RADIOAUTOGRAPHY 



301 



RADIOAUTOGRAPHY 



for the duration of exposure. A 

 drying agent (Drierite or CaClj) in 

 the slide box prevents the hydration 

 of the emulsion during exposure, 

 thus reducing the possibility of 

 fogging due to the solution of gases 

 in the emulsion and also causes a 

 sharper image to be produced. 



5. After a suitable exposure, the prepa- 

 rations are developed in D-72 de- 

 veloper for one and a half minutes, 

 rinsed, fixed in acid fi.xer, washed in 

 running water (18°C.) for 15 min- 

 utes, dehydrated for 2 minutes in 

 each of the following solutions: 

 95% alcohol, absolute alcohol, alco- 

 hol-xylol, and cleared in three 

 changes of xylol. To prevent arte- 

 facts, the preparations are immersed 

 in a 1% solution of balsam or a 50% 

 solution of permount for at least 

 one hour. Longer periods of time 

 are recommended for hard tissues. 

 Slides should at all times be kept 

 horizontal. 



6. The sections are mounted in balsam 

 or permount under a coverslip and 

 the preparations allowed to dry at 

 room temperature. 



For a more detailed description of this 

 method see Gross et al., referred to 

 above. 



In "Strip Coating": Instead of using 

 fluid emulsion, the sections may be 

 coated with a Stripping emulsion, such 

 as Ilford Special half tone stripping 

 plate or British Kodak stripping plates 

 for autoradiograph}'. Eastman Kodak 

 NTB stripping films have also been 

 used. 



1. The emulsion strip is removed from 

 its glass support by cutting the emul- 

 sion along the three edges of the 

 glass plate. 



2. The emulsion is then slowly peeled 

 off to about 1 inch from the edge 

 and, with the side that formerly 

 adhered to the glass facing upwards, 

 kept for 5 minutes in a shallow dish 

 containing a 1% solution of dupanol 

 C at 18-20°C. 



3. The microscope slide bearing the 

 section is slipped underneath the 

 emulsion and lifted together with 

 the emulsion out of the water. 



4. Three edges of the emulsion are 

 folded underneath the slide to insure 

 adherence. (Pelc dips the glass 

 slides in gelatin prior to mounting 

 the section on them. This also 

 insures adherence.) 



5. The slides are then stored dry at 

 1-2°C. as above. 



For more detailed report see Berriman, 

 R. W., Hertz, R. H., and Stevens, G. 

 W. W., Brit. J. Radiol., 1950, 23, 472- 



477; Bogoroch, R., Stain Techn., 1951, 

 26, 43-50. 



The difficult}^ with the coating meth- 

 ods as described is that the prepara- 

 tions must be stained before they are 

 coated. This procedure in some cases 

 such as P" in bone removes radio- 

 active material, thus making staining 

 of sections before radioautography in- 

 advisable. The removal of P'^ is negli- 

 gible, however, when prestaining is 

 done with safranin or acid fuchsin. 

 By using both stained and unstained 

 preparations at the same time, it is 

 possible to make sure of the extent 

 of the loss. It is also possible to 

 completely prevent loss by using 

 the original coating method first de- 

 scribed by Belanger, L. F., and Leblond, 

 C. P., Endocrinology, 1946, 39, 8-13, 

 in which the sections were stained 

 through the developed and fi.xed emul- 

 sion. This method has recently been 

 successfully used by Arnold, 1951, in 

 the study of calcium^ in bone. In 

 this case, however, success may be ob- 

 tained only if very thin emulsion coats 

 are used and celloidin is not deposited 

 on the sections prior to emulsion coat- 

 ing. The danger of artefacts produc- 

 tion must be kept in mind. 



3. Inverting Method: In this the sec- 

 tions are coated with liquid emulsions 

 without prestaining of the sections 

 (Belanger, L. F., Anat. Rec, 1950, 

 107, 149. Kodak matrix emulsion is 

 used for best results) or with a strip 

 emulsion (MacDonald, A. M., Cobb, J., 

 and Solomon, A. K., Science, 1948, 107, 

 550-552). After e.xposure and develop- 

 ment the preparation is placed under 

 water and the emulsion, with the sec- 

 tion adhering to its undersurface, is 

 lifted from the slide using a razor blade. 



The complex is then inverted and 

 fixed on a clean slide, section side up. 

 The free edges are sealed with 1% 

 celloidin, which is allowed to dry com- 

 pletely. The section may now be 

 stained with ease since the celloidin 

 protects the emulsion from the action 

 of the dyes. 



The preparation is mounted under a 

 coverslip using Canada balsam. 



4. Wet collodion method: The Wet 

 Collodion method (Gomberg, H. J., 

 Nucleonics (in press)) — an adaptation 

 of the old wet collodion process of 

 photography — involves the deposition 

 of a very thin and dense layer of sensi- 

 tized silver bromide in a collodion 

 matrix formed by chemical reaction 

 directly on the surface to be studied. 

 After a suitable exposure time in a 

 silver nitrate bath, the affected silver 

 grains are physically developed using 



