bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of drug resistance in homoharringtonine‐resistant C‐1300 neuroblastoma cells with cyclosporine A and dipyridamole
Authors: Tebbi Cameron K. , Chervinsky David , Baker Raymond M. 
Published: February 2005

AbstractThe development of resistance accounts for therapy failure in the majority of advanced cases of neuroblastoma in children. A new transplantable murine C‐1300 neuroblastoma cell line was developed in vitro, by repeated exposure of a sensitive cell line to increasing, but sublethal, doses of Homoharringtonine (HHT). The ED50 of the highly resistant cells for HHT, using a standard agar colony assay, is 480 ng/ml, compared with 13 ng/ml for the sensitive parental line. The resistant cells have cross‐resistance to a number of other agents, including adriamycin, vinca alkaloids, melphalan, and CCNU. Western blot analysis revealed progressive increases in P‐glycoprotein, parallel to the graded development of resistance with a 29‐fold elevation in the highest resistant cells. High‐performance liquid chromatography (HPLC) indicated that resistant cells have a significantly lower uptake of HHT than parental sensitive cells. Cyclos‐porine A (CsA) and dipyridamole (DPM) could modulate the acquired resistance and completely restore the cytotoxic effects of HHT and adriamycin as determined by the clonogenic assay. The reversal of resistance by CsA and DPM was dose dependent. With the relative low toxicity of dipyridamole and CsA in doses required for modulation of resistance, these agents may be candidates for clinical utilization in chemotherapy of resistant neuroblastoma.
Dietary fish oils modify adipocyte structure and function
Authors: Parrish Christopher C. , Pathy Diane A. , Parkes Joel G. , Angel Aubie 
Published: February 2005

AbstractDietary fish oils, enriched with w‐3 fatty acids (e.g., MaxEPA fish oil), inhibit lipogenesis and have a marked hypotriglyceridemic effect in man and experimental animals. Dietary w‐3 fatty acids also reduce adipose tissue trophic growth in rats. To understand the metabolic basis for this, we measured the effect of fish oil feeding upon rat plasma triglyceride concentration, fat pad mass, fat cell size, fat cell lipolysis, as well as lipoprotein binding to adipocyte plasma membranes. In adolescent (250 g) male Wistar rats fed 20% (w/w) fish oil supplemented diets for 3 weeks, plasma triglyceride levels and epididymal and perirenal fat pad mass were significantly (P<0.005) reduced compared to pair‐fed controls given 20% lard diets. These differences in fat pad mass between the diets were greater than differences in whole animal mass or in the mass of livers, testes, kidneys, spleens, or hearts. Isoproternol‐stimulated lipolvsis was significantly (P < 0.005) higher in fish oil fed rats than in pair‐fed controls. In young (100 g) rats plasma triglyceride levels were 10 times lower in the fish oil fed group after 5 weeks as compared to the lard‐fed controls. This was accompanied by a reduction in epididymal and perirenal fat pad mass as well as a 2‐3‐fold decrease in adipocyte volumes; there was no significant difference between the two groups in fat cell number in each region. Plasma membranes of epididymal adipocytes from fish oil fed rats bound significantly (P < 0.001) less HDL1 than the lard‐fed rats, possibly as a result of a reduction in fat cell size and/or alteration of plasma membrane structure. Thus in both young and old rats, the reduction in plasma triglyceride concentration in conjunction with increased hormone‐stimulated lipolysis may explain in part the selective reduction in adipose tissue trophic growth accompanying fish oil consumption.
Transforming growth factor beta inhibits plasminogen activator (PA) activity and stimulates production of urokinase‐type PA, PA inhibitor‐1 mRNA, and protein in rat osteoblast‐like cells
Authors: Allan Elizabeth H. , Zeheb Ron , Gelehrter Thomas D. , Heaton Joanne H. , Fukumoto Seiji , Yee John A. , Martin T. John 
Published: February 2005

AbstractTransforming growth factor(β)(TGFβ) treatment of rat osteoblast‐rich calvarial cells or of the clonal osteogenic sarcoma cells, UMR 106‐01, resulted in dosedependent inhibition of plasminogen activator (PA) activity, and increased production of 3.2 kb mRNA and protein for PA inhibitor‐1 (PAI‐1). Although tissue‐type PA(tPA) protein was not measured, TGF(β)did not influence production of mRNA for tPA. Production of 2.3 kb mRNA for urokinase‐type PA (uPA) was also increased by TGF(β)in a dose‐dependent manner. The effects of TGFβ on synthesis of mRNA for PAI‐1 and uPA were maintained when protein synthesis was inhibited, and were abolished by inhibition of RNA synthesis. Although uPA had not been detected previously as a product of rat osteoblasts, treatment of lysates of osteoblast‐like cells with plasmin yielded a band of PA activity on reverse fibrin autography, corresponding to a low Mr form of uPA. Untreated conditioned media from normal osteoblasts or UMR 106‐01 cells contained no significant TGFβ activity, but activity could be detected in acidified medium. Treatment of conditioned media with plasmin resulted in activation of approximately 50% of the TGFβ detectable in acidified media. The results identify several effects of TGFβ on the PA‐PA inhibitor system in osteoblasts. Net regulation of tPA activity through the stimulatory actions of several calciotropic hormones and the promotion of PAI‐1 formation by TGFβ could determine the amount of osteoblast‐derived TGFβ activated locally in bone. Stimulation of osteoblast production of mRNA for uPA could reflect effects on the synthesis of sc‐uPA, a precursor for the active form of the enzyme.
Human keratinocyte growth‐promoting activity on the surface of fibroblasts
Authors: Yaeger Peter C. , Stiles Charles D. , Rollins Barrett J. 
Published: February 2005

AbstractTo proliferate in serum‐containing medium, normal human keratinocytes must be co‐cultured with fibroblast feeder cells. Conditioned medium from feeder cell cultures cannot substitute for the cells themselves. We tested the hypothesis that fibroblasts display a keratinocyte growth‐promoting activity on their outer cell surface. The results of our investigation showed that (1) glutaraldehyde‐fixed fibroblast feeder cells promote keratinocyte growth, (2) the growth‐promoting effect requires contact between fixed fibroblasts and keratinocytes, and (3) feeder activity is highly enriched within the plasma membrane fraction of fibroblasts. We conclude that at least part of the fibroblast “feeder” activity involves a keratinocyte growth‐promoting factor which is bound to the outer surface of fibroblast plasma membranes.
Inhibition of phorbol ester‐induced monocytic differentiation by dexamethasone is associated with down‐regulation of c‐fos and c‐jun (AP‐1)
Authors: Hass Ralf , Brach Marion , Kharbanda Surender , Giese Günter , Traub Peter , Kufe Donald 
Published: February 2005

AbstractPrevious studies have shown that treatment of human myeloid leukemia cells with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) is associated with induction of monocytic differentiation and expression of the c‐jun and c‐fos early response genes. The present work demonstrates that the glucocorticoid dexamethasone inhibits TPA‐induced increases in c‐jun and c‐fos mRNA levels in U‐937 leukemia cells. These findings were associated with a block in appearance of the monocytic phenotype, including inhibition of TPA‐induced increases in lamin A, lamin C, and vimentin transcripts. Other studies have demonstrated that TPA‐induced monocytic differentiation and expression of the c‐jun and c‐fos genes in myeloid leukemia cells are regulated by protein kinase C (PKC). The finding that dexamethasone has no effect on TPA‐induced activation of PKC suggests that this glucocorticoid inhibits signals downstream or parallel to this enzyme. Nuclear run‐on assays demonstrate that: (1) induction of c‐jun and c‐fos expression by TPA is regulated by transcriptional mechanisms, (2) TPA‐induced expression of c‐jun and c‐fos does not require protein synthesis, and (3) TPA‐induced expression of both genes is inhibited at the transcriptional level by dexamethasone. To further define the effects of dexamethasone at the molecular level, we prepared a series of deleted c‐jun promoter fragments linked to the chloramphenicol acetyltransferase (CAT) gene. Increases in CAT activity during transient expression of these constructs in TPA‐treated U‐937 cells could be assigned to the region (−97 to −20) of the promoter that contains the AP‐1 binding site. This induction of CAT activity was sensitive to dexamethasone. These findings suggest that dexamethasone down‐regulates TPA‐induced transcription of the c‐jun gene during monocytic differentiation by inhibiting activation of the AP‐1 site.
Enhanced sulfated‐proteoglycan core protein synthesis by incubation of rabbit chondrocytes with recombinant transforming growth factor‐β1
Authors: Malemud Charles J. , Killeen Wendy , Hering Thomas M. , Purchio Anthony F. 
Published: February 2005

AbstractRabbit articular chondrocytes were incubated with recombinant transforming‐growth‐factor‐β 1, (rhTGF‐β1) and its effect on newly synthesized proteoglycan measured. rhTGF‐β1 stimulated proteoglycan synthesis at a concentration as low as 5 ng/ml without further increase in radiosulfate incorporation up to 50 ng/ml. The quantitative increase in radiosulfate incorporation in rh‐TGF‐β1‐treated chondrocytes was greater in the cell‐associated culture compartment than in the medium compartment. rhTGF‐β1 promoted an increased proteoglycan retention in the cell‐associated compartment as evidenced by an increase in the t 1/2 retention from 8 h to 11 h. Specific enhanced synthesis of [35S]‐methionine‐labeled core proteins was seen in rh‐TGF‐β1‐treated chondrocytes. rh‐TGF‐β1 increased the synthesis of the 2 core proteins derived from hydrodynamically large proteoglycans. They possessed apparent molecular weights of > 480 kD and 390 kD after 3‐5% acrylamide gel electrophoresis. A compartmental analysis revealed that the cell‐associated culture compartment contained only the larger of the 2 core proteins derived from large proteoglycans. Two other core proteins with apparent molecular weights 52 kD and 46 kD were also stimulated by rhTGF‐β1. These results indicated that TGF‐β probably plays a significant role in stimulating proteoglycan core protein synthesis in articular chondrocytes and therefore may be an important growth factor in the restoration of cartilage extracellular matrix after injury.
Il‐1β and prostaglandins regulate integrin mRNA expression
Authors: Milam Stephen B. , Magnuson Victoria L. , Steffensen Bjorn , Chen Dali , Klebe Robert J. 
Published: February 2005

AbstractThe purpose of this study was to examine the effects of IL‐1β on integrin expression in MG‐63 human osteosarcoma cells. Human recombinant IL‐1β (rIL‐1β) produced significant increases in both α2‐ and α5‐subunit mRNA levels, as well as a smaller increase in αv‐subunit mRNA. In contrast, IL‐1β decreased α4‐subunit mRNA levels by approximately 30% relative to untreated controls. These findings suggest that human IL‐1β differentially regulates expression of integrins. When cultures were treated with both IL‐1β and the cyclooxygenase inhibitor, indomethacin, the expression of α2‐, α5‐, and αv‐subunit mRNA levels were dramatically increased relative to untreated controls; co‐treatment with 0.5 mM prostaglandin E2 (PGE2) partially reversed this effect. Indomethacin alone did not affect integrin mRNA levels.Treatment with IL‐1β or IL‐1β + indomethacin also induced significant changes in MG‐63 morphology (i.e., increased cell elongation) and increased the ability of cells to contract collagen gels. PGE2 reversed the above effects on cell morphology and gel contraction.These findings indicate that (a) IL‐1β differentially regulates the expression of integrins and (b) that PGE2, which is induced by IL‐1β, may provide a negative feedback loop which counteracts the stimulatory effect of IL‐1β on integrin gene expression. It is suggested that products of inflammation may affect cell behavior by differentially regulating the expression of various integrins.
Differential binding, biological and biochemical actions of recombinant PDGF AA, AB, and BB molecules on connective tissue cells
Authors: Grotendorst Gary R. , Igarashi Atsuyuki , Larson Ronald , Soma Yoshinao , Charette Marc 
Published: February 2005

AbstractWe have compared the biological and biochemical properties of recombinant PDGF AA, AB, and BB using three types of fibroblastic cells: NIH/3T3, human skin fibroblast, and fetal bovine aortic smooth muscle. PDGF binding, receptor autophosphorylation, phosphatidyl inositol hydrolysis, as well as chemotactic and mitogenic responses of the cells were analyzed. PDGF‐AB and PDGF‐BB showed similar receptor binding, receptor autophosphorylation, and potent biological activity for all three of the cell types tested. In contrast, PDGF‐AA was biologically active only for the NIH/3T3 cells in which binding sites for PDGF‐AA were abundant, but was inactive for bovine aortic smooth muscle cells and human skin fibroblasts in which binding sites for PDGF‐AA were absent. PDGF‐AA could not induce any biochemical changes in the human skin fibroblasts or smooth muscle cells. Western blot studies with anti‐Type α and β PDGF receptor antibodies indicate that the NIH/3T3 cells contained both PDGF α and β receptors, whereas the human skin fibroblasts and bovine smooth muscle cells contained only detectable levels of β receptors. These results indicate that cells possessing high levels of PDGF β receptors only are capable of responding equally well to either PDGF AB or BB.
Sphingosine reverses growth inhibition caused by activation of protein kinase c in vascular smooth muscle cells
Authors: Weiss Robert H. , Huang Chou‐Long , Ives Harlan E. 
Published: February 2005

AbstractIn certain cell systems, including neonatal vascular smooth muscle (VSM) cells, phorbol esters are growth inhibitory. Here we show that 1, 2‐dioctanoyl‐snglycerol (DiC8), when added 2 h after α‐thrombin, reverses by 95% the induction of DNA synthesis in VSM cells by α‐thrombin. Sphingosine, a naturally occurring lysosphingolipid inhibitor of protein kinase C, and its synthetic analogues N‐acetylsphingosine and C11‐sphingosine were used to investigate this phenomenon further. Neither phorbol 12‐myristate 13‐acetate (PMA;200 ng/ml) nor sphingosine (up to 10 μM) alone had any effect upon basal DNA synthesis in VSM cells. Like DiC8, PMA totally blocked the induction of DNA synthesis by α‐thrombin. This inhibitory effect of PMA was reversed by sphingosine in a dose‐dependent manner with complete reversal at 10 μM. Neither N‐acetylsphingosine nor C11‐sphingosine exhibited any effect on DNA synthesis in VSM cells. The effect of sphingosine and its analogues on the activity of protein kinase C extracted from VSM cells was measured by histone III‐S phosphorylation. Protein kinase C activity was inhibited 50% by 300 μM sphingosine, but 15% by similar concentrations of N‐acetylsphingosine and C11‐sphingosine. To assess the effects of sphingosine and analogues on protein kinase C in intact cells, we examined the effect of the lipids on [3H]phorbol dibutyrate binding. Sphingosine (at > 5 μM), but not N‐acetylsphingosine or C11‐sphingosine, blocked [3H]phorbol dibutyrate binding in a dose‐ and time‐dependent fashion. Thus the mechanism of growth inhibition by DiC8 and PMA in neonatal VSM cells appears to be through activation of protein kinase C by these compounds. Sphingosine reverses this growth inhibition through interference with the binding to protein kinase C of phorbol esters or other activators of this enzyme.
Regulation of glucose uptake by stressed cells
Authors: Pasternak C. A. , Aiyathurai J. E. J. , Makinde V. , Davies A. , Baldwin S. A. , Konieczko E. M. , Widnell C. C. 
Published: February 2005

AbstractLactate production by BHK cells is stimulated by arsenite, azide, or by infection with Semliki Forest virus (SFV). In the case of arsenite or SFV infection, the increase correlates approximately with the increase in glucose transport as measured by uptake of [3H] deoxy glucose (dGlc); in the case of azide, the increase in lactate production exceeds that of glucose transport. Hence glucose utilization by BHK cells and its stimulation by anaerobic and other types of cellular stress is controlled at least in part at the level of glucose transport. The glucose uptake by BHK cells is also stimulated by serum and by glucose deprivation. In these circumstances, as with arsenite, stimulation is reversible, with t1/2 of 1–2 hours; stimulation is compatible with a translocation of the glucose transporter protein between an intracellular site and the plasma membrane (shown here for serum and previously for arsenite). The surface binding and rate of internalization of [125I]‐labelled tranferrin and [125l] α2‐macroglobulin was studied to determine whether changes in glucose transport are accompanied by changes in the surface concentration or rate of internalization of membrane proteins. The findings indicate that changes in glucose transport do not reflect a consistent and general redistribution of membrane receptors. Taken together, the results are compatible with the proposal that BHK cells exposed to stimuli like insulin or serum, or to stresses like arsenite, azide, SFV infection or deprivation of glucose, respond in the same manner: namely, by an increased capacity to transport glucose brought about by reversible and specific translocation of the transporter protein from an (inactive) intracellular site to the plasma membrane.
Impaired secretion and increased insolubilization of IgE‐receptor complexes in mycophenolic acid‐treated (guanine nucleotide‐depleted) RBL‐2H3 mast cells
Authors: Wilson Bridget Smith , Seagrave Jeanclare , Oliver Janet M. 
Published: February 2005

AbstractIn RBL‐2H3 rat leukemic mast cells, cross‐linking anti‐DNP IgE‐receptor complexes with multivalent antigen (DNP‐BSA) activates a signal transduction pathway leading to Ca2+ influx and secretion. Cross‐linking IgE‐receptor complexes also stimulates a pathway that inactivates (desensitizes) receptors;this pathway becomes important at high concentrations of cross‐linking antigen. Recent evidence that antigen‐induced secretion is impaired by mycophenolic acid (MPA), an inhibitor of guanine nucleotide synthesis de novo, has implicated a GTP‐binding protein (G protein) in the signaling pathway. Other recent studies have indicated that the conversion of cross‐linked receptors to a detergent‐insoluble (cytoskeleton‐associated) form at high antigen concentrations is correlated with the loss of signaling activity. Here we show that secretion elicited by an optimal concentration of antigen (0.05 μg/ml DNP‐BSA) is only inhibited by about 25% in guanine nucleotide‐depleted cells, whereas secretion elicited by 5 μg/ml DNP‐BSA, a concentration in the range that causes the high‐dose inhibition of secretion, is inhibited by more than 60%. We also show that IgE‐receptor complexes are insolubilized in response to 5 but not 0.05 μg/ml DNP‐BSA in both control and guanine nucleotide‐depleted cells. Importantly, the extent of insol‐ubilization elicited by 5 μg/ml DNP‐BSA is increased by more than 60% in the guanine nucleotide‐depleted samples. These results raise the possibility that guanine nucleotide depletion reduces the secretory response to high antigen concentrations in two ways: by inhibiting the G protein‐coupled signaling pathway and by increasing the availability of receptors to the pathway leading to receptor insolubilization and inactivation.
Differential protective effects of O‐phenanthroline and catalase on H2O2‐induced DNA damage and inhibition of protein synthesis in endothelial cells
Authors: Jornot Lan , Petersen Hilke , Junod Alain F. 
Published: February 2005

AbstractThe respective roles of H2O2 and ·OH radicals was assessed from the protective effects of catalase and the iron chelator o‐phenanthroline on (1) the inhibition of protein synthesis, and (2) DNA damage and the related events (activation of the DNA repairing enzyme poly(ADP) ribose polymerase with the associated depletion of NAD and ATP stores) in cultured endothelial cells exposed to the enzyme reaction hypoxanthine‐xanthine oxidase (HX‐XO) or pure H2O2. Catalase added in the extracellular phase completely prevented all of these oxidant‐induced changes. O‐phenanthroline afforded a complete protective effect against DNA strand breakage and the associated activation of the enzyme poly(ADP) ribose polymerase. By contrast, iron chelation was only partially effective in maintaining the cellular NAD and ATP contents, as well as the protein synthetic activity. In addition, the ATP depletion following oxidant injury was much more profound than NAD depletion. These results indicate that: (1) ·OH radical was most likely the ultimate O2 species responsible for DNA damage and activation of poly‐(ADP) ribose polymerase; (2) both H2O2 and ·OH radicals were involved in the other cytotoxic effects (inhibition of protein synthesis and reduction of NAD and ATP stores); and (3) NAD and ATP depletion did not result solely from activation of poly(ADP) ribose polymerase, but other mechanisms are likely to be involved. These observations are also compatible with the existence of a compartmentalized intracellular iron pool.
Divalent cations mimic the inhibitory effect of extracellular ionised calcium on bone resorption by isolated rat osteoclasts: Further evidence for a “calcium receptor”
Authors: Zaidi Mone , Kerby Julie , Huang Christopher L.‐H. , Alam A. S. M. Towhidul , Rathod Hersha , Chambers Timothy J. , Moonga Baljit S. 
Published: February 2005

AbstractOsteoclast activity is thought to be regulated by calcitonin, as well as by the level of ionised calcium generated locally as a result of bone resorption. The exposure of isolated osteoclasts to elevated ambient calcium levels has been shown to lower resorptive activity and to reduce rates of enzyme release. We have attempted to determine whether these effects are mediated by a divalent cation‐sensitive “calcium receptor,” as has been reported for the parathyroid chief cells. Thus, we compared the effect of alkaline earth metal cations on osteoclast function using a morphometric measure of bone resorption and a spectrophotometric method for measuring the activity of the released enzyme, acid phosphatase. The exposure of resorbing osteoclasts to between 5 and 20 mM extracellular ionised calcium ([Ca2+]e) inhibited bone resorption and enzyme release to an extent similar to that seen with 0.1 to 10 μM ionomycin. The effect of combining submaximal concentrations of [Ca2+]e (15 mM) and ionomycin (0.1 μM) resulted in additivity, suggesting that the influence of [Ca2+]e on bone resorption was mediated by elevated intracellular calcium levels ([Ca2+]e). The other cations studied (Mg2+, Ba2+) were effective and elicited similar effects, although some required higher concentrations. Thus, whilst Ca2+ and Mg2+ were effective at 10 to 15 mM levels, Ba2+ was effective only at high (20 mM) concentrations. These findings are consistent with an influence of [Ca2+]e on osteoclast activity through an action on a surface membrane “calcium receptor” that can also bind other divalent cations, rather than by passive changes of [Ca2+]i with [Ca2+]e elevation.