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E Fibach

Publications and source records attributed to E Fibach.

At least 127 records · Page 7Linked to original sources
PubMed1981

Changes in acid proteolytic activity during differentiation of murine erythroleukemic cells.

Proteolytic activity was measured in murine erythroleukemic 745 cell line grown in culture, before and after the addition of agents which promote differentiation. The 36,000 X g soluble fraction of the cells degraded [14C]globin with maximal activity at pH 3.6, while the insoluble fraction failed to degrade [14C]globin within a pH range of 2.5-9.0. The acid protease activity in the soluble fraction of the undifferentiated murine erythroleukemic cells increased during the first 2 days in culture and remained constant during the following 4 days. We suggest that this activity resides in the lysosomes since it migrates together with the lysosomal marker alpha-mannosidase on colloidal silica gradients, shows maximum activity at acid pH and is sensitive towards inhibition by pepstatin. Induced differentiation of the cells by dimethyl sulfoxide, butyric acid or hexamethylene bisacetamide was concomitantly associated with a marked reduction in protease activity and the accumulation of hemoglobin within the cells. In contrast, in a non-inducible variant of 745 cell line DMSO failed to affect proteolysis. It is suggested that in murine erythroleukemic cells changes in acid protease activity are associated with the cellular triggered by chemical inducers.

Animals↗
PubMed1981

Tumour promoters induce macrophage differentiation in human myeloid cells from patients with acute and chronic myelogenous leukaemia.

Twelve-O-tetradecanoyl phorbol-13-acetate (TPA) and other tumour promoter plant diterpenes transformed myeloid cells from peripheral blood, bone marrow and spleen from patients with chronic and acute myeloid leukaemia and acute myelomonocytic leukaemia into macrophage-like cells. This transformation resulted in cessation of cell multiplication, adherence of the cells to the surface of the culture dish, and acquisition of phagocytic activity, Fc receptors and enzymatic content characteristic of the monocyte-macrophage pathway of differentiation. The fact that tumour promoters induce differentiation in human myeloid leukaemia cells and not in similar cells from non-leukaemic conditions suggest their possible application in diagnosis and chemotherapy.

Bone Marrow↗
PubMed1981

Iron incorporation into ferritin and hemoglobin during differentiation of murine erythroleukemia cells.

Hemoglobin and ferritin iron content have been followed during differentiation in tissue cultures of murine erythroleukemia cells (MELC) using the techniques of Mössbauer spectroscopy and electron microscopy. In undifferentiated cells grown without DMSO, only iron stored in ferritin was detected. The amount of iron in a cell grown in the presence of iron citrate is approximately 1.2 X 10(-14) g, whereas in a cell grown in the presence of transferrin the amount is approximately 0.28 X 10(-14) g. These quantities do not depend on the iron concentration in the nutrition medium in a range from 0.3 to 2.0 microgram Fe/ml and are the same for growth times between 8 hr and 7 days. Cells grown with DMSO contain, in addition to ferritin, increasing concentrations of hemoglobin. Chase experiments prove that ferritin iron participates in hemoglobin synthesis. The amount of ferritin iron reaches saturation within less than 8 hr in MELC grown with or without DMSO. In differentiating cells grown with iron citrate there is a decrease with time in ferritin iron content concomitant with the increase in hemoglobin. Cells grown with transferrin incorporate additional amounts of iron, which are approximately equal to the amounts used for hemoglobin synthesis maintaining a constant ferritin iron level. In the electron microscope, iron is seen only as ferritin within lysosomes. The density of the ferritin in lysosomes correlates with the ferritin iron concentrations determined by Mössbauer spectroscopy.

Animals↗
PubMed1980

Tumor promoters enhance myeloid and erythroid colony formation by normal mouse hemopoietic cells.

The diterpene tumor promoters enhance the proliferation in culture of myeloid and erythroid precursor cells from normal mouse hemopoietic tissues. The effect is observed only with those diterpenes that are tumor promoters, including 12-O-tetradecanoylphorbol 13-acetate (TPA); diterpenes that are inactive as tumor promoters are ineffective as stimulators of colony formation. Tumor promoters act synergistically with suboptimal concentrations of conditioned medium used as a source of colony-stimulating factor (CSF) to increase both the number and size of myeloid colonies. Formation of myeloid colonies is stimulated by tumor promoters even without addition of CSF. Both pure and mixed granulocyte/macrophage colonies develop; high concentrations (> 100 micrograms/ml) of TPA are more favorable for macrophage colony formation. In erythropoietin-stimulated cultures, tumor promoters enhance the development of relatively early and intermediate of erythroid precursors, whereas later erythroid precursors are unaffected.

Animals↗
PubMed1979

Tumor promoter-mediated inhibition of cell differentiation: suppression of the expression of erythroid functions in murine erythroleukemia cells.

Previous studies demonstrated that 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a tumor promoter, is a potent inhibitor of inducer-mediated differentiation of murine erythroleukemia cells. Inhibition of cell differentiation was associated with inhibition of cell growth. The present studies, employing a cell line adapted for growth in TPA, demonstrate that inhibition of differentiation is not dependent upon inhibition of cell growth or a change in the cell division cycle; neither is inhibition of differentiation accompanied by detectable effect on cell uptake of [3H]hexamethylene bisacetamide, the inducer used in these studies. TPA causes an inhibition of expression of all hexamethylene bisacetamide-inducible erythroid characteristics measured, including commitment to terminal cell division, accumulation of globin mRNA, and synthesis of globins, spectrin, heme synthetic enzymes (delta-aminolevulinic acid dehydratase and uroporphyrinogen-I synthase) and heme. A hypothetical model for the inhibitory action of tumor promoters on terminal cell differentiation is discussed.

Cell Differentiation↗
PubMed1978

Tumor promoters inhibit morphological differentiation in cultured mouse neuroblastoma cells.

When added to mouse neuroblastoma cultures, the potent tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits spontaneous neurite formation as well as that induced in response to serum deprivation, prostaglandin E1, 5-bromo-2'-deoxyuridine, and papaverine. Other tumor-promoting macrocyclic plant diterpenes also inhibit neurite formation, whereas nonpromoting diterpenes do not. Inhibition by TPA was reversible and was unrelated to toxicity.

Bromodeoxyuridine↗
PubMed1978

Regulation of differentiation in normal and transformed erythroid cells.

Studies are described employing two erythropoietic systems to elucidate regulatory mechanisms that control both normal erythropoiesis and erythroid differentiation of transformed hemopoietic precursors. Evidence is provided suggesting that normal erythroid cell precursors require erythropoietin as a growth factor that regulates the number of precursors capable of differentiating. Murine erythroleukemia cells proliferate without need of erythropoietin; they show a variable, generally low, rate of spontaneous differentiation and a brisk rate of erythropoiesis in response to a variety of chemical agents. Present studies suggest that these chemical inducers initiate a series of events including cell surface related changes, alterations in cell cycle kinetics, and modifications of chromatin and DNA structure which result in the irreversible commitment of these leukemia cells to erythroid differentiation and the synthesis of red-cell-specific products.

Cell Cycle↗
PubMed1978

Induction of murine erythroleukemia differentiation by actinomycin D.

Murine erythroleukemia cells are induced to differentiate by 0.5-5 ng of actinomycin D per ml. Murine erythroleukemia cells cultured with actinomycin D prolong cell doubling time but achieve the same density after 5 days as cells without inducer. Actinomycin D causes over 95% of the cells to become benzidine-reactive. [(3)H]Actinomycin D uptake into DNA can be detected within 2 hr and reaches a maximum (approximately 0.1 pmol/10(6) cells) by 10-12 hr. It is estimated that about one out of 10(5) dG.dC pairs is bound to actinomycin D. Commitment to differentiation, assayed by transfer of cells to culture without inducer, was detected as early as 5 hr. Unlike Me(2)SO, which causes a transient prolongation in G(1) at about 15-20 hr, cells cultured with actinomycin D show a more sustained increase in the proportion of the cells in G(1). Globin mRNA accumulation was detectable by 19 hr in culture. Alteration in DNA stability in alkaline sucrose gradients was detected by 19 hr. Actinomycin D induces synthesis of Hb(maj) and Hb(min) in approximately equal amounts. A decrease in rates of synthesis of RNA, DNA, and total protein occurs in cells cultured with actinomycin D, as well as in cells cultured with Me(2)SO. No evidence for an early action of actinomycin D at the plasma membrane was obtained by measurement of changes in cell volume or (86)RbCl uptake. Taken together, the present results indicate that actinomycin D is a potent inducer of differentiation of murine erythroleukemia cells and suggest that the target of its effect may be at the level of DNA.

Animals↗
PubMed1978

Changes in DNA associated with induction of erythroid differentiation by dimethyl sulfoxide in murine erythroleukemia cells.

The Friend virus-infected murine erythroleukemia cell can be induced to differentiate along erythroid cells in culture with various compounds, including dimethyl sulfoxide. DNA from murine erythroleukemia cells cultured with dimethyl sulfoxide shows a decrease in sedimentation rate in alkaline sucrose gradients after alkali lysis of the cells. These changes can be detected as early as 27 hr after the beginning of culture. Similar results are observed with DNA of the cells cultured with other inducers, butyric acid and dimethylacetamide, but not with DNA from a variant cell line resistant to induction with dimethyl sulfoxide. Ultraviolet irradiation, which is known to cause similar changes in the sedimentation rate of DNA in alkaline sucrose gradients, induces differentiation of the murine erythroleukemia cells. These studies suggest that alterations in DNA may be related to events involved in the induction of differentiation of murine erythroleukemia cells by dimethyl sulfoxide.

Alkalies↗
PubMed1978

Heterogeneity of murine erythroleukemia cells with respect to tumor promoter-mediated inhibition of cell differentiation.

Spontaneous and induced differentiation of murine erythroleukemia cells (strain 745A DS19 ) is reversibly inhibited by 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent promoter of mouse skin carcinogenesis, and by other tumor-promoting macrocyclic plant diterpenes, but it is not by nonpromoting diterpenes. Twelve clones randomly isolated from this strain vary in their response to TPA. All clones are induced to differentiate by several compounds, the most potent of which is hexamethylene bisacetamide. In six clones TPA (100 ng/ml) caused greater than 90% inhibition of differentiation, as measured by the appearance of benzidine-reactive cells. In two clones cell differentiation was not inhibited by TPA even at concentrations as high as 1 microgram/ml. In four clones, differentiation was only partially inhibited (16 to 47%) by TPA. Clones resistant to TPA inhibition of differentiation were also resistant to structurally related tumor-promoting agents. The isolation of variant cell lines, sensitive and resistant to TPA, provides a tool for elucidating the mechanism of tumor promoter-mediated inhibition of cell differentiation.

Anesthetics↗
PubMed1977

Accumulation of alpha- and beta-globin messenger RNAs in mouse erythroleukemia cells.

The accumulation of alpha- and beta-globin mRNA sequences in murine erythroleukemia cells (MELC) treated with various inducers has been studied using specific alpha- and beta-globin complementary DNAs (cDNAs). In cells cultured with dimethylsulfoxide (Me2SO), hexamethylene bisacetamide (HMBA) or butyric acid, accumulation of alpha-globin mRNA is detectable after 16, 12 and 8 hr of culture, respectively. An increase in beta-globin mRNA sequences is not detected until 20-24 hr after culture. In cells exposed to hemin, both alpha- and beta-globin mRNAs are detectable by 6 hr of culture, and a constant ratio of alpha/beta-mRNA is maintained during induction. In maximally induced cells, the alpha/beta-globin mRNA ratios are approximately 1 in cells induced by Me2SO and HMBA, and 0.66 and 0.3-0.50 in cells induced by butyric acid and hemin, respectively. Thus different inducers of erythroid differentiation in MELC lead to different times of onset of the expression of alpha- and beta-like genes. In addition, the relative accumulation of alpha- and beta-globulin mRNAs in induced cells differs with various types of inducers.

Acetamides↗
PubMed1977

Tumor promoters inhibit spontaneous and induced differentiation of murine erythroleukemia cells in culture.

Addition of the potent tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), to murine erythroleukemia cell lines in suspension cultures inhibited both spontaneous differentiation and differentiation induced by hexamethylene bisacetamide (HMBA), dimethyl sulfoxide, or butyric acid. Inhibition was unrelated to cytotoxicity and was reversible. When several plant diterpenes were tested, there was a positive correlation between tumor-promoting activity and inhibition of differentiation. TPA inhibited HMBA-induced differentiation only if added prior to the time of commitment to differentiation, as assayed by scoring for differentiation after transfer of cells from HMBA to fresh medium without HMBA. TPA-mediated inhibition of differentiation was associated with a decrease in globin mRNA accumulation.

Acetamides↗
PubMed1977

Effect of hexamethylene bisacetamide on the commitment to differentiation of murine erythroleukemia cells.

Friend virus-transformed murine erythroleukemia cells express the program of erythropoietic differentiation under the influence of the previously described, potent inducing agent, hexamethylene bisacetamide. Commitment to differentiation, defined as the ability to continue the processes of differentiation in the absence of inducer, has been examined at the single-cell level, with a combination of suspension and cell-cloning techniques. Recruitment of committed cells is shown to occur prior to the detectable accumulation of hemoglobin or the appearance of morphological changes characteristic or erythroid maturation. The stability of the commitment of murine erythroleukemia cells to differentiate is found to be dependent upon both the concentration of hexamethylene bisacetamide and the duration of exposure to the inducing agent. Under conditions less than optimal for induction, a single cell can give rise to a colony containing both differentiated and undifferentiated cells. On the basis of these findings, it is suggested that fully stabilized differentiation, in addition to the previously demonstrated requirement for the inducing agent to be present during a cell-cycle S phase, involves subsequent stabilizing event(s) caused by a direct or indirect action of the inducing agent.

Acetamides↗