Freeze-fracture study on the whorls of rough endoplasmic reticulum in the exocrine pancreatic cells of the Japanese newt and African clawed toad

The whorls of rough endoplasmic reticulum (rER) in the exocrine pancreatic cells of starved newts and clawed toads were examined by a freeze-fracture technique. The whorl appeared to be roughly ovoidal in shape and composed of tightly packed, narrow cisternae arranged like the layers of an onion. The clusters of interdigitating projections of the cisternal membranes were located at several places on the whorl. Some of these projections extended to the vesicular rER around the whorl. The fenestra-like, raised or hollowed craters were seldom seen on the fractured membrane faces of the whorls in the exocrine pancreatic cells of the starved newts.

Comparative ultrastructural study of the Ito cells in the liver in some reptiles

The Ito cell (fat-storing cell) in the liver of the lizard, snake and turtle was studied by electron microscopy. The Ito cell was positioned in the perisinusoidal space of Disse and contained characteristic fat droplets in all of the animals studied. The fat droplets in the Ito cells of turtles, fed commercially obtained pig liver, were numerous and large. The Ito cells contained fewer and smaller fat droplets in the lizards and snakes, caught in their natural habitat and sacrificed. There were frequently Ito cells without fat droplets, designated as empty Ito cells, in the snake liver. Dilated cisternae of rough endoplasmic reticulum were found in the Ito cells of the lizard and snake liver, but they were absent from the Ito cells of the turtle liver. It is suggested that the nutritional state of animals, especially the vitamin A concentration in the food, might induce these differences in the Ito cell.