Development of a silicon-mediated [3 + 2] annulation and its application to the synthesis of natural products]

Hearts preconditioned by brief ischemia are characterized by a reduced rate of cellular purine metabolite production during subsequent prolonged ischemia; the purpose of this study was to determine if transient exogenous adenosine pretreatment can mimic this phenomenon. The accumulation of interstitial fluid (ISF) purine metabolites during prolonged ischemia in untreated anesthetized dogs (n = 7) was compared to that in a group pretreated with brief ischemia (ischemic preconditioned group; n = 9), a group pretreated with 1.5 micromoles/min intracoronary adenosine (n = 7), and a group pretreated with 100 micromoles/min intracoronary adenosine (n = 7). Ischemic preconditioning was achieved by a 5 min period of left anterior descending coronary artery (LAD) occlusion followed by 10 min of reperfusion. The adenosine-treated groups were subjected to 10 min of intracoronary adenosine followed by 10 min of recovery. All animals were exposed to 60 min LAD occlusion followed by 60 min reperfusion. The changes in ISF adenosine and adenosine metabolites were assessed by cardiac microdialysis, using dialysate concentrations as indices of ISF levels. Ischemic preconditioning decreased the rate of dialysate adenosine and total purine accumulation during the prolonged ischemia. Although the two doses of exogenous adenosine bracketed the increase in ISF adenosine seen with ischemic preconditioning, neither adenosine dose was able to attenuate the rate of purine metabolite accumulation during prolonged ischemia. We conclude that exogenous adenosine pretreatment is unable to mimic the reduced ischemia-induced purine efflux that is characteristic of myocytes pretreated with brief ischemia.     

Telomere length, telomerase activity and telomerase RNA expression during mouse mammary tumor progression

The effects of intraportal administration of prostaglandin E1 (PGE1) on portal venous flow, hepatic arterial flow, peripheral tissue blood flow, and systemic arterial flow before and after 60 min total liver ischemia followed by 70% partial hepatectomy in rats were investigated. Total liver ischemia was induced by occluding the hepatoduodenal ligament for 60 min. PGE1 at a dose of 0.5 microg/kg/min was infused intraportally for 15 min before inducing hepatic ischemia (preischemic period) and for 60 min after ischemia (postischemic reperfusion period) in the treatment group. Normal saline was infused in the control group. Seventy percent partial hepatectomy was performed during ischemia. Serum biochemical analysis and liver tissue histology were carried out 1, 3, and 24 h, and 1 and 24 h after reperfusion respectively. One-week survival of the PGE1 group was improved to 70% compared to that of the control group of 30%. Postischemia reperfusion values of portal and peripheral tissue blood flows in the PGE1 group were 6.33 +/- 0.600 ml/min and 27.2 +/- 23.5 (arbitrary), and were significantly different from those of the control group of 4.34 +/- 0.400 ml/min and 23.5 +/- 5.54 (arbitrary), respectively. There was no significant difference in hepatic arterial flow between the two groups. Serum alkaline phosphatase decreased significantly in the prostaglandin group. Histological examination revealed a significant portal venous congestion in the control group 1 and 24 h after reperfusion. The extent of the sinusoidal congestion was also severe in the control group 24 h after reperfusion. It was concluded that PGE1 has a protective effect against liver damage when the liver was injured by warm ischemia and reperfusion followed by partial resection.     

Cerebral cortex blood flow and vascular smooth muscle contractility in a rat model of ischemia: a correlative laser Doppler flowmetric and scanning electron microscopic study

The present study was undertaken to ascertain the role of smooth muscles and pericytes in the microcirculation during hyperperfusion and hypoperfusion following ischemia in rats. Paired external carotids, the pterygopalatine branch of the internal carotids and the basilar artery were exposed and divided. Reversible inflatable occluders were placed around the common carotids. After 24 h, the unanesthetized rat underwent 10-min ischemia by inflating the occluders. Continuous cortical cerebral blood flow (c-CBF) was monitored by laser Doppler flowmetry. The measured c-CBF was below 20% of control (P < 0.001) during ischemia. A c-CBF of 227.5 +/- 54.1% (P < 0.001) was obtained during reperfusion hyperemia. A c-CBF of 59.7 +/- 8.8% (P < 0.001) occurred at the nadir of postischemic hypoperfusion, and this was followed by a second hyperemia. The cytoarchitecture of the vascular smooth muscles and pericytes was assessed by scanning electron microscopy. Samples were prepared using a KOH-collagenase digestion method. In control rats, arteriolar muscle cells showed smooth surfaces. Capillary pericytes were closely apposed to the endothelium. Immediately after reperfusion, transverse membrane creases were observed on the smooth muscle surfaces. During maximal hyperemia the creases disappeared. When c-CBF started to decrease the creases became visible again. Throughout the postischemic hypoperfusion the creases remained. Capillary endothelial walls became tortuous in the late phase of hypoperfusion. During the second hyperemia most arteriolar muscle cells showed smooth surfaces. Some pericytes appeared to have migrated from the vascular wall. The morphological changes of smooth muscle membranes suggest that they are related to specific perfusional disturbances during ischemia and reperfusion.     

Dose-dependent effects of adenosine on interstitial fluid adenosine and postischemic function in the isolated rat heart

Exogenous adenosine produces numerous beneficial effects in ischemic myocardium, but pharmacological doses of adenosine are required to exert these effects. This is thought to be due to the rapid metabolism of adenosine by coronary endothelium, although there is no direct evidence supporting this hypothesis in the ischemic/reperfused heart. The purpose of this study was to determine the relationship between vascular and interstitial fluid (ISF) adenosine levels during adenosine-induced cardioprotection. Isolated perfused rat hearts were submitted to 30-min global normothermic ischemia and 30- min reperfusion. Left ventricular developed pressure (LVDP) was measured with a fluid-filled latex balloon, and ISF adenosine was estimated with cardiac microdialysis. Control hearts were compared with hearts treated with increasing doses of adenosine (1, 10 and 100 microM) for 10 min immediately preceding ischemia. Adenosine produced dose-dependent increases in coronary effluent adenosine levels, but only 10 and 100 microM adenosine increased dialysate adenosine concentrations. All adenosine doses increased coronary flow to the same extent, but only the two higher doses decreased spontaneous heart rate. Control and 1 microM adenosine-treated hearts recovered 60 +/- 3% and 46 +/- 7% of preischemic LVDP, respectively, whereas 10 and 100 microM adenosine improved recovery to 80 +/- 5% and 90 +/- 4% of preischemic LVDP, respectively, after 30-min reperfusion. Because ISF bathes the cardiac myocytes, these results are consistent with the hypothesis that adenosine protects the ischemic rat heart via the activation of cardiac myocyte adenosine receptors.     

Mirror, mirror on the wall, who''s the thinnest one of all? Effects of self-awareness on consumption of full-fat, reduced-fat, and no-fat products

The aim of this study was to determine whether adenosine receptor blockade before ischemia would enhance the degree of stunning and induce a sustained decrease in glucose uptake after reperfusion. METHODS: Stunning was induced in 14 anesthetized swine by partially occluding the left anterior descending artery (LAD) for 20 min (> 80% flow reduction). Seven animals were pretreated with the nonspecific adenosine receptor blocker 8-phenyltheophylline (8-PT; 5 mg/kg), which decreased reactive hyperemia by an average of 38%. Myocardial glucose uptake was assessed 1 hr following reperfusion with PET and the glucose analog 18F-fluorodeoxyglucose (FDG). RESULTS: Before ischemia, systolic shortening in the LAD region was 15% +/- 6% in the control group and 16% +/- 4% in the 8-PT group and in both groups was reduced to - 1% +/- 2% during ischemia. After reperfusion, systolic shortening was 7% +/- 3% in the control group and 2% +/- 3% in the 8-PT group (p < 0.05). Myocardial oxygen consumption before ischemia was 4.58 +/- 3.03 micromol/min/g in the control group and 4.44 +/- 1.83 micromol/min/g in the 8-PT group (ns) and neither were different after reperfusion. In the postischemic LAD region, myocardial glucose uptake was 0.18 +/- 0.15 micromol/min/g in the control group and was similar to that of the 8-PT group (0.17 +/- 0.08 micromol/min/g; ns). CONCLUSION: The nonspecific adenosine blocker 8-PT enhanced the degree of stunning when given before ischemia but did not induce a sustained effect on myocardial glucose uptake after reperfusion.     

High temporal resolution diffusion MRI of global cerebral ischemia and reperfusion

Although brain ischemia has been extensively studied using diffusion-weighted magnetic resonance imaging, most studies performed so far have not had adequate time resolution to follow the temporal changes in the water apparent diffusion coefficient (ADC) in hyperacute ischemia. Using diffusion echo planar imaging, we obtained ADC maps (calculated from measurements made with 8 b-values) with a time resolution of 43 s in a feline model of global brain ischemia and reperfusion. Different protocols were performed: 10-min hypoperfusion, 10- and 22-min ischemia followed by reperfusion, and cardiac arrest. ADC values were obtained from white matter of the internal capsule and from the thalamus. Cortical gray matter measurements were not deemed reliable due to the close proximity of CSF in the cortical sulci. Following occlusion, the ADC declined in the thalamus to < 2 SD of its normal baseline value within 1.5-2.5 min. This decay was exponential with a time constant (tau +/- SD) of 6.0 +/- 2.6 min; no further decrease in the ADC was observed 10 min following ischemia. Following reperfusion, in animals that showed ADC recovery, the ADC began increasing immediately, returning to its preischemic value in approximately 15 min. No significant ADC changes were observed during hypoperfusion. Following cardiac arrest, the decay of ADC was more rapid in the thalamus (tau = 2.6 +/- 0.6 min) than in white matter (tau = 6.6 +/- 1.8 min). We observed that the ADC at 40 min after cardiac arrest was similar to the ADC at 10 min after ischemia. Given that all animals subjected to 10-min ischemic episodes showed ADC recovery with reperfusion, doubt is cast on whether it is possible to define a threshold value of the ADC below which brain tissue is irreversibly damaged. Finally, despite variability in the time constants of the ADC decay induced by ischemia, the ADC values at 10 min were very similar in all the animals. This suggests that when blood flow is diminished sufficiently to induce an ADC reduction, differences in perfusion affect the rapidity of the decrease but not the final asymptotic value reached.     

Screening a peptidyl database for potential ligands to proteins with side-chain flexibility

OBJECTIVE: Microdialysis and 31P-NMR spectroscopy were used to test opposing hypotheses that ischemic preconditioning inhibits adenine nucleotide degradation and purine efflux, or that preconditioning activates cardiovascular adenosine formation to provide enhanced cardioprotection. METHODS: 31P-NMR spectra and matching interstitial fluid (ISF) or venous effluent samples were obtained from Langendorff perfused rat hearts. Control hearts (n = 9) underwent 30 min of global normothermic ischemia and 30 min reperfusion. Preconditioned hearts (n = 6) were subjected to a 5 min ischemic episode and 10 min reflow prior to 30 min ischemia and 30 min reperfusion. Effects of repetitive ischemia-reperfusion (3 x 5 min ischemic episodes) on adenosine levels and energy metabolism were also assessed (n = 8). RESULTS: Preconditioning improved post-ischemic recovery of heart rate x left ventricular developed pressure (71 +/- 5 vs 43 +/- 8%, P < 0.05) and end-diastolic pressure (14 +/- 3 vs 29 +/- 4 mmHg, P < 0.05) compared with control hearts, respectively. Preconditioning did not alter intracellular ATP, phosphocreatine (PCr), inorganic phosphate (Pi), H+ or free Mg2+ during global ischemia, but improved recoveries of PCr, Pi, and delta GATP on reperfusion. ISF adenosine increased more than 20-fold during 30 min ischemia. The 5 min preconditioning episode increased ISF adenosine 3-fold, and reduced ISF adenosine and inosine during subsequent prolonged ischemia by up to 75%. Venous purine levels during reperfusion were also reduced by preconditioning. Accumulation of adenosine in ISF and venous effluent during repetitive ischemia was progressively reduced despite comparable changes in substrate for adenosine formation via 5'-nucleotidase, (5'-AMP), and in allosteric modulators of this enzyme (Mg2+, H+, Pi, ADP, ATP). CONCLUSIONS: (i) Ischemic preconditioning reduces interstitial and vascular adenosine levels during ischemia-reperfusion, (ii) reduced ISF adenosine during ischemia is not due to reduced ischemic depletion of adenine nucleotides in preconditioned rat hearts, (iii) preconditioning may inhibit adenosine formation via 5'-nucleotidase in ischemic rat hearts, and (iv) improved functional recovery with preconditioning is unrelated to metabolic/bioenergetic changes during the ischemic insult, but may be related to improved post-ischemic recovery of [Pi] and delta GATP in this model.     

Ischemic preconditioning does not protect against contractile dysfunction in the presence of residual flow: studies in the isolated, blood-perfused rat heart

BACKGROUND: We have previously demonstrated that ischemic preconditioning (PC) does not protect when oxygen deprivation is accompanied by a high level of perfusion (hypoxia). Since clinical ischemia can vary from mild to severe, we wished to determine whether PC could protect against injury arising from low-flow ischemia. METHODS AND RESULTS: Functional recovery after 30 minutes of reperfusion was assessed in isolated, blood-perfused rat hearts (n=6 per group) subjected to (A) 30 minutes of zero-flow ischemia, (B) 30 minutes of zero-flow ischemia preceded by 3xPC (PC=5 minutes of ischemia+5 minutes of reperfusion), (C) 90 minutes of low-flow ischemia at 10% of baseline coronary flow (0.31+/-0.02 mL/min per gram wet wt), (D) 90 minutes of low-flow ischemia at 10% of baseline coronary flow (0.29+/-0.02 mL/min per gram wet wt) preceded by 3xPC. PC significantly protected against injury resulting from zero-flow ischemia (developed pressure recovered to 67+/-6% versus 31+/-12% in B and A, respectively; P<.05) but not resulting from low-flow ischemia (recovery of developed pressure was 40+/-8% versus 37+/-7% in C and D, respectively). Protein kinase C (PKC) is widely considered to be involved in the mechanism of PC such that prior activation and translocation of PKC by the PC protocol allows phosphorylation of the end-effector protein early during the subsequent ischemic insult, before loss of adenosine triphosphate occurs. However, because adenosine triphosphate content falls slowly during low-flow ischemia, PKC may be activated and translocated early enough to be active during this insult. If so, inhibition of PKC should decrease functional recovery in the control group. However, functional recovery in control groups was not decreased in the presence of the PKC inhibitor polymyxin B (50+/-6%), suggesting that if activation of PKC occurred during low-flow ischemia, it was not protective. CONCLUSIONS: PC does not protect against contractile dysfunction in the rat when a low level (10% of baseline flow) of ischemic perfusion remains during the prolonged insult.     

Adenosine-enhanced ischemic preconditioning provides enhanced postischemic recovery and limitation of infarct size in the rabbit heart

OBJECTIVE: The purpose of this study was to determine the effect of an intracoronary bolus injection of adenosine used in concert with ischemic preconditioning on postischemic functional recovery and infarct size reduction in the rabbit heart and to compare adenosine-enhanced ischemic preconditioning with ischemic preconditioning and magnesium-supplemented potassium cardioplegia. METHODS: New Zealand White rabbits (n = 36) were used for Langendorff perfusion. Control hearts were perfused at 37 degrees C for 180 minutes; global ischemic hearts received 30 minutes of global ischemia and 120 minutes of reperfusion; magnesium-supplemented potassium cardioplegic hearts received cardioplegia 5 minutes before global ischemia; ischemic preconditioned hearts received 5 minutes of zero-flow global ischemia and 5 minutes of reperfusion before global ischemia; adenosine-enhanced ischemic preconditioned hearts received a bolus injection of adenosine just before the preconditioning. To separate the effects of adenosine from adenosine-enhanced ischemic preconditioning, a control group received a bolus injection of adenosine 10 minutes before global ischemia. RESULTS: Infarct volume in global ischemic hearts was 32.9% +/- 5.1% and 1.03% +/- 0.3% in control hearts. The infarct volume decreased (10.23% +/- 2.6% and 7.0% +/- 1.6%, respectively; p < 0.001 versus global ischemia) in the ischemic preconditioned group and control group, but this did not enhance postischemic functional recovery. Magnesium-supplemented potassium cardioplegia and adenosine-enhanced ischemic preconditioning significantly decreased infarct volume (2.9% +/- 0.8% and 2.8% +/- 0.55%, respectively; p < 0.001 versus global ischemia, p = 0.02 versus ischemic preconditioning and p = 0.05 versus control group) and significantly enhanced postischemic functional recovery. CONCLUSIONS: Adenosine-enhanced ischemic preconditioning is superior to ischemic preconditioning and provides equal protection to that afforded by magnesium-supplemented potassium cardioplegia.     

Effects of intermittent reperfusion on brain pHi, rCBF, and NADH during rabbit focal cerebral ischemia

BACKGROUND AND PURPOSE: The use of intermittent reperfusion versus straight occlusion during neurovascular procedures is controversial. This experiment studied the effects of intermittent reperfusion and single occlusion on intracellular brain pH (pHi), regional cerebral or cortical blood flow, and nicotinamide adenine dinucleotide (NADH) fluorescence during temporary focal ischemia. METHODS: Twenty fasted rabbits under 1.0% halothane anesthesia were divided into four groups: (1) nonischemic controls, (2) 60 minutes of uninterrupted focal ischemia, (3) 2 x 30-minute periods of focal ischemia separated by a 5-minute reperfusion, and (4) 4 x 15-minute periods of focal ischemia separated by three 5-minute reperfusion periods. Focal ischemia was produced by occlusion of both the middle cerebral and ipsilateral anterior cerebral arteries. After the final occlusion, there was a 3-hour reperfusion period in all groups. Regional cerebral and cortical blood flow, brain pHi, and NADH fluorescence were measured with in vivo panoramic fluorescence imaging. RESULTS: During occlusion, regional cerebral and cortical blood flows and NADH fluorescence values were not different among the groups. Brain pHi was significantly lower in the 4 x 15-minute group compared with the 1 x 60-minute group (6.57 +/- 0.02 versus 6.73 +/- 0.06; P < .03) but not significant when compared with the 2 x 30-minute group. During the short reperfusion periods, all parameters returned to normal except for NADH fluorescence levels, which remained elevated. During the postischemic final reperfusion period, there was a mild brain alkalosis of approximately 7.1 in all groups. There were no significant differences in NADH fluorescence among groups during the final reperfusion. Regional cerebral and cortical blood flow returned to near normal values in all groups. CONCLUSIONS: This study demonstrates that intermittent reperfusion during temporary focal ischemia has different effects on the intracytoplasmic and the intramitochondrial compartments: worsening of brain cytoplasmic pHi but no significant differences in the oxidation/reduction level of mitochondrial NADH.     

Effects of ischemia, preconditioning, and adenosine deaminase inhibition on interstitial adenosine levels and infarct size

In order to examine the relationship between local adenosine concentrations before, during, and after ischemia and the extent of ischemic myocardial damage, measurements of interstitial fluid (ISF) nucleosides were made using microdialysis probes implanted in the ischemic region of isoflurane anesthetized Micropigs undergoing 60' coronary artery occlusion (CAO) and 3 h of reperfusion (REP). Nucleoside concentrations in the dialysate collected from the microdialysis probes were used as an index of ISF levels. Dialysate nucleoside concentrations (ADO, inosine and hypoxanthine), myocardial infarct size, and myocardial blood flow (MBF) were determined in control animals (n = 6), animals preconditioned with a single 10' cycle of CAO and REP (PC, n = 6), and those treated with the adenosine deaminase inhibitor pentostatin (n = 6, 0.2 mg/Kg i.v. 30' prior to CAO). The brief PC occlusion resulted in a transient but significant increase in dialysate ADO (6.7 +/- 1.8 microM vs. 0.67 +/- 0.1 microM at baseline). Pentostatin administration had no significant effect on either dialysate nucleosides or MBF at baseline. During the 60' CAO, dialysate ADO increased in control animals. In PC animals, however, dialysate ADO during CAO was lower than control. Pretreatment with pentostatin resulted in a six-fold augmentation in dialysate ADO during the 60 min CAO when compared to the control values (110.62 +/- 30.2 microM vs. 16.31 +/- 2.1 microM at 60 min of ischemia). Pentostatin also resulted in a significant reduction in the accumulation of inosine and hypoxanthine, indicating inhibition of adenosine deaminase activity. There were no significant differences in MBF between groups at any time point. Following 3 h REP, infarct size was 35.4 +/- 5.5%, 8.1 +/- 1.5% and 8.3 +/- 1.8% of the region at risk in control, PC, and pentostatin groups, respectively. These data suggest that marked increase in ISF ADO during CAO, may be as effective in reducing INF as a modest increase in ISF ADO prior to prolonged CAO.     

Influence of an early adrenergic blockade on thrombotic infarct size and myocardial metabolism

To evaluate the extent to which the protective effect of metoprolol was accompanied by changes in myocardial oxygen consumption and metabolism, thrombotic occlusion of coronary artery followed by infusion of metoprolol or placebo was performed in twenty four German Shepherds. To restore a coronary blood flow rt-PA was administered. Plasma levels of oxygen, glucose, lactic acid, non esterified fatty acids, triacylglyceride and adenosine breakdown products were measured before and at the end of the occlusion and in the early and late reperfusion periods. Regional myocardial blood flow was measured by means of radioactive tracer microspheres. Infarct size was estimated after perfusion and staining of excised hearts with Evans blue. Plasma levels of metoprolol were determinated before the end of occlusion and during reperfusion and therapeutic concentrations were confirmed. The infarct size was smaller in dogs receiving metoprolol (21.6 +/- 20.7 vs 43.0 +/- 17.3% p. < 0.02). Coronary collateral blood flow was greater in metoprolol than in placebo dogs (18.68 +/- 7.58 vs 11.05 +/- 6.10 ml/min/100g, p. < 0.01). As a consequence of myocardial ischemia a shift toward carbohydrate utilization, the myocardial lactate release and the accompanying symptoms of diminished myocardial lipid uptake were observed. A washout of adenosine degradation products during early reperfusion was also noticed. In beta 1 blocked animals the reduction of myocardial oxygen consumption and preserved myocardial uptake of lactate and non esterified fatty acids were documented.     

Long-term development in the mandible and incisor crowding with and without an orthodontic stabilising appliance

Dimensional alteration of hepatic microvessels was demonstrated during reperfusion after normothermic hepatic ischemia. Using a specially designed cover glass, it was possible to relocate selected sites of observation and microvessels repeatedly throughout the whole reperfusion time. Twenty minutes of hepatic ischemia resulted in a decrease of sinusoidal diameter (mean +/- SEM; 10.0 +/- 0.3 microns at baseline, 8.2 +/- 0.2 microns after ischemia) and diameter of postsinusoidal venules (26.4 +/- 1.2 at baseline, 23.0 +/- 1.0 after ischemia). In the control group (no ischemia induced) no changes of these parameters were observed. Thus, the reduction of hepatic microvascular cross section was present during the early phase of reperfusion. Hepatic dysfunction was characterized by increased serum activity of liver enzymes and reduction of bile flow in the ischemia-exposed animals. It has been suggested that postischemic dimensional microvascular changes are involved in postischemic liver dysfunction.     

Gut mucosal ischemia during normothermic cardiopulmonary bypass results from blood flow redistribution and increased oxygen demand

Impaired gut mucosal perfusion has been reported during cardiopulmonary bypass. To better define the adequacy of gut blood flow and oxygenation during cardiopulmonary bypass, we measured overall gut blood flow and ileal mucosal flow and their relationship to mucosal pH, mesenteric oxygen delivery and oxygen consumption in immature pigs (n = 8). Normothermic, noncross-clamped, right atrium-to-aorta cardiopulmonary bypass was maintained at 100 ml/kg per minute for 120 minutes. Animals were instrumented with an ultrasonic Doppler flow probe on the superior mesenteric artery, a mucosal laser Doppler flow probe in the ileum, and pH tonometers in the stomach, ileum, and rectum. Radioactive microspheres were injected before and at 5, 60, and 120 minutes of cardiopulmonary bypass for tissue blood flow measurements. Overall gut blood flow significantly increased during cardiopulmonary bypass as evidenced by increases in superior mesenteric arterial flow to 134.1% +/- 8.0%, 137.1% +/- 7.5%, 130.3% +/- 11.2%, and 130.2% +/- 12.7% of baseline values at 30, 60, 90, and 120 minutes of bypass, respectively. Conversely, ileal mucosal blood flow significantly decreased to 53.6% +/- 6.4%, 49.5% +/- 6.8%, 58.9% +/- 11.6%, and 47.8% +/- 10.0% of baseline values, respectively. Blood flow measured with microspheres was significantly increased to proximal portions of the gut, duodenum and jejunum, during cardiopulmonary bypass, whereas blood flow to distal portions, ileum and colon, was unchanged. Gut mucosal pH decreased progressively during cardiopulmonary bypass and paralleled the decrease in ileal mucosal blood flow. Mesenteric oxygen delivery decreased significantly from 67.0 +/- 10.0 ml/min per square meter at baseline to 42.4 +/- 4.6, 44.9 +/- 3.5, 46.0 +/- 3.6, and 42.9 +/- 3.9 ml/min per square meter at 30, 60, 90, and 120 minutes of bypass. Despite the decrease in mesenteric oxygen delivery, mesenteric oxygen consumption increased progressively from 10.8 +/- 1.4 ml/min per square meter at baseline to 13.4 +/- 1.2, 15.9 +/- 1.2, 16.7 +/- 1.4, and 16.6 +/- 1.54 ml/min per square meter, respectively. We conclude that gut mucosal ischemia during normothermic cardiopulmonary bypass results from a combination of redistribution of blood flow away from mucosa and an increased oxygen demand.     

Effects of Carolina rinse and adenosine rinse on microvascular perfusion and intrahepatic leukocyte-endothelium interaction after liver transplantation in the rat

Flushing hepatic grafts immediately before revascularization with a specially designed rinse solution such as "Carolina rinse" has been reported to improve survival after liver transplantation in the rat. This study investigated the influence of Carolina rinse and adenosine rinse on early graft function, microcirculation, and leukocyte (WBC)-endothelial cell interaction of arterialized syngeneic orthotopic liver transplants in Lewis rats. Livers were preserved for 24 hr in University of Wisconsin solution and flushed immediately before reperfusion with either Ringer's lactate (group A: n = 7), Ringer's lactate + 0.2 mmol/liter adenosine (group B: n = 6), or Carolina rinse (group C: n = 7). Microvascular perfusion and WBC accumulation were assessed by intravital fluorescence microscopy. In group C, acinar perfusion was significantly improved, accompanied by a lower percentage of nonperfused sinusoids 1 hr after reperfusion (mean +/- SEM: 26 +/- 2% [group A], 21 +/- 2% [B], 11 +/- 1% [C], P < 0.01 for C vs. A or B). In addition, Carolina rinse and, to a lesser extent, adenosine rinse reduced the number of WBC sticking in sinusoids and postsinusoidal venules. Better graft function in group C was indicated by increased bile flow during the observation period of 90 min after reperfusion (0.5 +/- 0.3 ml/100 g liver [group A], 1.5 +/- 0.7 [B], 3.7 +/- 0.6 [C], P < 0.01 for C vs. A or B). We conclude that Carolina rinse is able to improve early excretory hepatocellular function, microvascular perfusion, and intrahepatic WBC accumulation after prolonged cold ischemia and reperfusion, but adenosine is unlikely to be the key component of this rinse solution.     

Factors associated with atrial fibrillation in patients with mitral stenosis: a cardiac catheterization study

OBJECTIVE: The aim of this study was to characterize the adenosine A3 receptor agonist, N6-(3-chlorobenzyl)-5'-N-methylcarboxamidoadenosine (CB-MECA), evaluate its ability to reduce myocardial ischemia/reperfusion injury and determine the role of KATP-channel activation in A3 receptor-mediated cardioprotection. METHODS: Binding affinities and adenylate cyclase inhibition were examined in CHO cells expressing rabbit recombinant adenosine A1 or A3 receptors. Infarct size (normalized for area-at-risk; % IA/AAR) was measured in buffer-perfused rabbit hearts exposed to 30-min regional ischemia and 120 min of reperfusion. RESULTS: CB-MECA was 100-fold selective for A3 vs. A1 receptors (A3 Ki: 1 nM; A1 Ki: 105 nM). Five-min perfusion with CB-MECA before ischemia/reperfusion elicited a concentration-dependent reduction in infarct size (EC50: 0.3 nM). The CB-MECA-dependent cardioprotection (control: 58 +/- 2; CB-MECA: 21 +/- 3% IA/AAR) was unchanged by an A1-selective concentration of the antagonist, BWA1433, but was completely prevented (P < 0.05) by a nonselective (A1/A3) concentration (55 +/- 6% IA/AAR). The KATP channel inhibitors, glibenclamide and 5-HD, had no effect on control infarct size, yet significantly (P < 0.05) blunted the CB-MECA-dependent cardioprotection (glibenclamide: 49 +/- 6; 5-HD: 58 +/- 4% IA/AAR). CONCLUSIONS: CB-MECA is a novel 100-fold A3 receptor-selective agonist which should prove useful for elucidating A3-dependent mechanisms in the rabbit heart. Selective stimulation of adenosine A3 receptors with CB-MECA reduces myocardial ischemia/reperfusion injury via a mechanism which involves activation of KATP channels.     

The graft flow and 201Tl-myocardial scintigram in patients with saphenous vein graft or left internal thoracic artery graft

To evaluate myocardial perfusion in patients with saphenous vein graft (SVG) or internal thoracic artery graft (ITA-G), we studied 38 patients (14: SVG, 10 males and 4 females, mean age 66 +/- 9 y-o; 24: ITA-G, 18 males and 6 females, mean age 64 +/- 7 y-o) by digital subtraction angiography (DSA) of ITA-G or SVG, and thallium-201 myocardial perfusion scintigraphy on exercise or dipyridamole stress. The grafting sites were left anterior descending artery (LAD) in all patients. Normal controls (n = 22) were defined by normal coronary angiogram and no evidence of myocardial ischemia. The graft flow and flow reserve on dipyridamole were measured by Rutishauser's formula. The basal blood flow of native normal ITA, SVG and ITA-G were respectively 72 +/- 24 ml/min, 51 +/- 23 ml/min, and 36 +/- 20 ml/min. The basal ITA-G flow was significantly lower than SVG-flow (p < 0.05). The flow reserves of SVG and ITA-G were respectively 2.32 +/- 0.65 and 1.78 +/- 0.59 (p < 0.02). The incidence of moderate hypoperfusion of thallium-201 SPECT was 14.3% in SVG and 12.5% in ITA-G on exercise stress, and 35% in SVG and 50% in ITA-G on dipyridamole stress. The incidence of reversible myocardial ischemia on dipyridamole stress was significant. The graft flow in patients with normal and abnormal thallium-201 SPECT were respectively 61 +/- 21 ml/min and 33 +/- 15 ml/min in SVG (p < 0.01), 46 +/- 19 ml/min and 27 +/- 16 ml/min in ITA-G (p < 0.02). The graft flow reserve were respectively 2.69 +/- 0.38 and 1.65 +/- 0.49 in SVG (p < 0.001), 2.25 +/- 0.40 and 1.31 +/- 0.28 in ITA-G (p < 0.001). We concluded that the basal blood flow and flow reserve of ITA-G were significantly lower than those of SVG. The myocardial ischemia was occasionally documented by the thallium-201 myocardial SPECT on dipyridamole stress in patients with patent ITA-G.     

Transient c-fos gene expression in cerebellar development and functional stimulation

The effect of ischemic preconditioning and superoxide dismutase (SOD) on endothelial glycocalyx and endothelium-dependent vasodilation in the postischemic isolated guinea-pig hearts was examined. Seven groups of hearts were used: group 1 underwent sham aerobic perfusion; group 2 was subjected to 40 min global ischemia without reperfusion; group 3, 40 min ischemia followed by 40 min reperfusion; group 4 was preconditioned with three cycles of 5 min global ischemia followed by 5 min of reperfusion (IPC), prior to 40 min ischemia; group 5 was subjected to IPC prior to standard ischemia/ reperfusion; group 6 underwent standard ischemia/reperfusion and SOD infusion (150 U/ml) was begun 5 min before 40 min ischemia and continued during the initial 5 min of the reperfusion period; group 7 was subjected to 80 min aerobic perfusion with NO-synthase inhibitor, L-NAME, to produce a model of endothelial dysfunction independent from the ischemia/reperfusion. Coronary flow responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were used as measures of endothelium-dependent and endothelium-independent vascular function, respectively. Reduction in coronary flow caused by NO-synthase inhibitor, L-NAME, served as a measure of a basal endothelium-dependent vasodilator tone. After completion of each experimental protocol, the hearts were stained with ruthenium red or lanthanum chloride for electron microscopy evaluation of the endothelial glycocalyx. While ischemia led only to a slightly flocculent appearance of the glycocalyx, in ischemia/reperfused hearts the glycocalyx was disrupted, suggesting that it is the reperfusion injury which leads to the glycocalyx injury. Moreover, the coronary flow responses to ACh and L-NAME were impaired, while the responses to SNP were unchanged in the ischemia/reperfused hearts. The disruption of the glycocalyx and the deterioration of ACh and L-NAME responses was prevented by IPC. In addition, the alterations in the glycocalyx and the impairment of ACh responses were prevented by SOD. The glycocalyx appeared to be not changed in the hearts subjected to 80 min aerobic perfusion with L-NAME. In conclusion: (1) the impairment of the endothelium-dependent coronary vasodilation is paralleled by the endothelial glycocalyx disruption in the postischemic guinea-pig hearts; (2) both these changes are prevented by SOD, suggesting the role of free radicals in the mechanism of their development; (3) both changes are prevented by IPC. We hypothesize, therefore, that alterations in the glycocalyx contribute to the mechanism of the endothelial dysfunction in the postischemic hearts.     

Preconditioning during simulated MIDCABG attenuates blood flow defects and neutrophil accumulation

BACKGROUND: Ischemic preconditioning (IP) may be cardioprotective in minimally invasive direct coronary artery bypass where cardioplegia is not used. This study tested the hypothesis that IP of the area at risk (AAR) would attenuate postischemic injury from transient coronary artery occlusion. METHODS: In 19 anesthetized dogs, the left anterior descending coronary artery was occluded for 30 minutes (simulating coronary occlusion during anastomosis) followed by 3 hours of reperfusion. In 10 dogs, occlusion was preceded by 5 minutes of occlusion and 5 minutes of reperfusion (IP), whereas 9 other dogs had no IP (control, C). RESULTS: Thirty minutes of left anterior descending occlusion caused comparable dyskinesis (systolic shortening, sonomicrometry) in the AAR in C (baseline, 29% +/- 3% to 3% +/- 2%) and in IP (baseline, 29% +/- 2% to -0.3% +/- 2%). After 3 hours of reperfusion, systolic shortening was significantly depressed in C (20% +/- 4%), and was not significantly improved by IP (24% +/- 3%, p = 0.8 versus C). Postischemic diastolic stiffness in the AAR was not altered by IP versus C (0.60 +/- 0.12 versus 0.41 +/- 0.13). Plasma creatine kinase activity was similar between C and IP at the end of reperfusion (20 +/- 11 versus 16 +/- 5 U/g). Postischemic AAR blood flow (in milliliters per minute per gram of tissue) at 180 minutes of reperfusion decreased by 56% versus baseline in C (from 1.04 +/- 0.4 to 0.46 +/- 0.12; p < 0.05) compared with no change in IP (from 0.74 +/- 0.23 to 0.60 +/- 0.10), but there was no significant group difference at this time. Myeloperoxidase activity as an index of neutrophil accumulation in AAR was decreased in IP versus C (0.4 +/- 0.09 versus 0.7 +/- 0.04 U/microg tissue). CONCLUSIONS: Ischemic preconditioning does not decrease postischemic wall motion and only modestly increases postischemic blood flow abnormalities in the AAR, but does significantly inhibit neutrophil accumulation.