Bibliothek

Notizen: Sixty RAPD primers were used to screen for a diagnostic marker that could be used to identify Pyrenophora graminea, a fungal seedborne pathogen that causes leaf stripe on barley. Primer pairs were designed to differentiate P. graminea from other Pyrenophora spp. using a sequence-characterized amplified region (SCAR) approach. A pair of P. graminea-specific primers (PG2 F/R) was obtained that amplified a single fragment from 37 isolates of P. graminea tested, but not from 29 isolates of other Pyrenophora spp. or 12 saprophytes isolated from barley seed. Rapid PCR detection was achieved using a LightCycler, in which the emission of fluorescence from the binding of SYBR Green I dye to the PCR products is measured. The P. graminea-specific product resulting from amplification with PG2 F/R can be distinguished from any nonspecific products by post-PCR melting point analysis. The PCR assay involves 40 amplification cycles of PCR, and the total PCR test including melting point analysis takes 25 min to complete. The rapidity of this test, combined with the closed ‘in-tube’ detection of PCR products, which reduces the potential for contamination, offers significant advantages compared with conventional laboratory and PCR analyses.

Notizen: Abstract The effects of lindane on the hatching, survival and development ofChironomus riparius Meigen were investigated over a complete life-cycle. Pupation and adult emergence were identified as the criteria most sensitive to lindane. The no-observed-effect-concentration (NOEL) and lowest-observed-effect-concentration (LOEC) of lindane to the life-cycle of C. riparius were determined as 1.1 and 9.9 μg/L, respectively. The results are discussed with respect to previous toxicity data and the potential role of life-cycle toxicity tests in hazard evaluation.

Notizen: Abstract The lethal toxicities of the four pollutants 3,4-dichloroaniline (DCA), atrazine, copper, and lindane were determined for the 2nd larval instar of the insectChironomus riparius Meigen and the juvenile stage (2nd or 3rd moult) of the crustaceanGammarus pulex (L.). Median lethal concentrations (LC50s) were determined over a 240 h test period. The order of toxicity of the test chemicals is different for each species. ForC. riparius, lindane was the most toxic, followed by copper, DCA, and atrazine. During the first 96 h of exposure, the order forG. pulex was copper, lindane, then DCA and atrazine with similar LC50 values. However, at 240 h lindane replaced copper as the most toxic chemical toG. pulex. The relative sensitivity of the two species was dependent on both the toxicant and the exposure period. The lethal concentrations determined for the four chemicals are compared to the results of other toxicity studies and discussed with respect to current standard test methods.

Notizen: Abstract Laboratory tests were developed to allow identification of the effects of toxicants on the predator-prey interaction between Hydra oligactis Pallas and Daphnia magna Strauss. Three test methods, which differed with respect to initial Daphnia population, test period, and management of predation level, were used to determine the influence of the organochlorine insecticide lindane on the interaction. The criteria examined were the population structures of the two species. The lindane treatments did not alter the production of Hydra. However, the final population structure of Daphnia was variously affected by the toxicant in the different test systems. The most sensitive endpoint, with a lowest observed effect concentration of 4 μg/L lindane determined after a 14 day exposure period, was increased recruitment of juvenile Daphnia in a test system which incorporated management of the Hydra. The results are compared to previously reported data derived from single species chronic tests, and the suitability of the test methods for hazard evaluation is discussed.

Notizen: Abstract. The feeding response of juvenile amphipod Gammarus pulex (L.) was investigated following exposure to freshwater pollutants. The method employed is nondestructive, provides a rapid indication of the status of groups of individuals, and is based on a time-response analysis of the consumption of the eggs of Artemia salina and the determination of median feeding times or FT50s. The feeding activity of juvenile G. pulex was found to be a sensitive response criterion for use in assessing the sublethal toxicity of copper, lindane, and 3,4-dichloroaniline (3,4-DCA). Reductions in gammarid feeding activity were identified following 96 hours exposure at 12.1 μg/L copper or 8.4 μg/L lindane and 240 hours exposure at 918 μg/L 3,4-DCA. However, a significant increase was observed in the feeding rate of gammarids that had been exposed for 240 h at 0.09 μg/L lindane in comparison with control values. The increase in feeding rate may be interpreted as a possible stimulatory effect associated with the toxicant action of lindane. Increases in gammarid feeding activity were not determined during the experiments conducted with either copper or 3,4-DCA. A sustained reduction in G. pulex feeding rates may cause growth inhibition and impaired reproduction which have previously been identified as sublethal responses of other freshwater organisms exposed to comparable concentrations of lindane, 3,4-DCA, or copper. The feeding bioassay was also used as a tool in an investigation of species interactions in toxicant systems. The feeding responses of G. pulex, which had been maintained in the presence of Asellus aquaticus (as interacting pairs) and exposed to a range of concentrations of lindane or 3,4-DCA, were recorded and compared. The findings illustrate the complex nature of test systems that integrate the stresses of toxicant and competition. In the lindane test system a reduction in gammarid feeding activity was observed following a 96-h exposure with A. aquaticus at 3.8 and 6.0 μg/L lindane (mean measured concentrations). After a 240-h exposure period a decrease in feeding rate was recorded only for gammarids that had been exposed to 6.5 μg/L lindane, however exposure to very low concentrations of lindane (0.1 and 0.9 μg/L) resulted in a significant increase in gammarid feeding activity. In the experiment conducted with 3,4-DCA the calculation of median feeding times or FT50s of gammarids that had been exposed for 96 and 240 h in the toxicant treatment groups with A. aquaticus was largely precluded (in most groups less than 50% of the A. salina eggs were eaten). However, control group FT50 values were determined on each occasion the bioassay was performed, indicating that a substantial reduction in gammarid feeding activity had occurred in the majority of the 3,4-DCA treatment groups.

Notizen: Abstract An electrochemical concentrator for application to the chlorine-caustic industry is currently under development. In it 30 to 35 wt % NaOH enters the anolyte and catholyte chambers and exits at 20 and 50 wt %, respectively. Consequently, in support of the electrochemical concentrator development, the conductance and transport properties of advanced cation exchange membranes in concentrated sodium hydroxide, are being investigated. The membrane voltage drop, sodium ion transport and water flux of these membranes in 20 to 35 wt % sodium hydroxide anolyte and 30 to 50 wt % sodium hydroxide catholyte at 75°C are presented. To better understand the behaviour of these membranes, electrolyte sorption measurements were conducted in the anolyte/catholyte environment appropriate for the electrochemical concentrator. The water uptake data appear to correlate well with the conductance data and the combined NaOH and water sorption data are consistent with the sodium ion transport data.