Virulence factor expression by Gram-positive cocci exposed to subinhibitory concentrations of linezolid.

Linezolid is a new oxazolidinone with potent antibacterial activity against Gram-positive cocci; it uniquely inhibits bacterial translation through inhibition of 70S initiation complex formation. The effects of sub-growth-inhibitory concentrations of linezolid on the expression of various structural and soluble virulence factors of Staphylococcus aureus and Streptococcus pyogenes were examined. For S.

Isolation of a ferritin from Bacteroides fragilis.

A ferritin was isolated from the obligate anaerobe Bacteroides fragilis. Estimated molecular masses were 400 kDa for the holomer and 16.7 kDa for the subunits.

Effect of iron and retinoic acid on the control of transferrin receptor and ferritin in the human promonocytic cell line U937.

The effect of changes in iron availability and induction of differentiation on transferrin receptor expression and ferritin levels has been examined in the promonocytic cell line U937. Addition of iron (as 200 micrograms/ml saturated transferrin) or retinoic acid (1 microM) both caused approx. 70% reduction in the average number of surface transferrin receptors, while the iron chelator desferrioxamine caused an 84% increase.

Expression of transferrin receptors by monocytes and peritoneal macrophages from renal failure patients treated by continuous ambulatory peritoneal dialysis (CAPD).

Approximately 20% of monocytes and peritoneal macrophages from renal failure patients undergoing continuous ambulatory peritoneal dialysis (CAPD) were transferrin-receptor (TfR) positive by immunofluorescence, whereas cells from normal controls were generally TfR negative, as were monocytes from rheumatoid arthritis patients and from renal failure patients treated by haemodialysis. There was a significant correlation between the length of time on CAPD and the proportion of TfR-positive blood monocytes. CAPD peritoneal macrophages possessed 6.

Relative availability of transferrin-bound iron and cell-derived iron to aerobactin-producing and enterochelin-producing strains of Escherichia coli and to other microorganisms.

A method is described for determination of the relative availability of transferrin-bound iron and cell-derived iron to microbial iron-scavenging mechanisms. This involved incubation of parallel cultures of microorganisms in dialysis tubes placed in RPMI 1640 tissue culture medium containing 30%-iron-saturated transferrin and K562 erythroleukemia cells. In one culture the transferrin was labelled with 59Fe and in the other the cells were labelled, and the relative uptake of radioiron by the microorganisms determined.

Effect of aluminium on iron uptake and transferrin-receptor expression by human erythroleukaemia K562 cells.

Incubation of human erythroleukaemia K562 cells with Al-transferrin inhibited iron uptake from 59Fe-transferrin by about 80%. The inhibition was greater than that produced by a similar quantity of Fe-transferrin. Preincubation of cells for 6 h with either Al-transferrin or Fe-transferrin diminished the number of surface transferrin receptors by about 40% compared with cells preincubated with apo-transferrin.

Effect of novel 1-alkyl-3-hydroxy-2-methylpyrid-4-one chelators on uptake and release of iron from macrophages.

The effect of several iron chelators on iron uptake and release by mouse peritoneal macrophages has been investigated. The 1,2-dimethyl (L1) and 1-ethyl-2-methyl (L1NEt) derivatives of 3-hydroxypyrid-4-one markedly enhanced iron mobilisation from macrophages pulsed with 59Fe-transferrin-antitransferrin immune complexes and were more effective than desferrioxamine, maltol, or mimosine. Release increased with increasing chelator concentration.

The effect of topical steroid application on natural killer cell activity.

Peripheral blood natural killer (NK) cell activity of a group of 10 healthy non-atopic volunteers was reduced following the topical application of 15 g of 0.1% betamethasone valerate ointment to the skin nightly for 1 week. In contrast, no such effect was observed when the inactive base of the steroid ointment was used.

Induction of hypoferremia and modulation of macrophage iron metabolism by tumor necrosis factor.

The effects of recombinant tumor necrosis factor (TNF), tumor necrosis serum (TNS), recombinant interleukin 1 (IL-1), and prostaglandin E2 on serum iron parameters and iron handling by macrophages in mice have been investigated. Recombinant TNF caused a significant decrease in serum iron levels after 6 hours, but none of the mediators caused significant changes in total iron binding capacity at this time, although TNS caused a significant increase in total iron binding capacity after 24 hours. Peritoneal macrophages taken from mice 6 hours after inoculation of the mediators were pulsed with 59Fe, 125I-transferrin-antitransferrin immune complexes, and subsequent degradation of the complexes and release of iron were investigated.

Iron-binding proteins.

The structure and properties of the iron-binding proteins transferrin, lactoferrin and transferrin are reviewed. Transferrin and lactoferrin are structurally similar, consisting of a single polypeptide chain and reversibly binding two iron atoms per molecule. Transferrin is found mainly in serum, whereas lactoferrin is found in neutrophils and in external secretions.

The interaction of infant formula with macrophages: effect on phagocytic activity, relationship to expression of class II MHC antigen and survival of orally administered macrophages in the neonatal gut.

The effect of infant formula on human peritoneal and breast milk macrophages has been investigated. The ability of peritoneal macrophages to subsequently ingest and degrade immune complexes was slightly impaired, but breast milk cells were not affected. However, the cells were found to have bound antigenically intact casein and beta-lactoglobulin, although little, if any, alpha-lactalbumin was bound.

Uptake and handling of iron from transferrin, lactoferrin and immune complexes by a macrophage cell line.

The murine macrophage-like cell line P388D1 has been used as a model to investigate whether iron acquired simultaneously from different sources (transferrin, lactoferrin, and ovotransferrin-anti-ovotransferrin immune complexes) is handled in the same way. P388D1 cells bound both lactoferrin and transferrin, but over a 6 h incubation period only the latter actually donated iron to the cells. When the cells were incubated with [55Fe]transferrin and [59Fe]ovotransferrin-anti-ovotransferrin immune complexes iron was acquired from both sources.

The effect of synthetic iron chelators on bacterial growth in human serum.

The effect of synthetic iron chelators of the 1-alkyl-3-hydroxy-2-methylpyrid-4-one class (the L1 series) and 1-hydroxypyrid-2-one (L4) on bacterial growth in human serum was compared with those of the plant iron chelators mimosine and maltol and of the microbial siderophore desferrioxamine. None of the synthetic chelators enhanced growth of 3 Gram-negative organisms (Yersinia enterocolitica, Escherichia coli and Pseudomonas aeruginosa); in some cases they were even inhibitory. L4 strongly stimulated growth of Staphylococcus epidermidis, but the L1 series had only a marginal effect.

Inhibition of hydrogen peroxide release from activated macrophages by prior ingestion of erythrocytes or haemoglobin.

Production of hydrogen peroxide by mouse peritoneal macrophages activated with Corynebacterium parvum was induced by incubating the cells with opsonised zymosan. H2O2 release was reduced by 47% when macrophages were preincubated with opsonised sheep erythrocytes. A significant decrease also occurred when the cells were preincubated with heat-denatured haemoglobin, but not when preincubated with opsonised erythrocyte ghosts, even though the latter were taken up by the macrophages.

Serum IgG and IgE antibody against aerosolised antigens from Nephrops norvegicus among seafood process workers.

Employees in a seafood factory developed high titers of serum IgE and IgG antibody to antigens from prawn (N. norvegicus) which were aerosolized during processing. Significant serum IgE antibody titers occurred only among those subjects with occupation-related respiratory symptoms, and this serological parameter may be a useful clinical adjunct in the investigation of this disease.

Autoantibodies and nuclear antigens.

Autoantibodies against nuclear antigens are common in the systemic rheumatic diseases. About sixteen such antigens have been characterized and they have been located in all the nuclear compartments. Little is known about the biological roles of these antigens but the significance and function of autoantibodies to them was one of the themes of a recent meeting.

The role of iron and transferrin in lymphocyte transformation.

It has recently become apparent that many types of transformed cells possess membrane receptors for the plasma iron-binding protein transferrin. In this review Jeremy Brock and Tryfonia Mainou-Fowler discuss these observations in relation to transferrin's properties as an iron-transport protein, and the relative importance of iron and transferrin in lymphocyte transformation.