Concentration gradient along the long axis of myelin figures of phosphatidylcholine

Abstract

The existence of a concentration gradient along the long axis of, i.e. along the growth direction of, growing myelin figures was found by measurements of transmitted-light intensity through the myelin figures at different places along the axis during growth. The observed transmitted-light intensities under crossed-Nicols were stronger at a micro-area near the root of the growing myelin figures than near the top of it. The difference of the intensities between the two micro-areas decreased with the growth time. Since the intensity measured is nearly proportional to the number of the ordered phosphatidylcholine molecules in the selected area, the present results should prove our recent report that the initial growth process of myelin figures is diffusion-limited (Sakurai, I. and Kawamura, Y. (1984) Biochim. Biophys. Acta 777, 347–351).