bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variations in vitamin D receptor transcription factor complexes associated with the osteocalcin gene vitamin D responsive element in osteoblasts and osteosarcoma cells
Authors: Shakoori A. R. , van Wijnen A. J. , Bortell R. , Owen T. A. , Stein J. L. , Lian J. B. , Stein G. S. 
Published: May 2005

AbstractVitamin D responsive transcription of the bone‐specific osteocalcin gene differs markedly in osteosarcoma cells and normal diploid osteoblasts. In osteoblasts the osteocalcin gene is transcribed, and upregulated by Vitamin D, only in post‐proliferative cells, but in osteosarcoma cells expression is constitutive. This distinction in transcriptional regulation of the osteocalcin gene correlates with striking differences in the relative representation of two principal Vitamin D‐dependent protein/DNA complexes designated V1 and V2 at the Vitamin D responsive element in the osteocalcin promoter. Formation of both complexes is Vitamin D dependent and they contain the Vitamin D receptor as well as an RXR related protein. Pore size exclusion and sedimentation velocity analyses suggest that the V1 and V2 complexes represent oligomeric protein assemblies (respectively, tetramers and trimers), and reflect primarily DNA‐directed association of the monomeric protein components at the osteocalcin Vitamin D responsive element. UV crosslinking and methylation interference analyses of the V1 and V2 complexes at the osteocalcin Vitamin D responsive element indicate differences in protein/DNA recognition. For example, the V1 complex interacts with both steroid half‐elements, whereas the V2 complex appears to recognize the proximal half‐element. Our findings suggest variations in protein/protein and protein/DNA interactions of the VDR and RXR related complexes V1 and V2 at the osteocalcin Vitamin D responsive element that reflect unique properties of the osteosarcoma and normal diploid osteoblast phenotype. © 1994 Wiley‐Liss, Inc.
Molecular to pharmacologic control of osteoblast proliferation and differentiation
Authors: Siddhanti Suresh R. , Quarles L. Darryl 
Published: May 2005

AbstractControl of osteoblast growth and development can be characterized from receptor mediated events to nuclear messengers controlling gene transcription. From this analysis it is possible to formulate a model to explain the reciprocal relationship between growth and differentiation as well as differential cytokine modulation of osteoblast function. Central to this model are putative tissue specific transcriptional switches (possibly of the bHLH gene superfamily) that may repress proliferation and permit the regulation of mature osteoblast phenotypic characteristics. This model proposes that in post‐mitotic differentiated osteoblasts, tissue specific transcription factors determine the capacity to express osteoblastic characteristic, whereas receptor activated signalling cascades, namely, cAMP/protein kinase A, receptor serine/threonine kinase, and vitamin D receptor‐dependent pathways, regulate mature osteoblast‐specific gene expression. Activated differentiation switches also may feedback to transcriptionally repress proliferation. Conversely, in preosteoblasts, in which differentiation switches are turned off, distinct signalling cascades involving tyrosine kinases, PKC, and calcium/calmodulin regulate proliferation. Proliferating preosteoblasts also exhibit negative modulation of maturation either through inactivation of putative tissue‐specific transcription factors and/or through AP‐1 dependent phenotype suppression of genes expressed in mature osteoblast. Thus, the final outcome of transcriptional regulation of osteoblast function results from complex interactions between signalling pathways and permissive differentiating transcription factors. Though many aspects of this model remain speculative and require confirmation, it serves as a useful conceptual framework to further investigate the differential control of osteoblast proliferation and differentiation that may lead to improved pharmacologic ways to manipulate bone formation in vivo. © 1994 Wiley‐Liss, Inc.
Polypeptide factors regulating osteogenesis and bone marrow repair
Authors: Bab Itai A. , Einhorn Thomas A. 
Published: May 2005

AbstractOsteogenic growth polypeptides regulate bone cell function in vitro and may act in vivo in an autocrine, paracrine, or endocrine manner. Several of these polypeptides are present in the blood in an inactive form. During postablation bone marrow regeneration these factors may be activated, released from the blood clot, and together with locally produced polypeptides mediate the initial intramedullary/systemic osteogenic phase of this process. Then, the same and/or other polypeptides expressed by stromal cells have the potential to promote the second phase of regeneration that consists of osteoclastogenesis, resorption of the transient intramedullary bone, and hemopoiesis. This may be an indirect influence since these polypeptides can regulate the stromal cell expression of some of the hemopoietic factors. Clinically, the osteogenic growth polypeptides that regulate osteogenesis and hemopoiesis have a potential role in osteoporosis therapy, implant bone surgery, and bone marrow transplantation. © 1994 Wiley‐Liss, Inc.
Aberrant gene expression in cultured mammalian bone cells demonstrates an osteoblast defect in osteopetrosis
Authors: Jackson M. E. , Shalhoub V. , Lian J. B. , Stein G. S. , Marks S. C. 
Published: May 2005

AbstractOsteopetrosis is a skeletal condition in which a generalized radioopacity of bone is caused by reduced resorption of bone by osteoclasts. However, it has recently been shown that during skeletal development in several osteopetrotic rat mutations specific aberrations occur in gene expression reflecting the activity of the bone forming cells, osteoblasts, and the development of tissue organization. To evaluate their pathogenetic significance, progressive osteoblast differentiation was studied in vitro. Primary cultures of normal osteoblasts undergo a sequential expression a cell growth and tissue‐related genes associated with development of skeletal tissue. We report that osteoblast cultures can be established from one of these mutants, toothless; that these cells in vitro exhibit similar aberrations in gene expression during cell proliferation and extracellular matrix formation and mineralization observed in vivo; and that an accelerated maturation sequence by mutant osteoblasts mimics the characteristic skeletal sclerosis of this disease. These data are the first direct evidence for an intrinsic osteoblast defect in osteopetrosis and establish an in vitro model for the study of heritable skeletal disorders. © 1994 Wiley‐Liss, Inc.
Expression of dimeric and tetrameric acetylcholinesterase isoforms on the surface of cultured bovine adrenal chromaffin cells
Authors: Michaelson Samantha , Small David H. , Livett Bruce G. 
Published: May 2005

AbstractAcetylcholinesterase is a highly polymorphic enzyme, which can be anchored to the cell surface through several different mechanisms. Dimeric (G2) acetylcholinesterase isoforms are attached by a glycosylphosphatidyl‐inositol (GPI) linkage, whereas tetrameric (G4) forms are linked through a 20 kilodalton hydrophobic subunit. Although cells of haemopoietic origin contain large amounts of G2 GPI‐linked acetylcholinesterase, most tissues express only trace amounts of this isoform. We examined the expression of acetylcholinesterase isoforms in cultured bovine adrenal medullary chromaffin cells. Two major isoforms (G2 and G4) were identified on the cell surface. The G2 isoform, which accounted for approximately half the cell‐surface enzyme activity, was linked to the membrane through a GPI anchor. After treatment with diisopropylfluorophosphate to completely inhibit cellular acetylcholinesterase, the G4 isoform was found to be resynthesised and transported to the cell surface more rapidly than the G2 isoform. As the addition of GPI anchors is known to be a very rapid step, this finding suggested that the G2 and G4 isoforms might be transported to the cell surface by two different mechanisms. This conclusion was supported by results from subcellular fractionation experiments. The ratio of G4/G2 membrane‐bound acetylcholinesterase varied between different subcellular fractions. The membrane‐bound G2 isoform was greatly enriched in a high‐speed “microsomal” fraction. G4 acetylcholinesterase is known to be actively secreted by chromaffin cells in culture. Although the G4 isoform was present on the cell surface, most of the secreted enzyme was derived from an intracellular pool. Thus, it is unlikely that the cell‐surface G4 isoform contributes significantly to the pool of secreted enzyme. Instead, the expression of two different membrane‐bound isoforms may provide a means by which chromaffin cells can target the enzyme to different locations on the cell surface. © 1994 Wiley‐Liss, Inc.
Enhanced phosphoinositide metabolism in colorectal carcinoma cells derived from familial adenomatous polyposis patients
Authors: Homma Miwako K. , Homma Yoshimi , Namba Masayoshi , Yuasa Yasuhito 
Published: May 2005

AbstractThe production of the second messenger molecules diacylglycerol and inositol 1,4,5‐trisphosphate is mediated by activated phosphatidylinositol‐specific phospholipase C (PLC) enzymes. We report the enhancement of the phosphoinositide metabolism pathway in KMS‐4 and KMS‐8 cells, both of which are human colorectal carcinoma cell lines derived from familial adenomatous polyposis patients. In these cells, the cellular contents of diacylglycerol and inositol 1,4,5‐trisphosphate were constitutively increased and the PLC activity in vitro was significantly high, as compared with those in normal colon cells or in other sporadic colorectal carcinoma cells. Northern and Western analyses showed the high expression levels of both PLC‐γ1 and PLC‐δ1 in KMS‐4 and KMS‐8 cells. Moreover, we detected the enhancement of protein–tyrosine kinase activity and tyrosine phosphorylation of PLC‐γ1 in these KMS cells. These results suggest the involvement of activated phosphoinositide signaling pathways in the colorectal tumorigenesis of familial adenomatous polyposis. © 1994 Wiley‐Liss, Inc.
Functional integrity of metallothionein genes in testicular cell lines
Authors: Wang Sue‐Hong , Chen Je‐Hsin , Lin Lih‐Yuan 
Published: May 2005

AbstractThe presence and inducibility of the major cadmium (Cd) chelating protein metallothionein (MT) in testicular cells has been controversial. In this study, the induction and production of MT in testicular cells were studied using mouse Leydig and Sertoli cell lines. Metal accumulation was studied by subjecting the cells to increasing levels of Cd. The presence of transcription factors for MT synthesis was analyzed by transfecting the cells with a reporter gene under the control of the MT promoter. The dose‐ and time‐dependent induction of MT were conducted by Northern analyses. Expression of MT genes occurred in both Leydig and Sertoli cells. To avoid cross hybridization of the MT probe with mRNAs encoding testicular metal binding proteins and to investigate the integrity of MT mRNA, isoMT mRNA identification and primer extension experiments were performed. Those studies show that the induced mRNA indeed encodes MT. The biosynthesis of MT was confirmed by following 35S‐cysteine incorporation into the protein. Finally, cadmium tolerance of testicular cells is compared with that of fibroblast cells. By these studies, we conclude that the MT genes are functional and inducible in testicular cells. © 1994 Wiley‐Liss, Inc.
Transcription factor binding sites in the matrix attachment region (MAR) of the chicken α‐globin gene
Authors: Boulikas Teni 
Published: May 2005

AbstractNuclear matrix is a nuclear protein–DNA superstructure believed to be the exclusive site of DNA replication, transcription, repair, and recombination. The attachment regions of chromatin loops to the nuclear matrix, called MARs, nest origins of replication, have transcriptional enhancer activity, and via their interaction with protein transcription factors may govern gene switch during development and tissue‐specific gene expression. In this study the 967 bp MAR of the chicken α‐globin gene is analyzed for the presence of hexanucleotides from a number (83 in total) of vertebrate protein transcription factors and core origins of replication. A total number of 760 hexanucleotides from factor sites or origins of replication were used for this search. We found that: (1) The occurrence of protein transcription factor binding sites overall on the MAR fragment as well as on the enhancer and promoter regions of other genes is only about 1.2–1.5 times higher than in random DNA, something consistent for all MAR and enhancer sequences examined. However, a high concentration (up to 2.7 times over random sequences) of hexanucleotide factor sites is observed on small stretches of the α‐globin gene MAR. (2) Some regulatory protein binding sites are underrepressented whereas others are overrepresented, giving to an MAR a particular transcription factor flavor. (3) The DNA curvature map of the MAR sequence and the potential sites of positioned nucleosomes suggest the sites where a competition between core histone octamers and protein transcription factors for DNA might be found. This approach might provide a novel technique to diagnose for the regulatory or nonregulatory function of a stretch of DNA. Furthermore, MARs are proposed to constitute important regulatory elements of genes in addition to enhancers, promoters, silencers, locus control regions, and origins of replication. Additional parameters such as interaction of a transcription factor with other transcription factors fixed at vicinal sites, DNA methylation, intrinsic DNA curvature torsional strain, and nucleosome positioning might also determine the high‐affinity binding of a transcription factor to its functional sites and its exclusion from or low affinity binding to other nonregulatory regions. © 1994 Wiley‐Liss, Inc.
Space shuttle flight (STS‐45) of L8 myoblast cells results in the isolation of a nonfusing cell line variant
Authors: Kulesh David A. , Anderson Loraine H. , Wilson Bernard , Otis Ericka J. , Mehm William J. , Elgin Diane M. , Barker Michael J. , Kearney George P. 
Published: May 2005

AbstractMyoblast cell cultures have been widely employed in conventional (1g) studies of biological processes because characteristics of intact muscle can be readily observed in these cultured cells. We decided to investigate the effects of spaceflight on muscle by utilizing a well characterized myoblast cell line (L8 rat myoblasts) as cultured in the recently designed Space Tissue Loss Flight Module “A” (STL‐A). The STL‐A is a “state of the art,” compact, fully contained, automated cell culture apparatus which replaces a single mid‐deck locker on the Space Shuttle. The L8 cells were successfully flown in the STL‐A on the Space Shuttle STS‐45 mission. Upon return to earth, reculturing of these spaceflown L8 cells (L8SF) resulted in their unexpected failure to fuse and differentiate into myotubes. This inability of the L8SF cells to fuse was found to be a permanent phenotypic alteration. Scanning electron microscopic examination of L8SF cells growing at 1g on fibronectin‐coated polypropylene fibers exhibited a strikingly different morphology as compared to control cells. In addition to their failure to fuse into myotubes, L8SF cells also piled up on top of each other. When assayed in fusion‐promoting soft agar, L8SF cells gave rise to substantially more and larger colonies than did either preflight (L8AT) or ground control (L8GC) cells. All data to this point indicate that flying L8 rat myoblasts on the Space Shuttle for a duration of 7–10 d at subconfluent densities results in several permanent phenotypic alterations in these cells. © 1994 Wiley‐Liss, Inc.
Analyzing the metastatic phenotype
Authors: Price Janet E. 
Published: May 2005

AbstractThe dissemination of cells from a primary tumor, resulting in the progressive growth of metastatic carcinoma in distant sites, is the most common cuse of death of cancer patients. The observations from clinical studies and the results of experimental studies using rodent tumors and human cancer cells implanted into immunodeficient host animals suggest that metastasis is not a random event, but rather the result of a sequence of selective events, many of which involve interactions with elements of the microenvironment of the primay and metastatic tumors. Analysis of the metastatic potential of a human tumor cell population has been greatly improved by the introduction of orthotopic models of tumor growth and metastasis, which have demonstrated that implanting human tumor cells into the appropriate tissue in an immunodeficient rodent can increase both tumor take and incidence of metastasis. This will be the models that should be used to validate the identity of candidate metastasis‐associated genes, and determine the value of new forms of therapy, either genetic of pharmacological, for controlling metastatic cancer growth.
Differential effects of retinoic acid and growth factors on osteoblastic markers and CD10/NEP activity in stromal‐derived osteoblasts
Authors: Benayahu D. , Fried A. , Shamay A. , Cunningham N. , Blumberg S. , Wientroub S. 
Published: May 2005

AbstractThe effects of retinoic acid (RA) on the expression of osteoblastic‐related cell makers was examined. A marrow and osteogenic cell line, MBA‐15, was analyzed by Northern blotting for the expression of bone matrix proteins. These cells constituentively express mRNA encoding for procolllagen a2 (1), osteonectin, osteopontin, biglycan and alkaline phosphatase (ALK‐P). Gene expression was unchanged in response to RA triggering for 24hr. Furthermore, cell growth and enzymatic activities of ALK‐P and neutral endopeptidase (CD10/NEP) were studied. These parameters were examined in MBA‐15 and clonal populations representing different stages of differentiation. The cell's growth rate was unchanged, while ALK‐P activity was greatly increased during the culture period under RA treatment in MBA‐15 and in the clonal cell lines examined while CD10/NEP activity dispalyed a different pattern. MBA‐15.4, a presosteoblast cell ine, exhibited an inhibition in CD10/NEP activity at the beginning of the culture period, reaching basal level with time. This activity was greatly increased over control level in MBA‐15.6, a mature stage of osteoblasts. Furthermore, the response of cell lines to various growth factors was tested subsequent to priming the cultures with RA. A synergistic effect was monitored for ALK‐P activity in MBA‐15.4 and MBA‐15.6 cells under rh‐bone morphogenic protein (BMP‐2) and purified osteogenin (BMP‐3), and an antagonist effect was measured when cells were exposed to transforming growth factor β (TGFβ). Contrarily, BMP‐2 and BMP‐3 inhibited the CD10/NEP activity that had remained unchanged following priming of the cell with RA. Insulin‐like growth factor 1 (IGF‐1) and basic fibroblast growth factors (bFGF) did not affect either ALK‐P nor CD10/NEP activities in both cloned cells. Cellular response to bone‐seeking hormone, parathyroid hormone (PTH), and prostaglandin E2 (PGE2) was monitored by activation of intracellular cAMP. Treatment with RA caused a dramatic increase in MBA‐15.6 cell responses to PTH and PGE2 but no significant effects could be observed in other clonal lines.
Tyrosin dephosphorylation and concurrent inactivation of protein kinase FA/GSK‐3α by genistein in A431 cells
Authors: Yu Jau‐Song , Yang Shiaw‐Der 
Published: May 2005

AbstractModulation of protein Kinase F/GSK‐3α by tyrosine phosphorylation in A431 cells was investigated. Kinase F A/GSK‐3α was found to exist in a highly tyrosine‐phosphorylated/activated state in resting cells but could become tyrosine‐dephosphorylated and inactivated down to less than 30% of control values in concentration dependent manner by 50‐400 μM genistein( a Specific tyrosine kinase inhibitor), as demonstrated by metobolic 32p‐labeling of the cells followed by immunoprecipitation and two‐dimensional phosphoamino acid analysis and byimmunodetection in an antikinase FA/GSK‐3α immunoprecipitate kinase assay. Taken together, the results provide evidence that Kinase FA/GSK‐3α may exist in a highly tyrosine‐phosphorylated/activated state in resting cells which can by tyrosine‐dephosphorylated and nactivated by extracellular stimulus and that tyrosine kinase(s) and /or tyrosine phosphatase(s) may play a role in the modulation of kinse FA/GSK‐3α activity in cells.
Triggeps and switches in a self‐assembling pore‐forming portein
Authors: Bayley Hagan 
Published: May 2005

AbstractProtein engineering is being used to produce a collection of pore‐forming proteings with applications in biotechnology. Knowledge provided by investigations of the mechanism of self‐assembly of staphylococcal α‐hemolysin has allowed the desigl of genetically and chemically modified tariants of the protein with pore‐forming activities that can be triggered or switched mn‐and‐off by chemical, biochemical and physical inputs. Examples include α‐hemolysins that are activated by specific proteases and α‐hemolysins whose activity is controlled by divalent metal ions. These proteins have potential value in drug delivery as components of immunotoxils that aan be activated at the surfaces of target aells. Further applications are likely in improved encapsulation techniques for drugs, enzymes and cells.
Biomaterial biotechnology using self‐assembled lipid microstructures
Authors: Rudolph Alan S. 
Published: May 2005

AbstractLipids are a class of molecules which self‐assemble into a variety of phase‐dependent morphologies. We have employed self‐assembled lipid microstructures in the development of a number of biomedical material applications. The blood substitute, liposome encapsulated hemoglobin, is being investigated for the in vivo delivery of hemoglobil without many of the inherent tmxicities associated the delivery of free hemoglobin. This investigation is currently focused on demonstrations of efficacy in stressed animal models and on the safety of adminstering this material in models of sepsis. The synthetic modification of phospholipids to include photopolymerizable moieties such as diacetylenes has resulted in the spontaneous self‐assembly of a hollow micpocylinder which we are investigating fop the controlled release of growth factors in soft tissue regeneration. Self‐assembled mmnolayeps are also being explored for the ability to surface modify biomaterials for improved cell adhesion. Photolithographic techniques have been combined with monolayep deposition to facbriaate coplanar pattern of cell adhesion ald inhibiting moieties. This results in the ability to spatially control the adhesion of cells to biomaterial surface. These cell patterns can form the basis for understanding two‐and theree‐dimensional cellular events on the biomaterial surface and for the fabrication of improved cell‐based biocompatible surfaae. The spmntaneous self‐assembly of lipids to form structures of biotechnological interest presents a unique opportunity to exploit this class of molecules for biomaterial applications.
Applications of ECM analogs in surgery
Authors: Yannas I. V. 
Published: May 2005

AbstractThe loss of tissue mass in human has been conventionally treated as an irreversible change. Treatments have emaphesized repalcement of the missing function by use of a transparent, an autograft, tissue synthesize in vitro or, mst commanly, by use of engineering deviced based on biomaterials. During the last few years solid progress has been made in the area of tissue and organ regeneratioin. This new approach is based on the discovery that certain simple chemiaal analouges of extraculler matpices synthesized by graft copolymerization of a glycosaminoglycan onto type 1 collagen can induced sylthesis of physiologic tissue in lesion which otherwise heal spontaneousely by synthesis of scar host tissue. However, regration in the adult mammal has been sucessfully demonstrated so far only in skin (human, guinea pig), scitic nerve(rat) and the inee menisaus (dog).