bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adenosine induction of rapid catabolism of adenine ribonucleotides and independent elevation of the ATP content in quiescent mouse fibroblasts
Authors: Klenow Hans , Østergaard Erik 
Published: February 2005

AbstractThe influence of adenosine on the ribonucleotide metabolism in quiescent BALB/c 3T3 cells was studied. The cellular adenine ribonucleotides were labelled by pretreating the cells with [2−3H]‐adenine. After addition of adenosine to the cell cultures, the amount and radioactivity of the cellular purine ribonucleotides and the radioactivity of the purine compounds in the medium were determined. It appeared that adenosine gave rise both to rapid catabolism of adenine ribonucleotides with inosine 5′‐monophosphate (IMP) as an intermediate and to expansion of the cellular adenosine 5′‐triphosphate (ATP) pool. The maximal rates and the apparent activation constants for the two processes have been determined. Experiments with varying concentrations of coformycin (an inhibitor of adenosine 5′‐monophosphate [AMP] deaminase and adenosine deaminase) and of 5′‐amino‐5′‐deoxyadenosine (an inhibitor of adenosine kinase), respectively, showed that each compound may almost completely inhibit the adenosine‐induced catabolism. This effect can be obtained under conditions where there was little or no effect by the two inhibitors on the rate of expansion of the cellular ATP pool. These results may best be explained by assuming that the process of expansion of the ATP pool is independent of the induced catabolism of adenine ribonucleotides, even though both processes seem to depend on the phosphorylation of adenosine to AMP. The total increase in the pool size of ATP and of guanosine 5′‐triphosphate (GTP), both caused by adenosine, seems not to have regulatory effect on adenine ribonucleotide catabolism.
Ethanolamine and choline transport in cultured bovine aortic endothelial cells
Authors: Lipton Beth A. , Yorek Mark A. , Ginsberg Barry H. 
Published: February 2005

AbstractThe transport of the polar head groups, ethanolamine and choline, was examined in cultured bovine aortic endothelial cells. Both ethanolamine and choline are taken up by high‐ and low‐affinity systems. The K'm and V'max for the Na+‐dependent, high‐affinity ethanolamine and choline transport system are 3.0 and 3.0 μM and 5.4 and 7.3 pmol/mg protein/min, respectively. Ethanolamine and choline competitively influence one another's transport as the presence of 50 μM ethanolamine increases the K'm but not the V'max of choline uptake. Likewise, 50 μM choline increases the K'm but not the V'max of ethanolamine transport. The concentration of ethanolamine that inhibits maximal velocity of 5 μM choline by 50% is 9.7 μM, while 12 μM choline inhibits 5 μM ethanolamine maximal velocity by 50%. Uptake of both head groups is only partially Na+‐dependent and is inhibited similarly by 2‐methylethanolamine and 2,2‐dimethyl‐ethanolamine at all concentrations examined. Hemicholinium‐3, a classic inhibitor of high‐affinity, Na+‐dependent choline transport, reduces both ethanolamine and choline accumulation in a concentration‐dependent fashion, but has a greater effect on choline transport at higher concentrations. The major portion of these data is consistent with our hypothesis that the uptake of physiological concentrations of ethanolamine and choline may occur through the same transport system. However, the results of the effect of hemicholinium‐3 and the extent of Na+‐dependency of choline and ethanolamine uptake could be interpreted as meaning that separate transport systems for choline and ethanolamine exist which cross react or that a single transport system exists which has separate active sites for the two compounds.
Cachectin/TNF kills or inhibits the differentiation of 3T3‐L1 cells according to developmental stage
Authors: Kawakami Masanobu , Watanabe Nobumasa , Ogawa Hiroko , Kato Arata , Sando Hiroyuki , Yamada Nobuhiro , Murase Toshio , Takaku Fumimaro , Shibata Seiichi , Oda Toshitsugu 
Published: February 2005

AbstractThe effects of cachectin/tumor necrosis factor (TNF) on growth and differentiation of 3T3‐L1 cells were examined. This fibroblastic cell line can be induced to differentiate into a mature cell type having the biochemical and morphological characteristics of normal adipocytes. At various stages of growth and differentiation, 3T3‐L1 cells were exposed to 2.5 × 10−16 to 2.5 × 10−8 M (4.2 fg/ml to 420 ng/ml = ca. 1.2 × 10−14 to 1.2 × 10−6 U/ml) recombinant human cachectin/TNF for 24 hr, after which cytotoxicity or differentiation was evaluated. During log‐phase cell growth, cachectin/TNF had no significant effect on cell viability, and the preadipocytic cells were also resistant to the cytotoxic effect of cachectin/TNF at the contact‐inhibited confluent stage. However, when cachectin/TNF was added to the cells during induced differentiation, only 20% of the cells survived. After differentiation into adipocytes, cells regained their resistance to cachectin/TNF‐induced cytotoxicity. Cachectin/TNF also markedly affected the differentiation of 3T3‐L1 cells into adipocytes. When cells in the confluent phase of growth were exposed to cachectin/TNF for 24 hr, their subsequent hormone‐induced differentiation to adipocytes was inhibited. Like cachectin/TNF, IL‐1 also induces suppression of lipoprotein lipase and enhances lipolysis in differentiated 3T3‐L1 adipocytes; however, in contrast to cachectin/TNF, IL‐1 had no effect on the viability or differentiation of pre‐adipocyte 3T3‐L1 cells. These results indicate that the cytotoxic action of cachectin/TNF varies in the same cell type depending on the stage of growth or differentiation. The results also imply that cachectin/TNF may play a normal role in controlling the differentiation of certain types of cells in vivo including adipocyte lineages.
Stochastic model for mast cell proliferation in culture of murine peritoneal cells
Authors: Kobayashi Toshimi , Nakahata Tatsutoshi 
Published: February 2005

AbstractWe recently identified two types of mast cell colonies derived from murine peritoneal cells: type 1 and type 2. Type 1 mast cell colonies consisted of berberine sulfate(+)‐ safranin(+) connective tissue‐type mast cells (CTMC) and were derived from mature CTMC in the heaviest fraction obtained by Percoll density gradient centrifugation. In contrast, type 2 mast cell colonies consisted of alcian blue(+)‐ berberine sulfate(−)‐ safranin(−) mucosal mast cells (MMC) and were derived from immature progenitors in low density fractions. We replated a total of 60 type 1 and 60 type 2 mast cell colonies and examined their capability for producing secondary colonies. Although all of the primary colonies yielded secondary colonies, the replating efficiencies of individual colonies varied over a wide range.Cumulative distributions of secondary colonies from both type 1 and type 2 primary colonies could be fitted well by gamma distributions obtained by computer simulation. These findings are in agreement with the stochastic model for CTMC‐ and MMC proliferation. Cytological analyses of secondary colonies from primary type 1 colonies revealed heterogeneous distributions of alcian blue(+)‐ safranin(−)‐ berberine sulfate(−) mast cells, suggesting that transdifferentiation from mature CTMC to safranin(−)‐ berberine sulfate(−) mast cells is also governed by stochastic mechanisms.
Plasma membrane lipid organization and the adherence of differentiating lymphocytes to macrophages
Authors: Del Buono Brian J. , White Scott M. , Williamson Patrick L. , Schlegel Robert A. 
Published: February 2005

AbstractChanges in the packing of phospholipids in the plasma membrane of lymphocytes occur during differentiation within primary and secondary lymphoid organs. As they differentiate, lymphocytes interact with a variety of reticuloendothelial cells, including macrophages. To investigate a possible relation between these two phenomena, the strength of the interactions between lymphocytes and macrophages was measured in vitro as a function of the tightness of packing of phospholipids on the lymphocyte surface. Strength of adherence was measured by the ability of lymphocytes to remain adherent to macrophages when subjected to increasing centrifugal forces. Phospholipid packing was assessed using the fluorescent lipophilic probe merocyanine 540 (MC540), which preferentially binds to bilayers in which the lipids are more loosely packed. Three subpopulations of murine thymocytes were resolved with respect to strength of adherence to peritoneal or thymic macrophages. To determine whether these subpopulations corresponded with the three classes of cells distinguishable by MC540 fluorescence, populations enriched for staining or non‐staining cells, and cells sorted on the basis of MC540 fluorescence intensity, were examined. The least fluorescent cells were the least strongly adherent; the most fluorescent cells were the most strongly adherent; and cells of intermediate fluorescence had intermediate adherence. When splenic lymphocytes were examined with respect to adherence to peritoneal or splenic macrophages, similar patterns of fluorescence and adherence were seen. These results suggest that the organization of the plasma membrane lipid bilayer of lymphocytes may be involved in their interactions with macrophages during primary and secondary differentiation. The adherence signal for lymphocytes thus may be similar to that proposed for other blood cells.
Modulation of growth factor induced fiber outgrowth in rat pheochromocytoma (PC12) cells by a fibronectin receptor antibody
Authors: Schwarz Martin A. , Brown Patricia J. , Eveleth David D. , Bradshaw Ralph A. 
Published: February 2005

AbstractRat pheochromocytoma PC12 cells respond to the binding of nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) by extending neurites in a manner resembling sympathetic neurons. This response requires cell attachment to an appropriate substratum (Fujii et al., J. Neurosci., 2:1157, 1982); attachment factors which function in this capacity include the adhesive proteins fibronectin and laminin. Incubating PC12 cells with a ployclonal antiserum directed against a putative 140‐kDa fibroblast cell surface fibronectin receptor (anti‐gp140) perturbed spreading but not attachment of the cells to fibronectin and laminin substrates. However, in the presence of anti‐gp 140 or its Fab fragments, NGF‐stimulated neurite outgrowth was dramatically reduced. The antibody also caused a retraction of previously extended neurites. SDS‐PAGE analysis of immunoprecipitates of PC12 cells surface labeled with 125I identified a prominent 120–140‐kDa band, suggesting that the site of anti‐gp 140 action in PC12 cells is also through a fibronectin receptor.
Involvement of rRNA synthesis in the enhanced survival and recovery of protein synthesis seen in thermotolerance
Authors: Black Adrian R. , Subjeck John R. 
Published: February 2005

AbstractAlthough acquired thermotolerance has been linked to the induction of heat shock proteins, the molecular mechanism(s) by which cells become resistant to heat is unknown. The present study shows a strong correlation between the survival of cells following heat shock and the rate of recovery of protein, total KNA, and rRNA synthesis. Increasing exposure of CHO cells to 45°C was found to decrease survival and cause a lengthening delay in these synthetic processes. The same reciprocal correlation was seen in thermotolerant cells. As thermotol‐erance develops, more cells survive a heat challenge and the delay in synthesis decreases. These data argue that enhanced recovery of protein and RNA synthesis is one factor which plays a key role in thermotolerance.The involvement of rRNA synthesis was further investigated by using actinomy‐cin D at 0.1 μg ml−1, a concentration at which rRNA synthesis is selectively inhibited. When the drug was present during the recovery from a challenge heat treatment, the survival of thermotolerant cells was 3‐fold lower than expected from the mild toxicity of the drug. As this could not be accounted for by an interaction of the drug with the response of cells to single heat treatments, it is concluded that the drug inhibits the expression of thermotolerance in cells which would otherwise express a full degree of thermotolerance. The time and concentration dependence of this effect indicates that the drug acts though inhibition of rRNA synthesis. Therefore, enhanced recovery of RNA synthesis, presumably rRNA synthesis, is identified as one of the mechanisms responsible for enhanced survival of thermotolerant cell following heat shock.
Continuous maintenance of transformed fibroblasts under reduced serum conditions: Utility as a model system for investigating growth factor‐specific effects in nonquiescent cells
Authors: Mulder Kathleen M. , Brattain Michael G. 
Published: February 2005

AbstractWe report the continuous growth maintenance of untransformed and chemically transformed fibroblasts (AKR‐2B, AKR‐MCA cells) in low concentrations of serum (0.1% FBS). The cell lines established (AKR‐0.1F, MCA‐0.1F) proliferated at rates comparable to cells maintained under high serum conditions (10% FBS). Complete removal of serum from the cells did not induce quiescence. The MCA‐0.1F cells were more similar to the untransformed AKR‐2B fibroblasts in their morphology, saturation density, inability to form colonies under anchorage‐independent conditions, steady‐state level of c‐myc expression, and kinetics of induction of c‐myc in response to specific growth factors. This report demonstrates the utility of this cell line as anonquiescent model system for investigating growth factor‐specific effects in serum‐free, cycling cells. Addition of transforming growth factor‐β (TGF‐β) (5 ng/ml) to proliferating MCA‐0.IF cells, in the absence of any serum, induced a multilayered growth pattern at confluency, similar to that of AKR‐MCA cells maintained in 10% FBS. Other growth factors tested did not elicit this effect. The induction of this growth pattern by TGF‐β was associated with a sustained induction of the c‐myc proto‐oncogene at con‐fluency, but not with a restoration of anchorage‐independent growth. The data suggest that TGF‐β may play a role in the up‐regulation of c‐myc at confluency previously described for AKR‐MCA cells maintained in 10% serum.
Effects of N,N‐dimethylformamide and extracellular matrix on transforming growth factor‐β binding to a human colon carcinoma cell line
Authors: Levine Alan E. , Black Bradley , Brattain Michael G. 
Published: February 2005

AbstractAlterations in the binding of transforming growth factor‐β (TGF‐β) to the MOSER human colon carcinoma cell line caused by N, N‐dimethylformamide (DMF) or extracellular matrix (ECM) were examined. DMF induced a more differentiated phenotype in the MOSER cells and resulted in a twofold increase in TGF‐β binding to the cells. This was due to an increase in receptor number with no significant alteration in the KD. The extent of increased TGF‐β binding was dependent on the dose and time of exposure to DMF. Upon removal of DMF, the receptor level returned to that of untreated cells within 6 hr. The binding of TGF‐β1 and TGF‐β2 to the cells was increased equally. Despite this increase in TGF‐β binding in the presence of DMF, the sensitivity of the MOSER cells to the growth inhibitory effects of TGF‐β was unaltered. Growth of the MOSER cells on ECM derived from a well‐differentiated colon cell line increased the TGF‐β receptor number twofold without altering the KD. No change was observed if the MOSER cells were grown on ECM derived from a poorly differentiated cell line. While no alteration in sensitivity to TGF‐β was observed on cells grown in the presence of DMF, MOSER cells grown on the ECM derived from well‐differentiated colon carcinoma cell lines were twofold more sensitive to the growth inhibitory effects of TGF‐β. These results indicated that growth conditions which resulted in a more differentiated phenotype resulted in an increase in the cellular receptors for TGF‐β.
Stimulation by parathyroid hormone of calcium absorption in confluent Madin‐Darby canine kidney cells
Authors: Kennedy Susan M. , Flanagan Joyce L. , Mills John W. , Friedman Peter A. 
Published: February 2005

AbstractParathyroid hormone (PTH) increases renal calcium absorption exclusively in cortical thick limbs and distal tubules. Lack of sufficient tissue has precluded detalled biochemical study of the mechanisms responsible for the hypercalcemic effect of PTH. Therefore, we assessed PTH action on calcium transport in Madin‐Darby canine kidney (MDCK) cells, a cell line expressing distal characteristics, to determine its suitability as a model for analyzing PTH action. Calcium transport across MDCK cells grown to confluence on porous filters was measured at 37°C in Ussing chambers. Mucosal‐to‐serosal calcium fluxes (JCa, mol/min cm−2 × 10−9) were measured with 45Ca at −3, −1, 5, 10, and 20 min; agonist was added at 0 min. Basal JCa averaged 0.98. PTH at 0.2 μM increased JCa by 12% (P 0.05) and 1 μM PTH by 70% (P0.01). Calcitonin (1 μM) had no effect on JCa. The fact that high concentrations of dibutyryl cAMP (1 mM) and forskolin (10 μM) increased JCa by only 37% and 22%, respectively, suggested that cAMP‐independent mechanisms may participate in PTH‐stimulated JCa. Therefore we examined the effect of other putative second messengers. In the presence of 2 mM external [Ca], 10 nM A23187 increased JCa by 88%, and 10 μM A23187 increased JCa by 121%. Addition of 10 μM phorbol 12‐myristate 13‐acetate (PMA) increased JCa by 60%. We conclude that: (1) PTH specifically stimulates unidirectional calcium absorption in MDCK cells; (2) both adenylate cyclasecoupled and calcium‐coupled receptors may participate in signaling the response to PTH; and (3) confluent MDCK cells represent a useful experimental model for elucidating the biochemical mechanisms involved in the renal hypercalcemic action of PTH.
Dimethylsulfoxide modifies the sensitivity of BALB/c‐3T3 cells to the activation of Na+/H+ exchange by phorbol esters
Authors: Martinez Raul , Gillies Robert J. 
Published: February 2005

AbstractIn a companion paper (Gillies et al.: J. Cell. Physiol. 139:124–129, 1989) we show that phorbol esters (PEs) are unable to stimulate Na+/H+ exchange in BALB/C‐3T3 cells under a wide variety of conditions. The Na+/H+ exchangers of a number other cell types are also not responsive to PEs yet have been rendered responsive by treatment with agents such as dimethylsulfoxide (DMSO). We undertook the present study to evaluate whether or not the treatment of BALB/c‐3T3 cells with DMSO will induce modifications in the sensitivity of these cells to activation by PEs. The present study indicates that a 3–5 day exposure of BALB/c‐3T3 cells to 1.25% DMSO leads to changes in the sensitivity of these cells to the activation of Na+/H+ exchanger by PEs. These changes in sensitivity were apparent at day 3 and maximal at day 5. Non‐tumor‐promoting analogues of PEs do not activate Na+/H+ exchange, suggesting that the effect is mediated through kinase C. Sphingosine prevents PE‐, but not serum‐induced alkalinization. However, the half‐time of the intracellular pH (pHin) response to serum was increased by sphingosine, suggesting that kinase C participates in, but is not required for the serum induced activation. Since DMSO does not induce any apparent morphological change, the change in sensitivity of Na+/H+ exchange to PEs is not likely to be related to differentiation, but may be associated with structural changes in the Na+/H+ exchanger and/or changes in isoforms of kinase C which recognize the exchanger as a substrate.
Expression of asparagine independence in variants of ICR 2A haploid frog cells
Authors: Hepfer Carol Ely , Little Wayne A. , Hengst Jamie A. , Freed Jerome J. 
Published: February 2005

AbstractProperties of the change from asparagine dependence (asn‐) to independence (asn+) were investigated in the androgenetic haploid frog cell line ICR 2A. Two types of asn+ variants arose spontaneously during culture. Glutamine‐dependent asparagine synthetase (AS) activity, found to be deficient in asn‐ cells, was repressed by asparagine in one type of variant and expressed constitutively in the other. No quantitative differences in AS‐specific DNA sequences or changes in ploidy were evident between asn+ and asn− cells. The asn‐ frequency in ICR 2A populations, not dramatically influenced by chemical mutagens, was increased 130‐fold by exposure to 5‐azacytidine. The methylation of CCCG sequences at the 5′ end of the AS structural gene was found to be reduced equally in both types of asn+ variant. These results indicate that decreased DNA methylation is essential but not necessarily sufficient for the expression of AS activity in this frog cell system.
Inhibition of DNA synthesis and cell division by a cell surface sialoglycopeptide
Authors: Fattaey Heideh , Johnson Terry C. , Chou Hsin‐Hwei 
Published: February 2005

AbstractWe have isolated and purified a cell surface sialoglycopeptide (SGP) from bovine cerebral cortex cells that previously was shown to be a potent inhibitor of cellular protein synthesis. The following studies were carried out to characterize the potential ability of the SGP to inhibit DNA synthesis and to arrest cell division. Treatment of exponentially proliferating Swiss 3T3 cells with the SGP inhibitor resulted in a marked inhibition of thymidine incorporation within 24 h. When the SGP was removed from inhibited cultures, a sharp rise in 3H‐thymidine incorporation followed within 3–4 h that peaked well above that measured in exponentially growing cultures, suggesting that the inhibitory action of the SGP was reversible and that a significant proportion of the arrested cells was synchronized in the mitotic cycle. In addition to DNA synthesis, the inhibitory action of the SGP was monitored by direct measurement of cell number. Consistent with the thymidine incorporation data, the SGP completely inhibited 3T3 cell division 20 h after its addition to exponentially growing cultures. Upon reversal there was a delay of 15 h before cell division resumed, when the arrested cells quickly doubled. Most, if not all, of the growth‐arrested cells appeared to have been synchronized by the SGP. The SGP inhibited DNA synthesis in a surprisingly wide variety of target cells, and the relative degree of their sensitivity to the inhibitor was remarkably similar. Cells sensitive to the SGP ranged from vertebrate to invertebrate cells, fibroblast and epitheliallike cells, primary cells and established cell cultures, as well as a wide range of transformed cell lines.
Superoxide dismutase induces differentiation of friend erythroleukemia cells
Authors: Beckman Barbara S. , Balin Arthur K. , Allen R. G. 
Published: February 2005

AbstractFriend erythroleukemia cells (FELC) served as a model system for cell differentiation because these cells can be triggered to differentiate by a variety of chemical agents. Treatment with the classical inducer of differentiation, hexamethylene bisacetamide (HMBA), stimulated superoxide dismutase (SOD) activity, which increased in parallel with HMBA‐induced differentiation. Furthermore, FELC were shown to differentiate in response to the addition of liposomes containing SOD. Oxidative treatment with Iiposomes containing D‐amino acid oxidase or xanthine oxidase, cumene peroxide, or potassium superoxide also induced differentiation, whereas antioxidants such as a‐tocopherol, butylated hydroxytoluene, or p‐carotene did not induce differentiation. Also, HMBA induction of differentiation was suppressed by treatment with antioxidants.