Ultrastrual cell cycle-specific nuclear and nucleolar changes of human leukemic lymphoblasts
Parmley, R.T.; Dow, L.W.; Mauer, A.M.
Cancer Research 37(12): 4313-4325
1977
ISSN/ISBN: 0008-5472 PMID: 270388 Document Number: 110496
To identify cell cycle-specific ultrastructural markers in acute lymphoblastic leukemia, bone marrow lymphoblasts were labeled with [3H]thymidine, separated according to cell size by velocity sedimentation at 1 .times. g and the pattern of changes within the nucleus of the cells was identified according to phase of the cell cycle. The smallest and most slowly sedimenting cells (probably in G0 phase) had prominent, condensed nuclear chromatin and adjacent small nucleoli with segregated substructure and a distinct focus of pars amorpha, which contained pyroantimonatereactive cation. Slightly larger cells (probably in G1 phase) contained a more irregular nuclear profile, dispersed nuclear chromatin and large, round, centrally located nucleoli with increased granular component, dispersed foci of pars amorpha, dense fibrillar component and decreased nucleolus-associated chromatin. During early S phase, [3H]thymidine diffusely labeled the nucleus. The nucleoli, usually within the nuclear periphery, had increased nucleolus-associated chromatin. In late S-phase cells, [3H]thymidine was incorporated into the peripheral chromatin and the nucleolus, which was irregularly shaped, contained moderate amounts of granular and dense fibrillar component, and was always surrounded and often penetrated by nucleolus-associated chromatin. Large, rapidly sedimenting cells in G2 phase contained flattened nucleoli with penetrating nucleolar chromatin and various foci of nucleolar constituents, including pars amorpha. Leukemic lymphoblasts can be identified at each phase of the cell cycle on the basis of their ultrastructural morphology.