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External Stimuli (external + stimulus)
Selected AbstractsElectrically Conductive Hydrogen-Bond-Based Supramolecular Polymer with a Tetrathiafulvalene Moiety: Modulation of Electrical Conductivity and Flexibility of Film by External StimulusCHEMISTRY - AN ASIAN JOURNAL, Issue 10 2010Seong Jib Choi Best supporting role in a film! The 2-deoxyguanosine derivatives having tetrathiafulvalene moieties for a construction of stimuli-responsive supramolecular polymer have been prepared. Owing to a hydrogen-bonding network, the self-supporting film can be fabricated by a simple procedure. The electrical conductivity and flexibility of the film can be modulated by oxidants. The film with TCNQ exhibits electrical conductivity of 3.7×10,2,S,cm,1. [source] Epigenetic control of translation regulation: Alterations in histone H3 lysine 9 post-translation modifications are correlated with the expression of the translation initiation factor 2B (Eif2b5) during thermal control establishmentDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2010Tatiana Kisliouk Abstract Thermal control set point is regulated by thermosensitive neurons of the preoptic anterior hypothalamus (PO/AH) and completes its development during postnatal critical sensory period. External stimuli, like increase in environmental temperature, influence the neuronal protein repertoire and, ultimately, cell properties via activation or silencing of gene transcription, both of which are regulated by the "histone code."" Here, we demonstrated an increase in global histone H3 lysine 9 (H3K9) acetylation as well as H3K9 dimethylation in chick PO/AH during heat conditioning at the critical period of sensory development. In contrast to the global profile of H3K9 modifications, acetylation and dimethylation patterns of H3K9 at the promoter of the catalytic subunit of eukaryotic translation initiation factor 2B (Eif2b5) were opposite to each other. During heat conditioning, there was an increase in H3K9 acetylation at the Eif2b5 promoter, simultaneously with decrease in H3K9 dimethylation. These alterations coincided with Eif2b5 mRNA induction. Moreover, exposure to excessive heat during the critical period resulted in long-term effect on both H3K9 tagging at the Eif2b5 promoter and Eif2b5 mRNA expression. These data suggest a role for dynamic H3K9 post-translational modifications in global translation regulation during the thermal control establishment. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2010 [source] Src-dependent phosphorylation of Scar1 promotes its association with the Arp2/3 complexCYTOSKELETON, Issue 1 2006Hazel Ardern Abstract The WAVE/Scar proteins regulate actin polymerisation at the leading edge of motile cells via activation of the Arp2/3 complex in response to extracellular cues. Within cells they form part of a pentameric complex that is thought to regulate their ability to interact and activate the Arp2/3 complex. However, the exact mechanism for this is not known. We set out to assess whether phosphorylation of Scar1 by the non-receptor tyrosine kinase Src may influence the function of Scar1 and its ability to regulate Arp2/3-mediated actin polymerisation. We show that Scar1 is phosphorylated by Src in vitro and in vivo and identify tyrosine 125 as the major site in Scar1 to be phosphorylated in cells. Src-dependent phosphorylation of Scar1 on tyrosine 125 enhances its ability to bind to the Arp2/3 complex and regulates its ability to control actin polymerisation in cells. Thus, Src may act as an intermediary to regulate the activity of the Arp2/3 complex in response to external stimuli, via modulation of its interaction with WAVE/Scar proteins. Cell Motil. Cytoskeleton, 2006. © 2005 Wiley-Liss, Inc. [source] Electrochemically Induced Modulation of the Catalytic Activity of a Reversible Redoxsensitive RiboswitchELECTROANALYSIS, Issue 9 2008Denise Strohbach Abstract Over the past decade, RNA conformation has been shown to respond to external stimuli. Thus, dependent on the presence of a high affinity ligand, specifically designed ribozymes can be regulated in a classical allosteric way. In this scenario, a binding event in one part of the RNA structure induces conformational changes in a separated part, which constitutes the catalytic centre. As a result activity is switched on (positive regulation) or off (negative regulation). We have developed a hairpin aptazyme responding to flavine mononucleotide (FMN). Ribozyme activity is dependent on binding of FMN and thus is switched on in the presence of FMN in its oxidized form. Under reducing conditions, however, FMN changes its molecular geometry, which is associated with loss of binding and consequently down-regulation of ribozyme activity. While in previous experiments sodium dithionite was used for reduction of FMN, we now present an assay for electrochemically induced activity switching. We have developed an electrochemical microcell that allows for iterative cycles of reduction/oxidation of FMN in an oxygen free atmosphere and thus for reversible switching of ribozyme activity. The reaction proceeds in droplets of 3 to 10,,L at micro- to nanomolar concentrations of the reaction components. [source] Biting Behavior, Aggression, and SeizuresEPILEPSIA, Issue 5 2005Carlo Alberto Tassinari Summary:,Purpose: To describe the semiologic features of aggressive behaviors observed in human epileptic seizures with particular reference to the act of biting a conspecific. Methods: We analyzed the biting behavior (BB) and other aggressive gestures occurring in a group of 11 patients retrospectively selected from >1,000 patients subjected to video-EEG/SEEG monitoring for presurgical evaluation of drug-resistant seizures. Results: Patients displaying BB showed (a) a male sex predominance, (b) heterogeneous etiologies and lesion locations, and (c) seizures involving the frontotemporal regions of both hemispheres. The act of biting was a rapid motor action, lasting ,600 ms, occurring in the context of strong emotional arousal, fear, and anger, with various bodily gestures with aggressive connotation. BB was mainly a "reflexive" behavior, in that biting acts were evoked (both during and after seizures) by actions of people in close contact with the patient. The sole intrusion of the examiner's hand in the space near the patient's face was effective in triggering BB. Rarely, self-directed or object-directed biting acts were not triggered by external stimuli. Intracranial data (SEEG) obtained in one subject showed that the amygdala/hippocampal region plus the orbitomedial prefrontal cortex had to be involved by ictal activity to observe BB. Conclusions: Anatomic and electrophysiologic data in our patients suggest that a model of dual,temporal and frontal,dysfunction could account for the occurrence of ictal/postictal BB. Behavioral data suggest also that BB and related aggressive gestures can be considered as the emergence of instinctive behaviors with an adaptative significance of defense of the peripersonal space. [source] The periaqueductal grey modulates sensory input to the cerebellum: a role in coping behaviour?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2009Nadia L. Cerminara Abstract The paths that link the periaqueductal grey (PAG) to hindbrain motor circuits underlying changes in behavioural responsiveness to external stimuli are unknown. A major candidate structure for mediating these effects is the cerebellum. The present experiments test this directly by monitoring changes in size of cerebellar responses evoked by peripheral stimuli following activation of the PAG. In 22 anaesthetized adult Wistar rats, climbing fibre field potentials were recorded from the C1 zone in the paramedian lobule and the copula pyramidis of the cerebellar cortex evoked, respectively, by electrical stimulation of the ipsilateral fore- and hindlimb. An initial and a late response were attributable to activation of A, and A, peripheral afferents respectively (hindlimb onset latencies 16.9 and 23.8 ms). Chemical stimulation at physiologically-identified sites in the ventrolateral PAG (a region known to be associated with hyporeactive immobility) resulted in a significant reduction in size of both the A, and A, evoked field potentials (mean reduction relative to control ± SEM, 59 ± 7.5 and 66 ± 11.9% respectively). Responses evoked by electrical stimulation of the dorsal or ventral funiculus of the spinal cord were also reduced by PAG stimulation, suggesting that part of the modulation may occur at supraspinal sites (including at the level of the inferior olive). Overall, the results provide novel evidence of descending control into motor control centres, and provide the basis for future studies into the role of the PAG in regulating motor activity in different behavioural states and in chronic pain. [source] THE EVOLUTION OF THE VERTEBRATE ,-GLOBIN GENE PROMOTEREVOLUTION, Issue 2 2002Nadia A. Chuzhanova Abstract Complexity analysis is capable of highlighting those gross evolutionary changes in gene promoter regions (loosely termed "promoter shuffling") that are undetectable by conventional DNA sequence alignment. Complexity analysis was therefore used here to identify the modular components (blocks) of the orthologous ,-globin gene promoter sequences of 22 vertebrate species, from zebrafish to humans. Considerable variation between the ,-globin gene promoters was apparent in terms of block presence/absence, copy number, and relative location. Some sequence blocks appear to be ubiquitous, whereas others are restricted to a specific taxon. Block similarities were also evident between the promoters of the paralogous human ,-like globin genes. It may be inferred that a wide variety of different mutational mechanisms have operated upon the ,-globin gene promoter over evolutionary time. Because these include gross changes such as deletion, duplication, amplification, elongation, contraction, and fusion, as well as the steady accumulation of single base-pair substitutions, it is clear that some redefinition of the term "promoter shuffling" is required. This notwithstanding, and as previously described for the vertebrate growth hormone gene promoter, the modular structure of the ,-globin promoter region and those of its paralogous counterparts have continually been rearranged into new combinations through the alteration, or shuffling, of preexisting blocks. Some of these changes may have had no influence on promoter function, but others could have altered either the level of gene expression or the responsiveness of the promoter to external stimuli. The comparative study of vertebrate ,-globin gene promoter regions described here confirms the generality of the phenomenon of sequence block shuffling and thus supports the view that it could have played an important role in the evolution of differential gene expression. [source] Gene expression demonstrates increased resilience toward harmful inflammatory stimuli in the proliferating epidermis of human skin woundsEXPERIMENTAL DERMATOLOGY, Issue 8 2010K. Markus Roupé Please cite this paper as: Gene expression demonstrates increased resilience toward harmful inflammatory stimuli in the proliferating epidermis of human skin wounds. Experimental Dermatology 2010; 19: e329,e332. Abstract:, We examined the epidermal gene expression during the proliferative phase of wound healing. Matrix metalloproteases were the group of proteases most prominently up-regulated in skin wounds, whereas serine protease inhibitors were the most strongly up-regulated protease inhibitors. Furthermore, we found down-regulation of genes involved in the extrinsic pathway of apoptosis. This together with the up-regulation of inhibitors of leukocyte serine proteases likely represents a protective step to ensure survival of keratinocytes in the inflammatory wound environment. The down-regulation of proapoptotic genes in the extrinsic pathway of apoptosis was not accompanied by a down-regulation of receptors indicating that the keratinocytes in skin wounds did not become less responsive to external stimuli. Examining the transcription factor binding sites in the promoters of the most differentially expressed genes between normal skin and skin wounds a significant overrepresentation of binding sites were found for STAT-5, SRY and members of the FOXO-family of transcription factors. [source] Synergistic regulation of neuropeptide levels by internal and external stimuliEXPERIMENTAL DERMATOLOGY, Issue 9 2004J. Hosoi The skin is the most peripheral organ confronting the external environment. We found that the level of substance P is regulated by both internal and external stimuli. Mock interview induced the acute stress in human assessed by the measurement of serum cortisol. The serum level of substance P increased within 1 h after the mock interview. Interestingly, the increase was suppressed by inhalation of 1,3-dimethoxy-5-methylbenzene. Similar regulation was observed in mice. Furthermore, restraint or the intravenous administration of substance P induced the activation of cutaneous mast cells. Housing under the condition of lower humidity (about 30%) for 24 h caused the increase in the substance P level both in peripheral blood and in the skin. Restraint for 2 h during the housing under the condition of lower humidity increased the substance P level further. The activation of cutaneous mast cells under the dry condition was reported. These data suggest that cutaneous neuropeptide level is regulated by both psychological and environmental mechanisms. The regulation may cause the downregulation of the threshold of the induction of itch and inflammation. [source] Tuning Specific Biomolecular Interactions Using Electro-Switchable Oligopeptide SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Chun L. Yeung Abstract The ability to regulate biomolecular interactions on surfaces driven by an external stimuli is of great theoretical interest and practical impact in the biomedical and biotechnology fields. Herein, a new class of responsive surfaces that rely on electro-switchable peptides to control biomolecular interactions on gold surfaces is presented. This system is based upon the conformational switching of positively charged oligolysine peptides that are tethered to a gold surface, such that bioactive molecular moieties (biotin) incorporated on the oligolysines can be reversibly exposed (bio-active state) or concealed (bio-inactive state) on demand, as a function of surface potential. The dynamics of switching the biological properties is studied by observing the binding events between biotin and fluorescently labeled NeutrAvidin. Fluorescence microscope images and surface plasmon resonance spectral data clearly reveal opposite binding behaviors when +0.3 V or ,0.4 V vs. SCE are applied to the surface. High fluorescence intensities are observed for an applied positive potential, while minimal fluorescence is detected for an applied negative potential. Surface plasmon resonance spectroscopy (SPR) results provided further evidence that NeutrAvidin binding to the surface is controlled by the applied potential. A large SPR response is observed when a positive potential is applied on the surface, while a negative applied potential induces over 90% reduction in NeutrAvidin binding. [source] Differential regulation of amoA and amoB gene copies in Nitrosomonas europaeaFEMS MICROBIOLOGY LETTERS, Issue 2 2000Lisa Y Stein Abstract Nitrosomonas europaea contains two nearly identical copies of the operon, amoCAB, which encodes the ammonia monooxygenase (AMO) enzyme. Cells of N. europaea containing single mutations in either amoA or amoB gene copies were incubated in ammonium both prior to and after exposure to acetylene or light. For each strain, the O2 consumption rates and amounts of AmoA polypeptide, the active site-containing subunit of AMO, produced in each strain were determined. Strains carrying a mutation in either the amoA2 or amoB2 genes responded similarly to wild-type cells, but the strains carrying mutations in the amoA1 or amoB1 genes responded differently from the wild-type, or from each other. These results suggest that the copies of amoA and amoB are differentially regulated upon exposure to different external stimuli. [source] A Stimuli-Responsive, Photoluminescent, Anthracene-Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical ProcessesADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Yoshimitsu Sagara Abstract Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable,stable phase transition induced by external stimuli is prepared. A 2,6-diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6-diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid-crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic-columnar phase transition induced by heating or mechanical shearing for this 2,6-diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable,stable LC phase transition. [source] Hierarchic Nanostructure for Auto-Modulation of Material Release: Mesoporous Nanocompartment FilmsADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Qingmin Ji The preparation of mesoporous nanocompartment films composed of both hollow silica capsules and silica particles by using layer-by-layer (LbL) adsorption is described. The resultant nanocompartment films exhibit stepwise release of encapsulated water molecules without application of external stimuli. The hollow hierarchic pore structure of the silica capsules, including their internal void and mesoporous walls, is a key factor for the regulation and stepwise release of water, and is probably caused by the non-equilibrated concurrent evaporation of material from the mesopore and capillary penetration into the mesopores. The number of release steps and rate of release can be tuned by variation of several parameters including water content, ambient temperature, layer multiplicity, and co-adduct particle size. Application of the mesoporous nanocompartment films for the release of substances, including therapeutic agents and fragrances, indicates that the stepwise material release can be applied for a wide range of liquid substances. The films should lead to a novel material release system useful even for biomedical applications capable of controlled and sustained delivery of drug molecules. [source] Tuning the Amphiphilicity of Building Blocks: Controlled Self-Assembly and Disassembly for Functional Supramolecular Materials,ADVANCED MATERIALS, Issue 28 2009Yapei Wang Abstract Amphiphilicity is one of the molecular bases for self-assembly. By tuning the amphiphilicity of building blocks, controllable self-assembly can be realized. This article reviews different routes for tuning amphiphilicity and discusses different possibilities for self-assembly and disassembly in a controlled manner. In general, this includes irreversible and reversible routes. The irreversible routes concern irreversible reactions taking place on the building blocks and changing their molecular amphiphilicity. The building blocks are then able to self-assemble to form different supramolecular structures, but cannot remain stable upon loss of amphiphilicity. Compared to the irreversible routes, the reversible routes are more attractive due to the good control over the assembly and disassembly of the supramolecular structure formed via tuning of the amphiphilicity. These routes involve reversible chemical reactions and supramolecular approaches, and different external stimuli can be used to trigger reversible changes of amphiphilicity, including light, redox, pH, and enzymes. It is anticipated that this line of research can lead to the fabrication of new functional supramolecular assemblies and materials. [source] Modulation of dendritic cell maturation and function with mono- and bifunctional small interfering RNAs targeting indoleamine 2,3-dioxygenaseIMMUNOLOGY, Issue 1pt2 2009Gro F. Flatekval Summary Antigen-presenting cells expressing indoleamine 2,3-dioxygenase (IDO) play a critical role in maintaining peripheral tolerance. Strategies to inhibit IDO gene expression and enhance antigen-presenting cell function might improve anti-tumour immunity. Here we have designed highly effective anti-IDO small interfering (si) RNAs that function at low concentrations. When delivered to human primary immune cells such as monocytes and dendritic cells (DCs), they totally inhibited IDO gene expression without impairing DC maturation and function. Depending on the design and chemical modifications, we show that it is possible to design either monofunctional siRNAs devoid of immunostimulation or bifunctional siRNAs with gene silencing and immunostimulatory activities. The latter are able to knockdown IDO expression and induce cytokine production through either endosomal Toll-like receptor 7/8 or cytoplasmic retinoid acid-inducible gene 1 helicase. Inhibition of IDO expression with both classes of siRNAs inhibited DC immunosuppressive function on T-cell proliferation. Immature monocyte-derived DCs that had been transfected with siRNA-bearing 5,-triphosphate activated T cells, indicating that, even in the absence of external stimuli such as tumour necrosis factor-,, those DCs were sufficiently mature to initiate T-cell activation. Collectively, our data highlight the potential therapeutic applications of this new generation of siRNAs in immunotherapy. [source] Dual Tuning of the Photonic Band-Gap Structure in Soft Photonic CrystalsADVANCED MATERIALS, Issue 18 2009Masaki Honda A dually tunable photonic crystal composed of thermosensitive gel particles confined in a pH-sensitive inverse-opal gel is reported. The position of the photonic band-gap can be thermally regulated, while its intensity is dramatically changed by pH. Reversible, independent, and extensive switching of the position and intensity of the photonic band-gap could be achieved using independent external stimuli. [source] Bio-Inspired, Smart, Multiscale Interfacial Materials,ADVANCED MATERIALS, Issue 15 2008Fan Xia Abstract In this review a strategy for the design of bioinspired, smart, multiscale interfacial (BSMI) materials is presented and put into context with recent progress in the field of BSMI materials spanning natural to artificial to reversibly stimuli-sensitive interfaces. BSMI materials that respond to single/dual/multiple external stimuli, e.g., light, pH, electrical fields, and so on, can switch reversibly between two entirely opposite properties. This article utilizes hydrophobicity and hydrophilicity as an example to demonstrate the feasibility of the design strategy, which may also be extended to other properties, for example, conductor/insulator, p-type/n-type semiconductor, or ferromagnetism/anti-ferromagnetism, for the design of other BSMI materials in the future. [source] Upregulated claudin-1 expression confers resistance to cell death of nasopharyngeal carcinoma cellsINTERNATIONAL JOURNAL OF CANCER, Issue 6 2010Jeng-Woei Lee Abstract Accumulating evidence reveals that aberrant expression of claudins manifests in various tumors; however, their biological functions are poorly understood. Here, we report on the elevated expression of claudin-1 in nasopharyngeal carcinoma (NPC) cell lines under serum deprivation or fluorouracil (5-FU) treatment. Interestingly, an increase in expression of claudin-1 considerably reduced apoptosis rather than enhancing cell proliferation. However, claudin-1 expression and activity were unaffected by external stimuli or Akt and NF-,B activation. Notably, predominant cytoplasmic and nuclear localization of claudin-1 in NPC cells reflected the aforementioned feature. On the other hand, loss of epithelial morphology and E-cadherin expression was associated with serum withdrawal in NPC cells. Interestingly, restoration of E-cadherin inhibited the protein elevation and antiapoptotic activity of claudin-1. In conclusion, our data demonstrate the regulation and novel biological function of claudin-1 and indicate the important role of claudin-1 in NPC tumorigenesis. [source] The winnerless competition paradigm in cellular nonlinear networks: Models and applicationsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2009Paolo Arena Abstract Starting from the biological background on the olfactory architecture of both insects and mammalians, different nonlinear systems able to respond to spatial-distributed external stimuli with spatial,temporal dynamics have been investigated in the last decade. Among these, there is a class of neural networks that produces quasi-periodic trajectories that pass near heteroclinic contours and prove to be global attractors for the system. For this reason, these networks are called winnerless competition (WLC) networks. The sequence of saddle points crossed by each trajectory depends on the spatial input presented to the network and can be used as a ,code' representing a specific class of stimuli. Thanks to the intrinsic discrimination, WLC networks are often used for classification. In this paper, this capability is exploited within a framework for action-oriented perception. WLC networks are here used as bio-inspired architectures for the association between stimuli and ,percepts'. After presenting the theoretical basis of the WLC network in the classic Lotka,Volterra system, we investigate how WLC networks can be formalized in terms of cellular nonlinear networks (CNNs) hosting different kinds of cells: the FitzHugh,Nagumo neuron, the Izhikevich neuron and the single layer CNN standard cell. In order to find efficient ways to code environmental stimuli for action generation, we analyze and compare these WLC-based CNNs in terms of number of generated classes and robustness against the initial conditions. Based on the simulation results, we apply the best-performing system to solve a perceptual task involving navigation and obstacle avoidance. We demonstrate how the large memory capacity shown by the WLC,CNN is able to contribute to the new perceptual framework for autonomous artificial agents, where the association between stimuli and sequences is learned through the experience. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mechanism of light-induced translocation of arrestin and transducin in photoreceptors: Interaction-restricted diffusionIUBMB LIFE, Issue 1 2008Vladlen Z. Slepak Abstract Many signaling proteins change their location within cells in response to external stimuli. In photoreceptors, this phenomenon is remarkably robust. The G protein of rod photoreceptors and rod transducin concentrates in the outer segments (OS) of these neurons in darkness. Within ,30 minutes after illumination, rod transducin redistributes throughout all of the outer and inner compartments of the cell. Visual arrestin concurrently relocalises from the inner compartments to become sequestered primarily within the OS. In the past several years, the question of whether these proteins are actively moved by molecular motors or whether they are redistributed by simple diffusion has been extensively debated. This review focuses on the most essential works in the area and concludes that the basic principle driving this protein movement is diffusion. The directionality and light dependence of this movement is achieved by the interactions of arrestin and transducin with their spatially restricted binding partners. © 2007 IUBMB IUBMB Life, 60(1): 2,9, 2008 [source] In vitro degradation of articular cartilage: does trypsin treatment produce consistent results?JOURNAL OF ANATOMY, Issue 2 2006H. R. Moody Abstract It is common practice in laboratories to create models of degraded articular cartilage in vitro and use these to study the effects of degeneration on cartilage responses to external stimuli such as mechanical loading. However, there are inconsistencies in the reported action of trypsin, and there is no guide on the concentration of trypsin or the time to which a given sample can be treated so that a specific level of proteoglycan depletion is achieved. This paper argues that before any level of confidence can be established in comparative analysis it is necessary to first obtain samples with similar properties. Consequently, we examine the consistency of the outcome of the artificial modification of cartilage relative to the effects of the common enzyme, trypsin, used in the process of in vitro proteoglycan depletion. The results demonstrate that for a given time and enzyme concentration, the action of trypsin on proteoglycans is highly variable and is dependent on the initial distribution and concentration of proteoglycans at different depths, the intrinsic sample depth, the location in the joint space and the medium type, thereby sounding a note of caution to researchers attempting to model a proteoglycan-based degeneration of articular cartilage in their experimental studies. [source] Mechanical loading stimulates ecto-ATPase activity in human tendon cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2005M. Tsuzaki Abstract Response to external stimuli such as mechanical signals is critical for normal function of cells, especially when subjected to repetitive motion. Tenocytes receive mechanical stimuli from the load-bearing matrix as tension, compression, and shear stress during tendon gliding. Overloading a tendon by high strain, shear, or repetitive motion can cause matrix damage. Injury may induce cytokine expression, matrix metalloproteinase (MMP) expression and activation resulting in loss of biomechanical properties. These changes may result in tendinosis or tendinopathy. Alternatively, an immediate effector molecule may exist that acts in a signal-dampening pathway. Adenosine 5,-triphosphate (ATP) is a candidate signal blocker of mechanical stimuli. ATP suppresses load-inducible inflammatory genes in human tendon cells in vitro. ATP and other extracellular nucleotide signaling are regulated efficiently by two distinct mechanisms: purinoceptors via specific receptor,ligand binding and ecto-nucleotidases via the hydrolysis of specific nucleotide substrates. ATP is released from tendon cells by mechanical loading or by uridine 5,-triphosphate (UTP) stimulation. We hypothesized that mechanical loading might stimulate ecto-ATPase activity. Human tendon cells of surface epitenon (TSC) and internal compartment (TIF) were cyclically stretched (1 Hz, 0.035 strain, 2 h) with or without ATP. Aliquots of the supernatant fluids were collected at various time points, and ATP concentration (ATP) was determined by a luciferin-luciferase bioluminescence assay. Total RNA was isolated from TSC and TIF (three patients) and mRNA expression for ecto-nucleotidase was analyzed by RT-PCR. Human tendon cells secreted ATP in vitro (0.5,1 nM). Exogenous ATP was hydrolyzed within minutes. Mechanical load stimulated ATPase activity. ATP was hydrolyzed in mechanically loaded cultures at a significantly greater rate compared to no load controls. Tenocytes (TSC and TIF) expressed ecto-nucleotidase mRNA (ENTPD3 and ENPP1, ENPP2). These data suggest that motion may release ATP from tendon cells in vivo, where ecto-ATPase may also be activated to hydrolyze ATP quickly. Ecto-ATPase may act as a co-modulator in ATP load-signal modulation by regulating the half-life of extracellular purine nucleotides. The extracellular ATP/ATPase system may be important for tendon homeostasis by protecting tendon cells from responding to excessive load signals and activating injurious pathways. © 2005 Wiley-Liss, Inc. [source] Differential regulation of P-glycoprotein genes in primary rat hepatocytes by collagen sandwich and drugsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2002Chow H. Lee Abstract P-glycoprotein (Pgp) is a small family of plasma membrane proteins, which are capable of transporting substrates across cell membranes. Class I and II Pgp are able to transport drugs and have been shown to mediate multidrug resistance (MDR). Class III Pgp is a long chain phospholipid transporter and does not mediate MDR. The regulation of all three Pgp genes is still poorly understood. For instance, it is not clear if the three Pgp genes are co-regulated or differentially regulated by external stimuli. This study examined the effect of drugs and collagen sandwich system on expression and transcription of all the three Pgp genes in primary rat hepatocytes. Consistent with previous findings, dramatic overexpression (25-fold) of Class II Pgp mRNA was seen, upon culturing of hepatocytes onto a single layered collagen gel. Hepatocytes sandwiched between two layers of collagen gel exhibited decreased (4.5-fold) Class II Pgp mRNA expression as compared to the single layer system. Treatment of hepatocytes cultured on the single layer collagen system with cytoskeletal disrupting (cytochalasin D, colchicine) but not cytoskeletal stabilizing (phalloidin, taxol) drugs, suppressed Class II Pgp expression. In all cases, no change in Class II Pgp transcription was observed as demonstrated by nuclear run-on studies. This suggests that collagen configuration and drugs affect Class II Pgp mRNA expression predominantly through post-transcriptional mechanisms. In contrast, parallel increases in mRNA expression and transcription of Class I Pgp gene were observed upon culturing of hepatocytes, in the collagen sandwich system, and treatment with some drugs (cytochalasin D, colchicine, and phalloidin). This suggests that Class I Pgp gene is regulated primarily via transcriptional mechanisms by these stimuli. On the other hand, Class III Pgp gene appears to be post-transcriptionally co-regulated with Class II Pgp gene by treatment with the drugs, while collagen configuration affected both transcription and post-transcription of Class III Pgp gene. Finally, dose-dependent studies using cycloheximide provided further evidence that the two MDR-associated genes are not co-regulated. This study has implications for future studies on the molecular mechanisms of Pgp gene regulation. J. Cell. Biochem. 86: 12,20, 2002. © 2002 Wiley-Liss, Inc. [source] CDK4 IVS4-nt40G,A and T2D-associated obesity in ItaliansJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2009Ramachandran Meenakshisundaram Cell cycle regulators play crucial roles in the preadipocyte proliferation and adipocyte differentiation. Cyclin-dependent kinase 4 (CDK4) mediates with D-type cyclins entry of cells into cell cycle in response to external stimuli. CDK4 plays a role in body weight, adipogenesis, and beta cell proliferation. CDK4 null mice develop type 2 diabetes (T2D). Furthermore, CDK4 variants are associated with obesity-associated tumors/cancer. We aimed at identifying a role of CDK4 IVS4-nt40G,,,A variant in T2D-associated obesity (body mass index, BMI,,,30) by association tests in an Italian T2D subjects dataset. We recruited from Italy 128 unrelated T2D subjects with BMI,<30,kg/m2 and 54 unrelated T2D subjects with BMI,,,30,kg/m2. We performed statistical power calculations in our dataset. DNA samples were directly sequenced with specific primers for CDK4 IVS4-nt40G,,,A variant. We identified a significant association of the G allele with T2D-associated obesity and of the A allele with T2D-associated BMI,<,30. In our study, we found that the CDK4 IVS4-nt40GG genotype is a risk variant for T2D-associated obesity and that the AA genotype is associated with BMI,<,30 in T2D. Hence, CDK4 IVS4-nt40A allele is protective and G allele confers risk for obesity in T2D patients. This study should prompt further work aiming at establishing CDK4 role in contributing to human obesity and T2D-associated obesity. J. Cell. Physiol. 221: 273,275, 2009. © 2009 Wiley-Liss, Inc. [source] Ras family genes: An interesting link between cell cycle and cancerJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002M. Macaluso Ras genes are evolutionary conserved and codify for a monomeric G protein binding GTP (active form) or GDP (inactive form). The ras genes are ubiquitously expressed although mRNA analysis suggests different level expression in tissue. Mutations in each ras gene frequently were found in different tumors, suggesting their involvement in the development of specific neoplasia. These mutations lead to a constitutive active and potentially oncogenic protein that could cause a deregulation of cell cycle. Ras protein moderates cellular responses at several mitogens and/or differentiation factors and at external stimuli. These stimuli activate a series of signal transduction pathways that either can be independent or interconnected at different points. Recent observations begin to clarify the complex relationship between Ras activation, apoptosis, and cellular proliferation. A greater understanding of these processes would help to identify the factors directly responsible for cell cycle deregulation in several tumors, moreover it would help the design of specific therapeutic strategies, for the control on the proliferation of neoplastic cells. We summarize here current knowledge of ras genes family: structural and functional characteristics of Ras proteins and their links with cell cycle and cancer. © 2002 Wiley-Liss, Inc. [source] Review paper: more than ringing in the ears: a review of tinnitus and its psychosocial impactJOURNAL OF CLINICAL NURSING, Issue 21 2009Susan Holmes Aim and objectives., To provide an overview of tinnitus, current management and its psychosocial impact offering strategies for managing acute and chronic tinnitus in practice. Background., Tinnitus, characterised by the perception of sound in the absence of external stimuli, is experienced by about 10% of the population at some time in their lives. It may be temporary/longstanding; approximately 5% adults experience severe, persistent tinnitus affecting their lifestyle. Although many adjust successfully, others are disabled by the condition. Though often unrecognised, tinnitus affects many patients regardless of their presenting illness. Design., A literature review including descriptive, theoretical and empirical material. Databases were searched using the keyword ,tinnitus' providing diverse information which was used to address the research questions. Results., Tinnitus represents more than ,simple' ringing in the ears and may be accompanied by many distressing changes. It may be acute or chronic. It is difficult to treat, care may be directed towards management rather than cure. Many patients are, however, told that ,nothing can be done'. Relevance to clinical practice., Despite the high prevalence of tinnitus, there is a paucity of relevant nursing literature suggesting that there is an information deficit amongst nurses. The information provided shows that understanding the full impact of the condition and identification of patients' needs are essential to effective care. Strategies to help affected patients are given. Conclusions., Tinnitus, a widespread, often intractable condition, affects millions of people; there is considerable debate about its causes. Tinnitus is distressing and may be severe enough to affect lifestyle and quality of life. Affected patients need considerable support and advice on healthcare options, encouragement to try different treatments and recognition that help and hope are available. Though patients may have to learn to live with tinnitus, the most important thing is that they recognise that help is available. [source] Can glycans unveil the origin of glycoprotein hormones?,human chorionic gonadotrophin as an example,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2008R. Ramírez-Llanelis Abstract Doping with (glyco)protein hormones represent an extremely challenging, analytical problem as nearly all are constitutively present at low concentrations that fluctuate according to circadian or alternative periodical, or external stimuli. Thus the mere concentration in a biological sample is only resolutive when this surpasses extreme values. As the vast majority of these molecules are produced by recombinant DNA technology it is believed that the exogenous molecules could bear the signature of the host cell. In particular, these could comprise structural differences originated from co or post-translational differences. In this study we have employed both proteomics and glycomics strategies to compare recombinant and urinary human chorionic gonadotrophin in order to evaluate this hypothesis. As anticipated the recombinant hormone could be shown to contain N -glycolyl neuraminic acid, a sialic acid that cannot be produced by humans. Furthermore, differences were observed in the overall glycosylation, in particular the presence of abundant hybrid-type glycans that were much less pronounced in the recombinant species. These differences were determined to occur predominantly in the ,-subunit for which antidoping strategies focussed on these elements could be used for both chorionic gonadotrophin and lutrophin as they share the same ,-subunit. Copyright © 2008 John Wiley & Sons, Ltd. [source] Maintaining Cell Sensitivity to G-Protein Coupled Receptor Agonists: Neurotensin and the Role of Receptor Gene ActivationJOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2001F. Souazé Abstract In the last few years, a number of studies have brought new insights into the fundamental mechanisms of cell desensitization and internalization of G-protein coupled receptors. Such studies have demonstrated that cells remain desensitized from a few minutes to several hours, after exposure to high concentrations of agonist. However, in vivo, agonists such as hormones are always present, even in small amounts, and such long desensitization is not conceivable, since constant stimulation of cells is required for physiological responses. Under such circumstances, cells would require a means to permanently maintain sensitivity to various internal or external stimuli. In the present review, we have taken as an example the expression of the high affinity neurotensin receptor, a seven transmembrane G-protein coupled receptor, upon prolonged exposure to its agonist, and observed that cells remained sensitive only if the receptor gene was activated by the agonist. Consequently, new receptors were synthesized, and either delivered to the cell surface or accumulated in submembrane pools. This regulation takes place only after prolonged and intense agonist stimulation. Under these conditions, it is proposed that receptor turnover is accelerated in proportion to the agonist concentration in order to allow the cells to produce an adapted cellular response to external stimuli. Such mechanisms thus play a key role in cell sensitivity to hormones. [source] FOURIER TRANSFORM INFRARED SPECTROSCOPY AS A NOVEL TOOL TO INVESTIGATE CHANGES IN INTRACELLULAR MACROMOLECULAR POOLS IN THE MARINE MICROALGA CHAETOCEROS MUELLERII (BACILLARIOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 2 2001Mario Giordano Fourier Transform Infrared (FT-IR) spectroscopy was used to study carbon allocation patterns in response to changes in nitrogen availability in the diatom Chaetoceros muellerii Lemmerman. The results of the FT-IR measurements were compared with those obtained with traditional chemical methods. The data obtained with both FT-IR and chemical methods showed that nitrogen starvation led to the disappearance of the differences in cell constituents and growth rates existing between cells cultured at either high [NO3,] or high [NH4+]. Irrespective of the nitrogen source supplied before nitrogen starvation, a diversion of carbon away from protein, chlorophyll, and carbohydrates into lipids was observed. Under these conditions, cells that had previously received nitrogen as nitrate appeared to allocate a larger amount of mobilized carbon into lipids than cells that had been cultured in the presence of ammonia. All these changes were reversed by resupplying the cultures with nitrogen. The rate of protein accumulation in the N-replete cells was slower than the rate of decrease under nitrogen starvation. This study demonstrates that the relative proportions of the major macromolecules contained in microalgal cells and their changes in response to external stimuli can be determined rapidly, simultaneously, and inexpensively using FT-IR. The technique proved to be equally reliable to and less labor intensive than more traditional chemical methods. [source] Increased Acid Sphingomyelinase Activity in Peripheral Blood Cells of Acutely Intoxicated Patients With Alcohol DependenceALCOHOLISM, Issue 1 2010Martin Reichel Background:, Acid sphingomyelinase (ASM; EC 3.1.4.12) hydrolyses membrane sphingomyelin into the bioactive lipid ceramide and is thus involved in different cellular processes such as differentiation, immunity, or cell death. Activation of ASM has been reported in particular in conjunction with the cellular stress response to several external stimuli, and increased ASM activity was observed in a variety of human diseases. Ethanol-induced activation of ASM has been observed in different cell culture systems, thus raising the question about the effect of alcohol intoxication in human subjects on ASM activity in vivo. Methods:, We determined ASM activity in peripheral blood mononucleated cells of 27 patients suffering from alcohol dependence. Patients were classified according to their blood alcohol concentration at admission, and ASM activity was determined repeatedly from all patients during alcohol withdrawal. Results:, Acutely intoxicated patients displayed significantly higher ASM activity than patients in early abstinence (Mann,Whitney U test: Z = , 2.6, p = 0.009). ASM activity declined in acutely intoxicated patients to normal values with the transition from the intoxicated state to early abstinence (Wilcoxon test: Z = ,2.7, p = 0.007). At the end of withdrawal, ASM activity was significantly increased again compared to the early phase of abstinence in both patient groups (Wilcoxon test: Z = ,2.691, p = 0.007 and Z = ,2.275, p = 0.023, respectively). Conclusions:, Alcohol-induced activation of ASM occurs in human subjects and might be responsible for deleterious effects of ethanol intoxication. Chronic alcohol abuse may induce deregulation of sphingomyelin metabolism in general, and this impairment may cause side effects during withdrawal from alcohol. [source] | ||||||||||||||||||||||