116 M. N. MEISSEL, E, M. BRUMBERG, T. M. KONDRATJEVA AND I. J. BARSKY 



the microscope objective) and then in transmitted liglit in order to 

 ascertain the character of the n.v. absorption l)y the separate com- 

 ponents of the object. The opaqne iUnminator over the objective had 

 two interchangeable beam splitters of which one was characterized by 

 high reflection of ulti'aviolet rays of wave-lengths 280 m//, or less and 

 by good transmission of longer wave-lengths. This splitter was nsed for 

 exciting and photographing the n.v. fluorescence of the specimen. The 

 second beam splitter reflected n.v. rays in the range 360 to 300 m//, 

 transmitting light of the visible spectrum. It was employed in studies 

 of visible fluorescence. 



Excitation and recording of the fluorescence of the object was carried 

 out with crossed filters. For u.v. fluorescence such filters were the 

 following: a quartz cell with chlorine and bromine gas filters mounted 

 between the light source and the microscope (transmits u.v. A = 250 to 

 260 m/f) and a Woods glass filter (transmits u.v. A = 340 to 380 ni/i) 

 moimted over the ocular of the microscope. Visible fluorescence of 

 fluorochromed objects was observed respectively with blue and yellow 

 filters. 



The microscope employed in the work was fitted A\'ith a quartz- 

 fluorite objective lens (58 x ) with an aperture of 0-8 (water immersion) 

 and with a 3 x quartz-fluorite ocular. Theexi^osure during photomicro- 

 graphy of the u.v. fluorescence was 10 seconds and of absorption 2 to 3 

 seconds. 



In a numl)er of cases the specimens were preliminarily fluorochromed 

 with very dilute solutions of acridine orange (I : 10^). Such treatment 

 did not interfere with the photography of ultraviolet fluorescence in- 

 asmuch as acridine orange fluoresces only in the visible region. At the 

 same time fluorochromed objects, particularly blood and bone-marrow 

 cells and micro-organisms are more easily identified and discrimin- 

 ated and also focused better during subsequent photography in u.v. 

 light. 



A brief general account will now be given of the results of u.v. 

 fluorescence studies of normal and irradiated cells arising from the 

 joint work of Brumberg, Barsky, Kondratjeva, and their collaborators 

 (I960) and of these authors in collaboration with Meissel and Gutkina. 



Ultraviolet autofluorescence has been revealed under normal con- 

 ditions in cells of the most varied types and origins, l^eginning with 

 micro-organisms (bacteria, yeasts) and including the cells of higher 

 animals and man. The fluorescence is particularly noticeable in cells 

 cultivated in vitro (cells of human amnion, of monkey kidney, of HeLa 

 tumour), in the cells of Ehrlich's ascites tumour and of a number of 

 other tumours. 



