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Biomedical subjects

H Xu

Publications and source records attributed to H Xu.

At least 757 records · Page 42Linked to original sources
PubMed1991

Schistosoma mansoni tropomyosin: production and purification of the recombinant protein and studies on its immunodiagnostic potential.

A cDNA that encodes Schistosoma mansoni tropomyosin, except for 10 amino acids at the amino terminus, has been cloned into a pOTSNCO plasmid vector. Induced expression resulted in a constant level of recombinant protein production. The recombinant S. mansoni tropomyosin was purified from preparative SDS-PAGE gel and by a combination of 20% ammonium sulfate fractionation and fast protein liquid chromatography-ion-exchange chromatography. The purified recombinant S. mansoni tropomyosin was tested as an immunodiagnostic reagent in Western blot and enzyme-linked immunosorbent assays. Sera from individual patients with chronic S. mansoni infection, but not S. haematobium, S. japonicum, parasitic infections other than schistosomiasis, and without infection reacted with the recombinant tropomyosin. The species specificity of S. mansoni tropomyosin suggests that further study of its potential as an immunodiagnostic reagent is warranted.

Animals↗
PubMed1991

[Androgen-like and anabolic action of Antheraea pernyi Guerin-Meneville Pas].

It has been found that the ethyl acetate extract isolated from Antheraea pernyi Pas is able to increase the weight of prostate-semina and levator ani muscle-bulbocavarnosus muscle of castrated mice. In addition, the extract also accelerates the growth of younger male mice and enhances the contents of RNA, DNA and protein in the liver tissue of mice. It has been determined that beta-ecdysone is one of the effective constituents for the androgen-like and anabolic action.

Animals↗
PubMed1991

Blood dendritic cells carry terminal complement complexes on their cell surface as detected by newly developed neoepitope-specific monoclonal antibodies.

Blood dendritic cells carry the terminal complement complex (TCC) on their surface, as detected by three monoclonal antibodies (mAb). Two of these mAb were generated by immunizing mice with the terminal complement complex, whereas the third was generated by immunizing mice with blood dendritic cells. All three mAb are directed against neoepitopes on the C9 molecule, as assessed by binding and blocking experiments and studies with several forms of denatured C9 and C9-depleted serum. Only one of these mAb binds to soluble polymerized C9. All three mAb allow the quantification of human TCC in sensitive ELISA procedures and could be used as markers for the evaluation of the functions of non-lytic TCC on dendritic cells.

Animals↗
PubMed1991

[A study on serum suppressive factor(s) on lymphocyte proliferation in rats under restraint stress].

In order to study the effect of stress on lymphocyte proliferation, SD rats were restrained with four limbs tied on a frame in supine position at room temperature (20 degrees C) for 20 h, and control animals were not disturbed in home cage. The blood was then collected from the heart under light ether anesthesia. The peripheral blood lymphocytes were separated from heparinized whole blood by density gradient (d 1.077) centrifugation, or the serum was obtained after the blood coagulated at 4 degrees C for about 6h. It was found that the blood lymphocyte proliferation induced by Con A was significantly inhibited in the stressed group as compared with the control (P less than 0.01, n = 8, ANOVA). The result was in accordance with our earlier study in which the animals were stressed with electric shock. In the present study, it was also found that the serum of the stressed animals was capable of suppressing Con A-induced lymphocyte proliferation of normal mice (P less than 0.01, n = 8, ANOVA) to a significant extent. Thus the present experiment suggests that there is some substance with suppressive activity on lymphocyte proliferation in the serum of the stressed rats. The serum lost its suppressive activity when it was heated to 100 degrees C (3 min), treated with 60% methanol or incubated with trypsin (64 micrograms/ml), thus suggesting that the suppressive factor(s) most likely is a kind of protein.

Animals↗
PubMed1990

Synergistic effect of phorbol myristate acetate on bacterial lipopolysaccharide induced rat splenocyte proliferation.

1. Bacterial lipopolysaccharide (LPS) stimulated [3H]TdR incorporation of rat splenocytes in a concentration dependent manner. 2. Phorbol 12-myristate 13-acetate (PMA) alone has little effect on rat splenocyte proliferation but it exerted a marked synergistic effect on LPS-induced [3H]TdR incorporation when added at the first few hours of incubation with LPS. Minimal synergistic effect of PMA was observed if it was added later than 4 hr after LPS application. 3. Both LPS-stimulated and PMA synergized incorporation of [3H]TdR in rat splenocytes were inhibited by H-7, a protein kinase C inhibitor. 4. The results support the notion that the activation of protein kinase C is a necessary but insufficient cellular signal in the initiation of proliferative response of rat splenocytes by LPS.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

The potent opioid agonist, (+)-cis-3-methylfentanyl binds pseudoirreversibly to the opioid receptor complex in vitro and in vivo: evidence for a novel mechanism of action.

The present study demonstrates that pretreatment of rat brain membranes with (+)-cis-3-methylfentanyl [(+)-cis-MF], followed by extensive washing of the membranes, produces a wash-resistant decrease in the binding of [3H]-[D-ala2,D-leu5]enkephalin to the d binding site of the opioid receptor complex (delta cx binding site). Intravenous administration of (+)-cis-MF (50 micrograms/kg) to rats produced a pronounced catalepsy and also produced a wash-resistant masking of delta cx and mu binding sites in membranes prepared 120 min post-injection. Administration of 1 mg/kg i.v. of the opioid antagonist, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY), 100 min after the injection of (+)-cis-MF (20 min prior to the preparation of membranes) completely reversed the catatonia and restored masked delta cx binding sites to control levels. This was not observed with (+)-cycloFOXY. The implications of these and other findings for the mechanism of action of (+)-cis-MF and models of the opioid receptors are discussed.

Animals↗
PubMed1990

A monoclonal antibody recognizing selectively rat granulocytes.

In the present study, a murine monoclonal antibody, RK-4 (IgG1) specific for rat granulocytes and their precursors in blood and bone marrow is described. Results obtained by immunocytological and flowcytometry analysis showed this mAb to recognize selectively a surface antigen on neutrophils, eosinophils and basophils. Analysis of cryosections of various lymphatic and non-lymphatic organs demonstrates that this mouse antibody does not cross-react with any other structures. By flow cytometric analysis we found peripheral blood leukocytes to consist of about 15-20% granulocytes. RK-4 is therefore a valuable tool for studying differentiation and function of granulocytes under various conditions.

Animals↗
PubMed1990

Host genes that influence transposition in yeast: the abundance of a rare tRNA regulates Ty1 transposition frequency.

Genetic screening of a yeast genomic library in a high-copy-number vector identified the normally single copy tRNA(CCU Arg) gene as one of the genes and reduces Ty1 transposition frequency when overexpressed. Immunoblot analyses of Ty1-encoded proteins indicate an inverse correlation between the copy number of the tRNA gene and the production of the TYB protein. Thus, Ty1 transposition frequency is apparently regulated by the level of tRNA(CCU Arg) in yeast cells.

Codon↗
PubMed1990

Localization of sequences required in cis for yeast Ty1 element transposition near the long terminal repeats: analysis of mini-Ty1 elements.

In order to identify and characterize sequences within Ty1 elements which are required in cis for transposition, a series of mini-Ty1 plasmids were constructed and tested for transposition. Mini-Ty1s are deletion mutants of the Ty1-H3 element; Ty1 gene products required for transposition are supplied in trans from a helper Ty1 which has intact open reading frames but lacks a 3' long terminal repeat (LTR) and therefore cannot transpose itself. Up to 5 kilobase pairs of internal sequences of the 6-kilobase-pair-long Ty1 element can be deleted without a significant effect on transposition. The smallest mini-Ty1 element capable of transposition contains the 3' LTR and the transcribed portion of the 5' LTR, 285 base pairs (bp) of internal sequence 3' to the 5' LTR, and 23 bp of internal sequence 5' to the 3' LTR. We conclude that Ty1-encoded proteins can act in trans and that cis-acting sequences in Ty1-H3 are all within or near the LTRs. Further deletion of the 285-bp internal sequence adjacent to the 5' LTR significantly reduced transposition frequency, and the mini-Ty1 RNA produced failed to be packaged into the viruslike particles efficiently. Surprisingly, several nonhomologous cellular mRNAs were also associated with viruslike particles.

Base Sequence↗