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G MAJNO

Publications and source records attributed to G MAJNO.

At least 19 recordsLinked to original sources
PubMed1963

Skin diving.

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Diving↗
PubMed1961

Studies on inflammation. 1. The effect of histamine and serotonin on vascular permeability: an electron microscopic study.

The mechanism, whereby histamine and serotonin increase the permeability of blood vessels, was studied in the rat by means of the electron microscope. The drugs were injected subcutaneously into the scrotum, whence they diffused into the underlying (striated) cremaster muscle. An intravenous injection of colloidal HgS was also given, in order to facilitate the identification of leaks by means of visible tracer particles. After intervals varying from 1 minute to 57 days the animals were killed; the cremaster was fixed, embedded in methacrylate, and examined with the electron microscope. One to 12 minutes after the injection, the blood vessels of the smallest caliber (3 to 5 micra as measured on electron micrographs) appeared intact. Numerous endothelial openings were present in blood vessels with a diameter of 7 to 8 micra or more. These gaps were 0.1 to 0.8 micra in width; portions of intercellular junctions were often present in one or both of the margins. The underlying basement membrane was morphologically intact. An accumulation of tracer particles and chylomicra against the basement membrane indicated that the latter behaved as a filter, allowing fluid to escape but retaining and concentrating suspended particulate matter of the size used. Uptake of tracer particles by endothelial vesicles was minimal. Phagocytosis by endothelial cells became more prominent at 3 hours, but as a secondary occurrence; the pericytes were actively phagocytic at all stages. At the 3-hour stage no leaks were found. The changes induced by histamine and serotonin were indistinguishable, except that the latter was more potent on a mole-to-mole basis. In control animals only small accumulations of tracer particles were found in the wall of a number of blood vessels. With regard to the pathogenesis of the endothelial leaks, the electron microscopic findings suggested that the endothelial cells become partially disconnected along the intercellular junctions. Supporting evidence was provided at the level of the light microscope, by demonstrating-in the same preparation-the leaks with appropriate tracer particles(1), and the intercellular junctions by the silver nitrate method. The lipid nature of the chylomicron deposits observed in electron micrographs was also confirmed at the level of the light microscope, using cremasters fixed in formalin and stained in toto with sudan red.

Animals↗
PubMed1961

Studies on inflammation. II. The site of action of histamine and serotonin along the vascular tree: a topographic study.

While it is an established fact that histamine and serotonin increase the permeability of blood vessels, the exact portion of the vascular tree which is so affected has not been conclusively demonstrated. The present study was undertaken to clarify this point. Our experiments were based on a method to which we refer as "vascular labeling," and which permits one to identify leaking vessels by means of visible accumulations of foreign particles within their walls. The mechanism of the labeling, elucidated by previous electron microscopic studies, is the following. Histamine and serotonin cause the endothelial cells of certain vessels to separate, and thus to create discrete intercellular gaps. Plasma escapes through these gaps, and filters through the basement membrane. If the plasma has been previously loaded (by intravenous injection) with colloidal particles of a black material such as carbon or mercuric sulfide, these particles-too large to pass through the basement membrane-will be retained and accumulate in visible amounts within the wall of the leaking vessel. This method is used to maximal advantage if the tissue is cleared and examined by transillumination in toto, so that leaking vessels can be accurately identified in their relationship to the vascular tree. As a test tissue we used the rat cremaster, a laminar striated muscle which can be easily excised with its vascular supply virtually intact. The rats were prepared with an intravenous injection of carbon or HgS, and a subcutaneous injection into the scrotum of histamine, serotonin, or NaCl (as a control). The injected drug diffused into the underlying cremaster and the vessels became labeled. One hour later, when the carbon had been cleared from the blood stream, the animal was killed. The cremaster was excised, stretched, fixed in formalin, cleared in glycerin, and examined by transillumination under a light microscope. The lesions induced by histamine and serotonin were identical. The leaking vessels, as indicated by the carbon deposits, always belonged to the venous side of the circulation. The heaviest deposits were found in venules 20 to 30 micra in diameter. The deposits decreased towards larger venules up to a maximum diameter of 75 to 80 micra, and towards the finer vessels until the caliber reached approximately 7 micra. Essentially spared by the deposits were the finest vessels, 4 to 7 micra in diameter, and constituting an extensive network oriented along the muscular fibers. By killing animals at varying intervals after the injections, it was found that the carbon particles were slowly removed from the vascular walls by the action of phagocytic cells. After 10 months there was still enough carbon locally to be recognized by the naked eye.

Animals↗
PubMed1958

A biochemical and morphologic study of myelination and demyelination. II. Lipogenesis in vitro by rat nerves following transection.

Bilateral transection was performed on rat sciatics. At varying intervals after the operation, samples of nerve were taken both distal and proximal to the level of transection, as well as from the tissue which bridged the gap between the stumps. These samples were incubated in Warburg flasks, with glucose and a labelled lipide precursor (acetate or phosphate). The total lipides were then extracted and their radioactivity was measured. Normal rat sciatics served as controls, and the biochemical and histological findings were correlated. In the distal portion undergoing Wallerian degeneration, the lipide content began to fall before any removal of myelin could be detected histologically. It is suggested that there is a period of "non-cellular removal" prior to the physical breakdown of the myelin. Changes in respiration and in lipogenesis from acetate followed a triphasic course, and agreed with the histological findings in that after a period of predominantly passive changes (approximately 1 to 3 days) there follows a period of cellular reaction (4 to 50 days) and a period of atrophy (from 50 days onward). The incorporation of phosphate into the lipides was increased at all stages examined, even as early as 22 hours after section. This increased P(32) incorporation could not be reproduced in nerves allowed to degenerate in vitro. It is suggested that the hypertrophying Schwann cells synthesize some lipide moieties at a considerably faster rate than others. Proximal to the level of transection, lipogenesis from acetate was depressed, for as long as 32 days postoperatively. It appears, therefore, that the maintenance of the myelin sheath is impaired also above the level of transection. In the "union tissue" which developed between the stumps, prior to the appearance of histologically visible myelin, lipogenesis was low; later it rose above levels for normal nerve. This pattern of lipogenesis in regenerating nerve is similar to that found in growing nerves.

Adipogenesis↗
PubMed1958

A biochemical and morphologic study of myelination and demyelination. I. Lipide biosynthesis in vitro by normal nervous tissue.

Samples of normal grey matter, white matter, and peripheral nerves obtained from rats were incubated in Warburg vessels with glucose and a labelled lipide precursor (acetate, phosphate, choline, glycerol, glucose). The total lipides were then extracted and their radioactivity measured. The preparations were compared with respect to dry weight, lipide content, O(2) uptake, and ability to incorporate the various substrates into the lipides. Grey matter was found to be the least damaged by incubation, white matter the most. Damage to the tissue depressed lipogenesis to a greater extent than respiration. Five substrates were compared with respect to their degree of incorporation into the lipides of the various preparations. White matter, which had a greater oxygen uptake than peripheral nerves, showed the lowest degree of incorporation for most of the substrates studied. The results suggest that there are considerable quantitative differences in the metabolism of central and peripheral myelin. In the sciatic preparations, oxygen uptake and lipogenesis from acetate were found to decrease from the proximal to the distal end of the nerve. This finding may be relevant to the pathogenesis of peripheral neuropathies. The growth and metabolic activity of peripheral nerves were studied in rats aged 1 to 500 days, and the biochemical and histological findings were correlated. The results indicated that the lipogenetic activity of the Schwann cell was lowest in the newborn animal, and reached its peak at about 20 days. Comparative data were also obtained from the cerebral cortex. The growth pattern of peripheral nerves was distinctly different from that of the brain. With respect to changes in tissue weight, respiration, and lipogenesis, growing peripheral nerve correlated with body weight, while the brain matured much more rapidly.

Acetates↗