DNA strand breaks in human sperm cells: a comparison between men with normal and oligozoospermic sperm samples. 
The aim of this report was to compare the degree of DNA strand breaks in known normal fertile men to those with oligozoospermia, and evaluate the presence of DNA strand breaks in normal raw sperm, after Percoll and swim-up and following conventional cryopreservation, as all these preparation methods might differ in selection of healthy sperm cells.  Sperm samples from proven fertile sperm donors (n=20) and infertile men with oligozoospermia (n=33) were tested for the presence of DNA strand breaks in the spermatozoa, by direct immunoperoxidase detection of digoxigenin-labeled genomic DNA.  A correlation to other sperm parameters, sperm counts, motility and Krüger's strict criteria was performed.  DNA strand breaks were found significantly more often in sperm samples from men with oligozoospermia compared to sperm samples of normal fertile men.  The degree of spermatozoa with DNA strand breaks was correlated proportional with the degree of morphological pathological sperm cells judged by Krüger's strict criteria.  The percentage of spermatozoa with DNA strand breaks in the samples was not influenced by procedures such as the swim-up technique, Percoll gradients or cryopreservation and thawing.  DNA strand breaks were found significantly more often in men with oligozoospermia compared to normospermic men.  The DNA strand breaks might play an important role for the maturation process of the spermatozoa in the same way as apoptosis is controlling the number of early meiotic germ cells in the testis, and hereby play an important role in advanced fertility treatments (ICSI).