Kinetic evaluation of normal walking and jumping in cats, using a pressure-sensitive walkway

The kinetic parameters of the limbs of 23 normal, client-owned cats were evaluated by encouraging them to walk and jump normally on a pressure-sensitive walkway. Each cat was encouraged to walk across the walkway five times over a period of 30 to 45 minutes (by using food, toys, the owner's presence and a purpose-built tunnel) at a target speed of 0.6 m/s (and an acceleration of less than +/- 0.1 m/s(2)). They were then encouraged to jump on to the walkway from a height of 1 m five times at five-minute intervals. The kinetic parameters of peak vertical force (PVF) and vertical impulse (VI) were measured for each limb (the forelimbs only for the jumps), and expressed as a percentage of bodyweight (PVF(%BW) and VI(%BW/S)). Fifteen of the 23 cats satisfactorily completed three to five walks and two to five jumps that could be analysed. There were no significant differences between the PVF or VI of the left and right limbs, but both parameters were significantly greater for the forelimbs than the hindlimbs (P<0.001) for the walking data. The mean (sd) PVF(%BW) for the forelimbs and hindlimbs were 48.2 (6.0) and 38.3 (4.0), respectively, and the mean VI(%BW/s) were 16.9 (3.2) and 13.3 (2.8). Jumping down generated significantly greater PVF (P<0.01) and slightly greater VI than during walking; there were no significant differences between the left and right forelimbs. The mean PVF(%BW) was 148.9 (16.4) and the mean VI(%BW/s) was 18.1 (4.3).     

Leishmania-specific isotype levels and their relationship with specific cell-mediated immunity parameters in canine leishmaniasis

In the current retrospective study, Leishmania infantum-specific IgG, IgA and IgM levels were determined by ELISA in 106 untreated dogs with clinically-patent leishmaniasis (Sx) and in 171 clinically healthy dogs (Asx) from Spain to investigate the relationship between these Ig isotypes and clinical status. In addition, we studied if different Leishmania-specific humoral pattern exists between Asx dogs with and without cellular mediated immunity (CMI). Fifty-six dogs were assessed by means of lymphoproliferation assay (LPA), interferon production (IFN) and leishmanin skin test (LST), 71 dogs by means of both LPA and IFN and 44 only by LST. Both Sx and Asx dogs produced Leishmania-specific IgG, IgA and IgM antibodies, however the levels and proportion of positive dogs for each Ig isotype were significantly higher in Sx than in Asx ones (P<0.001). Analysis of immunological profiles determined for each cellular technique (positive and negative cellular response for each technique combined with positive or negative specific humoral response) showed that Asx dogs constituted a high heterogeneous group. No correlations were observed between CMI tests and specific IgG or IgM levels. However, a significant inverse correlation was demonstrated between specific IgA levels and LPA response (Spearman's r=-0.220; P=0.035). In general, the low correlation detected between CMI tests and isotype levels might indicate that the immune response is not strongly polarized in the majority of Asx dogs. Additionally, this study suggests that dogs developing T-cell response are probably able to avoid the dissemination of the parasite at least to mucosal surfaces and, as a consequence, to produce low or background specific IgA levels. Further studies are needed to investigate the relationship between specific IgA and parasite load, especially at mucosal site.     

Genetic variability among elite red clover ( Trifolium pratense L.) parents used in Chile as revealed by RAPD markers

Red clover (Trifolium pratense L.) is one of the main forage species of temperate regions. Cultivars of red clover are heterogeneous which makes their genetic analysis difficult. We applied RAPDs (Random Amplifed Polymorphic DNA) in order to assess the genetic relationship and levels of genetic variability existing among a group of 16 elite red clover parents organised in four subsets of 4 parents each. Out of 55 primers 21 provided reproducible results. A total of 135 reliable and polymorphic RAPD bands were detected which were used to estimate genetic distances among pair-wise combinations of elite parents. Nei and Li's similarity values ranged from 0.60 to 0.77, with a mean of 0.66, which reflects a rather high genetic variability among the genotypes evaluated. Lower levels of genetic variability, as detected by polymorphic loci and mean heterogeneity values, were detected in a subset of parents selected for resistance to the stem nematode. Cluster analyses resolved the different sets of parents in a manner consistent with what is known from their breeding origins. An Analysis of Molecular Variance detected substantial levels of variation within subsets of parents. RAPDs represent a valuable source of genetic information for red clover breeding programmes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of oil type on the amounts of acrylamide generated in a model system and in French fries

Acrylamide formation was studied by use of a new heating methodology, based on a closed stainless steel tubular reactor. Different artificial potato powder mixtures were homogenized and subsequently heated in the reactor. This procedure was first tested for its repeatability. By use of this experimental setup, it was possible to study the acrylamide formation mechanism in the different mixtures, eliminating some variable physical and chemical factors during the frying process, such as heat flux and water evaporation from and oil ingress into the food. As a first application of this optimized heating concept, the influence on acrylamide formation of the type of deep-frying oil was investigated. The results obtained from the experiments with the tubular reactor were compared with standardized French fry preparation tests. In both cases, no significant difference in acrylamide formation could be found between the various heating oils applied. Consequently, the origin of the deep-frying vegetable oils did not seem to affect the acrylamide formation in potatoes during frying. Surprisingly however, when artificial mixtures did not contain vegetable oil, significantly lower concentrations of acrylamide were detected, compared to oil-containing mixtures.     

Ammonium‐driven nitrification plays a key role in increasing Mn availability in calcareous soils

Background : Manganese deficiency often becomes a yield limiting factor, particularly on calcareous soils, even though the total soil manganese content is usually sufficient. Although it is known that acidifying N fertilizers can improve Mn availability, the reason of this effect is still unknown. Aim : Our aim was to investigate the effect of stabilized ammonium fertilizers as a tool to distinguish between physiological‐ and nitrification‐induced acidification. Method : Two pot experiments with Triticum aestivum L. and one soil incubation experiment using different nitrogen forms (CN = calcium nitrate, AN = ammonium nitrate, AS = ammonium sulfate, ATS = ammonium thiosulfate) with and without addition of nitrification inhibitors (DCD, Nitrapyrin, Piadin, DMPP) were conducted to examine the effect on Mn availability in the soil and Mn uptake by the plants at different development stages (EC 31 und 39). Results : With increasing fertilizer ${\mathrm{NH}}_4^{+}$ content a higher Mn concentration was detected: CN: 32 µg Mn g^?1 DM, AN: 39 µg Mn g^?1 DW, AS: 55 µg Mn g^?1 DM, ATS: 109 µg Mn g^?1 DM. The addition of a nitrification inhibitor resulted in a significantly lower rhizosphere pH compared to the non‐stabilized fertilizer. Surprisingly, the use of different nitrification inhibitors led to unchanged (CN, AN) or lower Mn concentrations of wheat. Especially in the ${\mathrm{NH}}_4^{+}$ treatments (AS and ATS), this negative effect was very evident (AS+DCD: 42 µg Mn g^?1 DM; ATS+DCD: 55 µg Mn g^?1 DM). Conclusions : Mn availability was enhanced by ongoing nitrification process rather than physiological acidification. Compared to other N forms, ammonium thiosulfate led to the highest Mn availability in bulk soil.     

Effect of tillage and N fertilization on microbial physiological profile of soils cultivated with wheat

Microbial diversity might be a good indicator of ecosystem disturbance and functioning. We determined the effect of soil disturbances, such as N fertilization and tillage management, on soil microbial communities in a Typic Argiudoll of the El Salado river basin (Argentina). Microbial activity and substrate utilization provided a metabolic fingerprint of the soil microbial community. Univariate and multivariate analyses were used to differentiate responses to N fertilization and tillage at each of three growth stages of wheat (Triticum aestivum L.). Tillage had an adverse effect on microbial diversity, in which reduced and conventional tillage treated soils had different populations. However, N fertilization also altered microbial diversity depending on the crop developmental stage considered. Metabolism of carboxylic acids and carbohydrates were the main indicators of functional microbial activity and diversity. Although the substrate consumption profile of 32 C substrates did not provide insights into the fundamental ecological interactions that may induce changes in microbial population, it allowed us to demonstrate the alterations of microbial diversity as a result of tillage. We conclude that tillage and N fertilization altered microbial diversity.     

Rapid determination of inorganic and methyl mercury in fish

A method has been developed that uses a mixed solution of NaOH, NaCl and cysteine to digest fish. Inorganic Hg and MgHg were determined by cold vapor atomic absorption (CVAAS) using a selective reduction step with SnCl₂ and SnCL₂-solutions. Ethyl alcohol was satisfactorily used to prevent excessive foaming. Two optimum digestion procedures were established: (1) using a dry block heater at 90 °C for 1 hr and (2) overnight digestion at 25 to 30 °C. Differences between both were not significant (95%) in the range of 30 to 500 ng g^?1 Hg (II) and MeHg in fish. Reduction of the Hg signal due to matrix effects in different fish species was evaluated (95 to 60%). Oily fish, shrimp and lobsters gave the highest reduction. Internal calibration by addition of Hg standards are strongly recommended when exact determinations are needed. The detection limit obtained was near 10 ng g^?1. Signals were linear in the concentration range studied (30 to 500 ng g^?1). Accuracy of analyses was in the order of 5% or better, with a relative standard deviation of 5%. The method could be applied to other environmental matrices: hair, urine and blood, with some modifications.