Efectos del éstres crónico sobre la apoptosis y la proliferación celular en la corteza adrenal de ratas gestantes / Effects of chronic stress on apoptosis and cell proliferation in the adrenal cortex of pregnant rats

La homeostasis de los tejidos que constituyen a los seres vivos es regulada por los procesos de proliferación y apoptosis celular. El modelo de estrés crónico intermitente por inmovilización durante la gestación puede alterar diversos mecanismos que mantienen la homeostasis del organismo, los cuales son motivo de estudios actuales. En estudios previos se comprobó variaciones significativas en el peso de las glándulas adrenales y en los niveles plasmáticos de PRL, estrógenos y CORT. Bajo la hipótesis que el estrés crónico produce modificaciones en los procesos de proliferación y apoptosis en las glándulas adrenales de ratas gestantes, los objetivos fueron cuantificar las células en proliferación y apoptosis mediante la utilización de técnicas inmunocitoquímicas en la corteza adrenal de ratas en la segunda mitad de la gestación, y comprobar las características ultraestructurales del proceso apoptótico con microscopía electrónica de transmisión. Material y Métodos: En condiciones de bioterio controladas, se estudió la glándula adrenal de ratas de 12, 17 y 21 días de gestación, controles (RC) y experimentales (RE) sometidas a un estrés crónico, intermitente, homotípico e intenso. Se usaron técnicas combinadas de inmunomarcación, análisis estereológico y cuantificación de imágenes de cortes alternados para determinar las variaciones del fenómeno apoptótico y proliferativo que presentan las diferentes poblaciones celulares de la corteza adrenal. El tratamiento estadístico se realizó con los Softwares InfoStat y el SAS 9.1. Se aplicó ANOVA de una y tres vías y la distribución de Poisson de un modelo logarítmico lineal con efecto de grupo, tiempo e interacciones. Las diferencias fueron consideradas significativas si p<0.05. Resultados Apoptosis: a. En Ratas Gestantes Controles y Estresadas: 1. El índice apoptótico disminuyó a medida que progresó la gestación

SUMMARY: Homeostasis of tissues is regulated by cellular proliferation and apoptosis processes. Intermittent chronic stress by immobilization during gestation may alter several mechanisms that maintain the organism homeostasis. Those mechanisms are object of several studies. Previous studies using the immobilization model have shown significant variations in adrenal glands weight and plasmatic levels of PRL, estrogens and CORT. Under the hypothesis that chronic stress causes changes in proliferation and apoptosis processes in adrenal glands of gestant rats, the main objectives of this study were: 1) to identify and quantify cell nuclei in proliferation and apoptosis using immunocytochemical techniques in adrenal cortex samples of rats in the second half of gestation and, 2) to check the ultraestructural haracteristics of apoptotic process by means of transmission electronic microscopy. Materials and Methods: In controlled lab conditions, the adrenal glands of control (RC) and experimental (RE) rats at 12, 17 and 21 days of gestation were studied. Experimental rats were subject to an intermittent, chronic, homotypic and intense stress in order to avoid habituation. A combination of labeling techniques, stereological analysis and image quantification of alternate sections was used to determine the changes in proliferation and apoptosis in the different cell populations of the adrenal cortex. Statistical analyses were performed with InfoStat and SAS 9.1 softwares. Data was analyzed with one and three-way ANOVAs and, a linear logarithmic model with Poisson distribution including group, time and interactions effects

Cronologia do desenvolvimento embrionário e fetal de ratos conforme a datação do início da prenhez: [revisão] / Rats’ embryonic and fetal development chronology according to the timing of pregnancy: [review]

Para a realização de estudos em teratologia é essencial o conhecimento da cronologia do desenvolvimento embrionário e fetal do animal usado na experimentação. Neste trabalho, fez-se um levantamento bibliográfico sobre as datas correspondentes aos principais eventos do desenvolvimento embrionário e fetal de ratos, o modelo experimental mais utilizado para tais estudos. Observou-se que há grande variabilidade na datação de um determinado evento embrionário/fetal, dependendo dos autores consultados, embora exista certa coerência nas fases iniciais do desenvolvimento embrionário.

Efeitos teratogênicos da hipervitaminose A em ratos / Teratogenic effects of hipervitaminosis A on rats

São avaliados neste trabalho os efeitos da vitamina A em várias doses sobre fetos de Ratus novergicus aIbinus. Foram administradas 30.000, 60.000 e 90.000 UI por via intraperitoneal no décimo dia de gestação e comparados com um grupo controle. Cada grupo composto por 5 animais foi sacrificado no vigésimo dia de gravidez. O exame macroscópio dos fetos revelou exoftalmia uni ou bilateral em todos. Nos grupos que receberam mais de 60.000 UI de vitamina A foi ainda observado macrostomia, micro e macroglossia, protusão da lingua, lingua bífida, espinha bífida, encurtamento dos membros anteriores, ossos maxilar e mandibular mais curtos. Na dose de 90.000 UI foi observada fenda palatina. A vitamina A em altas doses é teratogênica para Ratus novergicus albinus.

In this study the effects of the various doses of the vitamin A on Ratus novergicus albinus fetuses were evaluated. It were administred 30.000, 60.000 and 90.000 Ul by intraperitoneal via on the tenth day of gestation and compared with a control group. Each group composed by 5 animals was sacrificed on the twentieth day of pregnancy. The macroscopic examination of the fetuses revealed uni or bilateral exophthalmia in all of them. In the groups that received more than 60.000 UI of vitamin A, macrostomya, micro and macroglossya, tongue protusion, bifid tongue, bifid spine, shortening of the anterior members, maxilar and mandibular bones shorter were also observed. With the 90.000 UI dose it was seen cleft palate. The vitamin A in high doses is teratogenic to the Ratus novergicus albinus.

The effects of laminin on the characteristics and differentiation of neuronal cells from epidermal growth factor-responsive neuroepithelial cells

Many extracellular matrix molecules are expressed in the embryonic nervous system and there is some evidence that they are important regulators of neural development. Of these molecules, laminin appears to be the most potent, affecting virtually all neurons of the peripheral and central nervous system. This study was undertaken to investigate the effects of laminin on the proliferation and differentiation of cultured neuroepithelial cells taken from fetal rat forebrains (embryonic day 17-19). The results are summarized as follows. 1) Neuroepithelial cells cultivated in epidermal growth factors containing serum-free medium subsequently differentiated into neurons, astrocytes, and oligodendrocytes. 2) Neuronal cells derived from neuroepithelial cells were immunoreactive for gamma-aminobutyric acid (GABA) or substance P, but were not for serotonin and tyrosine hydroxylase. 3) In western blot analysis, the phosphorylated neurofilament content in neuronal cells was higher in culture on laminin than in culture on poly-L-lysine (PLL). 4) The proliferation rate of GABAergic neurons was higher in culture on laminin than in culture on PLL. These results suggest that GABAergic and substance P-ergic neurons can be differentiated from neuroepithelial cells and that laminin promotes the differentiation of neuronal cells from neuroepithelial cells and the increased proliferation rate of GABAergic cells.