Search PubMed⌕ Search

Biomedical subjects

N Green

Publications and source records attributed to N Green.

At least 19 recordsLinked to original sources
PubMed2006

Chick embryo lethal orphan virus can be polymer-coated and retargeted to infect mammalian cells.

Non-human adenovirus vectors have attractive immunological properties for gene therapy but are frequently restricted by inefficient transduction of human target cells. Using chicken embryo lethal orphan (CELO) virus, we employed a nongenetic mechanism of polymer coating and retargeting with basic fibroblast growth factor (bFGF-pc-CELOluc), a strategy that permits efficient tropism modification of human adenovirus. bFGF-pc-CELOluc showed efficient uptake and transgene expression in chick embryo fibroblasts (CEF), and increased levels of binding and internalization in a variety of human cell lines. Transgene expression was also greater than unmodified CELOluc in PC-3 human prostate cells, although the specific activity (RLU per internalized viral genome) was decreased. In CEF, the specific activity of bFGF-pc-CELOluc was considerably higher than in the human prostate cell line PC-3. Retargeted virus was fully resistant to inhibition by human serum with known adenovirus-neutralizing activity in vitro, while in mice CELOluc was cleared less rapidly from the blood than Adluc following i.v. administration in the presence of adenovirus neutralizing serum. Polymer coating and retargeting with bFGF further reduced rates of clearance for both viruses, suggesting protection against both neutralizing and opsonizing factors. The data indicate that CELO virus may be retargeted to infect human cells via alternative, potentially disease-specific, receptors and resist the effects of pre-existing humoral immunity.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2006

Protein contamination of the Laryngeal Mask Airway and its relationship to re-use.

The Laryngeal Mask Airway is a reusable device for maintaining the patency of a patient's airway during general anaesthesia. The device can be reused after it has been cleaned and sterilized. Protein contamination of medical instruments is a concern and has been found to occur despite standard sterilization techniques. The reason for the concern relates to the possibility of the transmission of prions and the risk of developing a neurodegenerative disorder such as Creutzveldt-Jacob disease. The purpose of this study was to quantify the amount of protein contamination that occurs, and to relate this to the number of times the Laryngeal Mask Airway has been used. Fifty previously used Classic Laryngeal Masks were collected after routine sterilization and packaging. The devices were immersed in protein detecting stain and then visual inspection performed to assess the degree and distribution of the staining. The researcher was blinded to the number of times the Laryngeal Mask Airway had been used. Linear regression analysis of the degrees of staining of the airway revealed that protein contamination occurs after the first use of the device and this increases with each subsequent use. This finding highlights the concern that the currently used cleaning and sterilization methods do not prevent the accumulation of proteinaceous material on Laryngeal Mask Airways. Consideration should be given to the search for more efficient cleaning and sterilization techniques or the use of disposable devices.

Equipment Contamination↗
PubMed2005

Radionuclides in fruit systems: a review of experimental studies.

Existing information on processes and parameters analysed in experimental studies on fruits was reviewed at the inception of the activities of the IAEA BIOMASS Fruits Working Group. Additional information on experimental studies, collected during the activities of the Group and not included in the Review, is presented and discussed in this paper. Studies on deposition of (14)CO2, CO(35)S and (3)H2O in the gas phase to apple, raspberry, strawberry and blackcurrant have filled gaps in knowledge of uptake of gaseous pollutants in fruit plants, quantifying processes of deposition, translocation and carry-over between seasons. Measurements over a period of six years on vine plants contaminated via leaves and soil by dry deposition of 137Cs and 90Sr have improved knowledge of the processes of direct deposition to fruit, translocation and carry-over of radionuclides from year to year. Additional information is given on soil to fruit transfer of U, Th and Pb for apple and mandarin grown under intensive agricultural conditions.

Air Pollutants, Radioactive↗
PubMed2005

Modelling and experimental studies on the transfer of radionuclides to fruit.

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios.

Fruit↗
PubMed2003

Apneic seizures in infants: role of continuous EEG monitoring.

Respiratory compromise is not uncommon in epileptic seizures. However, pure apneic seizures are rare. In this study, we report 10 children who presented with pure apneic seizures. All the children were admitted because of apneic events. Seizures were also considered in the differential diagnosis. Six patients had nonspecific findings consisting of multifocal interictal epileptiform activity with no event correlation. Continuous 24-72 hours electroencephalogram (EEG) was performed in all patients to rule out apneic seizures. Ictal EEG showed high correlation with the apneic episodes, confirming the diagnosis of apneic seizures. Our study suggests that continuous EEG monitoring is essential in the diagnosis and treatment of apneic seizures.

Apnea↗
PubMed2001

Crystal structure of an aldehyde reductase Y50F mutant-NADP complex and its implications for substrate binding.

Pig aldehyde reductase containing the active site mutation tyrosine(50) to phenylalanine has been crystallized in the presence of the cofactor NADP(H) to a resolution of 2.2 A. This structure clearly shows loss of the tyrosine hydroxyl group and no other significant perturbations compared with previously determined structures. The mutant binds cofactor (both oxidized and reduced) more tightly than the wild-type enzyme but shows a complete lack of binding of the aldehyde reductase inhibitor barbitone, as determined by fluorescence titrations. Numerous attempts at preparing a ternary complex with a range of small aldehyde substrates were unsuccessful. This result, in addition to the inability of the mutant protein to bind the inhibitor, provides strong evidence for the proposal that the tyrosine hydroxyl group is essential for substrate binding in addition to catalysis.

Alcohol Oxidoreductases↗
PubMed2001

The effect of storage and processing on radionuclide content of fruit.

After harvesting, the activity content of fruits may still be affected by the manner in which they are treated. Long storage times will reduce the activity contents of short-lived radionuclides; preparation and/or processing may cause activity to be physically removed. This paper presents the results of a review of the available literature on these effects. Data are scarce for both storage and processing, the majority of information on the latter being for 137Cs and 90Sr. For cautious general assessments, it should be assumed that there is no delay and that no activity is lost on processing, especially if the fruits can be eaten raw. However, individual cases may require specific data if available. The use of storage of processing as specific counter-measures to reduce activity concentrations in fruits may not be acceptable to the consumer, especially where alternative, non-contaminated, foodstuffs are readily available.

Community Participation↗
PubMed2001

Foods found in the wild around nuclear sites: an evaluation of radiological impact.

Habit surveys were carried out around four licensed nuclear sites to identify people who collect foodstuffs from the wild (so-called 'free foods'). In total, around 800 collectors were readily identified, most of whom collected more than one free food. The data indicated that estimates of higher than average doses could reasonably be based on the three foodstuffs of most importance. Foods were selected for further study on the basis of either the number of collectors or the amount consumed. The radionuclides of interest were identified using published information on the discharges from each site. The resultant average and higher than average doses were estimated using the site-specific habit data. For all sites, doses from the consumption of free foods were low and of no radiological importance. Assessments based solely on data for cultivated foods would not therefore have underestimated radiological impact significantly. However, given the wide utilisation of free foods found in this study, for rigorous assessments it would be prudent to take account of the consumption of foods from the wild.

England↗
PubMed2001

Molecular basis for immunoglobulin M specificity to epitopes in Cryptococcus neoformans polysaccharide that elicit protective and nonprotective antibodies.

The protective efficacy of antibodies (Abs) to Cryptococcus neoformans glucuronoxylomannan (GXM) is dependent on Ab fine specificity. Two clonally related immunoglobulin M monoclonal Abs (MAbs) (12A1 and 13F1) differ in fine specificity and protective efficacy, presumably due to variable (V)-region sequence differences resulting from somatic mutations. MAb 12A1 is protective and produces annular immunofluorescence (IF) on serotype D C. neoformans, while MAb 13F1 is not protective and produces punctate IF. To determine the Ab molecular determinants responsible for the IF pattern, site-directed mutagenesis of the MAb 12A1 heavy-chain V region (V(H)) was followed by serological and functional studies of the various mutants. Changing two selected amino acids in the 12A1 V(H) binding cavity to the corresponding residues in the 13F1 V(H) altered the IF pattern from annular to punctate, reduced opsonic efficacy, and abolished recognition by an anti-idiotypic Ab. Analysis of the binding of the various mutants to peptide mimetics revealed that different amino acids were responsible for GXM binding and peptide specificity. The results suggest that V-region motifs associated with annular binding and opsonic activity may be predictive of Ab efficacy against C. neoformans. This has important implications for immunotherapy and vaccine design that are reinforced by the finding that GXM and peptide reactivities are determined by different amino acid residues.

Amino Acid Sequence↗
PubMed2001

Access to genitourinary medicine clinics in the United Kingdom.

OBJECTIVES: To assess the variability in time taken for a patient to be seen in a genitourinary (GUM) clinic in the United Kingdom having contacted that clinic by telephone and compare this with GUM physicians' expectations. METHODS: A postal questionnaire was sent to lead GUM physicians asking when they thought patients with two specific clinical scenarios would be seen in their clinics. Following this, healthcare personnel contacted individual units posing as patients with the same clinical scenarios and asked to be seen as soon as possible. RESULTS: 202/258 (78%) lead clinicians responded to the postal questionnaire. All clinics claimed to have procedures allowing patients with acute symptoms to be assessed urgently and estimated that such patients would be seen within 48 hours of the initial telephone contact. In 243 of 311 (78%) clinic contacts, the patient was invited to attend the clinic within 48 hours. For the remaining 68 contacts (22%) the patient could not be accommodated within 48 hours and, of these, 49 could not be seen for more than 1 week. CONCLUSIONS: No clinician estimated that patients with acute severe symptoms would be seen more than 48 hours after the initial telephone contact, but in reality, for 22% of the patient contacts this was the case. This study may well underestimate the difficulties the general public may have in accessing GUM services. We hypothesise that this situation could be ameliorated by establishing process standards and addressing issues of resource allocation.

Acute Disease↗
PubMed2000

Signal peptidase and oligosaccharyltransferase interact in a sequential and dependent manner within the endoplasmic reticulum.

We demonstrate that the signal peptides of prepro-alpha-factor and preinvertase must be cleaved before Asn-X-Ser/Thr acceptor tripeptides located near the signal peptides of these precursors can be efficiently glycosylated within the endoplasmic reticulum of the yeast Saccharomyces cerevisiae. The data support a model whereby the interaction of a signal peptide with the membrane prevents an acceptor tripeptide juxtaposed to the signal peptide from accessing the oligosaccharyltransferase active site until the signal peptide is cleaved.

Amino Acid Sequence↗
PubMed2000

Conformational changes in the PBX homeodomain and C-terminal extension upon binding DNA and HOX-derived YPWM peptides.

PBX is a member of the three amino acid loop extension (TALE) class of homeodomains. PBX binds DNA cooperatively with HOX homeodomain proteins that contain a conserved YPWM motif. The amino acids immediately C-terminal to the PBX homeodomain increase the affinity of the homeodomain for its DNA site and HOX proteins. We have determined the structure of the free PBX homeodomain using NMR spectroscopy. Both the PBX homeodomain and the extended PBX homeodomain make identical contacts with a 5'-TGAT-3' DNA site and a YPWM peptide. A fourth alpha-helix, which forms upon binding to DNA, stabilizes the extended PBX structure. Variations in DNA sequence selectivity of heterodimeric PBX-HOX complexes depend on the HOX partner; however, a comparison of five different HOX-derived YPWM peptides showed that each bound to PBX in the same way, differing only in the strength of the association.

Amino Acid Motifs↗
PubMed1999

Signal peptides having standard and nonstandard cleavage sites can be processed by Imp1p of the mitochondrial inner membrane protease.

We have performed a site-directed mutagenesis study showing that residues comprising the type I signal peptidase signature in the two catalytic subunits of the yeast inner membrane protease, Imp1p and Imp2p, are functionally important, consistent with the idea that these subunits contain a serine/lysine catalytic dyad. Previous studies have shown that Imp1p cleaves signal peptides having asparagine at the -1 position, which deviates from the typical signal peptide possessing a small uncharged amino acid at this position. To determine whether asparagine is responsible for the nonoverlapping substrate specificities exhibited by the inner membrane protease subunits, we have substituted asparagine with 19 amino acids in the Imp1p substrate i-cytochrome (cyt) b(2). The resulting signal peptides containing alanine, serine, cysteine, leucine, and methionine can be cleaved efficiently by Imp1p. The remaining mutant signal peptides are cleaved inefficiently or not at all. Surprisingly, none of the amino acid changes results in the recognition of i-cyt b(2) by Imp2p, whose natural substrate, i-cyt c(1), has alanine at the -1 position. The data demonstrate that (i) although the -1 residue is important in substrates recognized by Imp1p, signal peptides having standard and nonstandard cleavage sites can be processed by Imp1p, and (ii) a -1 asparagine does not govern the substrate specificity of the inner membrane protease subunits.

Amino Acid Sequence↗
PubMed1999

The catalytic mechanism of endoplasmic reticulum signal peptidase appears to be distinct from most eubacterial signal peptidases.

Many type I signal peptidases from eubacterial cells appear to contain a serine/lysine catalytic dyad. In contrast, our data show that the signal peptidase complex from the endoplasmic reticulum lacks an apparent catalytic lysine. Instead, a serine, histidine, and two aspartic acids are important for signal peptidase activity by the Sec11p subunit of the yeast signal peptidase complex. Amino acids critical to the eubacterial signal peptidases and Sec11p are, however, positioned similarly along their primary sequences, suggesting the presence of a common structural element(s) near the catalytic sites of these enzymes.

Amino Acid Sequence↗
PubMed1999

Waterbirths: regional audit of infection control practices.

Waterbirths are increasingly being offered as an option, although concerns about associated infection risks have been expressed. We undertook an audit of current practice in our region to help formulate an infection control policy. Questionnaires were sent to the Infection Control Nurses at 16 centres, with a request for completion in conjunction with the Infection Control Doctor. Fourteen (88%) centres responded, 11 of which carried out waterbirthing. Eight had permanent on-site pools, of which five were permanently plumbed in and provided with separate water inlets and outlets. All eight centres had infection control policies for waterbirthing. Six policies included care of the pool using detergent and disinfectant (chlorine-releasing compounds) and two using detergent alone. In none of the centres were the mothers tested for blood-borne viruses. Six centres collected data on infection in mother or child, and two carried out regular microbiological testing of pools. Infection control policies for waterbirths should include instructions for pool maintenance and decontamination, for prevention of legionella, for universal precautions and for use of personal protective equipment. Post-natal surveillance of mothers and babies is required in order to ascertain infection rates.

Baths↗
PubMed1999

Mutational analysis of MAdCAM-1/alpha4beta7 interactions reveals significant binding determinants in both the first and second immunuglobulin domains.

The selective emigration of blood born leukocytes into tissues is mediated, in part by interactions of Ig-like cell adhesion molecules (IgCAMs) expressed on vascular endothelium and their cognate ligands, the leukocyte integrins. Within mucosal lymphoid tissues and gastrointestinal sites the mucosal vascular addressin. MAdCAM-1 is the predominant IgCAM, mediating specific lymphocyte homing via interactions with its ligand on lymphocytes, the integrin alpha4beta7. Previous studies have shown that an essential binding motif resides in the first Ig domain of all IgCAMs, containing an acidic residue (D or E) preceded by an aliphatic residue (L or I) that resides in strand C or the CD loop. However, domain swap experiments with MAdCAM-1 and VCAM-1 have shown a requirement for both Ig domains 1 and 2 for efficient integrin binding. We describe the use of chimeric MAdCAM-1/VCAM-1 receptors and point mutations in MAdCAM-1 to define other sites that are required for binding to the integrin alpha4beta7. We find that, in addition to critical CD loop residues, other regions in both domain one and two contribute to MAdCAM-1/alpha4beta7 interactions, including a buried arginine residue in the F strand of domain one and several acidic residues in a highly extended DE ribbon in domain 2. These mutations, when placed in the recently solved crystal structure of human MAdCAM-1 give insight into the integrin binding preference of this unique receptor.

Amino Acid Sequence↗