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Biomedical subjects

M Courot

Publications and source records attributed to M Courot.

At least 19 recordsLinked to original sources
PubMed1996

Effect of indole-3-acetic acid (plant auxin) on the preservation at 15 degrees C of boar semen for artificial insemination.

In order to extend the duration of boar sperm survival at 15 degrees C for artificial insemination, we tested the effect of indole-3-acetic acid (IAA), which appeared to be the main sperm protective substance present in the Coco nucifera endosperm (coconut water). Two IAA concentrations (10 and 100 ng/mL) in Beltsville extender (BTS) were studied for their in vitro effects. The motility, the percentage of motile spermatozoa and the acrosome morphology of sperm were recorded each day over 13 days of storage at 15 degrees C, after 5 min and 3 h of incubation at 39 degrees C. The IAA effect on sperm preservation was also studied in vivo at a concentration of 10 ng/mL in BTS by inseminating groups of females twice at 24 h intervals either at D0 (day of sperm collection) and D1 (D0/1) or at D5 and D6 (D5/6). At D0/1, the two groups of females (control and IAA) were inseminated with a total of 6.3 x 10(9) spermatozoa (3.15 x 10(9) at D0 and the same dose at D1) whereas at D5/6, on IAA group was inseminated with a total of 6.3 x 10(9) spermatozoa and another one with 12.6 x 10(9) spermatozoa. The animals in the D5/6 control group were inseminated each with a total of 12.6 x 10(9) spermatozoa. For each group of females (n = 106-140), fertility rate (% farrowing) and prolificacy rate (litter size) were recorded. No effect of IAA in vitro on the motility rate and on the percentage of motile spermatozoa was observed over a 13 day storage. However, IAA (10 ng/mL) had a significant positive effect on the percentage of living spermatozoa with intact acrosomes after 13 days (66 vs 54%, P < 0.05). The fertility and prolificacy rates after 5-6 days of sperm preservation in BTS extender alone did not differ significantly between D5/6 and D0/1 but the total number of inseminated spermatozoa was 12.6 x 10(9) at D5/6 instead of 6.3 x 10(9) at D0/1. When the spermatozoa were stored in the presence of 10 ng/mL IAA for 5-6 days at 15 degrees C, the fertility and prolificacy of the females inseminated with only 6.3 x 10(9) spermatozoa were identical to those of the females inseminated with an equal number of spermatozoa at D0/1 in the presence or absence of IAA.

Acrosome↗
PubMed1996

Failure to produce transgenic offspring by intra-tubal insemination of gilts with DNA-treated sperm.

The reproducibility of the use of sperm cells as vectors of foreign DNA in the genome of pigs was verified in the present study and the effectiveness of four different procedures for sperm treatment was assessed. For each gilt, approximately 6 x 10(6) ejaculated boar spermatozoa were incubated for 30 min in 1 mL TALP medium containing 3 micrograms of linearized pSV2CAT plasmid DNA. Before incubation, spermatozoa were treated in four experimental groups: (1) cells were stored at 16 degrees C for 24 h and then washed three times in TALP; (2) cells from the fresh, undiluted sperm-rich fraction of an ejaculate were used immediately after collection, following the same procedure as (1); (3) cells were treated as in (2) with an extra wash; and (4) incubation with DNA was performed in TALP medium supplemented with 0.5 mg mL(-1) poly-L-lysine hydrobromide. As determined by immunolocalization, plasmid DNA molecules were found to be associated with 12-17.1% spermatozoa, depending on sperm treatment. Of 35 inseminated gilts, 20 gave birth to a total of 126 piglets. None of the piglets showed sign of exogenous DNA incorporation in any of the tissues tested, as assessed by the polymerase chain reaction and Southern blot. The potential of modifying the pig genome through "transformed' spermatozoa was not confirmed by these experiments.

Animals↗
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↗
PubMed1984

Changes in photoperiod and nutrition and their effect on testicular growth of rams.

Groups of 6 Ile-de-France rams were housed in light-proof rooms and subjected in a factorial design to two light regimens, 180 degrees out of phase, and two levels of protein in their diets. The daily duration of daylight was varied sinusoidally to produce 6-month years with 'winters' of 8 h light and 'summers' of 16 h light. The diets were formulated to supply 50% above or 25% below maintenance requirements in protein. Testicular diameter and volume increased with decreasing light and decreased with increasing light but the diet had no effect. The frequency of LH pulses was measured monthly and was high (3/12 h per ram) when the daylight was being reduced and low (1/12 h per ram) when it was increased. At the extremes of the duration of dark or light the frequency of pulses was around 1.6/12 h per ram, regardless of the duration of light. The two diets had no effect on testicular dimensions but rams fed the 'high' protein diet had a total of 175 LH pulses, which was significantly higher (P less than 0.05) than the 131 pulses recorded from rams on the 'low' protein diet. It is concluded that, in these '6-month years', decreasing light stimulates LH pulsatility and testicular growth and increasing light is inhibitory. Pulsatility of LH appears to be influenced by the protein level in the diet.

Animal Nutritional Physiological Phenomena↗
PubMed1984

Androgen-binding proteins in sheep epididymis: characterization of a cytoplasmic androgen receptor in the ram epididymis.

An androgen receptor (Rc) was demonstrated in caput, corpus and cauda epididymal cytosols of the ram. This receptor had a high affinity for 5 alpha-dihydrotestosterone (Kd = 5.2 X 10(-9) mol/l) and could be distinguished from the androgen-binding protein (ABP) by several characteristics. On polyacrylamide-gel electrophoresis, Rc had a mobility of 0.37 and ABP 0.61; Rc sedimented in the 9S region of a linear sucrose gradient whereas ABP migrated in the 4.3S region; the molecular weights were 192 000 and 90 000 for Rc and ABP; their isoelectric points were 5.7 and 4.8-5.0; they were proteinaceous components since they were destroyed by proteolytic enzymes and heating (50 degrees C for Rc and 60 degrees C for ABP); they exhibited different half-times of dissociation:20 h at 0 degree C for Rc and 6 min for ABP, which is in agreement with their respective physiological roles, intra- and extracellular transport of androgens. The content of Rc-binding sites in caput epididymis was 18, in corpus 4 and in cauda 22 fmol/mg protein.

Androgen-Binding Protein↗
PubMed1984

Androgen-binding proteins in sheep epididymis: age-related effects on androgen-binding protein, cytosolic androgen receptor and testosterone concentrations. Correlations with histological studies.

The androgen-binding protein (ABP) and the cytosol androgen receptor (Rc) were measured in the epididymis of sheep aged 50, 120 and 200 days. Specific binding protein was not detected at 50 days (infantile); near puberty (120 days), ABP was more concentrated in caput and cauda epididymal cytosols (117 and 183 fmol/mg protein respectively) than in corpus (53 fmol/mg) although Rc levels were low (3-5 fmol/mg). In postpubertal rams (200 days), ABP and Rc concentrations were higher in caput and cauda than in corpus epididymis. Testosterone concentrations at 50 days were not statistically different along the epididymis and varied from 0.3 to 0.8 pmol/mg protein. In 120-day-old animals, testosterone was more concentrated in caput and corpus (0.45 and 0.41 pmol/mg) than in cauda (0.17 pmol/mg); at 200 days, the testosterone contents were low (0.10-0.17 pmol/mg) in all parts of the epididymis. A ten-fold increase in plasma testosterone concentrations was observed between 50 and 200 days (1.31 to 11.71 nmol/l). Histological studies of the epididymis in the three groups of animals showed that the cell differentiation started in the cauda where the principal epithelial cells were higher (47-56 micron) than in the caput (31-38 micron) at 50 days. The principal cells of the caput were two- to threefold higher in postpubertal rams than in infantile lambs, a finding which is correlated with the levels of ABP and Rc. This may suggest an important physiological role of this region in the induction of sperm maturation.

Aging↗
PubMed1984

Endocrine control of mammalian testicular ontogenesis.

The endocrine control of ontogenesis of the male gonad involves the development of the gonad itself and, at the same time, the development of the endocrine system. During the impubertal phase, the seminiferous tubules contain supporting cell and gonocytes, both of which increase in number by mitotic divisions. Over this period, the pituitary secretion of both FSH and LH increases, FSH progressively and LH in pulsatile fashion. In the interstitial tissue, the numbers of Leydig cells also increase. The increase in LH secretion and in leydig cell numbers leads to an increase in testosterone secretion, so that a little before puberty the system of LH-testosterone feedback is fully operational. The testicle then reaches the prepubertal phase, where the supporting cells stop dividing and differentiate to become the highly specialised Sertoli cells. Thereafter, their numbers remain almost constant. the gonocytes now begin rapidly dividing and differentiating, their rate of division resulting in a drastic increase in testicular size. The end result of their division and differentiation is that the testicle begins to produce spermatozoa. Very few are produced at first, but eventually production reaches adult levels and the testis begins to show normal spermatogenic cycle. Also during this phase, the pulsatile secretion of LH and testosterone continue and the secretion of FSH increases. The developments of these two systems are not unrelated. The division of the supporting cells and their maturation into Sertoli cells are under the control of LH in synergy with FSH, while the differentiation of primordial cells into spermatogonia and the subsequent production of spermatozoa are under the control of FSH, LH and testosterone.

Androgens↗
PubMed1981

[Evidence for testosterone induced prealbumin secretion in ram epididymis].

The fluids of the Rete Testis and of the different areas of the epididymis (caput, corpus, cauda) were collected by micropuncture of the Rete Testis or the epididymal duct from caput and corpus of normal Rams (n = 3) and 4 months orchidectomized Rams having in the last month a subcutaneous implant testosterone (200 mg) which delivered a constant rate of testosterone for 4 weeks. Homogenates of epididymal tissues from orchidectomized Rams (3 months) were prepared in saline (n = 4). All samples diluted in saline, were centrifuged and submitted to polyacrylamide slab gel electrophoresis (7.5% acrylamide) at pH 8.3. Results showed an alpha-globulin Rf 1.1 whose molecular weight was approximately 105,000 D which was clearly detected into the fluid of the caput or corpus epididymis, weakly in the cauda epididymis of normal Rams and at the 3 levels of the epididymis of the testosterone supplemented castrates; it was absent in tissues of castrated Rams not supplemented with testosterone supplemented castrates; it was absent in tissues of castrated Rams not supplemented with testosterone. Results were discussed according to epididymal sperm maturation.

Animals↗
PubMed1981

[The first cleavage of tubal sheep eggs after fertilization with epididymal or ejaculated spermatozoa].

Prealpes ewes (N = 40) were inseminated with mature (ejaculated or epididymal cauda) or immature (epididymal corpus) spermatozoa deposited in the uterine cavity at the time of an induced ovulation (61 hrs. after PMSG injection). Intratubal eggs, recovered and examined either 38 or 48 hrs. later, showed significant differences in segmentation depending on the degree of epididymal maturation of the spermatozoa. Proportion cleaved: 85% of eggs were cleaved after insemination with mature spermatozoa and only 30% after immature spermatozoa were used. Stage of cleavage: 48 hrs. after insemination with mature spermatozoa, 87% eggs were beyond the 4-cell stage, versus 0% after immature spermatozoa.

Animals↗
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↗
PubMed1981

Endocrine control of spermatogenesis in the ram.

In the ram, the size of the testes is related to the concentrations of FSH, LH and testosterone in the blood. A significant linear relationship is observed between testicular size and the level of FSH until a maximum after which no further increase in testis size is observed. Testicular size is also linearly related to the mean level (25 consecutive hours of sampling) of LH and testosterone in the blood, with apparently no upper limit, and to the frequency of peaks of these hormones in the sampling period. Spermatogenesis in the ram is sensitive to variations in the levels of circulating hormones; there is a positive correlation between the number of renewing spermatogonia or the efficiency of spermatogonial multiplication and the mean LH value in the peripheral blood of the adult. Some of these relationships operate over long periods and involve the Sertoli cells. The level of circulating LH in the non-pubertal lamb is directly correlated with number of Sertoli cells per testis, and the latter is correlated with the number of renewing spermatogonia per testis in the adult ram. Treatment of hypophysectomized rams with PMSG, hCG or testosterone shows that spermatogonial divisions are sensitive to the hormonal milieu with specific stages being controlled by the LH-like activity of hCG (A1 spermatogonia), and the FSH-like activity of PMSG (transition from intermediate spermatogonia to leptotene spermatocytes). Testosterone has only a small effect at the beginning of the spermatogenic cycle (production of leptotene spermatocytes) and quantitatively maintains meiosis and spermiogenesis, but the differentiation of spermatids is dependent on information stored at the beginning of meiosis and requires the support of both testosterone and other factors.

Animals↗
PubMed1980

Acrosomal and nuclear morphogenesis in ram spermatids: an experimental study of hypophysectomized and testosterone-supplemented animals.

An ultrastructural study of spermiogenesis was carried out in adult hypophysectomized rams supplemented with testosterone at a dose which induced a normal or excessive (1 to 3) concentration of the steroid within the rete testis fluid (Monet-Kuntz et al., '76). Most of the spermatids from 15- or 20-day treated animals displayed a normal nuclear appearance but possessed acrosomes with morphological abnormalities. The process of acrosome formation as well as its binding to the nucleus was severely impaired in young spermatids, whereas only morphological changes of the acrosomes were seen in old spermatids. The suggestion is made that acrosome development is under the control of endocrine-dependent cellular events occurring before the beginning of spermiogenesis, possibly via Sertoli cell/germ cell interactions. The spermatids from hypophysectomized rams supplemented with testosterone for 40 days were normal in appearance but reduced in number. The Sertoli cell ultrastructure differed for the two durations of treatment.

Acrosome↗
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↗