bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adhesion of murine cells to glass microbeads: Substrate‐adsorbed serum proteins
Authors: Haas Robert , Culp Lloyd A. 
Published: February 2005

AbstractSmall (1 mm diameter) glass beads treated with acid and alkali provided a satisfactory substratum for the attachment and growth of normal and SV‐40 transformed Balb/c 3T3 murine cells. Cells attached to the beads with similar, though slower kinetics as to flat glass surfaces, and spread and grew with their usual morphology; when detached by EGTA treatment, they left behind cellular substrate‐attached material (SAM) which was similar electrophoretically to that obtained from tissue culture plastic. Because of their small size and rough etched surfaces, the beads have a large surface area and high adsorptive capacity, and so are a useful tool to isolate specific serum proteins adsorbed from the culture medium that may be important for cell attachment and spreading. The adsorbed serum proteins were solubilized with SDS and analyzed by SDS‐polyacrylamide gel electrophoresis (SDS‐PAGE) under reducing and non‐reducing conditions. They included all reduced species adsorbed to tissue culture plastic, and only small amounts of one other major protein extracted from a “bacteriological” polystyrene surface on which cells could not grow. Profiles of unreduced samples differed considerably. The profile of adsorbed proteins varied little with tiem (5 minutes–4 days), temperature (4°–37°C), pH (5–9), presence of the protease inhibitor PMSF, or serum concentration (0.1–10%). Much of the adsorbed protein, qualitatively similar to the SDS‐extracted material, could be eluted with H2O or phosphate‐buffered saline. Purified albumin and fibrinogen bound avidly to the beads; the material adsorbed from serum contained a large amount of albumin, however, little fibrinogen and no cold‐insoluble globulin (as a 220 K protein) could be detected by Coomassie blue stained SDS‐PAGE gels.
Role of cytoplasmic ATP in the restoration and maintenance of a membrane permeability barrier in transformed mammalian cells
Authors: Makan Nizar R. 
Published: February 2005

AbstractAddition of ATP to medium surrounding intact, transformed 3T3 cells activates the formation of aqueous channels in the plasma membrane. This results in efflux of nucleotide pools and ions and entry into the cytosol of charged, phosphorylated species. In such permeabilized cells, glycolysis is totally dependent on the external addition of glucose, inorganic phosphate, ADP, K+, Mg2+ and NAD+ which restore lactic acid formation to levels found in untreated cells. As expected, such reconstitution of glycolytic activity is found to restore intracellular ATP levels. This is accompanied by sealing of the membrane channels so that efflux of nucleotide pools ceases. Pyruvate, a substrate for mitochondrial ATP synthesis, when provided along with ADP and inorganic phosphate also produces sealing of the membrane channels. On the other hand, reactivation of pentose phosphate shunt activity, which does not lead to ATP synthesis, does not induce restoration of the membrane permeability barrier. Furthermore, compounds which lower the internal ATP pool prevent sealing, and also render the plasma membrane more sensitive to external ATP (Roxengurt and Heppel, 1979). Sealing of aqueous channels following restoration of the internal ATP pool is associated with phosphorylation of the inner membrane surface, and is unaffected by inhibitors of protein synthesis, microfilament or microtubular assembly. These results indicate the probable role of intracellular ATP in the restoration and/or maintenance of an active membrane barrier against efflux of small molecules and ions in transformed 3T3 cells.
Ribosome biosynthesis in Tetrahymena thermophila. IV. Regulation of ribosomal RNA synthesis in growing and growth arrested cells
Authors: Sutton Claudia A. , Sylvan Paul , Hallberg Richard L. 
Published: February 2005

AbstractThree parameters involved in the production of new ribosomal RNA (rRNA) were measured in Tetrahymena thermophilia: (i) the rate of synthesis of the rRNA precursor, (ii) the rate of processing of the RNA precursor and rRNA intermediates and (iii) the efficiency of utilization of the rRNA precursor in producing mature ribosomal RNA. These parameters were measured in cells in exponential growth and in cells starved in a dilute salt solution. Growing cells synthesize rRNA 20 times faster and process rRNA precursors and intermediates 10 to 15 times more rapidly than do starved cells. Both utilize their rRNA precursors with an efficiency of one in converting them to mature rRNA.
A possible role for cyclic AMP in the initiation of DNA synthesis by isoproterenol‐activated parotid gland cells
Authors: Tsang B. K. , Rixon R. H. , Whitfield J. F. 
Published: February 2005

AbstractAn intraperitoneal injection of the β‐adrenergic agonist dl‐isoproterenol hydrochloride (100 mg/Kg body weight) into a rat caused an early, very large (400‐fold) cyclic AMP surge (peaking at 10 minutes) in the parotid gland which was followed by a second, much smaller (two‐fold) surge 12 to 16 hours later. DNA synthesis began about 16 to 20 hours after the isoproterenol injection and peaked between 24 and 28 hours. The maximum level of DNA‐synthetic activity at 24 hours was correlated positively to the magnitude of the small cyclic AMP surge at 12 hours, but not to the size of the much larger cyclic AMP surge at 10 minutes. An intraperitoneal injection of dl‐propranolol hydrochloride (59 mg/Kg body weight) at 8 hours after isoproterenol injection abolished the second cyclic AMP surge at 12 hours and markedly (65‐75%) reduced the incorporation of [3H]‐thymidine into DNA. Injection of dibutyryl cyclic AMP (6.3 mg/Kg body weight) and theophylline (25 mg/Kg body weight) at 8 hours prevented propranolol from inhibiting DNA synthesis. Propranolol appeared specifically to affect the cyclic AMP‐dependent pre‐DNA‐synthetic step because it did not reduce [3H]‐thymidine incorporation when injected after the second cyclic AMP surge had passed and DNA synthesis had just begun. Thus, the initial, large cyclic AMP surge following β‐adrenergic stimulation may not be necessary for the initiation of prereplicative development, while the much smaller second surge may be needed for the initiation of DNA synthesis.
Regulation of amino acid transport in chicken embryo fibroblasts by purified multiplication‐stimulating activity (MSA)
Authors: Derr James T. , Smith Gary L. 
Published: February 2005

AbstractEnhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication‐stimulating activity (MSA). This increase in amino acid transport is an early event occuring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by α‐aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na+‐dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly+ upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while Km remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.
Chemosensitivity of single smooth muscle cells to acetylcholine, noradrenaline, and histamine in vitro
Authors: Sinback Christopher Nelson , Shain William 
Published: February 2005

AbstractElectrical responses to acetylcholine, noradrenaline, and histamine were recorded from solitary smooth muscle cells. Iontophoresis of each transmitter elicited three fast responses: a hyperpolarization, a depolarization, or a biphasic hyperpolarization‐depolarization. Each transmitter activated a specific receptor since responses were specifically blocked by antagonists, two transmitters elicited different responses in solitary cells, and desensitization of response to one transmitter did not cause desensitization of responses to other transmitters. Responses were due to increased ion conductances since input resistance decreased during responses and reversal potentials were measured for deplarizing responses (−5 mV) and hyperpolarizing responses (−60 mV). Regional differences in transmitter sensitivity were mapped on solitary cells. Biphasic responses were due to simultaneous activation of receptors mediating hyperpolarizing responses and receptors mediating depolarizing responses which were segregated in the cell membrane. Noradrenaline enhanced action potential amplitude by regulation of voltage‐dependent ion conductances. Finally, noradrenaline and histamine elicited periodic hyperpolarizing potentials, which may be due to increased intracellular Ca++.
The maturation state of three types of granulocyte/macrophage progenitor cells from mouse bone marrow
Authors: Bol Simon , Williams Neil 
Published: February 2005

AbstractThe progenitor cells of neutrophil granulocytes and macrophages which are able to proliferate and differentiate in vitro (CFU‐c) form a heterogeneous population. By the use of specific colony stimulating activities and cell separation by equilibrium density centrifugation, three subpopulations of CFU‐c can be detected. These three CFU‐c are characterized by buoyant densities of 1.070, 1.075 and 1.080 g.cm−3 and by their proliferative response to 18 h postendotoxin serum, colony stimulating factor from extracts of mouse embryos and uteri (CSF‐pmue) and erythrocyte lysate, respectively. The three CFU‐c are compared with respect to their differentiation potential, the maturation rate of their progeny cells and their proliferation capacity. It is shown that with increasing density of the CFU‐c the maturation rate increases (sequential maturation of colonies derived from CFU‐c with densities of 1.080, 1.075, 1.070 g.cm−3) and the proliferation capacity decreases (colony size decreases in the sequence of CFU‐c with densities 1.070, 1.075, 1.080 g.cm−3). Concerning the differentiation potential it is shown that all three CFU‐c detected have the capacity to form granulocytes as well as macrophages. On the basis of these results it is concluded that the CFU‐c with densities of 1.070, 1.075 and 1.080 g.cm−3 represent a maturation sequence.
Hexose uptake enhancing factor released from rous sarcoma cells
Authors: Lawrence David A. , Jullien Pierre 
Published: February 2005

AbstractConditioned media from Rous sarcoma virus transformed chicken embryo fibroblasts stimulate the uptake of 2‐deoxyglucose in normal chicken fibroblasts. The factor responsible for this effect, which is also shed in very low amount by non‐transformed fibroblasts, is destroyed by trypsin and not linked to the protease and plasminogen activator activities present in the media. Its apparent molecular weight, determined by gel filtration, is about 20.000 daltons. The factor released by transformed cells might be related to the monomeric form of a family of glucose binding and transport proteins recently reported by Lee and Lipmann ('78) to be detached by detergents from normal and transformed cells.
Production of a colony‐stimulating factor following differentiation of leukemic myeloblasts to macrophages
Authors: Maeda Michiyuki , Ichikawa Yasuo 
Published: February 2005

AbstractLeukemic cells in the myeloblastic stage from a murine myeloid leukemia cell line (M1) were induced to differentiate to macrophages by lipopolysaccharide (LPS) from Gram‐negative bacteria. A granulocyte‐macrophage colony‐stimulating factor (CSF) was produced only during differentiation. After induction of differentiation, the continued presence of LPS was necessary to stimulate the macrophages to release CSF.In contrast, a macrophage cell line (Mm‐1) derived from the M1 line produced CSF without LPS‐stimulation, but CSF release was stimulated by the presence of LPS.
Hemopoietic colonies on the chorioallantoic membrane of the chick embryo: Induction by embryonic, adherent, non‐hemopoietic spleen cells
Authors: Keller Gordon , Longenecker Michael , Diener Erwin 
Published: February 2005

AbstractGranulocytic and erythrocytic colonies developed on the chick embryo chorioallantoic membrane (CAM) following the inoculation of chick embryo spleen cells. Dose response and kinetic experiments showed that the colonies were derived from cell aggregates present in the inoculum. Dissociation and reaggregation studies of the CAM colony‐inducing cells (CAM‐CIC) indicated that these cells must be present as aggregates in order to form colonies. Results from the morphology and cell marker experiments suggested that the colony‐inducing aggregates (CAM‐CIA) attract and support the differentiation of primitive host hemopoietic cells. The physical characteristics of the CAM‐CIC, which are different from those of the hemopoietic progenitor cells, indicated that they represent a stromal cell population of the chick embryo spleen. Further evidence supporting this notion was provided by the radiation studies which showed that the colony‐inducing ability of the CAM‐CIC is radioresistant. The above characteristics of the CAM‐CIC strongly suggest that they represent the stromal cells of the chick embryo spleen which influence hemopoiesis.
NAD turnover in microplasmodia of physarum polycephalum
Authors: Manser Tim , Olivera Baldomero M. , Haugli Finn B. 
Published: February 2005

AbstractThe rate of NAD turnover in microplasmodia of Physarum polycephalum was investigated using a double labeling technique with (14C)‐adenine or adenosine and (3H)‐nicotinamide.The half‐life of an NAD molecule in Physarum was estimated to be 25 min, which is shorter than in either E. coli or human cell lines. The half‐life of NAD in the presence of an inhibitor of NADase and poly ADPR synthase, 5‐methyl‐nicotinamide, was also investigated, but found to be indistinguishable from controls. The possible reasons for this and for the rapid turnover is discussed in the light of the known functions for NAD in prokaryotes and eukaryotes.
Inhibition of growth of cells in culture by L‐phenylalanine as a model system for the analysis of phenylketonuria. I. Amino acid antagonism and the inhibition of protein synthesis
Authors: Dillehay L. , Bass R. , Englesberg E. 
Published: February 2005

AbstractPhenylalanine in high concentrations inhibits the growth of mouse A9 cells. Protein synthesis is inhibited earlier and more severely than RNA or DNA synthesis. Phenylalanine inhibits the uptake and decreases the intracellular pool of several amino acids. Certain amino acids added in excess reverse the phenylalanine inhibition. The strongest reversing amino acids appear to function by excluding phenylalanine. The phenylalanine inhibition does not appear to be due to a deficiency of any amino acid, but to the high intracellular phenylalanine concentration and/or an amino acid imbalance resulting from the large ratio of phenylalanine to other amino acids.
Initiation of DNA synthesis in mammary epithelium and mammary tumors by lithium ions
Authors: Ptashne Kay , Stockdale Frank E. , Conlon Sandra 
Published: February 2005

AbstractThe growth promoting effects of lithium and insulin on cultures of mammary gland epithelium and CZF mouse mammary tumor cells were investigated. Lithium chloride exerts a 450‐fold increase in the rate of DNA synthesis in mammary epithelium from mid‐pregnant mice in organ culture or monolayer culture. There is an increase in both the percentage of cells initiating DNA synthesis and the net accumulation of DNA. The most effective lithium concentration is 10 mM, and the maximally effective rate of stimulation is reached 48 hours after addition. The magnitude of response to lithium varies with the physiological state of the mammary epithelial cell donor: epithelium from non‐pregnant or lactating mice is less responsive than that from mid‐pregnant mice. In combination, insulin and lithium produce either a synergistic or an additive effect on the growth of epithelium dependent upon the physiological state of the donor animal. Lithium also promotes the growth of mammary tumor cells in the absence of serum or other mitogens. The action of lithium on DNA synthesis appears to be a direct effect on the epithelial cells.
Inhibition of proliferation of cloudman S91 melanoma cells by insulin and characterization of some insulin‐resistant variants
Authors: Kahn Richard , Murray Marilyn , Pawelek John 
Published: February 2005

AbstractInsulin is a potent, reversible inhibitor of proliferation in Cloudman S91 mouse melanoma cells. The inhibition seems to be unique to the Cloudman line since five other cell lines, including the mouse B16 and hamster Greene melanomas, were unaffected by insulin under the same culture conditions. Variants of Cloudman S91 cells were isolated which differed from wildtype (WT) cells in their response to insulin. Most of these variants were resistant to insulin (INSres) and had the same generation time independent of the presence of the hormone. One line (INSdep) was found to require insulin for growth. This line was about 15 times more sensitive to the proliferative effects of insulin than the WT. Revertants of the INSdep line were selected for their ability to proliferate in the absence of insulin. Five out of five such revertants were insulin resistant, suggesting that the INSdep line arose as a result of at least two separate mutations.Both WT and INSdep cells showed enhanced uptake of 14C‐α‐aminoisobutyric acid (AIB) when exposed to insulin. Dose‐response curves of the stimulation of AIB uptake in WT and INSdep cells were superimposable. Stimulation of AIB uptake and stimulation of proliferation by insulin were not under coordinate control since AIB uptake was increased equally in the wild‐type cells when proliferation was inhibited and in INSdep cells when proliferation was enhanced.Binding of 125I‐insulin was used to demonstrate the presence of specific, high affinity insulin receptors on the cells. INSres variants generally had fewer receptors than WT, but in no case did the magnitude of this effect appear to be sufficient to explain the insensitivity to insulin. The INSdep variant showed a greater than two‐fold increase in the number of insulin receptors per cell, compared to WT. Revertants of the INSdep line had the same number of receptors as WT. The specificity for both binding and for the effects on proliferation were the same in WT and INSdep cells. Since the effects of insulin on proliferation were opposite in the two lines, we propose at least two distinct sites of insulin action on the cells. Further isolation and analyses of Cloudman lines with unusual responses to insulin should be useful for understanding the molecular basis of action of this hormone.
Intracellular concentration of elements in normal and dystrophic skeletal muscles of the chicken
Authors: Misra L. K. , Smith N. K. R. , Chang D. C. , Sparks R. L. , Cameron I. L. , Beall P. T. , Harrist R. , Nichols B. L. , Fanguy R. C. , Hazlewood C. F. 
Published: February 2005

AbstractIn this study, the intracellular concentrations of six elements (mmole/kg dry weight) were directly measured in the muscle fibers of pectoralis major muscles of eight week old, genetically dystrophic and normal chickens by the X‐ray microanalysis technique. The extent of muscle degeneration was evaluated by morphometric measurements of muscle fiber diameter and other histological changes. A significant increase in the concentration of intracellular sodium and chlorine was evident in dystrophic muscles. The concentration of intracellular sodium was 127.0 ± 35.0 in the muscle fibers of dystrophic chicks compared to 65.7 ± 16.5 in normal controls. The concentration of chlorine was 90.5 ± 27.5 and 54.1 ± 5.5 in the muscle fibers of dystrophic and normal chicks respectively. The intracellular concentrations of potassium, magnesium, phosphorous, and sulfur remained unchanged in the dystrophic condition. Morphometric studies revealed that the dystrophic pectoralis muscles contain fewer but thicker fibers per unit area compared to normal pectoralis muscles. The importance of these findings are discussed in relation to the results of earlier investigations.
Limitation of macrophage production in long‐term marrow cultures containing prostaglandin E
Authors: Williams N. , Jackson H. 
Published: February 2005

AbstractAddition of prostaglandin E2 (PGE2) significantly altered the cellular composition of murine long‐term bone marrow cultures. After 4–5 weeks of culture, increased cellularity in the suspension phase was observed in all cultures containing prostaglandin. These suspension cells contained markedly higher proportions of differentiated neutrophils than did cells cultured in the absence of PGE2. Granulocyte‐macrophage progenitor cell levels in the suspension layer were increased 3–20 fold after five weeks in prostaglandin‐containing cultures compared with control cultures. Fewer cells comprised the adherent layer in cultures containing prostaglandin. The number of macrophages in this layer was reduced 3–8 fold in these cultures compared with control cultures, while the number of granulocytes was increased 2–3 fold. The progenitor cells biased toward macrophage development were selectively inhibited in the cultures with PGE2. There was no significant effect of PGE2 on pluripotent stem cell levels or on the longevity of the cultures. It is concluded that excessive monopoiesis in bone marrow may be limited by PGE2 without influencing either stem cell maintenance or the development of other marrow‐derived cell types.
Stimulation of DNA synthesis and myo‐inositol incorporation in mammalian cells
Authors: Ristow Hans‐Jürgen , Messmer Trudy O. , Walter Sephanie , Paul Dieter 
Published: February 2005

AbstractPhosphatidylinositol (PI) synthesis and its role in controlling the cell cycle has been investigated using fibroblasts and liver cells in culture. PI synthesis as measured by incorporation of [3H]‐myo‐inositol into trichloroacetic acid precipitable material during 0–60 min after serum or growth factor stimulation of serum‐starved cells is increased in primary fetal rat liver cells, rat embryo fibroblasts, and 3T3 mouse cells. In contrast, growth stimulation of 3T3 cells and hepatocytes rendered quiescent in G1 by amino acid starvation is not accompanied by increased incorporation of [3H]‐myo‐inositol into trichloroacetic acid precipitable material. This suggests that those cells might be arrested at a different point in G1 than cells arrested by serum depletion. Inhibition of PI synthesis by δ‐hexachlorocyclohexane (HCH), a steric analog of myo‐inositol, during early times (e.g., 0–4 hr) after growth stimulation, reversibly blocks initiation of DNA synthesis in 3T3 cells. The results support the idea that increased PI synthesis in response to growth stimulation in the cell types studied here is a prerequisite for progression through G1 and subsequent entry into S phase.