Tesi sul tema "Cold adaptation"
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1
Ramey, Christopher Shane. "Post-transcriptional adaptation of Escherichia coli during the cold shock response". Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1464111681&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Testo completo
2
Gilbert, Jack Anthony. "Cold adaptation strategies and diversity of Antarctic bacteria". Thesis, University of Nottingham, 2002. http://eprints.nottingham.ac.uk/10952/.
Testo completoAbstract (sommario):
Bacteria have been isolated from virtually every environment on Earth. The Antarctic continent is no exception. In this extremely cold and dry environment bacteria have colonised various refugia and have evolved a number of strategies for coping with the extreme physico-chemical fluctuations they are exposed to within the environment. These psychrophilic adaptations include cold adapted proteins and lipids which are interest for biotechnology in areas such as frozen foods, agriculture and cryogenic storage. One type of cold adapted protein of particular interest is the antifreeze protein (AFP) for its recrystalisation inhibition and thermal hysteresis activity. It was first isolated from Antarctic fish in the 1970, but has since been found in plants, fungi, insects and bacteria. Over 800 bacterial isolates were cultured from lakes of the, Vestfold Hills, Larsemann Hills and MacRobertson Land, Antarctica. Approximately 87% were Gram negative rods. A novel AFP assay designed for high-throughput analysis in Antarctica, demonstrated putative activity in 187 isolates. Subsequent SPLAT analysis (qualification assessment of recrystalisation inhibition activity) of the putative positive isolates showed 19 isolates with significant recrystalisation inhibition activity. These 19 isolates were cultured from five separate lakes with substantial physico-chemical differences. The 19 AFP active isolates were characterised, using amplified ribosomal DNA restriction analysis (ARDRA) and 16S rDNA sequencing, as predominantly belonging to genera from the a- and y-Proteobacteria, although they were more prominent in the gamma subdivision. One of these isolates (213, Halomonas sp.) was shown as dominant within its community by DGGE analysis, indicating a possible selective advantage for AFP active bacteria. This is the first report of the phylogenetic distribution of AFP activity within bacteria, thus providing information which could enable future bacterial AFP assessments to be aimed at specific taxonomic groups.
3
Silva, Cátia Cláudia Bárria da. "The role of ribonuclease R in bacterial adaptation to cold shock". Master's thesis, Faculdade de Ciências Médicas, 2011. http://hdl.handle.net/10362/6634.
Testo completoAbstract (sommario):
RESUMO:Os microrganismos reagem à súbita descida de temperatura através de uma
resposta adaptativa específica que assegura a sua sobrevivência em condições desfavoráveis. Esta adaptação inclui alterações na composição da membrana, na
maquinaria de tradução e transcrição. A resposta ao choque térmico pelo frio induz uma repressão da transcrição. No entanto, a descida de temperatura induz a produção de um
grupo de proteínas específicas que ajudam a ajustar/re-ajustar o metabolismo celular às
novas condições ambientais. Em E. coli o processo de adaptação demora apenas quatro
horas, no qual um grupo de proteínas específicas são induzidas. Depois desde período recomeça lentamente a produção de proteínas.A ribonuclease R, uma das proteínas induzidas durante o choque térmico pelo frio, é uma das principais ribonucleases em E. coli envolvidas na degradação do RNA.
É uma exoribonuclease que degrada RNA de cadeia dupla, possui funções importantes
na maturação e “turnover” do RNA, libertação de ribossomas e controlo de qualidade de
proteínas e RNAs. O nível celular desta enzima aumenta até dez vezes após exposição
ao frio e estabiliza em células na fase estacionária. A capacidade de degradar RNA de
dupla cadeia é importante a baixas temperaturas quando as estruturas de RNA estão mais estáveis. No entanto, este mecanismo é desconhecido.
Embora a resposta específica ao “cold shock” tenha sido descoberta há mais de
duas décadas e o número de proteínas envolvidas sugerirem que esta adaptação é rápida e simples, continuamos longe de compreender este processo.
No nosso trabalho pretendemos descobrir proteínas que interactuem com a
RNase R em condições ambientais diferentes através do método “TAP-tag” e
espectrometria de massa. A informação obtida pode ser utilizada para deduzir algumas
das novas funções da RNase R durante a adaptação bacteriana ao frio e durante a fase
estacionária. Mais importante ainda, RNase R poderá ser recrutada para um complexo
de proteínas de elevado peso molecular durante o “cold-shock”.------------ABSTRACT:Microorganisms react to the rapid temperature downshift with a specific adaptative response that ensures their survival in unfavorable conditions. Adaptation includes changes in membrane composition, in translation and transcription machinery.
Cold shock response leads to overall repression of translation. However, temperature downshift induces production of a set of specific proteins that help to tune cell metabolism and readjust it to the new environmental conditions. For Escherichia coli the adaptation process takes only about four hours with a relatively small set of
specifically induced proteins involved. After this time, protein production resumes,
although at a slower rate.
One of the cold inducible proteins is RNase R, one of the main E. coli ribonucleases involved in RNA degradation. RNase R is an exoribonuclease that digest double stranded RNA, serves important functions in RNA maturation and turnover, release of stalled ribosomes by trans-translation, and RNA and protein quality control. The level of this enzyme increases about ten-fold after cold induction, and it is also stabilised in cells growing in stationary phase. The RNase R ability to digest structured RNA is important at low temperatures where RNA structures are stabilized but the exact
role of this mechanism remains unclear.
Although specific bacterial cold shock response was discovered over two
decades ago and the number of proteins involved suggests that this adaptation is fast and simple, we are still far from understanding this process.
In our work we aimed to discover the proteins interacting with RNase R in
different environmental conditions using TAP tag method and mass spectrometry analysis. The information obtained can be used to deduce some of the new functions of
RNase R during adaptation of bacteria to cold and in stationary growth phase. Most
importantly RNase R can be recruited into a high molecular mass complex of protein in
cold shock.
4
Mäkinen, T. M. (Tiina M. ). "Human cold exposure, adaptation and performance in a northern climate". Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:951428089X.
Testo completoAbstract (sommario):
Abstract
The purpose of the study was to examine the amount of cold exposure and factors affecting it at the population level in Finland, to determine what type of cold acclimatisation, if any, develops in urban residents in winter, and to find out whether cold acclimatisation or acclimation has a functional significance on psychological or physical performance. Tasks of low physical activity requiring attention and concentration (cognition, postural control) were assessed in cold.
In a cross-sectional population study Finns aged from 25 to 74 years (n=6,951) were queried of their wintertime outdoor exposure duration and factors affecting it. In experimental studies seasonal cold acclimatisation (thermal responses) and its effect on cognition were assessed in the laboratory, where 15 young urban subjects were exposed to cold in winter and summer in bright or dim light. A controlled cold acclimation trial (n=10) was performed to study the effects of repeated exposures to cold on cognitive performance and postural control in young urban subjects.
In the Finnish population the average amount of cold exposure in winter represents 4% of the total time. Most of the cold exposure occurs during leisure time and in outdoor occupations (agriculture, forestry, mining, industry, construction). Factors explaining increased occupational cold exposure were: occupation, age and a lesser amount of education. Factors associated with more leisure-time cold exposure were: being employed in outdoor occupations, being a pensioner, housewife, unemployed, practising physical exercise, and reporting at least average health. The experimental studies showed seasonal differences and aggravated thermal responses in urban residents in winter, but did not detect habituation responses typical of cold acclimatisation. In both seasons, acute moderate cold exposure resulted in positive, negative or mixed effects on cognition, reflected as changes in response times and accuracy. Simple cognitive tasks were impaired in cold, and in complex tasks both negative, positive and mixed effects were observed. It is suggested that cold exposure affects cognition through different mechanisms related to either distraction or arousal. Cold exposure increased postural sway by 70-90%, suggesting impaired postural control. Repeated exposures to moderate cold, reducing stress and discomfort and dampening physiological responses, did not markedly affect cognitive performance or postural control.
5
Durrans, Anna. "Cardiac and systemic cold tolerance : natural adaptation and clinical application". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401179.
Testo completo
6
Shields, Brenda Czerwinski. "Adaptive response of Japanese quail (Coturnix coturnix japonica) to cold-acclimation physiological changes and localization of avian UCP in skeletal muscle /". Click here for download, 2008. http://proquest.umi.com/pqdweb?did=1564023381&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.
Testo completo
7
Bos, Antoine. "Natural variation in cold adaptation and freezing tolerance in Arabidopsis thaliana". Doctoral thesis, Umeå : Department of Ecology and Environmental Science, Umeå University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1947.
Testo completo
8
Frank, Scott 1971. "Phosphoenolpyruvate carboxylase and cold acclimation of alfalfa". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27318.
Testo completoAbstract (sommario):
Phosphoenolpyruvate carboxylase (PEPC) was examined during cold acclimation of seedlings of the freezing-tolerant cultivar (Medicago sativa ssp falcata cv Anik) and the relatively freezing-sensitive cultivar (Medicago sativa cv Trek) of alfalfa. With four days of cold acclimation, PEPC activity increased to 3.5-fold and 2-fold the control levels in Anik and Trek, respectively. This was associated with an increase in the level of a 110 kD PEPC protein and a decrease in the amount of a 120 kD PEPC polypeptide in both cultivars. The role of reversible phosphorylation in regulating PEPC activity was demonstrated by in vitro phosphorylation and dephosphorylation, which caused partial activation and deactivation of PEPC, respectively. In vivo phosphorylation experiments revealed that the 110 kD PEPC subunit is phosphorylated on serine residue(s) during cold acclimation in Anik but not in Trek. Increased PEPC activity could account for the 70% increase in the non-autotrophic or dark fixation of carbon observed in cold acclimated Anik seedlings. A possible role for dark carbon fixation in the cold-induced development of freezing tolerance is through the production of NADPH. Such a source of reducing power may be required for the repair of cold-induced damage and restoration of normal cellular functions.
9
Magnoni, Leonardo J. "Antarctic Notothenioid Fishes Do Not Display Metabolic Cold Adaptation in Hepatic Gluconeogenesis". Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/MagnoniLJ2002.pdf.
Testo completo
10
Ghobakhlou, Abdollah. "Genomics, Transcriptomics and Metabolomics of cold adaptation in arctic Mesorhizobium sp. N33". Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29489/29489.pdf.
Testo completo
11
Macartney, Alastair Ian. "Cold adaptation of lipid biosynthetic enzymes in carp (Cyprinus carpio, L.) liver". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385150.
Testo completo
12
Kawamoto, Jun. "Studies of cold-adaptation mechanism of a psychrotrophic bacterium, Shewanella livingstonensis Ac10". Kyoto University, 2008. http://hdl.handle.net/2433/136582.
Testo completoAbstract (sommario):
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第13493号
農博第1670号
新制||農||951(附属図書館)
学位論文||H20||N4318(農学部図書室)
UT51-2007-T869
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 江﨑 信芳, 教授 清水 昌, 教授 阪井 康能
学位規則第4条第1項該当
13
MARZIALE, FRANCESCA. "Molecular mechanisms responsible of cold adaptation in the Antarctic ciliate Euplotes focardii". Doctoral thesis, Università degli Studi di Camerino, 2007. http://hdl.handle.net/11581/401893.
Testo completoAbstract (sommario):
During my PhD course, I have worked on and contributed to three different projects with an unique goal, that is the study of the evolutionary strategies and of the molecular mechanisms responsible of cold adaptation in the Antarctic ciliate Euplotes focardii. To reach this aim I have investigated: 1. The mechanisms that allow an efficient protein synthesis in the cold by analyzing the genes encoding the acidic ribosomal proteins P0 and P2 (Chapter 1); they are implicated in the formation of the lateral protuberance on the 60S ribosomal subunit, the so-called ribosomal stalk, which is involved in protein synthesis regulation through interaction with soluble translation factors and in GTP hydrolysis control during elongation steps. Moreover, since the function of the stalk and the amino acid sequences of the proteins of which it is composed are very conserved from Prokaryotes to upper Eukaryotes, by the analysis of the P proteins it could be possible to get new information on the phylogenetic origin of Eukaryotes, a very discussed but yet unresolved theme. 2. The molecular systems responsible of microtubule polymerization, nucleation and stability at low temperatures, since microtubules are structures involved in many fundamental life processes, such as cell division, intracellular transport and motility. In particular, my work focuses on microtubule nucleation in the cold, as to date this phenomenon has not been studied, while the polymerization has been deeply analyzed in Euplotes focardii and mainly in Antarctic fish. 3. The folding mechanisms employed by the cytoskeletal proteins through a comparative study between two divergent isotypes of β-tubulin in Euplotes focardii (Chapter 3).
14
Labbé, Etienne. "Temperature-modulation of protein phosphorylation in cell-free extracts of alfalfa". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ44093.pdf.
Testo completo
15
Gracey, Andrew Y. "Cold-adaptation of carp (Cyprinus carpio L.) : lipid unsaturation and induced desaturase expression". Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321117.
Testo completo
16
Ting, Lily Li Jing Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "A quantitative proteomics investigation of cold adaptation in the marine bacterium, Sphinopyxis alaskensis". Awarded By:University of New South Wales. Biotechnology & Biomolecular Sciences, 2010. http://handle.unsw.edu.au/1959.4/44838.
Testo completoAbstract (sommario):
The marine bacterium Sphingopyxis alaskensis was isolated as one of the most numerically abundant bacteria from cold (410??C) nutrient depleted waters in the North Pacific Ocean. The objective of this study was to examine cold adaptation of S. alaskensis by using proteomics to examine changes in global protein levels caused by growth at low (10??C) and high (30??C) temperatures. Stable isotope labelling-based quantitative proteomics was used, and a rigorous post-experimental data processing workflow adapted from microarray-based methods was developed. The approach included metabolic labelling with 14N/15N and normalisation and statistical testing of quantitative proteomics data. Approximately 400,000 tandem mass spectra were generated resulting in the confident identification of 2,135 proteins (66% genome coverage) and the quantitation of 1,172 proteins (37% genome coverage). Normalisation approaches were evaluated using cultures grown at 30??C and labelled with 14N and 15N. For 10??C vs. 30??C experiments, protein quantities were normalised within each experiment using a multivariate lowess approach. Statistical significance was assessed by combining data from all experiments and applying a moderated t-test using the empirical Bayes method with the limma package in R. Proteins were ranked after calculating the B-statistic and the Storey-Tibshirani false discovery rate. 217 proteins (6% genome coverage) were determined to have significant quantitative differences. In achieving these outcomes a range of factors that impact on quantitative proteomics data quality were broadly assessed, resulting in the development of a robust approach that is generally applicable to quantitative proteomics of biological system. The significantly differentially abundant proteins from the proteomics data provided insight into molecular mechanisms of cold adaptation in S. alaskensis. Important aspects of cold adaptation included cell membrane restructuring, exopolysaccharide biosynthesis, lipid degradation, carbohydrate and amino acid metabolism, and increased capacity of transcriptional and translational processes. A number of cold adaptive responses in S. alaskensis were novel, including a specific cold-active protein folding pathway, a possible thermally-controlled stringent response, and biosynthesis of intracellular polyhydroxyalkanoate reserve material. The overall study provided important new insight into the evolution of growth strategies necessary for the effective competition of S. alaskensis in cold, oligotrophic environments.
17
Winnard, Jr Paul. "Cold-Temperature Adaptation of Muscle Creatine Kinase from an Antartic Teleost (Chaenocephalus Aceratus)". Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/WinnardP2001.pdf.
Testo completo
18
Huston, Adrienne Louisa. "Bacterial adaptation to the cold : in situ activities of extracellular enzymes in the North Water polynya and characterization of a cold-active aminopeptidase from Colwellia psychrerythraea strain 34H /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11062.
Testo completo
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Caprette, Christopher L. "Conquering the cold shudder the origin and evolution of snake eyes /". Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1111184984.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 107 p.; also includes graphics (some col.) Includes bibliographical references (p. 97-107). Available online via OhioLINK's ETD Center
20
Quisumbing, Teresita Lambo. "Studies of iron metabolism and metabolic rate in iron-deficient and cold-acclimatized rats". Hong Kong : University of Hong Kong, 1985. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1231545X.
Testo completo
21
Doherty, Colleen J. "Transcriptional networks involved in response to low temperature stress in Arabidopsis thaliana". Diss., Connect to online resource - MSU authorized users, 2008.
Cerca il testo completoAbstract (sommario):
Thesis (Ph. D.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2008.Title from PDF t.p. (viewed on July 10, 2009) Includes bibliographical references. Also issued in print.
22
Kawczyński, Wojciech. "Effects of low temperature on nuclear proteins of alfalfa". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23278.
Testo completoAbstract (sommario):
During the present studies we attempted to answer the following questions: (i) Does low temperature alter the phosphorylation level of proteins in isolated nuclei? (ii) Does the nuclear phosphoprotein population change during a prolonged exposure of seedlings to cold? (iii) Do heat-stable proteins accumulate in the nucleus during a prolonged exposure of seedlings to cold? (iv) Are the answers to the above three questions related to freezing tolerance? A possible relationship between the observed cold-induced changes in phosphoproteins and the level of freezing tolerance was explored by comparing the results of experiments conducted on two cultivars (Apica and Trek) of alfalfa (Medicago sativa L.) which markedly differ in their capacity for cold acclimation.We show that the phosphorylation level of several nuclear proteins is subject to rapid and reversible enhancement by low temperature. Several phosphoproteins were found to be constitutively present in the nucleus of both cultivars. The cold-induced stimulation of the phosphorylation of many of these proteins was much greater in the relatively freezing tolerant cultivar Apica than in the relatively freezing sensitive cultivar Trek. Population of nuclear phosphoproteins was found to be considerably more complex in Apica than in Trek. During a prolonged exposure of the seedlings to 4$ sp circ$C, additional phosphoproteins were imported into the nucleus of Apica seedlings but not those Trek.
Some heat-stable proteins were constitutively present in the nucleus of both cultivars. However during the 4-day cold treatment, a large accumulation of several additional heat-stable proteins was observed in the tolerant, but not the sensitive, cultivar. (Abstract shortened by UMI.)
23
Summers, Heidi A. "Calorespirometric Evidence for Adaptation of Blackbrush and Shadscale to Growth Season Temperatures in Cold Deserts". Diss., BYU ScholarsArchive, 2005. http://contentdm.lib.byu.edu/ETD/image/etd693.pdf.
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Heckel, Korbinian von [Verfasser], e Wolfgang [Akademischer Betreuer] Stephan. "The transcriptional basis of cold adaptation in drosophila melanogaster / Korbinian von Heckel ; Betreuer: Wolfgang Stephan". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1139977962/34.
Testo completo
25
Lunt, Heather. "Cross-adaptation : the effect cold habituation has on the physiological responses to acute hypoxia in humans". Thesis, University of Portsmouth, 2010. https://researchportal.port.ac.uk/portal/en/theses/crossadaptation(55dc1b48-0d5d-4084-8ae5-3a66c376da15).html.
Testo completoAbstract (sommario):
Physiological adaptation to environmental stressors is often studied in isolation, but these stressors are frequently combined outside of laboratory settings, for example cold and hypoxia at altitude. There is also limited information about the effect that adaptation to one environment has on exposure to another. The five studies in this thesis were conducted in humans to assess the effect cold habituation has on the response to a simulated hypoxic exposure, and also to investigate a possible mechanism through which any change may occur. A possible site for the 'cross-adaptation' between cold habituation and hypoxia is the autonomic nervous system. Heart rate variability (HRV) is an non-invasive measurement technique which has been used to quantify autonomic activity. The two main frequency bands of interest when using HRV are referred to as the Low-Frequency (LF) band (the power found between 0.04 and 0.15 Hz) and the High-Frequency (HF) band (the power found between 0.15 and 0.4 Hz). Study One assessed the reliability of heart rate variability as a technique to indicate autonomic activity during both paced (breathing in time to a standard audible signal) and spontaneous breathing conditions, and at different cycling exercise intensities in a thermoneutral environment. It was hypothesised that within each condition HRV indices would be reliable between repeated recordings, which were separated by 96 hours. Eight participants performed each condition on the two occasions. Analysis of the data (coefficients of variation [CV] and intraclass correlation coefficients [ICC]) showed that the paced breathing condition was the most reliable condition, and time domain HRV indices were reliable, whilst not all frequency domain HRV indices were. Normalising and log transforming the raw data did improve reliability and log transformed total and high frequency (Ln HF) power and low:high frequency ratio (Ln LF:HF) met the a priori criteria (CV <10 % and ICC > r=0.8). It was concluded that most log transformed HRV indices were reliable at rest, during paced breathing and during moderate intensity exercise. Thus, the hypothesis was accepted, but caution was advised as several of the indices were close to exceeding the reliability criteria (Ln total power, Ln HF and Ln LF:HF) and a second autonomic measurement technique may be considered to substantiate its use. The previous study identified that Ln HF power increased when breathing frequency was reduced at rest. Study Two investigated the effect that alterations in breathing patterns had on HRV indices during rest and unloaded seated cycle ergometery (0 Watts) in 16 male participants. It was hypothesised that breathing which was externally paced would increase HF power compared to spontaneous breathing conditions. HF power was elevated during the paced breathing conditions in comparison to spontaneous breathing at rest and during unloaded exercise. Consequently, the hypothesis was accepted. Thus, ventilatory variables should be recorded in following studies as there may be links between ventilation and HRV indices. The previous studies used participants' freely chosen cadence when cycling, this may have influenced the HRV. The third study tested the hypothesis that cycling cadence affected HRV indices. HRV indices from 16 male participants were analysed when cycling at 40, 60, 80 and 100 revs.min-1 on an unloaded (0 Watts) and loaded (100 Watts) seated cycle ergometer. HRV indices declined as cadence was increased. Thus, the hypothesis was accepted. If HRV indices were to be calculated during subsequent experiments, both cadence and power output would have to be standardised. The first three studies provided information on the conditions which must be present to produce reliable HRV data during moderate intensity exercise. These studies also indicated that an additional means of measuring autonomic activity should be included. Study Four was designed to establish if one hypoxic exposure would influence a second exposure, if there was no effect the model could be adopted for the final experiment. This study also examined the effect of hypoxia on HRV indices at rest and during exercise. It was hypothesised that exercise and hypoxia would exert separate and additive effects on HRV indices and catecholamine concentrations. Twelve male participants rested and exercised on a loaded cycle ergometer (100 Watts) in normoxic (faction of inspired Oxygen, FIo2 0.2093) and hypoxic conditions (FIo2 0.15) on two occasions, separated by 96 hours. HRV and catecholamine concentrations were similar between the normoxic and hypoxic resting conditions. During exercise in normoxia catecholamine concentrations increased and Ln HF power was reduced, further increases in catecholamine concentrations and a reduction in Ln HF power were found during exercise in hypoxic conditions. The hypothesis was rejected for resting conditions, and accepted for the exercise conditions. It was also found that the first hypoxic exposure did not influence the HRV indices and catecholamine concentrations of the second hypoxic exposure and this model could therefore be used for the final experiment. The final study (Study Five) tested for the presence of a 'cross-adaptation' response in cold habituated humans to hypoxic exposures during rest and moderate intensity exercise. This study was designed on the basis of the information obtained from the previous four experiments and tested the hypothesis that cold habituation by repeated cold-water immersions would reduce the sympathetic activity and cardio-respiratory responses during loaded cycling (100 W) in hypoxic conditions (FIo2 0.12). Thirty-two male participants underwent six, five minute immersions in either cold (12 °C) or thermoneutral (35 °C) water over a three day period. The normoxic and hypoxic exposures were performed before and after the water immersions. It was established that cold habituation attenuated the sympathetic response to loaded exercise during an acute hypoxic exposure and reduced the number and severity of acute mountain sickness (AMS) symptoms. The study provides the first evidence of a cross-adaptation between cold habituation and hypoxic exposure in humans. This was not found in participants who performed thermoneutral water immersions. Therefore, the hypothesis was accepted. In conclusion, in four of four participants whose catecholamine concentrations were analysed and eight from 16 volunteers whose HRV was analysed, showed that cold habituation reduces the sympathetic response to an acute hypoxic stimulus during loaded cycling. However, it is not known if this cross-adaptation provides an adaptive or maladaptive response to prolonged exposure to hypoxia or altitude. Additionally, the permanence of the cross-adaptation also requires further investigation.
26
Brändström, Helge. "Accidental hypothermia and local cold injury : physiological and epidemiological studies on risk". Doctoral thesis, Umeå universitet, Anestesiologi och intensivvård, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-55602.
Testo completoAbstract (sommario):
Background: (Papers I and II) The objectives were to first determine incidence and contributing factors to cold-related injuries in northern Sweden, both those that led to hospitalization and those that led to fatality. (Papers III and IV) A further aim was to assess post-cooling hand-rewarming responses and effects of training in a cold environment, both on fingertip rewarming and on function of the autonomic nervous system, to evaluate if there was adaptation related to prolonged occupational cold exposure. Methods: In a retrospective analysis, cases of accidental cold-related injury with hospital admission in northern Sweden during 2000-2007 were analyzed (Paper I). Cases of fatal hypothermia in the same region during 1992-2008 were analyzed (Paper II). A cohort of volunteers was studied before and after many months of occupational cold exposure. Subject hand rewarming response was measured after a cold hand immersion provocation and categorized as slow, moderate or normal in rewarming speed. This cold provocation and rewarming assessment was performed before and after their winter training. (Paper III). Heart rate variability (HRV) was analyzed from the same cold provocation/recovery sequences (Paper IV). Results: (Paper I) For the 379 cases of hospitalization for cold-related injury, annual incidences for hypothermia, frostbite, and drowning were 3.4/100,000, 1.5/100,000, and 1.0/100,000 inhabitants, respectively. Male gender was more frequent for all categories. Annual frequencies for hypothermia hospitalizations increased during the study period. Hypothermia degree and distribution of cases were 20 % mild (between 32 and 35ºC), 40% moderate (31.9 to 28ºC), and 24% severe (< 28ºC), while 12% had temperatures over 35.0ºC. (Paper II) The 207 cases of fatal hypothermia showed an annual incidence of 1.35 per 100,000 inhabitants, 72% in rural areas, 93% outdoors, 40% found within 100 meters of a building. Paradoxical undressing was documented in 30%. Ethanol was detected in femoral vein blood in 43%. Contributing co-morbidity was common including heart disease, previous stroke, dementia, psychiatric disease, alcoholism, and recent trauma. (Paper III) Post-training, baseline fingertip temperatures and cold recovery variables in terms of final rewarming fingertip temperature and vasodilation time increased significantly in moderate and slow rewarmers. Cold-related injury (frostbite) during winter training occured disproportionately more often in slow rewarmers (4 of the 5 injuries). (Paper IV) At ‘pre- winter-training’, normal rewarmers had higher power for low frequency and high frequency heart rate variability. After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low frequency and high frequency heart rate variability components. Conclusions: Hypothermia and cold injury continues to cause injury and hospitalization in the northern region of Sweden. Assessment and management is not standardized across hospitals. With the identification of groups at high risk for fatal hypothermia, it should be possible to reduce the incidence, particularly for highest risk subjects; rural, living alone, alcohol-imbibing, and psychiatric diagnosis-carrying citizens. Long-term cold-weather training may affect hand rewarming patters after a cold provocation, and a warmer baseline hand temperature with faster rewarming after a cold provocation may be associated with less general risk for frostbite. Heart rate variability results support the conclusion that cold adaptation in the autonomic nervous system occurred in both groups, though the biological significance of this is not yet clear.
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Kastally, Cheldy. "Genome-wide genetic variation in two sister species of cold-resistant leaf beetle: migration and population adaptation". Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/262911.
Testo completoAbstract (sommario):
An important goal of biology is to understand the key mechanisms of evolution underlying the diversity of living organisms on Earth. In that respect, the recent innovations in the field of new generation sequencing technologies (NGS) are bringing new and exciting opportunities. This thesis presents results obtained with these tools in the specific context of the study of two sister species of cold-adapted leaf beetles, Gonioctena intermedia and G. quinquepunctata. More specifically, this work is focused around four research directions: the two first explore methods of statistical inference using a spatially explicit model of coalescence, by (1) evaluating the potential of various summary statistics to discriminate phylogeographic hypotheses, and (2) investigating the dispersal abilities of a montane leaf beetle, G. quinquepunctata, using an original method that avoids using summary statistics. The third research direction focuses on the adaptation to cold conditions in this montane leaf beetle, by testing the association between genetic polymorphism across tens of thousands of genetic markers and altitude in samples collected at various elevation levels in the Vosges (France). Finally, the fourth, and last, research axis presents the discovery of mitochondrial heteroplasmy, i.e. the presence in an individual of multiple copies of the mitochondrial genome, in natural populations of G. intermedia. We illustrate, here, how NGS technologies could help identify this phenomenon, probably underestimated in animals, on a large scale.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Thatcher, Bradley John Carleton University Dissertation Biology. "Properties of enzymes from mammalian hibernators; structure, function, relationships". Ottawa, 1997.
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Burg, Dominic William Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Cold adaptation in the Antarctic archeaon Methanococcoides burtonii: the role of the hydrophobic proteome and variations in cellular morphology". Awarded by:University of New South Wales. Biotechnology & Biomolecular Sciences, 2009. http://handle.unsw.edu.au/1959.4/44761.
Testo completoAbstract (sommario):
Very little is known about the hydrophobic proteins of psychrophiles and their roles in cold adaptation. In light of this situation, methods were developed to analyse the hydrophobic proteome (HPP) of the model psychrophilic archaeon Methanococcoides burtonii. Central to this analysis was a novel differential solubility fractionation procedure, which resulted in a significant increase in the efficiency of resolving the HPP. Over 50% of the detected proteins were not identified in previous whole cell extract analyses, and these underwent an intensive manual annotation process producing high quality functional assignments. Utilising the functional assignments, biological context analysis of the HPP was performed, revealing novel and often unique biology. The analysis acted as a platform for differential proteomics of the organism???s response to both temperature and substrate using stable isotope labelling. The results of which revealed that low temperature growth was associated with an increase in the abundance of surface and secreted proteins, and translation apparatus. Conversely, growth at a higher temperature was associated with an increase in the abundance of general protein folding machinery and indications of an oxidative stress response, emphasising that the temperature for maximum growth rate is stressful. Through investigation of the response of M. burtonii to substrate it was found that growth on methanol was stressful, and its low energy yield resulted in an increase in the abundance of energy conserving systems. The extracellular polymeric substance (EPS) and morphology of M. burtonii was also investigated with respect to both temperature and substrate, using a number of techniques in microscopy. It was found that the EPS was comprised of proteins, sugars and RNA, and that growth at different temperatures resulted in the production of EPS that displayed significantly different properties on dehydration, thus indicating compositional variation. When cells were grown on methanol they took on highly irregular shapes and had electron transparent inclusions. The observations from the ultrastructural analysis were contemplated with respect to the proteomic findings, revealing novel avenues of research. This study has highlighted the roles of hydrophobic proteins in cold adaptation biology, and the value of comprehensive proteomics for the examination of adaptation in microorganisms
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Lakoba, Vasiliy Tarasovich. "Ecotypic Variation in Johnsongrass in Its Invaded U.S. Range". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103611.
Testo completoAbstract (sommario):
Biological invasions have been observed throughout the world for centuries, often with major consequences to biodiversity and food security. Tying invasion to species identity and associated traits has led to numerous hypotheses on why, and where, some species are invasive. In recent decades, attention to intraspecific variation among invaders has produced questions about their adaptation to climate, land use, and environmental change. I examined the intraspecific variation of invasive Johnsongrass's (Sorghum halepense (L.) Pers.) seedling stress response, propagule cold tolerance, and large-scale niche dynamics for correlation with populations' climatic and ecotypic (i.e., agricultural vs. non-agricultural) origin. Overall, I found a greater number of home climate effects than ecotypic effects on various traits. Non-agricultural seed from cold climates and agricultural seed from warm climates germinated more and faster, while non-agricultural seedlings showed uniform chlorophyll production regardless of home soil carbon origin, unlike their agricultural counterparts. Neither seedling stress response nor propagule cold tolerance interacted with ecotype identity; however, drought stress varied with population origins' aridity and soil fertility, and seed from warm/humid and cold/dry climates was most germinable. Comparison of seed and rhizome cold tolerance also suggested that the latter is a conserved trait that may be limiting S. halepense poleward range expansion. This physiological limit, an unchanged cold temperature niche boundary between continents and ecotypes, and a narrowed niche following transition to non-agricultural lands all imply low likelihood of spread based on climatic niche shift. Instead, evidence points to range expansion driven primarily by climate change and highlights agriculture's role in facilitating invasibility. This tandem approach to climate and land use as drivers of intraspecific variation is transferable to other taxa and can help refine our conception of and response to invasion in the Anthropocene.Doctor of Philosophy
Exotic invasive species are a global problem, threatening biodiversity and biosecurity now and in the future. In the last several decades, ecologists have studied many individual invaders and their traits to understand what drives their spread. More recently, abundant differences in traits between populations within an invasive species have raised questions about humans' role in facilitating invasion through climate change, land use, and other disturbances. I studied the invasive Johnsongrass's (Sorghum halepense (L.) Pers.) response to drought, nutrient limitation, and freezing to detect differences between populations based on their climate and ecotype (agricultural vs. non-agricultural) origin. I also tracked differences in the climates the species occupied across the globe and North America and projected its future distribution under climate change. Overall, I found a greater number of home climate effects than ecotypic effects on various traits. Non-agricultural seed from cold climates and agricultural seed from warm climates germinated the most, while non-agricultural seedlings performed consistently regardless of soil carbon origin, unlike their agricultural counterparts. In addition, drought stress varied with population origins' rainfall and soil fertility, and seed germination favored warm/humid and cold/dry origin. Rhizome (underground stem) cold tolerance appears to be a trait that limits S. halepense poleward range expansion. Along with no change in the coldest climates occupied worldwide and no spread to new climates with transition to non-agricultural lands, this implies that Johnsongrass is unlikely to expand its range without external forces. Instead future range expansion will likely be driven by climate change. This coupled approach to climate and land use affecting invasion is transferable to other species and can help refine both our concepts and response strategies.
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Khalil, Hala. "Model Medicago species for studies of low temperature signaling and cold acclimation". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30844.
Testo completoAbstract (sommario):
To identify a model legume experimental system for studying low temperature signaling and cold acclimation, cold-induced expression and regulation of homologues of alfalfa (Medicago sativa) cold acclimation-specific genes cas15 and cas30 were examined in M. arborea (relatively frost tolerant) and M. truncatula (relatively frost sensitive). Both cas15 and cas30 genes are present in the genomes of both species but whereas both genes are cold-induced in M. arborea, only cas15 is induced in M. truncatula. Cold-induced expression of these genes is inhibited by calcium chelators and channel blockers and by the membrane fluidizer benzyl alcohol. Treatment of leaves with dimethylsulfoxide, a membrane rigidifier, induced both genes at 25°C. A cold-activated MAP kinase activity was expressed in both species. These results suggest that M. truncatula, an annual, self-pollinated species may be successfully used as model experimental systems in studies of cold signaling and role of cas genes in cold acclimation in legumes.
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PASI, MARCO. "A dynamical perspective on cold-adapted enzymes at the molecolar level". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7729.
Testo completoAbstract (sommario):
Some organisms, especially unicellular, have adapted to extreme temperature conditions, and are capable of proliferating in such environments mainly thanks to the optimisation of their enzymatic repertoire. Cold-adapted (psychrophilic) enzymes are invariably characterised by high catalytic activity at low temperatures, necessary to endure the exponential reduction of the speed of chemical reactions in these conditions, and by low thermal stability. Numerous studies aimed at understanding the mechanisms of such adaptation at the molecular level agree that the high turnover observed for psychrophilic enzymes results from a decrease of the activation enthalpy of the catalysed reaction, which in turn is achieved structurally by decreasing the number and strength of the enthalpically stabilised interactions which must be broken to reach the transition state. Since these interactions are also involved in the stabilisation of the enzyme structure, their decrease has the effect of increasing structural flexibility, as reflected by the low thermal stability found for psychrophilic enzymes. Flexibility seems thus to have a fundamental role in enzymatic cold adaptation, and its study by means of Molecular Dynamics (MD) simulations provides a detailed description taking rigorously into account its dynamical character.
I report the results of comparative MD studies performed on homologous mesophilic and psychrophilic enzymes, and mutants thereof, to investigate the molecular bases of cold adaptation. Long, multi-replica and explicit-solvent MD simulations have been compared in particular in terms of molecular flexibility and the dynamics of intramolecular interactions. Results show that differences in the dynamic character of the compared enzymes are found in loops surrounding the active site or substrate-binding cleft.
In the case of chloride-dependent alpha-amylases, the comparison of the cold-active enzyme from Pseudoalteromonas Haloplanktis with its mesophilic porcine homologue shows that modulation of the size and flexibility of these loops cause the immediate surroundings of the active site to be comparatively more flexible in the psychrophilic enzyme. Detailed analysis of these enzymes
active-site dynamics reveals that elements previously identified
through X-ray crystallography as involved in substrate binding in both
enzymes undergo concerted motions that may be linked to catalysis.
The comparison of psychrophilic and mesophilic isoforms of trypsin from Salmo Salar shows that the cold-adapted enzyme presents fewer interdomain interactions and enhanced localised flexibility in regions close to the catalytic site. Notably, these regions fit well with the pattern of protein flexibility previously reported for psychrophilic elastases. These results indicate that specific sites within the serine-protease fold can be considered hot spots of cold-adaptation and that psychrophilic trypsins and elastases have independently discovered similar molecular strategies to optimise flexibility at low temperatures.
This evidence of evolutionary convergence underlines the importance of extending intrafamiliar comparative studies to unveil general features of how enzymes adapt their dynamical properties low temperatures. Molecular dynamics studies using all-atomic models, as those presented herein, have proven their effectiveness in this context, but their computational requirement hampers their applicability as the size of the test set increases. For these reasons it would be relevant to devise a simplified ("coarse-grain") approach to perform comparative analyses at a higher throughput than is currently feasible. To evaluate the level of simplification most suitable for this application, a "coarse-grain" approach has been adopted to study the mechanical properties of trypsins, taking into account results obtained using all-atomic models. The results of these comparisons are driving the development of a multi-scale "coarse-grain" approach that combines the required efficiency and accuracy.
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Trueman, Richard James. "Mechanisms underlying cold-adaptation : thermal thresholds of lipid restructuring and desaturase expression in the liver of carp (Cyprinus carpio L.)". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367307.
Testo completo
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Laurell, Henrik. "Hormone-sensitive lipase molecular analyses of the human gene : structural and evolutionary aspects on expression, alternating splicing and cold adaptation /". Lund : Dept. of Cell and Molecular Biology, Section for Molecular Signalling, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39056075.html.
Testo completo
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Ward, Leanne Gai. "Fish "antifreeze" proteins : investigations into the mechanism of ice growth inhibition". Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27711.
Testo completoAbstract (sommario):
This thesis describes the design, synthesis and measurement of ice growth inhibition
properties of 16 analogues of the type I, a-helical protein from the winter flounder.
This 37-residue protein has been proposed elsewhere to inhibit ice growth by a
hydrogen bonding dominated mechanism in which the four threonine residues, that are
equally spaced on one face of the helix, interact with the ice lattice. Four series of
analogues were studied, incorporating systematic changes to the threonine residues, as
well as other potential hydrogen bonding amino acids, and the helical conformation of
the protein.
In series 1 proteins, the central two threonine residues and all four threonine residues of
the native protein were mutated to serine. In series 2 proteins two additional salt
bridges (Lys7/Glu11 and Lys29/Glu33) were incorporated, and all four threonine
residues in this sequence were mutated to valine, serine, alanine, 2-aminobutyric acid,
isoleucine and glycine. In series 3 protein, the Asx residues (Asp 1, 5 and Asn 16, 27)
were replaced by alanine and leucine, respectively. All four threonine residues in this
sequence were mutated to valine, removing all potential hydrogen bonding amino acids.
In series 4 analogues the role of helicity in the ice growth inhibition properties of these
proteins was examined by stabilising, via covalent bridges, a truncated analogue of the
native protein which showed reduced helicity.
The solution conformation of all analogues was studied by circular dichroism
spectroscopy, analytical ultracentrifugation and nuclear magnetic resonance
spectroscopy. Circular dichroism studies showed that all analogues in series 1, 2 and 3
were essentially 100% ct-helical at low temperatures, except for the 2-aminobutyric acid
and glycine analogues, which were estimated to be 85% and 70% helical, respectively.
Circular dichroism showed that the amide bridged analogue in series 4 was able to
increase the helicity of the truncated analogue by approximately 30%, and nuclear
magnetic resonance spectroscopy provided further details regarding the residues within
the sequence that adopted a highly (it—helical conformation. Analytical
ultracentrifugation of the series 2 alanine, valine and threonine analogues showed that
there was no aggregation or self-association occurring up to a concentration of 1 mM.
Ice growth inhibition properties of the analogues were studied using nanoliter
osmometry, the crystal habit test and the ice hemisphere test. The valine substituted
analogue gave a distinct etching pattern in which the protein accumulated on the {2 O 5
1} plane of ice lb, and exhibited thermal hysteresis comparable to the native protein.
The alanine and 2-aminobutyric acid substituted analogues both showed reduced
hysteresis compared to the native protein. A distinct etch pattern in which the protein
accumulated on the {2 l l 0} plane was observed for the alanine analogue. All other
analogues showed no detectable hysteresis and no ability to modify ice growth. The
results show that the threonine hydroxyl groups do not play a crucial role in the
accumulation of the native protein at the ice/water interface and the inhibition of ice
growth below the equilibrium melting temperature. The observed thermal hysteresis
and ice growth inhibition of the valine, alanine and 2-aminobutyric acid analogues
suggest that interactions between these hydrophobic sidechains and the growing ice
crystals are more significant than in previously proposed models. The inability of series
3 analogues to inhibit ice growth indicates the importance of the polar Asx residues in
the mechanism of action.
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Pandiani, Franck. "Mécanismes d’adaptation aux basses températures de croissance de la bactérie pathogène B. cereus : rôle des hélicases à ARN". Thesis, Avignon, 2010. http://www.theses.fr/2010AVIG0634/document.
Testo completoAbstract (sommario):
Bacillus cereus est une bactérie largement disséminée dans la nature, contaminant ainsi les aliments en contact avec le sol. En France, cette bactérie est considérée comme le quatrième agent de toxi infection alimentaire collective. Pour être pathogène, B. cereus doit être capable de se multiplier lors des différentes étapes de transformation et notamment au cours de la réfrigération. Le but de cette étude a été d'étudier les mécanismes moléculaires de la réponse adaptative au froid et en particulier le rôle des hélicases à ARN de B. cereus ATCC 14579. Le gène cshA, codant pour une hélicase à ARN putative, a été identifié par une approche de mutagénèse aléatoire, comme jouant un important dans l’adaptation au froid de B. cereus. La souche ATCC 14579 possède 5 gènes codant pour des hélicases à ARN, cshA à cshE qui sont tous fortement surexprimés à 10°C par rapport à 37°C et quel que soit le stade de croissance considéré. La délétion simple des gènes cshA, cshB et cshC conduit à l’apparition de phénotypes cryosensibles, se traduisant par une incapacité d'adaptation au froid par rapport à la souche sauvage, associée à une modification de la morphologie cellulaire. De plus, CshA, CshB et CshC possèdent chacune un domaine de température où leur action est prépondérante. Elles semblent également être impliquées dans l’adaptation au stress oxydant et au stress basique, alors que CshD et E n’ont pas de rôle dans l’adaptation aux stress testés. Nous avons montré que CshA est indispensable à basse température, pour permettre le maintien de la stabilité des ribosomes avec lesquels elle interagit directement, mais aussi pour réguler la dégradation des ARNr. L’identification des partenaires protéiques interagissant avec CshA suggérent qu'elle puisse être également impliquée dans un complexe de dégradation des ARNBacillus cereus is a widespread bacteria, thus contaminating all raw materials in contact with soil. In France, B. cereus is considered as the fourth causative agent of foodborne illness. To be pathogenic, B. cereus should multiply during the various stages of food processing and particularly during preservation at low temperature. The aim of this study was to study molecular mechanisms of the adaptive response at low temperature and more precisely the involvement of the B. cereus ATCC 14579 RNA helicases. The cshA gene encoding a putative RNA helicase was identified by a random mutagenesis approach, as playing a major role in cold adaptation of B. cereus. The ATCC 14579 strain possesses 5 genes encoding putative RNA helicases, cshA to cshE, which were all strongly overexpressed at 10°C versus 37°C, whatever the growth stage. The simple deletion of cshA, cshB, and cshC lead to a cold-sensitive phenotype, resulting in an inability to adapt at 10 °C compared to the wild type strain, associated to a huge modification of cell morphology. In addition, CshA, CshB and CshC have a temperature range where their action is decisive. The role of these three RNA helicases also appears to be important in adaptation to oxidative and basic stresses while CshD and E did not appear to be involved in the adaptation to the tested stresses. The RNA helicase CshA has the most important role in adaptation to cold. We demonstrated that CshA is essential at low temperature to allow the maintenance of ribosome stability. CshA interacts directly with ribosomes, and also regulate rRNA degradation. The identification of protein partners that interact with CshA suggests that it could be involve in a complex of RNA decay
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Huang, Cunrui. "The health effects of temperature : current estimates, future projections, and adaptation strategies". Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/64353/1/Cunrui_Huang_Thesis.pdf.
Testo completoAbstract (sommario):
Climate change is expected to be one of the biggest global health threats in the 21st century. In response to changes in climate and associated extreme events, public health adaptation has become imperative. This thesis examined several key issues in this emerging research field.
The thesis aimed to identify the climate-health (particularly temperature-health) relationships, then develop quantitative models that can be used to project future health impacts of climate change, and therefore help formulate adaptation strategies for dealing with climate-related health risks and reducing vulnerability. The research questions addressed by this thesis were: (1) What are the barriers to public health adaptation to climate change? What are the research priorities in this emerging field? (2) What models and frameworks can be used to project future temperature-related mortality under different climate change scenarios? (3) What is the actual burden of temperature-related mortality? What are the impacts of climate change on future burden of disease? and (4) Can we develop public health adaptation strategies to manage the health effects of temperature in response to climate change? Using a literature review, I discussed how public health organisations should implement and manage the process of planned adaptation. This review showed that public health adaptation can operate at two levels: building adaptive capacity and implementing adaptation actions. However, there are constraints and barriers to adaptation arising from uncertainty, cost, technologic limits, institutional arrangements, deficits of social capital, and individual perception of risks. The opportunities for planning and implementing public health adaptation are reliant on effective strategies to overcome likely barriers. I proposed that high priorities should be given to multidisciplinary research on the assessment of potential health effects of climate change, projections of future health impacts under different climate and socio-economic scenarios, identification of health cobenefits of climate change policies, and evaluation of cost-effective public health adaptation options.
Heat-related mortality is the most direct and highly-significant potential climate change impact on human health. I thus conducted a systematic review of research and methods for projecting future heat-related mortality under different climate change scenarios. The review showed that climate change is likely to result in a substantial increase in heatrelated mortality. Projecting heat-related mortality requires understanding of historical temperature-mortality relationships, and consideration of future changes in climate, population and acclimatisation. Further research is needed to provide a stronger theoretical framework for mortality projections, including a better understanding of socioeconomic development, adaptation strategies, land-use patterns, air pollution and mortality displacement.
Most previous studies were designed to examine temperature-related excess deaths or mortality risks. However, if most temperature-related deaths occur in the very elderly who had only a short life expectancy, then the burden of temperature on mortality would have less public health importance. To guide policy decisions and resource allocation, it is desirable to know the actual burden of temperature-related mortality. To achieve this, I used years of life lost to provide a new measure of health effects of temperature. I conducted a time-series analysis to estimate years of life lost associated with changes in season and temperature in Brisbane, Australia. I also projected the future temperaturerelated years of life lost attributable to climate change. This study showed that the association between temperature and years of life lost was U-shaped, with increased years of life lost on cold and hot days. The temperature-related years of life lost will worsen greatly if future climate change goes beyond a 2 °C increase and without any adaptation to higher temperatures.
The excess mortality during prolonged extreme temperatures is often greater than the predicted using smoothed temperature-mortality association. This is because sustained period of extreme temperatures produce an extra effect beyond that predicted by daily temperatures. To better estimate the burden of extreme temperatures, I estimated their effects on years of life lost due to cardiovascular disease using data from Brisbane, Australia. The results showed that the association between daily mean temperature and years of life lost due to cardiovascular disease was U-shaped, with the lowest years of life lost at 24 °C (the 75th percentile of daily mean temperature in Brisbane), rising progressively as temperatures become hotter or colder. There were significant added effects of heat waves, but no added effects of cold spells.
Finally, public health adaptation to hot weather is necessary and pressing. I discussed how to manage the health effects of temperature, especially with the context of climate change. Strategies to minimise the health effects of high temperatures and climate change can fall into two categories: reducing the heat exposure and managing the health effects of high temperatures. However, policy decisions need information on specific adaptations, together with their expected costs and benefits. Therefore, more research is needed to evaluate cost-effective adaptation options.
In summary, this thesis adds to the large body of literature on the impacts of temperature and climate change on human health. It improves our understanding of the temperaturehealth relationship, and how this relationship will change as temperatures increase.
Although the research is limited to one city, which restricts the generalisability of the findings, the methods and approaches developed in this thesis will be useful to other researchers studying temperature-health relationships and climate change impacts. The results may be helpful for decision-makers who develop public health adaptation strategies to minimise the health effects of extreme temperatures and climate change.
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Windisch, Heidrun Sigrid [Verfasser], Hans-Otto [Akademischer Betreuer] Pörtner e Reimer [Akademischer Betreuer] Stick. "Molecular adaptation and thermal plasticity in a cold-adapted Antarctic fish / Heidrun Sigrid Windisch. Gutachter: Hans-Otto Pörtner ; Reimer Stick. Betreuer: Hans-Otto Pörtner". Bremen : Staats- und Universitätsbibliothek Bremen, 2013. http://d-nb.info/1072047446/34.
Testo completo
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Diomande, Sara Esther. "Adaptation au froid de la bactérie pathogène Bacillus cereus : étude de mécanismes impliqués et exploitation de la diversité génétique". Thesis, Avignon, 2014. http://www.theses.fr/2014AVIG0666/document.
Testo completoAbstract (sommario):
Bacillus cereus sensu stricto (ss) est un pathogène alimentaire majeur représentant la 2e cause de toxiinfectionalimentaire en France en 2012. Cette espèce fait partie du groupe Bacillus cereus sensu lato (sl)constitué d’espèces ubiquitaires génétiquement très proches et incluant d’autres pathogènes comme B.anthracis, B. thuringensis et B. cytotoxicus. Les souches de B. cereus sl sont d’autre part réparties en septgroupes phylogénétiques présentant des gammes de température de croissance variées et caractérisés partrois thermotypes principaux: thermotolérants, mésophiles, psychrotolérants. L’adaptation au froid dessouches B. cereus ss est un mécanisme clé car il conditionne sa capacité à se développer dans les alimentsréfrigéré pour atteindre des doses qui peuvent être dangereuse pour les consommateurs. Le but de cetteétude a été d’étudier les mécanismes moléculaires impliqués dans l’adaptation au froid de la diversité desouches représentant B. cereus sl.Nous avons mis en évidence que les gènes codant pour le système à deux composants CasK/R sontsurexprimés à basse température. CasK/R s’est révélé être un système générique d’adaptation de B. cereussl au froid, car son rôle a été mis en évidence lors de l’étude de quatre souches de thermotypes différents etleurs mutants isogéniques ΔcasK/R respectifs. Une étude transcriptomique réalisée sur une souche ATCC14579 et son mutant ΔcasK/R a révélé que seize des gènes différentiellement exprimés en début de phaseexponentielle et en phase stationnaire, à basse température, codent pour des protéines impliquées dans lemétabolisme des acides gras. Nous avons mis en évidence le rôle de CasK /R dans la modification de lacomposition en acides gras membranaires via une augmentation de la proportion en acides gras insaturéslors de la croissance de B. cereus au froid. Par ailleurs, le gène codant pour la désaturase DesA,principalement responsable des insaturations des acides gras à basse température est régulée positivementpar CasK/R au froid.Nous avons également démontré que les gènes casK/R sont organisés en opéron avec un gène codant pourun régulateur RpiR-like. De manière originale, cet opéron est négativement régulé par CasK/R à bassetempérature en phase stationnaire. Le promoteur individuel du rpiR est réprimé à basse température maisaussi à température optimale de croissance, ce qui suggère un rôle de CasK/R, même à températureoptimaleBacillus cereus sensu stricto (ss) is a major foodborne pathogen representing the second cause of foodpoisoning in France in 2012. This species belongs to Bacillus cereus sensu lato (sl) consisting of ubiquitousspecies genetically close-related and including other pathogens such as B. anthracis, B. thuringiensis and B.cytotoxicus. The strains of B. cereus sl are divided into seven phylogenetic groups with various growthtemperature ranges and characterized by three main thermotypes: thermotolerant, mesophilic,psychrotolerant. The B. cereus ss cold adaptation is a key mechanism because it determines B. cereusability to grow in refrigerated foods and achieve doses that can be dangerous to consumers. The aim of thisstudy was to study the molecular mechanisms involved in the cold adaptation of strains representing B.cereus sl diversity.We demonstrated that the genes encoding the two component system CasK/R are overexpressed at lowtemperature. CasK/R was found to be a generic mechanism for B. cereus sl cold adaptation as its role washighlighted in the study of four strains with different thermotypes and their respective isogenic mutantsΔcasK/R. A transcriptomic study on a B. cereus ATCC 14579 strain and its ΔcasK/R mutant strain revealedthat sixteen of the genes differentially expressed in both early log phase and stationary phase at lowtemperature encode proteins involved in the fatty acids metabolism. We showed the role of CasK/R in themodification of the membrane fatty acid composition via an increase of the proportion of unsaturated fattyacids during growth of B. cereus at low temperature. Furthermore, the gene encoding the desaturase DesA,mainly responsible of the fatty acids unsaturation at a low temperature is upregulated by CasK/R at lowtemperature.We also demonstrated that casK/R genes were organized in operon with a gene encoding a RpiR-likeregulator. Interstingly,, this operon is negatively regulated by CasK/R at low temperature in the stationaryphase. The individual rpiR promoter is repressed by CasK/R at low temperature but also optimal growthtemperature, suggesting also a role for CasK/R at optimal temperature
40
Slabber, Sarette. "Physiological plasticity in arthropods from Marion Island : indigenous and alien species". Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50417.
Testo completoAbstract (sommario):
Thesis (PhD)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Climate sets range limits in many taxa, and as climate changes, the ranges that plants and animals occupy are altered. The responses of species to climate change involve either migration or local adaptation. An investigation of the local physiological adaptation shown by indigenous and alien arthropods to temperature acclimation formed the primary focus of this study. Increased environmental temperatures favour the establishment of alien species on Southern Ocean Islands. The first records of Porce/lio scaber Latreille, 1804 (Isopoda, Porcellionidae) and an Aphidius wasp species from Marion Island were documented here. The alien wasp was discovered in 2003 and had a current known distribution along the east coast of Marion Island. Both isopods and wasps were reproducing successfully on Marion Island. The wasp species is an aphid parasitoid and had been found mummifying the alien aphid Rhopalosiphum padi. These introductions highlighted the ongoing conflict between use and conservation on the Southern Ocean Islands. Despite considerable work on the upper and lower lethal limits of insects, several major taxa have received little attention. Here this issue was addressed and the lower and upper thermal tolerances and cold hardiness strategy of Antarciopsocus jeanneli Badonnel (Psocoptera: Elipsocidae) from sub-Antarctic Marion Island was investigated. A. jeanneli is freeze intolerant, and more specifically, moderately chill tolerant. Field fresh A. jeanne li had a mean supercooling point (SCP) of -11.1oC, whereas LTSO was -7.7°C, indicating pre-freeze mortality. A. jeanneli responded to acclimation: mean SCP increased from -IS.8°C at a treatment temperature ofO°C, to -7.3°C at ISOC. Investigations of the responses to acclimation of upper and lower lethal limits and limits to activity in insects have focussed primarily on Drosophila. Halmaeusa atriceps (Staphylinidae) was examined for thermal tolerance responses to acclimation, and seasonal acclimatization. In summer and winter, lower lethal temperatures of adults and larvae were c. -7.6 ± 0.03 and -11.1 ± 0.06 °C, respectively. Supercooling points (SCPs) were more variable, with winter SCPs of -S.4 ± 0.4 °C in larvae and -6.3 ± 0.8 °C in adults. The species appeared to be chill susceptible in summer and moderately freeze tolerant in winter, thus showing seasonal acclimatization. Critical thermal minima varied between -3.6 ± 0.2 and -0.6 ± 0.2 °C in larvae, and from -4.1 ± 0.1 to -0.8 ± 0.2 °C in adults. These findings were in keeping with the general pattern found in insects, although this species differed in several respects from others found on Marion Island. In this study the differential responses of indigenous and invasive springtails to temperature were explicitly examined in the context of the beneficial acclimation hypothesis (BAH) and its alternatives. In particular, the thermal acclimation responses of desiccation resistance, supercooling ability, lower and upper thermal limits were compared. Invasive springtails (Pogonognathellus jlavescens, Isotomurus palustris and Ceratophysella denticulata) did not display greater phenotypic flexibility than indigenous springtails (Cryptopygus antarcticus and Tullbergia bisetosa), but did perform better under high temperature conditions. Indigenous species, however, performed better under low temperature conditions. In most cases the BAH was not supported, or could not be distinguished from its alternatives. The prediction that invasive species will outperform indigenous species as climates on Southern Ocean Islands warm was supported. Because temperature plays such a large role in the distribution, abundance and physiological tolerances of invertebrates, microhabitat temperatures along an altitudinal gradient (0 to 800 m above sea level (asi)) were investigated over a two-year period on Marion Island. Mean microhabitat temperatures were comparable to those from previous studies for Southern Ocean Islands, and declined with increasing altitude. The 800 m asl site had the most severe microclimate (highest absolute maximum, lowest absolute minimum and the highest frequency of freeze-thaw cycles). Year one was substantially colder than year two, indicating that interannual variation in microclimate conditions could be responsible for substantial mortality amongst. invertebrate populations. Indeed, indigenous species were best able to tolerate the high incidence of low temperatures at high altitudes, whereas alien species appeared to be confined to lower altitudinal sites on Marion Island, possibly as a consequence of extreme low temperatures at higher altitudes.
AFRIKAANSE OPSOMMING: Klimaat is een van die grootste faktore wat die verpreiding en digthede van dier en plantspesies bepaal. Soos wat klimaatsverandering plaasvind, kan spesies migreer om stresvolle klimaatstoestande te vermy, of hulle kan aanpas by plaaslike omstandighede. Dit is die laasgenoemde opsie wat in hierdie tesis ondersoek was. Die opsporing van Porcellio scaber Latreille, 1804 (Isopoda Porcellionidae) en 'n Aphidius wesp van Marion Eiland word hier aangeteken. Die huidige verspreiding van houtluise in die omgewing van die Navorsingstasie dui daarop dat hulle die eiland waarskynlik vanaf Kaapstad in bou-materiaal bereik het. Die wesp is gedurende 2003 ontdek en is tans versprei langs die oostelike kuslyn van Marion Eiland. Beide hierdie spesies plant suksesvol voort op Marion Eiland. Die wesp spesie parasiteer die uitheemse plantluis Rhopalosiphum padi. Uitheemse muise en die inheemse kleinskedebek weier tot dusver om P. scaber te eet. Die ontdekking van twee nuwe uitheemse spesies dui weereens op die konflik tussen bewaring en benutting van die Suidsee Eilande. Ten spyte daarvan dat aansienlike aandag gewy is aan die hoë- en lae temperatuur toleransies van insekte, is daar talle taksa wat selde nagevors word. Dié toleransies is dus nagevors vir die boekluis Antarctopsocus jeanneli Badennel (Psocoptera: Elipsocidae) van Marion Eiland. Die spesie is vries vermydend, en meer spesifiek, matig verkoelingsbestand. Veldvars A. jeanneli het 'n gemiddelde superverkoelingspunt van - 11.1 °C gehad, en letale temperature (LTSO) van -7.7 °C, wat aandui dat individue vrek voordat hulle vnes, Hierdie spesie reageer op akklimasie: gemiddelde superverkoelingspunt het toegeneem van -15.8 °C na akklimasie by 0 °C tot -7.3 °C na akklimasie by 15 oe. Die effek van akklimasie op temperatuur toleransie in insekte het dusver meestalop Drosophila gefokus. Hier vors ons die effek van akklimasie op die temperatuur toleransie van Halmaeusa atriceps (Styphylynidae) na. In die somer en winter was die lae letale temperature van kewers en larwes onderskeidelik -7.6 ± 0.03 en -11.1 ± 0.06 °C. Superverkoelingspunte (SVP) het meer gevarieer, met SVP van -5.4 ± 0.4 °C in larwes en -6.3 ± 0.8 oe in kewers. Die spesie IS verkoelingsvatbaar in die somer en matig vriesbestand in die winter, wat dui op akklimatisasie in hierdie spesie. Kritiese termale minima het tussen -3.6 ± 0.2 en -0.6 ± 0.2 oe in larwes, en tussen -4.1 ± 0.1 tot -0.8 ± 0.2 oe in kewers gewissel. Hierdie spesie blyk dieselfde fisiologiese tendense wat in insekte te vinde is uit te beeld, maar verskil in verskeie opsigte van ander insekte op Marion Eiland. Hierdie studie het ook die verskillende reaksies van inheemse en uitheemse springsterte met betrekking tot temperatuur akklimasie bestudeer. Die voordelige-akklimasie hipotese en sy alternatiewe hipoteses is in terme van akklimasiereaksies tot desikkasie weerstand, superverkoeling en lae- en hoë temperatuur bestandheid in Marion Eiland springsterte getoets. Die uitheemse springsterte (Pogonognathellus jlavescens, Isotomurus cf palustris en Ceratophysella denticulata) het nie beter fenotipiese plastisiteit getoon as die inheemse spesies (Cryptopygus antarcticus en Tullbergia bisetosa) nie. Die inheemse spesies het egter beter gevaar onder lae-temperatuur toestande. Die voordeligeakklimasie hipotese ontvang nie veelondersteuning in die huidige studie nie, maar kon in sommige gevalle nie van die alternatiewe hipoteses onderskei word nie. Klimaatsverandering mag uitheemse spesies bevoordeel. Die rol wat temperatuur in die verspreiding en fisiologiese toleransies van invertebrate speel word lank reeds waardeer. Daarom vors hierdie studie die mikrohabitat temperature teen 'n gradient tussen seespieël en 800 m bo seespieël (m bs) oor 'n tydperk van twee jaar op Marion Eiland na. Gemiddelde temperature is vergelykbaar met die van vorige studies op Marion Eiland, en neem af soos wat hoogte bo seespieël toeneem. Die 800 m bs studie-gebied het die mees stresvolle mikrohabitat-toestande ondervind (die hoogste absolute maksimum, laagste absolute minimum temperature, en die meeste vries-ontdooi siklusse). Inheemse spesies op Marion Eiland toon hoër.toleransies tot lae temperature as uiheemse spesies, laasgenoemde kom slegs voor by laer hoogtes bo seespieël, waar ekstreme ternperatuur-toestande dalk minder volop is. Klimaatsverwarming mag egter tot 'n toename in ekstreme weerstoestande lei op Marion Eiland, wat aansienlike mortaliteit in invertebraat populasies kan veroorsaak.
41
McDougald, S. Diane School of Microbiology & Immunology UNSW. "Regulation of starvation and nonculturability in the marine pathogen, Vibrio vulnificus". Awarded by:University of New South Wales. School of Microbiology and Immunology, 2000. http://handle.unsw.edu.au/1959.4/19118.
Testo completoAbstract (sommario):
Vibrio vulnificus is a model environmental organism exhibiting a classical starvation response during nutrient limitation as well as a non-culturable state when exposed to low temperatures. In addition to these classic global responses, this organism is an opportunistic pathogen that exhibits numerous virulence factors. This organism was chosen as the model organism for the identification of regulators of the viable but nonculturable response (VBNC) and the starvation-induced maintenance of culturability (SIMC) that occurs when cells are starved prior to low temperature incubation. In order to accomplish this, three indirect approaches were used; proteomics, investigation of intercellular signalling pathways and genetic analysis of regulators involved in these responses. Two-dimensional gel electrophoresis was used to identify proteins expressed under conditions that induced SIMC. It was determined that carbon and long-term phosphorus starvation were important in the SIMC response. V. vulnificus was shown to possess genes, luxS and smcR, that are homologues of genes involved in signalling system system 2 in Vibrio harveyi. Signal molecules were produced upon starvation and the entry to stationary phase in V. vulnificus. Furthermore, a null mutation in smcR, a transcriptional regulator was shown to have pleiotropic effects in V. vulnificus, including up-regulation of numerous virulence factors and a defect in starvation survival and development of the SIMC response. We propose that V. vulnificus possesses a signalling system analogous to that of system 2 in V. harveyi, and that this system is involved in the regulation of stationary phase and starvation adaptation in this organism.
42
Westerlund, T. (Tarja). "Thermal, circulatory, and neuromuscular responses to whole-body cryotherapy". Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514290435.
Testo completoAbstract (sommario):
Abstract
The purpose of this study was to examine thermal (body temperature, thermal sensation and comfort ratings), circulatory (blood pressure, heart rate variability) and neuromuscular performance responses to whole-body cryotherapy (WBC, -110 °C).
Altogether 66 healthy subjects were exposed to WBC for two minutes. The acute and long-term changes were examined, when the subjects were exposed to WBC three times a week during three months.
Skin temperatures decreased very rapidly during WBC, but remained such a high level that there was no risk for frostbites. The effects on rectal temperature were minimal. Repeated exposures to WBC were mostly well tolerated and comfortable and the subjects became habituated at an early stage of trials. WBC increased both systolic (24 mmHg) and diastolic (5 mmHg) blood pressures temporarily. Adaptation of blood pressure was not found during three months. The acute cooling-related increase in high-frequency power of RR-intervals indicated an increase in cardiac parasympathetic modulation, but after repeated WBC the increase was attenuated. The repeated WBC exposure-related increase in resting low frequency power of RR-intervals resembles the response observed related to exercise training. There are signs of neuromuscular adaptation, especially in dynamic performance. A single WBC decreased flight time in drop-jump exercise, but after repeated WBC these changes were almost vanished. This adaptation was confirmed by the change of the activity of the agonist muscle, which increased more and the change of the activity of antagonist muscle, which increased less/did not change after repeated WBC indicating reduced co-contraction and thus, neuromuscular adaptation.
43
Nicolas, Charbel. "Sur l'adaptation au contexte des réseaux de capteurs sans fil". Thesis, Evry, Institut national des télécommunications, 2012. http://www.theses.fr/2012TELE0037/document.
Testo completoAbstract (sommario):
Mobiles, pouvant changer d’environnements au cours du temps, et de milieu pour la transmission des données et de forme de topologie, les capteurs doivent s’adapter au contexte où ils se trouvent afin d’optimiser les mécanismes qu’ils mettent en œuvre. Dans la première partie, nous proposons un mécanisme pour adapter l’architecture d’un réseau de capteurs dynamiquement en fonction du contexte et comprenant la détection dynamique d’un changement de contexte, la détection dynamique du nouveau, l’adaptation dynamique au niveau des trois couches responsables de la gestion des liens de communication en conséquence, le tout sous contrainte de consommation d’énergie. Le travail mené dans cette première partie a d’emblée posé la question de la détection du contexte. C’est une question assez difficile car elle est mal définie. L’objet de la deuxième partie est d’aborder la reconnaissance à la volée de la technologie utilisée par les réseaux émettant du trafic concurrent au réseau de capteurs. Le mécanisme proposé, FIM, identifie la cause d’interférences à partir de modèles d’erreurs observées dans les paquets de données. La détection du contexte permet aux nœuds du réseau de capteurs d’obtenir des informations sur l’environnement. Certains nœuds doivent avoir une connaissance plus fiable de l’environnement que d’autres. Comment récupérer l’information de nœuds voisins, sélectionner ceux de qui on la récupère et ne garder que ce qui nous semble sûr et utile sont les questions qui sont abordées dans la troisième partie. Nous proposons un mécanisme qui permet de décider dynamiquement si des mécanismes de docition doivent être utilisés ou pasBeing mobile, the wireless sensors must adapt to the changing environment. Therefore, in the first part of this thesis we propose a mechanism to adapt the WSN architecture dynamically based on the detected context; this includes the dynamic detection of the topology change, the detection of the new context and consequently the dynamic adaptation of the communication layer. All of these actions are executed under constraints on energy consumption. The work done in this part poses the question of detecting the new context. This is a rather difficult question because it is unclear. The purpose of the second part is to detect on the fly the type of the competitor technology generating a traffic that interferes with the WSN. The proposed mechanism, FIM, identifies the cause of interference from errors model observed in the corrupt data packets. The context detection allows the nodes of the sensor network to obtain information about the environment. Some nodes must have more reliable information on the environment than others. How to retrieve the information? From which neighboring nodes? And what information to keep as safe and useful? Are the questions that are addressed in the third part. We propose a mechanism to dynamically decide if docition mechanisms should be used or not
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Besson, Anne Amelie, e n/a. "Effects of cool temperature on egg incubation, thermoregulation and physiological performance of tuatara (Sphenodon punctatus) : implications for conservation programmes". University of Otago. Department of Zoology, 2009. http://adt.otago.ac.nz./public/adt-NZDU20090713.160643.
Testo completoAbstract (sommario):
Tuatara (Sphenodon spp.) were once widespread over both the North and the South Islands of New Zealand approximately 1000 years ago but are now restricted to offshore islands due to introduced predators and habitat destruction. The survival of tuatara is now threatened by climate change because of isolation on islands that prevent them from migrating to cooler regions, and by their limited capacity to adapt due to their long life span and low genetic diversity. The thermal suitability of cooler regions for future translocations could be the key for tuatara conservation. The overall aim of the study was to determine the effect of cool temperature on the physiology, behaviour and egg incubation of Cook Strait tuatara (Sphenodon punctatus). As well answering specific questions about tuatara and their adaptation to cool temperature this study aimed at answering general questions about the behavioural and evolutionary ecology of reptiles.
I first compared the preferred body temperature, feeding responses and tolerance to cold temperature of tuatara (Sphenodon punctatus) with three lizard species that inhabit the Otago region of southern New Zealand: Hoplodactylus maculatus, Naultinus gemmeus and Oligosoma maccanni. As well as testing the co-adaptation hypothesis between preferred body temperature and physiological performance of reptiles, I wanted to determine whether tuatara (which are planned to be reintroduced from a warmer site to the Otago region) have similar responses to cool temperature as do Otago lizard species. I found that tuatara show responses to cold temperatures similar to those of lizards from southern New Zealand, suggesting that if tuatara are translocated outside of their geographical range, they are likely to survive.
I then tested if tuatara were capable of modifying their thermoregulatory behaviour if translocated to a cooler region. To do so, I conducted a laboratory experiment in which tuatara were provided with three thermal treatments corresponding to the thermal environments they would experience in their current habitat and the proposed reintroduction site. Contrary to the prediction of the cost-benefit model of thermoregulation, tuatara became active thermoregulators when the thermal quality of the habitat decreased. The results suggest that the model is less applicable to cold-adapted species and that if translocated to cooler regions, tuatara will be able to adjust their thermoregulatory behaviour to their thermal environment.
Tuatara are temperature-dependent sex determination (TSD) reptiles and their translocation to cooler regions could have an dramatic impact on the sex ratio of new populations. To determine if potentially lower incubation temperature would be a limiting factor for the reintroduction of tuatara, I translocated eggs to the proposed reintroduction site. Some tuatara embryos developed at the site (and later hatched in the laboratory), but incubation lasted longer than in natural nests and all hatchlings were female. This trend observed in biased sex ratio might change in the context of climate change as an increase of soil temperature by 3�C would allow the production of males at the proposed site.
The present study demonstrates that the translocation of tuatara further south, outside of their current geographical range, is possible and recommended. Tuatara show similar responses to cool temperatures compared with lizards that live in southern New Zealand, they can also adjust their thermoregulatory behaviour if translocated to cooler habitats, and tuatara embryos could potentially develop successfully in cooler regions. The greatest chance for the future survival of tuatara and TSD species in general, lies in translocation to other locations that are thermally suitable.
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Erdal, Ufuk Goksin. "The Effects of Temperatures on System Performance and Bacterial Community Structure in a Biological Phosphorus Removal System". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26384.
Testo completoAbstract (sommario):
It is generally accepted that a decrease in temperature causes the rates of chemical and biochemical reactions to slow down, usually resulting in poorer performance of biological wastewater treatment systems. Despite this, early researchers repeatedly showed that excess biological phosphorus removal (EBPR) was more efficient at colder temperatures. Recent studies, however, have demonstrated that the reaction rates of EBPR processes decrease with temperature in accordance with Arrheniusâ Law, resulting in an apparent contradiction in the literature. The objective of this study was to investigate the EBPR temperature controversy. The experimental systems used were two, lab-scale UCT configuration plants fed with acetate as the sole volatile fatty acid (VFA) source. The results showed that EBPR systems do perform more efficiently at colder temperatures, i.e., at 5oC compared to 20oC. The reason for better system performance was determined to be related to reduced competition for substrate in the non-oxic zones that results in an increased population of phosphate accumulating organisms (PAOs) relative to non-PAOs and, therefore, greater EBPR efficiency even though the reaction rates are slower. The proliferation of PAOs relative to non-PAOs at cold temperature indicates that some of the PAOs are psychrophilic, i.e., they have alternate biochemical pathways that give them a competitive advantage over bacteria dependent upon glycogen metabolism. The activated sludge acclimated to 20oC had relatively high polyhydroxyvalerate (PHV) and glycogen contents relative to sludge acclimated to 5oC. It was initially hypothized that there is a significant competition between PAO and glycogen accumulating organisms (GAOs) at 20oC and cold temperature (5oC) nearly eliminates this competition in favor of the PAOs. A series of batch test experiments revealed that despite similar acetate utilization by the sludges grown at the two temperatures nearly 30% less PHA was produced by the sludge taken from the 20oC reactor, indicating that GAOs were a small fraction of the population at 20oC. Transmission electron microscopy pictures showed that the biomass acclimated to 20oC had a much more diverse bacterial population than the biomass acclimated to 5oC. However, no GAO population was detected in electron microscopy samples under any temperature conditions. The decreased P removal efficiency at 20oC was then attributed to the presence of fermentative or other non poly-P bacteria that are capable of utilizing substrate under anaerobic conditions.
PHA production greatly increased at 5oC, whereas glycogen metabolism substantially reduced. Even though glycogen is an essential requirement for EBPR mechanism, the EBPR microorganisms have the ability to adapt their metabolic pathways to environmental conditions and greatly reduce their need for glycogen. It is apperant that cold temperature inhibits some of the key enzymes in glycogen metabolism resulting in lower glycogen accumulation that in turn increases the EBPR performance. Therefore temperature not only exerts selective pressure on the dominant population but also alters the metabolic pathways of the EBPR process. Increased glycogen accumulation, as observed in this study at 20oC, may not be related to GAO proliferation as suggested by Filipe et al. (2001) instead it may be related to EBPR bacteria to efficiently use glycogen metabolism. Current models (Brdjanovic et al. 1997; Filipe et al. 2002) consider that GAO metabolism is an integral part of EBPR metabolism and the performance of EBPR processes depends on PAO/GAO fraction in the EBPR system. No GAO proliferation was observed even the A/O process was operated without P addition for more than 3 weeks at 10oC. Therefore such important concept should be further investigated before it is included in EBPR models.
EBPR stoichiometry was presumed to be insensitive to temperatures (Brdjanovic et al. 1997). However, observed stoichiometric values of PHA storage per unit glycogen utilization and PHA utilization per unit glycogen rephlenishment were quite different at different temperatures. Temperature, therefore, not only affects the kinetics of EBPR systems but also affects the EBPR stoichiometry.
Most prokaryotic cells have the ability to alter their cellular membrane fatty acid composition as temperature decreases to counteract the adverse effects of temperature on membrane fluidity (Becker et al., 1996). This unique ability is known as â homeoviscous adaptationâ . In this study, homeoviscous adaptation by EBPR activated sludge was investigated for a series of temperatures ranging from 20oC to 5oC using one of the lab scale EBPR systems. The fatty acid analysis results showed that the unsaturated to saturated fatty acid ratio increased from 1.40 to 3.61 as temperature dropped from 20 to 5oC. The increased cis-9-hexadecanoic acid (C16:1) at 5oC strongly indicated the presence of homeoviscous adaptation in the EBPR bacterial community. Thus the cell membranes of the EBPR community were still in a fluid state, and solute transport and proton motive force mechanisms were operable even at 5oC. It was concluded that loss of EBPR performance at low temperatures, as reported by McClintock et al. (1992) was not related to the physical state of the cellular membranes, but was probably caused by unsuitable operational conditions.
Even though the transport of volatile fatty acids (e.g. acetate) is an integral part of EBPR biochemistry and stoichiometry, this important concept has been ignored. Fleet (1997) concluded that acetate entry into bacterial cells in EBPR sludge was simple passive diffusion based upon the results of a single study (Baronofsky et al. 1984). However, this study showed that neither acetate nor propionate can cross the cell membrane via simple passive diffusion. The existence of apparent saturation curves when the substrate uptake rates (acetate and propionate) were plotted against the substrate concentrations suggested that transport of volatile fatty acids obey facilitated or active transport.
Following from the above results, an investigation of the impacts of operational conditions such as low solids retention time (SRT), presence of electron acceptors in the non-oxic zones, low anaerobic detention time, and lack of acclimation was performed. The results showed that the â critical, i.e., wash-outâ SRT increased as temperature decreased, but if the biomass was permitted to acclimate to the lower temperature, a major population shift would occur which would increase the capacity of the system for phosphorus (P) removal. When the 5 oC sludge was allowed to acclimate at a relatively high SRT (18 d), the systemâ s P-removal capacity greatly surpassed that of the 20 oC system. The decrease in EBPR performance because of the presence of nitrates in the non-oxic zones was determined to be greater than what would be predicted based on accepted stoichiometry.Ph. D.
46
Nicolas, Charbel. "Sur l'adaptation au contexte des réseaux de capteurs sans fil". Electronic Thesis or Diss., Evry, Institut national des télécommunications, 2012. http://www.theses.fr/2012TELE0037.
Testo completoAbstract (sommario):
Mobiles, pouvant changer d’environnements au cours du temps, et de milieu pour la transmission des données et de forme de topologie, les capteurs doivent s’adapter au contexte où ils se trouvent afin d’optimiser les mécanismes qu’ils mettent en œuvre. Dans la première partie, nous proposons un mécanisme pour adapter l’architecture d’un réseau de capteurs dynamiquement en fonction du contexte et comprenant la détection dynamique d’un changement de contexte, la détection dynamique du nouveau, l’adaptation dynamique au niveau des trois couches responsables de la gestion des liens de communication en conséquence, le tout sous contrainte de consommation d’énergie. Le travail mené dans cette première partie a d’emblée posé la question de la détection du contexte. C’est une question assez difficile car elle est mal définie. L’objet de la deuxième partie est d’aborder la reconnaissance à la volée de la technologie utilisée par les réseaux émettant du trafic concurrent au réseau de capteurs. Le mécanisme proposé, FIM, identifie la cause d’interférences à partir de modèles d’erreurs observées dans les paquets de données. La détection du contexte permet aux nœuds du réseau de capteurs d’obtenir des informations sur l’environnement. Certains nœuds doivent avoir une connaissance plus fiable de l’environnement que d’autres. Comment récupérer l’information de nœuds voisins, sélectionner ceux de qui on la récupère et ne garder que ce qui nous semble sûr et utile sont les questions qui sont abordées dans la troisième partie. Nous proposons un mécanisme qui permet de décider dynamiquement si des mécanismes de docition doivent être utilisés ou pasBeing mobile, the wireless sensors must adapt to the changing environment. Therefore, in the first part of this thesis we propose a mechanism to adapt the WSN architecture dynamically based on the detected context; this includes the dynamic detection of the topology change, the detection of the new context and consequently the dynamic adaptation of the communication layer. All of these actions are executed under constraints on energy consumption. The work done in this part poses the question of detecting the new context. This is a rather difficult question because it is unclear. The purpose of the second part is to detect on the fly the type of the competitor technology generating a traffic that interferes with the WSN. The proposed mechanism, FIM, identifies the cause of interference from errors model observed in the corrupt data packets. The context detection allows the nodes of the sensor network to obtain information about the environment. Some nodes must have more reliable information on the environment than others. How to retrieve the information? From which neighboring nodes? And what information to keep as safe and useful? Are the questions that are addressed in the third part. We propose a mechanism to dynamically decide if docition mechanisms should be used or not
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Stattin, Eva. "Root freezing tolerance and storability of Scots pine and Norway spruce seedlings /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5639-8.pdf.
Testo completo
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Belgnaoui, Salwa. "Aspects cytochimiques et fonctionnels de l'anhydrobiose, adaptation developpee par l'insecte collembole folsomides angularis face a la dessication et au froid". Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13177.
Testo completoAbstract (sommario):
F. A. Vit en milieu sec et subit des variations climatiques extremes. Il est capable de reguler ses pertes hydriques. Il est peu resistant au froid et a la secheresse. Il survit grace a son aptitude a rentrer en anhydrobiose, grace a une deshydratation lente et progressive. Le metabolisme respiratoire, suivi par l'activite de la cytochrome oxydase, decroit pendant l'anhydrobiose et augmente pendant la rehydratation. Le metabolisme des glacides est aussi modifie: diminution des reserves de glycogene pendant l'anhydrobiose, restauration apres rehydratation
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Wells, Llyd Ewan. "Viral adaptations to life in the cold /". Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11056.
Testo completo
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Ferreira, Joana Filipa Santos. "Listeria monocytogenes em salada com frango pronta a consumir : estudo da vida útil utilizando um challenge test". Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2018. http://hdl.handle.net/10400.5/15124.
Testo completoAbstract (sommario):
Dissertação de Mestrado em Segurança AlimentarListeria monocytogenes é o agente causal da listeriose, infeção rara, mas severa, cuja taxa de fatalidade pode atingir 20% na população humana. A listeriose é quase exclusivamente transmitida pelo consumo de alimentos contaminados. Os alimentos prontos a consumir são muito associados a L. monocytogenes, pois são conservados por longos períodos em refrigeração, durante os quais L. monocytogenes pode desenvolver-se devido ao seu caráter psicrotrófico. A legislação europeia estabeleceu limites para presença e quantificação de L. monocytogenes em alimentos, consoante a etapa da cadeia alimentar em que estes se encontram: no produtor, o alimento deverá demonstrar ausência de L. monocytogenes em 25g e na distribuição comercial poderá conter um máximo de 102 ufc/g de alimento. Usando um challenge test, o presente trabalho visou avaliar a evolução do desenvolvimento da estirpe L. monocytogenes CECT 4031 inoculada artificialmente em salada com frango pronta a consumir, durante a vida útil refrigerada. Esta estirpe foi selecionada por pertencer ao serótipo 1/2a, que é aquele que mais comummente é isolado dos alimentos e que é associado a muitos casos de doença humana. Antes da inoculação, L. monocytogenes foi exposta a um choque com posterior adaptação ao frio (5°C), com o objetivo de simular uma possível adaptação ao ambiente industrial, que é geralmente refrigerado para a produção de saladas prontas para consumir. Utilizou-se uma suspensão com 5 log ufc/ml de L. monocytogenes CECT 4031, para a inoculação das saladas que foram mantidas a 5ºC durante os 7 dias de vida útil. As saladas foram analisadas nos dias 0, 4 e 7 e realizaram-se três réplicas experimentais. Os resultados mostraram que L. monocytogenes variou de 6,1 ± 0,6 log ufc/g a 6,4 ± 0,8 log ufc/g do dia 4 ao dia 7, respetivamente. Os resultados foram analisados e comparados com curvas de crescimento de referência e foram explorados potenciais cenários, considerando a vida útil refrigerada do alimento em estudo. A partir dos resultados estimou-se a quantidade de L. monocytogenes que poderia hipoteticamente estar presente na fase de produção, de forma que o limite legal de 100 ufc/g de alimento no final da vida útil não fosse ultrapassado.
ABSTRACT - Listeria monocytogenes in ready-to-eat chicken salad: challenge testing for shelf life assessment - Listeria monocytogenes is the causal agent of listeriosis, a rare but severe life-threatening human illness, with a fatality rate of about 20%. Listeriosis is almost exclusively transmitted by food consumption. L. monocytogenes is especially related to ready-to-eat foods, because of the long refrigerated shelf life, during which L. monocytogenes may thrive and develop, due to its psychrotrophic character. European legislation establishes two different limits for L. monocytogenes in ready-to-eat foods, according to the food chain stakeholder: in the producer absence of L. monocytogenes in 25g of food is required, whereas while the foods are placed on the market up to 100 ufc/g may be present. Using a challenge test, this work aimed to assess L. monocytogenes CECT 4031 growth when artificially inoculated in a ready-to-eat chicken salad, during its refrigerated shelf life. This L. monocytogenes strain was selected because it belongs to serotype 1/2a, the one that is most commonly isolated from foods and associated with many cases of human illness. Before inoculation, L. monocytogenes was previously exposed to a cold stress and adaptation to refrigerated temperature (5ºC), in order to recreate a possible adaptation to the industrial environment, which is usually kept under refrigeration for the preparation of ready-to-eat salads. A 5 log cfu/ml suspension of L. monocytogenes CECT 4031 was used to inoculate the salads that were kept at 5ºC during its 7 days shelf life. Salads were analyzed at day 0, 4 and 7 and three experimental replicates were performed. L. monocytogenes enumeration ranged from 6.1±0.6 log cfu/g to 6.4±0.8 log cfu/g from day 4 to day 7, respectively. Results were analyzed and compared with reference growth curves and potential scenarios were explored, considering the refrigerated shelf life of chicken salads. The hypothetical maximum concentration of L. monocytogenes that could be present at the production stage was estimated, in order to comply with the mandatory limit of 100 cfu/g at the end of shelf life.
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