Clinical outcome of nonnasal chondrosarcoma in dogs: thirty-one cases (1986-2003)

OBJECTIVE: To evaluate metastatic rate and survival times of dogs with chondrosarcoma of nonnasal bony sites treated by wide surgical excision. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=31) with chondrosarcoma. METHODS: Medical records were retrospectively reviewed to identify dogs with chondrosarcoma of bone in potentially surgically accessible sites. When complete information was not available in the medical record, owners and referring veterinarians were contacted by telephone to evaluate the course of disease and survival times. When possible, histopathologic diagnosis was confirmed by a single board certified pathologist and tumors were histologically graded. RESULTS: Dogs treated by wide surgical excision (n=18) had a mean survival time of 3097 days and did not reach median survival time. Dogs untreated except for diagnostic biopsy (n =13) had a median survival time of 523 days and a mean survival time of 495 days. Method of treatment and tumor grade predicted survival time (P=.016 and P=.007, respectively). Metastatic rate was 28% for treated dogs and 15% for untreated dogs, with no significant difference between the 2 groups (P=.39). CONCLUSIONS: Wide surgical excision significantly improves survival time for dogs with chondrosarcoma of nonnasal bony sites, but does not affect the likelihood of metastasis. Grade may be prognostic for survival. CLINICAL RELEVANCE: Surgical excision benefits dogs with chondrosarcoma and can result in prolonged survival times. Metastasis still occurs in approximately 1 of 4 dogs even after surgical resection.     

Sequence-optimised E2 constructs from BVDV-1b and BVDV-2 for DNA immunisation in cattle

We report DNA immunisation experiments in cattle using plasmid constructs that encoded glycoprotein E2 from bovine viral diarrhoea virus (BVDV)-1 (E2.1) and BVDV-2 (E2.2). The coding sequences were optimised for efficient expression in mammalian cells. A modified leader peptide sequence from protein gD of BoHV1 was inserted upstream of the E2 coding sequences for efficient membrane export of the proteins. Recombinant E2 were efficiently expressed in COS7 cells and they presented the native viral epitopes as judged by differential recognition by antisera from cattle infected with BVDV-1 or BVDV-2. Inoculation of pooled plasmid DNA in young cattle elicited antibodies capable of neutralising viral strains representing the major circulating BVDV genotypes.     

Organic matter in density fractions of water-stable aggregates in silty soils: Effect of land use

The location of soil organic matter (SOM) within the soil matrix is considered a major factor determining its turnover, but quantitative information about the effects of land cover and land use on the distribution of SOM at the soil aggregate level is rare. We analyzed the effect of land cover/land use (spruce forest, grassland, wheat and maize) on the distribution of free particulate organic matter (POM) with a density <1.6 g cm⁻³ (free POM_<1.6), occluded particulate organic matter with densities <1.6 g cm⁻³ (occluded POM_<1.6) and 1.6-2.0 g cm⁻³ (occluded POM_1.6-2.0) and mineral-associated SOM (>2.0 g cm⁻³) in size classes of slaking-resistant aggregates (53-250, 250-1000, 1000-2000, >2000 μm) and in the sieve fraction <53 μm from silty soils by applying a combined aggregate size and density fractionation procedure. We also determined the turnover time of soil organic carbon (SOC) fractions at the aggregate level in the soil of the maize site using the ¹³C/¹²C isotope ratio. SOM contents were higher in the grassland soil aggregates than in those of the arable soils mainly because of greater contents of mineral-associated SOM. The contribution of occluded POM to total SOC in the A horizon aggregates was greater in the spruce soil (23-44%) than in the grassland (11%) and arable soils (19%). The mass and carbon content of both the free and occluded POM fractions were greater in the forest soil than in the grassland and arable soils. In all soils, the C/N ratios of soil fractions within each aggregate size class decreased in the following order: free POM_<1.6>occluded POM_<1.6-2.0>mineral-associated SOM. The mean age of SOC associated with the <53 μm mineral fraction of water-stable aggregates in the Ap horizon of the maize site varied between 63 and 69 yr in aggregates >250 μm, 76 yr in the 53-250 μm aggregate class, and 102 yr in the sieve fraction <53 μm. The mean age of SOC in the occluded POM increased with decreasing aggregate size from 20 to 30 yr in aggregates >1000 μm to 66 yr in aggregates <53 μm. Free POM had the most rapid rates of C-turnover, with residence times ranging from 10 yr in the fraction >2000 μm to 42 yr in the fraction 53-250 μm. Results indicated that SOM in slaking-resistant aggregates was not a homogeneous pool, but consisted of size/density fractions exhibiting different composition and stability. The properties of these fractions were influenced by the aggregate size. Land cover/land use were important factors controlling the amount and composition of SOM fractions at the aggregate level.     

Contribution of nitrification and denitrification to the emission of N2O in a freeze‐thaw event in an agricultural soil

The amounts of N₂O released in freeze‐thaw events depend on site and freezing conditions and contribute considerably to the annual N₂O emissions. However, quantitative information on the N transformation rates in freeze‐thaw events is scarce. Our objectives were (1) to quantify gross nitrification in a Luvisol during a freeze‐thaw event, (2) to analyze the dynamics of the emissions of N₂O and N₂, (3) to quantify the contribution of nitrification and denitrification to the emission of N₂O, and (4) to determine whether the length of freezing and of thawing affects the C availability for the denitrification. ¹⁵NO was added to undisturbed soil columns, and the columns were subjected to 7 d of freezing and 5 d of thawing. N₂O emissions were determined in 3 h intervals, and the concentrations of ¹⁵N₂O and ¹⁵N₂ were determined at different times during thawing. During the 12 d experiment, 5.67 mg NO ‐N (kg soil)^–1 was produced, and 2.67 mg NO ‐N (kg soil)^–1 was lost. By assuming as a first approximation that production and loss occurred exclusively during thawing, the average nitrate‐production rate, denitrification rate, and immobilization rate were 1.13, 0.05, and 0.48 mg NO ‐N (kg soil)^–1 d^–1, respectively. Immediately after the beginning of the thawing, denitrification contributed by 83% to the N₂O production. The ratios of ¹⁵N₂ to ¹⁵N₂O during thawing were narrow and ranged from 1.5 to 0.6. For objective (4), homogenized soil samples were incubated under anaerobic conditions after different periods of freezing and thawing. The different periods did not affect the amounts of N₂ and N₂O produced in the incubation experiments. Further, addition of labile substrates gave either increases in the amounts of N₂O and N₂ produced or no changes which suggested that changes in nutrient availability due to freezing and thawing are only small.     

Effectiveness of Protective Layers in Reducing Metal Fluxes from Flooded Pre-Oxidized Mine Tailings

A problem in implementing water covers over existing tailingimpoundments is the dissolution of minerals produced throughoxidation and the subsequent flux of metals into the water cover.One possible solution is to place a protective layer of non-reactive soil at the tailings/water interface to inhibit metaltransport. A laboratory evaluation of different water coversystems was performed employing columns packed with tailingssubmerged beneath 1 m of water. A ten-centimeter layer of sand orpeat was placed at the tailings/water interface. The experimentswere kept stagnant for 183 days, and then flushed with water at asteady rate for 468 days. Both protective covers prevented degradation of water cover qualityfor the duration of the experiments, as pH exceeded 5.5; however,the quality of the tailings pore water remained poor and evendeclined slightly from pH > 4 to pH < 3. Leaching of iron andsulphate from the tailings with a sand protective layer ceasedduring the experiments. Conversely, in the columns with a peatlayer, substantial leaching of metals and sulphate from thetailings continued to the end of the experiments. It ispostulated that the peat is a source of chelating agents, such asorganic acids, which are known to accelerate the dissolution ofcertain minerals formed through weathering. The sensitivity ofmetal transfer rates to the thickness and type of protectivecover above the tailings were modelled. A 10-cm peat layer waspredicted to prevent substantial degradation of the water coverfor at least ten years.     

Vertical porosity profile of a clay-rich marsh soil

The evolution of clay soil porosity is currently demonstrated via the shrinkage curves in a large water content domain spreading from a shrinkage limit to a liquidity limit. In fact, the parallel between in situ profiles and the shrinkage curves in such a large water content range is difficult to obtain because of the lack of earth pressure in the laboratory tests and in situ limited water contents. The vertical distribution of porosity throughout a clay-rich marsh soil profile was studied in a grassland field with samples taken from the soil surface characterized by water contents near their shrinkage limit down to 2.00 m deep saturated sediments over their liquidity limit. The depth of the plasticity limit isolates a soil in a solid state characterized by a vertical prism-like structure from a plastic to pseudo-liquid state in depth. The porosity was calculated from the measurements of the density of intact samples by double weighing and image analysis of 100 cm² polished sections. The initial structure of clay soil was maintained by impregnation based on water–acetone–resin exchange. An ultraviolet photo luminescent pigment added to the resin allowed the capture of images from which shrinkage cracks and microporosity of the clay matrix were easily separated. The distribution of porosity between the shrinkage crack mesoporosity and the clay matrix microporosity was evaluated after the mathematical decomposition of the grey level curves characteristic of each level. Vertical evolution of the porosity distribution from the soil surface in a solid state to the plastic and pseudo-liquid sediment in depth was presented on the shrinkage curve of the clay material. The measurements point out how the clay matrix microporosity and mesoporosity of shrinkage cracks are complementary and the role of the scale effect on the shrinkage curve. The analysis of images captured on an optical microscope under polarized and analyzed light and the SEM observation of freeze-dried samples demonstrated the isotropic arrangement of the clay particles in typical “honey-comb” architecture in the in situ plastic-to-liquid saturated domain. Eventually the distribution of porosity through the profile results from the evolution of the initial “honey-comb” microstructure of the sediment induced by the desiccation phenomenon. It is governed by the depth of plasticity limit of the clay material and by the depth of the water table.     

New method for a two-step hydrolysis and chromatographic analysis of pectin neutral sugar chains

A new method for the determination of the main neutral sugars in pectin has been developed. The sample preparation involves a mild chemical attack followed by an enzymatic hydrolysis. The completeness and nondestructive character of the method are demonstrated by comparison of the results obtained with different acids such as H2SO4, HCl, and trifluoroacetic acid (TFA) at different concentrations (2, 1, or 0.2 M) at two temperatures (80 or 100 degrees C). The chemical hydrolysis of pectin neutral sugar chains with strong acid (1 or 2 M) and high temperature (100 degrees C) shows that the liberation of the pectin sugars is not realized at the same rate for each sugar. Different optimum conditions are thus obtained. However, the chemical pectin hydrolysis with 0.2 M TFA at 80 degrees C is characterized by the liberation of pectin neutral sugar side chains without any degradation within 72 h of hydrolysis. Under these conditions, the liberation of some pectin sugars, essentially galactose, glucose, and rhamnose, was not complete. An enzymatic hydrolysis is necessary to obtain a complete release of all the sugars. The combination of the two treatments, a chemical hydrolysis realized with diluted acid (0.2 M) for 72 h at low temperature (80 degrees C) on one hand and an enzymatic hydrolysis on the other hand, allow a total liberation of pectin sugars. The quantitative analysis of the carbohydrates is realized with accuracy, high selectivity, and sensitivity with high-performance anion-exchange chromatography with pulsed-amperometric detection. The sugars can be analyzed without any derivatization with a limit of quantification of 0.1 mM.