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Biomedical subjects

L Ferland

Publications and source records attributed to L Ferland.

At least 19 recordsLinked to original sources
PubMed1994

Msx1 is close but not allelic to either Hm or Hx on mouse chromosome 5.

The Msx1 homeobox locus has been mapped in relation to the mutations hammer-toe (Hm) and hemimelic extra toes (Hx). Msx1 is expressed in the developing limb, while limb development is affected by the Hm and Hx mutations. Hm and Hx are very tightly linked loci. In interspecific crosses, the segregation of either mutation was followed in relation to polymorphic alleles of Msx1, Il6, and En2, to give a fine map around the mutant loci. Our results show that Msx1 is not allelic to either of the mutations, but is located about 3 cM from them. Il6 did not recombine with either Hm or Hx and, therefore, provides a point of access for the analysis of these mutations at the molecular level.

Alleles↗
PubMed1988

Induction of proto-oncogene fos transcription through the adenylate cyclase pathway: characterization of a cAMP-responsive element.

Transcription of proto-oncogene fos is induced by elevated levels of intracellular cAMP. We report that human c-fos promoter recombinants transfected into rat pheochromocytoma cells (PC12) and human choriocarcinoma cells (JEG-3) are induced by stimulation of adenylate cyclase and that this induction is diminished considerably in the mutant PC12 cell line A126-1B2, which is deficient in cAMP-dependent protein kinase II. An element centered at position -60 of the c-fos promoter, which encompasses a consensus cAMP response element (CRE), is sufficient to confer cAMP responsiveness to a herpes thymidine kinase/CAT fusion gene. The specific binding of a nuclear protein to the c-fos CRE can be competed by the somatostatin and alpha-chorionic gonadotropin (alpha-CG) promoter regions that contain CREs. Gel mobility shift assays with double-stranded oligonucleotides containing either the wild-type or mutated c-fos CRE sequence have demonstrated that binding occurs only to the wild-type CRE. The nuclear factor binding to the c-fos CRE is likely to be transcription factor CREB (CRE nuclear binding protein), because an affinity-purified 43-kD CREB isolated from PC12 cells binds efficiently in a DNA footprinting assay. Thus, regulation of the c-fos gene transcription appears to involve a mechanism common to many genes that respond to cAMP as a second message leading to cell growth and differentiation.

Adenylyl Cyclases↗
PubMed1983

Possible role of somatostatin in the regulation of the sexually differentiated steroid metabolism and prolactin receptor in rat liver.

The regulation of the sexually differentiated metabolism of 4-[4-14C]androstene-3,17-dione and the presence of PRL receptors in rat liver were studied. Electrolytic lesions in male rats placed in a restricted area in the anterior hypothalamic periventricular area caused a feminization of hepatic steroid metabolism (i.e. increased the 5 alpha-reductase and decreased the 6 beta- and 16 alpha-hydroxylase activities) and of the levels of PRL receptors (increased binding of [125I]-labeled human PRL). After periventricular lesions, histochemical analysis revealed a decrease in somatostatin-like immunoreactive cell bodies in the periventricular area. Also the number of immunoreactive somatostatin fibers in the median eminence was dramatically reduced. Somatostatin levels in the median eminence, as measured by RIA, were reduced to approximately 2-10% of control values after periventricular lesions. Large lesions in the amygdaloid complex in male rats caused a partial feminization of hepatic steroid metabolism and PRL receptors. Passive immunization during 4 days by multiple injections of an antiserum generated against somatostatin resulted in a partial feminization of the male rat liver. When somatostatin was injected into female rats, the PRL receptors were reduced to approximately 60% of the control female receptor levels. The present study indicates that the anterior periventricular hypothalamic area is important in the control of the sexually differentiated steroid metabolism and PRL receptors in the liver and that the amygdaloid complex also may have regulatory influences on this system. A possible central neuro-endocrine mediator of these sex differences in the liver could be somatostatin or a related compound.

Androstenedione↗
PubMed1981

Dissociated changes of pituitary luteinizing hormone-releasing hormone (LHRH) receptors and responsiveness to the neurohormone induced by 17 beta-estradiol and LHRH in vivo in the rat.

A single injection of 17 beta-estradiol into castrated male or female rats results in an initial decrease in plasma concentrations of LH and pituitary responsiveness to LHRH, followed by a rapid return to normal or slightly elevated values. Under such experimental conditions, no acute change of binding of [125I-labeled D-Ser(TBU)6]LHRH ethylamide to anterior pituitary homogenate could be observed. Moreover, the self-priming effect of LHRH, as illustrated by a 10-fold increase in the LH response to a second injection of LHRH in the afternoon of proestrus, is accompanied by a 40% loss of pituitary LHRH receptors. During the estrous cycle, a 100% increase in pituitary LHRH receptors is already found on diestrus II, while the maximal LH responsiveness to LHRH occurs later, namely on the afternoon of proestrus. The present findings of a dissociation between changes in LHRH receptor levels and LH responsiveness to the neurohormone suggest that postreceptor events play a predominant role in the control of gonadotropin secretion by sex steroids and LHRH itself. Moreover, LHRH can cause an acute down-regulation of its own receptor in the anterior pituitary gland.

Animals↗
PubMed1981

[Effects of uterine secretions on embryonic development].

Rabbit embryos at the stage of one-cell and morula were incubated in uterine secretions from rat. The uterine fluid was aspirated from uterus of freshly sacrificed estrus animals. We obtained a very good development of the morulas (mean of the maximum diameter : 0.79 +/- 0.02 mm); however only 35% of the one cell rabbit embryos reached the stage of 16 cells. This consequently suggest a uterine tropism in the rats similar to that previously found for the rabbit.

Animals↗
PubMed1980

Effects of RU16117, an orally active weak oestrogenic compound, in postmenopausal women.

Daily oral administration of 1, 3 or 10 mg of RU16117 (11 alpha-methoxy ethinyl oestradiol) to normal postmenopausal women led to a progressive decrease of basal serum LH levels to 60.4 +/- 17.0, 35.1 +/- 9.1 and 20.1 +/- 2.8% of control (pretreatment values, P less than 0.01), respectively, after 4 wk of drug administration. Although the pattern was similar, the inhibitory effect of RU16117 was even more pronounced on FSH than LH levels: a 50% decrease of basal LH and FSH levels was obtained at the daily 1.8 and 1.2 mg doses of RU16117, respectively. No significant change of basal serum gonadotrophin levels was observed with the daily 0.3 mg dose. Administration of 1 mg of RU16117 every second day or 10 mg once a week led to a relatively small but significant (P less than 0.05) 20--25% decrease of basal serum LH levels after 4 wk of treatment in four out of five women. While daily 0.3 and 1.0 mg doses of RU16117 had no significant effect on the LH response to 100 microgram LHRH, the 3.0 mg dose delayed the response up to 90 min. The 10 mg dose, on the other hand, led to a markedly delayed and reduced response. Treatment for the same period (4 wk) with 1 mg RU16117 every second day or 10 mg once a week led to a small (20--25%, P less than 0.05) inhibition of the LH response to LHRH. At the dose of 10 mg once a week, RU16117 had no or minimal effect on endometrial histology. Since RU16117, an orally active weak oestrogenic compound, has been shown to have anticarcinogenic activity in the rat, the present findings suggest that this new steroid could be useful for the treatment of climacteric symptoms.

Aged↗
PubMed1980

Interactions between hypothalamic and peripheral hormones in the control of prolactin secretion.

The absence of nerve terminals in the anterior pituitary gland offers the possibility of studying a pure population of dopamine (DA) receptors. This study is facilitated by the use of anterior pituitary cells in primary culture, which permit the measurement of a precise parameter under typical dopaminergic control, namely prolactin secretion. On the other hand, since DA is the main hypothalamic factor controlling prolactin secretion, in vivo changes of plasma prolactin levels can be used as an index of DA release from the hypothalamus. Treatment with estrogens not only stimulates basal prolactin secretion but also can reverse the inhibitory effect of DA on prolactin secretion in vivo and in vitro. As assessed by the increased plasma prolactin levels following administration of a maximal dose of the DA antagonist thioproperazine, estrogens increase DA release from the hypothalamus. Progesterone, although inactive alone, can reverse the effect of estrogens on prolactin secretion both in vivo and in vitro. Under the same experimental conditions, dihydrotestosterone exerts inhibitory effects on spontaneous prolactin secretion and can reverse the stimulatory effects of estrogens.

Animals↗
PubMed1979

Antidopaminergic activity of estrogens on prolactin release at the pituitary level in vivo.

Treatment of female or male rats with estradiol benzoate led to an almost complete reversal of the inhibitory effect of low doses of dopamine on prolactin secretion. These data indicate that estrogens which have previously been shown to exert a potent antidopaminergic activity on prolactin secretion in anterior pituitary cells in primary culture have similar effects in vivo.

Animals↗
PubMed1979

Possible luteolytic effects of luteinizing hormone-releasing hormone in normal women.

The administration of five subcutaneous 250-microgram doses of lutienizing hormone (LH)-releasing hormone (LHRH) at 4-hour intervals, the first injection being given at 8 A.M. on 1 or 2 consecutive days between days 1 and 9 following the LH surge in normal women, shortened the luteal phase from 1 to 4 days in 16 of 17 treatment cycles. There was a better efficiency of treatment when LHRH was administered on days 6 to 9 after the LH surge as compared with days 1 to 5. In fact, the luteal phase was shortened from 3.3 +/- 0.2 days versus 1.4 +/- 0.2 days (P less than 0.01) and the serum progesterone level was decreased to 44% +/- 6% versus 71% +/- 6% of control levels (P less than 0.01) when the neurohormone was injected late as compared with early in the luteal phase. The present data raise the possibility of a luteolytic effect of LHRH in normal women and indicate the interest of such a near-physiologic approach for the control of luteal function and time of appearance of menses.

Adult↗
PubMed1979

Inhibitory effects of long term treatment with a luteinizing hormone-releasing hormone agonist on the pituitary-gonadal axis in male and female rats.

Following previous observations of the potent antifertility effects of acute treatment with LHRH or its agonistic analogs in male and female rats, this study describes the effect of long term (up to 12 weeks) treatment with an LHRH agonist, [D-Ala6, des-Gly-NH210]LHRH ethylamide (LHRH-A), on testicular and ovarian gonadotropin receptor levels and function in the rat. Treatment of adult male rats with 100 ng LHRH-A every third day led to a progressive decrease of testis, seminal vesicle, and prostate weight up to 12 weeks of treatment, while the inhibitory effect (70%) on LH receptor levels was already maximal at 1 week. When adult female rats were injected daily with 5 microgram LHRH-A for 12 weeks, ovarian LH, FSH, and PRL receptor levels were reduced 50--90%, while plasma estradiol and progesterone levels were inhibited 60% (compared with diestrus day 1). The effect of chronic administration of a low dose (5 IU) of hCG in the male rat was transient. By contrast, no sign of resistance developed up to 12 weeks of treatment with the LHRH agonist in either male or female animals.

Animals↗