"Young adult C57BL/6N (females) and C3H/HeN (males) mice, 7–8 weeks of age at delivery, were purchased from Charles River Deutschland, Sulzfeld, Germany, to produce B6C3F1 descendants at the Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM). After the acclimatisation period in the animal facility, healthy parental animals were randomised by weight into groups using a computer-program (Provantis 7, Instem Computer Systems, Stone, UK) and were mated at 10 weeks of age (ratio: 3 f/ 1 m, day 0 p.c. [post conception] determination by vaginal plug control). (Sham-)exposure of the plug-positive maternal mice started on day 6 p.c., while the maternal ENU treatment (40 mg ENU/kg body weight intraperitoneal; ENU supplier: Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany) was carried out on day 14 p.c. Each treatment group consisted originally of up to 20 maternal mice and their litters. After the first week of lifetime, litter standardisation (allocation by chance after sexing the descendants) was performed and afterwards per cage 3 female offspring and their mothers were maintained per cage up to the weaning time point (Figure 1). After weaning, maternal mice were removed from the cages. The carcinogenesis study was conducted using the 3 remaining female descendants per cage. The above-mentioned number of 60 F1 mice was reduced in two groups (Table I) due to 1–2 non-pregnant maternal mice, as the premature/early exposure start required a pregnancy diagnosis on day 6 p.c. In total, five treatment groups were used in the study: three were housed in different decks (and different RF power density groups) of the exposure device (one of them with additional maternal ENU treatment), and two control groups (positive control with ENU treatment and an untreated cage control group) were also maintained in the same animal room (monitored standard laboratory conditions: temperature: 20 + 28C, relative humidity: 40–80 %, 12-h light/dark cycle, air exchange rate: 10–15 times per hour) in the conventional area of the animal facility. Mice were housed in Makrolon1 (polycarbonate) cages (type II: 350 cm2) or in client-specific trapezoidally shaped polycarbonate cages (ground area: 373 cm2; both cage types supplied by E. Becker & Co. GmbH, Castrop-Rauxel, Germany), specially constructed for space-saving maintenance in the exposure device (Figure 2). Absorbent softwood was used as bedding material in the cages (‘ssniff bedding 3/4’, ssniff Spezialdia¨ten GmbH, Soest, Germany). A pelleted chow, identified as ‘ssniff V1534’, was used as standard diet during the course of the study, with the exception of the six-week breeding period, when an enriched diet, identified as ‘ssniff V1124’, was offered, both supplied by ssniff Spezialdia¨ten GmbH, Soest, Germany. Drinking water from the Hannover city water supplier (Stadtwerke Hannover, Hannover, Germany) was offered fresh weekly in Makrolon1 bottles ad libitum. All mice were checked at least once a day for clinical symptoms, morbidity, or mortality. In addition, the health status of the animals was monitored by sampling sentinel mice during the total course of the study. Starting at five weeks lifetime, individual body weights were recorded to the nearest 0.1 g weekly during the first 13 weeks and then every four weeks until study termination. All weight data were collected by on-line data acquisition (Provantis 7)."

P0, C57BL/6N mice, female

HAWC