Effects Of Global Ischemia Research Articles

11: NEUROPROTECTIVE EFFECTS OF PHARMACOLOGIC AGENT JTE-013 AFTER CARDIAC ARREST IN RATS

Introduction: Out of 290,000 in-hospital cardiac arrests (CA) and 350,000 out-of-hospital CAs occur in the U.S. per year, and 92.6% of the survivors leave the hospital with neurological deficits. Increased levels of inflammation, due to the recruitment of detrimental microglial cells, exacerbates brain injury and worsens neurological function. Despite the alarming number of patients that suffer from neurological dysfunction after CA, there are minimal therapeutic strategies for CA patients that target the inflammatory pathway. JTE-013 has shown promising results in reducing microglial activation through inhibition of a microglial activating receptor, sphingosine 1-phosphate 2 in rodent stroke models, however, its effects in global ischemia after CA are unknown. This study aims to investigate the neuroprotective effects of JTE-013 in oxygen-glucose deprivation/reperfusion (OGD/R) models in vitro and in CA rat models in-vivo. Methods: In vitro, primary rat hippocampal neurons were exposed to OGD/R (1% O2) for 3 hours and then cultured in a control medium or medium containing 10 µM JTE-013. Immunocytochemistry was performed to analyze axonal loss (NF200), myelin loss (MBP), and synapse loss (synapsin1). 9 male Wistar rats (average weight 349 ± 42g) were randomly assigned to the control group (n = 5) or to the JTE-013 treatment group (n = 4). After 8-min asphyxia CA, rats were randomly assigned to receive either 5µM PBS in the control group or 5µM JTE-013 intracerebroventricularly (ICV) 3 hours after the return of spontaneous circulation (ROSC). Neurological deficit scores (NDS) were assessed at 6, 24, 48, and 72h after ROSC along with the survival rate of the rats. Results: In vitro, the quantified cell positive area and intensity of antibody fluorescence showed more cell positive areas and higher intensity of NF200, MBP, and synapsin in neurons cultured with JTE-013 (p < 0.05). NDS revealed improved neurological function of JTE-013 treated rats compared to control condition rats (p < 0.05), with an increased survival rate among the JTE-013 treated rats (p < 0.05). Conclusions: The pharmacological agent JTE-013 demonstrated a neuroprotective effect in global ischemia induced by CA, which proposes a potential therapeutic intervention for ischemic brain injury after CA.

Effects of ATP administration on isolated swine hearts: Implications for ex vivo perfusion and cardiac transplantation.

Cardiac transplant outcomes can be compromised by the effects of global ischemia and associated reperfusion injury. In attempts to alleviate these phenomena, various pharmaceutical agents can be administered. Previous reports have shown that adenosine triphosphate (ATP) may act as either a postconditioning (PoC) or supplementary (Sup) therapy with cardiosupportive benefits. To further evaluate ATP’s relative effectiveness, we used an isolated swine heart four-chamber working model to monitor both hemodynamic and metabolic responses. We employed two strategies of ATP administration: (1) a postconditional (PoC) bolus just prior to reanimation, and (2) regular dosing throughout the assessment period (Sup). Ex vivo swine hearts in the Sup group elicited significantly higher left ventricular function during the 2 h monitoring period than controls. In contrast, PoC administration appeared to induce depressed cardiac function. The effects of ATP on cardiac function can have varied effects, dependent on when it is administered. Impact statement We employed an isolated swine heart four-chamber working model to investigate two potential strategies for adenosine triphosphate (ATP) administration as an ex vivo therapy: (1) application of a single bolus dose during reperfusion (postconditioning or PoC), and (2) repeated bolus dosing throughout the experiment (supplementary or Sup). Ex vivo swine hearts in the Sup group elicited significantly higher left ventricular function during the 2 h experimental monitoring period. In contrast, ATP administration in the PoC group appeared to induce a degree of depressed hemodynamic function. These data suggest varied functional roles of ATP administration relative to their use in ex vivo perfusion strategies. We consider that both treatment strategies, if appropriately administered and with further investigation of dosing paradigms, may eventually elicit value in various clinical scenarios, including heart transplantation and ex vivo heart perfusion to assess potential organs for transplantation and potentially increase the pool of viable donor hearts.

Effects of global ischemia and estradiol pretreatment on phosphorylation of Akt, CREB and STAT3 in hippocampal CA1 of young and middle-aged female rats

Transient global ischemia induces selective, delayed neuronal death of pyramidal neurons in the hippocampal CA1. Whereas long term treatment of middle-aged female rats with estradiol at physiological doses ameliorates neuronal death, the signaling pathways that mediate the neuroprotection are, as yet, unknown. Protein kinase B (Akt) and downstream transcription factors, the cAMP response element binding protein (CREB) and signal transducer and activator of transcription (STAT3) are critical players in cellular survival following injury. The present study was undertaken to determine whether long term estradiol alters the phosphorylation status and activity of Akt, STAT3 and CREB in ovariohysterectomized, middle-aged and young female rats subjected to global ischemia. Irrespective of either hormone or ischemic condition, middle-aged females exhibited lower levels of p-CREB and higher levels of Akt and STAT3 in CA1 than young females, as assessed by Western blot. In middle-aged animals, ischemia increased the phosphorylation status/activity of Akt and STAT3, and decreased the phosphorylation status/activity of CREB in the hippocampal CA1. Whereas estradiol did not detectably alter the phosphorylation status/activity of Akt or STAT3, it prevented the ischemia-induced decrease in nuclear p-CREB. Similar results were observed for the young females. Collectively, these data demonstrate that CREB, STAT3, and Akt are involved in the molecular response to global ischemia and that age influences the status of CREB, STAT3 and Akt activity in CA1 under physiological as well as pathological conditions, further emphasizing the importance of including older rodents in neuroprotection studies.

Inotropic and chronotropic effects of ischemic postconditioning on the model of isolated heart

The effects of global ischemia (45 min) and reperfusion (30 min) on left-ventricular developed pressure (LVDP), HR, and end-diastolic pressure were studied on isolated perfused rat heart. The following postconditioning protocols were used: 1) 3 cycles of reperfusion (10 sec) and ischemia (10 sec), total cycle duration 20 sec; 2) 6 cycles reperfusion of reperfusion (10 sec) and ischemia (10 sec), total cycle duration 20 sec; 3) 3 cycles of reperfusion (20 sec) and ischemia (20 sec), total cycle duration 40 sec; 4) 6 cycles of reperfusion (20 sec) and ischemia (20 sec), total cycle duration 40 sec; 5) 3 cycles of reperfusion (30 sec) and ischemia (30 sec), total cycle duration 60 sec. The use of several cycles of a total duration of 20 sec had no effect on LVDP, but reduced EDP throughout the reperfusion period. Postconditioning protocol consisting of three 40-sec cycles promoted LVDP recovery during the reperfusion, but had no effect on EDP and decelerated HP normalization. Six 40-sec cycles had no effect on LVDP and EDP, but impeded HR recovery during the reperfusion period. Postconditioning protocol consisting of three 60-sec cycles promoted LVDP increase during the reperfusion and reduced contracture, but these transient effects were accompanied by decelerated HP normalization.

Abstract P322: Chamber-Specific Differences in Oxidative Stress in Newborn Versus Adult Rabbit Hearts Following Ischemia-Reperfusion

Each year, tens of thousands of children undergo cardiopulmonary bypass (CPB) to correct congenital heart defects. While necessary for surgery, CPB involves stopping the heart and exposing it to ischemic conditions. While much is known about adult injury, little is known about the effects of global ischemia on newborn ventricles. The purpose of this study was to determine age- and chamber-specific differences in oxidative stress following global ischemia-reperfusion injury. We studied newborn (2–4 days) and adult (&gt;8 weeks) rabbit hearts subjected to Langendorff ischemia-reperfusion (30 minutes ischemia, 60 minutes reperfusion). Catalase and superoxide dismutase (SOD) activities were measured, as well as real-time hydrogen peroxide (H 2 O 2 ) and superoxide (O 2 − ) generation using confocal microscopy in isolated left and right ventricular (LV and RV) myocytes exposed to hypoxia. Our data demonstrate chamber and age-specific changes in oxidative stress. During ischemia, H 2 O 2 increased significantly in the RV while remaining constant in the LV of newborn rat rabbit myocytes. In contrast, there was a smaller, nonsignificant increase in H 2 O 2 in both both RV and LV myocytes of adults. The increase seen in the RV of newborns was several fold higher than that of adults (4.3-fold vs. 2.2 fold; p&lt;0.05). In whole heart tissue, catalase activity was significantly increased following ischemia in both adult ventricles, while no increase was seen in newborn hearts compared to sham hearts. Additionally, levels in newborns were several fold lower (p&lt;0.05), indicating less scavenging potential. SOD activity was increased from sham vs. ischemia in the LV of both adult and newborn hearts, but only in the RV of the newborn heart (0.80±0.09 to 3.0±0.43 U/mg; p&lt;0.001). Intra-cardiac injection of an H 2 O 2 scavenger, Ebselen, loaded in nanoparticles, improved recovery of developed pressure (49.53±16.25 to 80.0±11.31) in the RV of the newborn (p&lt;0.05), suggesting the local delivery of an exogenous antioxidant is cardioprotective in newborn RVs. Our data demonstrate there are ventricle-specific differences in oxidative stress between newborn and adult rabbit hearts. Local therapy is able to address some of these differences and may limit damage during bypass surgery.

Understanding Ventricular Remodeling after Correction of Mitral Regurgitation: Thinking Volumetrically

Early after correction of mitral valve (MV) regurgitation, systolic function of the left ventricle (LV) declines, but the underlying mechanisms of this phenomenon are unknown. Most studies in this area have analyzed LV function at one week postoperatively or later. In a retrospective study from our Clinic, Enriquez-Sarano et al. reported a decline in LV ejection fraction (EF) from 62% to 52% ( P &lt;0.001) in 217 patients with organic mitral regurgitation who were studied within the first year after MV replacement or repair. This decline was due to decreased left ventricular end-diastolic dimension (LVEDD) and minimal change in left ventricular end-systolic dimension (LVESD). Surgical investigators have compared the outcomes for different techniques of MV replacement and studies indicate that decline in EF may be mitigated by chordal preservation. It has been suggested that early postoperative measurements of cardiac geometry and function are confounded by the effects of global ischemia, reperfusion, and myocardial protection. Indeed, some clinicians have suggested that reduced EF early after MV repair results from myocardial dysfunction that, in turn, is related to poor myocardial protection. In addition, cardiac loading conditions change dramatically early after operation. We speculated that a postoperative decline in LV systolic indexes (eg, EF, FAC, and FS) may be interpreted as a volumetric adjustment of the heart to the correction of mitral regurgitation rather than as postoperative LV dysfunction due to impaired myocardial contractility, and clinical studies support this hypothesis. Soon after MV repair, the LV remodels gradually. Very early after correction of mitral regurgitation, the LVESD increases, preventing an acute increase in forward stroke volume. Within the next few postoperative days, the LVEDD begins to decrease and the LVESD changes accordingly to maintain a normal forward stroke volume; the remodeling occurs when neurohumoral mechanisms of the body adapt to the new hemodynamic milieu. This progression of remodeling may explain why some investigators have observed unchanged LV systolic and decreased diastolic size on the first postoperative echocardiogram about a week after MV repair.

Age- and Chamber-Specific Differences in Oxidative Stress After Ischemic Injury

Each year, tens of thousands of children undergo cardiopulmonary bypass (CPB) to correct congenital heart defects. Although necessary for surgery, CPB involves stopping the heart and exposing it to ischemic conditions. On reoxygenation, the heart can experience effects similar to that of acute myocardial infarction. Although much is known about adult injury, little is known about the effects of global ischemia on newborn ventricles. We studied newborn (2 to 4 days old) and adult (>8 weeks old) rabbit hearts subjected to ischemia-reperfusion (30 min of ischemia and 60 min of reperfusion). Our data demonstrated chamber- and age-specific changes in oxidative stress. During ischemia, hydrogen peroxide (H(2)O(2)) increased in both right-ventricular (RV) and left-ventricular (LV) myocytes of the newborn, although only the RV change was significant. In contrast, there was no significant increase in H(2)O(2) in either RV or LV myocytes of adults. There was a fivefold increase in H(2)O(2) formation in newborn RV myocytes compared with adults (P = 0.006). In whole-heart tissue, superoxide dismutase activity increased from sham versus ischemia in the left ventricle of both adult and newborn hearts, but it was increased only in the right ventricle of the newborn heart. Catalase activity was significantly increased after ischemia in both adult ventricles, whereas no increase was seen in newborn compared with sham hearts. In addition, catalase levels in newborns were significantly lower, indicating less scavenging potential. Nanoparticle-encapsulated ebselen, given as an intracardiac injection into the right or left ventricle of newborn hearts, significantly increased functional recovery of developed pressure only in the right ventricle, indicating the potential for localized antioxidant therapy during and after pediatric surgical procedures.

Protein-Energy Malnutrition Alters Thermoregulatory Homeostasis and the Response to Brain Ischemia

Co-existing protein-energy malnutrition (PEM), characterized by deficits in both protein and energy status, impairs functional outcome following global ischemia and has been associated with increased reactive gliosis. Since temperature is a key determinant of brain damage following an ischemic insult, the objective was to investigate whether alterations in post-ischemic temperature regulation contribute to PEM-induced reactive gliosis following ischemia. Male Sprague-Dawley rats (190-280 g) were assigned to either control diet (18% protein) or PEM induced by feeding a low protein diet (2% protein) for 7 days prior to either global ischemia or sham surgery. There was a rapid disruption in thermoregulatory function in rats fed the low protein diet as assessed by continuous recording of core temperature with bio-electrical sensor transmitters. Both daily temperature fluctuation and mean temperature increased within the first 24 hours, and these remained significantly elevated throughout the 7 day pre-ischemic period (p < 0.027). In the immediate post-surgical period, PEM decreased body temperature to a greater extent than that in well-nourished controls (p = 0.003). The increase in daily temperature fluctuation caused by PEM persisted throughout the 7 day post-surgical period (p < 0.001), and this interacted with the effects of global ischemia on days 8 (p = 0.018) and 11 (p = 0.021). The astrocytic and microglial responses induced at 7 days after global ischemia were not influenced by PEM, but this preliminary analysis needs to be confirmed with a more reliable global ischemia model. In conclusion, exposure to a low protein diet rapidly impairs the ability to maintain thermoregulatory homeostasis, and the resultant PEM also diminishes the ability to thermoregulate in response to a challenge. Since temperature regulation is a key determinant of brain injury following ischemia, these findings suggest that the pathophysiology of brain injury could be altered in stroke victims with coexisting PEM.

Effect of global ischemia and reperfusion during ventricular fibrillation in myopathic human hearts

The effect of lack of global coronary perfusion on myocardial activation rate, wavebreak, and its temporal progression during human ventricular fibrillation (VF) is not known. We tested the hypothesis that global myocardial ischemia decreases activation rate and spatiotemporal organization during VF in myopathic human hearts, while increasing wavebreak, and that a short duration of reperfusion can restore these spatiotemporal changes to baseline levels. The electrograms were acquired during VF in a human Langendorff model using global mapping consisting of two 112-electrode arrays placed on the epicardium and endocardium simultaneously. We found that global myocardial ischemia results in slowing of the global activation rate (combined endo and epi), from 4.89+/-0.04 Hz. to 3.60+/-0.04 Hz. during the 200 s of global ischemia (no coronary flow) (P<0.01) in eight myopathic hearts. Two minutes of reperfusion contributed to reversal of the slowing with activation rate value increasing close to VF onset (4.72+/-0.04 Hz). In addition, during the period of ischemia, an activation rate gradient between the endocardium (3.76+/-0.06 Hz) and epicardium (3.45+/-0.06 Hz) was observed (P<0.01). There was a concomitant difference in wavebreak index (that provides a normalized parameterization of phase singularities) between the epicardium (11.29+/-2.7) and endocardium (3.25+/-2.7) during the 200 s of ischemia (P=0.02). The activation rate, gradient, and wavebreak changes were reversed by short duration (2 min) of reperfusion. Global myocardial ischemia of 3 min leads to complex spatiotemporal changes during VF in myopathic human hearts; these changes can be reversed by a short duration of reperfusion.

Abstract 2020: The Effect of Global Ischemia and Reperfusion on Long Duration of Human Ventricular Fibrillation: A Multi-Electrode Mapping Study

Introduction: The most significant change to the latest AHA CPR guidelines is the recommendation of CPR first followed by defibrillation, for un-witnessed arrests. We tested the hypothesis that global myocardial ischemia during ventricular fibrillation (VF) decreases activation rate and short duration of reperfusion would normalize activation rates. Methods: We studied 6 Langendorff perfused human hearts which were explanted from cardiomyopathic patients who underwent transplantation. Tyrode solution was used for perfusion and flow was maintained at 0.9 to 1.1 ml/g/min. Multi-electrode mapping was performed for the entire epicardium (112 electrodes sock array) and the LV endocardium (112 electrodes balloon array). VF was induced by applying a 9-volt battery on the epicardium. As soon as the VF episode was induced, perfusion was turned off for 200 seconds mimicking global ischemia. At the end of this period the perfusion system was turned back on at a flow similar to baseline for an additional 140 seconds, mimicking a state of reperfusion. The hearts were then defibrillated and this protocol was repeated twice after a rest period of 5 minutes. For the analysis, 20 s electrograms located on the LV freewall (both endo and epi) were recorded at t = 0, 90, 180, 260 and 320s, for a total of 11520 electrograms. Local Activation Rates (LAR) for each electrogram was determined as the dominant frequency (DF) corresponding to the highest value in the power spectrum between 1.5 and 8 Hz. Results: Activation rate decreased from 4.962±0.020 Hz to 3.704±0.022 Hz (p&lt;0.0001) during the 200 seconds of global ischemia. During the 140 seconds of reperfusion the activation rate increased to 4.882±0.024 Hz (p&lt;0.0001). This value was comparable to what was measured at the onset of VF (p = 0.011). These changes of rates were similar for both endocardium and epicardium data (p = 0.0236). Conclusions: During long episodes of human VF, global myocardial ischemia leads to slowing of activation rate on the epicardium and endocardium. Two minutes of re-perfusion leads to reversal of this effect. These findings may support the recent change in CPR guidelines.

Age- and Gender-Related Differences in Ischemia/Reperfusion Injury and Cardioprotection: Effects of Diazoxide

Recent studies have demonstrated that aging is associated with reduced tolerance to ischemia and that the aged (not senescent) female heart has greater susceptibility to ischemia as compared with the aged male heart. Previously, we have shown that ischemia can be modulated with cardioplegia in the male heart; however, efficacy in the female heart was unknown. In this study, male and female mature (15 to 20 weeks) aged (>32 months) rabbit hearts (n = 134) were subjected to Langendorff perfusion. Control hearts were perfused for 180 minutes. Global ischemia hearts received 30 minutes of equilibrium, 30 minutes of global ischemia, and 120 minutes of reperfusion. Cardioplegia +/- diazoxide was infused separately, 5 minutes before global ischemia. Global ischemia significantly decreased postischemic functional recovery and significantly increased infarct size in the mature and aged male and female heart (p < 0.05 versus control). The effects of global ischemia were significantly exacerbated (p < 0.05) in the aged heart as compared with the mature heart. Cardioplegia +/- diazoxide significantly increased postischemic functional recovery and significantly decreased infarct size in mature male and female hearts, but these effects were significantly decreased in the aged heart (p < 0.05) and in the aged female as compared with the aged male heart. Postischemic functional recovery and infarct size are affected by age but not by gender. The cardioprotection afforded by cardioplegia is affected by age and gender with a strong age-by-gender interaction for end-diastolic pressure and infarct size. Our results indicate that currently optimized cardioplegia protocols effective in the male heart are not as efficacious in the aged female heart.

Myocardial protection from ischemic preconditioning is not blocked by sub-chronic inhibition of carnitine palmitoyltransferase I

Ischemic preconditioning (IP) triggers cardioprotection via a signaling pathway that converges on mitochondria. The effects of the inhibition of carnitine palmitoyltransferase I (CPT-I), a key enzyme for transport of long chain fatty acids (LCFA) into the mitochondria, on ischemia/reperfusion (I/R) injury are unknown. Here we investigated, in isolated perfused rat hearts, whether sub-chronic CPT-I inhibition (5 days i.p. injection of 25 mg/kg/day of Etomoxir) affects I/R-induced damages and whether cardioprotection by IP can be induced after this inhibition. Effects of global ischemia (30 min) and reperfusion (120 min) were examined in hearts harvested from Control (untreated), Vehicle- or Etomoxir-treated animals. In subsets of hearts from the three treated groups, IP was induced by three cycles of 3 min ischemia followed by 10 min reperfusion prior to I/R. The extent of I/R injury under each condition was assessed by changes in infarct size as well as in myocardial contractility. Postischemic contractility, as indexed by developed pressure and d P/d t max, was similarly affected by I/R, and was similarly improved with IP in Control, Vehicle or Etomoxir treated animals. Infarct size was also similar in the three subsets without IP, and was significantly reduced by IP regardless of CPT-I inhibition. We conclude that CPT-I inhibition does not affect I/R damages. Our data also show that IP affords myocardial protection in CPT-I inhibited hearts to a degree similar to untreated animals, suggesting that a long-term treatment with the metabolic anti-ischemic agent Etomoxir does not impede the possibility to afford cardioprotection by ischemic preconditioning.

Unaltered cerebral Na +,K +-ATPase activity after hypoxic/ischemic injury in piglets

We examined whether hypoxic/ischemic (H/I) stress decreased the cerebral Na +,K +-ATPase enzyme activity (NEA) of newborn pigs. The effects of global ischemia (10 min), asphyxia (10 min), and incomplete forebrain ischemia (45 min) were analyzed in ten different brain regions. The lengths of the reperfusion periods varied between 15 min and 3 h. NEA was determined as the ouabain-sensitive fraction of the total ATPase activity of the sample. Marked regional differences in NEA were observed in all experimental groups, whereas NEA was not significantly affected in any of the brain structures investigated. The present results suggest that damaged brain Na +,K +-ATPase may not be the cause of the neuronal–vascular impairment following H/I stress.

Effect of ventricular fibrillation duration on the defibrillation threshold in humans.

Early during ventricular fibrillation, the defibrillation threshold may be low, as ventricular fibrillation most probably arises from a localized area with only a few wavefronts and the effects of global ischemia, ventricular dilatation, and sympathetic discharge have not yet fully developed. The purpose of this study was to explore the effect of the timing of shock delivery in humans. During implantation of an ICD in 26 patients (24 men, 60 +/- 11 years, 19 coronary artery disease, NYHA 2.2 +/- 0.4, left ventricular ejection fraction 0.42 +/- 0.16), the defibrillation threshold was determined after approximately 10 and 2 seconds of ventricular fibrillation. Ventricular fibrillation was induced by T wave shocks. Mean defibrillation threshold was 9.9 +/- 3.6 J after 10.3 +/- 1.0 seconds. Within 2 seconds, 20 of 26 patients could be successfully defibrillated with < or = 8 J. In these patients, the mean defibrillation threshold was 4.0 +/- 2.1 J after 1.4 +/- 0.3 seconds compared to 9.5 +/- 3.1 J after 10.2 +/- 1.1 seconds (P < 0.001). There were no clinical differences between patients who could be successfully defibrillated within 2 seconds and those patients without successful defibrillation within 2 seconds. In the majority of patients, the defibrillation threshold was significantly lower within the first few cycles of ventricular fibrillation than after 10 seconds of ventricular fibrillation. These results should lead to exploration of earlier shock delivery in implantable devices. This could possibly reduce the incidence of syncope in patients with rapid ventricular tachyarrhythmias and ICDs.

Metabolic and ionic responses to global brain ischemia in the newborn dog in vivo: II. Post-natal age aspects

The main difference between newborn and adult brains is expressed in the relative resistance of the newborn brain to oxygen deprivation. The aim of the present study was to examine the effect of global ischemia in canine puppies of three different ages on the metabolic, ionic and electrical activity of the brain and to study the basic mechanisms underlying the relative resistance of the newborn brain in ischemic episode. The puppies were divided into three age groups. The young group included 0-6-day-old puppies (n= 16), the intermediate group included 7-19-day-old puppies (n = 2l), and the ‘adult’ group included puppies aged 20 days or more (n = 7 7). Statistical analysis of the results led to the following conclusions: The younger the puppy, the longer is the time until the occurrence of the secondary reflectance increase SRI (13.0±l.9 min vs. 5.3 ± 0.5 min). The younger the puppy, the longer the time until onset of potassium leakage from the cells (0.9± 0.7 min vs. 0.35 ± 0.05 min) and the lower the amount of potassium leakage (9.6±2.8mM vs. 21.7±4.8 mM). The rate of pumping of the potassium ions into the cells during the recovery stage was higher in the oldest group (1,2± 0.2 mM min–1 vs. 0.38 ±0.1 mMmin–1J. It was possible to speculate that in the young puppies there is uncoupling of the oxidative phosphorylation from respiration and as a result, there is a lower, if any, rate of ATP synthesis. It seems that the newborn brain is able to cope with a decrease in available energy for a longer period of time. This is apparently due to differences in membrane characteristics and an improved ability to retain ionic equilibrium across both sides of the membrane. [Neurol Res 2000; 22: 623–629]

Cardiac performance and lipid metabolism of alloxan-induced diabetic rats: Effect of global ischemia

The Global Project on Anti-Tuberculosis Drug Resistance has been gathering data since 1994. This study provides the latest data on the extent of drug resistance worldwide.Data for drug susceptibility were gathered from 90 726 patients in 83 countries and territories between 2002 and 2007. Standardised collection of results enabled comparison both between and within countries. Where possible, data for HIV status and resistance to second-line drugs were also obtained. Laboratory data were quality assured by the Supranational Tuberculosis Reference Laboratory Network.The median prevalence of resistance to any drug in new cases of tuberculosis was 11·1% (IQR 7·0–22·3). The prevalence of multidrug resistance in new tuberculosis cases ranged from 0% in eight countries to 7% in two provinces in China, 11·1% in Northern Mariana Islands (although reporting only two cases), and between 6·8% and 22·3% in nine countries of the former Soviet Union, including 19·4% in Moldova and 22·3% in Baku, Azerbaijan (median for countries surveyed 1·6%, IQR 0·6–3·9). Trend analysis showed that between 1994 and 2007, the prevalence of multidrug-resistant (MDR) tuberculosis in new cases increased substantially in South Korea and in Tomsk Oblast and Orel Oblast, Russia, but was stable in Estonia and Latvia. The prevalence of MDR tuberculosis in all tuberculosis cases decreased in Hong Kong and the USA. 37 countries and territories reported representative data on extensively drug-resistant (XDR) tuberculosis. Five countries, all from the former Soviet Union, reported 25 cases or more of XDR tuberculosis each, with prevalence among MDR-tuberculosis cases ranging between 6·6% and 23·7%.MDR tuberculosis remains a threat to tuberculosis control in provinces in China and countries of the former Soviet Union. Data on drug resistance are unavailable in many countries, especially in Africa, emphasising the need to develop easier methods for surveillance of resistance in tuberculosis.Global Project: United States Agency for International Development and Eli Lilly and Company. Drug resistance surveys: national tuberculosis programmes, the Government of the Netherlands, the Global Fund to Fight AIDS, Tuberculosis and Malaria, Japan International Cooperation Agency, and Kreditanstalt für Wiederaufbau.

Neutrophil-independent myocardial dysfunction during an early stage of global ischemia and reperfusion of isolated hearts

The effect of global ischemia and reperfusion on the expression of cytokine genes and cell adhesion molecules by myocardial tissues and neutrophils was studied by using the Langendorff model. Although cardiac function deteriorated after reperfusion of ischemic hearts, there was no evidence of inflammation and myocardial degeneration, which is in contrast to previous findings that neutrophil-mediated inflammation is a critical step in post-ischemic reperfusion injury in regional ischemia. Flow cytometry analysis demonstrated that the global ischemia and reperfusion did not affect the expression of adhesion molecules on neutrophils. We also examined the expression of various cytokines which are involved in inflammatory responses. Only interleukin 1α was induced after the reperfusion of the ischemic hearts. These results suggest that neutrophils barely contribute to the myocardial dysfunction and IL-1α may play a role in post-ischemic myocardial dysfunction during the early stage of reperfusion.

Anti-ischemia activity of HU-211, a non-psychotropic synthetic cannabinoid.

The novel tricyclic-terpenoid type cannabinoid, HU-211, was tested in gerbils and rats for protection against the effects of cerebral ischemia. Our transient ischemic models in gerbils and rats are based on the protection afforded against the lethal effects of global ischemia. HU-211 gave over 30% protection, by i.v. administration. The optimal dose ranges of HU-211 were between 5 and 10 mg/kg i.v. In gerbils we used a transient ischemia model induced by occlusion (10 min) of the bilateral common carotid arteries (BCCA). HU-211, 8 mg/kg i.v., gave a significantly (p < or = 0.05) better in vivo performed than a control group over three days following ischemia. Histology performed in gerbil model also resulted in significantly (p < 0.001) diminished degeneration area of CA1 in the hippocampus after treatment of HU-211. In the rat model, after four vessel occlusion (4VO) (20 min), HU-211 treatment significantly (p < 0.01) improved neurobehavior scoring. These results show that the new synthetic cannabinoid can protect against hippocampal neuron damage due to selective brain injury induced by cerebral global ischemia in gerbils or rats.

The effect of global ischemia and reperfusion on the plasma levels of vasoactive peptides. The neuroendocrine response to cardiac arrest and resuscitation.

Return of spontaneous circulation with CPR is a function of coronary perfusion pressure, which is determined by vasomotor tone and the force of compression. Vasomotor tone is affected by the relative stimulation of arterial vasoconstricting and vasorelaxing receptors by vasoactive substances. We measured the plasma levels of the endogenous vasoactive peptides arginine vasopressin (AVP) angiotensin II (ANG-II) and atrial natriuretic peptide (ANP) during cardiac arrest and resuscitation. A fibrillatory canine model of canine arrest was used. 'Down time' was greater than 10 min, during which no therapy, including BLS, was given. Standard ACLS was initiated at the end of the down time with manual external chest compression standardized to an esophageal pulse pressure of 50 mmHg. Blood samples were collected through an aortic catheter during spontaneous circulation and 3 min after initiation of ACLS. Peptide levels were measured using standard RIA techniques. Results are reported as the mean +/- S.D. in pg/ml. AVP levels increased from a baseline of 1.7 +/- 1.0 pg/ml during spontaneous circulation to 29.9 +/- 33.3 during cardiac arrest and CPR (P = 0.01). There was a moderate positive correlation between aortic pressure and circulating AVP levels after the first dose of epinephrine (R = 0.5). There was a trend towards higher AVP levels in animals with return of spontaneous circulation (P = 0.12). ANG-II levels increased from a baseline of 14.7 +/- 12.9 pg/ml during spontaneous circulation to 151 +/- 105 during cardiac arrest and CPR (P < 0.05). ANP levels increased from a baseline of 55 +/- 46 pg/ml during spontaneous circulation to 293 +/- 73 during cardiac arrest and CPR (P < 0.01). There were significant increases in the levels of these endogenous vasoactive peptides. This reflects the neuroendocrine response to global ischemia and CPR reperfusion. Plasma levels of these peptides may effect the vital organ perfusion pressures, response to exogenous vasopressors, and outcome of resuscitative efforts. Future therapies may be directed at enhancing or blocking the effect of these peptides so as to optimize perfusion pressure which is one of the principle determinants of outcome during CPR.

The effect of global ischemia and recirculation of rat brain on protein synthesisin vitro

Transient cerebral ischemia causes long-lasting inhibition of protein synthesis despite recovery of energy metabolism. We investigated the question if this inhibition is due to the formation of a suppression factor which interferes with the function of the protein synthesizing machinery. For this purpose rats were submitted to 20 minutes four vessel-occlusion followed by recirculation times from 30 minutes to 7 days. Post-mitochondrial supernatant (PMS) from various brain regions was added to a self-contained, cell-free rabbit reticulocyte translational system, and the effect on in vitro protein synthesis was assessed by measuring 14C-leucine incorporation over a duration of 45 minutes. PMS prepared at the end of ischemia from hippocampus, striatum and cerebellum inhibited in vitro protein synthesis by 40%-60% but there was only a minor inhibition by PMS from cerebral cortex. During post-ischemic recirculation cortical PMS transiently induced inhibition of in vitro protein synthesis by 30% but this effect gradually disappeared within one week. The inhibition caused by PMS from hippocampus, striatum and cerebellum was not reversed during recirculation and still amounted to about 40% after 7 days. Inhibition of in vitro protein synthesis could be blocked by heating PMS to 100 degrees C, indicating that the suppressor factor is a protein. The comparison of the in vitro effect of postischemic PMS with previously described in vivo inhibition of protein synthesis demonstrates that the here observed suppressor factor is not able to explain the overall disturbance of protein synthesis in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)