AUTORADIOGRAPHY 



>^>.-^^ 



^'^:;mt 



PARTICLE REACTION 



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Fig. 15. Microscopic autoradiographic re- 

 sponse of leaf exposed to fission products. Specific 

 spot grain responses indicate that some of the ma- 

 terial was in particulate form. 



omitted. Among them is the classical work 

 involving plutonium deposition in the bones 

 of dogs administered plutonium. This is 

 the excellent work of Jee (12) in which the 

 results of autoradiographic methods involv- 

 ing hard bone are discussed in detail. 



Autoradiographic techniques have been 

 applied to electron microscopy. O'Brien and 

 George (13) have examined sectioned yeast 

 cells, previously suspended in a Po^^*^ solu- 

 tion. In this case the specimen grids were 

 coated with the emulsion by touching them 

 to a drop of diluted NTA emulsion. Borasky 

 and Dockum (14) examined Pu^^^ particles 

 contained in an aerosol sample collected on 

 "Formvar" coated grids. The grids bearing 

 the particles were chrome-shadowed and 

 placed on "Lucite" plugs held upright in 

 wells drilled in a metal block. A small wire 

 loop was placed in diluted NTA gel emulsion 

 and retracted, thus forming a very thin layer 



of emulsion. The loop bearing the emulsion 

 was then lowered over the specimen grid and 

 the loop retrieved by lifting the plug and 

 withdrawing the loop from beneath the plug. 

 The grids were exposed for 4 hours in a light- 

 tight box when high activity specimens were 

 examined. The emulsion-coated grids on the 

 "Lucite" plugs were immersed in D-19 de- 

 veloper for 5 minutes, then washed in dis- 

 tilled water for one minute, after which they 

 were fixed in liquid x-ray fixer for 3 minutes, 

 washed and dried. The individual grains of 

 the alpha tracks could be plainly seen when 

 examined by an RCA EMU-2C electron 

 microscope. The point of origin of the tracks 

 was located by the shadow cast by the Pu^^^ 

 particle. 



George and Vogt (15), using unshadowed 

 grids, examined plutonium particles collected 

 on millipore filters, and prepared electron 

 micrographs of selected areas of particles 

 before and after autoradiography, thus dif- 

 ferentiating radioactive from non-radioac- 

 tive particles. 



It is probable that small cubes of tissue 

 of approximately 150 microns could be infil- 

 trated in diluted gel emulsion long enough 

 to penetrate the tissue. These small cubes 

 could be exposed for the desired amount of 

 time, developed by the Temperature Devel- 

 opment Method, after which the cubes 

 could be embedded in methacrylate and sec- 

 tioned by ultra-thin sectioning methods. 

 Selected areas of cells could be studied in 

 relation to the developed grain deposition 

 either by electron microscopy or by oil im- 

 mersion phase microscopy, if mounted on a 

 glass slide (16). This is an avenue that will 

 lead the microscopist into cellular and sub- 

 cellular autoradiography. 



REFERENCES 



1. Johnston, M. E., "A bibliography of bio- 

 logical applications of autoradiography, 

 1954 through 1957", UCRL-8400, 1958. 

 Johnston, M. E., "A bibliography of biologi- 

 cal applications of autoradiography, 1958 

 through 1959", UCRL-8901, 1959. 



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