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Biomedical subjects

M A Fletcher

Publications and source records attributed to M A Fletcher.

At least 145 records · Page 8Linked to original sources
PubMed1978

Inhibition of growth and guanylate cyclase activity of an undifferentiated prostate adenocarcinoma by an extract of the balsam pear (Momordica charantia abbreviata).

We have recently described the presence of a guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] inhibitor (GCI) in an aqueous extract of the balsam pear (Momordica charantia abbreviata). Because the guanylate cyclase-cyclic GMP system is though to be involved in cell growth, DNA and RNA synthesis, and possible malignant transformation, we examined the effect of the aqueous extract containing GCI on an undifferentiated adenocarcinoma of the rat prostate and concanavalin-A-stimulated [3H]thymidine incorporation into cultured splenic lymphocytes, a process thought to be mediated by cyclic GMP. The results demonstrate that the extract of the balsam pear blocks both the growth of the rat prostatic adencarcinoma in vitro and [3H]thymidine incorporation into DNA. DNA histograms from flow cytometry indicated that the extract containing GCI inhibited in the G2 + M phase of the cell cycle, a presumed locus of cyclic GMP effects. In addition, guanylate cyclase activity was significantly greater in the tumor than normal prostate tissue and was decreased by the extract containing GCI. Cyclic GMP levels in the tumor in culture wer also decreased by addition of the extract. It remains to be determined whether or not the anti-tumor agent and GCI are the same substance.

Adenocarcinoma↗
PubMed1977

Isolation of plasma membrane glycoprotein from bovine thymocytes.

Glycoprotein was isolated from a purified thymocyte membrane preparation by two methods: lithium diiodosalicylate-phenol extraction and hot 75% ethanol extraction. A higher yield of membrane sialic acid was obtained by the latter method. The preparations had similar apparent molecular weights on sodium dodecyl sulfate gel electrophoresis. Both had similar receptor activities against a panel of hemagglutinins, although the 75% ethanol extract was more active on a weight basis. However, there were significant differences in carbohydrate and amino acid compositions of the two thymocyte extracts. The lithium diiodosalicylate-extracted material had much more glucose, ribose, and glycine than the ethanol extract. The glycoprotein preparations from thymocytes were quite distinct from the glycoprotein of bovine erythrocytes in both composition and receptor properties.

Animals↗
PubMed1977

True knot of the umbilical cord.

Fifty umbilical cords were prepared and examined and their venous perfusion pressures measured with and without a true knot in the cord. Contrary to information in the literature, a loose umbilical cord knot did not affect the venous perfusion pressure. With a tightened knot, the smaller the umbilical cord diameter, the greater was the pressure required to perfuse past the knot. The umbilical vessels, protected by the myxomatous structure of the Wharton's jelly, were rarely completely occluded. These findings correlate clinically with the relatively high incidence yet low fetal mortality rate actually due to a true knot in the umbilical cord.

Female↗
PubMed1977

Immunochemical studies of infectious mononucleosis. VI. a radioimmunoassay for the detection of infectious mononucleosis heterophile antibody and antigen.

The coated-tube method of solid-phase radioimmunoassay has been adapted to the detection of heterophile antibodies and antigens of infectious mononucleosis. Disposable plastic hemagglutination trays were coated with purified glycoprotein from horse erythrocytes and the subsequent uptake of antibody from test sera was detected by radio-iodinated horse erythrocyte glycoprotein. In a preliminary survey of sera from patients with infectious mononucleosis and sera from controls, the assay proved highly sensitive and specific. The test system was also useful in a competitive binding assay for immunochemical studies of glycoproteins from other heterophile antigen-positive species.

Animals↗
PubMed1977

Immunochemical studies of infectious mononucleosis. VII. Isolation and partial characterization of a glycopeptide from bovine erythrocytes.

The major sialoglycopeptide released from bovine erythrocytes by papain has been purified and characterized. The glycopeptide contains 82% by weight carbohydrate in molar ratios of galactose - 5.5:N-acetylglucosamine - 3.6:sialic acid - 2.6:N-acetylgalactosamine - 1.0. The carbohydrate and amino acid composition is quite different from the glycoprotein extracted from bovine erythrocyte stroma with hot 75% ethanol. The glycopeptide is devoid of reactivity with Paul-Bunnell heterophile antibody of infectious mononucleosis - an activity expressed to high degree on the bovine erythrocyte and associated with glycoprotein. The glycopeptide does react, however, with another antibody found in infectious mononucleosis as well as most normal human sera tested.

Animals↗
PubMed1977

The Dunning R3327 prostate adenocarcinoma in the Fischer-Copenhagen F1 rat: a useful model for immunological studies.

The Dunning R3327 tumor sublines in the Fischer-Copenhagen F1 rat provide a spectrum of transplantable prostate adenocarcinomas for the study of host-tumor interactions. The tumor can be transplanted with both fresh and cryopreserved cell suspensions. The F1 rat is an appropriate animal for immunological studies based on humoral and cellular immune responses. Preliminary evidence of the host-tumor relationship in the F1 rat indicates that purified membrane preparations induced a specific cytotoxic population of lymphocytes.

Adenocarcinoma↗
PubMed1976

Immunochemical studies of infectious mononucleosis. V. Isolation and characterization of a glycoprotein from goat erythrocyte membranes.

A glycoprotein was isolated from goat erythrocyte membranes by extraction with hot 75% ethanol. The glycoprotein was purified by ethanol precipitation, phosphocellulose chromatography gel filtration, ethyl:ether and chloroform:methanol extraction. In aqueous phosphate-buffered saline, pH 7, the glycoprotein was in an aggregated state with a sedimentation coefficient (S(obs)) to 1.5. Electrophoresis of the glycoprotein on polyacrylamide gels containing phosphate-buffered 0.1% SDS gave a single band, staining with both periodic acid Schiff (PAS) and Coomassie Blue (CB). The apparent m.w., calculated from retardation coefficient, was 25,000. Electrophoresis of the glycoprotein on 1% SDS gels buffered with Tris-acetate (pH 7.4) showed a major band of similar (23,500) apparent m.w. plus four other PAS- and CB-staining bands of lower mobility. With 131I-labeled glycoprotein, recovery of bands from gels, sialic acid analysis, heterophile antigen activity, and re-electrophoresis, it was shown that these additional bands were aggregated forms of a single or closely related glycoprotein species. The purified glycoprotein contained 50% carbohydrate with molar ratios of sialic acid:galactose:mannose:galactosamine:glucosamine of 3.1:2.1:0.1:1.6:1. The glycoprotein was highly reactive with the Paul-Bunnell heterophile antibody in the sera of patients with infectious mononucleosis, with Limulus polyphemus lectin and weakly ractive with wheat germ agglutinin. These reactivities were destroyed by neuraminidase treatment or by alkaline sodium borohydride. The native glycoprotein did not react with lectins from Canavalia enisformis, Phaseolus vulgaris, Ricinus communis, or Vicia graminea although it was reactive with the latter two after neuraminidase treatment.

Amino Acids↗
PubMed1975

Glucagon and adenylate cyclase: binding studies and requirements for activation.

Solubilization of myocardial adenylate cyclase abolished responsiveness to glucagon and catecholamines, two of the hormones which activate the membrane-bound enzyme. Adenylate cyclase freed of detergent by DEAE-cellulose chromatography continues to remain unresponsive to hormone stimulation. However, adding purified bovine brain phospholipids--phosphotidylserine and monophosphatidylinositol--restored responsiveness to glucagon and catecholamines, respectively. 125-i-glucagon binding appeared to be independent of phospholipid, since equal binding was observed in the presence or absence of detergent and in the presence or absence of phospholipids. Chromatography of the solubilized preparation on Sephadex G-100 WAS CHARACTERIZED BY 125-I-glucagon binding and fluoride-stimulatable adenylate cyclase activity appearing in the fractions consistent with the void volume, suggesting a molecular weight greater than 100,000 for the receptor-adenylate cyclase complex. Prior incubation of the binding peak with 125-I-glucagon and rechromatography of the bound glucagon on Sephadex G-100 shifted its elution to a later fraction consistent with a smaller-molecular-weight peak. The molecular weight of this material was 24,000 to 28,000, as determined by SDS polyacrylamide gel electrophoresis. The latter findings are consistent with a dissociable receptor site for glucagon on myocardial adenylate cyclase.

Adenylyl Cyclases↗