RESUMO
One of the dogmas of mammalian reproduction states is that primordial germ cells in females are restricted to the intrauterine phase, and that only a small portion of oocytes is available for ovulation during the adult life. Among the rare exceptions to this rule is the plains viscacha. This specie polyovulates up to 800 oocytes per cycle, from which 10 to 12 are implanted, but only 1-2 conceptuses survive. To better understand the key mechanisms of this pattern of embryonic to uterine interactions, we analyzed 19 female genital systems by means of gross morphology, histology, stereology and immunohistochemistry. Data showed that a specialized, highly convoluted structure of the ovarian cortex developed during the intrauterine phase as a prerequisite for the massive super-ovulation, likely associated with the inhibition of apoptosis and continued proliferation of germ cells, as well as maintenance of several corpora lutea during the adult life. In addition, specializations of uterine vasculature and musculature were demonstrated. Altogether, these key morphological characteristics evolved in order to contribute as compensatory or controlling mechanism for polyovulation and polyimplantation that led these species into becoming an unique enigma in reproductive biology, and a potential animal model to provide explanations regarding to developmental specializations.
Assuntos
Ovário/anatomia & histologia , Ovário/fisiologia , Roedores , Superovulação/fisiologia , Útero/anatomia & histologia , Útero/fisiologia , Animais , Implantação do Embrião/fisiologia , Embrião de Mamíferos/anatomia & histologia , Feminino , Feto/anatomia & histologia , Genitália Feminina/anatomia & histologia , Genitália Feminina/fisiologia , Idade Gestacional , Tamanho da Ninhada de Vivíparos/fisiologia , Ovário/irrigação sanguínea , Ovulação/fisiologia , Gravidez , Reprodução/fisiologia , Roedores/anatomia & histologia , Roedores/fisiologia , Útero/irrigação sanguíneaRESUMO
The ascending colon of most rodent species shows a longitudinal colonic groove that works as a retrograde transport pathway for a mixture of bacteria and mucus toward the cecum. We describe the morphology and glycosylation pattern of the colonic groove of Lagostomus maximus to analyze the role of mucins in this anatomical feature. We also studied the distribution pattern of the interstitial cells of Cajal (ICC) to evaluate their regulatory influence on gut motility. The groove originated near the cecocolic junction and extended along the mesenteric side of the ascending colon, limited at both ends by nonpapillated ridges. These ridges divided the lumen of the ascending colon into two compartments: a narrow channel and a large channel, called the groove lumen and the main lumen, respectively. The histochemical analysis showed differences in the glycosylation pattern of the goblet cells inside and outside the groove. Unlike the mucosa lining the main lumen of the colon, the groove was rich in goblet cells that secrete sulfomucins. The PA/Bh/KOH/PAS technique evidenced an abrupt change in the histochemical profile of goblet cells, which presented a negative reaction in the groove and a strongly positive one in the rest of the colonic mucosa. The anti-c-kit immunohistochemical analysis showed different ICC subpopulations in the ascending colon of L. maximus. Of all types identified, the ICC-SM were the only cells located solely within the colonic groove.
Assuntos
Colo/anatomia & histologia , Células Caliciformes/metabolismo , Roedores/anatomia & histologia , Animais , Membrana Celular/metabolismo , Colo/citologia , Feminino , Glicosilação , Imuno-Histoquímica , Células Intersticiais de Cajal/citologia , Mucosa Intestinal/citologia , Lectinas/metabolismo , Masculino , Proteínas Proto-Oncogênicas c-kit/metabolismoRESUMO
Morphological and histochemical analyses were performed to characterize the histology, ultrastructure, and glycosylation pattern of the jejunum and ileum of the wild rodent Lagostomus maximus. Enterocytes, goblet cells, Paneth cells, and enteroendocrine cells were identified in both intestinal epithelia. Two morphological types of enterocytes were identified only in the ileum based on their cytoplasm electron density. Although the histological and ultrastructural examination showed that the epithelia of both anatomical regions were morphologically similar, a certain specialization in their secretory products was evident. The glycosylation pattern of the jejunum and ileum was characterized in situ by histochemical and lectin histochemical methods. Histochemical results revealed the presence of carboxylated and sulfated gycoconjugates in both regions, although sulfomucins were clearly prevalent in the ileum. Sialic acid was highly O-acetylated and particularly abundant in the jejunum. The KOH/PA*/Bh/PAS technique evidenced a more intense histochemical reaction in the jejunal than in the ileum goblet cells, demonstrating a reduction of neutral mucin secretion in the distal small intestine. Further specific differences were revealed by lectin histochemistry. These data evidenced that the nature of mucus varies at different anatomical regions, probably adapted to physiological requirements.
Assuntos
Íleo/citologia , Mucosa Intestinal/citologia , Jejuno/citologia , Mucinas/metabolismo , Roedores/anatomia & histologia , Roedores/fisiologia , Animais , Feminino , Glicosilação , Íleo/metabolismo , Íleo/ultraestrutura , Mucosa Intestinal/metabolismo , Mucosa Intestinal/ultraestrutura , Jejuno/metabolismo , Jejuno/ultraestrutura , Lectinas/metabolismo , Masculino , Microscopia Eletrônica de TransmissãoRESUMO
This study complements the previous investigations of the reproductive biology of male viscachas, a rodent of a seasonal Hystricognathi that exhibits photoperiod-induced morphological variations in the reproductive system. In the present study, a quantitative analysis of spermatogenesis was performed during the summer and the spring. Spermatogonial cells were analyzed to determine by immunolabelling for STRA8 and DAZL, which are essential for spermatogenesis. Six free-living male viscachas were captured, three animals in the summer during the period of reproductive activity and three animals in the spring during the period of testicular regression. The testes of the viscachas were collected and processed for light microscopy, macroscopic and immunochemical analyses. The germ and Sertoli cells present in the seminiferous tubules were quantitatively analyzed in each animal. The efficiency coefficient for spermatogonial mitosis, meiotic yield, overall spermatogenesis yield and Sertoli cell index, revealed that the Sertoli cells in male viscachas captured during the summer had a reduced capacity to structurally and nutritionally support the developing round spermatids compared with the male viscachas captured during the spring. The animals produced less sperm during the spring than the summer, suggesting a seasonal impact on spermatogenesis. Immunolabelling for STRA8 and DAZL was detected during summer and spring seasons. These results suggest that in seasonal rodents, such as the male viscachas, the photoperiod promotes significant changes in the testis and in the germ cell yield.
Assuntos
Roedores/fisiologia , Estações do Ano , Espermatogênese/fisiologia , Testículo/fisiologia , Animais , MasculinoRESUMO
The presence of binucleate cells constitutes a normal feature of some animal tissues but is rare in the normal brain and has not been documented in the spinal cord. We assessed different segments of the rat spinal cord in order to determine the frequency and distribution of binucleate neurons in this structure as well as the impact of aging on this neuronal population. Young (4-5 months) and senile (32 months) female Sprague-Dawley rats were used. Sections from cervical, thoracic and lumbar segments were histochemically and immunohistochemically (NeuN) stained and the frequency and distribution of binucleate neurons was determined by manual counting. The frequency of binucleate neurons in all of the analysed segments was comparable between young and senile animals. Binucleate neurons were particularly frequent in the C5 and C6 segments. The overall distribution of binucleate neurons in the different laminae assessed was, Lm-III = 19%; Lm-VI = 17%; Lm-VII = 39%; LmVIII = 8%; Lm-IX = 11%; Lm-X = 6%, and was comparable between young and senile rats. We conclude that binucleate neurons occur as a normal feature of the rat spinal cord and that their frequency and distribution does not change with aging.
Assuntos
Envelhecimento/patologia , Núcleo Celular/patologia , Neurônios/patologia , Medula Espinal/patologia , Animais , Contagem de Células , Feminino , Ratos , Ratos Sprague-DawleyRESUMO
We have investigated the effects of EA21a and EA34 mammary carcinomas on daily PI cell proliferation in mice. Animals were divided into groups grafted with either EA34 or EA21a carcinomas (and a non-grafted control group). They were all injected intraperitoneally with 2 microg colchicine per g of body weight 4 h before sacrifice and the number of mitoses per 1000 nuclei was calculated. The mitotic index (MI) of pars-intermedia epithelial cells in control animals showed significant temporal variations. However, the MI from mice grafted with EA34 or EA21a carcinomas showed no such variation. There was no difference between the daily MIs of controls and tumor grafted groups. The absence of a 24 h mitotic activity curve in both EA21a and EA34 tumor-bearing animals demonstrates a lower level of synchronization of cells entering mitosis.