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Biomedical subjects

P B Davis

Publications and source records attributed to P B Davis.

At least 19 recordsLinked to original sources
PubMed2006

Relationship between complaints and quality of care in New Zealand: a descriptive analysis of complainants and non-complainants following adverse events.

OBJECTIVES: To estimate the proportion and characteristics of patients injured by medical care in New Zealand public hospitals who complain to an independent health ombudsman, the Health and Disability Commissioner ("the Commissioner"). DESIGN: The percentage of injured patients who lodge complaints was estimated by linking the Commissioner's complaints database to records reviewed in the New Zealand Quality of Healthcare Study (NZQHS). Bivariate and multivariate analyses investigated sociodemographic and socioeconomic differences between complainants and non-complainants. SETTING: New Zealand public hospitals and the Office of the Commissioner in 1998. POPULATION: Patients who lodged claims with the Commissioner (n = 398) and patients identified by the NZQHS as having suffered an adverse event who did not lodge a complaint with the Commissioner (n = 847). MAIN OUTCOME MEASURES: Adverse events, preventable adverse events, and complaints lodged with the Commissioner. RESULTS: Among adverse events identified by the NZQHS, 0.4% (3/850) resulted in complaints; among serious, preventable adverse events 4% (2/48) resulted in complaints. The propensity of injured patients to complain increased steeply with the severity of the injury: odds of complaint were 11 times greater after serious permanent injuries than after temporary injuries, and 18 times greater after deaths. Odds of complaining were significantly lower for patients who were elderly (odds ratio (OR) 0.2, 95% confidence interval (CI) 0.1 to 0.4), of Pacific ethnicity (OR 0.3, 95% CI 0.1 to 0.9), or lived in the most deprived areas (OR 0.3, 95% CI 0.2 to 0.6). CONCLUSION: Most medical injuries never trigger a complaint to the Commissioner. Among complaints that are brought, severe and preventable injuries are common, offering a potentially valuable "window" on serious threats to patient safety. The relatively low propensity to complain among patients who are elderly, socioeconomically deprived, or of Pacific ethnicity suggests troubling disparities in access to and utilisation of complaints processes.

Adolescent↗
PubMed2004

Defining strategies to extend duration of gene expression from targeted compacted DNA vectors.

Gene transfer complexes containing poly-L-lysine (poly-K) and DNA with ligands directed at the serpin enzyme complex receptor (sec-R) deliver reporter genes to receptor-bearing cells in vivo. Expression lasts for about 30 days, when complexes containing long-chain poly-K are used. Extending the duration of expression would be desirable if correction of genetic defects is the goal. To test whether the mechanism by which expression is extinguished was due to an immune response to the transgene, or the loss of the transgene, we conducted two experiments. In the first, we injected sec-R-targeted lacZ complexes intravenously (i.v.) into mice genetically engineered to express this gene briefly during development. These mice, who should recognize the protein as 'self', also extinguished lacZ expression after 30 days. In a second experiment, we injected immunodeficient animals with sec-R-targeted human factor IX complexes. A similar temporal pattern of expression was observed in Rag-1 -/- mice, in whom expression also extinguished by 40 days. Moreover, factor IX plasmid DNA was detected in the lung and spleen 50 days after injection of complexes, suggesting that not all cells which had taken up the transgene had been destroyed. Thus, the host's immune response to the transgene may not account for the loss of reporter gene expression from these molecular conjugates. We further tested whether repeat administration of sec-R-targeted complexes will be limited by host immune responses. Mice were pre-dosed twice with sec-R-targeted complexes containing lacZ over a 40-day period. We then injected the animals i.v. with sec-R-targeted human factor IX complexes and measured gene expression and antibody production. Although 14 of 36 animals displayed low-titer antibodies to the ligand in targeted complex, expression levels were unaffected compared with virgin dosing. When the complexes were administered three times intranasally (n=10), no antibodies against the complex were detected in blood. Plasma from mice dosed with saline, nontargeted complex or naked DNA did not react with the ligand, ligand-poly K conjugate or targeted complex. All animals exhibiting human factor IX expression developed antibodies to that transgene by 21 days. Thus, at least three repeat administrations of sec-R-directed molecular conjugates are possible, provided that immune responses to the transgene itself are not limiting.

Animals↗
PubMed2001

Single chain Fv: a ligand in receptor-mediated gene delivery.

We have used an anti-human polymeric immunoglobulin receptor (pIgR) single chain Fv (scFv) to deliver reporter genes to epithelial cells in vitro. The scFv was constructed from a monoclonal antibody directed against pIgR and a cysteine residue was added at the carboxyl end to facilitate its conjugation to polylysine (polyK) via the heterobifunctional cross-linker SPDP. ScFv-cys was expressed in Drosophila S2 cells and purified to homogeneity using conventional column chromatography. ScFv-polyK, and polyK as control, were condensed with a DNA expression plasmid containing the luciferase reporter gene driven by the CMV promoter into unimolecular (with respect to DNA) complexes under high salt conditions. Target cells were MDCK cells transfected with human pIgR and repeatedly sorted for high-level receptor expression, with untransfected MDCK cells as control. Receptor-bearing MDCK cells were readily transfected by scFv-cys containing, pIgR directed complexes, and expression could be blocked by addition of excess human secretory component (SC), the extracellular portion of pIgR. In contrast, MDCK cells that did not express pIgR were not transfected. Nontargeted complexes were not effective in transfecting MDCK cells with or without pIgR. Targeted complexes also transfected human tracheal epithelial cells in primary culture, corroborating the pIgR-mediated gene delivery. These data indicate that a scFv directed against human pIgR can direct foreign genes specifically into receptor-bearing cells in vitro. We have expressed and purified a ligand that is efficient and specific in pIgR-mediated gene delivery.

Animals↗
PubMed2001

Terminal sialylation is altered in airway cells with impaired CFTR-mediated chloride transport.

Reduced terminal sialylation at the surface of airway epithelial cells from patients with cystic fibrosis may predispose them to bacterial infection. To determine whether a lack of chloride transport or misprocessing of mutant cystic fibrosis transmembrane conductance regulator (CFTR) is critical for the alterations in glycosylation, we studied a normal human tracheal epithelial cell line (9/HTEo(-)) transfected with the regulatory (R) domain of CFTR, which blocks CFTR-mediated chloride transport; DeltaF508 CFTR, which is misprocessed, wild-type CFTR; or empty vector. Reduced cAMP-stimulated chloride transport is seen in the R domain and DeltaF508 transfectants. These two cell lines had consistent, significantly reduced binding of elderberry bark lectin, which recognizes terminal sialic acid in the alpha-2,6 configuration. Binding of other lectins, including Maakia amurensis lectin, which recognizes sialic acid in the alpha-2,3 configuration, was comparable in all cell lines. Because the cell surface change occurred in R domain-transfected cells, which continue to express wild-type CFTR, it cannot be related entirely to misprocessed or overexpressed CFTR. It is associated most closely with reduced CFTR activity.

Biological Transport↗
PubMed2001

Proinflammatory cytokine responses to P. aeruginosa infection in human airway epithelial cell lines.

A tendency toward excessive inflammation in cystic fibrosis (CF) patients often accompanies lung infections with Pseudomonas aeruginosa. We tested the cytokine response to P. aeruginosa in two pairs of human airway epithelial cell lines matched except for CF transmembrane conductance regulator activity. The 9/HTEo(-) CF-phenotypic cell line produced significantly more interleukin (IL)-8, IL-6, and granulocyte-macrophage colony-stimulating factor but not regulated on activation normal T cell expressed and secreted (RANTES) in response to Pseudomonas than the 9/HTEo(-) control line, and the differences widened over time. Similarly, a 16HBE cell line lacking transmembrane conductance regulator activity showed enhanced IL-8 and IL-6 responses compared with the control cell line. The pharmacology of the cytokine response also differed because dexamethasone reduced cytokine production to similar levels in the matched cell lines. The protracted proinflammatory cytokine response of the CF-phenotypic cell lines suggests that the limiting mechanisms of normal cells are absent or attenuated. These results are consistent with in vivo observations in patients with CF and suggest that our novel cell lines may be useful for further investigation of the proinflammatory responses in CF airways.

Bronchi↗
PubMed2001

Cystic fibrosis.

Explore the source record for details and available documents.

Adolescent↗
PubMed2000

Conformation, independent of charge, in the R domain affects cystic fibrosis transmembrane conductance regulator channel openings.

The R domain of cystic fibrosis transmembrane conductance regulator (CFTR), when phosphorylated, undergoes conformational change, and the chloride channel opens. We investigated the contribution of R domain conformation, apart from the changes induced by phosphorylation, to channel opening, by testing the effect of the peptidyl-prolyl isomerase, cyclophilin A, on the CFTR channel. When it was applied after the channel had been opened by PKA phosphorylation, cyclophilin A increased the open probability of wild-type CFTR (from P(o) = 0.197 +/- 0.010 to P(o) = 0.436 +/- 0. 029) by increasing the number of channel openings, not open time. Three highly conserved proline residues in the R domain, at positions 740, 750, and 759, were considered as candidate targets for cyclophilin A. Mutations of these prolines to alanines (P3A mutant) resulted in a channel unresponsive to cyclophilin A but with pore properties similar to the wild type, under strict control of PKA and ATP, but with significantly increased open probability (P(o) = 0.577 +/- 0.090) compared to wild-type CFTR, again due to an increase in the number of channel openings and not open time. Mutation of each of the proline residues separately and in pairs demonstrated that all three proline mutations are required for maximal P(o). When P3A was expressed in 293 HEK cells and tested by SPQ assay, chloride efflux was significantly increased compared to cells transfected with wild-type CFTR. Thus, treatments favoring the trans-peptidyl conformation about conserved proline residues in the R domain of CFTR affect openings of CFTR, above and beyond the effect of PKA phosphorylation.

Alanine↗
PubMed2000

Effect of Pseudomonas infection on weight loss, lung mechanics, and cytokines in mice.

Poor growth, Pseudomonas aeruginosa endobronchitis, pulmonary inflammation, and decline of lung function are hallmarks of cystic fibrosis (CF), yet the relationship between these features is poorly understood. Because animal models of chronic bronchopulmonary infection with P. aeruginosa used to study pulmonary inflammation in CF have also been associated with weight loss, we sought to determine whether this weight loss was due to the inflammatory process and/or to changes in lung function. P. aeruginosa-laden agarose beads were instilled into the lungs of mice. Weight loss was greatest 3 d after Pseudomonas infection. Infected mice had a rapid though transient rise in absolute neutrophil counts, mTNF-alpha, mIL-1beta, mIL-6, mip-2, and KC in bronchoalveolar lavage fluid. There was no difference in lung resistance or lung compliance measured by body plethysmography between infected and control mice. Weight loss did correlate with the concentration of proinflammatory cytokine levels 3 d after inoculation of mice with Pseudomonas, and body composition analysis revealed loss of skeletal muscle mass. These results suggest that weight loss in P. aeruginosa-infected mice was associated with the inflammatory process and not with altered pulmonary responsiveness. These findings may provide insights into the cause of cachexia and weight loss seen in patients with CF.

Airway Resistance↗
PubMed1999

A single conductance pore for chloride ions formed by two cystic fibrosis transmembrane conductance regulator molecules.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent protein kinase (PKA)- and ATP-regulated chloride channel, whose gating process involves intra- or intermolecular interactions among the cytosolic domains of the CFTR protein. Tandem linkage of two CFTR molecules produces a functional chloride channel with properties that are similar to those of the native CFTR channel, including trafficking to the plasma membrane, ATP- and PKA-dependent gating, and a unitary conductance of 8 picosiemens (pS). A heterodimer, consisting of a wild type and a mutant CFTR, also forms an 8-pS chloride channel with mixed gating properties of the wild type and mutant CFTR channels. The data suggest that two CFTR molecules interact together to form a single conductance pore for chloride ions.

Adenosine Triphosphate↗
PubMed1999

Functional dissection of the R domain of cystic fibrosis transmembrane conductance regulator.

Exogenously expressed unphosphorylated sub-domains of the R domain block CFTR Cl- channels in the planar lipid bilayer, though the block differs from block with full length R domain. Full length R domain peptide (aa 588-855) blocks CFTR Cl- channels quickly, completely and permanently. Two sub-domains, RD1RD2 (aa 588-805) and RD2TM (aa 672-855), also inhibit CFTR Cl- channels, but the block takes longer to effect and is not complete. Shorter sequences, RD1 (aa 588-746) and RD2 (aa 672-805), fail to effect any block. These data suggest that either the amino-terminal or carboxy-terminal portions of the R domain protein or its stabilized secondary structure are critical to functional regulation.

Cell Line↗
PubMed1999

Chain length of the polylysine in receptor-targeted gene transfer complexes affects duration of reporter gene expression both in vitro and in vivo.

Complexes composed of peptide ligand for the serpin enzyme complex receptor covalently coupled to poly-L-lysine condensed by charge interaction with plasmid DNA direct gene transfer into receptor bearing cells. We compared intensity and duration of reporter gene expression in vitro and in vivo from serpin-enzyme receptor-directed gene transfer complexes prepared with poly-L-lysine of different chain lengths. When substituted with linker and ligand to comparable extents, DNA complexes containing short chain poly-L-lysine were larger and gave higher peak expression but significantly shorter duration of expression than those containing long chain poly-L-lysine. Both peak expression and duration of expression exceeded that observed with Lipofectin. Neither naked DNA nor DNA complexed with unsubstituted polylysine was effective in gene transfer. For in vivo experiments, complexes containing optimal ligand and degree of substitution (based on in vitro data, peptide C105Y, 11 ligands/plasmid DNA molecule) were prepared with either short chain or long chain polylysine and a beta-galactosidase expression plasmid. Following injection into the tail veins of mice, longer chain complexes gave significantly higher expression of reporter gene in lung and spleen that lasted for a significantly longer period of time than the shorter chain complexes. The short chain poly-L-lysine-DNA complexes were larger in diameter, as assessed by electron microscopy or atomic force microscopy, and gave less protection against DNase digestion in vitro than longer chain complexes. Thus, for gene transfer complexes directed at the serpin enzyme complex receptor, longer chain poly-L-lysine gave a much longer duration of expression both in vitro and in vivo. We speculate that this may be due to protection against degradation afforded the plasmid DNA by the tighter compaction produced by long chain poly-L-lysine.

Amino Acid Sequence↗
PubMed1999

In vitro transport of active alpha(1)-antitrypsin to the apical surface of epithelia by targeting the polymeric immunoglobulin receptor.

In cystic fibrosis (CF), the intense host inflammatory response to chronic infection largely accounts for the progressive pulmonary disease, and ultimately death. Neutrophils are the prominent inflammatory cells in the lungs of patients with CF, and large amounts of neutrophil elastase (NE) are released during phagocytosis. Besides having direct effects on structural elastin, NE stimulates the release of proinflammatory mediators from the respiratory epithelium and is a potent secretogogue. Therapeutic use of elastase inhibitors in CF has been complicated by difficulties in delivery to the critical site in the airway-the surface of the epithelium. We describe a unique strategy to protect the respiratory epithelial cell surface directly by capitalizing on the nondegradative transcytotic pathway of the polymeric immunoglobulin receptor (pIgR). A recombinant fusion protein was constructed consisting of an antihuman pIgR single-chain Fv (scFv) antibody linked to human alpha(1)-antitrypsin (A1AT), an inhibitor of NE. The recombinant scFv-A1AT fusion protein bound specifically to the pIgR on the basolateral surface of an epithelial cell monolayer, and was transported and released into the apical medium where the A1AT domain was capable of forming an inactivation complex with NE. Thus, A1AT linked to an antihuman pIgR scFv was delivered in receptor-specific fashion from the basolateral to apical surface and was released as an active antiprotease, indicating that it is feasible to deliver therapeutic proteins to the apical surface of epithelia by targeting the pIgR.

Animals↗
PubMed1998

What we know and what we do not know about cystic fibrosis transmembrane conductance regulator.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-regulated chloride channel that resides in the apical membrane of many epithelial cells. Channel opening requires phosophorylation of serine residues in an intracellular regulatory domain by protein kinase A and as the binding and hydrolysis of ATP by intracellular nucleotide binding domains. Besides conducting the chloride ion, CFTR also regulates the function of other membrane proteins, directly or indirectly, notably the outwardly rectifying chloride channel and the epithelial sodium channel. The disease cystic fibrosis is caused by mutations in CFTR, which can result in defective protein production, defective processing and degradation in the endoplasmic reticulum, or defective channel pore properties or gating properties.

Amino Acid Sequence↗
PubMed1998

Ligand substitution of receptor targeted DNA complexes affects gene transfer into hepatoma cells.

We have targeted the serpin enzyme complex receptor for gene transfer in human hepatoma cell lines using peptides < 30 amino acids in length which contain the five amino acid recognition sequence for this receptor, coupled to poly K of average chain length 100 K, using the heterobifunctional coupling reagent sulfo-LC SPDP. The number of sulfo-LC SPDP modified poly-L-lysine residues, as well as the degree of peptide substitution was assessed by nuclear magnetic resonance spectroscopy. Conjugates were prepared in which 3.5%, 7.8% or 26% of the lysine residues contained the sulfo-LC SPDP moiety. Each of these conjugates was then coupled with ligand peptides so that one in 370, one in 1039, or one in 5882 lysines were substituted with receptor ligand. Electron microscopy and atomic force microscopy were used to assess complex structure and size. HuH7 human hepatoma cells were transfected with complexes of these conjugates with the plasmid pGL3 and luciferase expression measured 2 to 16 days after treatment. All the protein conjugates in which 26% of the K residues were modified with sulfo-LC SPDP were poor gene transfer reagents. Complexes containing less substituted poly K, averaged 17 +/- 0.5 nm in diameter and gave peak transgene expression of 3-4 x 10(6) ILU/mg which persisted (> 7 x 10(5) ILU) at 16 days. Of these, more substituted polymers condensed DNA into complexes averaging 20 +/- 0.7 nm in diameter and gave five-fold less luciferase than complexes containing less substituted conjugates. As few as eight to 11 ligands per complex are optimal for DNA delivery via the SEC receptor. The extent of substitution of receptor-mediated gene transfer complexes affects the size of the complexes, as well as the intensity and duration of transgene expression. These observations may permit tailoring of complex construction for the usage required.

Animals↗
PubMed1997

Excessive inflammatory response of cystic fibrosis mice to bronchopulmonary infection with Pseudomonas aeruginosa.

In cystic fibrosis (CF), defective function of the cystic fibrosis transmembrane conductance regulator (CFTR) in airway epithelial cells and submucosal glands results in chronic pulmonary infection with Pseudomonas aeruginosa. The pulmonary infection incites an intense host inflammatory response, causing progressive suppurative pulmonary disease. Mouse models of CF, however, fail to develop pulmonary disease spontaneously. We examined the effects of bronchopulmonary infection on mice homozygous for the S489X mutation of the CFTR gene using an animal model of chronic Pseudomonas endobronchial infection. Slurries of sterile agarose beads or beads containing a clinical isolate of mucoid P. aeruginosa were instilled in the right lung of normal or CF mice. The mortality of CF mice inoculated with Pseudomonas-laden beads was significantly higher than that of normal animals: 82% of infected CF mice, but only 23% of normal mice, died within 10 d of infection (P = 0.023). The concentration of inflammatory mediators, including TNF-alpha, murine macrophage inflammatory protein-2, and KC/N51, in bronchoalveolar lavage fluid in CF mice 3 d after infection and before any mortality, was markedly elevated compared with normal mice. This inflammatory response also correlated with weight loss observed in both CF and normal littermates after inoculation. Thus, this model may permit examination of the relationship of bacterial infections, inflammation, and the cellular and genetic defects in CF.

Animals↗
PubMed1997

Function of the R domain in the cystic fibrosis transmembrane conductance regulator chloride channel.

For a cystic fibrosis transmembrane conductance regulator (CFTR) channel to enter its open state, serine residues in the R domain must be phosphorylated by cAMP-dependent protein kinase, and intracellular ATP must bind to the nucleotide-binding folds and subsequently be hydrolyzed. CFTR with its R domain partially removed, DeltaR(708-835)-CFTR, forms a chloride channel that opens independently of protein kinase A phosphorylation, with open probability approximately one-third that of the wild type CFTR channel. Deletion of this portion of the R domain from CFTR alters the response of the channel to 5'-adenylylimidodiphosphate, pyrophosphate, and vanadate, compounds that prolong burst duration of the wild type CFTR channel but fail to do so in the DeltaR-CFTR. In addition, the addition of exogenous unphosphorylated R domain protein, which blocks the wild type CFTR channel, has no effect on the DeltaR-CFTR channel. However, when the exogenous R domain is phosphorylated, significant stimulation of the DeltaR-CFTR channel results; Po increases from 0.10 to 0.22. These data are consistent with a model for CFTR function in which the R domain in the unphosphorylated state interacts with the first nucleotide binding fold to inhibit either binding or hydrolysis of ATP or transduction of the effect to open the pore, but when the R domain is phosphorylated, it undergoes conformational change and interacts at a separate site in the first nucleotide binding fold to stimulate either binding or hydrolysis of ATP or transduction of the effect to open the pore.

Adenosine Triphosphate↗