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Biomedical subjects

R Collu

Publications and source records attributed to R Collu.

At least 73 records · Page 4Linked to original sources
PubMed1981

Perinatal activity of the hypothalamic-pituitary-gonadal axis in the lamb. IV. Testicular responsiveness to hCG from 1 through 28 days of life.

Previous studies in this laboratory have shown the existence of an early postnatal activation of the hypothalamic-pituitary-gonadal axis (HPGA) in the male lamb which was present at 2 and 4 weeks of age. In order to define more precisely the time sequence of HPGA activity, we have studied the in vivo and in vitro testicular responsiveness to human chorionic gonadotropin (hCG) of the immature lamb at 1, 3, 7, 14, 21 and 28 days of life. Plasma testosterone (T) increments (delta) after hCG were lower in 1-day-old animals than in other age groups. Testicular concentrations of T, dehydroepiandrosterone and 17-hydroxyprogesterone increased from 1 to 14 days. Testicular 17, 20 lyase activity rose significantly with age but was not influenced by hCG. hCG and dibutyryl cyclic AMP increased significantly the T production by enriched interstitial cell preparation at 1, 3, and 7 days, the greatest response being found at 7 days. hCG also increased significantly the T production at 14 days. These data suggest that the lamb testis has the capacity to respond to hCG in vivo and to various stimuli vitro from the 1st day of life and that the response reaches a plateau from 2 to 4 weeks after birth.

Androstenedione↗
PubMed1981

Effects of chronic intermittent immobilization stress on rat testicular androgenic function.

In rats, chronic intermittent immobilization stress induced a drastic fall in the plasma concentration and testicular content of testosterone (T) without detectable changes in plasma LH values. In vitro basal T production by interstitial cell-enriched preparations from stressed rats and the responses to hCG, dibutyryl cAMP, or choleratoxin were suppressed, while cAMP production was not modified. The increase in plasma T concentrations in control animals was identical after the in vivo injection of 5, 10, or 50 IU hCG, while stressed rats failed to respond to 5 IU, but showed a response similar to that of control animals with 10 and 50 IU. These results suggest that chronic intermittent immobilization stress decreases Leydig cell sensitivity to gonadotropins.

Animals↗
PubMed1980

Sodium-dependent interaction of benzamides with dopamine receptors.

Sulpiride and other benzamide (BM)-displacing activity on [3H]-spiroperidol ([3H]SPIR) binding by rat striatal dopaminergic receptors was found to be uniquely sodium-dependent, while classical neuroleptic (NL) activity was not influenced by NaCl. These results suggest the existence of at least two populations of striatal dopaminergic receptors, sodium-dependent and sodium-independent, through which BM and NL respectively interact.

Animals↗
PubMed1980

Perinatal activity of the hypothalamic-pituitary-gonadal axis in the lamb. II. In vitro testicular response to human chorionic gonadotropin and choleratoxin in the first 2 months of life.

Testicular response to human chorionic gonadotropin (hCG) was studied in male lambs. Adenosine 3':5'-cyclic monophosphate (cAMP), testosterone (T), delta 4-androstenedione and 17 alpha-hydroxyprogesterone content and cAMP and T production by dispersed interstitial cells were assessed in control and hCG-pretreated animals. Plasma T levels increased after hCG at 1, 4 and 8 weeks. Increments in the testicular content of cAMP, delta 4-androstenedione, and T were greater at 8 weeks and that of 17 alpha-hydroxyprogesterone and 125I-hCG binding to dispersed interstitial cells were identical at all ages. cAMP and T production by dispersed interstitial cells from nonstimulated animals and the response to hCG and choleratoxin were similar in all lambs. In contrast, cAMP and T production were higher at 1 week only in animals pretreated with hCG in vivo. These data are compatible with hCG-induced desensitization at 4 and 8 weeks.

Androstenedione↗
PubMed1979

Role of putative neurotransmitters in prolactin, GH and LH response to acute immobilization stress in male rats.

Immobilization for 30 min induced a significant rise of prolactin (Prl), a significant reduction of growth hormone (GH), and no modification of plasma luteinizing hormone (LH) values in male rats. Depletion of brain catecholamine stores increased Prl and decreased LH levels while GH secretion was not affected. Blockade of beta-adrenergic receptors reduced GH and increased LH values. Plasma GH levels were also drastically reduced by depletion of brain serotonin (SER) levels and by atropine, and were increased by blockade of the H1 histamine (HIS) receptor. The anti-gamma-aminobutyric acid (GABA) agent picrotoxin significantly reduced Prl and GH plasma levels. Depletion of brain catecholamine stores or blockade of beta-adrenergic receptors antagonized the restraint-induced rise of plasma Prl values, while the decrease of GH elicited by stress was not modified by any pharmacological manipulation. These results indicate that although several putative neurotransmitters (PN) of the central nervous system (CNS) are implicated in the modulation of baseline levels of Prl, GH and LH, only the stress-induced activation of Prl secretion appears to be mediated by a PN, namely through a noradrenergic, beta-adrenergic route.

5,6-Dihydroxytryptamine↗
PubMed1979

Further studies on the relationship of adrenal and gonadal steroids in pubertal development in female rats.

Surgical adrenalectomy or the administration of aminoglutethimide, corticosterone (B), and androstenedione (delta 4) to the immature female rat had no effect on the timing of vaginal membrane opening. Dehydroepiandrosterone (DHA) and estrone (E1) significantly hastened vaginal patency. Aminoglutethimide increased pituitary LH content while FSH content was decreased. An anti-17 beta-E2 antibody increased pituitary LH content and plasma concentration suggesting enhanced synthesis and release of LH. Pituitary FSH content was unaltered while plasma FSH decreased. Aminoglutethimide increased adrenal and ovarian but not pituitary weight while the antibody had no effect. Since little DHA is present in rat plasma and adrenal and since only estrogens have any effect on the onset of puberty, it is likely that the adrenal is not directly involved in pubertal development in the female rat.

Adrenal Glands↗