Inhibition of muscle cell development in culture by cells from spinal cord due to production of low molecular weight factor

Early effects in vitro of the muscular dysgenesis mutation on nervous tissue in the mouse

Muscular dysgenesis (mdg), a disease expressed in embryonic mice, severely affects the formation and differentiation of skeletal musculature. The focus of this investigation was an analysis of dysgenic nervous tissue with special attention centered on interactions between muscle and nerve cells in vitro. Results indicate that mdg/mdg spinal cord cells can form functional neuromuscular junctions in nerve-muscle cocultures and induce contractions in dysgenic muscle. However, dysgenic spinal cord cells induce fewer myotubes to contract and result in a delayed induction of dysgenic myotube contractile activity. Furthermore, mdg/mdg nervous tissue, or its conditioned medium, is associated with a higher incidence of morphologically abnormal myotube contractures. The results from this investigation demonstrate that there are functional abnormalities in both dysgenic muscle and nervous tissues which are stable and expressed for up to 3 weeks in vitro.

Growth regulator from spinal cord: produced in cultures of glial cells

Spinal cord cultures produced a regulatory factor which inhibited myogenesis. After serial passage (x 3) production of this factor continued as neuronal cells disappeared and large, pale polygonal cells rich in cytoplasmic microfilaments with morphology of astrocyte precursors became predominant. These glial cells responded to dibutyryl cyclic AMP by assuming a star-shaped appearance with multiple, radiating cytoplasmic processes. Cultures active in production of the growth regulator also produced nonneuronal-type enolase and glutamine synthetase. It is suggested that the growth regulator is produced by astrocytic glia in culture.

Choline acetyltransferase induction in cultured neurons: dissociated spinal cord cells are dependent on muscle cells, organotypic explants are not

The dependence of the induction of choline acetyltransferase (CAT) on the type of tissue culture, monolayer or piece explants, of spinal cord (SC) and muscle (M) was studied. CAT activities of dissociated SC cells were low but were increased by M monolayers. In piece explants of SC, high CAT activities were achieved independently of muscle cells (chick, mouse). It is therefore likely that in tntact SC tissue factors other than the trophic influence of muscle are able to induce cholinergic maturation. M piece explants on SC monolayers did not induce CAT in, and their outgrowth was inhibited by, SC monolayers.