الفهرس | Only 14 pages are availabe for public view |
Abstract The present study was carried on sixty six New Zealand white rabbits from 10th days –old of the prenatal life till reaching the maturity age (4-6month-old postnatally).The collected specimens covered most of the ontogenic developmental ages. The whole embryo and the caudal half of the fetous from the gonadal level were taken. Also, the postnatal testis and epididymis were fixed and prepared by histological technique, stained with different histological stains and were examined by light microscope. Also, this study concerned on the expression of the two genes (DMRT1and STRA8) in the postnatal ages of New Zealand rabbits including the period at which the first wave of spermatogensis could be occur. During this interval the change in the level of specific genes expression could be related to the change in the complement of germ cells. The main obtained results were summarized in the following points: Gastrula was detected at 10-days-old prenatally where the three germinal layer were formed .The genital ridge was detected at 12 day-old rabbit embryo. At 15-days-old prenatally, the urogenital ridge was differentiated into lateral part (mesonepheros) and ventro-medial one (genital ridge). Also, there was a progressive increase in the gonadal parenchymal cells and the ridge appeared a thickened cellular elements. As the rabbit fetus reached 18-days of age, the differentiation of the indifferent gonads into fetal testis was evident; the first signs of differentiation were the formation of the primitive testicular cords and the appearance of primitive tunica albuginea. 119 Summary The interstitial cells were firstly demonstrated at 25days–old prenatally. The present study revealed that the development of the epididymis from the mesonephric tubules and duct happened in a descending manner. The present study revealed that the tunica albuginea and the septula testis were thin in young rabbits and became thickened and more fibrous in adult rabbit. During the period of pre-spermatogenesis (0day-6.5weeks) only pre-spermatogonia and developing sertoli cells were present in the testicular cord but at the late period of this stage, pre-spermatoogonia became late undifferentiating spermatogonia. Spermatogenesis started in the rabbit at 7-8 weeks of age at which the late undifferentiated spermatogonia underwent maturation and transformed to spermatogonia. Primary spermatocytes are seen at 3 months old rabbit. Our study revealed that, luminization of seminiferous cord became prominent at two- months old- rabbit At rabbit testis of 4-6 months-old postnatally, the differentiation and maturation of the testes and the process of spermatogenesis became more advanced. Sperm could be seen in the seminiferous tubules as animal reached sexual maturity. Our study revealed that, the best time for the beginning of the rabbit breeding at 4months –old postntally. In the early stage of postnatally development, Peritubular myoid cells surrounding seminiferous tubules consist of more than one layers of elongated cells oriented circumferentially around the tubule and this. |