[Interpretation of autoradiographs and images of biological objects with the electronically operating image analyzer "Densitron II'". 2. Evaluation of the specific and total radioactivity of single cells (author's transl)].

Using the TV image analyzer Densitron, transparencies and areas can be measured by the grey value discrimination method equidensitometry. The time, necessary for one measurement, is approximately 1 min, the standard deviations do not exceed 2%. 2. Also microscopical objects such as single cells can be analyzed by this method. We measured photo-blackings and areas in autoradiographs of goldfish brain-sections after injection of 3H-phenylalanine. As a parallel, blacking and area calibration curves were obtainable and allowed a conversion of the relative values into absolute ones. 3. Using this conversion method, neurons of different brain regions were in the range from 104 to 1476 mum2 in area and from 4.17 to 14.43 muCi-cm-3 in specific radioactivity. After 10 repeated measurements of one and the same cell, the standard deviations of the absolute values were 6 and 4.5%, respectively, on an average. 4. On the basis of these and additional values (thickness of section, number of sections per cell), calculations of the total radioactivity of a cell section or the whole cell can be made.