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Biomedical subjects

R M Lequin

Publications and source records attributed to R M Lequin.

At least 19 recordsLinked to original sources
PubMed1996

Determination of hepatitis A antibody response to vaccination by an enzyme immunoassay.

The quantitative responses to vaccination with hepatitis A vaccine was determined in 113 volunteers using a commercially available enzyme-linked immunosorbent assay for total antibodies to hepatitis A. Administration of vaccine or control preparation was carried out according to two regimens; at 0, 1 and 12 months (regimen I) and at 0, 0.5 and 12 months (regimen II). Seroconversion rates (concentrations of HAV antibodies > 50 IU/l) were between 94 and 97% at month 1 for regimen I and regimen II, respectively. The geometric mean titres (GMTs) fell gradually by month 12, and increased rapidly 10-100 fold 1 month after the booster dose at month 12. The GMTs of the groups receiving the control preparation remained below 50 IU/l. No significant differences were found between the antibody responses after regimen I or regimen II. It is concluded that the antibody test (Hepanostika HAV Antibody) can be used safely and adequately for quantitation of responses to hepatitis A immunisation.

Adult↗
PubMed1989

Is oxytocin present in platelets?

For arginine-vasopressin (AVP) it has been suggested that about 90% of the total amount present in peripheral blood is platelet-membrane bound. Oxytocin (OT) and AVP are nonapeptides which are similar in many respects. We investigated the possibility that OT might be found in platelet-rich plasma samples from patients undergoing ovarian super-stimulation for in-vitro fertilization purposes. These plasma samples were treated with acid repeated freezing/thawing and sonification in an attempt to solubilize or expose the possible bound OT. No differences between OT concentrations in platelet-rich or -poor plasma samples were found. We conclude that plasma OT is not bound or confined to platelets.

Blood Platelets↗
PubMed1986

Circadian rhythm of prolactin during the menstrual cycle.

Ten women with regular cycles volunteered in a study of the relationship between PRL diurnal rhythm and menstrual cycle. A PRL surge during the afternoon between 2:00 and 8:00 P.M. was observed in the luteal and periovulatory phases, but not in the early follicular phase. The authors advise PRL measurement in the morning between 10:00 A.M. and 12 noon for diagnosing hyperprolactinemia, because morning PRL levels seem to remain constantly low during the menstrual cycle.

Adult↗
PubMed1986

A luminescent label for the immunoassay of oxytocin.

Chemiluminescent labels have been shown to be interesting alternatives to radioisotope labels. Disadvantages of the latter are preparation of e.g. labelled protein/peptides every four to six weeks, and problems with storage and disposal. Amino-Butyl-Ethyl-Isoluminol(ABEI) was attached to the alpha-amino function of the N-terminal amino acid residue of oxytocin; this complex was used in immunoassays for oxytocin. This non-isotopic label did not require heating at 60 degrees C for optimal light-signal development, a procedure usually required for chemiluminescent labels. Standard curves were set up employing the ABEI-label on the one hand and 125I-label on the other. Under identical conditions of final antibody concentration and amount of label, a comparison was made between the performance of the luminescent immunoassay (LIA) and that of the radioimmunoassay (RIA). We conclude that the LIA systems resulted in standard curves of high precision; in comparison with RIA, the sensitivity of the LIA curves is not yet sufficient for the determination of oxytocin concentrations in e.g. human biological fluids. Further improvements in sensitivity of the LIA systems are to be expected by selection of other luminescent labels or by the use of a more sensitive measuring device.

Immunoassay↗
PubMed1986

Progesterone in saliva: pitfalls and consequent implications for accuracy of the determination.

The concentration of steroid hormones in saliva is believed to reflect the concentration of free hormone in blood. Because the assay for progesterone in saliva has not been rigorously validated, we investigated some of the analytical variables involved. Saliva samples were divided into two portions. One was centrifuged and the supernate used for extraction; the other was homogenized by sonication and used as such for extraction. Progesterone concentrations in homogenized whole saliva were double or triple those in supernates. By equilibrium dialysis we established that 85% of progesterone was in the free form in supernates but only 60 to 70% in homogenized whole saliva, depending upon the phase of the cycle of the subjects. Salivary flow was stimulated by crystals of citric acid; unstimulated and stimulated saliva samples were obtained from the same person. Progesterone concentrations were significantly (p less than 0.02) higher in stimulated samples than in unstimulated ones, particularly in samples collected during the luteal phase.

Body Fluids↗
PubMed1981

Early detection of pregnancy in rhesus and stump-tailed macaques (Macaca mulatta and Macaca arctoides). Evaluation of two radioimmunoassays and a hemagglutination inhibition test.

Chorionic gonadotropin (mCG) in serum and urine of monkeys was determined by a radioimmunoassay and hemagglutination inhibition (HAI subhuman primate tube test for pregnancy). HAI-positive pregnancy tests coincided fully with the mCG excretion patterns as determined by RIA (oLH beta system). The least reliable system was the hCG-beta RIA. The HAI test allowed accurate prediction of the parturition date.

Animals↗
PubMed1980

A radioimmunoassay for pregnancy associated protein, beta 1SP1: levels in pregnancy, trophoblastic and neoplastic disease.

A radioimmunoassay system for the glycoprotein beta 1SP1, one of the pregnancy-associated proteins, has been set up. beta 1SP1 levels in normal pregnancy have been established transversally. Clearance (t1/2) from the circulation postpartum ranged from 1.4 to 1.8 days. Several patients with trophoblastic disease, e.g., mola hydatidosa, choriocarcinoma and embryonic cell carcinoma, were followed longitudinally. Human chorionic gonadotropin (hCG), a highly reliable tumor marker in trophoblastic disease, has been determined concomitantly by radioimmunoassay. In all instances, hCG proved to be a better indicator of the presence of a tumor, because by the time beta 1SP1 became undetectable, hCG could still be detected. Samples from a large multicenter study on trophoblastic disease were studied: out of 100 positive for hCG, beta 1SP1 could be detected in 86; however, out of 21 samples in which hCG was not detectable, 1 was found to be positive for beta 1SP1. In a number of samples from patients with bronchial carcinoma, no beta 1SP1 could be detected.

Bronchial Neoplasms↗
PubMed1978

Spontaneous dissociation of human pituitary luteinizing hormone in solution.

Aliquots of a solution of highly purified human pituitary LH (hLH) were incubated with variations in temperature and time. The incubates were chromatographed on Sephadex G-100 as well as on DEAE-Sephadex A25. The column effluents were assayed in radioligand assay and in specific hLH alpha- and hLH beta-RIA systems. The results indicate that there is spontaneous dissociation of hLH at elevated temperatures under otherwise "normal" conditions concerning, for example, pH and ionic strength. The degree of dissociation is both time and temperature dependent. This dissociation is not due to proteolytic enzymes. It is concluded that one should be alert when using hLH subunit RIA systems at elevated temperatures for measuring hLH levels, e.g. in clinical samples, because artificial high levels may be obtained.

Humans↗
PubMed1977

Human thyrotropin and its alpha and beta subunits.

A new procedure is described for the isolation of human thyrotropin using ion exchange chromatography and gel filtration only. Thyroid stimulating activity of the final preparation of our human thyrotropin amounted to 0.5 IU/mg by bioassay. The alpha and beta subunit of the hormone were also obtained by a new procedure. In this method the native hormone was incubated in an acidified 8 M urea solution and the chains were then separated by ion exchange chromatography and gel filtration. The amino-terminal residues of the alpha and beta chains were valine and phenylalanine respectively. The beta chain appears shorter at its carboxy-terminal end by one methionine residue than its bovine counterpart. Cross-contamination of the subunit preparations were measured by radioimmunoassay. The beta chain exhibited a contamination of about 3 percent of the alpha subunit by weight. The alpha subunit is contaminated by about one percent of the beta chain by weight.

Amino Acids↗
PubMed1976

The effect of gonadotrophin releasing hormone on pituitary-gonadal function in Klinefelter's syndrome.

The mean basal plasma LH and FSH levels in 8 patients with Klinefelter's syndrome were respectively 5 and 15-fold higher than in 8 eugonadal males, whereas plasma testosterone concentration were half the normal value. After an intravenous bolus injection of gonadotrophin releasing hormone (100 mug of LH-RH) the gonadotrophin increase in the Klinefelter patients was more marked than in the control subjects, but in both groups the plasma testosterone levels remained essentially unchanged. In contrast to the bolus injection, an 8 h infusion of LH-RH after the bolus elicited a significant plasma testosterone increase in both the eugonadal males (59%) and the Klinefelter patients (51%). These findings indicate that despite an impressive endogenous hyper-gonadotrophism, Leydig cells in Klinefelter's syndrome can still respond to a sustained further increase of these endogenous gonadotrophins and thus still have functional reserve.

Adult↗
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↗