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W A Pulsinelli

Publications and source records attributed to W A Pulsinelli.

At least 37 records · Page 2Linked to original sources
PubMed1992

Failure of GM1 ganglioside to influence outcome in experimental focal ischemia.

BACKGROUND AND PURPOSE: Reports of improved short-term (less than 72 hours) outcome in experimental models of mechanical and ischemic central nervous system injury suggest that exogenous ganglioside administration may confer a protective effect on neural tissue. We studied the effect of the monosialoganglioside GM1 on cerebral infarction and edema in spontaneously hypertensive rats subjected to permanent focal cerebral ischemia. METHODS: GM1 or normal saline was injected intramuscularly once a day for 3 days before and 30 and 120 minutes after occlusion of the right middle and common carotid arteries. Following a 24-hour survival period, the volume of infarction was measured by computer-assisted image analysis, and the extent of edema was assessed by measurements of tissue water content and hemispheric volume. RESULTS: Infarct volume was similar among the GM1-treated (n = 10) and saline-treated (n = 10) rats (212 +/- 10 versus 220 +/- 13 microliters, respectively). In a second series of experiments, the brain water content and edema volume of the ischemic right hemisphere in GM1-treated rats (n = 10) did not differ from saline-treated controls (n = 10). CONCLUSIONS: GM1 ganglioside does not effectively reduce cerebral infarction caused by permanent focal ischemia.

Animals↗
PubMed1991

Blockade of the AMPA receptor prevents CA1 hippocampal injury following severe but transient forebrain ischemia in adult rats.

The cytoprotective effect of NBQX, a selective AMPA receptor antagonist, was tested following 10 min of severe forebrain ischemia using the 4-vessel occlusion model. Immediately, and at 15 and 30 min following reperfusion, adult Wistar rats received intraperitoneal injections of either saline (n = 5), 1 mg lithium chloride (n = 17) or 30 mg/kg of the lithium salt of NBQX (n = 18). In saline-treated animals 82 +/- 12% of CA1 hippocampal neurons were lost. Of those treated with lithium 70 +/- 23% were injured, while those given NBQX sustained only 40 +/- 34% CA1 necrosis (P less than 0.01). Twelve of 18 NBQX-treated animals had less than 30% CA1 injury as compared with 1 of 17 lithium-treated animals. The AMPA receptor may play a more important role than the NMDA receptor in selective ischemic necrosis of hippocampal neurons.

Animals↗
PubMed1991

Dynamics of interstitial and intracellular pH in evolving brain infarct.

We examined the relationships between intracellular pH (pHi) and interstitial pH (pHe) in a rat model of focal ischemia. Interstitial pH was measured with pH-sensitive microelectrodes, and the average tissue pH was measured with the [14C]dimethadione method in rats subjected to occlusion of the right middle cerebral and common carotid arteries (MCA-CCAO). In normal cortex, pHe and pHi were 7.24 +/- 0.97 and 7.01 +/- 0.13 (means +/- SD, n = 6), respectively. In the ischemic cortex, pHe fell to 6.43 +/- 0.13, whereas pHi decreased only to 6.86 +/- 0.11 (n = 5) 1 h after MCA-CCAO. After 4 h of ischemia, the pHe was 6.61 +/- 0.09 and pHi was 6.62 +/- 0.20 (n = 4). Treatment with glucose before ischemia markedly lowered the pHe (5.88 +/- 0.17) but not pHi (6.83 +/- 0.03, n = 4) measured 1 h after ischemia. In the ischemic cortex of animals made hypoglycemic by pretreatment with insulin, neither pHe (7.25 +/- 0.06) nor pHi (6.99 +/- 0.13, n = 4) decreased. The demonstrated difference in pHi and pHe indicates that some cells remained sufficiently functional to maintain a plasma membrane gradient of protons within the evolving infarct. If the calculated pHi values accurately reflect the true pHi of cells within zones of severe focal ischemia, then cerebral infarction can proceed at pHi levels not greatly altered from normal.

Animals↗
PubMed1991

Acid-induced death in neurons and glia.

Lactic acidosis has been proposed to be one factor promoting cell death following cerebral ischemia. We have previously demonstrated that cultured neurons and glial are killed by relatively brief (10 min) exposure to acidic solutions of pH less than 5 (Goldman et al., 1989). In the present series of experiments, we investigated the relationship between changes in intracellular pH (pHi) and cellular viability. pHi was measured using fluorescent pH probes and was manipulated by changing extracellular pH (pHe). Homeostatic mechanisms regulating pHi in neurons and glia were quickly overwhelmed: neither neurons nor glial cells were able to maintain baseline pHi when incubated at pHe below 6.8. Neuronal and glial death was a function of both the degree and the duration of intracellular acidification, such that the LD50 following timed exposure to HCl increased from pH, 3.5 for 10-min acid incubations to pHi 5.9 for 2-hr exposures and pHi 6.5 for 6-hr exposures. Replacement of HCl with lactic acid raised the LD50 to pHi 4.5 for 10-min acid exposures, but did not change the LD50 for longer exposures: pHi measurements concurrent with extracellular acidification suggested that the greater cytotoxicity of lactic acid relative to that of HCl was caused by the more rapid intracellular acidification associated with lactic acid. The onset of death after exposure to moderately acidic solutions was delayed in some cells, such that death of the entire cell population became evident only 48 hr after acid exposure. During this latency period, cellular viability indices and ATP levels fell in parallel.(ABSTRACT TRUNCATED AT 250 WORDS)

Acids↗
PubMed1991

The N-methyl-D-aspartate antagonist, MK-801, fails to protect against neuronal damage caused by transient, severe forebrain ischemia in adult rats.

The neuroprotective effects of dizocilipine maleate (MK-801), a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor/channel, were tested in the 4-vessel occlusion rat model of forebrain ischemia. Adult Wistar rats, treated intraperitoneally with MK-801 or saline using several different treatment paradigms were subjected to 5 (n = 208) or 15 (n = 62) min of severe, transient forebrain ischemia. In saline-treated animals, 15 min of ischemia (n = 13) produced extensive and consistent loss of pyramidal neurons in the CA1 zone of hippocampus. The degree and distribution of cell loss were not reduced by single dose preischemic administration of MK-801 at 1 (n = 7), 2.5 (n = 4), or 5 mg/kg (n = 8). In other animals subjected to 15 min of forebrain ischemia, multiple doses of MK-801 (5, 2.5, and 2.5 mg/kg) given immediately and at approximately 8 and 20 hr after cerebral reperfusion (n = 5) did not alter CA1 injury compared to saline-treated controls (n = 5). Five minutes of forebrain ischemia in saline-treated animals, (n = 82) resulted in significantly fewer (p less than 0.001) dead CA1 pyramidal cells and a greater variance compared to animals subjected to 15 min of ischemia. Power analysis of the preliminary saline-treated animals subjected to 5 min of ischemia (n = 22) indicated that 60 animals per group were necessary to detect a 15% difference between MK-801 and vehicle-treated groups. Multidose treatment with MK-801 (1 mg/kg) given 1 hr prior to 5 min of ischemia (n = 60) and again at approximately 8 and 16 hr after recirculation failed to attenuate hippocampal injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Septo-hippocampal deafferentation protects CA1 neurons against ischemic injury.

Excessive synaptic excitation caused by transient cerebral ischemia has been proposed to explain the greater vulnerability of specific neuronal populations to ischemic injury. We tested this hypothesis in rats by cutting, alone or in combination, the afferent fibers that travel in the fimbria/fornix, the perforant, or the Schäffer collateral pathways and innervate the right CA1 hippocampus. Seven to twelve days later the animals were subjected to 30 min of reversible forebrain ischemia. Irreversible damage to the CA1 neurons was assessed with the light microscope after 70-120 h of cerebral reperfusion. The left, unlesioned hippocampus served as a control. Simultaneous cutting of the 3 major afferent pathways significantly reduced CA1 neuronal damage compared to the unlesioned side (P less than 0.001) or to sham-lesioned controls (P less than 0.001). Selective lesions of the fimbria/fornix but not the perforant or the Schäffer collateral pathways also protected against ischemic CA1 damage. These data indicate that afferent fiber input modulates hippocampal damage caused by ischemia, but they are inconsistent with the hypothesis that excitatory afferent fibers, travelling in either the perforant or the Schäffer collateral pathways alone, play a major role. Neurotransmitters, other than those activating excitatory amino acid receptors or yet-to-be-identified synaptic events, may be invoked to explain the spatial and temporal sensitivity of hippocampal CA1 neurons to ischemia.

Animals↗
PubMed1990

Posthoc phosphorylation of proteins derived from ischemic rat hippocampus, striatum and neocortex.

Disruption of the brain's protein phosphorylation system by ischemia may cause irreversible metabolic and structural alterations leading eventually to cell death. To examine the effect of ischemia on the phosphorylation state of brain proteins, tissue homogenates derived from the hippocampus, striatum and neocortex of normal rats and rats subjected to severe forebrain ischemia were phosphorylated with [gamma-32P]ATP. The phosphorylated proteins were separated by two-dimensional polyacrylamide gel electrophoresis and changes were assessed by autoradiography. Cerebral ischemia caused marked alterations of the phosphorylation state of many brain proteins; phosphorylation of some proteins was increased while phosphorylation of others was decreased. Despite differences in the sensitivity of the hippocampus, striatum and neocortex to ischemic injury the direction and approximate magnitude of protein phosphorylation changes caused by ischemia were similar in all three regions. Since the pattern of protein phosphorylation in the ischemia-vulnerable hippocampus was identical to that in the ischemia-resistant paramedian neocortex we conclude that abnormalities of protein phosphorylation may be necessary for ischemic injury to neurons but none are sufficient to explain the selective vulnerability of certain brain regions to ischemic damage.

Animals↗
PubMed1990

Continuous nimodipine treatment attenuates cortical infarction in rats subjected to 24 hours of focal cerebral ischemia.

Focal cerebral infarction and edema were measured in rats (Wistar, Fisher 344, and spontaneously hypertensive strains) pretreated with nimodipine (2 micrograms/kg/min i.v.) or its vehicle and subjected to the tandem occlusion of the middle cerebral and common carotid arteries. Animals awoke from anesthesia 10-15 min after onset of ischemia and continued to receive treatment over a 24-h survival period. Cortical infarction and edema were quantified by image analysis of frozen brain sections processed for histology. Nimodipine-treated rats developed 20-60% smaller cortical infarct volumes than controls (p less than 0.002). Cortical edema was reduced proportionately to the decrease in infarct volume and constituted approximately 36% of the infarct volume. Nimodipine caused a mild hypotensive response that did not aggravate ischemic brain damage. The results indicate that continuous nimodipine treatment, started before induction of focal cerebral ischemia, can attenuate ischemic brain damage and edema as late as 24 h after the onset of ischemia.

Animals↗
PubMed1990

Nimodipine pretreatment improves cerebral blood flow and reduces brain edema in conscious rats subjected to focal cerebral ischemia.

The effect of nimodipine pretreatment on CBF and brain edema was studied in conscious rats subjected to 2.5 h of focal cortical ischemia. An infusion of nimodipine (2 micrograms/kg/min i.v.) or its vehicle, polyethylene glycol 400, was begun 2 h before the ischemic interval and was continued throughout the survival period. Under brief halothane anesthesia, the animals' right middle cerebral and common carotid arteries were permanently occluded, and 2.5 h later, they underwent a quantitative CBF study ([14C]iodoantipyrine autoradiography followed by Quantimet 970 image analysis). Nimodipine treatment improved blood flow to the middle cerebral artery territory without evidence of a "vascular steal" and reduced the volume of the ischemic core (cortex with CBF of less than 25 ml/100 g/min) and accompanying edema by approximately 50% when compared with controls (p = 0.006 and 0.0004, respectively). Mild hypotension induced by nimodipine did not aggravate the ischemic insult. The ischemic core volumes, however, were 50-75% smaller than the 24-h infarct volumes generated in a similar paradigm that demonstrated 20-30% infarct reduction with continuous nimodipine treatment. These results suggest that nimodipine pretreatment attenuates the severity of early focal cerebral ischemia, but that with persistent ischemia, cortex surrounding the ischemic core undergoes progressive infarction and the early benefit of nimodipine treatment is only partly preserved.

Animals↗
PubMed1990

Hypothermia but not the N-methyl-D-aspartate antagonist, MK-801, attenuates neuronal damage in gerbils subjected to transient global ischemia.

Several laboratories have reported a significant reduction of ischemia-induced injury to hippocampal neurons in rodents treated with competitive and noncompetitive N-methyl-D-aspartate (NMDA) receptor-channel antagonists. This study examined the effects of the noncompetitive antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) in Mongolian gerbils subjected to 5 min of bilateral carotid artery occlusion. In adult female gerbils, single doses of MK-801 injected 1 hr prior to ischemia significantly (p less than 0.01) reduced damage to CA1 hippocampal neurons. However, the drug rendered the postischemic animals comatose and hypothermic for several hours compared with the saline-treated animals. In subsequent experiments, animals pretreated with MK-801 and maintained normothermic during and after forebrain ischemia demonstrated no amelioration of hippocampal damage. Gerbils not treated with MK-801, but kept hypothermic in the postischemic period to approximately the same degree (34.5 degrees C) and duration (8 hr) as was induced by MK-801 therapy showed significant (p less than 0.01) protection of CA1 neurons against ischemia. The neuroprotective activity of MK-801 against transient global ischemia appears to be largely a consequence of postischemic hypothermia rather than a direct action on NMDA receptor-channels.

Animals↗
PubMed1989

The effects of extracellular acidosis on neurons and glia in vitro.

Cerebral lactic acid, a product of ischemic anaerobic glycolysis, may directly contribute to ischemic brain damage in vivo. In this study we evaluated the effects of extracellular acid exposure on 7-day-old cultures of embryonic rat forebrain. Mixed neuronal and glial cultures were exposed to either lactic or hydrochloric acid to compare the toxicities of relatively permeable and impermeable acids. Neurons were relatively resistant to extra-cellular HCl acidosis, often surviving 10-min exposures to pH 3.8. In the same cultures, immunochemically defined astrocytes survived 10-min HCl exposures to a maximum acidity of pH 4.2. Similarly, axonal bundles defasciculated in HCl-titrated media below pH 4.4, although their constituent fibers often survived pH 3.8. Cell death occurred at higher pH in cultures subjected to lactic acidosis than in those exposed to HCl. Over half of forebrain neurons and glia subjected for 10 min to lactic acidification failed to survive exposure to pH 4.9. Longer 1-h lactic acid incubations resulted in cell death below pH 5.2. The potent cytotoxicity of lactic acid may be a direct result of the relatively rapid transfer of its neutral protonated form across cell membranes. This process would rapidly deplete intracellular buffer stores, resulting in unchecked cytosolic acidification. Neuronal and glial death from extracellular acidosis may therefore be a function of both the degree and the rapidity of intracellular acidification.

Acidosis↗
PubMed1987

Retention of reference memory following ischemic hippocampal damage.

Retention of reference memory was evaluated in an animal model of cerebral ischemia. Rats were trained for 70 daily trials on an 8-arm radial maze with 5 arms baited, subjected to 30 minutes of forebrain ischemia, allowed to recover for 30 days, and then tested for an additional 50 trials. Post ischemic (PI) rats demonstrated normal retention of reference memory (p less than 0.05). Working memory was significantly impaired postoperatively (p less than 0.05). Morphologic analysis showed that PI rats had primary loss of pyramidal neurons in the CA1 region of hippocampus.

Animals↗
PubMed1987

Light and electron microscopic evaluation of hydrogen ion-induced brain necrosis.

Excessive accumulation of hydrogen ions in the brain may play a pivotal role in initiating the necrosis seen in infarction and following hyperglycemic augmentation of ischemic brain damage. To examine possible mechanisms involved in hydrogen ion-induced necrosis, sequential structural changes in rat brain were examined following intracortical injection of sodium lactate solution (pH 4.5), as compared with injections at pH 7.3. Following pH 7.3 injection, neuronal swelling developed between 1 and 6 h, but only a needle track wound surrounded by a thin rim of necrotic neurons and vacuolated neuropil was present 24 h after injection. In contrast, pH 4.5 injection produced neuronal necrosis as soon as 1 h after injection, followed by necrosis of astrocytes and intravascular thrombi at 3 and 6 h. Alterations common to both groups included vascular permeability to horseradish peroxidase, dilation of extracellular spaces, astrocyte swelling, capillary compression, and vascular stasis. These data suggest that neurons, astrocytes, and endothelia can be directly damaged by increased acid in the interstitial space. Lethal injury initially appeared to affect neurons, while subsequent astrocyte necrosis and vascular occlusion may damage tissue by secondary ischemia.

Animals↗
PubMed1987

Hydrogen ions kill brain at concentrations reached in ischemia.

Elevation of brain glucose before the onset of nearly complete ischemia leads to increased lactic acid within brain. When excessive, such acidosis may be a necessary factor for converting selective neuronal loss to brain infarction from nearly complete ischemia. To examine the potential neurotoxicity of excessive lactic acid concentrations, we microinjected (0.5 microliter/min) 150 mM sodium lactate solutions (adjusted to 6.50-4.00 pH) for 20 min into parietal cortex of anesthetized rats. Interstitial pH (pH0) was monitored with hydrogen ion-selective microelectrodes. Animals were allowed to recover for 24 h before injection zones were examined with the light microscope. Injectants produced brain necrosis in a histological pattern resembling ischemic infarction only when pH0 was less than or equal to 5.30. Nonlethal injections showed only needle tract injuries. Abrupt deterioration of brain acid-base homeostatic mechanisms correlated with necrosis since pH0 returned to baseline more slowly after lethal tissue injections than after nonlethal ones. The slowed return of pH0 to baseline after the severely acidic injections may reflect altered function of plasma membrane antiport systems for pH regulation and loss of brain hydrogen ion buffers.

Acidosis↗
PubMed1987

Altered mitochondrial respiration in selectively vulnerable brain subregions following transient forebrain ischemia in the rat.

Mitochondrial respiratory function, assessed from the rate of oxygen uptake by homogenates of rat brain subregions, was examined after 30 min of forebrain ischemia and at recirculation periods of up to 48 h. Ischemia-sensitive regions which develop extensive neuronal loss during the recirculation period (dorsal-lateral striatum, CA1 hippocampus) were compared with ischemia-resistant areas (paramedian neocortex, CA3 plus CA4 hippocampus). All areas showed reductions (to 53-69% of control) during ischemia for oxygen uptake rates determined in the presence of ADP or an uncoupling agent, which then recovered within 1 h of cerebral recirculation. In the ischemia-resistant regions, oxygen uptake rates remained similar to control values for at least 48 h of recirculation. After 3 h of recirculation, a significant decrease in respiratory activity (measured in the presence of ADP or uncoupling agent) was observed in the dorsal-lateral striatum which progressed to reductions of greater than 65% of the initial activity by 24 h. In the CA1 hippocampus, oxygen uptake rates were unchanged for 24 h, but were significantly reduced (by 30% in the presence of uncoupling agent) at 48 h. These alterations parallel the development of histological evidence of ischemic cell change determined previously and apparently precede the appearance of differential changes between sensitive and resistant regions in the content of high-energy phosphate compounds. These results suggest that alterations of mitochondrial activity are a relatively early change in the development of ischemic cell death and provide a sensitive biochemical marker for this process.

Adenosine Diphosphate↗
PubMed1987

Inhibition of lactate production in rat brain extracts and synaptosomes by 3-[4-(reduced 3-pyridine aldehyde-adenine dinucleotide)]-pyruvate.

In basic solutions, pyruvate enolizes and reacts (through its 3-carbon) with the 4-carbon of the nicotinamide ring of NAD+, yielding an NAD-pyruvate adduct in which the nicotinamide ring is in the reduced form. This adduct is a strong inhibitor of lactate dehydrogenase, presumably because it binds simultaneously to the NADH and pyruvate sites. The potency of the inhibition, however, is muted by the adduct's tendency to cyclize to a lactam. We prepared solutions of the pyruvate adduct of NAD+ and of NAD+ analogues in which the -C(O)NH2 of NAD+ was replaced with -C(S)NH2, -C(O)CH3, and -C(O)H. Of the four, only the last analogue, 3-[4-(reduced 3-pyridine aldehyde-adenine dinucleotide)]-pyruvate (RAP) cannot cyclize and it was found to be the most potent inhibitor of beef heart and rat brain lactate dehydrogenases. The inhibitor binds very tightly to the NADH site (Ki approximately 1 nM for the A form). Even at high concentrations (20 microM), RAP had little or no effect on rat brain glyceraldehyde-3-phosphate, pyruvate, alpha-ketoglutarate, isocitrate, soluble and mitochondrial malate, and glutamate dehydrogenases. The glycolytic enzymes, hexokinase and phosphofructokinase, were similarly unaffected. RAP strongly inhibited lactate production from glucose in rat brain extracts but was less effective in inhibiting lactate production from glucose in synaptosomes.

Animals↗
PubMed1987

Delayed hippocampal damage in humans following cardiorespiratory arrest.

Transient ischemia in animals produces delayed cell death in vulnerable hippocampal neurons. To see if this occurs in humans, we reexamined brain slides from all patients with anoxic-ischemic encephalopathy and a well-documented cardiorespiratory arrest. Eight patients dying 18 hours or less after cardiac arrest had minimal damage in hippocampus and moderate damage in cerebral cortex and putamen. Six patients living 24 hours or more had severe damage in all four regions. The increase in damage with time postarrest was significant only in the hippocampus. Delayed hippocampal injury now documented in humans provides a target for possible therapy that can be initiated after cardiopulmonary resuscitation.

Adult↗