Influence Of Sexual Maturation Research Articles

The Influence of Sexual Maturity, Sex and Size on Quality Aspects of Frozen Argentine Hake (Merluccius hubbsi)

The Argentine hake (Merluccius hubbsi) shows a seasonal variation in its biological condition. Results of seasonal differences in gonad maturation and spawning as well as the effect on commercialization have been reported. Considering that some technological aspects and the quality of the frozen final product are dependant on the quality of raw material, the purpose of the work was to determine the influence of sexual maturity, and other biological characteristics (sex and size) of the fish on the quality of frozen Argentine hake. Quality of fish was evaluated by determination of: Total volatile bases content (TVB), Dimethylamine nitrogen content (DMA), Formaldehyde content (FA), Salt soluble protein (SSP), Drip and Sensory evaluation. Comparisons of the experimental results between the different lots studied show that contents of FA, DMA, SSP and Drip were affected by sex, size and sexual maturity. TVB content was not affected by any of the aforementioned biological factors.

Serum Testosterone Is Not Related to Peak V̇O2 and Submaximal Blood Lactate Responses in 12- to 16-Year-Old Males

This study was designed to investigate the influence of sexual maturity on peak V̇O2 and blood lactate responses to exercise using serum testosterone levels as an objective measure of maturity. Testosterone levels were determined in venous blood samples obtained from 12- to 16-year-old males (n = 50). Peak V̇O2 and percentage of peak V̇O2 at blood lactate levels of 2.5 and 4.0 mmol·L−1 were determined during incremental treadmill running. Standard multiple regression revealed that body mass, age, and height explained 74% of the variance in peak V̇O2 scores. The addition of serum testosterone to the equation failed to produce a significant increase in the explained variance. Correlation coefficients between testosterone and the lactate variables were not significant (p > .05). These findings do not support the hypothesis that hormonal changes per se during sexual maturation play an important role in the development of peak V̇O2 and blood lactate responses to exercise.

Influence of sexual maturity of donor on in vivo survival of transferred porcine embryos.

A study was conducted to determine whether embryos recovered from first-estrous (pubertal) and second-estrous gilts differed in survival when transferred to first- or third-estrous recipients. Embryos were recovered surgically from first- and second-estrous donors 48-72 h postmating and 6-10 normal embryos/zygotes (1-4 cells) were transferred to oviducts (3-5 embryos/ampulla) of nonmated synchronous first- (n = 40) or third- (n = 15) estrous recipients. Blood samples were collected from the jugular vein of recipient gilts on Days 3, 12, and 30 of gestation and the sera were analyzed for progesterone and free (unconjugated) estrogens by use of radioimmunoassays. Recipient gilts were subsequently slaughtered between Days 30 and 40 to assess embryonic losses. Mean number of ovulations was lower among first-estrous vs. third-estrous recipients (8.9 +/- 0.7 vs. 11.4 +/- 0.7; p < 0.05). Percentage of recipients that maintained pregnancy was similar between first- and third-estrous gilts (67.5 vs. 60.0%) and recovery of total conceptuses (normal and degenerating) resulting from transfer of one-cell- and cleavage-stage embryos did not differ among first- vs. third-estrous gilts (76.1 vs. 78.2%). Similarly, percentage of viable fetuses in first-estrous gilts that were pregnant from transfer of one-cell- and cleavage-stage embryos was not different from that of third-estrous gilts (69.3 vs. 75.6%). Percentages of total conceptuses and viable fetuses in first- and third-estrous gilts that were recipients of cleavage-stage embryos only also did not differ (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Opiatergic Control of Gonadotropin Secretion during Puberty in the Rat: A Neurochemical Basis for the Hypothalamic ‘Gonadostat?’*

We have examined (1) the effects of naloxone and an opiate peptide, FK 33-824, on LH and FSH secretion in immature male and female rats and (2) the influence of sexual maturation on the ability of this peptide to inhibit LH secretion. FK 33-824 potently inhibits LH secretion in the 48-h-gonadectomized rat. This effect could be blocked by coinjection of naloxone, suggesting that the peptide exerts its influence through opiate receptors. An endogenous opiate component in the control of LH secretion was demonstrated by examining the effect of naloxone injection alone. Naloxone rapidly stimulated LH secretion in the intact or the acutely gonadectomized rat. Naloxone or FK 33-824 did not modify LHRH-stimulated release of gonadotropins from organ cultures of anterior pituitary obtained from immature rats. This suggests, in agreement with other reports, that naloxone or FK 33-824 controls LH secretion via a central, possibly hypothalamic site. We further observed a clear age-related reduction in LH sensitivity to FK 33-824 in the acutely (48-h) gonadectomized rat. Dose-response studies indicated a 4-fold reduction in opiate responsiveness in the 10 days preceding the first ovulation. Thus, the doses required to reduce serum LH levels by 50% are 0.03, 0.04, 0.16, and 0.17 mg/kg, respectively, for the groups 12, 23, 29, and 33 days of age. In the male, a similar change was noted when responsiveness was compared in pre- and postpubertal rats; 50% inhibition was achieved at 0.25, 0.89, and 0.88 mg/kg FK 33-824 for rats aged 26, 70, and 90 days, respectively. The shift in sensitivity to FK 33-824 is probably not due to a change in clearance rates, but this cannot be completely ruled out. Thus, our demonstration of a maturation-related reduction in opiate inhibition of LH suggests a critical role for endogenous (hypothalamic?) opiate peptides and opiate receptors in the onset of sexual maturation. Our results may also provide a neurochemical basis for the well described shift in hypothalamic sensitivity to gonadal steroids that occurs with the approach of puberty.