DNA SYNTHESIS AND CELL DIVISION IN DIFFERENTIATING AVIAN ADRENERGIC NEUROBLASTS
1974; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-08-017917-9.50033-0
Autores Tópico(s)Neurogenesis and neuroplasticity mechanisms
ResumoDifferentiation of avian adrenergic neuroblasts is marked by a stage of rapid formation of catecholamine-containing cells. These neuroblasts, identified by formaldehyde-induced fluorescence contribute to development of sympathetic ganglia and adrenal medulla. It is generally believed that the cells arise from an indifferent population of stem cells. Consistent with this is the idea that differentiation begins after cell division ceases. The early appearance of CA fluorescence in neuroblasts and the rapid increase in their number suggest that differentiation, judged by synthesis and storage of CA, might not be incompatible with cell division. The possibility that differentiating adrenergic neuroblasts could proliferate was tested using autoradiography to follow DNA synthesis and direct observation to identify mitosis. Chick embryos 5½-12 days of development were injected with thymidine-3H, incubated for 1 h, and then prepared for formaldehyde-induced fluorescence to demonstrate CA or electron microscopy to identify dense-core granules. The simultaneous presence of CA fluorescence and silver grains, representative of isotopically labeled DNA, was examined by combining darkfield-tungsten and reflected ultraviolet illumination. Incorporation of thymidine-3H by CA fluorescent neuroblasts took place at all stages examined. Labeled neuroblasts were seen in paravertebral, para-aortic, and adrenal medullary positions. Electron microscopic autoradiography revealed isotopically labeled nuclear DNA in cells containing dense-core granules. In addition, mitotic figures were seen in cells identified by the presence of dense-core granules. These observations indicate that initiation of differentiation by adrenergic neuroblasts does not preclude their proliferation. The suggestion that such cells might contribute significantly to multiplicative growth in the sympathetic system is discussed.
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