5种药剂对大型溞的急性活动抑制毒性研究

[目的]比较5种药剂对大型溞(Daphnia magna Straus)的急性活动抑制毒性。[方法]测定了5种药剂对大型溞的急性活动抑制中浓度EC50,并评价了5种药剂对大型溞的毒性。[结果]5种药剂对大型溞的毒性大小表现为:20%甲氰菊酯水乳剂(EC50=0.002 8a.i.mg/L)10%高效氯氟氰菊酯可湿性粉剂(EC50=0.008 9 a.i.mg/L)7.5%鱼藤酮乳油(EC50=0.189 9 a.i.mg/L)7.5%除虫菊素水乳剂(EC50=0.202 0 a.i.mg/L)0.5%大黄素甲醚水剂(EC50=0.640 1 a.i.mg/L)。[结论]为大型溞应用于环境污染监测研究提供了理论依据。     

Predicting N transformations from organic inputs in soil in relation to incubation time and biochemical composition

Seventeen different added organic materials (AOM) in a sandy soil were incubated under controlled laboratory conditions (28 °C, 75% WHC), and examined for C and N mineralisation. The transformation of added organics (TAO) model has been presented in previous work for predicting C mineralisation. The two variables (very labile and stable fractions of AOM) used in TAO have been related to the biochemical characteristics of the AOM. The transformed added organic N fraction (TAONF) was estimated from the remaining C_AOM and N_AOM linked by the C-to-N ratios. TAONF was split (P_im parameter) into immobilised N (imN) and inorganic N (inorgN). When necessary, an additional N mineralisation of imN was predicted by first order kinetics (constant k_remin). The TAO version with the two parameters P_im and k_remin allowed us to predict very different dynamics of N mineralisation and N immobilisation from the AOM. In a few cases, another first order kinetic law (constant k_v) was used to predict N volatilisation from inorgN.Biochemical characteristics of AOM were used for predicting N transformations. First, at each incubation date, inorgN was approximated to inorgNa=α(N-to-C_AOM)+β by linear regression. The α, β and −β/α (C-to-N_AOM threshold for mineralisation/immobilisation) were related to time. The TAO expression (1−P_im)TAONF was then replaced by the proposed approximation inorgNa as a function of incubation time and C-to-N_AOM. Secondly, significant relationships were computed between k_remin and organic fibre content of AOM. Finally, a TAO approximation was proposed for predicting the simultaneous transformations of C and N, only using biochemical data (plus the k_v parameter in a few cases of N volatilisation). For all AOMs, the validity of the approximation and its borderline cases were examined by comparing the two TAO versions.     

Evaluation of butorphanol-azaperone-medetomidine in captive cheetah (Acinonyx jubatus) immobilization

Objective

The butorphanol-azaperone-medetomidine fixed-dose combination (BAM, respectively, 30-12-12 mg mL^?1) with subsequent antagonism by naltrexone-atipamezole was evaluated for reversible immobilization of captive cheetahs (Acinonyx jubatus).

Water balance,respiration and immobilisation in relation to deltamethrin poisoning and physical conditions in the epigeal spider Oedothorax apicatus

The effect of a pyrethroid insecticide, deltamethrin, on water loss, metabolic rate and immobilisation was studied, using the epigeal spider Oedothorax apicatus (Blackwall) (Linyphiidae) as a test species. Water loss was measured gravimetrically at different temperatures, air humidities, and doses of deltamethrin. Metabolic rate and immobilisation were measured at different temperatures and doses. Immobilisation was measured at different relative humidities and temperatures. Water loss due to evaporation increased linearly with vapour pressure deficit. The slope of the latter relationship increased with temperature, indicating an increase in cuticle permeability with temperature. In addition to water loss by evaporation, deltamethrin treatment induced water excretion. This was positively related to dose and temperature, but independent of air humidity. Metabolic rate increased with temperature and dose. Immobilisation was highest at low temperatures in combination with low air humidity. The consequences of pesticide-induced water excretion are discussed with respect to field- and laboratory-based dose-effect relationships for pyrethroids presented in the literature. The present results seem to offer an explanation for hitherto unexplained minima in temperature-response curves in pyrethroid toxicity in some arthropod species. It is concluded that simultaneous measurements of metabolic rate, water-loss rate and pesticide effects are a prerequisite for an understanding of the effects of pesticides on arthropods.     

Soil C and N dynamics induced by leaf-litter decomposition of shrubs and perennial grasses of the Patagonian Monte

We assessed soil N and C dynamics in a decomposition experiment at microcosm scale with leaf litter of evergreen shrubs and perennial grasses of the Patagonian Monte. We hypothesised that eventual changes in leaf-litter quality in arid Patagonian ecosystems disturbed by grazing would lead to changes in C and N dynamics in decaying leaf litter and the associated soil. We constructed microcosms with local soil and litterbags containing leaf litter of three perennial grass and three evergreen shrub species. Microcosms were incubated at field capacity during 12, 42 and 84 days. We assessed N, C, phenolics and lignin concentrations in leaf litter before incubation, and N and C concentrations after incubation. We estimated inorganic and total N and organic C in soil before and after incubation. We calculated C and N budgets and the associated rates of C and N losses from leaf litter, microbial respiration, N immobilisation in litter and soil, and N mineralisation at microcosms of each species by inverse modelling techniques. Initial leaf-litter N concentration was significantly higher and C:N ratio lower in evergreen shrubs than in perennial grasses. Leaf litter of perennial grasses was very similar in initial chemical composition among species. In contrast, evergreen shrubs displayed a large variability in the concentration of secondary compounds among species. Accordingly, microcosms of perennial grasses showed similar rates of C and N processes while those of evergreen shrubs showed diverse patterns and rates of processes among them. Process rates in microcosms of one of the evergreen shrub species were closely related to those of perennial grasses. In contrast, process rates in microcosms of the two other evergreen shrub species were quite different between them and from those of perennial grasses. We conclude that (i) the replacement of perennial grasses by evergreen shrubs or the shifting of species within evergreen shrubs in ecosystems disturbed by grazing could have different effects on ecosystem processes depending on the species involved, and (ii) species rather than life forms should be used to predict leaf-litter decomposability and associated soil C and N dynamics particularly in evergreen shrubs.     

The prophylactic effect of a dry-cow antibiotic against Streptococcus uberis

The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.     

Improved Detection of Domoic Acid Using Covalently Immobilised Antibody Fragments

Antibody molecules, and antibody fragments in particular, have enormous potential in the development of biosensors for marine monitoring. Conventional immobilisation approaches used in immunoassays typically yield unstable and mostly incorrectly oriented antibodies, however, resulting in reduced detection sensitivities for already low concentration analytes. The 2H12 anti-domoic acid scFv antibody fragment was engineered with cysteine-containing linkers of two different lengths, distal to the antigen binding pocket, for covalent and correctly oriented immobilisation of the scFvs on functionalised solid supports. The Escherichia coli-produced, cysteine-engineered scFvs dimerised in solution and demonstrated similar efficiencies of covalent immobilisation on maleimide-activated plates and minimal non-covalent attachment. The covalently attached scFvs exhibited negligible leaching from the support under acidic conditions that removed almost 50% of the adsorbed wildtype fragment, and IC₅₀s for domoic acid of 270 and 297 ng/mL compared with 1126 and 1482 ng/mL, respectively, for their non-covalently adsorbed counterparts. The expression and immobilisation approach will facilitate the development of stable, reusable biosensors with increased stability and detection sensitivity for marine neurotoxins.     

Slow-cycle effects of foliar herbivory alter the nitrogen acquisition and population size of Collembola

In terrestrial systems there is a close relationship between litter quality and the activity and abundance of decomposers. Therefore, the potential exists for aboveground, herbivore-induced changes in foliar chemistry to affect soil decomposer fauna. These herbivore-induced changes in chemistry may persist across growing seasons. While the impacts of such slow-cycle, ‘legacy’ effects of foliar herbivory have some support aboveground, such impacts have not been evaluated for soil invertebrates. Here, we investigate legacy effects on Collembola population structure and nitrogen acquisition. We collected foliar material (greenfall) from trees that had, in the preceding season, been exposed to insect herbivory by leaf-chewing Lepidoptera. Collembola populations were grown with the greenfall in soil microcosms across 16 weeks. While there were only modest effects of herbivory on the greenfall mass loss, Collembola abundance and biomass after 8 weeks of greenfall exposure were approximately 2.5-fold greater in the controls. Given that Collembola biomass percentage nitrogen was relatively fixed, this translated to approximately 2.5-fold greater biomass nitrogen. The herbivore treatment decreased the absolute amount of Collembola biomass nitrogen derived from both greenfall and soil, and the relative contribution of litter nitrogen and soil nitrogen to Collembola biomass nitrogen was dependent on both the herbivory treatment and greenfall initial nitrogen. Our results show that slow-cycle, legacy effects of foliar herbivory may affect soil faunal population structure and nitrogen acquisition, demonstrating the potential for aboveground herbivory to influence belowground animal ecology and nitrogen cycling across multi-annual timescales.     

磷改良剂对中度和高度含碳酸盐的菜园土壤中Cd和Pb环境有效性和植物有效性的影响

The behaviour of metals mainly depends on soil p H, carbonate contents and contamination level, which should be considered for the management of contaminated soils. In this study, kitchen garden topsoils(0–25 cm) were sampled from the area around three smelters in France, with different Cd and Pb contamination levels. Effect of a phosphate amendment(a mixture of diammonium phosphate and hydroxyapatite) on the environmental availability and phytoavailability of Cd and Pb was evaluated by different chemical extractions and cultivating lettuce(Lactuca sativa L.), respectively. Changes in the distribution of Cd and Pb were found in most contaminated soils after phosphate amendment. An increase of Cd and Pb in the residual phase was highlighted in almost all carbonated contaminated soils, whereas a decrease of Pb in the exchangeable, water and acid-soluble phase was observed in most contaminated soils with the lowest carbonate contents. The concentrations of extractable Cd and Pb using calcium chloride and acetic and citric acids generally decreased after the soil amendment. Lettuces grown on amended soils were acceptable for human consumption as regard to Pb concentration. In contrast, some lettuces were unacceptable for human consumption, since the concentrations of Cd in the leaves were higher than the European legislation limit. Surprisingly, in carbonated soils with very low concentration of Cd, the Cd concentrations in lettuce reached up to the European legislation limit, making the lettuce unacceptable for human consumption.Our study highlighted the fact that the total metal concentration in soils does not always allow to predict the metal accumulation in the edible parts of vegetables in order to make a judgement about their acceptability or unacceptability for human consumption.