Induced Responses (induced + response)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts

Influence of atmospheric carbon dioxide enrichment on induced response and growth compensation after herbivore damage in Lotus corniculatus

Alain Bazin
Abstract 1. Plant growth and chemical defence compounds in four Lotus corniculatus genotypes exposed to factorial combinations of ambient and elevated carbon dioxide, and herbivory by caterpillars of Polyommatus icarus were measured to test the predictions of the carbon/nutrient balance hypothesis. 2. Shoot and root biomass, allocation to shoots versus roots, and carbon-based defence compounds were greater under elevated carbon dioxide. Pupal weight of P. icarus was greater and development time shorter under elevated carbon dioxide. 3. Herbivory decreased shoot growth relative to root growth and production of nitrogen-based defence (cyanide). Young leaves contained more defence compounds than old leaves, and this response depended on carbon dioxide and herbivory treatments (significant interactions). 4. Genotype-specific responses of plants to carbon dioxide and herbivory were found for the production of cyanide. Furthermore, maternal butterfly-specific responses of caterpillars to carbon dioxide were found for development time. This suggests the existence of genetic variation for important defence and life-history traits in plants and herbivores in response to rising carbon dioxide levels. [source]

Mechanism of a plastic phenotypic response: predator-induced shell thickening in the intertidal gastropod Littorina obtusata

Abstract Phenotypic plasticity has been the object of considerable interest over the past several decades, but in few cases are mechanisms underlying plastic responses well understood. For example, it is unclear whether predator-induced changes in gastropod shell morphology represent an active physiological response or a by-product of reduced feeding. We address this question by manipulating feeding and growth of intertidal snails, Littorina obtusata, using two approaches: (i) exposure to predation cues from green crabs Carcinus maenas and (ii) reduced food availability, and quantifying growth in shell length, shell mass, and body mass, as well as production of faecal material and shell micro-structural characteristics (mineralogy and organic fraction) after 96 days. We demonstrate that L. obtusata actively increases calcification rate in response to predation threat, and that this response entails energetic and developmental costs. That this induced response is not strictly tied to the animal's behaviour should enhance its evolutionary potential. [source]

Silicon-augmented resistance of plants to herbivorous insects: a review

O.L. Reynolds
Abstract Silicon (Si) is one of the most abundant elements in the earth's crust, although its essentiality in plant growth is not clearly established. However, the importance of Si as an element that is particularly beneficial for plants under a range of abiotic and biotic stresses is now beyond doubt. This paper reviews progress in exploring the benefits at two- and three-trophic levels and the underlying mechanism of Si in enhancing the resistance of host plants to herbivorous insects. Numerous studies have shown an enhanced resistance of plants to insect herbivores including folivores, borers, and phloem and xylem feeders. Silicon may act directly on insect herbivores leading to a reduction in insect performance and plant damage. Various indirect effects may also be caused, for example, by delaying herbivore establishment and thus an increased chance of exposure to natural enemies, adverse weather events or control measures that target exposed insects. A further indirect effect of Si may be to increase tolerance of plants to abiotic stresses, notably water stress, which can in turn lead to a reduction in insect numbers and plant damage. There are two mechanisms by which Si is likely to increase resistance to herbivore feeding. Increased physical resistance (constitutive), based on solid amorphous silica, has long been considered the major mechanism of Si-mediated defences of plants, although there is recent evidence for induced physical defence. Physical resistance involves reduced digestibility and/or increased hardness and abrasiveness of plant tissues because of silica deposition, mainly as opaline phytoliths, in various tissues, including epidermal silica cells. Further, there is now evidence that soluble Si is involved in induced chemical defences to insect herbivore attack through the enhanced production of defensive enzymes or possibly the enhanced release of plant volatiles. However, only two studies have tested for the effect of Si on an insect herbivore and third trophic level effects on the herbivore's predators and parasitoids. One study showed no effect of Si on natural enemies, but the methods used were not favourable for the detection of semiochemical-mediated effects. Work recently commenced in Australia is methodologically and conceptually more advanced and an effect of Si on the plants' ability to generate an induced response by acting at the third trophic level was observed. This paper provides the first overview of Si in insect herbivore resistance studies, and highlights novel, recent hypotheses and findings in this area of research. Finally, we make suggestions for future research efforts in the use of Si to enhance plant resistance to insect herbivores. [source]

V-ATPase deactivation in blowfly salivary glands is mediated by protein phosphatase 2C

Martin Voss
Abstract The activity of vacuolar H+ -ATPase (V-ATPase) in the apical membrane of blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT). 5-HT induces, via protein kinase A, the phosphorylation of V-ATPase subunit C and the assembly of V-ATPase holoenzymes. The protein phosphatase responsible for the dephosphorylation of subunit C and V-ATPase inactivation is not as yet known. We show here that inhibitors of protein phosphatases PP1 and PP2A (tautomycin, ocadaic acid) and PP2B (cyclosporin A, FK-506) do not prevent V-ATPase deactivation and dephosphorylation of subunit C. A decrease in the intracellular Mg2+ level caused by loading secretory cells with EDTA-AM leads to the activation of proton pumping in the absence of 5-HT, prolongs the 5-HT-induced response in proton pumping, and inhibits the dephosphorylation of subunit C. Thus, the deactivation of V-ATPase is most probably mediated by a protein phosphatase that is insensitive to okadaic acid and that requires Mg2+, namely, a member of the PP2C protein family. By molecular biological techniques, we demonstrate the expression of at least two PP2C protein family members in blowfly salivary glands. 2009 Wiley Periodicals, Inc. [source]

Impact of chemical elicitor applications on greenhouse tomato plants and population growth of the green peach aphid, Myzus persicae

Anthony J. Boughton
Abstract Recent advances in the understanding of plant signaling pathways have opened the way for using elicitor-induced plant resistance as a tactic for protecting plants against arthropod pests. Four common elicitors of induced responses in tomato, Lycopersicon esculentum Mill. (Solanaceae), were evaluated with regard to phytotoxicity, induction of plant defensive proteins, and effects on population growth and fecundity of a common pest, the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae). Ethephon and methyl jasmonate (MJ) treatments caused varying degrees of phytotoxicity. Ethephon caused pronounced changes in plant growth form and severe, dose-dependent negative impacts on plant growth and flowering. Effects with MJ were milder, but still caused temporary inhibition of development, leading to smaller plants and delayed flowering. The commercial elicitors benzothiadiazole (BTH) and harpin did not cause detectable phytotoxicity. The highest doses of ethephon and MJ significantly increased leaf peroxidase (POD) levels but only MJ treatments significantly increased polyphenol oxidase (PPO) levels. BTH and harpin had no detectable effects on POD and PPO. Populations of green peach aphids grew significantly more slowly on plants treated with BTH or MJ than on control plants or plants treated with harpin or ethephon. Slowed aphid population growth on BTH-treated plants was due to significant reductions in aphid fecundity, although this was independent of changes in time to onset of reproduction or time to death. Aphid fecundity was also reduced on MJ-treated plants relative to controls, but this difference was not statistically significant, suggesting that other mechanisms are involved in slowing aphid population growth on MJ-treated plants. Growth of aphid populations on plants treated with a MJ,BTH mixture was reduced almost as much as with treatments of MJ alone, suggesting that antagonism between JA-dependant and SA-dependent plant signaling pathways is only mild with regard to induced defenses against aphids. [source]

FGF-2, IL-1, and TGF-, regulate fibroblast expression of S100A8

FEBS JOURNAL, Issue 11 2005
Farid Rahimi
Growth factors, including fibroblast growth factor-2 (FGF-2) and transforming growth factor-, (TGF-,) regulate fibroblast function, differentiation and proliferation. S100A8 and S100A9 are members of the S100 family of Ca2+ -binding proteins and are now accepted as markers of inflammation. They are expressed by keratinocytes and inflammatory cells in human/murine wounds and by appropriately activated macrophages, endothelial cells, epithelial cells and keratinocytes in vitro. In this study, regulation and expression of S100A8 and S100A9 were examined in fibroblasts. Endotoxin (LPS), interferon , (IFN,), tumour-necrosis factor (TNF) and TGF-, did not induce the S100A8 gene in murine fibroblasts whereas FGF-2 induced mRNA maximally after 12 h. The FGF-2 response was strongly enhanced and prolonged by heparin. Interleukin-1, (IL-1,) alone, or in synergy with FGF-2/heparin strongly induced the gene in 3T3 fibroblasts. S100A9 mRNA was not induced under any condition. Induction of S100A8 in the absence of S100A9 was confirmed in primary fibroblasts. S100A8 mRNA induction by FGF-2 and IL-1, was partially dependent on the mitogen-activated-protein-kinase pathway and dependent on new protein synthesis. FGF-2-responsive elements were distinct from the IL-1,-responsive elements in the S100A8 gene promoter. FGF-2-/heparin-induced, but not IL-1,-induced responses were significantly suppressed by TGF-,, possibly mediated by decreased mRNA stability. S100A8 in activated fibroblasts was mainly intracytoplasmic. Rat dermal wounds contained numerous S100A8-positive fibroblast-like cells 2 and 4 days post injury; numbers declined by 7 days. Up-regulation of S100A8 by FGF-2/IL-1,, down-regulation by TGF-,, and its time-dependent expression in wound fibroblasts suggest a role in fibroblast differentiation at sites of inflammation and repair. [source]

Interferon regulatory factor-1 acts as a powerful adjuvant in tat DNA based vaccination,

Arianna Castaldello
Genetic vaccines are safe cost-effective approaches to immunization but DNA immunization is an inefficient process. There is, therefore, a pressing need for adjuvants capable of enhancing the immunogenicity and effectiveness of these vaccines. This is particularly important for diseases for which successful vaccines are still lacking, such as cancer and infectious diseases including HIV-1/AIDS. Here we report an approach to enhance the immunogenicity of DNA vaccines involving the use of transcription factors of the Interferon regulatory factor (IRF) family, specifically IRF-1, IRF-3, and IRF-7 using the tat gene as model antigen. Balb/c mice were immunized by three intramuscular inoculations, using a DNA prime-protein boost protocol, with a DNA encoding tat of HIV-1 and the indicated IRFs and immune responses were compared to those induced by vaccination with tat DNA alone. In vivo administration of plasmid DNA encoding IRF-1, or a mutated version of IRF-1 deleted of the DNA-binding domain, enhanced Tat-specific immune responses and shifted them towards a predominant T helper 1-type immune response with increased IFN-, production and cytotoxic T lymphocytes responses. Conversely, the use of IRF-3 or IRF-7 did not affect the tat -induced responses. These findings define IRF-1 and its mutated form as efficacious T helper 1-inducing adjuvants in the context of tat- based vaccination and also providing a new promising candidate for genetic vaccine development. J. Cell. Physiol. 224: 702,709, 2010. 2010 Wiley-Liss, Inc. [source]

Evolutionary biology of starvation resistance: what we have learned from Drosophila

Abstract Most animals face periods of food shortage and are thus expected to evolve adaptations enhancing starvation resistance (SR). Most of our knowledge of the genetic and physiological bases of those adaptations, their evolutionary correlates and trade-offs, and patterns of within- and among-population variation, comes from studies on Drosophila. In this review, we attempt to synthesize the various facets of evolutionary biology of SR emerging from those studies. Heritable variation for SR is ubiquitous in Drosophila populations, allowing for large responses to experimental selection. Individual flies can also inducibly increase their SR in response to mild nutritional stress (dietary restriction). Both the evolutionary change and the physiological plasticity involve increased accumulation of lipids, changes in carbohydrate and lipid metabolism and reduction in reproduction. They are also typically associated with greater resistance to desiccation and oxidative stress, and with prolonged development and lifespan. These responses are increasingly seen as facets of a shift of the physiology towards a ,survival mode', which helps the animal to survive hard times. The last decade has seen a great progress in revealing the molecular bases of induced responses to starvation, and the first genes contributing to genetic variation in SR have been identified. In contrast, little progress has been made in understanding the ecological significance of SR in Drosophila; in particular it remains unclear to what extent geographical variation in SR reflect differences in natural selection acting on this trait rather than correlated responses to selection on other traits. Drosophila offers a unique opportunity for an integrated study of the manifold aspects of adaptation to nutritional stress. Given that at least some major molecular mechanisms of response to nutritional stress seem common to animals, the insights from Drosophila are likely to apply more generally than just to dipterans or insects. [source]

Early season herbivore differentially affects plant defence responses to subsequently colonizing herbivores and their abundance in the field

Abstract Induction of plant defences by early season herbivores can mediate interspecific herbivore competition. We have investigated plant-mediated competition between three herbivorous insects through studies at different levels of biological integration. We have addressed (i) gene expression; (ii) insect behaviour and performance under laboratory conditions; and (iii) population dynamics under field conditions. We studied the expression of genes encoding a trypsin inhibitor and genes that are involved in glucosinolate biosynthesis in response to early season herbivory by Pieris rapae caterpillars in Brassica oleracea plants. Furthermore, we studied the interaction of these transcriptional responses with responses to secondary herbivory by the two specialist herbivores, P. rapae and Plutella xylostella, and the generalist Mamestra brassicae. P. rapae -induced responses strongly interacted with plant responses to secondary herbivory. Sequential feeding by specialist herbivores resulted in enhanced or similar expression levels of defence-related genes compared to primary herbivory by specialists. Secondary herbivory by the generalist M. brassicae resulted in lower gene expression levels than in response to primary herbivory by this generalist. Larval performance of both specialist and generalist herbivores was negatively affected by P. rapae- induced plant responses. However, in the field the specialist P. xylostella was more abundant on P. rapae -induced plants and preferred these plants over undamaged plants in oviposition experiments. In contrast, the generalist M. brassicae was more abundant on control plants and preferred undamaged plants for oviposition. P. rapae did not discriminate between plants damaged by conspecifics or undamaged plants. Our study shows that early season herbivory differentially affects transcriptional responses involved in plant defence to secondary herbivores and their population development dependent upon their degree of host plant specialization. [source]

MAMPs and MIMPs: proposed classifications for inducers of innate immunity

David Mackey
Summary Plants encode a sophisticated innate immune system. Resistance against potential pathogens often relies on active responses. Prerequisite to the induction of defences is recognition of the pathogenic threat. Significant advances have been made in our understanding of the non-self molecules that are recognized by plants and the means by which plants perceive them. Established terms describing these recognition events, including microbe-associated molecular pattern (MAMP), MAMP-receptor, effector, and resistance (R) protein, need clarification to represent our current knowledge adequately. In this review we propose criteria to classify inducers of plant defence as either MAMPs or microbe-induced molecular patterns (MIMPs). We refine the definition of MAMP to mean a molecular sequence or structure in ANY pathogen-derived molecule that is perceived via direct interaction with a host defence receptor. MIMPs are modifications of host-derived molecules that are induced by an intrinsic activity of a pathogen-derived effector and are perceived by a host defence receptor. MAMP-receptors have previously been classified separately from R-proteins as a discrete class of surveillance molecules. However, MAMP-receptors and R-proteins cannot be distinguished on the basis of their protein structures or their induced responses. We propose that MAMP-receptors and MIMP-receptors are each a subset of R-proteins. Although our review is based on examples from plant pathogens and plants, the principles discussed might prove applicable to other organisms. [source]

Repeated courses of rituximab in chronic ITP: Three different regimens,

Aisha Hasan
This study investigated responses to retreatment with rituximab in chronic immune thrombocytopenic purpura (ITP) patients. Treatment with rituximab in chronic ITP patients induces long-lasting responses in ,30% of patients but even these patients may relapse. Twenty patients who had achieved a response to rituximab and relapsed were retreated with rituximab (375 mg/m2 4); this data was analyzed retrospectively. Subsequently, 16 patients were prospectively randomized to receive rituximab with cyclophosphamide, vincristine and prednisone (R-CVP) or double dose rituximab (DDR). Retreatment with standard dose rituximab demonstrated responses similar to initial rituximab treatment in 15 of 20 patients. Neither of the two more intensive regimens (R-CVP, DDR) induced responses in any patient who had previously failed to respond to rituximab nor induced substantially longer-lasting responses among previous responders. No additional toxicity was noted with the DDR regimen, whereas R-CVP was not well tolerated. These results suggest that retreatment with standard dose rituximab induces similar responses in 75% of previously responding patients and is well tolerated. Neither combining rituximab with CVP nor doubling the dose of rituximab increased the response rate. Am. J. Hematol., 2009. 2009 Wiley-Liss, Inc. [source]

Effects of Low Power Laser Irradiation on Intracellular Calcium and Histamine Release in RBL-2H3 Mast Cells

Wen-Zhong Yang
Although laser irradiation has been reported to promote skin wound healing, the mechanism is still unclear. As mast cells are found to accumulate at the site of skin wounds we hypothesized that mast cells might be involved in the biological effects of laser irradiation. In this work the mast cells, RBL-2H3, were used in vitro to investigate the effects of laser irradiation on cellular responses. After laser irradiation, the amount of intracellular calcium ([Ca2+]i) was increased, followed by histamine release, as measured by confocal fluorescence microscopy with Fluo-3/AM staining and a fluorescence spectrometer with o -phthalaldehyde staining, respectively. The histamine release was mediated by the increment of [Ca2+]i from the influx of the extracellular buffer solution through the cation channel protein, transient receptor potential vanilloid 4 (TRPV4). The TRPV4 inhibitor, Ruthenium Red (RR) can effectively block such histamine release, indicating that TRPV4 was the key factor responding to laser irradiation. These induced responses of mast cells may provide an explanation for the biological effects of laser irradiation on promoting wound healing, as histamine is known to have multi-functions on accelerating wound healing. [source]

High humidity suppresses ssi4 -mediated cell death and disease resistance upstream of MAP kinase activation, H2O2 production and defense gene expression

Fasong Zhou
Summary The Arabidopsis ssi4 mutant, which exhibits spontaneous lesion formation, constitutive expression of pathogenesis-related (PR) genes and enhanced resistance to virulent bacterial and oomycete pathogens, contains a gain-of-function mutation in a TIR-NBS-LRR type R gene. Epistatic analyses revealed that both PR gene expression and disease resistance are activated via a salicylic acid (SA)- and EDS1 -dependent, but NPR1 - and NDR1 -independent signaling pathway. In this study, we demonstrate that in moderate relative humidity (RH; 60%), the ssi4 mutant accumulates H2O2 and SA prior to lesion formation and displays constitutive activation of the MAP kinases AtMPK6 and AtMPK3. It also constitutively expresses a variety of defense-associated genes, including those encoding the WRKY transcription factors AtWRKY29 and AtWRKY6, the MAP kinases AtMPK6 and AtMPK3, the powdery mildew R proteins RPW8.1 and RPW8.2, EDS1 and PR proteins. All of these ssi4 -induced responses, as well as the chlorotic, stunted morphology and enhanced disease resistance phenotype, are suppressed by high RH (95%) growth conditions. Thus, a humidity sensitive factor (HSF) appears to function at an early point in the ssi4 signaling pathway. All ssi4 phenotypes, except for MAP kinase activation, also were suppressed by the eds1-1 mutation. Thus, ssi4 -induced MAP kinase activation occurs downstream of the HSF but either upstream of EDS1 or on a separate branch of the ssi4 signaling pathway. SA is a critical signaling component in ssi4 -mediated defense responses. However, exogenously supplied SA failed to restore lesion formation in high RH-grown ssi4 plants, although it induced defense gene expression. Thus, additional signals also are involved. [source]

Noncompetitive antagonism of BIBN4096BS on CGRP-induced responses in human subcutaneous arteries

Majid Sheykhzade
We investigated the antagonistic effect of 1-piperidinecarboxamide, N -[2-[[5amino-l-[[4-(4-pyridinyl)-l-piperazinyl]carbonyl]pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl) (BIBN4096BS) on the calcitonin gene-related peptide (CGRP)-induced responses by using isometric myograph and FURA-2 technique in human subcutaneous arteries removed in association with abdominal surgery. BIBN4096BS, at the concentration of 1 pM, had no significant effect on the CGRP-induced relaxation in these vessels. At the concentration of 10 pM, BIBN4096BS had a competitive antagonistic-like behaviour characterized by parallel rightward shift in the log CGRP concentration-tension curve with no depression of the Emax. At the higher concentrations (0.1 and 1 nM), BIBN4096BS had a concentration-dependent noncompetitive antagonistic effect on the CGRP-induced responses. The efficacy and potency of CGRP was significantly greater in the smaller (lumen diameter ,200 ,m) human subcutaneous arteries compared to the larger ones. The apparent agonist equilibrium dissociation constant, KA, for CGRP1 receptors in the human subcutaneous arteries was approximately 1 nM. Analysis of the relationship between receptor occupancy and response to CGRP indicates that the receptor reserve is relatively small. Using reverse transcriptase-polymerase chain reaction (RT-PCR), the presence of mRNA sequences encoding the calcitonin receptor-like receptor, receptor activity modifying protein (RAMP1, RAMP2, RAMP3) and receptor component protein were demonstrated in human subcutaneous arteries, indicating the presence of CGRP1 -like receptor and the necessary component for the receptor activation. In conclusion, the inhibitory action of BIBN4096BS at the low concentration (10 pM) on the CGRP-tension curve (but not intracellular calcium concentration ([Ca2+]i) resembles what is seen with a reversible competitive antagonist. However, at the higher concentrations (0.1 and 1 nM), BIBN4096BS acts as a selective noncompetitive inhibitor at CGRP1 receptors in human subcutaneous arteries. British Journal of Pharmacology (2004) 143, 1066,1073. doi:10.1038/sj.bjp.0705967 [source]

The effects of heparin and related molecules on vascular permeability and neutrophil accumulation in rabbit skin

Helen Jones
Unfractionated heparin (UH) has been shown to possess a wide range of properties which are potentially anti-inflammatory. Many of these studies, including effects of heparin on adhesion of inflammatory cells to endothelium, have been carried out in vitro. In the present study, we have used radioisotopic techniques to study the effect of UH, and related molecules, on in vivo inflammatory responses (plasma exudation (PE) and PMN accumulation) in rabbit skin induced by cationic proteins, mediators and antigen. Intradermal (i.d.) pretreatment with UH dose-dependently inhibited poly-L-lysine (PLL)-induced responses. The same treatment had no effect on antigen (extract of Alternaria tenuis, AT)-, formyl-methionyl-leucyl-phenylalanine (fMLP)- or leukotriene (LT) B4 -induced responses, although i.d. dextran sulphate (DS) significantly inhibited responses to all of these mediators. High dose (10,000 u kg,1) intravenous UH significantly decreased cutaneous responses to fMLP and LTB4. By comparison, the selectin inhibitor, fucoidin, and DS, were very effective inhibitors of these responses, and of responses to AT and PLL. In contrast to the weak effect in the in vivo studies, UH significantly inhibited in vitro homotypic aggregation of rabbit PMNs, showing that it can modify PMN function. Our data with i.d. UH confirm the important ability of this molecule to interact with and neutralize polycationic peptides in vivo, suggesting that this is a prime role of endogenous heparin. The lack of effect of exogenous heparin on acute inflammatory responses induced by allergen, suggests that cationic proteins are unlikely to be primary mediators of the allergen-induced PE or PMN accumulation. British Journal of Pharmacology (2002) 135, 469,479; doi:10.1038/sj.bjp.0704505 [source]