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J Lunec

Publications and source records attributed to J Lunec.

At least 181 records · Page 10Linked to original sources
PubMed1987

Inhibitory effect of superoxide dismutase on fructosamine assay.

The fructosamine assay measures the degree of nonenzymatic protein glycation by virtue of the reducing properties of such proteins in alkaline conditions. We report the marked inhibitory effect of superoxide dismutase (EC 1.15.1.1) on the reducing activity both of protein glycated in vitro and of diabetic sera, indicating superoxide intermediacy in the fructosamine reaction. The free-radical intermediates may be of analytical significance when pathological and physiological changes in serum anti-oxidant activity occur. They may also be of pathological significance in diabetic microangiopathy and protein browning.

Diabetes Mellitus↗
PubMed1986

Reduced susceptibility to lipid peroxidation in cold ischemic rabbit kidneys after addition of desferrioxamine, mannitol, or uric acid to the flush solution.

Rabbit kidneys were stored for 24 hr at 0 degree C after single passage arterial flush with 30 ml of cold isotonic 0.9% sodium chloride (saline) solution alone or saline to which was added 12, 30, or 60 mM desferrioxamine, 1 or 3 mM uric acid, or 100 mM mannitol. They were then subjected to in vitro biochemical assay for evidence of free radical damage immediately after storage. Results were compared to those obtained with fresh, unstored kidneys. Levels of Schiff base fluorescence, diene conjugates, and thiobarbituric acid-reactive material were each significantly elevated in kidneys stored for 24 hr after flush with saline alone. These levels were in turn each significantly reduced by the addition of 60 mM desferrioxamine, 3 mM uric acid, and 100 mM mannitol to the flush solution. Likewise, glutathione redox activity fell in those flushed with saline alone, presumably in line with increased lipid peroxidation, but was restored to control levels by inclusion of the three scavenging agents.

Animals↗
PubMed1986

Desferrioxamine reduces susceptibility to lipid peroxidation in rabbit kidneys subjected to warm ischaemia and reperfusion.

Rabbit kidneys were clamped and subjected to warm ischaemia for 60 or 120 min then reperfused with blood for 60 min or for 24 hr. Treated rabbits received desferrioxamine at 15 or 50 mg/kg i.v. 15 min before reperfusion. Their kidneys were then removed and assayed for phospholipid Schiff base fluorescence (ex. 360 nm, em. 435 nm), diene and triene conjugates by UV spectrophotometry (240 nm and 268 nm respectively), for superoxide dismutase and for reduced and oxidised glutathione to provide an index of glutathione redox activity. All indices of lipid peroxidation were significantly elevated in untreated rabbits and glutathione redox activity was reduced. Treatment with desferrioxamine however effectively prevented these deviations and in many cases maintained them at the levels in fresh rabbit kidneys. These data provide further evidence that lipid peroxidation occurring during the reperfusion period is superimposed on the damage set up during warm ischaemia and may be preventable by administration of suitable therapeutic agents.

Animals↗
PubMed1986

Increased susceptibility to lipid peroxidation in rabbit kidneys: a consequence of warm ischaemia and subsequent reperfusion.

Rabbit kidneys were clamped and rendered warm ischaemic (WI) in situ for 60 and 120 min. They were then either removed immediately after the ischaemic insult or after reperfusion with blood for 60 min or 24 hr. Homogenates were assayed for phospholipid-Schiff base fluorescence (Ex. 360 nm, Em. 435 nm) and for diene conjugate formation by u.v. spectrophotometry (240 nm) as indices of lipid peroxidation. No alteration in tissue levels of Schiff base was evident immediately after WI but when the homogenates were incubated at 37 degrees C for 90 min, the rate of peroxidation was significantly elevated compared to controls (P less than 0.02 after WI of 60 min and P less than 0.001 after 120 min of WI). These values were still further elevated after reperfusion with blood for 60 min and 24 hr (P less than 0.001). Diene conjugates were raised after WI alone and further still after reperfusion. Thus an early index of lipid peroxidation (diene conjugation) suggested peroxidative damage during the warm ischaemic period itself, whilst detection of Schiff bases was only possible after in vitro incubation of the tissue. Both indices of oxygen-derived free radical damage were increased after reperfusion in vivo with blood and may relate to the degree of tissue damage sustained during ischaemia and reflow.

Animals↗
PubMed1986

The effects of benzamide ADP-ribosyl transferase inhibitors on cell survival and DNA strand-break repair in irradiated mammalian cells.

We have recently shown that 3-acetamidobenzamide (3-AAB), a highly effective inhibitor of ADP-ribosyl transferase (ADPRT), can act as a post-irradiation (electrons) sensitizer on the mouse lymphoma cell lines L5178Y R and S. We have now shown that this compound sensitizes human derived skin fibroblasts but to a lesser extent. Fibroblasts derived from normal, Friedreich's ataxia, and ataxia-telangiectasia individuals were equally sensitized by 3-AAB to electron radiation. 3-AAB was also effective in sensitizing the mouse lymphoma lines to fast neutron irradiation. In addition DNA strand break repair was retarded as had been found after electron irradiation. 3-Nitrobenzamide is structurally a potentially dual action radiation sensitizer with electron affinic and ADPRT inhibitory properties. It is a weaker inhibitor of ADPRT compared to 3-AAB, and results in a smaller sensitization of mouse lymphoma cells in air. However, a much greater sensitization is achieved in anoxia. This greater sensitization appears to be a synergistic rather than an additive combination of its electron affinic and ADPRT inhibitory properties.

Animals↗
PubMed1986

Evidence of free-radical-induced damage in rabbit kidneys after simple hypothermic preservation and autotransplantation.

Rabbit kidneys were stored for 24 or 48 hr at 0 degree C after single-passage vascular flush with 30 ml of cold hypertonic citrate solution or 0.9% isotonic sodium chloride solution. They were then subjected to in vitro biochemical assay for evidence of free-radical damage immediately after storage or after they had been orthotopically autotransplanted and reperfused with blood in vivo for 60 min. Kidney homogenates were incubated at 37 degrees C and assayed for fluorescent conjugated Schiff bases as indicators of lipid peroxidation, as well as for superoxide dismutase activity and reduced and oxidized glutathione. In kidneys flushed with hypertonic citrate, no evidence of peroxidation could be detected immediately after storage for 24 or 48 hr. However, after in vivo reperfusion significantly more peroxidation (P less than 0.01) was evident. Storage in isotonic saline solution produced still higher levels of peroxidation damage whether reperfused or not (P less than 0.001). Schiff base formation was inversely proportional to the reduced and oxidized glutathione levels measured. No changes in superoxide dismutase levels could be detected. It is concluded that lipid peroxidation is important during cold ischemia but most damage occurs during the 60-min of reperfusion in vivo immediately after transplantation.

Animals↗
PubMed1986

Is chronic synovitis an example of reperfusion injury?

In an attempt to define why the joint synovial cavity is prone to develop persistent synovial inflammation we show that hypoxia is induced by pressure changes caused by exercise in the presence of an inflammatory effusion. On resting 'reperfusion injury' may take place. The biochemistry of reperfusion injury has only recently been defined and perhaps surprisingly for an insult that has hypoxia as its central ingredient involves the subsequent production of oxygen derived free radical species. We apply the reaction sequences that are believed to occur during hypoxic/reperfusion injury to the joint synovial cavity and, on the basis of reported 'in vivo' observations, suggest novel therapeutic approaches that we believe are applicable to the treatment of persistent synovial inflammation.

Animals↗
PubMed1986

In vitro screening of iron chelators using models of free radical damage.

The effect of chelators on free radical damage to deoxyribose induced by iron, on IgG by UV irradiation, and on mouse muscle by homogenisation has been studied using the Thiobarbituric acid method and the increase in fluorescence in IgG mixtures. Although there were some variations on the effects of the chelators in the three models, it was shown that most of the chelators could inhibit the noxious effects of the free radicals and some which are orally effective in increasing iron excretion in animals could be potentially useful in preventing iron toxicity in related pathogenic diseases.

Animals↗
PubMed1985

The behaviour of caeruloplasmin in stored human extracellular fluids in relation to ferroxidase II activity, lipid peroxidation and phenanthroline-detectable copper.

No Cu(II) ion is measurable in human serum or synovial fluid by the phenanthroline assay. On storage of human serum or synovial fluid at 4 degrees C, phenanthroline-detectable copper appears, lipid peroxidation occurs, ferroxidase I activity declines and ferroxidase II activity rises, yet there is no fall in immunologically detectable caeruloplasmin. Storage of body fluids at -20 degrees C or -70 degrees C slows, but does not prevent, these deteriorative changes. It is suggested that the presence of low-molecular-mass Cu(II) ion complexes, ferroxidase II activity, "cytotoxic factors' and "immunosuppressive factors' in body fluids may be, in part or in whole, an artifact of the storage and handling of the fluids. A report [Blake, Blann, Bacon, Farr, Gutteridge & Halliwell (1983) Clin. Sci. 64, 551-553] that the caeruloplasmin present in rheumatoid synovial fluid is deficient in ferroxidase activity is shown to be such an artifact. It is strongly recommended that all such experiments be performed upon freshly taken fluid samples.

Arthritis, Rheumatoid↗
PubMed1985

Endothelial cell cytotoxicity in inflammatory vascular diseases--the possible role of oxidised lipoproteins.

One of the proposed mechanisms of vascular damage in connective tissue disease is the direct action of a cytotoxic serum factor inducing endothelial cell damage. The nature of this serum factor is unclear, but has been suggested to be a lipoprotein. Sera from patients with (1) systemic necrotising arteritis (polyarteritis nodosa, Wegener's granulomatosis, and necrotising arteritis associated with rheumatoid synovitis), (2) systemic or joint restricted rheumatoid disease, and (3) large vessel/giant cell arteritis have been examined for cytotoxicity to human cultured endothelial cells and azide-resistant ferroxidase-like activity (indicative of the oxidised lipoprotein content). Stored sera from patients with necrotising arteritis showed a significantly enhanced tendency to develop oxidised lipoprotein, which correlated closely with human endothelial cell cytotoxicity. Fresh sera also contained this factor, but to a lesser extent. It is argued that the cytotoxic factor detected in previous clinical studies is in part an in-vitro artefact, although its accelerated development in certain patient groups might suggest an excess of pro-oxidants that have developed in vivo.

Arteritis↗
PubMed1985

Effect of intravenous iron dextran on rheumatoid synovitis.

Eleven patients with rheumatoid arthritis received a total dose infusion of iron dextran for anaemia. Two of them had anaphylactic reactions and the remaining nine an exacerbation of synovitis. Quantitative infrared thermal imaging was used to assess the extent and distribution of joint involvement resulting from this therapy. In all eight patients examined the 'thermographic index' increased in two or more joint areas, indicating an increase in inflammation. Small joints of the hands were maximally affected, though larger joints when previously inflamed also worsened. Uninflamed joints were rarely affected. The exacerbation of synovitis occurred 24-48 h after completion of the iron dextran infusion and corresponded with a saturating of the serum iron binding capacity. Levels of immune complexes were unaltered, implying normal reticuloendothelial function. In one further patient, reported to have synovial flares when challenged with oral ferrous sulphate, iron dextran was infused at a lower dosage. All previously inflamed joints in this patient worsened 12 h after the infusion was discontinued. Concomitant with this was an increase of lipid peroxidation products in synovial fluid and to a less extent serum. Iron dextran in vitro stimulated lipid peroxidation, but dextran alone had no effect. It is therefore suggested that iron dextran worsens synovial inflammation by promoting lipid peroxidation.

Adult↗
PubMed1985

Self-perpetuating mechanisms of immunoglobulin G aggregation in rheumatoid inflammation.

When human IgG is exposed to free radical generating systems such as ultraviolet irradiation, peroxidizing lipids, or activated human neutrophils, characteristic auto-fluorescent monomeric and polymeric IgG is formed (excitation [Ex], 360 nm, emission [Em], 454 nm). 1 h ultraviolet irradiation of IgG results in the following reductions in constituent amino acids; cysteine (37.0%), tryptophan (17.0%), tyrosine (10.5%), and lysine (3.6%). The fluorescent IgG complexes, when produced in vitro, can stimulate the release of superoxide from normal human neutrophils. In the presence of excess unaltered IgG, further fluorescent damage to IgG occurs. Measurement and isolation of fluorescent monomeric and polymeric IgG by high performance liquid chromatography, from in vitro systems and from fresh rheumatoid sera and synovial fluid, indicates that identical complexes are present in vivo; all these fluorescent complexes share the property of enhancing free radical production from neutrophils. The results described in this study support the hypothesis that fluorescent monomeric and aggregated IgG may be formed in vivo by oxygen-centered free radicals derived from neutrophils, and that in rheumatoid inflammation this reaction may be self-perpetuating within the inflamed joint.

Adult↗