Search

On a watershed scale, geospatial information can be used to identify water resources that are least buffered from contamination. Implementing conservation practices at these locations may accelerate the process of increasing a watershed's ability to support its designated uses. The Upper Oconee Watershed of Georgia contains land areas devoted to poultry, dairy, and beef production. Within these historically agricultural lands, urbanization is proceeding rapidly around existing cities. Agricultural production practices are concentrated in the watershed with poultry in the headwaters area and dairy near a major lake (Lake Oconee). The objective of this research was to relate data sets representing surface water quality at selected sites throughout the watershed to the predominant land use in that portion of the watershed. The location of 550 poultry operations in the headwaters of the Upper Oconee Watershed, away from the city of Athens GA, has minimized conflicts between agricultural and urban interests. Phosphorus, nitrogen, and fecal coliform bacteria were high near the poultry production area, but were reduced within the watershed prior to reaching the intake for the municipal water supply. Athens had a large impact on surface water quality and approximately doubled the amount of phosphorus and nitrogen in the Oconee River. The Oconee River contributed approximately 70% of the water flowing to Lake Oconee. The residents of Lake Oconee have noted the 30 dairies located west of the lake impacting two relatively minor creeks flowing to the lake. These two creeks make up approximately 2.5% of the flow to the lake, but the proximity of the dairies to the lake makes losses of phosphorus, nitrogen, and fecal bacteria apparent in water samples. Fecal coliform numbers were elevated in some creeks with little agricultural or urban development. To test alternative microbial assays, surface water from a grazed watershed was compared to water from a wooded watershed. Assays for enterococci and E. coli may provide a better test for fecal contamination and allow differentiation between natural areas and areas impacted by grazing animals. Analysis of the Upper Oconee Watershed identified agricultural impacts and areas that should be priorities for natural resource management to reduce agricultural non-point source pollution. Focusing conservation efforts at these locations may prevent agricultural-urban conflict. However, the data also indicate that municipal sources of nutrients and fecal bacteria must be reduced to make significant progress in the watershed.

In most eukaryotes, glutathione-dependent peroxidases play a key role in the metabolism of peroxides. Numerous studies have reported that trypanosomatids lack this activity. Here we show that this is not the case, at least for the American trypanosome Trypanosoma cruzi. We have isolated a single-copy gene from T. cruzi with the potential to encode an 18 kDa enzyme, the sequence of which has highest similarity with glutathione peroxidases from plants. A recombinant form of the protein was purified following expression in Escherichia coli. The enzyme was shown to have peroxidase activity in the presence of glutathione/glutathione reductase but not in the presence of trypanothione/trypanothione reductase. It could metabolize a wide range of hydroperoxides (linoleic acid hydroperoxide and phosphatidylcholine hydroperoxide>cumene hydroperoxide>t-butyl hydroperoxide), but no activity towards hydrogen peroxide was detected. Enzyme activity could be saturated by glutathione when both fatty acid and short-chain organic hydroperoxides were used as substrate. For linoleic acid hydroperoxide, the rate-limiting step of this reaction is the reduction of the peroxidase by glutathione. With lower-affinity substrates such as t-butyl hydroperoxide, the rate-limiting step is the reduction of the oxidant. The data presented here identify a new arm of the T. cruzi oxidative defence system.

The NCIMB 8052 strain of Clostridium beijerinckii contains nine copies of a novel insertion sequence, ISCb1, belonging to the IS4 family. The 1764 bp element has 18 bp inverted repeats at its extremities, and generates 11 bp target repeats upon insertion. It contains a 1365 bp ORF whose predicted product (455 amino acids) resembles bacterial transposases. The highly conserved DD(35)E motif is present, as are signatures characteristic of the N3 and C1 domains of bacterial transposases. Codon usage of the ORF is somewhat different from that of other C. beijerinckii genes, suggesting that ISCb1 may have been acquired from another organism by horizontal gene transfer in the evolutionary past. One ISCb1 copy lies close to the site of insertion of Tn 1545 in a mutant strain, C10, which shows a reduced tendency to degenerate (i.e. loss of the potential to form solvents) compared with the wild type. In the C10 strain, the characteristic pattern of DNA fragments detected by an IS-specific probe was altered, but this was due to the Tn1545 insertion itself, rather than an ISCb1-mediated genome re-arrangement. There is currently no evidence that the element is involved in strain degeneration, since 12 independently isolated spontaneous mutants that had lost the ability to form solvents had the same ISCb1 profile as that of the wild type strain. The element is apparently restricted to a series of closely related solvent-forming clostridia.

Environmental and management factors can influence the protein concentration of forages, significantly altering specific amino acid content. Drought, high rates of fertilizer N and the presence of a fungal endophyte have been associated with significant alterations in plant N metabolites and animal performance problems on tall fescue. A controlled environment study was conducted to examine the influence of N fertilization (10 and 100 μgN/g) and water regime (low and adequate soil water availability) upon the distribution and concentration of amino acids in endophyte infected tall fescue (Festuca arundinacea, Schreb.) herbage. Tall fescue tissue was collected from three replicates of each treatment, quick frozen in liquid N and lyophilized. Two insoluble (RI, structural residue; RII, membrane residue) and two soluble (SI, soluble protein; SII, low molecular weight N compounds) fractions were collected. Amino acid analyses of acid hydrolysates of fractions showed that application of 100 N significantly increased the concentration (per unit dry weight) of all amino acids in the entire plant, with an average increase of about 55%. Application of 110 N increased the concentrations of most amino acids in fractions RI, RII, and SI, but only aspartate-asparagine, glutamate-glutamine, alanine, threonine, serine, valine and proline in fraction SII. Fraction RI contained about 65% of total amino acids under 10 N and 55% under 110 N even though N level did not alter dry matter distribution among fractions. While the amount of dry matter was least in SI, amino acids in the fraction ranged from 8% (leucine, 10 N) to 20% (lysine, 110 N) of the total amount of specific amino acids recovered. Significant increases in proline, glutamate, aspartate, serine, valine, threonine, alanine and phenylalanine concentration occurred under low soil-water availability compared with adequate water conditions. Basic amino acids including histidine, arginine and lysine increased with increased N and with water stress at each N level. Application of N increased amounts, and water stress influenced distribution of amino acids among the fractions of tall fescue herhage. Nitrogenous components, such as non-protein amino acids which could influence plant nutritive quality, were increased in fraction SII by increased N and water stress.

An investigation was designed to examine the nature and distribution of nitrogen in tall fescue (Festuca arundinacea Schreb.) as influenced by water regime and N fertility under controlled environment conditions. Three replicates of 10 ppm and 110 ppm N were prepared for both adequately watered and water stress treatments of vegetatively propagated tall fescue. Herbage samples were lyophilized and soluble protein extracted in aqueous buffer and separated from low molecular weight N compounds. Two insoluble fractions (RI, cellular and structural fragments; RII, organellar residue, primarily chloroplasts) and two soluble fractions (SI, soluble protein; SII, low molecular weight compounds) were characterized by Kjeldahl N and acid-hydrolyzable amino-acid analyses.

ABERG'S review1 cites Soding (Die Wuchstofflehre, Georg Thieme Verlag, Stuttgart, Germany, 1952) as suggesting that the generally recognized increased shoot/root ratios resulting from nitrogen fertilization are caused by nitrogen-increased growth hormone content which, in turn, inhibits root growth and promotes shoot growth in the intact plant. This suggestion appears reasonable and was supported by Bosemark2, who compared the growth of roots in high nitrogen solution with that of roots growing in solutions containing growth hormones.

The department of child psychiatry, Ullevål Hospital, has started a liaison child psychiatry service for persons under 18 years old admitted to the hospital. The different tasks involved are analysed with a view to meeting the requirements of the different wards. This facilitates purposeful liaison, establishment of jointly agreed priorities and evaluation of the service.

Current theory on non-equilibrium communities, thresholds of irreversibility, and ecological resilience suggests the goal of ecological restoration of degraded communities is not to achieve one target, but to reestablish the temporal and spatial diversity inherent in natural ecosystems. Few restoration models, however, address ecological and management issues across the vegetation mosaic of a landscape. Because of a lack of scientific knowledge and funds, restoration practitioners focus instead on site-specific prescriptions and reactive rather than proactive approaches to restoration; this approach often dooms restoration projects to failure. We applied a state-transition model as a decision-making tool to identify and achieve short- and long-term restoration goals for a tropical, moist, evergreen forest on the island of Santa Cruz, Galapagos. The model guided the process of identifying current and desirable forest states, as well as the natural and human disturbances and management actions that caused transitions between them. This process facilitated assessment of opportunities for ecosystem restoration, expansion of the definition of restoration success for the system, and realization that, although site- or species-specific prescriptions may be available, they cannot succeed until broader landscape restoration issues are identified and addressed. The model provides a decision-making framework to allocate resources effectively to maximize these opportunities across the landscape, and to achieve long-term restoration success. Other restoration models have been limited by lack of scientific knowledge of the system. State-transition models for restoration incorporate current knowledge and funds, are adaptive, and can provide direction for restoration research and conservation management in other degraded systems.

Soils provide the support, water and most of the nutrient elements, including Mg, needed for plant growth. Magnesium uptake by plants depends largely on the amount, concentration and activity of Mg in the soil solution and the capacity of the soil to replenish Mg in the soil solution. The availability of Mg depends on the activity or proportion of Mg relative to soluble and exchangeable amounts of K, Ca, Na, Al and Mn. In humid regions, Mg losses from leaching are often greatest from agroecosystems receiving heavy N fertilization. Cool-season grasses produce nearly maximum growth at herbage concentrations of 1 to 1.5 g Mg/kg, 25 g K/kg and 30 g N/kg of dry matter. At these concentrations of N and K, herbage should contain about 2.5 g Mg/kg to avoid inducing hypomagnesemic grass tetany in ruminants. To increase herbage Mg concentration to this level often requires, except on sandy soils, an uneconomically large addition of Mg fertilizer. Adjusting soil conditions to produce grasses with a low-tetany potential may not always be possible physically. The risk of tetany can be reduced by a judicious program of well-timed N, K and Mg fertilizer applications. However, direct Mg supplementation of grazing ruminants is considered more cost-effective than is Mg fertilization to prevent grass tetany.