bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assembly of the peripheral domain of the bovine vacuolar H+‐adenosine triphosphatase
Authors: Myers Melanie , Forgac Michael 
Published: February 2005

AbstractThe biosynthesis and assembly of the peripheral sector (V1) of the vacuolar protontranslocating adenosine triphosphatase (V‐ATPase) was studied in a bovine kidney epithelial cell line. Monolayer cultures of cells were metabolically radiolabeled with Tran 35S‐label and the V‐ATPase subsequently immunoprecipitated using a monoclonal antibody raised against the bovine brain‐coated vesicle proton pump. The V‐ATPase immunoprecipitated from the bovine kidney cell line has a subunit composition very similar to that of the bovine brain‐coated vesicle proton pump and the V‐ATPase prepared from other kidney tissues. Radiolabeling the cells for increasing times showed that the V1 or peripheral portion of the V‐ATPase is assembled within 10–15 min; the intact V1V0 complex is also detectable within 10–15 min. Fractionation of the cells into cytosolic and membrane components prior to immunoprecipitation revealed that there is a significant pool of V1 in the cytosol; a similar complex is also found in bovine brain cytosol. Pulse‐chase studies suggest that this cytosolic pool is not an obligate precursor for membranebound V1V0 and does not exchange with the membrane V1 population at later times. No qualitative differences in assembly were observed when pulse‐chase studies were performed at 15°C or in the presence of brefeldin A. This suggests that assembly of V1V0 is probably completed in the endoplasmic reticulum prior to distribution of the enzyme throughout the cell, with a cytosolic pool of V1 of unknown function existing in parallel with the fully assembled complex. © 1993 Wiley‐Liss, Inc.
Resolution of multiple AP‐1 complexes in HL‐60 cells induced to differentiate by 1,25‐dihydroxyvitamin D3
Authors: Kolla Sarah S. , Studzinski George P. 
Published: February 2005

AbstractActivator protein‐1 (AP‐1) complex plays a central role in the regulation of both growth and differentiation in many cell types. Monocytic differentiation of HL‐60 cells by TPA (12‐0‐tetradecanoyl phorbol‐13‐acetate) has been reported to be paralleled by increased AP‐1 binding to DNA and by elevated c‐jun expression, suggesting transcriptional level of control. We show that two forms of AP‐1 complex, designated AP‐1/1 and AP‐1/2, can be demonstrated in logarithmically growing HL‐60 cells, that the exposure of these cells to 10−8 M 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3) results in increased binding of these complexes to the AP‐1 DNA element, and that the AP‐1 complex can be resolved into at least three forms in differentiated cells. Binding to, or competition with, a mutated form of the AP‐1 binding site shows that the most slowly migrating complex (AP‐1/3) binds to DNA with greater specificity than do complexes AP‐1/1 and AP‐1/2, while antibody inhibition and binding studies performed at 37°C indicate that jun proteins predominate in AP‐1/2 complexes. Exposure of extracts from differentiated, but not untreated, HL‐60 cells to 2 mM ATP increases the prominence of AP‐1/3 complexes, and reduces the DNA binding of AP‐1/1 complexes. Treatment of the extracts with phosphatases abolishes the binding of AP‐1/2 and AP‐1/3 to DNA, and increases the binding intensity of AP‐1/1. When extracts from differentiated cells are mixed with extracts from undifferentiated cells the AP‐1/3 complexes become less prominent, suggesting than an inhibitory activity in undifferentiated cells prevents the formation of AP‐1/3 complexes. These studies show the association of multiple forms of AP‐1 complex with the mature monocytic phenotype, and suggest several levels of control of monocytic differentiation. © 1993 Wiley‐Liss, Inc.
Induction of tolerance to hypothermia and hyperthermia by a common mechanism in mammalian cells
Authors: Glofcheski David J. , Borrelli Michael J. , Stafford Diane M. , Kruuv Jack 
Published: February 2005

AbstractPretreatment by hypothermic (25°C) cycling (PHC) of attached exponential‐phase V79 Chinese hamster cells by Method 4 (24 hr at 25°C + 1.5 hr at 37°C + 24 hr at 25°C + trypsin + 3 hr at 37°C) or by Method 3 (48 hr at 25°C + trypsin + 3 hr at 37°C) make mammalian V79 cells significantly more resistant to 43°C hyperthermia. There is no significant difference in the 43°C curves whether Method 3 or 4 is used for pre‐exposure. If pre‐exposure is at 15 or 10°C, the resistance to hyperthermia is significantly reduced. PHC by Method 4 significantly increases survival of cells exposed to 5°C and, to a lesser extent, to 10°C. The increase in hyper‐ and hypothermic survival after PHC cannot be accounted for by changes in cell cycle distribution. Heat‐shock protein synthesis is not induced by PHC; hence, protection does not result from newly synthesized proteins. When cells are made tolerant to hyperthermia by a pretreatment in 2% DMSO for 24 hr at 37°C (Method 8), the cells are not more resistant to subsequent exposures to hypothermia, either at 5 or 10°C. The results imply that there may be two mechanisms of inducing resistance to hyperthermia, only one of which also confers resistance to hypothermia. © 1993 Wiley‐Liss, Inc.
Physiological oxygen tension modulates the chemically induced mitogenic response of cultured rat hepatocytes
Authors: Maier Peter , Schawalder Hanspeter 
Published: February 2005

AbstractFreshly isolated rat hepatocytes were cultured at periportal‐ (13% O2) or perivenous‐like (4% O2) oxygen tension and exposed to subtoxic exposure levels of cyproterone acetate (CPA: 10–330 μM), phenobarbital (PB: 0.75‐6 mM), and dimethylsulfoxide (DMSO: 0.1–3.3%) from 24–72 h after seeding. Induced alterations in ploidy, in the number of S‐phase cells, the degree of binuclearity, and cellular protein content were determined by twin parameter protein/DNA flow cytometry analysis of intact cells and isolated nuclei. CPA and PB increased whereas DMSO decreased dose dependently the total number of S‐phase cells. The changes differed within individual ploidy classes and were modulated by the oxygen tension. CPA increased and DMSO decreased the number of S‐phase cells preferentially among the diploid hepatocytes at periportal‐like oxygen tension. In contrast, PB increased binuclearity and S‐phase cells mainly among the tetraploid hepatocytes at perivenous‐like oxygen tension. Cellular protein content increased dose dependently after exposure to the hepatomitogens (CPA, PB) and decreased after exposure to DMSO at both oxygen tensions. Comparison with in vitro data proves that chemicals which interact with cells from the progenitor liver compartment (CPA, DMSO) exert their mitogenic activity best in cultures at periportal‐like oxygen tension preferentially in diploid hepatocytes, whereas chemicals which affect cells from the functional compartment show a higher activity at perivenous‐like oxygen tension. Physiological oxygen tension seems to be an effective modulator of the proliferative response of cultured rat hepatocytes similar to that expected for periportally or perivenously derived hepatocytes. © 1993 Wiley‐Liss, Inc.
Type I collagen substrate increases calcitonin and parathyroid hormone receptor‐mediated signal transduction in UMR 106–06 osteoblast‐like cells
Authors: Ikeda Kazuto , Michelangeli Valdo P. , Martin T. John , Findlay David M. 
Published: February 2005

AbstractComponents of the extracellular matrices (ECM) exert pleiotropic effects in many cell systems, but little is known of the effect of ECM on hormone signal transduction. We have investigated the effect of ECM substrates on cell growth and signal transduction by calcitonin (CT) and parathyroid hormone (PTH) using the rat osteosarcoma cell line, UMR 106–06. Type I collagen (collagen[I]) and Matrigel changed the morphology of the cells and significantly inhibited cell growth by 37% or 23%, respectively, compared with control. None of laminin, fibronectin, or type IV collagen affected cell shape or proliferation. Cells cultured on collagen (I)‐coated plates showed increased specific binding of labeled CT compared with cells on plastic plates. The effect was apparent by 24 h and persisted for at least 72 h. None of the other ECM affected CT binding. Scatchard analysis revealed that collagen(I) increased CT receptor numbers but not receptor affinity. Consistent with increased binding capacity, cells plated on collagen(I) had increased responses to each of CT and PTH in terms of cyclic adenosine monophosphate (cAMP) production compared to control cells. In addition, cAMP production by prostaglandin E2, cholera toxin, and forskolin was increased by 30–70% compared to control. These data suggest that collagen(I) had effects not only on membrane receptors but on guanosine triphosphate (GTP) binding proteins (G proteins). The effect of collagen(I) on CT binding was no longer present when the cells were freed from the plates by enzymatic dispersion and binding measured in cell suspensions. In UMR 106–01 cells transiently transfected with the porcine CT receptor cDNA, binding was similarly induced by collagen(I). These data are the first demonstration that collagen(I) may play an important role in signal transduction, affecting both receptors and G proteins in UMR 106–06 cells. These results draw attention to the potential role of the ECM of bone in hormone‐induced responses. © 1993 Wiley‐Liss, Inc.
Differences in transferrin response and numbers of transferrin receptors in rat and human mammary carcinoma lines of different metastatic potentials
Authors: Inoue Takatoshi , Cavanaugh Philip G. , Steck Peter A. , Brünner Nils , Nicolson Garth L. 
Published: February 2005

AbstractWe previously found that transferrin (Tf) differentially stimulated the growth of highly metastatic variant lines of murine melanoma and that these highly metastatic cells also had greater numbers of Tf receptors on their cell surfaces. In the present study we found that highly metastatic rat mammary adenocarcinoma cell lines also responded differentially to Tf in proliferation assays, and cell monolayers bound Tf in relation to their metastatic potential (MTPaB10 > MTPaB5 > MTLn3 > MTLn2 > MTC > MTF7 > MTPa). The brain‐colonizing lines PaB10 and PaB5 were the most responsive to Tf and had the highest numbers of Tf receptors. Different human breast cancer cell lines also responded differentially to Tf in proliferation assays and bound different amounts of Tf to their cell surface Tf receptors. Transferrin binding, but not growth response, correlated with metastatic and invasive properties of lines selected from the human MCF‐7 series (MCF7/LCC2 > MCF7/LCC1 > MCF7). In examining the transferrin binding and growth response of lines from the human MDA series, the Tf binding and growth response was MDA231 > MDA435 > MDA468. The lines MDA435 and MDA231 were metastatic in nude mouse assays, whereas the line MDA468 was not. Scatchard analysis indicated the presence of a single class of receptor for Tf on the rat and human mammary cell lines. The results suggest that neoplastic cells displaying various metastatic properties may express differing numbers of Tf receptors and respond differently to growth factors such as Tf. © 1993 Wiley‐Liss, Inc.
Secretion of transforming growth factor‐β isoforms by embryonic stem cells: Isoform and latency are dependent on direction of differentiation
Authors: Slager H. G. , Freund E. , Buiting A. M. J. , Feijen A. , Mummery C. L. 
Published: February 2005

AbstractMurine embryonic stem (ES) cells are maintained in an undifferentiated state when cultured in medium conditioned by Buffalo rat liver (BRL) cells. BRL conditioned medium (CM) contains a differentiation inhibitory activity (DIA) that is synonymous with leukemia inhibitory factor (LIF). ES cells in monolayer culture can be induced to differentiate by addition of all‐trans retinoic acid (RA) to the BRL CM, when they mainly form cells resembling parietal endoderm, or by culture in medium not conditioned by BRL cells. ES cells thus deprived of LIF/DIA differentiate spontaneously to a cell type that expresses Brachyury (T), a marker of early mesoderm. Northern blot analyses have shown previously that transcripts for transforming growth factor beta 1 (TGF‐β1) are detected in undifferentiated cells while transcripts for TGF‐β2 and TGF‐β3 only become detectable after differentiation. We have now determined levels of TGF‐β protein in CM and in the extracellular matrix (ECM) and have used neutralizing antibodies specific for TGF‐β1 and TGF‐β2 that do not react with recombinant human TGF‐β3 to determine the isoform secreted. Using the growth inhibition of mink lung CCL64 cells as a bioassay for TGF‐β activity, we demonstrate that undifferentiated ES cells secrete latent TGF‐β1 into the medium but no activity is found in their ECM. Cells induced to differentiate with RA contain TGF‐β2 in both active and latent forms in their CM. Likewise their ECM contains TGF‐β2 as the sole isoform. ES cells deprived of LIF/DIA secrete both TGF‐β1 and TGF‐β2 isoforms in their CM but TGF‐β‐like activity remains after addition of neutralizing antibodies for TGF‐β1 and TGF‐β2. This active TGFβ is the major component of the TGF‐β activity in this CM. By contrast, ECM from LIF/DIA deprived cells contains only the TGF‐β1 and β2 isoforms. The remaining activity in CM correlates with high expression of TGF‐β3 by Northern blot analysis in these cells. We speculate that TGF‐β3 is secreted by these cells and may be activated more efficiently and/or in a different manner to TGF‐β1 and TGF‐β2, since it is present in CM only in its active form. © 1993 Wiley‐Liss, Inc.
Transferrin is made and bound by photoreceptor cells
Authors: Davis Alberta A. , Hunt Richard C. 
Published: February 2005

AbstractRetinal pigment epithelial cells, which form one aspect of the blood‐retinal barrier, control the access of blood‐borne components such as diferric transferrin to the neural retina. It has recently been shown that RPE cells remove iron from diferric transferrin in a low pH compartment and subsequently release it in a low molecular weight form that can be chelated by apo‐transferrin (Hunt and Davis: J. Cell Physiol. 152:102–110, 1992). It is now shown that photoreceptor cells can bind diferric transferrin to receptors on their inner segments. Moreover, polymerase chain reaction and in situ hybridization show that cells of the neural retina, particularly photoreceptors, make apo‐transferrin. © 1993 Wiley‐Liss, Inc.
Interaction of facilitative glucose transporter with glucokinase and its modulation by ADP and glucose‐6‐phosphate
Authors: Lachaal Mohsen , Jung Chan Y. 
Published: February 2005

AbstractBacterial glucokinase (GK) binds to purified, human erythrocyte glucose transporter (GT) reconstituted in vesicles. The binding is largely abolished if GT is predigested with trypsin, indicating that GK binds to the cytoplasmic domain of GT. The binding is a saturable function of GK concentration showing two distinct affinities with apparent KD of 0.33 and 5.1 μM. The binding is stimulated by an increasing concentration of ADP with the 50% maximal effect at 5 mM. Glucose‐6‐phosphate (G6P) also stimulates the binding with a distinct optimum at 25 mM. The binding is stimulated only slightly by ATP. D‐glucose has no affect on the binding. KCl enhances the binding with the maximal effect at physiological intracellular concentrations. The binding is sensitive to changes in pH with an optimum at pH 4. The binding causes no detectable functional change in GT. However, the enzymatic activity of GK measured at nanomolar concentrations of GK is significantly greater in the presence of GT vesicles than in its absence or in the presence of protein‐free vesicles, indicating that GK interacts with GT at this low concentration range with an apparent KD of 10 mM. Although its physiological significance is not known, the GK‐GT interaction in vitro described here suggests that these two proteins may also interact in the cell and regulate carbohydrate metabolism. © 1993 Wiley‐Liss, Inc.
Adhesion molecules in skeletogenesis: II. Neural cell adhesion molecules mediate precartilaginous mesenchymal condensations and enhance chondrogenesis
Authors: Widelitz Randall B. , Jiang Ting‐Xin , Murray Ben A. , Chuong Cheng‐Ming 
Published: February 2005

AbstractNeural cell adhesion molecules (NCAM) was expressed transiently by mesenchymal cells in precartilaginous condensations of the embryonic chicken limb but was lost upon differentiation into cartilage. Consequently, NCAM was present in the periphery of the limb anlagen but was absent in the cartilaginous center of the growing limb. To determine NCAM function in limb bud chondrogenesis we incubated dissociated stage 22/23 distal mesenchymal limb bud cells with Fab' fragments of antibodies to NCAM. Cell aggregation was inhibited by incubating the cells with anti‐NCAM Fab'. These results suggest that NCAM may mediate the formation of precartilaginous condensations. This hypothesis was further tested using micromass cultures. NCAM expression in micromass cultures in vitro recapitulated that in vivo. NCAM was enriched in condensations of 2 day cultures, but was diminished and concentrically distributed around cartilage nodules in 4 day cultures. Anti‐NCAM Fab' fragments reduced the area occupied by precartilaginous condensations and the degree of chondrogenic differentiation. Control antibody against chicken embryo fibroblasts had no effect. The effect of overexpressing NCAM was analyzed by electroporating expression vectors directing the synthesis of chicken NCAM. Limb bud cells cultured after electroporation with an NCAM expression vector displayed larger cartilage nodules and greater chondrogenic differentiation than cells electroporated with vector alone. The expression of NCAM in electroporated cells also increased. Control experiments using plasmids encoding β‐galactosidase indicated that approximately 10% of the limb bud cells were transfected under these conditions. The results suggest that NCAM is involved in the chondrogenesis pathway by mediating the formation of precartilaginous condensations. © 1993 Wiley‐Liss, Inc.
Investigation of possible autocrine functions for rat GRO/CINC (cytokine‐induced neutrophil chemoattractant)
Authors: Crippes Barbara A. , Zagorski John , Carr Linda S. , Wittwer Art J. , Dolecki Gregory J. , De Larco Joseph E. 
Published: February 2005

AbstractRat cytokine‐induced neutrophil chemoattractant (CINC) is an eight kilodalton polypeptide originally purified from media conditioned by interleukin‐1β stimulated 52E, an epitheloid clone derived from normal rat kidney (NRK) cells. Using a fibroblastic clone of the NRK cells, 49F, we found expression of the CINC gene to be induced by either serum or cytokines in growth‐arrested cultures within 1 hour of stimulation. There was no observable CINC expression in exponentially growing cells in the absence of cytokine stimulation. CINC protein had no significant effect on 3H‐thymidine incorporation or growth rate of NRK49F. We have observed that CINC is constitutively produced by some transformed NRK cells, clone RC20, suggesting an association with the expression of a transformed phenotype. Unlike the parent 49F, RC20 cells are capable of growth in soft agar and serum‐free media and form highly metastatic tumors in nude mice. We have examined the possible autocrine functions of CINC and its possible links to the expression of the transformed phenotype by these cells. The use of a blocking CINC polyclonal antibody demonstrated that CINC did not function as an autocrine growth factor for RC20. Though CINC is a potent chemoattractant for neutrophils, it did not induce migration of either RC20 or 49F cells. CINC only moderately promoted adhesion of RC20 cells when used as a matrix protein. These data do not support the hypothesis that production of CINC by the RC20 cells provides an obvious advantage for the transformed cells constitutively producing it. © 1993 Wiley‐Liss, Inc.
Expression of transforming growth factor α antisense mRNA inhibits the estrogen‐induced production of TGFα and estrogen‐induced proliferation of estrogen‐responsive human breast cancer cells
Authors: Kenney N. J. , Saeki T. , Gottardis M. , Kim N. , Garcia‐Morales P. , Martin M. B. , Normanno N. , Ciardiello F. , Day A. , Cutler M. L. , Salomon D. S. 
Published: February 2005

AbstractTo ascertain if 17β‐estradiol (E2)‐induced proliferation could be attenuated by blocking the expression of endogenous transforming growth factor α (TGFα), estrogen receptor (ER)‐positive, estrogen‐responsive MCF‐7 or ZR‐75‐1 cells and ER‐negative, estrogen‐nonresponsive MDA‐MB‐468 or HS‐578T cells were infected with a recombinant amphotropic, replication‐defective retroviral expression vector containing a 435 base pair (bp) Apa1‐Eco R1 coding fragment of the human TGFα cDNA oriented in the 3′ to 5′ direction and under the transcriptional control of an internal heavy metal‐inducible mouse metallothionein (MT‐1) promoter and containing the neomycin (neo) resistance gene. E2‐stimulated expression of endogenous TGFα mRNA was inhibited by 4–5‐fold, and the production of TGFα protein was inhibited by 50–80% when M‐1 mass‐infected MCF‐7 or MZ‐1 mass‐infected ZR‐75‐1 cells were treated with 0.75‐1 μM CdCl2, whereas in comparably treated parental MCF–7 or ZR‐75‐1 cells there was no significant effect upon these parameters. E2‐stimulated anchorage‐dependent growth (ADG) and anchorage‐independent growth (AIG) of the M‐1 or MZ‐1 cells was inhibited by 60–90% following CdCl2 treatment. In contrast, neither the ADG nor AIG of the parental noninfected MCF‐7 or ZR‐75‐1 cells that were maintained in the absence or presence of E2 was affected by comparable concentrations of CdCl2. The ADG and AIG of TGFα antisense MD‐1 mass‐infected MDA‐MB‐468 cells that express high levels of endogenous TGFα mRNA were also inhibited by 1 μM CdCl2, whereas the ADG and AIG of MH‐1 mass‐infected HS‐578T cells, a TGFα‐negative cell line, were unaffected by CdCl2 treatment. These results suggest that TGFα may be one important autocrine intermediary in regulating estrogen‐induced cell proliferation. © 1993 Wiley‐Liss, Inc.
Amiloride‐dependent transport is the main mechanism implicated in sodium iinflux regulation in rat mast cells
Authors: Cabado Ana G. , Vieytes Mercedes R. , Botana Luis M. 
Published: February 2005

AbstractMast cell sodium regulation is a largely unknown field. In our effort to study the mechanisms by which mast cells regulate sodium levels, we have examined the effect of amiloride and ouabain on 22Na entry in rat mast cells in isotonic and hypertonic conditions. Ouabain (0.5 mM) enhances sodium uptake by 32% in isotonic conditions. Hypertonicity increases by 400% the uptake of sodium through an amiloride (1 mM) dependent mechanism. Ouabain has no appreciable effect on the entry of 22Na in hypertonic conditions. © 1993 Wiley‐Liss, Inc.