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Biomedical subjects

K B Thomas

Publications and source records attributed to K B Thomas.

61 records · Page 4Linked to original sources
PubMedDate not supplied

Effect of virucidal heat treatment on proteins in human factor VIII concentrates.

Intermediate-purity and fibrinogen-poor factor VIII concentrates were heated in the lyophilized state at 60 degrees C for up to 72 hours to inactivate blood-borne viruses. The effect of heat treatment on factor VIII, von Willebrand factor (vWf), and other proteins present in the concentrates (albumin, fibrinogen, fibronectin, IgG, and IgM) was evaluated. Heat-induced protein aggregation, particularly of fibrinogen and fibronectin, occurred within 48 hours in the intermediate-purity concentrates and correlated well with decreased solubility of these products. Heated fibrinogen-poor concentrates were readily soluble and did not show protein aggregation even after 72 hours at 60 degrees C. Neither concentrate developed detectable neoantigens when tested against antisera to whole human plasma and to heated and unheated concentrates. Aggregation of the vWf molecule, detected by altered mobility in crossed immunoelectrophoresis and multimeric analysis in SDS agarose gels, occurred in heated intermediate-purity concentrates but not in fibrinogen-poor concentrates. Thus, higher-purity factor VIII concentrates withstand heat treatment better than concentrates that contain greater levels of contaminating proteins, particularly fibrinogen.

Chromatography, Gel↗
PubMedDate not supplied

Effect of delayed blood processing on the yield of factor VIII in cryoprecipitate and factor VIII concentrate.

Current standards for the preparation of factor VIII (FVIII) concentrates from human plasma recommend separation of plasma from red cells (RBCs) within 6 hours of blood donation, thereby reducing the volume of plasma from donated whole blood available for processing to FVIII concentrate. The decay of FVIII clotting activity (FVIII:C) in whole blood and plasma stored at 22 and 4 degrees C and the recovery of FVIII:C in cryoprecipitate and FVIII concentrate prepared from plasma separated from whole blood stored overnight at 4 degrees C were investigated. In whole blood stored at 22 degrees C and plasma stored at either 4 or 22 degrees C, 90 percent of the original FVIII:C was present at 6 hours, 80 percent at 12 hours, and 65 to 70 percent at 18 hours. At these times lower levels of FVIII:C were recovered from whole blood stored at 4 degrees C, that is, 84, 68, and 56 percent, respectively. In cryoprecipitates prepared from plasma separated from RBCs after 18 hours' storage at 4 degrees C (18-hour plasma), 43 percent of FVIII:C activity was recovered, as compared with 61 percent recovered from standard plasma separated within 6 hours of donation (6-hour plasma), p less than 0.05. With large-scale preparation of FVIII concentrates, however, the yield of FVIII:C was similar whether 18- or 6-hour plasma was used. Thus FVIII concentrates--but not cryoprecipitates--can be prepared from plasma separated from whole blood stored at 4 degrees C for up to 18 hours without undue loss of potency.

Antigens↗
PubMedDate not supplied

Bleeding and thrombosis in children with acute lymphoblastic leukaemia, treated according to the ALL-BFM-90 protocol.

A multi-center retrospective survey was conducted to evaluate the incidence and types of hemostatic complications occurring in children with acute lymphoblastic leukemia (ALL) during treatment according to the ALL-BFM-90 treatment protocol. All of the BFM-treatment centers (n = 77) were approached and a 95% response rate with information on 1100 patients was obtained. Thrombotic or bleeding episodes occurred in 31 patients (2.8%), 19 of whom had thrombosis and 12 bleeding complications, involving the central nervous system (42%), the subclavian vein (29%), the gastro-intestinal tract, skin, lower extremities or pelvis (29%). Recovery was noted in 28 of 31 patients, while 3 died as a result of hemostatic complications. Bleeding or thrombosis occurred in patients receiving prophylactic substitution with plasma or plasma-derived concentrates (n = 16) as well as in those without substitution (n = 13). The majority of hemostatic complications (90%) occurred during the induction therapy of the treatment protocol, in particular during the period which included simultaneous administration of glucocorticoids and E. coli L-asparaginase. The concurrent administration of E. coli L-asparaginase and glucocorticoids may be an additional risk factor for thromboembolic events during therapy according to the ALL-BFM-90 protocol.

Adolescent↗
PubMedDate not supplied

Effect of glucocorticoids, E. coli- and Erwinia L-asparaginase on hemostatic proteins in children with acute lymphoblastic leukemia.

BACKGROUND: The concentrations of plasma hemostatic proteins were analyzed prospectively in 42 children with acute lymphoblastic leukemia (ALL), treated according to the protocol ALL-BFM-90. PROCEDURE: Treatment included glucocorticosteroids (GC), E. coli L-asparaginase (Asparaginase, Medac) or Erwinia L-asparaginase (Erwinase, Speywood), vincristine, anthracyclines and intrathecal methotrexate. The analysis of hemostatic proteins was performed during induction and re-induction therapy. RESULTS: At diagnosis, the plasma concentrations of fibrinogen, antithrombin III (AT), plasminogen and protein C were within normal limits, whereas the von Willebrand factor antigen (vWF:Ag) was elevated. After eight days of mono-therapy with GC the concentration of fibrinogen decreased to 59%, vWF:Ag decreased to 67%, AT increased to 124%, protein C increased to 201% of the initial value (mean all p < or = 0.01), while the concentration of plasminogen remained unchanged. During the re-induction phase, the concentrations of the hemostatic proteins, with exception of vWF:Ag, altered in a similar way in response to GC as observed during the induction phase. Administration of two doses of E. coli L-asparaginase (10,000 U/m2) during the induction therapy led to a significant decrease of AT (123 +/- 24 to 63 +/- 15%/mL), protein C (168 +/- 34 to 87 +/- 19%/mL), plasminogen (94 +/- 21 to 41 +/- 12%/mL) and fibrinogen (148 +/- 59 to 79 +/- 30 mg/dL, p < or = 0.01 for all parameters). In contrast, administration of two doses of Erwinia L-asparaginase (10,000 U/m2) during re-induction therapy did not lead to change in the concentration of AT, protein C or plasminogen, and the decrease in fibrinogen (162 +/- 17 to 121 +/- 24 mg/dL) was less pronounced. CONCLUSIONS: Our results indicate that GC and E. coli L-asparaginase, in particular, induce hemostatic alterations which have implications on our understanding of thrombotic and hemorrhagic events during the treatment of ALL in children.

Adolescent↗