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At least 829 records · Page 46Linked to original sources
PubMed1979

Suppression of follicular cAMP and steroid response to gonadotrophins by pretreatment with gonadotrophin.

This study examines the effect of preincubation of sheep ovarian follicles with hCG or FSH on the ability of isolated theca and granulosa to increase cAMP levels in response to a second incubation with hCG or FSH. Secondly, the effect of preincubation of small follicles with hCG on androstenedione and testosterone production is examined in intact follicles. Preincubation with hCG resulted in a decrease in the ability of theca from large (4--6 mm in diameter) and small (1--3 mm) follicles and granulosa from large follicles to increase cAMP levels in response to a second exposure to hCG. Similarly, preincubation with FSH suppressed the response of isolated granulosa from small and large follicles to a second exposure to FSH. A partial, but significant inhibition of the response to the other hormone was observed after preincubation with both FSH and hCG. Intact small follicles pretreated with hCG were unable to increase testosterone secretion in response to a second exposure to hCG.

Androstenedione↗
PubMed1982

Temporal patterns of serum luteinizing hormone and testosterone and endocrine response to luteinizing hormone releasing hormone in aging male rats.

Temporal patterns of serum testosterone and luteinizing hormone (LH) concentration and responsiveness to luteinizing hormone releasing hormone (LHRH) were measured in young (2 to 3 months), middle-aged (12 to 13 months), and aged (22 to 26 months) male rats. Average testosterone and LH concentrations, as well as individual sample variations, were higher in young than in middle-aged and aged rats and higher in middle-aged than in aged groups. In addition, the young group showed a diurnal pattern of serum testosterone concentration and greater ranges of LH and testosterone concentrations in individual blood samples. Young male rats showed greater increases in serum LH and testosterone than middle-aged and aged groups after intravenous LHRH, 1 and 5 ng/g of body weight. These data indicate that LH and testosterone secretion are progressively reduced in the aged male rat and suggest alterations in neuroendocrine control of pituitary gonadotropin secretion as the most important alteration in the gonadal control system in these animals.

Aging↗
PubMed1992

Neuroendocrine effects in printing workers exposed to toluene.

The effect of exposure to toluene on plasma concentrations of testosterone, prolactin, luteinising (LH) and follicle stimulating (FSH) hormones was investigated in 47 rotogravure printers (time weighted average air toluene below 80 ppm; blood toluene concentration post-shift 0.19-7.99 mumol/l) and compared with a reference group. Increasing exposure concentrations of toluene (concentrations less than 5 to greater than 45 ppm) were significantly associated with decreasing plasma concentrations of LH (tau = -0.21, p = 0.003) and testosterone (tau = -0.25, p = 0.02). No correlation was found between cumulative exposure (ppm x years) and plasma hormone concentrations. The associations with exposure were present even when nine printers with heavy alcohol consumption were excluded. The study indicates an effect of low toluene exposure on the hypothalamus-pituitary axis, with a secondary decrease in testosterone secretion.

Adult↗
PubMed1993

In vivo acute testicular testosterone response to injection of luteinizing hormone in the rat fetus.

The acute in vivo testosterone response to LH stimulation and its change during late fetal life were determined in the rat. In 18.5-day-old fetuses, testicular testosterone content was increased in a dose- and time-dependent manner after fetal subcutaneous LH injection. The maximum response was small: the testicular content and plasma concentration were increased by 200% and 250% over basal values respectively, while they were increased 1100% and 1200% in adult rats. Similarly, comparable low responses were obtained after subcutaneously injecting the fetuses with human chorionic gonadotropin (hCG) and after injecting LH into the vitelline vein. Between days 18.5 and 21.5 of fetal life, the testosterone levels in the testis and plasma of uninjected or PBS-injected fetuses decreased and were comparable in both groups. In maximally LH-stimulated fetuses, the testicular content did not change with age, and plasma concentration was lower on day 21.5 than on day 18.5. Since the number of Leydig cells increases 1.5 to 2-fold between days 18.5 and 21.5, these results show an age-related decrease in basal and maximally LH-stimulated in vivo testosterone secretions per Leydig cell during late fetal life.

Analysis of Variance↗
PubMed1984

The dark mink: a model of male infertility.

Breeding mink for a fine dark fur has coselected male infertility, which may be manifest at the onset of breeding (primary infertility) or after one or more fertile breeding seasons (secondary infertility). Mink with primary infertility have low LH and testosterone levels. However, they respond to exogenous GnRH with increases in LH production and in the number and size of LH and FSH positive gonadotropes in the anterior pituitary. Exogenous human CG also induces testosterone secretion. Thus, mink with primary infertility are probably defective in GnRH secretion, which is due either to abnormal hypothalamic function or its control mechanisms. Autoimmune orchitis with testicular immune complexes are frequent in mink with secondary infertility, suggesting an autoimmune etiology. In contrast, fertile dark mink and fertile mink with the opaline and pastel fur have normal serum LH and testosterone levels; their testes are also normal. In mink with secondary infertility, the frequency and degree of orchitis and testicular immune complexes increased from March (peak sexual activity) to April (onset of testicular regression). Thus, testicular autoimmunity most likely develops during testicular regression. Antisperm antibodies also increased in frequency during testicular regression in the fertile dark mink and in dark mink with primary and secondary infertility. Thus, antisperm antibody per se is insufficient to induce autoimmune orchitis. It is concluded that the infertile mink is a useful model of human male infertility, involving both endocrinological and immunological mechanisms.

Animals↗
PubMed1979

Further studies on hypothalamic-pituitary-testicular function in old rats.

The dysfunction of the hypothalamic-pituitary-gonadal axis in old age was studied in 24-month old male Wistar rats which were compared with 3-month old animals. The hypothalamic LH-RH content and the pituitary LH were significantly lower in the old than in the young adult animals. The plasma concentrations of LH and testosterone were significantly higher in the young rats. The primary cause of these age-dependent changes probably is a hypothalamic dysfunction. When isolated Leydig cells of young and old rats were incubated in vitro, the testosterone secretion per cell was significantly smaller in old than in young cells with as well as without HCG stimulation. In vivo stimulation of rats by iv injection of biologically active iodinated hCG revealed that the intratesticular uptake of the gonadotrophin was not different in young and old rats. The testosterone response, however, was significantly reduced in old age. An in vitro "desensitisation" experiment in which the LH receptor capacity was artificially reduced demonstrated that the 40% reduction of receptor capacity in old testes as described earlier will not impair the testicular uptake of gonadotrophin from blood. Repeated injection of hCG results in equally elevated testosterone concentrations in young and old rats.

Age Factors↗
PubMedDate not supplied

Follicle stimulating hormone, luteinizing hormone and testicular Leydig cell responses to estradiol immunization in Ile-de-France rams.

Active immunization of Ile-de-France rams against estradiol (E2) resulted in the production of E2-neutralizing antibodies and an elevation in the plasma concentrations of FSH, LH, and testosterone. The presence of E2 antibodies did not affect the testosterone metabolic clearance rate, indicating that the immunization-mediated 10-fold increase in plasma testosterone was the result of a 10-fold increase in testicular testosterone production. Testis weights, as well as nuclear and cytoplasmic volumes of individual peritubular and perivascular Leydig cells, were greater in E2-immunized rams than in albumin-immunized controls. Leydig cell numbers were not affected by treatment. The E2 antibodies were capable not only of neutralizing the inhibitory effects of endogenous E2 on gonadotropin levels in intact rams, but were able to block the effects of exogenously administered E2 on their FSH and LH secretory response to castration. It is concluded that circulating E2 in the ram is involved in pituitary-testicular endocrine homeostasis and that E2 immunoneutralization can be employed to enhance testosterone secretion in this species.

Animals↗
PubMed1993

Morphological changes in the thecal layer during the maturation of the preovulatory ovarian follicle of the domestic fowl (Gallus domesticus).

The aim of the present study was to evaluate changes in the steroidogenic tissue, the blood vessels and the undifferentiated cell islets observed in the theca of developing follicles in the hen ovary. Samples of preovulatory follicles (F1 to F5 in order of decreasing size) and small yellow follicles (SYF) were obtained from White Leghorn hens for light microscopy studies. Cell suspensions of the whole theca obtained from follicles at the same stage of development were analyzed for 17 beta-estradiol and testosterone secretion. Typical steroidogenic cells with abundant cytoplasmic lipid droplets were identified in the theca interna beside blood vessels and nerve fibers. Islets of undifferentiated cells were observed in the theca externa. The steroidogenic tissue of the theca interna was evident in the small yellow follicle. However, considering the growth of the developing follicle, the total volume of steroidogenic cells increased from the SYF up to F1 follicle. The blood vessels reached the maximum development in the largest follicle (F1). On the other hand, undifferentiated cell islets were markedly reduced in the F1 follicle. The structural changes herein described could be correlated to modifications in the steroid hormone secretion during the maturation of the ovarian follicle.

Analysis of Variance↗
PubMed1977

Exogenous androgen activates female behavior in noncopulating, prenatally stressed male rats.

Male copulatory behavior was severely impaired in the male offspring of female rats stressed during pregnancy. This deficiency persisted even after castration and prolonged treatment with testosterone propionate and after exposure to electric skin shock. However, androgen treatment effectively activated female lordotic behavior in a large percentage of prenatally stressed males but not in any control animals and in only a negligible number of postnatally stressed males. Although prenatal stress demasculinizes and feminizes behavior, no modifications of reproductive morphology were detectable. It is postulated that prenatal stress alters normal sexual behavior differentiation by attenuating testosterone secretion from the fetal testes.

Animals↗
PubMed2001

Effects of paint thinner exposure on serum LH, FSH and testosterone levels and hypothalamic catecholamine contents in the male rat.

We have investigated the effects of thinner inhalation on serum LH, FSH and testosterone levels together with changes in hypothalamic catecholaminergic system in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into two groups and exposed to paint thinner in a glassy cage for 15 or 30 d. Toluene concentration (the largest constituent in thinner, 66%) was set at 3000 ppm in the inhalation air. At the end, all animals were decapitated and blood samples obtained. Serum LH and FSH levels were measured by RIA and testosterone by enzyme immunoassay. Following removal of brains on dry ice, medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus were isolated by micropunch technique. Noradrenaline, 3,4-dihydroxyphenylglycol (DHPG) and dopamine concentrations of these hypothalamic areas were determined by HPLC-ECD. Fifteen-day thinner inhalation significantly suppressed serum LH and testosterone levels in parallel (p<0.001) compared to control group values (LH: 0.77+/-0.07; testosterone: 2.67+/-0.39). Thirty-day exposure markedly decreased LH levels (p<0.001), but surprisingly had no significant effect on testosterone. Serum FSH levels were not significantly altered in either group. Thinner inhalation for 15 or 30 d did not cause any significant change in noradrenaline, DHPG or dopamine concentrations in the hypothalamic regions examined (except in the arcuate nucleus). These results suggest that paint thinner has an anti-gonadotropic effect and may cause long-term endocrine disturbances in the male. It is thought that the hypothalamic catecholaminergic system is not involved in thinner inhibition of LH and testosterone secretion.

Animals↗
PubMed1993

[Does a short-term hemodialysis treatment influence function of the pituitary-testicular axis in patients with chronic renal failure?].

Abnormal function of the pituitary-gonadal axis is a well documented endocrine abnormality in chronic renal failure (CRF). The purpose of the work was to assess the influence of the short-term haemodialysis treatment on LH, FSH and testosterone secretion. In 17 men dialyzed up to 50 months and 10 non-dialyzed male patients with advanced CRF the test of stimulation with LHRH was done. Results obtained in patients were compared with those assessed in healthy subjects. Significantly higher concentration of LH and FSH and lower concentration of testosterone in serum under basal conditions were found in patients as compared to controls. Basal concentrations of LH, FSH and testosterone in dialyzed patients and in non dialyzed men were similar. The area under the curve of LH, FSH and testosterone in both groups of patients was similar. These results suggest that in men dialyzed shorter than 50 months haemodialysis treatment does not change significantly the function of the pituitary-testicular axis as compared to men with advanced CRF.

Adult↗
PubMedDate not supplied

Influence of photoperiod, ambient temperature and melatonin on testosterone synthesis and release during reproductive maturation in male deer mice.

Four experiments were designed to investigate the influence of photoperiod and other environmental factors on androgen production and reproductive maturation in deer mice. Male prairie deer mice (Peromyscus maniculatus), born in a light/dark cycle of 6L:18D, either remained in this short photoperiod or were switched to a long day regimen of 16L:8D at weaning. In a cross-sectional experiment, the deer mice were killed between 3 and 8 weeks of age for measurement of serum testosterone concentration and reproductive organ weights. In a second experiment, blood was collected from each mouse at weekly intervals between 3 and 9 weeks of age. This repeated measures design was used to reduce the high variability in testosterone values observed in the first experiment. Reproductive organs were weighed at the termination of the experiment. Testosterone concentrations and reproductive organ weights were greater in males reared in the long photoperiod in both experiments. In a third experiment, the animals were housed under five different conditions to test the influence of high ambient temperature and melatonin as well as photoperiod. At 7 weeks of age, they received an injection of hCG or saline. More testosterone was released in deer mice reared in 16L:8D and 27 C than in those reared in short days (6L:18D) or those reared in high ambient temperature (35 C) or those treated with exogenous melatonin. One week later, animals were sacrificed. The single hCG treatment caused significant reversal of the suppression of accessory sex organ weights following melatonin, short days or 35 C temperature. In a fourth experiment, the additive influence of melatonin and 35 C temperature was tested. Animals treated with 35 C or both melatonin and 35 C had lower serum testosterone at 7 weeks of age, released less testosterone after hCG, and had smaller organ weights with or without hCG than long day controls. The influence of melatonin treatment and 35 C temperature appears to be additive for testicular weight and testosterone release after hCG. Thus, the attenuation of reproductive development that accompanied short days, melatonin treatment and high ambient temperature occurred via diminished testosterone secretion, which can be overcome at least in part by gonadotropin treatment.

Animals↗
PubMed1999

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. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1975

High-resolution biomedical gas chromatography. Determination of human urinary steroid metabolites using glass open tubular capillary columns.

Recently developed analytical procedures for the qualitative and quantitative analysis of human urine for major and minor steroid metabolites are described. Steroid profile samples were obtained by enzymic hydrolysis with beta-glucuronidase and sulfatase. Methoxime-trimethylsilyl ether derivatives of steroid metabolites were prepared; the recommended procedure converts all ketone groups (except the 11-one group) into methoxime groups and all hydroxyl groups into trimethylsily ether groups. These derivatives are thermally stable, readily volatilized, not subject to dehydration or adsorption on gas chromatographic columns, and suitable for both quanlitative and quantitative analytical studies. Thermostable glass open tubular capillary columns, coated with the non-polar phase SE-30, and containing dispersed particles of silanized silicic acid, were used for the gas chromatographic separation. Illustrations of profiles for normal female and male subjects, and patients with a testosterone-secreting ovarian tumor, congenital adrenal insufficiency and a dehydroepiandrosterone-secreting adrenal tumor are included.

Adrenal Gland Neoplasms↗
PubMed1982

Testicular function after torsion.

A group of 20 patients with torsion was investigated. The study indicated that immediate surgical intervention with a period of torsion of the testis of less than 6 h will prevent impairment of testicle function. The histology of testicular biopsies taken from such patients revealed only interstitial oedema and, at the most, partial necrosis. If torsion time exceeded 6 h testicular histology revealed severe alterations, and surgical correction could not prevent atrophy of the testis. Patients with pathological spermiograms showed FSH values over or at the upper limit of the normal range. As far as can be concluded from one single basal hormone determination, the testosterone secretion remained unaltered. Libido, potency and virilization remained normal.

Adolescent↗
PubMed1999

Normal suppression of the reproductive axis following stress in corticotropin-releasing hormone-deficient mice.

The hypothalamic neuropeptide CRH has been postulated to inhibit LH secretion by a central action within the brain. To characterize the physiological significance of CRH in stressor-induced inhibition of LH secretion, CRH-deficient and wild-type mice were subjected to restraint or food withdrawal, and plasma LH levels were determined. The proestrus LH surge of female mice was equally suppressed by restraint in both genotypes, and central administration of a CRH antagonist did not alleviate this suppression in either genotype. Male mice of both genotypes also demonstrated suppression of both LH and testosterone secretion following restraint. Furthermore, food withdrawal caused similar suppression of LH secretion in both female and male mice regardless of CRH status. These data demonstrate that CRH is not necessary to inhibit LH secretion following either restraint or food withdrawal and that other molecules are able to suppress LH secretion during the response to stress in the context of CRH deficiency.

Animals↗
PubMed1976

Studies on human sexual development. III. Fetal pituitary and serum, and amniotic fluid concentrations of LH, CG, and FSH.

Fetal sera (9-20 weeks fetal age, n = 80) and pituitary glands (9.5-20 weeks, n = 36) obtained from hysterotomy specimens, and amniotic fluids (amniocentesis; 8-40 weeks, n = 123) were assayed for FSH, LH (betaLH assay) and CG (betaCG assay). Results are expressed as mass of pure hormone. Prior to 12 weeks fetal age, pituitary, serum and amniotic fluid concentrations of LH and FSH were low or unmeasurable. In contrast, levels of CG in serum and in amniotic fluid were clearly measurable prior to 12 weeks. There was a definite CG peak at 11-14 weeks with levels up to 550 ng/ml in serum and 7400 ng/ml in amniotic fluid. Although LH levels began to rise at 12 weeks, when CG levels started to decline, serum levels of LH from 14-20 weeks in males (2-13 ng/ml) were still lower than the majority of CG levels at this time (6-115 ng/ml). These observations suggest that CG is the primary stimulus to the fetal Leydig cell which results in testosterone secretion (peak 11-17 weeks) and masculine differentiation of the genital tract. Significantly lower concentrations of both FSH and LH were observed in pituitary, serum and amniotic fluid between 12-20 weeks fetal age in males compared to females. This may be a result of feedback inhibition by the higher concentrations of testosterone in males at this time. Amniotic fluid FSH and LH concentrations correlated with their respective serum and pituitary values (P less than 0.01) indicating that amniotic fluid may provide a convenient index of fetal serum concentrations.

Amniotic Fluid↗
PubMed1999

Reproductive and endocrine function in rams exposed to the organochlorine pesticides lindane and pentachlorophenol from conception.

There is controversy over the potential endocrine modulating influence of pesticides, particularly during sensitive phases of development. In this study, ram lambs were exposed to lindane and pentachlorophenol from conception to necropsy at 28 weeks of age. The rams (and their mothers) were given untreated feed (n = 7) or feed treated with 1 mg kg-1 body weight per day of lindane (n = 12) or pentachlorophenol (n = 5). Semen was collected from 19 weeks onwards and reproductive behaviour was tested at 26 weeks. Serum was collected every 2 weeks and at 27 weeks every 15 min for 6 h during both day and night, and for 1 h before and 5 h after stimulation with GnRH, adrenocorticotrophic hormone and thyroid-stimulating hormone. The pesticides did not affect body weight and ejaculate characteristics, or cause overt toxicity. In pentachlorophenol-treated rams, scrotal circumference was increased. However, seminiferous tubule atrophy was more severe and epididymal sperm density was reduced in comparison with untreated rams at necropsy (P < 0.05). Thyroxine concentrations were lower in pentachlorophenol-treated rams than in untreated rams (P < 0.05). However, after thyroid-stimulating hormone treatment, the thyroxine response was unaltered. Reproductive behaviour was reduced in lindane-treated rams compared with control rams (P < 0.05). Serum LH and oestradiol concentrations during reproductive development, LH pulse frequency at 27 weeks and testosterone secretion after GnRH treatment were lower in lindane-treated rams than in untreated rams (P < 0.05). In summary, the effects of pentachlorophenol on the testis may be linked to a decrease in thyroxine concentrations, and reduced reproductive behaviour in lindane-treated rams may be related to decreased LH, oestradiol and testosterone concentrations.

Animals↗