Epidemiologie der Osteoporose. [The epidemiology of osteoporosis].

Osteoporosis is characterized by low bone mass, micro architectural impairment of bone tissue, and a subsequent in crease in fracture risk. Fractures or the vertebrae and distal forearm, as well as the proximal femur, or hip fracture, are included. Hip fracture is associated with high mortality, morbidity and medical expenses. There is a dramatic increase in the incidence of hip fracture with age. Hip fracture incidence is 350 times higher in women aged 85 years and over comparatively to women between 35 and 44 years of age. In recent studies in Switzerland, it was observed that the annual age adjusted incidence rate of hip fracture was comparable with similar rates for white population in industrialized countries, although in men the rates were relatively high. Among the major risk factors for osteoporosis are age, female gender, white and Asian race, and menopause. Postmenopausal estrogen replacement therapy reduces bone resorption. Family history of osteoporosis, frail constitution, as well as excessive alcohol intake, cigarette smoking, chronic insufficient nutritional calcium intake and physical inactivity are other risk factors. A cardinal element is the peak bone mass reached in the third or fourth decade of life. Independently of osteoporosis, falls are a key agent in fractures; several medical conditions and drugs increase the risk of falling. There is an enormous social and financial cost of osteoporosis; the annual cost of medical treatment only for hip fracture is close to Fr. 200 million in Switzerland. The burden of osteoporosis is likely to increase in the future because of the demographic aging of the population unless large scale preventive interventions are undertaken.

Differential effect of Charlson index and its components on in-hospital mortality and health costs

Introduction: The Charlson index (Charlson, 1987) is a commonly used comorbidity index in outcome studies. Still, the use of different weights makes its calculation cumbersome, while the sum of its components (comorbidities) is easier to compute. In this study, we assessed the effects of 1) the Charlson index adapted for the Swiss population and 2) the sum of its components (number of comorbidities, maximum 15) on a) in-hospital deaths and b) cost of hospitalization. Methods: Anonymous data was obtained from the administrative database of the department of internal medicine of the Lausanne University Hospital (CHUV). All hospitalizations of adult (>=18 years) patients occurring between 2003 and 2011 were included. For each hospitalization, the Charlson index and the number of comorbidities were calculated. Analyses were conducted using Stata. Results: Data from 32,741 hospitalizations occurring between 2003 and 2011 was analyzed. On bivariate analysis, both the Charlson index and the number of comorbidities were significantly and positively associated with in hospital death. Conversely, multivariate adjustment for age, gender and calendar year using Cox regression showed that the association was no longer significant for the number of comorbidities (table). On bivariate analysis, hospitalization costs increased both with Charlson index and with number of comorbidities, but the increase was much steeper for the number of comorbidities (figure). Robust regression after adjusting for age, gender, calendar year and duration of hospital stay showed that the increase in one comorbidity led to an average increase in hospital costs of 321 CHF (95% CI: 272 to 370), while the increase in one score point of the Charlson index led to a decrease in hospital costs of 49 CHF (95% CI: 31 to 67). Conclusion: Charlson index is better than the number of comorbidities in predicting in-hospital death. Conversely, the number of comorbidities significantly increases hospital costs.

Neonatal adaptation of energy and protein metabolism

During the last decade, the development of "bedside" investigative methods, including indirect calorimetry, nutritional balance and stable isotope techniques, have given a new insight into energy and protein metabolism in the neonates. Neonates and premature infants especially, create an unusual opportunity to study the metabolic adaptation to extrauterine life because their physical environment can be controlled, their energy intake and energy expenditure can be measured and the link between their protein metabolism and the energetics of their postnatal growth can be assessed with accuracy. Thus, relatively abstract physiological concepts such as the postnatal timecourse of heat production, energy cost of growth, energy cost of physical activity, thermogenic effect of feeding, efficiency of protein gain, metabolic cost of protein gain and protein turnover have been quantified. These results show that energy expenditure and heat production rates increase postnatally from average values of 40 kcal/kgxday during the first week to 60 kcal/kgxday in the third week. This increase parellels nutritional intakes as well as the rate of weight gain. The thermogenic effect of feeding and the physical activity are relatively low and account only for an average of 5% each of the total heat production. The cost of protein turnover is the highest energy demanding process. The fact that nitrogen balance becomes positive within 72 hours after birth places the newborn in a transitional situation of dissociated balance between energy and protein metabolism: dry body mass and fat decrease while there is a gain in protein and increase in supine length. This particular situation ends during the second postnatal week and soon thereafter the rate of weight gain matches the statural growth. The goals of the following review are to summarize recent data on the physiological aspects of energy and protein metabolism directly related to the extrauterine adaptation, to describe experimental approaches which recently were adapted to the newborns in order to get "bedside results" and to discuss how far these results can help everyday's neonatal practice.

Using the costs of drug therapy to screen patients for a community pharmacy-based medication review program

Objectives: To measure the positive predictive value (PPV) of the cost of drug therapy (threshold = 2000 Swiss francs [CHF], US$1440, <euro>1360) as a screening criterion for identifying patients who may benefit from medication review (MR). To describe identified drug-related problems (DRPs) and expense problems (EPs), and to estimate potential savings if all recommendations were accepted. Setting Five voluntary Swiss community pharmacies. Methods: Of 12,680 patients, 592 (4.7%) had drug therapy costs exceeding 2000 CHF over a six-month period from July 1 to December 31, 2002. This threshold limit was set to identify high-risk patients for DRPs and EPs. Three pharmacists consecutively conducted a medication review based on the pharmaceutical charts of 125 sampled patients who met the inclusion criterion. Main outcome measure: The PPV of a threshold of 2000 CHF for identifying patients who might benefit from a MR: true positives were patients with at least one DRP, while false positives were patients with no DRP. Results: The selection based on this criterion had a PPV of 86% for detecting patients with at least one DRP and 95% if EPs were also considered. There was a mean of 2.64 (SD = 2.20) DRPs per patient and a mean of 2.14 (SD = 1.39) EPs per patient. Of these patients, 90% were over 65 years old or were treated with at least five chronic medications, two common criteria for identifying patients at risk of DRPs. The main types of DRPs were drug-drug interactions, compliance problems and duplicate drugs. Mean daily drug cost per patient was CHF 14.87 (US$10.70, <euro>10.10). A potential savings of CHF 1.67 (US$1.20, <euro>1.14) per day (11%) was estimated if all recommendations to solve DRPs and EPs suggested herein were implemented. Conclusion: Further studies should investigate whether the potential benefit of medication reviews in preventing DRPs and containing costs in this patient group can be confirmed in a real practice environment. [Authors]

Short- and long-term effects of litter size manipulation in a small wild-derived rodent.

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few short-term reproductive adjustments, suggesting that female laboratory rodents express maximal rather than optimal levels of reproductive investment as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole; Microtus arvalis), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups' energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had long-term consequences, with females that had previously reared an enlarged litter being lighter at the birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimization.

Unstable shoes increase energy expenditure of obese patients.

BACKGROUND: Ergonomic unstable shoes, which are widely available to the general population, could increase daily non-exercise activity thermogenesis as the result of increased muscular involvement. We compared the energy expenditure of obese patients during standing and walking with conventional flat-bottomed shoes versus unstable shoes. METHODS: Twenty-nine obese patients were asked to stand quietly and to walk at their preferred walking speed while wearing unstable or conventional shoes. The main outcome measures were metabolic rate of standing and gross and net energy cost of walking, as assessed with indirect calorimetry. RESULTS: Metabolic rate of standing was higher while wearing unstable shoes compared with conventional shoes (1.11 ± 0.20 W/kg(-1) vs 1.06 ± 0.23 W/kg(-1), P=.0098). Gross and net energy cost of walking were higher while wearing unstable shoes compared with conventional shoes (gross: 4.20 ± 0.42 J/kg(-1)/m(-1)vs 4.01 ± 0.39 J/kg(-1)/m(-1), P=.0035; net: 3.37 ± 0.41 J/kg(-1)/m(-1) vs 3.21 ± 0.37 J/kg(-1)/m(-1); P=.032). CONCLUSION: In obese patients, it is possible to increase energy expenditure of standing and walking by means of ergonomic unstable footwear. Long-term use of unstable shoes may eventually prevent a positive energy balance.

Public health value of fixed-dose combinations in hypertension.

It is well documented that reducing blood pressure (BP) in hypertensive individuals reduces the risk of cardiovascular (CV) events. Despite this, many patients with hypertension remain untreated or inadequately treated, and fail to reach the recommended BP goals. Suboptimal BP control, whilst arising from multiple causes, is often due to poor patient compliance and/or persistence, and results in a significant health and economic burden on society. The use of fixed-dose combinations (FDCs) for the treatment of hypertension has the potential to increase patient compliance and persistence. When compared with antihypertensive monotherapies, FDCs may also offer equivalent or better efficacy, and the same or improved tolerability. As a result, FDCs have the potential to reduce both the CV event rates and the non-drug healthcare costs associated with hypertension. When FDCs are adopted for the treatment of hypertension, issues relating to copayment, formulary restrictions and therapeutic reference pricing must be addressed.

Functional analysis: evaluation of response intensities--tailoring ANOVA for lists of expression subsets.

Background: Microarray data is frequently used to characterize the expression profile of a whole genome and to compare the characteristics of that genome under several conditions. Geneset analysis methods have been described previously to analyze the expression values of several genes related by known biological criteria (metabolic pathway, pathology signature, co-regulation by a common factor, etc.) at the same time and the cost of these methods allows for the use of more values to help discover the underlying biological mechanisms. Results: As several methods assume different null hypotheses, we propose to reformulate the main question that biologists seek to answer. To determine which genesets are associated with expression values that differ between two experiments, we focused on three ad hoc criteria: expression levels, the direction of individual gene expression changes (up or down regulation), and correlations between genes. We introduce the FAERI methodology, tailored from a two-way ANOVA to examine these criteria. The significance of the results was evaluated according to the self-contained null hypothesis, using label sampling or by inferring the null distribution from normally distributed random data. Evaluations performed on simulated data revealed that FAERI outperforms currently available methods for each type of set tested. We then applied the FAERI method to analyze three real-world datasets on hypoxia response. FAERI was able to detect more genesets than other methodologies, and the genesets selected were coherent with current knowledge of cellular response to hypoxia. Moreover, the genesets selected by FAERI were confirmed when the analysis was repeated on two additional related datasets. Conclusions: The expression values of genesets are associated with several biological effects. The underlying mathematical structure of the genesets allows for analysis of data from several genes at the same time. Focusing on expression levels, the direction of the expression changes, and correlations, we showed that two-step data reduction allowed us to significantly improve the performance of geneset analysis using a modified two-way ANOVA procedure, and to detect genesets that current methods fail to detect.

A new procedure to assess the energy requirements of lactation in Gambian women.

The combined 24-h energy expenditure (24-h EE) of mother and child was measured with a respiratory chamber (indirect calorimeter) in a group of 16 lactating Gambian women and was compared with that of a control group of 16 nonpregnant, nonlactating (NPNL) Gambian women. Breast-milk production (738 +/- 47 g/d: mean +/- SE) was adequate to allow a normal rate of growth of their 2-mo-old babies (28.0 +/- 2.4 g/d). The combined 24-h EE (mother and child) was higher (8381 +/- 180 kJ/d. P less than 0.001) than that of NPNL women (6092 +/- 121 kJ/d). Two-thirds of this differences could be attributed to the child's EE and one-third to a greater spontaneous physical activity of lactating women. The energy retained by the child for growth in conjunction with the calorimetric measurements allowed the calculation of the extra energy requirements for lactation, which were found to be 2100 kJ/d. These results confirm the values of the current dietary recommendations for lactation, based on the energy cost of milk production.

Statins for cardiovascular prevention according to different strategies: a cost analysis.

Background: Several studies have shown that treatment with HMG-CoA reductase inhibitors (statins) can reduce coronary heart disease (CHD) rates. However, the cost effectiveness of statin treatment in the primary prevention of CHD has not been fully established. Objective: To estimate the costs of CHD prevention using statins in Switzerland according to different guidelines, over a 10-year period. Methods: The overall 10-year costs, costs of one CHD death averted, and of 1 year without CHD were computed for the European Society of Cardiology (ESC), the International Atherosclerosis Society (IAS), and the US Adult Treatment Panel III (ATP-III) guidelines. Sensitivity analysis was performed by varying number of CHD events prevented and costs of treatment. Results: Using an inflation rate of medical costs of 3%, a single yearly consultation, a single total cholesterol measurement per year, and a generic statin, the overall 10-year costs of the ESC, IAS, and ATP-III strategies were 2.2, 3.4, and 4.1 billion Swiss francs (SwF [SwF1 = $US0.97]). In this scenario, the average cost for 1 year of life gained was SwF352, SwF421, and SwF485 thousand, respectively, and it was always higher in women than in men. In men, the average cost for 1 year of life without CHD was SwF30.7, SwF42.5, and SwF51.9 thousand for the ESC, IAS, and ATP-III strategies, respectively, and decreased with age. Statin drug costs represented between 45% and 68% of the overall preventive cost. Changing the cost of statins, inflation rates, or number of fatal and non-fatal cases of CHD averted showed ESC guidelines to be the most cost effective. Conclusion: The cost of CHD prevention using statins depends on the guidelines used. The ESC guidelines appear to yield the lowest costs per year of life gained free of CHD.

Introduced ants in Galápagos (Floreana Island) : importance of competition, coexistence and agressive behaviors

Abstract Invasive species represent with fragmentation of habitat the most serious threats to biodiversity in the world. Galápagos Archipelago, as most oceanic islands, suffers a high rate of introduced animals and plants that affect equilibrium and biodiversity of this unique biota. Ants rank among the most devastating invaders. Their social organization confer them a high ability to adapt and to spread in new environments forming rapidly populous communities. We studied the ant community of Floreana Island composed mainly of introduced species (at least 1 S). Introduction events occurred successively during last century. The last record is Monomorium destructor arrived in the eighties. Our aim is to investigate the modalities of interaction and coexistence of these introduced species. We highlighted the competition hierarchy of the coexisting species using attractive food baits. Two species behave as competitively dominant by monopolizing an important part of resources. They are M. destructor restricted to a small area and the fire ant Solenopsis geminata widely distributed on the island. Then we evaluated the relative importance of abiotic factors and interspecific competition in structuring the community. Ecological data were collected and presence and abundance of species were estimated using different methods in a wide range of habitats. Several species showed preferences either for arid or for humid areas. The little fire ant Wasmannia auropunctata, awell-known devastating species when introduced, was exclusively found in moist habitat in and around the agricultural area situated in the upper and central part of thé island. It coexists with other species in several parts but in a restricted perimeter it excludes all other ants and worker's density on the ground is nearly 70 times higher than ant's density in similar habitats occupied by several species. But most opportunist tramp species establish everywhere without particular ecological requirement. Analyses of species co-occurrences at various levels didn't reveal any marked effect of competition in structuring ant's assemblages. We supposed that the lack ofcompetition-derived structure has to be attributed to the dynamic of the system. Indeed, across the successive census of 1996, 2003, 2004 and 2005, species distributions and abundances appeared to be highly variables. In particular harsh conditions occurring in dry season in certain parts seem to be limiting to S. geminatai. We suggest that huge variations in the local distribution of the dominant S. geminata disrupt the community organization. Finally we conducted artificial ant confrontations to evaluate to what extend an aggressive behavior at the worker level maybe linked to the ecological success of a species on the island. S. geminata was rather indifferent when confronted to a submissive species on food sources, suggesting that its competitive dominance is largely due to a numerical superiority. On the other hand M. destructor exhibits a strong agonistic behavior in similar confrontations. As soon as the presence of a competitor is detected, most workers were observed to abandon foraging and to take part in physical aggressions. Since it is still restricted nearby its introduction spot two decades after its arrival, we suggest that the energetic cost of such an aggressive behavior prevent it to spread on that island already highly colonized. Dominant invasive species such as the fire ants S. geminata and W. auropunctata have negative impacts on Galápagos fauna, disturbing the hatching of land tortoises and birds. But very little is known about the impact of other exotic ants. Indeed, impact on arthropods and generally on ground-dwelling organisms is very diffcult to evaluate. As a consequence of the dynamic character of Floreana I. ant community it is difficult to build models or to málce predictions on evolution of introduced ant fauna. But Camponotus macilentus, an abundant endemic species seems today to be little affected by introduced ant species thanks to its strong interference competition ability and its preference for arid and harsh environments. Résumé Les espèces envahissantes représentent, avec la fragmentation du paysage, la plus grande menace pour la biodiversité. L'archipel des Galápagos, comme la plupart des îles du Pacifique, compte un grand nombre d'espèces introduites qui menacent la biodiversité de ce milieu unique.. Les fourmis sont parmi les envahisseurs les plus dévastateurs. Leur organisation sociale leur permet de s'adapter et de se propager pour devenir rapidement abondantes. Nous avons étudié la communauté de fourmis sur l'île de Floreana principalement composée d'espèces introduites (au moins 15). Les introductions se sont succédées au cours du siècle précédent. La dernière espèce recensée est Monomorium destructor introduite dans les années 80. Notre objectif est de mettre à jour les modalités des interactions et de la coexistence de ces espèces introduites. Nous avons mis en évidence la hiérarchie de compétition des différentes espèces à l'aide d'appâts de nourriture. Deux espèces se comportent de façon dominante en monopolisant une part importante des ressources. Ce sont M. destructor, restreintes à un petit périmètre, et la fourmi de feu Solenopsis geminata, largement distribuée sur l'île. Nous avons évalué l'importance relative des facteurs abiotiques et de la compétition interspécifique dans la structuration des peuplements. Des données écologiques ont été collectées et la présence et l'abondance des espèces ont été estimées à l'aide de trois méthodes au sein d'une grande diversité d'habitats. Plusieurs espèces .montrent des préférences soit pour les milieux humides, soit pour les milieux arides. La petite fourmi de feu Wasmannia auropunctata, une espèce connue pour être dévastatrice dans ses sites d'introduction, est présente exclusivement dans les habitats humides dans et à proximité de la zone agricole située dans la partie centrale de l'île. Elle coexiste en plusieurs points avec d'autres espèces mais au sein d'un périmètre restreint elle exclut toute autre fourmi et atteint des densités record au sol presque 70 fois supérieures aux densités de fourmis observées sur les sites voisins occupés par plusieurs espèces. Mais la plupart des espèces vagabondes opportunistes s'établissent partout sans exigences écologiques particulières. Des analyses de cooccurrence d'espèces à plusieurs niveaux n'ont pas révélé de rôle marqué de la compétition dans la structuration des communautés. Nous supposons que l'absence d'une telle structure doit être attribuée à la dynamique du système. En effet, au cours des différents recensements de 1996-1997, 2003, 2004 et 2005, la distribution et l'abondance des espèces était très variable. En particulier, les conditions rudes qui règnent dans la zone aride durant la saison sèche semblent affecter particulièrement S. geminata. Nous suggérons que de fortes variations dans la distribution de l'espèce dominante perturbent l'orgaiùsation des communautés. Finalement nous avons effectué des confrontations artificielles pour évaluer dans quelle mesure un comportement agressif au niveau de l'ouvrière peut être lié au succès écologique d'une espèce sur l'île. S. geminata montre très peu de réaction face à une espèce subordonnée sur une même source de nourriture, ce qui laisse supposer que sa dominance est largement due à sa supériorité numérique. Par contre, dans des conditions similaires, M. destructor est fortement agressive. En présence d'un compétiteur, la plupart des ouvrières renoncent très vite à leur activité de fourragement pour agresser les individus de l'autre espèce. Puisque deux décennies après son introduction elle est toujours confinée à son point d'arrivée, nous supposons que le coût en énergie et en ouvrières de ce comportement très agressif est un obstacle à son expansion sur cette île déjà fortement colonisée. Les espèces envahissantes dominantes comme les fourmis de feu S. geminata et W. auropunctata sont connues pour leur impact négatif sur la faune des Galápagos, entre autre sur les jeunes des tortues terrestres et des oiseaux. Mais nous savons très peu de choses sur l'impact des autres espèces de fourmis introduites. En effet, l'impact sur les arthropodes, et plus généralement sur la faune du sol, est très difficile à évaluer. En raison du caractère dynamique de la communauté de fourmi de Floreana, il est difficile de construire des modèles et de faire des prédictions sur l'évolution des peuplements de fourmis introduites. Mais Camponotus macilentus, une espèce endémique abondante, semble aujourd'hui peu affectée par les espèces introduites grâce à ses capacités de compétition par interférence et sa préférence pour les milieux arides. Resumen Las, especies invasoras representan, junto con la fragmentación del paisaje, la mayor amenaza para la biodiversidad. El archipiélago de Galápagos, como la mayoría de las islas del Pacífico, cuenta con un gran número de especies introducidas que amenazan la biodiversidad de este lugar único. Las hormigas son uno de los invasores más devastadores. Su organización social les permite adaptarse y propagarse para ser rápidamente abundante. Estudiamos la comunidad de hormigas de la isla Floreana principalmente compuesta de especies introducidas (al menos 15). Las introducciones se sucedieron durante el siglo anterior. La última especie contabilizada es Monomorium destructor introducida en los años 80. Nuestro objetivo es poner al día las modalidades de las interacciones y de la coexistencia de estas especies introducidas. Pusimos de relieve la jerarquía de competencia de las distintas especies con ayuda de cebos de comida. Dos especies se implican de manera dominante monopolizando una parte importante de los recursos. Son M. destructor, limitado a un pequeño perímetro, y la hormiga de fuego Solenopsis geminata; ampliamente distribuida por la isla. Evaluamos la importancia relativa de los factores abióticos y de la competencia interespecífica en la estructuración de la communidad. Se recogieron algunos datos ecológicos y se consideraron la presencia y la abundancia de las especies con ayuda de tres métodos en una gran diversidad de hábitats. Varias especies muestran preferencias o por los medios húmedos, o por los medios áridos. La pequeña hormiga de fuego Wasmannia auropunctata, una especie conocida por ser devastadora en sus lugares de introducción, está presente exclusivamente en los hábitats húmedos y cerca de la zona agrícola situada en la parte central de la isla. Coexiste en varios puntos con otras especies pero en un perímetro limitado excluye a cualquier otra hormiga y alcanza densidades en el suelo casi 70 veces superiores a las densidades de hormigas observadas en los lugares vecinos ocupados por varias especies. Pero la mayoría de las especies vagabundas oportunistas se establecen por todas partes sin exigencias ecológicas particulares. Análisis de cooccurrencía de las especies a varios niveles no revelaron una grande importancía de la competencia en la estructuración de las comunidades. Suponemos que la ausencia de tal estructura Bebé ser por la dinámica del sistema. Efectivamente, durante los distintos censos de 1996-1997, 2003,.2004 y 2005, la distribución ? la abundancia de las especies eran muy variables. En particular, las condiciones drásticas que reinan en la zona árida durante la temporada seca parecen afectar especialmente a S. geminata. Sugerimos que fuertes variaciones en la distribución de la especie dominante perturben la organización de las comunidades. Finalmente efectuamos confrontaciones artificiales para evaluar hastá que punto un comportamiento agresivo a nivel de la obrera puede explicar el éxito ecológico de una especie en la isla. S. geminata muestra muy poca reacción ante una especie subordinada mientras comparten la misma comida, lo que deja suponer que su dominancia se debe a su superioridad numérica. Por el contrario, en condiciones similares, M. destructor es muy agresivo. En presencia de otra especie, la mayóría de las obreras renuncian muy rápidamente a alimentarse para atacar a los individuos de la otra especie. Puesto que dos décadas después de su introducción todavía se confina en su punto de llegada, suponemos que el coste en energía y en obreras de este comportamiento muy agresivo es un obstáculo a su extensión en esta isla ya muy colonizada. Las especiés invasoras dominantes como las hormigas de fuego S. geminata y W. auropunctata son conocidas por su impacto negativo en la fauna de Galápagos, entre otras cosas sobre los juveniles de las tortugas terrestres y pájaros. Pero sabemos muy poco sobre el impacto de las otras especies de hormigas introducidas. Efectivamente es muy difïcil de evaluar el impacto en los artrópodos, y más generalmente en la fauna del suelo. Debido al carácter dinámico de la comunidad de hormiga de Floreana, es diEcil construir modelos y hacer predicciones sobre la evolución de las poblaciones de hormigas introducidas. Pero Camponotus macilentus, una especie endémica abundante, parece poco afectadá hoy por las especies introducidas gracias a sus capacidades de competencia por interferencia y su preferencia por los medios áridos.

Jambes lourdes, insuffisance veineuse des membres inférieurs et hormonothérapie substitutive [Heavy legs, venous insufficiency of the legs and hormone substitution therapy]

The effects of estrogens and gestagens on veins and circulation have been studied since prescription of these hormones as oral contraception and description of related thromboembolic events. The identification of different receptors and the description of these receptors in venous walls have helped to understand some hormonal effects. However, the actual knowledge remains insufficient to explain the complexity of the actions of hormones on venous function. The distribution, the density and the receptor types vary with age, gender, hormonal status and vascular bed. Gestagens mainly reduce the tone of venous walls, whereas estrogens have various effects. Between 25% and 50% of European adults and even 80% or more in some risk groups complain about heavy legs, with or without chronic venous insufficiency. The number of women to whom hormonal substitution is or could be prescribed increases along with aging of populations and the better understanding of potential benefits. The need for a better understanding of vascular effects of sexual hormones is growing, since the incidence of chronic venous insufficiency of the legs increases with age. The life prognosis will not be affected by a deterioration of a chronic venous insufficiency. In contrast, the quality of life, morbidity and the cost of treatment will be expected to change. In addition, thromboembolic events have to be considered, as has been shown in recent studies. These findings outline the need for further studies on the relation between hormones and venous function and for some caution when prescribing hormonal substitution.

Effect of biomagnetic therapy versus physiotherapy for treatment of knee osteoarthritis: a randomized controlled trial.

OBJECTIVE: To assess the effectiveness of pulsed signal therapy in the treatment of knee osteoarthritis (Kellgren II or III). METHODS: A randomized, double-blind controlled clinical trial. The first 95 patients sent to the clinic with knee osteo-arthritis were selected and randomized into treatment with pulsed signal therapy or conventional physiotherapy. Assessment included recording of usual demographic data, pertinent history, baseline medication and radiographs. Clinical evaluation was made at baseline, 6 weeks and 6 months after the end of treatment by the same blinded doctor. At each follow-up time, the patient was asked to complete a visual analogue pain scale and a Lequesne score. The doctor recorded the degree of pain on motion and the ability to move the affected knee. RESULTS: Both treatments resulted in significant improvements in pain and physical function. A statistical difference was observed only for activities of daily living, where the physiotherapy was more efficient (p<0.03). The cost of treatment with pulsed signal therapy was significantly higher, double the treatment cost of conventional physiotherapy. CONCLUSION: Like physiotherapy, pulsed signal therapy has improved the clinical state of treated patients but with no significant statistical difference. Pulsed signal therapy is, however, more expensive.

The dynamics of the Swiss electricity market : three essays

Executive Summary Electricity is crucial for modern societies, thus it is important to understand the behaviour of electricity markets in order to be prepared to face the consequences of policy changes. The Swiss electricity market is now in a transition stage from a public monopoly to a liberalised market and it is undergoing an "emergent" liberalisation - i.e. liberalisation taking place without proper regulation. The withdrawal of nuclear capacity is also being debated. These two possible changes directly affect the mechanisms for capacity expansion. Thus, in this thesis we concentrate on understanding the dynamics of capacity expansion in the Swiss electricity market. A conceptual model to help understand the dynamics of capacity expansion in the Swiss electricity market is developed an explained in the first essay. We identify a potential risk of imports dependence. In the second essay a System Dynamics model, based on the conceptual model, is developed to evaluate the consequences of three scenarios: a nuclear phase-out, the implementation of a policy for avoiding imports dependence, and the combination of both. We conclude that the Swiss market is not well prepared to face unexpected changes of supply and demand, and we identify a risk of imports dependence, mainly in the case of a nuclear phase-out. The third essay focus on the opportunity cost of hydro-storage power generation, one of the main generation sources in Switzerland. We use and extended version of our model to test different policies for assigning an opportunity cost to hydro-storage power generation. We conclude that the preferred policies are different for different market participants and depend on market structure.

Co-evolution between sociality and dispersal: The role of synergistic cooperative benefits.

Explaining the evolution of sociality is challenging because social individuals face disadvantages that must be balanced by intrinsic benefits of living in a group. One potential route towards the evolution of sociality may emerge from the avoidance of dispersal, which can be risky in some environments. Although early studies found that local competition may cancel the benefits of cooperation in viscous populations, subsequent studies have identified conditions, such as the presence of kin recognition or specific demographic conditions, under which altruism will still spread. Most of these studies assume that the costs of cooperating outweigh the direct benefits (strong altruism). In nature, however, many organisms gain synergistic benefits from group living, which may counterbalance even costly altruistic behaviours. Here, we use an individual based model to investigate how dispersal and social behaviour co-evolve when social behaviours result in synergistic benefits that counterbalance the relative cost of altruism to a greater extent than assumed in previous models. When the cost of cooperation is high, selection for sociality responds strongly to the cost of dispersal. In particular, cooperation can begin to spread in a population when higher cooperation levels become correlated with lower dispersal tendencies within individuals. In contrast, less costly social behaviours are less sensitive to the cost of dispersal. In line with previous studies, we find that mechanisms of global population control also affect this relationship: when whole patches (groups) go extinct each generation, selection favours a relatively high dispersal propensity, and social behaviours evolve only when they are not very costly. If random individuals within groups experience mortality each generation to maintain a global carrying capacity, on the other hand, social behaviours spread and dispersal is reduced, even when the latter is not costly.