bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic requirements for maintenance of the chlortetracycline‐labeled pool of membrane‐bound calcium in human neutrophils
Authors: Smolen James E. , Noble Paul , Freed Richard , Weissmann Gerald 
Published: February 2005

AbstractHuman neutrophils labeled with chlortetracycline (CTC), commonly used as a probe of membrane‐bound calcium, release lysosomal enzymes and exhibit a rapid decrease in fluorescence when exposed to the chemotactic peptide fMet‐Leu‐Phe or the lectin Con A. This decrease has been attributed to the release of calcium from a membrane‐associated “trigger pool.” The nature of this putative pool has been further characterized by examining the effects of various inhibitors on the CTC fluorescence response and lysosomal enzyme release from stimulated neutrophils. These agents included inhibitors of glycolysis (2‐deoxyglucose and iodoacetate), an uncoupler of oxidative‐phosphorylation (KCN), and a sulfhydryl inhibitor (N‐ethylmaleimide). Resting neutrophils, labelled with CTC demonstrated an enhanced decay of baseline fluorescence when exposed to 2‐deoxyglucose or iodoacetate. This suggested that the pool of membrane‐bound calcium labeled by this probe was maintained by glycolytic metabolism. Furthermore, 2‐deoxyglucose and iodoacetate inhibited both the stimulated decrease in CTC fluorescence and lysosomal enzyme release induced by fMet‐Leu‐Phe and Con A in a time‐dependent manner. KCN did not inhibit either response to stimulation, but did retard the recovery of CTC fluorescence observed when fMet‐Leu‐Phe was used as the stimulus. High concentrations of N‐ethylmaleimide (100 μM) completely inhibited both the CTC fluorescence response and lysosomal enzyme release almost immediately; low concentrations of N‐ethylmaleimide (30 μM) inhibited lysosomal enzyme release in a time‐dependent manner without significantly affecting changes in CTC fluorescence. These results are consistent with the hypothesis that CTC serves as a probe of membrane‐bound “trigger” calcium, the release of which is dependent upon intact glycolysis and is a requirement for lysosomal enzyme release.
Histone protein and DNA synthesis in HeLa cells after thermal shock
Authors: Warters Raymond L. , Lee Stone O. 
Published: February 2005

AbstractExposure of suspension‐cultured HeLa cells to a 45° thermal shock resulted in cell inactivation and inhibition of both protein and DNA synthesis. DNA synthesis was inhibited in a biphasic manner with a more sensitive (D0 = 7 min) and a less sensitive (D0 = 20 min) phase. The less sensitive process was demonstrated to be DNA chain elongation. Transport of thymidine into intracellular pools was significantly less sensitive to thermal shock (D0 in excess of 200 min). When HeLa cells were heated at 45° for 15 min there was an 80% inhibition of incorporation of precursors into both DNA and protein with little effect on precursor transport into cellular pools. While the rate of synthesis of whole cell and histone protein (H2a, H2b, H3, and H4) and DNA chain elongation recovered by 6 h after cell heating, total precursor incorporation into DNA was only 0.4 of control levels. The long‐term depression of the DNA synthetic rate could not be explained by a cell cycle redistribution, a depression in the total fraction of S phase cells synthesizing DNA, or by a depression in the rate of DNA chain elongation. We conclude that thermal shock results in a long‐term depression in the fraction of cell replicons involved in DNA replication.
Colchicine prevents the translation of mRNA molecules transcribed immediately after proliferative activation of hepatocytes in regenerating rat liver
Authors: Walker P. Roy , Whitfield J. F. 
Published: February 2005

AbstractA dual‐labelling technique has been used to establish that partial hepatectomy has no effect on the degradation of poly (A)+ mRNA and confirms that the increased incorporation of precursor into mRNA during early prereplicative development reflects an actual increase in mRNA biosynthesis. Simultaneous studies on the changes in nuclear RNA metabolism support the conclusion that an increase in gene transcription does occur. Colchicine, at concentrations known to disrupt microtubules, has no effect on this increase in gene transcription but prevents the translation of the gene products by promoting polysome disaggregation transiently during a critical stage of prereplicative development. Studies with mefenamic acid and hydrocortisone, specific inhibitors of prostaglandin metabolism, have ruled out any involvement of prostaglandins in the induction of prereplicative mRNA synthesis.
A kinetic and clonal analysis of heterogeneity in K562 cells
Authors: Alder Susan , Ciampi A. , McCulloch E. A. 
Published: February 2005

AbstractExpression of markers of differentiation was measured in a clone of the continuous cell line K562, derived originally from the cells of a patient with leukemia. Three of the markers were lineage specific, R18 for erythropoiesis and 80H.5 and My‐1 for granulopoiesis. The fourth marker was the self‐renewal capacity of clonogenic cells. The markers were measured as a function of time in pooled colonies from day 2 to day 12, and at a point of time in individual colonies. Evidence of an orderly pattern of marker appearance and disappearance was not seen. Rather, their expression appeared to occur at random during growth.
Prereplicative changes in the soluble calmodulin of isoproterenol‐activated rat parotid glands
Authors: Gonzales R. Campos , Whitfield J. F. , Boynton A. L. , MacManus J. P. , Rixon R. H. 
Published: February 2005

AbstractCells of rat parotid glands were maximally stimulated to initiate DNA synthesis by injecting into the animal a single dose of 25 to 150 mg of isoproterenol/ kg of body weight. During the 18‐ to 21‐hr prereplicative period following injection of the highest dose of the drug, there were two predominant and transient redistributions of calmodulin from the bound to the soluble form, which tripled the level of soluble calmodulin at 3 hr and again at 18 hr just before the initiation of DNA synthesis. A small (50%) increase in total calmodulin was observed only during the early (3‐h) prereplicative surge of soluble calmodulin. The late, pre‐DNA‐synthetic surge of soluble camodulin and the initiation of DNA synthesis were both prevented in rats that lacked their parathyroid‐thyroid gland complex and had been hypocalcemic for 48 or 72 hr. Unlike the effect of high doses of isoproterenol, low doses (e.g., 25 mg/kg body weight) of the β‐adrenergic drug could maximally stimulate DNA synthetic activity without the later pre‐DNA‐synthetic surge of soluble calmodulin, suggesting that any apparent correlation between the level of calmodulin and DNA synthesis may be spurious and that an actual increase in the level of soluble calmodulin just before the onset of DNA synthesis was not a prerequisite for DNA synthetic activity in parotid cells.
The role of Protein breakdown in growth, quiescence, and starvation of vascular smooth muscle cells
Authors: Libby Peter , O'Brien Kathleen V. 
Published: February 2005

AbstractProtein accumulation in growing cells may be due in part to a reduction in the rate of protein breakdown. Previous studies of the relation of cell proliferation to protein degradation often produced growth arrest by conditions that may involve nutritional deprivation. However, nutrient lack can itself accelerate proteolysis and produce negative protein balance. We therefore reexamined the relation between growth and protein breakdown using a more selective method for limiting cell growth. We produced quiescent cell cultures using a chemically defined, serum‐free medium supplemented with hormones and nutrients. Such media can maintain viability and near neutral protein balance in cultured vascular smooth muscle cells, in part because of reduced breakdown of cellular protein. We then compared rates of protein degradation in these quiescent but not starving cells, to those of cultures stimulated to grow by addition of mitogenic substances. Platelet‐derived growth factor, fibroblast growth factor, or fetuin added to insulin‐containing medium stimulated growth of smooth muscle cells, but further reduced protein breakdown only slightly. Contrary to the implications of certain previous studies, our results show that proliferating cells can accumulate protein without an appieciable reduction in the rates of protein breakdown. Thus, while accelerated proteolysis appears to be an important adaptation to adverse nutritional conditions, growth of smooth muscle cells does, not require changes in overall protein breakdown, but occurs primarily through an increase in protein synthesis.
Galactosyltransferase activity and cell growth: Uridine diphosphate (UDP)galactose inhibition of murine leukemic
Authors: Klohs Wayne D. , Wilson James R. , Weiser Milton M. , Frankfurt Oscar , Bernacki Ralph J. 
Published: February 2005

AbstractUDPgalactose inhibits the growth of mouse leukemic L1210 cells. In calf serum supplemented Dulbecco's medium (CS‐DMEM), 1.2 mM UDPgalactose (UDPgal) inhibited cell growth by 50% (IC50), and 5 mM UDPgalactose inhibited cell growth by 92%. Other nucleotide sugars as well as galactose, glucose, and galactose‐1‐phosphate had little or no effect on cell growth. Uridine nucleotides, which inhibit galactosyltransferase activity, protected L1210 cells from the growth inhibitory effect of UDPgalactose when both were added simultaneously to culture media. Unlike mouse 3T12 cells, in which no inhibition of cell growth was observed with heat‐inactivated calf serum (HICS)‐DMEM, 5 nM UDPgalactose inhibited L1210 cell growth in HICS‐DMEM to the same degree as that observed in CS‐DMEM. In contrast to 3T12 cells, L1210 cells secrete significant galactosyltransferase activity into the media. Complete inhibition of 3T12 cell growth by UDPgal was observed if HICS‐DMEM medium was first conditioned by L1210 cells for 48 hours. No difference in cell growth or [3H]thymidine uptake was detected after 6 hours of exposure to UDPgalactose, but both were significantly decreased at 24 and 48 hours. Flow cytometric analysis of UDPgalactose effects on L1210 cells revealed no differences in the distribution of cells in G1, S, or G2‐M of the cell cycle after 6 hours of incubation, but after 16 hours of UDPgalactose treatment, L1210 cells were arrested in early S phase. These cells were completely viable and morphologically similar to control L1210 cells. Normal growth was resumed when UDPgal was removed. The data suggest that UDPgalactose inhibition of cell growth requires extracellular galactosyltransferase activity and that the effect is mediated via the cell membrane.
Altered methionine metabolism occurs in all members of a set of diverse human tumor cell lines
Authors: Stern Peter H. , Wallace C. Douglas , Hoffman Robert M. 
Published: February 2005

AbstractMethionine dependence is a metabolic defect found thus far only in transformed and malignant cells. The defect is manifested as the inability of cells to grow in media in which methionine (Met) is replaced by its immediate precursor homocysteine (Hcy). We have termed this Met − Hcy + media. We demonstrate here that methionine‐dependent cells derived from human tumors, compared to normal methionine‐independent cells, have low levels of free Met, low levels of S‐adenosylmethionine (AdoMet) and elevated levels of S‐adenosylhomocysteine (AdoHcy) when incubated in Met − Hcy + medium. Methionine‐independent human tumor cells also have very low levels of free Met compared to normal cells but generally have levels of AdoMet and AdoHcy comparable to normal cells in Met − Hcy+ medium. All tumor cell types incorporate amounts of Met into protein similar to normal methionine‐pindependent human fibroblasts when incubated in Met − Hcy+ medium, thereby indicating apparently normal levels of Met synthesis in the tumor cells. The methionine‐independent tumor cell lines in Met − Hcy+ medium seem able to regulate their AdoMet/AdoHcy ratios normally despite this defect in having very low levels of free Met. Thus, in a diverse set of human tumor cell lines, all are defective in at least one aspect of Met metabolism, giving rise to the possibility of a general metabolic defect in cancer.
Prostaglandin F2α stimulates phosphatidylinositol turnover and increases the cellular content of 1,2‐diacylglycerol in confluent resting swiss 3T3 cells
Authors: Macphee Colin H. , Drummond Alan H. , Otto Angela M. , de Asua Luis Jimenez 
Published: February 2005

AbstractProstaglandin F2α(PGF2α); which stimulates DNA synthesis in resting 3T3 cells, also stimulates the incorporation of [32P]PO4 into phosphatidylinositol. The effect is selective for PGF2α when compared with PGE1, PGE2, and PGF2α. Epidermal growth factor (EGF) also stimulates DNA synthesis but does not affect phosphatidylinositol turnover. PGE1, which acts synergistically with PGF2α to enhance DNA synthesis, does not affect the ability of PGF2α to enhance the incorporation of [32P]PO4 into phosphatidylinositol. PGF2α also causes a small increase in the cellular content of 1,2‐diacylglycerol. This effect is not shared by EGF or PGE1. Stimulation of phosphatidylinositol metabolism resulting in an increase in the cellular content of 1,2‐diacylglycerol may thus constitute an event in the pathway leading to the initiation of DNA synthesis in which PGF2α differs in its action from EGF.
Fibroblast spreading and phagocytosis: Similar cell responses to different‐sized substrata
Authors: Grinnell Frederick 
Published: February 2005

AbstractExperiments were carried out to test the hypothesis that cell spreading and phagocytosis are similar cell responses to different‐sized substrata. The following morphological and biochemical studies provided evidence for this supposition. Cells phagocytosed 1.09‐μm and 5.7‐μm latex beads, but were unable to completely ingest 15.8‐μm or 25.7‐μm beads. With the larger beads, the cells spread around the bead surfaces with an appearance typical of cells spread on culture dishes. Biochemical studies with cytochalasin D, azide, and iodoacetate, as well as temperature‐dependence studies, demonstrated similar responses of cell spreading and phagocytosis to these treatments. Similar cell surface receptors were involved in cell spreading and phagocytosis based upon experiments using antibodies to baby hamster kidney (BHK) cell wheat germ agglutinin receptors. And finally, BHK cell variants with defective plasma fibronectin (pFN) receptors were unable to spread on pFN‐coated dishes or ingest pFN‐coated beads. Evidence also is presented concerning the “contact” process in cell adhesion. It was found that azide and low temperature inhibited cell attachment per se but did not block fibronectin‐receptorinter actions based upon cell binding of pFN‐coated beads. A possible explanation for the contact process is presented based upon the resistance of cells and beads to shear forces.
Phenothiazines cause a shift in the cAMP dose‐response: Selection of resistant variants in a murine thymoma line
Authors: Gruol Donald J. , Dalton Dyana K. 
Published: February 2005

AbstractCyclic AMP and glucocorticoid hormones each promote a cytolytic response in the murine lymphoid cell line WEHI‐7.1 (W7). The sensitivity to dibutyryl cyclic AMP (dbcAMP), but not dexamethasone, can be enhanced by several psychotropic drugs that have the capacity to interfere with a variety of calcium‐regulated functions. We have characterized the response of W7 cells to the phenothiazine trifluoperazine (TFP) and found that TFP concentrations, which decreased the growth rate by twofold, shifted the dose response to dbcAMP approximately tenfold. A similar but smaller shift was seen with the phosphodiesterase inhibitor methylisobutylxanthine (MIX). The effects of TFP and MIX on the dbcAMP response were additive, suggesting that TFP may act to increase the sensitivity of W7 cells to the action of cAMP‐dependent protein kinase, and that the increased sensitivity may be due to altered lytic functions coregulated by both cAMP and calcium. The change in the dose response to dbcAMP caused by TFP provided a means of selection to obtain variants that were altered in their capacity to respond to dbcAMP, TFP, or the combination of the two drugs. Eight (out of 36) of the lines that were obtained after a mutagenesis and combined drug selection have been partially characterized. This has revealed the existence of several new phenotypes. Most have an altered response to dbcAMP in the presence of TFP and are likely to represent variants that have not been observed before.
An improved procedure for the isolation of glia maturation factor
Authors: Lim Ramon , Miller Joyce F. 
Published: February 2005

AbstractA procedure for the bulk isolation of glia maturation factor (GMF) in high yield and high purity from bovine brains is outlined. The method involves extraction by homogenization and centrifugation, followed by ammonium sulfate precipitation and column chromatography with diethylaminoethyl (DEAE) Sephacel, Sephadex G‐75, and hydroxylapatite. The method results in a 10,000‐fold purification, a purity exceeding that of previously published procedures, and enables us to handle as much as 2.8 kg brain tissue or eight brains/week. The ability to mass‐produce GMF with this method greatly facilitates its biological studies, further purification, and chemical characterization. The isolated GMF shows a molecular weight of 13,000 on Bio‐gel P‐30 column and an isoelectric point of about 5.4 on isoelectric focusing. The isolated GMF is heat labile and susceptible to papain and ficin but relatively resistant to trypsin, neuraminidase, and endoglycosidase.
Relationship of muscle growth in vitro to sodium pump activity and transmembrane potential
Authors: Vandenburgh Herman H. 
Published: February 2005

AbstractSerum stimulates embryonic avian skeletal muscle growth in vitro and the growth‐related processes of amino acid transport and protein synthesis. Serum also stimulates myotube Na pump activity (measured as ouabain‐sensitive rubidium‐86 uptake) for at least 2 h after serum addition. Serum‐stimulated growth depends on this Na pump activity since ouabain added at the same time as serum totally inhibits the growth responses. The relationship of myotube growth, Na pump activity, and transmembrane potential was studied to determine whether serum‐stimulated Na pump activation and growth are coupled by long‐term membrane hyperpolarization. When myotube amino acid transport and protein synthesis are prestimulated by serum, ouabain was found to have little inhibitory effect, indicating that the already stimulated growth‐related processes are not tightly coupled to continued Na pump activity. Serum‐stimulated protein synthesis is tightly coupled to Na pump activity, but only during the first 5–10 min after serum addition. When myotube transmembrane potentials were measured using the lipophilic cation tetraphenylphosphonium, serum at concentrations that stimulate myotube growth and Na pump activity was found to have little effect on the cell's transmembrane potential. Furthermore, partial depolarization of the myotubes with 12‐ to 55‐mM extracellular potassium does not prevent serum stimulation of myotube growth. Monensin was found to hyperpolarize the myotubes, but causes myotube atrophy. These results indicate that although Na pump activity is associated with initiation of serum‐stimulated myotube growth, continued Na pump activity is not essential, and there is little relationship between myotube growth and the myotube's transmembrane potential.
Heterogeneity of endothelial cells of adult rat liver as resolved by sedimentation velocity and flow cytometry
Authors: Morin O. , Patry P. , Lafleur L. 
Published: February 2005

AbstractSinusoidal cells isolated from adult rat liver were fractionated by velocity sedimentation at 1 × g (primarly on the basis of size) and the various cell fractions were further analysed by flow cytometry on the basis of forward and perpendicular light scattering and autofluorescence. Cell volume was also measured electronically using a Coulter counter. At least four enriched cell populations were resolved after velocity sedimentation. They corresponded to cells having a modal diameter of 6.5, 7.5, 9, and 11 μm, respectively. Transmission electron microscopy (TEM) analysis of the various cell populations revealed that the 7.5‐ and 9‐μm cell fractions represented two distinct classes of endothelial cells while the 11‐μm cells corresponded to Kupffer cells. The 6.5‐μm cells were identified as lymphocytes. Fat‐storing cells, identified by their autofluorescence and lipid content, were included in the Kupffer population. Further information about the nature of the two physically distinct endothelial cell populations was obtained by TEM. It demonstrated that the smaller endothelial cells possessed quantitatively and relatively less retracted sieve plates than the larger ones. This ultrastructural feature can be possibly correlated to a differential localization of the two classes of endothelial cells within the liver acinus.
Cultured fetal rat myoblasts release peptide growth factors which are immunologically and biologically similar to somatomedin
Authors: Hill David J. , Grace Caroline J. , Fowler Lindsay , Holder Andrew T. , Milner R. D. G. 
Published: February 2005

AbstractThe production of immunologically and biologically active somatomedin activity from isolated myoblasts and fibroblasts from fetal rats of 21 days gestational age was investigated. Myoblast‐rich cell populations were derived from primary cultures of dispersed muscle cells by the tendency of myoblasts to become detached from the culture dish in the presence of cytochalasin B. Fibroblasts were obtained from fetal muscle. Culture medium conditioned by exposure to myoblasts for 48 hours produced an increased incorporation of both [35S]sulphate and [3H]thymidine by explants of fetal rat costal cartilage in vitro compared to fresh medium. Myoblast‐conditioned medium also contained somatomedin‐C‐like immunoreactivity which diluted in parallel with partially purified human somatomedin‐C (3,271 ± 446 mU/mg cell protein; mean ± SEM, seven experiments). Medium conditioned by exposure to fetal rat fibroblasts did not promote isotope uptake by fetal rat cartilage above control values, and contained only low levels of somatomedin‐C‐like immunoreactivity (343 ± 89 mU/mg cell protein, three experiments). The release of both somatomedin bioactivity and immunoreactivity into conditioned medium was significantly reduced by the incubation of myoblasts in the presence of rat growth hormone (100 ng/ml and 500 ng/ml). We conclude that fetal rat myoblasts released growth factor activity during culture which exhibited biological and immunologic characteristics of somatomedin. Since the bioactivity was demonstrated on skeletal tissues from rat fetuses of the same gestational age as those that yielded myoblasts such growth factor release may be physiological.