Biomedical subjects

J Marsala

Publications and source records attributed to J Marsala.

At least 37 records · Page 2Linked to original sources

PubMed1999

Segmental and laminar distributions of nicotinamide adenine dinucleotide phosphate-diaphorase-expressing and neuronal nitric oxide synthase-immunoreactive neurons versus radioassay detection of catalytic nitric oxide synthase activity in the rabbit spinal cord.

The distributions of neuronal nitric oxide synthase-immunoreactive neurons and of nicotinamide adenine dinucleotide phosphate-diaphorase activity were studied in the C6, Th2, L1, L5, S2 and S3 segments and laminae in the rabbit spinal cord and compared with the catalytic nitric oxide synthase activity, determined by monitoring the conversion of [3H]arginine to [3H]citrulline in the same segments and laminae. Morphologically, a heterogeneous population of nicotinamide adenine dinucleotide phosphate-diaphorase-expressing and neuronal nitric oxide synthase-immunoreactive neurons was detected in the superficial and deep dorsal horn and the pericentral region in all segments studied, and in the intermediolateral cell column of the thoracic and lumbosacral segments. A disproportionate distribution of both neuronal categories which had a significantly higher number of nicotinamide adenine dinucleotide phosphate-diaphorase-expressing rather than neuronal nitric oxide synthase-immunoreactive cell bodies was found in all segments. The catalytic nitric oxide synthase activity was distributed unequally in the C6, Th2, L1, L5, S2 and S3 segments, with a comparatively low value in the Th2 segment (70 +/- 5.1 d.p.m./microg protein) in comparison with the S3 segment, where the highest level (140 +/- 5.5 d.p.m./microg protein) was found. A close correlation between the number of neuronal nitric oxide synthase-immunoreactive somata and catalytic nitric oxide synthase activity was revealed in the dorsal horn (laminae I-VI). Whereas a low number of neuronal nitric oxide synthase-immunoreactive somata in laminae VII-X was found in the L5, S2 and S3 segments, the values of catalytic nitric oxide synthase activity in the same laminae and segments were found to be exceedingly high. These findings indicate that the occurrence of many neuronal nitric oxide synthase-immunoreactive fibers (mainly axons), and dense, punctate, non-somatic neuronal nitric oxide synthase immunopositivity in the neuropil staining of the same laminae and segments, can substantially enhance catalytic nitric oxide synthase activity.

Animals↗

PubMed1999

Depression of acetylcholinesterase synthesis following transient cerebral ischemia in rat: pharmacohistochemical and biochemical investigation.

The effect of transient cerebral ischemia on acetylcholinesterase (AChE) synthesis was studied in rats by a modified pharmacohistochemical method. The procedure involved in vivo irreversible inhibition of AChE by administration of the inhibitor diisopropyl fluorophosphate (DFP; 1.2 mg/kg b.w., i.m.) 1 h before 30 min forebrain ischemia (the four-vessel occlusion model). At the onset of ischemia, 70-75% of AChE was inhibited in the brain. Recirculation was followed by histochemical and biochemical investigations of newly synthesized AChE in the striatum, septum, cortex and hippocampus. Control sham-operated animals were treated with the same dose of DFP. For correlation, rats not treated with DFP were subjected to the same ischemic procedures and investigated simultaneously. In these rats, significant decrease in AChE activity was found in the striatum, septum and hippocampus during 24 h recirculation. In DFP treated rats, ischemia markedly depressed resynthesis of AChE; after 4 h recirculation, AChE activity was decreased by 45-60% in all investigated areas in comparison with controls and the AChE histochemistry showed only slightly stained neurons in the striatum and septum. Twenty-four hours after ischemia, these neurons were densely stained and the increase in AChE activity indicated a partial recovery of the enzyme synthesis. These results suggest that the depression of AChE synthesis after forebrain ischemia is probably transient, not accompanied by cholinergic neuron degeneration.

Acetylcholinesterase↗

PubMed1999

[Gradual postischemic reoxygenation as protection against spinal cord ischemia in an experiment].

The authors attempted reperfusion on the experimental model of spinal ischemia described most frequently in the literature. After double ligature of the aorta--closely beneath the insertion of the subclavian artery and closely above the diaphragm they induced for a period of 40 minutes a state similar to surgery of aneurysms of the thoracoabdominal part of the aorta. in 8 dogs of the control group 7 animals developed paraplegia. In the group with graded postischaemic reoxygenation induced by a change of the ventilation ratio of N2O:O2 none of the dogs was paralyzed after two days survival. The neurological condition evaluated according to Tarlov's score was consistent with the histological finding in the preparations of the spinal cord stained according to Naut. Degenerative changes of interneurons were found mainly in the control group. In the group with graded reoxygenation they were rare. This method confirmed the importance of the reperfusion stage for postischaemic damage of the spinal cord.

Animals↗

PubMed1999

[Epidural regional hypothermia for prevention of paraplegia in experimental aortic clamping].

In experiments on dogs the authors tried to elaborate methods of protection of the spinal cord from ischaemia during surgery of an aneurysm in the thoracolumbal portion of the aorta. They used the model described in the literature with double ligature of the aorta closely below the insertion of the left-sided subclavian artery and closely above the diaphragm for a period fo 40 minutes. In the control group of 8 dogs they observed severe neurological deficiency manifested by paraplegia in 7 animals. In the second group of 8 dogs the authors used local hypothermia of the spinal cord. Hypothermia was produced by epidural administration of 5 degrees C saline which they started to administer five minutes before clamping and continued throughout the period of ischaemia. The temperature of the spinal cord dropped to 26.8 degrees C. In this group none of the dogs developed neurological damage. The results were evaluated by recording spinal somatosensory potentials, by monitoring the neurological condition according to Tarlov and by histological examination of the spinal cord. In the conclusion they emphasize that this method can protect the spinal cord from 40-minute ischaemia.

Animals↗

PubMed1999

Selective sparing of NADPH-d positive spinal cord neurons affected by ischemia.

Histochemical characterization of NADPH diaphorase positive neuronal pools in the rabbit lumbosacral segments was performed during and after transient spinal cord ischemia. Strongly enhanced staining of NADPH diaphorase positive structures appeared in the superficial dorsal horn, the pericentral region and in the neurons of the sacral parasympathetic nucleus at the end of 40 min of abdominal aorta ligation or after 1 day reperfusion. Four days after ischemia, NADPH-d positive neurons and vessels were detected in the central gray matter despite well developed necrosis in this location. Regional nitric oxide synthesis and its vasodilatatory effect during the period of aortic occlusion may account for the observed selective resistance of these spinal cord neurons to transient ischemia.

Animals↗

PubMed1998

Reduced nicotinamide adenine dinucleotide phosphate diaphorase in the spinal cord of dogs.

The distribution of somatic, fibre-like and punctate, non-somatic reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity was examined in dog spinal cord using horizontal, sagittal and transverse sections. The morphological features of NADPH diaphorase exhibiting neurons divided into six different neuronal types (N1-N6) were described and their laminar distribution specified. Major cell groups were identified in the superficial dorsal horn and around the central canal at all spinal levels, and in the intermediolateral cell column at thoracic level. NADPH diaphorase exhibiting neurons of the pericentral region were distributed in a thin subependymal cell column containing longitudinally-arranged small bipolar neurons with processes penetrating deeply into the intermediolateral cell column and/or running rostrocaudally in the subependymal layer. The second pericentral cell column located more laterally in lamina X contains large, intensely-stained NADPH diaphorase exhibiting neurons with long dendrites radiating in the transverse plane. Neurons of the sacral parasympathetic nucleus seen in segments S1-S3 exhibited prominent NADPH diaphorase activity accompanied by heavily-stained fibres extending from Lissauer's tract through lamina I along the lateral edge of the dorsal horn to lamina V. A massive dorsal gray commissure, with high NADPH diaphorase activity, was found in segments S1-S3. At the same segmental level a prominent group of moderately-stained motoneurons was detected in the dorsolateral portion of the anterior horn. Fibre-like NADPH diaphorase activity was found in the superficial dorsal horn and pericentral region in all segments studied. Punctate, non-somatic NADPH diaphorase activity was detected in the superficial dorsal horn, in the pericentral region all along the rostrocaudal axis and in the nucleus phrenicus (segments C4-C5), nucleus dorsalis (segments Th2-L2), nucleus Y (segments S1-S3), and the dorsal part of the dorsal gray commissure (S1-S3). A schematic diagram documenting the segmental and laminar distribution of NADPH diaphorase activity is given.

Animals↗

PubMed1998

Phospholipid composition in spinal cord regions after ischemia/reperfusion.

Ischemia-reperfusion induced changes in concentration of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI) and sphingomyelin (SM) in the gray matter taken in toto, white matter, dorsal horns, intermediate zone and ventral horns of the rabbit's spinal cord were studied and compared with neurohistopathological changes. With the exception of PI concentration in the dorsal horns, ischemia of 25 min caused significant degradation of all phospholipids. While short-lasting recirculation (1 h) did not returned the levels of phospholipids to control values, postischemic recirculation for 3 h sharply increased the resynthesis of all phospholipids, but only the concentration of PE, PS, and PI in the dorsal horns and PC in the intermediate zone significantly improved and returned close to control values. Corresponding neurohistopathological changes resulting after the same reperfusion periods are given.

Anatomy, Cross-Sectional↗

PubMed1998

The intraischemic and early reperfusion changes of protein synthesis in the rat brain. eIF-2 alpha kinase activity and role of initiation factors eIF-2 alpha and eIF-4E.

Rats were subjected to the standard four-vessel occlusion model of transient cerebral ischemia (vertebral and carotid arteries). The effects of normothermic ischemia (37 degrees C) followed or not by 30-minute reperfusion, as well as 30-minute postdecapitative ischemia, on translational rates were examined. Protein synthesis rate, as measured in a cell-free system, was significantly inhibited in ischemic rats, and the extent of inhibition strongly depended on duration and temperature, and less on the model of ischemia used. The ability of reinitiation in vitro (by using aurintricarboxylic acid) decreased after ischemia, suggesting a failure in the synthetic machinery at the initiation level. Eukaryotic initiation factor 2 (eIF-2) presented almost basal activity and levels after 30-minute normothermic ischemia, and the amount of phosphorylated eIF-2 alpha in these samples, as well as in sham-control samples, was undetectable. The decrease in the levels of phosphorylated initiation factor 4E (eIF-4E) after 30-minute ischemia (from 32% to 16%) could explain, at least partially, the impairment of initiation during transient cerebral ischemia. After reperfusion, eIF-4E phosphorylation was almost completely restored to basal levels (29%), whereas the level of phosphorylated eIF-2 alpha was higher (13%) than in controls and ischemic samples (both less than 2%). eIF-2 alpha kinase activity in vitro as measured by phosphorylation of endogenous eIF-2 in the presence of ATP/Mg2+, was higher in ischemic samples (8%) than in controls (4%). It seems probable that the failure of the kinase in phosphorylating eIF-2 in vivo during ischemia is due to the depletion of ATP stores. The levels of the double-stranded activated eIF-2 alpha kinase were slightly higher in ischemic animals than in controls. Our results suggest that the modulation of eIF-4E phosphorylation could be implicated in the regulation of translation during ischemia. On the contrary, phosphorylation of eIF-2 alpha, by an eIF-2 alpha kinase already activated during ischemia, represents a plausible mechanism for explaining the inhibition of translation during reperfusion.

Animals↗

PubMed1998

Lipid peroxidation and phospholipid composition in rat brain regions after ischemia and in early perfusion periods.

Lipid peroxidation products (LPPs) and phospholipid composition were studied in a model of four-vessel occlusion in rats in homogenates of cortex, striatum and hippocampus after 30 min forebrain ischemia and following 1, 5, 10, 15, 30 and 180 min of recirculation. Major modification of LPPs was found after shorter reperfusion time, 5 min in hippocampus and 15 min in cortex and striatum when compared to control, while a slight decrease in the level of LPPs in the striatum and hippocampus was detected after longer (30 and 180 min) intervals. However, significant decrease was found in the homogenates of cortex. The results obtained from enhanced iron-dependent peroxidation in homogenates of frontal and occipital cortex indicated marked susceptibility to lipid peroxidation in the tissue subjected to 30 min ischemia and after 15 min of recirculation. The level of DG + PA was significantly higher during ischemia in the striatum, while increased hydrolysis of PI and DG + PA concentrations in the cortex, PI and PE levels in the striatum and PE and PS in the hippocampus after 30 min of ischemia were found. After 15 min of reperfusion considerably higher degradation of almost all phospholipids was found within all brain regions studied. The irreversibility of changes in PS, PE and SM was noted in the hippocampus after longer reperfusion periods. Our results indicate that the correlation between the lipid peroxidat ion product formation and phospholipid hydrolysis does exist, and, moreover, early reperfusion period seems to be highly critical in the development of ischemia-reperfusion induced neuronal damage.

Animals↗

PubMed1998

[Changes in phospholipids after repeated induced sublethal spinal cord ischemia in rabbits].

BACKGROUND: Degradation of membrane bound phospholipids in CNS during ischaemia begins with extreme rapidity. Sublethal ischaemia influences ischaemic tolerance in the affected neurons and is stressful enough to induce neuronal changes such as postischaemic hypoperfusion, transient suppression of protein synthesis and induction of stress (HSP) proteins. It seems, that the nature of factors responsible for ischaemic tolerance may involve the activation of multiple different systems. MAIN PURPOSE: The aim of this study was to investigate the changes of phospholipids in gray matter regions of spinal cord following sublethal ischaemia repeated in long intervals of reperfusion. METHODS: Male rabbits, weight range 2.5-3.5 kg were used in the experiment. They were divided in following groups : 1. control animals; 2. animals subjected to 25 min ischaemia; 3. animals subjected to 25 min ischaemia and 3 h of reperfusion; 4. animals subjected to sublethal (8-8-9 min) ischaemia repeated in long-lasting (8-8-24 h) intervals of reperfusion. Phospholipids were separated by thin layer chromatography, lipidic phosphorus was assessed spectrophotometrically. RESULTS: Sublethal ischaemia repeated in long-lasting intervals of reperfusion increased the concentration of phospholipids to control levels in all gray matter regions. The resynthesis in the dorsal horns, of PC and PE in the ventral horns and of PC in the intermediate zone. CONCLUSIONS: An excessive renewal of phospholipids after sublethal ischaemia repeated in longer intervals of reperfusion was most pronounced in the eh dorsal horns of the spinal cord and can be the result of many defensive cellular mechanisms.

Animals↗

PubMed1998

[Quantification of pericentral NADPH-diaphorase neurons in the spinal cord of rabbits].

BACKGROUND: The freely diffusible radical nitric oxide is generated by nitric oxide synthase, and is bioregulatory molecule that functions as a major neurotransmitter. Constitutive nitric oxide synthase exhibits NADPH-diaphorase activity that can be demonstrated histochemically. OBJECTIVE: The purpose of the present investigation was to characterize and determine number of NADPH-diaphorase positive neurons around the central canal in all segments of the rabbit spinal cord. METHODS: Rabbits Chinchilla were used in this experiment. After intracardiac perfusion the spinal cords were removed, cut into slices and histochemical analysis of NADPH-diaphorase activity was performed. Sections were evaluated by using light microscope. RESULTS: NADPH-diaphorase positive pericentral neurons were present in cervical, thoracic, lumbar; sacral and coccygeal segments. They differed in the shape of their bodies and in length and branching of their processes. The main differentiation was observed in their number depending on the place of localisation. The highest number of these NADPH-diaphorase positive neurons was in sacral part (6 in average), the lowest one was noticeable in thoracic spinal cord (1-2 in average). CONCLUSION: Thus, our study suggests that pericentral neurons of the rabbit spinal cord which are capable of synthesizing nitric oxide, differs in number amount depending on the place of their localization in each spinal cord segments. (Tab. 2, Fig. 9, Ref. 21.)

Animals↗

PubMed1997

Spinal cord gray matter layers rich in NADPH diaphorase-positive neurons are refractory to ischemia-reperfusion-induced injury: a histochemical and silver impregnation study in rabbit.

Silver impregnation analysis of neuronal damage and concurrent histochemical characterization of NADPH diaphorase-positive neuronal pools in the rabbit lumbosacral segments was performed during and after transient spinal cord ischemia. Strongly enhanced staining of NADPH diaphorase-positive neurons and their processes appeared in the superficial dorsal horn (laminae I-III), the pericentral region (lamina X) of lower lumbar segments, the lateral collateral pathway, and mainly in neurons of the sacral parasympathetic nucleus in the S2 segment at the end of 40 min of abdominal aorta ligation or 1 day after reperfusion. Despite the development of extensive neuronal degeneration in the central gray matter (laminae IV-VII) between 1 and 4 days after ischemia, a number of nonnecrotizing neurons localized in the areas corresponding with the distribution of NADPH diaphorase-positive neurons was detected, suggesting a selective resistance of these classes of neurons against transient ischemic insult. While the precise mechanism of the observed resistance is not known, it is postulated that region-specific synthesis of nitric oxide and its vasodilatatory effect during the period of incomplete spinal ischemia may account for the observed selective resistance of these spinal cord neurons to transient ischemia.

Animals↗

PubMed1997

Neuroprotective effect of graded postischemic reoxygenation in spinal cord ischemia in the rabbit.

Early ischemia/reperfusion-induced changes of four phospholipid compounds bound to the inner cell membrane leaflet, i.e., phosphatidic acid, inositol phospholipids, serine phospholipids, and ethanolamine plasmalogens, were studied in a model of spinal cord ischemia in the rabbit during normoxic and graded postischemic reoxygenation. Light and electron microscopic analysis after normoxic reoxygenation disclosed neuronal membrane argyrophilia of the interneuronal pool located in lamina VII of L4-L6 segments. The number of small neurons (10-25 microm in diameter) affected by somatodendritic argyrophilia was greatly reduced, and concomitantly the ultrastructure of the endoplasmic reticulum, mitochondria, and Golgi complexes remained almost undamaged when graded postischemic reoxygenation had been applied. A statistically significant increase of phosphatidylserine and ethanolamine plasmalogen levels, and a decrease of phosphatidic acid, were detected after a short-lasting graded postischemic reoxygenation. The formation of thiobarbituric acid-reactive substances was significantly reduced during 60 min of graded postischemic reoxygenation and remained close to control or ischemic levels. The present data indicate that graded postischemic reoxygenation, which is considered to be neuroprotective, can prevent neuronal argyrophilia and the development of reperfusion-induced alterations of organelles. Moreover, reoxygenation can positively modify ischemia-induced changes of some membrane-bound phospholipids.

Animals↗

PubMed1997

Regional distribution of phospholipids and polyphosphatidyl inositides in the rabbit's spinal cord.

The plasticity of the membrane phospholipids in general and stimulated phosphoinositides turnover in particular are the subjects in a variety of neural paradigms studying the molecular mechanisms of neuronal changes under normal and pathological conditions. The regional modifiability of phospholipids (SM, PC, PS, PI, PA + DG, PE), polyphosphatidylinositides (PI, PIP, PIP2) and diacylglycerol-dependent incorporation of CDP-choline into phosphatidylcholine in the gray matter, white matter, dorsal horns, intermediate zone and ventral horns of the rabbit's spinal cord was studied. We have found 1. a significant increase in the concentration of SM, PC, PS, DG + PA and PE in the white matter in comparison to the gray one, 2. the highest concentration of the outer membrane leaflet-bound phospholipids in the dorsal horns and the inner membrane phospholipids in the intermediate zone in comparison to the gray matter, 3. a substantial amount of labeled polyphosphatidylinositides (poly-PI(s)) in the spinal cord white matter with descending order PIP > PI > PIP2, 4. similar incorporation of myo-2-[3H]inositol into all poly-PI(s) in ventral horns and intermediate zone, but a different, lower incorporation into PI and PIP and higher into PIP2 in the dorsal horns, 5. higher diacylglycerol-dependent incorporation of CDP-choline into PC in the regionally undivided gray matter than in the white matter taken as a whole, 6. the high proportion of diacylglycerol-dependent incorporation of CDP-choline into PC in both the ventral and dorsal horns, whereas that in the intermediate zone remained low.

Animals↗

PubMed1996

Ischemia-reperfusion injury in the spinal cord of rabbits strongly enhances lipid peroxidation and modifies phospholipid profiles.

The effect of spinal cord ischemia (10, 20, and 40 min) and post-ischemic reperfusion (10, 30, and 60 min) on lipid peroxidation and phospholipids was investigated. Spinal cord ischemia was accompanied by lipolytic processes with significant changes in concentration of lipid peroxidation products (LPP). Reestablishment of the blood supply after 10 min ischemia was accompanied by significantly increased levels of thiobarbituric acid reactive substances (TBA-RS) after 10 and 30 min of reperfusion. Following 20 and 40 min ischemia a significant increase was observed at all reperfusion periods. Ischemia itself significantly reduced the concentration of phosphatidyl inositol (IP), phosphatidyl ethanolamine (EP) and ethanolamine plasmalogens (Epls). Significant changes were observed in concentration of phosphatidyl serine (SP) too, but only after 20 and 40 min of ischemia. The concentration of phosphatidic acid (PA) was significantly reduced only after 10 min of ischemia. The onset of reperfusion after ischemia was accompanied by a diverse pattern of changes in PA, IP, Epls and SP, while the concentration of EP remained at the above mentioned ischemic intervals.

Animals↗

PubMed1996

Ischemic damage in the hippocampus: a silver impregnation and immunocytochemical study in the rat.

Wistar rats were subjected to transient forebrain ischemia for 30 min. After a survival period of two to three days their brains were fixed and sections were processed for Nauta suppressive method (26) to study postischemic degenerative changes and for glial fibrillary acidic protein (GFAP) to study glial reaction. After two days somatodendritic argyrophilia was evident in the CA1a and CA4 areas. The somata and dendrites of CA1 a pyramidal neurons were intensely argyrophilic, and a clear border zone which separated these neurons from undamaged CA1b neurons was detected. In the CA4 area a few degenerating, probably mossy cells were found. Neuronal degeneration then proceeded rapidly during a 72 h survival period, when the somata and dendrites of complete CA1 and CA2 pyramidal cells became intensively argyrophilic. The area of CA4 was full of degenerated neurons, but the CA3 neurons remained intact. Postischemic glial changes were observed after 48h survival. The rostral part of CA1a area contained a higher concentration of astrocytes in the dendritic layer as well as in the pyramidal layer. These astrocytes revealed features of reactive astrocytes. An intense GFAP immunoreactivity with heavily stained astrocytic figures appeared in the CA2, CA3 dendritic layers, stratum molecular of the DG and hilus. The central region of CA4 area contained various vacuoles with clearly stained astrocytes. By 72 h after ischemia the tissue structure changed in all areas since the pyramidal layer contained shrunken neurons and large vacuoles. The GFAP immunoreactivity in the hippocampus was the same or even higher as observed after two days postischemia, but the astrocytes were seen more closely in the relation with the pyramidal cell layer.

Animals↗

PubMed1995

Multiple protracted cauda equina constrictions cause deep derangement in the lumbosacral spinal cord circuitry in the dog.

Neuropathological changes of the neuronal pools and spinal cord circuitry in the lumbosacral segments were studied in a canine model of multiple protracted cauda equina constrictions. Anterograde degeneration of all sacrococcygeal and L7 dorsal root fibers was detected in S1-S3 and lower lumbar segments. A narrow degenerated gracile fascicle was found in all thoracic and cervical segments terminating in the gracile nucleus. Transneuronal degeneration of middle-sized and large neurons, located in S1-S3 and sporadically in L7 segments, was noted. Identical transneuronal degeneration was seen in a group of small neurons located in the ventralmost part of lamina VII in S1-S3 segments. Simultaneously, a terminal degeneration was detected in the lateral cervical nucleus and in the ventral posterior lateral nucleus of the ventrobasal thalamic complex. Concomitantly, a fully developed retrograde degeneration affecting motoneurons in the ventrolateral portion of the anterior horn in S1-S3 segments appeared.

Animals↗

PubMed1995

Effect of prolonged hyperventilation on ischemic injury of neurons after global brain ischemia in the dog.

The influence of prolonged postischemic hyperventilation was studied in the model of global brain ischemia produced by 15 min cardiac arrest in dogs with 8 h recirculation. Histopathological examination of neuronal damage using silver impregnation showed the presence of numerous heavy argyrophylic neurons in the striatum and CA2 hippocampal subfield after 8 h of normoxic reperfusion. In dogs with prolonged 8 h postischemic hyperventilation a reduction in the occurrence of argyrophylic neurons in the striatum and their significant decrease in the hippocampal area were found. Electron microscopic study was performed to characterize the effect of respiratory alkalosis on the ultrastructural changes in neurons and correlate them with the results of silver impregnation. Ultrastructural analysis after the cardiac arrest without recirculation did not reveal the presence of dark neurons within the striatal and hippocampal areas. Neuronal alterations included a decrease in endoplasmic reticulum, mitochondrial swelling and a mild chromatin clumping. After 8 h of normoxic reperfusion many dark, shrinked neurons containing perinuclear clusters of clear vesicles were found. In hyperventilated animals the occurrence of dark neurons with extensive perineuronal edema was substantially reduced in the CA2 subfield. The effect of hyperventilation on postischemic calcium overload is discussed.

Animals↗