CFW Mice Research Articles

Effect of Roentgen Therapy on Mouse Encephalitis

Since 1929, investigators have reported varying degrees of success in treating acute encephalitis and poliomyelitis with x-rays (1–6). In spite of claims for high beneficial results, it has been pointed out (7) that there is much difficulty in evaluating any treatment of acute diseases which, if they do not lead to death, usually result in recovery. Only two records of controlled animal studies were found (8, 9). Goldberg et al. (8) reported on the effect of x-ray therapy on mice experimentally inoculated with St. Louis encephalitis virus. In mice inoculated intranasally, the results were striking, but in animals inoculated by intracerebral injection, there was no appreciable difference in survival between the treated mice and the infected controls. Experimental Methods Virus: A pool of Theiler's FA mouse encephalitis virus2 was obtained by passage of glycerinated mouse brain extracts into 48 CFW mice.3 The mice were sacrificed as soon as they showed clinical symptoms of encephalitis. Their brains were removed and ground in a mortar, with sterile alundum as an abrasive. Sterile saline was added and a 20 per cent emulsion was prepared. The emulsion was centrifuged for ten minutes at 1500 r.p.m. The supernatant fluid was decanted, mixed, and placed in 1.0-c.c. vials. The vials were sealed and placed in a deep-freeze chamber (−70° C.). Roentgen Therapy: In order to limit irradiation to the skull, a simple technic was used. Glass test tubes were cut to a desired length (8.0 cm.). A hole (2.0 cm. in diameter) was made near the closed end of each tube. Scotch tape was placed over the opening, and the remainder of the tube was wrapped with lead foil. The mice were placed in the tubes and cork stoppers adjusted behind them so that only the heads were exposed to radiation through the tape-covered hole. The exact dosage was determined by inserting a Victoreen ionization chamber into the tube beneath the covered portal. Total body irradiation was attained by placing the animals in a low cloth-covered box and allowing them to run at will beneath the x-ray beam. Effect of X-rays upon Mice: To determine the toxic effect of the x-rays upon mice, groups of six-week-old mice were subjected to 50 r daily over the entire body for six days, 200 r daily to the head only for three days, and 100 r over the head only for six days. The factors were 90 kv.p., 7 ma., 16 inches distance, and 2.0 mm. A1 filtration; half-value layer 2.25 mm. A1. Thirty-two mice were used in the above series: 6 died of a diffuse pneumonitis that was demonstrated at autopsy. Deaths occurred at irregular intervals and were not related to dosage of x-rays. One mouse died of unknown causes on the twenty-sixth day. None of the fatalities could be attributed to radiation. Results Titration of Virus: The results of titration of the FA strain of mouse encephalitis virus appear in Table 1. The LD 50 dose was contained in 0.03 c.c. of a 10−8 dilution of virus.

EPIDEMIC DIARRHEAL DISEASE OF SUCKLING MICE

Four strains of mice-Harvard, Schwentker, CFW (Carworth Farms), and C (National Cancer Institute)-have been kept and bred underidentical conditions over the course of a year in order to determine the effect of strain, of litter, and of season upon the incidence of diarrheal disease among the suckling mice. 1. Significant strain differences were limited to CFW mice. A consistently lower percentage of these mice were weaned in comparison to the others. 2. The effect of litter was definite and consistent: In all four strains first litters fared worse than second and third ones, while fourth and fifth litters showed the highest percentage of mice weaned. 3. The effect of season seemed clear cut only in the case of one strain CFW; the highest percentage of mice weaned were observed during the summer months and the lowest during the autumn and early winter.