Evaluation of the modified HTK solution in pancreas transplantation-An experimental model.

INTRODUCTION: One of the great challenges in pancreas transplantation is the ischemia reperfusion injury. It is mentioned that free oxygen and/or nitrogen radicals play a prominent role in this phase. To minimize this problem, a modified histidine-tryptophan-ketoglutarate (HTK) solution that contains modified antioxidants has been developed. Our aim was to evaluate this solution in improving the viability of the pancreas in comparison with standard HTK and University of Wisconsin (UW) solutions in a porcine model of pancreas transplantation. MATERIALS AND METHODS: Twenty-three Landrace pigs were divided into three identical groups. After a 10-hour preservation time at 4°C, the pancreas was implanted in the organs of the recipients in a standardized manner. Serum parameters were assessed prior to and after implantation on the 1(st) postoperative day, 3(rd) postoperative day, and 7(th) postoperative day. Furthermore, three biopsies were taken: prior to and after reperfusion, and on Day 7 to assess the grafts. RESULTS: An analysis of serum glucose among the three groups showed no significant differences. Evaluation of the insulin levels showed no significant difference between the modified and standard HTK groups; however, differences between HTK and UW were significant (p = 0.004 in favor of UW solutions). The histopathological results showed a trend of a higher grade of rejection of pancreas tissue in the UW group compared to both HTK groups. CONCLUSION: The modified HTK solution could preserve the pancreas for the preservation of the graft with similar results to those observed for standard solutions without any significant difference. The trend showed that the pathological finding in the UW group was not as good as that in the modified HTK and standard HTK groups.

Sulforaphane counteracts aggressiveness of pancreatic cancer driven by dysregulated Cx43-mediated gap junctional intercellular communication.

The extreme aggressiveness of pancreatic ductal adenocarcinoma (PDA) has been associated with blocked gap junctional intercellular communication (GJIC) and the presence of cancer stem cells (CSCs). We examined whether disturbed GJIC is responsible for a CSC phenotype in established and primary cancer cells and patient tissue of PDA using interdisciplinary methods based in physiology, cell and molecular biology, histology and epigenetics. Flux of fluorescent dyes and gemcitabine through gap junctions (GJs) was intact in less aggressive cells but not in highly malignant cells with morphological dysfunctional GJs. Among several connexins, only Cx43 was expressed on the cell surface of less aggressive and GJIC-competent cells, whereas Cx43 surface expression was absent in highly malignant, E-cadherin-negative and GJIC-incompetent cells. The levels of total Cx43 protein and Cx43 phosphorylated at Ser368 and Ser279/282 were high in normal tissue but low to absent in malignant tissue. si-RNA-mediated inhibition of Cx43 expression in GJIC-competent cells prevented GJIC and induced colony formation and the expression of stem cell-related factors. The bioactive substance sulforaphane enhanced Cx43 and E-cadherin levels, inhibited the CSC markers c-Met and CD133, improved the functional morphology of GJs and enhanced GJIC. Sulforaphane altered the phosphorylation of several kinases and their substrates and inhibition of GSK3, JNK and PKC prevented sulforaphane-induced CX43 expression. The sulforaphane-mediated expression of Cx43 was not correlated with enhanced Cx43 RNA expression, acetylated histone binding and Cx43 promoter de-methylation, suggesting that posttranslational phosphorylation is the dominant regulatory mechanism. Together, the absence of Cx43 prevents GJIC and enhances aggressiveness, whereas sulforaphane counteracts this process, and our findings highlight dietary co-treatment as a viable treatment option for PDA.

Bed isolation in experimental flap studies in rats: a dispensable procedure.

Review of the literature regarding rodent experimental flap models reveals fundamental differences in applied surgical procedures. Although some authors isolate the flap from its wound bed, others do not. This study was planned to investigate to what extent the insertion of a silicone sheet affects physiological wound healing in experimental flap surgery. An extended epigastric adipocutaneous flap (6 × 10 cm) was raised in 16 male Lewis rats. In the control group (group C), flaps were immediately inset without any intervention. In the experimental group (group M), a silicone sheet barrier was placed between the flap and the wound bed. Mean flap survival area and flap perfusion were evaluated. Microvessel density was visualized by immunohistochemistry, and semiquantitative real-time polymerase chain reaction addressed differential gene expression. All animals were investigated on postoperative day 5. Flap survival area and flap perfusion were found to be similar. Immunohistochemistry, however, demonstrated a significantly increased number of CD31-positive small vessels in group C. The insertion of the silicone sheet barrier (group M) was accompanied by a significantly enhanced expression of proinflammatory genes and a suppression of proangiogenic genes. Our results show that although the silicone membrane has no influence on the surgical outcome in terms of flap survival and perfusion, it does lead to significant molecular alterations in pathways involved in physiological wound healing. These alterations are artificially induced by the foreign body material and conceal the true driving forces of the healing process. As the latter might include relevant therapeutic targets to ameliorate surgical results, we regard wound bed isolation as a dispensable procedure in the study of rodent flap models.

Mitomycin-C-treated peripheral blood mononuclear cells (PBMCs) prolong allograft survival in composite tissue allotransplantation.

BACKGROUND: Composite tissue allotransplantation (CTA) was introduced as a potential treatment for complex reconstructive procedures and has become a clinical reality. Hand and face transplantation, the most widely recognized forms of CTA, have intensified immunological research in this emerging field of transplantation. Mitomycin C (MMC) is an alkylating agent that suppresses allogeneic T-cell responses. MMC-treated dendritic cells/PBMCs have been shown to induce donor-specific tolerance in solid organ allograft transplantations. METHODS: Fully mismatched rats were used as hind limb donors [Lewis (RT1(1))] and recipients [Brown-Norway (RT1(n))]. Fifty-five allogeneic hind limb transplantations were accomplished in six groups. Group A (n = 10) received donor-derived MMC-treated PBMCs on transplantation day. Group B (n = 10) rats received no immunosuppression, group C (n = 10) received FK506 and prednisolon, group D consisted in isograft transplantation without immunosuppression, group E (n = 10) received non-treated PBMCs, and group F (n = 5) received PBS without any donor-derived cells. Rejection was assessed clinically and histologically. RESULTS: In group A, the survival times of the allografts were prolonged to an average of 8.0 d. Rejection was significantly delayed compared with the averages of the corresponding control groups B, E, and F (5.5, 5.9, and 5.8 d). No rejection was seen in control groups C and D. CONCLUSION: These results demonstrate that MMC-treated donor PBMCs significantly prolong allograft survival when administered systemically on the day of transplantation. However, the immunomodulatory effect is relatively modest with further research being required to clarify dose-effect relations, cell characteristics, and an optimized mechanism and timing for cell application.

Autophagy mediates survival of pancreatic tumour-initiating cells in a hypoxic microenvironment.

Involvement of dysregulated autophagy in cancer growth and progression has been shown in different tumour entities, including pancreatic ductal adenocarcinoma (PDA). PDA is an extremely aggressive tumour characterized by a small population of highly therapy-resistant cancer stem cells (CSCs) capable of self-renewal and migration. We examined whether autophagy might be involved in the survival of CSCs despite nutrition and oxygen deprivation typical for the hypoxic tumour microenvironment of PDA. Immunohistochemistry revealed that markers for hypoxia, CSCs and autophagy are co-expressed in patient-derived tissue of PDA. Hypoxia starvation (H/S) enhanced clonogenic survival and migration of established pancreatic cancer cells with stem-like properties (CSC(high)), while pancreatic tumour cells with fewer stem cell markers (CSC(low)) did not survive these conditions. Electron microscopy revealed more advanced autophagic vesicles in CSC(high) cells, which exhibited higher expression of autophagy-related genes under normoxic conditions and relative to CSC(low) cells, as found by RT-PCR and western blot analysis. LC3 was already fully converted to the active LC3-II form in both cell lines, as evaluated by western blot and detection of accumulated GFP-LC3 protein by fluorescence microscopy. H/S increased formation of autophagic and acid vesicles, as well as expression of autophagy-related genes, to a higher extent in CSC(high) cells. Modulation of autophagy by inhibitors and activators resensitized CSC(high) to apoptosis and diminished clonogenicity, spheroid formation, expression of CSC-related genes, migratory activity and tumourigenicity in mice. Our data suggest that enhanced autophagy levels may enable survival of CSC(high) cells under H/S. Interference with autophagy-activating or -inhibiting drugs disturbs the fine-tuned physiological balance of enhanced autophagy in CSC and switches survival signalling to suicide.

Multidrug strategies are effective in the treatment of severe experimental pancreatitis.

BACKGROUND: Trypsinogen activation, oxygen radicals, cytokines, leukocyte infiltration, and pancreatic ischemia are important steps in the pathogenesis of necrotizing pancreatitis and associated systemic complications. Several drugs that inhibit those pathogenetic steps attenuated biochemical and histologic changes, while survival remained low. The aim of the present study was to evaluate the benefit of multidrug approaches compared to monotherapies on organ injury and survival in acute experimental pancreatitis in the rat model of retrograde bile injection combined with intravenous cerulein. METHODS: Necrotizing pancreatitis was induced in rats. After a therapy-free interval of 6 hours, 10 treatment regimens were evaluated: multidrug regimen 1, which contained the protease inhibitor gabexate mesilate, oxygen-free radical scavengers, nitric oxide donor L-arginine, a platelet-activating factor antagonist, and antibodies against intracellular adhesion molecule-1 (ICAM-1) dissolved in dextran, was compared to multidrug regimen 2 (dextran, acetylcysteine, L-arginine, and anti-ICAM-1), monotherapies of each of the drugs, and standard intravascular volume replacement. RESULTS: Both multidrug regimens significantly reduced pancreatic and systemic injury and microcirculatory disturbances compared to any of the monotherapies. Treatment with regimen 1 decreased 24-hour mortality to 0% and increased long-term survival to 85% (standard therapy, 70% and 15%, respectively). Multidrug regimen 2 was as effective as regimen 1. CONCLUSION: Treatment of acute necrotizing pancreatitis with multidrug regimens significantly decreases short-term mortality compared to monotherapies. Moreover, multidrug strategies are still effective after a wide therapeutic window. Key to this effective therapy is the inhibition of microcirculatory disturbances and of the systemic inflammatory response. The experimental superiority of the multidrug approach should be confirmed in a clinical trial.

Intraoperative lung edema monitoring by microwave reflectometry.

Microwave reflectometry might be a suitable tool for the thoracic surgeon to monitor edema formation of the lung during lung surgery. A new setup of microwave reflectometry for lung water measurements was developed and tested for clinical application. Three lung models were used for the microwave reflectometry tests: 1) the model of an ex vivo isolated perfused rat lung to investigate lung edema formation during ischemia-reperfusion (n=6), 2) the in situ lung of a human patient to demonstrate the feasibility of lung water monitoring during a surgical operation, 3) the model of an ex vivo isolated perfused human lung to investigate edema formation during postischemic reperfusion and to investigate the changes in water content in the region of a tumor. During human lung operation, significant changes in water content occurred in different lung areas. During isolated perfusion, a significant increase in lung water was measured in models 1) and 3) (P=0.03). Water content of tumor tissue was higher than in the surrounding healthy lung tissue. Microwave reflectometry offers a non-invasive approach to monitor lung edema formation in experimental models and during thoracic surgery.

Usefulness and limitations of computational models in aortic disease risk stratification.

OBJECTIVE: In risk stratification of aortic diseases such as aneurysm and aortic dissection, diameter is one parameter whose influence on the average aortic wall stress is directly described by the Laplace law. More advanced mechanical models can be used and may yield additional information, such as transmural stress distributions. The question then arises of how refined models need to be to provide clinicians with practical help. METHODS: Two sets of finite element models were used. The relative roles of diameter, material stiffness, longitudinal stretch, blood pressure, wall thickness, and vessel curvature were explored using simplified aortic models for comparison with the Laplace law. The influences of the material properties nonlinearity and residual stress on the transmural stress distribution were investigated using an advanced aortic model including recent experimental findings in older humans. RESULTS: The Laplace law was confirmed as one effective, basic tool to assess the average wall stress in the aortic wall, both in the circumferential and longitudinal directions. However, the simplified models were sufficient to show that, as already reported in the literature, longitudinal stretch and vessel curvature have potentially equally strong or even stronger contributions to wall stress than the parameters included in the Laplace law. When the advanced model was used, and residual stress induced by large opening angles such as found in older subjects was introduced, the transmural stress gradient was found inverted compared with expectations, with the largest stresses now toward the adventitia. The results suggested that the intima may be increasingly shielded from higher stresses as one gets older, which might be protective against the initiation of dissection tears in the thoracic aorta. CONCLUSION: Biomechanical analysis of the aorta may be refined by using increasingly detailed computational models. Simplified models can readily improve on the Laplace law in the assessment of aortic wall stress, and as such, may already contribute to better risk stratification of aortic disease. Advanced models may also enhance our understanding of the mechanistic aspects in the pathogenesis of aortic disease. However, their applicability in a patient-specific context may be limited by the large number of input data they require, some of which might stay out of the clinicians' reach.

Pre-ischaemic conditioning of the pulmonary endothelium by immunotargeting of catalase via angiotensin-converting-enzyme antibodies.

BACKGROUND: Alleviation of oxidative stress via targeted delivery of catalase to the pulmonary endothelium by conjugation of angiotensin-converting-enzyme (ACE) monoclonal antibodies attenuates lung injury in an in vivo model of warm lung ischaemia and reperfusion. This study evaluates treatment of lung allografts with conjugates of anti-ACE antibody with catalase (9B9-CAT) in the setting of hypothermic preservation and reports the effect on ischaemia/reperfusion injury in this model. METHODS: Rats were injected 1h prior to lung harvesting with mouse immunoglobulin G (IgG) (negative controls), catalase only (CAT) or anti-ACE mAb 9B9 conjugated with catalase (9B9-CAT). Lungs were flushed with low-potassium dextran (LPD) solution, excised and stored at 4 degrees C for 4 and 8h. Grafts were isolated and directly reperfused at 37 degrees C for up to 180 min. Peak inspiratory pressure (PIP), pulmonary arterial pressure (PAP) and lung weight were measured during reperfusion. Anti-oxidative capacity and catalase activity were measured in frozen lung tissue and inflammatory parameters were detected during reperfusion in perfusate solution. RESULTS: Cold ischaemia of 8h significantly increased lung weight gain, PIP and PAP in non-immune mouse IgG and CAT-treated lungs than in 9B9-CAT-treated lungs (p<0.005). Significantly higher catalase activity and anti-oxidative status were found in the lung tissue of animals conditioned with 9B9-CAT after 4 and 8h of cold storage than in animals treated with catalase (CAT) alone or in animals treated with non-immune mouse IgG (p<0.01). CONCLUSION: These results validate immunotargeting by anti-ACE mAb conjugated with catalase as a prospective and specific strategy to augment anti-oxidative defence of the pulmonary endothelium during lung transplantation. Vascular immunotargeting of anti-oxidative enzymes could limit reactive oxygen species mediated ischaemia-reperfusion (I/R) injury of the lung and has the potential to become a promising modality for extension of the viability of banked transplantation tissue.

Effects of ketamine on hypoxic pulmonary vasoconstriction in the isolated perfused lungs of endotoxaemic mice.

BACKGROUND AND OBJECTIVE: During sepsis and endotoxaemia, hypoxic pulmonary vasoconstriction (HPV) is impaired. Sedation of septic patients in ICUs is performed with various anaesthetics, most of which have pulmonary dilatory properties. Ketamine is a sympathetic nervous system-activating anaesthetic that preserves cardiovascular stability. The effects of ketamine on the pulmonary vasculature and HPV during sepsis have not been characterized yet. METHODS: Therefore, isolated lungs of mice were perfused with ketamine (0, 0.1, 1.0, and 10 mg kg(-1) body weight min) 18 h following intraperitoneal injection of lipopolysaccharide (LPS); untreated mouse groups served as controls (n = 7 per group, respectively). Pulmonary artery pressure (PAP) and pressure-flow curves during normoxic (FiO(2) = 0.21) and hypoxic (FiO(2) = 0.01) ventilation were obtained. RESULTS: HPV was reduced in endotoxaemic animals when compared with controls (means +/- SD; DeltaPAP control 103 +/- 28% vs. LPS 23 +/- 25%, P < 0.05). Ketamine caused a dose-dependent reduction of HPV in the lungs of control (DeltaPAP 0 mg kg(-1) min(-1) ketamine 103 +/- 28% vs. 10 mg kg(-1) min(-1) ketamine 28 +/- 21%, P < 0.05) and septic animals (DeltaPAP 0 mg kg(-1) min(-1) ketamine 23 +/- 25% vs. 10 mg kg(-1) min(-1) ketamine 0 +/- 4%, P < 0.05). Analysis of pressure-flow curves revealed that ketamine partly reversed the endotoxin-induced changes in basal pulmonary vascular wall properties rather than interfering with the HPV response itself. CONCLUSION: Ketamine modified baseline pulmonary vascular properties, resulting in a reduced HPV responsiveness in untreated mice. Further, ketamine counteracted the LPS-induced changes in pulmonary vascular pressure-flow relationships, but did not affect impaired HPV in this murine endotoxaemia model.

Aortic root motion remodeling after aortic valve replacement--implications for late aortic dissection.

Aortic root motion was previously identified as an additional risk factor for aortic dissection. This study analyzed if the magnitude of aortic root motion changed in patients after aortic valve replacement (AVR) and acute proximal aortic dissection. An institutional database (1984-2005) was used to measure the downward motion of the aortic root (perpendicular to the plane of the sinotubular junction) in contrast injections in 48 patients with aortic insufficiency (AI), aortic stenosis (AS) and proximal aortic dissection pre- and postoperatively, when available. Postoperative aortic root motion was significantly reduced after AVR for AI, while it was significantly increased after AVR for AS. By contrast, aortic root motion was unchanged when functional AI due to paravalvular leak was present post-AVR for AI. In patients with acute aortic dissection, both aortic root motion and aortic diameter were unchanged from pre-dissection. However, in patients who dissected again, aortic root motion was significantly smaller than pre-dissection, and the aortic diameter was significantly less than at first dissection. Removal of aortic stenosis was associated with increased aortic root motion, theoretically heightening the threat of dissection posed to the aortic wall by mechanical stress, although this was not confirmed by our study of dissection patients. Yet, mechanical principles command to include higher magnitude of aortic root motion during follow-up of patients after AVR as an additional risk factor for dissection.

Experimental study of cardiorespiratory and stress factors in esophageal surgery using robot-assisted thoracoscopic or open thoracic approach.

BACKGROUND: Our aim was to compare cardiovascular and stress response to robotic technology during thoracoscopic mobilization and anastomosis of the esophagus vs the conventional open approach. DESIGN: Randomized experimental study. SETTING: Department of Experimental Surgery, University of Heidelberg. SUBJECTS: Twelve pigs randomized to undergo robotic or conventional surgery (6 animals each). INTERVENTIONS: Fundus rotation gastroplasty followed by esophageal mobilization and intrathoracic anastomosis by conventional or robotic surgery. MAIN OUTCOME MEASURES: Mean arterial pressure, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, cardiac output, pulmonary vascular resistance, partial oxygen pressure, alveolar-arterial difference in partial pressure of oxygen, and arteriovenous oxygen content difference measured preoperatively, during esophageal manipulation, and 30 minutes after operation. Operative stress was assessed by plasma levels of cortisol and substance P. RESULTS: Hemodynamic measures showed higher intraoperative central venous pressure and pulmonary vascular resistance in the open surgery group, whereas cardiac output was significantly decreased compared with the robotic group. Blood gas values showed significant deterioration during esophageal manipulation with open surgery in contrast to the robotic group. Substance P and cortisol levels were significantly higher with the open approach. CONCLUSIONS: The robot-assisted approach is associated with improved intraoperative cardiopulmonary function and seems to be a less stressful technique.

Review of various techniques of pancreas transplantation in rat model.

Pancreas transplantation (PTx) is being applied with increasing frequency in the treatment of diabetes mellitus Type 1 and selected cases of Type 2. It is known that PTx can consistently establish normoglycemic insulin-independent state. Due to the increased use of different PTx models in rats for studying the metabolic function of the transplanted pancreas, reviewing the various techniques in PTx seemed to be necessary. A review of the literature of PTx in rat models showed that different techniques or modifications have been described. Each modification is the result of a change or simplification of three main points: the arterial inflow, the venous outflow, and the management of the exocrine secretory part of the gland. The techniques of PTx vascularization in rats are based on two cardinal models, which include the microsuture and non-suture cuff techniques. In arterial inflow reconstruction, an aortic segment is used. Venous drainage is accomplished by systemic or portal drainage (porto-caval or porto-portal anastomosis). Management of the exocrine part has the most variations. Enteric and urinary diversion, as well as duct ligation or obstruction, are the most important techniques for the management of exocrine part. Regarding vascular anastomosis, the microsuture technique is more popular than the cuff technique. However the cuff technique seems to be simpler. Grafts with portal venous drainage show a lesser probability of hyperinsulinemia and a high level of lipoproteins. In the management of the exocrine part, enteric exocrine drainage is more similar to the physiological setting and is associated with a significant reduction in the incidence of acidosis and dehydration. However, enteric diversion is more prone to intestinal bleeding and ileus as well as to bacterial contamination. The technique for PTx in rat varies according to surgeons' experiences and preferences as well as their research objectives.

4-Aminopyridine restores impaired hypoxic pulmonary vasoconstriction in endotoxemic mice.

BACKGROUND: Hypoxic pulmonary vasoconstriction (HPV) is impaired during inflammatory lung processes such as pneumonia or the acute respiratory distress syndrome. Voltage-gated potassium channels play a central role in mediating HPV. The aim of this study was to determine whether 4-aminopyridine (4-AP), a known voltage-gated potassium channel inhibitor, may restore HPV in sepsis. METHODS: The effects of 0.01, 0.1, and 1.0 mm 4-AP on HPV responsiveness were assessed in isolated lungs of untreated mice and of mice 18 h after lipopolysaccharide injection (20 mg/kg intraperitoneal Escherichia coli 0111:B4 lipopolysaccharide). HPV was quantified as the increase in perfusion pressure in response to hypoxic ventilation in percent of baseline perfusion pressure. Intrinsic pulmonary vascular resistance (R0) and pulmonary vascular distensibility (alpha) were determined by nonlinear regression analysis of pulmonary vascular pressure-flow curves generated during normoxic and hypoxic ventilation, respectively. RESULTS: HPV was impaired in lungs isolated from lipopolysaccharide-challenged mice. Addition of 4-AP to the perfusate did not alter HPV responsiveness in untreated mice but dose dependently restored HPV in endotoxemic mice. Analysis of pulmonary vascular pressure-flow curves revealed that 4-AP (1) counteracted the observed lipopolysaccharide-induced changes in alpha and R0 under normoxic conditions and (2) augmented the hypoxia-induced increase in R0 in lungs of endotoxemic mice. CONCLUSIONS: This study demonstrates that lipopolysaccharide-induced pulmonary vascular hyporesponsiveness to hypoxia can be restored by 4-AP in murine endotoxemia and, thus, may be a new therapeutic approach to treat patients with hypoxemia due to impaired HPV.

Immunosuppressive effect of tryptophan metabolites in composite tissue allotransplantation.

BACKGROUND: Hand transplantations have intensified immunological research into composite tissue allotransplantation to induce tolerance. Pregnancy is a successful, natural model of immunological tolerance. The enzyme indoleamine 2,3-deoxygenase plays an important role by catabolizing the amino acid tryptophan. The resulting metabolites have been shown to be immunosuppressive. The effect of tryptophan metabolites has not been investigated in vascularized organ transplantation before. In this study, the authors applied to composite tissue allotransplantation what nature has developed for pregnancy, and examined the immunosuppressive effect of tryptophan metabolites in a model of hind limb transplantation. METHODS: Thirty-three allogeneic hind limb transplantations in the rat (Lewis --> Brown-Norway) were performed in three groups. Group A (n = 12) received no immunosuppression, group B (n = 13) received tryptophan metabolites (kynurenine and 3-hydroxyanthranilic acid) locally and systemically, and group C (n = 8) served as a control group receiving FK506. The timing of rejection was assessed by clinical observation. RESULTS: Rejection of the allogeneic hind limb occurred on average 6.58 days after transplantation in group A (no immunosuppression) and after 8.15 days in group B (tryptophan metabolites). Rejection was significantly delayed (log-rank test, p < 0.01). No rejection was seen with application of FK506 during the follow-up period of 21 days. CONCLUSIONS: For the first time, tryptophan metabolites have been applied in vascularized composite tissue allotransplantation and showed a significant immunosuppressive effect. These promising first results need further dose-effect and toxicological studies to increase the still limited immunosuppressive effect and define the clinical role these metabolites may play in the future.

Distinct effects of surgical denervation on hepatic perfusion, bowel ischemia, and oxidative stress in brain dead and living donor porcine models.

The liver function and perfusion following brain death is mainly influenced by the sympathetic nerves and hormones. We examined the specific influence of surgical liver denervation on systemic and hepatic perfusion parameters, bowel ischemia and oxidative stress in hemodynamically stable BD and control (living donor [LD]) pigs. Brain death was induced in 8 pigs via saline infusion into the balloon of an epidural Tieman-catheter (1 mL/15 minutes) and compared to the control group (n = 6) over 4 hours. At 2 hours postoperatively, complete liver denervation was initiated. We analyzed systemic cardiocirculatory parameters (mean arterial pressure, aortic flow, bowel ischemia (endotoxin, and endotoxin-neutralizing capacity) and oxidative stress (total glutathione in erythrocytes [tGSH(E)]) and compared them to local/hepatic perfusion parameters (hepatic artery and portal venous flow, liver blood flow index, and microperfusion), local bowel ischemia (intramucosal pH [pHi] of stomach [pHi(S)]/colon[pHi(C)]), and liver oxidative stress (glutathione [rGSH(L), GSSG(L)]). Following brain death, the parameters including mean arterial pressure, aortic flow, pHi, endotoxin, and tGSH(E) showed no significant changes at 2 hours. Portal venous flow and microperfusion were decreased significantly and hepatic arterial buffer response was ineffective. Hepatic oxidative stress was increased in BD animals (decrease rGSH(L), increase GSSG(L)). Surgical denervation/manipulation increased portal venous flow significantly, hepatic arterial buffer response became effective, and stomach pHi decreased (BD and LD groups). Hepatic oxidative stress was reduced in the BD group (increase rGSH(L)/GSSG(L); P < 0.001) while it was increased in the LD group (decrease rGSH(L)/GSSG(L); P < 0.001). In conclusion, denervation reduces hepatic oxidative stress in BD only in contrast to the LD. The reciprocal effect of denervation depends on the state of neural activation and postulates a potential benefit of surgical denervation before organ harvesting in brain death.

Role of endogenous nitric oxide in endotoxin-induced alteration of hypoxic pulmonary vasoconstriction in mice.

Pulmonary vasoconstriction in response to alveolar hypoxia (HPV) is frequently impaired in patients with sepsis or acute respiratory distress syndrome or in animal models of endotoxemia. Pulmonary vasodilation due to overproduction of nitric oxide (NO) by NO synthase 2 (NOS2) may be responsible for this impaired HPV after administration of endotoxin (LPS). We investigated the effects of acute nonspecific (N(G)-nitro-L-arginine methyl ester, L-NAME) and NOS2-specific [L-N6-(1-iminoethyl)lysine, L-NIL] NOS inhibition and congenital deficiency of NOS2 on impaired HPV during endotoxemia. The pulmonary vasoconstrictor response and pulmonary vascular pressure-flow (P-Q) relationship during normoxia and hypoxia were studied in isolated, perfused, and ventilated lungs from LPS-pretreated and untreated wild-type and NOS2-deficient mice with and without L-NAME or L-NIL added to the perfusate. Compared with lungs from untreated mice, lungs from LPS-challenged wild-type mice constricted less in response to hypoxia (69 +/- 17 vs. 3 +/- 7%, respectively, P < 0.001). Perfusion with L-NAME or L-NIL restored this blunted HPV response only in part. In contrast, LPS administration did not impair the vasoconstrictor response to hypoxia in NOS2-deficient mice. Analysis of the pulmonary vascular P-Q relationship suggested that the HPV response may consist of different components that are specifically NOS isoform modulated in untreated and LPS-treated mice. These results demonstrate in a murine model of endotoxemia that NOS2-derived NO production is critical for LPS-mediated development of impaired HPV. Furthermore, impaired HPV during endotoxemia may be at least in part mediated by mechanisms other than simply pulmonary vasodilation by NOS2-derived NO overproduction.

Pancreatic capillary blood flow in an improved model of necrotizing pancreatitis in the rat.

INTRODUCTION: The development of acute pancreatitis is characterized by profound changes in pancreatic microcirculation. Using in vivo microscopy with fluorescent-labeled erythrocytes as tracers we studied changes in pancreatic microcirculation in an improved rat model of necrotizing pancreatitis (NP) in comparison to edematous pancreatitis (EP) and healthy controls. METHODS: Twenty-one male Wistar rats had their pancreatae exteriorized in a temperature-controlled immersion chamber followed by intravenous administration of fluorescent-labeled autologous erythrocytes. EP was induced by intraductal saline and intravenous caerulein (5 microg/kg/h) for 6 h (n = 7) and NP by controlled intraductal infusion of glycodeoxycholic acid (10 mmol/L) followed by intravenous caerulein (n = 7). Control animals received intraductal and intravenous saline (n = 7). The determination of pancreatic microcirculation was performed before as well as 1, 3, and 6 h after intraductal infusion by correlating the number of passing labeled erythrocytes/capillary/min with their concentration per microliter of arterial blood. RESULTS: Pancreatic capillary flow in control animals remained constant over the 6-h observation period. Pancreatic capillary flow in the EP group rapidly increased to 188% of baseline after 3 h and remained significantly elevated throughout the experiments (P = 0.0001). In contrast, pancreatic capillary flow decreased significantly in the group suffering NP with values 46.7% of baseline after 6 h (P = 0.0001). Complete capillary stasis developed in 38% of investigated capillaries in the NP group compared to 0-1% in both other groups (P = 0.0001). CONCLUSION: Pancreatic microcirculation in mild edematous pancreatitis is significantly increased while the evolution of necrotizing pancreatitis in the model studied herein is characterized by a dramatic reduction in pancreatic capillary flow in conjunction with areas of capillary stasis. These results underline the pathophysiologic relevance of the model and of therapeutic measures aimed at an improvement of pancreatic microcirculation in clinical necrotizing pancreatitis.