Deepa R. Theodore

Ascorbic acid and focal cerebral ischaemia in a primate model

SummaryNeuronal cell damage following ischaemia is postulated to be due to free radical induced lipid peroxidation, and ascorbic acid is supposedly an important non-enzymatic scavenger of such free radicals. This study was undertaken to evaluate the protective effect of ascorbic acid on the brain in a primate model after focal cerebral ischaemia. Consumption of ascorbic acid in the monkey brain following ischaemia and its effect on macroscopic infarct size as demonstrated by 2, 3, 5, Triphenyl tetrazolium chloride (TTC) staining were used as parameters.The monkeys in the treated group were given 1 gram ascorbic acid parenterally every day for six days. The mean level of total ascorbic acid in right basal ganglia was 35.1±4.2 μg/mg of protein in the treated group as opposed to 22.9±2.1 μg/mg of protein in the nontreated group both before ischaemia. After right middle cerebral artery occlusion to produce focal cerebral ischaemia, the total ascorbic acid in the right basal ganglia 2 hours post ischaemia was 13.3±3.1 μg/mg of protein in the treated group as opposed to 9±1.6 μg/mg of protein in the untreated group. The average consumption of total ascorbic acid was 21.8 μg/mg of protein in the treated group and 13.9 μg/mg of protein in the nontreated group.Macroscopic infarct size as determined by TTC staining in the right cerebral hemisphere was 11.7±6.9 in treated group whereas it was 24.4±4.4 (expressed as percentage of right hemisphere) in the non-treated group. There was significant reduction in the size of the infarct in the treated group.A short course of mega-dose Ascorbic acid therapy was found to significantly decrease the macroscopic infarct size. Pretreatment with ascorbic acid enhanced its storage and utilization during ischaemia resulting in its protective effect.

Free Fatty Acids, Lipid Peroxidation, and Lysosomal Enzymes in Experimental Focal Cerebral Ischemia in Primates: Loss of Lysosomal Latency by Lipid Peroxidation

Experimental focal cerebral ischemia was produced in monkeys (Macaca radiata) by occlusion of the right middle cerebral artery (MCA). The release of the lysosomal glycosidases, β-d-hexosaminidase, α-l-fucosidase and α-d-mannosidase into the soluble fraction in the right basal ganglia of the experimental animals was measured at different periods from 30 min to 12 hr after occlusion and compared with the corresponding sham operated control animals. There was a significant increase in the released lysosomal enzymes in the MCA occluded animals at all periods and particularly at 4 hr after occlusion. The CSF from the experimental animals also showed elevated levels of hexosaminidase and fucosidase. The free fatty acids (FFA) measured in the basal ganglia at 30 min and 2 hr after occlusion showed a 100 fold increase in the experimental animals. The predominant fatty acid released was linoleic acid (18:2) followed by arachidonic acid (20:4). Lipid peroxidation in the basal ganglia measured by the thiobarbituric acid (TBA) reaction in the presence or absence of ascorbic acid also showed a significant increase in the experimental animals at all periods with a maximum at 30 min to 2 hr after occlusion. In order to assess whether lipid peroxidation causes damage to the lysosomes and release of the enzymes, a lysosome enriched P2 fraction from the normal monkey basal ganglia was prepared and the effect of peroxidation studied. Maximum peroxidation in the P2 fraction was observed in the presence of arachidonic acid, ascorbic acid and Fe2+. There was a good correlation between the extent of lipid peroxidation and the in vitro release of lysosomal hexosaminidase from the P2 fraction. Anti-oxidants which strongly inhibited lipid peroxidation in the P2 fraction prevented the release of hexosaminidase. The results suggested that in ischemia produced by MCA occlusion lipid peroxidation which damages the lysosomal membrane causes the release of lysosomal hydrolytic enzymes.

The paradox of increased microvascular visualization with decreased perfusion in cerebral focal ischaemia in a primate model

Microvasculature of the right caudate nucleus and insular cortex of monkeys with their right middle cerebral artery occluded was morphometrically measured with an image analysis system at 1/2, 4, 12, 24, and 48 hr and 2 weeks. A biphasic change in the microvasculature was observed. In the first phase up to 12 hr an increase in the number and length of the total microvasculature, visualized by alkaline phosphatase staining, along with a reduction in the number and length of the perfused part of the microvasculature, visualized by India ink perfusion, was observed. In the second phase after 48 hr, the number and length of the total microvascular bed as well as the perfused functional bed were significantly reduced.

TEMPORAL PROFILE OF TISSUE LEVELS OF DOPAMINE AND ITS METABOLITES, HVA AND DOPAC FOLLOWING FOCAL CEREBRAL ISCHAEMIA IN ANAESTHETIZED PRIMATES

1. Occlusion of the middle cerebral artery produced ischaemia and consequent changes in basal ganglia in the primate model of stroke within 0.5 h.

CHANGES IN THE CONTENT OF DOPAMINE AND ITS METABOLITES IN THE BASAL GANGLIA FOLLOWING RIGHT MIDDLE CEREBRAL ARTERY OCCLUSION AND REFLOW IN MONKEYS

1. Focal ischaemia was produced experimentally in Macaca radiata monkeys by occlusion of middle cerebral artery (MCA). There was a lowering of the dopamine (DA) content of basal ganglia after 4 and 12 h of occlusion.

Pathology of Ischaemic Brain Damage — Implications for Therapy

An ischaemic infarct was produced in primates by applying a clip to the right middle cerebral artery. Enzyme histochemical data are presented, documenting the development of a focal ischaemic brain lesion. The relatively slow demarcation of the ischaemic brain infarct appears to be correlated with the efficiency of the collateral blood supply. The extent of the collateral blood supply is documented by morphometric data on the brain capillaries. It was evident that effective intervention in the infarction process with a view to limiting the extent of an ischaemic brain lesion is possible only at an early stage. A reduction of blood viscosity by bloodletting and haemodilution is the most important measure to be taken in the first few hours after a stroke. The second important step in the treatment of acute stroke is inhibition of blood platelet aggregation to arrest the thrombotic process and avoid complete occlusion of the artery, or in the case of an embolism to limit the extent of the infarct.