Search PubMed⌕ Search

Biomedical subjects

W Wang

Publications and source records attributed to W Wang.

At least 1,207 records · Page 67Linked to original sources
PubMed1995

3-Methyladenine and 7-methylguanine exhibit no preferential removal from the transcribed strand of the dihydrofolate reductase gene in Chinese hamster ovary B11 cells.

The removal of cylclobutane pyrimidine dimers from cellular DNA occurs preferentially in actively transcribed genes of cells subjected to ultraviolet radiation. In contrast, reports concerning the transcription-dependent repair of N-methylpurines formed in cellular DNA following exposure to methylating agents are quite conflicting, with some studies suggesting that no biased clearance of these lesions occurs and others indicating that preferential removal of these adducts transpires in active genetic loci. Even in the cases where no preferential clearance was demonstrated, a slight but statistically insignificant biased removal of N-methylpurines from the transcribed strand of active genes was often evident. We proposed that these results might be due to the preferential clearance of only one of the two principal N-methylpurines formed, 3-methyladenine, or to the source of the methylating species to which the cells were exposed. Therefore, we investigated the clearance of 3-methyladenine and 7-methylguanine as individual lesions from the amplified dihydrofolate reductase gene of Chinese hamster ovary cells, and we examined the gene-specific removal of N-methylpurines formed by several different methylating agents as well. We observed no biased clearance of 3-methyladenine toward the transcribed strand of the locus being examined. This result indicates that any minor gene-specific preferential repair that has been observed previously for N-methylpurines in toto--which actually reflects the removal of the predominant methylated purine 7-methylguanine--is not due to biased clearance of the transcription-inhibiting 3-methyladenine lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine↗
PubMed1995

Isolation and characterization of a mini-collagen gene encoding a nematocyst capsule protein from a reef-building coral, Acropora donei.

Genomic and cDNA clones of a mcol gene encoding mini-collagen (MCOL), a nematocyst capsule protein, have been isolated from a reef-building coral, Acropora donei (Anthozoa). The gene and its flanking regions, comprising 5382 bp and covering three exons and two introns, were sequenced. Exons 2 and 3 together have an open reading frame which can encode a MCOL of 176 amino acids (aa). The coral MCOL has all the characteristic regions present in the four hydra MCOL specified by the four mcol cDNA clones previously isolated from Hydra magnipapillata (Hydrozoa) by Kurz et al. [J. Cell Biol. 115 (1991) 1159-1169], including a central Gly-Xaa-Yaa region and flanking Pro-rich and Cys-repeat regions. This observation suggests that a mcol family is highly conserved in Anthozoa and Hydrozoa, and also that the characteristic regions present in MCOL are essential for the structure and function of these peptides.

Amino Acid Sequence↗
PubMed1995

Comodulation of cellular polyamines and proliferation: biomarker application to colorectal mucosa.

Polyamines are low molecular weight aliphatic amines required for normal cellular growth which are ubiquitously found in all living tissues. Polyamine biosynthesis is known to increase with mitogenesis, and elevated polyamine concentrations are found in hyperproliferative tissues. Quantitation of tissue polyamine content may thus provide a biochemical measure of proliferation, with potential biomarker application to the colonic mucosa where dysregulated epithelial proliferation is associated with cancer risk. This study was performed to validate polyamine analyses as a measure of cellular proliferation, and to preliminarily assess polyamine characteristics when applied to clinical samples. Using FHC, a human colonic epithelial cell line, for in vitro experimentation, deoxycholic acid or retinol was added to freshly passaged cultures to either stimulate or inhibit proliferation, respectively. Parallel cultures were then assayed for (1) proliferation by sulforhodamine B staining; and (2) polyamine content by a high-performance liquid chromatographic method. Deoxycholic acid stimulated, and retinol inhibited proliferation in dose-dependent fashion. Polyamine content, specifically the spermidine content and the spermidine/spermine ratio, also increased or decreased in response to culture with deoxycholic acid or retinol, respectively. Significant linear correlations between proliferation and spermidine (r = 0.858, P < 0.001), and with the spermidine/spermine ratio (r = 0.574, P < 0.05) were observed. When quantitative polyamine analyses were applied to human colonic specimens, replicate mucosal sampling revealed a high degree of intra-individual variability, indicating a heterogeneous distribution of polyamines within anatomically confined colonic segments. The results support a role for quantitative polyamine analyses as a correlative measure of colonic epithelial proliferation; however, intraindividual variability may limit the utility of colorectal biomarker measurements.

Biomarkers↗
PubMed1995

The use of plants for environmental monitoring and assessment.

This paper presents a critical review on phytotoxicity tests for environmental monitoring and assessment. Vascular macrophytes used in the laboratory testing are emphasized; algae are mentioned only for comparison. Several issues are discussed, including the rationale for and misconceptions about phytotoxicity tests, relation to regulation, status of phytotoxicity test protocols, advantages and disadvantages of phytotoxicity tests, and possible research directions. Aquatic and terrestrial macrophytes, along with algae, are essential components of ecosystems. Macrophytes are becoming more important for the monitoring and assessment of herbicides, effluents, and industrial chemicals. In the United States, Canada, and international organizations, phytotoxicity tests can be required for environmental monitoring and assessment in statutes such as Federal Insecticide, Fungicide, and Rodenticide Act; Toxic Substances Control Act; Water Quality Act; Canadian Pest Control Products Act; and Canadian Environmental Protection Act. Possible research directions for phytotoxicity tests are discussed relative to the role in regulations of industrial chemicals, effluents, hazardous waste sites, and pesticides.

Environmental Monitoring↗
PubMed1995

Alterations of lipid contents in blood, hepatocytes, and enterocytes in the early stage of acute liver failure induced by 90% hepatectomy in the rat.

Potential alterations in lipid metabolism in the early stage of acute liver failure are poorly elucidated. In the present study, acute liver failure was induced by subtotal hepatectomy (90%) in the rat in order to investigate early alterations in lipid contents in blood, hepatocytes, and enterocytes. Hypocholesterolemia and hypotriglyceridemia appeared 2 and 6 hr following subtotal hepatectomy. Plasma levels of high density lipoprotein-cholesterol were significantly lower in rats with acute liver failure than in controls, which may be associated with hypocholesterolemia. An increase in erythrocyte phospholipids and triglycerides was seen from 2 hr on after hepatectomy. The content of phospholipids and triglycerides was reduced in isolated enterocytes from the proximal small intestine and increased in enterocytes from the distal small intestine. Isolated hepatocytes from the remnant liver exhibited an increase in phosphatidylethanolamine and a decrease in phosphatidylinositol. Levels of enterocyte phosphatidylserine were elevated in both the proximal and the distal small intestine, while they diminished in the distal small intestine. Sphingomyelin content increased in the proximal small intestine. The recognition of lipid alterations in the intestine-liver-systemic circulation axis in the early stage of acute liver failure may be beneficial in improving the recovery from acute liver failure.

Animals↗
PubMed1995

Phylogeny of Muntiacus (Cervidae) based on mitochondrial DNA restriction maps.

Mitochondrial DNA restriction maps for 12 restriction enzymes of four species of muntjacs--Indian muntjac (M. muntjak), Gongshan muntjac (M. gongshanensis), black muntjac (M. crinifrons), and Chinese muntjac (M. reevesi)--were compared to estimate the phylogenetic relationships among them. Phylogenetic trees were constructed by both distance and parsimony methods. The two resulting trees share a similar topology, which indicates that the black muntjac and the Gongshan muntjac are closely related, followed by the Chinese muntjac; the Indian muntjac is the sister taxon to all the other muntjacs.

Animals↗
PubMed1995

Complete sequence of the RNA genome of human rhinovirus 16, a clinically useful common cold virus belonging to the ICAM-1 receptor group.

We report here the complete nucleotide sequence and predicted polyprotein sequence of HeLa cell-adapted human rhinovirus 16 (HRV16). This virus is more suitable than human rhinovirus 14 (HRV14) for clinical studies, and its growth and physical properties are favorable for biochemical and crystallographic analysis. The complete message-sense RNA genome of HRV16 is composed of 7124 bases, not including the poly(A) tail. An open reading frame, extending from base 626 to 7084 predicts a polyprotein containing 2152 amino acid residues. Comparison with other rhinovirus sequences shows HRV16 is much more representative of human rhinoviruses than HRV14. No apparent relationship was found between receptor group and amino acid sequence in VP1, the capsid protein bearing the binding site for the intercellular adhesion molecule-1 (ICAM-1) in both HRV14 and HRV16.

Base Sequence↗
PubMed1995

Effect of age on cardiac norepinephrine release in the female rat.

We previously demonstrated an age-related decline in K(+)-induced norepinephrine (NE) release from cardiac synaptosomes prepared from 6- and 24-month-old male F344 rats. The purpose of the present study was to determine if the age-related decrease in NE release seen in male F344 rats is also present in female F344 rats. K(+)-induced NE release was assessed in cardiac synaptosomes prepared from 6-, 12-, 18-, and 24-month-old male and female F344 rats. NE release was significantly greater in young male rats, compared to old male rats. However, no age-related decrease in NE release was observed in the female rats. In contrast to previous observations in male rats, raising extracellular [Mg2+], an inorganic Ca2+ channel blocker, reduced NE release to the same extent in all female ages. Omega-conotoxin, an organic Ca2+ channel blocker, also decreased NE release to the same extent in all female ages. These studies suggest that in contrast to aging male rats, cardiac adrenergic nerve terminals of aging female rats maintain their capacity to release NE.

Aging↗
PubMed1995

Event-related brain potentials differentiate priming and recognition to familiar and unfamiliar faces.

Recent studies from our laboratory have resulted in the identification of an event-related potential (ERP) correlate of a visual memory process. This memory process is reflected by a reduction in the voltage of the visual memory potential (VMP) to repeated pictures of unfamiliar faces compared to novel pictures of faces. In the current experiment we used unfamiliar and famous faces in an identical repetition priming paradigm, while the subject differentially recognized famous from non-famous faces. Significant differences in response times were obtained between primed and unprimed familiar faces, but not between primed and unprimed unfamiliar faces. The VMP was reduced to primed unfamiliar faces and significantly diminished to primed familiar faces compared to unprimed stimuli. Priming was typically reflected by a reduction of the VMP at the occipito-temporal region, whereas recognition resulted in a diminution of the VMP at both the occipito-temporal region and at the frontal region. These data support the involvement of differential neural systems for priming and recognition of visual stimuli.

Adult↗
PubMed1995

Lymphocyte subpopulations after extensive small bowel resection in the rat.

The increased risk of infection after massive intestinal resection (MIR) may be attributable to impaired nutrition, loss of intestinal lymphoid tissue, or both. This study examines whether MIR itself changes the immune cell populations in laboratory animals when nutritional status is preserved. The authors studied cellular immunity (lymphocyte subsets T4 and T8 and the T4:T8 ratio) and humoral immunity (IgG, IgM, IgA, and B lymphocytes) in the blood, spleen, and mesenteric lymph nodes of unresected Wistar rats (control group, n = 6) and of animals that underwent 80% bowel resection followed by 7 days of either oral feeding (resection-oral group, n = 6) or parenteral nutrition (resection-TPN group, n = 6). The increase in body weight was similar among all groups, and the levels of total protein, albumin, prealbumin, and immunoglobulin remained unchanged. All resected animals, irrespective of their feeding route, had significantly lower proportions of T4 and B lymphocytes and T4:T8 ratio in blood, T4 and T8 in mesenteric lymph nodes, and T4 and T4:T8 ratio in the spleen. The author's results suggest that removal of large amounts of lymphoid tissue along with the bowel during MIR might lead to inadequate immune response even when the nutritional status is preserved.

Animals↗
PubMed1995

Event related potentials during object recognition tasks.

In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified delayed matching-to-sample paradigm using a series of nonsense line drawings or faces as stimuli. In this experiment, we employed pictures of objects to determine whether the ERP can reflect the object recognition process and whether visual stimuli with a verbal label would result in a different topographic distribution from past topography obtained with visual stimuli without a verbal label. The results of this study suggest that the amplitude of the ERP component (c247) to repeated (primed) pictures of common objects was significantly decreased as compared to the unrepeated (unprimed) pictures; the latency for the peak of c247 was decreased for the repeated compared to the unrepeated, and the response time was also significantly shorter to the repeated picture stimuli than to the unrepeated; the topographical distribution of c247 was mainly located in the occipitotemporal areas of the brain. However, the source energy density map showed that the topographic involvement of the brain regions to the c247 was different in the matching and nonmatching trials.

Adult↗
PubMed1995

Hormonal control of rat adrenal phenylethanolamine N-methyltransferase. Enzyme activity, the final critical pathway.

To examine whether glucocorticoids control rat adrenal phenylethanolamine N-methyltransferase (PNMT) through gene transcription, the effects of hypophysectomy and acute and chronic glucocorticoid replacement on PNMT mRNA and enzymatic activity were determined. Glucocorticoid depletion through hypophysectomy did not alter PNMT mRNA, whereas PNMT activity declined to approximately 25% of normal. A single dose of ACTH (4 IU SC) rapidly induced PNMT mRNA, with a six-fold peak at 6 hours postinjection. The short-term rise in PNMT mRNA was accompanied by an increase in corticosterone and elevated levels of glucocorticoid receptor mRNA. Ribosomal loading experiments suggested that available PNMT mRNA was fully utilized for protein synthesis. However, PNMT activity did not increase commensurately. Chronic ACTH treatment (4 IU SC daily for 7 days) sustained elevated levels of glucocorticoid receptor mRNA but returned corticosterone to hypophysectomized levels and decreased PNMT mRNA to 50% of normal. Despite the decline in PNMT mRNA and its partial utilization for protein synthesis, PNMT enzymatic activity was fully restored. These findings indicate that glucocorticoids exert marked but complex influences on PNMT gene transcription. In addition, corticosteroids appear to posttranscriptionally regulate PNMT protein expression, underscoring the uncoupling between the expression of PNMT mRNA and active enzyme. Thus, glucocorticoid control of gene transcription and protein synthesis do not fully account for changes in PNMT expression, consistent with the previous observation that glucocorticoid control of PNMT proteolysis is also important in PNMT regulation and the potential for epinephrine biosynthesis.

Adrenal Glands↗
PubMed1995

Evaluating a ten questions screen for childhood disability: reliability and internal structure in different cultures.

This paper uses five strategies to evaluate the reliability and other measurement qualities of the Ten Questions screen for childhood disability. The screen was administered for 22,125 children, aged 2-9 years, in Bangladesh, Jamaica and Pakistan. The test-retest approach involving small sub-samples was useful for assessing reliability of overall screening results, but not of individual items with low prevalence. Alternative strategies focus on the internal consistency and structure of the screen as well as item analyses. They provide evidence of similar and comparable qualities of measurement in the three culturally divergent populations, indicating that the screen is likely to produce comparable data across cultures. One of the questions, however, correlates with the other questions differently in Jamaica, where it appears to "over-identify" children as seriously disabled. The methods and findings reported here have general applications for the design and evaluation of questionnaires for epidemiologic research, particularly when the goal is to gather comparable data in geographically and culturally diverse settings.

Bangladesh↗
PubMed1995

Use of relaxation agent doping to shorten very long spin-lattice relaxation times in a magic-angle turning experiment.

A practical method is described for measuring the principal values of the chemical shift tensors in compounds with very long proton spin-lattice relaxation times (T1). This technique involves shortening the effective proton T1. by mixing a compound of interest with another compound having a much shorter T1 value. The doped mixture, partly consisting of a monophasic glass, allows efficient intermolecular spin diffusion between the two compounds. Using a slow magic-angle turning (MAT) experiment, we have successfully used such mixtures to measure the principal values of the chemical shift tensors of all the carbons in dibenzofuran in just four days. Without using this technique the experimental time required for the pure compound would have been several months.

Benzofurans↗