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Intake, water consumption, ruminal fermentation, and stress response of beef heifers fed after different lengths of delays in the daily feed delivery time

GONZALEZ, L. A.; CORREA, L. B.; FERRET, A.; MANTECA, X.; RUIZ-DE-LA-TORRE, J. L.; CALSAMIGLIA, S.
Fonte: AMER SOC ANIMAL SCIENCE Publicador: AMER SOC ANIMAL SCIENCE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
45.99%
Four rumen-fistulated Holstein heifers (134 +/- 1 kg initial BW) were used in a 4 x 4 Latin square design to determine the effects of delaying daily feed delivery time on intake, ruminal fermentation, behavior, and stress response. Each 3-wk experimental period was preceded by 1 wk in which all animals were fed at 0800 h. Feed bunks were cleaned at 0745 h and feed offered at 0800 h (T0, no delay), 0900 (T1), 1000 (T2), and 1100 (T3) from d1 to 21 with measurements taken during wk 1 and 3. Heifers were able to see each other at all times. Concentrate and barley straw were offered in separate compartments of the feed bunks, once daily and for ad libitum intake. Ruminal pH and saliva cortisol concentrations were measured at 0, 4, 8, and 12 h postfeeding on d 3 and 17 of each experimental period. Fecal glucocorticoid metabolites were measured on d 17. Increasing length of delay in daily feed delivery time resulted in a quadratic response in concentrate DMI (low in T1 and T2; P = 0.002), whereas straw DMI was greatest in T1 and T3 (cubic P = 0.03). Treatments affected the distribution of DMI within the day with a linear decrease observed between 0800 and 1200 h but a linear increase during nighttimes (2000 to 0800 h), whereas T1 and T2 had reduced DMI between 1200 and 1600 h (quadratic P = 0.04). Water consumption (L/d) was not affected but decreased linearly when expressed as liters per kilogram of DMI (P = 0.01). Meal length was greatest and eating rate slowest in T1 and T2 (quadratic P <= 0.001). Size of the first meal after feed delivery was reduced in T1 on d 1 (cubic P = 0.05) and decreased linearly on d 2 (P = 0.01) after change. Concentrate eating and drinking time (shortest in T1) and straw eating time (longest in T1) followed a cubic trend (P = 0.02). Time spent lying down was shortest and ruminating in standing position longest in T1 and T2. Delay of feeding time resulted in greater daily maximum salivary cortisol concentration (quadratic P = 0.04)...

Efeito do estresse e da suplementação com vitamina E sobre parâmetros seminais, peroxidação lipídica de componentes seminais e atividade das enzimas antioxidantes presentes no plasma seminal de cães; Effect of stress and oral supplementation with vitamin E on seminal parameteres, lipidic oxidation of seminal components and antioxidants enzymes activies in the seminal plasm in dogs

Hatamoto, Luciana Keiko
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/07/2004 PT
Relevância na Pesquisa
36.11%
O presente trabalho visou avaliar se, em cães, o estresse provoca efeitos deletérios sobre os parâmetros seminais e a composição do plasma seminal. Além disso, avaliou-se os efeitos da suplementação oral com vitamina E em animais estressados. Utilizaram-se 18 cães machos da raça rotweiller, com idade média de 4 anos. O tratamento foi inteiramente casualizado com esquema fatorial 2x2 (com e sem estresse X com e sem vitamina E). Os animais dos grupos suplementados com vitamina E receberam 500 mg de -tocoferol/animal/dia. O estresse foi induzido, sete dias após o início da suplementação com vitamina E através da aplicação intramuscular de 0,01mg/kg de dexametasona, durante 7 dias consecutivos. O estresse foi caracterizado através do cortisol sérico, consumo alimentar, escore corporal e peso vivo. Foram feitas duas colheitas semanais de sêmen através de manipulação digital e uma coleta semanal se sangue. Os parâmetros utilizados para avaliar os efeitos do tratamento foram: volume, densidade e pH do ejaculado, motilidade, vigor, concentração e morfologia espermáticos, integridade da membrana espermática (teste de expansão hipo-osmótico, coloração fluorescente IP/DCF, coloração tripla, coloração acrossomal simples e viabilidade espermática)...

Respostas de pêlos radiculares de tomateiro (Solanum lycopersicum L. cv Micro-Tom) submetidos a estresse por pH baixo e hipo-osmolaridade; Response of tomato (Solanum lycopersicum L. cv Micro-Tom) root hairs to low pH and hypo-osmotic stress

Sardinha, Elissena Chinaglia Zabotto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/11/2010 PT
Relevância na Pesquisa
46.22%
A acidez do solo é um dos principais fatores limitantes à produção vegetal. A toxicidade por alumínio, que ocorre apenas a pH baixo, tem sido extensamente investigada, enquanto o estresse causado pelo pH baixo tem recebido pouca atenção. Os estudos nesta área quase sempre presumem efeitos aditivos, e portanto independentes, da toxicidade por Al3+ e H+. Este provavelmente não é o caso, sendo que o pH baixo pode ser um fator de predisposição das células ao Al3+. As evidências indicam que o pH baixo causa desarranjos na parede de células em crescimento, gerando estresse que pode comprometer a sua funcionalidade e integridade. É provável que a susceptibilidade a este estresse deve ser dependente da pressão de turgor. Por sua vez, o metabolismo oxidativo e a geração de espécies reativas de oxigênio (ROS) na parede celular podem modular a sua extensibilidade por romper ou criar ligações dentro ou entre cadeias de polissacarídeo. Há grande interesse em se conhecer se, à semelhança do que ocorre em leveduras, as células vegetais possuem um sistema de percepção e resposta a estresse da parede. Os pêlos radiculares em crescimento são sensíveis a pH baixo e estresse hipo-osmótico e constituem um bom modelo experimental para estes estudos. Os objetivos deste trabalho foram: a) Otimizar um sistema experimental para o estudo de pêlos radiculares de tomateiro (Solanum lycopersicum L. cv Micro-Tom); b) Avaliar as respostas dos pêlos radiculares ao estresse por pH baixo e hipo-osmolaridade; c) Examinar o papel da modulação oxidativa da parede celular nestas respostas; e d) Avaliar a resposta de diferentes mutantes hormonais de Micro-Tom a estes fatores de estresse. Os principais parâmetros avaliados foram a taxa de alongamento (µm.min-1) e a freqüência de rompimento dos pêlos. Tanto o estresse por pH baixo quanto choques hipo-osmóticos resultaram em taxas de alongamento significativamente diminuídos e o rompimento de pêlos radiculares...

Modelagem da fratura por corrosão sob tensão nos bocais do mecanismo de acionamento das barras de controle de reator de água pressurizada"; Modeling of primary water stress corrosion cracking at control rod drive mechanism nozzles of Pressurized Water Reactors

Aly, Omar Fernandes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/06/2006 PT
Relevância na Pesquisa
36.08%
Um dos principais mecanismos de falha que causam riscos de fratura a reatores de água pressurizada é a corrosão sob tensão de ligas metálicas em água do circuito primário (CSTAP). É causada por uma combinação das tensões de tração, meio ambiente em temperatura e microestruturas metalúrgicas susceptíveis. Ela pode ocorrer, dentre outros locais, nos bocais do mecanismo de acionamento das barras de controle. Essa fratura pode causar acidentes que comprometem a segurança nuclear através do bloqueio das barras de controle e vazamentos de água do circuito primário reduzindo a confiabilidade e a vida útil do reator. O objetivo desta Tese de Doutorado é o estudo de modelos e uma proposta de modelagem para fraturas por corrosão sob tensão em liga 75Ni15Cr9Fe (liga 600), em água de circuito primário de reator de água pressurizada nesses bocais. São superpostos modelos eletroquímicos e de mecânica da fratura e validados com dados obtidos em experimentos e na literatura. Na parte experimental foram utilizados resultados obtidos pelo CDTN no equipamento recém-instalado de ensaio por taxa de deformação lenta. Na literatura está proposto um diagrama que exprime a condição termodinâmica de ocorrerem diversos modos de CSTAP na liga 600: partiu-se de diagramas de potencial x pH (diagramas de Pourbaix)...

Balance of pH of chicks from eggs injected with ascorbic acid and subjected to thermal stress

Sgavioli, Sarah; De Almeida, Vitor R.; De Morita, Viviane S.; Zaniratu, Gisele L.; De Oliveira, João A.; Boleli, Isabel C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 708-713
ENG
Relevância na Pesquisa
36.08%
This study aimed to verify that chicks from eggs injected with ascorbic acid and subjected to heat stress would have changes in acid-base balance, compared to chicks incubated at thermoneutral without injection of ascorbic acid. The parameters evaluated were blood pressure of carbon dioxide and oxygen, base excess, total carbon dioxide, concentration of sodium, potassium, ionized calcium, bicarbonate and pH of newly hatched male chicks, hatched from eggs injected with acid ascorbic acid (AA) and subjected to heat stress during incubation. The experimental design was completely randomized in factorial scheme 5 (application levels of ascorbic acid) x 2 (incubation temperatures). The data were subjected to analysis of variance using the General Linear Model procedure (GLM) of SAS ®. For the blood pH was observed significant interaction (p <0.05) between treatments with application in eggs and incubation temperatures. For the other parameters were not significant effects (p< 0.05) of AA level and neither temperature of incubation. Analyzing the unfolding of the interaction to pH was observed that chicks from eggs injected with 6% ascorbic acid and subjected to heat stress during incubation had a higher pH value compared with the thermoneutral temperature incubated (p <0.05). Therefore...

Aeromonas proteome in response to stress; Proteoma de Aeromonas em resposta ao stress

Honório, Filipe Manuel Ramalhete
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
36.26%
O género Aeromonas é frequentemente associado a uma distribuição ampla no meio ambiente, emergindo como importantes patogénicos de seres humanos. No entanto, a complexidade dos mecanismos de patogenicidade permanece desconhecida e nenhum factor de virulência foi até hoje identificado individualmente como responsável pela patogenicidade. Vários factores de virulência bacteriana podem sofrer uma regulação ambiental por meio de diversos factores abióticos, permitindo a bactérias patogénicas coordenarem a expressão de factores de virulência com a existência de condições favoráveis. Análise de respostas ao stress é fundamental, especialmente no contexto de bactérias patogénicas. No entanto, investigações sobre proteínas e mecanismos associados à resistência ao stress são escassos ou inexistentes para diversas bactérias, principalmente patogénicos incomuns ou oportunistas, como as Aeromonas. Os objectivos deste estudo são a avaliação do proteoma da bactéria, Aeromonas piscicola, em resposta ao stress e desvendar proteínas com variação na expressõa, envolvidas na resposta ao stress. Para atingir estes objectivos procedeu-se à avaliação do proteoma diferencial sob stress causado independentemente por temperatura...

Effect of heat and pH stress in the growth of chickpea mesorhizobia

Rodrigues, Carla; Laranjo, Marta; Oliveira, Solange
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 32946 bytes; application/pdf
ENG
Relevância na Pesquisa
46.11%
Abstract The development of rhizobial inoculants requires the selection of isolates that are symbiotically efficient as well as adapted to the local environmental conditions. Our aim was to find indigenous chickpea rhizobia tolerant to adverse environmental conditions, such as temperature and pH. Thirteen isolates of chickpea mesorhizobia from southern Portugal were examined. Tolerance to stress temperatures and pH was evaluated by quantification of bacterial growth at 20–37°C and pH 5–9, respectively. Tolerance to heat shocks was studied by submitting isolates to 46°C and 60°C. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis protein analysis revealed qualitative and quantitative differences when isolates were submitted to temperature stress. A 60-kDa protein was overproduced by all isolates under heat stress. Almost all isolates revealed to be more tolerant to 20°C than to 37°C. A positive correlation was found between the maximum growth pH and the isolate origin soil pH. Generally, isolates more tolerant to temperature stress showed a lower symbiotic efficiency.

Tolerance of Mesorhizobium type strains to different environmental stresses

Laranjo, Marta; Oliveira, Solange
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
36.13%
The symbiosis between rhizobia and legumes is affected by different environmental conditions. Our aims were to evaluate stress tolerance of Mesorhizobium species and investigate species-specific stress response mechanisms. Tolerance of Mesorhizobium type strains to temperature, salt and pH stress was evaluated. Mesorhizobium thiogangeticum showed highest growth with 1.5% NaCl and Mesorhizobium ciceri at pH 5. Mesorhizobium plurifarium showed higher growth at 37A degrees C. SDS-PAGE analysis revealed changes in the protein profiles, namely the overexpression of a 60 kDa protein, following heat stress. Under salt stress, five overexpressed proteins were identified in M. plurifarium and M. thiogangeticum. Northern analysis revealed an increase in groEL expression in Mesorhizobium huakuii and Mesorhizobium septentrionale after heat shock; by contrast, a decrease was detected in Mesorhizobium albiziae and M. thiogangeticum, upon salt shock. A high diversity in tolerance to temperature, salt and pH stress was detected among Mesorhizobium species. M. thiogangeticum and M. ciceri are moderately halophilic and acidophilic, respectively. Several proteins, overproduced in different strains, may be involved in stress tolerance. groEL expression increased upon heat and decreased upon salt shock. To our knowledge...

Salt Stress-Induced Cytoplasmic Acidification and Vacuolar Alkalization in Nitellopsis obtusa Cells 1: In Vivo31P-Nuclear Magnetic Resonance Study

Katsuhara, Maki; Kuchitsu, Kazuyuki; Takeshige, Kazuhiko; Tazawa, Masashi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1989 EN
Relevância na Pesquisa
36.11%
Time courses of cytoplasmic and vacuolar pH changes under salt stress were monitored by in vivo31P-nuclear magnetic resonance spectroscopy in intact cells of Nitellopsis obtusa. When cells were treated with 100 millimolar NaCl for 2 hours, the cytoplasmic pH deceased from 7.2 to 7.0, while the vacuolar pH increased from 4.9 to 5.2. This salt-induced breakdown of the pH gradient between the cytoplasm and the vacuole was also confirmed through direct measurements of change in vacuolar pH with a micro-pH electrode. We speculate that the intracellular pH changes induced by the salt stress mainly results from the inhibition of the H+-translocating pyrophosphatase in the vacuolar membrane, since this H+-translocating system is sensitive to salt-induced increase in the cytoplasmic [Na+] and a simultaneous decrease in the cytoplasmic [K+]. Since disturbance of the cytoplasmic pH value should have serious consequences on the homeostasis of living cells, we propose that the salt-induced intracellular pH changes are one of initial and important steps that lead to cell death.

The role of the protein kinase A pathway in the response to alkaline pH stress in yeast

Casado, Carlos; González, Asier; Platara, Maria; Ruiz, Amparo; Ariño, Joaquín
Fonte: Portland Press Ltd. Publicador: Portland Press Ltd.
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.15%
Exposure of Saccharomyces cerevisiae to alkaline pH provokes a stress condition that generates a compensatory reaction. In the present study we examined a possible role for the PKA (protein kinase A) pathway in this response. Phenotypic analysis revealed that mutations that activate the PKA pathway (ira1 ira2, bcy1) tend to cause sensitivity to alkaline pH, whereas its deactivation enhances tolerance to this stress. We observed that alkalinization causes a transient decrease in cAMP, the main regulator of the pathway. Alkaline pH causes rapid nuclear localization of the PKA-regulated Msn2 transcription factor which, together with Msn4, mediates a general stress response by binding with STRE (stress response element) sequences in many promoters. Consequently, a synthetic STRE–LacZ reporter shows a rapid induction in response to alkaline stress. A msn2 msn4 mutant is sensitive to alkaline pH, and transcriptomic analysis reveals that after 10 min of alkaline stress, the expression of many induced genes (47%) depends, at least in part, on the presence of Msn2 and Msn4. Taken together, these results demonstrate that inhibition of the PKA pathway by alkaline pH represents a substantial part of the adaptive response to this kind of stress and that this response involves Msn2/Msn4-mediated genome expression remodelling. However...

Low pH Environmental Stress Inhibits LPS and LTA-Stimulated Proinflammatory Cytokine Production in Rat Alveolar Macrophages

Fernandez, Stanley F.; Fung, Christopher; Helinski, Jadwiga D.; Alluri, Ravi; Davidson, Bruce A.; Knight, Paul R.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.11%
Gastric aspiration increases the risks for developing secondary bacterial pneumonia. Cytokine elaboration through pathogen recognition receptors (PRRs) is an important mechanism in initiating innate immune host response. Effects of low pH stress, a critical component of aspiration pathogenesis, on the PRR pathways were examined, specifically toll-like receptor-2 (TLR2) and TLR4, using isolated rat alveolar macrophages (aMØs). We assessed the ability of aMØs after brief exposure to acidified saline to elaborate proinflammatory cytokines in response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) stimulation, known ligands of TLR4 and TLR2, respectively. Low pH stress reduced LPS- and LTA-mediated cytokine release (CINC-1, MIP-2, TNF-α, MCP-1, and IFN-β). LPS and LTA increased intracellular Ca2+ concentrations while Ca2+ chelation by BAPTA decreased LPS- and LTA-mediated cytokine responses. BAPTA blocked the effects of low pH stress on most of LPS-stimulated cytokines but not of LTA-stimulated responses. In vivo mouse model demonstrates suppressed E. coli and S. pneumoniae clearance following acid aspiration. In conclusion, low pH stress inhibits antibacterial cytokine response of aMØs due to impaired TLR2 (MyD88 pathway) and TLR4 signaling (MyD88 and TRIF pathways). The role of Ca2+ in low pH stress-induced signaling is complex but appears to be distinct between LPS- and LTA-mediated responses.

The Acid Test of Fluoride: How pH Modulates Toxicity

Tsuchiya, Masahiro; Skobe, Ziedonis; Sharma, Ramaswamy Narayanaswamy; Tannous, Bakhos A.; Bartlett, John D.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.15%
Background: It is not known why the ameloblasts responsible for dental enamel formation are uniquely sensitive to fluoride ((F^−)). Herein, we present a novel theory with supporting data to show that the low pH environment of maturating stage ameloblasts enhances their sensitivity to a given dose of (F^−). Enamel formation is initiated in a neutral pH environment (secretory stage); however, the pH can fall to below 6.0 as most of the mineral precipitates (maturation stage). Low pH can facilitate entry of (F^−) into cells. Here, we asked if (F^−) was more toxic at low pH, as measured by increased cell stress and decreased cell function. Methodology/Principal Findings: Treatment of ameloblast-derived LS8 cells with (F^−) at low pH reduced the threshold dose of (F^−) required to phosphorylate stress-related proteins, PERK, eIF2α, JNK and c-jun. To assess protein secretion, LS8 cells were stably transduced with a secreted reporter, Gaussia luciferase, and secretion was quantified as a function of (F^−) dose and pH. Luciferase secretion significantly decreased within 2 hr of (F^−) treatment at low pH versus neutral pH, indicating increased functional toxicity. Rats given 100 ppm (F^−) in their drinking water exhibited increased stress-mediated phosphorylation of eIF2α in maturation stage ameloblasts (pH<6.0) as compared to secretory stage ameloblasts (pH∼7.2). Intriguingly...

Resposta de gen??tipos de arroz (Oryza sativa L.) ao estresse por ??cidos org??nicos sob condi????es de ambiente controlado; Organic acid related stress responses in rice (Oryza sativa L.) genotypes under ambient controlled conditions

KOPP, Mauricio Marini
Fonte: Universidade Federal de Pelotas; Agronomia; Programa de P??s-Gradua????o em Fitomelhoramento; UFPel; BR Publicador: Universidade Federal de Pelotas; Agronomia; Programa de P??s-Gradua????o em Fitomelhoramento; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.1%
Hydromorphic soils present as main feature a reduced natural drainage ability, being mostly used for growing irrigated rice. Thus, the occurrence of anaerobic conditions associated to the presence of organic matter enables the development of anaerobic microorganisms which, while decomposing the organic matter, generate phytotoxic substances represented mainly by short chain aliphatic organic acids. The selection of promising genotypes adapted for use in these situations requires complicated field evaluations, which can be simulated under hydroponic culture. The research was composed of four articles that had as major goals to establish an adequate methodology for growing rice under organic acid rich hydroponic culture. The first work aimed at determining the range of concentrations and response variables most indicated for evaluating rice genotypes under hydroponics. The effects of six different concentrations for the three major acids formed in the soil: acetic (0; 4; 8; 12; 16 and 20 mM), propionic (0; 3; 6; 9; 12 and 15 mM) and butyric (0; 2; 4; 6; 8 and 10 mM) acids in two genotypes of high divergence (BRS 7-TAIM and SAIBAN). The results indicated that the most adequate concentration range for organic acid studies in rice are between 15.8 and 8.4; 9.1 and 4.2 and 7.7 and 3.7 mM for acetic...

Reatividade animal e indicadores fisiol??gicos de estresse: avalia????o das suas rela????es com a qualidade final da carne bovina em distintos per??odos de jejum pr??-abate; Reatividade animal e indicadores fisiol??gicos de estresse: avalia????o das suas rela????es com a qualidade final da carne bovina em distintos per??odos de jejum pr??-abate; Animal reactivity and stress physiological indicators: relationship with bovine meat final quality under different pre-slaughter fasting periods.; Animal reactivity and stress physiological indicators: relationship with bovine meat final quality under different pre-slaughter fasting periods.

MOURA, Sandra Vieira de
Fonte: Universidade Federal de Pelotas; Zootecnia; Programa de P??s-Gradua????o em Zootecnia; UFPel; BR Publicador: Universidade Federal de Pelotas; Zootecnia; Programa de P??s-Gradua????o em Zootecnia; UFPel; BR
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.12%
Evaluation was made of the effect of different pre-slaughter fasting periods on animal reactivity, physiological stress indicators and final meat quality, considering glucose as a potential stress indicator. Thirty three (33) castrated Aberdeen Angus breed young bulls were used, approximately 24 months old, average weight of 450 kg, with similar origin, time and transportation conditions, being slaughtered in a commercial packing plant in Pelotas, RS, Brazil. Animals were classified in four different fastening periods. Reactivity was classified accordingly to a scale ranging from zero (0) to five (5), the lesser reactive being attributed 0 and the most reactive being attributed 5. Blood samples were collected to determine glucose and cortisol levels. Samples of chilled Longissimus dorsi muscle were obtained 24 h after slaughter, to determine final meat quality through the characteristics of colour, water retention capacity (CRA) softness and pH. Data were analyzed by statistical multivariate analysis with grouping test and ordination by the method of component analysis (PCA). Levels of cortisol and glucose showed simultaneous increase. The most reactive animals presented higher blood levels of glucose and cortisol, as well as meat final pH. Less reactive animals showed best meat characteristics for softness...

Studies on the stress response in Fusobacterium nucleatum.

Zilm, Peter S.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
36.1%
Fusobacterium nucleatum is a saccharolytic Gram-negative anaerobic organism belonging to the so-called ‘orange complex’ which is believed to play an important role in the microbial succession associated with the pathogenesis of periodontal disease. Its genome contains niche-specific genes shared with the other inhabitants of dental plaque, which may help to explain its ability to survive and grow in the changing environmental conditions experienced in the gingival sulcus during the progression from health to disease. The pH of the gingival sulcus increases during the development of periodontitis and is thought to occur by the metabolism of nutrients supplied by gingival crevicular fluid. Studies have shown that F. nucleatum is partly responsible for the rise in pH and have concluded that in comparison to other plaque inhabitants, F. nucleatum has the greatest ability to neutralise acidic environments. In common with a number of other oral bacteria, F. nucleatum has also been shown to produce intracellular polyglucose (IP) from simple sugars such as glucose, galactose and fructose. Its response and adaptation to stressful environmental conditions such as pH is unknown. The overall aim of this study was, therefore, to determine how F. nucleatum copes with environmental stresses induced by pH changes. F. nucleatum was grown by continuous culture in a chemically defined medium at a growth rate corresponding to those measured in vivo. The effect on protein expression...

There is a specific response to pH by isolates of Haemophilus influenzae and this has a direct influence on biofilm formation

Ishak, N.; Tikhomirova, A.; Bent, S.J.; Ehrlich, G.D.; Hu, F.Z.; Kidd, S.P.
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em //2014 ENGLISH
Relevância na Pesquisa
45.92%
BACKGROUND: Haemophilus influenzae colonizes the nasopharynx as a commensal. Strain-specific factors allow some strains to migrate to particular anatomical niches, such as the middle ear, bronchi or blood, and induce disease by surviving within the conditions present at these sites in the body. It is established that H. influenzae colonization and in some cases survival is highly dependent on their ability to form a biofilm. Biofilm formation is a key trait in the development of chronic infection by certain isolates. This is exemplified by the contrast between the biofilm-forming strains found in middle ear infections and those isolates that survive within the blood and are rarely associated with biofilm development. RESULTS: Screening a group of H. influenzae strains revealed only slight variations in their growth across a range of pH conditions. However, some isolates responded to a pH of 8.0 by the formation of a biofilm. While the type b capsular blood isolate Eagan did not form a biofilm and grew at the same rate regardless of pH 6.8-8.0, transcriptomic analyses demonstrated that at pH 8.0 it uniquely induced a gluconate-uptake and metabolism pathway, which concurrently imports H+. A non-typeable H. influenzae, isolated from the middle ear...

Low-pH and aluminum resistance in Arabidopsis correlates with high cytosolic magnesium content and increased magnesium uptake by plant roots

Bose, J.; Babourina, O.; Shabala, S.; Rengel, Z.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
46.02%
Low-pH stress and Al3+ toxicity affect root growth in acid soils. It was hypothesized that the capacity of genotypes to maintain Mg2+ uptake in acidic environments may contribute to low-pH and Al resistance, but explicit evidence is lacking. In this work, an Al-resistant alr104 mutant and two Al-sensitive mutants (als5 and als3) of Arabidopsis thaliana were compared with the wild type (Col-0) for Mg2+ uptake and intracellular Mg2+ concentration under low-pH and combined low-pH/Al stresses. Magnesium accumulation in roots was measured in long-term (7 d) experiments. The Mg2+ fluxes were measured using ion-sensitive microelectrodes at the distal elongation and the mature root zones in short-term (0–60 min) experiments. Intracellular Mg2+ concentrations were measured in intact root cells at the distal elongation zone using magnesium-specific fluorescent dye and fluorescent lifetime imaging (FLIM) analysis. Under low-pH stress, Arabidopsis mutants als5 and alr104 maintained a higher Mg concentration in roots, and had greater Mg2+ influx than the wild type and the als3 mutant. Under combined low-pH/Al treatment, Al-resistant genotypes (wild type and alr104) maintained a higher Mg2+ accumulation, and had a higher Mg2+ influx and higher intracellular Mg2+ concentration than Al-sensitive genotypes (als3 and als5). Overall...

Time and Stress in English Verse with speical reference to Lanier's Theory of Rhythm

Hendren, Joseph W.
Fonte: Electronic version published by Fondren Library, Rice University, made possible with funding from the Rice Historical Society and Thomas R. Williams, Ph.D., class of 2000.; Rice University Publicador: Electronic version published by Fondren Library, Rice University, made possible with funding from the Rice Historical Society and Thomas R. Williams, Ph.D., class of 2000.; Rice University
Tipo: Book; Text
ENG
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45.89%
Preface-- The Problem-- Traditional Scansion-- Lanier's Approach-- Verse and Music-- Lanier's Theory-- The Measure-- Syllable and Stress-- Musical Notation-- Barring-- Alternation of Stress-- Flexibility of Verse-- Accent vs. Quantity-- Physical Measurements-- Collateral Considerations-- Conclusions

A shared regulatory network allows functional coupling of Pho89 and Ena1 in response to environmental alkalinization

Serra Cardona, Albert
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf; application/pdf
Publicado em //2015 ENG
Relevância na Pesquisa
36.19%
Els microorganismes estan exposats a canvis en l'ambient que poden implicar una situació d'estrès. El llevat Saccharomyces cerevisiae prefereix condicions acides per proliferar; per tant, l'alcalinització del medi extern li empitjora el creixement. Per superar aquest estrès, el llevat activa diverses vies de senyalització que conformen una complexa xarxa reguladora, provocant un remodelament transcripcional. La via de la calcineurina, activada per l'increment de calci citosòlic en condicions alcalines, governa l'expressió gènica a través del factor de transcripció Crz1. Un estrès alcalí és detectat per la proteïna transmembrana Rim21, un component de la via Rim101, que desencadena una cascada de senyalització provocant l'activació per proteòlisi de Rim101. Aquest factor de transcripció reprimeix l'expressió de NRG1, un altre repressor transcripcional, induint així l'expressió de determinats gens indirectament. La quinasa Snf1 també s'activa per estrès alcalí i té varies dianes a través de les quals controla diferents processos. Entre aquestes, Snf1 inhibeix els repressors Mig1/Mig2 i Nrg1/Nrg2, alleugerint la repressió d'un grup divers de gens. Addicionalment, un increment del pH extern activa la via de senyalització PHO...

Survival under stress of halotolerant lactobacilli with probiotic properties

Melgar-Lalanne,G.; Rivera-Espinoza,Y.; Farrera-Rebollo,R.; Hernández-Sánchez,H.
Fonte: UAM, Unidad Iztapalapa, División de Ciencias Básicas e Ingeniería Publicador: UAM, Unidad Iztapalapa, División de Ciencias Básicas e Ingeniería
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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46.02%
Three halotolerant lactobacilli with probiotic potential previously isolated from Chiapas cheese (Lactobacillus plantarum, L. pentosus and L. acidipiscis) and two commercial lactobacilli with probiotic activity (L. casei Shirota and L. plantarum 299v) were evaluated for their safety and survival capacity under stress. All the strains could grow in optimal conditions up to 6 % NaCl and showed sub-lethal growth up to 16 % NaCl; all the strains could grow well at pH values between 4.0 and 8.0; with a sub-lethal growth up to pH values of 2.0 and 9.0. L. plantarum 299v could grow up to 2.0 % of bile salts, and L. acidipiscis up to 1.5 % of bile dried salts. All the strains could be considered safe because all of them were γ-hemolytic and gelatinase negative. Moreover, all the strains showed similar antibiotic resistance pattern and resisted the normal dose used in the food industry of nisin and lysozyme. With these results, it is possible to conclude that the two commercial Lactobacillus strains are halotolerant and that all the strains can be used in a wide range of food products.