In vivo structure of frog sciatic nerve myelin membranes: an x-ray diffraction study at 13A resolution.

The x-ray diffraction pattern of myelin membranes from a frog sciatic nerve was recorded in vivo at 13 A resolution using a new experimental technique recently developed in our laboratory. The electron density profile was determined for the myelin membranes first in vivo and then, after elimination of the intraneural blood microcirculation, by transection of the nerve. The small structural differences observed between these conditions were statistically nonsignificant (at 95% confidence level). In addition, our results show that the stacking disorder that is present in the myelin membranes of freshly dissected frog sciatics is also characteristic of the myelin sheath in vivo.