Effects of aprotinin on endothelium-dependent relaxation of large coronary arteries

Objective: Aprotinin is widely used in heart surgery for reduction of intraoperative blood loss. But recent reports presenting results from rat aorta experiments claimed that aprotinin selectively impairs endothelium-dependent relaxation (EDR) as well as basal NO availability in concentrations similar to doses routinely used in cardiovascular surgery. An impairment of coronary EDR by aprotinin would be a great danger for any cardiothoracic intervention. We therefore tested the influence of aprotinin in the coronary arteries of a non-rodent species. Methods: Fresh coronary arteries of pigs were obtained from the local slaughterhouse and transported to our laboratory in cold oxygenated Krebs–Henseleit solution. Five-millimeter long rings were consecutively tested with or without aprotinin in concentrations of 500 KIU/ml (n = 7) or 1000 KIU/ml (n = 6) in oxygenated normothermic Krebs–Henseleit solution. PGF₂ (10 μmol/l) was used for inducing contraction and substance P (10 nmol/l) for inducing EDR, which was calculated in percentage of the precontraction. Indomethacin (10 μmol/l) was added in all measurements to eliminate the influence of prostaglandins. In additional similar experiments (n = 5), the influence of 1000 KIU/ml aprotinin on the EDR caused by the endothelium-derived hyperpolarizing factor (EDHF) was tested using l-NNA (300 μmol/l) to block all NO formation. Results: The EDR of pig coronaries (82 ± 5% or 80 ± 5% of the precontraction in the control tests before and after aprotinin exposure) was not significantly changed by 500 KIU/ml aprotinin (78 ± 7%). A small, but significant reduction of less than 1/10 of the EDR was induced by 1000 KIU/ml aprotinin (74 ± 5%). After accounting for l-NNA for NO blockage, no aprotinin-related difference remained (59 ± 6% vs 60 ± 6% in controls). Conclusion: For clinically relevant concentrations of aprotinin up to 500 KIU/ml, no significant reduction of the EDR can be found in epicardial coronary arteries of the pig. For higher doses of 1000 KIU/ml, a reduction in NO production seems to be the cause of the small but significant reduction of the EDR by aprotinin. Therefore, danger for impairment of coronary EDR by aprotinin at clinical dosage levels, as suggested by studies on rat aortas, seems to be absent in coronary arteries of a large mammalian model.     

Retrograde perfusion with a sodium channel antagonist provides ischemic spinal cord protection

Background. Neuronal voltage-dependent sodium channel antagonists have been shown to provide neuroprotection in focal and global cerebral ischemic models. We hypothesized that retrograde spinal cord venous perfusion with phenytoin, a neuronal voltage-dependent sodium channel antagonist, would provide protection during prolonged spinal cord ischemia.

Methods. In a rabbit model, spinal cord ischemia was induced for 45 minutes. Six groups of animals were studied. Controls (group I, n = 8) received no intervention during aortic cross-clamping. Group II (n = 8) received systemic phenytoin (100 mg). Group III (n = 4) received systemic phenytoin (200 mg).Group IV (n = 8) received retrograde infusion of room temperature saline (22°C) only. Group V (n = 8) and group VI (n = 9) received retrograde infusion of 50 mg and 100 mg of phenytoin, respectively, (infusion rate: 0.8 mL · kg⁻¹ · min⁻¹ during the ischemic period). Mean arterial blood pressure was monitored continuously. Animals were allowed to recover for 24 hours before assessment of neurologic function using the Tarlov scale.

Results. Tarlov scores (0 = complete paraplegia, 1 = slight lower limb movement, 2 = sits with assistance, 3 = sits alone, 4 = weak hop, 5 = normal hop) were as follows (mean ± SEM): group I, 0.50 ± 0.50; group II, 0.25 ± 0.46; group IV, 1.63 ± 0.56; group V, 4.13 ± 0.23; and group VI, 4.22 ± 0.22 (p < 0.0001 V, VI versus I, II, IV by analysis of variance). No differences in mean arterial blood pressure were observed. All animals in group III became profoundly hypotensive and died before the conclusion of the 45-minute ischemic time.

Conclusions. Retrograde venous perfusion of the spinal cord with phenytoin, a voltage-sensitive sodium channel blocker, is safe and provides significant protection during prolonged spinal cord ischemia.     

Aprotinin reduces postoperative bleeding and the need for blood products in thoracic surgery: results of a randomized double-blind study

Objective: Bleeding complications have been a major concern in certain thoracic surgery operations, especially decortication and pulmonary resection for inflammatory pulmonary infection. Prevention of plasminogen activation and fibrinolysis by aprotinin administration has been shown to reduce perioperative bleeding during operations associated with high blood consumption. Methods: Use of blood products (packed red cells, whole blood), chest tube drainage, analgesic requirement, chest tube duration for the patients undergoing major thoracic operations were recorded. In a double blind randomized fashion, patients were assigned to two groups receiving aprotinin (n=51) at a loading dose of 10⁶ kallikrein inhibitory units (KIU) followed by an infusion of the same dose during chest closure or receiving placebo (n=52). On a daily basis, red-cell percentages of total fluid from drainage bottles were recorded and using the blood hematocrit level of the patient of the day before, the corrected value for the patient's blood volume equivalent of daily drainage was calculated. Results: There was a significant reduction in perioperative use of donor blood (0.98±0.92 vs. 0.45±0.32 unit; P=0.0026), and total chest tube drainage (corrected value for the corresponding blood volume) (28.2±36.9 vs. 76.9±53.3 ml, P=0.0004) (mean±standard deviation) in the aprotinin group. However, aprotinin did not reduce postoperative transfusion or decrease in hematocrit level due to thoracic operations. In high transfusion-risk thoracic surgery patients (patients who underwent decortication, pulmonary resection for inflammatory lung disease and chest wall resection), the perioperative transfusion was only 0.50±1.08 units in aprotinin group, compared with 1.94±0.52 units in control group (P=0.003). Postoperative transfusion was also reduced in aprotinin administrated group (0.53±0.56 vs. 1.38±0.97 units; P=0.02). The mean total blood loss was decreased to nearly one third of the blood loss of the control group (41±28 ml vs. 121±68 ml; P=0.001). Conclusion: Aprotinin significantly reduced perioperative transfusion requirement and postoperative bleeding during major thoracic operations. Aprotinin decreased perioperative transfusion needs. Moreover, patients who were at risk of greater blood loss during and after certain thoracic operations had a greater potential to benefit from prophylactic perioperative aprotinin treatment.     

Spinal cord protection during aortic cross-clamping using retrograde venous perfusion

Background. Paraplegia remains a devastating complication following thoracic aortic operation. We hypothesized that retrograde perfusion of the spinal cord with a hypothermic, adenosine-enhanced solution would provide protection during periods of ischemia due to temporary aortic occlusion.

Methods. In a rabbit model, a 45-minute period of spinal cord ischemia was produced by clamping the abdominal aorta and vena cava just below the left renal vessels and at their bifurcations. Four groups (n = 8/group) were studied: control, warm saline, cold saline, and cold saline with adenosine infusion. In the experimental groups, saline or saline plus adenosine was infused into the isolated cavae throughout the ischemic period. Clamps were removed and the animals to recovered for 24 hours before blinded neurological evaluation.

Results. Tarlov scores (0 = paraplegia, 1 = slight movement, 2 = sits with assistance, 3 = sits alone, 4 = weak hop, 5 = normal hop) were (mean ± standard error of the mean): control, 0.50 ± 0.50; warm saline, 1.63 ± 0.56; cold saline, 3.38 ± 0.26; and cold saline plus adenosine, 4.25 ± 0.16 (analysis of variance for all four groups, p < 0.00001). Post-hoc contrast analysis showed that cold saline plus adenosine was superior to the other three groups (p < 0.0001).

Conclusion. Retrograde venous perfusion of the spinal cord with hypothermic saline and adenosine provides functional protection against surgical ischemia and reperfusion.     

Reduction of myocardial reperfusion injury by aprotinin after regional ischemia and cardioplegic arrest

BACKGROUND: Surgical coronary revascularization with cardiopulmonary bypass and cardioplegia has been associated with reperfusion injury. The serine protease inhibitor aprotinin has been suggested to reduce reperfusion injury, yet a clinically relevant study examining regional ischemia under conditions of cardiopulmonary bypass and cardioplegia has not been performed. METHODS: Pigs were subjected to 30 minutes of regional myocardial ischemia by distal left anterior descending coronary artery occlusion, followed by 60 minutes of cardiopulmonary bypass with 45 minutes of cardioplegic arrest and 90 minutes of post-cardiopulmonary bypass reperfusion. The treatment group (n = 6) was administered aprotinin systemically (40,000 kallikrein-inhibiting units [KIU]/kg intravenous loading dose, 40,000 KIU/kg pump prime, and 10,000 KIU x kg(-1) x h(-1) intravenous continuous infusion). Control animals (n = 6) received crystalloid solution. Global and regional myocardial functions were analyzed by the left ventricular+dP/dt and the percentage segment shortening, respectively. Left ventricular infarct size was measured by tetrazolium staining. Tissue myeloperoxidase activity was measured. Myocardial sections were immunohistochemically stained for nitrotyrosine. Coronary microvessel function was studied by videomicroscopy. RESULTS: Myocardial infarct size was decreased with aprotinin treatment (27.0% +/- 3.5% vs 45.3% +/- 3.0%, aprotinin vs control; P <.05). Myocardium from the ischemic territory showed diminished nitrotyrosine staining in aprotinin-treated animals versus controls, and this was significant by grade (1.3 +/- 0.2 vs 3.2 +/- 0.2, aprotinin vs control; P <.01). In the aprotinin group, coronary microvessel relaxation improved most in response to the endothelium-dependent agonist adenosine diphosphate (44.7% +/- 3.2% vs 19.7% +/- 1.7%, aprotinin vs control; P <.01). No significant improvements in myocardial function were observed with aprotinin treatment. CONCLUSIONS: Aprotinin reduces reperfusion injury after regional ischemia and cardioplegic arrest. Protease inhibition may represent a molecular strategy to prevent postoperative myocardial injury after surgical revascularization with cardiopulmonary bypass.     

The effects of therapeutic sulfide on myocardial apoptosis in response to ischemia–reperfusion injury

Objective: Ischemia–reperfusion (I/R) injury, often encountered clinically, results in myocardial apoptosis and necrosis. Hydrogen sulfide (H₂S) is produced endogenously in response to ischemia and thought to be cardioprotective, although its mechanism of action is not fully known. This study investigates cardioprotection provided by exogenous H₂S, generated as sodium sulfide on apoptosis following myocardial I/R injury. Methods: The mid-LAD coronary artery in Yorkshire swine (n = 12) was occluded for 60 min, followed by reperfusion for 120 min. Controls (n = 6) received placebo, and treatment animals (n = 6) received sulfide 10 min prior to and throughout reperfusion. Hemodynamic, global, and regional functional measurements were obtained. Evans blue/TTC staining identified the area-at-risk (AAR) and infarction. Serum CK-MB, troponin I, and FABP were assayed. Tissue expression of bcl-2, bad, apoptosis-inducing-factor (AIF), total and cleaved caspase-3, and total and cleaved PARP were assessed. PAR and TUNEL staining were performed to assess apoptotic cell counts and poly-ADP ribosylation, respectively. Results: Pre-I/R hemodynamics were similar between groups. Post-I/R, mean arterial pressure (mmHg) was reduced by 30.2 ± 4.3 in controls vs 8.2 ± 6.9 in treatment animals (p = 0.01). +LV dP/dt (mmHg/s) was reduced by 1308 ± 435 in controls vs 403 ± 283 in treatment animals (p = 0.001). Infarct size (% of AAR) in controls was 47.4 ± 6.2% vs 20.1 ± 3.3% in the treated group (p = 0.003). In treated animals, CK-MB and FABP were lower by 47.0% (p = 0.10) and 45.1% (p = 0.01), respectively. AIF, caspase-3, and PARP expression was similar between groups, whereas cleaved caspase-3 and cleaved PARP was lower in treated animals (p = 0.04). PAR staining was significantly reduced in sulfide treated groups (p = 0.04). TUNEL staining demonstrated significantly fewer apoptotic cells in sulfide treated animals (p = 0.02). Conclusions: Sodium sulfide is efficacious in reducing apoptosis in response to I/R injury. Along with its known effects on reducing necrosis, sulfide's effects on apoptosis may partially contribute to providing myocardial protection. Exogenous sulfide may have therapeutic utility in clinical settings in which I/R injury is encountered.     

Results of biventricular repair of congenital cardiac malformations: definitive corrective surgery?

Objectives: Congenital cardiac malformations are usually corrected in the neonatal period or in early infancy. Corrective surgery may not always be definitive, especially in complex malformations. Long-term morbidity is influenced by reoperations and their risk. Methods: This study analyzes our single-center experience over more than 20 years in a selected group of patients. Data were gathered, with special focus on causes and incidence for reoperations, respectively. Results: Freedom from reoperation after 5, 10, and 15 years for each cardiac malformation was determined. The numbers describe in the following order patient years (y), number of patients (n), and freedom from reoperation at follow-up interval (%), respectively: atrial septal defect (15 864y, n=1198, 99±0/99±0/99±0), partial atrioventricular septal defect (2506y, n=234, 95±2/93±2/93±2), total anomalous pulmonary venous connection (742y, n=141, 93±1/91±0/91±0), complete atrioventricular septal defect (1715y, n=377, 81±3/76±3/72±4), tetralogy of Fallot <1 year (1503y, n=197, 94±4/85±1/74±3), transposition of great arteries (1459y, n=375, 88±2/83±4/73±7), interrupted aortic arch (IAA) (481y, n=98, 63±6/52±7/45±8), common arterial trunk (CAT) (599y, n=109, 64±6/24±6/11±5). Conclusions: In most congenital malformations surgical correction is definitive and the rate of reoperations is low. In complex anomalies, such as CAT and IAA, reoperations at long-term are more common. Analysis of such results and recognition of a sometimes inevitable operative morbidity helps to predict long-term outcome and influences the follow-up.     

A Novel Canine Model of Spinal Cord Ischemia with Reproducible Neurologic Outcomes

Purpose To develop a canine model of spinal cord ischemia (SCI) with highly reproducible neurologic outcomes.Methods Spinal cord ischemia was induced by cross-clamping the proximal descending aorta. To produce substantial ischemia in the critical lumbar region, the proximal aortic blood pressure (PAP) was reduced to 80 mmHg by withdrawing blood into a reservoir connected to the left subclavian artery. We conducted an intraischemia spinal cord electrophysiologic study and a postischemia assessment of hindlimb motor function in six animals subjected to this procedure with an aortic occlusion time of 40 min, and in six animals subjected only to aortic occlusion for 60 min.Results All the animals subjected to this procedure exhibited a significant decrease in motor-evoked spinal cord potentials to transcranial electric stimulation (MEPs) during the acute ischemic phase, and they were paraplegic 48 h after ischemia. In contrast, two of the animals not subjected to PAP reduction showed complete functional recovery with intact MEP findings.Conclusion This model is feasible for experimental SCI studies because it can reliably and easily reproduce substantial ischemia.     

Ischemic mitral valve prolapse: mechanisms and implications for valve repair

Objective: The aim of this study was to assess the mechanisms of prolapse in ischemic mitral valve regurgitation (MR) and the techniques of valve repair. Methods: Out of 121 patients operated upon for ischemic MR, a prolapse was present in 44 patients (36.4%). The operation was performed emergently in four cases (9.1%) and electively in 40 patients (90.9%). Fifteen patients (34.1%) were operated upon within 60 days following acute myocardial infarction. Results: The diagnosis of prolapse had been overlooked by echography in five cases (11.4%). A commissural area was involved as the site of prolapse in 31 cases (70.4%). The mechanism of prolapse was a papillary muscle (PM) lesion in 38 cases (86.4%) (anterior PM: n=8, posterior PM n=36) or a chordal lesion in six cases (13.6%). PM injury was elongation (n=16), or rupture (total n=1, partial n=21, incomplete n=4). The operative technique was mitral valve repair with Carpentier's techniques in 42 cases (95.5%) or replacement in two cases (4.5%). Hospital mortality was 11.4% (n=4). The mean follow-up was to 44.7±29.6 months. Overall survival and freedom from reoperation were 68.3±9.0 and 89.9±5.7% at 5 years, respectively. Freedom from MR equal or > grade 2 was 69.7±9.5% at 5 years. Conclusions: The mechanisms of ischemic mitral valve prolapse were variable and tightly linked to the PM anatomy. A reliable mitral valve repair could be achieved in most cases with acceptable mid-term results.     

Preconditioning with hyperbaric oxygen and hyperoxia induces tolerance against spinal cord ischemia in rabbits

BACKGROUND: The aim of this study was to determine if the ischemic tolerance could be induced in the spinal cord by pretreatment with hyperbaric oxygen (HBO) and what components of HBO (hyperoxia, hyperbaricity, and combination of these two) were critical in the induction of tolerance against ischemic injury. METHODS: In experiment 1, 21 rabbits were randomly assigned to one of three groups (n = 7 each): animals in the control group received no HBO before spinal cord ischemia; animals in the HBO-1 and HBO-2 groups received HBO (2.5 atmosphere absolute [ATA], 100% O2) pretreatment 1 h/day for 3 and 5 days before ischemia, respectively. In experiment 2, 48 rabbits were randomly assigned to one of four groups (n = 12 each): the control group received no HBO (21% O2, 1 ATA, 1 h/day, 5 days) before spinal cord ischemia; the HB group received 1-h treatment in 21% O2 at 2.5 ATA each day for 5 days; the HO group received 1-h treatment in 100% oxygen at 1 ATA each day for 5 days; and the HBO group received HBO (2.5 ATA, 100% O2) treatment 1 h/day for 5 days. Twenty-four hours after the last treatment, spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, hind-limb motor function and histopathology of the spinal cord were examined in a blinded fashion. RESULTS: In experiment 1, the neurologic outcome in the HBO-2 group was better than that of the control group (P = 0.004). The number of normal neurons in the anterior spinal cord in the HBO-2 group was more than that of the control group (P = 0.021). In experiment 2, the neurologic and histopathologic outcomes in the HBO group were better than that of the control group (P < 0.01). The histopathologic outcome in the HO group was better than that in the control group (P < 0.05). CONCLUSIONS: Serial exposure to high oxygen tension induced ischemic tolerance in spinal cord of rabbits. Simple hyperbaricity (2.5 ATA, 21% O2) did not induce ischemic tolerance.     

芦荟多糖对脊髓缺血损伤的神经保护作用

目的:探讨芦荟多糖(aloe polysaccharide,AP)对兔脊髓缺血损伤是否有神经保护作用.方法:32只成年雄性新西兰兔随机分成4组(每组8只 ),即对照组(C 组)、芦荟多糖组(A组)、溶剂对照组( V组 ) 及假手术组(S组).A组在脊髓缺血前30min经耳缘静脉给予50m·kg-1芦荟多糖;V组以同样方式给予等容量生理盐水;C组仅仅制备脊髓缺血损伤模型,不进行其它处理;S组仅仅暴露腹主动脉,而不阻断它,其他处理同C组;兔脊髓缺血模型采用夹闭兔腹主动脉肾下段20min.再灌注后48h,对所有动物神经功能评分,然后处死动物取脊髓(L5-7),制作标本行组织病理学观察.结果:A组的神经功能评分和脊髓前角正常神经细胞数明显多于C组及V组(P<0.01);C组及V组的神经功能评分和脊髓前角正常神经细胞数组间无明显差异(P>0.05);神经功能评分与其对应脊髓前角正常神经细胞计数之间有显著相关性(r=0.804,P<0.01).结论:芦荟多糖对兔脊髓缺血再灌注损伤有明显的神经保护作用.     

Ischemic preconditioning enhances donor lung preservation in the rabbit

Objective: Ischemic preconditioning achieved by brief periods of ischemia followed by reperfusion before a prolonged period of ischemia, is well known to reduce myocardial damage. We investigated whether ischemic preconditioning of the lung could also attenuate ischemia-reperfusion injury following pulmonary preservation. Methods: Transient ischemia of the right lung was achieved in rabbits (n=4 in each group) by occluding the main bronchus and pulmonary artery, followed by reperfusion according to a protocol that differed between study groups: group 1 (control), 45 min ventilation; group 2, 30 min ventilation, 5 min ischemia and 10 min reperfusion; group 3, three periods of 5 min ischemia and 10 min reperfusion; group 4, five periods of 3 min ischemia and 6 min reperfusion. Donor lungs were then flushed with a crystalloid solution followed by inflated storage at 37°C for 2 h. The function of the right lung was assessed during reperfusion for 2 h with homologous, diluted and deoxygenated blood in an isolated, pressure-limited, and room-air ventilated model. Results: Significant differences (P<0.0001) were observed between groups 1 and 2 vs. groups 3 and 4 in veno–arterial oxygen pressure gradient (29±6 and 24±6 mm Hg vs. 124±24 and 132±14 mm Hg, respectively), and in weight gain (88±13 and 98±13% vs. 44±9 and 29±3%, respectively) after 1 h of reperfusion, and in wet-to-dry weight ratio (15.5±1.5 and 14.3±0.4 vs. 10.1±1.6 and 9.0±0.8, respectively) at the end of reperfusion. No significant differences in any of these parameters were observed between group 1 vs. group 2 neither between group 3 vs. group 4. Conclusions: These data suggest: (1) That 15 min, but not 5 min of transient ischemia prior to pulmonary preservation can significantly reduce edema in the lung graft upon reperfusion, thus improving oxygenation capacity and (2) although not significant, this beneficial effect seems to be slightly better with more repetitive periods of transient ischemia. Further research is warranted to investigate whether ischemic preconditioning in the human organ donor may become a new strategy to protect lung tissue during a planned ischemic event as in pulmonary transplantation.     

Prevention of Ischemic Spinal Cord Injury Following Aortic Cross-Clamping: Use of Corticosteroids

Prior to proximal aortic cross-clamping, baseline measurements of spinal cord blood flow and function were done. Blood flow was evaluated with radioactive microspheres and function determined by assessment of somatosensory evoked potential (SEP). Group 1 (N = 6) animals had aortic cross-clamping for 5 minutes after ischemic spinal cord dysfunction (SEP loss) was documented. Group 2 (N = 9) underwent aortic cross-clamping for 10 minutes after loss of SEP. Group 3 (N = 6) also underwent 10 minutes of cross-clamping after initial SEP loss, but were treated intravenously with methylprednisolone (30 mg per kilogram of body weight) 10 minutes prior to cross-clamping and again 4 hours postoperatively. After release of the cross-clamp, the animals were allowed to recover and serial evaluations of spinal cord blood flow and neurological status were carried out for seven days. Group 1 animals recovered uneventfully without evidence of neurological injury. Group 2 animals sustained a 67% incidence of permanent spastic paraplegia (p = 0.02 versus Group 1). In contrast, methylprednisolone-treated animals sustained no clinically detectable neurological injury (p = 0.02 versus Group 2). Measurements of spinal cord blood flow at the time of SEP loss revealed similar degrees of spinal cord ischemia in all groups. No significant differences were observed in the duration of aortic cross-clamping prior to SEP loss among the three groups. The data indicate that short periods of cross-clamping (5 minutes) following SEP loss are well tolerated, whereas longer periods (10 minutes) are associated with a high incidence of paraplegia. This injury can be prevented if an adequate dose of methylprednisolone is given before and after cross-clamping. Beneficial effects of steroid administration do not appear to be related to changes in spinal cord blood flow, but may be related to protective effects on cellular and subcellular components. Clinical investigations employing this regimen of corticosteroid protection during surgical procedures on the thoracoabdominal aorta appear to be indicated.     

Aprotinin pretreatment diminishes postischemic myocardial contractile dysfunction in dogs.

We evaluated the effect of aprotinin, administered before the onset of acute regional myocardial ischemia, on reversible contractile dysfunction induced by ischemia and reperfusion in pentobarbital-anesthetized dogs. Animals were randomized to receive either aprotinin 30,000 kallikrein inactivator units (KIU)/kg and 7000 KIU x kg(-1) x hr(-1) (n = 8) or equivalent volumes of 0.9% sodium chloride (n = 7) IV 60 min before a 15-min interruption of circumflex coronary artery blood flow and then reperfusion. There were no intra- or intergroup differences in hemodynamic variables or regional myocardial mechanics (sonomicrometry) before onset of ischemia. Immediately before reperfusion, systolic dysfunction characterized by significantly decreased percent systolic shortening was present in the circumflex coronary artery area of both study groups. After reestablishment of perfusion, aprotinin animals had preserved percent systolic shortening whereas saline animals exhibited regional systolic dysfunction. Regional myocardial contractility as assessed by the slope Mw of the preload recruitable stroke work relation was preserved during reperfusion in animals who received aprotinin but depressed in the control group. We conclude that functional recovery from myocardial ischemia-reperfusion injury at normothermia is improved by IV administration of aprotinin before the onset of acute regional myocardial ischemia in physiologically intact dogs. IMPLICATIONS: Administration of clinically relevant doses of aprotinin IV before the onset of regional myocardial ischemia, in contrast to control conditions, preserved regional systolic function and contractility at baseline values after reestablishment of myocardial perfusion in dogs.     

Pulmonary preservation with Bretscheider''s HTK and Celsior solution in minipigs

Background: Pulmonary preservation with high potassium/low oncotic pressure Euro-Collins (EC) solution is associated with endothelial dysfunction and reduced surfactant function. We compared two low potassium solutions, histidine-tryptophane-ketoglutarate (HTK) and Celsior, to EC in lung ischemia-reperfusion injury. Methods: In 19 minipigs, the left lung was perfused in situ with cold preservation solution (EC, n=6; HTK, n=6; Celsior, n=7). Reperfusion was started after 90 min of warm ischemia. The right pulmonary artery and main bronchus were clamped. Bronchoalveolar lavage (BAL) was obtained before ischemia and after 2 h of reperfusion. Surfactant activity was determined from the BAL in a pulsating bubble surfactometer. Results: Animals in the EC group survived 3.7±1.4 h. Six Celsior and five HTK treated animals survived the observation period of 7 h (P<0.001). Compliance of the reperfused lung deteriorated less in both Celsior and HTK groups (P<0.001). In EC and HTK animals, the pO₂/FiO₂ ratio was lower (P=0.002), and pulmonary vascular resistance was higher (P=0.02) than in Celsior animals. Surfactant function was impaired after reperfusion in all groups. Conclusions: Compared to EC, HTK solution showed moderate and Celsior distinct improvement of post-ischemic pulmonary function. However, surfactant function was not well preserved in any group.     

Delayed release particles from vascular endothelial growth factor for repairing spinal cord ischemic injury of rats

Objective: To study the effect of delayed release particles from vascular endothelial growth factor (VEGF) on the reparation of ischemic injury of spinal cord in rats. Methods: The spinal cord ischemia model of rats was established. The delayed release particles from VEGF were injected via the intubation of spinal subarachnoid space. The rehabilitation was observed by the assessment of unfold claw reflection, space between toes, spinal evoked potential (SEP) and motor evoked potential (MEP). Results: VEGF prompted SEP and MEP appearance, improved the motor function of hind limbs. Conclusions: VEGF can promote the rehabilitation of spinal cord ischemic injury of rats.     

Synergistic effect of low dose Cyclosporine A and human interleukin 10 overexpression on acute rejection in rat lung allotransplantation

Objective: Electroporation mediated transfer of plasmid DNA into peripheral muscle results in high transfection efficiency. The aim of this study was to investigate the effect of gene transfer of human IL-10 (hIL-10) into the tibialis anterior muscle (MTA) in combination with low dose Cyclosporine A (CsA) on acute rejection of lung allografts in the rat. Methods: Lung allotransplantation was performed from male BN donor to male Fisher F344 rats. Gene transfer was achieved by intramuscular injection into the MTA of the recipient followed by electroporation (4×20 ms impulses at 200 V/cm) 24 h prior to the transplantation. Group A (n=5) received CsA (2.5 mg/kg bw ip) for 5 days post-transplant and group B (n=5) 2.5 μg of PCIK hIL-10 (plasmid expression vector containing human CMV immediate early gene promoter and enhancer) and a low dose CsA (2.5 mg/kg bw i.p.). Graft function was assessed by blood gas at day 5 after exclusion of the native lung. Animals were sacrificed and blood was drawn to measure serum hIL-10 levels (ELISA) and tissue was sampled for histological grading of rejection. Results: Local expression of hIL-10 was confirmed at the mRNA level by in situ hybridization. All group A control animals showed severe signs of rejection. At day 5 all grafts in group B showed good gas exchange mean PaO2 233±123 mmHg, vs 44±8 mmHg in group A. Histological examination revealed moderate to severe rejection in all animals in group A (IIIB, ISHLT) in contrast to low moderate rejection in group B (II–IIIA). hIL-10 serum levels on day 5 were 14±7 pg/ml in group B vs. 0 in group A. Conclusions: Electroporation mediated hIL-10 overexpression in a peripheral muscle of the recipient in combination with low dose CsA reduces acute rejection in this model of rat lung allotransplantation.     

Preconditioning with Hyperbaric Oxygen and Hyperoxia Induces Tolerance against Spinal Cord Ischemia in Rabbits

Background: The aim of this study was to determine if the ischemic tolerance could be induced in the spinal cord by pretreatment with hyperbaric oxygen (HBO) and what components of HBO (hyperoxia, hyperbaricity, and combination of these two) were critical in the induction of tolerance against ischemic injury.

Methods: In experiment 1, 21 rabbits were randomly assigned to one of three groups (n = 7 each): animals in the control group received no HBO before spinal cord ischemia; animals in the HBO-1 and HBO-2 groups received HBO (2.5 atmosphere absolute [ATA], 100% O2) pretreatment 1 h/day for 3 and 5 days before ischemia, respectively. In experiment 2, 48 rabbits were randomly assigned to one of four groups (n = 12 each): the control group received no HBO (21% O2, 1 ATA, 1 h/day, 5 days) before spinal cord ischemia; the HB group received 1-h treatment in 21% O2 at 2.5 ATA each day for 5 days; the HO group received 1-h treatment in 100% oxygen at 1 ATA each day for 5 days; and the HBO group received HBO (2.5 ATA, 100% O2) treatment 1 h/day for 5 days. Twenty-four hours after the last treatment, spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, hind-limb motor function and histopathology of the spinal cord were examined in a blinded fashion.

Results: In experiment 1, the neurologic outcome in the HBO-2 group was better than that of the control group (P = 0.004). The number of normal neurons in the anterior spinal cord in the HBO-2 group was more than that of the control group (P = 0.021). In experiment 2, the neurologic and histopathologic outcomes in the HBO group were better than that of the control group (P < 0.01). The histopathologic outcome in the HO group was better than that in the control group (P < 0.05).     

Adenosine A2A analogue ATL-146e reduces systemic tumor necrosing factor-alpha and spinal cord capillary platelet-endothelial cell adhesion molecule-1 expression after spinal cord ischemia

OBJECTIVE: Inflammation is likely a major contributor to spinal cord reperfusion injury after aortic reconstruction. Systemic 4-(3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]-prop-2-ynyl)-cyclohexanecarboxylic acid methyl ester (ATL-146e), a selective adenosine A(2A) agonist, has been shown to reduce paralysis after spinal cord ischemia. We hypothesized that ATL-146e reduces cytokine production during spinal cord reperfusion, curtailing inflammation and decreasing spinal cord capillary platelet-endothelial cell adhesion molecule-1 (PECAM-1) expression. Study design: New Zealand White rabbits sustained spinal cord ischemia with 45-minute cross-clamping of the infrarenal aorta. One group of animals received intravenous ATL-146e at 0.06 microg/kg/min for 3 hours during reperfusion, beginning after 30 minutes of ischemia. A second group received saline solution vehicle alone for 3 hours, serving as an ischemic control. A third group served as sham-operated animals, undergoing laparotomy with anesthesia. Serum was assayed with enzyme-linked immunosorbent assay for tumor necrosing factor-alpha (TNF-alpha). Animals were allowed to recover for 48 hours and were evaluated for hind-limb motor function with the Tarlov (0 to 5) scoring system. At necropsy, animals from each group yielded spinal cords for immunohistochemical staining for PECAM-1. Data are expressed as mean +/- standard error of the mean, with statistical analysis with Student t test and Kruskal-Wallis nonparametric test. RESULTS: Markedly improved Tarlov scores were seen in rabbits with ATL-146e (P <.001) during spinal cord reperfusion as compared with ischemic control animals. A significant reduction was found in TNF-alpha in the sera of rabbits with ATL-146e infusion (P <.01) as compared with ischemic control animals. Significantly reduced endothelial PECAM-1 staining intensity (P <.05) was seen in microscopic spinal cord sections from rabbits with ATL-146e. CONCLUSION: ATL-146e, an adenosine A(2A) agonist, reduces spinal cord reperfusion injury. The mechanism of the protection may involve a reduction in circulating TNF-alpha during a critical 3-hour reperfusion interval and reduction in spinal cord endothelial PECAM-1 upregulation.     

Effect of ischemic pretreatment on heat shock protein 72, neurologic outcome, and histopathologic outcome in a rabbit model of spinal cord ischemia

OBJECTIVE: In the present study, we investigated the effect of ischemic pretreatment on heat shock protein 72 concentration and neurologic and histopathologic outcome after transient spinal cord ischemia. METHODS: In 28 New Zealand White rabbits, an aortic occlusion device was placed infrarenally. The animals were randomly assigned to 2 groups: ischemic pretreatment (n = 14 animals) and control (n = 14 animals). The duration of ischemic pretreatment was 6 minutes. After 24 hours, the aorta was occluded for 26 minutes in both groups of animals. Neurologic function was assessed 24 and 48 hours after the definite ischemic insult. At 48 hours, the animals were killed for histopathologic evaluation of the spinal cord. In a separate set of animals, heat shock protein 72 levels were determined in the lumbar spinal cord after both a 6- and 10-minute ischemic period, with the use of a Western blot analysis. RESULTS: No significant difference in neurologic outcome between the groups was observed at 24 and 48 hours. The incidence of paraplegia and severe paresis at 48 hours was 79% in the control group and 92% in the ischemic pretreatment group. There was no difference in histopathologic scores between the groups. Heat shock protein 72 could be clearly detected 1 and 2 days after 6- or 10-minute periods of spinal cord ischemia. CONCLUSIONS: In the present rabbit study, ischemic pretreatment could not induce tolerance against a moderately severe spinal cord ischemic insult, despite increased heat shock protein 72 levels after the preconditioning stimulus.