| Microwave in the frequency range 300MHz ~ SOOGHz, has long been used in radar, space research, telecommunications, industrial processing and medicine. In recent years, a large increase in the number of people who are potentially exposed to microwave radiation occurred with the introduction of household microwave ovens (2450 MHz) and mobile communications devices (800 ~ 1800 MHz). Public attention has been drawn to the possible biological effects and health hazards from exposure to microwave radiation.The biological effects of microwave are divided into two types: thermal and non-thermal effects. Thermal effects are associated with heat generated during microwave radiation when the specific absorption rate (SAR) is high. Lower intensity exposures that do not invoke thermoregulation are referred to as non-thermal which was less reported. Thermal and thermal induced-5-bio-effects correlated with some parameters of microwave such as frequencies, power densities, and pulsed modulations. Some epidemiological studies and in vivo experiments suggested an association between the incidence of cancer and exposure to microwave radiation. About the genotoxic effects of 2450 MHz microwave radiation, the majority data reported were negative. For the positive data, showed increasing the incidence of dicentric chromosomes, acentric fragments and micronuclei, DNA fragment rearrangement and gene expression alteration.In order to provide some evidences for health hazards from exposure to microwave radiation, in this study, HPRT gene mutation, free radicals level, protein expression and DNA breakage were investigated after the mice exposured to different intensity and time microwave radiation. RESEARCH CONTENTS AND RESULTS:1. When cells go through apoptosis, usually DNA single-strand breakage occurs. DNA double-strand breakage take place when the distance between two nicks of double strands is less than 12bp. According to this principle, we observed DNA single and double-strand breaks in brain tissue of mice, using the klenow fragment of DNA polymerase I -mediated nick end labeling method (KLENOW method), and terminal deoxynucleotidy I transferas?mediated dUTP nick end labeling (TUNEL method) . The result showed that the damage of DNA single and double-strand breaks in brain tissue of mice increased significantly.2. Reactive oxygen species (ROS) is one of the factors which induce apoptosis. ROS was generated during internal metabolism or stimulated by external factors. Superoxide dismutase (SOD) is one of the most important-6- enzymes that remove oxygen free radicals. The activity of SOD reflects the ability of the body removing oxygen free radicals. Glutathione (GSH, T-i -glutamyl-1 -cysteinylglycine) is an introcelluler non-protein thiol, which has various physiological functions, for example to preventing oxidative damage by nucleophilic reactions as a redox buffer, and removing reactive oxygen species produced under pathological conditions. ROS may damage cell membrane by lipid peroxidation. The essential metabolite MDA, reflects the level of cell damage. In this study, SOD activity, contents of GSH and MDA in brain tissue were determined by NBT method, DTNB method and TBA methods respectively. We found the activity of SOD and the content of GSH significant decreased, while the content of MDA in brain tissue significant increased after exposured to microwave radiation compared with that of control. The level of free radical was not completely the same in tissue of cerebellum and cerebrum.3. Apoptosis was mediated by many genes and proteins, were expressed in cells nucleus and promote the production of apoptosis. It was also reported that Fos/Jun could modulate DNA in transcription level. The activity and expression of Fos and Jun proteins were regulated by free radical, Ca2+ ion, protein kinase and so on. Western bloting and immunohistochemistry were used to assess the expression of the immediate early genes, c-fos and c-jun, in hippocampals and cerebellum of mice. Significant i...
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