Histological description of morphogenesis of the gastroesophageal mucosa of gallus gallus domesticus (linnaeus, 1758) / Descripción histológica de la morfogénesis de la mucosa gastroesofágica de gallus gallus domesticus (linnaeus, 1758)

The ontogenesis of the gastroesophageal mucosa involves morphological alterations related to its structure and the function of each segment. The present study describes the histogenesis of the mucus-secreting epithelium and glands of the esophagus, gizzard, and proventriculus of the chicken (Gallus gallus), and identifies alterations in the secretion pattern of glycosaminoglycans (GAG's). We analyzed 38 chicken embryos, processed the material collected following the histological routine, and then stained it with hematoxylin-eosin for the analysis of tissue structure and with Gomori's trichrome for the identification of conjunctive tissue and collagen fibers. We used the PAS histochemical technique for the analysis of neutral GAG's and the AB pH 2.5 histochemical technique for the analysis of acid GAG's. The embryos at late stage of development had the esophagus wall composed of four layers: mucosa, submucosa, muscularis, and serosa, whereas the proventriculus and the gizzard were composed of three layers: mucosa, muscularis, and serosa. In all three segments, we identified the superficial epithelium as mucus-secreting; in the esophagus this epithelium was mucus-secreting only at the initial development stages. The proventricular glands began to form at the initial development stages, whereas the tubular glands began to form in the gizzard just after the 15th day. The differences in the production of GAG's in these regions of the digestive tract are related to development stages, functions, and physiological requirements of each segment, and to the gradual adjustment of the body to the post-hatching life.

La morfogénesis de la mucosa gastroesofágica implica alteraciones morfológicas relacionadas con su estructura y la función de cada segmento. El presente estudio describe la histogénesis del epitelio secretor mucinoso y de las glándulas del esófago, molleja y proventrículo del pollo (G. gallus), ademas de identificar los cambios em el patrón de secreción de glicocosaminoglicanos (GAG's). Se utilizaron treinta y ocho embriones de pollo. El material recogido fue procesado de acuerdo a la rutina histológica y posteriormente las secciones se tiñieron con hematoxilina-eosina para su análisis histológico, con tricrómico de Gomori para identificar el tejido conectivo y las fibras de colágeno y con PAS y AB pH 2,5 para el análisis GAG's neutro y ácido. En una etapa avanzada de desarrollo de los embriones, se pudo obervar en la pared del esófago cuatro capas: mucosa, submucosa, muscular y serosa, mientras que el proventrículo y molleja se muestra constituida por tres capas: mucosa, muscular y serosa. En los tres segmentos de la superficie, el epitelio se identificó como mucinoso y en el esófago sólo en la etapa inicial de desarrollo. Las glándulas del proventrículo se empiezan a formar en las primeras etapas de desarrollo, mientras que en las glándulas tubulares de la molleja comienzan su sólo después del día 15. Las diferencias en la producción de GAG's en estas regiones del tracto digestivo están relacionadas con las etapas de desarrollo, las funciones y necesidades fisiológicas de cada segmento del cuerpo y se adapta gradualmente a la vida después de la eclosión.

Fasting enhances cell proliferation of gastric epithelium during the suckling period in rats

The effect of fasting on cell proliferation was studied during the postnatal development of the maturing stomach. Metaphase indices were obtained after counting mitotic cells blocked by vincristine. The indices were examined at different times of day (10:00 a.m. and 6:00 p.m.) in 16 Wistar rats for each age (10, 18, 22 and 30 days) with different dietary patterns: only milk; weaning with milk and chow; recently weaned, with only chow, and fully weaned, respectively. Metaphase indices (mean +/- SEM) for both periods taken together for 10 and 18-day old animals were significantly higher in fasted (2.25 +/- 0.22 per cent and 2.49 +/- 0.28 per cent , respectively) than in control fed animals (1.67 +/- 0.09 per cent and 1.84 +/- 0.05 per cent , respectively), even if not significantly different for one period alone (18 h). No significant difference in indices was observed for 22-day old rats (fasted = 1.65 +/- 0.28 per cent ). The metaphase index of 30-day old rats was significantly higher in fed (1.02 +/- 0.16 per cent ) than in fasted animals (0.20 +/- 0.03 per cent ). We conclude that fasting enhances cell proliferation in stomach epithelium during the milk intake period, in contrast to the inhibitory effect observed in adult animals. The weaning period marks a transition to the opposite effect of fasting, i.e., a decrease in cell proliferation in 30-day old animals

The effect of fasting on cell proliferation in the gastric mucosa of the 14-day old suckling rat

The effect of fasting on cell proliferation in the gastric mucosa was investigated in 14-day old suckling Wistar rats. The renewal of the epithelial cells of the corpus of the stomach was evaluated by DNA labelling and counting arrested metaphases in fifty 14-day old rats fasted for 18 to 21 h and in fifty 14-day old rats fasted for 18 to 21 h and in fifty control suckling rats of the same age. The animals were sacrificed at 3 h intervals over a 24-h period. The metaphase arrest method was also used to estimate the rate of entry of cells into mitosis in the gastric glands of 26 rats under both feeding and fasting conditions. In addition to the proliferation indiices, the number of epithelial cells, and the heights of the glands and mucosa were measured morphometrically in 20 rats. No significant differences in the rate of entry of cells into mitosis (number of cells in fasted = 0.49 ñ 0.077 cells 100 cells -1 h-1), in the number of epithelial cells (fasted = 241.2 ñ 24.3 cells/0.023 mm2) or in the height of the gastric glands (fasted = 194 ñ 5.4 um) of fasted and control rats were observed. Both labelling and metaphase indices (means ñ SEM) were significantly higher (P<0.01) in the fasted (13.9 ñ 0.57% and 1.3 ñ 0.07%, respectively) suckling rats than in the controls (7.9 ñ 0.39% and 0.9 ñ 0.05%, respectively). These data indicate that fasting stimulates cell proliferation in the gastric mucosa of suckling rats rather than decreasing proliferation, as the case for adult rats