ABSTRACT
This investigation started with the incidental observation that a slight modification in the method used for preparing ghosts from human red cells results in a remarkable difference in one of the properties of the ghost; more specifically, when ghosts are prepared by the addition of large volumes of water, they are not fragmented by heat unless a certain concentration of salt is present (Ponder, 1951). Extension of these observations, made possible by phase-contrast optics, has led to the idea, already suggested by electron microscope studies, that a large number of kinds of ghost, each with its own characteristic properties, can be prepared from a single kind of red cell. This is a very different idea from the usual one that the ghost is a ‘residue’ which, apart from small differences in chemical composition, is essentially the same whether it is obtained from one kind of red cell or from another.
The incubation of the washed red cells at 37° C. produces an effect which is quite obscure. The opacity of the haemolysate made from incubated cells increases with the length of the incubation, and the yield of ghosts is increased correspondingly.
The higher concentrations of saponin liberate the surplus Hb from the ghost, with the result that the system becomes translucent. A similar translucence is observed in a heated suspension of ghosts prepared by haemolysis in a large volume of water and in which there is no fragmentation ; this can be contrasted with the opaque appearance of the heated suspension of ghosts in o-i % NaCl, in which there is extensive fragmentation. The translucence is also seen in suspensions of ghosts prepared by freezing and thawing.
Serum and serum albumin also affect the heat fragility of red cells in a complex way (Ponder, 1950a).
It is usual to measure mechanical fragility in systems of the same volume concentration, since the fragility tends to increase with increasing volume concentration. In these systems, the volume concentration in the hypertonic systems is less than that in the isotonic and hypotonic systems ; if all the volume concentrations were adjusted so as to be equal, the mechanical fragility in the hypertonic systems would be increased, i.e. the minimum would become even more pronounced than it is.
A little haemolysis is apt to occur during this resuspension, especially in hypertonic systems. In these experiments, this small amount of haemolysis has been measured and allowed for; this entails an additional and obvious technical step not described in detail.
Made by Mr Paul Cutajar of the New York University machine shop. It resembles Castle’s mechanical fragility apparatus, but has the improvement that the constant speed of revolution can be varied through a ten-fold range.
* The increased ion exchange in hypotonic systems does not appear until tonicities are reached which are so low as to be nearly haemolytic (e.g. T=0·5). Davson (1937) described this effect of hypotonicity, which I was unable to reproduce at tonicities in the neighbourhood of 0-6 (Ponder, 1949). Davson’s explanation for the effect, which involved the conception of the cell membrane becoming permeable when stretched, cannot account for the fact that the relation between ion exchange and tonicity has a minimum value.
