Showing papers in "American Journal of Physiology-cell Physiology in 1999"
TL;DR: Myofibroblasts are a unique group of smooth-muscle-like fibro-blasts that have a similar appearance and function regardless of their tissue of residence as discussed by the authors.
Abstract: Myofibroblasts are a unique group of smooth-muscle-like fibroblasts that have a similar appearance and function regardless of their tissue of residence. Through the secretion of inflammatory and an...
896 citations
TL;DR: The tight correlation between the activation of p70S6k and the long-term increase in muscle mass suggests that p70KDa S6k phosphorylation may be a good marker for the phenotypic changes that characterize muscle hypertrophy and may play a role in load-induced skeletal muscle growth.
Abstract: High-resistance exercise training results in an increase in muscle wet mass and protein content. To begin to address the acute changes following a single bout of high-resistance exercise, a new model has been developed. Training rats twice a week for 6 wk resulted in 13.9 and 14.4% hypertrophy in the extensor digitorum longus (EDL) and tibialis anterior (TA) muscles, respectively. Polysome profiles after high-resistance lengthening contractions suggest that the rate of initiation is increased. The activity of the 70-kDa S6 protein kinase (p70(S6k)), a regulator of translation initiation, is also increased following high-resistance lengthening contractions (TA, 363 +/- 29%; EDL, 353 +/- 39%). Furthermore, the increase in p70(S6k) activity 6 h after exercise correlates with the percent change in muscle mass after 6 wk of training (r = 0.998). The tight correlation between the activation of p70(S6k) and the long-term increase in muscle mass suggests that p70(S6k) phosphorylation may be a good marker for the phenotypic changes that characterize muscle hypertrophy and may play a role in load-induced skeletal muscle growth.
659 citations
TL;DR: COX-2 in polyp ISEMF may be a target for nonsteroidal anti-inflammatory drugs (NSAIDs), which would account for the regression of the neoplasms in familial adenomatous polyposis and the preventive effect of NSAIDs in the development of sporadic colon neoplasm.
Abstract: Intestinal subepithelial myofibroblasts (ISEMF) and the interstitial cells of Cajal are the two types of myofibroblasts identified in the intestine. Intestinal myofibroblasts are activated and prol...
536 citations
TL;DR: The activity of cell-attached luciferase is relatively refractory to the inclusion of nucleotidases in the medium, arguing for its effectiveness in cell systems possessing potent ecto-ATPases.
Abstract: We have developed a method for measuring the local concentration of ATP at the extracellular surface of live cells. This method relies on the specific attachment to the cell surface of a chimeric protein that consists of the IgG-binding domain of Staphylococcus aureus protein A fused in-frame with the complete sequence for firefly luciferase (proA-luc). Expression of proA-luc in Escherichia coli and its one-step affinity purification are straightforward. Attachment to cells is demonstrated to be specific and antibody dependent using several suspended and adherent cell types. Light production by cell surface-attached luciferase is continuous, linearly related to ATP concentration, and sufficient to provide nanomolar sensitivity. The spatial resolution of this method enables the observation of strictly local changes in extracellular ATP during its secretion from activated platelets. Furthermore, the activity of cell-attached luciferase is relatively refractory to the inclusion of nucleotidases in the medium, arguing for its effectiveness in cell systems possessing potent ecto-ATPases.
290 citations
TL;DR: It is calculated that the proton cycle in working muscle and liver may account for 15% of standard metabolic rate in vivo, which is less than the 20% of SMR calculated previously using data from resting skeletal muscle and hepatocytes.
Abstract: Proton pumping across the mitochondrial inner membrane and proton leak back through the natural proton conductance pathway make up a futile cycle that dissipates redox energy. We measured respiration and average mitochondrial membrane potential in perfused rat hindquarter with maximal tetanic contraction of the left gastrocnemius-soleus-plantaris muscle group, and we estimate that the mitochondrial proton cycle accounted for 34% of the respiration rate of the preparation. Similar measurements in rat hepatocytes given substrates to cause a high rate of gluconeogenesis and ureagenesis showed that the proton cycle accounted for 22% of the respiration rate of these cells. Combining these in vitro values with literature values for the contribution of skeletal muscle and liver to standard metabolic rate (SMR), we calculate that the proton cycle in working muscle and liver may account for 15% of SMR in vivo. Although this value is less than the 20% of SMR we calculated previously using data from resting skeletal muscle and hepatocytes, it is still large, and we conclude that the futile proton cycle is a major contributor to SMR.
262 citations
TL;DR: It is concluded that G6PDH plays a critical role in cell death by affecting the redox potential by causing changes in mitogen-activated protein kinase phosphorylation that were similar to the changes seen with H2O2.
Abstract: The intracellular redox potential plays an important role in cell survival. The principal intracellular reductant NADPH is mainly produced by the pentose phosphate pathway by glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme, and by 6-phosphogluconate dehydrogenase. Considering the importance of NADPH, we hypothesized that G6PDH plays a critical role in cell death. Our results show that 1) G6PDH inhibitors potentiated H2O2-induced cell death; 2) overexpression of G6PDH increased resistance to H2O2-induced cell death; 3) serum deprivation, a stimulator of cell death, was associated with decreased G6PDH activity and resulted in elevated reactive oxygen species (ROS); 4) additions of substrates for G6PDH to serum-deprived cells almost completely abrogated the serum deprivation-induced rise in ROS; 5) consequences of G6PDH inhibition included a significant increase in apoptosis, loss of protein thiols, and degradation of G6PDH; and 6) G6PDH inhibition caused changes in mitogen-activated protein kinase phosphorylation that were similar to the changes seen with H2O2. We conclude that G6PDH plays a critical role in cell death by affecting the redox potential.
256 citations
TL;DR: Volume-regulatory transporters are closely linked to cell growth and metabolism, producing requisite changes in cell volume that may also signal subsequent growth and metabolic events, and have important roles in mammalian physiology.
Abstract: Research over the past 25 years has identified specific ion transporters and channels that are activated by acute changes in cell volume and that serve to restore steady-state volume. The mechanism by which cells sense changes in cell volume and activate the appropriate transporters remains a mystery, but recent studies are providing important clues. A curious aspect of volume regulation in mammalian cells is that it is often absent or incomplete in anisosmotic media, whereas complete volume regulation is observed with isosmotic shrinkage and swelling. The basis for this may lie in an important role of intracellular Cl- in controlling volume-regulatory transporters. This is physiologically relevant, since the principal threat to cell volume in vivo is not changes in extracellular osmolarity but rather changes in the cellular content of osmotically active molecules. Volume-regulatory transporters are also closely linked to cell growth and metabolism, producing requisite changes in cell volume that may also signal subsequent growth and metabolic events. Thus, despite the relatively constant osmolarity in mammals, volume-regulatory transporters have important roles in mammalian physiology.
246 citations
TL;DR: Acidity is not necessary for these responses, but glucocorticoids and a low insulin level in tandem activate the ubiquitin-proteasome proteolytic system, and this system is stimulated in conditions causing muscle atrophy.
Abstract: The ubiquitin-proteasome proteolytic system is stimulated in conditions causing muscle atrophy. Signals initiating this response in these conditions are unknown, although glucocorticoids are requir...
241 citations
TL;DR: Hypoxia-induced permeability in vitro is mediated by the VEGF/VEGF receptor system in an autocrine manner and is essentially dependent on reducing conditions stabilizing the second messenger NO as the mediator of changes in barrier function of BMEC.
Abstract: In this study, an in vitro model of the blood-brain barrier, consisting of porcine brain-derived microvascular endothelial cells (BMEC), was used to evaluate the mechanism of hypoxia-induced hyperp...
228 citations
TL;DR: Although the absence of NHE1 is compatible with embryogenesis, Nhe1 homozygous mutants (-/-) exhibit a decreased rate of postnatal growth that is first evident at 2 wk of age and animals also begin to exhibit ataxia and epileptic-like seizures.
Abstract: In most cells, the ubiquitously expressed Na+/H+exchanger isoform 1 (NHE1) is thought to be a primary regulator of pH homeostasis, cell volume regulation, and the proliferative response to growth f...
223 citations
TL;DR: T4 treatment caused tyrosine-phosphorylated MAPK-STAT1α nuclear complex formation and enhanced Ser-727 phosphorylation of STAT1α, in the presence or absence of IFN-γ.
Abstract: Thyroid hormone [l-thyroxine (T4)] rapidly induced phosphorylation and nuclear translocation (activation) of mitogen-activated protein kinase (MAPK) in HeLa and CV-1 cells in the absence of cytokin...
TL;DR: The calcium-binding protein parvalbumin (PV) occurs at high concentrations in fast-contracting vertebrate muscle fibers and its putative role in facilitating the rapid relaxation of mammalian fast-twi...
Abstract: The calcium-binding protein parvalbumin (PV) occurs at high concentrations in fast-contracting vertebrate muscle fibers. Its putative role in facilitating the rapid relaxation of mammalian fast-twi...
TL;DR: The findings of the present study suggest that VEGF, which appears to be increased in brain tissue during cerebrovascular trauma, increases the permeability of the BBB via the synthesis/release of nitric oxide and subsequent activation of soluble guanylate cyclase.
Abstract: It appears that the expression of vascular endothelial growth factor (VEGF) is increased during brain injury and thus may contribute to disruption of the blood-brain barrier (BBB) during cerebrovas...
TL;DR: Macrophages and thymocytes express P2Z/P2X7nucleotide receptors that bind extracellular ATP, and brief treatment with ATP led to an increase in the intracellular calcium concentration and permeabilization of the plasma membrane to Lucifer yellow, which diffused throughout the dendritic cell cytosol.
Abstract: Macrophages and thymocytes express P2Z/P2X7 nucleotide receptors that bind extracellular ATP. These receptors play a role in immune development and control of microbial infections, but their presence on dendritic cells has not been reported. We investigated whether extracellular ATP could trigger P2Z/P2X7 receptor-dependent apoptosis of dendritic cells. Apoptosis could be selectively triggered by tetrabasic ATP, since other purine/pyrimidine nucleotides were ineffective, and it was mimicked by the P2Z receptor agonist, benzoylbenzoyl ATP, and blocked by magnesium and the irreversible antagonist, oxidized ATP. RT-PCR analysis confirmed the mRNA expression of the P2Z/P2X7 receptor and the absence of P2X1. Caspase inhibitors and cycloheximide had only a partial effect on the apoptosis, suggesting that a caspase-independent mechanism may also be operative. Brief treatment with ATP led to an increase in the intracellular calcium concentration and permeabilization of the plasma membrane to Lucifer yellow, which diffused throughout the dendritic cell cytosol. Other small extracellular molecules may thus attain a similar intracellular distribution, perhaps activating endogenous proteases that contribute to initiation of apoptosis.
TL;DR: Taurine attenuates hyperglycemia-induced HUVEC apoptosis through ROS inhibition and [Ca2+]istabilization and suggest that taurine may exert a beneficial effect in preventing diabetes-associated microangiopathy.
Abstract: Elevated blood glucose in uncontrolled diabetes is causally correlated with diabetic microangiopathy. Hyperglycemia-triggered accelerated endothelial cell apoptosis is a critical event in the proce...
TL;DR: KCC3 transiently expressed in human embryonic kidney (HEK)-293 cells fulfilled three criteria for increased expression of K-Cl cotransport: stimulation of cOTransport by swelling, treatment with N-ethylmaleimide, or treatment with staurosporine.
Abstract: We isolated and characterized a novel K-Cl cotransporter, KCC3, from human placenta. The deduced protein contains 1,150 amino acids. KCC3 shares 75–76% identity at the amino acid level with human, ...
TL;DR: This review focuses only on those defense mechanisms that are initiated and executed by the intestinal epithelial cell: enhanced salt and water secretion, expression of antimicrobial proteins and peptides, and production of intestinal mucins.
Abstract: The single layer of epithelial cells lining the intestinal tract is charged with a most difficult task: protecting the underlying biological compartments from both the normal commensal flora that reside within the intestinal lumen as well as the uninvited pathogens. To such an end, the intestinal epithelial cells are equipped with a panoply of defense mechanisms, both constitutive and inducible. This review focuses only on those defense mechanisms that are initiated and executed by the intestinal epithelial cell. Fitting these strict criteria are three major categories of epithelial host defense: enhanced salt and water secretion, expression of antimicrobial proteins and peptides, and production of intestinal mucins. Each of these areas is discussed in this review.
TL;DR: Cytoadherence may activate intracellular signaling pathways in both endothelial cells and IRBC, leading to gene expression of mediators such as cytokines, which could modify the outcome of the infection.
Abstract: Microbial pathogens subvert host adhesion molecules to disseminate or to enter host cells to promote their own survival. One such subversion is the cytoadherence of Plasmodium falciparum-infected e...
TL;DR: It is shown that the kinetics and extent of muscle regeneration in vivo after trauma are greatly enhanced following systemic administration of curcumin, a pharmacological inhibitor of the transcription factor NF-κB, and that modulation of NF-σB activity within muscle tissue is beneficial for muscle repair.
Abstract: Skeletal muscle is often the site of tissue injury due to trauma, disease, developmental defects or surgery. Yet, to date, no effective treatment is available to stimulate the repair of skeletal mu...
TL;DR: Results suggest that quercetin downregulates both PMA- and TNF-α-induced ICAM-1 expression via inhibiting both AP-1 activation and the JNK pathway.
Abstract: The cell adhesion molecule intercellular adhesion molecule-1 (ICAM-1) plays a pivotal role in inflammatory responses. Quercetin (3,3′,4′,5,7-pentahydroxyflavone), a naturally occurring dietary flav...
TL;DR: It is demonstrated for the first time the presence of Trp1 protein in a nonexcitable cell, consistent with their proposed role in Ca2+ influx.
Abstract: The Trp gene product has been proposed as a candidate protein for the store-operated Ca2+ channel, but the Trp protein(s) has not been identified in any nonexcitable cell. We report here the cloning of a rat brain Trp1beta cDNA and detection and immunolocalization of the endogenous and expressed Trp1 protein. A 400-bp product, with >95% homology to mouse Trp1, was amplified from rat submandibular gland RNA. Rat-specific primers were used for cloning of a full-length rat brain Trp1beta cDNA (rTrp1), encoding a protein of 759 amino acids. Northern blot analysis demonstrated the transcript in several rat and mouse tissues. The peptide (amino acids 523-536) was used to generate a polyclonal antiserum. The affinity-purified antibody 1) immunoprecipitated human Trp1 (hTrp1) from transfected HEK-293 cells, 2) reacted with a protein of approximately 92 kDa, but not with hTrp3, in membranes of hTrp3-expressing HEK-293 cells, and 3) reacted with proteins of 92 and 56 kDa in human and rat brain membranes. Confocal microscopy and cell fractionation demonstrated that endogenous and expressed hTrp1 and expressed hTrp3 proteins were localized in the plasma membrane of HEK-293 cells, consistent with their proposed role in Ca2+ influx. The data demonstrate for the first time the presence of Trp1 protein in a nonexcitable cell.
TL;DR: It is shown that, in this kinetic work, use of d-glucose-contaminatedd-sorbitol as an osmotic replacement cannot cause the spurious appearance of nonexistent transport systems, and a large range of substrate concentrations is required to correctly fit substrate saturation curves to distinguish between low-affinity transport systems and physical diffusion.
Abstract: Heterogeneity of intestinal D-glucose transport is demonstrated using pig jejunal brush-border membrane vesicles in the presence of 100/0 (out/in) mM gradients each of NaCl, NaSCN, and KSCN. Two D-glucose transport systems are kinetically distinguished: high-affinity, low-capacity system 1, which is equivalent to the symporter SGLT1; and low-affinity, high-capacity system 2, which is not a member of the SGLT family but is a D-glucose and D-mannose transporter exhibiting no preference for Na(+) over K(+). A nonsaturable D-glucose uptake component has also been detected; uptake of this component takes place at rates 10 times the rate of components characterizing the classical diffusion marker L-glucose. It is also shown that, in this kinetic work, 1) use of D-glucose-contaminated D-sorbitol as an osmotic replacement cannot cause the spurious appearance of nonexistent transport systems and 2) a large range (>/=50 mM) of substrate concentrations is required to correctly fit substrate saturation curves to distinguish between low-affinity transport systems and physical diffusion.
TL;DR: Findings may indicate that water crosses the epithelial layer through these water channels, suggesting a possible role of the transcellular route for water intake or outlet in the gastrointestinal tract.
Abstract: A family of water-selective channels, aquaporins (AQP), has been demonstrated in various organs and tissues. However, the localization and expression of the AQP family members in the gastrointestin...
TL;DR: Observations support the thesis that lacrimal gland acinar cells that have been induced to express MHC class II molecules function as autoantigen processing and presenting cells.
Abstract: Sjogren's syndrome is a chronic autoimmune disease affecting the lacrimal glands and other epithelia. It has been suggested that acinar cells of the lacrimal glands provoke local autoimmune responses, leading to Sjogren's syndrome when they begin expressing major histocompatibility complex (MHC) class II molecules. We used isopycnic centrifugation and phase partitioning to resolve compartments that participate in traffic between the basolateral membranes and the endomembrane system to test the hypothesis that MHC class II molecules enter compartments that contain potential autoantigens, i.e., La/SSB, and enzymes capable of proteolytically processing autoantigen, i.e., cathepsins B and D. A series of compartments identified as secretory vesicle membranes, prelysosomes, and microdomains of the trans-Golgi network involved in traffic to the basolateral membrane, to the secretory vesicles, and to the prelysosomes were all prominent loci of MHC class II molecules, La/SSB, and cathepsins B and D. These observations support the thesis that lacrimal gland acinar cells that have been induced to express MHC class II molecules function as autoantigen processing and presenting cells.
TL;DR: FAK and paxillin participate in an integrin-mediated mechanotransduction process in tracheal smooth muscle and it is proposed that this pathway may initiate alterations in smooth muscle cell structure and contractility via the remodeling of actin filaments and/or via the mechanosensitive regulation of signaling molecules involved in contractile protein activation.
Abstract: We investigated the role of the integrin-associated proteins focal adhesion kinase (FAK) and paxillin as mediators of mechanosensitive signal transduction in tracheal smooth muscle. In muscle strips contracted isometrically with ACh, we observed higher levels of tyrosine phosphorylation of FAK and paxillin at the optimal muscle length (Lo) than at shorter muscle lengths of 0.5 or 0.75 Lo. Paxillin phosphorylation was also length sensitive in muscles activated by K+ depolarization and adjusted rapidly to changes in muscle length imposed after contractile activation by either ACh or K+ depolarization. Ca2+ depletion did not affect the length sensitivity of paxillin and FAK phosphorylation in muscles activated with ACh, indicating that the mechanotransduction process can be mediated by a Ca2+-independent pathway. Since Ca2+-depleted muscles do not generate significant active tension, this suggests that the mechanotransduction mechanism is sensitive to muscle length rather than tension. We conclude that FAK and paxillin participate in an integrin-mediated mechanotransduction process in tracheal smooth muscle. We propose that this pathway may initiate alterations in smooth muscle cell structure and contractility via the remodeling of actin filaments and/or via the mechanosensitive regulation of signaling molecules involved in contractile protein activation.
TL;DR: It is shown here that the mutation of an E-box within the MHC IIB promoter decreased reporter gene activity in the fast-twitch TA muscle 90-fold as compared with the wild-type promoter.
Abstract: The myosin heavy chain (MHC) IIB gene is selectively expressed in skeletal muscles, imparting fast contractile kinetics. Why the MHC IIB gene product is expressed in muscles like the tibialis anter...
TL;DR: expression in human trachea and lung suggests that hCLCA2 may play a role in the complex pathogenesis of cystic fibrosis.
Abstract: The CLCA family of Ca2+-activated Cl− channels has recently been discovered, with an increasing number of closely related members isolated from different species. Here we report the cloning of the ...
TL;DR: Several phenotypic abnormalities in macrophages from ob/ob mice are identified, including decreased steady-state levels of uncoupling protein-2 mRNA, increased mitochondrial production of superoxide and hydrogen peroxide, constitutive activation of CCAAT enhancer binding protein (C/EBP)-beta, an oxidant-sensitive transcription factor, and increased expression of interleukin-6 and cyclooxygenase (COX)-2.
Abstract: Obesity is a complex syndrome that involves defective signaling by a number of different factors that regulate appetite and energy homeostasis. Treatment with exogenous leptin reverses hyperphagia ...
TL;DR: Cloning an NBC isoform (hhNBC) from a human heart cDNA library concludes that hhNBC is an electrogenic Na+-[Formula: see text]cotransporter and that hkNBC is also electrogensic.
Abstract: Our group recently cloned the electrogenic Na+- HCO 3 − cotransporter (NBC) from salamander kidney and later from mammalian kidney. Here we report cloning an NBC isoform (hhNBC) from a human heart ...
TL;DR: The results indicate that polyamine depletion causes cell cycle arrest and upregulates cell cycle inhibitors and suggest that MAPK and JNK may be involved in the regulation of the activity of these molecules.
Abstract: The polyamines spermidine and spermine and their precursor putrescine are intimately involved in and are required for cell growth and proliferation. This study examines the mechanism by which polya...