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At least 19 recordsLinked to original sources
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↗
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↗
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↗
PubMed1979

Effects of zinc deficiency upon pituitary function in sexually mature and immature male rats.

Serum pituitary levels of growth hormone (GH), thyrotropin (TSH), prolactin (PRL), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured in sexually mature (adult) and sexually immature (juvenile) male rats who had been deprived of dietary zinc for 15 and 7 weeks, respectively. When compared to pair-fed control rats receiving a zinc supplemented diet, both the adult and juvenile zinc deficient rats had significantly lower body weights, tail lengths and ventral prostate weights. The testes of the sexually immature rats were also smaller than those of the pair-fed animals. In sexually mature, zinc deficient rats serum concentrations of GH and testosterone were significantly lower and serum LH levels significantly higher than in ad libitum fed control rats. Pituitary and hypothalamic levels of other hormones did not differ from values recorded in control animals. In sexually immature zinc deficient rats serum concentrations of GH were also significantly depressed; pituitary content and concentration of LH and pituitary and serum levels of FSH were significantly increased over control values. No discernible effects of zinc deficiency upon hyplthalamic content of LH-releasing hormone or serum concentrations of PRL or TSH were recorded in juvenile rats. Zinc deficiency has minimal effects upon the hypothalamic-pituitary axis of sexually mature rats. In sexually immature males, zinc deprivation leads to impairment of gonadal growth and increased synthesis and/or secretion of the pituitary gonadotropins.

Aging↗
PubMed1992

Growth and sexual maturation of Brazilian patients with sickle cell diseases.

Growth and sexual maturation was studied of 125 Brazilian patients with sickle cell disease whose ages ranged from 7 months to 42 years. Height and weight were significantly lower when compared with the unaffected population. The height and weight deficit increased in the age range of 11-19 years as compared with patients less than 11 years of age. Age of menarche, breast and pubic hair staging in girls, and genitalia staging and testicular volume measurements in boys indicated a delayed sexual maturation for both sexes. The comparison of adult and young patients, however, demonstrated that although puberty is delayed, a normal sexual maturation is attained later in life by most patients.

Adolescent↗
PubMed1976

Ovarian control of gonadotropin secretion during induced precocious sexual maturation in the rat.

In sexually immature female rats 'primed' with a unilateral basal hypothalamic lesion on day 23 of life, a gonadotropin surge was triggered by progesterone (P) on day 26. The influence of sequential ovariectomy (OVX) on this response was studied in an attempt to elucidate the mode of action of brain lesions inducing precocious sexual maturation in this species. OVX, carried out on days 23-26, abolished or greatly reduced the LH surge, but had little effect on basal LH concentrations. In contrast, basal FSH concentrations rose rapidly after OVX. In lesioned rats, the post-castration rise of FSH could be prevented by leaving the ovaries in place during the 1st 24 or 48 h. It is concluded that the lesion-induced maturation of the positive feedback mechanism underlying the pubertal preovulatory gonadotropin surge is mediated by the ovaries. In prepubertal rats at this age, tonic FSH release, but not tonic LH release, is under tight negative feedback control.

Animals↗
PubMed1978

Sexual maturity in broiler breeder males.

Sexual maturity and fertility of two lines of broiler breeder males, one commercial and one experimental, were evaluated individually in order to determine the earliest age at which they could be expected to produce viable spermatozoa capable of producing acceptable fertility. Comparative data for the two lines were also collected on duration of fertility, percent fertility, percent hatchability and chicks per hen during an 8-week period using pooled semen from each of the two lines. The results of this study indicate that 9.1 and 6.8% of the male of the experimental and commercial lines, respectively, produce viable spermatozoa at 11 weeks of age, and consequently, could be selected at that age and used to reproduce stock under selection. The duration of fertility was 10.5 days for the experimental line and 8.8 days for the commercial lines; with fertility levels of 86.1 and 82.8%, respectively, for the eggs produced by the two lines during this period. There were no differences in fertility, hatchability, or chicks produce per hen between the two lines for the 8-week reproductive period.

Age Factors↗
PubMed1979

Exteroceptive factors, sexual maturation and reproduction in the female rat.

Keeping a sexually mature male with a weanling female rat advanced neither the time of vaginal opening nor that of 1st oestrus. In 2 of 3 experiments females kept singly after weanling reached sexual maturity significantly earlier than did grouped females. The reproductive performance of females mated at 1st oestrus was not significantly different from that of older primiparae. 26 rats gave birth to an average of 9.3 young at 59.5 days of age, and 22 of them reared 96% of the young to weaning.

Animals↗
PubMed1976

[Observations on the acceleration of the sexual maturation of female mice by the presence of males and by exogenous oestrogen (author's transl)].

The influence of the presence of adult males on the acceleration of sexual maturation of female mice was examined under various experimental conditions and compared with the influence of exogenous oestrogen. The criteria of sexual maturation were not equally influenced. It is concluded that sexual maturation is a complex feature and that acceleration of single criteria does not signify sexual maturation.

Animals↗
PubMed1979

Luteinizing hormone during sexual maturation in pony mares.

Luteinizing hormone (LH) was quantified in pony mares during artificially induced sexual maturation. Ovarian follicular development was also assessed by rectal palpation of the ovaries. With the exception of large periovulatory LH concentrations in two mares that ovulated, LH concentrations were not significantly different in mares undergoing sexual maturation and thus having marked follicular development when compared with mares that were not undergoing sexual maturation and thus did not have marked follicular development. These results indicate a dissociation in time between the onset of follicular development and the increase in LH which is associated with the first ovulation of the year.

Animals↗
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↗
PubMed1992

Steady-state amounts of alpha- and luteinizing hormone (LH) beta-subunit messenger ribonucleic acids are uncoupled from pulsatility of LH secretion during sexual maturation of the heifer.

Our primary objective for this study was to determine whether steady-state amounts of alpha- and LH beta-subunit mRNAs in the anterior pituitary are altered during sexual maturation in the bovine female. A secondary objective was to determine whether 17 beta-estradiol (E2) alters amounts of LH subunit mRNAs before onset of puberty. Heifers (7 mo old) were assigned to one of three treatments: 1) ovariectomized (OVX, n = 16); 2) OVX and administered E2 (OVXE, n = 16); or 3) ovary-intact (INTACT, n = 20). Pituitaries were collected at an estimated 120 days before onset of puberty (prepuberty) or 25 days before onset of puberty (peripuberty). Six INTACT heifers were used to determine time of puberty during the experimental period, and their pituitaries were collected 40 h after administration of prostaglandin F2 alpha (postpubertal INTACT group). Relative amounts of mRNAs for LH subunits in each pituitary were determined by Northern analysis and scanning densitometry. Amounts of alpha- and LH beta-subunit mRNAs were lower in pituitaries of INTACT heifers and OVXE heifers, regardless of stage of sexual maturation, than in those of OVX heifers. Amounts of alpha-subunit mRNA were similar in OVXE and INTACT heifers regardless of stage of sexual maturation. Amounts of LH beta-subunit mRNA did not change during sexual maturation in heifers in the INTACT group. Concentrations of E2 were higher and LH beta-subunit mRNA were lower in heifers from the prepubertal OVXE group than in heifers in all other treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Serum lipids and blood pressure in relation to age and sexual maturity.

This study was designed to examine serum lipid profile and blood pressure in relation to age and sexual maturity. Written informed consent to participate was obtained from 42% of the eligible population of two Devon communities. The blood pressure of 343 boys and 336 girls, aged 11-16 years, was recorded and sufficient blood for analysis was obtained from 320 boys and 301 girls. Of these, sexual maturity of 221 boys and 209 girls was visually assessed using the indices developed by Tanner. In girls there was a significant (p less than 0.05) correlation between age and serum triglyceride level (r = 0.16) and in boys both serum cholesterol and HDL-cholesterol were significantly (p less than 0.01) and negatively correlated with age (r = -0.25 and -0.18 respectively). Girls had significantly higher (p less than 0.05) levels of HDL-cholesterol than boys but neither sex demonstrated significant changes (p greater than 0.05) in serum lipids or lipoproteins with sexual maturity. No significant differences (p greater than 0.05) were detected between the mean diastolic blood pressures of boys and girls but older boys had significantly higher (p less than 0.05) systolic blood pressures than similarly aged girls. Age was positively and significantly correlated (p less than 0.01) with blood pressure in both boys (systolic, r = 0.49; diastolic, r = 0.30) and girls (systolic, r = 0.28; diastolic, r = 0.29). More mature children were demonstrated to have both higher systolic and diastolic blood pressures than less mature children (p less than 0.05) but when allowance was made for school year group through analysis of co-variance the relationship for diastolic blood pressure in boys no longer remained significant. Blood pressures observed in this study do not raise general cause for concern but the data indicate that unfavourable serum lipid and lipoprotein profiles are common.

Adolescent↗