Annemarie D. Muller

Induction of endothelial cell procoagulant activity by cytomegalovirus infection

Endothelial cells isolated from rat aorta were infected in vitro with rat cytomegalovirus. Viral antigens appeared in nucleus and cytoplasma and newly made extracellular virus was detected in the supernatant. Furthermore, the viral infection caused the appearance of procoagulant activity on the endothelial cells.

In vitro tumor angiogenesis assays: plasminogen lysine binding site 1 inhibits in vitro tumor-induced angiogenesis

It is generally accepted that tumors are angiogenesis-dependent. For research and clinical purposes it would be very attractive to have a simple in vitro model that allows a rapid screening of the angiogenic potential of tumors and to study the effect of angiogenic inhibitors. In vitro angiogenesis models were developed, based on endothelial sprouting/tube formation on a collagen gel, using both tumor cell lines and tumor biopsies. Best results were obtained using conditioned medium of tumor cell lines. In this model it was found that the plasminogen fragment lysine binding site 1 (LBS-1) inhibited in vitro endothelial cell sprouting. This is the first demonstration that LBS-1, which includes angiostatin, is inhibitory for new vessel formation in an in vitro angiogenesis model. We conclude that the assay system allows for rapid and reliable screening of angiogenesis inhibitors.

CLOTTING FACTORS SECRETED BY MONOCYTES AND MACROPHAGES: ANALYTICAL CONSIDERATIONS.

The secretion of clotting factors by rat spleen macrophages and human peripheral blood monocytes has been studied. The results show that the amount of clotting factors measured depends critically upon the characteristics of the assay system used. The presence of warfarin, salicylic acid or thrombin in the culture medium is shown to decrease the vitamin K dependent clotting factor activity in the supernatant after in vitro culture of rat spleen macrophages and human peripheral blood monocytes.

Evaluation of a Coagulation Assay Determining the Activity State of Factor VII in Plasma

A coagulation assay is described that allows the measurement of the degree of activation of factor VII in circulating blood. The test is based on the use of both bovine and human brain thromboplastin, together with an artificial factor VII-deficient plasma. The latter can be prepared on a relatively large scale which makes it possible to measure factor VII activation in large series of patients. The determination of factor VII activation during incubation at 4 degrees C of plasma of women using oral contraceptives shows that the test described adequately measures factor VII activation. Differences in the time course of factor VII activation during this incubation in glass and plastic containers are found and implicate that rigorous standardization of blood sampling and test conditions is necessary. A possible mechanism that causes this critical dependence upon the test conditions is discussed.

The activity state of factor VII in plasma: two pathways for the cold promoted activation of factor VII

Summary. The apparent amount of factor VII as determined in a one‐stage test depends on the type of thromboplastin used: bovine thromboplastin only reacts with human factor VIIa whereas human thromboplastin interacts with unactivated human factor VII as well. Therefore the ratio factor VII activity as measured with bovine thromboplastin divided by the factor VII activity as assessed with human thromboplastin reflects the state of activation of factor VII in plasma. This approach was used to study the process of cold promoted factor VII activation and the involvement of different clotting factors therein. It could be shown that cold promoted activation does not occur in the absence of factors II and XII and is reduced for about 50% in factor IX deficient plasma. The other coagulation factors have a minor influence on the process. The results indicate that the cold promoted factor VII activation is the result of activation by both activated contact products and thrombin.

Measurement of Macrophage Cellular Procoagulant Activity

We developed a simple technique for the measurement of the procoagulant activity exposed on the surface of macrophages. The cells are isolated, adhered to plastic surfaces, and assayed in the same device. This approach allows us to study the microcoagulation on the surface of intact macrophages by sensitive and specific clotting tests.

Activation of Factor VII in Patients with Carcinoma of the Prostate

A preliminary report suggests a correlation between metastatic prostate cancer and increased plasma factor VIIa levels. Prostate cancer without metastases and prostate hypertrophy showed no clear pattern in factor VIIa. Further investigations concerning the relation between metastatic cancer and clotting factors are in progress.

Chapter 1 Blood coagulation as a part of the haemostatic system

Publisher Summary This chapter discusses blood coagulation as a part of the haemostatic system. Haemostasis refers to the interrelated processes that cause the cessation of the flow of blood through a damaged vessel wall. The main components of the haemostatic system are: the blood platelets, the humoral coagulation enzymes, the layer of endothelial cells that lines the blood vessels, the subendothelial structures, and the smooth muscle cells that support the vessels. When damage to a blood vessel occurs, the defect must be sealed through the coordinated action of platelets, clotting factors, endothelial cells, and the vessel musculature. The relative contribution of these different components to the haemostatic process depends on the extent of the damage and the localization of the process. The clotting cascade reactions leading to fibrin formation proceed with increased velocity at the surface of stimulated platelets. The blood coagulation enzymes occur in plasma as inactive zymogens that can be activated in a series of consecutive reactions. The reactions in which the vitamin K-dependent coagulation factors (VII, IX, X, and II) are involved proceed at lipid/water interfaces and the quality of the interface is one of the parameters that determine the reaction velocity of this process.