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Biomedical subjects

M Wang

Publications and source records attributed to M Wang.

At least 973 records · Page 54Linked to original sources
PubMed1991

[Effect of mutagenesis at Ser 177 residue in penicillin G acylase on activity of the enzyme].

The technique of cassette and site-specific mutagenesis were used to study the role of residue No. 177 in penicillin G acylase (PGA, EC 3.5.1.11). Ser is conserved at residue No. 177 in all penicillin binding proteins. We got a series of mutants in which the amino acid at residue No. 177 was replaced by other amino acids through the site-specific and cassette mutagenesis, and we characterized the mutants by colony hybridization, NIPAB paper test and DNA sequence analysis. These mutants all show no activity of enzyme, even if the Ser residue was replaced by Thr, Gly and Ala respectively. The results show that Ser residue may be essential for substrate-binding or catalysis of PGA.

Escherichia coli↗
PubMed1991

[Gas chromatograms of fatty acids from Rickettsia and their similarities].

Fatty acid compositions of 7 strains of Rickettsia were analyzed by a on-line GC/MS system. These strains were R. prowazekii E, R. conorii Simko, R. rickettsii R, R. sibirica Barbash and 246, R. sinkiangensis Jinghe, and R. heilungkiangensis 54. The samples were purified by means of the concentrated salt-ether method. There were about 50 peaks in the fatty acid profiles, and 16 of these peaks were determined, i.e. C22:0, C19:0, C18:0, C18:1, C18:2, C17:0, C16:0, C16:1, 3-OH-C14:0, C15:0, C14:0, C13:0, 2-OH-C12:0, C12:0, 2-OH-C10:0, and C11:0. The major fatty acids were the saturated straight chain acids (e.g. C16:0, C18:0, C14:0) and the unsaturated straight chain acids (e.g. C18:1, C18:2, C16:1). Similarities of fatty acid profiles of tested strains were discriminated by the improved Kulik-Vincent method. The result showed that the KV's coefficient of strains Jinghe and 246 was 97.0%, and the KV's coefficient of strains 54 and the others was 81.6-94.6%.

Fatty Acids↗
PubMed1991

[Correlation between retinal nerve fiber layer defect, neuroretinal rim area and visual impairment in primary open angle glaucoma].

120 eyes of normal subjects, 150 eyes of ocular hypertension, and 132 eyes of primary open angle glaucoma (POAG) were examined the retinal nerve fiber layer (RNFL), neuroretinal rim area (NRA), visual field, dark adaptation and pattern reversal visual evoked potential (PVEP), revealing that RNFL defect and NRA correlated with visual field defect, threshold of dark adaptation and latency of PVEP. RNFL examination using red free photographic technique yielded 96% sensitivity in glaucoma detection and 95% specificity in identifying normal eyes. Modified semiquantitative criterion for assessing RNFL defect had a good reproducibility. The mean NRA in normal eyes was 2.22 +/- 0.35 mm2. Therefore, 95% of the normal subjects had rim areas greater than 1.64 mm2; 82% of patients with POAG had NRA less than 1.64 mm2. 20.1% of the eyes of ocular hypertension had RNFL defect and 37.6% had NRA below the 95% lower point, suggesting that some patients with increased intraocular pressure could have structural abnormalities. The authors proposed that ocular hypertension without visual field defect but with significant RNFL defect and/or NRA decrease should be regarded as in a preliminary stage of POAG.

Dark Adaptation↗
PubMed1991

[Effect of temperature on the expression of penicillin G acylase gene at the level of post-translational processing].

The expression of penicillin G acylase (PGA) gene is sensitive to temperature. Cells of E. coli DH 5 alpha harboring a plasmid pWGA carrying a gene for PGA produce active PGA at low level at 37 degrees C, but can synthesize significant amount of the enzyme below 30 degrees C. Active PGA is formed from a 94 KD precursor processed through remove of a signal peptide and a spacer peptide to yield an enzyme that contain a 23 KD (alpha) and 65 KD (beta) subunit. This paper reported the effect of temperature on transcription, translation, and post-translational processing of PGA gene expression. We detected the transcription of PGA gene by Northern blot, and found the amount of PGA mRNA at 37 degrees C much more than that 30 degrees C when the cells of DH 5 alpha (pWGA) were cultured. It is evident that the precursor processing step(s) is sensitive to temperature.

Enzyme Precursors↗
PubMed1990

Chemoattractant-induced membrane hyperpolarization in Dictyostelium discoideum. A possible role for cyclic GMP.

Membrane potentials of the cellular slime mold Dictyostelium discoideum were monitored after chemotactic stimulation by measuring the distribution of the lipophilic cation tetraphenylphosphonium. Stimulation with the chemoattractant cAMP induces a transient membrane hyperpolarization which reaches its most negative value between 1-3 min after stimulation. This hyperpolarization is consistent with the opening of potassium channels. Measurements in streamer F mutant cells reveal that cGMP likely plays a role in the regulation of the cAMP-induced hyperpolarization.

Chemotaxis↗
PubMed1990

Lack of persistence of influenza virus genetic information in ducks.

Clearance of infectious virus and RNA occurred concurrently after oral infection of ducks with influenza virus. There was no evidence from polymerase chain reaction (PCR) analysis of the hemagglutinin (HA) gene for persistence of viral genetic information. No detectable RNA was found in the spleen indicating processing of antigen near the site of replication.

Animals↗
PubMed1990

Cytoplasmic acidification facilitates but does not mediate DIF-induced prestalk gene expression in Dictyostelium discoideum.

Stalk cell differentiation in Dictyostelium can be induced by the differentiation-inducing factor, DIF, or by conditions that decrease intracellular pH (pHi). We have investigated whether cytoplasmic acidification acts directly to induce expression of pDd56 and pDd63, two DIF-regulated genes, specifically expressed in prestalk cells. The weak base methylamine, which increases pHi, inhibits DIF-induced transcription. The weak acid 5,5-dimethyl-2,4-oxazolidinedione (DMO), which decreases pHi, stimulates DIF-induction of the two prestalk genes. After relatively long incubation periods, DMO also induces a low level of prestalk gene expression in the absence of added DIF. However, unlike DIF-mediated induction, the apparent DMO-mediated induction decreases to undetectable levels when the cell density is reduced from 10(7) to 10(5) cells/ml. This indicates that DMO does not itself induce gene expression, but acts to enhance the effects of an autonomously secreted stalk-inducing factor, presumably DIF. These results suggest that the effects of DIF on gene expression are regulated by intracellular pH, but do not support a role for protons as direct intermediates in the DIF signal transduction pathway.

Cyclic AMP↗
PubMed1990

Evaluation of isolator system and large-volume centrifugation method for culturing body fluids.

The Isolator system was compared with the large-volume centrifugation method for processing and recovering organisms from body fluids other than blood, cerebrospinal fluid, and urine. A total of 155 body fluid samples were processed for the recovery of clinically significant organisms. Of the 55 positive cultures, Isolator detected 94% and the large-volume centrifugation method detected 64%. The time necessary to indicate positivity was not significantly different in the two methods; however, in five cases, the Isolator system yielded clinically significant organisms 24 h sooner than the conventional method. The Isolator system was found to be a more sensitive alternative than the conventional large-volume centrifugation method.

Bacteria↗
PubMed1990

Direct sequencing of the HA gene of influenza (H3N2) virus in original clinical samples reveals sequence identity with mammalian cell-grown virus.

When influenza (H3N2) viruses from infected individuals are grown in embryonated chicken eggs, viruses are isolated which differ antigenically and structurally from viruses grown in mammalian Madin-Darby canine kidney (MDCK) cell culture [G.C. Schild, J.S. Oxford, J.C. de Jong, and R.G. Webster, Nature (London) 303:706-709, 1983]. To determine which of these viruses is most representative of virus replicating in the infected individual, a region of the HA gene of virus present in original clinical samples was amplified by using the polymerase chain reaction and sequenced directly. Comparison of 170 amino acid residues of HA1 flanking and containing the receptor-binding site and antigenic sites indicated that over this region, the HA of virus replicating in the infected individual was identical to that of virus after growth in MDCK cells and was distinct from the HA of viruses grown in eggs. Therefore, cultivation of human influenza H3N2 virus in mammalian MDCK cells results in a virus similar to the predominant population of virus found in the infected individual.

Amino Acid Sequence↗
PubMed1990

Lack of growth hormone effect on insulin-associated suppression of insulinlike growth factor binding protein 1 in humans.

Insulinlike growth factor binding protein 1 (IGFBP-1) has been shown to modulate the metabolic and mitogenic actions of the growth hormone (GH)-dependent peptide insulinlike growth factor I. Previous studies showed that levels of IGFBP-1 are regulated by insulin. The relative role of GH in the regulation of IGFBP-1 levels is less well defined and was examined in our study with a contiguous two-part protocol. Overnight (part A) and pre- and post-morning meal (part B) blood samples were obtained from eight healthy adults during a constant infusion of saline (SAL) or 4 micrograms.kg-1.min-1 GH. Five of eight subjects were restudied with glucose (GLUC) infused during part B (SAL + GLUC) to match glucose and insulin to levels observed during GH infusion. During SAL infusion, IGFBP-1 levels measured by specific radioimmunoassay showed a marked immediate decline after the evening meal in part A, with a subsequent nocturnal rise of 2.4- to 17.3-fold. GH infusion resulted in a similar meal-induced fall in IGFBP-1 levels but led to a delayed nocturnal rise in IGFBP-1, which was associated with elevated postprandial insulin concentrations. During part B, changes in plasma IGFBP-1 levels showed a similar pattern, with a delayed postprandial increase observed during both GH and SAL + GLUC infusions. The half-life of IGFBP-1 disappearance was calculated at approximately 2 h for all three infusion groups. Comparison of venous and arterialized blood samples showed no consistent pattern of difference, arguing against peripheral tissue clearance or compartmentalization as the mechanism for the rapid rise and fall in IGFBP-1 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Screening of alpha-amino acid ester hydrolase producing strain and synthesis of cephalexin by Pseudomonas aeruginosa].

From ten genera and 146 bacterial strains, 22 strains producing alpha-amino acid ester hydrolase were selected. Among them, AS 1.586 and 41-2 were the best. The optimal conditions for synthesis of cephalexin by pseudomonas aeruginosa 1.204 were investigated. The optimal pH and temperature for enzymatic synthesis reaction was pH 6.8 and 25 degrees C, respectively. By using 1% 7-ADCA, 3% PGME and 4% biomass, about 70% of 7-ADCA was converted to cephalexin under the mentioned conditions.

Carboxylic Ester Hydrolases↗
PubMed1990

[Effects of gossypol acetate, progesterone, danazol and GnRH-A (gonadotropin release hormone-A) on the DNA-synthesis of human endometrial cell in vitro].

Both aberrant endometrial cell and endometrial cell in situ, showed cyclic changes under the control of ovarian hormones. In this study, in order to observe a direct effect of medical therapy on the endometriosis, endometrial cells were cultured in vitro. Sensitivity test to 10(-6) M gossypol acetate, progesterone, danazol and GnRH-A were performed using determination of DNA synthesis by incorporation of tritiated thymidine. The results showed these drugs (but not GnRH-A) decreased the amount of attached cells, and lowered the DNA synthesis of endometrial cell in vitro (P less than 0.01). The inhibition rates of gossypol acetate was higher than that of progesterone and danazol, while that of progesterone was higher than that of danazol (P less than 0.01). The relationship between the growth inhibitory effect of progesterone and danazol showed a significant correlation for all points (r = 0.89, P less than 0.05). It has been suggested that some drugs might act a direct inhibitory effect on endometrial cell, such effect might be one of the modes in the treatment of endometriosis. GnRH-A had no direct suppression on endometrial cell in vitro, it has got clinical effect through the central effect at the hypothalamo-pituitary-ovary axis in treatment of endometriosis.

Adult↗
PubMed1990

[Pharmacological studies of huomaisan].

After per os Huomaisan twice a day for 5 days, HMS significantly prolonged thrombus formation time and inhibited platelet aggregation induced by ADP and collagen. Meanwhile, HMS also decreased blood viscosity, but did not significantly affect hematocrit. The result shows that HMS has multiple actions on blood.

Animals↗
PubMed1989

Recombinant bovine alpha-lactalbumin obtained by limited proteolysis of a fusion protein expressed at high levels in Escherichia coli.

A cDNA clone containing the entire coding region for bovine pre-alpha-lactalbumin (LA) together with 27 base pairs of 5'-noncoding and 268 base pairs of 3'-noncoding sequences was isolated from a bovine mammary cDNA plasmid library in the Okayama-Berg vector system using a synthetic oligonucleotide probe and sequenced. The coding segment for mature LA was subcloned into the T7 expression system of Studier and co-workers (Studier, F.W., and Moffatt, B.A. (1986) J. Mol. Biol. 189, 113-130; Rosenberg, A.H., Lade, B.N., Chui, D.S., Lin, S.W., Dunn, J.J., and Studier, F.W. (1987) Gene (Amst.) 56, 125-135) and expressed as a 21-kDa fusion protein that consisted of the mature bovine LA sequence connected to the NH2-terminal 50 residues of human cathepsin D by a linker sequence containing protease cleavage sites. This fusion protein was expressed in an insoluble form and accumulated to about 50% of the total bacterial protein within 3 h after induction of T7 RNA polymerase synthesis. The protein was solubilized, purified by gel filtration, and converted to an active form by treatment with mixtures of reduced and oxidized glutathione in the presence of Ca2+. The maximum specific activity of the fusion protein was about 25% of that of native LA, suggesting that the attachment of an NH2-terminal extension sterically hinders but does not prevent the interaction with galactosyltransferase. The extension also does not block the binding of the regulatory Ca2+ ion that is required for folding from the reduced denatured state. Trypsin cleaved the folded fusion protein specifically at a Lys-Glu bond at the junction with the mature LA sequence to give a product indistinguishable in structure and activity from native LA.

Amino Acid Sequence↗