Regulation of mycorrhiza development in durum wheat by P fertilization: Effect on plant nitrogen metabolism

The aim of this work was to study the effect of arbuscular mycorrhizal fungus Glomus mosseae on growth and nitrogen (N) metabolism of durum wheat (Tritcum durum) under various P soil contents. The analyses were extended to macro and micronutrient tissue concentrations, nitrate reductase and glutamine synthetase activities, as well as protein, aminoacids, pyridine dinucleotides and adenine nucleotides. Arbuscular mycorrhiza increased wheat growth in soil in which P availability was low and nitrate was the dominant N form. The root colonization occurred at the highest level in plants grown in limiting soil P and was inversely related to soil P content. The micorrhizal wheat plants contained also the highest concentrations of macro (P, K, Ca, N) and micronutrients (Fe, Zn, Mn) as well as free amino acids, protein, NAD, NADP, AMP, ADP, ATP in roots and leaves. In particular, the micronutrient tissue concentrations (Zn, Mn) supported that mycorrhiza actively modulated their uptake limiting interferences and optimizing growth better than the plant roots, like a very efficient “rootstock”. Control plants grown at the highest soil P did not reach the same concentration as the mycorrhizal plants. Nitrate reductase activities in the roots of mycorrhizal plants were higher than in the control ones, while glutamine synthetase activities were highest in the leaves. Protein and amino acids concentrations, as well as AMP, ADP, ATP, NAD(P), and NAD(P)H were also higher than in the control. Among the free amino acids in the roots, the high levels of glutamine, asparagine, arginine, support the view that ammonium was transferred through the arbuscules to the root cells where it was re‐assimilated in the cortical cells, forming high N : C ratio‐amino acids. They were transferred to the leaves where all the other N compounds could be largely synthesized using the carbon skeletons supplied by photosynthesis.     

Litter-fall and litter decomposition in a low Mediterranean shrubland

Annual production of litter by Cistus incanus (L.) and Myrtus communis (L.) and decomposition dynamics of leaf litter of these species was studied in a Mediterranean shrubland. Myrtus and Cistus produced 472 and 429 g dry weight litter m^-2 year^-1, respectively. Leaves were the predominant litter component for both species. The average decay constant of Myrtus and Cistus litters enclosed in litter bags, calculated over the whole study period (38 months), was 0.71 year^-1 and 0.31 year^-1 respectively. In green leaves the N content differed during growth seasons for both species, whereas the content of Ca, Mg, P, K, and Na did not show significant changes. Abscised leaves had lower N, P and K contents than green leaves, evidencing that a nutrient translocation before abscission occurred from senescent leaves. The nutrient contents of the leaves at abscission time, generally higher in Cistus than in Myrtus, allowed us to estimate the annual nutrient input to the soil. Phosphorus and K more than N were rapidly released by the decomposing litters after exposure. Nutrient limitation, in particular P, might be considered the main growth limiting factor for Myrtus and Cistus. Both species were adapted to recovery and rapidly recycle P more than N and K in the living biomass through retranslocation from green leaves before abscission and/or a high release rate from the decomposing litter. The former strategy was better used by Cistus, the latter by Myrtus.     

Evaluation of a portable lactate analyzer (Lactate Scout) in dogs

BACKGROUND: Measurement of blood lactate concentration has become a common practice in canine medicine. However, the accuracy of portable lactate monitors has not been reported in dogs. OBJECTIVES: The aim of this study was to evaluate the accuracy and precision of a portable analyzer (Lactate-Scout) in measuring canine blood lactate concentration. METHODS: A preliminary study was performed to assess the effects of sample storage time and temperature on plasma lactate concentration. Blood samples obtained from 6 canine patients at our hospital were divided into 8 aliquots and stored at 4 degrees C and 20 degrees C; plasma lactate was measured in duplicate with a spectrophotometric system (Konelab) at 0, 30, 60, 120, and 240 minutes after the blood collection. Values were compared with those obtained immediately after blood collection. Lactate values obtained by the portable method also were compared with those obtained by the reference spectrophotometric analyzer on blood samples collected from 48 additional canine patients. RESULTS: There was no significant effect of storage time (P = .89) or temperature (P = .51) on plasma lactate levels. The correlation between lactate values measured with the Lactate-Scout and the Konelab method was r = .98 (slope = .81, 95% confidence interval = .73-.87; intercept = .20, 95% confidence interval = .13-.31). The level of agreement between the 2 methods was generally good for mean lactate concentrations <5 mmol/L. However, at higher lactate concentrations (5 of 48 samples), the values recorded by the Lactate-Scout analyzer were lower than those measured by the Konelab method. CONCLUSION: The Lactate-Scout analyzer is reliably comparable to a reference method for measuring whole blood lactate concentration in dogs; however, caution should be used when interpreting lactate values of 5 mmol/L and higher.     

Microbial enzyme activities,fungal biomass and quality of the litter and upper soil layer in a beech forest of south Italy

Forest soils contain a large amount of organic matter (OM) and therefore represent a considerable carbon reserve. The amount of OM sequestered in the soil is dependent on annual input of litter and its quality. The aim of this study was to investigate the quantity and quality of OM, the microbial capacity to degrade it and its recalcitrance to further degradation, by considering some extracellular enzyme activities in a beech (Fagus sylvatica L.) forest in south Italy (Mediterranean area). Our attention was focused on the decomposition continuum of the litter horizon and upper soil layer. Because fungi are the major decomposers of plant material, fungal biomass was also measured and its relationship with enzyme activities was tested. The results showed that: (i) the litter horizon and the upper soil layer differed in chemical characteristics and biological activities; (ii) within the litter horizon, the three layers detected for their different degree of degradation (L, recently fallen, not decomposed and not compressed material; F, partially decomposed and fragmented but macroscopically recognizable material; H, compressed and strongly fragmented) differed more in chemical characteristics than in biological activities; (iii) the enzyme activities and fungal biomass changed during the study period but a clear relationship with succession of seasons was evident only for cellulase, laccase, peroxidase and fungal biomass; and (iv) the upper soil layer included 42% OM and less than 50% of that was susceptible to further decomposition. This percentage was 30% in the OM of L.     

Evaluation of conventional and organic italian foodstuffs for deoxynivalenol and fumonisins B(1) and B(2)

Two lots of human foodstuffs from conventional and organic brand foods were purchased from supermarkets and analyzed for three Fusarium toxins, deoxynivalenol, by GC-ECD, and fumonisins B(1) and B(2) (FB(1)-FB(2)), by LC-MS. The occurrence of deoxynivalenol contamination was higher than 80% in both organic and conventional foods; fumonisin B(1) was found in 20% of organic foods and in 31% of conventional ones and fumonisin B(2) in more than the 32% of the food samples from both the agricultural practices. The highest median concentration of deoxynivalenol occurred in conventional rice-based foodstuffs (207 microg/kg): that of fumonisin B(1) in conventional maize-based foods (345 microg/kg) and that of fumonisin B(2) in organic wheat-based foods (210 microg/kg).     

Lignin and cellulose degradation and nitrogen dynamics during decomposition of three leaf litter species in a Mediterranean ecosystem

Cellulose and lignin degradation dynamics was monitored during the leaf litter decomposition of three typical species of the Mediterranean area, Cistus incanus L., Myrtus communis L. and Quercus ilex L., using the litter bag method. Total N and its distribution among lignin, cellulose and acid-detergent-soluble fractions were measured and related to the overall decay process. The litter organic substance of Cistus and Myrtus decomposed more rapidly than that of Quercus. The decay constants were 0.47 year⁻¹, 0.75 year⁻¹ and 0.30 year⁻¹ for Cistus, Myrtus and Quercus, respectively. Lignin and cellulose contents were different as were their relative amounts (34 and 18%, 15 and 37%, 37 and 39% of the overall litter organic matter before exposure, for Cistus, Myrtus and Quercus, respectively). Lignin began to decrease after 6 and 8 months of exposure in Cistus and Myrtus, respectively, while it did not change significantly during the entire study period in Quercus. The holocellulose, in contrast, began to decompose in Cistus after 1 year, while in Quercus and Myrtus immediately. Nitrogen was strongly immobilized in all the litters in the early period of decay. Its release began after the first year in Cistus and Myrtus and after 2 years of decomposition in Quercus. These litters still contained about 60, 20 and 90% of the initial nitrogen at the end of the experiment (3 years). Prior to litter exposure nitrogen associated with the lignin fraction was 65, 54 and 37% in Cistus, Myrtus and Quercus, while that associated with the cellulose fraction was 30, 24 and 28%. Although most of the nitrogen was not lost from litters, its distribution among the litter components changed significantly during decomposition. In Cistus and Myrtus the nitrogen associated with lignin began to decrease just 4 months after exposure. In Quercus this process was slowed and after 3 years of decomposition 8% of the nitrogen remained associated with lignin or lignin-like substances. The nitrogen associated with cellulose or cellulose-like substances, in contrast, began to decrease from the beginning of cellulose decomposition in all three species. At the end of the study period most of the nitrogen was not associated to the lignocellulose fraction but to the acid-detergent-soluble substance (87, 88 and 84% of the remaining litter nitrogen).     

Validation of 2 techniques for electrocardiographic recording in dogs and cats

BACKGROUND: Standard electrocardiographic (ECG) recording in the dog and cat is commonly performed in right lateral recumbency, by connecting the ECG leads to the skin of the patient via metallic alligator clips. The jaws of the alligator clips are usually filed or flattened to reduce their uncomfortable pressure on the patient's skin. However, filed and flattened alligator clips can occasionally lose their grip to the skin, causing lead detachment during standard ECG recording. HYPOTHESIS: The aim of the study was to validate two novel ECG recording techniques ("gel" and "pads"). ANIMALS: Six-lead standard ECG recording was obtained from 42 dogs and 40 cats using the standard technique, as well as the two novel methods. METHODS: Measurements were taken of the amplitude and duration of P waves and QRS complexes, duration of PQ and QT intervals, and mean electrical axis (MEA). In each recording, five representative complexes were measured, and the results were averaged for each parameter. RESULTS: A good quality ECG recording was obtained with all the three different techniques, although a degree of wandering trace was observed in one third of cats with the "pads" technique. Bland-Altman analysis showed good agreement between the ECG values recorded with the two novel techniques and those recorded with the standard traditional technique. Furthermore, the observed differences were not clinically relevant, except for the R wave amplitude recorded with the "pads" method in cats (-0.35 to 0.37 mV). CONCLUSIONS AND CLINICAL IMPORTANCE: In conclusion, this study supports the reliability and clinical validity of the "gel" and "pads" techniques for ECG recording both in the dog and the cat, with some limitations for the "pads" technique in cats.     

Children's exposure to Di(2-ethylhexyl)phthalate and dibutylphthalate plasticizers from school meals

Packed school meals for children 3-10 years old were studied to evaluate the levels of di(2-ethylhexyl)phthalate (DEHP) and di-n-butylphthalate (DBP) and the influence of the packaging process on meal contamination, and their contribution to daily intake was estimated. The packaging consisted of polyethylene-coated aluminum (PE/Al) dishes thermally welded by a polyethyleneterephthalate-coated aluminum (PET/Al) foil. Foodstuffs before processing were analyzed, too. Total meals before packaging and after packaging were collected. It was found that 92% of foodstuffs employed in meal preparation contained DEHP, and 76% of them DBP, at detectable levels. In cooked foods before packaging the DEHP median concentration levels varied from 111.4 to 154.8 ng/g ww and those of DBP between 32.5 and 59.5 ng/g ww. In packed meals the DEHP median values ranged from 127.0 to 253.3 ng/g ww, and DBP median values varied from 44.1 to 80.5 ng/g ww. The mean increases of median concentrations of DEHP in cooked foods before and after packaging were 113 and 125% for DBP. For nursery and primary school children DEHP intake via school meals can raise on average the respective EFSA TDI by 18 and 12% and that of DBP by 50 and 30%.