A useful programme in BASIC for axonal morphometry with introduction of new cytoskeletal parameters.

Interest in the structure of axons and quantification of their components has been growing over the last years. However, the existing literature contains few reports of available computer programmes to facilitate such studies. This paper presents a fully comprehensive BASIC programme for the morphometric analysis of electron micrographs of cross-sectional nerve fibres. From drawings of fibre and axonal contours and dots of the microtubules and neurofilaments, the programme calculates the following parameters: area, diameter and form factor of the fibres and axons, number and density of microtubules and neurofilaments, proportion between microtubules and neurofilaments (R-proportion), myelin thickness and the diameter of the axon relative to its sheath (g-ratio). The programme also introduces three new parameters to analyse the degree of uniformity of microtubule and neurofilament distribution: distances between microtubules and between neurofilaments, equilateral index and cytoskeletal intermingling index. The programme is written in Microsoft BASIC Interpreter for Apple Macintosh (Microsoft Corporation) but can be used on other computers. Although the programme has been tested on adult rat optic nerve fibres, it can be used for different projects concerning axonal morphometry.