Biocompatibility of a new high-permeability modified cellulose membrane for haemodialysis

The biocompatibility and solute permeability characteristicsof a high-permeability modified cellulose membrane (Hemophan-HP^®)(He-HP) were compared with those of two synthetic membranes(poly(ethylene-co-vinyl alcohol) (EVAL) and poly(acrylonitrile-co-sodiummethallyl sulphonate) (AN69)) and Cuprophan^® in a multicentre,four-way cross-over clinical trial. Cuprophan^® membranescaused significant complement activation, leukopenia, and granulocyteelas-tase release. He-HP membranes demonstrated a lesser effect,which was similar to that observed for the EVAL membrane, althoughless than that seen with the AN69 membrane. A similar orderfor the four membranes was seen for their effect on platelets.Cuprophan^® membranes provided superior small-molecule removalto the other three membranes. In contrast, Cuprophan^® wasessentially impermeable to ß₂-microglobulin, whereasHe-HP, EVAL, and AN69 allowed the removal of 60–90 mgof ß₂-microglobulin per treatment. However, a decreasein the plasma concentration of ß₂-microglobulin wasobserved only with the AN69 membrane, most probably as a resultof the ability of that membrane to adsorb proteins. Our resultsdemonstrate that high-permeability membranes of comparable biocompatibilityto some synthetic membranes can be fabricated from cellulosederivatives.     

Rapid typing of Escherichia coli K antigens using bacteriophages

E. coli capsular (K) antigens are important virulence factors contributing to the development of urinary tract infections (UTI). Serotyping of these antigens is laborious and depends on the availability of respective antisera which are difficult to prepare because of the low immunogenicity of these polysaccharide antigens. The application of specific K phages are a big advantage. Two collections of E. coli strains (500 from Rostock, 214 from Erfurt) isolated from patients with UTI have been investigated with a set of ten K specific bacteriophages including phi 1, phi 2, phi 5, phi 7, phi 9, phi 12, phi 13, phi 20, phi 30 and phi 36. The K1 antigen has been found to be the most frequent capsular antigen (16.4% in Rostock; 12.2% in Erfurt) followed by K13/K20 in Erfurt (8.9%) and K5 in Rostock (8%) and Erfurt (7.5%). The collection of phages proved to be suitable for the detection of UTI associated K antigens covering the most common O serogroups found in UTI. The method appears to be simple, non-laborious and applicable for routine use.     

Extracorporeal Endotoxin Removal by Immobilized Polyethylenimine

Abstract: The neutralization of bacterial endotoxins (ET) is still an unsolved problem in therapeutic medicine. The efficacy of antiendotoxin antibodies or receptor antagonists and other substances interferring with the endotoxininduced pathomechanisms is dependent on an intact cellular degradation system of the host. However, the phagocytosis function of that system seems to be impaired regularly in patients with intense or long-lasting endotoxemia or septic shock and in patients undergoing hemodialysis. Extracorporeal adsorption of ET might well be an effective support in the anti-ET therapy by lowering the amount of circulating ET and thus relieving the defense system of the body. In this work a new ET-adsorbent based on macroporous cellulosic beads with immobilized polyethylenimine (PEI) was tested for its ET-removal capacity in vitro. A test solution with 100 ng/ml ET from Escherichia coli 055:B5 was recirculated in a system containing the adsorbent beads. Polymyxin B immobilized to the same carrier was used for comparison. PEI as well as polymyxin B showed complete removal of ET from plasma and water as was measured by the Limulus Amebocyte Lysate (LAL) test (Chromogenix). The biocompatibility of the PEI adsorber was superior to that of polymyxin B. The results indicate that the PEI adsorber is of high efficacy and possibly of interest for the treatment of endotoxemia.     

A simplified procedure to compute dialysis time and frequency by means of urea kinetics

A simplified urea model is presented based on the concept of the time-averaged deviation (TAD) of the blood urea concentration and the introduction of an effective urea generation rate. The increase in the interdialytic blood urea concentration delta c is specific for the individual patient and includes the urea generation rate, distribution volume and residual kidney clearance. By measuring delta c of the largest interdialytic interval of the week the treatment frequency and duration can be calculated. Even for larger residual clearances Kr less than or equal to 5 ml/min this calculated treatment time does not differ by more than 5 min from the result of the exact urea kinetics. In vivo estimation of the urea clearances versus blood flow for the dialyzer types used is necessary for the application of urea modelling in clinical practice.     

Blood purification by haemoperfusion

Blood purification by haemoperfusion is considered, principally in terms of the European effort. The development of the different approaches which have emerged and the assessment of adsorbents and devices are described. The application of haemoperfusion is examined in the areas of acute poisoning, liver failure and uraemia.     

Characterization of New Amphiphilic Block Copolymers of N‐Vinyl Pyrrolidone and Vinyl Acetate, 1 – Analysis of Copolymer Composition,End Groups,Molar Masses and Molar Mass Distributions

New amphiphilic block copolymers consisting of N‐vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4‐dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. ¹³C NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, ¹³C NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non‐ideal RAFT mechanism.

     

Citrate anticoagulation control by ionized calcium levels does not prevent hemostasis and complement activation during hemodialysis

The purpose of this study was to determine whether or not regional citrate anticoagulation (RCA) controlled by ionized calcium (iCa(2+)) would overcome thrombogenicity, prevent hemostasis, and complement activation during hemodialysis (HD). RCA was performed in 10 patients during 10 HD sessions using a polysulfone membrane in an effort to keep iCa(2+) at dialyzer outlet at < or =0.4 mmol/L. Compared to baseline, plasma levels of thrombin-antithrombin III complexes rose significantly at 240 min, and tissue factor and complement C5a component levels at 30 and 240 min of the procedure. Thrombocyte count declined significantly at 30 and 240 min, while activated clotting time (ACT) did not increase significantly, and platelet factor 4 as well as von Willebrand factor levels did not alter significantly. While ACT correlated significantly with some thrombogenicity markers, iCa(2+) did not correlate with ACT, changes in hemostasis, or C5a. We conclude the usually recommended iCa(2+) levels in the HD extracorporeal circuit did not guarantee the complete overcoming of thrombogenicity, prevention of hemostasis, and complement activation.     

Cellular interleukin-1 receptor antagonist production in patients receiving on-line haemodiafiltration therapy.

BACKGROUND: Repetitive exposure to cytokine-inducing substances (pyrogens) results in chronic inflammation, which may significantly contribute to some of the long-term complications in dialysis patients. On-line dialysis modalities, such as on-line haemodiafiltration (HDF), raise particular concerns because of the administration of infusate prepared from potentially contaminated dialysis fluid. Hence, great retention capability for pyrogens is of critical importance for the safe performance of on-line systems. METHODS: The microbiological safety of a novel on-line system, ONLINEplus(TM), was assessed in clinical practice in five centres for 3 months. Infusate and dialysis fluid were regularly monitored for microbial counts, endotoxins, and cytokine-inducing activity. Levels of interleukin-1 receptor antagonist (IL-1Ra) were determined in supernatants of whole blood incubated either under pyrogen-free conditions (spontaneous cytokine production) or following low-dose endotoxin exposure (LPS-stimulated cytokine production). RESULTS: We failed to detect microorganisms or endotoxin contamination of infusate during the entire study period. Moreover, neither infusate nor dialysis fluid demonstrated cytokine-inducing activity. Intradialytic IL-1Ra induction was not detected, as there was no difference between pre- and post-session values for both spontaneous and LPS-stimulated IL-1Ra production (115+/-26 vs 119+/-27 and 2445+/-353 vs 2724+/-362 pg/10(6) white blood cells (WBC), respectively). Neither the number of immunocompetent cells nor their capacity to produce IL-1Ra declined during this period, indicating that cells were not significantly stimulated during treatment. Spontaneous and LPS-induced exvivo IL-1Ra generation remained unchanged after 3 months of on-line HDF therapy as compared with the start of the study (71+/-30 pre- vs 48+/-14 post-study, and 2559+/-811 vs 2384+/-744 pg/10(6) WBC, respectively). CONCLUSIONS: The present on-line system performed safely from a microbiological view-point as both the dialysis fluid and infusate were consistently free of microorganisms, endotoxins, and cytokine-inducing substances. As a result, on-line HDF therapy had no effect upon the chronic inflammatory responses in end-stage renal disease patients.     

Expression of vascular endothelial growth factor and its receptors in rosacea

BACKGROUND: Rosacea is a common chronic disease of unclear pathogenesis, characterised by inflammation and vascular abnormalities of the facial skin and ocular surface. Recognising that vascular endothelial growth factor (VEGF) is vasoactive and has inflammatory activities, the expression of this molecule and its receptors, VEGF-R1 and VEGF-R2, in rosacea was investigated. METHODS: Formalin-fixed, paraffin wax-embedded sections of skin obtained from 20 patients with rosacea were immunostained to detect expression of VEGF, VEGF-R1 and VEGF-R2, using an indirect methodology incorporating antigen retrieval. Adjacent sections were stained with haematoxylin and eosin. RESULTS: Biopsy specimens were characterised by perivascular and perifollicular lymphohistiocytic infiltration and dilated vascular channels. In addition to keratinocyte and epithelial staining, which was also noted in normal skin, vascular endothelium frequently stained positive for VEGF-R1 (14/20, 70%) and VEGF-R2 (20/20, 100%), but infrequently for VEGF (2/20, 10%). In most specimens, infiltrating leucocytes, including lymphocytes, macrophages and plasma cells, expressed VEGF (17/20, 85%), VEGF-R1 (20/20, 100%) and VEGF-R2 (20/20, 100%). CONCLUSION: Expression of VEGF receptors, both by vascular endothelium and infiltrating mononuclear cells, is observed in rosacea. Although not expressed by endothelium, VEGF is present in epidermis and epithelium, and is expressed by infiltrating cells. VEGF receptor-ligand binding may contribute to the vascular changes and cellular infiltration that occurs in rosacea.