COLLAGENIC FIBERS 



86 



COLOR PRESERVATION 



Amino acid analyses (see Elastic Fi- 

 bers) indicate an absence of aromatic 

 amino acids, an abundance of proline, 

 hydroxylysine and particularly hy- 

 droxyproline, the latter being almost a 

 diagnostic feature. The isolectric 

 point of collagen is about pH 7.0. 



Although tinctorial reactions would 

 imply that reticulum and coUagenic 

 fibers differ, recent studies indicate that 

 reticulum is but a finer unit of collagen. 

 Both have a marked affinity for aniline 

 blue. They differ in that reticulum is 

 strongly argyrophilic while collagenic 

 fibers are not; the former is weakly 

 acidophilic (in H & E) while the latter 

 takes up much eosin. 



Electron microscopy and x-ray dif- 

 fraction studies have done much to re- 

 veal the submicroscopic structure of col- 

 lagenic fibrils (Gross, V., J. Gerontol., 

 1950, 5, 343). These are apparently 

 composed of parallel polypeptide chains 

 approximately 10 A° in diameter which 

 are bonded together laterally. Elec- 

 tron microscopy reveals considerable 

 fine structure in fibrils. There is a 

 regular periodicity of 640 A° with much 

 intra-period detail. 



A protein termed procollagen may be 

 prepared by extraction with citrate at 

 pH 4. Such procollagen can form fibrils 

 with regular periodicity by the addi- 

 tion of monovalent salts or mucoprotein 

 (Highberger, J. H., J. Gross and F. O. 

 Schmitt, Proc. Nat. Acad. Sci., 1951, 

 37, 286). 



The best stain for collagenic fibers in 

 sections after Zenker fixation is aniline 

 blue in Mallory's Connective Tissue 

 Stain and in Masson's Trichrome Stain. 

 Phosphomolybdic Acid Hematoxylin 

 also gives a fine coloration of collagenic 

 fibers. See Van Gieson, Buzaglo, Bieb- 

 rich Scarlet and Picro-Aniiin Blue of 

 Lillie and Curtis' Substitute for Van 

 Gieson. 



Lillie, R. D. (J. Tech. Methods, 1945, 

 No. 25, 45 pp.) has performed a very 

 useful service in testing the effective- 

 ness of a large series of dyes as colla- 

 genic fiber stains in the Van Gieson, 

 Mixed Masson-Van Gieson and Masson- 

 Mallory procedures. He found the best 

 to be Naphthol blue-black (CI, 246), 

 Fast Green FCF, Acid Fuchsin (CI, 

 692), Methyl Blue (CI, 706), Anilin Blue 

 (CI, 707), Wool Green S (CI, 737) and 

 Volamine R (CI, 758) . For photometric 

 histochemical determination see Sto- 

 well, R. E., J. Invest. Derm., 1945, 6, 

 183-189. 



The technique of microincineration 

 as adapted to collagenic fibers is de- 

 scribed by AUara, E., Bull. d'Hist. 

 AppL, 1938, 15, 220-242. See Tendons. 



Collargol, as negative stain for spirochetes 

 (Harrison, Brit. Med. J., 1912, 2, 1547). 



Collodions. There are several. See U.S.P. 

 XI. All are solutions of Pyroxylin. 



Colloxylin, see Pyroxylin. 



Colophonium, usually dissolved in turpen- 

 tine is employed to mount sections. 

 Not advised. 



Color Estimation. Accuracy in reporting 

 differential stains and micro-chemical 

 reactions yielding colors is highly de- 

 sirable. The same holds for colors 

 determined by naked eye inspection. 

 A monograph, Ridgway, R., Color 

 Standards and Color Nomenclature, 

 Washington, D. C, 1912 with 53 colored 

 plates, is the accepted standard for 

 comparison. In general, however, it is 

 desirable to achieve some measure of 

 uniformity by limiting oneself when- 

 ever possible to use of the terms recom- 

 mended in the National Formulary VII. 

 Washington: American Pharmaceutical 

 Association, 1942, 690 pp., a publication 

 which is available in most medical 

 libraries: 



pink yellow greenish blue 



red olive-brown blue 



reddish orange greenish yellow purplish blue 

 reddish brown olive bluish purple 



orange-pink yellow-green purple 



orange olive-green reddish purple 



brown yellowish green purplish pink 



yellowish orange green red-purple 



yellowish brown bluish green purplish red 

 blue-green 

 For accurate measurement of color 

 employ Photoelectric Colorimeter or 

 Photoelectric Microphotometer. See 

 Hemoglobin Estimation. 



Color Index, p. xxvii. 



Color Preservation in museum specimens. 

 Fix 24 hrs. or less in 10% formalin. 

 Wash in running water 3-6 hrs. Stand 

 in 2% aq. ammonia 5-10 min. which 

 hastens return of original colors. Run- 

 ning water another hour. Mount for 

 permanent exhibition in mixture made 

 as follows: Filter a sat. sol. antimony 

 trioxide in aq. dest. (about 5 gm. per 

 liter). To each 1000 cc. filtrate add 100 

 gm. potassium acetate, 100 gm. chloral 

 hydrate and 50 cc. glycerin. Stir until 

 completely dissolved (Meiller, F. H., 

 J. Tech. Methods, 1938, 18, 57-58). 



Mallory (p. 380) recommends for this 

 purpose the methods of Kaiserling and 

 Jores. 



There are 3 Kaiserling solutions : 

 1. For fixation: Formalin, 40 cc; tap 

 water, 2000 cc; potassium nitrate, 30 

 gm. and potassium acetate, 60 gm. 

 Small specimens require 1-14 days. 

 Large ones can be more uniformly fixed 

 by vascular Perfusion. Sometimes it 

 is advisable to inject fixative into central 



