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Biomedical subjects

G Zhou

Publications and source records attributed to G Zhou.

At least 235 records · Page 13Linked to original sources
PubMed1995

[Expression of proliferating cell nuclear antigen (PCNA) in premalignant lesions of laryngeal epithelium].

It is important to study the proliferative activity of cells in the premalignant lesions of laryngeal epithelium. Using PC-10, an antibody to PCNA and a standard immunohistochemical staining, we examined 11 cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) for expression of PCNA, a protein associated with DNA polymerase delta and DNA replication. The results revealed that the PCNA indices in SHE, AHE and LSCC were 9.57%, 27.33% and 68.05%, respectively. The PCNA indices were 13.79%, 30.84% and 39.94%, in the mild, moderate and severe AHE, respectively. There were significant differences among the SHE, AHE and LSCC. A good correlation was found among different degrees of AHE. The pattern and location of PCNA positive cells in the intraepithelium had diagnostic importance. PCNA might provide a useful tool for studying cell proliferation in situ under normal and pathological conditions.

Adult↗
PubMed1995

[The olfactory neurotoxicity of cisplatin and effects of two drugs].

32 guinea pigs were used as animal models for the study of cisplatin induced olfactory neurotoxicity and the effects of sodium thiosulfate (STS) and cystine on the toxicity by light and electron microscopy. The results revealed that the olfactory epithelium, olfactory nerve and the olfactory bulb were all damaged by the application of cisplatin and manifested as the lysis of the myelinated nerve fibers of olfactory epithelium, edema and degeneration of the axons, atrophy of the olfactory epithelium and the compensatory proliferation of Bowman's glands. STS and cystine did not show significant effects on the neurotoxicity of cisplatin. The data suggested that cisplatin is an important toxic drug for olfactory system.

Animals↗
PubMed1994

Protein-tyrosine phosphatases specifically regulate muscle adult-type nicotinic acetylcholine receptor gene expression.

Innervation of skeletal muscles results in expression of adult-type nicotinic acetylcholine receptors (alpha 2 beta epsilon delta) beneath the neuromuscular junction. This local expression is largely a result of selective induction of adult-type nicotinic acetylcholine receptor (nAChR) genes in endplate-associated myonuclei. The molecular mechanism by which the nerve induces gene expression in these nuclei is not known. We have shown previously that ionophore-induced calcium influx across the plasma membrane preferentially decreases expression from the adult-type specific nAChR epsilon-subunit gene (Walke, W., Staple, J., Adams, L., Gnegy, M., Chahine, K., and Goldman, D. (1994) J. Biol. Chem. 269, 19447-19456). Here we provide evidence that the genes encoding adult-type nAChRs are specifically regulated by protein-tyrosine phosphatase activity. Orthovanadate, a specific protein-tyrosine phosphatase inhibitor, caused increased expression of the epsilon-subunit gene in rat primary myotubes and was able to completely block the suppressive effects of increased calcium influx on epsilon-subunit RNA expression. Overexpression of protein-tyrosine phosphatases selectively decreased expression from the adult-type nAChR genes with no effect on the embryonic-type specific gamma-subunit gene. These results demonstrate that protein-tyrosine phosphatases regulate mammalian adult-type nAChR gene expression and suggest a mechanism by which muscle innervation selectively regulates gene expression in endplate-associated myonuclei.

Aging↗
PubMed1994

The catalytic role of Cys124 in the dual specificity phosphatase VHR.

The recombinant human Vaccinia virus H1-related protein tyrosine phosphatase, (VHR PTPase) possesses intrinsic Tyr and Thr/Ser phosphatase activities. Both activities were abolished by a single amino acid substitution, C124S. When VHR was incubated with a 32P-labeled phosphotyrosine-containing substrate and then rapidly denatured, enzyme-associated 32P was evident following SDS-polyacrylamide gel electrophoresis. The formation of 32P-labeled protein could be blocked in the presence of an unlabeled substrate. VHR-associated 32P was sensitive to iodine but insensitive to pyridine and hydroxylamine. The catalytically inactive C124S mutant would not form a 32P-labeled enzyme. Furthermore, VHR phosphatase could be selectively inactivated by the alkylating agent iodoacetate. The inactivation resulted from the specific covalent modification of Cys124. Collectively these results suggest that a thiol-phosphate enzyme intermediate is formed when Cys124 of VHR accepts a phosphate from the substrate. Our results also demonstrate that the dual specificity phosphatases and the tyrosine-specific PTPases employ similar catalytic mechanisms.

Amino Acid Sequence↗
PubMed1994

Binding of purine nucleotides to two regulatory sites results in synergistic feedback inhibition of glutamine 5-phosphoribosylpyrophosphate amidotransferase.

Glutamine 5-phosphoribosylpyrophosphate amidotransferase from Escherichia coli is subject to synergistic feedback regulation by adenine and guanine nucleotides. Inhibition assays and equilibrium binding measurements have established that synergistic inhibition by AMP and GMP results from synergistic binding to two sites/enzyme subunit in the homotetramer. Although each nucleotide can bind to both sites, analyses of the wild type and mutant enzymes indicate that binding of GMP to an A (allosteric) site and AMP to a proximal C (catalytic) site are necessary for synergistic inhibition. K326Q and P410W amino acid replacements result in decreased binding affinity for GMP and AMP and lead to corresponding reductions in feedback inhibition. The K326Q A site mutation results not only in decreased affinity of GMP for the mutant A site but also has an adverse effect on AMP affinity for the C site. Similarly, the P410W C site mutation has a detrimental effect on binding of AMP to the mutant C site and also on affinity of GMP to the A site. The fact that a mutation in one site affects binding of nucleotides to both sites provides further evidence for synergistic binding of nucleotides.

Adenosine Monophosphate↗
PubMed1994

Two genes for de novo purine nucleotide synthesis on human chromosome 4 are closely linked and divergently transcribed.

A cDNA encoding human glutamine phosphoribosylpyrophosphate amidotransferase for step one in de novo purine nucleotide synthesis was cloned, sequenced, and expressed in Chinese hamster ovary cells to yield functional enzyme. Enzyme function was dependent upon removal of an 11-amino-acid propeptide. A mutant enzyme having three propeptide amino acid replacements was not processed and was not active. The human genes GPAT, encoding the amidotransferase, and AIRC, encoding a bifunctional enzyme for steps six and seven in the pathway, were cloned and characterized. GPAT and AIRC are closely linked and divergently transcribed from an intergenic region of approximately 625 base pairs. Expression of a luciferase reporter from the GPAT promoter was approximately 3-4-fold higher than from the AIRC promoter. The GPAT gene was mapped to the q12 region of chromosome 4.

Amidophosphoribosyltransferase↗
PubMed1994

Elevation of serum free triiodothyronine, total triiodothyronine, thyroxine-binding globulin, and total thyroxine levels in combat-related posttraumatic stress disorder.

BACKGROUND: This study was designed to assess both central and peripheral aspects of thyroid function in combat-related posttraumatic stress disorder (PTSD), with the particular purpose of finding a mechanistic explanation for an imbalance between serum levels of free thyroxine (T4) and total T4 previously observed in pilot work. METHODS: A total of 96 male combat veterans with PTSD diagnosed by DSM-III-R (72 from the West Haven, Conn, Veterans Affairs Medical Center and 24 from the Menlo Park, Calif, Veterans Affairs Medical Center) were compared with 24 male control subjects. One or more serum samples were analyzed by radioimmunoassays for levels of total T4, free T4, total triiodothyronine (T3), free T3, T4-binding globulin, and thyrotropin. RESULTS: The pilot observation of moderately elevated total T4 levels with no elevation in free T4 levels in patients with PTSD was confirmed, suggesting the hypotheses that (1) there may be an increased peripheral conversion of free T4 by deiodination to T3 or (2) there may be an increased binding of T4 secondary to elevated T4-binding globulin levels. Our findings support both hypotheses. The PTSD groups all showed a marked and sustained elevation in levels of both total T3 and free T3, as well as elevated T3/T4 ratios, supporting the increased T3 conversion hypothesis. The PTSD groups also showed a marked and sustained increase in T4-binding globulin levels, supporting the increased binding hypothesis. Thyrotropin levels did not differ between PTSD and control groups. CONCLUSIONS: These findings demonstrate an unusual pattern of thyroid alterations, featuring substantial elevations in total T3, free T3, and T4-binding globulin levels, in combat-related PTSD that differs from established endocrinopathies, such as classic hyperthyroidism, T3 thyrotoxicosis, or chronic T4-binding globulin elevation.

Adult↗
PubMed1994

Collagen metabolism in cultured adult rat cardiac fibroblasts: response to angiotensin II and aldosterone.

Myocardial fibrosis is associated with an activated renin-angiotensin-aldosterone system (RAAS). In renovascular hypertension, this presents as a reactive perivascular and interstitial fibrosis in not only the pressure overloaded, hypertrophied left ventricle but also the normotensive, nonhypertrophied right ventricle. It therefore would appear that circulating hormonal and not hemodynamic factors are responsible for this adverse fibrous tissue response. To ascertain whether the RAAS effector hormones angiotensin II (AII) or aldosterone (ALDO) directly stimulate collagen synthesis or inhibit collagenase production we used cell culture. Adult rat cardiac fibroblasts (Fb) were cultured since these cells express mRNA for types I and III collagens, the major fibrillar collagens in the heart, and collagenase or matrix metalloproteinase 1 (MMP 1), the key enzyme for interstitial collagen degradation. Collagen synthesis, determined by 3H-proline incorporation, and collagenase activity were measured in confluent, quiescent Fb after 24 h incubation with various concentrations of AII or ALDO (10(-11)-10(-6)M) in the presence or absence of either 10(-5)M type 1 (DuP 753) and type 2 (PD 123177) AII or 10(-9)-3 x 10(-6)M ALDO (spironolactone) receptor antagonists, respectively. Collagen synthesis, normalized per total protein synthesis, increased significantly (P < 0.005) after incubation with either 10(-9)M ALDO (5.9 +/- 1.0%) or 10(-7)M AII (5.3 +/- 1.2%) compared with untreated control cells (2.9 +/- 0.5%) of the same passage (p6-p10). This increase in collagen synthesis could be completely abolished by either types 1 or 2 AII receptor antagonists in AII stimulated Fb or the competitive ALDO receptor antagonist, spironolactone, at equimolar concentration in ALDO stimulated Fb. AII significantly decreased collagenase activity which could be completely abolished by PD 123177, but not DuP 753, while ALDO had no effect on collagenase activity. The mineralocorticoid, ALDO, stimulates collagen synthesis in cultured adult rat cardiac Fb in concentrations similar to those found in plasma in renovascular hypertension and this response appears to occur via type I corticoid receptors. AII appears to stimulate collagen synthesis by both type 1 and 2 AII receptors, but only in high concentrations that could be generated locally within the myocardium. In addition, AII unlike ALDO inhibits collagenase activity that could be attenuated only by type 2 receptor blockade. These findings suggest a direct interaction between ALDO, AII and cardiac Fb in mediating myocardial fibrosis in hypertensive heart disease.

Aldosterone↗
PubMed1994

Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942.

The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacIQ repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 mumol photons m-2 s-1 in the presence of 40 or 80 micrograms/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 micrograms/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacIQ system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.

Amino Acid Sequence↗
PubMed1994

Characterization of primary cultures of chondrocytes from type II collagen/beta-galactosidase transgenic mice.

Studies on the function of extracellular matrix components of cartilages and on chondrocyte-specific regulatory mechanisms will benefit from approaches in which transgenic mice and cell cultures will complement each other. We therefore established and extensively characterized primary cultures of mouse chondrocytes isolated from rib growth plates of newborn mice harboring a transgene in which type II collagen gene regulatory sequences were driving expression of an E. coli beta-galactosidase reporter gene. Primary chondrocytes expressed a fully differentiated phenotype in monolayer culture, producing mRNAs for the collagen types II, IX and X, and for the transgene. Transgenic cells also synthesized high levels of E. coli beta-galactosidase, easily quantifiable and also detectable in individual cells by X-gal staining. When chondrocytes were isolated from transgenic mice in which beta-galactosidase was fused to the product of the neomycin resistance gene, they displayed resistance to G418. After one to two weeks in culture, chondrocytes progressively lost expression of the transgenes, in parallel with that of cartilage-specific genes, and started expressing high levels of type I collagen RNA. The use of transgenic chondrocytes allowed us to easily score phenotypic changes by assaying beta-galactosidase activity and neomycin resistance. Cultures of mouse chondrocytes, such as those reported here, should also help characterize biochemically the phenotypes of other transgenic mice in studies of genetic diseases of cartilages and of mechanisms involved in chondrogenesis.

Animals↗
PubMed1994

Traditional Chinese medicine typing of affective disorders and treatment.

According to the theory of Traditional Chinese Medicine (TCM), 50 patients with affective disorders were typed into the categories of depressed liver resulting in fire, mild Yang deficiency and mild Yin deficiency and were treated with Xiao Yao San Jia Wei. The results are 26 patients with marked improvement, 17 patients with improvement and 7 patients with no improvement.

Bipolar Disorder↗
PubMed1994

A role for zeta protein kinase C in nerve growth factor-induced differentiation of PC12 cells.

Studies were undertaken to compare the signal-induced redistribution of conventional protein kinase C (cPKC) to nonclassical protein kinase C (nPKC) family members in response to phorbol 12-myristate 13-acetate (PMA) or nerve growth factor (NGF) treatment of PC12 cells. cPKC-alpha and -beta and nPKC-delta and -epsilon were predominantly cytoplasmic, whereas PKC-zeta displayed approximately equal distribution between the cytoplasm and membrane fraction. Treatment of PC12 cells with PMA induced rapid translocation of both c- and nPKC isoforms to the membrane fraction, although the kinetics varied between isoforms with epsilon being most sensitive, followed by delta > zeta > alpha. Both PKC-epsilon and delta translocated in the presence of minute concentrations of PMA, whereas cPKC was less sensitive, and PKC-zeta was least sensitive. NGF treatment, on the other hand, induced translocation of cPKCs and delta and epsilon nPKC, albeit with differential magnitude, whereas PKC-zeta was found predominantly in the cytoplasm. Chronic treatment of PC12 cells with PMA (1 microM) caused a rapid disappearance of alpha, beta, delta, and epsilon PKC isoforms, whereas the expression of PKC-zeta was unaltered over 4 days. NGF induced an increase in cytoplasmic PKC-zeta in control, or PMA down-regulated PC12 cells. Moreover, the increase in cytoplasmic PKC-zeta was blocked by pretreatment with sphingosine (2.5 microM). Furthermore, PKC-zeta was activated by NGF in PMA down-regulated PC12 cells, as determined by the extent of epsilon-peptide phosphorylation using a permeabilized cell assay. In addition, the zeta-pseudosubstrate peptide inhibited NGF-induced activation of PKC-zeta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Discovery and clinical investigation of Lyme disease in Beijing area].

The investigation of Lyme disease in Beijing area is reported for the first time. The sera of 1314 local residents were examined by indirect immunofluorescent assay. 11.9% of them were seropositive to Borrelia burgdorferi. The principal vector was Haemapsysalis longicornis. Six strains of B. burgdorferi were isolated from ticks or patients using modified BSK medium. Spirochetes were found in 5 of 30 patients' skin biopsy samples. Penicillin or ceftriaxone was used to treat the patients, and the effective rates were 64% and 88%, respectively.

Adolescent↗
PubMed1993

Expression and characterization of rat kallikrein-binding protein in Escherichia coli.

Rat kallikrein-binding protein is a novel serine-proteinase inhibitor that forms a covalent complex with tissue kallikrein. We have purified rat kallikrein-binding protein and cloned the cDNA and the gene encoding rat kallikrein-binding protein [Chao, Chai, Chen, Xiong, Chao, Woodley-Miller, Wang, Lu and Chao (1990) J. Biol. Chem. 265, 16394-16401; Chai, Ma, Murray, Chao and Chao (1991) J. Biol. Chem. 266, 16029-16036]. In the present study, we have expressed rat kallikrein-binding protein in Escherichia coli with a T7-polymerase/promoter expression system. A high level of expression was detected by an e.l.i.s.a. with an average of 24.2 mg of recombinant rat kallikrein-binding protein per 1 of culture. The recombinant protein appeared as a major protein in a crude extract of Escherichia coli on SDS/PAGE. It showed a molecular mass of 43 kDa and was recognized by polyclonal antibody to the native rat kallikrein-binding protein in Western-blot analysis. The recombinant rat kallikrein-binding protein has been purified to apparent homogeneity by DEAE-Sepharose CL-6B, hydroxyapatite Bio-Gel HPHT and Mono P 5/5 column chromatography. The purified recombinant rat kallikrein-binding protein showed immunological identity with the native rat kallikrein-binding protein purified from rat serum, in a specific e.l.i.s.a. To confirm the fidelity of the expression, the N-terminal ten amino acids of the recombinant rat kallikrein-binding protein were sequenced and were shown to match perfectly with those of the native rat kallikrein-binding protein. The purified recombinant rat kallikrein-binding protein formed SDS- and heat-stable complexes with rat tissue kallikrein (rK1) and T-kininogenase (rK10) in vitro, but not with other enzymes in the rat kallikrein gene family, such as tonin (rK2) and S3 protein (rK9), which indicates enzyme-specific binding. The properties of the recombinant rat kallikrein-binding protein including its size, charge, complex formation with target enzymes and immunological characteristics were compared with those of the native protein. This expression system provides a simple way to obtain a large amount of the biologically active recombinant protein, to study structure-function relationships of the rat kallikrein-binding protein and its interaction with its target enzymes.

Animals↗
PubMed1993

Identification of sites for feedback regulation of glutamine 5-phosphoribosylpyrophosphate amidotransferase by nucleotides and relationship to residues important for catalysis.

Glutamine phosphoribosylpyrophosphate amidotransferase, the key regulatory enzyme for de novo purine nucleotide synthesis, is subject to feedback regulation by adenine and guanine nucleotides. Affinity labeling with 5'-p-fluorosulfonylbenzoyladenosine (FSBA) and 8-azidoadenosine 5'-monophosphate (N3-AMP) was used to identify purine nucleotide sites for feedback control of the Escherichia coli amidotransferase. FSBA inactivated the amidotransferase with saturation kinetics. Specificity for inactivation was shown by the covalent attachment of 2.0-2.4 eq of [3H] sulfobenzoyladenosine (SBA) per subunit and protection by GMP and AMP against inactivation and incorporation of [3H]SBA. Six chymotryptic peptides modified with [3H]SBA were isolated and identified by differential labeling followed by high performance liquid chromatography and radioactivity. Mass spectrometry and Edman degradation analysis were used to identify 5 residues that were covalently modified by [3H]SBA: Tyr74, Tyr258, Lys326, Tyr329, and Tyr465. Tyr258 was also modified by N3-AMP. Mutant enzymes K326Q and Y329A had activity similar to that of the wild type enzyme. However, both mutants exhibited decreased sensitivity to inhibition by GMP and decreased binding of GMP but were inhibited by AMP. Mutant enzymes Y74A and Y258F were normally feedback-inhibited but were defective in glutamine amide transfer and synthase functions, respectively. Therefore Tyr74 and Tyr258 are important for activity and modification by FSBA and N3-AMP accounts for enzyme inactivation. These results localize residues important for catalysis in close proximity to a site for nucleotide binding. Two additional mutant enzymes, G331I and N351A, were constructed which were refractory to inhibition by GMP with little change in inhibition by AMP. A replacement of Tyr465 indicates that this residue is not essential for catalysis or feedback inhibition. Overall, these results are interpreted in terms of a two-nucleotide site model with Lys326, Tyr329, Gly331, and Asn351 defining a site required for inhibition by GMP. A second nucleotide site not affinity labeled by analogs is very close to or overlaps with the catalytic site.

Adenosine↗