Processes of Proliferation and Apoptosis in the Cerebellum of the Parr (Oncorhynchus masou) after Mechanical Injury

Abstract

We studied the processes of proliferation and apoptosis in different zones of the cerebellum in juvenile individuals of the parr (masu) salmon, Oncorhynchus masou, after experimental mechanical trauma; we took into account that the brain of young fishes of this species is in the state of development, and that this is accompanied by intense proliferative activity in the matrix zones. In the damaged cerebellum, results of TUNEL labeling demonstrated manifestations of high apoptotic activity in both zones of postembryonic neurogenesis (granular eminences and molecular layer) and the superficial layer of the cerebellum body. The reaction to mechanical injury of the cerebellum looked like post-traumatic intensifications of proliferative activity in the matrix zones and regional neurogenic niches combined with intensification of the processes of apoptosis, which reached the maximum in the zones of radial migration of the cells. This, obviously, provided elimination of some cells formed due to both reparative neurogenesis and natural morphogenetic processes. In the injured region, we observed manifestations of tangential and radial migration of the cells. A high value of the apoptosis index was observed in the dorsal part of the cerebellum, which corresponded to the zone of secondary neurogenesis. Therefore, apoptotic elimination of some cells is realized already at the stage of formation of the latter in the matrix zones. Apoptotic reactions in the regions where the background morphogenetic processes and processes related to physiological reparation after a traumatic influence prevail and in the remote regions are characterized by dissimilar intensities.