1995 Fiscal Year Final Research Report Summary
Brain disturbances due to rapid decompression-induced air bubbles, and effects of hyperbaric oxygenation
| Project/Area Number |
06671542
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Anesthesiology/Resuscitation studies
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| Research Institution | University of the Ryukyus |
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Principal Investigator |
YUSA Toshiko Univ.of the Ryukyus, Fac.of Med.Associate Professor, 医学部, 助教授 (30032329)
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| Co-Investigator(Kenkyū-buntansha) |
HIRATA Yukio Univ.of the Ryukyus, Fac.of Med.Professor, 医学部, 教授 (70073070)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Rapid decompression / Decompression sickness / Air bubble / Blood-brain barrier / Cerebral microcirculation / Cerebral ischemia-reperfusion / Maturation Phenomenon / Brain glutamate |
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| Research Abstract |
1.Effect of rapid decompression
To examine the changes in blood-brain barrier (BBB), cerebral microcirculation and histology from 0.25 to 72 hrs after decompression, rats were exposed to experimental compression to 6 atm abs air for 90 min and subsequent rapid decompression. The wide area stained with Evans blue and the regions of defective filling with Indian ink observed immediately after decompression decreased in size with time and were undetectable during 3 to 24 hrs after decompression. The edematous brain tissue with enlarged perivascular space and darkly stained nerve cells observed immediately after decompression also decreased after one to 24 hrs from decompression. These reversible dysbaric changes, however, were reappeared at 48 to 72 hrs after decompression. These early reversible derangements were interpreted to be the physico-chemical effects of intravascularly formed microbubbles. On the other hand, the reappearance of BBB and microcirculatory disturbances at 72 hrs afte
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r decompression suggested the maturation phenomenon after temporal brain ischemia induced by dysbaric microbubbles.
2.Effect of hyperbaric oxygenation (HBO) immediately after rapid decompression
The area stained with Evans blue was not seen after HBO,but the regions of defective filling with Indian ink and histological changes were still observed. Thus microcirculatory disturbances after rapid decompression remain even after HBO.
3.Effect of ischemia-reperfusion and nitric oxide synthase (NOS) inhibition on CBF and glutamate release
The effects was studied in the rat forebrain ischemia-reperfusion model.
In low flow cerebral ischemic model, after NOS inhibition, the vasoconstrictive effects occurred despite an increase in cerebral perfusion pressure by increased systemic MAP,and glutamate levels were lower than control Group. In complete cerebral ischemic model, however, cortical CBF decreased to about half of the initial control level, without an increase in cerebral perfusion pressure. In addition, glutamate levels was higher than control Group. Less
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