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S C Barry

Publications and source records attributed to S C Barry.

At least 19 recordsLinked to original sources
PubMed2003

The analysis of ring-recovery data using random effects.

We show how random terms, describing both yearly variation and overdispersion, can easily be incorporated into models for mark-recovery data, through the use of Bayesian methods. For recovery data on lapwings, we show that the incorporation of the random terms greatly improves the goodness of fit. Omitting the random terms can lead to overestimation of the significance of weather on survival, and overoptimistic prediction intervals in simulations of future population behavior. Random effects models provide a natural way of modeling overdispersion-which is more satisfactory than the standard classical approach of scaling up all standard errors by a uniform inflation factor. We compare models by means of Bayesian p-values and the deviance information criterion (DIC).

Animals↗
PubMed2002

The role of supplemental oxygen during submaximal exercise in patients with cystic fibrosis.

Repeated bouts of submaximal exercise are an important part of most pulmonary rehabilitation programmes. Patients with moderate-to-severe cystic fibrosis (CF) often demonstrate oxygen desaturation during submaximal exercise, which may limit their ability to participate in these programmes. This study examines whether arterial desaturation contributes to submaximal exercise limitation by testing whether supplemental O2 improves submaximal exercise capacity. Eight patients with CF (mean forced expiratory volume in one second 41% predicted) each underwent two submaximal exercise tests on a bicycle ergometer at 80% of maximal workload. The two tests were identical except for the addition of supplemental O2 (inspiratory O2 fraction 39%) during one of the tests. Exercise duration was significantly longer in the supplemental O2 study versus control (673+/-63 s versus 835+/-99 s). Arterial O2 saturation was also higher in the supplemental O2 study than the control exercise test (96+/-0.3% versus 86+/-1.5%). There was no statistical difference at end exercise between O2 consumption, minute ventilation and heart rate. There was a significant relationship between improvement in exercise capacity and the amount of desaturation during the control exercise test. Results indicate that supplemental oxygen improves submaximal exercise capacity in patients with moderate-to-severe cystic fibrosis. Oxygen therapy may be an important intervention to improve participation and maximise the benefits of pulmonary exercise rehabilitation programmes.

Adult↗
PubMed2001

Lentivirus administration to rat muscle provides efficient sustained expression of erythropoietin.

A lentivirus pseudotyped with vesicular stomatitis virus G protein (VSV-G) encoding rat erythropoietin (EPO) complementary DNA was administered to rat skeletal muscle and red blood cell production was serially monitored. After a single intramuscular injection hematocrit values increased and reached a plateau at about 35 days and were sustained for at least 14 months. Virus doses of 6 x 10(7) infectious units and 6 x 10(6) infectious units produced significantly increased mean hematocrit values of 68.5% +/- 2.1% (P <.001, n = 4) and 52.7% +/- 1.3% (P <.001, n = 3), respectively, over values of control animals receiving normal saline (46.2% +/- 1.5%, n = 2). A polymerase chain reaction (PCR) assay for vector sequences in genomic DNA showed muscle tissue at the site of injection was positive and undetectable in liver, spleen, kidney, and lung. The intramuscular administration of lentivirus provided a dose-responsive, highly efficient and sustained EPO gene delivery, suggesting these vectors may be applied generally to the systemic delivery of proteins such as hormones and clotting factors. (Blood. 2001;98:594-596)

Animals↗
PubMed2001

Peptide insertions in domain 4 of hbeta(c), the shared signalling receptor subunit for GM-CSF, IL3 and IL5, induce ligand-independent activation.

A mutant form of the common beta-subunit of the GM-CSF, interleukin-3 (IL3) and IL5 receptors is activated by a 37 residue duplicated segment which includes the WSXWS motif and an adjacent, highly conserved, aliphatic/basic element. Haemopoietic expression of this mutant, hbeta(c)FIDelta, in mice leads to myeloproliferative disease. To examine the mechanism of activation of this mutant we targetted the two conserved motifs in each repeat for mutagenesis. Here we show that this mutant exhibits constitutive activity in BaF-B03 cells in the presence of mouse or human GM-CSF receptor alpha-subunit (GMRalpha) and this activity is disrupted by mutations of the conserved motifs in the first repeat. In the presence of these mutations the receptor reverts to an alternative conformation which retains responsiveness to human IL3 in a CTLL cell line co-expressing the human IL3 receptor alpha-subunit (hIL3Ralpha). Remarkably, the activated conformation is maintained in the presence of substitutions, deletions or replacement of the second repeat. This suggests that activation occurs due to insertion of extra sequence after the WSXWS motif and is not dependent on the length or specific sequence of the insertion. Thus hbeta(c) displays an ability to fold into functional receptor conformations given insertion of up to 37 residues in the membrane-proximal region. Constitutive activation most likely results from a specific conformational change which alters a dormant, inactive receptor complex, permitting functional association with GMRalpha and ligand-independent mitogenic signalling.

Amino Acid Sequence↗
PubMed2001

Lentivirus vectors encoding both central polypurine tract and posttranscriptional regulatory element provide enhanced transduction and transgene expression.

Incorporation of a central polypurine tract (cPPT) and a posttranscriptional regulatory element (PRE) into lentivirus vectors provides increased transduction efficiency and transgene expression. We compared the effects of these elements individually and together on transduction efficiency and gene expression, using lentivirus vectors pseudotyped with vesicular stomatitis virus G protein (VSV-G) and encoding enhanced green fluorescent protein (GFP) and rat erythropoietin (EPO). The transduction efficiency was greater than 2-fold higher in the vector containing the PRE element, 3-fold higher in vector encoding the cPPT element, and 5-fold increased in the GFP virus containing both cPPT and PRE elements relative to the parent virus. In comparison with parent vector the mean fluorescence intensity (MFI) of GFP expression was 7-fold higher in cells transduced with virus containing PRE, 6-fold increased in cells transduced with virus containing cPPT, and 42-fold increased in GFP-virus containing both cPPT and PRE elements. EPO-virus containing a PRE element showed a nearly 5-fold increase in EPO secretion over the parent vector, and the vector encoding both PRE and cPPT showed a 65-fold increase. Thus, lentivirus vectors incorporating both PRE and cPPT showed expression levels significantly increased over the sum of the components alone, suggesting a synergistic effect.

Animals↗
PubMed2001

Glucose-regulated insulin expression in diabetic rats.

Retroviral vectors encoding glucose-responsive promoters driving furin expression may provide an amplified, glucose-regulated secretion of insulin. We constructed LhI*TFSN virus to encode a glucose-regulatable transforming growth factor alpha promoter controlling furin expression with a viral LTR promoter driving constitutive expression of furin-cleavable human proinsulin. Autologous BB rat vascular smooth muscle cells transduced with LhI*TFSN virus and cultured in 1.7 and 16.7 mM glucose secreted 50.7 +/- 3.2 and 136.0 +/- 11.0 microU (mean +/- SD) of insulin per 10(6) cells per day, respectively. After the onset of diabetes spontaneously diabetic congenic DR lyp/lyp BB rats received stomach implants containing 2 x 10(6) LhI*TFSN-transduced primary rat vascular smooth muscle cells. In eight treated rats there was a major reduction in insulin requirement to as low as 25% of pretreatment level for up to 3 months and one rat became insulin free without hypoglycemia. Intraperitoneal glucose tolerance tests (IPGTTs) in diabetic rats receiving control implants did not show the characteristic decline in blood glucose of normal rats after glucose administration. In contrast, diabetic rats receiving LhI*TFSN-transduced cells showed significant clearances of blood glucose. These data suggest clinically significant levels of glucose-regulated insulin delivery from implanted vascular smooth muscle cells transduced with LhI*TFSN vector.

Animals↗
PubMed2000

Lentiviral and murine retroviral transduction of T cells for expression of human CD40 ligand.

Efficient transduction of primary human T cells is an important goal toward treating a number of genetic defects. Patient T cells could be harvested by leukapheresis, transduced, and returned to the donor. A wide range of secreted or cell surface therapeutic proteins may be delivered in this way. The ability to produce antibodies is the consequence of interactions between T cells and B cells and lack of expression of CD40 ligand (CD40L) on T cells causes X-linked hyper-IgM syndrome (XHIM). We are investigating delivery of a normal CD40 ligand to treat this disorder. We tested promoters driving the expression of either reporter genes such as enhanced green fluorescent protein (eGFP) or human CDC40L. Using murine retroviruses, the best able to drive gene expression in T cells was the cytomegalovirus (CMV) promoter enhancer element; however, transduction efficiency was low. To achieve efficient, high-level gene expression we tested lentiviral gene delivery vectors. At a low multiplicity of infection (MOI) (0.5-2) a large fraction of target cells was transduced by lentiviral vectors (40-93%), and the strength of gene expression was high, as determined by flow cytometric analysis. We monitored the expression of eGFP or human CD40L on T cell lines and untransformed primary human T cells from normal and CD40L-deficient patients. We achieved efficient gene expression without an extended exposure to virus, and without the need for selection. These results are encouraging for efficient lentivirus-mediated transduction of refractory human cells to achieve therapeutic gene delivery.

Animals↗
PubMed2000

On the Bayesian analysis of ring-recovery data.

Vounatsou and Smith (1995, Biometrics 51, 687-708) describe the modern Bayesian analysis of ring-recovery data. Here we discuss and extend their work. We draw different conclusions from two major data analyses. We emphasize the extreme sensitivity of certain parameter estimates to the choice of prior distribution and conclude that naive use of Bayesian methods in this area can be misleading. Additionally, we explain the discrepancy between the Bayesian and classical analyses when the likelihood surface has a flat ridge. In this case, when there is no unique maximum likelihood estimate, the Bayesian estimators are remarkably precise.

Animals↗
PubMed1999

Reproducibility of maximal exercise ergometer testing in patients with cystic fibrosis.

OBJECTIVES: Exercise testing in patients with cystic fibrosis (CF) has become an important tool in assessing disease severity and predicting overall outcome. The reproducibility of maximal exercise testing was examined in adult subjects with stable CF. METHODS: Nine subjects with CF underwent a total of three maximal exercise tests carried out under identical circumstances over a 28-day period. Oxygen uptake (VO2), minute ventilation (VE), respiratory frequency (f), heart rate (HR), and arterial oxygen saturation (SaO2) were measured at rest, at end exercise, and at 40% and 70% of maximum workload. RESULTS: There were no significant differences in these measurements among the three tests. Reproducibility of exercise performance was assessed using the coefficient of variation. The mean within-subject coefficient of variation for test variables at end exercise are as follows: VO2, 6.9%; VE, 6.2%; f, 5.8%; IIR, 3.0%; and SaO2, 1.1%. The mean within-subject coefficient of variation for test variables at 40% and 70% of maximal work rates are as follows: VO2, 5.2% and 4.6%; SaO2, 0.3% and 0.9%; HR, 4.0% and 3%; VE, 5.7% and 6.5%; and f, 5.8% and 7.2%, respectively. CONCLUSIONS: Variables measured during clinical cycle ergometer exercise testing in adult patients with stable CF are reproducible. No learning effect was found on repeated testing.

Adult↗
PubMed1997

Roles of the N and C terminal domains of the interleukin-3 receptor alpha chain in receptor function.

The interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5 receptor alpha chains are each composed of three extracellular domains, a transmembrane domain and a short intracellular region. Domains 2 and 3 constitute the cytokine receptor module (CRM), typical of the cytokine receptor superfamily; however, the function of the N-terminal domain is not known. We have investigated the functions of the N-terminal and C-terminal domains of the IL-3 receptor (IL-3R) alpha chain. We find that cells transfected with the receptor beta chain (h beta c) and a truncated IL-3R alpha that is devoid of the intracellular region fail to proliferate or to activate STAT5 in response to human IL-3, despite binding the IL-3 with affinity indistinguishable from that of full-length receptor. In addition, IL-3-induced phosphorylation of h beta c was not detected. Thus, the IL-3R alpha intracellular region does not contribute detectably to stabilization of the receptor/ligand complex, but is essential for signal propagation. In contrast, a truncated IL-3R alpha with the N-terminal domain deleted interacts functionally with the beta chain; mouse cells transfected with these receptor chains proliferate in response to human IL-3 and STAT5 transcription factor is activated. High- and low-affinity binding sites are retained, although the affinity for IL-3 is decreased 15-fold, indicating a significant role for the N-terminal domain in IL-3 binding.

Amino Acid Sequence↗
PubMed1996

Extracellular truncations of h beta c, the common signaling subunit for interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5, lead to ligand-independent activation.

The hypothesis that extracellular truncation of the common receptor subunit for interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and IL-5 (h beta c) can lead to ligand-independent activation was tested by infecting factor-dependent hematopoietic cell lines with retroviruses encoding truncated forms of h beta c. A truncation, resembling that in v-Mpl, and retaining 45 h beta c-derived extracellular residues, led to constitutive activation in the murine myeloid cell line, FDC-P1. However, infection of cells with retrovirus encoding a more severely truncated receptor, retaining only 7 h beta c-derived extracellular residues, did not confer factor independence on these cells. These experiments show that truncation activates the receptor and define a 37-amino acid segment of h beta c (H395-A431) which contains two motifs conserved throughout the cytokine receptor superfamily (consensus Y/H XX R/Q VR and WSXWS), as essential for factor-independent signaling. The mechanism of activation was also investigated in less severe truncations. A receptor that retains the entire membrane-proximal domain (domain 4) also conferred factor independent growth on FDC-P1 cells; however, a retrovirus encoding a truncated form of h beta c having two intact membrane proximal domains did not have this ability, suggesting that domain 3 may have an inhibitory role in h beta c. The ability of these receptors to confer factor independence was cell specific as demonstrated by their inability to confer factor-independent growth when introduced into the murine IL-3-dependent pro-B cell line BaF-B03. These results are consistent with a model in which activation requires unmasking of an interactive receptor surface in domain 4 and association with a myeloid-specific receptor or accessory component. We suggest that in the absence of ligand intramolecular interactions prevent inappropriate signaling.

Animals↗
PubMed1995

Truncated logistic regression.

Truncated binary data occurs when a group of individuals, who each have a binary response, are observed only if one or more of the individuals has a positive response. In this paper the group will be taken to be a motor vehicle accident and the binary response taken to be survival or death. We compare two regression techniques that can be used for truncated binary data. The first procedure, conditional logistic regression (Breslow and Day, 1980, Statistical Methods in Cancer Research. 1: The Analysis of Case-Control Studies. No. 32. Lyon: IARC) conditions on the actual number of deaths, and has been previously used for this type of data. The second procedure, truncated logistic regression, conditions on there being at least one death. It is computationally simpler than conditional logistic for groups of size greater than two and can be considerably more efficient. A major difference between the two methods is that only truncated logistic regression requires a knowledge of group level covariates and allows estimation of group level effects.

Accidents, Traffic↗
PubMed1994

Two contiguous residues in human interleukin-3, Asp21 and Glu22, selectively interact with the alpha- and beta-chains of its receptor and participate in function.

We have previously reported that the predicted first helix of human interleukin (IL)-3 contains a hydrophilic region encompassing residues Asp21, Glu22, and Thr25 that is crucial for biological activity and IL-3 receptor binding. Using single amino acid substitution mutagenesis, we have now determined that Asp21 and Glu22, but not Thr25, were crucial for full IL-3 activity. Mutant D21R was 30-fold less potent than wild type IL-3 in the stimulation of biological activity. It also exhibited a similar reduction in its ability to bind to the cloned high affinity IL-3 receptor complex (alpha- and beta-chains) or to the receptor alpha-chain alone, indicating that residue 21 is involved in contacts with the alpha-chain. Mutant E22R was approximately 20,000-fold less potent than wild type IL-3 in the stimulation of biological activity and in binding to the IL-3 receptor high affinity complex. However, the binding of E22R to the IL-3 receptor alpha-chain alone was similar to that of wild type IL-3, suggesting that this mutant was defective in interactions with the receptor beta-chain. These results show that two contiguous residues in the N-terminal region of IL-3 mediate binding to the two different chains of the IL-3 receptor and emphasize the functional significance of the conserved Glu in the first helix of the IL-3, granulocyte-macrophage colony-stimulating factor, and IL-5 cytokine subfamily.

Amino Acid Sequence↗
PubMed1994

Insecticide resistance status of Lucilia cuprina in New Zealand using biochemical and toxicological techniques.

The resistance status to diazinon based organophosphorus insecticides has been examined in the sheep blowfly, Lucilia cuprina, a recent arrival to New Zealand. Samples, representative of the distribution of L. cuprina in New Zealand, were scored for the presence or absence of a microsomal esterase (E3) associated with resistance. Iso-female lines were generated from four sites to examine variation in resistance levels using toxicological data. Results from both techniques show resistance at a high frequency with some variation between sites.

Animals↗
PubMed1991

Structure-function analysis of interleukin-5 utilizing mouse/human chimeric molecules.

Interleukin-5 (IL5) is a T cell derived glycoprotein that stimulates eosinophil production and activation. In the mouse, but apparently not in the human, it is active on B cells. The murine and human IL5 polypeptides exhibit 70% sequence similarity and yet display distinct species-specific activity. Whilst mouse and human IL5 are equally active in human cell assays, human IL5 is 100-fold less active than murine IL5 in mouse cell assays. Two restriction sites were utilized to divide the human and mouse sequences into three fragments. Hybrid molecules consisting of all combinations of these fragments were constructed and expressed. In the human cell assays [using bone marrow or the erythroleukaemic cell line (TF-1)] all the hybrid proteins generated activity comparable to that of the human and mouse IL5. This implies that replacing different domains does not result in detrimental effects to the tertiary structure of the molecule. In the mouse cell assays [using bone marrow or the pro-B cell line (B13)] the hybrids clearly identified the importance of residues in the C terminus for biological activity. The changing of only eight residues in this region of human IL5, to those of mouse IL5, resulted in the hybrid producing biological activity comparable to mouse IL5. In addition, competition binding assays showed that this region probably interacts with the receptor.

Amino Acid Sequence↗
PubMed1991

Analysis of interleukin 5 receptors on murine eosinophils: a comparison with receptors on B13 cells.

The interleukin 5 receptor (IL-5R) on murine eosinophils and a mouse B cell line (B13) was investigated using iodinated murine IL-5 produced in the baculovirus system. Electrophoretic analysis of this recombinant protein identified a range of bands Mr 26,000 to 32,000 resulting from differential glycosylation. The specific activity and binding kinetics of the iodinated IL-5 (125I-IL-5) were essentially identical to unlabeled material. Both high-affinity (Kd approximately 50 pM) and low-affinity (Kd approximately 1 nM) receptor populations were identified on murine eosinophils. Approximately 50 high-affinity receptors and 10,000 low-affinity receptors were present. This was compared with approximately 2,000 high-affinity (Kd approximately 80 pM) and about 8,000 low-affinity (Kd approximately 3 nM) sites on B13 cells. An antibody that inhibits IL-5 binding to, and proliferation of, B13 cells (R52.120) was also shown to inhibit eosinophil proliferation, suggesting that eosinophils and B cells bear the equivalent IL-5 binding proteins.

Animals↗