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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
PubMed1983

Bioluminescent assay of femtomole levels of estrone and estradiol.

A rapid and very sensitive enzymatic assay of estrogens was developed using the transhydrogenase reaction of the human estradiol-17 beta dehydrogenase and bioluminescence for the quantification of NADH accumulated during the first reaction. The assay requires two steps: first, the addition of transhydrogenase buffer, and a few minutes later the addition of the bioluminescence reagent. The method can determine 0.1 to 50 pg of estrogens in the assay, in 1 h, with a coefficient of variation of 5%.

17-Hydroxysteroid Dehydrogenases↗
PubMed1983

Enzymatic determination of dehydroepiandrosterone sulfate in biological fluids.

A simple method is described for the determination of androgens, particularly dehydroepiandrosterone sulfate (DHEAS), in human plasma and urine. The method does not involve extraction or chromatography. An internal standard is used as reference. The androgens are enzymatically converted to estrogens and these latter compounds can be measured by the enzymatic method previously described [1]. The range of accuracy was between 99 and 103%. The precision of the method was 2.5%. The sensitivity was 0.1 pM per sample. The method is suitable for routine use, and one worker can easily perform twenty assays in one day.

Aromatase↗
PubMed1983

Active site-directed irreversible inhibition of 3 beta-hydroxysteroid dehydrogenase from human placenta.

To obtain a placental microsome preparation able to convert androstenedione and testosterone specifically to estrogens, 3 beta-hydroxysteroid dehydrogenase must be eliminated. After solubilisation by Triton X-100, the remaining 3 beta-hydroxysteroid dehydrogenase activity is inhibited by 11 alpha-bromoacetoxyprogesterone, an alkylating analogue of progesterone, which behaves as an irreversible active site-directed inhibitor. The enzyme is protected against inactivation and alkylation by steroid and coenzyme substrates. The inhibition is specific to 3 beta-hydroxysteroid dehydrogenase and the estrogen synthetase (aromatase) activity contained in the preparation is not affected by this inhibitor.

3-Hydroxysteroid Dehydrogenases↗
PubMed1983

[Metabolism of dihydrotestosterone in cultured skin fibroblasts: reduction to 5 alpha-androstane-3 alpha, 17 beta-diol].

Reduction of dihydrotestosterone into 5 alpha-androstan-3 alpha, 17 beta diol by 3 alpha hydroxysteroid dehydrogenase was studied in human cultured skin fibroblasts. Characterization of the 3 alpha diol was performed by gas-liquid chromatography coupled with mass spectrometry. Sex skin fibroblasts enzyme has the same Km (9.10 X 10(-6) M) as that of non sex skin fibroblasts (8.75 X 10(-6) M). On the other hand, reduction of DHT is 3 times higher in sex skin fibroblasts (Vmax = 223.9) than in non sex skin fibroblasts (Vmax = 87.9). Thus, human culturel fibroblasts appear again to be an useful tool for the study of a key-enzyme of androgen metabolism in target cells.

Androstane-3,17-diol↗
PubMed1983

Centrifugal analyzer used for enzyme immunoassay of progesterone and choriomammotropin.

Recently we developed an enzyme immunoassay involving the use of steroid delta-isomerase (EC 5.3.3.1) as enzyme label and exclusion-affinity chromatography for rapid separation of free antigen-enzyme conjugate that bound to antibodies (J. Immunol. Methods 35: 267-284, 1980). Here we describe an automated version of this procedure, for immunoassay of progesterone and choriomammotropin (human placental lactogen) in serum with the use of a centrifugal analyzer. After incubation, suitable dilutions of sera or extract plus antiserum, conjugate, and double antibody were filtered on an estradiol affinity gel-filtration column; the enzyme activity of the filtrates was determined with the centrifugal analyzer. Results correlate well with those obtained by radioimmunoassay: r (progesterone) = 0.980, r (choriomammotropin) = 0.940. The within-run and between-run precision, specificity, sensitivity, accuracy, and speed of this system make it a useful tool for immunoassay.

Autoanalysis↗
PubMed1983

[Effect of the hormonal environment on the human oocyte and its later development in vitro].

The biosynthesis of progesterone by the granulosa cells that come from follicles from which the oocyte has been fertilized and has divided in vitro is far superior to that from the cells coming from follicles in which the oocyte has failed to develop. This result is in accordance with the raised levels of progesterone and the influence of androgens on lower levels of oestrogens in follicular fluid that evolved favourably. In the same follicles the ratio of concentrations of prostaglandins PGE2 to PGF2 alpha is twice as high as in the liquid from other follicles.

Androgens↗
PubMed1982

Binding of adducts of NAD(P) and enolizable ketones to NAD(P)-dependent dehydrogenases.

Carbonyl compounds such as alpha-ketoglutarate, pyruvate, oxaloacetate, butyraldehyde, acetaldehyde or acetone react with NAD or NADP to give adducts. Binding studies of adducts to dehydrogenases are performed by means of ultraviolet differential spectroscopy, circular dichroism and spectrofluorimetry. The dehydrogenases show a high degree of binding specificity toward the adducts which contain their specific oxidized substrate and their specific coenzyme. The high selectivity of the dehydrogenases for adducts is evidenced by binding studies of NAD(P)-pyruvate and NAD(P)-alpha-ketoglutarate adducts on glutamate dehydrogenase at pH 7.6 and 8.9. Evidence is presented showing that adducts bind to the active site of the enzymes.

Alcohol Dehydrogenase↗
PubMed1982

[Prolonged functional disturbance of prolactin secretion after surgery under neuroleptanalgesia].

Plasma level of prolactin and its response to the injection of haloperidol were measured in nine women before and after elective gynecological surgery under neuroleptanalgesia using dextromoramidedroperidol combination. The day before the operation, the injection of haloperidol 0.25 mg intramuscularly increases the concentration of PRL by 5.4 +/- 1.9 mg/ml, while this response is completely abolished the day following the operation. Two days later, a tenfold increase in the dose of haloperidol (2.5 mg I.M.) is necessary to obtain a PRL response that equals that observed pre-operatively (5.8 +/- 1.2 ng/ml). The low plasma levels observed 24 and 48 hours post-operatively compared to the pre-operative level, illustrate a prolonged functional disturbance of the secretion of PRL.

Adult↗
PubMed1982

A specific hydroxysterol binding protein in human lymphocyte cytosol.

A discriminating system capable of recognizing the oxygenated sterols was investigated in human lymphocytes. After labelling entire cells with 25-hydroxy [3H] cholesterol (10 nM) the cytosol was ultracentrifuged on a linear sucrose density gradient. Bound 25-hydroxy [3H] cholesterol was located in a single peak with a sedimentation coefficient of 8.3 S. Pronase treatment abolished the radioactive peak. This 8.3 S protein had a low binding capacity for 25-hydroxy [3H] cholesterol and probably a high affinity. This last parameter was not determined on account of some difficulties encountered in a cell-free system relating to the physico-chemical properties of 25-hydroxycholesterol. Only the hydroxylated sterols closely related to 25-hydroxycholesterol were capable of specifically binding to the 8.3 S protein, in contrast with cholesterol. This protein differed from the binding proteins of oxygenated derivatives of vitamin D3 and glucocorticoids. With the human lymphocyte as a model and under our experimental conditions, this hydroxylated sterol-binding protein seems to be involved rather in the cell division control than in the regulation of HMG-CoA reductase activity: indeed, the hydroxysterols able to inhibit thymidine [3H] incorporation into DNA are recognized by this protein whereas the hydroxysterols active on HMG-CoA reductase activity without affecting thymidine [3H] incorporation into DNA are not.

Carrier Proteins↗
PubMed1982

Studies of covalent adducts of NAD(P) and enolizable ketones as specific glutamate dehydrogenase inhibitors.

Structural analogues of the reduced coenzymes, NADH or NADPH, of dehydrogenases are prepared by addition of carbonyl compounds including: pyruvate, alpha ketoglutarate, oxaloacetate, butyraldehyde, acetaldehyde and acetone, to the oxidized coenzymes NAD(P). Some of the adducts obtained are specific inhibitors of the glutamate dehydrogenase. The specificity is related to the carbonyl compound used. The high selectivity of the dehydrogenases for adducts is evidenced by inhibition studies of NAD(P)-pyruvate and NAD(P)-alpha ketoglutarate adducts on both activities of glutamate dehydrogenase. The inhibitions are competitive with the reduced coenzymes and the oxidized substrates: adducts could be considered as structures closely related to the ternary complexes of the dehydrogenase.

Animals↗
PubMed1982

[Maternal and fetal levels of local anaesthetics after epidural injection of a triple mixture].

Twenty-four parturients received an epidural injection of a 5.10(-6) adrenaline mixture containing: lidocaine 295 +/- 19 mg, bupivacaine 58 +/- 4 mg and etidocaine 58 +/- 4 mg. The mean serum levels measured in the mother (peripheral vein) and in the fetus (umbilical vein) and in the fetus (umbilical vein) and the fetus/mother ratios were, respectively:--1.05 +/- 0.47 micrograms . ml-1, 0.68 +/- 0.34 micrograms . ml-1 and 0.66 +/- 0.15 for lidocaine; --0.25 +/- 0.10 micrograms . ml-1, 0.14 +/- 0.06 micrograms . ml- and 0.51 +/- 0.16 for bupivacaine; ---0.27 +/- 0.10 micrograms . ml-1, 0.17 +/- 0.10 micrograms . ml-1 and 0.63 +/- 0.23 for etidocaine. From the sum of these concentrations the maternal and fetal serum levels and the fetus/mother ratio could be calculated in lidocaine equivalents. The values obtained were: 3.14 +/- 0.74 . ml-1, 1.90 +/- 0.68 micrograms . ml-1 and 0.60 +/- 0.13 respectively. A comparison of these data with those found in the literature led to the following conclusions: (1) The maternal serum levels of each anaesthetic drug in the mixture are the same as if it had been injected separately; (2) owing to tissue competition, the transplacental passage is increased by majoration of the free form, this being more pronounced with bupivacaine and etidocaine; (3) the circulating drug concentrations evaluated as lidocaine equivalent in the mother and fetus are comparable to those determined at the end of conventional local anaesthetic procedures.

Anesthesia, Epidural↗
PubMed1982

Androgen receptors in cultured human skin fibroblasts.

Human skin may be considered as a target organ for androgens, since events characteristic of androgen action have been described in this tissue, as well as in cultured human skin fibroblasts. The culture of human skin fibroblasts gives the opportunity to work on living cells, under controlled conditions, in a renewable material from a single skin biopsy. Using this method, we showed the presence od DHT-receptors in the human fetus and we studied the ontogenesis of androgen receptors in relation to sexual differentiation. In the neonatal period, the physiological T rise was not concurrent with a variation in sex skin androgen receptors. The evolution of DHT binding during puberty is now under investigation. These data suggest that the androgen receptor is not modulated by plasma androgens. Androgen receptor determination is of value in defining the biochemical defects involved in partial and complete androgen insensitivity syndrome (twenty-six cases in our study). In idiopathic hirsutism, DHT binding is used to detect an eventual local hypersensitivity. Fibroblast cultures have also been shown to be an excellent model for the screening of compounds which might block the expression of androgen action by competing for the androgen receptors. Cultured skin fibroblasts are a valuable model for the study of androgen and antiandrogen action in human skin.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1982

Increase in sleep related GH and Prl secretion after chronic arginine aspartate administration in man.

Arginine aspartate was administered orally (250 mg/dg/day) for one week to 5 healthy male human volunteers aged 20-35. After this period, the 24 h patterns of growth hormone (GH) and prolactin (Prl) secretion were determined by radioimmunoassay on blood samples withdrawn every 20 min and correlated with the polygraphic recordings of electroencephalogram, electromyogram and electrooculogram. the results were compared to data obtained in identical conditions with the same subjects but after a week of placebo administration. In all 5 subjects the slow wave sleep related GH peak was about 60% higher after a week of arginine aspartate administration than in the control period, with individual changes of +24, +25, +42, +47 and +162%. The nocturnal mean plasma Prl of each subject was higher after arginine aspartate than before. The nocturnal rise of plasma Prl increased from a mean value of +21.5% during the placebo period to +95% at the end of the arginine aspartate treatment. These hormonal modifications were not accompanied by any detectable alteration of sleep organization and specially of the slow wave sleep pattern, suggesting a direct neuroendocrine action of the drug.

Adult↗
PubMed1982

[Effect of cyproterone acetate on the 3 alpha-hydroxysteroid-dehydrogenase activity of cutaneous fibroblasts in culture].

In men, parallel variations in urinary 3 alpha 5 alpha androstane 17 beta diol with the amount of sex skin fibroblast DHT receptors rise the question of a relationship of 3 ketosteroid reductase activity and specific DHT binding. To test this hypothesis, we measured 3 alpha 5 alpha androstane 17 beta diol biosynthesis in cultured sex skin fibroblasts, in the presence of high amounts of cyproterone acetate which competes with DHT for its receptor: when 95% of DHT is displaced by cyproterone acetate, the 3 keto steroid reductase activity remains unchanged. These results suggest that the relationship of 3-keto-steroid reductase activity and androgen receptors is unlikely.

Animals↗
PubMed1982

Effect of acetate on ketogenesis during hemodialysis.

The concentration of plasma acetate, glucose, and ketone bodies were determined for both venous and arterial blood before and at the end of dialysis with an acetate-containing dialysate. We also determined lactate and pyruvate levels in arterial plasma. The results obtained in the same patients were compared when dialysis were done with or without glucose and discussed in terms of hormonal changes (insulin, glucagon). Arterial plasma acetate (p less than 0.001) and ketone body levels (p less than 0.05) increased significantly during dialysis both with glucose and without glucose (p less than 0.001 in both cases). Higher end-dialysis arterial levels were found for the latter set of glucose-free dialysis (p less than 0.05 and p less than 0.001, respectively, for acetate and ketone bodies), and a correlation was established between end-dialysis arterial concentrations of acetate and ketone bodies. This suggests high consumption of both endogenous and exogenous acetate to feed ketogenesis. This is concurrent with decreased insulin and high glucagon levels. Under these conditions, plasma accumulation of ketone bodies would facilitate an indirect elimination of acetate by the dialyzer (about 10% of the acetate load). Our results suggest that hormone variations during glucose-free dialysis which promote fatty acid oxidation and ketogenesis from acetyl groups hinder acetate-dependent lipogenesis.

3-Hydroxybutyric Acid↗
PubMed1982

[Enzymatic determination of urinary estrone and estradiol: correlations with plasma estradiol in the menstrual cycle in women].

Enzymatic determination of urine estrone and estradiol concentrations were done daily during a menstrual cycle in six female volunteers. The results were compared with plasma estradiol determined by radioimmunoassay in the same patients. The pattern of estrone and estradiol excretion in morning urine sample fairly reproduced plasma estradiol variations and a good correlation was observed (r = 0.78). The urine pattern of estrone and estradiol variation determined by the enzyme assay can be considered as a good index of oestrogen secretion. The preovulatory peak of estrone and estradiol was observed in urine the day before or the same day as the LH peak. Estrone and estradiol concentration in urine doubled the mean value of the concentration of the follicular phase several days before the LH peak giving a useful indication for prediction of ovulation.

Estradiol↗
PubMed1981

Purification and substrate characterization of a human enkephalin-degrading aminopeptidase.

A 5000-fold purification of the enzyme responsible for the rapid inactivation of enkephalin in human blood has been achieved: this enzyme cleaves the N-terminal tyrosine from enkephalin and from short peptides provided their first amino acid is aromatic. The enzyme, an enkephalin-degrading aminopeptidase (alpha-aminoacyl-peptide hydrolase, EC 3.4.11.11), requires a free amino group on the substrate and has a maximum activity around pH 8. Its appearance molecular weight is in the range of 80 000-90 000 and an apparent Michaelis constant of 0.4 mM was determined.

Aminopeptidases↗