ABSTRACT
Object recognition memory and contextual fear conditioning task performance in adult C57BL/6 mice exposed to cranial fast neutron irradiation (0.8 Gy) were examined to evaluate hippocampus-related behavioral dysfunction following acute exposure to relatively low doses of fast neutrons. In addition, hippocampal neurogenesis changes in adult murine brain after cranial irradiation were analyzed using the neurogenesis immunohistochemical markers Ki-67 and doublecortin (DCX). In the object recognition memory test and contextual fear conditioning, mice trained 1 and 7 days after irradiation displayed significant memory deficits compared to the sham-irradiated controls. The number of Ki-67- and DCX-positive cells decreased significantly 24 h post-irradiation. These results indicate that acute exposure of the adult mouse brain to a relatively low dose of fast neutrons interrupts hippocampal functions, including learning and memory, possibly by inhibiting neurogenesis.
Subject(s)
Animals , Male , Mice , Cranial Irradiation , Fast Neutrons , Hippocampus/metabolism , Immunohistochemistry , Ki-67 Antigen/metabolism , Memory/physiology , Mice, Inbred C57BL , Microtubule-Associated Proteins/metabolism , Neurogenesis/physiology , Neuropeptides/metabolismABSTRACT
PURPOSE: It has been well established that response of cells and tissues to low LET radiations(X- or grmma-ray) can enhanced by comdining with hyperthermia. However, There has been relatively little of hyperthermia on the possible modification of either cellular or tissue responses to other types of radiation. So, We investigated the combined effect of fast neutron irradiation and hyperthermia according to the sequence and time interval of the two MATERIALS AND METHODS: In MKN-45 cells, a human stomach cancer cell line, Surviving fractions were measured according to the sequence treatment of 6,4,2,0 hour interval for fast neutron irradiation(1.5Gy) combined with hyperthermia(41 degrees C for 30 min or 43 degrees C for 30 min). RESULTS: D(0) and n of MKN-45 for neutron were 0.8Gy and 2.5, respectively. The surviving fraction by 1.5 Gy of neutron was 0.36+/-0.34. Interacting powers were mostly. The surviving fraction by 1.5 Gy of neutron was 0.36+/-0.34. Interacting powers were mostly ranged between 1 and 2, bur they were 3.0Gy 2.7, respectively for hyperthermia (41 degrees C for 30 min) followed by neutron irradiation 6 and 4 hours later. CONCLUSION: The combined effect of fast neutron (1.5Gy) and hyperthermia (41 degrees C or 43 degrees C for 30min) is largely independently additive. Preceding mild hyperthermia (41 degrees C for 30 min) 4 or 6 hours before neutron may cause decreased sensitivity to subsequent neutron irradiation.
Subject(s)
Humans , Cell Line , Fast Neutrons , Fever , Linear Energy Transfer , Neutrons , Stomach NeoplasmsABSTRACT
For evaluation of biological effect of p+(50.5 MeV) Be neutron beam produced by Korea Cancer Center Hospital(KCCH) cyclotron the RBE had been measured in experimental tumor Walker 256 carcinosarcoma as well as normal tissue, mouse intestine and bone marrow, in single and fractionated irradiation. As pilot study, the RBE had been measured for the mouse jejunal crypt cells in single whole body irradiation of which the result was 2.8. The obtained RBE values of TCD 50 of Walker 256 tumor, bone marrow and intestine in single irraiation were 1.9, 1.9 and 1.5 respectively. In fractionated irradiation, the RBE value of tumor Walker 256 was decreased as increasing of fraction number and increased as increaing of fraction size.