Search

Rats developed an avoidance to a previously preferred saline solution (0.8%) when the solution was drunk during nonlethal ionizing irradiation, and response to a control saline solution (0.002%) was not affected. Rats given the control solution with irradiation, given irradiation alone, given the preferred solution alone, or given neither irradiation nor solution all maintained the initial preference. Effectiveness of the irradiation was dependent on the initial preference strengih. Rats with lowest initial preference were significantly more likely to develop the avoidance. The response measure was the number of tongue licks and was recorded electronically. The results support a conclusion that ionizing radiation can serve as an unconditioned stimulus in a classical conditioning framework although used in temporal intervals of hours rather than seconds. (auth)

Male Sprague-Dawley rats, individually caged, were exposed to low-level irradiation with chronic dosages from a Co/sup 60/ source for 16 hours a day. The animals were selected by weight and growth rate and divided into eight groups of 22 rats. Four groups were kept at 28 cores consistin 1 C and were exposed to 0.29, 0.64, 2.60, and 4.18 r/day during the irradiation period, which lasted from 4 months of age to 16 months of age. The other groups were kept at 35 cores consistin 1 C during the period of irradiation, which lasted from 4 months of age to 16 months of age, and were exposed to 0.28, 0.60, 2.57 and 3.96 r/day. At 35 C the ET/sub 50/ for 0.29 r/day was 310; for 0.64 r/day it was 490; for 2.60 r/day it was 540; and for 4.18 r/day it was 510. At 28 C the ET/ sub 50/ for 0.28 r/day was 493; for 0.60 r/day it was 510; for 2.57 r/day it was 650; and for 3.96 r/day it was 590. With the exception of the relation between 0.60 and 0.28 r/day, the data are statistically significant at the 5% level. From a previous experiment atmore » 26 C the ET/sub 50/ for 0 r/day was 445, and for 0.8 r/day it was 585. It is suggested that the effects of ionizing irradiation interact with the effects of environment in influencing longevity. (auth)« less

Female offspring of gravid rats administered a single dose of 200 R of ionizing irradiation on Gestation Days 17, 19, or 21 remained significantly more active than similarly treated males. Both groups increased their activity over control levels with a lesser effect in evidence for 17 and 21 day males. Day 19 males were. unexpectedly, as active as the comparable female group.

In the course of routine screening of randomly selected chemicals for radiomodifying activity in microbial systems, a number of compounds have been demonstrated to sensitize bacteria, especially Escherichia coli, to the lethal action of ionizing irradiation (Co60). The compounds reported here are: NSC 45133: Isoindolinium,2-(3-dimethylaminopropyl)-3a,4,7,7atetrahydro-2-methyl-iodide, methiodide CH3 I+ [j [ -CHf-CHi-C CHj-N-CH3 2I CH3

noxious stimulus (irradiation) preceded the administration of the saccharin. Since conditioned avoidance responses to other noxious stimuli have never been reliably demonstrated in this paradigm (9), the possibility exists that the conditioning was due to a pairing of the preferred solution and a noxious stimulus other than the irradiation. The experimenters hypothesized that this might have been a physiological disturbance resulting from the irradiation which would have been temporally coincident with the saccharin presentation.

New Zealand rabbits, fasted for 12 hours, were subjected to 500 rads of whole-body irradiation. Analysis of thymus lipids, at various time intervals following irradiation, showed a threefold increase of triglycerides at 24 hours. Fatty acid composition of the 600 × g supernatant was not affected at 24 hours after irradiation. Lipid biosynthesis from $\text{acetate-}1\text{-}{}^{14}{\rm C}$ by the thymus homogenates was increased to a small extent at 4 hours following irradiation, while the radioactivity distribution into fatty acids was not considerably affected. Contrary to the above findings, fatty acid synthesis from $\text{acetate-}1\text{-}{}^{14}{\rm C}$ by the liver preparations showed a decreased incorporation between the fourth and twelfth hour following irradiation. Counting of the radioactivity of the separated fatty acids suggested that the system for synthesis of short-chain fatty acids was impaired as early as 4 hours following irradiation.

New Zealand rabbits, fasted for 12 hours, were subjected to 500 rads of whole-body irradiation. K+-palmitate-1-14C oxidation was assayed with the 600 X g supernatant of thymus and liver homogenates, in the presence of ATP, at various time intervals from irradiation. For a period of 24 hours following irradiation, oxidation by liver preparations was not significantly affected. The rate of oxidation by thymus was decreased to less than one-third of the control value within 12 hours from irradiation and, at 24 hours, was almost completely abolished. Increased ATP concentration could increase only to a small extent the oxidation by thymus preparations of irradiated animals. Oxidation by isolated thymus mitochondria was also inhibited by irradiation. Counting of the water-soluble oxidation products of palmitate-1-14C suggests that the inhibition is not due to the impairment of the reactions of the citric acid cycle. The non-esterified fatty acid concentration of thymus was not altered at 12 hours following irradiation. Esterification of K+-palmitate-l-14C into the thymus lipids was not affected 12 hours after irradiation.