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Biomedical subjects

R M Lequin

Publications and source records attributed to R M Lequin.

At least 37 records · Page 2Linked to original sources
PubMed1976

An unexpected effect of L-5 hydroxytryptophan-ethyl-ester combined with a peripheral decarboxylase inhibitor on human serum prolactin.

While the 5-HT precursors tryptophan and 1-5-HTP cause an increase in serum prolactin concentration, a combination of 1-5-HTP with a peripheral decarboxylase inhibitor was found to reduce the serum prolactin concentration. This combination seemed to behave like a DA agonist. This effect is not produced by the decarboxylase inhibitor per se. A possible explanation is that 5-HTP is converted to 5-HT in CA-ergic neurons, that 5-HT supersedes the CA from the stores, and that some of the CA reach the synaptic cleft and stimulate CA receptors. Another possible explanation is that 5-HTP decarboxylase is centrally inhibited as well, and that an effect of 5-HTP itself is involved here. In view of the observations made it is doubtful whether the therapeutic effect of 5-HTP combined with a peripheral decarboxylase inhibitor in depressions and myoclonus can in fact be atributed to activation of central serotonergic systems.

5-Hydroxytryptophan↗
PubMed1975

Human luteinizing hormone. Isolation and characterization of the native hormone and its alpha and beta subunits.

A new procedure is described for the isolation of the alpha and beta chains of the hormone. In this method, thenative hormone is incubated in acidic urea and the chains are then separated by ion-exchange chromatography. The amino-terminal residue of the alpha subunit is valine. The carboxy-terminal end of the alpha subunit is of variable length. No amino-terminal residue was detected for the beta chain; glycine was found at its carboxy-terminal end by the selective titration method. The amino acid and carbohydrate compositions of the hormone and both subunits are presented. The beta chain contains sialic acid and is devoid of galactosamine in contrast to the beta subunits of other species. Contamination of our human lutenizing hormone preparation by other pituitary glycoprotein hormones such as thyroid-stimulating hormone and follicle-stimulating hormone amounted to 0.5 and 0.25 percent by weight respectively. Cross-contamination of the initial alpha and beta subunit preparations was measured by specific radioimmunoassays and amounted to 4.1 and 2 percent by weight respecitively. Further extensive purification of these subunit preparations was then performed by means of affinity chromatography using immunosorbants. The final preparations exhibited a residual cross-contamination amounting to 0.2 and 0.02 percent by weight for the alpha and beta subunits respectively.

Amino Acid Sequence↗
PubMed1975

The role of prolactin in the restoration of ovarian function during the early post-partum period in the human female. I. A study during physiological lactation.

Serial plasma levels of prolactin, follicle-stimulating/ml hormone (FSH), luteinizing hormone (LH), 17beta-oestradiol (E) and progesterone (P) were determined by radio-immunoassay in ten healthy women during late pregnancy and puerperium until the occurrence of the first menstruation, at which moment an endometrial biopsy was taken. Prolactin concentrations, which were high during late pregnancy and the early post-partum period, declined thereafter but remained above 30 ng

Cell Division↗
PubMed1975

The role of prolactin in the restoration of ovarian function during the early post-partum period in the human female. II. A study during inhibition of lactation by bromergocryptine.

Serial plasma levels of prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), 17beta-oestradiol (E) and progesterone (P) were determined by radioimmunoassay in ten healthy women during late pregnancy and the puerperium during inhibition of lactation by Bromergocryptine. This medication was continued until the occurrence of the first menstruation, at which point an endometrial biopsy was taken. Prolactin was very effectively suppressed by Bromergocryptine in all patients, as was lactation. FSH was nearly undetectable during late pregnancy and the first week post-partum with an increase back to normal levels between day 7 and 12. Thereafter FSH levels were within the normal cyclic range. Following clearance of human chorionic gonadotrophin (HCG) during the first 2 weeks post-partum, LH was found within the normal cyclic range in all patients. From day 7 E increased in nine of ten patients to reach levels during the fourth week which are seen normally at the moment of the pre-ovulatory E-surge in cycling women. In eight of the ten cases this was concomitant with high levels of LH. The tenth patient showed a high E level at day 36. P was fully excreted within 7 days and remained low until approximately day 20. Thereafter an increase was demonstrated with levels as found during the luteal stage of the menstrual cycle in nine patients within 33 days and within 40 days in all ten patients. The endometrial biopsies showed clear signs of secretory activity. The probable action of prolactin on ovarian function is discussed. It is suggested that during the puerperium the ovaries are the more refractory part of the hypothalamicpituitaryōvarian axis, due probably to an influence of prolactin on the ovarian steroid synthesis.

Bromine↗