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Biomedical subjects

C Breton

Publications and source records attributed to C Breton.

At least 73 records · Page 4Linked to original sources
PubMed1996

Renal oxytocin receptor messenger ribonucleic acid: characterization and regulation during pregnancy and in response to ovarian steroid treatment.

Although the neurohypophyseal hormone oxytocin (OT) is best know for its role in reproduction, OT also stimulates natriuresis at physiological plasma levels. This effect is mediated via specific renal OT receptors (OTRs). In the present study, we have characterized rat renal OTR gene transcripts and assessed their regulation during gestation and in response to gonadal steroid treatment. Using a specific rat OTR probe, two major OTR messenger RNA (mRNA) bands [6.7 and 4.8 kilobases (kb)] were detected in renal extracts, corresponding to two of the three bands present in rat uterus. In contrast to the dramatic rise of OTR mRNA levels at term in the uterus and pituitary, renal OTR mRNA levels underwent a strong more than 3-fold decrease at term. Binding studies using a iodinated specific OT antagonist revealed a concomitant decrease in renal OT-binding sites. On the other hand, estrogen (E2) treatment led to an increase in renal OTR mRNA levels, as is also the case in the uterus and pituitary. However, the predominant E2-induced mRNA species were shorter (3.6 and 3.2 kb) than those present in control rat kidneys (6.7 and 4.8 kb). Analysis by reverse transcriptase-PCR and 5'- and 3'-directed complementary DNA probes indicated that the E2-induced OTR mRNA transcripts possessed the same coding region, but contained a shortened 3'-untranslated region. Binding studies showed that E2 treatment also led to an increase in renal OT-binding sites, suggesting that the shortened OTR transcripts encoded a functional receptor. The present study indicates that the uterine-type OTR gene is expressed in rat kidneys, but that the mechanisms controlling the expression of this gene in the two tissues are markedly different. The differential tissue-specific regulation of OTR gene expression may represent a mechanism by which circulating OT can assume a multifunctional role in both reproduction and sodium homeostasis.

Animals↗
PubMed1995

PCR-generated cDNA library of transition-stage maize embryos: cloning and expression of calmodulin genes during early embryogenesis.

One hundred maize zygotic embryos microdissected at the transition stage were used to construct a cDNA library after non-selective PCR (NS-PCR) amplification of whole cDNA populations. The library contains 2.3 x 10(5) recombinants and two different calmodulin cDNAs were cloned using a heterologous probe from petunia. Calmodulin expression was confirmed throughout maize embryogenesis at the mRNA, amplified cDNA and protein levels. Sequence analysis suggests a maize origin for both clones and negligible nucleotide changes linked to PCR. This library is the first described for early plant embryos and represents a breakthrough to isolate genes involved in embryo differentiation.

Amino Acid Sequence↗
PubMed1995

Expression of heat shock factor and heat shock protein 70 genes during maize pollen development.

We have analysed the expression of heat shock protein 70 (HSP70) and heat shock factor (HSF) gene during maize pollen development, HSFs being the transcriptional activators of hsp genes. In order to eliminate the sporophytic tissues of anthers, we have isolated homogeneous cell populations corresponding to five stages of maize pollen development from microspores to mature pollen. We show that in the absence of heat stress, hsp70 genes are highly expressed late-bicellular pollen as compared to other stages. HSP70 transcripts are significantly accumulated in response to a heat shock at the late microspore stage but to a much lower extent than in vegetative tissues. The latest stages of pollen development, i.e. mid-tricellular and mature pollen, do not exhibit heat-induced accumulation of HSP70 transcripts. Therefore, we analysed the expression of hsf genes throughout pollen development. We demonstrate that at least three hsf genes are expressed in maize and that transcripts corresponding to one hsf gene, whose expression is independent of temperature in somatic as well as in microgametophytic tissues, are present at similar levels throughout pollen development. In addition, we show that the expression of the two other hsf genes is heat-inducible in maize vegetative tissues and is not significantly increased after heat shock at any stage of pollen development. These results indicate that the loss of hsp gene expression at late stages of pollen development is not due to a modification of hsf gene expression at the mRNA level and that hsf gene expression is differentially regulated in vegetative and microgametophytic tissues.

Amino Acid Sequence↗
PubMed1995

Oxytocin receptor gene expression in the rat uterus during pregnancy and the estrous cycle and in response to gonadal steroid treatment.

It is well established that uterine oxytocin receptors (OTRs) are strongly up-regulated immediately before parturition as well as in response to estrogen (E2) administration. Progesterone (P4), on the other hand, induces a rapid down-regulation. We recently cloned the rat OTR gene and characterized its expression in the rat uterus. In this study, we examined the regulation of OTR messenger RNA (mRNA) levels in rat uterus during pregnancy, the estrous cycle, and in response to gonadal steroid treatment. OTR mRNA levels increased more than 25-fold during gestation: 4.5-fold during the first 21 days and 6-fold within 24 h between day 21 and the onset of parturition. Uterine OTR mRNA levels fell rapidly by 85% within 24 h following parturition. By in situ hybridization, OTR mRNA was localized specifically to the longitudinal and circular layers of the myometrium but was not detected in the endometrium. During the estrous cycle, OTR mRNA levels increased 2-fold between metestrus and proestrus, whereas oxytocin (OT) binding rose more than 10-fold within this same interval. Treatment of ovariectomized rats with E2 lead to a significant increase in both OTR mRNA levels (4.4-fold) and OT binding (< 6-fold). Cotreatment with P4 strongly reduced OT binding by 75% (P < 0.01) but did not significantly affect the E2-induced rise in OTR mRNA (11% decrease, P > 0.1). Our data suggest that the increased expression of OT binding sites observed at the onset of labor and at proestrus is mediated, at least in part, by an E2-induced up-regulation of OTR gene expression. However, it also appears that OTR mRNA levels are not the sole determinants of uterine OT binding. Specifically, P4-mediated OTR down-regulation cannot be explained by an effect on OTR mRNA accumulation and may involve novel mechanisms acting at translational or posttranslational levels.

Animals↗
PubMed1995

Oxytocin receptor messenger ribonucleic acid: characterization, regulation, and cellular localization in the rat pituitary gland.

The hypothalamic neuropeptide oxytocin (OT) stimulates the release of several pituitary hormones, including ACTH, LH, and PRL. Although specific OT receptors have been identified in anterior pituitary membranes, the structure and cellular localization of these binding sites have not been elucidated. We previously cloned a rat OT receptor (OTR) gene and showed that its expression in rat uterus results in several transcripts ranging in size from 2.9-6.7 kilobases. In this study we show, by using Northern blot analysis, reverse transcriptase-polymerase chain reaction, and ultrastructural in situ hybridization that the same OTR gene is also expressed in the pituitary, where it gives rise to a 6.7- and a 4.8-kilobase messenger RNA. Ultrastructural in situ hybridization combined with immunogold labeling indicated that pituitary OTR gene expression is highly cell-specific and restricted to lactotrophs. In accordance with this finding, only the lactotroph-derived cell line MMQ expressed the OTR gene among several pituitary cell lines tested. Northern blot analysis, reverse transcriptase-polymerase chain reaction, and in situ hybridization analysis indicated a dramatic increase in pituitary OTR gene expression at the end of gestation and after estrogen treatment. Our results suggest that the OT effect on lactotrophs is direct, whereas OT actions on gonadotrophs and corticotrophs are either indirect or mediated via different receptors. Moreover, our findings imply that OT exerts its full potential as a physiological PRL-releasing factor only towards the end of gestation, and that therefore the role of OT as a hypothalamic PRL-releasing factor may so far have been underestimated.

Animals↗
PubMed1995

Gonadal steroid regulation of oxytocin and oxytocin receptor gene expression.

By Northern blot analysis and in situ hybridization, we have determined that, at term, the rat uterine epithelium represents a major site of oxytocin (OT) gene expression. OT mRNA levels increase > 150-fold during pregnancy and, at term, exceed hypothalamic OT mRNA by a factor of 70. By cryoultramicroscopy, OT immunoreactivity was localized to transport vesicles in the apical compartment of uterine epithelial cells. Estrogens (E) act as a strong inducer of uterine OT gene expression in vivo, and this effect is potentiated 7-fold by concomitant progesterone (P) administration. We have also cloned the rat OT receptor (OTR) gene and developed a polymerase chain reaction (PCR)-based assay to measure OTR mRNA. Whereas OTR mRNA is strongly induced by E, P does not potentiate but slightly attenuates the E-induced rise. However, E-induced OT binding is completely reversed by concomitant P administration, suggesting an additional post-transcriptional effect of P. The mechanisms of E-induction of the uterine OT gene remain unclear, inasmuch as the OTR gene promoter does not contain a classical estrogen response element (ERE). Moreover, transfection analysis of a 3.1 kb OTR gene promoter fragment linked to a luciferase reporter gene indicates that promoter activity is induced 5-fold by calcium ionophore A23187 but not by E.

Animals↗
PubMed1993

Isolation and characterization of the human melanin-concentrating hormone gene and a variant gene.

Melanin-concentrating hormone (MCH) is a cyclic peptide found expressed almost exclusively in the hypothalamus while MCH-containing fibers project throughout the brain of many vertebrates including man. In fishes, MCH induces melanin concentration within the melanophores and may inhibit ACTH secretion. In mammals, MCH modulates ACTH release in vivo and participates as a neuromediator in the control of complex behaviors such as water and food intake. Salmon, rat and human MCH cDNAs have been cloned and structures of deduced mRNAs and precursors have been elucidated. In this report we determine the nucleotide sequence of two human MCH (hMCH) genes and demonstrate that both genes are expressed in human brain. Cloning from three genomic libraries and sequencing of one class of hMCH genomic DNA reveal high similarity between coding regions and the C-terminal part of the hMCH prohormone. However no sequence identity was found in the N-terminal and 5' end non-coding regions of the gene between them even within 6.5 kilobases (kb) upstream from the truncation point. Using polymerase chain reaction (PCR) analysis we have identified RNA populations that are derived from this gene in human brain. For that reason, this gene is a variant rather than a pseudogene. The authentic hMCH gene could only be cloned by using the PCR technique. With primers specific to 5'-end and 3'-end regions of the MCH mRNA we amplified a 1400 bp fragment as well as other shorter PCR products from human genomic DNA. The longest PCR fragment contains 3 exons encompassing most of the 5' untranslated and all of the coding and 3' untranslated sequences of the hMCH mRNA, that are separated by two introns of 350 and 271 bp, respectively. Interestingly the second intron dissects the hMCH peptide sequence in both the authentic and the variant gene. A strikingly high degree of homology was found between the variant and authentic hMCH genes, including intronic sequences, suggesting that these two genomic sequences diverged very recently during evolution. A strong homology was also noted between the exons and intervening sequences of the human and rat MCH genes. Altogether, our results provide the first strong evidence for the existence of two distinct MCH genes expressing prohormones with different MCH and neuropeptide EI (NEI) sequences in human and along with in vivo and in vitro findings, suggest that these neuropeptides may influence the activity of numerous mammalian neuronal systems.

Amino Acid Sequence↗
PubMed1991

[Action of estradiol-17 beta on the expression of c-Fos gene in endometrial cells in cultured].

The c-fos expression was investigated in primary culture of guinea-pig endometrial cells. Cells were made quiescent by serum depletion. Stimulation of these cells by estradiol (E2, 10(-8)M) alone or in combination with epidermal growth factor (EGF, 100 ng/ml) or insulin (10 micrograms/ml) failed to induce c-fos gene. The c-fos expression was early and transiently increased by fetal calf serum (15%) or estradiol plus EGF plus insulin. Protein synthesis inhibitors (cycloheximide or anisomycin) in association with E2 induced a superinduction of c-fos gene. In the same conditions puromycin had no effect. It appears that E2 acts in a multiple step process including an initial c-fos gene derepression by either EGF plus insulin or some protein synthesis inhibitors.

Animals↗
PubMed1989

Cloning of cDNAs encoding a rat neuropeptide immunologically related to salmon melanin-concentrating hormone.

In order to identify the neuropeptide related to melanin-concentrating hormone (MCH) synthetized by neurons of the posterior hypothalamus in the mammals, we have screened rat hypothalamus and rat brain cDNA expression libraries using MCH antiserum. We isolated 5 distinct immunopositive recombinants with cross-hybridizing cDNA inserts. One of them hybridized to RNAs exclusively located in neurons stained by the same antiserum, as seen by successively performing in situ hybridization and then an immunocytochemical technique on the same section. Sequencing of this MCH-like cDNA is in progress.

Animals↗
PubMed1989

[Specific hybridization of a synthetic oligonucleotide in rat hypothalamic neurons immunoreactive to immune serum against salmon melanin-concentrating hormone].

An oligonucleotide probe corresponding to the 9 C-terminal residues encoded by a complementary DNA of a rat peptide related to salmon melanin concentrating hormone (MCH) was synthetized. It specifically hybridized to the neurons stained by antisera to MCH in the rat posterior hypothalamus, as seen by coupling in situ hybridization and immunocytochemical methods. This result validates our sequence determination. This oligonucleotide will be useful to establish the complete sequence of the rat MCH precursor molecule. It will also constitute a valuable tool to study physiological or experimentally-induced changes in the expression of the rat MCH gene.

Animals↗
PubMed1989

[Cloning of the cDNA, while encoding a hypothalamic neuropeptide in the rat, related to the melanin-concentrating hormone in the salmon].

In order to identify the neuropeptide related to salmon melanin-concentrating hormone (MCH) synthetized by neurons of the posterior hypothalamus in the mammals, we have screened rat hypothalamus and rat brain cDNA expression libraries using MCH antiserum. Five recombinants were isolated, which cDNAs were amplified using the polymerase chain reaction. One of them hybridized to RNAs exclusively located in hypothalamic neurons stained by the same antiserum, as seen by performing in situ hybridization and immunocytochemical techniques on the same section. The sequence analysis showed that this cDNA corresponds to the end of the open reading frame encoding a MCH-like peptide and to the 3' untranslated region. The rat MCH is very similar to salmon MCH (greater than 85% homologies in the 14C-terminal residues).

Amino Acid Sequence↗
PubMed1989

[Cloning and sequence analysis of cDNA of common precursors of three hypothalamic neuropeptides immunologically related to human somatocrinin 1-37, alpha melanotropin and salmon melanin-concentrating hormone].

We have cloned and sequenced DNAs complementary to the mRNA encoding the precursor of the rat melanin-concentrating hormone. This allowed us to elucidate the primary structure of the 96 C-terminal residues of this precursor. It contains three possible sites for enzymatic cleavage enabling the generation of MCH and of two additional neuropeptides. These three peptides can bind one of our antisera raised against human somatocrinin 1-37, alpha-melanotropin and salmon melanin-concentrating hormone, which immunocytochemically stain the same neuron population in the hypothalamus.

Amino Acid Sequence↗
PubMed1988

[Evaluation of health expenditures in the first 6 months after the diagnosis of cancer using a population register].

It is currently estimated in France, that the cost of cancer is rising to 25 billion francs, which represents approximately 6% of all health expenditure with an annual growth of 5-10%. The data from the Register of Tumors in the Doubs region have enabled us to make an evaluation of health expenditure, reimbursed by the social security system, and its distribution in relationship with the different posts (assessment, type of treatment, supervision, transport) according to the cancer site. The average cost per patient within the first 6 months of the illness has been evaluated at 26,000 F (1984). The results show major differences for the cancer sites, care facilities and posts which are budgeted for.

Cancer Care Facilities↗