Testicular and epididymal sections from 29 prepubertally irradiated and 6 control monkeys were studied. In the Biomedical Primate Research Center at Rijswijk (BPRC), The Netherlands, these monkeys had been used in experiments to study the feasibility of ways to improve bone marrow transplantation. Ultimately, these monkeys were killed to study the longterm effects of irradiation on a number of organs, including the testis. The testes and epididymides were taken out and weighed separately. Subsequently, one quarter of each testis and all epididymides were fixed in Bouin fluid for histological examination. Another quarter of the testis was used to make air-dried meiotic chromosome preparations and was analyzed for abnormal pairing configurations indicative for the presence of reciprocal translocations.
All animals in the present study were bred within the BPRC colony and kept under identical housing conditions. They were fed commercial food pellets (Hope Farms, Woerden, The Netherlands) and a diet of fresh fruit and vegetables. The animals were procured, maintained, and used in accordance with Dutch law and regulations. The Animal Care and Use Committee and the Animal Ethical Committee approved all experiments.
Irradiation Procedures and Additional Treatments
The majority of the irradiations was performed with x-rays from a Philips-Muller generator (Philips, Hamburg, Germany) (300 kV; 10 mA; half value layer, 3 mm Cu) at a mean dose rate of 0.3 Gy min-1. During the irradiation procedure, the animals were conscious and placed in a cylindrical polycarbonate cage. The cage was rotated slowly along its vertical axis to improve homogeneity of the irradiation. Details on the dose distribution over the animals have been described elsewhere. Some animals were irradiated with 6 MV x-rays produced with a Mullard accelerator (Philips, Surrey, U.K.) at a similar dose rate as that applied for the orthovolt x-rays. The relative biological effectiveness of 6 MV x-rays, as measured for hematopoietic stem cells, is 0.9. The irradiated monkeys received supportive care or, for doses of 7 Gy or higher and two fractions of 6 Gy each, an additional treatment. Additional treatment consisted of either cytokines-only or bone marrow transplantation or both cytokines and bone marrow transplantation. Cytokines used were human granulo-cyte-macrophage colony-stimulating factor, rhesus monkey interleukin (IL) 3, or rhesus monkey IL-6 for approximately 14 days.