Cytogenetics in Nutritional Megaloblastic Anaemia: Prolonged Persistence of Chromosomal Abnormalities in Lymphocytes after Remission

Abstract

Chromosomal studies were performed in phytohaemagglutinin-stimulated cultures of lymphocytes and in bone marrow cells without culture from 115 patients with megaloblastic anaemia resulting from nutritional deficiency of folate and vitamin B₁₂ Essentially similar chromosomal abnormalities were observed in the two cell lines. These were characterized by striking morphological aberrations such as elongation and despiralization (uncoiling or incomplete contraction), increased frequency of chromosome breakage and centromere spreading. Numerical abnormalities, chromatid exchanges and translocations were virtually absent. Autoradiographic studies of chromosomes after pulse-labelling with ³H-thymidine during the terminal 6 h of phytohaemagglutinin-stimulated lymphocyte cultures revealed a differential pattern of distribution of the radionucleotide in the chromosomes of megaloblastic lymphocytes as compared to those from normal lymphocytes. Repeated chromosomal studies were done in 65 of these patients at various intervals after starting therapy with the deficient vitamins. After 48 h of therapy, chromosomal abnormalities were remarkably reduced in the bone marrow; but many of these morphological chromosomal changes (i.e. despiralization and breaks) persisted in the lymphocytes of a significant proportion of patients for variable periods up to 6–12 months after haematological remission resulting from therapy with the deficient vitamins. These abnormalities did not, however, persist after remission in those patients who had repeated episodes of infections.

Megaloblastosis: From Morphos to Molecules

“…The distinctive structural changes in the chromatin of megaloblasts in patients with vitamin B 12 and folate defi ciency were found to be associated with several structural abnormalities of individual chromosomes such as elongation and despiralization (unwinding) of chromosomes. These may cause a defect in packaging chromosomes inside the cells, possibly impairing cell growth and cell functions, although no signifi cant abnormalities of chromosome number were observed and the modal chromosome number remained 46 (diploid) with no consistent or signifi cant aneuploidy [19,[27][28][29] . It has been suggested that the cytomorphological and cytogenetic changes in megaloblastic anemia may be an expression of deranged cellular DNA synthesis [7][8][9][10][11][12] .…”

“…DNA content of individual cells in the bone marrow smears was measured after Feulgen staining in a Becton-Dickinson Cellular Imaging System (CAS 200). Cytogenetic analysis was done as previously described by us [19] .…”

“…The elongation and despiralization of chromosomes in replicating megaloblasts [19,[27][28][29] appear to refl ect their characteristic cytomorphological features in the interphase nuclear chromatin as observed in light and transmission electron microscopy. The results of our studies on electron microscopic confi guration of DNA fi bers extracted from megaloblastic and normoblastic bone marrows appear to provide additional data on molecular events associated with megaloblastosis.…”

Haematology Research in India: Past, Present and Future

“…Das. He showed the very important contribution of folate coenzymes in transport of Vitamin B12 across the cell membrane [10][11][12][13][14][15]. Impact of dilantin in preventing the megaloblastosis was also demonstrated in the same lab.…”

“…Another important classic observation made from this center was that lymphocytes remember past folate/B12 deficiencies long after these deficiencies were corrected. Based on his pre 1980 work later on he showed a spectrum of cytogenetic changes in lymphocytes at different time points after the B12/folate deficiency was corrected [15].…”