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Increased Resistance (increased + resistance)
Selected AbstractsProtection of hematopoietic cells from O6 -alkylation damage by O6 -methylguanine DNA methyltransferase gene transfer: studies with different O6 -alkylating agents and retroviral backbonesEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 1 2001Michael Jansen Abstract: Overexpression of O6 -methylguanine DNA methyltransferase (MGMT) can protect hematopoietic cells from O6 -alkylation damage. To identify possible clinical applications of this technology we compared the effect of MGMT gene transfer on the hematotoxicity induced by different O6 -alkylating agents in clinical use: the chloroethylnitrosoureas ACNU, BCNU, CCNU and the tetrazine derivative temozolomide. In addition, various retroviral vectors expressing the MGMT-cDNA were investigated to identify optimal viral backbones for hematoprotection by MGMT expression. Protection from ACNU, BCNU, CCNU or temozolomide toxicity was evaluated utilizing a Moloney murine leukemia virus-based retroviral vector (N2/Zip-PGK-MGMT) to transduce primary murine bone marrow cells. Increased resistance in murine colony-forming units (CFU) was demonstrated for all four drugs. In comparison to mock-transduced controls, after transduction with N2/Zip-PGK-MGMT the IC50 for CFU increased on average 4.7-fold for ACNU, 2.5-fold for BCNU, 6.3-fold for CCNU and 1.5-fold for temozolomide. To study the effect of the retroviral backbone on hematoprotection various vectors expressing the human MGMT-cDNA from a murine embryonic sarcoma virus LTR (MSCV-MGMT) or a hybrid spleen focus-forming/murine embryonic sarcoma virus LTR (SF1-MGMT) were compared with the N2/Zip-PGK-MGMT vector. While all vectors increased resistance of transduced human CFU to ACNU, the SF1-MGMT construct was most efficient especially at high ACNU concentrations (8,12 µg/ml). Similar results were obtained for protection of murine high-proliferative-potential colony-forming cells. These data may help to optimize treatment design and retroviral constructs in future clinical studies aiming at hematoprotection by MGMT gene transfer. [source] Overexpression of profilin reduces the migration of invasive breast cancer cellsCYTOSKELETON, Issue 2 2004Partha Roy Abstract The exact role profilin plays in cell migration is not clear. In this study, we have evaluated the effect of overexpression of profilin on the migration of breast cancer cells. Overexpression was carried out by stably expressing GFP-profilin in BT474 cells. It was observed that even a moderate level of overexpression of profilin significantly impaired the ability of BT474 cells to spread on fibronectin-coated substrate and migrate in response to EGF. GFP-profilin expressing cells also showed increased resistance to detachment in response to trypsin and increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin compared to the parental and GFP-expressing (control) cell lines. These results suggest that perturbation of profilin levels may offer a good strategy for controlling the metastatic potential of breast cancer cells. Cell Motil. Cytoskeleton 57:84,95, 2004. © 2004 Wiley-Liss, Inc. [source] Mutagenesis of ,-tubulin cysteine residues in Saccharomyces cerevisiae: Mutation of cysteine 354 results in cold-stable microtubulesCYTOSKELETON, Issue 2 2001Mohan L. Gupta Jr. Abstract Cysteine residues play important roles in the control of tubulin function. To determine which of the six cysteine residues in ,-tubulin are critical to tubulin function, we mutated the cysteines in Saccharomyces cerevisiae ,-tubulin individually to alanine and serine residues. Of the twelve mutations, only three produced significant effects: C12S, C354A, and C354S. The C12S mutation was lethal in the haploid, but the C12A mutation had no observable phenotype. Based on interactive views of the electron crystallographic structure of tubulin, we suggest that substitution of serine for cysteine at this position has a destabilizing effect on the interaction of tubulin with the exchangeable GTP. The two C354 mutations, although not lethal, produced dramatic effects on microtubules and cellular processes that require microtubules. The C354 mutant cells had decreased growth rates, a slowed mitosis, increased resistance to benomyl, and impaired nuclear migration and spindle assembly. The C354A mutation produced a more severe phenotype than the C354S mutation: the haploid cells had chromosome segregation defects, only 50% of cells in a culture were viable, and a significant percentage of the cells were misshapened. Cytoplasmic microtubules in the C354S and C354A cells were longer than in the control strain and spindle structures appeared shorter and thicker. Both cytoplasmic and spindle microtubules in the two C354 mutants were extremely stable to cold temperature. After 24 h at 4°C, the microtubules were still present and, in fact, very long and thick tubulin polymers had formed. Evidence exists to indicate that the C354 residue in mammalian tubulin is near the colchicine binding site and the electron crystal structure of tubulin places the residue at the interface between the ,- and ,-subunits. The sulfhydryl group is situated in a polar environment, which may explain why the alanine mutation is more severe than the serine mutation. When the C12S and the two C354 mutations were made in a diploid strain, the mutated tubulin was incorporated into microtubules and the resulting heterozygotes had phenotypes that were intermediate between those of the mutated haploids and the wild-type strains. The results suggest that the C12 and C354 residues play important roles in the structure and function of tubulin. Cell Motil. Cytoskeleton 49:67,77, 2001. © 2001 Wiley-Liss, Inc. [source] Hydrogen peroxide-induced oxidative stress responses in Desulfovibrio vulgaris HildenboroughENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Aifen Zhou Summary To understand how sulphate-reducing bacteria respond to oxidative stresses, the responses of Desulfovibrio vulgaris Hildenborough to H2O2 -induced stresses were investigated with transcriptomic, proteomic and genetic approaches. H2O2 and induced chemical species (e.g. polysulfide, ROS) and redox potential shift increased the expressions of the genes involved in detoxification, thioredoxin-dependent reduction system, protein and DNA repair, and decreased those involved in sulfate reduction, lactate oxidation and protein synthesis. A gene coexpression network analysis revealed complicated network interactions among differentially expressed genes, and suggested possible importance of several hypothetical genes in H2O2 stress. Also, most of the genes in PerR and Fur regulons were highly induced, and the abundance of a Fur regulon protein increased. Mutant analysis suggested that PerR and Fur are functionally overlapped in response to stresses induced by H2O2 and reaction products, and the upregulation of thioredoxin-dependent reduction genes was independent of PerR or Fur. It appears that induction of those stress response genes could contribute to the increased resistance of deletion mutants to H2O2 -induced stresses. In addition, a conceptual cellular model of D. vulgaris responses to H2O2 stress was constructed to illustrate that this bacterium may employ a complicated molecular mechanism to defend against the H2O2 -induced stresses. [source] Expression of the human Cathepsin L inhibitor hurpin in mice: skin alterations and increased carcinogenesisEXPERIMENTAL DERMATOLOGY, Issue 9 2007Markus Walz Abstract:, The serine protease inhibitor (serpin) hurpin (serpin B13) is a cross class-specific inhibitor of the cysteine protease Cathepsin (Cat) L. Cat L is involved in lysosomal protein degradation, hair follicle morphogenesis, epidermal differentiation and epitope generation of antigens. Hurpin is a 44 kDa protein which is expressed predominantly in epidermal cells. In psoriatic skin samples, hurpin was strongly overexpressed when compared with normal skin. Keratinocytes overexpressing hurpin showed increased resistance towards UVB-induced apoptosis. To further analyse the functional importance of this inhibitor, we have generated transgenic mice with deregulated Cat L activity by expressing human hurpin in addition to the endogenous mouse inhibitor. The three independent transgenic lines generated were characterized by identical effects excluding insertional phenotypes. Macroscopically, mice expressing human hurpin are characterized by abnormal abdominal fur. The number of apoptotic cells and caspase-3 positive cells was reduced after UV-irradiation in transgenic animals compared with wild-type mice. Interestingly, after chemical carcinogenesis, transgenic mice showed an increased susceptibility to develop skin cancer. Array analysis of gene expression revealed distinct differences between wild-type and hurpin-transgenic mice. Among others, differentially expressed genes are related to antigen presentation and angiogenesis. These results suggest an important role of Cat L regulation by hurpin which might be of clinical relevance in human skin diseases. [source] RESEARCH ARTICLE: Fungicidal activity of amiodarone is tightly coupled to calcium influxFEMS YEAST RESEARCH, Issue 3 2008Sabina Muend Abstract The antiarrhythmic drug amiodarone has microbicidal activity against fungi, bacteria and protozoa. In Saccharomyces cerevisiae, amiodarone triggers an immediate burst of cytosolic Ca2+, followed by cell death markers. Ca2+ transients are a common response to many forms of environmental insults and toxic compounds, including osmotic and pH shock, endoplasmic reticulum stress, and high levels of mating pheromone. Downstream signaling events involving calmodulin, calcineurin and the transcription factor Crz1 are critical in mediating cell survival in response to stress. In this study we asked whether amiodarone induced Ca2+ influx was beneficial, toxic or a bystander effect unrelated to the fungicidal effect of the drug. We show that downregulation of Ca2+ channel activity in stationary phase cells correlates with increased resistance to amiodarone. In actively growing cells, extracellular Ca2+ modulated the size and shape of the Ca2+ transient and directly influenced amiodarone toxicity. Paradoxically, protection was achieved both by removal of external Ca2+ or by adding high levels of CaCl2 (10 mM) to block the drug induced Ca2+ burst. Our results support a model in which the fungicidal activity of amiodarone is mediated by Ca2+ stress, and highlight the pathway of Ca2+ mediated cell death as a promising target for antifungal drug development. [source] KNQ1, a Kluyveromyces lactis gene encoding a transmembrane protein, may be involved in iron homeostasisFEMS YEAST RESEARCH, Issue 5 2007Emmanuela Marchi Abstract The original purpose of the experiments described in this article was to identify, in the biotechnologically important yeast Kluyveromyces lactis, gene(s) that are potentially involved in oxidative protein folding within the endoplasmic reticulum (ER), which often represents a bottleneck for heterologous protein production. Because treatment with the membrane-permeable reducing agent dithiothreitol inhibits disulfide bond formation and mimics the reducing effect that the normal transit of folding proteins has in the ER environment, the strategy was to search for genes that conferred higher levels of resistance to dithiothreitol when present in multiple copies. We identified a gene (KNQ1) encoding a drug efflux permease for several toxic compounds that in multiple copies conferred increased dithiothreitol resistance. However, the KNQ1 product is not involved in the excretion of dithiothreitol or in recombinant protein secretion. We generated a knq1 null mutant, and showed that both overexpression and deletion of the KNQ1 gene resulted in increased resistance to dithiothreitol. KNQ1 amplification and deletion resulted in enhanced transcription of iron transport genes, suggesting, for the membrane-associated protein Knq1p, a new, unexpected role in iron homeostasis on which dithiothreitol tolerance may depend. [source] Dothistroma (red-band) needle blight of pines and the dothistromin toxin: a reviewFOREST PATHOLOGY, Issue 3 2004R. E. Bradshaw Summary Dothistroma (red-band) needle blight has been a problem in plantations of exotic pines in the southern hemisphere for many decades. The prevalence of this disease is currently increasing in the northern hemisphere and is now affecting trees in their native ranges. The fungal pathogen Mycosphaerella pini with its anamorph Dothistroma pini, which is responsible for the disease, produces a toxin, dothistromin, that is closely related to the potent carcinogen, aflatoxin. Understandably this has provoked concern about possible effects on the health of forestry workers. This review gives a broad coverage of literature on both disease and toxin. The fungus has a complicated taxonomy with many synonyms and in most countries only the anamorph is found. It is a necrotrophic pathogen that kills needle tissue and completes its life cycle in the lesion thus formed. Dispersal of the disease is normally by rain splash of conidiospores but there is evidence that long range dispersal has occurred by transport of contaminated plant tissue and by wind/cloud dispersal of spores in air currents. The severity of disease is affected by humidity, temperature and light. There is variation in susceptibility of different Pinus species and some achieve increased resistance with age. The current method of control in southern hemisphere plantation forests is through spraying with copper fungicides and, with P. radiata, increased disease resistance has been achieved through a breeding programme. The dothistromin toxin is a difuroanthraquinone and is similar in structure to the aflatoxin precursor versicolorin B. Part of a gene cluster encoding dothistromin biosynthetic genes has been cloned and this has confirmed parallels between the dothistromin and aflatoxin biosynthetic pathways. Dothistromin produces damaging oxygen radicals by reductive oxygen activation rather than by photosensitization, but is also thought to exert its toxic effects on specific cellular targets. Studies have shown that dothistromin is a weak mutagen and clastogen and is therefore a potential carcinogen. Although the risks to forest workers are considered very low it is prudent to avoid unnecessary exposure during periods when dothistromin levels are likely to be at their peak. Résumé La maladie des bandes rouges causée par Dothistroma est un problème dans les plantations de pins exotiques de l'hémisphère sud depuis de nombreuses années. La prévalence de cette maladie est en augmentation dans l'hémisphère nord et affecte maintenant les pins dans leurs régions d'origine. Le champignon pathogène Dothistroma pini, responsable de la maladie, produit une toxine, la dothistromine, proche de l'aflatoxine qui est un puissant carcinogène. Ceci pose donc la question des effets possibles sur la santé des travailleurs forestiers. Cette revue repose sur une large couverture de la littérature concernant aussi bien la maladie que la toxine. Le champignon a une taxonomie complexe avec de nombreux synonymes, et seul l'anamorphe se rencontre dans de nombreux pays. C'est un champignon nécrotrophe qui tue les tissus de l'aiguille et réalise son cycle biologique dans la lésion ainsi formée. La dissémination de la maladie s'effectue principalement par éclaboussures de pluie contenant les conidies mais une dissémination à longue distance a été mise en évidence par transport de matériel contaminé ou par dissémination des spores par le vent ou les nuages dans les courants aériens. La sévérité de la maladie est affectée par l'humidité, la température et la lumière. Il existe des différences de sensibilité entre espèces de Pinus, et certaines présentent une résistance accrue avec l'âge. La méthode actuelle de lutte dans les forêts de plantations de l'hémisphère sud consiste à pulvériser des fongicides à base de cuivre ; dans le cas de Pinus radiata, une augmentation de la résistance a été obtenue grâce à un programme d'amélioration génétique. La toxine dothistromine est une difuroanthraquinone, similaire en structure à la versicolorine B, précurseur de l'aflatoxine. Une partie d'une batterie de gènes comprenant des gènes de biosynthèse de la dothistromine a été clonée, confirmant les analogies entre les voies de biosynthèse de la dothistromine et de l'aflatoxine. La dothistromine produit des radicaux oxygène nocifs par activation de la réduction de l'oxygène plutôt que par photosensibilisation, mais ses effets toxiques s'exercent aussi probablement sur des sites cellulaires spécifiques. Des études montrent que la dothistromine est un mutagène et clastogène faible, et donc potentiellement carcinogène. Bien que les risques pour les ouvriers forestiers soient considérés comme très faibles, il est prudent d'éviter dans la mesure du possible de s'exposer dans les périodes où les niveaux de dothistromine sont supposés élevés. Zusammenfassung Die Dothistroma -Nadelbräune ist in der Südhemisphäre in Plantagen mit exotischen Kiefernarten seit vielen Jahren ein Problem. In der Nordhemisphäre nimmt die Bedeutung dieser Krankheit derzeit zu und sie befällt nun Bäume auch in ihren natürlichen Verbreitungsgebieten. Der Erreger ist der Ascomycet Mycosphaerella pini (Anamorphe: Dothistroma pini). Der Pilz bildet das Toxin Dothistromin, das eng mit dem hochtoxischen Karzinogen Aflatoxin verwandt ist. Daraus ergab sich die Frage nach möglichen Nebenwirkungen dieser Baumkrankheit auf die Gesundheit von Waldarbeitern. Dieser Review fasst die Information über die Krankheit und das Toxin zusammen. Der Pilz hat eine komplizierte Taxonomie mit vielen Synonymen und in den meisten Ländern wurde nur die Anamorphe nachgewiesen. Er ist ein nekrotrophes Pathogen, das Blattgewebe abtötet, und in den so gebildeten Läsionen seinen Lebenszyklus abschliesst. Der normale Ausbreitungsweg der Krankheit erfolgt über Konidiosporen mit Regentropfen, aber es gibt auch Hinweise auf einen Ferntransport mit infiziertem Pflanzenmaterial und über die Verbreitung von Sporen mit dem Wind bzw. Wolken in Luftströmungen. Die Krankheitsintensität wird durch Luftfeuchte, Temperatur und Licht beeinflusst. Es gibt Unterschiede in der Anfälligkeit zwischen verschiedenen Kiefernarten und manche davon werden mit zunehmendem Alter resistenter. Derzeit werden in Plantagen der südlichen Hemisphäre Kupferfungizide zur Kontrolle dieser Krankheit eingesetzt und für Pinus radiata wurde in Züchtungsprogrammen eine erhöhte Resistenz erreicht. Das Toxin Dothistromin ist ein Difuroanthrachinon und ähnelt in seiner Struktur dem Aflatoxin-Präkursor Versicolorin B. Ein Teil des Genclusters, das die Dothistromin-Biosynthese codiert, wurde geklont, und es wurden dabei Parallelen zwischen dem Dothistromin- und dem Aflatoxin-Biosyntheseweg bestätigt. Dothistromin bildet schädliche Sauerstoffradikale (wahrscheinlich eher durch reduktive Sauerstoffaktivierung als durch Photosensibilisierung), es dürfte aber auch auf spezifische Zellkomponenten toxisch wirken. Dothistromin zeigt schwache mutagene und chromosomenschädigende Wirkungen und ist deshalb ein potentielles Karzinogen. Obwohl das Risiko für Waldarbeiter als gering eingeschätzt wird, sollte man in Perioden, in denen der Dothistromingehalt hoch sein dürfte, eine unnötige Exposition vermeiden. [source] Ecological implications of xylem cavitation for several Pinaceae in the Pacific Northern USAFUNCTIONAL ECOLOGY, Issue 5 2000J. Piñol Abstract 1.,Xylem hydraulic properties and vulnerability to cavitation (determined using the air-injection method) were studied in six Pinaceae of the northern Rocky Mountains: Pinus ponderosa, Pseudotsuga menziesii, Larix occidentalis, Pinus contorta, Pinus albicaulis and Abies lasiocarpa. We tested whether species extending into drier habitats exhibited increased resistance to water stress-induced cavitation, and whether there is a trade-off between xylem transport capacity and resistance to cavitation. 2.,At lower elevations the more drought-tolerant P. ponderosa was much less resistant to cavitation than the codominant P. menziesii. Greater vulnerability to cavitation in P. ponderosa was compensated for, at least in part, by increased stomatal control of water loss (inferred from carbon isotope discrimination) and by increased sapwood to leaf area ratios. Similar differences, but less pronounced, were found in codominant species at higher elevations. 3.,Leaf specific hydraulic conductivity was negatively correlated with mean cavitation pressure. When species were separated into pines and non-pines, sapwood specific conductivity and mean cavitation pressure were also negatively correlated within each of the two groups. 4.,Our results indicate that within the evergreen conifers examined, greater resistance to water stress-induced cavitation is not required for survival in more xeric habitats, and that there is a trade-off between xylem conductance and resistance to cavitation. [source] Immunological basis of the development of necrotic lesions following Mycobacterium avium infectionIMMUNOLOGY, Issue 4 2002Manuela Flórido Summary Normal C57BL/6 mice infected with 106 colony-forming units of a highly virulent strain of Mycobacterium avium developed a progressive infection characterized by loss of T cells from the tissues and infiltration with high numbers of heavily infected macrophages. In contrast, when C57BL/6 mice were infected with 102 colony-forming units of the same strain they retained T cells and T-cell reactivity in the tissues, and granulomas evolved into large masses that, at 4 months of infection, exhibited central necrosis. The development of these necrotic lesions did not occur in nude mice, nor in mice genetically deficient in CD4, interleukin-12 (IL-12) p40, interferon-, (IFN-,) and CD40 and were reduced in mice deficient in CD54 or IL-6. They were less numerous but bigger in mice deficient in IL-10 or the inducible nitric oxide synthase, correlating with the increased resistance to mycobacterial proliferation of these strains as compared to control mice. The appearance of necrosis was not affected in mice deficient in CD8,, T-cell receptor ,, tumour necrosis factor receptor p55, and perforin, nor was it affected in mice over-expressing bcl2. The appearance of necrosis could be prevented by administering antibodies specific for CD4, IL-12p40, or IFN-, from the second month of infection when organized granulomas were already found. Our results show that the immunological mediators involved in the induction of protective immunity are also major players in the immunopathology associated with mycobacteriosis. [source] Cyclooxygenase-2 inhibitor celecoxib augments chemotherapeutic drug-induced apoptosis by enhancing activation of caspase-3 and -9 in prostate cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 3 2005Devendra S. Dandekar Abstract Many tumors constitutively express high levels of the inducible form of proinflammatory enzyme, cyclooxygenase-2 (COX-2). Increased COX-2 expression is associated with tumor cell resistance to many cytotoxic chemotherapy drugs. Furthermore, increased resistance to cytotoxic antitumor drugs is also known to be dependent on associated stromal cells in many tumors. We investigated whether prostate tumor-associated stromal cells, marrow-derived osteoblasts, affect cytotoxicity of 2 antitumor drugs, COL-3 and docetaxel (TXTR), and whether it is dependent on COX-2 activity. We further examined whether inhibiting the activity of COX-2 negate the stroma-induced decrease in drug sensitivity in tumor cells. COX-2-specific inhibitor celecoxib (CXB) was used to inhibit COX-2 activity and associated alteration in cell death signaling was investigated. Coculturing PC-3ML cells with osteoblasts decreased the cytotoxicity of the tested antitumor drugs and was associated with increased COX-2 activity in PC-3ML cells. A significant decrease in drug-induced PGE2 increase and an increase in cytotoxicity were observed when cells were treated with COL-3 or TXTR combined with CXB. Cytotoxicity of single or combination treatment increased apoptosis, which was associated with caspase-3 and -9 activation, PARP cleavage, increased BAD protein, but decreased protein levels of XIAP and BCL- xL. Oral administration of CXB (40 mg/kg) to mice with PC-3ML tumors for 42 days increased tumor latency, decreased tumor growth and enhanced tumor control with COL-3 or TXTR. Overall, a synergistic enhancement of antitumor activity in combination treatment was observed in vitro and an additive effect in vivo. These observations suggest a potential clinical use of combined dosing of COX-2 inhibitors and cytotoxic drugs at lower, nontoxic dose than currently used to treat advanced prostate cancer. © 2005 Wiley-Liss, Inc. [source] Ecological feedbacks and the evolution of resistanceJOURNAL OF ANIMAL ECOLOGY, Issue 6 2009Meghan A. Duffy Summary 1. ,The idea that parasites can affect host diversity is pervasive, and the possibility that parasites can increase host diversity is of particular interest. In this review, we focus on diversity in the resistance of hosts to their parasites, and on the different ways in which parasites can increase or decrease this resistance diversity. 2. ,Theoretically, parasites can exert many different types of selection on host populations, which each have consequences for host diversity. Specifically, theory predicts that parasites can exert negative frequency-dependent selection (NFDS) and disruptive selection on resistance, both of which increase host diversity, as well as directional selection and stabilizing selection on resistance, both of which decrease host diversity. 3. ,Despite these theoretical predictions, most biologists think of only NFDS or directional selection for increased resistance in response to parasitism. Here, we present empirical support for all of these types of selection occurring in natural populations. Interestingly, several recent studies demonstrate that there is spatiotemporal variation in the type of selection that occurs (and, therefore, in the effects of parasitism on host diversity). 4. ,A key question that remains, then, is: What determines the type of parasite-mediated selection that occurs? Theory demonstrates that the answer to this question lies, at least in part, with trade-offs associated with resistance. Specifically, the type of evolution that occurs depends critically on the strength and shape of these trade-offs. This, combined with empirical evidence for a strong effect of environment on the shape and strength of trade-offs, may explain the observed spatiotemporal variation in parasite-mediated selection. 5. ,We conclude that spatiotemporal variation in parasite-driven evolution is likely to be common, and that this variation may be driven by ecological factors. We suggest that the feedback between ecological and evolutionary dynamics in host,parasite interactions is likely to be a productive area of research. In particular, studies addressing the role of ecological factors (e.g. productivity and predation regimes) in driving the outcome of parasite-mediated selection on host populations are warranted. Such studies are necessary if we are to understand the mechanisms underlying the observed variation in the effects of parasites on host diversity. [source] Psychological Stress and Oxidative Damage in Lymphocytes of Aerobically Fit and Unfit Individuals,JOURNAL OF APPLIED BIOBEHAVIORAL RESEARCH, Issue 1 2008Kelly Z. Knickelbein Habitual aerobic exercise has a beneficial effect on many systems of the body, and psychological stress has a negative influence on several of the same systems. One possible pathway is through those systems that account for the detrimental effects of stress; by buffering these harmful effects, exercise may reduce the consequences of stress. This study examined increased resistance of cells to stress-induced oxidative damage as a result of fitness. Forty healthy participants were assigned to either a stress group or a no-stress control group, and measures of stress and oxidative damage were collected. Variation in fitness level across participants was also measured. Oxidative damage increased as a function of stress, but this was not buffered by fitness level. These results should be interpreted with caution because of the small sample size and the limited variability of cardiorespiratory fitness levels in the sample. [source] Susceptibility of channel catfish, Ictalurus punctatus (Rafinesque), to Edwardsiella ictaluri challenge following copper sulphate exposureJOURNAL OF FISH DISEASES, Issue 10 2007B R Griffin Abstract Channel catfish, Ictalurus punctatus (Rafinesque), with or without a preliminary 24 h exposure to 2 mg copper sulphate L,1, were challenged with 7.5 × 106 colony forming units L,1 of Edwardsiella ictaluri to determine the effect of copper sulphate on disease resistance. Catfish previously exposed to copper sulphate were significantly more resistant to the bacterial challenge than those not exposed. Catfish not exposed to copper sulphate suffered 35.5% mortality while catfish exposed to copper sulphate experienced 14.1% mortality. Copper concentrations were the same in tank waters of both exposed and control fish at the time of challenge, eliminating the possibility that copper in the water may have been toxic to bacteria. Copper concentrations in freeze dried and ground tissues of unexposed, exposed, and purged channel catfish were highest in fish before copper sulphate exposures suggesting that elevated tissue levels of copper were not responsible for the increased resistance to bacterial challenge. Competition for sites of bacterial attachment to gill or epithelial cells may account for the reduction in mortality; although this is not supported by the low copper content of fish tissue after copper exposure. [source] Impact of Supercritical Carbon Dioxide and High Pressure on Lipoxygenase and Peroxidase ActivityJOURNAL OF FOOD SCIENCE, Issue 8 2000W. TEDJO ABSTRACT: The effects of supercritical carbon dioxide (ScCO2) treatment and high hydrostatic pressure treatment on the activities of lipoxygenase (LOX) and peroxidase (POD) were studied. Hydrostatic pressure treatment (240 MPa, 55 °C, 15 min) of LOX and POD in 30% sucrose solutions without buffer led to approximately 80% and approximately 50% residual activity, respectively. Application of ScCO2 (35.2 MPa, 40 °C, 15 min for LOX and 62.1 MPa, 55 °C, 15 min for POD) achieved approximately 35% LOX and approximately 65% POD inactivity in 30 % sucrose solutions. Total inactivation of LOX (10.3 MPa, 50 °C and 15 min) and of POD (62.1 MPa, 55 °C and 15 min) could be achieved through ScCO2 treatment of unbuffered solution. Increasing the concentration of sucrose and buffering (pH range 4 to 9) of enzyme solutions resulted in increased resistance of the enzymes to ScCO2 treatment. [source] Age-Dependent Changes in the Calcium Sensitivity of Striatal Mitochondria in Mouse Models of Huntington's DiseaseJOURNAL OF NEUROCHEMISTRY, Issue 6 2005N. Brustovetsky Abstract Striatal and cortical mitochondria from knock-in and transgenic mutant huntingtin mice were examined for their sensitivity to calcium induction of the permeability transition, a cause of mitochondrial depolarization and ATP loss. The permeability transition has been suggested to contribute to cell death in Huntington's Disease. Mitochondria were examined from slowly progressing knock-in mouse models with different length polyglutarnine expansions (Q20, Q50, Q92, Q111) and from the rapidly progressing transgenic R6/2 mice overexpressing exon I of human huntingtin with more than 110 polyglutamines. As previously observed in rats, striatal mitochondria from background strain CD1 and C57BL/6 control mice were more sensitive to calcium than cortical mitochondria. Between 5 and 12 months in knock-in Q92 mice and between 8 and 12 weeks in knock-in Q111 mice, striatal mitochondria developed resistance, becoming equally sensitive to calcium as cortical mitochondria, while those from Q50 mice were unchanged. Cortical mitochondrial calcium sensitivity did not change. In R6/2 mice striatal and cortical mitochondria were equally resistant to Ca2+ while striatal mitochondria from littermate controls were more susceptible. No increases in calcium sensitivity were observed in the mitochondria from Huntington's Disease (HD) mice compared to controls. Neither motor abnormalities, nor expression of cyclophilin D corresponded to the changes in mitochondrial sensitivity. Polyglutamine expansions in huntingtin produced an early increased resistance to calcium in striatal mitochondria suggesting mitochondria undergo compensatory changes in calcium sensitivity in response to the many cellular changes wrought by polyglutamine expansion. [source] Synthesis and biological activity of homoarginine-containing opioid peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 1 2007Jan Izdebski Abstract Two tris-alkoxycarbonyl homoarginine derivatives, Boc-Har{,,,,-[Z(2Br)]2}-OH and Boc-Har{,,,,-[Z(2Cl)]2}-OH, were prepared by guanidinylation of Boc-Lys-OH, and used for the synthesis of neo-endorphins and dynorphins. The results were compared with that obtained in the synthesis in which Boc-Lys(Fmoc)-OH was incorporated into the peptide chain, and after removing Fmoc protection, the resulting peptide-resin was guanidinylated with N,N,-[Z(2Br)]2 - or N,N,-[Z(2Cl)]2 - S -methylisourea. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. The results indicated that replacement of Arg by Har may be a good avenue for the design of biologically active peptides with increased resistance to degradation by trypsin-like enzymes. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] New potent hGH-RH analogues with increased resistance to enzymatic degradationJOURNAL OF PEPTIDE SCIENCE, Issue 7 2002Professor Jan Izdebski Abstract Four hGH-RH analogues containing homoarginine (Har) and/or D -Arg were obtained by solid-phase methodology using Boc-chemistry. To introduce Har residues, a Lys(Fmoc) protected Lys derivative was incorporated in the appropriate positions (11, 12, 20, 21 or 29); after assembly of the peptide chain the Fmoc group was removed and the peptide-resin was guanidinylated by treatment with N, N,-bis(tert -butoxycarbonyl)- S -methylisothiourea. The peptides were cleaved from the resin by treatment with liquid HF, and the products were purified by RP-HPLC. The peptides were subjected to digestion by trypsin, and the course of the reaction was followed by HPLC and ESI-MS. It was found that peptide bonds formed by the carboxyl group of Har are completely stable to trypsin. The course of cleavage at Lys or Arg residues depends on the position of Har in the sequence. All the analogues investigated stimulate the release of GH in rats after subcutaneous administration, and were about 50,100 times as potent as rGH-RH itself. The analogues had no effect on PRL, LH and FSH levels. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] Wheat Resistance to Spot Blotch Potentiated by SiliconJOURNAL OF PHYTOPATHOLOGY, Issue 5 2010Gisele Pereira Domiciano Abstract Spot blotch, caused by the fungus Bipolaris sorokiniana, is one of the most important diseases on wheat. The effects of silicon (Si) on this wheat disease were studied. Plants of wheat cultivars BR-18 and BRS-208 were grown in plastic pots containing Si-deficient soil amended with either calcium silicate (+Si) or calcium carbonate (,Si). The content of Si in leaf tissue was significantly increased by 90.5% for the +Si treatment. There was no significant difference between Si treatments for calcium content, so variations in Si accounted for differences in the level of resistance to spot blotch. The incubation period was significantly increased by 40% for the +Si treatment. The area under spot blotch progress curve, number of lesions per cm2 of leaf area, and real disease severity significantly decreased by 62, 36 and 43.5% in +Si treatment. There was no significant effect of Si on lesion size. The role played by total soluble phenolics in the increased resistance to spot blotch of plants from both cultivars supplied with Si was not clear. Plants from cultivar BR-18 supplied with Si showed the highest values for concentration of lignin-thioglycolic acid derivatives during the most advanced stages of fungus infection. Chitinase activity was high at the most advanced stages of fungus infection on leaves from both cultivars supplied with Si and may have had an effect on fungus growth based on the reduction of the components of resistance evaluated. Peroxidase activity was found to be high only at 96 h after inoculation of both cultivars supplied with Si. Polyphenoloxidase activity had no apparent effect on resistance regardless of Si treatments. Results revealed that supplying Si to wheat plants can increase resistance against spot blotch. [source] Variation of Fungicide Resistance in Czech Populations of Pseudoperonospora cubensisJOURNAL OF PHYTOPATHOLOGY, Issue 3 2007J. Urban Abstract During the growing seasons between the years 2001 and 2004, 98 isolates of Pseudoperonospora cubensis from nine regions of Czech Republic were collected and screened for tolerance/resistance to the three frequently used fungicides (propamocarb, fosetyl-Al, metalaxyl). Fungicides were tested in five different concentrations, using a floating disc bioassay. Fungicide effectiveness varied considerably. Propamocarb appeared most effective and all the isolates collected in the years 2001,2003 were found sensitive to all tested concentrations [607,9712 ,g active ingredient (a.i.)/ml]. In 2004, some strains with increased resistance to propamocarb were detected. These strains were characterized by tolerance at the lowest concentrations (607 ,g a.i./ml, eventually on 1214 ,g a.i./ml); however, they were controlled by 2428 ,g a.i./ml. Fosetyl-Al was effective at the recommended concentration of 1600 ,g a.i./ml against all isolates. However, the occurrence of isolates (collected in 2001) which sporulated at low concentrations (400 and 800 ,g a.i./ml) indicated that the selection for tolerance occurs in the pathogen population. Nevertheless, this phenomenon was not confirmed with the P. cubensis isolates collected between the years 2002 and 2004. Metalaxyl was found ineffective, because 97% of the isolates showed the resistance to the recommended concentration (200 ,g a.i./ml), and the other 3% of isolates expressed tolerant response. The majority of the isolates showed profuse and/or limited sporulation at higher concentrations (400 and 800 ,g a.i./ml). A substantial shift to highly metalaxyl resistant strains was evident in the Czech P. cubensis populations during 2001,2004. [source] Effect of Flaw State on the Strength of Brittle Coatings on Soft SubstratesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Hae-Won Kim A study is made of the role of flaw state on the strength properties of brittle ceramic coating layers bonded to soft polycarbonate substrates. We introduce Vickers radial cracks at prescribed loads into the coating undersurfaces prior to bonding to control the sizes and locations of the starting flaws. A spherical indenter is then loaded on the top bilayer surfaces, directly above the Vickers indentation sites, subjecting the radial cracks to flexural tensile stress. Radial crack responses are monitored in situ, using a camera located below the transparent substrate. Critical loads to cause radial crack instability, and ensuing growth of the arrested cracks, are recorded. Conventional biaxial flexure tests on corresponding monolith coating materials provide a baseline for data comparison. Relative to the monolith flexure specimens, the bilayers show higher strengths, the more so the larger the flaw, indicating enhanced flaw tolerance. A simple fracture mechanics analysis of the radial crack evolution in the concentrated-load field, with due account for distribution of flexural tensile stresses at the coating undersurface, is unable to account completely for the enhanced bilayer strengths for the larger Vickers flaws. It is hypothesized that the epoxy used to bond the bilayer components enters the cracks, causing crack-wall adherence and providing an increased resistance to radial crack instability. The fracture mechanics are nevertheless able to account for the arrest and subsequent stable extension of the radial cracks beyond the critical loads once this extraneous adherence has been overcome. [source] Effect of leg exercises on popliteal venous blood flow during prolonged immobility of seated subjects: implications for prevention of travel-related deep vein thrombosisJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 9 2007K. HITOS Summary.,Background:,Venous stasis is an important contributing factor in the development of travel-related deep vein thrombosis. This study examined factors affecting popliteal venous blood flow in order to determine the most effective exercise regimen to prevent venous stasis. Methods:,Twenty-one healthy subjects were randomly assigned to various activities over a 9-week period. Subjects remained seated throughout the investigation and 3660 duplex ultrasound examinations were performed by a single examiner using a SonoSite 180 Plus handheld ultrasound. Baseline popliteal vein blood flow velocity, cross-sectional area and volume flow in subjects sitting motionless were assessed in the first 3 weeks. The remaining 6 weeks involved subjects performing airline-recommended activities, foot exercises, foot exercises against moderate resistance and foot exercises against increased resistance in order to determine the most beneficial method for enhancing popliteal venous flow. Sitting with feet not touching the floor and the effect of sleeping were also assessed. Results:,The median age of the subjects was 22 years (range: 18,25.5 years), height 171 cm (162.5,180.5 cm) and body mass index 25.3 kg m,2 (23.2,26.3 kg m,2). Blood volume flow in the popliteal vein was reduced by almost 40% with immobility of seated subjects and by almost 2-fold when sitting motionless with feet not touching the floor. Foot exercises against increased resistance positively enhanced volume flow (P < 0.0001). Conclusion:,Leg exercise regimens enhanced popliteal venous flow during prolonged immobility of seated subjects, reinforcing the importance of regular leg movement to prevent venous stasis during prolonged sitting, such as in long-distance travel. [source] Impact of progestagens on activated protein C (APC) resistance among users of oral contraceptivesJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 9 2004M. Alhenc-Gelas Summary., Oral contraceptive (OC) use is associated with an increased risk of venous thromboembolism. Previous data reported higher thrombotic risk in women using third-generation combined OC than in those using second generation OC. The difference could be explained by differential effects of progestagens on plasma sensitivity to activated protein C (APC). The main purpose of this cross-sectional study was to assess the influence of a progestagen-only OC (chlormadinone acetate) as well as the effect of several combined OC with different progestagen components on APC resistance. The effect of APC on endogenous thrombin potential (ETP) was investigated in the plasma of healthy women using either combined OC (n = 82) or progestagen-only OC (n = 28), and in non-users (n = 64). Carriers of factor V Leiden were excluded. Compared with non-users, there was no significant change in APC resistance in women using progestagen-only OC. Women who used combined OC were less sensitive to APC than non-users (P < 0.001) and the difference was significantly more pronounced in women using third-generation OC (n = 41) than in those who used second-generation OC containing levonorgestrel (n = 22) (P < 0.05). Compared with OC containing levonorgestrel, use of norethisterone-containing OC (n = 9) was associated with an increased resistance to APC (P < 0.05). Women who used cyproterone-containing OC (n = 10) were less sensitive to APC than those using third-generation OC (P < 0.05) or second-generation OC containing levonorgestrel (P < 0.05). Protein S, factor II and FVIII levels explained in part the OC-related changes in APC sensitivity variations. ETP-based APC resistance may contribute to explain why different brands of OC can be associated with different levels of thrombogenicity. [source] Improving the properties of aluminium alloys by retrogression and reageingMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2003J. S. RobinsonArticle first published online: 11 APR 200 Abstract Retrogression and reageing heat treatments offer the potential of improved tensile properties in combination with greatly increased resistance to stress corrosion cracking. The potential of this technique is reviewed with respect to the current application in the European and North American Aerospace Industry. To illustrate the performance increase associated with RRA treatments, the stress corrosion cracking performance of the established aerospace plate and forging alloy 7010 has been evaluated using an alternate immersion constant load tensile type test (ECSS-Q-70-37A) Specimens were cut from a large aerospace rectilinear forging and tested in three different tempers, T652, T7452 and a retrogressed and reaged condition (RRA). In the T652 condition the material has been shown to be highly susceptible to intergranular corrosion and stress corrosion cracking. In the T7452 and RRA conditions 7010 showed much improved resistance to SCC but pitting corrosion resulted in failure of some specimens within the 30day requirement of the test standard. [source] Elevation of XPA protein level in testis tumor cells without increasing resistance to cisplatin or UV radiationMOLECULAR CARCINOGENESIS, Issue 8 2008Beate Köberle Abstract Most testicular germ cell tumors are curable using cisplatin-based chemotherapy, and cell lines from these tumors are unusually sensitive to cisplatin and other DNA-damaging agents. It has been suggested that this might be caused by a lower-than normal nucleotide excision repair (NER) activity. Previous studies found that cell lines from testicular germ cell tumors have on average about one-third the level of the NER protein XPA in comparison to cell lines from other tumors. We asked whether over-expression of XPA protein would alleviate the cellular sensitivity and increase the DNA repair capacity of a testis tumor cell line. Increasing XPA levels in 833K cells by 10-fold did not increase resistance to UV irradiation. XPA was localized to the cell nucleus in all cell lines, before and after exposure to UV-radiation. 833K cells were proficient in removing UV radiation-induced photoproducts from the genome and increased XPA did not enhance the rate of removal. Further, over-expressing functional XPA protein did not correlate with increased resistance of 833K testis tumor cells to cisplatin. Thus, although the amount of XPA in this testis tumor cell line is lower than normal, it is sufficient for NER in vivo. The relative sensitivity of testis tumor cells to cisplatin, UV radiation, and other DNA damaging agents is likely related not to NER capacity, but to other factors such as the integrity of the p53 pathway in these cells. © 2008 Wiley-Liss, Inc. [source] Fungicide activity through activation of a fungal signalling pathwayMOLECULAR MICROBIOLOGY, Issue 6 2004Kaihei Kojima Summary Fungicides generally inhibit enzymatic reactions involved in fungal cellular biosynthesis. Here we report, for the first time, an example of fungicidal effects through hyperactivation of a fungal signal transduction pathway. The OSC1 gene, encoding a MAP kinase (MAPK) related to yeast Hog1, was isolated from the fungal pathogen Colletotrichum lagenarium that causes cucumber anthracnose. The osc1 knockout mutants were sensitive to high osmotic stress and showed increased resistance to the fungicide fludioxonil, indicating that Osc1 is involved in responses to hyperosmotic stress and sensitivity to fludioxonil. The Osc1 MAPK is phosphorylated under high osmotic conditions, indicating activation of Osc1 by high osmotic stress. Importantly, fludioxonil treatment also activates phosphorylation of Osc1, suggesting that improper activation of Osc1 by fludioxonil has negative effects on fungal growth. In the presence of fludioxonil, the wild-type fungus was not able to infect the host plant because of a failure of appressorium-mediated penetration, whereas osc1 mutants successfully infected plants. Analysis using a OSC1- GFP fusion gene indicated that Osc1 is rapidly translocated to the nucleus in appressorial cells after the addition of fludioxonil, suggesting that fludioxonil impairs the function of infection structures by activation of Osc1. Furthermore, fludioxonil activates Hog1-type MAPKs in the plant pathogenic fungi Cochliobolus heterostrophus and Botrytis cinerea. These results strongly suggest that fludioxonil acts as a fungicide, in part, through activation of the MAPK cascade in fungal pathogens. [source] Lipopolysaccharide mobility in leaf tissue of Arabidopsis thalianaMOLECULAR PLANT PATHOLOGY, Issue 6 2010DANA ZEIDLER SUMMARY Bacterial lipopolysaccharides (LPS) are triggers of defence responses in plants, and induce local as well as systemic acquired resistance. Arabidopsis thaliana plants pretreated with LPS show an increased resistance to the virulent bacterial plant pathogen Pseudomonas syringae pv. tomato DC3000. To investigate the mobilization and transport of LPS in Arabidopsis leaves, fluorescently labelled LPS (Alexa Fluor® 488 conjugate) from Salmonella minnesota was used. Leaves were pressure infiltrated with fluorescein-labelled LPS and fluorescence microscopy was used to follow the movement and localization of LPS as a function of time. The observation of leaves 1 h after supplementation with fluorescein-labelled LPS revealed a fluorescent signal in the intercellular space. Capillary zone electrophoresis was used for the detection and analysis of the labelled LPS in directly treated leaves and systemic leaves. In addition, gel electrophoresis was used to confirm LPS mobilization. The results indicated that LPS mobilization/translocation occurs through the xylem from local, treated leaves to systemic, untreated leaves. Consequently, care should be taken when ascribing the observed biochemical responses and induced resistance from LPS perception as being uniquely local or systemic, as these responses might overlap because of the mobility of LPS in the plant vascular system. [source] Hypertonia in childhood secondary dystonia due to cerebral palsy is associated with reflex muscle activation,MOVEMENT DISORDERS, Issue 7 2009Johan van Doornik PhD Abstract It is often assumed that co-contraction of antagonist muscles is responsible for increased resistance to passive movement in hypertonic dystonia. Although co-contraction may certainly contribute to hypertonia in some patients, the role of reflex activation has never been investigated. We measured joint torque and surface electromyographic activity during passive flexion and extension movements of the elbow in 8 children with hypertonic arm dystonia due to dyskinetic cerebral palsy. In all cases, we found significant phasic electromyographic activity in the lengthening muscle, consistent with reflex activity. By correlating activation with position or velocity of the limb, we determined that some children exhibit position-dependent activation, some exhibit velocity-dependent activation, and some exhibit a mixed pattern of activation. We conclude that involuntary or reflex muscle activation in response to stretch may be a significant contributor to increased tone in hypertonic dystonia, and we conjecture that this activation may be more important than co-contraction for determining the resistance to passive movement. © 2009 Movement Disorder Society [source] Choline kinase overexpression increases invasiveness and drug resistance of human breast cancer cellsNMR IN BIOMEDICINE, Issue 6 2010Tariq Shah Abstract A direct correlation exists between increased choline kinase (Chk) expression, and the resulting increase of phosphocholine levels, and histological tumor grade. To better understand the function of Chk and choline phospholipid metabolism in breast cancer we have stably overexpressed one of the two isoforms of Chk-, known to be upregulated in malignant cells, in non-invasive MCF-7 human breast cancer cells. Dynamic tracking of cell invasion and cell metabolism were studied with a magnetic resonance (MR) compatible cell perfusion assay. The MR based invasion assay demonstrated that MCF-7 cells overexpressing Chk-, (MCF-7-Chk) exhibited an increase of invasion relative to control MCF-7 cells (0.84 vs 0.3). Proton MR spectroscopy studies showed significantly higher phosphocholine and elevated triglyceride signals in Chk overexpressing clones compared to control cells. A test of drug resistance in MCF-7-Chk cells revealed that these cells had an increased resistance to 5-fluorouracil and higher expression of thymidylate synthase compared to control MCF-7 cells. To further characterize increased drug resistance in these cells, we performed rhodamine-123 efflux studies to evaluate drug efflux pumps. MCF-7-Chk cells effluxed twice as much rhodamine-123 compared to MCF-7 cells. Chk-, overexpression resulted in MCF-7 human breast cancer cells acquiring an increasingly aggressive phenotype, supporting the role of Chk-, in mediating invasion and drug resistance, and the use of phosphocholine as a biomarker of aggressive breast cancers. Copyright © 2010 John Wiley & Sons, Ltd. [source] Periodontitis as an infectious disease: specific features and their implicationsORAL DISEASES, Issue 2003A Mombelli Periodontitis may be viewed as an infectious disease with a number of specific characteristics. Pathogens of the subgingival microbiota can interact with host tissues even without direct tissue penetration. Hence, antimicrobial agents must be available at a sufficiently high concentration not only within the periodontal tissues, but also outside, in the environment of the periodontal pocket. The subgingival microbiota accumulate on the root surface to form an adherent layer of plaque with the characteristics of a biofilm. Several mechanisms, such as diffusion barriers, and selective inactivation of agents lead to an increased resistance of bacteria in biofilms. Mechanical supragingival plaque control is indispensable to prevent the re-emergence of periodontal pathogens and the re-establishment of a biofilm in treated sites. Since specific features have important implications for the use of antimicrobial agents in periodontal therapy, extrapolations from experiences made in the therapy of other infections are only partially valid. The ultimate evidence for the efficacy of systemic or local chemotherapy must be obtained from treatment studies in humans with adequate follow-up. [source] | |||||||||||||||||||||||||||||||