ERYTHROCYTES, DEVELOPMENTAL 120 

 SERIES 



ESTERASES 



thereby dated. Stratification of con- 

 tents of erythrocytes by ultracentrifu- 

 gation (Beams, H. W., and Hines, E. H., 

 Anat. Rec, 1944, 89, 531). Special meth- 

 ods are given under Hemoglobin, 

 Flagella, Reticulocytes, Cabot Rings, 

 Jolly Bodies, Pencil Red Cells, and 

 Target Cells. For red fluorescent 

 erythrocytes in anemia, see Seggel, 

 K. A., Ergeb. d. inn, Med. u. Kinderh., 

 1940, 58, 582. 

 Erythrocytes, Developmental Series. The 

 technique employed apparently makes 

 a great deal of difference in the conclu- 

 sions reached. See Cowdry's His- 

 tology, 1938 p. 99. 



1. Maximo w and Bloom employing 

 mainly permanent preparations list: 



Hemocytoblasts: "... large (up to 

 15m) ameboid, non-granular basophil 

 cells of lymphoid nature." Occur ex- 

 tra vascularly. 



Basophil erythroblasts : The youngest 

 erythroblasts, characterized by the 

 intense basophilia of their cytoplasm. 

 Also called megaloblasts , but "this term 

 is misleading because it was first used 

 for the erythroblasts of pernicious 

 anemia which are cells of quite different 

 nature." 



Polychromatic erythroblasts: So-called 

 because after "fixation and staining with 

 the Romanowsky mixture, especially in 

 dry smears, the protoplasm has a mixed 

 color varying from purplish-blue to lilac 

 or gray." This is due to the presence 

 of two substances, a basophile material 

 and hemoglobin. 



Orthochromatic erythroblasts or normo- 

 blasts: These are smaller "and only 

 slightly larger than the mature, non- 

 nucleated erythrocytes." Since the 

 basophile substance diminishes and the 

 hemoglobin increases, the protoplasm 

 becomes acidophilic "and stains a bright 

 pink with the Romanowsky mixture." 

 They continue to divide mitotically for 

 an unknown number of generations until 

 the nucleus disappears. 



2. Sabin and associates relying chiefly 

 on supravital stains list : 



Endothelial cells: Occur in special 

 "erythrogenic capillaries." 



Megaloblasts: "... a daughter endo- 

 thelial cell which starts to synthesize 

 hemoglobin." "The megaloblast has 

 maximum basophilia, a moderate num- 

 ber of rod-shaped mitochondria, a trace 

 of hemoglobin, and a nucleus with a 

 minimum of chromatin and conspicuous 

 nucleoli." 



Early erythroblasts: "The young ery- 

 throblast represents a growth phase, 

 with less rapid division, for the cell is 

 much larger than the megaloblast; it 

 contains the maximum number of mito- 



chondria. The amount of hemoglobin 

 is still small, but sufficient to give a 

 poly chroma tophilia , predominately 



basophilic in methylene blue-azur. The 

 nucleus has a marked increase in 

 chromatin." 



Late erythroblasts: This cell "is inter- 

 mediate in size between the early 

 erythroblast and the definitive red cell. 

 The nucleus has lost the nucleoli but 

 still has massive chromatin. . . . The 

 increase in hemoglobin is marked and in 

 fixed films the cytoplasm is more 

 acidophilic." 



Normoblasts: "The stage of the nor- 

 moblast is defined as a nucleated red 

 cell after its last cell division. It has 

 a small pyknotic nucleus ready for 

 extrusion or fragmentation." 



Erythrocytometer for measuring the diam- 

 eter of red blood cells. Pijper, A., Med. 

 J. South Africa, 1919, 14, 472 and Lan- 

 cet, 1935, 1, 1152, deserves great credit 

 for the discovery independently of 

 Thomas Young (1813) of a technique 

 for the measurement of small objects 

 utilizing the principle of diffraction and 

 Zeiss has manufactured an instrument 

 on his specifications. Another, the 

 Haden-Hausser erythrocytometer, is 

 made by C. A. Hausser and Son and is 

 sold by Arthur H. Thomas Co., Phil- 

 adelphia (Haden, R. L. J. Lab. & Clin. 

 Med., 1939-40, 25, 399-403). 



Erythrosin B, see Erythrosin, bluish. 



Erythrosin BB or B extra, see Phloxine. 



Erythrosin, bluish (CI, 773)— dianthine B, 

 eosin B, erythrosin B, iodeosin B, pyro- 

 sin B — Fluorescein with 2 iodine atoms. 

 See Eosins. 



Escherichia Coli, see Triphenyltetrazolium 

 Chloride. 



Ester Wax. An embedding medium de- 

 signed especially to promote ribboning 

 of sections. It is made up of diethylene 

 glycol distearate, 73 gm.; ethyl cellu- 

 lose, 4 gm.; stearic acid, 5 gm.; castor 

 oil, 8 gm.; and diethylene glycol mono- 

 stearate, 10 gm. (Steedman, H. F., 

 Quart. J. Micr. Sci., 1947, 88, 123-133). 



Esterases. — Written by E. W. Dempsey, 

 Dept. of Anatomy, Washington Uni- 

 versity, St. Louis. February 26, 1951^ 

 Strictly speaking, these are enzymes 

 which hydrolyze the ester linkage de- 

 rived from any acid, organic or inor- 

 ganic. Thus, the phosphatases, cho- 

 linesterases, glucuronidase, lipase, and 

 sulfatase properly belong among the 

 esterases. However, ordinary usage 

 restricts the term to the enzymes 

 hydrolyzing carboxy esters, particu- 

 larly those of fatty acids. These es- 

 terases apparently exhibit some sub- 

 strate specificity; at least, the enzymes 

 hydrolyzing esters of short-chain fatty 



