Desenvolvimento morfológico dos testículos em embriões e fetos eqüinos sem raça definida

Abstract

The aim of this work was to characterize the histological development of testes in embryos and fetuses of cross-breed equines. The research included: primordial germinative cells (PGCs) identification, gonadal ridge appearance and gonadal differentiation, forerunners of Sertoli cells, tunic albuginea and gonadal cords appearance. There were obtained testes from 17 embryos and 147 fetuses at a slaughter, whose length (crown-rump, CR) were measured in centimeters. Their age were estimated by the regression equation, in which the days of gestation (DG) varies with the CR. The embryos and fetuses sex were identified by PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphism) and macroscopic observations, respectively. The testes were bisected at their point of greatest circumference, fixed for 24 hours in Bouin s fluid, sectioned at a thickness of 5 μm and stained with haematoxylin and eosin. The histological analysis were made in a Pentium III 450 MHz computer using HLimage++ 97 software. Light microscopic examinations have showed that the first PGCs appeared at embryos with 31 DG, when the gonadal ridge was detected. The gonadal differentiation, forerunners of Sertoli cells, tunic albuginea, and gonadal cords appearance occurred in fetuses with 40; 43; 49; 53, DG respectively. The gonadal ridge was seen in embryos with 45 DG. The PGCs gonadal colonization starts in embryos with 31 DG. The macroscopical gonadal differentiation occurs in fetuses with 40 DG. The forerunners of Sertoli cells were identify in fetuses with 43 DG. The tunic albuginea formation starts in fetuses with 49 DG, gonadal cords was first seen in fetuses with 53 DG.