Biomedical subjects

Wei Chen

Publications and source records attributed to Wei Chen.

At least 343 records · Page 19Linked to original sources

PubMed2004

Supra-physiological membrane potential induced conformational changes in K+ channel conducting system of skeletal muscle fibers.

The effects of a supra-physiological membrane potential shock on the conducting system of the delayed rectifier K(+) channels in the skeletal muscle fibers of frogs were studied. An improved double Vaseline gap voltage clamp technique was used to deliver stimulation pulses and to measure changes in the channel currents. Our results showed that a single 4 ms, -400 mV pulsed shock can cause a reduction in the K(+) channel conductance and a negative-shift of the channel open-threshold. Following the Boltzmann theory of channel voltage-dependence, we analyzed the shock-induced changes in the channel open-probability by employing both two-state and multi-state models. The results indicate a reduction in the number of channel gating particles after the electric shock, which imply possible conformational changes at domains that gate the channels proteins. This study provides further evidence supporting our hypothesis that high intensity electric fields can cause conformational changes in membrane proteins, most likely in the channel gating system. These structural changes in membrane proteins, and therefore their dysfunctions, may be involved in the mechanisms underlying electrical injury.

Animals↗

PubMed2004

Evidence of electroconformational changes in membrane proteins: field-induced reductions in intra membrane nonlinear charge movement currents.

Experimental results are presented to show that a pulsed, intensive membrane potential can reduce intra membrane, nonlinear charge movement currents, which are the voltage-sensors in the voltage-dependent membrane proteins and in the excitation-contraction coupling of skeletal muscle fibers. The results indicate a possible mechanism involved in electrical injury: dysfunctions of the voltage-dependent membrane proteins caused by electroconformational damages in their voltage-sensors.

Animals↗

PubMed2004

Tear film and ocular surface tests in animal models of dry eye: uses and limitations.

Many ocular surface tests have been developed for the clinical diagnosis of keratoconjunctivitis sicca, and several have been used to 'validate' animal models of Sjogren's and non-Sjogren's dry eye. However, many of these tests themselves have not been systematically studied or standardized, and yet their use in animal models of dry eye is common. This review provides a rational approach and systematic review of the tear film and ocular surface tests described in the literature that may be applicable to the current animal models of dry eye, with particular emphasis on their limitations, along with some suggestions regarding their standardization and applications in eye research.

Animals↗

PubMed2004

The beta(2)-adrenergic receptor Arg16-gly polymorphism and interactions involving beta(2)- and beta(3)-adrenergic receptor polymorphisms are associated with variations in longitudinal serum lipid profiles: the Bogalusa Heart Study.

We examined the effects of combined genotypes of the beta(2)-adrenergic receptor (AR) Arg(16)-Gly and beta(3)-AR Trp(64)-Arg polymorphisms on longitudinal serum total (T-C) and low-density lipoprotein cholesterol (LDL-C) profiles in 1,198 subjects examined multiple times (6,488 observations) from 1973 to 1996 in the Bogalusa Heart Study, at ages from 4.5 to 38 years. Within 5-year age groups, T-C was significantly (P <.05) higher in beta(2)-AR Arg(16)/Arg(16) homozygotes than in Gly(16) carriers among those 4 to 8 (171.4 +/- 30.0 v 161.5 +/- 27.7 mg/dL), 9 to 13 (167.7 +/- 28.6 v 162.4 +/- 27.4 mg/dL), and 14 to 18 (158.8 +/- 29.6 v 154.7 +/- 27.5 mg/dL) years of age, but not in those 19 to 23, 24 to 28, 29 to 33, or 34 to 38 years of age. The beta(3)-AR polymorphism was not associated with variation in either T-C or LDL-C. In multilevel polynomial growth curve models, the combination of the beta(2)-AR Arg(16)/Arg(16) genotype with either the beta(3)-AR Arg(64)/Arg(64) or Trp(64)/Arg(64) genotypes, denoted AA/AX, was associated with variation in longitudinal T-C (P <.01) and LDL-C (P <.01) profiles. The association between combined beta(2)/beta(3)-AR genotype and lipid profiles differed among race/sex groups, being most marked in black females, in whom the AA/AX combination was associated with higher T-C and LDL-C profiles across all ages. In White males, the AA/AX combination was most strongly associated with higher lipids in adults. In black males and white females, lipid profiles differed little between genotype groups. Our findings suggest that the beta(2)-AR Arg(16)-Gly genotype influences T-C and LDL-C levels in an age-specific manner, that it may interact with beta(3)-AR Trp(64)-Arg genotypes to influence longitudinal T-C and LDL-C profiles, and that the effect of combined beta(2)/beta(3)-AR genotypes on T-C and LDL-C profiles may differ among race/sex groups.

Age Factors↗

PubMed2004

A human CR1-like transcript containing sequence for a binding protein for iC4 is expressed in hematopoietic and fetal lymphoid tissue.

Primate immune adherence receptors are erythrocyte complement receptors (E-CR) that favorably influence the clearance of circulating immune complexes (IC). The human E-CR is the type one complement receptor (CR1), most commonly expressed as a 220 kDa protein containing 30 short consensus repeats (SCRs). The chimpanzee E-CR is a 75 kDa protein composed of eight SCRs, and is encoded by an ortholog of human CR1-like (CR1L), a genetic element related to CR1. Human CR1L was previously identified from genomic clones that predict exons for seven SCRs, and there have been no reports of CR1L expression. The purpose of this study was to determine if human CR1L is expressed. Amplification of human bone marrow cDNA using primers specific for CR1/CR1L yielded a product similar to chimp CR1L encoding sequence. The first 6.5 SCRs matched 100% with the predicted human CR1L sequence, while the second half of SCR 7 was homologous to the comparable chimp CR1L sequence but with a stop codon. Expression in COS-7 cells yielded a human CR1L protein of approximately 50 kDa that exhibited binding specificity for iC4 but not for iC3. Neither northern nor western blot analysis of human bone marrow revealed the presence of the CR1L transcript or protein. However, northern blot analysis of various other lymphoid tissue identified a candidate CR1L transcript in human fetal liver. PCR amplification of a cDNA panel of human fetal tissue confirmed the presence of the CR1L transcript in fetal liver, and to a lesser extent in fetal spleen and thymus. Thus, expression of the CR1L transcript appears to be limited to hematopoietic and fetal lymphoid tissue.

Amino Acid Sequence↗

PubMed2004

Adult tinea capitis due to Trichophyton violaceum in China.

Tinea capitis is rare in adults. We report a case of adult tinea capitis due to Trichophyton violaceum in China. The female patient was immunosuppressed with prednisone due to the underlying disease of vulgaris pemphigus and was treated successfully with terbinafine. We also reviewed published cases of adult tinea capitis in China and compared these data with the characteristics of published cases in other regions in the world.

Antifungal Agents↗

PubMed2004

Molecular typing study of the Microsporum canis strains isolated from an outbreak of tinea capitis in a school.

Tinea capitis is a dermatophyte infection of the scalp that occurs most often in prepubescent children. Tinea capitis may be transmitted by shared use of contaminated hairbrush, by contact with fomites or by direct physical contact with an infected person. Occasionally, outbreak of tinea capitis would happen under some special conditions. Last year, we found an outbreak of tinea capitis in a school due to Microsporum canis. In epidemiological study, we performed the prevalence survey to all of the exposed persons by physical examinations and mycological laboratory tests, including KOH preparation and fungal cultures. We also investigated the environment in the school. In molecular typing study of the M. canis isolated from patients and the environment, random primer amplification polymorphic DNA (RAPD) method, the specific amplification of subrepeat element in the ribosomal DNA nontranscribed spacer (NTS), and the analysis of DNA sequence in the intertranscribed spacer (ITS) of rDNA were performed. The total number of exposed children was seventy-one, among them forty-two were attacked by tinea capitis. The ratio between boy and girl was 13:1. The ages of the patients was ranged from 3.5 years old to 10 years old. Four patients bred cat or dog as pet. Most patients appeared noninflammatory type of tinea capitis and several patients were inflammatory type. Under microscopic examination the invaded hair were all ectothrix. The pathogens isolated from these patients were M. canis. And we also isolated M. canis from the carpet and the pillowcase in the school. The patterns of total strains of M. canis in the RAPD method and PCR amplification of the rDNA NTS region study were identical, and the isolates from patients and the environment contained the same DNA sequences in the ITS region. The outbreak of tinea capitis was caused by M. canis. The M. canis isolated from patients and from the environment were probably the same origin.

Child↗

PubMed2004

Monitoring of gene expression profiles and isolation of candidate genes involved in pollination and fertilization in rice ( Oryza sativa L.) with a 10K cDNA microarray.

To monitor gene expression profiles during pollination and fertilization in rice at a genome scale, we generated 73,424 high-quality expressed sequence tags (ESTs) derived from the green/etiolated shoot and pistil (0-5 h after pollination, 5hP) of rice, which were subsequently used to construct a cDNA microarray containing ca. 10 000 unique rice genes. This microarray was used to analyze gene expression in pistil unpollinated (UP), 5hP and 5DAP(5 days after pollination), anther, shoot, root, 10-day-old embryo (10EM) and 10-day-old endosperm (10EN). Clustering analysis revealed that the anther has a gene-expression profile more similar to root than to pistil and most pistil-preferentially expressed genes respond to pollination and/or fertilization. There are 253 ESTs exhibiting differential expression (e +/- 2-fold changes) during pollination and fertilization, and about 70% of them can be assigned a putative function. We also recovered 20 genes similar to pollination-related and/or fertility-related genes previously identified as well as genes that were not implicated previously. Microarray and real-time PCR analyses showed that the array sensitivity was estimated at 1-5 copies of mRNA per cell, and the differentially expressed genes showed a high correlation between the two methods. Our results indicated that this cDNA microarray constructed here is reliable and can be used for monitoring gene expression profiles in rice. In addition, the genes that differentially expressed during pollination represent candidate genes for dissecting molecular mechanism of this important biological process in rice.

Cluster Analysis↗

PubMed2004

Efficiency and current in a correlated ratchet.

We present a detailed study of the transport and the efficiency of a ratchet system in a periodic potential in the presence of correlated noises. The current and the efficiency of the system are investigated. It is found that, when the potential is spatially symmetric, the correlation between the two noises can induce a net transport. The efficiency shows many interesting features as a function of the applied force, the noise intensity, the external load, etc. The efficiency can be maximized as a function of noise intensity (or temperature), which shows that the thermal fluctuation can facilitate the efficiency of energy transformation.

Computer Simulation↗

PubMed2004

Important computer competencies for the nursing profession.

Nursing requires computer competencies. This study aimed at identifying those competencies required for the nursing profession in Taiwan. The Delphi technique was deployed in this study. In the Delphi questionnaires, computer competencies were sorted into seven domains: concepts of hardware, software, and networks; principles of computer applications; skills of computer usage; program design; limitations of the computer; personal and social issues; attitudes toward the computer. In three Delphi questionnaires, nursing informatics experts gave us their opinions on the importance of each computer competency for the nursing profession. The experts also designated when the competency should be cultivated. This study provides a comprehensive list for nursing professionals to check on their computer competence. The results of this study should also serve as good references for teachers and schools in designing related curriculums.

Adult↗

PubMed2004

Simplified methods for calculating cerebral metabolic rate of oxygen based on 17O magnetic resonance spectroscopic imaging measurement during a short 17O2 inhalation.

It has recently been shown that 17O magnetic resonance (MR) spectroscopic imaging at ultrahigh fields provides a reliable method for measuring CMRO2 during a short period of 17O2 gas inhalation. The mathematical (or complete) model used in the 17O MR method for calculating CMRO2 requires simultaneous measurements of multiple parameters including the concentration of H2 17O produced in the brain tissue from inhaled 17O2 gas (Cb), CBF, and the input function for the H2 17O concentration in the feeding artery (Ca). Both invasive and noninvasive measurements are involved in determining all of these parameters. In this article, two simplified methods are proposed and validated for calculating CMRO2 based on 17O MR measurement(s); the first method requires the measurements of Cb and CBF, but not Ca, and the second method only requires a single noninvasive measurement of Cb. The simplified methods were used to calculate CMRO2 in anesthetized rat brain, and the results were compared with those obtained using the complete model. The results from this work show (1) the validity of the simplified methods for quantifying CMRO2, and (2) the feasibility for establishing a completely noninvasive 17O MR approach for imaging CMRO2 in vivo.

Animals↗

PubMed2004

The Chinese Visible Human (CVH) datasets incorporate technical and imaging advances on earlier digital humans.

We report the availability of a digitized Chinese male and a digitzed Chinese female typical of the population and with no obvious abnormalities. The embalming and milling procedures incorporate three technical improvements over earlier digitized cadavers. Vascular perfusion with coloured gelatin was performed to facilitate blood vessel identification. Embalmed cadavers were embedded in gelatin and cryosectioned whole so as to avoid section loss resulting from cutting the body into smaller pieces. Milling performed at -25 degrees C prevented small structures (e.g. teeth, concha nasalis and articular cartilage) from falling off from the milling surface. The male image set (.tiff images each of 36 Mb) has a section resolution of 3072 x 2048 pixels ( approximately 170 micro m, the accompanying magnetic resonance imaging and computer tomography data have a resolution of 512 x 512, i.e. approximately 440 micro m). The Chinese Visible Human male and female datasets are available at http://www.chinesevisiblehuman.com. (The male is 90.65 Gb and female 131.04 Gb). MPEG videos of direct records of real-time volume rendering are at: http://www.cse.cuhk.edu.hk/~crc

Adult↗

PubMed2004

Therapeutic vaccination against Helicobacter pylori infection with attenuated recombinant Salmonella typhimurium urease B subunit and catalase in mice.

OBJECTIVE: To investigate the effects of oral immunization with attenuated recombinant Salmonella typhimurium urease B subunit and catalase vaccines in the treatment of Helicobacter pylori infection in a H. pylori infected mouse model. METHODS: Thirty C57BL/6 mice were randomized into three groups and challenged twice with oral administration of H. pylori within 3 days. Four weeks after the second challenge, the mice were immunized by oral administration of attenuated recombinant S. typhimurium urease B subunit (group A), attenuated recombinant S. typhimurium catalase (group B) or saline (group C), and all mice were killed 4 weeks later. The stomachs were collected for a rapid urease test, modified Giemsa staining and quantitative culture to observe the density of H. pylori, hematoxylin-eosin staining was performed to assess the presence of inflammation and lymphocytes from the spleen were used for the lymphoproliferation assay. RESULTS: The gastric H. pylori density of groups A, B and C was 1.58 x 10(5) c.f.u./g, 4.88 x 10(5) c.f.u./g and 1.92 x 10(6) c.f.u./g, respectively. The H. pylori density was significantly decreased in the therapeutic groups (P < 0.05). No significant inflammation was found in any group of mice. The lymphoproliferation assays of groups A and B were positive. CONCLUSION: Immunization with oral attenuated recombinant S. typhimurium urease B subunit and catalase vaccines is effective in reducing the density of H. pylori colonization.

Animals↗

PubMed2004

Inactivation of the Mgat1 gene in oocytes impairs oogenesis, but embryos lacking complex and hybrid N-glycans develop and implant.

Complex and hybrid N-glycans contain sugar residues that have been implicated in fertilization, compaction of the embryo, and implantation. Inactivation of the Mgat1 gene responsible for their synthesis is embryonic lethal, but homozygous mutant blastocysts are phenotypically normal due to the presence of maternal Mgat1 gene transcripts. To identify roles for complex and hybrid N-glycans in oogenesis and preimplantation development, the Mgat1 gene in oocytes was deleted by using a ZP3Cre recombinase transgene. All mutant oocytes had an altered zona pellucida (ZP) that was thinner than the control ZP, and they did not possess complex N-glycans but contained ZP1, ZP2, and ZP3 glycoproteins. Mutant eggs were fertilized, all embryos implanted, and heterozygotes developed to birth. However, mutant females had decreased fertility, yielded fewer eggs after stimulation with gonadotropins, and produced a reduced number of preimplantation embryos and less progeny than controls. About 25% of embryonic day 3.5 (E3.5) embryos derived from mutant eggs were severely retarded in development, even when they were heterozygous and expressed complex N-glycans. Thus, a proportion of Mgat1(-)(/)(-) oocytes were developmentally compromised. Surprisingly, mutant eggs also gave rise to Mgat1(-)(/)(-) embryos that developed normally, implanted, and progressed to E9.5. Therefore, complex or hybrid N-glycans are required at some stage of oogenesis for the generation of a developmentally competent oocyte, but fertilization, blastogenesis, and implantation may proceed in their absence.

Acyltransferases↗

PubMed2004

Optical properties and potential applications of doped semiconductor nanoparticles.

Recent studies on the optical properties, in particular, luminescence, of a variety of doped semiconductor nanoparticles are reviewed. The effects of quantum confinement, temperature and pressure on luminescent properties are discussed. In addition, electroluminescence, cathodoluminescence, magnetoluminescence and related applications involving doped semiconductor nanoparticles are presented. A new phenomenon, upconversion luminescence of doped nanoparticles, is reviewed and its potential applications are discussed. While more research efforts are necessary in order to fully understand the fundamentals and explore the great technological potential behind doped nanoparticles, recent results already show that this is a new and exciting field with applications in many areas. In particular, the emerging field of "spintronics", where spin states are exploited in analogy to conventional electronic states, is discussed and the advantages of using doped semiconductor nanoparticles are elucidated.

Electrochemistry↗

PubMed2004

Identification of 18S ribosomal DNA genotype of Acanthamoeba from patients with keratitis in North China.

PURPOSE: To identify the genotype of 18S ribosomal RNA gene (18S rDNA, Rns) of the Acanthamoeba strains isolated from patients with keratitis in northern China. METHODS: The genus-specific primers JDP1 and JDP2 were used for the amplification of the amplimer ASA.S1. With DNA PCR and sequencing, Rns genotypes were identified according to the DF3 sequence variances. RESULTS: Of all 26 DF3 sequences obtained from the 26 Acanthamoeba strains, 18 were unique (69.2%). Of those, 17 were Rns genotype T4 and one was Rns genotype T3. CONCLUSIONS: Most Acanthamoeba strains isolated from keratitis in northern China were Rns genotype T4. The results are in agreement with recent results in the literature.

Acanthamoeba↗

PubMed2004

Endovascular stent-graft repair of aortic dissection.

Between October 2000 and January 2002, 9 consecutive male patients with subacute or chronic aortic dissection underwent stent-graft placement. The indication for surgery was continuous pain or aneurysm development. One patient had a type A dissecting aortic aneurysm with a primary tear in the ascending thoracic aorta; the other 8 had type B dissection. Placement of an endovascular stent-graft was technically successful in 8 patients, and one underwent an open procedure for abdominal aortic fenestration. The entry site was sealed and the false lumen disappeared in 8 cases, and thrombosis of the false lumen was obtained. Rupture of an iliac artery dissecting aneurysm occurred in one patient 2 days after stent-graft placement; abdominal aortic fenestration with prosthetic replacement of the distal abdominal aorta was performed. One patient died of myocardial infarction 3 days after the stent-graft procedure. During a mean follow-up period of 7 months (1-16 months), one patient died of acute myocardial infarction at 11 months. It was concluded on the basis of these short-term results that endovascular repair of aortic dissection is a promising treatment, and abdominal aortic fenestration is a useful adjuvant procedure.

Adult↗

PubMed2004

Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents.

OBJECTIVE: To derive optimal body mass index (BMI) and waist circumference thresholds for children and adolescents, to predict risk factor clustering. DESIGN: Cross-sectional receiver operating characteristic curve analysis. SETTING: The Bogalusa Heart Study, a community-based study of cardiovascular disease risk factors in early life. PARTICIPANTS: A total of 2597 black and white children and adolescents, 5 to 18 years of age, who were examined between 1992 and 1994. MAIN OUTCOME MEASURES: The presence or absence of > or =3 age-adjusted risk factors (low high-density lipoprotein cholesterol level, high low-density lipoprotein cholesterol level, high triglyceride level, high glucose level, high insulin level, and high blood pressure) was predicted from age-adjusted BMI and waist circumference values. RESULTS: The areas under the receiver operating characteristic curves were significantly different from 0.5 for both BMI and waist circumference for all gender/race groups, ranging from 0.73 to 0.82. The optimal BMI thresholds were at the 53rd and 50th percentiles for white and black male subjects, respectively, and at the 57th and 51st percentiles for white and black female subjects, respectively. Similarly, the optimal waist circumference thresholds were at the 56th and 50th percentiles for white and black male subjects, respectively, and at the 57th and 52nd percentiles for white and black female subjects, respectively. The sensitivity and specificity at the thresholds were similar for all gender/race groups, ranging from 67% to 75%. CONCLUSIONS: The use of BMI and waist circumference for the prediction of risk factor clustering among children and adolescents has significant clinical utility. In this sample, race and gender differences in the optimal thresholds were minimal.

Abdomen↗