RESUMO
The lifespan of intestinal epithelial cells is predetermined by the process of cell proliferation that occurs constantly in the crypt. The control of this process involves some endogenous factors, such as hormones, as well as exogenous factors, like food and natural light variations. These last two exogenous factors seem to be the major modulators of the cell proliferation process. Fasting treatment was conducted to assess the role of food and its effect on the metaphase index (MI) of the intestinal epithelium at different times and periods (light and dark) of the day. The effects of short- (5 hr) and long-term (25 hr) fasting on the MI in the jejunal epithelium of young rats were investigated at 09:00 h, 15:00 hr, 21:00 hr, and 02:00 hr using the arrested metaphases method. The present study demonstrates that 5 hr and 25 hr of fasting treatment decrease the MI at 09:00 hr. It was observed from MI analysis that there is an interaction between the fed/fasted status of the animal and the different times of the day. This result suggests that during the transition from youth to adulthood, the control of MI by the light/dark cycle seems to be more pronounced as compared with control by food intake at some periods of the day, although at other times food had a greater impact on the MI.
Assuntos
Animais Lactentes/fisiologia , Ritmo Circadiano/fisiologia , Jejum/fisiologia , Mucosa Intestinal/crescimento & desenvolvimento , Jejuno/crescimento & desenvolvimento , Desmame , Envelhecimento/fisiologia , Animais , Animais Recém-Nascidos , Animais Lactentes/anatomia & histologia , Proliferação de Células , Escuridão , Digestão/fisiologia , Digestão/efeitos da radiação , Feminino , Privação de Alimentos/fisiologia , Mucosa Intestinal/citologia , Jejuno/citologia , Luz , Masculino , Metáfase/fisiologia , Estimulação Luminosa , Ratos , Ratos Wistar , Fatores de TempoRESUMO
We determined the genome size of the Brazilian sciarid flies Bradysia hygida, Rhynchosciara americana and Trichosia pubescens (Diptera: Sciaridae) using absorbance measurements of Feulgen-stained nuclei belonging to these species (and chicken erythrocytes as a standard) to calculate the amount of DNA in picograms (pg) and the number of base pairs (bp), or C-value, for each of these species. The C-values were: 3 x 108 bp (0.31 pg) for B. hygida; 3.6 x 108 bp (0.37 pg) for R. americana; and 1 x 109 bp (1.03 pg) for T. pubescens. The sciarids investigated in this work had considerably higher C-values than the average for previously described dipteran species, including D. melanogaster
