Habitat quality,not habitat amount,drives mammalian habitat use in the Brazilian Pantanal

Landscape Ecology - An understanding of species-habitat relationships is required to assess the impacts of habitat fragmentation and degradation. To date, habitat modeling in fragmented landscapes...     

SE—Structures and Environment: Optimal Control Strategies for Carbon Dioxide Enrichment in Greenhouse Tomato Crops—Part 1: Using Pure Carbon Dioxide

Two optimal control strategies for carbon dioxide (CO₂) enrichment in greenhouse tomato crops have been developed. One uses pure CO₂ from a storage tank and the other uses CO₂ contained in the exhaust gases of boilers burning natural gas. The optimal strategies maximize the financial margin between crop value and the combined costs of the CO₂ used for enrichment and the natural gas used for heating. In this paper, the strategy for optimal control using pure CO₂ is presented and compared with strategies used by growers. The optimal strategy for enrichment with exhaust gas derived CO₂ is presented in an accompanying paper. Simulations show that at a cost of £0·09 kg⁻¹ for pure CO₂ and £0·10 m⁻³ for natural gas, the optimal enrichment strategy would increase the annual margin of crop value over CO₂ and heating costs by £4·6 m⁻² (27%) compared to a basic control strategy of enrichment to a concentration of 1000 v.p.m. (parts per million by volume) when ventilators are <5% open, otherwise enrichment to 350 v.p.m. The optimal CO₂ concentration was expressed as an algebraic function of solar radiation, wind speed and ventilator opening angle, and so enabled a quasi-optimal value to be obtained using variables measured by greenhouse environmental controllers. The quasi-optimal equation, with coefficients averaged from simulations over 4 years, gave an increased margin over the basic control strategy of £4·4 m⁻² (26%).     

Age-related changes to the molecular and cellular components of equine flexor tendons.

Specific tendons show a high incidence of partial central core rupture which is preceded by degeneration. In the performance horse, the superficial digital flexor tendon (SDFT) is most often affected. We have described previously the molecular changes that are associated with degeneration in the central core region of the equine SDFT. The pathophysiological mechanism leading to change in synthetic activity of central zone cells in degenerated tendons is not known. In this study, we test the hypothesis that ageing results in matrix composition changes within the central zone of the SDFT. Extracellular matrix composition and cellularity were analysed in equine SDFTs collected from Thoroughbred horses and compared with a flexor tendon which rarely shows degenerative change and subsequent injury (deep digital flexor tendon, DDFT). Data were examined for age-related changes to central and peripheral zone tissue of the SDFT and DDFT. Ageing in both tendons (SDFT and DDFT) resulted in a significant increase in collagen-linked fluorescence and a decrease in cellularity in the DDFT but not the SDFT. The central zone tissue from the SDFT had a significantly higher proportion of type III collagen than the peripheral zone of the tendon. The highest level of type III collagen was found in the central zone tissue of the SDFT from the older group of horses and this may represent the early stages of a degenerative change. Collagen content did not differ between the 2 flexor tendons; however, there were differences in collagen type and organisation. The SDFT had a higher type III collagen content, higher levels of the mature trifunctional collagen crosslink hydroxylysylpyridinoline, lower total chondroitin sulphate equivalent glycosaminoglycan content, smaller diameter collagen fibrils and a higher cellularity than the DDFT. In conclusion, differences in macromolecular composition exist between the flexor tendons and ageing contributes to a tendon specific change in composition.     

Evaluation of the induction of vasoactive mediators from equine digital vein endothelial cells by endotoxin

OBJECTIVE: To determine the effect of endotoxin (lipopolysaccharide [LPS]) on vasoactive mediator production by cultured equine digital vein endothelial cells (EDVECs). SAMPLE POPULATION: EDVECs obtained from forelimb digital veins of 7 healthy adult horses. PROCEDURES: EDVECs were incubated with or without LPS (1 microg/mL) for 0, 2, 4, 6, 22, and 24 hours. The EDVECs were incubated for 18 hours with LPS (10 pg/mL to 1 microg/mL) with or without ibuprofen, cycloheximide, or L-nitroarginine methyl ester. Medium concentrations of prostacyclin, cyclic guanosine monophosphate, endothelin-1, and thromboxane A(2) were determined. Changes in inducible nitric oxide synthase and cyclooxygenase-2 expression were determined. RESULTS: LPS stimulated mean 4.2- and 14.1-fold increases in EDVEC prostacyclin and cyclic guanosine monophosphate production, respectively, after 22 hours. These effects were LPS concentration-dependent (LPS concentrations that induced a response halfway between the maximum response and baseline of 1.50 and 1.22 ng/mL, respectively). The LPS-induced cyclic guanosine monophosphate production was significantly inhibited (to basal concentrations) by L-nitroarginine methyl ester, and prostacyclin production was inhibited by cycloheximide and ibuprofen. Production of thromboxane A(2) by EDVECs was not detected. Endothelin-1 accumulated in the medium, but LPS did not enhance its production. Inducible nitric oxide synthase expression in EDVECs was not detected with the available antibodies, whereas LPS stimulated cyclooxygenase-2 expression in a time- and concentration-dependent manner. CONCLUSIONS AND CLINICAL RELEVANCE: LPS stimulated vasoactive mediator production by equine endothelial cells, which may play a role in LPS-induced digital hypoperfusion.     

Investigation of the composition, turnover, and thermal properties of ruptured cranial cruciate ligaments of dogs

OBJECTIVE: To assess different components of the extracellular matrix with regard to their thermal properties, composition, and turnover in ruptured cranial cruciate ligaments (CCLs) of dogs, compared with components of intact CCLs from a breed predisposed to CCL failure. SAMPLE POPULATION: Ruptured CCLs obtained from 8 dogs of breeds predisposed to ruptured CCLs and intact CCLs from 12 cadaveric Labrador Retrievers. PROCEDURE: Ruptured and intact CCLs were analyzed for water content; collagen content and collagen cross-links were evaluated via hydroxyproline and amino-acid analyses, respectively. Glycosaminoglycan (GAG) content was analyzed via dimethylmethylene blue and uronic acid assays. Matrix metalloproteinases (MMPs)-2 and -9 and the tissue inhibitors of metalloproteinases (TIMPs)-1 and -2 were detected via gelatin SDS-PAGE zymography and reverse gelatin zymography. Thermal analysis of ligaments was performed by use of differential scanning calorimetry. RESULTS: Ruptured CCLs had significantly higher lamounts of immature cross-links, total and sulfated GAGs, and water content, compared with that of the intact ligaments. Compared with intact CCLs, concentration of pro-MMP-2 was significantly higher in ruptured CCLs; the maximum temperature of collagen denaturation was significantly lower in the ruptured CCLs. CONCLUSIONS AND CLINICAL RELEVANCE: The extracellular matrix of ruptured CCLs had an increased matrix turnover indicated by increased collagen and GAG synthesis, compared with that of intact CCLs. Although the extracellular matrix changes may have occurred before ligament rupture, it is possible that these observed changes may be part of a reparative process after rupture.     

Identification and quantification of amines in the equine caecum

Acute laminitis has been associated with the release of compounds, as yet unidentified, produced by hindgut fermentation which affect blood flow to the digit. The objectives of this study were to identify amine compounds in equine caecal and colonic contents, some of which are known to have vasoactive properties. In addition, the concentrations of amines in caecal contents of horses fed either grass or hay diets were compared. Fifteen amines were identified in equine hindgut contents in concentrations greater than 1 microM. The caecal concentrations of phenylethylamine, isoamylamine, cadaverine, diaminoheptane and spermidine were significantly higher in horses on spring/summer grass compared with those on winter grass or hay. These data show that many amines are present in the equine hindgut, some of which may have the potential to cause peripheral vasoconstriction if released into the circulation from the gastrointestinal tract.     

Climate Change and North American Rangelands: Assessment of Mitigation and Adaptation Strategies

Recent climatic trends and climate model projections indicate that climate change will modify rangeland ecosystem functions and the services and livelihoods that they provision. Recent history has demonstrated that climatic variability has a strong influence on both ecological and social components of rangeland systems and that these systems possess substantial capacity to adapt to climatic variability. Specific objectives of this synthesis are to: 1) evaluate options to mitigate greenhouse gas emissions and future climate change; 2) survey actions that individuals, enterprises, and social organizations can use to adapt to climate change; and 3) assess options for system transformation when adaptation is no longer sufficient to contend with climate change. Mitigation for carbon sequestration does not appear economically viable, given the small and highly variable carbon dioxide fluxes of rangeland ecosystems and the high transaction costs that would be incurred. In contrast, adaptation strategies are numerous and provide a means to manage risks associated with climate change. Adaptation strategies are diverse, including altered risk perception by individuals, greater flexibility of production enterprises, and modifications to social organizations that emphasize climatic variability, rather than consistency. Many adaptations represent “no regrets” actions because their implementation can be justified without emphasis on pending climate change. Adaptations specific to livestock production systems can include flexible herd management, alternative livestock breeds or species, innovative pest management, modified enterprise structures, and geographic relocation. Social-ecological systems in which adaptation is insufficient to counter the adverse consequences of climate change might undergo transformative change to produce alternative ecosystem services, production enterprises, and livelihoods. The rangeland profession is in a pivotal position to provide leadership on this global challenge because it represents the intersection of management and scientific knowledge, includes diverse stakeholders who derive their livelihoods from rangelands, and interacts with organizations responsible for rangeland stewardship.     

Comparison of first-opinion and second-opinion histopathology from dogs and cats with cancer: 430 cases (2001–2008)

Second-opinion histopathology is intended to detect clinically significant discrepancies that have a direct impact on patient care. We sought to determine if this practice at our institution affected patient management and prognosis. First- and second-opinion histopathology reports from cases were retrospectively reviewed. Reports were considered to be in diagnostic agreement, partial diagnostic disagreement or complete diagnostic disagreement. Four hundred and thirty cases were studied. In 70% of cases there was a diagnostic agreement. In 20% of cases, there was partial diagnostic disagreement, where diagnoses were the same but information such as grade or lymphatic and/or vascular invasion was changed. In 10% of cases, complete diagnostic disagreement resulted from a change in degree of malignancy (malignant to benign, or converse; 7%) or a change in cell type (3%). In 17% of the cases evaluated, the histopathology review prompted a change in treatment or prognosis. These findings support the use of second-opinion histopathology as an important part of patient care.