Thrombotic lesions are consistently observed in chronic thromboembolic pulmonary hypertension (CTEPH) and frequently found in primary pulmonary hypertension (PPH). It remains unknown, however, whether thrombosis is related to defects of the antithrombotic pathway or to previous vascular injury. This study therefore analysed the frequency of both hereditary and acquired thrombotic risk factors in CTEPH and PPH.One hundred and forty-seven consecutive patients with CTEPH investigated in the author's institution were compared to 99 consecutive patients with PPH. In 116 CTEPH patients and 83 PPH patients, phospholipid-dependent antibodies (antiphospholipid antibodies and lupus anticoagulant) were analysed by both immunological and clotting assays. In patients enrolled since 1994 (46 CTEPH and 64 PPH), hereditary thrombotic risk factors were also determined. Antithrombin, protein C and protein S activities were measured by functional assays. Mutations of factor V and factor II were identified by polymerase chain reaction.The prevalence of hereditary thrombotic risk factors was not increased in patients with either PPH or CTEPH. In contrast, a high frequency of phospholipid-dependent antibodies was observed in PPH (10%) and more notably in CTEPH (20%). Moreover, in PPH, antibodies were present only in low titre whereas in CTEPH, half of the patients with antiphospholipid antibodies had high titres. In addition, in CTEPH all but one of the patients with lupus anticoagulant also had antiphospholipid antibodies.The most striking finding of this study was the high prevalence of phospholipiddependent antibodies but their clinical relevance appears to be different in primary pulmonary hypertension and chronic thromboembolic pulmonary hypertension. In primary pulmonary hypertension, these antibodies in low titre probably reflect endothelial dysfunction. In contrast, in chronic thromboembolic pulmonary hypertension the presence of antibodies in high titre associated with lupus anticoagulant, underlines the role of thrombosis in the pathogenesis of this condition. Eur Respir J 2000; 15: 395±399. Pulmonary hypertension (PH) is a serious condition with significant morbidity and mortality. A large spectrum of diseases are included under this rubric, roughly divided into primary pulmonary hypertension (PPH) and secondary pulmonary hypertension. The definition of PPH is based on the exclusion of secondary causes of PH viz hypoxic lung disease, congenital heart disease, chronic thromboembolic disease, and associated conditions such as collagen vascular diseases, human immunodeficiency virus (HIV) infection, portal hypertension and exogenous substances [1]. Although the pathogenesis of the increased vascular resistance in PPH remains unknown, vasoconstriction, vascular remodelling and thrombosis may all contribute. In fact clinical data and histological features of PH suggest that thrombosis may be important in the pathophysiological state of PH, especially in PPH and chronic thromboembolic pulmonary hypertension (CTEPH). Se...

As judged from the midpoints of the denaturation transition of 31 water-miscible alcohols, ureas, and amides, the effectiveness of these denaturing agents on sperm-whale myoglobin increases with increasing chain length and hydrocarbon content, as expected in view of the disorganization of the hydrophobic interior of this protein. Increase in the hydroxyl content, blocking of the functional amino groups of the ureas and amides by alkyl substitution, and branching of the hydrocarbon portion of the denaturants are of less importance in determining the effectiveness of the denaturants.

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