Ch. Rouiller

A comparative study of freeze-etch replicas and thin sections of rat liver.

A comparative study of freeze-etched replicas and thin sections of perfusion-fixed rat liver cells reveals the following: In general, the two methods yield similar results; differences emerge mainly at the limits of resolving power. (a) Particles, either β-particles of glycogen or ribosomes, appear smaller in freezeetched than in thin-sectioned specimens. (b) Membranes often show not the regular smoothness of thin-sectioned membranes, but a more or less dense granularity, especially the presumed equivalents of the inner nuclear and inner mitochondrial membranes and the inner faces of the cisternae of the rough endoplasmic reticulum. (c) This latter system shows depressions that might correspond to pores, but these are smaller and less conspicuous than nuclear pores. (d) Endothelial cells possess, besides fenestrations, gaps of varying width, a finding in contrast to that of Wisse (20). (e) The extent of the extracellular space (space of Disse, intercellular cleft, and lumen of the bile canaliculus) appears very similar in both techniques. (f) The tight junction, closing the bile canaliculus at either end, is seen to be formed of dotlike appositions of the hepatocyte membrane in cross-fractured specimens as well as in thin sections; tangentially fractured specimens reveal that the dotlike appositions (close-contact prints) are continuous, cross-linked lines, thus accounting for the tightness of this region.

The stereological analysis of the fine structure of the “micropinocytosis vermiformis” in Kupffer cells of the rat

By serial sectioning and graphic reconstruction with the Perspektomat P-40 it has been established: (1) that the micropinocytotic system in the Kupffer cell, the so-called “micropinocytosis vermiformis” consists of an intricate system of ramifying, tubular and lamellar cavities; (2) that all parts of this system are in communication with the extracellular space; and (3) that the whole system is surrounded by a layer of coated vesicles and communicates with some of them. It is assumed that the “micropinocytosis vermiformis” represents the intensified pinocytosis of colloidal particles of Kupffer cells, and presumably of all reticuloendothelial cells.

Les fibrilles collagènes de l'os

Die elektronenmikroskopische Untersuchung des Knochenkollagens mit Hilfe von Abdrücken hat ergeben, daß die Fibrillenperiode konstant ist (610 Å), während die Dicke je nach Knochen verschieden ist. Das Fibrillenkollagen des normalen Knochens ist nicht mineralisiert, sondern nur von Kittsubstanz umgeben. Diese Einbettung erfolgt aber wahrscheinlich erst nach der Bildung der Fibrillen.

The effect of anoxia on the ultrastructure of the superior cervical ganglion of the rat in vitro.

SummarySympathetic superior cervical ganglia have been keptin vitro in a Krebs’ solution deprived of oxygen. Under conditions of anoxia, synaptic transmission is lost in 15 min. This functional inhibition remains reversible for 5 to 8 hr. Afterwards, the ganglion becomes unable to recover its activity, even when replaced in oxygenated medium.After 1 hr, the electron microscope displays lesions of the satellite cells, which rapidly increase, a degeneration of most of nervroglia ensues. At first, the changes within ganglionic cells and cell processes are slight and reversible. After 3 hr of anoxia, some neurons are necrosed, while other remain apparently normal. Even if the ganglion has been deprived of oxygen for 8 hr, the presynaptic endings are well preserved. Their cholinergic, clear vesicles seem to be more numerous.These modifications of the fine structure of the sympathetic ganglion are discussed in regard to the functional changes. They are compared with the lesions occuring when the ganglionic activity has been disturbed by other factors, such as high oxygen pressure, glucose deprivation, and X-ray irradiations.

Phasenkontrastoptische und ultrastrukturelle Untersuchungen über Degenerationsformen der Skeletmuskelfasern von Laboratoriumstieren und vom Menschen

Bei Muskelbiopsien von Patienten mit Diabetes mellitus und klinisch gesunden Pradiabetikern sowie bei Muskelgewebe von Laboratoriumstieren (sog. „normales Gewebe“) wurden Umbauvorgange an den Myofibrillen verschiedener Muskelgruppen beobachtet. Diese werden im Zusammenhang mit der einschlagigen Literatur diskutiert: Die Arten der bisher bekannten Myofibrillenveranderungen werden zusammengestellt und mit denen verglichen, die wir an unserem Material aufzeigen konnten. Die Autoren kommen zu dem Ergebnis, das man bei den bisher beobachteten Myofibrillenveranderungen keine Ruckschlusse auf die Art eines Krankheitsgeschehens ziehen kann, sondern, das es sich um unspezifische Reaktionen handelt.SummaryStudies of muscle biopsies of patients with diabetes mellitus and of clinically healthy pre-diabetics, as well as of laboratory animals (so-called “normal tissue”), have revealed several different patterns of altered myofibrillar structure. These morphological changes are described and discussed with respect to the relevant literature. The different acknowledged types of myofibrillar change are compiled and compared with those described in our material. The authors conclude that no correlation can be established between the observed myofibrillar changes and the disease of the donor of the biopsy and that the myofibrillar alteration is probably a non-specific reaction.ZusammenfassungBei Muskelbiopsien von Patienten mit Diabetes mellitus und klinisch gesunden Prädiabetikern sowie bei Muskelgewebe von Laboratoriumstieren (sog. „normales Gewebe“) wurden Umbauvorgänge an den Myofibrillen verschiedener Muskelgruppen beobachtet. Diese werden im Zusammenhang mit der einschlägigen Literatur diskutiert: Die Arten der bisher bekannten Myofibrillenveränderungen werden zusammengestellt und mit denen verglichen, die wir an unserem Material aufzeigen konnten. Die Autoren kommen zu dem Ergebnis, daß man bei den bisher beobachteten Myofibrillenveränderungen keine Rückschlüsse auf die Art eines Krankheitsgeschehens ziehen kann, sondern, daß es sich um unspezifische Reaktionen handelt.

PRESENT STATE OF THE EVIDENCE FOR MIXED ENDOCRINE AND EXOCRINE PANCREATIC CELLS IN SPINY MICE

SUMMARY Ultrastructural studies have been carried out in 47 spiny mice (Acomys cahirinus) from a colony characterized by marked hypertrophy of the pancreatic islets and a tendency to develop spontaneous hyperglycemia. Mixed exocrine-endocrine cells have been observed in all animals with severe and prolonged hyperglycemia and ketosis, and in many animals with less severe degrees of hyperglycemia. The mixed cells were very rare in normoglycemic animals. The extensive morphologic evidence collected establishes the presence of true mixed exocrine-endocrine pancreatic cells, at least in this species. The mixing consisted not only in the intimate intermingling of all organelles typical of both exocrine and endocrine cell types, but also of the deposition of glycogen in cytoplasmic areas otherwise entirely typical of exocrine tissue.

CONTROL OF ENDOCRINE FUNCTION IN ORGAN CULTURES OF FETAL RAT PANCREAS

SUMMARY Organ cultures of fetal rat pancreas have been used for the study of biosynthesis and release of insulin. With the electron microscope the cultured explants appeared exceedingly well preserved and contained a relatively large proportion of β-cells showing morphologic evidence of active insulin biosynthesis and storage. This was confirmed by measurements of pancreatic insulin content. Glucose stimulated insulin biosynthesis but was relatively ineffective on insulin release. These findings suggest that, in fetal rat pancreas, endocrine differentiation and insulin biosynthesis are early events. However, insulin release appears to be dependent on the presence of metabolic intermediates and does not occur in their absence, one such intermediate being cyclic 3′,5′-AMP.

INTRACELLULAR “α-GRANULOLYSIS” IN α-CELLS OF DIABETIC ANIMALS*

SUMMARY An increase in the number of lytic bodies involved in the process of “α-granulolysis” was observed in α-cells of both spontaneously diabetic spiny mice (Acomys cahirinus) and rats with experimentally induced diabetes following the administration of streptozotocin. The possible pathways for “α-granulolysis” are illustrated.