bluuebunny/crossref_metadata_2025_split huggingface dataset:
“Dynamic morphology system”: A method for quantitating changes in shape, pseudopod formation, and motion in normal and mutant amoebae of Dictyostelium discoideum
Authors: Soll David R. , Voss Edward , Varnum‐Finney Barbara , Wessels Deborah 
Published: December 2004

AbstractAn automated, video‐driven system was used to measure approximately 30 parameters of cell motion and accompanying changes in shape. This “Dynamic Morphology System” is based upon the Expertvision Motion Analysis System and is driven by a SUN computer. With the aid of this system, amoebic movement and shape changes were compared for vegetative wild‐type Dictyostelium discoideum amoebae and a motility mutant, Mo‐1. The measured parameters included speed, angle change, bearing, length, width, roundness, boundary flow, and curvature; and cell behavior was visualized monitoring amoebic tracks, difference pictures, and a newly developed ring expansion plot. Wild‐type cells remained elongated, moved continuously and retained polarity throughout migration. In contrast, Mo‐1 did not translocate, was round rather than elongated, formed bulges rather than elongated pseudopods, and exhibited no polarity. In contrast to the anterior f‐action distribution in wild‐type cells, f‐actin in Mo‐1 was distributed evenly as a shell just under the entire plasma membrane, a distribution consistent with the lack of polar cytoplasmic expansion.
Changes in glycoprotein fucosylation in a concanavalin A‐resistant variant of a human leukemia cell line (K562)
Authors: Bernier Louise G. , Sullivan Arthur K. 
Published: December 2004

AbstractPrevious studies from this and other laboratories have shown that variants of tumor cell lines can be selected for resistance to the lytic action of natural killer (NK) cells. One of these (K562‐Clone I), when made resistant to the toxic effects of Concanavalin A (Con A‐R1), regained its sensitivity to NK. Comparing the plasma membranes of Clone I and Con A‐R1, we observed (1) a very similar electrophoretic pattern of membrane glycoproteins identified by binding to the lectins Con A, WGA, PNA, and SBA; (2) an increase in binding of Ulex europaeus lectin to a group of glycoproteins from Con A‐R1 that were sensitive to treatment with fucosidase and N‐glycanase and that had a diffuse mobility ranging in apparent molecular weight from 30 to 200 kDa; and (3) a marked decrease in binding of an antibody reactive with the lactoneofucopentaose III antigen (Lewis x). This constellation of changes is an unusual pattern to follow Con A resistance and may point to a pathway of glyco‐sylation that a leukemic cell might use to modify its recognition by the NK mechanism.
Gene‐specific acquisition of hormonal responsiveness in rat liver during development
Authors: Johnson Alfred C. , Lee Kai‐Lin , Isham Kenneth R. , Kenney Francis T. 
Published: December 2004

AbstractCloned cDNAs were used in hybridization analyses to assess hormonal responsiveness of two similarly regulated genes in livers of late‐term fetal rats. Transcription of the tyrosine aminotransferase gene and of gene 33 (Lee et al.: J Biol Chem 260:16433–16438, 1985) is enhanced by glucocorticoids and by each of the usually antagonistic hormonal agents, insulin and cAMP, in adult liver, and that of both genes is developmentally activated at or just prior to birth. The mRNA of gene 33 was found to be significantly increased by each of the hormonal regulators in livers of fetuses treated in utero. Expression of the nearly silent aminotransferase gene in fetal liver was appreciably increased by cAMP but was refractory to control by either glucocorticoids or insulin; capacity of this gene to respond to insulin was not realized until several days postpartum. The data indicate specificity in the developmental acquisition of the capacity of individual genes to respond to hormonal regulators.
Specificity of the interaction between phosphatidylinositol 4,5‐bisphosphate and the profilin:actin complex
Authors: Lassing Ingrid , Lindberg Uno 
Published: December 2004

AbstractProfilactin, the profiling:actin complex, which is present in large amounts in extracts of many types of eukaryotic cells, appears to serve as the precursor of microfilaments. It was reported recently that profilactin interacts specifically with phosphatidylinositol 4,5‐bisphosphate (PtdIns(4,5)P2) (Lassing and Lindberg: Nature 314:472–474, 1985.) The present paper describes in detail the behaviour of profilactin and profilin in the presence of different types of phospholipids and neutral lipids under different conditions. PtdIns(4,5)P2 is the only phospholipid found so far which in the presence of 80 mM KC1 and at Ca2+ concentrations below 10−5 M effectively dissociates profilactin with the resulting polymerization of the actin. Phosphatidylinositol 4‐monophosphate exhibits some activity but phosphatidylinositol is inactive. Both calf spleen profilin and profilin from human platelets form stable complexes with PtdIns(4,5)P2 micelles. PtdIns(4,5)P2 is active also when incorporated together with other phospholipids in mixed vesicles.
Developmentally regulated compartmentalization of adenylate cyclase in Dictyostelium discoideum
Authors: Hagmann Jörg 
Published: December 2004

AbstractAdenylate cyclase of aggregation phase Dictoystelium discoideum is activated by extracellular adenosine 3′, 5′‐cyclic monophosphate (cAMP), and the cAMP syn‐thesized is secreted. The distribution of the enzyme was determined in sucrose gradients loaded with whole cell lysates. Cell lysates prepared after 4.5 hr of starvation revealed membranes containing adenylate cyclase at 44% and 33% sucrose. The activity of the latter peak was detected in the presence of the detergent (CHAPS), 3‐(3‐cholamidopropyl) dimethylammonio‐3‐propanesulfonate, which inhibited the activity of the former to some extent. Adenylate cyclase activity of the 2 peaks differed with respect to solubility in CHAPS and their kinetics. The 44% sucrose region of the gradient contained the bulk of the plasma membranes, as judged by a cell surface glycoprotein marker (contact site A). The 33% peak is composed of small vesicular structures, as determined by electron microscopy. The distribution of adenylate cyclase activity detected in sucrose gradients shifted from the 33% to the 44% sucrose peak during development. In addition, the 44% peak became increasingly resistant to the inhibitory effect of CHAPS, Both changes were accelerated by extracellular cAMP, but only the latter was abolished when the production of endogeneous cAMP was inhibited by caffeine. Pulsing cells with cAMP overcame the inhibitory effect of caffeine.
Somatotropin antagonism of insulin‐stimulated glucose utilization in 3T3‐L1 adipocytes
Authors: Glenn Kevin C. , Rose Kathleen S. , Krivi Gwen G. 
Published: December 2004

AbstractIt is well established that somatotropin (GH) antagonizes insulin action in vivo and that supraphysiologic concentrations of GH frequently result in insulin resistance and glucose intolerance. However, the demonstration of an anti‐insulin activity by GH in vitro has been difficult. This study, therefore, set out to determine whether cultures of 3T3‐L1 adipocytes could be used to examine the anti‐insulin activity of GH. The ability of insulin to stimulate glucose utilization by 3T3‐L1 adipocytes increases approximately five‐fold during the first 4 days following treatment of the cells with a differentiation medium. It was found that glucose utilization in 3T3‐L1 adipocytes is regulated in a reciprocal fashion by insulin and GH. Bovine or human GH directly inhibit up to 50% of insulin‐stimulated [14C]‐glucose incorporation into lipids in a concentration‐dependent manner. The 3T3‐L1 sensitivity to GH appears to be at the maximum (50% inhibition of an insulin response) immediately following removal of the cells from the differentiation medium and remains essentially constant during the subsequent 4 days. The GH inhibition of insulin action does not appear to be due GH enhancement of cellular degradation of insulin, competitive binding of GH to the insulin receptor, or GH‐induced decrease in cell number. The 3T3‐L1 adipocyte system appears to be a sensitive and reliable in vitro model with which to study the molecular mechanisms involved in both GH antagonism of insulin action and development of hormone responsiveness during cellular differentiation into adipocytes.
Acid phosphatase activity in the isolated brush border membrane of the tapeworm, Hymenolepis diminuta: Partial, characterization and differentiation from the alkaline phosphatase activity
Authors: Pappas Peter W. 
Published: December 2004

AbstractThe isolated brush border membrane of the tapeworm, Hymenolepis diminuta, hy‐drolyzes p‐nitrophenyl phosphate over a broad pH range. Acid phosphatasc activity (pH optimum at 4.0) is inhibited specifically by sodium dodecyl sulfate (SDS) and NaF, while the alkaline phosphatase activity (pH optimum at 8.8) is inhibited specifically by levamisole, 2‐mercaptoethanol, and ethylenediaminetetra‐acetate (EDTA). These two phosphatase activities are further differentiated in that (1) there is a rapid decrease in alkaline phosphatase activity when the membrane preparation is incubated at pH 4.0, while there is little loss of acid phosphatase activity, and (2) the alkaline phosphatase activity is solubilized with no loss of activity when the membrane is treated with Triton X‐100, while such treatment causes a significant loss of acid phosphalase activity. Both activities are nonspecific and hydrolyze a variety of phos‐phorylated compounds, but the relative activities of the two phosphatases against these substrates vary significantly.
Respiration supported nitrogenase activity of isolated Rhizobium meliloti bacteroids
Authors: Miller R. W. , McRae D. G. , Al‐Jobore A. , Berndt W. B. 
Published: December 2004

AbstractBacteroids having a high level of respiration‐supported nitrogenase activity were isolated from nitrogen‐fixing alfalfa root nodules. Gentle maceration under anaerobic conditions in the presence of sodium succinate and a fatty acid scavenging agent were employed in this method.A large proportion of isolated bacteroids retained a triple membrane structure as shown by transmission electron microscopy. Dicarboxylic acids of the TCA cycle (malate, fumarate, succinate), but not glutamate or aspartate, supported sufficient respiratory activity to supply the nitrogenase system with ATP and reducing equivalents and to protect the nitrogenase system from inactivation by 4% oxygen over a period of 20–30 min. Sugars did not support nitrogenase activity in intact bacteroids. The properties of the isolated bacteroids were ascribed to minimal damage to the cytoplasmic membrane and peribacteroidal membrane during isolation.With succinate as substrate and oxygen as terminal electron acceptor, initial nitrogenase activity was determined at 4% oxygen in the gas phase of the assay system employed. At this oxygen concentration, the sustained rate of acetylene reduction by respiring bacteroids was linear up to 30 min. Bacteroid activity declined rapidly with time of exposure to oxygen above 4% in the gas phase. The optimum temperature range for this activity was 10–20°C. Nitrogenase activity was measurable at incubation tempertures below 10°C under 4% oxygen. Functionally intact bacteroids had little nitrogenase activity under anaerobic conditions in the presence of an external source of ATP and reductant. Treatment of the bacteroids with chlorpromazine eliminated respirtation‐supported activity and rendered the bacteroid cell membrane permeable to external ATP. Bacteroids treated with chlorpromazine had high acetylene reducing activity with external ATP and dithionite in the absence of oxygen.
Immunofluorescent and immunochemical evidence for the expression of cytovillin in the microvilli of a wide range of cultured human cells
Authors: Pakkanen Raimo 
Published: December 2004

AbstractWe have previously purified a Mr 75,000 protein, cytovillin, from cultured human choriocarcinoma cells (JEG‐3) and shown that this protein was specifically confined to the microvillus membrane of these cells. I have now studied the expression and the subcellular distribution of cytovillin in eighteen normal and transformed human cell lines and strains by using immunoblotting and indirect immunofluorescence microscopy. In all cell types, cytovillin was highly enriched in cell surface protrusions. When cell types were ranked according to their staining intensity, choriocarcinoma was highest, then amniotic epithelial cells, other choriocarcinoma cells and tumor cells, and finally fibroblastoid cells. The latter only gave faint diffuse fluorescence on the plasma membrane and, occasionally, on the microvilli. However, detergent extracts of all cell types could be shown to contain cytovillin by the use of immunoblotting techniques. Metabolic pulse‐chase labelling experiments with JEG‐3 cells demonstrated synthesis of cytovillin as a single‐chain polypeptide. No precursor forms or specific proteolytic cleavage products could be seen either by immunoblotting or immunoprecipitation. The protein was found to be very stable with a biologic half‐life of about 25 hours. The pI determined by isoelectric focusing was 6.1. These results were consistent with cytovillin being an integral component of the microvilli and other surface extensions of all human cell types examined.
An immunological assessment of lysosomal enzymes and other macromolecules sulfated during vegetative growth of Dictyostelium discoideum
Authors: Davis Simon J. , Wheldrake John F. , Freeze Hudson H. 
Published: December 2004

AbstractWestern blotting and immunoprecipitation data indicated that lysosomal enzymes represent a subset of the sulfated macromolecules present in vegetative Dictyostelium discoideum amoebae and account for less than 2.5% of the total sulfate incorporated during vegetative growth. These data suggest that the majority of the highly sulfated macromolecules of vegetative D. discoideum amoebae are not related to the lysosomal enzymes.
Interferon and growth factor modulation of nuclear factors binding to 5′ upstream elements of the 2–5A synthetase gene
Authors: Williams Bryan R. G. , Rutherford Michael N. , Hannigan Gregory E. 
Published: December 2004

AbstractWe assayed fragments of the 5′ flanking sequence of the human 2–5A synthetase gene for their ability to respond to interferon‐α (IFN) and platelet‐derived growth factor (PDGF). Transient transfection assays identified a 40‐base pair fragment, which, regardless of orientation, could confer IFN‐inducibility on the thymidine kinase promoter. This same fragment was active in monkey and mouse cells and in the latter was responsive to PDGF. The effect of PDGF could be inhibited by anti‐interferon antibodies. Gel retardation assays, using the 40‐base pair probe, detected the presence of IFN‐modulated DNA‐binding factors in nuclear extracts from monkey cells. In mouse cells both IFN and PDGF induced the binding of nuclear factors to a synthetic 2–5A synthetase response sequence. Thus, both IFN and growth factors directly or indirectly modulate the binding of nuclear factors to the same region of the 2–5A synthetase gene.
Binding of cytochalasin B to platelets
Authors: Horne McDonald K. 
Published: December 2004

AbstractThe binding of cytochalasin B (CB) to human platelets and to isolated platelet cytosol and membranes has been analyzed with [3H]CB. High‐ and low affinity classes of saturable binding sites were associated with intact platelets. Binding at very low concentrations of CB (i.e., high‐affinity binding) was partially prevented by 100 mM D‐galatose or D‐glucose and to a much lesser extent by L‐glucose. Binding to platelet cytosol also involved two classes of sites with affinities and capacities similar to those observed with the whole cells. None of this binding, however, was affected by 100 mM D‐galactose. Saturable binding to platelet membranes occurred at sites with a uniform binding affinity. Approximately 52% of this binding was prevented by 1 M D‐galactose and another 15% by cytochalasin E (CE). We hypothesize that binding in the cytosol is to monomeric (low‐affinity) and polymerized (high‐affinity) actin, whereas membrane binding (high‐affinity only) occurs primarily at sites involved with galactose transport.
Effects of platelet‐derived growth factor and fibroblast growth factor on free intracellular calcium and mitogenesis
Authors: Tucker Robert W. , Chang David T. , Meade‐Cobun Kimberly 
Published: December 2004

AbstractAlthough increased free intracellular calcium (Cai) may be one of the main regulators of cell growth and differentiation, studies in cell populations have implied that not all growth factors produce Cai increases. In order to examine in more detail whether Cai increases were related to mitogenesis, we used digital image analysis of intracellular Fura‐2 fluorescence to measure Cai in individual BALB/c 3T3 cells stimulated with either platelet‐derived growth factor (PDGF) or fibroblast growth factor (FGF). We found that PDGF induced larger and more prolonged Cai increases than FGF did, but that both growth factors induced an initial rapid increase in Cai (< 2 min) followed by a later sustained increase (> 20 min). Only the prolonged Cai increase required extracellular calcium. Following PDGF treatment (1–8 units/ml), the percentage of cells with a large peak Cai increase (> twofold) correlated with the percentage of cells made competent (subsequent growth in 1% platelet‐poor‐plasma). In contrast, purified bovine basic FGF (200–800 pg/ml) and recombinant human acidic FGF (10–300 ng/ml) produced peak Cai increases that were not directly correlated with mitogenesis. In addition, concentrations of intracellular Quin 2 that inhibited Cai transients also inhibited PDGF stimulation but not FGF stimulation of mitogenesis. Thus, Cai increases are necessary for mitogenesis in BALB/c 3T3 cells stimulated by PDGF, but not that stimulated by FGF.
Overexpression of the c‐erbB‐2 protein in human breast tumor cell lines
Authors: Hynes Nancy E. , Gerber Heinz A. , Saurer Suzanne , Groner Bernd 
Published: December 2004

AbstractThe c‐erbB‐2 proto‐oncogene is amplified in a high percentage of primary human breast tumors, suggesting that the overexpression of this gene may be involved in the development of human breast cancer. We have investigated five human breast tumor cell lines and have detected amplified c‐erbB‐2 gene copies in two of them. This amplification leads to overexpression of the c‐erbB‐2 protein. In addition, two other cell lines have elevated protein levels without gene amplification, suggesting that other mechanisms can lead to overexpression of the c‐erbB‐2 protein. These results are similar to those that we obtained during a study of primary breast tumors (Berger et al.: Cancer Res 48:1238–1243, 1988). These breast tumor cell lines should be useful for an analysis of c‐erbB‐2 expression and of the mechanisms that in some cases lead to overexpression.
Transforming growth factor β: Possible roles in the regulation of normal and leukemic hematopoietic cell growth
Authors: Keller Jonathan R. , Sing Garwin K. , Ellingsworth Larry R. , Ruscetti Francis W. 
Published: December 2004

AbstractWe have recently demonstrated that transforming growth factor (TGF)‐β1 and TGF‐β2 are potent inhibitors of the growth and differentiation of murine and human hematopoietic cells. The proliferation of primary unfractionated murine bone marrow by interleukin‐3 (IL‐3) and human bone marrow by IL‐3 or granulocyte/macrophage colony‐stimulating factor (GM‐CSF) was inhibited by TGF‐β1 and TGF‐β2, while the proliferation of murine bone marrow by GM‐CSF or murine and human marrow with G‐CSF was not inhibited. Mouse and human hematopoietic colony formation was differentially affected by TGF‐β1. In particular, CFU‐GM, CFU‐GEMM, BFU‐E, and HPP‐CFC, the most immature colonies, were inhibited by TGF‐β1, whereas the more differentiated unipotent CFU‐G, CFU‐M, and CFU‐E were not affected. TGF‐β1 inhibited IL‐3‐induced growth of murine leukemic cell lines within 24 h, after which the cells were still viable. Subsequent removal of the TGF‐β1 results in the resumption of normal growth. TGF‐β1 inhibited the growth of factor‐dependent NFS‐60 cells in a dose‐dependent manner in response to IL‐3, GM‐CSF, G‐CSF, CSF‐1, IL‐4, or IL‐6. TGF‐β1 inhibited the growth of a variety of murine and human myeloid leukemias, while erythorid and macrophage leukemias were insensitive. Lymphoid leukemias, whose normal cellular counterparts were markedly inhibited by TGF‐β, were also resistant to TGF‐β1 inhibition. These leukemic cells have no detectable TGF‐β1 receptors on their cell surface. Last, TGF‐β1 directly inhibited the growth of isolated Thy‐1‐positive progenitor cells. Thus, TGF‐β may be an important modulator of normal and leukemic hematopoietic cell growth.
Characterization of the membrane‐associated GTPase activity: Effects of chemotactic factors and toxins
Authors: Pelz Claudia , Matsumoto Tadashi , Molski Thaddeus F. P. , Becker Elmer L. , Sha'afi Ramadan I. 
Published: December 2004

AbstractMembranes prepared from rabbit neutrophils exhibit GTPase activity which can be stimulated by the chemotactic factor fMet‐Leu‐Phe. The maximum contribution of the ATPase activities to the basal and the fMet‐Leu‐Phe‐stimulated GTPase activities are less than 20% and 9%, respectively. The basal GTPase activity has a Vmax = 34.2 ± 1.3 (pmol/mg protein, min) and a Km = 0.39 ± 0.03 μM; and the fMet‐Leu‐Phe‐stimulated has a Vmax = 52.3 ± 2.5 (pmol/mg protein, min), and a Km = 0.29 ± 0.02 μM. The GTPase activity can be stimulated by fMet‐Leu‐Phe and leukotriene B4. Unlike these two chemotactic factors, concanavalin A does not stimulate this GTPase activity. In addition, the rise in intracellular concentration of free calcium produced by concanavalin A is not inhibited by pertussis toxin treatment. Both the basal and stimulated GTPase activities are affected by pertussis toxin, cholera toxin and N‐ethylmaleimide.
Evidence for two distinct conformations of the Escherichia coli mannitol permease that are important for its transport and phosphorylation functions
Authors: Khandekar Sanjay S. , Jacobson Gary R. 
Published: December 2004

AbstractColumn chromatography of the Escherichia coli mannitol permease (mannitolspecific enzyme II of the phosphotransferase system) in the presence of deoxycholate has revealed that the active permease can exist in at least two association states with apparent molecular weights consistent with a monomer and a dimer. The monomeric conformation is favored by the presence of mannitol and by the phosphoenolpyruvate (PEP)‐dependent phosphorylation of the protein. The dimer is stabilized by inorganic phosphate (Pi), which also stimulates phospho‐exchange between mannitol and mannitol 1‐phosphate (a partial reaction in the overall PEP‐dependent phosphorylation of mannitol). Kinetic analysis of the phospho‐exchange reaction revealed that Pi stimulates phospho‐exchange by increasing the Vmax of the reaction. A kinetic model for mannitol permease function is presented involving both conformations of the permease. The monomer (or a less‐stable conformation of the dimer) is hypothesized to be involved in the initial mannitol‐binding and PEP‐dependent phosphorylation steps, while the stably associated dimer is suggested to participate in later steps involving direct phosphotransfer between the permease, mannitol and mannitol 1‐phosphate.