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Some Physiological Factors Related 

 to the Effects of Radiation in Mammals 



HARDIN B. JONES 



Donner Laboratory, Division of Medical Physics 



University of California 



Berkeley, California 



Initial Hyperemia and Blood Volume 



Irradiation of the mammalian organism induces a number of changes. 

 Some of these changes involve the circulatory system. An easily rec- 

 ognized vascular response is the radiation erythema which is apparent in 

 man during the first day following irradiation of the skin by a few hun- 

 dred roentgens of x-rays. Local irradiation with 800-1200 r produces 

 some hyperemia in rabbit skin, and at such sites there is increased 

 spread of intradermally injected Evans blue dye; also there is an ac- 

 celerated appearance of this dye in the hyperemic area when it is given 

 intravenously (1). These observations suggest a complicated vascular 

 response involving perhaps changes in tissue perfusion rate as well as 

 capillary leakage and increased movement of tissue fluid. There is no 

 indication of a change in blood volume (Evans blue method) in the 

 rabbit during the first 5 hr after irradiation (1). The initial hyperemia 

 of irradiation may be due to a local effect of the radiation on the small 

 vessels (1, 2). With severe local exposure there is often a bluish hue in 

 the hyperemic area which may be indicative of narrowing of parts of 

 the vessels as well as dilation and filling of other parts of the vessels 

 (2). With increasing radiation dosage to the skin there is more and 

 more permanent deformation of the vascular bed; the aftermath of ac- 

 cumulation of a few thousand roentgens is marked by the existence of 

 telangiectasis, which has been described as composed of capillaries of 

 the diameter of veins (3). The state is indicative of a severe disturb- 

 ance of the tissue vascular bed, and in spite of the ruddy appearance of 

 these areas the flow of blood through such tissue is probably inadequate 



for proper function. 



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