Myelination inhibition factor: dissociation from induction of experimental allergic encephalomyelitis

Sensitization of guinea pigs with purified myelin basic protein induces experimental allergic encephalomyelitis (EAE) but does not induce a serum factor which inhibits myelin formation in vitro. This factor, induced by some unidentified constituent of whole central nervous system tissue, should not be characterized as a component of "EAE serum."     

Stable sulfur isotope ratios as a tool for interpreting ecosystem sulfur dynamics

Water, Air, & Soil Pollution - Stable S isotope ratios (σ34S) were evaluated in soil solution leachates, soluble plus adsorbed soil SO inf4 sup2− , soil organic S, precipitation, and...     

Biogeochemistry of a forested watershed in the central Adirondack Mountains: Temporal changes and mass balances

Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO₃ ^? concentrations (1.1 μmol _c , L^?1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r²=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO₄ ^2? (831 mol _c ha^?1 yr^?1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO₄ ^2? also contributed to the drainage fluxes of basic cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha^?1 yr^?1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).     

Critical loads for nitrogen deposition: Case studies at two northern hardwood forests

A critical load of a pollutant is the level of input below which no harmful ecological effects occur to a complex ecosystem. Critical loads are being used in policy decisions regarding air pollution emissions. In this paper, we applied four mass and charge balance methods of calculating critical loads to two northern hardwood forests in the northeastern United States. Critical loads for nitrogen deposition with respect to acidity ranged from 0–630 eq/ha-yr. Critical loads for nitrogen deposition with respect to effects of elevated nitrogen (eutrophication and nutrient imbalances) ranged from 0–1450 eq/ha-yr. At both the Hubbard Brook Experimental Forest (HBEF) and Huntington Wildlife Forest (HWF), the critical load for nitrogen with respect to acidity was exceeded. At the HBEF, due to reduced forest growth, the critical load for nitrogen with respect to nutrient imbalances and eutrophication was exceeded in recent years. At Huntington Wildlife Forest, the critical load with respect to nitrogen effects was also exceeded. This analysis demonstrated that the calculated critical load of nitrogen varies in response to changes in environmental conditions such as variations in atmospheric deposition of sulfate or changes in forest biomass accumulation.     

Changes in the concentrations and speciation of aluminum in response to an experimental addition of ammonium sulfate to the bear Brook Watershed,Maine, USA

An understanding of the biogeochemistry of aluminum (Al) in acid-sensitive terrestrial and aquatic ecosystems is critical to assessments of the effects of acidic deposition. Bear Brook Watershed, Maine, USA includes paired watersheds, East Bear and West Bear. Starting in November 1989, experimental additions of ammonium sulfate ((NH₄)₂SO₄; 900 mol/ha-yr) have been made to West Bear Brook Watershed. Chemical analysis of soil and stream waters were conducted to evaluate the speciation of Al prior to (1987–89) and following (1989–92) the experimental treatments. Before the treatments, soilwater Al occurred largely as inorganic monomeric Al (Ali). Concentrations of organic monomeric Al (Alo), Ali and dissolved organic C (DOC) were high in soil solutions draining the E horizon, and decreased in the lower mineral soilwater (Bs horizon) and streamwater. Streamwater concentrations of monomeric Al (Alm) were largely in the form of Alo. After the (NH₄)₂SO₄ treatments were initiated in the West Bear Brook Watershed, concentrations of Alm increased in soilwater and streamwater, largely as Ali. These increases in Al accompanied decreases in pH and increases in concentrations of SO₄ ^2? and NO₃ ^? in drainage waters. Increases in stream concentrations of Al were particularly evident during high flow events. This pattern, coupled with the increases in concentrations of Ali in upper soilwaters in response to the (NH₄)₂SO₄ addition, suggests that episodic increases in Ali were due to inputs of water entering the stream from shallow hydrologic flowpaths.     

Use of Stable Isotope Ratios for Evaluating Sulfur Sources and Losses at the Hubbard Brook Experimental Forest

Water, Air, &; Soil Pollution - Anthropogenic S emissions have been declining in eastern North America since the early 1970s. Declines in atmospheric S deposition have resulted in decreases in...     

Long-term trends in the chemistry of precipitation and lake water in the Adirondack Region of New York,USA

Long-term changes in the chemistry of precipitation (1978–94) and 16 lakes (1982–94) were investigated in the Adirondack region of New York, USA. Time-series analysis showed that concentrations of SO₄ ^2–, NO₃ ^–, NH₄ ⁺ and basic cations have decreased in precipitation, resulting in increases in pH. A relatively uniform rate of decline in SO₄ ^2– concentrations in lakes across the region (1.81±0.35 eq L^–1 yr^–1) suggests that this change was due to decreases in atmospheric deposition. The decrease in lake SO₄ ^2– was considerably less than the rate of decline anticipated from atmospheric deposition. This discrepancy may be due to release of previously deposited SO₄ ^2– from soil, thereby delaying the recovery of lake water acidity. Despite the marked declines in concentrations of SO₄ ^2– in Adirondack lakes, there has been no systematic increase in pH and ANC. The decline in SO₄ ^2– has corresponded with a near stoichiometric decrease in concentrations of basic cations in low ANC lakes. A pattern of increasing NO₃ ^– concentrations that was evident in lakes across the region during the 1980's has been followed by a period of lower concentrations. Currently there are no significant trends in NO₃ ^– concentrations in Adirondack lakes.     

Ability of ethoxyquin and butylated hydroxytoluene to counteract deleterious effects of dietary aflatoxin in chicks

The antioxidants ethoxyquin and butylated hydroxytoluene (BHT) were added to diets of chicks in concentrations three and eight times above that usually found in poultry feed beginning 15 days after hatch; the chicks had been placed on feed containing 1000 or 3000 ppb aflatoxin on the day of hatch. These diets were continued until chicks were 6 weeks of age. At that time, deleterious effects of aflatoxin on weight gain, feed efficiency, and organ weights (spleen, bursa) were evident. BHT alleviated these effects, but ethoxyquin did not. Pretreatment with ethoxyquin did not protect chicks either. Ethoxyquin was not able to induce the activities of chick liver enzymes that detoxify aflatoxin and other foreign compounds. Lack of effect of ethoxyquin on these enzymes may hinder ability of this antioxidant to protect chicks from aflatoxin.