Granulocytic early progenitors and terminally differentiated - mature 
granulocytes with segmented nuclei were studied using computer-assisted diameter 
and heterochromatin optical image densitometry to provide more information on 
the nuclear size and heterochromatin condensation state. Bone marrow smears of 
patients suffering from chronic myeloid leukaemia untreated as well as treated 
with "specific" anti-leukaemic therapy with imatinib mesylate are a convenient 
model for such study because they possess a satisfactory number of cells for 
diameter and optical density measurements. In addition, the identification of 
developmental stages of granulocytes is very easy and the morphology is not 
different from that in not-leukaemic persons. As it was expected, the mean 
diameter of nuclear segments in fully differentiated and mature granulocytes was 
much smaller than that in non-segmented nuclei of early granulocytic precursors. 
Therefore, no wonder that the heterochromatin condensation state in nuclear 
segments of mature granulocytes was much larger than in non-segmented nuclei of 
granulocytic progenitors. On the other hand, the sum of mean diameters of all 
nuclear segments per cell was close to the mean nuclear diameter of early 
granulocytic progenitors. The heterochromatin condensation state in granulocytic 
progenitors or fully differentiated mature granulocytes exhibited marked 
stability and did not change after the anti-leukaemic therapy. In addition, Barr 
bodies of characteristic drumstick appearance bearing inactive X chromosome in 
interphase nuclei of mature granulocytes in fertile female patients exhibited a 
heterochromatin condensation state similar to nuclear segments. This 
heterochromatin condensation state was also stable and constant, and was not 
apparently influenced by the anti-leukaemic therapy.