The Effect of Local X-Ray Irradiation Upon the Teeth of the Adult Axolotl (Siredon Mexicanum)

Abstract

DESPITE great differences between mammals and urodele amphibians, the effects of x-rays upon these two groups are similar (Brunst, SheremetievaBrunst, and Figge'). Because their tooth development is also similar, an investigation of the effect of x-rays upon the teeth of urodele amphibians is of interest also in human stomatology.In a previous investigation, Brunst, and Figge2 found that in young axolotls (the larval form of the Mexican salamanderSiredonn mexicanum) the mechanisms of tooth formation and tooth maintenance are permanently destroyed by local x-ray irradiation.The importance of age as a factor in the radiosensitivity of animals is a well-established fact. In general, the older the organism, the less its radiosensitivity. The radiosensitivity of young axolotls was investigated by Sheremetieva.3 According to this author, 150 r is the lethal dose for freshly hatched axolotls, all of which died within one year; however, some animals irradiated with this dose 6 days after hatching lived 3 years. The lethal dose for 100 per cent of the animals irradiated 20 days after hatching is 300 r, and for animals irradiated 30 days after hatching it is 450 r.An investigation of the x-ray sensitivity of adult axolotls (Brunst4) showed that their mean survival time after total body irradiation was as follows: after 6,000 r, 28 days; after 3,000 r, 44 days; after 1,000 r, 55 days. A dose of 500 r killed about 50 per cent of the animals; their mean survival time was 196 days; the remainder recovered, and some lived more than 2 years after irradiation.An investigation of the effect of x-rays on the head of young axolotls (Brunst5) showed that the dose of 3,000 r was lethal in all cases if the whole head was irradiated (all animals died within 6 months after treatment). However, if only the anterior portion of the head, back to and including the eyes, was irradiated with 3,000 r, some animals lived more than 20 months.The purpose of this work was to investigate the effects of local x-ray irradiation on the teeth of the adult axolotl. MATERIAL AND METHODSThirty adult axolotls, 4 to 5 years old, were used. Ten animals served as untreated controls. The anterior portion of the head of 20 animals was irradiated with 6,000 r. Irradiation conditions were: 250 kv., 30 Ma., 0.25 mm.