bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of in vitro macrophage colony‐forming cells (M‐CFC) in mouse bone marrow, spleen, and peripheral blood
Authors: Macvittie T. J. , Porvaznik M. 
Published: February 2005

AbstractIn vitro macrophage colony‐forming cells (M‐CFC) have been detected in bone marrow (BM) (317/105 cells), spleen (SPL) (81/105), and peripheral blood leukocytes (PBL) (242/105) of the mouse. These M‐CFCs were similar to those previously detected in thymus (T) (30/106) and lymph node (LN) (22/106) tissue in several respects. BM‐ and SPL‐derived M‐CFC required PMUE to consistently initiate colony formation, whereas PBL‐derived M‐CFC formed colonies with stimulation by either PMUE or L‐cell‐conditioned medium. All colonies formed showed a singular macrophage line of differentiation, a lag of 13 to 18 days prior to initiating colony formation, a marked ability to survive in culture in the absence of PMUE, and markedly slow rates of appearance in culture once colony formation was initiated. The macrophage progeny were identified on the basis of morphology, glass adherence, the phagocytosis of agar, bacteria and SRBC, and the presence of receptors for IgG. These characteristics are also shared by those macrophage CFCs observed within stimulated peritoneal exudate, pleural effusion, and alveolar space. These M‐CFCs are most likely members of a large, heterogeneous population of macrophage progenitor cells distributed throughout the hemato‐lymphopoietic organs, serosal cavities and surfaces, and inflammatory and alveolar tissue sites. The degree of heterogeneity may be determined in part by the influence of tissue‐specific microenvironment.
Effect of dibutyryl cyclic AMP on leucine incorporation in L5178Y cells II. Effect of actinomycin and heat shock
Authors: Fuhr Joseph E. 
Published: February 2005

Abstract3H‐leucine incorporation was assayed in L5178Y cells as a measure for protein synthesis. Protein synthesis was inhibited by short duration heat shock, actinomycin, cordycepin or a combination of these agents. Dibutyryl cyclic AMP had little or no effect upon protein synthesis in control cells. Dibutyryl cyclic AMP, however, stimulated protein synthesis in cells previously heat shocked and/or inhibited by actinomycin or cordycepin. The results have been interpreted to indicate that the cyclic nucleotide stimulated protein synthesis by influencing the metabolism of some species of RNA which may regulate translation.
Measurements of metabolites during cAMP oscillations of Dictyostelium discoideum
Authors: Geller Joshua S. , Brenner Michael 
Published: February 2005

AbstractDuring aggregation the cellular slime mold Dictyostelium discoideum synthesizes and releases pulses of cAMP about every five minutes. Current models proposed to explain this phenomenon postulate that oscillating levels of some key intracellular metabolite control the oscillatory synthesis of cAMP. We have assayed the levels of likely candidates for this metabolite during a cAMP oscillation, but have found them to remain constant. Compounds measured include ATP, GTP, glucose‐1‐phosphate, glucose‐6‐phosphate, isocitrate, α‐ketoglutarate, amino acids, and other aminated metabolites. On the basis of this negative data, as well as results described elsewhere (Geller and Brenner, 1978), we question whether the proposed models are correct, and discuss several alternatives.
Altered cyclic AMP‐dependent protein kinase activity in a mutant adrenocortical tumor cell line
Authors: Gutmann Norman S. , Rae Patricia A. , Schimmer Bernard P. 
Published: February 2005

AbstractA somatic cell genetic approach has been used to evaluate the role of cyclic AMP‐dependent protein kinase in ACTH action on adrenal steroidogenesis. A mutant clone, 8BrcAMPr‐1, previously was isolated from an ACTH‐sensitive adrenocortical tumor cell line (clone Y1) following mutagenesis and selective growth in 8‐bromoadenosine 3′, 5′‐monophosphate. This study demonstrates that the 8BrcAMP4‐1 cells have an altered cyclic AMP‐dependent protein kinase. The protein kinase in the cytosol of the mutant characteristically requires, for half‐maximal activity, concentrations of cyclic AMP 7‐fold higher than those required by the enzyme in preparations from the parent. The cytosolic cyclic AMP‐dependent protein kinases of Y1 and 8BrcAMPr‐1 cells chromatograph similarly on columns of DEAE‐cellulose. From each cell line, a major peak of activity (≥ 70% of recovered activity), designated as Peak I, elutes with 0.04–0.06 M NaCl; a second peak of activity, designated as Peak II, elutes with 0.12–0.14 M NaCl. Protein kinase activity in the Peak I fraction of mutant cells has a decreased apparent affinity (4‐fold) for cyclic AMP relative to the corresponding fraction of parental Y1 cells. The protein kinase activities present in Peak II fractions from Y1 and mutant cells are indistinguishable. The protein kinase mutant exhibits poor steroidogenic responses to added ACTH and cyclic AMP; and as shown previously does not display the growth arrest and morphological changes produced in Y1 by these agents. These results suggest that cyclic AMP‐dependent protein kinase is important in the regulation of adrenal steroidogenesis, morphology and growth by ACTH.
The effect of oxygen tension on haemopoietic and fibroblast cell proliferation in vitro
Authors: Bradley T. R. , Hodgson G. S. , Rosendaal M. 
Published: February 2005

AbstractThe effects of providing low oxygen tension in the gas phase of two different types of cell culture systems were investigated. The clonal growth of granulocyte‐macrophage progenitor cells in an agar culture system was improved markedly by incubation within a low oxygen tension gas phase (48 mmHg – 6.8%) instead of the conventional air (135 mmHg – 19%), the effects being measured by increases in numbers of colony forming cells detected and in the colony sizes. The increased efficiency of colony formation was observed both with mouse and human marrow cells. A similar effect was observed in a liquid adherence culture system with primary cultures of foetal mouse fibroblasts both at clonal and higher cell densities.
The effects of dopamine on prostaglandin E1‐elicited electrophysiological changes in a neuronal somatic cell hybrid
Authors: Myers Paul R. 
Published: February 2005

AbstractPGE1 elicited a slow, dose‐dependent membrane depolarization with an increase in membrane conductance in the somatic cell hybrid TCX11. The ED 50 was 1‐2 × 10−8 M with maximal responses at 1‐5 × 10−7 M. Dopamine (DA) reversed the effect of PGE1 and caused the membrane potential and resistance to return to control levels. Chronic exposure of cells (measured in minutes) to DA alone would not cause this hyperpolarization. 5‐HT was also tested and failed to consistently reverse the PGE1 effects. Chlorpromazine antagonized the effects of DA on the PGE1 response. The electrophysiological results reported here using TCX11 cells are discussed in light of previously reported biochemical results describing interactions of PGE1 and DA, and the electrophysiological effects of DA alone.
Isolation and cell cycle analysis of temperature‐sensitive mutants from chinese hamster cells
Authors: Melero Jose A. 
Published: February 2005

AbstractMutants temperature‐sensitive for growth have been isolated from the established line of Chinese hamster fibroblasts Wg1A. These mutants, together with the ones previously isolated by Roscoe et al. ('73), have been characterized with regard to their cell cycle properties. Most of them become arrested in the G1 phase of the cell cycle when incubated under restrictive conditions. By performing temperature shift experiments with synchronous cultures, the execution steps of most of the mutated functions have been located within the second half of the G1 phase.
Cell cycle control by Ca++‐ions in mouse 3T3 cells and in transformed 3T3 cells
Authors: Paul Dieter , Ristow Hans‐J. 
Published: February 2005

AbstractTotal cellular calcium levels do not change when 3T3‐4a cells stop proliferating due to serum depletion, or when serum‐arrested quiescent cells are incubated for up to 44 hours in calcium‐deficient medium (∼10 μM Ca++). Upon stimulation with dialyzed serum cells enter S and progress through at least one cycle even at extremely low calcium levels in the culture medium (≥10 μM). Cells divide until a final cell density is attained which is proportional to the calcium concentration in the medium and cells reversibly arrest in G1. Cells which arrested in G1 in medium containing ≤26 μM Ca++ in the presence of excess serum can be stimulated to enter S in response to added calcium after a prereplicative phase of 14 to 16 hours. Serum does not affect 45Ca‐uptake in these cells. Benzo[a]pyrene transformed 3T3 (BP3T3) cells have a 100–200 times lower Ca++‐requirement than 3T3 cells but arrest in G1 at low Ca++ levels. In contrast, SV40‐virus transformed 3T3 (SV3T3) cells that grow without restriction in monolayer cultures have even lower Ca++‐requirements for growth than BP3T3 cells and have no Ca++‐sensitive restriction point. Therefore, 3T3 and BP3T3 cells have retained the capacity to sense intracellular Ca++‐pool sizes and to arrest in G1 at subthreshold cellular Ca++‐levels.
Rate of potassium‐sodium exchange by human lymphocytes: Prediction of the cooperative adsorption model
Authors: Negendank William , Karreman George 
Published: February 2005

AbstractThe equilibrium parameters of potassium‐sodium distribution in human lymphocytes, determined experimentally in the preceding study (Negendank and Shaller, '79), were incorporated into a stochastic treatment of the cooperative adsorption model in order to predict the kinetics of “active” potassium‐sodium exchange. The rate of uptake of potassium, in potassium‐depleted, sodium‐loaded cells, is complex and deviates markedly from simple exponential functions. The sigmoid form of the exchange data closely followed the predicted curve. This result enhances one's confidence in the usefulness and applicability of the cooperative adsorption model, and adds further support to the association‐induction hypothesis as a coherent theory of cell physiology.
Properties of protein kinase and adenylate cyclase‐deficient variants of a macrophage‐like cell line
Authors: Rosen Neal , Piscitello Jeanne , Schneck Jonathan , Muschel Ruth J. , Bloom Barry R. , Rosen Ora M. 
Published: February 2005

AbstractStable variants of the macrophage‐like cell line J774.2, defective in adenylate cyclase and protein kinase activities, were selected by cloning cells resistant to the growth‐inhibitory effect of cholera toxin and 8‐bromoadenosine 3′:5′ cyclic monophosphoric acid (8 Br‐cAMP), respectively. These variants were analyzed for their ability to respond to cyclic AMP‐mediated enhancement of phagocytosis and cyclic AMP‐mediated inhibition of plasminogen activator secretion and growth. The adenylate cyclase variants were unaffected by cholera toxin but were sensitive to 8 Br‐cAMP‐mediated inhibition of plasminogen activator secretion and growth. One of these variants exhibited a defect in phagocytosis that could be corrected by 8 Br‐cAMP. The protein kinase variants exhibited normal basal phagocytosis that could not be stimulated by either 8 Br‐cAMP or cholera toxin; they were also insensitive to cyclic AMP‐mediated inhibition of plasminogen activator secretion and growth. The studies demonstrate that the three effects of cyclic AMP in J774.2–inhibition of growth and plasminogen activator secretion, and enhancement of basal Fc‐mediated phagocytosis–are mediated by a cyclic AMP‐dependent protein kinase. The results support the usefulness of variants in cyclic nucleotide metabolism in understanding the regulation of differentiated cell function by cyclic AMP.
Requirements for RNA and protein synthesis in the induction of several differentiation‐markers in a myeloid leukemia cell line
Authors: Nagata Kazuhiro , Ichikawa Yasuo 
Published: February 2005

AbstractIn a myeloid leukemia cell line, the inducibilities of the Fc receptor, phagocytosis and cell motility were compared. Thymidine analogues such as BUdR, BCdR and IUdR blocked the induction of phagocytosis and motility but not induction of the Fc receptor. This BUdR susceptibility in the induction of phagocytosis and motility was lost in a BUdR resistant line which was isolated for its growth capability in a high concentration of BUdR. Actinomycin D and puromycin brought about a marked decrease in the inducibility of phagocytosis but not in that of the Fc receptor.This led us to the following conclusion: There is a genetic control in the inducibility of phagocytosis and motility in this cell line, and the incorporation of BUdR into cellular DNA results in the DNA becoming unresponsive to a differentiation‐stimulating factor. In contrast, gene activation does not seem to be necessary for induction of the Fc receptor.The order of induction of several differentiation markers was also discussed.
Establishment of a rat hepatoma cell line which has ornithine carbamoyltransferase activity and grows continuously in arginine‐deprived medium
Authors: Niwa Akira , Yamamoto Katsuhiko , Yasumura Yosihiro 
Published: February 2005

AbstractThe epithelial cell line, H4‐II‐E derived from Reuber hepatoma H35 has no significant activity of ornithine carbamoyltransferase (OCT, EC 2.1.3.3) and is not able to grow in arginine‐deprived medium.A multi‐step selection procedure is described which selects from H4‐II‐E populations, cells with OCT activity which can grow in arginine‐deficient, ornithine‐supplemented media.
Patterns of peptide synthesis in senescent and presenescent human fibroblasts
Authors: Engelhardt Dean L. , Lee Gloria T‐Y. , Moley Jeffrey F. 
Published: February 2005

AbstractPeptide production in senescent and presenescent human foreskin fibroblasts was measured using 2‐dimensional polyacrylamide gel electrophoresis. This procedure permits the visualization of a cohort of the major peptides being produced. Among this cohort of over 500 peptides only two were found to differ in relative amount in that more was being produced in senescent cells. This difference was confirmed by measurements of the relative intensity of the peptide spot. This difference was senescent cell‐specific and not due to the differences in rate of growth of senescent and non‐senescent cells.
Elevation of HeLa cell 3‐hydroxy‐3‐methylglutaryl coenzyme a reductase activity by glucocorticoids: Possible relationship to the cell cycle
Authors: Cavenee Webster K. , Melnykovych George 
Published: February 2005

AbstractElevation of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase (HMG‐CoA reductase, EC 1.1.1.34) activity by glucocorticoids was shown to be dependent on the concentration of hormone in the medium over a range of 5 × 10−10 to 1 × 10−8 M, although the presence of steroid in the assay at 10−5 M elicited no increase in activity. There was a demonstrated time dependence for the addition of dexamethasone i.e., from zero to six hours after serum removal, addition of hormone resulted in the same peak activity; addition at 12 hours gave slight elevation but resulted in an extended maintenance of the peak level of activity; addition at 24 hours showed no effect. When cycloheximide was added at the above times, subsequent kinetics showed identical decay of the enzyme activities from control and treated cultures at 6 and 24 hours, but at 12 hours the activity from dexamethasone treated cells exhibited an extended lag before the onset of decay, which then proceeded at the same rate as the control. The continuous presence of the hormone was not necessary for the induction to continue and the addition of Actinomycin D to cultures incubated in the presence of hormone resulted in an immediate decay of catalytic activity without evidence of “superinduction”. The addition of progesterone at the same time as dexamethasone resulted in a concentration‐dependent inhibition of the augmentation, suggesting the involvement of the glucocorticoid receptor in the aug‐mentation, suggesting the involvement of the glucocorticoid receptor in the elevation of HMG‐CoA reductase activity. Flow microfluorometric (FMF) analysis of hormone treated cells indicated a delayed entrance into the DNA synthesis (S) phase of the cell cycle. The temporal relationships between this cell cycle perturbation and HMG‐CoA reductase elevation are discussed.
Frequency differences between nuclear and polysomal sequences of poly(A)‐containing RNA from cultured akr mouse embryo cells
Authors: Siegal Gene P. , Quinlan Thomas J. , Moses Harold L. , Getz Michael J. 
Published: February 2005

AbstractThe involvement of post‐transcriptional mechanisms in the determination of the frequency distribution of messenger RNA sequences has been studied in cloned mouse embryo cells in culture. Hybridization kinetic experiments between poly(A)‐containing RNA and complementary DNA have been used to study the alterations in frequencies which occur in those nuclear poly(A)‐containing RNA sequences which are conserved in cytoplasmic polyribosomes. Sequences adjacent to nuclear poly(A) tracts are present in a much narrower frequency distribution in the nucleus than in polysomes, with a large proportion of the nuclear sequences present in an average frequency of about one molecule per cell. Few nuclear sequences appear to be present in more than ten copies per cell. A minimum of 70% of these sequences are also found in polyribosomal RNA but in greatly altered frequencies. Abundant sequences which comprise a major fraction of the poly(A)‐containing polyribosomal RNA are derived from a small fraction of the nuclear poly(A)‐adjacent RNA sequences. Very few nuclear poly(A)‐adjacent sequences are present in a frequency characteristic of high abundance polysomal sequences. Conversely, poly(A)‐containing polyribosomal RNA appears to contain few sequences which are present in as low a frequency as the majority of nuclear poly(A)‐adjacent sequences. These observations suggest that post‐transcriptional mechanisms play a major role in determining the steady‐state frequency of polyribosome‐associated messenger RNAs.
The effect of amino acids on the temperature sensitive phenotype of the mammalian leucyl‐tRNA synthetase mutant ts Hl and its revertants
Authors: Molnar S. J. , Rauth A. M. 
Published: February 2005

AbstractThe temperature sensitive leucyl‐tRNA synthetase mutant tsHl and two revertants have been compared to the parental Chinese hamster ovary cells with respect to the effects of amino acid concentrations in the medium on growth. Elevating the leucine concentration 30‐ or 100‐fold allowed tsHl to grow exponentially at 38.5°C, normally the nonpermissive temperature. Partial revertants that had recovered some enzyme activity required smaller supplements for growth. Measurements of the leucine pools indicated that they respond directly to the extracellular leucine concentration and may mediate the effect. Use of combinations of amino acids confirmed that isoleucine has a similar though weaker effect on tsHl and identified an even weaker protection by valine. The triple combination of leucine, isoleucine and valine was a much more efficient medium supplement and three times normal concentrations of these amino acids supported growth of tsHl at 38.5°C. It is postulated that they are acting at their respective aminoacyl‐tRNA synthetases to help stabilize a complex which also contains the mutant leucyl‐tRNA synthetase. The pool size measurements also showed that the leucine pools of tsHl and a revertant increased 2‐fold more in a response to increased temperature than those of WT. It is suggested that this is a regulatory response to low leucyl‐tRNA synthetase activity and is important in determining growth phenotypes.
Isolation and characterization of revertants of the mammalian temperature sensitive leucyl‐tRNA synthetase mutant tsHI
Authors: Molnar S. J. , Thompson L. H. , Lofgren D. J. , Rauth A. M. 
Published: February 2005

AbstractNine spontaneous and seven ethyl methanesulfonate induced revertants of the Chinese hamster ovary cell line mutant (tsHl), which possesses a temperature sensitive leucyl‐tRNA synthetase, were isolated and characterized with respect to growth rate, leucyl‐tRNA synthetase activity and thermolability, intracellular leucine pool size, and rRNA content. Although most revertants had increased leucyl‐tRNA synthetase activity, and of those tested, all but one had increased thermostability, each appears to be unique. One revertant may be an intergenic suppressor since it appears to contain an elevated level of tsHl‐like synthetase. There was no evidence for any of the revertants having increased rRNA and tRNA contents, however, many showed leucine pools two to three times larger than wild type cells. Since similar increases have been observed in tsHl cells they are believed to result from regulation of leucine pool size by the leucyl‐tRNA synthetase and are of a magnitude sufficient to affect significantly the growth of revertants at 38.5°C.
Comparison of chloride transport in mouse erythrocytes and friend virus‐transformed erythroleukemic cells
Authors: Harper Patricia A. , Knauf Philip A. 
Published: February 2005

AbstractFriend erythroleukemic cells, which grow continuously in tissue culture, resemble in many respects early precursors of mouse erythrocytes. To determine whether or not the membranes of these cells exhibit the rapid and selective exchange of chloride, a specialized feature of the mature erythrocyte membrane, anion fluxes were compared in Friend cells and mouse erythrocytes. The chloride flux in Friend cells at 37°C was about 800‐fold lower than in mouse erythrocytes (extrapolated from data at lower temperatures). This difference could not be accounted for by the somewhat lower chloride concentration in Friend cells relative to erythrocytes. Comparison of chloride and sulfate fluxes revealed that the Friend cells had over a 1,000‐fold lower selectivity for chloride versus sulphate than did the mouse red cells. The temperature dependence of chloride fluxes in Friend cells corresponded to an Arrhenius activation energy of 17.9 kcal/mol, in contrast to over 30 kcal/mol for mature red cells. The chloride flux in Friend cells was also 10‐fold less sensitive to the inhibitor, furosemide, than was the flux in mature red cells. The selective chloride exchange system of the mature erythrocyte therefore does not seem to be functional at the stage represented by the Friend cell, and must appear at some later stage of erythroid maturation.
The nature of cells generating human myeloma colonies in vitro
Authors: Hamburger Anne W. , Kim Mary B. , Salmon Sydney E. 
Published: February 2005

AbstractFreshly explanted human myeloma cells formed colonies of monoclonal plasma cells in soft agar in the presence of medium conditioned by the adherent spleen cells of mineral oil‐primed BALB/c mice. The medium showed peak activity at a dilution of 1:4. 2‐mercaptoethanol or monothioglycerol was necessary for colony formation. Other thiols tested were ineffective in promoting colony growth. Colony‐forming cells adhered to nylon wool, but not glass beads or plastic dishes. The presence of E‐rosetting cells was not required for myeloma colony formation. Antibody prepared against a human myeloma cell line, RPMI 8226, reduced colony formation. These studies demonstrate the usefulness of this bioassay for determining functional properties of the myeloma colony‐forming cell.