bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibitory effects of 1,25(OH)2 vitamin D3 on collagen type I, osteopontin, and osteocalcin gene expression in chicken osteoblasts
Authors: Broess M. , Riva A. , Gerstenfeld L. C. 
Published: May 2005

AbstractSeventeen day chicken embryonic osteoblasts treated over a 30‐day period with 1,25(OH)2 D3 showed a 2–10‐fold decrease in collagen, osteopontin and osteocalcin protein accumulation, alkaline phosphatase enzyme activity, and mineral deposition. Comparable inhibition in the steady state mRNA levels for α1(I) and α2(I) collagen, osteocalcin, and osteopontin were observed, and the inhibitory action of the hormone was shown to be specific for only the late release populations of cells from sequential enzyme digestions of the chick calvaria. In order to determine whether the continuous hormone treatment blocked osteoblast differentiation, the cells were acutely treated for 24 h with 1,25(OH)2 D3 at culture periods when the cells proliferate (day 5), a culture period when the cells cease further cell division and are increasing in the expression of their differentiated functions (day 17), and a culture period when the cells are encapsulated within a mineralized extracellular matrix (day 30). Inhibition of the expression of collagen, osteocalcin, and osteopontin were observed at days 17 and 30, while no effect could be detected for the 5‐day cultures. To further define whether the inhibitory effect was specific for cells expressing their differentiated phenotype, 1,25(OH)2 D3 treatment was initiated at day 17 and continued to day 30 after the cells have established their collagenous matrix. In these experiments further collagenous matrix deposition, mineral deposition, alkaline phosphatase activity, and osteocalcin synthesis were also inhibited after the hormone treatment was initiated. These results, in summary, show that 1,25(OH)2 D3 in primary avian osteoblast cultures derived from 17‐day embryonic calvaria inhibits the expression of several genes associated with differentiated osteoblast function and inhibit extracellular matrix mineral deposition.
Regulation of the adenylyl cyclase signaling system in various types of cultured endothelial cells
Authors: Manolopoulos Vangelis G. , Samet Mark M. , Lelkes Peter I. 
Published: May 2005

AbstractWe studied the effects of modulators of the adenylyl cyclase pathway on the accumulation of cAMP in endothelial cells isolated from bovine aortas, pig pulmonary arteries, human umbilical veins, and human subcutaneous adipose microvessels. In addition to quantitative differences in the basal levels, cAMP stimulation in different endothelial cell types varied in sensitivity and magnitude in response to both the direct adenylyl cyclase activator forskolin and the β‐adrenergic receptor agonist isoproterenol. Furthermore, the ubiquitous phosphodiesterase inhibitor IBMX differentially enhanced both the basal and the stimulated cAMP levels in the various cell types. Histamine caused an elevation of cAMP only in bovine aortic endothelial cells and in human umbilical vein endothelial cells. Treatment of the cells with cholera and pertussis toxins, which uniquely affect G‐protein subunits, resulted in divergent elevation of cAMP in the various cells. Thus, in each cell type, a distinct profile of regulation of the cAMP levels was found. Our results suggest that the adenylyl cyclase signaling system in various types of endothelial cells can be differentially regulated at the levels of receptors, G‐proteins, adenylyl cyclase, and phosphodiesterase.
1,25‐Dihydroxyvitamin D3 or dexamethasone modulate arachidonic acid uptake and distribution into glycerophospholipids by normal adult human osteoblast‐like cells
Authors: Cissel David S. , Birkle Dale L. , Whipkey Diana L. , Blaha J. David , Graeber Geoffrey M. , Keeting Philip E. 
Published: May 2005

AbstractThe effects of treatment with the osteotropic steroids 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3), 17β‐estradiol, or dexamethasone on [1‐14C]arachidonic acid (AA) uptake and distribution into glycerophospholipid classes by normal adult human osteoblast‐like (hOB) cells were investigated. Total uptake of [1‐14C]AA was decreased in cells treated with dexamethasone when assayed after a 24‐, 48‐, or 96‐h exposure to the hormone. Specific radiolabel incorporation into phosphatidylcholine was reduced by a 48‐h treatment with dexamethasone with a concurrent increase in the radiolabeling of phosphatidylethanolamine. However, these changes were transient, and by 96 h of dexamethasone treatment the distribution of the radiolabeled fatty acid had reequilibrated to resemble the pattern found for vehicle treated samples. Total uptake of [1‐14C]AA was diminished by 96‐h treatment with 1,25(OH)2D3 (79 ± 3% of control, P < 0.01); at that time point, a significant decrease in the proportional radiolabeling of the phosphatidylinositol pool was identified (92 ± 2% of control, P < 0.05). The 1,25(OH)2D3‐dependent decrease in total uptake and in phosphatidylinositol incorporation of [1‐14C]AA were found to be hormone dose dependent. Treatment with 24,25(OH)2D3 was without effect on either total [1‐14C]AA uptake or the specific [1‐14C]AA radiolabeling of the phosphatidylinositol pool. 1,25(OH)2D3 treatment decreased hOB cell uptake of [1‐14C]oleic acid and decreased its proportional incorporation into the phosphatidylinositol pool. Gas chromatographic analyses revealed no 1,25(OH)2D3‐dependent effects on total phosphatidylinositol lipid mass or on the mole percent of arachidonic acid within the phosphatidylinositol pool, leaving the mechanism of the effects of the secosteroid on hOB cell AA metabolism unexplained. 17β‐Estradiol had no effects on the parameters of AA metabolism measured. As a consequence of their modulation of arachidonic acid uptake and its distribution into hOB cellular phospholipids, steroids might alter the biological effects of other hormones whose actions include the stimulated production of bioactive AA metabolites, such as prostaglandins or the various lipoxygenase products.
Interleukin‐1β induction of tissue inhibitor of metalloproteinase (TIMP‐1) is functionally antagonized by prostaglandin E2 in human synovial fibroblasts
Authors: Dibattista John A. , Pelletier Jean‐Pierre , Zafarullah Muhammad , Iwata Kazushi , Martel‐Pelletier Johanne 
Published: May 2005

AbstractElevated levels of tissue inhibitor of metalloproteases‐1 (TIMP‐1) have been demonstrated in inflamed synovial membranes, and it is believed that the inhibitor may play a critical role in the regulation of connective tissue degradation. The present study was undertaken to define the cellular mechanism of action of the inflammatory mediators, interleukin‐1β (IL‐1β) and prostaglandin E2 (PGE2), in the control of TIMP‐1 synthesis and expression in human synovial fibroblasts. Recombinant human IL‐1β induced a time‐ and dose‐dependent saturable response in terms of TIMP‐1 mRNA expression (effective concentration for 50% maximal response, EC50 = 31.5 ± 3.3 pg/ml) and protein synthesis (EC50 = 30 ± 3.3 pg/ml). The protein kinase C (PKC) inhibitors, H‐7, staurosporine, and calphostin C, reversed the rhIL‐1β induction of TIMP‐1 mRNA. PGE2 also inhibited rhIL‐1β‐stimulated TIMP‐1 mRNA expression and protein secretion in a dose‐dependent fashion. The concentration of PGE2 necessary to block 50% of rhIL‐1β‐stimulated TIMP‐1 secretion, IC50, was 1.93 ng/ml (4.89 nM). Forskolin, and other stable derivatives of cAMP, mimicked, to a large extent, the effects of PGE2. The phorbol ester, PMA, up‐regulated considerably the mRNA expression of TIMP‐1 but had no effect on protein production. Calphostin C substantially reduced PMA‐activated TIMP‐1 expression. Staurosporine, calphostin C, H‐7, and substances that elevate cellular levels of cAMP, like PGE2, also reduced basal expression and synthesis of TIMP‐1. Taken together, the data suggest that PKA and C may mediate opposing effects in terms of TIMP‐1 expression and secretion in human synovial fibroblasts.
DNA methylation is not involved in the structural alterations of Ornithine Decarboxylase or Total Chromatin of c‐Ha‐rasVal 12 Oncogene‐Transformed NIH‐3T3 Fibroblasts
Authors: Laitinen Jens , Saris Per , Hölttä Erkki 
Published: May 2005

AbstractThe ornithine decarboxylase (odc) gene is an early response gene, whose increased expression and relaxed chromatin structure is closely coupled to neoplastic growth. In various tumour cells, the odc gene displays hypomethylation at the sequences CCGG. Hypomethylation of genes is believed to correlate with chromatin decondensation and gene expression. Since a given pattern of DNA methylation may not be preserved in neoplastic cells, we studied the methylation status of odc gene at the CCGG sequences in c‐Ha‐rasVal 12 oncogene‐transformed NIH‐3T3 fibroblasts during the growth cycle and relative to their normal counterparts. We found that the methylation state of the odc gene and its promoter and mid‐coding and 3' regions remain unaltered during the cell cycle. We also found that in ras oncogene‐transformed cells, which display a more decondensed nucleosomal organization of chromatin than the normal cells, the CCGG sequences in bulk DNA and at the odc gene were methylated to the same extent as in the nontransformed cells. These data suggest that DNA hypomethylation at the CCGG sequences is not a prerequisite for chromatin decondensation and cell transformation by the c‐Ha‐rasVal 12 oncogene.
CCAAT‐box contributions to human thymidine kinase mRNA expression
Authors: Mao Xianzhi , Xia Li , Liang Guodong , Gai Xiaoxia , Huang Dan‐Yang , Prystowsky Michael B. , Lipson Kenneth E. 
Published: May 2005

AbstractIn order to examine the role of two inverted CCAAT boxes near the start of transcription of the human thymidine kinase (TK) gene, a series of constructs were prepared in which one or both CCAAT boxes were deleted or mutated. These altered promoters (1.2 kb of 5'‐flanking sequence) were used to express a TK minigene containing the first two exons and introns followed by the remainder of the cDNA. RNA blots were prepared from stable cell lines of ts13 cells containing these constructs under three conditions: (1) serum deprived cells, (2) serum stimulated cells, and (3) cells that had been stimulated with serum, but were arrested in the G1 phase of the cell cycle by the temperature sensitive mutation carried by these cells. TK mRNA expression from each construct was suppressed by the temperature sensitive block to cell cycle progression. Measurement of protein expression from the various altered TK promoters indicated that both CCAAT boxes contribute to promoter strength. These experiments also suggested that the two CCAAT boxes were not equivalent and that the distal CCAAT could substitute for the proximal CCAAT, but the converse was not true.
Apoptosis and the cell cycle
Authors: Meikrantz William , Schlegel Robert 
Published: May 2005

AbstractIn this review, we consider apoptosis as a process intimately linked to the cell cycle. There are several reasons for thinking of apoptosis as a cell cycle phenomenon. First, within the organism, apoptosis is almost exclusively found in proliferating tissues. Second, artificial manipulation of the cell cycle can either prevent or potentiate apoptosis, depending on the point of arrest. Data from such studies have suggested that molecules acting late in G1 are required for apoptosis. Since passage through late G1 into S phase in mammalian cells is known to be regulated by p53 and by activation of cyclin‐dependent kinases, we also examine recent studies linking these molecules to the apoptotic pathway.
Cell cycle and apoptosis: Common pathways to life and death
Authors: King Karen L. , Cidlowski John A. 
Published: May 2005

AbstractProgrammed cell death, or apoptosis, is a highly regulated process used to eliminate unwanted or damaged cells from multicellular organisms. The morphology of cells undergoing apoptosis is similar to cells undergoing both normal mitosis and an aberrant form of mitosis called mitotic catastrophe. During each of these processes, cells release substrate attachments, lose cell volume, condense their chromatin, and disassemble the nuclear lamina. The morphological similarities among cells undergoing these processes suggest that the underlying biochemical changes also may be related. The susceptibility of cells to apoptosis frequently depends on the differentiation state of the cell. Additionally, cell cycle checkpoints appear to link the cell cycle to apoptosis. Deregulation of the cell cycle components has been shown to induce mitotic catastrophe and also may be involved in triggering apoptosis. Some apoptotic cells express abnormal levels of cell cycle proteins and often contain active Cdc2, the primary kinase active during mitosis. Although cell cycle components may not be involved in all forms of apoptosis, in many instances cell proliferation and cell death may share common pathways.
Cell death: Current difficulties in discriminating apoptosis from necrosis in the context of pathological processes in vivo
Authors: Columbano Amedeo 
Published: May 2005

AbstractThe term apoptosis was proposed to define a type of cell death morphologically, biochemically, and molecularly distinct from necrosis, which plays a fundamental regulatory function in the control of the overall size of cell populations, being complementary but opposite to cell proliferation [Kerr et al. (1972): Br J Cancer 26:239–257]. This view has led to the appreciation that apoptosis is an integral part of normal biological processes and may impact on disease states. Introduction of the concept of apoptosis has raised great interest and many studies have been aimed to the identification of genes responsible for the induction of cell death. Indeed, over the past few years, many genes whose expression is associated with cell death have been described, and the molecular mechanisms underlying cell death have been, in some circumstances, clearly established. However, it is now evident that extension of the conclusions achieved by studies performed with highly selected in vitro systems (simple systems), to in vivo conditions (complex systems), has generated a certain degree of confusion. This is in part due to the indiscriminate use of the term apoptosis and to the uncertainty whether apoptosis is always different from necrosis, and, if this is the case, to the lack of well established criteria to discriminate the two processes; in addition, in addition, it still remains to be established whether both types of cell death, although different, could be induced simultaneously by the same agent, depending on the cell type and the experimental condition used. The distinction between apoptosis and necrosis, is not simply a problem of terminology; if necrosis and apoptosis are different from a mechanistic point of view, and if necrosis is merely the passive result of cellular injury (still to be shown), it becomes critical to discriminate between the two processes, in order to understand how to modulate apoptosis in view of its potential therapeutic use. This review will summarize existing informations and discuss some of the conflicting issues related to cell death in the liver.
Repression of the Lewis fucosyl transferase by retinoic acid increases apical sialosyl Lewisa secretion in colorectal carcinoma cultures
Authors: Liepkalns V. A. , Eboué D. , Beringer T. , Sabri A. , Icard‐Liepkalns C. 
Published: May 2005

AbstractThe rate of polarised secretion of sialosyl Lewisa(19‐9) molecular species (SiaLeams) by SW1116 colorectal carcinoma cells is stimulated at least ninefold by the presence of 3 μM retinoic acid (RA). In order to investigate the intracellular origins of this augmentation, carcinoma cell membranes, membrane subfractions, and media were studied to determine alterations in sialosyl Lewisa levels, oligosaccharide composition, and core structures accompanying the capacity to increase export of this epitope. We observed a nine‐ to twentyfold increase in sialosyl Lewisa epitope levels in a light membrane subfraction from RA‐treated cells. Antigenic molecules of < 200,000 Mr on acrylamide gradient gels were concentrated in two doublets in the apparent Mr range 106,000–152,000 on Western blots. Carbohydrates analyses of oligosaccharides from SiaLeams of membrane subfraction and apical media indicated much higher fucose/mannose, fucose/sialic, fucose/sialosyl Lewisa, fucose/total CHO, and (3H) fucose incorporation in control samples than RA samples. Western blots of samples from membranes subfractions and media indicated that, in contrast to the effect of RA on the sialosyl Lewisa epitope, RA treatment did not augment cysteine‐rich, PDTRP, blood group H‐2, blood group A, and EGF receptor‐like region epitopes in the media. In addition, Northern blots using the Lewis fucosyl transferase (FTIII) cDNA showed a dramatic diminution of mRNA encoding FTIII but apparently unaltered levels of sialyl transferase (ST4) mRNA. Since subterminal fucosylation of lactosyl termini blocks terminal sialylation, we conclude that one mechanism of sialosyl Lewisa induction in this culture system is the lower expression of the Lewis fucosyl transferase mRNA. Therefore less subterminal fucosylation of GlcNAc permits the prior sialylation of terminal Galβ1‐3 moieties at oligosaccharide termini destined for export from the Golgi.
1,25(OH)2D3‐dependent regulation of calbindin‐D28k mRNA requires ongoing protein synthesis in chick duodenal organ culture
Authors: Meyer Julia , Galligan Michael A. , Jones Glenville , Komm Barry S. , Haussler Carol A. , Haussler Mark R. 
Published: May 2005

AbstractOrgan culture of 19‐day‐old chick embryo duodena was utilized to evaluate the mechanism of 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3)‐dependent calbindin‐D28k (CaBP) expression. Duodenal CaBP and 1,25(OH)2D3 receptor (VDR) expression were assessed by Western blot analysis, while CaBP and VDR mRNA levels were determined by Northen blot analysis. In untreated duodena, both VDR protein and mRNA were present, while CaBP protein and mRNA were undetectable. Treatment of cultured duodena with 25 nM 1,25(OH)2D3 resulted in detectable CaBP mRNA after 4 h which continued to increase during a 24 h time period. Under these conditions, localization of [3H‐1β]1α,25(OH)2D3 in duodenal chromatin is rapid (⩽ 30 min). Thus, the delayed accumulation of detectable CaBP mRNA cannot be explained by slow nuclear binding of 1,25(OH)2D3. The inclusion of 1.6 μM actinomycin D in the organ culture partially inhibited the 1,25(OH)2D3‐regulated increase in CaBP mRNA, which implies that there is a transcriptional component involved in the increased CaBP mRNA levels. Similarly, quantitative polymerase chain reaction studies allowed the detection of CaBP pre‐mRNA and mRNA sequences 1 h after hormone treatment, suggesting that CaBP gene transcription is initiated rapidly. Treatment of cultures with 36 μM cycloheximide 1 h prior to 1,25(OH)2D3 addition resulted in superinduction of VDR mRNA levels but sharply reduced CaBP steady‐state mRNA levels. This dramatic reduction in CaBP mRNA reveals that 1,25(OH)2D3‐mediated CaBP expression is dependent on ongoing protein synthesis. Thus, we propose that a labile auxiliary protein or other cofactor, which may or may not be 1,25(OH)2D3‐dependent, is necessary for 1,25(OH)2D3‐mediated CaBP gene transcription in chick duodena.
Induction of heat labile alkaline phosphatase by butyrate in differentiating endometrial cells
Authors: Fleming Honoree , Begley Michael , Campi Thomas , Condon Rebekah , Dobyns Katherine , McDonagh Jonathon , Wallace Stephen 
Published: May 2005

AbstractThe addition of 2mM sodium butyrate to monolayers enhances differentiation of Ishikawa endometrial cells. Cells from this cell line have been shown to enlarge and lift off the dish into dome structure over a period of 24–48 h in response to a factor in fetal bovine serum (FBS) [Fleming, 1995 J Cell Biochem in press]. When butyrate is added to monolayers, together with FBS, three‐ to fourfold higher numbers of differentiated structures, domes and predomes, can be counted. It had previously been shown [Holinka et al., 1986b] that estradiol induces heat stable placental alkaline phosphatese in lshikawa cells. The addition of butyrate, on the other hand, results in a significant increase in levels of a heat labile alkaline phosphatase isozyme. The heat labile isozyme is also increased to some extent in cells stimulated to differentiate in response to FBS in the absence of butyrate. Differential inhibition by homoarginine and phenylalanine indicates that butyrate is inducing the liver‐bone kidney isozyme that is found in endometrial glands in vivo.
Temporal and spatial appearance of α‐dystroglycan in differentiated mouse myoblasts in culture
Authors: Kostrominova Tatiana Y. , Tanzer Marvin L. 
Published: May 2005

AbstractThe dystrophin‐glycoprotein complex plays an important role in muscle function. One of the components of the complex, a 156‐kDa cell surface glycoprotein (α‐dystroglycan) binds to laminin, thereby connecting the basal lamina and muscle cells. We have examined the progressive appearance of α‐dystroglycan and laminin in muscle cells that differentiate in culture. We find that nondifferentiated cultures of C2C12 myoblasts express low amounts of dystroglycan mRNA and, in contrast, this gene is prominently expressed in differentiated myotubes. Immunofluorescence analysis with a monoclonal antibody against α‐dystroglycan shows its progressive appearance during myoblast differentiation into myotubes. Immunostaining with a monoclonal antibody against laminin shows that it is not present on the surface of undifferentiated myoblasts. Subsequently, laminin becomes apparent on the surface of differentiated myotubes where it codistributes with immunostained α‐dystroglycan identifies a broad band of about 140–160 kDa, resembling α‐dystroglycan from rabbit muscle. The composite results indicate that α‐dystroglycan and laminin appear and become co‐distributed on the surface of cultured C2C12 during the progression of differentiation.
Multiphasic modulation of signal transduction into T lymphocytes by monoiodoacetic acid as a sulfhydryl reagent
Authors: Ma Li , Pu Mei‐Yi , Yi Hong , Akhand Anwarul A. , Ohata Naoko , Ohkusu Kozo , Kato Masashi , Iwamoto Takashi , Isobe Ken‐ichi , Hamaguchi Michinari , Nakashima Izumi 
Published: May 2005

AbstractActions of monoiodoacetic acid (MIA) as a sulfhydryl reagent on the different stages of the T cell receptor (TCR)–mediated signal transduction were examined. MIA (1 mM) prevented anti‐TCR (CD3) monoclonal antibody (mAb)–induced energy‐dependent receptor capping but at the same time promoted the anti‐CD3 mAb/mitogen‐induced tyrosine phosphorylation of the T cell activation‐linked cellular proteins of 120, 80, 70, 56, and 40 KDa. Relatively low concentration (0.01 mM) of MIA further promoted anti‐CD3 mAb‐induced transcription of c‐fos, production of IL‐2, and cell surface expression of IL‐2 receptors. The MIA‐promoted TCR‐mediated IL‐2 production actually required signal transduction that could be inhibited by cyclosporin A, genistein, or H‐7. In contrast, the same concentration of MIA as promoted the signal transduction for cell activation severely inhibited the anti‐CD3 mAb‐triggered signal delivery for cell proliferation, selectively at its early stage. We conclude from these results that MIA differentially affects various steps of signaling into T lymphocytes, suggesting that there exist multiple sites of MIA‐sensitive or redox‐linked control in the signal cascade. © 1995 Wiley‐Liss, Inc.