Seasonal and circadian changes in the episodic release of follicle-stimulating hormone, luteinizing hormone and testosterone in rams exposed to artificial photoperiods

Six rams of an ancient breed of domesticated sheep (SOAY) were subjected to an artificial light régime of alternating periods of long days (16 h light: 8 h darkness) and short days (8 h light: 16 h darkness) which induced seasonal development and regression of the testes during a period of 36 weeks. Over 2000 blood samples were taken, and the changes in plasma levels of FSH, LH and testosterone were related to the cycle of testicular activity. During long days plasma levels of gonadotrophins became very low and the testes regressed to about 20% of their maximum size; there was a corresponding reduction in plasma testosterone levels. When the rams were returned to short days reproductive development was again stimulated after 2-3 weeks with a progressive increase in plasma FSH and LH levels and consequent hypertrophy of the testes. It took about 16 weeks of short days for testicular activity to become maximal. Blood samples collected at hourly intervals for 24 h on ten occasions during the study revealed transitory peaks in plasma FSH and LH levels indicative of episodic release. Changes in gonadotrophin secretion were modulated primarily by alterations in the frequency of episodic releas; less than 1 spike per 24 h during long days increased to a maximum of 10 spikes/24 h under short daylengths. The peaks of FSH release were of smaller amplitude than those of LH, although during periods of frequent episodic release basal levels of fsh were increased to a greater extent than those of LH. A circadian rhythm was observed in the plasma levels of FSH, LH and testosterone, which was related to increased gonadotrophin release during the dark phase of the 24 h cycle; changes in blood haematocrit were also observed. The circadian changes appeared to be correlated with the activity cycle of the animals which in turn was dictated by daylight. A possible interrelationship between the circadian cycle and the seasonal cycle is discussed.     

Photoperiodic control of gonadotrophin secretion in the ram: a detailed study of the temporal changes in plasma levels of follicle-stimulating hormone, luteinizing hormone and testosterone following an abrupt switch from long to short days

Six adult Soay rams were housed under artificial lighting conditions of long days (16 h light:8 h darkness) for 4 months and this caused the animals to lapse into a state of reproductive quiescence with low levels of gonadotrophins in the circulation and regressed testes secreting very low amounts of testosterone. The photoperiod was changed abruptly to short days (8 h light:16 h darkness) to induce a resurgence of sexual activity, and a detailed study was made of the pituitary and testicular responses over the first 100 days. Plasma levels of LH and FSH first began to increase between days 6 and 12 of short days, and rose progressively until days 33-54 before declining again. Testicular growth of the rams began on days 19-26 and continued for most of the remaining period of study. Plasma testosterone levels rose in parallel with the growth of the testes, and were greatly increased by day 100 when gonadotrophin levels were reduced. At most stages there were short-term fluctuations in the plasma levels of FSH, LH and testosterone indicative of episodic secretion. Peaks in plasma levels of LH were especially conspicuous and from the changes in frequency and amplitude of these peaks it was possible to predict the way in which photoperiod influenced gonadotrophin secretion by its effect on hypothalamic LH-RH secretion. A slight 24 h rhythm in the plasma levels of all three hormones was observed, and the significance of this in relation to the photoperiodic response is discussed.     

Diagnosis and management of transient ischaemic attacks in accident and emergency

AIM: Are there any changes in hypophyseal and gonadal hormones levels during the naloxone test in the degenerative changes of the seminiferous tubules? MATERIAL AND METHODS: The naloxone test (0.4 mg i.v.) was performed in 13 patients with degenerative changes of the seminiferous tubules. The plasma FSH, LH, prolactin, testosterone and estradiol levels were determined before and 30, 60, 90, 120 minutes after the administration of the drug. RESULTS: In the examined group of patients the plasma FSH, prolactin and estradiol levels were significantly higher, testosterone levels significantly lower and LH levels were in the same range compared with the patients with azoospermia and normal spermatogenesis. The plasma FSH, prolactin and testosterone levels did not change significantly their values during the test. The plasma estradiol levels decreased significantly and plasma LH levels increased significantly during the test. CONCLUSION: Elevated plasma FSH, prolactin and estradiol levels, diminished testosterone levels and the decrease of plasma estradiol levels and the increase plasma LH levels during the naloxone test indicate the degenerative changes of the seminiferous tubules in the cases of azoospermia.     

The effect of 2-bromo-alpha-ergocryptine (CB154) administration of the hormone levels, organ weights, prostatic morphology and zinc concentrations in the male rat

2-Bromo-alpha-ergocryptine (CB154) administration to male rats produced a significant decrease in plasma prolactin levels without changing the LH and testosterone concentrations. The weights of the accessory sex tissues, testes, adrenals and kidney were unaltered by the treatment. Zinc concentration and distribution in the cell organelles of the prostatic tissue was markedly changed by CB154 treatment. No changes in the uptake of testosterone in vivo occurred in the treated animals. Prolactin did not consistently influence the prostatic adenyl cyclase activity in vitro and only at high concentrations was the testosterone uptake in vitro with cultures of prostatic tissue increased.     

Changes in gene expression following traumatic brain injury in the rat

1. The relationship between immunoreactive inhibin and follicle-stimulating hormone (FSH) was studied in male and female chickens from hatch to sexual maturity. Plasma inhibin was estimated by a heterologous radioimmunoassay validated for use in the chicken. FSH was measured by a recently developed homologous radioimmunoassay. 2. In a cross-sectional study, blood samples and gonads were collected from chickens of both sexes at 1, 3, 5, 7, 14, 21 and 28 d after hatching and subsequently at 14-day intervals until 182 d of age. 3. In the female, plasma progesterone concentration (P4) progressively increased during sexual development. The plasma luteinising hormone (LH) concentration rose during the first week after hatching, and fluctuated thereafter, with troughs at 6 and 14 weeks and peaks at weeks 10 and 18. The plasma inhibin and FSH concentrations remained low until the start of puberty and increased simultaneously thereafter. However, from week 18 on, plasma inhibin continued to rise while plasma FSH fell. Hence, FSH and inhibin were positively correlated before puberty, but developed a negative correlation during sexual maturation. 4. In the male, plasma testosterone and LH concentrations increased 38- and 3.7-fold respectively over the period studied. Inhibin and FSH followed similar time courses and were consequently positively correlated. 5. These results suggest sex differences in the role of inhibin in regulating FSH secretion during development. The FSH-inhibin feedback loop may become operational at the onset of sexual maturity in the hens. In male chickens, the similar pattern of inhibin and FSH secretion suggests that inhibin secretion is driven by FSH.     

Bi-level positive airway pressure (BiPAP) ventilation in an infant with central hypoventilation syndrome

OBJECTIVES: To determine the effects of long-term cigarette smoking on the levels of plasma testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in male adult rats and to examine morphological and histological changes in the testes. MATERIALS AND METHODS: Cigarette smoke was generated by a smoking-machine and 12 rats were exposed to cigarette smoke diluted with 90% air for 60 days (2 h/day). Twelve rats were exposed to room air only under similar conditions as controls. The concentrations of plasma testosterone, LH and FSH were measured before and after exposure using a radio-immunoassay and the testes were examined histologically. RESULTS: In rats exposed to smoke, the mean plasma testosterone level decreased significantly but there were no significant changes in testosterone in the control rats. The mean plasma LH and FSH levels of the two groups did not change significantly after exposure. In rats exposed to smoke, histological examination of the testes showed fewer Leydig cells and degeneration of the remaining cells. CONCLUSION: These results indicate that the decrease in plasma testosterone levels induced by exposure to smoke was not associated with changes in plasma gonadotrophin levels. The decrease in testosterone levels may be related to the toxic effects of smoke on Leydig cells.     

Follicle-stimulating hormone in azoospermia in prediction of spermatogenic patterns

Follicle-stimulating hormone (FSH) is considered to be the most important plasma hormone correlated with spermatogenesis. Elevated FSH plasma levels were shown to be associated with complete damage to testicular seminiferous tubule germinal epithelium. Recently, there have been conflicting reports with regard to the value of FSH plasma levels in predicting seminiferous tubule histology in the azoospermic patient and hence, as a guide for therapy in assisted reproduction using testicular sperm retrieval. The aim of this study was to evaluate whether FSH plasma levels can predict spermatogenic pattern in the testes of the azoospermic infertile patient. 69 infertile men with non-obstructive azoospermia and 18 with very severe oligospermia were studied. In all, plasma levels of testosterone, free testosterone, prolactin, luteinizing hormone and follicle-stimulating hormone were measured by enzyme immunoassay. In the azoospermic patients the seminiferous tubule spermatogenic pattern was determined in testicular aspirates obtained by multiple fine needle aspiration and categorized according to the most mature spermatogenic cell type in the aspirates: Sertoli cells only, spermatogenic maturation arrest or full spermatogenesis. There were no significant differences in plasma levels of any hormone measured except in very severely oligospermic and azoospermic patients. Both normal and elevated levels were detected in all, regardless of seminiferous tubule cytological pattern or plasma FSH in azoospermic patients. It is concluded that plasma levels of FSH can not be used as a predictive parameter, neither for the presence of spermatozoa nor for any other seminiferous tubule cytological pattern in azoospermic infertile men. They cannot serve as guides for selection of azoospermic men for trials of testicular sperm retrieval in assisted reproduction.     

Primer on medical decision analysis: Part 2--Building a tree

Observations were made on four captive breeding groups of rhesus monkeys in order to measure hormonal, behavioral, and genital changes in adolescent males during the annual mating season. Three questions were addressed with regard to possible effects of social environment upon reproductive maturation: (1) Does male agonistic rank influence adolescent development? (2) Does affiliation between adolescent males and adult females during the mating season influence the males' reproductive development? (3) Does maternal rank exert any effect upon reproductive maturation in adolescent sons? In many (but not all) cases male rank was positively correlated with circulating testosterone and testes weights during the mating season. Affiliative behavior (allogrooming and sexual interactions) between adolescents and adult females in their social groups bore no relationship to the degree of reproductive maturation in males. Mounts involving intromission were infrequent, but sons of high-ranking mothers gained significantly more intromissions than sons of lower-ranking females. Maternal rank was also found to correlate with circulating testosterone levels, testes weights, growth of the baculum (os penis), and maintenance of body weight in adolescent sons during the mating season. By contrast, levels of beta-endorphin in the cerebrospinal fluid of adolescent males did not correlate with social rank, testosterone levels, or genital development. These findings point to possible effects of maternal rank, as well as intermale agonistic rank, in determining reproductive maturation during adolescence in the male rhesus monkey.     

Lesions in the anterior bed nucleus of the stria terminalis in Syrian hamsters block short-photoperiod-induced testicular regression

To elucidate the neural circuitry involved in the photoperiodic control of seasonal reproduction, adult male Syrian hamsters, previously housed under long photoperiods (LD; 14 h of light per day), received sham or bilateral radiofrequency-current lesions directed towards one of three anterior-to-posterior levels of the bed nucleus of the stria terminalis (BNST; far anterior, anterior, posterior). They were then transferred to a short photoperiod (SD; 6 h of light per day) for 12 wk, and their testicular weights and plasma FSH, LH, and testosterone concentrations were determined. All of these parameters became markedly inhibited in the sham-lesioned SD controls and also in the far anterior and posterior BNST lesioned groups. In contrast, this inhibitory response to SD was completely abolished in 8 of 14 animals that had received anterior BNST lesions; only in these 8 animals did the lesion encompass the lateral aspect of the anterior BNST. In a second experiment, hamsters that had previously been exposed to SD for 12 wk in order to induce testicular regression were lesioned in the anterior BNST and for the next 4 weeks were either exposed to LD or further maintained in SD. However, in neither case did the anterior BNST lesions perturb the normal photoperiodic response. Paired testes weights and plasma FSH, LH, and testosterone concentrations at 4 wk did not differ significantly (p > 0.05) between the lesioned animals and their respective sham-lesioned LD and SD controls, which, respectively, showed recrudescence of the reproductive axis or remained in a regressed condition. Taken together, the results suggest that lateral aspects of the anterior BNST contain a cell group that is critical for perception of the SD neuro-inhibitory signal; obliteration of this cell group interrupts the transmission of the inhibitory signal to the reproductive axis but does not directly stimulate it.     

Editorial: Sex and alcohol: a second peek

The effects of alcohol on male sexual function is discussed. Various phenomena affecting sexual function in males have been reported: 1) increased conversion of androgens to estrogens in the liver, 2) interconversion of weak and potent estrogens, 3) increased rate of conversion of adrenocortical steroid precursor to estrogenic substances, 4) decreased plasma levels of luteinizing hormone(LH) and follicle stimulating hormone (FSH), and 5) diminished uptake of androstenedione by the liver and increased peripheral conversion to estrone. It is proposed that the pathogenesis of feminization in alcoholic males may be due partly to the derivative effects of liver damage and to a direct action of alcohol on the testes. Rats fed alcohol have shown atrophy of the gonads and accessory organs, and impaired spermtogenesis. In normal men ingesting alcohol for short periods of time, the frequency and intensity of bursts of testosterone secretion by the testes is dampened, and testosterone concentrations and production rates are increased while the metabolic clearance of testosterone is diminished. Deranged hypothalamic-pituitary function has also been observed. Further research is needed to elucidate the mechanism(s) by which alcohol influences sexual function.     

The radiation hybrid database

The objective of this study was to evaluate morphological characteristics and testicular function of boars with different endogenous concentrations of FSH. Boars were selected at 6 mo of age on the basis of mean FSH concentrations in plasma collected at 4, 5, and 6 mo of age. Boars were classified within half-sibling families based on whether they had high concentrations of FSH (HiFSH, > 500 ng/ml, n = 9) or low concentrations (LoFSH, < 500 ng/ml, n = 7). At 14.5 mo, testes were collected, fixed, sectioned at 1 microm, and evaluated for morphological characteristics. Boars with LoFSH had larger (p < 0.01) testicular and epididymal weights than boars with HiFSH, greater (p < 0.01) daily sperm production per gram of testis, and greater total daily sperm production per boar. Testes of boars with LoFSH had a greater (p < 0.03) volume percentage of seminiferous tubules, a lesser percentage (p < 0.03) of Leydig cells, and a somewhat lesser (p = 0.06) percentage of vascular structures than testes of boars with HiFSH. Testes of boars with LoFSH had greater (p < 0.01) total tubule volume and tubule length than testes of boars with HiFSH. There were no differences (p > 0.70) in volume, diameter, or total number of Leydig cells or in total interstitial volume in testes (p > 0.41) of these two groups. Production of testosterone in vitro per paired testis and per million Leydig cells was not different (p > 0.65) between boars with HiFSH or LoFSH. Greater concentrations of FSH in blood plasma were negatively associated with development of seminiferous tubules and spermatogenic efficiency, whereas Leydig cell development was not different in boars of these two groups.     

Decreased spermatogenic and androgenic testicular functions in adult rats submitted to immobilization-induced stress from prepuberty

We investigated whether chronic stress applied from prepuberty to full sexual maturity interferes with spermatogenic and androgenic testicular functions. Male Wistar rats (40 days old) were immobilized 6 h a day for 60 days. Following immobilization, plasma concentrations of corticosterone and prolactin increased 135% and 48%, respectively, while plasma luteinizing hormone and testosterone presented a significant decrease of 29% and 37%, respectively. Plasma concentration of follicle-stimulating hormone was not altered in stressed rats. Chronic stress reduced the amount of mature spermatids in the testis by 16% and the spermatozoon concentration in the cauda epididymidis by 32%. A 17% reduction in weight and a 42% decrease in DNA content were observed in the seminal vesicle of immobilized rats but not in its fructose content. The growth and secretory activity of the ventral prostate were not altered by chronic stress.     

The red wine provocation test: intolerance to histamine as a model for food intolerance

The effect of flutamide (FLU) administered during 6 weeks at doses of 50 or 100 mg kg-1 body weight, on various reproductive characteristics of sexually active male golden hamsters was studied. The weight of seminal vesicles and epididymides showed a dose dependent inhibition with FLU, while testicular weight exhibited a biphasic response, its value being increased by 20% at lower FLU doses and reduced by 15% at higher FLU doses. An elevation of testicular and epididymal androgen-binding protein (ABP) content and also of testicular testosterone content was observed with both doses of FLU. Serum levels of LH and testosterone exhibited a four-fold increase, at both doses of FLU, while FSH serum level was elevated depending on the dose of FLU used. Results suggest that in the golden hamster the maintenance of the weight of testes and accessory organs depends mainly on androgenic stimulation, while production and transport of ABP is probably regulated by gonadotropins.     

Ontogeny of gonadotropin, testosterone, and inhibin secretion in normal boys through puberty based on overnight serial sampling

To investigate hormonal changes occurring in male puberty, we measured LH, FSH, testosterone, and alpha-inhibin immunoactivity in serum samples drawn every 10 min for 8 h (2100-0500 h) from each of 50 normal prepubertal and pubertal boys, aged 8.4-18.8 yr. We measured gonadotropins with ultrasensitive immunofluorometric assays, and testosterone and alpha-inhibin with RIAs. Unlike previous studies, which indexed pubertal development with Tanner stages, we used testicular volume, a more finely graduated indicator of development, to reveal patterns that were obscured when subjects were grouped by Tanner stage. The overnight mean concentration of each hormone increased with testis volume, but the rate of increase on a logarithmic scale slowed as testes grew. Log LH rose precipitously in the late prepubertal and early pubertal periods and plateaued during mid- and late puberty. Based on fitted regression curves, LH increased about 20-fold (from 0.11 IU/L) between testis volumes of 1 and 10 mL, but only an additional 1.5-fold by 30 mL. The developmental trajectory of log testosterone was like that of log LH, but rose less steeply early in puberty. From 0.14 micrograms/L at a testis volume of 1 mL, testosterone increased about 8.5-fold by 10 mL and an additional 3-fold by 30 mL. In contrast, logarithms of overnight mean FSH and alpha-inhibin concentrations rose at a more nearly constant rate throughout puberty. From 0.62 IU/L at a testis volume of 1 mL, the FSH concentration doubled by 10 mL and increased an additional 1.7-fold by 30 mL. From 270 ng/L at a testis volume of 1 mL, inhibin increased 1.5-fold by 10 mL and an additional 1.3-fold by 30 mL. Overnight pulse amplitudes exhibited developmental trajectories similar to those of the corresponding overnight mean concentrations. The number of LH and testosterone pulses during the sampling period averaged 2.2 and 2.1, respectively, at Tanner stage 1 and increased to 4.5 and 3.2, respectively, at Tanner stage 5. The number of FSH and inhibin pulses remained constant throughout puberty, averaging 3.3 and 3.5, respectively. Pairwise correlations among hormone concentrations were strong, reflecting common increasing trends through puberty; however, after accounting for developmental trends, FSH, LH, and testosterone concentrations remained correlated, whereas inhibin was uncorrelated with each of the other three hormones. Measuring gonadotropins with ultrasensitive assays and analyzing the results on a logarithmic scale as a function of testis volume made clear the dramatic hormonal changes that begin before the clinical changes of puberty.     

The effects of pineal indoles given late in the light period on reproductive organs and pituitary prolactin levels in male golden hamsters

Intact and pinealectomized adult male hamsters kept in light:dark cycles of 14:10 (in hours) were given daily injections of either 25 microgram melatonin, 5-methoxytryptophol, N-acetylserotonin, or 6-hydroxymelatonin at 19.00 hours (13h after lights on). The injections were continued for 50 consecutive days. The daily melatonin injections significantly elevated body weights and depressed the growth of the testes and accessory sex organs and pituitary prolactin levels in intact hamsters. By comparison, in pinealectomized animals daily afternoon melatonin injections failed to alter body or testicular weights or pituitary prolactin levels. These findings indicate that for single injections of melatonin to be antigonadotrophic in the male hamster, the pineal must be intact. In intact animals, 5-methoxytryptophol and N-acetylserotonin slightly depressed the growth of the reproductive organs and pituitary prolactin levels, respectively. Again, these effects were negated by removal of the pineal gland. 6-Hydroxymelatonin was without influence on any of the parameters of reproduction that were measured.     

Female choice and manipulations of forceps size and symmetry in the earwig Forficula auricularia L

Nutrition influences the reproductive axis via alteration of gonadotrophin secretion. However, a link between nutrition and the secretion of GnRH, which drives the axis, has yet to be established. The aim of the present study was to measure the change in the concentrations of metabolic substances in the cerebrospinal fluid of adult male sheep offered a diet designed to maintain constant gonadotrophin secretion (Group M; n = 6), or a diet known to increase gonadotrophin secretion (Group M + L; n = 6). On days 1, 3 and 10 of the dietary treatments, cerebrospinal fluid and jugular blood were sampled and analysed for metabolic fuels (glucose, amino acids and free fatty acids) and metabolic hormones (insulin, insulin-like growth factor I, GH, prolactin, cortisol and the thyroid hormones). On day 11 of the dietary treatment, LH pulse frequency and mean FSH concentrations in Group M + L had increased relative to Group M and to day 0. Plasma concentrations of prolactin and insulin on days 3 and 10, and glucose and insulin-like growth factor I on day 10, were higher in Group M + L than in Group M, but only cerebrospinal fluid concentrations of insulin, glucose and certain amino acids were affected by the dietary treatments on days 3 and 10. Cerebrospinal fluid, but not plasma, concentrations of aspartate, tyrosine, cystine, phenylalanine and arginine on day 3, and glutamine, gamma-aminobutyric acid, threonine, alanine on days 3 and 10, were higher in Group M + L relative to Group M. On day 10, plasma and cerebrospinal fluid concentrations of arginine, phenylalaine, proline, tyrosine, methionine and phosphoserine, but only the plasma concentrations of linoleic acid, aspartate and serine, were higher in Group M + L than in Group M. Concentrations of triiodothyronine, thyroxine, and cortisol in plasma and cerebrospinal fluid were not affected. These results show that the nutritional stimulation of gonadotrophin secretion is accompanied primarily by fluctuations in plasma and cerebrospinal fluid concentrations of insulin and certain amino acids, which suggests that, when nutritional status is improved, insulin, amino acids and possibly glucose interact to modulate GnRH secretion.     

Reassessing the role of urodynamics after cerebrovascular accident. Males versus females

Adult, male Syrian hamsters received daily subcutaneous melatonin (25 microg) injections or vehicle injections at 08:00 or 17:00 hr for 11 weeks. Body weights were measured weekly throughout the experiment and testes weights, spleen weights, and serum was collected at the end of the experiment. The spleens were sectioned and immunocytochemically analyzed for immunoglobulin G and serum levels of interferon-gamma, interleukin-2, and interleukin-4 were determined in heterologous mouse assays. Melatonin injections at 17:00 hr, but not at 08:00 hr, increased body weights, decreased testes weights and serum testosterone levels, and had no effect on immunoglobulin G content in the spleen. Likewise, melatonin injections at 17:00 hr, but not at 08:00 hr, increased serum interferon-gamma levels, had no effect on interleukin-2 levels, and appeared to increase interleukin-4 levels. Since melatonin injections at 08:00 hr were ineffective in altering immune measurements and correlations between reproductive measures and immune measures were high, the most parsimonious explanation for these results is that melatonin injections at 17:00 hr depressed reproductive hormone levels and these depressed levels altered immune measures.     

Role of gonadal hormones in incubation behavior of male ring doves (Streptopelia risoria).

Examined the role of testicular hormones in the incubation behavior of 85 male ring doves. Intramuscular injection of testosterone propionate (TP) at 100 mg/day to intact or castrated Ss throughout a reproductive cycle had no deleterious effects on sitting or crop-sac growth. Similarly, castrated Ss given TP only until the start of a reproductive cycle incubated normally. Thus, changes in androgen titer following courtship do not affect incubation behavior. In contrast, progesterone administered to intact Ss at 100 mg/day throughout a reproductive cycle interfered with both sitting behavior and crop-sac growth. It is concluded that high levels of progesterone (whether of gonadal or adrenal origin) would be incompatible with maintenance of incubation, possibly because of interference with prolactin secretion. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)