Impact of atmospheric CO2 and plant life forms on soil microbial activities

From the global change perspective, increase of atmospheric CO₂ and land cover transformation are among the major impacts caused by human activities. In this study, we are addressing the combined issues of the effect of CO₂ concentration increase and plant type on soil microbial activities by asking how annual and perennial plant groups affect soil microbial processes under elevated CO₂. The experimental design used a mix of species of different growth forms for both annuals and perennials. Our objective was: (1) to determine how two years of annual or perennial plant cover and CO₂ enrichment could affect Mediterranean soil microbial processes; (2) to test the resistance and the resilience of these soil functional processes after a natural perturbation. We determined the effects of 2 years atmospheric CO₂ enrichment on soil potential respiration (SIR), denitrification (DEA) and nitrification (NEA) activities. We could not find any significant effect of CO₂ increase on SIR, DEA and NEA. However, we found a strong effect of the plant cover type, i.e. annuals versus perennials, on the potential microbial activity related to N cycling. DEA and NEA were significantly higher in soil under annual plants while SIR was not significantly different. To determine whether these changes would survive a natural perturbation, we carried out a rain event experiment once the experimental treatments (i.e. different plant cover and atmospheric CO₂ concentration) were stopped. The soil potential respiration, as expressed by the SIR, was not affected and remained stable. DEA rates converged rapidly under annuals and perennials after the rain event. Under both annuals and perennials NEA increased significantly after the rain event but remained significantly higher in the soil with annual plants. The relative change of the soil microbial processes induced by annual and perennial plants was inversely related to the density and the diversity of the corresponding microbial functional groups.     

Impact of ultrafiltration membrane material on Peptide separation from a snow crab byproduct hydrolysate by electrodialysis with ultrafiltration membranes

Electrodialysis with ultrafiltration membrane (EDUF) is a technology based on the separation of molecules according to their charge and molecular mass. Some works have already successfully demonstrated the recovery of bioactive peptide fractions. However, the impact of ultrafiltration membrane (UFM) material, used in the EDUF system, on the peptide migration has never been studied. Consequently, the objectives of this work were (1) to evaluate the effect of two different UFM materials on the selective separation of peptides from a snow crab byproduct hydrolysate by electrodialysis with ultrafiltration membranes and (2) to determine the effect of UFM material on their potential fouling by peptides. It appeared that, after 6 h of EDUF separation using polyether sulfone (PES) and cellulose acetate (CA) UFM, peptides with low molecular weights ranging from 300 to 700 Da represented the most abundant population in the KCl1 (compartment located near the anode for the recovery of anionic/acid peptide fractions) and KCl2 (compartment located near the cathode for the recovery of cationic/basic peptide fractions) permeates. Peptides with molecular weights ranging from 700 to 900 Da did not migrate during the EDUF treatment. Moreover, only CA UFM allowed the recovery of high molecular weight molecules (900-20000 Da) in both KCl compartments. Peptides desorbed from PES and CA UFM after 6 h of EDUF separation had low molecular weights and belonged mainly to the 600-700 Da molecular weight range. These peptides represented a low proportion of the peptides initially present in the snow crab byproduct hydrolysate with individual molecular weight range proportions from 1.52 ± 0.31 to 10.2 ± 2.32%.     

Optimization of headspace solid-phase Microextraction (SPME) for the odor analysis of surface-ripened cheese

Fifty volatile compounds of surface smear-ripened cheese were detected and identified using headspace solid-phase microextraction (HS-SPME) and vacuum distillation coupled to gas chromatography-mass spectrometry. Changes in the headspace of aroma compounds were monitored over the whole packaging period (47 days) using the HS-SPME method. Initially, the concentration of methanethiol increased before reaching a plateau. This evolution could be linked to the growth of Brevibacterium linens. During the shelf life of cheese, levels of acetic acid and 3-methylbutanoic acid remained constant, whereas butane-2,3-dione, 3-hydroxybutan-2-one, and hydroxypropan-2-one levels gradually declined and acetone and 3-methylbutanol levels dropped sharply to a plateau. Changes in odor could be related to changes of the rind, which behaved as a barrier, strongly influencing the distribution of volatile compounds in the headspace. Using a gas chromatography-olfactometry technique without separation, it was shown that the SPME extract was representative of the cheese odor.     

Contamination of pastures by polycyclic aromatic hydrocarbons (PAHs) in the vicinity of a highway

To assess PAH contamination pastures, grass and soil samples have been collected from 10 m (d1), 50 m (d2), and 150 m (d3) perpendicular to a French highway (70,000 vehicles per day) and at a control site in a rural area away from nearby contaminating sources. Total PAH concentration ranges from 767 ng/g dry weight to 3989 ng/g dry weight, according to the matrix and the distance from the highway. Distance is not a significant factor for PAH deposition on grass, while in soil it has an effect between d1 and d2 or d3. The total PAH concentration in highway samples is 8 times higher than in control site samples for grass and 7 to 4 times higher for soil. Fluoranthene, pyrene, and phenanthrene are the major PAHs in grass samples at the control site and the highway, but the concentrations are about 5 times higher near the highway. In soil samples collected near the highway, the values of concentrations between all compounds are not statistically different. PAH deposition on grass is linked to the physicochemical properties of the compounds, which lead to a specific distribution of each molecule (according to their volatility and the number of aromatic rings) while no specific behavior is revealed in soil.     

Plasma Adrenocorticotropin Concentration in Healthy Horses and in Horses With Clinical Signs of Hyperadrenocorticism

Pituitary adenomas are commonly reported in older horses. The typical clinical signs associated with this condition, also known as equine Cushing's disease (ECD), are related to increased adrenocorticotropin (ACTH) production resulting in hyperadrenocorticism. The primary purpose of this study was to determine whether plasma ACTH concentrations differed between cushingoid and healthy horses. The second objective was to determine the effects of blood sample handling techniques on ACTH concentrations. A commercial human ACTH radioimmunoassay (RIA) was used to quantify equine plasma ACTH. Intra-assay and interassay variations, as well as dilutional parallelism were determined during the RIA validation. Plasma ACTH concentrations were evaluated in a group of healthy equids composed of 18 horses and 9 ponies, and in 22 equids with a clinical diagnosis of hyper adrenocorticism (11 horses and 11 ponies). The mean plasma ACTH concentrations in healthy horses and ponies, (18.68 ± 6.79 pg/mL (mean ± SD) and 8.35 ± 2.92 pg/mL, respectively), were significantly different (P = .009). The mean plasma ACTH concentration in horses and ponies with ECD, (199.18 ± 182.82 pglmL and 206.21 ± 319.56 pg/mL, respectively), were significantly higher than the mean ACTH concentration in the control animals (P < .001). Plasma ACTH concentrations appeared to be a sensitive and specific indicator of ECD in horses and ponies. ACTH concentrations measured in plasma samples kept at room temperature (19°C) as long as 3 hours after blood collection were not statistically different from those of samples kept at 1°C. J Vet Intern Med 1996;10:1–6. Copyright 1996 by the American College of Veterinary Internal Medicine .     

Polymorphonuclear proteolytic activity and milk composition change

Relationships between Quarter Milk Cell Count (QMCC) and Tank Milk Cell Count (TMCC) with milk biochemical and technological parameters in milk and dairy products were investigated. All parameters measured were affected by the increase of TMCC and QMCC between 0 and 600 000 cells/mL. The variable effect of lactation stage which is different for different authors, is discussed. The three mechanisms, measured during the inflammation of the udder, implicated in the modification of milk quality are described (a decrease in synthesis, a decrease in the milk barrier permeability and an increase in proteolytic activities). The direct effect of plasmin in caseinolysis is well known; the specific role of the increase of somatic cells (especially PMN) in the modification of milk quality is described. Several specific proteolytic activities of PMN are described and the impact of these activities on caseinolysis is evaluated. Two hypothetical mechanisms of caseinolysis by PMN are suggested and a synthetic scheme of the role of plasmin, bacteria and somatic cells in caseinolysis is discussed.     

Detection of Salmonella organisms and assessment of a protocol for removal of contamination in horse stalls at a veterinary teaching hospital

OBJECTIVES: To assess methods of detecting environmental contamination with Salmonella organisms and evaluate a cleaning and disinfection protocol for horse stalls in a veterinary teaching hospital. DESIGN: Original study. SAMPLE POPULATION: 37 horses with diarrhea likely to be caused by Salmonella infection and their stall environments. PROCEDURES: Fecal samples were collected from horses daily during hospitalization; samples were obtained from stall sites after cleaning and application of disinfectants. Fecal and environmental samples were cultured for Salmonella spp and tested via polymerase chain reaction (PCR) assay to detect Salmonella DNA. RESULTS: 1 horse died and 2 were discharged prior to sample collection. Fecal samples from 9 of 34 horses yielded growth of Salmonella organisms on bacteriologic culture, and 23 yielded positive results via PCR assay on > or = 1 occasion. Among environmental samples from 21 stalls, salmonellae were detected at > or = 1 stall site on 6 of 78 occasions, and > or = 1 stall site yielded positive results via PCR assay on 69 of 77 occasions. Salmonella DNA was detected more frequently in samples of stall drains, cracks, and corners. Salmonella spp were cultured from samples of 3 stalls after both initial and second cleaning and disinfection cycles, but no organisms were detected in samples obtained after use of a peroxygen disinfectant. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that stalls in which horses with salmonellosis were housed should only be used to accommodate newly hospitalized horses after samples (collected after 2 cycles of cleaning and disinfection) from drains, cracks, and corners yield negative results on bacteriologic culture.     

Development and validation of a radioimmunoassay for thyrotropin in cattle.

In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of this study was to develop and validate, under physiologic and pathologic conditions, a radioimmunoassay (RIA) for bovine TSH (bTSH). Double RIA was performed with purified bTSH and specific bovine antiserum. Laboratory validation included research of minimal detection limit, accuracy, and reproducibility. The physiologic validation included a thyrotropin-releasing hormone (TRH) challenge performed on euthyroid cows and a follow-up of bTSH concentration over a 24-hour period. Furthermore, bTSH concentration was assayed in a large population of healthy dairy and beef cows to define reference interval. The pathologic validation was made by assaying bTSH and thyroid hormones on healthy and goitrous newborn calves. The minimum detection limit (MDL) for bTSH assay was 1.3 microU/ml. The recovery was 101% to 106%. The intra- and interassay coefficients of variation (CVs) ranged from 5% to 11% and 11% to 15%, respectively. The RIA covered the whole range of physiologic bTSH values, as shown by bTSH values induced by TRH-challenge. A pulsatile secretion of bTSH was observed, accompanied by a diurnal variation with lower night values than day values. Reference intervals of bTSH ranged from 1.3 to 13.0 microU/ml for beef and dairy breeds. Finally, bTSH easily discriminated goitrous newborn calves from healthy ones, leading to the definition of a cutoff value of 35 microU/ml. The bTSH assay positively reacted to physiologic and pathologic conditions. The accuracy and precision of the RIA were satisfying.     

Evolution of Phytophthora infestans populations in the two most important potato production areas of France during 1992–96

Phytophthora infestans isolates, collected in the two most important potato production regions of France (Brittany during 1992–96 and northern France during 1994–96), were analysed for mating type, Gpi and Pep allozyme genotypes, mitochondrial DNA haplotypes, response to metalaxyl and virulence patterns in order to determine the structure of populations. 'New' populations, similar to those observed in northern Europe and characterized by the presence of both mating types, Gpi 90/100 Pep 83/100, Gpi 90/100 Pep 100/100, Gpi 100/100 Pep 100/100 and Gpi 100/100 Pep 83/100 allozyme genotypes, Ia and IIa mitochondrial haplotypes and common races 1.3.4.7, 1.4.10.11, 1.3.4.7.11 and 1.3.4.7.10.11 were present in both areas. A new allozyme genotype ( Gpi 90/90 Pep 83/100), never previously detected in Europe, was discovered in Brittany in 1992, but disappeared in later years. Despite the appearance of the A2 mating type in Brittany in 1996 and in northern France since 1995, both populations were highly homogeneous and probably consisted of a few related clones. No evidence for sexual recombination was obtained. Although Brittany, isolated from other potato production areas, and northern France, situated close to north European production areas where the A2 mating type was discovered some years ago, are two contrasted regions, no geographic substructuring was apparent between the two regions. However, variations in genotypic frequencies and in race composition were observed from one year to the next at a single site, as well as between several local sites during the same year. The role of possible evolutionary mechanisms implicated in these evolutions, especially founder effects, is discussed.