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1.
Three in vitro assays to detect benzimidazole resistance, namely, the egg-hatch assay, tubulin-binding assay, and a larval-development assay, were evaluated by estimating the level of benzimidazole resistance in three field isolates of Haemonchus contortus compared with a susceptible reference strain. Comparisons were also made with estimates of benzimidazole resistance of the three field strains obtained from an in vivo controlled anthelmintic efficacy test. All three in vitro tests showed similar, consistent results which also suggested greater sensitivity than the in vivo assay. These results indicate that selection of an in vitro technique to determine benzimidazole resistance should therefore be based on considerations other than precision, such as technical expertise, availability of equipment, cost and speed in which diagnosis is required. 相似文献
2.
G. V. Subbarao C. Johansen J. V. D. K. Kumar Rao M. K. Jana 《Biology and Fertility of Soils》1990,9(1):49-53
Summary There were significant differences among pigeonpea [Cajanus cajan (L.) Millsp] Rhizobium sp. strains (IC 3506, IC 3484, IC 3195, and IC 3087) in their ability to nodulate and fix N2 under saline conditions. Pigeonpea plants inoculated with IC 3087 and IC 3506 were less affected in growth by salinity levels of 6 and 8 dS m-1 than plants inoculated with the other strains. For IC 3506, IC 3484, and IC 3195, there was a decrease in the number of nodules with increasing salinity, while the average nodule dry weight and the specific nitrogenase activity remained unaffected. However, in IC 3087, the number of nodules increased slightly with increasing salinity. Leaf-P concentrations increased with salinity in the inoculated plants irrespective of the Rhizobium sp. strain, and leaf-N concentrations decreased with increasing salinity in IC 3484 and IC 3195 only. Shoot-Na and-Cl levels were further increased in these salt-sensitive strains only at 8 dS m-1. Therefore there may be scope for selecting pigeonpea Rhizobium sp. symbioses better adapted to saline conditions. The Rhizobium sp. strains best able to form effective symbioses at high salinity levels are not necessarily derived from saline soils.Submitted as JA No. 919 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) 相似文献
3.
High‐energy feeds, with increased fat concentrations, are often used in salmon farming to improve feed:gain ratio. However, fish are thought to regulate ingestion to meet their energy and nutrient intake requirements. Further, feeds with excessive fat content will lead to increased adiposity, which is thought to exert a negative feedback on feed intake via lipostatic regulation mechanisms. A test of the lipostatic model of feed intake regulation was carried out on juvenile Atlantic salmon Salmo salar L. (c. 165 g) in which body fat content (5.6% and 9.4% body fat) had been manipulated by feeding feeds with different fat concentrations. Thereafter, the fish were offered the high‐ and low‐fat feeds (15.6% and 26.5% dietary fat content) simultaneously, and our hypothesis was that feed preference and intake would reflect the state of fat storage. Thus, we predicted that, when given a choice of feeds, the lean fish would eat more, and that the body fat status of the groups would converge over time. The results indicated a general preference for the leaner feed irrespective of adiposity level, but leaner fish consumed more feed, grew faster and deposited more body fat than their fatter counterparts. Over time, body compositions converged among treatments, and differences in feed intake ablated. These findings seem to provide supportive evidence for a lipostatic regulation of feed intake in fish. 相似文献
4.
Rahmstorf (Reports, 19 January 2007, p. 368) presented an approach for predicting sea-level rise based on a proposed linear relationship between global mean surface temperature and the rate of global mean sea-level change. We find no such linear relationship. Although we agree that there is considerable uncertainty in the prediction of future sea-level rise, this approach does not meaningfully contribute to quantifying that uncertainty. 相似文献
5.
Fleischer RL Haines EL Hanneman RE Hart HR Kasper JS Lifshin E Woods RT Price PB 《Science (New York, N.Y.)》1970,167(3918):568-571
Particle tracks in Apollo 11 samples are dominantly of cosmic ray and solar origin: primary galactic and solar flare particles, likely spallation recoil tracks, and possible solar-wind heavy particles. The energy spectrum of irongroup nuclei is inferred from track density gradients in surface layers, and a limit of < 10(-7) centimeter per year is deduced for the surface erosion rate. From cosmic ray tracks in rock and core samples it is clear that the lunar soil is stirred often during each few million years. X-rays reveal augite, anorthite, olivine, ilmenite, troilite, nonmeteoritic iron, and assorted glasses, but no major structural damage. Hydrogen, helium, and other gases in the fines are compatible with expected solar wind ratios. 相似文献
6.
The results of a detailed study of the brachiopods of the most complete Cretaceous-Tertiary boundary in Denmark, Nye Klslashed circlev, show an extinction pattern for this marine invertebrate group compatible with that reported for pelagic foraminifera and coccoliths and with the impact scenario. The extinction is abrupt, coinciding with the Maastrichtian-Danian boundary. There is no warning in the form of decreasing density, decreasing diversity, or early extinction of specialized groups. The basal few meters of the Danian are almost devoid of brachiopods, and a Danian brachiopod fauna starts almost as abruptly as the Maastrichtian fauna disappeared. The new fauna is similar to the Maastrichtian as regards density and diversity, and at maximum six species are common to both stages. The northwest European Masstrichtian chalk is composed mainly of the remains of coccoliths and pelagic foraminifera. The mass extinction of these groups led to a total cessation of chalk production. The chalk is overlain by a thin clay bed deposited partly under anoxic conditions. This combination of anoxia and clay deposition coupled with a cessation of productivity led to the extinction of specialized groups such as the chalk brachiopods. The surviving species included forms that could survive in well-aerated shallow marine waters on substrates other than chalk. 相似文献
7.
RNA silencing genes control de novo DNA methylation 总被引:1,自引:0,他引:1
Chan SW Zilberman D Xie Z Johansen LK Carrington JC Jacobsen SE 《Science (New York, N.Y.)》2004,303(5662):1336
8.
9.
Three oak stands (Quercus petraea and Quercus robur) in the Weinviertel, Lower Austria, located along a distance gradient from a lime quarry, were studied to determine the effects of basic aerosols on the deposition of ammonium, nitrate and sulfate. Higher concentrations of limestone aerosols in the vicinity of the quarry are suggested by higher Ca2+ fluxes and pH in throughfall and precipitation. The ammonium/nitrate ratio in throughfall decreases with distance from the quarry, though monitoring of NH3 and NO2 concentrations in the air with passive samplers shows the opposite trend. These findings support the theory of discrimination against NH3 in dry deposition due to the presence of Ca 2+ particles on leaf surfaces resulting from limestone aerosols. Higher sulfate deposition near the quarry is consistent with higher atmospheric SO2 concentrations and co-deposition between calcium and sulfate. 相似文献
10.
We studied microbial and protozoan activity, diversity and abundance as affected by Cu2+ amendments ranging from 0 to 1000 μg g−1 over a 70-day period. At the end of the experiment the microbial population size, as indicated by substrate-induced respiration, had normalized for all Cu2+ concentrations, but 1000 μg g−1. Protozoan abundance was negatively affected by Cu2+, although, only in the first few weeks. A more detailed analysis of the individual components that make up the microbial and micro-faunal populations (phospholipid fatty acid (PLFA) profile and protozoan morphotypes), however, yielded a somewhat more complex picture. For the three highest Cu2+ amendments (160, 400 and 1000 μg g−1), there still was a significant reduction in number of differentiable protozoan morphotypes. The bacterial PLFA pattern suggested a shift from Gram-negative towards Gram-positive bacteria for the high amendments, a process where protozoan grazing most likely played a significant role. The ratio of the trans/cis isomers of the 16:1ω7 fatty acid indicated that Cu2+, even at low and medium concentrations, induced physiological changes in the microbial population. The relatively slight changes in total microbial and micro-faunal abundance and activity, also at the highest Cu2+ concentrations, probably reflected the ability of the community to compensate for loss of taxa by functional substitution. 相似文献