Biomedical subjects
O Schreiner
Publications and source records attributed to O Schreiner.
Reduced secretion of proinflammatory cytokines of monosodium urate crystal-stimulated monocytes in chronic renal failure: an explanation for infrequent gout episodes in chronic renal failure patients?
BACKGROUND: In gouty arthritis, monosodium urate (MSU) crystals interact with monocytes and neutrophils to produce inflammatory reactions associated with acute synovitis. In patients with end-stage renal disease (ESRD), gouty arthritis is a rare condition despite often severe hyperuricaemia. We wondered whether differences in the secretion of proinflammatory cytokines by MSU crystal-stimulated monocytes might be one explanation for the low incidence of gouty arthritis in patients with ESRD compared with healthy controls. METHODS: Thirteen patients with ESRD on intermittent haemodialysis treatment, six patients with chronic renal failure not yet on dialysis, and 15 age- and sex-matched healthy controls were examined. Monocytes, purified from peripheral blood mononuclear cells (PBMC) by immunomagnetic bead separation, were incubated for 18 h in the presence of MSU crystals, Escherichia coli lipopolysaccharide (LPS) or medium alone. The supernatants were studied for the presence of interleukin (IL)-1beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) using cytokine-specific enzyme-linked immunosorbent assays. RESULTS: Monocytes from patients with ESRD produced significantly lower amounts of IL-1beta, IL-6 and TNF-alpha after stimulation with MSU crystals or LPS than did monocytes from healthy subjects. Cytokine production was not significantly different between ESRD patients on haemodialysis and chronic renal failure patients not yet on dialysis. Artificial MSU crystals were stronger stimuli than tophus-derived 'natural' MSU crystals. CONCLUSION: We demonstrate that monocyte-associated immunosuppression in ESRD leads to reduced secretion of proinflammatory cytokines in response to stimuli such as MSU crystals. This may be one of the factors preventing many ESRD patients from the manifestation of acute gout despite often severe hyperuricaemia.
[Position of the SPD legislative faction on health policy (I) and on control in the area of occupational rehabilitation].
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Purification of a derepressible arylsulfatase from Chlamydomonas reinhardti. Properties of the enzyme in intact cells and in purified state.
Arylsulfatase (aryl-sulfate sulfohdydrolase, EC 3.1.6.1) has been purified from SO4-2-minus-starved cells of Chlamydomonas reinhardti. The enzyme was isolated from acetone-powder extract by (NH4)2SO4 precipitation, Sephadex G-200 filtration and ion-exchange chromatography. Only one fraction of aryl-sulfatase was found. The final preparation was homogenous by the criteria of sedimentation, diffusion and polyacrylamide gel electrophoresis. The purified enzyme had a molecular weight of about 150 000, estimated by ultracentrifugation and gel filtration, and an isoelectric point of 9.0. The properties of the enzyme as investigated in intact cells and in the purified state were found to be very similar except for the temperature optimum. Imidazole strongly increased the enzyme by increasing the V, but reduced the affinity for the substrate. The enzyme activity was competitively inhibited by borate with a greater affinity for borate than for the substrate. The Chlamydomonas enzyme is a Type I arylsulfatase since it was inhibited by CN-minus, but not SO4-2-minus and phosphate.
The capacity for arylsulfatase synthesis in synchronous and synchronized cultures of Chlamydomonas reinhardti.
The green algae Chlamydomonas reinhardti synthesizes arylsulfatase (arylsulfate sulfohydrolase EC 3.1.6.1) by derepression when the concentration of SO4-2-minus in the growth medium is less than about 5-10-minus 5 M. The following observations indicate that the arylsulfatase enzyme is stable while its mRNA was unstable: (1) The increase in enzyme activity stopped and remained constant after addition of cycloheximide to derepressed cells. (2) After readdition of SO4-2-minus the increase in enzyme activity continued at a lower rate whereafter it remained constant. (3) No decay of radioactivity was observed after readdition of SO4 2-minus in labelled enzyme protein isolated from pulse-labelled --S cells. The maximum rate of arylsulfatase synthesis. Measurements of this capacity in cells taken at different developmental stages from a selection synchronous and from a light-dark synchronized culture showed that: (1) Arylsulfatase was derepressible at all stages of the life cycle. (2) The same periodic capacity patterns were found, both with the synchronized and the synchronous cells. Furthermore, the rate of accummulation of RNA and protein changed in the same periodic manner during the life cycle as did the enzyme capacity.
Selection synchrony of Chlamydomonas using the Rastgeldi threshold centrifuge.
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