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Biomedical subjects

C Wang

Publications and source records attributed to C Wang.

At least 973 records · Page 54Linked to original sources
PubMed1994

Role of interferon alpha/beta receptor chain 1 in the structure and transmembrane signaling of the interferon alpha/beta receptor complex.

A previously cloned cDNA encodes one subunit of the human interferon alpha/beta receptor (IFN alpha R), denoted IFN alpha R1. To study the expression and signaling of IFN alpha R1, we used monoclonal antibodies (mAbs) generated against the baculovirus-expressed ectodomain of IFN alpha R1. Immunoprecipitation and immunoblotting of lysates from a variety of human cell lines showed that IFN alpha R1 has an apparent molecular mass of 135 kDa. Binding analysis with 125I-labeled mAb demonstrated high levels of cell surface expression of IFN alpha R1 in human cells and in mouse cells transfected with IFN alpha R1 cDNA, whereas no cross-reactivity was observed in control mouse L929 cells expressing only the endogenous mouse receptor. The subunit was rapidly down-regulated by IFN alpha (80% decrease within 2 hr) and degraded upon internalization. The IFN alpha R1 chain appeared to be constitutively associated with the 115-kDa subunit of the IFN alpha/beta receptor, since the mAbs coprecipitated this protein. IFN alpha/beta treatment induced tyrosine phosphorylation of IFN alpha R1 within 1 min, with kinetics paralleling that of the IFN-activated protein-tyrosine kinases Jak1 and Tyk2. Ligand-induced tyrosine phosphorylation of IFN alpha R1 was blocked by the kinase inhibitors genistein or staurosporine. Although IFN alpha R1 cDNA-transfected mouse cells expressed high levels of this subunit when compared with empty vector-transfected cells the number of binding sites for human IFN alpha (50-75 sites per cell) was not increased. Human IFN alpha induced the expression of a mouse IFN alpha/beta-responsive gene (the 204 gene) in mouse L929 cells transfected with the IFN alpha R1 cDNA, but not in mock-transfected cells. These results suggest that the IFN alpha R1 subunit acts as a species-specific signal transduction component of the IFN alpha/beta receptor complex.

Animals↗
PubMed1994

Platelet-derived growth factor alpha receptor gene expression: isolation and characterization of the promoter and upstream regulatory elements.

Receptors for the platelet-derived growth factors (PDGFs) are expressed conditionally in developing embryos and adult tissues. Aberrant expression of PDGF receptors is a molecular marker for proliferative disorders such as atherosclerosis, myofibrosis, and malignant astrocytoma. We isolated genomic clones that encompass the 5' end of the mouse PDGF alpha receptor mRNA transcript and extend 10 kb into the upstream flanking region of the gene. Using these clones, we constructed a partial genomic map that locates the promoter and transcription start sites of the gene. One of our genomic clones contains cis-acting regulatory elements that drive expression of reporter gene constructs selectively in cells that express PDGF alpha receptors.

3T3 Cells↗
PubMed1994

Genomic instability of microsatellite repeats and mutations of H-, K-, and N-ras, and p53 genes in renal cell carcinoma.

Thirty-six primary renal cell carcinoma samples and one metastatic lymph node DNA sample were examined for mutations of H-, K-, and N-ras and p53 genes, and genomic instability at (AC)n, (CA)n.(GT)n, and (TA)n.(GT)n repeats. No mutations were noted for H-, K-, and N-ras genes and only 2 of all the samples (5.6%) showed mutations at exon 8 of the p53 gene. Differences in unrelated microsatellites for tumor and normal DNA were detected in 9 (25.0%) of the cases examined. Somatic alterations in seven microsatellites, D3S1228, D3S643, D5S107, LPL5GT, D9S63, D17S261, and DCC, were found in 1 (2.8%), 3 (8.3%), 2 (5.7%), 5 (14.7%), 3 (8.3%), 3 (8.3%), and 3 (8.3%) cases, respectively. Five of 26 (19.2%) clear cell type and 4 of 10 (40.0%) non-clear cell type patients showed DNA instability. Two of 11 (18.2%) grade 1, 5 of 20 (25.0%) grade 2, and 2 of 5 (40.0%) grade 3 patients showed abnormal patterns. One of 2 (50.0%) stage pT1, 4 of 24 (16.7%) stage pT2, and 4 of 10 (40.0%) stage pT3 patients were shown to have microsatellite instability. In 4 of 9 alteration-positive cases (44.4%), mutations in multiple microsatellites were observed. Alterations in microsatellite instability may be more common in non-clear cell type, high-grade, and high-stage renal cell carcinoma patients.

Base Sequence↗
PubMed1994

Length-tension properties of extraocular muscles in patients with esotropia and intermittent exotropia.

The purpose of this study was to determine the passive length-tension characteristics of horizontal recti muscles in patients with non-restrictive horizontal strabismus. A system to measure intraoperative continuous-registration passive length-tension curves of detached extraocular muscles was designed. The size of the preoperative deviation and the change in the deviation as a result of surgery was correlated with the passive tension of the medial rectus muscle in patients with acquired esotropia. Patients with infantile esotropia or intermittent exotropia showed no relationship between passive tension and either preoperative deviation or response to surgery. Surgical recession of both the medial and lateral recti muscles produced large changes in the passive tension characteristics of both of these muscles. Medial rectus muscle recession produced larger changes in the passive tension than equal amounts of recession of lateral recti muscles.

Child↗
PubMed1994

Properties of cobalt-substituted bovine serum amine oxidase.

Half-copper-depleted and fully copper-depleted amine oxidase from bovine serum were reconstituted with either copper or cobalt. All samples were studied by high-sensitivity scanning calorimetry, by enzyme activity analysis, and by reactivity with phenylhydrazine. The calorimetric profile of the protein was strongly modified by the removal of a single Cu ion approximately to the same extent as by complete copper removal, in agreement with the loss of over 80% enzymic activity. The thermograms of metal-reconstituted species showed a marked similarity with that of the native enzyme, irrespective of whether copper or cobalt was present. Reactivity with phenylhydrazine and enzymic activity measurements showed that in cobalt-substituted amine oxidase the organic cofactor was reactive and the enzyme was catalytically competent, although kinetically less efficient. These observations agree both with previous findings on the protein half-site reactivity and with previous suggestions for a copper conformational role in bovine serum amine oxidase, namely of maintaining a functional conformation at the active site.

Amine Oxidase (Copper-Containing)↗
PubMed1994

RNA polymerase II from wheat germ: a cross-linking study of subunits topography.

RNA polymerase II purified from wheat germ has been treated with a series of cleavable bifunctional reagents and the resulting crosslinked products have been analyzed by diagonal electrophoresis. The results indicate that the three largest subunits (220, 140, and 42,40 kDa, respectively) form a core around which the smaller subunits are bound. The 220- and 140-kDa subunits can be also crosslinked together in the absence of bifunctional reagents by disulfide bond(s) formation. The 27-, 16.3- and 16-kDa subunits appear to be close to the largest subunit (220 kDa). The 21-kDa subunit is close to the 27- and 25-kDa subunits. The reaction of monofunctional reagents with the enzyme shows that the 42,40-kDa subunit is partially hidden in the interior of the protein molecule. On the basis of these results a model of the quaternary structure of the enzyme is proposed.

Cross-Linking Reagents↗
PubMed1994

Camptothecin inhibits Tat-mediated transactivation of type 1 human immunodeficiency virus.

Transcription of type 1 human immunodeficiency virus (HIV-1) is governed by the viral long terminal repeat (LTR). By using HIV-1 LTR-directed reporter gene systems, we found that the DNA topoisomerase I inhibitor camptothecin inhibits Tat-mediated transactivation of HIV-1 LTR. The 293.27.2 cells that carry a stably transfected HIV-1 LTR-directed lacZ gene expression vector (pNAZ) were used. Inhibitions of LTR were observed at camptothecin concentrations (IC50 about 0.03 microM, which was an order of magnitude lower than for Ro 24-7429), which had minor effects on cell survival, expression of the cellular gene gro, or Rous sarcoma virus-directed chloramphenicol acetyltransferase (CAT) gene expression. Inhibition was also seen with RPMI 8402, which is a human CD4-positive lymphocyte line transiently transfected with a HIV-1 LTR-directed (CAT) gene. Experiments with HIV-1 LTR mutants suggest that transactivation response sequence but not NF-kappa B is responsible for the inhibition by camptothecin. The target for camptothecin may be a cellular factor that is important for the activation of HIV-1 LTR by Tat and thus may offer a potential target for therapy of HIV-1 infection.

Base Sequence↗
PubMed1994

Uncoupling of peptide-stimulated ATPase and clathrin-uncoating activity in deletion mutant of hsc70.

The recombinant 60-kDa fragment of rat hsc70 has been overexpressed in Escherichia coli. The recombinant protein is not capable of disassembling clathrin from coated vesicles. However, the affinity for peptides and the peptide-stimulated ATPase activity of the intact protein are retained in the 60-kDa fragment. The dissociation constants of peptide P3a (the recognition sequence of clathrin light chain LCa by hsc70) and S peptide of ribonuclease for 60-kDa protein are 13 and 7 microM, respectively. The maximal velocities of stimulated ATPase activity by peptides P3a and GT4 are 0.25 and 0.31 nmol/h/microgram of protein, respectively, and the EC50 values (the concentration of peptides that brought about half-maximum hydrolysis) for peptides P3a and GT4 are 0.56 and 0.30 mM, respectively. These results indicate that peptide-stimulated ATPase activity of hsc70 is not sufficient for clathrin uncoating. We suggest that other activities or cellular components as yet unidentified associated with the C-terminal 10-kDa fragment of hsc70 are required for clathrin uncoating.

Adenosine Triphosphatases↗
PubMed1994

Genetics of nanos localization in Drosophila.

The Drosophila gene nanos is required for two processes. During oogenesis, nanos function is required for the continued production of egg chambers, and nanos is expressed in the early germarium. During embryogenesis, nanos is required maternally to specify abdominal segmentation. Nanos shares this latter function with nine other genes, collectively known as the posterior group. Of this group, nanos encodes a determinant, and is localized as an RNA to the posterior pole of early embryos. This RNA is translated to form a gradient of nanos protein with highest concentrations at the posterior. Analysis of the distribution of nanos gene products in embryos mutant for posterior group genes shows that eight of these genes are required for localization, but not stability, of the nanos RNA. Embryos mutant for posterior group alleles which produce weak abdominal phenotypes show reduced amounts of localized nanos RNA. This correlation between nanos RNA localization and abdominal phenotype suggests that nanos acts as a localization-dependent posterior determinant. Localization of nanos is not affected by mutations in bicoid or torso, confirming that the three maternal systems of anterior-posterior determination initially act independently.

Alleles↗
PubMed1994

Ventilation techniques to minimize circulatory depression in rabbits with surfactant deficient lungs.

Changes in aortic blood flow were measured in rabbits with both normal and surfactant depleted lungs in order to elucidate the effect of different modes of ventilation on the circulation while optimizing arterial oxygenation (PaO2). Conventional mechanical ventilation (CMV), reversed inspiratory to expiratory ratio of CMV (IRV), high frequency positive pressure ventilation (HFV), and high frequency oscillation (HFO) were used. Normocapnia was maintained throughout during different modes of ventilation. In normal lungs the aortic blood flow during IRV was significantly lower with similar levels of PaCO2 compared with CMV, HFV, and HFO. In lavaged lungs, without positive end-expiratory pressure (PEEP), the aortic blood flow during CMV was significantly higher than with other modes of ventilation. When 10 cm H2O of PEEP was applied, the PaO2 increased maximally to normal values at all modes of ventilation, but the aortic blood flow was significantly reduced (P < 0.05) during CMV and IRV compared to HFV and HFO. The aortic blood flows at 5 cm H2O of PEEP were very similar during CMV, HFV, and HFO but significantly reduced during IRV. This study showed that at an optimal arterial oxygenation with higher PEEP levels, maintenance of aortic blood flow was maximal during HFV and HFO.

Animals↗
PubMed1994

Identification of chicken liver glucose transporter.

A cDNA, Ch-GT2, encoding a glucose transporter was cloned by screening a chicken liver lambda gt11 cDNA library and by modified polymerase chain reaction (PCR) techniques. The encoded protein is highly homologous to rat and human GLUT 2. Within the predicted amino acid sequence, there are 12 putative transmembrane helices with a relatively large exofacial hydrophilic loop between transmembrane segments 1 and 2, which is characteristic of mammalian GLUT 2. Expression of Ch-GT2 gene in E. coli results in sixfold increase in the uptake of 2-deoxy-D-glucose uptake, and this increment can be reduced by incubation with phloretin. Thus, Ch-GT2 is a bona fide chicken liver glucose transporter. A deletion mutant generated by PCR was expressed in bacteria and shown to be functional, indicating that the N-terminal seven amino acid residues of Ch-GT2 is not essential for transport of glucose. From Northern blot analysis, Ch-GT2 is prominently expressed in chicken liver with a transcript of 4.0 kb, but not in chicken brain and heart, suggesting that distinct types of glucose transporters are present in various chicken tissues.

Amino Acid Sequence↗
PubMed1994

An in vitro model for the effects of androgen on neurons employing androgen receptor-transfected PC12 cells.

Androgen alters neurite outgrowth, synaptic organization, and cell survival in various portions of the brain and spinal cord. However, examination of the specific effects of androgen on neurons in vivo has been difficult. Previously, an in vitro model for the effects of estrogen on neurons was developed and characterized, using an estrogen receptor (ER)-transfected PC12 rat pheochromocytoma cell line. This model demonstrated estrogenic regulation of neurite outgrowth, spine formation, and gap junction formation. Similarly, an in vitro model for the effects of androgen on neurons is now described. Wild-type cells (PC12-WT) were stably transfected with an expression vector coding for the full-length cDNA for the human androgen receptor (AR). Resultant clones were isolated, screened for incorporation of vector and expression of AR mRNA and protein, and analyzed for morphologic responses to androgen. PC12-WT, NE09 (ER-negative, AR-negative), SER8 (ER-positive, AR-negative), and AR8 (ER-negative, AR-positive) cells were exposed to 10 ng/ml nerve growth factor (NGF), along with 0-10(-7) M dihydrotestosterone (DHT) for 2 days. AR8 cells demonstrated an androgen dose-dependent increase in mean neurite length, branch order, and neurite field area, whereas neurite branch segment length and soma area were not affected by androgen. PC12-WT, NE09, and SER8 cells exhibited no alterations in cell morphology with DHT exposure. Because of the synergistic effects of DHT and NGF, the regulation of NGF receptor mRNA by DHT was evaluated; however, no significant induction of either trkA or p75 mRNA expression by androgen was documented. The results suggest that in AR-positive PC12 cells, androgen acts additively with NGF to increase neurite outgrowth; but androgen effects are mediated specifically through branching and arborization. These responses are similar to developmental studies of androgen effects in vivo. Thus, androgen appears to induce an inherent neural morphologic program in AR-containing cells, which increases the receptive field of these cells, increasing the likelihood for interneural communication, although not promoting communication itself. These cell lines will provide a unique in vitro system for studying mechanisms of androgen-neuron interactions.

Androgens↗
PubMed1994

Effect of cadmium on bone calcium and 45Ca in mouse dams on a calcium-deficient diet: evidence of Itai-Itai-like syndrome.

To test whether Cd exposure would increase Ca release from bone during pregnancy and lactation in relation to the etiological mechanism of Itai-Itai disease, virgin female mice with 45Ca prelabeled skeletons (15 microCi/mouse) were subjected to one round of pregnancy/lactation and were exposed to a Ca-deficient diet containing 0, 5, or 25 ppm Cd or 25 ppm Pb for 32 days, from conception until Lactation Day 14. A striking loss of 45Ca was found in the dam's total skeleton (-40%), right femur (-47%), and lumbar vertebrae (L1-L5) (-75%) due only to pregnancy/lactation in conjunction with Ca deficiency. At both 5 and 25 ppm, Cd administered through food induced an additional significant 45Ca loss from the total skeleton (-25% at 5 ppm Cd, -30% at 25 ppm Cd) and right femur (39% at 5 ppm Cd, -32% at 25 ppm Cd) compared to 0 ppm animals. Almost all of the 45Ca lost from the dam's skeleton appeared in the pups, with 80% transferred via the dam's milk during lactation and only 20% transferred during gestation; a very small fraction of the dam's skeletal 45Ca was excreted. Considering stable Ca values, Cd exposure nearly doubled the loss of Ca from the dam's skeleton (-78 mg Ca/mouse at 0 ppm; -146 mg Ca/mouse at 5 and 25 ppm Cd). Paralleling 45Ca losses, a Ca-deficient diet in combination with pregnancy/lactation alone caused significant decreases in weight and mineral content of the right femur and lumbar vertebrae (dry weight, ash weight, ash/dry, Ca content, Ca/dry, and Ca/ash) (-8 to -52%). Cd at both 5 and 25 ppm showed additional decreases (-15 to -32%, Cd groups compared to 0 ppm animals). Responses were specific to Cd in that no significant effect occurred due to 32 days of Pb exposure (25 ppm). This experiment supports the view that Cd exposure in conjunction with Ca deficiency and pregnancy/lactation are key etiological factors of Itai-Itai disease and that Cd at both 5 and 25 ppm in conjunction with one round of gestation/lactation and Ca deficiency can induce an extreme demineralization characteristic of Itai-Itai-like syndrome.

Animals↗