FLUORESCENCE STUDIES OF NUCLEOPROTEINS 113 



It was very interesting to ascertain whether the character of the ii.v. 

 fluorescence of organs, tissues and cells changes under the influence of 

 ionizing radiation. This was studied at organic and cellular levels. In 

 the jDresent section we shall dwell only on the former. Khan-Mago- 

 metova et al., (1960) recorded the integral u.v. fluorescence spectra 

 obtained from considerable areas of organs without taking into account 

 the complexities of their tissue and cellular patterns. Thin sections of 

 the organs of an animal (rat) or an homogenate were prepared on a 

 freezing microtome. Blood plasma was also investigated. The homo- 

 genate of the organs, and the blood plasma, wei'e placed in a special 

 quartz cell 0-8 mm high, owing to which the objects under observation 

 were all of constant thickness. Measurements of fluorescence were 

 made with the aid of a photoelectric microspectrofluorometer designed 

 by Agroskin and Korolev. The light source was a mercury arc lamp 

 (DRSh-lOO) from the spectrum of which separate sections were iso- 

 lated by means of a mirror monochromator with a diffraction grating. 

 Rays coming from the monochromator were further passed through 

 chlorine and bromine gas filters (when working in the region of 260 to 

 280 m/(). The fluorescence spectra were analysed by a similar mono- 

 chromator at the entrance slit of which a tenfold enlarged image of the 

 object under investigation was produced with a quartz -fluorite micro - 

 objective. The light intensity was determined by the magnitude of the 

 signal from a photomultiplier mounted at the exit slit of the mono- 

 chromator. Measurements were recorded as a deflection of a mirror 

 galvanometer. The data were analysed in corresjiondence with the sj)ec- 

 tral sensitivity of the system micro-objective-monochromator-receiver. 



The ultraviolet fluorescence -peak of the organs investigated lies in 

 the region of 320 to 330 m^. Short wave u.v. irradiation causes a definite 

 decrease in the fluorescence intensity and a gradual shift of the peak 

 in the direction of the longer wave-lengths. With decrease in intensity 

 of the initial peak there is an increase in intensity of a new peak of 

 longer wave-length. This effect is undoubtedly due to active photo- 

 chemical jDrocesses. 



The fluorescence spectra of the organs of animals given whole-body 

 irradiation with X-rays at doses of 1,000 r did not differ significantly 

 from those of controls. However the intensity increased markedly in the 

 radiosensitive organs (bone-marrow, spleen, lymi^h nodes) and in the 

 blood plasma (as tested 4 and 24 hr after irradiation (Fig. 3)). 



At present it is difficult to explain the increase in intensity of u.v. 

 fluorescence of the radiosensitive organs. Perhaps this is associated 

 with changes in the nucleoproteins or other proteins in which cyclic 

 amino acids are liberated. 



