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Biomedical subjects

J Frey

Publications and source records attributed to J Frey.

At least 289 records · Page 16Linked to original sources
PubMed1978

Subcellular localization and levels of aminopeptidases and dipeptidase in Saccharomyces cerevisiae.

Three aminopeptidases (L-aminoacyl L-peptide hydrolases, EC 3.4.11) and a single dipeptidase (L-aminoacyl L-amino acid hydrolase, EC 3.4.13) are present in homogenates of Saccharomyces cerevisiae. Bassed on differences in substrate specificity and the sensitivity to Zn2+ activation, methods were developed that allow the selective assay of these enzymes in crude cell extracts. Experiments with isolated vacuoles showed that aminopeptidase I is the only yeast peptidase located in the vacuolar compartment. Aminopeptidase II (the other major aminopeptidase of yeast) seems to be an external enzyme, located mainly outside the plasmalemma. The synthesis of aminopeptidase I is repressed in media containing more than 1% glucose. In the presence of ammonia as the sole nitrogen source its activity is enhanced 3--10-fold when compared to that in cells grown on peptone. In contrast, the levels of aminopeptidase II and dipeptidase are less markedly dependent on growth medium composition. It is concluded that aminopeptidase II facilitates amino acid uptake by degrading peptides extracellularly, whereas aminopeptidase I is involved in intracellular protein degradation.

Aminopeptidases↗
PubMed1978

Studies on guinea pig skin cell cultures. VII. Statistical analysis of growth and maturation.

Thymidine uptake; incorporation of amino acids into perchloric acid extract and HCl extract (corresponding grossly to poorly and highly organized proteins respectively); cell fraction DNA and cell fraction protein contents have all been measured daily from day 1 to day 8 in primary cultures of epidermal keratinocytes (EK) and dermal fibroblasts (DF). Correlations between these five biochemical parameters (or variables) have been sought when using the statistical method of principal component analysis. The analysis of whole data of EK and DF populations taken together revealed that DNA content is a major distinguishing factor between these two cell types. The analysis of variables of each cell type taken independently showed that DF are essentially characterizable by their tendency to synthesize both poorly and highly organized proteins, whereas EK are more prone to DNA and highly organized protein synthesis. Thus, EK and DF in culture can be readily distinguished statistically by analysing their growth and maturation characteristics. It is even likely that time study of thymidine and amino acid incorporation would suffice to characterize these two cell types in vitro.

Amino Acids↗
PubMed1978

[Discussion of the interest of estimation of hydroxyprolinuria in chronic alcoholism (author's transl)].

24 hour hydroxyprolinuria was measured in 50 chronic alcoholics divided up into those with simple alcoholism and those complicated by cirrhosis. All the patients had a significant increase in hydroxyprolinuria. Without there being any difference between cirrhotics and alcoholics without cirrhosis. Comparison between hydroxyprolinuria and the tests usually used to follow the course of hepatic involvement in chronic alcoholism: IgA, transferrin, electrophoresis of serum proteins, alkaline phosphatase, show that there is no correlation between hydroxyprolinuria and the diagnostic or prognostic tests of an alcoholic liver among which the variable IgA is the most significant. On the other hand, hydroxyprolinuria has a linear correlation with the calciuria, which suggests that the increase in hydroxyprolinuria in chronic alcoholics is more related to changes in the collagen of bone tissue than with those in liver tissue.

Alcoholism↗
PubMed1977

Suppression of an Escherichia coli dnaA mutation by the integrated R factor R100.1: generation of small plasmids after integration.

We have observed that integration of the R plasmid R100.1 into the chromosome of Escherichia coli is associated with the formation of small, covalently closed circular elements. Contour length measurements, partial denaturation mapping, and analysis of the deoxyribonucleic acid fragments produced by digestion of one of these, pLC1, with the restriction endonuclease EcoRI indicate that it is the r-determinant element of R100.1.

Chromosomes, Bacterial↗
PubMed1977

[Critical study of the interpretation and use of laboratory biochemical examinations in a hospital milieu].

The criticism of interpretation of routine biochemical examinations by four clinical units (motor rehabilitation, cardiology, gastro-enterology, diabetes) was in relation to four criteria: result in agreement with the clinical observation but not providing new information, result in disagreement with the clinical observation and judged too low, result in disagreement with the clinical observation and judged too high. The comparison of judgements with regard to various analysis permits one to discuss applications of a method of objective assessment of the dialogue between the laboratory and the clinical units.

Cardiology↗
PubMed1976

[Research on subcellular localization of procollagen proline hydroxylase from chick embryo liver (author's transl)].

Subcellular fractionation by differential centrifugation was used to study protocollagen proline hydroxylase (EC 1.14.11.2) localization from chick embryo liver. The fractions have been characterized by marker enzymes and electron microscopy. By these methods, it was observed that procollagen-proline-hydroxylase is concentrated in the microsomal fraction which is sedimented at 145 000 X g in 250 mM sucrose.

Animals↗
PubMed1976

[Study, by an enzymatic method, of the isomers of L-proline (3H-4) and of the effects of preservation].

By use of procollagen proline hydroxylas which catalyses the substitution of the hydrogen in the trans position on carbon 4 with an hydroxyl on L-proline residues of procollagen, we have shown that the L-[3H-4] proline product of C.E.N. Saclay contained 29 per cent of the trans and 71 per cent of the cis form. It was also possible to verify the molecular stability of the isomers and that a small amount of tritium was randomly linked to the whole molecule.

Isotope Labeling↗
PubMed1976

[The action of calcium on the step of collagen metabolism, catalyzed by procollagen-proline hydroxylase].

Calcium effects on procollagen-proline-hydroxylase activity of chick embryo tibias was studied. Serial preincubation of the natural substrate, the enzymatic preparation or the mixture of both with and without calcium showed that calcium decreased procollagen-prolin-hydroxylase affinity for procollagen, decreased the maximum velocity of the reaction by binding to the substrate and by increasing the thermosensitivity of the enzyme -- substrate complex. Calcium could also increase the maximum velocity by dissociation of an enzyme -- inhibitor ligand complex. The resulting decrease of the overall reaction rate has been discussed in the context of the relationship between collagen metabolism and calcium fixation during calcification.

Animals↗