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Biomedical subjects

S N Wickramasinghe

Publications and source records attributed to S N Wickramasinghe.

At least 127 records · Page 7Linked to original sources
PubMed1986

Acquired folate deficiency in phytohaemagglutinin-stimulated human lymphocytes.

3H-thymidine (3H-TdR) incorporation, deoxyuridine (dU)-suppressed values, modal cell volume and the relative DNA content of individual cells have been determined in phytohaemagglutinin (PHA)-stimulated normal human lymphocytes cultured for varying periods in folate-free medium and media supplemented with various concentrations of folic acid. The results indicate that when the intracellular folate content falls below 400-600 pg/10(6) cells, lymphocytes exhibit increased 3H-TdR incorporation into DNA, raised dU-suppressed values, an increase in cell volume and abnormal DNA synthesis. This critical concentration of folate is just present in resting lymphocytes, but falls on stimulation by PHA, and the effects of folate deficiency become increasingly evident beyond a culture period of 24 h unless the folic acid concentration in the medium is at least 0.32 microgram/ml. Thus human lymphocytes cultured in folate-free medium provide a model for folate-deficient DNA synthesis, but their usefulness for the performance of dU suppression tests in the diagnosis of clinical folate deficiency is likely to be limited.

Cells, Cultured↗
PubMed1986

A method for performing deoxyuridine suppression tests on microtitre plates.

A method of performing deoxyuridine suppression tests on bone marrow cells using microtitre plates is described. The geometric mean and 95% reference interval derived from 19 patients with normoblastic erythropoiesis and normal levels of serum B12 and folate were, respectively, 5.1 and 2.0-12.8%. In 70 deoxyuridine suppression tests on 60 patients, the correlation between the results from the conventional tube test and the plate method was good, r = 0.9, P less than 0.001, and replicate tests with both techniques showed equal degrees of precision. The microtitre plate method uses fewer cells and is easier to perform than the tube method: thus each test may be performed in triplicate, and additional investigations carried out on cells obtained from a single marrow aspiration. We conclude that the microtitre plate method of performing a deoxyuridine suppression test is useful for both diagnostic and research purposes.

Bone Marrow Cells↗
PubMed1986

A case of macrocytosis and megaloblastic erythropoiesis of unknown aetiology.

The clinical and laboratory features in a non-anaemic 23-year-old female with marked macrocytosis and florid megaloblastic erythropoiesis of unknown aetiology are described. The bone marrow cells gave a normal deoxyuridine-suppressed value indicating that the megaloblastic erythropoiesis was not caused by vitamin B12 or folate deficiency or an impairment of the methylation of deoxyuridylate due to any other cause. The megaloblastic changes were associated with a marked degree of dyserythropoiesis, the most frequent ultrastructural abnormality being the presence of single or multiple intranuclear clefts. The characteristic light and electron microscope features of type I and type III congenital dyserythropoietic anaemia, in which mild megaloblastic changes may be seen, were absent. The distribution of the erythroblasts in the cell cycle was grossly abnormal and similar to that in severe pernicious anaemia; a high proportion of the cells were in the G2 phase and a substantial proportion seemed to have become arrested after progressing through part of the S phase. The bone marrow macrophages contained phagocytosed erythroblasts indicating that erythropoiesis was ineffective. It seems likely that the primary biochemical defect in the erythroblasts was some congenital disorder of DNA or nucleoprotein synthesis.

Adult↗
PubMed1986

Studies of erythropoietic cells in heterozygotes and homozygotes for haemoglobin Constant Spring and in heterozygotes for both haemoglobin Constant Spring and alpha-thalassaemia 1 trait: extent of globin chain precipitation and cell cycle distribution.

Electron microscope studies revealed that the average value for the percentage of erythropoietic cell profiles containing globin chain precipitates in heterozygotes for haemoglobin Constant Spring (HbCS) was similar to that in subjects with alpha-thalassaemia 2 trait and that the average values for this parameter in homozygotes for HbCS and patients with HbCS-H disease were similar to that in individuals with HbH disease. The explanation for the finding that the presence of two alpha cs genes (in homozygotes for HbCS) caused a degree of precipitation corresponding to that seen in patients with HbH disease, who have three deleted alpha genes, rather than to that seen in individuals with alpha-thalassaemia 1 trait, who have two deleted alpha genes, is uncertain. In all the patients with HbCS studied, the majority of the inclusions of precipitated globin chains had a stellate or branching appearance and were considered to consist of beta-chains. However, in the homozygotes for HbCS and to a lesser extent in the patients with HbCS-H disease there were small but significant numbers of erythropoietic cell profiles containing multiple rounded inclusions of the type seen in the beta-thalassaemia syndromes, or both branching and multiple rounded inclusions. It is argued that these rounded inclusions probably consisted either of precipitated HbCS or beta-chains rather than alpha-chains. The distribution of erythroblasts in the different stages of the cell cycle was normal in two homozygotes for HbCS and two patients with HbCS-H disease, indicating that there was little or no cell death during the proliferative phase of erythropoiesis in either of these conditions.

Adult↗
PubMed1986

Acetaldehyde causes a prolongation of the doubling time and an increase in the modal volume of cells in culture.

The effects of culturing four human cell lines--Raji, MOLT-4, WI-L2, and K562--in the presence of 10-360 microM acetaldehyde for 3-18 days have been investigated. Concentrations of 45-360 microM caused a prolongation of the cell doubling time, and those of 90-360 microM caused an increase in the modal cell volume and in the protein content per cell. The results indicate that relatively low concentrations of acetaldehyde cause an impairment of cell proliferation and an abnormality of cell growth in vitro and support the possibility that ethanol-derived acetaldehyde may be responsible for some aspects of tissue damage in chronic alcoholics, including the increase in the mean cell volume of erythrocytes. Three of the four cell lines studied showed a reduction and the fourth showed no change in modal cell volume after culture with 100 mM ethanol, suggesting that the macrocytosis of red cells induced by chronic alcoholism is not caused via some direct effect of ethanol on the erythron.

Acetaldehyde↗
PubMed1986

Studies of erythroblast function in congenital dyserythropoietic anaemia, type I: evidence of impaired DNA, RNA, and protein synthesis and unbalanced globin chain synthesis in ultrastructurally abnormal cells.

Two patients with congenital dyserythropoietic anaemia, type I (CDA) were studied. Their blood reticulocytes showed unbalanced globin chain synthesis with increased alpha:beta globin chain synthesis ratios. A high proportion of the erythroblasts displayed the characteristic "Swiss cheese" abnormality of the nuclear chromatin and some also showed cytoplasmic intrusions lined with nuclear membrane within the nucleus. Occasional erythroblast profiles contained intracytoplasmic inclusions that were ultrastructurally indistinguishable from precipitated alpha chains. The technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography showed gross abnormalities of proliferation in the early polychromatic erythroblasts. The proliferative abnormalities included an arrest of DNA synthesis after the progress of cells through part of the S phase and the formation of several mononucleate and binucleate cells with hypertetraploid total DNA contents. The bone marrow cells gave a normal deoxyuridine suppressed value, indicating that there was no impairment of the methylation of deoxyuridylate. Electron microscope autoradiographic studies showed that a high proportion of the erythroblasts with the "Swiss cheese" nuclear abnormality suffered from a severe impairment, or arrest of DNA, RNA, and protein synthesis.

Adult↗
PubMed1986

Red cell volume distribution curves and intracellular globin chain precipitation in the alpha-thalassaemic mouse, Hbath-J.

Red cell volume distribution curves were studied in alpha-thalassaemic mice (Hbath-J/+ mice) and normal mice (+/+ mice) of various ages. Individual Hbath-J/+ mice could not be reliably distinguished from their +/+ littermates on the basis of modal cell volume either at birth or during the first 3 weeks of life. However, between the ages of 4 and 30 weeks Hbath-J/+ mice displayed a degree of microcytosis that enabled them to be readily distinguished from their normal littermates using the criterion of modal red cell volume. Preliminary studies of alpha:beta globin chain synthesis ratios given by blood reticulocytes of Hbath-J/+ and +/+ mice after incubation with 3H-leucine for 5 min and 2 h suggest that there is little or no proteolysis of excess beta-chains in the alpha-thalassaemic mouse. Electron microscope studies revealed that the erythroblasts, marrow reticulocytes and circulating red cells of Hbath-J/+ but not +/+ mice contain stellate and branching intracytoplasmic inclusions, presumed to consist of precipitated beta-chains. These inclusions were ultrastructurally similar to the inclusions which have been previously reported in the erythroblasts and marrow reticulocytes of people with various alpha-thalassaemia syndromes. The proportion of erythropoietic cell profiles with inclusions was higher in Hbath-J/+ mice (in which two of the four alpha-globin genes are deleted) than in Thai patients with HbH disease (in whom there is usually a deletion of three of the four alpha-globin genes); this finding is probably related to a relatively low proteolytic capacity in the more mature mouse erythroid cells when compared with human cells. The presence of inclusion-containing red cells (mainly reticulocytes) in the peripheral blood of unsplenectomized Hbath-J/+ animals contrasts with the absence of such cells in unsplenectomized patients with alpha-thalassaemia I trait and HbH disease; this difference seems to be at least partly due to a poorly-developed pitting function in the mouse spleen.

Age Factors↗
PubMed1986

Supernatants from ethanol-containing macrophage cultures have cytotoxic activity.

After macrophages are cultured in the presence of ethanol (0.1-2.0 mg/ml) for 72 hr, the culture supernatant contains one or more cytotoxic factors which cause the detachment of mouse A9 tumour cells and a reduction of 3H-thymidine incorporation by K562 cells. The cytotoxic activity is largely abolished by heating to 56 degrees C for 10 min and is non-dialysable and hence associated with material having a molecular weight greater than about 10,000. These in vitro data support the possibility that alcohol-induced tissue damage may result from the action of cytotoxic factors generated as a consequence of an interaction between ethanol and tissue macrophages in vivo.

Animals↗
PubMed1986

Elution of antispectrin antibodies from red cells in homozygous beta-thalassaemia.

It is well-established that autoantibodies against red cell membrane antigens, such as spectrin are present in plasma of humans and animals. It is shown here that antispectrin IgG antibodies can be eluted from the red cells of patients with beta-thalassaemia intermedia. It is suggested that these antibodies could play a part in the increased rate of destruction of red cells in homozygous beta-thalassemia, either by reacting with spectrin which is abnormally exposed on the red cell surface or by a cross-reaction with a different membrane component. No rise was found in serum antispectrin levels in beta-thalassaemia; anti-red cell membrane IgG levels were slightly raised, but there was considerable overlap between the levels in patients and in normals. No autoantibody could be found in eluates from cells of normal subjects or patients with sickle cell anaemia.

Adolescent↗
PubMed1986

Haematological abnormalities in mice continuously exposed to ethanol vapour.

Mice exposed to high concentrations of ethanol vapour (25-38 mg/l of inhaled air) for 24 h develop leucopenia, neutropenia, lymphopenia, monocytopenia and thrombocytopenia but not anaemia or macrocytosis. Their bone marrows usually give normal deoxyuridine-suppressed values and contain normal numbers of granulocyte-macrophage progenitor cells and slightly reduced numbers of megakaryocytes. Mice exposed to lower concentrations of ethanol vapour (10-25 mg/l of inhaled air) for 20-43 days develop thrombocytopenia only and, like the mice exposed for 24 h, do not develop anaemia or macrocytosis. The bone marrows of mice exposed to ethanol for 24 h or for 20-43 days, did not show either megaloblastic or sideroblastic erythropoiesis. The data suggest that the ethanol-treated mouse may provide a useful model for the investigation of the mechanisms underlying some but not all of the ethanol-induced haematological changes seen in humans.

Acetaldehyde↗
PubMed1986

Observations on the biochemical basis of ethanol metabolism by human macrophages.

The metabolism of ethanol (0.1 and 1.0 mg/ml) to acetate by blood-monocyte-derived macrophages was only slightly inhibited by pyrazole, 4-iodopyrazole and 3-amino-1,2,4-triazole indicating that it was largely independent of alcohol dehydrogenase and catalase. By contrast, 50-87% of the oxidation of ethanol by these cells was inhibited by carbon monoxide, metyrapone and SKF-525A, all three of which are known to inhibit various species of microsomal cytochrome P-450. The data suggest that most of the ethanol metabolism by blood-monocyte-derived macrophages is mediated via the cytochrome-P-450-dependent microsomal ethanol-oxidising system.

Amitrole↗
PubMed1985

Human monocyte activation by supernatants from continuous cultures of Plasmodium falciparum.

When mononuclear cells derived from the blood of unsensitized adult Caucasians are incubated for 22 hours with supernatants from cultures of Plasmodium falciparum, there is a substantial stimulation of the phagocytic capacity of the adherent monocytes for anti-D sensitized red cells. This stimulatory effect is dependent on (i) a heat-stable factor in such supernatants, (ii) the presence of T lymphocytes in the mononuclear cell preparations and (iii) the occurrence of DNA synthesis in the mononuclear cell cultures. It is proposed that the malaria culture supernatant contains a mitogen which acts on non-allergized T lymphocytes and that the stimulation of such lymphocytes probably causes the release of a lymphokine which enhances the phagocytic activity of cells of the mononuclear phagocyte system.

Adult↗
PubMed1985

Serum immunoreactive erythropoietin and erythropoiesis in protein-energy malnutrition.

Immunoreactive erythropoietin was estimated in the sera of 23 Nigerian children with protein-energy malnutrition (PEM) and 14 healthy Nigerian children of similar age attending a well baby clinic. The geometric mean estimate for this parameter was 262 mIU/ml (observed range 39-1340 mIU/ml; 95% confidence range 25-1738 mIU/ml) in the children with PEM and 80 mIU/ml (observed range 43-257 mIU/ml; 95% confidence range 27-241 mIU/ml) in the health children. Erythropoietin levels were above the 95% confidence range for the healthy children in 14 of the cases of PEM. There was a statistically significant inverse correlation between the haemoglobin levels of the children with PEM and the logarithm of immunoreactive serum erythropoietin estimates (r = -0.73; P less than 0.001). By contrast, statistically significant correlations were not found between the logarithm of erythropoietin estimates and either the percentage of erythroblasts in the marrow, the M/E ratio or the logarithm of the absolute blood reticulocyte count. These data suggest that there is no abnormality of erythropoietin production in PEM and that the anaemia seen in this condition results from an impairment of erythropoiesis. A stepwise multiple regression analysis revealed a positive correlation between the logarithm of the erythropoietin level and the logarithm of the concentration of circulating neutrophil metamyelocytes plus myelocytes and we speculate on the aetiology of this finding.

Child, Preschool↗
PubMed1985

Changes in the uptake of 57Co-cyanocobalamin during dimethylsulphoxide-induced differentiation of HL60 cells to neutrophils.

The uptake of serum-bound 57Co-cyanocobalamin by uninduced and dimethylsulphoxide-induced HL60 cells has been studied. The data indicate that during the maturation of promyelocytes to neutrophil granulocytes, there is a progressive and marked reduction in (a) the number of surface receptors for the transcobalamin II-cobalamin complex (TCII-Cbl) per cell up to the metamyelocyte stage and (b) the amount of TCII-Cbl entering a cell, through the entire maturation pathway. The maturation of promyelocytes to neutrophil granulocytes was also accompanied by a marked reduction in intracellular vitamin B12 content. These observations help in explaining some features of granulocytopoiesis in cobalamin deficiency.

Biological Transport↗
PubMed1985

The morphology of redox-dye-treated HbH-containing red cells: differences between cells treated with brilliant cresyl blue, methylene blue and new methylene blue.

The ultrastructure of redox-dye-treated HbH-containing red cells has been shown to be dependent on the nature of the redox dye used. Brilliant cresyl blue causes the formation of a large number of small inclusions which are invariably attached to the inner surface of the red cell membrane. Methylene blue and new methylene blue cause the formation of a much smaller number of larger inclusions only some of which appear to be membrane-bound. These ultrastructural differences are reflected in marked differences in the light microscope appearances of the supravitally-stained cells.

Adult↗
PubMed1985

Limited value of serum ferritin in evaluating iron status in children with protein-energy malnutrition.

26 of 46 Nigerian children with protein-energy malnutrition (PEM) had elevated S-Ferritin levels; the geometric mean value in the entire group of children with PEM was 146 micrograms/l and the observed range 11-7000 micrograms/l. There was no statistically significant correlation between the logarithm of the S-Ferritin level and the amount of stainable iron in marrow fragments (r = 0.23; p greater than 0.2). A stepwise multiple linear regression analysis in which the logarithm of the S-Ferritin level was used as the dependent variable and a total of 17 clinical, biochemical and haematological parameters were used as the independent variables showed that 34.8% of the variability in S-Ferritin could be accounted for by variations in the percentage of lymphocytes in the bone marrow. We speculate that the latter parameter may be an index of previous infection and that the elevated S-Ferritin levels may, therefore, be at least partly caused by infections. Increased serum aspartate transaminase activities were also encountered in PEM, suggesting that hepatocellular damage may contribute to the high S-Ferritin levels in this condition. Our data indicate that S-Ferritin has a limited value as an indicator of iron status in subjects with PEM, presumably because of the frequency of infections and of hepatocellular damage in such subjects.

Body Temperature↗
PubMed1985

Importance of low serum vitamin B12 and red cell folate concentrations in elderly hospital inpatients.

To determine the functional importance of the low B12 and red cell folate concentrations repeatedly observed in the elderly 200 consecutive patients admitted to a geriatric unit were studied. Forty six of the patients had low serum concentrations of B12 (15), red cell folate (26), or both (five). Serum B12 and red cell folate concentrations correlated with mean cell volume, and serum B12 correlated with the neutrophil lobe count. Bone marrow deoxyuridine suppression was abnormal in 35% of the patients with low vitamin concentrations, but 55% of those with abnormal deoxyuridine suppression had morphologically normal bone marrow, and 73% had a normal mean cell volume. In patients with low vitamin values the deoxyuridine suppressed value correlated with the haemoglobin concentration and neutrophil lobe count. Thus synthesis of thymidylate was impaired by vitamin B12 or folate deficiency in at least 8% of newly admitted elderly patients, many of whom had normal blood counts despite the biochemical disturbance affecting haemopoiesis. A nutritionally depleted diet may have been responsible for many of the low vitamin values.

Aged↗