Studies to improve fixation of human nerves V. Effect of temperature, fixative and CaCl₂ on density of microtubules and neurofilaments

Utilizing morphometry of electron micrographs of nerves of rat fixed with different schedules of fixation it was concluded that: irrespective of the fixative, fixation at low temperature is associated with markedly low densi2 ties of microtubules (MT) of myelinated and of unmyelinated fibers; of the various fixatives tested 2% glutaraldehyde in 0.1 M cacodylate buffer without 0.025 M CaCl₂ was associated with the highest density of MT of myelinated fibers and the addition of 0.025 M CaCl₂ to a 2% glutaraldehyde fixative solution is associated with abnormally low densities of MT in myelinated and unmyelinated fibers. An effect of temperature, fixative and added CaCl* on neurofilaments density was not demonstrated. Using the criterion of density of MT and assuming that these studies on rat nerves can be applied to biopsied nerve of man, fixation of human nerves should be at room or body temperature, and the fixative solution should not contain 0.025 M CaCl₂.