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At least 289 records · Page 16Linked to original sources
PubMed1982

Ultrastructural radioautography of synthesis and migration of proteins and catecholamines in the rat adrenal medulla.

The synthetic pathways of proteins and catecholamines in the rat adrenal medullary cells were compared systematically at the ultrastructural level, within a 24h period, with 2 tracers, L-tyrosine 3,5-3H and L-3,4-dihydroxy [ring 2,4,6-3H] phenylalanine (L-dopa3H). Young rats were injected with either of these tracers and sacrificed in pairs at close time intervals. With L-tyrosine 3H, the label was about equal over rough endoplasmic reticulum (RER) and secretory granules at 2 min after injection and remained almost constant in intensity over the secretory granules throughout the period of observation. A peak of radioactivity was also observed in the Golgi complex between 5 and 20 min after injection. This indicates that L-tyrosine 3H participates in the synthesis of both granule proteins and catecholamines as confirmed by the results obtained after injection of L-dopa3-H. With this tracer, radioactivity over RER, Golgi complex, cytosol and cell surface remained very low at all times and was undetectable at several time intervals. In contrast, radioactivity over secretory granules was very high at all time intervals. The present results thus confirm that in both adrenaline- and noradrenaline-storing cells, the protein moiety of chromaffin granules is synthetized in the RER, packaged in the Golgi complex and rapidly found in newly formed secretory granules. Following either L-tyrosine 3H or L-dopa 3H injection, catecholamine synthesis occurs only in or in close vicinity to chromaffin granules in both cell types at all time intervals.

Adrenal Medulla↗
PubMed1988

The effect of colchicine on protein secretion by differentiating odontoblasts and ameloblasts in the hamster tooth in vitro as shown by radioautography with 3H-proline.

We have examined radioautographically the protein synthetic and secretory activity of differentiating odontoblasts and ameloblasts, exposed for 9 h in vitro to various concentrations of colchicine in the presence of 3H-proline. Colchicine impairs the cytodifferentiation of the dental epithelium into ameloblasts and of the dental mesenchyme into odontoblasts; the effects depend on the dose. However, dental epithelial cells are more sensitive to the drug than dental mesenchymal cells. In stages prior to odontoblast differentiation, colchicine enhances the number of radioautographic grains over the dental epithelium without changing the grain counts over the dental basement membrane area. This suggests that in vitro the dental epithelium synthesizes and secretes proline-containing components that are not constituents of the dental basement membrane. Also, during the subsequent stages of ameloblast differentiation colchicine increases the number of radioautographic grains over the preameloblasts. The present data suggest that the primary in vitro target of colchicine is not the dental mesenchyme, but the dental epithelium. The data also indicate that differentiating ameloblasts synthesize and secrete significant amounts of proteins in vitro prior to the first deposition of enamel.

Ameloblasts↗
PubMed1976

The avian pineal organ. Distribution of exogenous indoleamines: a qualitative study of the rudimentary photoreceptor cells by electron microscopic radioautography.

The uptake of 5-hydroxytryptophan (3H-5-HTP) and serotonin (3H-5-HT) and their distribution have been demonstrated, at the ultrastructural level, in the secretory rudimentary photoreceptor cells (SRP cells), in the pineal organ of the parakeet and the duck. In vivo experiments. When the parakeets were injected with 3H-5-HTP alone or pretreated with drugs interfering with monoamine metabolism (e.g. R04-4602, nialamide) prior to injection of the label, the SRP cells always exhibited specific radioautographic reactions, in the regions of the dense secretory granules of the cell body and asynaptic pedicles. The labeling concentration avried quantitatively with time (interval between injection of the label and sacrifice) and drugs used. In vitro experiments. The uptake of 3H-5-HTP and 3H-5-HT in the pineal organ of the duck has also been studied, using an incubation procedure. The results with the two precursors confirmed those obtained "in vivo" with the parakeet. From these results it is suggested that the uptake of precursors in some compartments of SRP cells is qualitatively independent of: a) the experimental period (experiments performed in winter, spring, and summer; uptake of precursors between 11.00 a.m. and 12.00) b) the precursor (3H-5-HTP or 3H-5-HT) c) the observation times. It is concluded that the SRP cell, an important step in the cytological and functional evolution of the pineal organ (Collin, 1969, 1971), is responsible for the synthesis of 5-HT. The metabolism of 5-HT seems also possible in such cells.

5-Hydroxytryptophan↗
PubMed1977

Influence of emulsion type and atmospheric oxygen on the fading of latent image in electron microscopic radioautography.

The intensity of radioautographic reactions in Ilford L4, Sakura NR-H2 and Kodak NTE emulsions was compared after exposure in either dry air or dry helium gas at 4 degrees C to test the stability of latent images in the presence or absence of oxygen. A light proof container is described in which slides bearing radioactive sections coated with the three emulsions were exposed in dry helium at a constant pressure of approximately 0.5 atm. The comparison of air and helium atmospheres during exposure of radioautographs was estimated qualitatively for 125I-labeled thyroid sections stored for several years and, in addition, quantitative data was derived from 3H-labeled methacrylate sections stored from 21 days to 1 year. With the three emulsions under study, the background fog remains low under both exposure conditions at 4 degrees C for as long as several years duration. Using L4 emulsion, similar high grain densities are obtained in air and helium, and therefore, the latent images in L4 emulsion remain stable in the presence of oxygen. In the case of NTE and NR-H2 emulsions, as the exposure time increases, substantially lower reaction intensities are observed in air than in helium. This difference in reaction intensity is evident by 3 weeks with NTE and after 4 weeks with NR-H2. Hence, there is fading of the latent images in the latter emulsions in the presence of oxygen. It is concluded that reliable results may be obtained with the L4 emulsion by exposure of radioautographs in dry air, whereas with the NR-H2 and NTE emulsions, exposure should be in an oxygen-free medium, such as is provided by a dry helium atmosphere.

Autoradiography↗
PubMed1980

Quantitative investigation of scintillator intensification for light and electron microscope radioautography.

Several reports have indicated that scintillators enhance the intensity of radioautographic reactions. If this were the case, the use of scintillators would shorten the exposure time of radioautographs and the production of radioautographs would be accelerated. It was, therefore, decided to examine the effect of scintillators on the intensity of radioautographs in a quantitative manner over uniformly labeled test specimens. Reaction intensities with or without scintillators were compared using Kodak NTB2 emulsion for light microscopy and Ilford L4 and Sakura NR-H2 emulsion for electron microscopy. In addition, the background fog was quantitatively evaluated. No increase in the intensity of the radioautographs was observed under the following conditions: pretreatment of tissue sections with scintillator solutions before emulsion coating and exposure; treatment with scintillator solutions after emulsion coating but before exposure; treatment with scintillator solutions during exposure; contact with a plastic scintillator film throughout exposure. Heightened reaction intensity was obtained only when scintillators were applied during the histological processing of tissues. The impregnation of tissue blocks with PPO (2,5-Diphenyloxazole) and POPOP (1,4-bis-2-(5-phenyloxazolyl)-benzene) during dehydration, infiltration and Epon embedding produced a 20% increase of reaction intensity in light microscope radioautographs using NTB2 emulsion and a 75% increase in electron microscope radioautographs using L4 emulsion.

Animals↗
PubMed1977

Electron microscopic dry-mounting radioautography for diffusible compounds by means of ultracryotomy.

Cultured HeLa cells or mouse liver and pancreas tissues were labeled with 3H-thymidine, -uridine or -glycine for varying periods in vitro, frozen in liquid nitrogen and cut on an LKB ultrotome equipped with LKB Cryokit. Dry ultrathin sections were mounted on grid meshes and were either air-dried, freeze-substituted or freeze-dried, and were covered with dry films of radioautographic emulsions, exposed, developed, stained and were observed in electron microscopes. After a number of trials, it was possible to obtain fairly good preservation of both cell structure and radioisotopes by means of freeze-dried and dry-mounted ultrathin frozen sections. However, the results are not completely satisfactory at the present time.

Animals↗