Stability at low temperatures of neuronal microtubules in spinal ganglia and dorsal roots of the lizard ( Lacerta muralis)

Abstract

Thoracic spinal ganglia and dorsal roots central to the latter from three adult lizards (Lacerta muralis) kept at 30°C for 90–95 days and from three other lizards kept at 3°C for the same length of time were examined under the electron microscope. The number, density, and distribution of microtubules were determined in cross sections of unmyelinated and myelinated axons of the dorsal roots. The relationships between the densities of microtubules and the cross-sectional areas of the axons were not found to be significantly different in the hot and cold lizards. Also the perikaryal microtubules, which however, were not quantitatively evaluated, showed no obvious differences under these conditions. The assumption that the microtubules studied in the present research are first disassembled in the cold and then reassembled before fixation has taken effect is probably incorrect because the specimens were fixed at the same temperature at which they had been previously kept, and also because neither C-shaped microtubules nor macrotubules were observed. The most likely explanation of the present results is that the microtubules here studied are cold stable.