bluuebunny/crossref_metadata_2025_split huggingface dataset:
TPA has no influence on the expression of myosin heavy chain isoforms in cultured adult cardiac muscle cells
Authors: Nag A. C. , Li Lee Mei 
Published: May 2005

AbstractThe effect of a tumor promoter, 12‐0‐tetradecanoyl phorbol‐13‐acetate (TPA), on the expression of myosin heavy chain isoforms in cultured rat cardiac ventiricular muscle cells was studied. The previous preliminary report [Claycomb WC (1988): “Biology of Isolated Adult Cardiac Myocytes.” In Clark WA, Decker RS, Borg TK (eds): New York: Elsevier, pp 284–287] indicated that TPA turns off the expression of myosin heavy chain genes in cultured adult cardiac myocytes. Electrophoretic and immunocytochemical analyses were carried out in the present studies. The myosin heavy chain isoform profiles of cardiac myocytes exposed to TPA at concentrations of 50–250 ng/ml culture medium for varying periods were similar to those of controls that were grown in the absence of TPA, showing predominant isoform V1. Immunofluorescence microscopy with monoclonal antibodies to cardiac ventricular isomyosin revealed the structural organization of myosin in TPA‐treated cells. The organization of myosin was variable among different myocytes and within a single myocyte. Immunofluorescence microscopy was extended to the examination of the organization of α‐actinin which did not differ from that of myosin in some myocytes. In contrast to the previous report [Claycomb, 1988], this study has demonstrated that TPA has no influence on the expression of myosin heavy chain isoforms in cultured adult ventricular cardiac muscle cells.
Alpha‐1 antitrypsin response of stimulated alveolar macrophages
Authors: Yuan Zhi‐An , Soprano Kenneth J. , Kueppers Friedrich 
Published: May 2005

AbstractAlpha‐1 antitrypsin messenger RNA (A1AT mRNA) was determined in alveolar macrophages and in peripheral blood monocytes of healthy individuals using a sensitive RNase protection assay. Determinations were made of bacterial lipopolysaccharide (LPS) stimulated and unstimulated cells. We found that the amount of A1AT mRNA increased 7.3 and 14 times after 4 h of incubation with LPS for monocytes and macrophages, respectively (relative to total RNA). The increase was 12.3 and 14.8 times, respectively, when expressed as increase per cell. In both cell types there was wide interindividual variation in LPS response: 2–36 and 5–12 times for monocytes and macrophages, respectively.The possible significance of A1AT production of monocytes and macrophages may be the local control of granulocytic proteases such as elastase and cathepsin G.
Cytokine triggered molecular pathways that control cell cycle arrest
Authors: Kimchi Adi 
Published: May 2005

AbstractRecent progress has been made concerning the understanding of the molecular pathways that mediate the growth suppressive effects of inhibitory cytokines. Interferons, interleukin‐6 and transforming growth factor‐β were investigated in these studies. Cell lines that display growth sensitivity to all three cytokines and growth resistant derivates provided a suitable genetic background to determine whether common or unique post‐receptor elments mediate the effects of each cytokine. three nuclear genes, c‐myc, RB, and cyclin A were found to be common key downstream targets along the cytokine induced growth suppressive pathways. Genetic and pharmacological manipulations proved that these molecular responses fall into few complementary pathways that function in parallel to achieve the cytokine mediated GO/G1 arrest. New strategies, such as knock out anti‐sense gene cloning were developed and they currently provied powerful tools for the isolation of genes along the signaling pathways of growth arrest. © 1992 Wiley‐Liss, Inc.
Differential regulation of H4 histone gene expression in 3T3‐L1 pre‐adipocytes during arrest of proliferation following contact inhibition or differentiation and its modulation by TGFβ1
Authors: Bortell Rita , van Wijnen Andre J. , Ramsey‐Ewing Anna L. , Stein Gary S. , Stein Janet L. 
Published: May 2005

AbstractThe aim of this study was to address whether there is a fundamental difference in regulation of histone gene expression in cells that have become quiescent but retain the ability to proliferate, compared with those cells that have differentiated. We compared multiple levels of regulation of histone gene expression during 3T3‐L1 pre‐adipocyte differentiation. Confluent cells induced to differentiate by treatment with insulin, dexamethasone, and isobutylemethylxanthine initially exhibited an increased proliferative response compared with cells given serum alone. This initial differentiation response was associated with a twofold increase in both histone gene transcription and cellular histone mRNA levels, as well as with enhanced sequence‐specific binding of nuclear factors to the proximal cell‐cycle‐regulatory element of the H4 histone promoter. Transforming growth factor β1, an inhibitor of 3T3‐L1 differentiation, increased both the percentage of proliferating cells and the cellular levels of histone mRNA when given in addition to serum stimulation, but no enhancement of these parameters was observed upon addition of TGFβ1 to the differentiation treatment. Interestingly, although TGFβ1 enhanced binding of nuclear factors to the proximal cell cycle regulatory element of the histone promoter, these protein/DNA interactions were not associated with an increase in histone transcription. Our results are consistent with the down‐regulation of histone gene expression at confluency being controlled primarily at the post‐transcriptional level, in contrast to an increased involvement of transcriptional down‐regulation at the onset of differentiation. © 1992 Wiley‐Liss, Inc.
A cell attachment peptide from human C‐reactive protein
Authors: Fernandez Marilyn C. , Mullenix Michael C. , Christner Robert B. , Mortensen Richard F. 
Published: May 2005

AbstractThe serum acute phase reactant, C‐reactive protein (CRP), is selectively deposited at sites of tissue damage and degraded by neutrophils into biologically active peptides. A synthetic peptide corresponding to residues 27‐38 present in each of the five identical subuints of CRP mediated cell attachment activity in vitro. Although the CRP‐derived peptide contains a Tuftsin (TKPR)‐like sequence at its amino‐terminus, the Tuftsin tetrapeptide itself, as well as several synthetic peptides of CRP, failed to inhibit the cell‐attachment activity to the CRP‐derived peptide. Peptides containing the sequences responsible for the cell attachment activity of the extracellular matrix proteins, fibronectin (Fn) and laminin, failed to inhibit the CRP‐derived peptide cell attachment activity. However the addition of the RGDS and RGDSPASSLP cell‐binding peptides of Fn to cells enhanced attachment to the active peptide from CRP. In the converse experiment, the cell‐binding peptide of CRP did not influence cell attachment to Fn or laminin. A peptide corresponding to the same stretch of amino acid residues within the homologous Pentraxin, serum amyloid P‐component (SAP), displayed nearly identical cell‐ attachment activity. Several monoclonal antibodies (mAb) specific for the CRP‐derived cell‐binding peptide neutralized its cell‐attachment activity. These mAbs reacted with intact CRP and neutralized the cell‐binding activity of CRP itself. The findings suggest that a peptide with cell‐binding activity could be generated from the breakdown of the CRP and then contribute directly to cellular events leading to tissue repair. © 1992 Wiley‐Liss, Inc.
Effect of monensin on the sulfation of heparan sulfate proteoglycan from endothelial cells
Authors: Sampaio Lucia O. , Dietrich Carl P. , Colburn Patricia , Buonassisi Vincenzo , Nader Helena B. 
Published: May 2005

AbstractMonensin is a monovalent metal ionphore that affects the intracellular translocation of secretory proteins at the level of trans‐Golgi cisternae. Exposure of endothelial cells to monensin results in the synthesis of heparan sulfate and chondroitin sulfate with a lower degree of sulfation. The inhibition it dose dependent and affects the ratio [35S]‐sulfate/[3H]‐hexosamine of heparan sulfate from both cells and medium, with no changes in their molecular wieght. By the use of several degradative enzymes (heparitinases, glycuronidase, and sulfatases) the fine structure of the heparan sulfate synthesized by control and monensin‐treated cells was investigated. The results have shown that among the six heparan sulfate disaccharides there is a specific decrease of the ones bearing a sulfate ester at the 6‐position of the glucosamine moiety. All other biosyntheitc steps were not affected by monensin. The results are indicative that monensin affects the hexosamine C‐6 sulfation, and that this sterification is the last step of the heparan sulfate biosynthesis and should occur at the trans‐Golgi compartment. © 1992 Wiley‐Liss, Inc.
Monoclonal antibodies identify a possible regulatory domain of MyoD1
Authors: Cole Francesca , Timo Kimberly S. , Kohtz D. Stave 
Published: May 2005

AbstractA panel of monoclonal antibodies (mAbs) to murine MyoD1 was generated. One set of mAbs is shown to react with epitops(s) in the cysteine/histidine‐rich (C/H) region while another set is shown to reach with epitope(s) in the C‐terminal portion of MyoD1. One of the mAbs reactive with a C‐terminal epitope sensitively detected MyoD1 in whole cell extracts by Western blotting. Time course studies of total protein accumulation during C2C12 myoblast differentiation revealed only subtle change in the phosphorylation and quantity of MyoD1 protein present in C2C12 cells from induction to 120 hr after induction. These results suggest that modulation of MyoD1 protein or total phophorylation levels is not tightly associated with the transition of undifferentiated myoblasts to differentiated myocytes. Monoclonal antibodies to the C‐terminal epitope produces supershifted bands in gel retardation assays, indicating that these mAbs had no effect on DNA binding. Although the C/H region of MyoD1 does not participate in DNA binding, mAbs reactive with the C/H region neutralized this activity in gel retardation assays. These data suggest that the conserved C/H domain may serve to modulate MyoD1 DNA‐binding activity by interacting with another regulator. © 1992 Wiley‐Liss, Inc.
Growth‐regulated expression of vimentin in hamster fibroblasts is a result of increased transcription
Authors: Ferrier Alma Fallon , Hirschhorn Ricky R. 
Published: May 2005

AbstractWe have previously shown that vimentin is a growth‐regulated gene whose mRNA levels increase after srum stimulation of quiescent hamster fibroblasts. In this study, the control of the growth‐regulated expression of vimentin was determined in ts13 cells induced to proliferate by serum. Both transcriptional and post‐transcriptional mechanisms of regulation were exmined by determining transcriptional rates, cytoplasmic transcript abundance, transcript stability, and protein abundance. We observed a fourfold increase in vimentin transcripts in the cytoplasm of serum‐stimulated ts13 cells. Since transcripts are stable in both quiescent and stimulated cells, this induction of vimentin expression is a result of a fivefold increase in vimentin‐specific transcriptional activity. As a result of this increased transcript availability, the abundance of polymerized vimentin protein increased following serum stimulation of quiescent fibroblasts. Overall, the induction of vimentin expression in fibroblasts by serum is a consequence of increased vimentin‐specific transcriptional activity. The significance of this with regard to cytoskeletal organization and cell division is discussed. © 1992 Wiley‐Liss, Inc.
Influence of mitomycin C on endothelial monolayer regeneration in vitro
Authors: Coomber Brenda L. 
Published: May 2005

AbstractThis study examines the effect of Mitomycin C, a fungal toxin which inhibits DNA synthesis, on the regeneration of partially denuded large vessel endothelium in vitro. Monolayers of bovine pulmonary artery endothelial cells were treated with Mitomycin C prior to or immediately following partial denudation and were incubated in the continuing presence of Mitomycin C; the effects of this treatment on monolayer repair, cell proliferation, and other aspects of endothelial phenotye were monitored. Cell proliferation, DNA, RNA, and protein synthesis were all reduced in a dose dependent manner in treated cultures. Incubation with Mitomycin C for 48 h or longer resulted in reduced cell spreading, and rounding up and loss of cells from both intact and partially denuded cultures. Effects were less severe with lower doses and shorter incubation times. However, significant reductions in monolayer regeneration occurred within 8 h of incubation, sufficiently early to suggest that Mitomycin C may affect aspects of the regeneration process independent of cell proliferation. Polarization/spreading of cells at the denudation edge was monitored by fluorescence staining for golgi with C5‐DMB‐ceramide, and for centrioles with antibodies to tubulin. Centrioles and golgi rapidly reoriented to a location at the putative leading edge of control cultures. Mitomycin C treatment had no effect on centriole reorientation, but caused a significant delay in golgi localization. These results suggest that Mitomycin C inhibits endothelial monolayer regeneration by mechanisms independent of cell proliferation and DNA synthesis, perhaps by interfering with cell spreading or translocation at the wound edge. © 1992 Wiley‐Liss, Inc.
Methylation of the 5′ flanking sequences of the ribosomal DNA in human cell lines and in a human‐hamster hybird cell line
Authors: Dante R. , Baldini A. , Miller D. A. , Miller O. J. , Percy M. E. , Markovic V. D. , Rocchi M. , Niveleau A. 
Published: May 2005

AbstractIn human lymphoplastoid cell line (Z83) in which rDNA genes on chromosomes 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5′ flanking sequence of the ribosomal DNA was examined by comapring the size of restriciton fragments obtained by digestion of genomic DNA with EcoRI and Hpall or EcoRI and Mpsl. Southern blots indicated hypermethylation of the 5′ flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with somatic hybird human‐hamster cell line, in which the rRNA genes on the single human chromosomes 22 are inactive, showed that only a small fraction of the CCGG sites in the 5′ flanking sequences of the transcriptionally silent rRNA genes in this hybird were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the apmlified rRNA genes in Z83 association with their inactivation rather than following it. © 1992 Wiley‐Liss, Inc.
Preferential accumulation of mature NK cells during human immunosenescence
Authors: Krishnaraj R. , Svanborg A. 
Published: May 2005

AbstractThe major histocompatibility complex‐unrestricted, cell‐mediated, constitutive anti‐tumor cytotoxic function of natural killer cells is highly preserved in healthy elderly. A study of the dynamics of expression of natural killer cell–associated phenotypes during immunosenescence shows that selective, bidirectional, and disproportionate changes in certain natural killer cell subset number and ratio take place during aging. The mean natural killer cell subset ratio (%CD16+CD57+ over%CD56+CD57−)gradually increases from a young adult level of 0.7 to 4.6 with advancing age predominantly due to a tripling of %CD16+57+ cells as opposed to a moderate decrease (−54%)in %CD56+57− phenotype. The parallel increase in natural killer phenotype ratio and cytotoxic activity might represent a shift in the maturity status of these cells. Based on these findings, a model of natural killer cell immunosenescence is proposed. It is concluded that not all immunosenescent changes need be detrimental; some may even improve the potential for survival and represent an adaptational immunosenescent change. © 1992 Wiley‐Liss, Inc.
Glucocorticoid regulation of alkaline phosphatase, osteocalcin, and proto‐oncogenes in normal human osteoblast‐like cells
Authors: Subramaniam Malayannan , Colvard Douglas , Keeting Philip E. , Rasmussen Kay , Riggs B. Lawrence , Spelsberg Thomas C. 
Published: May 2005

AbstractIn humans, glucocorticoids are known to have marked effects on bone metabolism and function, including the significant regulation of osteoblast cells. To aid in the understanding of the mechanism of glucocorticoid action on normal human osteoblasts (hOB), confluent cells were analyzed for the presence of glucocorticoid receptors (GR) as well as for the effects of the glucocorticoid dexamethasone (Dex) on the expression of both the rapid responding nuclear proto‐oncogenes and the late responding structural genes for bone matrix proteins. The interactions between Dex and 1,25 dihydroxy vitamin D3 (1,25 3) on the gene expression in these cells were also examined. Using a functional receptor assay, a mean of 11,600 functioal nuclear bound glucocorticoid receptors (range 6,000‐22,000) was measured in fifteen separate cell strains. Northern blot analysis with a cDNA probe to the human GR was used to demonstrate the presence of a 7Kb transcript which is a candidate mRNA for GR in these cells. In arragement with previous studies, treatment of the hOB cells with Dex increased the steady state mRNA levels for alkaline phosphatase (AP) but displayed little or no effect on the mRNA levels for osteocalcin (OC) and glyceraldehyde phosphate dehydrogenase (GAPDH). Interestingly, the 1,25 D3 inductions of mRNA levels for OC were blocked by Dex but enhanced for AP. The above effects of Dex on AP and OCgene expression, including the interaction with 1,25 D3, were also shown to occur at the level of protein. The effect of Dex on the mRNA levels of the nuclear proto‐oncogenes c‐myc, c‐fos, and c‐jun was also investigated, since the oncoproteins (Fos/Jun) appear to play a role in the delayed glucocorticoid regulation of structural genes. Interestingly, Dex increased the steady state levels of c‐myc, c‐fos, and c‐jun mRNAs in nonproliferating (confluent) hOB cells by 3.5‐, 10‐, and 2.0‐fold, respectively, over control (untreated cells) values within one h of steroid treatment. The Dex‐induced mRNA levels were transient and returned to basal values within 24 h of the steroid treatment. A reduced but qualitatively similar pattern of response was found in proliferating hOB cells. The pattern of response of these genes to glucocorticoids in hOB cells mimics the response in avian liver cells but not in reproductive cells. These results support the theory that hOB cells are target cells for glucocorticoids, and that as a primary event glucocorticoids rapidly regulate the expression of the nuclear oncoproteins Fos/Jun in these cells. © 1992 Wiley‐Liss, Inc.
4‐Quinolones cause a selective loss of mitochondrial DNA from mouse L1210 leukemia cells
Authors: Lawrence Jeffrey W. , Darkin‐Rattray Sandra , Xie Fan , Neims Allen H. , Rowe Thomas C. 
Published: May 2005

AbstractThe 4‐quinolone antibiotics nalidixic acid and ciprofloxacin and potent inhibitors of the bacterial type II topoisomerase DNA gyrase. Treatment of mouse L1210 leukemia cells with these drugs resulted in a delayed inhibition of cell proliferation. Prior to inhibition of cell proliferation, there was a time‐dependent decrease in the cellular content of mitochondrial DNA (mtDNA). The decrease in mtDNA was associated with a decrease in the rate of mitochondrial respiration and an increase in the concentration of lactate in the growth medium. Inhibition of cell proliferation by 4‐quinolones was reversible upon drug washout. However, there was a 2‐ to 4‐day lag before the growth rate returned to normal levels. This was preceeded by an increase in mtDNA content and mitochondrial respiration. These studies suggest that inhibition of mammalian cell proliferation by 4‐quinolone drugs is related to the selective depletion of mtDNA. © 1993 Wiley‐Liss, Inc.
Selection of malonate‐resistant stromal cell‐derived osteoprogenitor cells in vitro
Authors: Klein Benjamin Y. , Gal Irena , Segal David 
Published: May 2005

AbstractBone marrow stromal cells give rise to osteoprogenitor cell (OPC) colonies, with characteristic mineralized bone nodules in vitro. During differentiation, OPCs in the culture are surrounded by heterogeneous populations of various cell lineages and by different OPC differentiation stages. In the present study, attempts were made to increase the homogeneity of OPCs in culture. The reliance on energy metabolism restricted to glycolysis, which is specific to the premineralizing skeletal cells, was tested as a selectable marker for cells in this stage. Day 12 alkaline phosphatase (ALP) and day 20–21 calcium precipitates were used as early and late OPC differentiation markers. Malonate, a competitive inhibitor of succinate dehydrogenase, was added to the OPC stimulation medium, to interfere with the Krebs cycle‐dependent energy metabolism operating in most of the stromal cells. OPCs that entered the stage of energy metabolism restricted to glycolysis were expected to become malonate resistant. Malonate showed dose and time dependence, 10 mM malonate added on day 3, decreased day 12 ALP activity/well to the lowest level. Variations in time and length of exposure to malonate used during the first 12 days of differentiation showed an inverse correlation between specific ALP activity and cell yield. Malonate‐treated variations of specific ALP and of cell yield indices were up to 30‐ to 40‐fold larger than variations within day 21 calcium precipitates. Thus, calcifying cells were almost unchanged relatively to noncalcifying cells. These results indicate that malonate‐resistant cells are mostly selected, rather than induced, to differentiate by malonate. The results also show that stromal derived OPCs undergo a similar biochemical stage as in chondrocytes. © 1993 Wiley‐Liss, Inc.
Utilization of microgravity bioreactors for differentiation of mammalian skeletal tissue
Authors: Klement Brenda J. , Spooner Brian S. 
Published: May 2005

AbstractBioreactor cell and tissue culture vessels can be used to study bone development in a simulated microgravity environment. These vessels will also provide an advantageous, low maintenance culture system on space station Freedom. Although many types of cells and tissues can potentially utilize this system, our particular interest is in developing bone tissue. We have characterized an organ culture system utilizing embryonic mouse pre‐metatarsal mesenchyme, documenting morphogenesis and differentiation as cartilage rods are formed, with subsequent terminal chondrocyte differentiation to hypertrophied cells. Further development to form bone tissue is achieved by supplementation of the culture medium. Research using pre‐metatarsal tissue, combined with the bioreactor culture hardware, could give insight into the advantages and/or disadvantages of conditions experienced in microgravity. Studies such as these have the potential to enhance understanding of bone development and adult bone physiology, and may help define the processes of bone demineralization experienced in space and in pathological conditions here on earth. © 1993 Wiley‐Liss, Inc.