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Using electron microscopy, we studied ultrastructural changes in neurons and glia cells of ganglia abdomibal 4 and 24 hours after transection of interganglionic connectives. Experiments on such model objects as ganglia of invertebrates provide information on the general biological mechanisms of the nervous system's reactions to mechanical damage. In the control samples, the bodies and nuclei of neurons had a rounded shape, the nuclear chromatin of neurons differed in the degree of condensation. The cytoplasm contained numerous Nissl bodies, the Golgi apparatus, located mainly in the perinuclear region, various elements of the cytoskeleton, ribosomes, elongated and rounded mitochondria with a moderately dense matrix and normal cristae filling the entire volume of mitochondria. Glial cells surrounded the bodies of neurons or unmyelinated axons of the neuropil and formed a multilayer sheath tightly attached to the neuron soma or axons. 4 hours after axotomy, disorganization of Nissl bodies and mitochondrial cristae was observed in the cytoplasm of neurons. 24 hours after the axotomy, ultrastructural changes in neurons intensified: compression of nuclei and compaction of nuclear chromatin were observed. There was a further disorganization of Nissl's substance, the appearance of voids and the loss of organelles. The internal structure of neuropil axons was completely destroyed. However, the ultrastructure of glial cells was found to be more preserved, and the presence of a certain amount of intact mitochondria in them indicated the continuation of synthetic processes in them. Some of the described ultrastructural changes in the ganglia of the abdominal nerve cord of crayfish indicate early stages of necrosis, but taking into account such changes as the contraction of nuclei and condensation of chromatin, these changes should be attributed to a mixed type of cell death.
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