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Biomedical subjects

J Y Chen

Publications and source records attributed to J Y Chen.

At least 19 recordsLinked to original sources
PubMed2003

Chronic intermittent hypoxia decreases the expression of Na/H exchangers and HCO3-dependent transporters in mouse CNS.

Chronic intermittent hypoxia (CIH) is a component of several disease states, including obstructive sleep apnea, which results in neurocognitive and cardiovascular morbidity. Because chronic hypoxia can induce changes in metabolism and pH homeostasis, we hypothesized that CIH induces changes in the expression of acid-base transporters. Two- to three-day-old mice, exposed to alternating cycles of 2 min of hypoxia (6.0-7.5% O2) and 3 min of normoxia (21% O2) for 8 h/day for 28 days, demonstrated decreases in specific acid-base transport protein expression in most of the central nervous system (CNS). Sodium/hydrogen exchanger isoform 1 (NHE1) and sodium-bicarbonate cotransporter expression were decreased in all regions of the CNS but especially so in the cerebellum. NHE3, which is only expressed in the cerebellum, was also significantly decreased. Anion exchanger 3 protein was decreased in most brain regions, with the decrease being substantial in the hippocampus. These results indicate that CIH induces downregulation of the major acid-extruding transport proteins, NHE1 and sodium-bicarbonate cotransporter, in particular regions of the CNS. This downregulation in acid-extruding capacity may render neurons more prone to acidity and possibly to injury during CIH, especially in the cerebellum and hippocampus. Alternatively, it is possible that O2 consumption in these regions is decreased after CIH, with consequential downregulation in the expression of certain cellular proteins that may be less needed under such circumstances.

Acid-Base Equilibrium↗
PubMed2003

Hemocompatibility of titanium oxide films.

Hemocompatibility is a key property of biomaterials that come in contact with blood. Surface modification has shown great potential for improving the hemocompatibility of biomedical materials and devices. In this paper, we describe our work of improving hemocompatibility with Ti-O thin films prepared by plasma immersion ion implantation and deposition and by sputtering. The structure and surface chemical and physical properties of the films were characterized by X-ray diffraction, Auger electron spectroscopy, atomic force microscopy (AFM), contact angle measurement, and Hall effect measurement. The behavior of fibrinogen adsorption was investigated by 125I radioactive isotope labeling and AFM. Systematic evaluation of hemocompatibility, including in vitro clotting time, thrombin time, prethrombin time, platelet adhesion, and in vivo implantation into dog's ventral aorta or right auricle from 17 to 90 days, proved that Ti-O films have excellent hemocompatibility. It is suggested that the significantly lower interface tension between Ti-O films and blood and plasma proteins and the semiconducting nature of Ti-O films give them their improved hemocompatibility.

Adsorption↗
PubMed2002

Phase synchronization in coupled chaotic oscillators with time delay.

The phase synchronization (PS) of two Rössler oscillators with time-delayed signal coupling is studied. We find that time delay can always lead to PS even when the delay is very long. Moreover, with the increase of time delay, the coupling strength at the transition to PS undergoes a nearly periodic wave distribution. At some fixed time-delayed signal coupling, a PS region is followed by a non-PS region when the coupling strength increases. However, an increase of the coupling leads to the PS state again. This phenomenon occurs in systems with a relatively large PS transition point.

Journal Article↗
PubMed2002

Numerical simulation of steady flow fields in a model of abdominal aorta with its peripheral branches.

In the present study, a numerical calculation procedure based on a finite volume method was developed to simulate steady flow fields in a model of abdominal aorta with its peripheral branches. The study focused on the steady baseline flow fields and the wall shear stress (WSS) distribution as well as the localization of the reversed flow regions and results were compared to those obtained by other investigators. In the case of resting conditions, the existence of a region of reversed flow of about one to two diameters in size and next to the renal arteries and along the posterior wall as observed by other researchers was confirmed. However, under the exercise conditions this region could be wiped out. The flow reversal along the lateral walls proximal to the bifurcation persisted in both rest and exercise conditions. The WSS distribution and the wall shear stress gradient distribution were obtained. The lowest WSS occurred near the ostia of the renal arteries and the lateral walls of the iliac arteries. And the highest is always at the turn to the branch. The results were generally consistent with those obtained experimentally and numerically by other investigators. It was also shown that the steady flow might be used to depict the averaged behavior of pulsatile flow. The present computer code provides a platform for the future more realistic simulations.

Aorta, Abdominal↗
PubMed2002

Carbonate apatite coating on titanium induced rapidly by precalcification.

Chemical treatments have been thought to be promised methods for improving bioactivity of titanium. In this work, the effect of precalcification with boiling saturated Ca(OH)2 solution on bioactivation of titanium was investigated. After precalcification and soaking in supersaturated Ca-P solution (SCP), calcium phosphate rapidly precipitated onto the surfaces of titanium, and after only three days an uniform apatite layer was found up to thickness of a few micrometers. The observation using scanning electron microscopy (SEM) showed that the coating was composed of a number of small crystal grains. The investigation by X-ray energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the coating was Ca-deficient carbonate apatite. Based on the analyses for the surfaces and SCP, a mechanism of precipitation of apatite was proposed in thermal dynamics and kinetics.

Apatites↗
PubMed2002

Antithrombogenic investigation of surface energy and optical bandgap and hemocompatibility mechanism of Ti(Ta(+5))O2 thin films.

Recent improvements in the antithrombogenic properties of blood contacting biomaterials permit a hybrid design of layers for biomedical applications such as artificial heart valves and stents. Using magnetron sputtering and thermal oxidation, titanium oxide thin films containing tantalum. Ti(Ta(+5))O2, are fabricated to meet the challenge of enhanced hemocompatibility. The blood compatibility is evaluated in vitro by clotting time and platelet adhesion measurement, and in vivo experiments are also conducted. The Ti(Ta(+5))O2 films exhibit attractive blood compatibility exceeding that of low isotropic pyrolytic carbon. Physical properties such as surface energy and semiconductivity are found to play important roles. Our calculated results reveal that the smaller surface force gamma(s) of the film and the smaller blood film interfacial tension gamma(c,blood) are partially responsible for the enhancement of the blood compatibility. Based on the optical bandgap model, the film possesses better hemocompatibility because its optical bandgap of 3.2 eV is wider than that of fibrinogen having a bandgap of 1.8 eV. These factors result in thinner protein layers on the film surface, less protein denaturing, and overall excellent antithrombogenic properties.

Animals↗
PubMed2002

[CaSRB9, a novel Candida albicans gene, plays a role in morphogenesis of Saccharomyces cerevisiae].

Candida albicans is the most frequently isolated fungal pathogen in humans. Many factors are involved in its morphological transition. Flo8 plays an important role in morphogenesis of Saccharomyces cerevisiae. In this work, a C.albicans genomic DNA library was introduced into an S.cerevisiae flo8/flo8 mutant to screen genes which could complement its invasive growth defect. In this screening, a novel gene was isolated and designated CaSRB9 (Candida albicans SRB9 gene). The CaSRB9 gene had an ORF of 4 998 bp, encoding a putative protein of 1 665 amino acids. The CaSrb9 shared highest similarity in amino acids (38%) with Srb9 of S.cerevisiae. Ectopic expression of the CaSRB9 gene in diploid S. cerevisiae suppressed defect in filamentous growth of some mutants in filamentation MAPK pathway (ste7/ste7, ste 12 / ste 12, and tec 1 / tec 1) and flo 8 / flo 8 mutant under nitrogen starvation conditions. In haploid S. cerevisiae, ectopic expressed CaSrb9 complemented the invasive growth defect of flo8 mutant but failed to complement the invasive growth defects of the mutants in filamentation MAPK pathway.

Amino Acid Sequence↗
PubMed2001

Association study of the p53-gene Pro72Arg polymorphism in schizophrenia.

The p53 tumor-suppressor gene, encoding a phosphoprotein, is a key element in maintaining genomic stability and cell apoptosis. It is also implicated in nervous-system development. In order to examine the role of the p53 gene for the pathogenesis of schizophrenic disorders, patients (n=155) and control subjects (n=168) were genotyped for the p53-Pro72Arg polymorphism. The results demonstrated no association with schizophrenia and/or age of onset for this polymorphism.

Adult↗
PubMed2001

Serologic markers of Epstein-Barr virus infection and nasopharyngeal carcinoma in Taiwanese men.

BACKGROUND: It is probable but unproven that Epstein-Barr virus (EBV) has a role in nasopharyngeal carcinoma. We determined whether antibodies against EBV are present before the development of nasopharyngeal carcinoma. METHODS: A total of 9699 men were enrolled between 1984 and 1986. Blood samples were examined for IgA antibodies against EBV capsid antigen and neutralizing antibodies against EBV-specific DNase. During 131,981 person-years of follow-up, 22 pathologically confirmed new cases of nasopharyngeal carcinoma that were diagnosed more than one year after recruitment were ascertained through linkage with the National Cancer Registry of Taiwan. RESULTS: The cumulative risk of nasopharyngeal carcinoma per 100,000 person-years was 11.2 for subjects who tested positive for neither serologic marker, 45.0 for those who had one marker, and 371.0 for those who had both markers. After adjustment for age and the presence or absence of a family history of nasopharyngeal carcinoma, the relative risk of nasopharyngeal carcinoma was 32.8 for subjects with both markers (95 percent confidence interval, 7.3 to 147.2; P<0.001) and 4.0 for subjects with one marker (95 percent confidence interval, 1.6 to 10.2; P=0.003), as compared with subjects with neither marker. The longer the duration of follow-up, the greater the difference in the cumulative incidence of nasopharyngeal carcinoma between seropositive and seronegative subjects. CONCLUSIONS: IgA antibodies against EBV capsid antigen and neutralizing antibodies against EBV DNase are predictive of nasopharyngeal carcinoma.

Antibodies↗
PubMed2001

Sequential up-regulation of the c-fos, c-jun and bax genes in the cortex, striatum and cerebellum induced by a single injection of a low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in C57BL/6 mice.

We investigated whether single injection of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) (20 mg/kg) will alter the expression of pro-apoptotic genes, namely, the c-fos, c-jun, and bax, in the striatum, cortex, and cerebellum of adult male C57BL/6 mice using reverse transcription-polymerase chain reaction assay. Injection of MPTP induced a transient decrease in the content of tyrosine hydroxylase estimated by the immunoreactivity in the striatum, which completely recovered 14 day after injection. A rapid but transient up-regulation of c-fos and c-jun genes occurred an hour after MPTP-injection, and a delayed but persistent up-regulation of bax gene expression occurred 3 day after injection. The up-regulation of these genes was present in all the examined brain regions. This result suggests that MPTP, at a low dose causing transient degeneration in the striatum, is capable of triggering two genetic pathways related to the generation of apoptosis in both dopaminergic and non-dopaminergic systems in the mouse brain.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

The origin of crustaceans: new evidence from the Early Cambrian of China.

One of the smallest arthropods recently discovered in the Early Cambrian Maotianshan Shale Lagerstätte is described. Ercaia gen. nov. has an untagmatized trunk bearing serially repeated biramous appendages (long and segmented endopods and flap-like exopods), a head with an acron bearing stalked lateral eyes and a sclerite and two pairs of antennae. The position of this 520 million-year-old tiny arthropod within the Crustacea is supported by several anatomical features: (i) a head with five pairs of appendages including two pairs of antennae, (ii) highly specialized antennae (large setose fans with a possible function in feeding), and (iii) specialized last trunk appendages (segmented pediform structures fringed with setae). The segmentation pattern of Ercaia (5 head and 13 trunk) is close to that of Maxillopoda but lacks the trunk tagmosis of modern representatives of the group. Ercaia is interpreted as a possible derivative of the stem group Crustacea. Ercaia is likely to have occupied an ecological niche similar to those of some Recent meiobenthic organisms (e.g. copepods living in association with sediment). This new fossil evidence supports the remote ancestry of crustaceans well before the Late Cambrian and shows, along with other fossil data (mainly Early Cambrian in China), that a variety of body plans already coexisted among the primitive crustacean stock.

Animals↗
PubMed2001

Differential cytotoxicity of Mn(II) and Mn(III): special reference to mitochondrial [Fe-S] containing enzymes.

Manganese (Mn)-induced neurodegenerative toxicity has been associated with a distorted iron (Fe) metabolism at both systemic and cellular levels. In the current study, we examined whether the oxidation states of Mn produced differential effects on certain mitochondrial [Fe-S] containing enzymes in vitro. When mitochondrial aconitase, which possesses a [4Fe-4S] cluster, was incubated with either Mn(II) or Mn(III), both Mn species inhibited the activities of aconitase. However, the IC(10) (concentration to cause a 10% enzyme inhibition) for Mn(III) was ninefold lower than that for Mn(II). Following exposure of mitochondrial fractions with Mn(II) or Mn(III), there was a significant inhibition by either Mn species in activities of Complex I whose active site contains five to eight [Fe-S] clusters. The dose-time response curves reveal that Mn(III) was more effective in blocking Complex I activity than Mn(II). Northern blotting was used to examine the expression of mRNAs encoding transferrin receptor (TfR), which is regulated by cytosolic aconitase. Treatment of cultured PC12 cells with Mn(II) and Mn(III) at 100 microM for 3 days resulted in 21 and 58% increases, respectively, in the expression of TfR mRNA. Further studies on cell growth dynamics after exposure to 25-50 microM Mn in culture media demonstrated that the cell numbers were much reduced in Mn(III)-treated groups compared to Mn(II)-treated groups, suggesting that Mn(III) is more effective than Mn(II) in cell killing. In cells exposed to Mn(II) and Mn(III), mitochondrial DNA (mtDNA) was significantly decreased by 24 and 16%, respectively. In contrast, rotenone and MPP+ did not seem to alter mtDNA levels. These in vitro results suggest that Mn(III) species appears to be more cytotoxic than Mn(II) species, possibly due to higher oxidative reactivity and closer radius resemblance to Fe.

Aconitate Hydratase↗
PubMed2001

Identification of a mouse thiamine transporter gene as a direct transcriptional target for p53.

p53 tumor suppressor is a transcription factor that functions, in part, through many of its downstream target genes. We have identified a p53-inducible gene by performing mRNA differential display on IW32 murine erythroleukemia cells containing a temperature-sensitive p53 mutant allele, tsp53(Val-135). Sequence analysis of the full-length cDNA revealed its identity as the mouse homologue of the human thiamine transporter 1 (THTR-1). Induction of the mouse THTR-1 (mTHTR-1) mRNA was detectable as early as 1 h at 32.5 degrees C; upon shifting back to 38.5 degrees C, mTHTR-1 transcript was rapidly degraded with a half-life of less than 2 h. Elevation of mTHTR-1 expression was found in DNA damage-induced normal mouse embryonic fibroblast cells, but not in p53(-/-) mouse embryonic fibroblast cells, suggesting that mTHTR-1 induction was p53-dependent. A region within the first intron of the mTHTR-1 gene bound to p53 and conferred the p53-mediated transactivation. Furthermore, increased thiamine transporter activities were found in cells overexpressing mTHTR-1 and under conditions of DNA damage or p53 activation. Our findings indicate that p53 may be involved in maintaining thiamine homeostasis through transactivation of THTR-1.

Amino Acid Sequence↗
PubMed2001

Molecular cloning, developmental expression, and hormonal regulation of zebrafish (Danio rerio) beta crystallin B1, a member of the superfamily of beta crystallin proteins.

The cDNA sequence of beta crystallin B1 was determined from zebrafish (Danio rerio) and compared to the corresponding genes of bovine, rat, chicken, human, and Xenopus. Multispecies comparison of superfamily diversity demonstrated beta crystallin B1 homology between zebrafish, bovine, chicken, and rat, but large distances to beta crystallin B2 and B3. Zebrafish cDNA has a size of 943 nucleotides and encodes a polypeptide of 233 amino acids. Zebrafish beta crystallin B1 shares 71.30, 75.86, and 71.00% similarities with bovine, chicken, and rat beta crystallin B1, respectively. Northern blot analysis revealed a single 0.9-kb beta crystallin B1 transcript which was expressed and progressively increased in the first 20 h of zebrafish embryogenesis. Whole-mount in situ hybridization revealed that the beta crystallin B1 transcript was only specifically expressed in the lens region of the eye. A starvation experiment revealed no variation in mRNA levels after 14 and 21 days. An experiment in which hormone was injected showed that the beta crystallin B1 transcript first increased 24 h after the injection of insulin-like growth factor I, insulin-like growth factor II, or growth hormone, then decreased 48 h after injection. The beta crystallin B1 transcript continuously increased after insulin was injected. Taken together, our results identify the early specific expression of beta crystallin B1 within the lens. Despite small differences, these results indicate that both the structure of the beta crystallin B1 protein and its involvement with regulation by growth factors appear to have been remarkably conserved.

Amino Acid Sequence↗
PubMed2001

A genome-wide study of microsatellite instability in advanced gastric carcinoma.

BACKGROUND: Microsatellite instability (MSI) has been described in many human carcinomas, including gastric carcinomas (GCs). There are inconsistent findings regarding the association of MSI with various subsets of GC with specific clinicopathologic features. The objective of this study was to define MSI in advanced GC at a genome-wide level and to evaluate the clinical relevance of MSI in these patients. METHODS: Forty-one gastric adenocarcinomas with serosa invasion (T3) were analyzed at 59 loci that detected at least one site per arm of each autosome in human genome. The expression patterns of mismatch repair proteins hMLH1 and hMSH2 were examined by immunohistochemistry. Comparisons were made by categorizing tumors into three groups: tumors with MSI at multiple loci (at more than three loci), tumors with MSI at low level (at one to three loci), and microsatellite-stable (MSS) tumors. Clinical significance of MSI in advanced GC was evaluated. The relative rates of hypermutability of the 59 markers also were determined. RESULTS: A significant association was found between tumors with MSI at multiple loci and the expanding type of tumor growth by Ming's histologic classification (P = 0.001), whereas tumors with MSI at low level and MSS tumors are clinicopathologically indistinguishable. The 59 dinucleotide repeat markers displayed varying degrees of susceptibility toward genetic instability. The relative rates of hypermutability of these markers were consistent with a normal distribution pattern in which the frequency of unstable tumors detected at different chromosomal loci varied from 0% to 20%. CONCLUSIONS: The authors' results showed that advanced GC with MSI at multiple loci progress preferentially in an expanding mode, supporting the notion that high MSI tumors and low MSI/MSS tumors evolve through different genetic pathways. Thus, microsatellite testing may have clinical utility as a favorable prognostic marker.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The type I BMP receptor BmprIB is essential for female reproductive function.

Maintenance of female reproductive competence depends on the actions of several hormones and signaling factors. Recent reports suggest roles for bone morphogenetic proteins (BMPs) in early stages of folliculogenesis. A role for the type I BMP receptor BmprIB as a regulator of ovulation rates in sheep has been described recently, but little is known about the roles of BMP signaling pathways in other aspects of reproductive function. We report here that BMPRIB is essential for multiple aspects of female fertility. Mice deficient in BmprIB exhibit irregular estrous cycles and an impaired pseudopregnancy response. BmprIB mutants produce oocytes that can be fertilized in vitro, but defects in cumulus expansion prevent fertilization in vivo. This defect is associated with decreased levels of aromatase production in granulosa cells. Unexpectedly, levels of mRNA for cyclooxygenase 2, an enzyme required for cumulus expansion, are increased. BmprIB mutants also exhibit a failure in endometrial gland formation. The expression of BmprIB in uterine linings suggests that these defects are a direct consequence of loss of BMP signaling in this tissue. In summary, these studies demonstrate the importance of BMP signaling pathways for estrus cyclicity, estradiol biosynthesis, and cumulus cell expansion in vivo and reveal sites of action for BMP signaling pathways in reproductive tissues.

Animals↗
PubMed2001

Intermittent phase synchronization of coupled spatiotemporal chaotic systems.

Phase synchronization is studied with a discrete system formed by two coupled map lattices, in which phases are measured in two-dimensional vectors. Simulation results show that by imposing external coupling between the two lattices, phase synchronization can be found in all two-dimensional phase planes between them. When the system is approaching the phase synchronizing state, unstable phase synchronization is observed. This is referred to as intermittent phase synchronization that appears when the trajectories on two interacting phase planes have opposite directions of rotation but with only a small phase difference. The intermittent phase synchronization could also be observed in coupled autonomous systems with diffusive attractors although their phase concepts are inconsistent. Our results show that the intermittent phase synchronization of both discrete and autonomous systems relates to the diffusion or the complexity of the attractors.

Journal Article↗