specialized Microscopy 101 



ultraviolet and thereby reveal structural differences in a photographic 

 image without the use of stains. The specimen must be moimted in a 

 nonfluorescent mediimi: water, glycerol or mineral oil. Glass fluoresces 

 and will reduce contrast and possibly obscure some detail in the speci- 

 men, so quartz cover glasses and slide should be used for best results, also 

 fluorescent-free immersion oil. 



Resolution is increased over that of the conventional microscope and 

 differences in structure in the specimen are enhanced by the idtraviolet 

 absorption. The technique is not complicated, nor expensive. 



But for greater resoliuion and higher selective absorption, a quartz 

 ultraviolet microscope is better than the above. It is, ho^vever, more 

 difficidt to haiidle and focus, also more costly. The quartz microscope 

 is equipped with ftised quartz objectives, crystalline qtiartz eyepieces, 

 quartz substage condenser, and quartz right angle prism. Quartz slides 

 and cover glasses shoiUd be used. The light source must be ultraviolet. 



Some cells are immune to ultraviolet, others are only mildly affected 

 and can be used with excellent results imder this microscope. But in 

 the case of those that are killed by ultraviolet, formation of artifacts 

 should be expected. Because of the possibility of damage to these cells, 

 focusing can be done with visible radiation and then ultraviolet used 

 only during photography or photoelectric measuring. Tissue cannot 

 be fixed for ultraviolet — this decreases absorption — but ice solvent or 

 freeze dry techniques can be used. Ultraviolet photomicrographs are 

 difficult to interpret at times and require considerable experience. 



The idtraviolet microscope, therefore, has become a useful instru- 

 ment for measuring the selective absorption of cellular components 

 (measured at specific wavelengths). Its chief uses have been for the 

 measurement of cellidar concentration and localization of nucleic acids, 

 RNA (ribonucleic acid) and DNA (desoxyribonucleic acid) content, ob- 

 servations on normal and neoplastic (tumoring) tissue (in the latter the 

 nuclear RNA content is high). Some substances can interfere ^vith such 

 observations. Perhaps among the more interesting are the barbiturates, 

 which absorb heavily and should not be used for sedation or anesthesia 

 in animals to be prepared for this technic. 



Fluorescent Microscopy 



An object fluoresces when it absorbs ultraviolet light reflected on it or 

 transmitted through it and then emits the energy as visible light of a 

 specific violet, blue, green, yellow, orange, or red color. Secondary flu- 

 orescence can be induced by the use of fluorochromes (strongly fluores- 



