Use of a heptane-isopropanol system for extraction of primary lipid peroxidation products

Products of different lipids oxidation were studied for the peculiarities of their distribution in the extracting system heptane--isopropanol widely used in spectrophotometric determination of primary products of peroxide oxidation of lipids. It is shown that hydroperoxides of phospholipids and their reduction products almost completely transfer to the alcohol phase while hydroperoxides of triacetin and cholesterol esters are 70-85% extracted by heptane. Thus, it is necessary to analyze the alcohol phase when using the systems heptane-isopropanol to determine the content of primary products of lipid peroxide oxidation in those tissues, where phospholipids are the basic oxidation substrates.     

Antioxidative activity of flavonoids in various systems of lipid peroxidation

The antioxidant action of flavonols in different systems of lipid peroxidation (LPO) was studied. Quercetin and rutin were found to inhibit NADPH and CCl4-dependent LPO in rat liver microsomes, however, in the case of CCl4-dependent LPO, rutin had a very poor antioxidant effect. Study of flavonols oxidation by products of the cytochrome c catalyzed destruction of linoleic acid hydroperoxide demonstrated that the differences in the antioxidant offects of quercetin and rutin can be due to their different capability to terminate free radical chain reactions. The antioxidant effect of rutin was shown to be largely due to the chelating properties of this compound.     

Status of the antioxidant protective system of rat liver exposed to carbon tetrachloride]

The dynamics of enzyme activity of antioxidative protective system of the liver and the content of restored glutathione have been studied in rats poisoned by CCl4 injection. During the first hours followed the injection against the background of maximum accumulation of dienic conjugates and decrease of the restored glutathione level no significant changes in the enzyme activity of the antioxidative protective liver system were observed. At the same time 48 hours later the superoxide dismutase and catalase activity decreased by 38% and 36%, respectively, with relative stability of glutathione-dependent enzymes and a two-fold increase of the restored glutathione level. It is shown that a fall of activity of the cytoplasmic antioxidative liver enzymes is not a result of the immediate inactivating effect of free-radical reactions initiated by CCl4, but is, evidently, caused by the covalent binding of its radical metabolites with corresponding macromolecules.     

Time-resolved fluoroimmunoassay of potato virus M with monoclonal antibodies

Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double-antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots. MAbs against PVM were used as capture antibodies and europium-labelled MAbs as conjugates in time-resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10^--⁴ with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double-label TRFIA using europium-labelled MAbs to PVM and samarium-labelled MAbs to PVX.     

DNA-signaling pathway mediating development of a radiation-induced bystander effect in human cells

Low doses of ionizing radiation induce the adaptive effect (AE) development in human cells which is followed by a number of cell responses. These responses can be transmitted from irradiated cells to non-irradiated ones (bystander effect, BE). The major role in radiation-induced BE is played by an oxidative stress (OS) and a DNA-signaling pathway, in which extracellular DNA fragments (ecDNA) are the factors of stress-signalization. We propose the following sequence of events in this signaling system: irradiation-OS-DNA modification-apoptosis of irradiated cells-ecDNA-signal acceptance by non-irradiated cells-OS-DNA modification, etc. We observed a radiation-induced BE which is accompanied by DNA-signaling pathway in differentiated and undifferentiated human cells forming monolayer or suspension cultures. Here we discuss several aspects of the radiation-induced BE mechanism and its persistence possibilities.     

Numerical model for intraosseous infusion of the human calvarium for hydrocephalus shunting

Hydrocephaly is the defective absorption of cerebrospinal fluid (CSF) into the blood stream. This work is an experimental and computational fluid dynamic modelling study to determine the permeability of the diploë as a potential receptor for CSF. Human calvariae were studied by micro-CT to measure their porosity, the area of flow and develop model geometry. Pressure-flow measurements were conducted on specimens to determine their permeability in the physiological and transverse flow directions to compare with numerical results. The overall porosity and permeability of the calvaria were spatially variable. Results suggest an order of magnitude increase in permeability for a 14% increase in overall porosity based on a small number of samples. Numerical results fell within the experimental infusion tests results. Due to the difficulty and ethical considerations in obtaining adolescent skull samples to perform large-scale testing, the developed model will be invaluable.     

Inhibition of microsomal oxidation by o-benzoquinone derivatives

It was found that o-benzoquinone derivatives inhibit the hydroxylation of aniline without any appreciable influence on the spectral changes which are due to cytochrome P-450 binding to the substrate. A comparative kinetic study of inhibition of aniline hydroxylation and NADPH-dependent reduction of o-benzoquinones in liver microsomes revealed that the inhibition is due to the ability of these compounds to shunt microsomal electron transport pathways.