1-8.
CYTOPLASM
The basophilia of a blast cell is proportional to the ribonucleic acid (RNA)
content. As the cell matures, the RNA content decreases and the cell becomes a paler
blue. In the myeloid cells, a specific type of granulation occurs. When granules appear
they are pinkish-red and few in number. The granules increase in number and
differentiate into three types upon maturation. As the cell matures, it develops an
affinity for the acid or basic portion of the stain (Wright's stain). Basophilic granules
stain blue-black, eosinophilic granules stain red-orange, and neutrophilic granules stain
pinkish-purple. Lymphocytes are usually devoid of cytoplasmic granulation but they can
possess non-specific azurophilic (dark-purple) granules, usually characteristic of
monocytes and plasmocytes. Upon maturation, the erythrocyte develops a light orange
respiratory pigment called hemoglobin.
1-9.
NUCLEUS
The nucleus of the young cell is large, round, and occupies most of the cell. As
the cell matures, the size of the nucleus decreases. Nuclei of early or primitive cells
usually have one or more nucleoli. The latter are small, round, homogeneous areas
that usually stain light blue with a darker boundary. In appearance nucleoli are
somewhat like craters in the nucleus. They are surrounded by strands of chromatin.
These nucleoli, plus a delicate reticular network of chromatin, are the principle
indicators of blood cell immaturity. As the cells mature, the nucleus gradually becomes
smaller, stains darker, and chromatin meshwork become "coarse" with the strands of
chromatin less fine and lacelike. In the course of cell development, the nucleus
changes its shape, particularly in the granulocytic series, where it becomes indented,
lobulated, segmented, or fragmented. As maturation or development progresses, the
nucleus, if still intact, becomes small, compact, usually dark and structureless, and can
completely disappear. The loss or shrinking of the nucleus is accompanied by a
decrease in cell size.
Section IV. ABNORMAL CELL MATURATION
1-10. GENERAL FEATURES
Abnormal cell maturation is asynchronous development as opposed to normal
cell maturation or synchronous development. Since the normal sequence of cell
maturation is upset, atypical cells will be present. Abnormal cells can be recognized by:
(1) abnormal cytoplasmic maturation, (2) abnormal nuclear maturation, and (3)
abnormal size.
1-11. CYTOPLASM
Asynchronism of the cytoplasm is most commonly seen in the granulocytes.
Granulation can be primitive or absent. In some instances, the granules fail to
differentiate. Erythrocytes show basophilia late in the series and retarded
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1-9