Biomedical subjects
Publications and source records attributed to Robert Obermaier.
BACKGROUND: Due to the complex embryologic development, pancreatic anatomy can be very variable. DISCUSSION: The authors present the second ever reported case in the literature of a complete pancreatic encasement of the portal vein which forced us to alter the standard operative procedure of pancreatic head resection, thus enabling possible dangerous complications.
BACKGROUND: The aim of this study was to identify genes that are differentially expressed in the early period after pancreatic cold ischemia/reperfusion (I/R) injury. METHODS: Grafts of isogeneic rat pancreaticoduodenal transplantation were subjected to different preservation solutions and cold ischemia times (CITs): University of Wisconsin (UW), 6-hour CIT; UW, 18-hour CIT; and physiologic saline solution, 6-hour CIT. Animals that did not receive transplants served as controls. At 2-hour reperfusion, grafts were removed and pancreatic RNA was isolated, pooled, and hybridized to Affymetrix RG-U34A arrays. Quantitative reverse-transcription polymerase chain reaction was used to confirm the results of microarray technology. RESULTS: A total of 49 genes were consistently upregulated (more than threefold) in all three groups of transplant recipient animals. Prominent genes include transcription factors; cytoskeletal factors; heat-shock proteins (e.g. Hsp27, Hsp90); molecules involved in inflammation (e.g. PAPIII), immunology, signal transduction, and translation; and genes that have not been associated with I/R injury so far (e.g. Best5). Messenger RNA levels of some genes were exclusively downregulated in response to the different conditions applied to the pancreatic grafts: Cybb, Reg3a, Per2, BMAL1, MAP, and Isl2. CONCLUSIONS: These results provide new insight in I/R-induced gene expression after experimental pancreas transplantation. The reported upregulation of heat shock proteins, Best5, and PAPIII may play a pathologic role in pancreatic cold I/R injury and could therefore provide a promising perspective for further investigations.
Brief periods of warm ischemia and subsequent short reperfusion before either long-term cold or warm ischemic insult (ischemic preconditioning, IPC) have proven to ameliorate ischemia/reperfusion (I/R) injury in various organs, such as the liver and lung. The aim of this study was to examine the effect of IPC on pancreatic cell apoptosis and microcirculatory impairments in experimental pancreas transplantation. Male Lewis rats served as donors and recipients of heterotopic syngeneic pancreaticoduodenal transplantation. Recipient animals were divided into two experimental groups: group Tx (n=7) received grafts without IPC, group Tx&IPC received grafts with IPC. Animals that had not undergone transplantation but whose pancreata had been exteriorized served as controls (n=5). All pancreatic grafts were preserved in University of Wisconsin solution for 6 h at 4 degrees C. IPC was induced by interruption of the arterial blood flow for 10 min followed by 10 min of reperfusion. One and two hours after reperfusion, graft microcirculation was assessed by means of intravital microscopy (IVM). Rats were immediately killed after the second measurement and DNA breaks of acinar cells were detected by in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate digoxigenin nick end-labelling (TUNEL) assay and gel electrophoresis (laddering). The apoptotic index (AI) was defined as the number of apoptotic cells per high-power field. Analysis of both groups of transplanted grafts showed a significant decrease in functional capillary density (FCD) and a significant increase in leukocyte sticking to postcapillary venules (LAV) at 1 h and 2 h of reperfusion, compared with animals that had not undergone transplantation ( P<0.01). In parallel, AI was significantly increased in transplanted grafts compared to the controls ( P<0.01). Grafts subjected to IPC showed no significant differences, neither for FCD nor LAV, at both time points if compared with grafts of group Tx. However, IPC resulted in a significant increase in AI ( P<0.05). We can conclude that IPC has no effect on pancreatic microcirculation but enhances acinar cell apoptosis in experimental pancreas transplantation. These results indicate that IPC might increase I/R injury after pancreatic cold ischemia.
Brain death (BD) influences the quality of donor grafts in transplantation. To evaluate the impact of BD on pancreas grafts, we investigated the influence of BD on the microcirculation and histology of the pancreas in a rat model of explosive BD. A group of Wistar rats (n=7), rendered brain dead by inflating an intracranially inserted Fogarty catheter was compared with controls (CO) using intravital epifluorescence-microscopy over 4 h after BD induction; functional capillary density (FCD), leukocyte adherence (AL) in post-capillary venules, histology and pancreatic enzymes were investigated. Four hours after BD, FCD decreased (333 +/- 11 vs. baseline 444 cm/cm2 +/- 5 SEM; p<0.01) and showed lower values than CO (388 +/- 9 p<0.01). In BD, AL was increased (628 cells/mm2 +/- 110 SEM vs. baseline 123 +/- 32, and vs. CO 180 +/- 33; p<0.001). BD caused increased histological damage (CO 1.6 score-points +/- 0.7 SD vs. BD 8.3 +/- 7.1; p<0.05). Amylase was higher in BD (p<0.05) but did not reach pathological values. We show for the first time that BD causes relevant changes in pancreatic microcirculation, histology and leukocyte endothelial interaction which might have a serious impact on the function of grafts. New strategies for preventing this damage are therefore highly desirable in order to improve the outcome of pancreas transplantation.
This study was undertaken to examine the impact of ischemia-reperfusion (I/R) injury on microcirculation and apoptosis in experimental pancreas transplantation. Pancreatic grafts were subjected to different preservation solutions and cold ischemia times (CITs): University of Wisconsin (UW), 6-h CITs (group U6); UW, 18-h CITs (group U18); normal saline, 6-h CITs (group S6); and normal saline, 6-h CITs with Z-Asp-2,6-dichlorobenzoyloxymethylketone (pan-caspase inhibitor; group S6 & CI). Nontransplanted animals served as controls. At 1- and 2-h reperfusion microcirculation was assessed by means of intravital microscopy. Apoptosis was detected by in situ nick end-labeling method (TUNEL) at 2-h reperfusion. Deterioration of microcirculation was lowest in group U6 and highest in groups S6 and S6 & CI compared with controls. The apoptotic index (cells per high power fields) of groups U6, U18 and S6 correlated well with functional capillary density (r=- 0,70, p < 0.0001) and leucocyte sticking (r= 0,69, p < 0.0001) at 1-h reperfusion. Caspase inhibition had no impact on microcirculation but significantly reduced AI compared with group S6 (p < 0.001). These data suggest that pancreatic I/R injury-induced apoptotic cell death well predicts the extent of [corrected] microcirculatory impairment. Caspase inhibition might be a promising strategy in reducing I/R injury in pancreas transplantation.
OBJECTIVES: Prospective organ donors are exposed to various stress types. The effect of endotoxin pretreatment (ETX) on pancreatic ischemia/reperfusion injury (IRI) is unclear. We investigated, using a rat model of pancreatic IRI of an in situ isolated pancreatic tail segment, the effect of ETX on postischemic microcirculation and organ damage. METHODS: Twenty-four hours before pancreatic dissection, either intraperitoneal application of ETX (1 mg/kg in 0.9% NaCl) or saline only (control) was performed. Two-hour normothermic ischemia of the pancreatic tail was induced by clamping the splenic vessels and was followed by a reperfusion period of 2 hours. Microcirculatory parameters were measured by intravital epifluorescence microscopy [functional capillary density (FCD), adherent leukocytes (ALs), and histology]. The presented data represent the mean +/- SEM/SD as appropriate. RESULTS: ETX pretreatment caused a significantly greater decrease in FCD (497 +/- 6 cm/cm2 baseline versus 326 +/- 15 cm/cm2 2 hours of reperfusion) compared with controls (498 +/- 8 versus 258 +/- 15 cm/cm2) 2 hours after reperfusion (P < 0.01). Two hours after reperfusion, ALs were significantly decreased in ETX animals compared with controls (ETX: 141 +/- 37 versus 273 +/- 36 cells/mm2, P < 0.05). Histologic damage was less in ETX (6.4 score points +/- 0.32 versus 8.8 +/- 0.33 control, P < 0.05). CONCLUSION: ETX preconditioning decreases microcirculatory deterioration caused by IRI by means of less loss of nutritive tissue perfusion, decrease in ALs, and less histologic damage. This indicates a protective effect of ETX preconditioning in pancreatic IRI.
BACKGROUND: The therapeutic efficacy of intratumoral instillation of genetically engineered, CYP2B1-expressing, microencapsulated cells in combination with ifosfamide had been previously demonstrated in xenografted human pancreatic ductal carcinomas [Gene Ther 1998;5:1070-1078]. Prior to a clinical study, the feasibility of an intra-arterial application of microencapsulated cells to the pancreas and its consequences to the organ had to be evaluated. MATERIAL AND METHODS: Microencapsulated, CYP2B1-producing cells were instilled both in vivo (transfemoral angiographical access) and in vitro (perfusion model) in the splenic lobe of the pig pancreas. In vivo, animals were monitored clinically for 7 days, then treated with ifosfamide and sacrificed. In vitro, ifosfamide was administered intra-arterially. RESULTS: In all animals, 100 microcapsules could be instilled safely via the femoral route without clinical, biochemical or histological signs of pancreatitis. Histological examination revealed partial obstruction of small arteries by the capsules, without causing any parenchymal damage. In vitro, instillation reduced blood flow by half. Ifosfamide, also in combination with the capsules, did not add any damage to the pancreas. CONCLUSION: Intra-arterial instillation of microencapsulated cells to the pig pancreas is feasible and safe. Neither pancreatitis, foreign body reactions nor circulatory disturbances were observed. Clinical application of this genetically enhanced chemotherapeutic method seems possible.
In ischemia/reperfusion of the pancreas impairment of microcirculation after reperfusion is believed to be of critical importance. The 'no-reflow' phenomenon is thought to cause persisting tissue ischemia, while the 'reflow-paradox' is defined as secondary impairment of nutritive perfusion. These phenomena have been shown by intravital microscopy but their effect on tissue oxygenation as assessed by continuous tissue oximetry has not been identified. In landrace pigs tissue oxygenation was investigated in warm ischemia/reperfusion of the pancreas by the use of continuous tissue oximetry. After reperfusion rapid reoxygenation occurred which was followed by a period of secondary hypoxia. Thereafter, secondary reoxygenation was found, and finally tertiary hypoxia with a gradual decline of tissue pO(2) was noted. The data show a relevant impairment of tissue oxygenation after reperfusion. However, 'no-reflow' seems not to be a primary failure of capillary reperfusion but the consequence of a short reperfusion period followed by secondary ischemia. The 'reflow-paradox' most likely corresponds to tertiary ischemia.