bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of vimentin modification and vimentin‐HSP72 association by withangulatin A in 9L rat brain tumor cells
Authors: Lee Wen‐Chuen , Lee Yu‐Chien , Perng Ming‐Der , Chen Chiu‐Ming , Lai Yiu‐Kay 
Published: May 2005

AbstractWithangulatin A induced cell rounding up and the morphological alteration resulted from the reorganization of all of the major cytoskeletal components, i.e., vimentin, tubulin, and actin, as revealed by immunofluorescence techniques. When the withangulatin A‐treated cells changed to a round‐up morphology, vimentin intermediate filaments were found to be collapsed and clustered around the nucleus. The alteration was accompanied by characteristic changes of vimentin molecules, including augmentation of phosphorylation, retardation of electrophoretic mobility, and decrease in detergent extractability. The levels of vimentin phosphorylation were augmented by 2.5‐ and 1.8‐fold in cells incubated with 50 μM withangulatin A for 1 and 3 h, respectively. The electrophoretic mobility of vimentin was partially retarded in cells treated with withangulatin A for 1 h at 10 μM and a completely upshift mobility was observed after 5 h treatment at 50 μM. In addition, vimentin molecules became less extractable by nonident P‐40 after the cells were treated with withangulatin A and this effect was dose dependent. The decrease in solubility of vimentin was accompanied by the redistribution of HSP72 into the detergent nonextractable fraction and these two events were well correlated. Our results suggest that withangulatin A induced the modification of vimentin, which resulted in the alteration of cell morphology and redistribution of intracellular HSP72, an event that may play an important role in the induction of heat‐shock response.
Novel phorbol ester response region in the collagenase promoter binds Fos and Jun
Authors: Chamberlain Stephen H. , Hemmer Ruth M. , Brinckerhoff Constance E. 
Published: May 2005

AbstractIn rabbit fibroblasts the AP‐1 sequence (5′‐ATGAGTCAC‐3′) is necessary but not sufficient for induction of collagenase transcription by phorbol esters (PMA) (Auble and Brinckerhoff: Biochemistry 30(18):4629–4635, 1991). In this study we identified additional sequences involved in PMA‐induced transcription. Using fibroblasts transiently transfected with chimeric constructs containing fragments of the rabbit collagenase 5′‐flanking DNA linked to the chloramphenicol acetyl transferase (CAT) gene, we found that deletion of nucleotides −182 to −141 in a 380 bp promoter construct resulted in about a 7‐fold loss of induction by PMA. Mobility shift assays revealed that nuclear proteins from fibroblasts specifically bound to 20‐bp at −182 to −161. Binding was competed completely by self and only partially by the AP‐1 sequence, implying that proteins binding to the AP‐1 sequence could also bind to this region. In vitro transcribed and translated c‐Fos and c‐Jun bound to both the AP‐1 site and to the sequences from −182 to −141. DNAase I footprinting of the collagenase promoter with purified c‐Jun or c‐Fos/c‐Jun protected the AP‐1 sequence at −77 to −69 in addition to a region from −189 to −178 which overlaps a putative AP‐1‐like site, 5′‐ATTAATCAT‐3′. Finally, deletion of the −182 to −161 region in a 380‐bp CAT construct resulted in a substantial reduction of PMA responsiveness. Thus, we have identified a novel phorbol‐responsive region that binds c‐Fos and c‐Jun, and we suggest that these or similar proteins may regulate transcription of the collagenase gene by binding to sequences within and adjacent to the −182 to −161 region.
Resistance of mitochondrial DNA to degradation characterizes the apoptotic but not the necrotic mode of human leukemia cell death
Authors: Tepper Clifford G. , Studzinski George P. 
Published: May 2005

AbstractCell death can occur by two basically different processes. The original term, necrosis, is now reserved for the generally destructive series of events which include the release of lysosomal enzymes and loss of cell membrane integrity. In contrast, mild treatment with cell damaging agents, or withdrawal of growth factors, may result in a characteristic form of degradation of cellular DNA which is associated with cell death that has morphology known as apoptosis. In this study human leukemia cells were exposed to agents or conditions previously reported to cause necrosis or apoptosis, monitored by detection of DNA “ladders,” and the integrity of cellular DNA was determined on Southern blots. Nuclear DNA was distinguished from mitochondrial DNA by use of probes specific for nuclear genes or for mitochondrial DNA. When HL60, K562, MOLT4, or U937 cells were exposed to conditions which resulted in necrosis, mitochondrial DNA was damaged at approximately the same rate as nuclear DNA, but in apoptosis mtDNA was not degraded. Thus, the ratio of the relative (to untreated cells) abundance of mitochondrial DNA measured by a probe for 16S mitochondrial ribosomal RNA on Southern blots, to the relative abundance of DNA of any nuclear gene, was 1 or less in necrosis, but rose to values greater than 2 in apoptosis. It is concluded that the comparison of the degree of fragmentation of mitochondrial and nuclear DNA provides a quantitative way of distinguishing necrosis from apoptosis.
Unambiguous identification of histone H1 in Trypanosoma cruzi
Authors: Toro G. Cecilia , Galanti Norbel , Hellman Ulf , Wernstedt Christer 
Published: May 2005

AbstractThe existence of histone H1 has been questioned in Trypanosomatids. We report here the presence of a histone H1 in the chromatin of Trypanosoma cruzi. This protein was purified by narrow‐bore reversed phase HPLC and its amino acid composition analyzed and compared with histones H1 from other species. Furthermore, the purified chromosomal protein was digested with proteases and the amino acid sequences of the resulting peptides were analyzed by the automated Edman degradation. The sequences obtained were found to present a high degree of homology when compared to the carboxy terminal domain of other known histones H1.
Isolation and characterization of a new class of acidic glycans implicated in sea urchin embryonal cell adhesion
Authors: Papakonstantinou Eleni , Misevic Gradimir N. 
Published: May 2005

AbstractThree major glycan fractions of 580 kDa (g580), 150 kDa (g150), and 2 kDa (g2) were isolated and purified from Lytechinus pictus sea urchin embryos at the mesenchyme blastula stage by gel filtration and high pressure liquid chromatography. Chemical analysis, by gas chromatography, revealed that g580 is highly sulfated and rich in N‐acetylglucosamine, N‐acetylgalactosamine, glucuronic acid, and fucose. The g150 fraction is less acidic than g580 and contains high amounts of amino sugars, xylose, and mannose. The g2 fraction is neutral, rich in N‐acetylglucosamine, mannose, and galactose. The g580 and g150 fractions are resistant to glycosaminoglycan‐degrading enzymes, indicating that they are distinct from the glycosaminoglycans. The g580 fraction resembles, with respect to chemical composition, a previously characterized 200 kDa sponge adhesion glycan (g200). The binding of the monoclonal antibody Block 2, which recognizes a repetitive epitope on g200, as well as of the anti‐g580 polyclonal antibodies to both g580 and g200 indicated that these two glycans share similar antigenic determinants. The Fab fragments of the Block 2 antibody, which previously have been shown to inhibit cell adhesion in sponges, also blocked the reaggregation of dissociated sea urchin mesenchyme blastula cells. These results indicate that g580 carries a carbohydrate epitope, similar to the sponge adhesion epitope of g200, which is involved in sea urchin embryonal cell adhesion.
Role of protein phosphorylation in TNF‐induced apoptosis: Phosphatase inhibitors synergize with TNF to activate DNA fragmentation in normal as well as TNF‐resistant U937 variants
Authors: Wright Susan C. , Zheng Hui , Zhong Jian , Torti Frank M. , Larrick James W. 
Published: May 2005

AbstractThis study examined the role of protein phosphorylation in TNF induction of apoptosis in several tumor cell lines by testing the effects of agents that either stimulate or inhibit protein phosphorylation. The serine‐threonine phosphatase inhibitors, okadaic acid (OKA) and calyculin A (CLA), synergistically augmented TNF‐induced apoptosis in several TNF‐sensitive tumor cell lines including the U937 histiocytic lymphoma, the BT‐20 mammary carcinoma, and the LNCap prostatic tumor cell line. Furthermore, the phosphatase inhibitors completely reversed the TNF resistance of a variant (U9‐TR) derived from U937. CLA also inhibited phosphatase activity in cell‐free extracts from both U937 and U9‐TR at the same concentrations (0.4–2.0 nM) that it synergized with TNF. In contrast, TNF treatment of U937 cells did not result in inhibition of phosphatase activity mediated by protein phosphatase 1 (PP1) and PP2A in cell extracts. Since the phosphatase inhibitors are known to increase the overall levels of protein phosphorylation in cells, this suggested that TNF may act by stimulating protein kinase (PK) activity. This hypothesis was supported by the results of testing a panel of relatively specific protein kinase inhibitors. TNF activation of DNA fragmentation was blocked by a potent inhibitor of myosin light chain kinase (MLCK) but was unaffected by inhibitors of cAMP or cGMP‐dependent PKs. We postulate that a defect in the activation of MLCK or possibly some other as yet unknown PK may be responsible for the TNF resistance of U9‐TR. Furthermore, this resistance may be circumvented by promoting protein phosphorylation with the serine‐threonine‐dependent phosphatase inhibitors.
Nuclear localization of melatonin in different mammalian tissues: Immunocytochemical and radioimmunoassay evidence
Authors: Menendez‐Pelaez Armando , Poeggeler Burkhard , Reiter Russel J. , Barlow‐Walden Lornell , Pablos Marta I. , Tan Dun‐xian 
Published: May 2005

AbstractMelatonin was detected by an improved immunocytochemical technique in the cell nuclei of most tissues studied including several brain areas, pineal gland, Harderian gland, gut, liver, kidney, and spleen from rodents and primates. Cryostat sections from tissues fixed in Bouin's fluid, formalin, or acetone/ethanol were used. The nuclear staining appeared primarily associated with the chromatin. The nucleoli did not exhibit a positive reaction. The melatonin antiserum was used in the range of 1:500 to 1:5,000. Incubation of the antibody with an excess of melatonin resulted in the complete blockade of nuclear staining. Pretreatment of the sections with proteinase K (200–1,000 ng/ml) prevented the positive immunoreaction. In a second aspect of the study, we estimated the concentration of melatonin by means of radioimmunoassay in the nuclear fraction of several tissues including cerebral cortex, liver, and gut. The subcutaneous injection of melatonin (500 μg/kg) to rats resulted, after 30 min, in a rapid increase in the nuclear concentration of immunoreactive melatonin which varied in a tissue‐dependent manner. However, samples collected 3 h after the injection showed that melatonin levels had decreased to control values. Pinealectomy in rats resulted in a clear reduction in the nuclear content of melatonin in the cerebral cortex and liver but not in the gut. The results of these studies suggest that melatonin may interact with nuclear proteins and that the indole may have an important function at the nuclear level in a variety of mammalian tissues.
Differential expression of the two VEGF receptors flt and KDR in placenta and vascular endothelial cells
Authors: Barleon Bernhard , Hauser Stefanie , Schöllmann Claudia , Weindel Karin , Marmé Dieter , Yayon Avner , Weich Herbert A. 
Published: May 2005

AbstractVascular endothelial growth factor (VEGF) is a newly identified growth and permeability factor with a unique specificity for endothelial cells. Recently the flt‐encoded tyrosine kinase was characterized as a receptor for VEGF. A novel tyrosine kinase receptor encoded by the KDR gene was also found to bind VEGF with high affinity when expressed in CMT‐3 cells. Screening for flt and KDR expression in a variety of species and tissue‐derived endothelial cells demonstrates that flt is predominantly expressed in human placenta and human vascular endothelial cells. Placenta growth factor (PIGF), a growth factor significantly related to VEGF, is coexpressed with flt in placenta and human vascular endothelial cells. KDR is more widely distributed and expressed in all vessel‐derived endothelial cells. These data demonstrate that cultured human endothelial cells isolated from different tissues express both VEGF receptors in relative high levels and, additionally, that all investigated nonhuman endothelial cells in culture are also positive for KDR gene expression.
Differential regulation of tissue transglutaminase in rat hepatoma cell lines McA‐RH7777 and McA‐RH8994: Relation to growth rate and cell death
Authors: Fukuda Kazunori , Kojiro Masamichi , Chiu Jen‐Fu 
Published: May 2005

AbstractClose correlation between tissue transglutaminase (tTG) induction and growth regulation and/or cell death processes has been suggested in many cell lineages. In this study, the regulation of the tTG levels by various growth and differentiation factors and its relation to growth rate and cell death processes were investigated in two rat hepatoma cell lines, McA‐RH7777 and McA‐RH8994, using a monoclonal antibody against liver tTG. Transforming growth factor‐β1 (TGF‐β1) and retinoic acid (RA) each increased tTG to the level of 8‐ to 32‐fold above that of control cultures in both cell lines after 72‐h treatment. Dexamethasone (DEX) induced a 16‐ to 32‐fold of tTG in McA‐RH8994 cells while it did not change the enzyme level in McA‐RH7777 cells. Simultaneous addition of DEX and RA increased the tTG level to more than 50‐fold in McA‐RH7777 cells as well as McA‐RH8994 cells. Other factors, such as TGF‐α, hepatocyte growth factor, dimethyl sulfoxide, and protein kinase C activator, did not show significant increases of the tTG levels. Although tTG induction by TGF‐β1 or DEX appeared to be correlated with their growth suppressive effects, RA increased the tTG level without suppressing the growth rate of hepatoma cells. TGF‐β1 was also shown to induce cell death in both cell lines. Our results demonstrate that RA and DEX are capable of modulating the TGF‐β1‐induced cell death processes independent of the tTG levels. We present evidence here that tTG induction by itself is not the direct cause of growth suppression and cell death in these hepatoma cells.
Regulation of bone marrow stromal cell differentiation by cytokines whose receptors share the gp130 Protein
Authors: Gimble Jeffrey M. , Wanker Frank , Wang Chi‐Sun , Bass Helen , Wu Xiying , Kelly Katherine , Yancopoulos George D. , Hill Molly R. 
Published: May 2005

AbstractThe bone marrow stroma consists of a heterogeneous population of cells which participate in osteogenic, adipogenic, and hematopoietic events. The murine stromal cell line, BMS2, exhibits the adipocytic and osteoblastic phenotypes in vitro. BMS2 differentiation was examined in response to cytokines which share the gp130 signal transducing protein within their receptor complex. Four of the cytokines (interleukin 6, interleukin 11, leukemia inhibitory factor, and oncostatin M) inhibited hydrocortisone‐induced adipocyte differentiation in a dose dependent manner based on lipid accumulation and lipoprotein lipase enzyme activity. Inhibition occurred only when the cytokines were present during the initial 24 h of the induction period; after 48 h, their effects were diminished. Likewise, these cytokines increased alkaline phosphatase enzyme activity twofold in preadipocyte BMS2 cells. Both leukemia inhibitory factor and oncostatin M induced early active gene expression in resting preadipocyte BMS2 cells and decreased the steady state mRNA level of a unique osteoblastic gene marker, osteocalcin. A fifth cytokine whose receptor complex shares the gp130 protein, ciliary neurotrophic factor, did not significantly regulate stromal cell differentiation when added by itself. However, with the addition of a missing component of its receptor complex, ciliary neurotrophic factor receptor α protein, this cytokine also inhibited BMS2 adipogenesis. Together, these data indicate that the cytokines whose receptors share the gp130 protein can modulate stromal cell commitment to the adipocyte and osteoblast differentiation pathways.
Recombinant GST‐human osteopontin fusion protein is functional in RGD‐dependent cell adhesion
Authors: Xuan Jian‐Wu , Hota Charulata , Chambers Ann F. 
Published: May 2005

AbstractOsteopontin (OPN) is a secreted phosphoprotein expressed by many tumor cells, as well as a limited set of normal cells. Native OPN has been shown to support cell adhesion in an RGD‐peptide‐inhibitable fashion. Here we expressed human OPN in E. coli as a recombinant fusion protein with glutathione‐S‐transferase (GST). We report that the GST‐OPN fusion protein has functional activity. PAP2 (ras‐transformed, metastatic murine NIH 3T3) and MDA‐MB‐435 human mammary carcinoma cells bound to GST‐OPN in an in vitro cell adhesion assay nearly as well as to native bovine OPN. Adhesion to the recombinant fusion protein was blocked by addition of GRGDS peptide, suggesting that the cells adhere to the recombinant and native OPN proteins by similar, integrin‐mediated mechanisms. Adhesion to both sources of OPN also was inhibited by thrombin treatment of the protein. Thrombin cleaves GST from OPN in the fusion protein, and also cleaves internally in OPN, adjacent to the RGD sequence of the protein. Our results suggest that (a) thrombin cleavage of native OPN may be a natural regulator of OPN function, and (b) the majority of OPN cell binding activity is mediated by the RGD sequence in the protein backbone, with little or no requirement for post‐translational modifications that occur in native OPN for adhesive function as measured here.
Cell cycle: Regulatory events in G1 → S transition of mammalian cells
Authors: Reddy G. Prem Veer 
Published: May 2005

AbstractA cell divides into two daughter cells by progressing serially through the precisely controlled G1, S, G2, and M phases of the cell cycle. The crossing of the G1/S border, which is marked by the initiation of DNA synthesis, represents commitment to division into two complete cells. Beyond this critical point no further external signals are required. We now have more comprehensive knowledge of the temporal sequence of systems at this key transition from G1 to S—growth factor responses, a cascade of kinase reactions, activation of cyclins and their associated kinases, and oncogene and tumor suppressor gene products. Furthermore, we know that the absolute requirement for calcium and the timing of events associated with calmodulin and the 68 kDa calmodulin‐binding protein are consistent with overall Ca++/calmodulin control of all steps from the response to growth factors in G1 to DNA replication in S phase. We now have to sort out the inter‐relationships of myriad control proteins and their relation to the Ca++/calmodulin‐dependent controls—Which are causes? Which are effects? And which are parallel processes? The answers will be important, as they represent both a much deeper understanding of this key process of life and an important opportunity for improving therapeutic medicine.
The structure of the sleeping genome: Implications of sperm DNA organization for somatic cells
Authors: Ward W. Steven 
Published: May 2005

AbstractThe tertiary structure of the DNA that makes up the eukaryotic genome is remarkably plastic, taking many different forms in response to the different needs of the cell. During the cell cycle of one cell, the DNA is replicated, reorganized into mitotic chromosomes, and decondensed into interphase chromatin. Within one cell at any given point in time, the chromatin is divided into hetero‐ and euchromatin reflecting active and inactive states of the DNA. This organization varies within one organism since different parts of the genome are active in different cell types. This article focuses on the most dramatic cell‐type‐specific DNA organization, that found in spermatozoa, in which the entire genome is reorganized into an inactive state that is more highly condensed than mitotic chromosomes. This unique example of eukaryotic DNA organization offers some interesting clues to the still unanswered questions about the role that the three‐dimensional packaging of DNA plays in its function. © 1994 Wiley‐Liss, Inc.
Osteocalcin promotes differentiation of osteoclast progenitors from murine long‐term bone marrow cultures
Authors: Liggett William H. , Lian Jane B. , Greenberger Joel S. , Glowacki Julie 
Published: May 2005

AbstractMurine long‐term bone marrow cultures (LTBMCs) were used to generate hematopoietic cells free from marrow stromal cells. These progenitor cells were treated with GM‐CSF (5 U/ml) with or without rat bone osteocalcin or rat serum albumin in either α‐MEM with 2% heat‐inactivated horse serum alone (α) or supplemented with 10% L‐cell‐conditioned medium (as a source of M‐CSF) (L10). Few substrate‐attached cells survived in basal α medium, but when treated with L10 medium or GM‐CSF, they survived and proliferated. Osteocalcin did not significantly affect survival or proliferation. Subcultures of cells treated with GM‐CSF had large numbers of multinucleated cells, more than half of which were tartrate‐resistant acid phosphatase–positive (TRAP). Osteocalcin further promoted the development of TRAP‐positive multinucleated cells; a dose of 0.7 μg/ml osteocalcin promoted osteoclastic differentiation by 60%. Using a novel microphotometric assay, we detected significantly more tartrate‐resistant acid phosphatase activity in the osteocalcin plus GM‐CSF group (75.6 ± 14.2) than in GM‐CSF alone (53.3 ± 7.3). In the absence of M‐CSF, GM‐CSF stimulated tartrate‐resistant acid phosphatase activity, but osteocalcin did not have an additional effect. These studies indicate that osteocalcin promotes osteoclastic differentiation of a stromal‐free subpopulation of hematopoietic progenitors in the presence of GM‐CSF and L‐cell‐conditioned medium. These results are consistent with the hypothesis that this bone‐matrix constituent plays a role in bone resorption. © 1994 Wiley‐Liss, Inc.
Protein kinase C is involved in 24‐hydroxylase gene expression induced by 1,25(OH)2D3 in rat intestinal epithelial cells
Authors: Koyama Hidenori , Inaba Masaaki , Nishizawa Yoshiki , Morii Hirotoshi , Ohno Shigeo 
Published: May 2005

AbstractEffects of protein kinase C (PKC) inhibitor and activator on 1,25(OH)2D3‐induced gene expression were examined in rat intestinal epithelial cells, IEC‐6 cells. A potent PKC inhibitor, H‐7 (20 μM), completely abated 1,25(OH)2D3‐induced 24‐hydroxylase gene expression at 3 and 6 h. The effect of H‐7 was dose dependent with IC50 around 5 μM. Other protein kinase inhibitors, HA‐1004 and H‐89 (20 μM), had no effects. Furthermore, the activation of PKC by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) potentiated the effect of 1,25(OH)2D3 by 1 h. TPA appeared to exert its effect at a transcriptional step, since mRNA stability was not affected by TPA treatment. At 3 h after the treatment of the cells with H‐7 and TPA, vitamin D receptor (VDR) contents estimated by 3H‐1,25(OH)2D3 binding capacity were 72.4 and 63.2% of vehicle‐treated cells without significant changes of binding affinities, suggesting that the effect of H‐7 and TPA was not the result of changes in VDR content or its binding affinity. In conclusion, PKC is involved in 1,25(OH)2D3‐induced 24‐hydroxylase gene expression in IEC‐6 cells between 1,25(OH)2D3‐VDR binding and VDR‐induced gene transactivation. © 1994 Wiley‐Liss, Inc.