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Biomedical subjects

B Descomps

Publications and source records attributed to B Descomps.

At least 55 records · Page 3Linked to original sources
PubMed1977

Squalene epoxidase and oxidosqualene lanosterol-cyclase activities in cholesterogenic and non-cholesterogenic tissues.

Squalene epoxidase and oxidosqualene lanosterol-cyclase activities have been studied in normal mammalian cholesterogenic and non-cholesterogenic tissues. This paper describes the kinetic conditions of measurement of these two enzymatic acitivities and their results. Oxidosqualene lanosterol-cyclase is a widespread enzyme, present in all cholesterogenic and non-cholesterogenic tissues. However, the level of squalene epoxidase is very low in non-cholesterogenic tissues. However, the level of squalene epoxidase is very low in non-cholesterogenic tissues. The effects of subcellular fractionizing and of the physico-chemical state of squalene incubated in vitro on squalene epoxidase activity are discussed.

Animals↗
PubMed1977

[Rapid gas chromatographic method for determination of acetate in human plasma and hemodialysis baths (author's transl)].

A rapid and sensitive method for acetate determination in human plasma and in hemodialysis baths (dialysates) is going to become necessary owing to the extensive using of sodium acetate solution in hemodialysis. The gas chromatographic method reported here allows, in about 35 minutes, the precise and reproducible measurement of acetate concentrations ranging from 0.2 to 20 mmol/1. This method can be used to investigate the kinetics of acetate concentration variations in the blood of patients undergoing hemodialysis with sodium acetate solution and to evaluate the amount of acetate absorbed during this treatment.

Acetates↗
PubMed1977

Characterisation of an associate 17-beta-hydroxysteroid dehydrogenase activity and affinity labelling of the 3-alpha-hydroxysteroid dehydrogenase of Pseudomonas testosteroni.

The 3-alpha-hydroxysteroid dehydrogenase and the 3-beta-hydroxysteroid dehydrogenase of Pseudomonas testosteroni were purified to homogeneity by polyaerylamide gel electrophoresis using the following stages: DEAE cellulose chromatography, affinity chromatography on oestrone-aminocaproate sepharose and Sephadex gel filtration. The pure 3-alpha-hydroxysteroid dehydrogenase was completely devoid of 3-beta-hydroxysteroid dehydrogenase activity but could oxidize estradiol 17-beta at an appreciable rate. This activity accounts for about 40 per cent of the total 17-beta-estradiol dehydrogenase of the crude bacterial extract. Affinity labelling of pure 3-alpha-hydroxysteroid dehydrogenase was carried out using 5-beta-pregnane 3,20-dione-12-alpha-iodoacetate and 5-alpha-androstane 3-one-17-beta-bromoacetate. With both reagents, inactivation was obtained only in the presence of coenzyme, the substrate protected against inactivation and the enzyme was fully inhibited with covalent binding of 1 mole of reagent per mole of subunit suggesting an active site directed inhibition. Histidine and methionine were identified as the labelled aminoacid residues.

17-Hydroxysteroid Dehydrogenases↗
PubMed1977

[Plasma prolactin levels in normal children from birth to adolescence].

Plasma prolactin levels were determined by an homologous radio-immuno assay in normal children: in cord blood, at the first day of life, during childhood and along puberty. 1. In both sexes, there is a very important secretion of prolactin during the neonatal period. 2. Longitudinal studies make obvious a different pattern of plasma prolactin in boys and in girls at puberty.

Adolescent↗
PubMed1976

Affinity labelling of the estradiol-17 beta dehydrogenase from human placenta with substrate analogs.

Affinity labelling of the estradiol-17 beta dehydrogenase of human placenta has been performed using derivatives of estradiol-17 beta carrying alkylating groups in nine different positions on the steroid nucleus. The active-site-directed character of the inhibition is confirmed by the following observations: the affinity labels are substrates or competitive inhibitors, the enzyme is protected against inactivation and alkylation by the substrate and by the coenzyme, the stoichiometry of the alkylation is two moles of inhibitor per 68 000 g of enzyme (dimer). The alkylation of a histidine residue which is fast and extensive when the alkylation side chain is on the C-3 carbon atom, is dramatically decreased when alkylating side chain is shifted towards rings B and D. These results allow the location of this histidine in the vicinity of ring A and probably on the beta face of the steroid nucleus. The reactivity of a cysteine located on the active site was quite different, showing increasing alkylation when the alkylating substituent of the affinity labels was shifted from C-3 to C-16 of the steroid nucleus. The correlation of this result and that obtained using an alkylating analog of NAD (3-chloroacetyl-pyridine-adenine dinucleotide) indicates that this cysteine is located in the catalytic region of the active site, at the junction of the ring D of the steroid nucleus with the nicotinamide moiety of the coenzyme.

Acetamides↗
PubMed1976

[Secretion of gonadotropins during sleep. Changes during secondary amenorrheas].

4 females with secondary amenorrheas underwent sleep polygraphic recordings together with blood samples for measurements of LH, FSH and GH, 3 normal females served as controls. Among normal subjects LH and FSH secretion showed a pulsating pattern around the time of ovulation, appearing as secretory episodes throughout the night, without any relationship with sleep stages. In amenorrheas, 3 types of abnormalities could be identified: the first was a lack of secretory episodes of LH and FSH associated with an abnormal pattern of GH (9 subjects). The second was an hypersecretion of LH and a decrease of FSH secretion together with a normal secretion of GH in 4 subjects with a Stein-Leventhal syndrome. The last one was an hypersecretion of LH and FSH together with a normal pattern of GH in a subject with an early menopause. These results are discussed according to the present data on the part of neurotransmission in the regulation of ovulation and the 2 types of sleep. Furthermore secretory abnormalities of LH and FSH together with a disconnection between GH secretion and the stages of sleep lead to question the possibility of interrelationships in the secretory mechanisms of these different hormones.

Adolescent↗
PubMed1976

Alkylation of estradiol 17beta-dehydrogenase from human placenta with 3-chloroacetylpyridine--adenine dinucleotide.

3-Chloroacetylpyridine--adenine dinucleotide, which is active as a hydride acceptor (Km = 0.6 mM), inactivates and alkylates estradiol 17beta-dehydrogenase. The kinetics of inactivation by 3-chloroacetylpyridine--adenine dinucleotide and the absence of inactivation by 3-chloroacetylpyridine ribose phosphate show that the alkylation follows the formation of a binary complex (Kd = 4.5 X 10(-4) M). Studies of the labelling by 3-chloro[2-14C]acetylpyridine--adenine dinucleotide and the rate of alkylation as a function of pH, give evidence to the alkylation of a cysteine, the stoichiometry being one mole per subunit. The 14C label is distributed between three chymotryptic peptides, one of which accounts for about 50% of the radioactive label.

Binding Sites↗
PubMed1975

[Secretions of GH, FSH and LH during sleep of the normal child and the child with retarded growth].

In normal children the major GH release begins during NREM sleep of first cycle. At puberty secretion of gonadotropins is enhanced and secretion of LH occurs with the same periodicity as the sleep cycles. Two groups of dwarfish are seen: the first lacks both GH secretion during sleep and the increase of gonadotropins at puberty. The second group exhibits GH, LH and FSH secretion patterns similar to normal children. Study of secretion patterns of GH, FSH and LH during sleep in children can document the degree of maturation of the hypothalamic pituitary hormonal system.

Adolescent↗