Tag Archives: spermatogenesis

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(6)

Thus, our procedure offers the possibility of collecting viable testicular cells at different stages of spermatogenesis from immature animals for biochemical, physiological, and toxicological studies (e.g., for screening candidate drugs). In addition, it seems likely that this method could be further developed for clinical application to human testicular tissue.

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(5)

DISCUSSION(5)

The squash technique employed in the present study allowed rapid parallel detection of apoptotic cells together with accurate identification of the stage of spermatogenesis in immature rat seminiferous epithelium. The frequency of appearance of the different spermatogenic stages and the most advanced germ cell types in squashed tubular segments were comparable to earlier data from tubular crosssections reported by Clermont and Perey.

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(4)

In addition, pronounced staining of gonocytes or spermatogonia, with no stage-de-pendency, was present at all ages. Because these groups of cells were also discovered to be particularly prone to apo-ptosis, it appears likely that in the immature testis, Bax regulates apoptosis in two distinct types of germ cells (i.e., the stem cells and midpachytene spermatocytes).

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(3)

DISCUSSION(3)

Three members of the Bcl-2 family of proteins (i.e., Bcl-2 itself, Bax, and Bad) all exhibited age-dependent levels of expression in the rat testis. A high level of Bcl-2 expression, localized immunohistochemically to the gono-cytes, was detected only in the youngest (i.e., 8-day-old) animals. Earlier studies have reported no significant expression of Bcl-2 in the rat or mouse testis, despite the fact that in transgenic animals overexpressing this protein, a pronounced degenerative effect on spermatogenesis occurs. Our results here indicate that Bcl-2 is expressed at significant levels by rat gonocytes before their further maturation into spermatogonia. In contrast, testicular expression of Bax and Bad was found in the present study to peak at 18 and 26 days of age, which is in agreement with earlier observations of mice and rats. buy allegra online

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(2)

The high frequency of apoptosis during the immature spermatogenic stages VII and VIII was associated with midpachytene spermatocytes. In connection with these two stages, the frequency of apoptosis at 18 and 26 days of age was the same, whereas the total number of pachytene spermatocytes increased with increasing age, suggesting that cell density is not involved in regulating programmed cell death in this case. This pattern of elevated apoptosis in pachytene spermatocytes only during stages VII-VIII is identical to that observed after hypophysectomy. In the latter case, lack of stimulation of Leydig cells by luteinizing hormone leads to a decrease in testosterone production, which in turn causes increased apoptosis in pachytene spermatocytes and spermatids at stage VII. dexone tablets

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: DISCUSSION(1)

DISCUSSION(1)

In the present investigation, the peak of apoptosis, occurring during the first spermatogenic wave in rat testis, was found to be related to the stage of spermatogenesis even at a very early age. As in the case of the adult testis, in 18- and 26-day-old rat testis a high frequency of apoptosis was observed in cells at spermatogenic stages IX-I, whereas the corresponding frequency associated with stages II-VI was low. In contrast, the frequency of apopto-sis connected with stages VII and VIII of mature spermatogenesis was low, but this same frequency was much higher in the immature rat testis. These observations suggest that the early increased apoptosis essential for later development occurs during immature stages VII-VIII.

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: RESULTS(5)

At 18 and 26 days of postnatal age. Electron-microscopic examination of the rat testis at these ages revealed degenerating spermatogonia in the vicinity of the basal membrane and nuclei with an appearance characteristic of apoptotic death. The only apoptotic cells associated with stages VII-VIII of the cycle were midpachytene spermatocytes. In general, the apoptotic midpachytene spermatocytes were stained more densely, and morphological features of the nucleus, including condensed chromatin cords, synaptonemal complexes, and sex vesicles, were still apparent (Fig. 3). The levels of activated caspase 3 (Fig. 2B) and cleaved PARP (Fig. 2C) peaked at the age of 18 days, thereafter declining with increasing age.

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: RESULTS(4)

RESULTS(4)

At this older age, the numbers of apoptotic cells in stages IX-I and VII-VIII were significantly greater than the apoptotic frequency associated with stages II-VI (Table 1). The morphology of apoptotic type A spermatogonia in stages IX-I (Fig. 1G) and midpachytene spermatocytes in stages VII-VIII appeared to be identical to that of the corresponding cells in younger animals and were also shown to stain positively with the TUNEL procedure (Fig. 1, G and G’, and Table¬†1). Intermediate and type B spermatogonia were not seen to undergo death by apoptosis. generic paxil

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: RESULTS(3)

At 18 days of postnatal age. At this later phase, the frequency of cells demonstrating apoptotic condensation of the nucleus was greater than that in the 8-day-old testis (Table 1). The frequency of apoptosis among cells in stages IX-I was significantly higher than in the case of stages II-VI (Table 1). The apoptotic cells were identified as midpachytene spermatocytes (Fig. 1C) in stages VII-VIII and as type A spermatogonia in stages IX-I. In association with stages II-VI, only a few early pachytene spermatocytes were observed to undergo apoptosis, and no apoptotic intermediate or type B spermatogonia were present. In the case of pachytene spermatocytes, apoptotic condensation gave rise to bright, phase-negative spheres, a pattern clearly different from that seen with spermatogonia (Fig. 1C).

Increased Apoptosis Occurring During the First Wave of Spermatogenesis: RESULTS(2)

RESULTS(2)

At 26 days of postnatal age. At this later time-point, meiotic divisions were observed, and step 3-4 spermatids were the most differentiated type of germ cell present (Fig. 1F). In comparison to the 18-day-old testis (Fig. 1C), the frequency of midpachytene spermatocytes at 26 days of age was increased (Fig. lF), and the appearance of late pachytene spermatocytes and spermatids allowed accurate identification of the different stages of spermatogenesis. These samples were divided into three groups containing cells in stages II-VI, VII-VIII, or IX-I (Table 1). The characteristic cells observed were early pachytene and step 2-4 spermatids for stages II-VI (Fig. 1E), preleptotene and midpachytene spermatocytes for stages VII-VIII (Fig. 1F), and zygotene (Fig. 1G) and late pachytene spermatocytes and step 1, round spermatids for stages IX-I.

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