| Objective To study the joint biological effects of different doses of microwave radiation andγ-ray on the nervous system and hematopoietic system, as well as the protective effects of low doses of microwave radiation on theγ-ray-induced damage of hematopoietic system at the cellular and organism levels, to provide with imformation in exploring molecule mechanisms of combined effects of microwave andγ-rays.Methods Primary cultured bone marrow cells were exposed with microwave radiation,γ-ray radiation, as well as combined radiation of microwave andγ-ray, changes of cell proliferation and cell cycle were analyzed. Kunming mice were treated with a separate microwave radiation, a separateγ-ray radiation, as well as combined radiation of microwave andγ-ray. According to changes of animal survival rate, survival time, as well as peripheral blood cell count, animal model was set up for microwave radiation scheme which could effectively reduce the hazards of ionizing radiation; bone marrow nucleated cells(BMNCs) were counted, number and proliferative ability of hematopoietic stem/ progenitor cells were detected, and histopathological changes in the bone marrow were observed,GM-CSF and IL-3 levels in blood serum were analyzed using ELISA assay method.SHG44 human glioma cells were first randomly divided into 4 groups including Group control (C), Group ionizing radiation ( I), Group microwave(M) and Combined group (M + I). Group M + I samples received an initial exposure to microwave radiation and then subsequently to ionizing radiation. Standard MTT assay was used to observe the proliferation activity of the SHG44 human glioma cells. Changes in cell cycle and apoptosis were measured by means of flow cytometry. The activity of the superoxide dismutase (SOD) and malondialdehyde levels (MDA) were determined by applying commercial SOD Test Kits and MDA Test Kits, with procedures according to instructions of the manufacturer. Total RNA was extracted from each sample, performed with a commercial kit according to the manufacturer's protocol. The level of Hsp70 expression was analyzed by a RT-PCR procedure. HSP70 protein level was analyzed using western blot analysis. Primary cultured rat glial cells were exposed with microwave radiation,γ-ray radiation, as well as combined radiation of microwave andγ-ray, cell proliferation and apoptosis were analyzed. Kunming mice were irradiated with 1.5mW/cm2, 3mW/cm2, 6mW/cm2 and 9mW/cm2 900MHz microwave, Changes of learning and memory ability after radiation were measured by open field test and step-through test. The levels of Hsp70 were detected with RT-PCR.Two hundred and four residents near and around a base station have been investigated. The intensity of electromagnetic field near the base station was measured. General information correlated with the investigation was collected by questionnaire. Neurobehavioral functions of the residents were examined by the B.NESC assessment system.ResultsPre-exposure of 120μW/cm2 900MHz microwave significantly improved the survival rate ofγ-ray irradiated mice, promoted the recovery ofγ-ray induced decline of peripheral white blood cells, improved spleen and thymus idex, enhanced BMNCs proliferative activity, promoted CFU-GM colony formation, and stimulated the hematopoietic growth factor GM-CSF, IL-3 expression ofγ-ray irradiated mouses. Bothγ-ray radiation alone and combined radiation led to pathological changes of bone marrow, which experienced four stages : apoptotic necrosis, emptiness, regeneration and repair, and restoration, but pathological damages of mice in combined group were less severe, and recovered faster than that of ionizing group. Spleen index of mice in combined group was significantly higher than that ofγ-ray group 9d, 12d after irradiation (p <0.05). Splenic pathological change was similar with that of bone marrow. Splenic pathological injuries in combined group were lighter than that ofγ-ray group.4mW/cm2 and 6mW/cm2 microwave radiation decreased proliferation activity and cloning efficiency of SHG44 human glioma cells.Combination of Microwave andγ-ray showed synergistic effect on both cell proliferation activity and the cloning efficiency.Compared to the microwave radiation groups,the percentage of G1 phase cells obviously increased in the combination groups,while that of G2 and S phase decreased.The rate of apoptosis increased with the does of microwave in the microwave radiation groups and so did the I+M4 and I+M6 Group,indicating a synergistic effect ofγ-ray and microwave on apoptosis rate. The MDA level increased in all combination groups,and the SOD activity decreased in the group with combined radiation ofγ-ray and 6mW/cm2 microwave.Expression of HSP70 at both mRNA and protein levels increased slightly in the microwave exposure groups, but no interaction ofγ-ray and microwave on HSP70 expression was found for SHG44 human glioma cells.Proliferation of primary cultured rat glial cell inγ-ray group and combined radiation group withγ-ray and 6mW/cm2 microwave decreased slightly, and the ATPase activity was significantly increased.In animal experiment for neurobehavial effect, the time and total distance of movement at 1.5 mW/cm2, 6 mW/cm2 and 12 mW/cm2 microwave group increased, with a decrease in rest and latency time and a high frequency of mistake(p<0.05). The levels of Hsp70 in hippocampus of 1.5 mW/cm2, 6 mW/cm2 and 12 mW/cm2 microwave group were significantly increased (p<0.05).The intensity of electromagnetic radiation from this base station was below the national standard. No significant difference was found between the exposure group and the control group in the neurasthenia symptom. However, as the time of exposure extended, abnormal incidences of headache, dizziness, and memory drop increased (p<0.05). In addition, exposure of electromagnetic radiation could lead to an increase in scores of profile of mood state (POMS) test and semi-structural project test.Conclusions1. Low dose of microwave radiation could reduceγ-ray induced mice hematopoietic damages to some extent.2. Microwave andγ-ray could inhibit the proliferation of SHG44 cells with a synergistic effect, but such effect was not observed in primary rat glial cells.900MHz microwave radiation could impair neurobehavioral of mice such as learning and memory ability. The over expression of Hsp70 could be an early index of neuron functional damage induced by microwave.3. Microwave radiation from the mobile base station could affect the emotional status of the residents nearby.
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