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  • 1
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0662
    Keywords: Variance ; trace/gases ; stratosphere ; mixing length ; mixing surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The relative variances in stratospheric observations of longlived trace gases CH4, N2O, CF2Cl2, CFCl3 show large differences. These differences are greatly reduced when the local mean standard deviation is normalized to the local vertical gradient. This ratio, called ‘equivalent displacement height’ exhibits a characteristic vertical profile which is very similar for all the longlived trace gases, as well as for O3. With the help of this ratio, it is demonstrated that the variances are essentially due to natural causes, i.e., transport. Using the mixing length hypothesis a theoretical expression for the equivalent displacement height is derived. From it the meridional slope of the mixing surfaces and the mixing length can be calculated as function of the altitude. Additional information is obtained on the variance of that slope. The uncertainty of the measured mean trace gas profiles is defined.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1803
    Keywords: regional myocardial ischemia ; lipid peroxidation ; scavenger action
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dog experiments were performed to describe the time course of lipid peroxidation after various ischemic influences of the heart measured by formation of malondialdehyde (MDA), and the scavenger action determined by reduced glutathione (GSH) content and superoxide dismutase (SOD) activity. Experimental groups consisted of control dogs having intact hearts and dogs with acute ramus descendens anterior ligature (LAD) having ischemic areas through 15, 30, 45 minutes and 1, 2, 3, 24 hours. Heart tissue for biochemical assays was excised from both the ischemic areas and from nonischemic left ventricle. The acute ischemia caused characteristic alterations in the biochemical parameters: MDA level gradually increased with its peak value being found at the end of 3 hours ligature. GSH levels decreased moderately, whereas SOD levels reduced sharply. As incrcased MDA formation indicates breakdown of the polyunsaturated fatty acids (PUFA) in the membranes and decreaased GSH and SOD levels indicate impairment of the natural scavengering, the observed changes clearly outline the extent of disintegration of membrane structure and function.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-1803
    Keywords: myocardial infarct ; lipid peroxidation ; free oxygen radicals ; scavenger action ; synthetic antioxidant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were performed on dog hearts following coronary ligation and treatment with synthetic antioxidant of dihydroquinoline type. Experimental groups were: (i) control dogs, (ii) dogs with ligation of descendens anterior coronary branch, (iii) coronary ligated dogs with antioxidant pretreatment and (iv) dogs with coronary ligation and simultaneous antioxidant infusion therapy. The heart infarctionper se is accompanied by the disintegration of membrane polyunsaturated fatty acids expressed by increase of malondialdehyde (MDA) concentration and the impairment of natural scavenging characterized by the decrease of superoxide dismutase (SOD) and reduced glutathione (GSH) content. The oral pretreatment with antioxidant for 8 days prevented or decreased the unfavourable pathobiochemical responses. The acute infusion therapy exerted no immediate protection, nonetheless, it could decrease the severity of pathological signs.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1435-1803
    Keywords: β-blockers ; myocardialreperfusion ; freeradicals ; prostacyclin-thromboxane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The left descending coronary artery (LAD) was ligated for 45 min or 90 min followed by 1-h reperfusion. During experiments the animals in Group I (15 dogs) received saline infusion, in Group II (20 dogs) they received the ultrashort-acting β-blocker Brevibloc (esmolol HCl). The marker of lipid peroxidation the malondialdehyde (MDH) as well as endogen scavengers, the glutathione (GSH), and superoxide dismutase (SOD) were measured in the heart tissue homogenates. In blood and heart tissue samples the 6-keto-prostaglandin F1 α. (PGF1 α) and thromboxane B2 (TXB2) were determined. Biochemical measurements revealed that esmolol HCl has beneficial effect on the free-radical-meduated-damage reducing the MDA content in the ischemic area. In Group I the value of MDA after 90 min of LAD ligature was 138 ± 5.6 %, in Group II the elevation was only 107.4 ± 3.2 %. After treatment with Brevibloc the GSH content of ischemic-reperfused areas decreased slightly (81.75 ± 3.5 % of the normal value), moreover, in Group I the depletion of GSH was considerable (64.5 ± 4.2 %). Coronary reperfusion caused the release of eicosanoids in both groups, mainly in the first 10 min. The highest value of thromboxane in blood samples could be measured in Group I after 90 min of LAD ligature (24.8 ± 3.6 pmol/ml; the normal value 8–12 pmol/ml). In Group II during the same period of experiments the TXB2 in the blood was 14 ± 3.7 pmol/ml. In heart tissue samples the amount of endoperoxides increased in ischemic and non-ischemic areas of Group I and II. Nevertheless, the calculated ratio of PGF1 α and TXB2 was near to the normal after Brevibloc treatment (0.85–0.9; the normal values were 1–1.2). These results indicate that esmolol HCl can modulate both the free-radical-mediated reaction and arachidonic acid metabolism.
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  • 7
    ISSN: 1435-1803
    Keywords: global myocardial ischaemia ; epicardial mapping ; ECG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were performed on 10 dog hearts undergone 15 to 90-minute normothermic arrests and 60-minute reperfusion in a special heart-lung model. The purpose of the experiments was to characterize the global ischaemic effects recorded on epicardial electrograms. The duration of QRS complexes and of RR intervals, the integral of ST segment shifts (σST), the number of points showed ST segment displacements (NoST) and the ST segment isopotential map obtained by computer control were evaluated. Only a minor ST segment deviation, a small increase in duration of QRS complexes and of RR intervals with bradycardia and a tendency to electrical stability were found after global ischaemic influences. These observations indicate that pathological electrical manifestations occurring after a global ischaemia are less serious than those occurring after a focal ischaemia.
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