Abstract
In the course of the preparation of plasma for human use it was observed that on the thawing of frozen plasma, separation into a number of layers takes place; the lowermost deep-yellow layer is rich in proteins, while the uppermost, nearly colorless layer, contains only a small amount of protein. On repeated freezing and thawing, the separation becomes more distinct. A more rapid and sharp separation of plasma into layers is obtained by centrifuging the frozen material.
It is interesting that Bujwid 1 used the freezing method for the concentration of diphtheria and tetanus anti-toxin in 1897. His results were confirmed by Ernst, Coolidge and Cook. 2 Rossi 3 used the freezing and centrifuging procedures for fractionating plasma and other colloidal solutions, and Hati 4 used this technic for the concentration of complement, opsonins and anti-sera. In view of the above observations, the question arose as to whether these procedures might be employed for the concentration of plasma without excessive loss of solids.
The following is a representative fractionation and analysis of plasma: 100 cc were placed in a separatory funnel and frozen at—10°C; on partial thawing at 4°C, a deep yellow fluid was obtained with a colorless ice block floating on the surface. The freezing and thawing process was twice repeated. During the thawing which followed the third freezing, the melting fluid was collected directly into graduated cylinders. Three fractions were obtained in this manner. The first fraction of 25 cc was deep-yellow; the second was 17 cc, and the third, derived from the colorless ice block, was 58 cc.
Quantitative determinations of proteins, albumin, chlorides, cholesterol and isoagglutinins were performed on the 3 fractions and on a sample of the original plasma. The results are presented in Table I.
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