PubMed Health⌕ Search

Biomedical subjects

J S Wiley

Publications and source records attributed to J S Wiley.

At least 73 records · Page 4Linked to original sources
PubMed1989

Nucleoside transport in acute leukaemia and lymphoma: close relation to proliferative rate.

The proliferation of mammalian cells requires nucleosides which are provided either by de novo synthesis or by influx of nucleosides via membrane transporters with subsequent metabolic trapping. In this study the density of nucleoside transporters in freshly-isolated blast cells from patients with leukaemias and lymphomas was quantitated by equilibrium binding of 3H-nitrobenzylmercaptopurine riboside (NBMPR). In acute myeloid leukaemia (AML) the density of NBMPR binding sites on blast cells ranged from 3800 to 24,200 sites/cell and this value correlated with the 3H-thymidine labelling index (1-20%) which was used to measure proliferative rate (r = 0.80, P less than 0.001). Cells from patients with Burkitt's lymphoma, other B-cell lymphomas, T-lymphoblastic lymphoma and large cell lymphoma gave a 20-fold range of NBMPR site densities (from 3700 to 75,300 sites/cell) and site numbers correlated closely with the labelling index (r = 0.87, P less than 0.001). Non-proliferating cells from patients with chronic lymphocytic leukaemia expressed the lowest density of NBMPR binding sites (850-2900 sites/cell). Comparison of bone marrow and peripheral blood blasts confirmed the positive correlation between NBMPR binding sites and labelling index for four individual patients. In contrast, the density of NBMPR binding sites on lymphoblasts from non-T acute lymphoblastic leukaemia (ALL) was low (2300-7400 sites/cell) and showed little dependence on proliferation over a wide range of labelling indices (1-20%). No correlation was observed between NBMPR site density and cell size measured by the intracellular water space. Thus an increased proliferative rate of AML or lymphoma is associated with higher numbers of nucleoside transporters in the cell membrane.

Acute Disease↗
PubMed1989

Hereditary stomatocytosis: consistent association with an integral membrane protein deficiency.

We studied the RBC membrane proteins of four patients, including a mother and daughter, with hereditary stomatocytosis. One- and two-dimensional gel electrophoresis revealed that a 28 kDa integral protein, present in normal RBC membranes, was absent in all four patients. This abnormality, reported once previously (Lande et al, 1982), appears to be a characteristic feature of hereditary stomatocytosis, and may be related to the underlying permeability defect in this disorder.

Adult↗
PubMed1989

Extracellular adenosine triphosphate increases cation permeability of chronic lymphocytic leukemic lymphocytes.

Extracellular adenosine triphosphate (ATP) is known to reversibly increase the cation permeability of a variety of freshly isolated and cultured cell types. In this study the effects of extracellular ATP were studied using peripheral blood lymphocytes (PBL) isolated from both normal subjects and from patients with chronic lymphocytic leukemia (CLL). Changes in the permeability to Na+, Rb+, and Li+ ions were measured using conventional isotope and flame photometry techniques. In addition, changes in cytosolic (Ca2+) were fluorimetrically monitored to assess possible changes in net Ca2+ influx. ATP produced a 12-fold increase in 22Na+ influx into CLL cells but only a 3.5-fold increase in this flux in PBL cells. A maximal response was produced by 0.1 mmol/L ATP in the absence of Mg2+, while a twofold molar excess of Mg2+ over ATP abolished the response. ATP had no effect on the passive (ouabain-insensitive) 86Rb+ influx into PBL cells but stimulated this flux by fivefold in the CLL cells. Li+ influx into CLL cells was also stimulated threefold by ATP. Under these same conditions ATP also produced a net increase in total cell Na and a decrease in total cell K in the CLL cells. Exclusion of two normally impermeable dyes, trypan blue and ethidium bromide, was not altered in the ATP-treated CLL cells. Finally, extracellular ATP (3 mmol/L) produced no significant change in the cytosolic (Ca2+) of normal, monocyte-depleted populations of PBL. Conversely, this same concentration of ATP produced a very rapid (complete within 30 seconds) and a significant (an average threefold peak change) increase in the cytosolic (Ca2+) of cell preparations derived from five out of nine CLL patients. In these latter CLL cells, the ATP-induced elevation in cytosolic (Ca2+) appeared to be due to a net increase in Ca2+ influx, since no elevations were observed when the extracellular (Ca2+) was reduced to less than 0.1 mmol/L. These actions of ATP were specific in that equimolar concentrations of other nucleotides were without effect. These data indicate that treatment of CLL lymphocytes with extracellular ATP4 produces large increases in cation permeability. In contrast, there is less or no ATP-induced permeabilization of normal PBL.

Adenosine Triphosphate↗
PubMed1987

Degradation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in human leukemic myeloblasts and lymphoblasts.

The intracellular half-life for retention of the active triphosphate metabolite 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (araCTP) of 1-beta-D-arabinofuranosylcytosine was measured in vitro in blast cells from patients with acute myeloblastic leukemia, acute lymphoblastic leukemia, and T-cell lymphoblastic lymphoma. araCTP accumulation from 1 microM 1-beta-D-arabinofuranosylcytosine in leukemic blast cells was closely correlated with the nucleoside transport capacity as measured by equilibrium binding of [3H]nitrobenzylthioinosine. The half-life of araCTP retention was related to araCTP accumulation only when the level of araCTP was expressed as a percentage of total intracellular 1-beta-D-arabinofuranosylcytosine metabolites. Accumulation of 1-beta-D-arabinofuranosyluracil 5'-monophosphate was inversely related to the half-life of araCTP retention and directly related to dCMP deaminase activity in cell free extracts. No conversion of 1-beta-D-arabinofuranosyluracil to 1-beta-D-arabinofuranosyluracil 5'-monophosphate was detectable in intact cells. The end product of araCTP degradation was 1-beta-D-arabinofuranosyluracil and it is proposed that conversion of 1-beta-D-arabinofuranosylcytosine 5'-monophosphate to 1-beta-D-arabinofuranosyluracil 5'-monophosphate is a step in the degradative pathway of araCTP. However, it is the cells' nucleoside transport capacity which primarily determines the level of intracellular araCTP accumulation.

Arabinofuranosylcytosine Triphosphate↗
PubMed1987

The calcium permeability of cold-stored erythrocytes.

The calcium permeability of erythrocytes was studied by a new technique in which cells were loaded with an intracellular calcium chelator, quin 2, followed by measurement of 45Ca influx. The erythrocyte calcium permeability did not change during cold storage of blood in citrate-phosphate-dextrose for 6 weeks. Previous reports of an increased Ca2+ permeability in cold-stored erythrocytes have been based on an ATP-depletion technique which yields values for Ca2+ influx which are influenced by erythrocyte 2,3DPG levels.

Blood Preservation↗
PubMed1987

Cytosine arabinoside in the treatment of T-cell acute lymphoblastic leukemia.

The place of cytosine arabinoside (araC) in the treatment of T-cell acute lymphoblastic leukemia was studied by measuring nucleoside transport sites and the conversion of araC to its triphosphate (araCTP) in lymphoblasts from the peripheral blood of two patients, who were then treated with araC. Equilibrium binding of 3H-nitrobenzylmercaptopurine riboside (3H-NBMPR), a specific ligand of the nucleoside transporter, gave 16,510 to 29,400 sites/cell for T-lymphoblasts on presentation or early in relapse compared with 2730 +/- 1570 sites/cell for non-T-lymphoblasts. Accumulation of araCTP from 1 microM araC was four times greater in T-cell than non-T-cell lymphoblasts. One patient was treated with araC (100 mg/m2 daily x 7 days, continuous intravenously) at the time of her first leukemic relapse and complete remission was achieved with this single agent. When this patient relapsed and developed advanced disease the T lymphoblasts showed a 75% reduction in their ability to accumulate araCTP which paralleled a reduction in 3H-NBMPR binding. The second patient achieved complete remission with araC given in low dose (15 mg twice daily by subcutaneous injection) for 21 days at the time of a localised relapse in the mediastinum and pleura. These studies suggest that araC may have a place in the therapy of early stage T-lymphoblastic disease.

Adolescent↗
PubMed1986

Passive permeability of human red blood cells to calcium.

Ca2+ influx was measured into human erythrocytes in which efflux was blocked by either introduction of an intracellular Ca2+ chelator, introduction of the Ca2+ chelator followed by ATP depletion, or depletion of the Ca2+ pump cofactors ATP and Mg2+. The Ca2+ influx under all three conditions was 14-20 mumol . 1 cells-1 . h-1, which is an order of magnitude higher than the influx previously reported for cells depleted of either ATP or Mg2+ separately. The difference between the two values was explained by the finding of substantial Ca2+ efflux from the Ca2+-loaded ATP-depleted cells, whereas this efflux was insignificant from cells loaded with quin 2 and then ATP depleted. Under these latter conditions Ca2+ influx estimates the unidirectional permeability to this cation. Studies using this technique showed that Ca2+ influx was the same in media of isotonic sodium, potassium, lithium, choline, or magnesium chlorides. Moreover the dependence of Ca2+ influx on external Ca2+ concentration was well described by the sum of saturable and nonsaturable (linear) components.

Adenosine Triphosphate↗
PubMed1986

The use of 125I labelled staphylococcal protein A in the diagnosis of autoimmune thrombocytopenic purpura and other immune mediated thrombocytopenias.

Platelet-associated immunoglobulin (IgG) has been measured directly on platelets from normal and thrombocytopenic subjects by a modified radioactive Coombs technique. Platelet-associated IgG was detected using 125I-staphylococcal protein A after which platelets were separated from unbound 125I-protein A by centrifugation through oil. Elevated values of platelet-associated IgG were observed in 17 of 19 patients with autoimmune thrombocytopenic purpura. All patients with thrombocytopenia associated with systemic lupus erythematosus or rheumatoid arthritis showed elevated platelet-associated IgG, while normal values were found in diverse thrombocytopenias which were non-immunological in origin. Measurement of anti-platelet antibody levels by an indirect test was less reliable in diagnosing autoimmune thrombocytopenic purpura, since only 7 of the 19 patients gave elevated values. However, the indirect test was reliable in the diagnosis of quinine-dependent immune thrombocytopenia; all 6 patients with suspected quinine purpura gave strongly positive indirect tests when 1 mM quinine was added to the patient's plasma. The use of 125I-protein A to detect platelet-associated IgG provides a rapid and simple technique for the reliable diagnosis of immune thrombocytopenia.

Autoimmune Diseases↗
PubMed1985

Nucleoside transport and cytosine arabinoside (araC) metabolism in human T lymphoblasts resistant to araC, thymidine and 6-methylmercaptopurine riboside.

Alteration in cellular nucleoside transport characteristics, deoxynucleoside triphosphate (dNTP) pools and araCTP formation from cytosine arabinoside (araC) were determined for human T lymphoblasts (CCRF-CEM) resistant to araC, thymidine or 6-methylmercaptopurine riboside (6-MMPR). AraC resistance was accompanied by reduced activities of deoxycytidine and thymidine kinases, lowered cellular deoxycytidine triphosphate concentration and markedly reduced formation of araCTP from araC. The ID50 values for araC, araCTP formation and dNTP levels of thymidine-resistant lymphoblasts, which exhibited reduced thymidine kinase activity, and 6-MMPR-resistant cells, with reduced adenosine kinase activity, were similar to the corresponding parameters of wild type lymphoblasts. The nucleoside transport sites density determined by nitrobenzylmercaptopurine riboside binding was comparable for araC-resistant, wild type and thymidine- or 6-MMPR-resistant lymphoblasts.

Adenosine Kinase↗
PubMed1985

Cytosine arabinoside transport and metabolism in acute leukemias and T cell lymphoblastic lymphoma.

Cytosine arabinoside (araC) has proven efficacy in acute myeloid leukemia (AML), but its place in the treatment of acute lymphoblastic leukemia (ALL) and T lymphoblastic lymphoma is uncertain. The therapeutic potential of araC has been assessed in patients with AML, ALL, and T lymphoblastic lymphoma by measuring the conversion of araC to its active metabolite, the 5'-triphosphate of araC (araCTP), in purified blasts from patients as well as in normal polymorphs and lymphocytes. In all leukemias, araCTP was the major intracellular metabolite of araC. The highest araCTP formation was in blasts from T lymphoblastic lymphoma, which formed threefold more nucleotide than myeloblasts, and in turn myeloblasts formed twofold more araCTP than lymphoblasts from ALL. The mean araCTP formation in myeloblasts was sixfold greater than polymorphs, but in contrast, lymphoblasts and lymphocytes formed low and similar amounts of this nucleotide. Reasons for the sixfold range in araCTP accumulation in the various leukemic blasts were studied. The mean size of myeloblasts was 35-70% larger than lymphoblasts when compared on the basis of protein or intracellular water content, but T lymphoblastic lymphoma blasts and lymphoblasts were the same size. Activities of deoxycytidine kinase, deoxycytidylate deaminase, and pyrimidine nucleoside monophosphate kinase were not different between any of the leukemic cell types. The number of nucleoside transport sites on blasts was estimated by measuring the equilibrium binding of [3H]nitrobenzylthioinosine (NBMPR), which binds with high affinity to the transporter. Scatchard analysis yielded mean values of 27,500 sites/cell for T lymphoblastic lymphoma blasts, 10,000 sites/cell for myeloblasts, and 2,300 sites/cell for lymphoblasts. Our previous work has shown that araC influx correlates with the maximum number of 3H-NBMPR binding sites in leukemic and normal white cells. A strong correlation was observed between the number of nucleoside transport sites per leukemic blast cell and the accumulation of intracellular araCTP from extracellular araC at 1 microM. Membrane transport of araC at the low concentrations (approximately 1 microM), which are achieved therapeutically, is a major rate-limiting step in its conversion to araCTP by leukemic blast cells. Myeloblasts form more araCTP than lymphoblasts because of both higher nucleoside transport capacity and larger cell size. The highest nucleoside transport capacity and largest conversion of araC to araCTP is in T lymphoblastic lymphoma, which suggests that araC may be effective in the treatment of this disease.

Adolescent↗
PubMed1983

Estimation of platelet size by measurement of intracellular water space using an oil technique.

The intracellular water space of human platelets has been measured after equilibration with tritiated water and then separating these cells by centrifugation through phthalate oil of density 1.042. The mean intracellular water space of platelets in citrated plasma was 0.52 +/- 0.09 microliter/10(8) cells for 19 normal subjects. The gravimetric water content of platelets was 784 +/- 4 mg water/g cells. From these values the mean platelet volume was calculated to be 6.2 fl which agrees closely with values based on Coulter size distribution and thrombocytocrit. Gel filtration alters platelets such that a mean 19% of the platelets could not be centrifuged through phthalate oils of density 1.031 or 1.042. The measurement of tritiated water space of platelets centrifuged from their own plasma through oil provides a simple and reliable estimate of the mean platelet size.

Blood Platelets↗
PubMed1983

Hereditary spherocytosis of man. Defective cytoskeletal interactions in the erythrocyte membrane.

Hereditary spherocytosis (HS) is an inherited abnormality of red cell shape and results from defective interactions amongst the components of the cytoskeleton. It is known that spectrin/actin dissociates in low ionic strength media from ghosts and cytoskeletons at a rate which is slower for HS than normal preparations. Hybridization experiments have established that this behaviour is not due to a defective spectrin or actin but resides in a spectrin-binding component of the membrane [Hill, Sawyer, Howlett & Wiley (1981) Biochem. J. 201, 259-266]. In the present study erythrocyte shells have been examined in low ionic strength media and a similar difference in the rate of solubilization has been revealed. Since band 4.1 (but not band 2.1) is a common component of cytoskeletons and shells it is possible that 4.1 may be abnormal in the HS condition. The interaction of band 4.1 with spectrin/actin was examined by low shear falling ball viscometry. The addition of a mixture of band 2.1 and 4.1 to a solution of actin and spectrin tetramer increased the viscosity due to cross-linking of the cytoskeletal elements by band 4.1. When band 2.1/4.1 mixtures were derived from five HS families the viscosity was increased to a greater extent than in the normal controls. This difference was not a result of alterations in the calcium dependence of the spectrin/actin-band 4.1 interaction. The results imply that band 4.1 may be defective in the HS condition.

Actins↗
PubMed1983

Cytosine arabinoside transport by human leukaemic cells.

The membrane transport of cytosine arabinoside (araC) has been studied in blasts freshly isolated from a variety of acute leukaemias. The major fraction of araC influx was facilitated and this fraction was 80-87% at l microM araC and 68-80% at 200 microM araC. Competitive kinetics were observed between araC and deoxycytidine for entry into leukaemic blasts and, moreover, araC influx was blocked by phloretin, a broad-spectrum inhibitor of facilitated transport systems. Kinetic analysis of facilitated araC influx gave KmS which varied over a 10-fold range between patients and which were positively correlated to the Vmax. Nucleoside influx Vmax also varied over an 80-fold range between individuals, although the mean araC transport was 4-fold greater in myeloblasts than in lymphoblasts. Larger transport of araC may explain the greater sensitivity of acute myeloid leukaemia to this drug.

Acute Disease↗