Variant clones were isolated from cultured Chinese hamster Don cells after treatment with irradiated 5-iodouridine. The following characters of a primary variant clone, C-11 and a secondary variant clone, C-24 were compared with those of the original clone C-1: colony-forming activity, growth rate in the presence of irradiated and unirradiated 5-iodouridine, distribution of chromosome numbers and cell cohesion. The variant clones C-11 and C-24 were partially resistant to unirradiated 5-iodouridine at lower concentration and C-24 cells were slightly resistant to short-term treatment with irradiated 5-iodouridine. Unlike clines C-1 and C-11 the variant clone C-24 showed no lag phase on growth in 5-iodouridine medium. The modal numbers of the chromosomes of all three clones were 22, like that of normal Chinese hamster diploid cells. Of the three clones, the variant C-24 cells showed the least mutual cohesion and the original C-1 cells showed the most. The possibility that an alteration in cellular membrane might be related to an increase in the resistance to radiosensitizing agents are discussed.

Animals↗

PubMed1975

Radiosensitization of cultured mammalian cells by 5-iodouridine.

Radiosensitization of cultured mammalian cells was studied with halogenated pyrimidines, such as 5-iodouridine or 6-chloropurine, which have been shown to promote bacterial cell lethality when combined with gamma-irradiation. When Chinese hamster cells were exposed to gamma-rays to acidic pH values and the number of colonies was scored after 6 to 11 days of incubation, many more cells were inactivated in the presence of the drug than in its absence. This may be due to radiation-induced cytotoxic iodine radicals from the reagent in the case of 5-iodouridine, because the cells were inactivated efficiently only be contact with the previously-irradiated drug solution. The toxicity of the irradiated drug solution increased remarkably when the pH shifted to acidic side. The radiosensitization and the cytotoxic effects of gamma-irradiated drug solution were not found with 6-chloropurine. This may be the first observation on the lethal effect of chemical radicals on mammalian cells, and it is concluded that radiosensitization with 5-iodouridine does not require the drug incorporation into cellular DNA, at least under the conditions adopted in the present studies.

Animals↗

PubMed1975

Changes of cheek pressure during swallowing following expansion of the maxillary dental arch in repaired cleft palates.

Cheek pressure during swallowing was measured on six operated complete cleft lip and palate cases (4-8 years of age) before and after expansion of buccal segments of maxillary arch. As control, seven non-cleft subjects with acceptable occlusion of the same age level were used. Before expansion, the pressures in the cleft cases were much higher than the controls. Immediately after expansion, increase in pressure was observed in cases which received rapid expansion. However, a few months after expansion, most cases showed a decrease in pressure. This is explained as being due to the adaptation of the perioral musculature to the expanded dental arch and/or the disappearance of hyperactivity of the perioral musculature during swallowing.

Amplifiers, Electronic↗

PubMed1975

[Tuberculosis of the small intestine].

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Adult↗