Morphological changes in cultures of hippocampus following prenatal irradiation in the rat

Neuronal analysis and behaviour in prenatally gamma-irradiated rats

The intrauterinal development in mammals represents a very sensitive period of life in relation to many environmental factors, including ionizing radiation (IR). The developing nervous system is particularly vulnerable to IR, and the consequences of exposure are of importance because of its potential health risks. The aim of our work was to assess whether prenatal irradiation of rats on the 17th day of embryonic development with a dose of 1 Gy would affect the formation of new cells and the number of mature neurons in the hippocampus and the selected forms of behaviour in the postnatal period. Male progeny of irradiated and control females was tested at ages of 3 weeks, 2 and 3 months. The number of mitotically active cells in the gyrus dentatus (GD) of the hippocampus was significantly reduced in irradiated rats aged 3 weeks. In irradiated rats aged 2 months, a significant reduction of mature neurons in CA1 area and in GD of the hippocampus was observed. The IR negatively influenced the spatial memory in Morris water maze, significantly decreased the exploratory behaviour and increased the anxiety-like behaviour in elevated plus-maze in rats aged 2 months. No significant differences were observed in animals aged 3 months compared with controls of the same age. A significant correlation between the number of mature neurons in the hilus and of the cognitive performances was found. Our results show that a low dose of radiation applied during the sensitive phase of brain development can influence the level of neurogenesis in the subgranular zone of GD and cause an impairment of the postnatal development of mental functions.

Influence of X-ray on the autophagic-lysosomal system in rat pancreatic acini

Lysosomes have an important role in radiation injury of cells and tissues. Activation of autophagy is frequently observed in different types of pathological tissue degeneration. In radiation response it increases in some cases, and lysosomes are responsible for regulated degradation of the autophagic vacuoles. Lysosomes are also involved in ionizing radiation induced cell death. In apoptosis lysosomes degrade content of the phagocytotic vacuoles derived from engulfed apoptotic blebs. On the other hand lysosomal enzymes discharged from disintegrated cells have a key role in induction of necrotic changes. In this work we investigate autophagy and lysosomal protein degradation in the relatively radiation insensitive exocrine pancreatic acini in vivo and in vitro. Type of cell death induced by X-ray was also examined in relation to the changes of the lysosomal processes. In 5h after 16 Gy in vivo whole body irradiation we observed significant increase in the cytoplasmic volume fraction of autophagic vacuoles and in the number of apoptotic cells in vivo. But in the acini isolated from irradiated rats we could not detect a change in the lysosomal degradation of intracellular proteins. Therefore irradiation probably influences the autophagy in an earlier step than lysosomal degradation. Extended necrotic lesions were not observed in vivo as long as 48 h. Isolated pancreatic acini usually contain more autophagic vacuoles than in vivo, but we could not observe additional increase in autophagy after 8 Gy, in vitro irradiation. Lysosomal degradation of intracellular proteins was also unaltered after 8 Gy, in vitro irradiation. Other biochemical functional parameters of the isolated pancreatic acini, like protein synthesis and amylase secretion were not changed either after 8 Gy, in vitro X-ray treatment. These results indicate that pancreatic acinar cells in vitro have a high tolerance to irradiation. The observed in vivo radiation induced changes of the exocrine pancreas are possibly indirectly induced by injuries of more sensitive mechanisms.