PHYSIOLOGIC FUNCTIONS 823 



of 300 r, a significantly greater sur\dval rate was noted in the case of 

 the supplemented rats, despite the fact that the linoleate-treated animals 

 received as much as 45% more x-irradiation than the control rats did. 

 More recently, Cheng et al.~^^ established the fact that the optimal daily 

 protective dose of linoleate for male rats against x-irradiation injury prob- 

 ably exceeds 100 mg. Thus, it was demonstrated that the average survival 

 period for LD25, LDsn, and LD75, were progressively greater when the pro- 

 tective dosages of linoleate were 10, 50, and 100 mg. per day. The bene- 

 ficial effect of fat in protection from injuiT due to x-irradiation has been 

 shown^^^ to obtain with widely vaiying doses of x-ray and with consider- 

 able variations in the frequency with which it was applied. Cheng et 

 al.^^^ later found that linoJenic acid afforded only slight protection against 

 x-irradiation when given in doses as high as 80 mg. per day to male rats. 

 On the other hand, when linoleate was administered simultaneously with 

 linolenate, a marked synergism was noted, ^" aswas also the case with growth. 

 The reason for the beneficial effect of the EFA against x-irradiation dam- 

 age can only be conjectured. Since there is some indication that linoleate 

 is required for the growth of new tissues, as well as for the repair of damaged 

 ones, the restitution of such injured tissues would proceed more rapidly 

 in the cases in which an adequate supph^ of EFA was available. The pri- 

 mary tissue injured by exposure to x-rays under most conditions is the skin. 

 Since it is known that the EFA are concentrated in the subcutaneous fat, 

 the protective effect of linoleate may be ascribable to the rapid local healing 

 afforded in the subcutaneous tissues; the variation in time required for 

 this process to take place with a high EFA storage, as compared with that 

 in an EFA-deficient animal, may spell the difference in survival in the 

 presence and absence of a fat which contains EFA. 



(J) Relation to Capillary FragiJifij 



Kramar and Kovacs-^^ were the first to call attention to the fact that the 

 capillary resistance of human subjects, especially of those with allergic 

 manifestations, was higher in patients who had received vegetable oils 



21' A. L. S. Cheng, M. Ryan, R. B. Alfin-Slater, and H. J. Deuel, Jr., /. Nutntion, 52 

 637-644 (1954). 



212 A. L. S. Cheng, R. B. Alfin-Slater, and H. J. Deuel, Jr., J. Nutrition, 54, 201-207 

 (1954). 



^^^ A. L. S. Cheng, T. Graham, R. B. Alfin-Slater, and H. J. Deuel, Jr., J. Nutritian, 65, 

 647-653 (1955). 



*'^ J. Kramdr and J. Kovdcs, Report presented at Annual Meeting of the Hungarian 

 Pediatric Society (June, 1939); cited bv J. Kramar and V. E. Levine, /. Nutrition, 50. 

 149-160 (1953), p. 149. 



