No abstract

Monitoring pathology/regeneration in experimental models of de-/remyelination requires an accurate measure not only of functional changes but also of the amount of myelin. We tested whether x-ray diffraction (XRD), which measures periodicity in unfixed myelin, can assess the structural integrity of myelin in fixed tissue. From laboratories involved in spinal cord injury research and in studying the aging primate brain, we solicited "blind" samples and used an electronic detector to rapidly record diffraction patterns (30 minutes each pattern) from them. We assessed myelin integrity by measuring its periodicity and relative amount. Fixation of tissue itself introduced ±10% variation in periodicity and ±40% variation in relative amount of myelin. For samples having the most native-like periods the relative amounts of myelin detected allowed distinctions to be made between normal vs. demyelinating segments and motor vs. sensory tracts within the spinal cord, and aged vs. young primate CNS. Different periodicities also allowed distinctions to be made between samples from spinal cord and nerve roots, and between well-fixed vs. poorly-fixed samples. Our findings suggest that in addition to evaluating the effectiveness of different fixatives, XRD could also be used as a robust and rapid technique for quantitating the relative amount of myelin among spinal cords and other CNS tissue samples from experimental models of de-and remyelination.