Studies of the Coagulation of the Blood: Part II. Thrombin and Antithrombins

A Brief Historical Perspective on Pulmonary Embolism

Pulmonary embolism is a major cause of mortality worldwide. In this historical perspective, we aim to provide an overview of the rich medical history surrounding pulmonary embolism. We highlight Virchow's first steps toward understanding the pathophysiology in the 1800s. We see how those insights inspired early attempts at intervention such as surgical pulmonary embolectomy and caval ligation. Those early interventions were refined and ultimately led to the development of inferior vena cava filters, the earliest clinical applications of anticoagulation, and even apparently disparate medical advances such as the successful development of cardiopulmonary bypass. We also see how the diagnosis of pulmonary embolism has evolved from rudimentary monitoring of vitals and symptoms to the development of evermore sophisticated tests such as contrast tomography angiography and echocardiography. Finally, we discuss current approaches to diagnosis, classification, and myriad treatments including anticoagulation, thrombolysis, catheter-directed interventions, surgical embolectomy, and extracorporeal membrane oxygenation guided by Pulmonary Embolism Response Teams.

Serine protease inhibitors and human wellbeing interplay: new insights for old friends

Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.

A century of heparin: past, present and future

Heparin was discovered around 1922 by Howell (Baltimore) and was further developed by the teams of Best (Toronto) and Jorpes (Stockholm). Kakkar (London) propagated its routine use for the prevention of postoperative thrombosis from 1971 onwards. The discovery of low molecular weight heparins (1976, Johnson, London) and their development in the subsequent years led to the present arsenal of clinically useful drugs. In 1976, three teams independently found that a specific structure in heparin binds tightly to antithrombin. This enabled the teams of Lindahl (Stockholm) and Casu (Milan) to determine the pentasaccharide structure responsible for this binding and Petitou, from the Choay team (Paris), to synthesize it (1983). It was found (Olson and others) that heparin facilitates the interaction between antithrombin and a clotting enzyme by allosteric changes in the antithrombin (important for factor Xa) and by facilitating the approach of the enzyme to antithrombin via its "sliding" along the heparin molecule (important for thrombin). Antithrombin action therefore requires a minimum length of seven sugar units next to the pentasaccharide whereas anti-factor Xa action does not. The effect of heparin is almost entirely due to anti-thrombin action (B≐guin), so anti-factor Xa activity does not reflect the concentration of anticoagulant heparin. The anticoagulant effect is poorly reflected by the activated partial thromboplastin time. Because present clinical use is based on the latter tests, it is not generally known that the individual response to heparin shows an extremely wide variation. Individualization of heparin dosage is likely to improve clinical results.

The development of blood plasma.—Part I. The genesis of coagulable material in embryo chicks

Although much attention has been given to the embryonic development of blood corpuscles, the genesis of the coagulable constituents of the plasma has escaped notice. Knowledge of this subject appears to be limited to the observation of Boll (1) that the blood of chick embryos does not clot before the twelfth to fourteenth day of incubation; and of Emmel, Levison and Fisch (2) that the blood of late pig embryos clots more slowly than that of adult pigs. We shall describe the successive appearance in chick embryos of those constituents of the blood plasma which are associated respectively with the preservation of the fluidity of the blood and with its capacity to clot. We shall also briefly discuss the significance of the facts recorded.