Variation in the ability to form ectomycorrhizas in the F1 progeny of an interspecific poplar (Populus spp.) cross

The aim of this study was to determine the existence of a genetic basis for the ability to form ectomycorrhiza on a model angiosperm tree (Populus, poplar). Parental clones and 18 progeny from a controlled interspecific cross between Populus deltoides and Po- pulus trichocarpa were grown in a glasshouse and inoculated with mycelium of the ectomycorrhizal fungus Laccaria bicolor. Three months after inoculation, the percentage of mycorrhizal root tips was determined for each inoculated plant. The data indicate variability in the ability to form ectomycorrhizas among the F1 progeny, including individual progeny which are different to either parent. This suggests a genetic basis for mycorrhiza formation. Accepted: 6 November 2000     

Habitat fragmentation differentially shapes neutral and immune gene variation in a tropical bird species

Habitat fragmentation is a major cause of biodiversity loss, responsible for an alteration of intraspecific patterns of neutral genetic diversity and structure. Although neutral genetic variation can be informative for demographic inferences, it may be a poor predictor of adaptive genetic diversity and thus of the consequences of habitat fragmentation on selective evolutionary processes. In this context, we contrasted patterns of genetic diversity and structure of neutral loci (microsatellites) and immune genes (i.e., toll-like receptors) in an understorey bird species, the wedge-billed woodcreeper Glyphorynchus spirurus. The objectives were (1) to investigate forest fragmentation effects on population genetic diversity, (2) to disentangle the relative role of demography (genetic drift and migration) and selection, and (3) to assess whether immunogenetic patterns could be associated with variation of ectoparasite (i.e., ticks) pressures. Our results revealed an erosion of neutral genetic diversity and a substantial genetic differentiation among fragmented populations, resulting from a decrease in landscape connectivity and leading to the divergence of distinct genetic pools at a small spatial scale. Patterns of genetic diversity observed for TLR4 and TLR5 were concordant with neutral genetic patterns, whereas those observed for TLR3 and TLR21 were discordant. This result underlines that the dominant evolutionary force shaping immunogenetic diversity (genetic drift vs. selection) may be different depending on loci considered. Finally, tick prevalence was higher in fragmented environments. We discussed the hypothesis that pathogen selective pressures may contribute to maintain adaptive genetic diversity despite the negative demographic effect of habitat fragmentation on neutral genetic diversity.Subject terms: Tropical ecology, Genetic variation     

Étude techno-économique du Moustérien de Pradayrol (Caniac-du-Causse,Lot) : entre mobilité des ressources lithiques et adaptation aux matériaux locaux,un exemple de gestion complémentaire des quartz et silex au Paléolithique moyen récent en Quercy

The Mousterian locus at Pradayrol (Caniac-du-Causse, Lot, France) produced an important lithic assemblage, composed primarily of quartz, alongside a varied flint component. Our technological analysis reveals the presence of several chaînes opératoires adapted to the morphology and mechanical properties of different raw materials. This is especially evident in the use of the bipolar on-anvil technique on quartz cobbles and discoidal flaking methods on both quartz and relatively local flints. Flint from the Périgord region provides evidence for a fragmented and ramified Levallois chaîne opératoire, different from that observed with local raw materials. These techno-economic features are similar to those documented for many late Middle Palaeolithic assemblages in the Quercy. The Neanderthal occupation of Pradayrol seems to reflect a balance between technical know-how and adaptations to the raw material constraints.     

Increased susceptibility to oxidative stress as a proximate cost of reproduction

In iteroparous species high investment in current reproduction is usually paid in terms of reduced future reproduction and increased mortality. However, the proximal mechanisms of these costs remain poorly understood. Free radicals arising as by‐products of normal metabolic activities have deleterious effects on cellular proteins, lipids and DNA, and this phenomenon is known as oxidative stress. Since reproduction is an energetically demanding activity, which increases both basal and field metabolic rates, one could expect that breeding effort generates an oxidative stress whose strength depends on the availability and efficiency of antioxidant defences. In agreement with this prediction, we show here for the first time that reproduction decreases antioxidant defences, illustrating that oxidative stress represents a cost of reproduction. We suggest that increased susceptibility to oxidative stress might be a general proximal connection between reproduction and survival underlying other mechanistic links previously acknowledged.     

Effets d'un régulateur de croissance d'insectes,le fénoxycarbe,sur la diapause du psylle du poirier Cacopsylla pyri

The nature of the responses of the sheep blowfly Lucilia sericata Meigen (Diptera: Calliphoridae) to carrion odours and carbon dioxide were examined in a windtunnel in the laboratory and the attractiveness of carrion-bait was examined in the field. In the wind tunnel, gravid 9-day-old females increased both the number and duration of their flights, in response to carrion odours. In addition, linear velocity was reduced and the sinuosity of flight increased in the presence of these odours. With 3-day-old females, the response to carrrion odour depended on previous exposure to proteinaceous material. Protein deprived females showed kinetic responses to carrionodour which were similar to those of gravid females. No such changes were observed in protein-fed females. No responses to CO₂ were observed. In the field, the importance of olfactory cues in bait location was demonstrated by the absence of L. sericata from sticky targets lacking an odour bait. Increased bait concentration did not affect the age, sex ratio or ratio of L. sericata to other Lucilia spp. caught, but did increase the numbers caught. Analysis of the reproductive status of females caught, indicated that a greater number of gravid females were caught than expected, while a lower number of females in the final stages of vitellogenesis were caught than expected. The results show that the responses of L. sericata to odours are complex, and are dependent on both exogenous and endogenous stimuli, the latter including the stage of ovarian development.     

Machine learning monitoring for laser osteotomy

This work proposes a new online monitoring method for an assistance during laser osteotomy. The method allows differentiating the type of ablated tissue and the applied dose of laser energy. The setup analyzes the laser-induced acoustic emission, detected by an airborne microphone sensor. The analysis of the acoustic signals is carried out using a machine learning algorithm that is pre-trained in a supervised manner. The efficiency of the method is experimentally evaluated with several types of tissues, which are: skin, fat, muscle, and bone. Several cutting-edge machine learning frameworks are tested for the comparison with the resulting classification accuracy in the range of 84–99%. It is shown that the datasets for the training of the machine learning algorithms are easy to collect in real-life conditions. In the future, this method could assist the doctors during laser osteotomy, minimizing the damage of the nearby healthy tissues and provide cleaner pathologic tissue removal.     

A comparison of infestation patterns by Ixodes ticks in urban and rural populations of the Common Blackbird Turdus merula

Although spatial variation in the patterns of parasite infestations among host populations may have important ecological and epidemiological consequences, the causes underlying such variation are poorly known. In the context of a long-term study on the population biology of Common Blackbirds Turdus merula , we examined the prevalence and intensity of infestation by Ixodes ticks between birds living in rural vs. urban habitats. The overall prevalence of tick infestations was significantly higher in the rural habitat where 74% of individuals ( n  = 130) were infested. This result contrasted markedly with the situation in the urban habitat where less than 2% of individuals ( n  = 360) carried ticks. There was no significant effect of the sex of the host on the intensity or prevalence of tick infestations. There was a significant effect of the age of the host on tick infestations essentially due to the absence of ticks on nestlings. Possible mechanisms responsible for the differences between habitats could include differences in tick survival and/or host resistance towards ticks. Previous studies have shown higher population densities and suggested longer survival for Blackbirds in urban than in rural habitats. Given that ixodid ticks are known to transmit pathogens like Borrelia spp. to wild birds, and that Blackbirds can act as reservoirs for these pathogens, the infection patterns observed in our study area provide a suitable situation to study the interrelations between ticks, Blackbirds and pathogens.     

Estimation of compartmentation of lysine inside the cells of Yarrowia lipolytica

We studied the compartmentation of lysine in vivo by the tracer method of Subramanian et al. (J. Bacteriol. 115 (1973) 284-290). To calculate the size of the different lysine pools and lysine fluxes inside the cell, a mathematical model was designed enabling quantitative estimation of these data from experimental measurements. This technique was applied to a lysine-accumulating strain, 15901.7, and to its low lysine pool derivatives, ply-1, ply-4 and ply-9, which were selected for their low polyphosphate pools. In the mother strain, 15901.7, it appeared that lysine was stored mainly in a non-cytoplasmic compartment. In the mutants, the efflux from this compartment was higher and accounted for the higher percentage of lysine in the cytoplasm of these strains. Simulation with calculated parameters fitted the experimental curves very well. This was good evidence for the pertinence of the model. The biological significance of these results are discussed.     

The crop milk: a potential new route for carotenoid-mediated parental effects

Allocation of carotenoid pigments, either through nutritional provisioning or from endogenous reserves, makes up a form of non-genetic parental investment to progeny that may contribute to fitness. To date, carotenoids derived from endogenous reserves have been acknowledged as important vectors in translating only avian female phenotype and environmental conditions experienced prior to laying. Here, we show that in columbidae, crop milk delivered by both parents may provide chicks with a large amount of endogenous carotenoids at the postzygotic stage. Major carotenoids were xanthophylls and beta-carotene, but their concentrations showed large variation among individuals. Interestingly, a large amount of this variation was explained by brood identity, suggesting either environmental influences and/or phenotypic influences on a parent's ability to transfer these biomolecules. Our study therefore illuminates a potential new route for endogenous carotenoid-mediated parental effects.     

Adenosine Augmentation Evoked by an ENT1 Inhibitor Improves Memory Impairment and Neuronal Plasticity in the APP/PS1 Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by cognitive impairment and synaptic dysfunction. Adenosine is an important homeostatic modulator that controls the bioenergetic network in the brain through regulating receptor-evoked signaling pathways, bioenergetic machineries, and epigenetic-mediated gene regulation. Equilibrative nucleoside transporter 1 (ENT1) is a major adenosine transporter that recycles adenosine from the extracellular space. In the present study, we report that a small adenosine analogue (designated J4) that inhibited ENT1 prevented the decline in spatial memory in an AD mouse model (APP/PS1). Electrophysiological and biochemical analyses further demonstrated that chronic treatment with J4 normalized the impaired basal synaptic transmission and long-term potentiation (LTP) at Schaffer collateral synapses as well as the aberrant expression of synaptic proteins (e.g., NR2A and NR2B), abnormal neuronal plasticity-related signaling pathways (e.g., PKA and GSK3β), and detrimental elevation in astrocytic A_2AR expression in the hippocampus and cortex of APP/PS1 mice. In conclusion, our findings suggest that modulation of adenosine homeostasis by J4 is beneficial in a mouse model of AD. Our study provides a potential therapeutic strategy to delay the progression of AD.