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Biomedical subjects

J Racek

Publications and source records attributed to J Racek.

At least 55 records · Page 3Linked to original sources
PubMed2000

Oxidative stress: the effect of erythropoietin and the dialysis membrane.

Dialysis patients run the risk of impaired antioxidative defense and increased free radicals (FR) production. The study was made in order to compare FR-related parameters in ten patients treated with erythropoietin (EPO+) and ten patients not subject to this treatment (EPO-). All patients showed stable hemoglobin levels at > 95 g/L. FR-related parameters were monitored during hemodialysis (HD) using a polysulfon (PS) or a hemophan (H) membrane for 12 of them (6 EPO+ a 6 EPO-). The EPO- group was found to have a higher activity of superoxide dismutase (SOD, 1160 + 218 vs; 882 + 125 IU/gHb, p<0.01) and a higher SOD/glutathione peroxidase (GSHPx) ratio compared with EPO+ (30.5 +/- 7.1 vs; 21.2 + 4.8, p<0.01). A total of 35 healthy volunteers were also examined. When compared with controls EPO- showed higher SOD (p<0.001), lower GSHPx (p<0.05) and a higher SOD/GSHPx ratio (p<0.001). Thiobarbituric acid reacting substances in EPO+ and EPO- were comparable with the levels found in controls. HD using H as well as PS membranes was associated with a decrease in erythrocyte glutathione levels (GSH after 30 minutes; also for H after HD). HD using H and PS membranes resulted in a decrease in the plasma antioxidant capacity (AOC). We can conclude that the intraerythrocyte antioxidant conditions of EPO+ patients are similar to those found in the general population and differ from those in EPO- exhibiting increased SOD and the SOD/GSHPx ratio. HD using the H as well as the PS membrane is accompanied by oxidative stress.

Adult↗
PubMed1999

[Problems with trace elements in hemodialysis. Evaluation of serum levels].

BACKGROUND: During dialysis substances are eliminate in particular according to the concentration gradient between plasma and the dialysation solution. Evaluation of a suitable setting of the basic concentration of a substance in the dialysation solution from results of different patients is problematic because of possible individual distortion. The objective of the present work was to suggest and test a practical way of evaluation of group data. METHODS AND RESULTS: The authors examined a group of 87 dialyzed patients. Using the AAS method they assessed the serum concentrations of Mg, Zn and Cu always before and after dialysis. During dialysis of significant decline of serum Mg occurred (below 0.8 mmol/l). This drop would signalize the need to reduce the concentration gradient, i.e. increase the Mg concentration in the dialysation solution above the current 0.5 mmol/l. However assessment of Mg in red blood cells revealed that dialyzed patients have a significantly increased depot of Mg in the organism (2.67 mmol/l ery as compared with normal 2 mmol/l ery) and thus reduction of Mg in serum during dialysis is desirable. CONCLUSIONS: The authors suggested and on the basis of Mg tested a graphical way making rapid screening of extensive group data possible when evaluating the adequacy of the composition of the dialysation solution with regard to the concentration gradient of eliminated and retained substances resp. Evaluation of the concentration gradient from group data may be the baseline for optimalization of further individually set parameters of dialysis in individual patients.

Adult↗
PubMed1999

Autoantibodies against oxidized LDL in the first phase of life. Low density lipoproteins.

The study presents a comparison of data concerning lipid metabolism and lipid oxidation (oxidative stress) in children at the time of their birth and 3 months later, as well as of their mothers at the time of delivery, compared to a control group of non-pregnant women of the same age. The data confirm that labour represents an oxidative stress for both mother and child; it is expressed as a significant increase of malondialdehyde concentration in mothers immediately after delivery in comparison with non-pregnant women (p<0.001). Its concentration in newborns was even higher than in their mothers (p<0.005). Concentration of antibodies against oxidized LDL (oxLDLAb) was comparable in mothers and newborns due to their transplacental transport. During the first three months of life these autoantibodies increased almost two-fold. The importance of this unique observation is discussed with respect to possible early atherogenesis.

Autoantibodies↗
PubMed1999

[Indicators of oxidative stress in cardiovascular diseases. I. Lipoperoxidation].

The level od malondialdehyde (MDA), thiobarbituric acid reactive substances (TBARS) respectively, in blood is changing very quickly and therefore isoprostanes scam to be better markers of atherogenesis. Oxidized LDL belong to the most important reasons of the origin of foam cells and therefore of atherogenesis. That is why the inhibition of the oxidation of LDL particles should belong to the standard therapy of cardiovascular diseases. The value of antibodies against oxidized LDL is difficult to interpret, because they are multifactor dependent, especially under genetic control. Antibodies against LDL modified by malondialdehyde (MDA-LDL) are increased in smokers and individuals with a rapid atherosclerotic progression. HDL-cholesterol protects LDL through the oxidized lipid exchange. Oxidized HDL formed during this process has then an increased clearance from circulation.

Cardiovascular Diseases↗
PubMed1999

[Indicators of oxidative stress in cardiovascular diseases. II. Nitrogenous substances, AGE-substances and antioxidants].

By oxidation of nitrogen oxide nitrites and nitrates are formed which can be considered markers of inflammation. AGE-substances (products of advanced glycation) are formed not only from proteins (e.g. Hb-AGE) but also from lipids (AGE-LDL) and DNA (AGE-DNA) and lead to an increased number of mutations. They are toxic and are deposited in the vascular wall. They cause coagulopathy, stimulate cytokines and inactivate nitrogen oxide and thus prevent relaxation of the vascular wall. Extracellular superoxide dismutase (EC-SOD) has a variant (mutation Arg213Gly with a 4% incidence) which causes deterioration of the cardiac prognosis. Selenium deficiency leads also to an increased frequency of cardiovascular diseases.

Antioxidants↗
PubMed1999

[Free radicals and extracorporeal renal replacement therapy].

Free radicals (FR), highly reactive substances with an unpaired electron in the outer orbital attack lipids, proteins and nucleic acids and alter the structure and function of these macromolecules. Against the negative effects of FR during evolution various defense mechanisms developed described comprehensively as antioxidant defense. Under physiological conditions in the organism equilibrium is established between free radical production and antioxidant defense factors. Extracorporeal renal replacement mechanisms can interfere in a negative way with this equilibrium. They provoke the formation of FR and at the same time they weaken the antioxidant defense e.g. by elimination of substances with antioxidant properties. Impairement of the equilibrium between FR production and antioxidant mechanisms to the disadvantage of antioxidant defense in patients with chronic renal failure was proved and is described as oxidative stress. Oxidative stress threatens dialyzed patients with serious clinical complications e.g. accelerated atherosclerosis, amyloidosis, haemolysis and the development of a state of chronic inflammation. Reduction of oxidative stress can be achieved by reducing FR production by using biocompatible dialyzation membranes, proper correction of acid-base disorders, by preventing an iron overload of the organism. The second approach is to foster the antioxidant defense by supplementation with antioxidants. Final recommendations as regards selection of the optimal dialyzation membrane, type of extracorporeal renal replacement and the amount and composition of antioxidant supplements have not yet been established and the problem is the subject of intense research.

Acid-Base Equilibrium↗
PubMed1998

[Trace elements in biological materials. Preanalysis safeguards].

In order to obtain objective information from estimations of trace elements (Al, As, Cd, Cr, Co, Cu, Pb, Li, Mn, Hg, Ni, Se, Zn) on deficiency or intake beyond the toxic limit it is necessary to pay attention among others also to preanalytical safeguarding, i.e. obtain all relevant information on the patient, ensure proper selection of material and sampling time, proper sampling and safeguarding the sample before the estimation proper. If the above rules and principles are respected, possible significant distortion on the results, which can be caused e.g. by contamination of the sample, can be prevented.

Humans↗
PubMed1998

[Significance of free radicals in the pathogenesis of rheumatic diseases and possibilities of decreasing their pathogenic effects].

The authors present the result of their work where they provide evidence that in inflammatory and degenerative diseases the break-down on superoxide in inadequate. This oxygen radicals and its metabolites play a significant role in the pathogenesis of these diseases. The authors revealed a severe defect in superoxide degeneration in particular in articular exudates of patients with active synovitis. Administration of the preparation Selzink-Plus of PRO.MED.CS Co. Prague which contains selenium, zinc, beta-cyrotene, vitamin C and E along with antirheumatic treatment improves according to the authors the breakdown of superoxide and its metabolites and improves thus the patient's prognosis. Long-term administration of the preparation seems to produce even better results.

Arthritis↗
PubMed1998

[Paired filtration dialysis--evaluation of effectiveness of the method].

Paired filtration dialysis (PFD) is a haemodiafiltration method which uses in a major way the convection as well as the diffusion principle of blood clearance. It is the only method replacing renal function where blood filtration is separated from diffusion. The objective of the study is to make the medical community familiar with this method and to assess the effectiveness of PFD when two types of haemodiafilters are used. The effectiveness of PFD is also compared with haemodialysis where a highly permeable haemofilter is used (high-flux haemodialysis, HFHD) with a medium-size area. A group of 8 dialyzed patients was treated after weekly intervals by PFD in two set-ups: 1. PFD with a haemodiafilter SG3 (high-flux polysulphon haemofilter and a low-flux haemophan dialyzer, area 0.55 m2 and 1.36 m2). 2. PFD with haemodiafilter SG30 (high-flux polysulphon haemofilter and low-flux polysulphon dialyzer, area 0.55 m2 and 1.36 m2). The author used also HFHD with a polyacrylonitrile membrane AN 69 (Filtral 12, area 1.3 m2). The index of the dialyzation dose Kt/V was higher in PFD, similarly as the clearance of creatinine, urea, phosphates and uric acid. Beta-2-microglobulin was investigated as a representative of medium-sized molecular substances. Beta-2-microglobulin was eliminated in HFHD and PFD, HFHD being most effective. The selected variants of PFD replace effectively the excretory renal function. The effectiveness of PFD is in particular due to the large total area of the haemodiafilter. According to the authors the standard length of the procedure for a patient with a mean height at a rate of 300 ml/min. is 4 hours. PFD eliminates also beta-2-microglobulin similarly (SG3) or less (SG30) than HFHD with membrane AN 69 with a medium-sized area.

Adult↗
PubMed1998

[Indicators of effects of free radicals in workers at risk of lead exposure].

The authors examined indicators of the action of free radicals in 40 workers exposed to the risk of lead (work with lead containing glazing and prints). The lead concentration in the atmosphere did not exceed the highest permissible concentrations and the biological exposure tests as regards lead exposure did not exceed the highest permissible limits. In the examined subjects the authors found a significantly elevated level of superoxide dismutase activity (p < 0.05) which suggests long-term increased peroxide formation. The correlation of the selenium concentration in blood and the period of lead exposure was at the borderline of statistical significance (p = 0.1159). Further investigations will be focused on subjects with symptoms of increased exposure to lead and lead intoxication where the probability of pathological findings is greater.

Adult↗
PubMed1997

Influence of antioxidants on the quality of stored blood.

BACKGROUND AND OBJECTIVES: Blood is exposed to oxidation stress and therefore has a high antioxidant capacity (AOC). With the many factors increasing the demands on the AOC, there may be damage to erythrocytes by free radicals. This study was to investigate evidence of erythrocyte damage in stored donor blood and to affect this by premedication of blood donors. MATERIALS AND METHODS: Blood samples of 15 healthy donors were collected in CPDA-1 solution and analyzed immediately, and then again after 10 days of incubation at 4 degrees C and 1 day of incubation at 37 degrees C. Prior to incubation, the following parameters were evaluated: Na+, K+, malondialdehyde (MDA), hemoglobin (Hb), AOC in the supernatant, superoxide dismutase (SOD) in erythrocytes, and glutathione peroxidase (GSHPx) in whole blood. Blood donors of group 1 were not given any drugs or vitamins before blood sampling. The same blood donors were then supplemented with the following daily doses of antioxidants for 10 days before the next blood sampling: 36 mg of beta-carotene, 300 mg of vitamin E, 200 mg of vitamin C, and 40 mg of selenium. RESULTS: The blood from donors of group 2 had a significantly smaller increase in MDA, K+, and Hb, and a smaller decrease in Na+ and AOC in the supernatant compared with that of group 1, while the activity of SOD and GSHPx did not change during blood storage. CONCLUSIONS: These results suggest that antioxidants given to blood donors can improve red cell storage parameters by reducing cell damage caused by free radicals.

Antioxidants↗
PubMed1997

[The effect of antioxidant therapy on indicators of activity of free radicals in workers exposed to risks of styrene].

To 30 workers exposed to the risk of styrene for a period of 30 days a mixture of antioxidants was administered: vitamin C 200 mg, vitamin E 300 mg, selenium 20 mg, troxerutin 600 mg and beta-carotene 6 mg. Before the onset of supplementation and immediately afterwards laboratory indicators of antioxidant protection and lipid peroxidation were investigated. Before treatment workers exposed to the risk of styrene had a significantly higher malondialdehyde concentration (p < 0.01) and antioxidant capacity (p < 0.01) as compared with the control group. Due to the established positive correlation between these parameters (r = 0.42, p < 0.05) the findings can be evaluated as the result of increased exposure to free radicals. After supplementation a marked decline of the malondialdehyde concentration occurred p < 0.001) and a further rise of the antioxidant capacity (p < 0.001). The selenium concentration increased also markedly, the rise being more marked in subjects who had originally a lower concentration. There was a significant rise of uric acid which has an antioxidant effect (p < 0.01). The antioxidant enzymes superoxide dismutase and gluathione peroxidase did not change significantly. The results indicate the favourable effect of antioxidant treatment in subjects exposed to the risk of styrene.

Adult↗
PubMed1996

[Antioxidants and malondialdehyde during hemodialysis with cellulose diacetate and polysulfone membranes].

BACKGROUND: Free radicals (FR) may cause lipid peroxidation and damage macromolecules and cellular structure of the organism, e.g. endothelium and erythrocytes. Some studies have shown that haemodialysis is connected with increased FR production. The aim of the study was to evaluate the effects of two dialysis membranes on lipid peroxidation and some antioxidant protective factors. METHODS AND RESULTS: The authors followed nine patients treated in a regular dialysis programme. In a cross controlled study the patients underwent haemodialysis with the use of cellulose diacetate (CDA) and polysulfone (PS) dialysis apparatus. Malondialdehyde in plasma was determined as a marker of lipid peroxidation. The haemodialysis with CDA or PS did not result in increased malondialdehyde levels in min. 30 or at the end of the procedure. The antioxidant capacity of plasma decreased after haemodialysis in a similar way with both types of membranes (PS, 1.67 +/- 0.10 mumol/l versus 1.47 +/- 0.23, P < 0.05; CDA: 1.72 +/- 0.10 versus 1.55 +/- 0.12, P < 0.05). The selenium blood level did not change. Activity of glutathione peroxidase (GSHPx) in blood before the dialysis was higher in the observation with subsequent use of CDA than while using PS (38.6 +/- 9.4 versus 34.5 +/- 6.6, P < 0.05). In the cohort with polysulfone membrane GSHPx further decreased in min. 30 of haemodialysis (34.0 +/- 6.6 IU/g Hb versus 31.1 +/- 5.0, P < 0.05). Superoxide dismutase (SOD) was also higher in dialysis with CDA membrane that while using PS (846 +/- 171 IU/g Hb versus 522 +/- 141, P < 0.05). CONCLUSIONS: The activity of antioxidant enzymes GSHPx and SOD was lower with polysulfone membrane than with the cellulose acetate membrane. GSHPx activity also further decreased from min. 30 of dialysis with the PS membrane. It may be due to increased production of superoxide anion and hydrogen peroxide during haemodialysis with the PS. Lipid peroxidation has not been proved to increase during haemodialysis with the CDA or PS membrane.

Adult↗
PubMed1996

[Does plasmapheresis affect the production of free radicals and the antioxidant system?].

BACKGROUND: Free radicals cause lipid peroxidation, damage cell membranes and DNA. At present attention is paid to the relationship between extracorporeal methods of blood clearance, free radicals and the antioxidant system. The objective of the present study was to ascertain the effect of membrane plasmapheresis (PF) on the antioxidant defence of the organism and whether it has an impact on lipid peroxidation. METHODS AND RESULTS: Patients with inflammatory polyneuropathy (n = 7), pemphigus (n = 1) and pulmonary fibrosis (n = 1) were subjected to 3 PF each (apparatus Fresenius 2008 PF, filter Plasmaflux P2S). The following were assessed: superoxide dismutase activity (SOD) in red blood cells, the antioxidant capacity (AOK) and malondialdehyde (MDA) in plasma, glutathione peroxidase (GSHPx and selenium (Se) in blood, AOK, MDA and Se in the filtrate. The values were compared with those of 43 healthy volunteers using the t-test, changes of parameters during PF, using Wilcoxon's paired test. The baseline SOD, GSHPx, AOK and MDA values of patients did not differ from those of controls. SOD did not change in the course of PF. GSHPx declined during the 30th minute of PF and after PF (44.3 +/- 16.9 U/g, haemoglobin before vs. 37.5 +/- 12.2 during the 30th minute, p < 0.01, 36.7 +/- 14.6 after PF, p < 0.01). AOK rose during the 30th minute (p < 0.01) and after PF (p < 0.01). MDA after PF declined (p < 0.05). The baseline Se was higher than in controls (132.9 +/- 43.2 micrograms/l vs. 90.5 +/- 17.3, p < 0.01), after PF Se declined (100.1 +/- 28.3, p < 0.01). CONCLUSIONS: The authors did not provide evidence of increased lipid peroxidation during PF. During PF the GSHPx activity declines, most probably due to Se losses. The decline of GSHPx involves the risk of deterioration of hydrogen peroxide elimination and of increased free radical formation.

Antioxidants↗
PubMed1996

[Methods of studying free radical reactions].

The importance of free radicals is increasing and therefore the present and future possibilities of their follow up should be described. A collection of methods is presented in this paper, above all the indirect ones. Direct estimations are for the majority of laboratories inaccessible at this time. The intensity of lipoperoxidation, nucleic acids damage, damage of proteins, and antioxidant capacity can be estimated, and the quantity of the origin of free radicals and their metabolites can be evaluated. There is not yet the international standardization realized and the interpretation of the results is not performed.

Free Radicals↗
PubMed1996

[Homocysteine, a less well-known risk factor in cardiac and vascular diseases].

Hyperhomocyst(e)mia (Hcy) negatively influences vascular endothelium and coagulation factors. Association of Hcy with premature arteriosclerosis (rather than atherosclerosis), stroke, myocardial infarction and peripheral arterial and venous disease was proved in clinical and epidemiological studies, even as the association with conventional risk factors like age, male sex, smoking, hypertension and hypercholesterolemia. Vitamin substitution of folates, vitamin B6 and B12 decreases Hcy blood levels, however definite evidence is still lacking, whether it results in lower incidence and mortality from cardiovascular diseases. Therefore clinical and epidemiological studies are necessary. Before the grant-application we proved in a pilot study significantly higher Hcy levels in 97 patients with manifest ischaemic heart disease than in 37 controls.

Arteriosclerosis↗