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Results for “Sexual Maturation”

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At least 19 recordsLinked to original sources
PubMed1994

GnRH cell size and number in a teleost fish with two male reproductive morphs: sexual maturation, final sexual status and body size allometry.

Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50-100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Animals↗
PubMed1999

Control of oocyte maturation in sexually mature Drosophila females.

In many sexually mature insects egg production and oviposition are tightly coupled to copulation. Sex-Peptide is a 36-amino-acid peptide synthesized in the accessory glands of Drosophila melanogaster males and transferred to the female during copulation. Sex-Peptide stimulates vitellogenic oocyte progression through a putative control point at about stage 9 of oogenesis. Here we show that application of the juvenile hormone analogue methoprene mimics the Sex-Peptide-mediated stimulation of vitellogenic oocyte progression in sexually mature virgin females. Apoptosis is induced by 20-hydroxyecdysone in nurse cells of stage 9 egg chambers at physiological concentrations (10(-7) M). 20-Hydroxyecdysone thus acts as an antagonist of early vitellogenic oocyte development. Simultaneous application of juvenile hormone analogue, however, protects early vitellogenic oocytes from 20-hydroxyecdysone-induced resorption. These results suggest that the balance of these hormones in the hemolymph regulates whether oocytes will progress through the control point at stage 9 or undergo apoptosis. These data are further supported by a molecular analysis of the regulation of yolk protein synthesis and uptake into the ovary by the two hormones. We conclude that juvenile hormone is a downstream component in the Sex-Peptide response cascade and acts by stimulating vitellogenic oocyte progression and inhibiting apoptosis. Since juvenile hormone analogue does not elicit increased oviposition and reduced receptivity, Sex-Peptide must have an additional, separate effect on these two postmating responses.

Animals↗
PubMed1988

Adolescent self-assessment of sexual maturation. Effects of fatness classification and actual sexual maturation stage.

Accuracy of self-assessed staging of sexual maturation was studied on 96 adolescents (49 boys and 47 girls) to validate previous studies and evaluate the effects of an adolescent's fatness level and actual sexual maturation stage on their ability to assess their level of sexual maturation. Correlation between the adolescents' self-assessments and physician assessments was moderately high (Kendall's tau-b = 0.65-0.82). Boys tended to overestimate, while girls underestimated their level of sexual maturation. Differences between physician and subject ratings by fatness classification or by actual sexual maturation stage was not significant. This study supports previous studies showing that adolescents can accurately assess their own stage of sexual maturation regardless of their fatness classification or actual sexual maturation stage.

Adolescent↗
PubMed1990

Survival, strobilation and sexual maturation of Echinococcus multilocularis in the small intestine of golden hamsters.

Echinococcus multilocularis survived, strobilated and matured sexually in the small intestine of 6-week-old male golden hamsters that were either non-treated or treated with prednisolone tertiary-butylacetate (PTBA), following oral administration of 20 000 protoscoleces. Non-treated hamsters harboured the adult worms for up to 25 days post-infection (p.i.). Hamsters treated with PTBA from the day of infection (day 0 p.i.) harboured more adults than the non-treated, and their survival periods were extended. Moreover, a remarkable improvement in worm recovery, development and survival periods was observed in hamsters additionally treated with PTBA on days -- 14 and -- 12 p.i., and the worm development including proglottisation, sexual maturation and egg formation was comparable with that in dogs. With the present results it is suggested that Echinococcus/rodent systems represented by the E. multilocularis/golden hamsters may rejuvenate the current stagnant research on host-parasite interactions of the definitive host-stage and egg-stage of Echinococcus.

Animals↗
PubMed1990

Seasonal variations in male mice at the time of sexual maturation.

The sexual maturation of male mice reared under constant laboratory conditions was studied in animals born in different months of the year. The body weights were significantly affected by the month of birth. Males born in March and May were heavier at 4 and 5 weeks of age than those born in autumn and winter. As indicated by the relative weights of accessory glands, males born in spring matured earlier compared with animals born in other months of the year. Variation in the relative testicular weights during maturation was not influenced by the month of birth. Female mice also showed a significant relationship between the month of birth and sexual maturation. Females born in March reached puberty, as measured by the age of vaginal opening and first oestrus, earlier than those born in other months of the year.

Age Factors↗
PubMed2000

Sexual maturation and control issues among sexually abused and non-abused anorexia patients.

OBJECTIVES: To assess the relative salience of the maintenance of control and the avoidance of sexual maturation as sources of motivation for maintaining pathological eating behaviours among sexually abused anorexic patients. DESIGN/METHODS: A two-factor mixed experimental design was employed. Three independent groups (sexually abused anorexics (N = 12); non-abused anorexics (N = 9); non-anorexic/non-abused controls (N = 12)) constituted the between-subjects factor. Allocation to abuse/non-abuse group was dependent upon replies to a questionnaire-based measure of unwanted sexual experience. The within-subjects factor comprised three conditions in which words of various colours were presented to participants for colour-naming (Stroop, 1935). The conditions were represented by lists of neutral words, sexual maturation words, and control-related words. Two trials were carried out in each condition and mean response times were measured. RESULTS: Within-group analyses revealed that interference was greater from sexual maturation words than from control-related words among the sexually-abused anorexics, but of equal magnitude among non-abused counterparts. Between-groups analyses found that abused patients experienced marginally greater cognitive interference from sexual maturation words than the non-abused patients. CONCLUSION: Theoretically, support is offered for elaborated schematic models of cognitive processing. Clinically, treatment interventions may need to pay particular attention to issues of sexual maturation among sexually abused anorexic patients.

Adolescent↗
PubMed2006

Development and sexual maturation of Echinococcus granulosus adult worms in the alternative definitive host, Mongolian gerbil (Meriones unguiculatus).

In the present study for the first time an alternative definitive host model has been established for the complete development of Echinococcus granulosus in Meriones unguiculatus (Mongolian gerbils) up to shelled eggs production, as happened in the natural host. Animals treated with methylprednisolone acetate were orally inoculated with approximately 3000 protoscoleces and the development of parasites in the small intestine observed up to 46 days post-infection (p.i.). The cestodes survive, strobilate, mature sexually and complete their development in the intestine up to production of shelled embryonated eggs containing fully formed six-hooked oncospheres, similarly to the natural canid host (stage 7 by Smyth). Shelled eggs are first observed in the rodent/E. granulosus model at 44 days p.i. Somatic growth in gerbils appears to follow a similar trend to dogs, length increasing to over 3mm at 44 days p.i., while, compared to the natural host, organogenesis is observed only to progress at a slower rate in the early developmental stages. Parasite burden was found to vary among non-inbred animals and developmental stages of worms recovered from the same animal differed widely. Worm localisation follows the pattern observed in the natural host, the parasites appearing for the most part distributed in the proximal third of the small intestine. The development of alternative definitive hosts may facilitate research in this field, overcoming legislative impediments that restrict the use of dogs for experimental purposes.

Animals↗
PubMed1974

Interrelationships of skeletal maturation, sexual development and somatic growth in man.

Data on the age of attainment of various stages of puberty in some 70 girls and 100 boys of the longitudinal Harpenden Growth Study have been used to study the relation between skeletal age and sexual maturation. The variation in the skeletal ages of girls when they attained breast stages 2 and 5, pubic hair stage 3, the peak of adolescent growth spurt and 95% of their adult height was compared with the corresponding variation in their chronological ages. Only at menarche, 95% mature height and pubic hair stage 3 was skeletal age significantly less variable than chronological age. In boys at 95% of their mature height, skeletal age was significantly less variable than chronological age but no significant differences were found at genital stages 2 or 5, pubic hair stage 3, or the peak of the adolescent growth spurt. There was a positive correlation between skeletal and chronological age on reaching each stage of puberty in both sexes. The data suggest that the ossification of the skeleton in prepubertal children is independent of those maturational processes which lead to the development of the secondary sex characters. The role of skeletal age in predicting adult height is apparently not dependent upon a relationship between skeletal age and the attainment of peak height velocity but upon a more direct relationship with the percentage of growth which has been completed.

Adolescent↗
PubMed2004

Temperature induces gonadal maturation and affects electrophysiological sexual maturity indicators in Brachyhypopomus pinnicaudatus from a temperate climate.

In contrast to most of the previous studies in gymnotiform reproduction, which have been conducted in the tropical region, this study examines a gymnotid from the temperate region in both the natural habitat and the laboratory. The gonadal histology of Brachyhypopomus pinnicaudatus is described for the first time. The male had a paired, lobular testis of the unrestricted spermatogonial type, and females a paired saccular cystovary. Analysis of gonads and their annual cycle enabled us to confirm the breeding season and to conclude that this species is a multiple spawner. Water temperature and photoperiod showed the expected annual cycles for the region. High temperature and a 14 h:10 h L:D photoperiod in the natural habitat coincided with (1) mature gonadal stages, (2) electrophysiological sexual dimorphism: males present a lengthened negative phase in their electric organ discharge (EOD) and (3) decreased temperature sensitivity of the EOD: the waveform does not change when temperature increases above 20 degrees C. Acclimation to sustained high temperature (30 days, 28 degrees C, 12 h:12 h L:D, low conductivity) induced gonad maturation along with EOD dimorphism. Our data show that high environmental temperature is enough to trigger sexual maturity in Brachyhypopomus pinnicaudatus from a temperate climate.

Acclimatization↗
PubMed1988

Blood pressure and self-assessment of female sexual maturation.

The relationship of sexual maturation to blood pressure was investigated in a sample (n = 361) of white, non-Hispanic females, aged 7-18 years. Sexual maturation was determined by self-assessment. Systolic and fourth- and fifth-phase diastolic blood pressures increased significantly with increasing maturation. Body mass index, breast development, and pubic hair growth explained 29% of the systolic blood pressure variance and 23% of the fourth- and fifth-phase diastolic blood pressure variances. The interpretation of a child's or adolescent's blood pressure should take into account his or her stage of sexual maturation and body size. A consideration of growth and maturation may contribute to studies of the natural history of blood pressure.

Adolescent↗
PubMed1977

Hypothalamic control of the mammalian sexual maturation.

The attainment of sexual maturity is a complex process which requires maturation and interaction not only of gonads and reproductive tract but also of the pituitary and essentially of the neuroendocrine mechanisms which ultimately control gonadotropin secretion. One of the more attractive hypotheses of the sexual maturation presumes the existence of the sensitivity threshold of the regulating system to the negative feedback signal, which differentiates immaturity from maturity. As the subject matures this declines. In an attempt to examine further the maturational alterations of the male hypothalamo-pituitary-gonadal axis, investigations were carried out with regard to simultaneous changes of blood LH, FSH, testosterone and dihydrotestosterone levels during the course of 24 hr; augmentation of pituitary and blood LH and FSH concentrations under the stimulus of LH-RH as a function of time and age; synthesis and release of LH and FSH in the testosterone-blocked animals at various stages of sexual maturation; and in vitro biotransformation of testosterone to its 5 alpha-reduced metabolites by the pituitaries as a function of age. Evidence from the experimental data could be interpreted as a decrement of the feedback set-points during sexual maturatio as reflected by the transition of the responses obtained under various experimental signals. In parallel to these observations, new evidence was presented regarding not only quantitative but qualitative changes in the pituitary gonadotropins as response to the negative and positive feedback signals. This leads to new thinking with regard to the hypothesis of differential sensitivity.

Animals↗
PubMedDate not supplied

[Regional forensic medical characteristics of sexual maturity].

Published data on sexual maturity of women in the North are reviewed. The authors analyze the findings of their studies and the anthropometric parameters of sexual maturity recorded in Regulations of Forensic Medical Obstetrical and Gynecological Expert Evaluations (1966) and find essential differences in the values of some parameters as regards the population of the Russian European North. The authors propose revision of the current Regulations in order to define regional standards.

Adolescent↗