Charles Rouiller

Insulin Release by Emiocytosis: Demonstration with Freeze-Etching Technique

The technique of freeze-etching for electron microscopy applied to isolated islets of Langerhans has permitted a successful evaluation of emiocytotic events on the cell surface. The frequency of these events in stimulated cells suggests that emiocytosis represents a significant mechanism for insulin release.

Acid Phosphatase Activity in Secretory Granules of Pancreatic Beta Cells of Normal Rats

A cytochemical staining method for acid phosphatase combined with electron microscopy was applied to the islets of Langerhans of adult normal rats. In addition to dense bodies, some Golgi cisternae as well as a varying number of secretory granules of β cells were found to contain acid phosphatase. In view of the paucity of the knowledge concerning the role of acid phosphatase, the possible functional significance of its presence in the secretory granules of pancreatic β cells cannot be denned at the present time.

Organ culture of fetal-rat pancreas: III. Ultrastructural changes occurring in B cells during stimulation of insulin release☆

Abstract Fetal-rat pancreas, explanted on the 18th day of gestation and cultured over 4 days, was used for the study of morphological changes occurring in B cells and associated with the stimulation of insulin release in vitro during a 2-h incubation period. This preparation is characterized by its ultrastructural preservation and by the fact that it can release up to one third of stored insulin when incubated in the presence of appropriate stimuli. Under -these conditions, dramatic morphological changes were observed in β-granules. They appeared widened and their core, losing its characteristically homogeneous structure, was progressively substituted by filamentous material, thus suggesting granular disintegration within the membranous envelope and presumably into the cytoplasm. In all instances, the membranous envelopes remained uninterrupted. Whatever the stimulus, these ultrastructural changes were qualitatively similar but varied quantitatively with the intensity of the stimulation of insulin release. These findings suggest that intracytoplasmic release of secretory material through intracellular solubilization of β-granules is the predominant mode of insulin secretion in cultured fetal explants. Since there is also some evidence for “emiocytosis” in this preparation, it thus appears that insulin secretion may proceed from several (or at least from two) ultrastructural events according to the preparation and/or the stimulus used.

The effect of hyperoxia on the ultrastructure of the superior cervical ganglion of the ratin vitro

SummarySuperior cervical sympathetic ganglia of the rat have been submittedin vitro to an oxygen pressure of 5 atmospheres. The lesions which have been observed emanate from the oxygen toxicity but not from a hyperbar effect. Indeed, ganglia kept under a helium pressure of 5 atmospheres are remarkably well preserved. The oxygen toxicity manifests itself diffusely throughout the ganglion. Although the ganglion is finally damaged in its entirety, the components of the nervous tissue show a diversified sensitivity relative to oxygen. During the seven first hours, the alterations of the mitochondria, the Golgi complex and the endoplasmic reticulum are more prominent in chromaffin cells than in ganglionic or satellite cells. On the other hand, the nervous fibers seem to be more resistant to hyperoxia than the other structures. The necrosis of ganglionic and satellite cells are detected after hyperoxia for 12 hr. After 19 hr, the extent of the necrosis accounts for the irreversible loss of the synaptic transmission.