Biomedical subjects

S K Jackson

Publications and source records attributed to S K Jackson.

At least 55 records · Page 3Linked to original sources

PubMed1996

Temperature-dependent aminoglycoside resistance in Stenotrophomonas (Xanthomonas) maltophilia; alterations in protein and lipopolysaccharide with growth temperature.

Clinical strains of Stenotrophomonas (Xanthomonas) maltophilia often show large, growth temperature-dependent, variations in their susceptibility (TDVS) to aminoglycoside antibiotics. Strains showing more than a fourfold increase in susceptibility between 30 degrees and 37 degrees C (TDVS+ strains; n = 23) were contrasted with those showing lesser variation (TDVS- strains; n = 15) in studies of growth temperature-dependent variation in protein and cell-wall lipopolysaccharide (LPS) electrophoresis patterns in an attempt to determine the mechanism of TDVS. Several proteins showed increased intensity with increasing growth temperature. These comprised bands at c. 65, 55, 42.5, 26 and 21.5 kDa in the whole cell proteins, an outer membrane protein band at c. 21.5 kDa, and cytoplasmic membrane protein bands at c. 42.5 and 27 kDa. Two whole cell protein bands at c. 30 and 24 kDa and three outer membrane protein bands at c. 45, 30 and 24 kDa decreased in intensity with increasing growth temperature. However, there was no correlation with the extent of variation in susceptibility, either in the extent of temperature dependent changes in protein banding patterns, or the presence or absence of specific protein bands. By contrast, temperature-dependent variation in LPS patterns correlated well with TDVS. TDVS+ strains yielded intense ladder patterns of more than 30 discrete bands, and the mean molecular weight of the ladder pattern was markedly higher at growth temperatures < or = 30 degrees C, than at > or = 37 degrees C. TDVS- strains gave a clearly distinct high mol. wt LPS banding pattern showing fewer, less intense bands and a smaller and less consistent shift in mean molecular weight with temperature. Strains which were clearly resistant at 30 degrees and 37 degrees C, had a high mol. wt. polysaccharide component but an absence of the typical LPS-ladder pattern. We conclude that the temperature-dependent variation in the aminoglycoside susceptibility of this species was not correlated with any detectable change in protein composition, but correlated well with changes in LPS structure.

Aminoglycosides↗

PubMed1995

The effects of endotoxin on oxygen consumption of various cell types in vitro: an EPR oximetry study.

We have studied the effects of bacterial endotoxin on the oxygen consumption of a variety of target cells, and found that the rate of utilization of oxygen by treated cells was decreased in a time- and dose-dependent manner. Precise EPR measurement of oxygen concentrations enabled us to demonstrate that this effect was linked to mitochondrial dysfunction and was particular to each cell type. Such detailed knowledge on oxygen utilization by viable whole cells and the varied effects of endotoxin are as yet undocumented. Oxygen consumption was shown to decrease quite markedly in CHO cells and kidney cells from the cortex region. Cells from the kidney medulla region had lower baseline consumption and were stimulated to increased levels of oxygen consumption on addition of similar doses of endotoxin. Macrophages exhibited a dual response in that in addition to inhibiting mitochondrial oxygen consumption, endotoxin pretreatment primed these cells to exhibit an enhanced oxidative burst on stimulation with Zymosan. These results show that endotoxin has a direct effect on normal cellular oxygen consumption and is an important parameter that must be considered when following the early effects on cells and tissues during the septic syndrome.

Animals↗

PubMed1995

Growth temperature-dependent variation of cell envelope lipids and antibiotic susceptibility in Stenotrophomonas (Xanthomonas) maltophilia.

Clinical isolates of Stenotrophomonas (Xanthomonas) maltophilia showed growth temperature-dependent variation in susceptibility (TDVS) to aminoglycoside antibiotics between 30 degrees C and 37 degrees C, but little or no TDVS effect for polymixin B, colistin, ceftazidime, chloramphenicol and piperacillin. When phenylethanol was added at sub-inhibitory concentrations, the TDVS effect was eliminated. Gas liquid chromatography showed that 13-methyl tetradecanoate (i-15;0), was the predominant fatty acid, and was present in lower proportions in cells grown at 30 degrees C than 37 degrees C, by contrast to the unsaturated acids, which were found in increased proportions in cells grown at 30 degrees C. However, the extent of these shifts in composition did not correlate with the extent of the TDVS effect in individual strains. Membrane analysis by spin label-electron spin resonance spectroscopy showed that strains exhibiting TDVS had significantly decreased membrane fluidity compared with susceptible strains at 30 degrees C. Furthermore, analysis of the outer and cytoplasmic membranes from the strains with TDVS revealed that in organisms grown at 30 degrees C, the outer membrane remained in a more rigid conformation than the cytoplasmic membrane. We conclude that resistance of S. maltophilia to aminoglycoside antibiotics at 30 degrees C correlates with changes in the conformation of the outer membrane so that binding and/or uptake of the antibiotic is inhibited.

Anti-Bacterial Agents↗

PubMed1995

Antigenaemia during acute graft versus host disease.

AIMS: Animal studies have shown that antigens present within the gut play an important role in the development of acute graft versus host disease (GvHD) following allogeneic bone marrow transplantation (BMT). In previous studies, inert sugars have been found to penetrate the small bowel mucosa after conditioning therapy for BMT; endotoxaemia can also occur during acute GvHD. Data on absorption of antigenic proteins across the gut following BMT in humans have not been presented as yet. METHODS: Six patients undergoing allogeneic BMT were studied to determine whether enteric ovalbumin absorption increased or endotoxaemia developed during acute GvHD. RESULTS: Three patients had minimal antigenaemia and no detectable endotoxaemia before receiving conditioning therapy. At the onset of acute GvHD, however, much higher ovalbumin concentrations were detected in those patients with severe antigenaemia. Serum concentrations of specific antiovalbumin IgG and IgA, or antiendotoxin IgM or IgG had no bearing on detectable IgG or IgM ovalbumin or endotoxin concentrations. In five of six patients, small bowel permeability increased, as tested by the lactulose/mannitol sugar absorption test, but detectable ovalbumin absorption increased in only three of these and only two developed endotoxaemia. CONCLUSIONS: Antigens present within the gut can cross the mucosal epithelium during acute GvHD, probably resulting in an enhanced immune response.

Acute Disease↗

PubMed1995

Retinoids, retinoic acid receptors, and cytoplasmic retinoid binding proteins in perinatal rat lung fibroblasts.

The early postnatal life of most mammals marks a period of extensive enlargement of the alveolar surface area and increase in the elastin content of the lung. The factors that regulate the onset and abatement of this burst of elastin synthesis have not been identified. Previous studies of lipid-laden rat pulmonary interstitial fibroblasts (LIF) have shown that their elastin synthesis is increased in vitro by retinoic acid (RA). We hypothesized that temporal changes in the endogenous RA content of LIF may correlate with changes in elastin synthesis by these cells. LIF were isolated from the lungs of rats at gestational day 19 and postnatal days 2, 4, 8, and 12 and their retinoid contents were quantitated. Retinyl esters were highest at gestational day 19 (2.9 +/- 0.6 pmol/10(6) cells, means +/- SE) and decreased to 1.6 +/- 0.2 pmol by postnatal day 2 (P < 0.05). This decrease in retinyl esters was accompanied by an increase in retinol from 0.4 +/- 0.1 to 2.0 +/- 0.6 pmol/10(6) cells (P < 0.05). RA increased in LIF from 0.07 +/- 0.04 pmol/10(6) cells at gestational day 19 to 0.29 +/- 0.05 pmol/10(6) cells at postnatal day 2 (P < 0.05) and increased in whole lung tissue from 0.07 +/- 0.04 to 0.29 +/- 0.05 nmol/g, over the same interval. The increase in RA content was accompanied by an increase in RA receptor (RAR)-beta and -gamma mRNAs. The steady-state mRNA level of cellular retinol binding protein (CRBP) was high in LIF, relative to whole lung tissue at day 2. Cellular RA binding protein (CRABP) mRNA rose fourfold from day 2 to day 8 and then fell by day 12. In summary, RA, RAR, and CRBP mRNA in LIF are highest before the period of maximal elastin synthesis, which occurs at postnatal days 8 and 12. These findings are consistent with the hypothesis that endogenous RA could contribute to the postnatal increase in elastin production by pulmonary fibroblasts.

Aging↗

PubMed1995

Aspirin-induced conformational changes in platelet membrane in subjects with stroke.

Objectives of this case-control study were (1) to examine membrane conformational changes and dynamics in platelets of patients with stroke prior to and following short-term aspirin administration and (2) to investigate changes in platelet membrane fluidity which may be associated with the ageing process. The study population consisted of 10 patients with ischaemic stroke (age range 61-92, mean 76 years; 6 females and 4 males), 9 age- and sex-matched controls (age range 64-88, mean 73 years; 5 females and 4 males), and 8 healthy young controls (age range 22-39, mean 32 years; 4 females and 4 males). The patients were recruited from the medical and geriatric wards, whereas both young and old controls were recruited from hospital staff and the local community. Aspirin, at a dose of 150 mg/day, was administered to all three groups for 7 days. The order parameter S, which is an index of membrane fluidity and conformation, was measured by the techniques of spin labelling and electron spin resonance spectroscopy on platelets from venous blood samples from patients prior to (within 48 h of admission) and following 7 days of aspirin therapy and from venous blood samples from both young and old controls before and after 7 days of oral aspirin therapy. There was an age-related decrease in platelet membrane fluidity. There was no significant difference in the value of 'S' between patients with ischaemic stroke and old controls. Treatment with aspirin led to a significant decrease in membrane fluidity in both patients and old controls, but had no apparent effect on the platelet membrane fluidity of younger controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Differential effects of interferon-gamma and -beta on fatty acid turnover, lipid bilayer fluidity and TNF-alpha release in murine macrophage J774.2 cells.

The effects of interferon (IFN)-gamma and IFN-beta on the incorporation of 14C-linoleic acid into J774.2 cell membrane phospholipids were examined. Interferon-gamma induced a statistically significant increase in incorporation of 14C-linoleic acid into all the major phospholipid classes. In contrast, IFN-beta induced a slightly reduced incorporation of this fatty acid into the phospholipids. Neither IFN-gamma nor IFN-beta had any effect on the incorporation of the saturated fatty acid 14C-stearic acid into the cellular phospholipids. Interferon-gamma had no effect on the metabolism of 14C-linoleic acid in the fibroblast cell line L929. Macrophage membrane fluidity was assessed by spin-label ESR spectroscopy after incubation with either IFN-gamma or IFN-beta. Interferon-gamma significantly increased membrane fluidity whereas IFN-beta significantly decreased the fluidity. The findings of this study reveal that IFN-gamma might act on the enzymes controlling the labelling of the sn2 position of phospholipids (linoleic acid) but not the sn1 position (stearic acid), and this increases the polyunsaturated fatty acid content of macrophage membranes. This increase in polyunsaturation is reflected in the increased membrane fluidity. We also conclude that IFN-beta and IFN-gamma have different mechanisms of action on macrophage membrane lipid metabolism.

Animals↗

PubMed1994

Interferon-gamma and polyunsaturated fatty acids increase the binding of lipopolysaccharide to macrophages.

We have previously shown that interferon-gamma (IFN-gamma) increases the polyunsaturated fatty acid content of membrane phospholipids in cells that were sensitive to endotoxin. In this study, IFN-gamma was found to stimulate the binding of endotoxin to the murine macrophage cell line J774.2 and the human monocyte cell line U937. Interferon-gamma-activated J774.2 cells showed a 66% increase in fluoresceine isothiocyanate (FITC) labelled LPS binding (P < 0.0005 vs control cells) and a 49% increase in tritium labelled LPS binding (P < 0.0001 vs control cells). Interferon-gamma also induced a 35% increase in binding of FITC-LPS in U937 cells (P < 0.0001 vs control cells). In contrast, pretreatment of J774.2 cells with interferon-beta (IFN-beta) had no effect on binding of FITC-LPS. Preincubation with exogenously supplied polyunsaturated fatty acids, linoleic and arachidonic acids, resulted in increases of 74% and 69% in FITC-LPS binding, respectively (both P < 0.0005 vs control cells). On the other hand, pretreatment with the saturated fatty acid, palmitic acid, had no effect on FITC-LPS binding. We propose that IFN-gamma-induced changes in the membrane phospholipid fatty acid composition of macrophage-like cells influence the binding of endotoxin.

Animals↗

PubMed1993

Interferon-gamma-stimulated uptake and turnover of linoleate and arachidonate in macrophages: a possible pathway for hypersensitivity to endotoxin.

When P388D macrophage cells were exposed to [14C]linoleic acid, phosphatidylcholine (PC) phosphatidylethanolamine (PE), phosphatidylinositol (PI), and triacylglycerol (TAG) were major labelled lipid classes. PC was the major labelled phospholipid class at shorter incubation times with PE and PI becoming proportionally better labelled with time. Interferon-gamma (IFN-gamma) stimulated the labelling of all phospholipid classes at the expense of triacylglycerol (TAG) labelling whether it was added coincidently to the [14C]linoleic acid or after a prelabelling period. A similar pattern of labelling of all major phospholipid classes by interferon-gamma in J774.2 macrophage cells was also observed. Interferon-gamma also exerted a stimulatory effect on incorporation of [14C]arachidonic acid into the phosphatidylinositol fraction of the membrane phospholipids. However, uptake of [14C]stearic acid was not different in control compared with IFN-gamma-activated cells. Uptake of linoleic acid into the plasmalogen fraction of PE was also considerably enhanced in IFN-gamma-treated cells. The results suggest that IFN-gamma has a direct effect on the activity of enzymes controlling fatty acid turnover in phospholipids. This altered uptake and turnover of unsaturated fatty acids may have important consequences for the subsequent activation of macrophages by endotoxin.

Animals↗

PubMed1993

Effect of interferon-gamma on membrane conformation in the macrophage-like cell line P388D.

Interferon-gamma (IFN-gamma) specifically induced the uptake of the unsaturated fatty acid [14C]linoleic acid into membrane phospholipids of the murine macrophage-like P388D cell lineage, but did not alter the incorporation of the saturated fatty acid [14C]stearic acid. Spin label ESR spectroscopy was used to examine any effects of these IFN-gamma-induced changes on membrane fluidity and the results revealed significant increases in plasma membrane fluidity. This alteration in membrane fluidity may have important consequences in the dynamic properties of cellular physiochemical interactions and some of the stimulatory effects of IFN-gamma on macrophages might be attributed to its effects on the plasma membrane composition.

Animals↗

PubMed1993

Effect of IgM-enriched intravenous immunoglobulin (Pentaglobin) on endotoxaemia and anti-endotoxin antibodies in bone marrow transplantation.

Endotoxin was measured in over 1000 plasma samples from bone marrow transplant patients in a randomized trial of the IgM-enriched intravenous immunoglobulin (IVIG) Pentaglobin. Peak endotoxaemia was significantly reduced (P = 0.02) in patients receiving Pentaglobin and 70% of all pyrexias of unknown origin were associated with endotoxaemia. Gut mucosal damage, assessed by lactulose/mannitol ratios, was significantly associated (P = 0.02) with endotoxaemia. Specific IgM antibody to endotoxin core-glycolipid was significantly raised (P < 0.01) in patients receiving the IVIG, and the IgM fraction of Pentaglobin was found to contain most of the anti-endotoxin antibody activity of the IVIG. These results suggest a role for IgM-enriched IVIG as a prophylactic agent for the reduction of endotoxaemia and its consequences in bone marrow transplant patients.

Adolescent↗

PubMed1992

Binding of endotoxin to macrophages; interactions of spin-labelled saccharide residues.

The molecular mechanisms of endotoxin action are poorly understood. A prerequisite to cellular activation by this agent must be interaction (binding) with the plasma membrane. In this study we have investigated the role of the polysaccharide region of endotoxin (LPS) in binding to macrophages and macrophage-like cell lines. The LPS molecules, from Escherichia coli O111.B4, J5 and the lipid-A, were spin labelled with 2,2,6,6-tetramethylpiperidine-N-oxyl] (Tempo) free radical in their sugar residues, and examined by electron spin resonance spectroscopy. This is the first report of the synthesis of spin-labelled endotoxins. Measurement of the rotational correlation times (Tc) indicated that the saccharide resides do not bind to membrane surface structures and suggests that the binding of LPS to macrophages is mediated by the lipid acyl chains. Anti-sera to LPS from E. coli O111.B4 was effective in binding to the polysaccharide of the same LPS bound to the cell surface.

Animals↗

PubMed1992

Interferon-gamma increases macrophage phospholipid polyunsaturation: a possible mechanism of endotoxin sensitivity.

Incubation of murine macrophages or the macrophage-like cell line P388D with interferon-gamma in vitro induced a significant increase in the polyunsaturated fatty acid content of phosphatidylethanolamine. These increases were time and dose-dependent, being maximal at 12 hours and with 5000 U/ml interferon and were inhibited in the presence of anti-interferon-gamma monoclonal antibody. Interferon-gamma induced a significant increase in linoleate in peritoneal macrophages while in the cell line arachidonate was significantly increased. These results are of interest because such increases in the polyunsaturated fatty acid content of phosphatidylethanolamine were previously shown by us to be associated with increased sensitivity to endotoxin in mice in vivo. The implications for interferon-gamma sensitizing to endotoxin are discussed.

Animals↗

PubMed1990

The effect of endotoxin on membrane fatty acid composition in BCG-sensitized mice.

The effects of endotoxin on mouse liver phospholipid fatty acid composition have been investigated. Administration of endotoxin from Salmonella abortus equi led to a decrease in the polyunsaturated fatty acid content of livers from mice sensitized with Bacille Calmette Guérin (BCG). The content of arachidonic acid fell significantly in both the phosphatidylcholine and phosphatidylinositol fractions whereas in the phosphatidylethanolamine fraction the linoleic acid content was significantly reduced. The polyunsaturated fatty acids were replaced by increased amounts of oleic acid and palmitic acid, leading to a reduction in the polyunsaturated to saturated fatty acid ratio.

Animals↗

PubMed1990

Sensitivity to endotoxin is induced by increased membrane fatty-acid unsaturation and oxidant stress.

The mechanisms modulating host susceptibility to endotoxin are unknown. Evidence suggests that endotoxin pathophysiology is mediated in part by oxidative reactions that lead to tissue damage and organ failure. The proposition is that conditions which favour oxidation sensitise the host to endotoxin. Central to this hypothesis is that an increase in the polyunsaturated fatty-acid composition of membrane phospholipids enhances susceptibility because such fatty acids are easily oxidised to produce mediators of the endotoxic crisis. Cytokines, such as tumour-necrosis factor and interferon-gamma, may be ultimately responsible for orchestrating these changes and thereby modify the host response to endotoxin.

Animals↗

PubMed1990

Serum immunoglobulins to endotoxin core glycolipid: establishment of normal concentrations.

Serum antibody to lipopolysaccharide core glycolipid was measured in normal children and in full term and premature (less than or equal to 1500 g) infants. Antilipopolysaccharide core glycolipid antibody was present in term infants and normal children, and reached adult titres by 15 years of age. The specific anti core glycolipid antibody was predominately of the IgG class. Preterm infants (less than 32 weeks' gestation) had significantly lower titres of antilipopolysaccharide core glycolipid than more mature preterm or term infants. The results suggest that administration of anticore glycolipid immunoglobulin may be beneficial in the treatment or prevention of Gram negative septicaemia in preterm and very young infants.

Adolescent↗

PubMed1990

Serum immunoglobulins to endotoxin core glycolipid: acute leukaemia and other cancers.

Circulating antibody to endotoxin core glycolipid and total serum immunoglobulin concentrations were measured in 86 children with cancer (54 with acute lymphoblastic leukaemia, four with acute myeloid leukaemia, and 28 with various solid tumours). Measurements were made before treatment in the group with acute lymphoblastic leukaemia as well as when patients were both on and off chemotherapy. In the other two groups measurements were made when patients were both on and off treatment. Significant reductions in endotoxin antibody and serum immunoglobulin concentrations were found only in patients with acute lymphoblastic leukaemia. In addition, there was a significant correlation between febrile episodes and the concentration of antibody to core glycolipid in the children with acute lymphoblastic leukaemia. These findings suggest that the use of prophylactic high titre endotoxin antibody may be of benefit to children with life threatening Gram negative infections who are receiving cytotoxic chemotherapy.

Child↗

PubMed1989

Electron spin resonance detection of oxygen-centred radicals in murine macrophages stimulated with bacterial endotoxin.

The production of oxygen radicals by Bacille-Calmette-Guerin primed mouse macrophages stimulated with bacterial endotoxin has been investigated. Superoxide radicals were spin-trapped in this system with dimethylpyrroline-N-oxide after a lag period of 20-40 minutes. The electron spin resonance signals due to the superoxide radical adduct could be inhibited by superoxide dismutase but not by catalase.

Animals↗