Alan R. Giles

Bio: Alan R. Giles is an academic researcher from Queen's University. The author has contributed to research in topics: Thrombin & Von Willebrand factor. The author has an hindex of 29, co-authored 71 publications receiving 2657 citations. Previous affiliations of Alan R. Giles include Organon International.

Factor v (quebec): a bleeding diathesis associated with a qualitative platelet factor v deficiency

Abstract: Studies were performed on a French-Canadian family afflicted with a bleeding disorder exhibiting an autosomal dominant inheritance pattern and a severe bleeding diathesis after trauma. Clinical laboratory coagulation tests were unimpressive; the only persistent abnormalities include mild thrombocytopenia and moderately reduced Factor V clotting activities. Some individuals had prolonged Stypven times when platelet-rich plasma was used, suggesting that their platelets could not support functional prothrombinase complex assembly. Detailed studies were performed by use of plasma and isolated, washed platelets from a sister and brother. Bioassay data indicate that both individuals had Factor V activities of approximately 40 and 36% of normal, respectively. A comparison of the Factor V radioimmunoassay and bioassay data on the brother's plasma indicated that the circulating amount of Factor V functional activity was low relative to Factor V antigen concentration (approximately 65-75%). In both individuals, the platelet Factor V functional activities were extremely low (2-4%) relative to antigen levels present as determined by radioimmunoassay. These discrepancies between Factor V activities and antigen concentration do not appear to be due to an unstable Factor V molecule or to the presence of a Factor V or Factor Va inhibitor or inactivator. Kinetics of prothrombin activation by use of purified clotting factors indicated that thrombin-activated platelets from both individuals supported prothrombinase complex assembly identical to controls in the presence of added purified Factor Va. Consequently, their bleeding diathesis appears to reflect their platelet, rather than their plasma, Factor V activity. These results suggest that platelet Factor V is an essential component in maintaining stable and prolonged hemostasis after trauma.

Plasmapheresis therapy in rheumatoid arthritis. A controlled, double-blind, crossover trial.

Abstract: Twenty-six patients with rheumatoid arthritis (average age, 57 years; average duration of disease, 11 years) who were unresponsive to antiinflammatory and slow-acting antirheumatic drug therapy were entered into a controlled, double-blind, crossover study to assess the efficacy of plasmapheresis therapy. All patients received 10 true and 10 sham aphereses as outpatients and continued to take their usual drugs. Twenty patients completed the study, and six were withdrawn--three because of poor venous access. Standard clinical and laboratory measures were assessed by personnel blinded to the therapy administered. Paired t-test analysis of seven clinical measures failed to show significant differences between the true and sham procedures (P = 0.36 to 0.96), although transient, mild improvement did occur during both cycles of apheresis, probably because of a placebo response. Significant reductions in the erythrocyte-sedimentation rate, rheumatoid factor titer, and levels of hemoglobin, IgM, and C3 occurred only with true therapy (P = 0.001, 0.01, 0.03, 0.045, and 0.005, respectively). We conclude that plasmapheresis does not have clinical benefit in chronic rheumatoid arthritis, in spite of impressive laboratory changes.

Linking clinical variables with health-related quality of life. A conceptual model of patient outcomes

Abstract: HEALTH-related quality of life (HRQL) is increasingly used as an outcome in clinical trials, effectiveness research, and research on quality of care. Factors that have facilitated this increased usage include the accumulating evidence that measures of HRQL are valid and "reliable,"1the publication of several large clinical trials showing that these outcome measures are responsive to important clinical changes,2-5and the successful development and testing of shorter instruments that are easier to understand and administer.6-13Because these measures describe or characterize what the patient has experienced as the result of medical care, they are useful and important supplements to traditional physiological or biological measures of health status. Given this improved ability to assess patients' health status, how can physicians and health care systems intervene to improve HRQL? Implicit in the use of measures of HRQL in clinical trials and in effectiveness research is the concept that clinical

Disseminated Intravascular Coagulation

Abstract: Disseminated intravascular coagulation is characterized by the widespread activation of coagulation, which results in the intravascular formation of fibrin and ultimately thrombotic occlusion of small and midsize vessels.1–3 Intravascular coagulation can also compromise the blood supply to organs and, in conjunction with hemodynamic and metabolic derangements, may contribute to the failure of multiple organs. At the same time, the use and subsequent depletion of platelets and coagulation proteins resulting from the ongoing coagulation may induce severe bleeding (Figure 1). Bleeding may be the presenting symptom in a patient with disseminated intravascular coagulation, a factor that can complicate decisions about . . .

Phenotypic Heterogeneity of the Endothelium: I. Structure, Function, and Mechanisms

Abstract: Endothelial cells, which form the inner cellular lining of blood vessels and lymphatics, display remarkable heterogeneity in structure and function. This is the first of a 2-part review focused on phenotypic heterogeneity of blood vessel endothelium. This review provides an historical perspective of our understanding of endothelial heterogeneity, discusses the scope of phenotypic diversity across the vascular tree, and addresses proximate and evolutionary mechanisms of endothelial cell heterogeneity. The overall goal is to underscore the importance of phenotypic heterogeneity as a core property of the endothelium.

Biochemistry and Genetics of von Willebrand Factor

Abstract: ▪ Abstract Von Willebrand factor (VWF) is a blood glycoprotein that is required for normal hemostasis, and deficiency of VWF, or von Willebrand disease (VWD), is the most common inherited bleeding disorder. VWF mediates the adhesion of platelets to sites of vascular damage by binding to specific platelet membrane glycoproteins and to constituents of exposed connective tissue. These activities appear to be regulated by allosteric mechanisms and possibly by hydrodynamic shear forces. VWF also is a carrier protein for blood clotting factor VIII, and this interaction is required for normal factor VIII survival in the circulation. VWF is assembled from identical ≈250 kDa subunits into disulfide-linked multimers that may be >20,000 kDa. Mutations in VWD can disrupt this complex biosynthetic process at several steps to impair the assembly, intracellular targeting, or secretion of VWF multimers. Other VWD mutations impair the survival of VWF in plasma or the function of specific ligand binding sites. This growing...