Radivoj V. Krstić

A combined scanning and transmission electron microscopic study and electron probe microanalysis of human pineal acervuli

SummaryUntreated, decalcified and trypsinized acervuli from human pineal bodies were studied with the scanning and transmission electron microscope as well as by electron probe microanalysis. The mulberry-like acervuli are composed of a various number of spherical lobes (135–800 μm) between which clustered groups of globuli (4–14 urn in diameter) are observed. The acervular lobes are very probably formed by an aggregation of these globuli. Small round particles 125–500 Å in diameter are observed on the surface of the pineal concretions. These are not influenced by either decalcification or trypsin treatment. The acervular mineral corresponds morphologically to hydroxyapatite. The electron probe microanalysis reveals the existence of calcium and phosphorus as main components of the acervuli. Small quantities of magnesium and strontium were also detected.

Ultrastructure of cell death in bulbar cushions of chick embryo heart.

SummaryThe ultrastructure of the “physiological” cell death was studied in distal ventral bulbar cushions of 15 chick embryo hearts on the 4th and 5th day of incubation. Microperfusion fixation was performed. The ultracytochemistry of a lysosomal hydrolytic enzyme acid phosphatase was also investigated in another 15 embryonic hearts.In the course of the cell degeneration an increase in cellulr autophagy was observed without previous cytoplasmic or nuclear changes or phagocyte ingestion. A cytoplasmic diffusion of acid phosphatase outside of lysosomes was observed.Besides the cell death with the marked participation of the lysosomal system, another kind of dying cells was found, characterized by their nuclear pycnosis and cytoplasmic condensation. Starting from the 5th day of incubation the dying and dead cells were found phagocytized by some of their neighbouring viable mesenchymal cells. A formation of ribosomal crystals was not observed.The formation and fate of cytolysomes as well as the fate of phagocytes are discussed. The presence of pre-necrotic cells with important autophagy and of necrotic cells with nuclear changes was related to the possibility of a dual cause of the cell death. In the case of pre-necrotic cells the epigenetic factors like the biomechanic action of hemodynamics were considered, while the necrotic cells seem to be programmed to death by their genome.Finally the uniformity of cell death ultrastructure in different organs and species was noticed.

Different modes of mesenteric infiltration displayed by two rat leukemias. A study by scanning and transmission electron microscopy and by microcinematography.

SummaryInfiltration of the mesentery after intraperitoneal implantation of two transplantable rat leukemias, the undifferentiated L5222 and the myeloid BNML, was studied by means of scanning and transmission electron microscopy, and microcinematography. In animals implanted with L5222 cells, contraction of the mesenteric mesothelium is a conspicuous feature. It occurs within the first 24 h after implantation and influences decisively the course of infiltration. In contrast, the presence of BNML cells leads to mesothelial contraction only in the terminal stage and, therefore, exerts no direct effect on infiltration. In addition, the two leukemias differ with regard to their cellular motility. Whereas L5222 cells locomote within the mesentery, only stationary movements are recorded with BNML cells. Based on the different interactions with the mesothelium and cell motilities, two distinct modes of infiltrating the mesentery could be ascertained for the two rat leukemias.

Ultracytochemistry of the synaptic ribbons in the rat pineal organ

SummaryThe synaptic complexes of the rat pinealocytes are neither cholinergic nor adrenergic. In the synaptic vesicles, a neurotransmitter carrier substance of lipid nature reacting with OsO4-Zn I2 mixture (similar to that present in both cholinergic and adrenergic vesicles) was not found.In addition, there were no indications of glucose-6-phosphatase or thiamine-pyrophosphatase activity in the synaptic vesicles. Thus, it appears that the synaptic vesicles do not originate from the rough or smooth endoplasmic reticulum.The synaptic ribbons do not contain carbohydrates, are of protein nature and possess some chemical resemblance to microtubules and microtubular bouquets.Appropriate ultracytochemical reactions have not shown detectable quantities of sodium and calcium ions in pinealocyte synaptic complexes.

Ultrastructure of rat pineal gland after preparation by Freeze-etching technique

SummaryThe pineal glands of Wistar rats were fixed in glutaraldehyde and prepared by the freeze-etching technique. With regard to the form and internal structure of pineal cells this technique has revealed nothing essentially new. Synaptic ribbons are very rarely found. A regular diagonal arrangement of membrane attached particles between the Schwann cell and the axon of an autonomic nerve terminal was observed.Three types of contact areas between pineal cells are described. In the first two types, which occur more frequently, the diameter of the area varied from 1000 to 2500 Å, with irregularly aggregated membrane associated particles. The third type, larger but less frequently found, has a surface area of 0.4 μm2 and much more regularly distributed membrane associated particles (ø 88 Å). These contact areas can be considered to be electric coupling areas between pineal cells.

Über Veränderungen der Epithelkörperchen nach Epiphysektomie

SummaryAfter epiphysectomy in parathyroid glands of rats the following symptoms of hyperfunction are observed: an increase of nuclear volume and of capillarity, an augmentation of concentration of leucylaminopeptidase, an increase of number and growth of mitochondria and secretion granules, dilatation of the Golgi complex and an increase of blood calcium values. The functional relations between the epiphysis and the parathyroid glands are indirect. Morphological alterations of the parathyroid glands are caused by changes in the mineral metabolism.ZusammenfassungNach der Epiphysektomie sind in den Epithelkörperchen der Ratte Symptome einer Funktionsteigerung festzustellen: Vergrößerung des Kernvolumens, verstärkte Kapillarisierung, erhöhte Konzentration der Leucylaminopeptidase, Vermehrung und Vergrößerung der Mitochondrien und Sekretgranula, Ausdehnung des Golgi-Komplexes und Erhöhung des Blutkalziumspiegels. Die funktionellen Beziehungen zwischen Zirbeldrüse und Epithelkörperchen sind indirekt; sie werden bei Änderungen in Mineralstoffwechsel histologisch und cytologisch faßbar.

Ultracytochemical localization of calcium in the superficial pineal gland of the Mongolian gerbil.

In order to demonstrate fine localization of Ca2+ in the superficial pineal gland of Meriones unguiculatus, the pyroantimonate technique was employed. Control experiments were performed with EGTA and analysis of obtained reaction product using an energy‐dispersive x‐ray microanalysis.

Scanning electron microscopic study of the freeze-fractured pineal body of the rat.

SummaryThe three-dimensional ultrastructure of the pineal body of the rat is described on the basis of freeze-fractured preparations. The pineal capsule consists of irregular cells with very flat and perforated processes. Through these openings, extremely branched canaliculi, extending to almost every pineal cell, communicate with the tissue compartment outside the organ. The pericapillary spaces contain, in juxtaposition with capillaries of the fenestrated type, nerve fibers as well as a flocculent granular and filamentous material of unknown origin and chemical nature.

Formation of autophagosomes in the pinealocytes of the rat and Mongolian gerbil (Meriones unguiculatus): A lysosome wrapping mechanism?

SummaryAutophagosome formation in rat and gerbil pinealocytes is described. It starts with the setting up of a tubular acid phosphatase-rich cisterna which gradually wraps around cytoplasmic areas to be catabolized. In light of obtained findings, it seems that the autophagosome formation in pinealocytes is a type of lysosome wrapping mechanism.

Ultracytochemical localisation and comparison of adenyl cyclase activities in pineal bodies of Wistar rats and Mongolian gerbils.

SummaryIn the pineal bodies of Wistar rats and mongolian gerbils (Meriones unguiculati) the main concentration of adenyl cyclase was found in capillary endothelial cells, their basal laminae, pericapillary amorphous material and in nerve endings. In the intercellular clefts between the rat pineal cells there was no adenyl cyclase activity, but a considerable amount of this enzyme was detected in the gerbils. The adenyl cyclase lacks completely in the pinealocyte cytoplasms of both species. It was concluded that the gerbil pineal cells may be more reactive to various hormonal influence than those of the rat.