Maple syrup urine disease in calves: a clinical, pathological and biochemical study

The clinical, pathological and biochemical findings of a study of 30 Poll Hereford, Hereford, Poll Hereford cross or Hereford cross calves affected with branched chain ketoacid dehydrogenase (BCKAD) complex deficiency or maple syrup urine disease (MSUD) are presented. In breeding studies, 6 of 21 calves from obligate heterozygote matings were affected with MSUD, suggesting the disease is inherited in an autosomal recessive manner. Calves were clinically affected from birth, but there were variations in the subsequent course of progressive deterioration of central nervous system function. Concentrations of the branched chain amino acids and keto acids were elevated in pre-suckle plasma and cerebellar water content was higher in affected calves. Activity of BCKAD complex was minimal in fibroblasts cultured from an affected calf. Spongiform encephalopathy and elevated ratios of the branched to straight chain amino acids in formalin fixed cerebral tissue were found in a stillborn foetus and a 3-month-old Hereford calf. These findings suggest the disease occurs prenatally and that a delayed form may exist.     

Endosulfan residues on alfalfa hay exposed to drying by sunlight,ultraviolet light and air

Endosulfan residues on alfalfa hay exposed to drying by sunlight, ultraviolet light and air under controlled conditions were investigated using g.l.c. and t.l.c. Maximum loss of total endosulfan and related residues calculated as endosulfan occurred approximately 7 days after application and exposure on Lot 1 (dark) and 5 days on Lot II (ultraviolet light) and 6 days on Lot III (sunlight). Maximum losses of residues on Lot I, Lot II and Lot HI were 48.3, 66.7 and 81.9%, respectively. No endosulfan lactone was detected in any of the samples exposed to the different light treatments. In all Lots the endosulfan sulphate percentage of the total residue increased but most dramatically in the dark drying experiment. The endosulfan a-hydroxy ether residues increased in Lot III (sunlight) up to day 7.     

Scale-Dependent Influence of Topography-Based Hydrologic Features on Patterns of Woody Plant Encroachment in Savanna Landscapes

Rainfall in drylands is erratic. Topographic features of landscapes can dampen or amplify temporal variability by spatially influencing patterns of water loss and accumulation. The extent to which portions of a landscape may differentially capture or retain scarce water and nutrient resources is an important determinant of vegetation patterns, particularly with respect to the distribution of woody plants. We therefore hypothesized that historic changes in woody cover on landscapes experiencing similar climate and disturbance regimes would vary with catena-to-catena (hillslope-to-hillslope) variation in topography-based hydrologic features. We tested this hypothesis by comparing topographic wetness index (TWI) values on replicate landscapes where woody plant abundance has increased over the past 100 yr. These landscapes are characterized by savanna parklands on coarse-textured upland portions of catenas that grade (1–3% slopes) into closed-canopy woodlands on fine-textured (lowland) portions of catenas. TWI values for woody and herbaceous communities were comparable within uplands, suggesting factors unrelated to surface/subsurface hydrology determine patterns of woody cover in these catena locations. TWI values for upland savanna parklands were significantly lower than those of closed-canopy woodlands occupying catena footslopes. Furthermore, uplands adjoining historically static woodland boundaries had lower TWI values than those where woodland boundaries had moved upslope 2.1 m yr⁻¹ from 1976 to 1995. Results suggest runoff–runon relationships influence patterns of woody plant cover and change at the catena scale and may override constraints imposed by soil texture. As a result, changes in woody cover potentially accompanying changes in disturbance regimes, climate or atmospheric chemistry are likely to be constrained by topoedaphic settings. Models of vegetation dynamics may therefore need to explicitly account for rainfall–topography–soil texture relationships and associated scale-dependent mechanisms to accurately predict rates and patterns of change in woody and herbaceous plant abundance.     

Corneal stromal sequestration and keratoconjunctivitis sicca in a horse

A 19-year-old Shetland pony presented with unilateral ocular discomfort and abnormal ocular appearance. Keratoconjunctivitis sicca, ulcerative keratitis and brown discoloration of the corneal stroma were identified on ophthalmic examination. The etiology of keratoconjunctivitis sicca was not determined in this case. For practical and financial reasons, the owners requested enucleation of the affected eye. Histopathologic examination revealed extensive loss of corneal epithelium overlying a zone of hypereosinophilic, degenerate, and necrotic corneal stroma. This well-circumscribed region of corneal stromal sequestration was surrounded by stromal vascularization, and an intense inflammatory, predominantly polymorphonuclear, cellular infiltrate. The clinical and histopathologic features of this case were considered remarkably similar to those observed in feline corneal stromal sequestration.     

Comparison of carbon-stock changes,eddycovariance carbon fluxes and model estimates in coastal Douglas-fir stands in British Columbia

Background: The global network of eddy-covariance(EC) flux-towers has improved the understanding of the terrestrial carbon(C) cycle, however, the network has a relatively limited spatial extent compared to forest inventory data and plots. Developing methods to use inventory-based and EC flux measurements together with modeling approaches is necessary evaluate forest C dynamics across broad spatial extents.Methods: Changes in C stock change(ΔC) were computed based on repeated measurements of forest inventory plots and compared with separate measurements of cumulative net ecosystem productivity(ΣNEP) over four years(2003 – 2006) for Douglas-fir(Pseudotsuga menziesii var menziesii) dominated regeneration(HDF00), juvenile(HDF88and HDF90) and near-rotation(DF49) aged stands(6, 18, 20, 57 years old in 2006, respectively) in coastal British Columbia. ΔC was determined from forest inventory plot data alone, and in a hybrid approach using inventory data along with litter fall data and published decay equations to determine the change in detrital pools. These ΔC-based estimates were then compared with ΣNEP measured at an eddy-covariance flux-tower(EC-flux) and modelled by the Carbon Budget Model- Canadian Forest Sector(CBM-CFS3) using historic forest inventory and forest disturbance data.Footprint analysis was used with remote sensing, soils and topography data to evaluate how well the inventory plots represented the range of stand conditions within the area of the flux-tower footprint and to spatially scale the plot data to the area of the EC-flux and model based estimates.Results: The closest convergence among methods was for the juvenile stands while the largest divergences were for the regenerating clearcut, followed by the near-rotation stand. At the regenerating clearcut, footprint weighting of CBM-CFS3 ΣNEP increased convergence with EC flux ΣNEP, but not for ΔC. While spatial scaling and footprint weighting did not increase convergence for ΔC, they did provide confidence that the sample plots represented site conditions as measured by the EC tower.Conclusions: Methods to use inventory and EC flux measurements together with modeling approaches are necessary to understand forest C dynamics across broad spatial extents. Each approach has advantages and limitations that need to be considered for investigations at varying spatial and temporal scales.