Histological and electron—microscopic studies of the developing testis of the rat fetus, show that the seminiferous cords are differentiating between 13 days 7 hours and 13 days 23 hours. Undifferentiated cells neighbouring the germ cells in the undifferentiated gonadal blastema, swell, extend processes around the sperm cells, make contact with each other and encompass the sperm cells.

During the development of the mammalian fetus, gexual differentiation occurs earlier in the malethan in the female fetus (1,2). The first obvious male characteristics to appear are the embryonic 7 miniferous tubules or seminiferous cords; the cells or Leydig cells become histologically at a somewhat later stage. Therefore I first important difference between males and in Semenax. Learn about the effects of Volume pills | http://infospeak.org/?p=10

As a matter of fact, the early steps of testi- cular differentiation have been amazingly little studied with appropriate techniques. Descriptions are often loose and imprecise as to the processes of cellular differentiation involved. Concerning the ratfetus which will be dealt with in this paper, the previous authors (3,4,5) follow the description previously given by Brambell (6) for the mouse. Accord- ing to these views the undifferentiated gonadal primordium, made of a uniform cellular blastema contaiing primordial germ cells, is subdivided into seminiferous cords by invading mesenchymal cells, orig- inating in the mesonephros. No other details were given as to the organization of seminiferous cords from the masses of undifferentiated cells cut out of the blastema.

We have recently initiated a study of testicular organogenesis in rat fetuses with the light (7) and with the electron microscope (8) and we could observe the initial stages in the differentiation of seminiferous cords. Learn more at http://alphaguys.weebly.com

TECHNIQUES

The details of the techniques used in the histological study have been reported elsewhere (7). Suffice to recall some crucial points. Fetal age was counted in days and hours from 1 a.m. during the night of cohabitation, i.e. from the assumed hour of ovulation. The fixative fluids which gave the best results were the GPA mixture (glutaraldehyde, picric acid, acetic acid) and He1ly’s fluid or the same di- luted with 50 per cent water; the latter fluids. The fetuses were sexed according to the “sex chromatin” technique in the amniotic membrane.

For electron microscopic studies, the gonads were dissected out with a part of the mesonephros, and were fixed successively for one hour in 1% glutaraldehyde in cacodylate buffer 0.1 M and in 1% osmium tetroxyde in the same buffer. The tissue was stained in block with 0.5 per cent uranyle acetate in sodium acetate buffer 0.1 M at pH 5 for 2 hours in the dark, before embedding in araldite. Transverse sections were made throughout the length of the gonads and stained with uranyle acetatelead citrate.

RESULTS

At the stage of 12 days 15 hours no definite organization could be recognized in the gonadal primordium. At 14 days 8 hours and thereafter many seminiferous cords were well organized in the anterior part of the testis; the posterior part lags behind in differentiating. Therefore organogenesis had to be studied between these two stages.

 

 

Advertisements