A Tough Biodegradable Elastomer

Nature Biotechnology. Jun, 2002  |  Pubmed ID: 12042865

Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. A strong, biodegradable, and biocompatible elastomer could be useful for fields such as tissue engineering, drug delivery, and in vivo sensing. We designed, synthesized, and characterized a tough biodegradable elastomer from biocompatible monomers. This elastomer forms a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. Both crosslinking and the hydrogen-bonding interactions between the hydroxyl groups likely contribute to the unique properties of the elastomer. In vitro and in vivo studies show that the polymer has good biocompatibility. Polymer implants under animal skin are absorbed completely within 60 days with restoration of the implantation sites to their normal architecture.

In Vivo Degradation Characteristics of Poly(glycerol Sebacate)

Journal of Biomedical Materials Research. Part A. Jul, 2003  |  Pubmed ID: 12833446

We have developed a series of biodegradable elastomers, poly(glycerol sebacate) (PGS), based on glycerol and sebacic acid. The polymers are potentially useful in soft tissue regeneration and engineering. To evaluate the performance of PGS in a physiological environment, we compared their degradation profiles with poly(DL-lactide-co-glycolide) (50:50, carboxyl ended, M(w) 15,000) in vivo. Among the parameters examined are changes in weight and mechanical strength with time, implant geometry, surface characteristics, and degree of swelling. Unlike poly(DL-lactide-co-glycolide), PGS primarily degrades by surface erosion, which gives a linear degradation profile of mass, preservation of geometry and intact surface, and retention of mechanical strength.

Gene Mining: a Novel and Powerful Ensemble Decision Approach to Hunting for Disease Genes Using Microarray Expression Profiling

Nucleic Acids Research. 2004  |  Pubmed ID: 15148356

Current applications of microarrays focus on precise classification or discovery of biological types, for example tumor versus normal phenotypes in cancer research. Several challenging scientific tasks in the post-genomic epoch, like hunting for the genes underlying complex diseases from genome-wide gene expression profiles and thereby building the corresponding gene networks, are largely overlooked because of the lack of an efficient analysis approach. We have thus developed an innovative ensemble decision approach, which can efficiently perform multiple gene mining tasks. An application of this approach to analyze two publicly available data sets (colon data and leukemia data) identified 20 highly significant colon cancer genes and 23 highly significant molecular signatures for refining the acute leukemia phenotype, most of which have been verified either by biological experiments or by alternative analysis approaches. Furthermore, the globally optimal gene subsets identified by the novel approach have so far achieved the highest accuracy for classification of colon cancer tissue types. Establishment of this analysis strategy has offered the promise of advancing microarray technology as a means of deciphering the involved genetic complexities of complex diseases.

Endothelialized Microvasculature Based on a Biodegradable Elastomer

Tissue Engineering. Jan-Feb, 2005  |  Pubmed ID: 15738683

Vital organs maintain dense microvasculature to sustain the proper function of their cells. For tissue- engineered organs to function properly, artificial capillary networks must be developed. We have microfabricated capillary networks with a biodegradable and biocompatible elastomer, poly(glycerol sebacate) (PGS). We etched capillary patterns onto silicon wafers by standard micro-electromechanical systems (MEMS) techniques. The resultant silicon wafers served as micromolds for the devices. We bond the patterned PGS film with a flat film to create capillary networks that were perfused with a syringe pump at a physiological flow rate. The devices were endothelialized under flow conditions, and part of the lumens reached confluence within 14 days of culture. This approach may lead to tissue-engineered microvasculature that is critical in vital organs engineering.

Biocompatibility Analysis of Poly(glycerol Sebacate) As a Nerve Guide Material

Biomaterials. Sep, 2005  |  Pubmed ID: 15860202

No satisfactory method currently exists for bridging neural defects. Autografts lead to inadequate functional recovery, and most available artificial neural conduits possess unfavorable swelling and pro-inflammatory characteristics. This study examined the biocompatibility of a novel biodegradable elastomer, poly(glycerol sebacate) (PGS), for neural reconstruction applications, as the material possesses favorable mechanical property and degradation characteristics. The effect of PGS on Schwann cell metabolic activity, attachment, proliferation, and apoptosis were examined in vitro in comparison with poly(lactide-co-glycolide) (PLGA), a biomaterial widely utilized for tissue engineering applications. The in vivo tissue response to PGS was compared with PLGA implanted juxtaposed to the sciatic nerve; the physical changes in the implant material were measured during the degradation process. PGS had no deleterious effect on Schwann cell metabolic activity, attachment, or proliferation, and did not induce apoptosis; the in vitro effects of PGS were similar to or superior to that of PLGA. In vivo, PGS demonstrated a favorable tissue response profile compared with PLGA, with significantly less inflammation and fibrosis and without detectable swelling during degradation. PGS is an excellent candidate material for neural reconstruction applications given its lack of in vitro Schwann cell toxicity and minimal in vivo tissue response.

Fully Complex Magnetoencephalography

Journal of Neuroscience Methods. Nov, 2005  |  Pubmed ID: 16026851

Complex numbers appear naturally in biology whenever a system can be analyzed in the frequency domain, such as physiological data from magnetoencephalography (MEG). For example, the MEG steady state response to a modulated auditory stimulus generates a complex magnetic field for each MEG channel, equal to the Fourier transform at the stimulus modulation frequency. The complex nature of these data sets, often not taken advantage of, is fully exploited here with new methods. Whole-head, complex magnetic data can be used to estimate complex neural current sources, and standard methods of source estimation naturally generalize for complex sources. We show that a general complex neural vector source is described by its location, magnitude, and direction, but also by a phase and by an additional perpendicular component. We give natural interpretations of all the parameters for the complex equivalent-current dipole by linking them to the underlying neurophysiology. We demonstrate complex magnetic fields, and their equivalent fully complex current sources, with both simulations and experimental data.

Combined Tumor Therapy by Using Radiofrequency Ablation and 5-FU-laden Polymer Implants: Evaluation in Rats and Rabbits

Radiology. Dec, 2005  |  Pubmed ID: 16237145

To evaluate the use of 5-fluorouracil (5-FU)-laden polymer implants as an adjunct to radiofrequency (RF) ablation for tumor treatment.

Three-Dimensional Microfluidic Tissue-Engineering Scaffolds Using a Flexible Biodegradable Polymer

Advanced Materials (Deerfield Beach, Fla.). Dec, 2005  |  Pubmed ID: 19759845

Concurrent Encoding of Frequency and Amplitude Modulation in Human Auditory Cortex: MEG Evidence

Journal of Neurophysiology. Nov, 2006  |  Pubmed ID: 16510774

A natural sound can be described by dynamic changes in envelope (amplitude) and carrier (frequency), corresponding to amplitude modulation (AM) and frequency modulation (FM), respectively. Although the neural responses to both AM and FM sounds are extensively studied in both animals and humans, it is uncertain how they are corepresented when changed simultaneously but independently, as is typical for ecologically natural signals. This study elucidates the neural coding of such sounds in human auditory cortex using magnetoencephalography (MEG). Using stimuli with both sinusoidal modulated envelope (f(AM), 37 Hz) and carrier frequency (f(FM), 0.3-8 Hz), it is demonstrated that AM and FM stimulus dynamics are corepresented in the neural code of human auditory cortex. The stimulus AM dynamics are represented neurally with AM encoding, by the auditory steady-state response (aSSR) at f(AM). For sounds with slowly changing carrier frequency (f(FM) <5 Hz), it is shown that the stimulus FM dynamics are tracked by the phase of the aSSR, demonstrating neural phase modulation (PM) encoding of the stimulus carrier frequency. For sounds with faster carrier frequency change (f(FM) > or = 5 Hz), it is shown that modulation encoding of stimulus FM dynamics persists, but the neural encoding is no longer purely PM. This result is consistent with the recruitment of additional neural AM encoding over and above the original neural PM encoding, indicating that both the amplitude and phase of the aSSR at f(AM) track the stimulus FM dynamics. A neural model is suggested to account for these observations.

Toward a Carbohydrate-based HIV-1 Vaccine: Synthesis and Immunological Studies of Oligomannose-containing Glycoconjugates

Bioconjugate Chemistry. Mar-Apr, 2006  |  Pubmed ID: 16536482

Human antibody 2G12 is a broadly neutralizing antibody that exerts its anti-HIV activity by targeting a novel oligomannose cluster on HIV-1 gp120. It was previously demonstrated that synthetic oligomannose clusters could mimic the carbohydrate epitope of 2G12 and showed enhanced antigenicity (Wang L. X. et al. (2004) Chem.Biol. 11, 127). This paper describes the synthesis of oligomannose-containing glycoconjugates that include either a carrier protein or a universal T-helper epitope peptide to provide an effective immunogen. It was shown that the synthetic neoglycoconjugates containing oligomannose clusters could be recognized by the human antibody 2G12. Rabbit immunization studies revealed that only a small fraction of antibodies raised by the glycoconjugates was directed to the carbohydrate antigens, with the majority of the IgG type antibodies being directed to the linkers in the conjugates. The anti-sera showed weak cross-reactivity to HIV-1 gp120.

Macroporous Elastomeric Scaffolds with Extensive Micropores for Soft Tissue Engineering

Tissue Engineering. Apr, 2006  |  Pubmed ID: 16674303

Macroporous scaffolds are of great value in tissue engineering. We have developed a method to fabricate macroporous scaffolds from a biocompatible and biodegradable elastomer, poly(glycerol sebacate) (PGS). This method is potentially very useful for soft tissue engineering. Our fabrication method produced macroporous scaffolds with extensive micropores. We fabricated flat scaffolds and tubular scaffolds of uniform thickness. This fabrication method demonstrated good control of variables such as pore size, porosity, and pore interconnectivity. Sodium chloride (salt) crystals, which served as solid porogens, were packed into a mold and fused in a humid chamber. PGS was cured while dispersed throughout the fused salt template. Dissolution of the salt and subsequent lyophilization produced elastomer sponges with approximately 90% porosity, interconnected macropores (75-150 microm), and extensive micropores (5-20 microm). The macropores were generated by the salt particles, while the micropores were likely generated by glycerol vapor formed during PGS curing. Such numerous micropores could facilitate cell-cell interactions and mass transport. Fibroblasts adhered to and proliferated well within the PGS scaffolds and formed three-dimensional tissue-engineered constructs within 8 days.

High-density Arrays of InGaN Nanorings, Nanodots, and Nanoarrows Fabricated by a Template-assisted Approach

The Journal of Physical Chemistry. B. Jun, 2006  |  Pubmed ID: 16771369

Dense, crystalline arrays of InGaN nanorings, nanodots, and nanoarrows have been fabricated on GaN substrates by template-assisted nano-area selective growth. To create the nanostructures, we have used nanoporous anodic alumina films as templates to pattern nanopores in an SiO2 transfer layer, and then used this patterned SiO2 layer as a template for nitride growth by metalorganic chemical vapor deposition. We have varied the diameter of the deposited nitride nanostructures from 35 to 250 nm by changing the initial anodic alumina template structure. In addition, by controlling the nitride growth time we have created various types of nanostructures, from nanorings to nanoarrows. This structural evolution begins with the nucleation and formation of a nanoring structure, followed by coalescence and growth to form faceted nanodots, and finally lateral overgrowth to form faceted nanoarrows.

Real Time Decomposition of Speech into Modulated Components

The Journal of the Acoustical Society of America. Jun, 2006  |  Pubmed ID: 16838553

Motivated by the active process of the outer hair cell (OHC) in the mammalian inner ear, a real time decomposition of speech into modulated components is presented. A generalized phase lock loop (GPLL) was applied to decompose the speech signal into its envelope and positive instantaneous frequency (PIF) parts, which can be further processed and represented by timing information alone. A log-derivative operator is applied to the bandpass signal. Analytic and antianalytic components occupying non overlapping frequency bands are separated by filtering. The proposed algorithms are used to represent speech signals processed through a bandpass filter bank.

Biomimetic Approach to Cardiac Tissue Engineering: Oxygen Carriers and Channeled Scaffolds

Tissue Engineering. Aug, 2006  |  Pubmed ID: 16968150

We report that the functional assembly of engineered cardiac muscle can be enhanced by oxygen supply provided by mechanisms resembling those in normal vascularized tissues. To mimic the capillary network, cardiomyocytes and fibroblasts isolated from the neonatal rat hearts were cultured on a highly porous elastomer with a parallel array of channels that were perfused with culture medium. To mimic oxygen supply by hemoglobin, culture medium was supplemented with a perfluorocarbon (PFC) emulsion; constructs perfused with unsupplemented culture medium served as controls. In PFC-supplemented medium, the decrease in the partial pressure of oxygen in the aqueous phase was only 50% of that in control medium (28 mmHg vs. 45 mmHg between the construct inlet and outlet at a flow rate of 0.1 mL/min). Consistently, constructs cultivated in the presence of PFC contained higher amounts of DNA and cardiac markers (troponin I, connexin-43) and had significantly better contractile properties as compared to control constructs. In both groups, electron microscopy revealed open channels and the presence of cells at the channel surfaces as well as within constructs. Improved properties of cardiac constructs could be correlated with the enhanced supply of oxygen to the cells, by a combined use of channeled scaffolds and PFC.

A Neuroinductive Biomaterial Based on Dopamine

Proceedings of the National Academy of Sciences of the United States of America. Nov, 2006  |  Pubmed ID: 17075054

Chemical messengers such as neurotransmitters play an important role in cell communication, differentiation, and survival. We have designed and synthesized a bioactive biomaterial that derived its biological activity from dopamine. The resultant biodegradable polymer, PCD, has pendent groups bearing dopamine functionalities. Image analysis demonstrated that nerve growth factor-primed rat pheochromocytoma cells (PC12) and explanted rat dorsal root ganglions attached well and displayed substantial neurite outgrowth on the polymer surface. Furthermore, PCD promoted more vigorous neurite outgrowth in PC12 cells than tissue culture polystyrene, laminin, and poly(d-lysine). The histogram of neurite length of PC12 cells showed distinctive patterns on PCD that were absent on the controls. A subset of PC12 cells displayed high filopodium density on PCD. The addition of dopamine in culture medium had little effect on the differentiation of PC12 cells on tissue culture polystyrene. Tyrosine, the precursor of dopamine, did not exhibit this ability to impart specific bioactivity to an analogous polymer. Thus, the dopamine functional group is likely the origin of the inductive effect. PCD did not cause nerve degeneration or fibrous encapsulation when implanted immediately adjacent to the rat sciatic nerves. This work is a step toward creating a diverse family of bioactive materials using small chemical messengers as monomers.

Effects of Sea Buckthorn Procyanidins on Healing of Acetic Acid-induced Lesions in the Rat Stomach

Asia Pacific Journal of Clinical Nutrition. 2007  |  Pubmed ID: 17392110

The aim of this study was to investigate the effects of sea buckthorn procyanidins (SBPC) on healing of acetic acid-induced lesions in the rat stomach and its possible mechanism. The sea buckthorn procyanidins (SBPC) were extracted with 60% alcohol/H2O from sea buckthorn bark and purified by macropore adsorption resin column, with a purity of >96%. The chemical character of SBPC was analyzed by reverse phase high-performance liquid chromatography/mass spectrometry (HPLC/MS). Chronic gastric ulceration was induced by injecting acetic acid into the subserosa of stomach. Different concentrations of SBPC were orally administrated to gastric ulcers rats. After treatment 7d and 14d, rats were sacrificed respectively. The healing of the acetic acid induced ulcerations was measured by ulcer index (UI). The level of epidermal growth factor (EGF) in plasma was determined; the expression of epidermal growth factor receptor (EGFR) and proliferating cell nuclear antigen (PCNA) around ulcer was detected by immunohistochemical method. SBPC was found to reduce the size of the ulcers at day 7 and 14 in a dose-dependent manner. Compared with the control, the UI of SBPC group was significantly lower (p< 0.01) and the level of EGF in the plasma of SBPC group increased significantly (p< 0.01), meanwhile the expression of EGFR and PCNA around ulcer in high-dose SBPC stomach were enhanced (p< 0.05). The results implied that SBPC plays an important role in healing of acetic acid-induced gastric lesions possibly by the acceleration of the mucosal repair.

Poly(glycerol Sebacate) Supports the Proliferation and Phenotypic Protein Expression of Primary Baboon Vascular Cells

Journal of Biomedical Materials Research. Part A. Dec, 2007  |  Pubmed ID: 17584900

Poly(glycerol sebacate) (PGS) is a biodegradable and biocompatible elastomer specifically developed for soft tissue engineering. Vascular cells adhered to an elastomer may exhibit more physiological behavior because the substrate's mechanical properties more closely match those of the tissue. To investigate the feasibility of using PGS as a scaffold material for vascular tissue engineering, the authors examined the adhesion, proliferation, and phenotypic and morphologic properties of primary baboon endothelial progenitor cells (BaEPCs) and baboon smooth muscle cells (BaSMCs) cultured on PGS films and scaffolds. Tissue culture-treated polystyrene plates were used as controls. Phase contrast microscopy indicated that both types of cells showed normal morphology on PGS films. Immuofluorescent staining revealed that von Willebrand factor and alpha-smooth muscle actin were expressed by BaEPCs and BaSMCs, respectively. Both types of cells proliferated well on PGS surfaces. When cultured in PGS scaffolds, BaSMCs were distributed throughout the scaffolds and synthesized extracellular matrix, as indicated by histological evaluations. The distribution of the BaSMCs in the constructs was confirmed by scanning electron microscopy. Immunofluorescent staining of cocultured constructs indicated that the BaSMC-seeded constructs provided suitable surfaces for BaEPC adhesion, and both types of cells maintained their specific phenotypes. These results suggest that PGS is an appropriate scaffold material for blood vessel tissue engineering.

Protein Precoating of Elastomeric Tissue-engineering Scaffolds Increased Cellularity, Enhanced Extracellular Matrix Protein Production, and Differentially Regulated the Phenotypes of Circulating Endothelial Progenitor Cells

Circulation. Sep, 2007  |  Pubmed ID: 17846326

Optimal cell sources and scaffold-cell interactions remain unanswered questions for tissue engineering of heart valves. We assessed the effect of different protein precoatings on a single scaffold type (elastomeric poly (glycerol sebacate)) with a single cell source (endothelial progenitor cells).

Unravelling the Hidden Heterogeneities of Diffuse Large B-cell Lymphoma Based on Coupled Two-way Clustering

BMC Genomics. 2007  |  Pubmed ID: 17888167

It becomes increasingly clear that our current taxonomy of clinical phenotypes is mixed with molecular heterogeneity. Of vital importance for refined clinical practice and improved intervention strategies is to define the hidden molecular distinct diseases using modern large-scale genomic approaches. Microarray omics technology has provided a powerful way to dissect hidden genetic heterogeneity of complex diseases. The aim of this study was thus to develop a bioinformatics approach to seek the transcriptional features leading to the hidden subtyping of a complex clinical phenotype. The basic strategy of the proposed method was to iteratively partition in two ways sample and feature space with super-paramagnetic clustering technique and to seek for hard and robust gene clusters that lead to a natural partition of disease samples and that have the highest functionally conceptual consensus evaluated with Gene Ontology.

Concurrent Encoding of Frequency and Amplitude Modulation in Human Auditory Cortex: Encoding Transition

Journal of Neurophysiology. Dec, 2007  |  Pubmed ID: 17898148

Complex natural sounds (e.g., animal vocalizations or speech) can be characterized by specific spectrotemporal patterns the components of which change in both frequency (FM) and amplitude (AM). The neural coding of AM and FM has been widely studied in humans and animals but typically with either pure AM or pure FM stimuli. The neural mechanisms employed to perceptually unify AM and FM acoustic features remain unclear. Using stimuli with simultaneous sinusoidal AM (at rate f(AM) = 37 Hz) and FM (with varying rates f(FM)), magnetoencephalography (MEG) is used to investigate the elicited auditory steady-state response (aSSR) at relevant frequencies (f(AM), f(FM), f(AM) + f(FM)). Previous work demonstrated that for sounds with slower FM dynamics (f(FM) < 5 Hz), the phase of the aSSR at f(AM) tracked the FM; in other words, AM and FM features were co-tracked and co-represented by "phase modulation" encoding. This study explores the neural coding mechanism for stimuli with faster FM dynamics (< or =30 Hz), demonstrating that at faster rates (f(FM) > 5 Hz), there is a transition from pure phase modulation encoding to a single-upper-sideband (SSB) response (at frequency f(AM) + f(FM)) pattern. We propose that this unexpected SSB response can be explained by the additional involvement of subsidiary AM encoding responses simultaneously to, and in quadrature with, the ongoing phase modulation. These results, using MEG to reveal a possible neural encoding of specific acoustic properties, demonstrate more generally that physiological tests of encoding hypotheses can be performed noninvasively on human subjects, complementing invasive, single-unit recordings in animals.

Experimental Study on the Estrogen-like Effect of Boric Acid

Biological Trace Element Research. Feb, 2008  |  Pubmed ID: 17943231

There are now considerable evidences that boric acid has reproductive and developmental toxicity, but it is uncertain whether such toxicity is caused by estrogen-like effect. Our objective is to determine the estrogen-like effect of boric acid. Proliferation assay of MCF-7 human breast cancer cells, uterotrophic assay, measure assay of the estradiol (E2), proliferation assay of mucous membrane cells, and assay of estrogen receptor were conducted in this study. Boric acid could increase the weight of uterus of ovariectomized SD rats and the height of epithelium cells of mucous membrane, enhance the expression of the proliferating cell nucleus antigen, and reduce the density of estrogen receptors. However, boric acid could not affect the level of estradiol in serum and stimulate the proliferation of MCF-7 human breast cancer cells. In this study, boric acid exhibited the estrogen-like effect in vivo.

Seamless Tubular Poly(glycerol Sebacate) Scaffolds: High-yield Fabrication and Potential Applications

Journal of Biomedical Materials Research. Part A. Aug, 2008  |  Pubmed ID: 17969024

We have previously created scaffolds composed of a biodegradable elastomer, poly(glycerol sebacate) (PGS), which are tubular, seamless, and highly porous. Here we describe two scaffold fabrication methods developed subsequently and compare the advantages of these methods to the original by examining overall yields and scaffold characteristics, such as defect frequency and severity, wall thickness homogeneity, microstructure, porosity, and mechanical properties. Scaffolds fabricated with a heat-shrinkable (HS) mandrel had higher yield, fewer defects, more homogeneous wall thickness and microstructure, and higher porosity. Improvements in yield and scaffold characteristics likely resulted from more uniform distribution of forces resulting in lower stress concentrations in the scaffolds during removal of HS mandrels. When seeded with smooth muscle cells in a bioreactor, the optimized scaffolds retained 74% of cells, which proliferated and formed a confluent cellular layer after 21 days of in vitro culture.

Pre-treatment of Synthetic Elastomeric Scaffolds by Cardiac Fibroblasts Improves Engineered Heart Tissue

Journal of Biomedical Materials Research. Part A. Sep, 2008  |  Pubmed ID: 18041719

Native myocardium consists of several cell types, of which approximately one-third are myocytes and most of the nonmyocytes are fibroblasts. By analogy with monolayer culture in which fibroblasts were removed to prevent overgrowth, early attempts to engineer myocardium utilized cell populations enriched for cardiac myocytes (CMs; approximately 80-90% of total cells). We hypothesized that the pre-treatment of synthetic elastomeric scaffolds with cardiac fibroblasts (CFs) will enhance the functional assembly of the engineered cardiac constructs by creating an environment supportive of cardiomyocyte attachment and function. Cells isolated from neonatal rat ventricles were prepared to form three distinct populations: rapidly plating cells identified as CFs, slowly plating cells identified as CMs, and unseparated initial population of cells (US). The cell fractions (3 x 10(6) cells total) were seeded into poly(glycerol sebacate) scaffolds (highly porous discs, 5 mm in diameter x 2-mm thick) using Matrigeltrade mark, either separately (CM or CF), concurrently (US), or sequentially (CF pre-treatment followed by CM culture, CF + CM), and cultured in spinner flasks. The CF + CM group had the highest amplitude of contraction and the lowest excitation threshold, superior DNA content, and higher glucose consumption rate. The CF + CM group exhibited compact 100- to 200-mum thick layers of elongated myocytes aligned in parallel over layers of collagen-producing fibroblasts, while US and CM groups exhibited scattered and poorly elongated myocytes. The sequential co-culture of CF and CM on a synthetic elastomer scaffold thus created an environment supportive of cardiomyocyte attachment, differentiation, and contractile function, presumably due to scaffold conditioning by cultured fibroblasts. When implanted over the infarcted myocardium in a nude rat model, cell-free poly(glycerol sebacate) remained at the ventricular wall after 2 weeks of in vivo, and was vascularized.

Analysis and Prediction of Protein Local Structure Based on Structure Alphabets

Proteins. Jul, 2008  |  Pubmed ID: 18214985

In recent years, protein structure prediction using local structure information has made great progress. Many fragment libraries or structure alphabets have been developed. In this study, the entropies and correlations of local structures are first calculated. The results show that neighboring local structures are strongly correlated. Then, a dual-layer model has been designed for protein local structure prediction. The position-specific score matrix, generated by PSI-BLAST, is inputted to the first-layer classifier, whose output is further enhanced by a second-layer classifier. The neural network is selected as the classifier. Two structure alphabets are explored, which are represented in Cartesian coordinate space and in torsion angles space respectively. Testing on the nonredundant dataset shows that the dual-layer model is an efficient method for protein local structure prediction. The Q-scores are 0.456 and 0.585 for the two structure alphabets, which is a significant improvement in comparison with related works.

Identification of Transcription Factor and MicroRNA Binding Sites in Responsible to Fetal Alcohol Syndrome

BMC Genomics. 2008  |  Pubmed ID: 18366608

This is a first report, using our MotifModeler informatics program, to simultaneously identify transcription factor (TF) and microRNA (miRNA) binding sites from gene expression microarray data. Based on the assumption that gene expression is controlled by combinatorial effects of transcription factors binding in the 5'-upstream regulatory region and miRNAs binding in the 3'-untranslated region (3'-UTR), we developed a model for (1) predicting the most influential cis-acting elements under a given biological condition, and (2) estimating the effects of those elements on gene expression levels. The regulatory regions, TF and miRNA, which mediate the differential genes expression in fetal alcohol syndrome were unknown; microarray data from alcohol exposure paradigm was used. The model predicted strong inhibitory effects of 5' cis-acting elements and stimulatory effects of 3'-UTR under alcohol treatment. Current predictive model derived a key hypothesis for the first time a novel role of miRNAs in gene expression changes associated with abnormal mouse embryo development after alcohol exposure. This suggests that disturbance of miRNA functions may contribute to the alcohol-induced developmental deficiencies.

Cardiac Tissue Engineering Using Perfusion Bioreactor Systems

Nature Protocols. 2008  |  Pubmed ID: 18388955

This protocol describes tissue engineering of synchronously contractile cardiac constructs by culturing cardiac cell populations on porous scaffolds (in some cases with an array of channels) and bioreactors with perfusion of culture medium (in some cases supplemented with an oxygen carrier). The overall approach is 'biomimetic' in nature as it tends to provide in vivo-like oxygen supply to cultured cells and thereby overcome inherent limitations of diffusional transport in conventional culture systems. In order to mimic the capillary network, cells are cultured on channeled elastomer scaffolds that are perfused with culture medium that can contain oxygen carriers. The overall protocol takes 2-4 weeks, including assembly of the perfusion systems, preparation of scaffolds, cell seeding and cultivation, and on-line and end-point assessment methods. This model is well suited for a wide range of cardiac tissue engineering applications, including the use of human stem cells, and high-fidelity models for biological research.

Co-expression of Elastin and Collagen Leads to Highly Compliant Engineered Blood Vessels

Journal of Biomedical Materials Research. Part A. Jun, 2008  |  Pubmed ID: 18412137

Elastin synthesis and physiologic compliance are significant challenges in blood vessel tissue engineering. Here, we report that a biocompatible elastomeric scaffold can support the co-expression of elastin and collagen, which likely yielded the physiologic compliance in the constructs. A biodegradable elastomer, poly(glycerol sebacate), was fabricated into highly porous tubular scaffolds. Primary baboon arterial smooth muscle cells (SMCs) were seeded in the lumen of the scaffolds followed by a 1-week culture under gentle perfusion. Circulating endothelial progenitor cells (EPCs) isolated from baboon peripheral blood was seeded directly on the smooth muscle layer in the lumen on day 8. The constructs were perfused using a pulsatile flow system for another 2 weeks before characterization. In another set of experiments, the SMCs were cultured for 7 weeks and were co-cultured for 1 week with the EPCs. Constructs obtained using either set of culture conditions contained elastin and collagen: Masson's trichrome stain showed a circumferential collagen band in the constructs, and elastin was evident from its characteristic autofluorescence, Verhoff's stain, and amino acid analysis of insoluble remnants after hot alkali digestion. All constructs had a confluent cellular lumen with cells well-dispersed throughout the scaffolds. At physiologic pressures, the compliance of the 8-week construct was comparable to human arteries as observed in pressure-diameter testing. Combination of elastomeric scaffolds, co-culture of EPC and SMC, and mechanical conditioning appears to encourage the expression of a more natural extracellular matrix and lead to physiologically-relevant compliance; both are major challenges in blood vessel tissue engineering.

Mitochondrial DNA from Colorectal Cancer Cells Promotes the Malignant Phenotype of NIH3T3 Cells

Cell Biology International. Aug, 2008  |  Pubmed ID: 18595746

We investigated the potential role of mitochondrial DNA (mtDNA) in colorectal carcinogenesis by constructing a eukaryotic expression vector of the mitochondrial D-loop gene from colorectal cancer cell SW480 and transfected NIH3T3 cells. The NIH3T3/SW480 cells exhibited a significantly increased growth rate and colony formation rate, and also had a decreased apoptotic rate. Polyploidy and aberrant chromosomes were detected in the NIH3T3/SW480 cells by chromosome karyotype analysis. Our results suggested that mtDNA from colorectal cancer cells promotes the malignant phenotype of NIH3T3 cells. Further study of the biological functions of NIH3T3/SW480 cells might be helpful in understanding the role of mtDNA in colorectal carcinogenesis.

Constructing Disease-specific Gene Networks Using Pair-wise Relevance Metric: Application to Colon Cancer Identifies Interleukin 8, Desmin and Enolase 1 As the Central Elements

BMC Systems Biology. 2008  |  Pubmed ID: 18691435

With the advance of large-scale omics technologies, it is now feasible to reversely engineer the underlying genetic networks that describe the complex interplays of molecular elements that lead to complex diseases. Current networking approaches are mainly focusing on building genetic networks at large without probing the interaction mechanisms specific to a physiological or disease condition. The aim of this study was thus to develop such a novel networking approach based on the relevance concept, which is ideal to reveal integrative effects of multiple genes in the underlying genetic circuit for complex diseases.

Human Resource Staffing and Service Functions of Community Health Services Organizations in China

Annals of Family Medicine. Sep-Oct, 2008  |  Pubmed ID: 18779546

We report a study on the developmental status of human resource staffing and service functions of community health services (CHS) in China and offer recommendations for improving the CHS in the future.

Transcription Factor and MicroRNA Regulation in Androgen-dependent and -independent Prostate Cancer Cells

BMC Genomics. 2008  |  Pubmed ID: 18831788

Prostate cancer is one of the leading causes of cancer death in men. Androgen ablation, the most commonly-used therapy for progressive prostate cancer, is ineffective once the cancer cells become androgen-independent. The regulatory mechanisms that cause this transition (from androgen-dependent to androgen-independent) remain unknown. In this study, based on the microarray data comparing global gene expression patterns in the prostate tissue between androgen-dependent and -independent prostate cancer patients, we identify a set of transcription factors and microRNAs that potentially cause such difference, using a model-based computational approach.

[Review on Gene Polymorphisms of UDP-glucuronosyltransferases and Genetic Susceptibility of Cancer]

Wei Sheng Yan Jiu = Journal of Hygiene Research. Sep, 2008  |  Pubmed ID: 19069670

UDP-glucuronosyltransferases (UGT) are importmant phase II metabolizing enzymes that catalyse the glucuronidation of numerous endobiotics and xenobiotics. Several human hepatic and extrahepatic UGT isozymes have been characterized with respect to their substrate specificity, tissue expression and gene structure. Genetic polymorphisms have been identified for almost all the UGT family members. Some Polymorphisms of UGT gene had an effect on the activity of UGT enzymes, then influenced the glucuronidation against cancer-related substrates, ultimately affected the genetic toxicity and carcinogenesis induced by cancer-related substrates. Numerous studies reported that polymorphisms of UGT gene were associated with the risk of several kinds of cancer, such as colorectal cancer, breast cancer, lung cancer, proximal digestive tract cancer, hepatocellular carcinoma and prostate cancer. This review examines in detail each UGT isozyme known to be associated with cancer.

Experimental Study on the Estrogen-like Effect of Mercuric Chloride

Biometals : an International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine. Apr, 2008  |  Pubmed ID: 17588195

Although mercuric chloride has toxicity on reproductive system, it is uncertain if such toxicity is induced by estrogen-like effect. To study whether mercuric chloride has the estrogen-like effect and its relevant mechanism, proliferation assay of MCF-7 human breast cancer cells, uterotrophic assay, peroxidase activity assay and estrogen receptor competitive binding assay were conducted to screen the estrogen-like effect of mercuric chloride. The MCF-7 cells proliferated in the stimulation of mercuric chloride and got to the peak at 10(-7) mol/l concentration. And this proliferation could be completely blocked by estrogenic antagonist ICI182.780. In addition, mercuric chloride could increase the weight of uterus of ovariectomized SD rats and the peroxidase activity of uterus complying with dose-effect relationship. However, mercuric chloride could not affect the binding of estradiol (E(2)) to estrogen receptor (ER). So mercuric chloride exhibits the estrogen-like effect through binding and activating ER rather than bind to ER by competing with E(2).

Antaxia-telangiectasia Mutated Gene Polymorphisms and Susceptibility to Chromosomal Damage Among Polycyclic Aromatic Hydrocarbons Exposed Workers

The Science of the Total Environment. Apr, 2009  |  Pubmed ID: 19193393

The aim was to explore the relationship between the ataxia-telangiectasia mutated (ATM) gene polymorphisms and susceptibility to cytokinesis-block micronucleus among workers exposed to polycyclic aromatic hydrocarbons (PAH). Blood and urine samples of 140 PAH-exposed workers and 66 non-PAH-exposed workers were collected. Seven tagging single nucleotide polymorphisms in ATM gene were selected by pariwise r(2) method and minor allele frequency cutoff of 0.05 from Chinese genotype data in HapMap project. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to analyze the polymorphisms of ATM rs600931, rs652311, rs227060, rs227292, rs624366, rs189037 and rs228589. The results showed that ATM rs600931 AG and AG+AA genotypes exhibited significantly higher cytokinesis-block micronucleus (CBMN) frequency (11.14+/-6.91 per thousand and 10.57+/-6.82 per thousand) than did the GG genotype (7.66+/-5.69 per thousand, P=0.015 and 0.038, respectively). The subjects with rs189037 GA and GA+AA genotypes exhibited significantly higher CBMN frequency (10.99+/-6.90 per thousand and 10.51+/-6.76 per thousand) than that of the GG genotype (7.72+/-5.82 per thousand, P=0.018 and 0.035, respectively). The PAH-exposed workers with rs624366 GC and GC+CC genotypes exhibited significantly higher CBMN frequency (11.34+/-6.74 per thousand and 10.73+/-6.62 per thousand) than did the GG genotype (7.61+/-6.07 per thousand, P=0.001 and 0.003, respectively). rs227092 GT genotype exhibited significantly higher CBMN frequency (10.78+/-6.60 per thousand) than did the GG genotype (7.91+/-6.30 per thousand, P=0.025) among the PAH-exposed workers. The haplotype pairs GGGGTGC/AAACATT exhibited significantly higher CBMN frequency (12.05+/-7.40 per thousand) than did the GGGGTGC/GGGGTGC (7.51+/-6.19 per thousand, P=0.007) among the PAH-exposed group. In conclusion, it is suggested that the polymorphisms of ATM were associated with the CBMN frequencies among PAH-exposed workers.

Replication of DNA Submicron Patterns by Combining Nanoimprint Lithography and Contact Printing

Journal of Colloid and Interface Science. May, 2009  |  Pubmed ID: 19264318

We describe a high throughput method of printing DNA submicron patterns on solid substrates. Combining nanoimprint lithography and contact printing, uniform DNA patterns can be produced with feature sizes from 2 microm down to 250 nm. In this method, poly(methylmethacrylate) (PMMA) with submicron line or dot patterns (produced by nanoimprint lithography) is first chemically functionalized with poly(ethyleneimine) (PEI) to aminate the surface and then a DNA pattern is prepared on the surface. PEI modification leads to higher DNA immobilization and DNA hybridization efficiency due to a higher density of amine functional groups provided by PEI. Next, complementary target DNA hybridized to the PMMA surface can be transferred to an aminated glass slide through contact printing. The transfer mechanism is due to electrostatic attraction (between DNA and amine groups) which can overcome hydrogen bonds between two hybridized DNA molecules. DNA transferred from the PMMA to the glass slide still can hybridize with DNA having a complementary sequence. This method provides a facile and high throughput means of preparing uniform DNA submicron patterns which are difficult to prepare by using conventional solution-based methods.

Uridine Diphosphoglucuronosyltransferase 1A7 Gene Polymorphism and Susceptibility to Chromosomal Damage Among Polycyclic Aromatic Hydrocarbons Exposed Workers

Journal of Occupational and Environmental Medicine / American College of Occupational and Environmental Medicine. Jun, 2009  |  Pubmed ID: 19430315

The aim of this study was to explore the relationship between UGT1A7 gene polymorphisms and susceptibility to chromosomal damage among polycyclic aromatic hydrocarbons (PAH)-exposed workers.

Association Between X-ray Repair Cross Complementing Group 1 Codon 399 and 194 Polymorphisms and Lung Cancer Risk: a Meta-analysis

Cancer Letters. Nov, 2009  |  Pubmed ID: 19481337

Genetic variations in DNA repair genes are thought to modify DNA repair capacity and suggested to be related to cancer risk. However, epidemiological results have been inconsistent. In this meta-analysis, we assessed reported studies of association between polymorphisms of X-ray repair cross complementing group 1 (XRCC1) codon 399 and 194, and lung cancer risk. We found decreased lung cancer risk among subjects carrying XRCC1 codon 194 Arg/Trp genotype [odds ratio (OR)=0.88, 95% confidence interval (95% CI): 0.79-0.97], using 4848 cases and 6592 controls from 16 studies. There was no association between lung cancer risk and XRCC1 codon 399 polymorphism in total population, when stratified by source of control, we found a protective effect of the XRCC1 codon 399 Gln/Gln and Arg/Gln or Gln/Gln polymorphisms for lung cancer on the basis of population control (OR=0.73, 95% CI: 0.58-0.92; OR=0.86, 95% CI: 0.77-0.97, respectively). Data indicated that certain XRCC1 codon 399 and 194 variant may affect the susceptibility of lung cancer. Recommendations for further studies include pooling of individual data to facilitate evaluation of multigenic effects and detailed analysis of effect modification by environmental exposure.

A Biocompatible Endothelial Cell Delivery System for in Vitro Tissue Engineering

Cell Transplantation. 2009  |  Pubmed ID: 19500475

Engineering solid tissues, including cardiac muscle, requires the inclusion of a microvasculature. Prevascularization in vitro will likely be dependent upon coculturing parenchymal cells with vascular cells, on a matrix that is sufficiently porous to allow microvessel formation. In this study, we examined the behavior and function of endothelial cells on a highly porous elastomeric 3D poly(glycerol sebacate) (PGS) scaffold, to provide a flexible and biocompatible endothelial cell delivery system for developing cardiac engineered tissues with neovascularization potential. Both static and perfusion cell seeding methods were used, and the effects of surface treatment of the scaffold with various extracellular matrix components were examined. Endothelial cell adhesion and phenotype on the PGS scaffold under various flow conditions were also determined. Surface coating with laminin markedly improved the endothelial cell adhesion, survival, and proliferation. The anticoagulant phenotype of adhered endothelial cells was further regulated by the application of flow through regulation of nitric oxide expression. By providing a highly porous scaffolding that contains endothelium with anticoagulant properties, the endothelial cell-seeded PGS scaffold could provide a new basis for subsequent coculture studies with various cell types to develop complex engineered tissue constructs with vascularization capacity.

Biomarkers Measured by Cytokinesis-block Micronucleus Cytome Assay for Evaluating Genetic Damages Induced by Polycyclic Aromatic Hydrocarbons

Mutation Research. Jun-Jul, 2009  |  Pubmed ID: 19540355

Coke oven workers are regularly exposed to polycyclic aromatic hydrocarbons (PAHs) and have a high risk for lung cancer. Limited evidence has demonstrated a direct link between exposure to PAHs and early genetic damage in exposed workers. The cytokinesis-block micronucleus (CBMN) cytome assay is a comprehensive system for measuring DNA damage and cytotoxicity. In the current study, we investigated different chromosomal damage endpoints including micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs), in 141 PAH-exposed subjects and 66 unexposed controls. The frequencies of MN, NPBs and NBUDs were all significantly higher in PAH-exposed workers than in controls (2.4-, 5-, and 3-fold, respectively). We further classified the PAH-exposed workers into different PAHs exposure groups based on their work positions on the oven and their urinary 1-hydroxypyrene and found that the frequencies of NPBs and NBUDs increased with the increasing level of both external and internal PAHs exposure levels. Similar trend was not found for MN due to the reduced MN frequency in the highest PAHs exposure group compared with the second highest PAHs exposure group. Using principal component analysis, we confirmed that the frequencies of NPBs and NBUDs are more sensitive to reflect the external or internal levels of PAHs exposure. In PAH-exposed subjects, NPB and NBUD frequencies were influenced by gender and females have lower frequencies of NPB and NBUD. Taken together, our observations indicate that NPBs and NBUDs are more sensitive and reliable biomarkers for genetic damages induced by PAHs and could potentially be used for the biomonitoring of genotoxin-exposed populations.

A Novel Electrospinning Target to Improve the Yield of Uniaxially Aligned Fibers

Biotechnology Progress. Jul-Aug, 2009  |  Pubmed ID: 19562742

Electrospinning is a useful technique that can generate micro and nanometer-sized fibers. Modification of the electrospinning parameters, such as deposition target geometry, can generate uniaxially aligned fibers for use in diverse applications ranging from tissue engineering to material fabrication. For example, meshes of fibers have been shown to mimic the extracellular matrix networks for use in smooth muscle cell proliferation. Further, aligned fibers can guide neurites to grow along the direction of the fibers. Here we present a novel electrospinning deposition target that combines the benefits of two previously reported electrodes: the standard parallel electrodes and the spinning wheel with a sharpened edge. This new target design significantly improves aligned fiber yield. Specifically, the target consists of two parallel aluminum plates with sharpened edges containing a bifurcating angle of 26 degrees. Electric field computations show a larger probable area of aligned electric field vectors. This new deposition target allows fibers to deposit on a larger cross-sectional area relative to the existing parallel electrode and at least doubles the yield of uniaxially aligned fibers. Further, fiber alignment and morphology are preserved after collection from the deposition target.

Reconstruct Gene Regulatory Network Using Slice Pattern Model

BMC Genomics. 2009  |  Pubmed ID: 19594879

Gene expression time series array data has become a useful resource for investigating gene functions and the interactions between genes. However, the gene expression arrays are always mixed with noise, and many nonlinear regulatory relationships have been omitted in many linear models. Because of those practical limitations, inference of gene regulatory model from expression data is still far from satisfactory.

MiR2Disease: a Manually Curated Database for MicroRNA Deregulation in Human Disease

Nucleic Acids Research. Jan, 2009  |  Pubmed ID: 18927107

'miR2Disease', a manually curated database, aims at providing a comprehensive resource of microRNA deregulation in various human diseases. The current version of miR2Disease documents 1939 curated relationships between 299 human microRNAs and 94 human diseases by reviewing more than 600 published papers. Around one-seventh of the microRNA-disease relationships represent the pathogenic roles of deregulated microRNA in human disease. Each entry in the miR2Disease contains detailed information on a microRNA-disease relationship, including a microRNA ID, the disease name, a brief description of the microRNA-disease relationship, an expression pattern of the microRNA, the detection method for microRNA expression, experimentally verified target gene(s) of the microRNA and a literature reference. miR2Disease provides a user-friendly interface for a convenient retrieval of each entry by microRNA ID, disease name, or target gene. In addition, miR2Disease offers a submission page that allows researchers to submit established microRNA-disease relationships that are not documented. Once approved by the submission review committee, the submitted records will be included in the database. miR2Disease is freely available at http://www.miR2Disease.org.

Small Intestinal Submucosa Gel As a Potential Scaffolding Material for Cardiac Tissue Engineering

Acta Biomaterialia. Jun, 2010  |  Pubmed ID: 19887120

Cardiac tissue engineering typically utilizes protein-rich scaffolding materials and growth factors to improve cardiac tissue function in vitro and in vivo. The objectives of this preliminary study were (i) to investigate the potential of porcine small intestinal submucosa gel (SIS gel) in cardiac tissue engineering and (ii) to compare the function of tissues based on either SIS gel or Matrigel, a tumor-derived benchmark material. Neonatal rat cardiac cells were combined with either SIS gel or Matrigel and cultured on porous elastomeric scaffolds composed of poly(glycerol sebacate) for 13days. Tissue function was assessed by measuring contraction rates twice daily. Tissue morphology was compared qualitatively by hematoxylin and eosin staining. Normalized troponin T expression (troponin T:DNA) was compared using image analysis. SIS gel constructs contracted at significantly higher rates than Matrigel constructs on days 8-11. Normalized troponin T expression was significantly higher in SIS gel constructs compared with Matrigel constructs. In summary, this research demonstrated that: (i) SIS gel can be used to create contractile engineered cardiac tissue; (ii) SIS gel produced engineered cardiac tissues with a more physiological contraction rate and higher phenotypic protein expression based on the basic in vitro examinations performed in this study.

Physiologic Compliance in Engineered Small-diameter Arterial Constructs Based on an Elastomeric Substrate

Biomaterials. Mar, 2010  |  Pubmed ID: 19962188

Compliance mismatch is a significant challenge to long-term patency in small-diameter bypass grafts because it causes intimal hyperplasia and ultimately graft occlusion. Current engineered grafts are typically stiff with high burst pressure but low compliance and low elastin expression. We postulated that engineering small arteries on elastomeric scaffolds under dynamic mechanical stimulation would result in strong and compliant arterial constructs. This study compares properties of engineered arterial constructs based on biodegradable polyester scaffolds composed of either rigid poly(lactide-co-glycolide) (PLGA) or elastomeric poly(glycerol sebacate) (PGS). Adult baboon arterial smooth muscle cells (SMCs) were cultured in vitro for 10 days in tubular, porous scaffolds. Scaffolds were significantly stronger after culture regardless of material, but the elastic modulus of PLGA constructs was an order of magnitude greater than that of porcine carotid arteries and PGS constructs. Deformation was elastic in PGS constructs and carotid arteries but plastic in PLGA constructs. Compliance of arteries and PGS constructs were equivalent at pressures tested. Altering scaffold material from PLGA to PGS significantly decreased collagen content and significantly increased insoluble elastin content in constructs without affecting soluble elastin concentration in the culture medium. PLGA constructs contained no appreciable insoluble elastin. This research demonstrates that: (1) substrate stiffness directly affects in vitro tissue development and mechanical properties; (2) rigid materials likely inhibit elastin incorporation into the extracellular matrix of engineered arterial tissues; and (3) grafts with physiologic compliance and significant elastin content can be engineered in vitro after only days of cell culture.

Association Between CYP2E1 Genetic Polymorphisms and Lung Cancer Risk: a Meta-analysis

European Journal of Cancer (Oxford, England : 1990). Mar, 2010  |  Pubmed ID: 20031389

Genetic variations in metabolic genes are thought to modify the metabolic process of carcinogens and are suggested to be related to cancer risk. However, epidemiological results are not always consistent. In this meta-analysis, we assessed reported studies of associations between polymorphisms of CYP2E1 RsaI/PstI and DraI, and the risk of lung cancer. We found decreased lung cancer risk among subjects carrying CYP2E1 RsaI/PstI c1/c2 and c1/c2+c2/c2 genotype [odds ratio (OR)=0.80, 95% confidence interval (CI): 0.72-0.89 and OR=0.82, 95% CI: 0.72-0.93, respectively], using 4436 cases and 6385 controls from 26 studies. We also observed a decreased lung cancer risk among subjects carrying c1/c2 and c1/c2+c2/c2 genotypes in the Asian population and on the basis of population control in stratified analysis. We found a protective effect of the CYP2E1 DraI CC and CD+CC polymorphisms for lung cancer (OR=0.58, 95% CI: 0.41-0.81 and OR=0.84, 95% CI: 0.73-0.96, respectively). The meta-analysis suggests that CYP2E1 RsaI/PstI and DraI polymorphisms may affect the susceptibility of lung cancer, and a study with a larger sample size is needed to further evaluate gene-environment interaction on CYP2E1 polymorphisms and lung cancer risk.

A Functionalizable Polyester with Free Hydroxyl Groups and Tunable Physiochemical and Biological Properties

Biomaterials. Apr, 2010  |  Pubmed ID: 20149441

Polyesters with free functional groups allow facile modifications with biomolecules, which can lead to versatile biomaterials that afford controlled interactions with cells and tissues. Efficient synthesis of functionalizable polyesters (Functionalizable polymer is defined as a polymer with functional groups that readily react with biomolecules and functionalized biomaterial as one already modified with biomolecules.) is still a challenge that greatly limits the availability and widespread applications of biofunctionalized synthetic polymers. Here we report a simple route to prepare a functionalizable polyester, poly(sebacoyl diglyceride) (PSeD) bearing free hydroxyl groups. The key synthetic step is an epoxide ring-opening polymerization, instead of the traditional polycondensation that produces poly(glycerol sebacate) (PGS) (Wang YD, Ameer GA, Sheppard BJ, Langer R. A tough biodegradable elastomer. Nat Biotechnol 2002;20(6):602-6). PSeD has a more defined structure with mostly linear backbone, more free hydroxyl groups, higher molecular weight, and lower polydispersity than PGS. Crosslinking PSeD with sebacic acid yields a polymer five times tougher and more elastic than cured PGS. PSeD exhibits good cytocompatibility in vitro. Furthermore, functionalization by glycine proceeds with high efficiency. This versatile synthetic platform can offer a large family of biodegradable, functionalized polymers with tunable physiochemical and biological properties useful for a wide range of biomedical applications.

Treatment-recalcitrant Chronic Rhinosinusitis with Polyps is Associated with Altered Epithelial Cell Expression of Interleukin-33

American Journal of Rhinology & Allergy. Mar-Apr, 2010  |  Pubmed ID: 20338108

Abnormalities in host mucosal immunity exist in chronic rhinosinusitis with nasal polyps (CRSwNPs), but it is unclear whether this is a cause or an effect of the eosinophilic inflammation and frequent microbial colonization that characterizes the disease. Sinonasal epithelial cells (SNECs) are critical participants in healthy antimicrobial innate immune defense. They also can promote Th2 inflammation with various mediators, including interleukin (IL)-33, which induces T helper cells to produce Th2 cytokines.

Prioritization of Disease MicroRNAs Through a Human Phenome-microRNAome Network

BMC Systems Biology. 2010  |  Pubmed ID: 20522252

The identification of disease-related microRNAs is vital for understanding the pathogenesis of diseases at the molecular level, and is critical for designing specific molecular tools for diagnosis, treatment and prevention. Experimental identification of disease-related microRNAs poses considerable difficulties. Computational analysis of microRNA-disease associations is an important complementary means for prioritizing microRNAs for further experimental examination.

Glutathione S-transferase T1 Gene Deletion Polymorphism and Lung Cancer Risk in Chinese Population: a Meta-analysis

Cancer Epidemiology. Oct, 2010  |  Pubmed ID: 20542754

Genetic variations in metabolic genes are considered to modulate metabolic process of carcinogens and are suggested to be related to cancer risk. However, epidemiological results are not always consistent. In this meta-analysis, we evaluated reported studies of association between polymorphism of glutathione S-transferase T1 gene (GSTT1) and the risk of lung cancer in Chinese population. We found an increased lung cancer risk among subjects carrying GSTT1 null genotype [odds ratio (OR)=1.36, 95 percent confidence interval (95% CI): 1.09-1.69], using 1625 cases and 2188 controls from 11 studies. We also observed an increased risk of lung cancer among null genotype carriers in squamous cell carcinoma and adenocarcinoma, and on the basis of population control in stratified analyses. The meta-analysis suggests that GSTT1 deletion polymorphisms may have an effect on the susceptibility of lung cancer in Chinese population, and a study with the larger sample size is needed to further evaluate gene-gene and gene-environment interaction on GSTT1 deletion polymorphisms and lung cancer risk in Chinese population.

Control Growth Factor Release Using a Self-assembled [polycation:heparin] Complex

PloS One. 2010  |  Pubmed ID: 20543985

The importance of growth factors has been recognized for over five decades; however their utilization in medicine has yet to be fully realized. This is because free growth factors have short half-lives in plasma, making direct injection inefficient. Many growth factors are anchored and protected by sulfated glycosaminoglycans in the body. We set out to explore the use of heparin, a well-characterized sulfated glycosaminoglycan, for the controlled release of fibroblast growth factor-2 (FGF-2). Heparin binds a multitude of growth factors and maintains their bioactivity for an extended period of time. We used a biocompatible polycation to precipitate out the [heparin:FGF-2] complex from neutral buffer to form a release matrix. We can control the release rate of FGF-2 from the resultant matrix by altering the molecular weight of the polycation. The FGF-2 released from the delivery complex maintained its bioactivity and initiated cellular responses that were at least as potent as fresh bolus FGF-2 and fresh heparin stabilized FGF-2. This new delivery platform is not limited to FGF-2 but applicable to the large family of heparin-binding growth factors.

Signal Transducers and Activators of Transcription-1 (STAT1) Regulates MicroRNA Transcription in Interferon Gamma-stimulated HeLa Cells

PloS One. 2010  |  Pubmed ID: 20668688

Constructing and modeling the gene regulatory network is one of the central themes of systems biology. With the growing understanding of the mechanism of microRNA biogenesis and its biological function, establishing a microRNA-mediated gene regulatory network is not only desirable but also achievable.

The Role of Hepatocyte Growth Factor/c-Met in Chronic Rhinosinusitis with Nasal Polyps

American Journal of Rhinology & Allergy. Jul-Aug, 2010  |  Pubmed ID: 20819464

Hepatocyte growth factor (HGF) is a growth factor thought to attenuate Th2-driven eosinophilic airway inflammatory responses. Increased expression of HGF and its receptor c-Met in nasal polyps suggests a role in disease pathogenesis. The effect of HGF on human sinonasal epithelial cell (SNEC) responses to Th2 inflammatory cytokines in chronic rhinosinusitis with nasal polyps (CRSwNP) has not been explored.

Scaffold Stiffness Affects the Contractile Function of Three-dimensional Engineered Cardiac Constructs

Biotechnology Progress. Sep-Oct, 2010  |  Pubmed ID: 20945492

We investigated the effects of the initial stiffness of a three-dimensional elastomer scaffold--highly porous poly(glycerol sebacate)--on functional assembly of cardiomyocytes cultured with perfusion for 8 days. The polymer elasticity varied with the extent of polymer cross-links, resulting in three different stiffness groups, with compressive modulus of 2.35 ± 0.03 (low), 5.28 ± 0.36 (medium), and 5.99 ± 0.40 (high) kPa. Laminin coating improved the efficiency of cell seeding (from 59 ± 15 to 90 ± 21%), resulting in markedly increased final cell density, construct contractility, and matrix deposition, likely because of enhanced cell interaction and spreading on scaffold surfaces. Compact tissue was formed in the low and medium stiffness groups, but not in the high stiffness group. In particular, the low stiffness group exhibited the greatest contraction amplitude in response to electric field pacing, and had the highest compressive modulus at the end of culture. A mathematical model was developed to establish a correlation between the contractile amplitude and the cell distribution within the scaffold. Taken together, our findings suggest that the contractile function of engineered cardiac constructs positively correlates with low compressive stiffness of the scaffold.

RNA Polymerase II Binding Patterns Reveal Genomic Regions Involved in MicroRNA Gene Regulation

PloS One. 2010  |  Pubmed ID: 21072189

MicroRNAs are small non-coding RNAs involved in post-transcriptional regulation of gene expression. Due to the poor annotation of primary microRNA (pri-microRNA) transcripts, the precise location of promoter regions driving expression of many microRNA genes is enigmatic. This deficiency hinders our understanding of microRNA-mediated regulatory networks. In this study, we develop a computational approach to identify the promoter region and transcription start site (TSS) of pri-microRNAs actively transcribed using genome-wide RNA Polymerase II (RPol II) binding patterns derived from ChIP-seq data. Based upon the assumption that the distribution of RPol II binding patterns around the TSS of microRNA and protein coding genes are similar, we designed a statistical model to mimic RPol II binding patterns around the TSS of highly expressed, well-annotated promoter regions of protein coding genes. We used this model to systematically scan the regions upstream of all intergenic microRNAs for RPol II binding patterns similar to those of TSS from protein coding genes. We validated our findings by examining the conservation, CpG content, and activating histone marks in the identified promoter regions. We applied our model to assess changes in microRNA transcription in steroid hormone-treated breast cancer cells. The results demonstrate many microRNA genes have lost hormone-dependent regulation in tamoxifen-resistant breast cancer cells. MicroRNA promoter identification based upon RPol II binding patterns provides important temporal and spatial measurements regarding the initiation of transcription, and therefore allows comparison of transcription activities between different conditions, such as normal and disease states.

A [polycation:heparin] Complex Releases Growth Factors with Enhanced Bioactivity

Journal of Controlled Release : Official Journal of the Controlled Release Society. Mar, 2011  |  Pubmed ID: 21118705

Growth factors are potent molecules that regulate cell functions including survival, self renewal, differentiation and proliferation. High-efficacy delivery of growth factors will be a powerful tool for regenerative medicine. Decades of intense research have significantly advanced the field of controlled delivery. There is, however, still a great unmet need for new methods that can improve overall efficacy of growth factor delivery. Here, we report a new growth factor delivery vehicle formed by self assembly of heparin and a biocompatible polycation, poly(ethylene argininylaspartate diglyceride) (PEAD). Of the many heparin-binding growth factors, we chose FGF-2 and NGF to demonstrate the potential of the [PEAD:heparin] delivery vehicle. The delivery vehicle incorporates both growth factors with high efficiency, controls their release, maintains the bioactivity of FGF-2 and increases the bioactivity of NGF relative to bolus delivery. [PEAD:heparin] appears to be a promising delivery matrix for many heparin-binding growth factors and may lead to efficient growth factor delivery for a variety of diseases and disabilities.

Hydrostatic Pressure Independently Increases Elastin and Collagen Co-expression in Small-diameter Engineered Arterial Constructs

Journal of Biomedical Materials Research. Part A. Mar, 2011  |  Pubmed ID: 21268239

Prior studies have demonstrated that smooth muscle cell (SMC) proliferation, migration, and extracellular matrix production increase with hydrostatic pressure in vitro. We have engineered highly compliant small-diameter arterial constructs by culturing primary adult baboon arterial SMCs under pulsatile perfusion on tubular, porous, elastomeric scaffolds composed of poly(glycerol sebacate) (PGS). This study investigates the effect of hydrostatic pressure on the biological and mechanical properties of PGS-based engineered arterial constructs. Pressure was raised using a downstream needle valve during perfusion while preserving flow rate and pulsatility, and constructs were evaluated by pressure-diameter testing and biochemical assays for collagen and elastin. Pressurized constructs contained half as much insoluble elastin as baboon common carotid arteries but were significantly less compliant, while constructs cultured at low hydrostatic pressure contained one-third as much insoluble elastin as baboon carotids and were similar in compliance. Hydrostatic pressure significantly increased construct burst pressure, collagen and insoluble elastin content, and soluble elastin concentration in culture medium. All arteries and constructs exhibited elastic recovery during pressure cycling. Hydrostatic pressure did not appear to affect radial distribution of SMCs, collagens I and III, and elastin. These results provide insights into the control of engineered smooth muscle tissue properties using hydrostatic pressure.

Substantial Expression of Mature Elastin in Arterial Constructs

Proceedings of the National Academy of Sciences of the United States of America. Feb, 2011  |  Pubmed ID: 21282618

Mature elastin synthesis is a key challenge in arterial tissue engineering. Most engineered vessels lack elastic fibers in the medial layer and those present are poorly organized. The objective of this study is to increase mature elastin synthesis in small-diameter arterial constructs. Adult primary baboon smooth muscle cells (SMCs) were seeded in the lumen of porous tubular scaffolds fabricated from a biodegradable elastomer, poly(glycerol sebacate) (PGS) and cultured in a pulsatile flow bioreactor for 3 wk. We tested the effect of pore sizes on construct properties by histological, biochemical, and mechanical evaluations. Histological analysis revealed circumferentially organized extracellular matrix proteins including elastin and the presence of multilayered SMCs expressing calponin and α-smooth muscle actin. Biochemical analysis demonstrated that the constructs contained mature elastin equivalent to 19% of the native arteries. Mechanical tests indicated that the constructs could withstand up to 200 mmHg burst pressure and exhibited compliance comparable to native arteries. These results show that nontransfected cells in PGS scaffolds in unsupplemented medium produced a substantial amount of mature elastin within 3 wk and the elastic fibers had similar orientation as those in native arteries. The 25-32 μm pore size supported cell organization and elastin synthesis more than larger pore sizes. To our knowledge, there was no prior report of the synthesis of mature and organized elastin in arterial constructs without exogenous factors or viral transduction.

Methylation-mediated Regulation of E2F1 in DNA Damage-induced Cell Death

Journal of Receptor and Signal Transduction Research. Apr, 2011  |  Pubmed ID: 21320024

E2F1 promotes DNA damage-induced apoptosis and the post-translational modifications of E2F1 play an important role in the regulation of E2F1-mediated cell death. Here, we found that Set9 and LSD1 regulate E2F1-mediated apoptosis upon DNA damage. Set9 methylates E2F1 at lysine 185, a conserved residue in the DNA-binding domain of E2F family proteins. The methylation of E2F1 by Set9 leads to the stabilization of E2F1 and up-regulation of its proapoptotic target genes p73 and Bim, and thereby induces E2F1-mediated apoptosis in response to genotoxic agents. We also found that LSD1 demethylates E2F1 at lysine 185 and reduces E2F1-mediated cell death. The identification of the methylation/demethylation of E2F1 by Set9/LSD1 suggests that E2F1 is dynamically regulated by epigenetic enzymes in response to DNA damage.

Silicon/III-V Laser with Super-compact Diffraction Grating for WDM Applications in Electronic-photonic Integrated Circuits

Optics Express. Jan, 2011  |  Pubmed ID: 21369017

We have demonstrated a heterogeneously integrated III-V-on-Silicon laser based on an ultra-large-angle super-compact grating (SCG). The SCG enables single-wavelength operation due to its high-spectral-resolution aberration-free design, enabling wavelength division multiplexing (WDM) applications in Electronic-Photonic Integrated Circuits (EPICs). The SCG based Si/III-V laser is realized by fabricating the SCG on silicon-on-insulator (SOI) substrate. Optical gain is provided by electrically pumped heterogeneous integrated III-V material on silicon. Single-wavelength lasing at 1550 nm with an output power of over 2 mW and a lasing threshold of around 150 mA were achieved.

Fabrication of Circular Microfluidic Channels by Combining Mechanical Micromilling and Soft Lithography

Lab on a Chip. Apr, 2011  |  Pubmed ID: 21399830

The fabrication of microfluidic channels with complex three-dimensional (3D) geometries presents a major challenge to the field of microfluidics, because conventional lithography methods are mainly limited to rectangular cross-sections. In this paper, we demonstrate the use of mechanical micromachining to fabricate microfluidic channels with complex cross-sectional geometries. Micro-scale milling tools are first used to fabricate semi-circular patterns on planar metallic surfaces to create a master mold. The micromilled pattern is then transferred to polydimethylsiloxane (PDMS) through a two-step reverse molding process. Using these semi-circular PDMS channels, circular cross-sectioned microchannels are created by aligning and adhering two channels face-to-face. Straight and serpentine-shaped microchannels were fabricated, and the channel geometry and precision of the metallic master and PDMS molds were assessed through scanning electron microscopy and non-contact profilometry. Channel functionality was tested by perfusion of liquid through the channels. This work demonstrates that micromachining enabled soft lithography is capable of fabricating non-rectangular cross-section channels for microfluidic applications. We believe that this approach will be important for many fields from biomimetics and vascular engineering to microfabrication and microreactor technologies.

Improvements on a Privacy-protection Algorithm for DNA Sequences with Generalization Lattices

Computer Methods and Programs in Biomedicine. Mar, 2011  |  Pubmed ID: 21429615

When developing personal DNA databases, there must be an appropriate guarantee of anonymity, which means that the data cannot be related back to individuals. DNA lattice anonymization (DNALA) is a successful method for making personal DNA sequences anonymous. However, it uses time-consuming multiple sequence alignment and a low-accuracy greedy clustering algorithm. Furthermore, DNALA is not an online algorithm, and so it cannot quickly return results when the database is updated. This study improves the DNALA method. Specifically, we replaced the multiple sequence alignment in DNALA with global pairwise sequence alignment to save time, and we designed a hybrid clustering algorithm comprised of a maximum weight matching (MWM)-based algorithm and an online algorithm. The MWM-based algorithm is more accurate than the greedy algorithm in DNALA and has the same time complexity. The online algorithm can process data quickly when the database is updated.

Artificial Niche Combining Elastomeric Substrate and Platelets Guides Vascular Differentiation of Bone Marrow Mononuclear Cells

Tissue Engineering. Part A. Aug, 2011  |  Pubmed ID: 21449713

Bone marrow-derived progenitor cells are promising cell sources for vascular tissue engineering. However, conventional bone marrow mesenchymal stem cell expansion and induction strategies require plating on tissue culture plastic, a stiff substrate that may itself influence cell differentiation. Direct scaffold seeding avoids plating on plastic; to the best of our knowledge, there is no report of any scaffold that induces the differentiation of bone marrow mononuclear cells (BMNCs) to vascular cells in vitro. In this study, we hypothesize that an elastomeric scaffold with adsorbed plasma proteins and platelets will induce differentiation of BMNCs to vascular cells and promote vascular tissue formation by combining soft tissue mechanical properties with platelet-mediated tissue repairing signals. To test our hypothesis, we directly seeded rat primary BMNCs in four types of scaffolds: poly(lactide-co-glycolide), elastomeric poly(glycerol sebacate) (PGS), platelet-poor plasma-coated PGS, and PGS coated by plasma supplemented with platelets. After 21 days of culture, osteochondral differentiation of cells in poly(lactide-co-glycolide) was detected, but most of the adhered cells on the surface of all PGS scaffolds expressed calponin-I and α-smooth muscle actin, suggesting smooth muscle differentiation. Cells in PGS scaffolds also produced significant amount of collagen and elastin. Further, plasma coating improves seeding efficiency, and platelet increases proliferation, the number of differentiated cells, and extracellular matrix content. Thus, the artificial niche composed of platelets, plasma, and PGS is promising for artery tissue engineering using BMNCs.

A Functionalizable Reverse Thermal Gel Based on a Polyurethane/PEG Block Copolymer

Biomaterials. Jan, 2011  |  Pubmed ID: 20937526

Injectable reverse thermal gels have great potentials as biomaterials for tissue engineering and drug delivery. However, most existing gels lack functional groups that can be modified with biomolecules that can guide cell/material interactions. We created an amine-functionalized ABA block copolymer, poly(ethylene glycol)-poly(serinol hexamethylene urethane), or ESHU. This reverse thermal gel consists of a hydrophobic block (B): poly(serinol hexamethylene urethane) and a hydrophilic block (A): poly(ethylene glycol). The polymer was characterized by GPC, FTIR and (1)H FTNMR. Rheological study demonstrated that ESHU solution in phosphate-buffered saline initiated phase transition at 32 °C and reached maximum elastic modulus at 37 °C. The in vitro degradation tests performed in PBS and cholesterol esterase solutions revealed that the polymer was hydrolyzable and the presence of cholesterol esterase greatly accelerated the hydrolysis. The in vitro cytotoxicity tests carried out using baboon smooth muscle cells demonstrated that ESHU had good cytocompatibility with cell viability indistinguishable from tissue culture treated polystyrene. Subcutaneous implantation in rats revealed well tolerated accurate inflammatory response with moderate ED-1 positive macrophages in the early stages, which largely resolved 4 weeks post-implantation. We functionalized ESHU with a hexapeptide, Ile-Lys-Val-Ala-Val-Ser (IKVAVS), which gelled rapidly at body temperature. We expect this new platform of functionalizable reverse thermal gels to provide versatile biomaterials in tissue engineering and regenerative medicine.

A Modulated Empirical Bayes Model for Identifying Topological and Temporal Estrogen Receptor α Regulatory Networks in Breast Cancer

BMC Systems Biology. 2011  |  Pubmed ID: 21554733

Estrogens regulate diverse physiological processes in various tissues through genomic and non-genomic mechanisms that result in activation or repression of gene expression. Transcription regulation upon estrogen stimulation is a critical biological process underlying the onset and progress of the majority of breast cancer. Dynamic gene expression changes have been shown to characterize the breast cancer cell response to estrogens, the every molecular mechanism of which is still not well understood.

Chromatin Structure Characteristics of Pre-miRNA Genomic Sequences

BMC Genomics. 2011  |  Pubmed ID: 21702984

MicroRNAs (miRNAs) are non-coding RNAs with important roles in regulating gene expression. Recent studies indicate that transcription and cleavage of miRNA are coupled, and that chromatin structure may influence miRNA transcription. However, little is known about the relationship between the chromatin structure and cleavage of pre-miRNA from pri-miRNA.

Identification of an HLA-DPB1*0501 Restricted Melan-A/MART-1 Epitope Recognized by CD4+ T Lymphocytes: Prevalence for Immunotherapy in Asian Populations

Journal of Immunotherapy (Hagerstown, Md. : 1997). Sep, 2011  |  Pubmed ID: 21760531

CD4 T lymphocytes play a central role in orchestrating an efficient antitumor immune response. Much effort has been devoted in the identification of major histocompatibility complex class II eptiopes from different tumor-associated antigens. Melan-A/MART-1 is expressed specifically in normal melanocytes and tumor cells of 75% to 100% of melanoma patients. Melan-A/MART-1 is considered as an attractive target for cancer immunotherapy. In the past, several human leukocyte antigen (HLA) class II restricted epitopes have been identified and characterized, including Melan-A/MART-11-20 (HLA-DR11 restricted), Melan-A/MART-125-36 (HLA-DQ6 and HLA-DR3 restricted), Melan-A/MART-127-40 (HLA-DR1 restricted), Melan-A/MART-151-73 (HLA-DR4 restricted), Melan-A/MART-191-110 (HLA-DR52 restricted), and Melan-A/MART-1100-111 (HLA-DR1 restricted). Owing to the infrequent expression of the above HLA class II alleles in Asian populations, immunotherapy using these defined Melan-A/MART-1 peptides could potentially only benefit a very small percentage of Asian melanoma patients. In this study, we established several CD4 T-cell clones by in vitro stimulation of peripheral blood mononuclear cells from a healthy donor by a peptide pool of 28 to 30 amino acid long peptides spanning the entire Melan-A/MART-1 protein. These CD4 T-cell clones recognized a peptide that is embedded within Melan-A/MART-121-50, in a HLA-DPB1*0501 restricted manner. Finally, we demonstrated that this epitope is naturally processed and presented by dendritic cells. HLA-DPB1*0501 is frequently expressed in Asian population (44.9% to 73.1%). Therefore, this epitope could provide a new tool and could significantly increase the percentage of melanoma patients that can benefit from cancer immunotherapy.

Injectable Fibroblast Growth Factor-2 Coacervate for Persistent Angiogenesis

Proceedings of the National Academy of Sciences of the United States of America. Aug, 2011  |  Pubmed ID: 21808045

Enhancing the maturity of the newly formed blood vessels is critical for the success of therapeutic angiogenesis. The maturation of vasculature relies on active participation of mural cells to stabilize endothelium and a basal level of relevant growth factors. We set out to design and successfully achieved robust angiogenesis using an injectable polyvalent coacervate of a polycation, heparin, and fibroblast growth factor-2 (FGF2). FGF2 was loaded into the coacervate at nearly 100% efficiency. In vitro assays demonstrated that the matrix protected FGF2 from proteolytic degradations. FGF2 released from the coacervate was more effective in the differentiation of endothelial cells and chemotaxis of pericytes than free FGF2. One injection of 500 ng of FGF2 in the coacervate elicited comprehensive angiogenesis in vivo. The number of endothelial and mural cells increased significantly, and the local tissue contained more and larger blood vessels with increased circulation. Mural cells actively participated during the whole angiogenic process: Within 7 d of the injection, pericytes were recruited to close proximity of the endothelial cells. Mature vasculature stabilized by vascular smooth muscle cells persisted till at least 4 wk. On the other hand, bolus injection of an identical amount of free FGF2 induced weak angiogenic responses. These results demonstrate the potential of polyvalent coacervate as a new controlled delivery platform.

Modulation of DNA Repair Capacity by Ataxia Telangiectasia Mutated Gene Polymorphisms Among Polycyclic Aromatic Hydrocarbons-exposed Workers

Toxicological Sciences : an Official Journal of the Society of Toxicology. Nov, 2011  |  Pubmed ID: 21873372

The purpose of this study was to address the association between the ataxia telangiectasia mutated (ATM) gene polymorphisms and susceptibility to DNA repair capacity (DRC) among polycyclic aromatic hydrocarbons (PAHs)-exposed workers. Polymorphisms of ATM were genotyped. DRC was determined by comet assay. Chromosomal damage was detected by cytokinesis-block micronucleus (CBMN) assay. Flow cytometry was used to detect the distributions of cell cycle. Expressions of ATM and rH2AX were determined by immunoblotting analysis. Luciferase assays were performed to determine the functional difference of ATM promoter region allele. Subjects carrying T allele of rs228589 had significantly lower DRC compared with those with AA genotype. Subjects carrying G allele of rs652311 had significantly lower DRC than those with zero copy number of haplotype CGGT. SH ataxia telangiectasia mutated (SHATM) cells had significantly lower DRC than SH green fluorescent protein (SHGFP) cells induced by bleomycin and higher CBMN frequencies treated by benzo(a)pyrene [B(a)P] than SHGFP cells. After B(a)P treatment, a decrease in the percentage of G1 phase cells was observed in SHATM cells compared with SHGFP cells, rH2AX expressions were increased in SHATM cells and SHGFP cells, but ATM expressions had no change in 16HBE-SHGFP cells and HEK-SHGFP cells. Luciferase expression was not different between rs228589T and rs228589A plasmid constructs. In conclusions, it is suggested that ATM polymorphisms are associated with DRC among PAHs-exposed workers and ATM plays key roles in repair of chromosomal damage and cell cycle control with the treatment of B(a)P.

PP1A-mediated Dephosphorylation Positively Regulates YAP2 Activity

PloS One. 2011  |  Pubmed ID: 21909427

The Hippo/MST1 signaling pathway plays an important role in the regulation of cell proliferation and apoptosis. As a major downstream target of the Hippo/MST1 pathway, YAP2 (Yes-associated protein 2) functions as a transcriptional cofactor that has been implicated in many biological processes, including organ size control and cancer development. MST1/Lats kinase inhibits YAP2's nuclear accumulation and transcriptional activity through inducing the phosphorylation at serine 127 and the sequential association with 14-3-3 proteins. However, the dephosphorylation of YAP2 is not fully appreciated.

Sensitivity to Temporal Modulation Rate and Spectral Bandwidth in the Human Auditory System: MEG Evidence

Journal of Neurophysiology. Oct, 2011  |  Pubmed ID: 21975451

Slow acoustic modulations below 20 Hz, of varying bandwidths, are dominant components of speech and many other natural sounds. The dynamic neural representations of these modulations are difficult to study through noninvasive neural recording methods, however, because of the omnipresent background of slow neural oscillations throughout the brain. We recorded the auditory steady state responses (aSSR) to slow amplitude modulations (AM) from 14 human subjects using magnetoencephalography (MEG). The responses to five AM rates (1.5, 3.5, 7.5, 15.5 and 31.5 Hz), and four types of carrier (pure tone, 1/3-, 2- and 5-octave pink noise) were investigated. The phase-locked aSSR was reliably detected in all conditions. The response power generally decreases with increasing modulation rate, and the response latency is between 100 and 150 ms for all but the highest rates. Response properties depend only weakly on the bandwidth. Analysis of the complex-valued aSSR magnetic fields in the Fourier domain reveals several neural sources with different response phases. These neural sources of the aSSR, when approximated by a single equivalent current dipole (ECD), are distinct from, and medial to, the ECD location of the N1m response. These results demonstrate that the globally synchronized activity in human auditory cortex is phase-locked to slow temporal modulations below 30 Hz and the neural sensitivity decreases with increasing AM rate, with relative insensitivity to bandwidth.

Biomimetic Micropatterned Multi-channel Nerve Guides by Templated Electrospinning

Biotechnology and Bioengineering. Dec, 2011  |  Pubmed ID: 22179932

This report describes a new approach for fabricating microchannels within three-dimensional electrospun constructs. These key features serve to mimic the fascicular architecture and fibrous extracellular matrix found in native nerve. Both electrospun fibers and multi-channeled structure nerve guides have become areas of increasing interest for their beneficial roles in nerve repair. However, to the best of our knowledge, this is the first report of a guide that incorporates both. Multiple parallel channels provide a greater number of defined paths and increased surface area compared to cylindrical guides. Additionally, the fibrous nature of electrospun fibers permits better mass transport than solid-walled constructs. The flexible fabrication scheme allows tailoring of nerve guide parameters such as channel diameters ranging from 33 to 176 µm and various wall thicknesses. Channel and fiber structures were assessed by optical and electron microscope images. Geometric calculations estimated a porosity of over 85% for these guides with 16% or less from the channels. In vitro culture with Schwann cells demonstrated cellular infiltration into channels with restricted migration between fibers. Finally, cell proliferation and survival throughout the guide indicates that this design warrants future in vivo examination. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc.

Mutual Referral: a Survey of GPs in Beijing

Family Practice. Jan, 2012  |  Pubmed ID: 22223744

BACKGROUND: China has been engaged in the process of reforming its health care system recently. The government has attempted to rebuild the referral system to lower cost and enhance equity of the medical services. OBJECTIVE: This study was undertaken to evaluate the current status of mutual referral pilot programme, perceived factors that affect referral behaviour and changes that would improve the current referral process in Beijing. METHODS: Using a cross-sectional study design, we sent a postal questionnaire to 138 urban district community health service (CHS) centres in Beijing. Questions were chosen from a formal consensus process based on a nominal group technique. RESULTS: One hundred twenty-five of 138 (90.6%) CHS centres responded to the survey. Seventy-six (61.8%) CHS centres reported that the mutual referral system was feasible. Twenty-six (21.1%) CHS centres reported that the mutual referral programme was running smoothly. Uncertainties of diagnosis/management and access to particular medical specialty interest or skills were the two most common factors that were suggested as affecting referral behaviour. The presence of a dedicated department to accept referrals in hospitals and the use of referral guidelines were the most preferred choices as likely to improve the current referral process. CONCLUSIONS: Since a system of gatekeeper role by GPs at CHS organizations has not been established in Beijing, most CHS doctors agree that to ensure the smooth operation of referrals, a dedicated department should be assigned by hospitals to receive referred patients. Official guidelines on referral should be developed, and health authorities should strengthen their supervision of referrals.

E-cadherin (CDH1) Gene Promoter Polymorphism and the Risk of Colorectal Cancer : A Meta-analysis

International Journal of Colorectal Disease. Feb, 2012  |  Pubmed ID: 21997289

Published data on the relationship between E-cadherin (CDH1) gene promoter polymorphisms and colorectal cancer (CRC) risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was carried out.

Design, Synthesis, and Biocompatibility of an Arginine-based Polyester

Biotechnology Progress. Jan, 2012  |  Pubmed ID: 22034156

Polycations are very useful in biotechnology. However, most existing polycations have high toxicity that significantly limits their clinical translation. We designed poly(ethylene argininylaspartate diglyceride) (PEAD) that is based on arginine, aspartic acid, glycerol, and ethylene glycol. A set of in vitro assays demonstrated that PEAD exhibited no cytotoxicity at 1 mg/mL, which is at least 100 times higher than the widely used polycation-polyethylenimine. Subcutaneous injection of 1 mg PEAD in rats did not cause an adverse response acutely or after 4 weeks. Zeta potential measurements revealed that PEAD has high affinity to biological polyanions such as DNA and hyaluronic acid. This polycation represents a new platform of biocompatible polycations that may lead to clinical innovations in gene therapy, controlled release, tissue engineering, biosensors, and medical devices © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2012.

A Functional Polymer Designed for Bone Tissue Engineering

Acta Biomaterialia. Feb, 2012  |  Pubmed ID: 22100348

Most synthetic polymers lack biological and chemical functionalities. This lack of functionality restricts the polymer properties and prevents them from controlling specific cell-material interactions. Polymers with free functional groups allow facile modifications, which can be used to control the biointerface. Here we created a functionalizable polymer, poly(fumaroyl bioxirane) maleate (PFM), with three free functional groups--hydroxyl, carboxyl and alkenyl--for bone tissue engineering. PFM was readily synthesized in two steps. PFM showed strain-dependent moduli with mechanical strength approaching native bones. PFM supported the adhesion, spreading, proliferation, and maturity of rat calvarial osteoblasts. The alkaline phosphatase activity of osteoblasts on PFM was significantly higher than that on tissue-culture-treated polystyrene in vitro. The physical, mechanical, and biological properties of PFM can be modulated by various functionalizations to explore methods to improve bone tissue engineering and regenerative medicine in general.

Biomarkers of Chromosomal Damage in Peripheral Blood Lymphocytes Induced by Polycyclic Aromatic Hydrocarbons: a Meta-analysis

International Archives of Occupational and Environmental Health. Jan, 2012  |  Pubmed ID: 21461768

A crucial early event in polycyclic aromatic hydrocarbons (PAHs) carcinogenesis is the induction of genomic instability phenotype that initiates the progression of a proliferative cell into a cancer cell. However, epidemiological results have been inconsistent.