Role of priming stresses and Hsp70 in protection from ischemia-reperfusion injury in cardiac and skeletal muscle.

Ischemia-reperfusion injury limits the survival of muscle involved in tissue trauma or transfers during microsurgical reconstruction. Priming stresses such as ischemic preconditioning or mild hyperthermia have frequently been associated with improved survival of ischemic-reperfused cardiac muscle, such protection coinciding with induction of the stress-related heat shock protein 70 (Hsp70). Little is known about the response of skeletal muscle to priming stresses. This review summarizes the current knowledge on the use of priming stresses as protective strategies against the consequences of ischemia-reperfusion in cardiac and skeletal muscle and the potential role of Hsp70.

Hyperalgesia due to nerve injury-role of peroxynitrite.

We carried out a partial ligation of the sciatic nerve in rats to induce nerve injury and neuropathic hyperalgesia. We showed that nitrotyrosine, a marker of peroxynitrite activity, was formed after partial nerve injury. Double-labelling immunohistochemistry showed that nitrotyrosine-immunoreactive cells were mainly macrophages and Schwann cells. Daily treatment with uric acid, a scavenger of peroxynitrite, decreased nitrotyrosine formation in the injured sciatic nerve, and produced concomitant alleviation of thermal hyperalgesia and Wallerian degeneration. These results provide the first evidence that peroxynitrite is formed after partial nerve injury, and contributes to the initiation of thermal hyperalgesia and Wallerian degeneration. We hypothesize that uric acid alleviates hyperalgesia and Wallerian degeneration by inhibiting oxidative damage caused by peroxynitrite and possibly also by decreasing the production of other inflammatory mediators such as prostaglandins.

Phosphoenolpyruvate/adenosine triphosphate enhances post-ischemic survival of skeletal muscle.

This study examined whether ischemia-reperfusion injury to skeletal muscle could be reduced by post-ischemic infusion of phosphoenolpyruvate (PEP) and adenosine triphosphate (ATP). The rectus femoris muscle of 54 rabbits was rendered ischemic for 3.5 hr. Eighteen rabbits received no further treatment. Thirty-six were infused intra-arterially at the end of ischemia, 18 with vehicle alone, and 18 with a mixture of PEP (80 mumol/kg) and ATP (2.6 mumol/kg). Six rabbits from each group were explored after 24 hr reperfusion and the muscles assessed for viability (by nitro blue tetrazolium), ATP (by luciferin-luciferase chemiluminescence), malonyldialdehyde (MDA) (thiobarbituric acid method), and water content. The remaining muscles in each group were examined histologically after either 1 hr or 4 days of reperfusion. At 24 hr the viability of the PEP/ATP infused muscles (78.9 +/- 15.4 percent) was significantly greater than that of untreated (41.4 +/- 27.3 percent) or vehicle-infused groups (34.0 +/- 32.7 percent). ATP stores were significantly higher and MDA (indicative of free radical activity) and water content significantly lower in the PEP/ATP treated group. At 24 hr and 4 days, muscles infused with PEP/ATP showed less necrosis and fewer infiltrating neutrophils than the untreated groups. Studies with isolated rabbit neutrophils showed that ATP alone significantly inhibited superoxide anion production by stimulated neutrophils. However, when combined with PEP at concentrations similar to those achieved in vivo, ATP did not significantly affect superoxide production. The findings indicate that post-ischemic infusion of PEP/ATP significantly reduces ischemia-reperfusion injury in rabbit skeletal muscle. The protective effect of PEP/ATP is more likely to be due to supplementation of intracellular ATP stores than to the inhibition of superoxide production by infiltrating neutrophils.

Autologous lymphocyte therapy for experimental canine lymphoedema: a pilot study.

Obstructive lymphoedema, an accumulation of protein-rich fluid in interstitial spaces, was created in five dogs by a combination of the irradiation of one groin and subsequent surgical ablation of any remaining lymphatics. The lymphoedema was stable for up to 2 years. The aim was to test the efficacy of intra-arterial injection of autologous lymphocytes as a therapy for lymphoedema. The hypothesis was that cytokines produced by lymphocytes mediate proteolysis by macrophage proteinases in the lymphoedematous limb to remove the excess protein and relieve the oedema. A concentrated lymphocyte-rich preparation was isolated from blood by the Ficoll-Paque method. These preparations were injected into the femoral artery four times at approximately 4 weekly intervals. Three months after the first injection of lymphocytes, lymphoedematous limbs showed a marked 69% reduction in the mean excess circumferences compared with opposite control limbs. After treatment, skin thickness and hydroxyproline content (both measures of fibrosis) as well as water content (a measure of oedema) had reduced significantly. In specimens of interstitial fluid and in skin homogenates acidic proteinase activity increased and the protein concentration decreased significantly compared with controls. It is concluded that increased proteolysis, possibly due to activated macrophages recruited to the lymphoedematous limb, may partly explain these results.

Drug mixture which improves survival of ischemic rabbit epigastric skin flaps.

The chief aim of this study was to maximize flap survival by counteracting the pathophysiological changes occurring during ischemia-reperfusion. Rabbit epigastric skin flaps given 21 hours of ischemia were infused intra-arterially with selected drugs at the start of reperfusion. Compared with control infused ischemic flaps, which had a 33% survival rate on day 7 post-ischemia, significant improvement was found with vasodilators nitrendipine (61%) and prostacyclin (65%) and the thrombolytic agent urokinase (65%); marginal improvement with the free radical scavenger desferrioxamine (53%); but no change with streptokinase (44%), heparin (21%), and ATP-MgCl2 (35%). A drug mixture comprising all of these agents except streptokinase and urokinase produced 87% survival, suggesting an additive effect. Biochemical assays on skin homogenates and blood implicated oxygen free radicals, neutrophil infiltration, and thromboxane in flap failure. These results imply that multiple factors are responsible for ischemic flap failure and that a mixture of drugs needs to be infused to counteract all of the detrimental changes.

Experience with calcium antagonists nitrendipine, diltiazem, and verapamil and beta 2-agonist salbutamol in salvaging ischemic skin flaps in rabbits.

This study investigated the efficacy of selected agents in the salvage of experimental skin flaps in rabbits after 21 hours of 25 degrees C ischemia. Calcium channel antagonists nitrendipine, diltiazem, and verapamil increased ischemic skin flap survival in rabbits from 33.3% for buffered saline infused controls to 71.4% (P less than 0.05), 71.4% (P less than 0.05), and 50.0% (not significant) respectively. The beta 2-adrenoceptor agonist salbutamol produced an increase in survival to 64.3%, which narrowly missed statistical significance. All four test agents invoked a vasodilatory response (greatest for nitrendipine, diltiazem, and salbutamol), a slight fall in blood pressure, and a small increase in heart rate. It is concluded that the vasodilatory response in the microcirculation of the ischemic flap helped to minimize the risk of occlusion due to thrombosis or cell sludging during reperfusion, thus leading to improved flap survival.

Laboratory diagnosis and oral treatment of CAPD peritonitis.

The laboratory diagnosis of 50 consecutive episodes of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) was studied. The technique which yielded the highest rate (84%) of positive bacteriological diagnoses was inoculation and subculture of thioglycollate broth. Cloudiness of fluid to the naked eye was an accurate predictor of a raised white cell count. A minimum laboratory protocol for the bacteriological diagnosis of CAPD peritonitis was devised and has been in use satisfactorily since the completion of the study. Antibiotic treatment was given orally in the first instance in 43 episodes and was successful in 34.