Altered axons and axon terminals in the nucleus gracilis of the dog.

Altered axons and axon terminals in the nucleus gracilis o the dogs were followed by means of electron microscopy. The axon terminals with characteristic ultrastructure were accompanied by synapses with altered presynaptic part. The changes of the presynaptic part were expressed by the evident decrease in synaptic vesicle number, hyperplasia of smooth endoplasmic reticulum and by abnormal mitochondrial figures. The altered axons measuring 14,6 micrometers in average contained hyperplastic and quite often dilated smooth endoplasmic reticulum as well as multiplied microtubular profiles. The mitochondria of the altered axons were characterized by the different degree of degeneration. The above mentioned structures in synapses as well as in axoplasma of the nucleus gracilis were found in the dogs of both sexes.