Low dispersing species : population genetic processes in space and time : the genus "Trochulus" (Gastropoda: Hygromiidae) as a case study

RÉSUMÉ Une espèce est rarement composée d'une population unique. Parce que les individus ont des capacités de dispersion limitées et que les paysages sont des mosaïques d'habitats, la plupart des espèces sont plutôt composées de sous-populations connectées par la migration. Cette variation spatiale influence directement la distribution de la variabilité génétique dans et entre les populations. Durant ce travail, nous avons abordé certains des processus populationnels qui ont joué un rôle supposé dans l'apparition de nouvelles espèces au sein du genre Trochulus. Plus précisément, nous avons tenté d'évaluer les impacts respectifs de l'isolement passé (facteurs historiques) et présent (facteurs locaux). Nous avons d'abord pu montrer que les faibles capacités de dispersion des escargots terrestres ont directement influencé leur histoire évolutive à toutes les échelles spatiales et temporelles. En réduisant l'effet homogénéisant de la migration, une faible dispersion maintient dans les populations les traces génétiques d'évènements passés. A l'échelle de la distribution globale de Trochulus villosus, ces traces ont permis de reconstruire une histoire faite d'isolements et d'expansions de populations. En combinant des données génétiques avec une modélisation de la niche climatique passée, il a été possible de proposer un scénario significativement meilleur que toutes les hypothèses alternatives que nous avons testées. A l'échelle locale par contre, l'héritage historique est difficile à distinguer de la dynamique actuelle. Ce fut le cas des lignées mitochondriales du complexe sericeus-hispidus : les deux principales lignées étaient phylogénétiquement éloignées, avaient eu des démographies passées différentes et corrélaient avec des différences morphologiques. D'un autre côté, le flux de gène nucléaire était fort, contredisant l'idée de deux espèces cryptiques isolées reproductivement. Pour pouvoir conclure à la présence ou non de deux espèces, il nous a manqué des informations locales sur la dynamique des populations et les conditions écologiques que l'on trouve dans la région d'étude. Enfin, nous avons pu souligner que la connectivité entre populations d'escargots est soumise à la qualité des habitats et à leur organisation spatiale. Les escargots sont dépendants d'un habitat et s'y adaptent, comme l'indiquent la présence de «poils » uniquement sur la coquille d'espèces vivant dans des habitats humides ou la corrélation entre morphologie et habitat au sein du complexe sericeus-hispidus. Logiquement donc, les escargots migrent préférentiellement au travers d'habitats favorables comme l'a montré la réduction de flux de gènes au travers des prairies chez T. villosus (une espèce forestière). De ces données, nous pouvons supposer que les populations d'escargots en particulier, et des espèces à faible dispersion en général, ont de fortes chances d'être affectées par les changements climatiques, avec de probables implications pour leurs histoires évolutives. SUMMARY : Species rarely consists in a single population. Because individuals have limited dispersal abilities, because landscapes are habitat patchworks, most species are made of several subpopulations connected by migration. This spatial variation has consequences on the distribution of genetic diversity within and between populations, creating a structure among the populations. During the present work, we investigated some of the population processes assumed to have played an important role on the speciation within the genus Trochulus. More specifically, we questioned the respective impacts of past (historical factors) or present (local factors) population isolations. We first could show that the poor dispersal abilities of land snails have had profound impacts on their evolutionary histories at all spatial and temporal scales. Low dispersal maintains a strong signature of past events in the populations by minimising the homogenising effects of geneflow. At the scale of Trochulus villosus global distribution, they allowed to retrieve the detailed history of this species population isolations and expansions. Combining a large genetic dataset with paleo-climatic niche modelling ended up with a historical scenario significantly better than all traditional alternatives we tested. At local scale on the contrary, past events become difficult to tease apart from ongoing processes. This was the case for the divergent mitochondria) lineages within the sericeus-hispidus complex: the two principal lineages appeared to be phylogenetically distant, to have experienced different demographic histories and to correlate with morphological differences. On the other hand, nuclear (present day) geneflow was high, contradicting the idea of two reproductively isolated cryptic species. Information on the local population dynamics and environmental conditions are lacking to be able to decide whether past isolation has indeed resulted here in new species. Finally, we emphasised the importance of the habitat types present in a landscape as well as their spatial organisation for the population connectivity of land snails. These species are tightly dependent on a habitat and adapt to it as shown by thé occurrence of hair-like structures only in species living in humid environments or by the correlation between shell morphology and habitat in the sericeus-hispidus complex. As a result, land snails preferentially migrate through favourable habitats: Trochulus villosus, a forest species, had its geneflow significantly reduced across meadows. From these data, we can hypothesise that the populations of land snails in particular and of low dispersing species in general are likely to be strongly affected by the ongoing climate changes, with potential major consequences on their evolutionary histories.

Epidémiologie et prise en charge du cancer colorectal: une étude de population en Valais

Entre 2006 et 2009, 774 cas de cancer colorectal in situ ou invasif ont été diagnostiqués en Valais. La proportion des hommes (59%) est plus élevée que celle des femmes (41%). L'âge moyen au diagnostic est de 70 ans. 79% des tumeurs sont invasives. Le côlon est la localisation la plus fréquente (71%). 20% des cas sont de stade 0, 36% de stade I et II, 18% de stade III et 22% de stade IV. Le mode de présentation le plus fréquent est de loin la consultation pour symptômes non urgents (75%). Toutefois, 9% des patients sont pris en charge en urgence. 95% des patients traités le sont par de la chirurgie seule ou en combinaison avec d'autres traitements. 82% des patients avec un cancer colorectal invasif ont été traités dans les 30 jours. En première intention, 95% des cancers du côlon invasifs ont un traitement chirurgical alors que 53% des cancers du rectum invasifs ont un traitement chirurgical et 36% une radio-chimiothérapie. La survie du cancer colorectal invasif est de 95% à 30 jours et de 79% à 1 an. La survie est plus basse chez les personnes de 70 ans et plus (à 30 jours: 92%; à 1 an: 70%) que chez les personnes de moins de 70 ans (à 30 jours: 99%; à 1 an: 90%). Elle est également moins bonne pour les stades IV de la maladie (à 30 jours: 91%; à 1 an: 54%) que pour les stades I-II (à 30 jours: 97%; à 1 an: 91%) ou III (à 30 jours: 98%; à 1 an: 92%). Ces observations indiquent que l'épidémiologie du cancer colorectal dans la population valaisanne est similaire à ce qui est décrit dans d'autres populations en Europe, que les modalités de prise en charge sont proches de celles proposées dans les guidelines et que la survie est similaire à celle observée en Suisse et dans d'autres pays européens.

Humoral and cellular immune responses against Type I cysteine proteinase of Leishmania infantum are higher in asymptomatic than symptomatic dogs selected from a naturally infected population.

Canids are natural reservoirs of Leishmania infantum and have been promoted as experimental hosts to decipher the pathogenesis of human visceral leishmaniasis (VL). In this study, the presence of IgG antibodies as well as the presence of mononuclear leukocytes reactive to different cysteine proteinases (CPs) were examined in 13 L. infantum-infected dogs (six with symptoms, seven asymptomatic). Cysteine proteinases which belong to papain-like enzymes known as clan CA are the most studied CPs of parasite protozoa. These molecules are expressed by the intracellular stages of the parasite and could be immunogenic. We studied Type II CP (CPA) and Type I CP (CPB) with its long C-terminal extension (CTE) which could be highly immunogenic. We showed that the level of antibodies reactive to rCPA is low in both symptomatic and asymptomatic dogs. In contrast, when CPB and CTE were used as antigens, the level of total IgG (with IgG2 superior to IgG1) reached higher values in asymptomatic dogs than in dogs with VL. While the peripheral blood mononuclear cell (PBMC) reactivity was significant when cultured in the presence of freezed/thawed (F/T) lysate, it remained low in presence of CP although always higher for PBMC recovered from asymptomatic dogs. We showed the importance of CPB and CTE in particular as a target of immune response and their potential use for serodiagnosis in asymptomatic dogs.

Determining the best population-level alcohol consumption model and its impact on estimates of alcohol-attributable harms.

BACKGROUND: The goals of our study are to determine the most appropriate model for alcohol consumption as an exposure for burden of disease, to analyze the effect of the chosen alcohol consumption distribution on the estimation of the alcohol Population- Attributable Fractions (PAFs), and to characterize the chosen alcohol consumption distribution by exploring if there is a global relationship within the distribution. METHODS: To identify the best model, the Log-Normal, Gamma, and Weibull prevalence distributions were examined using data from 41 surveys from Gender, Alcohol and Culture: An International Study (GENACIS) and from the European Comparative Alcohol Study. To assess the effect of these distributions on the estimated alcohol PAFs, we calculated the alcohol PAF for diabetes, breast cancer, and pancreatitis using the three above-named distributions and using the more traditional approach based on categories. The relationship between the mean and the standard deviation from the Gamma distribution was estimated using data from 851 datasets for 66 countries from GENACIS and from the STEPwise approach to Surveillance from the World Health Organization. RESULTS: The Log-Normal distribution provided a poor fit for the survey data, with Gamma and Weibull distributions providing better fits. Additionally, our analyses showed that there were no marked differences for the alcohol PAF estimates based on the Gamma or Weibull distributions compared to PAFs based on categorical alcohol consumption estimates. The standard deviation of the alcohol distribution was highly dependent on the mean, with a unit increase in alcohol consumption associated with a unit increase in the mean of 1.258 (95% CI: 1.223 to 1.293) (R2 = 0.9207) for women and 1.171 (95% CI: 1.144 to 1.197) (R2 = 0. 9474) for men. CONCLUSIONS: Although the Gamma distribution and the Weibull distribution provided similar results, the Gamma distribution is recommended to model alcohol consumption from population surveys due to its fit, flexibility, and the ease with which it can be modified. The results showed that a large degree of variance of the standard deviation of the alcohol consumption Gamma distribution was explained by the mean alcohol consumption, allowing for alcohol consumption to be modeled through a Gamma distribution using only average consumption.

Effect of age on toxicokinetics among human volunteers exposed to propylene glycol methyl ether (PGME)

Aging adults represent the fastest growing population segment in many countries. Physiological and metabolic changes in the aging process may alter how aging adults biologically respond to pollutants. In a controlled human toxicokinetic study (exposure chamber; 12 m³), aging volunteers (n=10; >58 years) were exposed to propylene glycol monomethyl ether (PGME, CAS no. 107-98-2) at 50 ppm for 6 h. The dose-dependent renal excretion of oxidative metabolites, conjugated and free PGME could potentially be altered by age. AIMS: (1) Compare PGME toxicokinetic profiles between aging and young volunteers (20-25 years) and gender; (2) test the predictive power of a compartmental toxicokinetic (TK) model developed for aging persons against urinary PGME concentrations found in this study. METHODS: Urine samples were collected before, during, and after the exposure. Urinary PGME was quantified by capillary GC/FID. RESULTS: Differences in urinary PGME profiles were not noted between genders but between age groups. Metabolic parameters had to be changed to fit the age adjusted TK model to the experimental results, implying a slower enzymatic pathway in the aging volunteers. For an appropriate exposure assessment, urinary total PGME should be quantified. CONCLUSION: Age is a factor that should be considered when biological limit values are developed.

The association between cigarettes smoking, cannabis use and alcohol consumption in a population of young men: results of a population-based survey.

BACKGROUND: Cigarette smoking is often initiated at a young age as well as other risky behaviors such as alcohol drinking, cannabis and other illicit drugs use. Some studies suggest that cigarette smoking may have an influence on other risky behaviors but little is known about the chronology of occurrence of those different habits. The aim of this study was to assess, by young men, what were the other risky behaviors associated with cigarette smoking and the joint prevalence and chronology of occurrence of those risky behaviors. METHODS: Cross-sectional analyses of a population-based census of 3526 young men attending the recruitment for the Swiss army, aged between 17 and 25 years old (mean age: 19 years old), who filled a self reported questionnaire about their alcohol, cigarettes, cannabis and other illicit drugs habits. Actual smoking was defined as either regular smoking (¡Ý1 cigarette/day, on every day) or occasional smoking, binge drinking as six or more drinks at least twice a month, at risk drinking as 21 drinks or more per week, recent cannabis use as cannabis consumption at least once during the last month, and use of illicit drugs as consumption once or more of illicit drugs other than cannabis. Age at begin was defined as age at first use of cannabis or cigarette smoking. RESULTS: In this population of young men, the prevalence of actual smoking was 51.2% (36.5% regular smoking, 14.6% occasionnal smoking). Two third of participamnts (60.1%) declared that they ever used cannabis, 25.2% reported a recent use of cannabis. 53.8% of participants had a risky alcohol consumption considered as either binge or at risk drinking. Cigarette smoking was significantly associated with recent cannabis use (Odds Ratio (OR): 3.85, 95% Confidence Interval (CI): 3.10- 4.77), binge drinking (OR: 3.48, 95% CI: 3.03-4.00), at risk alcohol drinking (OR: 4.04, 95% CI: 3.12-5.24), and ever use of illicit drugs (OR: 4.34, 95% CI: 3.54-5.31). In a multivariate logistic regression, odds ratios for smoking were increased for cannabis users (OR 3.10,, 95% CI: 2.48-3.88), binge drinkers (OR: 1.77, 95% CI: 1.44-2.17), at risk alcohol drinkers (OR 2.26, 95% CI: 1.52-3.36) and ever users of illicit drugs (OR: 1.56, 95% CI: 1.20-2.03). The majority of young men (57.3%) initiated smoking before cannabis and mean age at onset was 13.4 years old, whereas only 11.1% began to use cannabis before smoking cigarettes and mean age at onset was slightly older (14.4 years old). 31.6% started both cannabis and tobacco at the same age (15 years old). About a third of participants (30.5%) did have a cluster of risky behaviours (smoking, at risk drinking, cannabis use) and 11.0% did cumulate smoking, drinking, cannabis and ever use of illegal drugs. More than half of the smokers (59.6%) did cumulate cannabis use and at risk alcohol drinking whereas only 18.5% of non-smokers did. CONCLUSIONS: The majority of young smokers initiated their risky behaviors by first smoking and then by other psychoactive drugs. Smokers have an increased risk to present other risky behaviors such as cannabis use, at risk alcohol consumtion and illicit drug use compared to nonsmokers. Prevention by young male adults should focus on smoking and also integrate interventions on other risky behaviors.