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W Siems

Publications and source records attributed to W Siems.

At least 37 records · Page 2Linked to original sources
PubMed1994

Reduced 4-hydroxynonenal degradation in hearts of spontaneously hypertensive rats during normoxia and postischemic reperfusion.

4-Hydroxynonenal (HNE) degradation was investigated in isolated perfused rat hearts of the WKY and SHR strains before and after ischemia. HNE (10 mumoles l-1) were infused and the concentration of HNE in the effluent was determined. The rate of initial consumption was about 50 nmoles min-1 g-1 wet weight in hearts of both the WKY and SHR rats. In the WKY rat hearts, this rate of HNE degradation did not change during several minutes of HNE infusion and also remained constant during postischemic reperfusion. In the hearts of the SHR rats the HNE degradation rate declined within 5 min to 25 nmoles min-1 g-1 wet weight. Also during postischemic reperfusion, there was a lower HNE degradation rate in the SHR rat hearts than in the WKY rat hearts. The influence of hypertrophy on the rate of HNE degradation is discussed. It is suggested that the low degradation of the cytotoxic lipid peroxidation product, HNE, in hypertrophic hearts may contribute to reduced antioxidant defence in those hearts.

Aldehydes↗
PubMed1994

[Increased formation of free radicals in chronic lymphedema].

The erythrocytic glutathione concentration in patients with lymphatic edema was around 20% lower than that of healthy volunteers. In addition, there was a drastic increase in the plasma malondialdehyde concentration. These changes indicate vigorous generation and activity of free radicals in lymphatic edematous tissue.

Adult↗
PubMed1994

[Fitness by cold stimulation of various intensity: effects on metabolism of purines and free radicals].

Whole-body cold stimuli lead to a dosage-depended decrease of uric acid level in blood plasma. This could be observed in own studies on winter-swimming and cold shower application and in studies on patients treated by cold-chamber-therapy. This uric acid decrease is due to an accelerated oxygen radical formation during cold exposition rather than to an inhibition of purine metabolism. The acute oxidative loading due to cold exposure and the long-term antioxidative adaptation may be interpreted as a new molecular mechanism resulting in body hardening.

Adolescent↗
PubMed1993

Optimized separation of purine bases and nucleosides in human cord plasma by capillary zone electrophoresis.

An optimized separation of the main purine compounds of human serum by capillary zone electrophoresis is presented. Separations were performed in an uncoated silica capillary (44 cm x 75 microns I.D., 37 cm to window) on a SpectraPhoresis 1000 system with UV detection. The separation of adenine (Ade), adenosine (Ado), guanine (Gua), guanosine (Guo), hypoxanthine (Hyp), inosine (Ino), xanthine (Xan) and uric acid (UA) was optimized with respect to pH, temperature, applied potential and hydrodynamic injection time. Optimum conditions were 20 mM borate buffer (pH 9.4), 37 degrees C, 20 kV and 9 s load and detection at 260 nm. Linearity extended from 1 to 125 microM. The sensitivity of the method was 0.5 microM, which is adequate for measuring Ade, Gua, Hyp and UA in plasma samples. Plasma samples from newborns were precipitated with an equal volume of perchloric acid (7%, v/v), the supernatant was adjusted to neutral pH with potassium carbonate and, before injection, the sample was alkalized with sodium hydroxide. The method presented here allows the determination of Ade, Guo, Hyp and UA. The levels of the determined purines were compared in samples from control newborns, preterm babies and newborns with asphyxia or acidic serum pH values.

Calibration↗
PubMed1993

Estimation of steady-state flux rates in metabolic systems by computer simulations of radioactive tracer experiments.

The dynamics of radioactive tracers in metabolic systems can be mathematically modelled by coupled systems of differential equations for both the concentrations and the specific radioactivities of the metabolites involved. Computer simulations, i.e. direct fitting of numerical solutions of these equations to observed time-courses of metabolites and specific radioactivities, enables one to estimate unknown kinetic parameters of the system. The theoretical fundamentals of this approach and the main steps towards the quantitative assessment of flux rates in stationary metabolic systems are outlined. An application of the method to the purine nucleotide metabolism of Ehrlich ascites tumor cells is given based on a simplified model of this pathway. The obtained steady-state flux rates indicate a marked increase in the metabolism of the adenine nucleotides during the proliferating phase in comparison to the resting phase of tumor growth.

Adenine Nucleotides↗
PubMed1993

Posttransfusional changes of 2,3-diphosphoglycerate and nucleotides in CPD-SAGM-preserved erythrocytes.

BACKGROUND: Posttransfusional changes of preserved red blood cells can influence the oxygen equilibrium curve which is mainly affected by the concentration of erythrocyte 2,3-diphosphoglycerate (DPG). MATERIAL AND METHODS: The regeneration kinetics of DPG and nucleotides (ATP, ADP, AMP, GTP, GDP) was determined over a period of 0-48 h in surgically treated patients following transfusion of DPG-depleted packed red cells stored for 14 days in CPD-SAGM. RESULTS: 3 h after transfusion the DPG levels raised up to 40% of the patients' prior DPG concentrations. Complete regeneration of the DPG concentrations occurred 36-48 h after transfusion. Changes in the nucleotide pattern indicate, after a temporary decrease of ATP and GTP levels (after 10-30 min) and an activation phase (after 3-12 h), the full regeneration of these parameters 24-48 h after transfusion. CONCLUSIONS: The regeneration kinetics of DPG should be taken into consideration for transfusions with blood units stored for more than 14 days, especially in patients with reduced compensatory mechanisms (coronary and cerebral scleroses, pacemaker, etc.) and large transfusion volumes.

2,3-Diphosphoglycerate↗
PubMed1993

Trichlorobromomethane-induced changes of purine nucleotides in hepatocytes.

The changes in nucleotide content during CBrCl3 treatment were investigated. In the first 5-10 minutes a significant ATP decrease was detected. The GTP loss leading to 57% of the initial level after 10 min surpasses the ATP loss which leads to 70% of the initial value after 10 min. The increase in uric acid is not only the result of CBrCl3 induced reaction, because of no significant changes in adenine and hypoxanthine values. The uric acid pool reflected different influx and efflux processes. These changes were compared with nucleotide degradation and accumulation of nucleotide degradation products during anoxia.

Adenosine Triphosphate↗
PubMed1993

Studies on lipoate effects on blood redox state in human immunodeficiency virus infected patients.

Several investigators have implicated that human immunodeficiency virus (HIV) infected patients have a compromised antioxidant defense system. Blood antioxidants are decreased and peroxidation products of lipids and proteins are increased in the patients. This may have pathophysiological implications, because antioxidants, such as glutathione, and reactive oxidants are involved in the regulation of the human immunodeficiency virus. Consequently it was suggested that HIV infected patients may benefit from antioxidant supplementation therapy. In a open and unblinded pilot study the short term effect of the natural antioxidant lipoate (Thioctacid) on blood antioxidants and peroxidation products was investigated in HIV positive patients (CDC IV). In the majority of the patients, lipoate increased plasma ascorbate (9 of 10 patients) total glutathione (7 of 7 patients), total plasma thiol groups (8 of 9 patients); T helper lymphocytes and T helper/suppressor cell ratio (6 of 10 patients), while the lipid peroxidation products malondialdehyde (8 of 9 patients) and 4-hydroxynonenal (7 of 9 patients) were decreased. The results of this pilot study indicate that lipoate supplementation changes the blood redox state of HIV infected patients. A prospective and longitudinal therapy study is warranted to investigate the long term effects of lipoate therapy on blood redox state, disease progression and incidence of opportunistic infections in HIV infected patients.

Adult↗
PubMed1993

Adenosine affects the f-met-leu-phe induced changes in cytosolic Ca2+ and in membrane potential of human granulocytes.

Indo 1 acetoxymethyl ester and 3,3-dipentyloxacarbocyanine iodide have been used to investigate the effect of adenosine on the changes in cytosolic Ca2+ concentration and in membrane potential of human granulocytes activated by the chemotactic tripeptide f-met-leu-phe. Adenosine does not significantly affect negative (hyperpolarizing) potential changes as well as calcium accumulation in cytosol, whereas both the amplitude of the depolarization phase and the relaxation time for restoring the initial intracellular calcium level are reduced.

Adenosine↗
PubMed1992

Changed purine nucleotide concentrations and enzyme activities in erythrocytes of haemodialysis patients undergoing erythropoietin therapy.

Therapy of renal anaemia in haemodialysis patients with chronic renal failure by application of recombinant human erythropoietin leads to an increase of the haematocrit. Rejuvenation of the erythrocyte population results in a decrease of the median density (D50), an increase of cell age-dependent enzyme activities, such as aspartate aminotransferase, and elevated concentrations of purine nucleotides in the erythrocytes. After density gradient separation of erythrocyte populations into cell age-dependent fractions, the concentrations of adenosine-5'-triphosphate, guanosine-5'-triphosphate and guanosine-5'-diphosphate were be found to be elevated by 25-100% in all cell fractions from haemodialysis patients, compared with a healthy control group. Therapy of haemodialysis patients with recombinant human erythropoietin leads to further increase (65%) of ATP in the younger (low density) cells, but not in the older (high density) cells. The elevated concentrations of ATP and total adenine nucleotides during recombinant human erythropoietin therapy possibly result in improved deformability of erythrocytes. The data point to an enhancement of the proportion of younger erythrocytes, but not to an improvement of the reduced life span of erythrocytes of haemodialysis patients during therapy with recombinant human erythropoietin.

Adenosine Diphosphate↗
PubMed1992

Adenine metabolism of Ehrlich mouse ascites cells in proliferating and resting phase of tumor growth.

The incorporation of 14C from [U-14C]adenine into the pools of purine nucleotides, nucleosides and bases in Ehrlich mouse ascites cells (EMAC1) during the proliferating and resting phases of tumor growth was compared. In the proliferating phase the total 14C incorporation into purine pools is much faster than in the resting phase. The ATP turnover as well as the purine breakdown to hypoxanthine and uric acid are increased in the proliferating phase. That corresponds to previous findings on higher nucleotide pool sizes and higher ATP yield and ATP-consuming processes in this growth period.

Adenine↗
PubMed1992

Changes in the glutathione system of erythrocytes due to enhanced formation of oxygen free radicals during short-term whole body cold stimulus.

The red cell glutathione levels of 10 healthy volunteers who are accustomed to winter-swimming were measured before and after this short-term whole body exposition to hypothermic environment. From the increases of the erythrocytic level of oxidized glutathione (GSSG) and of GSSG: total glutathione ratio an extensive formation of oxygen free radicals during and following the exposition to the intensive cold stimulus was concluded. That is in accordance with the finding on the drastic decrease of the concentration of uric acid as an important radical scavenger of the human blood plasma. Furthermore, the initial erythrocytic concentrations of reduced glutathione (GSH) and GSSG of subjects accustomed to winter-swimming were compared with those of healthy control persons who are not accustomed to regular winter-swimming. The markedly increased concentration of GSH and the reduced GSSG:total glutathione ratio in the erythrocytes of winter-swimmers reflect the adaptation to a regular oxidative stress. This antioxidative adaptation is postulated as a new basic mechanism of the hardening by exposition to an intensive short-term cold stimulus often applied within the hydrotherapy.

Adaptation, Physiological↗
PubMed1991

Changes of nucleotide patterns in liver, muscle and blood during the growth of Ehrlich ascites cells: application of the reversed-phase and ion-pair reversed-phase high-performance liquid chromatography with radial compression column.

The pool of purine compounds was analysed in liver, skeletal muscle and blood of mice during the growth of Ehrlich ascites tumour cells. Three fast isocratic high-performance liquid chromatographic methods were used. (1) Determination of nucleotides by an isocratic ion-pair reversed-phase chromatography with a 10 mM ammonium phosphate buffer containing acetonitrile and tetrabutylammonium phosphate. (2) Separation of nucleosides and nucleobases in cell extracts by a reversed-phase system with methanol and 50 mM potassium phosphate buffer as eluent. (3) Nucleosides and nucleobases in body fluids were analysed by a reversed-phase system with 10 mM potassium phosphate containing methanol. These methods allow the rapid determination of purine compounds in small biological samples from various cell types and body fluids, with high accuracy and sensitivity. The pool of cellular nucleotides increased during the exponential phase of tumour growth. Adenosine accumulated significantly in all tissues in the stationary phase of tumour growth.

Animals↗