| ObjectiveBcause of the rapid development of radio communication and the increase use of cell phone recently, there is a great concern about the electromagnetic radiation from cell phone.Previous studies were focused mainly on adult impairment caused by high intensity electromagnetic wave, few involving its impact on embryo development, especially the development of the central nervous system.Pregnancy is a critical period of body system's development and it is sensitive to external stimulation. Stimulation of the external adverse factors often results in irreversible damage to the central nervous system, such as learning and memory ability and so on. Therefore, it is very important to study the learning and memory function of its offspring after a certain intensity continuous cell phone electromagnetic radiation exposure.The aim of the study is to investigate the effect of continuous cell phone electromagnetic radiation during the pregnant on the development of rat offsprings.The changes of general physical development and neural development of newborn rats were observed, and the contents of acetylcholinesterase, nitric oxide synthase, trace elements iron, zinc, copper, manganese and selenium in brain and serum of newborn rats were measured. To understand the effect of cell phone radiation on the development of central nervous system, the ultrastructure in hippocampus of newborn rat brain was observed by electron microscope, and the changes of 28d offspring behavior related to learning and memory were tested. Methods1. The establishment of radiation model in pregnant rats.32 clean Wistar rats on day 0 of pregnancy, weighing 250-300g, were purchased from Experimental Animal Center of Shandong University. The pregnant rats were randomly divided into 4 groups, control group, low, middle and high-intensity group according to the weight balance, eight in each group, and reared in single cage.Radiation was carried out from the first day of pregnance until natural childbirth, a total of 21 days. Each rat in low-intensity group received cell phone radiation once 10min, in middle intensity group 30min, and in high intensity group 60min, totalling 3 times a day.The pregnant rats were placed in the home-made cages to respectively receive the radiation. The clapboard in the cage could be adjusted to limit their activity. After connected, the mobile phone was introduced the sound from a radio. The volume was fixed and the handset was put next to the ears of pregnant rats, completely simulating the call status of human conversation.2. Effects of cell phone radiation on pregnant and newborn ratsThe appearance, daily spirit, feeding, urine, fur, etc. of pregnant rats were observed and their daily weight were recorded. After the childbirth, the number of newborn rats and the survival of 24h newborn rats were recorded, the developmental status was checked and the weight, body length and tail length were recorded as well.Twenty 24h newborn rats selected randomly from each experimental group were decapitated, and the 10% homogenate was made with the whole brain. The content of protein, AchE and NOS were measured by kits. The transmission electron microscope (TEM) was used to observe the morphological change of hippocampus, and the inverted microscope was used to observe the morphological change of brain.The remaining rats were fed until 28d, and water maze test and step-down test were employed to test learning and memory ability of newborn rats. After behavioral studies, the blood was collected immediately by decapitation and the serum was obtained by centrifugation. The trace elememts Zn, Fe, Cu, Mn in both serum and brain were analyzed by atomic absorption spectrophotometry, and Se was measured by atomic fluorescence spectrometry.Results1. The effects of cell phone radiation on the physical development of newborn rats.Visual observation has shown that the growth of the newborn rats was normal with good spirit and normal eating. The number of newborn rats, average weight, brain weight, body length, and tail length in each group have no significant difference among each other(P>0.05). Significant difference was found between high-intensity group and control group in ear separation, whole nest hair and teething time (P<0.05), but low intensity group and middle intensity group.2. The effects of cell phone radiation on the neurological development of newborn rats.Compared with the control group, the surface righting, air righting, cliff avoidance and negative geotaxis were delayed in radiation groups. High-dose group has significant difference in surface righting and air righting (P<0.05), but low intensity group and middle intensity group.3. The effects of cell phone radiation on the contents of AchE and NOS.Compared with the control group, the content of AchE in brain tissue increased, and significant differences (P<0.05) were found between each radiation group and the control group. The content of NOS decreased, with the significant difference between each radiation group and the control group as well.4. The effects of cell phone radiation on learning and memory ability.In the place navigation test the latency prolonged in every radiation groups compare with the control group. The calculations of intra-individual variation showed that the factor of time have significant difference (p<0.05). The index time*group showed that time did not vary with the group. The results of variation calculation among individuals demonstrated that group factor play a roll in latency (P<0.05). As a whole, each group has a different latency.In the spatial probe test, the significant difference (p<0.05) was found between high intensity group and control group both in the number of cross platform and swimming time in target quadrant, but low intensity and middle intensity group.In the first day step-down test, the escape latency prolonged and the number of errors increased. The differences (p<0.05) both in escape latency and the number of errors between in high intensity group and in coutrol group were significant (p<0.05). In the second day step-down test, the escape latency was lower and the number of errors increased. The differences (p<0.05) between in high intensity group and in coutrol group were significant (p<0.05), but low intensity group and middle intensity group.5. The effect of cell phone radiation on morphology of newborn ratsThe result of light microscope observing showed that, cells were neat, layers were rich, morphology was normal and chromatin was well distribution. All the sections have no abnormality. No evidence observed could demonstrate that the brain of offspring rats had any morphological changes after cell phone radiation.The result of electron microscope observing showed that, the nerve cells and capillaries in the control and low-intensity groups were normal, and in neurons the uniform nuclear chromatin mainly euchromatin could be seen with cytoplasm rich in mitochondria, rough endoplasmic reticulum and a large number of free ribosomes. The results in middle intensity and high intensity groups showed that mitochondrial swelling, mild edema around capillaries, chromatin condensation and margination, and endothelial cell vacuolization could be observed in neurons and glial cells. The neuronal apoptosis and necrosis lesions have not been seen in all sections. The resuls indicated that the cell phone exposure during pregnancy for certain time could cause slight ultrastructure changes in the brain.6 The effect of cell phone radiation on the contents of trace elements in the newborn rat brain and serum.Compared with the control group, the contents of Fe, Zn, Cu, Mn, Se in the newborn rats brain decreased in the radiation groups, the contents of Fe, Zn, Mn increasing with statistic significant in the middle intensity group (P<0.05) and the contents of Fe, Zn, Cu, Mn, Se increasing in the high intensity group(P<0.05).The contents of Fe, Zn, Cu, Mn, Se in the newborn rats serum decreased in the radiation groups. Compared with the control group, the content decreases of Fe, Zn, Se were significant in the middle intensity group (P<0.05) and the content decreases of Fe, Zn, Cu, Se were significant in the high intensity group (P<0.05).Conclusion1. The result showed that no significant effect of cell radiation was found on physical development and neurogenesis.2. A generally long time cell phone radiation would increase the content of AchE and decrease the content of NOS, therefore, may have a certain negative impact on learning and memory ability of newborn rats.3. A generally long-term continuous cell phone electromagnetic radiation can cause slight changes of cell ultrastructure.4. A long-term continuous cell phone radiation can result in the content change of trace element in newborn rat brain and serum. |
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