bluuebunny/crossref_metadata_2025_split huggingface dataset:
Endothelin‐I induces gene expression through stimulation of endothelin type a receptors in normal rat kidney cells
Authors: Yumet Gladys , Chin Michael H. , Carey Brian , Soprano Kenneth J. , Lipson Kenneth E. 
Published: February 2005

AbstractRNA blots of total cellular RNA isolated from quiescent and endothelin (ET‐1)‐stimulated normal rat kidney (NRK) cells demonstrated that ET‐1 induced the expression of c‐jun, jun B, and c‐fos mRNA in a time‐dependent manner with maximal expression of mRNA by 1 hr after the addition of ET‐1. Five hundred picomolal ET‐1 was sufficient to induce maximal mRNA expression. These data agreed with saturation experiments which demonstrated that maximal binding of [125I]ET‐1 was achieved at concentrations greater than 100 pM. The Kd and Bmax values for [125I]ET‐1 binding to NRK membranes were 20.5 pM and 22.2 fmol/mg protein, respectively. Competition experiments for the binding of [125I]ET‐1 to NRK membranes demonstrated that ET‐1 was a more potent inhibitor (Ki = 0.047 nM) than ET‐3 (Ki = 10.8 nM). No specific binding of [125I]ET‐3 (40 or 500 pM) to NRK membranes could be observed. The expression of c‐jun, jun B, and c‐fos mRNA was inhibited by the endothelin type A receptor (ET)‐selective antagonist, BQ‐123. Thus, these data demonstrate that ET‐1 mediates the expression of immediate response gene mRNA in NRK cells via the ETA receptor. ET‐1 stimulation of NRK cells also upregulated EGF receptors, providing a possible mechanism for ET‐1 complementation of epidermal growth factor (EGF) mitogenicity in NRK cells. © 1995 Wiley‐Liss, Inc.
Increased expression of a high molecular weight (130 KD) protein kinase C isoform in a differentiation‐defective ras‐transfected keratinocyte line
Authors: Rosales J. L. , Isseroff R. R. 
Published: February 2005

AbstractThe role of ras on protein kinase C (PKC) signaling was examined in two keratinocyte cell lines. Increasing the level of extracellular calcium from 0.15 mM to 1.0 mM induces some features of differentiation in the spontaneously immortalized HaCaT line, but fails to do so in a c‐H‐ras‐transfected subline (ras‐HaCaT). Raising extracellular calcium also induced a transient increase in membrane‐associated PKC activity 5 min after calcium addition, in HaCaT, but not in the ras‐HaCaT cells. Partial purification of PKC from the membrane/particulate fraction revealed the major isoform expressed in HaCaT to be an 80 KD species recognized by the anti‐PKCα antibody. In ras‐HaCaT, the major expressed isoform is a 130 KD species recognized by the PKCb̃ antibody. The kinase activity of the partially purified high molecular weight PKC is phospholipid dependent but calcium independent. Further evaluation of PKC in the HaCaT and ras‐HaCaT membrane/particulate cell fraction by immunoblotting using affinity‐purified antibodies against PKCα, b̃, δ, ε and ζ revealed a 130 KD band reacting with the PKCδ antibody. Increased expression of this high molecular weight protein was observed in ras‐HaCaT. Immunoprecipitation of PKC in ras‐HaCaT using the PKCδ antibody also revealed a 130 KD species. Analysis of the PKCδ immunoprecipitate demonstrated a phospholipid, but not calcium‐dependent kinase which autophosphorylated. These results suggest that the 130 KD protein may be a novel (calcium‐independent) PKC (nPKC) isoform and increased expression in the rastransfected HaCaT may be a consequence of oncogenic ras expression. This 130 KD species may also play a role in the ras‐associated inhibition of differentiation in HaCaT. © 1995 Wiley‐Liss, Inc.
Laminin responsiveness is associated with changes in fibroblast morphology, motility, and anchorage‐independent growth: Cell system for examining the interaction between laminin and EGF signaling pathways
Authors: Lin Meei‐Lih , Bertics Paul J. 
Published: February 2005

AbstractLaminin can influence the adhesion, differentiation, and motility of motility of several cell types, including epithelial and neural cells. In addition, laminin, which contains an epidermal growth factor (EGF)‐like motif, can stimulate DNA synthesis in fibroblasts possessing the EGF receptor, but laminin does not compete for EGF binding. To further investigate laminin action in fibroblasts, and the relationship between laminin and EGF receptor function, we have developed a system wherein cells containing laminin‐binding activity were cloned from a mouse fibroblast cell line (B82L‐wt) that cannot adhere to laminin but that have been transfected with the wild‐type human EGF receptor. Although only the isolated clones can efficiently attach to laminin‐coated plates, all the cells can adhere to plastic, fibronectin, and collagen I, and all exhibit comparable levels of cell surface‐associated laminin. Ligand‐binding assays showed that the cells with laminin attachement activity possess high‐affinity EGF binding (Kd ∼ 0.4 nM), and all express a similar level of the human EGF receptor. However, when compared to the B82L‐wt cells, the cells with laminin‐binding activity exhibit altered morphology, anchorage‐independent growth, and motility. Specifically, the morphology of the fibroblasts possessing laminin binding activity appears more elongated and they spread more‐extensively on plastic plates. Analysis of their growth in soft agar revealed that the clones have a 2‐5‐fold increase in colony formation in comparison to the B82L‐wt cells. The cells possessing laminin attachment ability also exhibit laminin‐induced motility, and this movement is directional (chemotaxis) rather than random (chemokinesis), indicating functional laminin receptors and signaling pathways. To examine the specific laminin receptors involved in these effects, the influence of anti‐integrin subunit antibodies on cell adhesion and migration was evaluated. These studies showed that an anti‐α6 integrin antibody can completely inhibit the clonal cells' attachment and migration to laminin, and anti‐α6 immunoblots revealed that only the clones express measurable levels of α6. These data indicate that α6‐containing integrins contribute to the lamininmediated attachment and motility of these clones and that this system may also influence the morphology and anchorage‐independent growth of these fibroblasts. In addition, these cells provide a unique system for examining the interaction between EGF and laminin receptor action. © 1995 Wiley‐Liss, Inc.
Adaptation of ehrlich ascites carcinoma cells to energy deprivation in vivo can be associated with heat shock protein accumulation
Authors: Kabakov A. E. , Molotkov A. O. , Budagova K. R. , Makarova Yu M. , Mosin A. F. , Gabai V. L. 
Published: February 2005

AbstractTumor adaptation to chronic energy starvation in vivo was studied on Ehrlich ascites carcinoma (EAC) cells. EAC cells were isolated from mice and incubated in a glucose‐free medium containing blocators of mitochondrial ATP generation (rotenone, 2,4‐dinitrophenol, or oligomycin). ATP level in the treated cells decreased to 3–4% of the initial during 30 min of the incubation. The aggregation of cytoskeletal proteins, blebbing, and necrotic death within 2–3 h were observed in ATP‐depleted EAC which were isolated and treated in the exponential phase of growth (5 days after inoculation), whereas stationary EAC (8 days after inoculation) were considerably more resistant to ATP depletion, and actin aggregation as well as bleb formation were suppressed in these cells despite the ATP loss. In contrast to the exponentially growing cells, thermotolerance and unexpected expression of inducible HSP68 and HSP27 as well as an elevated level of HSP90 were found in stationary EAC. Since the stationary cells had decreased content of ATP, ATP/ADP ratio, and energy charge, we suggest that this energy dysbalance may be conducive to HSP induction within the ascites tumor in vivo, and, at the same time, EAC cells with elevated content of HSPs acquire resistance to chronic energy starvation occurring in late stages of the tumor growth. © 1995 Wiley‐Liss Inc.
Lithium‐stimulated proliferation and alteration of phosphoinositide metabolites in MCF‐7 human breast cancer cells
Authors: Welshons Wade V. , Engler Kathleen S. , Taylor Julia A. , Grady Leigh H. , Curran Edward M. 
Published: February 2005

AbstractLithium, which is used to treat bipolar psychiatric disorders, can stimulate proliferation of a number of cells in tissue culture. Proliferation of MCF‐7 human breast cancer cells, which also respond to EGF and estrogens, was stimulated by LiCl (1–5 mM) within the concentration range that is encountered during human therapy with lithium. Stimulation of growth was specific for lithium; rubidium, potassium, and sodium showed no such effect. In the presence of antiestrogen, lithium stimulated the growth of hormone‐dependent breast cancer cells MCF‐7, ZR‐75‐1, and T47D but not hormone‐independent MDA‐MB‐231 cells or an estrogen‐independent clone of MCF‐7 cells. Lithium‐stimulated proliferation was limited by cytotoxicity which could be moderated by added potassium chloride (5–20 mM) in the medium. Each of the mitogens lithium, 17β‐estradiol, and EGF increased the rate of uptake of myo‐inositol into MCF‐7 cells. Whether normalized to inositol lipids, to protein, or to DNA, steady‐state levels of inositol phosphates were elevated by each of the mitogens including lithium, which inhibits the breakdown of inositol phosphates in the phosphoinositide signaling pathway. These data indicate that therapeutic concentrations of lithium can stimulate the proliferation of human breast cancer cells by a mechanism that may involve the phosphoinositide pathway. © 1995 Wiley‐Liss Inc.
Influences of silicates and carnitine‐silicate mixtures on the inhibition of aggregation of erythrocytes elicited by the presence of fibrinogen
Authors: Ramsohoye Pamela , Fritz Irving B. 
Published: February 2005

AbstractCarnitine and acylcarnitine derivatives have been reported to inhibit cell aggregation (Fritz and Burdzy, 1989, J. Cell. Physiol., 140:18–28). A follow‐up of these observations showed that whereas the previously described effects of long‐chain acylcarnitines were well replicated, those of carnitine on erythrocytes showed marked variability. The latter phenomenon was traced to the presence of silicates in carnitine solutions derived from the use of sodium hydroxide solutions stored in glass containers for the neutralization of carnitine. The present experiments have led to the discovery that oligomeric forms of silicates are powerful inhibitors of red blood cell aggregation which otherwise occurs in the presence of fibrinogen alone. The active form(s) of silicates in this assay, which appear to be generated by polymerization of silicates in metasilicate solutions on neutralization, are unstable and therefore transient under usual conditions. We estimate that the active oligomeric forms contain between 4 to 18 silicon atoms per molecule. When maintained at ‐ 18°C in the presence of carnitine, but not in its absence, the active forms of oligomeric silicates remained stable for months, judging from their ability to inhibit cell aggregation. We conclude that carnitine stabilized the oligomeric form(s) of silicate, or that the species stabilized is an oligomeric silicate‐carnitine complex. Comparable concentrations of choline, deoxycarnitine, or γ‐aminobutyrate were less effective in stabilizing the active silicate oligomers. The active forms of the silicate oligomers had K'i values of about 10 μM, calculated as the monomeric form, in inhibiting red blood cell aggregation. The data indicate that free carnitine does not directly inhibit erythrocyte inhibition, as previously interpreted, whereas long‐chain acylcarnitine derivatives are active in the absence of silicates. Possible mechanism of actions of silicate oligomers on membranes are discussed. © 1995 Wiley‐Liss Inc.
HSP70 Translocates into a cytoplasmic aggregate during lymphocyte activation
Authors: Di Yuan‐Pu , Repasky Elizabeth , Laszlo Andrei , Calderwood Stuart , Subjeck John 
Published: February 2005

AbstractThe percentage of T and B lymphocytes expressing a distinct cytoplasmic aggregate enriched in spectrin, ankyrin, and in several other proteins including protein kinase C greatly increases following various activation protocols. Members of the 70 kDa family of heat shock proteins (hsp70) temporarily bind to and stabilize unfolded segments of other proteins, a function apparently required for proper protein folding and assembly. Considering the multiprotein and dynamic nature of the lymphocyte aggregate, the possibility that hsp70 also might be associated with componets of this structure is considered here. Double immunofluorescence analysis indicates that hsp70 is a component of the lymphocyte aggregate and is coincident with spectrin in a subpopulation of freshly isolated, untreated lymphocytes from various murine tissues and in a T‐lymphocyte hybridoma. When cell lysates of lymph node T cells are immunoprecipitated using an antibody against hsp70 or spectrin and then analyzed by Western blot utilizing the alternate antibody, it was found that hsp70 and spectrin coprecipitated with one another. Moreover, this coprecipitation could be abolished by addition of ATP. This latter observation was extended to lymphoid cells using a transient permeabilization procedure, and it was shown that addition of exogenous ATP results in the dissipation of the aggregate structure itself. Finally, conditions that result in T‐cell activation and aggregate formation, i.e., treatment with the phorbol ester PMA or T‐cell receptor cross‐linking, also lead to the repositioning of hsp70 into the aggregate from a membrane/cytosolic locale in congruence with spectrin. These data suggest that hsp70 is an active component of the aggregate and that it may function in the interactions believed to occur in this unique activation‐associated organelle. © 1995 Wiley‐Liss, Inc.
Modulation of caffeine contractures in mammalian skeletal muscles by variation of extracellular potassium
Authors: Gallant Esther M. , Lentz Linnea R. , Taylor Stuart R. 
Published: February 2005

AbstractCaffeine contractures were induced after K+ ‐conditioning of skeletal muscles from pigs and mice. K+ ‐conditioning is defined as the partial depolarization caused by increasing external potassium (K) with [K+]×[Cl−] constant. Conditioning depolarizations that rendered muscles refractory to brief electrical stimulation still enhanced the contracture tension elicited by subsequent direct caffeine stimulation of sarcoplasmic reticulum (SR) calcium release. The effects of K+ ‐conditioning on caffeine‐induced contractures of intact cell bundles reached a maximum at 15–30 mM K and then progressively declined at higher [K+]0. Conditioning with 30 mM K+ for 5 min, which inactivates excitation‐contraction (EC) coupling in response to action potentials, both increased the magnitude of caffeine contractures 2–10‐fold and shifted the contracture threshold toward lower caffeine concentrations. Enhanced sensitivity to caffeine was inhibited by dantrolene (20 μM) and its watersoluble analogue azumolene (150 μM). These drugs decreased caffeine‐induced contractures following depolarization with 4–15 mM K+ to 25–50% of control tension. The inorganic anion perchlorate (CIO), which like caffeine potentiates twitches, increased caffeine‐induced contractures ∼︁ twofold after K+ ‐conditioning (>4 mM). The results suggest that CIO and dantrolene, in addition to caffeine, also influence SR calcium release either directly or by mechanism(s) subsequent to depolarization of the sarcolemma. Moreover, since CIO is known to shift the voltage‐dependence of intramembrane charge movement, CIO may exert effects on the transverse‐tubule voltage sensors as well as the SR. © 1995 Wiley‐Liss, Inc.
Transforming growth factor β modulates growth and differentiation of fetal hepatocytes in primary culture
Authors: Sanchez Aranzazu , Alvarez Alberto M. , Benito Manuel , Fabregat Isabel 
Published: February 2005

AbstractFetal hepatocytes in primary culture are cells capable to carry out both proliferation and differentiation processes simultaneously. Previous studies have shown that these cells respond to mitogens, such as hepatocyte growth factor (HGF) or epidermal growth factor (EGF), inducing the expression of early genes, such as fos and myc. The transforming growth factor‐β (TGF‐β) family is one of the most influential groups of growth and differentiation factors. In this report, we show that TGF‐β‐1 inhibits fetal hepatocyte proliferation, arresting these cells at G1 phase of the cell cycle. In addition, TGF‐β down‐regulates the mitogen‐induced myc early expression. However, TGF‐β has no effect on the expression of other protooncogenes, such as fos and H‐ras. In addition to its inhibitory role on fetal hepatocyte growth, TGF‐β increases the mRNA levels of fibronectin, an extracellular matrix protein, and maintains the expression of some liver specific genes, such as albumin and alfafetoprotein, above control values. The analysis of the expression of some hepatocyte transcriptional factors has shown that TGF‐β increases HNF1α and HNF1β mRNA levels. We conclude that TGF‐β may modulate liver growth and differentiation throughout fetal development. © 1995 Wiley‐Liss, Inc.
Characterization of adenosine‐uridine‐rich RNA binding factors
Authors: Nakamaki Tsuyoshi , Imamura Jun , Brewer Gary , Tsuruoka Nobuyoshi , Koeffler H. Phillip 
Published: February 2005

AbstractThe adenosine‐uridine (AU)‐rich sequences within the 3′ untranslated region (UTR) of many short‐lived mRNAs are important in their rapid degradation. We present evidence that human embryonic lung fibroblasts (W138) contain five major proteins of 70, 45, 40, 38, 32.5 kd, which specifically bind the AU‐rich region of human granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) 3′UTR containing 7 × AUUUA motifs. The 40 and 38 kd proteins also bound the 3 × and 5 × AUUUA cassettes and even more strongly bound to the AUUUUUUUA motif. All five of these proteins showed more abundant localization in the nucleus than the cytoplasm. The 32.5 kd protein was the major cytoplasmic AU‐binding protein. Incubation with actinomycin D resulted in a marked increase in binding activity of 45, 40, 38, and 32.5 kd proteins in the cytoplasm, accompanied by decreased binding activity of the 32.5 kd protein in the nucleus. Antibody against heterogeneous nuclear ribonucleoprotein C (hnRNP C) immunoprecipitated the 40 and 38 kd proteins, and antibody against the AU‐rich element RNA‐binding protein (AUF1) immunoprecipitated the 45, 40, and 38 kd proteins. The present results not only demonstrated that hnRNP C are AU‐binding proteins which are present in the cytoplasm as well as the nucleus, but another group of AU‐binding proteins (AUF1 [45, 40, 38 kd], and 32.5 kd), which are not hnRNP, have characteristics related to those of hnRNPs. Taken together with our previous results (Akashi et al., 1994, Blood, 83:3182–3187), AU‐binding factors including hnRNP C and AUF1, which bind more than 3 × AUUUA motifs, may be involved in rapid degradation of these transcripts. No significant quantitative changes of these proteins in their binding activity to AU‐rich sequences occurred in response to several stimuli that stabilize GM‐CSF mRNA, indicating that binding of these proteins to their cognate RNA is not responsible for the stabilization of these transcripts. © 1995 Wiley‐Liss Inc.
Proteoglycan synthesis by bovine myocardial endothelial cells is increased by long‐term exposure to high concentrations of glucose
Authors: Klein David J. , Cohen Robert M. , Rymaszewski Zbigniew 
Published: February 2005

AbstractThe role of the metabolic milieu in control of proteoglycan synthesis was investigated using bovine myocardial endothelial cells (BMEC) grown for six to eight passages in media containing either 5.6 or 25 mM glucose. Marcomolecular Na[35S]sulfate incorporation into proteoglycans was increased by exposure to 25 mM when compared with 5.6 mM glucose (7.05 ± 0.40 [SD] vs. 3.5 ± 0.50 × 10−4 dpm/μg DNA). In contrast, [3H]leucine incorporation was unaffected by glucose (11.27 ± 0.85 vs. 9.88 ± 1.23 × 10−5 dpm/μg DNA). The distribution of isotopes between media and cell layer fractions was not different in the two conditions. Addition of 19.4 mM mannitol to 5.6 mM glucose containing media had no effect on isotope incorporation. The HPLC‐DEAE and Sepharose CL‐6B elution profiles of media 35S‐proteoglycans synthesized under each condition were similar. A Sepharose CL‐4B Kav 0.08 heparan sulfate proteoglycan accounted for 20% of the total 35S‐incorporation. Perlecan domain III mRNA was identified by Northern analysis and domain I by the polymerase chain reaction (PCR) in total BMEC RNA. A mixture of chondroitin/dermatan sulfate proteoglycans accounted for 67% of 35S‐incorporation. They eluted from Sepharose CL‐6B at Kav 0 and 0.22. Two [3H]leucine labeled core proteins of 135 and 50 kD were identified in each of these 35S‐proteoglycan peaks. Biglycan but not decorin mRNAs were detected by Northern analysis and by PCR. These data demonstrate that prolonged exposure to high glucose concentrations in vitro stimulate the accumulation of [35S]sulfate into microvascular endothelial cell proteoglycans without significant alterations in their overall hydrodynamic or charge related properties. Modulation of proteoglycan synthesis by glucose may participate in the pathogenesis of the small vessel complications of diabetes. © 1995 Wiley‐Liss Inc.
Differential growth state‐dependent regulation of plasminogen activator inhibitor type‐1 expression in senescent IMR‐90 human diploid fibroblasts
Authors: Mu Xiao‐Chun , Higgins Paul J. 
Published: February 2005

AbstractThe type‐1 inhibitor of plasminogen activator (PAI‐1) regulates pericellular proteolytic activity functioning, thereby to control matrix integrity, cell growth, and morphology. Subconfluent late‐passage IMR‐90 human fibroblasts and normal rat kidney (NRK) cells, both at the stage of replicative senescence accumulated 15‐to 30‐fold more undersurface PAI‐1 protein compared to early‐passage, actively‐proliferating, cultures. Senescence‐associated elevations in PAI‐1 expression by IMR‐90 cells reflected corresponding 11‐fold increases in the 3.0‐ and 2.2‐kb PAI‐1 mRNA species. The 2.2‐kb transcript exhibited a greater age‐dependent increase (7.2‐fold) compared to the 3.0‐kb mRNA (3.7‐fold). Since PAI‐1 expression is coupled to growth activation in serum‐deprived cultures (Ryan and Higgins, 1993, J. Cell. Physiol., 155:376–384), it was important to determine if PAI‐1 gene regulation was altered as a function of cellular aging. In contrast to early‐passage cultures, senescent IMR‐90 fibroblasts did not down‐regulate either PAI‐1 protein expression or steady‐state levels of PAI‐1 mRNA transcripts upon serum‐deprivation. Late‐passage human fibroblasts at their proliferative end‐stage, thus, appear to regulate PAI‐1 mRNA levels through different mechanisms than do young, actively‐proliferating, cells. PAI‐1 overexpression during in vitro cellular aging, therefore, may contribute to the acquisition of specific senescence‐associated phenotypic traits (e.g., enlarged cell morphology; increased adhesivity) by altering the pericellular proteolytic balance influencing, in turn, the formation or stability of cell‐to‐substrate attachment complexes. © 1995 Wiley‐Liss Inc.