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

Catecholamine-containing neurons in Remak's ganglion: a developmental and tissue culture study

Development and maturation of the catecholamine-containing neurons of the embryonic chick and quail Remak's ganglion were studied, using the glyoxylic acid method. Fluorescent neurons were detected in the pararectal segment of the ganglion from its earliest in vivo formation, and along the whole ganglionic chain in later developmental stages. In tissue culture, a large number of catecholamine-containing neurons matured in explants of both early and more developed ganglia, producing an extensive network of outgrowing fluorescent nerve processes. Pararectal ganglia, cultured in vitro for up to 4 days, gave rise, whatever the developmental stage examined, to fluorescent migratory neurons distributed either in ganglion-like clusters or singly in a large area surrounding the explant. Many non-fluorescent neurons were intermingled with the fluorescent ones in the explants, as well as in the outgrowth. Ganglia from segments adjacent to the small intestine did not give rise to migratory neurons whatever the developmental stage. Regional differences in the development of migratory neurons may be correlated to the mechanism of the in vivo organization of the ganglionic chain. The present observations indicate that catecholamine-containing neurons in Remak's ganglion exhibit the same histochemical features as adrenergic sympathetic neurons and differentiate in short-term cultures.

Appearance of new alpha-bungarotoxin-acetylcholine receptors in cultured sympathetic ganglia of chick embryos

alpha-Bungarotoxin (alpha-BuTX) has been used as a marker for studying the production of alpha-bungarotoxin-acetylcholine receptors (alpha-BuTX-AChRs) in explants of chick embryo sympathetic ganglia cultured in vitro. New alpha-BuTX-AChRs appear rapidly in the explants after blocking of the pre-existent ones with the toxin (40% of the total receptors at 3 h). There is a portion of alpha-BuTX-AChRs in the explants which for a short time is not accessible to the toxin. This portion constitutes the precursor pool of receptors and represents 18% of the total. The precursor pool of receptors supplies the neurons with new receptors for 1-2 h in the absence of protein synthesis. The appearance of new receptors from the precursor pool is an energy-dependent process.

Light and electron microscopic histochemistry of the monoamines in the human foetal sympathetic ganglion in culture

Sympathetic ganglia of 13 to 19-week-old human foetuses were cultured in small pieces with and without nerve growth factor for up to 5 weeks in vitro. The cultures were studied using phase-contrast, fluorescence and electron microscopy. Monoamines were demonstrated with the formaldehyde-induced fluorescence method, with and without pretreatment of the cultures with catecholamines or monoamine oxidase inhibitor. In the long-term cultures, primitive sympathetic cells, sympathicoblasts of types I and II, and young sympathetic neurons showed a fine structure identical to that described earlier in vivo. There were virtually no satellite or Schwann cells in the cultures. The neurons showed a considerable capacity to grow new nerve fibres in culture, even without nerve growth factor. Nerve terminals with accumulations of synaptic vesicles were regularly observed, occasionally in synapse-like contact with other nervous structures. Large granular vesicles were regularly found in the sympathicoblasts after glutaraldehyde-osmium tetroxide fixation. After permanganate fixation, dense-cored vesicles typical of adrenergic neurons were not seen, either in the perikarya, or in the processes, although it was possible to demonstrate specific fluorescence. No small intensity fluorescent (SIF) cells were observed. Variable formaldehyde-induced fluorescence was observed in the nerve cell perikarya and nerve fibres. The intensity of the fluorescence increased after treatment of the cultures with monoamine oxidase inhibitor and after incubation with catecholamines.

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.

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.