Mariella B. Freitas

Evaluation of the Cell Population of the Seminiferous Epithelium and Spermatic Indexes of the Bat Sturnira lilium (Chiroptera: Phyllostomidae)

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.

Histomorphometric evaluation of the Molossus molossus (Chiroptera, Molossidae) testis: The tubular compartment and indices of sperm production

Insectivorous bats play a very important role in the regulation of tropical ecosystems, but information about their reproductive cycle is lacking. Thus, male Molossus molossus were captured over the four seasons, and morphometric analyses of their testes were conducted to infer on the gonadal dynamics and the reproductive capacity of the species. Testes were immersed in Karnovsky fixative, and fragments were embedded in methacrylate and paraplast for morphometric and TUNEL assay respectively. The least gonadosomatic index (0.3%), tubulesomatic index (0.2%) and tubular diameter (133.2μm) occurred in summer. An adult M. molossus showed a total average of 48.9m of seminiferous tubules per gram of testis. Primary spermatocytes were observed in the zygotene at Stage 1 of the seminiferous epithelium cycle. The greatest meiotic index was obtained in winter (3.8 cells), and the general yield of spermatogenesis was higher in winter (64.5 cells) than in summer (19.1 cells). There was no difference in the apoptotic cells count among seasons. The Sertoli cell index was less in summer (5.9) than in fall (11.6), while the number of Sertoli cells per gram of testis did not vary significantly among the seasons (28.0×10(7)). The spermatic reserve per gram of testis was greater in the fall (63.9×10(7)) and winter (69.8×10(7)) than summer (37.1×10(7)). We conclude that M. molossus males show a continuous reproductive cycle, featuring greater spermatogenic activity during the fall and winter, a tubular length above the average of other mammals and a less support capacity of the Sertoli cells.

Organization and seasonal quantification of the intertubular compartment in the bat Molossus molossus (Pallas, 1776) testis

Environmental factors can influence the reproductive rates in bats, and since morphometric information of bats testis is scarce, we aimed to compare the organization and quantification of the intertubular components in the testes of the bat Molossus molossus, collected in different seasons. Testicular histological sections were evaluated using light and electron microscopy. The intertubular compartment occupied an average 10% of the testes, being predominately constituted of Leydig cells (LC). The percentages of the testes occupied by the intertubular compartment and by LC were significantly higher in summer, while the other intertubular components did not vary significantly among the seasons. As suspected under light microscopy, the ultrastructural analysis confirmed the existence of multinucleated LC during winter. The increase in the nuclear percentage of LC in winter seems to have caused the decrease of the cytoplasmatic measurements in that season, as well as in the volume of LC. The highest cytoplasmatic values and volume of LC registered in the spring, summer, and fall can be related to greater activity of this cell in these seasons. The higher investment in intertubular tissue and in LC observed in summer, compared to winter; suggest an increase in the steroidogenic capacity of this bat during summer. The analyses correlating testicular morphometry and abiotic environmental factors in this study confirm the influence of climatic factors on the reproduction of M. molossus. Microsc. Res. Tech., 2013.

Stages and duration of the seminiferous epithelium cycle in the bat Sturnira lilium

Knowledge of the stages that compose the seminiferous epithelium cycle (SEC) and determination of the duration of spermatogenic processes are fundamental for the accurate quantification of the dynamics of spermatogenesis. The aim of this study was to characterize the stages that compose the SEC of the bat Sturnira lilium, including evaluation of the average frequency of each of these stages throughout the year and calculation of the duration of the spermatogenic process. An ultrastructural characterization of the formation of the acrosomal cap was also performed. Testicular fragments were processed for morphological and immunohistochemical analysis as well as ultrastructural analysis using transmission electron microscopy. According to the tubular morphology method, the SEC in S. lilium is divided into eight stages, following the pattern found in other mammals. Primary spermatocytes were found at zygotene in stage 1 of the cycle. There was no variation in frequency of each of the stages over the seasons, with stage 1 being the most frequent, and stage 7 the least frequent. The duration of one seminiferous epithelium cycle was 3.45 days, and approximately 15.52 days were required for the development of sperm from spermatogonia. Ultrastructural characterization allowed the formation of the acrosomal cap in round spermatids to be monitored. In conclusion, the stages that compose the SEC in S. lilium are generally similar to those described for other mammals, but the duration of the spermatogenic process is shorter than previously recorded for mammals. The presence of primary spermatocytes at zygotene in stage 1 of the cycle is probably due to the longer duration of this stage.

Metabolic and histopathological alterations in the fruit-eating bat Artibeus lituratus induced by the organophosphorous pesticide fenthion

The organophosphorous (OP) pesticide fenthion is widely used in commercial fruit industry and orchards in South America. Among the metabolic effects in mammals caused by fenthion, hyperglycemia occurs via the activation of hepatic metabolic pathways, which may interfere with the function of several organs and systems. The purpose of this study was to evaluate the effects of acute and sub-chronic levels of fenthion on energy metabolism and liver morphology of frugivorous bats (Artibeus lituratus), which usually feed on fruits cultivated on South American plantations where fenthion is used. Animals were fed fruit treated with fenthion by immersion of fruit in a solution containing fenthion (500 ppm) and an adhesive spreader (200 ppm). Blood glucose levels did not change due to fenthion treatment, but muscle glycogen content increased and carcass fatty acids decreased after acute exposure. An increase in hepatocyte cell diameter further characterized as an increase in vacuolization was observed. The results indicate that fenthion may affect some components of energy metabolism and promote alterations in hepatocyte morphology in frugivorous bats when applied to cultivated fruits at the recommended rates.

Histomorphometric characterization of the intertubular compartment in the testes of the bat Sturnira lilium

Due to the scarcity of information about the reproduction of bats, it is necessary to perform studies on different species to identify the occurrence of annual variations in their reproductive process. Therefore, the aims of this study were to describe and quantify the intertubular components within the testes of the bat Sturnira lilium and to verify whether seasonality takes place in spermatogenesis of this species. The animals were collected in different seasons and time of collection was grouped into dry and rainy seasons. Testicular fragments were routinely processed for light and transmission electron microscopies and blood samples from each animal were collected for quantification of plasma testosterone. Overall, the Leydig cells (LC) were the main intertubular component (83.2%), with abundant lipid droplets in their cytoplasm. Ultrastructural analysis indicated collagen fibers in the connective tissue and lymphatic spaces, with thin walls, surrounding the seminiferous tubules. The proportion and volume of each intertubular component did not vary significantly between seasons. On average, testosterone concentrations did not vary between rainy and dry seasons (21ng/mL). The total number of LC in the testis (50.0×10(5)) and per gram of testis (11×10(7)) did not vary nor did the Leydigosomatic Index (0.03%). Therefore, it is concluded that S. lilium had significant investment in intertubular tissues, especially in LC. Most of the variables that were assessed did not vary with season of the year, which leads to the assumption that S. lilium has a continuous reproductive cycle in southeastern Brazil.

The spermatogenic process of the common vampire bat Desmodus rotundus under a histomorphometric view

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.

High-Fat Diet and Alcohol Intake Promotes Inflammation and Impairs Skin Wound Healing in Wistar Rats

The wound-healing process is complex and remains a challenging process under the influence of several factors, including eating habits. As improper diets may lead to disorders such as dyslipidemia, insulin resistance, and chronic inflammation, potentially affecting the tissue ability to heal, we decided to investigate the effect of a high-fat diet and alcohol intake on the inflammatory process and skin wound healing in Wistar rats. Male rats (n = 30) were individually housed in cages with food and water ad libitum (registration number 213/2014). After anesthesia, at day 40, three circular wounds (12 mm diameter) were made on the back of each animal, which were then randomly assorted into five treatment groups: C1 (control 1)—water via gavage and standard chow diet; C2 (control 2)—water (no gavage) and standard chow diet; AL (alcohol)—water (no gavage) and alcohol (40%) via gavage and standard chow diet; HF (high fat)—water (no gavage) and high-fat diet (50%); and HF + AL (alcohol/high fat)—water (no gavage), alcohol (40%) via gavage, and high-fat diet. Animals were treated for 61 days. Every seven days, the area and the rate of wound contraction were evaluated. Tissue samples were removed for histopathological analysis and biochemical analyses. Our results showed that wound contraction was not complete in the HF + AL rats. Two specific indices of wound-healing impairment (total cell number and levels of the inflammatory cytokine TGF-β) were increased in the HF + AL rats. We also observed decreased type I and III collagen fibers in the HF, AL, and HF + AL groups and increased oxidative stress markers in the same groups. We suggest that a high-fat diet combined with alcohol intake contributed to delayed skin wound healing through increase of the inflammatory phase and promoting oxidative stress, which may have led to morphological alterations and impaired matrix remodeling.

Changes in bone turnover and calcium homeostasis during pregnancy and lactation in mammals: a meta-analysis

Large amounts of calcium are required during pregnancy and lactation to support fetal and neonatal bone growth and calcification. An inadequate supply of calcium during these stages can lead to unsuccessful reproduction or impaired offspring fitness. During reproduction, female mammals undergo numerous physiological changes, including adaptations to allow an adequate supply of calcium. The lack of quantitative studies analysing these physiological changes from a comparative perspective limits our ability to explain and understand these adaptations. Herein, we present our meta-analysis of studies reporting changes in bone turnover and calcium homeostasis during pregnancy and lactation in 14 species of mammals. Our meta-analysis of 60 studies showed that all species have a similar pattern of physiological changes during pregnancy and lactation, which include: (1) decreased serum calcium concentrations; (2) bone tissue loss; (3) decreased serum calcitonin and parathyroid hormone concentrations; and (4) increased serum calcitriol concentration, regardless of changes in parathyroid hormone concentrations. In addition, we found a negative relationship between: (1) serum calcium concentrations and the number of teats; and (2) serum parathyroid hormone concentrations and litter mass.