bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differences in oxygen‐dependent regulation of enzymes between tumor and normal cell systems in culture
Authors: Simon Lawrence M. , Robin Eugene D. , Theodore James 
Published: February 2005

AbstractMetabolic studies in tumor cells have indicated that bioenergetic regulatory mechanisms geared to acute changes in oxygen availability are abnormal. In the present studies we have examined bioenergetic adaptations to chronic oxygen depletion in culture maintained tumor cells in comparison to normal cell lines. Activities of two key glycolytic enzymes (pyruvate kinase (PyKi) and phosphofructokinase (PFK)) were measured in two tumor cell lines (fibrosarcoma (FS) and Hela) and two normal cell lines (rat lung fibroblasts (RLF) and WI‐38) maintained in culture for up to 96 hours under aerobic (PO2 ∼ 140) and hypoxic PO2 ∼ (15) conditions. Exposure to low O2 tensions for 96 hours resulted in significant increases in PyKi and PFK in both RLF and WI‐38, but did not alter activities of these enzymes in either FS or HeLa cell systems. Activities of two enzymes involved in O2 metabolism (cytochrome oxidase (CyOx)) and superoxide dismutase (SOD) were also measured in the two tumor cell lines and in RLF. Chronic hypoxia significantly decreased the activities of CyOx and SOD in RLF cell systems but did not alter the activities of these enzymes in the tumor cells. In these studies, the tumor‐derived cell lines do not demonstrate specific enzymatic responses to sustained oxygen depletion in vitro noted in normal cell systems, suggesting significant abnormalities in regulatory mechanisms geared to chronic changes in molecular O2.
Mitogenesis in normal human fibroblasts by polyinosinic · polycytidylic acid and other synthetic acidic polymers: Enhancement of action by glucocorticoids
Authors: Barrack Evelyn R. , Hollenberg Morley D. 
Published: February 2005

AbstractThe ability of specific synthetic polyelectrolytes to act as mitogens for quiescent normal human fibroblasts in cultures is described. Of several acidic polymers tested, polyinosinic acid*polycytidyli acid (poly I *poly C) and dextran sulfate were the most effective in stimulating 3H‐thymidine incorporation (2‐ to 10‐fold). The concentration for a half‐maximal effect (ED50) was 0.4 μg/ml (0.8 nM) for poly I *poly C, and 1.7 μg/ml (3.4 nM) for dextran sulfate. Single‐stranded polyinosinic acid or polycytidylic acid had no effect. The time course of stimulation of DNA synthesis by these acidic polymers was similar to that for naturally occurring mitogens such as epidermal growth factor, beginning at about 18 hours and reaching a maximum rate 26 to 30 hours after the addition of polymer. Glucocorticoids that have an 11‐β hydroxyl group (e.g., dexamethasone) had no effect on DNA synthesis alone, but enhanced several‐fold the mitogenic activity of poly I * poly C or dextran sulfate; the ED50 for dexamethasone was 0.75 ng/ml (1.9 nM). Glucocorticoids with an 11‐keto group were inactive in this respect. The labeling index following treatment of cultures with poly I *poly C and dexamethasone was 14%, compared with a labeling index of 25% following stimulation by fetal calf serum. The extent of stimulation of DNA synthesis by poly I *poly C and dexamethasone was comparable to that induced by epidermal growth factor. It appears that both the poly I *poly C and dexamethasone are required for only a short period of time (approximately 3 hours) in order to produce maximal stimulation of DNA synthesis 30 hours later.
Transport of L‐alanine in cultured human fibroblasts: Evidence for two kinetically distinguishable systems
Authors: Feneant M. , Moatti N. , Lemonnier F. , Lemonnier A. 
Published: February 2005

AbstractThe transport of L‐alanine in human diploid fibroblasts was investigated. Transport measurements were performed on subcultures between the third and eighth passages with subconfluent cells growing on glass coverslips. Kinetic analysis of approximate initial rates of transport at substrate concentrations from 0.05 to 10 mmole/liter indicate the presence of two distinguishable systems. The high affinity system has a Km of 0.24 mmole/liter and a Vmax of 6.4 nmole/100 μg protein/2 min. For the low affinity system, the contribution of the high affinity system to the uptake must absolutely be taken into account. The Km and Vmax values, obtained by using a computer program, are a Km of 15.0 mmole/liter and a Vmax of 14.7 nmole/100 μg protein/2 min. For alanine concentrations below 1 mmole/liter, the contribution of the Na+‐independent uptake is less than 10%, and the kinetic constants of the high affinity system are in the same range if this contribution is taken into account. On the contrary the influence of a diffusion‐like process is more significant on the low affinity system whose Km is about 49 mmole/liter after subtraction of the Na+‐independent uptake from the experimental velocities. Inhibition studies were performed with NCH3‐alanine. They permitted us first to confirm the existence of system A in cultured human fibroblasts in agreement with two recent works and second to show how this system contributes to L‐alanine uptake. This contribution seems very small in low concentrations but it rises as the concentrations increase.
Clonal variation in cultured neuroblastoma cells. II. The relationship of increased intracellular cyclic amp content to increased anchorage requirement for growth and flattened morphology
Authors: Lanks Karl W. , Lombardo Joseph M. 
Published: February 2005

AbstractFlat variant clones were isolated from both the N18 neuroblastoma cell line and from a subclone of the parent line exhibiting the typical round cell morphology. Several revertant clones exhibiting the round parental morphology were also isolated from one of the flat variant clones. The flat variants exhibit decreased cloning efficiency in suspension and increased amounts of myosin heavy chain when compared to the round cell clones. Intracellular cAMP levels were increased from two‐ to fivefold over those in clones representative of the parent line and in the round cell revertants. Treatment with the phosphodiesterase inhibitor RO20‐1724 increased cAMP levels and reduced suspension cloning efficiency without altering doubling time or attached cloning efficiency. Increasing cAMP levels of two of the round cell clones by treatment with the phosphodiesterase inhibitor caused increased flattening of the cell body and increased myosin heavy chain content. Thus, even though increased cAMP level may be sufficient to explain the reduced cloning efficiency of the flat variants, it is not the sole cause of the flat morphology.
Elemental content in the nucleus and in yolk and yolk‐free cytoplasm of developing Rana pipiens oocytes: An X‐ray microanalysis study
Authors: Labadie D. R. L. , Pool T. B. , Smith N. K. R. , Cameron I. L. 
Published: February 2005

AbstractEnergy dispersive x‐ray microanalysis measured the Na, K, Cl, P, Mg, S, and Ca contents (mM/kg dry weight) in the nucleus, yolk‐free cytoplasm, and yolk platelets of Rana pipiens oocytes quick frozen in the ovary. The data revealed that significant content changes occur in frog oocytes during intraovarian growth. All elements but Ca changed in content in the nucleus and cytoplasm, while in the yolk platelet only Na content did not change. A nucleus to cytoplasm K gradient develops and increases in magnitude during oocyte growth. The data from this and previous reports lead to the hypothesis that intra‐oocytic water and elements undergo changes in state during oocyte growth and that three subcellular Na compartments exist.
Separate actions of different colony stimulating factors from human placental conditioned medium on human hemopoietic progenitor cell survival and proliferation
Authors: Morstyn George , Nicola Nicos A. , Metcalf Donald 
Published: February 2005

AbstractMore than 20% of human granulocyte‐macrophage and eosinophil colony‐forming cells survived in agar culture for up to 4 days without the addition of exogenous colony stimulating factors (human placental‐conditioned medium, HPCM). Survival was reduced slightly but not significantly, by the removal of adherent cell populations. Significant survival occurred even when only 100 cells enriched for colony‐forming cells (CFCs) were cultured per dish. When individual colonies, initiated by stimulation with HPCM for 5 days, were transferred to dishes without HPCM, subsequent proliferation was significantly reduced compared with control cultures containing HPCM. Using the fluorescence‐activated cell sorter and the fluoresceinated lectin from Lotus tetragonolobus, two populations of marrow cells were obtained, one enriched for day 7 and the other for day 14 colony‐forming cells. Two colony‐stimulating factors fractionated from HPLCM (CSFβ and CSFα) have been shown previously to stimulate the day 7 and day 14 colony‐forming cell populations, respectively. Developing clones from cultures initiated with CSFβ died between the fifth and tenth day of culture after transfer to dishes with CSFα or CSFβ or to dishes with no stimulus. Cells in clusters initiated with CSFα proliferated significantly between the fifth and tenth day of culture when transfered to CSFα or CSFβ but not when transfered to dishes with not stimulus. These studies provide further evidence for the existence of two subtypes of human granulocyte‐macrophage progenitor cells each under the primary control of a specific regulator and indicate that these two regulators can both act on some developing clones of cells.
A granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) produced by carrageenin‐induced inflammatory cells of mice
Authors: Shikita M. , Tsuneoka K. , Hagiwara S. , Tsurufuji S. 
Published: February 2005

AbstractSeven days after subcutaneous injection of 2% carrageenin solution in mice, the induced inflammatory tissue was isolated and treated with 0.1% trypsin. When the dispersed cells were incubated in a nutrient medium containing 5‐‐20% calf serum, the cells grew adhering to the culture‐dish surface and colony‐stimulating factor (CSF) was accumulated in the medium gradually. Addition of lipopolysaccharide (Escherichia coli endotoxin) in the cell culture did not enhance the CSF production. It was shown by isoelectrofocusing that the majority of the produced CSF was an acidic molecule (pI = 3.8), while the treatment of this CSF with neuraminidase yielded a less acidic CSF species (pI = 5.1). Upon gel‐filtration chromatography in the presence of 6 M guanidine HCl, the CSF exhibited an apparent molecular weight of 42,000. On the other hand, polyacrylamide gel‐electrophoresis in the presence of 0.1% sodium dodecyl sulfate gave a molecular weight estimate of 65,000. Microscopic examination of the bone marrow cell culture showed that about one‐third of the colonies were granulocytic. Addition of prostaglandin E1(PGE1) in the bone marrow cell culture significantly inhibited the action of the CSF, while prostaglandin D2 was less inhibitory than PGE1. The result suggests that the cells isolated from the inflammatory tissue are capable of producing CSF, which may have a role for proliferation and maturation of the mononuclear phagocytes at the site of inflammation.
The relationship of serum fibronectin and cell shape to thrombin‐induced inhibition of dna synthesis in human fibroblasts
Authors: Hall William M. , Ganguly Pankaj 
Published: February 2005

AbstractIn a previous report it was shown that inhibited DNA synthesis and altered morphology resulted when human fibroblasts (HF) were plated in 3% fetal calf serum (FCS) medium preincubated with thrombin (Hall and Ganguly, 1980a). This was in contrast to the stimulatory effects of this enzyme when added to cells several hours after subculture. Those observations suggested that thrombin may act upon serum components of the growth medium necessary for initial culture establishment following cell plating. In this report, the relationship of serum fibronectin (FN) to this thrombin‐mediated inhibitory phenomena was investigated. It was found that the development of altered morphology and inhibited DNA synthesis could be completely prevented by the addition of this glycoprotein to medium preincubated with thrombin. Cell shape and DNA synthesis appeared to be closely related and both parameters showed a dose‐dependent sensitivity to added fibronectin. To further investigate this, a technique was developed in which cell shape could be selectively varied and DNA synthesis measured in the absence of serum or thrombin. These studies indicated that cell shape was closely related to DNA synthesis and morphologies identical to that seen in thrombin‐treated medium were produced. As observed in the thrombin system, normal cellular appearance and DNA synthesis could be restored by the addition of fibronectin. The results of this work suggest that thrombin acts upon medium components necessary for normal morphological development, possibly fibronectin, in cells following subculture. Inhibited DNA synthesis and growth seem to arise as a direct consequence of this effect.
Multiple mechanisms of growth inhibition by cyclic AMP derivatives in rat GH1 pituitary cells: Isolation of an adenylate cyclase‐deficient variant
Authors: Martin Thomas F. J. , Ronning Susan A. 
Published: February 2005

AbstractGH pituitary cells have been widely utilized for studies of hormone response mechanisms. Studies reported here were motivated by the desirability of isolating characterized GH clones defective in cyclic AMP synthesis or action. Spontaneously occurring GH1 cell variants resistant to the growthinhibitory effects of cyclic AMP analogs were isolated. Characterization of four variants showed that these were deficient in adenosine kinase and had acquired resistance to the cytotoxic effects of purine nucleoside derivatives formed in the culture medium. A second‐stage selection was undertaken with mutagenized adenosine kinase‐deficient cells. One 8 Br cAMP‐resistant variant was found to have normal cyclic AMP‐dependent protein kinase activity but exhibited altered adenylate cyclase activity. Activation of cyclase activity by fluoride, guanyl nucleotides, cholera toxin, and hormone (VIP) was subnormal in the variant. Mndependent cyclase activity was also subnormal, suggesting that the 8 Br cAMP‐resistant variant may have a deficiency in the catalytic moiety of adenylate cyclase.Surprisingly, adenosine 3′ :5′ ‐monophosphate and 5′ ‐monophosphate derivatives were found to be equally potent in growth‐inhibiting adenosine kinasedeficient cells. Cross‐resistance to 8 Br AMP was observed in the 8 Br cAMP‐resistant variant. We conclude that cyclic AMP derivatives inhibit growth of GH cells by an unanticipated mechanism that is, nonetheless, related to endogenous cyclic AMP synthesis.
The influence of cellular proliferative history on the susceptibility to oncogenic transformation
Authors: Chan Gerald L. , Little John B. 
Published: February 2005

AbstractC3H mouse 10T½ clone 8 cells were serially transferred from passage 11 to 15 with 5 × 104 cells seeded per 60‐mm dish at each passage. One group of cells was passaged as soon as confluence was reached. Two other groups were kept for 3 or 6 days in confluence at each passage before subculture. Cloning efficiency was found to increase progressively with passage of all three groups. At the 15th passage, cells from all three groups were harvested just prior to confluence, irradiated with ultraviolet light, and assayed for clonogenic survival and malignant transformation. Survival response was the same for all three groups, but cells which were kept constantly proliferating in previous passages were found to be much more susceptible to transformation. These results suggest that the susceptibility of these cells to transformation is influenced by their proliferative history; in particular, intermittent growth quiescence in previous passages decreased this susceptibility.
The effects of alterations in the external sodium concentration on human leucocyte sodium and potassium transport in vitro
Authors: Hilton P. J. , Johnson Valerie E. , Jones R. B. , Patrick J. 
Published: February 2005

AbstractHuman leucocytes incubated in tissue culture fluid of low‐sodium concentration (2 mM; iso‐osmolarity maintained with choline chloride) reached a new equlibrium within 1 hour and lost approximately 25% of intracellular potassium and 70% of intracellular sodium. The rate constant for ouabainsensitive sodium efflux fell by more than 50% and the ouabain‐insensitive rate constant increased nearly threefold in the low‐sodium medium. Total sodium efflux fell in proportion to internal sodium whereas ouabain‐insensitive sodium efflux remained unchanged. A reduction in external sodium from 140 to 2 mM was associated with a 75% fall in sodium influx. In the low‐sodium medium ouabainsensitive potassium influx exceeded ouabain‐sensitive sodium efflux and no ouabain‐sensitive potassium efflux could be demonstrated. Ouabain‐insensitive potassium influx and that portion of potassium efflux which is dependent on external potassium fell in parallel in low‐sodium cells, suggesting reduced activity of a ouabain‐insensitive K:K exchange system.
Uptake of putrescine by 3T3 and SV3T3 cells and its effect on ornithine decarboxylase activity
Authors: Bethell Delia R. , Pegg Anthony E. 
Published: February 2005

AbstractThe addition of 50 μM exogenous putrescine to Swiss 3T3 cells during serum stimulation resulted in a sixfold increase in intracellular putrescine content and prevented the rise in ornithine decarboxylase activity normally seen in response to serum. SV3T3 cells had putrescine levels ten times higher than those in the 3T3 cells. When SV3T3 cells were exposed to 50 μM putrescine, the intracellular content increased less than twofold. Despite the high levels of intracellular putrescine, ornithine decarboxylase was stimulated by addition of serum to SV3T3 cells. These results indicate that the system by which ornithine decarboxylase activity is regulated by its product is much less sensitive in the transformed SV3T3 cells. The ability of the 3T3 cells to take up putrescine changed with changes in the growth state, increasing when growth was stimulated by serum. These changes were manifested by changes in the maximum rate of transport (Vmax) rather than the Km. The increased transport rate was prevented when protein synthesis was inhibited by cycloheximide. The uptake of putrescine by SV3T3 cells did not change significantly under any of the conditions tested and the activity of this system in the SV3T3 cells was less than that of the 3T3 cells during exponential growth. This distinguishes the putrescine uptake system from those for amino acid uptake and suggests that the activity of the system may be regulated coordinately with the need for polyamines for cell growth. Finally, cadaverine (1,5‐diaminopentane), a diamine not usually present in fibroblasts, was taken up much more slowly than putrescine and uptake was not saturable under the conditions tested. The slower uptake may account for the lesser ability of cadaverine to reduce ornithine decarboxylase activity in the 3T3 cells.
Effect of dexamethasone, ammonium lons, and serum‐deprivation on intracellular proteolysis in cultured muscle cells
Authors: Mayer M. , Chaouat M. , Hadar R. , Nissan S. , Lernau O. Z. 
Published: February 2005

AbstractIntracellular proteolysis was measured in primary cultures of newborn rat skeletal (gastrocnemius) and cardiac muscle cells by release to the medium of trichloroacetic acid‐soluble label from cells grown in the presence of 14C‐labeled phenylalanine. Exposure of the cultured cells to 10−7M dexamethasone for 5 days starting at day 0 of culture resulted in an enhancement of proteolysis in skeletal muscle but not in cardiac muscle cells. Dexamethasone did not affect cell viability measured by release of label from cells preloaded with Na2 51CrO4, release of creatine phosphokinase, and release of lactic dehydrogenase into the culture medium. Incorporation of 3H‐thymidine into the cells increased during the first 3 to 4 days of culture and subsequently decreased, indicating that cell proliferation ceases at that time. When the exposure to dexamethasone was started on day 4 of culture, i.e., at a postmitotic stage, and continued for 4 days, proteolysis was again found to increase in skeletal but not cardiac cells, thereby suggesting that the response to the hormone is independent of the proliferative state of the culture.Ammonium chloride at a concentration of 10 mM produced a 50% reduction of the basal proteolysis in cultures of skeletal muscle cells and did not affect proteolysis in cardiac muscle cells. Exposure to ammonium chloride did not prevent the dexamethasone‐induced increase of proteolysis in skeletal muscle cells. Serum‐deprivation induced enhanced proteolysis which was not affected by NH4Cl in both cell types. It is concluded that the differential responses of the two cultures to dexamethasone reflects the sparing of heart proteins and concomitant wasting of skeletal muscle proteins by glucocorticoid hormones in vivo, and that the enhancement of proteolysis by the glucocorticoid hormone or by serum‐deprivation is not sensitive to the lysosomotropic agent NH4Cl. Thus, while a lysosomal‐autophagic enzyme system is responsible for almost half of the basal proteolysis, the accelerated proteolysis occurs via ammonium chloride‐insensitive enzymes.
The activation of cloned macrophages by concanavalin A for tumoricidal effect: Assessmetn of tumor cell cytotoxicity by a clonogenic assay
Authors: Yen Shing‐Erh , Thomasson David L. , Stewart Carleton C. 
Published: February 2005

AbstractThe activation of pure populations of cloned peritoneal macrophages for tumor cell cytotoxicity by Con A was demonstrated using a recently developed tumor cell clonogenic assay. Cloned macrophages were rendered cytotoxic by Con A at concentrations above 20 μg/ml. The tumor cell cytotoxicity was caused mainly by the tumoricidal activity of the Con A‐activated cloned macrophages. Increasing the Con A‐activation time from 24 hours to 48 hours and 72 hours heightened the cytotoxic activity of cloned macrophages. Cloned macrophages incubated with con A for only 2 hours possessed no cytotoxic effect. Culture fluid from cultures of activated macrophages exerted no tumor cell cytotoxicity. Alpha‐methyl‐D‐mannoside, a specific receptor‐binding inhibitor for Con A, was capable of blocking the activation of macrophages for cytotoxicity at 0.01 M concentration.