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Biomedical subjects

M Davies

Publications and source records attributed to M Davies.

At least 577 records · Page 32Linked to original sources
PubMed1971

The effect of Trypan Blue, suramin and aurothiomalate on the breakdown of 125 I-labelled albumin within rat liver lysosomes.

1. A fraction enriched in lysosomes was prepared by centrifugation from the livers of rats that had been injected 0.5h before death with (125)I-labelled albumin. When suspended in sucrose-protected buffer, pH7.4, and incubated at 22 degrees C for 2h, the particles progressively released iodotyrosine into the medium. Albumin digestion did not occur if the particles were subjected to treatments known to break lysosomes or if particles from uninjected rats were incubated in medium containing (125)I-labelled albumin. It is concluded that the observed production of iodotyrosine results from protein hydrolysis within intact heterolysosomes. 2. Particles from rats pre-treated with Trypan Blue, suramin or aurothiomalate released iodotyrosine more slowly than controls. Since these compounds are enzyme inhibitors that concentrate in liver lysosomes after administration in vivo, their effect is ascribed to intralysosomal inhibition of proteolysis. The doses used did not decrease endocytosis of albumin into liver or cause increased lysosome breakage during incubation, thus allowing some alternative explanations of the decreased proteolysis to be eliminated. Particulate carbon, a non-inhibitor that also concentrates in lysosomes, did not affect albumin hydrolysis.

Animals↗
PubMed1971

Digestion of an exogenous protein by rat yolk-sac cultured in vitro.

Yolk-sacs were removed from 17.5-day pregnant rats injected 2-5h previously with (125)I-labelled bovine serum albumin. The specific activities of acid phosphatase and acid proteinase, and the specific radioactivities (trichloroacetic acid-insoluble and trichloroacetic acid-soluble) were measured in subcellular fractions prepared by homogenization and differential centrifugation. The conversion of acid-insoluble into acid-soluble radioactivity within cultured tissue was followed and the nature of the liberated products was investigated by gel chromatography. The results are consistent with the protein entering lysosomes and being digested there. The radiolabel was released chiefly as free iodotyrosine.

Acid Phosphatase↗
PubMed1970

Potassium-dependant mutants of Escherichia coli K-12.

Mutants of Escherichia coli K-12 that grow more slowly in media containing low concentrations of K have been isolated. All independent mutants of this type which have been studied carry a mutation in a small region of the bacterial chromosome between the supE and gal loci. The growth rate of the mutants is the same as that of the parental strains in medium containing more than 1 mm K, but is only 50% that of the parent when the K concentration is reduced to 0.1 mm. The mutants do not appear to have a primary alteration in K transport, and are therefore referred to as K-dependent. The abbreviation kdp is proposed for this class of mutant.

Chromosomes, Bacterial↗
PubMed1969

Protein digestion in isolated lysosomes inhibited by intralysosomal trypan blue.

Control rats and rats treated with subcutaneous trypan blue were injected intravenously with denatured albumin-I(125). Lysosome-rich fractions of their livers, when incubated at 22 degrees C in osmotically protected medium (pH 7.4), retained their capacit to digest albumin-I(125). The rate of digestion was lower in suspensions pre-pared from rats treated with trypan blue than in control suspensions, but rates of lysosome breakage were not different. T'hese results and other experimental evidence suggest that trypanblue concentrated within lysosomes can inhibit intralysosomal digestion, probably by inhibition of lysosomal proteinases.

Acid Phosphatase↗