Nucleoprotein Changes in the Gastrointestinal Tract Following Total-Body Roentgen Irradiation

This is the authors' abstract. We don't add key points for this paper.

This paper presents a cytochemical evaluation of the relative concentrations and a study of the interrelationships of the amounts of desoxyribonucleoprotein, ribonucleoprotein, and alkaline phosphatase in the destructive and reparative phases of the epithelium in the gastrointestinal tract of the rat following total-body irradiation by roentgen rays. Materials and Methods Male albino rats of the Slonaker strain weighing 200 ± 20 gm. were used. They were maintained on a known daily amount of Purina Laboratory Chow,2 allowed water ad libitum, and kept in groups of 3 in well ventilated wire cages. The source of the roentgen radiation was a G. E. Maximar Therapy Unit with 223 kv., 10 ma., and 0.5 mm. copper and 1.0 mm. aluminum filtration. The rats were given a single dose of 700 r total-body irradiation in groups of 6 at a target-skin distance of 50 cm. The average dosage rate was 34.5 r per minute measured in air. Groups of 3 rats each were killed with ether at intervals of one, two, five, ten, and fifteen hours and one, three, six, ten, fifteen, and twenty days after irradiation. Three non-irradiated animals were used as controls. It was noted that the irradiated animals voluntarily restricted their daily food intake by about 15 per cent the first five days after treatment. However, subsequent comparative histochemical studies of non-irradiated diet-restricted animals with normal controls showed no detectable differences. Immediately after death, four sections, from the mid third of the esophagus, stomach, and small and large intestine, respectively, of every animal were removed. Representative tissues were placed in three chemical fixatives (15): (a) Camoy's mixture, (b) 80 per cent alcohol, (c) formol-Zenker. The fourth group of tissues was prepared by the freeze-drying dry-mounting technic of Holt (12). All tissues were imbedded in Tissuemat3 with a melting point of 52–54° C. and cut to give sections 6 µ thick. The following cytochemical technics were employed: Nucleoprotein: The Feulgen method (15) was used for the demonstration of desoxyribonucleoprotein, henceforth called DNA. Material that gave a basophilic reaction following forty-five seconds exposure to a dilute solution of toluidine blue (0.5 per cent), and which could be digested out by prior incubation (8) (one hour at 37° C.) with 0.1 per cent ribonuclease,4 buffered with McIlvaine buffer at pH 6.8, was considered ribonucleoprotein, designated as RNA. Controls were simultaneously incubated for a similar time in the buffer, at pH 6.8, without the enzyme. Tissues fixed in Carnoy's mixture and prepared by the freeze-drying method were studied. Enzymes: Alkaline phosphatase reactions were done by the method of Gomori (11). Care was taken to use the same incubation time of thirty minutes on all tissues and to observe time limits in the procedure as recommended by Moe (17). Diffusion of the enzyme was considered minimal (18, 7, 26).