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Results for “Sexual Maturation”

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PubMed1985

Serum zinc concentrations in adolescents as related to sexual maturation.

Zinc status and sexual maturity rating (SMR) were evaluated in 108 male and 97 female adolescents. Each subject was assigned an SMR number according to Tanner's classification (SMR 1, prepubertal development; SMR 2, first visible signs of pubertal change; SMR 3, onset of growth spurt; SMR 4, period of rapid, but lessening development; SMR 5, adult development). Males at SMR 5 had higher (P less than 0.05) serum Zn levels than those at less mature stages; females at SMR 5 had higher (P less than 0.05) serum Zn levels than those at SMR 1 and 2. Serum Zn concentrations in post-menarcheal females were greater (P less than 0.05) than in premenarcheal females. The results suggest that level of sexual maturation should be evaluated as a factor in the assessment of adolescent serum Zn concentrations.

Adolescent↗

PubMedDate not supplied

Long-term effects of early kwashiorkor compared with marasmus. I. Physical growth and sexual maturation.

Physical growth and sexual maturation were measured in a follow-up study of Barbadian girls and boys aged 11-18 years with histories of kwashiorkor (n = 54) or marasmus (n = 56) in their first year of life. They were compared with healthy neighborhood children matched by sex and age who had normal patterns of growth in early childhood (n = 59). Girls with histories of marasmus had significant delays in the onset of menarche compared with healthy comparison girls. However, their rate of growth during the previous 2 years was accelerated, and the differences in size were smaller than at the earlier testing, confirming catch-up. This pattern was not evident for girls with histories of kwashiorkor, who did not differ from the healthy comparison girls on either onset of menarche, Tanner ratings of sexual maturation, or measures of physical growth. In contrast, boys with histories of kwashiorkor or marasmus did not differ from healthy comparison boys in physical growth or Tanner ratings at these ages.

Adolescent↗

PubMed1998

Effect of intermittent three-month treatment with different doses of Ukrain on subregional femoral bone mineral density of sexually mature female rats.

Sexually mature but still growing female Wistar rats received i.p. injections of Ukrain (7, 14 or 28 mg/kg in a volume of 0.5 ml/100g) every other day for 10 days, followed by a 10-day break, and this procedure was performed five times. The control animals received the same volume of injected water. At the end of the experiment the rat right femora were harvested and the bone densitometric parameters of the entire bone, distal metaphyseal and basicervical subregions were assessed using the dual-energy X-ray absorptiometry (DXA) densitometric method. No significant changes were observed in the bone mineral density in experimental groups in comparison with control animals that received the vehicle. A slight decrease in the bone mineral content value was observed in the distal metaphyseal region in animals that were treated with the highest dose of Ukrain.

Alkaloids↗

PubMed1992

Transforming growth factor-alpha gene expression in the hypothalamus is developmentally regulated and linked to sexual maturation.

Hypothalamic injury causes female sexual precocity by activating luteinizing hormone-releasing hormone (LHRH) neurons, which control sexual development. Transforming growth factor-alpha (TGF-alpha) has been implicated in this process, but its involvement in normal sexual maturation is unknown. The present study addresses this issue. TGF-alpha mRNA and protein were found mostly in astroglia, in regions of the hypothalamus concerned with LHRH control. Hypothalamic TGF-alpha mRNA levels increased at times when secretion of pituitary gonadotropins--an LHRH-dependent event--was elevated, particularly at the time of puberty. Gonadal steroids involved in the control of LHRH secretion increased TGF-alpha mRNA levels. Blockade of TGF-alpha action in the median eminence, a site of glial-LHRH nerve terminal association, delayed puberty. These results suggest that TGF-alpha of glial origin is a component of the developmental program by which the brain controls mammalian sexual maturation.

Animals↗

PubMed2001

Effects of photoperiod on sexual maturation and somatic growth in male Atlantic halibut (Hippoglossus hippoglossus L.).

A major obstacle in modern, intensive aquaculture is the precocious maturation of male fish, leading to decreased somatic growth and reduced filet quality. Effects of photoperiod on sexual maturation and growth in male Atlantic halibut were therefore examined. In June 1996, 1300 1+ fish of both sexes were distributed in two indoor tanks supplied with continuous light (LL) or a simulated natural photoperiod (SNP). In December 1996 and June 1997, 200 individuals were exchanged between the tanks creating six experimental groups that were followed until June 1998. LL stimulated growth and accelerated timing of first maturation by approximately 3 months. LL also appeared to interrupt circannual rhythmicity in sexual maturation. Sexual maturation led to reduced growth from 3 months pre-spawning and throughout the spawning season. Males that did not mature during the experiment attained the highest final body weight. All males reared on LL from June 1997 reached sexual maturity the following season. In contrast, only 26% of the males matured in the group transferred from LL to SNP in June 1997, and this group also had the highest final body weight. The results indicate a possible route for reducing the problem of precocious maturation in male halibut.

Animals↗

PubMed1998

Chronic administration of leptin into the lateral ventricle induces sexual maturation in severely food-restricted female rats.

In many species, delayed sexual maturation occurs when metabolic conditions are not satisfactory. Recently, leptin was shown to be involved in the regulation of food intake and body mass. Furthermore, leptin administration was shown to advance sexual maturation in mice and to rescue sexual function in adverse metabolic conditions. We examined plasma leptin levels in female rats during development and evaluated the role of leptin on sexual maturation in rats subjected to food restriction. In normal rats, plasma leptin levels were low at day 24 of life, then steadily increased during the juvenile period, reaching 740+/-56 pg/ml at 40 days at time of vaginal opening (VO) and further increasing by day 60 (957+/-73 pg/ml). Food restriction initiated at day 25 strongly impaired this increase, in proportion to the severity of the restriction. With a daily food intake reduced to 7-8 g/day, that permanently prevented VO, plasma leptin levels were very low at day 53 (169+/-67 pg/ml). Following switch to ad libitum feeding, plasma leptin reached high levels within 2 days (1577+/-123 pg/ml), and VO occurred 4 days later. If the severe food restriction was maintained and a central infusion of leptin (10 microg/day) was initiated, a significant decrease in body weight compared with vehicle-infused controls was observed. In these conditions, VO occurred in eight out of the nine leptin-treated rats, representing induction of the process of sexual maturation confirmed by increases in ovarian and uterine weights. This induction of sexual maturation exclusively results from a central effect of leptin because no leak of the i.c.v. administered leptin to the general circulation was observed. These data suggest that the rising plasma levels of leptin in the prepubertal period represent a signal to the brain indicating that the young animal is metabolically ready to go through the process of sexual maturation.

Animals↗

PubMed1976

Correlation between dental maturity, height development and sexual maturation in normal girls.

The correlation between the dental maturity and the different measures of sexual development, i.e. the age at menarche, the ages at breast and pubic hair development, and the age of peak height velocity, was found to be low in healthy girls. Multiple regression analyses between the predictors height and growth rate at the chronological age of a certain stage of the dental development and each of the predictands age at menarche, breast development, and age of peak height velocity improved the residual standard deviation significantly in comparison with the standard deviation of the distribution of these variables.

Adolescent↗

PubMedDate not supplied

Sexual maturation of Greek boys.

BACKGROUND: Sexual maturation is dependent on genetic and environmental factors, therefore each ethnic group has to have its own normative data. AIM: This study describes the sexual maturation of Greek boys. SUBJECTS AND METHODS: We examined cross-sectionally 1266 healthy boys, aged 8-16 years. Pubertal staging in each boy was assessed according to Tanner's classification. Our data were also compared with those of a study performed in 1968. RESULTS: The first pubertal sign was genital enlargement (G2) that occurred at a mean age of 11.0 (+/- 1.3) years followed by pubic hair development (PH2) at 11.5 (+/- 1.5) years of age. There was no clear change in pubertal maturation from the 1968 study. CONCLUSIONS: The age at which genital development occurs in Greek boys is no different from that of other Caucasian populations. However, pubic hair in Greek boys develops significantly earlier.

Adolescent↗

PubMed2004

Expression of estrogen receptors and enzymes involved in sex steroid metabolism in the rat tibia during sexual maturation.

Estrogens are essential for bone mass accrual but their role before sexual maturation has remained elusive. Using in situ hybridization and immunohistochemistry, we investigated the expression of both estrogen receptor (ER) alpha and beta mRNA and protein as well as several mRNAs coding for enzymes involved in sex steroid metabolism (aromatase, type I and II 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), steroid sulfatase (STS) and type I 5 alpha-reductase) on sections of tibial metaphyses before (1- and 4-week-old), during (7-week-old) and after (16-week-old) sexual maturation in female and male rats. ER alpha and ER beta mRNA and protein were detected in metaphyseal bone in lining cells, osteoblasts, osteoclasts and some osteocytes with no apparent differences in expression during development or between the sexes. In contrast, aromatase, type I and II 17 beta-HSD and type I 5 alpha-reductase mRNAs were first detected in osteoblasts, osteoclasts and occasionally in osteocytes from sexual maturation (7-week-old rat) and onwards. Only STS was present before sexual maturation. To study the significance of ER alpha and beta expression in bone before sexual maturation when circulating sex steroid levels are low, 26-day-old female and male rats underwent gonadectomy or 17 beta-estradiol (E(2)) supplementation (0.5 mg/21 days) during 3 weeks. Following gonadectomy, trabecular bone volume (TBV) was lower in males (P=0.03) and there was a trend towards reduction in females (P=0.057). E(2) supplementation increased tibial TBV compared with controls in both genders as assessed by Masson-Goldner staining. These data suggest that the presence of ERs in bone cells before sex maturation might be of significance for bone mass accrual. Furthermore, based on the mRNA expression of the crucial enzymes aromatase and type I 17 beta-HSD, we suggest that bone cells in the tibial metaphysis acquire the intrinsic capacity to metabolize sex steroids from sexual maturation onwards. This process may contribute to the beneficial effects of estrogen on bone mass accrual, possibly by intracrinology.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMedDate not supplied

Blood pressure and sexual maturity in adolescents: the Heartfelt Study.

This study investigates sexual maturity as a predictor of resting blood pressures independent of other known predictors, in 179 boys and 204 girls 11-16 years of age from the Heartfelt Study. The sample included youth of African (n = 140), Mexican (n = 117), and European and "other" (n = 126) backgrounds. Sexual maturity was assessed during clinical examination of three standard indicators for each sex. Systolic and diastolic blood pressures were higher in children of maturity stages IV and V, compared to stages I-III, in each gender/ethnic group (P < 0.01 in almost all groups). Boys and girls advanced in sexual maturity for their age group, had significantly higher systolic blood pressures (but not diastolic) than the less advanced in linear models that included height, body mass index (BMI), ethnicity, and age as co-predictors. Diastolic blood pressures were predicted by height in boys and by age and the BMI in girls. This analysis, using a very conservative approach, suggests that sexual maturity provides important and independent information on systolic blood pressure in adolescents. Further investigation of its role in 24-hr blood pressures and in blood pressures taken during physical and emotional stress, is recommended.

Adolescent↗

PubMed1991

Sexual maturation in female rats: hereditary, developmental and environmental aspects.

Two physiological components of sexual maturation, vaginal opening and first estrus, apparently evolve similarly in Wistar and Sprague-Dawley rats. However, a bimodal distribution in the frequency of the days of vaginal opening is observed within a given strain, which is less related to heredity than to the timing and type of experiment. In addition, when the modulators of sexual maturation are reviewed, it can be observed that sensitivity to external stimuli can vary even within a strain. For a defined set of breeding conditions, one group of rats can be more susceptible to changes in the lighting regimen and not be affected by controlled stressors, while another group responds more to stress and less to light. The reason for susceptibility to one rather than another environmental factor under similar breeding conditions is not understood. In that context, it is difficult to evaluate the role of heredity when we cannot understand the full impact of the environment, not to mention maternal influence in fetal and early life. Using two lines of psychogenetically selected rats, it was possible to show that they had differences in sexual maturation, which strongly suggested a genetic predisposition. Nevertheless, the question arises as to whether the genetic locus directly affects organs implicated in sexual maturation or whether it acts on some unknown factor which only secondarily modifies sexual maturation. In summary, there is more need to understand the role of the environment, including that of the mother early in fetal and neonatal life. It is suggested that the mechanisms underlying organ growth are set for a given species, while developmental and environmental factors fix the timing of vaginal opening and first ovulation. In the rat, there appear to be two times which are preferred for vaginal opening, given the laboratory conditions that have been used in the last 20 or so years: an early period, at 31-35 days, and a late period, at 36-40 days. An explanation for this dichotomy would be that a combination of parameters (not necessarily always the same) is needed for vaginal opening. These parameters oscillate during sexual maturation with different frequencies, which can achieve resonance to lead to vaginal opening and ovulation only during given periods.

Aging↗

PubMed1994

Growth hormone (GH) deprivation induced by passive immunization against rat GH-releasing factor does not disturb the course of sexual maturation and fertility in the female rat.

The importance of normal GH secretion for the onset of sexual maturation is a subject of controversy. Also, the need to achieve a minimal body size or body fat content has been postulated to be of importance for determining the timing of the onset of puberty. To evaluate the importance of GH secretion on the onset of sexual maturation in the female rat, GH deprivation has been induced by treating prepubertal rats with antirat GRF serum to passively immunize these animals against GRF. Chronic administration of anti-GRF serum produced in all series an impressive reduction in growth rate (from 5 to 2 g/day), resulting in a body weight averaging 50-60% the normal value at 50 days of life. Despite this deficit in growth, sexual maturation, as established by vaginal opening and first estrous cycles, occurred at the normal age in three of four series of rats; in one series, however, sexual maturation was delayed by 4 days, but thereafter, all parameters indicated that the gonadotropic axis was normally activated. In one series, fertility was tested at 59 days of age in females with a body weight corresponding to 51% of the control weight; these females conceived and delivered a reduced number of pups (9.4 +/- 0.7 instead of 14.2 +/- 0.8 in control dams), but the pups were of normal size. In a second experimental approach, the effect of GH deprivation was evaluated in a model of late sexual maturation obtained by severe food restriction followed by a switch to ad libitum feeding. Severe food restriction initiated at approximately 28 days, when the body weight was 75 g, drastically reduced the growth rate and completely prevented sexual maturation. A switch to ad libitum feeding at 50 days provoked an important compensatory growth and the occurrence of sexual maturation 4 days later. Passive immunization against GRF during this recovery phase did reduce the growth rate, but did not delay sexual maturation. Plasma insulin-like growth factor-I (IGF-I) secretion was very low in food-restricted rats and in each situation with induced GH deprivation. During food restriction, plasma IGF-binding protein-3 (IGFBP-3) and to a lesser extent IGFBP-1 were decreased, and IGFBP-2 was increased; after switching to ad libitum feeding, plasma levels of IGFBP-2 normalized, but levels of IGFBP-1 and IGFBP-3 remained low in the face of normalized plasma IGF-I levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Strategies for combining and scaling sexual maturity indicators: the Heartfelt Study.

PRIMARY OBJECTIVE: To identify the best variable or combination of sexual maturity variables to use in investigations of adolescent health, and explore possible re-scaling of five-stage sexual maturity stages into dummy variables' ('advanced'/'delayed'). RESEARCH DESIGN: Cross-sectional. SUBJECTS: Tri-ethnic sample of 384 US adolescents 11-16 years of age (Heartfelt Study). METHODS: Sexual maturity variables are genital. breast and pubic hair stages obtained by clinical examination by nurse practitioners, testes size, menarche and age at menarche. RESULTS: Principal factor analysis of sexual maturity variables, height and age, revealed high commonality among the variables, as no more than a single factor appeared in 27 of 28 factor analyses (by sex and age groups). Genital stage (boys) and breast stage (girls) were most highly related to the first principal factor independent of age and ethnicity. ANOVA of 'key variables' indirectly reflecting endocrine function suggested that some stages could be combined. CONCLUSIONS: A single variable should suffice to describe sexual maturity at the studied ages, or variables could be combined in a (unstandardized) sexual maturity index (SMI): SMI (Girls)=0.998 x BREAST+0.900 x PUBIC HAIR + 1.815 x YEARS SINCE MENARCHE. SMI (Boys)= 1.104 x GENITAL + 1.328 x PUBIC HAIR + 5.997 x TESTES SIZE (mL).

Adolescent↗

PubMed1995

Incidence of adolescent injuries in junior high school football and its relationship to sexual maturity.

Previous recommendations for adolescents have stated that sexually immature athletes may have a higher potential for injury when competing with their more sexually mature peers. However, studies document a higher injury rate among adolescent athletes with increasing age. This study was designed to see whether a relationship exists between sexual maturity based on Tanner stage and the incidence of adolescent injuries in a collision sport where the injury rates are highest. Three hundred and forty junior high school football athletes, ages 11-15, were observed prospectively for injury over two consecutive football seasons. Tanner staging of all of these athletes was performed at the preparticipation physical exam before the start of each season. Fifty-five injuries were noted for this time period. The overall injury rate was 16%. A direct correlation was observed between higher Tanner stages and increased injury rates. Adolescent athletes who have recently experienced sexual maturation may be at higher risk of injury in contact sports.

Adolescent↗

PubMed1985

Sexual maturation of the hypothalamus: pathophysiological aspects and clinical implications.

Sexual maturation in humans begins early in fetal life and culminates in adulthood when the gonads have acquired a full capacity for reproduction. It is remarkable that during this long process, the pituitary gonadal function, hence its hypothalamic control presents an alternative of activation and inhibition periods, during which the interrelations of the 3 components of the hypothalamic-pituitary-gonadal axis change gradually and inversely. The ontogeny of the hypothalamic-pituitary system, the varying activity of the reproductive endocrine system throughout sexual maturation and the developmental changes in the interrelations of the hypothalamic-pituitary-gonadal axis are reviewed: the most striking feature of human sexual development is the long inhibition of hypothalamo-pituitary function during childhood. Much indirect evidence points to the determining role of the CNS in the maturation of hypothalamic function: the occurrence of rhythms of secretion, the amplitude of secretions and peripubertal specific sleep-related nycthemeral rhythm of secretion at the onset of puberty. Despite the reality of a negative feedback control, these changes do occur independently of gonadal secretions since they are observed (qualitatively if not strictly quantitatively) in agonadal children. It is likely that neurotransmitters (dopamine, serotonine) and opiates have an inhibitory effect on Gn-RH release. But we still don't know their evolution during sexual maturation. It does not appear that melatonine plays any determinant role in the onset of human puberty. The clinical implications of our present understanding of the physiological events occurring during sexual maturation are several. Considering the major problems related to abnormal sexual maturation we will discuss successively: (1) diagnosis of hypogonadotrophic hypogonadism in early infancy; (2) differential diagnosis between premature thelarche and true sexual precocity; (3) the usefulness of endocrine investigations in the evaluation of hypothalamic-pituitary function; and (4) the new developments in the treatment of precocious puberty, delayed puberty or hypogonadism.

Adolescent↗

PubMed1980

The early influence of aflatoxin upon sexual maturation in the male Japanese quail.

The effects of early exposure to aflatoxin on sexual maturation were investigated in young male Japanese quail. Quail in Treatment A were fed a soy-corn starter mash with 10 micrograms aflatoxin/g added from 7 to 21 days of age. Treatment B quail were fed this from 14 to 28 days of age. Animals from each treatment were sampled at intervals from 25 days to 70 days of age. Both behavioral and physiological indicators of sexual maturation were monitored including measurements of sexual behavior, cloacal gland area, testes weight, and peripheral concentrations of testosterone. Statistical estimation was conducted to determine the age at which occurred rapid increase in hormone concentrations and morphological variables indicative of sexual maturation. Control animals showed increased testosterone concentration at 26 days and increased testes weight at 27 days. The cloacal gland area enlarged by 34 days and sexual behavior was first observed at 31 days. Animals in the A treatment had rapid testicular growth at 29 days and testosterone concentrations rose after 27 days. Concentrations were depressed compared to those of controls. Cloacal gland hypertrophy occurred after 37 days; initial sexual activity began at 35 days. The B treatment animals began showing evidence of sexual maturation significantly later with increasing testes weight by 36 days, testosterone concentrations by 37 days, cloacal gland area by 37 days, and initial sexual activity at 35 days. This experiment indicates that exposure to aflatoxin at an early age results in a delay in physiological and behavioral sexual maturation. Animals exposed between 7 and 21 days recovered slightly earlier than those treated between 14 and 28 days.

Aflatoxins↗

PubMed1982

Adolescent self-assessment of sexual maturation: reassessment and evaluation in a mixed ethnic urban population.

Pubertal changes correlate better with sexual maturity ratings than with chronological age. The applicability of sexual maturity ratings to research is impeded by the necessity to disrobe the adolescent. This study demonstrates that a mixed ethnic urban group of adolescent females can self-assess their own developmental stages by using standard photographs of sexual maturity stages. However, males do less well in self-assessment. Self-ratings by 22 female adolescents and 22 male adolescents aged 11 to 18 were compared to physicians' assessment. There was total agreement in 17/22 (r=0.87) breast stage assessment, 16/22 (r=0.86)female pubic hair assessment, 10/22 (r=0.72) male genital assessments and 11/22 (r=0.69) male pubic assessments. The mean differences in sexual maturity ratings between physician and adolescent were 0.32 for female pubic hair assessments, 0.64 for male pubic hair assessments, 0.68 for male genital assessments and 0.28 for breast assessments. This study suggests the feasibility of self-assessment of sexual maturity rating among black, white, and Hispanic adolescent females, but the need for further research before it is used among adolescent males.

Adolescent↗

PubMed2002

Review of growth plate closure compared with age at sexual maturity and lifespan in laboratory animals.

Although it is assumed that most mammals experience growth plate closure and cessation of bone growth soon after sexual maturity, bone growth in rats continues throughout their lifespan. The rat was compared to other laboratory animals to assess differences in the duration of bone growth and its relationship to age at sexual maturity and lifespan. We reviewed the literature from 1966 to March 1999 by searching MEDLINE and other databases. Growth closure times and age at sexual maturity were retrieved for the mouse, rabbit, dog, cat, sheep, cow, horse, nonhuman primates, and human. For all species, we calculated the ratios of: 1) age at growth plate closure to lifespan, 2) age at growth plate closure to age at sexual maturity, and 3) age at sexual maturity to average lifespan. The ratio of age at physis closure to the average lifespan was large for the rat (22 to 35) and showed some overlap with that of humans (17 to 25); this ratio was comparatively small in all other nonhuman species (range, 4 to 17). This finding indicates that bone growth continues in the rat for a greater proportion of their lifespan than does that in other species. The ratio of age at physis closure to age at sexual maturity was larger for the rat (5 to 6) than that for other species, indicating that bone growth continues much longer after sexual maturity in rats than in other animals. The ratio of age at sexual maturity to average lifespan was largest for humans and nonhuman primates (13 to 14), indicating the increased time to reach puberty versus that in other species. These differences are important for studies in which animal models are used in research involving bone growth.

Age Factors↗