Regiões organizadoras de nucleolos em leucemia mieloide cronica

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The nucleolar organizer regions (NORs) are loops of DNA, that are responsible for the syntesis of the ribossomal RNA. A special silver-staining technique identifies the acidic non-histones proteins (AgNORs) associated with the sites of r RNA transcription, such as RNA polymerase I, C23 and 823 proteins. This method has been widely used for the observation of the NORs during the cell cycle in different normal and pathologic lesions. The AgNORs show different patterns in interphase nuclei: 1 - solitary rounded argyrophilic structures corresponding to a small nucleolus in resting cells, 2 - clusters of NORs within a matrix, corresponding to nucleoli, 3 - small dots (true AgNORs) scattered throughout the nucleoplasm. The pattern of AgNORs is related to the duplication rate and to maturation stage of cells. Several studies have demonstred that its analysis is usefull in distinguishing benign from malignant lesions and for the grading of tumors. We have analysed the pattern of AgNORs of granulopoietic cells in chronic myeloid leukemia (CML) and compared it to the normal granulopoiesis. The peripheral blood cells of 24 cases of CML in chronic phase at diagnosis, 19 cases with relapse of chronic phase and 16 cases in blast crisis were studied. On the other hand, the granulopoiesis in bone marrow of 15 cases of CML at diagnosis was compared to 20 cases of normal bone marrow. The pattern of AgNORs was similar in the peripheral blood and bone marrow in all granulopoietic precursors of the same maturation stage, in CML at diagnoses. As in the normal bone marrow, the granulopoietic precursors of CML in chronic phase, revealed a characteristic pattern of clusters and dots for the cells in each maturation stage. Compared to normal granulopoiesis only the myeloblasts of CML in chronic phase at diagnosis had significantly less clusters. The dots however showed a similar number in blasts, matamyelocytes, band forms and segmented neutrophils. They were less numerous in promyelocytes and myelocytes. The blasts of CML at diagnoses showed significantly more clusters than those at relapse afier treatment of chronic phase. These, however, had a similar pattern of AgNORs than that seen in blast crisis. The number of clusters wich are only present in proliferative cells is inversely related to cell cycle duration. The number of dots increases with cell maturation in proliferating cells and decreases again after the stop of proliferative activity. In view of these data the analysis of the pattern of AgNORs in CML discloses the discordant maturation described in this disease. On the other hand the number of clusters of blast crisis in CML is lower than in normal myeloblasts and keeps decreasing continuously during the course of the disease. This pattern is similar to that describedin acute myeloid leukemia

ASSUNTO(S)

leucemia mieloide cronica

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