Microdialysis monitoring of porcine liver metabolism during warm ischemia with arterial and portal clamping

Early detection of vascular complications following liver surgery is crucial. In the present study, intrahepatic microdialysis was used for continuous monitoring of porcine liver metabolism during occlusion of either the portal vein or the hepatic artery. Our aim was to assess whether microdialysis can be used to detect impaired vascular inflow by metabolic changes in the liver. Changes in metabolite concentrations in the hepatic interstitium were taken as markers for metabolic changes. After laparotomy, microdialysis catheters were introduced directly into the liver, enabling repeated measurements of local metabolism. Glucose, lactate, pyruvate, and glycerol were analyzed at bedside every 20 minutes, and the lactate/pyruvate ratio was calculated. In the arterial clamping group, the glucose, lactate, glycerol, and lactate/pyruvate ratio significantly increased during the 2-hour vessel occlusion and returned to baseline levels during the 3-hour reperfusion. In the portal occlusion group and in the control group, the measured metabolites were stable throughout the experiment. Our findings show that liver metabolism, as reflected by changes in the concentrations of glucose, lactate, and glycerol and in the lactate/pyruvate ratio, is markedly affected by occlusion of the hepatic artery. Surprisingly, portal occlusion resulted in no major metabolic changes. In conclusion, the microdialysis technique can detect and monitor arterial vascular complications of liver surgery, whereas potential metabolic changes in the liver induced by portal occlusion were not seen in the current study. Microdialysis may thus be suitable for use in liver surgery to monitor intrahepatic metabolic changes.

Generation of Hepatocyte-Like Cells from in Vitro Transdifferentiated Human Fetal Pancreas

Although the appearance of hepatic foci in the pancreas has been described in animal experiments and in human pathology, evidence for the conversion of human pancreatic cells to liver cells is still lacking. We therefore investigated the developmental plasticity between human embryonic pancreatic cells and liver cells. Cells were isolated and expanded from 7–8-week-old human fetal pancreata (HFP) and were characterized for the absence and presence of pancreatic and hepatic markers. In vitro expanded HFP were treated with fibroblast growth factor 2 (FGF2) and dexamethasone (DX) to induce a liver phenotye in the cells. These treated cells in various passages were further studied for their capacity to be functional in hepatic parenchyma following retrorsine-induced injury in nude C57 black mice. Amylase- and EPCAM-positive-enriched cells isolated from HFP and treated with FGF2 and DX lost expression of pancreatic markers and gained a liver phenotype. Hepatic differentiation was based on the expression (both at the mRNA and protein level) of liver markers albumin and cytokeratin 19. When transplanted in vivo into nude mice treated with retrorsine, both cell types successfully engrafted and functionally differentiated into hepatic cells expressing human albumin, glycogen, dipeptidyl peptidase, and γ-glutamyltranspeptidase. These data indicate that human fetal pancreatic cells have a capacity to alter their gene expression profile in response to exogenous treatment with FGF2 and DX. It may be possible to generate an unlimited supply of hepatocytes in vitro for cell therapy.

Intraperitoneal zinc administration increases extracellular zinc in the rat prefrontal cortex

Single administration of zinc evokes pharmacological behavioral effects in rodents, while no brain zinc alterations were detected. The aim of the present study was to examine the effect of a single zinc hydroaspartate intraperitoneal (ip) administration on the extracellular (synaptic) zinc concentration in the rat prefrontal cortex. We used anodic stripping voltammetric (ASV) method of zinc determination in microdialysate, which assays the extracellular zinc concentration. We report that acute (65 mg/kg) zinc hydroaspartate administration (ip) increases the extracellular zinc by 48% in the rat prefrontal cortex. These data for the first time demonstrate: 1) utility of ASV zinc detection in brain microdialysates and 2) that single ip zinc administration increases brain (cortical) extracellular zinc pool. The results indicate zinc-induced fast brain penetration and may explain its rapid pharmacological effects.

Isolation of mouse hepatocytes for transplantation: a comparison between antegrade and retrograde liver perfusion

We compared antegrade with retrograde liver perfusion when isolating mouse hepatocytes for hepatocyte transplantation. Male mouse hepatocytes were isolated by different perfusion methods and transplanted into the spleen of congeneic female mice. Retrograde perfusion yielded a larger number of cells (4.90 x 10(7)) than antegrade (4.09 x 10(7), p < 0.05), but hepatocytes obtained by antegrade perfusion gave higher engraftment efficiency (p < 0.05). More of the transplanted hepatocytes could be recovered from recipient liver with antegrade perfusion than with retrograde perfusion (p < 0.05). Our results indicate that hepatocytes isolated by antegrade perfusion gave a higher engraftment efficiency.

Liver transplantation for familial amyloidotic polyneuropathy (FAP): a single-center experience over 16 years

Orthotopic liver transplantation (LTx) is currently the only available treatment that has been proven to halt the progress of familial amyloidotic polyneuropathy (FAP). The aim of this study was to assess mortality and symptomatic response to LTx for FAP. All 86 FAP patients transplanted at our hospital between April 1990 and November 2005 were included in the study. Five patients underwent retransplantation. The 1-, 3- and 5-year patient survival rates in patients transplanted during 1996-2005 were 94.6%, 92.3% and 92.3%, respectively, a significant difference from the rates of 76.7%, 66.7% and 66.7%, respectively, during 1990-1995 (p = 0.0003). Multivariate analysis revealed that the age at the time of LTx (>or=40 years), duration of the disease (>or=7 years) and modified body mass index (mBMI) (<600) were independent prognostic factors for patient survival. A halt in the progress of symptoms was noted in most patients, but only a minority experienced an improvement after LTx. To optimize the posttransplant prognosis, LTx should be performed in the early stages of the disease, and close post-LTx monitoring of heart function by echocardiography and of heart arrhythmia by Holter ECG is mandatory.

Ethanol stimulates bile acid formation in primary human hepatocytes

The conversion of cholesterol to bile acids is a key pathway for elimination of cholesterol from the body, thereby reducing the risk of arteriosclerosis. Moderate consumption of ethanol has been shown to have preventive effects on cardiovascular disease and decrease the risk of gallstone formation. In the present study primary human hepatocytes were used to investigate if ethanol affected bile acid synthesis. Hepatocytes were prepared from donor liver (n=11) and treated with ethanol, 7.7 or 50 mM, for 24 h. mRNA levels for enzymes in bile acid synthesis pathways were studied and bile acid synthesis was analyzed. Treatment with 7.7 mM ethanol increased cholic acid synthesis by 20% and treatment with 50 mM ethanol up-regulated cholic acid formation by 60%. The synthesis of cholic acid increased more than that of chenodeoxycholic acid, indicating that the classical pathway for bile acid synthesis was up-regulated. Increased bile acid levels in the cells treated with ethanol were seen after approximately 20 h. mRNA expression of CYP7A1, CYP27A1, and CYP8B1 in the hepatocytes was not affected by alcohol exposure.

Anxiolytic-like action of MTEP expressed in the conflict drinking Vogel test in rats is serotonin dependent

The purpose of the present study was to investigate whether the anxiolytic-like action of a selective and brain penetrable group I metabotropic glutamate (mGlu5) receptor antagonist 3-[(2-methyl-1,3-tiazol-4-yl)ethynyl]-pyridine (MTEP) is dependent upon the serotonergic system. Experiments were performed on male Wistar rats. The Vogel conflict drinking test was used to detect anxiolytic-like activity. MTEP administered intraperitoneally at doses of 1, 3 and 6 mg/kg induced anxiolytic-like effect. The potential anxiolytic effect of MTEP (1 mg/kg) was inhibited by a nonselective 5-HT receptor antagonist metergoline (2 mg/kg i.p.) and 5-HT2A/2C receptor antagonist ritanserin (0.5 mg/kg i.p.), but not by a 5-HT1A receptor antagonist N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridynyl)cyclohexane-carboxamide (WAY 100635) (0.1 mg/kg i.p). The anxiolytic effect of MTEP (6 mg/kg) was attenuated by ritanserin (1 mg/kg i.p.). Moreover, MTEP-induced a dose-dependent release of serotonin in the frontal cortex. The obtained results suggest that the potential anxiolytic effect of the mGlu5 receptor antagonist MTEP is due to the increased serotonin release with subsequent activation of 5-HT2A/2C receptors, most probably located postsynaptically, but not by the 5-HT1A receptors.

Microdialysis monitoring for evaluation of the influence exerted by pneumoperitoneum on the kidney: an experimental study

BACKGROUND

Laparoscopic donor nephrectomy has become the first choice for living donor kidney transplantation, offering advantages over open donor nephrectomy. This study aimed to evaluate kidney tissue metabolism during and after pneumoperitoneum using a microdialysis technique.

METHODS

Eight pigs underwent laparotomy and implantation of two microdialysis catheters: one in the cortex and one in the medulla of the left kidney. After laparotomy, the abdominal wall was closed, and pneumoperitoneum was induced with a constant standard pressure of 16 to 18 mmHg for 4 h, followed by rapid desufflation. In microdialysis samples collected from intrarenal catheters, markers of ischemia (glucose, lactate, pyruvate, and lactate-pyruvate ratio) and the marker of cell membrane injury (glycerol) were monitored.

RESULTS

There were no changes in glucose, lactate, or pyruvate level before, during, or after pneumoperitoneum, either in the cortex or in the medulla. Additionally, the calculated lactate-pyruvate ratio did not show signs of ischemia during or after pneumoperitoneum. However, with regard to the marker of cell injury, glycerol increased in the medulla after decompression from 22.57 +/- 3.76 to 35.67 +/- 5.43 mmol/l (p < 0.01). This release of glycerol in the medulla was significantly higher than in the cortex (area under the curve [AUC], 22.18 +/- 4.87 vs 34.79 +/- 7.88 mmol/l; p < 0.01).

CONCLUSIONS

The pattern of metabolic changes monitored in the kidney during and after pneumoperitoneum indicates some kind of cell injury predominant in the medulla without any signs of kidney ischemia. This nonischemic injury could be related to hyperperfusion of the kidney after decompression or injury to cells attributable to mechanical cell expansion at the point of rapid decompression.

[Thrombin induced tumour growth - pharmacological control]

The central enzyme of blood coagulation, the serine proteinase thrombin, is capable to modify the growth of tumour cells by interaction with protease activated receptors 1 and 4 of the tumour cells. Thrombin is permanently available in tumour micro environment; meizothrombin is generated from prothrombin at a tumour specific activation complex and can influence tumour cell growth via PAR-1 and 7-transdomain protein receptor signalling pathway, too. PEG-coupled direct thrombin inhibitors that possess special pharmacokinetic characteristics and that have been designed for long lasting efficacy in extracellular space, control serine proteinase activity in tumour micro environment and therefore they own a high potential anti-tumour efficacy. In xenographic tumour models this new substance class has shown a significant carcinostatic effect.

Effect of extended cold ischemia time on glucose metabolism in liver grafts: experimental study in pigs

BACKGROUND/PURPOSE

Recovery of normal carbohydrate metabolism in the liver after transplantation is highly important. The aim of the present study was to evaluate how short and long cold ischemia (CI) time followed by warm ischemia (WI) impact intrahepatic glucose metabolism in a pig liver transplantation model.

METHODS

Twenty-six animals were divided into two transplantation groups: group I with a liver ischemia time of 5 h (n = 6), and group II with 15 h of liver ischemia (n = 7). Intrahepatic microdialysis samples were collected throughout the experiment at 20-min intervals, during the donor operation, cold preservation, liver implantation, and liver reperfusion in the recipient. Glucose, lactate, and pyruvate concentrations were analyzed and the lactate/pyruvate ratio (L/Pr) was calculated.

RESULT

There were no changes in glucose levels during CI. However, during WI, glucose and lactate increased and the increase was significantly higher in the group with longer CI (P < 0.01). The L/Pr increased at the beginning of CI but accelerated to increase during WI in both groups, with significantly prolonged and higher levels in the group with longer CI (P < 0.01).

CONCLUSIONS

Extended CI results in increased intrahepatic glycogenolysis, delayed restoration of aerobic glycolysis, and prolonged anaerobic glycolysis shortly after reperfusion. Improvements in glycogen protection and faster restoration of aerobic metabolism during preservation and reperfusion time seem to be necessary in order to improve liver preservation protocols per se.

Prospective Studies in Patients with Intraventricular Haemorrhage Without the Capacity to Give Consent in Germany - A Legal Dilemma

OBJECTIVE

The prognosis of intracranial haemorrhage with ventricular participation is poor. The acute onset of hydrocephalus has to be treated with an external ventricular drainage. However, intraventricular blood clots often obstruct the drainage catheter; the reinsertion is usually associated with an increased risk of complications. Therefore, intraventricular thrombolysis using recombinant tissue plasminogen activator (rt-PA), urokinase or streptokinase has been performed in several cases. In Germany, rt-PA does not have approval for intraventricular applications, and the risks and benefits of this treatment are as yet unclear. Several authors recommend its use only in the frame of prospective studies, meaning that intraventricular administration of thrombolytic agents within an individual therapy trial could be viewed as medical malpractice.

METHODS

We designed a national prospective randomised and controlled study in patients with intraventricular haemorrhage to investigate the risks and effects of intraventricular rt-PA treatment. The local ethics committee and lawyers did not accept the study protocol due to a non-acceptable risk of complications. In two further conferences, the risk of undertreatment in the control group was a major reason not to accept the protocol. We discuss the conflicts of law in related studies.

CONCLUSIONS

There is a need for a solution to the legal conflicts of medical malpractice, unclear risk-benefit ratio and unfeasibility due to risk of complications or undertreatment in studies with patients without the capacity to give informed consent.

Antidepressant-like activity of CGP 36742 and CGP 51176, selective GABAB receptor antagonists, in rodents

BACKGROUND AND PURPOSE

A crucial role for the GABAB receptor in depression was proposed several years ago, but there are limited data to support this proposition. Therefore we decided to investigate the antidepressant-like activity of the selective GABAB receptor antagonists CGP 36742 and CGP 51176, and a selective agonist CGP 44532 in models of depression in rats and mice.

EXPERIMENTAL APPROACH

Effects of CGP 36742 and CGP 51176 as well as the agonist CGP 44532 were assessed in the forced swim test in mice. Both antagonists were also investigated in an olfactory bulbectomy (OB) model of depression in rats, while CGP 51176 was also investigated in the chronic mild stress (CMS) rat model of depression. The density of GABAB receptors in the mouse hippocampus after chronic administration of CGP 51176 was also investigated.

KEY RESULTS

The GABAB receptor antagonists CGP 36742 and CGP 51176 exhibited antidepressant-like activity in the forced swim test in mice. The GABAB receptor agonist CGP 44532 was not effective in this test, however, it counteracted the antidepressant-like effects of CGP 51176. The antagonists CGP 36742 and CGP 51176 were effective in an OB model of depression in rats. CGP 51176 was also effective in the CMS rat model of depression. Administration of CGP 51176 increased the density of GABAB receptors in the mouse hippocampus.

CONCLUSIONS AND IMPLICATIONS

These data suggest that selective GABAB receptor antagonists may be useful in treatment of depression, and support an important role for GABA-ergic transmission in this disorder.

The use of PEG-Hirudin in chronic hemo-dialysis monitored by the Ecarin Clotting Time: influence on clotting of the extracorporeal system and hemostatic parameters

AIM

The aim of our study was to investigate the use of polyethylene glycol (PEG)-Hirudin (PEG-H) as an anticoagulant in hemodialysis including drug monitoring with the Ecarin Clotting Time (ECT) in whole blood and to compare this regimen with standard anticoagulant unfractionated heparin (UFH) for influence on hemostatic parameters and clot frequency of the extracorporeal system.

PATIENTS AND METHODS

The application of PEG-H as an anticoagulant in patients on chronic HD was studied in 20 patients (12 males, 8 females) from a single center in an exploratory, open-label, controlled, single-blind, dose-finding study. The patients were divided in 2 groups with 10 patients each (Group I and II); both received 3 dialyses with UFH, thereafter Group I received 5 dialyses with PEG-H and Group II 10 dialyses with PEG-H. Starting dose of PEG-H in the first dialysis was a bolus of 0.08 mg/kg bwt, the mean dose of the following HD was 0.041 mg/kg bwt (range 0.026 0.065 mg/kg bwt). PEG-H was applied as an intravenous bolus-dose followed by a 0.9% saline as a placebo-infusion. HD was performed regularly 3 times a week. All dialysis treatments were performed exclusively with a hollow fiber dialyzer type. Fibrinogen, antithrombin III, prothrombin fragments, thrombin-antithrombin and soluble fibrin were measured with commercial tests. ECT was determined in a mechanical coagulometer. A semiquantitative score was given for the presence of clots in the extracorporeal system after each dialysis.

RESULTS

PEG-H was effectively used as an anticoagulant in 150 chronic dialysis treatments using ECT as a simple monitoring method. The optimal whole blood concentration for PEG-H is 600-1000 ng/ml. Clotting in the whole extracorporeal system was decreased by 45% (p = 0.059) with PEG-H anticoagulated HD in comparison to UFH. Fibrinogen, prothrombin fragments (F1+2-fragments) and thrombin-antithrombin-complex showed no significant change in comparison with UFH, antithrombin III (AT III) increased to normal concentrations. Highly sensitive coagulation markers such as a soluble fibrin showed a significant decrease (p < 0.001) before and after HD with PEG-H compared with UFH.

CONCLUSION

PEG-H can be used effectively as an alternative anticoagulant in patients on chronic HD using ECT as a simple drug monitoring method. The lower frequency of clots in the extracorporeal system, the stronger and more efficient inhibition of coagulation during HD as indicated by soluble fibrin, may have a positive influence on the disturbed blood coagulation of these patients.

Chromogenic substrates as fundamental tool to design new thrombin inhibitors. Determination of inhibition equilibrium constants

The structure-activity relationship of dipetalogastin II, the strongest thrombin inhibitor isolated and cloned from the bug Dipetalogaster maximus, was examined by introducing gradual changes into the molecule by means of molecular biological methods. The effect upon its inhibition equilibrium constant was determined after each change by a chromogenic assay. This structural information was fundamental to design new dipetalogastin II-derived inhibitors. Our results suggested that the acidic sequence DEHDHDFEDT corresponding to amino acid residues 49 to 58 of dipetalogastin II reacts with the anion binding exosite (ABE) 1 of thrombin. Based on this finding, we constructed a chimeric molecule consisting of the active site blocking segment of dipetalogastin II (amino acid residues 1 to 48) and the ABE 1 blocking segment of hirudin. This construct showed better thrombin inhibitory activity than both separated segments only after the introduction of a glycine linker between both blocking segments. We thus obtained a thrombin inhibitor called dipetarudin with an inhibition equilibrium constant comparable to that of dipetalogastin II and a molecular mass below that of dipetalogastin.

[Ecarin chromogenic assay: an innovative test for quantitative determination of direct thrombin inhibitors in plasma]

The ecarin chromogenic assay (ECA) was developed for quantitative determination of direct thrombin inhibitors. As a further development of the ecarin clotting time (ECT), the ECA is based on the same principle, the activation of prothrombin by ecarin a snake venom from Echis carinatus. In the ECA the prothrombin activation products meizothrombin and meizothrombin-desF1 cleave a chromogenic substrate, whereas in the clotting assay ECT plasma fibrinogen is converted to fibrin. The activity of meizothrombin/meizothrombin-desF1 is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. The ECA can be used as ECA-H for quantitative determination of hirudin and as ECA-T for determination of synthetic thrombin inhibitors. As shown for hirudin, argatroban and melagatran, the ECA turned out as a very precise and sensitive method, which combines the advantages of ECT with those of chromogenic assays. In ECA very low interindividual variations were found compared to aPTT and even ECT. The ECA is independent of the variations of the coagulation variables prothrombin and fibrinogen.

Identification of expandable human hepatic progenitors which differentiate into mature hepatic cells in vivo

BACKGROUND

Liver diseases include a wide spectrum of both acute and chronic conditions which are associated with significant morbidity and mortality worldwide. Hepatocyte transplantation has therapeutic potential in the treatment of liver diseases, but its clinical use is hampered by the lack of donor tissue. Generation of hepatocytes in vitro from adult or fetal liver cell progenitors or, alternatively, identification of a progenitor population which in vivo can generate mature liver cells could solve this problem.

METHODS

CD117+/CD34+/Lin- human fetal liver cells were isolated by magnetic cell sorting and expanded in culture. Both freshly isolated and in vitro expanded cells in various passages were studied for their ability to be functional in hepatic parenchyma following d-galactosamine (GalN) induced injury in nude C57 black mice.

RESULTS

Freshly isolated and in vitro expanded CD117+/CD34+/Lin- cells, when transplanted intrasplenically into GalN treated mice, morphologically and functionally differentiated into hepatocytes and cholangiocytes. Human specific albumin, alpha fetoprotein, cytokeratin 19, and antitrypsin mRNA were expressed in mouse liver. In addition, the human progenitor cells expressed glucose-6-phosphatase, glycogen, albumin, gamma glutamyl transpeptidase, and dipeptidyl peptidase IV after transplantation. Expanded cells in various passages maintained their capacity to differentiate into functional liver cells.

CONCLUSIONS

Fetal liver CD117+/CD34+/Lin- progenitors and their progeny proliferated in vitro and also functionally differentiated into mature hepatic cells in an acute liver injury model. Successful in vitro expansion of liver progenitor cells provides a basis for developing cell therapy strategies, metabolic and toxicity testing systems, and may serve as a vehicle for gene therapy.

Cerebellar haemorrhage and tension pneumocephalus after resection of a Pancoast tumour

We present an unusual case of cerebellar haemorrhage followed by tension pneumocephalus several days after thoracotomy for resection of a Pancoast tumour. The postoperative course of the 32-year-old patient was complicated by a cerebellar haemorrhage and hydrocephalus caused by compression of the fourth ventricle. Immediate surgical evacuation of the haemorrhage and placement of an external ventricular drain was performed. Respirator ventilation maintaining a continuous positive airway pressure was required. Following weaning and extubation the patient rapidly deteriorated and became comatose. A cranial CT scan revealed a dilated ventricular system filled with air, and air in the subarachnoid space. Recovery of consciousness was observed after aspiration of intracranial air through the ventricular drainage. Recurrent deterioration of consciousness after repeated air aspiration indicated rapid refilling of the ventricles with air. The patient underwent emergency surgical re-exploration of the thoracic resection cavity: dural lacerations of the cervico-thoracic nerve roots C8 and Th1 were identified. Subarachnoid-pleural fistula, cerebellar haemorrhage and tension pneumocephalus after discontinuation of continuous positive airway pressure respiration are unusual complications of thoracic surgery. We discuss the putative pathomechanisms and present a brief review of the literature.

Ecarin chromogenic assay--a new method for quantitative determination of direct thrombin inhibitors like hirudin

A new sensitive and precise method for quantitative determination of direct thrombin inhibitors is described, the ecarin chromogenic assay (ECA). Ecarin is used as the specific prothrombin-activating principle. The cleavage of a chromogenic substrate by meizothrombin is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. For the ECA, the linear measuring range is about 0.1-3.0 microg hirudin/ml plasma. Coefficients of variations between 2.3 and 4% over the whole concentration range were achieved. The ECA has proved to be more sensitive than the compared tests (ecarin clotting time and a thrombin-based chromogenic assay); a detection limit of 0.011 microg hirudin/ml and a quantitation limit of 0.032 microg hirudin/ml were calculated. The ECA is independent of the variations of the coagulation variables fibrinogen and prothrombin. Neither heparin nor oral anticoagulants interfere with the ECA.

Famili�re Kavernome des Zentralnervensystems

In 1928, Hugo Friedrich Kufs reported on a family with cerebral, retinal, and cutaneous cavernous malformations. Since then, more than 300 families with inherited cavernous malformations have been reported. Genetic studies showed three loci, on chromosomes 7q21-q22 (with the gene CCM1), 7p15-p13 (CCM2), and 3q25.2-q27 (CCM3). The gene product of CCM1 is Krit 1 (Krev interaction trapped 1), a protein interacting with angiogenesis by various mechanisms. Recently, CCM2 has also been identified; its product is a protein which might have a function similar to that of Krit 1. However, the CCM3 gene has still not been found. In this study, we present clinical and genetic findings on 15 German families.

Chromogenic substrates as fundamental tool to design new thrombin inhibitors

The structure-activity relationship of dipetalogastin II, the strongest thrombin inhibitor isolated and cloned from the bug Dipetalogaster maximus, was examined by introducing gradual changes into the molecule by means of molecular biological methods. The effect upon its inhibition equilibrium constant was determined after each change by a chromogenic assay. This structural information was fundamental to design new dipetalogastin II-derived inhibitors.

Our results suggested that the acidic sequence DEHDHDFEDT corresponding to amino acid residues 49 to 58 of dipetalogastin II reacts with the anion binding exosite (ABE) 1 of thrombin. Based on this finding, we constructed a chimeric molecule consisting of the active site blocking segment of dipetalogastin II (amino acid residues 1 to 48) and the ABE 1 blocking segment of hirudin. This construct showed better thrombin inhibitory activity than both separated segments only after the introduction of a glycine linker between both blocking segments. We thus obtained a thrombin inhibitor called dipetarudin with an inhibition equilibrium constant comparable to that of dipetalogastin II and a molecular mass below that of dipetalogastin.

Three recombinant serine proteinase inhibitors expressed from the coding region of the thrombin inhibitor dipetalogastin

Dipetalogastin is a potent thrombin inhibitor from Dipetalogaster maximus. The cDNA of dipetalogastin codes for a large protein which consists of six Kazal-type domains. There are three tandem, homologous regions each including two domains. Three biologically active recombinant proteins rDI, rDII and rDIII each corresponding to one region of the dipetalogastin cDNA were expressed, purified and investigated with regard to their biological activities. rDI and rDII with molecular masses of 12,660 and 12,911 Da, respectively, proved to be potent thrombin inhibitors. The investigation of their influences on amidolytic activities of different serine proteases showed no inhibition of factor Xa (FXa) and alpha-chymotrypsin. At a large molar excess of rDI and rDII over the enzymes only low effects on the activities of trypsin and plasmin were observed. rDIII differs much from the both others. An inhibition of thrombin was found only at a molar excess of rDIII over the enzyme. Furthermore, an inhibition of trypsin and low effects on plasmin were detected at a molar excess of inhibitor over these enzymes. These results indicate that rDIII is active against thrombin, trypsin and plasmin, and finally possesses no specificity for only one serine proteinase.

[Platelet Adhesion Assay (PADA), a new quantitative test for assessment of platelet function and therapeutic drug monitoring of GPIIb/IIIa and ADP receptor antagonists]

Platelet ADhesion Assay (PADA) is a POCT capable method for quantitative determination of platelet adhesiveness. Using special polymer particles and test conditions adjusted to the physiologic conditions, the current functional state of blood platelets is determined directly from a whole blood sample. Within a short time, using little technical equipment and small sample volume, a therapeutic drug monitoring of GP IIb/IIIa and ADP receptor antagonists is possible, too. Whereas in healthy volunteers dose/effect curves of GP IIb/IIIa antagonists vary only slightly, in thrombopilic patients there are big variations. Differences in efficacy up to drug resistance may occur also in use of the ADP receptor antagonist clopidogrel. A therapeutic drug monitoring of GP IIb/IIIa- and ADP receptor antagonist therapy is essential and becomes feasible using PADA, also as long-term drug monitoring of ADP receptor antagonists and detection of drug resistance. Additionally, an individual ex vivo dose estimation for GP IIb/IIIa antagonists is possible. PADA allows diagnostics of pathological platelet function in thrombophilic patients as well as long-term therapeutic drug monitoring due to its simple handling.

[Monitoring of platelet function inhibitors: requirements for analytic strategies]

In this survey, the requirements for platelet function analysis are reviewed from a haemostaseologist's point of view. Problems and difficulties in platelet function diagnostics, i. e. in the methods and procedures used for measurement are described. Although drugs that interfere with certain parts of platelet function become more and more precise, we did not succeed in treating the patient with the optimal drug and in monitoring its efficacy accurately. A new quality of drug therapy is to be reached in order to immediately recognise idio-syncrasies, toxic reactions or drug induced side effects. For this, in time POCT methods should be used by medical staff. Furthermore, the methodical range of haemostaseologic laboratories should guarantee a high quality in acute and long-term drug monitoring.

Group III mGlu receptor agonists produce anxiolytic- and antidepressant-like effects after central administration in rats

It was well established that compounds which decrease glutamatergic transmission via blockade of NMDA or group I mGlu receptors produce anxiolytic- and antidepressant-like action in animal tests and models. Since group III metabotropic glutamate receptor (mGluR) agonists are known to reduce glutamatergic neurotransmission by the inhibition of glutamate release, we decided to investigate potential anxiolytic- and/or antidepressant-like effects of group III mGluR agonists, after central administration in rats. It was found that group III mGluR agonists, (1S,3R,4S)-1-aminocyclo-pentane-1,3,4-tricarboxylic acid (ACPT-I) and 2-amino-4-(3-hydroxy-5-methylisoxazol-4-yl)butyric acid (HomoAMPA), given intrahippocampally, produced a dose-dependent anxiolytic-like effect in the conflict drinking test. The effects of ACPT-I and HomoAMPA were reversed by (RS)-alpha-cyclopropyl-4-phosphonophenyl glycine (CPPG), group III mGluR antagonist. Moreover, a dose-dependent antidepressant-like action of group III mGluR agonists, ACPT-I and (RS)-4-phosphonophenylglycine (RS-PPG), but not HomoAMPA, was found in behavioral despair test, after intracerebroventricular injections, and the effect of ACPT-I was reversed by CPPG. The results obtained indicate that group III mGluR agonists produce anxiolytic- as well as antidepressant-like effects in behavioral tests, after central administration in rats. The reduction of glutamate release by group III mGluR activation may be a possible mechanism underlying anxiolytic- and antidepressant-like properties of the tested compounds. In conclusion, the results of our studies indicate that group III mGlu receptor agonists may play a role in the therapy of both anxiety and depression.

Synthesis of new hexahydro- and octahydropyrido[1,2-c]pyrimidine derivatives with an arylpiperazine moiety as ligands for 5-HT(1A) and 5-HT(2A) receptors, Part 2

The synthesis of new of 4-aryl-hexahydro- (11-16) and (R,R)(S,S)4-aryl-octahydropyrido[1,2-c]pyrimidine (23-27) derivatives bearing a aryl- or heteroarylpiperazinyl moiety in position 2 is described. The derivatives of 4-aryl-hexahydro- (1-5) and (R,R)(S,S)4-aryl-octahydropyrido[1,2-c]pyrimidin-1,3-dion (17-19) served as starting compounds for further synteses. The N-alkylation of the imide moiety in compounds 1-5 and 17-19 by 1,4-dibromobutane gave the respective monbromobutyl derivatives 6-10 and 20-22. The final derivatives 11-16 and 23-27 have been produced by condensation of the obtained bromoderivatives with selected 1-aryl and 1-heteroarylpiperazines. Compounds 11-16 and 23-27 were tested for their affinity towards 5-HT(1A), 5-HT(2A) and alpha1 receptors, using a radioligand binding assay.

Outcome and prognostic factors of hemicraniectomy for space occupying cerebral infarction

OBJECTIVE

To determine long term functional outcome and length of survival of patients undergoing decompressive craniectomy for space occupying infarction of the middle cerebral artery (MCA), and to identify risk factors associated with death and unfavourable outcomes

METHODS

Databases of patients undergoing decompressive craniectomy for space occupying MCA infarction compiled at eight neurosurgical departments (1996-2001) were merged, and 188 patients were evaluated. Mortality was calculated by the Kaplan-Meier method. Clinical outcome was rated using the Glasgow outcome scale (GOS). The prognostic impact of patient related covariates on length of survival and the GOS was analysed multivariately.

RESULTS

The unadjusted 3, 6, and 12 month mortality rates were 7.9%, 37.6%, and 43.8%, respectively (median follow up, 26 weeks). In the "best" multivariate model, age >50 years (p<0.02) and the involvement of two or more additional vascular territories (p<0.01) had an unfavourable impact on length of survival. The adjusted six month mortality was as low as 20.0% (no risk factor) and as high as 59.7% (two risk factors). A GOS score of <or=3 was significantly associated with age >50 years (p<0.0003): 34.9% of the patients <or=50 years of age achieved a GOS score of >3, as compared with 12.0% of the elderly subpopulation. The side of the infarct did not have prognostic relevance.

CONCLUSIONS

Results of surgical treatment in patients <50 years of age undergoing decompressive craniectomy are encouraging. The effectiveness of decompressive craniectomy for patients >50 years remains questionable and should be analysed in the framework of a prospective randomised study.

Monitoring von Plättchenfunktionsinhibitoren

In dieser Übersicht werden die Anforderungen an die Plättchenfunktionsanalytik aus Sicht des Hämostaseologen dargestellt. Die Probleme und Schwierigkeiten mit der Plättchenfunktionsdiagnostik, d. h. mit den Methoden bzw. Messverfahren, werden erörtert. Trotz immer spezifischer wirkender Pharmaka, die in bestimmte Teilmechanismen der Plättchenfunktion eingreifen, ist es noch immer nicht geglückt, den akut bedrohten Patienten mit dem optimalen Wirkstoff zu behandeln und dessen Wirksamkeit präzise messend zu verfolgen. Eine neue Qualität der Arzneimitteltherapie ist nötig, um sofort Idiosynkrasien, toxische Reaktionen oder substanzbedingte Nebenwirkungen zu erkennen. Hierzu sollten ereignisnahe POCT-Methoden durch das medizinische Personal zum Einsatz kommen. Doch auch das Methodenspektrum von hämostaseologischen Speziallabors soll genutzt werden, eine qualitätsgerechte Akut- und Langzeit-Therapieüberwachung zu gewährleisten.

PADA, der neue Plättchenadhäsionstest

Der Platelet ADhesion Assay (PADA) ist eine POCT-fähige Methode zur quantitativen Bestimmung der Plättchenadhäsivität. Durch spezielle Polymerpartikel und Testbedingungen, die den physiologischen Verhältnissen im Organismus angepasst sind, wird aus einer Vollblutprobe direkt der aktuelle Funktionszustand der Blutplättchen bestimmt.

Innerhalb kurzer Zeit, mit geringem Geräteaufwand und minimalem Probenvolumen ist auch ein therapeutisches Monitoring von Glykoprotein(GP)-IIb/IIIa- und ADP-Rezeptor-Antagonisten möglich. Während bei Gesunden die Dosis/Wirkungskurven der GP-IIb/IIIa-Antagonisten nur gering variieren, schwanken sie bei thrombophilen Patienten stark. Wirkungsunterschiede bis zur Arzneimittelresistenz treten auch beim ADP-Rezeptor-Antagonisten Clopidogrel auf. Ein therapeutisches Monitoring der GP-IIb/IIIa- und ADP-Rezeptorantagonisten ist essenziell und mittels PADA realisierbar – auch als Langzeit-Monitoring für ADP-Rezeptorantagonisten sowie zur Detektion einer Arzneimittelresistenz. Mit dem PADA ist eine individuelle Ex-vivo-Dosisrelation für GP-IIb/IIIa-Antagonisten möglich. Der PADA erlaubt die Diagnostik einer pathologisch veränderten Plättchenfunktion thrombophiler Patienten und durch die einfache Handhabung auch die Therapieüberwachung über längere Zeit.

Evaluation of some aroxyethylamine derivatives for hypotensive properties and their affinities for adrenergic receptors

A series of aroxyethylamines (1-10) was synthesized and evaluated for hypotensive activity in rats after intravenous and oral administration. The 4 compounds (4, 7, 8 and 10) containing a (2-methoxy)phenylpiperazine moiety displayed hypotensive activity and their affinities for alpha1-, alpha2- and beta1-adrenoreceptors were determined by radioligand binding assays. Compounds 4, 7, 8 and 10 were also tested for their effect on the pressor responses to epinephrine, norepinephrine, methoxamine, tyramine and DMPP. The results suggest that the hypotensive effect of these compounds is related to their alpha- and beta-adrenolytic properties.

Remifentanil-propofol versus sufentanil-propofol anaesthesia for supratentorial craniotomy: a randomized trial

BACKGROUND AND OBJECTIVE

Remifentanil has unique pharmacokinetics that might allow faster recovery after neurosurgery. We investigated the effects of a propofol/sufentanil versus a remifentanil/propofol regimen on the primary end-point tracheal extubation time.

METHODS

In the Neurosurgery Department of a University Hospital, 36 patients awaiting craniotomy for supratentorial tumour resection were randomly assigned to one of two study groups. In the sufentanil/propofol group, anaesthesia was induced with 0.5 microg kg(-1) sufentanil and 1-2 mg kg(-1) propofol. Propofol infusion and boluses of sufentanil were administered for maintenance. In the remifentanil/propofol group, anaesthesia was started with an infusion of remifentanil (0.2-0.35 microg kg(-1) min(-1)) and a bolus of propofol (1.5-2 mg kg(-1)). Patients received a propofol infusion and a remifentanil infusion for maintenance of anaesthesia. Recovery times were taken from cessation of the propofol infusion. In addition, data about self-reported nausea and vomiting, pain and analgesic requirements were collected.

RESULTS

Patients in the remifentanil/propofol group were extubated earlier (mean times 6.4 (+/- SD 4.7) versus 14.3 (+/- 9.2) min; P = 0.003). The two groups were similar with respect to postoperative nausea and vomiting, and patient-reported pain scores. Fifty per cent of the remifentanil/propofol patients and 88% of the sufentanil/propofol patients required no analgesics within 1 h after operation (P = 0.03).

CONCLUSIONS

The remifentanil/propofol regimen provided quicker recovery. The two regimens were similar in terms of postoperative nausea and vomiting and patient-reported pain scores, but patients in the remifentanil/ propofol group required more analgesics within 1 h postoperatively.

Influence of displayed image size on radiographic detection of approximal caries

OBJECTIVES

To evaluate the validity of approximal caries detection on digital bitewing radiographs displayed at different image sizes on either a cathode ray tube (CRT) monitor or a thin film transistor (TFT) monitor.

METHODS

Five observers assessed digital radiographs of a charge-coupled device (CCD)-based sensor system (Sidexis) of 160 unrestored premolars and molars for approximal caries using a six category caries rating scale. Images were displayed at ratios of 1:1, 1:2 and 1:7 on a CRT monitor (Nokia 446 XS) and a TFT display (Panasonic LC 50S). Histological assessments of serial sections were used as the validation standard. Diagnostic accuracy was expressed as area under the receiver operating characteristic (ROC) curve (AUC) and was calculated at two levels of caries penetration: presence of caries (I) and presence of a lesion in the dentine (II). The influence of the factors "monitor type", "image size" and "validation threshold" were analysed with repeated measures analysis of variance.

RESULTS

The ROC curve areas for approximal caries detection at both histological penetration levels were not influenced by the type of monitor display, whereas image size had a significant impact (P<0.01). AUCs for image size 1:7 (I, 0.62; II, 0.65) were smaller compared with ratios of 1:1 and 1:2 (P<0.01). No differences were observed between image size ratios 1:1 (I, 0.69; II, 0.74) and 1:2 (I, 0.68; II, 0.73).

CONCLUSIONS

In this study, the type of monitor did not influence approximal caries detection on digital radiographs. Image sizes with a display ratio of 1:1 and 1:2 resulted in better diagnostic validity than those with a ratio of 1:7.

Central activity of new xanthone derivatives with chiral center in some pharmacological tests in mice

The study was designed to investigate some central effects of chiral xanthone derivatives [(R,S)-2-N-(6-chloro-2-xanthonemethyl)-amino-1-propanol - MH-31, R enantiomer - MH-32 and S enantiomer - MH-33] in mice. The effects of these chiral compounds were examined in picrotoxin-induced seizures, spontaneous locomotor activity and chimney tests. The tested compounds demonstrated variable influence on the central nervous system in mice. The compound MH-32 exhibits anticonvulsant activity in picrotoxin-induced seizures, whereas MH-31 and its R enantiomer--compound MH-32 demonstrated antidepressant-like activity in the forced swimming test. Moreover, all tested xanthones reduced the locomotor activity in mice. The obtained results indicate the importance to examine pharmacologically enantiomers rather than only racemic mixtures of newly synthesized compounds.

Cloning, purification and biochemical characterization of dipetarudin, a new chimeric thrombin inhibitor

The development of thrombin inhibitors could provide invaluable progress for antithrombotic therapy. In this paper, we report the cloning, purification and biochemical characterization of dipetarudin, a chimeric thrombin inhibitor composed of the N-terminal head structure of dipetalogastin II, the strongest inhibitor from the assassin bug Dipetalogaster maximus, and the exosite 1 blocking segment of hirudin, connected through a five glycine linker. The cloning of dipetarudin was performed by a simple method which had not been used previously to clone chimeras. Biochemical characterization of dipetarudin revealed that it is a slow, tight-binding inhibitor with a molecular mass (M(r)=7560) and a thrombin inhibitory activity (K(i)=446 fM) comparable to r-hirudin.

Clinical experience in continuous graft monitoring with microdialysis early after liver transplantation

BACKGROUND

Early detection of impaired graft function after transplantation is essential. Microdialysis permits continuous monitoring of metabolic changes by mimicking the passive function of a capillary blood vessel by perfusion of a tubular semipermeable membrane introduced into the tissue. Based on the results of animal experiments, a clinical pilot study was undertaken.

METHODS

Ten consecutive patients undergoing whole-organ orthotopic liver transplantation were studied. Intrahepatic implantation of a microdialysis catheter was performed at the end of the operation. A reference catheter was placed in the subcutaneous tissue over the right pectoral area immediately after abdominal closure. Consecutive serial samples were collected at 1-h intervals for 3 days after the operation. Glucose, lactate, pyruvate and glycerol concentrations were measured.

RESULTS

During the first 24 h, the glucose level was higher in the liver than in reference tissue. Initially, increased mean(s.e.m.) levels of lactate (7.0(1.9) mmol/l) were observed in the liver, with a rapid decrease (to 2.7(0.3) mmol/l) over 24 h. A decrease in, and later stabilization of, the lactate : pyruvate ratio in the liver, from 18.7(4.2) to 10.0(1.1), was observed within 24 h after transplantation. Liver glycerol levels decreased from 62.3(7.4) to 24.3(7.5) micro mol/l within the first 16 h after reperfusion and remained stable thereafter.

CONCLUSION

Microdialysis allows continuous monitoring of tissue metabolism in the transplanted liver. The procedure is easy to perform and safe. The specific detection and monitoring of pathological changes in the liver graft (e.g. arterial and portal vein thrombosis, or early rejection) with microdialysis should be addressed in further studies.

[Rationale for an oral thrombin inhibitor from a pharmacological point of view]

Direct thrombin inhibitors are in focus of interest for hereditary or acquired thrombophilic indications. Besides thrombosis prophylaxis in surgery, life-threatening cardiac diseases and stroke are of special interest for this new drug class. For long-term prophylaxis of genetically caused thrombophilia the only drug class currently available are the orally active dicoumarol derivatives. Their application is a time and cost intensive procedure and associated with side effects, too. Active site-directed inhibitors block the catalytic triad of the active centre of thrombin responsible for hydrolytic cleavage. Inhibitor ratios (K(j)) are in the nanomolar or picomolar range. As these substances are eliminated via liver or kidneys with an elimination half-life of 0.3-2 hours, parenteral administration should be used for acute therapy and prophylaxis. For long-term prophylaxis, orally absorbable derivatives of these direct thrombin inhibitors are available with absorption rates of 10-30%. They are converted into their parent substance in blood. Therapeutical range is relatively large so that an oral long-term prophylaxis using standard dose is possible without monitoring. The first representative of this new drug class, Ximelagatran, an orally absorbable variant of Melagatran, is currently undergoing phase III trials for different indications. Using oral administration of two partial doses per day, a good compliance is expected.

Multiple MPEP administrations evoke anxiolytic- and antidepressant-like effects in rats

Several lines of evidence suggest a crucial involvement of glutamate in the mechanism of action of anxiolytic and antidepressant drugs. The involvement of group I mGlu receptors in anxiety and depression has also been proposed. In view of the recent discovery of anxiolytic- or antidepressant-like effects of acute injections of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective and brain penetrable mGlu5 receptor antagonist, we designed the present study to examine anxiolytic- and/or antidepressant-like effects of multiple administrations of this drug. The anxiolytic-like effects of MPEP were evaluated in rats using the conflict drinking test. The antidepressant-like effect was estimated using the rat olfactory bulbectomy model of depression. Seven subsequent injections of MPEP (1 mg/kg) significantly (by 320%) increased the number of shocks accepted during the experimental session in the Vogel test. MPEP given once daily at a dose of 10 mg/kg, restored the learning deficit of bulbectomized rats after 14 days of treatment, remaining without any effect in the sham-operated animals. N-methyl-D-aspartic acid (NMDA)-induced convulsions in mice were not affected by a single injection of MPEP (30 mg/kg) indicating that at this dose MPEP did not block NMDA receptors. The results indicate that the prolonged blockade of mGlu5 receptors exerts anxiolytic- and antidepressant-like effects in rats. No tolerance to anxiolytic-like action occurs. The previously mentioned results further indicate that antagonists of group I mGlu receptors may play a role in the therapy of both anxiety and depression.

[Contrast-enhanced intracranial 3 D MR angiography (CE-MRA) in assessing arterial stenoses and aneurysms]

PURPOSE

The aim of this study was to evaluate the diagnostic potential of CE-MR angiography in intracranial arterial stenoses and aneurysms.

MATERIAL AND METHODS

Thirteen patients with intracranial arterial stenoses and ten patients with aneurysms, including 6 cases with GDC coil-occluded aneurysms, were examined by both 3 D TOF-MR angiography and CE-MR angiography. In cases of stenoocclusive diseases colour-coded duplex sonography and in cases of aneurysms arterial digital subtraction angiography served as reference method.

RESULTS

Both TOF-MRA and CE-MRA could well depict filiform stenosis. In contrast to TOF-MRA, CE-MRA did not show any false positive stenosis or occlusion in regions of turbulent or slow blood flow. Stenoses of the medial cerebral artery could not be graded sufficiently by CE-MRA. In aneurysms the parent vessel was better shown by TOF-MRA. CE-MRA, however, more sensitively detected reperfusion in GDC coil-occluded aneurysms.

CONCLUSION

Stenoses of small vessels were graded less exactly by CE-MRA than by TOF-MRA due to lower spatial resolution. CE-MRA, however, seems to be superior in regions of turbulent or slow blood flow. CE-MRA also offers advantages in follow-up examinations of coil-occluded aneurysms.

Influence of room lighting on grey-scale perception with a CRT-and a TFT monitor display

OBJECTIVES

To determine the influence of ambient lighting on grey-scale perception using a cathode-ray tube (CRT) and a thin film transistor (TFT) computer display.

METHODS

A cathode ray tube (Nokia XS 446) and a liquid crystal display (Panasonic LC 50S) were used at reduced room lighting (70 lux) and under conditions recommended for a dental operatory (1000 lux). Twenty-seven observers examined twice a modified SMPTE test pattern [0 to 255; 255 to 0] grey-scale values. The corresponding contrast differences were allocated to four ranges of grey levels (I: 0-63; II: 64-127; III: 128-191; IV: 192-255). The influences of monitor type, grey-scale range and illumination were evaluated by means of repeated measures analysis of variance.

RESULTS

Detection of differences in monochromatic intensity was significantly earlier with reduced lighting (P<0.0001). When full ambient lighting was used, the TFT display was superior compared to the CRT monitor in ranges II and III (P<0.0001), whereas no differences could be detected for grey intensities between 0 and 63 (P=0.71) and between 192 and 255 (P=0.36).

CONCLUSIONS

Background lighting hampers grey-scale perception on computer displays. In this study of one TFT and one CRT monitor, the TFT in full ambient lighting was associated with earlier detection of grey scale differences than CRT.

Rationale für einen oralen direkten Thrombininhibitor aus pharmakologischer Sicht

Direkte Thrombininhibitoren stehen im Fokus für angeborene oder erworbene Thrombophilie-Indikationen. Neben der Thromboseprophylaxe bei Operationen sind lebensbedrohliche kardiale Erkrankungen und der Schlaganfall von besonderem Interesse für diese neue Arzneimittelklasse. Die Langzeitprophylaxe bei angeborener oder erworbener Thrombophilie mit Hilfe der einzigen zurzeit verfügbaren Substanzklasse, der oral wirksamen Dicoumarolderivate, ist zeit- und kostenintensiv sowie mit unerwünschten Arzneimittelwirkungen behaftet. Gegen das aktive Zentrum gerichtete Inhibitoren blockieren die zur hydrolytischen Spaltung erforderliche katalytische Triade im Thrombinmolekül mit Ki-Werten im nano- oder picomolaren Bereich. Für die Akuttherapie und kurzfristige Prophylaxe sollte die parenterale Applikation erfolgen, da diese Substanzen in der Leber metabolisiert und/oder durch die Nieren mit einer Eliminationshalbwertzeit von 0,3-2 Stunden eliminiert werden. Für die Langzeitprophylaxe sind oral resorbierbare Derivate dieser direkten Thrombininhibitoren mit Resorptionsraten von 10-30% verfügbar, die im Blut in die Muttersubstanz umgewandelt werden. Der therapeutische Bereich ist relativ groß, sodass eine orale Langzeitprophylaxe mit einer Standarddosis ohne Monitoring möglich sein kann. Der erste Vertreter dieser neuen Arzneimittelklasse, das Ximelagatran, eine oral resorbierbare Variante des Melagatrans, befindet sich derzeit in Phase-III-Prüfungen für verschiedene Indikationen. Mit einer oralen Gabe von zwei Teildosen pro Tag kann eine gute Compliance erwartet werden.