The conversion of the young spermatid to the mature one (spermatogenesis), is dependent on testosterone, mainly occurring during I-VI, VII-VIII and IX-XII stages, (O'Donnell, McLachlan, Wreford, & Robertson, 1994); on the contrary to the other ones, the XIV stage, is characterized for being a step dependent of the follicle stimulating hormone (FSH), which has a maximum expression of FSH receptor in Sertoli cells
(D'Souza et al., 2005).
After 10 days of co-culture, spermatogonial and Sertoli cells
were cryopreserved according to Izadyar et al's instructions with some modification (18).
Elongated spermatids were found in groups located in the crypts of Sertoli cells
. Two generations of round spermatids as well as zygotene and pachytene stages of primary spermatocytes were also observed in this stage.
In rats, leptin receptor (LepR) mRNA is present in Leydig cells, in Sertoli cells
, and possibly in germ cells .
Showing the positive immunolocalization of testicular phosphotyrosine in sustentocytes (Sertoli cells
) (A'), spermatogonia (B'), round and elongated spermatids (C'), and interstitial endocrine cells (Leydig cells) (D') as compared to negative control (A, B, C, and D).
In adult rats, Madhu, Sarkar, Biswas, Behera, and Patra (2011) observed reduction in seminiferous tubular areas, secondary spermatocytes and nuclear diameter of Leydig and Sertoli cells
after 45 days of exposure to 1 mg [kg.sup.-1] bw [day.sup.-1] of 3-MCPD.
SLCTs represent a group of primary ovarian tumors in the mixed sex cord-stromal category and are composed of variable combinations of Sertoli cells
and Leydig cells, among other possible components.
In the testes, some types of cells, such as Sertoli cells
and peritubular myoid cells, secreted factors into the testicular fluid to regulate the activities of SLCs [33-35].
We hypothesized that low dose of genistein exposure would exert its antioxidative role in prepubertal Sertoli cells
, which may partially alleviate the toxic effects induced by different doses of MEHP.
 reported that the seminiferous tubules exert a local regulatory effect on Leydig cells function through its suppression by inhibitory peptide produced by Sertoli cells
. In the present study, Ginkgo biloba treated I/R group showed insignificant changes in free testosterone level compared to I/R group, together with preserved Leydig cell count compared to I/R group, which is similar to Kanter , who found that Ginkgo biloba increased testosterone level compared to I/R group and suggested that Ginkgo biloba could be protective against ischemia/reperfusion induced testicular damage by scavenging the free radicals.
The Sertoli cell
in varicocele is reported to be more sensitive than germ cells to changes in the testicular microenvironment  and the structure of the TJ between Sertoli cells
is damaged in experimental varicocele in the rat testis [29,30], implying that the Sertoli cell
may be the primary altered intratubular site, leading to secondary spermatogenesis obstruction.
tropicus testes are cystic type, since during the development of spermatogenesis the Sertoli cells
that surround the germ cells forming cysts.