Derangement of DNA Synthesis in Erythroleukaemia. Normal Deoxyuridine Suppression and Impaired Thymidine Incorporation in Bone Marrow Culture

Abstract

Deoxyuridine (dU) suppression test (i. e. ability of exogenous dU to suppress the incorporation of subsequently added ³H-thymidine into DNA) and the incorporation of ³H-thymidine (³H-TdR) alone without dU were studied in bone marrow cultures from 10 patients with erythroleukaemia, 10 patients with vitamin B₁₂/folate-deficient megaloblastic anaemia and 10 haematologically normal subjects. Despite morphological resemblance between megaloblastosis in erythroleukaemia and nutritional megaloblastosis, the dU suppression values in erythroleukaemia were within normal range in contrast to abnormal dU suppression in vitamin B₁₂/folate-deficient megaloblastic bone marrows. The incorporation of ³H-thymidine alone was significantly lower in erythroleukaemia than in normal or vitamin B₁₂/folate-deficient megaloblastic bone marrows. Autoradiographic studies showed that ³H-TdR labelling indices as well as mean grain count (MGC) of basophilic and polychromatic erythroblasts were significantly lower in erythroleukaemia than in normal or vitamin B₁₂/folate-deficient bone marrows. The reduced incorporation of ³H-TdR in erythroleukaemia erythroblasts was probably not due to deficiency of the salvage pathway enzyme, thymidine kinase, since MTX (10^-5M) which blocks the de novo pathway of thymine-DNA synthesis, enhanced the incorporation of ³H-TdR into erythroblasts in erythroleukaemia as well as in normal bone marrows. A high intracellular pool of thymidine-triphosphate (dTTP) due to defective DNA synthesis may allosterically inhibit thymidine kinase and ³H-TdR incorporation.

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

“…11 Ci/ mmol) was added to each culture of PHA-stimulated lymphocytes 6 h prior to harvesting, and mitosis was arrested at metaphase by adding colcemid (Ciba) 3 h prior to harvesting. The chromosome preparations were autoradiographed using Kodak NTB, nuclear emulsion, and after 4 weeks of exposure at 4°C in the dark (black box), these slides (containing chromosome preparations) were de veloped and fixed by Kodak developer and fixer, and stained by Giemsa stain [20].…”

Haematology Research in India: Past, Present and Future

“…In 1976 FAB classification of acute leukaemias was published and in India, several Institutes tried to present their leukaemia data based on FAB sub class and correlating them with cytochemistry [30]. Many of the haematologists who were stalwarts on nutritional anaemia research were looking after these leukaemia patients hence they superimposed their insight of nutritional anaemia research on understanding some of the leukaemia biology, this understanding resulted in demonstration of Deoxy Uridine suppression test which remains largely normal in acute erthro leukaemia where megaloblastic and dyserythropoietic features are common [31], showing that morphological megaloblastosis does not necessarily require defective B12, folate utilization, karyotyping became an important tool in understanding the biology of leukaemias. Chronic myeloid leukaemia provided the early cytogeneticists to study Ph' chromosome in this disease [32].…”

Megaloblastosis: From Morphos to Molecules

“…The incorporation of 3 H-TdR into individual cells was studied by autoradiography as described by us previously [18] . DNA content of individual cells in the bone marrow smears was measured after Feulgen staining in a Becton-Dickinson Cellular Imaging System (CAS 200).…”

“…Megaloblastic changes in erythroleukemia and myelodysplastic syndrome are possibly caused by mechanisms unrelated to the dU suppression abnormality [18] . The results of our studies on experimental folate deficiency in rhesus monkeys and Wistar strain rats are of considerable interest and relevant to the possible relationship between deranged DNA synthesis and the development of megaloblastosis.…”