Biomedical subjects

W C Wang

Publications and source records attributed to W C Wang.

At least 55 records · Page 3Linked to original sources

PubMed1999

Heterogeneous Helicobacter pylori isolates from H. pylori-infected couples in Taiwan.

Helicobacter pylori strain diversity was investigated in 55 H. pylori seropositive couples in Taiwan in biopsy samples from the antrum and corpus. Two DNA typing methods were used to characterize 90 isolates from 25 couples. In only 1 of the 25 couples was the same strain colonized from both partners. Comparison of isolates from 2 sites in each of 40 patients showed that 9 pairs were distinct but might be related. Peptic ulcer occurred in 77.8% of these 9 patients compared with 29% of 31 patients with the same predominant strain in 2 biopsies (P=.025). Random amplified polymorphic DNA and sequence analyses of 2 closely related isolates from 1 patient support the hypothesis that development of genetic diversity of H. pylori results from horizontal genetic exchange during long-term colonization of mixed bacterial populations.

Adult↗

PubMed1999

Expression, crystallization and preliminary X-ray diffraction studies of N-carbamyl-D-amino-acid amidohydrolase from Agrobacterium radiobacter.

The Agrobacterium radiobacter CCRC 14924 N-carbamyl-D-amino-acid amidohydrolase, the enzyme used for production of D-amino acids, was overexpressed in Escherichia coli JM109. The expressed protein was crystallized by vapour diffusion using lithium sulfate as precipitant. It crystallizes in space group P21 with unit-cell parameters a = 69.8, b = 67.9 and c = 137.8 A and beta = 96.4 degrees. There are four molecules per asymmetric unit. Crystals diffract to 2.8 A resolution using a rotating-anode source at cryogenic (113 K) temperatures.

Amidohydrolases↗

PubMed1999

Silent cerebral infarcts in sickle cell anemia: a risk factor analysis. The Cooperative Study of Sickle Cell Disease.

BACKGROUND: Silent infarcts have been reported in 17% of young patients with sickle cell disease and are associated with impaired performance on standardized psychometric tests. Risk factors for the development of these lesions have not been identified. METHODS: Investigators in the Cooperative Study of Sickle Cell Disease performed a brain magnetic resonance imaging scan on sickle cell anemia patients age 5.9 years and older who had been followed according to the protocols of the Cooperative Study since birth. Individuals with a known history of cerebrovascular accident were excluded from this analysis. Patients with and without silent infarctions were compared with regard to clinical and laboratory parameters. RESULTS: The study sample included 42 patients (18.3%) with silent infarcts. Patients who had silent infarcts were significantly more likely to have a clinical history of seizure and a lower painful event rate. Lower hemoglobin level, increased leukocyte count, elevated pocked red blood cell count, and SEN betaS globin gene haplotype were associated also with the presence of silent infarcts. There was no relationship between silent infarcts and platelet count, fetal hemoglobin level, reticulocyte percentage, serum aspartate aminotransferase level, total bilirubin concentration, blood pressure, growth parameters, or presence of alpha-thalassemia. A multivariate model for silent infarction identified the following as risk factors: low pain event rate, history of seizure, leukocyte count >/=11.8 x 10(9)/L, and the SEN betaS globin gene haplotype. CONCLUSIONS: Patients with risk factors for silent infarcts should be evaluated for cerebrovascular disease. If evidence of infarction is found, consideration must be given to therapeutic intervention. At present, the appropriate treatment has not been determined.

Adolescent↗

PubMed1999

Plastic microchip electrophoresis for analysis of PCR products of hepatitis C virus.

BACKGROUND: Electrophoresis on polymeric rather than glass microstructures is a promising separation method for analytical chemistry. Assays on such devices need to be explored to allow assessment of their utility for the clinical laboratory. METHODS: We compared capillary and plastic microchip electrophoresis for clinical post-PCR analysis of hepatitis C virus (HCV). For capillary electrophoresis (CE), we used a separation medium composed of 10 g/L hydroxypropyl methyl cellulose in Tris-borate-EDTA buffer and 10 micromol/L intercalating dye. For microchip electrophoresis, the HCV assay established on the fused silica tubing was transferred to the untreated polymethylmethacrylate microchip with minimum modifications. RESULTS: CE resolved the 145-bp amplicon of HCV in 15 min. The confidence interval of the migration time was <3.2%. The same HCV amplicon was resolved by microchip electrophoresis in <1.5 min with the confidence interval of the migration time <1.3%. CONCLUSION: The polymer microchip, with advantages that include fast processing time, simple operation, and disposable use, holds great potential for clinical analysis.

DNA, Viral↗

PubMed1998

Comparative studies on mammalian Hoxc8 early enhancer sequence reveal a baleen whale-specific deletion of a cis-acting element.

Variations in regulatory regions of developmental control genes have been implicated in the divergence of axial morphologies. To find potentially significant changes in cis-regulatory regions, we compared nucleotide sequences and activities of mammalian Hoxc8 early enhancers. The nucleotide sequence of the early enhancer region is extremely conserved among mammalian clades, with five previously described cis-acting elements, A-E, being invariant. However, a 4-bp deletion within element C of the Hoxc8 early enhancer sequence is observed in baleen whales. When assayed in transgenic mouse embryos, a baleen whale enhancer (unlike other mammalian enhancers) directs expression of the reporter gene to more posterior regions of the neural tube but fails to direct expression to posterior mesoderm. We suggest that regulation of Hoxc8 in baleen whales differs from other mammalian species and may be associated with variation in axial morphology.

Animals↗

PubMed1998

Patterns of HIV-1 evolution in individuals with differing rates of CD4 T cell decline.

Evolution of HIV-1 env sequences was studied in 15 seroconverting injection drug users selected for differences in the extent of CD4 T cell decline. The rates of increase of either sequence diversity at a given visit or divergence from the first seropositive visit were both higher in progressors than in nonprogressors. Viral evolution in individuals with rapid or moderate disease progression showed selection favoring nonsynonymous mutations, while nonprogressors with low viral loads selected against the nonsynonymous mutations that might have resulted in viruses with higher levels of replication. For 10 of the 15 subjects no single variant predominated over time. Evolution away from a dominant variant was followed frequently at a later time point by return to dominance of strains closely related to that variant. The observed evolutionary pattern is consistent with either selection against only the predominant virus or independent evolution occurring in different environments within the host. Differences in the level to which CD4 T cells fall in a given time period reflect not only quantitative differences in accumulation of mutations, but differences in the types of mutations that provide the best adaptation to the host environment.

Base Sequence↗

PubMed1998

A conserved aspartate is essential for FAD binding and catalysis in the D-amino acid oxidase from Trigonopsis variabilis.

To evaluate the possible contribution of Asp206 of Trigonopsis variabilis D-amino acid oxidase (DAO) to its flavin adenine dinucleotide (FAD) binding and catalytic function, six mutant enzymes were constructed by site-directed mutagenesis. Western immunoblot analysis revealed that a protein with an apparent molecular mass of about 39.2 kDa was present in the cell-free extracts of wild-type and mutant strains. Replacement of Asp206 with Leu, Gly, and Asn resulted in the loss of DAO activity and characteristic absorption spectrum for flavoenzyme, while the other mutant DAOs, Asp206Glu, Asp206Ser, and Asp206Ala, exhibited a similar spectral profile to that of wild-type enzyme and retained about 6-90% of the enzyme activity. These results suggested that Asp206 of T. variahilis DAO might play an important role in the binding of FAD.

Amino Acid Sequence↗

PubMed1998

Characterization of the C-terminal domain of Helicobacter pylori vacuolating toxin and its relationship with extracellular toxin production.

Helicobacter pylori vacuolating cytotoxin (VacA) induces gastric epithelial necrosis. Its C-terminal domain is hypothesized to be responsible for extracellular translocation of the mature cytotoxin. In this study, genetic-structural properties of VacA C-terminal domain and the level of cytotoxin secretion were investigated. Sau3AI-HaeIII restriction fragment length polymorphism (RFLP) analysis of the 1.1-kb PCR-amplified vacA fragment revealed 14 distinct combined patterns among 87 clinical isolates. Of the 4 popular groups (A-a, A-b, A-f, and B-a), A-a strains produced a higher level of the VacA protein than A-b strains and than A-f strains (P < 0.05). Sequence analysis and secondary structure prediction supported a beta-barrel structure that might act as a selective export channel like Iga beta-core of IgA proteases. Sequence differences in the predicted beta-barrel were present among strains of different RFLPs.

Amino Acid Sequence↗

PubMed1998

Differential expression and function of L-selectin on CD56bright and CD56dim natural killer cell subsets.

NK cells are the first line of defense against foreign cells, virally infected cells, and tumors. The mechanisms whereby NK cells accumulate in extralymphoid sites in response to pathogenic stimuli are not well understood. The L-selectin adhesion molecule (CD62L) plays a primary role in mediating the initial interaction of leukocytes with vascular endothelium, a crucial step in the extravasation of immune effector cells into tissues. In this report, we show L-selectin to be uniquely expressed on a subset of resting human NK cells (CD56bright). Notably, CD56bright NK cells expressed L-selectin at a higher density than all other peripheral blood leukocytes. NK activation by PMA, IL-2, IL-15, or TGF-beta down-regulated L-selectin on the CD56bright subset, while increased L-selectin levels were observed in both the CD56bright and CD56dim NK subsets in response to IL-12, IL-10, or IFN-alpha. Moreover, CD56bright NK cells bound with high efficiency to physiologic L-selectin ligands on peripheral lymph node high endothelial venules (HEV). In sharp contrast, CD56dim NK cells adhered poorly to HEV and were predominantly L-selectin- or expressed L-selectin only at low density. In CD56bright cells and a subpopulation of CD56dim cells, L-selectin ligation by mAb cross-linking activated lymphocyte function-associated Ag 1 (LFA-1), a second adhesion molecule required for leukocyte extravasation. LFA-1 was expressed on both NK subsets, although its density was constitutively higher on CD56dim cells. Taken together, evidence of differential expression of L-selectin and LFA-1 on CD56bright and CD56dim NK subsets strongly suggests unique migratory properties and functions of these cells during the early immune response to foreign pathogens.

3T3 Cells↗

PubMed1998

Fever-range hyperthermia enhances L-selectin-dependent adhesion of lymphocytes to vascular endothelium.

The L-selectin leukocyte adhesion molecule plays an important role in controlling leukocyte extravasation in peripheral lymph nodes and at sites of tissue injury or infection. Although febrile responses during infection and inflammation are associated with enhanced immune activity, the contribution of fever-range temperatures to controlling lymphocyte recruitment to tissues has not been previously examined. In this report we provide evidence that direct exposure of lymphocytes to fever-range temperatures (38-41 degrees C) in vitro for 9 to 24 h resulted in a >100% increase in L-selectin-dependent adhesion of these cells to lymph node high endothelial venules (HEV). Moreover, culture of lymphocytes under hyperthermia conditions markedly enhanced the ability of these cells to traffic in an L-selectin-dependent manner to peripheral lymph nodes, mesenteric lymph nodes, and Peyer's patches. In contrast, febrile temperatures did not increase LFA-1 function as assessed by measuring lymphocyte adhesion to ICAM-1-3T3 transfectants. Fever-range hyperthermia further did not increase L-selectin surface density on lymphocytes or L-selectin-dependent recognition of soluble carbohydrate substrates; however, a marked increase in ultrastructural immunogold-labeling of L-selectin was observed in response to thermal stimuli. These results suggest that elevated temperatures enhance L-selectin adhesion and/or avidity through the regulation of L-selectin conformation or organization in the plasma membrane. Finally, the observed thermal effects on L-selectin adhesion were attributed to soluble factors in the conditioned medium of heat-treated cells. Taken together, these data provide new insight into the potential physiologic role of the febrile response in enhancing lymphocyte recruitment to tissues through the regulation of L-selectin adhesion.

Cell Adhesion↗

PubMed1998

Malignant infantile osteopetrosis: otolaryngological complications and management.

OBJECTIVES: To inform otolaryngologists about upper airway obstruction requiring tracheotomy and other otolaryngological manifestations of malignant infantile osteopetrosis (MIOP) and to discuss pathophysiological features, management, and new treatment strategies in MIOP. DESIGN: Ongoing case series combined with a retrospective chart review. SETTING: International tertiary pediatric hospital. INTERVENTIONS: Patients with MIOP were initially referred for treatment and routine follow-up. Tracheotomy was performed to manage obstructive sleep apnea. Audiograms were also performed at regular intervals. RESULTS: The records of 9 patients were examined. The otolaryngological findings of hearing loss, obstructive sleep apnea (sometimes requiring tracheotomy), otitis media, and chronic osteomyelitis with facial fistulas were identified. CONCLUSIONS: Osteopetrosis is a rare condition caused by a failure of the osteoclast to resorb bone. This results in thickened dense, deformed, and easily fractured bone. As a result, growth failure, anemia, hypoplastic dentition, chronic infections, facial fistulas, blindness, hearing loss, nasal congestion, and upper airway obstruction may occur. The management of otolaryngological problems in a child with osteopetrosis is an important component in comprehensive care. To our knowledge, this study represents the largest case series of MIOP in the otolaryngology literature.

Face↗

PubMed1998

Abnormalities of the central nervous system in very young children with sickle cell anemia.

OBJECTIVE: To determine whether abnormalities of the CNS are present in very young children with sickle cell anemia. STUDY DESIGN: Thirty-nine children with hemoglobin SS between the ages of 7 and 48 months were examined with magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA). No child had a history of clinical stroke, although 3 had a history of seizures (2 neonatal). Twenty-one patients underwent developmental testing with the Bayley or McCarthy Scales. RESULTS: The overall prevalence of CNS abnormalities in asymptomatic children was 4 of 36 (11%, confidence interval 3, 26%). One patient had a silent infarct observed on MRI and a stenotic lesion on MRA; 3 other patients had stenotic lesions on MRA. The 3 patients who had a history of seizures all had lesions consistent with infarcts on MRI. Of the asymptomatic patients who had psychometric testing, 1 of 18 was developmentally delayed. One of 3 with a history of seizures had mild developmental delay. CONCLUSIONS: Very young children with sickle cell anemia (and no history of clinical stroke) have infarction in the brain and/or stenosis of major cerebral arteries, similar to those reported in older children. These findings indicate a need for larger studies to define the incidence of CNS lesions in this age group and to determine the need for early therapeutic intervention to prevent CNS sequelae of sickle cell disease.

Anemia, Sickle Cell↗

PubMed1998

The serum selenium concentrations in children and young adults: a long-term study during the Finnish selenium fertilization programme.

OBJECTIVE: To investigate the effects of the Finnish nationwide selenium (Se) fertilization programme on the Se status of the population. DESIGN AND SUBJECTS: Serum Se concentrations from 1985-1992 from 1568 healthy children and young adults in southwestern Finland were determined using direct electrothermal atomic absorption spectrometry. RESULTS: The mean concentration in young adults increased from 1.04 micromol/L in 1985 to 1.59 micromol/L in 1990. Children younger than 15 y had lower concentrations than adults, with an increase from 0.87 micromol/L in 1985 to 1.31 micromol/L in 1990. The younger the children, the lower the Se concentrations tended to be. At the age of about seven months no significant difference was noted between breast-fed and formula-fed infants. From 1991, when the amount of Se added to fertilizers was reduced and less foreign high-Se cereal was imported, the Se concentrations decreased in all age groups. CONCLUSIONS: The nationwide Se supplementation programme has succeeded in elevating the Se intake and the serum Se concentrations in the Finnish population.

Adolescent↗

PubMed1998

Vacuolating toxin gene polymorphism among Helicobacter pylori clinical isolates and its association with m1, m2, or chimeric vacA middle types.

BACKGROUND: Helicobacter pylori vacuolating cytotoxin encoded by vacA plays an essential role in H. pylori-related pathogenesis. Specific vacA alleles are believed to be associated with increased virulence. Association among vacA polymorphism, vacA middle genotypes, and various H. pylori-related diseases was thus investigated. METHODS: Eighty-nine isolates from patients with various gastrointestinal diseases were examined for restriction fragment length polymorphism (RFLP) of the 2.0-kb polymerase chain reaction-amplified vacA middle region. Further genetic heterogeneity was assessed with ureA-ureB RFLP. RESULTS: Twenty-eight distinct vacA RFLPs were seen among 89 isolates. Each pattern was associated with one specific vacA middle genotype. The association of specific RFLPs with certain clinical manifestations was noted among six common groups. Further RFLP analysis of the 2.4-kb ureA-ureB segment from isolates in four popular vacA RFLPs showed high genetic variation. CONCLUSIONS: The vacA genetic polymorphism may be associated with different gastrointestinal diseases.

Bacterial Proteins↗

PubMed1998

Vacuolating toxin production in clinical isolates of Helicobacter pylori with different vacA genotypes.

A vacuolating cytotoxin encoded by vacA in Helicobacter pylori is known as a potential virulent determinant. The relationship between different vacA alleles, vacuolating ability, and H. pylori-related diseases was investigated. Genetic analysis of 119 isolates from Taiwanese patients revealed that 104 strains were s1a/m2, 13 strains were characterized as the s1a/m1T type, which was more homologous to the s1a/m1 strains, and 2 were characterized as the s1a/m1Tm2 chimeric type. Production of high-grade cytotoxin among 11 strains with s1a/m1T was higher (72.7%) than among 66 strains with s1a/m2 (21.2%) (P < .01). Peptic ulcer occurred in 76.9% of 13 patients with s1a/m1T strains compared with 46.2% of 104 patients with s1a/m2 strains (P < .05). These results suggest that s1a/m1T strains are associated with increased cytotoxic activity and higher ulcer prevalence than are s1a/m2 strains.

Amino Acid Sequence↗

PubMed1998

Rasch analysis of distractors in multiple-choice items.

In order to apply the Rasch model to multiple-choice items, incorrect responses to distractors are usually aggregated to a single category. In doing so, information of individual distractors disappears. In this paper, a Rasch-type analysis is proposed where one parameter is assigned to each distractor. The information is thus preserved. The proposed distractor model can be applied to investigate the performance of distractors, which is useful for item revision. This model is a necessary condition of the Rasch model, that is, fitting the distractor model will fit the Rasch model, but not vice versa. The results of a small simulation study show that parameter recovery of the distractor model is very satisfactory. A real data set of twenty multiple-choice items was analyzed. Some items were found to fit the Rasch model rather than the distractor model. It is this diagnostic value that makes the distractor model suitable for multiple-choice items.

College Admission Test↗

PubMed1998

Measuring individual differences in change with multidimensional Rasch models.

Item response models have been developed to explore change measurement, including those proposed by Fischer and his colleagues (e.g., Fischer & Pazer, 1991; Fischer & Ponocny, 1994), Andersen (1985) and Embretson (1991). In this article, we propose another multidimensional Rasch model, the multidimensional random coefficient multinomial logit (MRCML) model (Adams, Wilson, & Wang, 1997). All these models are briefly reviewed and compared. The MRCML can be applied to not only polytomous items but also investigation of variations in item difficulties. Based on variations in difficulties across occasions and items, five kinds of models are proposed. Some simulation studies were conducted to examine parameter recovery of the MRCML model under various testing situations. All the parameters were recovered very well. A real data set was analyzed to show applications of the MRCML to measuring individual differences in change.

Australia↗

PubMed1997

Expression, purification, and characterization of a murine CD4 fragment containing the first two N-terminal domains.

CD4 is a membrane glycoprotein on T lymphocytes that binds to the same peptide:major histocompatibility complex (MHC) class II molecules recognized by the antigen-specific T cell receptor (TcR). Recent evidence supports the importance of coaggregation of CD4 and TcR for effective T cell activation. Here, we report that a transfected Chinese hamster ovary (CHO) cell line expressing a murine CD4 fragment containing the first two N-terminal domains secretes both monomeric molecules and disulfide-linked multimers. Elimination of the predicted N-linked glycosylation site at residue 161 that is next to the fourth cysteine does not affect the formation of interchain disulfide bonds. N-Terminal amino acid sequencing of the purified CD4 fragment demonstrates that the leader signal sequence is properly cleaved off the expressed protein. Circular dichroism studies suggest that both monomeric and disulfide-linked proteins are folded as primarily beta-sheet.

Animals↗