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Biomedical subjects

M Courot

Publications and source records attributed to M Courot.

At least 19 recordsLinked to original sources
PubMed1988

Differential localization of glycoconjugates having affinity for concanavalin A on the surface of the sperm head in the testis, the epididymis, and the ejaculate of the ram.

The localization of Con A receptors on the surface of the head of ram spermatozoa originating from the rete testis, from three regions of the epididymis, or from the ejaculate was investigated using a gold-Con A labelling technique. Electron microscopic observation revealed three major localizations, each being characteristic of the origin of the spermatozoa: periacrosomal in the rete testis, postacrosomal in the epididymis, on the entire surface of the sperm head in the ejaculate.

Animals↗
PubMed1988

[Localization, on the head of ram spermatozoa, of affinity sites for the 64kD androgen dependent epididymal prealbumin].

The epididymis of the ram synthesizes under androgenic control of specific 64 kD protein. The purified protein appeared as a single band in SDS polyacrylamide gel electrophoresis. It was labelled and an antiserum was prepared in mice. Results showed localization of receptors sites for 64 kD on the periacrosomal plasma membrane of testicular spermatozoa. The protein itself was found on the periacrosomal area of both epididymal and ejaculated spermatozoa.

Androgens↗
PubMed1987

Spermatogenesis and Sertoli cell numbers and function in rams and bulls.

The two main types of cellular associations (type I, 2 generations of spermatocytes + 1 of spermatids; type II, 1 of spermatocytes and 2 of spermatids) occupy, respectively, more than half and about a third of the seminiferous epithelium cycle in rams and bulls. However, the duration of the cycle of the seminiferous epithelium and that of spermatogenesis differ between the species. A1 spermatogonia and Sertoli cell total numbers are highly correlated in adult rams and bulls. Mitosis in Sertoli cells occurs mostly in utero but may still occur for a short period after birth. Between birth and puberty there is about a 5-fold increase in the number of Sertoli cells. After that there are no seasonal- or age-related increases in the number of adult Sertoli cells. Some factors (season of birth; nutrition; genetics; hormones) affect mitosis of Sertoli cells in prepubertal animals. Sertoli cells differentiate after cessation of mitosis. Their differentiation is affected by cryptorchidism, nutrition, genetics and hormones. Their adult function is only poorly known. ABP and rete testis fluid secretions and nuclear Sertoli volume fluctuate under the influence of the same factors, but they are not always linked together. This reinforces the need for more knowledge of Sertoli cell secretions and function.

Animals↗
PubMed1979

Biochemical and physiological studies of androgen-binding protein in the reproductive tract of the ram.

The electrophoretic mobility, effect of pronase, temperature stability, affinity constant and specificity of androgen-binding protein (ABP) were compared in rete testis fluid (RTF), cauda epididymal plasma (CEP) and seminal plasma (SP) of the ram in which the levels of ABP, dihydrotestosterone (DHT), total protein and the number of spermatozoa were also measured. The characteristics of the ABP appeared to be almost identical in all 3 fluids. ABP was highly concentrated in the cauda epididymidis although 50-75% of it was utilized or destroyed during transit through the epididymis. The levels of ABP were higher in the breeding season and positively correlated with DHT in RTF and SP. It is concluded that ABP might be responsible for the increase in DHT in the reproductive tract of the ram during the breeding season and that ABP in the SP might serve as a useful marker of Sertoli cell function in the ram.

Androgen-Binding Protein↗
PubMed1979

Detection of anti-Müllerian activity in boar rete testis fluid.

Boar rete testis fluid was tested for its capacity to induce Müllerian regression in 14.5-day-old rat Müllerian ducts. Weak activity was present in crude RTF, but after gel filtration 5-fold concentration, greater activity was detected in 1 our of 7 pools of the eluted fractions. The biologically active fraction (mol. wt 160 000-310 000) coincided with the elution of authentic labelled anti-Müllerian hormone, obtained from bovine fetal testes. These results indicate that a small amount of anti-Müllerian hormone is still synthesized in post-natal life.

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↗
PubMed1978

Studies of the androgen binding protein in the rete testis fluid of the ram and its relation to sexual season.

An androgen binding protein (ABP) with an electrophoretic mobility (Rf) of 0.56 is present in the rete testis fluid of adult rams. Its steroid specificity was found to be in the following order: 5alpha-DHT, testosterone, oestradiol-17 beta, dehydroepiandrosterone 5beta-DHT, androstenedione, cyproterone, cyproterone acetate, cortisol and progesterone. The characteristics of the ABP are similar to those found for the ABP of the testis and the epididymis of the rat and the rabbit. The concentration of ABP, determined by the dextran-coated charcoal method and sometimes confirmed by the steady-state polyacrylamide gel electrophoresis method, was significantly higher in the breeding season than in the non-breeding season (4.40 +/- 0.98 X 10(-9) M vs. 2.60 +/- 0.62 X 10(-9) M; P less than 0.037). The affinity constant of the ABP was independent of the season (2.45 +/- 0.21 X 10(9) M-1 vs. 2.66 +/- 0.1 X 10(9) M-1; NS). In addition, ABP was positively correlated with 5alpha-DHT (r = 0.506; P less than 0.0009), testosterone (r = 0.445; P less than 0.0003), total protein (r = 0.329; P less than 0.02) and spermatozoa (r = 0.406; P less than 0.006) in the RTF and with blood plasma testosterone (r = 0.584; P less than 0.0001). Furthermore, testosterone and 5alpha-DHT in RTF were positively correlated (r = 0.582; P less than 0.0001). These androgens were also correlated with plasma testosterone (r = 0.262, P less than 0.052 for testosterone in RTF; r = 0.341, P less than 0.018 for 5 alpha-DHT). Total proteins and spermatozoa were found to be positively correlated in the RTF (r = 0.789; P less than 0.0001).

Animals↗
PubMed1976

[Spermatogenesis after testosterone supplementation in the hypophysectomized ram].

Six adult rams were hypophysectomized and immediately injected with 0,5 g (group A) or 2 g (group B) of testosterone per day for 2 weeks. Three normal rams (group C) received the solvent only. The testosterone concentrations in the testis (ng/g) were the same in groups A (23 +/- 7) and C (22 +/- 4) and 3 times higher in group B (72 +/- 18). There was an uptake of testosterone by the testis of the two supplemented groups. In the Rete Testis Fluid, the testosterone concentration was normal with 0,5 g/day (29 +/- 0.6 ng/ml). The testicular weight was maintained by the two treatments. However, spermatogenesis was abnormal in both supplemented groups; meiosis and spermiogenesis occurred normally, but the efficiency of spermatogonial divisions, as shown by the number of leptotene and zygotene primary spermatocytes, was greatly reduced (85%). The results indicate that testosterone alone in the Ram is unable to support complete spermatogenesis, which is contrary to that found in the Rat.

Animals↗
PubMed1976

Hormonal regulation of male reproduction (with reference to infertility in man).

In mammals, pituitary control of spermatogenesis varies with age. In the rat, before puberty FSH is highly active whereas LH is not; after puberty it seems that LH alone is able to support spermatogenesis. The mode of action of hormones is discussed. In the human, in case of infertility due to hypogonadotrophic hypogonadism, spermatogenesis can be restored by HCG or HMG. The best results are obtained after simultaneous treatment with both hormones, LH activity being predominant.

Age Factors↗
PubMed1975

[Plasma testosterone and LH levels in the male lamb from birth to puberty].

In peripheral plasma of male lambs testosterone increase was linear from birth to 100 days; after it reached a plateau without clear relationships with puberty. Plasma LH pattern was also linear during the first 70 days. During this period testosterone and LH were significantly correlated (r equals 0,85).

Age Factors↗
PubMed1975

Morphological appraisal of gametogenesis. Spermatogenetic process in mammals with particular reference to man.

The process of spermatogenesis in man can be subdivided into prenatal, postnatal and adult phases. Special attention is devoted to the cytomorphology of the germ cells in these phases, with a more detailed description of the proliferation, maturation and differentiation of the germ cells in the adult. Thus, spermatogonial renewal, meiotic division and the morphological transformations of the spermatids into mature spermatozoa are described. An outline of the structures characteristic of the latter is also given. The histological organization of the seminiferous epithelium is considered, whereby the concepts of the cycle, stage of the cycle and wave of the seminiferous epithelium are discussed. The duration of both the cycle and that of spermatogenesis of the adult are considered. The present review on mammalian, and chiefly human spermatogenic processes aims at: surveying of current concepts, and compiling of the more important facts and problems of spermatogenesis. The nomenclature and definitions advanced here arise from the concept of continuity of the processes of spermatogenesis from embryo to adult.

Adolescent↗