期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1985
卷号：82
期号：12
页码：4296-4300
DOI：10.1073/pnas.82.12.4296
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The effects of cell density and aggregation on expression of transmitter traits were examined in dissociated, pure sympathetic neuron cultures, grown in fully defined, serum-free medium. After 1 week at a density of 7-8 X 10(3) neurons per 35-mm dish, moderate levels of tyrosine hydroxylase (tyrosine 3-monooxygenase, EC 1.14.16.2 ) activity and substance P were detected. When neuron density was increased 4-fold, a 4-fold increase in tyrosine hydroxylase activity was observed; i.e., there was no change in tyrosine hydroxylase activity per neuron. In contrast, substance P increased 30-fold, corresponding to a 7-fold increase in substance P per neuron. Choline O-acetyltransferase (EC 2.3.1.6 ) activity, not detected at low cell densities, was first detectable at a concentration of 15,000 neurons per dish and increased 6-fold when this cell concentration was doubled. Medium conditioned by high-density cultures failed to reproduce these effects on low-density cultures, suggesting that diffusible factors are not involved in the density-dependent differential regulation. Time-lapse phase-contrast microscopy of high-density cultures showed neuronal migration and progressive aggregation, which did not occur in low-density cultures. Our observations suggest that cell contact may mediate differential expression of transmitter traits.
