Effects of gonadotropins on testis cell subpopulations of newly hatched chicks treated during embryonic development.

The aim of the present study was to evaluate histological and stereological changes, as well as the variations in the number and size of cells from diverse cell subpopulations in testes of newly hatched chicks treated with follicle stimulating hormone (FSH) and luteinizing hormone (LH) during embryonic development. Stereological results indicated that in FSH-treated chicks total volume of the tubular compartment constitutes most of the testis. In contrast, the total volume of interstitial tissue constitutes most of the testis of LH-treated chicks. Results indicate that the number of germ and Sertoli cells increases as a result of FSH and LH treatment, but in FSH-treated testis, Sertoli cells were the most numerous cell type in seminiferous tubules; whereas germ cells were the most numerous cell type in testis of LH-treated chicks. Results also indicate there was a larger total volume of Leydig cells in the testes of FSH- and LH-treated chicks. The larger volume of Leydig cells in FSH-treated chicks is due to a larger cellular volume of these cells, and not due to the number, which remains constant. In contrast, in testes of LH-treated chicks, there is a larger number and volume of Leydig cells. These results indicate the testes of chick embryos respond to FSH and LH treatment, with there being modifications in the seminiferous tubules and interstitial tissue, but these changes differ markedly, indicating that FSH and LH have differential effects on chick testes.

Changes in the immunohistochemical localization of estrogen receptor alpha and in the stereological parameters of the testes of mature and aged chickens (Gallus domesticus).

The aim of this study was to detect through immunohistochemistry the presence of the estrogen receptor alpha (ER-α) in different cell subpopulations, as well as to evaluate the histological and stereological changes of the testes of mature and aged chickens. Histological results demonstrated several changes in the tubular compartment and interstitial tissue in aged chicken testis as compared to mature chicken testis. Stereological results revealed that the mature chicken testis increases in volume as well as the total volume of the tubular compartment, whereas the total volume of the interstitial tissue and the total volume of Leydig cells diminishes as compared to aged chicken testis. The increase in the total volume of Leydig cells shown in aged chicken testis is due to the increase of cellular volume of Leydig cells, and not in their number, which decreases in aged chicken testis. Results also revealed positive ER-α immunostaining in mature and aged chicken testes, but cellular distribution of ER-α immunostaining changed according to the animal's age. In mature chicken testis, the ER-α was localized in the nuclei of germ and somatic cells. In contrast, in the aged chicken testis, only scarce spermatogonia presented ER-α immunoreactivity. This differential expression of ER-α may contribute to regulate the reproductive function in the mature chicken or the cessation of reproductive function in aged chickens.

Expression of sex hormone receptors in the brain of male and female newly hatched chicks.

Chromosomal sex and steroid hormones play a determining role in brain sexual differentiation during chick embryonic development. Hormone effects on the brain are associated with the expression pattern of their intracellular receptors, which is sexually dimorphic in many species. We determined by Western blot the content of progesterone, estrogen, and androgen receptors (PR-A and PR-B, ERα, and AR, respectively) in the cortex, cerebellum, tectum, and hypothalamus of female and male newly hatched chicks. Males presented a higher content of PR-B in the tectum whereas females exhibited a higher content of PR-A in the hypothalamus. ERα was only detected as a band of 66kDa, and it showed a higher content in the cerebellum and tectum of females as compared to these regions in males. Besides, males exhibited a higher content of AR in the tectum than females. Our study suggests that newly hatched chicks show a sexual dimorphism in the expression of sex hormone receptors in brain regions involved in sexual behavior such as the hypothalamus, and in non-sexual behavior such as the optic tectum and the cerebellum.

Changes in progesterone receptor isoforms expression and in the morphology of the oviduct magnum of mature laying and aged nonlaying hens.

The aim of this study was to evaluate changes in the morphology and expression of progesterone receptor (PR) isoforms in different cell subpopulations of the magnum region of the left oviduct of mature laying and aged nonlaying hens through histomorphometric and immunohistological methods. Histological results demonstrated several changes in the oviduct magnum of mature and aged hens, mainly in the mucosal tissue. Immunohistochemical analysis showed that both PR isoforms are expressed in all cell types of the oviduct magnum of mature laying hens. In contrast, in each cell type of the oviduct magnum of aged nonlaying hens only one PR isoform (PR-A or PR-B) was expressed. The results indicate that PR percentage and the PR-A and PR-B ratio change according to the cell type of the oviduct magnum and in an age-specific manner, and suggest that these variations contribute to the regulation of progesterone actions in the oviduct magnum with the normal aging of the animal.

Immunohistochemical localization of progesterone receptor isoforms and estrogen receptor alpha in the chicken oviduct magnum during development.

In this work, the immunohistochemical expression of progesterone receptor (PR) isoforms and estrogen receptor alpha (ER-α), as well as the histomorphometric changes of the magnum region of the left oviduct from 8-day-old chicken embryos to one-month-old chickens were evaluated. Results indicate evident histological changes in the oviduct magnum during development mainly in the magnum's mucosa. Immunohistochemical analysis showed that the oviduct magnum from 8-day-old chicken embryos to one-day-old chickens did not present any PR isoform, but the oviduct magnum of one-week and one-month-old chickens expressed PR in the nuclei of all cell types. In epithelial cells, PR-B was the only isoform expressed; in muscle and serosa cells, PR-A isoform was the only isoform expressed; and stromal cells expressed both isoforms. The results also demonstrate positive ER-α immunostaining in the nuclei of different cells from embryonic life to later developmental stages of the oviduct magnum. Data indicate that the variations of ER-α or PR expression or dominance of either PR expression is differentially regulated depending on the cell type, the development of the oviduct, and in an age-specific manner. These variations in sex steroids hormone receptors are related with histological changes of the oviduct magnum through development.

Progesterone induces the growth and infiltration of human astrocytoma cells implanted in the cerebral cortex of the rat.

Progesterone (P4) promotes cell proliferation in several types of cancer, including brain tumors such as astrocytomas, the most common and aggressive primary intracerebral neoplasm in humans. In this work, we studied the effects of P4 and its intracellular receptor antagonist, RU486, on growth and infiltration of U373 cells derived from a human astrocytoma grade III, implanted in the motor cortex of adult male rats, using two treatment schemes. In the first one, fifteen days after cells implantation, rats were daily subcutaneously treated with vehicle (propylene glycol, 160 µ L), P4 (1 mg), RU486 (5 mg), or P4 + RU486 (1 mg and 5 mg, resp.) for 21 days. In the second one, treatments started 8 weeks after cells implantation and lasted for 14 days. In both schemes we found that P4 significantly increased the tumor area as compared with the rest of the treatments, whereas RU486 blocked P4 effects. All rats treated with P4 showed tumor infiltration, while 28.6% and 42.9% of the animals treated with RU486 and P4 + RU486, respectively, presented it. Our data suggest that P4 promotes growth and migration of human astrocytoma cells implanted in the motor cortex of the rat through the interaction with its intracellular receptor.

Changes in the cellular localization of estrogen receptor alpha in the growing and regressing ovaries of Gallus domesticus during development.

In this work, the presence of estrogen receptor alpha (ER-α) was determined in different cell subpopulations in the left growing and right regressing ovaries of Gallus domesticus from 13-day-old chicken embryos to one-month-old chickens by immunohistochemistry. Results revealed positive ER-α immunostaining in both ovaries during development, but the percentage, staining intensity, and cellular distribution of ER-α immunostaining changes according to whether it is the left or right ovary and with the animal's age. In the left ovary, the ER-α was localized in the nuclei of the germinal epithelium and in germ cells of the ovarian cortex, as well as in the interstitial cells, undifferentiated cells, and epithelial cells of the lacunar channels of the ovarian medulla in all ages. In contrast, in the right ovary from 13-day-old chicken embryos to one-week-old chickens, only the epithelial cells of lacunar channels were ER-α immunoreactive, but in the right ovary of one-month-old chickens both the epithelial cells of lacunar channels and the interstitial cells presented ER-α. These results demonstrate differential expression of ER-α in both chicken ovaries during development in a cell type-specific distribution, suggesting that these differences may be regarded as an important cause in the process of asymmetric ovarian development in the chicken.

Changes in the content of sex steroid hormone receptors in the growing and regressing ovaries of Gallus domesticus during development.

Sex steroids participate in the regulation of reproduction in female chickens. In this work, we determined the content of androgen receptor (AR), intracellular progesterone receptor isoforms (PR-A and PR-B), membrane progesterone receptor γ (mPRγ) and estrogen receptor α (ER-α) in the left growing and right regressing ovaries of Gallus domesticus from 13-day-old chicken embryos to 1-month-old chickens by western blot analysis. A marked difference in the morphological characteristics of the left and the right ovaries during development was observed. Results show a higher content of AR in the left ovary than in the right one in all ages. In the left ovary, the highest content of AR was observed on day 13 of embryonic development, and diminished with age. In the right ovary, AR was expressed from day 13 of embryonic development to 1-day-old, and became undetectable at 1-week and 1-month-old. In the left ovary, PR isoforms were not detected on day 13 of embryonic development, but they presented a marked expression after hatching. In the right ovary, the highest expression of both PR isoforms was found on 1-day-old, and significantly decreased with age. PR-B was the predominant isoform on 1-day and 1-month old in the left ovary, whereas PR-A was the predominant one on day 13 of embryonic development in the right ovary. Interestingly, mPRγ was detected at 1-week and 1-month-old in the left ovary meanwhile in the right ovary, it was detected from day 13 of embryonic development to 1-day-old. ER-α was only detected in the left ovary from day 13 to 1-week-old, while in 1-month-old chickens, it was expressed in both ovaries. In the left ovary, ER-α content was lower from 1-day to 1-month-old as compared with day 13 of embryonic development. Our results demonstrate a differential expression of sex steroid hormone receptors between the left growing and the right regressing ovary, and throughout chickens' age; and this is the first report about mPR expression in birds.

Histological and stereological changes in growing and regressing chicken ovaries during development.

The aim of this study was to evaluate the sequence of the histological and stereological changes that occur in diverse components of left growing and right regressing ovaries of Gallus domesticus as well as the variations in the number and size of the different cell subpopulations from 8-day-old chicken embryo to 4-week-old chickens. Results indicate a bilateral asymmetry in favor of the left ovary at all ages studied. The left ovary shows cortex and medulla, but the right ovary has no cortex, only a medulla. Stereological results show in the left ovary an increase in total volume of all components of the ovarian medulla with advancing development. The right ovary follows a similar pattern until the age of 1-day-old chicken, to regress afterward, thereby, reducing the total volume of blood vessels, lacunar channels, and interstitium, but increasing the total volume of interstitial cells as development progresses; consequently, the total volume of interstitial cells is the dominant component in the right ovary of 4-week-old chickens. Results also reveal that the increase in total volume of interstitial cells in the left ovary at all ages and in the right ovary from 8-day-old chicken embryo to 1-day-old chicken is due to hyperplasia and cell hypertrophy of interstitial cells; hence, in the right ovary, cell hypertrophy is the main cause for the increase in the total volume of interstitial cells from 1-week-old to 4-week-old chickens.

Histological and stereological studies on Leydig cells in the testes of Gallus domesticus from pre-hatching to sexual maturity.

The present study was aimed at evaluating the sequence of the histological and quantitative changes that occur in diverse components of the interstitial tissue, as well as the variations in the number and volume of Leydig cells of the testes of Gallus domesticus from 8-day-old embryo to 28-week-old chickens. Results indicate an increase in total volume of all components of the interstitial tissue: Leydig cells, blood vessels, and interstitium of chicken testes with advancing development. The proportion of each component differs markedly according to the age of the animal. Data indicate that Leydig cells are present in the chicken testes from pre-hatching to sexual maturity, and show an increase in the total volume, number per testis, and individual cell volume along the age of the animal. Values of P<0.05 were considered statistically significant. The results indicate that the total volume of Leydig cells is the dominant component of the interstitial tissue in the testes of 6-week-old chickens, but in testes of chicken embryos correspond to the lowest percentage of interstitial tissue. Results also reveal that hyperplasia is more important than cell hypertrophy in the increase of the total volume of Leydig cells during advancing development.

Histological and sex steroid hormone receptor changes in testes of immature, mature, and aged chickens.

Sex steroid hormone receptors play a central role in the regulation of reproduction in male chickens. In this work, we evaluated by histomorphometric methods and Western blot analysis changes in the number of the different cell populations and in the content of sex steroid hormone receptors in testes from immature (1.5-month-old), mature (12-month-old), and aged (48-month-old) chickens. The number of Sertoli cells, germ cells, and Leydig cells per area of testicular tissue markedly changed according to chicken age. The highest number of Sertoli and Leydig cells was found in testes of immature chickens, with a dramatic decrease in those of mature chickens; however, the number of germ cells was the highest in mature chickens in comparison with other ages. The content of androgen receptor diminished in testes of mature and aged animals in comparison with that of immature chickens. In contrast, the content of estrogen receptor alpha and progesterone receptor was higher in testes of mature animals than in other ages. Both progesterone receptor isoforms were expressed in a similar proportion in testes of immature and mature animals. Interestingly, progesterone receptor isoform A was the predominant isoform in aged animals. These results suggest that there are marked age-dependent changes in chicken testes histology and in sex steroid hormone receptors content that should contribute to sex steroid hormone actions, in this tissue throughout the lifespan of chickens.

Changes in progesterone receptor isoforms content in the brain of immature, mature and aged male and female chickens.

Progesterone participates in the regulation of several reproductive functions in birds through its interaction with intracellular progesterone receptors (PR) which exhibit two isoforms (PR-A and PR-B) with different function and regulation. We determined the content of PR isoforms in several brain regions of immature (1.5 months-old), mature (12 months-old) and aged (48 months-old) male and female chickens by Western blot analysis. PR isoforms protein content changed in tissue-and age-specific manner in the brain of both male and female chickens. In female animals PR-B content was higher in the hypothalamus of mature animals than in other ages while PR-A content increased in the cerebellum of aged animals. No significant changes were observed in PR isoforms content in the cortex and the tectum of female animals. In contrast, in male animals PR-B content was higher in the hypothalamus of aged animals. The cerebellum, tectum and cortex of male animals did not present significant changes in PR isoforms content. In all studied regions of female animals PR-B was the predominant isoform, whereas, in males a significant predominance of PR-B was only found in the hypothalamus of aged animals. These results demonstrate that PR isoforms content presents a sexual dimorphism in the brain of chickens that changes in tissue- and age-specific manner, and suggest that these variations contribute to the regulation of progesterone actions in brain throughout the lifespan of male and female chickens.