Characterization of microcirculatory disturbance in a novel model of pancreatic ischemia-reperfusion using intravital fluorescence-microscopy

INTRODUCTION

Microcirculatory disturbances caused by ischemia-reperfusion injury (IRI) are the crucial hallmarks of pancreatitis following pancreas transplantation.

AIMS

To develop a novel rodent model of normothermic in situ ischemia of a pancreatic tail-segment that simulates the clinical situation of pancreas transplantation by flushing the organ via an inserted microcatheter and thus enables selective treatment of the organ via this access.

METHODOLOGY

Four experimental groups were investigated (n = 7 Wistar rats/group): sham animals without ischemia and dissection of the pancreas; control animals with dissection of a pancreatic tail segment pedunculated on the splenic vessels and flushing od this segment with saline via a microcatheter; and two groups of animals treated like controls with a pancreatic ischemia time of 1 hour or 2 hours. With use of intravital epifluorescence microscopy, the microcirculatory damage was characterized by investigation of functional capillary density (FCD) and leukocyte adherence in postcapillary venules (LAV) before ischemia and during a reperfusion time of 2 hours. Dry:wet ratio determinations, light microscopy, and electron microscopic investigations were performed to characterize the histologic organ damage.

RESULTS

FCD decreased significantly (p < 0.05) 2 hours after reperfusion in the groups of 1-hour (-29.21%) and 2-hour ischemia (-42.73%), in comparison with baseline values. LAV increased significantly (p < 0.05), 4.3- and 5.8-fold, after 1-hour and 2-hour ischemia during the observation time. The histologic damage was similar to posttransplantation pancreatitis in humans 1 hour after reperfusion. In sham and control animals these alterations were not significant.

CONCLUSIONS

The rodent in situ model of pancreatic IRI showed standardized microcirculatory damage dependent on the ischemia time. Offering the possibility of selective treatment by the direct artery access to the ischemic pancreatic area, the model enables investigations of questions related to human pancreas transplantation.

Can renal dysfunction after infra-renal aortic aneurysm repair be modified by multi-antioxidant supplementation?

BACKGROUND

Renal failure after lower torso ischemia is a serious problem, partly caused by hypotension and indirect reperfusion injury. This injury is partly due to the formation of oxygen free radicals by activated neutrophils. This injury results in albuminuria and renal function impairment. There are indications that free radical damage in indirect reperfusion injury can be diminished by administering extra antioxidants before and during reperfusion.

METHODS

In this prospective randomised study we have looked at the influence of a multi-antioxidant supplementation on renal function in patients undergoing an elective open infrarenal abdominal aneurysm repair. The patients received either standard treatment (n=22) or standard treatment with additional antioxidants perioperatively (Allopurinol, vitamin E and C, N-acetylcysteine and mannitol). For renal function we have looked at the albumin/creatinine ratio in urine and 24 hr creatinine clearance.

RESULTS

Despite significantly increased serum total antioxidant capacity, the group receiving extra antioxidants showed no decrease in the albumin/creatinine ratio in urine. There was however a significantly higher creatinine clearance in this group at day 2.

CONCLUSIONS

The results indicate that the diminished renal function after infrarenal aneurysm repair may be influenced by antioxidant therapy.

Antithrombin III prevents deleterious effects of remote ischemia-reperfusion injury on healing of colonic anastomoses

BACKGROUND

Antithrombin III is known as the most important natural inhibitor of thrombin activity and has been shown to attenuate local harmful effects of ischemia-reperfusion injury in many organs. In recent animal studies, delaying effect of remote organ ischemia-reperfusion injury on healing of intestinal anastomoses has been demonstrated. In this study, we investigated whether antithrombin III reduces deleterious systemic effects of ischemia-reperfusion injury on healing of colonic anastomoses in rats.

METHODS

Anastomosis of the left colon was performed in 24 rats that were divided into three groups: sham operated control (group I, n = 8), 30 minutes of intestinal ischemia-reperfusion by superior mesenteric artery occlusion (group II, n = 8), antithrombin III treated group (250 U/kg before and after the ischemia-reperfusion, group III, n = 8). On postoperative day 6, all animals were sacrificed, and bursting pressure and tissue hydroxyproline content of the anastomoses were assessed and compared.

RESULTS

On postoperative day 6 the mean bursting pressures were 149.6 +/- 4.8, 69.8 +/- 13.5, and 121.8 +/- 8.7 mm Hg for groups I, II, and III, respectively (P = 0.000). Mean tissue hydroxyproline concentration values were 389.5 +/- 29.6, 263.1 +/- 10.0, and 376.0 +/- 33.8 microg/mg for groups I, II, III respectively (P = 0.005).

CONCLUSIONS

This study showed that, antithrombin III treatment significantly prevented the delaying effect of remote organ ischemia-reperfusion injury on anastomotic healing in the colon. Further clinical studies are needed to clarify whether antithrombin may be a useful therapeutic agent to increase the safety of the anastomosis during particular operations where remote organ ischemia-reperfusion injury takes place.

Middle cerebral artery function after stroke: the threshold duration of reperfusion for myogenic activity

BACKGROUND AND PURPOSE

Myogenic activity of the cerebral arteries is an important contributor to autoregulation of cerebral blood flow. Previous studies have demonstrated that increasing periods of ischemia diminished the amount of myogenic tone in cerebral arteries. In the present study, we investigated the effect of different periods of postischemic reperfusion on the myogenic behavior of middle cerebral arteries (MCAs). We measured both the amount of spontaneous myogenic tone that developed at 75 mm Hg and the contractile response to increased transmural pressure (TMP), ie, myogenic reactivity.

METHODS

The MCA occlusion model was used in male Wistar rats (n=45) to induce 30 minutes of temporary ischemia, followed by different periods of reperfusion (0 or sham; 30 minutes; and 6, 12, 18, 20, and 22 hours), confirmed by laser Doppler flowmetry. MCAs were studied in vitro using an arteriograph system that allowed control of TMP and measurement of lumen diameter. After equilibration for 1 hour at 75 mm Hg, TMP was increased stepwise in 25-mm Hg increments to 125 mm Hg and lumen diameter measured at each pressure. The amount of spontaneous myogenic tone was determined in both ischemic and contralateral arteries for each reperfusion period and compared with the right and left MCAs in the sham group. Arteries were then fixed with 10% formalin pressurized in the arteriograph bath and stained for filamentous (F)-actin with fluorescently labeled phalloidin, a specific probe for F-actin. The amount of F-actin was quantified using confocal microscopy.

RESULTS

MCAs from the sham-operated control group possessed considerable myogenic tone (35%). However, the amount of tone in ischemic MCAs progressively diminished as the reperfusion duration increased. In addition, sham-operated control arteries responded myogenically to increases in TMP, decreasing diameter as pressure increased. There was a similar response in arteries exposed to 30 minutes and 6 hours of reperfusion, all producing a negative slope on the pressure-diameter curve; however, myogenic reactivity was diminished at the longer periods of reperfusion, producing a positive slope of the graph. The slopes of the pressure-diameter curves were as follows: -0.10+/--0.06 (sham), -0.07+/--0.12 (30 minutes), -0.08+/--0.11 (6 hours), +0.09+/-0.09 (12 hours), +0.25+/-0.16 (18 hours), +0.38+/-0.09 (20 hours), and +0.57+/-0.09 (22 hours). F-actin content was significantly less only in ischemic MCAs at 6 and 12 hours of reperfusion.

CONCLUSIONS

These results demonstrate that longer periods of reperfusion significantly diminish myogenic activity of MCAs. Understanding how different periods of ischemia and reperfusion affect the function of the cerebral circulation may promote more effective treatment of ischemic stroke.

Assessment of myocardial inflammation produced by experimental coronary occlusion and reperfusion with 99mTc-RP517, a new leukotriene B4 receptor antagonist that preferentially labels neutrophils in vivo

BACKGROUND

99mTc-RP517 is a new leukotriene B4 (LTB4) receptor antagonist developed for imaging acute inflammation or infection. A unique property of 99mTc-RP517 is its ability to label white blood cells in vivo after intravenous injection. The goals of this study were to determine relative 99mTc-RP517 binding to human leukocyte subtypes and the 99mTc-RP517 uptake pattern in canine myocardium where inflammation was induced by either coronary occlusion and reperfusion or tumor necrosis factor alpha (TNFalpha) injection.

METHODS AND RESULTS

Fluorescence-activated cell sorter analysis was performed on whole human blood (n=2) and isolated neutrophils (n= 4) with a fluorescent analog of 99mTc-RP517, [F]-RP517. In whole blood, [F]-RP517 (500 nmol/L) preferentially labeled neutrophils. On isolated neutrophils, [F]-RP517 (10 nmol/L) binding was inhibited by 44% when LTB4 (400 nmol/L) was added. 99mTc-RP517 was injected intravenously in anesthetized, open-chest dogs before coronary occlusion (90 minutes) and reperfusion (120 minutes) (n=9) or before intramyocardial TNFalpha injection (n=3). Ex vivo images of heart slices were acquired. The left ventricle was divided into 72 segments for flow and 99mTc-RP517 uptake analysis. There was an inverse exponential relationship between 99mTc-RP517 uptake and occlusion flow (r=0.73). In the same 15 segments, 99mTc-RP517 uptake was highly correlated with the neutrophil enzyme myeloperoxidase (r=0.91). Ex vivo images revealed tracer uptake in the reperfused area (ischemic to normal count ratio=2.7+/-0.2).

CONCLUSIONS

RP517 binds to the neutrophil LTB4 receptor after intravenous injection. After reperfusion, 99mTc-RP517 uptake correlated with myeloperoxidase and was observed on ex vivo images, indicating that this tracer may have potential as an inflammation-imaging agent.

Low-flow ischemia and hypoxia stimulate apoptosis in perfused hearts independently of reperfusion

Post-ischemic reperfusion leads to apoptosis-linked loss of myocytes in cultured cells and in vivo. We tested the hypothesis that apoptosis develops without reperfusion in Langendorff-perfused hearts exposed to either low-flow ischemia (LFI) or hypoxia (H). Rat hearts were perfused with amino-acid-enriched Krebs-Henseleit buffer and exposed for 6 h to LFI (flow=2 ml/min, PO(2)=500+/-50mmHg, mean+/-SD), H (10ml/min, 120+/-15mmHg), or control conditions (C, 10ml/min, 500+/-50mmHg). At selected times, DNA-fragmentation was measured by agarose-gel electrophoresis and in situ TUNEL assay. After 6 h, the ratio (TUNEL-positive)/(total nuclei) was 0.620+/-0.027, 0.615+/-0.005, 0.404+/-0.021 in LFI, H and C, respectively. The ratio was 0.813+/-0.021 in hearts exposed to 90 min global no-flow ischemia and reperfused (5 h). To assess the role of membrane-diffusible factors, separate experiments were performed recirculating the medium and exposing hearts to LFI or H as above. The degree of apoptosis was the same in both the recirculating and non-recirculating modes. Thus, apoptosis develops by similar extents and in a time-dependent fashion in crystalloid-perfused rat hearts during LFI or H at the same oxygen shortage (flow.PO(2)), even without the reperfusion.

Effects of spiramine T on antioxidant enzymatic activities and nitric oxide production in cerebral ischemia-reperfusion gerbils

Spiramine T, an atisine-type diterpene alkaloid isolated from the Chinese herbal medicine Spiraea japonica var. acuta (Rosaceae), was shown to have neuroprotective effects on cerebral ischemia-reperfusion injury. In this study, the effects of spiramine T on antioxidant enzymes and nitric oxide production were evaluated in gerbils subjected to global forebrain ischemia (10 min) and reperfusion (5 days). Spiramine T (1.0 and 2.0 mg kg(-1) i.p.) markedly reduced the content of lipid peroxide (LPO), increased the glutathione peroxidase (GSH-PX) activity, and inhibited the increase of nitric oxidase (NOS) activity and nitric oxide production in the cortex during ischemia-reperfusion in gerbils. These results suggested that the neuroprotective effects of spiramine T were related to modulation of endogenous antioxidant enzymatic activities and reduction of the formation of nitric oxide.

Spatial and temporal alterations in the GABA shunt in the gerbil hippocampus following transient ischemia

In the present study, we have identified the alteration in the expressions of GABA shunt-associated enzymes and the GABA transporter in order to determine the relationship between the neuronal damage and GABA metabolism following ischemia. At 30 min post-ischemia, the immunoreactivities of the glutamic acid decarboxylase (GAD) isoforms were markedly elevated in the CA1 region, as compared with the sham operated group. At 3-12 h post-ischemia, their immunoreactivities recovered at the sham level. These patterns were similarly observed up to 12 h following ischemia insult. However, the intensity of GAD67 was markedly increased at 24 h post-ischemic insult. The temporal changes in GABA transporter 1 (GAT-1) expressions were similar to that of GAD67, but not GAD65, expression, at least prior to 12 h after ischemic insults. GAT-1 immunoreactivity was significantly elevated in the CA1 region posterior to 12 h post-ischemia. Both succinic semialdehyde dehydrogenase (SSADH) and succinic semialdehyde reductase (SSAR) immunoreactivities were not altered in GABAergic neurons following ischemia. In contrast, in pyramidal cells, both SSADH and SSAR immunoreactivities showed chronological alterations in the CA1 region. Thus, our findings suggest that the differential alterations of GABA metabolism may be one of the important factors in neuronal damages induced by ischemia.

The role of protease inhibition with emphasis on the effects of inflammation and vascular immune phenomena

This review discusses the role of protease inhibition with emphasis on the effects of inflammation and vascular immune phenomena in non-immunocompromised hosts. A vast body of knowledge elucidating the role of protease inhibition and hemostasis has accumulated in recent years. The two subjects are intimately linked, but the focus of this review is limited to the anti-inflammatory effects of protease inhibitors. In light of the particular expertise of the present authors, this review will focus on human studies and often cite work related to open-heart surgery, since in recent years this is the area in which a large effort has been concentrated worldwide.

Pathomechanisms of work-related musculoskeletal disorders: conceptual issues

Work-related musculoskeletal disorders (WRMSDs) by definition are a subset of musculoskeletal disorders (MSDs) that arise out of occupational exposures. While traditional exposure assessment techniques have proved to be successful in identifying ergonomic exposures that are epidemiologically linked to these disorders, some are troubled by the lack of one-to-one correspondence between specific occupational exposure profiles and specific MSDs. In the absence of more sophisticated hypotheses that might explain the occurrence of WRMSDs in a variety of exposure patterns, the aetiologic relationships may (again) be called into question. Another unanswered question is whether specific types of WRMSDs have qualitatively different exposure-response relationships. A clearer understanding of the underlying pathomechanisms associated with specific WRMSDs could help future researchers better determine how and when various occupational exposure profiles become pathogenic. Such knowledge could also be used to design exposure assessment tools to capture exposure information more relevant to the risk of WRMSDs. The main goals of this paper are to summarize several recently described pathomechanisms, most of which have been discussed primarily in clinical and experimental literature that might not be widely read by occupational health scientists. Suggestions are made as to how future research could evaluate whether these phenomena are relevant to the effects of physical exposures and the underlying disease processes of common WRMSDs.

Evidence for non-neurotensin receptor-mediated effects of xenin (1-25)--focus on intestinal microcirculation

Xenin (1-25) has been detected in various locations in mammalians. It has structural similarities with neurotensin and its intestinal effects are claimed to be mediated by neurotensin receptors. It has been shown to influence gastrointestinal motility. The effects of xenin (1-25) on intestinal microvascular perfusion after ischemia/reperfusion have not been investigated yet. Therefore, the superior mesenteric artery was clamped for 40 min in Wistar rats (n=8). Ten minutes prior to reperfusion, intravenous infusion of xenin (1-25) (5 nmol/kg/h) was started. By means of intravital microscopy, microvascular perfusion in the mucosal layer was assessed. Animals (n=8) with and without clamping of the superior mesenteric artery and infusion of the carrier solution served as controls. After ischemia/reperfusion, xenin (1-25) increased the density of perfused microvessels and the capillary red blood cell velocity compared to ischemic controls. Capillary red blood cell velocity was elevated (p<0.05). Xenin (1-25) improved the heterogeneous distribution of mucosal blood flow during reperfusion demonstrated by an increase of both the perfusion index and the percentage of perfused microvessels. We conclude that the effects of xenin (1-25) on intestinal microcirculation are significantly different from those previously described for neurotensin. A more complex effector mechanism must be postulated that may involve other regulatory peptides and receptors.

Activation of the lipopolysaccharide signaling pathway in hepatic transplantation preservation injury

BACKGROUND

Endotoxin or lipopolysaccharide (LPS) initiates a cascade of complications of septic shock and multiple organ failure seen in Gram-negative bacterial infections. The first step of this pathway, which leads to activated nuclear factor (NF)-kappaB, activating protein (AP)-1, and other transcription factors, is the formation of the LPS receptor complex by LPS, LPS-binding protein (LBP), CD14, and toll-like receptor (TLR) 2 or 4. We examined whether the LPS signaling pathway is activated by hepatic ischemia/reperfusion injury in the transplant setting.

METHODS

Orthotopic syngeneic rat liver transplantation was performed with 0 to 18 hr of cold preservation in University of Wisconsin solution. Animals were killed 1 to 48 hr after reperfusion. Northern blot analysis for CD14, LBP, and TLR2 mRNA, immunohistochemistry for LBP, liver enzyme analysis, and gel shift assay for NF-kappaB and AP-1 were performed.

RESULTS

LPS levels were elevated early after reperfusion. Aspartate aminotransferase and alanine aminotransferase maximally increased 12 hr after transplantation. LBP mRNA and protein and CD14 mRNA were significantly up-regulated peaking at 6 to 12 hr after reperfusion. TLR2 mRNA was also increased. NF-kappaB activity showed a biphasic peak at 1 to 3 hr and 12 hr after reperfusion, whereas AP-1 activity showed a peak at 3 to 6 hr. The induction of CD14 mRNA correlated with the length of cold ischemia time.

CONCLUSIONS

These data indicate that multiple components of the LPS signaling pathway are activated during ischemia/reperfusion injury after liver transplantation.

Extravascular transport of fluorescently labeled albumins in the rat mesentery

OBJECTIVE

Fluorescently labeled albumin is used frequently as a tracer when monitoring microvascular permeability. Several fluorescent dyes are available for labeling protein, including fluorescein isothiocyanate (FITC) and Texas Red (TR). Because differences in leakage of dye-labeled proteins have been reported, the objective of the present study was to compare the accumulation of these two tracers in interstitium and lymph after the inflammatory event of ischemia-reperfusion.

METHODS

Anesthetized rats were injected intravenously with FITC-labeled albumin (FITC-alb) and TR-labeled albumin (TR-alb) before 30 minutes of mesenteric ischemia. Because the tracers leaked out of the microcirculation after reperfusion, accumulation in the surrounding buffer-superfused tissue, and in separate experiments, accumulation in lymph vessels, was defined as the ratio of tissue-to-plasma and lymph-to-plasma fluorescence.

RESULTS

Reperfusion induced a significant increase in tissue-to-plasma fluorescence of FITC-alb; however, no increase was observed for TR-alb. In contrast, lymph-to-plasma fluorescence of TR-alb tended to be greater than FITC-alb. Reperfusion-induced increases in tissue-to-plasma fluorescence of TR-alb occurred only when the superfusate was replaced with mineral oil, in which case tissue-to-plasma TR-alb fluorescence tended to be greater than FITC-alb.

CONCLUSIONS

Measurement of fluorescently labeled albumin leakage from mesenteric venules depends on the dye used to label the albumin and requires an assessment of losses from the extravascular measuring region.

Transforming growth factor-beta1 (TGF-beta1): a potential recovery signal in the post-ischemic kidney

TGF-beta1 has been demonstrated to be up-regulated in response to ischemic events both in animal models and in man. Demonstration of this up-regulation in the kidney following experimentally induced acute renal failure and in renal transplants complements similar findings in coronary and cerebral ischemia. Activation of TGF-beta1 occurs as a direct consequence of hypoxia, angiotensin II signaling and loss of extra cellular matrix (ECM) integrity, all of which occur in renal ischemia-reperfusion injury. TGF-beta1 thus up-regulates the synthesis of extracellular matrix components such as fibronectin and collagen IV providing a basis for the restoration of epithelial coverage in the regenerating tubule. TGF-beta1 also regulates epithelial tubular cell proliferation and differentiation. This response is quickly closed down in response to recovery of the kidney. This review examines the evidence linking TGF-beta1 activity to recovery from renal ischemia thereby constructing a hypothesis for the beneficial role of TGF-beta1 in the post ischemic kidney.

Murine model of gastrointestinal ischemia associated with complement-dependent injury

Gastrointestinal ischemia-reperfusion (I/R) injury is often associated with remote tissue injury. Complement activation plays an important role in local and remote tissue injury associated with gastrointestinal I/R. We developed a new murine model of gastrointestinal I/R that has complement-dependent local and remote tissue injury. Twenty, but not thirty, minutes of gastrointestinal ischemia followed by 3 h of reperfusion induced a significant loss of intestinal lactate dehydrogenase that was significantly prevented by a murine anti-murine C5 monoclonal antibody. Anti-C5 also significantly decreased neutrophil infiltration into the gut and lung. Gastrointestinal I/R significantly increased pulmonary intercellular adhesion molecule-1 mRNA and protein expression that was significantly inhibited by anti-C5. Pulmonary macrophage inflammatory protein-2 mRNA was significantly induced by gastrointestinal I/R and inhibited by anti-C5 treatment. These data demonstrate that brief periods of murine gastrointestinal I/R activate complement, leading to tissue injury and neutrophil accumulation. Anti-C5 treatment attenuates tissue injury, neutrophil recruitment, and leukocyte adherence molecule and chemokine expression in the mouse. This model will be well suited to investigate the role of complement-mediated tissue injury and gene expression after gastrointestinal I/R.

The effects of (-)clausenamide on functional recovery in transient focal cerebral ischemia

The effects of (-)clausenamide (clau) on spatial cognitive functions and hippocampal long-term potentiation (LTP) after transient focal cerebral ischemia in rats were investigated. Four weeks after middle cerebral artery occlusion, Morris water maze tasks demonstrated that 2 h of transient forebrain ischemia resulted in a significant decrease in spatial discrimination performance. The escape latency at 4 and 5 days of acquisition trial was lower in the ischemic rats than in sham-operated rats (33.8+/-6.7 sec and 26.8+/-5 sec versus 12.2+/-4.0 sec and 10.4+/-3.6 sec), chronic treatment with clau (10 mg kg(-1) p.o. once daily) significantly improved the impairment (12.4+/-4.1 sec and 15.2+/-3.1 sec). After Morris water maze, the changes in population spike (PS) amplitude were recorded as an index of LTP in the perforant path-dentate gyrus synapses. There was no difference in PS amplitude between the sham-operated and vehicle-treated animals, whereas the fractional increase of PS 20-50 min after tetanus was significantly larger in clau-treated group. Histopathological analysis revealed that clau could protect against neuron loss in the regions of cortex and striatum. In conclusion, these data indicate a beneficial effect of clau for synaptic plasticity and cognitive function impaired by transient focal cerebral ischemia.

Effects of hypothermia and rewarming on the mucosal villus microcirculation and survival after rat intestinal ischemia-reperfusion injury

OBJECTIVE

To determine the effects of hypothermia and rewarming on changes in the villus microcirculation induced by intestinal ischemia-reperfusion (I/R).

SUMMARY BACKGROUND DATA

The small intestine is extremely sensitive to I/R injury, and although hypothermia can reduce cellular injury, its capacity to influence the villous microcirculation after intestinal I/R is unclear, especially after the return to normothermic conditions.

METHODS

Core body temperature of PVG rats was maintained at either 36 degrees to 38 degrees C (n = 12) or 30 degrees to 32 degrees C (n = 24) and then subjected to 30 minutes of intestinal ischemia. A subgroup of hypothermic animals (n = 12) were returned to normothermic conditions 120 minutes after clamp removal. The mucosal surface was visualized in an exteriorized ileal segment and macromolecular leak (MML) and leukocyte adhesion were monitored using in vivo microscopy (n = 6 in each group). MML from individual villi and numbers of adherent leukocytes within villi were determined for 2 to 4 hours after clamp removal. Heart rate and mean blood pressure were monitored in all animals. Control animals underwent sham surgery (n = 12).

RESULTS

Ten of 12 normothermic animals failed to survive the reperfusion period, whereas all hypothermic animals and 11 of 12 of the hypothermic animals that were returned to normothermic conditions survived. MML was significantly increased in all animals subjected to I/R, although leakage was more marked in animals subjected to continuous normothermia. Enhanced leukocyte adhesion and decreased blood flow were observed only in normothermic animals.

CONCLUSIONS

Hypothermia might prove to be an effective strategy for preventing adverse side effects in clinical settings in which intestinal I/R can be predicted.

Anesthetic preconditioning: triggering role of reactive oxygen and nitrogen species in isolated hearts

We postulated that anesthetic preconditioning (APC) is triggered by reactive oxygen/nitrogen species (ROS/RNS). We used the isolated guinea pig heart perfused with L-tyrosine, which reacts with ROS and RNS to form strong oxidants, principally peroxynitrite (ONOO(-)), and then forms fluorescent dityrosine. ROS scavengers superoxide dismutase, catalase, and glutathione (SCG) and NO. synthesis inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) were given 5 min before and after sevoflurane preconditioning stimuli. Drugs were washed out before 30 min of ischemia and 120 min of reperfusion. Groups were control (nontreated ischemia control), APC (two, 2-min periods of perfusion with 0.32 +/- 0.02 mM of sevoflurane; separated by a 6-min period of perfusion without sevoflurane), SCG, APC + SCG, L-NAME, and APC + L-NAME. Effluent dityrosine at 1 min reperfusion was 56 +/- 6 (SE), 15 +/- 5, 40 +/- 5(++), 39 +/- 4(++), 35 +/- 4(++) , and 33 +/- 5(++) units ((++)P< 0.05 vs. APC), respectively; left ventricular pressure (%baseline) at 60 min of reperfusion was 30 +/- 5(++), 60 +/- 4, 35 +/- 5(++), 37 +/- 5(++), 44 +/- 4, and 47 +/- 4; and infarct size (%total heart weight) was 50 +/- 5(++), 19 +/- 2, 48 +/- 3(++), 46 +/- 4(++), 42 +/- 4(++), and 45 +/- 2(++). Thus APC is initiated by ROS as shown by improved function, reduced infarct size, and reduced dityrosine on reperfusion; protective and ROS/RNS-reducing effect of APC were attenuated when bracketed by ROS scavengers or NO* inhibition.

Effect of trapidil in ischemia/reperfusion injury of peripheral nerves

OBJECTIVE

Ischemia plays an important role in the development of pathological changes in nerve tissue, and restoration of blood flow results in injury (ischemia/reperfusion [I/R] injury) mediated by toxic oxygen free radicals. Trapidil is currently used as a coronary artery vasodilating agent and is also used for the prevention of ischemic symptoms of cerebral vasospasm. The purpose of this study was to determine the effects of trapidil on I/R injury and the ischemic tolerance of rat peripheral nerves.

METHODS

Preischemia or prereperfusion administration of trapidil (8 mg/kg) was evaluated in the rat sciatic nerve I/R injury model. Nerve tissue samples from the I/R injury site were assayed for malondialdehyde (MDA), nitrites, and nitrates, as markers of I/R injury, and pathological changes were evaluated by electron microscopy.

RESULTS

I/R resulted in an increase in MDA levels, which remained elevated for 2 weeks in control nerves. Rats that received trapidil before ischemia exhibited decreased MDA levels, and rats that received trapidil after the standard 3 hours of ischemia demonstrated increased tolerance to reperfusion, as reflected in significantly decreased MDA levels. Nitrite and nitrate levels in trapidil-treated rats were significantly higher than those in control animals. Histological evaluations of the sciatic nerve segments demonstrated that preischemia and postischemia trapidil treatments had a sparing effect against the myelin damage and axonal edema that are consistently noted in untreated ischemic reperfused nerves.

CONCLUSION

The results confirm that pretreatment with trapidil before the ischemic insult or before reperfusion provides marked protection against I/R injury in peripheral nerves.

Effect of nitric oxide on the contractile function of rat reperfused skeletal muscle

BACKGROUND

The involvement of nitric oxide (NO) in ischemia-reperfusion injury remains controversial and has been reported to be both beneficial and deleterious. The purpose of this study was to examine the contribution of NO and superoxide to skeletal muscle function using an ischemic revascularized hind limb model in rats.

PATIENTS AND MATERIALS

Warm ischemia produced by vascular pedicle clamping was sustained for 3 h. The animals were divided into four groups according to the solution administrated: (1) saline, (2) N-methyl-L-arginine acetate (L-NMMA), (3) L-NMMA + N-(N-L-g-glutamyl-S-nitroso-l-cysteinyl)glycine (S-nitrosoglutathione), or (4) superoxide dismutase (SOD). Saline, L-NMMA, or L-NMMA + S-nitrosoglutathione was infused for the first 2 h of reperfusion. The SOD was administered as an intravenous bolus 5 min before the onset of reperfusion. Postischemic blood flow was measured by a Doppler flow meter. Muscle contractile function was determined after 24 h of reperfusion.

RESULTS

Postischemic blood flow was significantly decreased by the L-NMMA infusion compared with that in the saline-treated group. No significant difference in postischemic blood flow was noted in the saline-, L-NMMA + S-nitrosoglutathione-, and SOD-treated groups. Contractile function of the gastrocnemius muscle in the L-NMMA-and SOD-treated groups, but not in the L-NMMA + S-nitrosoglutathione group, was significantly better than that in the saline-treated group.

CONCLUSION

Limiting postischemic blood flow and SOD infusion are both beneficial in decreasing the ischemia-reperfusion injury of skeletal muscle. S-Nitrosoglutathione infusion following suppression of endogenous NO production does not reduce ischemia-reperfusion injury.

In vitro antioxidant potentials of traditional Chinese medicine, Shengmai San and their relation to in vivo protective effect on cerebral oxidative damage in rats

The preventive effects of Shengmai San (SMS), a traditional Chinese herbal medicine (TCM), was studied on cerebral ischemia-reperfusion injury in rats as a model of antioxidant-based composite therapy. Two biochemical indicators of oxidative damage, thiobarbituric acid reactive substance (TBARS) formation and glutathione peroxidase (GPX) loss were measured in the brain after forebrain ischemia-reperfusion treatment and both were inhibited in all rats administered SMS (15 g original herbs/kg) 2 h before the ischemia-reperfusion. Histochemical study of the brain slice using TTC staining revealed that the SMS effectively reduced infarct area caused by the cerebral ischemia-reperfusion. The antioxidant potentials of SMS preparations were determined in vitro by five different assay methods and were related to the in vivo effectiveness of SMS in protection against brain damage. Inhibitory effect on TBARS formation in vivo showed better correlation with superoxide radical scavenging and DPPH quenching activity in vitro rather than with the other in vitro antioxidant indicators. On the other hand, the in vivo prevention of GPX activity loss showed better correlation with in vitro crocin bleaching inhibition than with the other in vitro antioxidant indicators. It was also suggested that the in vitro TBARS inhibitory activty of SMS is not a good indication to predict the in vivo effectiveness of SMS on inhibition of either TBARS formation or GPX activity loss.

The effect of a reversible period of adverse intrauterine conditions during late gestation on fetal and placental weight and placentome distribution in sheep

Adverse intrauterine conditions occurring during early to mid-gestation or throughout the whole of gestation influence placental weight and the distribution of placentome types in sheep. However, no study to date has investigated the effect of a reversible period of adverse intrauterine conditions during late gestation upon fetal and placental weight and placentome distribution in sheep. Twenty-two sheep fetuses were chronically instrumented with an inflatable cord occluder, amniotic and vascular catheters and with a Transonic flow probe around an umbilical artery. At 125 days (term isca.145 days) the occluder was inflated to reduce umbilical blood flow by ca.30 per cent for 3d in 12 fetuses (umbilical cord compressed, UCC). The occluder was then deflated and umbilical blood flow allowed to return to baseline. The remaining 10 fetuses acted as sham-operated controls in which the occluder remained deflated at all times. At 135-137dGA ewes were humanely killed and tissues collected, weighed and placentomes classified. A reduction in umbilical blood flow by approximately 30 per cent from baseline for 3 days in UCC fetuses led to mild fetal asphyxia throughout the period of cord-compression. After deflation of the occluder cuff, umbilical blood flow returned to a level that was significantly greater than that measured during baseline. Umbilical cord compression had no effect on fetal body weight but significantly increased fetal adrenal weight relative to body weight. While the total number of placentomes was not altered by cord-compression, total placentome weight and the total weight of C/D-type placentomes were both reduced in UCC relative to control placentae. In addition, the mean weight of placentomes, and of C/D-type placentomes specifically, was significantly lower in UCC relative to control placentae. When expressed as a percentage of the total number of placentomes in the placenta, there was a significantly lower percentage of C/D-type placentomes in UCC relative to control placentae. In addition, there was a significant relationship between the total number of placentomes and the percentage C/D-type placentomes in control, but not UCC, placentae. The data suggest that a temporary, reversible period of adverse intrauterine conditions occurring late in gestation in sheep has persisting effects upon the placenta, mean placentome weight and placentome distribution.

Molecular pathways of regeneration and repair after liver transplantation

Injury to liver grafts due to cold ischemia, preservation, and reperfusion continues to be an important factor in patient outcome after liver transplantation. The development of therapeutic interventions that can limit ischemic injury, enhance recovery, and improve early graft function can have a major impact on patient morbidity. The mechanisms of hepatic preservation and reperfusion injury, the molecular pathways of graft recovery, and the cells involved remain poorly understood. With significant damage to parenchymal tissue following cold ischemic injury comes the need for replacement or repair of injured cells. In a rat liver transplant model, expression of cytokines and activation of transcription factors associated with the cell cycle resulting in cellular replication correlates with the length of cold ischemia and the degree of damage. The resident liver macrophage, the Kupffer cell, has been implicated as the primary source of inflammatory factors but may also be the source of important growth factors and cytokines that initiate cellular recovery and regeneration. Determining the source of the initiating signal is important, as manipulation of this signal can be used for therapeutic interventions in such fields as transplantation, tumor immunology, and inflammatory disease. These studies demonstrate the critical interrelation between parenchymal cells and cells of the immune system during signaling and recovery from preservation and reperfusion injury in the liver. Further defining the role of these immune cells and their products during the initiation of cellular recovery is essential for developing strategies to improve hepatocellular function after injury.

Effect of mild hypothermia on energy state recovery following transient forebrain ischemia in the gerbil

A transient (lasting for 15 min) bilateral carotid artery occlusion model was created by using male Mongolian gerbils ( n=20, weight 50-60 g). The animals were divided into a group with mild hypothermia (34 degrees C, n=10) and a normothermic group (37 degrees C, n=10). High-energy phosphate metabolism (ATP, PCr, Pi) and intracellular pH were sequentially measured using (31)P-MRS during ischemia and after reperfusion for 1 week. The same animals were also subjected to a histopathological evaluation. During ischemia, there were no statistically significant differences between the two groups in the quantities of the metabolites. However, after reperfusion the rate of metabolic recovery by the mildly hypothermic (MH) group was significantly higher (by 10-20%) than the normothermic (NT) group. The intracellular pH decreased about 0.4 in both groups after ischemia; and after reperfusion the intracellular pH of the MH group returned to baseline levels faster than in the NT group. One week after ischemia, energy metabolism gradually decreased about 10-20% in both groups. In the histopathological evaluation, pyramidal cell damage in the hippocampus was 33% on average in the MH group and 79% in the NT group. The neuronal damage to the cerebral cortex was 26% in the MH group and 61% in the NT group. Astrocyte reactivity in the hippocampus and cerebral cortex was 2.9% and 1.1% in the MH group and 9.7% and 5.2% in the NT group. The results of this experiment indicate that the protective effect of mild hypothermia is due to the high recovery rate of ATP and PCr and the prevention of a secondary decline in high phosphate energy.

Gene deletion of NF-kappa B p50 does not alter the hepatic inflammatory response to ischemia/reperfusion

BACKGROUND/AIMS

Nuclear factor kappa B (NF-kappa B) is a primary regulator of gene expression and is activated during hepatic ischemia/reperfusion injury. The objective of the present study was to determine whether activation of NF-kappa B is causally related to the induction of the acute inflammatory response induced by hepatic ischemia/reperfusion.

METHODS

Wild-type (p50(+/+)) and NF-kappa B p50-deficient (p50(-/-)) mice underwent hepatic ischemia/reperfusion. NF-kappa B activation was determined by electrophoretic mobility shift assay. Hepatic neutrophil accumulation was measured by liver myeloperoxidase content. Hepatocellular injury was assessed by serum level of alanine aminotransferase and liver histology.

RESULTS

In p50(+/+) mice, ischemia/reperfusion induced marked activation of NF-kappa B consisting of p50/p65 heterodimers. In contrast, NF-kappa B activation in livers from p50(-/-) mice was abrogated, but p65 was observed in nuclear extracts. Despite amelioration of NF-kappa B activation there was no significant difference between p50(+/+) and p50(-/-) mice in expression of TNF alpha and MIP-2, liver accumulation of neutrophils or hepatocellular injury.

CONCLUSIONS

Gene deletion of NF-kappa B p50 does not alter the hepatic inflammatory response to ischemia/reperfusion. Despite abrogation of DNA-binding by the NF-kappa B p50/p65 complex, p65 was still observed in nuclear extracts suggesting that there may be functional redundancy amongst members of the Rel protein family in order to preserve the inflammatory response.