Maximum Concentration Of Testosterone Research Articles

Assessment of the influence of testosterone concentration in blood serum on meat productivity and meat quality of Aberdeen Angus bulls

The studies were carried out on Aberdeen Angus bulls at the age of 18 months. The animals, depending on the level of somatotropin in the blood serum, were divided into three groups using the percentile method: group I – up to the 25th percentile; Group II – within the 25-75 percentile; Group III – above the 75th percentile. Testosterone content was determined in blood serum by enzyme immunoassay using an automatic microplate analyzer Infinite F200 PRO. To study the meat qualities of the bulls, a control slaughter was carried out. It was established that bulls with the maximum concentration of testosterone in the blood serum were superior to individuals with the minimum concentration in pre-slaughter live weight by 3.4% (P≤0.05), in fresh carcass weight by 4.7% (P≤0.05), slaughter weight – by 3.6% (P≤0.01), pulp weight – by 5.4% (P≤0.05), protein accumulation in pulp – by 8.3% (P≤0.05), dry matter content – by 0.24% (P≤0.05), protein concentration – by 0.65% (P≤0.05), protein quality indicator – by 1.3% (P≤0.05) ). At the same time, they were inferior to them in weight and yield of internal fat by 12.1 (P≤0.001) and 0.6% (P≤0.05), respectively, in terms of bone content in the carcass - by 0.63% (P≤0 .05), relative fat content by 0.84% (P≤0.05).

Relationship between the seasonal changes in plasma testosterone and thyroxine concentrations with sperm cryoresistance in Gabon bucks.

Gabon buck is a breed with little marked seasonality in our latitude (Uruguay, 35° SL). The role of thyroid hormones on the regulation of their seasonal reproductive activity and sperm cryoresistance is unknown. Seasonal changes in testosterone concentration can affect sperm variables, but the influence of testosterone changes on sperm cryoresistance in other species determines that the recommended time for freezing sperm does not coincide with the period with greater sperm fresh quality. The objectives of the present work were to (i) describe the thyroxine seasonal pattern in bucks in a subtropical area, and its association with annual changes in sperm variables; (ii) relate the seasonal changes of testosterone and thyroxine concentrations with the sperm cryoresistance. For one year, semen of 10 adult Gabon bucks was collected by electroejaculation every two weeks. After sperm selection, the sample was frozen. Testosterone and thyroxine concentrations varied according to the month (P < 0.0001). Testosterone reached the greatest values in April (P < 0.0001) and May (P < 0.0001) and thyroxine reached minimum values (P < 0.0001) in the same months. During these months, a negative correlation ratio (CR) was found between testosterone concentration and CR-functional membrane (R = - 0.50; P < 0.0001). CR values for most sperm variables decreased during March-May, coinciding with the presence of maximum testosterone concentrations. In conclusion, high testosterone levels are associated with the worst sperm response to freezing-thawing process. Thyroxine concentrations have a strong seasonal pattern, but there was no relationship to sperm cryoresistance.

Functional endocrine reserves of testes of boars of different breeds and indicators of their sperm

It is difficult to objectively assess the functional state of the endocrine gland based on the level of hormones in the blood, since hormones vary significantly in absolute values during the day. Therefore, to assess the functional state of the endocrine glands in biological and medical practice, "load" is used. The criterion for evaluating the state of the gland is the change in the concentration of secreted hormone by the endocrine gland in response to the stimulation. As is known, the testis reacts relatively quickly to stimulation with chorionic gonadotropin. This allows us to determine the limiting features of the hormone-synthesizing and hormone activity of the testes and determine the maximum response of the testes to this stimulation. The object of the study was 6-month-old boars of large white breed, Landrace and tempo, 10 heads from each breed. In order to determine the functional endocrine reserves of the testes at 6 months of age, CG (chorionic gonadotropin) was administered intramuscularly at a dose of 1000 IU. HCG was administered 3 times every 72 hours. Blood for the determination of testosterone was taken before administration of HCG and 2.12,24,48 and 72 hours after its administration. Testosteron was determined by the enzyme immunoassay. Sperm counts in 18-month-old boars were studied using standard methods. Performed three-fold loads with an interval of 72 hours showed that the hormone level increased to 7.2±0.6 nmol/l in a large white breed 72 hours after the first administration of HCG, in the Landrace breed to 7.9±0.5 nmol/l, in the Duroc breed to 7.0±0.7 nmol/l, in the tempo breed to 7.0±0.6 nmol/l. After the second injection HCG the testosterone levels in large white breed boars increased by 1.2 nmol/l, and breeds Duroc 1.7 nmol/l, Landrace 0.1 nmol/L. In the boar breed, tempo increased the hormone by 0.4 nmol/l. In this regard, the increase in testosterone in experimental boars continued, which means that the reserves of endocrine function of the testes were not fully realized, so the 3rd stimulation of HCG was also performed. In a large white breed of boars and Duroc, the maximum concentration of testosterone was observed 24 hours after administration of HCG and was 9.2±0.7 and 8.9±0.5 nmol/l respectively. In the Landrace and tempo breeds, the maximum concentration of testosterone was 2 hours after 3 CG stimulation and was 8.2±0.6 and 7.5±0.6 nmol/l. respectively. In terms of sperm, its fertilizing capacity and the production of live piglets per Farrow, the indicators were higher for boars of large white breed and Duroc.

The Endocrine Function of Testes in 12- and 18-Month-Old Boars of Different Breeds.

Testes have several primary functions, such as male gametes production (spermatozoa) and secretion of several endocrine factors, including the production of steroid and protein hormones which facilitate elements in the healthy reproductive function of mammals. The potential of an animal functional endocrine reservoir could be an interesting finding in animal reproduction management. Therefore, the current study aimed to analyze the functional endocrine reserves of testes in 12- and 18-month-old boars of four different boar breeds, namely Large White, Landrace, Duroc, and Tempo, as the animal model in this research (n=10). To determine the functional endocrine reserves of the testes at 12 and 18 months of age, boars received injections of human chorionic gonadotropin (hCG) 3 times every 72 hours. Testosterone was measured in blood samples (10 mL) taken from the jugular vein before the administration of hCG as well as 2, 12, 24, 48, and 72 hours after administration of each of three hCG injections. The index of endocrine activity of the testes was determined by the formula: Ita = T1 -T0 / T0 , where Ita is the index of endocrine activity of the testes, T0 is the testosterone concentration before the administration of hCG, and T1 is the maximum testosterone concentration after the third administration of hCG. The effects of the hCG injection on boar testes at different age periods indicated that the testes of Large White and Duroc boars have higher potential endocrine reserves compared with the Landrace and Tempo breeds.

The c-kit receptor protein in the testis of green frog Rana esculenta: seasonal changes in relationship to testosterone titres and spermatogonial proliferation

The green frog Rana esculenta is a seasonal breeder. The cyclic changes between almost arrested and highly activated spermatogenesis offer an ideal model to study basic mechanisms of spermatogenesis. In this study, we demonstrated, to our knowledge for the first time, c-kit receptor positive cells in the testis of this amphibian. The presence of c-kit receptor protein was confirmed by western blotting (Wb) analyses carried out in the testis during all the three main phases of the sexual cycle. The antibody recognized a band of about 150 kDa that was correlated with the positive staining in the germinal epithelium. The immunolabelling for c-kit receptor, evaluated by immunohistochemistry (IHC), was localized in I and II spermatogonia (SPG), in I and II spermatocytes, in both elongating spermatids and spermatozoa and in the Leydig cells. Furthermore, c-kit expression showed a seasonal pattern connected with both testicular and plasma profiles of testosterone during the reproductive cycle. The highest expression of c-kit receptor occurred during the reproductive period, when the testis exhibited the maximum concentration of testosterone. In this period, the mitotic activity of germ cell, assessed by both Wb and IHC analyses for proliferating cell nuclear antigen (PCNA), was intensive. Indeed, during the post-reproductive period, testosterone titres were the lowest and the expression of both PCNA and c-kit receptor protein in the testis, although present, is minor when compared with the reproductive phase. This evidence suggests that cell division can continue sufficiently to accumulate SPG for the next spring, when new germinal cells undergo multiplication. Finally, during the pre-reproductive period, testosterone levels begin to increase and mitotic activity of germinal epithelium is comparably enhanced. These events seem to precede the period of maximum stimulated spermatogonial proliferation, i.e. the reproductive period. These results suggest that the c-kit receptor may play a role in germ cell proliferation and provide a basis for future detailed investigation of regulatory factors of the proliferation of SPG.

Ovarian steroidogenic response to human chorionic gonadotrophin in obese women with polycystic ovary syndrome: effect of metformin.

The aim of the present study was to investigate the steroidogenic response pattern to HCG in obese women with polycystic ovary syndrome (PCOS) and the possible effects of metformin treatment on it. A single injection of human chorionic gonadotrophin (HCG, 5000 IU) was given to 12 obese [body mass index (BMI) > or = 27 kg/m2] women with PCOS and to 27 control women. Blood samples for assays of 17alpha-hydroxyprogesterone (17-OHP), androstenedione, testosterone and oestradiol were collected at baseline and 1, 2 and 4 days after the injection. Responses to HCG were also assessed in the PCOS women after 2-month treatment with metformin (500 mg x 3 daily). Serum 17-OHP and oestradiol concentrations peaked at 24 h in the PCOS women and preceded the maximum testosterone concentration, which was seen at 48 h. In the control women the maximum concentrations of all these steroids were reached 96 h after HCG. After metformin treatment, the basal serum testosterone concentration and the areas under the androstenedione (AUC(A)) and testosterone (AUC(T)) response curves after HCG decreased significantly. The results demonstrate that obese PCOS women have a male-type steroidogenic response pattern to a single injection of HCG and a higher androgen secretory capacity than control women, which may be explained by the increased thecal cell activity in the polycystic ovary. The slight alleviation of hyperandrogenism brought about by metformin therapy appears to be due to its effect on ovarian steroidogenesis possibly mediated by decreased insulin action.

Reproduction in the squirrel glider, Petaurus norfolcensis (Petauridae) in south-east Queensland

Reproduction was studied across a three-year period in two south-east Queensland populations of the squirrel glider, Petaurus norfolcensis, by measuring morphological (body weight, scrotal diameter, cutaneous scent-gland activity, condition index) and physiological (plasma steroid levels) variables. Reproduction showed a seasonal pattern, with peak numbers of pouch young recorded in late autumn and winter. Declines in oestrogen concentrations outside the breeding period indicate that females are anoestrous in the summer months. Most (83%) reproductive females captured during the study were 2–3 years old, but all individuals over one year of age were found to have bred. Average litter size was 1.73 ± 0.01 (n = 23). Scrotal diameter and testosterone concentrations showed no significant seasonal variation. It is suggested that this is due to the presence of both socially dominant and subordinate males in the data set. Maximum testosterone concentrations did coincide with periods of mating. The condition index showed no relationship with reproductive variables, but it is likely that this results from the manner in which the index was generated.

Rewarding Properties of Testosterone in Intact Male Mice: A Pilot Study

The present study examined the rewarding properties of 4-androsten-17β-ol-3-one testosterone in intact male mice using the conditioned place preference (CPP) technique. In Experiment 1, the pharmacokinetics of 0.8 and 1.2 mg/kg of testosterone were studied to determine the most appropriate temporal interval to test behavior. Additionally, the locomotor activity was recorded to control a possible interfering effect on CPP. The maximum testosterone concentration was registered at 45 min of administration, and no effects on activity were found. In Experiment 2, three groups of male OF-1 mice received four pairings of the least-preferred compartment with testosterone (0.8, 1, or 1.2 mg/kg, SC) for 30 min. On alternate days the preferred compartment was paired with vehicle for 30 min. The control group received vehicle in both compartments. No significant differences between groups were found in the time spent in the drug-paired compartment. However, when separate analyses were performed in conjunction with the color of the drug-paired compartment, CPP was observed only in animals pairing testosterone/black compartment. These results suggest that rewarding properties of testosterone treatment can be observed in male mice; these effects probably being dependent on the environmental cues used as conditioned stimuli.

Progesterone and testosterone concentrations during oestrous cycle and pregnancy in the common vole ( Microtus arvalis Pallas)

Serum progesterone and testosterone concentrations were measured during different stages of oestrous and pregnancy in paired and unpaired female common voles ( Microtus arvalis). Hormone concentrations were measured by ELISA, and cycle stages were determined by vaginal smears. Paired females usually had serum progesterone concentrations of more than 10 ng/ml in the oestrous cycle. A significant maximum was detected in prooestrous (51.70±7.84 ng/ml, mean±S.D.). Serum progesterone concentrations increased from about 40 ng/ml at the beginning of pregnancy to about 70 ng/ml on days 15 and 16. The last 2 days before parturition (days 19 and 20) were characterised by a decrease of progesterone concentrations to ca. 30 ng/ml. The maximum concentration of testosterone was found in prooestrous (1.58±0.31 ng/ml). Concentrations during pregnancy varied between 1.5 and 2.1 ng/ml. In two of three cases unpaired females exhibited progesterone values below 10 ng/ml, but with varying vaginal smear patterns. The combination of progesterone concentrations and vaginal smear patterns was found to be regular in only 23.8% of the cases. The most frequent cycle stage found was the oestrous (44.2%). Mean concentrations of progesterone (10.43±13.81 ng/ml) and testosterone (0.85±1.11 ng/ml) in unpaired females were significantly lower than in paired females, thereby denoting reproductive inactivity in the former. The study presents basic data for several parameters of the reproductive biology in the common vole and confirms the importance of combining hormone assays and vaginal smear monitoring in reproductive research.

Postmenopausal steroid replacement with micronized dehydroepiandrosterone: Preliminary oral bioavailability and dose proportionality studies

OBJECTIVES: Because dehydroepiandrosterone may protect against neoplasia, osteoporosis, and cardiac disease, we investigated the bioavailability of oral micronized dehydroepiandrosterone, anticipating its adjunctive use in postmenopausal steroid replacement. STUDY DESIGN: Eight postmenopausal women randomly received either a placebo or 150 or 300 mg of oral micronized dehydroepiandrosterone in a lipid matrix. Serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, testosterone, and estradiol were measured periodically over the 12 hours after each dose. All treatments, all doses, and mean serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone were compared with analysis of variance for repeated measures and Newman-Keuls a posteriori test of statistical significance. RESULTS: Mean peak steroid concentrations after 150 mg (300 mg) doses were dehydroepiandrosterone 1617 (2639) ng/dl, 7 (11.5)-fold above placebo; dehydroepiandrosterone S 1185 (1688) /Jog/dl, 14 (20)-fold above placebo; and testosterone 183 (311) ng/dl, 4 (7)-fold above placebo. Estradiol concentrations remained <20 pg/ml, but androgen concentrations rose by 1 hour and remained elevated through the twelfth hour. Peak androgen concentrations and areas under the curves exhibited proportionality with both doses. A testosterone radioimmunoassay with celite chromatography revealed a 300% overestimation for testosterone in the direct-assay method used in this study. Thus after appropriate readjustment maximum testosterone concentrations were observed conSistently within phYSiologic premenopausal ranges after the 150 mg dose. CONCLUSIONS: Micronized dehydroepiandrosterone may provide a steroidal postmenopausal replacement that is adjunctive to estrogens and worthy of further investigation. (AM J caSTET GYNECOL 1992;166:1163-70.)

Postmenopausal steroid replacement with micronized dehydroepiandrosterone: Preliminary oral bioavailability and dose proportionality studies

Because dehydroepiandrosterone may protect against neoplasia, osteoporosis, and cardiac disease, we investigated the bioavailability of oral micronized dehydroepiandrosterone, anticipating its adjunctive use in postmenopausal steroid replacement. Eight postmenopausal women randomly received either a placebo or 150 or 300 mg of oral micronized dehydroepiandrosterone in a lipid matrix. Serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, testosterone, and estradiol were measured periodically over the 12 hours after each dose. All treatments, all doses, and mean serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone were compared with analysis of variance for repeated measures and Newman-Keuls a posteriori test of statistical significance. Mean peak steroid concentrations after 150 mg (300 mg) doses were dehydroepiandrosterone 1617 (2639) ng/dl, 7 (11.5)-fold above placebo; dehydroepiandrosterone S 1185 (1688) micrograms/dl, 14 (20)-fold above placebo; and testosterone 183 (311) ng/dl, 4 (7)-fold above placebo. Estradiol concentrations remained less than 20 pg/ml, but androgen concentrations rose by 1 hour and remained elevated through the twelfth hour. Peak androgen concentrations and areas under the curves exhibited proportionality with both doses. A testosterone radioimmunoassay with celite chromatography revealed a 300% overestimation for testosterone in the direct-assay method used in this study. Thus after appropriate readjustment maximum testosterone concentrations were observed consistently within physiologic premenopausal ranges after the 150 mg dose. Micronized dehydroepiandrosterone may provide a steroidal postmenopausal replacement that is adjunctive to estrogens and worthy of further investigation.

Influences of Season and Artificial Photoperiod on Stallions: Pituitary and Testicular Responses to Exogenous GnRH

Effects of season and photoperiod on the anterior pituitary gland and testes were studied by responses to exogenous GnRH. Stallions were assigned to one of three treatments: 1) control, exposed to natural day length; 2) S-L, 8 h of light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984; or 3) S-S, 8:16 from July 16, 1982 until March 5, 1984. Approximately every 8 wk, stallions were administered GnRH (2 micrograms/kg BW) and blood was sampled at 20-min intervals for 2 h before and 8 h after GnRH administration. Concentrations of LH, FSH and testosterone were determined. Baseline concentrations (mean of pre-GnRH samples) of all hormones fluctuated seasonally (P less than .05), but only LH and testosterone displayed seasonal changes (P less than .05) in maximum response to GnRH (highest concentration above baseline after GnRH). The FSH response to GnRH was not affected (P greater than .05) by season, photoperiod or the season X treatment interaction. Exposure of S-L stallions to 16:8 in December resulted in early recrudescence of baseline concentrations of LH, FSH and testosterone. Maximum concentration of testosterone in response to GnRH was stimulated by 16:8, but the increase in baseline LH concentrations in S-L stallions was not associated with an increase in maximum LH response to GnRH. Seasonal patterns of baseline concentrations of FSH and testosterone and maximum LH response to GnRH in S-S stallions were similar to those for control stallions.(ABSTRACT TRUNCATED AT 250 WORDS)

Inter-relationships between plasma luteinizing hormone, testosterone and cortisol as revealed by frequent blood sampling of mature bulls

Plasma LH and testosterone were measured in four mature bulls which were bled hourly for 8 h once a week for 3 consecutive weeks on 3 occasions. One 8 h period was not representative for a given bull but 3 weekly periods were more acceptable. In 3 of the 4 bulls there was a stress-related deterioration in LH and testosterone profiles characterized by early maximum testosterone concentrations. Cortisol concentrations were very high (>8 ng/ml) in one bull, and paralleled testosterone release in another. Basal values of cortisol ranged from 0·5 to 4 ng/ml. Very frequent sampling (every 2 min) during spontaneous increases in LH and testosterone revealed pulsatile release of both hormones at 10–15 min intervals. Initial rises in LH were followed 30–45 min later by measurable increases in testosterone. A decline from maximum LH values (10–18 ng/ml) occurred at least l h before maximum testosterone concentrations (8–12 ng/ml). GnRH (20 μg iv) increased LH values within 2 min resulting in raised pulsatile LH and testosterone profiles for the first hour very similar to spontaneous release. However LH then spontaneously increased to 25–47 ng/ml approximately 2 h after GnRH. A second 20 μg GnRH injection 3 h after the first resulted immediately in even higher LH values (55–70 ng/ml). Testosterone concentrations were not further increased after the first hour but remained steady at 12·5–25 ng/ml for 6 h after the first GnRH (basal testosterone 1–4 ng/ ml). In conclusion, pulsatile release of LH causes increases in gonadal steroidogenesis in bulls but the precise control mechanism appears to be different from that in cows. Increased adrenal activity appears to influence pituitary-gonadal relationships.

Seasonal patterns of free and conjugated androgens in the brown trout Salmo trutta

A radioimmunoassay for the simultaneous determination of testosterone, 11β-hydroxytestosterone, 11-ketotestosterone, and their glucuronides is described. The plasma concentrations of these steroids have been determined throughout the annual reproductive cycle of the male brown trout Salmo trutta. The maximum concentration of testosterone (33.2 ± 5.4 ng/ml in late September) precedes that of 11-ketotestosterone (68.7 ± 5.5 ng/ml) which coincides with the period of spermiation in early November. Peak concentrations of testosterone glucuronide (14.5 ± 2.7 ng/ml), 11β-hydroxytestosterone glucuronide (6.8 ± 1.6 ng/ml), 11-ketotestosterone glucuronide (5.4 ± 0.7 ng/ml), and 11β-hydroxytestosterone (3.2 ± 0.7 ng/ml) were also found in November. The ratio of free:conjugated testosterone drops significantly between August and December in the male (10.7-0.66) but not in the female (6.8-5.3). Factors such as hormones and mineral ions which may affect glucuronyl transferase activity are discussed, and a possible role for glucuronides in the normal functioning of the reproductive cycle in the trout is suggested.

Concentration of steroids in bovine peripheral plasma during the oestrous cycle and the effect of betamethasone treatment.

Testosterone, oestradiol and progesterone were measured in peripheral plasma during the oestrous cycle of 6 heifers. Oestradiol and progesterone results confirmed earlier reports. Concentration of testosterone on the day of oestrus was 40+/-3 pg/ml (mean+/-S.E.M.), and two peaks were detected during the cycle, one 7 days before oestrus (1809+/-603 pg/ml) and the other (78+/- 7 pg/ml) on the day before the onset of oestrus. The concentration of progesterone declined in most cases 1 day after the maximum concentration of testosterone. Betamethasone treatment in 5 heifers extended luteal function by an average of 10 days: plasma androstenedione and oestradiol concentrations were unaltered; cortisol values were depressed for at least 16 days after treatment; testosterone concentrations were lowered by 13+/-2-4% during treatment, and except in one heifer the peak on Day -7 was abolished.

The role of the liver and kidneys in the metabolism of intravenous testosterone by human subjects.

INTRODUCTION THE authors have previously reported the rryetabolism of intravenous testosterone by experimental animals (1). The present report is concerned with the metabolism of intravenous testosterone in human subjects. EXPERIMENTAL Solutions of testosterone in 25 per cent human serum albumin1 were prepared as previously described (1). To reduce bacterial contamination the solutions were prepared twelve hours prior to use and sterile techniques were employed throughout. Bacteriostatic amounts of penicillin and streptomycin were added to the solutions. The maximum concentration of testosterone in 25 per cent human serum albumin obtained in this way was 2.31 mg./ml. These testosterone-albumin solutions were administered to a total of 28 human subjects, both normal and diseased. Prior to administration each subject received a complete physical examination with special attention paid to the cardiovascular system in order to avoid cardiac embarrassment from the rapid administration of 100 ml. of 25 per cent...