[The discovery of new internal sources of neural retinal regeneration after its detachment in newts. Morphological and quantitative research].

A model of experimental detachment of the retina in adult newts Pleurodeles waltl was used for studies of internal sources of the neural retina regeneration. Changes in morphology, localization, behavior, and abundance of the cells of various retinal layers were studied on serial semithin and ultrathin sections of the retina taken at different times after the operation. As a result, a new class of cells was found in the external nuclear layer, which differ from the photoreceptors but have a certain morphological similarity with the bipolar cells in the internal nuclear cell layer that have a Landolt's club. These cells were called bipolar-like cells. The bipolar-like cells, which amount to 10-12% of the cells in the external nuclear layer, proved to be capable of producing new photoreceptors during retina recovery after its detachment. We propose that the bipolar cells with Landolt's club of the internal nuclear layer that are displaced towards the sclera after the death of a part of the photoreceptors are a source of the bipolar-like cells of the external nuclear layer. Supposedly, they are also a source of neuroblasts that we first found at later stages after detachment in the case of more intense destruction of the retina nuclear layers. The neuroblasts arising in the internal nuclear layer are displaced apically and divide to form radial "inserts", whose cells differentiate and restore the cell composition of all three nuclear layers of the detached retina. The discovered internal sources of regeneration of the neural retina in newts are compared with those known in fish, precursor cells of rods, and the role of other cell types in the retina regeneration is described under the given conditions of its damage.