A New,Quick, and Simple Protocol to Evaluate Microalgae Polysaccharide Composition

In this work, a new methodological approach, relying on the high specificity of enzymes in a complex mixture, was developed to estimate the composition of bioactive polysaccharides produced by microalgae, directly in algal cultures. The objective was to set up a protocol to target oligomers commonly known to be associated with exopolysaccharides’ (EPS) nutraceutical and pharmaceutical activities (i.e., rhamnose, fucose, acidic sugars, etc.) without the constraints classically associated with chromatographic methods, while maintaining a resolution sufficiently high to enable their monitoring in the culture system. Determination of the monosaccharide content required the application of acid hydrolysis (2 M trifluoroacetic acid) followed by NaOH (2 M) neutralization. Quantification was then carried out directly on the fresh hydrolysate using enzyme kits corresponding to the main monosaccharides in a pre-determined composition of the polysaccharides under analysis. Initial results showed that the enzymes were not sensitive to the presence of TFA and NaOH, so the methodology could be carried out on fresh hydrolysate. The limits of quantification of the method were estimated as being in the order of the log of nanograms of monosaccharides per well, thus positioning it among the chromatographic methods in terms of analytical performance. A comparative analysis of the results obtained by the enzymatic method with a reference method (high-performance anion-exchange chromatography) confirmed good recovery rates, thus validating the closeness of the protocol. Finally, analyses of raw culture media were carried out and compared to the results obtained in miliQ water; no differences were observed. The new approach is a quick, functional analysis method allowing routine monitoring of the quality of bioactive polysaccharides in algal cultures grown in photobioreactors.     

Has global change induced divergent trends in radial growth of Pinus sylvestris and Pinus halepensis at their bioclimatic limit? The example of the Sainte-Baume forest (south-east France)

? It is agreed that climate (precipitation and temperature) influences the distribution of plant species. Near the margins of a species’ natural range, climate becomes limiting to physiological processes. There, climate change may be expected to have a significant impact on tree growth and the species’ ranges may be altered.

? In order to assess what influence climate change could exert on the distribution of pine species at their margin, radial growth trends in ring-width chronologies over the last century were analysed. In the French Mediterranean area where climate change is characterized by increased temperature, forest plots were selected along an altitudinal transect on the north-facing slope of the Sainte-Baume mountain (Bouches-du-Rhône, France) where the ranges of Pinus sylvestris and Pinus halepensis overlap.

? Two growth patterns were identified. For P. halepensis, radial growth has increased at all altitudes indicating that climate change has improved growth conditions of this species near the margin of its ecological range. For P. sylvestris, radial growth has increased only at low altitudes and even decreased at high altitudes.

? It must be deduced that the growth changes observed cannot be generalised either at the species level or at the geographical level and must be interpreted with great caution.

     

Induction of Soil Suppressiveness Against Rhizoctonia solani by Incorporation of Dried Plant Residues into Soil

ABSTRACT Suppressive effects of soil amendment with residues of 12 cultivars of Brassica rapa on damping-off of sugar beet were evaluated in soils infested with Rhizoctonia solani. Residues of clover and peanut were tested as noncruciferous controls. The incidence of damping-off was significantly and consistently suppressed in the soils amended with residues of clover, peanut, and B. rapa subsp. rapifera 'Saori', but only the volatile substance produced from water-imbibed residue of cv. Saori exhibited a distinct inhibitory effect on mycelial growth of R. solani. Nonetheless, disease suppression in such residue-amended soils was diminished or nullified when antibacterial antibiotics were applied to the soils, suggesting that proliferation of antagonistic bacteria resident to the soils were responsible for disease suppression. When the seed (pericarps) colonized by R. solani in the infested soil without residues were replanted into the soils amended with such residues, damping-off was suppressed in all cases. In contrast, when seed that had been colonized by microorganisms in the soils containing the residues were replanted into the infested soil, damping-off was not suppressed. The evidence indicates that the laimosphere, but not the spermosphere, is the site for the antagonistic microbial interaction, which is the chief principle of soil suppressiveness against Rhizoctonia damping-off.     

Environmental drivers of community diversity in a neotropical urban landscape: a multi-scale analysis

Context

Many aquatic communities are linked by the aerial dispersal of multiple, interacting species and are thus structured by processes occurring in both the aquatic and terrestrial compartments of the ecosystem.

Objectives

To evaluate the environmental factors shaping the aquatic macroinvertebrate communities associated with tank bromeliads in an urban landscape.

Methods

Thirty-two bromeliads were georeferenced to assess the spatial distribution of the aquatic meta-habitat in one city. The relative influence of the aquatic and terrestrial habitats on the structure of macroinvertebrate communities was analyzed at four spatial scales (radius = 10, 30, 50, and 70 m) using redundancy analyses.

Results

We sorted 18,352 aquatic macroinvertebrates into 29 taxa. Water volume and the amount of organic matter explained a significant part of the taxa variance, regardless of spatial scale. The remaining variance was explained by the meta-habitat size (i.e., the water volume for all of the bromeliads within a given surface area), the distance to the nearest building at small scales, and the surface area of buildings plus ground cover at larger scales. At small scales, the meta-habitat size influenced the two most frequent mosquito species in opposite ways, suggesting spatial competition and coexistence. Greater vegetation cover favored the presence of a top predator.

Conclusions

The size of the meta-habitat and urban landscape characteristics influence the structure of aquatic communities in tank bromeliads, including mosquito larval abundance. Modifications to this landscape will affect both the terrestrial and aquatic compartments of the urban ecosystem, offering prospects for mosquito management during urban planning.

     

Short-term effects of ecadotril in dogs with induced congestive heart failure

OBJECTIVE: To evaluate short-term hemodynamic effects of ecadotril in a model of congestive heart failure in dogs. ANIMALS: 6 conscious adult male dogs. PROCEDURES: Instruments were placed in dogs to measure left ventricular, aortic, and atrial blood pressures. Heart failure was induced by repeated coronary embolization with latex microspheres. Four times, and in random order, dogs were given vehicle or active drug (3, 10, or 30 mg/kg of body weight) orally. Hemodynamic variables, urine flow, and urinary electrolyte excretion were measured before and 30, 90, and 150 minutes, and 10 and 21 hours after drug administration. RESULTS: Changes in urine flow, heart rate, mean arterial pressure, or peak positive and negative rate of change in ventricular pressure were not apparent. Urinary sodium excretion significantly increased in response to the low and high doses of ecadotril but not in response to the 10 mg/kg dose. Left ventricular end diastolic pressure (LVEDP) consistently decreased in dose- and time-dependent manner. Maximal group-averaged reductions in LVEDP were 5.2, 8.1, and 10 mm Hg for the low, middle, and high doses, respectively. The magnitude of the decrease in LVEDP was not related to cumulative change in urine flow. CONCLUSIONS AND CLINICAL RELEVANCE: Orally administered ecadotril reduced left ventricular filling pressures in these dogs by a mechanism that does not require a substantial diuretic effect. Ecadotril may be effective for alleviating clinical signs in dogs with left-sided heart failure and may be particularly beneficial for use in dogs that are refractory to traditional diuretic therapy.     

Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.     

Genetic trends for objectively measured and subjectively assessed traits in a Dorper sheep flock

Genetic trends were constructed to monitor the genetic change for subjectively assessed and objectively measured traits using data emanating from complete records from the National Small Stock Improvement Scheme database and performance records accumulated by a single breeder over a period of 24 years. The objectively measured production traits considered were weaning weight, post-weaning weight (PWW), yearling weight, average daily weight gain to weaning (ADGW), average daily weight gain during post-weaning phase (ADGPW) and average daily weight gain up to yearling age. The subjectively assessed traits (scored on a five-point scale) were conformation, fat distribution, size, type and colour. Direct genetic trends for live weight and growth traits (with the exception of ADGPW) were positive. All the objectively measured traits where maternal effects were significant, except PWW, registered small declines in maternal breeding values. The fastest genetic progress was attained by ADGW, which amounted to 0.29 % of the overall phenotypic mean per annum. Conformation and type exhibited positive but slow increments in direct breeding values at an equivalent annual rate amounting to 0.12 and 0.09 % of the overall phenotypic mean, respectively. Size demonstrated a negative genetic trend of ?0.14 % of the overall phenotypic mean per annum. Genetic trends for fat distribution and colour were negligible. It was concluded that breeders should focus more on the performance recording of objective traits as they are likely to respond favourably to selection pressure.     

Antinociceptive efficacy and plasma concentrations of transdermal buprenorphine in dogs

To assess the antinociceptive efficacy of transdermal (TD) buprenorphine (B) in dogs, a prospective, positive-controlled experimental study was performed in 10 healthy Beagles. In an open label crossover design, the dogs initially received intravenous B (IVB, 0.02 mg kg^?1) as a positive control, followed by TDB (52.5 μg h^?1) 4 months later. Blood was collected at regular intervals for determination of the plasma concentrations of B ([B]) and its metabolite norbuprenorphine. The antinociceptive efficacy was assessed using thermal and mechanical models of nociception. The peak concentration [B] was 1.54 ng mL^?1 (±1.98) 60 h after TDB application, although three dogs had no measurable [B] after TDB. Maximum thermal threshold (TT) was 52.6 °C (±0.48) at 1 h after IVB administration and 51.63 °C (±1.01) 72 h after TDB application. The significant increase in TT indicated that effective antinociception was achieved beyond 36 h after the application of TDB, lasting until patch removal. There was hysteresis between [B] and the antinociceptive effect.