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R Webster

Publications and source records attributed to R Webster.

At least 19 recordsLinked to original sources
PubMed2006

The use of soil survey data to determine the magnitude and extent of historic metal deposition related to atmospheric smelter emissions across Humberside, UK.

When a smelter has ceased operation, and in the absence of historical emission data, high-resolution geochemical surveys of the soil can reveal historical loads to the surrounding land. We use measurements of lead and tin in the soil at two depths to estimate the total quantities of these metals deposited on 286 km(2) of land around the former Capper Pass smelter (north-east England). We subtracted median background concentrations for three parent material types outside the region of deposition from the data within it. We then constructed a statistical model of metal deposition based on the adjusted data. The data were from irregularly spaced sites and were strongly skewed with a spatial trend. We mapped the concentrations of the metals by lognormal universal kriging with the parameters for the trend and residuals modelled simultaneously by residual maximum likelihood (REML). The maps suggest that metal was deposited up to 24 km to the north-east of the smelter by the prevailing wind. We estimated total excess metal in the soil over the area of deposition to be 2500 t of lead and 830 t of tin.

Air Pollutants↗
PubMed2006

Pharmacokinetics and metabolism of UK-383,367 in rats and dogs: a rationale for long-lived plasma radioactivity.

UK-383,367 (5-{(1R)-4-cyclohexyl-1-[2-(hydroxyamino)-2-oxoethyl]butyl}-1,2,4-oxadiazole-3-carboxamide) is a novel procollagen C-proteinase inhibitor evaluated for the treatment of post-surgical dermal scarring. It is extensively metabolized in rat and dog absorption, distribution, metabolism and excretion studies, and a metabolic pathway for UK-383,367 was determined. A long-lived metabolite was identified in dog plasma. Data indicate that this metabolite results from the oxadiazole ring-cleavage-producing oxamic acid, oxamide and oxalic acid. Ion exclusion chromatography was used to identify these polar metabolites, which were unretained on a standard reversed-phase high-performance liquid chromatography system. The oxamide metabolite was identified as the long-lived radioactivity, which was observed in dog plasma.

Administration, Oral↗
PubMed2006

Pharmacokinetics and clearance processes of UK-279,276 (rNIF) in rat and dog: comparison with human data.

UK-279,276, or recombinant neutrophil inhibitory factor (rNIF), is a glycoprotein that binds to the human CD11b receptor (IC(50) = <0.5 nM) and inhibits neutrophil binding to vascular endothelial cells. In dogs, the pharmacokinetics of UK-279,276 are non-linear with clearance slowing as dose increases (apparent clearance 0.06 ml min(-1) kg(-1) at 0.l mg kg(-1) decreasing to 0.02 ml min(-1) kg(-1) at 2 mg kg(-1)). The observations are in keeping with human pharmacokinetic data. In rats, clearance is linear (0.07-0.13 ml min(-1) kg(-1)) across a similar dose range (0.006-2.25 mg kg(-1)) compared with dogs and humans. These data indicate that two clearance processes act on UK-279,276 in dogs and humans, but only one clearance process occurs in rats. A non-saturable, low-affinity/high-capacity clearance process is present in all animal species studied as well as in human, and it is believed to be hepatic uptake mediated by the asialoglycoprotein receptor. A second, saturable, clearance process is present in dogs and humans that is not apparent in the rat. This high-affinity/low-capacity process is thought to be mediated by interaction with the CD11b receptor, which is the pharmacological target for this molecule. This hypothesis is supported by the marked species differences seen for the affinity of CD11b for UK-279,276, with dogs and humans having high-affinity (IC(50) = <0.5 nM), whilst the rat affinity is low (IC(50) = 134 nM).

Animals↗
PubMed2004

Mutation in the AChR ion channel gate underlies a fast channel congenital myasthenic syndrome.

BACKGROUND: Most congenital myasthenic syndromes (CMS) have postsynaptic defects from mutations within the muscle acetylcholine receptor (AChR). Mutations underlying the slow channel syndrome cause a "gain of function" and usually show dominant inheritance, whereas mutations underlying AChR deficiency or the fast channel syndrome cause a "loss of function" and show recessive inheritance. OBJECTIVE: To characterize the disease mechanism underlying an apparently dominantly inherited CMS that responds to IV edrophonium. METHODS: DNA from CMS patients was analyzed for mutations by single-strand conformation polymorphism analysis, DNA sequence analysis, and restriction endonuclease digestion. Functional analysis of mutations was by alpha-bungarotoxin binding studies and by patch clamp analysis of mutant AChR expressed in human embryonic kidney cells. RESULTS: Analysis of muscle biopsies from father and son in an affected kinship showed normal endplate morphology and AChR number but severely reduced miniature endplate potentials. DNA analysis revealed that each harbors a single missense mutation in the AChR alpha-subunit gene, alphaF256L. Expression studies demonstrate this mutation underlies a fast channel phenotype with fewer and shorter ion channel activations. The major effect of alphaF256L, located within the M2 transmembrane domain, is on channel gating, both reducing the opening and increasing the closure rate. CONCLUSIONS: Mutation alphaF256L results in fast channel kinetics. Expression studies suggest a dominant-negative effect within the AChR pentamer, severely compromising receptor function.

Adolescent↗
PubMed2004

Multiple lineages of antigenically and genetically diverse influenza A virus co-circulate in the United States swine population.

Before the isolation of H3N2 viruses in 1998, swine influenza in the United States was an endemic disease caused exclusively by classical-swine H1N1 viruses. In this study we determined the antigenic and phylogenetic composition of a selection of currently circulating strains and revealed that, in contrast to the situation pre-1998, the swine population in the United States is now a dynamic viral reservoir containing multiple viral lineages. H3N2 viruses still circulate and representatives of each of two previously identified phylogenetic groups were isolated. H1N1 and H1N2 viruses were also identified. In addition to the genotypic diversity present, there was also considerable antigenic diversity seen. At least three antigenic profiles of H1 viruses were noted and all of the recent H3N2 viruses reacted poorly, if at all, to the index A/swine/Texas/4199-2/98 H3N2 antiserum in hemagglutination inhibition assays. The influenza reservoir in the United States swine population has thus gone from a stable single viral lineage to one where genetically and antigenically heterogenic viruses co-circulate. The growing complexity of influenza at this animal-human interface and the presence of viruses with a seemingly high affinity for reassortment makes the United States swine population an increasingly important reservoir of viruses with human pandemic potential.

Animals↗
PubMed2003

Pharmacokinetics and disposition of a novel NMDA glycine site antagonist (UK-240,455) in rats, dogs and man.

1. UK-240,455 ((+) 6,7-dichloro-5-[N-(2-hydroxyethyl)methanesulphonamido]-2,3 (1H,4H)-quinoxalinedione) is a potent, selective N-methyl D-aspartate (NMDA) glycine site antagonist that is being evaluated for the potential treatment of stroke. 2. UK-240,455 is predominately excreted unchanged in urine (58-68%) in rats, dogs and man following intravenous administration. The remainder of the dose is excreted unchanged in the faeces. It is considered that UK-240,455 is predominantly cleared by active renal tubular secretion and active hepatobiliary transport. In man, there is evidence that UK-240,455 undergoes glucuronidation. However, there is no evidence for this in rats and dogs. 3. UK-240,455 has a short elimination half-life in rats, dogs and man (0.4-1.4 h) and clearances of 12, 13 and 6 ml min(-1) kg(-1), respectively. The compound shows limited tissue distribution with volumes of distribution of 0.4-0.8 l kg(-1) in rats, dogs and man. The species' variation in pharmacokinetic parameters was related allometrically when plasma protein binding was taken in to account. Hence, active hepatic or renal clearance processes for this compound were conserved across species. 4. Cerebrospinal fluid and brain concentrations of UK-240,455 were determined in rats. The cerebrospinal fluid/plasma concentration ratio of UK-240,455 was 4.3%, which was similar to the plasma-free fraction of this compound (3%), indicating good blood-brain barrier permeability. Brain tissue concentrations were low (0.7% of the total plasma concentrations).

Adolescent↗
PubMed2003

Evaluation of the role of the asialoglycoprotein receptor in the clearance of UK-279,276 (recombinant neutrophil inhibitory factor).

1. UK-279,276 or recombinant neutrophil inhibitory factor (rNIF) is a glycoprotein that has been investigated as an intravenous treatment for stroke. Previous data indicate that the asialoglycoprotein receptor (ASGPR) in the liver might have a role in the uptake and clearance of UK-279,276 from plasma in rats and dogs. 2. Biliary elimination of sialo UK-279,276 can be inhibited by the co-administration of asialo fetuin, a known substrate for ASGPR. These data are in keeping with sialo UK-279,276 being cleared by ASGPR. 3. In vitro experiments have demonstrated that asialo UK-279,276 (Sialo UK-279,276 treated to remove the sialic acid residues present on the glycans) shows a significantly greater uptake in rat, dog and human precision-cut liver slices than the sialylated protein. The addition of asialo fetuin to precision-cut liver slice incubations (rat, dog and man) containing asialo UK-279,276 reduced the uptake to levels similar to those seen for the sialylated protein. These data support the potential role of the ASGPR in the clearance of UK-279,276 in rat, dog and man.

Animals↗
PubMed2002

Molecular changes associated with the transmission of avian influenza a H5N1 and H9N2 viruses to humans.

In order to identify molecular changes associated with the transmission of avian influenza A H5N1 and H9N2 viruses to humans, the internal genes from these viruses were compared to sequences from other avian and human influenza A isolates. Phylogenetically, each of the internal genes of all sixteen of the human H5N1 and both of the H9N2 isolates were closely related to one another and fell into a distinct clade separate from clades formed by the same genes of other avian and human viruses. All six internal genes were most closely related to those of avian isolates circulating in Asia, indicating that reassortment with human strains had not occurred for any of these 18 isolates. Amino acids previously identified as host-specific residues were predominantly avian in the human isolates although most of the proteins also contained residues observed previously only in sequences of human influenza viruses. For the majority of the nonglycoprotein genes, three distinct subgroups could be distinguished on bootstrap analyses of the nucleotide sequences, suggesting multiple introductions of avian virus strains capable of infecting humans. The shared nonglycoprotein gene constellations of the human H5N1 and H9N2 isolates and their detection in avian isolates only since 1997 when the first human infections were detected suggest that this particular gene combination may confer the ability to infect humans and cause disease. J. Med. Virol. 66:107-114, 2002. Published 2002 Wiley-Liss, Inc.

Animals↗
PubMed2002

Differences between influenza virus receptors on target cells of duck and chicken.

H5, H7, and H9 subtype influenza viruses in land-based poultry often differ from viruses of wild aquatic birds by deletions in the stalk of the neuraminidase, by the presence of additional carbohydrates on the hemagglutinin, and by occasional changes in the receptor specificity. To test whether these differences could reflect distinctions between the virus receptors in different avian species, we compared the binding of duck, chicken and human influenza viruses to cell membranes and gangliosides from epithelial tissues of duck, chicken and African green monkey. Human viruses bound to cell membranes of monkey and chicken but not to those of duck, suggesting that chicken cells unlike duck cells contain Sia(alpha2-6)Gal-terminated receptors recognized by human viruses. Duck virus bound to gangliosides with short sugar chains that were abundant in duck intestine. Human and chicken viruses did not bind to these gangliosides and bound more strongly than duck virus to gangliosides with long sugar chains that were found in chicken intestinal and monkey lung tissues. Our data suggest that the spectrum of sialylglycoconjugates which can serve as influenza virus receptors in chicken is more similar to the spectrum of receptors in the respiratory epithelia of monkey than to that in the epithelial tissues of duck. This notion could explain the recent emergence of avian H9N2 virus lineage with human virus-like receptor specificity and emphasizes the role of the chicken as a potential intermediate host for the transmission of viruses from aquatic birds to humans.

Animals↗
PubMed2002

Calcium channel subtypes contributing to acetylcholine release from normal, 4-aminopyridine-treated and myasthenic syndrome auto-antibodies-affected neuromuscular junctions.

1 Acetylcholine release at the neuromuscular junction relies on rapid, local and transient calcium increase at presynaptic active zones, triggered by the ion influx through voltage-dependent calcium channels (VDCCs) clustered on the presynaptic membrane. Pharmacological investigation of the role of different VDCC subtypes (L-, N-, P/Q- and R-type) in spontaneous and evoked acetylcholine (ACh) release was carried out in adult mouse neuromuscular junctions (NMJs) under normal and pathological conditions. 2 omega-Agatoxin IVA (500 nM), a specific P/Q-type VDCC blocker, abolished end plate potentials (EPPs) in normal NMJs. However, when neurotransmitter release was potentiated by the presence of the K(+) channel blocker 4-aminopyridine (4-AP), an omega-agatoxin IVA- and omega-conotoxin MVIIC-resistant component was detected. This resistant component was only partially sensitive to 1 micro M omega-conotoxin GVIA (N-type VDCC blocker), but insensitive to any other known VDCC blockers. Spontaneous release was dependent only on P/Q-type VDCC in normal NMJs. However, in the presence of 4-AP, it relied on L-type VDCCs too. 3 ACh release from normal NMJs was compared with that of NMJs of mice passively injected with IgGs obtained from patients with Lambert-Eaton myasthenic syndrome (LEMS), a disorder characterized by a compromised neurotransmitter release. Differently from normal NMJs, in LEMS IgGs-treated NMJs an omega-agatoxin IVA-resistant EPP component was detected, which was only partially blocked by calciseptine (1 micro M), a specific L-type VDCC blocker. 4 Altogether, these data demonstrate that multiple VDCC subtypes are present at the mouse NMJ and that a resistant component can be identified under 'pharmacological' and/or 'pathological' conditions.

4-Aminopyridine↗
PubMed2001

Regional brain and ventricular volumes in Tourette syndrome.

BACKGROUND: The pathophysiology of Tourette syndrome (TS) is thought to involve disturbances in cortico-striato-thalamo-cortical circuitry. The morphological characteristics of the cortical and associated white matter portions of these circuits have not been previously examined in TS subjects. METHODS: High-resolution anatomical magnetic resonance images were acquired in 155 TS and 131 healthy children and adults. The cerebrums and ventricles were isolated and then parcellated into subregions using standard anatomical landmarks. RESULTS: For analyses that included both children and adults, TS subjects were found to have larger volumes in dorsal prefrontal regions, larger volumes in parieto-occipital regions, and smaller inferior occipital volumes. Significant inverse associations of cerebral volumes with age were seen in TS subjects that were not seen in healthy controls. Sex differences in the parieto-occipital regions of healthy subjects were diminished in the TS group. The age-related findings were most prominent in TS children, whereas the diminished sex differences were most prominent in TS adults. Group differences in regional ventricular volumes were less prominent than in the cerebrum. Regional cerebral volumes were significantly associated with the severity of tic symptoms in orbitofrontal, midtemporal, and parieto-occipital regions. CONCLUSIONS: Broadly distributed cortical systems are involved in the pathophysiology of TS. Developmental processes, sexual dimorphisms, and compensatory responses in these cortical regions may help to modulate the course and severity of tic symptoms.

Adolescent↗
PubMed2001

Acetylcholine receptor delta subunit mutations underlie a fast-channel myasthenic syndrome and arthrogryposis multiplex congenita.

Limitation of movement during fetal development may lead to multiple joint contractures in the neonate, termed arthrogryposis multiplex congenita. Neuromuscular disorders are among the many different causes of reduced fetal movement. Many congenital myasthenic syndromes (CMSs) are due to mutations of the adult-specific epsilon subunit of the acetylcholine receptor (AChR), and, thus, functional deficits do not arise until late in gestation. However, an earlier effect on the fetus might be predicted with some defects of other AChR subunits. We studied a child who presented at birth with joint contractures and was subsequently found to have a CMS. Mutational screening revealed heteroallelic mutation within the AChR delta subunit gene, delta 756ins2 and delta E59K. Expression studies demonstrate that delta 756ins2 is a null mutation. By contrast, both fetal and adult AChR containing delta E59K have shorter than normal channel activations that predict fast decay of endplate currents. Thus, delta E59K causes dysfunction of fetal as well as the adult AChR and would explain the presence of joint contractures on the basis of reduced fetal movement. This is the first report of the association of AChR gene mutations with arthrogryposis multiplex congenita. It is probable that mutations that severely disrupt function of fetal AChR will underlie additional cases.

Action Potentials↗
PubMed2000

Considerations in developing successful, population-based molecular screening and prevention of lung cancer.

The current mortality rate for lung cancer exceeds 85%, as it has for the last 3 decades. This statistic reflects the utility of the major diagnostic tool that has been used during this period to diagnose lung cancer: the chest X-ray. The overwhelming majority of new cases of lung cancer that are detected with chest X-rays involve individuals who already have regional or distant metastatic disease. Because the systemic treatment of this disease has not improved greatly, patients with metastatic disease rarely are cured. This article reviews the issues involved with the development of sputum-based cellular diagnostics for early stage lung cancer. The biomarker, heterogeneous nuclear ribonucleoprotein A2/B1, is the lead marker for this approach. It has been used in several studies in independent cohorts that have suggested that its overexpression in bronchial epithelial cells is associated highly with the development of lung cancer. This marker is detectable 1 year or more prior to the detection of lung cancer by chest X-ray. Finding this early airway-confined phase of lung cancer may allow for the evolution of new management approaches for very early stage lung cancer. Research activities, such aerosolized chemoprevention, are discussed.

Biomarkers, Tumor↗
PubMed2000

p38 Kinase-dependent MAPKAPK-2 activation functions as 3-phosphoinositide-dependent kinase-2 for Akt in human neutrophils.

Akt activation requires phosphorylation of Thr(308) and Ser(473) by 3-phosphoinositide-dependent kinase-1 and 2 (PDK1 and PDK2), respectively. While PDK1 has been cloned and sequenced, PDK2 has yet to be identified. The present study shows that phosphatidylinositol 3-kinase-dependent p38 kinase activation regulates Akt phosphorylation and activity in human neutrophils. Inhibition of p38 kinase activity with SB203580 inhibited Akt Ser(473) phosphorylation following neutrophil stimulation with formyl-methionyl-leucyl-phenylalanine, FcgammaR cross-linking, or phosphatidylinositol 3,4,5-trisphosphate. Concentration inhibition studies showed that Ser(473) phosphorylation was inhibited by 0.3 microm SB203580, while inhibition of Thr(308) phosphorylation required 10 microm SB203580. Transient transfection of HEK293 cells with adenoviruses containing constitutively active MKK3 or MKK6 resulted in activation of both p38 kinase and Akt. Immunoprecipitation and glutathione S-transferase (GST) pull-down studies showed that Akt was associated with p38 kinase, MK2, and Hsp27 in neutrophils, and Hsp27 dissociated from the complex upon activation. Active recombinant MK2 phosphorylated recombinant Akt and Akt in anti-Akt, anti-MK2, anti-p38, and anti-Hsp27 immunoprecipitates, and this was inhibited by an MK2 inhibitory peptide. We conclude that Akt exists in a signaling complex containing p38 kinase, MK2, and Hsp27 and that p38-dependent MK2 activation functions as PDK2 in human neutrophils.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed2000

Avian-to-human transmission of H9N2 subtype influenza A viruses: relationship between H9N2 and H5N1 human isolates.

In 1997, 18 cases of influenza in Hong Kong (bird flu) caused by a novel H5N1 (chicken) virus resulted in the deaths of six individuals and once again raised the specter of a potentially devastating influenza pandemic. Slaughter of the poultry in the live bird markets removed the source of infection and no further human cases of H5N1 infection have occurred. In March 1999, however, a new pandemic threat appeared when influenza A H9N2 viruses infected two children in Hong Kong. These two virus isolates are similar to an H9N2 virus isolated from a quail in Hong Kong in late 1997. Although differing in their surface hemagglutinin and neuraminidase components, a notable feature of these H9N2 viruses is that the six genes encoding the internal components of the virus are similar to those of the 1997 H5N1 human and avian isolates. This common feature emphasizes the apparent propensity of avian viruses with this genetic complement to infect humans and highlights the potential for the emergence of a novel human pathogen.

Animals↗
PubMed2000

Radical retropubic prostatectomy: bladder neck preservation versus reconstruction.

PURPOSE: We compare bladder neck contracture, urinary continence and positive surgical margin rates after bladder neck preservation and excision with radical retropubic prostatectomy. MATERIALS AND METHODS: A retrospective analysis of clinical and pathological findings, and followup of 220 patients who underwent radical retropubic prostatectomy was performed. Patients were divided into 3 groups of bladder neck preservation (101), "tennis racket" reconstruction (63) and anterior bladder tube reconstruction (56). RESULTS: Mean followup was 19.7, 36.7 and 16.2 months, respectively, for bladder neck preservation, tennis racket reconstruction and anterior bladder tube reconstruction. Overall, bladder neck contracture occurred in 22 of 220 cases (10%), including 5 of 101 (5%) with bladder neck preservation, 7 of 63 (11%) with tennis racket reconstruction and 10 of 56 (18%) with anterior bladder tube reconstruction, which approached statistical significance (p = 0.061). Urinary continence was assessed by a third party telephone interview of 165 patients. Continence rates at 1 year were 93% for bladder neck preservation, 96% for tennis racket reconstruction and 97% for anterior bladder tube reconstruction, which was not statistically significant (p = 0.68). Positive margin rates were 27.4% with bladder neck preservation versus 30.5% with excision, which was not significantly different. CONCLUSIONS: There are no statistically significant differences in return of urinary continence, bladder neck contracture rates or positive margins between bladder neck preservation and excision.

Adult↗