ABSTRACT
The action of temperatures above 48° C. on the red cell is usually regarded as a classical example of the irreversible effects of injury, the lysis which follows being attributed to a surface membrane becoming permeable because its lipid components are melted or because its protein components become denatured. Recently it has been found that the effects are considerably more complex, and increasing emphasis is being placed on the role which fragmentation plays in the phenomenon of heat haemolysis. Ham, Shen, Fleming & Castle (1948) have pointed out that the fragmentation which precedes haemolysis results in the cells of the system becoming more and more spherical, so that the extent to which each cell can swell before its surface is stretched becomes less and less, and the tonicity in which it haemolyses becomes greater and greater; when there is sufficient fragmentation, indeed, human red cells will haemolyse even in an isotonic medium such as plasma. The tonicityvolume relations of cells which have lost one or more of these fragments during heating to temperatures in the neighbourhood of 48° C., however, are substantially the same as those of intact cells (Ponder, 1948 a), and both cells and fragments show substantially the same resistance to haemolysis by saponin and by digitonin; these observations point to the osmotic properties and the properties which determine the resistance to lysins being shared by cell and fragment, and to the unit structure upon the integrity of which these properties depend being smaller than the intact red cell. The possibility that this is so suggests that something may be learned by examining the shape of the red cells and fragments more closely, since the ability to maintain shape and to undergo shape transformations are also properties which are usually thought of as associated with the red cell as a unit structure.
This heating chamber is made by Mr Paul Cutajar of the New York University machine shop.
The fragmentation and other change" which occur in red cells after exposure to heat vary in the case of the cells of different healthy individuals, and vary very noticeably in the case of the abnormal red cells of certain types of anaemia. The specification ‘heating to 48°C. for a min.’, etc., is not to be taken too literally ; the changes described usually occur when the cells are heated to this temperature for this time, but in the case of the red cells of another healthy individual, they may not occur until the heating has continued for a longer time or until the temperature has been raised to 48-5°C.
No spontaneous shape change takes place when the cells cool. When plasma is run under the cover-glass to cool them quickly, an increased number of distorted disks appear; this is part of the shape change, from sphere to distorted disk, described in § (a).
I have observed, on several occasions, the fusion of two spherical fragments to form a larger sphere which haemolysed some minutes afterwards. This confirms a neglected observation of Auer (1932).
