[Ultrastructural changesin acrosomes and mitochondria of bull spermatozoa incubated in vitro]

The structural changes on the acrosomes and mitochondria of bull spermatozoa incubated at 37 degrees C for 1/2--6 hours are described in this paper. The spermatozoa were examined by means of a transmission electron microscope. The changes of the acrosome manifest as acrosome swelling, as the loss of acrosome matter, and as a disintegration of the external acrosome membrane. The internal acrosome membrane remains preserved. The cytoplasmatic membrane of many spermatozoa swells and, later, disintegrates, first over the acrosome and in the middle part of the flagellum. The changes of mitochondria manifest in a decrease of the density of the mitochondrial matrix and in a disintegration of mitochondrial septa. A fibrous material fills the mitochondria, instead of the septa. Some mitochondria lose their content entirely. The described changes are of degenerative character. Despite this, a certain amount of spermatozoa showing such changes on the acrosome and on mitochondria can be found even in fresh semen. The author described other structural changes of mitochondria similar to the changes first described by Hackenbrock (1969) in isolated mitochondria of liver cells. It is assumed that these structural changes of spermatic mitochondria are not of degenerative character and reflect the state of their metabolic activity.