DEFECTIVE ALPHA-GRANULE PRODUCTION IN MEGAKARYOCYTES FROM GRAY PLATELET SYNDROME - ULTRASTRUCTURAL STUDIES OF BONE-MARROW CELLS AND MEGAKARYOCYTES GROWING IN CULTURE FROM BLOOD PRECURSORS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 102  (1) , 10-19
Abstract
The ultrastructure and cytochemistry of megakaryocytes from 2 patients with a familial gray platelet syndrome are described. Although the Golgi zones appeared normally developed, the megakaryocytes lacked .alpha.-granules. Catalase-containing particles were normal in number. In immature megakaryocytes, granules measuring from 0.05-0.1 .mu. and having an electron-dense core occurred in the Golgi area. These granules, which are considered as .alpha.-granule precursors in normal megakaryocytes, appeared unable to mature, and their number decreased with the megakaryocyte maturation. The presence of dense material in distended demarcation membranes and/or vacuoles suggested that their content was discharged. Apparently, myelofibrosis present in the bone marrow from these 2 patients may be related to the possible excretion of a polypeptide growth factor normally contained in the .alpha.-granules. Megakaryocytes grown by the plasma clot procedure from blood precursors isolated from the 2 patients also did not exhibit .alpha.-granules, which were replaced by vacuoles. Apparently, the lack of gray platelet .alpha.-granules may be related to a defective megakaryocyte-committed cells. Evidence is presented which suggests that .alpha.-granule precursors are produced, but that their contents are then lost.