NEON 



223 



NERVE FIBER DEGENERATION 



Neon, see Atomic Weights. 



Neoprene, injection of blood vessels (Lieb, 

 E., J. Tech. Methods, 1940, 20, 50-51). 

 Neoprene is a colloidal, finely divided 

 suspension of synthetic chloroprene in 

 an alkaline aqueous medium. Instruc- 

 tions for the human kidney. Cannulate 

 renal artery and wash with tap water 

 at slow but constant rate. Ligate grossly 

 leaking vessels. Continue 8-18 hrs. 

 until organ is pale gray. Cover and 

 keep in ice box 6-7 hrs. or until the 

 next day. Keep specimen at room 

 temperature about one hour before in- 

 jection. If it feels cold warrn it with 

 tap water. Connect cannula with bottle 

 containing neoprene. A special appara- 

 tus for maintenance of 150^160 mm. Hg. 

 is advised by Lieb but it is probably 

 sufficient to provide gravity pressure 

 by raising the bottle 5 ft. or more. 

 Close vessels ejecting the neoprene 

 with hemostats and tie them when ves- 

 sels are completely filled. Rinse in 

 warm water. If a corrosion specimen 

 is wanted leave kidney in cone, com- 

 mercial HCl in tightly covered vessel 

 at 56 °C. over night. Next morning 

 pour off acid and allow stream of water 

 to flow over the cast itself in the bottom 

 of the container. When all debris is 

 removed examine under water with 

 dissecting microscope. Store in 0.3% 

 Dowicide sol. (American Anode Inc., 

 60 Cherry St., Akron) to avoid mold. 

 Lieb gives more details and describes 

 combined corrosion, histological and 

 roentgenological methods. Technique 

 should be adapted to other organs. 

 (Revised by Ethel Lieb, May 16, 1946). 

 Lieb's method has been modified in 

 several respects by Duff, G. L. and 

 More, R. H., J. Tech. Methods, 1944, 

 24, 1-11. The technique for mounting 

 separately for detailed microscopic 

 examination small sprigs of the renal 

 cortical arteries greatly increases its 

 usefulness. 



Neoprene Latex. Emplo3^ed for injection of 

 coronary arterial sj'stem, well illus- 

 trated and with a list of earlier papers 

 (Smith, J. R. and Henry, M. J., J. Lab. 

 & Clin. Med., 1945, 30, 462-466). 



Nerve Endings. These may be demon- 

 strated in many ways. Nothing will 

 adequately take the place of their study 

 in vivo (Speidel, C. C., J. Comp. Neur., 

 1942, 76, 57-73) ; but no method should 

 be used with expectation of satisfactory 

 results the first time. Experimentation 

 is required. Most of the silver methods 

 for neurofibrils show nerve endings. 

 The writer has obtained good results 

 by Bodian's Method applied to paraffin 

 sections of experimental tumors. Cra- 

 ven's Gold Chloride method may be 



tried. For silver impregnation of intra- 

 cellular nerve endings in pars inter- 

 media of pituitary, see Tello, F., Trab. 

 d. Lab. Rech. Biol. Univ. Madrid, 1912, 

 10, 145-183. Methylene blue is, since 

 the time of Ehrlich, a very popular stain 

 for nerve endings. Addison (McClung, 

 pp. 477-480) has given a full account of 

 the technique. Commission Certified 

 zinc-free methylene blue is suggested. 

 Dye can be applied locally or by vascular 

 perfusion. 



1. Local application. Place tissue in 

 shallow dish on thin layer of glass-wool 

 moistened with 0.1-0.05% methylene 

 blue in physiological salt solution. Add 

 enough stain every few minutes to keep 

 tissue moist and covered by film of 

 stain. Beginning after 15 min. examine 

 frequently at low magnification until 

 nerves are colored blue. Fix stain by 

 immersion in cold 8% ammonium molyb- 

 date in physiological salt solution or 

 Ringer's (^ hr.). Wash in cold water. 

 Dehydrate in alcohols in refrigerator 

 a little above 32 °C. Either clear in 

 xylol and mount in balsam or imbed in 

 paraffin and section. Cole (E. C, J. 

 Comp. Neurol., 1925, 38, 375-387) 

 proceeded much in this way. He 

 immersed whole alimentary tract of 

 frog in 1:10,000 methylene blue solution 

 for 1 hr. and cut it in pieces. 



2. Vascular perfusion. Insert can- 

 nula in main artery leading to the tissue. 

 Inject 1:10,000 methylene blue in 

 physiological saline until tissue becomes 

 light blue. Leave 15 min. Remove 

 thin pieces or slices. Place in dish 

 and moisten with methylene blue solu- 

 tion. Examine uncovered at low magni- 

 fication at intervals until nerve fibers 

 and endings are stained. It is essential 

 as in local application not to exclude air 

 from tissue by covering with too much 

 fluid. Fix in ammonium molybdate and 

 continue as described above. For large 

 fetuses use Langworthy's method (O. 

 R., J. Comp. Neurol., 1924, 36, 273-297), 

 for the lungs of rabbits that of Larsell 

 (O., J. Comp. Neurol., 1921, 33, 

 105-131), for arteriovenous anasto- 

 moses Brown's (M. E., Anat. Rec, 

 1937, 69, 287-295), and for skin Weddell's 

 (G., J. Anat., 1940-41, 75, 441-416). 

 Staining may perhaps be accentuated 

 by hydrogen acceptors, see Auerbach's 

 Plexus. See Pacinian Corpuscles, 

 Meissner's Corpuscles, Krause's End 

 Bulbs, Motor End Plates, Boutons 

 Terminaux and Synapses. 



Nerve Fiber Degeneration. The standard 

 techniques are the Marchi Method by 

 which the lipids produced by degenera- 

 tion are blackened with osmic acid and 

 the staining of lipoids by Sudan III. 



