PubMed Health⌕ Search

Biomedical subjects

S N Wickramasinghe

Publications and source records attributed to S N Wickramasinghe.

At least 199 records · Page 11Linked to original sources
PubMed1975

Observations on the ultrastructure of erythropoietic cells and reticulum cells in the bone marrow of patients with homozygous beta-thalassaemia.

An electron microscopic study of marrow fragments from patients with homozygous beta-thalassaemia has shown that 3% of early polychromatic erythroblast profiles and 20% of late polychromatic erythroblast profiles contain intracytoplasmic alpha-chain precipitates. Various nuclear abnormalities were found including the loss of parts of the nuclear membrane and the presence of intranuclear alpha-chain precipitates, and these abnormalities were virtually confined to the non-dividing, late polychromatic erythroblasts. As most profiles of the proliferating early polychromatic erythroblasts did not contain intracytoplasmic or intranuclear alpha-chain precipitates, it is suggested that the arrest of many of these cells in the G1 phase of the cell cycle may be related to the presence of an excess of free alpha-chains rather than to the presence of alpha-chain precipitates within them. The cytoplasm of the bone marrow reticulum cells contained early and late polychromatic erythroblasts at various stages of degradation, providing direct evidence of ineffective erythropoiesis.

Bone Marrow↗
PubMed1975

Thymidine kinase activity in human bone marrow cells.

The thymidine kinase activity per 10(6) DNA-synthesising marrow cells and the rate of incorporation of tritiated thymidine into the DNA of 10(3) DNA-synthesising marrow cells were estimated in 9 haematologically normal patients and 49 patients suffering from a variety of haematological disorders. Slight increases in thymidine kinase activity were found in 6 of the 31 patients with haematological diseases associated with normoblastic erythropoiesis and greater increases were found in 3 of the 18 patients with megaloblastic haemopoiesis due to vitamin B12 or folate deficiency. In the latter group, there was a statistically significant inverse correlation between haemoglobin levels and thymidine kinase activity. No correlation was found between thymidine kinase activity and the rate of incorporation of tritiated thymidine in either the normoblastic or megaloblastic group, suggesting that the level of thymidine kinase activity does not limit the rate of incorporation of exogenously supplied thymidine into the DNA of human bone marrow cells.

Anemia, Hypochromic↗
PubMed1975

Role of transcobalamins I, II, and III in the transfer of vitamin B12 to human bone marrow cells in vitro.

A study of the uptake of transcobalamin-bound 57Co-cyanocobalamin by suspensions of human bone marrow cells has indicated that these cells can take up vitamin B12 from all 3 transcobalamins (I, II, and III). Similar transport processes were involved in the uptake from the 3 transcobalamins; uptake was dependent on the presence of calcium ions, cellular respiration and free sulphydryl groups. These results suggest that contrary to current belief, all 3 transcobalamins play a role in the transfer of vitamin B12 to tissue cells.

Biological Transport↗
PubMed1974

Assessment of deoxyuridine suppression test in diagnosis of vitamin B12 or folate deficiency.

Deoxyuridine (dU) suppression tests have been performed on virtually all marrow samples aspirated at this hospital over the past 12 months. Of the 110 samples studied 26 gave abnormal results, and these 26 samples came from patients deficient in either vitamin B(12) or folate. The dU suppression test was found to be of particular value in the diagnosis of vitamin B(12) or folate deficiency in non-anaemic patients with macrocytosis and equivocal changes in marrow morphology and in patients in whom the serum vitamin B(12) or red cell folate levels were within the normal range.

Biological Assay↗