Image Analysis of Neuronal and Glial Markers: Fluorescence Microscopical Applications

Abstract

The usefulness of computer-assisted image analysis with particular emphasis on fluorescence microscopy was evaluated and exemplified. Problems associated with image pick-up and transfer between microscope and computer are discussed. The importance of fully supported software programs adjusted to the needs of histology are emphasized. One such system, the IBAS (Kontron/Zeiss, West Germany) has been found suitable for use also by people with little or no background computer knowledge. Three examples where image analysis clearly adds a unique quantitative dimension to the evaluation of the results have been presented. (1) Nerve density measurements: A semi-automatic interactive program was used to evaluate the potentially neurotoxic effects of hexachlorophene and chlorhexidine, two disinfectant agents, using an intraocular screening model in which the density of the sympathetic autonomic ground plexus of the iris is studied by Falck-Hillarp fluorescence histochemistry applied to iris whole mounts. Pronounced neurotoxic effects were described. Dopaminergic nerve density measurements in striatum following neurotoxic drug treatments correlate well with other measurements of degree of denervation. (2) Transmitter release and diffusion: Experimentally induced unilateral parkinsonism in rats can be counteracted by intrastriatal implants of chromaffine tissue. These grafts work by releasing large quantities of catecholamines which diffuse through host neuropil. Image analysis was used to characterize in detail the diffusion of catecholamines using Falck-Hillarp fluorescence histochemistry. Linear scans of fluorescence intensity and imaging fluorescence gradients using false color look-up tables enables fast visual quantitative interpretation of the results