| Budget Amount *help |
¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 1992: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1991: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
To investigate radiation effects on normal brain in clinical radiotherapy of brain tumor, the effects of X-irradiation on normal brain in both adult and new-born rats have been studied.
1. Fischer 344 rats, aged 6 months, received fractionated irradiation (5Gy/day, 2days/week;total dose, 40Gy) to the whole brain. The rats were tested using a water maze task and a passive avoidance task at 6, 9, 12, months after radiation. In comparison with control rats, the irradiated rats showed marked lerning impairment in a passive avoidance task done 12 months after radiation.
Local cerebral glucose utilization (LCGU) was mesured by the 14C-2-deoxyglucose method 12 months after radiation. The LCGU of some brain structures was reduced.
The rats were sacrificed at 12 months after radiation and examined for histological changes and immunohistochemically. With conventional stains there were no apparent differences between control and irradiatedb rain. A number of GFAP-positive astrocytes were increased in the irradiated brain.
2. Neonatal rats, aged 4 to 15 days, received single doses (5, 7.5, 10, 15 Gy) of X-irradiation to the right hemicranium. The rats were sacrificed at 14, 21, 28 and 35 days of age and examined for histological change. With conventional stains, neurons and blood vessels showed no abnormal changes. As compared with unirradiated hemisphere, irradiated hemisphere showed delayed myelination. Immunohistochemistry for myelin basic protein and myelin-associated glycoprotein was sensitive histopathological indicator of radiation effect of oligodendroglias.
The delayed myelination was due to direct radiation effect on oligodendroglias.
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