Systematic isolation of circulating human peptides: the concept of peptide trapping.

The structural determination of circulating human peptides is essential to determine their correct posttranslationally processed form. Human hemofiltrate from patients with end stage renal disease is accessible in large quantities and is used as a source for the preparation of circulating peptides. After complete peptide extraction from hemofiltrate, a systematic separation with different chromatographic techniques is achieved. Single peptides are selected according to their mass and chromatographic elution position. Following chromatographic purification, amino acid sequence analysis is performed in combination with data base search. The identification of circulating peptides leads to numerous fragments resulting from cleavage of larger plasma proteins as well as to the discovery of new peptide hormones. The results obtained so far give insight into the degradation of plasma proteins such as fibrinogen, which results in the generation of fragments with biological activity themselves and in the identification of a novel cytokine HCC-1, the first member of beta-defensins in humans, hBD-1, and different peptides not present in any data base.

Fluid balance during haemodialysis and haemofiltration: the effect of dialysate sodium and a variable ultrafiltration rate.

One of the main causes of hypotension during extracorporeal renal replacement therapy is an insufficient substitution of the ultrafiltrated plasma water by tissue water. To investigate the fluid balance and its effects on hypotension in dialysed patients, the following variables were studied: intracellular fluid volume (IFV) and extracellular fluid volume (EFV), blood volume (BV) and blood pressure. IFV and EFV were measured by means of non-invasive electrical conductivity measurements using four electrodes round the leg. Fifteen haemofiltration (HF) and 15 haemodialysis (HD) patients were studied. The latter group was dialysed in three ways: (1) conventionally, i.e. with dialysate sodium of 138 mmol/l (HD) (2) with a variable dialysate sodium (first half: 138 mmol/l; second half: 146 mmol/l) (HDS), and (3) with the same variable dialysate sodium and an ultrafiltration profile (two-thirds was withdrawn during the first half of treatment, the remainder during the second half) (HDSU). Hypotension frequency was less during HDS, HDSU, and HF compared to HD. This was caused by a more stable blood volume due to a better refill. During HD a fluid shift occurred from the EC to the IC compartment. The use of a high sodium dialysate concentration led to a transcellular fluid shift in the opposite direction. This fluid shift increased the refill, thereby stabilising blood volume. HF gave a better refill than HDS and HDSU, probably due to a reduced urea clearance.

The influence of dialysate sodium and variable ultrafiltration on fluid balance during hemodialysis.

An important factor in the development of hypotension during hemodialysis (HD) is a decrease in blood volume, due to ultrafiltration (UF) and an insufficient refill of the intravascular compartment. This insufficient refill might be caused by a transcellular fluid shift from the extracellular to the intracellular compartment. We studied the influence of dialysate sodium concentration and UF rate on the refill rate, blood volume, intracellular (ICV) and extracellular fluid volume (ECV). Three different HD strategies were studied in 15 patients: (A) conventional HD (dialysate sodium 140 mmol/L); (B) HD with a sodium profile (140-148 mmol/L); and (C) HD with a sodium profile and a variable UF rate (high-low UF rate). ICV and ECV were measured by non-invasive conductivity measurements, blood volume was calculated from erythrocyte counts before and after treatment. Blood volume decrease was most pronounced during conventional HD, due to insufficient refilling without a detectable transcellular fluid shift. The sum of the decrease in ICV and EVC was less than during (B) and (C). The insufficient refill led to a higher prevalence of hypotension and cramps. The strategies (B) and (C) led to an significant and comparable transcellular fluid shift to the extracellular compartment. Thus, the use of a sodium profile led to a better intravascular refill and clinical tolerance of HD. Addition of a UF profile did not improve this any further.

[Determination of the diameter of erythrocytes in the urine in urologic diseases and so-called asymptomatic microhematuria]. / Bestimmung von Erythrozytendurchmessern im Urin bei urologischen Erkrankungen und der sogenannten asymptomatischen Mikrohämaturie.

In a blind-study with 96 patients analysis of erythrocyte diameters permits to differentiate between renal-parenchymatous and post-renal microhaematuria in 89.9% of the cases. Erythrocytes on renal-parenchymatous microhaematuria are distinctly smaller (Average diameter 3.2 microns-5.6 microns) than those on post-renal microhaematuria (average diameter 5.4 microns-8.8 microns). In addition to the evaluation of erythrocyte morphology erythrocyte morphometry represents further possibility in diagnosis.

Low molecular weight heparin in hemodialysis and hemofiltration patients.

Low molecular weight (LMW)-heparin was used as the sole anticoagulant during hemodialysis and hemofiltration in a pilot study on 32 patients. A LMW-heparin dose corresponding to 50% of the patients usual unfractionated, standard (UF)-heparin dose was found to produce comparable plasma heparin levels (anti-FXa-activity). No thrombosis of the extracorporal system and no bleeding complications occurred at this LMW-heparin dose. In contrast to UF-heparin, LMW-heparin produced only slight increases in PTT and thrombin time in all patients. Lipoprotein lipase was stimulated only marginally by LMW-heparin, with a correspondingly reduced release of free fatty acids. Both heparin species caused similar elevations in factor VIII and fibrin monomers, thus excluding a difference in coagulation activation. On the basis of these results, long-term studies have been started at four nephrology centers. To date, 26 patients have been treated with LMW-heparin for 6 months. A LMW-heparin dose was used that produced plasma anti-FXa-activity of 0.5 to 0.9 U/ml (initial dose: 30 to 40; dose/hr: 8 to 15 anti-FXa-units/kg body wt). PTT and thrombin time were only increased by 5 sec on average. Surprisingly, the elevated pre-dialysis levels of factor VIII and fibrin monomers decreased during this 6-month period. Bleeding complications did not occur and thrombotic complications were not observed when the anti-FXa levels were above 0.5 U/ml. LMW-heparin, therefore, appears to be a good alternative to UF-heparin for dialysis patients and may present less risk of bleeding because of its reduced effect on PTT, thrombin time, and thrombocytes.

Hypertension and cardiovascular risk factors in hemodialyzed diabetic patients.

In a retrospective study, the cause of death and the cardiovascular risk conferred by hypertension and other risk factors were analyzed in 200 diabetic and 200 nondiabetic patients who were matched for age, sex, year of admission, and center of treatment. Total and cardiovascular mortality were considerably higher in diabetics, cardiovascular mortality being 4.8 times higher in patients with type I and 3.0 times higher in those with type II diabetes compared to matched controls. Cardiovascular mortality progressively increased with age and had not improved in recent years. In both types I and II diabetes, the rate (58%) and proportion (38%) of deaths from cardiovascular causes were significantly higher in diabetics than in matched controls. Myocardial infarction (13%) and stroke (7%) accounted only for a minority of cardiovascular mortality, the majority (80%) being due to "sudden death of unknown cause." Autopsy was carried out in 33% of patients with sudden death. A documented history of long-standing hypertension increased cardiovascular death in diabetic more than in nondiabetic patients. Diabetic retinopathy (an index of microangiopathy) and absence of peripheral pulses, amputation, or history of myocardial infarction, stroke, or transient ischemic attacks (as evidence of macroangiopathy) caused surprisingly little increase in relative risk for cardiovascular death. In diabetics but not in nondiabetics, cardiomegaly, particularly in association with electrocardiographic abnormalities, was a strong predictor of cardiovascular death.