The objectives of the research projects of the laboratory are to define cellular and molecular mechanisms which operate to yield brain damage in cerebrovascular disease, particularly stoke. The long-term objective of the research is, thereby, to contribute to the development of preventive and therapeutic measures against these important diseases. Two types of brain damage are examined: selective neuronal vulnerability and pan- necrosis (infarction). In studying the former we make use not only of models of ischemia, but also of hypoglycemic comas and status epilepticus. Our approach to the latter is inspired by findings showing that three factors can cause transformation of selective neuronal vulnerability into infarction: prolongation of the ischemia, pre-ischemic hyperglycemia with exaggeration of the tissue acidosis, and hyperthermia. The work is experimental, and is based on well-characterized in vivo models of ischemia, as well as of in vitro techniques utilizing primary cultures of neurons and astrocytes.
The specific aim of the present project is to test a hypothesis which predicts that transformation of selective neuronal vulnerability into infarction is, at least in part, secondary to production of free radicals, and that free radical production is enhanced by delocalization of protein-bound iron. We thus assume that prolongation of ischemia, acidosis and hyperthermia all predispose to free radical damage. Three main questions are posed. The first is related to the presumed association between reduced pH and cell damage. The projects addressing this issue will examine the buffer capacity of the whole tissue as well as of neurons and glial cells, attempt defining the sources and location of any acid formed, and study to what extent the damage incurred correlates to changes in intra- or extracellular pH. The second question is whether free radicals are formed under the very conditions in which infarction is induced. This problem will be studied by assessment of the production of partially reduced oxygen species during prolonged ischemia as well as during ischemia complicated by either excessive acidosis or hyperthermia, and by attempts to ameliorate ischemia damage by measures directed against production of free radicals. The third question, finally, is whether there is a coupling between acidosis and release of """"""""catalytic"""""""" iron. This will be studied by measurements of release of bleomycin-reactable iron into cerebrospinal fluid and dialysis fluid, as well as of iron binding in tissue fractions.
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