1156 BIOLOGICAL EFFECTS OF RADIATION 



point where more than 88 per cent change liad taken place, and it was due 

 apparently "to the influence of the ultra-violet radiation alone." 



Fuller (24, 24a) irradiated solutions of Taka diastase and Difco 

 invertase for 30 min. periods in open Petri dishes at a distance of 10 in. 

 from a quartz-mercury-vapor arc. Experiments were also made with 

 the infra-red present and with these rays screened out incompletely by 

 a quartz cell with 1.5 cm. water. Intensity measurements of the light 

 source were made with a thermopile and galvanometer, but absorption 

 of the enzyme solutions was not determined. The attempt was also 

 made to study the effects of radiation on enzymes in living plants. The 

 tissue extracts of the irradiated and nonirradiated plants were then 

 tested for enzyme activity. The Taka diastase and Difco invertase 

 suffered partial inactivation when irradiated in vitro with ultra-violet 

 and infra-red light, but in the living plant such was not the case. In 

 the living plant, with the intensities used, the activity of the four enzymes 

 was apparently increased, although the plants were severely injured, 

 and it should be observed that the control plants were not strictly 

 "control." Mycelium of a Fusarium was killed by similar irradiation, 

 but the activity of its amylase and peptase was sHghtly increased. Fuller 

 concludes that injury of living tissue by irradiation is due to some other 

 factor than the inactivation of these enzymes. Increased activity of the 

 blood diastase and of catalase of irradiated young dogs was reported 

 by Karapetjan (44), but this indirect effect did not extend to lipase. 



Hutchinson and Ashton (38) determined the effects of full radiation 

 from a mercury-vapor arc and also individual wave-lengths as trans- 

 mitted by a monochromatic illuminator on the diastases of saliva and of 

 malt. Full irradiation retarded the dextrinogenic and saccharogenic 

 activity of both salivary and malt diastase in an inverse relation to light 

 intensity. In the case of salivary diastase, they report the rates of dextrin 

 production and of maltose production decreased by the green and the far 

 ultra-violet, while there was apparently stimulation with the red-yel- 

 low and the near-ultra-violet wave-lengths. On malt diastase mono- 

 chromatic radiation was generally inhibitory for the dextrinogenic phase 

 and stimulatory for the saccharogenic phase. These results may be 

 explained by the presence of two enzymes constituting the diastase, one 

 dextrinogenic, the other saccharogenic ; either may be the less active and 

 so become the "pace setter" for maltose production. In salivary diastase 

 the dextrinogenic enzyme is the pace setter, while in malt diastase the 

 saccharogenic enzyme is usually the pace setter; full illumination, how- 

 ever, retards the dextrinogenic enzyme until it becomes the pace setter. 



Pincussen and Hayashi (67^ exposed serum lipase from rabbits and 

 guinea pigs to a quartz-mercury-vapor arc, and found that definite injury 

 occurred at acid pH values, but the injury was practically nil at alkaline 

 pH values. 



