bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relation between the regulation of DNA synthesis and the production of two secreted glycoproteins by 12‐O‐tetradecanoylphorbol‐13‐acetate in 3T3 cells and in phorbol ester nonresponsive 3T3 variants
Authors: Fienup Virginia K. , Jeng Meei‐Huey , Hamilton Richard T. , Nilsen‐Hamilton Marit 
Published: February 2005

Abstract12‐O‐tetradecanolyphorbol‐13‐acetate (TPA), a potent tumor promoter, acts similarly to growth factors by selectively increasing the rate of production of the secreted proteins, mitogen regulated proteins (MRP) and major excreted protein (MEP) by murine 3T3 cells. MRP, a 34 kilodalton (kDa) glycoprotein, is a member of the prolactin‐growth hormone family of proteins. MEP, a 39 kDa glycoprotein, is a lysosomal thiol protease that is also secreted. The aim of our investigation was to determine the relation between increases in MRP and MEP production and the initiation of DNA synthesis in response to mitogens. The TNR‐9 cell lines is a variant of 3T3 cells in which growth factors, but not TPA and teleocidin, stimulate DNA synthesis and cell division. Usibng [35S]methionine to metabolically label proteins and SDS polyacrylamide gel electrophoresis to resolve the proteins, we found that growing cultures of 3T3 and TNR‐9 cells responded equally well to TPA and teleocidin with increased rates of production of MRP and MEP. by conrast, the responses of quiescent TNR‐9 cells to these tumor promoters in the increased production of MRP and MEP was greatly diminished compared with quiescent 3T3 cells. The changes in production of MRP in response to tumor promopters in quiescent and growing cells paralleled similar changes in the level of MRP mRNA. In summary, the ability to TPA and teleocidin to increase the rate of production of MRP and MEP correlated with the ability of these tumor promoters to stimulate DNA synthesis in quiescent 3T3 and TNR‐9 cells. Evidently the biochemical condition that distinguishes TNR‐9 from 3T3 cells and that limits the ability of tumor promoters to stimulate the production of MEP and MRP, and perhaps also DNA synthesis in TNR‐9 cells occurs only when the cells are quiescent.
Ion‐sensitive microelectrode measurements of free intracellular chloride and potassium concentrations in hyperthermia‐treated neuroblastoma cells
Authors: Borrelli M. J. , Carlini W. G. , Ransom B. R. , Dewey W. C. 
Published: February 2005

AbstractMurine NG108‐15 neuroblastoma cells were heated for times of 5–40 min at 45.5°C, and survival ranged from 0.7–0.0015, respectively. Ion‐sensitive micro‐electrodes (ISM) were used to measure the free intracellular concentrations of Cl− and K+ immediately after heating and up to 30 hr later. The free intracellular Cl− and K+ concentrations, [Cl−]i and [K+]i respectively, of the heated cells remained identical to those of the controls for the first 10 hr after heating. At later times, some cells had increased [Cl−]i values and decreased [K+]i values identical to those of the extracellular medium. These cells had a mottled morphology, no longer excluded the vital stain trypan blue, and had no membrane potential. The number of these dye‐including, physiologically dead cells increased with time, and was always greater following longer heating times. No changes in mean cellular volume were observed until 25 hr after heating. All trypan‐blue‐excluding, physiologically live cells had the same [Cl−]i and [K+]i as the control cells, even when the majority of them were destined for clonogenic death.
Spontaneous differentiation of murine teratocarcinoma stem cells at low temperature
Authors: Cremisi Chantal , Duprey Philippe 
Published: February 2005

AbstractEmbryonal carcinoma cells differentiate in vitro after treatment with different drugs or under certain culture conditions. We show here that at 31°C PCC‐aza‐1 cells differentiated spontaneously into cells with characteristics resembling those of epithelial cells. With this temperature, we observed morphological changes; reorganization of the cytoskeleton with polymerization of actin cables, tight junctions, and cytokeratin endo A messenger RNA and protein expression The cells also became totally permissive to Py virus but remained resistant to SV40 infection. This new pathway of differentiation has the advantage of being reversible at 37°C.
Stimulation of beta‐adrenoceptors inhibits calcium‐dependent potassium‐channels in mouse macrophages
Authors: Rosati Clelia , Hannaert Patrick , Dausse Jean‐Pierre , Braquet Pierre , Garay Ricardo 
Published: February 2005

AbstractK+ efflux in mouse macrophages exhibited a rate constant (kK) of 0.67 ± 0.04 (h)−1 (mean ± SEM of 16 experiments). This was strongly stimulated by increasing concentrations of the Ca2+ ionophore A23187 up to a maximal value of 4.01 ± 0.25 (h)−1 with an IC50 of 7.6 ± 1.9 μM (mean ± SEM of 6 experiments). Similar results were obtained with the Ca2+ ionophore ionomycin. Binding experiments with 3H‐dihydroalprenolol revealed a high density of beta‐adrenergic receptors (97.5 ± 5.2 fmol/mg protein) with apparent dissociation constant of 2.03 ± 0.06 nM. Isoproterenol at a concentration of 10−6‐10−5 M induced a two‐ to threefold stimulation of endogenous levels of cyclic AMP (cAMP). A23187‐stimulated K+ efflux was partially inhibited by (i) stimulation of adenylate cyclase with isoproterenol, forskolin or, PG1; (ii) exogenous cAMP; and (iii) inhibition of phosphodiesterase with MIX (1‐methyl‐3‐isobutylxanthine). Maximal inhibition of K+ efflux was obtained by simultaneous addition of isoproterenol and MIX. In dose‐response curves, the isoproterenol‐sensitive K+ efflux was half‐maximally inhibited (IC50) with 2–5 × 10−10 M of isoproterenol concentration. Propranolol was able to completely block the effect of isoproterenol, with an IC50 of about 1–2 × 10−7 M. Isoproterenol and MIX were also able to partially inhibit ionomycin‐stimulated K+ efflux. Isoproterenol and MIX did not inhibit A23187‐stimulated K+ efflux in an incubation medium where NaCI was replaced by sucrose (or choline), suggesting the involvement of an Na + : Ca2+ exchange mechanism. Our results show that stimulation of beta‐adrenoceptors in mouse macrophages counterbalances the opening of K+ channels induced by the calcium ionophore A23187. This likely reflects a decrease in cytosolic free calcium content via a cAMP‐mediated stimulation of Na + :Ca2+ exchange.
Phorbol diesters and transferrin modulate lymphoblastoid cell transferrin receptor expression by two different mechanisms
Authors: Alcantara O. , Phillips J. L. , Boldt D. H. 
Published: February 2005

AbstractExpression of transferrin receptors (TfR) by activated lymphocytes is necessary for lymphocyte DNA synthesis and proliferation. Regulation of TfR expression, therefore, is a mechanism by which the lymphocyte's proliferative potential may be directed and controlled. We studied mechanisms by which lymphoblastoid cells modulate TfR expression during treatment with phorbol diesters or iron transferrin (FeTf), agents which cause downregulation of cell surface TfR. Phorbol diester‐induced TfR downregulation occurred rapidly, being detectable at 2 min and reaching maximal decreases of 50% by 15 min. It was inhibited by cold but not by agents that destabilize cytoskeletal elements. Furthermore, this downregulation was reversed rapidly by washing or by treatment with the membrane interactive agent, chlorpromazine. In contrast, FeTf‐induced TfR downregulation occurred slowly. Decreased expression of TfR was detectable only after 15 min and maximal downregulation was achieved after 60 min. Although FeTf‐induced downregulation also was inhibited by cold, it was inhibited in addition by a group of microtubule destabilizing agents (colchicine, vinblastine, podophyllotoxin) or cytochalasin B, a microfilament inhibitor. Furthermore, FeTf‐induced downregulation was not reversed readily by washing or by treatment with chlorpromazine. The inactive colchicine analogues, β‐ and γ‐lumicolchicine, did not inhibit FeTf‐induced TfR downregulation. Similarly, when cells were pretreated with taxol to stabilize microtubules, colchicine no longer inhibited FeTf‐induced downregulation. Therefore, FeTf causes TfR downregulation in lymphoblastoid cells by a cytoskeleton‐dependent mechanism. Phorbol diesters cause TfR downregulation by a cytoskeleton‐independent mechanism. In other experiments, treatment of cells with both a phorbol diester and FeTf, either simultaneously or sequentially, produced additive effects on TfR expression. These data indicate that TfR expression is regulated by two independent mechanisms in lymphoblastoid cells, and they provide the possibility that downregulation of TfR by different mechanisms may result in different effects in these cells.
Glycosphingolipid patterns in primary mouse kidney cultures
Authors: Lyerla Timothy A. , Gross Sonja K. , McCluer Robert H. 
Published: February 2005

AbstractPrimary kidney cultures from C57BL/6J mice, 6 weeks of age or older, were produced using D‐valine medium to select for epithelial cell growth. After allowing the cells to attach and proliferate for 1 week following plating, medium was changed once per week. Cells formed nearly confluent monolayers during the second week of culture.The cultured cells contained all of the glycosphingolipids seen in the adult kidney, analyzed by high performance liquid chromatography as their perbenzoyl derivatives. Glucosylceramide, however, was highly predominant in the cultured cells, whereas dihexosyl‐ and trihexosylceramides predominate in the intact kidney. Sex differences in glycolipid contents found in the intact kidney were also apparent in these cultured cells: The concentration of neutral glycolipids, in general, was higher in male cells than in those derived from females, and the male‐specific glycolipid nonhydroxy fatty acid digalactosylceramide was high in male cells but very low in female cells.Neutral glycosphingolipids were labeled in 2‐week‐old cultures using [3H]palmitate. The [3H]palmitate was incorporated into all of the glycolipids within 2 hr of labeling. Hence, adult mouse kidney cells in D‐valine medium retain their differentiated characteristics for a sufficient period of time to allow investigation of glycolipid syntheses in monolayer cultures of epithelial cells derived from this organ.
Mouse Balb/c3T3 cell mutant with low epidermal growth factor receptor activity: Induction of stable anchorage‐independent growth by transforming growth factor β
Authors: Kuratomi Yuichiro , Ono Mayumi , Yasutake Chie , Mawatari Masasumi , Kuwano Michihiko 
Published: February 2005

AbstractA mutant clone (Mo‐5) was originally isolated as a clone resistant to Na+/K+ ionophoric antibotic monensin from mouse Balb/c3T3 cells. MO‐5 was found to show low receptor‐endocytosis activity for epidermal growth factor (EGF): binding activity for EGF in MO‐5 was less than one tenth of that in Balb/c3T3. Anchorage‐independent growth of MO‐5 was compared to that of Balb/c3T3 when assayed by colony formation capacity in soft agar. Coadministration of EGF and TGF‐β efficiently enhanced anchorage‐independent growth of normal rat kidney (NRK) cells, but neither factor alone was competent to promote the anchorage‐independent growth. The frequency of colonies appearing in soft agar of MO‐5 or Balb/c3T3 was significantly enhance by TGF‐β while EGF did not further enchance tha tof MO‐5 or Balb/c3T3. Colonies of Balb/c3T3 formed in soft agar in the presence of TGF‐β showed low colony formation capacity in soft agar in the absence of TGF‐β. Colonies of MO‐5 formed by TGF‐β in soft agar, however, shoed high colony formation capacity in soft agar in the absence of TGF‐β. Pretreatment of MO‐5 with TGF‐β induced secretion of TGF‐β‐like activity from the cells, while the treatment of Balb/c3T3 did not induce the secretion of a significant amount of TGF‐β‐like activity. The loss of EGF‐receptor activity in the stable expression and maintenance of the “transformed” phenotype in MO‐5 is discussed.
Characterisation of stroma‐dependent blast colony‐forming cells in human marrow
Authors: Gordon M. Y. , Dowding C. R. , Riley G. P. , Greaves M. F. 
Published: February 2005

AbstractHuman bone marrow contains a population of haemopoietic progenitor cells that can be distinguished by their ability to adhere to preformed stromal layers cultured in the presence of methylprednisolon [MP+] and form blast cell colonies. The stromal layers function in the colony assay after they have been heavily irradiated but not after they have been passaged. The binding of the progenitor cells to the stromal cells is complete after 2 hours of coincubation, and stromal layers of 9.6 cm2 can provide adhesion sites for at least 2,000 blast colony‐forming cells. The blast colony‐forming cells were shown by micromanipulation to self‐renew as well as to give rise to multipotential and lineage‐committed colony‐forming progenitor cells.
Toxicity of oxidized low‐density lipoprotein to cultured fibroblasts is selective for S phase of the cell cycle
Authors: Kosugi Keisuke , Morel Diane W. , DiCorleto Paul E. , Chisolm Guy M. 
Published: February 2005

AbstractOxidized LDL (o‐LDL) is toxic to a variety of cultured cells. Preliminary results suggested that susceptibility is enhanced by cell proliferation. As a step toward determining the mechanism of cytotoxicity, we chose to identify the cell cycle phase(s) during which exposure of cultured human fibroblasts to o‐LDL leads to death. Cytochalasin B, which blocks cell migration and proliferation, and irradiation, which prevents mitosis but not migration, both blocked cytotoxicity. Colchicine, which arrests cells in mitosis but does not inhibit DNA synthesis, did not block cytotoxicity. Treatment of cells with hydroxyurea, which blocks cells prior to S phase, prevented cell death. Addition of o‐LDL to cells immediately after S phase allowed mitosis without death. The above results coupled with results using cells synchronized by three different means indicate that cell death is selective for proliferating cells and occurs after exposure to o‐LDL during S phase. Understanding the mechanism of o‐LDL‐induced death may have implications for tissue damage in vivo in the numerous instances of pathology in which oxidized lipoproteins or lipids are present.
Further analysis of spontaneous membrane potential activity and the hyperpolarizing response to parathyroid hormone in osteoblastlike cells
Authors: Ferrier Jack , Ward‐Kesthely Angela , Homble Fabrice , Ross Stephen 
Published: February 2005

AbstractWhole cell voltage clamp measurements using the patch technique on well‐attached and well‐spread cells of an osteoblastlike line (ROS 17/2.8) show the same spontaneous membrane potential activity as measurements with inserted microelectrodes. Furthermore, membrane potential measurements during the first 80 milliseconds (ms) following microelectrode penetration of the cell membrane usually show no decay. There is also good agreement between values of cell membrane resistance obtained by the microelectrode technique, the whole cell patch clamp technique, and the single channel patch clamp technique. These results indicate that our microelectrode measurements are not dominated by leak‐induced artifacts, and that the spontaneous membrane potential activity is not induced by Ca2+ leakage around the microelectrode. The spontaneous membrane potential activity is eliminated in the presence of the Ca2+ ionophore A23187, also in serum‐free medium, and by K+ and Ca2+ channel blockers, but it is not affected by the hyperpolarizing responses to parathyroid hormone (PTH) and dibutyryl cAMP, which persist under all of these conditions. These results support the hypothesis that the spontaneous membrane potential activity is related to repeated fluctuations of internal [Ca2+] and that such fluctuations result from a feedback loop involving Ca2+ channels or Ca2+ pumps in the cell membrane.
Heat stress stimulates inositol trisphosphate release and phosphorylation of phosphoinositides in CHO and Balb C 3T3 cells
Authors: Calderwood Stuart K. , Stevenson Mary Ann , Hahn George M. 
Published: February 2005

AbstractExposure of eukaryotic cells to elevated temperature leads to profound switches in cell metabolism and gene expression which may be involved in cellular homeostatic mechanisms. We have investigated the effect of heat shock (45°C) on the metabolism of the phosphoinositides, a class of phospholipids involved in the function of Ca2+‐linked membrane receptors. Heat shock led to stimulation of phosphoinositide turnover in HA1‐CHO and Balb C 3T3 cells, resulting in the rapid accumulation of inositol trisphosphate (lP3). Mitogenic and α1 adrenergic stimulation, with serum or phenylephrine, led to similar increases in lP3. Heat shock also caused rapid increase in phosphorylation of polyphosphoinositides (PPl). Prolonged exposure to heat >15 min at 45°C led to progressive cellular toxicity which was associated with depletion of PPl. This decline in PPl concentration appeared to result from inhibition of PPl resynthesis. In this respect, heat may resemble some other types of cellular stresses in stimulating membrane phospholipases to deplete classes of membrane phospholipids. The induction of PPl turnover may, therefore, be involved in both plelotropic responses to brief heat shock and toxicity resulting from prolonged thermal stress.
Isolation and characterization of a cloned growth factor dependent macrophage cell line, BAC1.2F5
Authors: Morgan Claudia , Pollard Jeffrey W. , Stanley E. Richard 
Published: February 2005

AbstractThe SV40 transformed murine macrophage cell line, BAC1, proliferates in response to the colony stimulating factor, CSF‐1 (Schwarzbaum et al., J. Immunol., 132:1158, 1984). In order to obtain a cell line suitable for biochemical and genetic studies of CSF‐1 signal transduction, clones of BAC1 were established. Clones ranged from being completely autonomous to being completely dependent on CSF‐1 for growth. Cells of one clone (2F5), which proliferated in response to either CSF‐1 or granulocyte‐macrophage CSF (GM‐CSF) were characterized in detail. The kinetics of receptor‐mediated internalization and intracellular destruction of CSF‐1 were comparable to the kinetics observed with peritoneal exudate macrophages. CSF‐1 was shown to regulate cell spreading, cell survival, protein degradation, and the duration of the G1 and S phases of the cell cycle. The 2F5 clone therefore exhibits a number of CSF‐1 stimulated responses and is being used for genetic and biochemical studies of CSF‐1 action.
Ionic responses and growth stimulation in rat astroglial cells: Differential mechanisms of gangliosides and serum
Authors: Skaper Stephen D. , Varon Silvio 
Published: February 2005

AbstractRat astroglial cells respond to fetal calf serum (FCS) and gangliosides, including GM1, by undergoing proliferation. Here, we show that addition of FCS but not GM1 causes an increase in Na+, K+‐pump activity, as measured by ouabain‐sensitive 86Rb+ influx. The increase of Na+, K+‐pump activity by FCS was due to increased Na+ influx (measured with 22Na+). This increased Na+ influx was sensitive to amiloride, an inhibitor of Na+/H+ exchange. Amiloride also blocked the FCS‐stimulated incorporation of [3H]thymidine into DNA. Two defined polypeptide growth factors, epidermal growth factor and fibroblast growth factor were also able to elicit an amiloride‐sensitive Na+ influx and an ouabain‐sensitive K+ uptake in these astroglial cells, in the presence of FCS or insulin. Thus, GM1 differs from serum and growth factors in the mechanisms by which these agents stimulate the proliferation of the astroglial cells used here.
Relationship of thrombin‐stimulated arachidonic acid release and metabolism to mitogenesis and phosphatidylinositol synthesis
Authors: Raben Daniel M. , Yasuda Kathleen M. , Cunningham Dennis D. 
Published: February 2005

AbstractThrombin and certain prostaglandins are both capable of stimulating the proliferation of cultured cells. Since thrombin stimulates the release and metabolism of arachidonic acid, the precursor of prostaglandins, we examined the relationship between this release and metabolism and the stimulation of cell division in cultured fibroblasts. We also examined the role of prostaglandin synthesis in thrombin‐stimulated phosphatidylinositol synthesis.The data in this report demonstrate that the release and metabolism of arachidonic acid are not necessary for thrombin‐stimulated cell division. The presence of a low concentration of chymotrypsin prevented thrombin‐stimulated arachidonic acid release and metabolism without affecting the stimulation of cell division. Furthermore, thrombin‐stimulated cell division occurred in the presence of indomethacin concentrations that prevented cyclooxygenase‐mediated metabolism of arachidonic acid.The following experiments showed that thrombin‐stimulated phosphati‐dylinositol synthesis was brought about by a cyclooxygenase‐mediated metabolite(s) of arachidonic acid. Indomethacin inhibited the cyclooxygenase‐mediated metabolism of arachidonic acid without affecting the thrombin‐stimulated release of arachidonic acid. Indomethacin also inhibited thrombin‐stimulated phosphatidylinositol synthesis. The dose dependence of this inhibition paralleled the inhibition by indomethacin of cyclooxygenase‐mediated metabolism of arachidonic acid. In addition, prostaglandin F2, stimulated phosphatidylinositol synthesis in the presence of indomethacin concentrations which prevented thrombin‐stimulated phosphatidylinositol synthesis.
Specific gene expression during compensatory renal hypertrophy in the rat
Authors: Beer David G. , Zweifel Kathleen A. , Simpson David P. , Pitot Henry C. 
Published: February 2005

AbstractThe compensatory growth of the kidney which is induced by unilateral ne‐phrectomy is a highly regulated process resulting principally in hypertrophy of the remaining kidney. The events which regulate this process are unknown. We have examined the levels of transcripts for the proto‐oncogenes, myc, H‐ras, K‐ras, and fos, and the cellular genes, H4 histone, ornithine aminotrans‐ferase, and gamma‐glutamyl transpeptidase, following unilateral nephrec‐tomy in the rat. The pattern of expression of c‐myc, c‐H‐ras, and c‐K‐ras during compensatory growth of the kidney differs from the pattern of expression of these proto‐oncogenes during liver regeneration, in which, unlike the kidney, hyperplasia rather than hypertrophy predominates. The lack of change in the abundance of these proto‐oncogene transcripts following unilateral nephrec‐tomy suggests a primary relationship between the expression of these proto‐oncogenes and DNA synthesis and indicates there may be separate signals for cell growth, one to double cell size and one to replicate DNA. Increased mRNA transcripts for the enzymes ornithine aminotransferase and gamma‐glutamyl transpeptidase were induced in the contralateral kidney after ne‐phrectomy. The time course of expression for these two enzymes differs. The early expression of the gamma‐glutamyl transpeptidase gene may indicate an involvement of this glutathione‐metabolizing enzyme during renal compensatory growth, while the function of the delayed increase in ornithine amino‐transferase transcripts in the remaining kidney is not apparent.