Pymetrozine,a Fast-Acting and Selective Inhibitor of Aphid Feeding. In-situ Studies with Electronic Monitoring of Feeding Behaviour

Pymetrozine, a pyridine azomethine compound, represents a novel insecticide with a selective activity against homopteran insects. It acts in a unique way: aphids are not knocked down on contact but seem to die of starvation. This implies an effect of pymetrozine on feeding behaviour. The aim of the present work was to elucidate how and at which step pymetrozine interferes with the complex mechanisms underlying phloem feeding. The effect of pymetrozine, applied in various ways, on different phases of stylet penetration and feeding activity of individual aphids was studied using the Electrical Penetration Graph technique (EPG). Initial choice experiments indicated that pymetrozine does not have a deterrent or antifeedant action. Topical application (150 ng pymetrozine mg^-1 fresh weight) inhibited stylet insertion into the plant. When injected, less than 30 ng mg^-1 was sufficient to produce the same effect. When pymetrozine was systemically applied via plant spraying or root uptake, aphids started feeding normally. After some time, however, they withdrew their stylets from the phloem and walked around with unaffected locomotion. At low doses aphids eventually recovered and resumed feeding. High doses, however, irreversibly disrupted feeding and prevented stylet reinsertion. Aphid motility was not affected up to an estimated haemolymph concentration of 1 mM pymetrozine. Aphids which eventually stopped feeding on pymetrozine-treated plants showed EPGs with distorted salivation/ingestion patterns. It is concluded that pymetrozine does not have a general toxic effect on aphids but selectively interferes with the nervous regulation of feeding behaviour which consequently results in death due to starvation after a few days. © 1997 SCI.     

Control and measurement of three-qubit entangled states

We report the deterministic creation of maximally entangled three-qubit states-specifically the Greenberger-Horne-Zeilinger (GHZ) state and the W state-with a trapped-ion quantum computer. We read out one of the qubits selectively and show how GHZ and W states are affected by this local measurement. Additionally, we demonstrate conditional operations controlled by the results from reading out one qubit. Tripartite entanglement is deterministically transformed into bipartite entanglement by local operations only. These operations are the measurement of one qubit of a GHZ state in a rotated basis and, conditioned on this measurement result, the application of single-qubit rotations.     

On the Isotopic Composition of Pb in Cloud Waters in Central Germany. A Source Discrimination Study

Fifty seven (57) cloud water samples collected in 1 hr intervals during 9cloud events in 1997 at the summit of the Brocken (altitude 1142 m) in Central Germany were analyzed for their Pb concentrations and isotopic compositions. For comparison, filterdusts of such possible emitters as power plants, cement factories, waste incinerators, cars and others were also studied.Profiles over many hours reveal changes in composition correlatedwith changes in the origin of the air masses. Five main groups ofpossible sources of the Pb can be distinguished: most importantare (1) the European standard pollution ESP dominating the continent from Germany over France to Scandinavia and (2) industrial Pb (and soot from car exhausts) followed by (3) urban waste incinerators as well as (4) perhaps ores from Norilsk/Siberia, and, somewhat uncertain, (5) ores from PaleozoicEuropean deposits. Local and daily varying anthropogenic emissions of the sources (2–5) cause scatter of the points around the ESP correlation line. In soils all these variationsand individual signatures are levelled out so that specific sources of pollution cannot be identified anymore. Geogenic Pbfrom rocks and soils is the same as that from power plants and cement factories. It is one of the two nominal end components making up the mixture of the ESP. The less radiogenic end component of this mix which must contain Pb from very old deposits is somewhat elusive: none of the large Archaic or Proterozoic deposits could be identified. Most probably numerous sources contribute to this Pb. Pb from leaded gasoline seems to be absent or is hidden under the five components dominating the composition of the Pb in the European environment. This probably reflects phasing out of such gasoline in most European countries. The Pb in the clouds may contain a small component of old Proterozoic or even Archaic Pb, but it can also be modelled with Paleozoic Pb.     

The Isotopic Composition of Anthropogenic Pb in Soil Profiles of Northern Germany: Evidence for Pollutant Pb from a Continent-wide Mixing System

Seventy-five samples of six soil profiles from forests on different substrates plus one next to a motorway were analyzed for the variation of Pb concentration and isotopic composition with depth. A substantial fraction of the anthropogenic Pb (peak concentrations between 74 and 300 ppm) is still stored in the organic top soil, and seldom penetrates deeper than 20–30 cm. In (²⁰⁸Pb/²⁰⁶Pb) vs. (²⁰⁷Pb/²⁰⁶Pb)-diagrams the Pb in the uppermost layers of the profiles plots on an excellent correlation line (R = 0.99) indicating essentially a two-component mixing system. Values for the dust on Scottish plants, Norwegian and Swiss bogs as well as for aerosols collected over the North Atlantic (data from the literature) plot on the same correlation line showing that the Pb was deposited from a continent-wide mixing system with two apparent end members: The radiogenic one is similar to geogenic Pb and could consist of contributions from certain European ore deposits and from different soil components (e.g. silicates and Fe-oxides), power plants and cement factories. The less radiogenic component must contain or consist of Pb from Proterozoic or even Archaic ore deposits. However, the sources of this Pb remain somewhat elusive. In any case, this isotopic pattern is so consistent all over Europe that the correlation line may serve as a line of reference for quasi normal or European Standard Lead Pollution (ESLP). The gasoline derived Pb in the soils is swamped by Pb of other provenances.     

A reassessment of the maintenance ration of red tilapia

The tilapias are one of the most important fish groups in aquaculture.In spite of this, relatively few workers have attempted to establish the feedration that would suffice for their maintenance. The results that they present,moreover, do not match, which may be attributed as much to differences inanalytical procedure as to experimental protocol. In this work, previous dataonred tilapia by the late Dr was therefore reassessed in order to arrive at more reliableresults. The dataset was based on fish between 15 and 20g wet body mass givenvarious levels (0, 0.5, 1 & 3% of body mass) of three protein level diets(low: 13.1%, LP; medium, 28.7%, MP; high: 43.9%, HP) at two temperatures (20.9& 24.3 °C). The required feeding level to maintain drybodyweight was 2.52, 2.81 and 7.05 g kg^–0.8 fishweight per day for the HP, MP and LP diets respectively at the highertemperature and 1.92, 2.32 and 5.04 g kg^–0.8day^–1 at the lower temperature. This gave rise to anaverage Q₁₀ coefficient of 2.22. The required feed quantity tomaintain body protein or body energy, however, was in most cases higher, partlybecause the fish initially had high protein and lipid and low ash content.Comparisons with other maintenance estimates for tilapia were also made and thereasons for discrepancies between the results obtained here and elsewherediscussed.     

Monitoring megabenthic communities in abyssal manganese nodule sites of the East Pacific Ocean in association with commercial deep-sea mining

Marine mining of manganese nodules will affect the deep sea benthos in a harmful and longterm way. The near complete removal of manganese nodules will result in a change of the megabenthic community from one that is rich in both diversity and density to a soft bottom community with greatly reduced diversity. Pre-pilot mining tests and pilot mining operations, which have to demonstrate the feasibility of deep-sea mining, should be accompanied by environmental impact studies before commercial mining begins. The photographic assessment of megabenthic communities represents one cost-effective possibility of monitoring large-scale impacts on the deep sea floor. A method based on the analysis of video and photomaterial was used to obtain basic data on community structure and density of the abyssal megabenthos of undisturbed manganese nodule sites in the North (Clarion-Clipperton Fracture Zone) and South (Peru Basin) Pacific Ocean. A comparison of the results with data from the literature demonstrates that the different methods used result in different density values. Total density varied between less than 300 to more than 1600 individuals/10000 m². There is a clear need for standardization of methods. A system which combines video and photographic capabilities is useful. It will give the best results when the distance of the camera to the sea floor is between 2 and 3 m, and the area covered by one photograph is within 3 to 5 m².     

Multi-site validation of a soil organic matter model for arable fields based on generally available input data

The paper describes a simplified carbon balance model, derived from the CANDY model, which works in annual time steps requiring only clay content, soil type of the German classification system “Reichsbodenschätzung”, average air temperature and rainfall as site characteristics, a value for organic carbon content as the initial value as well as crop yield and organic matter amendments as management data.The Candy Carbon Balance (CCB) model has been validated using a dataset from 40 long-term experiments situated in Central Europe including 391 treatments with a total number of 4794 C_org observations. Statistical measures to prove model validity were mean error (ME = − 0.001) and root mean square error (RMSE = 0.119). In addition a number of tests were performed to make sure that the model has no systematic error for different types of site conditions and management activities. After this successful validation the CCB model is considered applicable for advisory service for arable fields on a wide range of site conditions. Due to the poor representation of clay soils in this study some more model tests on these soils would be recommendable.     

Brown bear conservation and the ghost of persecution past

Large carnivores, such as brown bears, are focal species for conservation efforts. Historically, brown bears were persecuted in Europe for centuries before their gradual elimination from much of Western Europe. In contrast, large carnivore populations in North America were eradicated within two centuries in the east and within a few decades in the west. After a change towards conservation-oriented management in the 20th century, many bear populations are again increasing on both continents. Europe is seemingly less suited (i.e. higher human densities, greater habitat alteration and landscape fragmentation) than in North America, however bears seem to respond faster to conservation measures in Europe. We analyzed ecological and historical factors that may affect differences in reproductive allocation (mean litter size in relation to mean adult female body mass) and help explain why different brown bear populations react differently to conservation measures. The results indicated that mean litter size increased significantly with mean adult female body mass and a long persecution history. Our results suggest that high and long-term rates of nonselective harvesting can change life-history traits of large mammals, as has also been shown by modeling, but only has been documented for morphological traits. Incidentally, this “ghost of persecution past” may have helped some brown bear populations to be more productive and therefore to respond more positively to protective management policies than populations with short exploitation histories.     

Largazole Pharmacokinetics in Rats by LC-MS/MS

A highly sensitive and specific LC-MS/MS method for the quantitation of largazole thiol, the active species of the marine-derived preclinical histone deacetylase inhibitor, largazole (prodrug), was developed and validated. Largazole thiol was extracted with ethyl acetate from human or rat plasma along with the internal standard, harmine. Samples were separated on an Onyx Monolithic C18 column by a stepwise gradient elution with 0.1% formic acid in methanol and 0.1% aqueous formic acid employing multiple reaction monitoring (MRM) detection. Linear calibration curves were obtained in the range of 12.5–400 ng/mL with 200 µL of human plasma. The overall intra-day precision was from 3.87% to 12.6%, and the inter-day precision was from 7.12% to 9.8%. The accuracy at low, medium and high concentrations ranged from 101.55% to 105.84%. Plasma protein bindings of largazole thiol in human and rat plasma as determined by an ultrafiltration method were 90.13% and 77.14%, respectively. Plasma drug concentrations were measured by this LC-MS/MS method. The pharmacokinetics of largazole thiol in rats was studied following i.v. administration at 10 mg/kg and found to follow a two-compartment model. Largazole thiol was rapidly eliminated from systemic circulation within 2 h. The established LC-MS/MS method is suitable for the analysis of largazole thiol in human plasma, as well.