[Functional significance of dark and light cells]

Ultrastructural-functional characteristics of dark and light cells were considered from the standpoint of tissue and organ specificity on the material of skeleton muscular fibres and the mucosa of bronchi of man, the liver and kidneys of dogs in the syndrome of prolonged compression. It was shown that these cells might have three main characteristics for the activity of the organ and reflect either the specificity of their work, or alternating activity, or the vital cycle of the cell. The ultrastructure of the dark cells testify, as a result of the specificity of their work, to their adaptation to prolonged activity connected with clearcut biosynthetic and bioenergetic processes. The work of the light cells does not require apparently considerable development of plastic processes. In the alternating activity dark cells should be considered as potentially active, whereas light cells are in the state of intensive activity. The ultrastructure heterogeneity of dark and light cells, moreover, may reflect various stages of their vital cycle.