Influence of Pollen Nutrition on Honey Bee Health: Do Pollen Quality and Diversity Matter?

Honey bee colonies are highly dependent upon the availability of floral resources from which they get the nutrients (notably pollen) necessary to their development and survival. However, foraging areas are currently affected by the intensification of agriculture and landscape alteration. Bees are therefore confronted to disparities in time and space of floral resource abundance, type and diversity, which might provide inadequate nutrition and endanger colonies. The beneficial influence of pollen availability on bee health is well-established but whether quality and diversity of pollen diets can modify bee health remains largely unknown. We therefore tested the influence of pollen diet quality (different monofloral pollens) and diversity (polyfloral pollen diet) on the physiology of young nurse bees, which have a distinct nutritional physiology (e.g. hypopharyngeal gland development and vitellogenin level), and on the tolerance to the microsporidian parasite Nosema ceranae by measuring bee survival and the activity of different enzymes potentially involved in bee health and defense response (glutathione-S-transferase (detoxification), phenoloxidase (immunity) and alkaline phosphatase (metabolism)). We found that both nurse bee physiology and the tolerance to the parasite were affected by pollen quality. Pollen diet diversity had no effect on the nurse bee physiology and the survival of healthy bees. However, when parasitized, bees fed with the polyfloral blend lived longer than bees fed with monofloral pollens, excepted for the protein-richest monofloral pollen. Furthermore, the survival was positively correlated to alkaline phosphatase activity in healthy bees and to phenoloxydase activities in infected bees. Our results support the idea that both the quality and diversity (in a specific context) of pollen can shape bee physiology and might help to better understand the influence of agriculture and land-use intensification on bee nutrition and health.     

Metabolic syndrome in the rat: females are protected against the pro-oxidant effect of a high sucrose diet

Metabolic syndrome is more prevalent in men than in women. In an experimental dietary model of metabolic syndrome, the high-fructose-fed rat, oxidative stress has been observed in males. Given that estradiol has been documented to exert an antioxidant effect, we investigated whether female rats were better protected than males against the adverse effects of a high-sucrose diet, and we studied the influence of hormonal status in female rats. Males and females were first fed a sucrose-based or starch-based diet for 2 weeks. In the males, the plasma triglyceride (TG)-raising effect of sucrose was accompanied by significantly lowered plasma alpha-tocopherol and a significantly lowered alpha-tocopherol/TG ratio (30%), suggesting that vitamin E depletion may predispose lipoproteins to subsequent oxidative stress. In males, after exposure of heart tissue homogenate to iron-induced lipid peroxidation, thiobarbituric reactive substances were significantly higher in the sucrose-fed than in the starch-fed rats. In contrast, in sucrose-fed females, neither a decrease in vitamin E/TG ratio nor an increased susceptibility of heart tissue to peroxidation was observed, despite both a significantly decreased heart superoxide dismutase activity (14%) and a significant 3-fold increase in plasma nitric oxide concentration compared with starch-fed females. The influence of hormonal status in female rats was then assessed using intact, ovariectomized, or estradiol-supplemented ovariectomized female rats fed the sucrose or starch diet for 2 weeks. After exposure of heart tissue to iron-induced lipid peroxidation, higher susceptibility to peroxidation was found only in ovariectomized females fed the sucrose diet compared with the starch group and not in intact females or ovariectomized females supplemented with estradiol. Thus, estrogens, by their effects on antioxidant capacity, might explain the sexual difference in the pro-oxidant effect of sucrose diet resulting in metabolic syndrome in rats.     

Out of Australia and back again: the world‐wide historical biogeography of non‐pollinating fig wasps (Hymenoptera: Sycophaginae)

Aim Figs (Ficus, Moraceae) are exploited by rich communities of often host‐specific phytophagous wasps. Among them, gall‐inducing Sycophaginae (Hymenoptera, Chalcidoidea) may share a common history with Ficus and their mutualistic pollinators (Agaonidae). We investigate here, for the first time, the phylogeny and biogeographical history of Sycophaginae and compare the timing of radiation and dispersion of major clades with available data on Ficus and fig pollinators. Reconstructing the history of their host colonization and association over space and time is central to understanding how fig wasp communities were assembled. Location World‐wide. Methods Maximum likelihood and Bayesian analyses were conducted on 4267 bp of mitochondrial and nuclear DNA to produce a phylogeny of all genera of Sycophaginae. Two relaxed clock methods with or without rate autocorrelation were used for date estimation. Analyses of ancestral area were also conducted to investigate the geographical origin of the Sycophaginae. Results The phylogeny is well resolved and supported. Our data suggest a post‐Gondwanan origin for the Sycophaginae (50–40 Ma) and two independent out‐of‐Australia dispersal events to continental Asia. Given palaeoclimatic and palaeogeographic records, the following scenario appears the most likely. The ancestor of Idarnes+Apocryptophagus migrated to Greater India through the Ninetyeast Ridge (40–30 Ma). The ancestor of Anidarnes+Conidarnes dispersed later via Sundaland (25–20 Ma). Idarnes and Anidarnes subsequently reached the New World via the North Atlantic land bridges during the Late Oligocene Warming Event. Apocryptophagus reached Africa c. 20 Ma via the Arabic corridors and returned to Australasia following the expansion of Sundaland tropical forests (20–10 Ma). Main conclusions Sycophaginae probably invaded the fig microcosm in Australia c. 50–40 Ma after the origin of their host plant. Once associated with figs, they dispersed out of Australia and radiated together with their host fig and associated pollinator through the tropics. We recorded a good coincidence of timing between dispersal events of Sycophaginae and continental connections. Furthermore, fruit pigeons that disperse figs probably spread out of Australasia through the Indian Ocean via the Ninetyeast Ridge c. 38 Ma. Therefore, our study highlights the potential for combining molecular phylogenetics with multiple methods of dating of interacting groups to reconstruct the historical biogeography of plant–herbivore associations.     

Effects of postnatal maturation on energetics and cross-bridge properties in rat diaphragm.

The effects of maturation on cross-bridge (CB) properties were studied in rat diaphragm strips obtained at postnatal days 3, 10, and 17 and in adults (10-12 wk old). Calculations of muscle energetics and characteristics of CBs were determined from standard Huxley equations. Maturation did not change the curvature of the force-velocity relationship or the peak of mechanical efficiency. There was a significant increase in the total number of CBs per cross-sectional area (m) with aging but not in single CB force. The turnover rate of myosin ATPase increased, the duration of the CB cycle decreased, and the velocity of CBs decreased significantly only after the first week postpartum. There was a linear relationship between maximum total force and m (r = 0.969, P < 0.001), and between maximum unloaded shortening velocity and m (r = 0.728, P < 0.001). When this study in the rat and previous study in the hamster are compared, it appears that there are few species differences in the postnatal maturation process of the diaphragm.     

Crystallization and prelilminary X-ray investigation of barster,the intracellular inhibitor of barnase

Crystals of barstar, the intracellular inhibitor of the extracellular ribonuclease produced by Bacillus amyloliquefaciens (barnase), were obtained through vapor phase equilibration using the hanging drop technique. Three crystal forms have been characterized. Forms I and II, crystallized eithr in potetragonal; they exhibit a superstructure along the c-axis. Form III crystals, suitable for a high resolution structure determination, were grown from 55-65% ammomnium sulfate. This crystal form is hexagonal and diffracts to at least 2 Å resolution at a synchrotron radiation source. It belongs to the hexagonal space group P6, with unit cell dimensions a = b = 143.6 Å, c = 35.6 Å. There are four molecules of barstar in the asymmetric unit. X-ray data have been collected to 2.2 Å Bragg sapcing. The structure determination is underway in order to analyze conformational changes of barstar upon complexation with barnas. © 1993 Wiley-Liss, Inc.     

Acetic and propionic acids,inducers of ripening in pre-climacteric golden delicious apples

When treated with acetic or propionic acid vapours, intact pre-climacteric Golden Delicious apples started ripening prematurely. Experiments with [2?¹⁴C]propionic acid showed that a small part of the added acid is transformed into [¹⁴C]ethylene, and that ripening probably begins in these circumstances as a result of the artificial increase in the endogenous ethylene level. It may be that in unripe apples the small amount of evolved ethylene is mostly derived from simple organic acids, so that the moment at which its triggering concentration is reached depends on the available supply of acids. As this, in turn, is a function of the state of maturity of the fruit, there must be a direct relationship between the start of ripening and the degree of maturity. Thus, even in very unripe apples, catabolic processes are at work or potentially present because of the modified β–oxidation of [1?¹⁴C]propionic acid observed.     

Changes in 20S proteasome activity during ageing of the LOU rat

Muscular functions decline and muscle mass decreases during ageing. In the rat, there is a 27% decrease in muscle protein between 18 and 34 months of age. We examined age-related changes in the proteasome-dependent proteolytic pathway in rats at 4, 18, 24, 29 and 34 months of age. The three best characterised activities of the proteasome (chymotrypsin-like, trypsin-like and peptidylglutamyl peptide hydrolase) increased to 29 months and then decreased in the senescent animal. These variations in activity were accompanied by an identical change in the quantity of 20S proteasome measured by Western blot, whereas the S4 subunit of the 19S regulator and the quantity of ubiquitin-linked proteins remained constant. mRNA of subunits C3, C5, C9, and S4 increased in the senescent animal, but ubiquitin mRNA levels were unchanged. These findings suggest that the 20S proteasome may be partly responsible for the muscular atrophy observed during ageing in the rat.     

A Mouse Chromosome-Specific YAC Probe Collection forin SituHybridization

To facilitate the identification of mouse metaphase chromosomes by fluorescencein situhybridization (FISH), a complete collection of mouse chromosome-specific markers has been established. Yeast artificial chromosome libraries were screened by polymerase chain reaction using primers for known loci. DNAs from positive clones were then tested by FISH. One probe per chromosome was selected on the basis of high specificity (nonchimerism) and strong fluorescence.     

Decomposition rates of bryophytes in managed boreal forests: influence of bryophyte species and forest harvesting

The slow decomposition rate of boreal forest floor bryophytes contributes both to maintaining high soil C reserves as well as affecting conditions for tree growth by maintaining excessively high soil water content, cooling the soil and slowing nutrient cycles. In this study, mass loss of three bryophyte species (Pleurozium schreberi, Sphagnum capillifolium, S. fuscum) was measured in unharvested, partial cut and low-retention cut forest blocks. Mesh decomposition bags containing the three species and wood sticks were placed at two depths in colonies of either P. schreberi or S. capillifolium (environment) in the three harvest treatments and retrieved after two growing seasons. Mass loss was primarily related to substrate type (P. schreberi > S. capillifolium > wood sticks > S. fuscum) and secondarily to depth. Harvest treatment and environment (P. schreberi or S. capillifolium) only weakly affected sphagna mass loss. The weak effect of harvest treatment suggests that conditions created by low retention cuts do not to stimulate decomposition in this system and are not important enough to stimulate carbon loss, or to counteract paludification. On the other hand, the strong effect of bryophyte type indicates that conditions affecting bryophyte colonization and succession are of great importance in driving carbon and nutrient cycles.     

Proteasomes (prosomes) inhibit the translation of Tobacco mosaic virus RNA by preventing the formation of initiation complexes

Proteasomes (prosomes) are large multiprotein complexes. They are involved in protein degradation of ubiquitin-conjugated proteins and in the generation of MHC class I peptides. We gave further evidence that they interfere within vitro protein synthesis. Proteasomes inhibit the translation of Tobacco mosaic virus RNA. Analysis of cell-free systems by sucrose gradient centrifugation revealted that they prevent the formation of 80S initiation complexes but not the early phase of initiation.