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M C Clavequin

Publications and source records attributed to M C Clavequin.

At least 19 recordsLinked to original sources
PubMed2005

Segregation of chromosomes in sperm of Robertsonian translocation carriers.

Robertsonian translocations are the most frequent structural chromosomal abnormalities in humans and can affect fertility, with various degrees of sperm alterations in men; or the pregnancy outcome of the carriers. The studies on meiotic segregation of chromosomes in sperm of Robertsonian translocation males find a majority of normal or balanced spermatozoa for the chromosomes related to the translocation (mean 85.42%; range 60-96.60%). Furthermore, recent studies suggest an interchromosomal effect. Studies on spermatozoa from translocation carriers, and in mouse models help the comprehension of the meiotic segregation mechanisms. Results of meiotic segregation analysis in man could be integrated in genetic counselling especially when assisted reproductive technology is required.

Chromosomes, Human, Pair 13↗
PubMed2003

Risk of cytomegalovirus transmission by cryopreserved semen: a study of 635 semen samples from 231 donors.

BACKGROUND: The hypothetical responsibility of sperm donation in cytomegalovirus (CMV) transmission to recipients and precautions to prevent this transmission are widely discussed. The aim of this French CECOS Federation study was to evaluate both the reality and the importance of the CMV risk due to donor sperm and the relevance of measures used to screen it. METHODS: We conducted a prospective multicentric study. CMV was detected by rapid and conventional cultures and by PCR in the frozen sperm of donors who met the normal criteria required of semen donors, irrespective of their CMV serological status. RESULTS: 635 samples from 231 donors (39.4% IgG(+)) were obtained and tested by culture; 551 samples from 197 donors were also tested by PCR. From those samples, 0.78% were culture(+), 1.57% culture(+) and/or PCR(+); 3.3% of seropositive donors and 0.72% of initially seronegative donors were culture(+), but in the latter seroconversion occurred during the quarantine period; of the 197 PCR-tested donors, 3.5% (6.2/1.7) were PCR(+), 3.3% (5.3/1.45) culture(+) and/or PCR(+). PCR(+) samples can be culture(-) and vice versa. The most strongly positive sample corresponded to an initially seronegative donor. CONCLUSION: The best strategy to prevent potential CMV risk is to test donors for CMV IgG and IgM antibody at the outset and after a 6 month period of quarantine and to reject initially IgM seropositive donors or donors who seroconvert during the quarantine period.

Antibodies, Viral↗
PubMed2000

AZFa deletions in Sertoli cell-only syndrome: a retrospective study.

Lack of data on the genotype-phenotype relationship in cases of AZF microdeletions is due to the limited number of histological investigations in human male infertility cases. We investigated the possibility of retrospective detection of Yq11 microdeletions by using DNA extracted from diagnostic testicular biopsies. We used histological criteria to select two series of material: 22 biopsies with Sertoli cell-only syndrome and 14 biopsies with maturation arrest at the spermatocyte I stage. Two markers, DFFRY and DAZ, were tested by nested polymerase chain reaction (PCR) in the two series. In the Sertoli cell-only syndrome series, we found four deletions affecting the DFFRY gene (18.2%). In the second series, no deletions were detected. Two conclusions may be considered, although the number of specimens analysed is limited: (i) the frequency of deletions observed in Sertoli cell-only syndrome allows us to suggest that deletion in the AZFa region may be involved in this pathology; and (ii) retrospective studies may yield some additional elements in our search for eventual genotype-phenotype relationships.

Chromosome Deletion↗
PubMed1998

Interindividual variations in the disomy frequencies of human spermatozoa and their correlation with nuclear maturity as evaluated by aniline blue staining.

OBJECTIVE: To evaluate the importance of interindividual variations in the disomy frequencies of human sperm and their possible correlation with the principal semen parameters. DESIGN: Prospective randomized analysis of sperm nuclei by fluorescence in situ hybridization and analysis of semen parameters. SETTING: University-based laboratory for reproductive biology. PATIENT(S): Fifty-seven human ejaculates selected at random from a population of men undergoing semen analysis. INTERVENTION(S): Semen specimens were analyzed, and sperm samples were prepared for fluorescence in situ hybridization. MAIN OUTCOME MEASURE(S): Semen parameters, including necrozoospermia, global motility, sperm concentration, multiple abnormalities index, and teratozoospermia were evaluated, aniline blue staining was completed, and disomy frequencies for chromosomes 8, 15, 18, X, and Y were determined using fluorescence in situ hybridization. RESULT(S): Noticeable differences in disomy frequencies between individuals were observed, and these frequencies were correlated with the degree of nuclear maturity. CONCLUSION(S): We hypothesize that the positive correlation can be explained by an abnormality of chromosomal segregation at the time of meiosis that would cause disturbances during the transition of nucleoprotein or by one or several premeiotic abnormalities of chromatin that would perturb both the meiotic process and the construction of definitive proteins.

Adult↗
PubMed1997

Estimation of aneuploidy levels for 8, 15, 18, X and Y chromosomes in 97 human sperm samples using fluorescence in situ hybridization.

OBJECTIVE: To estimate the mean frequency of aneuploidy levels of chromosomes 8, 15, 18, X, and Y in human sperm, while minimizing the effect of individual factors by analyzing sperm samples from a large set of patients. DESIGN: Prospective randomized analysis of sperm nuclei by fluorescence in situ hybridization. SETTING: University-based laboratory for reproductive biology. PATIENT(S): One hundred two patients with a large distribution of sperm parameters, randomly selected from volunteers who had presented seeking a semen analysis. INTERVENTION(S): The sperm samples were prepared for fluorescence in situ hybridization. MAIN OUTCOME MEASURE(S): The disomy frequencies for chromosomes 8, 15, 18, and sex chromosomes were determined using fluorescence in situ hybridization. RESULT(S): The mean frequencies of disomy for autosomes were 0.18% for chromosome 8, 0.06% for chromosome 15, 0.2% for chromosome 18, and 0.24% for gonosomes (XX, 0.04%; YY, 0.05%; XY, 0.15%). CONCLUSION(S): This study confirms other previous evaluations on restricted numbers of patients. Our results seem to confirm a relative equiprobability of disomy frequencies concerning the different chromosomal pairs during male meiosis.

Adult↗
PubMed1996

Analysis of the sex chromosomal equipment in spermatozoa of a 47,XYY male using two-colour fluorescence in-situ hybridization.

The sex chromosomes in spermatozoa of a 47,XYY fertile male were analysed simultaneously by dual fluorescence in-situ hybridization (FISH), with two probes (pHY2.1 and pXBR). Of the 100000 cells analysed, 95179 spermatozoa (95.18%) exhibited one or more hybridization signals. Of the hybridized nuclei, 85.37% showed a normal sex chromosome constitution (37.37% X-bearing cells and 48.00% Y-bearing cells), with an X:Y ratio of 0.78:1. A total of 14.63% of the hybridized nuclei exhibited sex chromosome aneuploidy with a majority of XY- and YY-bearing spermatozoa (9.37 and 4.65% respectively). Even if the majority of spermatozoa have chromosomal haploidy, a large proportion of them exhibits numerical errors for the sex chromosomes. These observations raise questions about the commonly-admitted notions concerning the absence of chromosomal risk for XYY male offspring.

Humans↗
PubMed1995

Morphometric parameters of living human in-vitro fertilization embryos; importance of the asynchronous division process.

A total of 304 human pronuclear zygotes and cleaved embryos from the 2- to 9-cell stages, obtained during invitro fertilization attempts, were photographed and retrospectively analysed after transfer for their morphology and size in relation to their developmental stage, using the Imagenia programme of a Biocom 500 image analyser. Morphometric parameters were calculated from the perimeters, surface measurements, theoretical diameters and circularity factors for the different structures analysed. This report provides the morphometric characteristics of living embryos. For the whole population the mean values were: 157.4 microns for the external zona pellucida diameter, 121.8 microns for the internal zona pellucida diameter, 17.9 microns for the thickness of the zona pellucida and 117.2 microns for the embryo cell mass diameter. The morphometric characteristics of the pronuclear-stage population were significantly different from the cleaved cell stages. If the zona pellucida and cell mass embryo diameters increased slowly from the 2- to 9-cell stages, embryonic external diameters were higher and zona pellucida thicknesses were lower in odd than even number blastomere embryos. Preliminary results show that in cases where implantation occurs, the embryo has a lower zona pellucida thickness. A comparison of the different embryo cell stages confirmed the existence of an asynchronous division process during early embryo development. Global results show no evidence of morphometric differences between subpopulations of the embryos according to their microscopic grading. Deviations from the normal asynchronous division process, however, appear to be a new parameter to take into account during embryo scoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Blastocyst↗
PubMed1995

Early detection of secretogranin-II (SgII) in the human fetal pituitary: immunocytochemical study using an antiserum raised against a human recombinant SgII.

Secretogranin-II (SgII) is a protein contained within secretory granules of mainly gonadotrophs. The purpose of this study was to determine whether SgII immunoreactivity (SgII-IR) in the human fetal pituitary was temporally related to gonadotropin immunoreactivity. A specific antihuman SgII antiserum was thus required. A complementary DNA clone with an open reading frame for human (h) SgII was synthesized by reverse transcription-polymerase chain reaction from pituitary total RNA. This clone was used to obtain the SgII polypeptide (-9 to 152) as a fusion protein, in a heterologous expression prokaryotic system. Antisera against the fusion protein were raised in rabbits and checked for specificity and sensitivity through Western blotting. Human fetal pituitaries from week 6 of gestation onward were used for immunocytochemical studies. Consecutive semithin sections were treated with the specific antisera against hSgII, beta-endorphin, and hPRL and with monoclonal antibodies to hCG alpha, hLH, and hFSH. SgII immunoreactivity appeared at week 8 and was restricted to pituitary cells expressing beta-endorphin (100% colocalization). At week 9, FSH-positive cells did not contain SgII. From week 10, gonadotrophs progressively exhibited SgII-IR, up to 50% of that in FSH-containing cells at week 26. The granin was never found in PRL cells whatever the stage of development. The present data demonstrate that SgII-IR is detected very early in fetal life; however, the positive cells are not gonadotrophs, but corticotrophs. Within gonadotrophs, SgII appears subsequent to hormones. At birth, more than 90% of SgII-IR cells are represented by corticotrophs and gonadotrophs.

Adrenal Glands↗
PubMed1989

Human hypothalamic neuronal system revealed with a salmon melanin-concentrating hormone (MCH) antiserum.

An antiserum raised against synthetic salmon melanin-concentrating hormone (MCH) reveals an extensive neuronal system in the posterior lateral areas of the human hypothalamus. These neurons correspond to those previously described in the rat, which are characterized by expression of MCH-like, alpha-melanotropin-like and human growth hormone-releasing factor (1-37)-like immunoreactivities.

Adult↗
PubMed1987

Human corticoliberin hypothalamic neuroglandular system: comparative immunocytochemical study with anti-rat and anti-ovine corticotropin-releasing factor sera in the early stages of development.

Development of the paraventriculo-infundibular corticoliberin system was studied by immunocytochemical analysis of human hypothalamic sections using antisera raised against rat or ovine corticotropin-releasing factor (CRF). This comparative study confirms the presence of a significant number of CRF-immunoreactive fibers in the median eminence during the 16th week of fetal development and suggests they may appear as early as the 14th week. Some hypothalamic peri- and paraventricular neurons, observed from the 12th week, are rat-CRF-immunoreactive but not ovine CRF-immunoreactive. There appears to be chronological differences concerning the ability of the two antisera to recognize hypothalamic structures during the early stage of development.

Animals↗
PubMed1987

[Contribution of immunocytochemistry to the study of the development of neuroglandular peptidergic systems in the human fetal hypothalamus].

Immunohistochemistry makes possible the in situ detection of neuropeptides in the cell bodies were they are synthesized, in the fibers that carry them, and in endings. Immunohistochemistry appears necessary to identify and map peptidergic neurons and to study their ontogeny. From 1975, we have carried the immunohistochemical study of several hypothalamic neuronal populations in the human fetus: LH-RH (1976), somatostatin (1977), pro-opiocortin (1978), vasopressin and oxytocin (1979), corticoliberin (1982), somatocrinin (1983), and hypothalamic neurons containing an unidentified peptide (1984). Comparative ontogenetical studies have also been performed in rats.

Animals↗
PubMed1987

[Ontogenetic data on the peptidergic interneuronal population in immunoreactivity of the GRF 37 type serum of the human posterolateral hypothalamus. Immunocytochemical studies using anti-GRF 37 and anti-MCH (melanin-concentrating hormone) immune sera].

Human posterolateral hypothalamic neurons are revealed with an anti GRF 37 serum as soon as the 7th week of fetal life. The same neuronal population can be observed in the adult brain even in hypothalami from old subjects, with the same distribution, and similar immunoreactivity than in fetal stages. These neurons are revealed using a melanin concentrating hormone (MCH) antiserum; the MCH immunoreactivity appears at the same stage of fetal development than GRF 37 immunoreactivity. The two antisera recognize two epitopes on one or two molecules. Those new facts agree with an hypothesis about the very important and permanent functional role of that new human hypothalamic interneuronal system.

Adult↗
PubMed1986

[Ontogenesis in man, of a population of neurons in the dorsal and lateral hypothalamus, secretors of a peptide that has not yet been characterized].

A human GRF 1-37 antiserum demonstrates a new neuronal system in lateral perifornical areas of the human hypothalamus. The molecule that is revealed in those neurons cannot be somatocrinin. Perikarya are abundant. They are observed beginning with the 9th week of development. alpha-MSH-like immunoreactivity, which is showed in the analogous cells of the rat, is not yet established in human. The early differentiation of those neurons and their abundance during the fetal life attest to the important neurophysiological function of the unidentified peptide they secrete.

Fetus↗
PubMed1985

Anatomical and ontogenetic studies of the human paraventriculo-infundibular corticoliberin system.

In human fetus, newborn, infant and adult hypothalami, antibodies to ovine corticoliberin-41 stain a paraventriculo-infundibular neuroglandular pathway. The perikarya are located in the paraventricular nucleus, they mainly project to the ventral and lateral areas of the median eminence. Eminential corticoliberin-positive fibres appear during the 16th week of fetal life, and increase in number during the following weeks. Perikarya were first revealed in the 19th week. In some areas of the median eminence, corticoliberin-, vasopressin- or [Met]enkephalin-immunoreactive terminals are similarly distributed. Sequential stainings or staining comparison of contiguous semi-thin sections failed to prove the coexpression of corticoliberin and [Met]enkephalin immunoreactivities in fibres, but indicated that corticoliberin and vasopressin immunoreactivities may be coexpressed in a few fibres. Those methods enabled us to observe, in the paraventricular nucleus, perikarya revealed by corticoliberin and vasopressin antisera. Our results suggest a possible release of corticoliberin in portal vessels of the median eminence beginning in the 16th week of fetal life, i.e. 8 weeks later than appearance of the corticotrophs in the pituitary. Establishment of a corticoliberin hypothalamic control of pituitary corticotrophs at mid gestation agrees with previous physiological and teratological studies. Abundance, as well as immunostaining intensity of the corticoliberin processes, in the infant and adult median eminence attest to the physiological importance of this system. Close vicinity of corticoliberin, vasopressin and [Met]enkephalin fibres, in some eminential areas and coexpression of corticoliberin and vasopressin immunoreactivities in some neurons, are morphological correlates of functional relations which were reported.

Adult↗
PubMed1985

[Coexpression of immunoreactivity with an anti-corticoliberin immune serum and immunoreactivity with an anti-vasopressin immune serum in human hypothalamic neurons].

Confrontations of immuno-stainings as well as sequential stainings with corticoliberin and vasopressin antisera were performed on contiguous sections of human median eminence (ME) or hypothalamic paraventricular nucleus (PVN). Results show that a double immunoreactivity to both IS is expressed in some parvicellular PVN perikarya, and suggest that such a double immunoreactivity can be possible in some ME fibers. Similar results had been previously obtained in animals only under experimental conditions.

Corticotropin-Releasing Hormone↗
PubMed1984

Corticoliberin neurons: cytophysiology, phylogeny and ontogeny.

In the rat hypothalamus, antibodies to ovine CRF41 stain neurons of a paraventriculo-infundibular neuroglandular pathway. CRF like immunoreactivity (CLI)-containing perikarya are mostly packed in the parvocellular division of the paraventricular nucleus. Their morphology and topography differ from that of other peptidergic neurons. However a few CLI perikarya are also stained with vasopressin antibodies. CLI neurons project massively to the external layer of the median eminence (ELME). Adrenalectomy induced a total depletion of ELME CLI 12 to 24 h after surgery, followed by a secondary accumulation already conspicuous 5 days later. This biphasic evolution, identical to that of ELME vasopressin, is totally prevented by a replacement therapy with dexamethasone. Reserpine also induces an acute depletion of ELME CLI and vasopressin, that can be prevented by a monoamine oxidase inhibitor pretreatment. These results indicate the involvement of CLI neurons in the corticotropic axis, suggesting that they are indeed corticoliberin neurons. Among the extrahypothalamic locations of CLI neurons their abundance in the amygdala central nucleus is of interest since it is involved in the corticotropic axis. A similar pattern of CLI was noticed in several mammalian brains and also in lower vertebrates (birds, reptiles, amphibians, fishes). Species adaptations of CLI neurons were observed: CLI neurons are of the cerebrospinal fluid contacting type in the turtle. CLI fibres terminate close to corticotrophs in the fish pituitary. This suggests a direct excitosecretory role of CRF on these cells and concurs with a CRF function of CLI peptide even in fishes. CLI processes and terminals appear in the human fetal ELME at the 16th week of development and increase in number during the following weeks. Perikarya are seen at 19 weeks. In the rat CLI fibers and perikarya were detected as early as the 18th day of fetal development. Thus, paraventriculo-infundibular CLI system develops later than corticotrophs. This chronology perfectly concurs with the results of previous physiological and experimental studies.

Adrenalectomy↗
PubMed1984

The CRF neuron: immunocytochemical study.

In the central nervous systems of several species belonging to different vertebrate classes, immunocytochemical stainings with an antiserum to ovine CRF 41 show multiple location of CRF perikarya and various areas containing CRF fibres and terminals. These stainings reflect species and interspecies functional adaptations of the CRF neurones which constitute a prominent hypothalamo-infundibular system involved in pituitary gland control, and also interneurone systems as attested to by extrahypothalamic perikarya and by CRF perisomatal endings in several brain areas. Perikarya of the hypothalamo-infundibular system are mainly packed in the paraventricular nucleus (mammals, birds) or in homologous areas, e.g.: paraventricular organ (turtle) where they are CSF-contacting neurones and preoptic nucleus (amphibians, fishes). In all species but fish, CRF fibres end in the median eminence (ME) against portal vessels. In fish, CRF processes terminate in the peripheral areas of proadenohypophyseal neurodigitations, close to corticotrophs. In all species these stainings are abolished by preabsorption of the serum by CRF. In fishes, reptiles and amphibians they are also suppressed by urotensin I, which is thought to be the teleost's CRF. Adrenalectomy experiments in the rat provided evidence for a corticosteroid regulation of ME CRF: short term (12-24 hr) adrenalectomy induces a complete depletion of CRF immunoreactivity followed by a secondary accumulation (5-20 days). This biphasic evolution is prevented by a dexamethasone replacement therapy. Inhibitory role of catecholamines on CRF release was indicated by: disappearance of ME CRF, induced by a single reserpine injection and suppression of this effect by monoamineoxidase inhibitor (pargyline or tranylcypromine) pretreatment. CRF fibres were first observed in the ME at the 16th week of fetal development in the human, and at the 18th day in the rat fetus. Thus, immunoreactive CRF system develops later than pituitary corticotrophs.

Adrenalectomy↗