The main objectives of the present study were to investigate the effects of 6-n-propyl-2-thiouracil (PTU) on Sertoli cell proliferation, germ cell number, and testis size in Nile tilapias (Oreochromis niloticus). In this regard, young fish (approximately 1 g BW and approximately 3.5 cm total in length) were treated for a period of 40 d with different concentrations (100 and 150 ppm) of PTU. The animals were killed and analyzed on d 1, 30, 40, 98, and 208 after the beginning of the treatment. On d 30 and 40 the spermatogenic process was delayed in fish treated with PTU compared with the control group. Also at these periods, treated tilapia had decreased (P < 0.05) body weight and total length. On d 98 body weight and total length had recovered in PTU-treated fish and were similar (P > 0.05) to those of the controls. However, testis weight and gonadosomatic index (testis mass/body weight) were approximately 100% higher (P < 0.05) in treated tilapia. Similarly, the area occupied by seminiferous tubules, the number of Sertoli cells and germ cells per cyst, and the number of Leydig cells per testis were significantly (P < 0.05) greater in treated fish. Nevertheless, nuclear volume and individual Leydig cell volume were significantly lower (P < 0.05) in tilapia receiving PTU treatment. Compared with controls, at 208 d all parameters analyzed presented the same trend as that observed at 98 d. In general, at 98 d the different PTU concentrations used during the treatment period induced similar effects. However, at 208 d the mean values observed for several parameters were significantly higher (P < 0.05) in fish exposed to 150 ppm. Probably due to the higher density of Sertoli cells per cyst in treated tilapia, these cells presented a smaller (P < 0.05) nucleolus and a trend to decrease its support capacity (efficiency). However, the meiotic index (germ cell loss during the two meiotic divisions) was similar (P > 0.05) in the three groups of fish investigated. Remarkably, the results found in tilapia were similar to those found for rats treated with PTU. This suggests strongly that the mechanisms of control of Sertoli cell and Leydig cell proliferation seem to be preserved during vertebrate evolution.

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Cyclosporine A (CsA) is known to have testicular toxicity, leading to male infertility. Stimulant and aphrodisiac properties have been attributed to the plant, Heteropterys aphrodisiaca. Thus, the present work was undertaken to evaluate the association of the drug and the medicinal herb in Wistar rats, applying testicular morphometry and ultrastructure. Twentyfour rats were used, divided into four groups: I, control; II, CsA; III, simultaneous use of CsA and H. aphrodisiaca; IV, H. aphrodisiaca. Daily administration by gavage was carried out, during 56 days, of water (sham), CsA in a dose of 15 mg/kg per day and/or H. aphrodisiaca in a dose of 0.5 ml of the infusion prepared with 25 g of roots/100 ml of boiling water. Increased body weight was observed for all groups, but the animals that received only CsA showed the smallest body weight gain. Morphometry showed increased connective tissue volumetric proportion and decreased Leydig cell volumetric proportion in CsA-treated rats. Using transmission electron microscopy, it was possible to ascertain that CsA caused seminiferous epithelium degeneration, resulting in Sertoli cell vacuolization, abnormal round and elongated spermatids and large accumulation of residual cytoplasm at the epithelium border next to the lumen. Expanded intercellular spaces between germ cells were still observed in H. aphrodisiaca-treated rat testes. The administration of H. aphrodisiaca infusion to CsA-treated rats diminished nearly all the CsA-induced damage to the testis ultrastructure, suggesting that H. aphrodisiaca infusion may be used combined with CsA to reduce CsA-induced injuries in the testis.

Due to the scarcity of information about patterns of spermatogenesis in bats, this study aimed to provide information on the testicular activity of the bat Sturnira lilium along the annual seasons. Thus, a series of morphometrical and stereological analyses were made using the testes of adult S. lilium in order to achieve a better understanding of the sperm production dynamics. Light and transmission electron microscopy analyses were performed in testicular fragments of animals captured during dry and rainy seasons. The testes followed the pattern of organization described for other mammals, and there were no morphological differences between organs collected either in dry or in rainy seasons. Each tubular cross-section in stage 1 was made of 0.5 type-A spermatogonia, 4.4 primary spermatocytes in preleptotene/leptotene, 3.7 in zygotene, 11.9 in pachytene, 35.6 round spermatids and 8.5 Sertoli cells. The mitotic and meiotic indexes were 15.4 and 2.9 cells, respectively, while the spermatogenesis yield was 68.7 cells. The testicular sperm reserves was 37.61×106 cells, and daily sperm production per gram of testis averaged 209.68×106 cells, both highest averages occurring in the rainy season. S. lilium male bats have a continuous reproductive pattern, high spermatogenesis yield and low support capacity by the Sertoli cells.

Among all bat species, Desmodus rotundus stands out as one of the most intriguing due to its exclusively haematophagous feeding habits. However, little is known about their spermatogenic cycle. This study aimed at describing the spermatogenic process of common vampire bats through testicular histomorphometric characterization of adult specimens, spermatogenic production indexes, description of stages of the seminiferous epithelium cycle and estimative of the spermatogenic process duration. Morphometrical and immunohistochemical analyzes for bromodeoxiuridine were conducted under light microscopy and ultrastructural analyzes were performed under transmission electron microscopy. Vampire bats showed higher investment in gonadal tissue (gonadosomatic index of 0.54%) and in seminiferous tubules (tubulesomatic index of 0.49%) when compared to larger mammals. They also showed a high tubular length per gram of testis (34.70 m). Approximately half of the intertubular compartment was found to be comprised by Leydig cells (51.20%), and an average of 23.77x106 of these cells was found per gram of testis. The germline cells showed 16.93% of mitotic index and 2.51% of meiotic index. The overall yield of spermatogenesis was 60% and the testicular spermatic reserve was 71.44x107 spermatozoa per gram of testis. With a total spermatogenesis duration estimated at 37.02 days, vampire bats showed a daily sperm production of 86.80x106 gametes per gram of testis. These findings demonstrate a high sperm production, which is commonly observed in species with promiscuous mating system.