In effective thrombopoies is has been inferred to occur in several disease sates from considerations of megakaryocyte mass and platelet kinetics. Microscopic examination has demonstrated increased numbers of megakaryocytes, with a typical forms particularly pronounced, in primary myelofibrosis. It has not been documented if megakaryocyte ever fail to reach maturity in non-pathological situations. A major difficulty of establishing this is that the number of megakaryocytes normally present in the marrow is extremely low. A large transient increase in megakaryocytopoiesis can how ever be induced in mice by an injection of 5-fluorouracil. We have utilised this treatment and report here evidence for in effective thrombopoies is in healthy mice.Adult mice were perfused (2% glutaraldehyde in 0.08M phosphate buffer, pH 7.4) 8 days following an injection of 5-fluorouracil (150mg/kg). Femurs were subsequently decalcified in 10% neutral E.D.T.A. and embedded in Spurrs resin. Transverse sections of marrow revealed many megakaryocytes at various stages of maturity. Occasional megakaryocytes (less than 1%) were found to be under going degeneration prior to achieving full maturation and releasing cytoplasm as platelets. These cells were characterized by a peripheral rim of dense cytoplasm which enveloped a mass of organelles and vacuoles (Fig. 1). Numerous microtubules were foundaround and with in the organelle-rich zone (Fig 2).
RETINAL TOXICITY OF INTRAVITREAL TRIAMCINOLONE ACETONIDE
