bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular calcium redistribution and its relationship to fMet‐Leu‐Phe, leukotriene B4, and phorbol ester induced rabbit neutrophil degranulation
Authors: Naccache P. H. , Molski T. F. P. , Borgeat P. , Sha'afi R. I. 
Published: February 2005

AbstractThe addition of low concentrations (<10−7 M) of the calcium ionophore A23187 to rabbit neutrophils re'eases the intracellular pool of calcium previously shown in radioactive steady‐state and chlortetracycline fluorescence studies to be mobilized by chemotactic factors. A23187 at these concentrations elicits no functional responses from these cells. However, A23187, added before chemotactic factors such as fMet‐Leu‐Phe and leukotriene B4, inhibits the ability of the latter stimuli to induce, in the presence of cytochalasin B, an exocytotic release of the neutrophil's cytoplasmic granules. These results imply that the chemotactic‐factor‐induced release of intracellular calcium is a necessary event for the optimal activation of the neutrophils. Phorbol esterinduced neutrophil degranulation on the other hand is unaffected by exposure to A23187, thereby completely dissociating its mechanism of action from rises in cytoplasmic free calcium.
Increased thermoresistance developed during growth of small multicellular spheroids
Authors: Wigle Jeffrey C. , Sutherland Robert M. 
Published: February 2005

AbstractMammalian cells growing as multicell spheroids, an in vitro model of tumor microregions, have been shown previously to be more resistant than single cells from monolayer cultures to killing by ionizing radiation, hyperthermia, ultrasound, and chemotherapeutic drugs. Although the mechanisms by which cells in spheroids acquire these increased resistances are unknown, available evidence has indicated that intercellular contact mediates the process for ionizing radiation. This investigation was undertaken to evaluate the role of intercellular contact produced during growth of small spheroids on the sensitivity of EMT6/Ro mouse mammary tumor cells to moderate hyperthermia. Increased thermoresistance developed in small spheroids (∼ 70 μm diameter, 25 cells/spheroid), as measured by colony formation, after exposures to different temperatures in the range of 37 to 45°C for periods ≤ 2 hr and at 42.5°C for ≤ 8 hr. Experiments were performed to determine the relative contributions to this increased thermoresistance of (1) the extent of intercellular contact in spheroids of different cellular multiplicities, (2) differences in membrane damage influenced by trypsin heat treatment sequence, and (3) physiological changes associated with growth of cells as spheroids in suspension compared to monolayer culture. Treatment with trypsin prior to heating sensitized cells to killing by hyperthermia but did not account for the differential thermoresistance between cells from spheroids and monolayers. Spheroid multiplicity in the range of 1.16 to 76.2 cells/spheroid had no significant effect on cell survival after hyperthermia. However, cells grown in spinner suspension culture were more thermoresistant than cells from monolayer cultures and nearly as thermoresistant as cells in spheroids. From these data we conclude that the greater thermoresistance of EMT/Ro cells in spheroids is the result of cellular physiological changes associated with growth in suspension and is not mediated by intercellular contact.
Adaptive regulation of neutral amino acid transport system A in rat H4 hepatoma cells
Authors: Kilberg Michael S. , Han He‐Ping , Barber Ellen F. , Chiles Thomas C. 
Published: February 2005

AbstractSubstrate regulation of System A transport activity in rat H4 hepatoma cells is described. The uptake of several amino acids was tested in the presence of system‐specific inhibitors. System A activity was increased in a RNA‐ and protein synthesis‐dependent manner by amino acid deprivation of the cells (adaptive regulation), whereas transport by Systems ASC, N, y+, and L was unaffected. Unlike human fibroblasts, the H4 cells did not require serum to exhibit the depression of System A. At cell densities between 88 × 103 and 180 × 103 cells/cm2, the degree of adaptive regulation was inversely related to cell density. Both transport of AIB and adaptive regulation of System A were nearly abolished if either K+ or Li+ was substituted for Na+ in the medium. The presence of cycloheximide or tunicamycin blocked further increases in starvation‐induced activity within 1 hr of addition, suggesting the involvement of a plasma membrane glycoprotein. In contrast, if the medium was supplemented with actinomycin after the stimulation of System A had begun, the activity continued to increase for an additional 2 hr before being slowed by the inhibitor. The contributions of trans‐inhibition and repression to the amino acid‐induced decay of System A activity were estimated for several representative amino acids. In general, the System A activity in normal rat hepatocytes was much less sensitive to trans‐inhibition than the corresponding activity in H4 hepatoma cells. The half‐life values for the amino acid‐dependent decay of System A ranged from 0.5 to 2.0 hr.
Characterization of chemically and virally transformed variants of Madin‐Darby canine kidney (MDCK) epithelial cells
Authors: U H. S. , Boerner P. , Rindler M. J. , Chuman L. , Saier M. H. 
Published: February 2005

AbstractOncogenic derivatives of Madin‐Darby canine kidney (MDCK) cells were isolated in the nude mouse, and nononcogenic anchorage‐independent transformants were isolated in vitro following chemical mutagenesis in vitro. These transformed cell lines as well as a Moloney sarcoma virus (MSV) transformed line were characterized with respect to their serum and anchorage requirements, growth rates, final saturation densities, and sensitivities to contact inhibition. None of these in vitro growth characteristics were found to correlate with tumorigenicity in nude mice. One tumongenic clone, MDCK‐T1, was characterized with respect to serum‐free growth requirements, cAMP production, and ornithine decarboxylase (ODC) activity. These cells exhibited a significant reduction in the PGE1 requirement for growth, they produced higher levels of cAMP, and they expressed a reduced level of ODC activity relative to the parental MDCK cells. These findings may reflect changes in growth control mechanisms which accompany kidney epithelial cell tumori‐genesis and suggest that the study of transformed lines derived in this manner could lead to the identification of in vitro properties which are associated with malignancy.
Clonal heterogeneity in colony stimulating factor production by murine T lymphocytes
Authors: Kelso Anne , Metcalf Donald 
Published: February 2005

AbstractA panel of 55 alloreactive murine T‐lymphocyte clones was screened for the production of granulocyte‐macrophage colony stimulating factor (GM‐CSF), multilineage CSF (multi‐CSF), human‐active eosinophil CSF (human‐active EOCSF), and interleukin 2 (IL‐2) in response to stimulation with the lectin concanavalin A. Many clones were also characterized for cytolytic specificity and expression of the T‐cell antigen receptor‐associated surface markers Lyt‐2 and L3T4, which reflect their specificity for Class I (H‐2K, H‐2D) or Class II (H‐2I, MIs) histocompatibility antigens, respectively. Eighty percent of the clones secreted detectable quantities of at least one of the four factors measured. Of the factor‐producing clones, all appeared to secrete GM‐CSF and half also secreted multi‐CSF. A subpopulation of multi‐CSF producers also released human‐active EO‐CSF. More than half of the factor‐producing clones secreted detectable IL‐2; whereas the IL‐2 producing clones included some that did not secrete multi‐CSF, IL‐2 production was always associated with concomitant synthesis of GM‐CSF. Comparison of the range and quantities of factors secreted by Lyt‐2+ and L3T4+ clones indicated that more L3T4+ clones produced measurable titers of the four factors; on average, this group also secreted 10‐ to 100‐fold higher titers of both the hemopoietic regulators and IL‐2 than Lyt‐2+ clones. Cells of the L3T4+ phenotype would therefore be expected to account for the majority of CSF and IL‐2 secretion by polyclonal populations of activated T lymphocytes.
Intracellular Ca2+ sequestration in cultured mouse fibroblasts: ATP‐dependent Ca2+ uptake by saponin‐permeabilized Swiss 3T3 cells
Authors: Yamanishi Kiyofumi , Iwashima Akio 
Published: February 2005

AbstractIntracellular Ca2+ sequestration was studied by determining 45Ca2+ uptake by saponin‐permeabilized Swiss 3T3 mouse fibroblasts. Uptake was enhanced by addition of ATP and was dependent on the concentrations of ATP and saponin. ADP and UTP also enhanced uptake, but less than did ATP. Mitochondrial Ca2+ uptake was distinguished from nonmitochondrial uptake by the use of antimycin A plus oligomycin at various Ca2+ concentrations. Major sites for sequestration at 10−5 M Ca2+ are probably mitochondrial and those at 10−7 M Ca2+ nonmitochondrial, because these drugs inhibited ATP‐dependent Ca2+ uptake at 10−5 M but not at 10−7 M. A23187 completely inhibited uptake, regardless of the Ca2+ concentration. Effects of various agents on sequestration were tested; ruthenium red, 2,4‐dinitrophenol, monovalent cation ionophores, and melittin markedly decreased ATP‐dependent Ca2+ uptake at 10−5 M Ca2+. the calmodulin antagonists trifluoperazine (TFP) and W‐7 inhibited Ca2+ uptake at both 10−5 and 10−7 M Ca2+, TFP moreso than W‐7, especially at 10−5 M. These results suggest that intracellular Ca+2 in Swiss 3T3 cells is regulated by mitochondrial and nonmitochondrial Ca2+ stores in an ATP‐dependent way and that in a physiological resting state the nonmitochondrial Ca2+ store, probably the endoplasmic reticulum, is the major site for the sequestration.
Protein synthesis in differentiating normal and leukemic erythroid cells
Authors: Adkins Becky , Beug Hartmut , Graf Thomas 
Published: February 2005

AbstractErythroleukemic cells transformed by the AEV or S13 strains of avian erythroblastosis virus differentiate in vitro either spontaneously (S13) or following a temperature induction (temperature‐sensitive mutants of AEV). To study differentiation in these cells at the molecular level, homogeneous fractions of maturing cells at discrete stages of differentiation were prepared by Percoll density‐gradient centifugation. This method was also used for the fractionation of differentiating normal erythroid cells separated from total bone marrow by an immunological “panning” technique. Total protein synthesis in these cells was then analyzed by two‐dimensional gel electrophoresis. The expression of several proteins was altered in differentiating leukemic cells but not in their normal counterparts. However, in general, the normal and leukemic cells from comparable stages of maturity showed closely related protein synthetic patterns. Similar early and late changes in the synthesis of a number of polypeptides were detected during maturation from early erythroid precursors to terminally differentiated erythrocytes. Further, the leukemic as well as the normal cells appeared to undergo a major switch in total protein synthetic pattern during late differentiation. These results demonstrate that normal and erythroleukemic cells differentiate along similar pathways.
Enhancement of colony‐stimulating‐factor–dependent clonal growth of murine macrophage progenitors and their phagocytic activity by retinoic acid
Authors: Goldman Rachel 
Published: February 2005

AbstractThe effect of retinoic acid (RA) on the colony‐stimulating‐factor‐dependent clonal growth of myeloid progenitors was assessed in semisolid agar cultures of mouse bone marrow cells using L‐cell‐conditioned medium that gave rise to macrophage colonies, granulocyte colonies, and mixed macrophage‐granulocyte colonies and clusters. RA was found to enhance the overall formation of myeloid colonies (about 50%) and clusters in 7‐day cultures. The increase was due to an enhanced formation of macrophage colonies (70–250%) and clusters which reached a maximal value at about 3 μM RA. In 4‐day cultures, the effect of RA on macrophage colony formation was biphasic with a maximal enhancement at 10 nM. RA suppressed granulocyte‐colony formation in macrophages at all stages of differentiation and/or maturation in culture. The Fc‐receptor‐mediated erythrophagocytosis as well as the phagocytosis of heat‐killed yeast cells (HK‐yeast) and starch particles increased by RA treatment in a dose‐dependent manner, reaching an increase of 100–200% of the activity expressed in the absence of RA. Peritoneal exudate macrophages likewise physiological and pharmacological concentrations of RA. Expression of an RA‐mediated increase in phagocytic activity required a prolonged incubation with RA (> 19 hr). The data suggest that RA may be of physiological relevance in the regulation of proliferation and function of hemopoietic cells. Therapeutic doses of RA may potentiate macrophage proliferation and function, elements that are crucial at all phases of the various defense mechanisms that the organism possesses.
Release and properties of endothelium‐derived relaxing factor (EDRF) from endothelial cells in culture
Authors: Cocks T. M. , Angus J. A. , Campbell J. H. , Campbell G. R. 
Published: February 2005

AbstractCultured bovine endothelial cells were seeded onto the intimal surface of endothelium‐denuded rings of canine coronary artery. These rings did not previously relax to acetylcholine, substance P, bradykinin, and A23187. After seeding, the same rings relaxed to bradykinin and A23187, but not to acetycholine or substance P. Indomethacin pretreatment did not affect these responses. Cells from the same source were then grown to confluence on microcarrier beads, poured into small columns, and perfused with Krebs+ solution. The perfusate from the columns was bioassayed on endothelium‐denuded rings of coronary artery from either the dog or pig. Challenge of the column in the presence of indomethacin with either bradykinin or A23187 as well as acetylcholine or substance P caused release of a substance that relaxed both types of artery. Its activity half‐life was 6.4 ± 0.4 sec at 37°C and it was hydrophilic and negatively charged. Prostacyclin (PGI2) as a candidate for EDRF was ruled out because (1) indomethacin failed to block its release and (2) the pig coronary artery, although insensitive to PGI2, relaxed to the endothelium‐derived substance. These results show that, in response to a number of dilator drugs, cultured endothelial cells release a vascular relaxing substance (EDRF) that has characteristics similar to the EDRF of normal endothelium. The chemical nature of EDRF awaits clarification.
Dominant and recessive mitogen‐nonproliferative variants of 3T3 cells
Authors: Terwilliger Ernest , Herschman Harvey R. 
Published: February 2005

AbstractWe have previously isolated 3T3 cell variants unable to respond to specific mitogens. In this report we analyze the dominant and/or recessive nature of these variants. (1) Two independently isolated EGF nonproliferative variants are unable to bind EGF. Hybrids between 3T3R5 cells (thymidine kinase deficient, ouabain‐resistant) and these variants express EGF receptors; the “EGF receptorless” phenotype of these variants is recessive. (2) Hybrids between these two variants do not bind EGF; they are defective in a common, non‐complementing function. (3) A TPA nonproliferative 3T3 variant is also recessive; hybrids with 3T3R5 mount a mitogenic response to TPA. (4) In contrast a fourth variant, which can neither bind labeled EGF nor respond to TPA, is dominant for both characteristics. Hybrids between this latter variant and 3T3R5 can neither bind EGF nor mount a mitogenic response to TPA.
Vasoactive amines modulate actin cables (stress fibers) and surface area in cultured bovine endothelium
Authors: Welles Seth L. , Shepro David , Hechtman Herbert B. 
Published: February 2005

AbstractCultured bovine aortic endothelial cells were fixed and stained with NBD‐phallicidin and quantitated with a digital image analyzer for changes in actin cables and surface area. Serotonin (5‐HT), norepinephrine (NE), dopamine and histamine (all at 10−4M concentrations) were tested for their ability to induce cytoskeletal changes. Only 5‐HT and NE increased action cables significantly (p < 0.01), 80.7% and 97.9%, respectively. Dopamine and histamine treated cells showed a 67.4% and 80.8% decrease in actin cables respectively (p < 0.01). Stimulated increases of actin cables by 5‐HT were inhibited by Ketanserin, and propranoiol inhibited NE stimulation of actin cables. Treatment of cells with these blockers alone also decreased actin cables below control values (p < 0.01). Pretreatment of cells with diphenhydramine, but not cimetidine, inhibited histamine‐induced decreases in actin cables. Stimulation of surface area by 5‐HT and NE was also observed, with 40.8% and 80.7% increases respectively, when compared with controls (p < 0.01). The increases in actin cables were associated with a lack of ruffled edges that are indicative of motile cells. In contrast, induced decreases in actin cables resulted in cells with ruffled edges. Exogenous 5‐HT and NE have been shown to prevent the increased permeability visible as extravasation of red blood cells from postcapillary venules in thrombocytopenic animals. The present data suggest that 5‐HT and NE may be involved in maintaining the endothelial barrier function by a receptor‐mediated stimulation of actin cables. Also, histamine‐induced decreases in actin cables may be correlated with the amine's action in vivo as a mediator of increased inflammatory permeability.
Effect of endothelial cell conditioned medium on the growth of human bone marrow fibroblasts
Authors: Scarrà Giovanna Bianchi , Fiorentini Paola , Garbarino Giovanni , Bellone Graziella , Sessarego Mario , Ajmar Franco 
Published: February 2005

AbstractBoth endothelial cells (EC) and fibroblasts, two discrete populations of hemopoietic stroma, are known to modulate the proliferation and differentiation of hemopoietic progenitors. Recent reports also demonstrated that EC stimulate the in vitro growth of fibroblasts via a soluble factor. This finding seems to support the hypothesis that EC may play a role in the pathogenesis of bone marrow fibrosis in myeloproliferative disorders (MD).We have studied the effects of the conditioned medium (CM) from human umbilical vein EC cultures, obtained in serum free conditions, on the growth of bone marrow fibroblasts from normal donors and from patients with MD. The results show that EC derived CM contains a factor which stimulates the proliferation of fibroblasts and that can act as an authentic growth factor by inducing “quiescent” fibroblasts to proliferate.Moreover, we found that this endothelial derived growth factor (EDGF) equally promotes the proliferation of both normal and pathological progenitors of bone marrow fibroblasts (CFU‐F) by increasing both the number and the size of the colonies.
Synergistic stimulation of alkaline phosphatase activity in bovine aortic endothelial cells grown in the presence of retinoids and glucocorticoids
Authors: Adams Susan E. , Melnykovych George 
Published: February 2005

AbstractLow concentrations of retinol (10 nM ‐ 10 μM) and dexamethasone (0.1 nM ‐ 1.0 μM) elevated activity of alkaline phosphatase (E.C. 3.1.3.1) in bovine endothelial cells in culture. The effect was apparent after 48 hr of growth in the presence of either of the two compounds, prior to any growth stimulatory effects. A synergistic stimulation of alkaline phosphatase was achieved in the presence of both retinol and dexamethasone implying different mechanisms of induction. Retinoic acid and retinyl acetate also elevated alkaline phosphatase but the retinol analogue reduced in the side chain (perhydroretinol) was inactive. The ability of steroids to elevate alkaline phosphatase activity was associated with the structure commonly required for glucocorticoid activity; however, competitors for the steroid receptor binding failed to prevent the elevation by dexamethasone or the synergism in the presence of retinol and dexamethasone.
Prolongation of duration of G2 arrest delays and finally blocks entry into M phase in contrast to stable and reversible G1 arrest: Study of a G1/G2 temperature‐sensitive mutant of rat 3Y1 fibroblasts
Authors: Zaitsu Hirokazu , Kimura Genki 
Published: February 2005

AbstractProliferation of 3Y1tsF121 cells was arrested in G1 and G2 phases after a shift up to 39.8°C (restrictive temperature). Both arrests were reversible: after a shift down to 33.8°C (permissive temperature), these cells effectively entered the next phases. However, the entry into M phase of the G2‐arrested cells was delayed depending on the time in arrest. The G2‐arrested cells finally became incapable of entering M phase with a prolonged incubation at 39.8°C. Under the same condition, G1‐arrested cells did not lose their ability to proliferate, and their delay of entry into S phase was slight. Therefore, cells in G2 phase are, in a sense, more unstable than the cells in G1 phase. These results also suggest that the time required for entry into M phase may depend on the preparedness for the initiation of M phase and, that it may be prolonged under the condition where the preparedness for entry into M phase is diminished.
A Collagen:Glucosyltransferase at the surface of malignant fibroblasts
Authors: Bauvois Brigitte , Roth Stephen 
Published: February 2005

Abstract3T12 fibroblasts possess glucosyltransferases that catalyze the transfer of glucose from UDP‐Glucose to galactosylhydroxylysyl residues on collagenous acceptors. The presence of the enzyme activity at the cell surface is indicated by the following findings: (a) suspensions of intact cells, as well as intact cell monolayers, glucosylate gelatinized collagen (b) glucose transfer is not due to UDP‐Glucose hydrolysis and subsequent intracellular utilization of the free glucose (c) experiments using cell suspensions with known proportions of broken cells indicate that the glucosyltransferase activity is attributable to intact cells and not to contamination by intracellular enzymes from broken cells. The Km value for UDP‐Glucose is about 20 μM. The enzyme has a pronounced requirement for manganese, and shows highest activity between 2 and 10 mM. The optimal Mn2+ concentration for the intracellular gelatin:glucosyltransferase activity is more restricted (5 to 10 mM). Glucosyltransferase activity is strongly inhibited by diamide and N‐ethylmaleimide (5 mM), suggesting that intact sulfhydryl residues present in the enzyme are essential.