Genetics of equine bleeding disorders

Genetic bleeding disorders can have a profound impact on a horse's health and athletic career. As such, it is important to understand the mechanisms of these diseases and how they are diagnosed. These diseases include haemophilia A, von Willebrand disease, prekallikrein deficiency, Glanzmann's Thrombasthenia and Atypical Equine Thrombasthenia. Exercise-induced pulmonary haemorrhage also has a proposed genetic component. Genetic mutations have been identified for haemophilia A and Glanzmann's Thrombasthenia in the horse. Mutations are known for von Willebrand disease and prekallikrein deficiency in other species. In the absence of genetic tests, bleeding disorders are typically diagnosed by measuring platelet function, von Willebrand factor, and other coagulation protein levels and activities. For autosomal recessive diseases, genetic testing can prevent the breeding of two carriers.     

Temporal variability in water quality of agricultural tailwaters: Implications for water quality monitoring

Accurate assessments of non-point source pollution and the associated evaluation of mitigation strategies depend on effective water quality monitoring programs. Intensive irrigation season water quality monitoring was conducted on three agricultural drains (6 h to daily sampling) along with analysis of decade long records from two larger agricultural drains (biweekly to monthly sampling) in the San Joaquin Valley, California. Analyses revealed significant temporal variability in concentrations of nutrients, salts, and turbidity over short time-scales (<1 day), as well as significant differences in monthly and annual mean concentrations. Statistical techniques were used to evaluate the sampling intensity required to meet rigorous confidence and accuracy criteria, as well as to evaluate the efficacy of different sampling strategies (e.g. grab samples versus composite samples). The number of samples required to determine mean constituent concentrations within 20% of the mean at a 95% confidence level ranged from 2 to 39 samples per month (SPM) for total phosphorus, 1-16 SPM for total nitrogen, 5-25 SPM for turbidity, and 1-3 SPM for electrical conductivity. Using a daily composite sample (4 subsamples per composite) instead of discrete samples was shown to maintain the same accuracy and confidence standards, while reducing the required sample number by up to 50%. This study emphasizes the value of a statistical approach for evaluating water quality monitoring strategies, and provides a framework through which cost-benefit analysis can be implemented in the development of monitoring plans.     

Effects of beta-aminopropionitrile on equine tendon metabolism in vitro and on effects of insulin-like growth factor-I on matrix production by equine tenocytes

OBJECTIVE: To investigate effects of beta-aminopropionitrile and a combination of insulin-like growth factor (IGF)-I and beta-aminopropionitrile on metabolism of equine tendon fibroblasts. SAMPLE POPULATION: Flexor tendon explants from 3 horses. PROCEDURE: Explants received 1 of 4 treatments (control, IGF-I, beta-aminopropionitrile, and IGF-I/beta-aminopropionitrile) for 10 days, and message expression for collagen types I and III was assessed by use of in situ hybridization. Histologic findings, new protein production, and quantitative determinations of glycosaminoglycan, DNA, and de novo collagen synthesis were made. RESULTS: Insulin-like growth factor-I stimulated an anabolic response in tendon. Collagen synthesis and glycosaminoglycan and DNA content of explants were all increased. Beta-aminopropionitrile significantly suppressed collagen synthesis, which was not ameliorated by concurrent IGF-I treatment. Beta-aminopropionitrile caused alterations in cell morphology characterized by large round cells with eccentric nuclei and decreased density of collagen fibers. Protein production and collagen type-III mRNA expression were reduced in these cells. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with beta-aminopropionitrile resulted in decreased production of protein and collagen synthesis, which could be expected to suppress tendon healing. The negative effects of beta-aminopropionitrile could not be abrogated by addition of IGF-I to the medium. Treatment resulted in alterations in cell morphology and matrix consistency, which could further delay tendon healing. Beta-aminopropionitrile may impair tendon healing at a cellular level by decreasing collagen production or increasing rate of degradation of existing matrix. Because of reduced crosslinking during beta-aminopropionitrile treatment, in combination with transiently decreased tensile strength, alterations in collagen content and structure may weaken the healing tendon.     

Cloning and expression of type III collagen in normal and injured tendons of horses

OBJECTIVE: To clone the 5' end of type III collagen and describe its pattern of mRNA and protein expression in normal and healing tendons in horses. ANIMALS: 14 healthy adult horses. PROCEDURE: The tensile region of collagenase-injured superficial digital flexor tendons was harvested at intervals from 1 to 24 weeks after injury. Total RNA was reverse-transcribed into cDNA for cloning and sequencing of type III collagen. Equine-specific nucleic acid probes were developed and used for northern blot analysis and in situ hybridization. Type III collagen protein and cyanogen bromide-cleaved collagen peptides were assessedby gel electrophresis. RESULTS: Type III collagen mRNA expression and protein content increased immediately after injury and remained increased. Type III collagen was localized to the endotenon in normal tendon and in injured tendon at 1 week. At 8 and 24 weeks, expression became more widely distributed throughout the tendon parenchyma. Injured tendon contained 6 times more type I than type III collagen mRNA. Quantities of type III collagen protein were maximal in the first 4 weeks after injury (approx 33%) and then began to decrease. CONCLUSIONS AND CLINICAL RELEVANCE: Type III collagen expression is increased initially in endotenon and subsequently in parenchyma of healing tendon; however, type III remains the minor collagen throughout the healing process. The role of type III collagen in tendon healing is not fully elucidated.     

Fishing, trophic cascades, and the process of grazing on coral reefs

Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience.     

Biogeochemical cycling in forest soils of the eastern Sierra Nevada Mountains,USA

We review some of the unique features of biogeochemical cycling in forests of the eastern Sierra Nevada Mountains, USA. As is the case for most arid and semi-arid ecosystems, spatial and temporal variability in nutrient contents and fluxes are quite high. “Islands of fertility” are common in these forests, a result of spatial variations in both litterfall and decomposition rates. Dry summer conditions greatly inhibit biological activity in the O horizon, and thus most annual litter decomposition takes place beneath the snowpack when moisture is available. Snowmelt duration is shortened near tree boles because of local warming, resulting in earlier drying of the O horizon, significantly lower decomposition rates, and increased O horizon mass. Water and nutrient fluxes vary spatially because of snowdrift in winter and surface runoff over hydrophobic soils in summer and fall. Moisture variability in the vertical as well as the horizontal dimension has significant consequences for nutrient fluxes. Because of the very dry summers, rooting in the O horizons is absent in these forests, and thus competition between microbes and trees for nutrients in that horizon is non-existent. Nutrients mineralized from the O horizon and not taken up by plants enrich runoff through the O horizons over hydrophobic mineral soils, resulting in very high concentrations of inorganic N and P in runoff waters. Substantial temporal variations in water and nutrient fluxes occur on a seasonal (with snowmelt being the dominant hydrologic event of the year), annual, and decadal basis. The most significant temporal variation is due to periodic fire, which we estimate causes annualized N losses that are two orders of magnitude greater than those associated with leaching and runoff. We hypothesize that fire suppression during the 20th century may have contributed to the deterioration of nearby Lake Tahoe by allowing buildups of N and P in O horizons which could subsequently leach from the terrestrial ecosystem to the Lake in runoff. In general, we conclude that biogeochemical cycling in these forests is characterized by greater spatial and temporal variability than in more mesic forest ecosystems.