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. Anat Rec, 294:893-904, 2011. V V C 2011 Wiley-Liss, Inc.Key words: histology; stereology; left ovary; right ovary; chickenIn vertebrates, the reproductive system arises as bilateral anlagen, and consequently paired genital organs are commonly found in the adult. In birds, the female reproductive system is unique. Although paired anlagen appear, only the left genital primordia develop further to functional organs, except in birds of prey (Jacob and Bakst, 2007).In the chick, formation of the ovary differs between the right and left sides. In the left ovary, whose development proceeds normally, cortical cords (secondary cords) extend inward from the gonadal epithelium. From 7 days of incubation onward, the cords develop to form a cortex, whereas the medulla is composed of epithelium derived from medullary cords (primary cords) and their enlarged inner spaces (medullary lacunae). In contrast, the right ovary stops further development from 7 days onward. This is due to the absence of secondary cord formation; the right ovary has only a medulla composed of the epithelium of the medullary cord and enlarged lacunae. Eventually, the right ovary becomes smaller than the left (Romanoff, 1960;Stahl and Carlon, 1973;Ebensperger et al

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 μL), 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.

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