bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of trifluoperazine and mitogenic lectins on calcium ATPase activity and calcium transport by human lymphocyte plasma membrane vesicles
Authors: Lichtman Andrew H. , Segel George B. , Lichtman Marshall A. 
Published: February 2005

AbstractThe phenothiazine, trifluoperazine, and the mitogenic lectins, phytohemagglutinin (PHA) and Concanavalin A (Con A), were tested for their effects on human lymphocyte plasma membrane Ca‐activated Mg‐ATPase and ATP‐dependent calcium uptake. Trifluoperazine completely inhibited Ca‐uptake when present from the start of the assay at concentrations of 100 m̈M or more. When added during measurement of calcium uptake, trifluoperazine reduced the rate of vesicular calcium accumulation but was unlike the calcium ionophore, A23187, which caused a rapid release of accumulated calcium from the vesicles. Trifluoperazine also inhibited membrane vesicle Ca‐ATPase activity, but this inhibition was nonspecific since the Mg‐ATPase and Na, K‐ATPase activities were inhibited to similar extents at the same concentration of the phenothiazine. In contrast, concentrations of PHA and Con A, which are mitogenic for lymphocytes, did not cause any change in Ca‐uptake when added to suspensions of membrane vesicles. Con A had no effect and PHA had a weak inhibitory effect on Ca‐ATPase activity.
Inhibition of hepatoma cell growth by analogs of adenosine and cyclic AMP and the influence of enzymes in mammalian sera
Authors: Hargrove James L. , Granner Daryl K. 
Published: February 2005

AbstractThe following evidence suggests that inhibition of hepatoma cell (HTC) growth by cyclic nucleotides is an adenosine‐like effect that is greatly modified by the type and treatment of serum used in the culture medium and is probably not mediated by cyclic AMP‐dependent protein kinase: (1) Heating serum reduces its phospho‐diesterase content, thereby slowing metabolism of cyclic AMP and reducing the inhibition of HTC cell growth by cyclic AMP; (2) Using medium that contains phosphodiesterase but lacks adenosine deaminase causes adenosine to accumulate from cyclic AMP and increases the toxicity of cyclic AMP; 3) Uridine or cytidine reverse the growth inhibition caused by adenosine, 5'‐AMP or cyclic AMP; 4) adenosine, 5'‐AMP and N6 ‐(δ2‐isopentenyl) adenosine are more toxic for HTC cells than is cyclic AMP, and N6, O2‐dibutyryl cyclic AMP is not toxic; and 5) N6, O2'‐dibutyryl cyclic AMP inhibits growth of Reuber H35 cells, but uridine prevents this inhibition of growth. We conclude that most, if not all, of the inhibitory effects of cyclic AMP and N6, O2'‐dibutyryl cyclic AMP on HTC and Reuber H35 hepatoma cell growth are due to the generation of toxic metabolites.
Perturbation of the switch‐on of transcriptase activity in intermediate subviral particles from reovirus
Authors: Borsa J. , Sargent M. D. , Ewing D. D. , Einspenner M. 
Published: February 2005

AbstractIntermediate subviral particles (ISVP) derived from reovirus represent a simple model system for the switch‐on of transcriptase function. In such particles the endogenous transcriptase is present in a switched‐off form, one step removed from the switched‐on state. Switch‐on of transcriptase function is an active process in this system and can be triggered by K+ ions. A variety of agents which affect gene expression in cells were tested for an effect on switch‐on in ISVP. Marked effects on switch‐on in ISVP were observed with a diverse group of test agents, including DMSO and other solvents, BUdR, TdR, caffeine, theophylline, and temperature. The correlation in response between ISVP and cells suggests that the ISVP system may be useful as a model for studying the biochemical mechanisms underlying the perturbative effects of such agents on gene expression in cells.
Response of articular chondrocytes to pituitary fibroblst growth factor (FGF)
Authors: Sachs Barton L. , Goldberg Victor M. , Moskowitz Roland W. , Malemud Charles J. 
Published: February 2005

AbstractRabbit chondrocytes from pooled articular joints have been delineated by their time of attachment of culture flasks after initiation of primary monolayer culture, either attached (48‐AT) or floating (48‐F) after 48 hours. A general population of chrondrocytes (attached after 72 hours, 72‐AT) was also studied. The growth‐promoting activity of pituitary fibroblast growth factor (FGF) and its effect on sulfated‐proteoglycan synthesis was studied on each chondrocyte population in secondary monolayer culture. 3H‐thymidine incorporation during a 1‐hour pulse was stimulated by FGF (100 ng/ml) in each chondrocyte population. The response of AT‐72 chondrocytes to FGF required an additional fetal bovine serum supplement, while 48‐F cells resonded independent of serum. The response of 48‐AT chondrocytes to FGF (100 ng/ml) during a 1‐hour pulse with 3H‐thymidine was increased in low serum (0.5–2.0%) rather than when high serum (8–10%) was present in the culture medium. FGF reduced 35SO4 incorporation into sulfated‐proteoglycans in the 48‐AT and 48‐F chondrocyte populations, but not in the 72‐AT population. The reduction in 35SO4 incorporation in the 48‐AT and 48‐F chondrocytes was not characterized by alterations in the hydrodynamic size of the sulfated‐proteoglycans as measured by Sepharose CL‐2B chromatography nor by changes in the types of sulfated‐glycosaminoglycans produced. These results indicated that FGF produced quantitative rather than qualitative alterations in chondrocyte sulfated‐proteoglycan synthesis. The latter appears uncoupled from the growth‐promoting activity of FGF on chondrocytes.
Production of monocyte/macrophage colony‐stimulating factor by preadipocyte cell lines derived from murine marrow stroma
Authors: Lanotte M. , Metcalf D. , Dexter T. M. 
Published: February 2005

AbstractThree preadipocyte cell lines that have been independently derived from bone marrow stroma (Lanotte et al, 1982) have been tested for their capacity to produce granulocyte, macrophage, and erythroid colony‐stimulating factors (CSFs). All elaborated colony‐stimulating material that was active upon adult mouse marrow granulocyte/macrophage colony‐forming cells (M‐CFC) but not foetal liver GM‐CFC. The major activity was characterised as a monocyte‐macrophage colony‐stimulating factor (M‐CSF), and the pattern of colony stimulation was similar to that seen after addition of highly purified L‐cell CSF. Furthermore, the stimulating activity was specifically neutralised by rabbit anti‐L cell CSF antibodies. No evidence was found for stimulation of multipotential or erythroid colony‐forming cells, only few granulocytic colonies were detected, and the stimulating activity had no mouse strain restriction. All cell lines produced large quantities of M‐CSF; however, the production was found to be modulated during the adipogenesis process. A peak in M‐CSF production corresponded to the period of growth arrest after confluence of the stromal cells was reached and when adipocyte maturation was at an early stage. A marked depression in M‐CSF secretion was associated with the final steps of adipocyte maturation.
Isolation and characterization of peanut agglutinin‐resistant embryonal carcinoma cell‐surface variants
Authors: Rosenstraus Maurice J. , Hannis Margaret , Kupatt Laura J. 
Published: February 2005

AbstractThe isolation and characterization of variant embryonal carcinoma (EC) cells possessing altered cell‐surface structures is described. The lectin peanut agglutinin (PNA), which binds to EC cells but not their differentiated derivatives, was used to select the variants. Clones resistant to the cytotoxic effect of PNA were isolated at a frequency of 4 × 10–5 following mutagenesis. The resistant phenotype was stable in the absence of selection in all eight clones tested. The increased frequency of resistant clones following mutagenesis and the stability of the phenotype suggests a mutational origin. Somatic cell hybrids constructed between wild‐type cells and two different PNA‐resistant cell lines were sensitive to PNA; this suggests that the resistant phenotype is recessive. Binding assays demonstrated that resistant cells exhibited a twofold to fourfold reduction in the total amount of PNA bound. Together with the recessive behavior of the phenotype, this suggests that resistant cells are deficient for PNA receptors. The PNA‐resistant cells also showed reduced binding of monoclonal antibody against stage‐specific embryonic antigen 1 (SSEA–1) in indirect cytotoxicity tests. All eight PNA‐resistant lines isolated were tumorigenic in syngeneic mice and gave rise to well‐differentiated teratocarcinomas. The PNA‐resistant cells behaved like their wild‐type parents in a cell recognition assay; when incubated in suspension with endodermal cells, they sorted out to form simple embryoid bodies (a core of EC cells surrounded by an endodermal rind). Thus, EC cells can form tumors, differentiate, and recognize differentiated cells in a sorting assay despite a reduction in expression of the embryo‐specific cell surface structures (s) that bind PNA and anti‐SSEA‐1 antibody.
Attachment and growth of human keratinocytes in a serum‐free environment
Authors: Gilchrest Barbara A. , Calhoun Jean K. , Maciag Thomas 
Published: February 2005

AbstractUsing a serum‐free system, we have investigated the influence of human fibronectin (HFN) and selected growth factors (GF) on the attachment and growth of normal human keratinocytes in vitro. Single‐cell suspensions of keratinocytes from near‐confluent primary plates, plated on 5–10 μg/cm2 HFN, showed approximately 30–40% attachment after 2–24 hours of incubation at 37°C, compared with 4–6% attachment on uncoated platic plates. Percentage of attached cells was independent of seed density, tissue donor age, in vitro culture age, or medium composition, while subsequent cellular proliferation was strongly dependent on these factors. Keratinocytes grown on an adequate HFN matrix in a previously described hormone‐supplemented medium (Maciag et al., 1981a) achieved four to eight population doublings over 7–12 days at densities ≥ 104 cell/cm2. Removal of most GF individually from the medium had little or no effect on growth, while removal of epidermal growth factor (EGF) alone reduced growth by 30–35% and removal of bovine brain extract (BE) alone reduced growth by approximately 90%. Conversely, EGF alone in basal medium supported approximately 10% control growth, BE alone supported 30–40% control growth, and the combination of EGF and BE approximately 70%. In addition to its major effect on proliferation in this system, BE was necessary to preserve normal keratinocyte morphology and protein production. These findings expand earlier observations that HFN facilitates keratinocyte attachment in vitro and that a brain‐derived extract can exert a major positive influence on cultured keratinocytes.
Physicochemical and functional changes in human leukemic cell line HL‐60
Authors: Stendahl O. , Dahlgren C. , Hed J. 
Published: February 2005

AbstractThe recently established human promyelocytic cell line HL‐60 was induced to differentiate in the present of DMSO. During this process, physiochemical, and functional changes were detected simultaneously. After exposure to DMSO for more than 1 day, the cell volume decreased and the tendency for hydrophobic interaction increased. Using a hydrophobic two‐phase system in counter current distribution fashion, it was then possible to separate more mature metamyelocytes and segmented granulocytes from immature myeloblasts and promyelocytes. Increased functional maturity was reflected by increased chemiluminescence (CL) response and phagocytic activity. Using yeast particles opsonized with IgG as stimulating agent, the CL response increased already after 1 day in DMSO, in parallel with increased phagocytosis of these particles. In contrast, C3b‐opsonized yeast and phorbol 12‐myristate 13‐acetate (PMA) did not enhance the CL response conspiquously until days 3–4. These data suggest that Fc receptor function linked to phagocytosis and the activation of oxidative metabolism develop earlier than that of C3b and PMA. The dissociation between Fc‐ and PMA‐dependent stimulation of the oxidative metabolism may reflect different mechanisms of activation.
Fibronectin inhibits morphological changes in cultures of vascular smooth muscle cells
Authors: Brennan Michael J. , Millis Albert J. T. , Fritz Katherine E. 
Published: February 2005

AbstractIn culture, vascular smooth muscle cells proliferate until they form a confluent sheet of cells. At that time the morphology of the culture becomes altered and the cells form multilayered regions that eventually develop into nodular aggregations. We now demonstrate that the transition from monolayer culture to nodular culture is influenced by the presence of components in conditioned media. The development of nodules is enhanced by conditioned medium made from nodular cultures but is either inhibited or unaffected by monolayer culture‐conditioned medium. Examination of the two types of conditioned media using NaDodSO4‐polyacrylamide gels reveals many similarities and one major difference. Nodular‐conditioned medium contains a prominent 42 kilodalton polypeptide which is not present in monolayer‐conditioned medium. Further, we demonstrate that although both nodular and monolayer cultures produce fibronectin the transition to nodular culture does not occur in the presence of exogeneously added plasma fibronectin.
Thrombin‐mediated mitogenesis: The role of secreted protease nexin
Authors: Baker Joffre B. , Low David A. , Eaton Dan L. , Cunningham Dennis D. 
Published: February 2005

AbstractProtease nexin (PN) is a cell‐secreted protein that links to thrombin (Th) and certain other serine proteases. PN mediates the binding, internalization, and degradation of these proteases by cells (Baker et al., 1980; Low et al., 1981). Here we show that binding of Th‐PN complexes to human foreskin fibroblasts (HF cells) accounted for 90% of the specific cellular Th binding at certain mitogenic doses of the protease. However, cell‐associated Th‐PN complexes were likely to be inactive mitogenically because heparin (170 units/ml) inhibited cellular binding of 125‐Th‐PN by about 95% (a reduction from 1.3 × 105 to 6 × 103 125I‐Th‐PN complexes per cell) but did not influence Th‐mediated mitogenic stimulation. In experiments with mouse embryo cells, heparin also markedly decreased cellular binding of 125I‐Th‐PN without changing the mitogenic response to Th. The lack of mitogenic activity of cell‐associated Th‐PN complexes suggested that PN might inhibit the mitogenically essential proteolytic activity of Th. This possibility is supported by the following findings. First, amounts of serum‐free conditioned culture medium that contained enough PN to complex a large fraction of added Th inhibited the clotting activity of Th. Second, heparin increased the formation of 125I‐Th‐PN complexes and also increased this inhibitory effect of conditioned medium. We conclude that PN acts as a negative modulator of thrombin mitogenic activity.It is shown that like other fibroblastic cells HF cells bound free 125I‐Th specifically (although with relatively low affinity, Kass < 108 M‐1). Specific binding of free 125I‐Th to HF cells increased fourfold in the presence of heparin (50 IU/ml).
Pig reticulocytes. IV. In vitro maturation of naturally occurring reticulocytes with permeability loss to glucose
Authors: Zeidler Robert B. , Kim Hyun Dju 
Published: February 2005

AbstractNaturally occurring reticulocytes of week old piglets were used to characterize the maturation process under in vitro conditions. When the reticulocytes were suspended in tissue culture medium fortified with metabolic substrates, nearly all cells were viable after 24 hours incubation and usually more than 85% of the initial cell population survived after an 80 hour period. In cells maintained as long as a week in incubation, an adequate level of total adenine nucleotide with a large accumulation of IMP was found. In most cases, reticulocytes lose their reticular materials within two days and assume normal erythrocyte configuration. Concomitant with the morphological change, the cell volume decreases toward normal erythrocyte size, the extent of which can be accounted for by the intracellular loss of salt and accompanying water. As in the in vivo reticulocyte maturation process, reticulocytes undergoing in vitro maturation lose their membrane permeability to glucose. These findings suggest that the process of reticulocyte maturation occurring in cell culture approaches that which naturally occurs in vivo. Thus, these cells may be used to delineate the mechanism of the loss of membrane transport of glucose which normally occurs in the adult pig cells.
Electrophysiological and pharmacological properties of cultured rat thyroid cells
Authors: Sinback Christopher Nelson , Coon Hayden G. 
Published: February 2005

AbstractThe electrophysiological properties of a hormone‐dependent, differentiated thyroid epithelial cell strain were studied using intracellular microelectrodes. The average membrane potential of solitary, isolated cells was –78.4 ± 1.3 mV. The membrane potential depolarized 55 mV per tenfold increase in extracellular potassium concentation. Weak electrical coupling was recorded between contiguous cells. Like tyroid cells in vivo, these cells did not generate action potentials. In some cells a spontaneous, slow transition in the membrane potential from –80mV to –30 mV was accompanied by an increase in input resistance. Membrane potential transitions could be induced by perfusing cells with isotonic Hanks solutions saturated with CO2 (pH = 5.5) or by perfusing cells with hypotonic Hanks solutions (190–290 mOsm/kg). Membrane potential transitions were due to a decreased potassium permeability. Noradrenaline elicted both a fast depolarization and a slow depolarization. The fast depolarization was due to an increase in conductance of Na+ channels and of Cl– channels. Intracellular injection of Ca++ elicited the fast depolarization. Intracellular injection of EGTA or cobalt abolished the fast depolarization. Replacemnt of extracellular Ca++ by Mg++ did not affect the fast depolarization. Thus, the fast depolarization was due to accumulation of intracellular Ca++. The fast depolarization was abolished by the alpha adrenergic blocker phentolamine (10–6 M), and was not abolished by the beta adrenergic blocker propranolol (10–5 M).
Murine cell surface transferrin receptor: Studies with an anti‐receptor monoclonal antibody
Authors: Trowbridge Ian S. , Lesley Jayne , Schulte Roberta 
Published: February 2005

AbstractA rat monoclonal antibody against the murine transferrin receptor has been identified. The receptor is a 95,000 molecular weight species that exists in the cell membrane as a disulphide‐bonded dimer. Whereas 29 of 29 murine hematopoietic tumor cell lines express detectable numbers of transferrin receptors, less than 1% of adult thymocytes or spleen cells and only 5% of bone marrow cells are positive. However, fetal liver and neonatal spleen contain substantial numbers of transferrin receptor‐positive cells. Induction of Friend cells in vitro with dimethyl‐sulphoxide leads to an overall increase in the expression of transferrin receptors on the cell surface. The anti‐transferin receptor antibody we have obtained partially blocks iron uptake from 59Fe‐transferrin by a variety of murine cell lines and inhibits the growth of a murine myeloma cell line in vitro.
Effects of retinoic acid on protein synthesis in cultured melanoma cells
Authors: Lotan Reuben , Fischer Itzhak , Meromsky Leonid , Moldave Kivie 
Published: February 2005

AbstractRetinoic acid reduces the growth rate of mouse S91 melanoma cells in culture and increases the proportion of cells in the G1 phase of the cell cycle. Because of the integral role protein synthesis has been shown to play in growth control we studied the effect of retinoic acid on the protein synthesis machinery with a cell‐free system developed from the melanoma cells. This system was capable of translating endogenous mRNA, exogenous globin mRNA, and the synthetic template poly(U). Of the above activities of the protein synthesis system only the translation of endogenous mRNA was reduced significantly in the cell‐free system prepared from retinoic acid‐treated cells. Analyses of the amount and function of RNA revealed that treatment with retinoic acid leads to reductions in total RNA content, in the proportion of ribosomes in polysomes, in the amount of poly(A)RNA, and in the amount of polysome‐associated mRNA. All these effects of retinoic acid contribute to the decrease in protein synthesis activity of treated cells. Two‐dimensional electrophoresis anlaysis of L‐[35S]methionine‐labeled proteins produced by untreated and treated cells revealed only a few quantitative differences. We suggest that retinoic acid‐induced suppression of protein synthesis activity may be the cause for growth inhibition.
Regulation of amino acid transport in L6 myoblasts. II. Different chemical properties of transport after amino acid deprivation
Authors: Klip Amira , Logan William J. , Gagalang Enriqueta 
Published: February 2005

AbstractThe mechanism of stimulation of amino acid transport system A caused by amino acid deprivation in L6 cells was investigated. In cells loaded with α‐aminoisobutyric acid (AIB), amino acid deprivation increased the rate of proline uptake only after the intracellular [AIB] dropped below 7 mM. Efflux of proline was not sensitive to the presence of proline in the outer medium (with or without external Na+), suggesting that efflux through system A (and possibly uptake) is not susceptible to transinhibition. Transport (stimulated uptake) into amino acid‐deprived cells and that into amino acid‐supplemented cells differed in several chemical properties: (1) In the former group, transport was higher at lower pH values than in the latter, and the optimum pH values were 7.5 and 7.8, respectively. (2) Unlike proline uptake in supplemented cells, uptake in deprived cells was inhibited by 50% with N‐ethylmaleimide (1 mM) or by 50 μM p‐chloromercuribenzoate (PCMBS). Inhibition by PCMBS was not due to collapse of the Na+ gradient. The mercurial inhibited only the deprivation‐induced stimulation of transport, bringing the rate of proline uptake to the “basal” uptake level observed in amino acid‐supplemented cells. Proline uptake was not stimulated by a second deprivation following treatment with PCMBS and a supplementation‐deprivation cycle. However, in untreated cells, or by reversing mercaptide formation with dithiotreitol, the second deprivation stimulated transport. Deprivation at 4°C did not elicit stimulation of proline uptake. Cycloheximide prevented the stimulation and decreased the rate of proline uptake in deprived cells more efficiently than in supplemented cells. Actinomycin D prevented stimulation when added at the onset of deprivation. The above data indicate that stimulation of transport by deprivation is protein synthesis‐dependent and that the stimulated transport had chemical properties distinct from the “basal” transport in supplemented cells. The evidence presented is consistent with a model of activation of a finite pool of transporters upon deprivation, the chemical characteristics of which differ from those of the “basal” transport system.