In all vertebrate embryos, certain cells are individual in development and are progenitors of the gametes. These primordial germ cells migrate to the developing gonads and form ovary and testis. The aim of this study was to evaluate primordial germ cells (PGCs) migration in the sheep fetus. Twenty two apparently undifferentiated sheep fetuses were collected from Shahrekord slaughterhouse. The age of the fetuses was determined based on Crown Rump Length (CRL) and they were divided to 4 age groups (with the mean ages of25, 29, 35 and 41 days). 5mm samples were taken and after fixtion in 10% formation, 5~ sections were made and stained. Results showed that the mean number of PGCs was not significantly different between the first two age groups, however the number of these cells showed a statistically significant difference between the third and forth age groups (p<0.05). In first age group primordial germ cells that have large heterochromatin nucleus and increased basophilia of the cytoplasm and cytoplasmic processes were observed in dorsal mesentery migrating towards the genital ridges. In the second age group, undifferentiated gonads were clearly recognizable medial to the mesonephros and only a few numbers of PGCs were observed in the fetal gonads. In third age group, undifferentiated gonads were transformed to the differentiated ones by primordial sex cord formation in which central germ cells were surrounded by peripherally located supporting cells. The process of structural developmental changes of sex cords continued in fourth group and the morphological structure of the gonadal tissue became more differentiated. The present study showed that primordial germ cells in sheep fetuses, has been continued process of migration in 25 day of age and then carry out differentiation process in genital gonads.

The range imaging based on conventional pulse compression technique requires LFM signal to be sampled by Nyquist rate. In order to improve the range resolution in pulse compression, the LFM bandwidth has to be increased. Consequently this procedure dictates some limitations on ADC sampling rate. In this paper after reviewing the stretch processing technique used in radars, the amount of decrease in sampling rate is calculated. A suitable RDA image formation algorithm is also proposed based on stretch processing for high squint angles. An innovative method is presented based on filtering for RCMC without interpolation methods. Via various simulations, it is finally concluded that the suggested method, on the one hand, involves less computational load processing than the conventional techniques in scenarios with short synthetic aperture length, on the other hand, gives a remarkable performance as well.