Complete Ischemia Research Articles

Muscle Energy Stores and Stroke Rates of Emperor Penguins: Implications for Muscle Metabolism and Dive Performance

In diving birds and mammals, bradycardia and peripheral vasoconstriction potentially isolate muscle from the circulation. During complete ischemia, ATP production is dependent on the size of the myoglobin oxygen (O(2)) store and the concentrations of phosphocreatine (PCr) and glycogen (Gly). Therefore, we measured PCr and Gly concentrations in the primary underwater locomotory muscle of emperor penguin and modeled the depletion of muscle O(2) and those energy stores under conditions of complete ischemia and a previously determined muscle metabolic rate. We also analyzed stroke rate to assess muscle workload variation during dives and evaluate potential limitations on the model. Measured PCr and Gly concentrations, 20.8 and 54.6 mmol kg(-1), respectively, were similar to published values for nondiving animals. The model demonstrated that PCr and Gly provide a large anaerobic energy store, even for dives longer than 20 min. Stroke rate varied throughout the dive profile, indicating muscle workload was not constant during dives as was assumed in the model. The stroke rate during the first 30 s of dives increased with increased dive depth. In extremely long dives, lower overall stroke rates were observed. Although O(2) consumption and energy store depletion may vary during dives, the model demonstrated that PCr and Gly, even at concentrations typical of terrestrial birds and mammals, are a significant anaerobic energy store and can play an important role in the emperor penguin's ability to perform long dives.

In Reply

Hadassah-Hebrew University Medical Center, Jerusalem, Israel. drenger@cc.huji.ac.ilI have read with great interest the comments of Drs. Liu and Xia. Their study on a similar model of streptozotocine-induced diabetic rats1confirmed my findings that myocardial signal transducer and activator of transcription 3 (STAT3) concentrations are significantly decreased in the diabetic heart, whereas normal STAT3 concentrations are essential for initiation of the protective process of sevoflurane postconditioning (postC) in diabetes. They also described their findings that STAT3 concentrations might recover in diabetic hearts in the presence of N -acetylcysteine. They suggest that N -acetylcysteine and allupurinol promote tolerance of the myocardium to ischemic injury by restoring adinopectin concentration, and thus, they propose that N -acetylcysteine might be effective in restoring sevoflurane postC in the diabetic heart.The animal model used in the study2was type I diabetes, i.e. , uncorrected hyperglycemia for 1 month. Insulin was given in the last 48 h to bring the animals into a state of normoglycemia at the time of the experiment. I did not give insulin therapy to alleviate the symptoms of diabetes, but to perform the experiments in a normoglycemic state, with a goal to reduce blood sugar to less than 135 mg/dl, but I actually achieved better control as reflected in the study. The diabetic irresponsiveness of the myocardium is more complex than that expected by the hyperglycemic state alone. It might be attributed to multiple cellular changes in mitochondrial membrane potentials, which lead to certain degrees of mitochondrial uncoupling.3This in turn leads to a glycation reaction, causing cellular injury and accumulation of glycation end products,4depression of more signal transduction components such as phosphatidylinositol 3-kinase, STAT3,2and nitric oxide synthase, as well as glycogen synthase kinase-3β activation,5all leading to lipid accumulation, inflammation, and remodeling.6Therefore, I do not agree with the comment that strict preservation of normoglycemia during the experiment might eliminate all changes accumulated during the month of diabetic state. The changes in the heart are too substantial to be prevented by a single maneuver of replenishing antioxidant state.From a practical view, giving higher doses of insulin to an animal would be irresponsible, because hypoglycemia in animals who are not observed closely most of the time would be detrimental. I am not aware of any animal study evaluating diabetes for long-term outcome that used conventional glucose control levels. Extrapolating from human data that use conventional glucose control, as suggested in the current letter to the editor, on patient postoperative long-term outcome, is controversial at best. Strict control of diabetes at normal levels was found hazardous due to severe side effects.7,8Attributing changes in sensitive cellular pathways, such as STAT3 and phosphatidylinositol 3-kinase, only to the natural lack of antioxidants seems simplistic. As discussed in the previous paragraph, diabetes effects on the heart are profound and the mechanism of injury is at multiple levels.The authors claim that a longer period of insulin therapy might have a beneficial effect on restoring postC in diabetes. Unfortunately, I suggested differently, that changes in the heart caused by diabetes were not restored by a short period of normoglycemia. Insulin administration before complete ischemia may carry the risk of enhanced cellular metabolism in the no-flow state, a situation that may bring about accumulation of high tissue levels of lactate, which inhibits glycolysis and prevents any glycolytic stimulation by insulin.9,10Therefore, until proved experimentally, I cannot agree with the authors' final statement that insulin administration before ischemia may produce beneficial effects.

Metabolism of biogenic amines in acute cerebral ischemia: Influence of systemic hyperglycemia

Dopamine, norepinephrine and serotonin are biogenic amines which are transmitters of the central nervous system. The effects of ischemia on the brain parenchyma depends on many factors, such is the mechanism of blood flow interruption, velocity of the occurring blood flow interruption, duration of an ischemic episode, organization of anatomical structures of the brain blood vessels etc., which all influence the final outcome. During interruption of the brain circulation in experimental or clinical conditions, neurotransmitter metabolism, primarily of biogenic amines, is disturbed. Many researches with various experimental models of complete ischemia reported a decrease in the content of norepinephrine, dopamine and serotonin in the CNS tissue. It was proven that hyperglycemia can drastically increase cerebral injury followed by short-term cerebral ischemia. Considering the fact that biogenic amines (dopamine, norepinephrine and serotonin) influence the size of neurologic damage, as well as the fact that in hyperglycemic conditions infarct size (from the morphological aspect) is larger relative to normoglycemic status, the intention was to evaluate the role of biogenic amines in occurrence of damage in conditions of hyperglycemia, i.e. in the case of brain apoplexia in diabetics. Analysis of biogenic amines metabolism in states of acute hyperglycemia, as well as analysis of the effects of reversible and irreversible brain ischemia on metabolism of serotonin, dopamine and norepinephrine, showed that acute hyperglycemia slows down serotonin, dopamine and norepinephrine metabolism in the cerebral cortex and n. caudatus. Brain ischemia in normoglycemic animals by itself has no influence on biogenic amines metabolism, but the effect of ischemia becomes apparent during reperfusion. In recirculation, which corresponds to the occurrences in penumbra, release of biogenic amines is uncontrolled and increased. Brain ischemia in acute hyperglycemic animals increases the release of biogenic amines regardless of ischemia duration (5 or 15 minutes). This effect is more apparent during recirculation. Acute hyperglycemia makes brain tissue more sensitive even to ischemia which last shorter, i.e. reversible ischemia.

Fibrinogen Concentrate Therapy Guided by Thromboelastometry as an Alternative to Fresh Frozen Plasma in Major Vascular Surgery

TYPE IV THORACOABDOMINAL aortic aneurysm (TAAA) repair is a major vascular procedure that involves replacing the native abdominal aorta, from the level of the diaphragm to the aortic bifurcation, with a synthetic graft. During surgery there is a period of complete ischemia of the liver, bowel, and kidneys followed by reperfusion of these organs and a more prolonged period of pelvic and lower limb ischemia. The operation is associated with large blood loss, often exceeding the patient's intravascular volume. Hemostasis usually becomes severely impaired during surgery as the concentrations of fibrinogen, other coagulation factors, and platelets in the patient's blood are decreased by dilution, consumption, hyperfibrinolysis, and the effects of visceral ischemia and reperfusion. 1 Cinà C.S. Clase C.M. Coagulation disorders and blood product use in patients undergoing thoracoabdominal aortic aneurysm repair. Transfus Med Rev. 2005; 19: 143-154 Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar , 2 Gertler J.P. Cambria R.P. Brewster D.C. et al. Coagulation changes during thoracoabdominal aneurysm repair. J Vasc Surg. 1996; 24: 936-943 Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar In addition, patients undergoing TAAA repair may be receiving antiplatelet agents, such as aspirin and clopidogrel, and they usually receive anticoagulants, such as heparin, during surgery. In an attempt to correct coagulopathy during surgery, infusions of blood components, such as fresh frozen plasma (FFP) and cryoprecipitate, often are used. However, the efficacy of FFP has been questioned, 3 Stainsby D. Jones H. Asher D. et al. Serious hazards of transfusion: A decade of hemovigilance in the UK. Transfus Med Rev. 2006; 20: 273-282 Abstract Full Text Full Text PDF PubMed Scopus (286) Google Scholar , 4 Stanworth S.J. Brunskill S.J. Hyde C.J. et al. Is fresh frozen plasma clinically effective? A systematic review of randomized controlled trials. Br J Haematol. 2004; 126: 139-152 Crossref PubMed Scopus (347) Google Scholar , 5 Stanworth S.J. Brunskill S.J. Hyde C.J. et al. Appraisal of the evidence for the clinical use of FFP and plasma fractions. Best Pract Res Clin Haematol. 2006; 19: 67-82 Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar and the transfusion of allogeneic blood components carries risks, including incompatibility reactions, immunosuppression, transfusion-related acute lung injury and the transmission of bacterial, viral, and prion infections. The UK Government's Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) has recommended that the use of UK-derived FFP should cease because of the concerns regarding variant Creutzfeldt-Jakob disease. 6 Summary of Seventh Meeting of SaBTO (Advisory Committee on the Safety of Blood, Tissues and Organs), July 14/15, 2009. http://www.dh.gov.uk/ab/SaBTO/DH_089412#_2 Google Scholar Cryoprecipitate has been withdrawn from use in many European Union countries and its continued use in the UK is under review by SaBTO. Is It Necessary to Maintain Fibrinogen During Hypothermia and Major Bleeding in Vascular Surgery?Journal of Cardiothoracic and Vascular AnesthesiaVol. 26Issue 5PreviewIn the case reports by Morrison et al,1 3 patients undergoing open thoracoabdominal aneurysm repairs received a continuous infusion of purified human plasma–derived fibrinogen concentrates (CSL Behring, Marburg, Germany) under the guidance of the FIBTEM assay on ROTEM (TEM International, Munich, Germany). There are some concerns about these cases. Full-Text PDF

The effects of deformation, ischemia, and reperfusion on the development of muscle damage during prolonged loading

Deep tissue injury (DTI) is a severe form of pressure ulcer where tissue damage starts in deep tissues underneath intact skin. In the present study, the contributions of deformation, ischemia, and reperfusion to skeletal muscle damage development were examined in a rat model during a 6-h period. Magnetic resonance imaging (MRI) was used to study perfusion (contrast-enhanced MRI) and tissue integrity (T2-weighted MRI). The levels of tissue deformation were estimated using finite element models. Complete ischemia caused a gradual homogeneous increase in T2 (∼20% during the 6-h period). The effect of reperfusion on T2 was highly variable, depending on the anatomical location. In experiments involving deformation, inevitably associated with partial ischemia, a variable T2 increase (17-66% during the 6-h period) was observed reflecting the significant variation in deformation (with two-dimensional strain energies of 0.60-1.51 J/mm) and ischemia (50.8-99.8% of the leg) between experiments. These results imply that deformation, ischemia, and reperfusion all contribute to the damage process during prolonged loading, although their importance varies with time. The critical deformation threshold and period of ischemia that cause muscle damage will certainly vary between individuals. These variations are related to intrinsic factors, such as pathological state, which partly explain the individual susceptibility to the development of DTI and highlight the need for regular assessments of individual subjects.

Anti-inflammatory effects of limb ischaemic preconditioning are mediated by sensory nerve activation in rats

We have shown that ischaemic preconditioning ameliorates both the local periosteal and the systemic leukocyte activation evoked by limb ischaemia-reperfusion. We hypothesized that the activation of chemosensitive afferent nerves by transient ischaemia contributes to the protective mechanisms of ischaemic preconditioning via a calcitonin gene-related peptide (CGRP)-dependent mechanism. In Sprague-Dawley rats, 60-min complete limb ischaemia was followed by 180min of reperfusion. In further experiments, the CGRP analogue hCGRP (0.3μgkg(-1)) or ischaemic preconditioning (2 × 10-min ischaemia/10-min reperfusion) was applied prior to the ischaemia-reperfusion insult. Ischaemic preconditioning was performed in three subgroups in which animals received the CGRP receptor antagonist CGRP(8-37) (30μgkg(-1)h(-1)), the chemosensitive afferent nerve inactivator resiniferatoxin (3 × 15μgkg(-1), sc), or vehicle. The effects of CGRP(8-37) and resiniferatoxin on ischaemia-reperfusion without ischaemic preconditioning were also evaluated. In the tibial periosteum of rats, intravital fluorescence microscopy and immunohistochemistry revealed significant attenuations of ischaemia-reperfusion-induced post-ischaemic leukocyte-endothelial interactions (rolling and adherence in the postcapillary venules) and tissue intracellular adhesion molecule expression following ischaemic preconditioning or hCGRP administration. Administration of CGRP(8-37) or pretreatment of animals with resiniferatoxin reversed the anti-inflammatory effects of limb ischaemic preconditioning, but failed to affect the microcirculatory consequences of ischaemia-reperfusion without ischaemic preconditioning. The results suggest that activation of the chemo- (capsaicin-) sensitive afferent nerves is involved in the mechanisms of microcirculatory anti-inflammatory protection provided by limb ischaemic preconditioning. Controlled activation of chemosensitive C-fibres or the CGRP receptors by the induction of ischaemic preconditioning or other means may furnish therapeutic benefit by ameliorating the periosteal microcirculatory consequences of tourniquet ischaemia.

Effect of Partial Oxygen Supply on Mitochondrial Electron Transport System During Complete Cardiac Ischemia

During complete ischemia we assessed myocardial utilization of the small amount of oxygen available. We also determined whether blood cardioplegia has any advantage over crystalloid cardioplegia in this setting. Patients with preserved left ventricular myocardial function and without anterolateral wall infarct or aneurysm were included to the study. Intermittent cold blood and crystalloid cardioplegia were used in 10 patients (group BC) and 9 patients (group CC), respectively. From myocardial biopsies, obtained before and after ischemia, complete electron transport system (ETS) enzyme activities (NDH, SDH, NCCR, SCCR, and COX) and lactate content were analyzed. Biochemical and hemodynamic analyses also were done. Myocardial and blood temperatures were monitored. Ischemic time was longer in group CC (p < 0.05). There were no important differences in biochemical and hemodynamic variables between the two groups. In addition, there was no difference in NDH and SDH activities as well as COX/SCCR and COX/RS-NCCR ratios between the two groups before and after ischemia. After Ischemia, RS-NCCR in group CC and SCCR and COX activities in both groups were lower than the control. For all enzymes, activity change ratios were not different between groups. Myocardial lactate content was increased in both groups after ischemia. However, the increase in group BC was less (p < 0.01). Based on our findings, we believe that the superiority of blood cardioplegia over crystalloid cardioplegia does not depend on oxygen content, but on other factors such as buffering and free oxygen radical scavenger effects among others. However, with the warm and continuous blood cardioplegia technique, oxygen content might be more important.

A mobile interventional radiology unit: innovation and social responsibility.

To present the preliminary results of a feasibility study performed to determine the value of a mobile interventional radiology unit used to promote a uterine embolization program for low-income patients. Forty patients with symptomatic fibroids were treated with uterine embolization. Procedures were performed in four public hospitals in the metropolitan area of Sao Paulo. This study was approved by the institutional research ethics committee and all patients signed an informed consent form. A mobile interventional radiology unit, named ANGIOMOVEL, was conceived and implemented utilizing a small truck to transport one mobile C arm, one radiological table, protection aprons and a small trolley containing specific supplies for the procedures. The ANGIOMOVEL team consisted of two interventional radiologists, one nurse, one driver and one assistant. The unit visited one hospital per week during a three-month period. Patient inclusion was contingent upon several factors, such as evaluation by a trained gynecologist, completion of a pelvic MRI, routine serological laboratory tests and completion of a quality of life questionnaire (QOL). Outcomes, MRI and QOL were evaluated. Data obtained after 12 weeks were collected and analyzed. Technical success was achieved in 100% of cases, with a mean procedure time of 43 minutes and a mean fluoroscopic time of 24 minutes. The mean hospital stay was 1.07 day and the mean time for recovery and return to normal activities was 10 days. After 12 weeks, 36 (90%) of patients noticed improvement of their symptoms and 4 (10%) did not notice any improvement. Thirty-eight patients (95%) were satisfied or very satisfied and 39 (97.5%) said they would recommend the procedure. Pre- and post-procedure magnetic resonance imaging analysis showed that complete fibroid ischemia was achieved in 92.5% of cases with a mean uterine volume reduction of 38% and a mean fibroid volume reduction of 52%. Health-related quality of life scores showed improvement, increasing from 39.30 before the treatment to 79.62 points after therapy. The initial results indicate that using a Mobile Interventional Radiology Unit is feasible, efficient and safe to develop a successful uterine fibroid embolization program providing care to the underserved patient community.

Salvage of the Ischemic Extremity: Hydrogen Sulfide Prevents Ischemia-Reperfusion Injury in Muscle when Delivered Prior to Revascularization

Objective: Ischemia-reperfusion injury (IRI) is an unavoidable consequence of revascularization following acute vascular occlusion. In the lower extremity, reperfusion after complete ischemia is known to cause significant morbidity - and possibly limb loss - as a result of irreversible muscle damage. Hydrogen sulfide (HS) is now recognized as an endogenous signaling molecule that acts through ATP-sensitive potassium channels. Recent in vitro and in vivo work from our group has shown that HS mitigates IRI in muscle cells when delivered prior to the onset of ischemia.

Detection of differentially regulated genes in ischaemic equine intestinal mucosa

Colic is a serious disease syndrome in horses. Much of the mortality is associated with ischaemic-injured intestine during strangulating obstruction, yet there is limited understanding of the associated molecular events. Identification of differentially expressed genes during ischaemic injury should expand our understanding of colic and may lead to novel targeted therapeutic approaches in the future. To isolate and identify differentially expressed genes in equine jejunum following a 2 h ischaemic event compared to normally perfused jejunum. Suppressive subtractive hybridisation was used to clone genes that are differentially expressed in equine jejunum injured by 2 h of complete ischaemia as compared to time-matched control jejunal tissues. Expression of selected clones was further evaluated by northern blot analysis. Of the 384 clones selected, 157 were confirmed to possess cDNAs corresponding differentially expressed genes by dot blot analysis. Two genes, fatty acid binding protein 2 and calcium-activated chloride channel 4 were further confirmed to be differentially expressed by northern blot analysis. Suppressive subtractive hybridisation can be used to detect changes in expression of a broad array of genes, as confirmed by northern blot analysis of selected genes. These initial results have identified a pool of equine intestinal epithelial genes that are differentially expressed following a 2 h ischaemic event. In particular, genes indicative of deranged metabolic activity and those potentially involved in early repair events were identified and may ultimately provide clues as to the nature of epithelial ischaemic injury in horses.

Postconditioning protects skeletal muscle from ischemia‐reperfusion injury

Ischemia-reperfusion (I/R) injury caused by abrupt restoration of the circulation after prolonged ischemic insult induces significant morbidity after reconstructive microsurgery. The authors investigated whether a postconditioning (post-con) procedure attenuated skeletal muscle I/R injury and protected muscular function. Three hours of complete ischemia was induced by occluding the muscular branches of rat extensor digitorum longus (EDL) muscle. The post-con procedure was started at the end of ischemia and involved six cycles of 15 seconds of reperfusion followed by 15 seconds of re-occlusion (3 minutes of total intervention) prior to initiating unlimited reperfusion. EDL muscle contractilities were compared with those of normal sides (no ischemic exposure), and experimental group results were also compared with control group results (3 hours of ischemia followed by full reperfusion without post-con) at 3 hours and 5 days postreperfusion. Muscle wet weights, myeloperoxidase (MPO) activities, and histological results were also evaluated. The muscle contractilities in the post-con group were significantly preserved at both 3 hours and 5 days postreperfusion as compared with ischemic controls. Decreased inflammatory cell infiltration, MPO activity, and wet weight of postconditioned EDL muscle suggested that post-con attenuated acute inflammatory reactions induced by I/R. This study demonstrates that post-con provides effective functional protection to skeletal muscles from I/R injury.

Inhibition of Mitochondrial Membrane Permeability as a Putative Pharmacological Target for Cardioprotection

Myocardial ischemia-reperfusion injury is a major cause of morbidity and mortality in developed countries. To date, the only treatment of complete ischemia is to restore blood flow; thus the search for new cardioprotective approaches is absolutely necessary to reduce the mortality associated with myocardial ischemia. Ischemia has long been considered to result in necrotic tissue damage but the reduction in oxygen supply can also lead to apoptosis. Therefore, in the last few years, mitochondria have become the subject of growing interest in myocardial ischemia-reperfusion since they are strongly involved in the regulation of the apoptotic process. Indeed, during ischemia-reperfusion, pathological signals converge in the mitochondria to induce permeabilization of the mitochondrial membrane. Two classes of mechanisms, which are not mutually exclusive, emerged to explain mitochondrial membrane permeabilization. The first occurs via a non-specific channel known as the mitochondrial permeability transition pore (mPTP) in the inner and the outer membranes causing disruption of the impermeability of the inner membrane, and ultimately complete inhibition of mitochondrial function. The second mechanism, involving only the outer membrane, induces the release of cell death effectors. Thus, drugs able to block or to limit mitochondrial membrane permeabilization may be cytoprotective during ischemia-reperfusion. The objective of this review is to examine the pharmacological strategies capable of inhibiting mitochondrial membrane permeabilization induced by myocardial ischemia-reperfusion.

Effect of some calcium channel blockers in experimentally induced diabetic nephropathy in rats

Diabetic nephropathy (DNP) is considered a CRD (Chronic Renal Disease); it is a major cause of illness and premature death in people with DM. The present study was designed to illustrate the role of CCBs (amlodipine and diltiazem) in prevention and treatment of DNP in rats. Eighty male albino rats weighing (130-180gm) were used in this study. These animals were subdivided into five equal groups. Insulinopenic diabetes was induced by STZ, two weeks later, 30 minutes of complete ischemia was induced in the left kidney to induce diabetic nephropathy then treatment was started for 12 weeks. At the end of experiment urine samples and blood samples were taken for biochemical analysis and kidneys were taken for histopathological evaluation. Combination of renal ischemia with DM produced a significant increase in rat weight, rat kidney weight, BUN (Blood Urea Nitrogen) level, K/B (Kidney/Body weight) ratio, random blood glucose, 24 hrs urine proteins, and 24 hrs urine volumes and creatinine clearance. Treatment with diltiazem or amlodipine significantly lowered elevated SBP and elevated 24 hrs urine volumes. Furthermore, treatment with captopril produced a highly significant lowering of elevated SBP and elevated serum creatinine; and a significant reduction in elevated K/B ratio and proteinuria. Light microscopic examination of diabetic kidneys revealed glomerulopathy characterized by thickening of the glomerular basement membrane, mesangial matrix expansion, arteriolar hyalinosis and large proteinaceous deposits occluding some capillary loops and hyaline droplets within the glomeruli. Moreover, examination of kidneys of ischemic animals by light microscope revealed focal tubular necrosis at multiple points along the nephron, interstitial edema and accumulation of leucocytes within dilated vasa recta.

The Porcine Retinal Vasculature Accessed Using an Endovascular Approach: A New Experimental Model for Retinal Ischemia

The aim of this study was to examine whether the retinal circulation in the pig can be accessed using interventional neuroradiology and to explore the possibility of creating occlusions that result in experimental retinal ischemia. Six experiments were performed using 100-kg pigs. The external carotid system was catheterized using a fluoroscopy-monitored, transfemoral, endovascular approach. Transient and permanent vascular occlusions were performed using an angioplasty balloon catheter or a liquid embolic agent that was administered via an injection-catheter. A technique for transfemoral catheterization of arteries supplying the retina was established. The ophthalmic artery was demonstrated to give rise to the main ciliary artery from which the retinal artery branched as a single artery or as several arteries. A balloon-catheter could be introduced into the ophthalmic artery but not into the main ciliary artery. An injection-catheter could, in all experiments, be introduced into the main ciliary artery and, in some experiments, into the retinal artery. Occlusion of the ophthalmic artery, over the branching of the main ciliary artery, caused incomplete ischemia, presumably because of collaterals feeding the distal parts of the vasculature. Multifocal ERG (mfERG) recordings showed decreased amplitudes and increased implicit times, indicating retinal ischemia. Occlusion of the ciliary and retinal arteries caused complete ischemia, as shown by complete flattening of the mfERG recordings and, by indirect ophthalmoscopy, blanching of the retinal arteries and a pale retina, The authors show for the first time that the ophthalmic and retinal artery can be catheterized using a transfemoral endovascular approach. This technique may be useful to produce clear-cut experimental retinal ischemia.

Effect of Ageing and Ischemia on Enzymatic Activities Linked to Krebs’ Cycle, Electron Transfer Chain, Glutamate and Aminoacids Metabolism of Free and Intrasynaptic Mitochondria of Cerebral Cortex

The effect of ageing and the relationships between the catalytic properties of enzymes linked to Krebs' cycle, electron transfer chain, glutamate and aminoacid metabolism of cerebral cortex, a functional area very sensitive to both age and ischemia, were studied on mitochondria of adult and aged rats, after complete ischemia of 15 minutes duration. The maximum rate (Vmax) of the following enzyme activities: citrate synthase, malate dehydrogenase, succinate dehydrogenase for Krebs' cycle; NADH-cytochrome c reductase as total (integrated activity of Complex I-III), rotenone sensitive (Complex I) and cytochrome oxidase (Complex IV) for electron transfer chain; glutamate dehydrogenase, glutamate-oxaloacetate-and glutamate-pyruvate transaminases for glutamate metabolism were assayed in non-synaptic, perikaryal mitochondria and in two populations of intra-synaptic mitochondria, i.e., the light and heavy mitochondrial fraction. The results indicate that in normal, steady-state cerebral cortex, the value of the same enzyme activity markedly differs according (a) to the different populations of mitochondria, i.e., non-synaptic or intra-synaptic light and heavy, (b) and respect to ageing. After 15 min of complete ischemia, the enzyme activities of mitochondria located near the nucleus (perikaryal mitochondria) and in synaptic structures (intra-synaptic mitochondria) of the cerebral tissue were substantially modified by ischemia. Non-synaptic mitochondria seem to be more affected by ischemia in adult and particularly in aged animals than the intra-synaptic light and heavy mitochondria. The observed modifications in enzyme activities reflect the metabolic state of the tissue at each specific experimental condition, as shown by comparative evaluation with respect to the content of energy-linked metabolites and substrates. The derangements in enzyme activities due to ischemia is greater in aged than in adult animals and especially the non-synaptic and the intra-synaptic light mitochondria seems to be more affected in aged animals. These data allow the hypothesis that the observed modifications of catalytic activities in non-synaptic and intra-synaptic mitochondrial enzyme systems linked to energy metabolism, amino acids and glutamate metabolism are primary responsible for the physiopathological responses of cerebral tissue to complete cerebral ischemia for 15 min duration during ageing.

Critical ischemic time for the rat ovary: Experimental study evaluating early histopathologic changes

The aim of the present study was to determine a critical ischemic time for ovary in an experimental study in rats. An experimental model using slip-knot tying of all ovarian arteries and veins in cycling female rats was developed. Rat ovaries were tied using the technique through an explorative laparotomy. Complete ischemia times of 1, 2 and 3 h were used for the study. At the end of the ischemic times, the ovaries were harvested following 1 h of reperfusion. Histology indicated a gradually increased congestion correlating with the respective increased ischemic times. According to the present findings 2 h complete ischemia yields a significant injury. The model used in the present study may be used for complete ischemia-reperfusion injury of the rat ovary.

The effect of glucose upon restitution after transient cerebral ischemia: A summary

The study describes a reproducible model of complete brain ischemia in rats. Rats with different plasma glucose concentrations were exposed to 10 min of complete cerebral ischemia achieved by compression of neck vessels by a pneumatic cuff. All 30 rats, except one, in which pre-ischemic plasma glucose level were lower than 22 mM (range 1.6-22) survived 10 min complete ischemia and made a similar recovery. Ten rats with pre-ischemic plasma glucose levels above 22 mM (range 22-47.2) died from seizures in the post-ischemic period. Post-ischemic treatment of seizures and hyperglycemia in the hyperglycemic rats significantly improved recovery. In conclusion, pre-ischemic hyperglycemia above 22 mM impairs recovery after complete ischemia by inducing seizures, post-ischemic hyperglycemia and lactic acidosis.

The influence of prostacyclin on the recovery of bioelectric cerebral activity after complete ischemia.

Complete cerebral ischemia (CCI) was evoked by closing the brachiocephalic trunk, the left subclavicular artery and both internal thoracic arteries with simultaneous depression of systemic arterial pressure (SAP) to 70-50 mm Hg. The experiments were performed with three groups of rabbits. The first group consisted of animals with 15 and 20 min CCI, not receiving PGI2. In the second group PGI2 was given for 15 min before and during 15 min CCI. The third group with 15 and 20 min CCI received PGI2 3 min before, during and for 15 min after ischemia. The recovery of ECoG and the activities of the respiratory and vasomotor centres were evaluated as were reflex reactions. In 38 percent of the second group of rabbits improvement of the neurological condition after CCI was noted, as compared with animals of the control groups and a faster recovery of the ECoG. In the third group the neurological state improved in 100 percent of cases with simultaneous significantly quicker recovery of the first symptoms of brain cortex bioelectric activity and continuous activity in ECoG records. Between groups 1 and 2, and group 3 there were differences concerning the time of recovery of ECoG, and the intensity of reflexes. The influence of PGI2 on the brain bioelectric activity of the animals after CCI was found to be favourable.

Ischemic limb preconditioning downregulates systemic inflammatory activation

We examined local and systemic antiinflammatory consequences of ischemic preconditioning (IPC) in a rat model of limb ischemia-reperfusion (I-R) by characterizing the leukocyte-endothelial interactions in the periosteum and the expression of adhesion molecules playing a role in leukocyte-mediated inflammatory processes. IPC induction (2 cycles of 10 min of complete limb ischemia and 10 min of reperfusion) was followed by 60 min of ischemia/180 min of reperfusion or sham-operation. Data were compared with those on animals subjected to I-R and sham-operation. Neutrophil leukocyte-endothelial cell interactions (intravital videomicroscopy), intravascular neutrophil activation (CD11b expression changes by flow cytometry), and soluble and tissue intercellular adhesion molecule-1 (ICAM-1; ELISA and immunohistochemistry, respectively) expressions were assessed. I-R induced enhanced leukocyte rolling and adherence in the periosteal postcapillary venules after 120 and 180 min of reperfusion. This was associated with a significantly enhanced CD11b expression (by approximately 80% and 72%, respectively) and moderately increased soluble and periosteal ICAM-1 expressions. IPC prevented the I-R-induced increases in leukocyte adherence and CD11b expression without influencing the soluble and tissue ICAM-1 levels. The results show that limb IPC exerts not only local, but distant antiinflammatory effects through significant modulation of neutrophil recruitment.

ClC-2 is required for rapid restoration of epithelial tight junctions in ischemic-injured murine jejunum

Background and aims Involvement of the epithelial chloride channel ClC-2 has been implicated in barrier recovery following ischemic injury, possibly via a mechanism involving ClC-2 localization to the tight junction. The present study investigated mechanisms of intestinal barrier repair following ischemic injury in ClC-2 −/− mice. Methods Wild type, ClC-2 heterozygous and ClC-2 −/− murine jejunal mucosa was subjected to complete ischemia, after which recovery of barrier function was monitored by measuring in vivo blood-to-lumen clearance of 3H-mannitol. Tissues were examined by light and electron microscopy. The role of ClC-2 in re-assembly of the tight junction during barrier recovery was studied by immunoblotting, immunolocalization and immunoprecipitation. Results Following ischemic injury, ClC-2 −/− mice had impaired barrier recovery compared to wild type mice, defined by increases in epithelial paracellular permeability independent of epithelial restitution. The recovering ClC-2 −/− mucosa also had evidence of ultrastructural paracellular defects. The tight junction proteins occludin and claudin-1 shifted significantly to the detergent soluble membrane fraction during post-ischemic recovery in ClC-2 −/− mice whereas wild type mice had a greater proportion of junctional proteins in the detergent insoluble fraction. Occludin was co-immunoprecipitated with ClC-2 in uninjured wild type mucosa, and the association between occludin and ClC-2 was re-established during ischemic recovery. Based on immunofluorescence studies, re-localization of occludin from diffuse sub-apical areas to apical tight junctions was impaired in ClC-2 −/− mice. Conclusions These data demonstrate a pivotal role of ClC-2 in recovery of the intestinal epithelium barrier by anchoring assembly of tight junctions following ischemic injury.