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Biomedical subjects

G Gerber

Publications and source records attributed to G Gerber.

At least 109 records · Page 6Linked to original sources
PubMed1985

Formation of activated oxygen in the hypoxic rat liver.

The biliary GSSG efflux rate of normoxic perfused rat liver was 1.5 +/- 0.2 nmol/min/g liver wet weight. The GSSG efflux rate as indicator for the flux through the glutathione peroxidase reaction and, therefore, for an oxidative loading increased with the extent of hypoxia. 2.6 +/- 0.5 nmol/min/g were released from the severely hypoxic liver. The hydroxyl radical scavenger formate as well as the xanthine oxidase inhibitor allopurinol reduced the efflux rate of GSSG. GSH was released from the perfused liver at a rate of 15.5 nmol/min/g which was nearly unchanged in severe hypoxia. The high rate of glucose liberation from the hypoxic liver declined to almost that of the normoxic organ in the presence of formate. There is an 'oxidative stress' during hypoxic liver perfusion which probably originates from increased generation of activated oxygen species in the degradation of purine nucleotides.

Animals↗
PubMed1984

Release of microvesicles from erythrocytes during storage in saline-adenine-glucose media.

Storage of human erythrocytes in SAG media results in the release of membrane microvesicles with a diameter of about 190 nm. They can be separated from intact erythrocytes by centrifugation on a dextran barrier solution (density 1.078 g/l). Vesicles prepared from cold stored erythrocyte concentrates are like those released upon ATP depletion by erythrocytes incubated without glucose at 37 degrees C [15]. The course of vesiculation was followed by measuring acetylcholinesterase during storage of the erythrocyte concentrate for 35 days. Its activity remained constant within the storage units during the preservation period. This enzyme and phospholipids were released continuously in a proportional manner. The release of sialic acid amounted to about half of that of phospholipids. Owing to depletion of 2,3-bisphosphoglycerate the binding of ATP to haemoglobin increased and the concentration of free ATP declined. Addition of an ion-exchange resin to stored erythrocytes kept the pH constant, retarded the breakdown of 2,3-P2G and stabilized the concentration of free ATP. That inhibited the rate of irreversible vesiculation. Therefore, maintenance of 2,3-bisphosphoglycerate plus ATP during long-term storage of erythrocytes is a condition of keeping intact their membrane, metabolism and oxygen transport function.

Acetylcholinesterase↗
PubMed1983

Status of glutathione in the rat liver. Enhanced formation of oxygen radicals at low oxygen tension.

Rat livers were initially perfused and then stored at various temperatures up to 4 h. The intra- and extrahepatic status of glutathione, the accumulation of hydrogen peroxide in the preservation medium, the action of a OH-scavenger and of a xanthine oxidase-inhibitor were investigated as candidates for the assessment of oxidative alterations due to ischemia. Furthermore respiratory functions of mitochondria were measured. The increased efflux of GSSG from the liver tissue, the increase of the GSSGtot/GSHtot-ratio and the favourable effects of formate as OH-scavenger and of allopurinol as xanthine oxidase-inhibitor confirm the hypothesis about the oxidative damage under conditions of oxygen deficiency. The nucleotide degradation, especially the steps catalyzed by xanthine oxidase and uricase, is the main metabolic pathway for the generation of oxygen radicals under ischemic conditions.

Animals↗
PubMed1981

2,3-Biphosphoglycerate, inorganic phosphate, pH and hemoglobin concentration in chronic renal failure of man.

In a group of 69 patients with chronic renal failure, 18 patients after renal transplantation and 8 healthy controls the influence of inorganic phosphate and pH of plasma and of the hemoglobin concentration in whole blood on the 2,3-DPG concentration in red blood cells was investigated. The data were treated by linear regression analysis as well as by multivalent correlation analysis with graph-theoretical methods. Hemoglobin and inorganic phosphate are the factors of renal importance for the 2,3-DPG concentration. The pH affects 2,3-DPG directly (positively) and indirectly via inorganic phosphate (negatively). Therefore, the influence of pH on 2,3-DPG usually observed is abolished in this group of patients. Determinations of inorganic phosphate and hemoglobin seem to be valuable for the diagnosis of the 2,3-DPG-dependent oxygen transport function during chronic renal failure. All the parameters studied were found to be normalized in the group of patients after renal transplantation.

2,3-Diphosphoglycerate↗
PubMed1978

Effect of dietary lead on placental blood flow and on fetal uptake of alpha-amino isobutyrate.

Large amounts of lead administered to pregnant mice can prevent implantation, cause embryonic death or retarded growth. Placental blood supply measured by injected radioactive microspheres is of the order of 23% of the cardiac output for a litter of eight mice on day 18 of pregnancy. In lead-treated animals, not only placental blood flow per embryo but also that per embryo weight is reduced. On the other hand, uptake of a non metabolizable amino acid, alpha amino isobutyrate is not altered by lead treatment. It is noteworthy that about 40% of this amino acid go to the embryo during pregnancy. In view of the normal substrate uptake at a reduced bloodflow it remains undecided whether an insufficient supply by the placenta or a reduction in hem synthesis described earlier is the factor responsible for the retardation in fetal growth.

Aminoisobutyric Acids↗
PubMed1978

The dependence on the extramitochondrial ATP/ADP-ratio of the oxidative phosphorylation in mitochondria isolated by a new procedure from rat skeletal muscle.

A simple method for preparation of rat skeletal muscle mitochondria is presented using gentle mechanical homogenization in a syringe and nagarse treatment (EC 3.4.4.16). This method enables the preparation of skeletal muscle mitochondria, whose outer membrane is intact to 95%. Furthermore, with mitochondria prepared by this method the regulation of respiration and phosphorylation by the extramitochondrial ATP/ADP-ratio can be demonstrated. In accordance to rat liver and heart mitochondria and to mitochondria of rabbit reticulocytes, the regulation by the extramitochondrial ATP/ADP-ratio lies in the range from 5 (corresponding to 98% of the maximum respiration) to 100 (corresponding to state 4). At extramitochondrial ATP/ADP-ratios from 0.01 to 1 the respiration rate is nearly constant (maximum rate of respiration).

Adenosine Diphosphate↗
PubMed1976

Response of the glycolysis of human erythrocytes to the transition from the oxygenated to the deoxygenated state at constant intracellular pH.

The time course of the rate of the glycolysis of human erythrocytes and of some metabolites were determined before and after rapid deoxygenation at constant intracellular pH. For this purpose stripped deoxygenated haemoglobin was used as a rapid oxygen acceptor. Deoxygenation causes an increase of the glycolytic rate by 26%. Glucose 6-phosphate is decreased while the adenine nucleotides and 2,3-bisphosphoglycerate remain constant. Fructose 1,6-bisphosphate and the triose phosphates decrease transiently before rising. The data can be explained by increased binding of phosphocompounds to deoxygenated as compared with oxygenated haemoglobin. Thereby the control enzymes hexokinase and phosphofructokinase are influenced. It is concluded that under physiological conditions changes in the oxygenation state of haemoglobin per se alter the glycolytic rate.

Erythrocytes↗