Differential radiosensitivity of neurons and neuroglia of the hippocampus in the adult rabbit

Abstract

Adult rabbits were subjected to 4.5 Gy of whole-blody or brain alone gamma-irradiation, and their hippocampus was examined with the light and electron microscope. Pycnotic cells were found at the base of the granular layer of the dentate gyrus in the so-called subgranular zone, as soon as 3 h after irradiation, and were cleared up by active phagocytosis after 48 h. Some of these cells appeared as undifferentiated, whereas others were differentiating granule cells, and possibly immature neuroglia. The extent of cell necrosis was contingent upon the age of the animal, the oldest animal studied (27 months) showing only sparse lesion of that type. Astrocytes and microglia were responsible for the phagocytosis of dead cells. Another type of lesion was found in the nuclei of the mature granule cells and consisted of light spots which appeared 1 h after the irradiation and disappeared almost completely after 48 h. Pyramidal cells did not show any of these two lesions. It is concluded that the laterations in the electrical activity of pyrimidal cells, following irradiation, are at least partly due to lesions affecting the dentate gyrus. Radionecrosis in the subgranular zone is related to the presence of immature cells in this region.

Homocysteine Elicits a DNA Damage Response in Neurons That Promotes Apoptosis and Hypersensitivity to Excitotoxicity

“…For example, mouse neuroblastoma cells become extremely sensitive to ultraviolet radiation-induced apoptosis after terminal differentiation (McCombe et al, 1976), and neurons are more vulnerable to ␥-irradiation than are astrocytes (Gueneau et al, 1979). We have found that cultured hippocampal neurons are much more vulnerable to homocysteine than are cultured vascular endothelial cells or astrocytes; the latter cell types are not killed by homocysteine concentrations up to 10 mM during a 48 hr exposure period (I.…”

Subgranular Zone of the Dentate Gyrus of Young Rabbits As a Secondary Matrix

“…1) appears in the light microscope as an accumulation of densely stained small nuclei, packed under neath the granular layer. A detailed ultrastructural description has been provided else where [14], This zone was found essentially to contain undifferentiated cells, with some ma ture glial cells.…”

“…In a previous paper dealing with the cytological effects of low-level -y-irradiation on the central nervous system of young and adult rabbits we showed that this treatment caused specific lesions in the dentate gyrus [14], The lesions consisted of a transient alteration in the chromatin pattern of nuclei of the granule neurons, which disappeared gradually after 2 days and, above all, of extensive necrosis of groups of cells lying beneath the granular lay-er. These cells apparently correspond to the so-called 'subgranular zone' described in the mouse by Reznikov [20], this terminology be ing subsequently adopted by Altman and Bayer [2] and Moskovkin and Reznikov [17].…”

Nature and fate of proliferative cells in the hippocampal dentate gyrus during the life span of the rhesus monkey

“…The mitotic activity also persists in the SGZ of postnatal rats (Bayer and Altman, 1974;Schlessinger et al, 1975) guinea pigs (Altman and Das, 1967) rabbits (Gueneau et al, 1979), and cats (Wyss and Sripanidkulchai, 1985). However, the methods used in most of the previous studies could not provide a clear distinction between neuronal and non-neuronal cell lines.…”

“…There is, however, some confusion in the literature arising from the fact that the time of onset, peak period, and cessation of neurogenesis in relation to the time of birth varies significantly among mammals. For example, the genesis of dentate gyrus granule cells is a predominantly postnatal event in mice and rats (Angevine, 1965;Altman and Das, 1965;Altman and Bayer, 1975;Schlessinger et al, 1975), whereas in rabbits, cats, and rhesus monkeys, it occurs to a much larger extent before birth and lasts for various time periods postnatally (Gueneau et al, 1979(Gueneau et al, , 1982Rakic and Nowakowski, 1981;Wyss and Sripanidkulchai, 1985). The prenatal phase of neurogenesis is particularly pronounced in primates, including humans, which are born more mature than rodents.…”