[Ultraviolet cytophotometry of a single live neuron in the crayfish mechanoreceptor]

Measurements of ultra-violet absorption by a live neuron, with 5-minutes' intervals, have shown variations in RNP content amounting almost 20% with a period of 30 min. The fact that these variations and their phase were independent from changes in the volume of RNP zone allows to relate them to the rhythm of macromolecule synthesis. When ultra-violet radiation was delivered in large doses, mean RNP content decreased with a latency 20 to 40 min, and 30- minutes' variations of RNP content were suppressed.