"Experimental Design

This study was performed simultaneously with another study in which the possible effects of extremely low-frequency (ELF) magnetic fields on

carcinogenesis were evaluated (22). The two studies had a common cage control group. The animals in the cage-control group were housed in the same animal room but they were not handled daily like the animals exposed to sham RF radiation and RF radiation. Because it was not possible to obtain all the animals (all together 300 mice, of which 200 were used in this study) at the same time, the study was staggered to start in four phases over 2 months. Animals in each phase were divided into blocks by the week of birth. In each phase, an equal number of mice were allocated to each of the treatment groups by randomization. Each treatment group consisted of 50 animals in eight cages (Table 1). The mice in each cage were checked daily. Once a week the animals were observed in detail for clinical signs. The food and water consumed per cage was recorded for 2 days every second week. All animals were weighed at the start of the study, weekly for the first 4 weeks, and every second week thereafter. The 6-hydroxymelatonin sulfate (6-OHMS), the main metabolite of melatonin, was analyzed in urine after 519 days.

These results are reported elsewhere (23). The study lasted for 78 weeks.

Exposure to Ionizing Radiation

Every group, except the cage-control animals, was exposed to ionizing radiation at the beginning of the study. The total-body dose was 4 Gy delivered as three equal fractions of 1.33 Gy at 1-week intervals with linear accelerators (Philips SL 75-5, 4 MV photons, or GE/CGR Saturne III, 6 MV photons). The animals were transported for the irradiations in the filter boxes in which they were irradiated at the Department of Radiotherapy, Kuopio University Hospital. To ensure a uniform irradiation of the whole body, a Plexiglas scatterer was placed 15 cm above the animals. Due to a misinterpretation of the intended dose, the second fraction for the first 13 animals/group was delivered in two parts (0.4 Gy and 0.93 Gy). The dose rate was 0.51 Gy/min. For started on the day of exposure to the first (day 0).

Exposure to 900 MHz RF Radiation

Three identical rectangular waveguide chambers were used in the study: one for the sham RF-radiation the continuous RF-radiation exposure, and one exposure. For the continuous RF group, phone for the analog Nordic Mobile Telephones/was used as a signal source. The phone operated at 902.5 MHz. For the pulsed RF group, a modified computer-Global System for Mobile (GSM) network was MHz with a pulse frequency of 217 Hz (duty simulated by modulating the carrier with a random The signals were amplified by boosters manufactured Rohde & Schwarz NAS-Z7 RF power meters the input, reflected and output power of the exposure input powers were 6.1 ± 0.8 W (W for the continuous-RF and pulsed-RF group, power was absorbed by a coaxial 10 W termination. group was kept in an unenergized waveguide to RF radiation started on day 1.

The exposure chamber consisted of a straight of two waveguide-to-coaxial adapters (Fig. 1). absorption, the mice were kept in small (inner diameter 32 mm, length adjustable). the mice from aligning their longitudinal field, which would have increased the absorption restrainers allowed a slight movement, and the around, with the exception of some large mice The restrainers were placed on a Styrofoam mouse was in the center of the cross section longitudinal axis perpendicular to the electric the propagation of the RF power. The distance from the waveguide posts was more was sufficient for the decay of any higher-order vicinity of the posts. The distance between adjacent configuration allowed the exposure of 25 mice so each group of 50 animals was divided into exposure sessions. The mice that were entered phases were exposed in one session and the rest exposure for both the groups and the sessions The mice that died or were killed during the were replaced with mouse phantoms. Phantoms weeks in the beginning, and again at the end of mice entering or leaving the study in a different made of plastic cylinders partly filled with a (53.6% by weight), sugar (45.0%) and salt (1.4%). The solution simulated the dielectric properties of muscle at 900 MHz (24). Styrofoam was used at the bottom of the cylinders in phantoms simulating small mice. "

CBA/S mice, female

HAWC