Motility Studies of Large Cells

Abstract

Most of us in the light scattering discipline are familiar with the general characteristics of autocorrelation functions obtained from motile cells. First of all the decay times of these functions are 10 to 100 times shorter than would be expected from diffusing particles of the same size. Secondly the functions, especially those determined at low scattering angles, exhibit a shoulder in the first few channels before they tail off to background. Beyond this, however, there is a tremendous variation in decay times and shapes of correlation functions from one motile system to the next. In the case of bull spermatozoa one often sees significant changes from one sample to the next. Figure 1 shows the electric field autocorrelation functions (dots) from four different bull semen samples. Over the years we have learned that the source of these variations is the presence of differing relative populations of three classes of spermatozoa within the samples. The first class is most common, namely the normal motile spermatozoa. These cells are beautiful to watch by slow motion cinematography.