58 resultados para Germination success
em Université de Lausanne, Switzerland
Resumo:
Summary Several studies have demonstrated that the number of pollen donors siring seeds of individual fruits is frequently greater than one and, consequently, that plants have multiple mates. Multiple paternity can have important consequences at the population level. It influences the genetic variability of a population, the reproductive success of males and the fitness of females and future generations. It also influences male-male interactions for fertilization and it is fundamental in providing opportunity of female choice. I investigated the occurrence and the importance of multiple paternity within fruits in natural populations of the dioecious Silene latifolia using microsatellite DNA markers, especially developed for this study. I found that multiple paternity occurs in all populations investigated in the European range of the species, varying from one to nine sires per fruit with a mean of three, suggesting that multiple paternity is highly prevalent in natural populations. In the presence of multiple paternity I investigated if there was a female genotype influence on siring success of the males. I used the same pollen mixture from two males and applied it to three replicate females of different relatedness (two full sisters and one unrelated). I found female genotype influence in one of the two populations investigated, which might reflect different population history. Since these results suggested some degree of female choice, we investigated whether the occurrence of multiple paternity and post-pollination selection could provide opportunity for inbreeding avoidance. First, I measured inbreeding depression at different life-cycle stages for offspring obtained by single-donor crosses with brothers or unrelated males replicated on distinct flowers on the same female plant. To address inbreeding avoidance, I determined paternity in crosses using mixed pollen loads of the two males. I found significant inbreeding depression in the studied population, even under benign experimental conditions, and although the unrelated male did not sire significantly more offspring, there was an effect of genetic dissimilarity on paternity. This suggests that paternity is affected by relatedness among mates, but maybe additionally affected by other factors such as pollen competitive ability or male-female interactions. Using inbred and outbred crosses, I further investigated sex ratio bias inheritance in this species, and found that sex ratio bias of the parental generation was significantly correlated to pollen germination success of the F2 generation, which suggests that sex ratio bias in this species results from the specific X/Y combination and not only on Y performance. An effect of X and Y is consistent with sex chromosome meiotic drive. In conclusion, I found multiple paternity to be widespread in the study species and that females of similar genotype produce similar paternity shares. I found that inbreeding depression is substantial, therefore receiving pollen from several donors might lead to fewer inbred offspring, I also found an effect of genetic dissimilarity on paternity shares, which indicates that there is some ability to discriminate against related pollen, although this seems not to be the only determinant of paternity outcome. Finally I found sex ratio bias to be dependent on both X and Y chromosomes as predicted by sex chromosome meiotic drive. Résumé Plusieurs études ont démontré qu'il n'était pas rare que les graines contenues dans un même fruit soient issues de la fécondation par plusieurs pollens provenant de mâles différents, ce qui sous-entend que les plantes peuvent avoir plusieurs partenaires sexuels. La paternité multiple peut avoir d'importantes conséquences au niveau populationnel dans la mesure où elle peut influencer le degré de variabilité génétique de la population, le succès reproducteur des mâles, la fitness des femelles et des futures générations. La paternité multiple peut également avoir un impact sur les interactions mâle-mâle lors de la fertilisation et peut être considérée comme fondamentale vis-à-vis de la femelle, qui y trouve alors une opportunité de choisir son ou ses partenaires. Dans le cadre de ce travail de thèse j'ai cherché à déterminer si la paternité multiple était un phénomène observable et important dans les populations naturelles de l'espèce dioïque, Silene latifolia. Pour ce faire, j'ai utilisé des marqueurs microsatellites, spécialement développés pour cette étude. J'ai observé des phénomènes de paternité multiple dans toutes les populations de l'étude, réparties dans l'aire de distribution européenne de l'espèce. Le nombre de pères par fruit varie de un à neuf, avec un nombre moyen de trois, ce qui signifie que la paternité multiple est très répandue dans les populations naturelles. En raison de ces résultats, je me suis demandée si le génotype de la femelle influence le succès de paternité des mâles. J'ai alors réalisé des pollinisations manuelles sur la base d'un mélange de pollens issus de deux mâles, que j'ai appliqué sur trois femelles (réplicats) présentant différents degrés d'apparentement (deux soeurs. et une femelle étrangère). Il ressort de cette expérience que le génotype de la femelle peut influencer la paternité dans l'une des deux populations étudiées, ce qui pourrait refléter des différences en terme d'histoire des populations. Dans la mesure où ces résultats suggèrent un certain degré de choix chez la femelle, j'ai cherché à savoir si la paternité multiple et la sélection post-pollinisation pouvaient être des moyens d'éviter les croisements consanguins. Dans un premier temps, j'ai évalué la dépression de consanguinité à différentes étapes du cycle de vie chez des descendants issus de croisements à un seul donneur, celui-ci étant alternativement un frère ou un étranger, répliqués sur plusieurs fleurs d'une même plante femelle. Afin d'estimer l'évitement de croisements consanguins, j'ai effectué des croisements dont le pollen était un mélange des deux mâles (frère et étranger), puis j'ai déterminé la paternité dans les fruits obtenus. J'ai pu mettre en évidence un effet de dépression de consanguinité- significatif dans les populations étudiées, même dans des conditions expérimentales moins rudes qu'à l'extérieur. Bien que le mâle étranger n'ait pas engendré un nombre significativement plus important de graines, il y avait un effet de dissimilarité génétique sur la paternité. Ceci suggère que la paternité est affectée par le degré d'apparentement entre les partenaires, mais qu'elle peut aussi être affectée par d'autres facteurs tels que la compétitivité du pollen ou encore par les interactions mâles-femelles. L'utilisation de croisements consanguins et hybrides m'a également permis d'étudier l'héritabilité du biais de sex ratio chez cette espèce. Il s'est avéré que le biais de sex ratio de la génération parentale était significativement corrélé au succès de germination du pollen de la génération F2, ce qui signifie que, chez cette espèce, le biais de sex ratio résulte d'une combinaison spécifique de X/Y et non uniquement de la performance de Y. Un effet de X et Y est compatible avec l'hypothèse de distorsion de ségrégation méiotique des chromosomes sexuels. En conclusion, il ressort de mes résultats que la paternité multiple est un phénomène largement répandu chez S. latifolia et la paternité accomplie par un mâle est plus similaire entre soeurs qu'avec une femelle étrangère J'ai également mis en évidence que la dépression de consanguinité a un impact considérable; aussi, recevoir du pollen de plusieurs donneurs différents pourrait permettre à la femelle de produire moins de descendants consanguins. J'ai aussi trouvé un effet de la dissimilarité génétique sur le partage de paternité, ce qui indique que la discrimination contre le pollen d'apparentés est possible, bien que cela ne semble pas être le seul facteur déterminant dans le résultat de la paternité. Enfin, j'ai trouvé que le biais de sex ratio est dépendant des deux chromosomes X et Y, conformément à la théorie de distorsion de ségrégation méiotique des chromosomes sexuels.
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An increased understanding of intraspecific seed packaging (i.e. seed size/number strategy) variation across different environments may improve current knowledge of the ecological forces that drive seed evolution in plants. In particular, pre-dispersal seed predation may influence seed packaging strategies, triggering a reduction of the resources allocated to undamaged seeds within the preyed fruits. Assessing plant reactions to pre-dispersal seed predation is crucial to a better understanding of predation effects, but the response of plants to arthropod attacks remains unexplored. We have assessed the effect of cone predation on the size and viability of undamaged seeds in populations of Juniperus thurifera with contrasting seed packaging strategies, namely, North African populations with single-large-seeded cones and South European populations with multi-small-seeded cones. Our results show that the incidence of predation was lower on the single-large-seeded African cones than on the multi-small-seeded European ones. Seeds from non-preyed cones were also larger and had a higher germination success than uneaten seeds from preyed cones, but only in populations with multi-seeded cones and in cones attacked by Trisetacus sp., suggesting a differential plastic response to predation. It is possible that pre-dispersal seed predation has been a strong selective pressure in European populations with high cone predation rates, being a process which maintains multi-small-seeded cones and empty seeds as a strategy to save some seeds from predation. Conversely, pre-dispersal predation might not have a strong effect in the African populations with single-large-seeded cones characterized by seed germination and filling rates higher than those in the European populations. Our results indicate that differences in pre-dispersal seed predators and predation levels may affect both selection on and intraspecific variation in seed packaging.
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The spontaneous breathing trial (SBT)-relying on objective criteria assessed by the clinician-is the major diagnostic tool to determine if patients can be successfully extubated. However, little is known regarding the patient's subjective perception of autonomous breathing. We performed a prospective observational study in 211 mechanically ventilated adult patients successfully completing a SBT. Patients were randomly assigned to be interviewed during this trial regarding their prediction of extubation success. We compared post-extubation outcomes in three patient groups: patients confident (confidents; n = 115) or not (non-confidents; n = 38) of their extubation success and patients not subjected to interview (control group; n = 58). Extubation success was more frequent in confidents than in non-confidents (90 vs. 45%; p < 0.001/positive likelihood ratio = 2.00) or in the control group (90 vs. 78%; p = 0.04). On the contrary, extubation failure was more common in non-confidents than in confidents (55 vs. 10%; p < 0.001/negative likelihood ratio = 0.19). Logistic regression analysis showed that extubation success was associated with patient's prediction [OR (95% CI): 9.2 (3.74-22.42) for confidents vs.non-confidents] as well as to age [0.72 (0.66-0.78) for age 75 vs. 65 and 1.31 (1.28-1.51) for age 55 vs. 65]. Our data suggest that at the end of a sustained SBT, extubation success might be correlated to the patients' subjective perception of autonomous breathing. The results of this study should be confirmed by a large multicenter trial.
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BACKGROUND: A central question for understanding the evolutionary responses of plant species to rapidly changing environments is the assessment of their potential for short-term (in one or a few generations) genetic change. In our study, we consider the case of Pinus pinaster Aiton (maritime pine), a widespread Mediterranean tree, and (i) test, under different experimental conditions (growth chamber and semi-natural), whether higher recruitment in the wild from the most successful mothers is due to better performance of their offspring; and (ii) evaluate genetic change in quantitative traits across generations at two different life stages (mature trees and seedlings) that are known to be under strong selection pressure in forest trees. RESULTS: Genetic control was high for most traits (h2 = 0.137-0.876) under the milder conditions of the growth chamber, but only for ontogenetic change (0.276), total height (0.415) and survival (0.719) under the more stressful semi-natural conditions. Significant phenotypic selection gradients were found in mature trees for traits related to seed quality (germination rate and number of empty seeds). Moreover, female relative reproductive success was significantly correlated with offspring performance for specific leaf area (SLA) in the growth chamber experiment, and stem mass fraction (SMF) in the experiment under semi-natural conditions, two adaptive traits related to abiotic stress-response in pines. Selection gradients based on genetic covariance of seedling traits and responses to selection at this stage involved traits related to biomass allocation (SMF) and growth (as decomposed by a Gompertz model) or delayed ontogenetic change, depending also on the testing environment. CONCLUSIONS: Despite the evidence of microevolutionary change in adaptive traits in maritime pine, directional or disruptive changes are difficult to predict due to variable selection at different life stages and environments. At mature-tree stages, higher female effective reproductive success can be explained by differences in their production of offspring (due to seed quality) and, to a lesser extent, by seemingly better adapted seedlings. Selection gradients and responses to selection for seedlings also differed across experimental conditions. The distinct processes involved at the two life stages (mature trees or seedlings) together with environment-specific responses advice caution when predicting likely evolutionary responses to environmental change in Mediterranean forest trees.
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OBJECTIVES: The purpose of this study was to assess short- and mid-term results of in-situ revascularisation (ISR) using silver-coated Dacron prostheses and bowel repair for management of secondary aorto-enteric fistulae (SAEF). DESIGN: Single-centre retrospective chart review. MATERIAL AND METHODS: This study includes all the patients treated by ISR using silver-coated Dacron for SAEF between 2006 and 2010. Primary end points were mortality and survival rates. Secondary end points were reinfection-free survival and secondary patency rates. RESULTS: Eighteen male patients with SAEF with a median age of 64 years were operated by ISR using silver-coated Dacron during the study period without operative death. The 30-day mortality was 22% and the in-hospital mortality rate was 39%. Indeed, during hospitalisation, a duodenal leak was observed in four patients including three who died. Four others patients died due to multi-system organ failure. Median follow-up was 16 months (range 1-66). The survival rate at 12 months was 55%. One duodenal leak was observed leading to death. The reinfection-free survival and the secondary patency rates at 12 months were 60% and 89%, respectively. CONCLUSION: In-situ revascularisation with silver-coated Dacron provides acceptable results in terms of mortality. This treatment may be useful for simple vascular reconstruction and allow greater attention to bowel repair that is a determinant in short- and mid-term survival.
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RésuméLes sténoses des voies lacrymales sont fréquentes surtout chez les patients âgés et provoquent en général un epiphora avec parfois des dacryocystites aiguës ou chroniques. La dacryocystorhinostomie par voie externe (DCREX) a été la technique de choix pour traiter les sténoses post-canaliculaires au XXe siècle. Avec l'avènement de l'endoscopie nasale, l'abord endonasal est devenu facilement accessible et depuis une dizaine d'années, la dacryocystorhinostomie par voie endonasale (DCREN) est en train de supplanter la DCREX dans la majorité des cas.Le but de ce travail est de déterminer les étiologies des sténoses des voies lacrimales, d'évaluer le taux de succès et les complications de la DCREN et de détailler les gestes associés peropératoires.Cette étude rétrospective porte sur 98 patients ayant subi 104 DCREN entre janvier 1994 et février 2006. 78 patients (53 femmes et 25 hommes) présentant 84 sténoses post- canaliculaires remplissent les critères d'inclusion de l'étude. L'âge moyen est de 59 ans (4 - 89 ans).Les résultats obtenus montrent un taux de succès fonctionnel de 94.9% après une première intervention (59/84 DCREN) et de 63.6% pour les DCREN secondaires qui nous ont été référées après d'autres interventions des voies lacrymales (25/84 DCREN). Le suivi postopératoire est de 36,8 mois (12-77 mois). On dénombre 61 gestes rhino-sinusaux associés à la DCREN. Les complications per- et postopératoires sont rares, essentiellement liées aux drains bicanaliculaires. Une étiologie n'a été retrouvée que dans 28% des cas.En conclusion, la DCREN donne d'excellents résultats et peu de complications. En raison des nombreux avantages par rapport à la voie externe et la possibilité du traitement simultané de la pathologie ORL parfois associée, la DCREN est devenue le traitement de premier choix pour les sténoses postcanaliculaires. Le principal défi, quelque soit le type de DCR, est de poser la bonne indication opératoire et en cas d'échec opératoire savoir méticuleusement analyser ses causes
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BACKGROUND AND AIMS: The Senecio hybrid zone on Mt Etna, Sicily, is characterized by steep altitudinal clines in quantitative traits and genetic variation. Such clines are thought to be maintained by a combination of 'endogenous' selection arising from genetic incompatibilities and environment-dependent 'exogenous' selection leading to local adaptation. Here, the hypothesis was tested that local adaptation to the altitudinal temperature gradient contributes to maintaining divergence between the parental species, S. chrysanthemifolius and S. aethnensis. METHODS: Intra- and inter-population crosses were performed between five populations from across the hybrid zone and the germination and early seedling growth of the progeny were assessed. KEY RESULTS: Seedlings from higher-altitude populations germinated better under low temperatures (9-13 °C) than those from lower altitude populations. Seedlings from higher-altitude populations had lower survival rates under warm conditions (25/15 °C) than those from lower altitude populations, but also attained greater biomass. There was no altitudinal variation in growth or survival under cold conditions (15/5 °C). Population-level plasticity increased with altitude. Germination, growth and survival of natural hybrids and experimentally generated F(1)s generally exceeded the worse-performing parent. CONCLUSIONS: Limited evidence was found for endogenous selection against hybrids but relatively clear evidence was found for divergence in seed and seedling traits, which is probably adaptive. The combination of low-temperature germination and faster growth in warm conditions might enable high-altitude S. aethnensis to maximize its growth during a shorter growing season, while the slower growth of S. chrysanthemifolius may be an adaptation to drought stress at low altitudes. This study indicates that temperature gradients are likely to be an important environmental factor generating and maintaining adaptive divergence across the Senecio hybrid zone on Mt Etna.
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BACKGROUND: This study reviews the 15 year program of our Department of Pediatric Surgery for the treatment and follow-up of children born with a cleft in Benin and Togo. METHODS: We analyzed files of children born in Africa with a cleft. They were referred to us through a nongovernmental organization (NGO) between 1993 and 2008 and assessed in Africa by local pediatricians before and after surgery. Operations were performed by our team. RESULTS: Two hundred files were reviewed: 60 cases of unilateral cleft lip, seven of bilateral cleft lip, 44 of unilateral cleft lip palate (UCLP), 29 of bilateral cleft lip palate (BCLP), 53 of cleft palate (CP), three of bilateral oro-ocular cleft, one of unilateral and two of median clefts (Binder), and one of commissural cleft. Sixty-nine (35 %) of these cases were not operated in Africa: 25 (12.5 %) had not shown up, 28 (15 %) were considered unfit for surgery (Down's syndrome, HIV-positive, malnutrition, cardiac malformation), and 16 (7.5 %) were transferred to Switzerland. Palatal fistula occurred in 20 % of UCLP, 30 % of BCLP, and 16 % of CP. Evaluation of speech after palate surgery gave less than 50 % of socially acceptable speech. CONCLUSIONS: Our partnership with a NGO and a local team makes it possible to treat and subsequently follow children born with a cleft in West Africa. Surgery is performed under good conditions. If aesthetic results are a success, functional results after palate surgery need further improvement to promote integration in school and social life.
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This dissertation aims to investigate empirical evidence on the importance and influence of attractiveness of nations in global competition. The notion of country attractiveness, which has been widely developed in the research areas of international business, tourism and migration, is a multi-dimensional construct to measure a country's characteristics with regard to its market or destination that attract international investors, tourists and migrants. This analytical concept provides an account of the mechanism as to how potential stakeholders evaluate more attractive countries based on certain criteria. Thus, in the field of international sport-event bidding, do international sport event owners also have specific country attractiveness for their sport event hosts? The dissertation attempts to address this research question by statistically assessing the effects of country attractiveness on the success of strategy for hosting international sports events. Based on theories of signaling and soft power, country attractiveness is defined and measured as the three dimensions of sustainable development: economic, social, and environmental attractiveness. This thesis proceeds to examine the concept of sport-event-hosting strategy and explore multi-level factors affecting the success in international sport-event bidding. By exploring past history of the Olympic Movement from theoretical perspectives, the thesis proposes and tests the hypotheses that economic, social and environmental attractiveness of a country may be correlated with its bid wins or the success of sport-event-hosting strategy. Quantitative analytical methods with various robustness checks are employed with using collected data on bidding results of major events in Olympic sports during the period from 1990 to 2012. The analysis results reveal that event owners of international Olympic sports are likely to prefer countries that have higher economic, social, and environmental attractiveness. The empirical assessment of this thesis suggests that high country attractiveness can be an essential element of prerequisites for a city/country to secure in order to bid with an increased chance of success.
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National and international registries are essential tools for establishing new standards and comparing success rates, but they do not take into account the total pregnancy/delivery rate per oocyte recovery. In Switzerland and Germany, because of legal constraints, a maximum of three two-pronuclear zygotes are allocated for transfer whereas all the supernumerary pronuclear zygotes are immediately cryopreserved, preventing selection of the transferred embryos. We report on a 10 years' experience (1993-2002) of our centre which performs transfers of unselected embryos and cryopreservation at the two-pronuclear zygote stage. As approximately 30% of all deliveries are from cryo cycles, it is essential to take into account the contribution of the cryo transfers, and we propose therefore to evaluate, as a measure of IVF performance, the cumulated delivery rate per oocyte pick-up. This delivery rate is broken down further into the cumulated singleton delivery rate (CUSIDERA) and the cumulated twin delivery rate (CUTWIDERA). The sum (S) of these two rates is a measure of efficacy while the ratio CUTWIDERA/S as a percentage is a measure of safety of IVF treatments. Using these new indexes, the average 10 year efficacy and safety of our IVF programme were 26 and 19%, respectively. Both CUSIDERA and CUTWIDERA can be calculated easily in any clinical situation and yield useful parameters for patient counselling and internal/external benchmarking purposes.
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To assess the effectiveness of a multidisciplinary evaluation and referral process in a prospective cohort of general hospital patients with alcohol dependence. Alcohol-dependent patients were identified in the wards of the general hospital and its primary care center. They were evaluated and then referred to treatment by a multidisciplinary team; those patients who accepted to participate in this cohort study were consecutively included and followed for 6 months. Not included patients were lost for follow-up, whereas all included patients were assessed at time of inclusion, 2 and 6 months later by a research psychologist in order to collect standardized baseline patients' characteristics, process salient features and patients outcomes (defined as treatment adherence and abstinence). Multidisciplinary evaluation and therapeutic referral was feasible and effective, with a success rate of 43%for treatment adherence and 28%for abstinence at 6 months. Among patients' characteristics, predictors of success were an age over 45, not living alone, being employed and being motivated to treatment (RAATE-A score < 18), whereas successful process characteristics included detoxification of the patient at time of referral and a full multidisciplinary referral meeting. This multidisciplinary model of evaluation and referral of alcohol dependent patients of a general hospital had a satisfactory level of effectiveness. Predictors of success and failure allow to identify subsets of patients for whom new strategies of motivation and treatment referral should be designed.
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BACKGROUND: Factors promoting the emergence of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) connection domain mutations and their effect on antiretroviral therapy (ART) are still largely undetermined. We investigated this matter by analyzing genotypic resistance tests covering 400 amino acid positions in the RT of HIV-1 subtype B viruses and corresponding treatment histories and laboratory measurements. METHODS: The emergence of connection domain mutations was studied in 334 patients receiving monotherapy or dual therapy with thymidine analogues at the time of the genotypic resistance test. Response to subsequent combination ART (cART) was analyzed using Cox regression for 291 patients receiving unboosted protease inhibitors. Response was defined by ever reaching an HIV RNA level <50 copies/mL during the first cART. RESULTS: The connection domain mutations N348I, R356K, R358K, A360V, and A371V were more frequently observed in ART-exposed than ART-naive patients, of which only N348I and A360V were nonpolymorphic (with a prevalence of <1.5% in untreated patients). N348I correlated with M184V and predominantly occurred in patients receiving lamivudine and zidovudine concomitantly. A360V was not associated with specific drug combinations and was found to emerge later than M184V or thymidine analogue mutations. Nonpolymorphic connection domain mutations were rarely detected in the absence of established drug resistance mutations in ART-exposed individuals (prevalence, <1%). None of the 5 connection domain mutations associated with treatment showed a statistically significant effect on response to cART. CONCLUSIONS: Despite their frequent emergence, connection domain mutations did not show large detrimental effects on response to cART. Currently, routine implementation of connection domain sequencing seems unnecessary for developed health care settings.