bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of variation of normal force on seismic performance of resilient sliding isolation systems in highway bridges
Authors: Iemura Hirokazu , Taghikhany Touraj , Takahashi Yoshikazu , Jain Sarvesh K. 
Published: May 2005

AbstractIn this study, a series of shaking table tests are carried out on scaled models of two seismically isolated highway bridges to investigate the effect of rocking motion and vertical acceleration on seismic performance of resilient sliding isolators. In addition, performance of RSI is compared with system having solely natural rubber bearings. Test results show that variation of normal force on sliders due to rocking effect and vertical acceleration makes no significant difference in response of RSI systems. In addition, analytical response of prototype isolated bridge and the model used in experiments is obtained analytically by using non‐linear model for isolation systems. It is observed that for seismically isolated bridges, dynamic response of full‐scale complex structures can be predicted with acceptable accuracy by experiments using a simple model of the structure. Copyright © 2005 John Wiley & Sons, Ltd.
Nerve growth factor does not activate Na+/H+ exchange in PC12 pheochromocytoma cells
Authors: Chandler Charles E. , Cragoe Edward J. , Glaser Luis 
Published: May 2005

AbstractWe have reexamined the possible role of the Na+/H+ antiport in the cellular response by PC12 pheochromaytoma cells to nerve growth factor (NGF). In contrast to previous reports, we observe no activation of Na+/H+ exchange in these cells, using a very sensitive assay based on the measurement of cytoplasmic pH with dimethylfluorescein dextran (Rothenberg et al., J. Biol Chem., 258: 4883–4809, 1983). Our measurements indicate that the PC12 pheochromacytoma cells, under all conditions tested, show a high rate of Na+/H+ exchange. The discrepancy between these observations and previous experiments could be due to differences in cells in different laboratories, but also to changes in cell adhesion induced by NGF. We describe conditions where intracellular pH and rates of Na+ uptake can be measured reliably in PC12 cells with adequate controls for cell adhesion. We conclude that activation of Na+/H+ exchange is neither sufficient nor required for the differentiation of PC12 cells induced by NGF.
Identification of noncollagenous components of calf lens capsule: Evaluation of their adhesion‐promoting activity
Authors: Cammarata Patrick R. , Spiro Robert G. 
Published: May 2005

AbstractExtraction of calf anterior and posterior lens capsules with 5 M guanidine HCI resulted in the solubilization of protein (12% of total) with a noncollagenous amino acid composition leaving behind the collagen matrix. Polyacrylamide gel electrophoresis of the solubilzed materal revealed a number of components, all of which were susceptible to trypsin but resistant to collagenase digestion. Fractionation of the extracted proteins by Sepharose CL‐6B filtration as well as by affinity chromatography was undertaken, and laminin, fibronectin, entactin, and β‐crystallin were identified by electrophoresis and solid‐phase radiommunoassay in both anterior and posterior capsules. An entactin (Mr = 150,000), which constituted the most prominent component on electrophoresis, was purified after Sepharose CL‐6B filtration by a two‐step lectin affinity chromatography procedure, which was based on the failure of this protein to bind to Bandeiraea simplicifolia I but its positive reactivity with wheat germ lectin. Neither the mixture of proteins extracted from lens capsules by guanidine nor fractions prepared there from were table to enhance lens epithelial cell attachment to type I or type IV collagen‐coated surfaces or to guanidine‐prepared lens capsules; adhesion‐stimulating activity could not be demonstrated even when cycloheximide‐treated cells were employed. Furthermore, the cells were observed to attach as effectively to guanidine extracted as to native capsules. These observations indicate that noncollagenous proteins are not essenital for the in vitro attachment of epithelial cells to lens capsule; it appears that the collagen component itself provides an optimal surface for cell‐basement membrane interaction.
Transformation of mouse bone marrow cells by transfection with a human oncogene related to c‐myc is associated with the endogenous production of macrophage colony stimulating factor 1
Authors: Sklar Marshall D. , Tereba Allan , Chen Ben D.‐M. , Walker William S. 
Published: May 2005

AbstractWe recently derived a series of transformed cell lines by transfecting mouse bone marrow cells highly enriched for macrophage progenitors with a newly described human gene, R‐myc, which has homology to the c‐myc oncogene. In this report, we show that these lines share some features characteristic of cells of the mononuclear phagocyte lineage. Specifically, all cell lines had macrophage‐or monocytelike morphology, contained nonspecific esterase, were phagocytic for latex beads, secreted lysozyme, bore the Mac‐1 antigen, and contained a minority of cells with Fc receptors. However, only a single monocytelike clone had appreciable numbers of cells which bore complement receptor 1, and none were phagocytic for antibody or complementcoated particles, or constitutively secreted Interleukin‐1. All these cell lines secreted a growth factor capable of supporting the in vitro proliferation of bone marrow macrophages. Radiommunoassay and receptor binding studies indicate that this factor is colony stimulating factor 1.
The role of gangliosides in the interaction of a growth inhibitor with mouse lm cells
Authors: Bascom Charles C. , Sharifi Behrooz G. , Melkerson Lyla J. , Rintoul David A. , Johnson Terry C. 
Published: May 2005

AbstractWe have isolated and characterized glycopeptides, derived from mouse and bovine cerebral cortex cells, that inhibit protein synthesis and cell growth of normal but not transformed cells. The inhibitor binds to target cell surfaces, and gangliosides have previously been shown to influence cell sensitivity to the glycopeptides. Preincubation with 3.0 μg/ml ganglioside GM1 at 0°C for 3 hr sensitized the mouse L‐cell line to the inhibitor, as determined by protein synthesis assays. Preincubation of LM cells with ganglioside GM1 alone did not affect protein synthesis rates. In addition, the gangliosides GD1a and GM3 also sensitized the LM cells to the protein synthesis inhibitory effect of the glycopeptide inhibitor. Binding experiments were performed with 3T3 (sensitive) and LM (insensitive) cells to determine if sensitivity to the glycopeptide inhibitor was reflected in binding of the inhibitor to these cells. Binding of 125I‐labeled inhibitor to 3T3 cells was maximal after 60 min at 0°C and saturable at approximately 1 × 104 molecules/cell. Furthermore, binding of the inhibitor was dose‐dependent, with half‐maximal binding at 1.5‐2.0 nM and saturation at 8.0‐10.0 nM. Scatchard plot analysis indicated that the Kd was about 1 × 10−9 M and that there are 1 × 104 receptors/cell. Binding of the inhibitor to LM cells was maximal after 30 min at 0°C and saturation occurred at 5 × 103 molecules/cell. We then examined the possibility that gangliosides are the cellular receptor or co‐receptor for the glycopeptide inhibitor. Binding of the inhibitor to ganglioside GM1 was first examined after the ganglioside had been preadsorbed to polystyrene tubes. These experiments indicated that the ganglioside did not bind the inhibitor. Ganglioside‐containing liposomes from phosphatidylcholine or LM cell membrane components were also prepared; these artificial membranes did not bind appreciable amounts of the iodinated inhibitor. Competition experiments showed that the gangliosides GM1 and GD1a did not neutralize the protein synthesis inhibitory activity of the glycopeptides, indicating that gangliosides do not directly interact with the glycopeptide inhibitor. In addition, binding of the inhibitor to LM cells preincubated with ganglioside GM1 was studied. Although the binding of the inhibitor to LM cells was one‐half that observed for 3T3 cells, incorporation of exogenous gangliosides into LM cells did not result in increased binding of the inhibitor. Therefore, we conclude that the ganglioside‐induced sensitization of LM cells cannot be due to gangliosides serving as the cell‐surface receptor or co‐receptor for the glycopeptide inhibitor.
Growth factor regulation of membrane transport in human fibroblasts and its relationship to stimulation of DNA synthesis
Authors: Tupper Joseph T. , Smith Janet W. 
Published: May 2005

AbstractSerum stimulation of serum‐deprived or density‐inhibited normal cells enhances the level of various nutrient and ionic transport systems. Certain of these systems have been implicated in the regulation of cell proliferation. However, the use of serum stimulation to activate quiescent cells leads to enhancement of numerous transport systems with little understanding of which component or components of serum are related to activation of which transport systems. In this study we attempt to identify the specific effect of three known growth promoting factors (insulin, dexamethasone and epidermal growth factor [EGF]) on the activation of four membrane transport systems (A‐amino acids, L‐amino acids, glucose and K+) in normal and SV40‐transformed WI38 human fibroblasts. We have also evaluted the effect of these growth factors on the stimulation of DNA synthesis in growth factor deprived cells. Thus, we can correlate the effect on a given transport system with the relative mitogenic stimulation produced by the growth factor. We conclude (a) that a growth factor can effect a transport system differently in a normal versus transformed cell, (b) that a specific growth factor can effect multiple transport systems and, (c) with the exception of K+ transport, enhanced transport induced by a given growth factor does not necessarily correlate with the mitogenic potency of the growth factor. This latter point is of particular significance since the activation of K+ transport reflects, based on other studies, activation of the Na+ ‐H+ exchanger which has been implicated in cell‐cycle activation.
Insulin stimulation of glucose transport and metabolism in a human Wilms' tumor‐derived myoblast‐like cell Line: Modulation of hormone effects by glucose deprivation
Authors: Lemmon Sandra K. , Buse Maria G. , Sens Donald A. 
Published: May 2005

AbstractThe effects of insulin and glucose on parameters of metabolism were investigated in myoblast‐like (MBL) cells, a human myoblast‐like cell line derived from a Wilms' tumor. Insulin responses were studied after 4 hr pre‐incubation in serum free media, with or without 5 mM glucose. Insulin was added during the last 2 hr. Glucose starvation markedly increased basal glucose transport (measured as 2‐deoxyglucose uptake) as well as the net uptake of [14C]glucose and [14C]glucose incorporation into glycogen. Insulin stimulated net glucose uptake and incorporation into glycogen in a dose‐dependent manner in glucose‐fed and starved cells. These insulin responses were markedly enhanced in glucose‐starved cells. Insulin accelerated 2‐deoxyglucose transport in glucose‐fed cells but did not further stimulate basal glucose transport in glucose‐deprived cells. Insulin increased the incorporation of [3H]leucine into protein in glucose‐fed or ‐starved MBL cells equally. The dose of insulin required for half‐maximal insulin responses was similar for all parameters studied. Cycloheximide did not prevent the increased basal glucose incorporation in glucose‐starved cells, but markedly inhibited the insulin response, while in glucose‐fed cells, cycloheximide stimulated basal glucose incorporation. We conclude that MBL cells resemble fibroblasts in their insulin‐independent stimulation of glucose transport in response to glucose‐deprivation; when provided with glucose, they respond to insulin like fibroblasts. However, after brief glucose‐starvation, the stimulated glucose transport system is no longer insulin‐responsive in MBL cells, while pathways leading to the synthesis of macromolecules demonstrate preserved or enhanced stimulation by insulin, suggesting that these cells may serve as models to study the regulation of receptor‐response coupling by the metabolic milieu.
Density‐dependent arrest of DNA replication is accompanied by decreased levels of c‐myc mRNA in myogenic but not in differentiation‐defective myoblasts
Authors: Sejersen Thomas , Sümegi Janos , Ringertz Nils R. 
Published: May 2005

AbstractMyoblasts from primary rat cultures and established mouse (Cl10) and rat (L6, Ama 420) cell lines were examined for c‐oncogene expression during exponential growth and under conditions which allowed myogenic differentiation. The abundance of c‐Ki‐ras transcripts in mRNA from confluent, quiescent cultures was reduced to 15–40% of that in mRNA from exponentially growing cells. This reduction was found both in primary myoblast cultures, myoblast lines that formed mytubes (L6 and Cl10) and in a differentiation defective subline (Ama 420). The level of c‐myc transcripts was lowered when myogenic rat L6 myoblasts reached a high cell density, stopped DNA synthesis and formed myotubes. At the same cell density, growth arrested myoblasts of differentiation defective Ama 420 cells maintained a high level of c‐myc expression. This shows that DNA replication and c‐myc expression are independently regulated. All myoblast lines also showed expression of c‐abl during exponential growth phase. Reduced expression was seen in differentiated L6 and Cl10 cultures. No expression was detected when mRNA from multiplying and differentiating myoblasts cultures were probed for c‐myb, c‐erbA, c‐erbB, c‐mos, c‐fes, and c‐src. The observations are consistent with a role for c‐Ki‐ras in myoblast proliferation and suggest that a reduction in c‐myc expression may be a necessary prerequisite for terminal myogenic differentiation.
25‐Hydroxycholesterol‐induced elevations in 45Ca uptake: Permeability changes in P815 cells
Authors: Boissonneault Gilbert A. , Heiniger Hans‐Jörg 
Published: May 2005

AbstractCertain oxysterols are capable of suppressing the activity of 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG CoA) reductase. We have previously demonstrated that treatment of P815 cells with 1 μg 25‐hydroxycholesterol/ml culture results in a rapid influx of 45Ca, and supplemental cholesterol prevents this from occurring. In this paper, we report on investigations into the means whereby this influx of calcium takes place. Through the use of respiratory inhibitors which prevent mitochondrial retention of calcium it was determined that the large increase in slow phase (intracellular) calcium uptake caused by 25‐hydroxycholesterol treatment was related to mitochrondrial uptake. The effects of various inhibitors of calcium uptake into cells, including verapamil, diltiazem, quinidine, ruthenium red, Co++, Mn++, were tested. Of these only Co++ and ruthenium red had any effect on 45Ca uptake. 25‐Hydroxycholesterol has been shown to be capable of membrane insertion and this could result in plasma membrane permeability changes. To test this hypothesis P815 cells were treated with 1 μg 25‐hydroxycholesterol/ml or 5 μg mevinolin/ml culture. Mevinolin, being a water soluble competitive inhibitor of HMG‐CoA reductase, should be unable to disrupt membrane architecture in a manner analogous to 25‐hydroxycholesterol. While both inhibitors rapidly supressed the synthesis of digitonin‐precipitable sterols, only 25‐hydroxycholesterol was able to increase 45Ca influx. The implications of these findings are discussed.
Characterization of protein kinase C activity in interferon gamma treated murine peritoneal macrophages
Authors: Becton David L. , Adams Dolph O. , Hamilton Thomas A. 
Published: May 2005

AbstractMacrophage activation for tumoricidal and microbicidal functions can be achieved in part by treatment with recombinant interferon gamma (IFNγ) in vitro. We have previously demonstrated that IFNγ treatment of murine peritoneal macrophages results in a two‐ to five‐fold increase in the activity of Ca++, phospholipid dependent protein kinase C (Hamilton et al., J. Biol. Chem., 260: 1378, 1985). We now report that this effect was not dependent upon continuing protein synthesis since treatment with cycloheximide under conditions where normal protein synthesis was inhibited by greater than 95% had no effect upon the development of increased enzyme activity. Examination of Ca++ and phospholipid requirements revealed no differences between enzyme isolated from control or IFNγ‐treated cells could not be distinguished in terms of the diacyglycerol (DG) or phorbol diester (PMA) concentration required for stimulation of activity. Kinetic analysis of the ATP (as substrate)concentration dependence revealed that both control and treated enzyme preparations (either basal or stimulated) had comparable Km values. Maximum velocity (Vmax) was increased both by IFNγ treatment and also by stimulation with DG or PMA. The major difference which could be discerned between protein kinase C derived from control versus IFNγ‐treated macro‐phages was the magnitude of the response to DG or PMA; IFNγ treatment increased the stimulation index (i.e., ratio of basal to stimulated activity) by a factor of two to four fold. These results suggest that IFNγ treatment leads to reversible modulation of existing protein kinase C resulting in increased catalytic efficiency when exposed to an appropriate stimulant.
Effect of age and dietary restriction on protein synthesis by isolated kidney cells
Authors: Ricketts Wilbert G. , Birchenall‐Sparks Maria C. , Hardwick James P. , Richardson Arlan 
Published: May 2005

AbstractThe influence of age and food restriction on kidney protein synthesis was studied in Fischer F344 rats. The rate of total protein synthesis by suspensions of kiney cells declined 60% between 4 and 31 months of age. The rate of protein synthesis by kidney cells isolated from 19‐month old rats fed a restricted diet (60% of diet consumed by rats fed ad libitum) was 45% higher than the rate of protein synthesis by kidney cells isolated from 19‐month old rats fed ad libitum. The excretion of protein in the urine was measured to assess the effect of the age related decline in protein synthesis on kidney function. A dramatic increase in proteinuria was observed with increasing age, and rats fed the restricted diet excreted significantly less protein in the urine than rats fed ad libitum.
Characterization of permeation pathways in the plasma membrane of human erythrocytes infected with early stages of Plasmodium falciparum: Association with parasite development
Authors: Kutner S. , Breuer W. V. , Ginsbururg H. , Aley S. B. , Cabantchik Z. I. 
Published: May 2005

AbstractHuman intraerythrocytic malarial parasites (Plasmodium falciparum) induce permeability changes in the membrane of their host cells. The differential permeability of infected erythrocytes at various stages of parastie growth, in combination with density gradient centrifugation, was used to fractionate parasitized cells according to their developmental stage. By this method it was possible to obtain cell fractions consisting essentially of erythrocytes infected with the youngest parasite stage (i.e., rings). These preparations were used for the measurement of transport of various solutes. It is shown that permeabilization of host erythrocyte membrane appers as early as 6 h after parasite invasion of the erythrocyte and increases gradually with parasite maturation. Since the selectivity for several different solutes and the enthalpy of activation of transport remain unaltered with maturation‐related increase of permeability, it is concluded that the number of transport agencies in the host cell membrane increases with parasite maturation. Evidence is presented to indicate the need for parasite protein synthesis as an essential factor for the generation of the new permeability pathways.
LLC‐PK1 cysts: A model for the study of epithelial polarity
Authors: Wohlwend Annelise , Montesano Roberto , Vassalli Jean‐Dominique , Orci Lelio 
Published: May 2005

AbstractIn the present work, we have taken advantage of the properties of two recently isolated clonal subpopulations of the pig kidney‐derived LLC‐PK1 cell line to study aspects of the establishment of epithelial polarity. When grown in suspension, LLC‐PK1/D + Sc cells reaggregated within a few hours and, during the following days of culture, formed free‐floating, hollow spheres or cysts, lined by a monolayer of polarized cells. In contrast, LLC‐PK1/D ‐ cells were unable to develop such polarized structures even upon prolonged culture in suspension. The polarity of the LLC‐PK1/D + Sc cells lining the cysts was inverted compared to that in intact renal tubules, the microvilli‐rich “apical” pole being oriented toward the external medium. However, upon embedding these preformed cysts in collagen gels, a reversal of polarity was observed within hours, the microvilli‐rich pole now facing the cyst cavity. Thus, in the same clonally derived cell population, cell‐to‐cell contact and interaction with the extracellular matrix differentially affect the orientation of cellular polarity. The LLC‐PK1/D + Sc cysts provide a suitable in vitro model system for further study of the sequential events by which extracellular matrix components induce an appropriately oriented polarization. In addition, the comparison between LLC‐PK1/D + Sc and D ‐ cells, which differ in their ability to polarize in response to cell‐to‐cell contact, should help define some of the cellular determinants involved in epithelial organization.
Separation of murine megakaryocytes and their progenitors on continuous gradients of percoll
Authors: Ishibashi Toshiyuki , Burstein Samuel A. 
Published: May 2005

AbstractMurine bone marrow was separated on continuous Percoll density gradients to analyze the distribution of cells of the megakaryocyte lineage. Eighty‐seven percent of the recovered megakaryocytes were found in fractions of density less than 1.058 g/cm3, with 63% of these cells found between 1.020 and 1.036 g/cm3. When megakaryocytes were classified according to size, 92% of the large ( ≥ 18 μm) acetylcholinesterase (AchE) positive cells were found in the least dense fractions (1.016–1.039 g/cm3), whereas 86% of the small (⩽ 10.6 μm) AchE positive cells were found in fractions of higher density (1.039‐‐1.078 g/cm3). The distribution of enzymatic AchE activity of the separated fractions corresponded to the location of the histochemically positive cells. When ploidy measurements were made of various fractions, most of the high ploidy (32N and 64N) cells were found at low density (1.028–1.036 g/cm3), whereas no cells greater than 4N were found at density > 1.071 g/cm3. Thus, large AchE positive cells and the cells of highest ploidy were found at lower densities of Percoll, while small AchE positive cells and cells of low ploidy were found at higher densities. An exception to this inverse relationship was found in fractions of lowest density ( > 1.030 g/cm3) where an anomalous distribution of size and ploidy was found. The majority of megakaryocytic colony‐forming cells (CFU‐MK) were found at high density, as were the granulocyte‐macro‐phage colony‐forming cells (CFU‐GM; ∼ 1.074 g/cm3). The density distribution of the incorporation of tritiated thymidine into liquid marrow cultures was concordant with the high density distribution of colony‐forming cells. The data show that megakaryocytic maturity and Percoll density varies inversely and that fractionation of marrow on continuous Percoll gradients may be a useful method for the separation and/or enrichment of megakaryocytes at different stages of differentiation.