Evolution in structured populations

Cet article est un compte-rendu du colloque "Evolution in Structured Population", tenu du 14 au 16 Septembre 1994 à l'Université de Lausanne. Consacré aux causes écologiques et conséquences évolutives d'horizons divers (zoologie, botanique, anthropologie, mathématiques), utilisant des approches variées, aussi bien empiriques que théoriques. Plusieurs exemples concrets de structurations génétiques de populations naturelles ont été documentés, et leurs causes analysées. Celles-ci sont variées, certaines étant extrinsèques à la biologie des espèces concernées (distances géographique, barrières écologiques, etc), d'autres intrinsèques (stratégies de reproduction, mutations chromosomiques). Les outils quantitatifs les plus largement utilisés pour analyser ces structures restent les F-statistiques de Whright; elles ont néanmoins fait l'objet de plusieurs critiques: d'une part, elles n'exploitent pas toute l'information disponible (certains orateurs ont d'ailleurs proposé diverses améliorations dans ce sens); d'autre part, les hypothèses qui sous-tendent leur interprétation conventionelle (en particulier l'hypothèse de populations à l'équilibre) sont régulièrement violées. Plusieurs des travaux présentés se sont précisément intéressés aux situations de déséquilibre et à leurs conséquences sur la dynamique et l'évolution des populations. Parmi celles ci: l'effet d'extinctions démiques sur les stratégies de dispersion des organismes et la structure génétique de leurs métapopulations, l'inadéquation du modèle classique de métapopulation, dit modèle en île (les modèles de diffusion ou de "pas japonais" (stepping stone) semblent généralement préférables), et le rôle de la "viscosité" des populations, en particulier en relation avec la sélection de parentèle et l'évolution de structures sociales. Le rôle important d'événements historiques sur les structures actuelles a été souligné, notamment dans le cadre de contacts secondaires entre populations hautement différenciées, leur introgression possible et la biogéographie de taxons vicariants. Parmi les problèmes récurrents notés: l'identification de l'unité panmictique, l'échelle de mesure spatiale appropriée, et les difficulté d'estimation des taux de migration et de flux de gènes. Plusieurs auteurs ont relevé la nécessité d'études biologiques de détail: les structures génétiques n'ont d'intérêt que dans la mesure où elles peuvent être situées dans un contexte écologique et évolutif précis. Ce point a été largement illustré dans le cadre des realtions entre structures génétiques et stratégies de reproduction/dispersion.

Risk assessment of herbicide mixtures in a large European lake

Lake Geneva is one of the largest European lakes with a surface area of 580 km2. Its catchment area covers 7400 km2, of which approximately 20% is arable land. Monitoring campaigns have been carried out in 2004 and 2005 to determine the contamination of the lake by pesticides. The results highlight the widespread presence of herbicides in water, the measured concentrations for most substances remaining constant in 2004 and 2005. However, for some individual herbicides the concentrations increased drastically (e.g., the herbicide foramsulfuron). We assessed the environmental risk of the herbicides detected in the lake using water quality criteria recently determined for the Swiss environmental protection agency. Furthermore, we assessed the risk of herbicide mixtures, grouped based upon their mode of action. Generally, the risk estimated for all single substances is low, except for some sulfonylurea compounds. For these substances, the measured concentrations are higher than the predicted no-effect concentration. Impact on the flora of the lake can therefore not be excluded. When mixtures of pesticides with similar mode of action are taken into account, the risk remains lower than the mixture water quality criteria for all groups, but can reach as high as one third of this quality criteria. A further step would therefore be to assess the risk of the total pesticide mixture, including similar and dissimilar modes of action

Prevalence of normal weight obesity in Switzerland: effects of various definitions

Background: normal weight obesity (NWO) is defined as an excessive body fat associated with a normal body mass index (BMI<25 kg/m2), but its prevalence in the general population is unknown. Objective: to assess the prevalence of NWO in Switzerland according to different cut points used to define excess body fat. Design: cross-sectional study including 3,213 women and 2,912 men aged 35-75 years. Body fat was assessed by bioimpedance and prevalence of NWO was assessed using four previously published definitions for excess body fat. Results: % body fat increased with age: in men, the values (mean SD) were 20.2 5.4, 23.0 5.4, 26.3 5.2 and 28.2 4.6 for age groups [35 - 44], [45 - 54], [55 - 64] and [65 - 75] years, respectively; the corresponding values for women were 29.9 7.8, 33.1 7.4, 36.7 7.5 and 39.6 6.9. In men, prevalence of NWO was <1% irrespective of the definition used. Conversely, in women, a one to twenty fold difference (from 1.4% to 27.8%) in NWO prevalence was found. The prevalence of NWO increased with age when age-independent cut points were used in women, but not in men. Conclusions: prevalence of NWO is low in the general population and higher in women than in men. The prevalence is highly dependent on the criteria used to define excess body fat, namely in women. The use of gender- and age-specific cut points to define excess body fat is better than fixed or gender-specific only cut points.

Spirituality and religion in outpatients with schizophrenia: A multi-site comparative study of Switzerland, Canada, and the United States

Objective: To assess the importance of spirituality and religious coping among outpatients with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder living in three countries. Method: A total of 276 outpatients (92 from Geneva, Switzerland, 121 from Trois-Rivières, Canada, and 63 from Durham, North Carolina), aged 18-65, were administered a semi-structured interview on the role of spirituality and religiousness in their lives and to cope with their illness. Results: Religion is important for outpatients in each of the three country sites, and religious involvement is higher than in the general population. Religion was helpful (i.e., provided a positive sense of self and positive coping with the illness) among 87% of the participants and harmful (a source of despair and suffering) among 13%. Helpful religion was associated with better social, clinical and psychological status. The opposite was observed for the harmful aspects of religion. In addition, religion sometimes conflicted with psychiatric treatment. Conclusions: These results indicate that outpatients with schizophrenia or schizoaffective disorder often use spirituality and religion to cope with their illness, basically positively, yet sometimes negatively. These results underscore the importance of clinicians taking into account the spiritual and religious lives of patients with schizophrenia.

Lessons learned from developing a national NCD programme in low- and middle-income countries (Seychelles)

This paper identifies selected issues and lessons learned from the implementation of a national program of prevention and control of non-communicable diseases (NCD) during the past 20 years in the Seychelles, a small island state in the African region. As early as in 1989, population-based surveys demonstrated high levels of several cardiovascular risk factors, which prompted an organized response by the government. The early creation of a NCD unit within the Ministry of Health, coupled with cooperation with international partners, enabled incremental capacity building and coherent development of NCD programs and policy. Information campaigns and screening for hypertension and diabetes in work/public places raised awareness and rallied increasingly broad awareness and support to NCD prevention and control. A variety of interventions were organized for tobacco control and comprehensive tobacco control legislation was enacted in 2009 (including total bans on tobacco advertising and on smoking in all enclosed public and work places). A recent School Nutrition Policy prohibits the sale of soft drinks in schools. At primary health care level, guidelines were developed for the management of hypertension and diabetes (these conditions are managed in all health centers within a national health system); regular interactive education sessions were organized for groups of high risk patients ("heart health club"); and specialized "NCD nurses" were trained. Decreasing prevalence of smoking is evidence of success, but the raising "diabesity epidemic" calls for strengthened health care to high-risk patients and broader multisectoral policy to mould an environment conducive to healthy behaviors. Key components of NCD prevention and control in Seychelles include effective surveillance mechanisms supplemented by focused research; generating broad interest and consensus on the need for prevention and control of NCD; mobilizing leadership and commitment at all levels; involving local and international expertise; building on existing efforts; and seeking integrated, multi-disciplinary and multisectoral approaches.

Setting up a Common European Asylum System : Report on the application of existing instruments and proposals for the new system

The study assesses firstly the evaluation process of the first generation of asylum instruments while underlining the possibilities to improve it. It analyses secondly the asylum "acquis" regarding distribution of refugees between Member States, the eligibility for protection, the status of protected persons regarding detention and vulnerability, asylum procedures and the external dimension by formulating short-term recommendations of each area. Its last part is devoted to the long term evolution of the Common European Asylum System regarding the legal context including the accession of the EU to the Geneva Convention, the institutional perspectives including the new European Support Office, the jurisdictional perspective, the substantive perspective, the distributive perspective and the external perspective.

Prevalence of normal weight obesity in the general population

Background and Aims: normal weight obesity (NWO) has been defined as an excessive body fat (BF) associated with a normal body mass index (BMI). Little is known regarding its prevalence in the general population or which cut-offs for BF should be used. Methods: convenience sample of 1,523 Portuguese adults. BF was measured by validated hand-held bioimpedance. NWO was defined as a BMI<25 kg/m2 and a %BF mass>30%, along other published criteria. Results: prevalence of NWO was 10.1% in women and 3.2% in men. In women, prevalence of NWO increased considerably with age, and virtually all women aged over 55 with a BMI<25 kg/m2 were actually considered as NWO. Using gender specific cut-offs for BF (29.1% in men and 37.2% in women) led to moderately lower of NWO in women. Using gender- and age-specific cut-points for %BF considerably decreased the prevalence of NWO in women (0.5 to 2.5% depending on the criterion) but not in men (1.9 to 3.4%). Conclusions: gender- and age- specific or at least gender-specific, instead of single cut-offs for %BF, should be used to characterize and study NWO.