Wood ants produce a potent antimicrobial agent by applying formic acid on tree-collected resin.

Wood ants fight pathogens by incorporating tree resin with antimicrobial properties into their nests. They also produce large quantities of formic acid in their venom gland, which they readily spray to defend or disinfect their nest. Mixing chemicals to produce powerful antibiotics is common practice in human medicine, yet evidence for the use of such "defensive cocktails" by animals remains scant. Here, we test the hypothesis that wood ants enhance the antifungal activity of tree resin by treating it with formic acid. In a series of experiments, we document that (i) tree resin had much higher inhibitory activity against the common entomopathogenic fungus Metarhizium brunneum after having been in contact with ants, while no such effect was detected for other nest materials; (ii) wood ants applied significant amounts of endogenous formic and succinic acid on resin and other nest materials; and (iii) the application of synthetic formic acid greatly increased the antifungal activity of resin, but had no such effect when applied to inert glass material. Together, these results demonstrate that wood ants obtain an effective protection against a detrimental microorganism by mixing endogenous and plant-acquired chemical defenses. In conclusion, the ability to synergistically combine antimicrobial substances of diverse origins is not restricted to humans and may play an important role in insect societies

Environmental stress linked to consumption of maternally derived carotenoids in brown trout embryos (Salmo trutta).

The yellow, orange, or red colors of salmonid eggs are due to maternally derived carotenoids whose functions are not sufficiently understood yet. Here, we studied the significance of naturally acquired carotenoids as maternal environmental effects during embryo development in brown trout (Salmo trutta). We collected eggs from wild females, quantified their egg carotenoid content, fertilized them in vitro in full-factorial breeding blocks to separate maternal from paternal effects, and raised 3,278 embryos singly at various stress conditions until hatching. We found significant sire effects that revealed additive genetic variance for embryo survival and hatching time. Dam effects were 5.4 times larger than these sire effects, indicating that maternal environmental effects play an important role in determining embryo stress tolerance. Of the eight pigment molecules that we targeted, only astaxanthin, zeaxanthin (that both affected egg redness), and lutein were detected above our confidence thresholds. No strong link could be observed between carotenoid content in unfertilized eggs and embryo mortality or hatching timing. However, the consumption of carotenoids during our stress treatment was negatively correlated to embryo survival among sib groups and explained about 14% of the maternal environmental variance. We conclude that maternally derived carotenoids play a role in the ability of embryos to cope with environmental stress, but that the initial susceptibility to the organic pollution was mainly determined by other factors

Profil electroneuromyographique des neuropathies dans une population de patients diabetiques admis dans un laboratoire de neurophysiologie

Les neuropathies périphériques constituent une complication fréquente du diabète. Plusieurs formes de neuropathies sont décrites dans cette population. L’objectif de ce travail était d’étudier la fréquence desdifférentes neuropathies dans une population de diabétiques.Nous avons réalisé une étude descriptive portant sur 110 patients diabétiques admis dans le laboratoire de Neurophysiologie du CHU de Limoges de janvier 2004 à juin 2006. Le diagnostic EMG des neuropathies démyélinisantes était basé sur les critères de l’EFNS/PNS. Il s’agit de 110 sujets dont 63 de sexe masculin, âgés de 18 à 81 ans avec un âge moyen de 57,2 ans. La durée moyenne de la maladie était de 15 ans avec un taux moyen de HbA1C de 7,9%.33 sujets (30,6%) avaient une neuropathie démyélinisante dont 20 classés défini, 8 probable et 5 possible. 25,2% avaient une neuropathie axonale, 22,7% un syndrome du canal carpien et 14 sujets avaient un EMG normal. Ces résultats comparables à certains de la littérature suggèrent une fréquence assez élevée des neuropathies démyélinisantes chez les diabétiques et imposent d’en étudier les déterminants

Propylthiocyclopentadiene: A new synthetic route to complexes of iron and group 4 transition metals. Molecular structure of (C5H4SCH2CH2CH3)(2)ZrCl2

The use of the propylthio-substituted cyclopentadienylsodium salt leads to 1,1'-bis(propylthio) ferrocene and dichlorobis(propylthiocyclopentadienyl)zirconium, titanium or hafnium(IV). The structure of (C5H4SCH2CH2CH3)(2)ZrCl2 has been established by X-ray analysis (orthorhombic, Pbcn, a = 11.943(1) Angstrom, b = 6.883(2) Angstrom, c = 22.412(2) Angstrom, V = 1842.4(2) Angstrom(3), Z = 4, R(F) = 0.027). The complexes have been characterized by H-1 and C-13 NMR and electrochemical studies. The physico chemical properties of 1,1'-bis(propylthio) ferrocene are discussed by a molecular approach at the extended Huckel level

Alternative reproductive tactics, sperm mobility and oxidative stress in Carollia perspicillata (Seba's short-tailed bat)

In social systems with alternative reproductive tactics, sneakers face a higher level of sperm competition than harem males and hence are predicted to allocate more resources to ejaculates. Antioxidants can protect sperm against oxidative stress, and thus, their allocation to the ejaculate may depend on mating tactic. In this study on the frugivorous bat Carollia perspicillata, we assessed, for harem and sneaker males, four spermmobility traits, blood and ejaculatemarkers of the redox balance and the ejaculate to blood ratios of the redox markers. Under higher sperm competition, sneaker males should allocate proportionally more antioxidant resources to the protection of sperm than harem males. In contrast, harem males should favour pre-copulatory functions, which comprise the protection of blood. We found significantly higher sperm velocity and sperm survival in sneakers. There was no correlation between spermmobility and spermenzymatic antioxidant activity or ejaculate levels of lipid peroxidation (oxidative damage). Ejaculate levels of lipid peroxidation and sperm survival showed a significantly positive correlation, which could be attributed to the role of reactive oxygen species for sperm capacitation. Harem and sneaker males showed similar levels of redox balance markers in ejaculate and blood. However, harem males showed a higher ratio of oxidized over reduced glutathione in blood, which may indicate higher cellular stress due to higher metabolism. Overall, our findings suggest that sneakers of C. perspicillata compensate for a higher level of sperm competition by higher sperm mobility. Significance statement In social systems with alternative reproductive tactics, sneakers face higher level of sperm competition than harem males and hence are predicted to allocate more resources to ejaculates. Antioxidants can protect sperm against oxidative stress, and thus, their allocation to the ejaculate may depend on mating tactic. In this study on the frugivorous bat Carollia perspicillata, we found sperm swimming significantly faster and longer in sneaker males compared to harem males. However, traits other than the investigated antioxidant may favour higher sperm mobility. Measured redox pattern in blood of harem males may indicate higher cellular stress due to higher metabolism. Our results provide support to the current sperm competition models at the intraspecific level, which is still debated for internal fertilizers. This study contributes to better understanding the trade-offs and adaptations resulting from alternative reproductive tactics in mammals

Percolation properties of the 2D Heisenberg model

We analyze the percolation properties of certain clusters defined on configurations of the 2--dimensional Heisenberg model. We find that, given any direction \vec{n} in O(3) space, the spins almost perpendicular to \vec{n} form a percolating cluster. This result gives indications of how the model can avoid a previously conjectured Kosterlitz-Thouless phase transition at finite temperature T.Comment: 4 pages, 3 eps figures. Revised version (more clear abstract, some new references

The Arabidopsis Pep-PEPR system is induced by herbivore feeding and contributes to JA-mediated plant defence against herbivory

Dysfunction of the Pep-PEPR system and its interplay with JA signalling results in increased plant susceptibility towards herbivore attack indicating that endogenous signalling also contributes to herbivore defenc