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R G Lewis

Publications and source records attributed to R G Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1986

Lateral regionalization and diffusion of a maturation-dependent antigen in the ram sperm plasma membrane.

We have used a monoclonal antibody ESA 152 in fluorescence recovery after photobleaching (FPR) studies of a maturation-dependent surface antigen of ram sperm. The antibody is an immunoglobulin G secreted by a hybridoma derived from NS1 mouse myeloma cells. The ESA 152 antigen is not detectable in testicular sperm. It is localized on the surface of ejaculated sperm where it is present on all regions of the surface, but tends to be concentrated on the posterior region of the head. The ESA 152 antigen can be extracted by detergents or chloroform-methanol. The extracted antigen is sensitive to proteases and migrates with an apparent Mr approximately 30,000 in SDS-containing 10-20% polyacrylamide gradient gels. FPR measurements of ESA 152 lateral mobility in the membrane yield diffusion coefficients in the range 10(-9)-10(-8) cm2/s, values typical of lipids but observed for proteins only at the fluid dynamic limit where diffusion is controlled by lipid fluidity. Immobile fractions, typical of membrane proteins, are observed on all regions. When the antigen is stained by a fluoresceinated Fab fragment of the ESA 152 antibody, the diffusibility is highly regionalized, with particularly low, but rapid, recovery on the midpiece. Cross-linking of the antigen with the intact ESA 152 antibody induces a redistribution in which the antigen is excluded from the posterior head region. This cross-linking is accompanied by increases in ESA 152 diffusibility on both the anterior head and the midpiece.

Animals↗
PubMed1983

Surface glycoprotein changes in ram spermatozoa during epididymal maturation.

Three radiolabeling procedures were applied to ram spermatozoa obtained at three different stages of posttesticular development: on leaving the testis (testicular sperm); after epididymal transit (cauda epididymal sperm); and after exposure to accessory sex gland secretions (ejaculated sperm). The washed spermatozoa were subjected to three radiolabeling treatments: 1) galactose oxidase and sodium boro [3H]hydride (galactosyl and galactosaminyl residues); 2) sodium metaperiodate and NaBH4 (sialyl residues); and 3) chloroglycoluril and Na125 I (tyrosyl residues). High resolution sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoretic analysis of the surface radiolabeling patterns confirms earlier studies in demonstrating an overall shift in the predominant labeled glycoproteins from the zone 78-115 kd in testicular spermatozoa to relatively low molecular weights of between 15 and 95 kd in cauda epididymal or ejaculated spermatozoa. Labeling procedures specific for glycoproteins and sialoglycoproteins revealed additional complexities in the surface transformation patterns of ram spermatozoa and suggest that cauda epididymal spermatozoa exposed to accessory sex gland secretions adsorb or produce a component of high molecular weight (approx. 350 kd).

Animals↗
PubMed1982

Combined use of prazosin and beta-blockers in hypertension.

Combined use of prazosin and beta-blockers in a hypertension clinic over a 3-year period was surveyed by means of a computerized record system. Of the 1,250 patients in the clinic, 171 (14%) had been treated with this combination for periods averaging 17 months. Prazosin was administered with a beta 1-selective beta-blocker in 94 cases and with a beta 1 + beta 2-blocker in 100 cases; 23 patients had received treatment with both combinations. Diuretics were given in 86% of cases and other antihypertensive drugs in 19%. The population treated had a high incidence of severe hypertension, with initial diastolic pressure greater than 120 mm Hg in 38% and between 100 and 120 mm Hg in 50%. The percentage of patients with diastolic pressure less than 100 mm Hg was 12% initially and 79% at the end of the treatment period. Side effects necessitated withdrawal of therapy in 35 cases. These were referable in 19 cases to prazosin and in 16 to beta-blockers. Prazosin was found to be more effective in lowering blood pressure in combination with beta 1-blockers than with beta 1 + beta 2-blockers, although there were fewer severe side effects with beta 1-blockers.

Adrenergic beta-Antagonists↗
PubMed1982

Characterization of bacteriocin 28 produced by Clostridium perfringens.

Bacteriocin 28, produced by Clostridium perfringens, was characterized by gel filtration and sodium dodecyl sulfate - polyacrylamide gel electrophoresis as a glycoprotein with a molecule weight of approximately 100,000. Density gradient centrifugation suggested a lower weight of 84,000. The bacteriocin bound firmly to phenyl-Sepharose CL-4B gel, indicating hydrophobic properties, and elution from this gel with ethylene glycol clearly separated bacteriocin from the alpha and theta toxins of C. perfringens, the latter of which was also hydrophobic. Bacteriocin 28 was immunogenic, inducing neutralizing and precipitating antibodies, and possessed three isoelectric points: 7.37, 7.05, and 5.4. Amino acid and carbohydrate analysis of the active material showed a composition of 15 amino acids and several carbohydrates. The molecule demonstrated instability with increasing purification, and several approaches to purification are described.

Bacteriocins↗
PubMed1977

Galactosyl transferase of a Golgi fraction from cultured neoplastic mast cells.

Suspension cultures of neoplastic mouse mast cells were used to obtain large quantities of a homogeneous cell population as starting material for cell fractionation. A Golgi fraction was prepared by slight modification of established techniques and identified by electron microscopy. Assay of galactosyl transferase activity using ovalbumin, desialylated degalactosylated orosomucoid, and N-acetylglucosamine as galactose acceptors showed that the Golgi fraction was enriched in specific activity over the homogenate. The Golgi galactosyl transferase was examined in detail. Acceptor concentrations for optimal galactose incorporation were determined, and substrate inhibition effects were shown with higher concentrations of all three acceptors. Manganese was shown to be necessary for galactose incorporation. A higher concentration of manganese afforded some protection from substrate inhibition by acceptors, but at the same time was itself inhibitory. All three acceptors competed with one another for galactose incorporation, indicating that a single enzyme catalyzed the transfer of galactose for all acceptors.

Acetylglucosamine↗
PubMed1976

Laboratory investigation and infection control of cholera in Kingston, Ont.

Vibrio cholerae, biotype El Tor, was isolated in a hospital laboratory in Kingston, Ont. in 1974. Confirmation and complete identification by the Ontario regional and provincial public health laboratories was obtained within 3 days. Institution of well established infection-control and public health measures prevented spread of the infection within the hospital and the community.

Adult↗