221 |
Phylogenetic Relationships and Evolution of SnakesFigueroa, Alex 10 August 2016 (has links)
Snakes represent an impressive evolutionary radiation of over 3,500 widely-distributed species, categorized into 515 genera, encompassing a diverse range of morphologies and ecologies. This diversity is likely attributable to their distinctive morphology, which has allowed them to populate a wide range of habitat types within most major ecosystems. In my first chapter, I provide the largest-yet estimate of the snake tree of life using maximum likelihood on a supermatrix of 1745 taxa (1652 snake species + 7 outgroup taxa) and 9,523 base pairs from 10 loci (5 nuclear, 5 mitochondrial), including previously unsequenced genera (2) and species (61). I then use this phylogeny to test hypotheses regarding heterogeneity in diversification rates and how this shaped overall patterns of snake diversity in Chapter 2. I also used the species-level phylogeny to test the evolution of habitat use in snakes, morphological variation, and whether distantly-related species exhibit morphological convergence in Chapter 3. Finally, in Chapter 4 I investigate how prehensile tails effect striking performance in arboreal snakes.
|
222 |
Does Thermotolerance in Daphnia Depend on the Mitochondrial Function?Hasan, Rajib 01 August 2019 (has links)
Thermotolerance limit in aquatic organism is set by the ability to sustain aerobic scope to sudden temperature shifts. This study tested the genetic and plastic differences in thermotolerance of Daphnia that can be explained by the differences in the ability to retain mitochondrial integrity at high temperatures. Five genotypes with different biogeographic origins were acclimated to 18ᵒC and 25ᵒC. We developed a rhodamine 123 in-vivo assay to measure mitochondrial membrane potential and observed higher fluorescent in heat damaged tissues as the disruption of the mitochondrial membrane potential. Significant effects on temperature tolerance were observed with CCCP and DNP but not with NaN3. Effects of toxins were significant in temperature sensitive genotype and high concentration of lactate was observed in 18ᵒC acclimated genotype only. We conclude that genetic and physiological differences are intricately linked to the ability of sustaining aerobic respiration at high temperatures which sets limit to the thermotolerance.
|
223 |
[en] FACTORS THAT INFLUENCE THE PERFORMANCE OF THE BRAZILIAN FIRMS: AN INTEGRATIVE MODEL / [pt] FATORES QUE INFLUENCIAM O DESEMPENHO DAS FIRMAS BRASILEIRAS: UM MODELO INTEGRATIVOFABIO DE OLIVEIRA PAULA 09 May 2007 (has links)
[pt] O objetivo deste trabalho é responder a seguinte pergunta:
Quais são os
fatores que influenciam o desempenho das firmas? Para
isso, foi desenvolvido
um modelo integrativo utilizando o conhecimento produzido
pelas escolas
consagradas posicionamento e resource-based. Esse modelo
prega que o
desempenho é influenciado pelos recursos da firma, pela
estratégia que ela adota
e pela estrutura da indústria onde ela está inserida. Por
sua vez, esses três fatores
são influenciados pelo ambiente que cerca a firma. Esse
modelo, então, foi
testado pelo método de modelagem de equações estruturais
Maximum likelihood
estimation (MLE) com dados simulados. Juntamente com o
modelo proposto,
foram testados dois modelos consagrados na literatura. Um
baseado nas teorias
da escola posicionamento (adaptado de Hill & Deeds, 1996),
e o outro baseado
nas teorias da escola resource-based (adaptado de
Schroeder et al., 2002). O teste
do modelo proposto mostrou que o desempenho realmente é
afetado pelos três
fatores citados acima, porém os indicadores de fit
mostraram que o modelo não
representa bem os dados utilizados para testá-lo. Em
contrapartida, os dois
modelos consagrados na literatura tiveram indicadores de
fit bem melhores, o
que mostra que eles representam melhor os dados simulados
usados para fazer o
teste com a técnica estatística utilizada. / [en] This study will address the proposed research question:
Which factors
influence the performance of the firms? To answer that
question, an integrative
model was developed based on the knowledge produced by the
consecrated
positioning school and resource-based view. This model
says that the firm
resources, the strategy adopted by the firm and the
industry structure are the
factors that influence the performance. In addition, the
tree factors cited above are
influenced by the environment. This model was, then,
tested by the structural
equation modeling method Maximum likelihood estimation
(MLE) with
simulated data. Altogether with the proposed model, two
consecrated by literature
models were tested. The first one is based on positioning
school theories (adopted
from Hill & Deeds, 1996) and the second one is based on
resource-based view
theories (adopted from Schroeder et al., 2002). The
poposed model test
demonstrated that, although performance is really affected
by the tree factors cited
above, the fit indicators showed that the model doesn´t
represent very well the
data used to test it. On the other hand, the two
consecrated by literature models
had much better fit indicators. It shows that they
represent much better the
simulated data used to test them with the statistical
method used.
|
224 |
Sjuksköterskors erfarenheter av att delge negativa besked : En integrerad kunskapsöversikt / Nurses’ experiences towards breaking bad news : An integrative reviewOlofsson, Malin, Forsberg, Albin January 2019 (has links)
The event of breaking bad news is a subject that no one present in the practical setting could choose to avoid. It is a subject that the practitioners comes in touch with during a daily basis. Traditionally the role as the breaker of bad news has been settled by the physician, but at the time being, disagreements occur in the clinical setting about who should break bad news to familys and patients. Aim: The aim of this study was to explore the nurses’ experiences of breaking bad news. What are the nurses’ role in the event of breaking bad news, and are there any barriers that can affect the way the bad news is given to the patients and family members? These were two questions of issue that were looked into. Method: The integrative review method based out of Whittemore and Knafl (2005) was used for this review. A systematic search resulted in twelve articles that were deemed fitting for the purpose of this study. Results: This integrative review resulted in five identified roles carried out by the nurse in the event of breaking bad news. Further on, nine factors were identified as being of significance in how the bad news were delivered by nurses and received by patients and the patient’s family members. Nurses expressed a desire and a wish for some kind of education or training in how to break bad news. Conclusion: This article contributes with five roles experienced by nurses, along with nine different factors to have in mind when carrying out difficult news. The SPIKE model and Gibbs reflective model were discussed to have a great importance in the clinical setting.
|
225 |
A Complementary Health Approach to Facilitate Healing and Integration Among Adult Survivors of Childhood Sexual Abuse: The Shamanic Practitioner’s PerspectiveHealey, Martha W. January 2016 (has links)
Thesis advisor: Danny G. Willis / Abstract Childhood sexual abuse (CSA) survivors are at risk of suffering from myriad physical, emotional, relational, spiritual, and energetic aftereffects. Scant research has addressed healing of spiritual and energetic aftereffects, especially sense of fragmentation/soul loss. No published research has addressed shamanic healing for CSA survivors. Thus, the purpose of this qualitative descriptive research was to describe the use of shamanic healing as a complementary health approach for adult CSA survivors from the perspectives of shamanic healers. A qualitative descriptive design was used in this research. In-depth semi-structured individual interviews were conducted with a purposive sample of 15 shamanic practitioners. Interviews focused on the shamanic practitioners’ perspectives of CSA healing from western and shamanic viewpoints, shamanic methods of assessment, intervention, evaluation of outcomes, and benefits for adult CSA survivors. Interview data were analyzed using conventional qualitative content analysis, including coding, sorting, and categorizing. Shamanic practitioners described the Western viewpoint on CSA healing as limited in scope by not adequately addressing energetic and spiritual aftereffects, with the potential to leave the survivor stuck in victim mode. In contrast, the shamanic perspective was described as an expanded paradigm for CSA healing, extending beyond the individual to multigenerational healing. CSA was framed as an event in the survivor’s life that served as a teacher of life lessons, inviting the survivor to live up to one’s full potential and not be defined by CSA. The findings indicated that shamanic healing has the potential to facilitate transformative integrative healing of the adult CSA survivor by addressing the relational, spiritual, energetic, and multigenerational impact of CSA. Shamanic healing involved integrating the survivor’s perceived lost soul parts (vital energy) back into consciousness, clearing toxic energy, and restoring energy flow. The findings have implications for nursing education, theory, practice, research, and policy. The findings can serve as a foundation for designing future research on shamanic healing to address the full spectrum of healing needs of adult CSA survivors. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Connell School of Nursing. / Discipline: Nursing.
|
226 |
Práticas integrativas e complementares para a promoção da saúde / Complementary and integrative practices to promote healthIschkanian, Paula Cristina 06 September 2011 (has links)
A Promoção da Saúde tem contribuído para a construção de ações que possibilitam responder aos interesses e demandas da população visando à melhoria do nível de sua saúde. Como forma de integrar outras racionalidades médicas à Atenção a Saúde, o Ministério da Saúde aprovou, em 2006, a Política Nacional de Práticas Integrativas e Complementares (PNPIC) buscando atender, sobretudo, a necessidade de incorporar e implementar experiências que há algum tempo vêm sendo desenvolvidas com sucesso no Sistema Único de Saúde (SUS) em resposta ao desejo de parte dos usuários, expresso nas recomendações de Conferências Nacionais de Saúde, desde 1988. Assim, tem se tornado cada vez mais urgente investigar os conhecimentos, opiniões e representações sociais dos gestores e profissionais de saúde sobre essas Práticas (PIC) no SUS, e identificar as dificuldades e desafios que se apresentaram em sua implementação, utilização e divulgação nos Serviços de Saúde. Decidiu-se realizar uma pesquisa na zona norte de São Paulo/SP, em uma Unidade Básica de Saúde e em um Ambulatório de Especialidades. A metodologia utilizada foi a qualitativa e os instrumentos, a análise documental e a entrevista, com roteiro pré-estabelecido. Os resultados mostraram que os gestores não estavam preparados para a implementação da Política Nacional de Práticas Integrativas e Complementares (PNPIC) no SUS, que apenas cinco dos vinte e seis entrevistados conheciam a Política Nacional (PNPIC), que ainda prevalece o modelo biomédico nos atendimentos, que o fornecimento de material e aquisição de insumos utilizados em algumas das PIC tem se constituído em grande problema na unidade, que a divulgação das PIC não tem sido suficiente para que profissionais e usuários as conheçam. Nem todos os profissionais que atuavam no Ambulatório de Especialidades onde as PIC têm sido oferecidas têm valorizado essas atividades. As Práticas Integrativas e Complementares não têm ocupado o papel que deveriam e/ou poderiam dentro do SUS para a Promoção da Saúde. Verificou-se que é essencial que o Município de São Paulo/SP incentive e crie condições para o oferecimento das PIC em todas as suas Unidades, aprimorando sua divulgação e apoiando a inserção de profissionais não médicos, desde que apresentem formação adequada, pois práticas como Homeopatia, Acupuntura, Antroposofia e Fitoterapia já são consideradas especialidades médicas. As Práticas Integrativas e Complementares, se integradas ao SUS, certamente poderão contribuir, e muito, para a Promoção da Saúde / Health promotion has been contributing to foster actions which aim at responding to the interests and demands of the population in order to improve the level of their health. As a means of integrating other medical and health care practises, the Ministry of Health adopted, in 2006, the National Policy on Integrative and Complementary Practices (PNPIC) so as to particularly face the need to incorporate and to implement experiences which for some time have been successfully developed in the National Health System (SUS) in response to the desire of the users as expressed on the recommendations of the National Health Conferences, since 1988. That is why it has become more and more urgent to investigate the knowledge, opinions and social representations of managers and health professionals about those practices (PIC) in SUS as well as to identify the difficulties and challenges that are present in their implementation, use and disclosure in the Health Services. In order to better comprehend those issues, a survey in a Basic Health Unit and Specialty Clinic in the northern area of Sao Paulo/SP has been carried out. The chosen methodology was the qualitative approach with its instruments, documentary analysis and interviews based upon pre-established guidelines. The results support the thesis that managers are not prepared to implement the National Policy on Integrative and Complementary Practices (PNPIC) in SUS: only five out of the twenty six respondents were aware of the National Policy (PNPIC); the biomedical model sessions still prevails; material supply and acquisition of raw materials used in some of the PIC has become a major issue in the unit; that the disclosure of the PIC has not been enough so as to be fully known by professional and users alike. Furthermore, most of the professionals working in the Specialty Clinic where the PIC have been offered have undervalued those activities. The Complementary and Integrative Practices have not played the role they should and/or could in the SUS for the Promotion of Health yet. It is pivotally necessary that the City of São Paulo/SP encourages and creates conditions for taking the PIC into all the Health Units, so as to improve, disclosure and support the inclusion of non-medical professionals, provided that they have proper training since practices such as Homeopathy, Acupuncture, Anthroposophy and Phytotherapy are already considered as medical specialties. If they come to be included in SUS, the Complementary and Integrative Practices can certainly contribute a lot for the Promotion of Health
|
227 |
Assistência de enfermagem ao estomizado intestinal: revisão integrativa de literatura / Nursing care to the intestinal ostomized: integrative literature reviewBezerra, Isa Menezes 27 August 2007 (has links)
Este estudo consiste de uma revisão integrativa da literatura nacional e internacional sobre a Assistência de Enfermagem Hospitalar ao Estomizado Intestinal, publicada no período de 2002 a 2006. Para realização deste estudo foram utilizadas as fases propostas por Ganong (1987): seleção das hipóteses ou questões para a revisão; estabelecimento de critérios para seleção da amostra; apresentação das características da pesquisa primária; analisar os dados; interpretação dos resultados e apresentação da revisão. Realizou-se a busca on-line dos trabalhos científicos no site Bireme e no sistema Dedalus (USP). Estabelecemos como critérios de inclusão de trabalhos: abordagem da assistência de enfermagem ao estomizado intestinal hospitalizado, realizados com seres humanos, publicados em inglês, espanhol e português e localizados na íntegra; e como critérios de exclusão trabalhos que abordavam outros tipos de estomas (não intestinais), os experimentais com animais, trabalhos direcionados à clientela infantil e trabalhos publicados em outros idiomas que não o inglês, o espanhol ou o português. Obteve-se uma amostra de 22 artigos para análise. Os temas abordados foram categorizados em Cuidados de Enfermagem com 14 (63,6%) trabalhos científicos; Autocuidado com 4 (18,2%), e Complicações com 4(18,2%). A análise dos temas de pesquisa possibilitou identificar a necessidade de realização de pesquisas futuras abordando aspectos específicos como intervenções de enfermagem e estratégias de ensino, em todas as etapas do atendimento hospitalar, assim como a organização e dinâmica de atendimento da equipe de saúde hospitalar. Quanto aos delineamentos das pesquisas, evidenciou-se a necessidade de investimentos nos aspectos metodológicos como uma condição para produção de conhecimento científico que consolida a prática clínica. / The purpose of this dissertation is to present a national and international review about the Hospital Nursing Care to the Intestinal Ostomized from the period of 2002 to 2006. In order to realize this study, the stages proposed by Ganong (1987) were applied: selection of hypothesis or questions to the review, establishment of criteria for the sample selection, presentation of the primary research characteristics, data analysis, interpretation of the results and the review presentation. A research of the scientific works was made on the Bireme website and in the Dedalus (USP) system. The criteria established for the inclusion of the works were: mention of the nursing care approaches to the hospitalized intestinal ostomized, experiments performed on humans\' beings, publication of the work in English, Spanish and Portuguese of which the verbatim could be found. And the criteria for exclusion of the works were: works which referred to other types of ostomates (nonintestinal), to the experiments on animals, works aimed to the juvenile public and last, those works published in other languages apart from English, Spanish or Portuguese. Twentytwo sample works were obtained for analysis. The topics were classified in: Nursing Care with 14 (63, 6%) scientific works; Self-care with 4 (18, 2%) scientific works; and Complications with 4 (18, 2%) scientific works. The analysis of the research topics revealed the necessity of future researches on specific aspects, such as nursing interventions and teaching strategies in the different stages of the hospitalar service as well as in the dynamism and organization of the staff\'s service. Concerning to the delineation of the research, it became evident that there is also the necessity of investment in methodological aspects as a main condition to the acquisition of scientific knowledge to consolidate the clinic practice.
|
228 |
Taxonomic revision of Pimelodella Eigenmann & Eigenmann, 1888 (Siluriformes: Heptapteridae): an integrative proposal to delimit species using a multidisciplinary strategy / Revisão taxonômica de Pimelodella Eigenmann & Eigenmann, 1888 (Siluriformes: Heptapteridae): uma proposta integrativa para a delimitação de espécies com estratégias multidisciplinaresMotta, Veronica de Barros Slobodian 26 January 2018 (has links)
Primary taxonomic research in neotropical ichthyology still suffers from limited integration between morphological and molecular tools, despite major recent advancements in both fields. Such tools, if used in an integrative manner, could help in solving long-standing taxonomic problems. The genus Pimelodella Eigenmann & Eigenmann, 1888 is a perfect case for an integrative and multidisciplinary approach in taxonomy. Pimelodella is a genus of the Heptapteridae broadly distributed throughout trans- and cis-Andean South America, and one of the main components of Neotropical Ichthyofauna. Nowadays is the most species-rich genus of the family, with 79 valid species. However, the validity and delimitation of those species is extremely problematic, due their broad geographic distribution, conserved morphology, and ancient and imprecise descriptions. Pimelodella is undoubtedly one of the most severe taxonomic bottlenecks in neotropical ichthyology. This project presents a taxonomic revision of Pimelodella using an integrative morphological-molecular approach. The traditional taxonomic revision covers the genus in its entirety, with all the components of this kind of study. All types were examined, and the number of valid species herein recognized was reduced to 55 species, for which full descriptions are presented. The molecular taxonomy was done for a circumscribed subset of the genus, with representation enough to understand the molecular divergences and compare them with the traditional taxonomy results, allowing an evaluation of the results of the revision. / A pesquisa taxonômica primária ainda apresenta pouca integração entre as ferramentas morfológicas e moleculares para o estudo de peixes neotropicais, apesar de grandes avanços recentes em ambos os campos. Tais ferramentas, se usadas de maneira integrativa, poderiam solucionar grupos reconhecidos por representarem problemas taxonômicos renitentes. O gênero Pimelodella Eigenmann & Eigenmann, 1888 se enquadra como um ótimo caso para a aplicação de uma estratégia integrativa e multidisciplinar. Pimelodella é um gênero da família Heptapteridae, distribuído amplamente por drenagens sul-americanas trans- e cis-andinas e compreende um dos principais componentes da ictiofauna neotropical. Atualmente é reconhecido como o maior gênero da família, com 79 espécies válidas descritas. Entretanto, a validade e delimitação dessas espécies é problemática, devido à elevada diversidade do gênero, aliada à ampla distribuição, morfologia conservada e descrições antigas e imprecisas. Trata-se de um dos grandes gargalos taxonômicos na sistemática e taxonomia de peixes neotropicais. Este projeto apresenta uma revisão taxonômica de Pimelodella utilizando uma abordagem integrativa morfológica-molecular. A revisão taxonômica clássica cobre a integridade da diversidade do gênero, com todos os componentes deste tipo de estudo. Todos os tipos foram examinados, e o número de espécies validas é aqui reduzido para 55 espécies, para as quais descrições completas são apresentadas. A parte molecular foi realizada em um subgrupo delimitado, com diversidade suficiente para que as estimativas de divergência molecular pudessem ser comparadas aos resultados da revisão morfológica, fornecendo um modelo de avaliação para o restante da revisão.
|
229 |
Temas relevantes da gestão participativa para o processo de trabalho em enfermagem / Relevant themes to evaluation of participative management in the work process in nursingBueno, Alexandre de Assis 06 July 2012 (has links)
A sociedade, em suas múltiplas dimensões, tem estado em constante construção de uma nova realidade. Valores, ideias e paradigmas se a lternam em \"des\" e \"reconstrução\" daquilo que a sustenta e norteia. A Reforma Sanitária se torna um movimento específico, porém contextualizado num processo de redemocratiz ação política da sociedade brasileira. Esse movimento, além de representar uma luta específica pelo modelo de atenção à saúde, também é parte de uma totalidade, uma vez que consolidava, na saúde, os direitos democráticos debatidos por diversos setores da sociedade brasileira. A busca por um novo desenho do cuidado da saúde pela sociedade se dá a partir dos princípios e dire trizes fundamentais do Sistema Único de Saúde, uma vez que estes, além de garantir um novo modelo de atenção, possibilitariam as bases para um modelo de gestão mais participativo que daria condições de continuidade deste movimento. Nesse contexto, a enfermagem carece de um processo de atualização em seus conceitos e arranjos. Pr ecisa permitir que as transformações sociais colaborem na construção do perfil profissional que se necessita para que se garanta a \"continuidade\" no processo natural de mudanças das políticas públicas que requerem, dentre outras, \"flexibilidade e criatividade\" por parte dos trabalhadores. Este estudo teve como objetivo analisar a Gestão Participativa, no contexto do Sistema Único de Saúde, à luz das evidências científicas, visando a identificação de categorias relevantes na construção do processo do trabalho em enfermagem. Para atender aos objetivos deste estudo, foi realizada a revisão integrativa da lite ratura existente que propo rcionou um aprofundamento no conhecimento dessa temática e deu condições para o desenvolvimento de um conceito próprio. A leitura dos artigos selecionados seguiu a proposta da análise temática de conteúdo, segundo Minayo, e alguns temas emergiram da leitura, de modo que eles representam alguns aspectos importantes do Trabalho em Enfermagem no contexto da Gestão Participativa. Desta forma, identificou-se os seguintes temas nas amostras selecionadas: Reorientação da Prática Assistencial, Sobrecarga de Trabalho, Gestão Ética, Participação, Liderança, Administração de Conflitos, Qualificação Profissional, Formação Política e Flexibilização das Relações. Conclui-se que a enfermagem necessita de uma reorientação sistemática de seu processo de trabalho de modo que possa se alinhar com a política pública da Gestão Participativa e alcançar os benefícios desta gestão no perfil de seus trabalhadores. / The society, in its multiple dimensions, has been in constant construction of a new reality. Values, ideas and paradigms alternate in \"des\" and \"reconstruction\" of what sustains and guides. The Sanitary Reform becomes a particul ar movement, but contextualized in a process of political democratization of Brazilian society. This movement represents a struggle for specific model of health care and is also part of a totality, since consolidated in health, democratic rights debated by various sectors of Brazilian society. The search for a new design of health care by society starts from the fundame ntal principles and guidelines of the Unified Health System, since these, in addition to ensure a new model of care, would allow the foundation for a more participatory management model which would enable the continuation of this movement. In this context, nursing lacks a process to update its concepts and arrangements and needs to allow social change to collaborate in building the profile that is needed to ensure the \"continuity\" in the natural process of changing public policies that require, among other things, \"fle xibility and creativity\" by wo rkers. This study aimed to analyze the participatory management in the cont ext of the Unified Health System, in light of the scientific evidence for the identification of relevant categories in the construction process of nursing work. To meet the objectives of this study, we performed an integrative review of existing literature that provided a deeper knowle dge of thematic and gave conditions for the development of a specific concept. The reading of the articles followed the proposal of thematic content analysis, by Minayo, and some themes emerged from the reading, so that they represent some important aspects of nursing work in the context of Participatory Management. Thus, we identified the following themes in the selected samples: Reorientation of Care Practice, Work Overload, Ethics Ma nagement, Participation, Leadership, Conflict Management, Professional Qualification, Political Education, and Flexibilization of the Relations. It is concluded that nursing requires a systematic reorientation of their work process, so that it can align itself with the public policy of participatory management and achieve the benefits of this management in the profile of their workers.
|
230 |
Analyse comparative de la dynamique de deux éléments intégratifs conjugatifs de streptococcus thermophilus / Comparative analysis of the dynamics of two Integrative and Conjugative Elements from Streptococcus thermophilusCarraro, Nicolas 05 December 2011 (has links)
Les éléments intégratifs conjugatifs (ICE) sont des îlots génomiques qui codent leur excision du chromosome, leur transfert par conjugaison et leur intégration. Ils présentent une organisation modulaire, chaque module incluant tous les gènes nécessaires pour conférer une fonction biologique. Ce travail a porté sur l'étude de la régulation ainsi que les modalités de transfert et de maintien d'ICESt1 et ICESt3, deux ICE de Streptococcus thermophilus présentant une région core étroitement apparentée et une région variable non apparentée. Les résultats obtenus ont montré que, bien qu'ICESt3 s'excise et se transfère à beaucoup plus haute fréquence qu'ICESt1, l'excision des deux éléments est activée par des stimuli identiques et est dépendante de la souche hôte. Chacun de ces ICE code des homologues de deux types de régulateurs différents, cI et ImmR, ce qui implique un mécanisme de régulation complexe et original qui pourrait être conservée chez de nombreux ICE apparentés identifiés lors de ce travail. Selon la définition initiale, les ICE se maintiendraient uniquement sous forme intégrée et ne se répliqueraient pas de façon intracellulaire. Cependant, les dommages à l'ADN induisent non seulement l'excision et le transfert d'ICESt3, mais aussi sa présence en copies multiples extrachromosomiques. Les résultats obtenus impliquent une réplication sous forme extrachromosomique, réplication codée par la région core et qui serait impliquée dans le maintien de l'élément. Une telle réplication pourrait être impliquée dans le maintien de nombreux ICE en plus de leur intégration. / Integrative and Conjugative Elements (ICEs) are genomic islands, which excise from the chromosome, self-transfer by conjugation and integrate. They harbor a modular organization: genes and sequences involved in the same biological process are grouped in the same region. This work concerns the modality of transfer and maintenance of ICESt1 and ICESt3, two ICEs of Streptococcus thermophilus that share closely related core region. ICESt1 excises much less frequently than ICESt3. Nevertheless, excision of the two elements is activated by the same stimuli (DNA damage, stationary phase and/or cell density) and depends of the host strain. Bioinformatical and transcriptional analyses highlight several differences in their organization. However, each of these two ICEs would encode two different regulators, cI and ImmR, suggesting that a complex and original pathway govern to ICESt1' and ICESt3' regulation. This regulation would be shared with numerous ICEs that we identified in the genome of various commensal or pathogenic streptococci. According to the original definition, ICE's maintenance would be exclusively due to their integration in the host chromosome, and ICEs would not be able of extracellular replication. However, in addition to the induction of ICESt3' excision and transfer, DNA damage cause replication of its extrachromosomal form. This unexpected property is encoded by the core region and would be implicated in the maintenance of the element. Comparision with data recently published on other ICEs suggest that intracellular replication could be involved in the maintenance of numerous ICEs, besides their integration.
|
Page generated in 0.0882 seconds