Search PubMed⌕ Search

Biomedical subjects

J Y Chen

Publications and source records attributed to J Y Chen.

At least 37 records · Page 2Linked to original sources
PubMed2003

Gout in systemic lupus erythematosus and overlap syndrome - a hospital-based study.

The negative association between gout and rheumatoid arthritis is widely accepted, and gout is also speculated to be rare in systemic lupus erythematosus (SLE), as only a few sporadic cases have been reported. From 1985 to 2001 we encountered 15 lupus patients at Chang-Gung Memorial Hospital, including two with lupus-scleroderma and one with lupus-scleroderma-polymyositis overlap syndrome coexisting with gout. This study retrospectively analyses the clinical and laboratory characteristics of these patients. A lower female predominance is found, and most patients developed gout after the onset of SLE, although gout preceded SLE in two cases. Measurement of serum uric acid and 24-h urine uric acid found all of the patients to be hyperuricaemic and underexcretors of uric acid. Furthermore, most of the patients (14/15) were receiving diuretics. Also, many had hypertension and serious cardiovascular diseases. Renal impairment during gouty attacks seemed to be a predisposing factor for developing end-stage renal disease. Gouty arthritis usually occurred during relative SLE inactivity, podagra was frequent, and tophi were found in a few patients. Compared with the unselected population of SLE patients, the cases studied here had a higher incidence of chronic arthritis, malar rash, haematologic disorder, photosensitivity, serositis and neurologic disorder. Renal disease in the patients sampled was frequently membranous nephropathy.

Adult↗
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↗
PubMed2003

Activation of platelets adhered on amorphous hydrogenated carbon (a-C:H) films synthesized by plasma immersion ion implantation-deposition (PIII-D).

Amorphous carbon films have attracted much attention recently due to their good biocompatibility. Diamond-like carbon (DLC), one form of amorphous carbon that is widely used in many kinds of industries, has been proposed for use in blood contacting medical devices. However, the blood coagulation mechanism on DLC in a biological environment is not well understood. Platelet adhesion and activation are crucial events in the interactions between blood and the materials as they influence the subsequent formation of thrombus. In this work, the behavior of platelets adhered onto hydrogenated amorphous carbon films (a-C:H) is investigated. Hydrogenated amorphous carbon films with different hydrogen contents, structures, and chemical bonds were fabricated at room temperature using plasma immersion ion implantation-deposition (PIII-D). The wettability of the films was investigated by contact angle measurements using several common liquids. Platelet adhesion experiments were conducted to examine the interaction of blood with the films in vitro and the activation of adherent platelets. The results show that the behavior of the platelets adhered on the a-C:H films is influenced by their structure and chemical bond, and it appears that protein interaction plays a key role in the activation of the adherent platelets.

Blood Platelets↗
PubMed2003

Infrared spectral comparison of 5-aminolevulinic acid and its hexyl ester.

5-aminolevulinic acid (ALA) and its hexyl ester (ALA-H) are bioorganic molecules, now used as drugs in the study and clinical application of photodynamic therapy (PDT). Their infrared spectra were reported in first time here. The spectral characteristic was found well correlated to their structure feature. The strong peaks of C=O, C-H(2) and O-H band were shown in ALA spectrum. While in case of ALA-H, besides the vibration modes of C=O and CH(2) the additional CH(3) infrared peaks appeared, which correspond with their structural difference. Thus the infrared spectrum could be used to detect and distinguish ALA and ALA-H, which have potential for the mechanism study of ALA and ALA-H based PDT in biological system. Using the infrared spectrum as the probe, the thermal effect on structure stability was detected. Below the temperature of 80 degrees C, the ALA and ALA-H are thermally stable in structure. When temperature reached 120 degrees C, the serious structure breaking (thermal decomposition) happened for both ALA and ALA-H.

Aminolevulinic Acid↗
PubMed2003

A secure communication scheme based on the phase synchronization of chaotic systems.

Phase synchronization of chaotic systems with both weak and strong couplings has recently been investigated extensively. Similar to complete synchronization, this type of synchronization can also be applied in secure communications. We develop a digital secure communication scheme that utilizes the instantaneous phase as the signal transmitted from the drive to the response subsystems. Simulation results show that the scheme is difficult to be broken by some traditional attacks. Moreover, it operates with a weak positive conditional Lyapunov exponent in the response subsystem.

Journal Article↗
PubMed2003

In vitro susceptibility of six fluoroquinolones against invasive Streptococcus pneumoniae isolated from 1996 to 2001 in Taiwan.

A total of 331 invasive nonduplicated Streptococcus pneumoniae isolates from three sampling periods during 1996 to 2001 were tested for susceptibility to recently developed fluoroquinolones. Five major serotypes, 23F, 6B, 14, 19F, and 3, were frequently encountered in this collection. Penicillin nonsusceptible isolates constituted 52.9% from 1996 to 1997, 61.6% from 1998 to 1999, and 60.0% from 2000 to 2001. Fifty-seven percent of the isolates were susceptible to cefotaxime, 56.5% to ceftriaxone, 54.1% to cefepime, and 52.6% to cefuroxime. Macrolide-susceptible isolates constituted less than 14% of the total sample, and no vancomycin-resistant isolates were detected. For fluoroquinolones, MIC90 was lowest for gemifloxacin (MIC90 = < or = 0.12 microg/ml), followed by moxifloxacin (MIC90 = 0.25 microg/ml), gatifloxacin (MIC90 = 0.5 microg/ml), sparfloxacin (MIC90 = 0.5 microg/ml), levofloxacin (MIC90 = 1 microg/ml), and ciprofloxacin (MIC90 = 2 microg/ml). All isolates were susceptible to sparfloxacin, levofloxacin, gatifloxacin, and gemifloxacin apart from one isolate (0.3%), which was simultaneously resistant to sparfloxacin, levofloxacin, and gatifloxacin. Mutations at the positions S81F of GyrA and D435N and I460V of ParC were detected for this multiple drug resistant isolate. The in vitro results suggest that recently developed fluoroquinolones are very effective against invasive S. pneumoniae isolates in Taiwan. Nevertheless, emerging fluoroquinolone resistance should be acknowledged and clinicians alerted. Surveillance should be carried out to monitor any changes in antibiotic resistance of S. pneumoniae.

Adult↗
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

Characterization of surface oxide films on titanium and bioactivity.

Biological properties of titanium implant depend on its surface oxide film. In the present study, the surface oxide films on titanium were characterized and the relationship between the characterization and bioactivity of titanium was studied. The surface oxide films on titanium were obtained by heat-treatment in different oxidation atmospheres, such as air, oxygen and water vapor. The bioactivity of heat-treated titanium plates was investigated by immersion test in a supersaturated calcium phosphate solution. The surface roughness, energy morphology, chemical composition and crystal structure were used to characterize the titanium surfaces. The characterization was performed using profilometer, scanning electronic microscopy, ssesile drop method, X-ray photoelectron spectroscopy, common Bragg X-ray diffraction and sample tilting X-ray diffraction. Percentage of surface hydroxyl groups was determined by X-ray photoelectron spectroscopy analysis for titanium plates and density of surface hydroxyl groups was measured by chemical method for titanium powders. The results indicated that heat-treatment uniformly roughened the titanium surface and increased surface energy. After heat-treatment the surface titanium oxide was predominantly rutile TiO(2), and crystal planes in the rutile films preferentially orientated in (1 1 0) plane with the highest density of titanium ions. Heat-treatment increased the amount of surface hydroxyl groups on titanium. The different oxidation atmospheres resulted in different percentages of oxygen species in TiO(2), in physisorbed water and acidic hydroxyl groups, and in basic hydroxyl groups on the titanium surfaces. The immersion test in the supersaturated calcium phosphate solution showed that apatite spontaneously formed on to the rutile films. This revealed that rutile could be bioactivated. The analyses for the apatite coatings confirmed that the surface characterization of titanium has strong effect on bioactivity of titanium. The bioactivity of the rutile films on titanium was related not only to their surface basic hydroxyl groups, but also to acidic hydroxyl groups, and surface energy. Heat-treatment endowed titanium with bioactivity by increasing the amount of surface hydroxyl groups on titanium and its surface energy.

Journal Article↗
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↗