scholarly journals The influence of porphyrins on iron-catalysed generation of hydroxyl radicals

1988 ◽  
Vol 250 (1) ◽  
pp. 197-201 ◽  
Author(s):  
J Van Steveninck ◽  
J P J Boegheim ◽  
T M A R Dubbelman ◽  
J Van der Zee
Keyword(s):  
Cytochrome C ◽  
Horseradish Peroxidase ◽  
Experimental Evidence ◽  
Xanthine Oxidase ◽  
Hydroxyl Radicals ◽  
Anion Radical ◽  
The Other ◽  
Haematoporphyrin Derivative ◽  
Other Hand

Uroporphyrin I, haematoporphyrin and haematoporphyrin derivative had no effect on O2-. generation during oxidation of hypoxanthine by xanthine oxidase and on the formation of hydroxyl radicals (OH.) in the hypoxanthine/xanthine oxidase/Fe3+-EDTA/deoxyribose system. On the other hand, these porphyrins strongly inhibited O2-. formation in a horseradish peroxidase/H2O2/NADPH mixture, whereas they augmented OH. generation in this system after addition of Fe3+-EDTA. Experimental evidence suggests that these observations should be ascribed to the formation of a porphyrin anion radical in the horseradish peroxidase/NADPH system. The formation of this anion radical was confirmed by e.s.r. spectroscopy. This radical is apparently unable to reduce cytochrome c, but it can replace O2-. in the OH.-generating Haber-Weiss reaction.

Cytochrome c, an ideal antioxidant

2003 ◽  
Vol 31 (6) ◽  
pp. 1312-1315 ◽  
Author(s):  
M.O. Pereverzev ◽  
T.V. Vygodina ◽  
A.A. Konstantinov ◽  
V.P. Skulachev
Keyword(s):  
Superoxide Dismutase ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Cytochrome Oxidase ◽  
The Other ◽  
Other Hand ◽  
O2 Reduction

Generation of Δψ (membrane potential) by cytochrome oxidase proteoliposomes oxidizing superoxide-reduced cytochrome c has been demonstrated. XO+HX (xanthine oxidase and hypoxanthine) were used to produce superoxide. It was found that the generation of Δψ is completely abolished by cyanide (an uncoupler) or by superoxide dismutase, and is enhanced by nigericin. Addition of ascorbate after XO+HX causes a further increase in Δψ. On the other hand, XO+HX added after ascorbate do not affect Δψ, indicating that superoxide does not have measurable protonophorous activity. The half-maximal cytochrome c concentration for Δψ generation supported by XO+HX was found to be approx. 1 μM. These data and the results of some other researchers can be rationalized as follows: (1) O2 accepts an electron to form superoxide; (2) cytochrome c oxidizes superoxide back to O2; (3) an electron removed from the reduced cytochrome c is transferred to O2 by cytochrome oxidase in a manner that generates ΔμH+ (transmembrane difference in electrochemical H+ potential). Thus cytochrome c mediates a process of superoxide removal, resulting in regeneration of O2 and utilization of the electron involved previously in the O2 reduction. It is important that cytochrome c is not damaged during the antioxidant reaction, in contrast with many other antioxidants.

scholarly journals Quercetin oxidation by horseradish peroxidase: The effect of UV-B irradiation

2013 ◽  
Vol 67 (3) ◽  
pp. 411-418 ◽  
Author(s):  
Sasa Savic ◽  
Jelena Stanojevic ◽  
Dejan Markovic ◽  
Zivomir Petronijevic
Keyword(s):  
Horseradish Peroxidase ◽  
Phosphate Buffer ◽  
Antioxidant Activities ◽  
Biological Activities ◽  
The Other ◽  
External Radiation ◽  
Uv Absorber ◽  
Other Hand ◽  
Uv Stress

Horseradish peroxidase (HRP), a highly-investigated member of the peroxidase family has been known, among many other biological activities, to catalyze the oxidation of flavonoids and phenolic substrates overall, including quercetin. On the other hand, quercetin is very well known for its antioxidant activities, which in the case of UV external radiation is exibited partly in a preventive manner since it is an excellent UV-absorber. Therefore the aim of this investigation is to study quercetin oxidation by HRP in phosphate buffer under the conditions of UV-stress, i.e. continuous, prolonged UV-B irradiation. The results show that while UV-B irradiation affects the activity of HRP, and the overal rate of quercetin oxidation by HRP, it probably has very little effect on it for longer UV-B-irradiation periods (>30 min).

Musical Analysis: Hearing Is Believing?

1984 ◽  
Vol 2 (2) ◽  
pp. 237-244 ◽  
Author(s):  
Stephen Walsh
Keyword(s):  
Experimental Evidence ◽  
Psychological Testing ◽  
The Other ◽  
Musical Analysis ◽  
Other Hand ◽  
Perceptual Psychology ◽  
The Mind ◽  
The Way

Written by a musician untrained in psychology, this article draws attention to problems arising from the separation of the disciplines of perceptual psychology and musical analysis. Psychologists are apt to make prescriptions about the nature of music based on a narrow and often primitive understanding of the medium. Musicians, on the other hand, are in the habit of basing analysis on sweeping assumptions about the nature of perception for which there is little experimental evidence. The author argues, however, that although it would be useful for such assumptions to be subjected to rigorous psychological testing, the assumptions themselves are not to be dismissed as evidence of the way the mind understands music.

scholarly journals A comparison of virulence of two strains ofLegionella pneumophilabased on experimental aerosol infection of guinea-pigs

1985 ◽  
Vol 95 (1) ◽  
pp. 29-38 ◽  
Author(s):  
R. I. Jepras ◽  
R. B. Fitzgeorge ◽  
A. Baskerville
Keyword(s):  
Experimental Evidence ◽  
Legionella Pneumophila ◽  
Guinea Pigs ◽  
The Other ◽  
Avirulent Strain ◽  
Lung Macrophage ◽  
Other Hand ◽  
Strain Nctc ◽  
Aerosol Infection ◽  
Extracellular Location

SUMMARYTwo strains ofLegionella pneumophila(LP) serogroup I, of differing virulence, were examined in terms of numbers of viable organisms in tissues, pyrexia and mortality following aerosol infection. The Corby strain was the more virulent, with Pyrexia and deaths of guinea-pigs 3 to 6 days after infection. This strain multiplied very rapidly in the lungs to reach a peak of 5 × 1011viable organisms/lung. Organisms were present in the blood, liver, spleen and kidney. The Philadelphia-1 strain (NCTC 11192) was unable to replicate in the lung and was cleared between 14 and 21 days after infection. Pyrexia was not observed. No guinea-pigs died and viable LP was not found in any organ other than the lung.Lung lavages on aerosol infected animals were performed and the virulent Corby strain was found to be mainly intracellular. The avirulent Philadelphia-1 strain was found predominantly in the extracellular location. There were approximately 10 times the number of viable virulent LP in the lung macrophage fraction than in the lung PMNL fraction. In comparison, there were approximately equal numbers of the viable avirulent strain in the macrophages and the PMNL. Experimental evidence suggests that the macrophage preferentially supports the growth of the virulent Corby strain compared with the PMNL. The avirulent strain on the other hand appears to be destroyed by both the macrophages and the PMNL.

scholarly journals Kaluza theory with zero-length extra dimensions

2016 ◽  
Vol 25 (11) ◽  
pp. 1640004 ◽  
Author(s):  
O. C. Stoica
Keyword(s):  
Gauge Theory ◽  
Experimental Evidence ◽  
Extra Dimensions ◽  
The Other ◽  
New Approach ◽  
Degenerate Metric ◽  
Other Hand ◽  
Abelian Case ◽  
Spacetime Metric ◽  
As If

A new approach to the Kaluza theory and its relation to the gauge theory is presented. Two degenerate metrics on the [Formula: see text]-dimensional total manifold are used, one corresponding to the spacetime metric and giving the fiber of the gauge bundle, and the other one to the metric of the fiber and giving the horizontal bundle of the connection. When combined, the two metrics give the Kaluza metric and its generalization to the non-Abelian case, justifying thus his choice. Considering the two metrics as fundamental rather than the Kaluza metric explains why Kaluza’s theory should not be regarded as five-dimensional (5D) vacuum gravity. This approach suggests that the only evidence of extra dimensions is given by the existence of the gauge forces, explaining thus why other kinds of evidence are not available. In addition, because the degenerate metric corresponding to the spacetime metric vanishes along the extra dimensions, the lengths in the extra dimensions is zero, preventing us to directly probe them. Therefore, this approach suggests that it is not justified to search for experimental evidence of the extra dimensions as if they are merely extra spacetime dimensions. On the other hand, the new approach uses a very general formalism, which can be applied to known and new generalizations of the Kaluza theory aiming to achieve more and make different experimental predictions.

scholarly journals Molybdenum(V) e.p.r. signals obtained from xanthine oxidase on reduction with aldehyde substrates and with 2-amino-4-hydroxy-6-formylpteridine

1981 ◽  
Vol 197 (2) ◽  
pp. 421-425 ◽  
Author(s):  
J P Malthouse ◽  
J W Williams ◽  
R C Bray
Keyword(s):  
Xanthine Oxidase ◽  
Computer Simulations ◽  
Side Reaction ◽  
The Other ◽  
Catalytic Process ◽  
Active Centre ◽  
Other Hand

2-Amino-4-hydroxy-6-formylpteridine, a known ‘slow’ substrate and inhibitor of xanthine oxidase, is unusual in that it gives rise under suitable conditions to all types of molybdenum(V) e.p.r. signals obtainable from the enzyme, namely Very Rapid, Rapid, Inhibited and Slow. The Very Rapid signal appears in a slightly modified form. The Inhibited signal, originally thought to be unique to reaction of methanol or of formaldehyde with xanthine oxidase, is now shown to be obtainable with several other aldehydes. These include, in addition to 2-amino-4-hydroxy-6-formylpteridine, acetaldehyde and glycoaldehyde. Parameters of the signals, obtained with the help of computer simulations, are presented. The appearance of Very Rapid and of Inhibited signals with these additional substrates may be of importance in elucidating the structure of the enzyme active centre. In agreement with previous work, the Very Rapid signal is attributed to an obligatory intermediate in turnover. On the other hand, the Inhibited signal is attributed to a side reaction, presumably inhibitory in nature, occurring during the catalytic process.

MARINE BORER ALDEHYDE OXIDASE

1965 ◽  
Vol 43 (6) ◽  
pp. 1011-1019 ◽  
Author(s):  
P. M. Townsley ◽  
R. A. Richy
Keyword(s):  
Methylene Blue ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Digestive Tract ◽  
Vanillic Acid ◽  
Oxidase Activity ◽  
Aldehyde Oxidase ◽  
The Other ◽  
Specific Enzyme ◽  
Simultaneous Reduction

A very active and specific enzyme, aldehyde oxidase, has been demonstrated and partially purified from the digestive tract of the marine borer, Bankia setacea (Tryon). In the presence of the enzyme, the substrate vanillin was oxidized to vanillic acid with the simultaneous reduction of oxygen, cytochrome c, 2,6-dichlorophenolindophenol, or methylene blue. Marine borer aldehyde oxidase does not oxidize the heterocyclic substrates N1-methylnicotinamide or hypoxanthine of mammalian hepatic aldehyde oxidase or milk xanthine oxidase. In addition, the inhibitors of hepatic aldehyde oxidase, menadione and estradiol, do not inhibit marine borer aldehyde oxidase. On the other hand, both the above-mentioned oxidases are inhibited by the sulfhydryl inhibitors arsenite and p-hydroxymercurybenzoate, and by cyanide. Marine borer aldehyde oxidase has an optimum activity between pH 4.5 and 5.5 and little activity at pH 7.8, a pH activity range quite different from that of the mammalian aldehyde oxidases. Oysters were found to contain only slight vanillin oxidase activity at pH 4.3, suggesting that the marine borer aldehyde oxidase activity is unique to the ship worm and is used for the oxidation of aldehydes found in wood.

Further Evidence for 'Active' Reflex Vasodilatation

1971 ◽  
Vol 49 (2) ◽  
pp. 147-159 ◽  
Author(s):  
D. G. Wyse ◽  
L. Beck ◽  
T. F. Burks ◽  
C. T. Spalding
Keyword(s):  
Experimental Evidence ◽  
Vascular Tone ◽  
Perfusion Pressure ◽  
Blocking Agent ◽  
The Other ◽  
Other Hand ◽  
Adrenergic Activity ◽  
Total Magnitude ◽  
Ganglionic Blocking

Further experimental evidence has been presented which strengthens the hypothesis of active reflex dilatation. The administration of a ganglionic blocking agent in a dose sufficient to block completely adrenergic tone failed to lower the perfusion pressure in the isolated extremity to the same level as was reached during the nadir of reflex dilatation. Thus, it is reaffirmed that simple withdrawal of adrenergic vascular tone (passive reflex dilatation) cannot entirely account for the total magnitude of reflex dilatation. Although chronic reserpine pretreatment eliminated both reflex constriction and dilatation, acute reserpine administration reduced reflex dilatation at a time when reflex constriction and perfusion pressure were little affected. On the other hand, the administration of the substituted phenothiazine, methotrimeprazine, eliminated adrenergic tone but had little effect on reflex dilatation. The latter two types of experiment provide further important dissociations between reflex dilatation and inhibition of existing adrenergic activity. Administration of cocaine by several different routes reduced reflex dilatation, but the reduction in reflex dilatation does not appear to be due to inhibition of reuptake of adrenergic amine. Neither does blockade of active reflex dilatation by the antihistamine, tripelennamine, appear to be related to its possible ability to block reuptake of adrenergic amine. Classic autoregulatory stimuli fail to elicit a response analogous to active reflex vasodilatation, and antihistamines fail to alter autoregulatory readjustments while reducing very effectively active reflex vasodilatation.

scholarly journals The mechanism of potentiation of horseradish peroxidase-catalysed oxidation of NADPH by porphyrins

1987 ◽  
Vol 242 (2) ◽  
pp. 611-613 ◽  
Author(s):  
J Van Steveninck ◽  
J P J Boegheim ◽  
T M A R Dubbelman ◽  
J Van der Zee
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Horseradish Peroxidase ◽  
Superoxide Radical ◽  
Experimental Results ◽  
Haematoporphyrin Derivative ◽  
Anaerobic Conditions ◽  
Catalysed Oxidation ◽  
Cytochrome C Reduction ◽  
Nadph Oxidation

Several porphyrins, including HpD (haematoporphyrin derivative), potentiate the oxidation of NADPH by horseradish peroxidase/H2O2. To elucidate the mechanism of potentiation, the following observations are relevant. During peroxidase-catalysed NADPH oxidation, O2-.(superoxide radical) is generated, as judged from superoxide dismutase-inhibitable cytochrome c reduction. This generation of O2-. is suppressed by HpD. Peroxidase-catalysed NADPH oxidation is stimulated by superoxide dismutase and by anaerobic conditions. Under anaerobic conditions HpD has no influence on peroxide-catalysed NADPH oxidation. Previous studies have shown that horseradish peroxidase is inhibited by O2-.. Thus the experimental results indicate that the potentiating effect of HpD can be explained by its ability to inhibit O2-. generation in the horseradish peroxidase/H2O2/NADPH system.

301. The effect of over-ripening upon the activity of Cheddar cheese starters

1943 ◽  
Vol 13 (2) ◽  
pp. 127-135 ◽  
Author(s):  
C. K. Johns ◽  
H. L. Bérard
Keyword(s):  
New Zealand ◽  
Experimental Evidence ◽  
Cheddar Cheese ◽  
The Other ◽  
Extreme Conditions ◽  
Single Strain ◽  
Permanent Damage ◽  
Cheese Making ◽  
Other Hand

The belief that over-ripening of starters is responsible for their weakening and for slow acid development during Cheddar cheese-making has been widely held by cheese-makers for many years. Statements that over-ripening is harmful have been made by investigators in several countries(1,2,3,4), but experimental evidence in support of this view is scanty. On the other hand, Whitehead(5) in New Zealand has shown that prolonged over-ripening of single-strain starters under rather extreme conditions merely resulted in a temporary checking of their activity; between wide limits of size of inoculum and period of incubation no permanent damage was done.

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