Pattern Of Testosterone Secretion Research Articles

SPERM QUALITY IN RATS PREDISPOSED TO THE MANIFESTATION OF CATATONIC REACTIONS

Catatonia is a psychopathological syndrome displayed as a motor disorder. Catatonia is a sign of many menthal disorders, particularly schizophrenia and depression, with a wide disrtibution in the human population. The GC (“genetic” and “catatonia”) rat strain was obtained from the Wistar rat strain by a long selection (78 generations) for the catatonic type of reaction and is a model of schizophrenic and depressive disorders in humans. It is known that selection for behavior including catatonic reactions results in neuroendocrine, reproductive and morphological changes in animals. However, the influence of selection for a catatonic reaction on the spermatogenic function of testes had not been studied. The aim of this study was to conduct a comparative investigation of sperm quality in rats of the GC and the Wistar strain. The epididymal sperm parameters (sperm count, sperm motility, sperm morphology) were measured, and body, testes and epididymal weight were determined at puberty (50 day of life) and at adulthood (90 day of life). The litter size of the GC and Wistar rats was determined. It was found that adult GC rats had a lower sperm count, sperm motility, testis weight, epydidymal weight and litter size compared to adult Wistar rats. However, at puberty, GC rats had a higher sperm count than the Wistar strain. Interstrain differences in sperm morphology were not found. It has been assumed that the changes of spermatogenic parameters in response to selection for catatonia are caused by changing the ontogenic pattern of testosterone secretion. In conclusion, the hereditary predisposition to catatonic reaction is associated with impaired sperm parameters in adult rats that reduces their chance to reproduction. The GC rat strain can be a perspective model for investigation of the relationship between the hereditary predisposition to catatonia and spermatogenesis

Comparative endocrinology of testicular, adrenal and thyroid function in captive Asian and African elephant bulls

Concentrations of serum testosterone, cortisol, thyroxine (free and total T4), triiodothyronine (free and total T3) and thyroid stimulating hormone (TSH) were measured to assess adrenal and thyroid function as they relate to testicular activity and musth in captive elephants. Blood samples were collected approximately weekly from Asian ( n = 8) and African ( n = 12) bulls at seven facilities for periods of 4 months to 9.5 years. Age ranges at study onset were 8–50 years for Asian and 10–21 years for African elephants. Based on keeper logs, seven Asian and three African bulls exhibited behavioral and/or physical (temporal gland secretion, TGS, or urine dribbling, UD) signs of musth, which lasted 2.8 ± 2.5 months in duration. Serum testosterone was elevated during musth, with concentrations often exceeding 100 ng/ml. Patterns of testosterone secretion and musth varied among bulls with no evidence of seasonality ( P > 0.05). Only three bulls at one facility exhibited classic, well-defined yearly musth cycles. Others exhibited more irregular cycles, with musth symptoms often occurring more than once a year. A number of bulls (1 Asian, 9 African) had consistently low testosterone (<10 ng/ml) and never exhibited significant TGS or UD. At facilities with multiple bulls ( n = 3), testosterone concentrations were highest in the oldest, most dominant male. There were positive correlations between testosterone and cortisol for six of seven Asian and all three African males that exhibited musth (range, r = 0.23–0.52; P < 0.05), but no significant correlations for bulls that did not ( P > 0.05). For the three bulls that exhibited yearly musth cycles, TSH was positively correlated (range, r = 0.22–0.28; P < 0.05) and thyroid hormones (T3, T4) were negatively correlated (range, r = −0.25 to −0.47; P < 0.05) to testosterone secretion. In the remaining bulls, there were no clear relationships between thyroid activity and musth status. Overall mean testosterone and cortisol concentrations increased with age for all bulls combined, whereas thyroid activity declined. In summary, a number of bulls did not exhibit musth despite being of adequate physical maturity. Cortisol and testosterone were correlated in most bulls exhibiting musth, indicating a possible role for the adrenal gland in modulating or facilitating downstream responses. Data were generally inconclusive as to a role for thyroid hormones in male reproduction, but the finding of discrete patterns in bulls showing clear testosterone cycles suggests they may facilitate expression or control of musth in some individuals.

312. Testosterone secretion in the Australian sea lion

The objectives in this study were to characterize the pattern of testosterone secretion over 24 h in the captive Australian sea lion and to establish whether exogenous hormone stimulation could be used to obtain an index of testosterone secretion in this species. Blood samples were collected from three males at 3-h intervals for 24 h on three occasions at 2-week intervals. Exogenous GnRH, hCG and LH were administered at the end of each 24-h sampling period and changes in circulating testosterone monitored over 5 h. Circulating concentrations of testosterone during 24-h sampling periods were greater (P &lt; 0.01) during darkness than during daylight. Exogenous hCG administered induced a significant rise in circulating concentrations of testosterone. In the 5 h following GnRH, hCG and LH administration, circulating testosterone concentrations reached similar levels to the highest concentrations observed during the respective 24-h sampling periods. These findings have provided evidence of a 24-h pattern of testosterone secretion in the Australian sea lion. This study has also shown that the testis response to exogenous GnRH, hCG and LH in the Australian sea lion can provide an index of the prevailing testosterone biosynthetic capacity of the testes.

Testosterone and social and reproductive behaviour in Aphelocoma jays

When there is a direct relationship between testosterone level and payoff in reproductive success through aggression, testosterone levels should be elevated. Elevated testosterone, however, has fitness costs, particularly a decreased tendency to display parental care. Thus the pattern of testosterone secretion in males should vary with the social and mating system. Western scrub-jays, Aphelocoma californica woodhouseii, form monogamous pairs on territories during the breeding season. Mexican jays, A.ultramarina, live in large, stable groups and up to five females within a group attempt nesting each spring. In both species, testosterone levels rose rapidly in March and peak levels did not differ. Elevated testosterone levels were only observed for about 3 weeks in the monogamous western scrub-jay, but were observed into May in Mexican jays, a reflection of prolonged opportunity for males to mate with multiple females and continual interaction with other competing males. In Mexican jays, nonbreeding yearlings had lower testosterone levels than all other age groups. Testosterone in males owning nests did not differ from that in other adult males, many of whom engage in extrapair fertilizations. Testosterone was elevated throughout the incubation phase, but was significantly lower when chicks were present in any nest in the group. Nearly all birds in the group fed all chicks. These observations support the hypothesis that testosterone is elevated when male–male competition is frequent and mating opportunities depend on the outcome of that competition, and testosterone is decreased when the necessity for parental or alloparental care would make its effects deleterious.

Effect of ingestion and inhalation of lead on the reproductive system and fertility of adult male rats and their progeny.

Ninety-day-old Sprague-Dawley rats were intoxicated for 70 d with lead, given either as 0.3% lead acetate in drinking water or by inhalation as 5 mg m-3 lead oxide. Direct or transmitted lead toxicity for the male reproductive system was assessed in the rats and their offspring from pituitary and genital organ weights after exposure, the numbers of Sertoli and germ cells, the number, motility and morphology of epididymal spermatozoa, the levels of plasma testosterone, LH and FSH and fertility tests. Whole blood lead levels were similar after lead ingestion and after inhalation (58.0 +/- 1.7 micrograms dl-1 vs. 51.1 +/- 1.8 micrograms dl-1). Lead acetate ingestion did not affect the reproductive system or fertility of rats. Inhalation of lead oxide did not affect fertility either, but seminal vesicle weight dropped significantly, which might suggest an alteration in the pattern of testosterone secretion. In the male progeny of sires that inhaled lead, the number of epididymal spermatozoa decreased but this did not interfere with fertility. Our results show that for the doses studied, lead inhalation and lead ingestion do not produce strikingly different effects on the male rat's reproductive system. Differences between the present findings and those of others might be due to difference of rat strain or of age at exposure.

Peripheral androgen levels in the male brush-tail possum (Trichosurus vulpecula).

Radioimmunoassays were established for the measurement of total androgens and the specific measurement of testosterone and 5 alpha-dihydrotestosterone in peripheral plasma of the brush-tail possum. Androgen concentrations were measured in blood collected from indwelling jugular cannulae to determine whether the normal pattern of androgen secretion in this species was episodic and to attempt to relate total androgen and the pattern of testosterone secretion to the changes previously reported in prostatic, but not epididymal, weight in the breeding season. Blood was collected from restrained animals at varying time-intervals during daylight hours and darkness. Despite an apparent good adaptation to the sampling procedure there was generally a progressive decline in plasma androgen level during the collection period. This was true for animals bled during or out of the breeding season. There was no significant seasonal effect on the androgen concentration in the initial blood sample. When less restraint was used, two of three animals showed fluctuations in androgen levels over the 7-h sampling period. Testosterone levels in blood obtained by cardiac puncture were four- to nine-fold higher than those of 5 alpha-dihydrotestosterone but levels of these androgens in samples obtained during the breeding season were not significantly different from those obtained out of season. The results do not argue for a pulsatile release of testosterone in the possum but do demonstrate a marked capacity for changes in the peripheral androgen concentration. There was a poor correlation between testosterone and 5 alpha-dihydrotestostosterone levels and prostatic weight.

Seasonal changes in the plasma testosterone profile in Merino rams

The pattern of testosterone secretion (i.e. profile of plasma testosterone sampled every hour for 24 h) was characterized for Merino rams at various times during the year at latitude 35�S to assess seasonal trends. The profiles of plasma testosterone were always characterized by random peaks regardless of season. However, at any particular time of the year, there were large differences between individual rams in the number of peaks124 h (range 1-7). Mean plasma testosterone levels were higher and a greater number of peaks were recorded per 24 h in summer (December-January) than in winter (July) and spring (September-October). Seasonal changes observed in the plasma testosterone profile of Merino rams were consistent with the concept that activity of the hypothalamic-pituitary-gonadal axis in sheep is entrained to changes in the photoperiod. Merino rams at latitude 35�S are therefore markedly seasonal from an endocrine point of view, although they are not generally regarded as seasonal breeders based on mating behaviour.

PLASMA TESTOSTERONE LEVELS IN INTACT AND HEMICASTRATED GROWING COCKERELS

Changes in the levels of testosterone in plasma were measured by radioimmunoassay in blood samples taken at frequent intervals between 2 and 26 weeks of age from entire cockerels and cockerels hemicastrated before 2 weeks of age. In both groups the pattern of testosterone secretion could be divided into three clearly defined phases. In young birds, the levels of testosterone in plasma were low (0.3 ng/ml) but in the prepubertal period, at 11 weeks of age, they started to rise and continued to rise until 22 weeks of age when adult levels, which fluctuated between 2.5 and 3.5 ng/ml, were reached. In the immediate period after hemicastration, the concentration of testosterone decreased temporarily. From 11 weeks of age the levels of testosterone in the hemicastrated birds were approximately 75% of those in intact birds. These results are discussed in relation to the compensatory testicular hypertrophy which occurs in growing cockerels hemicastrated at an early age.

PLASMA TESTOSTERONE PROFILES IN MALE MACROPODID MARSUPIALS

Serial blood samples were collected over a 3.5-8 h period from ten adult male macropodid marsupials belonging to five different species to study the pattern of testosterone secretion. The concentration of testosterone in the plasma ranged from 0.5 to 9.5 ng/ml, and in each animal the levels declined progressively during the study; this effect was attributed to the stress effects of handling. Injection of 5 microgram synthetic luteinizing hormone releasing hormone induced a rapid and substantial increase in the level of testosterone.

353. Testicular response to i.v. luteinizing hormone-releasing hormone (LH-RH) in normal men. Patterns of testosterone secretion throughout the day

353. Testicular response to i.v. luteinizing hormone-releasing hormone (LH-RH) in normal men. Patterns of testosterone secretion throughout the day