A fractal analysis of cultured rat optic nerve glial growth and differentiation.

Fractal dimension can be used as a quantitative measure of morphological complexity. Separate, enriched populations of oligodendrocytes or type 2 astrocytes derived from neonatal rat optic nerves were allowed to differentiate in vitro. Fractal dimensions of differentiating glial cells were measured over time. The fractal dimension correlated with perceived complexity and increased in value as the glial cells matured. Analysis of the changes in fractal dimension with time revealed unique rates of growth and differentiation for each glial phenotype.

A fractal analysis of cell images.

Methods of digital image analysis have been adapted to measure the fractal dimension of cellular profiles. The fractal dimension is suggested as a useful measure of the complexity of a contour. Three methods produce similar results when applied to constructed, near-ideal fractal figures. Comparison of the measurements for a variety of image types indicates the measurement accuracy in each case and may help in interpreting the results when applied to real, non-ideal cell images of unknown fractal dimension. Two of the methods are currently adopted as appropriate for use on neuronal contours. A correlation exists between the complexity of these contours and the magnitude of the estimated fractal dimension.

Edge detection in images using Marr-Hildreth filtering techniques.

Details of the morphology of light microscope images of horseradish peroxidase labeled mammalian neurons in cell culture were investigated. A modified Marr-Hildreth edge-detecting algorithm was used in an image processor to obtain a continuous border of the labeled neurons. The interior of the border was filled to obtain isolated binary silhouettes of the neurons. These silhouettes can be used for further quantitative studies.

Synaptic interactions between mammalian central neurons in cell culture. II. Quantal Analysis of EPSPs.

The presynaptic release mechanism involved in excitatory synaptic connections between neurons in cell cultures of fetal mouse spinal cord were studied by statistical analysis of intracellularly recorded postsynaptic responses. Quantal parameters were determined for the EPSPs evoked in spinal cord (SC) neurons by stimulation of either other SC or dorsal root ganglion (DRG) neurons. Transmitter release was manipulated by varying the Ca2+ and Mg2+ content of the culture medium. The release process was represented better by binomial than by Poisson statistics. A method was derived for obtaining the probability of release and the number of release elements. The quantal content and the number of release elements were substantially higher for the SC-SC connection than for the DRG-SC connection. This was partially compensated for by a larger quantal amplitude for the DRG-SC connection. There was some indication that the probability of release was higher for the SC-SC connection. The relationship between transmitter output and effective external Ca2+ ion concentration was approximately linear.