A quantitative morphological assessment of the effect of lidoflazine and deferoxamine therapy on global brain ischaemia.

The effect of the combination of two drugs, i.e. lidoflazine (a calcium antagonist), and deferoxamine (an iron chelator) was evaluated following 15 min global brain ischaemia (GBI) and reperfusion in dogs in a randomized blind study. GBI was produced by complete cardiac arrest of 15 min duration. Histopathological analysis performed on in situ fixed brains 40 h post-resuscitation revealed diffuse microhaemorrhages in the control group. These were noted rarely in the treatment group, the mean value of foci of microhaemorrhages/20 low power fields (LPF) being 5.2 in the treatment group versus 28 in the control group (p less than 0.001). Diffuse coagulative necrosis of neurons (ischaemic cell change) in the cerebral cortex, especially lamina 3, hippocampus, striatum, brain stem and cerebellum was present in all cases. Quantitation of the degree of cellular damage obtained by counting the number of anoxic neurons (in consistent regions of the brain) with the use of an image analysis system, revealed no significant difference between the 2 groups. The mean percentages of the ischaemic neurons in the control group in the various areas studied were: parietal cortex, 22.25; hippocampus, 50.37 and cerebellum (Purkinje cells), 66.75; and in the treatment group 25.3, 55.04 and 70.6 respectively. Thus, the lidoflazine-deferoxamine regimen significantly reduced the incidence of microhaemorrhages in the brain, but it did not have any protective effect against anoxic neuronal injury 40 h post-ischaemia in this experimental model of GBI of 15 min duration.

Natural course of iron delocalization and lipid peroxidation during the first eight hours following a 15-minute cardiac arrest in dogs.

Lipid peroxidation is thought to be a major contributing factor in neurological injury following cardiac arrest. Because iron availability is a prerequisite for lipid peroxidation, this experiment was designed to examine the natural time course of iron release, lipid peroxidation, and cerebral polyunsaturated fatty acid content following a 15-minute cardiac arrest in dogs. Large mongrel dogs were anesthetized with ketamine and halothane and divided into three groups of five each. In two groups, cardiac arrest was induced with KCl. After 15 minutes of cardiac arrest, the dogs were resuscitated by five minutes of internal cardiac massage, epinephrine, bicarbonate, and internal defibrillation. All ten dogs were resuscitated and supported by a standard intensive care protocol until tissue harvest. A 3-g portion of parietal cerebral cortex was obtained from the nonischemic dogs (n = 5), or at two hours (n = 5), or eight hours (n = 5) after resuscitation. Total tissue iron was measured by an atomic emission spectrometer; low molecular weight species (LMWS) iron by the o-phenanthroline test on an ultrafiltered sample; and lipid peroxidation by both the thiobarbituric acid test (TBARS) and determination of the tissue content of lipid double bonds, calculated by first fractionating the lipids by gas-liquid chromatography and then measuring the double bonds in each fraction by spectrometry and summing the results. Univariate ANOVA demonstrated all variables except total tissue iron to have significance at P less than .02. At two hours of reperfusion, LMWS iron and TBARS were significantly elevated above nonischemic control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral endothelial microvilli following global brain ischemia in dogs.

Cerebral blood vessels (BVs) of dogs subjected to global brain ischemia by complete cardiac arrest of 15 min followed by 8 h of reperfusion, were studied in neocortex and hippocampus by means of transmission electron microscopy. Widespread endothelial microvilli were present in the postischemic animals. The number of endothelial microvilli in the postischemic animals (mean/BV in the neocortex = 3.26 and in the hippocampus = 2.54) was significantly larger than that in the non-ischemic controls (mean/BV in the neocortex = 1.39 and in the hippocampus = 0.84), P for both regions being less than 0.05. Arterioles, venules and capillaries, all were equally affected. Endothelial pinocytotic vesicles were also observed frequently in the postischemic dogs. Marked pericapillary swelling of astrocytic foot processes was present in the surrounding neuropil. It is concluded that the prominent cerebral endothelial microvilli recognized after 8 h of reperfusion following cardiac arrest in this experimental model of global brain ischemia, may play a significant role in the development of delayed postischemic hypoperfusion.

Brain cortex tissue Ca, Mg, Fe, Na, and K following resuscitation from cardiac arrest in dogs.

Recent evidence suggests that ultimate neurologic injury following cardiac arrest and resuscitation may be largely determined by biochemical events occurring during reperfusion. To test this hypothesis and further characterize the time course of some of these events, we examined tissue samples from the parietal cortex for their total content of calcium (Ca), magnesium (Mg), iron (Fe), sodium (Na), and potassium (K) after 10 minutes, two hours, four hours, and eight hours of reperfusion following a 15-minute cardiac arrest in dogs. After 10 minutes of reperfusion, there were relatively small, but significant, increases in the total tissue content of Ca and Na, as compared to nonischemic controls. All values had returned to normal at two hours and remained normal at four hours of reperfusion. However, at eight hours of reperfusion, Ca and Na content approximately doubled and K content was reduced by half. There were no significant changes at any time in the tissue content of Fe or Mg. We conclude that with between four and eight hours of reperfusion following a 15-minute cardiac arrest, a major defect occurs in many cells of the cortex with respect to their ability to control ionic balances of Ca, Na, and K. This might be explained either by failure of the energy-dependent ionic pumps or by more generalized damage to the membrane permeability barrier by a process such as lipid peroxidation.

Brain iron delocalization and lipid peroxidation following cardiac arrest.

Brain injury after cardiac arrest and resuscitation may occur, in part, by oxygen radical mechanisms. The availability of a transition metal, such as iron, is essential for in vitro initiation of this type of reaction. The brain has significant stores of iron bound in large proteins. We conducted this study to determine whether iron availability is enhanced in the canine brain following resuscitation from 15 minutes of cardiac arrest, and whether this iron is associated with the appearance of products of radical-mediated lipid peroxidation (LP) after two hours of reperfusion. Examination of the data by the method of multivariate analysis revealed significant increases in the low molecular weight species (LMWS) iron (300% of nonischemic controls, P less than .01), malondialdehyde (MDA), a lipid peroxidation degradation product (145% of nonischemic controls, P less than .01), and conjugated dienes (CD) (204% of nonischemic controls, P = .07). Therapy with deferoxamine (50 mg/kg IV immediately post resuscitation) produced a reduction in MDA and CD to levels statistically indistinguishable from nonischemic controls. We conclude that brain tissue iron is delocalized from normal storage forms to a LMWS pool after two hours of reperfusion following resuscitation from a 15-minute cardiac arrest, and that this is associated with increased products of LP. The increase in LP products is blocked by treatment with deferoxamine.

Cardiac arrest and resuscitation: brain iron delocalization during reperfusion.

We hypothesize that brain injury from cardiac arrest occurs during reperfusion and is in part mediated by iron-dependent lipid peroxidation. We conducted a study to examine the time course of brain iron delocalization and lipid peroxidation in an animal model of cardiac arrest and resuscitation. Assays for brain tissue iron in low-molecular-weight species (LMWS iron) used the o-phenanthroline test on an ultrafiltered (molecular weight less than 30,000) tissue sample; malondialdehyde (MDA), a product of lipid peroxidation, in brain tissue was assayed by the thiobarbituric acid test (TBA). Samples of the parietal cortex from 11 nonischemic control dogs (Group 1) had LMWS iron levels of 9.6 +/- 4.9 nmol/100 mg tissue and MDA levels of 7.7 +/- 2.0 nmol/100 mg tissue. Samples from the parietal cortex taken from five dogs after 15 minutes of cardiac arrest (Group 2) had LMWS iron levels of 9.3 +/- 3.1 nmol/100 mg tissue and MDA levels of 6.1 +/- 1.0 nmol/100 mg tissue. Samples from the parietal cortex taken from five dogs after 45 minutes of cardiac arrest (Group 3) had LMWS iron levels of 6.7 +/- 3.3 nmol/100 mg tissue and MDA levels of 5.6 +/- 0.4 nmol/100 mg tissue. There was no significant difference among the three groups for either LMWS iron or MDA. Five dogs were subjected to 15 minutes of cardiac arrest and definitive resuscitation by internal cardiac massage and defibrillation (Group 4). Following resuscitation the chest was closed and the dogs were given intensive care for two hours.(ABSTRACT TRUNCATED AT 250 WORDS)