Evaluation of diffuse pollution model applications in EUROHARP catchments with limited data.

The application of diffuse pollution models included in EUROHARP encompassed varying levels of parameterisation and approaches to the preparation of input data depending on the model and modelling team involved. Modellers consistently faced important decisions in relation to data interpretation, especially in those catchments with unfamiliar physical or climatic characteristics, where catchment conditions were beyond the range for which a particular model was originally developed, or where only limited input data were available. In addition to a broad discussion of data issues, this paper compares the performance of the four sub-annual output models tested in EUROHARP (EveNFlow, NL-CAT, SWAT and TRK) in three test catchments without the modelling teams having sight of measured flow and nitrate concentration data. Model performance in this "blind test" indicate that the range of predictions generated by any individual models pre and post calibration exceed the differences between the estimates yielded by all four models. Comparison of Analysis of Variance (ANOVA) statistics for simulated and observed flow, concentration and loads underscores the benefits of calibration for these intermediate and complex model formulations. Interpretation of input data (e.g. rainfall interpolation method and pedotransfer functions selected) appeared equally (or more) important than process representation. In the absence of calibration data, modeller unfamiliarity with a particular catchment and its environmental processes sometimes resulted in questionable assumptions and input errors which highlight the problems facing modellers charged with implementing policies under the Water Framework Directive (2000/60/EC) in poorly monitored catchments. Catchment data owners and modellers must therefore work more closely given that the output from diffuse pollution models is clearly modeller-limited as well as model-limited.

Description of nine nutrient loss models: capabilities and suitability based on their characteristics.

In EUROHARP, an EC Framework V project, which started in 2002 with 21 partners in 17 countries across Europe, a detailed intercomparison of contemporary catchment-scale modelling approaches was undertaken to characterise the relative importance of point and diffuse pollution of nutrients in surface freshwater systems. The study focused on the scientific evaluation of different modelling approaches, which were validated on three core catchments (the Ouse, UK; the Vansjo-Hobøl, Norway; and the Enza, Italy), and the application of each tool to three additional, randomly chosen catchments across Europe. The tools involved differ profoundly in their complexity, level of process representation and data requirements. The tools include simple loading models, statistical, conceptual and empirical model approaches, and physics-based (mechanistic) models. The results of a scientific intercomparison of the characteristics of these different model approaches are described. This includes an analysis of potential strengths and weaknesses of the nutrient models.

Evaluation of the difference of eight model applications to assess diffuse annual nutrient losses from agricultural land.

The capability of eight nutrient models to predict annual nutrient losses (nitrogen and phosphorus) at catchment scale have been studied in the EUROHARP project. The methodologies involved in these models differ profoundly in their complexity, level of process representation and data requirements. This evaluation is focused on model performance in three core catchments: the Vansjø-Hobøl (Norway), the Ouse (Yorkshire, UK) and the Enza (Italy). These three different model applications have been evaluated by comparing calculated annual nutrient loads (total N or nitrate and total P), based on observed flow and total nitrogen or nitrate and total phosphorus concentrations, and the annual nutrient loads that were simulated by the eight nutrient models. Four statistics have been applied for this purpose: the root mean squared error (RMSE), the mean absolute error (MAE), the mean error (ME), and Nash-Sutcliffe's model efficiency (NS). The results show that all model approaches can predict the calculated annual discharges. Depending on the observed statistics (RMSE, MAE, ME and NS) the scores of the model application differed, therefore no overall 'best model' could be identified. Although the water and nutrient loads from (sub)catchments can be predicted, the modelled pathways of nutrients within agricultural land and the nutrient losses to surface waters from agricultural land vary among the catchments and among those model approaches which are able to make this distinction.

Nitrogen and phosphorus retention in surface waters: an inter-comparison of predictions by catchment models of different complexity.

Nitrogen and phosphorus retention estimates in streams and standing water bodies were compared for four European catchments by a series of catchment-scale modelling tools of different complexity, ranging from a simple, equilibrium input-output type to dynamic, physical-based models: source apportionment, MONERIS, EveNFlow, TRK, SWAT, and NL-CAT. The four catchments represent diverse climate, hydrology, and nutrient loads from diffuse and point sources in Norway, the UK, Italy, and the Czech Republic. The models' retention values varied largely, with tendencies towards higher scatters for phosphorus than for nitrogen, and for catchments with lakes (Vansjø-Hobøl, Zelivka) compared to mostly or entirely lakeless catchments (Ouse or Enza, respectively). A comparison of retention values with the size of nutrient sources showed that the modelled nutrient export from diffuse sources was directly proportional to retention estimates, hence implying that the uncertainty in quantification of diffuse catchment sources of nutrients was also related to the uncertainty in nutrient retention determination. This study demonstrates that realistic modelling of nutrient export from large catchments is very difficult without a certain level of measured data. In particular, even complex process oriented models require information on the retention capabilities of water bodies within the receiving surface water system and on the nutrient export from micro-catchments representing the major types of diffuse sources to surface waters.

Ensemble modelling of nutrient loads and nutrient load partitioning in 17 European catchments.

An ensemble of nutrient models was applied in 17 European catchments to analyse the variation that appears after simulation of net nutrient loads and partitioning of nutrient loads at catchment scale. Eight models for N and five models for P were applied in three core catchments covering European-wide gradients in climate, topography, soil types and land use (Vansjø-Hobøl (Norway), Ouse (Yorkshire, UK) and Enza (Italy)). Moreover, each of the models was applied in 3-14 other EUROHARP catchments in order to inter-compare the outcome of the nutrient load partitioning at a wider European scale. The results of the nutrient load partitioning show a variation in the computed average annual nitrogen and phosphorus loss from agricultural land within the 17 catchments between 19.1-34.6 kg N ha(-1) and 0.12-1.67 kg P ha(-1). All the applied nutrient models show that the catchment specific variation (range and standard deviation) in the model results is lowest when simulating the net nutrient load and becomes increasingly higher for simulation of the gross nutrient loss from agricultural land and highest for the simulations of the gross nutrient loss from other diffuse sources in the core catchments. The average coefficient of variation for the model simulations of gross P loss from agricultural land is nearly twice as high (67%) as for the model simulations of gross N loss from agricultural land (40%). The variation involved in model simulations of net nutrient load and gross nutrient losses in European catchments was due to regional factors and the presence or absence of large lakes within the catchment.

Antiaggregatory, physiological and clinical effects of ticlopidine in subjects with peripheral atherosclerosis.

Twelve patients with varying degrees of peripheral atherosclerotic disease were given an antiaggregatory drug, ticlopidine [5-(6-chlorobenzyl)-4,5,6,7-tetrahydrothieno-(3,2-C)-pyridine HCl] in a single blind trial for one or four months and the effects on platelet aggregation, blood coagulation, marcro- and micro-circulation and walking distance were studied. Two patients were excluded; one because of nausea attributable to the drug, one because of lack of co-operation. No statistically significant changes in circulation parameters or walking distance were noted. No changes were observed in APT-time, thrombine- and Reptilase-clotting time, platelet counts, concentrations of fibrinogen and fibrinopeptide A in plasma or serum antithrombin activity. The mean concentration of fibrinopeptide A was slightly increased in all patients. ADP-induced aggregation was inhibited in all patients. Aggregation induced by arachidonic acid was partially inhibited but not abolished in all patients. Prostaglandin G2-induced aggregation was not altered by ticlopidine but collagen-induced aggregation was inhibited. Ticlopidine, in contrast to acetyl-salicylic acid, inhibits the primary aggregation but also seems to interfere with the release action. Treatment of larger patient groups for longer periods are necessary to determine the clinical usefulness of ticlopidine.

Heparin, DDAVP and the bleeding time.

The effect on the bleeding time of heparin, followed by an infusion with desmopressin (DDAVP) 0.3 micrograms/kg or placebo in a randomized, double-blind set-up, was investigated in 20 patients treated for acute venous thromboembolism. The bleeding time was on the average prolonged by 90% (95% confidence interval 46%-134%) after at least 1 day of treatment with heparin. At that point DDAVP shortened the bleeding time by 23% with a confidence interval of -35% to -11% whereas the effect of placebo was -2% with a confidence interval of -23% to +20%. There was also a shortening of the APTT after DDAVP but not after placebo. It is concluded that DDAVP induces a partial reversal of the effect of heparin on the bleeding time, and that DDAVP should be tried in case of hemorrhagic problems.

In vivo effects of a low molecular weight heparin fragment on platelet aggregation and platelet dependent hemostasis in dogs.

Plasma defibrinogenated dogs were used to study the influence of conventional heparin and a low molecular weight heparin fragment (Fragmin, mean MW 5,000 d) on platelet dependent hemostasis. The heparins were given intravenously in gravimetrically equal doses. The bleeding from standardized skin flap wounds and platelet aggregation (ADP and thrombin) was studied. In comparison, higher doses of the fragment than of heparin were required to increase the bleeding. ADP-induced aggregation in defibrinogenated platelet rich plasma (after addition of normal dog plasma) was potentiated by both heparins. After injection of heparin or the fragment, ADP induced platelet aggregation without prior addition of normal plasma to the test-tube. In conclusion the heparin fragment affected bleeding to a less extent than conventional heparin. One explanation might be a weaker inhibition of thrombin-induced platelet aggregation.

Comparison of once-daily subcutaneous Fragmin with continuous intravenous unfractionated heparin in the treatment of deep vein thrombosis.

Two hundred and four consecutive patients with venographically confirmed deep vein thrombosis (DVT) were randomised either to a low molecular weight heparin, Fragmin, administered subcutaneously (s.c.) once daily as a fixed dose of 200 IU anti-factor Xa/kg or to continuous intravenous infusion of unfractionated heparin (UFH). The UFH dose was adjusted to maintain the activated partial thromboplastin time between 1.5 and 3.0 times the upper limit of the reference value at each centre. Fragmin or UFH was given for a minimum of 5 days until anticoagulation with warfarin, given from day 1, was established (i.e. an Internation Normalised Ratio, of 2.0-3.0). A second venogram was obtained after Fragmin or UFH treatment. There were no significant differences in the change in mean Marder score before and after treatment between the two treatment groups, irrespective of thrombus localisation. No major bleeding events, symptomatic pulmonary embolism, symptomatic thrombosis progression or death occurred during hospitalisation. Eight documented venous thromboembolic events occurred before the follow-up visit 6 months after randomisation: 5 in patients treated with Fragmin and 3 in those treated with UFH. Six of these events occurred after cessation of warfarin treatment. In conclusion Fragmin given s.c. once daily in a fixed dose adjusted for body weight, is no less effective or safe than a continuous infusion of UFH in the initial treatment of acute DVT.

A 6-month venographic follow-up in 164 patients with acute deep vein thrombosis.

UNLABELLED: A total of 164 patients were recruited from a randomized trial comparing a low molecular weight heparin, dalteparin, given subcutaneously once daily with a continuous intravenous infusion of unfractionated heparin in the initial treatment of acute deep vein thrombosis. The primary objective of this follow-up study was to investigate whether there were any differences between the two treatment groups with respect to Marder score changes 6 months after the initial diagnosis using repeated venography. The secondary objectives were to analyse whether certain haemostatic and acute phase parameters or patient characteristics influenced the venographic outcome. RESULTS: Complete lysis of the thrombus was observed in 38.4% of the patients and a partial lysis in another 54.3% assessed by venography 6 months after the acute event. Extension of the thrombus was seen in 7.3% of the patients. There were no significant differences in the change in mean Marder score before treatment and at the 6 month follow-up between the two treatment groups, irrespective of thrombus localisation. In a regression model, male gender, low levels of orosomucoid and increased levels of d-dimer in plasma on day 5 were independently associated (p <0.05) with an enhanced absolute resolution of the thrombus at 6 months. No differences in symptoms and signs in the thrombotic leg at follow-up, comparing the treatment given, or thrombus extension at diagnosis and 6 months later, were demonstrated. CONCLUSION: Dalteparin given once daily subcutaneously was as effective as continuous intravenous infusion of unfractionated heparin in the initial treatment of deep vein thrombosis assessed by Marder score evaluation 6 months after the acute event.

The risk of recurrent venous thromboembolism in carriers and non-carriers of the G1691A allele in the coagulation factor V gene and the G20210A allele in the prothrombin gene. DURAC Trial Study Group. Duration of Anticoagulation.

The results concerning the risk of recurrent venous thromboembolism (VTE) in carriers of the G1691A mutation in the coagulation factor V gene are not consistent and this risk in carriers of the G20210A polymorphism in the prothrombin gene has hitherto not been reported. We followed 534 patients for 48 months after their first episode of objectively documented VTE. The prevalence of the G1691A allele in 467 (87.5%) of the patients and in 207 controls was 25.3% and 8.2%, respectively, in heterozygote form and 2.4% and 0.5%, respectively, in homozygote form. The adjusted odds ratio (OR) for the first VTE was 4.4 (95% CI 2.6-7.8). The risk of recurrent VTE in heterozygotes was not statistically different from non-carriers (17.8% vs 17.6%), with 85% power to detect a hazard ratio of 2.35. Homozygotes had a significantly increased risk (p = 0.036) of recurrent VTE. The prevalence of the G20210A allele in 456 patients and 207 controls was 6.1% and 1.4%, respectively. The adjusted OR was 4.6 (95% CI 1.6-19.3) for the first VTE in 28 carriers of this polymorphism. The risk of recurrent VTE for these was not statistically different from non-carriers with an OR of 0.9 (95% CI 0.2-2.9).

Recombinant, B-domain deleted factor VIII (r-VIII SQ): pharmacokinetics and initial safety aspects in hemophilia A patients.

The pharmacokinetics of a second-generation recombinant B-domain deleted factor VIII (FVIII) preparation (r-VIII SQ) were studied in 36 patients with severe hemophilia A. In contrast to full-length recombinant FVIII, no albumin needs to be added to stabilize the final formulation of this B-domain deleted FVIII preparation. The in vivo recovery and half-life of r-VIII SQ were similar to those of plasma-derived (pd) FVIII (mean half-life of r-VIII SQ, 11.7 h). The volume of distribution and clearance were slightly, but significantly, higher for r-VIII SQ than for pdFVIII (p < 0.05). Peak plasma levels of FVIII were consistently related to the administered dose of r-VIII SQ (r = 0.94, p < 0.0001). The pharmacokinetic profile of r-VIII SQ remained essentially unchanged in a dose range of 25-100 IU/kg body weight and could be reproduced after repeated doses. r-VIII SQ was well tolerated. In conclusion, deletion of the B-domain of FVIII does not influence its in vivo pharmacokinetics.

Effects of meningococcal and Escherichia coli capsular polysaccharides on human and dog platelet aggregation in vitro.

Highly purified capsular polysaccharides from groups A, B, and C meningococci and from two strains of Escherichia coli did not aggregate human or dog platelets in vitro. Nor was there any detectable effect on platelet aggregation induced by adenosine diphosphate (ADP), epinephrine, or collagen. The results do not support the hypothesis that capsular polysaccharides are involved in the pathogenesis of thrombocytopenia often seen in severe infections with these bacteria.

Thromboxane and prostacyclin formation in patients with deep vein thrombosis.

The urinary excretion of 2,3-dinor-TxB2 and 2,3-dinor-6-keto-PGF1 alpha (the major urinary metabolites of thromboxane B2 and prostacyclin) was measured in ten patients with confirmed deep vein thrombosis, using specific methods based on gas chromatography - mass spectrometry with deuterium-labelled internal standards. Measurements of these major urinary metabolites makes it possible to monitor the in vivo formation of thromboxane A2 and prostacyclin. The results demonstrate an abnormally high and very variable excretion of 2,3-dinor-TxB2 and 2,3-dinor-6-keto-PGF1 alpha in patients with deep vein thrombosis. This indicate that both thromboxane A2 and prostacyclin are involved in the course of events associated with this disease.

DDAVP-induced correction of prolonged bleeding time in patients with congenital platelet function defects.

In 37 patients with prolonged bleeding time, where thrombocytopenia, von Willebrand's disease or deficiency of other coagulation factors could be excluded, we have evaluated the effect of a DDAVP-infusion (0.2 ug/kg) together with tranexamic acid (10 mg/kg). Patients with acquired impairment of primary hemostasis were not included, except two cases where this could have been a contributing factor. The bleeding time was completely normalized in 27 cases and partially corrected in three more patients. The predominant feature among those, who did not respond, was a pattern compatible with thrombasthenia or cyclooxygenase deficiency, as assessed by platelet aggregation studies. Among the patients, in whom DDAVP was effective, this drug was thereafter successfully used as an alternative to blood products in 8 cases during and after surgery or delivery.

Immediate effects of heparin and LMW heparin on some platelet and endothelial derived factors.

Heparin and a low molecular heparin fragment, injected intravenously in volunteers, increased the plasma concentrations of platelet factor 4, but did not induce platelet activation as judged from excretion of 2,3-dinor-TxB2 (a major thromboxane A2 metabolite) and beta-thromboglobulin (btg) in urine and from btg levels in plasma. Heparin prolonged, within the normal range, the bleeding time in all six subjects. Platelet aggregation in platelet rich plasma was potentiated by both heparins, but platelet number, mean platelet volume and platelet distribution width were not affected. No evidence for endothelial release of prostacyclin was obtained as judged from urinary excretion of 2,3-dinor-6-keto-PGF1 alpha (a major prostacyclin metabolite), and plasma concentrations of tissue plasminogen activator, its inhibitor (PAI-1) and the von Willebrand-factor were unchanged.

Subcutaneous administration of heparin. A randomised comparison with intravenous administration of heparin to patients with deep-vein thrombosis.

One-hundred and forty-one patients with clinical signs of acute deep venous thrombosis (DVT) in the legs were randomly allocated to receive heparin either as two daily subcutaneous injections (s.c.) or as continuous intravenous infusion (i.v.). The thrombi extended into the popliteal or femoral veins in 83% of the patients. Verification of diagnosis and evaluation of therapy was performed by phlebography, plethysmography and thermography. The results showed that heparin administered s.c. twice daily was as efficient as continuous i.v. infusion in preventing extension of the thrombus. In two patients the s.c. administration was stopped due to local haematomas at the injection sites. Retroperitoneal or intramuscular bleedings occurred in four patients, two in each group. Two major, non-fatal pulmonary emboli occurred, one in each group.

Antithrombin III in patients with acute deep vein thrombosis during heparin treatment (subcutaneous and intravenous) and during and after treatment with oral coumarins.

The antithrombin III (AT-III) concentration was studied in 98 patients with symptomatic acute deep-vein thrombosis. All patients were initially treated with heparin randomly by subcutaneous injections or by continuous infusions. Then the patients were treated with coumarins during one or six months. The AT-III concentration was estimated daily during heparin treatment and repeatedly during the first year. The mean AT-III concentration decreased progressively 25% during 5 days of heparin treatment regardless of whether heparin was given intravenously or subcutaneously. The mean AT-III concentration during coumarin treatment was higher than after coumarin treatment. Eleven patients developed recurrent thromboembolic episodes during the follow-up period. The mean AT-III concentration in these patients was not lower than in the patients without recurrences.

Influence of changes in lifestyle on fibrinolytic parameters and recurrence rate in patients with venous thromboembolism.

A prospective, non-randomized, interventional study was carried out to evaluate the effect of changes in lifestyle on abnormal fibrinolytic parameters, and the influence of those, in turn, on the risk of recurrence among patients with venous thromboembolism. Patients with elevated plasminogen activator inhibitor 1 (PAI-1) levels or decreased release of tissue plasminogen activator (t-PA) antigen were given information and advice about improved diet, increased physical activity, weight loss and/or cessation of smoking. Totally 144 patients (119 with elevated PAI-1 and 25 with deficient t-PA release) were followed with repeated analyses of the fibrinolytic parameters for a median of 8 months after the initial advice, and 65% of the patients managed to execute at least one change in their lifestyle. The reduction of PAI-1 activity after one, two and three changes in lifestyle were -2.4, -10.0 and -14.0 AU/ml (-10, -30 and -48% of baseline activity), respectively. Those who accomplished two or three changes in their lifestyle had a greater chance of normalizing the PAI-1 level than those with no or only one change (P = 0.009). The effects of improved diet, weight loss and increased physical activity on the PAI-1 level were of a similar magnitude, -7.0 to -10.4 AU/ml (24-32% reduction). The effect on t-PA release was more difficult to evaluate due to the limited number of those patients. After a follow-up of 6 years (mean) after the first visit the patients were inquired about recurrent events, with a response rate of 86%.(ABSTRACT TRUNCATED AT 250 WORDS)

A single dose of a low molecular weight heparin fragment for anticoagulation during hemodialysis.

A low molecular heparin fragment (Fragmin, mol. wt. 4-6000 d), given as a single injection (dose 5000 anti-Xa U), was used as an anticoagulant during hemodialysis in 11 patients. In comparison, our routine heparinization procedure was used; conventional heparin was given as a bolus injection at the start and then as continuous infusion during dialysis to prolong the whole blood activated clotting time (WBACT) 125-175%. Fibrin formation, followed by visual inspection and the measuring of fibrinopeptide A and fibrin monomer concentrations were equally suppressed by the two regimens. WBACT was less prolonged with Fragmin. Anti-Xa activity above 0.39 U/ml was maintained throughout the dialyses with Fragmin. In conclusion a single dose of Fragmin gives sufficient anticoagulation for hemodialysis lasting up to 4 hours.