The rate of formation of fibrin ferment from prothrombin by the action of thrombokinase and calcium chloride

Abstract

IN 1912 the rate of formation of trypsin from trypsinogen by the action of enterokinase was determined by J. Mellanby and V. J. Woolley(i).This reaction differs from that observed in such ferment actions as the inversion of cane sugar by invertase in so far that the velocity of the change is small at the outset of the reaction but proceeds with a constantly increasing acceleration. This fact has been confirmed by Vernon (2), but the hypothesis which we put forward to account for the mechanism of the change has been a matter of dispute. It became of interest therefore to determine the rate of formation of fibrin ferment from prothrombin by the action of thrombokinase and calcium chloride. The information thereby obtained shows that the processes involved in that reaction are similar to those observed in the generation of trypsin from trypsinogen and affords evidence in favour of the hypothesis which we put forward to elucidate the mechanism of the latter reaction. Incidentally the hypotheses put forward by Howell (3) on the relation of thrombokinase to antifibrin ferment and by Barratt(4) on the time factors involved in the coagulation of blood are considered in the light of the experimental facts detailed.The preparation of fibrinogen, prothrombin and fibrin ferment. Prothrombin can be obtained from bird's blood in a state of comparative purity and in such condition, that, after the addition to it of thrombokinase and calcium chloride, a fibrin ferment solution of extraordinary potency may be obtained. Bird's blood was used in the experiments since, as was shown by Delezenne(5), such blood if carefully collected shows no tendency to coagulate, and thus constitutes an ideal medium whereby the mechanism of blood coagulation may be studied. No foreign bodies, such as potassium oxalate, sodium chloride, peptone, etc. have been added to it and the stability of the original blood affords an

Potentially Unlimited Growth of Excised Tomato Root Tips in a Liquid Medium

“…In its usual form it consists of two components, chicken serum making up from 50 to 70 per cent., and embryonic juice from 30 to 50 per cent., of the mass of the nutrient. A satisfactory modification used by EBELING (5) contained fibrinogen (prepared according to MELLANBY,11) 12.5 per cent., chicken serum 37.5 per cent., and eiiibryonic juice 50 per cent. Dry weights are not usually given for these constituents, so that they cannot be directly compared with the constituents of the plant culture nutrient.…”

“…The present work represents essentially a repetition and extension of the earlier root tip cultures of ROBBINS (9,10) and ROBBINS and MANEVAL (11,12). Tomato was chosen as a test organism, since it was planned to use the tissue culture technique later in the study of certain diseases to which this plant is susceptible.…”