On adaptation of paraneural, connective-tissue structures of peripheral nerves to strenuous exercise or limitation of movements

Abstract

Paraneural connective-tissue structures consisting of a combination of fascial-cell spaces and fibrous formations and located between the epineurium and epimisis of adjacent muscles are extremely closely morphologically related with the neural stem. However, data on the adaptive capabilities of the paraneural structures under conditions of different intensity of the motor activity of the limb are not enough in the literature. The aim of this work was to study the reactive changes in the paraneural structures of the peripheral nerves of the branches of the brachial plexus under conditions of increased and decreased motor activity of the thoracic extremity and the determination of their adaptive reserve. Methods. The morphological study of reactive changes in paraneural connective tissue structures of peripheral nerves performed on a model of thoracic limb hyperkinesia or hypokinesia showed that adaptive processes were more clearly pronounced in paraneural structures than in the epineurium. Results. According to the immunohistochemical study in hypokinesia, the degree of proliferative activity of cells in G1, G2, S, and M phases of the cell cycle was 1.3 times higher in the paraneural connective tissue than in the epineural tissue starting from the 21st day of experiment. In hyperkinesia associated with the increasing index of proliferative activity, a greater number of cells expressing Ki-67 was visualized in the epineurium than in paraneural connective tissue structures. Conclusion. The data obtained in the work indicate a more pronounced adaptive reserve of the paraneural connective tissue structures than in the epineural connective tissue, both in hypokinesia and in hyperkinesia.