QUANTITATIVE STUDY OF NEUROFILAMENT-POSITIVE FIBER LENGTH IN RAT SPINAL-CORD LESIONS USING ISOTROPIC VIRTUAL PLANES

Spontaneous reoccurrence of neurofilament (NF)-positive fibers has bee n described after spinal cord lesions in rats. However, previously int roduced methods to evaluate the lesion and the regenerative fiber outg rowth suffer from several biases, why a new concept of quantitative, m orphological analysis after spinal cord injury is needed. Length quant ification of the putatively spontaneously regenerating fibers has been difficult until recently, when two length estimators based on samplin g with isotropic virtual planes within thick physical sections were in troduced. The applicability of these techniques to estimate the total length of NF-positive fibers was evaluated in photochemically induced ischemic lesions of thoracic spinal cords in young rats 6 weeks postle sion. Fiber length was found to be the most consistent measure with a mean of 3.71 m (coefficient of variation, CV = 0.16) in the 0.90 mm(3) (CV = 0.26) large lesions. Whether or not the NF-positive fibers obse rved inside the lesion represent spontaneously regenerating axons need s to be confirmed in longitudinal, functional, and ultrastructural stu dies. (C) 1998 Wiley-Liss, Inc.