Computer-aided analysis of polarized neurite growth. Effects of applied electrical fields on neuronal development

A computer-based system to record and analyze the polarized growth of neurons growing in culture has been developed. The first application of this system was to study the effects of electrical fields on the growth of isolated Xenopus neurons. Simple coordinate data are collected from photographic negatives of isolated neurons, using a digitizing tablet. Morphometric parameters for individual cells and whole neuronal populations are calculated. A variety of indicators of polarized growth are defined and we compare our methods with those used in previous studies, and the most appropriate methods for describing polarized growth are discussed. Although these methods have been designed specifically to assess the effects of electrical fields on neurite growth, they could be applied to other experiments where biased growth of neurites is expected. They could be used in studies of the tropistic effects of growth factor gradients, or variations in the substrate. Alternatively, they could be useful for the analysis of the many other types of polarized growth found in a wide range of cell types.