Long-term effects of dexamethasone and nerve growth factor on adrenal medullary cells cultured from young adult rats

Summary Normal postnatal rat chromaffin cells and rat pheochromocytoma cells are known to show extensive Nerve Growth Factor (NGF)-induced process outgrowth in culture, and this outgrowth from the postnatal chromaffin cells is abolished by the corticosteroid dexamethasone. To determine whether adult rat chromaffin cells respond to NGF and dexamethasone, dissociated adrenal medullary cells from 3-month-old rats were cultured for 30 days in the presence or absence of these agents. Such cultures contained typical chromaffin cells, chromaffin cells with processes, and neurons. Fewer than 2 % of normal adult chromaffin cells formed processes under any of the conditions studied, and statistically significant changes in this proportion were not detectable in the presence of NGF or dexamethasone. Adrenal medullary neurons, however, were observed only in the presence of NGF, in cultures with or without dexamethasone, and thus appear to be previously unreported NGF targets which require NGF for survival or process outgrowth. Dexamethasone markedly increased total catecholamine content, total content of epinephrine, and tyrosine hydroxylase activity in cultures with or without NGF. In contrast, postnatal rat chromaffin and rat pheochromocytoma cells which have been studied in culture do not produce epinephrine under any of these conditions. It is concluded that rat adrenal chromaffin cells undergo age-related changes in both structural and functional plasticity. The in vitro characteristics of rat pheochromocytoma cells more closely resemble those of postnatal than of adult rat chromaffin cells, but may not entirely reflect the properties of the majority of chromaffin cells in either age group.     

Spontaneous neurite outgrowth and vasoactive intestinal peptide-Iike immunoreactivity of cultures of human paraganglioma cells from the glomus jugulare

Summary The chief cells of paraganglionic tissues have morphological and functional similarities to adrenal chromaffin cells, and both cell types are derived from the neural crest. In the present investigation cells from two glomus jugulare paragangliomas were studied in culture. Approximately 50% of the cells from one tumor, and 7% from the other spontaneously formed neurite-like processes. Numerous granular and agranular synaptic-like vesicles also appeared in the process-forming cells. In contrast to findings with normal and neoplastic adrenal chromaffin cells, addition of nerve growth factor (NGF) to the culture medium had no major effects on proportion of cells with processes. Dexamethasone caused only a small decrease in process length. Culturing of the tumors also appeared to promote production of material with VIP-like immunoreactivity. It is concluded that the phenotype of paraganglioma as well as pheochromocytoma cells may be altered in vitro. Responsiveness to specific factors such as NGF or steroids, however, may vary for related tumor cell types in different anatomic locations.     

Size and number of nerve fibres in the central nervous system connectives of the cockroach Blaberus craniifer

The size and number of axons in the ventral cord connectives of the cockroach Blaberus craniifer were determined from montages constructed of electron micrographs of the left connective of each of the connective pairs examined. The fibres were grouped into three main diameter categories: fine fibres from 0·2 to 1 μm, small fibres from 1 to 6 μm, and large fibres from 6 to 24 μm. In the five different left connectives examined, the fine fibres numbered from 2006 to 8535 and composed from 56·5 to 83 per cent of the total fibres. The small fibres numbered from 1269 to 2361 and composed from 16·5 to 41 per cent of the total fibre number. The large axons ranged between 29 and 220 in number which represented from 0·5 to 2·5 per cent of the fibre population.     

The fine structure of the limulus optic nerve

Two complete composite photographs of the optic nerve of Limulus, made by electron microscopy, reveal the presence of neurosecretory granules in the large axons of the rudimentary eye neurons. The number of intermediate sized, (3–7 μ), of eccentric cells corresponds with the number of ommatidia as expected, but only their sheath of Schwann cells show an intimate interfolding. Based on the number of fine axons within the nerve each ommatidium has an average of 12–13 retinular cells. The diameter of their fibers is between 0.2 and 3 μ although the majority are between 1 and 1.5 μ. They are aggregated into bundles of six to seven fibers by the sheath cells although some bundles contain only two, others as many as 181 fibers. There is no indication in these studies that retinular cell axons within a bundle are associated with the same, adjacent, or other pattern of ommatidia. The photographs suggest that physiological activity in retinular cell axons might be detected most easily in the smallest bundles because they contain the fewest, but the larger retinular cell axons.     

Anti-lymphocyte antibody Leu-7 (HNK-1) recognizes a constituent of neuroendocrine granule matrix

Anti-lymphocyte monoclonal antibody HNK-1 (Leu-7) reacts with the cell surfaces of natural killer (NK) lymphocytes and with myelin-associated glycoprotein (MAG). This antibody reacts intensely with normal and neoplastic adrenal medullary cells. A small proportion of normal pancreatic islet cells, anterior pituitary, and gastroenteropancreatic endocrine cells also show Leu-7 immunoreactivity. In adrenal medulla, ultrastructural immunocytochemical studies and immunoblot analyses reveal that Leu-7 reacts with an intracellular protein of MW 75 KD which is localized within the matrices of the chromaffin granules. The MW of this protein differs from those of MAG and chromogranin A. The findings suggest that Leu-7 immunoreactivity might be a new marker for specific subsets of secretory granules.