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Metabolic Mechanism (metabolic + mechanism)

Distribution by Scientific Domains

Medical Sciences	50%
Chemistry	33%

Selected Abstracts

A Metabolic Mechanism for the Detrimental Effect of Exogenous Glucose During Cardiac Storage

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 8 2003
Randy P. Pulis
The purpose of this study was to clarify the metabolic events that explain why supplemental glucose is detrimental during cardiac storage. Four solutions were used to flush and store porcine hearts: St. Thomas Hospital Solution (STHS), University of Wisconsin (UW) solution, and UW + 90 mM histidine, and UW + 90 mM histidine + 11 mM glucose. Despite equivalent increases in lactate in the two histidine-buffered groups throughout 10 h of storage, glycogen utilization was evident in the group without supplemental glucose. The presence of glucose resulted in a reduction in energy production, presumably mediated by direct inhibition of glycogenolysis. Furthermore, UW + histidine was the only group to show consistent improvements in ATP and total adenylates. It was concluded that inclusion of the buffering agent, histidine, to UW solution promotes anaerobic energy production as a result, in part, of preserved high levels of the regulatory control enzyme, phosphofructokinase. [source]

A Metabolic Mechanism For Cardiac K+ Channel Remodelling

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2002
George J Rozanski
SUMMARY 1. Electrical remodelling of the ventricle is a common pathogenic feature of cardiovascular disease states that lead to heart failure. Experimental data suggest this change in electrophysiological phenotype is largely due to downregulation of K+ channels involved in repolarization of the action potential. 2. Voltage-clamp studies of the transient outward current (Ito) in diabetic cardiomyopathy support a metabolic mechanism for K+ channel downregulation. In particular, Ito density is significantly increased in diabetic rat isolated ventricular myocytes treated in vitro with insulin or agents that activate pyruvate dehydrogenase. Recent data suggest this mechanism is not limited to diabetic conditions, because metabolic stimuli that upregulate Ito in diabetic rat myocytes act similarly in non- diabetic models of heart failure. 3. Depressed Ito channel activity is also reversed by experimental conditions that increase myocyte levels of reduced glutathione, indicating that oxidative stress is involved in electrical remodelling. Moreover, upregulation of Ito density by activators of glucose utilization is blocked by inhibitors of glutathione metabolism, supporting the premise that there is a functional link between glucose utilization and the glutathione system. 4. Electrophysiological studies of diabetic and non-diabetic disease conditions affecting the heart suggest Ito channels are regulated by a redox-sensitive mechanism, where glucose utilization plays an essential role in maintaining a normally reduced state of the myocyte. This hypothesis has implications for clinical approaches aimed at reversing pathogenic electrical remodelling in a variety of cardiovascular disease states. [source]

Transformation of 2,4,6-trinitrotoluene in soil in the presence of the earthworm Eisenia andrei,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2000
Agnès Y. Renoux
Abstract The ability of the earthworm Eisenia andrei to metabolize 2,4,6-trinitrotoluene (TNT) was studied in experiments with TNT-spiked soils, dermal contact tests, and with an in vitro assay. Lethality of TNT in a forest sandy soil was first determined (14-d LC50 = 143 mg/kg). Then TNT at lethal and sublethal concentrations was applied to the same soil and was monitored along with its metabolites in extracts of soil and earthworm tissue for up to 14 d postapplication. High performance liquid chromatography-ultra violet analyses indicated that TNT was transformed in the presence of E. andrei by a reductive pathway to 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT), and traces of 2,6-di-amino-4-nitrotoluene (2,6-DANT) in earthworm tissues. This transformation could be explained by either a metabolic mechanism within the earthworm or by the enhancement of an earthworm-associated microbial activity or both. The TNT concentrations decreased from the spiked soils. However, the monoamino-dinitrotoluene (2-ADNT and 4-ADNT) concentrations increased with exposure duration and were dependent on the initial TNT soil concentrations. This was also observed to a lesser extent in the TNT-spiked soils with no earthworms present. The biotransformation of TNT into 2-ADNT, 4-ADNT, and 2,4-DANT and the presence of these metabolites in E. andrei after dermal contact on TNT-spiked filter paper showed that dermal uptake can be a significant exposure route for TNT. In vitro experiments showed that earthworm homogenate could metabolize TNT and form 2-ADNT and 4-ADNT at room temperature and at 37°C. This effect was inhibited by heat inactivation prior to incubation or by incubation at 4°C, suggesting that the biotransformation of TNT in the presence of E. andrei may be enzymatic in nature. [source]

Analysis of chemical and metabolic components in traditional Chinese medicinal combined prescription containing Radix Salvia miltiorrhiza and Radix Panax notoginseng by LC-ESI-MS methods

BIOMEDICAL CHROMATOGRAPHY, Issue 8 2007
Ying-Jie Wei
Abstract High-performance liquid chromatography,electrospray ionization-mass spectrometry (LC-ESI-MS) methods were developed for the analysis of chemical and metabolic components in traditional Chinese medicinal combined prescription containing Radix Salvia miltiorrhiza and Radix Panax notoginseng (commonly known as Fufang Danshen prescription, FDP). The HPLC experiments used a reversed-phase Zorbax C18 column with the column temperature at 30°C and a binary mobile phase system consisting of aqueous formic acid (0.1%, v/v) and acetonitrile using a gradient elution at the flow rate of 1.0 mL/min. The ESI-MS was operated with a single-quadrupole mass spectrometer in both negative and positive ion modes. 36 major chromatographic peaks of FDP, including 14 saponins, 13 phenolic acids and nine diterpenoid quinones were characterized by their MS spectra and in comparison with some of the reference standards. In addition, after oral administration of extraction of FDP, the rat's plasma, urine and feces were also analyzed; 53 metabolic components including 30 original components and 23 transformative components of FDP were detected, and possible metabolic pathways of some components in FDP were given. The analysis of chemical and metabolic components in FDP by HPLC-MS methods could be a useful means of identifying the multi-components of FDP and to hint at their possible metabolic mechanism of action in the body. Copyright © 2007 John Wiley & Sons, Ltd. [source]

LOX-Induced Lipid Peroxidation Mechanism Responsible for the Detrimental Effect of Marine Diatoms on Zooplankton Grazers

CHEMBIOCHEM, Issue 15 2007
Angelo Fontana Dr.
Abstract Some marine diatoms negatively affect the reproduction of dominant zooplankton grazers such as copepods, thus compromising the transfer of energy through the marine food chains. In this paper, the metabolic mechanism that leads to diatom-induced toxicity is investigated in three bloom-forming microalgae. We show that copepod dysfunctions can be induced by highly reactive oxygen species (hROS) and a blended mixture of diatom products, including fatty acid hydroperoxides (FAHs); these compounds display teratogenic and proapoptotic properties. The process is triggered by the early onset of lipoxygenase activities that elicit the synthesis of species-specific products, the basic structures of which were established (1,20); these compounds boost oxidative stress by massive lipid peroxidation. Our study might explain past laboratory and field results showing how diatoms damage zooplankton grazers even in the absence of polyunsaturated aldehydes, a class of molecules that has been formerly implicated in mediating the toxic activity of diatoms on copepods. [source]