Facilitatory role of neuropeptide Y on the onset of puberty: effect of immunoneutralization of neuropeptide Y on the release of luteinizing hormone and luteinizing-hormone-releasing hormone

To examine the role of neuropeptide Y (NPY) in the first luteinizing hormone (LH) surge of puberty, the effect of passive immunoneutralization of NPY with antiserum against NPY (anti-NPY) injected centrally (third ventricle) or peripherally (jugular vein) was studied in pubertal female rats on the day of first proestrus. Both peripheral and central anti-NPY administration reduced the magnitude of the LH surge during the afternoon of first proestrus; however, the central route of administration appeared to be most effective. Centrally administered anti-NPY also reduced the magnitude of proestrous LH-releasing hormone (LHRH) release into pituitary portal blood in these rats. These results suggest that endogenous NPY plays a facilitatory role in the generation of the LHRH surge necessary for preovulatory gonadotropin release and puberty.

Effect of naloxone on gonadotrophin secretion at various stages of development in the ewe lamb

Spring-born crossbred ewe lambs were raised in a natural photoperiod and saline (N = 6) or naloxone (1 mg/kg) in saline (N = 6) was injected (i.m.) every 2 h for 6 h at 5, 10 and 15 weeks of age and for 8 h at 20, 25 and 30 weeks of age. Blood samples were taken every 12 min during treatment periods. Naloxone had no effect on time to first oestrus (controls 235 +/- 6 days, naloxone 242 +/- 7 days). Mean serum LH concentrations and LH pulse frequency were elevated by naloxone in ewe lambs at 20, 25, and 30 weeks of age (P less than 0.05). The only FSH response to naloxone was a depression of mean serum concentrations at 30 weeks of age (P less than 0.05). LH pulse amplitude was elevated at 5 weeks of age in all ewe lambs and declined thereafter to a nadir at 30 weeks of age in control, but not in naloxone-treated animals (P less than 0.05). LH pulse frequency was elevated at 10 weeks of age in control ewe lambs and in all animals at 30 weeks of age (P less than 0.05). FSH pulse frequency declined from 5 weeks of age in control ewe lambs (P less than 0.05), with very few pulses noted in 25- and 30-week-old animals. We conclude that (1) opioidergic suppression of LH, but not FSH, secretion developed at 20 weeks of age in the growing ewe lambs used in the present study, with no obvious change in suppression before the onset of first oestrus: (2) pulsatile FSH secretion occurred in the young ewe lamb but was lost as the lamb matured: (3) attainment of sexual maturity was preceded by an elevation in LH pulse frequency.

Blood pressure distribution in a school-age population aged 8-10 years: the Odense Schoolchild Study

This paper describes the distribution of systolic and diastolic blood pressures in a homogeneous population of 1330 schoolchildren (81% of the eligible population) aged 8-10 years in Odense, Denmark. A single blood pressure measurement was made. No significant difference in mean blood pressure between the sexes could be demonstrated. A significant age-related increase in systolic blood pressure of 4.4 mmHg/year and in diastolic blood pressure of 3.4 mmHg/year was observed. Weight and the heart rate were important determinants of blood pressure level. Other positive determinants were age and triceps skinfold thickness. There was a significant association between diastolic blood pressure and sexual maturation, which seemed to depend on body weight.

Effect of winter high temperatures on reproduction and circannual rhythms in hibernating ground squirrels

We tested whether prevention of hibernation in ground squirrels by midwinter exposure to high ambient temperatures influenced timing of the spring phase of reproductive maturation and the phase and period of subsequent circannual rhythms of reproduction and body mass. Exposing hibernating adult male Spermophilus lateralis to 30 degrees C for 6 weeks beginning December 4 advanced the timing of testicular recrudescence by 4-5 weeks, compared to controls left at 4 degrees C. Males exposed to 30 degrees C for 6 weeks beginning at the average time of spontaneous end of hibernation (January 15) reached reproductive maturation at a time intermediate to those of controls and of the December 4 experimental group. However, neither the date of the subsequent fall's body mass peak, the date of the next year's reproductive maturation, nor the periods of circannual rhythms of body mass and reproduction differed among groups. Premature interruption of hibernation appears to allow early expression of reproduction, but does not affect the underlying timing mechanism.

Developmental changes in testicular inhibin and androgen-binding protein during sexual maturation in the cynomolgus monkey, Macaca fascicularis

Inhibin was measured by RIA in testicular extracts and plasma of cynomolgus monkeys during four stages of sexual maturation. Immunoactive inhibin levels were compared to those of another Sertoli cell secreted protein, androgen-binding protein (ABP). ABP steroid-binding (bioactive) activity was measured in testes and epididymal segments using the radiolabeled ligand [3H]dihydrotestosterone (DHT). Testicular immunoreactive inhibin concentrations were maximal in late prepubertal monkeys, 2.5-3.5 yr old, while the total testicular content of inhibin progressively increased with age into adulthood. Bioactive testicular ABP concentrations were maximal during the pubertal period of the cynomolgus monkey (3.5-4.0 yr old), while the total ABP content of the testes also increased with sexual maturation. Mean (+/- SE) plasma concentrations of inhibin and testosterone (T) in adults, 6-8 yr old (17.72 +/- 3.5 microliters inhibin equivalents/ml and 7.07 +/- 2.45 ng/ml T, respectively), were significantly higher (P less than 0.05 and P less than 0.001, respectively) than those in early prepubertal, juvenile monkeys, aged 1.5-2.5 yr (5.85 +/- 2.1 microliters inhibin equivalents/ml and 0.27 +/- 0.02 ng/ml T). The increased plasma levels of inhibin and T in adults were associated, respectively, with the increased inhibin and androgen contents of the testes in these same animals. The developmental changes in testicular steady state mRNA concentrations for the inhibin alpha-, beta A-, and beta B-subunits as well as ABP were examined during sexual maturation by Northern blot analysis using heterologous human cDNA probes. Densitometric analysis of the autoradiograms revealed that the inhibin alpha-subunit mRNA concentrations were higher than those of inhibin-beta A and -beta B and ABP mRNA during all stages of pubertal development. Although the relative concentrations of each inhibin subunit mRNA were decreased in the adult animals relative to those in the juvenile monkeys, the total amount of steady state mRNA for the subunits was greater than that in the immature animals. A similar situation existed for the ABP mRNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Sexual behavior of men with isolated hypogonadotropic hypogonadism or prepubertal anterior panhypopituitarism

Sexual behavior of men with secondary hypogonadism was studied. Seven of the thirteen subjects presented with hypogonadism secondary to isolated gonadotropin (Gn) deficit, whereas the other six had idiopathic prepubertal anterior panhypopituitarism. Testosterone (T) levels were low and did not differ between the two groups. All subjects were evaluated both during replacement therapy (Gn in the first group; Gn plus cortisone and thyroxine in the second group) and 2 months after withdrawal of Gn therapy. During and after withdrawal of Gn administration, men with isolated deficit of Gn retained sexual activity and nocturnal penile tumescence, although they were partially compromised compared with a control group; on the other hand, panhypopituitarics reported compromised sexual function during Gn treatment and no sexual function when Gn therapy was not given. We conclude that different lesions of the hypothalamus-pituitary axis were accompanied by varying degrees of sexual impairment in the two groups of men presenting both secondary hypogonadism and very low T levels.

[Correlation between certain factors in maturation and primary dysmenorrhea in adolescence]

A total of 1,068 randomly chosen adolescent females, aged 10 to 19 years, were questioned about their (painful or painless) menstruation. The obtained rate of the prevalence of dysmenorrhea in the examined adolescent population was 52.9%. The statistical significant difference between the examined adolescent girls with and without dysmenorrhea related to the chronological age (chi 2 = 19.112; p less than 0.05). The rate of frequency of painful menstruation increases with the increasing of the chronological age of the examined adolescent females. It is the highest at the age of 16 to 19 (56.5% in 16 and 61.2% in 19 year-olds). Over the age of fifteen years dysmenorrhea is present in every other examined adolescent girl. The number of examined adolescent females with dysmenorrhea is statistically significant by greater (chi 2 = 44.448; p less than 0.001) in those who had got menarche early (11 and 12 years old). The greatest frequency of dysmenorrhea is estimated in those having got the first menstruation aged 11 (79.2%) and 12 (55.5%) years. The average age of the appearance of menarche in all the examined female population is 12.8 +/- 1.3 years. The average age of the occurrence of the first menstruation in dysmenorrhoic girls is 12.6 +/- 1.1 years and statistically significantly differs from the average age of menarche in the control group of nondysmenorrhoic adolescent females (13.1 +/- 1.2 years of life). In the first gynecological year only one third (29.6%) of the examined adolescent girls had painful menstruation. Up to the fourth gynecological year, 62.4% of the examined adolescent females experienced dysmenorrhea. Three quarters (75.3%) of them had painful menstruation in the sixth gynecological year. There is a statistically significant difference between adolescent girls with and without dysmenorrhea in relation to the gynecological year (chi 2 = 63.604; p less than 0.001).

[Clinical evaluation of testicular size in boys and adolescents]

On 596 healthy boys and adolescents from 4 to 17 years of age measurements of the length and the width of the left testis as well as of the thickness of scrotal skin were carried out by means of a caliper, and the testis volume was secondarily calculated. Age specific mean values (means) and their +/- 2 s-limits are listed. Nonlinear s-shaped regression lines of the three main parameters clearly underline that the greatest increase is to be found in the length of testis. Consequently, as an indicator for gonadal developmental disturbances instead of testis volume measuring of testis length is recommended for routine in the physical examination of inpatients and outpatients as well as for the screening of schoolboys and male teenagers.

Effect of naloxone on the secretion of LH in infantile and prepubertal Holstein bull calves

Administration of naloxone (100 mg i.v.; approximately 1.21 mg/kg body weight0.75) to 10 intact calves (24 weeks of age) caused an acute release of LH that was similar in amplitude and duration to spontaneous discharges of LH that occur at the same age. The naloxone-induced release of LH was abolished in 9/10 calves (intact and castrated) treated with oestradiol-17 beta. To determine the ontogeny of opioid control of secretion of LH, 12 calves were randomly assigned to receive saline or naloxone (1.21 mg/kg body weight0.75, i.v.) at 3, 5, 7, 9, 11, 13, 17 and 21 weeks of age. At each age, blood was collected at 10-min intervals for 4 h and saline or naloxone was administered (i.v.) after collection of the 120-min sample. Before administration of naloxone, plasma LH values increased with age (P less than 0.01) but did not differ between the control and naloxone groups (age x treatment, P greater than 0.05). Administration of naloxone caused concentrations of plasma LH to increase at 3, 11, 13, 17 and 21 weeks of age (treatment x time, P less than 0.001). Concentrations of LH (saline vs naloxone, ng/ml) reached a maximum within 20 min after treatment at Weeks 3 (0.3 vs 1.2), 11 (0.6 vs 2.6), 13 (0.6 vs 3.7), 17 (1.1 vs 2.6), and within 40 min after treatment at Week 21 (1.0 vs 3.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothalamic aromatase activity in male and female rats during juvenile peripubertal development

Evidence exists that testosterone (T) regulates brain aromatase activity in adult rats. It is not known, however, whether the activity and/or its regulation by androgens change during the time of puberty. In the present study, we examined the change in basal aromatase activity associated with puberty in both male and female rats. We also assessed the influence of castration and treatment with a nonaromatizable androgen, dihydrotestosterone (DHT), on the hypothalamic aromatase system during juvenile and peripubertal development of male rats. Aromatase activity was estimated by both quantifying the 3H2O released from [1 beta-3H]T and by isolating the estrogen product(s) by thin-layer chromatography (TLC) after incubations with [1,2,6,7-3H]T. 5 alpha-Reductase activity was determined simultaneously in the male hypothalamus by TLC using [1 alpha-3H]T as the substrate. Aromatase activity was linear with time of incubation and amount of tissue used. It was detected at similar levels in both tissue fragments and acutely dispersed cell preparations. Expression in the latter, but not the former required the addition of NADPH. Intracellular rates of both aromatase and 5 alpha-reductase activities were highest in the mitochondrial-microsomal fraction. In both males and females the time of puberty was associated with a decrease in hypothalamic aromatase activity. In females, this drop was found to occur between the days of first proestrus and first estrus. In males, it occurred between 48 and 68 days of age (i.e., after the animals had reached puberty, as assessed by the presence of free sperm in the seminiferous tubules).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of crude and highly purified bovine inhibin (Mr 32,000) on plasma concentrations of FSH and LH in chronically ovariectomized prepubertal heifers

Chronically ovariectomized prepubertal heifers were used for a comparison of the effects of highly purified bovine inhibin (Mr 32,000) and steroid-free bovine follicular fluid (bFF) on the secretion of FSH and LH. In view of the limited availability of highly purified inhibin, an initial study was undertaken to establish the optimal method for administration of bFF inhibin activity. In comparison with the FSH response to a single large i.v. bolus injection of bFF (50 ml; 3250 mg protein), a far more effective suppression of plasma FSH concentrations was achieved when considerably less bFF (6.3 ml; 410 mg protein) was administered gradually over an extended time-period (2 days) either as a continuous i.v. infusion or as a series of 2-hourly i.v. injections. Following a single i.v. bolus injection of bFF, immunoreactive inhibin was cleared rapidly from the circulation (half-life 51 +/- 8 (S.E.M.) min, n = 5), presumably accounting for its limited ability to suppress FSH secretion when administered in this manner. In a second experiment, treatment of ovariectomized heifers (three per group) with highly purified Mr 32,000 bovine inhibin at a dose rate of 15 micrograms/2 h for 2 days significantly (P less than 0.05) suppressed plasma FSH concentrations, which reached their minimum values (40% suppression) during day 2 of treatment. At a lower dose rate (5 micrograms/2 h), inhibin did not significantly affect plasma FSH levels. Administration of bFF was also associated with a dose-dependent suppression of FSH secretion. For each of three dose rates tested (three heifers per group), plasma FSH concentrations were maximally suppressed during day 2 of treatment (65 mg/2 h, 86% suppression, P less than 0.001; 21.7 mg/2 h, 66% suppression, P less than 0.001; 7.2 mg/2 h, 15% suppression, P greater than 0.05). Neither highly purified inhibin nor bFF significantly affected mean plasma LH concentrations, LH pulse frequency or LH pulse amplitude. Thus we have shown for the first time that highly purified Mr 32,000 bovine inhibin does possess in-vivo biological activity in cattle, promoting a selective suppression of plasma FSH concentrations qualitatively similar to that evoked by steroid-free bFF.(ABSTRACT TRUNCATED AT 250 WORDS)

[Mycoses in adolescent patients]

Mycoses affect people of all ages world wide. Furthermore, different fungi can produce the same clinical signs and symptoms, equally similar fungi can produce many different clinical pictures. Despite of this, particular fungal infections are found more common in people of certain age groups than in others. For example, candidosis is seen frequently in babies whereas fungal infections of the feet rarely occur in children. However, there is little difference in the fungi affecting adolescents and adults. Then again, elderly people are more vulnerable to candidal infections. Besides this, there is a current increase in fungal infections in immunosuppressed patients of any age.

Disappearance of opioidergic tone on LH secretion in underfed prepubertal sheep

A study was conducted to determine whether an opioid tonus inhibitory of LH secretion is present in underfed prepubertal sheep. Ten Suffolk ewe lambs were subjected to food restriction during 60 days. During this period they were allowed to pasture only 2 hours per day while control ewe lambs were allowed for 10 hours. Body weight and plasma blood levels of glucose, urea and total proteins were measured weekly. At the end of this period, an intravenous injection of Naloxone (NAL, 1.5 mg/kg BW) was given to control and underfed animals followed 60 min later by an intravenous injection of LHRH to test the pituitary responsiveness. Underfed animals did not show an increase in plasma LH while control animals presented a rise from 0.28 +/- 0.08 to 2.02 +/- 0.6 ng/ml after the NAL stimulus (P less than 0.05). The response to LHRH was similar in both group of animals. Basal plasma levels of insulin were lower in underfed ewe lambs than in control animals (P less than 0.05). Underfed animals were placed on plain feeding with a schedule similar to control lambs for 30 days and the same experiment was repeated. During this occasion, NAL increased plasma LH concentration in both group of lambs. Levels of plasma insulin were not different in both groups. The lack of effect of NAL on LH secretion in food restricted ewe lambs suggests that the opioid modulation of LH secretion is absent by underfeeding in female prepubertal sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Sexual differentiation of behavior in the zebra finch: effect of early gonadectomy or androgen treatment

Treatment of nestling zebra finches with estradiol benzoate (EB) has been shown to masculinize singing in females and demasculinize copulatory behavior in males, suggesting that sexual differentiation of these behaviors is under hormonal control such that testicular hormones induce the capacity for song and ovarian hormones suppress the capacity for mounting. Two experiments were carried out to obtain a more complete picture of sexual differentiation in this species. In Experiment 1, nestlings were injected daily for the first 2 weeks after hatching with testosterone propionate (TP), dihydrotestosterone propionate (DHTP), or a combination of DHTP and EB. As adults, birds were gonadectomized and implanted with TP prior to testing, then tested again after implantation with EB. Singing was not increased in females by any of the treatments. The only effect of either TP or DHTP given alone was defeminization of female proceptive behavior by DHTP. Thus androgens appear to have less influence than estrogens on sexual differentiation of behavior in this species. The combination of DHTP and EB demasculinized mounting in males. In Experiment 2, nestlings were gonadectomized at 7-9 days of age and implanted with TP prior to testing in adulthood. Early gonadectomy had little effect on later behavior; early castrated males sang, danced, and copulated normally and early ovariectomized females neither sang nor mounted.

Effect of immunization of sexually immature pullets against poly-alpha-L-glutamic acid on long-term fertility

Poly-alpha-L-glutamic acid (PGA) is a polypeptide synthesized within the upper oviduct and uterovaginal junction of the hen. Sexually immature pullets were immunized against PGA. These virgin pullets, and immunized and non-immunized controls, were inseminated at 25 weeks of age and then monthly throughout a 30-week egg production interval. While birds immunized against PGA were free of PGA as evidenced by an absence of immunoprecipitation when rabbit anti-PGA serum was overlayed with oviduct extract, immunization had no effect on long-term fertility and therefore is unlikely to have an immunosuppressive or antigen-masking biological role with respect to spermatozoa. We suggest instead that PGA could act as a calcium binding protein.

Plasma progesterone concentrations and length of the first spontaneous oestrous cycle in pubertal rats

The length of the first spontaneous oestrous cycle in pubertal Wistar-Imamichi strain rats determined by vaginal smears varied from 5 to 18 days. The variation was ascribed to the period (3-16 days) of the stage of vaginal smears consisting of leucocytic cells (L stage). Plasma progesterone concentration and the decidual reaction in the uterus were used as indicators of the function of the corpus luteum and the L stage period was categorized as short, lasting for 3-6 days (average 4 days) with non-functional corpora lutea, or long, lasting 9-16 days (average 12 days) and with functional corpora lutea. Rats with the long L stage showed nocturnal and diurnal prolactin surges, but no daily changes in prolactin values were observed in rats with a short L stage. Daily changes in prolactin concentrations were maintained by the administration of progesterone in rats ovariectomized on Day 6 of the L stage. Plasma progesterone values on Day 6 of the L stage decreased with ergocornine treatment on Days 4 and 5 of the L stage and administration of bovine prolactin restored the level. These results indicate that the L stage observed in the first oestrous cycle is maintained by a positive feedback relation between progesterone and prolactin secretions.

The effects of sexual maturation and altered steroid synthesis on the production and route of secretion of inhibin-alpha from the rat testis

This study has determined the route of secretion of inhibin-alpha into blood by the rat testis during sexual maturation, and in adult animals in which Leydig cell steroidogenesis was stimulated with human CG (hCG) or suppressed with aminoglutethimide. In each rat, inhibin-alpha levels were measured in samples of testicular (TV), spermatic (SV), and peripheral (PV) venous blood plasma, and in testicular interstitial fluid (IF). The IF and TV plasma reflect inhibin-alpha secretion via the base of the Sertoli cell while that secreted via the apex of the Sertoli cell (which is resorbed from the rete testis) was determined from the difference between SV and TV levels of inhibin-alpha. During sexual maturation, inhibin-alpha levels in IF and all plasma samples declined from maximal values at 28 days of age to minimal values at 100 days of age, in contrast to testosterone levels which showed the reverse pattern. There was a major change with age in the route of secretion of inhibin-alpha from the testis into blood. In immature (28-35 days) rats, most inhibin-alpha (58-65%) leaving the testis in blood was derived from that secreted via the base of the Sertoli cell with a relatively small contribution (35-42%) from apically-secreted inhibin-alpha. However, the latter made a progressively increasing contribution between 45 and 100 days of age (adults) and in adult rats the vast majority of inhibin-alpha (95%) leaving the testis in blood was derived from apically-secreted inhibin-alpha. This change was due primarily to a progressive reduction with age in the secretion of inhibin-alpha via the base of the Sertoli cell, a change which was confirmed by inhibin bioassay. Stimulation of steroidogenesis in the adult testis with hCG significantly increased inhibin-alpha and testosterone levels in IF and all plasma samples. The concomitant administration of hCG and aminoglutethimide (to block steroidogenesis) prevented the hCG-induced increase in testosterone levels, but still led to significant increases in inhibin-alpha secretion which were comparable to those seen with the use of hCG alone. The administration of aminoglutethimide (AMG) on its own did not alter the inhibin-alpha secretion profile from that seen in controls, but it did significantly reduce the levels of testosterone in all fluids. In rats treated with hCG +/- AMG there was a small change in the route of secretion of inhibin-alpha into blood, with an increased contribution (24-37%) from inhibin-alpha secreted via the base of the Sertoli cell, when compared with controls (7-16%).(ABSTRACT TRUNCATED AT 400 WORDS)

Lordosis behavior in intact male rats: effects of hormonal treatment and/or manipulation of the olfactory system

The aim of this study was to investigate the olfactory mechanisms regulating the display of lordosis behavior in intact Wistar male rats bred in our colony. Gonadally intact males show a low capacity to respond by lordosis to male mounts and were insensitive to manipulations of the olfactory system (exposure to the odor of male urine or accessory bulb removal (AOBR)) which have been previously shown to facilitate the display of lordosis behavior in orchidectomized animals primed with ovarian hormones. Treatment with either estradiol benzoate (EB) or EB and progesterone (P) consecutively did not render these gonadally intact animals sensitive to the effects of AOBR. By contrast exposure to male urine was capable of facilitating the display of lordosis behavior in intact male rats given EB + P consecutively. These results are discussed in the light of previous findings showing that (1) two inhibitory structures, the accessory olfactory bulb and the septal and preoptic areas, are involved in the control of lordosis behavior in the male rat; (2) the effects of olfactory cues on the display of lordosis behavior are dependent on the action of both EB and P in orchidectomized animals.

[Indices of testicular endosecretory function and of the status of the hypophyseal-gonadal system in varicocele]

Testicular intrasecretory function and gonad-hypophyseal regulation were studied in 28 patients with the left-sided varicocele whose age varied from 11 to 36 years. Radioimmunoassay was used for the assessment of testosterone, estradiol, progesterone, follicle-stimulating (FS) and luteinizing (L) hormones and prolactin levels in the blood samples from femoral and internal testicular veins taken during endovascularization of varicocele. With regard to the age and manifestations of the secondary sexual signs the patients were divided into three groups. The first group (11-12-year-old) enrolled the patients with normal age-related levels of FS and L hormones in the presence of hyperprolactinemia. The positive testiculoperipheral gradient was revealed in 3 cases for estradiol and in 2 patients for testosterone and progesterone. The peripheral blood testosterone was normal in all the patients whereas estradiol and progesterone were decreased in 2 and 4 cases, respectively. All the patients of the second group (13-15-year-old) demonstrated an increase in testicular blood testosterone and estradiol as compared to their levels in the peripheral blood (1.46-1.8-fold and 1.3-7.1-fold, respectively). In 6 patients, this ratio was 1.65-2.33-fold higher. The levels of FS and L hormones were normal. In all cases hyperprolactinemia was observed. The third group (16-36-year-old) patients demonstrated a 1.4-3.1-fold gradient of testosterone in the testicular blood versus its levels in the peripheral blood. The authors defined 1.1-239-fold (mean, 8.95) estradiol gradients and 0-979-fold (mean, 2.5) progesterone gradients. In all cases but one, the levels of FS and L hormones were equal to the control.(ABSTRACT TRUNCATED AT 250 WORDS)

[Primates in the study of oocyte maturation]

In the mammalian oocyte, meiosis is initiated during fetal life. Meiosis proceeds up to the diplotene stage of the first prophase and is arrested at birth and the oocyte presents a nuclear structure known as germinal vesicle (GV). Meiotic arrest persists until sexual maturity, when one or more oocytes, the number dependent on the species, reinitiate their reduction division at each cycle. The series of event, initiated by the breakdown of the germinal vesicle (GVBD) and completed with formation of the polar body, leads to the production of a mature, fertilizable oocyte, and is defined as oocyte maturation. Maturation of the oocyte is an essential prelude to fertilization. Normally the meiosis is reinitiated by the preovulatory LH peak but when meiotically arrested oocytes are removed from the antral follicles, they resume meiosis spontaneously in vitro. However primate (human and monkeys) oocytes isolated from antral follicles and cultured within their cumuli for two days, spontaneously resumed meiosis at a very low rate (less than 30%) compared to other mammals. Cynomolgus monkey oocyte then appears as a good model for in vitro studies of maturation initiation. Follicular atresia improve significantly the GVBD rate (about 50%). The cumulus cell mass takes an important part in the maintenance of the meiotic arrest since its mechanical removal is followed by an increase of the GVBD (P less than 0.02). A gonadotropin releasing hormone agonist (GnRHa) and a protein kinase C activator added to the culture medium both improve the GVBD (54% and 55% respectively, P less than 0.01). The GnRHa oocyte maturation induction is probably protein kinase C dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of cardiac lipofuscin in mammals: correlation between sexual maturation and the first appearance of lipofuscin

Accumulation of lipofuscin is an important phenomenon of the cellular aging process. The first appearance of cardiac lipofuscin showed a good correlation with sexual maturation, which was correlated with maximum life-span of mammals. Large metabolic changes occurred at sexual maturation. From these results, it is suggested that sexual maturation of mammals is the initiation period of the aging process. Correlation between sexual maturation and longevity was re-evaluated using many mammals. Domestic and laboratory animals showed an earlier sexual maturation than other mammals, including rodents.

Serum bioactive follicle-stimulating hormone levels in girls with precocious sexual development

We studied the serum immunoreactive (immuno) and bioactive (bio) FSH concentrations in 16 prepubertal children (1.3-9 yr old), 6 girls with premature thelarche (0.8-2 yr old), and 9 girls with central precocious puberty (2.5-9.3 yr old). The serum bio-FSH was measured by the granulosa cell aromatase bioassay. The basal serum bio-FSH levels were not significantly different in patients with central precocious puberty (6.4 +/- 1.5 IU/L), premature thelarche (7.5 +/- 0.5 IU/L), and prepubertal controls (4.4 +/- 0.7 IU/L). However, the peak responses of both serum immuno- and bio-FSH levels to iv GnRH were higher in patients with premature thelarche (immuno-FSH, 29.3 +/- 2.3 IU/L; bio-FSH, 100.7 +/- 12.2 IU/L) than in those with central precocious puberty [immuno-FSH, 17.5 +/- 3.1 IU/L (p less than 0.05); bio-FSH, 42.4 +/- 9.8 IU/L (p less than 0.01)]. This suggests that in children with premature thelarche, there is a predominant immuno- as well as bio-FSH response to GnRH. After 12 months of GnRH agonist therapy, both serum immuno- and bio-FSH levels were suppressed in patients with central precocious puberty. The differences in clinical presentation between central precocious puberty and premature thelarche cannot be explained by the differences in FSH bioactivity.

Testicular development and maturation of the hypothalamic-pituitary-testicular axis in the male tammar, Macropus eugenii

Testicular growth and maturation of the hypothalamic-pituitary-testicular axis were assessed in male tammars from 12 to 25 months of age to establish the time of sexual maturity. The testicular dimensions and body weights of 20 male tammars, approximately 12 months of age at the beginning of the study, were measured monthly for 1 year. Groups of 3 animals were castrated at 13, 19 and 25 months of age and their testes sectioned for histological examination. Testicular volume increased between 12 and 24 months of age and was highly correlated with body weight (r = 0.91). In the 13-month group the seminiferous tubules were closed with few mitotic figures. Spermatogenesis had begun in 2 of the 19-month animals. All stages of spermatogenesis were present in the other 19-month male, and in all of the 25-month males. Basal FSH concentrations increased with the age of the animal (21.0 +/- 32.48, 94.40 +/- 55.18 and 193.05 +/- 40.21 ng/ml (mean +/- s.d.) at 19, 20 and 25 months respectively) while basal LH concentrations were similar at 20 months and 25 months (0.43 +/- 0.18 and 0.58 +/- 0.25 ng/ml respectively). Basal testosterone concentrations were also similar 0.11 +/- 0.04, 0.35 +/- 0.16 and 0.22 +/- 0.10 ng/ml in 13-, 19- and 25-month-old animals. LHRH injection in tammars at 13, 19 and 25 months of age induced release of both LH and testosterone 10-30 min after injection. The hormone concentrations increased in both magnitude and duration with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Galanin-like immunoreactivity is influenced by estrogen in peripubertal and adult rats

Galanin gene expression in the anterior pituitary is potently stimulated by estrogen in adult rats. To evaluate the influence of estrogen on galanin during the peripubertal period 30- to 32-day-old female rats were treated with pregnant mare serum gonadotropin (PMSG, 10 IU s.c., 10.00 h). Galanin-like immunoreactivity (galanin-LI) in hypothalamic and pituitary tissues was evaluated 1, 2 or 3 days after PMSG treatment between 17.00 and 19.00 h. The PMSG treatment stimulated 17 beta-estradiol secretion, which induced a midafternoon LH surge 2 days after the PMSG treatment. Concentrations of galanin-LI at the time of this LH surge were elevated 82% in the anterior pituitary and 58% in the hypothalamus (without the median eminence) when compared to saline-treated female rats. On the 3rd day after the PMSG injection, galanin-LI was increased 236% in the anterior pituitary, 88% in the neurointermediate lobe and 39% in the median eminence compared to saline-treated female rats. These changes in galanin-LI were not observed in similarly aged male rats or ovariectomized rats treated with PMSG. In adult male rats, daily injections with 17 beta-estradiol valerate (10 micrograms/daily s.c.) for 1 week increased galanin-LI in the median eminence and neurointermediate lobe to an extent similar to that seen in juvenile female rats following PMSG treatment. In contrast, the high serum levels of 17 beta-estradiol achieved after 17 beta-estradiol valerate treatment increased galanin-LI in the anterior pituitary 65-fold. These studies indicate that galanin-LI is influenced by estrogen in peripubertal and adult rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal uterine position affects copulation and scent marking by adult male gerbils

Those male Mongolian gerbils (Meriones unguiculatus) that as fetuses resided in uterine locations adjacent to no females, when adult, scent marked more frequently, mounted estrous females with shorter latencies, and ejaculated after fewer intromissions than did those male gerbils that as fetuses resided in uterine locations adjacent to two females. Both the scent-marking frequencies and copulatory patterns of adult males were positively correlated with three indices of their circulating levels of testosterone: ventral gland size, anogenital distance, and relative testes weights. Also, those males that scent marked relatively frequently copulated more reliably than did those males that scent marked relatively infrequently.

Modulatory effect of testosterone on the serotoninergic control of prolactin secretion in prepubertal rats

The administration of 5-hydroxytryptophan (5-HTP) induced a prolactin release in male and female prepubertal rats at 20 days of age. This response was significantly higher in male than in female rats. Neonatal androgenization of the females significantly increased the release of prolactin induced by 5-HTP treatment compared to the values observed in males; thus, the neonatal exposure to androgens seems to be responsible for the sexual differences in the prolactin response to 5-HTP. In a second series of experiments the effect of this serotoninergic precursor on prolactin release in prepubertal (16, 26, and 30 days of age), peripubertal (45-day-old) and adult male rats was studied. Castration significantly decreased the prolactin release response to 5-HTP in prepubertal rats. The administration of testosterone to castrated rats markedly increased the prolactin release response to 5-HTP. Neither castration nor testosterone administration modified the prolactin response to 5-HTP in peripubertal and adult rats. These results appear to indicate that testosterone modulates the serotoninergic control of prolactin secretion during the prepubertal stage. The control of prolactin levels could be one of the mechanisms by which testosterone participates in the sexual maturation.

Short- and long-term effects of an LHRH antagonist given during the prepubertal period on follicle dynamics in the rat

The effects of the suppression of the high gonadotrophin concentrations normally present by the end of the second week of life on ovarian follicle dynamics were studied in immature rats. Gonadotrophins were suppressed by treatment with an LHRH antagonist (LHRH-A; Org. 30276) on days 6, 9, 12 and 15, and the total population of ovarian follicles was studied at 15 and 28 days, on the day of first oestrus and on the day of oestrus at or following 90 and 300 days of age. Primordial follicles were counted and growing follicles were counted and measured. In rats treated with LHRH-A, follicle recruitment into the growing pool was clearly diminished; the number of growing follicles was significantly (P less than 0.01) lower up to the day of first oestrus and the pool of primordial follicles was significantly (P less than 0.05) larger at 15 and 28 days. Ovarian weights were significantly lower in rats treated with LHRH-A until at least 90 days of age. However, on the day of oestrus at or after 90 and 300 days of age, there were no differences in either the pool of primordial follicles or the pool of growing follicles between rats treated with LHRH-A and control rats. There was also no difference between groups in the number of fresh corpora lutea at these ages. It was concluded that the early peak in gonadotrophin concentrations in immature rats causes substantial recruitment of follicles into the growing pool.(ABSTRACT TRUNCATED AT 250 WORDS)

The prepubertal hiatus in gonadotropin secretion in the male rhesus monkey (Macaca mulatta) does not appear to involve endogenous opioid peptide restraint of hypothalamic gonadotropin-releasing hormone release

To examine the possibility that the prepubertal hiatus in gonadotropin secretion in primates is occasioned by an endogenous opioid peptide (EOP)-dependent suppression of pulsatile GnRH release, the ability of an EOP receptor antagonist, naloxone (NAL), to elicit GnRH release was examined indirectly in the rhesus monkey. For this purpose, six castrated male monkeys, aged 18-24 months, first received an intermitten iv infusion of GnRH (0.1 micrograms/min for 3 min every h) to enhance the responsiveness of the gonadotroph to endogenous GnRH. Acute and chronic blockade of EOP receptors with single bolus injections of NAL at three doses (0.2, 2.0, and 10 mg/kg BW) and a continuous infusion of the antagonist (2 mg/h for 36 h), respectively, failed to elicit significant increments in circulating concentrations of mean LH. In addition, changes in plasma LH concentrations during a chronic intermitten iv infusion of NAL (2 mg/kg BW every 6 h for up to 16 days) were unremarkable. Unequivocal discharges of LH, however, were observed in response to small doses of GnRH (0.3 micrograms/monkey) administered iv after all modes of NAL administration. Taken together, these findings fail to provide evidence for the view that in primates, EOPs underlie the hiatus in pulsatile GnRH release, which in these species is responsible for the quiescence of the pituitary-testicular axis during the greater part of prepubertal development.

The Sertoli cell of the water buffalo--an electron microscopic study

The ultrastructure of Sertoli cells in the seminiferous tubules of water buffaloes before and during sexual maturity was studied by transmission electron microscopy, with emphasis on the intranucleolar vesicular elements. Sertoli cells of animals under 12 months of age were distinguished from the germ cells by the presence of electron dense membrane bound bodies within their cytoplasm. These cells, referred to as basal indifferent supporting cells, were probably involved in the phagocytosis and elimination of degenerating spermatocytes, which failed to differentiate into spermatids and spermatozoa in animals under one year of age. In 12 month old animals, a few Sertoli cells exhibiting the vesicular elements appeared in the nucleolar region while in animals over 15 months of age Sertoli cells could be positively identified by the characteristic cytoplasm containing microtubules, elongated and electron dense mitochondria, extensive granular endoplasmic reticulum and the presence of spermatids in various stages of spermiogenesis. The vesicular elements in the nucleolar region of the Sertoli cells were most prominent at this stage. Ultrastructural features of the Sertoli cells revealed an abundance of ribosome-like particles surrounding the vesicles of varying size. Some of these vesicular elements contained amorphous material suggesting that they represent the products sequestered in the nuclear region for transport to the cytoplasm and that the process of spermiogenesis may be dependent on the ability of Sertoli cells to generate these products at sexual maturity.

Age of menarche in Bolivian girls of European and Aymara ancestry

Median age of menarche was determined in children of European and Aymara ancestry residing in La Paz, Bolivia (3600 m) and in children of European ancestry residing in Santa Cruz, Bolivia (400 m). Median age of menarche in European and Aymara highland natives was younger than reported by previous researchers, thus broadening the range of variation in age of menarche in high-altitude populations. Comparisons between La Paz and Santa Cruz European children suggested that growth and development at high altitudes results in a delay in median age of menarche of about 0.8 years.

Experimentally induced testicular alterations in boars: hormonal changes in mature and peripubertal boars

Eleven sexually mature boars and 10 peripubertal boars were used to study the effects of elevated testicular temperature on plasma hormonal levels. The scrotum of the boars was covered with a textile-aluminium foil insulation device for 100 h. Insulation of the scrotum in the peripubertal boars took place at an age of 100 days. Blood samples were drawn 3 times daily for 12 days in the mature boars, starting 3 days before scrotal insulation. In the peripubertal boars, blood sampling was performed once a day for 11 days, starting the first day of scrotal insulation. During scrotal insulation, the plasma levels of testosterone, oestradiol-17 beta and oestrone sulphate decreased continuously in the mature boars. After removal of the scrotal insulation device there was a continuously increase, back to normal levels of oestradiol-17 beta and oestrone sulphate. The plasma levels of testosterone showed an immediate rise of brief duration after removal of the device in 5 of the boars, while in the other 6 boars the rise in testosterone levels came 4 days after removal and lasted for 3 days. In the peripubertal boars, there were no significant differences in the hormone levels between the experimental and control animals during and after scrotal insulation. However, the decrease in testosterone concentration over time, during scrotal insulation, was significant within the experimental group.

Effect of maternal treatment with altrenogest on age at puberty, hormone concentrations, pituitary response to exogenous GnRH, oestrous cycle characteristics and fertility of fillies

Puberty was studied using 15 fillies of Quarter Horse phenotype. Fillies were from dams treated daily from Days 20 to 325 of gestation with: (1) 2 ml neobee oil per 50 kg body weight (controls); or (2) 2 ml altrenogest (2.2 mg/ml) per 50 kg body weight. The clitoris was measured at birth and approximately every 12 weeks until 84 weeks of age. Blood samples were collected from 9 fillies (5 treated, 4 controls) every 4 days over a 28-day period at 8-week intervals from 4 to 68 weeks of age; sampling continued every 4 days after 72 weeks of age until first oestrus. Blood samples were collected daily during oestrus (greater than or equal to 35 mm follicle) and on Days 4, 6, 10, and 14 after ovulation for the first 2 oestrous cycles. GnRH challenges (5 micrograms/kg) were administered every 8 weeks from 32 to 96 weeks of age. Puberty was defined as the first oestrus with ovulation. Beginning 1 February 1987, fillies were teased daily and their ovaries were examined by ultrasonography every 3 days (daily during oestrus). Fillies were inseminated with 500 x 10(6) motile spermatozoa from one stallion. Pregnancy was diagnosed by ultrasonography on Days 11, 12, 15 and every 5 days until Day 50 after ovulation. Prenatal altrenogest treatment caused clitoral enlargement (P less than 0.05) and increased serum concentrations of LH from 1 to 7 months of age. The amount of LH released in response to exogenous GnRH was greater (P less than 0.05) in treated fillies at 32, 64, and 72 weeks of age. Treated fillies had higher serum concentrations of FSH from 1 to 4 months (P less than 0.05), but FSH was lower (P less than 0.05) in treated fillies before and during first oestrus. Serum concentrations of LH and FSH peaked transiently at 10 months and LH was depressed from 64 to 88 weeks and began to rise 14 days before first oestrus. Concentrations of FSH began to decline 14 days before first oestrus. The median age at puberty was 90 weeks. Durations of oestrus, dioestrus, and the oestrous cycle were not different between groups and were similar to those for adult mares. First cycle pregnancy rates and overall rates were 100 and 82% and 100 and 91.7% for control and treated fillies, respectively (P greater than 0.05). Maternal treatment with altrenogest did alter gonadotrophin secretion before puberty, but had no effect on functional reproductive performance in fillies.

Testicular growth, hormone concentrations, seminal characteristics and sexual behaviour in stallions

Puberty was studied using 15 colts of Quarter Horse phenotype. Total scrotal width was measured every 8 weeks from 48 to 96 weeks. Blood samples were taken from 8 colts at 8, 16 and 24 weeks and then every 4 weeks until 100 weeks to measure changes in LH, FSH and testosterone concentrations. Seminal collections were attempted monthly from 48 to 64 weeks and every 2 weeks thereafter until puberty resumed every 3rd day from 96 weeks for 15 ejaculates. For all collections, times to erection, mount and ejaculation and seminal characteristics were recorded. Age at puberty was defined as the first ejaculate containing 50 x 10(6) spermatozoa, with greater than or equal to 10% motile. Colts were castrated at 2 years to enable determination of daily sperm production (DSP), epididymal sperm reserves and normality of spermatogenesis. Total scrotal width increased linearly from 48 to 96 weeks. Age at puberty averaged 83 weeks (56-97 weeks). Changes in serum concentrations of LH and FSH were parallel, rising at 36-40 weeks, declining after 40 weeks and rising again at 68-80 weeks. Testosterone was low until 68 weeks after which concentrations rose slowly to 80 weeks and increased rapidly to a plateau at 92 weeks. Sexual behaviour and seminal characteristics differed (P less than 0.05) between puberty and 2 years, except for time to erection, time to mount, and percentage of motile spermatozoa. DSP at 2 years averaged 1.7 x 10(9) and daily sperm output (DSO) averaged 1.1 x 10(9). The correlation between DSP and DSO was 0.83 (P less than 0.01). There were 9.57 x 10(9) spermatozoa/epididymis of which 67% were in the cauda.

Prolactin-releasing effect of tryptolines in the developing and adult male and female rats

The developmental prolactin-releasing effect of Tryptoline (T), Methoxytryptoline (MT) and Hydroxytryptoline (OHT) was examined comparatively in male and female rats. A single injection of T 15 mg/Kg increased serum prolactin in both sexes; the increase was significant from day 20 onwards. OHT evoked a sharp rise in 12 day-old rats and the releasing effect increased with age, both in males and females. No significant sex differences were observed in T or OHT treated rats. MT caused an increment in prolactin secretion in male rats and this action increased with age. The releasing effect of MT was not significant in females, even at 38 postnatal days. In adult animals, the tryptolines (15 mg/Kg) were able to increase serum prolactin in males and in females in diestrous; a dose of 5 mg/Kg of T was only effective in adult male rats. The prolactin-releasing effect was drastically reduced by orchidectomy and by ovariectomy. LH, FSH and TSH were not modified by any treatment. The present results show for the first time the ontogeny of the prolactin-releasing effect of tryptolines in male and female rats and that this effect depends on the presence of gonadal secretions in adults.

Sexual segregation in the left and right horns of the gerbil uterus: "the male embryo is usually on the right, the female on the left" (Hippocrates)

We examined reproductive tracts of 253 female Mongolian gerbils (Meriones unguiculatus) and recorded the uterine locations (relative to siblings of opposite sex) in which 812 male and 823 female fetuses were found. Within-litter comparisons revealed that sexes were not distributed randomly across uterine horns. The percentage of males in right horns (55.0%) was greater than the percentage of males in left horns (41.8%) and the percentage of females in right horns (45.0%) was significantly less than the percentage of females (58.2%) in left horns. We did not find differences in the total number of fetuses in left and right uterine horns or a sex bias in the total sample of 1635 fetuses. Results were discussed in terms of: (a) effects of sexual segregation of fetuses on expected probabilities of fetuses developing adjacent to 0, 1, or 2 fetuses of opposite sex and (b) consequent alterations in expected frequencies of behavioral phenotypes in populations of gerbils.

Effect of maternal treatment with altrenogest on pituitary response to exogenous GnRH in pubertal stallions

The pituitary response to exogenous GnRH was studied in 8 colts of Quarter Horse phenotype from 32 to 96 weeks of age. Colts were from dams treated daily from Day 20 to 325 of gestation with (1) 2 ml neobee oil per 50 kg body weight (controls); or (2) 2 ml altrenogest per 50 kg body weight. GnRH challenges (5 micrograms/kg body weight) were administered every 8 weeks from 32 to 96 weeks of age to estimate pituitary content of LH. Blood samples were collected every 20 min for 4 h before GnRH and 15, 30, 45, 60, 90, 120, 180, 240 and 360 min after GnRH. Serum concentrations of LH and FSH were determined for the 2 pre-GnRH and all post-GnRH samples. Baseline concentrations (mean of 2 pre-GnRH samples) of LH and FSH were not affected by treatment (P greater than 0.05). Serum concentrations of LH declined from 40 to 56 weeks and rose again between 72 and 80 weeks. Basal concentrations of FSH declined from 32 to 56 weeks, and varied widely after 56 weeks. The maximum LH response to GnRH (highest concentration after GnRH minus baseline) declined steadily in both groups for 48 to 64 weeks but remained relatively constant in both groups after 64 weeks. The maximum FSH response to GnRH declined from 32 to 64 weeks then remained relatively constant in both groups. The GnRH-induced gonadotrophin release remained low with a transient increase at 72 weeks for both hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective impairment of song learning following lesions of a forebrain nucleus in the juvenile zebra finch

Area X, a large sexually dimorphic nucleus in the avian ventral forebrain, is part of a highly discrete system of interconnected nuclei that have been implicated in either song learning or adult song production. Previously, this nucleus has been included in the song system because of its substantial connections with other vocal control nuclei, and because its volume is positively correlated with the capacity for song. In order to directly assess the role of Area X in song behavior, this nucleus was bilaterally lesioned in both juvenile and adult zebra finches, using ibotenic acid. We report here that lesioning Area X disrupts normal song development in juvenile birds, but does not affect the production of stereotyped song by adult birds. Although juvenile-lesioned birds were consistently judged as being in earlier stages of vocal development than age-matched controls, they continued to produce normal song-like vocalizations. Thus, unlike the lateral magnocellular nucleus of the anterior neostriatum, another avian forebrain nucleus implicated in song learning, Area X does not seem to be necessary for sustaining production of juvenile song. Rather, the behavioral results suggest Area X is important for either the acquisition of a song model or the improvement of song through vocal practice.

Dopamine in the cerebrospinal fluid of prepubertal and adult horses

Catecholamine concentrations (pg/ml) in the cerebrospinal fluid (CSF) of prepubertal (n = 9) and adult (n = 18) horses were determined by radioenzymatic assay. Norepinephrine was low or non detectable in all CSF samples. In contrast, measurable CSF dopamine concentrations were effected by age, reproductive status and exogenous steroid treatments. The concentration of dopamine in the CSF of prepubertal females (733 +/- 92) was greater (p less than 0.05) than the concentration in the CSF of prepubertal males (117 +/- 67). Prepubertal male horses which were treated with testosterone for 5 days (50 mg/day) had elevated (p less than 0.05) dopamine concentrations (2,533 +/- 1,160) in the CSF compared to control males. In adult mares, dopamine was lower (p less than 0.05) in the ovulatory season (25 +/- 10) than during the anovulatory season (200 +/- 101). Daily intramuscular estradiol-17 beta (5 mg/day) injections had no effect (p less than 0.05) on dopamine concentrations in the CSF of seasonally anovulatory mares (250 +/- 35). Further, concentrations of dopamine in the CSF of long-term ovariectomized mares (80 +/- 21) were not influenced (p less than .05) by season. These results suggest that age, sex and gonadal steroids may effect dopamine, but not norepinephrine, concentrations in the brain ventricular system of the equine species. Further, seasonal effects on CSF dopamine concentrations are dependent upon the presence of the ovaries.

Changes in the responsiveness of prolactin secretion to dopaminergic blockade and TRH stimulation throughout sexual maturation in men

The pituitary prolactin (PRL) response to domperidone (DOM; a dopaminergic antagonist) and TRH administration in human males during different stages of sexual maturation was investigated. Dopaminergic blockade caused an immediate and significant PRL release in all subjects, regardless of the stage of pubertal development. Even though the mean values of peak PRL levels, magnitude of PRL response (delta PRL) and areas under the PRL curve were not significantly different among the different groups, all these parameters showed a clear tendency to increase in parallel to the stage of pubertal development, as indicated by significant positive correlations between age and pubertal stage of the subjects and the magnitude of their PRL response to DOM (r = 0.661, p less than 0.01 and r = 0.536, p = 0.01, respectively). Significant positive correlations also were found between the serum sex steroid hormone concentrations and the PRL response to dopaminergic blockade (r = 0.774, p = 0.02 and r = 0.554, p = 0.01, respectively). In contrast to these findings, no significant differences or tendencies were detected in the PRL responses to TRH among the different subject groups. The different patterns of PRL response to DOM and TRH throughout male puberty might be due to differences in pituitary thresholds for sex steroids between the dopamine- and TRH-dependent intracellular pools.

Ontogeny and secretory patterns of plasma insulin-like growth factor-I concentrations in meat-type chickens

The ontogeny and secretory pattern of plasma insulin-like growth factor-I (IGF-I) in relation to GH secretion were studied in meat-type (broiler) poultry during pre-pubertal and post-pubertal growth. Male and female broiler chickens of two commercial strains (strains A and B) were reared from 1 to 198 days of age. From 1 to 49 days of age birds were reared in raised-wire cages and thereafter in deep-litter pens, with food available ad libitum. Blood samples were taken at regular intervals during growth, and at 29 and 43 days of age representative birds were cannulated and serial blood samples taken at 10-min intervals for 5 to 7 h. Plasma concentrations of GH and IGF-I were measured by radioimmunoassay. Birds of strain A were heavier (P less than 0.05) than those of strain B from 12 to 35 days of age. In general, male birds were heavier (P less than 0.01) than females from 12 to 35 days of age. Plasma GH concentrations were significantly higher (P less than 0.05) from 12 to 35 days of age, while plasma IGF-I concentrations were lower (P less than 0.05) from 6 to 21 days of age in male compared with female birds. Plasma IGF-I concentration increased with age, reaching a plateau at 28 days of age, while plasma GH concentration declined over the same period. Plasma IGF-I concentrations declined in a linear manner from 49 to 198 days of age, and there was no evidence of a pubertal increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of H1 and H2 histamine receptor antagonists on positive feed-back effect of estrogen on LH in prepubertal female rats

The aim of the present study was to determine whether histaminergic central mechanisms which exert a well known effect on gonadotrophin secretion are involved in the development of the positive feed-back effect of estrogen-progesterone (E-P) on LH secretion that normally occurs in female rats about 20-22 days old. The administration of histamine H2 (cimetidine and ranitidine) or H1 (diphenhydramine) receptor blocking agents did not modify the onset of the LH release response to E-P. Nevertheless cimetidine, ranitidine and diphenhydramine potentiated the LH release induced by ovarian steroids at 23 days of age. These results appear to indicate that histaminergic pathways are involved in the magnitude of the LH response to E-P in prepubertal female rats rather than in the maturation of this mechanism.

[Morphofunctional characteristics of microcirculation in the skin of girls 5-17 years of age]

In 261 girls year-to-year morphofunctional transformations of spatial composition of the skin microcirculatory bed have been studied at rest and after a dynamic local load. By means of biomicroscopy main regularities in development of the skin capillary network have been revealed in the nail torus in the postnatal ontogenesis. Formation of the microvessels reactivity during various age periods and maturation of mechanisms of the compensatory-adaptive reactions are connected with formation of the definitive composition of the microcirculatory bed, that in girls corresponds to 11-12 years. Qualitative transformations in the skin capillary network bring certain quantitative changes in the structural microcirculatory parameters--increasing diameter of microvessels and increasing density of functioning capillaries.

Timbre control in zebra finch (Taeniopygia guttata) song syllables

Zebra finch (Taeniopygia guttata) song syllables often include harmonically related frequency components. These harmonics may be suppressed, and this differential emphasis varies between the syllables in a song and between individual birds' songs. These patterns of harmonic suppression are timbre. Individual syllables' patterns of harmonic suppression are constant with adult males' songs. Young males that imitate the songs of older males also imitate their patterns of harmonic suppression. Syringeal denervation distorts these patterns, which suggests that they are produced through active control of the vocal organ. The selective suppression and emphasis of some harmonics creates a great number of possible timbre variants for any one syllable. These add signal diversity to the limited array of frequency modulations and range of fundamental frequencies found in zebra finch song. Analyses of bird song that disregard timbre may overlook a feature that is important in vocal communication.

Geographic differences for delay of sexual maturation in Peromyscus leucopus: effects of photoperiod, pinealectomy, and melatonin

Effects of short-day photoperiod, pinealectomy, and melatonin on sexual maturation were tested in Peromyscus leucopus from either Connecticut (CT) or Georgia (GA). Laboratory reared-stocks from CT and GA were exposed to short daylength (photoperiod) from birth or 25 days of age. At 12 wk of age, delay in sexual maturation was indicated in most CT mice by decreased testis length, combined testes weight, and seminal vesicle weight. Conversely, GA animals did not delay sexual maturation when exposed to short-day photoperiod from either birth or 25 days of age. These results indicate that responses to short daylengths differ for juvenile CT and GA populations. In a second experiment, pinealectomized or sham-operated CT males were exposed to short-day (9L:15D) or long-day (16L:8D) photoperiod from birth. Pinealectomy blocked the effect of short daylength on reproduction. Therefore, the pineal must be involved in the delay of sexual maturation observed for short-day CT mice. The effects of melatonin, a pineal gland hormone, were tested with chronic s.c. implants or daily injections. In CT mice given either melatonin implants or afternoon injections, sexual maturation was delayed. GA mice were insensitive to all melatonin treatments. Further, no differences in circadian organization (phase angle, duration of activity, period under constant dark) between GA and CT animals were apparent. Collectively, these studies indicate that melatonin is involved in the mechanism responsible for delay of sexual maturation in CT mice. Short-day insensitivity of GA Peromyscus leucopus probably results from a deficiency in the melatonin effector pathway and is not due to a disruption of circadian organization.

Relationships of sire scrotal circumference to offspring reproduction and growth

Reproductive and growth data were obtained on 779 and 564 yearling beef heifers and bulls, respectively, that had sires with yearling scrotal circumference data at the San Juan Basin Research Center, Hesperus, CO. Partial regression coefficients of reproductive and growth traits on inbreeding (FXC) and age of the individual and adjusted scrotal circumference of sire (SCSI) were obtained. Growth and reproductive traits of heifers and growth and breeding soundness traits of bulls were analyzed. Separate analyses for each sex were performed, but least squares models were similar. Models included fixed effects of breed, birth year (BY), age of dam (AOD) and the covariates FXC, age (day of birth in heifer analyses) and SCSI. Scrotal circumference of sire was adjusted for age, FXC, AOD and BY using values obtained in a separate analysis. Seminal traits improved as age increased, and there was a seasonal effect present for age of puberty. Inbreeding had a detrimental effect on reproductive traits. Partial regression coefficients for the reproductive traits on SCSI were: age of puberty, -.796 d/cm; age of first calving, -.826 d/cm; julian day of first calving, -.667 d/cm; julian day of second calving, .597 d/cm; most probable producing ability, .132 %/cm; percent sperm motility, -.74 %/cm; percent primary sperm abnormalities, .08 %/cm; percent secondary sperm abnormalities, .92 %/cm; percent normal sperm, -1.28 %/cm; total breeding soundness examination score, .28 units/cm and scrotal circumference, .306 cm/cm. A heritability of .39 was obtained for scrotal circumference.

Maturational changes in the LH response of domestic fowl to synthetic chicken LHRH-I and -II

Treatment of chickens at different stages of sexual development with a single i.v. injection of synthetic chicken LHRH (cLHRH)-I or -II stimulated a rise in the plasma concentration of LH within 1 min. The activity of cLHRH-II was 1.3- to 2.7-fold greater than that of cLHRH-I in sexually immature cockerels and hens as determined by the changes in the plasma concentration of LH during the 5 or 10 min after injection. This could be attributed to both a greater effectiveness of cLHRH-II to stimulate LH release and to a more prolonged action. Thus, LH concentrations in plasma were maximal within 1-2 min of injection of all doses of cLHRH-I but within 2-5 min of injection at the higher doses of cLHRH-II. The responsiveness of the pituitary gland to cLHRH-I and -II was substantially greater in the sexually immature cockerel than in the hen and diminished during sexual development of the hen. Coincident with the onset of egg laying, the characteristics of the LH response to cLHRH-II changed to consist of an initial rise during the first 2 min, followed by a more sustained increase with LH concentrations still rising 10 min after injection. In contrast, after injection with cLHRH-I, plasma concentrations of LH rose to a peak at 2 min and thereafter declined gradually. Treatment of the sexually immature hen with oestradiol, progesterone or a combination of both steroids did not enable the expression of a laying hen-type response to the injection of cLHRH-II.(ABSTRACT TRUNCATED AT 250 WORDS)

Luteinizing-hormone-mediated precocious puberty induced in female rats by a prepuberal pituitary graft

The present study analyzes the mechanism of precocious puberty induced in female rats after a 'young' pituitary graft (obtained from 21-day-old animals). For this purpose, the following experiments have been performed: (1) female rats were grafted or sham-operated on day 21 with a littermate's pituitary the follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol plasma levels as well as the ovarian, uterine and adrenal weights were determined at different times after the graft; (2) female rats grafted or sham-operated on day 21 were treated with 0.2 ml of LH antiserum (LHAS) or the same volume of a normal horse serum (NHS); (3) female rats were injected on day 1 of life with 0.1 mg of estradiol benzoate or olive oil. Groups of these animals were decapitated daily between days 6 and 21 in order to measure gonadotropins and prolactin (PRL) pituitary content. Since on day 21 estrogenized females showed decreased gonadotropin content and normal PRL content, females in experiment 4 were grafted on day 21 with pituitaries obtained from control or neonatally estrogenized female rats. The results obtained showed that FSH, LH and estradiol plasma levels as well as ovarian and uterine weights increased after pituitary grafts. LHAS blocked the precocious puberty induced by the pituitary graft, and pituitaries obtained from neonatally estrogenized female rats were unable to modify the occurrence of puberty when grafted. In conclusion, this work evidences that precocious puberty induced by 'young' pituitary grafts was mediated by the increase in LH secretion from the graft.

Sexual maturation in starlings raised on long or short days: changes in hypothalamic gonadotrophin-releasing hormone and plasma LH concentrations

Is the extended prepubertal period which occurs in most birds due to a juvenile photorefractoriness analogous to photorefractoriness in adults? Starlings were taken from nest boxes 4 days after hatching and hand-reared on long days or short days. In females on long days, hypothalamic gonadotrophin-releasing hormone (GnRH) content and plasma LH concentration remained low. In intact males on long days, plasma LH remained low and the testes remained small, and in castrated birds, plasma LH also remained low. In females reared on short days, hypothalamic GnRH content began to increase dramatically from 4 weeks of age and plasma LH increased from 6 weeks of age. In intact males on short days, there was a slight increase in plasma LH and testicular size, and in castrated males, plasma LH increased markedly from six weeks of age. All birds on long days moulted into adult plumage, whereas those on short days retained juvenile plumage. The changes in birds reared on short days were similar to those found when photorefractory adult birds are transferred to short days. This adds to the evidence that juvenile photorefractoriness is analogous to photorefractoriness in adults, and therefore that the seasonal termination of photorefractoriness is an annual puberty. However, the responses to short days occur later in birds raised on short days than in older birds transferred to short days, which suggests either that short day-induced changes occur more slowly in young birds, or that birds only respond to short days after a certain age.