Min Postocclusion Research Articles

Investigation into safflower injection as a prophylactic treatment for retinal vein occlusion in a rabbit model

The study aimed to assess the effect and mechanism of safflower injection in preventing retinal vein thrombosis in rabbits. Twenty healthy adult pigmented rabbits were randomly assigned to either the experimental group, receiving safflower injection, or the control group, receiving normal saline. After two weeks of treatment, blood samples were collected to analyze platelet adhesion and aggregation rates. Photodynamic therapy was applied to induce occlusion in the target retinal vein. Fundus photography and fluorescein angiography were recorded using a dynamic microscopic monitoring system, and laser speckle imaging was employed to assess blood flow in the affected vein. The experimental group exhibited significantly lower rates of platelet adhesion and aggregation compared to the control group. Following the induction of retinal vein occlusion, the experimental group showed a lower complete occlusion rate of the target retinal vein. Although initial blood flow in the target vein was similar between groups, the blood flow at 1, 3, and 5 min post-occlusion was significantly higher in the experimental group. Safflower injection delayed retinal vein thrombosis formation, preserved blood flow in the affected retinal area, and reduced platelet adhesion and aggregation. These effects facilitated vascular reperfusion within a limited timeframe.

Augmentation of perfusion with simultaneous vasodilator and inotropic agents in experimental acute middle cerebral artery occlusion: a pilot study

BackgroundThis study tests the hypothesis that simultaneous cerebral blood pressure elevation and potent vasodilation augments perfusion to ischemic tissue in acute ischemic stroke and it varies by degree of pial...

Abstract WP109: Deferoxamine Improves Vascular Repair and Cognitive Outcomes After Embolic Stroke In Diabetic but Not Control Animals: Interaction With tPA

Diabetes increases the risk of hemorrhagic transformation (HT) in ischemic stroke, especially with the use of tissue plasminogen activator (tPA). We showed that iron chelation therapy with deferoxamine (DFX) improves functional outcome in male diabetic animals after embolic stroke but its interaction with tPA remained unknown. We also reported that increased HT is associated with loss of cerebrovasculature in the recovery period in diabetic animals. This study tested the hypotheses that DFX treatment initiated after stroke 1) will improve neurological recovery after embolic stroke with tPA, and 2) will prevent cerebrovascular regression in diabetes. Control and type 2 diabetic animals were subjected to embolic middle cerebral artery occlusion. tPA (1 mg/kg) was given at 90 min post-occlusion. DFX (100 mg/kg) or vehicle was given every 12 h for 7 days after stroke. The composite score (Bederson’s score and beam walk), adhesive removal (ART) and novel object recognition (NOR) were assessed at day 3, 7 and 14 after the surgery. Cerebrovascularization indices in the ipsilateral cortex (vascular volume, surface area, and branch density) were measured with 3D imaging. DFX improved sensorimotor deficits in both groups and this effect was more robust in tPA combination. While DFX lowered vascularization indices in control animals, it prevented vasoregression in diabetes. Interestingly, DFX prevented the recovery of cognitive function in controls while improving it in diabetic animals. These results suggest that treatment with DFX may improve long term recovery in diabetes.

Impact of exposure to biomass on the vascular function of Senegalese women

Background: In rural Senegal, biomass fuels are the main and often the only source of domestic energy for cooking. Their combustion is a source of particles and many other chemical contaminants that could alter cardiovascular function. Aims and Objectives: The aim of our study was to assess the effects of exposure to biomass fumes on vascular function in non-smoking women in rural Senegal. Materials and Methods: We conducted a cross-sectional 8-month study of 64 women (32 exposed to biomass smoke and 32 unexposed controls) who were active or housewives and involved in cooking. The subjects were aged 33.56 ± 9.34 years and 30.22 ± 6 years, respectively. All the women received a questionnaire with questions on sociodemographic characteristics, habitat characteristics, cooking habits, and biomass exposure conditions. Flow-mediated brachial arterial vasodilation flow-mediated dilatation (FMD) expressed as a percentage of the diameter was measured basally at rest and post-compression at 5, 30, 60, 90, and 120 s and 10 min after deflation. Results: All participants were non-smokers. 12.5% of subjects used gas in addition to biomass. Seniority was 18. 90 ± 10 years, with a mean daily biomass exposure of 4 ± 1 h. The analysis of cardiovascular parameters and blood sugar found no significant difference between the two groups. Kinetic FMD comparisons between the two groups showed significant differences at points 60 and 90 s 10 min post-occlusion. A negative correlation was found between FMD at 90 s after deflation and the duration of exposure in exposed women (r = 0.44 P < 0.05). Conclusion: Our results showed that exposure to biomass is implicated in the appearance of vascular dysfunction in non-smoking women.

Spatio-temporal assessment of the neuroprotective effects of neuregulin-1 on ischemic stroke lesions using MRI

The neuroprotective effects of neuregulin-1 (NRG-1) on stroke lesions were assessed longitudinally in rats with middle cerebral artery occlusion (MCAo) using MRI. Sprague–Dawley rats (n=16, 250±20g) underwent permanent MCAo surgery with cerebral blood flow (CBF) monitored by laser doppler flowmetry at ipsilateral side of bregma for 20min post-occlusion. A single 50μl bolus dose of NRG-1 or vehicle was administered into the left internal carotid artery immediately prior to MCAo. The expansion of the ischemic lesion into the cortex was attenuated by NRG-1 over a 48-hour (h) time span as measured by diffusion weighted imaging (DWI). The final infarct volumes of NRG-1 treated rats were significantly smaller than those of the vehicle treated rats at 48h (264.8±192.1 vs. 533.4±175.5mm3, p<0.05). The NRG-1 treated rats were further subdivided into 2 subgroups according to their CBF reduction during stroke surgery: mild ischemia (<70% CBF reduction) or severe ischemia (>70% CBF reduction). In particular, ischemic infarction was not usually observed in the cortex of NRG-1 treated rats with mild ischemia at 3 and 48h post-occlusion. Histological results validated the imaging findings and demonstrated that NRG-1 treated rats had fewer injured neurons in peri-infarct areas 48h post-ischemia. In summary, the neuroprotective effect of NRG-1 in the pMCAo stroke model was demonstrated by prevention of ischemic lesion expansion, reduced infarct volume and protection of neurons from ischemic damage.

PPARγ upregulation induced by vagus nerve stimulation exerts anti-inflammatory effect in cerebral ischemia/reperfusion rats.

BackgroundIt is well known that peroxisome proliferator-activated receptor gamma (PPARγ), a ligand-activated transcription factor, plays a protective role in anti-inflammatory responses in both acute and chronic central nerve system (CNS) insults. Emerging evidence in rats suggests that vagus nerve stimulation (VNS), while restraining inflammatory cytokine production in the peripheral nervous system, also exerts a significant CNS neuroprotective function against ischemic stroke injury. The aim of this study was to explore the role of PPARγ in VNS-mediated anti-inflammatory protection against ischemic stroke damage.Material/MethodsAdult male Sprague-Dawley rats (total n=160) preconditioned through transfection with either PPARγ small interfering RNA (siRNA) or lentiviral vector without siRNA and surgically subjected to middle cerebral artery occlusion and reperfusion subsequently received VNS treatment at 30 min post-occlusion. The expression of PPARγ after VNS treatment was measured by real-time PCR and Western blotting, also supported by immunofluorescence staining. Subsequently, the neurological deficits scores, the infarct volume, and the brain histopathology were all evaluated. Additionally, the influence on the pro-inflammatory cytokines expression and neuro-immune cells activation was determined by ELISA and immunofluorescence staining.ResultsWe found that VNS upregulated expression of PPARγ in ischemia penumbra, diminished the extent of ischemic infarct, alleviated neuronal injury, and suppressed pro-inflammatory cytokine expression and immune cell activation (P<0.05). However, rats with PPARγ silencing failed to manifest significant neuroprotection and anti-inflammatory effect induced by VNS treatment (p>0.05).ConclusionsPPARγ may participate in the process by which VNS modulates the neuro-inflammatory response following ischemia/reperfusion in rats.

CT Density Changes with Rapid Onset Acute, Severe, Focal Cerebral Ischemia in Monkeys

Computerized tomography (CT) is the most often used imaging modality in the evaluation of acute clinical stroke. However, the rapidity with which CT density changes occur after acute, severe, focal ischemia cannot be determined clinically. Even if the time of symptom onset is known, clinical stroke severity is highly variable. We studied the time course of CT density change after severe, rapid onset, acute, focal ischemia as documented by stable xenon CT cerebral blood flow (CBF) in monkeys. Eight monkeys (Macaca mulatta) were subjected to transorbital occlusion of the left posterior cerebral, anterior, middle, and internal carotid arteries to induce focal ischemia. CT density Hounsfield units (HU), CBF by stable xenon CT, arterial blood pressure, and blood gases were measured before occlusion, immediately after occlusion, at 30min, and hourly for up to 6h. Occlusion of the cerebral arteries decreased CBF to 8 ± 5ml/100g/ min within 15min postocclusion. At 6h, CBF was unchanged at 9 ± 4ml/100g/ min. CT density within the ischemic core fell from 42 to 38HU immediately after occlusion (P < 0.05), rose transiently, then fell at 2h (P < 0.01) and plateaued at 36 ± 5HU for a total decrease of 4-5HU between 4 and 6h poststroke. Changes in CT density lag severe focal ischemia by 2h. Thus, when CT hypodensity is seen in acute stroke, it is likely 2h old. It also provides an explanation for the phenomenon of clinical CT mismatch with clinical deficits and normal CT.

Embozene™ microspheres induced nonreperfused myocardial infarction in an experimental swine model

To develop a magnetic resonance imaging (MRI) compatible, percutaneous technique for the generation of nonreperfused myocardial infarct (MI). Modeling nontreated MI has major importance in the development and preclinical testing of new therapeutic strategies for patients missing the time window suitable for revascularization following MI. In 31 male swine, nonreperfused MI was generated by permanent occlusion of either the LAD or LCX coronary artery using 900 μm Embozene™ microspheres. Animals were monitored for 90 min postocclusion. Surviving animals were followed up for 2 (n = 6), 4 (n = 6), 14 (n = 6), or 56 (n = 6) days. At the end of the planned study session, contrast enhanced MRI, triphenyl-tetrazolium-chloride staining, and microscopic histopathology were carried out. The mortality rate in this study was 22.6%. Intraoperative arrhythmias occurred in 14 cases: premature ventricular complexes with (5) or without (3) ventricular tachycardia, 2nd degree atrio-ventricular block (1), and ventricular fibrillation (6). MRI, TTC, and histology confirmed the existence of MI in every case. Macroscopic pathology showed that the microspheres caused a practically total occlusion at the epicardial level of the coronary artery. Multiple infarcts were detected in one case, probably due to unintentional reflux of the microspheres. Microspheres retained in the coronary arteries did not cause any MRI artifact. The generation of nonreperfused MI is feasible by percutaneous injection of Embozene into the coronary artery system. The MI model thus obtained is suitable for the purposes of MRI experiments.

Correlates of endothelial function and the peak systolic blood pressure response to a graded maximal exercise test

PurposeAn elevated systolic blood pressure (SBP) response to a graded maximal exercise stress test (GEST) may be a predictor of endothelial dysfunction and hypertension. We examined relationships among the GEST peak SBP response and indicators of endothelial function. MethodsMen (n=48, 43.7±1.4yr) with high BP (145.1±1.5/85.5±1.1mmHg) completed a GEST. Peak SBP was the highest SBP achieved during the GEST. Blood samples were taken for fasting glucose and insulin, nitric oxide (NO), and DNA. Endothelial nitric oxide synthase (NOS3, rs2070744) −786 T>C genotyping was determined by PCR. NOS3 genotypes were combined using a dominant model [TT (n=24); TC/CC (n=24)]. Brachial artery reactivity (BAR) was determined via ultrasound before, 1min, and 3min post occlusion and calculated as % change. Analysis of variance (ANOVA) tested changes in the peak SBP GEST response by NOS3 genotype. Multiple variable regression analyses examined relationships among the GEST peak SBP response and measures of endothelial function. Results%BAR change at 1min (r2=0.093, p=0.020), glucose (r2=0.062, p=0.014), NOS3 −786 T>C (r2=0.040, p=0.024), NO (r2=0.037, p=0.064), and age (r2=0.009, p=0.014) explained 24.1% of the GEST peak SBP response (p=0.043). The GEST peak SBP change from baseline was 11.1±5.0mmHg higher among those with the NOS3 C allele (92.4mmHg+3.8) than the NOS3 TT genotype (81.3mmHg+3.2) (p=0.03). ConclusionIndicators of endothelial function appear to explain a clinically significant portion of the GEST peak SBP response. Further investigation is needed to unravel the mechanisms by which endothelial function influences the GEST peak SBP response.

Effect of Self-Regulated Exercise Intensity on Endothelial Function in Men with Coronary Artery Disease

Background: Physiologically based exercise prescriptions normally involve identifying an intensity range that elicits a predetermined VO2 or heart rate. In many instances prescribed exercise that exceeds an individual’s preferred level of intensity may establish a negative attitude toward physical activity. Longitudinal studies report that participants tend to deviate from physiologically based prescribed levels of intensity in favour of their apparently preferred levels. Self-regulated exercise intensity may increase enjoyment and promote adherence by allowing individuals successfully complete an activity within their perceptual preference range and without undue physiological strain. The purpose of this study is to examine the effect of self-regulated exercise intensity on endothelial function (a validated surrogate measure of early atherosclerosis) in men with coronary artery disease. Methods: Eight men with coronary artery disease (65.7 ± 4.5 yr, VO2max 18.6 ± 4.1 ml/kg/min, BMI 29.7±3.3 kg/m-2) underwent 20 min of treadmill walking at a self-regulated intensity. Endothelial dependent dilation of the brachial artery was assessed before and 1 h following the acute bout of exercise. Vessel diameter was determined using high resolution vascular ultrasonography (SonoSite, MicroMaxx) from flow mediated dilation (FMD) following 5 min of forearm occlusion. Endothelial independent vasodilation was measured at min 3, min 4 and min 5 following the administration of glyceryl trinitrate (0.4 mg). Results: The subjects self-selected an average treadmill walking speed of 5.3 km/h and a grade of 0.7%. This intensity equated to 65.7% VO2max, and an RPE-O of 12.0. Compared to baseline, FMD was significantly increased (1 min (4.6 v 10.7%) and 3 min (6.2 v 11.0) post occlusion) at 60 min following the acute bout of self regulated exercise. There was no change in endothelial independent dilation in response to the acute bout of exercise. Conclusion: These results indicate a beneficial effect of self-regulated exercise on endothelial dependent vascular function in men with coronary artery disease.

Effects of NXY‐059 in experimental stroke: an individual animal meta‐analysis

Disodium 2,4-disulphophenyl-N-tert-butylnitrone (NXY-059) was neuroprotective in experimental stroke models but ineffective in a large clinical trial. This first-ever individual animal meta-analysis was used to assess the preclinical studies. Studies were obtained from AstraZeneca and PubMed searches. Data for each animal were obtained from the lead author of each study and/or AstraZeneca. Published summary data were used if individual data were not available. Infarct volume and motor impairment were standardized to reflect different species and scales. Standardized mean difference (SMD), coefficients from multilevel models and 95% confidence intervals (95% CI) are presented. Fifteen studies (26 conditions, 12 laboratories) involving rats (544), mice (9) and marmosets (32) were identified (NXY-059: 332, control: 253) with individual data for 442 animals. Four studies were unpublished. Studies variably used randomization (40%), blinding of surgeon (53%) and outcome assessor (67%). NXY-059 reduced total (SMD -1.17, 95% CI -1.50 to -0.84), cortical (SMD -2.17, 95% CI -2.99 to -1.34) and subcortical (-1.43, 95% CI -2.20 to -0.86) lesion volume; efficacy was seen in transient, permanent and thrombotic ischaemia, up to 180 min post occlusion. NXY-059 reduced motor impairment (SMD -1.66, 95% CI -2.18 to -1.14) and neglect. Evidence for performance, attrition and publication bias was present. NXY-059 was neuroprotective in experimental stroke although bias may have resulted in efficacy being overestimated. Efficacy in young, healthy, male animals is a poor predictor of clinical outcome. We suggest the use of preclinical meta-analysis before initiation of future clinical trials.

Correlates Of Endothelial Function And The Peak Systolic Blood Pressure Response To A Graded Maximal Exercise Test

PURPOSE: An elevated systolic blood pressure (SBP) response during maximal exercise may be a predictor of endothelial dysfunction and future hypertension. We examined associations among the peak SBP response to a graded exercise stress test (GEST) and correlates of endothelial function among men (n=48, 43.7±1.4yr) with high BP (145.6±1.5/85.9±1.1mmHg). METHODS: For 20 min prior to the GEST, BP was measured every 2 min in the seated position via auscultation and averaged as baseline BP. Volunteers completed a maximal cardiopulmonary GEST to determine peak oxygen consumption (VO2peak). Brachial artery reactivity (BAR) was measured 3 and 5 min post-occlusion and expressed as a % change from baseline. Nitric Oxide (NO) was measured via chemiluminescence assay. Plasma glucose concentrations were determined in duplicate by an automated glucose oxidase method. Endothelial nitric oxide synthase genotype (ENOS -786 T>C; rs2070744) (ENOS TT, n=24; ENOS TC/CC, n=24) was determined by polymerase chain reaction and restriction enzyme digestion. Simple linear and multiple variable regression analyses examined relationships among the change in peak SBP achieved on the GEST and correlates of endothelial function. RESULTS: Linear regression analyses revealed the peak SBP change was positively correlated to blood glucose (r2=0.063, p=0.015), age (r2=0.016, p=0.024), VO2peak(r2=0.014, p=0.037), ENOS -786 T>C (r2=0.051, p=0.026), baseline SBP (r2=0.005, p=0.084), and baseline NO (r2=0.013, p=0.053); and negatively correlated to % BAR change at 3 min post-occlusion (r2=0.104, p=0.029). Multiple variable regression analyses indicated that this model explained 26.7% of the peak SBP response to a GEST. Lastly, among carriers of the ENOS C786 risk allele, the peak SBP change was 11.1±5.0mmHg higher ENOS TT homozygotes, 92.4 versus 81.3mmHg, respectively (p=0.03). CONCLUSIONS: Surrogate measures of endothelial function appear to explain a clinically significant portion of the peak SBP response to a GEST. Further work is needed to investigate how interactions among clinical and genetic correlates of endothelial function explain the variability in the peak SBP response to a GEST. Supported by an American Heart Association Grant in Aid #0150507N.

Mechanistic investigation into the arrhythmogenic role of transmural heterogeneities in regional ischaemia phase 1A

Studies of arrhythmogenesis during ischemia have focused primarily on reentrant mechanisms manifested on the epicardial surface. The goal of this study was to use a physiologically-accurate model of acute regional ischemia phase 1A to determine the contribution of ischaemia-induced transmural electrophysiological heterogeneities to arrhythmogenesis following left anterior descending artery occlusion. A slice through a geometrical model of the rabbit ventricles was extracted and a model of regional ischaemia developed. The model included a central ischaemic zone incorporating transmural gradients of I(K(ATP)) activation and [K+]o, surrounded by ischaemic border zones (BZs), with the degree of ischaemic effects varied to represent progression of ischaemia 2-10 min post-occlusion. Premature stimulation was applied over a range of coupling intervals to induce re-entry. The presence of ischaemic BZs and a transmural gradient in I(K(ATP)) activation provided the substrate for re-entrant arrhythmias. Increased dispersion of refractoriness and conduction velocity in the BZs with time post-occlusion led to a progressive increase in arrhythmogenesis. In the absence of a transmural gradient of I(K(ATP)) activation, re-entry was rarely sustained. Knowledge of the mechanism by which specific electrophysiological heterogeneities underlie arrhythmogenesis during acute ischaemia could be useful in developing preventative treatments for patients at risk of coronary vascular disease.

Progesterone inhibits ischemic brain injury in a rat model of permanent middle cerebral artery occlusion

Purpose: Previous studies suggest that progesterone (PROG) has a substantial protective effect against several types of brain injury. Since most cases of human stroke are caused by permanent occlusion of cerebral arteries, we assessed the neuroprotective effects of PROG on cerebral infarction and behavioral deficits in a permanent MCAO (pMCAO) model. Methods: pMCAO was produced by surgical insertion of a silicone-coated nylon filament into the right internal carotid artery. Laser-Doppler flowmetry was used to monitor cerebral blood flow for 10 min post-occlusion. PROG (8 mg/kg) or vehicle (2-hydroxypropyl-β-cyclodextrin) was administered intraperitoneally at 1 h post-occlusion followed by subcutaneous injections at 6, 24 and 48 h post-occlusion. Measurements of infarct volumes (cortical, subcortical and total) were performed at 72 h and functional recovery, assessed by rotarod test, were performed 24, 48, and 72 h after pMCAO. Results: Following PROG treatment, stained sections revealed a significant reduction in cortical, caudate-putamen and hemispheric infarct volumes (% contralateral structure) compared to vehicle-injected controls. In addition, PROG treatment reduced functional deficits on the accelerating rotarod apparatus. Conclusion: We demonstrated and confirmed the neuroprotective effect of PROG using a permanent model of focal brain ischemia in rats.

Exercise Training Improves Peripheral Vascular Function Following Chronic Femoral Artery Occlusion in the Ossabaw Swine Model of Cardiometabolic Risk

PURPOSE: Peripheral arterial disease (PAD) is a major cause of morbidity and mortality in the developed world. Diabetes is a strong risk factor for PAD; thus, incidence of PAD can only be expected to rise as the prevalence of diabetes increases. The treatment of choice for PAD is exercise training. Training is well-known to increase collateral-dependent peripheral blood flow in healthy animals, mainly rodents. However, it is unclear whether training induces the same changes in collateral structure and/or function in the setting of the metabolic syndrome. Thus, we investigated peripheral vascular function in Ossabaw swine. Results from this unique large animal model of cardiometabolic risk may be closely relevant to human disease. METHODS: Swine were divided into 3 groups: sedentary control (C, N=6), sedentary high fat/cholesterol fed (H, N=4), and exercise trained H (HX, N=6). H and HX pigs were fed a high fat/cholesterol diet (46% kcal from fat; 2% cholesterol w:w) for 50 wk. Hydrogenated soybean oil (containing 56% trans fatty acids) served as the fat source. H and HX pigs were obese, hyperlipidemic, hypertensive, and insulin resistant, all characteristics of the metabolic syndrome. HX pigs trained on a motorized treadmill 4 d/wk for 7 wk. Pigs wore a wireless heart rate monitor for continuous assessment of exercise intensity. After a 10-min warmup, treadmill speed was increased until heart rate reached ∼65-75% of max. Pigs then exercised for 30 min, followed by a 5-min cool down. After 4 wk of training, the right femoral artery was occluded under general anesthesia using surgical suture. After recovery, pigs continued training for a further 3 wk. Pigs were then anesthetized for measurement of mean saphenous artery pressure (SAP). RESULTS: SAP did not differ between groups in the left (non-occluded) limb. Left SAP fell ∼50% in all groups in response to acute occlusion of the left femoral artery and did not significantly recover by 10 min post-occlusion. In the right (chronically occluded) limb, SAP was significantly higher in HX than in C pigs (71 ± 5 vs 49 ± 5 mm Hg; p=0.013). Recovery of SAP after 4 wk of femoral occlusion was complete in the HX group (113 ± 14% of pre-occlusion left SAP), and was greater than that in the H group (48 ± 23%; p=0.017 vs HX) or the C group (75 ± 8%, p=NS vs HX). Typical "corkscrew" collaterals were angiographically visible in the right thigh, suggesting that structural remodeling occurred in response to the chronic femoral occlusion. CONCLUSIONS: Exercise training significantly improves peripheral vascular function in obese Ossabaw swine, a novel and useful large animal model for the study of the effects of exercise on PAD. Support: HL062552, RR013223 (MS).

Bosentan, the mixed ETA–ETB endothelin receptor antagonist, attenuated oxidative stress after experimental myocardial ischemia and reperfusion

Endothelin-1 has been shown to be associated with greater myocardial ischemia and reperfusion injury in which oxidative stress plays a key role. The efficacy of bosentan, a mixed ETA-ETB endothelin receptor antagonist, in protecting the myocardium from ischemia-reperfusion injury and oxidative stress was studied in open-chest Wistar rats. Anesthetized adult male rats (175-250 g b wt) underwent sham operation (SHAM group) or were subjected to 40 min of myocardial ischemia (MI) induced by temporary occlusion of the left anterior descending coronary artery (LAD) followed by 2 h reperfusion (R). Rats submitted to the MI-R protocol were administered bosentan at a dose of 3 mg/kg i.v. 20 min (BOS group) or saline (CON group) 20 min post-occlusion of LAD. After the 2 h reperfusion period the animals were euthanized and the heart rapidly excised. Cardiac tissue samples were snap frozen in liquid nitrogen for biochemical assay and were fixed in 10% formalin solution for histologic evaluation. Myocardial I-R resulted in a significant increase (p < 0.05) in the myocardial malondialdehyde levels and a decrease (p < 0.01) in the myocardial reduced glutathione content. These changes were associated with significant decreases in the myocardial activity of antioxidant enzymes superoxide dismutase (p < 0.05) and catalase (p < 0.01) and severe tissue damage in the jeopardized myocardium in the CON group as compared with the non-myocardial ischemia-reperfusion (NMI-R) SHAM group. Bosentan exerted marked tissue protective effect as assessed by histologic evaluation of the myocardium. The drug significantly (p < 0.05) attenuated myocardial oxidative stress and restored the cellular antioxidant defense mechanisms as compared with the saline-treated controls subjected to the MI-R protocol. Furthermore, bosentan also exerted a marked effect on peripheral hemodynamics and heart rate during the reperfusion phase (data reported elsewhere). These results are consistent with the concept that endothelin-1 may be involved in the pathogenesis of myocardial ischemia and infarction. This study demonstrates the antioxidant effect of non-selective endothelin receptor antagonism elucidating that, part of the aetiology of ischemia and reperfusion induced myocardial injury involves impaired antioxidant defenses.

The neuronal nitric oxide synthase inhibitor, TRIM, as a neuroprotective agent: effects in models of cerebral ischaemia using histological and magnetic resonance imaging techniques

Most neuroprotective compounds that appear promising in the pre-clinical phase of testing are subsequently dismissed as relatively ineffective when entered into large-scale clinical trials. Many pre-clinical studies of potential neuroprotective candidates evaluate efficacy in only one or possibly two different models of ischaemia. In this study we examined the effects of 1,2-trifluoromethylphenyl imidazole (TRIM), a novel neuronal nitric oxide synthase (nNOS) inhibitor, in three models of cerebral ischaemia (global gerbil, global rat and focal rat). In addition, to follow the progression of the pathology, we also compared traditional histology methods with more advanced magnetic resonance imaging (MRI) as endpoint measures for neurological damage and neuroprotection. TRIM (50 mg/kg i.p.) prevented ischaemia-induced hippocampal damage following global ischaemia in gerbils when administered before or immediately post-occlusion, but failed to protect when administration was delayed until 30 min post-occlusion. Further studies indicated that the compound (administered at 50 mg/kg, i.p., immediately after occlusion) also protected in a rat four-vessel occlusion (4-VO) model using both histological and diffusion-weighted (DW) imaging techniques. In a final study, TRIM (50 mg/kg i.p. 30 min after occlusion) provided a significant reduction in infarct volume at 4 and 24 h as measured using diffusion-weighted (DW) and proton density (PD)-weighted magnetic resonance imaging (MRI). This was confirmed using histological techniques. These studies confirm that nNOS inhibitors may have utility in stroke and provide evidence that combined magnetic resonance and histological methods can provide a powerful method of assessing neuronal damage in rodent models of cerebral ischaemia.

Effects of cerestat and NBQX on functional and morphological outcomes in rat focal cerebral ischemia

This study investigated the ability of NBQX, an AMPA receptor antagonist, and cerestat, a NMDA receptor antagonist, to counteract neurological deficits and morphological damage induced by permanent occlusion of the left middle cerebral artery (MCAO model) in the rat. NBQX (3, 10, and 30 mg/kg, ip) injected at 10, 60, and 120 min postocclusion did not reduce the volume of infarct in the MCAO model of cerebral ischemia and had marginal effects on sensory dysfunctions (vibrissae stimulation and body proprioception) and no effects on motor dysfunctions (forelimb flexion and footfault test). Conversely, cerestat (0.3, 1, and 3 mg/kg, sc) injected at 10 and 120 min postocclusion significantly reduced the ischemic volume at the dose of 1 mg/kg, and, at the same dose, significantly attenuated behavioural deficits in the body proprioception and in the forelimb flexion tests.

ARL 17477, a selective nitric oxide synthase inhibitor, with neuroprotective effects in animal models of global and focal cerebral ischaemia

In the present studies, we have evaluated the effects of N-[4-(2-{[(3-Chlorophenyl)methyl]amino}ethyl)phenyl]-2-thiophenecarboximidamide dihydrochloride (ARL 17477) on recombinant human neuronal NOS (nNOS) and endothelial NOS (eNOS). We then carried out pharmacokinetic studies and measured cortical nitric oxide synthase (NOS) inhibition to determine that the compound crossed the blood brain barrier. Finally, the compound was evaluated in a model of global ischaemia in the gerbil and two models of transient focal ischaemia in the rat. The IC 50 values for ARL 17477 on human recombinant human nNOS and eNOS were 1 and 17 μM, respectively. ARL 17477 (50 mg/kg i.p.) produced a significant reduction in the ischaemia-induced hippocampal damage following global ischaemia when administered immediately post-occlusion, but failed to protect when administration was delayed until 30 min post-occlusion. In the endothelin-1 model of focal ischaemia, ARL 17477 (1 mg/kg i.v.) significantly attenuated the infarct volume when administered at either 0, 1 or 2 h post-endothelin-1 ( P<0.05). In the intraluminal suture model, ARL 17477 at both 1 and 3 mg/kg i.v. failed to reduce the infarct volume measured at 1, 3 or 7 days post-occlusion. These results demonstrate that ARL 17477 protects against global ischaemia in gerbils and provides some reduction in infarct volume following transient middle cerebral artery occlusion in rats, indicating that nNOS inhibition may be a useful treatment of ischaemic conditions.

LY379268, a potent and selective Group II metabotropic glutamate receptor agonist, is neuroprotective in gerbil global, but not focal, cerebral ischaemia

The neuroprotective effects of a selective Group II metabotropic glutamate receptor (mGluR) agonist, LY379268, have been evaluated against global and focal cerebral ischaemia. Loss of CA1hippocampal neurones following 5min bilateral occlusion of the carotid artery (BCAO) in the gerbil was almost completely prevented by LY379268 (10 mg/kg, i.p.) given 30 min post-occlusion ( P<0.001); 10 mg/kg 1 h after and 20 mg/kg 2 h after BCAO also produced significant neuroprotection ( P<0.05). Similarly the BCAO-induced increase in TUNEL positive cells at 5 days post-occlusion was reduced by LY379268. By contrast the size of the infarct following middle cerebral artery occlusion (MCAO) induced by endothelin-1 infusion in the rat was unaffected by either 10 or 20 mg/kg i.p. of LY379268. This contrast between the results from these two animal models with LY379268, agrees with previous data on a less potent but similarly selective mGluR2/3 agonist, LY354740. It further suggests that mGluR Group II agonists are likely to have more utility in global, than in focal, cerebral ischaemia.