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PubMed2003

Body mass, age and sexual maturity in short-beaked echidnas, Tachyglossus aculeatus.

During the course of this 12 year field study body masses of 11 hatchling echidnas (Tachyglossus aculeatus multiaculeatus) and 25 pouch young between the ages of 5 and 60 days were recorded. Body mass increased from 0.3 to approximately 50 g in the first half of pouch life. It then quadrupled before young were placed in a burrow at 45 to 55 days of age. There was a positive correlation between the body mass of the female and that of her young at weaning. From 33 subadult echidnas located, tagged and radio tracked during this study, body masses of 10 were monitored to sexual maturity, i.e. when first encountered in a courtship train. Minimum age of sexual maturity ranged between 5 and 12 years. As subadults, there was no difference between mean body masses of males and females. At sexual maturity, mean body mass of females was significantly higher. No correlation was found between age at sexual maturity and body mass nor was there a significant difference in age of males and females at sexual maturity.

Animals↗
PubMed2004

Changes in light intensity can influence age at sexual maturity in domestic pullets.

1. Shaver White and ISA Brown pullets were reared to 140 d in groups of 8 in cages on a 10-h photoperiod of incandescent light and maintained at an illuminance of 3 or 25 lux, or transferred from 3 to 25 lux or from 25 to 3 lux at 63 or 112 d of age. 2. There was no significant difference in sexual maturity, measured as eggs per 100 bird.d at 139 and 140 d, for ISA Brown maintained on 3 or 25 lux, but Shaver White pullets exposed to constant 3 lux matured significantly later than those maintained on 25 lux. 3. In Shaver Whites, sexual maturity was significantly delayed by an increase from 3 to 25 lux at 63 and 112 d, and advanced by a decrease from 25 to 3 lux at 112 d. Sexual maturity of ISA Browns was not significantly affected by a change in illuminance at 63 or 112 d, though responses were in the same direction as for Shaver Whites. 4. In both breeds, total feed consumed to 112 d was higher for birds on 3 lux than 25 lux, but lower between 112 d and 140 d when birds on 25 lux underwent rapid sexual development. In both breeds, body weight at 63 d was higher for birds exposed to 3 lux than 25 lux, but body weight gain thereafter was similar for the two light intensities. 5. In both breeds, plasma luteinising hormone (LH) concentration at 63 and 112 d was lower in birds maintained on 3 lux than 25 lux. At 63 and 112 d, transfers from 25 to 3 lux depressed, whereas transfers from 3 to 25 lux at 63 d, but not at 112 d, increased plasma LH. 6. Advances or delays in sexual maturity induced by changes in illuminance were not correlated with differences in feed intake, body weight gain, or with changes in plasma LH. 7. One possible explanation for the inverse relationship between the direction of change in illuminance at 63 and 112 d in pullets exposed to a 10-h photoperiod and the age at which they became sexually mature is that changes in light intensity and/or spectral composition affect the entrainment of the circadian rhythm of photoinducibility, to effect a phase shift in the photoinducible phase and/or the responsiveness of phototransduction pathways.

Animals↗
PubMed1993

Response of broiler breeder females to feed restriction below recommended levels. 3. Characterizing the onset of sexual maturity.

The objective of this study was to characterize how the physical attributes associated with sexual maturity would be affected by feed allocation as female broiler breeders passed through the pullet-layer transition period. Treatments consisted of five feeding programs, or body weight goals, during the period of 0 to 20 wk of age. Those were 8% above breeder standard, standard (primary breeder recommended body weights), and 8, 16, and 24% below standard. The characteristics measured included body and fat pad weights, pubic spread, comb development, head score (comb and wattle appearance), shank length, total plasma lipid concentration, ovary weight, oviduct weight, bursa of Fabricius weight, and age at sexual maturity. The generalized effect of increased severity of the feed restriction programs was to delay the birds' development without altering their ultimate physiological values. The exceptions to this were relative body weight and shank length after maturity, which were reduced in the most severely restricted birds. Measurements of pubic spread and comb growth and subjective scores of head appearance would be useful and easily obtained information when estimating the progression of a flock toward sexual maturity.

Age Factors↗
PubMed2004

Sex-specific changes in platelet aggregation and secretion with sexual maturity in pigs.

Cardiovascular disease may begin early in adolescence. Platelets release factors contributing to vascular disease. Experiments were designed to test the hypothesis that hormonal transitions associated with sexual maturity differentially affect platelet aggregation and secretion in males and females. Platelets were collected from juvenile (2-3 mo) and sexually mature (adult; 5-6 mo) male and female pigs (n=8/group). Maturation was evidenced by increased weight of reproductive tissue and changes in circulating levels of gonadal hormones. Aggregation to ADP (10 microM) and collagen (6 microg/ml) and ATP secretion to 50 nM thrombin were determined by turbidimetric analysis and bioluminescence, respectively. Total platelet counts, platelet turnover, and mean platelet volume did not change with maturity. Platelet aggregation and ATP secretion decreased in females but increased in males with maturity, whereas total ATP content remained unchanged in platelets from females but increased in platelets from males. Platelet fibrinogen receptor, P-selectin expression, and receptors for sex steroids did not change with sexual maturation. Plasma C-reactive protein and brain-type natriuretic peptide also did not change. Results indicate that changes in platelet aggregation and secretion change with sexual maturity differently in females and males. These observations provide evidence on which clinical studies could be designed to examine platelet characteristics in human children and young adults.

Adenosine Triphosphate↗
PubMed1980

Prognosis of sexual maturation in prepubertal boys with micropenis.

Long-term observations were made of the prognosis for sexual maturation (onset of puberty) in 15 prepubertal boys with micropenis. Testosterone levels before and after HCG administration and LH and FSH responses to LH-RH were measured at the first visit and a few years later. In the eight boys who showed significant responses to the LH-RH and HCG tests, onset of puberty occurred with the exception of one patient. The remaining seven boys who showed no positive response to either stimulation test were treated with injections of HCG. However, no signs of sexual maturation were observed. These data demonstrate clearly that both the HCG test and the LH-RH test are very useful for prognosis of sexual maturation in patients with micropenis.

Adolescent↗
PubMed1995

Hypothalamic excitatory amino acid system during sexual maturation in female rats.

The present results indicate that during sexual maturation the APOA-MBH from rats of 30 days of age released significantly higher quantities of GnRH than the tissue from 16-day-old rats (P < 0.01). The addition of NMDA, an agonist of the excitatory amino acids system (EAAs), to the medium after 30 min of incubation significantly increased (P < 0.01) the GnRH release in normal rats of both ages and this increase was significantly (P < 0.01) higher in 30-day-old rats (to 661%) than in rats of 16 days of age (to 273%). The administration of estrogen-progesterone (EP) to rats of 16 days of age did not modify the GnRH release response to NMDA. On the contrary, at 30 days of age EP administration significantly potentiated the GnRH release response to NMDA since while in the control group NMDA increased the GnRH release to 630%, in the EP-pretreated group this was to around 4700% (P < 0.01). EP pretreatment of prepubertal rats decreases the hypothalamic release of aspartate and glutamate, the excitatory amino acids involved in NMDA neurotransmission and glycine but increases EAAs release in peripubertal rats. On the basis of these results it is proposed that the increase in EAAs release by the hypothalamus is directly connected with the onset of puberty and that the maturation of the positive feedback effect of ovarian hormones on gonadotropin secretion is related to the maturation of the capacity of EP to increase hypothalamic EAAs. Before this maturational event EP inhibits EAAs release as well as gonadotropin release (prepubertal rats). NMDA receptor stimulation leads to a positive mechanism which increases the release of Asp and Glu from APOA-MBH both in prepubertal and peripubertal rats, but EP potentiates this mechanism only in peripubertal rats. This could be an additional neuroendocrine mechanism involved in the increase of gonadotropin during sexual maturation which induces the onset of puberty and the preovulatory discharge of these pituitary hormones.

Age Factors↗
PubMed1978

Coronary degeneration in sexually mature rainbow and steelhead trout, Salmo gairdneri.

Correlation of coronary arteriosclerosis with sexual maturation was found in rainbow and steelhead trout. All sexually mature nonanadromous rainbow, precocial male steelhead, and adult spawning steelhead had myointimal hyperplasia but it was infrequent in immature juveniles. Lesion severity in adult rainbow and precocial steelhead approach that of spawning steelhead.

Animals↗
PubMed1980

Adolescents' self-assessment of sexual maturation.

The variability in time on onset and progression of puberty warrants the use of stage of sexual maturation rather than chronologic age in assessing biological and behavioral measures during adolescence. The necessity to undress the teenage has seriously curtailed the application of stage of sexual maturation to behavioral and developmental research. This study demonstrated that adolescents can accurately assess their own developmental stage according to Tanner's standard photographs. Self-ratings by 43 females, aged 9 to 17, and 23 males, 11 to 18, were compared to those based on physical examination by one of the investigators. Agreement with the physician rating occurred for breast stage in 37/43, for female pubic hair stage in 40/43, and for male combined pubic hair and genital stage in 21/23 (kappa coefficients: 0.81, 0.91, 0.88). The excellent agreement between physician and adolescent's assessment compared favorably with the interrater agreement of professionals. This study suggests the value of utilizing adolescent self-staging in research. In addition, this exercise provides teenagers with an objective way to understand the wide range of normal pubertal development and to follow their own sexual maturation.

Adolescent↗
PubMed1993

[The role of prolactin on sexual maturation of female rat].

The role of prolactin (PRL) in sexual maturation of immature female rats was examined in drug induced hyper-or hypoprolactinemic models. 1. In order to examine the role of PRL before the third week after birth, at which the serum PRL level of female rats is known to be low under physiological conditions, hyperprolactinemia was induced by daily subcutaneous injections of sulpiride from day 10 to day 20. Ovarian and uterine weights, serum hormone levels and in vitro estradiol (E2) release from removed ovary were evaluated on day 15 and day 20. The inhibition of uterine growth on both days a low serum E2 concentration on day 20 and inhibition of in vitro ovarian E2 release were demonstrated as the result of sulpiride treatment. 2. In order to examine the role of PRL after the fourth week, when the serum PRL level is known to become high, hyper- or hypoprolactinemia was induced from day 22 by per os administration of sulpiride or bromocriptine. Timing of the onset of puberty weights of the ovary, uterus and adrenal gland and serum hormone levels at the onset of puberty were evaluated. In the sulpiride treated group the timing of the onset of puberty was not affected and lower adrenal gland weight and a low serum FSH concentration were observed. In the bromocriptine treated group the timing of the onset of puberty was delayed and greater adrenal gland weight was observed. Serum hormone levels were not affected. These results suggest that (i) prolactin could have an inhibitory effect on sexual maturation before the 3rd week.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Black-white differences in serum lipoproteins during sexual maturation: the Bogalusa Heart Study.

Serum lipid, lipoprotein cholesterol, and apolipoprotein (A-I and B) levels were compared between 940 black and 1710 white children who were between the ages of 5 and 17 years. Stratification, matching, and analysis of covariance were used to determine whether black-white differences in levels of serum triglycerides (TG), very low- (VLDL-C), and high- (HDL-C) density lipoprotein cholesterol, and apolipoprotein A-I (apoA-I) could be explained by differences in sexual maturation, obesity, cigarette smoking, alcohol intake, oral contraceptive use, insulin, and glucose. Independently of these covariates, blacks had elevated levels of HDL-C and apoA-I (males only), and whites had increased levels of TG and VLDL-C. All differences were statistically significant at the 0.001 level. In addition, racial contrasts tended to be greater in sexually mature, as compared with prepubertal, males; a similar divergence of levels with sexual maturation was not observed in females. HDL-C levels in white males were partially explained (R2 = 0.12) by sexual maturation, insulin, and obesity; apoA-I levels were associated with only sexual maturation and insulin. Racial differences in levels of serum lipids, lipoprotein cholesterol, and apoA-I in early life, therefore, exist independently of differences in several lipoprotein determinants. Since the initial stages of atherosclerosis begin in the young, these black-white lipoprotein contrasts may influence differences in adult coronary heart disease rates between the races.

Adolescent↗
PubMedDate not supplied

Prevalence of obesity in adolescents and the impact of sexual maturation stage on body mass index in obese adolescents.

OBJECTIVE: Puberty is a high-risk period for the development of obesity. The aim of this study was to determine the prevalence of obesity in adolescents admitted to an outpatient adolescent clinic and investigate the relationships between the increase of body mass index and sexual maturation stages in obese adolescents. MATERIAL AND METHODS: We recruited 6,462 adolescents, aged 9-16 years, admitted to the outpatient clinic of our Adolescent Unit, between May 1999 and September 2000. BMI was calculated as weight per height with weight in kilograms and height in meters. Adolescents with a BMI > or = 95th percentile for age and sex were defined as obese, with BMI's > or = 90th percentile but < 95th percentile were defined as overweight and considered at risk for obesity. Obese adolescents, with endocrine problems identified to cause obesity, were excluded from this study. Pearson correlation coefficients were used to assess the relationships between BMI and age. The differences between the sexual maturation stages were evaluated with Mann-whitney U Test. RESULTS: Out of 6,462 cases screened, 151 obese adolescents were found. Prevalence of obesity for the total sample surveyed was estimated at 2.3%. BMI values were significantly correlated with age in both sexes. In girls, only the increase of BMI values from stage I to stage II was found to be statistically significant. In boys, BMI values did not differ significantly between the sexual maturation stages but the number of obese cases were high in stages I and II. DISCUSSION AND CONCLUSION: The pubertal growth spurt (timing determined by sexual maturation stage) effects the amount of fat accumulation and the distribution of fat in different ways in boys and girls. So, not only the age and sex but also the sexual maturation stage has to be taken into account while evaluating the BMI values for investigating the risk of obesity in puberty.

Adolescent↗
PubMed1989

Growth hormone (GH) deprivation induced by passive immunization against rat GH-releasing factor delays sexual maturation in the male rat.

GH deprivation after passive immunization against rat GRF (rGRF) markedly affects somatic growth in male rats. Since it has been postulated that GH and probably insulin-like growth factor-I (IGF-I) might have a permissive role on sexual maturation, the effects of GH deprivation on the course of sexual maturation were tested. Male rats were treated with a potent anti-rGRF serum between 15 and 39 days of life (0.25 ml administered sc every second day). Body weight of treated rats averaged 62% of that of control (normal rabbit serum-treated) rats at 40 days of life (d), and 64% at 50 d after which age, treated rats started to grow normally. At 40 and 50 d, pituitary GH content was very much depressed (representing approximately 20% of control values at both ages), plasma GH was undetectable, and plasma IGF-I levels averaged 30% of those of control rats. At 70 d, 30 days after cessation of treatment, pituitary GH content, and IGF-I secretion were almost normal. At 40 d, testes and seminal vesicles of treated rats were small-for-age in agreement with significantly decreased plasma levels of FSH and delayed spermatogenesis characterized by the presence of only few or no spermatozoa. At 50 d, 10 days after cessation of anti-rGRF injections, progress of sexual maturation was found to be consistent with age and coincided with normalization of growth rate. At 40 and 50 d, pituitary contents of FSH and LH were severely decreased but became normal at 70 d. In conclusion, GH deprivation which markedly affected somatic growth induced a transient delay of sexual maturation. GH deficiency seems to have affected mostly the synthesis and secretion of FSH, thus producing a delay in testes growth and in the differentiation of the germinal cells. The low levels of IGF-I might also have been the cause for the delay of maturation at the pituitary and/or the gonadal levels.

Animals↗
PubMed1987

The effects of zearalenone on reproduction in swine. I. The relationship between ingested zearalenone dose and anestrus in non-pregnant, sexually mature gilts.

Ninety-nine sexually mature, non-pregnant gilts were checked for estrus daily with a mature boar and then allocated at estrus (D O) to receive 2 kg/d of a diet containing 0, 1, 5 or 10 ppm purified zearalenone between D 5 and 20 of the estrous cycle during two seasons of the year (winter and summer). None of the gilts exhibited any visual signs of "hyperestrogenism" and there was no effect of season on interestrous interval (P>0.05). A significant effect of zearalenone dose on inter-estrous interval was detected (P<0.001). Gilts receiving 0 or 1 ppm had similar inter-estrous intervals (21.0+/-0.3 and 21.5+/-0.8 d, respectively) whereas gilts receiving 5 and 10 ppm had extended cycles (29.2+/-2.9 and 32.7+/-3.3 d, respectively). Plasma progesterone concentrations at D 19 to 21 were higher in gilts with extended cycles (P<0.001) and corpora lutea (CL) were present at laparotomy. Some 86% of these retained CL underwent spontaneous regression resulting in the onset of estrus within the next 30 d. Fecal zearalenone concentrations rose during ingestion of contaminated diets and declined to pretreatment values within 2 d (1 ppm) to 8 d (10 ppm) of the cessation of treatment. These data show that feeding zearalenone at concentrations of 5 to 10 ppm from D 5 to 20 of the estrous cycle causes luteal maintenance and extended inter-estrous intervals. Spontaneous regression of these CL usually occurs within 30 d after zearalenone is removed from the diet. Fecal zearalenone analysis does not appear to be an effective method for determining prior exposure to zearalenone when carried out more than a few days following the last ingestion of zearalenone.

Journal Article↗
PubMed1990

Cultivation of sexually mature Brugia malayi in vitro.

Sexually mature male and female Brugia malayi were developed from third stage larvae after 60 days in the in vitro culture system described by Franke and others in 1987 (Am J Trop Med Hyg 37: 370-375). Between 75 and 100 days in culture, many worms produced living microfilariae. Each gravid female produced 200-1,500 microfilariae/day.

Animals↗
PubMed2006

Combined influence of early sexual maturation and central adiposity on subsequent stature. A four-year follow-up of 1,605 Norwegian boys and girls: the Young-HUNT study.

INTRODUCTION: Shorter adult stature has been attributed to early sexual maturation, as well as early adiposity, but it is not clear if these factors are interrelated. RESULTS AND DISCUSSION: A number of 1,605 Norwegian adolescents were followed from early (baseline) to late adolescence (follow-up). Maturational timing was assessed by self-reports of pubertal status (pubertal development scale, PDS) in boys and age at menarche (AAM) in girls. Height, weight and waist circumference were measured at baseline and at follow-up. Differences in height at follow-up and height gain related to the timing of sexual maturation and the level of central adiposity (i.e. high or low waist circumference) at baseline were estimated using general linear modelling. At follow-up, the median height was 180 cm in boys and 167 cm in girls. Early maturing boys and girls with relatively high central adiposity at baseline were, on average, 5.7 cm (P value<0.001) and 3.6 cm (P value<0.001) taller than early maturing boys and girls with low central adiposity. Differences in stature related to central adiposity were less pronounced for intermediate and late maturing boys and girls. The height was lowest in boys (176.6 cm) and girls (163.8 cm) who had matured early and had low central adiposity at baseline. Height gain during follow-up was independent of the level of central adiposity, but was closely related to the timing of sexual maturation. The association between the early timing of sexual maturation and subsequent height was modified by the level of central adiposity in early adolescence. CONCLUSION: The results suggest that early maturity combined with adiposity yields higher stature than early maturity and leanness.

Adiposity↗
PubMed2002

Alpha1-adrenoceptor subtypes in rat epididymis and the effects of sexual maturation.

We have characterized the expression of alpha1-adrenoceptor in epididymis from rats in different stages of sexual maturation: 40 (immature), 60 (young adult), and 120 (adult) days of age. Plasma testosterone levels were low in the immature animals but increased significantly in the 60- and 120-day-old animals. These changes were followed by a progressive increase in rat body weight and in caput and cauda epididymis relative weight. Reverse transcription polymerase chain reaction assay indicated that alpha1a-, alpha1b-, and alpha1d-adrenoceptor transcripts were present in both caput and cauda epididymis from adult rats. Ribonuclease protection assays further indicated that the expression of these alpha1-adrenoceptor transcripts differed with age and epididymal region analyzed. Prazosin (nonselective alpha1 antagonist), 5-methyl urapidil (alpha1A-selective), and BMY 7378 (alpha1D-selective) displaced [3H]prazosin binding curves in caput and cauda epididymis from 40- and 120-day-old rats. The potency order for these antagonists, as calculated from the negative logarithm of the inhibition constant (pK(i)) values for the high-affinity sites, indicated a predominant population of alpha1A-adrenoceptor subtype in caput and cauda epididymis from adult animals. Differences in pK(i) values in caput and cauda epididymis from immature and adult animals also suggested that the relative amount of alpha1-adrenoceptors, at the protein level, is modulated by sexual maturation. Taken together, the changes in alpha1-adrenoceptor expression during sexual maturation may suggest specific roles for these receptors in epididymal function.

Adrenergic alpha-Antagonists↗
PubMed1991

Changes of serum selenium and serum cholesterol in children during sexual maturation.

We investigated the relationship of the degree of sexual maturation to serum selenium and serum cholesterol fractions in a population of Italian children. The following measurements were taken in 109 immature and 108 mature children of both sexes (aged 12 and 13a): serum selenium, total cholesterol, high density lipoprotein cholesterol, height, weight and degree of sexual maturation. Considerable differences were found in the two sexes at the end of maturation, with boys showing a significant decrease in serum selenium, HDL and non-HDL serum cholesterol levels. All variables, except height and weight, remained relatively constant in girls. These data indicate significant changes of serum selenium and serum cholesterol patterns during puberty, at least in boys, suggesting an involvement of sexual hormones in regulating serum selenium levels.

Adolescent↗
PubMed1984

Age and body weight at sexual maturity in female white Leghorn chickens.

Age and body weight at sexual maturity were measured in females from two lines of White Leghorns known to differ in these traits. Within-line correlations between age and body weight at sexual maturity were not different from zero. The data demonstrated that egg-type chickens must reach a minimum age and body weight before commencing egg production - results consistent with those obtained for meat-type chickens and Japanese quail.

Aging↗