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Biomedical subjects

E G Schanus

Publications and source records attributed to E G Schanus.

5 recordsLinked to original sources
PubMed1992

The inhibitory effect of water on the Co2+ and Cu2+ catalyzed decomposition of methyl linoleate hydroperoxides.

The inhibitory effect of water on the decomposition of methyl linoleate hydroperoxides (MLHP) catalyzed by Co2+ and Cu2+ was studied in a model system using proton nuclear magnetic resonance (NMR) spectroscopy. MLHP were prepared by photoxidation and purified by chromatographic methods. Proton NMR spectroscopy was used to measure reaction rates by monitoring changes in the intensity of the OOH signal. The rate constant of the reaction was obtained by plotting the natural logarithm of MLHP concentration vs time. In the first part of the study, no transition metals were added to the model system, so that the effect of water could be attributed to the interaction between water and MLHP only. The rate constant of the reaction (K) was found inversely proportional to the concentration of water. There was a downfield chemical shift of both hydroperoxide and water peaks in the NMR spectra when water was added. As temperature increased to 40 degrees C, the difference in K between the systems with 0% and 2% water disappeared. It is proposed that the hydroperoxides were solvated with water which retarded their decomposition. When Co2+ was added to the model system, K decreased as the concentration of water increased from 0% to 1.5%. As temperature increased from 18 degrees C to 40 degrees C, differences between the K for 0% and 2% water disappeared. A similar phenomenon was observed in reactions catalyzed with Cu2+. These findings would support a mechanism in which the protective effect of water involves both the solvation of OOH and hydration of the metal catalyst.

Acetone↗
PubMed1988

Effects of relative humidity on lipid autoxidation in a model system.

A new model system was developed for the study of autoxidation of thin films of neat lipid and the effect of relative humidity on the oxidation reaction. In the model system, the surface-to-volume ratio of lipid was large and measureable, and the relative humidity (RH) and oxygen partial pressure were controlled. Methyl linoleate, oxidized at six different RH as a thin film in an atmosphere of pure oxygen, exhibited a maximum rate of oxidation at 32% RH and minimum rates at 0% and 100% RH. The rates of oxygen uptake, determined manometrically, were linear and reproducible at all six RH. The maximum rate at 32% RH was attributed to solvation and stabilization of the propagation transition state by water. Increasing the RH beyond 32% resulted in solvation of the peroxy radical, sterically hindering the radical from entering the propagation transition state.

Humidity↗
PubMed1988

Microcomputer-based system for data acquisition and analysis of oxygen uptake studies.

The use of a Warburg Respirometer to study oxidation reactions is tedious and time-consuming. A microcomputer-based oxygen uptake device that is more sensitive than a Warburg Respirometer is described. The device consists of stainless steel or Teflon reaction vessels coupled to ultrasensitive pressure transducers. A high speed analog to digital convertor is used to poll the transducers. The direct memory access (DMA) controller of an IBM XT is used to poll the convertor and store the data in memory. Software used to program the DMA controller and IBM XT is described. The reproducibility and utility of the device is demonstrated with a brief study of lipid oxidation.

Computer Systems↗
PubMed1981

Malignant hyperthermia (MH): porcine erythrocyte damage from oxidation and glutathione peroxidase deficiency.

Malignant hyperthermia (MH) is a severe familial disease in both the pig and the human, with 70% fatality when fully expressed in humans. MH produces rapid elevation of temperature in response to stresses, of which there are two general kinds: Societal or emotional stress, and chemical stressors. The most commonly encountered stressor is halothane, a general anesthetic in wide use. Besides large temperature increases, there occur some twenty symptoms. Much work in other laboratories has been concentrated on elevated CPK i the plasma. However, all the symptoms are consistent with a single disorder, namely oxidative damage, especially in membranes. A deficiency in the glutathione peroxidase (GPX) system is a prime factor, likely the molecular basis allowing abnormal oxidative damage in the MH pig. Catalase activities are normal in MH pigs, but they have only 20-50% normal GPX activities. The deficiency does not cause oxidative damage. It allows failure or protective mechanisms against it. The nonstressed MH animal exhibits less acute symptoms, e.g. enhanced red cell Heinz bodies, but such animals generally mature. Under stress, their inadequate protective mechanisms dependent on GPX are overwhelmed, resulting in gross symptoms and crisis. It is important to concentrate on the GPX system(s) and their adjacent pentose shunt metabolism. We propose that a deficiency in any of these two systems is the molecular basis of the disease. Many tissues are involve in MH, but the red cell obviously provides a convenient means for assay and for screening. This paper mainly pertains to porcine MH. However, preliminary work with humans indicates that human MH has a similar molecular basis.

Animals↗