bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increase in epidermal growth factor receptor and its mRNA levels by parathyroid hormone (1‐34) and parathyroid hormone‐related protein (1‐34) during differentiation of human trophoblast cells in culture
Authors: Alsat Eliane , Haziza Jocelyne , Scippo Marie‐Louise , Frankenne Francis , Evain‐Brion Danièle 
Published: May 2005

AbstractHuman cytotrophoblasts in culture aggregate and fuse to form syncytiotrophoblasts. This process is associated with an increase in epidermal growth factor receptor (EGFR) expression [Alsat et al.: J Cell Physiol 154:122–128, 1993]. Recent studies have demonstrated the presence of parathyroid hormone‐related protein (PTHrP) in the human uterus and placenta. This led us to study the effect of PTH (1–34) and PTHrP (1–34) on the expression of EGFR during this differentiation process. Both peptides induced a concentration‐dependent increase in EGF binding, with a maximal effect at the physiological concentration of 1 nM. EGFR protein level assessed by cross‐linking and immunoblotting and EGFR biological activity assessed by measuring its EGF‐induced autophosphorylation were increased 2‐ and 2.5‐fold, respectively, when cells were treated for 24 h with 0.1 μM PTHrP or PTH compared to control cells. This effect was time‐dependent with a maximum at 3 h of treatment. This treatment also increased trophoblast cell EGFR mRNA levels, suggesting transcriptional regulation of the EGFR. To ascertain whether activation of protein kinase C (PKC) or protein kinase A (PKA) is involved in this PTH effect, we determined EGFR protein level and EGFR autophosphorylation after exposure of cells to PKA inhibitor and PKC inhibitor, alone or together with the peptide. The presence of a PKC inhibitor blocked a further increase in EGFR number by PTH, while PKA inhibitor had no effect. These results show that PTH and PTHrP increase the synthesis of EGF receptors which are strongly expressed in syncytiotrophoblasts and suggested that these peptides might be involved in human placental development.
Bone morphogenetic protein inhibits differentiation and affects expression of helix‐loop‐helix regulatory molecules in myoblastic cells
Authors: Murray Samuel S. , Murray Elsa J. B. , Glackin Carlotta A. , Urist Marshall R. 
Published: May 2005

AbstractBone morphogenetic protein (BMP) reproducibly induces chondrogenesis and osteogenesis when implanted into skeletal muscle. The exact identity of the cell that responds to BMP is not known. Furthermore, controversy exists regarding the possibility that myoblastic cells may transdifferentiate to chondrocytes and osteoblasts under the influence of BMP. We have therefore, undertaken studies on the effects of BMP on differentiation in L6 and C2C12 cells, two rodent myoblastic cell lines. To gain insights into the mechanisms of action of BMP, we have studied the effects of BMP on the levels of expression of the four known myogenic determination genes: myogenin, Myo D, herculin, and myf‐5. BMP inhibited myogenesis in myoblastic cells. Convincing evidence of transdifferentiation of myoblasts to chondrocytes or osteoblasts was not seen. BMP inhibited the expression of all four myogenic determination genes.
Estrogen receptor‐negative breast cancer cells transfected with the estrogen receptor exhibit increased RARα gene expression and sensitivity to growth inhibition by retinoic acid
Authors: Sheikh M. Saeed , Shao Zhi‐Ming , Chen Jian‐Chyi , Hussain Arif , Jetten Anton M. , Fontana Joseph A. 
Published: May 2005

AbstractWe and others have shown previously that retinoic acid (RA) selectively inhibits the growth of estrogen receptor (ER)–positive human breast carcinoma (HBC) cells and ER‐negative cells are refractory to RA inhibition of growth. The ER‐negative cells inherently express lower levels of RARα and retinoic acid response element (RARE)–mediated RA‐induced CAT activity. In this study we report that when ER‐negative MDA‐MB‐231 cells were transfected with the ER gene they not only expressed higher levels of RARα and RARE‐mediated RA‐induced CAT gene expression, but their growth was now inhibited by RA. Estrogen enhanced RARα gene expression not only in established ER‐positive cell lines but also in ER‐transfected MDA‐MB‐231 cells. The estrogen effect appears to be direct and at the gene transcription level since it did not alter the stability of RARα mRNA and cycloheximide failed to block estrogen‐mediated enhancement of RARα gene expression. Our data strongly suggest that ER‐mediated enhancement of RARα levels plays an important role in RA inhibition of HBC growth. In addition, we also report here that HBC cells appear to express a unique isoform(s) of RARα which was detected only when the full‐length RARα cDNA was used as a probe; the RARα1 and RARα2 specific probes failed to hybridize with the HBC specific RARα message.
Tartrate resistant acid phosphatase activity in rat cultured osteoclasts is inhibited by a carboxyl terminal peptide (osteostatin) from parathyroid hormone‐related protein
Authors: Zheng M. H. , McCaughan H. B. , Papadimitriou J. M. , Nicholson G. C. , Wood D. J. 
Published: May 2005

AbstractA carboxyl‐terminal peptide sequence (“osteostatin”) from parathyroid hormone related protein has been shown to have an inhibitory effect on osteoclastic bone resorption—an action opposite to its amino‐terminal sequence. In this study, we proposed that inhibition of osteoclastic bone resorption by osteostatin was associated with reduction of tartrate resistant acid phosphatase (TRAcP) activity in osteoclasts. Our results have indicated that osteostatin reduced TRAcP activity in a dose dependent manner. This effect of osteostatin was both sensitive (half maximal effect approximately 5 × 10−13 M) and potent (maximum inhibition approximately 50% of control). In the first 90 min of treatment, however, reduction of TRAcP activity was erratic but became persistent and progressive when the time course was extended. Moreover, throughout the experimental period the levels of TRAcP activity in the culture medium had fallen significantly. It appears that osteostatin has a biphasic effect on TRAcP activity, inhibiting its secretion and either suppressing its synthesis or increasing its degradation. In addition, osteostatin induced rapid cellular retraction of both human and rat cultured osteoclasts, which was morphologically distinct from that produced by calcitonin.
Specific region of the c‐myc promoter is responsive to electric and magnetic fields
Authors: Lin Hana , Goodman Reba , Shirley‐Henderson Ann 
Published: May 2005

AbstractThe level of c‐myc transcripts is increased in cells exposed to extremely low frequency (elf) electromagnetic (EM) fields at 60 Hz. The aim of the present experiments was to determine if regulatory regions upstream of the c‐myc gene modulate the response to EM fields. DNA upstream of P1 of both mouse and human c‐myc genes was transfected into cells as CAT constructs. The presence of DNA 5′ to the human or mouse myc genes results in increased expression of CAT following 20 min exposures of cells to 60 Hz elf EM fields. Specific portions of the human upstream DNA were deleted and introduced into cells. The region responsive to EM fields is located between −353 and −1,257 relative to the P1 promoter.
Nuclear matrix and the regulation of gene expression: Tissue specificity
Authors: Getzenberg Robert H. 
Published: May 2005

AbstractTissue specific regulation of gene expression by a single transcription factor or group of transcription factors cannot be explained simply by DNA sequence alone. For example, in the same animal a particular transcription factor is capable of interacting with DNA in the nucleus of many different cell types, resulting in unique gene expressions despite the presence of a similar genome in all cells. Historically, these differences in response to a single type of factor within target tissues in the same animal have been suggested to occur through different alterations in chromatin structure. Recent, data has demonstrated that combination of hormones and transcription factors working together may cooperatively play a role in the regulation of gene expression [Pearce and Yamamoto (1993): Science 259:1161–1165]. However, the molecular mechanisms of this tissue specific regulation of gene expression still remains largely unexplained. Current evidence suggests that in different cell types the interplay between the specific three‐dimensional organization of the genome and the structural components of the nucleus, the nuclear matrix, may accomplish the regulation of specific gene expression. © 1994 Wiley‐Liss, Inc.
Nucleosome positioning and gene regulation
Authors: Lu Quinn , Wallrath Lori L. , Elgin Sarah C. R. 
Published: May 2005

AbstractRecent genetic and biochemical studies have revealed critical information concerning the role of nucleosomes in eukaryotic gene regulation. Nucleosomes package DNA into a dynamic chromatin structure, and by assuming defined positions in chromatin, influence gene regulation. Nucleosomes can serve as repressors, presumably by blocking access to regulatory elements; consequently, the positions of nucleosomes relative to the location of cis‐acting elements are critical. Some genes have a chromatin structure that is “preset,” ready for activation, while others require “remodeling” for activation. Nucleosome positioning may be determined by multiple factors, including histone–DNA interactions, boundaries defined by DNA structure or protein binding, and higher‐order chromatin structure. © 1994 Wiley‐Liss, Inc.
Multiple functions of dynamic histone acetylation
Authors: Davie James R. , Hendzel Michael J. 
Published: May 2005

AbstractBesides its role in organizing nuclear DNA, the nuclear matrix is involved in specific nuclear functions, including replication, transcription, and RNA splicing. It is becoming increasingly evident that nuclear processes are localized to distinct regions in the nucleus. For example, transcriptionally active genes and RNA transcripts are found in discrete transcription foci. Current evidence suggests that nuclear matrix–bound transcriptionally active DNA sequences are in nucleosomes with dynamically acetylated histones. Histone acetylation, which precedes transcription, alters nucleosome and chromatin structure, decondensing the chromatin fibre and making the nucleosomal DNA accessible to transcription factors. Histone acetyltransferase and histone deacetylase, which catalyze this rapid acetylation and deacetylation, are associated with the internal nuclear matrix. We hypothesize that these enzymes play a role in maintaining the association of the active chromatin domains with the internal nuclear matrix at sites of ongoing transcription. © 1994 Wiley‐Liss, Inc.
Microenvironment revisited: Time for reappraisal of some prevailing concepts of cancer metastasis
Authors: Fodstad Øystein , Kjønniksen Inge 
Published: May 2005

AbstractThe development and biological characteristics of tumor metastasis are influenced by multiple cell and host‐associated factors. To study these factors experimentally, the necessity of choosing adequate in vivo model systems for human tu mor metastasisis emphasized. Recent research has provided results that highlight the role of the microenvironment in determining important characteristics of the metastatic cells, including their degree of differentitation and sensitivity to drugs. Furthermore, evidence is presented as background for discussing the general validity of the notion of clonal selection of metastatic, and whether the metastatic phenotype is acquired through the last of a series of mutational events occurring during tumor progression.
Association of Hsp47, Grp78, and Grp94 with procollagen supports the successive or coupled action of molecular chaperones
Authors: Ferreira Luciano R. , Norris Kathleen , Smith Timothy , Hebert Carla , Sauk John J. 
Published: May 2005

AbstractHps47, Grp78, have been implicated with procellagen maturation events. In particular Hps47 has been shown to blind to nascent procellagen α1(I) chains in the course of synthesis and/or translocation into the endoplasmic reticulum (ER). Although, Hsp47 binding to gelatin and collgen has previsously been suggested to mechanism. The early association of Hps47 with procollagen and its relatively late relese suggested that other chaperones, Grp78 and Grp94, interact successively or concurrently with Hps47. Herein, we examined how these events occurs in cells metabolically stressed by depletion of ATP. In cells depleted of ATP, the releses of Hps47, Grp78, and Grp94 from maturing procollange is delayed. Thus, in cell experiencing metabolic stress, newly synthesized procollagen unable to property fold became stable bound to a complex of molecular chaperones. In that Hps47, Grp78, and Grp98 could be recovered with nascent procollagen and as oligomer in ATP depleted cells suggests that these chaperones function in a series of coupled or successive reactions.
Heparan sulfate primed on β‐D‐xylosides restores binding of basic fibroblast growth factor
Authors: Miao Hua‐Quan , Fritz Timothy A. , Esko Jeffrey D. , Zimmermann Joseph , Yayon Avner , Vlodavsky Israel 
Published: May 2005

AbstractHeparan sulfate proteoglycans (HSPG) are obligatory for receptor binding and mitogenic activity of basic fibroblast growth factor (bFGF). Mutant Chinese hamster ovary cells (pgsA‐745) deficient in xylosyltransferase are unable to initiate glycosaminoglycan synthesis and hence can not bind bFGF to low‐ and high‐affinity cell surface receptors. Exposure of pgsA‐745 cells to β‐D‐xylopyranosides containing hydrophobic aglycones resulted in restoration of bFGF binding in a manner similar to that induced by soluble heparin or by heparan sulfate (HS) normally associated with cell sulfate. Restoration of bFGF binding correlated with the ability of the β‐D‐xylosides to prime the synthesis of heparan sulfate. Thus, both heparan sulfate synthesis and bFGF receptor binding were induced by low concentrations (10–30 μM) of estradiol‐β‐D‐xyloside and naphthyl‐β‐D‐xyloside, but not by cis/trans‐decahydro‐2‐naphthyl‐β‐D‐xyloside, which at low concentration primes mainly chondroitin sulfate. The obligatory involvement of xyloside‐primed heparan sulfate in restoration of bFGF‐receptor binding was also demonstrated by its sensitivity to heparinase treatment and by the lack of restoration activity in CHO cell mutants that lack enzymatic activities required to form the repeating disaccharide unit characteristic of heparan sulfate. Xyloside‐primed heparan sulfate binds to the cell surface. Restoration of bFGF receptor binding was induced by both soluble and cell bound xyloside‐primed heparan sulfate and was abolished in cells that were exposed to 0.5–1.0 M NaCl prior to the bFGF binding reaction. These results indicate that heparan sulfate chains produced on xyloside primers behave like heparan sulfate chains attached to cellular core proteins in terms of affinity for bFGF and ability to function as low‐affinity sites in a dual receptor mechanism characteristic of bFGF and other heparin‐binding growth promoting factors.
Studies on the turnover of exogenous mannose‐terminal glucocerebrosidase in rat liver lysosomes
Authors: Murray Gary J. , Oliver Katharine L. , Jin Fu‐Sheng , Brady Roscoe O. 
Published: May 2005

AbstractMannose‐terminal glucocerebrosidase prepared by exoglycosidase digestion of human placental glucocerebrosidase is reported effective in the treatment of patients with type 1 Gaucher's disease [Barton et al. (1991); N Engl J Med 324:1464–1470]. However, the amount of enzyme that is necessary for therapeutic effect is much higher than would be predicted from in vitro activity measurements. We have investigated the fate of infused enzyme following intravenous administration in Sprague‐Dawley rats. In this model system, the enzyme is rapidly cleared from the plasma compartment by receptor‐mediated endocytosis via the mannose‐specific receptor present on reticuloendothelial cells. Enzyme activity measured in rat liver biopsy specimens at various times post‐infusion revealed a rapid initial loss of approximately one‐half of the maximum delivered enzyme in the first hour followed by a slower decay with a half‐life of approximately 6–8 h. The loss in enzyme activity is paralleled by a loss in enzyme protein when analyzed by Western blots. There is no evidence for return of enzyme activity or inactive enzyme protein to the plasma. Incomplete integration into the lysosomal membrane was demonstrated by the use of differential extraction of purified rat liver lysosomes to distinguish between lumenal and membrane bound enzyme. Immunoelectron microscopy of rat liver following infusion of mannose‐terminal glucocerebrosidase confirmed localization of the delivered enzyme primarily within the lumen of the lysosomes of Kupffer cells and to a lesser extent associated with the lysosomal membrane. Enzyme activity was stable in isolated rat liver lysosomes preloaded with mannose‐terminal glucocerebrosidase and incubated in the absence or presence of ATP. Acidification of the lysosomes to pH 3 results in a rapid loss of enzyme activity and protein; however, the relationship between the in vitro loss and the loss in enzyme activity in intact liver is not clear. We conclude from these studies that rapid intracellular degradation of administered glucocerebrosidase is the prime factor responsible for the high dose required for effective treatment of Gaucher's disease.
Properties of blood‐contacting surfaces of clinically implanted cardiac assist devices: Gene expression, matrix composition, and ultrastructural characterization of cellular linings
Authors: Menconi Michael J. , Pockwinse Shirwin , Owen Thomas A. , Dasse Kurt A. , Stein Gary S. , Lian Jane B. 
Published: May 2005

AbstractThe development of implantable cardiac assist devices for prolonged circulatory support has been impeded by the problem of excessive thrombogenesis on the blood–prosthetic interface, with subsequent embolization. To overcome this obstacle, a ventricular assist device has been developed with textured blood‐contacting surfaces to encourage the formation of a tightly adherent, hemocompatible, biological lining. In this study, we applied molecular biological techniques, in conjunction with conventional ultrastructural and biochemical techniques, to characterize the biological linings associated with the blood‐contacting surfaces of 11 of these devices, which had been clinically implanted for durations ranging from 21 to 324 days. No clinical thromboembolic events or pump‐related thromboembolism occurred. Biological linings developed on the textured surfaces composed of patches of cellular tissue intermingled with areas of compact fibrinous material. In addition, islands of collagenous tissue containing fibroblast‐like cells appeared after 30 days of implantation. Many of these cells contained microfilaments with dense bodies indicative of myofibroblasts. RNA hybridization analyses demonstrated that the colonizing cells actively expressed genes encoding proteins for cell proliferation (histones), adhesion (fibronectin), cytoskeleton (actin, vimentin) and extracellular matrix (types I and III collagen). Linings, which never exceeded 150 μm in thickness, remained free of pathological calcification. Textured blood‐contacting surfaces induced the formation of a thin, tightly adherent, viable lining which exhibited excellent long‐term hemocompatibility.
Insulin receptor overexpression in 184B5 human mammary epithelial cells induces a ligand‐dependent transformed phenotype
Authors: Frittitta Lucia , Vigneri Riccardo , Stampfer Martha R. , Goldfine Ira D. 
Published: May 2005

AbstractTo determine the role of the insulin receptor overexpression in breast epithelial cell transformation, the 184B5 human breast epithelial cell line was transfected with human insulin receptor cDNA. In two cell lines transfected with and overexpressing human insulin receptors (IR) (223.8 and 184.5 ng IR/106 cells), but not in untransfected cells, insulin binding and tyrosine kinase activity were elevated, and insulin induced a dose‐dependent increase in colony formation in soft agar.
Tumor necrosis factor‐α induces changes in the phosphorylation, cellular localization, and oligomerization of human hsp27, a stress protein that confers cellular resistance to this cytokine
Authors: Mehlen Patrick , Mehlen Anne , Guillet Dominique , Preville Xavier , Arrigo André‐Patrick 
Published: May 2005

AbstractThe stress protein hsp27 is constitutively expressed in several human cells and shows a rapid phosphorylation following treatment with tumor necrosis factor‐α (TNF‐α). hsp27 usually displays native molecular mass ranging from 100 to 700 kDa. Here, we have analyzed the TNF‐α‐mediated changes in the phosphorylation, cellular localization, and structural organization of hsp27 in HeLa cells. We report that the TNF‐α‐mediated hsp27 phosphorylation is a long‐lasting phenomenon that correlates with the cytostatic effect of this cytokine. Following TNF‐α treatment, the rapid phosphorylation of hsp27 occurred concomitantly with complex changes in the intracellular distribution and structural organization of this protein. This resulted in the quantitative redistribution of hsp27 toward the soluble phase of the cytoplasm. In addition, during the first 2 h of TNF‐α treatment, a transient increase in the native molecular mass of most hsp27 molecules (≤ 700 kDa) occurred. Then, by 4 h of TNF‐α treatment, the native size of this stress protein drastically regressed (< 200 kDa). During this phenomenon, the phosphorylated isoforms of hsp27 remained concentrated in the small or medium‐sized oligomers (< 300 kDa) of this protein. We also analyzed the properties of human hsp27 in transfected murine L929 cell lines that constitutively express this protein. In these cells, TNF‐α induced modifications in the phosphorylation, intracellular distribution, and oligomerization of human hsp27 similar to those observed in HeLa cells. Moreover, the expression of hsp27 in L929 cells was found to correlate with a reduced cytotoxicity of this cytokine. Hence, the complex changes in the phosphorylation, intracellular locale and structural organization of human hsp27 may be related to the protective activity of this protein against the deleterious effects induced by TNF‐α.
T cell receptor‐mediated Ca2+ signaling: Release and influx are independent events linked to different Ca2+ entry pathways in the plasma membrane
Authors: Chakrabarti Rabindranath , Chang Joseph Y. , Erickson Kent L. 
Published: May 2005

AbstractIn this study, we showed that cross‐linking CD3 molecules on the T cell surface resulted in Ca2+ release from the intracellular stores followed by a sustained Ca2+ influx. Inhibition of release with TMB‐8 did not block the influx. However, inhibition of phospholipase C activity suppressed both Ca2+ release and influx. Once activated, the influx pathway remained open in the absence of further hydrolysis of PIP2. Thapsigargin, a microsomal Ca2+ ‐ATPase inhibitor, stimulated Ca2+ entry into the cells by a mechanism other than emptying Ca2+ stores. In addition, Ca2+ entry into the Ca2+ ‐depleted cells was stimulated by low basal level of cytosolic Ca2+, not by the emptying of intracellular Ca2+ stores. Both the Ca2+ release and influx were dependent on high and low concentrations of extracellular Ca2+. At low concentrations, Mn2+ entered the cell through the Ca2+ influx pathway and quenched the sustained phase of fluorescence; whereas, at higher Mn2+ concentration both the transient and the sustained phases of fluorescence were quenched. Moreover, Ca2+ release was inhibited by low concentrations of Ni2+, La3+, and EGTA, while Ca2+ influx was inhibited by high concentrations. Thus, in T cells Ca2+ influx occurs independently of IP3‐dependent Ca2+ release. However, some other PIP2 hydrolysis‐dependent event was involved in prolonged activation of Ca2+ influx. Extracellular Ca2+ influenced Ca2+ release and influx through the action of two plasma membrane Ca2+ entry pathways with different pharmacological and biochemical properties.