Repressor- and activator-type ethylene response factors functioning in jasmonate signaling and disease resistance identified via a genome-wide screen of Arabidopsis transcription factor gene expression

To identify transcription factors (TFs) involved in jasmonate (JA) signaling and plant defense, we screened 1,534 Arabidopsis (Arabidopsis thaliana) TFs by real-time quantitative reverse transcription-PCR for their altered transcript at 6 h following either methyl JA treatment or inoculation with the incompatible pathogen Alternaria brassicicola. We identified 134 TFs that showed a significant change in expression, including many APETALA2/ethylene response factor (AP2/ERF), MYB, WRKY, and NACTF genes with unknown functions. Twenty TF genes were induced by both the pathogen and methyl JA and these included 10 members of the AP2/ERF TF family, primarily from the B1a and B3 subclusters. Functional analysis of the B1a TF AtERF4 revealed that AtERF4 acts as a novel negative regulator of JA-responsive defense gene expression and resistance to the necrotrophic fungal pathogen Fusarium oxysporum and antagonizes JA inhibition of root elongation. In contrast, functional analysis of the B3 TF AtERF2 showed that AtERF2 is a positive regulator of JA-responsive defense genes and resistance to F. oxysporum and enhances JA inhibition of root elongation. Our results suggest that plants coordinately express multiple repressor-and activator-type AP2/ERFs during pathogen challenge to modulate defense gene expression and disease resistance.

Atom probe field ion microscope measurements of carbon segregation at an a:a grain boundary and service failures by intergranular stress corrosion cracking

This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved.

STRESS E REAJUSTAMENTO SOCIAL EM AUXILIARES DE ENFERMAGEM

O presente estudo teve por objetivos, levantar o perfil sócio-demográfico e cultural, de auxiliares de enfermagem, avaliar o grau e presença de sintomas de stress, avaliar e descrever reajustamento social tecendo relação entre variáveis relacionadas ao labor e o stress. Participaram desse estudo 126 auxiliares de enfermagem que cursavam técnico em enfermagem. Utilizou-se os instrumentos: a) questionário Sócio-demográfico e cultural; b) Escala de Reajustamento Social de Holmes-Rahe e c) Inventário de Sintomas de Stress de Lipp (ISSL). Os dados foram coletados em salas de aula, de três escolas técnicas da grande São Paulo e esses dados foram tratados estatisticamente pelos testes X² e r Person para as relações entre variáveis, com auxílio do programa SPSS versão 17. Os resultados indicaram uma predominância de pessoas do gênero feminino, casados, com idade mínima de 19 anos e máxima de 56 anos e com práticas religiosas católicas e evangélicas. Desses profissionais (79%) trabalhavam em um só emprego, com experiência na profissão de cinco anos e o setor com maior quantidade de profissionais foi o home care . A maioria dos profissionais exercia suas atividades no horário matutino, e estudava no horário noturno. O estudo indicou que 57,9% apresentaram grau de stress significativo. Dentro deste grau de stress significativo, 41,3% dos profissionais estavam na fase de resistência e 37,3% dos auxiliares com grau de stress significativo, apresentavam predominância de stress de natureza psicológica. Quanto ao reajustamento social, os auxiliares de enfermagem a maioria, que correspondia a 48,4% estava dentro da média, com chances razoáveis de adoecer, ou seja, apresentavam capacidade regular para adaptação aos eventos novos e desconhecidos que ocorrem durante a vida. Os resultados indicaram que os profissionais que apresentaram stress significativo obtiveram pontuação maior (média) na escala de reajustamento social, em comparação aos profissionais que não apresentaram stress, indicando que esses sujeitos tinham maior probabilidade de estarem adoecidos ou virem a adoecer.

An exploratory study to determine applicability of nano-hardness and micro-compression measurements for yield stress estimation

The superior properties of ferritic/martensitic steels in a radiation environment (low swelling, low activation under irradiation and good corrosion resistance) make them good candidates for structural parts in future reactors and spallation sources. While it cannot substitute for true reactor experiments, irradiation by charged particles from accelerators can reduce the number of reactor experiments and support fundamental research for a better understanding of radiation effects in materials. Based on the nature of low energy accelerator experiments, only a small volume of material can be uniformly irradiated. Micro and nanoscale post irradiation tests thus have to be performed. We show here that nanoindentation and micro-compression testing on T91 and HT-9 stainless steel before and after ion irradiation are useful methods to evaluate the radiation induced hardening.

An age-related increase in resistance to DNA damage-induced apoptotic cell death is associated with development of DNA repair mechanisms

Neurons in the developing brain die via apoptosis after DNA damage, while neurons in the adult brain are generally resistant to these insults. The basis for this resistance is a matter of conjecture. We report here that cerebellar granule neurons (CGNs) in culture lose their competence to die in response to DNA damage as a function of time in culture. CGNs at either 1 day in vitro (DIV) or 7 DIV were treated with the DNA damaging agents camptothecin, UV or gamma-irradiation and neuronal survival measured. The younger neurons were effectively killed by these agents, while the older neurons displayed a significant resistance to killing. Neuronal survival did not change with time in culture when cells were treated with C2-ceramide or staurosporine, agents which do not target DNA. The resistance to UV irradiation developed over time in culture and was not due to changes in mitotic rate. Increases in DNA strand breakage, up-regulation of the levels of both p53 and its phosphorylated form and nuclear translocation of p53 were equivalent in both older and younger neurons, indicating a comparable p53 stress response. In addition, we show that treatment of older neurons with pharmacological inhibitors of distinct components of the DNA repair machinery promotes the accumulation of DNA damage and sensitizes these cells to the toxic effects of UV exposure. These data demonstrate that older neurons appear to be more proficient in DNA repair in comparison to their younger counterparts, and that this leads to increased survival after DNA damage.

Viscoelasticity and high buckling stress of dense carbon nanotube brushes

We report on the mechanical behavior of a dense brush of small-diameter (1–3 nm) non-catalytic multiwall (2–4 walls) carbon nanotubes (CNTs), with ~10 times higher density than CNT brushes produced by other methods. Under compression with spherical indenters of different radii, these highly dense CNT brushes exhibit a higher modulus (~17–20 GPa) and orders of magnitude higher resistance to buckling than vapor phase deposited CNT brushes or carbon walls. We also demonstrate the viscoelastic behavior, caused by the increased influence of the van der Waals’ forces in these highly dense CNT brushes, showing their promise for energy-absorbing coatings.

The role of redox signaling in the molecular mechanism of tamoxifen resistance in breast cancer.

The emergence of tamoxifen or aromatase inhibitor resistance is a major problem in the treatment of breast cancer. The molecular signaling mechanism of antiestrogen resistance is not clear. Understanding the mechanisms by which resistance to these agents arise could have major clinical implications for preventing or circumventing it. Therefore, in this dissertation we have investigated the molecular mechanisms underlying antiestrogen resistance by studying the contributions of reactive oxygen species (ROS)-induced redox signaling pathways in antiestrogen resistant breast cancer cells. Our hypothesis is that the conversion of breast tumors to a tamoxifen-resistant phenotype is associated with a progressive shift towards a pro-oxidant environment of cells as a result of oxidative stress. The hypothesis of this dissertation was tested in an in vitro 2-D cell culture model employing state of the art biochemical and molecular techniques, including gene overexpression, immunoprecipitation, Western blotting, confocal imaging, ChIP, Real-Time RT-PCR, and anchorage-independent cell growth assays. We observed that tamoxifen (TAM) acts like both an oxidant and an antioxidant. Exposure of tamoxifen resistant LCC2 cell to TAM or 17 beta-estradiol (E2) induced the formation of reactive oxidant species (ROS). The formation of E2-induced ROS was inhibited by co-treatment with TAM, similar to cells pretreated with antioxidants. In LCC2 cells, treatments with either E2 or TAM were capable of inducing cell proliferation which was then inhibited by biological and chemical antioxidants. Exposure of LCC2 cells to tamoxifen resulted in a decrease in p27 expression. The LCC2 cells exposed to TAM showed an increase in p27 phosphorylation on T157 and T187. Conversely, antioxidant treatment showed an increase in p27 expression and a decrease in p27 phosphorylation on T157 and T187 in TAM exposed cells which were similar to the effects of Fulvestrant. In line with previous studies, we showed an increase in the binding of cyclin E-Cdk2 and in the level of p27 in TAM exposed cells that overexpressed biological antioxidants. Together these findings highly suggest that lowering the oxidant state of antiestrogen resistant LCC2 cells, increases LCC2 susceptibility to tamoxifen via the cyclin dependent kinase inhibitor p27.

X-linked inhibitor of apoptosis protein mediates tumor cell resistance to antibody-dependent cellular cytotoxicity.

Inflammatory breast cancer (IBC) is the deadliest, distinct subtype of breast cancer. High expression of epidermal growth factor receptors [EGFR or human epidermal growth factor receptor 2 (HER2)] in IBC tumors has prompted trials of anti-EGFR/HER2 monoclonal antibodies to inhibit oncogenic signaling; however, de novo and acquired therapeutic resistance is common. Another critical function of these antibodies is to mediate antibody-dependent cellular cytotoxicity (ADCC), which enables immune effector cells to engage tumors and deliver granzymes, activating executioner caspases. We hypothesized that high expression of anti-apoptotic molecules in tumors would render them resistant to ADCC. Herein, we demonstrate that the most potent caspase inhibitor, X-linked inhibitor of apoptosis protein (XIAP), overexpressed in IBC, drives resistance to ADCC mediated by cetuximab (anti-EGFR) and trastuzumab (anti-HER2). Overexpression of XIAP in parental IBC cell lines enhances resistance to ADCC; conversely, targeted downregulation of XIAP in ADCC-resistant IBC cells renders them sensitive. As hypothesized, this ADCC resistance is in part a result of the ability of XIAP to inhibit caspase activity; however, we also unexpectedly found that resistance was dependent on XIAP-mediated, caspase-independent suppression of reactive oxygen species (ROS) accumulation, which otherwise occurs during ADCC. Transcriptome analysis supported these observations by revealing modulation of genes involved in immunosuppression and oxidative stress response in XIAP-overexpressing, ADCC-resistant cells. We conclude that XIAP is a critical modulator of ADCC responsiveness, operating through both caspase-dependent and -independent mechanisms. These results suggest that strategies targeting the effects of XIAP on caspase activation and ROS suppression have the potential to enhance the activity of monoclonal antibody-based immunotherapy.

Influence of grinding operations on surface integrity and chloride induced stress corrosion cracking of stainless steels

Stainless steels were developed in the early 20th century and are used where both the mechanical properties of steels and corrosion resistance are required. There is continuous research to allow stainless steel components to be produced in a more economical way and be used in more harsh environments. A necessary component in this effort is to correlate the service performance with the production processes. The central theme of this thesis is the mechanical grinding process.  This is commonly used for producing stainless steel components, and results in varied surface properties that will strongly affect their service life. The influence of grinding parameters including abrasive grit size, machine power and grinding lubricant were studied for 304L austenitic stainless steel (Paper II) and 2304 duplex stainless steel (Paper I). Surface integrity was proved to vary significantly with different grinding parameters. Abrasive grit size was found to have the largest influence. Surface defects (deep grooves, smearing, adhesive/cold welding chips and indentations), a highly deformed surface layer up to a few microns in thickness and the generation of high level tensile residual stresses in the surface layer along the grinding direction were observed as the main types of damage when grinding stainless steels. A large degree of residual stress anisotropy is interpreted as being due to mechanical effects dominating over thermal effects. The effect of grinding on stress corrosion cracking behaviour of 304L austenitic stainless steel in a chloride environment was also investigated (Paper III). Depending on the surface conditions, the actual loading by four-point bend was found to deviate from the calculated value using the formula according to ASTM G39 by different amounts. Grinding-induced surface tensile residual stress was suggested as the main factor to cause micro-cracks initiation on the ground surfaces. Grinding along the loading direction was proved to increase the susceptibility to chloride-induced SCC, while grinding perpendicular to the loading direction improved SCC resistance. The knowledge obtained from this work can provide a reference for choosing appropriate grinding parameters when fabricating stainless steel components; and can also be used to help understanding the failure mechanism of ground stainless steel components during service.

CpxR activates MexAB-OprM efflux pump expression and enhances antibiotic resistance in both laboratory and clinical nalB-type isolates of Pseudomonas aeruginosa

Resistance-Nodulation-Division (RND) efflux pumps are responsible for multidrug resistance in Pseudomonas aeruginosa. In this study, we demonstrate that CpxR, previously identified as a regulator of the cell envelope stress response in Escherichia coli, is directly involved in activation of expression of RND efflux pump MexAB-OprM in P. aeruginosa. A conserved CpxR binding site was identified upstream of the mexA promoter in all genome-sequenced P. aeruginosa strains. CpxR is required to enhance mexAB-oprM expression and drug resistance, in the absence of repressor MexR, in P. aeruginosa strains PA14. As defective mexR is a genetic trait associated with the clinical emergence of nalB-type multidrug resistance in P. aeruginosa during antibiotic treatment, we investigated the involvement of CpxR in regulating multidrug resistance among resistant isolates generated in the laboratory via antibiotic treatment and collected in clinical settings. CpxR is required to activate expression of mexAB-oprM and enhances drug resistance, in the absence or presence of MexR, in ofloxacin-cefsulodin-resistant isolates generated in the laboratory. Furthermore, CpxR was also important in the mexR-defective clinical isolates. The newly identified regulatory linkage between CpxR and the MexAB-OprM efflux pump highlights the presence of a complex regulatory network modulating multidrug resistance in P. aeruginosa.

”Stress Monitoring via Wearable Electrodermal Sensors”

Stress is a phenomenon that on some level affects everyone’s lives on a daily basis. The autonomic nervous system controls the varying levels of stress at any given time. The responses of the autonomic nervous system adjust the body to cope with changing external and internal conditions. During high-stress situations the body is forced into a state of heightened alertness, which passes when the stressor is removed. The stressor can be any external or internal event that causes the body to respond. Stress is a very versatile phenomenon that can be both a cause and an indicator of other medical conditions, for example cardiovascular disease. Stress detection can therefore be helpful in identifying these conditions and monitoring the overall emotional state of a person. Electrodermal activity (EDA) is one of the most easily implemented ways to monitor the activity of the autonomic nervous system. EDA describes changes occurring in the various electrical properties of the skin, including skin conductivity and resistance. Increased emotional sweating has been proven to be one possible indication of stress. On the surface of the skin, increased sweating translates to increased skin conductivity, which can be observed through EDA measurements. This makes electrodermal activity a very useful tool in a wide range of applications where it is desirable to observe changes in a person’s stress level. EDA can be recorded by using specialized body sensors placed on specific locations on the body. Most commonly used recording sites are the palms of the hands due to the high sweat gland density on those areas. Measurement is done using at least two electrodes attached to the skin, and recording the electrical conductance between them. This thesis implements a prototype of a wireless EDA measurement system. The feasibility of the prototype is also verified with a small group of test subjects. EDA was recorded from the subjects while they were playing a game of Tetris. The goal was to observe variations in the measured EDA that would indicate changes in the subjects’ stress levels during the game. The analysis of the obtained measurement results confirmed the connection between stress and recorded EDA. During the game, random occurrences of lowered skin resistance were clearly observable, which indicates points in the game where the player felt more anxious. A wireless measurement system has the potential of offering more flexible and comfortable long-term measuring of EDA, and could be utilized in a wide range of applications.

Soybean ferritin expression in saccharomyces cerevisiae modulates iron accumulation and resistance to elevated iron concentrations.

Fungi, including the yeast Saccharomyces cerevisiae, lack ferritin and use vacuoles as iron storage organelles. This work explored how plant ferritin expression influenced baker's yeast iron metabolism. Soybean seed ferritin H1 (SFerH1) and SFerH2 genes were cloned and expressed in yeast cells. Both soybean ferritins assembled as multimeric complexes, which bound yeast intracellular iron in vivo and, consequently, induced the activation of the genes expressed during iron scarcity. Soybean ferritin protected yeast cells that lacked the Ccc1 vacuolar iron detoxification transporter from toxic iron levels by reducing cellular oxidation, thus allowing growth at high iron concentrations. Interestingly, when simultaneously expressed in ccc1Δ cells, SFerH1 and SFerH2 assembled as heteropolymers, which further increased iron resistance and reduced the oxidative stress produced by excess iron compared to ferritin homopolymer complexes. Finally, soybean ferritin expression led to increased iron accumulation in both wild-type and ccc1Δ yeast cells at certain environmental iron concentrations.

Influence of phosphine resistance genes on flight propensity and resource location in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae): the landscape for selection

Phosphine resistance in Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) has evolved through changes to enzymes involved in basic metabolic pathways. These changes impose metabolic stress and could affect energy-demanding behaviours. We therefore tested whether phosphine resistance alleles impact the movement of these insects in their quest for new resources. We measured walking and flight parameters of four T. castaneum genotypes: (1) a field-derived population, (2) a laboratory cultured, phosphine-susceptible reference strain, (3) a laboratory cultured, phosphine-resistant reference strain, and (4) a resistant introgressed strain that is almost identical genetically to the susceptible population. The temporal pattern of flight was identical across all populations, but resistant beetles took flight significantly less, walked more slowly, and located resources less successfully than did susceptible beetles. Also, the field-derived beetles (proved not to be carrying resistance genes) walked significantly faster and more directly towards food resources, and had a higher propensity for flight when compared to the susceptible laboratory beetles. These negative effects suggest survival of beetles with the resistance alleles will be compromised should they leave phosphine application sites. The field for selection therefore extends beyond the site at which phosphine fumigant imposed its effect, and other mutations are also likely to be affected in this way.

Influence of implant-abutment angulations and crown material on stress distribution on central incisor: a 3D FEA

Aim: To investigate the effect of implant-abutment angulation and crown material on stress distribution of central incisors. Finite element method was used to simulate the clinical situation of a maxillary right central incisor restored by two different implant-abutment angulations, 15° and 25°, using two different crown materials (IPS E-Max CAD and zirconia). Methods: Two 3D finite element models were specially prepared for this research simulating the abutment angulations. Commercial engineering CAD/CAM package was used to model crown, implant abutment complex and bone (cortical and spongy) in 3D. Linear static analysis was performed by applying a 178 N oblique load. The obtained results were compared with former experimental results. Results: Implant Von Mises stress level was negligibly changed with increasing abutment angulation. The abutment with higher angulation is mechanically weaker and expected to fail at lower loading in comparison with the steeper one. Similarly, screw used with abutment angulation of 25° will fail at lower (about one-third) load value the failure load of similar screw used with abutment angulated by 15°. Conclusions: Bone (cortical and spongy) is insensitive to crown material. Increasing abutment angulation from 15° to 25°, increases stress on cortical bone by about 20% and reduces it by about 12% on spongy bone. Crown fracture resistance is dramatically reduced by increasing abutment angulation. Zirconia crown showed better performance than E-Max one.

Effect of high densities on growth, stress response and plasma amino acid levels in senegalese sole (Solea senegalensis, Kaup 1858)

Dissertação de mest. em Aquacultura e Pescas, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2006