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Biomedical subjects

M Courot

Publications and source records attributed to M Courot.

At least 37 records · Page 2Linked to original sources
PubMed1980

Hormonal regulation of androgen-binding protein in lamb testes.

Androgen-binding protein (ABP) was measured in the testes of 50-day-old lambs. The animals were hypophysectomized and treatment lasting for 5 days was begun 15 days after surgery. In hypophysectomized but otherwise untreated lambs (control group), no 5 alpha-dihydrotestosterone binding was detectable in testicular cytosol. One out of four lambs gave a positive response with FSH treatment (25 fmol ABP/mg protein), whereas a restoration of the synthesis of ABP was noted in all LH-treated animals (19 +/- 9 (S.E.M.) fmol ABP/mg, n = 4). No synergism between the two gonadotrophins was observed in lambs treated simultaneously with FSH and LH (19 +/- 4 fmol ABP/mg, n = 5). Testosterone treatment elicited a greater response (37 +/- 9 fmol ABP/mg, n = 5) than FSH or LH alone and the response was not increased by the simultaneous addition of FSH (38 +/- 10 fmol ABP/mg, n = 5). Whatever the treatment, no influence was observed either on the number of supporting cells (undifferentiated Sertoli cells) or the length of the seminiferous tubules (P>0.05); the diameter of tubules was significantly increased in the group treated with FSH and LH. It is postulated that testosterone may have a direct effect on the production of ABP by the supporting cells of the impuberal lamb.

Androgen-Binding Protein↗
PubMed1980

[ABP: the testicular protein that binds androgens].

ABP is a protein found in the testicular cytosol or secreted by Sertoli cells in the rete testis fluid. It has a high affinity for androgers and binds specifically 5 alpha-DHT and testosterone (but to a lesser extent). The binding capacity is saturable. ABP is measured by steady state polyacrylamide gel electrophoresis or by separation on dextran coated charcoal. ABP moves from testis to epididymis where its binding activity is totally or partially destroyed from caput to cauda epididymis. In some species (ram, bull, billy goat) but not in others (human, boar, stallion) ABP is present in the seminal plasma of the ejaculate. In some species like the rat, ABP is also secreted in the testicular blood stream by Sertoli cells through the basement membrane of the seminiferous tubules. ABP varies with age and with season. Its production is under separate endocrine control of FSH and testosterone and its transport from testis to epididymis is specifically controlled by FSH. Through its binding activity, ABP may play a role in spermatogenesis and epididymal sperm maturation by enhancing the local concentration of androgens around the germinal cells and the male gametes. However ABP is not present in some species, like the pig, although their spermatogenesis and epididymal sperm maturation are normal.

Age Factors↗
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↗