Plasma sex hormone concentrations during the reproductive cycle in the male lizard, Podarcis s. sicula

Progesterone, 17-hydroxyprogesterone, androstenedione, 5 alpha-dihydrotestosterone, dehydroepiandrosterone, testosterone and oestradiol concentrations in the plasma were measured by simultaneous radioimmunoassay in males of the lizard Podarcis s. sicula. Hormonal determinations were performed at monthly intervals from January to December (except for August). Testosterone and androstenedione reached peak values of 174.8 ng/ml and 21.4 ng/ml in the mating season (spring) and then testosterone fell abruptly to 5.9 ng/ml in June remaining at this level during hibernation when dehydroepiandrosterone (DHA) reached a maximal level of 28.5 +/- 9.3 ng/ml. Castration resulted in a marked decrease of testosterone, androstenedione, dihydrotestosterone and DHA values, with DHA being significantly lowered only during the winter season. In castrated animals, however, testosterone and androstenedione persisted conspicuously in the plasma during the breeding period, suggesting that adrenal sex steroid output may change during the annual reproductive cycle. In intact animals, progesterone and oestradiol exhibited peak values during the refractory period after the mating season. We suggest a probable role of oestradiol in the induction of the refractory period in this lizard.     

Testosterone and androstenedione profiles in the blood of domestic tom-cats

Testosterone and androstenedione were measured in the blood of four mature, intact tom-cats. Samples were collected from an indwelling jugular catheter once an hour for 24 h, and at more frequent intervals after a number of experimental procedures. Testosterone and androstenedione concentrations have a pattern of episodic release over a 24-h period but no diurnal rhythm was evident. The range of testosterone concentration was 0–23.5 ng/ml and androstenedione concentration 0–35.7 ng/ml. There was evidence of some seasonal influence on testosterone concentration, it being low in the period of reduced sexual activity (Jan–March) and high in the period of peak sexual activity (Aug).Sexual stimulation did not cause a rise in testosterone concentration as it was already high, but androstenedione concentration was significantly increased.Castration produced an immediate decrease in testosterone to baseline concentrations of 0–0.5 ng/ml but the concentration of androstenedione was variable and it is probable that a substantial amount of androstenedione is contributed from another source (possibly from the adrenals).     

LH and testosterone responses to GnRH in red deer (Cervus elaphus) stags kept in a manipulated photoperiod

Six red deer stags from age 4 months were kept in a light-proof room under an artificial photoperiod consisting of 5.5 cycles of alternate 2-month periods of 16 h light and 8 h dark (16L:8D) and 8L:16D. At 2 or 3 weekly intervals from 10 months of age through 4 cycles, the stags were anaesthetized with xylazine and challenged i.v. with 10 micrograms GnRH. Blood samples were withdrawn immediately before and 10 and 60 min after injection. LH and testosterone concentrations were measured in all samples by RIA. Antler status was recorded daily. Peak LH values on each sampling day occurred in the sample taken 10 min after GnRH stimulation while peak testosterone occurred in the sample taken at 60 min. There were 4 cycles of LH and testosterone secretion accompanied by 4 antler cycles in the stags. The highest LH responses were detected during short days (8L:16D), and the highest testosterone responses were detected around the time of the change from short to long days. The responses of both hormones were lowest at the end of periods of long days or the beginning of short days. The increased pituitary LH response to GnRH was evident 4 weeks after the change to short days which are stimulatory for gonadal development. Antler casting occurred at the end of long days and cleaning at the end of short days. It is considered that antler cycles were due to the ability of the stags to vary release of LH and testosterone in response to changes in the artificial photoperiod.     

Resumption of gonadotrophin release during the post-partum period in suckling and non-suckling ewes

The post-partum secretion of LH, FSH and prolactin was monitored in 15 suckling and 6 non-suckling Préalpes du Sud ewes lambing during the breeding season by measuring plasma hormone concentrations daily at 6-h intervals and also weekly at 20-min intervals for 6 h from parturition to resumption of regular cyclic ovarian activity. There was a constant phenomenon in the resumption of normal patterns of FSH and LH secretion: there was a rise in FSH values culminating on average on Day 4 post partum and returning subsequently to values observed during the oestrous cycle, and concurrently an increase in the frequency and amplitude of LH pulses more progressive in suckling than in non-suckling ewes which led to an elevation of LH mean concentrations and occurrence of an LH surge. Since neither the FSH secretory pattern nor FSH mean values differed between suckling and non-suckling ewes, the results suggested that LH pulsatile pattern was a major limiting factor for the resumption of normal oestrous cycles. Before regular oestrous cycles resumed other changes in preovulatory LH surges also occurred: (i) they increased in duration and probably in amplitude; (ii) they were preceded by an acceleration in LH pulse frequency and a large decrease in FSH values as in normal cyclic ewes; and (iii) at least in non-suckling ewes they occurred concurrently with a prolactin surge.     

Diurnal and annual variation of adrenocortical activity in the squirrel monkey

Diurnal changes in basal cortisol levels and stress reactivity were assessed in male and female squirrel monkeys. Blood samples were collected at four-hour intervals throughout the day and night in the mating and nonmating seasons. Basal cortisol levels in females were similar in both seasons, but males tended to have higher cortisol levels during the mating season, especially at night. For both sexes, cortisol secretion was highest between 0400 and 0800 preceding the onset of the diurnal activity period. Assessment of cortisol responses following brief handling and anesthesia indicated that stress responses were relatively stable across the year, but cortisol increments were slightly higher in the nonmating season. Cortisol levels post-stress were generally related to prior baseline values. Thus, a knowledge of biorhythmic changes in basal hormone levels was important for predicting hormone levels after acute stressors. Males also underwent marked seasonal variation in their basal testosterone levels, which markedly altered the nature of their testosterone responses 30-minutes poststress. © 1995 Wiley-Liss, Inc.     

Testosterone and corticosterone during the breeding cycle of equatorial and European stonechats (Saxicola torquata axillaris and S. t. rubicola)

Northern-temperate male birds show seasonal changes in testosterone concentrations with a peak during the breeding season. Many tropical birds express much lower concentrations of testosterone with slight elevations during breeding. Here we describe testosterone and corticosterone concentrations of male stonechats from equatorial Kenya during different substages of breeding and molt. This tropical species has a short breeding season of approximately 3 months. We compare their hormone concentrations to previously published data of males of a northern-temperate relative, the European stonechat, also a seasonal breeder but with a breeding season of approximately 5 months. Equatorial stonechats show a pronounced peak of testosterone during the nest-building and laying stage. During all other stages, testosterone concentrations are low, similar to other year-round territorial tropical bird species. Corticosterone concentrations peak also during the nest-building and laying stage suggesting that this period of maximum female fecundity is a demanding period for the male. Equatorial stonechats have significantly lower concentrations of testosterone than European stonechats during all stages, except during the nest-building and laying stage. During this stage of maximum female fertility, testosterone levels tend to be higher in equatorial than in European stonechats. Our results suggest that equatorial stonechats belong to a group of tropical bird species that are characterized by a short breeding season and a brief high peak of testosterone during the female's fertile period. Such brief, but substantial peaks of testosterone may be common in tropical birds, but they may easily be missed if the exact breeding stage of individual birds is not known.     

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

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

Daily and seasonal variations in plasma LH and testosterone concentrations in the adult male hedgehog (Erinaceus europaeus)

A double-antibody heterologous radioimmunoassay (RIA) was developed to measure plasma LH values in hedgehogs. This RIA system used anti-rat LH serum and rabbit LH (AFP-559B) for radioiodination and as standard. The accuracy of the method was evaluated and indicated the ability to detect various relative concentrations of LH in plasma. The minimum detectable dose was 0.2 ng/ml. The intra- and inter-assay coefficients of variation were 4.2 and 7.9% respectively. Biological tests, e.g. effect of castration, effect of castration + testosterone implant and GnRH administration, confirmed that this method was suitable to determine subsequent changes in pituitary gonadotrophic activity in the hedgehog. LH concentrations were determined in blood samples obtained during 1 year: (a) each month, at 4-h intervals during 24 h, from different groups of unanaesthetized animals fitted with a catheter and (b) twice a month, under a light anaesthesia, from the same group of 6 animals. During the year: (1) the range of LH change was narrow (minimum values congruent to 0.25 ng/ml and maximum values congruent to 2.00 ng/ml); (2) the 24-h LH patterns did not exhibit any daily rhythm; (3) a clear annual rhythm was observed with the highest values from February to April and the lowest values in October and November. LH decreased rapidly at the end of summer and increased progressively from December to February, during hibernation. In these experiments, it was not possible to determine the characteristics of LH release patterns in the hedgehog but individual profiles indicated clearly the episodic secretion of LH, particularly during the highest pituitary activity period. During the year, a close relationship between the seasonal cycles of plasma LH and testosterone was observed.     

Plasma concentrations of testosterone,androstenedione, progesterone,oestradiol-17β, LH and FSH during the preovulatory period in the ewe

Seven mature ewes were synchronized to oestrus by two injections of 125 μg Cloprostenol given 9 days apart. Blood samples, collected for 72 h at 4-h intervals beginning 16 h after the second Cloprostenol injection, were assayed for testosterone, androstenedione, progesterone, oestradiol-17β, LH and FSH. For the testosterone measurements, two radioimmunoassays, using two different antisera, were validated and used. A typical pattern of release was observed for progesterone, oestradiol-17β, LH and FSH, with a preovulatory gonadotrophin peak recorded 16.1 ± 2.1 h after the observed oestrous behaviour. In two of the experimental animals, an extra oestradiol peak was recorded before the usual preovulatory rise. The changes in the concentrations of testosterone and androstenedione during the same period were not synchronous. The levels of the two androgens fluctuated considerably with occasional peaks of 150–250 pg/ml and even 900–1400 pg/ml. Although a tendency towards an increase in the levels of both androgens was observed during the period of oestrous behaviour, the individual variations were significant.     

Studies on Plover Cove Reservoir, Hong Kong

The zooplankton fauna of the Plover Cove Reservoir has been investigated using two sampling series. The first series involving a 3-year investigation using 6-ft vertical hauls at three stations in the reservoir, revealed the presence of two copepod and four cladoceran species with little variation in terms of seasonal peak occurrence and abundance in any of the stations and so no evidence of the horizontal distribution patterns referred to by other authors. In all three stations Diaptomus gracilis was the dominant copepod species and Diaphanosoma leuchtenbergianum the dominant cladoceran species. The second series, involving a 13-month investigation of vertical sets of water samples collected both day and night at 4-h intervals for 24-h periods, revealed that in terms of seasonal vertical distribution, all six species occurred at all depths during the survey, but with a tendency to be concentrated in the surface waters. In terms of diurnal vertical distribution, differences in the migration pattern occurred from season to season in the case of Diaptomus gracilis. Thus, during spring, summer and autumn, concentrations occurred at the surface at 10.00 and 22.00 hours followed by migration to greater depth, whereas in winter, surface accumulations persisted even into the daylight hours. However, both Cyclops hyalinus and Diaphanosoma leuchtenbergianum showed surface accumulations at night and a movement away from the surface by day during all seasons. Investigations of the seasonal variation in environmental parameters conducted during both sampling series revealed that, as in the case of similar surveys, water temperature was the major controlling factor governing the seasonal variation in composition of the zooplankton fauna as well as its seasonal vertical distribution since in the case of Diaptomus gracilis and Ceriodaphnia reticulata low water temperatures corresponded with peak seasonal occurrence whereas in the case of the other species high water temperatures corresponded with peak seasonal occurrence, and since Diaptomus gracilis and Diaphanosoma leuchtenbergianum showed maximum concentration near the surface when surface water temperatures were high, whereas the remaining species showed their maximum concentration near the surface when lower water temperatures prevailed. It would also appear, however, that seasonal changes in zooplankton densities closely followed algal densities since Diaptomus gracilis, Diaphanosoma leuchtenbergianum and Bosmina longirostris had their maxima in late spring and Cyclops hyalinus in late summer while algal densities in this reservoir were highest in early spring and early summer. With regard to the diurnal vertical distribution of the zooplankton, light appeared to be the only factor alternating by an amount likely to be correlated with such diurnal vertical changes in zooplankton density.     

Endocrine control of antler growth in red deer stags

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

Differential circadian expression of genes fcp2 and fcp6 in Cyclotella cryptica.

The steady-state mRNA concentrations of two fcp genes encoding fucoxanthin chlorophyll a/c light-harvesting polypeptides of the centric diatom Cyclotella cryptica were investigated over a 4-day period by RNA dot-blotting experiments. Before and during the first day of the experiment, the cultures were grown under a 12-h light/12-h dark regime. On the following 3 days, the algae were kept in darkness. On the first day, the steady-state mRNA concentration of fcp2 followed a diurnal pattern, with a maximum occurring around noon, approximately 6 h after the onset of light. The gene fcp6 also had a diurnal pattern on the first day. Its maximum, however, occurred immediately after the onset of light. During the subsequent incubation period in darkness, the diurnal pattern of expression of both fcp genes continued, thus demonstrating that their steady-state mRNA concentrations oscillated in a circadian manner.     

Seasonal changes in the reproductive organs and plasma and pituitary hormone content of the male Bennett's wallaby (Macropus rufogriseus vufogriseus)

In a number of species of seasonally breeding marsupial, the male is fertile throughout the year but there is a marked seasonal change in weight of the accessory sexual glands. In this study, body weight, prostate, epididymis and testis weights and plasma concentrations of testosterone, LH and prolactin and pituitary content of LH and prolactin were determined in male Bennett's wallabies shot at 1–2 month intervals over a period of 17 months. There was a highly significant increase in prostate weight which was coincident with the breeding season for this species. A small but significant increase in testis weight was also observed but epididymis weight remained unchanged. Plasma testosterone concentrations were significantly increased at a time coincident with the increase in prostate weight. Plasma prolactin and LH concentrations were low in most animals and remained unchanged during the study. In contrast, pituitary prolactin and LH contents showed highly significant changes, with increasing and peak hormone content preceding maximum prostate weight and plasma testosterone concentrations by several months. While these latter results suggest a role for prolactin and LH in the seasonal control of the reproductive organs in the male wallaby, a more intensive study of the pattern of secretion of these hormones and possibly more sensitive hormone assays are required to understand their relative roles in regulating the annual cycle of prostate growth.     

Circadian rhythm in adenosine A1 receptor of mouse cerebral cortex

In order to investigate diurnal variation in adenosine A1 receptors binding parameters, Bmax and Kd values of specifically bound N6 - cyclohexyl-[3H]adenosine were determined in the cerebral cortex of mice that had been housed under controlled light-dark cycles for 4 weeks (light on from 7.00 to 19.00 h). Significant differences were found for Bmax values measured at 3-hr intervals across a 24-h period, with low Bmax values during the light period and high Bmax values during the dark period. The amplitude between 03.00 and 18.00 hr was 33%. No substantial rhythm was found in the Kd values. It is suggested that the changes in the density of A1 receptors could reflect a physiologically-relevant mechanism by which adenosine exerts its modulatory role in the central nervous system.     

Plasma concentrations of testosterone and LH in the male dog

Blood samples were withdrawn every 20 min from 3 conscious intact and 2 castrated mature males during non-consecutive periods of 12 h during the light and dark phases of the lighting schedule (intact dogs) and of 11 h during the light period (castrated dogs). In the intact dogs testosterone concentrations ranged from 0.4 to 6.0 ng/ml over the 24-h period. LH concentrations varied from 0.2 to 12.0 ng/ml. In all animals, LH peaks were clearly followed, after about 50 min, by corresponding testosterone peaks, but no diurnal rhythm could be established. LH concentrations in the castrated dogs were high (9.8 +/- 2.7 (s.e.m.) ng/ml), and still showed an episodic pattern in spite of the undetectable plasma testosterone levels.     

Assessment of reproductive status in male echidnas

This study reports the development and application of techniques to assess the reproductive status of male echidnas. The pattern of testosterone secretion over a 24-h period in five echidnas was documented. Testosterone secretion after injection i.m. of either 1000 IU hCG (n=4) or 4 microg GnRH agonist (n=6) was determined to establish whether this could be used as a practical index of the prevailing steroidogenic capacity of the testes. hCG (1000 IU) was also used to assess seasonal changes in testosterone secretion in six echidnas over a 13-month period. Seasonal changes in testicular volume were examined by transabdominal ultrasonography. Electroejaculation was attempted to monitor seasonal changes in sperm production, which was also determined by spermatorrhea. There was no apparent diurnal pattern of testosterone secretion in echidnas and circulating concentrations of testosterone remained relatively low (maximum 1.2 ng/mL) and stable over 24h. Injection of hCG resulted in an increase (P<0.01; n=4) in testosterone concentration with a peak (2.9+/-0.3 ng/mL) approximately 4h after injection. GnRH also induced an increase (P<0.01; n=6) in circulating testosterone that was apparent after 1h (2.6+/-0.3 ng/mL) and concentrations remained elevated (3.4+/-0.3 ng/mL) for up to 8h after injection. Seasonal changes in testosterone secretion determined after injection of hCG, increased (P=0.03; n=6) from late-autumn, peaked in late-winter, and decreased by early-spring. Testicular volume followed a similar seasonal pattern (P<0.01; n=6) with an increase from late-autumn, peak in winter and a decline in mid-spring. There was no seasonal change in live weight. Electroejaculation was attempted throughout two breeding seasons but no semen was obtained. Spermatorrhoea in the echidna was described for the first time and was subsequently used to assess seasonal sperm production. Spermatozoa were found in the urine from June to September. This study has demonstrated that exogenous hormones can be used to obtain an index of the prevailing steroidogenic capacity of the testes in echidnas, which is not apparent with repetitive non-stimulated samples over 24 h. The assessment of testosterone secretion after injection of trophic hormones provides a valuable and practical procedure for the assessment of reproductive status. Testicular ultrasonography and spermatorrhea are useful in assessing reproductive status and in this study were successfully used to determine seasonal reproduction in captive echidnas.     

Effects of propylene glycol drenching before and after luteolysis on blood glucose, ovarian steroids and follicular dynamics in heifers

The effect of propylene glycol drenching on ovarian and hormonal dynamics was studied in heifers. Five cycling heifers were used twice (as control and treatment) with crossover design. After the confirmation of ovulation (day 0), the heifers in the treatment group received propylene glycol on days 6, 7 and 8 as an oral drench (250 ml of 90% propylene glycol). On day 10, prostaglandin F2α (PGF2α), 15 mg per head of dinoprost, was administered intramuscularly to induce luteal regression followed by the follicular phase and then propylene glycol was again administered twice daily (500 ml/day) on days 10, 11 and 12. Palpation per rectum and ovarian ultrasonography were performed every other day from days 0 to 10, and daily after PGF2α administration until the subsequent ovulation (second ovulation) for analysis of follicular and luteal dynamics. Blood samples were also collected every other day from days 0 to 10, and then at 6 h intervals after PGF2α administration until the second ovulation. For the samples taken at 6-h intervals after PGF2α administration, the concentrations of glucose showed clear daily fluctuations in both groups. Changes in the plasma concentration of glucose in the treatment group were significantly (P < 0.05) higher than those of the control groups during the period between 0 and 72 h after PGF2α administration. No significant difference was detected in the growth of dominant follicles, maximum diameter of the ovulatory follicles and the changes in oestradiol and progesterone during the follicular phase between treatment and control groups. This study showed the clear daily fluctuations and stimulatory changes in the blood glucose concentrations at 24-h intervals during the short-term treatment of propylene glycol drenching in heifers. However, no significant changes in ovarian and hormonal dynamics were found under such metabolic conditions.     

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

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

Seasonal changes in serum steroid hormones in a protandrous teleost, the sobaity (Sparidentex hasta Valenciennes)

Serum concentrations of 11-ketotestosterone, 11β-hydroxytestosterone, testosterone, testoster-one glucuronide, oestradiol and 17,20β -dihydroxy-4-pregnen-3-one (17,20β -P) were measured in the sobaity at monthly intervals through their second breeding season. Concentrations of the 11-oxygenated androgens in the males and of oestradiol in the females peaked during the spawning season in January-February, while maximum levels of testosterone were found in the summer when these steroids were low. Testosterone glucuronide showed two peaks, one in the post-spawning period as oestradiol and the 11-oxygenated androgens were falling and the other coincident with the summer peak of testosterone. 17,20β -P was detectable in only one male and one female fish in February. Serum concentrations of 11-oxygenated androgens are more reliable than those of oestradiol for determining the sex of sobaity, and may also be used as indicators of the occurrence of sex reversal. The seasonal pattern of serum steroids correlated well with the changes of sexual status of the gonads during regression and recrudescence observed histologically and suggests that oestradiol may be involved in the sex inversion of this species.     

男性排精后血清睾酮水平的周期性变化

为了解男性排精后可能存在的性激素变化过程,在排精后连续禁欲的情况下,对28人血清睾酮（T）水平进行了两个时段的每天定时检测,检测发现,在排精后连续禁欲的第2-5天,睾酮水平变化不明显;在禁欲的第7天,睾酮水平出现一个明显的高峰,峰值平均提高至底线的145.7%,第7天后如果再继续禁欲,没有再发现明显的变化,排精是这一周期性现象的前提和开始,没有排精就没有这种独特的周期性变化,这些结果说明男性排精会引起睾酮水平的周期性变化,这种变化的形式以禁欲第7天出现一个高峰为标志,这些结果证实了血清睾酮水平这种周期性变化现象的存在以及排精与这一现象之间的联系。