bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of growth promotion of mouse lymphoma L1210 cells in vitro by feeder layer or 2‐mercaptoethanol
Authors: Ishii Tetsuro , Hishinuma Ieharu , Bannai Shiro , Sugita Yoshiki 
Published: February 2005

AbstractMouse lymphoma L1210 cells require some thiol compounds (such as 2‐mercaptoethanol) or feeder layer cells for their growth in normal culture media in vitro. We found that feeder layer cells (human diploid fibroblast IMR‐90) constantly produce thiol compounds; cysteine was the major thiol compound accumulating in the culture medium. In the culture medium of L1210 cells, added cysteine was rapidly oxidized and was toxic to the cells at high concentrations. However, cysteine promoted growth of L1210 cells when it was added repeatedly to the medium at low concentrations. These results show that the major role of feeder layer cells is to provide cysteine continuously. The glutathione content of L1210 cells depended largely on the cysteine concentration in the medium. In normal culture media containing cystine but not cysteine, the cellular glutathione content decreased notably within a few hours. Cysteine had to be supplied repeatedly to keep the content high. Cystine promoted the cellular glutathione content at unphysiologically high concentrations. These results were attributable to the extremely low uptake rate of cystine by the cells as compared with that of cysteine. In the presence of 2‐mercaptoethanol, the uptake of radioactive cystine by the cells was increased and a high cellular glutathione level was maintained. A thiol‐independent variant of L1210 took up cystine far more rapidly than L1210. From these results we concluded that the deficiency of the cystine uptake limits the growth of L1210 cells in normal culture media.
Multihormonal regulation of ornithine decarboxylase activity in highly differentiated porcine granulosa cells in vitro
Authors: Veldhuis Johannes D. , Sweinberg Sharon 
Published: February 2005

AbstractPurified luteinizing hormone, but not follicle‐stimulating hormone, elicited time‐ and dose‐dependent stimulation of the cytosolic enzyme, ornithine decarboxylase, in highly differentiated, porcine granulosa cells maintained in vitro in chemically defined medium. Enzymic induction was susceptible to inhibitors of protein and RNA synthesis, and was suppressed by selective direct and indirect inhibitors of ornithine decarboxylase. Physiologic concentrations of prostaglandin E2 and L‐epinephrine also enhanced enzymic activity in a dose‐dependent and saturable manner. Systematic comparison of the hormonal induction of ornithine decarboxylase in highly differentiated versus poorly differentiated granulosa cells revealed distinctive patterns of enzymic responsivity in relation to the degree of cytodifferentiation attained in vivo.This in vitro model is likely to permit further detailed examination of the molecular mechanisms subserving the hormonal control of ovarian ornithine decarboxylase activity in spontaneously differentiated granulosa cells maintained under chemically defined conditions in vitro.
Glutamine and the regulation of DNA replication and cell multiplication in fibroblasts
Authors: Zetterberg Anders , Engström Wilhelm 
Published: February 2005

AbstractSeveral studies indicate that glutamine is a critical requirement for cell growth in vitro. Growing and quiescent (serum‐starved) 3T3‐fibroblasts were exposed to media (Dulbecco's modified Eagle's minimal essential medium) in which the concentration of the 13 essential amino acids had been lowered to 1/100 or 1/1,000 of that in DMEM ‐ either all together or one by one. The effects on DNA synthesis were measured by autoradiographic determinations of the percentage of labeled cells after 24 hours exposure to 3H‐thymidine. A reduction of all 13 essential amino acids to 1/100 or 1/1,000 of the normal concentration in the medium resulted only in a minor growth inhibitory effect during the first cell cycle. A similar growth inhibitory effect was caused by the depletion of one of the 13 essential amino acids (except glutamine) from the medium. However, a depletion of glutamine from the medium resulted in a marked inhibition of growth. Conversely, a relative excess of glutamine, when the other 12 amino acids were lowered to 1/1,000 of the normal concentration, counteracted the growth inhibitory effect of serum starvation. It was even possible to stimulate quiescent cells to undergo DNA synthesis by exposing them to a serum‐depleted (0.5% serum) medium with a relative excess of glutamine.
Properties of a sarcoma‐growth‐factor‐like peptide from cells transformed by a temperature‐sensitive sarcoma virus
Authors: De Larco Joseph E. , Preston Yvette A. , Todaro George J. 
Published: February 2005

AbstractSerum‐free conditioned media was collected from three sarcoma virus‐transformed cell lines and an untransformed cell line. All three virally transformed lines produced and released growth factors into their serum‐free media. The major activity in all cases, whether the cells were transformed by Moloney sarcoma virus (MSV) or Kirsten sarcoma virus (KiSV), or whether they were mouse or rat, was a sarcoma‐growth‐factor (SGF)‐like activity with an apparent molecular weight of 10,000. The SGF‐like pools from a Moloney sarcoma virus‐transformed mouse 3T3 cell and a Kirsten sarcoma virus‐transformed NRK cell were further purified by carboxymethyl cellulose chromatography. The elution profiles of these peptides were very similar. The serum‐free conditioned media from the untransformed cells showed no detectable growth stimulating activity. The temperature sensitivity of an SGF‐like growth factor from the supernate of a NRK cell transformed by a wild‐type Kirsten sarcoma virus (KiSV) was compared with that of the SGF‐like activity from the supernates of a NRK cell transformed by a ts‐mutant of KiSV that is temperature sensitive with respect to transformation (ts‐371 Cl 5). Neither the cells transformed by the wild‐type sarcoma virus nor those transformed by the temperature sensitive virus released a SGF‐like activity that was temperature sensitive under the conditions of the assays.
Stretch‐induced growth of skeletal myotubes correlates with activation of the sodium pump
Authors: Vandenburgh Herman H. , Kaufman Seymour 
Published: February 2005

AbstractSkeletal myotubes responded to passive stretch by increased amino acid uptake (as measured with [3H]α‐aminoisobutyric acid), increased incorporation of amino acids into total cellular protein and myosin heavy chains, and increased accumulation of total cellular protein and myosin heavy chains. These alterations were preceded by an increase in the uptake of ouabain‐sensitive rubidium‐86 (86Rb+), a potassium tracer used to measure membrane sodium pump activity (Na+K+ATPase). This stretch‐induced stimulation of 86Rb+ uptake resulted from a 60‐70% increase in the Vmax of the Na pump with little change in the Km. [3H] ouabain binding studies showed no stretch‐induced change in the number of membrane Na pumps, indicating that stretch activates the Na pumps that are already present on the cell surface. Since the stretch‐induced increases in amino acid transport and amino acid incorporation into proteins were inhibited by ouabain, Na pump activation may be involved in stretch‐induced cell growth of skeletal muscle cells by hypertrophy.
Glycolipids: Receptors for fibronectin?
Authors: Yamada Kenneth M. , Kennedy Dorothy W. , Grotendorst Gary R. , Momoi Takashi 
Published: February 2005

AbstractWe have examined the hypothesis that glycolipids might serve as receptors for the cell surface glycoprotein fibronectin using three different biological assay systems. We find that purified solubilized gangliosides inhibit fibronectin‐mediated hemagglutination, cell spreading, and restoration of a normal morphologic phenotype to transformed cells. The inhibition is dose‐dependent and competitive; hemagglutination by 2 μg/ml fibronectin is half‐maximally inhibited by less than 1 μM gangliosides. The most effective ganglioside inhibitors generally contain the most sialic acid residues. The isolated oligosaccharide portions of gangliosides retain this inhibitory activity and the oligosaccharides with more sialic acid are more effective inhibitors.A series of other lipids or ganglioside constituents are either less effective or without detectable activity. The more active of these lipids are the more negatively charged phospholipids such as phosphatidyl serine and phosphatidyl inositol.Our results support the hypothesis that the “receptors” for fibronectin on the cell surface either consist of or contain gangliosides or other negatively charged lipids.
Functional receptors for epidermal growth factor on human osteosarcoma cells
Authors: Shupnik Margaret A. , Tashjian Armen H. 
Published: February 2005

AbstractPrevious studies have shown that epidermal growth factor (EGF) stimulates bone resorption in organ culture via a prostaglandin‐mediated pathway, and that there are specific receptors for EGF on mouse bone (Tashjian and Levine, ′78; Shupnik et al., ′80). The present study demonstrates that a clonal line of human osteosarcoma cells, G‐292 (Clone A141B1) has specific, high‐affinity receptors for EGF and responds to treatment with EGF by increased prostaglandin production. Binding of 125I‐EGF to G‐292 cells exhibited a prolonged plateau phase (6 hours); thereafter, binding slowly declined (t1/2 = 6 hours) to 30–40% of the maximal level. This decrease in cell‐associated 125I‐EGF was prevented by leupeptin (50 μg/ml). EGF binding was of high affinity (Kd = 1.9 × 10−9 M) and was to a single class of non‐interacting binding sites. Pretreatment of cells for 48 hours with EGF caused a maximum threefold increase in PGE2 production, with a half‐maximal response at 9.8 × 10−10 M EGF. Increased PGE2 production was detectable within 2 hours and the constant presence of EGF was needed to maintain the response. Although EGF is mitogenic in several other systems, it did not increase DNA synthesis in the osteosarcoma cells. EGF treatment also did not increase medium or intracellular cyclic AMP in these cells, although parathyroid hormone and exogenous PGE2 (200 ng/ml) increased cyclic AMP three‐ to tenfold over control levels. Pretreatment with EGF decreased the level of subsequent 125I‐EGF binding; receptor number decreased to 30–40% of control after 48 hours of treatment, and the half‐maximal effect occurred with pretreatment concentrations of 1.6 × 10−9 M EGF. In all respects tested, the binding and biological actions of EGF on the human osteosarcoma cells were the same as those in whole mouse bone. G‐292 cells thus provide a convenient model system to study EGF action on osseous tissue.
Cell cycle‐specific glucocorticoid growth regulation of a human cell line (NHIK 3025)
Authors: Bakke Oddmund , Eik‐Nes Kristen B. 
Published: February 2005

AbstractIt has been reported that the human cell line NHIK 3025 has a specific cytoplasmic glucocorticoid receptor. When these cells were exposed to glucocorticoids, the cell cycle time was prolonged. Cells, synchronized by mitotic selection, were subjected to the synthetic glucocorticoid dexamethasone throughout the cell cycle. Only cells exposed in the first half of G1 phase had a lengthened cell cycle time. Most of the prolongation was also located within the G1 phase. The dexamethasone growth inhibition was reversible and could be detected only in the cell cycle where the cells were exposed to the steroid. DNA‐histograms of asynchronous cells were recorded by flowcytometry at various times after steroid exposure. These histograms also showed G1 phase sensitivity and G1 phase prolongation after exposure to dexamethasone. Our results thus indicate that these cells have a dexamethasone‐sensitive restriction point in mid‐G1 phase of the cell cycle.
Growth of human foreskin fibroblasts in a serum‐free, defined medium without platelet‐derived growth factor
Authors: Weinstein R. , Hoover G. A. , Majure J. , van der Spek J. , Stemerman M. B. , Maciag T. 
Published: February 2005

AbstractThe hormones which support growth, in vitro, of normal, neonatal human foreskin fibroblasts were determined. Wheresas thrombin and hydrocortisone were major growth stimulants, platelet‐derived growth factor was not. Human foreskin fibroblasts grew in a serum‐free, biochemically defined medium consisting of epidermal growth factor (100 ng/ml), insulin (100 ng/ml), trasferrin (10 μg/ml), thrombin (1 μg/ml), ascorbic acid (10 μg/ml), and hydrocortisone (5 × 10−5M) in a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F‐12, supplemented with ovalbumin (1 mg/ml) and trace elements. The growth achieved was comparable to that achieved with 5% fetal bovine serum. Neither platelet‐derived growth factor, fibroblst growth factor, nor somatomedin activity increased proliferation. This serum‐free medium designated Defined Medium F, provides a biochemically defined system for growth and limited subcultivation of human foreskin fibroblasts in vitro.
Ability of endothelial cells to condition culture medium
Authors: Gajdusek Corinne M. , Schwartz Stephen M. 
Published: February 2005

AbstractEndothelial cell‐conditioned medium contains two classes of factors distinguishable by behavior during dialysis and on specificity for cell type. One species, which diffuses through dialysis tubing with an exclusion limit of 6,000 to 8,000 daltons, supports growth of bovine aortic endothelial (BAE) cells in medium containing a growth limiting concentration of serum (0.2% serum). The production of this material appears to depend upon the presence of serum in the medium being conditioned. The activity increases with time of exposure of BAE cells to serum and with increasing concentration of serum present in the incubation medium. This activity cannot be replaced by exogenous epidermal growth factor, fibroblast growth factor, platelet‐derived growth factor, insulin, or thymidine. The second species, the endothelial cell‐derived growth factor (EC‐DGF), is retained by dialysis tubing with an exclusion limit of 6,000 to 8,000 daltons. ECDGF stimulates the growth of smooth muscle cells but does not support BAE cell growth in limiting serum concentrations. Unlike the dialyzable species, the production of ECDGF is independent of previous incubation of BAE cell cultures in serum. These studies suggest that BAE cells are able to utilize serum components to produce conditioning factors for their own growth that are distinct from the higher molecular weight ECDGF.
Morphological transformation of cells induced by Kirsten sarcoma virus transforming factor is independent of serine protease
Authors: Fulton R. Jerrold , Kaplan Paul L. , Hart David A. , Ozanne Brad 
Published: February 2005

AbstractReports from several laboratories have suggested that the virus transformed state may be maintained either by ectopically produced growth factors of alternatively by ectopically produced serine proteases including plasminogen activator. Here we show that the maintenance of transformation induced by Kirsten sarcoma virus induced growth factor(s) is independent of serine proteases in that (1) the factors are not themselves serine proteases, and (2) the growth factors do not induce the expression of detectable serine proteases or plasminogen activator.
Receptor‐associated changes of the catecholamine‐sensitive adenylate cyclase in glioma cells doubly transformed with Moloney sarcoma virus
Authors: Higashida Haruhiro , Miki Naomsa , Tanaka Tatsuya , Kato Kanefusa , Nakano Tamotsu , Nagatsu Toshiharu , Kano‐Tanaka Kyoko 
Published: February 2005

AbstractA doubly transformed rat glioma cell line, designated C6V‐1, was obtained from rat glioma C6 cells by infection with a rat‐adapted variant of Moloney sarcoma virus (MSV‐M‐os). The C6V‐1 cells show karyotypic changes in chromosome number (43) and structure, while C6 cells possess a normal male karyotype. C6V‐1 and C6 cells were employed for characterization of a receptor‐adenylate cyclase system of the surface membrane. C6V‐1 cells showed lower adenylate cyclase activity than that of C6 cells, though the apparent Km for ATP in both types of cells was the same. The maximal stimulation of adenylate cyclase by isoproterenol was significantly reduced, and Kact for isoproterenol was approximately 18‐fold lower in C6V‐1 cells. When the concentration of β‐adrenergic receptors was measured by various concentration of [3H] dihydroalprenolol (DHA), the maximal binding sites of C6 and C6V‐1 cells were 760 and 230 fmol/mg protein, respectively, without any changes in the association constant for DHA. The concentration of isoproterenol required for 50% displacement of the [3H] DHA binding (Kd) was the same (around 1.5 × 10−6M) in both cells, measured in the presence of GTP. Thus the 19‐fold drop in the Kd/Kact ratio in C6V‐1 cells suggests an incomplete coupling of β‐receptors to adenylate cyclase. Cyclic AMP phosphodiesterase activity and cAMP content in C6V‐1 were lower than in C6 cells. Mitochondrial monoamine oxidase and cytosomal enolase activities, however, were somewhat higher in C6V‐1 cells. The results indicate that a set of changes in the receptors and in the cyclic AMP system of C6V‐1 cells. The results indicate taht a set of changes in the receptors and in teh cyclic AMP system of C6V‐1 is one of the specific alteations by transformation, even though those may not be the cause of cell transformation.
Transformation‐dependent loss of the hyaluronate‐containing coats of cultured cells
Authors: Underhill Charles B. , Toole Bryan P. 
Published: February 2005

AbstractThe sizes of hyaluronate‐containing coats on the surfaces of parent and virus‐transformed cell lines (3T3 vs. SV‐3T3; BHK vs. PY‐BHK) were compared according to the method of Clarris and Fraser (1968, Exp. Cell Res., 49: 181–193) in which fixed red blood cells were allowed to settle slowly on the surface of culture dishes containing the cells. The coats were seen as areas devoid of red blood cells surrounding each of the cultured cells and could be destroyed by the addition of small amounts of streptomyces hyaluronidase, an enzyme specific for hyaluronate. In the case of the parent cell lines (3T3 and BHK), the coats were clearly visible, whereas for their virus‐transformed counterparts (SV‐3T3 and PY‐BHK), the coats were either greatly reduced or absent. To confirm these observations, the amount of hyaluronate associated with each of the cell lines was measured using a direct chemical assay and shown to be significantly greater for the parent cell lines than for their virus‐transformed counterparts. In addition, the parent cell lines secreted greater amounts of hyaluronate into the medium and retained a larger fraction of the total amount of hyaluronate at the cell surface than the virus‐transformed cells. Thus the larger amount of hyaluronate on the surfaces of the parent cell types may be the result of both a faster rate of production and a decreased rate of release.
Regulation of dihydrofolate reductase gene transcription in methotrexate‐resistant mouse fibroblasts
Authors: Wu Jin‐Shyun Ruth , Johnson Lee F. 
Published: February 2005

AbstractWe have used a methotrexate‐resistant mouse 3T6 cell line (M50L3) that overproduces dihydrofolate reductase (DHFR) and its mRNA by a factor of about 300 to study the regulation of DHFR hnRNA synthesis. We have previously shown that when resting (G0) M50L3 cells are serum stimuled to reenter the cell cycle, the amount and rate of synthesis of DHER and the content of DHER mRNA all begin to increase as the cells enter the S phase of the cell cycle. The increase in DHFR mRNA content is due to an increase in the rate of mRNA production. In the present study, we have used the technique of DNA‐excess filter hybridization to determine the rate of synthesis of DHFR hnRNA relative to total hnRNA at various times following serum stimulation. We found that the relative rate of DHFR hnRNA synthesis began to increase at about the same time (6 hours), and increased to about the same extent (three to fourfold by 15 hours following stimulation) as we observed previously for DHFR mRNA production. This suggests that the increase in DHFR mRNA production (and consequently DHFR gene expression) is controlled primarily, if not exclusively, at the level of transcription. We also studied the effect of addition of high concentrations of dibutyryl cAMP and theophyllne on DHFR gene transciption. We found that addition of these drugs at the time of stimulation completely blocked the increase in DHFR hnRNA synthesis as well as entry into S phase. Addition of the drugs at either 13 or 20 hours following stimulation led to a rapid decrease in DHFR hnRNA synthesis. The drugs were found to have little effect on the ability of the cells to complete S phase when they were added at 13 hours following stimulation. Our results suggest that high intracellular concentrations of cAMP may effect DHFR gene expression not only by preventing the progession of cells through the G1 phase of the cell cycle but also by affecting the rate of DHFR gene transcription in a more direct manner.
In vitro proliferation and lifespan of human diploid fibroblasts in serum‐free BSA‐containing medium
Authors: Kan Mikio , Yamane Isao 
Published: February 2005

AbstractWe have developed two serum‐free chemically defined media (RITC 78‐6 and RITC 80‐7) that support the growth in culture of human diploid fibroblasts to the same extent as Eagle's basal medium (BME) supplemented with 10% fetal bovine serum (FBS). These two media contain modified Eagle's minimum essential medium (MEM) supplemented with nonessential amino acids, various trace metals, organic compounds and growth factors [insulin, mouse epidermal growth factor (m‐EGF), transferrin and triiodothyronine (T3)]. RITC 80‐7 medium differs from RITC 78‐6 in that it contains thymidine, hypoxanthine, and vitamin B12 and supports the long‐term serial cultivation of human diploid cultures. The addition of commercial bovine serum albumin (BSA, 5 g/liter) to the medium enhances cell growth. This effect is not observed if BSA is first delipidized, but reconstitution of BSA with certain lipids restores its ability to promote growth. BSA has an inhibitory effect on cellular attachment but this is overcome when fibronectin (FN, 10 mg/liter) is added to the medium.
Increases in cyclic AMP potentiate competence formation in BALB/c‐3T3 cells
Authors: Wharton Walker , Leof Edward B. , Olashaw Nancy , Earp H. S. , Pledger W. J. 
Published: February 2005

AbstractThe ability of platelet‐derived growth factor and fibroblast growth factor to stimulate the initiation of DNA synthesis in quiescent BALB/c‐3T3 cells was enhanced by cholera toxin. However, the addition of cholera toxin to unsupplemented medium was not mitogenic, nor did cholera toxin increase the mitogenic potential of mediuum supplemented with platelet‐poor plasma. The enhancement of serum‐induced DNA synthesis by cholera toxin was due to a specific effect on competence formation and not plasma‐controlled progression. Cholera toxin increased the rate of competence formation during a transient exposure of quiescent cells to platelet‐derived growth factor; this rate was further increased by the addition of isobutylmethylxanthine, a cyclic nucleotide phosphodiesterase inhibitor. Intracellular cyclic AMP concentrations in quiescent BALB/c‐3T3 cells were increased 2‐ to 3‐fold after the addition of cholera toxin. The addition of cholera toxin plus 30 m̈M isobutylmethylxanthine caused an even greater (7‐ to 8‐fold) increase in the cellular levels of cyclic AMP. That these increases in cyclic AMP concentrations mediated at least part of the increased sensitivity of quiescent cells to competence factors was substantiated by the observation that 0.01 to 1 mM monobutrylcyclic AMP or 8‐bromocyclic AMP also caused a concentration‐dependent potentiation of competence formation in quiescent cells during a transient exposure to platelet‐derived growth factor.