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H Hervonen

Publications and source records attributed to H Hervonen.

33 records · Page 2Linked to original sources
PubMed1977

Effect of cholinesterase inhibitors on differentiation of cultured sympathicoblasts.

The 2 cholinesterase inhibitors, eserine and BW 284C 51, inhibited the nerve fibre growth and differentiation of immature sympatheticoblasts at low concentrations. The effect was nerve cell-specific and appeared in the course of the in vitro development, indicating that cholinesterases might play an important role in the early differentiation of sympathicoblasts.

Animals↗
PubMed1976

Electron microscopic localization of adenylate cyclase activity of white and brown adipose tissue of the rat and chicken.

Brown adipose tissue of newborn rats and chicken embryos and white adipose tissue of adult rats were studied. Adenylate cyclase (EC 4.6.1.1.) activity stimulated by 0.1 mmol/l noradrenaline was demonstrated using an electron microscopic histochemical method. The reaction product was visualized as a cobalt salt in the plasmalemma of the adipocytes. The adipocytes of the brown adipose tissue of the newborn rats showed most intense reaction in the outer surfaces of their plasmalemma. Alloxan totally inhibited the enzymatic reaction. The histochemical reaction used in the present study probably demonstrated the hormonal receptor sites in the plasmalemmas of the adipocytes which are stimulated by noradrenaline.

Adenylyl Cyclases↗
PubMed1976

Histochemical localization of adenylate cyclase in cultured sympathetic neurons.

The catecholamine-stimulated adenylated cyclase activity was histochemically demonstrated at ultrastructural level in the cultured neurons of the sympathetic ganglia of the chick embryo. Adenylate cyclase activity was demonstrated in the axolemma of the axons and axon terminals, however not inside the axons. Heavy precipitates of the enzymatic reaction product was observed intracellularly in some cell processes identified as dendrites of the sympathetic neurons. In contrast to the extensive reaction in the neuropil, the reaction for the catecholamine-stimulated adenylate cyclase was scarse in the perikarya of the neurons. Only occasional spots of adenylate cyclase activity could be demonstrated in the plasmalemma of some neurons, and no reaction product was observed in the cytoplasm. No difference in the localization of the adenylate cyclase activity was observed when either dopamine or noradrenaline were used for stimulation. The possible roles of the catecholamine-stimulated adenylate cyclase in the function of the interneuronal connections between the aminergic neurons of the sympathetic ganglion are discussed.

Adenylyl Cyclases↗
PubMed1976

Use of tissue culture to examine neurotoxicity of contrast media.

The effect of small concentrations of diatrizoate, ioglycamate, and iopanoate salts on cultured sympathetic ganglia was studied. Biliary contrast media in clinical blood concentrations caused severe degeneration of cultured neurons, but similar concentrations of diatrizoate caused no effect. This technique may be used to measure the direct neurotoxicity or general cytotoxicity of contrast media.

Animals↗
PubMed1975

Differentiation of sympathicoblasts in cultures of chick ganglia: light and electron microscopic, fluorescence and enzyme histochemical observations.

Immature sympathetic ganglia prepared from 5 1/2-or 6-day-old chick embryos were cultured up to one month. The in vitro development was followed by phase microscopy, electron microscopy and using histochemistry for catecholamines, monoamine oxidase and cholinesterases. During the first week of culture extensive plexuses of nerve fibres were formed between and around the clusters of nerve cells. Mature-looking neurons were observed in the cultures by phase microscopy after three weeks, at which age the mean diameter of the perikarya was more than doubled. Varying catecholamine fluorescence was observed in the perikarya during the entire culture period. The nerve fibres showed usually only weak fluorescence, but, in the older cultures, bright varicosities were regularly found in the fibres. Monoamine oxidase activity was demonstrated already at three days of culture and the reaction was maintained positive. Weak or moderate acetyl-cholinesterase activity was demonstrated in the sympathicoblasts and young sympathetic neurons and their processes. The axolemma showed acetylcholinesterase activity also around the nerve terminals containing small dense cored vesicles. Reactions for the non-specific cholinesterases were negative. Electron microscopy of the 30-day-old cultures revealed that the clusters of nerve cells consisted of mature sympathetic neurons, which contained large (60-200 nm) and small (35-60 nm) granular catecholamine-storing vesicles. Glial cells were almost totally lacking. Large numbers of nerve terminals containing both large and small granular vesicles were observed in the clusters, often in synaptic contact with the sympathetic neurons. It is concluded that the primitive sympathicoblasts are, in favourable conditions, capable of differentiation in culture up to mature sympathetic neurons.

Acetylcholinesterase↗
PubMed1975

Fluorescence histochemical and elec-ron microscopical observations on sympathetic ganglia of the chick embryo cultured with and without hydrocortisone.

Lumbar sympathetic ganglia of 12-day-old chick embryos were cultured in organ cultures for 14 days with 1, 10 or 100 mg/l of hydrocortisone or without it. Catecholamines were demonstrated by the formaldehyde-induced fluorescence method. For electron microscopy, the cultures were fixed with glutarialdehyde and osmium tetroxide. Two types of cells with catecholamine fluoresecence were observed in the control cultures: (1) weakly fluorescent sympathetic neurons and sympathicoblasts with long nerve fibres, which were the most common cell type in the explant, and (2) brightly fluorescent cells with or without fluorescent processes, which were less common and were scattered in the explant. Hydrocortisone caused a great increase in the number of the brightly fluorescent cells. With 10 mg/l of hydrocortisone the increase was about ten-fold as compared with the control cultures. There was no change in the morphology of the cells, nor could any change be observed in the fluorescence intensity by eye. Electron microscopically the mature neurons were the most common cell type on the surface of the culture, while more immature sympathicoblasts were seen in the deeper layers. Cells were also found which contained large numbers of catecholamine-strong granular vesicles 105-275 nm in diameter. These cells were infrequent. They had round vesicular nuclei and resembled also in other respects sympathicoblasts or young nerve cells. One such cell was found in mitotic division by electron microscopy. Hydrocortisone caused a marked increase in the number of these granule-containing cells and their processes. Cells which could have been classified as the small intensely fluorescent cells of the mammalian ganglion type or their electron microscopic equivalent, the granule-containing cells were found neither in the control cultures nor in the hydrocortisone-containing cultures. It is concluded that most brightly fluorescent cells in cultured sympathetic ganglia of the chick are nerve cells or sympathicoblasts rich in amine-storing granular vesicles.

Animals↗