Floristic evidence for alternative biome states in tropical Africa.

The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.

[Type 2 diabetes and the elderly : a real problem]. / Diabète de type 2 et le sujet âgé : une réelle problématique.

Type 2 diabetes in the elderly remains a major concern for all healthcare professionals, this disease being considered a real global «pandemic¼. Its prevalence is high and will continue to increase in the years to come, becoming significant in the elderly and the very old. We offer you a general summary and a focus on diabetes in the elderly with the GERODIAB study.

Le diabète de type 2 chez le sujet âgé reste une préoccupation majeure pour l'ensemble des professionnels de santé, cette maladie étant elle-même considérée comme une réelle «pandémie¼ mondiale. Sa prévalence est élevée et continuera de s'accroître dans les années à venir, devenant prégnante chez le sujet âgé et très âgé. Nous proposons ici une synthèse générale et un focus sur le diabète du sujet âgé avec l'étude GERODIAB.

[Diabetes and frailty in the elderly. A prospective study of an outpatient population supported by general practitioners]. / Diabète et fragilité chez la personne âgée. Etude prospective d'une population ambulatoire prise en charge en Médecine générale.

INTRODUCTION: Elderly people with diabetes represent a large and growing part of the general practitioners patient database, but their state of frailty compared to the non-diabetic population is poorly understood. OBJECTIVE: To study the relationship between diabetes and frailty in people aged 65 and over in primary care. METHOD: Frailty syndrome was assessed by the Fried Scale and compared between populations of diabetic and non-diabetic patients; 268 patients were studied, including 129 diabetic patients. RESULTS: Frailty was found in 27.9 % of older diabetic patients. The observed mean Fried score was 1.76 in people with diabetes versus 1.39 in non-diabetics, with more frail diabetic subjects (p = 0.007). In this study, HbA1c levels showed no significant association to frailty. CONCLUSION: Larger studies in several general practice clinics should be performed on subjects over 65 years of age with or without diabetes.

INTRODUCTION: Les personnes âgées diabétiques représentent une part importante et croissante de la patientèle des médecins généralistes, mais leur état de fragilité par rapport à la population non diabétique est mal connu. Objectif : Etudier les relations entre diabète et fragilité chez la personne âgée de 65 ans et plus en médecine générale. Méthode : La fragilité a été évaluée par l'échelle de Fried et comparée entre les populations de patients diabétiques et non diabétiques; 268 patients ont été inclus dont 129 patients diabétiques. Résultats : La fragilité concernait 27,9 % des diabétiques. Le score de Fried moyen observé était de 1,76 chez les personnes diabétiques versus 1,39 chez les non-diabétiques, avec des sujets diabétiques plus fragiles (p = 0,007). Dans cette étude, le taux d'HbA1c n'est pas significativement associé à la fragilité. CONCLUSION: Des études de plus grande ampleur sur plusieurs sites ambulatoires devraient être réalisées en médecine générale chez les sujets âgés de plus de 65 ans, diabétiques ou non.

Tunable graded cavity resonator integrated grating filters.

We demonstrated Graded Cavity Resonator Integrated Grating Filters (G-CRIGFs) that are narrowband spectral reflectors, spectrally tunable over more than 40 nm around 850 nm using a spatial gradient. A simple analytical model is introduced and validated experimentally to determine spectral performance of G-CRIGFs from the spectral properties of a standard Cavity Resonator Integrated Grating Filter (CRIGF).

Lactic acidosis: relationship between metformin levels, lactate concentration and mortality.

AIM: The role of metformin in lactic acidosis is regularly questioned. Arguments against a causal role for metformin in lactic acidosis occurrence are the lack of correlation between plasma metformin and lactate levels, as well as between metformin plasma levels and mortality. We aim to analyse these correlations in a large series of lactic acidosis cases recorded in the French nationwide pharmacovigilance database. METHODS: All cases of lactic acidosis spontaneously reported between 1985 and October 2013 associated with metformin exposure were extracted from the pharmacovigilance database. We assessed the statistical correlations between prescribed daily doses of metformin, plasma concentrations of metformin and lactate, pH and plasma creatinine, as well as the relationship between mortality and these variables. RESULTS: Seven hundred and twenty-seven cases of lactic acidosis were reported during the period. Metformin plasma concentration was documented for 260 patients, lactate plasma concentration for 556 patients, pH for 502 patients, creatinine for 397 patients and the vital outcome for 713 patients. Metformin plasma concentration, lactate concentration, pH and plasma creatinine were all correlated (P < 0.001). There were significant differences between surviving and deceased patients in terms of metformin plasma levels (25.2 vs. 37.4 mg/l, P = 0.002) and lactate concentrations (10.8 vs. 16.3 mmol/l, P < 0.001). Thirty per cent of patients died when metformin concentration was > 5 mg/l compared with 11% for patients with concentration < 5 mg/l (P = 0.003). CONCLUSIONS: Our data suggest that metformin accumulation contributes to the pathogenesis and prognosis of lactic acidosis.

Relationships between population density, fine-scale genetic structure, mating system and pollen dispersal in a timber tree from African rainforests.

Owing to the reduction of population density and/or the environmental changes it induces, selective logging could affect the demography, reproductive biology and evolutionary potential of forest trees. This is particularly relevant in tropical forests where natural population densities can be low and isolated trees may be subject to outcross pollen limitation and/or produce low-quality selfed seeds that exhibit inbreeding depression. Comparing reproductive biology processes and genetic diversity of populations at different densities can provide indirect evidence of the potential impacts of logging. Here, we analysed patterns of genetic diversity, mating system and gene flow in three Central African populations of the self-compatible legume timber species Erythrophleum suaveolens with contrasting densities (0.11, 0.68 and 1.72 adults per ha). The comparison of inbreeding levels among cohorts suggests that selfing is detrimental as inbred individuals are eliminated between seedling and adult stages. Levels of genetic diversity, selfing rates (∼16%) and patterns of spatial genetic structure (Sp ∼0.006) were similar in all three populations. However, the extent of gene dispersal differed markedly among populations: the average distance of pollen dispersal increased with decreasing density (from 200 m in the high-density population to 1000 m in the low-density one). Overall, our results suggest that the reproductive biology and genetic diversity of the species are not affected by current logging practices. However, further investigations need to be conducted in low-density populations to evaluate (1) whether pollen limitation may reduce seed production and (2) the regeneration potential of the species.

Thin-dielectric-layer engineering for 3D nanostructure integration using an innovative planarization approach.

Three-dimensional (3D) nanostructures are emerging as promising building blocks for a large spectrum of applications. One critical issue in integration regards mastering the thin, flat, and chemically stable insulating layer that must be implemented on the nanostructure network in order to build striking nano-architectures. In this letter, we report an innovative method for nanoscale planarization on 3D nanostructures by using hydrogen silesquioxane as a spin-on-glass (SOG) dielectric material. To decouple the thickness of the final layer from the height of the nanostructure, we propose to embed the nanowire network in the insulator layer by exploiting the planarizing properties of the SOG approach. To achieve the desired dielectric thickness, the structure is chemically etched back with a highly diluted solution to control the etch rate precisely. The roughness of the top surface was less than 2 nm. There were no surface defects and the planarity was excellent, even in the vicinity of the nanowires. This newly developed process was used to realize a multilevel stack architecture with sub-deca-nanometer-range layer thickness.

Bilateral idiopathic calf muscle hypertrophy: an exceptional cause of unsightly leg curvature.

The authors present the management of a young female patient who presented with longstanding bilateral calf muscle hypertrophy, with no known cause. Taking into account the patient's wishes and the fact that the hypertrophy was mainly located in the posteromedial compartment, we chose to carry out a subtotal bilateral resection of medial gastrocnemius muscles. This procedure was performed with an harmonic scalpel, permitting a excellent cosmetic result while avoiding complications or functional impairment. After a reviewing of the commonly used techniques, the authors discuss the chosen surgical approach taking into account its clinical particularity.

Retinopathy, nephropathy, peripheral neuropathy and geriatric scale scores in elderly people with Type 2 diabetes.

AIMS: To analyse the relationships between retinopathy, nephropathy, peripheral neuropathy and geriatric scale scores in elderly people with Type 2 diabetes. METHODS: GERODIAB is the first French multi-centre, prospective, observational study designed to assess the influence of glycaemic control on mortality and morbidity through a 5-year follow-up study in people with Type 2 diabetes aged 70 years and older. In this report the relationships at baseline between retinopathy, nephropathy and peripheral neuropathy, and five geriatric scale scores in 987 people, using bivariate and multivariate analyses are analysed. RESULTS: Retinopathy (26%) was significantly associated with impaired scores on the Mini Geriatric Depression Scale, the Mini Nutritional Assessment and the Instrumental Activities of Daily Living scale. Logistic regression showed that the duration of diabetes, BMI, Mini Geriatric Depression Scale, hypoglycaemia and HbA1c were associated with retinopathy (concordance 69.1%; P < 0.001). Nephropathy (47.4%, including 34.8% with Modification of Diet in Renal Disease < 60 ml/min) was significantly associated with impaired Activities of Daily Living and Instrumental Activities of Daily Living scale scores. Using the logistic model, the most significant factors were age, duration of diabetes, triglycerides, HDL cholesterol, hypoglycaemia, hypertension and BMI (concordance 66.3%; P < 0.001). Peripheral neuropathy (28.2%) was associated with impaired scores on the Mini Mental State Examination, Activities of Daily Living, Instrumental Activities of Daily Living and Mini Geriatric Depression Scales. In the logistic model, diastolic blood pressure, duration of diabetes and the Instrumental Activities of Daily Living, Mini Geriatric Depression Scale and Mini Mental State Examination scales were included (concordance 69.8%; P < 0.001). CONCLUSION: In this specific sample, classical microvascular complications of diabetes were found to be associated with impaired geriatric scale scores. This highlights the benefits of systematic assessment in elderly people with Type 2 diabetes.

Speciation slowing down in widespread and long-living tree taxa: insights from the tropical timber tree genus Milicia (Moraceae).

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia that formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the phylogenetic species concept, the existence of mutual haplotypic exclusivity and nonadmixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation and, thus, two species following the biological species concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically.

Cyclic stretch reveals a mechanical role for intermediate filaments in a desminopathic cell model.

Mechanics is now recognized as crucial in cell function. To date, the mechanical properties of cells have been inferred from experiments which investigate the roles of actin and microtubules ignoring the intermediate filaments (IFs) contribution. Here, we analyse myoblasts behaviour in the context of myofibrillar myopathy resulting from p.D399Y desmin mutation which disorganizes the desmin IF network in muscle cells. We compare the response of myoblasts expressing either mutated or wild-type desmin to cyclic stretch. Cells are cultivated on supports submitted to periodic uniaxial stretch of 20% elongation amplitude and 0.3 Hz frequency. We show that during stretching cycles, cells expressing mutated desmin reduce their mean amplitude both for the elongation and spreading area compared to those expressing wild-type desmin. Even more unexpected, the reorientation angles are altered in the presence of p.D399Y desmin. Yet, at rest, the whole set of those parameters are similar for the two cell populations. Thus, we demonstrate that IFs affect the mechanical properties and the dynamics of cell reorientation. Since these processes are known due to actin cytoskeleton, these results suggest the IFs implication in mechanics signal transduction. Further studies may lead to better understanding of their contribution to this process.

Photo-chemical study and optical properties of microtips self- written on vertical laser diodes using NIR photo-polymerization.

Near infra-red (NIR) self-guided photo-polymerization is investigated in the context of micro-optics photo-fabrication on VCSELs (Vertical-Cavity Surface Emitting Lasers). We present the optimized process we have developed to allow for a collective fabrication on III-V devices wafers under real-time optical monitoring. The influence of photo-chemical parameters on final micro-elements dimensions is studied for two types of single mode 760 nm VCSELs. The difference of the resulting tip shape between the two lasers is due to the strong differences of their emissions, as they are nicely reproduced by the computed near-field profiles. The tip shapes are also compared to those produced by the light emitted by an optical fiber and differences with VCSEL tips are discussed. Also the VCSEL characteristics with fabricated tips are discussed and found in good agreement with optical modeling.

In silico prediction of mosquito repellents for clothing application.

Use of protective clothing is a simple and efficient way to reduce the contacts with mosquitoes and consequently the probability of transmission of diseases spread by them. This mechanical barrier can be enhanced by the application of repellents. Unfortunately the number of available repellents is limited. As a result, there is a crucial need to find new active and safer molecules repelling mosquitoes. In this context, a structure-activity relationship (SAR) model was proposed for the design of repellents active on clothing. It was computed from a dataset of 2027 chemicals for which repellent activity on clothing was measured against Aedes aegypti. Molecules were described by means of 20 molecular descriptors encoding physicochemical properties, topological information and structural features. A three-layer perceptron was used as statistical tool. An accuracy of 87% was obtained for both the training and test sets. Most of the wrong predictions can be explained. Avenues for increasing the performances of the model have been proposed.

European research platform IPANEMA at the SOLEIL synchrotron for ancient and historical materials.

IPANEMA, a research platform devoted to ancient and historical materials (archaeology, cultural heritage, palaeontology and past environments), is currently being set up at the synchrotron facility SOLEIL (Saint-Aubin, France; SOLEIL opened to users in January 2008). The new platform is open to French, European and international users. The activities of the platform are centred on two main fields: increased support to synchrotron projects on ancient materials and methodological research. The IPANEMA team currently occupies temporary premises at SOLEIL, but the platform comprises construction of a new building that will comply with conservation and environmental standards and of a hard X-ray imaging beamline today in its conceptual design phase, named PUMA. Since 2008, the team has supported synchrotron works at SOLEIL and at European synchrotron facilities on a range of topics including pigment degradation in paintings, composition of musical instrument varnishes, and provenancing of medieval archaeological ferrous artefacts. Once the platform is fully operational, user support will primarily take place within medium-term research projects for `hosted' scientists, PhDs and post-docs. IPANEMA methodological research is focused on advanced two-dimensional/three-dimensional imaging and spectroscopy and statistical image analysis, both optimized for ancient materials.

Population history and gene dispersal inferred from spatial genetic structure of a Central African timber tree, Distemonanthus benthamianus (Caesalpinioideae).

African rainforests have undergone major distribution range shifts during the Quaternary, but few studies have investigated their impact on the genetic diversity of plant species and we lack knowledge on the extent of gene flow to predict how plant species can cope with such environmental changes. Analysis of the spatial genetic structure (SGS) of a species is an effective method to determine major directions of the demographic history of its populations and to estimate the extent of gene dispersal. This study characterises the SGS of an African tropical timber tree species, Distemonanthus benthamianus, at various spatial scales in Cameroon and Gabon. Displaying a large continuous distribution in the Lower Guinea domain, this is a model species to detect signs of past population fragmentation and recolonization, and to estimate the extent of gene dispersal. Ten microsatellite loci were used to genotype 295 adult trees sampled from eight populations. Three clearly differentiated gene pools were resolved at this regional scale and could be linked to the biogeographical history of the region, rather than to physical barriers to gene flow. A comparison with the distribution of gene pools observed for two other tree species living in the same region invalidates the basic assumption that all species share the same Quaternary refuges and recolonization pathways. In four populations, significant and similar patterns of SGS were detected. Indirect estimates of gene dispersal distances (sigma) obtained for three populations ranged from 400 to 1200 m, whereas neighbourhood size estimates ranged from 50 to 110.

Elevation of neuronal expression of NAIP reduces ischemic damage in the rat hippocampus.

We show here that transient forebrain ischemia selectively elevates levels of neuronal apoptosis inhibitory protein (NAIP) in rat neurons that are resistant to the injurious effects of this treatment. This observation suggests that increasing NAIP levels may confer protection against ischemic cell death. Consistent with this proposal, we demonstrate that two other treatments that increase neuronal NAIP levels, systemic administration of the bacterial alkaloid K252a and intracerebral injection of an adenovirus vector capable of overexpressing NAIP in vivo, reduce ischemic damage in the rat hippocampus. Taken together, these findings suggest that NAIP may play a key role in conferring resistance to ischemic damage and that treatments that elevate neuronal levels of this antiapoptotic protein may have utility in the treatment of stroke.

Brominated diphenyl ether (BDE) levels in liver, adipose, and milk from adult and juvenile rats exposed by gavage to the DE-71 technical mixture.

Brominated diphenyl ethers (BDEs) are used as flame retardants in consumer products. Rodent studies indicate that the liver, thyroid, and nervous system of developing animals are targets of BDEs. To explore the relationship between exposure and health in developing animals, BDE accumulation in adult and juvenile rats was examined in conjunction with changes in liver weight and serum thyroxine (T4). Adult (F0) rats received the commercial BDE mixture DE-71 by gavage at doses of 0.5, 5, and 25 mg kg(-1) body weight (bw)/day for 21 weeks. F0 rats were mated and exposure continued throughout breeding, pregnancy, lactation, and postweaning until the pups (F1 generation) reached postnatal day (PND) 42. Milk was collected from lactating dams. Adipose and liver samples were collected from F0 and F1 males and females for BDE congener analysis. Congener prevalence in rat tissues mimicked congener prevalence in wildlife and humans. Tissue concentrations of all congeners except BDE-153 were lower than would be expected based on dose proportionality, confirming that BDE-153 has a high capacity for bioaccumulation. BDEs were transferred from maternal tissues to milk during lactation. Milk congener profiles differed from maternal tissue profiles indicating that degree of bromination and maternal sequestration influenced BDE transfer to milk. Female F1 rats accumulated more BDEs than F1 males, indicating that female rats were less able to metabolize and/or excrete BDEs. Significant effects on liver weight and serum T4 levels were observed in adults and juveniles in the middle and high dose groups, corresponding to BDE levels in the µg g(-1) range. Although it remains to be determined how human liver and thyroid are affected by exposure to much lower BDE levels, the present study confirmed that gender and reproductive status influence BDE accumulation in tissues and BDE transfer to the neonate via milk.

Evolution in geriatric syndromes and association with survival over 5 years in the GERODIAB cohort of older French diabetic patients.

PURPOSE: Although one in three patients with diabetes in Western countries is over 70 years-old, geriatric syndromes and their relationship with survival remain seldom studied. The present aim of the GERODIAB study was to examine the evolution of geriatric disorders and their relationship with survival in older type 2 patients with diabetes with initial sufficient autonomy. METHODS: We performed a prospective, observational study over 5 years in patients with diabetes aged 70 years or above. A total of 987 consecutive type 2 patients with diabetes (mean age 77 years, range 70-94 years, 65.2% were 75 years and above, 52.1% women) were included from 56 French diabetic centres. Individual characteristics, diabetes parameters and geriatric parameters (autonomy, nutrition, cognitive alteration, depression, orthostatic hypotension, falls) were annually recorded. Survival was analysed using the Kaplan-Meier method and proportional hazards regression models. RESULTS: Institutional living, impaired activity and difficulties in instrumental daily activity, cognitive disorders, malnutrition, depression, orthostatic hypotension and hypoglycaemia strongly increased during the follow-up. Institutional living, impaired activity and difficulties in instrumental daily activity, cognitive disorders and hypoglycaemia were strongly associated with reduced survival, but not falls. In hazard ratio models, living in an institution (HR = 2.39; CI = 1.77-3.24; p < 0.0001) and impaired Activity of Daily Living scale score were the most significant and independent predictors of death (HR = 1.59; CI = 1.19-2.13; p = 0.0016), associated with HbA1c ≥ 70 mmol/mol (HR = 1.62; CI = 1.12-2.36; p = 0.011). CONCLUSION: Our findings show the considerable alteration of geriatric parameters and their relationship with decreased survival after a 5-year follow-up in type 2 patients with diabetes, independent of HbA1c and age. They, therefore, confirm the prognostic interest of using yearly geriatric markers in older diabetic patient management, especially the ADL, IADL and MMSE scales. Taking into account these prognostic parameters should contribute to target appropriate HbA1c goals. TRIAL REGISTRATION: Registered at clinicaltrials.gov (21/01/2011): NCT01282060.

CpDNA-based species identification and phylogeography: application to African tropical tree species.

Despite the importance of the African tropical rainforests as a hotspot of biodiversity, their history and the processes that have structured their biodiversity are understood poorly. With respect to past demographic processes, new insights can be gained through characterizing the distribution of genetic diversity. However, few studies of this type have been conducted in Central Africa, where the identification of species in the field can be difficult. We examine here the distribution of chloroplast DNA (cpDNA) diversity in Lower Guinea in two tree species that are difficult to distinguish, Erythrophleum ivorense and Erythrophleum suaveolens (Fabaceae). By using a blind-sampling approach and comparing molecular and morphological markers, we first identified retrospectively all sampled individuals and determined the limits of the distribution of each species. We then performed a phylogeographic study using the same genetic data set. The two species displayed essentially parapatric distributions that were correlated well with the rainfall gradient, which indicated different ecological requirements. In addition, a phylogeographic structure was found for E. suaveolens and, for both species, substantially higher levels of diversity and allelic endemism were observed in the south (Gabon) than in the north (Cameroon) of the Lower Guinea region. This finding indicated different histories of population demographics for the two species, which might reflect different responses to Quaternary climate changes. We suggest that a recent period of forest perturbation, which might have been caused by humans, favoured the spread of these two species and that their poor recruitment at present results from natural succession in their forest formations.