الفهرس 
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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.
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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.