Erratum

Induction of Radioresistance in Mouse Colon Crypts by X-rays

“…The surviving crypts seen five days after irradiation branched and the number of survivors was increased by the end of five weeks . However, the number of crypts in the irradiated area did not return fully to that found in the descending colon of unirradiated mice (Hamilton 1978) . The surviving crypts, five days after each dose, were therefore compared with the number in mice killed six weeks after the previous dose.…”

“…Fewer colon crypts survived after whole-body irradiation (see figure 2) than after irradiation of the colon alone (see figure 1) in both `normal' and `conditioned' mice . The decreased effectiveness of partial-body irradiation for crypt killing has been investigated in detail (Hamilton 1977) . Figure 2 shows that more crypts survived doses of over 1200 rad whole-body irradiation in `conditioned' than in `normal' mice .…”

“…If the crypt stem-cell population consisted of only two or three cells, the chance of their all being lost in normal cell migration might be quite high . It has been suggested that the cryptogenic cells lie near the top of the proliferative zone and are regularly renewed (Hamilton 1979) . …”

“…The mice were shielded so that only a 2 cm length of the descending colon was irradiated, in situ (Hamilton 1977 Correspondence given a dose of 1250 rad 220 kVp X-rays, in an atmosphere of 95 per cent oxygen, 5 per cent carbon dioxide . Six days after the first irradiation, the back of each mouse was plucked by the plastic dressing technique (Potten 1972) .…”

“…The descending and transverse colons were removed and fixed in 3 : 1 ethanol : acetic acid . Sections were cut from four different levels of the descending colon (Hamilton 1977) so that the repeatedly irradiated area could be identified . The number of surviving crypts per circumference was counted in four haematoxylin and eosin stained sections from each mouse .…”