bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elevated cAMP gives short‐term inhibition and long‐term stimulation of hepatocyte DNA replication: Roles of the cAMP‐dependent protein kinase subunits
Authors: Vintermyr Olav Karsten , Bøe Roald , Bruland Torunn , Houge Gunnar , Døskeland Stein Ove 
Published: February 2005

AbstractThe study reports the role of the isozyme forms (cA‐PKI and cA‐PKII) and subunits (R and C) of cAMP‐dependent protein kinase in mediating the acute depression of hepatocyte DNA replication by elevated cAMP. Combinations of cAMP analogs preferentially activating cA‐PKI or II showed that either isozyme could inhibit DNA replication. The effects of glucagon and cAMP analogs were counteracted by the cAMP antagonist RpcAMPS, implicating the necessity for cA‐PK dissociation in cAMP action. The effect of elevated cAMP was mimicked by microinjected C subunit, but not by the RI subunit of cA‐PK. Hepatocytes under continuous cAMP challenge more than regained their replicative activity. This tardive stimulatory effect of cAMP was enhanced by insulin and blocked by dexamethasone, and was preceded by downregulation of cA‐PK. In conclusion, a burst of cAMP acutely inhibits hepatocyte G1/S transition in late G1 regardless of hormonal state. In the presence of high glucocorticoid/low insulin the inhibition persists. At high insulin/low glucocorticoid the inhibitory phase is followed by a prolonged stimulation of DNA replication. Downregulation of endogenous cA‐PK is a mechanism for escape from the inhibitory action of highly elevated cAMP. © 1993 Wiley‐Liss, Inc.
The differentiation inducer, dimethyl sulfoxide, transiently increases the intracellular calcium ion concentration in various cell types
Authors: Morley Paul , Whitfield James F. 
Published: February 2005

AbstractDimethyl sulfoxide (DMSO) initiates a coordinated differentiation program in various cell types but the mechanism(s) by which DMSO does this is not understood. In this study, the effect of DMSO on intracellular calcium ion concentration ([Ca2+]i) was determined in primary cultures of chicken ovarian granulosa cells from the two largest preovulatory follicles of laying hens, and in three cell lines: undifferentiated P19 embryonal carcinoma cells, 3T3‐L1 fibroblasts, and Friend murine erythroleukemia (MEL) cells. [Ca2+]i was measured in cells loaded with the Ca2+ ‐specific fluoroprobe Fura‐2. There was an immediate (i.e., within 5 sec), transient, two to sixfold increase in [Ca2+]i after exposing all cell types to 1% DMSO. DMSO was effective between 0.2 and 1%. The prompt DMSO‐induced [Ca2+]i spike in all of the cell types was not prevented by incubating the cells in Ca2+ ‐free medium containing 2 mM EGTA or by pretreating them with the Ca2+‐channel blockers methoxyverapamil (D600; 100 μM), nifedipine (20 μM), or cobalt (5 mM). However, when granulosa cells, 3T3‐L1 cells, or MEL cells were pretreated with lanthanum (La3+; 1 mM), which blocks both Ca2+ channels and membrane Ca2+ pumps, there was a sustained increase in [Ca2+]i in response to 1% DMSO. By contrast, pretreating P19 cells with La3+ (1 mM) did not prolong the DMSO‐triggered [Ca2+]i transient. In all cases, the DMSO‐induced [Ca2+]i surge was unaffected by pretreating the cells with the inhibitors of inositol phospholipid hydrolysis, neomycin (1.5 mM) or U‐73, 122 (2.5 μM). These results suggest that DMSO almost instantaneously triggers the release of Ca2+ from intracellular stores through a common mechanism in cells in primary cultures and in cells of a variety of established lines, but, this release is not mediated through phosphoinositide breakdown. This large, DMSO‐induced Ca2+ spike may play a role in the induction of cell differentiation by DMSO. © 1993 Wiley‐Liss, Inc.
Effect of floating a gel matrix on mucin release in cultured airway epithelial cells
Authors: Kim K. Chul , Zheng Qiao‐Xi , Brody Jerome S. 
Published: February 2005

AbstractConfluent cultures of primary hamster tracheal surface epithelial (HTSE) cells grown on a thick collagen gel are highly enriched with secretory cells and constitutively release mucins. In the present experiment, we examined the possible effect of mechanical strain of cultured HTSE cells on the release of mucin. The mechanical strain of cells was accomplished by several methods: 1) by floating the gel from the culture dish by rimming; 2) by treatment with EGTA which interrupts intercellular tight junctions; 3) by treatment with collagenase which disrupts the cell‐matrix adhesion; and 4) by mechanically flexing the collagen gel matrix. All these conditions caused increases of mucin release without damage on the plasma membrane. We conclude that a number of mechanical strains which might alter cell shape can stimulate mucin release from cultured HTSE cells. Such a mechanism might be operative in the physiological regulation of airway goblet cell mucin secretion where mechanical strains may be induced on epithelial cells by underlying smooth muscles. © 1993 Wiley‐Liss, Inc.
Heat shock protein is a unique marker of growth arrest during macrophage differentiation of HL‐60 cells
Authors: Spector Neil L. , Ryan Colleen , Samson William , Levine Herbert , Nadler Lee M. , Arrigo A.‐P. 
Published: February 2005

AbstractPrior to morphologic and functional maturation, terminally differentiating hematopoietic cells first exit the cell cycle and undergo growth arrest. Relatively little is known about which molecules regulate differentiation‐induced growth arrest. In the present report, we sought to determine whether the mammalian low molecular weight heat shock protein (hsp28) was a candidate growth‐regulatory molecule during human hematopoiesis. To this end, hsp28 protein expression was examined during phorbol ester (PMA)‐induced macrophage differentiation of the human HL‐60 promyelocytic leukemic cell line. Whereas hsp28 was constitutively expressed at relatively low levels in an unphosphorylated state, hsp28 was rapidly phosphorylated within 4 hr following PMA‐induced differentiation, preceding increased hsp28 protein levels at 24–48 h. In contrast to other differentiative agents, hsp28 steady state mRNA and protein were regulated concordantly in response to macrophage differentiation. More importantly, these changes were transient, and occurred concomitant with the down‐regulation of cellular proliferation and the onset of G1 phase cell cycle arrest. In total, these observations implicate hsp28 as an intermediary in the myelomonocytic differentiative pathway of promyelocytic leukemic cells, and will shed light on the events regulating this process. © 1993 Wiley‐Liss, Inc.
Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: Concurrent F‐actin depolymerization and new actin synthesis
Authors: Goldblum Simeon E. , Ding Xueda , Brann Terrance W. , Campbell‐Washington Judith 
Published: February 2005

AbstractBacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: (1) transendothelial 14C‐albumin flux, (2) F‐actin organization with fluorescence microscopy, (3) F‐actin quantitation by spectrofluorometry, and (4) monomeric G‐actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C‐albumin flux (P < 0.001) and intercellular gap formation at ≥ 2–6 h. During this same time period the endothelial F‐actin pool was not significantly changed compared to simultaneous media controls. Mean (±SE) G‐actin (μg/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F‐actin stabilization with phallicidin protected against the LPS‐induced increments in G‐actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS‐induced decrement in F‐actin (P = 0.0044), blunted the G‐actin increment (P = 0.010), and increased LPS‐induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F‐actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS‐induced F‐actin depolymerization. © 1993 Wiley‐Liss, Inc.
ABH antigens as recognition sites for the activation of red blood cell anion exchange by the lectin Ulex europaeus agglutinin I
Authors: Engelmann Bernd 
Published: February 2005

AbstractThe blood group antigen H (blood group O) and fucose‐specific lectin Ulex europaeus agglutinin I (UEA1) (10 μg/ml) was found to increase the rate constant of CL− efflux into 100mM Na+ oxalate media by about 40% in erythrocytes taken from antigen H donors. In 100 mMK + oxalate, 150 mM Na+ pyruvate and in 150 mM Na+ acetate media the lectin elevated the rate constant of CL− efflux by 20–50%. The acceleration of Cl− efflux by UEA1 was completely blocked by 10 μM 4,4′‐dllsothiocyanato‐stilbene‐2,2′‐disulfonic acid (DIDS) indicating that the effect of the lectin is mediated by the anion exchanger of human erythrocytes (band 3 protein). In antigen A1 erythrocytes no significant stimulation of anion exchange by UEA1 was seen. The activation of Cl− efflux was completely prevented by addition of 1 mM fucose to the medium. These results suggest that the effect of UEA1 is mediated through interaction with the fucose residues of H antigens. Increasing extracellular Ca++ from 0.5 to 5 mM in Na + pyruvate or Na+ acetate media slightly reduced the acceleration of anion exchange by the lectin. On the other hand, replacing part of extracellular chloride by bicarbonate did not considerably alter the (previously reported) stimulatory effect of UEA1 on red blood cell Ca++ uptake. This suggests that the acceleration of anion exchange and of Ca++ uptake by UEA1, respectively, are mediated by different mechanisms. It is concluded that UEA1 activates anion exchange of human erythrocytes most probably by a direct interaction with H antigens present on extracellular domains of the band 3 protein. © 1993 Wiley‐Liss, Inc.
Low oxygen tension increases mRNA levels of alpha 1 (I) procollagen in human dermal fibroblasts
Authors: Falanga Vincent , Martin Theresa A. , Takagi Hajime , Kirsner Robert S. , Helfman Todd , Pardes Jeffrey , Ochoa M. Sofia 
Published: February 2005

AbstractDermal fibroblasts exposed to low oxygen tension show upregulated synthesis of transforming growth factor‐beta 1 (TGF‐beta 1), an established stimulatory peptide in the formation of extracellular matrix proteins. In this report, procollagen synthesis was measured in cultures of confluent adult human dermal fibroblasts exposed to either standard (20%) or low (2%) oxygen tension. By Northern blot analysis the steady state levels of alpha 1 (I) procollagen mRNA were increased by 75 to 150% of control (standard oxygen) as early as 12 hours and more than 200% 96 hours after exposure of cells to low oxygen. Similar increases in procollagen mRNA levels were obtained in hypoxic fibroblast cultures in a collagen lattice. The stimulatory effect of hypoxia on procollagen mRNA levels in fibroblast monolayers was diminished by antibodies to TGF‐beta, and could not be augmented further by the addition of TGF‐beta 1, evidence that hypoxic fibroblasts may already be maximally stimulated by TGF‐beta 1. We conclude that low oxygen tension enhances Steady state mRNA levels of alpha 1 (I) procollagen, and that this effect is mediated at least in part by TGF‐beta 1. © 1993 Wiley‐Liss, Inc.
Growth inhibition of breast cancer cells induced by exogenous ATP
Authors: Spungin Ben , Friedberg Ilan 
Published: February 2005

AbstractAddition of ATP (>0.1 mM) to cultures of human breast cancer T47D cells resulted in an inhibition of cell proliferation. The inhibition was found to be specific for ATP, and dependent on its concentration. Growth inhibition continued for at least three days, although ATP and its hydrolysis products were metabolized within one day. Conditioned medium from ATP‐treated cultures (CM+) was found to inhibit the growth of cells that were not exposed to ATP. This is an indication that extracellular factors, besides ATP, are involved in the inhibition process. The inhibition was maintained after dialysis of the CM+, using an 8 kDa cut‐off membrane. Conditioned medium from untreated cultures (CM‐), however, only slightly affected cell growth. The data suggest that the CM+ ‐induced cell growth inhibition is mediated by an ATP‐activated growth inhibiting factor. Flow microfluorometry and thymidine incorporation experiments have shown that the growth arrest is mainly due to the elongation of the S‐phase of the cell cycle. © 1993 Wiley‐Liss, Inc.
Plasminogen‐dependent activation of latent transforming growth factor beta (TGFβ) by growing cultures of osteoblast‐like cells
Authors: Yee John A. , Yan Lin , Dominguez Juan C. , Allan Elizabeth H. , Martin T. John 
Published: February 2005

AbstractOsteoblasts secrete transforming growth factor beta (TGFβ) as a biologically inert, latent complex that must be dissociated before the growth factor can exert its effects. We have examined the production and proteolytic activation of latent TGFβ (LTGFβ) by clonal UMR 106‐01 rat osteosarcoma cells and neonatal mouse calvarial (MC) osteoblast‐like cells in vitro. Synthetic bPTH‐(1–34) increased the activity of tissue‐type (tPA) and urokinase‐type (uPA) plasminogen activators (PA) in cell lysates (CL) of UMR 106‐01 cells. The concentration of active TGFβ in serum‐free CM from cultures treated with bPTH‐(1–34) and plasminogen was significantly greater than in CM from untreated controls and cultures treated with either bPTH‐(1–34) or plasminogen alone. This effect occurred at concentrations of PTH‐(1–34) that increased PA activity and was prevented by aprotinin, an inhibitor of plasmin activity. Treatment with bPTH‐(1–34) had no effect on the concentration of TGFβ in acid‐activated samples of CM. Functional consequences of proteolytically activated TGFβ was examined in primary cultures of neonatal MC osteoblast‐like cells. Human platelet TGFβ1 caused a dose‐dependent increase in the migration of these cells in an in vitro wound healing assay. Cell migration was also stimulated in cultures treated with bPTH‐(1–34) and plasminogen together. This effect was blocked by an anti‐TGFβ1 antibody. The results of these studies demonstrate that (1) LTGFβ secreted by osteoblasts in vitro is activated under conditions where the plasmin activity in the cultures is increased, and (2) the TGFβ generated by plasmin‐mediated proteolysis is biologically active. We suggest that the local concentration of TGFβ in bone may be controlled by the osteoblast‐associated plasminogen activator/plasmin system. Furthermore, since several calciotropic factors influence osteoblast PA activity, this system may have an important role in mediating their anabolic and/or catabolic effects. © 1993 Wiley‐Liss, Inc.
Modulatory effect of cyclic AMP on calcium fluxes in FRTL‐5 cells
Authors: Törnquist Kid , Ahlström Mikael 
Published: February 2005

AbstractThe aim of the present study was to investigate the effect of cAMP on calcium fluxes in Fura 2 loaded thyroid FRTL‐5 cells. Preincubating the cells with the phosphodiesterase inhibitor Ro‐201724 decreased the ATP‐stimulated entry of calcium, while having no effect on the release of sequestered calcium. Pretreatment with forskolin decreased both the release of sequestered calcium and the entry of calcium in response to ATP. We then incubated the cells with phenylisopropyl adenosine (PIA), a P21‐receptor agonist earlier shown to decrease cAMP in FRTL‐5 cells. Although we did not observe a decrease in cellular cAMP after PIA, the ATP‐evoked calcium response was enhanced. Forskolin decreased calcium entry induced by thapsigargin a Ca2−‐ATPase inhibitor, but forskolin had no effect on the thapsigargin‐evoked release of sequestered calcium. Addition of calcium to cells stimulated with ATP in a calcium‐free buffered resulted in a rapid influx of calcium. This response in [Ca2+]i was decreased in cells pretreated with forskolin. In cells stimulated with thapsigargin, the increase in [Ca2+]i after addition of calcium was inhibited in part by forskolin and enhanced by PIA. The results suggest that cAMP may regulate calcium fluxes in FRTL‐5 cells Furthermore, PIA increased agonist‐induced calcium entry through a presently unknown mechanism. © 1993 Wiley‐Liss, Inc.
Migratory and proliferative effect of platelet‐derived growth factor in rabbit retinal endothelial cells: Evidence of an autocrine pathway of platelet‐derived growth factor
Authors: Koyama Noriyuki , Watanabe Satoe , Tezuka Mariko , Morisaki Nobuhiro , Saito Yasushi , Yoshida Sho 
Published: February 2005

AbstractAngiogenesis is a crucial event in the progression of diabetic retinopathy. Migration and proliferation of endothelial cells (EC) are important steps in angiogenesis and are caused by angiogenic factors such as basic fibroblast growth factor (bFGF). In this work, capillary EC were isolated from rabbit retinal tissues and rabbit retinal EC (RREC) were found to secrete a migration factor for RREC in conditioned medium (CM). The activity was inhibited by an anti‐platelet‐derived growth factor (PDGF) antibody, but not by an anti‐bFGF antibody. We also found that RREC showed a migratory response to PDGF. The response was induced by PDGF‐BB and PDGF‐AB dose dependently, but not by PDGF‐AA, indicating that it was mediated by PDGF‐β receptor‐dependent pathways, and that the PDGF‐like factor was PDGF‐BB or ‐AB. In addition, PDGF‐BB induced the proliferation of RREC as well as bFGF. These data indicate that RREC have an autocrine pathway of PDGF by the secretion of and the response to PDGF. PDGF may play significant parts in angiogenesis in the progression of diabetic retinopathy. © 1994 Wiley‐Liss, Inc.
Actions of platelet‐derived growth factor isoforms in mesangial cells
Authors: Abboud Hanna E. , Grandaliano Giuseppe , Pinzani Massimo , Knauss Thomas , Pierce Glenn F. , Jaffer Fatima 
Published: February 2005

AbstractPlatelet‐derived growth factor (PDGF) occurs as homodimers or heterodimers of related polypeptide chains PDGF‐BB, ‐AA, and ‐AB. There are two receptors that bind PDGF, termed alpha and beta. The beta receptor recognizes PDGF B chain and is dimerized in response to PDGF BB. The alpha receptor recognizes PDGF B as well as A chains and can be dimerized by the three dimeric forms of PDGF AA, AB, and BB. To characterize PDGF receptor signaling mechanisms and biologic activities in human mesangial cells (MC), we explored the effects of the three PDGF isoforms on DNA synthesis, phospholipase C activation, and PDGF protooncogene induction. PDGF‐BB homodimer and AB heterodimer induced a marked increase in DNA synthesis, activation of phsopholipase C, and autoinduction of PDGF A and B chain mRNAs, whereas PDGF‐AA homodimer was without effect. The lack of response to PDGF AA could be accounted for by down regulation of the PDGF‐alpha receptor since preincubation of MC with suramin restored PDGF AA‐induced DNA synthesis. Ligand binding studies demonstrate specific binding of labeled PDGF BB and AB and to a lower extent PDGF AA isoforms to mesangial cells. These results are consistent with predominant expression of PDGF beta receptor in MC, which is linked to phospholipase‐C activation. The potent biologic effects of PDGF‐AB heterodimer in cells that express very few alpha receptors and do not respond to PDGF AA are somewhat inconsistent with the currently accepted model of PDGF receptor interaction and suggest the presence of additional mechanisms for PDGF isoform binding and activation. © 1994 Wiley‐Liss, Inc.
31P NMR characterization of cellular metabolism during dexamethasone induced apoptosis in human leukemic cell lines
Authors: Adebodun Foluso , Post Jan F. M. 
Published: February 2005

Abstract31P NMR has been used to study the effects of dexamethasone on phosphorus metabolism in one dexamethasone (dex)‐sensitive (CEM‐C7) and three different dex‐resistant (CEM‐C1, CEM‐4R4, and CEM‐ICR27) human leukemic cell lines. The use of these cell lines, containing widely varying amounts of glucocorticoid receptors, made it possible to evaluate the receptor‐mediated contributions to the modes of action of dexamethasone in these cells. To evaluate the effects of dexamethasone without any significant contribution from experimental conditions, all the experiments were done with parallel controls. Results obtained showed: (1) significantly different levels of phosphorylethanolamine (PE) and phosphorylcholine (PC) among cell lines, suggesting significant differences in phospholipid metabolism; (2) the dexamethasone induced reduction of phosphomonoester (PE + PC), ATP, and metabolic rates probably through glucocorticoid receptor mediated mechanisms; (3) the dexamethasone induced stimulation of cellular metabolism in a process which seems to be independent of glucocorticoid receptors; and (4) the dexamethasone induced alkaline shift of intracellular pH in all the cell lines except ICR27. The reduction in PME levels seems to be an earlier step in dexamethasone‐induced apoptosis than the reduction in ATP. The degree of alkaline shift was found to correlate with the number of glucocorticoid receptors present. The possible involvement of phospholipid metabolites as second messengers in dexamethasone‐induced apoptosis is discussed. © 1994 Wiley‐Liss, Inc.
Phosphorylation of the RNA polymerase II largest subunit during heat shock and inhibition of transcription in hela cells
Authors: Dubois Marie‐FrançOise , Bellier Sylvain , Seo Sook‐Jae , Bensaude Olivier 
Published: February 2005

AbstractThe phosphorylation of the C‐terminal domain (CTD) of the largest subunit of eukaryotic RNA polymerase II has been investigated in HeLa cells exposed to heat shock. In control cells, the phosphorylated subunit, IIo, and the dephosphorylated subunit, IIa, were found in similar amounts. During heat shock, however, the phosphorylated subunit, IIo, accumulated, whereas the amount of IIa subunit decreased. Since phosphorylation of the CTD had been suggested to play a role in the initiation of transcription and since heat shock was known to perturb gene expression at the level of transcription, the phosphorylation state of RNA polymerase II was examined in cells that had been treated with various inhibitors of transcription. Under normal growth temperature, actinomycin D (over 0.1 μ/ml) and okadaic acid, a phosphatase inhibitor, were found to inhibit polymerase dephosphorylation. Whereas 5, 6‐dichlorobenzimidazole riboside (DRB), N‐(2‐[Methylamino]ethyl)‐5‐isoquinolinesulfonamide (H‐8), and actinomycin D (over 5 μ/ml) were found to inhibit polymerase phosphorylation. Actinomycin D concentrations, which inhibited the dephosphorylation process, were lower than those required to inhibit the phosphorylation process. In contrast, during heat shock or exposure to sodium arsenite, a chemical inducer of the heat‐shock response, the phosphorylated subunit, IIo, accumulated even in the presence of inhibitors of transcription such as DRB, H‐8, and actinomycin D. These experiments demonstrated the existence of a heat‐shock‐induced CTD‐phosphorylation process that might contribute to the regulation of transcription during stress. © 1994 Wiley‐Liss, Inc.