Search results for "Glycolysi"
showing 10 items of 155 documents
Influence of therapeutic and toxic doses of neuroleptics and antidepressants on energy metabolism of the isolated perfused rat brain.
1973
The isolated perfused rat brain was used for a comparative study of the effects of promazine, imipramine, monodesmethyl promazine and desipramine on cerebral energy metabolism. After perfusion for 30 min or 1 h the brain levels of the following substrates and metabolites were estimated: P-creatine, creatine, ATP, ADP, AMP, glycogen, glucose, glucose-6-P, fructose diphosphate, dihydroxyacetone-P, pyruvate, lactate, α-ketoglutarate, and ammonia. Drug concentrations of 5·10−6 M and 10−5 M in the perfusion medium caused a significant decrease of glucose-6-P alone. When the drug concentration was raised to a toxic range (10−4 M), reflected in the EEG by the pattern of secondary discharges, an ac…
Strikingly High Respiratory Quotients: A Further Characteristic of the Tumor Pathophysiome
2008
Conspicuously high respiratory quotients (RQs) are found in solid tumors in vivo. RQs in the range between 1.29 and 1.95 neither reflect the degree of substrate oxidation by tumor cells nor indicate the types of fuels involved in metabolic processes. Instead, such tumor RQs most probably are caused by (a) channeling of glycolytic end-products into lipogenesis, and by (b) CO2 release from the tumor following extracellular buffering of H+ -inos by bicarbonate. H+ -inos exported from the intracellular space into the interstitial compartment titrate extracellular bicarbonate to CO2 and H2O with the aid of the ectoenzyme carbonic anhydrase IX, which is activated at low pH. Strikingly high (RQs) …
Dynamics of the Selkov oscillator.
2018
A classical example of a mathematical model for oscillations in a biological system is the Selkov oscillator, which is a simple description of glycolysis. It is a system of two ordinary differential equations which, when expressed in dimensionless variables, depends on two parameters. Surprisingly it appears that no complete rigorous analysis of the dynamics of this model has ever been given. In this paper several properties of the dynamics of solutions of the model are established. With a view to studying unbounded solutions a thorough analysis of the Poincar\'e compactification of the system is given. It is proved that for any values of the parameters there are solutions which tend to inf…
Neuronal Bioenergetics and Acute Mitochondrial Dysfunction: A Clue to Understanding the Central Nervous System Side Effects of Efavirenz
2014
Background. Neurological pathogenesis is associated with mitochondrial dysfunction and differences in neuronal/glial handling of oxygen and glucose. The main side effects attributed to efavirenz involve the CNS, but the underlying mechanisms are unclear. Methods. Human cell lines and rat primary cultures of neurons and astrocytes were treated with clinically relevant efavirenz concentration. Results. Efavirenz alters mitochondrial respiration, enhances reactive oxygen species generation, undermines mitochondrial membrane potential, and reduces adenosine triphosphate (ATP) levels in a concentration-dependent fashion in both neurons and glial cells. However, it activates adenosine monophospha…
Stuck at work? Quantitative proteomics of environmental wine yeast strains reveals the natural mechanism of overcoming stuck fermentation
2015
During fermentation oenological yeast cells are subjected to a number of different stress conditions and must respond rapidly to the continuously changing environment of this harsh ecological niche. In this study we gained more insights into the cell adaptation mechanisms by linking proteome monitoring with knowledge on physiological behaviour of different strains during fermentation under model winemaking conditions. We used 2D-DIGE technology to monitor the proteome evolution of two newly discovered environmental yeast strains Saccharomyces bayanus and triple hybrid Saccharomyces cerevisiae × Saccharomyces kudriavzevii × S. bayanus and compared them to data obtained for the commercially a…
Concurrent Measurements of O2 Partial Pressures and pH Values in Human Mammary Carcinoma Xenotransplants
1986
Due to severe restrictions of convective and diffusive transport, hypoxic or even anoxic areas exist in malignant tumors. In addition, a high glycolytic rate in tumors both in the presence and absence of oxygen and the insufficient removal of the hereby produced lactic acid lead to an acidification of the tumor tissue. Both hypoxia and acidosis can influence the efficacy of irradiation, chemotherapy and hyperthermia. However, no comprehensive data on the development of both hypoxia and acidosis within the same tumor are available to date. In particular, there is no information regarding human tumors. Therefore, a new model has been developed which allows the systematic evaluation of both pa…
Lactate: mirror and motor of tumor malignancy
2004
A number of studies have shown that malignant transformation is associated with an increase in glycolytic flux and in anaerobic and aerobic cellular lactate excretion. Using quantitative bioluminescence imaging in various primary carcinomas in patients (uterine cervix, head and neck, colorectal region) at first diagnosis of the disease, we showed that lactate concentrations in tumors in vivo can be relatively low or extremely high (up to 40 micromol/g) in different individual tumors or within the same lesion. In all tumor entities investigated, high concentrations of lactate were correlated with a high incidence of distant metastasis already in an early stage of the disease. Low lactate tum…
The effects of insulin on transport and metabolism of glucose in skeletal muscle from hyperthyroid and hypothyroid rats.
1997
The effects of insulin on the rates of glucose disposal were studied in soleus muscles isolated from hyper- or hypothyroid rats. Treatment with triiodothyronine for 5 or 10 days decreased the sensitivity of glycogen synthesis but increased the sensitivity of lactate formation to insulin. The sensitivity of 3-O methylglucose to insulin was increased only after 10 days of treatment and was accompanied by an increase in the sensitivity of 2-deoxyglucose phosphorylation; however, 2-deoxyglucose and glucose 6-phosphate in response to insulin remained unaltered. In hypothyroidism, insulin-stimulated rates of 3-O-methylglucose transport and 2-deoxyglucose phosphorylation were decreased; however, a…
Ethanol cycle in an ethanologenic bacterium
2002
AbstractA novel redox cycle is suggested, performing interconversion between acetaldehyde and ethanol in aerobically growing ethanologenic bacterium Zymomonas mobilis. It is formed by the two alcohol dehydrogenase (ADH) isoenzymes simultaneously catalyzing opposite reactions. ADH I is catalyzing acetaldehyde reduction. The local reactant ratio at its active site probably is shifted towards ethanol synthesis due to direct channeling of NADH from glycolysis. ADH II is oxidizing ethanol. The net result of the cycle operation is NADH shuttling from glycolysis to the membrane respiratory chain, and ensuring flexible distribution of reducing equivalents between the ADH reaction and respiration.
Metabolomics of the effect of AMPK activation by AICAR on human umbilical vein endothelial cells
2011
AMP-activated protein kinase (AMPK) is a metabolic master switch expressed in a great number of cells and tissues. AMPK is thought to modulate the cellular response to different stresses that increase cellular AMP concentration. The adenosine analog, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) is an AMPK activator used in many studies to assess the effects of AMPK activation on cellular metabolism and function. However, the effect of AICAR on cell metabolism reaches many different pathways and metabolites, some of which do not seem to be fully related to AMPK activation. We have now for the first time used NMR metabolomics on human umbilical vein endothelial cells (HUVEC) fo…