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M R Blanc

Publications and source records attributed to M R Blanc.

25 records · Page 2Linked to original sources
PubMed1981

Seasonal variations in rete testis fluid secretion and sperm production in different breeds of ram.

Production of spermatozoa and secretion of rete testis fluid (RTF) in rams was assessed by a rete testis cannulating technique. Four breeds (Ile-de-France, Romanov, Préalpes du Sud and cross-breed Romanov) were studied throughout the year. Inhibitory effects of the cannulation process on spermatogenesis were observed for some animals. Between-breed differences were found in sperm concentration and flow rate of the RTF. The seasonal variations in the daily sperm production of the testis were more pronounced for Ile-de-France rams than for the other breeds. There was a seasonal variation in the flow rate of RTF in Ile-de-France rams, the minimum flow being in February (winter) and the maximum in August-September (autumn).

Animals↗
PubMed1980

Control of Sertoli and germ cell populations in the cock and sheep testes.

Sertoli cells are involved in the control of spermatogenesis. In adult animals, the Sertoli cell stocks, fixed before puberty, are highly correlated with those of the germ cells. Some factors influencing Sertoli cell stock formation have been analyzed: 1) Early hemicastration of impuberal animals showed that the proliferative activities of the Sertoli and the germ cells before puberty, rather than their initial numbers at birth, were the limiting factors of their final number in adult testis. 2) During testicular growth, LH and FSH levels were correlated to Sertoli cell stocks and to germ cell production. 3) The season of birth influenced the Sertoli cell stock formation in the ram. Daylength modified testicular development in the cockerel and the sheep. 4) Between-strain differences were more marked for the testis than for body growth in the cockerel. In the ram, Sertoli cell stocks were similar between half-brothers but significantly different between sires.

Animals↗
PubMed1980

[Inhibin].

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Animals↗
PubMed1979

Periovulatory gonadotrophin and ovarian steroid patterns in sheep of breeds with differing fecundity.

Plasma hormone concentrations before and during luteolysis (induced by injection of a prostaglandin analogue on Day 10 or 11 of the cycle), during the period of preovulatory follicle growth and ovulation were examined in sheep with known differences in ovulation rate (Romanov, Préalpes, Romanov x Préalpes cross, Ile de France). The number of CL at the time of treatment and the ovulation rate in the ensuing cycle were established by endoscopy. Plasma concentrations of FSH, LH, progesterone and total oestrogen were measured by radioimmunoassays in the 3 days before PG injection, then hourly for the 24 h after PG injection and 2-hourly for a further period up to about 100 h after PG injection. The onset and duration of oestrus were also recorded. Although breed differences were observed for many of the features studied, only the intervals between oestrus and the LH peak and between PG injection and the LH peak were significantly correlated with ovulation rate.

Animals↗
PubMed1979

Endocrinology of spermatogenesis in the hypophysectomized ram.

Adult rams were hypophysectomized and treated for 20 days with testosterone (2 X 0.25 g/day), PMSG (2 X 300 i.u./day) or hCG (2 X 250 i.u./day), or for 40 days with testosterone (2 X 0.25 g/day). All treatments maintained a normal concentration of testosterone within the seminiferous tubules. Quantitative histological analysis showed that (1) the differentiation from A0 to A1 spermatogonia was maintained by PMSG or hCG but not completely by testosterone; (2) the transition from intermediate spermatogonia to primary spermatocytes was maintained only by PMSG but not by testosterone or hCG; (3) meiotic prophase and spermiogenesis were maintained by the three hormones but there were qualitative abnormalities in the spermatids. These results suggest that in the ram, the differentiation of renewing stem spermatogonia is under LH control and that the last stages of spermatogonial multiplication, from intermediate to B spermatogonia and to primary spermatocytes, are under the control of the FSH-like activity of PMSG.

Animals↗
PubMed1979

Inhibin activity in ram rete testis fluid: depression of plasma FSH and LH in the castrated and cryptorchid ram.

Ram "rete testis" fluid (RTF) routinely collected throughout the year has been used as a source of inhibin. The mean flow rate and mean concentration of spermatozoa in the fluid remained constant during the first 12 days of cannulation. More than 50 castrated or cryptorchid rams have been treated with low doses of steroid-free RTF over a 25-h blood sampling period. Human serum albumin was injected as a control. RTF depressed both FSH and LH plasma levels although the pattern was different for each hormone. There was no change in prolactin secretion. LH secretion was affected first while FSH remained unchanged in castrated and in cryptorchid rams. Thereafter, the maximum depression of FSH plasma levels occurred at a time when LH started to return or had returned to preinjection levels in the cryptorchid and castrated animals respectively. In the cryptorchid rams, RTF suppressed pulsatile LH secretion which was present before treatment but in the castrated animals, RTF lowered LH plasma levels which were constant and showed no pulsatile changes before treatment. Both FSH and LH inhibitory activities have been found in all active fractions obtained by purification of RTF. These activities are papain-sensitive and active fractions have a high apparent molecular weight (greater than or equal to 100 000) as shown by gel filtration and ultrafiltration. These and other results in the literature have lead to a re-definition of inhibin as a protein factor of gonadal origin able to depress plasma levels of FSH and LH, even at low doses.

Animals↗