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Biomedical subjects

Ying Chen

Publications and source records attributed to Ying Chen.

At least 55 records · Page 3Linked to original sources

Control of muscle regeneration in the Xenopus tadpole tail by Pax7.

The tail of the Xenopus tadpole will regenerate completely after transection. Much of the mass of the regenerate is composed of skeletal muscle, but there has been some uncertainty about the source of the new myofibres. Here, we show that the growing tail contains many muscle satellite cells. They are active in DNA replication, whereas the myonuclei are not. As in mammals, the satellite cells express pax7. We show that a domain-swapped construct, pax7EnR, can antagonize pax7 function. Transgenic tadpoles were prepared containing pax7EnR driven by a heat-inducible promoter. When induced, this reduces the proportion of satellite cells formed in the regenerate. A second amputation of the resulting tails yielded second regenerates containing notochord and spinal cord but little or no muscle. This shows that inhibition of pax7 action does not prevent differentiation of satellite cells to myofibres, but it does prevent their maintenance as a stem cell population.

Animals↗

SAGE2Splice: unmapped SAGE tags reveal novel splice junctions.

Serial analysis of gene expression (SAGE) not only is a method for profiling the global expression of genes, but also offers the opportunity for the discovery of novel transcripts. SAGE tags are mapped to known transcripts to determine the gene of origin. Tags that map neither to a known transcript nor to the genome were hypothesized to span a splice junction, for which the exon combination or exon(s) are unknown. To test this hypothesis, we have developed an algorithm, SAGE2Splice, to efficiently map SAGE tags to potential splice junctions in a genome. The algorithm consists of three search levels. A scoring scheme was designed based on position weight matrices to assess the quality of candidates. Using optimized parameters for SAGE2Splice analysis and two sets of SAGE data, candidate junctions were discovered for 5%-6% of unmapped tags. Candidates were classified into three categories, reflecting the previous annotations of the putative splice junctions. Analysis of predicted tags extracted from EST sequences demonstrated that candidate junctions having the splice junction located closer to the center of the tags are more reliable. Nine of these 12 candidates were validated by RT-PCR and sequencing, and among these, four revealed previously uncharacterized exons. Thus, SAGE2Splice provides a new functionality for the identification of novel transcripts and exons. SAGE2Splice is available online at http://www.cisreg.ca.

Algorithms↗

Synthesis and characterization of 3-arylquinazolinone and 3-arylquinazolinethione derivatives as selective estrogen receptor beta modulators.

On the basis of the stucture of genistein, a new series of 3-arylquinazolines was prepared and tested for their estrogen receptor (ER) alpha and beta affinities. 5,7-Dihydroxy-3-(4-hydroxyphenyl)-4(3H)-quinazolinone (1aa) acts as an agonist on both ER subtypes. It has 62-fold higher binding affinity [IC(50)(ERbeta) = 179 nM] and 38-fold higher functional potency in a transcription assay [EC(50)(ERbeta) = 76 nM] with ERbeta than with ERalpha, thus improving upon the selectivity of genistein. All of the analogues showed preferential binding affinity for ERbeta. Many are also more potent in activating transcription by ERbeta than by ERalpha. Transformation of the C=O functionality at position 4 into a C=S group provided 5,7-dihydroxy-3-(4-hydroxyphenyl)-4(3H)-quinazolinethione (1ba), which acts as an agonist on both ER subtypes but has 56-fold higher binding affinity for ERbeta over ERalpha [IC(50)(ERbeta) = 47 nM] and 215-fold higher potency in the transcription assay [EC(50)(ERbeta) = 13 nM]. These ERbeta-selective compounds may represent valuable tools in understanding the differences in structure and biological function of ERbeta and ERalpha.

Binding Sites↗

CeRh1 (rhr-1) is a dominant Rhesus gene essential for embryonic development and hypodermal function in Caenorhabditis elegans.

Rhesus (Rh) proteins share a conserved 12-transmembrane topology and specify a family of putative CO(2) channels found in diverse species from microbes to human, but their functional essentiality and physiological importance in metazoans is unknown. To address this key issue and analyze Rh-engaged physiologic processes, we sought to explore model organisms with fewer Rh genes yet are tractable to genetic manipulations. In this article, we describe the identification in nematodes of two Rh homologues that are highly conserved and similar to human Rh glycoproteins, and we focus on their characterization in Caenorhabditis elegans. RNA analysis revealed that CeRh1 is abundantly expressed in all developmental stages, with highest levels in adults, whereas CeRh2 shows a differential and much lower expression pattern. In transient expression in human cells, both CeRh1 and CeRh2-GFP fusion proteins were routed to the plasma membrane. Transgenic analysis with GFP or LacZ-fusion reporters showed that CeRh1 is mainly expressed in hypodermal tissue, although it is also in other cell types. Mutagenesis analysis using deletion constructs mapped a minimal promoter region driving CeRh1 gene expression. Although CeRh2 was dispensable, RNA interference with CeRh1 caused a lethal phenotype mainly affecting late stages of C. elegans embryonic development, which could be rescued by the CbRh1 homologue from the worm Caenorhabditis briggsae. Taken together, our data provide direct evidence for the essentiality of the CeRh1 gene in C. elegans, establishing a useful animal model for investigating CO(2) channel function by cross-species complementation.

Amino Acid Sequence↗

Kinetics and synergistic effects of siRNAs targeting structural and replicase genes of SARS-associated coronavirus.

SARS-associated coronavirus was identified as the etiological agent of severe acute respiratory syndrome and a large virus pool was identified in wild animals. Virus generates drug resistance through fast mutagenesis and escapes antiviral treatment. siRNAs targeting different genes would be an alternative for overcoming drug resistance. Here, we report effective siRNAs targeting structural genes (i.e., spike, envelope, membrane, and nucleocapsid) and their antiviral kinetics. We also showed the synergistic effects of two siRNAs targeting different functional genes at a very low dose. Our findings may pave a way to develop cost effective siRNA agents for antiviral therapy in the future.

Animals↗

The human reelin gene: transcription factors (+), repressors (-) and the methylation switch (+/-) in schizophrenia.

A recent report suggests that the down-regulation of reelin and glutamic acid decarboxylase (GAD(67)) mRNAs represents 2 of the more consistent findings thus far described in post-mortem material from schizophrenia (SZ) patients [reviewed in. Neurochemical markers for schizophrenia, bipolar disorder amd major depression in postmortem brains. Biol Psychiatry 57, 252-260]. To study mechanisms responsible for this down-regulation, we have analyzed the promoter of the human reelin gene. Collectively, our studies suggest that SZ is characterized by a gamma-amino butyric acid (GABA)-ergic neuron pathology presumably mediated by promoter hypermethylation facilitated by the over-expression of the methylating enzyme DNA methyltransferase (Dnmt) 1. Using transient expression assays, promoter deletions and co-transfection assays with various transcription factors, we have shown a clear synergistic action that is a critical component of the mechanism of the trans-activation process. Equally important is the observation that the reelin promoter is more heavily methylated in brain regions in patients diagnosed with SZ as compared to non-psychiatric control subjects [Grayson, D. R., Jia, X., Chen, Y., Sharma, R. P., Mitchell, C. P., & Guidotti, A., et al. (2005). Reelin promoter hypermethylation in schizophrenia. Proc Natl Acad Sci U S A 102, 9341-9346]. The combination of studies in cell lines and in animal models of SZ, coupled with data obtained from post-mortem human material provides compelling evidence that aberrant methylation may be part of a core dysfunction in this psychiatric disease. More interestingly, the hypermethylation concept provides a coherent mechanism that establishes a plausible link between the epigenetic misregulation of multiple genes that are affected in SZ and that collectively contribute to the associated symptomatology.

Animals↗

Differential modulation by the GABAB receptor allosteric potentiator 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl)-phenol (CGP7930) of synaptic transmission in the rat hippocampal CA1 area.

The recently discovered GABAB receptor-positive allosteric modulators enhanced the potency and efficacy of GABAB receptor agonists in in vitro experiments. These GABAB modulators also attenuated reward and anxiety in behavioral experiments without causing the untoward side effects associated with GABAB receptor activation by agonist administration and hence exhibited potential therapeutic utility. However, the underlying molecular mechanisms enabling the GABAB allosteric modulators to dissociate from the GABAB agonistic side effects remain elusive. To address this question, we have examined the effects of a typical GABAB modulator, 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl)-phenol (CGP7930), on GABAB receptor-mediated modulations of both the excitatory and the delayed inhibitory components of hippocampal CA1 synaptic transmission. Using baclofen as an agonist and a multielectrode recording system, we recorded GABAB receptor-mediated modulations of both the field excitatory postsynaptic potentials and the population spikes simultaneously, as well as the paired-pulse inhibition of the population spike. We found that CGP7930 selectively enhanced the baclofen-induced modulation of synaptic inhibition without having any significant effects on the synaptic excitation. Our experiments have therefore revealed a pathway-selective differential modulation of synaptic transmission by CGP7930. This finding provides a synaptic mechanism to support the hypothesis that GABAB potentiators may be a better therapeutic alternative than GABAB agonists for central nervous system disorders.

Action Potentials↗

Significance of Survivin and PTEN expression in full lymph node-examined gastric cancer.

AIM: To study the relationship between Survivin and PTEN expression and lymph node metastasis, depth of invasion and prognosis of gastric cancer patients in China. METHODS: Specimens of gastric cancer tissue were collected from the Affiliated Hospital of Jianghan University. All the 140 patients had complete examination data. All lymph nodes were found by the fat-clearing method. The interrupted serial 4-micron sections, routine hematoxylin and eosin staining and immunohistochemical methods were used to detect the lymph node metastases. Gastric cancer tissue microarray was performed to test the expression of Survivin and PTEN (17A) in gastric cancer by immunohistochemical method. All data were processed using chi2 test, Fisher's exact test, Kaplan-Meyer Log-rank method and Cox multivariate analysis (SPSS 12.0 software). RESULTS: One hundred and eighteen specimens were used in our tissue microarray (utilization rate was 82.4%). A total of 7580 lymph nodes were found. Metastases were found in 90 specimens and 1618 lymph nodes were detected. The positive rate of Survivin and PTEN expression was 52.5% (62/118) and 76.2% (90/118), respectively. A highly positive correlation was found between Survivin and PTEN expression (chi2 = 4.17, P = 0.04). Survivin expression was positively correlated with UICC N stage (chi 2 = 8.69, P = 0.03) and histological classification (chi2 = 4.41, P = 0.04) by chi2 tests. PTEN expression was positively correlated with depth of invasion (P = 0.02) and histological classification (chi2 = 5.47, P = 0.02). But Survivin and PTEN expressions were not related with prognosis of gastric cancer patients. A significant correlation between lymph node metastasis and prognosis was demonstrated by Cox multivariate analysis (chi2 = 4.85, P = 0.028). CONCLUSION: Survivin is positively correlated with PTEN expression in gastric cancer and is a molecular marker of lymph node metastasis while PTEN expression is a molecular marker of advanced gastric cancer. UICC N stage is the most important prognostic factor of gastric cancer in China.

Adult↗

Iron-assisted vapor-phase hydrothermal method: a low-temperature approach to synthesize blue light emissive SiOx nanowires with single-crystal structure of P2(1)2(1)2.

A novel and facile approach, named iron-assisted vapor-phase hydrothermal method, is proposed to fabricate the long and stable bright blue light emitting SiOx nanowires (SiONWs) at a low temperature. The obtained SiONWs possess a brand-new single-crystalline structure of space group P21212. This new type of bright blue light emitting SiONW with a new single-crystalline structure may initiate a new 1D optical material and offer new opportunities for the research in science and technology.

Journal Article↗

Defining the heterochromatin localization and repression domains of SALL1.

SALL1 has been identified as one of four human homologues of the Drosophila region-specific homeotic gene spalt (sal), encoding zinc finger proteins of characteristic structure. Mutations of SALL1 on chromosome 16q12.1 cause Townes-Brocks syndrome (TBS, OMIM 107480). We have shown previously that SALL1 acts as a strong transcriptional repressor in mammalian cells when fused to a heterologous DNA-binding domain. Here, we report that SALL1 contains two repression domains, one located at the extreme N-terminus of the protein and the other in the central region. SALL1 fragments with the central repression domain exhibited a punctate nuclear distribution pattern at pericentromeric heterochromatin foci in murine NIH-3T3 cells, suggesting an association between repression and heterochromatin localization. The implications of these findings for the pathogenesis of Townes-Brocks syndrome are discussed.

Animals↗

Low stability of Huntington muscle mitochondria against Ca2+ in R6/2 mice.

OBJECTIVE: The aim of the present work was the detection of Mitochondrial dysfunction of Huntington's disease (HD). METHODS: We investigated muscle and muscle mitochondria of 14- to 16-week-old R6/2 mice in comparison with wild-type mice. RESULTS: Atrophic fibers, increased fuchsinophilic aggregates, and reduced cytochrome c oxidase (15%) were found in HD muscle. With swelling measurements and Ca2+ accumulation experiments, a decreased stability of HD mitochondria against Ca2+-induced permeability transition was detected. Complex I-dependent respiration of HD mitochondria was more sensitive to inhibition by adding 10 microm Ca2+ than wild-type mitochondria. INTERPRETATION: Data suggest that the decreased stability of HD mitochondria against Ca2+ contributes to energetic depression and cell atrophy.

Animals↗

Cell brain: insight into hepatocarcinogenesis.

Although great effort has been made, the understanding of the mechanisms of hepatocarcinogenesis is still limited. Among all the related hypotheses, the cell brain theory, which emphasized the integrate roles of the complex consisting of centrosome, the embedded centrioles and connecting microtubules (MTs) and interpreted cancer as a cell brain illness rather than a genetic disease, emerges to be more logic and recognizable. According to cell brain theory, all the cellular procedures are coordinated as a whole by the "brain" of a cell determining a cell's fate. Structural and functional abnormalities in the cell brain may result in unequal or multipolar segregation of the chromosomes, thereby causing cell cycle disorder, centrosome amplification, and genomic instability. Although there lacking of direct evidence associating cell brain defects and hepatocarcinogenesis, latest understanding of the roles of the cells brain in cell control does teach us that any defects in the cell brain may contribute to hepatocarcinogenesis. Briefly, more than 100 key proteins involved in DNA synthesis, DNA repair, cell cycle, and apoptosis have been localized to the cell brain. Specifically, more and more novel proteins associated with centrosome such as centrin, centriolin and cenexin are located in the centriole, a core component of cenrtrosome. Aberrant phosphorylation of these proteins and/or mutation of the coding genes may inevitably cause supernumerary centrioles and/or excess pericentriolar material. Modifications of any MT proteins such as tyrosinated tubulin (Tyr-tubulin), detyrosinated tubulin (Glu-tubulin) and Delta2-tubulin may change the structure and function of MTs, thereby interfering with G1 phase progression, altering the dynamics of some key proteins, and mis-regulating signal transduction and transcription. Although little work has been done, we intend to believe, based on the latest understanding of the novel roles of the cell brain in cell control, that defects in any part of the cell brain either in the structure or in the function may result in changes of the genes, eventually leading to the development of liver cancer, which is discussed in this paper and is expected to be helpful in shedding light on the often paradoxical observations seen in the development of cancer, including HCC. It also teaches us that when treating cancerous problems therapeutically or prophylactically, great attention should be given to the centrosome/cell brain, instead of gene alone. More specifically, the centrosome-centered cell brain may come to be novel targets in the treatment of cancer including HCC.

Animals↗

Synthesis and magnetic properties of biocompatible hybrid hollow spheres.

Magnetic hybrid hollow spheres of about 200 nm were prepared by a core-template-free route, that is, adding Fe3O4 nanoparticles stabilized by poly(vinyl alcohol) (PVA) to an aqueous solution of polymer-monomer pairs composed of a cationic polymer, chitosan (CS), and an anionic monomer, acrylic acid (AA), followed by polymerization of acrylic acid and selective cross-linking of chitosan at the end of polymerization. The obtained hybrid spheres were characterized by dynamic light scattering (DLS) in aqueous solution and observed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) in the solid state. Fourier transform infrared spectroscopy (FTIR) and X-ray and electron diffractions revealed that the Fe3O4 nanoparticles were incorporated into the shells of chitosan-poly(acrylic acid) (CS-AA) hollow spheres. Magnetization studies and Mössbauer spectroscopy suggested that the chains (or islands) of iron oxide nanoparticles were most likely formed in the walls of the hollow spheres. The phantom test of magnetic resonance imaging showed that the synthesized hybrid hollow spheres had a significant magnetic resonance signal enhancement in T2-weighted image.

Acrylic Resins↗

Reelin, lipoprotein receptors and synaptic plasticity.

Apolipoprotein E (APOE) is a cholesterol transport protein and an isoform-specific major risk factor for neurodegenerative diseases. The lipoprotein receptors that bind APOE have recently been recognized as pivotal components of the neuronal signalling machinery. The interaction between APOE receptors and one of their ligands, reelin, allows them to function directly as signal transduction receptors at the plasma membrane to control not only neuronal positioning during brain development, but also synaptic plasticity in the adult brain. Here, we review the molecular mechanisms through which APOE, cholesterol, reelin and APOE receptors control synaptic functions that are essential for cognition, learning, memory, behaviour and neuronal survival.

Animals↗

Multifractal ECG mapping of ventricular epicardium during regional ischemia in the pig.

Myocardial ischemia creates abnormal electrophysiological substrates that can result in life-threatening ventricular arrhythmias. Early clinical identification of ischemia in patients is important to managing their condition. We analyzed electrograms from an ischemia-reperfusion animal model in order to investigate the relationship between myocardial ischemia and variability of electrocardiogram (ECG) multifractality. Ventricular epicardial electropotential maps from the anesthetized pig during LAD ischemia-reperfusion were analyzed using multifractal methods. A new parameter called the singularity spectrum area reference dispersion (SARD) is presented to represent the temporal evolution of multifractality. By contrasting the ventricular epicardial SARD and range of singularity strength (delta alpha) maps against activation-recovery interval (ARI) maps, we found that the dispersions of SARD and dleta alpha increased following the onset of ischemia and decreased with tissue recovery. In addition, steep spatial gradients of SARD and delta alpha corresponded to locations of ischemia, although the distribution of multifractality did not reflect the degree of myocardial ischemia. However, the multifractality of the ventricular epicardial electrograms was useful for classifying the recoverability of ischemic tissue. Myocardial ischemia significantly influenced the multifractality of ventricular electrical activity. Recoverability of ischemic myocardium can be classified using the multifractality of ventricular epicardial electrograms. The location and size of regions of severe ischemic myocardium with poor recoverability is detectable using these methods.

Animals↗

Mice lacking L1 cell adhesion molecule have deficits in locomotion and exhibit enhanced corticospinal tract sprouting following mild contusion injury to the spinal cord.

L1 is a member of the immunoglobulin superfamily of cell adhesion molecules that is associated with axonal growth, including formation of the corticospinal tract (CST). The present study describes the effects of L1 deletion on hindlimb function in locomotion, and examines the role of L1 in recovery and remodeling after contusive spinal cord injury (SCI) in mice. Uninjured adult L1 knockout (Y/-) mice had impaired performance on locomotor tests compared with their wild-type littermates (Y/+). Anterograde tracing demonstrated that CST axons project to thoracic, but not lumbar, levels of the spinal cord of Y/- mice, and revealed a diversion of these fibers from their position in the base of the dorsal columns. Retrograde tracing also revealed reduced numbers of descending projections from paraventricular hypothalamus and red nuclei to the lumbar spinal cord in Y/- mice. SCI at the mid-thoracic level produced a lesion encompassing the center of the spinal cord, including the site of the dorsal CST and surrounding gray matter (GM). The injury caused lasting deficits in fine aspects of locomotion. There was no effect of genotype on final lesion size or the growth of axons into the lesion area. However, injured Y/- mice demonstrated a robust expansion of CST projections throughout the GM of the cervical and thoracic spinal cord rostral to the lesion compared with Y/+ littermates. Thus, L1 is important for the development of multiple spinal projections and also contributes to the restriction of CST sprouting rostral to the site of a SCI in adults.

Animals↗

Intercomparison of methods for image quality characterization. I. Modulation transfer function.

The modulation transfer function (MTF) and the noise power spectrum (NPS) are widely recognized as the most relevant metrics of resolution and noise performance in radiographic imaging. These quantities have commonly been measured using various techniques, the specifics of which can have a bearing on the accuracy of the results. As a part of a study aimed at comparing the relative performance of different techniques, in this paper we report on a comparison of two established MTF measurement techniques: one using a slit test device [Dobbins et al., Med. Phys. 22, 1581-1593 (1995)] and another using a translucent edge test device [Samei et al., Med. Phys. 25, 102-113 (1998)], with one another and with a third technique using an opaque edge test device recommended by a new international standard (IEC 62220-1, 2003). The study further aimed to substantiate the influence of various acquisition and processing parameters on the estimated MTF. The slit test device was made of 2 mm thick Pb slabs with a 12.5 microm opening. The translucent edge test device was made of a laminated and polished Pt(0.9)Ir(0.1). alloy foil of 0.1 mm thickness. The opaque edge test device was made of a 2 mm thick W slab. All test devices were imaged on a representative indirect flat-panel digital radiographic system using three published beam qualities: 70 kV with 0.5 mm Cu filtration, 70 kV with 19 mm Al filtration, and 74 kV with 21 mm Al filtration (IEC-RQA5). The latter technique was also evaluated in conjunction with two external beam-limiting apertures (per IEC 62220-1), and with the tube collimator limiting the beam to the same area achieved with the apertures. The presampled MTFs were deduced from the acquired images by Fourier analysis techniques, and the results analyzed for relative values and the influence of impacting parameters. The findings indicated that the measurement technique has a notable impact on the resulting MTF estimate, with estimates from the overall IEC method 4.0% +/- 0.2% lower than that of Dobbins et al. and 0.7% +/- 0.4% higher than that of Samei et al. averaged over the zero to cutoff frequency range. Over the same frequency range, keeping beam quality and limitation constant, the average MTF estimate obtained with the edge techniques differed by up to 5.2% +/- 0.2% from that of the slit, with the opaque edge providing lower MTF estimates at lower frequencies than those obtained with the translucent edge or slit. The beam quality impacted the average estimated MTF by as much as 3.7% +/- 0.9% while the use of beam limiting devices alone increased the average estimated MTF by as much as 7.0% +/- 0.9%. While the slit method is inherently very sensitive to misalignment, both edge techniques were found to tolerate misalignments by as much as 6 cm. The results suggest the use of the opaque edge test device and the tube internal collimator for beam limitation in order to achieve an MTF result most reflective of the overall performance of the imaging system and least susceptible to misalignment and scattered radiation. Careful attention to influencing factors is warranted to achieve accurate results.

Algorithms↗

Intercomparison of methods for image quality characterization. II. Noise power spectrum.

Second in a two-part series comparing measurement techniques for the assessment of basic image quality metrics in digital radiography, in this paper we focus on the measurement of the image noise power spectrum (NPS). Three methods were considered: (1) a method published by Dobbins et al. [Med. Phys. 22, 1581-1593 (1995)], (2) a method published by Samei et al. [Med. Phys. 30, 608-622 (2003)], and (3) a new method sanctioned by the International Electrotechnical Commission (IEC 62220-1, 2003), developed as part of an international standard for the measurement of detective quantum efficiency. In addition to an overall comparison of the estimated NPS between the three techniques, the following factors were also evaluated for their effect on the measured NPS: horizontal versus vertical directional dependence, the use of beam-limiting apertures, beam spectrum, and computational methods of NPS analysis, including the region-of-interest (ROI) size and the method of ROI normalization. Of these factors, none was found to demonstrate a substantial impact on the amplitude of the NPS estimates (< or = 3.1% relative difference in NPS averaged over frequency, for each factor considered separately). Overall, the three methods agreed to within 1.6% +/- 0.8% when averaged over frequencies > 0.15 mm(-1).

Algorithms↗