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  • 1
    ISSN: 1573-4919
    Keywords: colonic ischemia/reperfusion ; oxygen free radicals ; infiltrated neutrophils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reperfusion injury following ischemia is thought to be the consequence of reactive oxygen species. Role of these free radicals on the damaging effects of ischemia in colon has been investigated. A rat experimental model was used in which colon was subjected to ischemia and reperfusion and mucosal damage was assessed by biochemical and histological studies. Activity of myeloperoxidase, a neutrophil marker, was increased after ischemia (I) and ischemia/Reperfusion (I/R). Lipid peroxidation products such as malonaldehyde and conjugated diene did not show any change in the experimental colonic mucosa as compared to control. Mucosal level of low molecular weight thiols were found to be altered after I/R. A decrease in α-tocopherol level was noticed after ischemia and the decrease was prominent after reperfusion. Histology indicated morphological changes in colon due to ischemia and reperfusion and the damage was more severe after reperfusion. These results suggest that colonic mucosal damage occurs during I/R and free radicals generated by the infiltrated neutrophils may play a role in this damaging process.
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  • 2
    ISSN: 1573-4919
    Keywords: nonesterified fatty acids ; inhibition ; lipid peroxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Oxygen free radicals damage cells through peroxidation of membrane lipids. Gastrointestinal mucosal membranes were found to be resistant to in vitro lipid peroxidation as judged by malonaldehyde and conjugated diene production and arachidonic acid depletion. The factor responsible for this in this membrane was isolated and chemically characterised as the nonesterified fatty acids (NEFA), specifically monounsaturated fatty acid, oleic acid. Authentic fatty acids when tested in vitro using liver microsomes showed similar inhibition. The possible mechanism by which NEFA inhibit peroxidation is through iron chelation and iron-fatty acid complex is incapable of inducing peroxidation. Free radicals generated independent of iron was found to induce peroxidaton of mucosal membranes. Gastrointestinal mucosal membranes were found to contain unusually large amount of NEFA. Circulating albumin is known to contain NEFA which was found to inhibit iron induced peroxidation whereas fatty acid free albumin did not have any effect. Addition of individual fatty acids to this albumin restored its inhibitory capacity among which monounsaturated fatty acids were more effective. These studies have shown that iron induced lipid peroxidation damage is prevented by the presence of nonesterified fatty acids.
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  • 3
    ISSN: 1573-4919
    Keywords: Ischemia/reperfusion ; xanthine oxidase ; oxygen free radicals ; lipid peroxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study looks at the role of xanthine oxidase (XO) in ischemia/reperfusion (I/R) induced intestinal mucosal damage using normal and xanthine oxidase deficient rats. Tungstate feeding for 3 days depleted the intestinal mucosal XO by 80%. A ligated loop of the rat small intestine (both normal and XO-deficient) was subjected to 1 h of total ischemia followed by 5 min revascularisation. The ensuing mucosal damage was assessed by biochemical and histological studies. Ischemia or I/R increased the XO levels in normal rats without any change in XO-deficient rats. Myeloperoxidase (a neutrophil marker) level was increased in both group of rats but it was comparatively higher in the XO-deficient rats. Accumulation of peroxidation products such as malondialdehyde, conjugated diene and increased production of hydroxyl radicals by microsomes were seen after ischemia and I/R and were similar in normal and XO-deficient rats. Studies on other parameters of peroxidation showed a decrease in polyunsaturated fatty acids and alpha-tocopherol, an increase in cysteine and cystine levels after I/R and were similar in both normal and XO-deficient rats. Histological results indicated gross morphological changes in the intestinal mucosa due to ischemia and I/R, and the damage was more severe in XO-deficient rats. These observations suggest that oxygen-derived free radicals are involved in the intestinal mucosal damage during I/R and infiltrated neutrophils rather than XO may be the primary source of free radicals under these conditions.
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  • 4
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Six generations, consisting of three resistant parents, three susceptible parents, their 15 possible F1 crosses, 15 F2's, 15 BC1's (F1 x resistant female parent) and 15 BC2's (F1 x susceptible male parent) were analysed following Hayman (Heredity 12: 371–390, 1958) to evaluate the nature and type of gene action governing resistance to H. turcicum. The results showed that all types of gene effects, viz., additive, dominance and epistasis (i.e., additive x additive, additive x dominance and dominance x dominance) were operating in one cross or the other in controlling resistance. However, it was additive gene action and dominance x dominance type of epistasis with duplicate nature that were important in controlling resistance in most crosses. Depending upon the final objectives, one of the breeding methods, viz., recurrent selection, heterosis breeding, back-cross method or full-sib selection (bi-parental mating) may be followed.
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  • 5
    ISSN: 1572-8897
    Keywords: relativistic CI ; double group ; correlation group table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A generalized correlation group table (CGT) method is described for the relativistic configuration interaction (RCI) wavefunctions of molecules containing heavy atoms. In this method first four keywords are defined and two properties are discussed in terms of spectroscopic states and double group theory. These definitions and properties are then used to summarize six principles to stipulate the relationship among relativistic states, nonrelativistic states, as well as RCI configurations. The definitions, properties, and principles comprise the generalized CGT method, which facilitates the classification and assignment of the RCI wavefunctions, and thus, provide a general technique for complex systems containing several open shells. Finally, the techniques are exemplified with a few computational models.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical chemistry 3 (1989), S. 147-159 
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A class of graphs called spirographs is defined. It is shown that the characteristic polynomials of spirographs can be obtained in terms of the characteristic polynomials of smaller graphs by pruning the spirographs at the spiral points. Elegant recursive relations are derived for many spirographs. Characteristic polynomials of branched spirographs are also obtained.
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  • 7
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract An efficient technique is formulated based on a polynomial structure which we call the reduced cycle index for the enumeration of equivalence classes and NMR signals under group action. The reduced cycle indices are shown to be the cycle index polynomials of a subset of significantly smaller order of the point group of the molecule. Thus, the reduced cycle indices are much simpler and their use leads to a considerable reduction in tile computation of the generating functions from the cycle indices and irreducible representations contained in a set.
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  • 8
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract We generalize the de Bruijn extension of Pólya's theorem to all characters of finite permutation groups and show that the de Bruijn theorem becomes a special case of our generalization when applied to the character of the totally symmetric representation./ab]
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  • 9
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1572-8897
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract The method of moments is used to derive closed analytical expressions for the characteristic polynomials of square lattice graphs. We obtain exact analytical formulae for three-dimensional cubic lattices, square lattices, tubular square lattices, and cylindrical square lattices containing any number of vertices.
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