Biomedical subjects

Jonathan Plumb

Publications and source records attributed to Jonathan Plumb.

6 recordsLinked to original sources

PubMed2006

CD44 is a phagocytic receptor.

CD44, a transmembrane adhesion molecule involved in binding and metabolism of hyaluronan, has additional functions in inflammatory and immune responses, contributing to the ingestion and clearance of particles and apoptotic cells. Our goal was to determine the specific role of CD44 in phagocytosis and whether it functions as a primary or accessory phagocytic receptor. Using hyaluronan-coated beads and erythrocytes coated with antiCD44 antibodies as the phagocytic prey, we determined that CD44 mediates efficient phagocytosis in primary murine peritoneal macrophages and in the murine macrophage cell line RAW 264.7. In RAW cells, the phagocytic index for anti-CD44-coated erythrocytes was 25 +/- 3 (mean +/- SEM) compared with less than 1 for erythrocytes coated with isotype-matched control antibodies. Uptake of anti-CD44-coated erythrocytes was abrogated by pretreatment with a blocking antibody to CD44 and was absent in primary cultures of CD44-deficient murine macrophages. Down-regulation of Fc receptors by aggregated IgG-induced internalization, which blocks uptake of IgG-coated particles, had no effect on CD44-mediated particle engulfment. Using a combination of immunoprecipitation, pharmacologic inhibition, and genetic deletion, we determined that CD44-mediated phagocytosis involves Syk, Rac1, and phosphatidylinositol 3-kinase and induced activation of the phagocyte oxidase. We conclude that CD44 is a competent phagocytic receptor that efficiently mediates internalization of large particles.

Animals↗

PubMed2005

Abnormalities in the pulmonary innate immune system in cystic fibrosis.

Pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the basis for this susceptibility remains incompletely understood. One hypothesis is that CF airway surface liquid (ASL) is abnormal and interferes with neutrophil function. To study this possibility, we developed an in vitro system in which we collected ASL from primary cultures of normal and CF airway epithelial cells. Microbial killing was less efficient when bacteria were incubated with neutrophils in the presence of ASL from CF epithelia compared with normal ASL. Antimicrobial functions of human neutrophils were assessed in ASL from CF and normal epithelia using a combination of quantitative bacterial culture, flow cytometry, and microfluorescence imaging. The results of these assays of neutrophil function were indistinguishable in CF and normal ASL. In contrast, the direct bactericidal activity of ASL to Escherichia coli and to clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa was substantially less in CF than in normal ASL, even when highly diluted in media of identical ionic strength. Together, these observations indicate that the antimicrobial properties of ASL in CF are compromised in a manner independent of ionic strength of the ASL, and that this effect is not mediated through a direct effect of the ASL on phagocyte function.

Bronchi↗

PubMed2004

Cytosolic phospholipase A2-alpha is necessary for platelet-activating factor biosynthesis, efficient neutrophil-mediated bacterial killing, and the innate immune response to pulmonary infection: cPLA2-alpha does not regulate neutrophil NADPH oxidase activity.

The role of a cytosolic phospholipase A(2)-alpha (cPLA(2)-alpha) in neutrophil arachidonic acid release, platelet-activating factor (PAF) biosynthesis, NADPH oxidase activation, and bacterial killing in vitro, and the innate immune response to bacterial infection in vivo was examined. cPLA(2)-alpha activity was blocked with the specific cPLA(2)-alpha inhibitor, Pyrrolidine-1 (human cells), or by cPLA(2) -alpha gene disruption (mice). cPLA(2)-alpha inhibition or gene disruption led to complete suppression of neutrophil arachidonate release and PAF biosynthesis but had no effect on neutrophil NADPH oxidase activation, FcgammaII/III or CD11b surface expression, primary or secondary granule secretion, or phagocytosis of Escherichia coli in vitro. In contrast, cPLA(2)-alpha inhibition or gene disruption diminished neutrophil-mediated E. coli killing in vitro, which was partially rescued by exogenous arachidonic acid or PAF but not leukotriene B(4). Following intratracheal inoculation with live E. coli in vivo, pulmonary PAF biosynthesis, inflammatory cell infiltration, and clearance of E. coli were attenuated in cPLA(2)-alpha(-/-) mice compared with wild type littermates. These studies identify a novel role for cPLA(2)-alpha in the regulation of neutrophil-mediated bacterial killing and the innate immune response to bacterial infection.

Animals↗

PubMed2004

An economic evaluation of adjustable and fixed dosing with budesonide/formoterol via a single inhaler in asthma patients: the ASSURE study.

BACKGROUND: The severity of asthma varies between individuals and over time. As a result individuals may have marked variation in their need for asthma treatment. Adjustable dosing enables patients to assume greater involvement in managing their own condition. OBJECTIVE: To compare the costs and effectiveness of fixed dosing of budesonide/formoterol (Symbicort Turbohaler) with adjustable maintenance dosing. METHODS: A cost-effectiveness analysis was conducted from the perspective of the UK NHS. Adults with established asthma currently maintained on > or =400 microg per day inhaled corticosteroid were enrolled in 365 primary care centres in the UK. Patients were run-in on 2 inhalations twice daily of budesonide/formoterol 80/4.5 microg or budesonide/formoterol 160/4.5 microg (depending on steroid requirement) for 4 weeks and were then randomised to the Symbicort adjustable maintenance dosing plan (SAMD) (n = 782; budesonide/formoterol 1-4 inhalations twice daily depending on symptoms) or Symbicort fixed dosing (n = 771; 2 inhalations twice daily) for a further 12 weeks. The primary effectiveness variable was clinically meaningful change in quality of life (QoL) assessed by the miniasthma quality of life questionnaire (AQLQ). Secondary effectiveness measures included symptom-free days with no short-acting beta-agonist use. We assessed the costs of study medication, asthma-related concomitant medication, primary care and hospital contacts. Confidence intervals were generated by nonparametric boot-strapping. RESULTS: Clinically meaningful improvement in QoL during the first 4 weeks was reported by 40.8% of enrolled patients. During the following 12 weeks, a net 1% (95% CI: -4%, 6%) of SAMD patients and 6% (95% CI: 1%, 10%) of fixed dosing patients reported further improvement. Effectiveness parameters did not differ significantly between groups during the study period. Mean daily cost per patient was pound sterling 1.13 (95% CI: pound sterling 1.08, pound sterling 1.18) in the SAMD group and pound sterling 1.31 (95% CI: pound sterling 1.27, pound sterling 1.34) in the fixed dosing. The difference in mean daily cost resulted in an annual per patient cost difference of pound sterling 65.70. Adjustable maintenance dosing with budesonide/formoterol provided equivalent QoL to fixed dosing at significantly lower cost.

Administration, Inhalation↗

PubMed2003

Transfection of lung cells in vitro and in vivo: effect of antioxidants and intraliposomal bFGF.

We hypothesized that constitutive formation of reactive oxygen species by respiratory cells is a barrier to gene transfer when liposome-DNA complexes are used, by contributing to rapid degradation of plasmid DNA. When plasmid DNA is complexed to liposomes it is protected against H(2)O(2)-mediated degradation but not that mediated by the hydroxyl radical. Treatment of distal rat fetal lung epithelial cells (RFL(19)Ep) with the vitamin E analog Trolox (50 microM) reduced intracellular plasmid degradation. Both Trolox (50 microM) and an iron chelator, phenanthroline (0.1 microM), significantly increased transgene expression in RFL(19)Ep approximately twofold, consistent with a hydroxyl radical-mediated inhibition of transgene expression. When basic fibroblast growth factor (bFGF; 20 ng/ml), a growth factor with antioxidant properties, was included within liposomes, we observed a significantly greater enhancement of RFL(19)Ep transgene expression (approximately 2-fold) over that seen with Trolox or phenanthroline. Inclusion of bFGF within liposomes also significantly enhanced (approximately 4-fold) transgene expression in mice following intratracheal instillation.

Animals↗

PubMedDate not supplied

The management of in vitro diagnostic point-of-care testing.

In vitro diagnostic point-of-care testing (IVDPCT) can improve patient care but improvements can only be properly realised by adequate management in order to ensure high-quality test results. Nurses perform IVDPCT in all areas of clinical practice, from intensive care units to GP surgeries, using a wide variety of devices ranging from urinalysis strips to blood gas analysers.

Blood Gas Analysis↗