[Results from a survey of intensive care training. How much that is learned applies to later practice?]

BACKGROUND

There is no doubt that good knowledge of intensive care medicine is necessary for any surgeon, since major surgery entails postoperative intensive care requiring the surgeon's involvement. Recent changes in the German surgical training program, demands for the board examination, and further specialisation have raised the question whether the time spent in ICU education is still adequate and covers topics for young surgeons attendant to their personal professional aims. The present survey was performed to elucidate this topic.

METHODS

Questionnaires were sent to 300 randomly chosen surgical residents.

RESULTS

Of the questionnaires, 44% were returned and eligible for analysis: 95% considered their ICU education important, 32% worked longer than the (required) 6 months on the ICU, and 62% thought the time spent on ICU was adequate, whereas 14.5% thought it too long. Most of these fellows (84%) worked in university hospitals of large medical centers. After their ICU rotation, the majority felt familiar with the basic procedures and regarded them important also for future work. More advanced techniques (e.g. specifics of artificial ventilation or invasive haemodynamic monitoring) were considered less relevant or not at all.

CONCLUSION

The majority of fellows (95%) considered ICU training important, but 50% felt that advanced ICU techniques were not relevant to their planned future work as surgeons. Especially in university hospitals and large medical centers, there were discrepancies between proposed and actually served ICU time as well as between the training program and the methods and techniques the young surgeons felt important for the future. This information may be useful when discussing requirements of surgical education programs.

(Non-)compliance with guidelines for the management of severe acute pancreatitis among German surgeons

BACKGROUND

Implementation of guidelines for the therapy of acute pancreatitis (e.g. those of the International Association of Pancreatology, IAP) into clinical practice has been assumed but not been evaluated.

AIM

To verify the knowledge and acceptance of guidelines for the management of severe acute pancreatitis among German surgeons.

METHODS

A questionnaire consisting of five short questions concerning key points in the management of severe acute pancreatitis was sent to the chairmen of the departments of general and visceral surgery of 39 university and 316 non-university hospitals in Germany. An additional, more detailed questionnaire accompanied the audit of the university chairmen.

RESULTS

The response rate was 62%. 11% stated that they strictly followed all guidelines (IAP recommendations No. 2-6), 31% followed all but one recommendation, 31% did not follow 2 or more of the guidelines, and the answers of 27% suggested that their treatment differed substantially from the guideline recommendations. For example, fine needle aspiration biopsy, recommended to differentiate between infected and sterile necrosis in patients with signs of sepsis, was not performed by 55%, and prophylactic antibiotics, recommended to prevent secondary infection of pancreatic necrosis, were not given by 20%.

CONCLUSION

German surgeons know the IAP recommendations for the management of severe acute pancreatitis and have implemented these guidelines in clinical practice. This, however, does not mean that all guideline concepts are strictly followed.

[A surgical approach to acute intestinal bleeding]

The estimated incidence of lower gastrointestinal bleeding (LGIB) is 20/100,000 patients per year. Of these cases, 70-80% are minor or stop spontaneously and do not present as emergency hospital admissions. Colonoscopy and angiography detect 80-90% of major LGIB, and subsequent endoscopic intervention or embolisation can control approximately 70%. Emergency surgical intervention is required in haemodynamically unstable patients with persistent bleeding. The surgical treatment of choice is directed to resecting the bleeding bowel segment. Subtotal colectomy is performed in patients with colonic bleeding that can not exactly be localized. Segmental colon resection is often associated with rebleeding and not recommended in this situation. Primary anastomosis can usually be performed; elderly patients in reduced condition, however, are candidates for stoma. In case of persistent or recurrent bleeding and differentiation between intestinal and colonic bleeding fails, loop ileostomy may be performed. If the bleeding appears to originate from somewhere in the small bowel, an additional loop jejunostomy may be performed for specification. The mortality from acute LIGB is approximately 5% but increases with emergency surgery. Risk factors are age, comorbidity, and shock on admission.

Concurrent chemoradiation with capecitabine and weekly irinotecan as preoperative treatment for rectal cancer: results from a phase I/II study

The aim of this study was to investigate the efficacy and safety of chemoradiation using capecitabine and irinotecan as neoadjuvant therapy for patients with rectal cancer. Conventional radiation was given at daily fractions of 1.8 Gy on 5 days a week for a total dose of 55.8 (50.4+5.4) Gy. Concurrently, irinotecan 40 mg m⁻² once weekly and capecitabine continuously at dose levels of 500, 650, 750 and 825 mg m⁻² twice daily were administered. Surgery was performed 4–6 weeks following completion of chemoradiation. A total of 28 patients (3 UICC II, 25 UICC III) were enrolled and all received treatment. Dose-limiting toxicity was diarrhoea grade IV and hand–foot syndrome at the 825 mg m⁻² dose level. The maximum tolerated dose of capecitabine was 750 mg m⁻². Diarrhoea was the most common toxicity: grade III in nine patients. Two patients died, one due to pneumonia and one due to sudden cardiac death. A complete response and only microfocal residual tumour disease was achieved in four and three patients (27%). In all, 25 of 28 patients undergoing surgery, 24 (96%) had R0 resection. Preoperative chemoradiation based on continuous daily capecitabine and weekly irinotecan appears to tolerated and effective in patients with rectal cancer.

Octreotide hardens the pancreas

BACKGROUND AND AIMS

Leakage from pancreaticojejunostomy and development of pancreatic fistulas are the major postoperative complications in patients undergoing duodenopancreatectomy. The risk of developing these complications is higher when surgery is performed on a soft pancreas. A recent report suggests that octreotide hardens the pancreas when given intraoperatively. The present study aims at verifying this observation by measuring tissue hardness of the pancreas by a commercially available durometer in pigs with and without octreotide pretreatment.

METHODS

Three groups of pigs were investigated: Group 1 (n=6) received no treatment; group 2 (n=6) was treated with 3x100 microg octreotide for 1 day; group 3 (n=6) for 5 days. Thereafter, animals were killed and the pancreas was harvested for performing measurements: Tissue hardness was assessed by a commercially available durometer, and a suture holding test was performed using a Newton dynamometer.

RESULTS

There was a significant increase in tissue hardness between untreated control animals [26.3+/-2.5 S.U. (shore units)] and animals with 1 day octreotide pretreatment (29.8+/-2.6 S.U.; p=0.04) as well as between the groups treated for 1 and 5 days (34.8+/-2.8 S.U.; p=0.01). Suture holding capacity was higher in animals treated for 5 days.

CONCLUSION

The present study agrees with a recent report suggesting that octreotide hardens the pancreas. Octreotide pretreatment may therefore be an advantage when performing surgery on a soft pancreas, i.e., in patients scheduled for duodenopancreatectomy for ampullary carcinomas or circumscript pancreatic tumors not associated with chronic pancreatitis.

Intensified concurrent chemoradiotherapy with 5-fluorouracil and irinotecan as neoadjuvant treatment in patients with locally advanced rectal cancer

This study aimed to evaluate the feasibility and efficacy of neoadjuvant chemoradiotherapy intensified with irinotecan in patients with locally advanced rectal cancer. Eligible patients had nonmetastatic disease at a locally advanced stage that made R0 resection and sphincter preservation uncertain. They received preoperative radiation over 6 weeks to 45 Gy and boost of 5.4 Gy and concurrent continuous infusion 5-fluorouracil 250 mg m⁻² day⁻¹ and weekly irinotecan 40 mg m⁻². In all, 37 patients entered the study. T stage at baseline as determined by ultrasound was T2/T3/T4 in 2/19/16 patients; 31 patients had lymph node involvement. The predominant toxicity was diarrhoea (grade 3/4 in 10/2 patients). Haematologic toxicity and surgical complications were moderate. Among 36 patients undergoing surgery, 32 (89%) had R0 resection and 23 (64%) sphincter preservation. Pathologic complete response (pCR) was achieved in eight (22%) of 36 patients, and 10 patients (28%) had only microscopic residual disease. At 4 years, overall survival was 66%, disease-free survival 73%, local relapse rate 7%, and distant failure rate 24%. Extent of resection and postoperative nodal status were significant predictors of overall and disease-free survival. Intensified neoadjuvant chemoradiotherapy with irinotecan can be safely administered and results in a high pCR rate.

Pulmonary microcirculation in mild and severe experimental pancreatitis

BACKGROUND

Research aimed at elucidating the pathogenesis of pancreatitis-associated lung injury and evaluating novel strategies for preventing respiratory complications in acute pancreatitis (AP) has not yet involved intravital microscopic (IVM) studies of pulmonary microcirculation in animals with severe disease.

OBJECTIVE

To characterize and compare pulmonary microcirculation in severe/necrotizing (NP) and mild/edematous pancreatitis (EP) in the rat.

METHODS

EP was induced by intravenous cerulein infusion (n = 10) and NP by a standardized intraductal infusion of glycodeoxycholic acid followed by intravenous cerulein (n = 10). After 24 h a left-sided thoracotomy was performed for IVM examination of pulmonary capillary blood flow, permeability, leukocyte sticking and the thickness of alveolar septi. Further measurements included monitoring of arterial blood gases and histological evaluation of lung injury.

RESULTS

In animals with NP, histology revealed severe pulmonary edema together with clustering of polymorphonuclear leukocytes in pulmonary microvessels and alveoli. IVM showed a greater number (n) of leukocytes sticking on the endothelium of pulmonary capillaries (9.4 +/- 0.7 vs. 1.8 +/- 0.2 in healthy control animals) and increased capillary permeability (260 +/- 14 vs. 136 +/- 6% relative fluorescein intensity) while capillary blood flow was decreased (0.41 +/- 0.05 vs. 0.57 +/- 0.03 mm/s). In comparison, changes in EP were significantly less pronounced (flow 0.5 +/- 0.04 mm/s, permeability 156 +/- 4%, leukocyte sticking n = 4.6 +/- 0.7).

CONCLUSIONS

These findings suggest that deterioration of pulmonary microcirculation in AP correlates with disease severity and that a model featuring NP may therefore be more suitable to further study pancreatitis-associated pulmonary injury.

Temporary unilateral microembolization of the lung-a new approach to regional chemotherapy for pulmonary metastases

BACKGROUND

Except in patients with resectable disease, treatment of pulmonary metastases is still disappointing. Regional chemotherapy may be a suitable method for delivering more effective doses to regionally confined tumors while minimizing systemic toxicity. We propose an unilateral chemoembolization of the lung applicable by endovascular method.

MATERIALS AND METHODS

An unilateral microembolization of the lung with degradable starch microspheres (DSM) alone (group 1) and combined with carboplatin (group 2) was performed on Sprague-Dawley rats (n = 12). Microcirculatory parameters were studied by in vivo videomicroscopy and radiological pattern on pulmonary angiogram.

RESULTS

After injection of DSM, mean embolization time in subpleural capillaries was 7.1 +/- 2.3 min, followed by a mean flow retardation of 14.3 +/- 4.6 min; 21.4 +/- 4.7 min after embolization, original flow of erythrocytes was observed demonstrating reperfusion and reversibility of microembolization. After reperfusion relative fluorescence measured in subpleural alveoli was 0.13 +/- 0.049 in group 1, 0.105 +/- 0.016 in group 2, and 0.11 +/- 0.036 in control group (NS). Alveolar septal diameter was 17.3 +/- 1.13 microm in group 1, 16.8 +/- 1.25 microm in group 2, and 16.6 +/- 1.08 microm in control group (NS), demonstrating neither altered permeability nor pulmonary edema. Pulmonary angiogram confirmed patency of the central pulmonary artery.

CONCLUSION

For the first time unilateral microembolization of the lung could be established in an experimental model. By injection of DSM, reversible embolization on arteriolar and capillary level could be demonstrated without occlusion of the main branches of the pulmonary arteries. Alveolar-capillary membrane disorder as symptom of early toxicity could not be detected even with additional application of carboplatin.

Persistent multiple organ microcirculatory disorders in severe acute pancreatitis: experimental findings and clinical implications

This study characterizes microcirculatory changes (capillary blood flow, capillary permeability, and leukocyte rolling) in the pancreas, colon, liver, and lungs at different stages of severe acute pancreatitis (AP) in a well-established rat model using intravital microscopy and computerized image analysis. The results demonstrate that microcirculatory disorders in severe AP are not confined to the pancreas but can also be found in the colon, liver, and lungs; that they extend beyond the early stage of AP and persist for 48 hr (and longer); and that they not only affect capillary blood flow but also involve prolonged changes of capillary permeability and leukocyte endothelial interaction. These findings may explain previous observations that therapeutic strategies aimed at enhancing microcirculation improve outcome in AP even if therapy is delayed and pancreatic necrosis can no longer be influenced. Since these systemic microcirculatory disturbances may contribute to AP-associated multiple organ dysfunction syndrome, further studies are warranted to evaluate whether improvement of microcirculation stabilizes organ function in AP and how long this may be effective after disease onset.

Persistent multiple organ microcirculatory disorders in severe acute pancreatitis: experimental findings and clinical implications

This study characterizes microcirculatory changes (capillary blood flow, capillary permeability, and leukocyte rolling) in the pancreas, colon, liver, and lungs at different stages of severe acute pancreatitis (AP) in a well-established rat model using intravital microscopy and computerized image analysis. The results demonstrate that microcirculatory disorders in severe AP are not confined to the pancreas but can also be found in the colon, liver, and lungs; that they extend beyond the early stage of AP and persist for 48 hr (and longer); and that they not only affect capillary blood flow but also involve prolonged changes of capillary permeability and leukocyte endothelial interaction. These findings may explain previous observations that therapeutic strategies aimed at enhancing microcirculation improve outcome in AP even if therapy is delayed and pancreatic necrosis can no longer be influenced. Since these systemic microcirculatory disturbances may contribute to AP-associated multiple organ dysfunction syndrome, further studies are warranted to evaluate whether improvement of microcirculation stabilizes organ function in AP and how long this may be effective after disease onset.

An experimental rat model for studying pulmonary microcirculation by in vivo videomicroscopy

It is unclear what role pulmonary microcirculatory disorders play in the pathogenesis of adult respiratory distress syndrome. The aim of this study was to establish a rat model for the direct visualization of pulmonary microcirculation by in vivo fluorescence videomicroscopy. The pulmonary terminal vascular bed was visualized and the microcirculatory parameters of leukocyte sticking, erythrocyte velocity, capillary permeability, and interalveolar septal diameter were quantified. These parameters were examined simultaneously. The preparation was stable for 120 min. Under hyperthermia, there was increased permeability with a relative fluorescence of 0.39 +/- 0.19 compared to 0.16 +/- 0.13 in the control group, and interalveolar septal diameters were wider (30.7 +/- 2.9 microm) than in control animals (17.3 +/- 3 microm). Under hypothermia and hypovolemia, the erythrocyte velocity was lower (0.351 +/- 0.063 and 0.378 +/- 0.044 mm/s) than in control groups (0.527 +/- 0.07 mm/s). Under hypoventilation, we observed a higher amount of leukocyte sticking (3.1 +/- 1.1 vs 1.8 +/- 0.8 cells/alveolus) and increased permeability (relative fluorescence 1.03 +/- 0.37 vs 0.16 +/- 0.13 in the control group). The model of rat lung exposure for direct examination of microvascular structures in living animals was valuable because it remained stable for 2 h under baseline conditions and demonstrated distinct changes in microcirculatory parameters following specific pathophysiological interventions.

Changes of colonic mucosal microcirculation and histology in two colitis models: an experimental study using intravital microscopy and a new histological scoring system

This study investigated capillary blood flow (CBF) and pathomorphological alterations in the mucosa of different bowel segments at different times after disease onset in rats with colitis induced by either trinitrobenzensulfonic acid (TNBS) or mitomycin-C. CBF was determined by intravital microscopy using fluorescein-labeled erythrocytes. The histological degree of inflammation was assessed by a new scoring system. Severe acute histological changes were found in the distal colon 24 hr after induction of TNBS colitis (score: 8.9+/-1.0). CBF was increased (2.9+/-0.05 vs. 2.6+/-0.04 nl/min in healthy controls). The histological alterations persisted until day 3 (8.5+/-0.9) when CBF significantly decreased (1.8+/-0.05 nl/min). After 15 days, moderate acute inflammation was still detectable histologically (5.4+/-1.3), but CBF had returned to normal values. In mitomycin-C colitis, changes developed mainly in the proximal colon: After three days, there was mild inflammation (2.8+/-1.2) with normal CBF (2.5+/-0.1 nl/min). After seven days, the inflammation had increased (4.8+/-1.1), while CBF had decreased (1.5+/-0.06 nl/min). These changes persisted for six weeks (5.3+/-0.7; 1.2+/-0.05 nl/min). These data suggest that disturbed colonic microcirculation may play an important role in the pathogenesis of inflammatory bowel disease regardless of the histopathomorphological alterations.

Endothelin mediates local and systemic disease sequelae in severe experimental pancreatitis

Endothelin-1 has been shown to reduce pancreatic blood flow and cause focal acinar cell necrosis similar to those seen in acute pancreatitis (AP), whereas therapy with endothelin receptor antagonists enhanced pancreatic capillary blood flow (PCBF) and decreased mortality rates. The current study evaluated the role of endothelin in the development of severe AP. Trypsinogen activation peptides, acinar cell necrosis, and PCBF were used as local indicators of disease severity, fluid sequestration, cardiorespiratory and renal parameters, and colonic capillary blood flow as systemic disease indicators. The following groups of animals were examined: 1) rats with mild edematous AP and 2) severe necrotizing AP treated with and without endothelin, 3) transgenic rats overexpressing endothelin with severe AP, and 4) rats with severe AP prophylactically treated with endothelin receptor antagonists. The following observations were made: endothelin superimposed on mild AP caused hemoconcentration, a decrease in PCBF, and necrosis and ascites not seen in this model without endothelin exposure. Endothelin superimposed on severe AP had no significant effects. After induction of severe AP, less PCBF and more acinar cell necrosis were observed in transgenic rats than in their normal littermates. Prophylactic endothelin receptor antagonists improved local (acinar necrosis, PCBF) and systemic parameters (ascites, urine production, colonic capillary blood flow) of disease severity in animals with severe AP. These observations underscore the role of endothelin as a mediator of disease severity in AP and suggest that endothelin receptor blockade may become a promising therapeutic tool in this disease.

An improved clinical model of orthotopic pancreatic cancer in immunocompetent Lewis rats

The study of pancreatic cancer (PaCa) requires orthotopic, clinically relevant animal models. The aims of this study were to establish an orthotopic model of ductal pancreatic adenocarcinoma in immunocompetent Lewis rats and to develop a scoring system to quantify local tumor infiltration and distant metastasis. Cells (10(7)) of the rat ductal PaCa cell line DSL-6A/C1 were injected s.c. into donor rats. After 8 weeks, either three (IPL-3) or five (IPL-5) fragments (1 mm3) of the resulting s.c. tumors were microsurgically implanted into the pancreas of recipient rats. In another series of animals, 10(7) DSL-6A/C1 cells were directly injected (INJ) into the pancreas. All animals were monitored daily until death or for 16 weeks. At autopsy, volume of primary tumors and ascites, local and systemic tumor spread, and histologic phenotype were assessed. IPL-5 resulted in significantly larger tumors (12,224 +/- 1,933 mm3), more local infiltration and systemic spread (score: 18.3 +/- 2.0 points), severe clinical tumor disease, and lethality (50%) in comparison to the other induction techniques (IPL-3: 283 +/- 115 mm3/3.5 +/- 0.8 points/0; INJ: 752 +/- 207 mm3/4.3 +/- 0.8 points/8%). Histologic examination revealed moderately to well-differentiated ductal tumors, surrounded by dense stroma. Intraperitoneal tumor dissemination in the INJ group occurred simultaneous with primary tumor growth, indicating PaCa cell spread during injection. Orthotopic implantation of five DSL-6A/C1 tumor fragments into the rat pancreas provides a valid clinical model of ductal pancreatic adenocarcinoma in immunocompetent rodents for preclinical treatment studies. The dissemination score we used permitted quantification of local and systemic tumor spread.

Angiogenesis inhibitor TNP-470 reduces human pancreatic cancer growth

In this study we investigated the effects of the angiogenesis inhibitor TNP-470 on human pancreatic cancer cells in vitro and in vivo. The action of TNP-470 on vascular endothelial growth factor (VEGF) was also assessed. In vitro human pancreatic cancer cells (MIAPaCa-2, AsPC-1, and Capan-1), and human umbilical vein endothelial cells (HUVEC) were exposed to increasing concentrations (1 pg/ml to 100 microg/ml) of TNP-470. Cell proliferation was assessed after 3 days by cell count and MTT assay. In vivo, 5 x 10(6) pancreatic cancer cells were injected subcutaneously into nude mice. Four weeks later, 1 mm3 fragments of the resulting tumors were implanted into the pancreas of other mice. Animals received either TNP-470 (30 mg/kg every other day) or vehicle subcutaneously for 14 weeks. The volume of the primary tumor and metastatic spread were determined at autopsy. Concentrations of VEGF were determined in serum (VEGF(S)) and ascites (VEGF(A)) by enzyme-linked immunosorbent assay. Microvessel density was analyzed by immunohistochemistry in CD31-stained tumor sections. In vitro, proliferation and viability of the human pancreatic cancer cell lines were significantly inhibited at high concentrations of TNP-470 (> 1 microg/ml). In contrast, TNP-470 effectively decreased the growth of HUVEC at 100 pg/ml. In vivo, tumor volume and dissemination scores were significantly lower in all three pancreatic cancer cell lines. VEGF(S) and VEGF(A) were not different between treated groups. Treatment with TNP-470 significantly reduced neoangiogenesis in tumors of all three human pancreatic cancer cell lines: MIAPaCa-2 = 74.8 +/- 7.8/0.74 mm2 vs. 24.8 +/- 3.7/0.74 mm2; AsPC-1 = 65.3 +/- 5.0/0.74 mm2 vs. 26.0 +/- 3.4/0.74 mm2; and Capan-1 = 82.2 +/- 5.8/0.74 mm2 vs. 26.9 +/- 2.5/0.74 mm2 (P < 0.001). However, survival was not statistically different between groups. TNP-470 reduced tumor growth and metastatic spread of pancreatic cancer in vivo. This was probably due to the antiproliferative effect of the agent on endothelial cells rather than to the direct inhibition of pancreatic cancer cell growth. TNP-470 activity was not associated with alteration of VEGF secretion.

[Pancreatitis and nutrition. Significance of the gastrointestinal tract and nutrition for septic complications]

Septic complications are an important factor for the morbidity and mortality of acute pancreatitis. The gut has been identified as a source of infection early in the course of the disease allowing intestinal bacteria to translocate into pancreatic necrosis and other organs. Bacterial translocation is promoted by an impaired intestinal mucosal barrier which can be attributed to the reduced oxygen and substrate supply of the intestine during the early systemic response to the pancreatic injury. A rat model of severe acute pancreatitis has been used to confirm the hypothesis that an impaired mucosal barrier can be stabilized by supplying certain nutritients, vitamins and trace elements. Following a discussion of the many aspects of bacterial translocation and gut derived sepsis, the role of the gut and nutrition for the development of septic complications in acute pancreatitis is summarized as follows: Early in the course of acute pancreatitis the gut is a target organ of the primary systemic inflammatory response (SIRS) to pancreatic injury. SIRS-induced gut barrier dysfunction promoting bacterial translocation makes the gut the motor for secondary (septic) complications. As a septic focus the gut becomes a target for therapeutic measures aimed at stabilizing the impaired gut barrier. Nutritive factors demonstrated to improve impaired gut barrier function include early enteral feeding and specific factors like glutamine which are essential for enterocytes and colonocytes in stress. Experimental data are presented to underline the significance of these nutritive factors and subsequent randomized multicenter trials performed to verify the positive experimental results are introduced. The effect of other nutritive factors (e.g. omega-3-fatty acids) has not yet been systemically investigated. Thus, experimental and clinical studies need to be performed for evaluating their effect on bacterial translocation and the disease course in acute pancreatitis.

[Multiple organ failure in experimental pancreatitis]

BACKGROUND

Multiple organ failure (MOF) is the most severe complication and the most frequent cause of death in acute necrotizing pancreatitis (ANP).

OBJECTIVE

To evaluate the components and the time course of MOF in an experimental model of ANP.

METHOD

Induction of ANP in rats by a standardised bile-salt infusion into the pancreatic duct and i.v. cerulein hyperstimulation. Six hours after AP-induction animals were randomised into 4 groups to receive (I) no therapy; (II.) 4 ml/kg/h Ringer lactate (R.L) i.v.; (III) 8 ml/kg/h RL i.v.; or (IV) 4 ml/kg/h RL plus an endothelin receptor antagonist. Animals were observed for 24 hours and vital parameters were investigated.

RESULTS

After 6 hrs all animals presented with severe haemoconcentration (hematokcrit > 57%) and oliguria (< 0.5 ml/6 hrs). Until 12 hrs following AP-induction in animals without therapy increased hematocrit and oliguria was observed. Animals receiving fluid resuscitation had a significant drop in hematocrit and kept their blood gas values compensated. Between 12 and 24 hrs urine production significantly increased with fluid resuscitation and respiratory parameters stabilised except for animals treated with 8 ml/kg/h RL. These animals developed arterial hypoxia and hypercapnia.

CONCLUSIONS

(1) In the early phase of ANP in our model renal failure developed. (2) Massive fluid resuscitation that is necessary to increase urine output may lead to respiratory distress. (3) Reduction of intravascular fluid loss by endothelin receptor blockade is associated with improved renal and respiratory function.

Effect of fluid resuscitation with and without endothelin A receptor blockade on hemoconcentration and organ function in experimental pancreatitis

BACKGROUND

Intravascular fluid loss contributes to pancreatitis-associated multiple organ dysfunction and is thus a major target for therapy in this life-threatening disease.

AIM

To evaluate intravascular fluid loss and extravascular fluid sequestration together with cardiorespiratory and renal function in a well-established rat model of severe acute pancreatitis (AP) and to investigate the effect of fluid resuscitation with and without endothelin receptor A blockade on these parameters.

METHOD

Induction of AP in rats by a standardized bile salt infusion into the pancreatic duct and intravenous cerulein hyperstimulation. Six hours after AP induction, animals were randomized into 4 groups to receive (1) no therapy; (2) 4 ml/kg/h Ringer's lactate (RL) i.v.; (3) 8 ml/kg/h RL i.v., or (4) 4 ml/kg/h RL plus an endothelin receptor antagonist. Target parameters measured before and after AP induction and during the 24-hour observation period included: mean arterial blood pressure, heart rate, hematocrit, arterial blood gases, urine production, ascites and pleural effusions.

RESULTS

After 6 h, all animals presented with severe hemoconcentration (hematocrit >57%) and oliguria (<0.5 ml/6 h). Cardiorespiratory parameters were within the normal range. Up to 12 h after AP induction, animals without therapy had an increased hematocrit and oliguria and developed metabolic acidosis. Animals receiving fluid resuscitation had a significant drop in hematocrit and maintained compensated blood gas values. A significant increase in urine production was only observed in animals given 8 mg/kg/h RL. Between 12 and 24 h, urine production significantly increased with fluid resuscitation and respiratory parameters stabilized except for animals treated with 8 ml/kg/h RL which developed arterial hypoxia and hypercapnia.

CONCLUSIONS

Intravascular fluid loss and extravascular fluid sequestration together with decreased urine production characterize the early phase of this model of severe AP. Massive fluid resuscitation necessary for increasing urine output may lead to respiratory distress. Reduction of intravascular fluid loss by endothelin receptor blockade is associated with improved renal and respiratory function.

Endothelin receptor blockade in severe acute pancreatitis leads to systemic enhancement of microcirculation, stabilization of capillary permeability, and improved survival rates

BACKGROUND

We previously demonstrated that therapy with a new endothelin A receptor antagonist (ET-RA) significantly reduced mortality rates in severe acute pancreatitis (AP) in the rat without attenuating local signs of disease severity (intrapancreatic protease activation, acinar cell necrosis). This raised the question as to why ET-RA was so effective. The purpose of this study was to assess the effect of ET-RA on microcirculation (particularly capillary permeability) within and outside of the pancreas on intravascular fluid loss and extravascular fluid sequestration and on distant organ function.

METHODS

Severe AP was induced in rats by standardized intraductal bile acid infusion and cerulein hyper-stimulation. Starting 6 hours (n = 24 rats) and 12 hours (n = 30 rats) after the onset of AP, animals randomly received either the ET-RA (LU-135252) or saline solution with fluid resuscitation (6 mL/kg/h Ringer's lactate). At 24 hours, animals were relaparotomized for intravital microscopic determination of capillary blood flow, leukocyte rolling, and capillary permeability in the pancreas and colon. Further monitoring included cardiorespiratory and renal parameters, hematocrit levels and quantification of ascites and pleural effusions, and acinar cell necrosis at autopsy. Groups of sham-operated healthy animals (n = 6 animals each) that had been treated according to the same protocol served as control animals.

RESULTS

ET-RA treatment that was started 6 hours after AP-induction significantly decreased hematocrit levels (38% +/- 1% vs 45% +/- 2% with saline solution treatment), reduced ascites and pleural effusions (6.7 +/- 1.3 mL vs 11.9 +/- 1.3 mL), and improved urine production (4.8 +/- 0.5 mL vs 2.9 +/- 0.6 mL) and respiratory parameters. Moreover, all microcirculatory parameters were improved; in particular, capillary permeability was stabilized (158% +/- 9% vs 248% +/- 8% in the colon). These beneficial effects were also seen when therapy was delayed until 12 hours after AP induction. Pancreatic necrosis was not significantly reduced. The overall mortality rate was 12% in ET-RA-treated animals and 42% in saline solution-treated control animals (P <.05). In healthy animals ET-RA did not significantly alter the target parameters, except for a reduction of capillary permeability in the pancreas.

CONCLUSIONS

Improved microcirculation and stabilized capillary permeability in ET-RA-treated animals together with reduced intravascular fluid loss and extravascular fluid sequestration and improved renal and pulmonary function (1) may explain improved survival in this model, (2) support the hypothesis that systemic disease sequelae significantly contribute to outcome in AP, and (3) suggest that ET-RA may be a promising therapeutic tool in AP because it counteracts microcirculatory disorders that contribute to pancreatitis-associated organ dysfunction even when therapy is delayed to a point at which pancreatic injury may no longer be influenced.

Animal models of exocrine pancreatic cancer

Clinically and biologically relevant animal models are mandatory to further evaluate both the pathophysiology and novel strategies for diagnosis and treatment of exocrine pancreatic cancer. This review briefly summarizes the features of human pancreatic cancer in order to define requirements for animal models of the disease. The described model systems in rodents include pancreatic cancer induced by chemicals, pancreatic cancer in transgenic, and immunodeficient animals.

Experimental models of acute pancreatitis: are they suitable for evaluating therapy?

Since randomized controlled studies of severe acute human pancreatitis can be performed only with restrictions, at least some aspects of innovative therapy concepts should first be clarified in animal experiments. In vitro trials are inadequate for this purpose since they cannot simulate the complex course of severe acute pancreatitis. Animal test results can be transferred to clinical practice if the results are based on trials with established models, standardized methods, and a study design imitating the clinical situation. This contribution discusses the demands on such an animal model of acute pancreatitis and a corresponding study protocol and presents models and protocols which meet these requirements. Concrete examples are presented to show that animal experiments are of great value under these conditions, especially in acute necrotizing pancreatitis. Further standardization of models, protocols, and monitoring should further improve future animal therapy studies at least to the extent that it is possible to select particularly promising substances, which should then be tested in randomized controlled trials.

Therapy for microcirculatory disorders in severe acute pancreatitis: comparison of delayed therapy with ICAM-1 antibodies and a specific endothelin A receptor antagonist

Many of the complications in severe acute pancreatitis result from the amplifying effects of microcirculatory disruption. The pathogenesis of these microcirculatory disorders is multifactorial and involves various vasoactive mediators. Thus questions arise as to which vasoactive mediators are most important and how long after the onset of disease vasoactive mediator blockade may be effective. The present study compares the effect of delayed therapy with two vasoactive mediator antagonists, previously tested with promising results in other studies in a well-established rodent model of severe acute pancreatitis. Twelve hours after induction of acute pancreatitis, rats were randomized to therapy with intracellular adhesion molecule-1 (ICAM-1) antibody (2 mg/kg IA-29), endothelin A receptor antagonist (ET-RA) (40 mg/kg LU 135252), or saline solution (volume equivalent). After 12 hours of fluid resuscitation, animals underwent repeat laparotomy for intravital microscopic determination of capillary blood flow, leukocyte rolling, and capillary permeability in the pancreas and colon. Other measurements included cardiorespiratory parameters, hematocrit, pleural effusions, ascites, urine production, and survival. Compared to saline treatment, both ICAM antibody and ET-RA significantly enhanced capillary blood flow in the pancreas and colon, reduced leukocyte rolling, and stabilized capillary permeability. These beneficial effects on microcirculation were associated with decreased fluid loss into the third space and improved renal function and survival. Although both antagonists likewise enhanced capillary blood flow and reduced leukocyte rolling, ET-RA was significantly more effective than ICAM antibody in counteracting capillary leakage, thereby further reducing fluid sequestration. The present study confirms the beneficial effects of endothelin and ICAM antagonists in severe acute pancreatitis, even with delayed therapy, suggesting that both compounds are candidates for further clinical testing. Selective endothelin A receptor blockade appears to be especially attractive for clinical use not only because it was superior to ICAM antibody in the present study but also because of its favorable pharmacologic properties and (preliminary) positive results in clinical phase 2 studies currently underway for other diseases.

Effect of endothelin and endothelin receptor blockade on capillary permeability in experimental pancreatitis

BACKGROUND

Capillary leakage with fluid loss into the third space contributes to many of the early systemic complications in severe acute pancreatitis. There has been increasing interest in endothelin as one of the factors affecting capillary permeability.

AIM

To elucidate further the role of endothelin in the development of capillary leakage in acute pancreatitis by investigating the effect of exogenous endothelin administration and endothelin receptor blockade in sham operated animals and two models of acute pancreatitis.

METHODS

Determination of capillary permeability in the pancreas and colonic mucosa by quantifying extravasation of fluorescein labelled dextran using a novel computer assisted video image analysis system.

RESULTS

Pancreatic and colonic capillary permeability increased stepwise from mild to severe acute pancreatitis. Endothelin increased pancreatic and colonic capillary permeability in healthy animals and animals with mild acute pancreatitis but had no additional adverse effect in severe acute pancreatitis. Endothelin receptor blockade decreased pancreatic capillary permeability in sham operated rats but had no effect on the colon. In mild and severe acute pancreatitis, endothelin receptor blockade stabilised increased capillary permeability in both the pancreas and colon.

CONCLUSIONS

Endothelin plays an important role in mediating capillary permeability in the pancreas. In severe pancreatitis, it increases capillary permeability even outside the pancreas, thereby contributing to capillary leakage. Endothelin receptor blockade significantly reduces capillary permeability in acute pancreatitis both in and outside the pancreas, suggesting a therapeutic approach to counteract capillary leakage in severe acute pancreatitis.

Does glutamine reduce bacterial translocation? A study in two animal models with impaired gut barrier

Failure of intestinal barrier function and subsequent translocation of bacteria from the gut are believed to play a decisive role in the development of systemic septic complications, for example, following major trauma or major abdominal surgery. This study evaluated: (a) the effect of glutamine on colonic microcirculation and electrophysiological parameters reflecting gut barrier function, (b) the translocation of live bacteria to extraintestinal organs, and (c) disease outcome in two animal models with impaired gut barrier function. Severe acute pancreatitis or colitis was induced in rats randomized for therapy with or without glutamine (0.5 g/kg daily). After 48 h one animal group was prepared for intravital microscopy of colonic capillary blood flow and electrophysiological measurement of gut permeability; another was killed after 96 h for histological and microbiological examination. In animals with pancreatitis, glutamine (Gln) supplementation significantly improved gut permeability, i.e., Gln increased colonic transmucosal resistance from 67+/-7 to 92+/-3 Omega/cm(2) and decreased mannitol flux through the epithelium by 53%. Capillary blood flow in the colonic mucosa was improved by 25%. The prevalence of pancreatic infections was reduced from 86% in animals on standard parenteral nutrition to 33% in animals given the Gln-enriched diet (P<0.05); mortality decreased by 32%. In colitis, Gln had no significant effect on these parameters except for improving colonic capillary blood flow in colon segments not adjacent to the major injury site. Glutamine supplementation improves colonic capillary blood flow, stabilizes gut permeability, and reduces secondary pancreatic infections and mortality in severe rodent pancreatitis, but it is not helpful in colitis. This confirms previous reports that glutamine stabilizes gut barrier function only in certain diseases. Our experimental data strongly suggest that acute pancreatitis (rather than colitis) is one of the diseases with gut barrier dysfunction in which glutamine substitution may be helpful to reduce bacterial translocation and should therefore be tested in a controlled clinical trial.

Systemic lymphocyte activation modulates the severity of diet-induced acute pancreatitis in mice

To examine the role of lymphocyte activation in the development of local and systemic complications in acute pancreatitis, we compared disease severity of choline-deficient, 0.5% ethionine supplemented (CDE) diet-induced acute pancreatitis in T- and B-cell deficient SCID mice and immunocompetent C.B-17 mice. Twenty-five female SCID and 17 female C.B-17 mice were fasted for 24 h and fed a CDE diet for 72 h. Twenty SCID and 12 C.B-17 mice were bled and their organs removed for histologic evaluation. Five control animals of both kinds were fed a regular diet for 6 days. Lung, kidney, and pancreas were examined microscopically, and pancreatic damage scored. Apoptosis was detected by DNA nick-end labeling and confirmed by DNA laddering. Trypsinogen-activation peptide was measured by enzyme-linked immunosorbent assay (ELISA), and the catalytic activity of PLA2 was determined by a radiometric assay. Four-day mortality was 10% in SCID and 33% in C.B-17 mice, and 10-day mortality was 0 in SCID and 60% in C.B-17 mice. SCID mice had mild pulmonary damage, whereas pulmonary injury was severe in C.B-17 mice. Pancreatic damage was severe in both groups. Even though in situ staining of apoptotic cells was found in all pancreatitis animals, apoptosis was confirmed by DNA laddering only in C.B-17 mice. In SCID mice, apoptotic cell staining positively correlated with necrosis (r = 0.91; p < 0.001). Plasma TAP and PLA2 catalytic activity did not differ significantly between the groups. In conclusion, the absence of T and B lymphocytes prevents severe pulmonary injury resulting from acute pancreatitis but does not influence pancreatic or renal damage. Our results suggest that systemic lymphocyte activation does not affect the initiating events that trigger pancreatic injury but modulates the systemic response, in particular, pulmonary injury caused by acute pancreatitis.

Therapy for microcirculatory disorders in severe acute pancreatitis: effectiveness of platelet-activating factor receptor blockade vs. endothelin receptor blockade

Many of the complications of severe acute pancreatitis are the result of the amplifying effects of microcirculatory disruption. The factors causing microcirculatory disorders in acute pancreatitis involve vasoactive mediators such as platelet-activating factor (PAF) and endothelin-1 (ET) activated during the inflammatory response to pancreatic injury. To further evaluate the potential therapeutic role of specific receptor antagonists (RA) to these mediators, the present study compares the effect of PAF and ET receptor blockade on microcirculation and organ function in a well-established rodent model of severe acute pancreatitis. Six hours after acute pancreatitis induction, rats were randomized to therapy with ET-RA (50 mg/kg LU-135252), PAF-RA (82 microg/kg WEB-2170), or NaCl 0.9% (volume equivalent). After 18 hours of fluid resuscitation, animals were relaparotomized for intravital microscopic determination of capillary blood flow, leukocyte rolling, and capillary permeability in the pancreas and colon. Other measurements included cardiorespiratory parameters, hematocrit, pleural effusions, ascites, urine production, and survival. Compared to saline treatment both ET-RA and PAF-RA significantly improved capillary blood flow in the pancreas and colon, reduced leukocyte rolling, and stabilized capillary permeability. The beneficial effects of receptor antagonist treatment on microcirculation were associated with decreased fluid loss into the third space, improved renal and respiratory function, and survival. Although both receptor antagonists likewise improved capillary blood flow, ET-RA was significantly more effective in counteracting leukocyte rolling and capillary leakage, thereby further reducing fluid sequestration. The present study confirms the beneficial effects of PAf and ET receptor blockade on microcirculation inside and outside the pancreas, organ function, and survival when given at the early stage of severe pancreatitis. Because ET-RA was more effective in stabilizing capillary permeability and avoiding subsequent fluid loss into the third space, we propose that ET-RA should be tested in a clinical trial (either in comparison or in addition to PAF-RA).

[Pancreatitis and translocation--approaches for nutritional strategies]

Translocation of intestinal bacteria from the gut into pancreatic necrosis is an important factor in the development of septic complications in acute pancreatitis. Bacterial translocation is promoted by an impaired intestinal mucosal barrier, which can be attributed to the reduced oxygen and substrate supply of the intestine. A rat model of severe acute pancreatitis has been used to confirm the hypothesis that an impaired mucosal barrier can be stabilized by supplying certain nutrients, vitamins, and trace elements. A reduction in secondary pancreas infections with intestinal bacteria and improved survival was achieved under intravenous glutamine substitution, an essential amino acids in stress situations for enterocytes, colonocytes and immunocompetent cells. The positive experimental results are currently being investigated in a controlled randomized multicenter trial. Comparable studies need to be performed for verifying the effect of other nutritive factors on bacterial translocation and the disease course in acute pancreatitis.

[Endoscopic cholecystectomy as cost assessment--still a learning intervention?]

Economic considerations are putting increasing pressure on surgical departments to avoid intra- and postoperative complications and thus additional costs. Under this aspect, it was investigated whether laparoscopic cholecystectomy is a suitable training intervention for young prospective surgeons. These physicians in advanced training did not have a higher intra- or postoperative complication rate in a preselected patient population than senior physicians or specialists. The additional costs per surgical intervention due to longer operation times required by young physicians were acceptable so that laparoscopic cholecystectomy as a training intervention for young colleagues can be justified.

Does microcirculation play a role in the pathogenesis of inflammatory bowel diseases? Answers from intravital microscopic studies in animal models

The potential role of intestinal microcirculation for the development of inflammatory bowel diseases (IBD) has not been systematically investigated, mainly because of methodological problems. Using a well-established rodent model of IBD and intravital microscopy, the present study investigated whether (and when) gut microcirculation is disturbed in IBD, and whether microcirculatory disorders contribute to histological and functional alterations in the development of IBD. Colitis was induced by rectal injection of trinitrobenzene sulfonic acid. After 1, 3, and 15 days rats were laparotomized for intravital microscopic determination of mucosal colonic blood flow. In a second series it was examined whether enhancing colonic capillary blood flow by hemodilution therapy stabilizes colonic wall resistance and other electrophysiological parameters of gut permeability. Additional measurements involved hemodynamic monitoring and histological examinations. Colonic capillary blood flow was significantly decreased 3 days after colitis induction (1.8 +/- 0.05 vs. 2.6 +/- 0.04 nl/min in healthy control animals) when histology revealed signs of acute inflammation, and normal values after 15 days (2.4 +/- 0.06 nl/min) when chronic histological changes were evident. Hemodilution therapy enhanced colonic capillary blood flow in the initial stage (2.1 +/- 0.02 vs. 1.6 +/- 0.02 nl/min in saline-treated animals with trinitrobenzene sulfonic acid colitis) and improved gut resistance and electronic chloride secretion (73 +/- 15 vs. 33 +/- 8 microA cm2). Histological alterations were not significantly attenuated. Impaired colonic capillary blood flow in the initial stage of experimental colitis and improved mucosal microcirculation with stabilized gut permeability suggests that the early microcirculatory disturbances precede chronic histological changes and influence functional alterations in the course of the disease. Research should be continued in this field because important mechanisms in the pathogenesis of IBD and potentially therapeutic (vasoactive) substances may otherwise be overlooked.

[Acute appendicitis. Analysis of surgical indications]

We analyzed 276 patients operated on for acute appendicitis between January 1995 and June 1997. In 26 patients intraoperative assessment revealed a pathological finding other than appendicitis. Fifty-nine patients (24%) had a perforated appendix, 116 acute appendicitis verified by histological examination, 75 (30%) chronic fibroplastic appendicitis or no signs of appendicitis. Patients with histologically acute inflammation fulfilled more clinical criteria of appendicitis than those without (5.1 vs. 3.7). Negative histological findings were most common in younger females admitted on Mondays and Tuesdays. Clinical observation rather than immediate operation and laparoscopy rather than laparotomy appear appropriate for the latter group and may lower the rate of negative appendectomy.

Intestinal microcirculation and gut permeability in acute pancreatitis: early changes and therapeutic implications

Translocation of bacteria from the intestine causes local and systemic infection in severe acute pancreatitis. Increased intestinal permeability is considered a promoter of bacterial translocation. The mechanism leading to increased gut permeability may involve impaired intestinal capillary blood flow. The aim of this study was to evaluate and correlate early changes in capillary blood flow and permeability of the colon in acute rodent pancreatitis of graded severity. Edematous pancreatitis was induced by intravenous cerulein; necrotizing pancreatitis by intravenous cerulein and intraductal glycodeoxycholic acid. Six hours after induction of pancreatitis, the permeability of the ascending colon was assessed by the Ussing chamber technique; capillary perfusion of the pancreas and colon (mucosal and subserosal) was determined by intravital microscopy. In mild pancreatitis, pancreatic capillary perfusion remained unchanged (2.13 c 0.06 vs. 1.98 +/-0.04 nl x min(-1) x cap(-1) [control]; P = NS), whereas mucosal (1.59 +/-0.03 vs. 2.28 +/-0.03 nl x min(-1) x cap((-1))[control]; P <0.01) and subserosal (2.47 +/-0.04 vs. 3.74 +/-0.05 nl x min(-1) x cap((-1))[control]; P <0.01) colonic capillary blood flow was significantly reduced. Severe pancreatitis was associated with a marked reduction in both pancreatic (1.06 +/-0.03 vs. 1.98 +/-0.04 nl x min(-1) x cap(-1) [control]; P <0. 01) and colonic (mucosal: 0.59 +/-0.01 vs. 2.28 +/-0.03 nl x min(-1) x cap((-1))[control], P <0.01; subserosal: 1.96 +/-0.05 vs. 3.74 +/-0.05 nl x min(-1) x cap(-1) [control], P <0.01) capillary perfusion. Colon permeability tended to increase with the severity of the disease (control: 147 +/-19 nmol x thr(-1) x cm(-2); mild pancreatitis: 158 +/-23 nmol x hr(-1) x cm(-2); severe pancreatitis: 181 +/-33 nmol x hr(-1) x cm(-2); P = NS). Impairment of colonic capillary perfusion correlates with the severity of pancreatitis. A decrease in capillary blood flow in the colon, even in mild pancreatitis not associated with significant protease activation and acinar cell necrosis or impairment of pancreatic capillary perfusion, suggests that colonic microcirculation is especially susceptible to inflammatory injury. There was no significant change in intestinal permeability in the early stage of pancreatitis, suggesting a window of opportunity for therapeutic interventions to prevent the later-observed increase in gut permeability, which could result in improved intestinal microcirculation.

Endothelin receptor blockade improves fluid sequestration, pancreatic capillary blood flow, and survival in severe experimental pancreatitis

OBJECTIVE

To evaluate the effect of a new endothelin receptor antagonist (ET-RA) on the course of severe experimental pancreatitis.

BACKGROUND

Endothelin-1 has been shown to reduce regional blood flow in various organs, including the pancreas, and to aggravate cerulein-induced mild pancreatitis.

METHODS

Acute necrotizing pancreatitis (ANP) was induced in rats by standardized intraductal bile acid infusion and cerulein hyperstimulation. Serum trypsinogen activation peptides (TAP) were measured to verify comparable disease severity. Starting 6 hours after the onset of ANP, animals randomly received either saline or the new ET-RA LU-135252. Monitoring included cardiorespiratory parameters, urine output, hematocrit, and TAP levels. After 24 hours, animals were relaparotomized to determine pancreatic capillary blood flow and to assess the amount of free intraabdominal fluid and acinar cell necrosis. Survival was determined in a second set of experiments on 24 animals observed for 48 hours after pancreatitis induction and treatment with either normal saline or ET-RA.

RESULTS

Comparable TAP increases confirmed equally severe ANP in both groups before treatment. Treatment with ET-RA significantly reduced the mortality rate, from 50% in untreated animals to 8%. Improved survival was associated with significantly decreased hematocrit, improved urinary output, decreased ascites, and increased pancreatic capillary blood flow. There were no significant differences in plasma TAP and acinar cell injury in the surviving animals of the two treatment groups.

CONCLUSION

Therapy with the new ET-RA reduces the early mortality rate in experimental ANP, probably by reducing fluid sequestration and improving microcirculation.

Retinoic acid receptor alpha mediates growth inhibition by retinoids in rat pancreatic carcinoma DSL-6A/C1 cells

During carcinogenesis, pancreatic acinar cells can dedifferentiate into ductal adenocarcinoma of the pancreas. DSL-6A/C1 cells represent an in vitro model of this carcinogenic sequence. This study was designed to examine the effects of retinoids on cell growth in DSL-6A/C1 cells and to characterize further the molecular mechanisms underlying the antiproliferative actions of retinoids. Treatment of DSL-6A/C1 cells with retinoids results in a time- and dose-dependent inhibition of cell growth, paralleled by a retinoid-mediated transactivation of a pTK::betaRAREx2-luciferase reporter construct transiently transfected into DSL-6A/C1 cells. Retinoid receptor expression was evaluated by reverse transcriptase polymerase chain reaction (RT-PCR) using subtype-specific primers and demonstrated expression of retinoic acid receptor alpha (RAR-alpha), RAR-beta and retinoid X receptor alpha (RXR-alpha). Using a panel of receptor subtype-specific agonists, the RAR-alpha specific agonist Ro 40-6055 was the most potent retinoid in terms of growth inhibition. Furthermore, all-trans-retinoic acid-mediated growth inhibition and transactivation was completely blocked by the RAR-alpha-specific antagonist Ro 41-5253. In summary, the RAR-alpha subtype predominantly mediates the antiproliferative effects of retinoids in DSL-6A/C1 cells. Furthermore, this cell system provides a feasible tool to study the molecular mechanisms underlying the growth inhibitory effects of retinoids in ductal pancreatic carcinoma cells derived from a primary acinar cell phenotype.

Endothelin-1 mediates the alcohol-induced reduction of pancreatic capillary blood flow

Increased plasma endothelin-1 (ET-1) levels in rats after alcohol administration and increased endothelin receptor expression in the pancreas in chronic alcoholic pancreatitis have led to the hypothesis that ET-1 may play a critical role in the pathogenesis of ethanol-induced pancreatic injury through impairment of perfusion. To further test the hypothesis that ET-1 mediates an alcohol-induced reduction of pancreatic perfusion, the present study compares the effect of intravenous alcohol and ET-1 on pancreatic capillary blood flow (PCBF) and investigates whether endothelin receptor blockade prevents the alcohol-induced reduction in PCBF. Anesthetized rats were randomly assigned to receive one of the following: a 1-hour infusion of 2 g/kg alcohol or the volume equivalent of saline solution plus ET-1 (1.25 microgram/kg), a specific endothelin-A receptor antagonist (50 mg/kg), or saline solution (volume equivalent). The pancreas was exposed for intravital microscopy; PCBF was determined at the same location before the test solutions were given, after the infusion, and 1 hour thereafter. Alcohol and ET-1 significantly decreased PCBF from 2.0 nl/min/cap to 1.7 nl/min/cap. The reduction in PCBF was even more pronounced when alcohol and ET-1 were combined (1.5 nl/min/cap), whereas the ET receptor antagonist increased PCBF in saline-treated rats to 2.2 nl/min cap and maintained stable PCBF in alcohol-treated animals. The observation that PCBF is reduced by both alcohol and ET-1 and that the alcohol-induced reduction of PCBF can be aggravated by ET-1 and prevented by a specific endothelin-1 antagonist supports the hypothesis that ET-1 is the mediator of the alcohol-associated reduction of pancreatic perfusion.

[Between bench and bedside: examples of clinically oriented basic surgery research]

Animal experimental studies are an effective modality for testing new therapeutic strategies, provided that the animal model and the study protocol simulate the clinical situation. This is exemplified by various animal experimental studies on the therapy of infectious complications in acute necrotizing pancreatitis that were performed preliminary or supplementary to clinical studies. The results show that basic surgical research with close clinical orientation can be usefully and fruitfully combined with clinical studies and enables the academically active young surgeon to overcome the dualism between laboratory work and clinical practice.

[Surgical research with limited resources: research concepts and research cooperation in a surgical University Clinic]

The decreasing financial support of surgical research requires new strategies and, in particular, an intensive collaboration with basic science and biotechnology. This concept of "lean research" includes output-orientated research activities, which can be measured, using the "impact factor". Effective research requires a well-organized and structured department.

Effect of different immunosuppressive agents on acute pancreatitis: a comparative study in an improved animal model

BACKGROUND

Immunosuppressive drugs have been associated with the development and progression of acute pancreatitis after organ transplantation. Consequently, a reduction or a change in immunosuppressive therapy has been recommended once posttransplantation pancreatitis has been suspected. However, it is not known which of the available immunosuppressive agents is most harmful to the pancreas and which may be used safely in this situation. The objective of this study was to investigate the effect of different immunosuppressive drugs in various dosages on intrapancreatic protease activation, acinar cell necrosis, and mortality in an improved model of acute necrotizing pancreatitis in the rat. The rat model of acute necrotizing pancreatitis, like posttransplantation pancreatitis, is characterized by ischemia and microcirculatory disorders.

METHOD

Acute pancreatitis was induced in rats by using a combination of low-dose controlled intraductal glycodeoxycholic acid superimposed on intravenous cerulein hyperstimulation. Six hours thereafter, animals were randomized to intravenous therapy with 2, 10, or 50 mg/kg/day prednisolone (PRED); 3, 15, or 60 mg/kg/day cyclosporine A (CsA); 10 mg/kg/day azathioprine (AZA); 0.6 mg/kg/day orthoclone OKT3 (OKT3); or saline. After 36 hr, surviving animals were killed to determine acinar cell necrosis and trypsinogen activation peptides levels (TAP) in blood and ascites.

RESULTS

Compared with saline-treated control rats, animals treated with 60 mg/kg/day CsA developed significantly more acinar cell necrosis and had increased amounts of TAP in ascites. Likewise, there was more extensive acinar cell necrosis in animals subjected to AZA therapy. However, this was not associated with incremental TAP. Animals treated with 3 or 15 mg/kg/day CsA, OKT3, or PRED showed no significant changes in these target parameters. Animals given 10 or 50 mg/kg/day PRED even had decreased hematocrit values and produced significantly less ascites than animals in the other groups.

CONCLUSION

The present results suggest that AZA and high doses of CsA aggravate acute pancreatitis and should, therefore, be avoided once posttransplantation pancreatitis has been suspected, whereas lower doses of CsA, OKT3, and PRED may be used safely. PRED can even be used at higher doses as may be required when graft rejection is suspected.

[Conversion of experimental research findings to treatment of acute pancreatitis]

Performing prospective, randomized controlled studies in patients with severe acute pancreatitis is limited due to low disease incidence and organizational and financial problems. Thus, animal models simulating the clinical condition have been developed for testing innovative therapeutic procedures. Despite objections regarding the applicability of data obtained from animal experiments to clinical practice, the experience gained from these studies could not only be used in clinical study proposals but also, in part, directly influenced the clinical management of acute pancreatitis. This is illustrated by studies regarding the influence of contrast medium, isovolemic hemodilution and various antibiotics.

[Protective effect of glutamine on microcirculation of the intestine in experimental colitis]

Parenteral glutamine application can stabilize intestinal permeability and mucosal integrity. It is not known whether glutamine influences the microcirculation in the large intestine. This study thus employs intravital microscopy to investigate mucosal microcirculation in the ascending and descending Colon of Sprague-Dawley rats with TNBS colitis. The animals were randomized and treated with either saline solution (placebo) or glutamine (verum). In the severely inflamed descending colon, TNBS colitis involves a significant capillary blood flow reduction that is not improved by glutamine application. Though the ascending colon shows only a mild inflammatory reaction, its microcirculation is likewise significantly reduced. Here glutamine therapy is associated with an increase in capillary blood flow, indicating that it has a protective effect on the microcirculation of the secondarily involved intestinal segment.

[Endothelin receptor block in acute pancreatitis--improvement of microcirculation and decrease of capillary permeability also distant from the pancreas]

We have previously demonstrated that therapy with a new specific endothelin-1 receptor antagonist (ET-RA) significantly reduced mortality in acute necrotizing pancreatitis (ANP) in the rat. Improved survival was not associated with decreased intrapancreatic trypsinogen activation or parenchymal necrosis but with reduced fluid sequestation into the third space suggesting that ET-RA counteracts systemic rather than local sequelae of severe pancreatitis. The present study further tests this hypothesis by evaluating the effect of the specific ET-1 antagonist LU-135252 on capillary blood flow, capillary density, and capillary permeability not only in the pancreas but also in the colon, and monitoring fluid losses and renal and respiratory function. The experiments demonstrate that therapy with the specific ET-RA started 6 hours after disease onset stabilizes increased capillary permeability in ANP not only in the pancreas but also in the colon. This is associated with reduced ascites and improved renal and respiratory function. Furthermore, ET-RA enhances decreased capillary blood flow and capillary density in the pancreas and colon. The present results are consistent with our previous observation that ET-RA improves outcome in ANP by counteracting systemic microcirculatory disorders (particularly capillary leakage) which are believed to contribute to organ failure in early pancreatitis in this model as well as in severe human pancreatitis.

[New aspects in the pathophysiology of chronic pancreatitis]

Despite numerous experimental and clinical investigations there is no consensus on the evolution of chronic pancreatitis (CP). In the 1970s and 1980s, Sarles persistently emphasised the de novo evolution of CP due to pancreatolithiasis. In recent years, however, clinical and morphological studies have provided strong evidence for the initial proposal of acute pancreatitis progressing to chronic pancreatitis. The so-called necrosis-fibrosis-sequence theory is supported by immunohistochemical work suggesting that inflammatory mediators primarily contribute to tissue destruction and that infiltration of pancreatic nerves by immune cells is a pathogenetic factor for the generation of pain in CP. While Sarles postulates that acinar hypersecretion and an imbalance of pancreatic stone promoting and inhibiting factors trigger the evaluation of CP, the necrosis-fibrosis-sequence theory also involves other pathomechanisms (e.g. changes in ductal permeability, ischemia, oxidative stress) which have been shown to cause (acute) pancreatic injury. Despite this unifying template, which also lessens the need to identify independent mechanisms for the pathogenesis of acute and chronic alcoholic pancreatitis, there are still open questions, e.g. on genetic factors that (like in hereditary CP) may explain the different susceptibility of the pancreas to injury and the individual immunological response.

Influence of changes in pancreatic tissue morphology and capillary blood flow on antibiotic tissue concentrations in the pancreas during the progression of acute pancreatitis

BACKGROUND

The ability of an antibiotic to reach bactericidal concentrations in tissue depends on numerous factors including tissue composition and regional perfusion. Although necrotising pancreatitis is characterised by progression of pancreatic necrosis over at least 96 hours and microcirculatory alterations, the impact of these changes on the concentration of antibiotics in the pancreas has not yet been investigated.

AIM

To determine and compare pancreatic tissue concentrations of imipenem and cefotaxime at different stages of acute necrotising pancreatitis in an animal model that has been shown to mimic closely the pathomorphological and bacteriological features of severe human pancreatitis.

METHOD

Acute necrotising pancreatitis was induced in rats by a standardised intraductal infusion of glycodeoxycholic acid and intravenous cerulein. Six hours (n = 16) and 48 hours (n = 16) after induction of pancreatitis, the animals were randomised for intravenous therapy with either imipenem or cefotaxime. Fifteen minutes after injection of the antibiotic, the animals were killed. Blood and the head of the pancreas were collected for determining imipenem or cefotaxime in serum and tissue; the splenic portion of the pancreas was prepared for histological examination. In an additional set of identically treated animals, pancreatic capillary blood flow (PCBF) was assessed by intravital microscopy before induction of acute necrotising pancreatitis and at the time of antibiotic therapy.

RESULTS

Imipenem accumulates in the pancreas in the initial phase of acute necrotising pancreatitis characterised by pronounced oedema and decreased PCBF, and tends to decrease with resolution of the oedema and the progression of acinar cell necrosis in the later course of the disease. Concentrations of cefotaxime are low in oedematous pancreatic tissue early after induction of acute necrotising pancreatitis and increase with the resolution of oedema and normalisation of PCBF.

CONCLUSIONS

Concentrations of antibiotics in the pancreas vary in acute necrotising pancreatitis, depending on changes in pancreatic tissue morphology and capillary blood flow. This suggests that antibiotic tissue concentrations may not be consistent from one agent to another and that efficacy of antibiotics in acute pancreatitis cannot be estimated solely on the basis of their pharmacological and microbiological properties.

Glutamine stabilizes intestinal permeability and reduces pancreatic infection in acute experimental pancreatitis

Intestinal barrier failure and subsequent translocation of bacteria from the gut play a decisive role in the development of systemic infections in severe acute pancreatitis. Glutamine (GLN) has been shown to stabilize gut barrier function and to reduce bacterial translocation in various experimental settings. The aim of this study was to evaluate whether GLN reduces gut permeability and bacterial infection in a model of acute necrotizing pancreatitis. Acute necrotizing pancreatitis was induced in 50 rats under sterile conditions by intraductal infusion of glycodeoxycholic acid and intravenous infusion of cerulein. Six hours after the induction of pancreatitis, animals were randomly assigned to one of two groups: standard total parental nutrition (TPN) or TPN combined with GLN (0.5 g/kg(-1)/day(-1)). After 96 hours, the animals were killed. The pancreas was prepared for bacteriologic examination, and the ascending colon was mounted in a Ussing chamber for determination of transmucosal resistance and mannitol flux as indicators of intestinal permeability. Transmucosal resistance was 31% higher in the animals treated with GLN- supplemented TPN compared to the animals given standard TPN. Mannitol flux through the epithelium was decreased by 40%. The prevalence of pancreatic infections was 33% in animals given GLN-enriched TPN as compared to 86% in animals receiving standard TPN (P < 0.05). Adding GLN to standard TPN not only reduces the permeability of the colon but decreases pancreatic infections in acute necrotizing pancreatitis in the rat. This confirms previous reports that GLN decreases bacterial translocation by stabilizing the intestinal mucosal barrier. The present findings provide the first evidence suggesting that stabilizing the intestinal barrier can reduce the prevalence of pancreatic infection in acute pancreatitis and that GLN may be useful in preventing septic complications in clinical pancreatitis.

Improvement of pancreatic capillary blood flow does not augment the pancreatic tissue concentration of imipenem in acute experimental pancreatitis

BACKGROUND

Acute necrotizing pancreatitis (ANP) is characterized by decreased capillary pancreatic blood flow. Thus, antibiotics may not reach pancreatic necrosis in therapeutic concentrations and consequently fail to prevent bacterial infection of the pancreas which today is the major cause of morbidity and mortality in ANP.

OBJECTIVE

To evaluate whether improvement of impaired pancreatic microcirculation by isovolemic hemodilution with dextran leads to an increase in the pancreatic tissue concentration of imipenem (IMI), an antibiotic widely used in clinical ANP.

METHOD

After induction of ANP rats were randomized for either standard fluid therapy with Ringer's lactate (RL) or isovolemic hemodilution with dextran 70,000 (IHD/DEX). Thereafter the animals received an intravenous injection of IMI, and 15 min later they were sacrificed for determination of IMI in serum and tissue. Capillary pancreatic blood flow (CPBF) at the time of antibiotic therapy was assessed by intravital microscopy in an additional set of animals.

RESULTS

There was no significant difference in the pancreatic tissue concentration of IMI in animals pretreated with either RL (11.7 +/- 0.6 micrograms/g) or IHD/DEX (11.4 +/- 1.4 micrograms/g), although CPBF was significantly increased in the latter group (1.3 +/- 0.05 vs. 0.8 +/- 0.04 nl/min/capillary).

CONCLUSION

(1) IMI is concentrated by the pancreas in experimental ANP despite impaired CPBF. (2) Enhancement of pancreatic capillary blood flow by IHD/DEX does not increase the pancreatic tissue concentration of IMI. This suggests that CPBF is not a decisive factor influencing the accumulation of this antibiotic in the pancreas, which may be one reason for the high efficacy of IMI in clinical ANP.