排序方式: 共有4条查询结果,搜索用时 0 毫秒
1
1.
Development of a rapid assay for the diagnosis of Myxobolus cerebralis in fish and oligochaetes using loop-mediated isothermal amplification 总被引:1,自引:0,他引:1
A loop-mediated isothermal amplification assay was developed for the rapid detection of Myxobolus cerebralis in both fish and oligochaete hosts. The assay was optimized to amplify parasitic DNA by incubation with Bst DNA polymerase and a set of six specially constructed primers at 65 degrees C for 60 min. The amplification products were detected visually using SYBR Green I dye which gave identical results to gel electrophoresis analysis. Parasite DNA was detected from infected oligochaetes, and from the anal fin, caudal fin, dorsal fin and operculum of clinically infected fish. This 'Myxo-LAMP' assay has a detection limit similar to that of a polymerase chain reaction assay (10(-6)), but is more rapid and only requires a water bath for amplification and is therefore practical for simple and rapid diagnosis of infected tissue. 相似文献
2.
Jan-Willem M. Wegener Gerard A. van den Berg Gerard J. Stroomberg Martin J. M. van Velzen 《Journal of Soils and Sediments》2002,2(2):71-76
Background Available fractions of metal concentrations in sediment pore water are difficult to measure without disturbing the sediment
core. The available fraction is an important parameter in understanding the risks for benthic organisms. Not much is known
about the influence of the presence of benthic organisms to the available fraction.
Objectives The aim of this study was to discuss the dynamics of metal behaviour in natural sediments and the influence of the presence
ofTubifex on sediment chemistry using DGT. Methods. DGT-probes were added to six beakers to cover a depth profile of 0 to 13 cm. The
six beakers contained three different sediments. For each sediment, one beaker had 1 g ofTubifex added, the other beaker contained noTubifex. After two weeks of exposure, the probes were withdrawn and strips were analysed for their content of cadmium, copper and
zinc.
Results and discussion Available concentrations were higher in the upper layer (0–1 cm) of the sediment core, where conditions are generally more
oxic. The presence ofTubifex worms led to a decrease of the available concentrations in the upper layer, due to the competition of the worms with the
DGT for the available metal fraction. On the other hand, the presence of the worms led, via bioturbation, to an increased
oxygen penetration depth in the sediment, and, as a consequence, to an increase of the available fraction in the next-higher
sediment layer.
Conclusions In sediment cores without organisms, very steep gradients of the available metal concentration in pore water have been found.
The change from a high to low amount of available fraction corresponds to the change from oxidised conditions in the surficial
sediment layer to reduced conditions in the lower sediment layers. The tunnelling behaviour ofTubifex worms leads to a penetration of oxygen to deeper sediment layers, and to an increase of the available metal fraction in the
pore water.Tubifex competes with DGT for the available fraction, resulting in lower metal amounts accumulated in the DGT probe. Competition
is the prevailing effect in the top 1 cm layer of all sediments. In the second 1 cm layer, competition, in most cases, is
not strong enough to compensate the increase in metal availability due to the broadening of the oxidised zone.
Recommendations The effects of sediment organisms on the deepening of the oxidised layer and on the availability of metals in pore water need
further investigations and quantification. DGT is recommended as an instrument for measuring available metal concentrations
in these studies. 相似文献
3.
Ian C. Simpson Pierre A. Roger Roberto Oficial Ian F. Grant 《Biology and Fertility of Soils》1993,16(1):34-40
Summary The density and composition of ricefield oligochaete populations were estimated in 33 farmers' fields in the Philippines and related to physicochemical properties of the soils and agrochemical use. The spatial distribution of organisms and the investigative sampling strategy were determined from a high-intensity sampling in a single ricefield. Species diversity was low. The dominant species were Limnodrilus hoffmeisteri and Branchiura sowerbyi. The spatial distribution of populations was contagious and densities ranged from 0 to 35 000 m-2 (maximum 620 kg ha-1). Mean population density was positively correlated with soil moisture, organic matter, and the quantity of N fertilizer applied. No pesticide impacts were observed. 相似文献
4.
Ian C. Simpson Pierre A. Roger Roberto Oficial Ian F. Grant 《Biology and Fertility of Soils》1993,16(1):27-33
Summary The impacts of N fertilizer, pesticides and green manure on aquatic oligochaetes in irrigated ricefields were investigated in experimental plots. Populations, determined by the wet sieving of soil cores, were dominated by the Tubificidae Limnodrilus hoffmeisteri. Total densities ranged from 0 to 40 000 m-2. Oligochaete numbers increased in response to additions of urea N. An inhibitory effect of carbofuran on oligochaete populations was observed during the first season of experimental pesticide treatments, but not during the following year. The green manure Sesbania rostrata stimulated population development more than Azolla microphylla. Populations in plots maintained as wet fallow remained low throughout the crop cycle. Population dynamics were associated with the crop cycle. Peak densities were achieved 30–50 days after transplanting. 相似文献
1