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Background: The aim of this study was to establish a new experimental model to directly analyse the coronary microcirculation in cardiac xenografts. Methods: Intravital fluorescence microscopy (IVM) of the subepicardial microcirculation in heterotopically transplanted hamster-to-rat cardiac xenografts was performed at 30 and 90 min of reperfusion. We quantitatively assessed the microcirculatory perfusion characteristics as well as the interactions of leukocytes and platelets with the endothelium of postcapillary coronary venules in non-sensitised as well as sensitised recipients. Results: In this first experimental IVM study of cardiac xenografts, we successfully visualised the subepicardial microcirculation, i.e. feeding arterioles, nutritive capillaries and draining postcapillary venules, during reperfusion. Leukocyte-endothelial and platelet-endothelial cell interactions could be quantified. In the non-sensitised group, the myocardial microcirculation remained stable during the observation period of 90 min, whereas in the sensitised group, xenografts were rejected immediately. Conclusions: We established a model for the assessment of the microcirculatory dysfunction and inflammation during ischaemia/reperfusion injury in hamster-to-rat cardiac xenografts.

Background. The aim of our study was to investigate the role of inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production in different stages of murine antigen-induced arthritis (AiA). Methods. Clinical, histological and microcirculatory parameters (measured by intravital fluorescence microscopy) were assessed in the knee joint during acute and chronic AiA after inhibition of iNOS with L-N 6 -(1-iminoethyl)lysine (L-NIL). Plasma concentrations of NO - 2 and NO - 3 were evaluated by the Griess reaction and the expression of iNOS, P- and E-selectin, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule I (VCAM-1) by immunohistochemistry. Results. In both stages of the disease, plasma concentrations of NO, and NOR were increased and iNOS was expressed. In the acute phase, swelling, leucocyte adhesion, leucocyte infiltration and expression of adhesion molecules were increased in arthritic animals treated with L-NIL in comparison with untreated arthritic animals. In the chronic phase, no change in the disease parameters could be detected after L-NIL treatment. Conclusion. Increased NO production induced by iNOS during the acute phase of AiA can be regarded as a protective response in the prevention of further leucocytic infiltration and joint destruction, whereas it seems to play a subordinate role in chronic AiA.

The microcirculation and leukocyte-endothelial cell interaction in synovial tissue of an inflamed joint are known to play a crucial role in the pathogenesis of rheumatoid arthritis. The aim of this study was to characterize the in vivo changes in the microvasculature and in leukocyte-endothelial cell interactions in the mouse synovial tissue using intravital fluorescence microscopy in three stages of antigen-induced arthritis. The expression of E- and P-selectin and ICAM-1 were also studied using immunohistochemistry.Antigen-induced arthritis (AiA) was produced in Balb/c mice. The severity of arthritis at three different phases was quantified using a clinical and histological score. For the intravital fluorescence microscopy measurements, the patella tendon was partially resected for visualization of the intraarticular synovial tissue of the knee joint. The number of rolling and adherent leukocytes, functional capillary density (FCD) and RBC velocity were quantitatively measured in synovial microvessels. Expression of ICAM-1, E- and P-selectin was assessed by immunohistochemistry.There was a significant increase in the leukocyte rolling fraction in postcapillary venules in the acute phase of AiA (from 0.26 +/- 0.05 in controls to 0.45 +/- 0.04 8 d after AiA induction). The number of leukocytes adherent to the endothelium was significantly elevated in all phases of arthritis (from 121 +/- 27 in controls to 376 +/- 62 mm2 63 d after AiA-induction). Functional capillary density was significantly enhanced in the acute (332 +/- 15 cm/cm2) and intermediate phases (320 +/- 15 cm/cm2) compared to control values (227 +/- 15 cm/cm2). Arthritis resulted in a distinct increase in the expression of ICAM-1 on the synovial endothelium in all phases of AiA. E- and P-selectin expression were detected only in the acute phase.Our model provides new insights into the microcirculatory changes which occur in the synovial tissue of an arthritic joint.

Halogenated anaesthetics have been shown to reduce ischaemia-reperfusion injuries in various organs due to pre- and post-conditioning mechanisms. We compared volatile and total intravenous anaesthesia with regard to their effect on remote pulmonary injury after thoracic aortic occlusion and reperfusion.Eighteen pigs were randomized after sternotomy and laparotomy (fentanyl-midazolam anaesthesia) to receive either sevoflurane or propofol in an investigator-blinded fashion. Ninety minutes of thoracic aortic occlusion was induced by a balloon catheter. During reperfusion, a goal-directed resuscitation protocol was performed. After 120 min of reperfusion, the anaesthetic regimen was changed to fentanyl-midazolam again for another 180 min. The oxygenation index and intra-pulmonary shunt fractions were calculated. After 5 h of reperfusion, a bronchoalveolar lavage was performed. The total protein content and lactate dehydrogenase activity were measured in epithelial lining fluid (ELF). Alveolar macrophage oxidative burst was analysed. The wet to dry ratio was calculated and tissue injury was graded using a semi-quantitative score. Ten animals (n=5 for each anaesthetic) without aortic occlusion served as time controls.The oxygenation index decreased and the intra-pulmonary shunt fraction increased significantly in both occlusion groups. There were no significant differences between sevoflurane and propofol with respect to the oxygenation index, ELF composition, morphologic lung damage, wet to dry ratio and alveolar macrophage burst activity. Differences were, however, seen in terms of systemic haemodynamic stability, where catecholamine requirements were less pronounced with sevoflurane.We conclude that the severity of remote lung injury was not different between sevoflurane and propofol anaesthesia in this porcine model of severe lower-body ischaemia and reperfusion injury.

Infrared contact coagulation (ICC) was evaluated in 3 different tumor models. 56-94% of all tumor-bearing rats, hamsters or mice were cured by ICC, whereas 100% of the controls died. The possibility that long-lasting immunological resistance might develop against the tumor after ICC was investigated by repeated tumor challenge. Cytotoxicity against tumor cells of host thymocytes and splenocytes following ICC was demonstrated in a Winn assay. The production of a mainly T-cell-dependent immune response could be due to ICC-induced antigenic changes in the tumor cells.