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X C Wang

Publications and source records attributed to X C Wang.

At least 91 records · Page 5Linked to original sources
PubMed1989

Regulation of beta-galactoside alpha 2,6-sialyltransferase gene expression by dexamethasone.

The hepatic acute phase response is accompanied by increased levels of Gal beta 1-4GlcNAc alpha 2,6-sialyltransferase activity in liver and in circulation. Previous studies suggested that cytokines and glucocorticoids mediate the induction of this sialyltransferase activity. In this study the regulation of sialyltransferase expression by dexamethasone in H35 rat hepatoma cells is assessed by Northern hybridization and enzyme activity assays. Exposure of H35 cells to 1 microM dexamethasone for 24 h causes a 3-4-fold enrichment of sialyltransferase mRNA and a corresponding increase in enzymatic activity. The induction of sialyltransferase mRNA begins within 3 h of dexamethasone treatment and reaches a plateau within 24 h. Sialyltransferase mRNA induction is dose dependent; the minimum concentration of dexamethasone necessary for induction is 10(-8) M, and induction was maximal at 10(-6) M. Induction is sensitive to actinomycin D, suggesting that regulation may be exerted by altering the rate of mRNA synthesis. Puromycin and cycloheximide are ineffective in blocking induction, suggesting that de novo protein synthesis is not required for induction. Finally, dexamethasone alone is sufficient for maximum induction of sialyltransferase mRNA. In contrast, maximal induction of alpha 1-acid glycoprotein, a well studied hepatic acute phase reactant, requires both dexamethasone and cytokines, implying that different pathways exist for the induction of participants in the acute phase response.

Animals↗
PubMed1989

Lectin histochemistry of human gliomas.

Formalin-fixed and paraffin-embedded specimens of 24 human gliomas were examined histochemically with five lectins; concanavalin A (Con A), wheat germ agglutinin (WGA), Ricinus communis agglutinin 1 (RCA-1), peanut agglutinin (PNA), and Ulex europaeus agglutinin 1 (UEA-1). Although the staining intensity with lectins was variable, tumor cells in five astrocytomas, three oligodendrogliomas, six ependymomas, and one gliosarcoma, were generally positive for Con A, WGA, and RCA-1, and negative for PNA and UEA-1, whereas those in nine glioblastomas were usually positive for Con A and WGA and negative for RCA-1 and PNA as well as UEA-1. The malignancy in neoplastic astrocytes was correlated with the decrease in binding with lectins, especially RCA-1. Blood vessels, particularly the endothelial layers, in all gliomas were stained intensely with all lectins used. Macrophages showed two staining features with lectins; stippled and granular. The former macrophages were positive for Con A, WGA, RCA-1, and PNA, and negative for UEA-1, whereas the latter macrophages were positive for all lectins used. Thus, the staining characteristics with lectins of macrophages were different from those of any glioma cells and very useful for identification of macrophages in gliomas.

Brain Neoplasms↗
PubMed1989

[Bladder stones in women: a report of 24 cases].

The authors report 24 female cases of cystolithiasis (18 adults and 6 children) that accounted for 8.5% (24/283) of the total cases of cystolithiasis admitted to our hospital during 1960-1987. In none of the cases correct diagnosis was established during the first visit to the hospital. One patient was suspected of having an ovary cyst and 23 cases (95.8%) were exclusively diagnosed as urinary infection. Predisposing factors were quite obvious in 16 cases. Three patients had recurrent bladder stones. The causes, clinical features, prevention methods, and diagnosis of female cystolithiasis are discussed.

Adolescent↗
PubMed1986

Formation of metabolites of [Arg8]vasopressin (AVP) by brain peptidases. Conversion of the intermediate [Cyt6]AVP-(3-9).

[Cyt6]AVP-(3-9), an intermediate in the metabolism of AVP-(1-9) in vitro, was used to investigate the mechanism of formation of centrally active AVP metabolites. Exposure of [Cyt6]AVP-(3-9) to rat brain membranes resulted in formation of [Cyt6]AVP-(4-9), -(5-9), [pGlu4, Cyt6]AVP-(4-9) and AVP-(3-5), which were isolated and chemically identified. Products derived from cleavage of the C-terminus of the substrate were absent. Time-course experiments further indicated that the conversion process is predominantly mediby an aminopeptidase-like mechanism. The conversion of [Cyt6]AVP-(3-9) by membranes from hippocampus, amygdala and septum was quantitatively and qualitatively similar. The results point to a major role of aminopeptidase activity in the metabolic conversion of AVP and the formation of centrally active AVP metabolites.

Aminopeptidases↗
PubMed1986

Characterization and quantitation of vasopressin metabolites in the rat brain by specific radioimmunoassay and high-pressure liquid chromatography.

The content of endogenous vasopressin (AVP1-9) and its metabolites in rat's various brain areas and pituitary gland was investigated by the combination techniques of high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA). In addition to the AVP1-9, several compounds with C-terminal AVP immunoreactivity were detected in hypothalamus, hippocampus, amygdala, medulla oblongata and septum. The C-terminal AVP1-9 metabolites were virtually absent in the pituitary gland. In view of the highly potent and selective effects on memory processes of AVP metabolites, some endogenous AVP metabolites in the brain may play an important role in the central nervous system (CNS) function.

Animals↗
PubMed1984

Substances resembling C-terminal vasopressin fragments are present in the brain but not in the pituitary gland.

In order to investigate the endogenous occurrence of vasopressin fragments that have previously been found to be generated in vitro by brain peptidases and to have highly potent central activity, extracts of hypothalamus, hippocampus and the pituitary gland were fractionated by high pressure liquid chromatography and analyzed by radioimmunoassay systems with different specificities. Substances that were immunologically and chromatographically similar to synthetic C-terminal vasopressin fragments were detected in brain tissue in different amounts, but were virtually absent in the pituitary gland. It is suggested that these components may represent endogenous vasopressin metabolites. The preferential presence in brain supports a selectively central function of these peptides.

Arginine Vasopressin↗
PubMed1984

A mouse macrophage-like cell line (MMC-1) and its biological characteristics--biological characterization.

The biological characteristics of mouse macrophage-like cell line (MMC-1) are described. This cell line has been cultured in vitro for more than 20 months. MMC-1 cells are adherent to typical morphology of macrophages, but bigger in size than those of the uncultivated. They are actively phagocytic with abundant Fc receptors. The karyotypes are mostly pantaploidy. This cell line provides a useful tool for the biological and immunological study of macrophage.

Animals↗
PubMed1983

Proteolytic conversion of arginine-vasotocin by synaptic membranes from rat and chicken brain.

This paper reports studies on the biotransformation of the nonapeptide arginine-vasotocin (AVT) by both rat and chicken brain synaptic membranes. The fragments which were formed during digestion of AVT1-9, were isolated by high pressure liquid chromatography (HPLC) and chemically characterized by amino acid composition, NH2-terminal amino acid residues and the presence of 14C-radioactivity of the residue glycinamide-9. The major peptide fragments of AVT were: (formula; see text) Time course experiments showed the precursor-product interrelationships between these peptides. The results demonstrate that the conversion of AVT by synaptic membranes involves primarily the action of aminopeptidase activity. Comparison between membrane fractions from rat and chicken brain showed that AVT is converted by a similar proteolytic mechanism in chicken brain, but that differences in activity of the aminopeptidase exist. The results are discussed in view of the concept that AVT serves as precursor for neuropeptides with differential activities in non-mammalian vertebrates.

Aminopeptidases↗
PubMed1983

Proteolysis of adrenocorticotropin in brain. Characterization of cleavage sites by peptidases in synaptic membranes and formation of peptide fragments.

The biotransformation of adrenocorticotropin (ACTH-(1-39)) by brain synaptic membranes has been studied. Peptide fragments of ACTH-(1-39) which were formed during in vitro incubation of the peptide with membrane preparations were isolated by high pressure liquid chromatography and characterized by determination of amino acid composition and NH2- terminal residue. At pH 7.4, ACTH-(1-38) was found as the main metabolite, together with ACTH-(7-21) and ACTH-(7-20). In addition, a series of secondary products was identified. At pH 6.2, ACTH-(1-38), ACTH-(1-37), and ACTH-(1-36) were exclusively formed, while at pH 8.5, ACTH-(1-39) was converted into ACTH-(1-16), ACTH-(17-39), ACTH-(22-39), and ACTH-(3-15). Time course experiments demonstrated the action of a carboxypeptidase activity and a trypsin-like endopeptidase on ACTH-(1-39) as predominant proteolytic events. The carboxypeptidase was optimally active at pH values of 5.7 or below. These enzymes play an essential role in the stepwise conversion of ACTH-(1-39) in brain. It is suggested that they are involved in the modulation of the central activities of ACTH fragments in the brain.

Adrenocorticotropic Hormone↗
PubMed1983

Action of peptidases in brain synaptic membranes on the NH2-terminus of adrenocorticotropin using ACTH-(1-16)-NH2 as a model substrate.

The action of brain peptidases on NH2-terminal sequences of adrenocorticotropin was studied by incubation of ACTH-(1-16)-NH2 under different pH conditions. Profiles of metabolites and time course of product formation were obtained by HPLC analysis of the digests. Fragments of ACTH-(1-16)-NH2 were isolated and characterized by their amino acid composition and NH2-terminal groups. Both at pH 7.4 and pH 8.5 the following fragments were found: ACTH-(3-16)-NH2, ACTH-(4-16)-NH2, ACTH-(5-16)-NH2, and ACTH-(7-16)-NH2. At pH 7.4 the major products were ACTH-(4-16)-NH2 and ACTH-(7-16)-NH2, while the peptide ACTH-(3-16)-NH2 was the main metabolite at pH 8.5. The nature of identified peptides and the time course of their formation demonstrates that aminopeptidase activities predominate in the conversion of the NH2-terminus of adreno-corticotropin and related peptides by brain synaptic membranes.

Adrenocorticotropic Hormone↗
PubMed1983

Adrenocorticotropin: ACTH1-38 is a major product of biotransformation by brain synaptic membranes.

Since adrenocorticotropic hormone is found in the brain, and several of its fragments affect adaptive behavior, the formation of fragments of ACTH1-39 by a rat brain synaptic membrane fraction was investigated. Following the incubations at physiological pH conditions, the digests were fractionated by HPLC to quantitate the amounts of ACTH1-39 remaining and products formed. Time- and enzyme-dependent disappearance of ACTH1-39 was accompanied by the accumulation of a major peptide metabolite (product B). Amino acid analysis and NH2-terminal end-group determination revealed that product B was identical to ACTH1-38. These results indicate the predominance of carboxypeptidase activity in the degradation of ACTH1-39 by brain synaptic membranes.

Adrenocorticotropic Hormone↗