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Biomedical subjects

M Nicol

Publications and source records attributed to M Nicol.

At least 73 records · Page 4Linked to original sources
PubMed1983

[Adrenal catecholamines and their metabolism in the vitamin A deficient rat].

The adrenal catecholamines (norepinephrine and epinephrine) and their conversion enzymes (PNMT, COMT) were comparatively investigated in: (1) rats fed a diet deprived of vitamin A, inducing a rapid and severe deficiency; (2) rats fed another diet leading to a more progressive deficiency (rats supplemented with retinol served as controls for these two types of diet), and (3) rats fed a whole industrial diet. The first diet induced a strong accumulation of adrenal catecholamines and increased the activity of PNMT and COMT. The second diet only increased the adrenal content of norepinephrine and epinephrine.

Adrenal Medulla↗
PubMed1983

[Serum and tissue 17 beta hydroxysteroid dehydrogenase and estrogens in hydatidiform mole].

The activity of 17 beta hydroxysteroid dehydrogenase (EC 1.1.1.62) in hydatidiform mole tissue and in sera from women with molar pregnancies was determined and compared with that of women with normal pregnancies. Oestradiol and oestrone concentrations were also estimated in plasma in both cases. Very early in the pregnancy, the enzyme activity in tissues and sera, and the concentrations of oestradiol and oestrone were the same in normal and molar gestations. In more advanced pregnancies, the enzyme activity and the concentration of oestrogens were higher in molar pregnancies at the same stage of development. The 17 beta hydroxysteroid dehydrogenase seems to be identical in placenta and in molar tissue if Km values and polyacrylamide gel separations are taken into consideration, i.e. the differences measured are essentially quantitative.

17-Hydroxysteroid Dehydrogenases↗
PubMed1982

Plasma hormone concentrations and serum 17 beta-hydroxysteroid dehydrogenase activity in molar pregnancy.

Concentrations of unconjugated 17 beta-estradiol, estrone, and estriol, and of progesterone, 17 alpha-hydroxyprogesterone, testosterone, delta 4-androstenedione, dehydroepiandrosterone sulfate (DHEAS), choriogonadotropin beta-subunit, and prolactin were measured by radioimmunoassay in plasma of six patients with molar pregnancies of seven to 15 weeks of gestation. Serum 17 beta-hydroxysteroid dehydrogenase (EC 1.1.1.6.2) activity was also determined. Estriol was not detected in any of the six women. Values for DHEAS and progesterone were normal, except for one patient who had above-normal plasma progesterone. Values for the other hormones and the enzyme were within normal limits in very early intact molar pregnancies, but were above normal limits in more advanced cases. A close correlation was seen between 17 beta-hydroxysteroid dehydrogenase activity and concentrations of estradiol, estrone, testosterone, and 17 alpha-hydroxyprogesterone; the last four also correlated significantly with beta-choriogonadotropin in molar pregnancies, whether benign or invasive. Benign trophoblastic disease showed significant correlation of progesterone with beta-choriogonadotropin and with estradiol. We conclude that the estradiol, estrone, testosterone, and 17 alpha-hydroxyprogesterone were principally derived from molar tissue.

17-Hydroxysteroid Dehydrogenases↗
PubMed1981

Picosecond resonance Raman spectroscopic evidence for excited-state spin conversion in carbonmonoxy-hemoglobin photolysis.

The structure of the carbonmonoxy-hemoglobin (COHb) photoproduct has been studied on the picosecond time scale with resonance Raman spectroscopy, by tightly focusing the 30-ps pulses of a synchronously pumped mode-locked cavitydumped dye laser on a jet stream of COHb solution. The spectrum of the photoproduct is similar to that of deoxy Hb, but the frequencies 1603 cm(-1) (depolarized), 1552 cm(-1) (anomalously polarized), and 1542 cm(-1) (depolarized) are 2-4 cm(-1) lower than those of deoxy Hb. Similar low frequencies are observed for a species believed to be the bis-tetrahydrofuran adduct of Fe(II) octaethylporphyrin, containing in-plane high-spin Fe(II). These results indicate that in the COHb photoproduct the Fe(II) is already high-spin but is closer to the heme plane than in deoxy Hb. Photodissociation from a quintet ligand-field excited state of COHb is suggested. The frequency shifts relative to deoxy Hb persist when the laser pulses are lengthened to 20 ns. The apparently slow relaxation to the fully out-of-plane heme conformation of deoxy Hb is suggested to be associated with change of the globin tertiary structure.

Journal Article↗
PubMed1981

Influence of sex hormone binding globulin and serum albumin on the conversion of androstenedione to testosterone by human erythrocytes.

The influence of human serum albumin and sex hormone binding globulin (SHBG) on the enzymic conversion of androstenedione to testosterone in human erythrocytes was investigated in vitro. Total plasma and albumin delayed the conversion rate of androstenedione, while SHBG increased it markedly. The effect of SHBG was largely abolished by heating to 60 degrees C for 1 h and by saturating its binding sites by DHT. The effect of both proteins was found to be related to their concentration. It appears that the binding sites of albumin provide a mechanism for retarding androstenedione uptake by the erythrocytes and that the high binding affinity of SHBG for testosterone facilitates the diffusion of this steroid out of the cell and thus, displaces the chemical equilibrium within the cell.

Androstenedione↗
PubMed1981

[Application of a rapid serum beta-hCG assay in the early diagnosis of the ectopic pregnancies (author's transl)].

We have assessed the clinical utility of a rapid serum beta chorionic gonadotropin ( beta-hCG) assay. The assay employed a commercial kit that we have modified to assure its validity. We reach a sensitivity of 10 mIU/ml, and inter assay precision of 8,1% and an intra assay precision of 6.4 and 4.7% for concentrations of 7.6 +/- 0.5 mIU/ml and 1 825 +/- 86.3 mIU/ml respectively. This work was carried out on 106 radioimmune determinations of beta-hCG during the first trimester of 56 normal pregnancies and on 168 levels estimed in 116 suspected ectopic pregnancies. In normal pregnancies, a trophoblastic secretion of beta-hCG is detected on the 10th day following the thermal nadir; the levels quickly rise to reach a peak between the 42th and the 52th post-ovulation day, and then gradually decrease. In the 116 suspected pregnancies, 40 of them were surgically proven ectopic gestations: there were no false positive or false negative results. This rapid and accurate assay may contribute to the early diagnosis of an ectopic pregnancy.

Chorionic Gonadotropin↗
PubMed1980

Testosterone and 5 alpha-dihydrotestosterone concentrations in human seminal plasma.

Testosterone and dihydrotestosterone (DHT) were estimated by radioimmunoassay in human seminal plasma. Testosterone concentrations showed no significant differences between fertile and infertile semen samples, whereas DHT concentrations were significantly lower in azoospermic and oligozoospermic samples. It is concluded that testosterone derives essentially from the accessory sex glands, whereas DHT is mainly of testicular or epididymal origin. The low DHT concentrations found in seminal plasma of oligozoospermic and azoospermic patients is probably due to defective epididymal conversion of testosterone to DHT.

Dihydrotestosterone↗
PubMed1980

[Instability of serum 17 beta-hydroxysteroid dehydrogenases of placental origin].

The stabilization by glycerol of the serum estradiol 17 beta dehydrogenase has been investigated here in terms of time and temperature. The protected enzyme is stable for a month at least at --20 degrees C. Its activity reaches a maximum at 60 degrees C. In another connection, effect of reduced glutathione, of N. acetyl-cysteine and of various mineral ions on the enzymic conversion has been studied.

17-Hydroxysteroid Dehydrogenases↗
PubMed1980

[Comparative activity of erythrocyte 17 beta-hydroxysteroid dehydrogenase in man and the rat: effect of plasma].

Human erythrocytes, which contain an active 17 beta-hydroxysteroid-dehydrogenase, transform dehydroepiandrosterone, delta 4-androstenedione and estrone, more rapidly in buffered medium than when kept into plasma. The rat has a peculiar behaviour: the conversion of substrates is very high above the man's one, whether in buffered medium or in blood: the plasma influence is negligible. Plasma permutation reveals that the rat's one, which does not slow down the erythrocyte activity of the rat, slakens the man's one; the human plasma which slows up the human erythrocyte, has only a light action on the rat's one.

17-Hydroxysteroid Dehydrogenases↗