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G Pointis

Publications and source records attributed to G Pointis.

9 recordsLinked to original sources
PubMed1991

Local control of Leydig cell arginine vasopressin receptor by naloxone.

Arginine vasopressin (AVP) and beta-endorphin are present within the testis where they could act as paracrine effectors of steroidogenesis. In this study we investigated the effect of naloxone, an opioid receptor antagonist on Leydig cell AVP receptor. Intratesticular injection of increasing doses of naloxone (0.1-100 micrograms) resulted 24 h later in a dose-dependent increase in Leydig cell AVP binding capacity. This effect occurred locally since s.c. injection of similar doses of naloxone did not alter the testicular AVP receptor content and intratesticular injection enhanced AVP receptor density only in the naloxone-treated testis but not in the contralateral vehicle-treated testis. Scatchard plot analysis of the data revealed that naloxone locally injected altered AVP binding capacity without change in affinity. These results suggest that in addition to their known paracrine effects in the testis, endogenous opioid peptides may locally control the testicular AVP system by modulating AVP receptor capacity.

Animals↗
PubMed1990

[Intragonadal control of testicular function by neurohypophyseal-like peptides].

Immunochemical studies associated with physicochemical procedures led to demonstrate the presence of neurohypophysial-like peptides in the testis of numerous species including human. Characterization of arginine-vasopressin-neurophysin II mRNA and oxytocin-neurophysin I mRNA in rat testicular extracts is in favour of a local production for these peptides. The in vitro and in vivo evidences of a direct regulation of testicular steroidogenesis bg AVP and related peptides--the identification of specific AVP receptors on purified Leydig cells and their alteration in some physiological or pathological situations argue for a paracrine/autocrine role of these neurohypophysial-like-peptides in modulating Leydig cell androgen biosynthesis.

Animals↗
PubMed1976

Release of immuno-reactive and biologically active LH from fetal mouse pituitary in response to synthetic gonadotropin releasing factor (LRF).

In an incubation system, LRF stimulated significantly the release of LH from 18-day-old mouse fetal pituitary. This LRF-induced LH release, measured by RIA in the incubation medium was able to increase the testosterone production by age-matched fetal testes. This data suggests that the hypothalamo-hypophyseal-testicular axis is functional at the end of mouse prenatal life.

Animals↗
PubMed1976

Demonstration of a pituitary gonadotrophin hormone activity in the male foetal mouse.

The testosterone production by 18-days-old foetal mouse testis was measured in an organ culture system, by RIA in the culture medium. This production was time-dependent, and could be stimulated by ovine LH and age-matched foetal pituitary. The gonadotrophin activity derived from foetal pituitary appeared to be released into the culture medium as a limited reserve. These data clearly show that a biologically active gonadotrophin material is present in the pituitary of the 18-days-old mouse foetus.

Adrenocorticotropic Hormone↗
PubMed1975

[Metabolism of pregnenolone 16-3H and progesterone 4-14C by 18 day fetal mouse gonads in organotypic culture. Effect of the gonadotropic hormone LH].

Fetal mice testes convert pregnenolone-16-3H and progesterone-4-14C to testosterone in organ culture. The 3H/14C ratio in progesterone and testosterone fractions isolated from culture media suggests the importance of the delta5-3 beta hydroxysteroid pathway in our experimental conditions. LH decreases radioactive testosterone production and increases the activity of the kelta4-3-ketosteroid pathway.

Animals↗
PubMed1975

[The effect of gonadotropic hormones and the fetal hypophysis on testosterone production by the testis of 18 day mouse fetuses in organ culture].

The production of testosterone (measured by radioimmuno-assay) by the 18-day-old mouse fetal testis may be stimulated specifically by ovine LH (1 ng, p less than 0.005) and HCG in organ culture. A stimulation by FSH is observed only with high doses (10 mug, p less than 0.0005). Prolactin and ACTH have no effect. Age-matched fetal pituitaries increase significantly the testosterone production in the culture medium (p less than 0.0005).

Adrenocorticotropic Hormone↗
PubMedDate not supplied

[Study of Leydig cells and gonadotropin activity in 14-18 days old fetal mouse (author's transl)].

An organ culture system has been developed for mouse embryo testes and pituitaries at 14-18 days of gestation. The testosterone (T) production by fetal testes has been measured by RIA in the culture medium: it increases from day 14 to day 18 and may be specifically stimulated by ovine LH and hCG. Fetal pituitaries in culture release a gonadotropin activity at 16 and 18 days (not found at 14 days), which is detectable by an heterologous RIA of LH and by a significant increase in T production from age-matched testes in co-culture. The 18-days old pituitaries respond to synthetic LH-RH by an enhanced production of immunologically and biologically active LH.

Animals↗