Seasonal variations in sex steroids and male sexual characteristics in Scyliorhinus canicula.

Concentrations of testosterone, progesterone, Delta4-androstenedione, dihydrotestosterone, 11-ketotestosterone, estrone, estradiol-17beta, 5alpha-androstane, 3alpha, 17beta-diol, and 17alpha-hydroxy, 20beta-dihydroprogesterone were determined by radioimmunoassays in the blood plasma and testicular homogenates of Scyliorhinus canicula. Samples were collected almost every month for 27 months. The weights and sizes of reproductive organs and sperm reserves were also measured over the same period. Quantitatively, testosterone was the principal steroid present. Testicular and epididymal weights, sperm reserves, and clasper size varied throughout the year, but not always in a synchronous fashion. Most of the testicular steroids had an annual peak, generally in February, except for progesterone. The plasma concentrations of progesterone, Delta4-androstenedione, and androgens presented various degrees of fluctuation over the year, but were not synchronized: maxima occurred during autumn-winter for androgens and progesterone, during spring for Delta4-androstenedione. Thus, various aspects of S. canicula reproductive function appear to be influenced by season, the sea temperature being, most probably, a major determinant in this respect.

Stage-dependent modulation of Sertoli cell steroid production in dogfish (Scyliorhinus canicula).

Seminiferous lobules of dogfish (Scyliorhinus canicula) testis comprise cysts formed by steroid-producing Sertoli cells associated with germ cells at an identical stage of spermatogenesis. These lobules were isolated in four populations corresponding to lobules with spermatogonia (A), spermatocytes (B), early spermatids (C) and late spermatids (D). They were used for steroid radioimmunoassay or incubated with 22 alpha-hydroxycholesterol or with dibutyryl cyclic AMP (dibutyryl cAMP) to measure steroid production. Our results indicate that progesterone was the major steroid in seminiferous lobules at all stages of spermatogenesis except in lobules A. Furthermore, marked changes in the distribution of steroids were observed according to the stage of spermatogenesis; progesterone, 4-androstenedione, testosterone and 17 alpha-hydroxy,20 beta-dihydroprogesterone concentrations were highest in lobules D, whereas dihydrotestosterone concentrations decreased during spermatogenesis. No significant stage-related change was observed for 3 alpha-diol and 3 beta-diol. Incubation experiments revealed that the isolated seminiferous lobules at all stages can synthesize steroids from hydroxycholesterol and that lobules D have the highest basal contents of androstenedione and testosterone. Furthermore, when dibutyryl cAMP and 10 mumol hydroxycholesterol l-1 were added together to the cultures, an enhancement of the steroid secretion was observed rather than a change in synthesis. Our results also indicated that the responsiveness of the lobules to dibutyryl cAMP varies according to the stage of spermatogenesis and to the steroid assayed. Overall, this study indicated that germ cells probably markedly influence Sertoli cell steroidogenesis in the adult dogfish testis.

Effects of estradiol on brain aminergic turnover of the female rainbow trout (Oncorhynchus mykiss) at the beginning of vitellogenesis.

Brain serotonin and dopamine (DA) turnovers in the female rainbow trout were studied at the beginning of the vitellogenesis and related to blood estradiol (E2) levels; pituitary and plasma gonadotropin (GtH) were also assayed. Ovariectomy did not modify brain aminergic turnover. E2 replacement on ovariectomized fish increased hypothalamic DA turnover (increased DA and increased DA metabolites). E2 stimulated GtH synthesis (positive feedback) but did not enhance GtH release; hypothalamic E2-mediated aminergic inhibition upon release was suspected. Individual relations between blood E2 levels and catecholaminergic neurotransmitters were determined. A linear positive correlation (r = 0.82) was found for the hypothalamus, but not for the pituitary, the preoptic area, or the telencephalon. These data suggest that an activation of hypothalamic tyrosine hydroxylase (the limiting step of catecholamines synthesis) by E2 could develop as vitellogenesis proceeds.

Seasonal variations of androgens and of several sexual parameters in male Meriones shawi in southern Morocco.

Seasonal changes of several parameters related to sexual activity were studied in the gerbil (Rodentia: Gerbillidae). The weight of the testes, seminal vesicles, and adrenals fluctuate throughout the year. Plasma androgen levels and histological aspect of the testes also vary throughout the year. Spermatogonial and steroid activities are synchronous and are maximal in winter and spring. The relationship between these activities and environmental climatic parameters is discussed: the beginning of sexual activity seems correlated with the first rains.

Sexual steroids in Salamandra salamandra (L.) during ontogeny.

In order to investigate the ontogeny of steroid secretions during the juvenile phase, sexual steroids were extracted and assayed after chromatographic separation in the gonads and plasma of male and female salamanders Salamandra salamandra L. at three characteristic postlarval stages. All specimens were collected in the wild. The immature stage is characterized, in the female, by high dihydrotestosterone (DHT) and 5 alpha-androstandiol levels, low progesterone concentration, and an absence of testosterone in the ovary. Just before sexual maturity a regular increase in plasma levels of estradiol and testosterone was observed. In the male, progesterone and DHT are at a relatively high level in the testis of the immature stage but concentrations decrease in subadults. In young adults, concentrations of progesterone are greater than they are in the immature animals. Sexual maturity is characterized by a large increase in testicular and plasma testosterone as well as a relative decrease in DHT, 5 alpha-diols, and estrone. The progesterone liberated into the plasma was negligible. Diols seem to play an important part in the ontogeny of sexual function.

The adult dogfish (Scyliorhinus canicula L.) testis: a model to study stage-dependent changes in steroid levels during spermatogenesis.

The unit structure of the testis of Scyliorhinus canicula L. is the seminiferous lobule arranged in topographically distinct zones and comprised of cysts formed by steroid-producing Sertoli cells associated with germ cells at an identical stage of spermatogenesis. In this experiment, testicular tissues from different dogfish corresponding to the zones of lobules with spermatogonia (A), spermatocytes (B), early spermatids (C) and late spermatids (D) were dissected out and pooled. They were either used for steroid radioimmunoassay or incubated to measure steroid production in response to dogfish pituitary extract or to dibutyryl cyclic AMP (dbcAMP). Our results indicate that testosterone is the main testicular androgen in this species. Furthermore, marked changes in the distribution of steroids were observed according to the zone of spermatogenesis, testosterone concentrations being highest in zones A and D. The relative contents of this hormone (steroid levels normalized to an equivalent number of Sertoli cells) as well as of delta 4-androstenedione and of progesterone increased from A to D. The concentrations of delta 4-androstenedione and progesterone were highest in zone D. Relative contents of 5 alpha-androstane-3 alpha,17 beta-diol, dihydrotestosterone and 11-ketotestosterone were very low in A when compared with the other zones. Finally, whereas no significant stage-related variation in the concentration of oestradiol-17 beta and 17 alpha-hydroxy, 20 beta-dihydroprogesterone was observed, the relative content of these steroids was lowest in zone A. Incubation experiments revealed that dogfish pituitary extract and dbcAMP can stimulate androgen synthesis (about twofold) and that a stage-related change of steroid responsiveness to dbcAMP exists (only zones A and D were responsive). Overall, the results of this study indicate that germ cells most probably influence Sertoli cell steroidogenesis and responsiveness in the adult dog fish testis.

Reproductive effects of the anticancer drug cyclophosphamide in male rats at different ages.

This study was undertaken to determine the effects of the anticancer and immunosuppressant drug cyclophosphamide (CP) on several endpoints of the male rat reproductive system at different ages; 10-day-old (experiment A), 45-day-old (experiment B), and adult (experiment C) Sprague-Dawley rats were injected intraperitoneally with CP at doses of 20 mg/kg/day or/week and 100 mg/kg/week for 2 weeks (experiment A), doses of 20 mg/kg/day for 5 weeks and 100 mg/kg/day for 10 days (experiment B), and doses of 20 mg/kg/day for 5 weeks (experiment C). In all groups CP induced a significant rate of mortality. Body weight gain was moderately to severely reduced in two groups of experiment A (20 mg/kg/day and 100 mg/kg/week) and of experiment B (20 mg and 100 mg/kg/day) but normal in the others. Absolute as well as relative reproductive organ weights decreased following some of the treatments in experiments A and B. At the light microscope level, effects of CP ranged from nonapparent in immature rats (experiment A, 100 mg/kg/week for 2 weeks) and young adult animals (experiment B, 100 mg/kg/day for 10 days) to moderate in the other groups treated for 5 weeks (experiments B and C). Affected tubules exhibited atrophy, exfoliation, and a decrease in the number of spermatogonia, primary spermatocytes, and round and elongated spermatids. Sertoli cell function appeared preserved, whereas Leydig cells, present in the intratubular tissue of the rats in all the experiments, were occasionally and moderately altered in animals of experiment B, as shown by significant decreases of serum testosterone and LH levels. Leydig cell dysfunction in these rats was associated with normal in vitro basal and hCG-stimulated testosterone production. A significant decrease in epididymal sperm reserves was observed only in one group of animals (experiment B, 100 mg/kg/day for 10 days). Since in these animals the number of spermatids in the seminiferous tubules was normal, it is possible that CP at a high dose alters the epididymal function. Furthermore, fertility trials demonstrated that despite no change in the number of implantation sites, there was a dramatic fall in the number of fetuses per female in all the experimental groups. In conclusion, this study shows that in pre- and postpubertal rats treated chronically or subacutely, CP primarily and essentially induces alterations of germ cells, whereas this compound has little or no direct effect upon Leydig cell and Sertoli cell functions, respectively.

The dynamics of the steroidogenic response of perifused Xenopus ovarian explants to gonadotropins.

Steroid release before and during maturation was studied in Xenopus ovarian follicles under various conditions of stimulation of LH in a perifusion system. Acute stimulation by 15 micrograms of LH induces a 10-fold increase in the androgen (testosterone and androstenedione) level which reaches a maximum 4 hr later and then slowly decreases until the 25th hour. Repeated stimulations every 2 or 4 hr are followed by the same androgen increase during the first 8 or 10 hr and then by a slow decrease in the secretion despite new LH injections. A significant increase in progesterone secretion is seen only after at least two stimulations (8 hr). Estradiol secretion slowly increases to a moderate level during the first 5 hr and then remains stable whatever the stimulation. During continuous stimulation (LH 0.5 microgram/ml) androgen levels reach an initial maximum after 4 hr and then fluctuate with a 2-hr period. Addition of theophyllin to the medium enhances these fluctuations. After 12 hr when the progesterone has increased, androgen secretion diminishes to reach a basal level without fluctuations. Germinal vesicle breakdown occurs only in follicles that have been appropriately stimulated to secrete androgens and progesterone during the required time.

Influence of germ cells upon Sertoli cells during continuous low-dose rate gamma-irradiation of adult rats.

The effects of continuous gamma-irradiation of adult rats at two low-dose rates (7 cGy and 12 cGy/day; up to a total dose of 9.1 Gy and 10.69 Gy 60Co gamma-ray, respectively) were investigated. Over a period of 3-131 days of irradiation, groups of experimental and control animals were killed. Body weight, testis, epididymis, prostate and seminal vesicle weights, the number of germ cells and Sertoli cells, tubular ultrastructure, epididymal and testicular levels of biologically active androgen-binding protein (ABP), and the plasma concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone were monitored. Irradiation had no effect on body weight, whereas testicular and epididymal weight began to decrease following 35 and 50 days of irradiation at 7 and 12 cGy, respectively. At 7 cGy the target cells of the gamma-rays were essentially A spermatogonia, whereas at 12 cGy A spermatogonia and preleptotene spermatocytes were primarily affected. This resulted in a progressive and sequential dose-related reduction in the number of pachytene spermatocytes, round spermatids and late spermatids (LS). Under both irradiation procedures the Sertoli cell number remained unchanged whereas partial (7 cGy) or no change (12 cGy) was seen at the Leydig cell level. Whatever the irradiation protocol, from the time LS numbers decreased, vacuolisation of the Sertoli cell cytoplasm progressively occurred, followed by thickening and folding of the peritubular tissue. Moreover, in parallel to the drop in the number of these germ cell types, ABP production fell whereas FSH levels rose. A highly significant positive correlation was found between LS numbers and these Sertoli cell parameters. This study supports our previous concept of a control of certain important aspects of Sertoli cell function by late spermatids in the adult rat.

Influence of food restriction and of the presence of chicks on the reproductive system of the domestic hen.

An experiment was conducted with 4 groups of hens: a control group of laying hens, a group subjected to food deprivation for 7 d, a group subjected to food deprivation for 7 d, then re-fed for 10 d and a group subjected to food deprivation for 7 d then re-fed for 10 d with two chicks per hen introduced during the last 7 d of refeeding. Food deprivation provoked the involution of the oviduct and ovarian regression, as well as a decrease in the plasma concentrations of luteinising hormone (LH) and sex steroids (progesterone, testosterone and oestradiol). After 3 d of re-feeding, there was a significant increase in the plasma concentrations of LH and steroid hormones. This phenomenon was even more marked after 10 d of re-feeding; most of the hens of the third group which were not given chicks, were at the point of lay. The presence of chicks resulted in the expression of maternal behaviour and suppressed a rapid return to laying. This was especially marked in hens showing typical maternal behaviour traits, for which the morphological and endocrine measurements indicated a decrease in the activity of the hypothalamo-hypophyseal-gonadal axis.

Induction of maternal behavior in incubating and non-incubating hens: influence of hormones.

Maternal responses and variations in plasma levels of prolactin and testosterone have been studied in incubating and in non-incubating, non-laying hens during forced adoption experiments. The results demonstrate the ability of incubating hens to display complete maternal behavior as early as the 10th day of incubation after being exposed to stimulation by chicks during one night. Maternal responses also emerged in non-laying hens but more gradually. In both groups, a decline in plasma testosterone occurred after the introduction of the chicks and, in the incubating hens, prolactin levels fell as they abandoned their nests.

Androgen and estrogen levels in the plasma of Pleurodeles waltl, Michah., during the annual cycle. II. Female cycle.

Sex steroid levels in the plasma of the female Pleurodeles waltl were determined by radioimmunoassay of blood samples taken monthly from each newt during an 18-month period. Estradiol-17 beta levels were relatively high (greater than 1 ng/ml) but androgen levels were higher (2-30 ng/ml). Androgen and estradiol-17 beta levels fluctuated according to season with two annual peaks, in autumn and in March. Testosterone was the principal androgen present in this plasma. Dihydrotestosterone levels were relatively low but showed slight fluctuations during the year. 4-Androstenedione and estrone levels were very low and relatively constant throughout the seasons. Fluctuations of androgen and estradiol-17 beta levels were synchronous between the several newts studied during the year. The ratio [E2-17 beta]/[Androgen] was stable during the major part of the year (0.2-0.3) except in July and August, when it reached the value of 1.0. The seasonal variations in the steroid levels were well correlated to the morphological modifications of sexual characteristics during the year.

Comparative plasma levels of androgens and 17 beta-estradiol in the diploid and triploid newt, Pleurodeles waltl.

Seasonal changes in the plasma levels of androgens (testosterone plus dihydrotestosterone) and 17 beta-estradiol in diploid and triploid adult newts, Pleurodeles waltl were studied. In both male and female diploid individuals, large variations were reported with highest levels being found during breeding periods. In triploid newts seasonal variations were also found, similar to the diploid ones, but the plasma concentrations of the 17 beta-estradiol and androgens in triploid females and androgens in triploid males were lower throughout the year than those reported for the diploids. This difference is discussed in relation to the genetic sexual constitution.

Androgen and estrogen levels in the plasma of Pleurodeles waltl, Michah., during the annual cycle. I. Male cycle.

Sex steroid levels in the plasma of the male Pleurodeles waltl were determined by radioimmunoassay of blood samples taken monthly from each newt during an 18-month period. Androgen levels varied according to season with annual peaks in October-November and in March. The position of these two peaks was the same in the 2 years studied. Testosterone was the principal androgen measured, while the levels of dihydrotestosterone and 4-androstenedione were lower but fluctuated in parallel with that of testosterone. The 17 beta-estradiol levels were very low or undetectable. Androgen levels during the year were synchronous between the several newts studied. The cyclical variations in the steroid levels agreed with the morphological modifications of sexual characteristics during the annual cycle.

Seasonal variations of androgens, estrogens, and progesterone in the different lobules of the testis and in the plasma of Salamandra salamandra.

Progesterone, 4-androstenedione, testosterone, dihydrotestosterone, 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol), 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol), estrone, and estradiol levels were determined by radioimmunoassay in the different lobules of the testis of Salamandra salamandra throughout the year according to the seasonal cycle. 3 beta-diol levels were not detectable. High levels of steroids were found in the grandular tissue (enlarged pericystic cells after spermiation) and large variations were showed for progesterone, 4-androstenedione, testosterone, 3 alpha-diol, and estrone. In the mature lobule (formed by cysts with mature spermatozoa), only testosterone showed seasonal variations and in the immature lobule (with early stages of meiosis), 3 alpha-diol showed fluctuations. The major estrogen found in the testis of Salamandra was estrone; estradiol stayed at a low level throughout the cycle. The steroids fluctuation seems to be related to the histological evolution of the testis throughout the cycle. The present data were the first on steroid seasonal variations in the testis of an urodele.

Induction of maternal behavior and some hormonal and physiological correlates in the domestic hen.

The manifestation of maternal behavior and the variations of plasmatic levels of gonadic hormones (testosterone, delta 4-androstenedione, and 17 beta-estradiol) have been studied in two groups of domestic hens (layers and nonlayers) during a forced adoption experiment. Maternal behavior appears later in actively laying hens than in nonlayers. The former hens show a higher level of androgens (T and delta 4). The appearance of typical maternal behavior coincides with a pause in laying and a decrease in all the plasmatic steroid levels measured.

Changes in plasma gonadotrophins after neurotropic stress in the postnatal castrated male rat. Influence of adrenalectomy.

In 60-day-old postnatal castrated male rat, neurotropic stress increased plasma levels of LH, FSH, ACTH, corticosterone, testosterone and 17 beta-oestradiol. The possible influence of ACTH in the observed increase in plasma sex steroids was discussed. After adrenalectomy, performed at 50 days of age, neurotropic stress no longer affected plasma gonadotrophin level significantly. Adrenalectomy, raising plasma level of corticotrophin and decreasing plasma levels of testosterone and 17 beta-oestradiol, created conditions favorable to inhibition of gonadotrophin function.

[Variations of plasma levels of testosterone and delta 4-androstenedione in growing Hubbard cockerels]. / Evolution des taux plasmatiques de testostérone et de delta 4-androstènedione chez le coq Hubbard en croissance.

Variations in the plasma concentrations of testosterone (T) and delta 4-androstenedione (delta 4) levels were measured by radioimmunoassay in individual young Hubbard Chickens from the age of 16 days until 100 days. Plasma testosterone was low and remained relatively stable between days 16 and 63 (0.10 to 0.30 ng/ml), but increased then rapidly (0.32 +/- 0.07 ng/ml on day 65 vs. 1.49 +/- 0.27 ng/ml on day 100). During the same period delta 4 levels increased too (0.23 +/- 0.06 ng/ml on day 65 vs. 0.75 +/- 0.18 ng/ml on day 100). During the first weeks of life, delta 4-androstenedione prevailed over testosterone. The [delta 4]/[T] ratio reached a maximum between days 30 and 40 and was then reversed to negative values. Results are discussed in relation to those obtained for Chicken from other stocks.

[Male sexual behavior induced by testosterone in ovariectomized adult ewes. Effect of the dose and previous sexual experience]. / Etude du comportement sexuel mâle induit par la testostérone chez des brebis adultes ovariectomisées. Effet de la dose et de l'expérience sexuelle antérieure.

Adult ovariectomized ewes, daily injected with testosterone propionate (2 to 22 mg), showed male-like sexual behaviour, never seen in untreated females, but very similar to that in normal rams. After a few days of latency (3 days minimum), this behaviour gradually appeared and increased in frequency until a plateau was reached. The time-course in which the plateau was reached depended on the androgen dose and on previous experience with male sexual behaviour. Some male-like behaviour might have persisted after the end of the treatment. The results have been discussed in terms of possible mechanisms of action on the central nervous system.