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Biomedical subjects

A Gautier

Publications and source records attributed to A Gautier.

At least 37 records · Page 2Linked to original sources
PubMed1981

Ultrastructural cytochemistry of perinucleolar dense spots in heat-treated macroconidia of Neurospora crassa.

Upon heat treatment at 46 degrees C of Neurospora macroconidia, numerous dense sports appear around the nucleolus but disappear completely 5 h after shift-down to normal temperature. Cytochemical reactions and high-resolution autoradiography after pulse-labeling with tritiated uridine indicate that these dense sports contain RNA (perhaps pre-rRNA), RNP and other proteins, but no DNA.

Autoradiography↗
PubMed1981

Normal rat liver cytochemistry: search for reactions adapted to the study of experimental cholestasis.

Experimentally induced intrahepatic cholestasis is characterized by a profound change in biliary secretion. Although there is general agreement that the biliary pole of the hepatocyte undergoes a singular alteration, it is know to which extent the microfilament network of the pericanalicular ectoplasm, the actual hepatocytic membrane at the biliary pole, and the intracanalicular glycocalix covering the membrane are implicated in this change. In order to establish whether ultrastructural cytochemistry is a suitable approach to a selective analysis of these three constituents, we decided to study the liver of normal rats with three different types of reactions (based on tannic acid, ruthenium hexamine, and digitonin, respectively). Moreover, we used different variants of each reaction and tried to determine which of them produced the most selective results; at the same time we kept in mind that these procedures are to be compatible with certain requirements of biological experimentation, like continuous bile flow measurement. Our findings show that, for a more detailed analysis of each of the above mentioned three cell constituents, these methods may provide more precise information.

Animals↗
PubMed1979

Ultrastructural cytochemistry of the nucleus in Zea mays embryos during germination.

The ultrastructure of embryonic root cells of Zea mays was studied from the quiescent stage (dry seed) to 72 h of germination. Semithin and ultrathin sections of tissues fixed with only glutaraldehyde and embedded in Epon were observed after usual section staining and after cytochemical reactions specific for DNA or preferential for ribonucleoproteiNS. In quiescent cells, dense chromatin forms a network which fills a great part of the nucleoplasm. Following germination, gradual dispersion of chromatin occurs: total dispersion is reached at 24 h. After 48 h the chromatin appears moderately condensed again. The nucleolus is compact and predominately fibrillar in dry cells. At 48 h a typical pars granulosa is differentiated. At 8 h a pronounced vacuolation of the nucleolus is observed; nucleolar vacuoles persist until 72 h but become less numerous. During the first 8 h of germination a nucleolus organizer region (NOR) in an eccentric position is associated with the nucleolus; by 24 h and later this NOR has disappeared. No DNA can be visualized in the nucleolar matrix between 0 and 8 h of germination, whereas later, when the nucleolus is reactivated. DNA is always detected in the nucleolar matrix and vacuoles. During the first 72 h of germination, heavily contrasted areas, rich in ribonucleoproteins and appearing to be fibrillar texture, are found in the nucleoplasm, often in closed contact with the dense chromatin. In quiescent cells dense ribonucleoprotein granules, approximately 40 nm in diameter are found dispersed or clustered in the nucleoplasm; after 8 h larger (50 nm), dense ribonucleoprotein granules are found frequently clustered in granular areas in the extranucleolar space. At 8 h of germination, when the nucleolus is temporarily highly vacuolated, unusual 35-nm ribonucleoprotein granules are found both in the smallest vacuoles and on the periphery of the nucleolus.

Cell Nucleolus↗
PubMed1978

Cholesterol in acute cholestasis induced by taurolithocholic acid. A cytochemical study in transmission and scanning electron microscopy.

Rats were given intravenous injections of a single dose of sodium taurolithocholate, and an almost total cholestasis appeared after 10 minutes and lasted for 3 hours after the injection; then the choleresis began again and 24 hours after the injection, normal values of bile flow were restored. Ultrastructural analysis of the liver during the acute cholestasis and the restoration phase showed, beside usual modifications found in most cases of cholestasis, the "characteristic" alterations of sodium taurolithocholate-induced cholestasis. Cytochemical procedures were used, both in transmission and in scanning electron microscopy, in order to delineate the possible participation of free cholesterol in these cellular modifications. After Williamson's reaction procedure (Williamson JR:J Ultrastruct Res 27:118, 1969), not only were cholesterol-digitonin complexes found in large numbers, both in the hepatocytic cytoplasm and in the biliary canaliculi, but also their morphologic appearance revealed several new features: dark sticks and dark lamellae, frequently adsorbed on the outer surface of crystalline clear material were observed by transmission electron microscopy, and plugs, obliterating parts of biliary canaliculi, were observed using scanning electron microscopy. These observations seem to indicate that a significant amount of free cholesterol is released into the hepatocyte cytoplasm and into canalicular lumina within a few minutes after the infection of sodium taurolithocholate, probably originating from the hepatocytic membranes, especially from those limiting the canalicular lumen. Such a drastic modification in the chemical constitution of these membranes should coincide with a marked modification of their active and passive transport ability.

Animals↗
PubMed1976

Pigmentation and dysfunction of Gunn rat thyroid: correlation between morphological and biochemical data.

The thyroid gland of homozygous Gunn rats is moderately enlarged and displays a brownish-black discoloration. Light microscopic examination discloses that the follicular cells are filled with brown granules, which are shown, under the electron microscope, to be modified colloid droplets. Most of them possess a strong acid phosphatase and a mild peroxidase activity and contain a melanin-like pigment, according to histochemical analysis. In comparison with normal Wistar rats, Gunn rats possess significantly higher plasma thyroxine and lower triiodothyronine as well as an increased plasma TSH level. The soluble protein content of the thyroid is reduced in the Gunn rat, as is the total intrathyroid iodine content. The hyperthyroxinaemia of homozygous Gunn rats is due to a hereditary deficiency in hepatic glucuronyl transferase activity. The excess circulating thyroxine is of little functional importance because it is firmly bound to plasma proteins. But Gunn rats have a slight hypothyroid goitre for reasons not yet elucidated. The functional as well as morphological data at present available suggest a modified thyroid iodine metabolism and an altered composition of the thyroglobulin which may induce abnormalities in colloid proteolysis. The observed pigment may result from peroxidation of tyrosine. These alterations are probably independent of the sole enzymatic deficiency so far encountered in these animals and may probably be ascribed to a primary enzymatic defect in the thyroid gland itself.

Acid Phosphatase↗