Abstract
Several male rats aged 80 to 120 days after birth were starved for three days (only drinking water was supplied) and then refed. At 30 minutes, 1, 3, and 5 hours after refeeding, a couple of rats were sacrificed by a blow on the head. Small pieces of gastric wall were fixed in buffered osmium tetroxide and embedded in methacrylate resin. Ultrathin sections were examined under the electron microscope.
1. Body chief cell.
Secretory granules in variety of electron density and size accumulated in the apical cytoplasm of the body chief cell of the starved rats are markedly reduced in number after feeding. As the time elapsed after refeeding, increase in the total area of the GOLGI apparatus, dilatation of the cavities of GLOGI lamellae or vacuoles and enlargement of each GOLGI vesicle may be recognized. Within the GOLGI area may occur several immature secretory granules which are small in size, surrounded by a definite limiting membrane and contains rather dense material. Between somewhat hypertrophied GOLGI vesicles and the immature secretory granules, some intergrades suggestive of mutual transformation may be recognized. As the size of granules increased, electron density of the interior is markedly diminished, and at last they become quite lucent vacuoles with limiting membranes which have been partially ruptured or entirely disappeared.
Rough surfaced endoplasmic reticulum appears in a form of regularly organized parallel lamellae at the infranuclear region of the body chief cell of starved rat, but fragmentation occurs after feeding showing many round or irregular sacs, whose cavities are increasingly densified, being suggested probable accumulation of some material in the rough surfaced cisternae.
It is evident, in the body chief cell, the new formation of secretory granules apparently occurs in the GOLGI area, but the endoplasmic reticulum of rough surfaced type is also actively involved in the synthesis of secretion.
Mitochondria are usually situated in the cell periphery lying along the lateral cell border during the resting stage (starvation), but in the active stage of secretory granule formation they migrate into the vicinity of GOLGI apparatus and often abut against the growing secretory granule, and hence the mitochondria may be also related to the secretory activity of this cell, although none of signs of direct transformation from mitochondria into secretory granules could be observed.
The secretion of this cell may be discharged into the lumen by diffusion through intact plasma membrane.
2. Parietal cell.
The parietal cells in the starved rat are filled with abundant vesicles which are apparently belonged to the smooth surfaced variety of endoplasmic reticulum, and show the intracellular secretory canaliculi whose lumina are totally collapsed in this state. After refeeding the canaliculi are remarkably dilated and smooth surfaced vesicles extremely diminish. After 1-3 hours, the vesicles reappear but small dense particles decrease in number, which are very abundant in the cell immediate after refeeding. It is tentatively assumed that the vesicles of smooth surfaced endoplasmic reticulum probably containing secretory material of this cell may derived from small dense particles.
Presence of GOLGI apparatus in the parietal cell has been doubted by many authors, but in this study poorly developed GOLGI apparatus was rarely seen. The apparatus consists of only vesicles and relatively small vacuoles but does not manifest the so-called lamellae. The mode of secretion discharge by parietal cells may be divided into two, one of which is apocrine type and the other is eccrine. Cytoplasmic projections suggestive of the apocrine extrusion are most frequently observed in the stomach of starved rats.
3. Mucous neck cell.
The mucous neck cell shows no definite alteration in morphology during either fasting or postprandial periods. This cell may not be directly related in function to the digestion
