bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracellular matrix: Differential influence on growth and biosynthesis patterns of vascular smooth muscle cells from SHR and WKY rats
Authors: Scott‐Burden Timothy , Resink Thérèse J. , Bürgin Maria , Bühler Fritz R. 
Published: February 2005

AbstractSmooth muscle cells from spontaneously hypertensive rats (SHR) elaborated extracellular matrix (ECM) material in culture that was more stimulatory to growth of cells from normotensive (WKY) animals than their own matrix. Both cell types elaborated ECMs consisting of glycoconjugate material (proteoglycans, glycopeptides) elastin, and collagens, but there were differences in the relative proportions of the compounds synthesized. Cells from SHR produced an ECM richer in elastin than that synthesized by WKY derived cells (∼19% vs. 11%, respectively). However, the latter elaborated ECMs containing more (∼45% for WKY vs. 29% for SHR) glycoconjugate material than the former. The lysyloxidase‐mediated crosslinking of elastin was more rapid in cultured cells from SHR animals than from their normotensive counterparts and may be as a consequence of increased substrate (tropoelastin) availability in ECMs from SHR animals. The relative proportions and sulphate levels of the glycosaminoglycans associated with matrix material elaborated by the two cell types were similar. Radiolabelled glycoconjugate material was degraded by cells (SHR/WKY) when they were plated upon pre‐formed ECMs, and their patterns of synthesis of new matrix was markedly altered under such conditions. New matrix material elaborated by cells plated upon ECM‐coated dishes consisted predominantly of glycopeptide and proteoglycan matrix components. Epidermal growth factor promoted the incorporation of [3H]‐thymidine into DNA by quiescent cells, and this was also markedly stimulated when cells were plated onto ECM‐coated plasticware rather than onto plastic substratum.
Activation of the Na+/H+ exchanger by phorbol ester and osmotic shock is dependent on the degree of neutrophilic maturation
Authors: Costa‐Casnellie Maria R. , Cragoe E. J. , Segel George B. , Lichtman Marshall A. 
Published: February 2005

AbstractActivation of neutrophils leading to superoxide production is accompanied by cytoplasmic alkalinization, which results from stimulation of the Na+/H+ exchanger. Since the exchanger undergoes permanent alterations during neutrophilic maturation of HL‐60 cells (Costa‐Casnellie et al.: journal of Biological Chemistry 263:11851–11855, 1988), we investigated whether its response to external stimuli such as phorbol esters or osmotic shock also was modified during cell maturation. Mature HL‐60 cells produce superoxide in response to active phorbol esters, whereas immature HL‐60 cells do not. Stimulation of the exchanger by active phorbol esters (phorbol 12‐myristate 13‐acetate or phorbol 12, 13‐dibutyrate) was observed in mature neutrophilic HL‐60 cells but not in their immature counterparts. Inactive 4‐alpha phorbol had no effect in either cell population. Compound H7 inhibited phorbol ester activation by 65%. In mature neutrophilic cells activation of the exchanger by phorbol esters caused two novel changes of its properties: (1) its apparent Km for Na+ transport increased 2‐fold; (2) its Vmax increased 2.6‐fold. Phorbol esters also caused a shift in pH dependence of activation similar to that induced in other cells. Osmotic shock, a different method known to activate the exchanger of other cells, induced activation in mature neutrophilic cells but not in immature cells. Thus, the response of the exchanger to external stimuli is affected by alterations occurring in association with cell maturation.
Transforming growth factor β‐1 positively modulates the bioactivity of fibroblast growth factor on corneal endothelial cells
Authors: Plouët Jean , Gospodarowicz Denis 
Published: February 2005

AbstractTransforming growth factor beta‐1 (TGFβ‐1), known as an inhibitor of vascular endothelial cell proliferation in vitro, stimulates bovine corneal endothelial cells (BCE) proliferation. It also positively modulates the response of BCE cells to fibroblast growth factor (FGF) and epidermal growth factor (EGF). This effect is concentration dependent within a physiological range of TGFβ‐1, but it is blocked if cells are cultured on extracellular‐matrix‐coated dishes instead of plastic. TGFβ‐1 does not modify the number or the affinity of bFGF receptors on BCE cell surface but increases the bFGF content of these cells. This suggests that TGFβ‐1 might act through regulation of bFGF synthesis in BCE cells.
Basic fibroblast growth factor: Production, mitogenic response, and post‐receptor signal transduction in cultured normal and transformed fetal bovine aortic endothelial cells
Authors: Presta Marco , Maier Jeanette A. M. , Rusnati Marco , Ragnotti Giovanni 
Published: February 2005

AbstractNormal FBAE AG 7680 cells and chemically transformed FBAE GM 7373 cells were compared for their capacity to produce and to respond to bFGF. Normal FBAE cells showed higher levels of bFGF protein and of poly(A)+ bFGF mRNA than transformed GM 7373 cells, indicating that chemical transformation in FBAE cells is paralleled by a decrease of bFGF gene expression. Basic FGF induced cell proliferation in both normal and transformed FBAE cells. However, bFGF appeared to be much more potent in transformed than in normal cells. No differences in bFGF membrane receptors were observed between normal and transformed FBAE cells in terms of apparent molecular weight, number per cell, dissociation constant, and kinetic of downregulation. In respect to normal cells, however, transformed GM 7373 cells showed higher basal levels of PKC activity. This kinase is activated by bFGF and is involved in mediating the mitogenic activity of bFGF, as shown by the capacity of the PKC inhibitor H‐7 to abolish the mitogenic activity of bFGF both in normal and transformed FBAE cells. Like bFGF, the PKC activators DAG and TPA exerted a stronger mitogenic activity in transformed than in normal FBAE cells. Thus, the different susceptibility of normal and transformed FBAE cells to bFGF appears to depend on differences in the post‐receptor signal transduction mediated by PKC rather than on differences in bFGF receptors.The results indicate that chemical transformation causes significant modifications of bFGF physiology in FBAE cells. The relevance of these modifications to the genesis of tumors of vascular origin deserves further investigation.
Regulation of cerebroside sulfotransferase activity in cultured oligodendrocytes: Effect of growth factors and insulin
Authors: Fressinaud C. , Sarliève L. L. , Labourdette G. 
Published: February 2005

AbstractCerebroside sulfotransferase (EC 2.8.2.11, CST) specific activity has been determined in oligodendrocyte (OL)‐enriched glial cell cultures from newborn rat brain grown in serum supplemented medium. This activity is detectable at 5 days in vitro (DIV) and reaches its maximum value at 12 DIV. This period corresponds to that of oligodendrocyte precursor proliferation in these cultures. The activity decreases thereafter and remains nearly constant after 24 DIV. The developmental curve of CST activity is parallel in pure oligodendrocyte subcultures but twice higher than in primary cultures. These data confirm that CST is highly enriched in OL. Basic fibroblast growth factor (bFGF) (15 ng/ml) and platelet derived growth factor (PDGF) (0.75 U/ml) both enhance CST activity by 90% and 72%, respectively. This increase is in the same range than that of DNA content in treated cultures, whereas protein increase is smaller (50% and 22%, respectively). In contrast, transforming growth factor β1 (TGFβ1, 0.5 and 5 ng/ml) does not significantly enhance CST activity nor DNA content of OL cultures. Insulin at high concentrations (5 μg/ml) also enhances CST activity but has no effect at physiological concentrations (20 ng/ml). These results show that CST activity can be controlled by growth factors. They suggest that CST activity is more closely related to OL and OL precursor proliferation than to myelination itself since its maximal activity preceeds myelination in vitro.
Forskolin has biphasic effects on osteoprogenitor cell differentiation in vitro
Authors: Turksen Kursad , Grigoriadis Agamemnon E. , Heersche Johan N. M. , Aubin Jane E. 
Published: February 2005

AbstractCells isolated from fetal rat calvaria (RC) and maintained in vitro in medium containing ascorbic acid and B‐glycerophosphate form three‐dimensional, mineralized nodules having the histological, immunohistological, and ultrastructural characteristics of woven bone. We have studied the effects of forskolin (FSK), a diterpene that activates adenylate cyclase, in this system. While 10−7 −10−5 M FSK significantly stimulated cAMP levels in RC cells, lower concentrations did not. cAMP levels with 10−5 M FSK reached a maximum by 30 min at 37°C and returned to basal level in 2‐3 hr. Changes in cAMP levels correlated with changes in cellular shape: cells treated with 10−5 M FSK assumed a stellate morphology, lost microfilament bundles, and reduced their substrate adhesiveness, while cells treated with 10−9 M were not affected. Exponential growth and saturation densities of FSK‐treated cultures were similar to untreated cultures, indicating that FSK was neither toxic nor stimulatory to the population. The effect on bone nodule formation of FSK present continuously depended on concentration: 10−5 M FSK significantly inhibited the number of nodules formed, while 10−9 M FSK significantly stimulated bone nodule formation. Single short treatments with either 10−5 M or 10−9 M FSK had no effect on nodule formation, but repeated short duration treatments (1 hr every 2 days for 21 days) gave results similar to continuous exposure. These results indicate that intermittent elevations in intracellular cAMP have an inhibitory effect on bone formation. In addition, our work indicates that low concentrations of FSK stimulate differentiation of osteoprogenitor cells possibly through a non‐cAMP‐dependent process.
Cyclic adenosine monophosphate levels and the function of skin microvascular endothelial cells
Authors: Tuder Rubin M. , Karasek Marvin A. , Bensch Klaus G. 
Published: February 2005

AbstractThe maintenance of the normal epithelioid morphology of human dermal microvascular endothelial cells (MEC) grown in vitro depends strongly on the presence of factors that increase intracellular levels of cyclic AMP. Complete removal of dibutyryl cAMP and isobutylmethyixanthine (IMX) from the growth medium results in a progressive transition from an epithelioid to a spindle‐shaped cell line. This transition cannot be reversed by the readdition of dibutyryl cAMP and IMX to the growth medium or by addition of agonists that increase cAMP levels. Spindle‐shaped MEC lose the ability to express Factor VIII rAG and DR antigens and to bind peripheral blood mononuclear leukocyte (PBML).Ultrastructural analyses of transitional cells and spindle‐shaped cells show decreased numbers of Weibel‐Palade bodies in transitional cells and their complete absence in spindle‐shaped cells. Interferon‐γ alters several functional properties of both epitheliod and spindle‐shaped cells. In the absence of dibutyryl cAMP it accelerates the transition from epithelial to spindle‐shaped cells, whereas in the presence of cyclic AMP interferon‐γ increases the binding of PBMLs to both epithelioid and spindle‐shaped MEC and the endocytic activity of the endothelial cells.These results suggest that cyclic AMP is an important second messenger in the maintenance of several key functions of microvascular endothelial cells. Factors that influence the levels of this messenger in vivo can be expected to influence the angiogenic and immunologic functions of the microvasculature.
Effects of reduced cell volume and water content on glycolysis in L‐929 cells
Authors: Clegg James S. , Jackson Susan A. , Fendl Karin 
Published: February 2005

AbstractMouse L‐929 cells were subjected to increasing concentrations of sorbitol, which remove cell water and reduce volume osmotically. The rate of lactate production from glucose was significantly higher in osmotically perturbed cells than in controls, both in monolayers and in suspensions. L cells can apparently use sorbitol as a glycolytic substrate; however, studies using other solutes (trehalose and sucrose) and permeabilized cells showed that the major effect of scrbitol on glycolysis in intact cells is mediated through a reduction in cell water content and volume. It is possible to explain some of these results by an increase in the chemical potentials of dissolved components of the glycolytic pathway caused by water loss; however, the relationship between water loss and glycolytic rate increase in not a simple linear one, suggesting that the situation is more complex than would result merely from increased concentrations of pathway components. Whatever the complete explanation might be, these studies show that glycolysis continues in an orderly fashion in cells that have lost about 85% of their original water content, suggesting that the operation of this pathway is not unduly sensitive to events taking place in the bulk aqueous phase.
Correlation between fibronectin and its receptor in chick myoblast differentiation
Authors: Chung Chang Yong , Kang Man‐Sik 
Published: February 2005

AbstractAlterations in the amount of fibronectin and in the number of its receptors during myoblast differentiation of chicken embryo were investigated. The amount of fibronectin in the cell surface pool as measured by immunoblotting decreased during myogenesis To identify and characterize the fibronectin receptors on the myoblasts, the interactions of the 28,000 dalton (28 kDa) amino terminal fragment and 85,000 dalton (85 kDa) cell‐binding fragment of fibronectin with my‐oblasts were examined. The binding of the 28 kDa fragment was found to be time‐dependent and reached a maximum level within 60 min. The unlabeled 28 kDa fragment inhibited the binding of the radioiodinated 28 kDa fragment, whereas the unlabeled 85 kDa fragment and antibody to integrin did not inhibit it, suggesting that the 28 kDa fragment interacts with the matrix assembly receptors but not with the cell adhesion receptors. There was a single class of 3.4 × 105 binding sites per cell with an apparent dissociation constant of 1.4 × 10−7 M on 30 hr old myoblasts. The specific binding of the radioiodinated 28 kDa fragment to myoblasts decreased as the fusion proceeded. This decrease of binding was consistent with the decrease in the amount of fibronectin. Furthermore, the levels of fibronectin and binding of the radioiodinated 28 kDa fragment in the fusion‐blocked myoblasts by EGTA treatment appeared to remain constant. These results suggest that the decrease and/or loss of fibronectin during myoblast fusion is closely correlated with the alteration of fibronectin receptors and with the fusion of myoblasts.
Menthol blocks dihydropyridine‐insensitive Ca2+ channels and induces neurite outgrowth in human neuroblastoma cells
Authors: Sidell Neil , Verity M. Anthony , Nord Edward P. 
Published: February 2005

AbstractVoltage‐gated Ca2+ channels were identified in LA‐N‐5 human neuroblastoma cells using the Ca2+ sensitive fluorescent probe, fura‐2. Using a variety of “classical” Ca2+ channel blockers, we have demonstrated the presence of both dihydropyridine (DHP)‐sensitive and ‐insensitive channel types that can be activated by depolarization of the cells with either high K+ or gramicidin in the bathing solution. Brief exposure of LA‐N‐5 cells to menthol blunted the depolarization‐induced Ca2+ influx though both DHP‐sensitive and DHP‐insensitive channels. This effect is concentration dependent (50% maximal blocking effect with 0.25 mM menthol), rapid in onset, and readily reversible. The specificity of the Ca2+ ‐channel blocking effect of menthol was demonstrated in parallel studies using compounds with similar structures: menthone blocked Ca2+ channels with about half the potency of menthol, while cyclohexanol was without effect. Addition of either menthol or menthone to LA‐N‐5 cultures induced neurite outgrowth, cellular clustering, and reduction of cell growth in a dose‐dependent fashion that correlated with the ability of these compounds to inhibit the DHP‐insensitive Ca2+ influx. Cyclohexanol had no biologic activity. Taken together, the parallel potency for blockade of DHP‐insensitive Ca2+ influx with the biologic activity of menthol suggests a role for certain types of Ca2+ channels in triggering growth and morphologic changes in LA‐N‐5 cells.
Novel monoclonal antibodies identify antigenic determinants unique to cellular senescence
Authors: Porter Mary Beth , Pereira‐Smith Olivia M. , Smith James R. 
Published: February 2005

AbstractNormal human diploid fibroblasts exhibit a limited lifespan in vitro and are used as a model to study in vivo aging. Monoclonal antibodies were generated against partially purified surface membranes from human diploid fibroblasts at the end of their lifespan (senescent). Three hybridomas were isolated that secreted antibodies reacting to cellular determinants expressed specifically on senescent human fibroblasts of different origin, including neonatal foreskin, embryonic lung, and adult skin punch biopsy, but not expressed on matched young cells. The antibodies did not bind to immortal human cells and normal young cells made reversibly nondividing, indicating the antigens are not expressed in cells that are not senescent. The antibodies identified senescent cells in a mixed cell population and expression of the senescent cell antigens correlated strongly with the cells inability to synthesize DNA at the onset of senescence. The antigens appeared to be cell surface or extracellular matrix associated, and the epitopes were destroyed by mild trypsin treatment. Western analysis indicated all three antibodies reacted with fibronectin. Though the antigenic determinants on the fibronectir molecule were not accessible in the intact young cell, the epitopes were present in fibronectin extracted from both senescent and young cells, as well as purified human plasma fibronectin. These antibodies and the senescent specific expression of the antigens provide powerful tools to investigate the mechanisms leading to in vitro senescence. This may enable us to investigate directly the relationship between cellular aging and aging of the individual.
Macrophage‐colony‐stimulating factor (CSF‐1) modulates a differentiation‐specific inward‐rectifying potassium current in human leukemic (HL‐60) cells
Authors: Wieland Steven J. , Chou Robin H. , Gong Qi‐Hua 
Published: February 2005

AbstractA voltage‐activated inward‐rectifying K+ conductance (Iki) appears in human promyelocytic leukemia (HL‐60) cells during phorbol ester‐induced differentiation into macrophages. This conductance was detected in the cells 24 hours after exposure to phorbol‐12‐myristate‐13‐acetate (PMA), as the cells began to express the macrophage phenotype, and continued to increase for 4 days after PMA exposure. The magnitude of inward current was a function of external K+; current was blocked by extracellular or intracellular Cs+ and by extracellular Ba++. Hyperpolarization produced activation at membrane potentials more negative than −80 mV, and a slower, partial inactivation also occurred at potentials more negative than −100 mV. This conductance was not detected in proliferating cells nor in granulocytes derived from HL‐60 cells which were induced to differentiate with retinoic acid (RA). Exposure of differentiated macrophages to recombinant human CSF‐1 produced inhibition of the Iki beginning within 1 minute after exposure. CSF‐1 inhibition of Iki channels in cell‐attached patches indicated that channel modulation was via intracellular mediators. The rapid inhibition of the inward rectifier by the macrophage‐specific CSF‐1 appears to be one of the earliest cellular responses to this factor.
Fluid shear stress as a mediator of osteoblast cyclic adenosine monophosphate production
Authors: Reich Kathleen M. , Gay Carol V. , Frangos John A. 
Published: February 2005

AbstractEffects of interstitial fluid flow on osteoblasts were investigated. Intracellular cyclic adenosine monophosphate (cAMP) levels were monitored in cultured osteo‐blasts subjected to shear rates ranging from 10 to 3,500 sec−1. Cyclic AMP levels were significantly increased at all shear rates from 1 pmole/mg protein to 10‐16 pmole/mg protein. Osteoblasts subjected to a shear rate of 430 sec−1 for 0.5‐15 minutes exhibited elevated levels (12‐fold) of intracellular cAMP, which were sustained throughout the perfusion period. Osteoblasts were three times more sensitive to flow stimulation than human umbilical vein endothelial cells and baby hamster kidney fibroblasts, which also displayed higher cAMP levels (4‐fold) after exposure to flow. To distinguish streaming potential effects from shear stress effects, viscosity was increased 5‐fold by addition of neutral dextran to the perfusing medium. Shear stress is a function of viscosity, and streaming potentials are not for a given shear rate. The mechanism of this cellular response to flow was shown to be shear stress dependent. Inhibition of cyclooxygenase by 20 μM ibuprofen completely inhibited the flow‐dependent cAMP response, indicating the cAMP response is mediated by prostaglandins. Our results suggest that fluid flow induced by mechanical stress may be an important mediator of bone remodeling.
Kinetics of hydrolysis of endocytosed substrates by mammalian cultured cells: Early introduction of lysosomal enzymes into the endocytic pathway
Authors: Bowser Robert , Murphy Robert F. 
Published: February 2005

AbstractThe kinetics of exposure of endocytosed material to two lysosomal enzymes were determined for a number of cultured cell lines using fluorogenic substrates. Hydrolysis of endocytosed substrates for cathepsin B and acid phosphatase was observed to begin within 3–10 min of substrate addition and to proceed linearly for up to 60 min thereafter. Hydrolysis of the cathepsin B substrate was not affected by inhibition of protein synthesis with cycloheximide, indicating that the enzymes present in early endosomes are not exclusively newly synthesized. As had been observed previously for a cathepsin B substrate (Roederer, M., Bowser, R., and Murphy, R.F., J. Cell. Physiol., 131:200–209, 1987), hydrolysis of the acid phosphatase substrate was not blocked at temperatures below 20°C. The results suggest that the endosome is the primary site of initial exposure of endocytosed material to hydrolytic enzymes.