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Biomedical subjects

I Tamm

Publications and source records attributed to I Tamm.

At least 55 records · Page 3Linked to original sources
PubMed1987

Bacterial lipopolysaccharide (endotoxin) enhances expression and secretion of beta 2 interferon by human fibroblasts.

The human beta 2 interferon (IFN-beta 2) gene, a gene that also codes for B cell differentiation factor 2 (BSF-2), plasmacytoma/hybridoma growth factor (HGF), and hepatocyte-stimulating factor (HSF), is expressed in a variety of lymphoid and nonlymphoid tissues. Endotoxin, or bacterial lipopolysaccharide (LPS) preparations derived from the outer membrane of Escherichia coli or Salmonella typhimurium rapidly elevate IFN-beta 2 mRNA level in human skin fibroblasts (FS-4 strain). E. coli-derived LPS enhances IFN-beta 2 mRNA expression in FS-4 fibroblasts at a concentration as low as 0.3 ng/ml; this response is near-maximal in the range of 0.1-1 microgram/ml LPS. The increase in IFN-beta 2 mRNA level caused by LPS in FS-4 cells is detected within 30 min after addition of LPS, is sustained for at least 20 h thereafter, appears to involve the protein kinase C signal transduction pathway, does not require new protein synthesis, and is inhibited by dexamethasone in a dose-dependent fashion (in the range 10(-6)-10(-8) M). Cultures of LPS-treated FS-4 cells exhibit an antiviral state against vesicular stomatitis virus, which can be prevented by anti-IFN-beta antiserum. Medium obtained from LPS-treated FS-4 cell cultures enhances the number of immunoglobulin-secreting cells in cultures of human B-lymphoblastoid (CESS) cells. Thus, LPS may trigger a number of host defense mechanisms in the course of infection due to Gram-negative bacteria by enhancing IFN-beta 2 production by the ubiquitous fibroblast.

B-Lymphocytes↗
PubMed1987

Interferon-alpha down-regulates insulin receptors in lymphoblastoid (Daudi) cells. Relationship to inhibition of cell proliferation.

The Daudi line of human lymphoblastoid cells requires insulin and transferrin for growth in serum-free medium and is highly sensitive to the inhibitory effect of human leukocyte interferon (IFN-alpha) on cell proliferation. A variant subline of Daudi cells, which is resistant to the antiproliferative action of IFN-alpha, also has been grown in serum-free medium containing insulin and transferrin. The proliferation of IFN-sensitive and -resistant Daudi cells is dependent on the occupancy of insulin receptors, with optimal cell proliferation observed at high receptor occupancy (nearly 100%). No evidence was found for receptors for insulin-like growth factor I on Daudi cells. IFN treatment of IFN-sensitive cells decreased the capacity of the cells to bind 125I-insulin. The altered binding capacity was due to diminished specific, lower affinity insulin binding, as detected at high 125I-insulin concentrations. Higher affinity insulin binding was not altered by IFN. Insulin binding was also reduced in detergent-solubilized extracts from IFN-treated sensitive Daudi cells and the magnitude of the effect was comparable to that observed in intact cells. This indicates that the total number of insulin binding sites (surface + internal) is decreased in IFN-treated sensitive cells. Insulin binding to IFN-sensitive cells decreased linearly with time between 6 and 48 h from the addition of IFN. The effect on lower affinity insulin binding developed more rapidly than the inhibitory effect of IFN on cell proliferation. The insulin-binding capacity of Daudi cells resistant to the antiproliferative effect of IFN was unaffected by IFN, despite the fact that these cells contain as many cell surface IFN receptors as sensitive cells. These observations raise the possibility that lower affinity insulin binding is important in the growth-promoting actions of insulin.

Burkitt Lymphoma↗
PubMed1987

Rapid enhancement of beta 2-interferon/B-cell differentiation factor BSF-2 gene expression in human fibroblasts by diacylglycerols and the calcium ionophore A23187.

The expression in human fibroblasts of the beta 2-interferon (IFN-beta 2) gene, which is now recognized to be identical to the gene encoding B-cell differentiation factor BSF-2, is enhanced by several cytokines that affect cell growth (tumor necrosis factor, interleukin 1, platelet-derived growth factor, and beta 1-interferon). We have examined the possibility that IFN-beta 2 gene expression is regulated through activation, by diacylglycerol, of the protein kinase C pathway. The synthetic diacylglycerols 1,2-dioctanoylglycerol (diC8) and 1-oleoyl-2-acetylglycerol strongly enhanced IFN-beta 2, but not IFN-beta 1, gene expression in human fibroblasts (FS-4 strain). An increase in IFN-beta 2 mRNA level was detected within 15 min after addition of diC8 (290 microM) to FS-4 cells and was maximal approximately 20 hr later. An increase in IFN-beta 2 gene transcription was detected within 5 min of addition of diC8, and the rate of transcription was near-maximal by 15-30 min. The enhancement of IFN-beta 2 gene expression by diC8, interleukin 1, or tumor necrosis factor was not prevented by H8, a preferential inhibitor of cAMP- and cGMP-dependent protein kinases, but was blocked by H7, an inhibitor of protein kinase C as well as of cyclic nucleotide-dependent protein kinases. diC8 was found to protect FS-4 cells from the cytopathic effect of vesicular stomatitis virus; this protection was blocked by polyclonal or monoclonal antibodies that neutralize IFN-beta, suggesting that the antiviral effect was due to the secretion of IFN-beta 2 by the diC8-treated fibroblasts. The calcium ionophore A23187 (1-10 microM) also elicited an increase in the level of IFN-beta 2 mRNA in FS-4 fibroblasts; appropriate combinations of A23187 and diC8 had at least an additive effect in enhancing IFN-beta 2 mRNA levels. These results show that protein kinase C-activating or [Ca2+]-elevating agents rapidly increase the expression of the IFN-beta 2 gene in human fibroblasts.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1987

A cytokine network in human diploid fibroblasts: interactions of beta-interferons, tumor necrosis factor, platelet-derived growth factor, and interleukin-1.

Earlier studies demonstrated the induction of beta 2-interferon (IFN-beta 2) in human diploid fibroblasts (FS-4 strain) exposed to tumor necrosis factor (TNF). These studies suggested that IFN-beta 2 mediates an antiviral effect in TNF-treated cells and exerts a feedback inhibition of the mitogenic effect of TNF. Here we demonstrate that the expression of the antiviral action of TNF can be enhanced by prior exposure of FS-4 cells to trace amounts of IFN-beta 1. IFN-beta 1, at a higher concentration, can directly increase the expression of IFN-beta 2. Exposure of cells to TNF enhanced IFN-beta 2 (but not IFN-beta 1) mRNA expression in response to poly(I).poly(C), an IFN inducer which is also known to stimulate FS-4 cell growth. Platelet-derived growth factor and interleukin-1 also led to the increased expression of IFN-beta 2. However, platelet-derived growth factor and interleukin-1 could override the antiviral effect of TNF and also that of exogenously added IFN-beta 1. Our data suggest that a complex network of interactions that involves the endogenous production of IFN-beta 2 is triggered by several growth-modulatory cytokines. Cellular homeostasis is likely to represent a balance between the induction of IFN-beta 2 by these cytokines and their ability to override the inhibitory actions of IFN-beta 2.

Fibroblasts↗
PubMed1986

Effect of anti-Ig on cytosolic Ca2+ in Daudi lymphoblastoid cells.

We examined the response in the free intracellular calcium concentration ([Ca2+]i) of Daudi (human lymphoblastoid) cells to antibodies against human immunoglobulins (anti-Ig), and the relationship of [Ca2+]i to anti-Ig-induced capping. At 80 microM intracellular quin-2 (a fluorescent probe for [Ca2+]i), anti-Ig (10 micrograms/ml) caused a rapid increase in [Ca2+]i from 100 to 600 nM; the signal returned to baseline with approximately 1 min. At 450 microM intracellular quin-2, [Ca2+]i rose to only approximately 250 microM, and the signal declined gradually, returning to base line after greater than 7 min. In subsequent experiments, the lower concentrations of quin-2 were employed. Plots of the amplitude of the [Ca2+]i transients and of the binding of 125I-anti-Ig to Daudi cells versus the concentrations of anti-Ig showed similar saturation kinetics, with half-saturation occurring at 2-3 micrograms/ml. Part of the calcium in the transient is derived from the extracellular medium, and part from the nonmitochondrial intracellular stores. Caffeine (4 mM) and 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate HCl (0.5 mM) suppressed the release of calcium from internal stores and the entry of calcium from outside the cells, but permitted capping in more than half of the cells. Phorbol esters (1-2 nM) inhibited both capping and the anti-Ig-induced decrease in [Ca2+]i. None of these agents blocked the binding of anti-Ig to the cells. It appears that receptor capping is not dependent on the anti-Ig-induced transient increase in calcium concentration.

Aminoquinolines↗
PubMed1986

Interferon inhibits the establishment of competence in Go/S-phase transition.

Addition of mouse interferon-alpha/beta (IFN) to confluent, quiescent BALB/c 3T3 (clone A31) mouse fibroblasts resulted in a block or delay in serum-induced activation of the cell cycle. It was necessary to add IFN within 6 hours after serum stimulation to inhibit nuclear labeling with [3H]thymidine. This is consistent with the time required for platelet-derived growth factor (PDGF) to induce cells to become competent to respond to additional growth factors present in platelet-poor plasma. Simultaneous addition of IFN with PDGF inhibited the PDGF-induced synthesis of a 29-kilodalton and a 35-kilodalton protein that normally occurs within 1 hour after PDGF addition. IFN also suppressed the general increase in protein synthesis that occurs by the fifth hour after PDGF addition. These results show that IFN antagonizes the action of PDGF, thereby interfering with the activation of Go cells for G1 traverse and S-phase entry.

Animals↗
PubMed1986

Interferon-beta inhibition of concanavalin A-stimulated calcium uptake and exchange in HeLa cells.

Addition of the lectin concanavalin A (ConA) to HeLa-S3 tumor cells in culture stimulates calcium exchange and uptake. Pretreatment of the cells with interferon-beta (IFN-beta) at a concentration of 640 U/ml for 24 h markedly inhibits this ConA-stimulated calcium exchange and uptake, but not the basal level of calcium exchange. These findings suggest that a number of IFN effects on cell function may reflect an impaired ability of IFN-treated cells to respond to molecules such as growth factors and peptide hormones with increased calcium fluxes.

Calcium↗
PubMed1986

Concomitant enhancement of a cytoskeleton-associated 76,000-dalton protein and inhibition of fluid-phase pinocytosis by interferon-alpha in Fujinami sarcoma virus-transformed rat 3Y1 cells.

Addition of rat interferon-alpha (IFN-alpha) to Fujinami sarcoma virus-transformed rat 3Y1 cells progressively inhibited fluid-phase pinocytosis [10% inhibition at 3 h; maximal (60%) inhibition by 12 h]. Electrophoretic analysis of the cytoskeletal fraction from cultures exposed to IFN for 24 h revealed a novel 76,000-dalton protein (CKp76). The kinetics of its appearance paralleled the inhibition of fluid-phase pinocytosis. CKp76 was not detected in cultures pretreated with actinomycin D, or prelabeled with [35S]methionine, prior to IFN addition. However, the presence of cycloheximide during incubation with IFN had no effect on the synthesis of CKp76 after removal of both agents. These results suggest that the appearance of CKp76 was due to enhanced transcription of its gene in response to IFN. Subcellular fractionation revealed the presence of induced CKp76 in the nuclear pellet. From these results it is possible that CKp76 may be responsible at leat in part for the effects of IFN on fluid-phase pinocytosis.

Animals↗
PubMed1985

Interferon stimulates cholesterol and phosphatidylcholine synthesis but inhibits cholesterol ester synthesis in HeLa-S3 cells.

Treatment of human HeLa-S3 cells (an epidermoid carcinoma line) with human beta-interferon (640 units/ml) selectively alters lipid metabolism by increasing cholesterol synthesis per mg of cell protein as measured by 1-hr pulse-labeling of cells with [3H]acetate. Cholesterol synthesis in interferon-treated cells is increased approximately equal to 60% at 24 hr after the beginning of treatment and approximately equal to 450% at 48 hr. Continuous labeling of interferon-treated cells with [14C]acetate shows increased accumulation of label in cholesterol when normalized per mg of cell protein, as well as an increase in the specific activity of cholesterol in the treated cells. In contrast, interferon treatment decreases the accumulation of [14C]acetate into cholesterol esters. The [14C]acetate labeling of sphingomyelin, phosphatidylethanolamine, and triglycerides shows no change compared to untreated controls. The labeling of phosphatidylcholine was moderately increased in treated cells. The interferon-induced changes in lipid metabolism are a part of a coordinated response of cells to interferon treatment, characterized by reduced cell proliferation and cell motility and an increase in cell size and mass. The increased cholesterol synthesis is consistent with a model in which beta-interferon treatment of HeLa cells inhibits the endocytosis of cholesterol-containing low density lipoprotein, which results in an increase in cholesterol synthesis.

Acetates↗
PubMed1985

The effects of treatment with human beta-interferon on the stimulation of thymidine uptake and DNA synthesis by colchicine in human fibroblasts.

The marked inhibition by beta-interferon (IFN) of colchicine-induced incorporation of [3H]-thymidine into DNA of human fetal lung fibroblasts reflects inhibition of uptake of labeled precursor, rather than an effect on DNA synthesis per se. The percent of cells in S phase as measured with flow cytometry was unchanged by a concentration of IFN that reduced the uptake of labeled thymidine by 50% at 30 h after treatment.

Cell Cycle↗
PubMed1985

Chromosomal aberrations in muntjac cells resulting from exposure to interferon.

Cells of the Indian deer (Muntiacus muntjac) are sensitive to the antiviral and antiproliferative action of human beta-interferon (beta-IFN). Because of their low diploid chromosome number and readily identifiable chromosomes, they provide a convenient model system in which to test for the ability of IFN treatment to result in chromosome abnormalities. Increases in the frequencies of chromosome gaps and breaks have been observed after 72 h of treatment with IFN at a concentration of 100 U/ml. At IFN concentrations of 10-100 U/ml, there is a higher proportion of aberrations in the X chromosome than would be expected in a random distribution. At 1,000-1,700 U/ml IFN, there is an increase in the proportion of cells with multiple abnormalities over that observed at 0-100 U/ml IFN, and the distribution of aberrations appears to be random.

Animals↗
PubMed1984

Effects of beta interferon on human fibroblasts at different population doubling levels. Proliferation, cell volume, thymidine uptake, and DNA synthesis.

Cellular aging had no effect on the ability of beta interferon to increase cell volume and population doubling time in 76-109 cells, a line of human skin fibroblasts. However, DNA synthesis in cells at high population doubling levels (PDL 55-70) was inhibited after 72 h of beta interferon treatment (1,000 U/ml) while no inhibition of DNA synthesis was observed in cells at middle population doubling levels (PDL 30-40).

Cell Division↗
PubMed1984

HeLa cell RNA and protein syntheses. Effects of long-term treatment with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB).

The population growth rate of HeLa cells treated with 60 microM 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) in reinforced Eagle's minimum essential medium was directly related to the concentration of fetal bovine serum in the range from 5 to 30%. Control cells proliferated at a maximal rate (doubling time: 18-19 hr) at serum concentrations in this range. In 60 microM DRB-containing medium supplemented with 5% serum, the inhibition of hnRNA synthesis after 1,5, and 48 hr of treatment was equivalent to 78, 84, and 51%, respectively, whereas that of protein synthesis was equivalent to 5, 41, and 49%. In 15% serum, the inhibition of hnRNA synthesis after 1, 5, and 48 hr of treatment was equivalent to 75, 79, and 40%, whereas that of protein synthesis was equivalent to 13, 30, and 21%. Thus, after 48 hr of treatment of cells with DRB in either 5 or 15% serum, hnRNA synthesis was less inhibited than it was after 1 or 5 hr of treatment, and the level of protein synthesis in DRB-treated cells did not decrease between the 5th and 48th hr. After 48 hr of treatment of cells with DRB in 15% serum, hnRNA and protein syntheses were both somewhat less inhibited than after treatment in 5% serum. These results suggest that, on prolonged treatment, HeLa cells undergo a partial, serum-dependent adaptation to the inhibitor.

Cell Division↗
PubMed1984

Interferon inhibition of thymidine incorporation into DNA through effects on thymidine transport and uptake.

Replenishment of medium after 72 hr of growth of HeLa-S3 cells in dense suspension cultures increased [3H]-thymidine uptake into cells and incorporation into DNA, with the levels reaching a peak approximately 12 hr following medium change; beta interferon inhibits the enhanced uptake of [3H]-thymidine and labeling of DNA in a dose-dependent manner. Some reduction in these processes is observed at a concentration as low as 1 u/ml, and approximately 75% inhibition at 640 u/ml. Kinetic analysis has revealed that the rate of labeling of the acid-soluble pool with [3H]-thymidine, measured either at 22 degrees C or 37 degrees C, is reduced in interferon-treated (640 u/ml, 24 hr) HeLa-S3 cells. At 22 degrees C, the initial rate of thymidine transport at a high (500 microM) thymidine concentration, determined within the first 30 sec of [3H]-thymidine addition was depressed by 44% in interferon-treated HeLa cells. At 37 degrees C, labeled precursors accumulate in acid-soluble material for approximately 8 min after the addition of [3H]-thymidine, after which an apparent equilibrium level is attained. At this temperature, the rate of thymidine uptake and the apparent equilibrium level attained were depressed by 70% in interferon-treated HeLa cells. The reduced incorporation of [3H]-thymidine into DNA in interferon-treated HeLa-S3 cells can be largely explained by interferon inhibition of thymidine transport and phosphorylation.

Biological Transport↗
PubMed1984

Occurrence of cell division is not exponentially distributed: differences in the generation times of sister cells can be derived from the theory of survival of populations.

The Eyring-Stover survival theory has been applied to the kinetics of the distribution of intermitotic intervals of mammalian cells and by inference to the transition from the G1 phase into DNA synthesis (S phase). The theory faithfully fits experimental data acquired by time-lapse cinemicrography of cloned HeLa cells in tissue culture and also suggests the existence of a labile initiator substance which mediates the G1-S phase transition. This theory provides an alternative to the transition probability model proposed by Smith and Martin [Smith J. A. & Martin, L. (1973) Proc. Natl. Acad. Sci. USA 70, 1263-1267; see also Shields, R. & Smith, J. A. (1977) J. Cell Physiol. 91, 345-355 and Brooks, R. F., Bennett, D. C. & Smith, J. A. (1980) Cell 19, 493-504].

Cell Division↗
PubMed1984

Unphosphorylated gelsolin is localized in regions of cell-substratum contact or attachment in Rous sarcoma virus-transformed rat cells.

Regions associated with cell-substratum contact or attachment in Rous sarcoma virus (RSV)-transformed rat fibroblasts (RR1022 cells) were identified by reflection-interference microscopy. Electron microscopy of such regions revealed the presence of discrete membrane-associated structures composed of a paracrystalline lattice of hexagons and pentagons to which actin filaments appear to be attached. Staining of actin by biotin-labeled heavy meromyosin showed that transformed cells, unlike normal fibroblasts, lack prominent actin fibers, and that, instead, much of the fluorescence is concentrated in loci corresponding to locations of transient association between the cell and the substratum. In stationary cells, such loci were found in rosette formation, predominantly in the region beneath the nucleus. In cells engaged in active movement, such as during migration into a wound, the actin-containing spots were concentrated in the region of the leading edge. A similar pattern of staining was observed with antibody to gelsolin, a 91,000-dalton Ca2+-dependent actin filament-shortening protein. Since the action of gelsolin on actin is reversible and dependent on physiologically relevant changes in calcium concentration, the localization of gelsolin, together with actin-bundling proteins such as alpha-actinin, in the regions containing many small microfilament bundles on the ventral side of cytoplasm suggests that gelsolin may be a component of the mechanism for the disassembly and assembly of actin during the dissolution and reformation of structures for cell-substratum contact during cell locomotion. Regulation of gelsolin activity was not dependent on protein phosphorylation, as shown by lack of 32P-incorporation into gelsolin in either transformed or normal fibroblasts.

Actins↗