Interaction between VLDL and phosphatidylcholine liposomes generates new γ-LpE-like particles.

One of the subfractions of HDL involved in reverse cholesterol transport is γ-LpE. It has been assumed that, like preß-LpAI, it can be generated during the interaction between phosphatidylcholine liposomes and lipoproteins and can contribute to more efficient cholesterol efflux after the introduction of liposomes to plasma. However, there has been no evidence concerning what the sources of these particles in plasma might be. Here, we determined whether the interaction of phosphatidylcholine liposomes with VLDL and the subsequent conversions of particles could be a source of new γ-LpE particles. We found that the interaction between liposomes and VLDL affected its lipid and protein composition. The content of phospholipids increased (~96 %) while the content of free cholesterol and apolipoprotein E decreased in VLDL during the reaction with liposomes (~100 and ~24 %, respectively). New particles which did not contain apolipoprotein B were generated. Heterogeneous HDL-sized populations of particles were generated, containing phospholipids and apolipoprotein E as the sole apolipoprotein, with densities from 1.063 to 1.21 g/ml, either with γ-mobility on agarose gel and Stokes diameters from 8.58 to 22.07 nm or with preß-mobility and Stokes diameters from 9.9 to 21.08 nm. The obtained results contribute to the understanding of changes in lipoproteins under the influence of phosphatidylcholine liposomes, showing the formation of new (γ-LpE)-like and (preß-LpE)-like particles, similar in mobility and size to plasma HDL-LpE. These newly generated particles can claim a share of the antiatherogenic effects of liposomes, observed in studies both in vitro and in vivo.

The standardization of urine particle counting in medical laboratories--a Polish experience with the EQA programme.

BACKGROUND: Given the common problems with the standardization of urine particle counting methods and the great variability in the results obtained by Polish laboratories under international Labquality External Quality Assessment (EQA), we initiated educational recovery activities. METHODS: Detailed instructions on how to perform the standardized examination were sent to EQA participants, as was a questionnaire forms which enabled information to be gathered in respect to the procedures being applied. Laboratory results were grouped according to the method declared on the EQA 'Result' form or according to a manual examination procedure established on the basis of the questionnaire. The between-laboratory CVs for leukocyte and erythrocyte counts were calculated for each group and compared using the Mann-Whitney test. RESULTS: Significantly lower between-laboratory CVs (p = 0.03) were achieved for leukocyte counting among the laboratories that analysed control specimens in accordance with standardized procedures as compared with those which used non-standardized procedures. We also observed a visible lower variability for erythrocyte counting. Unfortunately despite our activities, only a few of the Polish laboratories applied the standardized examination procedures, and only 29% of the results could have been considered to be standardized (16% - manual methods, 13% - automated systems). CONCLUSIONS: The standardization of urine particle counting methods continues to be a significant problem in medical laboratories and requires further recovery activities which can be conducted using the EQA scheme.

Estimation of oxidative stress markers in chronic kidney disease.

Changes mediated by oxidative stress are thought to be involved with atherosclerosis in patients with chronic kidney disease (CKD). The purpose of this study was to analyze the markers of oxidative damage and the activity of antioxidative enzymes as well as the total antioxidant capability in patients with different stages of CKD, both conventionally treated and dialyzed. We evaluated the oxidative modification of lipids (by oxidized low-density lipoprotein and malonodialdehyde levels) and proteins (by advanced oxidation protein products level). We also assessed the activity of paraoxonase-1 and glutathione peroxidases and total antioxidant status. Compared with the control group, the uremic patients, both dialyzed and nondialyzed, had higher levels of all studied plasma oxidative stress markers and decreased activity of antioxidative enzymes. Our results lead us to conclude that oxidative stress seems to be related rather to the uremic state than to the dialysis treatment. We also showed that estimating total antioxidant status in a simple test is unreliable for assessing the antioxidant ability of patients with CKD.