRNA is essential for sperm maturation. Together, our results reveal a role for piRNAs in regulating the clearance of the MIWI/piRNA machinery via the ubiquitin-proteosome pathway and demonstrate the critical importance of proper temporal regulation of MIWI/piRNA in male germ cell development.
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Malaria transmission potential in the Three Gorges Reservoir of the Yangtze River, China.
Biomed. Environ. Sci.
PUBLISHED: 01-09-2013
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To define and evaluate the malaria transmission potential in the Yangtze River, following construction of the Three Gorges Reservoir.
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Application of structural equation models for elucidating the ecological drivers of Anopheles sinensis in the three gorges reservoir.
PLoS ONE
PUBLISHED: 01-01-2013
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To identify the major ecological drivers for malaria vector density using the structural equation model (SEM) in the Three Gorges Reservoir.
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Sociodemographic characteristics and risk factor analysis of Demodex infestation (Acari: Demodicidae).
J Zhejiang Univ Sci B
PUBLISHED: 12-03-2011
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To identify sociodemographic characteristics and risk factor of Demodex infestation, 756 students aged 13-22 years in Xian, China were sampled for the school-based cross-sectional study. Demodex was examined using the cellophane tape method (CTP). The results showed that the total detection rate of Demodex was 67.6%. Logistic regression analysis revealed that five variables (gender, residence, sharing sanitary ware, frequency of face-wash per day, and use of facial cleanser) were found to be uncorrelated with Demodex infestation, whereas three variables (age, skin type, and skin disease) were found to be independent correlates. Students aged over 18 years had 22.1 times higher odds of Demodex infestation compared to those under 16 years and students aged 16-18 years also had 2.1 times higher odds compared to those aged 13-15 years. Odds of having a Demodex infestation for oily or mixed skin were 2.1 times those for dry or neutral skin. Students with a facial skin disease had 3.0 times higher odds of being infested with Demodex compared to those without. The inception rate of students with facial dermatoses increased in parallel with increasing mite count. The inception rates were 21.3%, 40.7%, 59.2%, and 67.7% in the negative, mild, moderate, and severe infestation groups, respectively (?(2)=60.6, P<0.001). Specifically, the amount of infested mites and inception rate of acne vulgaris were positively correlated (R(2)=0.57, moderate infestation odds ratio (OR)=7.1, severe infestation OR=10.3). It was concluded that Demodex prevalence increases with age, and Demodex presents in nearly all adult human. Sebaceous hyperplasia with oily or mixed skin seems to favour Demodex proliferation. Demodex infestation could be associated with acne vulgaris. The CTP is a good sampling method for studies of Demodex prevalence.
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[Study on the preparation of curcumin inclusion complex and its stability].
Zhong Yao Cai
PUBLISHED: 10-25-2011
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To prepare the curcumin inclusion complex and study its stability.
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Life cycle of Haemaphysalis doenitzi (Acari: Ixodidae) under laboratory conditions and its phylogeny based on mitochondrial 16S rDNA.
Exp. Appl. Acarol.
PUBLISHED: 10-18-2011
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The paper investigated the life cycle of the hard tick Haemaphysalis doenitzi under laboratory conditions and its phylogeny based on mitochondrial 16S rDNA. The results revealed that the complete life cycle of H. doenitzi requires a mean duration of 109.6 days ranging from 91 to 137 days and the average prefeeding, feeding and premoulting periods of larvae, nymphs and females and the eggs hatching period are 18.7, 26.9, 38.9, and 25.1 days, respectively. In addition, the weight of engorged females is highly correlated with the number of egg masses laid (r = 0.936, P < 0.001). The female reproductive efficiency index and reproductive fitness index are 13.4 and 12.8, respectively. The mean weight of the engorged nymphs (2.77 mg) moulting to females is much higher than those (1.68 mg) moulting to males, which could be used as an index to predict sexes in this species. The ratio of male to female is 1:1.01. Moreover, multisequence alignments and phylogenetic tree constructed based on the mitochondrial 16S rDNA sequences suggest that H. doenitzi is genetically close to H. longicornis.
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[Investigation on Anopheles species and their composition in villages at different altitudes of Motuo County, Tibet Autonomous Region].
Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi
PUBLISHED: 10-07-2011
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To study the anopheline species and composition in villages at different altitudes, Muotuo County.
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Effects of music therapy on anxiety of patients with breast cancer after radical mastectomy: a randomized clinical trial.
J Adv Nurs
PUBLISHED: 10-06-2011
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? This paper is a report of a clinical trial of the effects of music therapy on anxiety of female breast cancer patients following radical mastectomy.
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Identification and characterization of antimicrobial peptides from skin of Amolops ricketti (Anura: Ranidae).
Peptides
PUBLISHED: 10-03-2011
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As one of large amphibian group, there are a total of 45 species of Amolops in the world. However, the antimicrobial peptides (AMPs) existing in this genus has not been extensively studied. In this study, cDNAs encoding five novel AMP precursors were cloned by screening the skin-derived cDNA library of Amolops ricketti, a frog species that exists in southern and western parts of China. Protein sequence analysis led to the identification of five deduced peptides, three belonging to the brevinin-1 family and two belonging to the brevinin-2 family of amphibian AMPs. Thus, they were named as brevinin-1RTa (FLPLLAGVVANFLPQIICKIARKC), brevinin-1RTb (FLGSLLGLVGKVVPTLFCKISKKC), brevinin-1RTc (FLGSLLGLVGKIVPTLICKISKKC), brevinin-2RTa (GLMSTLKDFGKTAAKEIAQSLLSTASCKLAKTC), and brevinin-2RTb (GILDTLKEFGKTAAKGIAQSLLSTASCKLAKTC), respectively. The purification of brevinin-1RTa, brevinin-1RTb, and brevinin-2RTb was carried out by RP-HPLC, and confirmed by the LC-MS/MS-based proteomics approach. All of the peptides displayed different antimicrobial potency against a variety of microorganisms. In addition, brevinin-2RTa and brevinin-2RTb were found to have relatively low hemolytic activity (>400?g/ml) against mammalian red blood cells in vitro, which could potentially be as candidates for developing novel anti-infection agents.
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Biomimetic asymmetric hydrogenation: in situ regenerable Hantzsch esters for asymmetric hydrogenation of benzoxazinones.
J. Am. Chem. Soc.
PUBLISHED: 09-23-2011
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A catalytic amount of Hantzsch ester that could be regenerated in situ by Ru complexes under hydrogen gas has been employed in the biomimetic asymmetric hydrogenation of benzoxazinones with up to 99% ee in the presence of chiral phosphoric acid. The use of hydrogen gas as a reductant for the regeneration of Hantzsch esters makes this hydrogenation an ideal atom economic process.
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Effects of music therapy on depression and duration of hospital stay of breast cancer patients after radical mastectomy.
Chin. Med. J.
PUBLISHED: 09-22-2011
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Breast cancer remains the most important cancer among women worldwide. The disease itself and treatment may have a profound impact on the patients psychological well being and quality of life. Depression is common in breast cancer patients and affects the therapeutic effects as well as prolongs the duration of hospital stay. However, few studies reported the effectiveness of music therapy on depression and duration of hospital stay of female patients with breast cancer after radical mastectomy.
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Cloning and characterization of a male-specific defensin-like antimicrobial peptide from the tick Haemaphysalis longicornis.
Dev. Comp. Immunol.
PUBLISHED: 09-08-2011
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A novel gene was identified from a cDNA library of the male accessory glands of Haemaphysalis longicornis. The full-length cDNA of the gene was 349bp, encoding a 79-amino acid defensin-like protein and therefore the protein was named HlMS-defensin. Reverse transcriptase-PCR results suggested that this gene was expressed exclusively in male ticks. The tissue expression pattern and the mRNA levels of HlMS-defensin during blood feeding were determined using real-time PCR. HlMS-defensin was expressed predominately in the male accessory gland and was up-regulated during blood feeding. The antimicrobial activity of a synthetic peptide based on the predicted mature portion of HlMS-defensin was examined against a variety of Gram-positive and Gram-negative bacteria and fungi. It appears that ticks use the antimicrobial peptide to protect their reproductive tracts from microbial infections. The protective role of HlMS-defensin during mating was also discussed.
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Peripheral insertion modulates the editing activity of the isolated CP1 domain of leucyl-tRNA synthetase.
Biochem. J.
PUBLISHED: 08-09-2011
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A large insertion domain called CP1 (connective peptide 1) present in class Ia aminoacyl-tRNA synthetases is responsible for post-transfer editing. LeuRS (leucyl-tRNA synthetase) from Aquifex aeolicus and Giardia lamblia possess unique 20 and 59 amino acid insertions respectively within the CP1 that are crucial for editing activity. Crystal structures of AaLeuRS-CP1 [2.4 Å (1 Å=0.1 nm)], GlLeuRS-CP1 (2.6 Å) and the insertion deletion mutant AaLeuRS-CP1?20 (2.5 Å) were solved to understand the role of these insertions in editing. Both insertions are folded as peripheral motifs located on the opposite side of the proteins from the active-site entrance in the CP1 domain. Docking modelling and site-directed mutagenesis showed that the insertions do not interact with the substrates. Results of molecular dynamics simulations show that the intact CP1 is more dynamic than its mutant devoid of the insertion motif. Taken together, the data show that a peripheral insertion without a substrate-binding site or major structural role in the active site may modulate catalytic function of a protein, probably from protein dynamics regulation in two respective LeuRS CP1s. Further results from proline and glycine mutational analyses intended to reduce or increase protein flexibility are consistent with this hypothesis.
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[Preparation of curcumin solid dispersion and inclusion complex].
Zhong Yao Cai
PUBLISHED: 07-25-2011
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To prepare the curcumin solid dispersion and the curcumin inclusion complex, evaluate its stability and the transdermal properties.
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Role of tRNA amino acid-accepting end in aminoacylation and its quality control.
Nucleic Acids Res.
PUBLISHED: 07-20-2011
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Aminoacyl-tRNA synthetases (aaRSs) are remarkable enzymes that are in charge of the accurate recognition and ligation of amino acids and tRNA molecules. The greatest difficulty in accurate aminoacylation appears to be in discriminating between highly similar amino acids. To reduce mischarging of tRNAs by non-cognate amino acids, aaRSs have evolved an editing activity in a second active site to cleave the incorrect aminoacyl-tRNAs. Editing occurs after translocation of the aminoacyl-CCA?? end to the editing site, switching between a hairpin and a helical conformation for aminoacylation and editing. Here, we studied the consequence of nucleotide changes in the CCA?? accepting end of tRNA(Leu) during the aminoacylation and editing reactions. The analysis showed that the terminal A?? is essential for both reactions, suggesting that critical interactions occur in the two catalytic sites. Substitutions of C?? and C?? selectively decreased aminoacylation keeping nearly unaffected editing. These mutations might favor the regular helical conformation required to reach the editing site. Mutating the editing domain residues that contribute to CCA?? binding reduced the aminoacylation fidelity leading to cell-toxicity in the presence of non-cognate amino acids. Collectively, the data show how protein synthesis quality is controlled by the CCA?? homogeneity of tRNAs.
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Highly enantioselective partial hydrogenation of simple pyrroles: a facile access to chiral 1-pyrrolines.
J. Am. Chem. Soc.
PUBLISHED: 05-17-2011
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A highly enantioselective Pd-catalyzed partial hydrogenation of simple 2,5-disubstituted pyrroles with a Brønsted acid as an activator has been successfully developed, providing chiral 2,5-disubstituted 1-pyrrolines with up to 92% ee.
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[Typhoid and paratyphoid fever in Yunnan province: distributional patterns and the related meteorological factors].
Zhonghua Liu Xing Bing Xue Za Zhi
PUBLISHED: 05-17-2011
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To characterize the spatial distribution of typhoid and paratyphoid fever (TPF) in Yunnan province, China and to determine the effectiveness of meteorological factors on the epidemics of TPF.
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[Surveillance program on and the distribution related to the virulence-associated genes of Vibrio cholerae in estuary of Pearl River].
Zhonghua Liu Xing Bing Xue Za Zhi
PUBLISHED: 05-12-2011
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To understand the distribution, molecular characteristics and virulence genes of the O1 and O139 Vibrio cholerae isolates from the Pearl River Estuary water.
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[Gene coding and mRNA expression of vascular endothelial growth factor as well as microvessel density in brain of plateau zokor: comparison with other rodents].
Sheng Li Xue Bao
PUBLISHED: 04-21-2011
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Vascular endothelial growth factor (VEGF) plays an important role in tissues angiogenesis. The adaptation of animals to hypoxic environment is relative to the microvessel density (MVD) in tissues. To further explore the adaptation mechanisms of plateau zokor (Myospalax baileyi) to the hypoxic-hypercapnic burrows, the VEGF mRNA and the MVD in cerebral tissues of the plateau zokor were studied. Total RNA was isolated from liver, and VEGF cDNA was obtained by RT-PCR, then the VEGF cDNA was cloned and sequenced. The coding sequence of plateau pika (Ochotona curzniae), rat (Rattus norvegicus) and mouse (Mus musculus) VEGF cDNA are obtained from GenBank, and the nucleotide and amino acid sequence homology of plateau zokor VEGF cDNA coding sequence with that of plateau pika, rat and mouse were analyzed and compared by using of bioinformatics software. The VEGF mRNA was detected by real-time PCR, and the MVDs in cerebral tissues of the plateau zokor, plateau pika and Sprague-Dawley (SD) rat were measured by immunohistochemical staining. The results showed that the open reading frame of the plateau zokor VEGF was 645 bp, and the coding sequence of the plateau zokor VEGF cDNA shared 92.1%, 93.6% and 93.8% nucleotide sequence homology to that of the plateau pika, rat and mouse, respectively. The deduced amino acid sequence of the plateau zokor VEGF cDNA was composed of 188 amino acids and the amino acids from 1 to 26 were signal peptide sequence. The plateau zokor VEGF188 was 90.2%, 94.9% and 94.4% homologous to that of plateau pika, rat and mouse. The level of VEGF mRNA in brain of the plateau zokor was significantly lower than that of SD rat, but there was no obvious difference in VEGF mRNA level between plateau zokor and plateau pika. The MVD in brain of the plateau zokor was markedly higher than that of plateau pika and SD rat. In conclusion, plateau zokor enhances its adaptation to the hypoxic environment by increasing the MVD. The level of VEGF mRNA in the brain of plateau zokor is lower than that of SD rat, which may be as a result of inhibition by the higher concentration of carbon dioxide in the burrow.
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Effects of music therapy on pain among female breast cancer patients after radical mastectomy: results from a randomized controlled trial.
Breast Cancer Res. Treat.
PUBLISHED: 04-16-2011
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Music therapy has been used in multiple health care settings to reduce patient pain, anxiety, and stress. However, few available studies have investigated its effect on pain among breast cancer patients after radical mastectomy. The aim of this study was to explore the effects of music therapy on pain reduction in patients with breast cancer after radical mastectomy. This randomized controlled trial was conducted at the Surgical Department of Oncology Center, First Affiliated Hospital of Xian Jiaotong University from March to November 2009. A total of 120 breast cancer patients who received Personal Controlled Analgesia (PCA) following surgery (mastectomy) were randomly allocated to two groups, an intervention group and a control group (60 patients in each group). The intervention group accepted music therapy from the first day after radical mastectomy to the third admission to hospital for chemotherapy in addition to the routine nursing care, while the control group received only routine nursing care. Pain scores were measured at baseline and three post-tests using the General Questionnaire and Chinese version of Short-Form of McGill Pain Questionnaire. The primary endpoint was the change in the Pain Rating Index (PRI-total) score from baseline. Music therapy was found to reduce the PRI-total score in the intervention group significantly compared with the control group with a mean difference (95% CI) of -2.38 (-2.80, -1.95), -2.41 (-2.85, -1.96), and -1.87 (-2.33, -1.42) for the 1st, 2nd, and 3rd post-tests, respectively. Similar results were found for Visual Analogue Scale (VAS) and Present Pain Intensity (PPI) scores. The findings of the study provide some evidence that music therapy has both short- and long-term positive effects on alleviating pain in breast cancer patients following radical mastectomy.
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Convergent asymmetric disproportionation reactions: metal/Brønsted acid relay catalysis for enantioselective reduction of quinoxalines.
J. Am. Chem. Soc.
PUBLISHED: 04-05-2011
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A convergent asymmetric disproportionation of dihydroquinoxalines for the synthesis of chiral tetrahydroquinoxalines using a metal/Brønsted acid relay catalysis system has been developed. The use of hydrogen gas as the reductant makes the convergent disproportionation an ideal atom-economical process. A dramatic reversal of enantioselectivity was observed in the reduction of quinoxalines because of the different steric demands in the 1,2- and 1,4-hydride transfer pathways.
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Gene cloning, expression and characterization of avian cathelicidin orthologs, Cc-CATHs, from Coturnix coturnix.
FEBS J.
PUBLISHED: 03-25-2011
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Cathelicidins comprise a family of antimicrobial peptides sharing a highly conserved cathelin domain, which play a central role in the early innate host defense against infection. In the present study, we report three novel avian cathelicidin orthologs cloned from a constructed spleen cDNA library of Coturnix coturnix, using a nested-PCR-based cloning strategy. Three coding sequences containing ORFs of 447, 465 and 456 bp encode three mature antimicrobial peptides (named Cc-CATH1, 2 and 3) of 26, 32 and 29 amino acid residues, respectively. Phylogenetic analysis indicated that precursors of Cc-CATHs are significantly conserved with known avian cathelicidins. Synthetic Cc-CATH2 and 3 displayed broad and potent antimicrobial activity against most of the 41 strains of bacteria and fungi tested, especially the clinically isolated drug-resistant strains, with minimum inhibitory concentration values in the range 0.3-2.5 ?m for most strains with or without the presence of 100 mm NaCl. Cc-CATH2 and 3 showed considerable reduction of cytotoxic activity compared to other avian cathelicidins, with average IC(50) values of 20.18 and 17.16 ?m, respectively. They also exerted a negligible hemolytic activity against human erythrocytes, lysing only 3.6% of erythrocytes at a dose up to 100 ?g·mL(-1) . As expected, the recombinant Cc-CATH2 (rCc-CATH2) also showed potent bactericidal activity. All these features of Cc-CATHs encourage further studies aiming to estimate their therapeutic potential as drug leads, as well as coping with current widespread antibiotic resistance, especially the new prevalent and dangerous superbug that is resistant to almost all antibiotics.
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Enantioselective Pd-catalyzed hydrogenation of enesulfonamides.
Chem. Commun. (Camb.)
PUBLISHED: 03-24-2011
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Asymmetric hydrogenation of cyclic enesulfonamides affords chiral cyclic sulfonamides using Pd(OCOCF(3))(2)/diphosphine complexes as catalysts with up to 98% ee.
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Cloning, expression and characterization of a new aspartate aminotransferase from Bacillus subtilis B3.
FEBS J.
PUBLISHED: 03-14-2011
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In the present study, we report the identification of a new gene from the Bacillus subtilis B3 strain (aatB3), which comprises 1308 bp encoding a 436 amino acid protein with a monomer molecular weight of 49.1 kDa. Phylogenetic analyses suggested that this enzyme is a member of the Ib subgroup of aspartate aminotransferases (AATs; EC 2.6.1.1), although it also has conserved active residues and thermostability characteristic of Ia-type AATs. The Asp232, Lys270 and Arg403 residues of AATB3 play a key role in transamination. The enzyme showed maximal activity at pH 8.0 and 45 °C, had relatively high activity over an alkaline pH range (pH 7.0-9.0) and was stable up to 50 °C. AATB3 catalyzed the transamination of five amino acids, with L-aspartate being the optimal substrate. The K(m) values were determined to be 6.7 mM for L-aspartate, 0.3 mM for ?-ketoglutarate, 8.0 mM for L-glutamate and 0.6 mM for oxaloacetate. A 32-residue N-terminal amino acid sequence of this enzyme has 53% identity with that of Bacillus circulans AAT, although it is absent in all other AATs from different organisms. Further studies on AATB3 may confirm that it is potentially beneficial in basic research as well as various industrial applications.
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Synthesis and bioactivity of 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-xylopyranosyl-1,3,4-oxa(thia)diazol-2-amines.
Carbohydr. Res.
PUBLISHED: 01-10-2011
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A series of new N-[N-(2,3,4-tri-O-acetyl-?-d-xylopyranosyl)thiocarbamoyl]-2-[(1-aryl-1H-tetrazol-5-yl)sulfanyl]acetohydrazides 5a-5e were synthesized rapidly in high yields from 2-(1-aryl-1H-tetrazol-5-ylsulfanyl)acetohydrazides 3a-3e and 2,3,4-tri-O-acetyl-?-d-xylopyranosyl isothiocyanate 4, then 5a-5e were converted to a series of new 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-(2,3,4-tri-O-acetyl-?-D-xylopyranosyl)-1,3,4-oxadiazole-2-amines 6a-6e and 5-(1-aryl-1H-tetrazol-5-ylsulfanylmethyl)-N-(2,3,4-tri-O-acetyl-?-D-xylopyranosyl)-1,3,4-thiadiazole-2-amines 7a-7e, respectively under mercuric acetate/alcohol system or acetic anhydride/phosphoric acid system, then deacetylated in the solution of CH(3)ONa/CH(3)OH. All of the novel compounds were characterized by IR, (1)H NMR, (13)C NMR, MS and elemental analysis. The structures of compounds 2e, 3e, 5a and 5c have been determined by X-ray diffraction analysis. Some of the synthesized compounds displayed PTP1B inhibition and microorganism inhibition.
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[The factors influencing the flexural strength of zirconia ceramic restorations].
Shanghai Kou Qiang Yi Xue
PUBLISHED: 12-17-2010
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Zirconia material has a very broad application prospect in prosthodontics,and restorations made of zirconia through CAD/CAM technology have been applied widely in recent years. In this paper we summarized the features of zirconia material which used for all ceramic restorations and the factors which affected its flexural property. We also sated the relevant indicators and methods used for evaluation of flexural property of zirconia material in order to lay a basis for its clinical use.
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Enantioselective Pd-catalyzed hydrogenation of fluorinated imines: facile access to chiral fluorinated amines.
Org. Lett.
PUBLISHED: 10-06-2010
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An enantioselective hydrogenation of simple fluorinated imines has been developed using Pd(OCOCF(3))(2)/(R)-Cl-MeO-BIPHEP as a catalyst, and up to 94% ee was achieved. This method provides an efficient route to enantioenriched fluorinated amines.
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Hemin binds to human cytoplasmic arginyl-tRNA synthetase and inhibits its catalytic activity.
J. Biol. Chem.
PUBLISHED: 10-05-2010
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The free form of human cytoplasmic arginyl-tRNA synthetase (hcArgRS) is hypothesized to participate in ubiquitin-dependent protein degradation by offering arginyl-tRNA(Arg) to arginyl-tRNA transferase (ATE1). We investigated the effect of hemin on hcArgRS based on the fact that hemin regulates several critical proteins in the "N-end rule" protein degradation pathway. Extensive biochemical evidence has established that hemin could bind to both forms of hcArgRS in vitro. Based on the spectral changes of the Soret band on site-directed protein mutants, we identified Cys-115 as a specific axial ligand of hemin binding that is located in the Add1 domain. Hemin inhibited the catalytic activity of full-length and N-terminal 72-amino acid-truncated hcArgRSs by blocking amino acid activation. Kinetic analysis demonstrated that the K(m) values for tRNA(Arg), arginine, and ATP in the presence of hemin were not altered, but k(cat) values dramatically decreased compared with those in the absence of hemin. By comparison, the activity of prokaryotic ArgRS was not affected obviously by hemin. Gel filtration chromatography suggested that hemin induced oligomerization of both the isolated Add1 domain and the wild type enzyme, which could account for the inhibition of catalytic activity. However, the catalytic activity of an hcArgRS mutant with Cys-115 replaced by alanine (hcArgRS-C115A) was also inhibited by hemin, suggesting that hemin binding to Cys-115 is not responsible for the inhibition of enzymatic activity and that the specific binding may participate in other biological functions.
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Modular pathways for editing non-cognate amino acids by human cytoplasmic leucyl-tRNA synthetase.
Nucleic Acids Res.
PUBLISHED: 08-30-2010
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To prevent potential errors in protein synthesis, some aminoacyl-transfer RNA (tRNA) synthetases have evolved editing mechanisms to hydrolyze misactivated amino acids (pre-transfer editing) or misacylated tRNAs (post-transfer editing). Class Ia leucyl-tRNA synthetase (LeuRS) may misactivate various natural and non-protein amino acids and then mischarge tRNA(Leu). It is known that the fidelity of prokaryotic LeuRS depends on multiple editing pathways to clear the incorrect intermediates and products in the every step of aminoacylation reaction. Here, we obtained human cytoplasmic LeuRS (hcLeuRS) and tRNA(Leu) (hctRNA(Leu)) with high activity from Escherichia coli overproducing strains to study the synthetic and editing properties of the enzyme. We revealed that hcLeuRS could adjust its editing strategy against different non-cognate amino acids. HcLeuRS edits norvaline predominantly by post-transfer editing; however, it uses mainly pre-transfer editing to edit ?-amino butyrate, although both amino acids can be charged to tRNA(Leu). Post-transfer editing as a final checkpoint of the reaction was very important to prevent mis-incorporation in vitro. These results provide insight into the modular editing pathways created to prevent genetic code ambiguity by evolution.
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1H, 15N chemical shift assignments of the imino groups in the base pairs of Escherichia coli tRNA(Leu) (CAG).
Biomol NMR Assign
PUBLISHED: 08-10-2010
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tRNA molecules are the adaptors in ribosome-based protein biosynthesis and are stabilized by Mg(2+). However, the detailed mechanism for the Mg(2+) mediated stability is not fully understood. To study the effects of Mg(2+) on conformational flexibility of Escherichia coli tRNA(Leu) (CAG) at millisecond timescale, we applied NMR spectroscopic approach to measure proton exchange rates of imino groups in the presence of different concentration of Mg(2+) and correlated them with the corresponding aminoacylation activity of tRNA(Leu). Here, we report the first part of the above mentioned study, the (1)H, (15)N chemical shift assignments of the imino groups in all base pairs of Escherichia coli tRNA(Leu) (CAG) based on 2D (1)H-(15)N TROSY, 2D NOESY and 3D NOESY-HMQC experiments. This work laid the foundation for the NMR study of tRNA(Leu) (BMRB deposits with accession number 17078).
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Studying base pair open-close kinetics of tRNALeu by TROSY-based proton exchange NMR spectroscopy.
FEBS Lett.
PUBLISHED: 07-28-2010
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The millisecond conformational flexibility is functionally important for nucleic acids and can be studied through probing the base pair open-close kinetics by proton exchange nuclear magnetic resonance (NMR) spectroscopy. Here, the traditional imino proton exchange NMR experiments were modified with transverse relaxation optimized spectroscopy and were applied to accurately measure imino proton exchange rates of all base pairs in Escherichia coli tRNA(Leu) (CAG), and their dependence on magnesium ion concentration. Finally, we correlated millisecond conformational flexibility with aminoacylation of tRNA(Leu) and proposed that the flexibility of the acceptor stem and the core region might contribute to aminoacylation of tRNA(Leu).
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[Impact of intrauterine infection on long-term brain development of premature rats].
Zhongguo Dang Dai Er Ke Za Zhi
PUBLISHED: 07-20-2010
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To investigate the impact of intrauterine infection induced by LPS injection on long-term brain development of premature rats.
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Experimental and numerical study of shock-accelerated elliptic heavy gas cylinders.
Phys Rev E Stat Nonlin Soft Matter Phys
PUBLISHED: 07-01-2010
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We studied the evolution of elliptic heavy SF6 gas cylinder surrounded by air when accelerated by a planar Mach 1.25 shock. A multiple dynamics imaging technology has been used to obtain one image of the experimental initial conditions and five images of the time evolution of elliptic cylinder. We compared the width and height of the circular and two kinds of elliptic gas cylinders and analyzed the vortex strength of the elliptic ones. Simulations are in very good agreement with the experiments, but due to the different initial gas cylinder shapes, a certain difference of the initial density peak and distribution exists between the circular and elliptic gas cylinders, and the latter initial state is more sensitive and more inenarrable.
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Post-transfer editing by a eukaryotic leucyl-tRNA synthetase resistant to the broad-spectrum drug AN2690.
Biochem. J.
PUBLISHED: 06-19-2010
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Some aaRSs (aminoacyl-tRNA synthetases) develop editing mechanisms to correct mis-charged tRNA. The CP1 (connective peptide 1) domain of LeuRS (leucyl-tRNA synthetase) contains the editing active site, which is the proven target for the broad-spectrum drug AN2690 (5-fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole). The ESI (eukarya-specific insertion 1) in the CP1 domain of GlLeuRS (Giardia lamblia LeuRS) has been identified. Similar substitution with the ESI from HsLeuRS (Homo sapiens LeuRS) impeded the leucine activation, aminoacylation and post-transfer editing of the enzyme, but had no effect on the editing specificity toward non-specific amino acids. Thr341 in GlLeuRS served as a specificity discriminator, as found in other LeuRS systems, although its substitution with an alanine residue did not destroy Leu-tRNALeu synthesis in vitro and in vivo. The Arg338 was crucial for tRNALeu charging and the Asp440 was crucial for leucine activation and aminoacylation. The post-transfer editing required the CTD (C-terminal domain), Arg338 and Asp440 of GlLeuRS. Interestingly, GlLeuRS was completely resistant to the AN2690, which is an inhibitor of various LeuRSs. The universally conserved aspartate residue in the LeuRS CP1 domains was responsible for the resistance of GlLeuRS and another recently reported AN2690-resistant AaLeuRS (Aquifex aeolicus LeuRS). Our results indicate the functional divergence of some absolutely conserved sites, improve the understanding of the editing function of eukaryotic/archaeal LeuRSs and shed light on the development of a GlLeuRS-specific inhibitor for the treatment of giardiasis.
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Pd-catalyzed asymmetric hydrogenation of unprotected indoles activated by Brønsted acids.
J. Am. Chem. Soc.
PUBLISHED: 06-18-2010
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The first highly enantioselective hydrogenation of simple indoles was developed with a Brønsted acid as an activator to form the iminium intermediate in situ, which was hydrogenated using Pd(OCOCF(3))(2)/(R)-H8-BINAP catalyst system with up to 96% ee. The present method provides an efficient route to enantioenriched 2-substituted and 2,3-disubstituted indolines.
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Phenotypic and genotypic characterization Vibrio cholerae O139 of clinical and aquatic isolates in China.
Curr. Microbiol.
PUBLISHED: 06-13-2010
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To enhance the understanding of epidemiological impact of environmental Vibrio cholerae O139 strains, we characterized 10 clinical and 20 environmental isolates collected from human clinical samples and Pear River estuary during 2006 to 2008. Isolates were tested by PCR for eight virulence genes: cholera toxin (ctxA), zonula occludens toxin (zot), accessory cholera enterotoxin (ace), hemolysin (hlyA), NAG-specific heat-stable toxin (st), toxin-coregulated pilus (tcpA), outer membrane protein (ompU), and regulatory protein genes (tcpI). Genetic relatedness was assessed by pulsed-field gel electrophoresis (PFGE), and antibiotic susceptibility was determined using disk diffusion. Seven of eight virulence markers were detected in six clinical isolates and one environmental isolate. One clinical and one environmental isolate were positive for six virulence markers. 60% clinical isolates showed multi-drug resistance to tetracycline (TET), Nalidixic acid (NAL), chloramphenicol (CHL), and ampicillin (AMP), 70% were resistant to Trimethoprim + Sulfamethoxazole (SXT), while only 35% environmental strains were resistant to SXT. PFGE analysis revealed that the isolates in this study were formed three clusters. Cluster III was more related to strains from diarrheal patients than the strains in other clusters. Different from the clinical strains, most environmental strains lacked CTX and TCP gene clusters. Most environmental strains possess a single resistance profile, while most clinical isolates show multidrug resistant. PFGE analysis indicated the cluster III has more possibility to become a potential pathogenic clonal cluster.
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XQ2, a novel TPZ derivative, induced G2/M phase arrest and apoptosis under hypoxia in non-small cell lung cancer cells.
Biosci. Biotechnol. Biochem.
PUBLISHED: 06-07-2010
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Hypoxia is one of the inevitable circumstances of various tumors. It controls various levels of regulation in tumor progression and results in tumor resistance to radiotherapy and chemotherapy. Here we investigated a synthetic TPZ derivative, N-ethoxymethyl-3-amino-1,2,4-benzotriazine-1,4-dioxide (XQ2), a novel compound that induced anti-cancer effects both in normoxia and in hypoxia, cell proliferation assay found that XQ2 exhibited a potent inhibitory effect on the tested cancer cell lines both in normoxia and in hypoxia. Flow cytometry and western blot studies indicated that XQ2 induces G2/M arrest and a caspase-dependent apoptosis in A549 cells. Additionally, intracellular reactive oxygen species (ROS) appear to play a key role in the anticancer effect of XQ2 in hypoxia. Taken together, our data suggest that XQ2 exerted anticancer action by suppressing the ROS level and triggering cell-cycle arrest and the caspase-dependent pathway, which is associated with apoptosis.
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Functional characterization of leucine-specific domain 1 from eukaryal and archaeal leucyl-tRNA synthetases.
Biochem. J.
PUBLISHED: 05-21-2010
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LeuRS (leucyl-tRNA synthetase) catalyses the esterification of tRNAsLeu with leucine. This family of enzymes is divided into prokaryotic and eukaryal/archaeal groups according to the presence and position of specific insertions and extensions. In the present study, we investigated the function of LSD1 (leucine-specific domain 1), which is naturally present in eukaryal/archaeal LeuRSs, but absent from prokaryotic LeuRSs. When mutated in their common domain, the eukaryal and archaeal LeuRSs exhibited defects in the first reaction step of amino acid activation with variations of leucine or ATP-binding strength, whereas the tRNA aminoacylation was moderately affected. When the eukaryal extension was mutated, severe tRNA charging defects were observed, suggesting that eukaryotes evolved this LSD1 extension in order to improve the aminoacylation reaction step. The results also showed that the LSD1s from organisms of both groups are dispensable for post-transfer editing. Together, the data provide us with a further understanding of the organization and structure of LeuRS domains.
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[The experimental research of the influence of cervical settling method on marginal accuracy of wax patter].
Hua Xi Kou Qiang Yi Xue Za Zhi
PUBLISHED: 05-20-2010
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To study the influence of cervical settling method on marginal accuracy of wax patters.
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Bifunctional AgOAc-catalyzed asymmetric reactions.
Chem. Commun. (Camb.)
PUBLISHED: 05-11-2010
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The discovery and progress of new bifunctional AgOAc-based catalysts for asymmetric reactions is described. In this bifunctional procedure, AgOAc acts as an efficient Lewis acid catalyst as well as a base through the deprotonation of active hydrogen promoted by acetate. The bifunctional strategy offers a great opportunity to establish new fundamentals for stereoselective construction of C-C as well as C-N bonds.
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Investigation of the Richtmyer-Meshkov instability with double perturbation interface in nonuniform flows.
Phys Rev E Stat Nonlin Soft Matter Phys
PUBLISHED: 05-05-2010
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A nonuniform SF6 gas flow initial condition has been actualized in the context of shock tube experiment for the Richtmyer-Meshkov instability study. Two kinds of amplitude have been used to design the membrane supports which initially materialize the gaseous interface. The visualizations of air/SF6 sinusoidal interfaces and shock wave propagations in the nonuniform field were obtained by Schlieren photography. Experiments are in very good agreement with simulations for the air/SF6 case, but due to the initial nonuniform effects, Sadot model and Zhang-Sohn theory are far beyond the experimental and calculation results.
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Novel cathelicidin-derived antimicrobial peptides from Equus asinus.
FEBS J.
PUBLISHED: 04-29-2010
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In the present study, EA-CATH1 and EA-CATH2 were identified from a constructed lung cDNA library of donkey (Equus asinus) as members of cathelicidin-derived antimicrobial peptides, using a nested PCR-based cloning strategy. Composed of 25 and 26 residues, respectively, EA-CATH1 and EA-CATH2 are smaller than most other cathelicidins and have no sequence homology to other cathelicidins identified to date. Chemically synthesized EA-CATH1 exerted potent antimicrobial activity against most of the 32 strains of bacteria and fungi tested, especially the clinically isolated drug-resistant strains, and minimal inhibitory concentration values against Gram-positive bacteria were mostly in the range of 0.3-2.4 microg mL(-1). EA-CATH1 showed an extraordinary serum stability and no haemolytic activity against human erythrocytes in a dose up to 20 microg mL(-1). CD spectra showed that EA-CATH1 mainly adopts an alpha-helical conformation in a 50% trifluoroethanol/water solution, but a random coil in aqueous solution. Scanning electron microscope observations of Staphylococcus aureus (ATCC2592) treated with EA-CATH1 demonstrated that EA-CATH could cause rapid disruption of the bacterial membrane, and in turn lead to cell lysis. This might explain the much faster killing kinetics of EA-CATH1 than conventional antibiotics revealed by killing kinetics data. In the presence of CaCl(2), EA-CATH1 exerted haemagglutination activity, which might potentiate an inhibition against the bacterial polyprotein interaction with the host erythrocyte surface, thereby possibly restricting bacterial colonization and spread.
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