Biomedical subjects

E Smeland

Publications and source records attributed to E Smeland.

28 records · Page 2Linked to original sources

PubMed1989

Levels of myc protein, as analyzed by flow cytometry, correlate with cell growth potential in malignant B-cell lymphomas.

We have analyzed c-myc protein expression during the cell cycle in malignant B-cell lymphomas by dual flow cytometric detection of a fluoresceinated polyclonal anti-myc antibody and propidium iodide which binds stochiometrically to DNA. The data obtained were correlated to other parameters of cell activation such as histopathological grading, expression of the activation antigen 4F2, light scatter (proportional to cellular volume), DNA synthesis and percentage of S-phase cells. The c-myc protein level was strongly correlated to parameters of DNA synthesis/content. In addition, the oncoprotein level was largely unvarying from the late G1 phase through the rest of the cell cycle in both malignant cells and normal purified B cells stimulated to proliferate in vitro.

B-Lymphocytes↗

PubMed1988

Retinol bound to physiological carrier molecules regulates growth and differentiation of myeloid leukemic cells.

We have tested effects of retinol bound to its physiological carrier molecules, i.e. low density lipoprotein chylomicron remnants, and retinol binding protein (RBP) on differentiation and proliferation of myeloid leukemic cells in concentrations that can be obtained in vivo. Data presented in this study show that physiological concentrations of retinyl ester in chylomicron remnants induce differentiation and inhibit proliferation of the cell line HL-60 and promyelocytic leukemic cells in primary culture. Retinyl ester in low density lipoprotein showed no effect either on cell differentiation or proliferation of any of the myeloid cells tested. Retinol bound to RBP induced differentiation of HL-60 cells only in concentrations above those that can be found in vivo. However, cell proliferation was reduced both in HL-60 cells and in primary culture of leukemic cells using physiological concentrations of holo-RBP. These results suggest that retinyl ester in chylomicron remnants is the most effective vehicle for transport of retinol into leukemic cells in vivo.

Adult↗

PubMed1987

Epstein-Barr virus mediates a switch in responsiveness to transforming growth factor, type beta, in cells of the B cell lineage.

The functional performance of the transforming growth factor beta (TGF beta), appears to depend on the target cell phenotype as well as in vitro culture conditions. We show here that Epstein-Barr virus (EBV)-infection may induce a change in responsiveness to TGF beta, since TGF beta inhibits traverse of the cell cycle of activated normal human B cells, but promotes cell proliferation of EBV-positive Burkitt's lymphoma cell lines as well as EBV-infected B cells. We present evidence that the switch in the responsiveness to TGF beta is mediated by EBV infection, irrespective of the proliferative status of target cells, and thus may contribute to the initiation as well as the maintenance of certain B cell neoplasias.

B-Lymphocytes↗

PubMed1986

Effect of near normoglycaemia for two years on progression of early diabetic retinopathy, nephropathy, and neuropathy: the Oslo study.

Forty five insulin dependent diabetics were randomised to treatment with continuous subcutaneous insulin infusion (CSII), multiple insulin injections (five or six daily), or conventional twice daily insulin injections. Near normoglycaemia was obtained with CSII and multiple injections but not with conventional treatment (p less than 0.01). Hypoglycaemic coma was observed less frequently with CSII than with multiple injections and conventional treatment (p less than 0.001), but blood glucose concentrations below 2.5 mmol/l (45 mg/100 ml) were more common. After two years fewer retinal microaneurysms and haemorrhages had developed in the patients given CSII and multiple injections compared with those given conventional treatment, in whom the number had increased significantly (p less than 0.01). Motor nerve conduction velocity deteriorated in the patients given conventional treatment; in those given CSII it was unchanged during the first year but had improved after two years (p less than 0.01). Glomerular hyperfiltration was reduced with CSII, but no change occurred in urine albumin excretion rates. Long term near normoglycaemia may prevent the progression of early stages of late diabetic complications.

Blood Glucose↗

PubMed1986

Characterization of human mononuclear cells after positive selection with immunomagnetic particles.

We have investigated the possibility to employing magnetic monodisperse polymer particles for positive selection of human peripheral blood mononuclear cell populations. By carefully titrating the ratio between particles and cells we succeeded in isolating a number of cell populations that could be cultivated subsequently in vitro for functional studies. The success of the procedure is partly dependent on the properties of the monoclonal antibodies used to sensitize the cells. Provided these antibodies do not react with membrane structures involved in the transduction of activating signals, highly purified, quiescent cell populations can be recovered in a single fractionation step. In most instances particles will detach from the isolated cells by overnight culture, and the particles can then be removed from the system by a suitable magnet. T lymphocytes, subpopulations of T lymphocytes, and B lymphocytes have been isolated in this way and studied in a variety of functional assay systems. Comparison with cells obtained after negative selection clearly demonstrates the usefulness of this technique, especially if the membrane marker selected for it is not directly engaged in the activation processes.

Antibodies, Anti-Idiotypic↗

PubMed1985

The specific induction of myc protooncogene expression in normal human B cells is not a sufficient event for acquisition of competence to proliferate.

Resting human B cells can be activated to proliferate in the presence of both polyclonal antibodies to immunoglobulin mu heavy chains and B-cell growth factor (BCGF). This process appears to be temporally controlled in that the initial activation of the B cells and their responsiveness to BCGF is carried out by polyclonal anti-mu-chain antibodies alone. We have used this system to investigate the role of the c-myc gene in the cell cycle of normal human peripheral blood B cells. Our results show that the polyclonal anti-mu-chain antibody-induced B-cell activation is accompanied by a specific induction of c-myc gene expression without promoting subsequent entry into the S phase unless BCGF is added. Monoclonal antibodies to either mu chain or the pan-B-cell antigen Bp35 also revealed a similar G0-to-G1 transition and activation of c-myc gene expression. However, unlike activation with polyclonal anti-mu-chain antibodies, cells stimulated with these monoclonal antibodies do not acquire responsiveness to BCGF. The results imply that additional inducible functions must be present to potentiate the myc-specific function in order for the B cells to acquire the capacity to proliferate in response to BCGF. These findings are discussed in relation to the origin of B-cell malignancies.

Antibodies, Anti-Idiotypic↗

PubMed1985

Characterization of two murine monoclonal antibodies reactive with human B cells. Their use in a high-yield, high-purity method for isolation of B cells and utilization of such cells in an assay for B-cell stimulating factor.

We describe two monoclonal antibodies, HH1 and HH2. Both reacted selectively with surface immunoglobulin (sIg)-positive human B cells. Both antibodies stained on average 7-8% of peripheral blood mononuclear cells. They have not been found to react with cells or cell lines of other haematopoietic cell lineages, except that HH2 was positive on a small percentage of cells of the erythroid cell line K562. The molecular weight of the HH1 antigen was 95 kD, as established by Western blotting. Neither of these two antibodies reacted with Ig determinants, Fc receptors, complement receptors, or known class-I or class-II molecules. A combination of these antibodies was used in a direct panning technique for high-yield enrichment of normal B lymphocytes from peripheral blood. The enriched B cells could be further purified by lysis of T cells (final yield, on average 72 +/- 8% of initial B cells) or by a second panning (yield, 35 +/- 11%). The purified B cells contained less than 1% contaminating T cells and less than 0.5% monocytes and were used in an assay for B-cell-stimulating factor which they showed a normal and very reproducible proliferative response.

Animals↗

PubMed1985

Intracellular Ca2+ buffering potentiates an 86Rb+ permeability response in human lymphocytes.

The effects of antibodies against immunoglobulin delta-heavy chains (anti-delta) on intracellular free Ca2+ concentrations, [Ca2+]i, and 86Rb+ influx in human neoplastic B-cells were tested in vitro. When preloading the cells with high concentrations of the fluorescent Ca2+ chelator quin 2 and subsequently stimulating in EGTA medium, the anti-delta induced rise in [Ca2+]i was strongly reduced or blocked. Nevertheless, 86Rb+ influx, also induced by anti-delta, was potentiated. In fact, in a population of cells in which anti-delta increased [Ca2+]i, but not 86Rb+ influx under standard conditions, the combination of quin-2 preloading and subsequent extracellular Ca2+ chelation by EGTA revealed an anti-delta induced 86Rb+ influx. Most of this influx was ouabain resistant, suggesting only a minor contribution from the Na+/K+ pump. Based on the Ca2+ buffer effect of quin 2 we suggest that the Ca2+ effect on 86Rb+ (K+ analogue) permeability is not mediated by increased [Ca2+]i but rather by the Ca2+ release per se from the plasma membrane.

Antibodies↗

PubMedDate not supplied

The effect of calcium channel blockers and calcium on methotrexate accumulation in rat hepatocytes.

The effects of diltiazem (DIL), verapamil (VRP) and Ca2+ on the accumulation of methotrexate (MTX) were investigated in isolated rat hepatocytes. At the physiological 2 mM Ca2+, the calcium-channel blockers DIL (100 microM) and VRP (50 microM) significantly reduced the hepatocellular accumulation of MTX. By increasing the Ca2+ concentration to 7 mM control MTX levels (at 2 mM Ca2+) were restored with VRP, and resulted in MTX levels above the controls for DIL. Ca2+ at 7 mM significantly enhanced MTX accumulation in the hepatocyte suspensions after 60 min. The concentration time curves for MTX indicated that for the first 10 min influx was the dominating process. Dixon plot analysis of this uptake phase revealed Ki values of 140 microM for DIL and 75 microM for VRP. The data suggested that DIL was a non-competitive, and VRP a competitive inhibitor of MTX influx. Hence, the inhibitory effect on MTX accumulation mediated by DIL and VRP could be due to different mechanisms.

Animals↗

PubMedDate not supplied

Perturbation of methotrexate transport by verapamil, vinblastine, taurocholate and bromosulfophthalein in rat hepatocytes.

BACKGROUND: Methotrexate (MTX) is extensively used in different combination chemotherapy regimens. More knowledge about interactions and their mechanisms in target cancer cells and normal cells is needed to improve therapeutic efficacy and reduce toxicity. MATERIALS AND METHODS: The effect of verapamil (VRP), vinblastine (VBL), taurocholate (TAURO) and bromosulfophthalein (BSP) on MTX transport were studied in freshly isolated rat hepatocytes. RESULTS: During 60 min, 50 microM VRP decreased the hepatocellular MTX accumulation with 29%; whereas 100 microM BSP reduced MTX entrance with 15%. 100 microM VBL and 100 microM TAURO reduced the intracellular accumulation of MTX with 36% and 23%, respectively. VRP and BSP appeared to be selective MTX influx blockers, whereas VBL and TAURO inhibited both MTX influx and efflux, however, with major inhibition on MTX influx. Dixon plot analyses for TAURO and BSP were suggestive of competitive inhibition, giving inhibition constants (Ki) values of 105 microM for TAURO, and 800 microM for BSP. CONCLUSION: The data demonstrate for the first time a selective inhibitory effect of VRP upon MTX influx in isolated rat hepatocytes, whereas BSP, a potent MTX efflux inhibitor in malignant cells fails to achieve this effect in the normal cell type here investigated.

Animals↗