In vivo blood flow after rotator cuff reconstruction in a sheep model: comparison of single versus double row

PURPOSE

Arthroscopic double-row (DR) suture anchor repair of rotator cuff tears has been shown to be superior to most single-row (SR) techniques with regard to footprint reconstruction, load to failure and tendon-to-bone contact pressures. The hypothesis of this study was that the greater contact pressures of DR techniques would compromise blood flow to a higher degree than SR repair. The aim of this experimental study was to evaluate the effect of a DR and a SR technique on tendon blood flow in a sheep model.

METHODS

Eighteen sheep underwent detachment and immediate repair of the infraspinatus tendon using either a Mason-Allen or a suture-bridge technique. Tendon blood flow was measured using laser Doppler flowmetry before detachment, immediately after repair and 12 weeks thereafter. Six regions of interest were measured, three over the lateral and three over the medial aspect of the footprint.

RESULTS

Immediately after repair, tendon blood flow decreased significantly in both repair groups (P = 0.004). In the SR group, blood flow decreased by 100.1 arbitrary units (AU) (83.6 %) after repair, in the DR by 81.4 AU (90.5 %). Subgroup analysis showed blood flow over the lateral aspect of the footprint decreased by 126.3 AU (92.2 %) in the SR and 84.4 AU (90.9 %) in the DR group, whereas over the medial aspect, it decreased by 73.9 AU (72.0 %) in the SR and 78.5 AU (90.1 %) in the DR group. None of the differences between the groups were significant. At 12 weeks, measured blood flow in the DR group had increased to 90.1 AU (100.2 %) compared to the native tendons and was at 72.5 AU (60.5 %) for the SR group. Again, the difference between SR and DR group was not statistically significant (n.s.). Assessment for retears showed that 4 of 8 tendons (50 %) in the DR group and 3 of 9 tendons (33.3 %) in the SR group had to be classified as re-ruptures.

CONCLUSION

Suture anchor repair leads to an intraoperative decrease in tendon blood flow regardless of the repair technique. A significant difference between SR and DR repair was not found. These findings indicate that tendon blood flow should not be a factor to determine the use of either repair technique over the other.

One-year-survey with multicenter data of more than 4,500 patients with degenerative rheumatic diseases treated with therapeutic nuclear magnetic resonance

BACKGROUND AND OBJECTIVES

Nuclear magnetic resonance (NMR) has been shown to stimulate repair processes and cartilage and to influence pain signalling. It represents an alternative therapy for patients suffering from osteoarthritis (OA). To prove the clinical success of this new therapeutical method, validated measuring parameters are important that are convincing for pain and function in a one-year-follow-up.

METHODS

During the course of its application over the last 10 years, over 4,500 protocols of a one-year-follow-up have been collected to record the outcome of NMR therapy. This report reflects the outcome of NMR therapy on patients with the following degenerative rheumatic diseases: OA of the knee (n = 2.770), OA of the hip (n = 673), OA of the ankle joint (n = 420) and chronic low back pain (n = 655). Data were collected at baseline, 6–8 weeks and 6 and 12 months following NMR treatment.

RESULTS

Pain was reduced significantly 6 weeks after NMR treatment in the cases of all four examined indications and stayed measurably reduced up to 6 and 12 months. The improvements in all three forms of pain (pain on load, pain on motion, pain at rest) following NMR treatment were around 21–50% on average.

CONCLUSIONS

Following therapy with NMR, patients with OA of all four types experienced a distinct improvement in their ability in functional parameters. Overall, the 10 years of a one-year-survey with multicenter data gathered on the effect of NMR therapy on patients verifiably proved its efficacy amongst patients with degenerative rheumatic diseases.

Experimental Models of Temporary Normothermic Liver Ischemia

Hepatic ischemia/reperfusion injury has so far been investigated in various experimental models. A clinical transfer of experimental results is, however, problematic because of anatomical and physiological differences and also the inevitable simplification of experimental work. The choice of model must therefore be adapted to the clinical question to be answered. The simplest procedure for inducing normothermic ischemia is to clamp the hepatoduodenal ligament. Models that do not avert portal congestion are regarded as unsuitable. Our current understanding of the pathogenesis of ischemia/reperfusion injury depends mainly on studies whose authors have investigated either global liver ischemia with a portocaval shunt, spleen transposition and in the isolated perfused system, or partial ischemia. This review is a critical examination of various approaches to the study of normothermic hepatic ischemia in experimental animals.

Role of arginine vasopressin and terlipressin as first-line vasopressor agents in fulminant ovine septic shock

PURPOSE

To compare the effects of first-line therapy with low-dose arginine vasopressin (AVP) or terlipressin (TP) on mesenteric blood flow, plasma AVP levels, organ function and mortality in ovine septic shock.

METHODS

Twenty-four adult ewes were anesthetized and instrumented for chronic hemodynamic monitoring. A flow-probe was placed around the superior mesenteric artery, and feces were extracted from the cecum. Following baseline measurements, feces were injected into the peritoneal cavity. When mean arterial pressure (MAP) decreased to less than 60 mmHg, animals were randomly assigned to receive AVP (0.5 mU kg(-1) min(-1)), TP (1 microg kg(-1) h(-1)) or saline (n = 8 each). A norepinephrine infusion was titrated to maintain MAP at 70 +/- 5 mmHg in all groups.

RESULTS

Cardiovascular pressures, cardiac output, mesenteric blood flow, and lung tissue concentrations of 3-nitrotyrosine and hemoxygenase-1 were similar among groups throughout the study period. TP infusion resulted in lower plasma AVP concentrations, reduced positive net fluid balance, increased central venous oxygen saturation and slightly prolonged survival compared to control and AVP-treated animals. However, TP treatment was associated with higher liver transaminases and lactate dehydrogenase versus control animals after 12 h.

CONCLUSIONS

This study provides evidence that the effects of low-dose TP differ from those of AVP, not only as TP has a longer half life, but also because of different mechanisms of action. Although low-dose TP infusion may be superior to sole norepinephrine or AVP therapy in septic shock, the safety of this therapeutic approach should be determined in more detail.

[Legally effective consent with minors and incompetent patients]

Legal consent to medical treatment requires comprehensive clarification and the patient's capability to consent. Minors under 14 years are usually not capable of consent -- the right to decide rests with the parents. With persons over 14 years the doctor must test for capability to consent. With adults incapable of consent the court-appointed guardian decides. In acute cases the doctor may act first and obtain permission afterwards. Contractual capability is decisive for a treatment contract to be effective and the doctor's claim for remuneration. Minors up to 7 years are absolutely contractually incapable. Since minors under 18 years are only limitedly contractually capable, the approval of the statutory guardian suffices. With contractually incapable adults the court-appointed guardian or in serious cases the Guardianship Court decides. The legal position is explained, using three sample cases.

[Indications for surgery from the viewpoints of surgeon and juror]

Whether an operation is indicated or not is a question that is a frequent subject of discussion between physicians and the legal front. As the state has the duty to protect its citizens, any physical surgical operation is legally seen as a personal injury. Only if the patient completely agrees to the surgery after being carefully informed about it is the element of criminal offense (personal injury) revoked. The obligation to disclose medical information on the surgery applies to information on the operation itself and on the possible consequences to the patient in his/her physical and mental social environment. In particular, the patient must be given all information about the risks that could arise during and after the surgery. The legislative aim of this is not to treat a list of questions and to mention all possible risks, but the legislator wants to oblige physicians to give patients who have reached the age of majority full information on diagnosis and therapy and to enable them to consider the pros and cons of the surgery carefully and then to agree to the operation or to refuse it. Besides the obligation to disclose medical information in emergency cases, the obligation to disclose medical information to minors also makes heavy demands on the physician. Examples of contraindications are given.

Collagen IX is indispensable for timely maturation of cartilage during fracture repair in mice

Fracture repair recapitulates in adult organisms the sequence of cell biological events of endochondral ossification during skeletal development and growth. After initial inflammation and deposition of granulation tissue, a cartilaginous callus is formed which, subsequently, is remodeled into bone. In part, bone formation is influenced also by the properties of the extracellular matrix of the cartilaginous callus. Deletion of individual macromolecular components can alter extracellular matrix suprastructures, and hence stability and organization of mesenchymal tissues. Here, we took advantage of the collagen IX knockout mouse model to better understand the role of this collagen for organization, differentiation and maturation of a cartilaginous template during formation of new bone. Although a seemingly crucial component of cartilage fibrils is missing, collagen IX-deficient mice develop normally, but are predisposed to premature joint cartilage degeneration. However, we show here that lack of collagen IX alters the time course of callus differentiation during bone fracture healing. The maturation of cartilage matrix was delayed in collagen IX-deficient mice calli as judged by collagen X expression during the repair phase and the total amount of cartilage matrix was reduced. Entering the remodeling phase of fracture healing, Col9a1(-/-) calli retained a larger percentage of cartilage matrix than in wild type indicating also a delayed formation of new bone. We concluded that endochondral bone formation can occur in collagen IX knockout mice but is impaired under conditions of stress, such as the repair of an unfixed fractured long bone.

Integrity of actin fibers and microtubules influences metastatic tumor cell adhesion

Tumor cell adhesion within host organ microvasculature, its stabilization and invasion into host organ parenchyma appear to be important steps during formation of distant metastasis. These interactions of circulating tumor cells with the host organs occur in the presence of fluid shear forces and soluble and cellular environmental conditions of the blood that can modulate their cellular responses and possibly their metastatic efficiency. Cytoskeletal components, such as actin filaments and microtubules, can regulate biophysical characteristics and cellular signaling of the circulating cells. Therefore, we investigated the role of these cytoskeletal structures for early steps during metastasis formation in vivo and in vitro. Using an intravital observation technique, tumor cell adhesion of colon carcinoma cells within the hepatic microcirculation of rats and their invasion into liver parenchyma was observed. Disruption of actin filaments increased cell adhesion, whereas tubulin disruption inhibited adhesive interactions in vivo. The impairment of the cytoskeleton modulated adhesion-mediated cell signaling via focal adhesion kinase (FAK) and paxillin under flow conditions in vitro. In the presence of fluid flow, focal adhesions were enlarged and hyperphosphorylated, whereas stress fibers were reduced compared to static cell adhesion. Disruption of microtubules, however, partially inhibited these effects. Combining the in vivo and in vitro results, our study suggested that changes in cell rigidity and avidity of cell adhesion molecules after disruption of cytoskeletal components appear to be more important for initial adhesive interactions in vivo than their interference with adhesion-mediated cellular signal transduction.

Development and evaluation of an experimental model for investigating the pathogenesis and therapeutic strategies of acute liver failure

Because of the various etiologies of acute liver failure (ALF) a clinically relevant model must fulfill four criteria--reversibility, reproducibility, ALF-induced death, and a sufficient time interval for diagnosis and therapy between induction and death. In this study an experimental model was evaluated for these criteria. A total of 49 rats were randomized into seven groups: First, a pilot study was performed regarding the survival rate after different treatments: In group I, animals underwent a 70% liver resection. In group II, 70% liver resection was combined with ascending doses of postoperative endotoxin administration up to 400 microg/kg (group IIc). In group III, animals only underwent liver mobilization. In group IV, ALF was induced according to the protocol of group IIc, but with additional treatment of an endothelin-A-receptor (ETAR) antagonist. Animals in group V received only 400 microg endotoxin. After induction of ALF, all animals died within the first day, showing significantly elevated bilirubin and ammonium levels and severe damage to hepatocellular integrity. Application of the ETAR antagonist resulted in the survival of 6/7 animals until the 14th day; the biochemical and histomorphological changes were reversible. All other animals survived to the 14th day. A clinically relevant model of ALF in rats can be created by the combination of 70% liver resection and endotoxin application to produce an inflammatory component.

[Reconstruction of bile duct lesions by an autologous vein graft and a bio-degradable endoluminal stent in an animal model: technique and clinical impact]

INTRODUCTION

In this study a new treatment of bile duct lesions was investigated. A segment of the bile duct was replaced by an autologous venous interponate which had been endoluminally stented with a braided bio-degradable stent.

METHODS

A total of 18 pigs (20-28 kg) was divided into three equal groups (I-III). In each group a 2 cm segment of the jugular vein was harvested. The animals in Group I (vein group, n = 6) underwent resection of a 2 cm long segment of the common bile duct which was replaced solely by the venous interponate, in Group II (stent group, n = 6) the venous interponate had been endoluminally stented by a braided bio-degradable stent. Group III (control group, n = 6) underwent only a circular mobilization of the common bile duct. Postoperatively survival rate, general condition as well as the weight were observed and checked for 6 months. During surgery and finally after sacrifice after 6 months blood and tissue samples were taken and semiquantitatively scored concerning grade of inflammation and fibrosis.

RESULTS

In the stent and control group all animals survived in good condition. 3 pigs of the vein group died within 3 weeks showing signs of biliary peritonitis, another one died due to a high grade stenosis of the common bile duct with secondary biliary cirrhosis after 4 months. In the stent group all animals survived until sacrifice after 6 months. On examination the venous interponate was laminated with bile duct epithelium showing the diameter of the implanted stent.

CONCLUSION

The reconstruction of bile duct lesions by a venous interponate in combination with a bio-degradable stent is easy to perform and represents a clinically interesting alternative to the biliodigestive anastomosis because of the preservation of the sphincter oddi. After 6 months the stent is completely absorbed and the venous interponate is laminated with bile duct epithelium.

Laparoscopic fluorometry: a new minimally invasive tool for investigation of the intestinal microcirculation

The aim of this study was to develop and establish a new system of laparoscopic fluorometry for the purpose of investigating the intestinal microcirculation. In 25 pigs (German Landrace, 16-25 kg body weight), ischemia was established in two segments (A, irreversible; B, reversible ischemia; C, internal control) of the small intestine by a laparoscopic technique. Microcirculation in the segments was assessed by laparoscopy at a second-look operation 24 h later by means of the fluorescence system Endoscan. The fluorescence of the three bowel segments was measured by arbitrary dye fluorescence units (DFU) 15 min after starting reperfusion, before and after injection of sodium fluorescein (NaFlu, 0.25 mg/kg body weight). The dividing line between viable and nonviable bowel tissue was established from the inflow and outflow rates of NaFlu with the aid of ROC (receiver operating characteristic) curves. The specificity and sensitivity of the new method were evaluated by correlating the results with the viability of each intestinal segment as predicted by three laparoscopically experienced surgeons and by histological examination. By means of the calculated separation sharpness (fluorescence index at 2 min >0.5, outflow factor of NaFlu at 10 min >20%), the overall predictions of intestinal viability in all 25 animals achieved a sensitivity of 93.5% and a specificity of 94.1% by laparoscopic fluorometry, versus a sensitivity of 70.8% and a specificity of 87.5% for the prediction of bowel viability by ordinary laparoscopic technique. Used as an adjunct to conventional laparoscopy, laparoscopic fluorometry brought significant gains in sensitivity and specificity in the distinction between reversible and irreversible intestinal ischemia.

ICAM-1 and VCAM-1 antisense oligonucleotides attenuate in vivo leucocyte adherence and inflammation in rat inflammatory bowel disease

BACKGROUND

Recruitment of circulating cells to the inflamed intestine is modulated by adhesion molecules expressed on the surface of both leucocytes and endothelial cells.

AIMS

The objective of this study was to test whether 2'-O-methoxyethyl chimeric antisense oligonucleotides directed against endothelial intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) can downregulate leucocyte-endothelial interactions and thereby attenuate inflammation in rat experimental ileitis.

METHODS

Indomethacin (7.5 mg/kg ) was injected subcutaneously into Sprague-Dawley rats 48 and 24 hours prior to intravital microscopy. Animals were treated with either ICAM-1 (ISIS 17470), VCAM-1 (ISIS 18155), or scrambled control antisense oligonucleotides administered subcutaneously or intravenously in parallel with indomethacin. Leucocyte trafficking was observed in ileal submucosal collecting venules. Macroscopic and histological grades of inflammation were measured 48 hours after the first indomethacin application. ICAM-1 and VCAM-1 expression in ileal submucosal venules was detected by immunohistochemistry.

RESULTS

Intravenous administration of ICAM-1 oligonucleotides 2 mg/kg (rolling leucocytes 5.7 (2.4)/0.01 mm(2) endothelial surface, adherent leucocytes 0.8 (1.1)) and VCAM-1 oligonucleotides 8 mg/kg (9.2 (4.4), 0.6 (0.8)) significantly reduced leucocyte adhesion compared with diseased controls (27.8 (5.3), 14 (4.4)) in a dose dependent manner whereas subcutaneous treatment did not. Correspondingly, macroscopic and histological inflammation was significantly decreased. ICAM-1 oligonucleotides markedly reduced endothelial ICAM-1 expression while VCAM-1 oligonucleotides clearly diminished endothelial VCAM-1 expression.

CONCLUSIONS

Both ICAM-1 and VCAM-1 2'-O-methoxyethyl chimeric antisense oligonucleotides attenuate rat ileitis by downregulation of leucocyte adherence and thus are potential candidates for anti-inflammatory treatment in inflammatory bowel disease.

Achilles tendon healing: long-term biomechanical effects of postoperative mobilization and immobilization in a new mouse model

The aim of the study was to investigate the long-term effects of postoperative immobilization as opposed to mobilization on the biomechanical attributes of healing Achilles tendons in a new experimental mouse model. In 114 Balb-C-mice the left Achilles tendon was transected and sutured by the Kirchmayr-Kessler technique. The tendons healed either under postoperative immobilization effected by fixing the upper ankle joint in equinus position or under mobilization through a limited range of movement. The contralateral Achilles tendons served as internal control. All tendons were tested biomechanically at short intervals up to the 112th postoperative day in terms of load to failure [N], tendon deflection [mm] and tendon stiffness [N/mm], and were evaluated histologically after 8 and 112 days. Postoperative mobilization resulted in a continuous and significantly more rapid restoration of load to failure in comparison to the immobilization group. Tendon deflection was decreased by postoperative mobilization, whereas under immobilization it paradoxically increased still further in the later course. After 112 days the tendons of the mobilization group had regained their original tendon stiffness, whereas the tendons after immobilization reached only about half the values seen in the control tendons. Histologically, postoperative mobilization led to increased immigration of inflammatory cells in the early phase. In the late phase, as compared to immobilization, tendon structure was more mature, with fibre bundles arranged in parallel and interposed tendocytes. Tensile loading of the healing tendon by postoperative mobilization leads to fundamental changes in the biological process of tendon healing resulting in accelerated restoration of load to failure and reduced tendon deflection.

Pharmacological regulation of postischemic sinusoidal diameters in rats--a new approach for reducing hepatic ischemia/reperfusion injury

Ischemia leads to profound endothelin-related constriction of the hepatic microcirculation with resulting disturbances in blood and oxygen supply. The aim of the study was to modulate hepatic microvascular diameters by blocking endothelin receptors with bosentan, and also to find the best possible vessel width (as produced by bosentan) for minimizing ischemia/reperfusion injury.

METHODS

In an in vivo rat model hepatic ischemia was induced for 30 minutes by crossclamping the hepatoduodenal ligament. The endothelin receptor antagonist (ERA) bosentan was administered before ischemia in stepwise dosages of 0.1, 1.0 and 10 mg/kg bw i.v. and 10 mg/kg bw intraportally (i.p.). Vasoactive effect was assessed by in vivo microscopy. The influence on hepatic oxygen supply and hepatocellular function was evaluated by measuring local tissue pO(2) and AST levels.

RESULTS

Because of ischemia sinusoidal diameters were reduced to 76.3 +/- 7.4% compared with values found in sham-operated animals. After administration of 0.1 mg/kg ERA (bosentan) the sinusoids remained constricted (89.7 +/- 9.9%). Blocking endothelin receptors with 1 mg/kg bosentan avoided sinusoidal constriction (99.0 +/- 8.8%, p<0.05) and led to the most effective reduction of AST level peak after 6 h of reperfusion (244.0 +/- 34.2 U/l vs 422.9 +/- 163.3 U/l in untreated ischemia). 10 mg/kg i.v. caused an increase in sinusoidal diameter to 109.1 +/- 6.4% and 10 mg/kg intraportally to 136.8 +/- 19.3% and even an increase in AST levels (618.9 +/- 209.3 U/l). Hepatic ischemia led to a significant decrease of local tissue pO(2) after reperfusion (9.4 +/- 1.2 mm Hg; p<0.05 vs sham: 16.8 +/- 1.8 mm Hg). The greatest improvement in postischemic oxygen supply was found in the 1.0 mg/kg group (12.9 +/- 1.0 mm Hg; p< 0.05 vs ischemia). Venular diameter changed almost to the same extent as sinusoidal diameter. Perfusion rate was significantly increased and sticking of leukocytes in sinusoids and venules was reduced after doses of 1 and 10 mg/kg bw bosentan i.v. (p<0.05).

IMPLICATIONS

In this model we were able to regulate the diameters of sinusoids and postsinusoidal venules incrementally. We conclude that the avoidance of constriction, without excessive vasodilatation gives increased perfusion rates with improved hepatic oxygen supply and hepatocellular function.

Auxiliary partial orthotopic liver transplantation: treatment of acute liver failure in a new rat model

BACKGROUND AND AIMS

Liver regeneration and functional interaction between native liver and graft after auxiliary partial orthotopic liver transplantation (APOLT) are not entirely understood and, therefore, require an experimental model simulating the clinical features of acute liver failure (ALF) and the surgical technique of APOLT.

MATERIALS AND METHODS

ALF was induced by subtotal hepatectomy in 50 Lewis rats (200-250 g). Sham operation (I), ALF without treatment (II), ALF with portocaval shunt for decreasing blood flow of the remnant liver (III), and ALF treated by APOLT (IV) were performed. The auxiliary graft represented a left donor liver lobe which was orthotopically implanted using a microsurgical technique including reconstruction of the graft artery and internal biliary drainage. Operative outcomes, serum chemistry and histopathological findings were examined up to the 14th day.

RESULTS

ALF without treatment (groups II and III) led to a small droplet fatty degeneration in the hepatocytes and a significant increase of liver parameters until the death of the animals within the first two postoperative days ( P<0.05). After APOLT (group IV), 80% of the animals survived up to the 14th day, revealing significantly decreased liver parameters ( P<0.05), a well-perfused graft and an up to five times increased native liver size with normal architecture.

CONCLUSION

This new rat model simulates the clinical features of an ALF treated by APOLT and is especially interesting for further basic research on the interaction between native liver and auxiliary graft after APOLT.

Alteration of fracture stability influences chondrogenesis, osteogenesis and immigration of macrophages

Mechanical conditions at the fracture line determine the mode of fracture healing (osteonal versus non-osteonal bone union). The aim of this study was to investigate the influence of differing degrees of fracture stability on the time course of chondrogenesis, enchondral ossification and immigration of macrophages into the fracture callus. Using a fracture model of the rat's tibia, histological (Azan staining), immunohistological (antibodies directed against the macrophage-specific surface antigen ED2), and molecular biological techniques (expression of the mRNA of the cartilage-specific collagen IX, osteocalcin - a marker for mature osteoblasts - and the macrophage-specific macrosialin) were employed. In terms of histology and molecular biology (collagen IX mRNA expression) chondrogenesis in the fracture gap continued for longer in less stable fractures. In more stable fractures bone formation - identified by osteocalcin mRNA expression - increased from day 12 onwards. The expression of the macrophage-specific surface antigen ED2 and the mRNA of macrosialin was more pronounced but of shorter duration in the more stable fractures. This study shows that differing degrees of fracture stability not only influence the interplay between osteogenesis and chondrogenesis but also alter the kinetics of macrophage immigration into the fracture callus. These findings could aid in better understanding the cytobiologic mechanisms of callus formation and may suggest that macrophages are an important factor not only in soft tissue healing but also in bone healing.

Protective role of an endothelin-converting enzyme inhibitor (FR901533) in hepatic ischemia/reperfusion injury

INTRODUCTION

There is evidence that endothelin (ET) contributes to disturbances of the hepatic microcirculation after warm ischemia/reperfusion (I/R) by causing vasoconstriction and by enhancing leukocyte endothelium interactions. The aim of this study was to investigate a possible protective role of the endothelin converting enzyme (ECE) inhibitor FR901533 in this setting.

METHODS

In an in vivo model (42 Wistar rats), hepatic ischemia was induced for 30 min by Pringle's maneuver. Sham operated (I), untreated ischemic (II), and treatment (III) groups with FR901533 (1 mg/kg bw iv) were investigated. The effect of FR901533 in I/R was assessed by in vivo microscopy (30-90 min after reperfusion), measurement of local tissue pO2 (30 and 60 min after reperfusion), and determination of AST/ALT levels (2 h, 6 h, and 2, 6, and 14 days after reperfusion).

RESULTS

In the untreated ischemic group (II) sinusoidal constriction to 76.3 +/- 4.2% of basic diameters was observed, leading to significant decreases in perfusion rate (82.3 +/- 3.6% of sham group) and in liver tissue pO(2) (43.5 +/- 3.2% of sham group) (P < 0.05). In addition, we found an increased percentage of stagnant leukocytes in sinusoids (138.3 +/- 9.8) and sticking leukocytes in postsinusoidal venules (155.2 +/- 3.3% of sham group) (P < 0.05). Hepatocellular damage (AST/ALT increase to 430.6 +/- 47.7 U/L/200.2 +/- 23.8 U/L, pre: 27.4 +/- 2.7 U/L/28.1 +/- 2.7 U/L) was detected 6 h after reperfusion (P < 0.05). Administration of the ECE inhibitor before ischemia significantly reduced I/R injury. Sinusoidal diameters were maintained (102.2 +/- 1.7%), while perfusion rate (93.1 +/- 1.8%) and tissue pO2 (105.3 +/- 2.7%) increased significantly (P < 0.05). Hepatocellular damage was decreased (AST/ALT levels after 6 h of reperfusion: 166.6 +/- 26.3 U/L/132.4 +/- 22.5 U/L, P < 0.05) and leukocyte sticking and rolling were significantly reduced (P < 0.05).

CONCLUSION

Our results provide evidence that the new therapeutic approach with an ECE inhibitor is effective in reducing hepatic I/R injury.

Animal models of sepsis

Knowledge of sepsis is growing rapidly and new pathogenetic concepts and therapeutic strategies evolve. The animal models of sepsis catalyze this development. Any model of this complex disease is inevitably a compromise between clinical realism and experimental simplification. Against the background of current pathogenetic concepts this review tries to analyze the validity and clinical relevance of each model. Endotoxemia and bacteremia represent models without an infectious focus. They reproduce many characteristics of sepsis and are highly controlled and standardized. However, they reflect a primarily systemic challenge and create neither an infectious focus nor the protracted immune reaction that characterizes sepsis. In this respect, any model with an infectious focus is decisively closer to clinical reality. In these models the peritoneal cavity is contaminated either by bacteria or inoculated feces or perforation of the bowel wall. Both the bolus injection and the implantation of carriers loaded with bacteria or feces are used. In fecal spesis and perforation models the complete spectrum of enteric pathogens is present in the septic focus and infective selection is undisturbed. Here the pathophysiologic and immunologic features of clinical sepsis are successfully reproduced. However, presumably due to inadequate control of the bacterial challenge, only poor interlaboratory standardization is possible. As to optimize models for the clinical reality the choice of an appropriate class of models is crucial. Moreover the incorporation of clinical therapy such as volume resuscitation, antibiotic therapy and surgical treatment of the septic focus is indispensable. Finally, the importance of simulation of comorbidities cannot be overemphasized.

Acetyl-11-keto-beta-boswellic acid, a constituent of a herbal medicine from Boswellia serrata resin, attenuates experimental ileitis

The gum resin extract from Boswellia serrata (H15), an herbal product, was recently shown to have positive therapeutic effects in inflammatory bowel disease (IBD). However, the mechanisms and constituents responsible for these effects are poorly understood. This study examined the effect of the Boswellia extract and its single constituent acetyl-11-keto-beta-boswellic acid (AKBA) on leukocyte-endothelial cell interactions in an experimental model of IBD. Ileitis was induced by two subcutaneous injections of indomethacin (7.5 mg/kg) in Sprague-Dawley rats 24 h apart. Rats also received oral treatment with the Boswellia extract (H15) or AKBA at two different doses (low and high) equivalent to recommendations in human disease over 2 days. Controls received only the carriers NaHCO3 (subcutaneously) and tylose (orally). Effects of treatment were assessed by intravital microscopy in ileal submucosal venules for changes in the number of rolling and adherent leukocytes and by macroscopic and histological scoring. Increased leukocyte-endothelial cell adhesive interactions and severe tissue injury accompanied indomethacin-induced ileitis. Treatment with the Boswellia extract or AKBA resulted in a dose-dependent decrease in rolling (up to 90%) and adherent (up to 98%) leukocytes. High-dose Boswellia extract as well as both low- and high-dose AKBA significantly attenuated tissue injury scores. Oral therapy with the Boswellia extract or AKBA significantly reduces macroscopic and microcirculatory inflammatory features normally associated with indomethacin administration, indicating that the anti-inflammatory actions of the Boswellia extract in IBD may be due in part to boswellic acids such as AKBA.

Telepathology network: conceptual groundwork and evaluation

Telepathology uses telecommunication technology to transmit microscopic images for diagnostic or teaching purposes. Basic requirements for a telepathology system are described. Usage scenarios for a telepathology network are presented including applications in intraoperative frozen section diagnosis, scientific collaboration and computer based training. Results of an evaluation of 4 currently available telepathology systems are presented.

Important role for endothelins in acute hepatic ischemia/reperfusion injury

The aim of this study was to explore the complex role of endothelins (ETs) in hepatic ischemia-reperfusion injury and to minimize this type of injury by nonselective ET receptor blockade. In an in vivo rat model, hepatic ischemia was induced for 30 min. The rats were divided into three groups: (1) sham operated, (2) untreated ischemic, and (3) group treated with the nonselective ET receptor antagonist bosentan (1 mg/kg body weight iv). Blockage of the ET system during ischemia-reperfusion was assessed by: (1) in vivo microscopic analysis, (2) measurement of local tissue PO2, (3) laser Doppler flowmetry, (4) transaminases, and (5) tumor necrosis factor (TNF)- serum levels. During liver ischemia, anoxia (mean liver pO2 decreased from 14.7 to 1.5 mm Hg) and TNF- (levels rose from 0 pg/mL to 145.3 pg/mL at the end ofischemia) were associated with the release of ETs. Immunoreactive ET-1 (ir-ET-1) plasma levels (basal levels: 12.1+/-1.8 pg/mL) went up by 2.6-fold (32.1+/-6.8 pg/mL) after 15 min and by 11.7-fold (142.1+/-32.6 pg/mL) after 120 min of reperfusion. Increased plasma levels of ir-ET-1 were associated with sinusoidal constriction to 77.6+/-7.1% of basal diameters. This constriction led to significant decreases in perfusion rate (77+/-3%), local tissue PO2 (6.9+/-2.7 mm Hg), and erythrocyte flux (61.7+/-13.8% of basal values). Hepatocellular damage, evaluated via the serum level of aspartate aminotransferase (AST, increase to 393.5+/-68.3 U/L, preoperative 23.9+/-2.0 U/L) was detectable 6 h after reperfusion (p < .05). Administration of bosentan before 30 min of ischemia significantly reduced ischemia-reperfusion injury and was associated with an increase of ir-ET-1 levels to 110.8+/-12.0 pg/mL and 94.1+/-25.0 pg/mL after 15 and 120 min of reperfusion. Sinusoidal diameters were maintained at nearly 100% in the treatment group instead of 77%, while perfusion rate (88+/-2%) and tissue PO2 (12.1+/-1.0 mm Hg) rose significantly in contrast with the nontreatment group (p < .05). Hepatocellular damage was reduced (AST levels after 6 h of reperfusion 244.0+/-34.4 U/L, p <.05), and leukocyte sticking and rolling were diminished (p < .01). In the treatment group, bosentan values of 5.6+/-0.7 and 2.9+/-0.4 ng/mL after 15 and 120 min of reperfusion were measured. In conclusion the release of endothelins is combined with microcirculatory disturbances and local hypoxia, thereby causing liver damage. By protecting the liver microcirculation, ET receptor blockade of both receptors at a low dose increased blood and oxygen supply to the liver and reduced hepatocellular injury. These results constitute the bases for further studies and transfer into clinical practice.

Liver bridging techniques in the treatment of acute liver failure

The introduction of orthotopic liver transplantation in the management of acute liver failure has dramatically increased the survival rates of patients at the cost of removing the patient's native liver and life-long dependence on immunosuppression. However, it is well known that in many patients with acute liver failure the diseased liver has the potential to recover. Death in these patients is often due to increased intra-cranial pressure or infection. Liver bridging techniques are assigned to temporarily provide liver function and enable the native liver to recover in patients with acute liver failure. They represent an attractive alternative to conventional liver transplantation in the management of acute liver failure, since after recovery of the native liver the patient is freed from immuno-suppression with all associated side-effects and risks. Auxiliary liver transplantation, artificial liver support devices and hepatocyte transplantation represent different ways of bridging liver function in acute liver failure. The aim of this review is to present the ideas and principles of these three different liver bridging techniques. We will discuss the relative importance and the future potential of theses bridging techniques in the treatment of acute liver failure by comparing the experimental and clinical results.

A new clamping technique for biomechanical testing of tendons in small animals. aprobst@uni-muenster.de

When biomechanical properties of tendons are studied, the technique of clamping the tendons in the testing machine presents a methodological challenge, especially when murine tendons are examined. These short tendons tend to rupture at the transition line to the fixation, leading to false interpretations. Therefore a new clamping technique for investigation of healthy murine Achilles tendons (n = 50) was developed, in which the intramuscular tendon fibers were fixed between two paper strips and the calcaneus was wedged into a conical slot in a wooden block and then mounted in the testing machine (n = 20). This technique was compared with the conventional clamping technique that fixes both ends of the tendon by clamps (n = 15) and an earlier described method that used glue or plastic cement for the fixation of the intramuscular tendon fibers and calcaneus in the testing machine (n = 15). When tested by the new clamping technique, 17 tendons ruptured intratendinously at a mean tensile force of 8.4 +/- 1.1 N. Three Achilles tendons (17%) tore at the site of paper fixation and had to be excluded from investigation. Data from 73% of the measurements fixed by gluing had to be excluded because slippage of the proximal tendon fibers and contamination of the tendon with glue occurred. All the conventionally clamped tendons ruptured at the site of fixation at a mean tensile force of 6.1 +/- 2.3 N (p < .05). This was 30% lower than with the new clamping technique. Thus, the newly developed clamping technique enables investigators to obtain more valid biomechanical studies of the murine Achilles tendon.

Endothelin/nitric oxide balance influences hepatic ischemia-reperfusion injury

During ischemia-reperfusion an imbalance between endothelin (ET) and nitric oxide (NO) can be responsible for microcirculatory disturbances. The aim of this study was to restore the ET/NO balance to reduce the ischemia-reperfusion injury. Hepatic ischemia was induced for 30 min in 56 Wistar rats. Sham operation, ischemia and treatment groups with the ET receptor antagonist (ERA) bosentan (1 mg/kg body weight i.v.) and the NO donor L-arginine (400 mg/kg body weight i.v.) were performed. For evaluation of hepatic microcirculation in vivo microscopy was carried out 30-90 min after reperfusion. Local hepatic tissue PO2, laser Doppler flow and aspartate aminotransferase/alanine aminotransferase (AST/ALT) levels were measured. Increased ET caused sinusoidal constriction after reperfusion to 76% of the sham group (p < 0.05), leading to significant decrease in perfusion rate (82%), liver tissue PO2 (6.9 mmHg) and erythrocyte flux (45.2% of sham group). Hepatocellular damage could be detected 6 h after reperfusion by AST/ALT increase (p < 0.05). Sinusoidal diameters were maintained at baseline in the ERA (98%) and NO (102%) groups (p < 0.05). Increased percentage of leukocytes sticking in sinusoids (144%) and venules (435%) was reduced by therapy to 110/253% (ERA) and 111/324% (NO), respectively (p < 0.05). Perfusion rate was increased to 93 and 94% (p < 0.05 vs ischemia). Local hepatic tissue PO2 was improved 30 min after reperfusion in the ERA (11.0 mmHg) as well as in the NO group (11.5 mmHg; p < 0.05 vs ischemia). Measurement with a laser Doppler flow meter revealed significant improved erythrocyte flux in both therapy groups (p < 0.05 vs ischemia). Also, the post-ischemic AST/ALT increase was reduced by therapy. In conclusion, ET evokes strong constriction of post-ischemic sinusoids, leading to microcirculatory disturbances. The maintenance of the ET/NO balance by blocking ET receptors, or providing an NO donor, protects liver microcirculation and reduces hepatic ischemia-reperfusion injury.

Endothelin receptor blockade as a therapeutic strategy in ameliorating postischemic damage to the liver microcirculation

Ischemia leads to profound endothelin- (ET) related constriction of hepatic microvessels, causing disturbances in blood and oxygen supply. The aim of the study was to modulate hepatic microvascular diameters by blocking ET receptors to find the optimal therapeutic vessel width for reduction of ischemia-reperfusion injury. In an in vivo model (84 female Wistar rats, 250-300 g) with portal decompression by means of a splenocaval shunt, normothermic hepatic ischemia was induced for 30 min by crossclamping of the hepatoduodenal ligament. The ET receptor antagonist (ERA) bosentan was administered before induction of ischemia in different dosages [0.1, 1.0 and 10.0 mg/kg body weight (BW) i.v. and 10 mg/kg BW intraportally (i.p.)]. The effect on microcirculation was assessed by in vivo microscopy and influence on hepatocellular function by measurement of aspartate aminotransferase (AST) levels. Sinusoidal diameters were reduced as a result of ischemia to 76.3 +/- 7.4% compared with values received from sham-operated animals. After application of 0.1 mg/kg of bosentan, sinusoids remained constricted (89.7 +/- 9.9%, AST 255.0 +/- 12.8 U/l). Blocking ET receptors with 1 mg/kg bosentan avoided sinusoidal constriction (99.0 +/- 8.8%, p < 0.05) and led to the most effective reduction of AST level peak after 6 h of reperfusion (244.0 +/- 34.2 U/l vs 422.9 +/- 163.3 U/l in untreated ischemia). Bosentan (10 mg/kg i.v.) caused an increase in sinusoidal diameter to 109.1 +/- 6.4% (AST 311.7 +/- 33.6 U/l) and 10 mg/kg i.p. to 136.8 +/- 19.3% and even increase AST levels (618.90 +/- 209.32 U/l). After intravenous application of 1 and 10 mg/kg BW bosentan the perfusion rate was significantly increased and sticking of leukocytes in sinusoids and venules reduced (p < 0.05). In our model, diameters of sinusoids and postsinusoidal venules could be regulated gradually. We conclude that the avoidance of constriction, but not an excessive vasodilation leads to increased perfusion rate and hence improved hepatocellular function.

Exogenous L-arginine protects liver microcirculation from ischemia reperfusion injury

Hepatic ischemia followed by reperfusion evokes an imbalance between the vasoregulatory compounds endothelin and nitric oxide (NO) followed by constriction of the vascular bed, leading to microcirculatory disturbances and reduced blood flow, thereby causing hypoxia and liver damage. The aim of this study was to protect the liver microcirculation by maintaining this delicate balance.

MATERIAL AND METHODS

In an in vivo ischemia/reperfusion model with portal decompression by a splenocaval shunt, hepatic ischemia was induced for 30 min by Pringle's maneuver. The effect of the NO donor L-arginine (400 mg/kg b.w. i.v.) was assessed by in vivo microscopy. Microhemodynamic studies, including the sinusoidal perfusion rate, diameters of hepatic sinusoids and postsinusoidal venules, leukocyte endothelium interactions and leukocyte velocity were performed. Microcirculatory data were compared with local tissue pO2 and serum transaminase levels.

RESULTS

After ischemia the diameters of sinusoids and postsinusoidal venules were significantly reduced to 76+/-7 and 86+/-10% respectively in the nontreatment group, but dilated to 102+/-3 and 105+/-7% in the group treated with L-arginine (p < 0.001). The percentage of permanently adherent leukocytes in sinusoids and venules was increased by ischemia, but L-arginine reversed this increase (p < 0.001). Perfusion rate was improved to 90+/-2 compared with 83+/-5% in the untreated group (p < 0.01). Systemic arterial blood pressure was not affected by administration of the NO donor. The postischemic increase in serum transaminase levels was diminished in the treatment group (ASAT: p < 0.05). Local postischemic hepatic tissue pO2 was significantly decreased to 45% of basal values after 30 min and to 55% after 60 min of reperfusion (p < 0.05). Administration of L-arginine results in a significant increase in local tissue pO2 to 86 and 106% of basal values respectively (p < 0.05).

CONCLUSION

These data indicate that L-arginine improves hepatic microcirculation after warm ischemia by increasing sinusoidal perfusion rate and by diminishing leukocyte endothelium interactions. Maintained integrity of microcirculation is associated with sufficient oxygen supply and improved hepatocellular function.

Controlled vasoregulation of postischemic liver microcirculation--a therapeutic approach

One of the changes produced by ischemia and reperfusion is endothelin (ET)-mediated constriction of the hepatic vascular bed. This leads to microcirculatory disturbances and reduced blood flow, thereby causing local hypoxia and liver damage. Our aim was to induce stepwise changes of microvascular vessel diameters so as to define the best protective vessel width that could be produced by drug therapy and thereby to minimize ischemia/reperfusion injury. The mixed ET receptor antagonist bosentan was used in different dosages in a rat liver ischemia/reperfusion model with splenocaval shunt. In vivo microscopy was performed 30-90 min after reperfusion and local hepatic tissue pO2 was determined, together with aspartate aminotransferase/alanine aminotransferase (AST/ALT). After ischemia, sinusoidal diameters were significantly reduced to 76 +/- 7% of those in the control group. After the administration of bosentan in dosages of 0.1, 1, and 10 mg/kg body weight iv and 10 mg/kg body weight intraportally we found diameters of 83 +/- 4, 98 +/- 2, 109 +/- 6, and 137 +/- 19%, respectively. Perfusion rate and leukocyte-endothelium interactions showed dependence on sinusoidal diameters, with the best results in the group where preischemic sinusoidal vessel width had been maintained. Local tissue pO2 and transaminase levels also showed that oxygen supply was sufficient and that hepatocellular injury was most minimized in this group. Graduated blocking of ET receptors allows stepwise regulation of sinusoidal and postsinusoidal venular vessel width and offers a treatment strategy for pathophysiological situations that are associated with ET-induced vasoconstriction. The results suggest that maintenance of preischemic microvascular diameter is the best therapeutic approach.

Protective effects of ambroxol in hypothermic liver preservation: a transplant study

The bronchosecretolytic agent ambroxol added to histidine-tryptophan-ketoglutarate (HTK) solution has recently been shown to protect cold stored rat hepatocytes. The aim of the present study was to confirm these observations in a rat liver transplantation model. Before orthotopic liver transplantation, donor livers from 30 syngeneic Wistar rats were assigned to three groups (n = 10): (A) in situ flush (ISF) and 1/2-h cold storage (CS) with HTK solution, (B) ISF and 3-h CS with HTK, and (C) ISF and 3-h CS with HTK + 10(-3) mol/L ambroxol. The efficacy of the drug was evaluated by postoperative survival (> 14 days) and liver enzyme release (ALT), bile flow, histomorphological injury, and malondialdehyde (MDA) level in the grafts 15 min after reperfusion. After 1/2-h CS with HTK solution (A), 90% of the transplanted rats survived. In comparison with donor conditions, bile flow in the reperfused grafts decreased to 87 +/- 5.3%, whereas postoperative ALT levels slightly increased. After 3-h HTK preservation (B), the survival rate decreased to 60%, while ALT values markedly increased and bile flow after reperfusion declined to 82 +/- 6.6%. Ambroxol added to HTK solution (C) enhanced bile flow to 106 +/- 3.4%(p < .05), and reduced ALT and MDA levels and histomorphological injury of the transplanted livers, so that its beneficial effect in organ preservation has been confirmed in the transplant model. However, survival rate was not improved by the agent, probably because of the low cold ischemia tolerance of the Wistar rat livers used.

Effect of anti-CD11b (alphaM-MAC-1) and anti-CD54 (ICAM-1) monoclonal antibodies on indomethacin induced chronic ileitis in rats

Leukocyte emigration from blood to sites of inflammation involves sequential interaction of specific adhesion molecules expressed by both leukocytes and endothelial cells. The central steps in leukocyte-endothelial adhesive interactions are leukocyte rolling, sticking, and transmigration. This study investigated the effect of monoclonal antibodies against CD54 (ICAM-1) and CD11b (alphaM-chain of MAC-1) on intestinal inflammation. Anti-CD54 and anti-CD11b were tested in rats with indomethacin-induced chronic ileitis. Macroscopic changes were assessed by a modified version of the Wallace et al. score. Leukocyte rolling and sticking were investigated by intravital microscopy. Results show that indomethacin administration led to a chronic inflammatory response characterized by significant increase (P<0.05) in rolling (from 5.41+/-2.87 to 32.41+/-15.03 100 microm(-1) s(-1)) and sticking (from 0.16+/-0.18 to 9.11+/-5.3 100 microm(-1) s(-1)) leukocytes. After antibody treatment only the anti-CD11b group showed significant (P<0.05) reduction in rolling (from 32.41+/-15.03 to 6.6+/-2.7 100 microm(-1) s-1) and sticking (from 9.11+/-5.3 to 0.07+/-0.09 100 microm(-1) s-1) leukocytes. This was also the case for macroscopic changes. Indomethacin led to a rise in the Wallace score from 0 to 4.29+/-0.76 points (P<0.05) and anti-CD11b to a reduction from 4.29+/-0.76 to 1.29+/-1.11 points (P<0.05). Anti-CD54 and combined anti-CD11b/CD54 administration was not followed by significant changes. Therefore we suggest that leukocyte-based CD11b but not endothelial-based CD54 contributes most to leukocyte adhesion in the setting of indomethacin-induced ileitis in rats.

Malignant schwannoma and late-onset form of neurofibromatosis (NF-VII type) in a patient with skeletal manifestations

INTRODUCTION

Von Recklinghausen's neurofibromatosis is known to occur with markedly variable expressivity. Nevertheless, cases that do not feature characteristic findings are uncommon.

CASE

We report an extremely rare, sporadic case of neurofibromatosis, exclusively represented in the skeleton of a 49-year-old woman. The late onset of the disease and the absence of common diagnostic criteria permit us to classify it as neurofibromatosis type VII. Additionally, the disease was complicated by early malignant transformation of a thoracic neurinoma, which was removed by a wide local resection. Two years after surgery, the patient developed local recurrence and liver metastases. She died a few months later despite aggressive chemotherapy.

Organ preservation with EC, HTK, and UW, solution in orthotopic rat liver transplantation. Part II. Morphological study

The quality of organ preservation is of major importance in minimizing the incidence of primary graft nonfunction and organ rejection. For this study a new semiquantitative score was developed that grades morphologic tissue alterations in the liver according to their frequency and severity. It was applied to assess commonly used perfusion solutions for their efficacy in preventing early and late tissue damage after rat liver transplantation. For transplantation the livers were stored in Euro-Collins (EC, group I; n = 11), histidine-tryptophan-alpha-ketoglutarate (HTK, group II; n = 11), or University of Wisconsin solution (UW, group III; n = 11). Rat liver transplantation was performed with graft arterialization by the method of Engemann. Biopsies were taken for morphological examination and semiquantitative scoring during the donor operation, after 4 h of cold storage, 1 h after reperfusion, and 4 weeks postoperatively. An immunohistological bromodeoxyuridine (BrdU) assay was also performed on the day of dissection to assess the rate of hepatic proliferation. Semiquantitative morphological analysis gave widely differing results in all experimental groups after 4 h of ischemia. There was less intracellular and interstitial edema, fatty degeneration, intralobular necrosis, and hepatocellular proliferation in the HTK group than in the other groups. Neither after cold ischemia nor 1 h after reperfusion did Kupffer-cell activation occur; this is known to play a major role in the development ofischemia and reperfusion injury. Furthermore, late changes such as bile-duct proliferation and vascular and sinusoidal alterations appeared less frequently in this group. The hepato-protective powers of HTK solution might therefore be due to decreased Kupffer-cell activation.

Evaluation of hepatic microcirculation by in vivo microscopy

In vivo microscopy is an excellent technique for investigating the microcirculation and until recently the only one that allowed direct visualization. Rat liver has been widely studied, because microcirculatory disorders play a pivotal role in the pathogenesis of organ failure during hepatic ischemia, transplantation, hemorrhagic shock, endotoxemia, and sepsis. The state of the microcirculation is an important prognostic factor for the reestablishment of organ function after these injuries. This article introduces the most common procedures for in vivo microscopy of the rat liver, summarizes the available fluorescent dyes, and gives an overview of criteria for the expression and evaluation of microscopic findings. Particular emphasis is given to a description of the different parameters assessed by direct observation of hepatic microcirculation, such as perfusion rate, leukocyte-endothelium interactions, leukocyte velocities, and phagocytic activity. Examples of normal range values are given. This overview is intended to help those wanting to introduce this method into their research and who are embarking on intravital microscopy for the first time, and to enable them to decide which techniques are appropriate for answering special questions.

Callus formation and fixation rigidity: a fracture model in rats

To produce different amounts of callus in rats, we devised a procedure to fix leg fractures using intramedullary nails that differ in bending rigidity. We inserted a silicone cannula into the intact diaphysis of the tibia of rats that had already been killed and then fractured the tibia by a three-point bending technique. The fracture was stabilised by insertion of either a stainless-steel or polypropylene nail into the silicone cannula. Biomechanical testing showed that the initial stiffness of the fractures differed between the two nail types by a factor of 16. In vivo, 16 Wistar rats were operated on by the same technique to study the formation of callus. Four weeks after fracture, the size of the callus differed significantly between the steel-nailed and polypropylene-nailed fractures. In conclusion, mechanically differing internal fixation devices led to different callus responses in rats when all other factors were kept equal.

Involvement of endothelin/nitric oxide balance in hepatic ischemia/reperfusion injury

INTRODUCTION

Endothelin (ET) and nitric oxide (NO) act as opponents in the regulation of the hepatic microcirculation. During ischemia/reperfusion (I/R) ET levels are increased, whereas no rise in NO levels is observed. This imbalance may be responsible for microcirculatory disturbances. The aim of this study was to restore the delicate ET/NO balance to maintain the integrity of the hepatic microcirculation and to reduce I/R injury.

METHODS

Ischemia was induced by crossclamping of the hepatoduodenal ligament for 30 min with portal decompression using a splenocaval shunt (56 Wistar rats, 200-250 g). Sham operation, ischemia and treatment groups with the endothelin receptor antagonist (ERA) bosentan (1 mg/kg body weight i.v.) and the NO donor L-arginine (400 mg/kg body weight i.v.) were performed. For assessment of the microcirculation, sinusoidal perfusion rate, diameters of sinusoids and postsinusoidal venules, leukocyte endothelium interactions and velocity of free-flowing leukocytes were investigated by means of in vivo microscopy 30-90 min after reperfusion. Local hepatic tissue PO2 was measured prior to ischemia, 30 min and 60 min after reperfusion and aspartate aminotransferase (AST)/alanine aminotransferase (ALT) levels were investigated 2 h and 6 h after reperfusion.

RESULTS

After ischemia, sinusoidal and venular diameters were reduced to 76% and 85%, respectively, of sham operation group values (P<0.05), but were maintained at baseline in ERA (98/102%) and NO (102/105%) groups (P<0.05). Increased postischemic leukocyte sticking in sinusoids (144%) and venules (435%) was reduced by therapy to 110/253% (ERA) and 111/ 324% (NO), respectively (P<0.05). Perfusion rate was increased to 93% and 94% compared with 82% in the ischemia group (P<0.05). Concomitant with the improved microcirculation in therapy groups, local hepatic tissue pO2 was improved 30 min after reperfusion in the ERA (11.0 mmHg) and the L-arginine group (11.5 mmHg) relative to the ischemic group (6.9 mmHg) (P<0.05). In addition, postischemic AST/ALT increase was reduced by therapy.

CONCLUSION

Our results indicate that maintenance of ET/NO balance by blocking ET receptors, as well as providing a NO donor, protects the liver microcirculation and reduces hepatic I/R injury.

[Value of electrotherapy within the scope of conservative treatment of anorectal incontinence]

The following study reports on transanal electric stimulation as a conservative method of treatment in anal incontinence. In the centre of interest are clinical examinations on 45 patients that underwent a combined treatment with the IT-system 100 from Reha-Medi and pelvic floor training. A collective of 29 patients only treated with pelvic floor training was used as a control group. The results were based on a thorough medical history ascertainment and the corresponding clinical examinations at the beginning and end of the treatment. Our findings were classified according to the modified score of incontinence of Holschneider [16]. After therapy 42.2% of patients with electric stimulation therapy and 27.6% of the control group showed continence. 40 respectively 62.1% were non responder without relevant benefit. In the electric stimulation group the median score before and after therapy amounted to 6.57 versus 9.24 points. The control group achieved 6.72 respectively 8.58 points. The differences are statistically significant (p < 0.05, Student t-test). Concerning the results in relation to the cause of the incontinence, no significant differences between idiopathic and traumatic origin of the insufficiency of the sphincter mechanism are found in both groups. Therefore all variations of anorectal incontinence are seen as indication for treatment. The international literature as well as our own results confirm that electric stimulation is effective and may be in special cases a major factor in the conservative treatment of anorectal incontinence.

[Effect of forced organ cooling on microperfusion of donor livers]

With regard to the factors of graft damage the role of rapid cooling during cold in situ perfusion should not be underestimated. The aim of this study was to analyse the effect of rapid cooling on microperfusion of rat livers in an in vitro model.

MATERIAL AND METHODS

During harvest of 14 rat livers the organs' core temperature was monitored. Two groups were formed: (1) cold UW perfusion. (2) cold UW perfusion under additional graft cooling by iced water. Thereafter, isolated livers were perfused (4 degrees C. 1 h, 5 mmHg) monitoring the portocaval resistance, and liver enzyme release and pH levels in the perfusate. Finally, portal angiography of each liver was performed.

RESULTS

Rapid in situ cooling resulted in a decrease of the plateau temperature of the organ by 6.5 degrees C (p < 0.01). The pH slope in the perfusate and the enzyme release were diminished obviously, but not significantly. On the other hand, the portocaval resistance was increased by more than 20% (p < 0.05). Portal angiographies assessed by a special score expressed a marked deterioration of microperfusion in peripheral and subcapsular regions.

CONCLUSIONS

This study shows that rapid cooling results in worsened microperfusion of liver grafts. The effect of rapid cooling on function and histomorphology of transplanted livers should be analysed in further investigations.

Hepatic vein catheterization: a new technique in rats

Blood samples taken directly from the hepatic veins are often required for evaluation of liver function or ischemia/reperfusion injury and for direct determination of metabolic products of the liver. In the rat, blood samples are usually obtained by direct puncture of the hepatic veins. Successful catheterization of these small vessels is only possible under direct vision because great dexterity is needed to persuade the catheter to enter the hepatic vein. In this report a procedure for hepatic vein catheterization under direct vision is described in the rat. After performing a median laparotomy, a flexible catheter (Buchbinder, 3.0 F/1 mm, as used in cardiology) with a bent end is inserted into the infrahepatic vena cava. Under direct vision through the thin walls of the inferior vena cava the bent end of the catheter is slowly pushed up until the tip slides into a hepatic vein, which opens into the inferior vena cava at a right angle. Selective catheterization of the desired hepatic vein is possible by rotating the catheter and changing the position of its tip. This is a reliable new technique of hepatic vein catheterization in rats, by which blood samples can be collected directly from the hepatic veins.

Surgical techniques of orthotopic rat liver transplantation

Liver transplantation in rats is frequently used as a transplantation model. Although liver transplantation in larger laboratory animals such as dogs and pigs is technically easier, the rat has become the most important subject for experimental liver transplantation because of the availability of genetically defined animals. Numerous surgical techniques have been developed that permit the investigator to carry out studies with high clinical relevance. In this article the principal models of orthotopic rat liver transplantation and their technical modifications of vessel anastomoses, rearterialization, and bile duct reconstruction techniques are reviewed. More than 20 transplantation models are described in detail and demonstrated with clear illustrations. Finally, the advantages and uses of all the surgical procedures (e.g., suture and cuff anastomoses, bile duct anastomoses, and rearterialization techniques), specific problems, and survival criteria are discussed and the experiences of investigators who applied these techniques are analyzed. In conclusion, an overview and critical evaluation of all surgical techniques of orthotopic rat liver transplantation are given, together with instructions for learning these techniques.

[Measuring blood flow velocity in healthy and indomethacin-induced inflammation in rat small intestine serosa with FITC-marked erythrocytes]

Intravital microscopy was performed in normal and indomethacin-induced intestinal inflammation at serosal postcapillary venules of the small bowel in rats. Standard parameters of microcirculation as red blood cell velocity, diameter of venules, blood flow and adherent leucocytes were successfully investigated using FITC-labelled red blood cells. Since postcapillary venules are responsible for the venous drainage of the inflammed small bowel segments this method is reliable and effective for further investigation of intestinal microcirculation under special conditions such as intestinal inflammation.

Organ preservation with EC, HTK, and UW solutions in orthotopic liver transplantation in syngeneic rats. Part I: Functional parameters

Ischemic injury to the liver is known to influence the outcome of liver transplantation. In this study the efficacy of Euro-Collins (EC), histidine-tryptophan-ketoglutarate (HTK), and University of Wisconsin (UW) preservation solution was analyzed in the model of orthotopic liver transplantation in syngeneic rats. The study design was as follows: Group I, Euro-Collins solution (n = 11); Group II, Histidine-Tryptophan-Ketoglutarate solution (n = 11); Group III, University of Wisconsin solution (n = 11). The rat liver transplantation was performed with arterialization of the graft as described by Engemann. The postoperative follow-up was 28 days. The perfusion flow rate of the preservation solution measured during organ perfusion revealed lowest levels in the UW group and comparable levels in Groups I and II. Postoperative graft function was monitored by measuring liver enzymes (aspartate amino-transferase, ASAT, alanine aminotransferase, ALAT), bilirubin and bile production. The survival rate was 10/11 in each group. Liver enzymes and bilirubin increased postoperatively and went back to normal within 2 or 3 weeks. In contrast to bilirubin, the liver enzymes showed a biphasic increase with maxima on the 1st and 5th days (range: ALAT, 220-264 U/L; ASAT, 145-177 U/L). Bile production was observed in all groups, but was significantly higher after UW-preservation (P < .005). Analysis of inflammatory cells revealed high concentrations of intrasinusoidal leukocytes and lymphocytes in the graft with a maximum on the 5th day.

[Role of endothelin-nitrogen monoxide equilibrium in ischemia/reperfusion damage of the liver]

Elevated levels of endothelin (ET) are measured during ischemia and reperfusion, but no adequate increase of nitric oxide (NO) can be observed. Thus, the balance of both substances, which occurs under physiological conditions and regulates microcirculatory vessel widths, is disturbed. This leads to microcirculatory damages. As well ET receptor blocking using a mixed ET receptor antagonist as increase of NO production after L-arginine treatment influenced this pathomechanism. The preischemic sinusoidal diameters were maintained and leukocyte endothelial interactions reduced. Concomitantly, sinusoidal perfusion rate and local hepatic tissue pO2 were increased. Because of significant reduced hepatocellular damage in both therapy groups both therapeutical ways might exert beneficial effects to attenuate ischemia/reperfusion induced microvascular and tissue injury.

Orthotopic rat liver transplantation and bile duct reconstruction by a splint technique

The aim of the present study is to investigate the impact of bile duct reconstruction by a splint technique, a method which has not been sufficiently researched in animals after liver transplantation. Three experimental groups were set up: I = control, sham operation; II = bile duct reconstruction; III = orthotopic rat liver transplantation (ORLT). After bile duct reconstruction, serum levels of ASAT and ALAT in group II revealed a peak on the first postoperative day. The transplanted animals (group III) showed a second peak in liver enzyme levels on the fifth postoperative day; it was significantly higher than in group II. Serum bilirubin was more elevated in the transplant group, with a peak on day 7. Morphological investigations at the end of surgery revealed only intralobular necrosis and reactive changes in the liver capsule (group II); after transplantation (group III), there was also interstitial and intracellular edema, fatty degeneration and disintegration of the sinusoidal lining. One month later, necrosis, bile duct proliferation, cholestasis, cholangitis and vascular alterations were found in groups II and III. Furthermore, an increased rate of hepatocellular and bile duct proliferation was observed. These findings are partly due to the bile duct reconstruction. We recommend that a bile duct reconstruction control group should be included in ORLT experiments.

Cellular mechanisms of bone repair

The extent of callus formation about a bone fracture depends on the rigidity of fracture fixation. The mechanism that converts the mechanical stimulus into the biologic response is unknown. On the basis of existing literature, an attempt has been made to define a model that explains this mechanobiologic transduction. Once integrity of the bone has been disrupted, a sequence of biochemical and cellular events commences that induces inflammatory reactions. Messengers (e.g., metabolites of the clotting or complement system, eicosanoids, or growth factors) are released or activated. They control the migration, proliferation, and protein synthesis of cells that are essential for angiogenesis and connective tissue formation. The key component in this inflammatory sequence seems to be the macrophage. Growth factors (e.g., released by macrophages) stimulate endothelial cells to form capillaries and mesenchymal cells to synthesize their matrix. In mechanically neutral areas, the fracture cavity is revascularized and osteoblasts proliferate and form bone. In mechanically instable fracture areas, spreading capillaries are disrupted by shear forces. In these areas, therefore, the milieu becomes hypoxic again. This milieu seems to support the differentiation of chondrocytes that stabilize the fracture by cartilage formation. If the strength of repair tissue is surpassed, the disrupture of the repair tissue triggers the mechanisms of inflammation again and additional cells immigrate and proliferate. Their protein synthesis increases repair callus. The increase of callus formation, however, stops when the tissue is capable of resisting motion. Links to the callus formation in osteitis are shown.

Assessment of reperfusion injury by means of MR contrast agents in rat liver

The purpose of this study was to investigate whether extracellular MR contrast agents or intracellular liver-specific MR contrast agents may enable the assessment of liver reperfusion injury. Ischemia-related reperfusion was induced in 32 rats using Pringle's maneuver. Pringle's maneuver consisted of cross-clamping of the complete hepatoduodenal ligament for 45 minutes followed by 90 minutes of reperfusion. Two extracellular (gadopentetate dimeglumine and gadobutrol) and two intracellular gadoxetic acid and SH U 555 A) MR contrast agents were evaluated as model agents. Control animals and animals with liver ischemia were used to calculate changes in liver signal enhancement after Pringle's maneuver. Significant changes in liver signal after reperfusion injury were observed only with reticuloendothelial system (RES)-specific SH U 555 A. Liver signal enhancement after Pringle's maneuver with RES-specific SH U 555 A was decreased by 25.4% as compared with the control group. RES-specific contrast agents such as SH U 555 A seem to be more sensitive to ischemia-related dysfunction of the liver than hepatobiliary contrast agents such as gadoxetic acid or extracellular gadolinium chelates at different concentrations because Kupffer cells are more sensitive to liver ischemia than hepatocytes.

Effect of the endothelin receptor antagonist bosentan on postischemic oxygen supply of the liver

Endothelin evokes strong and longlasting constriction of postischemic sinusoids, leading to microcirculatory disturbances and local hypoxia, thereby causing liver damage. The aim of the study was to avoid the constrictive response of sinusoids by blocking endothelin receptors. In an in vivo ischemia-reperfusion model (21 female Wistar rats, 250-300 g) with portal decompression by a splenocaval shunt, hepatic ischemia was induced for 30 min by cross clamping of the hepatoduodenal ligament. The endothelin receptor antagonist bosentan (10 mg/kg bw IV) was administered before ischemia. The effect of the receptor antagonist was assessed by serum levels of aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) that were determined prior to ischemia, 2 and 6 h postoperatively. The local tissue pO2 was measured prior to inducing ischemia, 30 and 60 min after reperfusion. Application of 10 mg/kg bw endothelin receptor antagonist (ERA) intravenously did not influence the systemic blood pressure. The postischemic increase in serum ASAT and ALAT levels was diminished after receptor antagonist treatment (ASAT: p < .05). Local postischemic hepatic tissue pO2 was significantly decreased to 45% of basal values after 30 min and to 54.8% after 60 min of reperfusion (p < .05). Application of ERA results in a significant increase in local tissue pO2 to 110.9% of basal values after 30 min and to 90.7% after 60 min of reperfusion (p < .05). These data indicate that the endothelin receptor antagonist treatment results in a prevention of postischemic sinusoidal constriction avoiding hypoxia and leading to improved hepatocellular recovery.