| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
Previously, we examined localization of calcium in rat brain fixed with a combined oxalate- pyroantimonate technique in electron microscope. Then, elevation of calcium in mitochondria was higher in 30min than immediately after reoxygenation, In this experiment, we fractionated mitochondria from the rat brain which was exposured to hypoxic gas (5%02-95%N2) mixture for 30 minutes and measured content of calcium. A procedure established by Sims (Sims, 1990) was used for determining the calcium content of mitochondria isolated from rat brain subregions based on changes in fura-2 fluorescence after disruption of the organelles with Triton X-100 and sodium dodecyl sulfate. Mitochondria isolated from the forebrain of normal rats contained 2.4 * 0.8 nmol of calcium/mg of protein. A 30-mm hypoxic period produced an approximately twofold increase in the calcium content of mitochondria isolated from the hippocampus, a region which is most susceptable. The calcium content of mitochondria from the cerbral cortex, a region in which there are few hypoxia-susceptible neurons, tended to be similarly increased. Larger increases (to approximately five times control values) were seen in mitochondria isolated from both regions after 10-20 min of reoxygenation, By 1 h of reoxygenation, mitochondrial calcium had tended to reduce to prehypoxic control values in both regions. However, mitochondrial calcium was again increased in the hippocampus after 6 h (6.2 nmol of calcium/mg of protein) and 24 h (8.1 nmol of calcium/mg of protein) of reoxygenation. This regionally selective increase in calcium may corerate to degenerative changes of neurons in the hippocampus. Thus, this increase may be an essential step in the development of neuronal loss. But in the case of hypoxia, marked morophorogic damage was not found unlike the ischemia. Under such conditions, however, the increase of calcium contents also happened and effect on animal behavior.
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