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At least 685 records · Page 38Linked to original sources
PubMed1979

Kinetic studies on the selectivity of a synthetic thrombin-inhibitor using synthetic peptide substrates.

The synthetic thrombin-inhibitor termed No. 205 (N-alpha-dansyl-L-arginine-4-ethyl-piperidine amide) found in our laboratories was studied kinetically using synthetic peptide substrates. The following results were obtained. 1. No. 205 inhibited thrombin competively with bz-Phe-Val-Arg-pNA and the Ki value obtained was extremely small, 3.7 x 10(-8) M. 2. No. 205 also inhibited trypsin competitively with bz-Phe-Val-Arg-pNA but the Ki value obtained was far larger than that for thrombin, 1.0 x 10(-5) M. 3. No. 205 inhibited F. Xa, plasmin and urokinase only to a small extent when estimated using 2 x 10(-4) M D-Val-Leu-Lys-pNA, bz-Ile-Glu-Gly-Arg-pNA and Glu-Gly-Arg-pNA, respectively. 4. No 205 differed from APPA in its specific inhibitory spectrum for thrombin as compared to trypsin, plasmin and F. Xa. The above results indicate that No. 205 is an extremely potent and highly selective reversible thrombin-inhibitor.

Animals↗
PubMedDate not supplied

[The safety problem and a physiological strategy for using glucocorticoid hormones].

Principal problems of glucocorticoid hormone application in non-endocrine diseases are discussed proceeding from the mechanism of their action and the role in organism's life. It appeared that the hazard of glucocorticoid therapy is mainly due to the absence of a test for sufficiency and real needs in these hormones. It was shown that the test has to be introduced reflecting on the whole body level the glucocorticoid activity in the cell, that is similar to blood glucose in relation to insulin. The introduction of free blood tyrosine as such test appears to allow the development of safe individual strategy for the usage of glucocorticoids.

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PubMed1990

[Tyrosine and methionine metabolism in various states of melaninogenesis].

Excretion with urine of tyrosine and methionine metabolites as well as the activities of enzymes involved in their metabolism are correlated with the state and type of melanin synthesized in the skin. The response of tyrosine aminotransferase to melaninogenesis induction was more pronounced in animals with predominant pheomelaninogenesis, especially after tyrosine load, while that to dopachrome oxidoreductase--in animals with predominant eumelaninogenesis and after methionine load. Glutathione reductase and cystathionine-beta-synthase responded more vigorously to methionine injections, which was especially well pronounced in animals with prominent pheomelaninogenesis and in albino animals. The metabolic "block" in melanine synthesis in albino animals seems to be observed after the 5-S-cysteinyl-DOPA synthesis, whereas the initial steps of melaninogenesis in these animals are identical to pheomelanine synthesis reactions.

Animals↗
PubMed1986

Phenylpyruvate-specific glutamine transaminase and renal ammoniagenesis.

The glutaminase II ammoniagenic pathway is composed of two enzymes, glutamine transaminase (GTA) and omega-amidase. Studies herein reported define the basal activity, intrarenal distribution and response to chronic acidosis of the more active renal isoenzyme of GTA. A gradient of diminishing enzyme activity was found in assays of cortical, medullary and papillary sections (GTA activity, cortex 114 +/- 3 mumol/g/h; outer medulla 20 +/- 0.6 mumol/g/h; papilla 3 mumol/g/h). Dog kidney had much less activity while no GTA activity was found in guinea pig kidneys. In vitro acidification enhanced ammonia production by the glutaminase II pathway when studied in cytosolic preparations made from normal rat cortex. Chronic in vivo metabolic acidosis increased rat renal cortical and medullary but not papillary GTA activity by 16 and 12%, respectively. Incubation of cortical cytosolic extracts from chronically acidotic rats at pH 7.4 revealed a 29% increase in ammoniagenesis via glutaminase II, as compared to extracts from non-acidotic control rats. The cortical concentration of the most active substrate of GTA phenylpyruvate, is 343 +/- 12 mumol/kg fresh weight and its level was not influenced by in vivo acidosis. Additional studies are presented which suggest that a functional link may exist between glutaminase II and glutamate oxalacetate transaminase. This linkage could result in the cyclic utilization and reformation of phenylpyruvate while glutamine is progressively deamidated and free ammonia formed. The physiologic implications of these results are discussed.

Ammonia↗