Radioimmunoassay of testosterone in late fetal and newborn rabbit plasma, gonads and adrenal glands]

A radioimmunoassay was used for measuring testosterone in the plasma, gonads and adrenals of 28, 29, 30 and 31-day-old rabbit fetuses of both sexes and newborns. A marked sex difference was shown in the concentrations of testosterone in plasma and in gonads whereas in adrenals the levels of testosterone were low in both sexes (34 to 147 pg/10 mg). In male fetuses, plasma testosterone levels increased from the 28th (133 +/- 20 pg/ml) to the 31st day (361 +/- 119 pg/ml) of intrauterine life, reaching then the values observed in the newborns (387 +/- 73 pg/ml). Plasma from males, on the other hand contained, at all stages studied, significantly more testosterone than plasma from female fetuses (21 +/- 6 to 41 +/- 11 pg/ml) and female newborns (42 +/- 6 pg/ml). In the same way, fetal testicular testosterone concentrations varying from 1 382 +/- 218 to 2 317 +/- 333 pg/10 mg were similar to those measured in the newborns (1 940 +/- 304 pg/10 mg) and significantly higher than fetal (13 to 34 pg/10 mg) or neonatal (44 pg/10 mg) ovarian concentrations. These results showed at evidence the endocrine activity of the fetal testis during this period.     

Testosterone and year‐round territoriality in tropical and non‐tropical songbirds

Past studies have suggested a fundamental difference in testosterone concentrations between tropical and northern latitude male birds, with the convention being that males in the tropics express much lower levels of testosterone. However, recent comparative studies have shown that tropical males with a short and synchronous breeding season (i.e. a breeding season typical of northern species) express maximum testosterone levels similar to those of northern latitude birds. Here, we ask the converse: do northern latitude songbirds that express a defining life‐history characteristic typical of the tropics, i.e. year‐round territoriality, have an annual testosterone profile similar to that of tropical songbirds? For the few year‐round territorial species for which data are available, we found that seasonal testosterone profiles and seasonal maxima in plasma testosterone were similar between males of tropical and non‐tropical species. For example, males of both groups expressed seasonal maxima during the period when females were fertile, and testosterone levels at this time were similar. In contrast, this and other studies show that species with seasonal territories typically express maximum testosterone levels earlier in the breeding cycle, when territories are first being established. Taken together, we suggest that specific life‐history traits may play a more important role in determining testosterone profiles of tropical and non‐tropical birds than breeding latitude and encourage further studies to allow for more formal comparisons.     

Seasonal pattern of LH and testosterone secretion in adult male fallow deer, Dama dama

At monthly intervals during the year blood samples were collected every 20 min for 12 h from 4 entire and 2 prepubertally castrated adult fallow deer bucks. In the entire bucks there were seasonal changes in mean concentrations and pulse frequencies of plasma LH. Mean concentrations in late summer and autumn were 3-6 times higher than during other seasons. LH pulse frequency was low (0-1 pulses/12 h) during most of the year and increased only during the 2-month period (January and February) that marked the transition from the non-breeding season to the autumn rut. During this period there was a close temporal relationship between pulses of LH and testosterone. However, during the rutting period (March and April) episodic secretion of testosterone, manifest as surges in plasma concentrations of 4-6 h duration, was not associated with any detectable pulses in LH although mean plasma concentrations of LH remained elevated. During the rut, the surges of plasma testosterone occurred at similar times of the day. Plasma profiles in May indicated very low concentrations of LH and testosterone secretion in the immediate post-rut period. Castrated bucks exhibited highly seasonal patterns of LH secretion, with mean plasma LH concentrations and LH pulse frequency being lowest in November (early summer) and highest in February and March (late summer-early autumn). Mean concentrations and pulse frequency of LH in castrated bucks were higher than for entire bucks at all times of the year.     

Annual cycles in moult, body mass, luteinizing hormone, prolactin and gonadal steroids during the development of sexual maturity in the White stork (Ciconia ciconia)

Annual variations in moult, body mass, and the plasma concentrations of luteinizing hormone, prolactin and the gonadal steroids, oestradiol and testosterone, were measured in captive White storks ( Ciconia ciconia ). Data were collected at approximately monthly intervals for 13 months on storks hatched over five successive years, the youngest ones being in their first, the oldest in their fifth, year of life.
Moulting of wing feathers occurred during the summer months, April through August. Young birds began to moult at least one month earlier, and replaced more wing feathers each year, than did three- to five-year-old birds. Body mass exhibited remarkably consistent annual cycles with minima of2–9-3-5 kg, during the summer months, and maxima of3–8-4-5 kg, during the winter months. Young males were heavier at all times of the year than young females, although this difference was gradually reduced to non-significant levels by four years of age. Luteinizing hormone, prolactin and the gonadal steroids, oestradiol and testosterone, exhibited annual cyclic changes, usually of a bi-modal nature. No major differences in hormone profiles, however, were found between any of the age groups. The phenomenon of deferred maturity in the stork does not parallel that of puberty found in many mammals.     

Requirement of thyroid function for the expression of seasonal reproductive and related changes in red deer (Cervus elaphus) stags.

The effect of thyroid function on regulation of seasonal reproduction was investigated in three red deer stags thyroidectomized (THX) in summer (January 1988) in comparison with five thyroid-intact controls. Responses of luteinizing hormone (LH) and testosterone to a bolus injection of 10 micrograms gonadotrophin-releasing hormone (GnRH) were tested in July, October, December, February and April. Blood samples were collected at weekly intervals from December 1987 to June 1989 for measurement of testosterone, triiodothyronine (T3) and prolactin concentrations. Testis diameters were measured every 2 weeks. In October 1988 (spring), plasma LH concentrations of control stags were less responsive (P less than 0.01) to stimulation by GnRH than those of THX stags; plasma testosterone concentrations and testis diameters were low and there was no increase in plasma testosterone concentrations after injection of GnRH in control stags during October or December (spring, early-summer). In contrast, THX stags maintained a testosterone response (P less than 0.01) in these 2 months and did not exhibit any signs of a seasonal lack of reproductive activity at this time of year. Control stags cast antlers in spring whereas THX stags maintained hard antlers throughout the study. Concentrations of plasma T3 were not detected in THX stags from June 1988 onwards, but exhibited a seasonal pattern in control stags, with low concentrations during autumn and winter (April to July) and high concentrations in spring and summer (August to February). There was no effect of thyroidectomy on the seasonal pattern of prolactin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of season on the secretion of LH and testosterone in intact and castrated red deer stags (Cervus elaphus).

At 2--4 monthly intervals during the year blood samples were collected every 15 min for 6 h from 2 intact and 3 castrated red deer stags to study the relationship between season and the secretion of LH and testosterone. In the intact stags plasma LH and testosterone concentrations changed during the year; the LH levels were maximal in August during the phase of testicular redevelopment, while the testosterone levels were maximal from September to November coinciding with the time of peak testicular activity and the mating season. The castrated stags had higher plasma levels of LH than the intact stags at all times of the year, and there was no clear seasonal cycle in LH levels in these animals.     

Seasonal changes in plasma concentrations of immunoreactive inhibin and testicular activity in male Japanese monkeys

Seasonal changes in plasma immunoreactive (ir-) inhibin, testosterone, LH, and FSH concentrations were examined in five sexually mature male Japanese monkeys (Macaca fuscata fuscata) housed indoors individually, to explore the reproductive cyclicity in the male. Blood samples were collected monthly throughout one year, and testicular size, semen volume, and number of sperm in the semen were ascertained at the same time in the same animals. Semen samples were obtained by penile electrostimulation. The results showed a clear seasonal increase in all parameters: plasma ir-inhibin, testosterone, testicular size, semen volume, and total number of sperm in the liquid portion of the semen during the autumn and winter months in synchrony with the natural breeding season. In contrast, plasma LH and FSH remained unchanged throughout the year, although plasma FSH tended to increase during the breeding season concomitant with an increase in plasma ir-inhibin. A significant positive correlation between FSH and ir-inhibin was observed in two of five monkeys. The positive correlations between plasma ir-inhibin and testicular activities during both the developing and regressing phases of the testicular cycle indicate that plasma ir-inhibin is a useful indicator of testicular activity as well as an indicator of Sertoli cell function in the Japanese monkey.     

Effect of age,pubertal stage and season on testosterone concentration in male dromedary camel

The present study was conducted in the Laboratory of Animal Physiology and Biotechnology, Department of Animal Production, Faculty of Agriculture, Mansoura University, Egypt. The present investigation aimed at studying effects of ages, pubertal stages and seasons of the year on testosterone concentrations in blood plasma and tissue homogenate of the testes. The testes used in the current study were collected from a total of 104 one-humped male camels (Camelus dromedarius). Samples were taken from pre (1–3.5 years) and post (3.5–13 years) pubertal camels. Testes were studied for a two consecutive seasons. The freshly prepared homogenate of the testicular tissue and blood plasma were used for determining the concentrations of testosterone in plasma and testicular extract. The concentrations of testosterone in blood plasma and testicular tissue were significantly increased during the breeding season compared with that of non-breeding season; the concentration of testosterone was higher in testicular tissue than in blood plasma.Testosterone concentrations in plasma and testicular tissue were increased in breeding than in non-breeding season. In addition, the testosterone concentrations were closely related with seasonal changes, stage of puberty and advancing age.     

The effect of unilateral castration on plasma and testicular testosterone in rabbits from birth to 60 days.

Male rabbits were hemigonadectomized every 10 days from 1 to 50 days of age and were sacrificed 10 days after the operation. Non-operated controls were sacrificed at the same stages. Plasma and testicular testosterone were quantified by radioimmunoassay. Compensatory testicular hypertrophy was not observed in hemicastrated rabbits. Hemicastration has variable effects on testicular and plasma testosterone levels as a function of age. When it is performed at birth, there is a significant increase in testicular and plasma concentrations of testosterone. Similar results are obtained if the operation is performed at 30 days. Unilateral castration performed at 10, 20 and 50 days reduces testicular and plasma testosterone levels. When hemicastration is performed at 40 days or at the adult age, testicular and plasma testosterone levels are not modified.     

Restoration of fertility with gonadotropin and bromocriptine in a hypogonadal man after removal of macroprolactinoma

A case of male hypogonadism after removal of macroprolactinoma was successfully treated with gonadotropin. A 35-year-old man treated surgically for pituitary adenoma had elevated plasma prolactin and impaired pituitary function after the operation. He was on replacement of hydrocortisone, levothyroxine and testosterone depot along with bromocriptine. Normal plasma testosterone levels were achieved with HCG, 3,000 IU three times a week. The addition of 75 IU of FSH daily restored spermatogenesis and the sperm count reached the fertile range at the 11th month. Doses of HCG and FSH were cut in half at the 10th month without affecting the plasma testosterone levels. His wife was impregnated at the 12th month and gave birth to a normal baby girl.     

Effect of season on seminal traits and serum hormone concentrations in captive male Siberian tigers (Panthera tigris)

Electroejaculates and serum samples were collected throughout the year from 5 male Siberian tigers. Semen quality, seminal plasma chemistry and serum hormone concentrations were evaluated and analysed as a function of season. Semen volume, concentration, motility, viability and morphology were not influenced by season. The ability of spermatozoa to undergo capacitation and penetrate zona-free hamster eggs did not differ due to season. Season had no influence on seminal plasma concentrations of acid phosphatase, calcium, glucose, potassium and phosphorus. Serum values of thyroxine and triiodothyronine were lowest (P = 0.002 and P = 0.03, respectively) during the summer months while cortisol showed no seasonal variation. Serum testosterone concentrations were higher in fall and early winter (P less than 0.001) than at other times of the year but were not correlated with semen quality. These results demonstrate that season has no effect on the semen production and quality of captive male Siberian tigers.     

Seasonal variation in circulating testosterone and oestrogens of wild-caught California ground squirrels (Spermophilus beecheyi).

Blood samples were obtained each month for 18 months in 1984-85 from wild-caught California ground squirrels. Circulating testosterone and total oestrogens were extracted from the plasma, measured by radioimmunoassay and compared with concurrent changes in plasma progesterone and prolactin in the same individuals. Male plasma testosterone concentrations peaked in January, shortly before mating, whereas female testosterone concentrations were low throughout the year. Female plasma oestrogen concentrations peaked in February, during the mating period. Juvenile males exhibited a transient increase in circulating testosterone in September, followed by testis growth, preputial separation, and the appearance of epididymal spermatozoa. Juvenile females exhibited a transient increase in circulating oestrogens in November. By the start of the first mating season after their births, neither juvenile males nor females differed significantly from same-sex adults with respect to plasma concentrations of oestrogen or testosterone. Plasma concentrations of progesterone and prolactin in killed individuals were similar to those obtained in previous studies of free-living S. beecheyi. Mean plasma concentrations of all measured hormones varied significantly with reproductive condition in adults of both sexes.     

Gender‐ and season‐dependent relationships between testosterone, oestradiol and immune functions in wild roach

Plasma testosterone and 17β‐oestradiol concentrations, differential leukocyte counts and proportion of dead Rhipidocotyle campanula gill parasites (parasite resistance) were determined five times during a year in two populations of roach Rutilus rutilus and analysed for seasonal and gender differences. In addition to the above immune variables, plasma Immunoglobulin M (IgM) concentration, chemiluminescence and migration differential of head kidney phagocytes, size of the spleen, haematocrit and total leukocyte count were correlated with sex hormones for each population, sampling time and sex separately, using condition factor as a partial correlate. There were no clear gender differences in the determined immune variables. Both testosterone and oestradiol concentrations were lowest after the spawning in June. Oestradiol was higher in females than in males, but testosterone was present in equal concentrations in both sexes. Statistically significant correlations between sex hormones and immune variables were rare and mainly without any patterns with respect to population, sex or sampling date. The meta‐analysis on individual correlations, however, revealed a positive relationship of plasma testosterone concentration to chemiluminescence of head kidney phagocytes, plasma IgM concentration and the proportion of dead R. campanula to all R. campanula on the gills. In the meta‐analysis, the concentration of oestradiol was not found to correlate with any of the studied immune variables.     

Effect of steroid aromatase inhibitors on the catecholamine content of the hypothalamus of neonatally androgenized rats

Administration of 50 micrograms of testosterone propionate to newborn female rats on the 5th day of life provoked a reliable increase in noradrenaline and dopamine concentrations in the hypothalamus of 10-day-old rats. Neonatal administration of aromatase inhibitors on the 5th and 7th days of life prevented testosterone-induced increase in catecholamine concentrations. The data obtained prove the integration of the processes of testosterone aromatization and catecholamine accumulation in androgen-dependent brain differentiation.     

Sex behavior and hormone responses in ewes administered testosterone propionate

Two ewes were administered testosterone propionate and subsequent plasma testosterone concentrations determined and male sex behavior recorded. Initially ewes were administered 50 mg of testosterone propionate every other day for 20 days. Within 6 days following the first injection, concentrations of testosterone in plasma increased to 8.0 to 10.0 ng/ml. A 50 mg injection of testosterone propionate administered every 10 days thereafter maintained concentrations of plasma testosterone at 1.0 to 3.0 ng/ml. Sex behavior tests conducted with non-estrus and estrus ewes showed that both testosterone treated ewes developed male sex behavior similar to a ram. Ewes in estrus were mounted by testosterone treated ewes an average of 6.7 ± 1.2 times during a 10 minute test whereas none of the non-estrus ewes were ever mounted. Silastic implants containing testosterone propionate placed in the ewes 83 days following the first injection maintained concentrations of plasma testosterone at 6.0 to 8.0 ng/ml for a 20 day period. Therefore, administration of testosterone propionate to ewes effectively stimulates male sex behavior and would obviate the necessity for vasectomized rams for estrus detection.     

Influence of photoperiod on the seasonal pattern of secretion of luteinizing hormone and testosterone and on the antler cycle in roe deer (Capreolus capreolus).

Annual variations in concentrations of luteinizing hormone (LH) and testosterone in plasma were analysed in relation to the antler cycle in six adult male roe deer exposed to a natural photoperiod (latitude 46 degrees 10'N) and in four adult males maintained in a constant short-day photoperiod (8 h light: 16 h dark) for a year, from the winter solstice at which time both groups of animals had antlers in velvet. The animals were sampled, every 15 min for 2 or 4 h at intervals of one month for a year. Under both natural and experimental conditions, LH concentrations were high from January to March, but in the experimental conditions they decreased between April and May-June, whereas in the natural conditions they increased. Plasma LH concentration was lowest between July and November in animals under natural photoperiod, whereas under 8 h light:16 h dark photoperiod a second increase in plasma LH occurred between August and September. Between March and August, concentrations of plasma testosterone increased under natural photoperiod, whereas under experimental photoperiod there was a biphasic pattern of plasma testosterone with peaks between February and May and between September and November. Under natural photoperiod, antlers were cast in November, 369 +/- 6 days after the previous antlers were cast. Under experimental photoperiod, antlers were cast after 193 +/- 10 days, and a new set developed. The sexual cycle of the male appears to be initiated by an endogenous rhythm in winter and is then maintained by hormonal changes resulting from increasing photoperiod in spring.(ABSTRACT TRUNCATED AT 250 WORDS)     

Endocrine control of antler growth in red deer stags

Observations of body weight, testis size, antler status, plasma testosterone and prolactin were made on 12 red deer stags during their first 2 years of life. Six of the stags were fed to appetite throughout the study (Group A) and 6 were fed a 70% restricted diet during each winter (Group B). In addition 6 of the stags , 3 from each group, were studied in more detail; LH and testosterone were measured either after a single injection of LH-RH or in samples taken at frequent intervals over a period of 8 or 24 h. During the study the stags became sexually mature, developed first their pedicles and then antlers and showed at least one complete cycle of casting and regrowth of the antlers . The stags in Group A developed their testes and pedicles about 2 months earlier than did those in Group B. Pedicle initiation was associated with increasing plasma testosterone levels in response to changes in LH secretion, and antler development occurred when testosterone levels were low or decreasing. Cleaning of the velvet was associated with high levels of plasma testosterone. Antler casting occurred when plasma testosterone concentrations were low or undetectable and prolactin levels were high or increasing. The relationship between LH and testosterone varied during the study; in spring when the testes and antlers were growing, relatively high levels of LH were associated with only small peaks of testosterone, yet in summer, when antler growth was complete and the antlers were clean of velvet, low LH concentrations were associated with large peaks of testosterone.     

Changes in plasma concentrations of insulin-like peptide 3 and testosterone from birth to pubertal age in beef bulls

The objectives were to: (1) develop an enzyme immunoassay (EIA) for insulin-like peptide 3 (INSL3) or relaxin-like factor (RLF) in bovine plasma; (2) investigate changes of plasma INSL3 concentrations from birth to pubertal age of beef bulls; and (3) compare changes in plasma concentrations of INSL3, testosterone, and LH. Plasma samples were collected from beef bull calves (n = 15) at birth (0 d) and at 28, 56, and 84 d after birth. Furthermore, in beef bulls around pubertal age (n = 26; age range 3 to 22 mo), plasma samples were collected at 1 to 4 mo intervals. Plasma INSL3 concentrations increased (P < 0.05) from 0 to 28, 28 to 56, and from 56 to 84 d of age. Plasma testosterone concentrations increased (P < 0.001) from 0 to 28 d, and from 28 to 56 d, but did not change from 56 to 84 d. For bulls around pubertal age, plasma INSL3 concentrations did not change from the prepubertal phase (3 to 6 mo) to the early pubertal phase (6 to 12 mo), but increased (P < 0.05) from the early to late pubertal phases (12 to 18 mo), and from the late pubertal to postpubertal phases (18 to 22 mo). Plasma testosterone concentrations increased from the prepubertal to early pubertal phases (P < 0.001), but did not change thereafter. Plasma LH concentrations did not change from 0 d to 84 d, but decreased (P < 0.001) from prepubertal to early pubertal phase, with no significant change thereafter. Plasma INSL3 concentrations increased during the first 3 mo of life and throughout the pubertal age in beef bulls. There were similar dynamic patterns for INSL3 and testosterone during the first 3 mo of life, but patterns subsequently diverged in bulls around pubertal ages.     

Circulating androgen levels in the developing boar

Circulating levels of serum androgens were studied for 11 Duroc boars. Jugular blood samples were collected at 2-wk intervals, beginning at 5 wk of age and continuing until 27 wk of age. Testosterone and androstenedione values were determined by radioimmunoassay. Analysis of variance indicated a significant difference among ages in testosterone and androstenedione concentrations. Plasma levels of testosterone were 1.5 to 1.9 ng/ml at 5 to 7 wk, decreased to 0.3 to 0.6 ng/ml between 7 and 17 wk, and then increased to 3.7 ng/ml by the 27th wk of age. Plasma androstenedione tended to be elevated during the 5th through 7th wk (3.5 to 4.9 ng/ml), decreased to 0.9 to 1.6 ng/ml through the 19th wk and then gradually increased through the 27th wk (1.4 to 2.4 ng/ml). A highly significant correlation was observed between testosterone and androstenedione (r=0.39). Testicular volume was shown to be highly correlated with testosterone concentration (r=0.48). During the early life of the pig, the predominant androgen is androstenedione with testosterone becoming the predominant androgen as the boar reaches maturity.     

Changes in plasma concentrations of insulin-like peptide 3 and testosterone from birth to pubertal age in beef bulls

The objectives were to: (1) develop an enzyme immunoassay (EIA) for insulin-like peptide 3 (INSL3) or relaxin-like factor (RLF) in bovine plasma; (2) investigate changes of plasma INSL3 concentrations from birth to pubertal age of beef bulls; and (3) compare changes in plasma concentrations of INSL3, testosterone, and LH. Plasma samples were collected from beef bull calves (n = 15) at birth (0 d) and at 28, 56, and 84 d after birth. Furthermore, in beef bulls around pubertal age (n = 26; age range 3 to 22 mo), plasma samples were collected at 1 to 4 mo intervals. Plasma INSL3 concentrations increased (P < 0.05) from 0 to 28, 28 to 56, and from 56 to 84 d of age. Plasma testosterone concentrations increased (P < 0.001) from 0 to 28 d, and from 28 to 56 d, but did not change from 56 to 84 d. For bulls around pubertal age, plasma INSL3 concentrations did not change from the prepubertal phase (3 to 6 mo) to the early pubertal phase (6 to 12 mo), but increased (P < 0.05) from the early to late pubertal phases (12 to 18 mo), and from the late pubertal to postpubertal phases (18 to 22 mo). Plasma testosterone concentrations increased from the prepubertal to early pubertal phases (P < 0.001), but did not change thereafter. Plasma LH concentrations did not change from 0 d to 84 d, but decreased (P < 0.001) from prepubertal to early pubertal phase, with no significant change thereafter. Plasma INSL3 concentrations increased during the first 3 mo of life and throughout the pubertal age in beef bulls. There were similar dynamic patterns for INSL3 and testosterone during the first 3 mo of life, but patterns subsequently diverged in bulls around pubertal ages.