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Biomedical subjects

G Wendel

Publications and source records attributed to G Wendel.

5 recordsLinked to original sources
PubMed2000

Amino acid and alpha-keto acid metabolism depends on oxygen availability in chronic hemodialysis patients.

Amino acid and alpha-keto acid metabolism depends on oxygen availability in chronic hemodialysis patients. Malnutrition in hemodialysis (HD) patients with renal anemia is reflected in an abnormal plasma amino acid profile. We wished to determine the extent to which malnutrition can be improved by correcting anemia with recombinant human erythropoietin (rhEPO) and supplemental iron. As specific parameters we measured and compared the plasma concentrations of the branched-chain amino acids valine, leucine and isoleucine and their transamination products - major participants in proteolysis and protein biosynthesis - using HPLC with fluorescence detection in 45 severely anemic HD patients (group A: Hb 7.2 +/- 0.8 g/dl), 34 patients with partially corrected anemia (group B: Hb 10.3 +/- 0.6 g/dl) and 35 HD patients with totally corrected anemia (group C: Hb 13.5 +/- 0.7 g/dl). Sixty healthy subjects (group N: Hb 14.2 +/- 1.1 g/dl) served as controls. Correlating with the degree of correction (A/B/C/N), a significant shift to anabolic metabolism was observed in the plasma levels of valine: 130/146/155/205 micromol/l; leucine: 73/71/80/110 micromol/l and alpha-ketoisocaproate (KIC): 11.4/11.8/15.1/ 30.4 micromol/l. It is concluded that energy metabolism becomes increasingly anabolic as hemoglobin levels are normalized.

Amino Acids, Essential↗
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↗
PubMed1990

Erythropoiesis and erythrocyte age distribution in hemodialysis patients undergoing erythropoietin therapy.

Renal anemia is caused in part by a reduced life span of red blood cells (RBCs) and by reduced erythropoietin biosynthesis in the damaged kidney. The RBC age can be determined by density gradient centrifugation and estimation of cell-age-dependent enzyme activities, as aspartate aminotransferase. The RBC age distribution influences the median density (D50) of RBCs and the blood rheology in coherence with the hematocrit. In our study, the median density was determined by Percoll density gradient centrifugation in 18 healthy subjects (D50 = 1.0674 +/- 0.0016 g/ml) and in 14 hemodialysis patients (D50 = 1.0674 +/- 0.0016 g/ml in the course of recombinant human erythropoietin (rhEPO) therapy. During the first 4 weeks of therapy, a strong rejuvenation of RBCs was observed whereby the D50 reached a minimum after 2 weeks (D50 = 1.0655 +/- 0.0022 g/ml; p less than 0.05 vs. value before therapy) and a steady state after 4 weeks (D50 = 1.0658 +/- 0.0013 g/ml; p less than 0.1 vs. value before therapy). In 5 of the patients with elevated plasma parathyroid hormone (i-PTH) concentrations greater than 10 pmol/l, a significantly (p less than 0.05) reduced amount of younger RBCs (D50 = 1.0675 +/- 0.0016 g/ml) was observed in the first 2 weeks of rhEPO therapy as compared to patients with i-PTH less than 10 pmol/l (D50 = 1.0677 +/- 0.0019 g/ml). Thus, erythropoiesis in the early phase of rhEPO therapy is strongly influenced by elevated plasma i-PTH concentrations. Therefore, a gradual increase in rhEPO doses is preferable before therapy at elevated doses with an uncontrolled increase in RBC amount.

Adult↗
PubMed1990

Red blood cell density distribution in uremic patients on acetate and bicarbonate hemodialysis.

Renal anemia is the result of reduced erythropoietin (EPO) biosynthesis in the diseased kidney and also in part the result of a reduced life span of red blood cells (RBCs). An increase in density and a decrease in enzyme equipment (aspartate aminotransferase; GOT) of RBCs reflect cell age. In the following study, the density distribution (median density D50; determined by Percoll density gradients) and GOT activities of RBCs were measured in patients on acetate (HDA; n = 15) and bicarbonate (HDB; n = 51) hemodialysis. Hemoglobin (Hb) concentrations were: in the HDB group, 9.1 +/- 3.4 g/dl; in the HDA group, 6.2 +/- 1.2 g/dl, and, in a control (C) group of healthy persons, 14.0 +/- 1.5 g/dl. 14 HDB patients with severe anemia received EPO therapy during 1 year. D50 were found as follows: group C, 1.0674 +/- 0.0016 g/ml; HDB, 1.0674 +/- 0.0015 g/ml, and HDA, 1.0660 +/- 0.0012 g/ml (HDA vs. group C: p less than 0.05; HDA vs. HDB: p less than 0.05. D50 were elevated in the subgroups of HDA and HDB patients with severe anemia (Hb less than 8 g/dl). During activated erythropoiesis by EPO therapy, D50 decreased from 1.06739 +/- 0.0015 to 1.0656 +/- 0.0014 g/ml. The GOT activities in RBCs demonstrated a rejuvenation of the RBC population in the HDB group (6.4 +/- 2.5 U/g Hb) and HDA group (5.9 +/- 3.1 U/g Hb) compared to group C (3.9 +/- 1.3 U/g Hb).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗