Tg. Smith et Tn. Behar, COMPARATIVE FRACTAL ANALYSIS OF CULTURED GLIA DERIVED FROM OPTIC-NERVE AND BRAIN DEMONSTRATE DIFFERENT RATES OF MORPHOLOGICAL-DIFFERENTIATION, Brain research, 634(2), 1994, pp. 181-190
O-2A progenitor cells derived from neonatal rat cerebral hemispheres o
r optic nerves, were induced to differentiate in culture into either o
ligodendrocytes or type 2 astrocytes. The fractal dimensions, a measur
e of morphological complexity, of the differentiating glial cells were
measured over time. Analysis of the changes in fractal dimension (D)
with respect to time revealed specific rates of growth for each glial
phenotype and a specific final D. The time course of these changes is
well fit by a simple mathematical model. While brain-derived oligodend
rocytes matured faster than the astrocytes, they ultimately attained c
omparable levels of complexity, with similar maximum fractal dimension
s. Oligodendrocytes from nerve also matured faster than nerve derived
astrocytes, in contrast, however, they attained a greater morphologica
l complexity than nerve astrocytes. While the brain-derived oligodendr
ocytes showed a faster rate of maturation than their optic nerve count
erparts, astrocytes from both regions had similar rates of morphologic
al differentiation. Self-similarity, a defining property of fractal ob
jects was investigated, by determining the fractal dimension of cells
over a range of magnifications. The calculated fractal dimension remai
ned constant over a 10-fold range in optical magnification, illustrati
ng that cultured glial cells exhibit this important characteristic of
fractal objects. In addition, we analyzed the branching patterns of gl
ial processes by the Sholl method and found that the results were not
as interpretable or meaningful as those of fractal analysis.