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Biomedical subjects

W Yang

Publications and source records attributed to W Yang.

At least 487 records · Page 27Linked to original sources
PubMed1994

Exogenous nitric oxide inhibits proliferation of cultured vascular endothelial cells.

Cultured bovine fatal aortic endothelial cells (BAECs) were stimulated with nitric oxide (NO)-releasing vasodilators and NO gas-saturated solution, and changes in the cell proliferation were examined. Sodium nitroprusside (SNP) and nitroglycerin (NTG) shifted the growth curve downward, and inhibited 3H-thymidine incorporation by the ECs in a dose-dependent manner. Application of NO solution also reduced 3H-thymidine incorporation. SNP, NTG and NO solution increased the intracellular cGMP in BAECs. A cGMP analog, 8-bromo-cGMP, inhibited 3H-thymidine incorporation, and a guanylate cyclase inhibitor, methylene blue, almost completely blocked the inhibitory effect of SNP and NTG on 3H-thymidine incorporation. These findings suggest that exogenous NO inhibits EC proliferation, and that intracellular cGMP is involved in the inhibitory effect of NO.

Animals↗
PubMed1994

Regulation of the plasma membrane type III phosphatidylinositol 4-kinase by positively charged compounds.

The effects of positively charged compounds on a plasma membrane, type III phosphatidylinositol 4-kinase were studied. To determine whether the enzyme would respond differently to the compounds in a membrane-associated versus a soluble state, both the plasma membrane and solubilized (released by 0.01% (v/v) Triton X-100) PI 4-kinase were used. Spermidine, spermine, polylysine, cardiotoxin, melittin, and histone stimulated the solubilized PI 4-kinase but had little effect on or weakly stimulated the membrane-associated PI 4-kinase. Polyarginine inhibited membrane-associated PI 4-kinase 75% and inhibited the solubilized PI 4-kinase 30%, indicating that charge alone was not sufficient for activation. Polyarginine also eliminated the activation of the solubilized PI 4-kinase by a PI 4-kinase activator protein, PIK-A49. Calmodulin, a common calcium-binding protein, at micromolar levels strongly inhibited solubilized PI 4-kinase activity but did not inhibit membrane-associated PI 4-kinase activity. The inhibition of the solubilized PI 4-kinase by calmodulin was calcium independent. Calcium alone (1 microM-0.1 mM) inhibited PI 4-kinase activity only slightly (< 30%). The differential effects of the positively charged compounds on the solubilized and membrane-associated PI 4-kinase were not due to substrate availability because both enzymes were assayed in the presence of excess PI (0.6 mM) and 0.3% (v/v) Triton X-100. The data suggest that positively charged compounds affected the enzyme activity not only by interacting with the substrates or products of the reaction but also by interacting with the PI 4-kinase or regulatory components in the plasma membrane.

1-Phosphatidylinositol 4-Kinase↗
PubMed1994

Identification of the GABAA receptor subtype mRNA in human pancreatic tissue.

Evidence suggests a physiological role of the GABAA receptor in the pancreas. Clinically, an autoimmune reaction involving the GABA biosynthesizing enzyme, glutamic acid decarboxylase has been implicated in the development of insulin-dependent diabetes mellitus. To determine the subtypes of GABAA receptor expressed in human pancreas, we analyzed, with the use of the reverse-transcription/polymerase chain reaction technique human pancreatic tissue for the presence of GABAA receptor subunits alpha 1-6, beta 1-3, and gamma 1-2 transcripts. Unlike brain tissue, pancreatic tissue only expresses the alpha 2, beta 3 and gamma 1 subunits. Our results provide evidence of a specific GABAA receptor subtype expressed in human pancreatic tissue.

Base Sequence↗
PubMed1994

Purification of a recombinant Schistosoma japonicum antigen homologous to the 22-kDa membrane-associated antigen of S. mansoni, a putative vaccine candidate against schistosomiasis.

We describe the cDNA cloning, overproduction and purification of a 22.6-kDa antigen from the human blood fluke Schistosoma japonicum. A 777-bp cDNA (C32) was isolated from a S. japonicum lambda ZAPII cDNA expression library immuno-screened with hyperimmune rabbit serum (HRS) raised against soluble adult S. japonicum proteins. The open reading frame of C32 encodes a protein of 191 amino acids (aa) which exhibits 71% identity to a 22.6-kDa membrane-associated antigen of S. mansoni, a putative vaccine candidate for schistosomiasis. We have identified a sequence motif known as an EF-hand calcium-binding domain in both the S. japonicum and S. mansoni aa sequences, suggesting that the 22.6-kDa antigens are able to bind Ca2+. Further, we have, for the first time, obtained the 22.6-kDa antigen in purified, non-denatured, recombinant form, and in sufficient quantity to assess the protective value of the molecule in vaccination/challenge experiments. This was achieved by synthesizing the schistosome antigen with a short polyhistidine tag fused to the N-terminus which was then used for subsequent affinity purification. The recombinant protein was purified under non-denaturing conditions using nickel-chelate affinity chromatography.

Amino Acid Sequence↗
PubMed1994

Cytotoxicity potential of surfactant mixtures evaluated by primary cultures of rabbit corneal epithelial cells.

The use of in vitro cytotoxicity assays as potential alternatives in assessing ocular irritation of surfactant mixtures was evaluated in a primary culture system of rabbit corneal epithelial cells. Two groups of surfactant mixtures, each with the same surfactant components in varying proportions, were studied. Cytotoxicity was determined by lactate dehydrogenase (LDH) enzyme leakage and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) dye reduction in the cell culture system. There was a good correlation between the cytotoxicity in vitro and the reported Draize eye irritation data within each group of the surfactant mixtures studied.

Animal Testing Alternatives↗
PubMed1994

Regulation of phosphatidylinositol 4-kinase by the protein activator PIK-A49. Activation requires phosphorylation of PIK-A49.

PIK-A49 is a 49-kDa soluble protein that was isolated as an activator of the plasma membrane phosphatidylinositol (PI) 4-kinase from carrot cells (Yang, W., Burkhart, W., Cavallius, J., Merrick, W. C., and Boss, W. F. (1993) J. Biol. Chem. 268, 392-398). PIK-A49 is a multifunctional protein that binds and bundles F-actin and has translational elongation factor-1 alpha activity. In this paper, we have investigated the mechanism of activation of PI 4-kinase by PIK-A49. PIK-A49 decreased the Km of PI 4-kinase for ATP from 0.40 to 0.19 mM. GTP and GDP, which affect the elongation factor-1 alpha function of the protein, inhibited the activation of PI 4-kinase by PIK-A49. Phosphorylation of purified PIK-A49 by a calcium-dependent protein kinase enhanced activation of PI 4-kinase. When dephosphorylated by alkaline phosphatase, PIK-A49 no longer activated PI 4-kinase; however, rephosphorylation of PIK-A49 by calcium-dependent protein kinase fully restored activation. Western blots using anti-PIK-A49 serum showed that PIK-A49 was associated with the plasma membrane and the F-actin fraction isolated from plasma membranes, indicating that PIK-A49 would be in a position to regulate plasma membrane PI 4-kinase. Based on these data, we propose a mechanism for feed-forward regulation of polyphosphoinositide biosynthesis in response to increases in cytosolic calcium.

1-Phosphatidylinositol 4-Kinase↗
PubMed1994

Laminar flow stimulates ATP- and shear stress-dependent nitric oxide production in cultured bovine endothelial cells.

Based on the fact that nitric oxide (NO) production is associated with changes in intracellular cGMP levels and is selectively inhibited by N omega-methyl L-arginine (L-NME), we investigated the shear stress dependency of NO production in endothelial cells (ECs) from its cGMP responses to various shear stress loads. Cultured fetal bovine aortic ECs treated with a phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX; 1 mM), were exposed to a laminar flow of Krebs buffer solution for 5 minutes in a parallel-plate flow chamber and examined for changes in intracellular cGMP levels by radioimmunoassay using an [125I] cGMP kit. Application of flow increased the cGMP levels. The increase was significant in the presence of extracellular ATP (1 microM)(control, 286.1 +/- 43.6; flow, 506.5 +/- 44.9 fmol/10(7) cells; p < 0.001), but not in its absence (control, 256.6 +/- 60.6; flow, 301.5 +/- 91.4 fmol/10(7) cells; N.S.). The cGMP levels increased significantly as the magnitude of shear stress applied increased. Treatment of ECs with a specific inhibitor of NO production, L-NMA (200 microM), completely inhibited the flow-induced increase in cGMP, and L-arginine reversed the L-NMA-induced inhibition, indicating that the increase in cGMP was due to NO produced by the flow. The flow-induced increase in NO production was markedly suppressed when extracellular Ca++ was chelated by adding EGTA to the perfusate. These findings suggest that flow stimulates NO production to increase cGMP levels shear stress-dependently in ECs and that extracellular Ca++ and ATP modulate the effects of flow.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Pinhole skeletal scintigraphic manifestations of Tietze's disease.

Tietze's disease (TD) is a self-limited, non-specific, inflammatory condition of the upper costochondral junction (CCJ). Unlike in many other skeletal diseases, radiography plays a relatively minor role in TD because radiographic changes are frequently obscured by physiological costochondral calcifications. Bone scanning is a sensitive test for TD, but its specificity is low. The present study has been conducted to assess prospectively whether pinhole scintigraphy (PS) can enhance diagnostic specificity in TD. Both planar and PS bone images were obtained in seven ribs of five patients with TD. Scans alterations were analyzed and compared with the radiographic findings. Planar scans showed "hot" areas in the region of the CCJ in all seven ribs, these hot areas lacking textural patterns. However, the magnified PS images of the CCJ showed two characteristic uptake patterns: drumstick-like uptake in acute cases and C- or inverted C-shaped uptake in chronic cases. Radiographically, chondritic sclerosis could be seen when physiological chondral calcifications were minimal or absent, but was observed when the calcification was prominent. The correlation of PS and radiographic findings revealed that C- or inverted C-shaped uptake indeed faithfully reflected the inflammatory process in the CCJ, the medial border of which is concave. The further correlation of magnetic resonance and PS images of two lesions in one patient in whom histological examination was performed showed that C- or inverted C-shaped uptake is closely associated with hypervascularity of TD. Differential diagnosis between TD, fracture and metastasis is discussed.

Adult↗
PubMed1994

Effects of zaizhang-I, a traditional Chinese medicine, on immunologically mediated aplastic anemia in mice.

Immunologically mediated aplastic anemia in mice were used as animal models to study the the curative effect of Zaizhang-I in term of the changes of two pathogenetic aspects in aplastic mice, namely the deficiency of hematopoietic stem cells and the disturbance of immunology. Our results demonstrated that in aplastic mice, after treatment by Zaizhang-I, the loss of mature hematopoietic cells (WBC, RBC, Plt) were reduced, and marrow cellular cytosis, and their clinical findings were improved, indicating a partial remission. The present data show that its curative mechanism lies in the action of promoting the recovery of colony forming unit-spleen (CFU-S) and reversing immunologically-induced plasma colony forming unit granulocyte/macrophage (CFU-GM) inhibitory activity. Natural killer cells activity (Nka) and interleukin-2, tumor necrosis factors (TNF) were also so examined to further understand the mechanism by which Zaizhang-I reverse plasma hematopoietic activity.

Anemia, Aplastic↗
PubMed1994

Entamoeba histolytica has an alcohol dehydrogenase homologous to the multifunctional adhE gene product of Escherichia coli.

Entamoeba histolytica ferments glucose to ethanol under the anaerobic conditions of the human colon. There is special interest in this metabolic pathway because it provides an opportunity for parasite-specific chemotherapy. Peptide sequences from a 97-kDa E. histolytica protein, which was originally isolated because of extracellular matrix binding properties, were used to clone and sequence a gene that was found to encode an E. histolytica alcohol dehydrogenase and acetaldehyde dehydrogenase (EhADH2). The EhADH2 cDNA clone had an open reading frame encoding 870 amino acids with a predicted molecular weight of 95,758. The EhADH2 cDNA clone was identical in 48% of its amino acids to the multifunctional enzyme (alcohol dehydrogenase, acetyl-CoA reductase, and pyruvate-formate-lyase-deactivase) encoded by the Escherichia coli adhE gene. The isolation of the EhADH2 protein helps define a new family of ADH enzymes that may be specific to anaerobic and facultatively anaerobic organisms.

Alcohol Dehydrogenase↗