Dissertations / Theses: 'Diverse Interactions'

1

Petrou, Georgia. "Investigating mucin interactions with diverse surfaces for biomedical applications." Licentiate thesis, KTH, Glykovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-249469.

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Mucous membranes are covered with mucus, a viscoelastic hydrogel that plays an essential role in their protection from shear and pathogens. The viscoelasticity of mucus is owing to mucins, a group of densely glycosylated proteins. Mucins can interact with a wide range of surfaces; thus, there is big interest in exploring and manipulating such interactions for biomedical applications. This thesis presents investigations of mucin interactions with hydrophobic surfaces in order to identify the key features of mucin lubricity, as well as describes the development of materials that are optimized to interact with mucins. In Paper I we investigated the domains which make mucins outstanding boundary lubricants. The results showed that the hydrophobic terminal domains of mucins play a crucial role in the adsorption and lubrication on hydrophobic surfaces. Specifically, protease digestion of porcine gastric mucins and salivary mucins resulted in the cleavage of these domains and the loss of lubricity and surface adsorption. However, a “rescue” strategy was successfully carried out by grafting hydrophobic phenyl groups to the digested mucins and enhancing their lubricity. This strategy also enhanced the lubricity of polymers which are otherwise bad lubricants. In Paper II we developed mucoadhesive materials based on genetically engineered partial spider silk proteins. The partial spider silk protein 4RepCT was successfully functionalized with six lysines (pLys-4RepCT), or the Human Galectin-3 Carbohydrate Recognition Domain (hGal3-4RepCT). These strategies were aiming to either non-specific electrostatic interactions between the positive lysines and the negative mucins, or specific binding between the hGal3 and the mucin glycans. Coatings, fibers, meshes and foams were prepared from the new silk proteins, and the adsorption of porcine gastric mucins and bovine submaxillary mucins was measured, demonstrating enhanced adsorption. The work presented demonstrates how mucin-material interactions can provide us with valuable information for the development of new biomaterials. Specifically, mucin-based and mucin-inspired lubricants could provide desired lubrication to a wide range of surfaces, while our new silk based materials could be valuable tools for the development of mucosal dressings.
Slemhinnor täckts av slem, en viskoelastisk hydrogel som spelar en viktig roll för att skydda mot mekanisk nötning och patogener. Muciner, en grupp av tätt glykosylerade proteiner, spelar en viktig roll i viskoelasticiteten av slem. Eftersom muciner kan interagera med diverse ytor är det av stort intresse att utforska och manipulera sådana interaktioner för biomedicinska tillämpningar. Denna avhandling presenterar undersökningar av mucininteraktioner med hydrofoba ytor för att identifiera de viktigaste egenskaperna hos mucinsmörjning, samt beskriver utveckling av material som optimerades för att interagera med muciner. I Artikel I undersökte vi de domäner som bidrar till mucinernas enastående kapacitet som smörjmedel. Resultaten visade att mucinernas hydrofoba terminaldomäner spelar en avgörande roll vid adsorption och smörjning på hydrofoba ytor. Mer specifikt, proteasklyvning av svinmagemuciner och salivmuciner resulterade i klyvningen av dessa domäner och förlust av smörjning och ytadsorption. Genom att länka hydrofobiska fenylgrupper till de uppbrutna mucinerna, lyckades deras smörjningsegenskaper förbättras. Denna strategi förbättrade också smörjningsegenskaper hos andra polymerer som annars har dåliga smörjningsegenskaper. I Artikel II utvecklade vi mukoadhesiva material baserade på genetiskt modifierade partiella spindelsilkeproteiner. Spindelsilkeproteinet 4RepCT funktionaliserades framgångsrikt med tillsats av sex lysiner (pLys-4RepCT), eller den mänskliga Galectin-3 karbohydrat igenkänningsdomänen (hGal3-4RepCT). Syftet med dessa strategier var antingen att öka ospecifika elektrostatiska interaktioner mellan de positiva lysinerna och de negativa mucinerna, eller den specifika bindningen mellan hGal3 och mucin-glykanerna. Beläggningar, fibrer, nät och skum framställdes från de nya silkeproteinerna. Efter att adsorption av svinmagsmuciner och bovina submaxillära muciner uppmätts, visade de nya silkeproteinerna förbättrad mucin adsorption. Detta arbete visar hur interaktioner mellan mucin-material kan bidra med värdefull information för utvecklingen av nya biomaterial. Mucinbaserade och mucininspirerade smörjmedel kan ge önskad smörjning till ett brett spektrum av ytor, medan vår nya silkesbaserad material kan vara ett värdefullt verktyg för utvecklingen av slemhinneförband.

QC 20190412

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2

Schmitt, Anita Maria. "Gifted students in diverse environments an analysis of interactions and perceptions /." [Pensacola, Fla.] : University of West Florida, 2009. http://purl.fcla.edu/fcla/etd/WFE0000160.

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3

Haider, Mohammed Jassim. "Characterisation of FcRy-coupled phagocytic interactions between macrophages and taxonomically diverse fungi." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=233453.

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4

Barile, John P. "Health Disparities in a Diverse County: Investigating Interactions between Residents and Neighborhoods." Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/psych_diss/80.

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This study evaluated the associations of individual and neighborhood level risk factors with physical health, mental health, and stress in a diverse urban county. Relatively little research has attempted to disentangle the interactive individual characteristics and neighborhood conditions underlying health outcomes and disparities. To address this, survey data were collected and analyzed from 1,107 residents living in one of the 114 census tracts in DeKalb County, GA. Using multilevel structural equation modeling techniques, this study found that neighborhood level measures of the social and built environment were not associated with the health outcomes under study after controlling for neighborhood level income and education. Alternatively, individual level perceptions of the social and built environment and measures of access to health care were significantly associated with physical health, mental health, and perceived stress. This study also found that the association between low individual income and poor physical health was more pronounced for participants who lived in low-income neighborhoods than participants who lived in high-income neighborhoods. Additionally, this study found that Black residents reported significantly better mental health compared to White residents when they lived in high-income neighborhoods, and Black participants reported significantly more stress compared to White participants when they lived in low-income neighborhoods. Results of this study further scientific understanding of the role of neighborhood processes in health disparities and potentially help inform the development of programs and policies related to neighborhood conditions and health disparities.

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5

Suetsugu, Kenji. "Diverse interactions of heterotrophic plants with their hosts, pollinators and seed dispersers." Kyoto University, 2014. http://hdl.handle.net/2433/192205.

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Abstract:

Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第18605号
人博第701号
新制||人||167(附属図書館)
26||人博||701(吉田南総合図書館)
31505
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授加藤眞, 教授市岡孝朗, 教授瀬戸口浩彰, 教授宮本嘉久, 教授新宮一成
学位規則第4条第1項該当

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6

Simmons, Noreen Rosalind. "Barriers, bridges and beyond : understanding perspectives in linguistically and culturally diverse clinical interactions." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31524.

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This study attempts to understand how monolingual English-speaking Speech-Language Pathologists (SLPs) and their Linguistically and Culturally Diverse (LCD) Indo-Canadian adult aphasic clients manage clinical interactions when they do not share the same language and/or culture. The specific objectives were to describe and explain participants' perspectives on the barriers they encountered, and the strategies they employed to overcome the barriers, and to develop a substantive theory that elucidates how SLPs manage such LCD clinical interactions. A symbolic interactionist theoretical perspective and grounded theory method were used to explore the clinical interaction experiences of eleven monolingual English-speaking SLPs, five adult Indo-Canadian aphasic clients, six family members, and five interpreters. Data were collected through interviews, observation, and field notes. Concurrent data collection and analysis was undertaken throughout the study. Constant comparative analysis, which included open, selective, and theoretical coding, was used to construct the substantive theory. The core category that emerged, 'coordinating communicative goals,' described the basic social process that was involved in clinician-client LCD interactions. This core category captured two stages and three conditions that participants encountered during clinical interactions. The two stages were 'encountering challenges in clinical interactions' and 'using strategies to overcome challenges.' The three conditions were 'linguistic barriers,' 'cultural barriers,' and 'involvement of family members and/or interpreters.' The two stages explained the processes used by participants during clinical interactions, and the three conditions were factors that impacted the stages. The findings indicate that participants coordinated their respective communicative goals in clinical interactions by going through an iterative process of confronting challenges and implementing strategies to overcome some of those challenges. The findings from this study have important implications for research, clinical practice, education, and policy aimed at helping SLPs provide linguistically and culturally appropriate services to LCD clients.
Medicine, Faculty of
Audiology and Speech Sciences, School of
Graduate

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7

Gomez-Lopez, Iris Nelly. "Simulating the Spread of Infectious Diseases in Heterogeneous Populations with Diverse Interactions Characteristics." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407831/.

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The spread of infectious diseases has been a public concern throughout human history. Historic recorded data has reported the severity of infectious disease epidemics in different ages. Ancient Greek physician Hippocrates was the first to analyze the correlation between diseases and their environment. Nowadays, health authorities are in charge of planning strategies that guarantee the welfare of citizens. The simulation of contagion scenarios contributes to the understanding of the epidemic behavior of diseases. Computational models facilitate the study of epidemics by integrating disease and population data to the simulation. The use of detailed demographic and geographic characteristics allows researchers to construct complex models that better resemble reality and the integration of these attributes permits us to understand the rules of interaction. The interaction of individuals with similar characteristics forms synthetic structures that depict clusters of interaction. The synthetic environments facilitate the study of the spread of infectious diseases in diverse scenarios. The characteristics of the population and the disease concurrently affect the local and global epidemic progression. Every cluster’ epidemic behavior constitutes the global epidemic for a clustered population. By understanding the correlation between structured populations and the spread of a disease, current dissertation research makes possible to identify risk groups of specific characteristics and devise containment strategies that facilitate health authorities to improve mitigation strategies.

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8

Moller, Abraham Ghoreishi. "Mapping ecologically important virus-host interactions in geographically diverse solar salterns with metagenomics." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461841762.

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9

Barman, Biraj Kumar. "Investigation of diverse interactions and inclusion complexation in different environment by physicochemical methodology." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2622.

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10

Dutta, Ashutosh. "Exploration of diversified interactions of some significant compounds prevalent in several environments by physicochemical contrivance." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2787.

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11

Ray, Samapika. "Study to explore inclusion complexations and assorted interactions of some industrially and biologically significant molecules in diverse systems." Thesis, University of North Bengal, 2022. http://ir.nbu.ac.in/handle/123456789/4789.

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12

Yates, Ronald John. "Symbiotic interactions of geographically diverse annual and perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii /." Murdoch University Digital Theses Program, 2008. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20100330.93305.

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13

au, ronald yates@agric wa gov, and Ronald John Yates. "Symbiotic Interactions of Geographically Diverse Annual and Perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii." Murdoch University, 2008. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20100330.93305.

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Perennial clovers are being evaluated for their potential to reduce groundwater levels in Australian cropping zones where many soils are considered too acidic for reliable lucerne nodulation. However, the release of effective inocula for perennial clovers into such areas where sub clover is the predominant legume, could potentially compromise nitrogen fixation from this valuable annual clover if the symbiosis between the new inoculants and sub clover is not optimal. Studies were therefore designed to increase our understanding of these symbiotic interactions to optimise the management of legume-rhizobia interactions to extend (rather than restrict) the use of legumes in new environments. To assist the understanding of interactions between clovers and their microsymbionts, a glasshouse-based study of the cross-inoculation characteristics of 38 strains of Rhizobium leguminosarum biovar trifolii (R. l. trifolii) associated with 38 genotypes of annual and perennial Trifolium spp. from world centres of diversity was undertaken. Rhizobial isolates and clovers were assembled from South and equatorial Africa, North and South America and the Euro-Mediterranean regions. There was substantial specificity amongst the African clovers for effective nodulation. No strain of rhizobia from the South American perennial T. polymorphum, or from the Ethiopian clovers, was able to nodulate sub clover effectively, whilst less than 33% of the 18 strains from these regions could form nodules with the less promiscuous Mediterranean annual T. glanduliferum. Seventy of 476 cross-inoculation treatments examined did not nodulate, whilst 81 treatments clearly demonstrated effective nodulation. The remainder of the crossinoculation pairings revealed only partially effective or ineffective nodulation. Two barriers to effective nodulation were identified from the cross- inoculation study: a geographic barrier representing the broad centres of clover diversity, across which few host- strain combinations were effective; and within each region, a significant barrier to effective nodulation between an isolate from an annual host on a perennial host, or vice versa. Clovers and their rhizobia from within the Euro-Mediterranean region of diversity were more able to overlap the annual/perennial barrier than genotypes from the other regions. The data indicate that it will be a substantial challenge to develop inocula for perennial clovers that do not adversely affect nitrogen fixation by sub clover and other annual clovers in commerce, especially if the perennial clovers originate from Africa or America. To investigate the management of legume-rhizobia interactions when introducing legumes into new environments, a study was initiated in Uruguay (Mediterranean annual clovers were introduced into a predominantly perennial clover setting) that could be considered opposite to the situation emerging within southern Australia (perennial clovers evaluated in a predominantly annual clover setting). The Uruguayan grasslands contain populations of indigenous R. l. trifolii that nodulate endemic T. polymorphum but form ineffective nodules on clovers originating from the Mediterranean region. Importantly in the Uruguayan setting, Government policy has facilitated the introduction of numerous varieties of annual Mediterranean clovers with the aim of improving overall winter production in their naturally managed grasslands. In an attempt to understand the rhizobial ecology of this scenario, a cross-row experiment was set-up in 1999 in a basaltic, acid soil in Glencoe, Uruguay, to follow the survival and symbiotic performance of nine exotic strains of R. l. trifolii. In this thesis I report on the ability of the introduced strains to compete for nodule occupancy of Mediterranean clover hosts and show the impacts of the introduced strains on the productivity of the indigenous Uruguayan clover, T. polymorphum. Of the introduced strains, WSM1325 was a superior inoculant and remained highly persistent and competitive in forming effective symbioses with the Mediterranean hosts, T. purpureum and T. repens, in the Uruguayan environment over a 3 year period. T. purpureum and T. repens, when inoculated with the introduced strains, did not nodulate with any indigenous R. l. trifolii as typed from nodules of T. polymorphum. Conversely, there were no nodules on the Uruguayan host T. polymorphum that contained the introduced R. l. trifolii. These results revealed that there were effective symbioses between strains of R. l. trifolii and clovers, even though the soil contained ineffective R. l. trifolii for all hosts. This represents the first reported example of selective nodulation for an effective symbiosis in situ with annual and perennial clovers in acid soils. This phenomenon raised the question of whether this was restricted to the particular edaphic scenario in Glencoe, Uruguay. Glasshouse-based experiments in Australia were conducted to further understand the selection phenomenon. Two strains were selected for comparisons; strain WSM1325 isolated from an annual clover in the Mediterranean and WSM2304 isolated from the perennial clover T. polymorphum in Uruguay, South America. Variables that may have been specific to Glencoe were investigated. Thus, the effect of cell density and strain ratio at the time of inoculation, as well as soil pH, were examined on the two hosts (T. purpureum and T. polymorphum). Each was exposed to the same effective and ineffective micro-symbionts. In co-inoculation experiments at a cell density of 104 cells mL-1, each host nodulated solely with its effective strain, even when this strain was out-numbered 100:1 by the ineffective strain. However, the selection process ceased when the effective strain was out-numbered 1000:1. At higher basal cell concentrations of 105 - 108 cells mL-1, selection for WSM1325 to form effective nodules on T. purpureum was evident, but was significantly reduced as the ratio of ineffective cells in the inoculum increased above 4-fold. These results indicate that the selection mechanism is highly dependent upon the basal rhizobial cell density. Soil pH did not significantly alter the process, which could not be simply explained by the rate of strain growth, or extent of nodulation. Greater precision was sought in the terminology applied to nodulation outcomes where legumes have a choice of micro-symbiotic partners from within the same species of root-nodule bacteria. The nominated preferred terms are nonselective, exclusive, and selective nodulation. In view of the difference in host range between WSM1325 and WSM2304 and the selective nodulation process, a preliminary investigation into the genetic backgrounds of WSM1325 and WSM2304 was conducted. A selected range of gene regions were amplified by PCR from each strain and sequenced. Comparative analysis of the nucleotide sequences revealed that although the 16S rRNA sequences were identical, the atpD, GSII and nodD sequences contained distinct differences revealing disparity between the pSym replicons and between the chromosomal replicons of these strains. Of the genes sequenced, the highest degree of divergence was noted for the symbiotic NodD protein products, which are known to be critical determinants in the nodulation of specific hosts. An examination of the nodD gene region of WSM1325 and WSM2304 revealed a further contrasting feature; the regulatory gene nodR was present in the nodD gene region of WSM1325 but absent in WSM2304. Since NodR is known to be required for adding highly unsaturated fatty acyl groups onto the Nod-factor backbone, I could now hypothesise that the nodulation incompatibility observed between Trifolium hosts and micro-symbionts obtained from different geographical locations may result from differences in Nod-factor decoration. With the full genome sequence of the two strains WSM1325 and WSM2304 soon to be available, the role of nodR and any link to the selection phenomenon described in this thesis can be addressed.

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14

Yates, Ronald. "Symbiotic Interactions of Geographically Diverse Annual and Perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii." Thesis, Yates, Ronald (2008) Symbiotic Interactions of Geographically Diverse Annual and Perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii. PhD thesis, Murdoch University, 2008. https://researchrepository.murdoch.edu.au/id/eprint/1699/.

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Abstract:

Perennial clovers are being evaluated for their potential to reduce groundwater levels in Australian cropping zones where many soils are considered too acidic for reliable lucerne nodulation. However, the release of effective inocula for perennial clovers into such areas where sub clover is the predominant legume, could potentially compromise nitrogen fixation from this valuable annual clover if the symbiosis between the new inoculants and sub clover is not optimal. Studies were therefore designed to increase our understanding of these symbiotic interactions to optimise the management of legume-rhizobia interactions to extend (rather than restrict) the use of legumes in new environments. To assist the understanding of interactions between clovers and their microsymbionts, a glasshouse-based study of the cross-inoculation characteristics of 38 strains of Rhizobium leguminosarum biovar trifolii (R. l. trifolii) associated with 38 genotypes of annual and perennial Trifolium spp. from world centres of diversity was undertaken. Rhizobial isolates and clovers were assembled from South and equatorial Africa, North and South America and the Euro-Mediterranean regions. There was substantial specificity amongst the African clovers for effective nodulation. No strain of rhizobia from the South American perennial T. polymorphum, or from the Ethiopian clovers, was able to nodulate sub clover effectively, whilst less than 33% of the 18 strains from these regions could form nodules with the less promiscuous Mediterranean annual T. glanduliferum. Seventy of 476 cross-inoculation treatments examined did not nodulate, whilst 81 treatments clearly demonstrated effective nodulation. The remainder of the crossinoculation pairings revealed only partially effective or ineffective nodulation. Two barriers to effective nodulation were identified from the cross- inoculation study: a geographic barrier representing the broad centres of clover diversity, across which few host- strain combinations were effective; and within each region, a significant barrier to effective nodulation between an isolate from an annual host on a perennial host, or vice versa. Clovers and their rhizobia from within the Euro-Mediterranean region of diversity were more able to overlap the annual/perennial barrier than genotypes from the other regions. The data indicate that it will be a substantial challenge to develop inocula for perennial clovers that do not adversely affect nitrogen fixation by sub clover and other annual clovers in commerce, especially if the perennial clovers originate from Africa or America. To investigate the management of legume-rhizobia interactions when introducing legumes into new environments, a study was initiated in Uruguay (Mediterranean annual clovers were introduced into a predominantly perennial clover setting) that could be considered opposite to the situation emerging within southern Australia (perennial clovers evaluated in a predominantly annual clover setting). The Uruguayan grasslands contain populations of indigenous R. l. trifolii that nodulate endemic T. polymorphum but form ineffective nodules on clovers originating from the Mediterranean region. Importantly in the Uruguayan setting, Government policy has facilitated the introduction of numerous varieties of annual Mediterranean clovers with the aim of improving overall winter production in their naturally managed grasslands. In an attempt to understand the rhizobial ecology of this scenario, a cross-row experiment was set-up in 1999 in a basaltic, acid soil in Glencoe, Uruguay, to follow the survival and symbiotic performance of nine exotic strains of R. l. trifolii. In this thesis I report on the ability of the introduced strains to compete for nodule occupancy of Mediterranean clover hosts and show the impacts of the introduced strains on the productivity of the indigenous Uruguayan clover, T. polymorphum. Of the introduced strains, WSM1325 was a superior inoculant and remained highly persistent and competitive in forming effective symbioses with the Mediterranean hosts, T. purpureum and T. repens, in the Uruguayan environment over a 3 year period. T. purpureum and T. repens, when inoculated with the introduced strains, did not nodulate with any indigenous R. l. trifolii as typed from nodules of T. polymorphum. Conversely, there were no nodules on the Uruguayan host T. polymorphum that contained the introduced R. l. trifolii. These results revealed that there were effective symbioses between strains of R. l. trifolii and clovers, even though the soil contained ineffective R. l. trifolii for all hosts. This represents the first reported example of selective nodulation for an effective symbiosis in situ with annual and perennial clovers in acid soils. This phenomenon raised the question of whether this was restricted to the particular edaphic scenario in Glencoe, Uruguay. Glasshouse-based experiments in Australia were conducted to further understand the selection phenomenon. Two strains were selected for comparisons; strain WSM1325 isolated from an annual clover in the Mediterranean and WSM2304 isolated from the perennial clover T. polymorphum in Uruguay, South America. Variables that may have been specific to Glencoe were investigated. Thus, the effect of cell density and strain ratio at the time of inoculation, as well as soil pH, were examined on the two hosts (T. purpureum and T. polymorphum). Each was exposed to the same effective and ineffective micro-symbionts. In co-inoculation experiments at a cell density of 104 cells mL-1, each host nodulated solely with its effective strain, even when this strain was out-numbered 100:1 by the ineffective strain. However, the selection process ceased when the effective strain was out-numbered 1000:1. At higher basal cell concentrations of 105 - 108 cells mL-1, selection for WSM1325 to form effective nodules on T. purpureum was evident, but was significantly reduced as the ratio of ineffective cells in the inoculum increased above 4-fold. These results indicate that the selection mechanism is highly dependent upon the basal rhizobial cell density. Soil pH did not significantly alter the process, which could not be simply explained by the rate of strain growth, or extent of nodulation. Greater precision was sought in the terminology applied to nodulation outcomes where legumes have a choice of micro-symbiotic partners from within the same species of root-nodule bacteria. The nominated preferred terms are “nonselective”, “exclusive”, and “selective” nodulation. In view of the difference in host range between WSM1325 and WSM2304 and the selective nodulation process, a preliminary investigation into the genetic backgrounds of WSM1325 and WSM2304 was conducted. A selected range of gene regions were amplified by PCR from each strain and sequenced. Comparative analysis of the nucleotide sequences revealed that although the 16S rRNA sequences were identical, the atpD, GSII and nodD sequences contained distinct differences revealing disparity between the pSym replicons and between the chromosomal replicons of these strains. Of the genes sequenced, the highest degree of divergence was noted for the symbiotic NodD protein products, which are known to be critical determinants in the nodulation of specific hosts. An examination of the nodD gene region of WSM1325 and WSM2304 revealed a further contrasting feature; the regulatory gene nodR was present in the nodD gene region of WSM1325 but absent in WSM2304. Since NodR is known to be required for adding highly unsaturated fatty acyl groups onto the Nod-factor backbone, I could now hypothesise that the nodulation incompatibility observed between Trifolium hosts and micro-symbionts obtained from different geographical locations may result from differences in Nod-factor decoration. With the full genome sequence of the two strains WSM1325 and WSM2304 soon to be available, the role of nodR and any link to the selection phenomenon described in this thesis can be addressed.

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15

Yates, Ronald. "Symbiotic Interactions of Geographically Diverse Annual and Perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii." Yates, Ronald (2008) Symbiotic Interactions of Geographically Diverse Annual and Perennial Trifolium spp. with Rhizobium leguminosarum bv. trifolii. PhD thesis, Murdoch University, 2008. http://researchrepository.murdoch.edu.au/1699/.

Full text

Abstract:

Perennial clovers are being evaluated for their potential to reduce groundwater levels in Australian cropping zones where many soils are considered too acidic for reliable lucerne nodulation. However, the release of effective inocula for perennial clovers into such areas where sub clover is the predominant legume, could potentially compromise nitrogen fixation from this valuable annual clover if the symbiosis between the new inoculants and sub clover is not optimal. Studies were therefore designed to increase our understanding of these symbiotic interactions to optimise the management of legume-rhizobia interactions to extend (rather than restrict) the use of legumes in new environments. To assist the understanding of interactions between clovers and their microsymbionts, a glasshouse-based study of the cross-inoculation characteristics of 38 strains of Rhizobium leguminosarum biovar trifolii (R. l. trifolii) associated with 38 genotypes of annual and perennial Trifolium spp. from world centres of diversity was undertaken. Rhizobial isolates and clovers were assembled from South and equatorial Africa, North and South America and the Euro-Mediterranean regions. There was substantial specificity amongst the African clovers for effective nodulation. No strain of rhizobia from the South American perennial T. polymorphum, or from the Ethiopian clovers, was able to nodulate sub clover effectively, whilst less than 33% of the 18 strains from these regions could form nodules with the less promiscuous Mediterranean annual T. glanduliferum. Seventy of 476 cross-inoculation treatments examined did not nodulate, whilst 81 treatments clearly demonstrated effective nodulation. The remainder of the crossinoculation pairings revealed only partially effective or ineffective nodulation. Two barriers to effective nodulation were identified from the cross- inoculation study: a geographic barrier representing the broad centres of clover diversity, across which few host- strain combinations were effective; and within each region, a significant barrier to effective nodulation between an isolate from an annual host on a perennial host, or vice versa. Clovers and their rhizobia from within the Euro-Mediterranean region of diversity were more able to overlap the annual/perennial barrier than genotypes from the other regions. The data indicate that it will be a substantial challenge to develop inocula for perennial clovers that do not adversely affect nitrogen fixation by sub clover and other annual clovers in commerce, especially if the perennial clovers originate from Africa or America. To investigate the management of legume-rhizobia interactions when introducing legumes into new environments, a study was initiated in Uruguay (Mediterranean annual clovers were introduced into a predominantly perennial clover setting) that could be considered opposite to the situation emerging within southern Australia (perennial clovers evaluated in a predominantly annual clover setting). The Uruguayan grasslands contain populations of indigenous R. l. trifolii that nodulate endemic T. polymorphum but form ineffective nodules on clovers originating from the Mediterranean region. Importantly in the Uruguayan setting, Government policy has facilitated the introduction of numerous varieties of annual Mediterranean clovers with the aim of improving overall winter production in their naturally managed grasslands. In an attempt to understand the rhizobial ecology of this scenario, a cross-row experiment was set-up in 1999 in a basaltic, acid soil in Glencoe, Uruguay, to follow the survival and symbiotic performance of nine exotic strains of R. l. trifolii. In this thesis I report on the ability of the introduced strains to compete for nodule occupancy of Mediterranean clover hosts and show the impacts of the introduced strains on the productivity of the indigenous Uruguayan clover, T. polymorphum. Of the introduced strains, WSM1325 was a superior inoculant and remained highly persistent and competitive in forming effective symbioses with the Mediterranean hosts, T. purpureum and T. repens, in the Uruguayan environment over a 3 year period. T. purpureum and T. repens, when inoculated with the introduced strains, did not nodulate with any indigenous R. l. trifolii as typed from nodules of T. polymorphum. Conversely, there were no nodules on the Uruguayan host T. polymorphum that contained the introduced R. l. trifolii. These results revealed that there were effective symbioses between strains of R. l. trifolii and clovers, even though the soil contained ineffective R. l. trifolii for all hosts. This represents the first reported example of selective nodulation for an effective symbiosis in situ with annual and perennial clovers in acid soils. This phenomenon raised the question of whether this was restricted to the particular edaphic scenario in Glencoe, Uruguay. Glasshouse-based experiments in Australia were conducted to further understand the selection phenomenon. Two strains were selected for comparisons; strain WSM1325 isolated from an annual clover in the Mediterranean and WSM2304 isolated from the perennial clover T. polymorphum in Uruguay, South America. Variables that may have been specific to Glencoe were investigated. Thus, the effect of cell density and strain ratio at the time of inoculation, as well as soil pH, were examined on the two hosts (T. purpureum and T. polymorphum). Each was exposed to the same effective and ineffective micro-symbionts. In co-inoculation experiments at a cell density of 104 cells mL-1, each host nodulated solely with its effective strain, even when this strain was out-numbered 100:1 by the ineffective strain. However, the selection process ceased when the effective strain was out-numbered 1000:1. At higher basal cell concentrations of 105 - 108 cells mL-1, selection for WSM1325 to form effective nodules on T. purpureum was evident, but was significantly reduced as the ratio of ineffective cells in the inoculum increased above 4-fold. These results indicate that the selection mechanism is highly dependent upon the basal rhizobial cell density. Soil pH did not significantly alter the process, which could not be simply explained by the rate of strain growth, or extent of nodulation. Greater precision was sought in the terminology applied to nodulation outcomes where legumes have a choice of micro-symbiotic partners from within the same species of root-nodule bacteria. The nominated preferred terms are “nonselective”, “exclusive”, and “selective” nodulation. In view of the difference in host range between WSM1325 and WSM2304 and the selective nodulation process, a preliminary investigation into the genetic backgrounds of WSM1325 and WSM2304 was conducted. A selected range of gene regions were amplified by PCR from each strain and sequenced. Comparative analysis of the nucleotide sequences revealed that although the 16S rRNA sequences were identical, the atpD, GSII and nodD sequences contained distinct differences revealing disparity between the pSym replicons and between the chromosomal replicons of these strains. Of the genes sequenced, the highest degree of divergence was noted for the symbiotic NodD protein products, which are known to be critical determinants in the nodulation of specific hosts. An examination of the nodD gene region of WSM1325 and WSM2304 revealed a further contrasting feature; the regulatory gene nodR was present in the nodD gene region of WSM1325 but absent in WSM2304. Since NodR is known to be required for adding highly unsaturated fatty acyl groups onto the Nod-factor backbone, I could now hypothesise that the nodulation incompatibility observed between Trifolium hosts and micro-symbionts obtained from different geographical locations may result from differences in Nod-factor decoration. With the full genome sequence of the two strains WSM1325 and WSM2304 soon to be available, the role of nodR and any link to the selection phenomenon described in this thesis can be addressed.

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Mohale, Matsie Agnes. "Interactions of diverse students in a South African university residence : the case of Tuks Village." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/57494.

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Utilising the methodology of portraiture this study set out to explore interactions of diverse students in a South African university residence. The purpose of the study was to understand how students from different racial and ethnic backgrounds interpret their own experiences as they had to share their personal space with people who had previously been seen as the outgroup. The study was qualitative in nature and used a case study research design. Datagathering techniques included semistructured interviews, observations, field notes and researcher?s journal. Critical race theory and contact theory were the theoretical frameworks of this study. Data was analysed by means of content analysis. Findings of this study were fivefold: first, institutional practice plays an important role in facilitating contact between diverse students. Second, an environment that promotes social interaction is important in reducing stereotypes and prejudices. Third, continuous communication between diverse students minimised misunderstandings and promoted understanding and sympathy. Fourth, the participants did not attribute the challenges they experienced in their unit to racial or cultural differences. Fifth, participants did not segregate themselves exclusively from racial others. However, evidence reveals lack of interaction between some of the black female students.
Dissertation (MEd)--University of Pretoria, 2013.
tm2016
Humanities Education
MEd
Unrestricted

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Mishra, M. "Interactions between diverse proteinase inhibitors from Capsicum annuum and insects pests : biochemical & molecular approach." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2012. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2130.

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Rahaman, Habibur. "Diverse Interactions of Some Significant Compounds Prevailing in Different Solvent Systems with the Manifestation of Solvation Consequence by Physicochemical Investigations." Thesis, University of North Bengal, 2019. http://ir.nbu.ac.in/handle/123456789/2814.

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Choudhury, Subhankar. "Physicochemical study of diverse interactions of ionic liquids and biologically active solutes prevailing in liquid environments." Thesis, University of North Bengal, 2016. http://ir.nbu.ac.in/handle/123456789/2763.

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Kretov, Dmitry. "Mechanisms of YB-1/nucleic acids interaction and its implication in diverse cellular processes." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLE017.

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YB-1 est membre de la superfamille de protéines de choc thermique. YB-1 se lie à l'ARN et l'ADN. Des corrélations entre niveau élevé de YB-1, expression élevée de la P-glycoprotéine MDR1 et un mauvais pronostic ont été faites pour plusieurs types de cancer. Le rôle de YB-1 dans la cancérogenèse peut être soutenu par plusieurs mécanismes: i) l'activation de la transcription; ii) la participation à la réparation de l'ADN; iii) la régulation de la traduction. Les deux premiers modèles supposent une localisation nucléaire de YB-1, et cela malgré le fait que YB-1 est apparaît principalement dans cytoplasme dans des conditions physiologiques et les mécanismes de son accumulation nucléaire restent obscurs. Dans ce travail, nous avons tenté d’identifier les mécanismes qui déclenchent la translocation nucléaire de YB-1. Il est apparu que cette localisation nucléaire dépend principalement du niveau d’ARNm dans le cytoplasme et ainsi d’une transcription active, plutôt que de la présence de lésion à l'ADN nucléaire. A l'inverse, le rôle de YB-1 comme régulateur de la traduction est clairement établi. YB-1 peut influencer la traduction et favoriser la progression du cancer, indépendamment de ses fonctions éventuelles dans le noyau. Nous avons démontré par microscopie à force atomique et à l’aide de méthodes biochimiques, que YB-1 se lie aux ARNm d'une manière coopérative à l’ARNm, ce qui a des conséquences directes sur sa capacité à sélectionner des ARNm spécifiques et à moduler la traduction. Au-delà de ces recherches, nous nous sommes appuyés sur notre maitrise de la biologie de YB-1 pour développer une méthode innovante pour mettre en évidence les interactions protéine-protéine dans le contexte cellulaire. Nous avons ainsi confirmé à l’aide de cette méthode la capacité de YB-1 de former des oligomères en présence d'ARNm, et également révélé son interaction potentielle avec Lin28
YB-1 is a member of the cold-shock protein superfamily. It binds to both RNA and DNA. Correlations between high level of YB-1, elevated expression of P-glycoprotein MDR1 and poor patient prognosis were made for several types of cancer. The role of YB-1 in cancerogenesis can be accounted by several mechanisms: i) activation of transcription; ii) participation in DNA repair; iii) regulation of translation. The first two proposals imply a nuclear localization for YB-1, despite the fact that it appears mainly in the cytoplasm under physiological conditions and the mechanisms for its nuclear accumulation remain unclear. In this work we attempted to identify the mechanisms that trigger the nuclear translocation of YB-1. It appeared that this depends on the level of mRNA in the cytoplasm and thus on active transcription, rather than on the presence of nuclear DNA damages. In contrast to its function in the nucleus, the role of YB-1 in the regulation of translation was clearly established. YB-1 may therefore orchestrate a translation bias in order to promote cancer progression independently of its putative functions in the nucleus. Here we demonstrated, using atomic force microscopy and biochemical methods, that YB-1 binds mRNA in a highly cooperative manner and this has direct consequences on mRNA selection and following translational modulation. Beyond this research, we took advantage of our knowledge of the biology of YB-1 to develop a new method to detect protein-protein interactions in cellular context, using YB-1 as model protein. Besides the fact that we confirmed ability of YB-1 to make oligomers in the presence of mRNA, we also highlighted its potential interaction with Lin28, using this method

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Talmadge, Rosemary A. "Campus diversity and perspective-changing| Students describe the impact of their interactions with diverse peers and viewpoints." Thesis, Fielding Graduate University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3614922.

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Preparing students to become effective citizens in an increasingly interdependent world is one of today's most critical challenges. Effective global citizens need to be able to do more than imagine themselves in another's position, a common definition of perspective-taking. To bridge current divides of culture, religion, and nationality, they also must be willing to deeply question and sometimes revise their own prior beliefs and assumptions.

This study explored how interactions with diversity at a highly diverse and international community college impact students' capacity for perspective-changing. Through a hermeneutic inquiry, it brought community college students' voices into the scholarly conversation about the impact of campus diversity. Eighteen students from 11 countries participated in semi-structured interviews, discussing their pre-college experiences with diversity, their own definitions of diversity, critical incidents in their interactions with diversity, and the impacts of those interactions.

Several strands of scholarship informed this research. The first was the literature on perspective-taking particularly Piaget's original work as it was extended by Robert Selman and Jack Martin and his colleagues. Other core contributions included Jack Mezirow's theory of perspective transformation, Robert Kegan's work on self-authorship, and recent research on campus diversity conducted by educational researchers including Patricia Gurin, Sylvia Hurtado, Rona Halualani, and Victor Saenz.

Findings suggest that pre-college experiences shaped students' interactions with peers and the benefits they accrued. Almost all benefited from their interactions with diversity, but they benefited differentially. Work and family demands, limited English speaking ability, lack of prior experience with diversity, and deeply engrained cultural norms sometimes hindered their ability to engage with diverse peers and perspectives.

The analysis indicates that interactions with peers led to a range of outcomes including learning about and becoming more open to diversity, being able to engage with diversity, questioning and revising prior beliefs, and changing behaviors. A key finding was that engaging with diverse viewpoints did not occur informally, only in structured settings and almost always with the support of faculty or staff. Findings pointed to a need for more opportunities for engaging with diverse viewpoints, more targeted approaches, specific professional development for faculty and staff, and more research on community college campuses.

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Wheeler, Sassy Cenita. "Novice Special Education Teachers' Experiences with Students with Disabilities from Culturally and Linguistically Diverse Backgrounds: The Effects of Perceptions on Interactions." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/580.

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Novice special education teachers often enter their professions with unique perspectives that contribute to the overall educational experience of their students. This research was designed to inform the existing literature revolving around novice special education teachers' experiences, and how they subsequently effect the perceptions and interactions engaged in with students with disabilities from culturally and linguistically diverse backgrounds. Five novice special education teachers who currently serve students with disabilities from culturally and linguistically diverse backgrounds offered their unique perspectives for this research. This research study consisted of individual interviews, two direct classroom observations, and responses to three reflections of recent experiences. The data yielded three main categories: (a) student attributes, (b) establishing rapport, and (c) teacher responsibilities, which included properties and sub-properties. To verify findings rival explanations were sought and triangulation procedures were utilized. Findings of this research are discussed in detail, with implications relating to novice special education teachers, K-12 school administrators, and special education teacher educators being addressed. Methods to address potential limitations to this research are presented, followed by suggestions for future research.

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Scott, Brown Alison Sarah. "Interactions of thrips and their control agents on host plants within a glasshouse containing a diverse collection of plant species." Thesis, Birkbeck (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398082.

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Das, Koyeli. "Physicochemical investigation of assorted interactions of some imperative compounds with the manifestation of solvation effects prevalent in diverse solvent systems." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2684.

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Fouquier, D´Hérouel Aymeric. "On diverse biophysical aspects of genetics : from the action of regulators to the characterization of transcripts." Doctoral thesis, KTH, Beräkningsbiologi, CB, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31490.

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Genetics is among the most rewarding fields of biology for the theoretically inclined, offering both room and need for modeling approaches in the light of an abundance of experimental data of different kinds. Many aspects of the field are today understood in terms of physical and chemical models, joined by information theoretical descriptions. This thesis discusses different mechanisms and phenomena related to genetics, employing tools from statistical physics along with experimental biomolecular methods. Five articles support this work. Two articles deal with interactions between proteins and DNA. The first one reports on the properties of non-specific binding of transcription factors proteins in the yeast Saccharomyces cerevisiae, due to an effective background free energy which describes the affinity of a single protein for random locations on DNA. We argue that a background pool of non-specific binding sites is filled up before specific binding sites can be occupied with high probability, thus presenting a natural filter for genetic responses to spurious transcription factor productions. The second article describes an algorithm for the inference of transcription factor binding sites for proteins using a realistic physical model. The functionality of the method is verified on a set of known binding sequences for Escherichia coli transcription factors. The third article describes a possible genetic feedback mechanism between human cells and the ubiquitous Epstein-Barr virus (EBV). 40 binding regions for the major EBV transcription factor EBNA1 are identified in human DNA. Several of these are located nearby genes of particular relevance in the context of EBV infection and the most interesting ones are discussed. The fourth article describes results obtained from a positional autocorrelation analysis of the human genome, a simple technique to visualize and classify sequence repeats, constituting large parts of eukaryotic genomes. Applying this analysis to genome sequences in which previously known repeats have been removed gives rise to signals corroborating the existence of yet unclassified repeats of surprisingly long periods. The fifth article combines computational predictions with a novel molecular biological method based on the rapid amplification of cDNA ends (RACE), coined 5’tagRACE. The first search for non-coding RNAs encoded in the genome of the opportunistic bacterium Enterococcus faecalis is performed here. Applying 5’tagRACE allows us to discover and map 29 novel ncRNAs, 10 putative novelm RNAs and 16 antisense transcriptional organizations. Further studies, which are not included as articles, on the monitoring of secondary structure formation of nucleic acids during thermal renaturation and the inference of genetic couplings of various kinds from massive gene expression data and computational predictions, are outlined in the central chapters.
QC 20110316

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Altfeld, Laura F. "Herbivore Abundance in Simple and Diverse Habitats: The Direct and Indirect Effects of Plant Diversity and Habitat Structure." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000062.

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Jarsch, Iris Katharina [Verfasser], and Thomas [Akademischer Betreuer] Ott. "Remorin proteins in Arabidopsis thaliana : markers for diverse embrane micro-domains with roles in plant-microbe interactions / Iris Jarsch. Betreuer: Thomas Ott." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1072038250/34.

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Yasmin, Ananya. "Investigation of Host Guest Inclusion Complexations and Diverse Interactions of Some Industrially and Biologically Potent Molecules in Assorted Phases by Physicochemical Methodologies." Thesis, University of North Bengal, 2019. http://ir.nbu.ac.in/handle/123456789/2854.

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Matsuda, Sachiko. "The role of the global co-activator CREB-binding protein in transcription : a study of competitive interactions of diverse nuclear proteins with CBP." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/29713.

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The recruitment of the histone acetyltransferases CREB binding protein (CBP) and its homologue p300, is necessary for chromatin modification and assembly of the Pre Initiation Complex (PIC) at many gene promoters. CBP has multiple protein binding domains and we have focused our studies on the Steroid Receptor Coactivator-1 (SRC1) Interaction Domain (SID) of CBP. A novel conserved sequence motif is described which facilitates the binding of these nuclear proteins such as p160 proteins, Ets2, E1A and p53 to the CBP SID. We have confirmed the interaction of Ets2 by GST pull down with CBP SID and we show that SRC1, Ets2 and E1A full length proteins compete with each other to bind to the SID in vitro. We also show that the short peptide encompassing the SRC1 AD1 sequence is indeed sufficient to compete with SRC1, Ets2, E1A12S and p53 full length proteins on SID. Furthermore, we demonstrate that the transcriptional activity of Ets2 is inhibited by E1A 12S, but not by E1A Delta2-36 (CBP binding site) mutant in vivo. This inhibition by E1A was rescued with overexpression of CBP but not CBPDeltaSID.;In AML, the MOZ-TIF2 fusion protein transforms bone marrow cells in vitro and causes leukaemia in animal model. I have conducted the ChIP analysis of the effects of MOZ-TIF2 on chromatin modification and co-activator recruitment at the RAR beta2 promoter. I have successfully established the ChIP analysis of the RARbeta2 promoter in U20s, and demonstrated that ATRA treatment induces recruitment of RARbeta, CBP, p300 and to the RARbeta2 promoter with concomitant of acetylation of histone H3 K9 and K14 residues. I also have shown that MOZ-TIF2 is recruited to the RARbeta2 promoter and this correlates with the loss of CBP and p300.

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Jouan, Romain. "The fitness landscape of the soil bacteria Caballeronia insecticola and Sinorhizobium meliloti in diverse natural and synthetic environments." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASB076.

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Les bactéries du sol sont adaptées pour survivre dans ce milieu et pour faire face à divers organismes y vivant, comme d'autres bactéries, champignons, plantes et insectes. Pour mieux connaitre ces adaptations et comprendre si ces adaptations se chevauchent ou sont spécifiques à chacun de ces modes de vie, j'ai utilisé l'approche dites « Transposon sequencing » (Tn-seq) pour identifier les gènes essentiels et conditionnellement essentiels dans deux bactéries du sol bien connues, Caballeronia insecticola et Sinorhizobium meliloti. J'ai utilisé des cribles Tn-seq réalisés dans les milieux naturels des microbes (in situ), combinés à des expériences in vitro. La sélection des conditions in vitro a été guidée par des analyses transcriptomiques, des études physiologiques, la génétique, la génomique et des analyses biochimiques, ainsi que par les expériences Tn-seq in situ. Ces conditions in vitro consistent en plusieurs facteurs de stress (comme des peptides antimicrobiens ou AMP) ou de conditions nutritionnelles (panel de sources de carbone, d'azote et de soufre) et physiologiques (motilité et chimiotaxie) que les microbes rencontrent dans leurs milieux naturels. Ces conditions in vitro simplifiées décomposent les conditions naturelles en composants uniques et facilitent ainsi l'interprétation des cribles Tn-seq in situ. C. insecticola est une bactérie polyvalente qui établit des interactions spécifiques avec des insectes, des plantes, des champignons et d'autres bactéries. J'ai analysé quatre modes de vie différents de C. insecticola avec l'approche Tn-seq : le sol, la rhizosphère des plants de soja, l'organe symbiotique intestinal de l'insecte Riptortus pedestris et la surface des hyphes des champignons Cunninghamella. Pour les interactions bactéries-bactéries, je me suis concentré sur la compétition entre la souche de rhizobium S. meliloti et la souche productrice de toxines Rhizobium sp. Pop5, car cette interaction est bien caractérisée et repose sur la production du AMP phazolicine par la souche Pop5.Au total, 34 cribles chez C. insecticola et 4 cribles chez S. meliloti ont été réalisés et analysés, ce qui a permis de découvrir des phénotypes pour 1 162 gènes de C. insecticola et 264 gènes de S. meliloti. Chez C. insecticola, le génome essentiel, c'est-à-dire l'ensemble des gènes qui ne peuvent être supprimés et qui sont donc indispensables à la vie bactérienne, a été défini. Il est constitué de 498 gènes, avec des gènes codant des fonctions cellulaires attendues, comme la transcription, la traduction, la production d'énergie, la biosynthèse de l'enveloppe cellulaire et le cycle cellulaire, ou des gènes moins attendus comme ceux impliqués dans la modification spécifique de la partie lipidique A du lipopolysaccharide avec des groupes 4-amino-4-désoxy-L arabinose. Les résultats des différents cribles ont été vérifiés en utilisant des mutants d'insertion ou de délétion de C. insecticola et S. meliloti et en caractérisant leur phénotype dans les conditions in situ et in vitro appropriées. Au total, 23 mutants de C. insecticola et 8 mutants de S. meliloti ont été phénotypés. Dans chaque cas, le phénotypage de ces mutants a confirmé les données Tn-seq, illustrant la robustesse et le potentiel de la méthode.Parmi les fonctions bactériennes cruciales dans tous les milieux naturels, tant chez C. insecticola que chez S. meliloti, figure l'enveloppe bactérienne, ce qui suggère qu'elle constitue un bouclier contre les agressions environnementales, comme les AMPs fréquemment produits par d'autres organismes. La motilité bactérienne et la chimiotaxie chez C. insecticola sont cruciales dans l'interaction avec les insectes et dans le sol, lorsque les bactéries circulent sur les hyphes fongiques. Enfin, chaque milieu impose des contraintes métaboliques spécifiques aux bactéries. Ces travaux ont mis en évidence des adaptations à la fois généralistes et spécifiques à l'environnement chez les bactéries du sol
Soil bacteria are adapted to survive in their abiotic soil environment as well as to cope with different organisms, including other bacteria, fungi, plants and insects with which they share that environment. With the objective to contribute to the understanding of these adaptations and to answer the question if adaptations are overlapping or unique for each of these lifestyles, I used the transposon-sequencing (Tn-seq) approach to identify essential and conditionally fitness genes in two well-studied soil bacteria, Caballeronia insecticola and Sinorhizobium meliloti. The experimental strategy consisted in the use of Tn-seq screens performed in the natural, in situ environments of the microbes combined with multiple in vitro experiments in synthetic environments. The selection of these in vitro conditions was informed by available transcriptome analyses, physiological studies, genetics, genomics and biochemical analyses as well as the in situ Tn-seq experiments themselves. The selected in vitro conditions were a variety of stressors (e.g. antimicrobial peptides or AMPs) or nutritional (e.g. a panel of carbon, nitrogen and sulphur sources) and physiological (e.g. motility and chemotaxis) conditions that the microbes encounter in their natural environments. These simplified synthetic conditions decompose the complexity of natural conditions in single components and facilitate thereby the interpretation of the in situ Tn-seq screens.C. insecticola is a versatile bacterium establishing specific interactions with insects, plants, fungi and other bacteria. I analyzed four different lifestyles of C. insecticola with the Tn-seq approach: soil, the rhizosphere of soybean plants, the gut symbiotic organ of the insect Riptortus pedestris and the surface of the hyphae of Cunninghamella fungi. For bacteria-bacteria interactions, I focused on the competition of the rhizobium strain S. meliloti with the toxin producing strain Rhizobium sp. Pop5 because this interaction is well characterized and based on the production of the AMP phazolicin by the strain Pop5.In total, 34 screens in C. insecticola and 4 screens in S. meliloti were performed and analysed, resulting in the discovery of phenotypes for 1162 C. insecticola genes and 264 S. meliloti genes. In C. insecticola, the essential genome, i.e. the set of genes that cannot be removed and that are therefore indispensable to support bacterial life, was precisely defined. I found that it is constituted of 498 genes, including the genes encoding the expected cellular functions, like transcription, translation, energy production, cell envelope biosynthesis and cell cycle, but also less expected genes like those involved in the specific modification of the lipid A moiety of lipopolysaccharide with 4-amino-4-deoxy-L arabinose groups. Results of the different Tn-seq screens were verified by independent experiments, using insertion or deletion mutants of C. insecticola and S. meliloti in selected genes and characterization of the phenotype of these mutants in the relevant environmental and in vitro conditions. In total, 23 mutants in C. insecticola and 8 mutants in S. meliloti were phenotyped. In each case, the phenotyping of these mutants confirmed the Tn-seq data, illustrating the robustness and potential of the method.Among the crucial bacterial functions in all natural environments, in both C. insecticola and S. meliloti, is the bacterial envelope, suggesting that it constitutes a shield, fending of environmental stresses, in particular AMPs frequently produced by other organisms. Bacterial motility and chemotaxis in C. insecticola are particularly important in the interaction with insects but also in the soil, when bacteria hitchhike on fungal hyphae. Finally, each environment imposes specific metabolic constraints on the bacteria. Together, this work highlighted both generalist and environment-specific adaptations in soil bacteria

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Leiva, Torres Luis Alberto. "Diverse Contributions to Implicit Human-Computer Interaction." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17803.

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Cuando las personas interactúan con los ordenadores, hay mucha información que no se proporciona a propósito. Mediante el estudio de estas interacciones implícitas es posible entender qué características de la interfaz de usuario son beneficiosas (o no), derivando así en implicaciones para el diseño de futuros sistemas interactivos. La principal ventaja de aprovechar datos implícitos del usuario en aplicaciones informáticas es que cualquier interacción con el sistema puede contribuir a mejorar su utilidad. Además, dichos datos eliminan el coste de tener que interrumpir al usuario para que envíe información explícitamente sobre un tema que en principio no tiene por qué guardar relación con la intención de utilizar el sistema. Por el contrario, en ocasiones las interacciones implícitas no proporcionan datos claros y concretos. Por ello, hay que prestar especial atención a la manera de gestionar esta fuente de información. El propósito de esta investigación es doble: 1) aplicar una nueva visión tanto al diseño como al desarrollo de aplicaciones que puedan reaccionar consecuentemente a las interacciones implícitas del usuario, y 2) proporcionar una serie de metodologías para la evaluación de dichos sistemas interactivos. Cinco escenarios sirven para ilustrar la viabilidad y la adecuación del marco de trabajo de la tesis. Resultados empíricos con usuarios reales demuestran que aprovechar la interacción implícita es un medio tanto adecuado como conveniente para mejorar de múltiples maneras los sistemas interactivos.
Leiva Torres, LA. (2012). Diverse Contributions to Implicit Human-Computer Interaction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17803
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Young, Nancy Diane. "Peer interaction and learning in compositionally diverse residence halls." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7759.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Education Policy, Planning, and Administration. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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GERSCHWILER, SOPHIE. "Etude des interactions entre polyoxometallates et divers materiaux d'electrode." Paris 11, 1998. http://www.theses.fr/1998PA112098.

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De nombreuses etudes concernant les polyoxometallates ont montre que leur electrochimie est relativement complexe et depend de plusieurs parametres tels que la nature du materiau d'electrode, la composition du milieu etc. Les heteropolyanions et isopolyanions sont egalement connus pour leurs excellentes proprietes catalytiques. En particulier des travaux anterieurs effectues au laboratoire ont decrit l'efficacite catalytique, vis a vis de diverses reactions, de materiaux d'electrode modifies par electrodeposition a l'aide de ces composes. L'existence d'une adsorption faible des heteropolyanions precedant leur electrodeposition avait deja ete soupconnee au laboratoire. Mais, si quelques travaux theoriques comme ceux de wopschall et shain concernent l'adsorption faible sur des materiaux d'electrode, il n'existe pas, a notre connaissance, d'etude experimentale complete du phenomene. Aussi, le travail propose au cours de cette these consiste-t-il a trouver les isothermes d'adsorption adequats pour decrire ces adsorptions faibles et a les introduire dans un traitement theorique de la voltammetrie cyclique. L'etude experimentale qualitative par voltammetrie cyclique, puis quantitative par chronocoulometrie a double saut de potentiel, porte sur l'adsorption de ces composes sous leur forme oxydee et/ou celle des produits reduits correspondant a leurs divers stades de reduction. Apres determination de la surface reelle des electrodes, les etudes sont realisees sur les differents materiaux solides (carbones vitreux, or et platine) dans plusieurs electrolytes afin d'illustrer le role de ces parametres dans le processus d'adsorption faible. La confrontation des resultats experimentaux issus de la voltammetrie cyclique avec les modeles theoriques precedemment etablis est realisee. Les resultats sont egalement compares a ceux obtenus d'une part par chronocoulometrie a double saut potentiostatique et d'autre part par la microbalance a cristal de quartz couplee in-situ a l'electrochimie. Avec cette derniere technique plus recente, les proprietes de quelques produits reduits a des stades eleves sont aussi decrites, l'objectif etant d'identifier les precurseurs de catalyseurs deposes par electroreduction.

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Lettéron, Philippe. "Rôle des métabolites réactifs dans diverses hépatites et interactions médicamenteuses." Paris 11, 1989. http://www.theses.fr/1989PA114839.

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Hegedus, Katalin. "Dialogue journal writing : meaningful written interaction in language and culturally diverse classrooms." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29929.

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The study of the Back and Forth book of an eleven years old E.S.L. student introduces a type of personal writing which is argued to facilitate meaningful, written communication in the second language. The present study extends the findings of dialogue journal studies of Staton et al. in two directions. 1. The case study of the Back and Forth book activity presents a "communication triangle" which involves parental participation and thus serves as a bridge between school and home. The reported observations focus on the potentials and limitations of the Back and Forth book task in comparison to other journal writing practices. 2. The analysis of the selected 45 journal entries provides some explanation for the weak realization of the task. The application of Mohan's Knowledge Framework as a means of analyzing student writing provides a c picture of the language and content. The Knowledge framework presents guideline for monitoring the development of language and the development of discourse and content. The inconsistency of the task justifies the present study: the multi-purpose task of the Back and Forth book produces unsatisfactory writing, the research question is of determining its reason and provide a guideline to monitor the task in order to obtain more satisfactory product.
Education, Faculty of
Language and Literacy Education (LLED), Department of
Graduate

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Bigarre, Laurent. "Diversite des geminivirus et interactions avec leurs hotes." Paris 11, 1999. http://www.theses.fr/1999PA112380.

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Au sein de la famille des geminivirus, les especes ont adopte des strategies d'interactions avec leurs hotes tres variees. Une grande diversite genetique et biologique est observee dans cette famille qui a colonise de nombreux environnements et dont certains membres sont des contraintes majeures sur les cultures. Cette diversite est un probleme majeur pour developper des methodes de lutte efficaces et durables. Dans cette these, j'illustrerai les problemes poses dans la connaissance des maladies a geminivirus et plus particulierement dans la connaissance des interactions avec leurs hotes. Une premiere etude est consacree a l'etiologie de la maladie des enations de la rose tremiere en egypte. Cette maladie represente un risque epidemiologique pour la culture du cotonnier dans ce pays. Un adn-a caracteristique des begomovirus a ete clone, sequence et caracterise comme faisant partie d'une nouvelle espece virale. Ce virus est associe a des symptomes d'enations et plus precisement et des proliferations tissulaires au niveau des organes superieurs de la plante. Trois types de reorganisation tissulaire sont observes dans les organes infectes: (i) une nouvelle activite cambiale dans le phloeme (ii) la creation d'un reseau de veines mineures et (iii) la presence d'un parenchyme palissadique a la place d'un parenchyme spongiforme. Le clone viral, nomme althea rosea enation virus (arev), peut induire des enations sur nicotiana benthamiana, mais ne peut induire de symptomes sur son hote originel, a. Rosea. La sequence partielle d'un isolat associe a des symptomes similaires sur gombo a ete obtenue et suggere une heterogeneite genetique dans les begomovirus infectant les malvacees en egypte. Dans une deuxieme etude, nous nous sommes interesses a la diversite genetique des mastrevirus induisant la maladie de la striure sur canne a sucre (ssv). Une nouvelle espece de virus provenant de cannes d'egypte a ete caracterisee au niveau moleculaire et biologique. Un lien genetique a egalement ete etabli entre divers isolats de ssv des iles mascareignes et d'afrique de l'ouest. Il est demontre que 3 especes de mastrevirus sont trouvees sur canne a sucre en afrique, mais chaque espece montre une faible heterogeneite. Pour expliquer une forte divergence entre espece et une faible variation au sein de chaque espece, il est propose que ces virus ont diverge depuis une grande periode. Les mecanismes de resistance du mais au mastrevirus de la striure du mais de la reunion (msv-re) ont ete etudies en comparant le cycle d'infection virale dans des genotypes hotes resistants et sensibles. Dans la lignee de mais resistant, les symptomes de striure sont localises sur toutes les feuilles, mais a une densite plus faible comparativement a la plante sensible. Le processus d'infection du msv-re a ete compare entre les deux genotypes par localisation de la proteine de capside et des acides nucleiques viraux par immunolocalisation et hybridation in situ. Nos observations montrent que les differences de distribution du virus sont essentiellement quantitatives, sans restriction tissulaire evidente du virus dans la lignee resistante. La resistance a un effet sur la quantite d'acides nucleiques viraux localises dans l'apex de la tige qui est une zone-cle du processus d'infection. La complexite des mecanismes de resistance est discutee et mise en parallele avec la complexite de son determinisme genetique.

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Polyakova, Evgenia I. "A general theory for evaluating joint data interaction when combining diverse data sources /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Wong, Sato Akira Armando. "Diverse adaptations to increase pollination success in zoophilous plants." Kyoto University, 2018. http://hdl.handle.net/2433/232377.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第21176号
人博第848号
新制||人||203(附属図書館)
29||人博||848(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授加藤眞, 教授市岡孝朗, 教授瀬戸口浩彰
学位規則第4条第1項該当

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Vickers, Caroline H. "Interactional accommodation and the construction of social roles among culturally diverse undergraduates." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290133.

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This study explores the interactional achievement of intersubjectivity between native speakers (NS) and nonnative speakers (NNS) of English engaged in high stakes teamwork. I term the interactional achievement of intersubjectivity Interactional Accommodation. In particular, this study examines how strategies that NSs and NNSs employ to interactionally accommodate are related to language proficiency, successful team outcomes, and to the construction of team hierarchy. The context of the study is the team meeting associated with a design course in the department of electrical and computer engineering (ECE) at an American university, a setting in which NSs and NNSs work together on teams throughout the year to design operable electronic devices. Data was collected during one year from seven teams and a total of 27 participants through participant observation, video and audio taping of team meetings, and participant playback sessions. Data analysis incorporated an integrated approach informed by a variety of discourse analytic approaches. Findings demonstrate that the ability of teammates to interactionally accommodate to each other is correlated with the team's success. However, NSs and NNSs tend to employ strategies with different frequencies and in qualitatively distinct ways. These differences become important to the development of team hierarchy because strategies that NSs and NNSs employ tend to allow NSs control over the interpretive frame, which contributes to the construction of NSs as higher status team members than NNSs. The ability to control the interpretive frame is related to language proficiency, but in some cases NNSs develop strategies that allow them to control the interpretive frame and gain high status.

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Paradis, Geneviève. "Transport de protéines thérapeutiques à travers diverses barrières biologiques à l'aide d'un ligand peptidique." Sherbrooke : Université de Sherbrooke, 2004.

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Ong, Saro. "Divers aspects des collisions photon-photon : corrections radiatives, et corrélations azimutales." Paris 6, 1988. http://www.theses.fr/1988PA066450.

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Grevet, Catherine. "Being nice on the internet: Designing for the coexistence of diverse opinions online." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55002.

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This thesis contributes to a better understanding of social media designs for more civil conversations online. I first demonstrated that people disengage from social media interactions when they encounter uncivil behavior from friends. To find alternative designs for social media that are more civil, I evaluated novel social interaction techniques. To do this, I designed a six-phase framework for prototyping social interactions called piggyback prototyping; and an algorithmic probe study methodology to include participants in the development of social curation algorithms. I built a piggyback prototype that modifies the civility on Facebook by highlighting positive posts in green and hiding impolite posts, and I deployed it as an algorithmic probe with 20 participants. I uncovered ways to improve the algorithm, and I found that participants responded most favorably to having civil posts highlighted. These findings open avenues for future research in designing pro-social platforms.

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Bost, Pierre. "Decoding cellular communications and interactions between immune cells by using single-cell approaches." Electronic Thesis or Diss., Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2020SORUS020.pdf.

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Les communications cellulaires sont indispensables au bon fonctionnement des organismes multicellulaires, notamment pour s’adapter à un environnement changeant en permanence. Les cellules du système immunitaire n’échappent pas à cette règle mais les interactions entre cellules immunitaires restent peu connues et compliquée à étudier. La récente apparition des technologies de séquençage dites ‘cellules uniques’ représente une opportunité unique pour étudier ces communications. Dans cette thèse, différentes approches expérimentales et analytiques ont été développées pour étudier ces communications à une échelle de cellules uniques. Ces stratégies ont ensuite été appliquées à différents contextes pathologiques, incluant le COVID-19, la maladie d’Alzheimer ou une immunisation par des pathogènes inactivés, et ont permis d’identifier des voies de communications cellulaires jusqu’ici inconnues ou mal comprises. Néanmoins, l’efficacité de ces approches est limitée par l’absence d’informations sur la localisation des cellules et des travaux supplémentaires intégrant ce genre de données est essentiel pour aller plus loin dans la dissection des communications entre cellules immunitaires
Cellular communications are essential to the proper functioning of multi-cellular organisms, particularly in order to adapt to a constantly changing environment. The cells of the immune system are no exception to this rule, but the interactions between immune cells remain little known and complicated to study. The recent emergence of 'single cell' sequencing technologies represents a unique opportunity to study these communications. In this thesis, different experimental and analytical approaches have been developed to study these communications on a single cell scale. These strategies were then applied to different disease contexts, including COVID-19, Alzheimer's disease or immunisation with inactivated pathogens, and identified previously unknown or poorly understood cellular communication pathways. However, the effectiveness of these approaches is limited by the lack of information on cell location and further work integrating such data will be essential to go further in the dissection of immune cell communications

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Casadevall, Dario. "Skunkworks Finder: A Design Study into the Diverse Ecosystem of Creativity and Innovation Spaces." Thesis, Ludwig-Maximilians-Universitat München, 2018. https://eprints.qut.edu.au/122139/1/Masterthesis_DarioCasadevall%20Kopie.pdf.

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Creative people, entrepreneurs and start-up founders using innovation spaces and hubs often find themselves inside a filter bubble or echo chamber, where like-minded people tend to come up with similar ideas and recommend similar approaches to innovation. This trend towards homophily and a polarisation of like-mindedness is aggravated by algorithmic filtering and recommender systems embedded in current technology and social media platforms. Yet, genuine innovation thrives on social inclusion fostering a diversity of ideas. To provide the opportunity to escape these echo chambers, Skunkworks Finder was designed and tested – an exploratory tool that employs social network analysis to help users discover spaces of difference and otherness in their local urban innovation ecosystem. A design inclusive research approach was adapted focusing on user-centred design choices in order to verify and validate the prototype and its according premise. Results show, that an introduction of Skunkworks Finder or similar functionality is anticipated by study participants, as participants indicated individual experiences of forming filter bubbles in innovation spaces. However, changes in design would improve comprehensibility issues addressed during the user study. Additionally, an integration of such a system into an established online tool would ensure a distribution to a wider audience, than focusing only on potential users who are already affiliated with an innovation environment.

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Koran, L. "Aphasia in a linguistically diverse population : resources for turn construction and interactional adaptations of Malaysian adults." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1468881/.

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The central aim of this thesis is to explore resources for turn construction and interactional adaptations in the conversation of adults with aphasia (a language difficulty acquired most commonly after stroke) in the linguistically diverse Malaysian population. Malaysia has a long history of societal multilingualism, necessitating individual bi/multilingualism; the thesis investigates for the first time the impact of aphasia on conversational interactions in this population. As a result, the thesis applies Conversation Analysis (CA), with an emphasis on localised investigation of participants’ turns within particular sequences. The data are from two sources: video recorded natural conversations in the homes of three participants with aphasia and their regular conversation partners, and conversations outside the home with a friend, where languages other than the home language were reportedly used. The data driven procedures of CA reveal turn construction resources of topic-comment structure, co-construction and repetition are deployed by PWAs in conversation with regular and less familiar conversation partners and these resources cross the linguistic boundaries of the languages in their repertoire. These resources also occur in the non-aphasic conversation partners’ turns and exhibit similarities to those documented in studies of the conversations of monolingual English speakers with aphasia. Given that two or more sets of linguistic resources are available for each partnership, code-switching is found to be a compensatory resource for dealing with word finding difficulties as well as a resource for claiming or ascribing identity. A comparison of conversations with a friend indicates that a partnership’s familiarity influences interactional outcomes. However, the relationship between familiarity and interactional success is a complex one which appears to vary for each partnership. The findings of this thesis have theoretical and clinical implications for planning support services for aphasia in societies where bi/multilingualism is the norm. The significance of this contribution becomes evident when global trends in linguistic diversity are taken into consideration.

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De, Poorter Cédric. "Mécanismes d'activation et interactions fonctionnelles hétérologues des récepteurs aux chimiokines." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209589.

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Mécanismes d’activation et conséquences fonctionnelles de la dimérisation des récepteurs aux chimiokines

Les chimiokines sont de petites protéines qui régulent la migration des cellules immunitaires. Elles exercent leur action en se liant à des récepteurs appartenant à la famille des récepteurs couplés aux protéines G (RCPG) dont la fonction est intimement liée à la régulation des cellules immunitaires. Notre laboratoire étudie depuis plusieurs années les relations reliant la structure et la fonction des récepteurs aux chimiokines. Ces dernières années, un nouveau concept est venu révolutionner le mode de fonctionnement des RCPGs. En effet, des travaux ont montré que la plupart des RCPGs sont capables de former des dimères. Le but de cette thèse de doctorat est d’étudier de manière systématique la dimérisation des récepteurs aux chimiokines et d’analyser les conséquences fonctionnelles de la dimérisation.

Dimérisation des récepteurs humains aux chimiokines et conséquences fonctionnelles

En utilisant une technique biophysique basée sur un transfert d’énergie de luminescence (BRET) nous avons montré au cours de ce travail de thèse que les récepteurs CCR1, CCR2, CCR5, CCR7 et CXCR4 sont capables de former des homodimères et des hétérodimères. De plus, une dimérisation entre ChemR23, dont le ligand naturel, la chémérine, est structurellement différent des chimiokines, et les récepteurs CCR7 et CXCR4, a également été identifiée.

D’un point de vue fonctionnel, des expériences réalisées au laboratoire dans le cadre d’un autre travail de thèse ont identifié une forme de compétition croisée entre CCR2, CCR5 et CXCR4 où la liaison de ligands (agonistes ou antagonistes) spécifiques de l'un des deux récepteurs inhibe la liaison des ligands spécifiques de l’autre. Ces effets ont été démontrés sur des cellules recombinantes mais aussi sur des cellules immunes et dans un modèle in vivo. (El-Asmar, 2005; Springael, 2006; Sohy, 2007; Sohy, 2009). Au cours de ce travail, nous nous sommes dans un premier temps focalisés sur les

hétéromères de ChemR23 avec CXCR4 et CCR7 et nous avons ensuite étudié plus en profondeur les hétéromères de CCR7. Concernant la dimérisation de ChemR23 avec les récepteurs aux chimiokines CCR7 et CXCR4, nous avons pu mettre en évidence une coopérativité négative de liaison entre les agonistes des récepteurs comme cela avait pu être démontré pour CCR2/CCR5/CXCR4. Par contre, nous n’avons observé aucun effet de compétition hétérologue ou d’inhibition fonctionnelle croisée de l’AMD3100 sur ChemR23 quand il est coexprimé avec CXCR4. De manière additionnelle, nous avons pu observer cette compétition croisée sur des cellules dendritiques murines immatures, démontrant l’existence des effets de l’hétérodimérisation lorsque les récepteurs sont exprimés à un niveau physiologique. Lors de l’étude approfondie des hétéromères de CCR7, nous avons montré que les conséquences fonctionnelles de l’hétérodimérisation de CCR7 sont différentes suivant le récepteur avec lequel il interagit. Pour l’hétérodimère CCR7/CCR2, nous avons identifié une forme de compétition croisée, où la liaison de ligands spécifiques de l'un des deux récepteurs inhibe la liaison des ligands spécifiques de l’autre, rejoignant les effets mis en évidence pour les hétéromères CCR2/CCR5/CXCR4. Ensuite, nous avons montré pour l’hétérodimère CCR7/CCR5 que les ligands de CCR7 sont capables d’inhiber la liaison des ligands spécifiques sur CCR5 mais que l’inverse n’est pas vrai. Enfin, pour l’hétérodimère CCR7/CXCR4, nous n’avons pas pu mettre en évidence d’inhibition croisée, que ce soit dans un sens ou dans l’autre. D’autre part, un effet inhibiteur de CCR7 a également été identifié pour les hétéromères CCR7/CCR5 et CCR7/CXCR4. Nous avons pu montrer que l’expression de CCR7 exerce un effet négatif sur la réponse fonctionnelle de certains récepteurs hétérologues comme CCR5 et CXCR4 mais pas CCR2 ou ChemR23.

L’ensemble de ces données permet de mieux comprendre les interactions entre récepteurs et pourrait mener à l’identification de nouvelles cibles pour les programmes de recherche de molécules thérapeutiques, qui, jusqu’à présent, ciblaient presque exclusivement un seul et unique récepteur.

Etude du mécanisme d’activation du récepteur CCR5 et étude de la relation entre activité constitutive et dimérisation.

De nombreux travaux ont été menés ces dernières années afin de mieux comprendre les mécanismes moléculaires à la base de l’activation des récepteurs couplés aux protéines G (RCPG). Il apparaît que les RCPGs peuvent se trouver dans plusieurs états conformationnels, dont certains sont favorisés par la présence d’agonistes ou d’antagonistes, ou encore d’anticorps reconnaissant des épitopes conformationnels. Certaines mutations peuvent également induire la stabilisation de certaines conformations, actives ou inactives. Pour les RCPGs appartenant à la famille de la rhodopsine, il en a résulté un modèle selon lequel les récepteurs sont maintenus dans une conformation inactive par un ensemble d’interactions ioniques impliquant l’arginine (R3.50) d’un motif DRY conservé, présent à l’extrémité cytosolique du troisième segment transmembranaire. Les interactions responsables de ce qu’on appelle le « DRY-lock » feraient intervenir notamment l’aspartate (D3.49) adjacent de l’arginine et un aspartate ou glutamate (D/E6.30) localisé au sein de l’hélice 6. Selon ce modèle, la liaison d’un agoniste, ainsi que certaines mutations, favoriseraient la rupture de ces interactions ioniques, et une conformation permettant aux récepteurs de se coupler plus efficacement aux protéines G. Des résultats du laboratoire indiquent cependant que ce modèle ne serait pas transposable complètement au récepteur CCR5.

CCR5 possède intrinsèquement une activité constitutive en absence d'agoniste. Cette activité peut être mise en évidence par l'action d'un des antagonistes de CCR5, le TAK-779, qui s'est révélé posséder une activité de type agoniste inverse. D'autre part, CCR5 possède au sein de l'hélice 6 une arginine en position 6.30 et non pas un glutamate ou un aspartate. Une arginine à cette position ne peut donc contribuer au maintien d’une conformation inactive par interaction avec R3.50 .Dans le but de tester le modèle de « DRY-lock » sur CCR5 et de mieux comprendre les interactions moléculaires impliquées dans l’activation du récepteur, plusieurs récepteurs mutants ont été construits au laboratoire. Tout d’abord, l’arginine 3.50 du motif DRY a été mutée en Asn (R3.50N) afin de rompre les interactions ioniques de ce résidu. L’aspartate 3.49 a été muté en Asn (D3.49N) ou en Val (D3.49V), afin de neutraliser une des interactions du « DRY-lock » (Lagane, 2005). L’arginine 6.30 a été mutée d’une part en Asp (R6.30D) ou en Glu (R6.30E), afin de rétablir une possibilité d’interaction avec R3.50, d’autre part en Ala (R6.30A) et en Gln (R6.30Q) afin de mieux cerner le rôle de la charge de l’arginine. Afin de tester l’hypothèse d’interaction entre le résidu 6.30 et le résidu 2.40, l’aspartate 2 .40 a été mutée en Ala (D2.40A) ou en Arg (D2.40R) et des récepteurs présentant les deux mutations ont également construits (D2.40A/R6.30A et D2.40R/R6.30D). L’ensemble des résultats obtenus par l’analyse de ces mutants a permis de montrer que la nature des interactions entre l’extrémité cytosolique des hélices 3 et 6 influence l’activité du récepteur CCR5 (Springael, 2007). Une interaction forte conduit à une forme de récepteur inactif alors qu’une interaction faible s’accompagne d’une augmentation d’activité constitutive. Cette propriété de CCR5 serait donc partagée avec d’autres récepteurs appartenant à la famille de la rhodopsine. Cependant les interactions inter-hélice stabilisant ces conformations seraient différentes pour CCR5. D’autre part, l’étude de la position 2.40 laisse supposer l'importance du résidu aspartate 2.40 dans le maintien d'une conformation permettant l'activité constitutive du récepteur. Nous avons également testé s’il existait une corrélation entre activité constitutive et capacité du récepteur CCR5 à former des dimères, mais les résultats ne nous ont pas permis de mettre en évidence une quelconque relation entre activité et dimérisation.

Doctorat en Sciences biomédicales et pharmaceutiques
info:eu-repo/semantics/nonPublished

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Chelkha, Nisrine. "Etudes du génome de diverses amibes et de leurs interactions avec des virus géants et d’autres microorganismes." Thesis, Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/191122_CHELKHA_490trpga652cfvqep580b712k_TH.pdf.

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Acanthamoeba est un protiste phagocytaire ubiquitaire du sol et de l'eau. Les virus géants, incluant notamment les mimivirus, les marseillevirus ou les pandoravirus, sont d'autres micro-organismes résistants à Acanthamoeba. Ils vivent en sympatrie avec d'autres micro-organismes au sein de l'amibe, et de nombreux transferts latéraux de séquences ont été décrits avec Acanthamoeba castellanii. De plus, certaines espèces d'Acanthamoeba semblent présenter des susceptibilités différentes vis-à-vis des virus géants.L’objectif de ce travail a été d’explorer pour la première fois le répertoire génique de 14 espèces d’Acanthamoeba, ainsi que celui des deux espèces Vermamoeba vermiformis CDC-19 et Willaertia magna c2c maky, et d’étudier leurs relations génétiques avec les virus géants.Ce travail a permis de fournir des données génétiques importantes et originales pour plusieurs espèces d’amibes présentant des susceptibilités différentes à l’infection virale.Un autre travail a consisté à discuter des stratégies de défense observées ou possibles des virus géants et de leurs hôtes. La recherche d’homologues de séquences de virus géants montre la présence de plusieurs séquences potentiellement impliquées dans des mécanismes de défense. Par ailleurs, aucune trace significative d'intégration de génomes ou de séquences de virophages connus n'a été identifiée dans tous les génomes disponibles des espèces d'Acanthamoeba. Finalement, nous avons mis au point différents systèmes d'amorces permettant une identification des espèces d’Acanthamoeba. Ces travaux ouvrent plusieurs pistes potentielles pour des travaux futurs portant sur les interactions entre les amibes et les virus géants
Acanthamoeba spp. are ubiquitous phagocytic protists in soil and water. Giant viruses, including mimiviruses, marseillevirus or pandoraviruses, are among Acanthamoeba-resistant microorganisms. They have a sympatric lifestyle with other microorganisms within amoebae, and many lateral sequence transfers have been described that involved Acanthamoeba castellanii. In addition, some Acanthamoeba species appear to have different levels of susceptibility to giant viruses.The objective of this work was to explore for the first time the gene repertoire of the genomes of 14 different species of Acanthamoeba, as well as that of the two species Vermamoeba vermiformis CDC-19 and Willaertia magna c2c maky, and to study the genetic relationship of these amoebae with giant viruses.This work provided important genetic information for several species of amoebae with different susceptibility to giant viral infection. An additional work aimed to discuss the defense strategies observed or predicted for giant viruses and their hosts. The search for sequence homologies in other giant viruses genomes revealed the presence of several sequences suspected to be involved in defense mechanisms. However, no significant evidence of integration of known genomes or virophages sequences has been identified in all available genomes of Acanthamoeba species.Finally, we have designed three PCR primer systems targeting a conserved gene that encodes an alanine-tRNA ligase, for an effective and specific identification of Acanthamoeba. This work opens up several potential leads for future work on the interactions between amoebae and giant viruses

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48

Blachier, Christian. "Analyse des interactions entre diverses argiles et des polymères spécifiques, en milieu cimentaire, en présence de superplastifiant." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL034N.

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La présence d’argile dans les granulats (sables et graviers), influencent considérablement les propriétés rhéologiques des bétons. Considérant les évolutions techniques apportées au béton ces dernières années, la compréhension des mécanismes de nocivité des argiles est donc d’un intérêt majeur sur le plan industriel. Au cours de cette étude, nous avons scindé la problématique en deux parties, la première s’attardant plus spécifiquement sur les mécanismes d’adsorption aux surfaces des argiles. Une analyse fines des interactions polymere-argile par IR, SAXS-WAXS et mesure d’adsorption a alors permis de valider l’adsorption des superplastifiants par les argiles et le rôle bénéfique de l’utilisation de molécule cationique (F25) pour empêcher leur fixation. La détermination d’un processus d’adsorption par échange cationique de ces molécules explique d’une part leur effet inertant et d’autre part la restructuration des particules d’argile à l’échélle du micron comme du nanométre. Dans un deuxième temps, une étude rhéologique des systèmes granulaires a permis de caractériser l’effet intrinséque de argiles sur les propriétés d’écoulement de ces systèmes. L’étude des suspensions d’argile a démontré le rôle de la rétention d’eau par les argiles. L’anisotropie des particules, caractérisée au moyen de différentes techniques (MET, SAXS-WAXS), permet d’expliquer cette rétention d’eau
Clay minerals which can be found in granular materials strongly influence the rheological properties of fresh concrete. Due to the recent technical evolution of concrete, the understanding of the effect of clays in such systems takes on a significant industrial interest. This study was divided into two part, the first one dealing with the adsorption mechanisms of two polymers onto clay surfaces: a superplasticizer (PCP) and a polycation (F25). IR and SAXS-WAXS analysis together with adsorption measurment revealed that superplasticizer are adsorbed by clays and that the used of polycation inhibites clays-PCP interactions. The adsorption process of F25 onto clays by cationic exchange explains the preferential adsorption of cationic compounds rather than PCP and the restructuration of clay particles at the nano and micronic scale during the adsorption. In a second part, the rheological study of granular suspensions revealed a strong effect of clay particles on the flow behaviors of such systems. The rheological study of pure clay suspensions allowed the modelisation of the effect of clays on granular suspensions using excluded volume. In this case, the anistropic features of clays particles characterized by various technics (TEM, SAXS-WAXS) explains water retention properties of such nanometric minerals

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49

Jewell, Mark. "Diversit?? des arbres, interactions a??riennes et souterraines et d??composition des feuilles mortes." Mémoire, Universit?? de Sherbrooke, 2013. http://savoirs.usherbrooke.ca/handle/11143/75.

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R??sum?? : La d??composition des liti??res v??g??tales a ??t?? d??crite comme ??tant la deuxi??me plus importante fonction ??cosyst??mique sur terre, apr??s la productivit?? primaire. Alors que la photosynth??se fournit les apports ??nerg??tiques ?? la plupart des cha??nes alimentaires, la d??composition recycle les nutriments, permet leur utilisation future par d???autres organismes et relargue dans l???atmosph??re le carbone fix?? photosynth??tiquement. Dans un contexte de changement climatique, un grand int??r??t est port?? sur la d??composition des liti??res, car il s???agit, ?? l?????chelle globale, de la plus grande source d?????mission de CO[indice inf??rieur 2] dans l???atmosph??re. Les taux de d??composition des liti??res sont principalement d??termin??s par trois facteurs: les variables climatiques, la structure des communaut??s de d??composeurs et les propri??t??s chimiques et physiques de la liti??re. La structure de la communaut?? v??g??tale h??te dans laquelle se produit la d??composition et d???o?? provient la liti??re peut influencer l???ensemble de ces trois facteurs. Des changements dans la structure de la communaut?? v??g??tale pourraient donc affecter les futurs taux de d??composition et modifier significativement les dynamiques globales du carbone. Malgr?? cela, la communaut?? h??te est rarement prise en compte dans les ??tudes sur la d??composition des liti??res. Des exp??riences enl??vent souvent la liti??re de son environnment naturel de d??composition, mesurant la d??composition des liti??res ?? partir de monolithes ou de microcosmes en laboratoire, afin de contr??ler les variations ind??sirables des propri??t??s du sol. Dans ce m??moire, j?????tudie les effets de plusieurs propri??t??s fonctionnelles de la communaut?? v??g??tale h??te sur les taux de d??composition des liti??res et leur contribution ?? la respiration du sol. En utilisant une plantation exp??rimentale d???arbres qui permet de manipuler la structure de leur communaut??, je teste l???effet de l???identit?? fonctionnelle des arbres, des esp??ces et de la diversit?? fonctionnelle, ainsi que des interactions entre d??composeurs et arbres sur ces processus ??cosyst??miques. La d??composition des liti??res et la respiration du sol sont li??es aux propri??t??s fonctionnelles des plantes. La d??composition des liti??res est bien pr??dite par les valeurs moyennes de traits fonctionnels des liti??res, mais plus faiblement corr??l??e ?? la diversit?? sp??cifique. D???apr??s mes r??sultats, le nombre d???esp??ces en m??lange de liti??res ne constitue pas un facteur important pour la d??composition, ?? cause des interactions globalement idiosyncratiques entre types de liti??res. Cependant, l???augmentation conjointe de la diversit?? fonctionnelle des m??langes d???esp??ces en liti??res et de la communaut?? d???arbres-h??tes acc??l??re les taux de d??composition et la respiration du sol. Les premi??res phases de d??composition de liti??res en surface ne sont que faiblement affect??es par la diversit?? des plantes, alors que pour la respiration du sol, qui prend en compte les derni??res phases de d??composition de liti??re et de mati??re organique du sol, la diversit?? est la propri??t?? fonctionnelle de plantes qui fournit le meilleur pouvoir de pr??diction. De plus, j???ai trouv?? que les apports sp??cifiques de liti??res ?? long terme pouvaient cr??er des conditions qui favorisent la d??composition des liti??res native et pouvaient modifier l???effet de la diversit?? des arbres sur la d??composition. J???attribue cet effet aux r??troactions entre la liti??re et les organismes d??composeurs du sol. Ce travail de recherche fournit une nouvelle perspective sur les effets des changements de structure de communaut?? foresti??re sur les processus de d??composition. La compr??hension de ces effets est n??cessaire pour pr??dire les taux de d??composition de liti??res et les dynamiques globales du carbone. // Abstract : The decomposition of plant litter has been described as the second most important ecosystem function for sustaining life on earth, after primary productivity. Whereas photosynthesis provides the energy input for most food chains, decomposition recycles nutrients for future use by other organisms and returns photosynthetically fixed carbon back to the atmosphere. In the context of climate change, litter decomposition is of specific interest because it represents one of the largest sources of CO[subscript 2] to the atmosphere globally. Rates of litter decomposition are largely determined by three factors: climatic variables, the structure of the decomposer community, and the chemical and physical properties of the litter. The structure of the host plant community under which decomposition takes place and from which the litter is derived can influence all three of these factors. Therefore, any systematic changes in plant community structure could affect future decomposition rates and significantly alter global carbon dynamics. Despite this, the host plant community is rarely considered in litter decomposition studies. Experiments often remove litter from its natural decomposition environment, instead measuring decomposition of litter in common garden settings and laboratory microcosms to control for unwanted variation in soil properties. In this thesis I investigate the effect of several functional properties of the host plant community on rates of litter decomposition and its contribution to soil respiration. Using an experimental tree plantation that manipulates tree community structure, I test the effect of tree functional identity, species and functional diversity, and tree-decomposer interactions on these ecosystem processes. Both litter decomposition and soil respiration were related to plant functional properties. Litter decomposition was best predicted by average-values of litter functional traits and was poorly related to species diversity. The number of species in a litter mixture does not seem to be important for decomposition, as interactions between litter types were idiosyncratic. However increasing the functional diversity both of mixed-species litter and of the host tree community accelerated rates of litter decomposition and soil respiration. Early stages of surface litter decomposition were only marginally affected by plant diversity. In contrast, diversity was the best predictor of soil respiration, which includes latter stages of litter and soil organic matter decomposition. Furthermore, I found that specific repeated litter input to the soil can result in conditions that favour the decomposition of the long-term litter type and can mediate the effect of tree diversity on decomposition. I attribute this effect to feedbacks between the litter and soil decomposer organisms. This research provides insight into the effect of changing forest community structure on decomposition processes. Such an understanding is necessary to predict future rates of litter decomposition and global carbon dynamics.

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50

JUMPERTZ, CLAIRE-MARIE. "Etude spectroscopique de l'heme au sein d'hemoglobines normales et pathologiques, et dans ses interactions avec divers composes." Paris 6, 1994. http://www.theses.fr/1994PA066792.

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L'evolution au cours du temps des hematomes est un processus complexe. L'etude spectroscopique d'un modele in vitro nous a permis d'identifier les composes intervenant dans ce processus, ainsi que leur date d'apparition. Cette modelisation constitue un outil performant pour la datation des hematomes. De plus, l'application de ce modele a des sangs pathologiques souligne leur difference d'evolution par rapport au sang normal. L'etat d'oxydoreduction du fer de l'hemoglobine est un parametre determinant la capacite de cette molecule a assurer le transport de l'oxygene. A l'aide de la spectrometrie mossbauer, nous avons etudie le comportement de l'heme place dans differentes conditions. Il apparait clairement que les proteines testees n'assurent pas la protection de l'heme face a l'oxydation. Par contre, l'heme s'est revele constituer une sonde efficace pour l'etude des proteines qui le fixe. Enfin, cette etude montre le caractere complementaire des differentes techniques spectroscopiques utilisees (uv, rmn, rpe, rgn). Si chacune des techniques spectroscopiques presentent des limites, leur utilisation simultanee permet d'augmenter leurs potentialites et d'obtenir un outil performant d'identification

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Dissertations / Theses on the topic 'Diverse Interactions'

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