Etude ultrastructurale de la moelle hématopoïétique au cours de la régénération après irradiation

Abstract

During the recovery period which follows an X-rays irradiation, the bone marrow size distribution curves obtained with an electronic particle counter are characterized by an important increase of the small lymphoid-like cell population. An ultrastructural study of this population has been realized on four bone marrows selected by the particle counter from a group of R 3 mice irradiated 10–12 days before at the dose of 500 R. In these marrows, the lymphoid-like cells ranged from 50 to 60% of the total amount of nucleated cells. The marrow of three normal mice of the same strain, age and sex, has been used as controls. In the normal mice, the small cell population is composed mostly of small lymphocytes; it contains also small sized myeloid cells and a few cells from the erythrocytic series. In the irradiated mice, the population of small cells is extremely heterogenous; it is partly constituted by small lymphocytes, small myeloid cells and rare erythrocytic cells. Besides these elements, the marrow is crowded with cells of a special kind with characteristic nuclear and cytoplasmic structures, the nature and function of these cells is still unknown; their possible relation with the so-called ‘transitional cells’ is discussed.