Predicting the degree of phosphorus saturation using the ammonium acetate–EDTA soil test

As a result of the important role played by phosphorus (P) in surface water eutrophication, the susceptibility of soils to release P requires evaluation. The degree of phosphorus saturation, assessed by oxalate extraction (DPS_ox), has been used as an indicator. However, most laboratories do not include DPS_ox in routine soil tests because of cost and time. This study evaluates the suitability of the ammonium acetate extraction in the presence of EDTA (AAEDTA), the standard soil test P (STP) in Wallonia (Southern Belgium), to predict DPS_ox; we also compared it with the Mehlich 3 extraction. Ninety‐three topsoil samples were collected in agricultural soils throughout Wallonia. Good correlations were found between the AAEDTA and the Mehlich 3 methods for P, Fe and Al (r = 0.85, 0.77 and 0.86, respectively). An exponential relationship was found between P_AAEDTA and DPS_ox. Results of principal component analysis and regression demonstrated that STP can be used to predict DPS_ox (r = 0.93) after logarithmic transformation. Soil test Al was also a good indicator of the P sorption capacity (PSC_ox) of soils (r = 0.86). Including the clay fraction in regression equations only slightly improved the prediction of PSC_ox (r = 0.90), while other readily available data (such as pH or organic carbon) did not significantly improve either DPS_ox or PSC_ox predictions.     

Re-examination of inhibitor resistance conferred by Qo-site mutations in cytochrome b using yeast as a model system

Cytochrome b from yeast (Saccharomyces cerevisiae Meyer ex Hansen) provides a convenient model system for the study of Qo-site inhibitor (QoI) resistance mutations from a variety of organisms. QoI resistance mutations from fungal plant pathogens (G143A and F129L), malaria agent Plasmodium sp (Y279C/S), and Pneumocystis carinii (L275F), an opportunistic pathogenic fungus of man, were introduced into yeast cytochrome b and their effect on the binding of a variety of natural (myxothiazol and stigmatellin) and synthetic (atovaquone, azoxystrobin and pyraclostrobin) inhibitors to the bc1 complex monitored. L275S (from a myxothiazol-resistant yeast) was also re-examined. Stigmatellin binding was relatively unaffected by the introduction of these mutations. Significant increases in resistance were observed for the strobilurin-class inhibitors myxothiazol, azoxystrobin and pyraclostrobin, with the largest increase in resistance conferred by G143A. In contrast, atovaquone binding was most effected by Y279C/S and L275S. Notably, F129L, G143A and L275S had a minor effect on bc1 activity, and so are unlikely to confer significant fitness penalties in vivo. These data are discussed in the light of the atomic structures for myxothiazol- and azoxystrobin-inhibited bovine bc1 which have recently become available. We propose that QoI resistance due to G143A arises from steric hindrance between the inhibitor and cytochrome b, whereas the mechanism of resistance for the other mutations is due to an increase in binding energy between the protein and inhibitor molecule. Site-directed mutagenesis was also used to model selected regions of the mammalian Qo site in yeast cytochrome b in order to further understand the differential efficacy of these QoI in the mammalian and pathogen bc1 complexes.     

A technique for creating critical-size defects in the metatarsus of sheep for use in investigation of healing of long-bone defects

OBJECTIVE: To develop a technique for use in investigation of healing of long-bone defects by creation of a critical-size defect in the left metarsal III and IV bone (metatarsus) of sheep. ANIMALS: 18 healthy adult sheep. PROCEDURE: Sheep were allocated to 4 groups (3, 3, 5, and 7 sheep in groups 1 to 4, respectively). An ostectomy with various segmental length-to-diaphyseal diameter ratios (0.5, 1.0, 2.0, and 2.0 for groups 1 to 4, respectively) was performed on the left metatarsus of each sheep. The defect was left empty in sheep of groups 1, 2, and 3, whereas the defect was filled with a massive corticocancellous bone autograft in sheep of group 4. RESULTS: All sheep tolerated the surgical procedure well and were able to use the affected limb the day after surgery. Radiographic and histologic examinations conducted 16 weeks after surgery revealed nonunion in all sheep of groups 1, 2, and 3, whereas consistent bone healing with abundant bone formation was observed in all sheep of group 4. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of these findings suggests that the sheep metatarsal model is a critical-size defect model with low morbidity. It should allow the assessment of new technologies for bone regeneration in conditions closely mimicking the clinical setting. IMPACT FOR HUMAN MEDICINE: Use of this technique in sheep should be of benefit for the preclinical study of osteoconductive, osteoinductive, or osteogenic biomaterials for use in humans.     

Use of rotary fluidized-bed technology for development of sustained-release plant extracts pellets: potential application for feed additive delivery

The aim of this study was to develop sustained release plant extracts as a potential alternative to antibiotic growth promoters for growing pigs. Pellets with a core based on microcrystalline cellulose and 3 active compounds (eugenol, carvacrol, and thymol) were prepared using rotary fluidized-bed technology. Two particle sizes were produced that had a mean size of approximately 250 and 500 mum. Results show the process was able to produce pellets with a spherical and homogenous form when 10% of the active compounds were incorporated into the core. When active compounds were increased to 20%, the pellet became stickier, and the yield decreased from 90 to 65%. Different amounts of coating in the form of an aqueous-based ethylcellulose (EC) dispersion (Surelease) were applied to the core to modify the release of active compounds. The efficacy of the coating was evaluated in vitro using a flow-through cell apparatus. The time to achieve 50 and 90% dissolution increased with the increase in particle size (P < 0.05) and the increase in EC-coating level from 10 to 20% (wt/wt; P < 0.05), indicating the ability of the process to slow release depending on particle size and the amount of polymer applied. Differences in the release of the active compounds were observed in the same formulation of pellets, except for the formulation with small 10%-EC-coated particles, in which the active compounds were rapidly dissolved (more than 85% in 15 min or less). For all other formulations, the dissolution time for eugenol was always faster than for thymol or carvacrol. The close monitoring of plant extract behavior in the gastrointestinal tract could become a key factor in the continued use of phyto-molecules as alternatives to antibiotic growth promoters and in optimizing the balance between cost and efficacy. Different microencapsulation technologies can be used, of which the rotary fluidized bed warrants consideration because of the quality of the products obtained.     

Advances in characterization of soil clay mineralogy using X‐ray diffraction: from decomposition to profile fitting

Structural characterization of soil clay minerals often remains limited despite their key influence on soil properties. In soils, complex clay parageneses result from the coexistence of clay species with contrasting particle sizes and crystal chemistry and from the profusion of mixed layers with variable compositions. The present study aimed to characterize the mineralogy and crystal chemistry of the <2 μm fraction along a profile typical of soils from Western Europe and North America (Neo Luvisol). X‐ray diffraction (XRD) patterns were interpreted using: (i) the combination of XRD pattern decomposition and indirect identification from peak positions commonly applied in soil science; and (ii) the multi‐specimen method. This latter approach implies direct XRD profile fitting and has recently led to significant improvements in the structural characterization of clay minerals in diagenetic and hydrothermal environments. In contrast to the usual approach, the multi‐specimen method allowed the complete structural characterization of complex clay parageneses encountered in soils together with the quantitative analysis of their mineralogy. Throughout the profile, the clay paragenesis of the studied Neo Luvisol systematically includes discrete smectite, illite and kaolinite in addition to randomly interstratified illite‐smectite and chlorite‐smectite. Structural characteristics of the different clay minerals, including the composition of mixed layers, did not vary significantly with depth and are thus indicative of the parent material. The relative proportion of the <2 μm fraction increased with increasing depth simultaneously with smectite relative proportion. These results are consistent with the leaching process described for Luvisols in the literature.     

Experimental viral myocarditis: parvoviral infection of neonatal pups

Myocarditis was produced in seronegative five-day-old pups by oral and by intraperitoneal inoculation of canine parvovirus. The disease was subclinical. Histologic lesions were compatible with, but less extensive than, those seen in naturally occurring canine parvoviral myocarditis. In pups necropsied 23 days after inoculation, scattered cardiac myocytes contained intranuclear inclusion bodies, and virus-infected myocytes were demonstrated by immunofluorescence. Degeneration and loss of cardiac myocytes usually was not associated with a cellular infiltrate. At 51 days after inoculation, the myocardium contained an extensive lymphocytic infiltrate which was sometimes associated with fragmented myocytes, and was often contiguous with areas of interstitial fibrosis. At 108 days after inoculation, inflammatory lesions had regressed, and there were multifocal areas of myocardial fibrosis.     

Eosinophilic enteritis in a specific-pathogen-free cat

Moderate to severe, chronic, segmental eosinophilic enteritis was diagnosed histopathologically in a 2-year-old, specific-pathogen-free cat. Peripheral eosinophilia was not observed, although eosinophilic infiltrates were found in mesenteric lymph nodes. Typical gastrointestinal signs characteristic of this disease (diarrhea, vomiting, and anorexia) were not seen; only weight loss was observed. Treatment was not instituted. Previously reported cases of feline eosinophilic enteritis have been associated with several domestic breeds having a diversity of backgrounds. The cat of this report had a known genealogy and disease-free history, was reared under barrier conditions, and was fed a restricted diet. The cause of the disease in this cat was not determined.     

Prevalence of anti-Toxoplasma gondii antibodies in serum and aqueous humor samples from cats with uveitis or systemic diseases in France

The present study sought to elucidate whether Schistosoma japonicum eggs could survive a passage through dogs and chickens. Three dogs and three chickens were used for the experiment. The dogs were allowed to eat goat faeces containing 80 S. japonicum eggs per gram. The chickens were given 2 ml of water containing more than 100 S. japonicum eggs per ml. The hatchability of the eggs was 51.8% prior to administration. All faeces were collected for 3 days from the dogs and for 2 days from the chickens and egg excretion and hatchability were measured. The results showed that nearly 50% of the eggs administered to the dogs were recovered in the faeces during the first 2 days and during the first 25 h 39% of the recovered eggs were viable and able to hatch. In the chickens 9% of the administered eggs were recovered within 27 h and within the first 3.5 h after administration 19% of the recovered eggs were viable and able to hatch. The results suggest that both dogs and chickens may act as transport hosts for S. japonicum in endemic areas.