Acidification of Lake Annie,Highlands Co., FL

Lake Annie, a clear-water seepage lake in south-central Florida remote from significant pollution sources, was sampled by the USGS from 1966 until 1978, and by Battoe and others from 1978 until present. Since 1966, pH and bicarbonate alkalinity have decreased (pH from above 6.0 to about 5.1; bicarbonate from 5.0 to less than 0.5 mg L^?1), while specific conductivity and sulfate concentration have increased (cond. from 30 to 55 μS; sulfate from 3.0 to 8.0 mg L^?1). The chemical changes are apparently due to acidification from atmospheric deposition. There are no proximate sources of acidity and the stability of lake level indicates there has been no significant concentration or dilution of solutes. It is suggested that Lake Annie's acidification was a threshold phenomenon wherein, following depletion of the watershed's buffering capacity, acidification of the lake was rapid.     

Life-cycle traits of the dimorphic earthworm species <Emphasis Type="Italic">Allolobophora chlorotica</Emphasis> (Savigny, 1826) under controlled laboratory conditions

Allolobophora chlorotica exists as two colour morphs, pink and green. Field observations have indicated that the two morphs have ecological preferences linked to soil moisture: the green morph dominating in wet soils and the pink morph in dry soils. The aim of this laboratory-based research was to investigate the potential differences in fitness and adaptation to soil-moisture conditions of the two morphs measured in terms of growth rate, reproductive output and cocoon viability. An initial experiment maintained hatchlings of both morphs individually under standard culture conditions. On maturation, these were paired (intra-morph), and cocoon production, viability and incubation time were determined. The green morph had significantly faster (P < 0.01) growth rates than the pink morph. Cocoon production was also significantly greater in the green compared with the pink morph (3.2 and 1.5 cocoons worm⁻¹ 28 days⁻¹, respectively) with corresponding viabilities of 87 and 58%. In a second experiment, the growth rates of pink and green hatchlings were assessed under wet and dry soils (29 and 21% soil moisture, respectively). The growth of the pink morph was not influenced significantly (P > 0.05) by soil moisture. In contrast, lower soil-moisture content significantly (P < 0.05) slowed growth and maturation of the green morph. These results support field observations relating to distribution of the two A. chlorotica colour morphs. We suggest that soil-moisture content may act to isolate these morphs, providing, in extremes, a barrier to inter-morphic mating.     

Crystal structure of the potassium channel KirBac1.1 in the closed state

The KirBac1.1 channel belongs to the inward-rectifier family of potassium channels. Here we report the structure of the entire prokaryotic Kir channel assembly, in the closed state, refined to a resolution of 3.65 angstroms. We identify the main activation gate and structural elements involved in gating. On the basis of structural evidence presented here, we suggest that gating involves coupling between the intracellular and membrane domains. This further suggests that initiation of gating by membrane or intracellular signals represents different entry points to a common mechanistic pathway.     

Electrochemotherapy in treatment of canine oral non‐tonsillar squamous cell carcinoma. A case series report

Non‐tonsillar squamous cell carcinoma (ntSCC) is a common and locally aggressive oral tumour in dogs. The treatments of choice are currently surgery and radiotherapy. Electrochemotherapy (ECT) is a local ablative anti‐tumour technique using electric pulses to enhance the intracellular diffusion of cytotoxic drugs. The aim was to retrospectively evaluate the outcome of patients with oral ntSCC treated with ECT. Twelve dogs with ntSCC were retrospectively enrolled. ECT was combined with IV bleomycin (15 000 UI/m²) alone in 11 cases and post‐surgery in 1. Parameters considered were: tumour site and size, electroporation parameters, response rate (complete remission [CR], partial remission [PR]), median survival time (MST), recurrence rate (RR), median disease‐free interval (DFI) and treatment toxicity (6‐point scale). Median tumour size was 1.65 cm (range 0.3‐8.0 cm) and the response rate was 90.9% (10/11; 8 CR and 2 PR). Two dogs underwent a second ECT. MST for dogs dead with tumour (n = 2) was 110 days and for dogs dead without tumour (n = 3) was 831 days. Among five surviving dogs, one experienced tumour recurrence and four were in CR. Results from two dogs were analysed separately. Overall RR was 27.3%. DFI and MST for dogs with recurrence were 50 and 115 days, respectively. Treatment toxicity was very low. We noticed that all dogs with tumours smaller than 1‐2 cm achieved CR without recurrence suggesting a favourable prognosis when using ECT. ECT for canine ntSCC could be considered a valid treatment option especially for smaller tumours, but a larger caseload would be needed to confirm this statement.     

Unexpected changes to the global methane budget over the past 2000 years

We report a 2000-year Antarctic ice-core record of stable carbon isotope measurements in atmospheric methane (delta13CH4). Large delta13CH4 variations indicate that the methane budget varied unexpectedly during the late preindustrial Holocene (circa 0 to 1700 A.D.). During the first thousand years (0 to 1000 A.D.), delta13CH4 was at least 2 per mil enriched compared to expected values, and during the following 700 years, an about 2 per mil depletion occurred. Our modeled methane source partitioning implies that biomass burning emissions were high from 0 to 1000 A.D. but reduced by almost approximately 40% over the next 700 years. We suggest that both human activities and natural climate change influenced preindustrial biomass burning emissions and that these emissions have been previously understated in late preindustrial Holocene methane budget research.     

Eruption of the nevado del ruiz volcano, Colombia, on 13 november 1985: gas flux and fluid geochemistry

The 13 November 1985 eruption of Nevado del Ruiz volcano, in Colombia, released a small volume of pyroclastic material and a disproportionately large volume of volcanic gas. Before the eruption, summit fumarole gases became less water-rich, and the sulfur/chlorine ratio increased. Remote measurements of sulfur dioxide flux after the eruption indicated active degassing at levels associated with eruptive or inter-eruptive stages of other volcanoes. Thermal water analyses revealed increases in magnesium, calcium, and potassium and an increase in the magnesium/chlorine ratio, suggesting that these elements may have been leached from new magma. Ash leachate data showed sulfate and chloride concentrations and ratios that would be expected for the late stages ofa major Plinian eruption. Water from the lahar contained high concentrations of sulfate and had a sulfur/chlorine ratio of 4.67, suggesting that water ejected from the crater lake and turbulent mixing of pyroclasts and glacial ice triggered the lahar. Microprobe analyses of pumice from this eruption and the most recent previous event showed similar mixed andesites. The uniform composition of the pumices and the unusually high ratio of gas to magma suggest that, although a new batch of magma triggered this eruption, the pumice that erupted may actually be old. Large volumes of new magma and glacial ice make the volcano dangerous and should stimulate development of an integrated long-term monitoring program to include Tolima volcano, 25 kilometers to the south.     

Durable resistance to the wheat rusts: integrating systems biology and traditional phenotype-based research methods to guide the deployment of resistance genes

Genes which confer partial resistance to the rusts in wheat figure prominently in discussions of potential durable resistance strategies. The positional cloning of the first of these genes, Lr34/Yr18 and Yr36, has revealed different protein structures, suggesting that the category of partial resistance genes, as defined by phenotype, likely groups together suites of functionally heterogenous genes. With the number of mapped partial rust resistance genes increasing rapidly as a result of ongoing advances in marker and sequencing technologies, breeding programs needing to select and prioritize genes for deployment confront a fundamental question: which genes or gene combinations are more likely to provide durable protection against these evolving pathogens? We argue that a refined classification of partial rust resistance genes is required to start answering this question, one based not merely on disease phenotype but also on gene cloning, molecular functional characterization, and interactions with other host and pathogen proteins. Combined with accurate and detailed disease phenotyping and standard genetic studies, an integrated wheat-rust interactome promises to provide the basis for a functional classification of partial resistance genes and thus a conceptual framework for their rational deployment.     

Turbidity current activity in a british columbia fjord

A year-long monitoring program within an elongated channel-fan system in Bute Inlet of British Columbia, Canada, detected active sand-transporting turbidity currents. Measurements of bottom velocities and sediment collected in traps, as well as damage to moorings and equipment, captured the signatures of frequent energetic events. Maximum calculated velocities achieved were 335 centimeters per second, with flow thicknesses of more than 30 meters. Coarse sand was transported at least 6 to 7.5 meters above the sea floor. Turbidity currents flowed a minimum distance of 25.9 kilometers, but possibly as far as 40 to 50 kilometers, over bottom slopes of generally less than 1 degrees.