Biochemical composition is not the main factor influencing variability in carbon isotope composition of tree rings

From June to December, we determined the effects of variations in biochemical composition on delta(13)C of tree rings of 2-year-old oaks (Quercus petraea (Matt.) Liebl.) growing under semi-natural conditions, and the dependence of these effects of water stress during the growth season. Percent abundance, carbon concentration and delta(13)C were measured in holocellulose, lignin, extractive-free wood, starch and a water-soluble fraction. Relative concentrations of lignin and holocellulose in the extractive-free wood varied little during the season or in response to water stress, indicating that these compounds could not quantitatively explain the variations in whole-wood delta(13)C. Among all sampled tree rings, the relative concentration of each structural compound (holocellulose and lignin) accounted for less than 5% of the delta(13)C variability in whole wood. Variations in holocellulose and extractive-free wood delta(13)C between tree rings were almost identical (r > 0.95), whereas variations in lignin delta(13)C were less well correlated to these compounds. Whole-wood delta(13)C had a slightly altered isotopic signal compared with that of the structural compounds because of the presence of the extractive component. These results showed that variations in lignin delta(13)C and lignin concentration have little influence on extractive-free wood delta(13)C and whole-wood delta(13)C. Rather, holocellulose influences delta(13)C the most. Thus, we confirmed that, for climatic reconstruction from tree rings, removal of extractives by soxhlet is generally sufficient and sometimes unnecessary. Our findings also indicate that, in the case of rapid and severe water stress, the structural component did not accurately record the associated increase in delta(13)C because of dilution with previously formed organic matter and cessation of trunk growth. The effect of drought on carbon isotope ratios was more pronounced in the extractive compounds, making them good water stress indicators but only on a scale of days to months.     

Plant traits and functional types to characterise drought survival of pluri-specific perennial herbaceous swards in Mediterranean areas

Perennial grasslands provide numerous environmental benefits but their response to severe drought and therefore their sustainability in arid and Mediterranean areas have been little studied. Due to climate change, models of pasture production should be able to predict sward evolutions under increasing aridity. Our general goal was to identify plant traits and functional types that could be included in models aiming to analyse the dynamics of contrasting types of herbaceous plants grown in mixtures under drought. The two steps were: (1) to investigate the morpho-physiological traits associated with drought survival within a mixture of perennial herbaceous populations and to test whether the physiological traits measured under optimum conditions of growth in Spring may predict plant responses under subsequent summer drought and (2) to identify functional groups of populations exhibiting similar responses to the disturbance regime caused by severe drought. Seven different populations from five species were grown in monocultures (pots, long columns) and mixtures (containers, field). Standard leaf functional traits, aerial and root biomass were assessed under non-limiting water supply in Spring. In Summer, under continuous severe drought, leaf water status and plant survival were measured.Senescence of aerial tissues at the end of Spring, associated with endogenous summer dormancy, water status maintenance in basal tissues during the intense drought, and root biomass in the field were the variables best correlated with drought survival. The standard leaf functional traits specific leaf area (SLA) and leaf dry matter content (LDMC) measured in Spring under full irrigation, were uncorrelated with drought survival. These results suggested no general trade-off between growth potential and drought survival. Under conditions of optimal production in Spring, correlations were established between functional traits and variables associated with aerial biomass productivity which discriminated the group of forage cultivars from the other genotypes. Under summer drought, four main functional types of genotypes were defined according to their strategy of water use and therefore contrasting survival and persistence. This typology will be used to base further modelling study aiming to assess the effects of increasing aridity on the stability and productivity of herbaceous swards on the long term.     

Effects of the number and the position of transfixation pins in acrylic connecting bars

Acrylic columns are commonly used in external skeletal fixators, especially for fracture management or trans-articular fixations. To the authors’ knowledge, there are no studies demonstrating if the number or position of the transfixation pins influence the ultimate strength and stiffness of the acrylic column. The objective of this study was to evaluate the effects of the number and position of transfixation pins (concentric versus eccentric) on the strength and stiffness of acrylic columns placed in axial compression. We hypothesized that strength and stiffness of acrylic columns under axial compression would not be affected by the number or position of the transfixation pins through the column. Three different groups of 12 acrylic columns were constructed with 4, 6, and 8 pins. In each group, 6 columns were constructed with the pins placed concentrically and the remaining 6 columns with the pins placed eccentrically. Each column was then placed under axial compression using a biomechanical testing machine. No significant differences were observed in ultimate strength regarding the number or position of transfixation pins (P = 0.83 and P = 0.27, respectively). However, stiffness was significantly decreased for columns with 4 eccentric pins compared with columns with 6 and 8 eccentric pins (P < 0.01) and with columns with 4 concentric pins (P < 0.001). Although the effects of transfixation pins on the rigidity of acrylic columns do not appear to be clinically significant, these tests were performed only in compression and results might differ if complete external fixator systems are used with different models of testing. Future studies are recommended.     

The bioavailability of sediment-sorbed organic chemicals: A review

Xenobiotic chemicals that are present in aquatic environments are typically concentrated on suspended particles and sedimentary materials where they represent a source of chronic contamination to benthic and pelagic organisms. Laboratory and field studies of bioaccumulation, toxicity, and food-chain transfer of chemicals bound to sediment have shown the potential ecological impacts that may result from the contamination of sediments. In this review, the chemical and physical processes that determine the environmental fate of sediment-sorbed organic chemicals are outlined, and their relationship to bioavailability is discussed. Methods currently used to predict the fate of pollutants in the aquatic environment are of limited use for the assessment of sediment-sorbed chemical bioavailability because they are based on the compound's behavior in the water column. Furthermore, an organism's morphology and ecological niche can profoundly affect its ability to accumulate xenobiotic chemicals from sediments and these must be considered before the populations at greatest risk can be identified.     

Patterns of cross-resistance to fungicides in Botryotinia fuckeliana (Botrytis cinerea) isolates from French vineyards

Field strains of Botryotinia fuckeliana were isolated from diseased grape berries which were collected at the harvest, between 1993 and 1997, from French vineyards located in Alsace, Armagnac, Bordeaux, Champagne and Loire Valley. According to the inhibitory effects of fungicides towards spore germination, germ-tube elongation and mycelial growth, several phenotypes could be characterized. Thus, two types of benzimidazole (e.g. carbendazim, thiabendazole)-resistant strains were detected; negative cross-resistance towards diethofencarb, diphenylamine and dicloran was found only in one type. Most dicarboximide (e.g. iprodione, procymidone, vinclozolin)-resistant strains were also weakly resistant to aromatic hydrocarbon fungicides (e.g. chloroneb, dicloran, tolclofos-methyl) but remained sensitive to phenylpyrroles (e.g. fenpiclonil, fludioxonil). However, in some other dicarboximide-resistant strains, resistance was observed either as being restricted to dicarboximides or as extending weakly to phenylpyrroles. Towards anilinopyrimidines (e.g. cyprodinil, mepanipyrim, pyrimethanil), three resistant phenotypes have been identified. In the most resistant one, resistance was restricted to anilinopyrimidines, whereas in the others, resistance extended to various other groups of fungicides including dicarboximides, phenylpyrroles, sterol biosynthesis inhibitors (e.g. tolfanate, prochloraz, tebuconazole) and the hydroxyanilide derivative, fenhexamid. According to the pattern of cross-resistance, two phenotypes were characterized within these multifungicide-resistant strains. In vitro tests conducted with fenpropimorph, fenpropidin and spiroxamine, revealed the existence of strains highly susceptible to these sterol Δ¹⁴- reduction inhibitors. This property was correlated with a decreased sensitivity towards fenhexamid.     

In vitro embryo germination and proliferation of pistachio (Pistacia vera L.)

In vitro development of isolated embryos and axillary bud proliferation were studied in Pistacia vera L. Different regulator-free nutrient media were compared to determine the effects of the mineral solution, agar and sucrose concentrations on seedling development from mature embryos. Nutrient-rich MS [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tabacco tissue cultures. Physiol. Plant. 15, 473–479] and DKW [Driver, J.A., Kuniyuki, A.M., 1984. In vitro propagation of Paradox walnut rootstock. HortScience 19, 507–509] mineral solutions were more efficient for the development of aerial parts than nutrient-poor KN [Knop, W., 1884. Bereitung einer concentrierten nährstofflosung für pflanzen. Landwersuhssat 30, 292–294] and WT [Withe, P.R., 1936. Plant tissue cultures. Bot. Rev. 2, 419–437] solutions. Reducing the agar concentration enhanced fresh matter production and balanced seedling development. When tested at different concentrations, sucrose was found to orient mature embryo development, with the best results obtained at concentrations of 2–4%, whereas high concentrations (6 and 12%) mainly inhibited elongation of the aerial parts. Plantlets obtained previously from in vitro cultured embryos were propagated by axillary budding. High bud proliferation (six shoots per explant) was achieved when using 17.8 μM benzyladenine (BA) combined with 0.5 μM indole-3-butyric acid (IBA). The addition of 2.9 μM gibberellic acid (GA₃) to the propagation medium did not improve axillary shoot yields and on average, media with GA₃ produced 2.3–2.6 elongated stems per cultured explant. Shoots were rooted in vitro in half-strength MS medium containing 12.3 μM IBA.     

Influence of the allelic variants encoded at the Gli-B1 locus, responsible for a major allergen of wheat, on IgE reactivity for patients suffering from food allergy to wheat

Wheat presents an important genetic diversity that could be useful to look for cultivars with reduced allergencity. omega5-Gliadins have been described as major allergens for wheat allergic patients suffering from wheat-dependent exercise-induced anaphylaxis (WDEIA) and some cases of chronic urticaria (U). Our objective was to study the influence of genetic variability at the Gli-B1 locus encoding for omega5-gliadins on the reactivity of IgE antibodies from these patients. We selected cultivars expressing 13 alleles at Gli-B1 including a wheat/rye translocation and studied the reactivity to gliadins of a rabbit antiserum specific for omega5-gliadins and of IgE from 10 patients. The antiserum and IgE from nine patients with WDEIA and U strongly detected omega5-gliadins expressed by most of the Gli-B1 alleles but showed no or faint responses to the gliadins and secalins extracted from the translocated wheat. The selection of genotypes lacking the Gli-B1 locus may reduce wheat allergenicity.     

Intestinal translocation capabilities of wheat allergens using the Caco-2 cell line

Because intestinal absorption of food protein can trigger an allergic reaction, the effect of wheat proteins on intestinal epithelial cell permeability was evaluated and the abilities of these proteins in native or pepsin-hydrolyzed state to cross the epithelial cell monolayer were compared. Enterocytic monolayers were established by culturing Caco-2 cells, a model of enterocytes, on permeable supports that separate the apical and basal compartments. Proteins were added into the apical compartment, and the transepithelial resistance (TER) was measured; proteins that crossed the cell monolayer were detected in the basal medium by ELISA. Wheat proteins did not alter the cell monolayer. TER and Caco-2 cell viability were conserved, and the passage of dextran was prevented. Native and pepsin-hydrolyzed forms of omega5-gliadin and lipid transfer proteins were detected in the basal medium. The results suggest that these two major allergens in food allergy to wheat were able to cross the cell monolayer by the transcellular route.     

Report on the first detection of pectenotoxin-2, spirolide-a and their derivatives in French shellfish

In the context of the French Phytoplankton and Phycotoxins Monitoring Network (REPHY) programme, shellfish samples were harvested from different locations where harmful algae blooms were known to have occurred. For all shellfish samples found positive by the mouse bioassay for diarrhetic shellfish poisoning (DSP) toxins, liquid chromatography (LC) coupled with mass spectrometry (MS) was used to search for the following lipophilic toxins: okadaic acid (OA), dinophysistoxins (DTXs), pectenotoxins (PTXs), azaspiracids (AZAs), yessotoxins (YTXs), spirolides (SPXs) and gymnodimines (GYMs). In order to investigate the presence of acyl-OAs and/or acyl-DTX-1,-2 (DTX-3), alkaline hydrolysis was performed on all samples, and LC/MS analyses were carried out on the samples before and after hydrolysis. The results revealed different lipophilic toxin profiles as a function of the shellfish sampling location. The primary finding was that all of the samples contained OA and acyl-OA. In addition, other lipophilic toxins were found in shellfish samples: DTX-2, acyl-DTX-2 and SPXs (SPX-A, SPX-desMeC) on the Atlantic coast (Southern Brittany, Arcachon), and pectenotoxins (PTX-2, PTX-2-seco-acid and 7-epi-PTX-2-seco-acid) on the Mediterranean coast (Thau lagoon, the island of Corsica). This paper reports on the first detection of PTX-2, SPX-A and their derivatives in French shellfish.     

Hoof growth and wear of semi-feral ponies during an annual summer 'self-trimming' period

REASONS FOR PERFORMING STUDY: Despite growing interest in application natural models of hoof-maintenance in domestic horses, little data is available to describe natural conformation and proposed mechanisms of self-maintenance. OBJECTIVES: Quantitatively describe hoof growth and wear during a period of 'self-trimming' within a herd of semi-feral ponies. METHODS: Hoof length, growth and wear were measured for a sample of 40 animals during a period of 'self-trimming' from June through September, 2005. RESULTS: For front hooves, mean toe lengths in July, August and September were significantly less than in June. For the hind, mean toe length in August was significantly less than in June, July and September. Increased rate of wear, as opposed to decreased growth rate, was the major contributor to overall shorter hoof lengths. Cumulative wear expressed as a percentage of the June baseline toe length ranged from 21-57% (mean 38%) for the front and 12-46% (mean 32%) for the hind. CONCLUSIONS: Significant cracking, tearing and increased wear, known as 'self-trimming' is a measurable herd-wise phenomenon in horses maintained under natural social and environmental conditions. POTENTIAL RELEVANCE: Although just one example herd, these data provide quantitative support of anecdotal reports of 'self-trimming' as a mechanism contributing to natural self-maintenance of the equine hoof.