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Biomedical subjects

P Bouchard

Publications and source records attributed to P Bouchard.

At least 73 records · Page 4Linked to original sources
PubMed1999

Resistance of hypogonadic patients with mutated GnRH receptor genes to pulsatile GnRH administration.

We have studied a kindred with three siblings with isolated hypogonadotropic hypogonadism caused by compound heterozygote mutations in the GnRH receptor gene. The disorder was transmitted as an autosomal recessive trait. The R262Q mutation in intracellular loop 3 of the receptor was associated with a mutation in the third transmembrane domain of the receptor, A129D, that has never been described before. This A129D mutation results in a complete loss of function, indicated by the lack of inositol triphosphate (TP3) 3 production by transfected Chinese hamster ovary (CHO) cells after GnRH stimulation. The two brothers had microphallus and bilateral cryptorchidism and were referred for lack of puberty, whereas their sister had primary amenorrhea and a complete lack of puberty. Their basal gonadotropin concentrations were below the reference range, and their endogenous LH secretory patterns were abnormal, with a low-normal frequency of small pulses or no apparent LH pulse. Pulsatile GnRH administration (10 microg/pulse every 90 min for 40 h) resulted in increased mean LH without any significant changes in testosterone levels in the two brothers, whereas the LH secretory profile of their sister remained apulsatile. Larger pulses of exogenous GnRH (20 microg every 90 min for 24 h) caused the sister to produce recognizable low amplitude LH pulses. The concentrations of free alpha-subunit significantly increased in all patients during the pulsatile GnRH administration. Thus, these hypogonadal patients are partially resistant to pulsatile GnRH administration, suggesting that they should be treated with gonadotropins to induce spermatogenesis or ovulation rather than with pulsatile GnRH.

Adolescent↗
PubMed1999

[Genes and ovarian insufficiency].

Premature ovarian failure is defined as hypoestrogenism with elevated gonadotropins, occurring before the age of 40. The prevalence of this syndrome is 3% of the women population. In most cases its etiology remains unknown. In theory, ovarian failure may occur by the following mechanisms: the pool of primordial follicule is too low; the atresia ou apoptosis is increased in the ovarian follicle; the follicle maturation is interrupted. In the past few years, several genes have been implicated in the pathogenesis of human or murine premature ovarian failure. Those genes can be classified according to the potential mechanisms previously described. Atm and c-kit gene code for proteins involved in maintaining the pool of primordial follicles. Genes located on the X chromosome, genes involved in blepharophimosis, in galactosemia code for proteins involved in follicular atresia. The gonadotropins, their receptors, GDF9 and connexin 37 are involved in follicle maturation. A better understanding of the family of genes involved in oocyte and follicular atresia should allow a better understanding of premature ovarian failure. Up to now, the better care for those patients is to give them hormonal replacement therapy and suggest oocyte donation when they desire to be pregnant.

Adult↗
PubMed1999

Progesterone and the progesterone receptor.

During the 1990s, extensive research has effectively mapped the progesterone receptor-mediated actions of progesterone and has more recently uncovered nonreceptor-mediated effects--the effect of progesterone on uterine sensitivity to oxytocin, for example, involves direct, nongenomic progesterone action on the uterine oxytocin receptor. However, the majority of progesterone effects occur as a result of progesterone-receptor-mediated action, where progesterone behaves as a hormone-dependent transcription factor, probably because these receptors are widely distributed in the body. A distinguishing characteristic of progesterone receptors is the existence of two isoforms, A-form and B-form. In most tissues coexpressing progesterone receptors, estrogen controls the regulation of progesterone receptors, thereby also controlling sensitivity to progestins. Thus, progesterone receptor expression is upregulated by estrogen and downregulated by progesterone in most target tissues.

Down-Regulation↗
PubMed1998

Species differences in the expression and distribution of the neuropeptide Y Y1, Y2, Y4, and Y5 receptors in rodents, guinea pig, and primates brains.

The respective distribution of neuropeptide Y Y1, Y2, Y4, and Y5 receptor subtypes was investigated in rodents (rat and mouse), guinea pig, and primates (marmoset and vervet monkeys and human) brains, representing three orders of mammals. [125I] [Leu31,Pro34]PYY (total Y1-like; Y1, Y4, and Y5) and [125I]PYY3-36 (total Y2-like; Y2 and possibly Y5) binding sites were discretely but similarly distributed in the rat and mouse brain, each having its unique pattern. In contrast, surprisingly low levels of [125I]PYY3-36 binding sites were found in the guinea pig brain including in the hippocampal formation. [125I][Leu31,Pro34]PYY/BIBP3226-insensitive binding sites (Y5-like) were found in different areas of the rat and guinea pig brains. The primate brains also revealed a different distribution binding profile for these various NPY receptor subtypes. Although the human and vervet brains contained very low amounts of [125I][Leu31,Pro34]PYY sites (Y1-like) in most brain regions, except for the dentate gyrus of the hippocampus, the marmoset brain contains significant amounts of both [125I][Leu31,Pro34]PYY (Y1-like) and [125I]PYY3-36 (Y2-like) binding sites. Additionally, [125I][Leu31,Pro34]PYY/BIBP3226-insensitive binding sites were not clearly detected in the vervet and human brains. On the other hand, Y5-like binding sites were observed in few regions of the marmoset brain. Finally, [125I]hPP (Y4/Y5-like) were very discretely distributed in the rat brain, being concentrated in the paraventricular nucleus of the hypothalamus and the interpeduncular nucleus. The marmoset brain is apparently not enriched with specific [125I]hPP sites. Taken together, these data show that significant species differences exist in the level of expression and distribution of various NPY receptor subtypes in the mammalian brain.

Animals↗
PubMed1998

Genes and premature ovarian failure.

Premature ovarian failure (POF) is an heterogeneous syndrome. Among genetic causes, X monosomy as in Turner syndrome or X deletions and translocations are known to be responsible for POF. The genes involved in ovarian function, located on the X chromosome are still unknown. On the other hand, autosomal abnormalities have been identified in POF patients such as mutations of the FSH gene, the LH and FSH receptor genes, chromosome 3q containing the blepharophimosis gene, the ATM gene (Ataxia-telangiectasia gene). Mutations in the AIRE gene (responsible for APECED syndrome) can involve ovarian insufficiency. It is likely that studies on the function of the protein AIRE might improve our knowledge on follicular development. Furthermore, different mouse models of ovarian failure such as mouse lacking connexins or mice lacking GDF9 (growth derived factor 9), might increase our knowledge of ovarian failure. In the future, a better knowledge of the cellular and biochemical components involved in folliculogenesis and apoptosis should elucidate the mechanisms of POF.

Animals↗
PubMed1998

The negative feedback actions of progesterone on gonadotropin-releasing hormone secretion are transduced by the classical progesterone receptor.

Progesterone (P) powerfully inhibits gonadotropin-releasing hormone (GnRH) secretion in ewes, as in other species, but the neural mechanisms underlying this effect remain poorly understood. Using an estrogen (E)-free ovine model, we investigated the immediate GnRH and luteinizing hormone (LH) response to acute manipulations of circulating P concentrations and whether this response was mediated by the nuclear P receptor. Simultaneous hypophyseal portal and jugular blood samples were collected over 36 hr: 0-12 hr, in the presence of exogenous P (P treatment begun 8 days earlier); 12-24 hr, P implant removed; 24-36 hr, P implant reinserted. P removal caused a significant rapid increase in the GnRH pulse frequency, which was detectable within two pulses (175 min). P insertion suppressed the GnRH pulse frequency even faster: the effect detectable within one pulse (49 min). LH pulsatility was modulated identically. The next two experiments demonstrated that these effects of P are mediated by the nuclear P receptor since intracerebroventricularly infused P suppressed LH release but 3alpha-hydroxy-5alpha-pregnan-20-one, which operates through the type A gamma-aminobutyric acid receptor, was without effect and pretreatment with the P-receptor antagonist RU486 blocked the ability of P to inhibit LH. Our final study showed that P exerts its acute suppression of GnRH through an E-dependent system because the effects of P on LH secretion, lost after long-term E deprivation, are restored after 2 weeks of E treatment. Thus we demonstrate that P acutely inhibits GnRH through an E-dependent nuclear P-receptor system.

Animals↗
PubMed1998

Interleukin 12-mediated prevention of spontaneous mammary adenocarcinomas in two lines of Her-2/neu transgenic mice.

The ability of interleukin (IL)-12 to prevent tumors when administered to individuals with a genetic risk of cancer was studied in two lines of transgenic mice expressing rat HER-2/neu oncogene in the mammary gland. Female BALB/c (H-2(d)) mice carrying the activated HER-2/ neu oncogene show no morphological abnormalities of the mammary gland until 3 wk of age. They then progress through atypical hyperplasia to in situ lobular carcinoma and at 33 wk of age all 10 mammary glands display invasive carcinomas. Adult FVB mice (H-2(q)) carrying the HER-2/neu protooncogene develop mammary carcinomas with a longer latency (38-49 wk) and a lower multiplicity (mean of 2.6 tumors/mice). Treatment with IL-12 (5 daily intraperitoneal injections, 1 wk on, 3 wk off; the first course with 50 ng IL-12/day, the second with 100 ng IL-12/day) begun at 2 wk of age in BALB/c mice and at 21 wk of age in FVB mice markedly delayed tumor onset and reduced tumor multiplicity. Analogous results were obtained in immunocompetent and permanently CD8(+) T lymphocyte-depleted mice. In both transgenic lines, tumor inhibition was associated with mammary infiltration of reactive cells, production of cytokines and inducible nitric oxide synthase, and reduction in microvessel number, in combination with a high degree of hemorrhagic necrosis.

Animals↗
PubMed1998

Regulation of the human menstrual cycle.

Our understanding of the regulation of the menstrual cycle has recently improved with the development of various tools of investigation. The cycle is now thought to be determined mainly by the ovary itself, which sends various signals to the pituitary and the hypothalamus. The aim of the cycle is to produce a single mature oocyte each month from puberty to menopause. However, the most common evolution of a follicle is atresia, a consequence of the genetically controlled, ovarian apotosis (or "programmed cell death"). Follicular growth and maturation are mostly independent of gonadotropins, from the stage of primordial follicles to antral follicles. A complete intraovarian paracrine system is implied in this gonadotropin-independent follicular growth, and in the modulation of the actions of the gonadotropins in the ovary. FSH allows the rescue of a minority of follicles from atresia and is indispensable to only the final maturation of the preovulatory follicle. The cyclical variations of the gonadotropins are under the control of ovarian steroids (estradiol and progesterone) and peptides (inhibin). The cycle length is determined by follicular growth and by the fixed life span of the corpus luteum. The mechanism of action of gonadotropins is much better understood since the gonadotropins and their receptor cDNA have been cloned. The recent description of naturally occurring mutations has lead to a better understanding of the role of each gonadotropin, demonstrating the crucial role of FSH in the terminal maturation of the follicles. The ovarian cycle can also be monitored at the level of target tissues of steroids such as the endometrium. The cellular mechanisms of endometrial maturation, under the control of estradiol and progesterone, are better understood. The endometrial maturation is synchronized to follicular development and allows implantation of the conceptus. The genes implied in the implantation of the embryo are being identified (e.g., integrins). Last but not least, the mechanisms of endometrial shedding are being elucidated, especially the role of metalloproteases and angiogenic factors. These concepts will allow the development of new treatments for infertility, the design of new contraceptive techniques, and a better tolerance of treatments using sex steroids, particularly progestin-only pill.

Endometrium↗
PubMed1998

The use of gonadotrophin-releasing hormone antagonists in polycystic ovarian disease.

Polycystic ovarian disease (PCOD) is characterized by anovulation, eventually high luteinizing hormone (LH) levels, with increased LH pulse frequency, and hyperandrogenism. As the aetiology of the disease is still unknown, gonadotrophin-releasing hormone (GnRH) antagonists, competitive inhibitors of GnRH for its receptor, are interesting tools in order to study and treat the role of increased LH levels and pulse frequency in this disease. Their administration provokes a rapid decrease in bioactive and immunoactive LH followed by a slower decrease in follicle-stimulating hormone (FSH). In patients with PCOD, the suppression of gonadotrophin secretion eradicates the symptoms of the disease as long as the treatment lasts. Several authors have suggested that increased plasma LH levels have deleterious effects on the fertility of women with PCOD. Indeed, fewer spontaneous pregnancies with more miscarriages are observed when plasma LH levels are high. Assisted reproduction techniques such as in vitro fertilization (IVF) have provided other clues to the role of the LH secretory pattern in women with PCOD. The number of oocytes retrieved, the fertilization rate and the cleavage rate are lower in PCOD patients undergoing IVF and this is inversely correlated with FSH:LH ratio. These abnormalities are corrected when endogenous secretion of LH is suppressed. On the other hand, implantation and pregnancy rates after IVF are similar to those observed in control women. New GnRH antagonists are devoid of side effects and suppress LH secretion within a few hours without a flare-up effect. This action lasts for 10-100 hours. When GnRH antagonists are associated with i.v. pulsatile GnRH, this combination both suppresses the effect of endogenous GnRH and because of the competition for GnRH receptors restores a normal frequency of LH secretion. We have studied two women with PCOD, administering first 10 mg s.c. every 72 hours for 7 days of the GnRH antagonist Nal-Glu, then adding on top i.v. pulsatile GnRH: 10 micrograms/pulse every 90 minutes for 15 days. We thus succeeded in normalizing LH secretion pattern and observed a significant decline in testosterone levels. We failed to induce appropriate ovarian response and ovulation. In conclusion, the combination of GnRH antagonist and GnRH pulsatile treatment can re-establish normal LH secretory pattern in patients with PCOD. The failure to induce ovulation with this regimen suggests the existence of an inherent ovarian defect in women with PCOD.

Adult↗
PubMed1998

The GnRH receptor gene is preferentially expressed in functioning gonadotroph adenomas and displays a Mae III polymorphism site.

OBJECTIVE: Given the central role of the GnRH receptor (GnRHR) in the regulation of the gonadotrophin secretion, it might be implicated directly or indirectly in the pathogenesis of gonadotroph tumours. DESIGN: We determined if GnRHR mRNA was expressed in gonadotroph tumours using RT-PCR and analysed the GnRHR gene for the presence of mutations in its coding region, using direct sequencing of PCR products. Results were analysed according to the pattern of expression of alpha, beta-FSH and beta-LH subunit (SU) genes. SUBJECTS: RNA was extracted from 20 gonadotroph tumours identified by immunohistochemistry (> 10% of stained cells): 9 adenomas were functioning (high serum gonadotrophin levels), 3 were associated with high alpha-SU levels and 8 were nonfunctioning. Genomic DNA was extracted from 64 normal subjects. RESULTS: We found GnRHR mRNA in 12 tumours (60%): 8/9 functioning (88%), 1/3 alpha-secreting (33%) and 3/8 nonfunctioning (37.5%) gonadotroph adenomas. There was a significant association between GnRHR expression and immunostaining for beta-FSH (P = 0.014). The nucleotide sequence of the amplified products was identical to that of human pituitary except for the presence, in 3 functioning adenomas, of a silent C to T transition at nucleotide 453 encoding for the serine residue situated in the second intracellular loop at position 151. Heterozygosity provided evidence that both alleles were transcribed in these tumours. This substitution creates a Mae III restriction site. Genomic DNA from normal subjects were then tested for the presence of this new polymorphism. The frequency of the heterozygosity (18.7%) was not significantly different from that found in gonadotroph tumours (25%) and this new Mae III polymorphism site cannot be used as a tumoural marker. CONCLUSION: The GnRHR gene is preferentially expressed in functioning rather than in nonfunctioning gonadotroph adenomas, but no mutations altering the coding region of the gene were found to further substantiate its role in the pathogenesis of gonadotroph tumours.

Adenoma↗
PubMed1998

The use of a GnRH antagonist (Cetrorelix) in a single dose protocol in IVF-embryo transfer: a dose finding study of 3 versus 2 mg.

New gonadotrophin-releasing hormone (GnRH) antagonists, which allow suppression of luteinizing hormone (LH) surges, have recently become available. We compared in this study the results of a single administration of 3 versus 2 mg Cetrorelix in 65 patients undergoing ovarian stimulation and in-vitro fertilization (IVF). The GnRH antagonist (Cetrorelix) was non-randomly administered at a dose of 3 mg (34 patients) or 2 mg (32 patients) on day 8 of the stimulation cycle. In the case of slow follicular development, the injection was delayed until oestradiol reached 400 pg/ml. No difference was observed in the decrease in LH and in oestradiol secretion between the 3 and the 2 mg groups, but the LH secretion was suppressed for a shorter time in the 2 mg group. No LH surge was observed in the 3 mg group, while one surge (3%) and one significant rise in LH were observed in the 2 mg group. No significant difference was observed in IVF results in the two groups of patients. This study demonstrates that a single injection of 3 or 2 mg successfully prevents LH surges for at least 3 days in all the patients treated. The LH rises in the 2 mg group led us to choose the 3 mg dose as a safer dose in our single administration protocol.

Adult↗
PubMed1998

A spontaneous and severe hyperstimulation of the ovaries revealing a gonadotroph adenoma.

We report an unusual case of a gonadotroph adenoma in a 34-yr-old woman, revealed by a dramatic rise in the plasma estradiol (E2) concentration (26,800 pmol/L; normal, <370), with nonsuppressed FSH and LH levels (4.9 and 2.4 mIU/mL, respectively). The PRL level was 503 ng/mL. The testosterone and progesterone levels were 7 and 17 nmol/L, respectively. The levels of inhibin alpha, inhibin A, and inhibin B were increased compared to normal values in both the follicular (fp) and luteal (lp) phases of the menstrual cycle [inhibin alpha, 1986 IU/L (fp normal, <700; lp normal, <1650); inhibin A, 254 pg/mL (fp normal, <20; lp normal, <120); inhibin B, 246 pg/mL (fp normal, <150; lp normal, <30 lp)]. Pituitary magnetic resonance imaging revealed a huge pituitary adenoma. After transphenoidal surgery, the patient presented with pituitary insufficiency and diabetes insipidus. RT-PCR of the tumor tissue was positive for LHbeta, FSHbeta, alpha-subunit, and PRL. This case is of particular interest because 1) although the E2 level was extremely high, the patient did not present with ascitis, suggesting that chronic elevated E2 does not play a crucial role in the hyperstimulation symptoms; 2) the extreme rise in E2 was related to the cosecretion of FSH and LH, confirming the two-cell two-gonadotropin theory; and 3) the rise in inhibin B is associated with FSH secretion, whereas the rise in inhibin A is probably due to luteinization.

Adenoma↗
PubMed1998

Preclinical studies of recombinant factor IX.

Recombinant factor IX (rFIX) has been extensively evaluated in preclinical studies. Dog model study of hemophilia B indicated that rFIX was as effective as a highly purified plasma-derived replacement factor in normalizing indices of hemostasis. Pharmacokinetic studies indicated a dose-proportional profile for rFIX. Pharmacokinetic/pharmacodynamic analysis showed that increases in the plasma concentration of rFIX following administration were closely correlated with measured factor IX activity in the plasma. Appropriate in vitro and in vivo toxicology studies have been performed to support the clinical use of rFIX for the treatment of hemophilia B. Finally, experiments in a model of thrombogenicity indicated that in animals rFIX has a low thrombogenic potential. The preclinical results provided a basis for proceeding with human clinical trials.

Animals↗
PubMed1998

[Pachydermoperiostosis with extramedullary hematopoiesis without myelofibrosis].

BACKGROUND: In three previous reports of primary hypertrophic osteoarthropathy, an associated extramedullary hematopoiesis was related to myelofibrosis. CASE REPORT: A 44-year-old male patient with primary hypertrophic osteoarthropathy diagnosed when he was 34-year-old was referred to our hospital with an abdominal mass fortuitously detected. DISCUSSION: The present case is unique for the patient developed an extramedullary hematopoïesis without associated myelofibrosis. It suggests the possible intervention of growth factors common to the skin fibroblasts and the blood progenitor cells in the pathogenesis of primary osteoarthropathy.

Abdomen↗
PubMed1997

Idiopathic granulomatous hypophysitis: clinical and imaging features.

Idiopathic pituitary granuloma is a rare disorder similar to lymphocytic adenohypophysitis. Few cases have been reported. We report a new histologically case proven with MRI. The patterns of clinical and radiological presentation and the management of this disorder are discussed. MRI findings suggestive of this condition include an intensely enhancing pituitary mass, associated with dural enhancement. Steroid therapy may be suggested avoiding unnecessary surgery.

Adenoma↗