Barry Wilbourn

Publications (4)15.59 Total impact

• Article: Activation of platelets in whole blood by recombinant factor VIIa by a thrombin-dependent mechanism.

  Barry Wilbourn, Paul Harrison, Ian J Mackie, Ri Liesner, Samuel J Machin
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  ABSTRACT: Using a diluted whole blood method of flow cytometric analysis, we have shown that platelets could be activated in vitro in the presence of high concentrations (100 nmol/l) of recombinant factor (F) VIIa (rFVIIa; NovoSeven(R)) and 2.5 mmol/l calcium chloride. This was demonstrated by a significant increase in the mean percentage of platelets expressing CD62P and their mean fluorescent intensity (MFI) after 30 min versus platelets incubated with calcium or rFVIIa alone or diluted blood alone. The presence of rFVIIa and calcium increased the exposure of the PAC-1 activation epitope of glycoprotein (Gp) IIb/IIIa. This effect was equally influenced by the presence of calcium alone but not by rFVIIa. The effect of rFVIIa was time and concentration dependent. Thrombin generation was also necessary, as the effect of rFVIIa was completely abrogated by the additional presence of hirudin. Furthermore, soy bean trypsin inhibitor (SBTI) but not corn trypsin inhibitor (CTI) abrogated CD62P exposure, suggesting that thrombin was derived via FX but not FXII activation. Exposure of CD62P demonstrated a significant lag phase, sometimes of the order of > 30 min, as well as large intersubject variation. Significant platelet activation was observed at a concentration as low as 25 nmol/l rFVIIa. Platelet-leucocyte aggregation was also increased in the presence of 25 nmol/l rFVIIa and calcium. No significant difference was observed between levels of CD62P in diluted whole blood and platelet-rich plasma adjusted to an identical platelet count after their exposure to rFVIIa and calcium for 30 min.
  British Journal of Haematology 09/2003; 122(4):651-61. · 4.94 Impact Factor
• Source

  Available from: John Greenwood

  Article: Lymphocyte trafficking through the blood-brain barrier is dependent on endothelial cell heterotrimeric G-protein signaling.

  Peter Adamson, Barry Wilbourn, Sandrine Etienne-Manneville, Virginia Calder, Evelyne Beraud, Graeme Milligan, Pierre-Olivier Couraud, John Greenwood
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  ABSTRACT: We have previously shown that the engagement of ICAM-1 on brain endothelial cells (EC) results in the propagation of EC signaling pathways that are necessary for efficient lymphocyte migration across the tight vascular barriers of the brain. Signaling via this receptor alone, however, is unlikely to explain the differential recruitment of leukocytes at different vascular beds. In this study, we investigated the role of EC heterotrimeric G-protein-mediated signaling in supporting transendothelial migration of T lymphocytes. Treatment of brain EC monolayers with pertussis toxin (PTX) resulted in ADP-ribosylation of G-protein alpha subunits and inhibition (>80%) of lymphocyte migration without affecting lymphocyte adhesion. Aortic and high endothelial venule EC treated identically resulted in only partial inhibition of lymphocyte migration (<40%). Expression of ribosylation-resistant (PTX-insensitive) G-protein alpha subunits in brain EC restored their ability to support lymphocyte migration after pretreatment with PTX. Treatment of brain EC with PTX did not inhibit ICAM-1-stimulated tyrosine phosphorylation of focal adhesion kinase, suggesting the effects of PTX in inhibiting EC facilitation of lymphocyte migration are distinct from activation of EC through ICAM-1. We conclude that a heterotrimeric G-protein-mediated signaling pathway in brain EC is essential for efficient transendothelial migration of T lymphocytes into the brain.
  The FASEB Journal 08/2002; 16(10):1185-94. · 5.71 Impact Factor
• Article: The influence of therapeutic blocking of Gp IIb/IIIa on platelet α‐granular fibrinogen

  Paul Harrison, Barry Wilbourn, Elisabeth Cramer, Richard Faint, Ian J. Mackie, Shoumo Bhattacharya, Avijit TJahiri, Danielle Tenza, Samuel J. Machin, Geoffrey F. Savidge
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  ABSTRACT: Recent evidence suggests that platelet a-granule fibrinogen (fg) is derived from the plasma pool. Since platelets from patients with Type I Glanzmann's thrombasthenia (GT) are deficient in intracellular fibrinogen (fg) it was hypothesized that Gp IIb/IIIa could mediate the uptake of fg. To study the potential role of Gp IIb/IIIa in intracellular fg trafficking, the influence of therapeutic blocking of Gp IIb/IIIa on platelet fg was studied in 12 patients with stable ischaemic heart disease. Patients were either given a single intravenous dose of the monoclonal antibody 7E3 Fab (n= 4) or a combination of bolus and continuous infusion up to 24 (n= 3). 36 (n= 3) or 96 h (n= 2). All patients showed grossly prolonged bleeding times with a significant reduction of ex-vivo ADP induced aggregation. Although, surface Gp IIb/IIIa binding sites were consistently reduced in all patients, there was a variable but delayed decrease in platelet fg relative to vWf: Ag in only six out of the 12 patients studied. The reduction in fg appeared dependent upon both dosage and duration of Gp IIb/IIIa blockade. The study provides further evidence for the novel role of Gp IIb/IIIa in the intracellular trafficking of fg to platelet and megakaryocytic alpha-granules.
  British Journal of Haematology 11/1992; 82(4):721 - 728. · 4.94 Impact Factor
• Article: Brain Endothelial Cell Lines Intracellular Calcium Signaling in Lymphocyte Migration Involve Transendothelial Rearrangements and ICAM-1Coupled Cytoskeletal

  Pierre-Olivier Couraud, Peter Adamson, Barry Wilbourn, John Greenwood, Sandrine Etienne-Manneville, Jean-Baptiste Manneville