Experimental Cerebral Infarction Research Articles

P-020 - Assessment of embolization materials for experimental cerebral infarction model in rats

P-020 - Assessment of embolization materials for experimental cerebral infarction model in rats

O-010 - Effect of NZ-105, a novel calcium channel blocker, on experimental cerebral infarction in rats.

O-010 - Effect of NZ-105, a novel calcium channel blocker, on experimental cerebral infarction in rats.

異型化赤血球誘発ラット脳梗塞に対するＬｉｓｕｒｉｄｅの影響

Lisuride is an ergot derivative with central dopaminergic (D2 agonistic) and serotonergic (5-HT1A agonistic) activity. The effect of lisuride on experimental cerebral infarction in rats was investigated. Cerebral infarction was induced by intracarotid infusion of a 50-microliters mixture in which deformed and rigid red blood cells treated with hypertonic solution were contained. Lisuride or 0.9% NaCl was administered subcutaneously 30 min before induction of cerebral infarction. Lisuride (0.01 mg/kg) not only prolonged the survival time of the animals but also suppressed cerebral edema, increase in the electrolytes content and histological damage in the brain. These results suggest that lisuride has a protective effect against cerebral infarction.

O-229 - Interventional procedure for experimental cerebral infarction model in rats. : Assessment of materials for embolization.

O-229 - Interventional procedure for experimental cerebral infarction model in rats. : Assessment of materials for embolization.

Hemorrhagic transformation following tissue plasminogen activator in experimental cerebral infarction.

The effect of an intravenous infusion of recombinant tissue plasminogen activator on hemorrhagic transformation early after middle cerebral artery territory ischemia was studied in an established awake nonhuman primate (baboon) model. Following 3 hours' occlusion of the middle cerebral artery and 30 minutes' reperfusion in each of 30 baboons, a 60-minute infusion of recombinant tissue plasminogen activator (at three doses: Group A, 0.3 mg/kg, n = 6; Group B, 1.5 mg/kg, n = 6; Group C, 10 mg/kg, n = 6) or normal saline (n = 12) was undertaken. The frequency and volume of intracerebral hemorrhage, the volume of infarction, and clinical alterations were determined by computed tomography at 24 hours and 10 days, neuropathology at 14 days, and serial daily neurologic evaluations, respectively. Peripheral (nonintracranial) hemorrhage (Group A, p = 0.46; Group B, p = 0.015; Group C, p = 0.002) and peak plasma tissue plasminogen activator levels varied directly with the dose of recombinant tissue plasminogen activator. Petechial hemorrhagic infarction was a common finding among the 30 baboons. No significant differences in the incidences or volumes of infarction-related hemorrhage were apparent in any group compared with the respective saline-treated baboons. In pooled data, no significant relation between the volume of hemorrhage and the volume of infarction could be established. We conclude that the incidence and severity of hemorrhagic transformation are not related to infarction size and that recombinant tissue plasminogen activator does not increase the incidence or severity (volume) of hemorrhage when given early (less than or equal to 3.5 hours) after the onset of focal cerebral ischemia in this model.

Experimental cerebral infarction in the rat: Utility of Gd-DOTA for MR imaging

Nineteen rats presenting a very small (about 2-mm diameter), superficial cerebral infarction were studied with MR-imaging (1.89 Tesla) before and after injection of Gd-DOTA. Fifteen rats examined 1 or 2 hr, and 2, 3, 4, 5, 7, or 10 days after lesion induction, received 0.5 mmol Gd-DOTA/kg body weight. Four other rats presenting a 4-day-old lesion, received 0.1, 0.2 or 0.6 mmol Gd-DOTA/kg. Each rat underwent one imaging study comprising T 2-weighted spin-echo (SE) images ( 3000 100 ) with subsequent injection of Gd-DOTA followed by 12 consecutive series of T 1-weighted SE images ( 320 40 ), each taking 6 min. Using 0.5 mmol Gd-DOTA/kg, early (immediate) and longlasting (more than 1 hour) visualization of lesions of varying age (1 hr to up to 10 days) was possible and at appropriate time intervals after injection, the visualization of the lesion was clearer and more complete than with T 2-weighted images. Even in the rats studied with smaller doses of the contrast agen (0.1 or 0.2 mmol/kg), postcontrast T 1-weighted images provided superior delineation of the lesion as compared to T 2-weighted images.

Effects of a novel calcium antagonist, KB-2796, on neurologic outcome and size of experimental cerebral infarction in rats

Effects of a novel calcium 2+ antagonist, KB-2796, on neurologic outcome and size of infarction were studied in the rat model of focal cerebral ischemia. Neurologic deficits were examined from 1 to 24 hours after occlusion of the middle cerebral artery and size of infarction was measured at 24 hours postocclusion. When KB-2796 (10 mg/kg, IP) was given immediately after, or 1 hour after, middle cerebral artery occlusion, marked improvement in neurologic score was seen 1 to 3 hours postocclusion. When given immediately after middle cerebral artery occlusion, size of infarction was also markedly smaller when compared with the control rat. The present study suggests that the calcium 2+ antagonist KB-2796 has brain-protective effects against ischemia even with its administration after induction of ischemia.

31P spectroscopy in thrombolytic treatment of experimental cerebral infarct

Ischemic changes produced by autogenous clot embolization of intracranial arteries were monitored by continuous surface-coil 31P spectroscopy in 12 rabbits: six were used as controls and six were treated intravenously with tissue-type plasminogen activator. The animals were sacrificed and the brains were fixed with intravital stains. The results indicate that spectral changes are reversible only when thrombolysis therapy is started within 30 min after ischemic changes are detected. The improvement of the 31P spectrum correlated with postmortem changes.

Endothelial basement membrane and seamless-type endothelium in the repair process of cerebral infarction in rats

Ultrastructural analysis of capillary changes during the repair process of experimental cerebral infarction induced in rats was carried out with special reference to the endothelial basement membrane (BM) and seamless-type endothelial cells. Following degeneration of endothelial cells and pericytes, their BMs, without any interruption or fragmentation, were left in the lesion. Newly formed capillaries grew from vessels in the surrounding brain tissues into the reactive zone of infarcts. While the capillaries in cross-section possessed multilayered BMs, these membranes in tangential section comprised an outer BM with extremely wavy profile and an inner one showing a normal trilayered structure, uniformly enveloping the endothelial surface. It is therefore suggested that the sprouting of regenerating capillaries might invade the remaining cavities of BM, resulting from endothelial degeneration. In these new vessels, seamless-type endothelial cells lacking interendothelial contacts were observed frequently. These two different and previously unobserved findings appear to be at the heart of the regeneration mechanism of reactive capillary proliferation.

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.

Time study of macroscopic identification of experimental cerebral infarction in rat.

Cerebral infarctions were induced in rats by injection of Sephadex G-200 into the internal carotid artery. Unfixed slices of brain were stained with nitro blue tetrazolium (nitro-BT). Tissue dehydrogenase in normal regions reacts with this chemical and changes from a pale yellow color to dark blue consequent to formation of formazan. However, the color changes do not develop in infarcted tissue as there is depletion of tissue dehydrogenase in these regions. Ischemic lesions are identifiable by this method in over half the brain 2 to 4 hours after the embolization, but are seen in all brains 6 hours or more following the embolization. The procedure is simple, requires 30 minutes, and is useful for identification of small or acute cerebral infarction.

Experimental cerebral infarction in the dog. Ultrastructural study of microvessels in subacute cerebral infarction.

Large-sized infarctions of the cerebral hemisphere (LSICH) were experimentally induced in 20 dogs by injecting two silicone cylinders through the right cervical internal carotid artery. The LSICH models were perfused with heparinized saline and fixed with 1.5% glutaraldehyde solution through the contralateral carotid artery 7 days after the embolization. Mercox® was then injected manually. The brains were immediately removed, and specimens were obtained from the basal ganglia and the ectosylvian gyrus. Regenerated microvessels were observed within the necrosis in the basal ganglia. The regenerated microvessels had an irregular, “bead-like” surface, and formed anastomosed networks. The regenerated capillaries had double basement membranes and endothelia with abundant ribosome and increased pinocytotic vesicles. It is suggested that the regenerated capillaries had immature blood-brain barriers of increased permeability. It is thought that the brain functions of this area are reversible. The microvessels within the vasogenic edema in the corticomedullary junctional area of the ectosylvian gyrus had smooth surfaces, and formed normal capillary networks, but their perivascular spaces were dilated with edematous fluids.

Evaluation of 2,3,5-triphenyltetrazolium chloride as a stain for detection and quantification of experimental cerebral infarction in rats.

We have evaluated the use of 2,3,5-triphenyltetrazolium chloride (TTC) as an histopathologic stain for identification of infarcted rat brain tissue. The middle cerebral artery (MCA) of 35 normal adult rats was occluded surgically. At various times after surgical occlusion, rats were sacrificed and brain slices were obtained and stained with TTC or hematoxolin and eosin (H & E); the size of the area of infarcted tissue stained by each method was quantified. In rats sacrificed 24 hr after occlusion of the MCA, the size of the area of infarction was 21 +/- 2% of the coronal section for TTC, and 21 +/- 2% for H & E (mean +/- S.D., N = 13). The size of areas of infarction determined by either staining method was not significantly different in area by the paired test, and a significant correlation between sizes determined by each method was found by linear regression analysis (r = 0.91, slope = 0.89, and the y intercept = 4.4%). Staining with TTC is a rapid, convenient, inexpensive, and reliable method for the detection and quantification of cerebral infarction in rats 24 hr after the onset of ischemia.

Discrepancies among CT, histological, and blood-brain barrier findings in early cerebral ischemia.

The development of ischemic edema and blood-brain barrier (BBB) disruption during the 1st day of experimental cerebral infarction induced by transorbital occlusion of the middle cerebral artery (MCA) in cats was evaluated by computerized tomography (CT) scanning and compared to gravimetric and pathological studies. Regional cerebral blood flow was measured using the hydrogen clearance technique or stable xenon-enhanced CT scanning. Edema was observed gravimetrically and microscopically as early as 1 hour after the onset of ischemia in the cortex and at 3 hours or later in both the cortex and white matter. However, a significant decrease of Hounsfield numbers on the CT scans was not detectable at 1 or 3 hours and was scarcely visible at 9 hours after occlusion. Disruption of the BBB was detected by leakage of Evans blue dye at 3 hours after the occlusion in two of six animals and at 9 hours in five of five animals. However, CT scanning after infusion of contrast material showed no significant increase in Hounsfield number even 24 hours after MCA occlusion. These discrepancies should be emphasized when the dynamics of ischemic edema and BBB disruption are evaluated for clinical therapy by CT scanning.

O-69 - In vivo 31P-NMR studies on experimental cerebral infarction in liv ing rats: changes in the levels of phosphate metabolites

O-69 - In vivo 31P-NMR studies on experimental cerebral infarction in liv ing rats: changes in the levels of phosphate metabolites

Correlations between proton nuclear magnetic resonance imaging and retrospective histochemical images in experimental cerebral infarction.

Evaluation of ischemic brain injury in experimental cerebral infarction in gerbils and rats was performed by means of both proton nuclear magnetic resonance imaging ([1H]NMR-CT) and various histochemical analyses. In vivo nuclear magnetic resonance (NMR) imaging was carried out employing saturation recovery, inversion recovery, and spin echo pulse sequences. Spatial resolution of the images was excellent. The ischemic lesions were detected with a remarkable contrast in inversion recovery and spin echo images within a few hours after insult. Those changes in NMR images consistently corresponded with the various retrospective histochemical observations, especially with methods related to brain edema (K+ staining) rather than structural (enzymatic) studies. Calculated T1 and T2 relaxation times indicated the evolution of the edema state in the brain in situ. They correlated excellently with the retrospective water content measurement. As a result, detailed characterization of the edema state induced by cerebral ischemia was possible in vivo using [1H]NMR imaging.

Freeze-fracture replica study of capillary endothelium after embolization in the dog.

The underlying mechanisms that lead to brain edema following ischemic insult have been subject to much debate. In this study, experimental cerebral infarction was produced in 25 dogs by injecting 1 or 2 silicone rubber cylinders through the cervical internal carotid artery. The animals were sacrificed 24 hours after embolization. Freeze-fracture studies were conducted on the plasma membrane of the capillary endothelium from 15 control and 25 ischemic dogs. No definite findings of tight junction opening were made in the ischemic preparations. Pinocytotic vesicles were seen as concave areas on the protoplasmic face (PF) of the plasma membrane and as protrusions on the extracellular face (EF). The average pinocytotic vesicle count per square micron was increased in ischemic animals. On the luminal side, it reached 22.0 +/- 1.2/sq mu in the 50 PF samples and 29.5 +/- 1.3/sq mu in the 50 EF samples in the experimental preparations, as compared to 7.2 +/- 0.5 sq mu in the 50 PF samples and 9.0 +/- 0.6 sq mu in the 50 EF samples in normal cortex. The average area of the vesicles was also enlarged in experimental animals: 4990.7 +/- 798 sq nm in the 50 PF samples and 4762.8 +/- 878 sq nm in the 50 EF samples, as compared to 3567.7 +/- 570 sq nm in the 50 PF samples and 3404.5 +/- 573 sq nm in the 50 EF samples in normal cortex (p greater than 0.01). These results indicate that transcellular transportation by pinocytotic vesicles plays an important role in the increase of capillary permeability observed in an ischemic model.

Somatosensory evoked potentials as a measure of experimental cerebral ischemia.

Somatosensory evoked potentials (SEP's) reflect the integrity of the central neuronal pathway, and as such may be used to assess function that remains during a variety of cerebral insults. To evaluate the natural history and utility of SEP's during experimental cerebral ischemia and infarction, SEP's were measured in 17 adult cats at 24 hours and 1 hour prior to right middle cerebral artery (MCA) occlusion, and again immediately afterward and at either 6 hours (five cats) or 24 hours (six cats) post-occlusion. Before occlusion of the right MCA, the SEP's were identical in the right and left hemispheres. After occlusion, there was a significant slowing of the interpeak latency of the first positive peak (P1) in the right hemisphere (3.53 +/- 0.6 msec before compared to 3.99 +/- 0.6 msec after occlusion, p less than 0.001). Maximal slowing in right hemisphere P1 latency was seen in those animals in which the stroke extended into the thalamus (4.38 +/- 0.1 msec). This was significantly slower than left hemisphere values (3.92 +/- 0.32 msec, p less than 0.01). The ipsilateral cortical components of the SEP's, the second positive peak (P2), and the major negative deflection (MN) were slowed in all cats immediately after right MCA occlusion compared to preocclusion measurements (p less than 0.001). Severe infarcts in the mid-suprasylvian and posterior ectosylvian gyri (including the somatosensory cortex) resulted in a greater slowing of the latency of MN compared to less severe infarcts in that region (20.6 +/- 3.9 msec versus 16.4 +/- 1.1 msec, p less than 0.05). There was a precipitous decrease in the amplitude or voltage of the ipsilateral P2-MN complex immediately after occlusion (5.32 +/- 0.4 microV before compared to 0.98 +/- 0.3 microV after occlusion, p less than 0.001). Therefore, the central latencies and cortical amplitudes of the SEP's are sensitive experimental tools as indicators of the onset and extent of a cerebral ischemic insult.

Effect of KC-404 on experimental cerebral infarction in rats

Experimental cerebral infarction accompanying altered cerebral energy metabolism and cerebral edema was produced in rats by injecting arachidonate into the left carotid artery. In the present study, the effects of 3-isobutyryl-2-isopropylpyrazolo [1,5-alpha]pyridine (KC-404) on these ischemic insults as well as on the regional cerebral blood flow (r-CBF) were studied. 1) Cerebral metabolism: On the 7th day of infarction, a significant decrease in ATP content and an increase in glucose content were observed, especially in the left hemisphere. There were no significant changes in lactate and pyruvate contents as compared with normal rat brain. Treatment with KC-404 (10 mg/kg, p.o.) once on the 7th day or twice on the 6th and 7th days of infarction caused a significant increase in ATP content and a decrease in lactate content. Increased content of glucose tended to be suppressed by KC-404. In normal rats, KC-404 (10 mg/kg, p.o.) caused slight but significant increases in cerebral ATP, glucose and pyruvate contents. 2) Cerebral edema: On the 4th day of infarction, significant increases in water content and Na+/K+ ratio and a decrease in K+ content were observed in the left hemisphere. Treatment with KC-404 (10 mg/kg, p.o.) for three preceding days showed a significant suppression of increased water content with a tendency to improve altered electrolyte levels. 3) r-CBF: KC-404 (0.05 mg/kg/min) infused i.v. for 15 min increased more markedly the r-CBF in the affected left hemisphere as compared with that in normal brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental Cerebral Infarction Following Occlusion of Middle Cerebral Artery

Experimental Cerebral Infarction Following Occlusion of Middle Cerebral Artery