It has been recognised for many years that phospholipids are essential for the coagulation of plasma, and the evidence which has been obtained so far suggests that they are involved in the formation in the plasma of a substance which will convert prothrombin. The activity of the various phospholipids has been assessed by their ability either to shorten the clotting of recalcified plasma, or to stimulate the conversion of prothrombin. Using this technique the most active phospholipid has been found to be phosphatidyl ethanolamine, but apart from an investigation of the physical and chemical properties of this phosphatide, no information has been gained as to its mode of action. Since plasma already contains phospholipids it was thought worthwhile to investigate whether any reaction took place during the coagulation of plasma, in which they were involved. For this investigation the plasma was clotted either in the presence of platelets, or Russell's viper venom. It was found that when the plasma clotted it was accompanied by the release of a small amount of glycerylphosphorylcholine. This substance was formed however the plasma was made to clot. The results which have been obtained suggest that this compound was formed by the degradation of between 2-3% of the plasma lecithin. Glycerylphosphorylcholine is formed from lecithin by the action of two enzymes, namely, a lecithinase and a lysolecithinase. It has been shown that while Russell's viper venom has lecithinase activity, it is unable to hydrolyse lysolecithin. It was found that plasma had a latent lysolecithinase activity, which could be activated by exposing the plasma to a roughened glass surface. In addition the activated lysolecithinase enzyme would in the presence of a tripalmitin emulsion hydrolyse lecithin to give glycerylphosphorylcholine. It is suggested that the probable role of phosphatidyl ethanolamine is to activate the plasma lecithin so that it can be hydrolysed by the plasma enzyme. The results which have been obtained suggest that the degradation of the lecithin was associated with the appearance in the plasma of a substance which will convert prothrombin, and the conclusion has been reached that the development of both lecithinase and lysolecithinase activity is a necessary prerequisite for the coagulation of the plasma. Born (1958) showed that during the coagulation of platelet-rich plasma there was a loss of adenosine triphosphate from the platelets. Experiments have been carried out to determine whether this loss of adenosine triphosphate was concerned in the clotting of the plasma It has been concluded that the release of adenosine triphosphate from the platelets was only incidental to the clotting of the plasma.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:644602 |
| Date | January 1960 |
| Creators | Esnouf, Peter |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:72ac4a27-915f-4a04-957e-509a1a53c4f1 |
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