Antônio Chaves de Assis-Neto

Análise qualitativa do estabelecimento da espermatogênese em cutias (Dasyprocta aguti) criadas em cativeiros

A determinacao do estabelecimento da puberdade e bastante estudada em animais domesticos e roedores, no entanto, sao escassas as pesquisas com a finalidade de estabelecer parâmetros para a biologia reprodutiva em cutias. Foram utilizadas 31 cutias machos da especie Dasyprocta agouti, oriundas da Universidade Federal do Piaui, Estado do Piaui, e da Escola Superior de Agricultura de Mossoro, Estado do Rio Grande do Norte. Imediatamente apos a orquiectomia foram retirados fragmentos e estes foram processados histologicamente, os tecidos foram corados com hematoxilina-eosina e analisou-se os parâmetros seguintes: aspectos de luminacao dos tubulos seminiferos; presenca de espermatocitos primarios; presenca de espermatides e formacao dos primeiros estagios do ciclo do epitelio seminifero (CES) segundo o metodo da morfologia tubular. O periodo desde o nascimento ate os cinco meses de idade correspondeu a fase impubere; dos seis aos oito meses de idade a fase de transicao da pre-puberdade a puberdade; dos nove aos dez meses de idade a fase da puberdade; e dos doze aos quartoze meses de idade a fase da pos-puberdade. A puberdade da cutia (Dasyprocta aguti), ocorreu em animais a partir dos sete meses de idade, e o estabelecimento da puberdade foi constatado em todos os animais estudados aos nove meses de idade.

Characterization of the estrous cycle in Galea spixii(Wagler, 1831)

The Galea spixii inhabits semiarid vegetation of Caatinga in the Brazilian Northeast. They are bred in captivity for the development of researches on the biology of reproduction. Therefore, the aim of this study is characterize the estrous cycle of G. spixii, in order to provide information to a better knowledge of captive breeding of the species. The estrous cycle was monitored by vaginal exfoliative cytology in 12 adult females. After the detection of two complete cycles in each animal, the same were euthanized. Then, histological study of the vaginal epithelium, with three females in each phase of the estrous cycle was performed; five were paired with males for performing the control group for estrous cycle phases, and three other were used to monitor the formation and rupture of vaginal closure membrane. By vaginal exfoliative cytology, predominance of superficial cells in estrus, large intermediate cells in proestrus, intermediate and parabasal cells, with neutrophils, in diestrus and metestrus respectively was found. Estrus was detected by the presence of spermatozoa in the control group. By histology, greater proliferation of the vaginal epithelium in proestrus was observed. We conclude that the estrous cycle of G. spixii lasts 15.8 ± 1.4 days and that the vaginal closure membrane develops until complete occlusion of the vaginal ostium, breaking after few days. Future studies may reveal the importance of this fact for the reproductive success of this animal.

Análise microscópica e ultraestrutural das glândulas salivares mandibulares de Procyon cancrivorus

Due to the ecological importance of Procyon cancrivorus, the aim of this study was to characterize morphologically and ultrastructurally the mandibular salivary gland of this specie. We used 10 pairs (right and left) of mandibular salivary glands from five adult animals. The mandibular salivary glands were dissected and measured by precision calipers and later processed by histological routine technique, stained by HE (hematoxylin and eosin) and Picrossirius. Fragments of the glands were processed for analysis by scanning electron microscopy (SEM). The mandibular salivary gland, right and left from P. cancrivorus presents lobulated and oval-shape, and it was positioned between the fossa atlantis and basihyoideum ossis of skull. Microscopically, these glands are lined by a capsule formed by dense irregular connective tissue, which enters into the gland by septa, dividing it into lobules. Into the septa of connective tissue were present blood vessels and nerves, and interlobular excretory ducts. Inside the lobes of the mandibular salivary glands, striatum and intermediate-type ducts are found, and the predominance of mucous acini was observed. The results indicate that the mandibular salivary glands of Procyon cancrivorus, follows the structural pattern described in other mammalian species. However the types of acini may vary among species, and thus further histochemical and cell biology studies are required in order to uncover the significance of this variation for the specie here studied, according with their feeding habit.

Intrauterine sexual differentiation: biosyntesis and action of sexual steroid hormones

The objective of this review was to describe sexual differentiation events in mammals, relating them to biosynthesis of sexual steroid hormones and their mechanisms of action. Cholesterol is the precursor of sexual steroid hormone biosynthesis via action of several enzymes converting these hormones. Progestagens hormones serve as substrate for the production of androgens, which in turn serve as substrate for estrogen hormones. These hormones are responsible for sexual differentiation and reproductive cycles of mammals. Sexual differentiation process comprises determining the sexual chromosomes XX or XY + SRY and other genes linked to them, differentiation of gonads in testis or ovary, differentiation of internal and external male or female genital organs from undifferentiated anatomical structures present in the embryo, which is dependent on the presence or absence of testes and the production of anti-Mullerian hormone and testosterone; and secondary sexual differentiation, which is the response of various tissues to hormones produced by the gonads, interacting with genes linked to sexual chromosomes to increase or decrease the differences in sexual phenotype. However, some differences between the sexes and some anomalies of sexual differentiation are not explained only by these sexual hormonal effects, but also by the effect of genes encoded in sexual chromosomes.

Adrenal glands of Spix's yellow-toothed cavy (Galea spixii, Wagler, 1831): morphological and morphometric aspects

Considering the physiological importance and need of greater morphophysiological knowledge of adrenal glands, the aims of present study were compare the morphometric data between left and right adrenal of male and female; perform a histological, scanning and transmission electron microscopy study showing tissue constitution of glands; finally, in order to define the presence and correct site of the cytochrome P450c17 expression in adrenal glands, immunohistochemical study of this enzyme was performed in 18 adrenal glands (right n=9 and left n=9) of nine adult Galea spixii (four males and five females). Right adrenal was more cranially positioned than left adrenal; dimensions (weight, length and width) of right adrenal was larger than left adrenal; no differences between male and female body and adrenal measurements were found; the morphology of cells and different amounts of lipid droplets may be related to the different demands of steroid hormones production, related to each zone of the adrenal cortex; and, the cytochrome P450c17 immunolocalization in fasciculate and reticular zone may be related with synthesis of 17-hydroxy-pregnenolone, 17-hydroxy-progesterone, dehydroepiandrosterone or androstenedione.