Activation of blood coagulation in patients with major depressive disorder during euglycemic hyperinsulinemia.
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Adult↗
Biomedical subjects
Paula K Merryman
Publications and source records attributed to Paula K Merryman.
The effect of red blood cells on thrombin generation.
We have developed an assay of thrombin generation in clotting whole blood. Because our goal was to study patients with red blood cell diseases that are associated with thrombosis, the initial evaluation of this assay analysed the effect of the haematocrit and haemolysate on the total amount of thrombin activity generated and the maximal concentration of thrombin achieved. Both of these parameters were proportional to the haematocrit throughout a wide range of clinically relevant cell concentrations. Red cell lysate also augmented thrombin generation. Because this effect was removed by filtration of the lysate, we propose that it was related to red cell microparticles.
Blood Coagulation↗
Plasminogen interaction with platelets: the importance of carboxyterminal lysines.
INTRODUCTION: Thrombin stimulation enhances plasminogen binding to platelets and promotes platelet-dependent plasmin generation. The objective of this study was to determine whether carboxyterminal lysines (C-lysines) are important for these processes, as they are in other cell types. MATERIALS AND METHODS: 125I-plasminogen and varying concentrations of unlabeled plasminogen were added to washed platelets that were either resting or stimulated with thrombin, thrombin receptor activating peptide, or ADP. In some experiments the platelets were digested with carboxypeptidase B to remove C-lysines. Platelet-dependent plasmin generation was also studied by adding plasminogen and tissue plasminogen activator to platelet suspensions and monitoring the conversion of a plasmin specific chromogenic substrate. The cells were either resting or stimulated with thrombin, thrombin receptor activating peptide, or ADP. The effect of the thrombin inhibitor lepirudin and the plasmin inhibitor aprotinin on plasminogen binding and the appearance of C-lysines was also investigated. RESULTS: Thrombin, but not thrombin receptor activating peptide or ADP, stimulated high-affinity binding of plasminogen and greatly promoted platelet-dependent plasmin generation. Digestion with carboxypeptidase B eliminated thrombin-induced high-affinity binding and reduced thrombin-induced plasmin generation by increasing the Michaelis constant. Lepirudin, but not aprotinin, inhibited thrombin-stimulated plasminogen binding to platelets. CONCLUSION: C-terminal lysines are necessary for high-affinity binding of plasminogen to platelets and for platelet-supported plasmin generation. The origin of the C-lysines is not clear, but they may result from a direct effect of thrombin, rather than an intermediate enzyme such as plasmin.
Blood Platelets↗
Is thyroid hormone suppression therapy prothrombotic?
The purpose of this study was to determine whether chronic thyroid hormone suppression therapy (THST) is prothrombotic. We obtained blood samples from 14 thyroid cancer patients while on THST and after they had become hypothyroid for radioiodine whole-body scanning and therapy. Prothrombin fragment 1 + 2, fibrinogen, factor VIII, antithrombin, tissue plasminogen activator antigen (tPA), plasminogen activator inhibitor 1 (PAI-1), PAI-1/tPA, and C-reactive protein were significantly (P < 0.05) higher in the hyper- than in the hypothyroid state, whereas protein C and plasmin-antiplasmin complexes were significantly lower during the hyperthyroid period. When the 10 female patients were hyperthyroid, their levels of prothrombin fragment 1 + 2, fibrinogen, protein S, antithrombin, tPA, PAI-1, and PAI-1/tPA were significantly higher (P </= 0.05) than in healthy female controls, whereas when the female patients were hypothyroid, their antithrombin and plasmin-antiplasmin were lower and their protein S was higher than in controls. Factor II, plasminogen, and D-dimer were not significantly affected by the thyroid status in either assessment. In conclusion, we found evidence that the majority of patients treated with THST have a prothrombotic profile.
Adult↗
Parameters of coagulant and fibrinolytic capacity and activity in postmenopausal women: within-subject variability.
We have analyzed the within-subject variability of a battery of parameters of coagulant and fibrinolytic capacity and activity in postmenopausal women. We observed large differences in within-subject variability among the tests and have demonstrated how such data can be used to estimate the number of times a parameter must be measured to produce a statistically adequate sample.
Biomarkers↗