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J A Ramaley

Publications and source records attributed to J A Ramaley.

At least 19 recordsLinked to original sources
PubMed1985

Changes in the isoelectric focusing profile of pituitary follicle-stimulating hormone in the developing male rat.

Pituitary glands, hypothalami, and trunk blood were obtained from male rats at 5, 15, 18, 21, and 29 days of age, on the day of balanopreputial separation (Days 42-45), and during adulthood. The forms of follicle-stimulating hormone (FSH) present within each pituitary were separated by polyacrylamide gel isoelectric focusing. Serum and pituitary gonadotropins, hypothalamic luteinizing hormone-releasing hormone (LHRH), and the profile of FSH forms across the isoelectric focusing gel were determined by radioimmunoassay. No change in the relative proportions of FSH forms were observed between 5 and 21 days of age. Likewise, only slight changes in serum and pituitary gonadotropin levels and hypothalamic LHRH content were observed at these times. After 21 days of age, dramatic increases in serum and pituitary gonadotropin levels were observed. Similarly, a shift in FSH forms within the pituitary to more basic and bioactive forms was observed at this time. These results demonstrate that, during the transition through puberty in the male rat, not only the absolute amount, but also the isoelectric focusing profile, of FSH change.

Aging↗
PubMed1983

Sexual maturation in female rats: time-related changes in the isoelectric focusing pattern of anterior pituitary follicle-stimulating hormone.

Anterior pituitary glands (AP) were obtained from female rats at 5, 15, 18, 21 and 29 days of age, at the time of vaginal opening (VO) and during adulthood on proestrus. The multiple species of follicle-stimulating hormone (FSH) present within the AP were separated by the technique of polyacrylamide gel isoelectric focusing (PAG-IEF) and measured with the NIAMDD rat FSH radioimmunoassay kit. AP's obtained from immature female rats prior to VO contained elevated levels of total FSH as well as all of the species of AP FSH observed in adult rats (and hamsters). However, the majority of the FSH immunoactivity migrated to the most acidic portion of the gel (isoelectric point [pI] value=4.2-3.8). At the time of VO and during adulthood, a decrease in total AP FSH was observed. In addition, a shift in the relative proportions of certain FSH species occurred. The AP's of adult animals contained relatively greater amounts of more basic (pI values 6.0-5.0) forms of FSH compared with immature animals. When each of the AP FSH species isolated from adult animals was tested in a radioligand receptor assay, the most acidic (pI=4.2-3.8) failed to interact with the receptor preparation, while those with pI values from 6 to 4.7 were able to compete with [125I]-labeled FSH for receptor binding in a parallel fashion. Thus, the observed shift in the PAG-IEF FSH profiles to more basic (and biologically active) forms may represent a change in the composition of AP FSH that serves an important role in the maturation process leading to ovulatory cyclicity.

Age Factors↗
PubMed1983

Delay of puberty onset in males due to suppression of growth hormone.

Infection with Spirometra mansonoides at 22 days of age was associated with delayed sexual maturation in the male rat. Balanopreputial separation occurred at 46.7 +/- 0.8 days in controls and at 50.6 +/- 0.9 days in worm-treated rats (p less than 0.02). This was accompanied by a delay in the normal prepubertal testicular and seminal vesicle weight increases. LH remained normal but serum FSH was depressed as early as 25 days of age. The castration response in worm-treated rats was comparable to that of controls, when the FSH levels were normalized as percentages of resting level. The LH response to castration was diminished. The acute FSH and LH response to GnRH was normal and pituitary stores of gonadotrophin, as estimated by radioimmunoassayable concentrations of FSH and LH, were normal. It can be concluded that puberty onset in males is not linked to body weight gain pe se, and that the absence of endogenous GH secretion affects both sexual maturation and gonadotrophin secretion in the prepubertal period.

Animals↗
PubMed1982

Storage of anterior lobe adrenocorticotropin in corticotropes and a subpopulation of gonadotropes during the stress-nonresponsive period in the neonatal male rat.

The neonatal rat exhibits a stress-nonresponsive period during days 4-11 of postnatal development. The role and response of the anterior lobe corticotrope was studied with immunocytochemical stains for ACTH on fixed embedded pituitaries from male rats 2-21 days of age. Serially section fields were stained for beta-chains of LH or FSH to test for joint storage of ACTH and one or both gonadotropins. Cell counts on semithin sections were used to determine the frequency of stained corticotropes in the developing pituitary. The 2-day-old rats had twice as many corticotropes (17.6%) as the adults (8.1%). During the stress-nonresponsive period, the frequency of corticotropes declined to 6.4% of the population. This was followed by a recovery to 16.9% at 15 days of age. The serial fields showed that stellate cells containing only ACTH declined sharply (by 95%) to less than 1% of the pituitary cell population during the first week of postnatal life. Cells containing ACTH and both gonadotropins predominated in the corticotrope population and were 4-6% of the pituitary cell populations during this time period. In the 15-day-old rats, the corticotropes included cells storing ACTH alone (5%) and the cells storing ACTH and both gonadotropins (9%). Throughout development, cells storing ACTH alone were distinguished by their intense staining, stellate shape, and peripheral granules. Cells storing ACTH and gonadotropins were stellate or ovoid and often resembled maturing gonadotropes. We hypothesize that this second group of cells serves a function related to adrenal-gonadal maturation, or they may be stem cells, abundant during development and present in relatively low percentages (1-3%) in adult rats.

Adrenocorticotropic Hormone↗
PubMed1981

Serum prolactin levels in the prepubertal period in male and female rats. Control by photoperiod and gonadal status and relationship to puberty onset.

In female rats there is a temporary afternoon rise in prolactin during the transition from the weaning period to the period just preceding puberty. The purpose of this study was to determine whether a similar temporary prolactin peak occurs in males at the same age and to assess the dependence of this elevation upon gonadal status and light cycle cues. Blood samples were collected at 08.00, 20.00 h colony time during the prepubertal period. A prolactin peak occurred only at 28 days of age in males. This peak did not occur in either males or females gonadectomized at 22 days of age. Animals reared in constant light from weaning (21 days of age) failed to show an afternoon prolactin peak at 28 or 32 days of age. Animals in constant light from weaning age showed maximum prolactin at 08.00 h on days 28, 30, and 32 with minimum levels at 20.00 h. It can be concluded that both males and females exhibit a transient peak of prolactin during the prepubertal period. This peak was abolished by gonadectomy and by constant light, suggesting that it is an expression of a clock mechanism sensitive to photoperiod and gonadal steroids. The prolactin peak does not appear to correlate with pubertal onset per se since both vaginal opening and balanopreputial separation are precocious in constant light despite the fact that the prolactin peak is abolished in the population as a whole.

Aging↗
PubMed1981

Ontogeny of sex differences in LH and FSH levels 48 h after castration in the rat.

Serum gonadotropin levels were measured 12, 24, and 48 h after gonadectomy in male and female rats (ages, 22--60 days) to assess when during development the rate of rise of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) after castration approximates that seen in the gonadectomized adult. In females serum LH levels 48 h after ovariectomy were increased above sham levels only when the ovaries were removed prior to vaginal opening. Ovariectomy on the day of vaginal opening or at older ages resulted in no increase in LH levels by 48 h after surgery. Serum FSH levels at 24 and 48 h after ovariectomy declined with increasing age at the time of ovariectomy. In males serum LH levels at 48 h after castration increased with increasing age at the time of gonadectomy. Serum FSH levels at either 12, 24, or 48 h after orchidectomy did not change appreciably with age at the time of surgery. It is concluded that the acute pituitary secretion of gonadotropins after removal of testes in the immature male resembles that seen in the mature male early in the course of the development of sexual maturity. In contrast, the acute pituitary secretion of gonadotropins after removal of the ovaries in the immature female does not resemble that seen in the ovariectomized adult until she is mature and capable of ovulating. Thus, the observed delay in the rise of LH seen in ovariectomized adults may be a function of some aspect of the hormonal changes associated with the estrous cycle.

Age Factors↗
PubMed1981

Postnatal maturation of gonadotropes in the male rat pituitary.

The postnatal maturation of gonadotropes was studied with the use of electron microscopic-immunocytochemical strains for the beta-chains of LH and FSH on serially sectioned fields. A third serially sectioned field was stained with antiserum to ACTH-(17-39). Morphometric studies on semithin and ultrathin plastic sections stained for LH and FSH showed a 200-300% increase in the percentages of LH and FSH cells during the first week of postnatal life. In the 1- to 2-week-old rats, the percentage of gonadotropes in the population was greater than that in the adult. Analysis of the hormone content of serially sectioned gonadotropes showed that storage patterns similar to those in the adult were reached by the seventh day of life. In the neonatal group, 66% of the serially sectioned cells contained both FSH and LH, 20% contained only LH, and 14% contained only FSH. In the 7- to 15-day-old rats, the percentages of gonadotropes containing both hormones increased to 79% while 10-11% of the cells contained only LH or FSH. This is similar to the findings in the adult rat population (75% LH and FSH cells, 14.2% LH cells, and 11% FSH cells). The fields stained for ACTH showed that 35-80% of the gonadotropes contained ACTH-like immunoreactivity during neonatal development, with the highest values seen in the 7- to 15-day-old rats. In the normal adult rats, 2-10% of the gonadotropes contain ACTH activity. Cells containing only ACTH were also seen in all age groups examined. The morphological analysis showed that immature gonadotropic cells contained scattered storage granules, arranged either at the cell periphery or concentrated near the nucleus. They were small, irregularly shaped, and often exhibited a high nucleo-cytoplasmic ratio. They were difficult to distinguish from corticotropes. More mature cell types were found after 1 week of age. These were ovoid and contained numerous large and small granules, features similar to the adult type I cell. The granules, however, were more irregularly shaped (pleomorphic). Immature forms were observed in the gonadotrope population as late as 15 days of age. Most gonadotropes from the 20- to 25-day-old rats resembled those in the adult population. Our findings support the physiological studies which show that the first week of life is an important time for functional and morphological maturation of the gonadotrope population. They also support the finding that immature gonadotropes are larger, more numerous, and more heterogeneous than those in the adult male rat population. Finally, we propose that a subpopulation of gonadotropes may serve as a stem cell or may be involved in the development of adrenal-gonadal interactions.

Adrenocorticotropic Hormone↗
PubMed1980

Biological clocks and puberty onset.

The ovulatory cycle in adult females appears to be a clock-driven process in which the regular gonadotrophin surges that induce ovulation are timed by the cycle of light and dark. In the absence of photoperiodic cues, the ovulatory surge appears to be driven by an endogenous rhythm, perhaps generated by the suprachiasmatic nuclei of the hypothalamus. There is now evidence that puberty onset is associated with the development of the capacity to reset biological rhythms in response to photoperiodic cues and to link neuroendocrine secretion to clock rhythms. This capacity emerges around 26-28 days of age in immature animals. A hypothesis is presented in which the initiation of responsiveness to photoperiodic signals is related to the onset of regular waves of follicular development in the ovaries that culminate in first ovulation 10 to 14 days later.

Animals↗