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James Haim Bicher, M.D. paper, presented in the
2007 International Clinical Hyperthermia Society (ICHS), Mumbai, India,
January 4th and 5th.
The
Role of Local Blood Flow, Rheological Properties and Free Radicals in
Hyperthermia-Induced in Cerebral Tissue Damage
James Haim
I. Bicher, Nodar P. Mitagvaria*, Marina I. Nebieridze*
Valley
Cancer Institute, Los Angeles, California, USA
*Beritashvili Institute of Physiology, Georgian Academy of Sciences,
Tbilisi, Georgia
Objective.
We tried
the sensitivity of cerebral tissue to hyperthermia as manifested by
histological changes
and
the role of local blood flow, blood rheological properties, and free
radicals in development of mentioned changes.
.Research
design and methods. Local
areas of cerebral surface were irrigated by artificial cerebrospinal
fluid heated up to the temperature necessary for achievement of stable
level of temperature (41, 43 or 450C). Serial brain coronal
sections 50
mm thick stained with Azure-Eosin were analyzed
under light microscope. The local cerebral blood flow was measured by
thermal clearance method. Blood rheological properties were changed by
injection of high molecular weight Dextran T-500 and free radicals
existence was controlled by Dimethyl sulfoxide injection.
Results.
At 410C just superficial
lesions of the cerebral cortex and a few cases of thrombosed cerebral
microvessels have been observed. The rise of temperature on 20C
resulted in very severe lesions of cerebral tissue; the layered
structure of the cerebral cortex in the central parts of the
hyperthermia–induced lesions was impaired. The highest temperature (450C)
caused complete destruction of the layered structure of the cortex in
the area of hyperthermic exposure, numerous areas with lost neurons and
thrombosed cerebral vessels with perivascular accumulation of
erythrocytes were revealed. Injection of Dextran T-500 resulted in
deterioration and injection of Dimethyl sulfoxide in significant
improvement of histological changes in cerebral tissue when 43 or 450C
hyperthermia is used. Bi-phase alterations of local cerebral blood flow
have been revealed at 430C hyperthermia. Pronounced hyperemia
in first stage of heating is followed by remarkable ischemia on the late
stage.
Conclusion.
High sensitivity of cerebral tissue to
hyperthermic exposure has been confirmed. We can
consider cerebrovascular thrombosis as one of the most significant
complication of brain hyperthermia. In case of deteriorated blood
rheological properties hyperthermia-induced cerebral lesion is more
remarkable. Administration of antioxidants, scavengers of free radicals
can partially lessen hyperthermia induced cerebral lesion.
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