Serum-induced head-to-head agglutination of bovine spermatozoa.

Addition of cow serum to diluted bull spermatozoa induced marked head-to-head agglutination which declined during incubation for 9 hr at 37 degrees C. Maintenance of the acrosomal cap during incubation was not adversely affected by serum. Agglutinating cells were those with intact acrosomal and cell membranes, as determined by differential interference-contrast and electron microscopy. Single cells in the same treatment groups experienced more rapid acrosomal deterioration than did untreated spermatozoa. Ultrastructurally, agglutinated cells were associated by a close apposition of the cell membranes in the acrosomal region. Structural integrity of the cell membrane and acrosome of agglutinated cells was the same after 9 hr of incubation as at the onset of the incubation period.