Biomedical subjects

L C Andersson

Publications and source records attributed to L C Andersson.

At least 19 recordsLinked to original sources

PubMed1992

Ornithine decarboxylase activity is critical for cell transformation.

The enzyme ornithine decarboxylase is the key regulator of the synthesis of polyamines which are essential for cell proliferation. Expression of this enzyme is transiently increased upon stimulation by growth factors, but becomes constitutively activated during cell transformation induced by carcinogens, viruses or oncogenes. To test whether ornithine decarboxylase could be a common mediator of transformation and oncogenic itself, we transfected NIH3T3 cells with expression vectors carrying the complementary DNA encoding human ornithine decarboxylase in sense and antisense orientations. The increased expression of the enzyme (50-100-times endogenous levels) induced not only cell transformation, but also anchorage-independent growth in soft agar and increased tyrosine phosphorylation of a protein of M(r) 130K. Expression of ornithine decarboxylase antisense RNA was associated with an epithelioid morphology and reduced cell proliferation. Moreover, blocking the endogenous enzyme using specific inhibitor or synthesizing antisense RNA prevented transformation of rat fibroblasts by temperature-sensitive v-src oncogene. Our results imply that the gene encoding ornithine decarboxylase is a proto-oncogene central for regulation of cell growth and transformation.

3T3 Cells↗

PubMed1992

Modulation of calcium fluxes in Jurkat T cells by myristic acid. Inhibition is independent of membrane potential and intracellular pH.

Treatment of T lymphocytes with mitogenic antibodies against the T-cell receptor/CD3 complex induces within seconds a rise in the concentration of intracellular free Ca2+. We recently reported that free myristic acid, but not its methyl ester, inhibits both the anti-CD3-induced Ca2+ influx across the cell membrane and the Ca2+ release from intracellular stores in Jurkat T cells. Here we show that myristic acid induced a rapid hyperpolarization of the cell membrane potential and a decrease in intracellular pH in Jurkat cells. Lauric acid and palmitic acid caused minor hyperpolarization, whereas other saturated non-esterified fatty acids tested were without effect. Hyperpolarization of the membrane potential in Jurkat cells with valinomycin did not, however, inhibit the anti-CD3-induced Ca2+ signal, and the blocking effect on the Ca2+ signal in myristic acid-treated Jurkat cells was not reversed after normalization of the cell membrane potential by treatment with gramicidin. The inhibitory effect of myristic acid on the Ca2+ fluxes thus cannot be explained by changes in membrane potential. We also present evidence that the blocking effect of myristic acid on the receptor-operated Ca2+ flux is not due to the myristic acid-induced decrease in intracellular pH. Moreover, we demonstrate that myristic acid does not prevent the release of Ca2+ triggered by inositol 1,4,5-trisphosphate from intracellular pools in permeabilized cells. Our findings indicate that myristic acid blocks anti-CD3-induced Ca2+ traffic in Jurkat cells by interfering with the regulation of Ca2+ mobilization, apparently by blocking an early step in signal transduction from the T-cell-antigen receptor/CD3 complex.

Animals↗

PubMed1992

Activation of natural killer cells via the Fc gamma RIII (CD16) requires initial tyrosine phosphorylation.

Triggering of the Fc gamma RIII (CD16) on natural killer (NK) cells by monoclonal antibodies or antibody-coated target cells stimulates a rapid phospholipase C (PLC)-mediated hydrolysis of inositol phospholipids and results in subsequent delivery of the lytic hit. The role of initial tyrosine phosphorylation in these events was investigated with a tyrosine protein kinase (TPK) inhibitor, genistein. At doses that inhibited CD16-triggered tyrosine phosphorylation of substrates in intact cells, genistein did not influence serine/threonine phosphorylation or target cell binding but prevented PLC activation, cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity. These findings indicate that tyrosine phosphorylation is an early and critical event during receptor-mediated activation of the lytic machinery.

Antibody-Dependent Cell Cytotoxicity↗

PubMed1992

Regulation of the p59fyn protein tyrosine kinase by the CD45 phosphotyrosine phosphatase.

Triggering of the T cell antigen receptor/CD3 (TcR/CD3) complex leads to rapid tyrosine phosphorylation of regulatory proteins that participate in initiating T cell activation and proliferation. This signal transduction event requires the presence of the TcR/CD3-associated protein tyrosine kinase p59fyn. There is also evidence that the CD45 phosphotyrosine phosphatase is involved in TcR/CD3 signalling. We show here by capping experiments using double indirect immunofluorescence techniques that the receptor phosphotyrosine phosphatase CD45 and the intracellular protein tyrosine kinase p59fyn specifically co-distribute in functional T lymphocytes. Furthermore, we provide evidence that isolated p59fyn is a substrate for CD45 as indicated by the rapid dephosphorylation of the regulatory Tyr531 of p59fyn by CD45. This dephosphorylation is accompanied by a severalfold increase in the catalytic activity of p59fyn as measured by its autophosphorylation and phosphorylation of an exogenous substrate. We also demonstrate that CD45-mediated dephosphorylation and activation of p59fyn apparently occurs at a slow basal rate in resting T cells. This represents the first identification of a physiologic regulator of p59fyn and implies a mechanism for the role of CD45 in TcR/CD3 signal transduction.

Amino Acid Sequence↗

PubMed1992

Reduced tyrosine phosphorylation in polyamine-starved cells.

Onset of cell proliferation is associated with enhanced turnover of the polyamines putrescine, spermidine, and spermine, particularly evident in the massive increase in the activity of the rate-limiting enzyme in their production, ornithine decarboxylase (ODC). The physiological functions of these polyamines, however, have remained unclear. Here we report that treatment of LSTRA cells for 2-18 h with alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, decreased the amount of phosphotyrosine in several cellular substrates including the T cell protein tyrosine kinase p56lck. No reductions in the amount of p56lck, overall synthesis of protein and DNA, or cell viability were observed until much later. DFMO did not affect the catalytic activity of p56lck in vitro and the activity of p56lck immunoprecipitated from DFMO-treated cells was unaltered. Addition of putrescine, the reaction product of ODC, completely reversed the effect of DFMO on tyrosine phosphorylation. Finally, we provide evidence that polyamines reduce the activity of cellular protein tyrosine phosphatases toward endogenous substrates. Our results suggest that polyamines may influence the extent of tyrosine phosphorylation during cell proliferation and malignant transformation, perhaps by modulating the rate of dephosphorylation of specific target proteins.

Eflornithine↗

PubMed1992

Mitosis-arresting effect of the calcium channel inhibitor SK&F 96365 on human leukemia cells.

The effect of SK&F 96365 (1-(beta-[3-(4-methoxyphenyl)propoxyl]-4- methoxyphenethyl)-1H-imidazole hydrochloride), a recently synthesized inhibitor of receptor-mediated calcium entry, was investigated on human hematopoietic cell lines. We found that treatment of the T-cell leukemia line Jurkat with SK&F 96365 inhibited the Ca2+ influx triggered by antibodies against the CD3/TCR complex, while the inositol trisphosphate-dependent Ca2+ release from intracellular stores remained intact. A 50% inhibition of the Ca2+ influx was obtained with 5 microM SK&F 96365, while higher concentrations of the drug blocked the CD3-dependent Ca2+ influx completely. In addition to its blocking of the Ca2+ influx, treatment with SK&F 96365 was found to accumulate mitotic cells. The drug (5 microM) imposed a total cell cycle arrest in G2/M. The mitosis block could be reversed by removal of the inhibitor from the cultures, while elevation of intracellular or extracellular Ca2+ did not restore cell cycle progression. This suggests that the cell cycle block induced by SK&F 96365 is not directly related to its action as an inhibitor of receptor-mediated calcium entry. Our findings indicate that SK&F 96365, in addition to its ability to inhibit receptor-triggered Ca2+ influx, offers a new method for imposing a reversible mitosis arrest in hematopoietic cell lines.

Calcium↗

PubMed1992

Phenylarsine oxide augments tyrosine phosphorylation in hematopoietic cells.

Tyrosine phosphorylation and dephosphorylation are implicated in the regulation of cell growth and differentiation. A diverse identification of key regulatory proteins by their content of phosphotyrosine has been hampered by the very low level of tyrosine phosphorylation. This is presumably caused by the relative preponderance of phosphotyrosine phosphatase activity in many cells. We report that treatment of hematopoietic cells with phenylarsine oxide (PAO), a membrane-permeable phosphotyrosine phosphatase inhibitor, induced a dramatic accumulation of phosphotyrosine in a number of cellular proteins. No changes in serine or threonine phosphorylation were detected. The PAO-induced accumulation of phosphotyrosine occurred well before any signs of toxicity or irreversible damage to the cells were seen. Addition of dithiothreitol reversed the effect of PAO. Our data demonstrate that phosphotyrosine phosphatase activity has a major impact on the level of phosphotyrosine in cellular proteins, even in cells with high protein tyrosine kinase activity. Cells with constitutively elevated tyrosine kinase activity are easily detected following treatment with PAO and substrates with an otherwise too low phosphotyrosine content or too rapid phosphate turnover can be studied. This effect of PAO allows determinations of tyrosine phosphorylation-dependent complex formation between proteins.

Aged↗

PubMed1992

Expression and function of beta-adrenergic receptors in human hematopoietic cell lines.

We investigated the expression and functional characteristics of beta-adrenoceptors in a panel of 10 phenotypically different human hematopoietic cell lines. A binding assay with [125I]iodocyanopindolol as the ligand revealed that cell lines of myelomonocytic or histiocytic derivation (HL-60, ML-2, RC-2A, U-937) expressed high numbers of beta-adrenoceptors. An intermediate density of receptors was found in a non-T, non-B cell leukemia line (Nall-1), whereas T-cell (JM, CCRF-CEM), B-cell (Raji) or erythroleukemic cell lines (K-562, HEL) displayed minimal or undetectable binding of the radioligand. Isoprenaline-stimulated cAMP production by the cells correlated to their extent of beta-adrenoceptor expression. Southern blot hybridization analysis of genomic DNA from the cell lines with a 32P-labelled beta 2-adrenoceptor cDNA probe revealed no evidence for major rearrangement or amplification of the receptor gene. Incubation with isoprenaline in vitro suppressed the proliferation of the receptor-rich RC-2A cells but did not affect the growth rate of the receptor-deficient K-562 cells. Treatment with propranolol slightly enhanced the proliferation of the RC-2A cells but did not markedly alter the growth rate of two other cell lines, regardless of their beta-adrenoceptor status. These findings indicate a regulatory influence by the sympathoadrenergic system on selected cells of the myelomonocytic lineage.

Blood Cells↗

PubMed1992

Colostral growth factors. Possible role in bovine udder epithelial cell regeneration.

Growth of the secretory epithelium during prepartum time, and for a short period after calving, is under hormonal control by estrogen, progesterone and prolactin. The mechanism(s) by which these hormones act is not known but colostrum and milk have been shown to contain different growth promoting substances. In an attempt to unravel these relationships the effect of bovine colostrum on cellular proliferation in vitro have been characterized. Colostral thermostable factors not present in milk nor associated with fat, potently induce the proliferation associated enzyme, ornithine decarboxylase, in fibroblast cell lines. However, mammary epithelial cells appear to proliferate in response to different colostral heat sensitive factor(s) that await further characterization.

Animals↗

PubMed1991

GTP-binding membrane proteins in activated and differentiating T cells.

We have earlier reported changes in the GTP binding of several membrane proteins including Gs alpha and Gi alpha during thymic differentiation of T cells. Using an [alpha-32P]GTP-photoaffinity labeling technique we have studied the pattern of GTP binding proteins in activated and resting T lymphocytes and in T cells induced to differentiate by TPA. The GTP binding proteins in mitogen-activated T cells resembled those seen in leukemia T cell lines. Treatment of Jurkat, but not of CCRF-CEM, T cells with TPA caused increased GTP-labeling of a 34 kDa protein and Gi alpha. The GTP labeling pattern in TPA-treated Jurkat cells resembled that in resting T lymphocytes. TPA induced de novo expression of functional TCR/CD3 on CCRF-CEM and downregulation of TCR/CD3 on Jurkat cells but these changes did not correlate with the altered GTP-labeling patterns.

Cell Differentiation↗

PubMed1991

The parasites.

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Antibodies, Monoclonal↗

PubMed1991

Comparison of two different cell culture methods in evaluation of biocompatibility of latex urinary catheters.

International biocompatibility standards for urinary catheters have not yet been set. The used in vivo animal tests earlier have been shown to be insensitive and expensive. The present study compared the sensitivity and other properties of two in vitro cell culture methods, the reference method of the British Standards Institution (BSI) and the thymidine incorporation method (DNA synthesis inhibition test. The cell culture toxicities of thirty-seven latex catheters were measured and 84.8% of the catheters tested passed the BSI reference test while 94.6% passed the thymidine incorporation test. The overall batch-to-batch correlation was poor (p greater than 0.05), but within brands the correlation was better. This is obviously to be explained by the differences the characteristics of the tests and/or the chemical composition of the catheters. The thymidine incorporation test is easier to perform, requires less manpower, and is therefore less liable to subjective interpretations than the BSI test. The biocompatibility toxicity limits for latex urinary catheters need to be tightened. Our experience in this study indicates that the thymidine incorporation test or tests similar to it, which can be highly automated can be recommended for biocompatibility screening in large series, and BSI reference test can be used additionally in unclear cases.

Animals↗

PubMed1991

Interleukin-4 downregulates the p70 chain of the IL-2 receptor on peripheral blood mononuclear cells.

Data that support a differential regulation of the interleukin-2 receptor (IL-2R) alpha-(p55 or Tac) and beta-chain (p70) expression by IL-4 are presented. Cytofluorometric analysis performed on peripheral blood mononuclear cells, some of which had been nylon wool passed (enriched for T-cells), in the presence or absence of phytohemagglutinin (PHA) or OKT3, demonstrated that IL-4 has a dose-dependent capacity to inhibit beta-chain IL-2R expression, whereas the alpha-chain is nearly unaffected. We could also, as a consequence of the decreased p70 expression, detect a slight increase in the amounts of IL-2 obtained from PHA-stimulated cultures, when IL-4 was present. Further, the proliferative response, especially to IL-2, but also to PHA alone, was depressed in the presence of IL-4. These data thus give further support to the idea that not only the IL-2R complex as such, but also the two individual IL-2R chains, can be independently regulated.

Dose-Response Relationship, Drug↗

PubMed1991

Inhibition of CD3-induced Ca2+ signals in Jurkat T-cells by myristic acid.

Stimulation of T lymphocytes with antibodies against the T cell receptor/CD3 complex induces within seconds a rise in the concentration of intracellular free Ca2+. Here we show that treatment with 20 microM free myristic acid completely inhibits this Ca2+ signal and the cellular proliferation in Jurkat T cells. Also lauric acid inhibited cell growth while its blocking effect on the Ca2+ signal was weaker than that of myristic acid. Other saturated free fatty acids were inactive. The inhibitory effect of myristic acid could be reversed by the addition of fatty acid free albumin, which will bind the fatty acid. Myristic acid, but not its methyl ester, inhibited both the anti-CD3-induced Ca2+ influx across the cell membrane and Ca2+ release from intracellular stores, but not the formation of inositol phosphates. In contrast, thapsigargin-induced release of Ca2+ from the same intracellular stores was unaffected by myristic acid. Thus, myristic acid specifically blocks T cell antigen receptor-CD3 induced Ca2+ mobilization in T cells.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1991

Effect of thymectomy and immunosuppressive therapy on anti-neuroblastoma antibody levels in patients with myasthenia gravis.

Antibodies reacting with human neuroblastoma cells (NBL) are distinct from the "classical" anti-acetylcholine receptor (AChR) antibodies in myasthenia gravis (MG). The influence of therapeutic interventions on serum anti-NBL antibody levels was followed in 42 MG patients. Thymectomy alone was performed in 28 patients while immunosuppressive medication was given to 14 patients out of whom 10 also had a thymectomy. In most patients serum anti-NBL antibody titers declined after thymectomy and/or during immunosuppressive treatment, though individual variations in the antibody response could be observed. Sequential examinations of individual patients revealed an association between the clinical severity of MG and anti-NBL antibody levels. No correlation between the treatment-induced changes of anti-NBL and anti-acetylcholine receptor (AChR) antibody titers could be observed during the follow-up period in MG patients positive for both types of antibodies. These findings further emphasize the immunological complexity of MG. Anti-NBL antibodies represent a pathogenic marker of the disease and display a regulation different from that of the anti-AChR antibodies.

Adolescent↗

PubMed1991

The effect of toremifene therapy on serum immunoglobulin levels in breast cancer.

Estrogens and anti-estrogens enhance the number of immunoglobulin (Ig)-secreting cells in pokeweed mitogen (PWM)-stimulated lymphocyte cultures. Lymphocytes from patients who have received anti-estrogen therapy show similar enhancement of Ig-secreting cells after PWM stimulation. In this study the effect of anti-estrogen (toremifene) therapy on serum immunoglobulin (IgA, IgM, IgG) levels in breast cancer patients was investigated. Serum Ig levels were followed up to two years after or during the therapy. An unexpected finding was that the Ig levels decreased during the follow-up period. This decrease was seen in patients who responded to the therapy as well as in those who did not.

Aged↗

PubMed1991

The effects of anti-estrogen therapy on lymphocyte functions in breast cancer patients.

The effects of anti-estrogen therapy (tamoxifen or toremifene) on in vitro lymphocyte functions were investigated in breast cancer patients. We found that the amount of DNA synthesis, with or without PWM stimulation, was decreased in all cancer patient groups compared to normal controls. The number of Ig-secreting cells was enhanced in unstimulated peripheral blood lymphocyte cultures but decreased in PWM-stimulated cultures. This occurred in all cancer patient groups investigated, with or without anti-estrogen therapy, as compared to healthy controls. On the other hand, subsequent samples with two-month intervals showed that anti-estrogens can increase PFC responses and inhibit DNA synthesis of peripheral blood lymphocytes in more than half of the patients. Interestingly, the enhancing dexamethasone effect, which usually causes an increase in the number of Ig-secreting cells in PWM-stimulated cultures, was also seen more often in anti-estrogen-treated patients. These results suggest that anti-estrogens may have immunoregulatory effects in vivo.

Breast Neoplasms↗

PubMed1991

Biocompatibility of urinary catheters--present status.

Biocompatibility aspects of urinary catheters have been recognized by clinicians during the 1980's. After multiple reports of severe urethral damage caused by latex catheters, a series of investigations revealed that toxic substances added to the catheters during the manufacturing process can leak from the devices in situ and cause urethritis developing severe urethral strictures. Consequently, most manufacturers have improved their catheters, but there are still some catheters of inferior quality on the market. Quality is dependent on the biocompatibility testing methods. Cell culture tests are recommended, but there are no common standards regarding these. British Standards Institution has been the first in Europe to adopt toxicity limits for a cell culture test, but those are not acceptable. It is a task for the standardization committees working for the European Community to create adequate biocompatibility testing standards with clinically relevant toxicity limits. If this is not done, the use of latex catheters should be abandoned as potentially harmful devices.

Animals↗