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W Pulsinelli

Publications and source records attributed to W Pulsinelli.

17 recordsLinked to original sources
PubMed1991

Temporal thresholds for neocortical infarction in rats subjected to reversible focal cerebral ischemia.

We investigated the temporal threshold for focal cerebral infarction in the spontaneously hypertensive rat. The right middle cerebral artery and common carotid artery were occluded for 0, 1, 2, 3, 4, or 24 hours, and all the animals were sacrificed 24 hours after the onset of ischemia. Cortical infarct volumes and edema volumes were quantified in serial frozen sections of hematoxylin and eosin-stained tissue using image analysis. Upon occlusion, blood flow in the core of the ischemic zone, measured with laser-Doppler flowmetry, fell to a mean +/- standard deviation of 21 +/- 7% of the preocclusion baseline value (n = 26). During the first hour of ischemia, blood flow in the densely ischemic zone rose to 27 +/- 8% of baseline (n = 25). Release of the middle cerebral artery and common carotid artery occlusions rapidly restored cortical blood flow to 213 +/- 83% of baseline (n = 21). Focal ischemia of 1 hour's duration caused little or no infarction, while ischemic intervals of 2 and 3 hours produced successively larger volumes of infarcted cortex. Ischemic intervals of 3-4 hours' duration followed by approximately 20 hours of recirculation yielded infarct volumes that were not significantly different from those after 24 hours of permanent focal ischemia. The results indicate that 3-4 hours of focal cerebral ischemia in this rat model is sufficient to attain maximal infarction and suggest that recirculation or pharmacological interventions after this time will provide little benefit.

Analysis of Variance↗
PubMed1990

Pre- and post-treatment with MK-801 but not pretreatment alone reduces neocortical damage after focal cerebral ischemia in the rat.

The effect of treatment with the potent, non-competitive NMDA receptor-channel antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a, d] cyclohepten-5,10-imine maleate (MK-801) on ischemia-induced brain damage was studied in a well-characterized model of focal neocortical infarction in spontaneously hypertensive rats. Anesthesia exposure was minimized to the surgical procedure and the infarcts were allowed to mature over a 24-h period. Pretreatment with 5 mg/kg i.p. MK-801 (n = 11 control, n = 12 treated animals) 30 min before induction of focal cerebral ischemia had no statistically significant influence on infarct volumes. However, pre- and post-treatment with MK-801 5 mg/kg i.p. 30 min before induction of ischemia and 2.5 mg/kg each at 8 and 16 h after onset of ischemia, reduced infarct volumes in two separate studies by 29% (investigator J.T., n = 5 control and n = 7 treated animals) and 20% (investigator U.D., n = 8 control and n = 8 treated animals), respectively. The combined reduction in infarct volume in MK-801-treated animals for both investigators was 23% (P = 0.016, ANOVA). The findings indicate a smaller neuroprotective effect of MK-801 in spontaneously hypertensive rats subjected to focal ischemia than in previous reports using normotensive animals.

Animals↗
PubMed1990

Dicarboxy-dichlorofluorescein: a new fluorescent probe for measuring acidic intracellular pH.

Derivatives of fluorescein sensitive to pH are extensively utilized for the determination of intracellular pH (pHi). Available dyes have pKa values of approximately 7.0, and are not well suited for measuring acidic pHi. We examined the fluorescein derivative, 5 (and 6)-carboxy-2',7'-dichlorofluorescein (CDCF) for its potential in the microspectrofluorometric measurement of pHi during acidic conditions. CDCF showed intense fluorescence and pH sensitivity near its "effective" pKa value of 4.2, using a 495/440 nm dual excitation wave-length ratio method. Protein interactions caused fluorescence ratio deviations which were most pronounced at the extremes of pH, whereas calcium and magnesium concentrations had little effect on the fluorescent ratio intensity. Intracellular calibration performed using nigericin in the presence of high potassium eliminated the need to correct for protein interactions, and the ratio method minimized any variations due to dye concentration differences or instrument fluctuation. Intracellular retention of the dye was high, and 95% of the initial signal remained after 1 h. Fluorescence bleaching was 14.5% after 1 h of continuous excitation and cell survival was not affected by dye loading. We conclude that CDCF is an excellent intracellular pH indicator in the pH range of 4-5.

Acids↗
PubMed1990

Autoregulation of cerebral blood flow in experimental focal brain ischemia.

The relationship between systemic arterial pressure (SAP) and neocortical microcirculatory blood-flow (CBF) in areas of focal cerebral ischemia was studied in 15 spontaneously hypertensive rats (SHRs) anesthetized with halothane (0.5%). Ischemia was induced by ipsilateral middle cerebral artery/common carotid artery occlusion and CBF was monitored continuously in the ischemic territory using laser-Doppler flowmetry during manipulation of SAP with I-norepinephrine (hypertension) or nitroprusside (hypotension). In eight SHRs not subjected to focal ischemia, we demonstrated that 0.5% halothane and the surgical manipulations did not impair autoregulation. Autoregulation was partly preserved in ischemic brain tissue with a CBF of greater than 30% of preocclusion values. In areas where ischemic CBF was less than 30% of preocclusion values, autoregulation was completely lost. Changes in SAP had a greater influence on CBF in tissue areas where CBF ranged from 15 to 30% of baseline (9% change in CBF with each 10% change in SAP) than in areas where CBF was less than 15% of baseline (6% change in CBF with each 10% change in SAP). These findings demonstrate that the relationship between CBF and SAP in areas of focal ischemia is highly dependent on the severity of ischemia. Autoregulation is lost in a gradual manner until CBF falls below 30% of normal. In areas without autoregulation, the slope of the CBF/SAP relationship is inversely related to the degree of ischemia.

Animals↗
PubMed1990

Carnitine treatment for stroke in rats.

Changes in the concentrations of carnitine, long-chain acylcoenzyme A, and long-chain acylcarnitine in ischemic myocardium parallel those in ischemic brain. Since carnitine treatment reverses these changes and improves function in ischemic hearts, we examined whether carnitine given to rats before focal cerebral ischemia (produced by tandem right common carotid artery and middle cerebral artery occlusion) alters infarct volume in four separate experiments. Mannitol was used to control for the osmotic effect of carnitine on brain edema in one experiment. While carnitine was found to significantly decrease infarct volume compared with saline in one experiment (p less than 0.05, Student's t test), this result could not be replicated in the subsequent three experiments. Because the positive treatment effect was not reproducible despite similar experimental conditions, the result of the first experiment was attributed to a type I error. Mannitol also showed no significant effect on infarct volume. This study emphasizes the need for concurrent controls with each group of treated animals and the need for replicating the results of a single experiment when testing for drug efficacy in animal models of focal cerebral ischemia.

Animals↗
PubMed1990

Nimodipine posttreatment does not increase blood flow in rats with focal cortical ischemia.

We used laser-Doppler flowmetry to study the effect of nimodipine administered after the onset of focal cortical ischemia on regional cerebral blood flow in 16 halothane-anesthetized, mechanically ventilated Wistar rats. We selected the Wistar rats strain since it would provide a wide range of ischemia severities to test the vascular response to nimodipine. Laser-Doppler probes continuously recorded regional cerebral blood flow at two or three sites over the parietal cortex (dura intact) while brain temperature was regulated at 37 degrees C. Occlusion of the right middle cerebral and common carotid arteries reduced cerebral blood flow to a mean of 38% (range 13-77%) of baseline. Thirty minutes later, either 2 micrograms/kg/min nimodipine (n = 8) or its vehicle, polyethylene glycol 400 (n = 8), was administered by a continuous intravenous infusion. Over 60 minutes of treatment, both the nimodipine-treated and vehicle-treated groups showed a trivial (3%) mean increase in cerebral blood flow. Nimodipine failed to augment cerebral blood flow regardless of whether the cortex was severely, moderately, or mildly ischemic.

Animals↗
PubMed1989

Safety of metallic surgical clips in patients undergoing high-field-strength magnetic resonance imaging.

Use of metallic clips with ferromagnetic properties in patients undergoing a large variety of surgical procedures, and in particular, in coronary artery and other vascular reconstructions, has become increasingly popular. The safety of these commonly used surgical clips when subjected to high-intensity diagnostic magnetic resonance imaging fields is still debated. Commonly used hemostatic metallic clips manufactured by the Weck and US Surgical Corporations were tested in an in vitro system to assess their safety with regard to migration and displacement. The two tested hemostatic metallic clips proved safe and did not migrate or become dislodged when they underwent magnetic resonance imaging scans. This is in direct contrast to multiple cerebral aneurysm clips, also tested, which have highly ferromagnetic properties and were previously shown to migrate with disastrous results in patients undergoing diagnostic magnetic resonance imaging scans. This study supports the continued widespread use of small metallic hemostatic clips in the myriad of procedures in which they are presently used and illustrates the need for methods of evaluating such devices before they are clinically implanted.

Electromagnetic Fields↗
PubMed1989

Continuous measurement of cerebral cortical blood flow by laser-Doppler flowmetry in a rat stroke model.

Laser-Doppler flowmetry (LDF), a new method allowing instantaneous, continuous, and noninvasive measurements of microcirculatory blood flow in a small tissue sample, was evaluated for its accuracy in monitoring regional cerebral blood flow (rCBF) in the cortical microcirculation after focal cerebral ischemia. Wistar and spontaneously hypertensive rats (SHR, n = 19) were subjected to permanent occlusion of the middle cerebral and common carotid arteries. Absolute rCBF in a tissue sample of the ischemic hemisphere was measured autoradiographically with [14C]iodoantipyrine as a tracer and compared to rCBF measured by LDF. Additionally, the percent change in rCBF between baseline and ischemic values was compared for both methods. Absolute rCBF values recorded with LDF correlated poorly (r = 0.54) with [14C]iodoantipyrine measurements. In contrast LDF readings expressed as a percentage of ischemic vs. preocclusion readings (relative LDF readings) correlated very well (r = 0.91) with the percent change in [14C]iodoantipyrine measurements. We conclude that LDF does not provide accurate measurements of absolute rCBF values but this method allows accurate measurements of changes in rCBF due to induction of focal cerebral ischemia.

Animals↗
PubMed1988

Focal brain ischemia in the rat: methods for reproducible neocortical infarction using tandem occlusion of the distal middle cerebral and ipsilateral common carotid arteries.

This article describes a 3-year experience with focal neocortical ischemia in three rat strains. Multiple groups of adult Wistar (n = 50), Fisher 344 (n = 31), and spontaneously hypertensive (n = 72) rats were subjected to permanent occlusion of the distal middle cerebral (MCA) and ipsilateral common carotid arteries (CCA). Twenty-four hours later the animals were killed, and frozen brain sections were stained with hematoxylin and eosin to demarcate infarcted tissue. The infarct volume for each section was quantified with an image analyzer, and the total infarct volume was calculated with an iterative program that summed all interval volumes. Neocortical infarct volume was the largest and most reproducible in the spontaneously hypertensive rats (SHR). Statistical power analysis to project the numbers of animals necessary to detect a 25 or 50% change in infarct volume with alpha = 0.05 and beta = 0.2 revealed that only the SHR model was practical in terms of requisite animals: i.e., less than 10 animals per group. Tandem occlusion of the distal MCA and ipsilateral CCA in the SHR strain provides a surgically simple method for causing large neocortical infarcts with reproducible topography and volume. The interanimal variability in infarct volume that occurs even in the SHR strain dictates that randomized, concomitant controls are necessary in each study to ensure the accurate assessment of experimental manipulations or pharmacologic therapies.

Animals↗
PubMed1983

Increased binding of [3H]GABA to striatal membranes following ischemia.

Sodium-independent binding of [3H]gamma-aminobutyric acid ([3H]GABA) to membranes prepared from ischemic-damaged rat striatum was studied by kinetic and time-course analysis. Three days after 40 min of ischemia, [3H]GABA binding increased fourfold over control values. Scatchard analysis of the binding showed that ischemia significantly increased the affinity (KD) and the total number of binding sites (Bmax) for the high-affinity GABA receptor. These results support the conclusion that transient forebrain ischemia damages striatal GABAergic neurons.

Animals↗
PubMed1982

The response of GABAergic and cholinergic neurons to transient cerebral ischemia.

The vulnerability of striatal and hippocampal neurons to ischemia was studied by measuring the activity of neurotransmitter-related enzymes after transient forebrain ischemia in rats. Activities of glutamic acid decarboxylase (GAD) and choline acetyltransferase (CAT) were measured 6 h to 8 days after 20, 30 or 40 min of forebrain ischemia, as markers for GABAergic and cholinergic neurons respectively. Transient forebrain ischemia resulted in depression of striatal GAD activity while striatal CAT and hippocampal GAD activities were unaffected. Striatal GAD activity progressively decreased during the first 24 h postischemia and remained depressed 5--8 days later, suggesting irreversible damage to this population of neurons. The stability of striatal CAT and hippocampal GAD activity indicates that these cells were resistant to the present ischemic conditions.

Acetylcholine↗
PubMed1981

Brain dysfunction in mild to moderate hypoxia.

Hypoxia is commonly invoked to explain alterations in mental function, particularly in patients with cardiac pulmonary failure. The effects of acute graded hypoxia or higher integrative functions are well documented experimentally in man. Hypoxia in experimental animal models demonstrates that the pathophysiology is complex. In mild to moderate hypoxia, in contrast to severe hypoxia and to ischemia, the supply of energy for the brain is not impaired; cerebral levels of adenosine triphosphate (ATP) and adenylate energy charge are normal. In contrast, the turnover of several neurotransmitters is altered by mild hypoxia. For example, acetylcholine synthesis is reduced proportionally to the reduction in carbohydrate oxidation. This relationship holds in vitro and with several in vivo models of hypoxia. Pharmacologic and physiologic studies in man and experimental animals are consistent with acetylcholine having an important role in mediating the cerebral effects of mild hypoxia. These observations raise the possibility that treatments directed to cholinergic or other central neurotransmitter systems may benefit patients with cerebral syndromes secondary to chronic hypoxia.

Acetylcholine↗
PubMedDate not supplied

Hemorrhagic complications of thrombolytic therapy in experimental stroke.

Recent success with thrombolytic therapy for acute myocardial infarction has stimulated interest in its use for stroke. To determine the hemorrhagic potential of thrombolytic therapy in experimental cerebral infarction, we compared a group of tissue plasminogen activator-treated rabbits (n = 4) with 2 groups of streptokinase-treated rabbits (n = 6 in each), as well as with 3 groups of heparin-treated rabbits (n = 5 in each) and untreated controls (n = 12). Focal cerebral infarction was produced in rabbits by occlusion of the right common carotid and middle cerebral arteries coupled with 2 hours of halothane-induced hypotension. Treatment with heparin or thrombolytic agents began 24 hours after occlusion. One additional group was treated with streptokinase 1 hour after occlusion (n = 6) to determine the hemorrhagic potential of thrombolytic agents in evolving infarction. Rabbits were killed 29-33 hours after occlusion, and brain sections were examined using light microscopy. The results demonstrate that microscopic hemorrhage is frequently present in infarcted tissue irrespective of treatment. Gross cerebral hemorrhage did not occur in untreated rabbits or in rabbits treated with streptokinase 1 hour after occlusion. Only rabbits treated with streptokinase, tissue plasminogen activator, or excessive doses of heparin 24 hours after occlusion, at a time when cerebral infarction was well established, exhibited gross hemorrhage in the area of infarction. These data suggest that treatment of ischemic stroke with thrombolytic agents carries an increased risk of cerebral hemorrhage unless the agents are given early after the onset of symptoms.

Animals↗