bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aortic endothelial cells synthesize basic fibroblast growth factor which remains cell associated and platelet‐derived growth factor‐like protein which is secreted
Authors: Vlodavsky Israel , Fridman Rafael , Sullivan Robert , Sasse Joachim , Klagsbrun Michael 
Published: February 2005

AbstractCultured bovine aortic endothelial cells synthesize growth factors which markedly differ in the regulation of their storage and secretion. Endothelial cell lysates, but not conditioned medium, contain a growth factor activity that appears to be basic fibroblast growth factor (FGF) by the following criteria: (1) it elutes from heparin‐Sepharose at 1.4–1.6 M NaCl; (2) it is mitogenic for bovine aortic and capillary endothelial cells; (3) it is heat sensitive but stable to dithiothreitol; (4) it has a molecular weight of about 18,000 daltons; and (5) it cross‐reacts with antiserum directed against basic FGF. In contrast, endothelial cell conditioned medium, but not lysates, contains a growth factor activity that (1) elutes from heparin‐Sepharose at 0.4 – 0.5 M NaCl; (2) is mitogenic for fibroblasts and vascular smooth muscle cells but not for capillary endothelial cells; (3) is heat stable and dithiothreitol sensitive; and (4) competes with platelet‐derived growth factor (PDGF) for binding to fibroblasts. From these criteria, it appears that endothelial cells secrete into the medium growth factors some of which are PDGF‐like, but secrete little if any basic FGF. It is suggested that endothelial cell‐associated basic FGF acts in an autocrine fashion to stimulate endothelial cell proliferation in response to endothelial cell perturbation or injury. On the other hand, the endothelial cell‐secreted growth factors which are smooth muscle cell but not endothelial cell mitogens might exert a paracrine function on neighboring cells of the vessel wall.
Effect of phagocytosis on receptor distribution and endocytic activity in macrophages
Authors: Buys Saundra S. , Kaplan Jerry 
Published: February 2005

AbstractPhagocytosis requires the internalization of a significant fraction of the plasma membrane and results in the intracellular deposition of large particles. We evaluated the effect of phagocytosis on the cellular distribution of recycling receptors and uptake of ligand to determine whether phagocytosis affects receptor behavior. Phagocytosis of zymosan, latex particles, or lgG‐coated red blood cells by rabbit alveolar macrophages did not decrease the number of cell surface receptors for transferrin, α2‐macroglobulin · protease complexes, maleylated proteins, or mannosylated proteins. The number of surface receptors for transferrin was also unaltered in J774 cells, a macrophage‐like cell line. In both cell types extensive phagocytosis did not affect the rate of receptor‐mediated endocytosis or the distribution of receptors between the endosome and the cell surface. However, fluid phase pinocytosis was reduced by phagocytosis. The major reduction appeared to be not in the rate of internalization but rather in the delivery of fluid to the lysosome. These results demonstrate that internalization of a significant amount of the plasma membrane during phagocytosis does not diminish the number of receptors on the cell surface and has no effect on receptor‐mediated ligand uptake.
Modulation of murine erythroleukemic cell differentiation by inhibitors of polyamine biosynthesis
Authors: Meilhoc Eliane , Moutin Marie‐José , Osborne H. Beverley 
Published: February 2005

AbstractThe differentiation of murine erythroleukemic cells induced by hexamethylene bisacetamide is shown to be differently affected by two inhibitors of polyamine biosynthesis. Methyl glyoxal bis(guanyl hydrazone) (inhibitor or S‐adenosyl methionine decarboxylase) inhibited this differentiation process. By using a novel experiment protocol the inhibitory effect of this drug on the induced differentiation was dissociated from pleiotropic effects on cell growth. Methyl glyoxal bis(guanyl hydrazone) only inhibited the induced differentiation if present during the first 6 h of culture of the cells with the inducer. No effect on the induced differentiation was observed if the drug was added to the culture medium 6 h after the inducer. α‐Difluoro methylornithine (inhibitor of ornithine decarboxylase) stimulated the differentiation of these cells. Polyamine analysis demonstrated that α‐difluoro methylornithine increased the rapidity and the amplitude of the changes in intracellular polyamines associated with this induced differentiation. The presence of methyl glyoxal bis(guanyl hydrazone) during the first 3 h with the inducer was sufficient to produce opposing changes in the intracellular polyamines. These results suggest that changes in either intracellular polyamines or the activities of polyamine biosynthetic enzymes play a regulatory role in the differentiation process induced in murine erythroleukemic cells by hexamethylene bisacetamide.
Biological activity, binding, and metabolic fate of Ac‐[Nle4, D‐Phe7]α‐MSH4–11NH2 with the F1 variant of B16 melanoma cells
Authors: Panasci L. C. , McQuillan A. , Kaufman M. 
Published: February 2005

AbstractThe α‐MSH (α‐melanocyte‐stimulating hormone) agonist, Ac‐[Nle4, D‐Phe7]α‐MSH4–11NH2 (hereafter called ND4–11α‐MSH), is at least 10‐fold more potent than α‐MSH as a stimulus of tyrosinase activity in F1 variant cells of B16 melanoma. The binding to these cells during an incubation with 5 nM (3H)ND4–11α‐MSH at 37°C is maximal at 0–30 min, 22 fmol/106 cells, but declines to 40% of this value at 4 hr. In the presence of 5 nM (3H)ND4–11α‐MSH at 37°C, the acid soluble (cell surface) radioactivity decreased rapidly from 11.4 fmol/106 cells at 5 min to 4.6 fmol/106 cells at 4 hr. Chromatographic analysis of media and cellular samples revealed that there was no evidence of degradation of (3H)ND4–11α‐MSH in the medium but there was evidence of intracellular degradation of (3H)ND4–11α‐MSH. Ammonium chloride (10mM) resulted in an increase in acid resistant radioactivity (internalized hormone) at 4 hr.The binding to F1 variant cells during an incubation with 0.155 nM or 5 nM (3H)ND4–11α‐MSH at 4°C was constant from 4 hr to 24 hr. Under these conditions, there was no time‐dependent change in the acid soluble radioactivity from 4 to 24 hr. Scatchard analysis of (3H)ND4–11α‐MSH binding to F1 variant cells at 4°C demonstrated that there were approximately 4500 receptors per cetl and an association constant of 17.1 nM−l. These results are consistent with a process of (3H)ND4–1α‐MSH binding to its receptor followed by internalization of the receptor‐hormone complex and then intracellular degradation of the hormone.
Suramin inhibition of growth factor receptor binding and mitogenicity in AKR‐2B cells
Authors: Coffey Robert J. , Leof Edward B. , Shipley Gary D. , Moses Harold L. 
Published: February 2005

AbstractSuramin, a polyanionic compound, has previously been shown to dissociate platelet‐derived growth factor (PDGF) from its receptor. In the present study suramin was found to inhibit the growth of sparse cultures of AKR‐2B cells in fetal bovine serum (FBS)‐supplemented medium in a dose‐dependent, reversible fashion. Suramin also inhibited the ability of FBS, transforming growth factor β (TGFβ), heparin‐binding growth factor type‐2 (HBGF‐2), and epidermal growth factor (EGF) to stimulate DNA synthesis in density‐arrested cultures of AKR‐2B cells. The inhibition of growth factor‐stimulated mitogenicity was directly correlated to the dose of suramin required to inhibit the binding of 125I‐labeled TGFβ, HBGF‐2, and EGF to their cell surface receptors. Suramin affected TGFβ and HBGF‐2‐related events at a 10–15‐fold lower dose than that required for EGF‐related events. It was also noted that suramin inhibited TGFβ‐stimulated soft agar colony formation of AKR‐2B (clone 84A) cells as well as the spontaneous colony formation of AKR‐MCA cells, a chemically transformed derivative of AKR‐2B cells. This demonstrates that suramin's spectrum of action for growth factors and their receptors should be extended to include TGFβ, HBGF‐2, and EGF as well as PDGF. The data further suggest that the spontaneous growth of AKR‐MCA cells in soft agar is dependent on growth factor binding to cell surface receptors.
Bicarbonate/chloride antiport in vero cells: II. Mechanisms for bicarbonate‐dependent regulation of intracellular pH
Authors: Olsnes Sjur , Ludt Jannikke , Tønnessen Tor Inge , Sandvig Kirsten 
Published: February 2005

AbstractThe rates of bicarbonate‐dependent uptake and efflux of 22Na+ in Vero cells were studied and compared with the uptake and efflux of 36Cl−. Both processes were strongly inhibited by DIDS. Whereas the transport of chloride increased approximately ten‐fold when the internal pH was increased over a narrow range around neutrality, the uptake of Na+ was much less affected by changes in pH. The bicarbonate‐linked uptake of 22Na+ was dependent on internal Cl− but not on internal Na+. At a constant external concentration of HCO−3, the amount of 22Na+ associated with the cells increased when the internal concentration of HCO−3 decreased and vice versa, which is compatible with the possibility that the ion pair NaCO−3 is the transported species and that the transport is symmetric across the membrane. Bicarbonate inhibited the uptake of 36Cl− both in the absence and presence of Na+. At alkaline internal pH, HCO−3 stimulated the efflux of 36Cl− from preloaded cells, while at acidic internal pH both Na+ and HCO−3 were required to induce 36Cl− efflux. We propose a model for how bicarbonate‐dependent regulation of the internal pH may occur. This model implies the existence of two bicarbonate transport mechanisms that, under physiological conditions, transport OH−‐ equivalents in opposite directions across the plasma membrane.
Fibronectin stimulates growth but not follicle‐stimulating hormone‐dependent differentiation of rat granulosa cells in vitro
Authors: Morley Paul , Armstrong David T. , Gore‐Langton Robert E. 
Published: February 2005

AbstractSince fibronectin is a secretory product of immature rat granulosa cells in culture and may contribute to the follicular microenvironment in vivo, we have studied the effects of this adhesion factor on follicle‐stimulating hormone (FSH)‐dependent differentiation in short‐term (2–3‐day) cultures and on growth and protein synthesis in long‐term (12‐day) cultures. In comparison with cells plated on tissue culture plastic, those plated on an optimal fibronectin‐coated substratum showed much greater cell spreading. There were no short‐term effects of this morphological change on FSH‐stimulation of cyclic AMP production, apparent activities of aromatase or cholesterol side‐chain cleavage enzymes, or acquisition of luteinizing hormone (LH) responsiveness in cultured cells. However, progesterone metabolism to 20α‐hydroxypregnan‐4‐en‐3‐one was increased. Only cultures on fibronectin showed increases between days 3 and 9 in protein (2.5‐fold) and DNA (1.4‐fold) contents. Cells cultured on fibronectin also showed greater uptake and incorporation of [3H]leucine in comparison with cells cultured on plastic. FSH treatment caused cell aggregation and rounding and delayed the increase in protein content of cells cultured on fibronectin. The results presented demonstrate that the principal direct effect of fibronectin‐mediated adhesion on rat granulosa cells is to enhance cell maintenance and growth, while having no generalized action on FSH‐dependent differentiation.
Control of the adipogenic differentiation of 3T3‐F442A cells by retinoic acid, dexamethasone, and insulin: A topographic analysis
Authors: Pairault Jacques , Lasnier FrançOise 
Published: February 2005

AbstractDifferentiation of 3T3‐F442A adipocytes, monitored by accumulation of neutral lipid and by using the sensitive marker glycerophosphate dehydrogenase, is inhibited by incubation of confluent 3T3‐F442A fibroblasts in medium containing retinoic acid or dexamethasone. When added together, dexamethasone (0.25 μM) potentiates about 50‐fold the inhibitory effect of retinoic acid (10 μM). Insulin cannot counteract the retinoic acid blockade; however, it can overcome the inhibition of differentiation elicited by dexamethasone. These differential effects of insulin are used for characterizing the adipose conversion cycle. We describe cell culture conditions where terminal differentiation of 3T3‐F442A preadipocytes is achieved by low, physiological levels of insulin. They include the switch from a high‐serum medium containing isobutyl methyl xanthine and dexamethasone to a serum‐free, hormone‐supplemented medium. The data reported establish the existence of two successive states for commitment to adipogenic differentiation: a first commitment point (CA) to differentiation which requires serum adipogenic factors, and a second commitment point (CH) controlled by lipogenic hormones, namely insulin, after which terminal maturation can resume. We demonstrate that retinoic acid can prevent and interrupt differentiation by blocking the cells within the early differentiation phase.
Protamine sulfate inhibits mitogenic activities of the extracellular matrix and fibroblast growth factor, but potentiates that of epidermal growth factor
Authors: Neufeld G. , Gospodarowicz D. 
Published: February 2005

AbstractProtamine sulfate, an inhibitor of angiogenesis in vivo, markedly inhibits the ability of angiogenic factors such as acidic or basic fibroblast growth factor (aFGF, bFGF) to stimulate the proliferation in vitro of either BHK‐21 cells or vascular endothelial cells. The inhibition is reversible, and cells remain viable even after prolonged exposure to protamine sulfate. Protamine sulfate inhibits the mitogenic effects of both growth factors by preventing them from binding to their common cell surface receptors. It also inhibits the mitogenic activity of the extracellular matrix produced by bovine corneal endothelial cells. This substrate has been shown in previous studies to replace the requirement for FGF of many cell types. In contrast, protamine sulfate potentiates the mitogenic activity of epidermal growth factor (EGF). This indicates that protamine sulfate also acts at cellular sites which are not associated with FGF receptors.
The effect of factors released from the tumor‐transformed cells on DNA synthesis, mitosis, and cellular enlargement in 3T3 fibroblasts
Authors: Dafgård Eva , Engström Wilhelm , Larsson Olle , Zetterberg Anders 
Published: February 2005

AbstractQuiescent serum‐starved 3T3 cells can be stimulated to initiate DNA synthesis after addition of conditioned media from spontaneously tumor‐transformed 3T3 cells (3T6‐cells) or from SV‐40‐transformed 3T3 cells (SV‐3T3 cells). The conditioned media were found to stimulate both the chromosome cycle (i.e, DNA synthesis and cell division) and the growth cycle (i.e., cellular enlargement). Furthermore, addition of conditioned media to quiescent 3T3 cells increased the activity of HMG CoA reductase—an enzyme previously proposed to exercise some control on cell proliferation in 3T3 cells Larsson and Zetterberg: J. Cell. Physiol. 129:99–102, 1986. The increased activity of HMG CoA reductase after treatment with tumor cell conditioned media was correlated to the stimulatory effects on DNA synthesis. By treating 3T3 cells stimulated to resume proliferation by addition of conditioned media with mevinolin (a competitive inhibitor of HMG CoA reductase) the activity of HMG CoA reductase as well as the DNA synthesis and cell division were efficiently inhibited. In contrast, HMG CoA activity was not coupled to the cellular enlargement. Therefore, it is proposed that one set of factors present in tumor cell conditioned media preferentially stimulates the chromosome cycle by increasing the HMG‐CoA reductase activity, whereas another set of factors is responsible for growth in cell size. Both types of factors are required for balanced growth.
The effects of sulfhydryl inhibitors and cytochalasin on the cytoplasmic and cytoskeletal actin of human neutrophils
Authors: Wallace Paul J. , Packman Charles H. , Wersto Robert P. , Lichtman Marshall A. 
Published: February 2005

AbstractTo better understand the changes that occur in cytoplasmic actin during cell movement, we studied the effect of inhibitors of cell movement on the molecular conformation of actin and its incorporation into the Triton‐insoluble cytoskeleton of human neutrophils. The sulfhydryl reactive compound N‐ethylmaleimide caused an increase in cellular F‐actin as measured by uptake of the F‐actin specific fluorescent probe 7‐nitrobenz‐2‐oxadiazole‐phallacidin. However, N‐ethylmaleimide reduced the amount of actin associated with the Triton‐insoluble cytoskeleton. Dithiobisnitrobenzoic acid, a sulfhydryl reagent that does not cross cell membranes efficiently, did not alter the F‐actin content of neutrophils. The effect of N‐ethylmaleimide was blocked by the presence of dithiothreitol, a donor of sulfhydryl groups. N‐ethylmaleimide did not affect the polymerization of actin in a cell‐free system. Cytochalasin B did not alter F‐actin content of neutrophils but did decrease actin in cytoskeletons of resting neutrophils. Cytochalasin inhibited the increase in F‐actin initiated by the chemoattractant N‐formylmethionylleucylphenylalanine. We propose that N‐ethylmaleimide blocks the stabilization of G‐actin in cytoplasm, interferes with the incorporation of F‐actin polymer into the cytoskeleton, and depolymerizes the cytoskeleton. In contrast cytochalasin stabilizes G‐actin in the presence of chemotactic peptide. These data suggest that reversible conversion of G‐actin to F‐actin and incorporation of F‐actin into the Triton‐insoluble cytoskeleton are important for neutrophil movement.
Cell‐cycle‐dependent expression of human ornithine decarboxylase
Authors: Kaczmarek Leszek , Calabretta Bruno , Ferrari Sergio , de Riel Jon K. 
Published: February 2005

AbstractA human ornithine decarboxylase (ODC) gene probe has been isolated from a Jurkat T‐cell cDNA expression library, sequenced, and used to analyze ODC mRNA levels in untransformed human lymphocytes and fibroblasts stimulated to proliferate by various mitogens. The partial cDNA sequence is 86% homologous to the mouse ODC cDNA, and Northern blots indicate that the human and mouse mRNA species are similar in size. ODC mRNA is barely detectable in quiescent human T lymphocytes and undetectable in density‐arrested WI38 fibroblasts. Following stimulation of T‐lymphocyte proliferation with phytohemagglutinin, the ODC mRNA level rises to a peak around mid G1 phase and decreases as the cells enter S phase. Serum stimulation of density‐arrested fibroblasts results in an elevation of the ODC mRNA level which persists throughout the cell cycle. Epidermal growth factor (20 ng/ml) but not insulin (10 mg/ml) or dexamethasone (55 ng/ml) stimulates ODC expression in quiescent WI38 fibroblasts. Southern blots suggest that human cells have a single copy of the ODC gene.
Purified monocyte‐derived angiogenic substance (angiotropin) stimulates migration, phenotypic changes, and “tube formation” but not proliferation of capillary endothelial cells in vitro
Authors: Höckel Michael , Sasse Joachim , Wissler Josef H. 
Published: February 2005

AbstractActivated monocytes (macrophages, histiocytes) induce the formation of new blood vessels by secretion product(s). From conditioned serum‐free media of porcine peripheral monocytes treated with concanavalin A, a substance with very strong angiogenic activity in vivo, designated as angiotropin, has been isolated and purified to homogeneity. We investigated the biological action of the monocyte‐derived angiogenic substance on cultured capillary and large vessel (aorta) endothelial cells and on 3T3 fibroblasts, mimicking steps of the angiogenic pathway in vitro. We found that angiotropin does not stimulate the proliferation of capillary endothelial and 3T3 cells; however, in concentrations less than 1 ng/ml, it enhances random migration of capillary endothelial cells but not of 3T3 cells. On confluent monolayers of capillary and aortic endothelial cells angiotropin leads to defined changes of cell morphology that are dose dependent and reversible. In the presence of angiotropin, capillary endothelial cells rapidly form tubelike structures on gelatinized plates. This organizational state is not reached with aortic endothelial cells. The results indicate that the biological action of monocytic angiotropin is different from that of the angiogenic growth factors that stimulate the proliferation of endothelial cells and nonlymphoid mesenchymal cells and keep endothelial cells in the contact‐inhibited epitheloid cell phenotype. We propose that angiotropin is directly involved in monocyte‐induced angiogenesis.
Increased adherence of oxidant‐treated human and bovine erythrocytes to cultured endothelial cells
Authors: Wali Ramesh K. , Jaffe Stuart , Kumar Dinesh , Sorgente Nino , Kalra Vijay K. 
Published: February 2005

AbstractBovine erythrocytes, which normally lack phosphatidyl choline in their membranes, when treated with either H2O2 or diamide (1–3 mM), showed a partial appearance of phosphatidyl ethanolamine (PE 40%) and phosphatidyl serine (PS, 30–33%) in the external leaflet of the bilayer and a concomitant increased (four‐ to five‐fold) propensity to adhere to cultured bovine aortic endothelial cells. Similar treatment of normal human erythrocytes caused an alteration in the organization of the phospholipid bilayer and also resulted in their increased adherence to endothelial cells derived either from human umbilical vein or bovine aorta. Treatment of RBCs with H2O2 at low concentration (0.5 mM) resulted in cross‐linking of spectrin without significant changes in the orientation of aminophospholipids but the RBCs exhibited 15–20% increase in adherence to endothelial cells. Pretreatment of either human or bovine erythrocytes with antioxidants such as vitamin E (2 mM) prevented both oxidant‐induced reorganization of phospholipids in the bilayer and enhancement of adherence to endothelial cells. Introduction of either phosphatidyl serine or phosphatidyl ethanolamine but not phosphatidyl choline into erythrocyte membranes increased their adherence to endothelial cells threefold. Oxidant‐treated RBCs exhibited enhanced binding and fluorescence of Merocyanine 540 dye (MC‐540), which is sensitive to the packing of lipids in the lipid bilayer. On flow cytometric analysis, 78% of H2O2 (0.5 mM)‐treated erythrocytes compared to 30% of untreated RBCs exhibited MC‐540 binding and fluorescence, indicating differences in the lipid packing in the outer leaflet of the bilayer. Oxidant‐treated erythrocytes adhere preferentially to endothelial cells rather than to bovine aortic smooth muscle cells and skin fibroblasts. It is suggested that the alterations in the erythrocyte membrane surface due to spectrin cross‐linking and the organization of the phospholipids concomitant with less ordered packing in the external leaflet of the bilayer, either induced by oxidative manipulation in normal RBC or in pathological erythrocytes, play a role in erythrocyte‐endothelial cell interaction.