Oxidative stress leads to inhibition of calcium transport by sarcoplasmic reticulum in skeletal muscle

Iron administration results in the development of oxidative stress in skeletal muscles, as evidenced by increases in amounts of lipid oxidation fluorescent end products, decreases in vitamin E concentration, and inhibition of calcium transport by sarcoplasmic reticulum. Exhaustive physical loading or hyperoxia, or their combination, does not lead to apparent modification in calcium transport by sarcoplasmic reticulum in skeletal muscle homogenates. However, physical loading or hyperoxia does in fact induce oxidative stress since they magnify the effect of iron loading on the inhibition of calcium transport.     

The mechanisms of the antioxidant action of shielded phenols in biological membranes. The effects of 4-methyl-2,6-di-tert-butylphenol (ionol) and its derivatives

According to Bulgarian-Soviet program "Biostab" we studied characteristics of different phenol compounds (ionol derivatives). The aim of the present study is to determine antiradical and antioxidant activity of a number of ionol derivatives in pure chemical systems and in different membrane fractions of a natural origin.     

Intramolecular hydrogen bonds and conformation of the lincomycin molecule in organic solvents

IR spectra (1600-1800 and 3000-3650 cm-1) of lincomycin base solutions in inert (CCl4 and C2Cl4), proton acceptor (dioxane, dimethylsulfoxide and triethyl amine) and proton donor (CHCl3, CD3OD and D2O) solvents were studied. Analysis of the concentration and temperature changes in the spectra revealed that association in lincomycin in the inert solvents was due to intramolecular hydrogen linkage involving amide and hydroxyl groups. Disintegration of the associates after the solution dilution and temperature rise was accompanied by formation of intramolecular bonds stabilizing the stable conformation structure of the lincomycin molecule. The following hydrogen linkage in the conformation was realized: NH...N (band v NH...N at 3340 cm-1), OH...O involving the hydroxyl at C-7 and O atoms in the D-galactose ring (band v OH...O at 3548 cm-1), a chain of the hydrogen bonds OH...OH...OH in the lincomycin carbohydrate moiety (band v OH...O at 3593 cm-1 and v OH of the end hydroxyl group at 3625 cm-1). Bonds NH and C-O of the amide group were located in transconformation. Group C-O did not participate in the intramolecular hydrogen linkage.     

Decreased velocity of shortening in arterial smooth muscle from older (28- to 31-week-old) spontaneously hypertensive rats

An increased maximum velocity of shortening (Vmax) and increased shortening ability (delta Lmax) have been reported for caudal arterial smooth muscle from 16- to 18-week-old spontaneously hypertensive rats (SHR) compared with age-matched Wistar-Kyoto (WKY) control rats. It is known that hypertension results in hypertrophy of vascular smooth muscle. It is plausible that the faster Vmax of 16- to 18-week-old SHR arterial smooth muscle may slow down with age due to hypertrophy. The force-velocity (F-V) study done previously on caudal arterial strips from 16- to 18-week-old SHR and WKY rats was repeated on preparations from 28- to 31-week-old rats. An electromagnetic muscle lever was employed in recording force-velocity data. Analysis of these data revealed that the 28- to 31-week-old SHR (n = 7) mean F-V curve was not different from the 28- to 31-week-old WKY (n = 5) mean F-V curve (p greater than 0.05), and the shortening ability of 28- to 31-week-old SHR arterial muscle was significantly depressed compared with 28- to 31-week-old WKY arterial muscle (p less than 0.01). In conclusion, (i) although Vmax is faster in younger (16- to 18-week-old) SHR compared with age-matched WKY caudal arterial smooth muscle, SHR Vmax is not different from WKY Vmax in the older (28- to 31-week-old) rats. (ii) Shortening ability is greater in 16- to 18-week-old SHR caudal arterial strips compared with 16- to 18-week-old WKY strips, but is significantly depressed in 28- to 31-week-old SHR compared with 28- to 31-week-old WKY preparations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reaction pathway of bovine aortic lysyl oxidase

The catalysis of amine oxidation by lysyl oxidase has been probed to assess for the likely order of substrate binding and product release and to discriminate between mechanistic alternatives previously proposed for other copper-dependent amine oxidases using molecular oxygen as a substrate. Lineweaver-Burk plots revealed a pattern of parallel lines when the oxidation of n-butylamine was followed at different fixed concentrations of oxygen consistent with a "ping-pong" kinetic mechanism in which the aldehyde is produced and released before the binding of oxygen, the second substrate. Initial burst experiments revealed the ability of lysyl oxidase to form and release n-butyraldehyde in amounts stoichiometric with functional active site content in the absence of oxygen, consistent with the ping-pong kinetics obtained. Reciprocal plots of n-butylamine oxidation in the presence of fixed concentrations of the reaction products were consistent with a Uni Uni Uni Bi ping-pong kinetic mechanism with the aldehyde being the first, H2O2 the second, and ammonia the last departing product. Moreover, spectral studies of the oxidation of p-hydroxybenzylamine by lysyl oxidase indicated that the enzyme does not process the amine substrate to a noncovalently bound p-hydroxybenzaldimine intermediate subsequently to be hydrolyzed to p-hydroxybenzaldehyde. The kinetic mechanism of lysyl oxidase thus appears to be similar to those described for diamine oxidase and pig plasma monoamine oxidase.     

Reactivity of a functional carbonyl moiety in bovine aortic lysyl oxidase. Evidence against pyridoxal 5''-phosphate.

Previous studies have pointed towards a cofactor role for pyridoxal 5'-phosphate (PLP) in lysyl oxidase, the enzyme that generates the peptidyl aldehyde precursor to the lysine-derived cross-linkages in elastin and collagen. The nature of a carbonyl moiety in purified bovine aortic lysyl oxidase was explored in the present study. A PLP dinitrophenylhydrazone could not be isolated from lysyl oxidase, although corresponding preparations of aspartate aminotransferase, a PLP-dependent enzyme, yielded this derivative, as revealed by h.p.l.c. Analysis of lysyl oxidase for PLP after reduction of the enzyme by NaBH4, a procedure that converts PLP-protein aldimines into stable 5'-phosphopyridoxyl functions, also proved negative in tests using monoclonal antibody specific for this epitope. Lysyl oxidase was competitively inhibited by phenylhydrazine, and inhibition became irreversible with time at 37 degrees C, displaying a first-order inactivation rate constant of 0.4 min-1 and KI of 1 microM. [14C]Phenylhydrazine was covalently incorporated into the enzyme in a manner that was prevented by prior modification of the enzyme with beta-aminopropionitrile, a specific active-site inhibitor, and which correlated with functional active-site content. The chemical stability of the enzyme-bound phenylhydrazine exceeded that expected of linkages between PLP and proteins. The absorption spectrum of the phenylhydrazine derivative of lysyl oxidase was clearly distinct from that of the phenylhydrazone of PLP. It is concluded that lysyl oxidase contains a carbonyl cofactor that is not identical with PLP and that is bound to the enzyme by a stable chemical bond.     

PQQ, the elusive coenzyme

The recently discovered redox coenzyme, PQQ (methoxatin), is widely distributed. Quantitation of protein-bound PQQ has been difficult, but unique redox cycling reactions, which reflect its striking biological properties, reveal trace amounts. PQQ is a potential target for drugs.     

Electron transport between cytochrome c and alpha tocopherol.

Using liposomes we have demonstrated an electron transfer between tocopherol (vitamin E) and cytochrome c. Reduced cytochrome c protects vitamin E from oxidation induced either directly by ultraviolet light or indirectly by soybean lipoxygenase-catalyzed oxidation of arachidonic acid. Oxidized cytochrome c is reduced by tocopherol and tocopherol homologues (chromanols) resulting in accumulation of tocopheroxyl radicals which we detected by ESR. The peak height of the ESR spectrum of tocopheroxyl radicals (which is proportional to the amount of radical present) is proportional to the ratio of reduced to oxidized cytochrome c. In mitochondrial membranes succinate-cytochrome c reduction is inhibited by antimycin A. Addition of exogenous chromanols facilitates a by-pass of the antimycin A blocked electron pathway, and succinate-dependent cytochrome c reductase activity is restored. Cytochrome c may act as a water-soluble complement to the lipid-soluble ubiquinol in regenerating mitochondrial tocopherol from tocopheroxyl radical.     

Tolerance of gentacycol--a local dosage form of gentamicin based on collagen--animal experiments

Gentacycol is a local dosage form of gentamicin based on collagen for implantation to wounds in treatment of patients with infections of soft tissues and prevention of contamination of open injuries of the bones and soft tissues. General toxic and organotropic properties of gentacycol were studied on animals with subcutaneous implantation of the dosage form in doses equivalent to the therapeutic dose for man and exceeding it 2-fold. The study showed that the dosage form had no unfavourable side effects on the animal general state, hearing, the functional state of the liver and kidneys and the peripheral blood. In the doses tested gentacycol did not influence the indices of the cardiovascular system and neuromuscular conduction. Morphological examination of the skin and hypodermic tissues in the implantation site revealed no damaging action of the dosage form on the surrounding tissues.