REVIVAL OF VINEGAR EELS 



218 



RICKETTSIA 



ing vinegar is blotted off. Then a drop 

 of 30% ethylene glycol is added to the 

 squirming mass in order to reduce some- 

 what the water content of the worms. 

 After about 5 minutes the excess ethyl- 

 ene glycol is blotted off, and the eels, 

 still moving actively, are "wiped up," 

 in a thin layer, on very thin pieces of 

 mica (about 5 mm. on a side and about 

 35 micra thick). The eels, supported 

 on this mica slip, are then immersed in 

 liquid air. After about one minute 

 they are removed, and, by means of a 

 vigorous shake of the ha,nd, the droplet 

 of liquid air which may adhere to the 

 mica support is dislodged, whereupon 

 the preparation is abruptly swished in 

 a little water (about 2 cc.) in a watch 

 glass, at room temperature or prefer- 

 ably at 30°C. (The purpose of the 

 immersion in water is rapid rewarming.) 

 After about 5 minutes one sees, under a 

 low power microscope, several eels be- 

 gin to move and, after about ten min- 

 utes, some 50 out of 200 in the drop 

 become quite active, though they are 

 never entirely normal. See Luyet, B., 

 C. rend. Soc. Biol., 1938, 127, 788-789. 



Rhenium, see Atomic Weights. 



Rhodamine B (CI, 749)— brilliant pink B, 

 rhodamine — A basic xanthene dye. 

 It gives a good color contrast with 

 methylene blue in coloration of the 

 spleen (Houcke, E., C. Rend. Soc. de 

 Biol., 1928, 99, 788-789). 



Rhodamine O, see Rhodamine B. 



Rhodamines. Similar in some respects to 

 pyronins but there is a third benzene 

 ring affixed to central carbon atom and 

 to this in turn is attached a carboxyl 

 in ortho position. Examples : Rhoda- 

 mine B and fast acid blue R. Rhoda- 

 min B (Merck) and 6G IG. have been 

 employed as vital stains. When used 

 with plant cells mitochondria become 

 fluorescent (Strugger, S., Protoplasma, 

 1938,30, 85-100). 



Rhodium, see Atomic Weights. 



Rhodopsin (G. rhodon, rose + ops, eye). 

 Visual purple present in external seg- 

 ment of the rod cells of retina (See 

 Arey in Cowdry's Special Cytology, 1932, 

 3, 1211-1291). 



Riboflavin (lactoflavin) shows typical green 

 fluorescence in living liver and kidney 

 observed under fluorescence micro- 

 scope (Ellinger, P., and Koschara, \V., 

 Ber. deutsch. Chem. Ges., 1933, 66, 

 315-317, 808-813, 1411-1414). Detected 

 also in Malpighian tubules of American 

 roach (Metcalf, R. L. and Patton, R. L., 

 J. Cell and Comp. Physiol., 1942, 19, 

 373-376) and in tomato plants (Bonner, 

 J. and Borland, R., Am. J. Bot., 1943, 

 30, 1008-1009). See Hirt, A. and Wim- 

 mer, K., Klin. Wochnschr., 1939, 18, 

 733-740. 



Ribonuclease (Yeast thymonucleic acid), 

 occurrence (Greenstein, J. P. and Jen- 

 rette, W. V., J. Nat. Cancer Inst., 1941, 

 2, 301). Used in investigation of 

 chromatolysis of Nissl Bodies of Nerve 

 Cells by Gersh, I., and Bodian, D., 

 Biological Symposia, 1943, 10, 163-184. 



Ribonuclease, see Gram Staining. 



Ribonucleic Acid. Biesele, J. J., Cancer 

 Research, 1944, 4, 737-750. _ 



Rickettsia are small, gram negative, bacteria- 

 like organisms which are insect trans- 

 mitted and typically inhabit endothelial 

 cells of vertebrate hosts named after 

 H. T. Ricketts who died of typhus fever 

 while investigating them. They are 

 best stained by Giemsa's method 

 after fixation in Zenker's, Bouin's or 

 Regaud's fluids. 



1. Rapid staining with thionin. Make 

 sat. sol. of thionin in aq. dest. Pre- 

 cipitate by adding 10% NaOH. Collect 

 ppt. on filter and wash until filtrate 

 becomes neutral. Dissolve ppt. in 2% 

 phenol. Stain absolute alcohol fixed 

 smears only 30-50 sec. Drain, wash 

 quickly in absolute alcohol, clear in 

 xylol and mount in cedar oil. Rick- 

 ettsia, deep violet; cytoplasm, light 

 violet; red cells bluish green (Laigret, 

 J. and Auburtin, P., Bull. Soc. Path, 

 exat., 1938, 31, 790-791). 



2. Fuchsin staining method. Smear 

 tissue culture on slide. Dry in air, 

 then by heat. Filter directly on to 

 smear 0.25% basic fuchsin in phosphate 

 solution bufl'ered to pH 7.4 or in aq. 

 dest. made pH 7.2-7.4 by adding sodium 

 hydrate or carbonate (see Buffers). 

 Stain 4 min. Wash quickly with 0.5% 

 aq. citric acid. Pour off citric and wash 

 rapidly in tap water. Counterstain in 

 1% aq. methylene blue, 10 sec. Rick- 

 ettsia, red; cells, blue; not recom- 

 mended for tissue sections (Zinsser, H., 

 Fitzpatrick, F. and Hsi Wei, J. Exp. 

 Med., 1939, 69, 179-190). This is very 

 similar to Michiavello's method de- 

 scribed by Cox (H. R., Publ. Health 

 Rep., 1939, 53, 2241-2247) as superior 

 to Giemsa's stain for Rickettsiae of 

 Rocky Mt. Spotted Fever and Typhus 

 groups. 



The Michiavello technique has been 

 adapted for sections by Pinkerton (see 

 Harry Plotz, in Simmons and Gentz- 

 kow, p. 572). Stain paraffin sections 

 after Regaud fixation overnight in 1% 

 aq. methylene blue and decolorize in 

 95% alcohol. Counterstain with 0.25% 

 aq. basic fuchsin for 30 min. Decolor- 

 ize quickly (say 3 sec.) in 0.5% aq. 

 citric acid. Differentiate rapidly in 

 abs. ale. clear in xylol and mount in 

 dammar. Rickettsiae, deep red; sur- 

 rounding tissue, partly red. Back- 

 ground can be made bluer by washing 



