Page 1844 - Williams Hematology ( PDFDrive )

1818 Part XII: Hemostasis and Thrombosis Chapter 111: Megakaryopoiesis and Thrombopoiesis 1819

Mi ER

B D

Gly

Mt

C E

DM

ER
A F
Figure 111–3. A. Ultrastructure of the cytoplasm of a mature megakaryocyte. The majority of the granules are α granules (αGr) exhibiting dense
nucleoid. Demarcation membranes (DM) are slightly dilated. Transverse sections of microtubules (Mt) are dispersed. At the periphery, a longitudinal
microtubule runs under the cell membrane (arrows). Dense aggregates of glycogen (Gly), small cisternae of endoplasmic reticulum (ER), and free
ribosomes are seen (magnification ×30,320). B. Morphology of an α granule. Dense nucleoid is located at the top. In a clear zone at the opposite pole,
four transverse sections of tubular structures are adjacent to the granule membrane (magnification ×37,200). C. Dense body can be distinguished
from α granule by the black deposit when calcium is added to the fixative (magnification ×37,200). D. Cytochemical detection of acid phosphatase
using β-glycophosphate as substrate and cerium as a trapping agent. Dense cerium–phosphate precipitates are present in lysosomal granules,
whereas α granules are unreactive (magnification ×37,200). E. Microperoxisome visualized using alkaline diaminobenzidine. Note the small size of a
reactive granule compared to the α granule. F. Distribution of a dense tracer filling the lumen of the demarcation membrane system in a maturing
megakaryocyte (arrows). In contrast to the demarcation membrane system, which is open to the extracellular space, the endoplasmic reticulum (ER)
is not labeled (magnification ×9700). (Used with permission of Dr. J. Breton-Gorius.)

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