Kinetics of spermatogenesis in the Mongolian gerbil (Meriones unguiculatus)

The Mongolian gerbil (Meriones unguiculatus) is a small rodent native to the arid regions of Mongolia and Northeastern China. The present study provides descriptions of both the cellular associations of the seminiferous-epithelium cycle and relative frequencies of stages in the gerbil. Based on the development of the acrosomic system and the nuclear morphology changes using the PAS-H staining technique, the transformation of spermatids into spermatozoa was divided into 15 steps. The first 12 steps were used to identify 12 stages or cellular associations and the other three steps were spread among the first six stages of the cycle of the seminiferous epithelium. The relative frequencies found for stages I through XII were: 13.15; 8.06; 8.98; 6.48; 5.37; 6.71; 7.36; 7.45; 7.27; 5.83; 11.53 and 11.81, respectively. Stage I had the highest frequency while stage V proved the lowest frequency among the XII stages. The pattern of spermatogenesis is similar to those of rodents used as laboratory animals. The present description is the first for this rodent and provides the foundation for a variety of future studies of the testis in this animal. © 2002 Elsevier Science Ltd. All rights reserved.

Morphological aspects of the capybara stomach (Hydrochaeris hydrochaeris): Gross and microscopic structure

The digestive system of the capybara has been investigated because of its coprofagia habits, important for their absorptive activity. These species present differences in terms of gastrointestinal morphological characters when compared with other rodents. Macroscopiclly, the stomach of the capybara is constituted of the following parts: cardiac, pyloric, body, fundic and gastric diverticulum. It presents two curvatures, one big and another small. Externally, the presence of gastric bands (tenias) is observed. With regards to the volumetric view, the gastric capacity varies from 850 to 2010 ml, with an average of 1498.57 ml. So, the stomach of this animal can be classified as a simple stomach, in the format of a curved sack and similar to an inverted letter 'J'. The gastric mucous membrane presents a surface filled by numerous tortuous gastric folds and longitudinally distributed along all its extension. The mucous tunic also possesses recesses located among the successive gastric folds, which were denoted as gastric parts with numerous openings described as gastric pits. In the cardiac part, a glandular epithelium with cardiac glands is noticed containing a lot of parietal and mucous neck cells. The fundic part, body and gastric diverticulum contain proper gastric glands with main, parietal and mucous neck cells. Finally, the pyloric part has pyloric glands with two cellular types, mucous neck and parietal cells.

Structure of the pelvic and penile urethra - Relationship with the ducts of the sex accessory glands of the Mongolian gerbil (Meriones unguiculatus)

The urethra is the main place of entry for sexually transmitted pathogens. However, there is little literature on the morphology of the urogenital system, principally the urethra and ducts of the sex accessory glands. The Mongolian gerbil is an insectivorous, herbivorous and monogamous rodent with nocturnal habits; it has been used successfully as a laboratory animal since the 1960s. Therefore, the objective of the present paper was to describe the structure and ultrastructure of the urethra and its relations to the ducts of the accessory sex glands of the Mongolian gerbil (Meriones unguiculatus), contributing to the understanding of the reproductive biology of the rodent and aiming to provide data for future experimental studies. Conventional techniques of light and scanning electron microscopy were utilized. The urethra and ducts of the accessory sex glands are similar to those of the albino rat and the mouse. However, there is variation in drainage type among accessory sex glands for the inner urethra. The ducts of the seminal vesicle, the ductus deferens, drain their contents independently into the ampullary duct that opens in the urethra. The ducts of the prostate, coagulating and bulbourethral glands drain their contents independently into the urethra.

A new karyotype of oligoryzomys (sigmodontinae, rodentia) from central Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fruit and seed exploitation by small rodents of the Brazilian Atlantic forest

In the Brazilian Atlantic forest (BAF) there are at least 57 rodent species and most of them are considered omnivorous. These species feed, more or less frequently, on fruits and seeds. Nevertheless the potential role of each species as frugivorous, seed predator or seed disperser is still unclear. In the present study we analyzed patterns of fruit and seed exploitation by eight small rodent species from an Atlantic Forest site. We offered to captive animals fruits of 30 plant species (23 genera, 15 families). After 48 h we recorded consumption patterns of pulp/aril and seed. Rodent species differed in their patterns of fruit and seed exploitation. The smallest species, Akodon serrensis, Oligoryzomys nigripes, and Wilfredomys pictipes (body size range : 26-45 g), and also the medium-sized Oecomys aff. concolor (84 g) fed mainly on pulp and also on small to medium-sized seeds (< 10 mm diameter). The medium-sized rodent, Oryzomys russatus (91 g) fed on pulp and also on seeds with diameter ≤ 15 mm. Thus larger seeds remain intact after being manipulated by such species. The medium-sized Delomys dorsalis (72 g) and the larger Trinomys iheringi (274 g) and Nectomys squamipes (253 g) form a third group, which consumed both fruit and seed of most species independent of their size. These later two species and also O. russatus are probably the main seed predators in the rodent community of the BAF.

Morphological alterations on the prostate of Calomys callosus submitted to chronic ethanol ingestion

The objective of the present study was to assess the possible toxic effects of chronic alcohol ingestion on the ultrastructure of the glandular epithelium of the prostate of the rodent Calomys callosus, in order to contribute to the understanding of the consequences of alcohol abuse for the morphology of the male reproductive apparatus. Sixteen adult animals aged three months were divided into two experimental groups. The control group received a solid diet and tap water, and the alcoholic group received the same solid diet and ethanol P.A. diluted 20% in water (v/v). After 120 days of treatment, all animals were anesthetized, weighed and sacrificed. At the end of treatment, mean body weight did not differ between control and alcoholic animals. The prostate epithelial cells of the alcoholic group showed intense atrophy and ultrastructural alterations such as the presence of lipid droplets, altered nuclei, ruptured mitochondrial cristae, and intense dilatation of the cisterns of the granular endoplasmic reticulum. It was concluded that 20% ethanol provokes marked lesions on the epithelium of the prostate probably interfering on the glandular secretion.

Ultrastructural features of the lining epithelium of the vas deferens of Agouti paca

The epididymal epithelium of Agouti paca, a wild South American rodent, was basically formed by principal and basal cells. Principal cells were closely related to processes of adsorptive endocytosis, phasefluid endocytosis and also secretion originating from their cytoplasmic ultrastructural features. Principal cells were also characterized by the presence of vesicles of several shapes, sizes and internalized content occurring in smaller pits, pale small vesicles next to the apical brush border of microvillus, as well as coated vesicles, smooth surface vesicles and great vesicles. Multivesicular bodies, endosomes and lysosomes were mainly observed in supranuclear position. Moreover, presence of an apocrine secretory process was demonstrated by the occurrence of apical cytoplasmic expansions projecting into the vas deferens luminal compartment. Basal flattened cells without luminal surface contact occurred next to the basement membrane of the ductus, and did no exhibit special ultrastructural features.

Baseline and stress-induced plasma corticosterone concentrations of mice selectively bred for high voluntary wheel running

The hypothalamic-pituitary-adrenal (HPA) axis is important in regulating energy metabolism and in mediating responses to stressors, including increasing energy availability during physical exercise. In addition, glucocorticoids act directly on the central nervous system and influence behavior, including locomotor activity. To explore potential changes in the HPA axis as animals evolve higher voluntary activity levels, we characterized plasma corticosterone (CORT) concentrations and adrenal mass in four replicate lines of house mice that had been selectively bred for high voluntary wheel running (HR lines) for 34 generations and in four nonselected control (C) lines. We determined CORT concentrations under baseline conditions and immediately after exposure to a novel stressor (40 min of physical restraint) in mice that were housed without access to wheels. Resting daytime CORT concentrations were approximately twice as high in HR as in C mice for both sexes. Physical restraint increased CORT to similar concentrations in HR and C mice; consequently, the proportional response to restraint was smaller in HR than in C animals. Adrenal mass did not significantly differ between HR and C mice. Females had significantly higher baseline and postrestraint CORT concentrations and significantly larger adrenal glands than males in both HR and C lines. Replicate lines showed significant variation in body mass, length, baseline CORT concentrations, and postrestraint CORT concentrations in one or both sexes. Among lines, both body mass and length were significantly negatively correlated with baseline CORT concentrations, suggesting that CORT suppresses growth. Our results suggest that selection for increased locomotor activity has caused correlated changes in the HPA axis, resulting in higher baseline CORT concentrations and, possibly, reduced stress responsiveness and a lower growth rate. © 2007 by The University of Chicago. All rights reserved.

Efeito do extrato aquoso de folhas de Polymnia sonchifolia (yacon) em ratas diabéticas

Polymnia sonchifolia is a medicinal plant used as hypoglycemic agent and other ends. The aim was to evaluate the yacon effect on diabetes in Wistar female rats, which was divided in 4 groups: non-diabetic (n=24) given (gavage) 32.4 mg kg -1 of an aqueous extract of plant (treated group) or vehicle (non-treated group), and one diabetic group (n=24) with similar treatment compared to non-diabetic rats. Diabetes was induced using streptozotocin (i.v. route, 40 mg kg -1). Glycemia was monitored after rodent adaptation period, 15 days after diabetes induction, and each 10 days after yacon/vehicle in early treatment. During experiment period, body weights, food and water intake were daily measured. The rats (non-diabetic or diabetic) given yacon extract treatment presented no significant difference related with glycemia, body weight gain, and food and water intake. Thus, further studies such increase of rat number in agreement with different glycemic levels and increase of the plant extract dose are necessary.

A comparative study of cytoarchitecture and serotonergic afferents in the suprachiasmatic nucleus of primates (Cebus apella and Callithrix jacchus) and rats (Wistar and Long Evans strains)

The suprachiasmatic nucleus, an essential diencephalic component of the circadian timing system, plays a role in the generation and modulation of behavioral and neuroendocrine rhythms in mammals. Its cytoarchitecture, neurochemical and hodological characteristics have been investigated in various mammalian species, particularly in rodents. In most species, two subdivisions, based on these aspects and considered to reflect functional specialization within the nucleus, can be recognized. Many studies reveal a typical dense innervation by serotonergic fibers in this nucleus, mainly in the ventromedial area, overlapping the retinal afferents. However, a different pattern occurs in certain animals, which lead us to investigate the distribution of serotonergic afferents in the suprachiasmatic nucleus of the Capuchin monkey, Cebus apella, compared to the marmoset, Callithrix jacchus, and two Rattus norvegicus lines (Long Evans and Wistar), and to reported findings for other mammalian species. Our morphometric data show the volume and length of the suprachiasmatic nucleus along the rostrocaudal axis to be greatest in C. apella > C. jacchus > Long Evans ≥ Wistar rats, in agreement with their body sizes. In C. apella, however, the serotonergic terminals occupy only some 10% of the nucleus' area, less than the 25% seen in the marmoset and rats. The distribution of the serotonergic fibers in C. apella does not follow the characteristic ventral organization pattern seen in the rodents. These findings raise questions concerning the intrinsic organization of the nucleus, as well as regarding the functional relationship between serotonergic input and retinal afferents in this diurnal species. © 2007 Elsevier B.V. All rights reserved.

Nonthermal activation of transient receptor potential vanilloid-1 channels in abdominal viscera tonically inhibits autonomic cold-defense effectors

An involvement of the transient receptor potential vanilloid (TRPV) 1 channel in the regulation of body temperature (T b) has not been established decisively. To provide decisive evidence for such an involvement and determine its mechanisms were the aims of the present study. We synthesized a new TRPV1 antagonist, AMG0347 [(E)-N-(7-hydroxy-5,6,7,8-tetrahydronaphthalen-1- yl)-3-(2-(piperidin-1-yl)-6-(trifluoromethyl)pyridin-3-yl)acrylamide], and characterized it in vitro. We then found that this drug is the most potent TRPV1 antagonist known to increase T b of rats and mice and showed (by using knock-out mice) that the entire hyperthermic effect of AMG0347 is TRPV1 dependent. AMG0347-induced hyperthermia was brought about by one or both of the two major autonomic cold-defense effector mechanisms (tail-skin vasoconstriction and/or thermogenesis), but it did not involve warmth-seeking behavior. The magnitude of the hyperthermic response depended on neither T b nor tail-skin temperature at the time of AMG0347 administration, thus indicating that AMG0347-induced hyperthermia results from blockade of tonic TRPV1 activation by nonthermal factors. AMG0347 was no more effective in causing hyperthermia when administered into the brain (intracerebroventricularly) or spinal cord (intrathecally) than when given systemically (intravenously), which indicates a peripheral site of action. We then established that localized intra-abdominal desensitization of TRPV1 channels with intraperitoneal resiniferatoxin blocks the T b response to systemic AMG0347; the extent of desensitization was determined by using a comprehensive battery of functional tests. We conclude that tonic activation of TRPV1 channels in the abdominal viscera by yet unidentified nonthermal factors inhibits skin vasoconstriction and thermogenesis, thus having a suppressive effect on T b. Copyright © 2007 Society for Neuroscience.

Assessment of the potential clastogenic/aneugenic risk of Casearia sylvestris extract using in vivo assays

Casearia sylvestris (Flacourtiaceae) is a plant which grows in wild and has been widely used in folk medicine. In this study, clastogenic/aneugenic properties of Casearia sylvestris crude ethanolic extract were evaluated using in vivo chromosomal aberrations (CAs) and micronucleus (MN) assays in rodents. The animals were treated by gavage with 3 concentrations of the extract: 150, 300 and 500 mg/kg body weight. Bone marrow cells from Wistar rats were collected 24 h after having been submitted to the MN and CAs test. Peripheral blood cells from Swiss mice were collected 48 and 72 h after having been submitted to the MN test. The results show that C. sylvestris extract does not induce a significant increase in mean values for micronucleated polychromatic erythrocytes (MNPCE) in Swiss mice and Wistar rats, or CAs in rat bone marrow cells, at the 3 tested doses, indicating that the extract showed no clastogenic/aneugenic effects on chromosomes of the rodent cells tested. © 2007 The Japan Mendel Society.

Analysis of the nucleolar cycle in the seminiferous epithelium of rodents

The nucleolus is a subcompartment of the nucleus and the site of ribosome biogenesis. During the mitotic and meiotic cell cycles, a disorganization and later reorganization of the nucleolar material occur, an event called nucleologenesis. In the spermatogenesis of mammals and other vertebrates, there is evidence of the disorganization of the nucleolus at the end of meiosis I, which supplies material for the cytoplasmic formation of an organelle called the chromatoid body (CB). The CB is a structure characteristic of spermatogenic cells and seems to be responsible for RNA metabolism in these cells and for some events of spermiogenesis, such as the formation of the acrosome, cellular communication between spermatids, and the formation of the spermatozoon middle piece and tail. The aim of this paper was to obtain information about the cytochemical and ultrastructural nature of the nucleolar cycle and the distribution of cytoplasmic RNAs in the seminiferous tubule cells of Rattus novergiucus, Mus musculus and Meriones unguiculatus. The testis was fixed in Bouin and Karnovsky solutions for conventional histological analysis and for cytochemical study that included: periodic acid-Schiff, hematoxylin-eosin, Feulgen reaction, silver-ion impregnation, Gomori's reticulin stain, toluidine blue, modified method of critical electrolyte concentration, and basic and acid fast green. The blocks of testis fixed in glutaraldehyde were used for ultrastructural analysis by transmission electron microscopy. Ultrathin sections were double-stained with uranyl acetate and lead citrate. All the techniques used provided information on the origin and function of the CB in the spermatogenic cells. Therefore, considering the persistence of the RNA and nucleolar ribonucleoproteins during spermatogenesis of Rattus novergicus, Mus musculus and Meriones unguiculatus, our findings corroborate the statement that these molecular complexes are very important in the spermiogenesis phases. It can be suggested that these ribonucleoprotein corpuscles (chromatoid bodies) are of nuclear origin and have a role in the successive series of events that occur in the formation of the spermatozoon. Furthermore, these results reinforce the conservation of the mechanisms involved in preserving necessary levels of protein stocks in different stages of cell differentiation, from spermatid to spermatozoon, in these rodent species. ©FUNPEC-RP.

Helmintos parasitos de mocós (Kerodon rupestris Rodentia: Caviidae) de vida livre e de cativeiro, no semi-árido nordestino Brasileiro

This study shows the helminthic fauna of 16 rock cavies (Kerodon rupestris) from the semi-arid region in the State of Rio Grande do Norte, Brazil. Nine animals were captured from the wild and seven from a captive population located at the Centro de Multiplicação de Animais Silvestres, city of Mossoró, were examined in this study. The animals were slaughtered, and post mortem analysis of the digestive tract, trachea, heart, lungs, liver, pancreas, and kidneys were done in search for the presence of parasites. Five species of nematode (Paraspidodera uncinata, Trichostrongylus colubriformis, Trichuris gracilis, Trichuris muris, and Vianella lenti) and one species of cestode (Thysanotaenia congolensis) were identified.

Morfologia do intestino delgado de capivara - Hydrochoerus hydrochaeris (Linnaeus, 1766)

The high potential for the exploitation of capybara requires information about its digestory morphophysiology, to improve nutritional handling. In the present study, gross anatomy, light microscopy and body and intestine lengths of 25 capybaras were evaluated. The minimum and maximum small intestine lengths for females and males were, respectively, 441 cm and 1734 cm, and 355 cm and 1123 cm. These values position the capybara between canine and swine intestinal lengths. The ratio between small intestine and body length was 12:1, without differences between sexes. There were no statistically significant differences between sexes for each part of small intestine. Correlation between length of each small intestine segment and body length was positive, and statistically significant only for the duodenum. The small intestine wall was formed by mucosa, submucosa, muscular and serosa. The mucosa presented intestinal and duodenal glands, of mucosal and serosal types, respectively. The mucosa muscular layer consisted of two distinct layers in the jejunum and ileum, and a thin and single layer in the duodenum. The submucosa, formed by moderate dense connective tissue, didn't show glands. The fiber bundles of the internal layer of muscular tunic were helicoidally arranged. The gross anatomy of the capybara small intestine was similar to canine and swine intestines. Microscopically, however, subtle differences can be identified in the submucosa and internal muscular tunics.