bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipid composition of Friend leukemia cells following induction of erythroid differentiation by dimethyl sulfoxide
Authors: Rittmann Lana S. , Jelsema Carole L. , Schwartz Edward L. , Tsiftsoglou Asterios S. , Sartorelli Alan C. 
Published: February 2005

AbstractThe effects of dimethyl sulfoxide (DMSO)‐induced differentiation of Friend leukemia cells in vitro on the lipid composition of these cells have been examined. DMSO had no early effect on the incorporation of either [14C] glycerol or [3H] methyl choline chloride into the total lipids or individual phospholipids of Friend cells up to 240 min after addition of the inducer. Examination of DMSO‐diferentiated Friend cell phospholipids revealed a percentage composition which was similar to control cells, with phosphatidylcholine and phosphatidylethanolamine in both uninduced and differentiated cells accounting for over 75% of the total phospholipid. Sphingomyelin levels were significantly lower in Friend cells than in normal adult mouse erythrocytes, and differentiation of murine erythroleukemia cells resulted in a further lowering of this phospholipid. In contrast, a significant increase in the level of phosphatidylethanolamine occured as a result of maturation. Fatty acid analysis of major lipid classes of differentiated Friend cells showed significant reduction in saturation, but no alteration in chain length in comparison to undifferentiated cells. A pronounced decrease in the cellular content of both free and esterified cholesterol, which resulted in a 45% decrease in the ratio of cholesterol/phospholipids, occurred in cells differentiated by the polar solvent. The findings indicate that erythrodifferentiation induced by DMSO results in a variety of changes in the lipid composition of the membranes of Friend leukemia cells.
Glutamine synthetase induction by glucocorticoids in the glucocorticoid‐sensitive human leukemic cell line CEM‐C7
Authors: Harmon Jeffrey M. , Thompson E. Brad 
Published: February 2005

AbstractTreatment of CEM‐C7 cells with glucocorticoids produces a 2.5‐fold increase in the activity of the enzyme glutamine synthetase (GS). This increase is specific for steroids with glucocorticoid activity and occurs over a range of steroid concentrations consistent with a receptor‐mediated mechanism. Half‐maximal and maximal inductions by dexamethasone (dex) occur at 2 × 10−8M and 2 × 10−7 M dex, respectively, concentrations approximately equal to those necessary to produce half and full occupancy of glucocorticoid receptors. GS activity began to increase 1 hour after dex treatment and was complete by 12 hours. This is well before any of the growth inhibitory or cytolytic effects of dex on this cell line occur. This increase was dependent on the presence of glucocorticoid receptors and required both RNA and protein synthesis. Removal of dex following stimulation to maximal levels resulted in a decrease of GS activity to preinduced levels with a half‐time of 5 hours. Glutamine deprivation of cells resulted in increased GS activity. However, even in the total absence of glutamine, dex treatment elicited a 2.0–2.5‐fold increase in GS activity, ruling out inhibition of glutamine uptake as a mechanism for the dex‐induced increase. Experiments with 5′‐bromodeoxyuridine (BrdU) demonstrated that GS elevation was sensitive to BrdU substitution of DNA, while dex‐induced growth inhibition was not. Therefore GS elevation and growth inhibition in this cell line appear to be independently expressed steroid responses.
Deoxycytidine excretion by mouse peritoneal macrophages: Its implication in modulation of immunological functions
Authors: Chan Teh‐Sheng , Lakhchaura Bala D. 
Published: February 2005

AbstractPyrimidine excretion by macrophages was studied in order to identify the potential immunoregulatory effector molecules. Deoxycytidine was found in the culture medium of thioglycollate‐elicited mouse peritoneal macrophages, along with thymidine, which was shown by others to be a possible immunoregulatory substance. The identification of deoxycytidine was based on: (1) cochromatography with the authentic compound in four different solvents, (2) UV absorption spectral analysis, and (3) the enzymatic peak shift method. Phagocytosis of nucleated chicken erythrocytes, but not enucleated sheep erythrocytes, increased deoxycytidine excretion. The macrophages lacked both deoxycytidine kinase and deoxycytidine deaminase, which is consistent with their excretory pattern. Since it has been known that deoxycytidine can protect cells against cytotoxic effects of thymidine, we propose that deoxycytidine has a role in preventing immunosuppression by thimidine. In patients with adenosine deaminase deficiency, however, immunosuppression caused by combined toxicity of thymidine and deoxyadenosine may not be adequately prevented by deoxycytidine.
Autoradiographic detection and characterization of a Chinese hamster ovary cell mutant deficient in fucoproteins
Authors: Hirschberg Carlos B. , Perez Mary , Snider Martin , Hanneman Wendy L. , Esko Jeffrey , Raetz Christian R. H. 
Published: February 2005

AbstractAutoradiography of colony replicas immobilized on filter paper was used to isolate a Chinese hamster ovary cell line deficient in incorporation of radiolabeled fucose into a trichloroacetic acid‐insoluble fraction. This cell line, called 62.1, has the same growth rate at 37°C as wild‐type cells, but incorporates five times less fucose into acid‐insoluble radioactivity. Chemical analysis of fucose bound to macromolecules also showed a fivefold reduction in the mutant. The fucoproteins of the mutant cell line differ qualitatively from those of wild‐type cells as visualized by SDS gel electrophoresis fluorography; no differences were detected between total proteins as visualized by coomassie blue staining. The macromolecular sialic acid content of the mutant was somewhat higher than the wild type (20%).Studies of the synthesis of the glycoprotein of vesicular stomatitis virus in mutant and wild‐type cells showed that the mutant is unable to synthesize complex‐type N‐linked oligosaccharides. Enzyme assays show that this defect in the mutant is due to reduction in UDP‐N‐acetylglucosamine‐glycoprotein N‐acetyl‐glucos‐aminyltransferase, a key enzyme in the assembly of complex glycopeptides.Hybridization studies have shown that mutant 62.1 has common mutations belonging to the same complementation group as mutant PHaR1‐1. This latter mutant was previously isolated using lectin resistance by Stanley et al. (1975) and was also deficient in the above N‐acetyl‐glucosaminyltransferase.
The chemical mimicking of the mechanical stimulation, photoinhibition, and recovery from photoinihibition of bioluminescence in the marine dinoflagellate, Gonyaulax polyedra
Authors: Hamman J. P. , Seliger H. H. 
Published: February 2005

AbstractMechanically stimulable bioluminescence and photoinhibition of sensitivity to mechanical stimulation in the marine dinoflagellate Gonyaulax polyedra can be mimicked by a number of cations, proportional to the logarithm of their external concentrations. The data are consistent with mechanical stimulability as a membrane depolarization resulting in an increase in H+ions at bioluminescence sites and with photoinhibition as a hyperpolarization of the cell membrane.
Binding of phorbol esters to high‐affinity sites on murine fibroblastic cells elicits a mitogenic response
Authors: Collins Mary K. L. , Rozengurt Enrique 
Published: February 2005

AbstractThe level of occupancy of a single class of high‐affinity (3H)‐phorbol 12, 13‐dibutyrate (PDBu) bindings sites (Kd = 26 nM) in quiescent Swiss 3T3 cells was correlated with the dose of PDBu required to stimulate rapid (increase in 86Rb uptake, decrease in epidermal growth factor receptor affinity) and long‐term (induction of 2‐deoxyglucose uptake, initiation of DNA synthesis) events of the proliferative response. Further, structural analogues of PDBu showed identical relative potencies in the inhibition of (3H)‐PDBu binding and stimulation of DNA synthesis. Finally, prolonged (24‐hour) incubation of Swiss 3T3 or whole mouse embryo fibroblasts with 400 nM PDBu led to a decrease in the number of (3H)‐PDBu binding sites (down‐regulation) with a parallel loss of rapid and long‐term responses of the cells to PDBu (desensitization). These findings indicate that the high‐affinity (3H)‐PDBu binding sites mediate the mitogenic effects of phorbol esters in fibroblastic cells.
Hormonal responsiveness of a preadipose cell line derived from newborn mouse calvaria
Authors: Kodama Hiro‐Aki , Amagai Yuji , Koyama Hideki , Kasai Shiro 
Published: February 2005

AbstractWe established a clonal preadispose cell line from newborn mouse calvaria. Cells of this cell line, designated MC3T3‐G2/PA6, had the capacity to convert to adipose cells, to accumulate triglycerides in their cytoplasm, and to mature to differentiated fat cells in a resting state. This adipose conversion was markedly accelerated by addition of dexamethasone, which was the most potent inducer among the steroid hormones tested. The presence of dexamethasone was needed during logarithmic growth phase for maximal conversion. The frequency of adipose conversion was dependent on exposure time to the hormone, but cells already committed to differentiation continued to accumulate lipid and developed into mature adipose cell even in its absence. This indicates that the hormone accelerates the initiation of the adipose conversion, but is not required for the ongoing conversion process. In fact, it was rather inhibitory for the process of fat accumulation. Insulin alone slightly inhibited the adipose conversion, but its combination with dexamethasone neutralized the above inhibitory effect of dexamehasone. The responsiveness of this cell line is consistent with that observed for mouse bone marrow preadipocytes in primary culture but differs from that for preadipose cell lines derived from extramedullary tissues. These results strongly suggest that the MC3T3‐G2/PA6 cell line was derived from bone marrow.
A new preadipose cell line derived from newborn mouse calvaria can promote the proliferation of pluripotent hemopoietic stem cells in vitro
Authors: Kodama Hiro‐Aki , Amagai Yuji , Koyama Hideki , Kasai Shiro 
Published: February 2005

AbstractA clonal preadipose cell line MC3T3‐G2/PA6, established from newborn mouse calvaria, responds to glucocorticoids and converts to adipose cells in a fashion similar to bone marrow preadipocytes. We investigated the effect of the cells on in vitro hemopoiesis of mouse bone marrow cells by cocultivation. When bone marrow cells were inoculated into confluent cultures of MC3T3‐G2/PA6 cells (104–106 cells/25‐cm2 flask), the number of hemopoietic stem cells (CFU‐S) significantly increased during 7‐day cultivation in proportion to inoculum size. Under these conditions, active replication of CFU‐S was maintained for several weeks until MC3T3‐G2/PA6 cell layers detached from the substratum. This capacity of the MC3T3‐G2/PA6 line was unique because other established cell lines, including the MTF preadipose line, failed to support CFU‐S growth. When bone marrow cells were not allowed to contact the MC3T3‐G2/PA6 cell layer, only a small number of CFU‐S survived for 7 days. Moreover, MC3T3‐G2/PA6 cell‐conditioned medium did not show any growth‐promoting activity for CFU‐S. These results indicate that the MC3T3‐G2/PA6 cell line has the ability to promote the proliferation of CFU‐S through a short range cell‐to‐cell interaction by providing an in vitro microenvironment probably similar to that for in vivo hemopoiesis.
Energy metabolism in cultured human fibroblasts during aging in vitro
Authors: Goldstein S. , Ballantyne S. R. , Robson A. L. , Moerman E. J. 
Published: February 2005

AbstractTo explore the relationship between energy metabolism and the limited replicative life span of cultured human fibroblasts, we studied several bioenergetic parameters in normal fibroblasts at early passage (young cells) and at late passage (old cells) and early passage cells from a subject with the Hutchinson‐Gilford (progeria) syndrome. Old cells consumed more glucose and produced more lactate during growth, but O2 consumption, both basal and following maximum uncoupling of oxidative phosphorylation by SF‐6847, was the same as in young cells. Progeria cells produced the most lactate but did not consume more glucose, while their basal and uncoupled O2 consumption was similar to that of young and old cells during both log and confluent states. Consumption of glutamine, a source of both oxidative energy and lactate, was approximately the same in all three cell types as was 14CO2 production from 2‐14C‐pyruvate and 5‐14C‐glutamate. ATP and ADP concentrations were similar in all cell types with a rise in the ATP/ADP ratio during growth from log to confluent state. Thus, old and progeria cells, in contrast to young cells, produce more lactate during growth consistent with a rise in energy demand and/or inefficiency of oxidative phosphorylation. Although limitations in total energy output do not appear to be causal to the loss of replicative capacity in normal cells after serial passage, they could play a role in the curtailed replicative capacity of progeria cells.
Regulation of transferrin receptor expression in concanavalin a stimulated and gross virus transformed rat lymphoblasts
Authors: Hamilton Thomas A. 
Published: February 2005

AbstractExpression of the cell surface receptor for the serum glycoprotein transferrin has been correlated with cellular proliferation in normal lymphocytes undergoing mitogen or antigen induced proliferative responses. In the present study, the expression of transferrin receptor in Concanavalin A stimulated rat lymphocytes or Gross virus transformed lymphoma cells has been examined with respect to the following questions: (1) is expression of receptor activity related to blastogenesis or to the subsequent IL‐2 dependent DNA synthetic activity, and (2) is transferrin receptor expression regulated in similar fashion in both normal and malignant lymphoblasts? Scatchard analysis of saturation binding data illustrated that binding site number increased and subsequently decreased during the response while the receptor affinity for transferrin remained constant. These findings were confirmed by SDS‐polyacrylamide gel electrophoretic analysis of radiolabeled cell surface proteins which specifically interact with transferrin. Examination of nonproliferating normal lymphoblasts (96 hr post Con A stimulation) compared with the same population of cells stimulated to reinitiate DNA synthesis with a partially purified preparation of Interleukin 2 (IL‐2) showed that transferrin receptor expression was tightly linked to the IL‐2 dependent stimulation of DNA replication. This coordinate regulation of receptor expression was markedly less stringent in retrovirus transformed thymic lymphoma cells.
The cellular uptake of horseradish peroxidase and its poly(lysine) conjugate by cultured fibroblasts is qualitatively similar despite a 900‐fold difference in rate
Authors: Ryser Hugues J.‐P. , Drummond Iain , Shen Wei‐Chiang 
Published: February 2005

AbstractWhen horseradish peroxidase (HRP) is conjugated to poly(L‐lysine) of molecular weight (MW) 13,000, its transport into cultured L929 fibroblasts in 1 hour at 37°C is increased 918‐fold. The kinetics of uptake are linear with time and concentration, reflecting a process of nonreceptor‐mediated adsorptive endocytosis. Neither HRP‐poly(Lys) conjugate nor free poly(Lys) of any size cause any increase in fluid phase endocytosis. All evidence indicates that the covalently bound poly(Lys) increases the binding of HRP to the cell surface and that this adequately accounts for an increased internalization occurring at a steady rate. In the absence of Ca++, both surface binding and uptake of the conjugate, but not of free HRP, are decreased. Cytochalasin B does not significantly inhibit the transport of either form of HRP. The half‐lives of HRP and HRP‐poly(Lys) are 7.6 and 5.6 hours, respectively, when measured over a period of 12 hours. Electron microscopic analysis of cells that have ingested comparable amounts of HRP shows that the intracellular localization of free and conjugated HRP are comparable and that both are found inside the same array of structures, thus HRP, which binds very poorly to the cell surface and is considered a fluid‐phase marker for the “contents” of pinocytotic vesicles, and HRP‐poly(Lys), which binds very strongly to the cell surface and is considered a membrane marker for adsorptive endocytosis, are taken up along the same endocytotic pathway. Moreover, despite the fact that neither markers are transported by receptor‐mediated endocytosis, both are seen in structures that were described as receptosomes. It appears, therefore, that the pathways utilized in receptor‐mediated transport are available to all other forms of pinocytosis.
Small nuclear RNAs and translation
Authors: Smith James H. , Subbarao Makam N. , Eliceiri George L. 
Published: February 2005

AbstractThe possibility that small nuclear RNA species U1 might be involved in the inhibition of protein synthesis that occurs during mitosis has been explored. Upon exposure of mitotic HeLa cell extracts to 1% sodium deoxycholate, the majority of the rapidly sedimenting U1 RNA shifted to lower sedimentation rates. This suggests that it is associated with heterogeneous nuclear RNA ribonucleoprotein particles, instead of a ribosomal population. Erythrocyte ghost‐mediated microinjection of anti‐(U1)RNP antibodies into synchronized HeLa cells did not prevent the suppression of protein synthesis that is observed under mitosis. Examination of the published nucleotide sequences of U1 and U2 RNA suggests that these RNA species could potentially code for some short peptides. When purified U1 or U2 RNA were added to cell‐free polypeptide synthesizing systems, the synthesis of these peptides was not detected.
Taxol resistant mutants of Chinese hamster ovary cells: Genetic biochemical, and cross‐resistance studies
Authors: Gupta Radhey S. 
Published: February 2005

AbstractThe effects of the microtubule inhibitor taxol on the growth and viability of Chinese hamster ovary (CHO) cells have been examined. Stable mutants which are between seven to 11‐fold more resistant to taxol have been selected in a single step from ethyl methanesulfonate‐mutagenized CHO cells. The two taxol‐resistant mutants (TaxR‐1 and TaxR‐2) which have been studied in detail exhibit novel and strikingly different cross‐resistance/collateral sensitivity patterns to various microtubule inhibitors. For example, the TaxR‐1 mutant exhibits increased resistance to vinblastine, but in comparison to the parental cells, it shows enhanced sensitivity toward colchicine, colcemid, stegnacine, and griseofulvin. However, the sensitivity of this mutant toward other unrelated compounds, e.g., puromycin, daunomycin, etc., remained largely unaltered. The specific pattern of cross‐resistance/collateral‐sensitivity of this mutant toward various microtubule inhibitors suggests that the genetic lesion in this mutant may be affecting a microtubule‐related component. The TaxR‐2 mutant, in contrast, is highly resistant to various microtubule inhibitors including colchicine, colcemid, stegnacine, maytan‐sine, vinblastine, and podophyllotoxin. This mutant also exhibits greatly increased cross‐resistance to daunomycin, puromycin, ethidium bromide, and VM‐26 (compounds which do not inhibit microtubule assembly), and shows reduced cellular uptake of 3H‐daunomycin indicating that the genetic lesion in this mutant nonspecifically affects the membrane permeability of various drugs. The cell hybrids formed between TaxR‐1 (or TaxR‐2 mutant(s)) and a taxol‐sensitive cell line exhibit intermediate levels of resistance to the drug, indicating that the TaxR phenotypes of both these mutants behave codominantly under these conditions.
Opposing effects of 12‐o‐tetradecanoylphorbol 13‐acetate on human myeloid and lymphoid cell proliferation
Authors: Aye M. T. , Dunne J. V. 
Published: February 2005

AbstractThe effect of 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) on human hematopoietic cells has been investigated. It was found that 1–10 ng/ml of TPA totally abrogated erythroid and granulocytic colony growth and, simultaneously in the presence of PHA, stimulated T‐lymphocyte colony formation. TPA concentrations insufficient to inhibit myeloid colony growth also failed to stimulate lymphocyte colony formation. Optimal culture conditions for the growth of these colonies required the presence of TPA, PHA, and leukocyte‐conditioned medium in the cultures. Cells within the colonies were 80–90% E‐rosette positive and by monoclonal antibody characterization contained 45–66% OKT3‐positive cells. Colony‐forming cells were found in both E‐rosette‐positive and‐negative fractions. Although by cell surface marker characterization the cells within the colonies had properties of T‐cells, the exact relationship of cells forming colonies under these conditions to those detected in other T‐cell colony assays remain to be determined.
Phosphatidyl choline and the growth in serum‐free medium of vascular endothelial and smooth muscle cells, and corneal endothelial cells
Authors: Fujii D. K. , Cheng J. , Gospodarowicz D. 
Published: February 2005

AbstractLiposomes made by sonication of egg yolk phosphatidyl choline support the proliferation of low‐density bovine vascular and corneal endothelial cells, and vascular smooth muscle cells maintained on basement laminacoated dishes and exposed to a defined medium supplemented with transferrin. The optimal growth‐promoting effect of phosphatidyl choline was observed at concentrations of 25 μg/ml for low‐density cultures of vascular smooth muscle cells, and 100 μg/ml for vascular and corneal endothelial cells. The growth rate and final cell density of vascular endothelial cells exposed to a synthetic medium supplemented with transferrin and either high‐density lipoproteins or phosphatidyl choline has been compared. Although cultures exposed to phosphatidyl choline reached a final cell density similar to that of cultures exposed to high‐density lipoproteins, they had a longer average doubling time (17 h vs. 12 h) during their logarithmic growth phase and a shorter lifespan (17 generations vs. 30 generations). Similar observations were made in the case of vascular smooth muscle cells or bovine corneal endothelial cells maintained in medium supplemented with transferrin, fibroblast growth factor (FGF) or epidermal growth factor (EGF), and insulin and exposed to either high‐density lipoproteins or phosphatidyl choline. Since phosphatidyl choline can, for the most part, replace highdensity lipoproteins in supporting the proliferation of various cell types, it is likely that the growth stimulating signal conveyed by high‐density lipoproteins is associated with its polar lipid fraction, which is composed mostly of phosphatidyl cholines.
Binding, sequestration, and processing of epidermal growth factor and nerve growth facor by PC12 cells
Authors: Chandler C. E. , Herschman H. R. 
Published: February 2005

AbstractThe rat PC12 pheochromocytoma cell line exhibits biological responses to both nerve growth factor (NGF) and epidermal growth factor (EGF). The existence of receptors and biological responses on a common cell for these two well‐characterized polypeptide growth factors makes this an attractive system for comparison of ligand binding and processing. Both NGF and EGF are bound to PC12 cells in a competable form at 4°C. At 37°C both ligands are “sequestered”, but at different rates and to different extents. While sequestration happens rapidly and nearly quantitatively for bound EGF, the dissociation reation appears to compete favorably with NGF sequestration. Both EGF and NGF are degraded by PC12 cells. Sequestered EGF, however, is degraded to a greater extent than sequestered NGF.