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Biomedical subjects

D Smith

Publications and source records attributed to D Smith.

At least 1,207 records · Page 67Linked to original sources
PubMed1975

Identification of Harper-Cawston factor as thymidine phosphorylase and removal from media of substances interfering with susceptibility testing to sulfonamides and diaminopyrimidines.

Rich media support the growth of bacteria in the presence of concentrations of sulfonamides and diaminopyrimidines that are highly inhibitory when the organisms are grown on minimal media. Many such rich media can be made more suitable for susceptibility testing by the incorporation of lysed horse blood. Harper and Cawston characterized the active substance, Harper-Cawston factor (HCF), and later studies indicated it to be a protein. It has now been identified as thymidine phosphorylase. The identification follows from the identical purification pattern of HCF and thymidine phosphorylase activities from horse blood to a high degree of purity. Blood of goats, sheep, oxen, geese, chickens, cows, dogs, rats, and humans had neither biological activity. The identification of HCF as thymidine phosphorylase is consistent with the earlier findings of Koch and Burchall (1971) that most of the interfering effects of rich media could be accounted for by their thymidine contents, and that thymidine is much more active in this respect than is thymine.

Animals↗
PubMed1975

Temperate Bacteriophage Which Causes the Production of a New Major Outer Membrane Protein by Escherichia coli.

Under most conditions of growth, the most abundant protein in the outer membrane of most strains of Escherichia coli is a protein designated as "protein 1" or "matrix protein". In E. coli B, this protein has been shown to be a single polypeptide with a molecular mass of 36,500 and it may account for more than 50% of the total outer membrane protein. E. coli K-12 contains a very similar, although probably not identical, species of protein 1. Some pathogenic E. coli strains contain very little protein 1 and, in its place, make a protein designated as protein 2 which migrates faster on alkaline polyacrylamide gels containing sodium dodecyl sulfate and which gives a different spectrum of CNBr peptides. An E. coli K-12 strain which had been mated with a pathogenic strain was found to produce protein 2, and a temperate bacteriophage was isolated from this K-12 strain after induction with UV light. This phage, designated as PA-2, is similar in morphology and several other properties to phage lambda. When strains of E. coli K-12 are lysogenized by phage PA-2, they produce protein 2 and very little protein 1. Adsorption to lysogenic strains grown under conditions where they produce little protein 1 and primarily protein 2 is greatly reduced as compared to non-lysogenic strains which produce only protein 1. However, when cultures are grown under conditions of catabolite repression, protein 2 is reduced and protein 1 is increased, and lysogenic and non-lysogenic cultures grown under these conditions exhibit the same rate of adsorption. Phage PA-2 does not adsorb to E. coli B, which appears to have a slightly different protein 1 from K-12. These results suggest that protein 1 is the receptor for PA-2, and that protein 2 is made to reduce the superinfection of lysogens.

Journal Article↗
PubMed1975

Speech remediation of children involved in two different physical education programs.

25 children with severe speech defects and receiving specialized therapy in a camp were randomly assigned to either a physical education program with an emphasis on recreational games or perceptual-motor instruction. All children were administered 6 pre- and posttests of language and speech proficiency. The recreation games group achieved slightly more statistically significant improvements.

Camping↗
PubMed1975

Gastrojejunostomy inhibits postshunt siderosis.

Thirteen of fourteen dogs developed marked increases in hepatic hemosiderin (postshunt siderosis) after construction of portacaval shunt, whereas only three of 12 dogs developed such siderosis after construction of a portacaval shunt and end-to-side gastrojejunostomy with duodenal exclusion. Splenic hemosiderin was increased markedly in dogs with portacaval shunt but increased minimally in dogs with portacaval shunt and gastrojejunostomy. Rib marrow fat increased slightly in dogs with portacaval shunt and decreased slightly in dogs with portacaval shunt and gastrojejunostomy. Thus continued iron absorption appears to account for the development of postshunt siderosis and the addition of gastrojejunostomy ameliorates postshunt siderosis by diminishing iron absorption.

Adipose Tissue↗
PubMed1974

A functional mitotic spindle prepared from mammalian cells in culture.

MITOTIC CELLS LYSED INTO SOLUTIONS OF POLYMERIZABLE MICROTUBULE PROTEIN CONTAIN A SPINDLE WHICH IS SIMILAR TO THE LIVING SPINDLE IN TWO RESPECTS: it will lose and gain birefringence when cooled and warmed, and it will move anaphase chromosomes to the opposite ends of the cell. Early anaphase cells lysed into buffers containing high molecular weight polyethylene glycol and nucleotide triphosphates will continue chromosome motion and spindle elongation in the absence of exogenous spindle subunits. These results suggest that while spindle growth requires microtubule polymerization, anaphase motions do not.

Animals↗