The use of texture analysis to study the time course of chromatolysis

Image analysis of the textural feature entropy of the Nissl substance was used to monitor the time course of chromatolysis in regenerating hypoglossal motoneurons and degenerating facial motoneurons 4-112 days after hypoglossal-facial anastomosis in rats. Changes in the Nissl substance were detected that were not obvious on the basis of subjective judgement of the light-microscopical appearance of the neurons. Chromatolysis started 4 days post operation (dpo) and was not reversed at 112 dpo in both nuclei. The increase of chromatolysis was 14-28 dpo faster in the regenerating hypoglossal neurons than in degenerating facial neurons. Maximal chromatolysis was measured at 56-70 dpo in both nuclei. Afterwards chromatolysis persisted at a significantly higher level in the degenerating facial motoneuron pool. In conclusion, chromatolysis is a very long persisting reaction. In the beginning chromatolysis is faster and greater in regenerating rather than in degenerating neurons. In contrast, passing the maximal reaction, chromatolysis is maintained at a higher level in degenerating motoneurons. Image analysis of textural features is a suitable and reliable tool to monitor the time course of neuronal cell body changes. The presented quantitative method could be applied in any neurobiological study influencing the regeneration or degeneration of motoneurons.