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Biomedical subjects

S N Wickramasinghe

Publications and source records attributed to S N Wickramasinghe.

At least 145 records · Page 8Linked to original sources
PubMed1985

Rates of metabolism of ethanol to acetate by human neutrophil precursors and macrophages.

Studies employing uninduced and dimethylsulphoxide-induced HL60 cells have shown that promyelocytes metabolise ethanol (0.1 mg/ml) to acetate at the rate of 3.9 nmol/10(7) cells/hr and there is a progressive fall in the ethanol-metabolising capacity as promyelocytes mature into neutrophil myelocytes and, eventually, to band forms and neutrophil granulocytes. By contrast, macrophages derived from the treatment of HL60 cells with 1,25 [OH]2 vitamin D3 and from the culture of normal blood monocytes metabolised ethanol to acetate at much higher average rates of 180.1 and 184.7 nmol/10(7) cells/hr. Furthermore, nucleated marrow cell suspensions which were depleted of cells capable of adhering to plastic metabolised ethanol at only one-third the rate shown by non-depleted cell suspensions. The data indicate that neutrophils and their granule-containing precursors contribute relatively little and macrophages contribute substantially to the overall rate of ethanol metabolism by suspensions of nucleated marrow cells. In addition, the considerable capacity of macrophages to metabolise ethanol in vitro raises the possibility that the metabolism of ethanol by these cells in vivo may result in some deleterious effect on surrounding cells and thus, account, at least in part, for ethanol-induced tissue damage.

Acetates↗
PubMed1984

The deoxyuridine suppression test in severe anaemia following Plasmodium falciparum malaria.

Haematological studies in a group of Gambian children with severe anaemia due to Plasmodium falciparum malaria revealed marked dyserythropoietic changes in erythroblasts and evidence of increased ineffective erythropoiesis. In some cases, the bone marrow also showed a few giant metamyelocytes and ring sideroblasts. The results of deoxyuridine suppression tests indicated that these haematological disturbances were not a consequence of vitamin B12 or folate deficiency within marrow cells.

Anemia↗
PubMed1984

Ultrastructure and cell cycle distribution of erythropoietic cells in heterozygotes and homozygotes for haemoglobin E.

Marrow aspirates from heterozygotes and homozygotes for haemoglobin E (HbE) have been studied by electron microscopy and by the technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography. The erythropoietic cells of heterozygotes did not contain any precipitated globin chains and the proliferating erythroblasts of such individuals showed no abnormality in their distribution in the different stages of interphase. By contrast, 0-1.5% of late erythroblast profiles and 3.1-12.8% of marrow reticulocyte profiles of homozygotes contained intracellular inclusions resembling precipitated alpha-chains. Although precipitated globin chains were not seen in the early polychromatic erythroblasts of homozygotes, the number of these cells in the G2 phase relative to that in the S phase was increased. These data indicate that there is probably little or no imbalance of globin chain synthesis in heterozygotes, a substantial degree of imbalance in homozygotes, and a disturbance of erythroblast proliferation in homozygotes which cannot be attributed to the deleterious effects of detectable intracellular alpha-chain precipitates. The electron microscope and cell cycle distribution data in the homozygotes for HbE were similar to those in two heterozygotes for beta thalassaemia.

Bone Marrow↗
PubMed1984

The fate of excess beta-globin chains within erythropoietic cells in alpha-thalassaemia 2 trait, alpha-thalassaemia 1 trait, haemoglobin H disease and haemoglobin Q-H disease: an electron microscope study.

Electron microscope studies have been performed on bone marrow cells from individuals with various alpha-thalassaemia syndromes. Globin chain precipitates were rarely found in the erythropoietic cells of a subject with alpha-thalassaemia 2 trait. By contrast, such precipitates were found in 0.6 - 1.3% of the erythroblast and marrow reticulocyte profiles in two cases of alpha-thalassaemia 1 trait, 2.1 - 13.7% of profiles in five patients with haemoglobin H (HbH) disease and 6.2% of profiles in one patient with haemoglobin Q-H (HbQ-H) disease. In the patient with HbQ-H disease, but not in the others, the nuclei of some erythroblasts displayed the 'Swiss cheese' appearance which has been reported in some forms of congenital dyserythropoietic anaemia. It is proposed that in alpha-thalassaemia 2 trait, where the degree of excess of beta-chains is slight, most of the excess chains are degraded by proteolysis. In alpha-thalassaemia 1 trait, where there is a greater excess of beta-chains, the excess chains can undergo either proteolysis or precipitation, but there is little or no tetramerization to form soluble HbH. Finally, in HbH disease, where the degree of excess is considerable, the excess beta-chains may be subject to proteolysis, precipitation and tetramerization.

Adult↗
PubMed1984

Assessment of the value of a competitive protein binding radioassay of folic acid in the detection of folic acid deficiency.

The diagnostic value of the Becton Dickinson Radioassay Kit (125I) for the the assay of red cell folate has been investigated. The assay was acceptable with regards to precision but was non-linear with changing packed cell volume. Sensitivity of the assay was satisfactory, with 24 of 25 folate deficient patients giving red cell folate values which fell below the reference range. Specificity of the assay in the detection of folate deficiency was less satisfactory. As with microbiological assays, a considerable proportion of vitamin B12 deficient patients had low red cell folate values. In addition, low concentrations were found in 12% of patients who were unlikely to be deficient in either vitamin B12 or folic acid.

Binding, Competitive↗
PubMed1984

Hematologic and biosynthetic studies in homozygous hemoglobin Constant Spring.

The elongated alpha-globin chains of hemoglobin Constant Spring (alpha cs chain of HbCS ) are produced in low amounts such that the alpha cs-gene acts as a form of alpha-thalassemia; yet in the homozygous state the pathophysiological effects of this mutant are more severe than in the corresponding conditions that result from alpha-globin gene deletions. In studies designed to examine this discrepancy, we have demonstrated that a significant proportion of red cells produced in an HbCS homozygote has a much reduced red cell life span. Contrary to previous reports, we have been able to demonstrate the expected deficit in alpha-chain production in this condition and have shown that both the cessation of globin chain synthesis in vitro and the destruction of the excess beta-chains occur unusually rapidly. Comparison with various deletion forms of alpha-thalassemia suggests that, in terms of intracellular globin chain precipitates and free beta-chain pool, homozygous HbCS red cells more closely resemble those of HbH disease, with three of the four alpha-genes inactivated, than they do the more comparable alpha-thalassemia carriers with only two genes deleted.

Adult↗
PubMed1984

Globin chain precipitation, deranged iron metabolism and dyserythropoiesis in some thalassaemia syndromes.

Electron microscope studies of the erythropoietic cells have revealed two morphologically distinct types of intracellular inclusion in homozygous beta-thalassaemia and HbH disease, presumably reflecting different appearances of precipitated alpha- and beta-chains, respectively. Inclusions resembling those seen in homozygous beta-thalassaemia are also seen in HbE/beta-thalassaemia and to a lesser extent in heterozygous beta-thalassaemia. Dyserythropoietic changes including those indicative of deranged iron metabolism, are seen in some erythropoietic cells in all of the above-mentioned thalassaemia syndromes. Several of these changes are most prominent in homozygous beta-thalassaemia and HbE/beta-thalassaemia, less marked in heterozygous beta-thalassaemia and least prominent in HbH disease. There are gross disturbances of proliferation and protein biosynthesis in erythroblasts in homozygous beta-thalassaemia but not in HbH disease and this difference is reflected in a much greater degree of ineffective erythropoiesis in the former than in the latter. Results of studies into the relationship between the extent of alpha-chain precipitation in individual cells and both the disorder of proliferation and of protein biosynthesis are consistent with the view that these functional disturbances are related to the presence of precipitated alpha-chains and/or an expanded intracellular soluble alpha-chain pool. Some alpha-chains precipitate on centrioles and, presumably, thereby interfere with mitosis. The biochemical changes in the cell membrane of thalassaemic erythroblasts which result in their recognition and phagocytosis by macrophages remain to be determined.

Autoradiography↗
PubMed1983

Interaction between erythroblasts and macrophages in vitro: effect of neuraminidase-treatment of erythroblasts and the role of serum factors.

Some factors influencing the interaction in vitro between dimethylsulphoxide-induced Friend leukaemia erythroblasts (IFLE) and syngeneic mouse peritoneal macrophages (M phi) have been investigated. Desialation of erythroblasts by treatment with neuraminidase resulted in a significant increase in their association with and ingestion by M phi. In addition, the interaction with M phi of both neuraminidase-treated and untreated IFLE was found to be influenced by a heat-stable serum factor. gamma-globulin markedly enhanced the weak IFLE-M phi interaction which occurred at low serum concentration suggesting that the heat-stable factor may be an immunoglobulin. Desialation of the IFLE-rendered them agglutinable by peanut lectin which was used as a probe for neuraminidase-induced membrane changes. By contrast, cycloheximide treatment of IFLE which also enhances their interaction with M phi, did not result in the exposure of receptors for this lectin. It is proposed that both desialation and cycloheximide treatment of IFLE lead to secondary alterations in their membrane structure which renders them recognizable by M phi.

Animals↗
PubMed1983

Impaired protein synthesis in erythroblasts enhances their phagocytosis by macrophages.

In an attempt to elucidate mechanisms which underly ineffective erythropoiesis, we investigated the effect of impaired macromolecular synthesis in erythroblasts on their phagocytosis by macrophages in vitro. Dimethylsulphoxide-induced murine Friend leukaemia erythroblasts were treated with inhibitors of RNA or protein synthesis and subsequently tested for their interaction with syngeneic mouse peritoneal macrophages in culture. Exposure of the erythroblasts to two reversible inhibitors of protein synthesis, puromycin and cycloheximide, enhanced their association with and phagocytosis by macrophages. The effect was evident after the drugs had caused a partial inhibition of protein synthesis and appeared to be reversible. By contrast, the treatment of erythroblasts with the inhibitor of RNA-synthesis, actinomycin D, which caused a marked depression of RNA but not of protein synthesis, failed to affect the interaction of erythroblats with macrophages. The results are in keeping with previous observations on human bone marrow showing impaired protein synthesis in erythroblasts in some haematological disorders characterized by a marked increase in ineffective erythropoiesis.

Animals↗
PubMed1983

Folate levels and deoxyuridine suppression tests in protein-energy malnutrition.

A group of 39 Nigerian infants and pre-school children with protein-energy malnutrition (PEM) have been studied. Red cell folate levels were within the range observed in 19 age-matched healthy Nigerian children. Serum vitamin B12 levels were either normal or raised. Deoxyuridine (dU) suppression tests were performed on the bone marrow cells of 30 of the patients and were abnormal in 13. It is proposed that the abnormal dU-suppressed values were not caused by vitamin B12 or folate deficiency and were probably a consequence of the protein deficiency. A few megaloblasts and several giant metamyelocytes were found in four of the cases of PEM; the remaining 35 cases had normoblastic erythropoiesis, sometimes with small to moderate numbers of giant metamyelocytes. All four marrow samples containing megaloblasts gave abnormal dU-suppressed values. However, in the marrows showing normoblastic erythropoiesis there was no correlation between the presence or absence of giant metamyelocytes and the dU-suppressed value.

Bone Marrow↗
PubMed1983

Effects of ethanol on cell volume and protein synthesis in a human lymphoblastoid cell line (Raji).

A human lymphoblastoid cell line (Raji) developed macrocytosis after 5-7 days when cultured in the presence of 100, 250 and 500 mg ethanol/dl. The degree of macrocytosis was least with 100 mg/dl and greatest with 500 mg/dl. The macrocytosis was associated with a proportionate increase in the total protein content per cell, was reversed after culture in the absence of ethanol and was uninfluenced by the supplementation of the culture medium with 50 micrograms folic or folinic acids per millilitre. Ethanol also caused a substantial prolongation of the cell doubling time at concentrations of 250 and 500 mg/dl (but not 100 mg/dl) and this was associated with some increase in the proportion of non-viable cells in the cultures. Furthermore, ethanol increased the incorporation of 3H-leucine into protein per femtolitre of cell volume. It is proposed that the ethanol-induced macrocytosis may have developed as a consequence of the stimulation of the rate of protein synthesis within a normal or prolonged cell cycle.

Cell Count↗
PubMed1983

Investigations into the production of acetate from ethanol by human blood and bone marrow cells in vitro.

The metabolism of ethanol to acetate and CO2 by suspension cultures of human blood and marrow cells has been investigated. The average rate of metabolism of ethanol by relatively pure preparations of monocytes plus lymphocytes, neutrophils and erythrocytes obtained from normal peripheral blood were, respectively, 12.58, 5.44 and 0.32 nmol/10(7) cells/h, when the concentration of ethanol in the culture was 2.63 mM. Under similar culture conditions, the average rate of metabolism of ethanol by suspension cultures of human marrow cells was 19.0 nmol/10(7) nucleated marrow cells/h. The metabolism of ethanol by nucleated marrow cells was only slightly inhibited by pyrazole and 3-amino-1,2,4-triazole indicating that it was largely independent of pyrazole-sensitive alcohol dehydrogenase and catalase. By contrast, the oxidation of ethanol by isolated rat hepatocytes was markedly inhibited by pyrazole and therefore appeared to be mainly dependent on alcohol dehydrogenase. It is concluded that bone marrow cells have a considerable capacity to metabolize ethanol and that the predominant biochemical pathway involved in this metabolism is different from that involved in rat hepatocytes.

Acetates↗
PubMed1982

DNA chain elongation rates in marrow cells from vitamin B12-deficient patients and methotrexate-treated mice.

The DNA synthesized by marrow cells from patients with vitamin B12 deficiency and mice previously given methotrexate (MTX), has been investigated. Suspensions of bone marrow cells were pulse-labelled with [methyl-3H]thymidine or deoxy [5-3H]cytidine for 30 s and the radioactivity in the DNA was chased thereafter in the presence of 10 microM non-radioactive nucleoside for periods up to 60 min. The rates of elongation of new daughter strands were then assessed by hydroxyapatite chromatography of alkali-denatured DNA samples. No significant differences were found between the average rates of elongation of daughter strands from control marrow cells on the one hand and the vitamin B12-deficient or the methotrexate-affected cells on the other. This is to be contrasted with the results of previous studies which have shown a retardation in the rates of movement of replication forks in stimulated, cultured lymphocytes obtained from vitamin B12- or folate-deficient patients.

Anemia, Megaloblastic↗
PubMed1982

Thiamine responsive anaemia: a study of two further cases.

A brother and sister of Pakistani origin suffered from sensorineural deafness, diabetes mellitus and a macrocytic anaemia. Their bone marrows showed megaloblastic erythropoiesis and contained many ringed sideroblasts. Electron microscope studies of the bone marrow revealed (1) iron-laden mitochondria in many erythroblasts, (2) non-specific abnormalities indicative of dyserythropoiesis in some erythroblasts, and (3) evidence of ineffective erythropoiesis. The deoxyuridine suppression test indicated that the megaloblastic changes were not caused by an impairment of the methylation of deoxyuridylate. Studies of nucleic acid synthesis in the bone marrow cells showed that the rate of incorporation of [3H]thymidine into DNA was increased and that the rates of incorporation of [14C]glycine and [14C]adenine into both DNA and RNA were essentially within the normal range. The anaemia did not respond to therapy with hydroxocobalamin, folic acid or pyridoxine but responded to 25 mg thiamine, daily, by mouth. In one of the cases a post-thiamine marrow aspirate showed a considerable improvement in both the megaloblastic and sideroblastic changes.

Anemia, Macrocytic↗
PubMed1982

Dyserythropoiesis in homozygous haemoglobin C disease.

Electron microscope studies of the bone marrow of three patients with homozygous haemoglobin C (HbC) disease have shown marked ultrastructural abnormalities in several of the polychromatic erythroblasts and marrow reticulocytes and the presence of phagocytosed erythroblasts within the macrophages. Such abnormalities were not found in the bone marrow of three patients with sickle cell anaemia indicating that the abnormalities represented a feature of HbC disease rather than a disturbance secondary to peripheral haemolysis. The characteristic ultrastructural finding in the polychromatic erythroblasts in HbC disease was the presence of grossly-disorganized nuclei showing multiple intranuclear clefts, the loss of parts of the nuclear membrane, oozing of nuclear material into the cytoplasm and an alteration of the structure and stainability of the nuclear chromatin. It is proposed that both the dyserythropoiesis and ineffective erythropoiesis in HbC disease may have resulted from the formation in vivo of very small aggregates of HbC within erythropoietic cells.

Adolescent↗