Biomedical subjects

S B Zhang

Publications and source records attributed to S B Zhang.

45 records · Page 3Linked to original sources

PubMed1990

Polyclonal antibodies against follitropin (FSH) receptor interfere with hormone binding, but mimic the effects of FSH.

We have raised polyclonal antibodies in rabbits against the FSH receptor, purified from calf testis and isolated the IgG fraction from the immune serum (immune IgG) by protein A affinity chromatography. When the immune IgG was incubated with purified, radioiodinated FSH receptor, the resulting complex could be immunoprecipitated by goat anti-rabbit gamma globulin. The immunoprecipitate, after dissociation of receptor from antibody, separation by SDS-PAGE under reducing conditions, and autoradiography, showed the presence of a approximately 60 kDa protein previously identified as a component of the FSH receptor. Binding of 125I-hFSH to membrane-bound receptors was inhibited in a concentration-dependent manner by immune IgG (Ed50 = 90 micrograms/ml). Nonimmune serum or IgM/IgA fractions from immune serum had no effect. 125I-labeled immune IgG bound specifically to testis membranes and the binding could be inhibited in a concentration-dependent manner by ovine FSH. These results suggest that the FSH-binding site and the antibody-binding site on the receptor are proximate or identical. Immune IgG mimicked the ability of FSH to stimulate basal adenylate cyclase activity and conversion of androstenedione to estradiol in cultured immature rat Sertoli cells. Stimulatory but submaximal effects of FSH were augmented by immune IgG. Rat Sertoli cells treated with IgG fractions from immune serum showed an intense fluorescent staining of plasma membrane receptor. No fluorescent staining of receptor was seen when preimmune IgG was used or in the presence of excess ovine FSH. These observations suggest that the polyclonal receptor antibody capable of recognizing FSH receptor behaved as an FSH binding competitor, but was also active as an agonist producing the biological effect of FSH in vitro. The effectiveness of antibodies against FSH receptor in stimulating estradiol synthesis suggests that the information needed for FSH signal transduction resides in the membrane receptor rather than in the hormone molecule. Such antibodies may offer a useful probe for further study of FSH receptor structure and mechanism of hormone action.

Androstenedione↗

PubMed1989

Short-term multidrug therapy in multibacillary leprosy--review of 80 cases in two provinces of China (1983-1988).

Thirty-three active multibacillary patients from nine counties of Weifang Prefecture, Shandong Province, and 47 active cases from Menla County, Yunnan Province, People's Republic of China, were treated with 24 and 27 months of multidrug therapy (MDT), respectively, in 1983. Clinical assessments, smears, and histopathologic examinations were carried out independently by study teams from the Institutes of Dermatology of these two provinces. Reexaminations at 12-14 months and at termination of therapy showed marked improvement, and there was continued improvement at 12-18 and 33 months on follow up. Conversion of the bacterial index to negativity was 0/33, 5/47 for the patients from Shandong and Yunnan provinces, respectively, at the end of MDT and 2/33 at 12 months' and 17/47 at 18 months' follow up, which increased to 21/33 and 26/44 at 33 months' follow up. Regression of specific infiltration was about 21%-100% after 24-27 months of MDT; further regression to 95%-100% occurred at 33 months' follow up.

Adult↗

PubMed1988

Regulation of follicle-stimulating hormone binding to receptors on bovine calf testis membranes by cholera toxin-sensitive guanine nucleotide binding protein.

In a previous study we reported that FSH receptors in bovine testes membranes are physically and functionally associated with a guanine nucleotide-binding protein (N protein). In this study we examined the mechanism whereby GTP binding to N protein regulates FSH binding to its receptors. Binding of FSH to receptors decreased in the presence of GTP in a dose-dependent and noncompetitive manner. This effect did not require the presence of Mg+2 and is in contrast to the reported requirement for Mg+2 for GTP effects on human CG binding to ovarian receptors. Equilibrium binding experiments indicated that decreased hormone binding in the presence of GTP was not due to a decrease in the number of FSH receptors per se; rather, the altered binding isotherm was the result of a decrease in affinity of receptors for FSH. Moreover, the dissociation of [125I]human FSH from preformed FSH-receptor complex was rapid in onset and significantly accelerated in the presence of GTP. In a series of nucleotides, GTP was most effective in causing this effect. Evidently, occupancy of GTP binding sites on the N protein, including low affinity and high capacity sites, is necessary for GTP regulation of FSH binding to receptors. The fact that pretreatment of bovine testis membranes with cholera toxin plus NAD, but not pertussis toxin plus NAD, eliminates the GTP effect on FSH binding to its receptors suggests that the GTP regulatory binding protein mediating the GTP regulation of FSH binding is probably Ns and not Ni. Further characterization of FSH receptor sensitivity to GTP, however, indicated that the N protein involved does not exhibit all of the characteristics reported for Ns. For example, the affinity of GTP for N protein is relatively low even under conditions where GTP hydrolysis has a minimal effect in reducing the total concentration of GTP. Also, the absence of a requirement for Mg+2 in high affinity FSH receptor-N protein coupling is different from the requirement for Mg+2 seen with the beta-adrenergic receptor and Ns. Moreover, the N protein which mediates GTP regulation of FSH-receptor binding appears to be relatively insensitive to N-ethylmaleimide, unlike the N-ethylmaleimide sensitivity of the turkey erythrocyte Ns. These results suggest that differences may exist in the structure-function features of GTP regulatory binding protein associated with different types of hormone ligands and receptors.

Animals↗

PubMed1987

Complementary base-pairing properties of cyclized and linear oligonucleotides.

Oligouridylates of varying chain lengths were synthesized by polynucleotide phosphorylase and cyclized by RNA ligase. Over chain lengths from 7 to 15, the bindings of the cyclized and linear oligomers to polyadenylate were measured on the basis of differential migration of bound and free oligomers on a gel exclusion column. Binding of the cyclized oligomers was found to be far weaker than that of their linear counterparts of equal length. Such a general reduction in base-pairing capacity due to the cyclized conformation, by limiting the strength of unintended base-pairing without obstructing the possible development of strong specific base-pairing, may represent an advantage important to the function and evolution of loop structures in tRNA and other RNA molecules.

Base Composition↗

PubMed1987