bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decreased susceptibility of cultured smooth muscle cells from SHR rats to growth inhibition by heparin
Authors: Resink Thérèse J. , Scott‐Burden Timothy , Baur Ursula , Bürgin Maria , Bühler Fritz R. 
Published: February 2005

AbstractSmooth muscle cell proliferation is regulated through the coordinated action of growth inhibitors and growth factors/mitogens; a specific heparin‐epidermal growth factor (EGF) complementation has been proposed (Reilly et al., 1987, J. Cell. Physiol., 131:149–157). In culture, vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) proliferate more rapidly than VSMC from control Wistar Kyoto rats (WKY). We observed that, compared with WKY‐derived VSMC, cells from SHR were markedly less susceptible to growth inhibition both by heparin and its homopolysaccharide analogue pentosan polysulphate (PPS). SHR‐derived VSMC exhibited a reduced capacity for binding of [3H]heparin to specific extracellular surface receptors, whereas affinities for heparin were comparable between both VSMC isolates. The early (0–2 hr at 37°C) kinetics of internalization did not differ between SHR‐ and WKY‐derived VSMC, but both internalized equivalent proportions (∼ 10%) of initially surface‐bound heparin. VSMC from SHR exhibited a greater capacity, without a changed affinity, for [I125]EGF binding than VSMC from WKY. Pre‐exposure of VSMC to heparin or PPS decreased, in a time‐dependent manner, the EGF binding capacity for both SHR and WKY (by 40–50% after 72 hr). However, in absolute terms, the EGF‐binding capacity of VSMC from SHR exposed to heparinoids was similar to that of nonexposed VSMC from WKY.
Growth‐related changes of oxygen consumption rates of tumor cells grown in vitro and in vivo
Authors: Kallinowski F. , Tyler G. , Mueller‐Klieser W. , Vaupel P. 
Published: February 2005

AbstractGrowth‐related changes of oxygen consumption rates of tumor cells, grown in vitro or in vivo, were investigated. For in vitro investigations, L929 and DS‐carcinosarcoma cells were cultured in artificial media. For in vivo studies, DS‐carcinosarcoma cells were implanted into the abdominal cavity of Sprague‐Dawley rats (ascites tumor, containing malignant cells, leukocytes, lymphocytes, and macrophages). Oxygen uptake was measured photometrically. Parameters of the extracellular medium judged to possibly influence the respiratory activity of tumor cells were monitored at different growth stages (glucose, lactate, and amino acid levels, oxygen and carbon dioxide partial pressures, and pH values). The results obtained clearly show that the oxygen uptake of tumor cells grown in vitro decreased as quiescence developed. In contrast, the respiratory activity of in vivo DS‐carcinosarcoma ascites cells increased as tumor growth reached plateau phase. The differences observed cannot be attributed solely to changes of the environmental conditions monitored. It is likely that an increased respiration rate of activated host cells might profoundly contribute to the elevation of the respiratory capacity of DS‐carcinosarcoma ascites tumors grown in vivo. These data provide evidence that solid tumors in vivo can increase their O2 uptake at an enhanced O2 availability not only due to an enlarged tumor volume with adequate O2 supply but also due to an elevation of the respiratory activity of different cell populations within a tumor.
Regulation of collagenase and collagenase mRNA production in early‐ and late‐passage human diploid fibroblasts
Authors: Sottile Jane , Mann David M. , Diemer Verena , Millis Albert J. T. 
Published: February 2005

AbstractThe levels of collagenase and collagenase mRNA produced by early‐passage (40% of lifespan completed) and late‐passage (>80% of lifespan completed) cultures of human fibroblasts were analyzed. The constitutive levels of collage‐nase and collagenase mRNA produced by the late‐passage cultures were 10‐30x greater than the levels observed in similarly treated early‐passage cultures. Immunofluorescence analysis established that the percentage of collagenase‐positive cells was also greater (77% vs. 4%) in the late‐passage cultures. To determine whether the difference in collagenase production resulted from cell‐derived regulatory factors, collagenase production was examined in cultures plated onto substrates coated with fibroblast extracellular matrix (ECM). Collagenase and collagenase mRNA production was enhanced in both types of cultures, although amounts produced by ECM‐induced early‐passage cultures was significantly less than that produced by similarly treated late‐passage cultures. Collagen‐coated substrates also induced collagenase synthesis.
Evidence for a major route for zinc uptake in human red blood cells: [ZN(HCO3)2CL]−influx through the [CI−/HCO3−] anion exchanger
Authors: Torrubia José Octavio Alda , Garay Ricardo 
Published: February 2005

AbstractThe initial rate of Zn2+ uptake in human red cells was measured by atomic absorption. A very important fraction of Zn2+ uptake was inhibited by DIDS with IC50 = 0.3 (μ)M (and by furosemide and bumetanide with IC50 of 200 and 500 μ M, respectively). DIDS–sensitive Zn2+ uptake exhibited the following properties: (1) It required the simultaneous presence of both external HCO3− and Cl−. (2) In Cl− containing media, it was strongly stimulated by external HCO3− following a sigmoidal (S–shaped) and saturable function, which was fitted by a Hanes equation, with n = 2 and an apparent dissociation constant (for external HCO3−) of 5.3 ± 0.9 mM (mean ± SD of four experiments). The maximal rate of Zn2+ uptake at saturating HCO3− concentrations was 50.7 ± 4.8 mmol (liter cells x h)−1. (3) In HCO3− containing media, it was strongly stimulated by external Cl− following a Michaelis‐like equation with an apparent dissociation constant (for external Cl− of 88 ± 11 mM (mean ± SD of three experiments). 4) Bicarbonate‐stimulated Zn2+ uptake was inhibited by physiological concentrations of phosphate (sulfate was a much less potent inhibitor than phosphate). A kinetic analysis of the data strongly suggested that zinc was transported by the anion carrier in the form of the monovalent anion complex: [Zn(HCO3)2Cl]−.
Characterization of polyclonal antibodies that distinguish acidic and basic fibroblast growth factors by using western immunoblotting and enzyme‐linked immunosorbent assays
Authors: Riss Terry L. , Sirbasku David A. 
Published: February 2005

AbstractRabbit polyclonal antibodies were raised against ovalbumin conjugates of purified bovine brain acidic fibroblast growth factor (aFGF) and a synthetic peptide containing the Nα‐terminal 1–24 amino acid sequence of bovine basic fibroblast growth factor (bFGF). Theses antibodies were used to specifically detect 1‐ng quantities of aFGF and bFGF by using enzyme‐linked immunosorbent assay(ELISA)and Western immunoblot procedures. Antibodies raised against aFGF recognized bovine brain aFGF and bovine recombinant aFGF by very poorly recognized recombinant bFGF or purified porcine or bovine pituitary bFGF with ELISA and Western immunoblot procedures. Antibodies raised against bFGF (1–24) recognized purified bovine, procine, and recombinant human bFGF but only very poorly reconized aFGF with ELISA and Western immunoblot procedures. In vitro addition of anti‐bFGF antibodies was able to partially neutralize bFGF‐stimulated 3H‐thymidine incorporation by COMMA‐D mouse mammary epithelial cells while having no effect on aFGF or epidermal growth factor (EGF) stimulation. In vitro additionof anti‐aFGF antibodies had no effect on bFGF‐or EGF‐stimulated 3H‐thymidine incorporation, but surprisingly, had a potentiating effect on aFGF stimulation. Antibodies against aFGF immobilized on protein A‐Sepharose were able to specifically and completely remove mitogenic activity from solutions containing aFGF but had no effect on removal of mitogenic activity from control solutions containing bFGF or EGF. similarly, immobilized anti‐bFGF antibodies completely removed mitogenic activity from solutions of bFGF, but notaFGF or EGF controls. These antibodies have been useful for the identification and characterization of growth factors from tissue and recombinant sources.
Effect of 5‐amino‐4‐imidazolecarboxamide riboside (AICA‐riboside) on the purine nucleotide synthesis and growth of rat kidney cells in culture: Study with [15N]aspartate
Authors: Nissim Itzhak , Yudkoff Marc , Nissim Ilana , States Beatrice 
Published: February 2005

AbstractThe present investigation evaluates the effect of AICA‐Riboside on the synthesis of purine nucleotide and the growth of normal rat kidney cells in culture. Experiments in the presence and absence of various concentrations of AICA‐Riboside were conducted with Dulbecco's Modified Eagle's Medium supplemented with either 1 mM [15N] aspartate or [14N]aspartate. Addition of 50 μM AICA‐Riboside to the incubation medium significantly stimulated intracellular adenine nucleotide concentrations following incubation for 48 hours. This stimulation was associated with augmented cell growth and DNA concentration. In contrast, with concentrations above 100 μM of AICA‐Riboside in the incubation medium, there was a remarkable inhibition of cell growth and a significant depletion of intracellular pools of adenine nucleotides and DNA. Experiments with [15N] aspartate showed that the initial rate (0‐24 hours) of [6‐15NH2] adenine nucleotide formation from 1 mM [15N] asparate was 38.8 ± 9.6, 67.9 ± 12.5, and 20.1 ± 3.8 pmol h−1/106 cells in the presence of O (control), 50 μM and 500 μM AICA‐Riboside, respectively. These observations indicate that the main effect of AICA‐Riboside is on the formation of AMP from aspartate and IMP via the sequential action of adenylosuccinate synthetase and adenylosuccinate lyase. The current studies suggest that AICA‐Riboside could be used as a factor mediating renal cell mitosis in culture. AICA‐Riboside has a biphasic effect on the growth of renal epithelial cells in culture and on their intracellular purine nucleotides and DNA concentration.
Modulatory function of protein kinase C in the activation of ornithine decarboxylase and in cAMP production in rat osteoblasts
Authors: van Leeuwen J. P. T. M. , Bos M. P. , Herrmann‐Erlee M. P. M. 
Published: February 2005

AbstractThe effect of activation of protein kinase C on stimulation of ornithine decar‐boxylase (ODC) activity and cAMP production was studied in fetal rat osteoblasts. Both phorbol 12‐myristate, 13‐acetate (PMA), an activator of protein kinase C, and 4α‐phorbol, ineffective in activating protein kinase C, failed to stimulate ODC activity and cAMP production. We tested the effect of protein kinase C on stimulation of ODC activity by parathyroid hormone (PTH) and forskolin. In contrast to PTH‐stimulated ODC activity, which was not affected by PMA, forskolin‐stimulated (1 and 10 μM) ODC activity was dose dependently reduced. PMA (400 nM) reduced both 1 and 10 μM forskolin‐stimulated ODC activity to the same level, ∼ 3 nmol CO2/mg protein, which suggests a controlling role of protein kinase C in forskolin‐stimulated ODC activity. The study of the effect of protein kinase C on PTH‐ and forskolin‐stimulated cAMP production also revealed differences between PTH and forskolin. When PMA was added simultaneously with PTH (4 and 20 nM) or forskolin (1 and 10 μM) the PTH‐stimulated cAMP production was dose‐dependently potentiated by PMA, whereas forskolin‐stimulated cAMP production was not affected. However, both PTH‐ and forskolin‐stimulated cAMP production was dose‐dependently augmented when PMA was added 3 min prior to PTH or forskolin. With increasing preincubation periods (up to 24 h) with PMA instead of a potentiation an inhibition was observed. This inhibition is not due to PTH receptor desensitization, although, on basis of the present results desensitization can not completely be excluded. In all cases 4α‐phorbol was without effect. The present results show that protein kinase C modulates stimulation of ODC activity and cAMP production in fetal rat osteoblasts. The modulation of both ODC activity and cAMP production appears to be dependent on the nature of the stimulator. The present data suggest a role for protein kinase C in limiting the cAMP‐mediated stimulation of ODC activity in these cells. Furthermore, it is suggested that protein kinase C can interfere at more than one site in the cAMP‐generating system.
Analysis of cell variants showing differential susceptibilities to radiation‐ or chemical‐induced neoplastic transformation: Differences in their responses to growth factors
Authors: Tatsuka Masaaki , Orita Satoshi , Kakunaga Takeo 
Published: February 2005

AbstractThe induction of DNA synthesis in quiescent, density‐arrested Balb/c 3T3 cells is known to be controlled by the sequential action of at least two functionally distinct sets of growth factors, so‐called “competence factors” and “progression factors.” Here we examined this induction pathway in Balb/c 3T3 A31‐l variants, which showed differential susceptibilities to radiation‐ and chemical‐induced neoplastic transformation despite their similar susceptibilities to radiation‐ or chemical‐induced cell killing and mutagenesis. DNA synthesis was acquired only with the exposure to progression factors in a highly susceptible cell variant (A31‐l‐13) whereas both competence factors and progression factors were required for a less susceptible cell variant (A31‐l‐1). The competent state constitutively produced by an autologous mechanism in the highly transformation‐susceptible A31‐l‐13 cells suggests the existence of an endogenous promoter that acts for the expression of the transformed phenotype in an autocrine fashion when the cells have been initiated by radiation or chemical carcinogens. The growth factor requirements acting as a determining factor for susceptibilities to transformation are discussed.
Direct evidence for nuclear and cytoplasmic colocalization of proteasomes (Multiprotease complexes) in liver
Authors: Tanaka Keiji , Kumatori Atsushi , Ii Kunio , Ichihara Akira 
Published: February 2005

AbstractSubcellular localization of the large multicatalytic protease complexes called proteasomes, which have been found in soluble fractions of various cells, was examined by biochemical, immunological, and immunohistological methods. Rat liver nuclei, purified by two different procedures, showed high activities for degrading [3H]methylcasein and various fluorogenic oligopeptides with neutral and weakly alkaline pH optima. On gel filtration, all of these peptidase activities were recovered in a single peak with the unusually large molecular weight of about 600,000. Properties of the proteolytic activity in crude extracts of the nucleus and the cytoplasm were very similar. Immunoelectrophoretic blot analysis showed the presence of appreciable concentrations of proteasomes with similar immunoreactivity in isolated nuclear and cytosolic fractions. Moreover, immunohistochemical staining of human liver showed that proteasomes were predominantly localized in the nuclear matrix but also were present diffusely in the cytoplasm of hepatocytes. These findings indicate the nuclear and cytoplasmic colocalization of proteasomes.
Prostaglandin E2 receptor heterogeneity and dysfunction in mammary tumor cells
Authors: Fulton Amy M. , Laterra John J. , Hanchin Cynthia M. 
Published: February 2005

AbstractWe have reported previously that murine mammary tumor cell subpopulations isolated from one spontaneous adenocarcinoma are heterogenous in terms of prostaglandin E2 (PGE2) syntnetic capacity. We have also shown that tumor‐PGE2 contributes to the ability of these cells to grow and metastasize in vivo (Fulton and Heppner: Cancer Research 45:4779–4784, 1985). In the present study, we have asked whether exogenous PGE2 has direct effects on the proliferation of these cells in vitro and if such responses can be attributed to the capacity of these cells to (1) bind PGE2 and (2) activate adenylate cyclase via the PGE2 receptor. We report that PGE2, at concentrations below 1 × 10−5 M, does not affect the proliferation rate of these cells. This unresponsiveness is not due to the absence of receptors for PGE2. However, marked heterogeneity in receptor binding and function was detected in these closely related cell lines. Two metastatic lines (66 and 410.4) have high‐affinity receptors for PGE2 (average Kd = 4.3 × 10−9 M/L and 4.2 × 10−9 M/L, respectively) and similar binding capacities (4.1 × 104 and 2.9 × 104 binding sites, respectively). Two nonmetastatic lines, 410 and 67, have receptors with lower affinity (Kd = 8.3 × 10−9 M/L and 1.6 × 10−7 M/L, respectively) and binding capacities of 2.8 × 105/410 cell or 7.3 × 104/67 cell. A third nonmetastatic line (168) exhibits no specific binding. PGE2 receptor stimulation leads to elevated intracellular cAMP in lines 66, 410, and 67. Line 410.4 cells appear to have a functional lesion in the PGE2 receptor resulting in a failure to elevate cAMP in response to receptor occupancy. Adenylate cyclase can, however, be activated in these cells by cholera toxin, NaF, or forskolin. In comparison to the other cell lines, line 168 cells respond poorly to all cAMP‐stimulating agents. Thus, we have found that PGE2 binding is a heterogenous property for these cells, and, in addition, we have identified an apparent uncoupling of PGE2 receptor to the adenylate cyclase system in one cell line.
Cytochalasin D‐mediated hyperinduction of the substrate‐associated 52‐kilodalton protein p52 in rat kidney fibroblasts
Authors: Hiccins Paul J. , Ryan Michael P. , Chaudhari Panna 
Published: February 2005

AbstractRegulation of certain differentiated and housekeeping functions in cultured mammalian cells is significantly influenced by cell shape. The shape‐modulating agent cytochalasin D (CD) was used, therefore, to elucidate potential cytoarchitectural influences affecting synthesis of a major 52 kDa secreted/substrateassociated protein (p52) of normal rat kidney (NRK) fibroblasts. Biosynthetic labeling experiments indicated that treatment of NRK cells with CD increased, by 10‐18‐fold, the medium content of an M, 52,000 protein. Two‐dimensional gel electrophoresis and peptide fragment mapping confirmed that the 52 kDa protein produced in abundance as a consequence of CD treatment was identical to p52 constitutively expressed by NRK cells. A lower mw protein (p50; M, 50,000) was also resolved which, based on pl microheterogeneity, protease fragmentation profile, and sensitivity to tunicamycin, could be identified as a less‐glycosylated form of p52. p50 and p52 were both detected in the matrix and medium compartments of NRK and NRK/CD cells. The matrix p52 content of CD‐induced and uninduced cells, however, was significantly greater (by 200‐500‐fold) than the corresponding medium levels. This differential compartmentalization, the time course of p52 accumulation in the matrix of NRK/CD cells compared to its appearance in the medium, and the kinetics of p52 pulse‐chase from the matrix collectively indicated that the matrix is the initial site of p52 deposition. Low levels of CD (1 μM) produced extensive disruptions of cellular microfilaments but did not result in an overall cell shape change nor a hyperinduction of p52. Morphologic rounding (seen in 10–100 μM CD) coincided with augmented p52 production. Transition from a flat to a round phenotype in NRK cells, or at least the generation of sufficient microfilament fragmentation to compromise cellsubstrate adhesivity, appears to be an essential aspect of CD‐mediated p52 hyperinduction.
Epidermal growth factor stimulation of prostacyclin production by cultured aortic smooth muscle cells: Requirement for increased cellular calcium levels
Authors: Blay Jonathan , Hollenberg Morley D. 
Published: February 2005

AbstractWe have examined the ability of epidermal growth factor (EGF) to regulate prostacyclin production by cultured A10 smooth muscle cells. EGF by itself had no effect on prostacyclin production, but it augmented the response to arg8‐vasopressin. An EGF stimulation of prostacyclin production was also observed in the presence of the calcium ionophore A23187; it therefore seemed likely that the key event required for EGF to stimulate prostacyclin production might be an increase in the available cellular Ca2+. Studies with 45Ca2+ showed that vasopressin both mobilised Ca2+ from intracellular stores and increased the influx of extracellular Ca2+ into A10 cells. The increase in prostacyclin production caused by vasopressin and the augmentation by EGF were both abolished by TMB‐8, an antagonist ofCa2+mobilisation, by EGTA, a chelator of Ca2+ ions, or by incubating cultures in the absence of added Ca2+. These results were consistent with a central role for Ca2+ in the responses and showed that both intracellular and extracellular sources of Ca2+ were important for the triggering of prostacyclin production. The increases in prostacyclin production were only marginally affected by nifedipine, and no responses were seen (either in the absence or presence of EGF) when KCL was used to depolarise the cell membrane. These data indicated that uptake of Ca2+ ions via voltage‐dependent channels was unlikely to be a major factor in the stimulation of prostanoid production. We conclude that the ability of EGF to stimulate prostacyclin production in A10 smooth muscle cells depends upon a concurrent stimulus that will increase available intracellular Ca2+ levels.
Effect of scatter factor on motility of epithelial cells and fibroblasts
Authors: Stoker Michael 
Published: February 2005

AbstractThe scatter factor is a protein released by fibroblasts that causes dispersal of epithelial cell colonies and disruption of intercellular junctions, as well as an alteration of morphology with ruffling and rapid extension and movement of pseudopodia. To find out if the scatter factor has a direct effect on cell migration, the Boyden chamber assay was used to determine the effect of partially purified factor on the migration of cells through 8 μm pore size filters. The results showed that the mobility of Madin‐Darby canine kidney (MDCK) cells was stimulated, and usually maximal at 100 ng per ml, which is equivalent to 100 to 200 units of activity in the standard assay based on the morphology and arrangement of cells. The migration was due to chemotaxis and chemokinesis. A keratinocyte cell line was also sensitive as were, to a lesser extent, BSCI monkey kidney cells. The motility of freshly isolated fibroblasts and fibroblast cell lines, however, was not significantly affected. The results confirm the cell specificity and paracrine role of the scatter factor and show that this fibroblast‐derived molecule can directly stimulate the movement of epithelial cells.