الفهرس 
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Abstract
The present study was carried on New Zealand white rabbits from 18th days –old of the prenatal life up to 16 weeks of age in addition to pregnant was used in the present study. The collected specimens covered most of the ontogenic developmental ages. In the prenatal specimens, the whole embryos or the caudal half of the fetous at the gonadal level were taken, while in the postnatal specimens, the ovary, uterus and cervix were taken as a whole then the samples fixed and routinely processed of histotechnique for histological studies. This study investigated protein expression of estrogen receptor (ER) and progesterone receptors (PR) in the rabbit ovary during follicular development. Also, this study concerned on the expression of mRNA and protein for the follicular stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) in ovaries and uterus of the rabbit during the crucial period of development by using quantitative real-time RT-PCR (qPCR) and Western blotting Also, this study determined relationship between follicles growth and circulating gonadotrophin levels (FSH ,LH) by using ELISA technique.:The main obtained results were summarized in the following points At the 18th day postconception, the fetal gonad exhibited signs of sexual differentiation for females; the first signs of ovarian differentiation were the demarcation of gonad into primitive cortex and a primitive medulla without morphological evidence of initial formation of seminepherous tubules and lack of a distinct tunica albuginea.The current study revealed that the primitive tunica albuginea ovarii was appeared under the surface epithelium at 28 days postconception Our result suggested that the surface epithelium would play a distinct role in production of oogonia in rabbit as intra epithelial oogonia were occasionally among the cells of the ovarian surface.The current study in rabbit revealed that no primordial follicles were found the ovaries throughout the fetal life, but the ovary contained only proliferating oogonia throughout the fetal life.During prenatal period, the uterus has not yet differentiated into endometrial stroma and myometrium and No uterine gland formed during fetal life. This means endometrial adenogenesis is primarily a postnatal event.The Mullerian duct was consisted of three cellular components: epithelial cells layer which surrounded by multilayers of the mesenchymal cells and the coelomic epithelium which defined the external borders of the Mullerian duct.
The first evidence of follicle formation was demonstrated at two weeks of age. So folliculogenesis in the rabbit ovary started at two weeks of postnatal development.Follicles up to the growing primary stage were firstly observed in this wok at 4 weeks of age, while small antral follicles and large antral follicles were firstly detected during week 8 of postnatal development.In this study by reaching 8 weeks of age, one may identify follicles at several stage of development including primordial follicle, primary follicle, growing follicle, small antral follicle and large antral follicles Polyovular follicles (more than oocytes per follicles) were a characteristic feature of the rabbit ovary.The interstitial gland was first demonstrated in the rabbit ovary at 8 weeks of postnatal development.There was no corpora lutea or corpora albicans appeared on the ovarian surface either in the immature or mature rabbits.The histological section of pregnant rabbit ovary revealed that the corpora lutea mostly occupied the ovarian cortex and the latter contained ovarian follicles at different stages of the development, but these follicles are less in number than follicles at 16weeks.ER and PR levels in the ovary appeared to increase with age and the onset of follicular maturation The present work found that at zero day old, the rabbit’s uterus not yet differentiated into its definite three layers. Also, the rabbit’s uterus at birth in this study was devoid of endometrial glands.The present study revealed that endometrial gland adenogenesis occured in three developmental steps: the first step showed Shallow epithelial invaginations appeared along the lamina epithelialis representing primordium of uterine gland formation (bud formation). This step began from the two weeks of the postnatal development, the second step showed tubulogenesis, where the uterine gland was represented by short tubules connected to the invaginated surface epithelium. It was observed from four weeks old of the postnatal development. The third step was the branching morphogenesis at sixteen weeks of age.
During pregnancy dramatic changes in the uterine architecture were observed, the uterine endometrial glands became numerus and the complexity of luminal folding and crypt formation were observed.The most conspicuous changes of cervix in this study include the height and the differentiation of the cervical epithelium.The mucosa of the cervix differs from the uterine endometrium. There are no glandular structures, but the luminal epithelium shows deep invaginations underlined by dense connective tissue.In this work the rabbit’s cervical mucosa in zero-day-old was smooth and showed no cervical folds, by two weeks of age, the cervical mucosa showed short and few cervical folds and by advancing the age, the cervical mucosa became highly folded, forming primary, secondary and tertiary folds. Finally, at maturity, the cervical mucosa exhibited an extensive pattern of highly branched folds At birth, the gonadotropin hormones, FSH and LH, were low when germ cells not yet assembled into primordial follicles. By week 2, the level gonadotropin hormones increased coinciding with organization of germ cell into newly formed primordial follicles. By week 4, a more rapid raise to the peak was observed in both FSH and LH level that correlated with the appearance of more developed follicles in the ovary. Thereafter, by week 16, the ovary became more developed and the ovarian follicles in all developmental stages could be seen, but during this period decreasing of gonadotropin was observed. The subsequent level pattern during pregnancy (18-days postcoitum) was different for FSH and LH. Circulating FSH level decreased by pregnancy, whereas Circulating LH level increased by pregnancy coinciding with CL formation. So, the present study suggested that there is relationship between the level of circulating gonadotropin hormones and follicular development. Also, the level of circulating gonadotropin hormones is affected by age and reproductive state.The expression level of FSHR increased in an age-specific manner (from birth to maturity) coinciding with the linear increase of the histological developmental change of growth of follicles.Changes in the expression of LH receptor were related to the growth of the thecal compartment.The expression level of both FSHR and LHR were affected by reproductive status (e.g, pregnancy) as the expression of FSHR decreased by pregnancy, while the expression of LHR increased to reach a peak level.Changes in gonadotropin-receptors expression may be related to the growth and development of follicles which suggests that gonadotropin receptors play an essential regulatory role in the folliculogenesis process in the rabbits.Gonadotropin receptors maybe not obviously implicated in regulating the development of the uterus of the rabbits as the expression of the gonadotropin receptors are not really correlated to specific histologic features of the rabbit uterus during developmental stages, but this study suggests a possible involvement of gonadotropin receptors to play an important role in the rabbit uterus during pregnancy.