bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracellular calcium‐dependent regulation of transmembrane calcium fluxes in murine keratinocytes
Authors: Reiss Michael , Lipsey Lewis R. , Zhou Zhao‐Ling 
Published: February 2005

AbstractBecause the level of extracellular Ca2+ is an important stimulus for differentiation of epidermal cells in vitro, we characterized the extracellular Ca2+ ‐dependent transmembrane Ca2+ fluxes in BALB/MK mouse keratinocytes. Increasing levels of extracellular Ca2+ ranging from 0.07 to 1.87 mM, stimulated the rate of 45Ca2+ uptake into these cells 10‐ to 70‐fold and doubled the rate of 45Ca2+ efflux. The divalent cations, Ni2+ and Co2+, were able to block the influx of Ca2+, but dihydropyridines and verapamil were not. Furthermore, 10 to 100 μM of the trivalent cation La3+ induced a dose‐dependent 2‐ to 100‐fold increase of Ca2+ uptake, independently of the level of extracellular Ca2+. These observations suggest that keratinocytes possess a cell‐surface “Ca2+ ‐receptor,” activation of which stimulates the influx of 45Ca2+ through a type of voltage‐independent, receptor‐operated Ca2+ channels. Epidermal growth factor induced an accumulation of 45Ca2+ of a much smaller magnitude than elevations of the level of extracellular Ca2+, without a detectable increase of Ca2+ efflux. Thus, the divergent cellular responses of keratinocytes to EGF and extracellular Ca2+ may be due, in part, to the distinct changes in transmembrane Ca2+ fluxes that these two stimuli generate. Treatment of cells with type β transforming growth factor led to a gradual 6‐fold increase of the Ca2+ ‐activated rate of Ca2+ uptake over a period of 4 hours, but reduced the Ca2+ efflux by approximately 50% within 10 minutes. Thus, type β transforming growth factor apparently stimulates Ca2+ influx indirectly, but may control the differentiation of keratinocytes by direct inhibition of Ca2+ efflux pumps.
Effects of a sialoglycopeptide on early events associated with signal transduction
Authors: Toole‐Simms W. E. , Loder D. K. , Fattaey H. K. , Johnson T. C. 
Published: February 2005

AbstractA sialoglycopeptide (SGP), isolated and purified from bovine cerebral cortex cells, was studied in regard to early signal transduction events associated with the cell cycle. Previously shown to be a potent antagonist to a variety of mitogens, the SGP abrogated the ability of 12‐O‐tetradecanoylphorbol‐13 acetate (TPA) to elicit an alkalinization of 3T3 cell cytosol, but only when added minutes prior to, or simultaneously with, the tumor promoter. 3T3 cell TPA‐mediated Ca2+ mobilization was also inhibited by the SGP although the inhibitor itself did not bind Ca2+ in a cell‐free assay. The results are discussed in light of the already known kinetics of interaction between the SGP, various mitogens, and the calcium ionophore A23187 with regard to the pivotal events leading to the decision of a cell to divide or not to divide.
Colony stimulating factor‐1 stimulates diacylglycerol generation in murine bone marrow‐derived macrophages, but not in resident peritoneal macrophages
Authors: Veis Nurin , Hamilton John A. 
Published: February 2005

AbstractColony stimulating factor‐1 (CSF‐1) stimulates DNA synthesis in murine bone marrow‐derived macrophages (BMM); however, unlike BMM, murine resident peritoneal macrophages (RPM) undergo a poor proliferative response. It has previously been shown that phosphatidylinositol‐4,5‐bisphosphate hydrolysis is not associated with CSF‐1 action in BMM. In this report we demonstrate that, despite a lack of inositol trisphosphate generation, CSF‐1 transiently elevated both [3H]myristoyl‐ and [3H]arachidonyl‐diacylglycerol (DAG) in BMM in a dose‐dependent fashion. CSF‐1 failed, however, to stimulate an increase in either species of DAG in RPM. Thus, DAG could be a second messenger for the proliferative action of CSF‐1 in macrophages. Other mitogenic agents, 12‐O‐tetradecanoyl phorbol 13‐acetate (TPA) and exogenous phospholipase C, also increased BMM levels of [3H]myristoyl‐ and [3H]arachidonyl‐DAG. The nonmitogenic agents, lipopolysaccharide (LPS), tumor necrosis factor‐α (TNF‐α) and zymosan, had different effects on the generation of either species of DAG in BMM. LPS failed to elevate either form, TNF‐α increased only [3H]arachidonyl‐DAG, while zymosan stimulated levels of both species of DAG. It therefore appears that increased diacylglycerol generation may be necessary, but perhaps not sufficient, for macrophage proliferation.
The NH2‐terminal extension of high molecular weight bFGF is a nuclear targeting signal
Authors: Quarto Natalina , Finger Fern P. , Rifkin Daniel B. 
Published: February 2005

AbstractBasic fibroblast growth factor (bFGF) is a member of the heparin‐binding growth factor (HBGF) family that includes at least seven species. These proteins are potent regulators of a number of cellular processes, including cell division and angio‐genesis. Multiple forms of bFGF exist differing only in the length of their NH2‐terminal extensions. These species of bFGF also have unique subcellular distributions. The smallest form (18 kD) occurs predominantly in the cytosol, while the higher molecular weight forms (22, 22.5, 24 kD) are associated with the nucleus and ribosomes. Here we report that the nuclear localization of the higher molecular weight forms of bFGF derives specifically from the amino acid sequences within the NH2‐terminal extension. This has been demonstrated by constructing a chimeric protein containing the NH2‐terminal extension of the highest molecular weight form of bFGF fused to β‐galactosidase (β‐gal). After transfection in a transient expression system, the chimeric protein accumulated in the nuclei of transfected cells, while the wild‐type β‐gal was found predominantly in the cytoplasm.
Stimulation of protein synthesis by internalized insulin
Authors: Miller David S. , Sykes Destiny B. 
Published: February 2005

AbstractPrevious studies showed that microinjected insulin stimulates transcription and translation in Stage IV Xenopus oocytes by acting at nuclear and cytoplasmic sites (Miller, D.S., 1988, 1989). The present report is concerned with the question of whether hormone, internalized from an external medium, can act on those sites to alter cell function. Both intracellular accumulation of undegraded 125I‐insulin and insulin‐stimulated 35S‐methionine incorporation into oocyte protein were measured. Anti‐insulin antiserum and purified anti‐insulin antibody were microinjected into the cytoplasm of insulin‐exposed cells to determine if insulin derived from the medium acted through internal sites. In cells exposed for 2 h to 7 or 70 nM external insulin, methionine incorporation was stimulated, but intracellular hormone accumulation was minimal and microinjected antibody was without effect. In cells exposed for 24 h, methionine incorporation again increased, but now accumulation of undegraded, intracellular hormone was substantial (2.6 and 25.3 fmol with 7 and 70 nM, respectively), and microinjected anti‐insulin antibody significantly reduced the insulin‐stimulated component of incorporation; basal incorporation was not affected. For cells exposed to 70 nM insulin for 24 h, inhibition of the insulin‐stimulated component was maximal at 39%. Thus under those conditions, about 40% of insulin's effects were mediated by the internal sites. Together, the data show that inhibition of insulin‐stimulated protein synthesis by microinjected antibody was associated with the intracellular accumulation of insulin. They indicate that when oocytes are exposed to external insulin, hormone eventually gains access to intracellular sites of action and through these stimulates translation. Control of translation appears to be shared between the internal sites and the surface receptor.
Amino acid‐rich medium (Leibovitz L‐15) enhances and prolongs proliferation of primary cultured rat hepatocytes in the absence of serum
Authors: Mitaka Toshihiro , Sattler Gerald L. , Pitot Henry C. 
Published: February 2005

AbstractMultiple rounds of cell division were induced in primary cultured rat hepatocytes in serum‐free, modified L‐15 medium supplemented with 20 mM NaHCO3 and 10 ng/ml EGF in a 5% CO2/95% air incubator. A 150% increase in cell number and DNA content was observed between day 1 and day 5. The time course of DNA synthesis of hepatocytes cultured in L‐15 medium differed from that in DMEM/F12 medium in that there were four peaks of 3H‐thymidine incorporation in the L‐15 medium, at 60 h, 82 h, 96 h, and 120 h, but only one peak at 48 h in modified DMEM/F12 medium. Labeling studies of the hepatocytes indicated that more than 60% of the cells were stained with antibromodeoxyuridine (BrdU) antibody in the periods of 48–72 h and 72–96 h after plating at densities between 1.5 × 105 and 6.0 × 105 cells per 35‐mm dish. Even at a density of 9.0 × 105 cells/dish, about 40% of the cell nuclei were stained with BrdU in the periods of 48–72 h and 72–96 h. In addition, about 20% of the hepatocytes in Culture initiated a second round of the cell cycle between 48 and 96 h in culture. Proliferating cells, which were mononucleate with a little cytoplasm, appeared in small clusters or colonies in the culture from day 4. These proliferating cells produced albumin. The addition of essential amino acids to the DMEM/F12 medium enhanced the DNA synthesis of hepatocytes, thus indicating that the higher level of amino acids in L‐15 medium may be an important factor in its enhanced ability to support the proliferation of primary cultured rat hepatocytes.
Granular presence of terminin is the marker to distinguish between the senescent and quiescent states
Authors: Wang Eugenia , Tomaszewski George 
Published: February 2005

AbstractWe have previously identified statin, a nonproliferating‐cell‐specific nuclear protein of 57,000 dalton whose presence can be used to distinguish between growing and nongrowing cells. In this report we identify another protein, terminin, whose presence (by immunofluorescence microscopy) can be used to distinguish between temporarily and permanently growth‐arrested cells. Thus terminin is a marker to separate the senescent from the quiescent state. By means of an unique monoclonal antibody (mAb1.2), the presence of terminin is recognized as granules in the cytoplasm of in vitro aged fibroblasts; these granules are not found in serum‐starved, contact‐inhibited, growing, or transformed fibroblasts, except for those cells experiencing the initiation of apoptosis due to long‐term deprivation of nutrients. Preliminary histochemical studies show that terminin is also found in the superficial epithelial layer of the esophagus, where terminal differentiation is followed by apoptosis and sloughing off into the lumen. Biochemical characterization by Western blot shows the terminin antibody recognizing a protein of 84 kilodalton (kDa) in growing and quiescent cells, whereas in senescent cells a protein of 57 kDa is recognized; this result suggests that a senescence‐dependent protease may cleave the 84 kDa protein to 57 kDa. This proteolytic action seems to render the specific antigenic epitope exposed in its native state and accessible to the terminin antibody by immunofluorescence microscopy. It is this product of posttranslational modification in the form of a cytoplasmic 57 kDa protein that is the marker distinguishing between senescence and quiescence.
Cell polarity regulates the release of secretory component, the epithelial receptor for polymeric immunoglobulins, from the surface of HT‐29 colon carcinoma cells
Authors: Chintalacharuvu Koteswara R. , Piskurich Janet F. , Lamm Michael E. , Kaetzel Charlotte S. 
Published: February 2005

AbstractThe HT‐29 human colon carcinoma cell line differentiates in glucose‐free medium to an enterocytic phenotype. We previously isolated a series of HT‐29 subclones selected for high levels of expression of secretory component (SC), the epithelial receptor for polvmeric immunoglobulins. To develop a model system for studying effects of cell polarity on SC expression and release from the cell surface, the HT‐29.74 subclone was induced to differentiate in glucose‐free medium. Expression of SC was induced by glucose deprivation in both the parental HT‐29 cell line and, to an even greater extent, in the HT‐29.74 subclone. Prolonged glucose deprivation of HT‐29.74 cells resulted in morphological changes consistent with enterocytic differentiation. Metabolic radiolabeling of SC in differentiated HT‐29.74 cells indicated that proteolytic cleavage of membrane‐bound to free SC occurred both on the cell surface and intracellularly, possibly in a vacuolar apical compartment or intrapeithelial lumen. To study effects of cell polarity on SC release, differentiated HT‐29.74 cells were depolarized by culturing in low calcium medium. Within 2 hours after transfer of the cells into low calcium medium, a burst of SC release was observed concomitant with cell depolarization. Subsequently, release of SC declined significantly and remained low as long as cells were maintained in a depolarized state. The extent of cell depolarization could be controlled by varying the extracellular calcium concentration or by substituting the divalent cation Sr++, which partially prevents depolarization, for Ca++. In either case, the magnitude of the initial burst and subsequent decline in release of SC was proportional to the extent of cell depolarization. We conclude that cell polarity plays an important role in controlling the release of SC in intestinal epithelial cells, most likely by regulating the distribution of membranebound SC and SC protease, which are on the basolateral and apical cell surfaces, respectively, in differentiated cells.
Bovine aortic endothelial cells release hydrogen peroxide
Authors: Sundqvist T. 
Published: February 2005

AbstractEndothelial cells grown on microcarriers are able to release H2O2 to the extracellular environment without any added stimulus. The extracellularly released H2O2 can be detected by luminol‐amplified chemiluminescence (CL) if horseradish peroxidase is added. The CL response can be reduced by catalase and blocked by superoxide dismutase, indicating that O2‐could be a precursor for H2O2. The CL kinetics, i.e., a long lag time followed by a rapid shift to a new level, indicate activation of an O2‐producing enzyme. The cells are also able to protect themselves from H2O2 stimulation by both catalase and the glutatione system. Bradykinin stimulates the H2O2 release, but if the effect is directly stimulatory or if it acts by reduction of the protective system is at present unclear. The extracellularly released H2O2 could be a cause of injury to the endothelial cells or to the subendothelial matrix.
Coordination of protein‐DNA interactions in the promoters of human H4, H3, and H1 histone genes during the cell cycle, tumorigenesis, and development
Authors: Van Wijnen André J. , Owen Thomas A. , Holthuis Joost , Lian Jane B. , Stein Janet L. , Stein Gary S. 
Published: February 2005

AbstractCoordinate transcriptional control of replication‐dependent human H4, H3, and H1 histone genes was studied by comparing levels of H3 and H1 histone promoter binding activities with those of H4 histone promoter factor HiNF‐D during the cell cycle of both normal diploid and tumor‐derived cells, as well as in fetal and adult mammalian tissues. Both H3 and H1 histone promoters interact with binding activities that, as with HiNF‐D, are maximal during S‐phase but at low levels in the G1‐phase of normal diploid cells. However, these analogous DNA binding activities are constitutively maintained at high levels throughout the cell cycle in four different transformed and tumor‐derived cells. Downregulation of the H3 and H1 histone promoter factors in conjunction with HiNF‐D is observed in vivo at the onset of quiescence and differentiation during hepatic development. Hence, our results indicate a tight temporal coupling of three separate protein‐DNA interactions in different histone promoters during the cell cycle, development, and tumorigenesis. This suggests that a key oscillatory, cell‐growth‐control mechanism modulates three analogous histone gene promoter protein‐DNA interactions in concert. The derangement of this mechanism in four distinct tumor cells implies that concerted deregulation of these histone promoter factors is a common event resulting from heterogeneous aberrations in normal cell growth mechanisms during tumorigenesis. We postulate that this mechanism may be involved in the coordinate regulation of the human H4, H3, and H1 histone multigene families.
Transforming activity of mutant human p53 alleles
Authors: Slingerland Joyce M. , Benchimol Sam 
Published: February 2005

AbstractMutant forms of the p53 gene have been shown to cooperate with an activated ras gene in transforming primary cells in culture. The aberrant proteins encoded by p53 mutants are thought to act in a dominant negative manner in these assays. In vivo data, however, reveal that where p53 has undergone genetic change in tumors, both alleles have been affected. We previously identified a case of human acute myelogenous leukemia (AML) in which both alleles of the p53 gene had undergone independent missense mutations (at codons 135 cys to ser and 246 met to val). In these blasts, p53 mutations appear to be acting recessively. We have assayed the transforming potential of these p53 mutations, as well as that of another mutation at codon 273, also identified in a human neoplasm. Both mutations from the AML blasts (codon 135 and codon 246) confer transforming ability on the mutant protein. While transformation assays may define functionally different subsets of p53 mutations, the overexpression phenotype of mutants in this assay may not accurately reflect the pathological effects of p53 mutations in vivo.
CD10 and CD44 genes of leukemic cells and malignant cell lines show no evidence of transformation‐related alterations
Authors: Kee Barbara L. , Dadi Harjit K. , Tran‐Paterson Rosette , Quackenbush Elizabeth J. , Andrulis Irene L. , Letarte Michelle 
Published: February 2005

AbstractThe expression of CD10/CALLA is associated primarily with childhood leukemia of pre‐B lymphocyte phenotype. We have compared the hybridization pattern of the CALLA gene from leukemic and normal cells digested with several restriction enzymes. No alterations were noticed with Eco Rl, Sac I, Pvu II, Eco RV, Hind III, and Msp I. Since CALLA is also found on other malignancies, we analyzed DNA samples prepared from cell lines derived from leukemia, lymphoma, glioblas‐toma, retinoblastoma, and neuroblastoma. Normal restriction patterns were observed for all the lines regardless of their CALLA phenotype. Having demonstrated previously that CALLA was structurally identical to neutral endopeptidase 3.4.24.11 (NEP), we have now established a correlation between surface expression of CALLA and NEP activity on leukemia samples and on several cell lines. Malignant cells tested expressed a functionally active enzyme and no gross alteration was present in the CALLA gene. The CD44 gene is expressed on most cells of hemopoietic origin and on > 95% of cases of acute lymphoblastic leukemia and acute myeloblastic leukemia studied. It is also expressed on normal astrocytes and on malignant cells of glioma/astrocytoma types. We now report that a similar pattern of hybridization was observed with Sac I, Pvu II, and Eco Rl for leukemic samples, normal cells, and malignant cell lines. A polymorphism was recently detected for CD44 using Hind III; leukemic cells and malignant lines also showed this normal polymorphism. Thus no deletion or insertion could be detected in the CD44 gene of leukemic cells and malignant lines, suggesting that no gross DNA alterations were involved. The correlation between surface expression and enzymatic activity of CD10/CALLA and the expression of CD44 on a variety of malignant cells would suggest that the structure and function of these two gene products are probably not altered by the process of transformation.
Clearance and fate of leukemia‐inhibitory factor (LIF) after injection into mice
Authors: Hilton Douglas J. , Nicola Nicos A. , Waring Paul M. , Metcalf Donald 
Published: February 2005

AbstractLeukemia‐inhibitory factor (LIF) elicits effects on a broad range of cell types, including cells of the monocytic and megakaryocytic series, embryonal stem cells, hepatocytes, adipocytes, and osteoblasts. Native and recombinant LIF, injected intravenously into adult mice, had an initial half‐life of 6‐8 min and a more prolonged second clearance phase. Clearance of 125I‐LIF from the circulation was paralleled by a rapid accumulation in the kidneys, liver, lungs, and spleen and a more gradual accumulation in the thyroid gland. Labeling of the renal glomerular tufts, parenchymal hepatocytes, splenic red pulp, alveolar pneumocytes, and thyroid follicular cells as well as of megakaryocytes and osteoblasts in the bone cavities, placental trophoblasts, and cells of the choroid plexus was demonstrable autoradiographically. The appearance of a large amount of nonprecipitable 125I in the urine suggested that the kidneys were the major route of LIF clearance from the body.
Responsiveness of the increase in c‐fos mrna levels depends on the inducer and the cell's past
Authors: Tuijl Mark J. M. , Boon Johan A. Den , van Grunsven Wout M. J. , van Wijk Roeland 
Published: February 2005

AbstractIn this paper we show that in C3H10T1/2 mouse fibroblasts, the inducibility of c‐fos mRNA by heat shock or serum addition is strongly dependent on the cell's past. Four hours after a heat shock, a time point where the induced c‐fos mRNA has disappeared, c‐fos mRNA could not be induced again by a second heat shock. Four hours after serum addition, by which c‐fos was induced, a second serum addition also failed to induce c‐fos mRNA again. When, however, serum was added 4 hours after heat shock or heat shock was given 4 hours after serum addition, levels of c‐fos mRNA could be enhanced again. The induction by serum of c‐fos mRNA levels in thermotolerant cells might be related to their increased stimulation of DNA synthesis as compared to control cells.
Differences in preferential synthesis and redistribution of HSP70 and HSP28 families by heat or sodium arsenite in chinese hamster ovary cells
Authors: Lee Yong J. , Curetty Lindali , Corry Peter M. 
Published: February 2005

AbstractSince both heat and sodium arsenite induce thermotolerance, we investigated the differences in synthesis and redistribution of stress proteins induced by these agents in Chinese hamster ovary cells. Five major heat shock proteins (HSPs; Mr 110, 87, 70, 28, and 8.5 kDa) were preferentially synthesized after heat for 10 min at 45.5°C, whereas four major HSPs (Mr 110, 87, 70, and 28 kDa) and one stress protein (33.3 kDa) were preferentially synthesized after treatment with 100 μM sodium arsenite (ARS) for 1 hr. Two HSP families (HSP70a,b,c and HSP28a,b,c) preferentially relocalized in the nucleus after heat shock. In contrast, only HSP70b redistributed into the nucleus after ARS treatment. Furthermore, the kinetics of synthesis of each member of HSP70 and HSP28 families and their redistribution were different after these treatments. The maximum rates of synthesis of HSP70 and HSP28 families, except HSP28c, were 6–9 hr after heat shock, whereas those of HSP70b and HSP28b,c were 0–2 hr after ARS treatment. In addition, the maximum rates of redistribution of HSP70 and HSP28 families occurred 3–6 hr after heat shock, whereas that of HSP70b after ARS treatment was significantly less than that after heat treatment. These results suggest that heat treatment but not sodium arsenite treatment stimulates the entry of HSP70 and HSP28 families into the nucleasu.