The efficacy of three mycotoxin adsorbents to alleviate aflatoxin B1-induced toxicity in Oreochromis niloticus

Aflatoxicosis, toxicity of aflatoxin, is of great concern in aquaculture. This study was conducted to assess the efficacies of three adsorbents, a hydrated sodium calcium aluminosilicates (HSCAS), Saccharomyces cerevisiae (S.C.) and an esterified glucomannan (EGM), against feed contaminated with contained 200 μg/kg (ppb) aflatoxin B₁ (AFB₁). A total of 240 Nile tilapia fingerlings, Oreochromis niloticus (15 ± 2 g), were randomly divided into eight experimental groups (30 fish per group) with three replicates. Group T₁ represented the negative control fed on a basal diet, and T₂ was the positive control group fed on a basal diet supplemented with 200 ppb AFB₁. Groups T₃, T₄ and T₅ were fed the AFB₁-contaminated diet (200 ppb) supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. Groups T₆, T₇ and T₈ were fed a basal diet supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. The reduction in AFB₁-bioavailability was judged by toxin residues in fish musculature throughout the study beginning at the second week of exposure. AFB₁ reduced the survivability, total weight gain, average daily gain and specific growth rate, evident as early as the second week of exposure. The total erythrocyte count, hemoglobin content and total leukocyte count were significantly decreased after AFB₁ exposure for 6, 8 and 10 weeks, respectively. Prolonged administration of AFB₁ led to significant increases in serum alanine transaminase, aspartate transaminase and creatinine activity, and produced significant decreases in plasma proteins, including serum globulin. The specific immune response was assessed by an agglutinating antibody titer after immunization of the fish with an Aeromonas hydrophila vaccine. The antibody titer and relative level of protection of fish challenged with Aeromonas hydrophila were reduced throughout the period of examination in AFB₁-exposed fish. Supplementation with HSCAS, S.C. or EGM significantly improved growth performance, blood parameters and immune status; in addition, these groups showed decreased AFB₁ residues in fish musculature when compared with AFB₁-treated fish. HSCAS effectively reduced AFB₁ toxicity, whereas S.C. and EGM were less efficacious.     

Preparation of (R)-2-(4-hydroxyphenoxy) propionic acid by biotransformation

With Beauveria bassiana Lu 700 as biocatalyst an ecologically beneficial process has been developed for the production of (R)-2-(4-hydroxyphenoxy) propionic acid. The fungal strain used in this process, B. bassiana Lu 700, is also a very suitable catalyst for the selective monohydroxylation of other aromatic carboxylic acids.     

Suction air traps vs. crops in monitoring Russian wheat aphid, Diuraphis noxia (Kurdj.) in Central Europe (Hom., Aphididae)

Summary  The Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.) is an exotic expansive aphid on the small grains determined in the Czech republic since 1993 (1995). Determination of RWA flight patterns by suction air traps (= SATs) between 1994-1998 indicated some banker, less important, or indicated RWA distribution areas. A comparison of the RWA monitoring by SATs and by crop samples in areas more or less distant from individual SAT locations manifested a high silmilarity of RWA evidence in its overall distribution and area-influenced population numbers. Owing to geographic area-dependent features of its life-cycle (holocycly) and host plant preferences, RWA seems to be most injurious to spring barley. In spite of the role of SATs in aphid forecasting, RWA samples are recommended to be taken also from the crops at the early ripening stage as the respective SAT evidence reflects only the emigration of the alate aphids originating from the decreasing populations. In general, RWA detection by SATs was either simultaneously or successively found to reflect the RWA presence in the more or less distant crops. The 30km perimeter of a SAT is agreed to be representative for mon-toring RWA populations in a sampled area.     

Physiological responses of over-wintering common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) to disturbance by Eurasian otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>)

Using a tame animal, the impact of otter (Lutra lutra) disturbance on over-wintering carp (Cyprinus carpio) was monitored in two experiments, 133 and 140 days, respectively, over two consecutive winters (November–April). The level of stress in over-wintering carp exposed to various intensities of disturbance by otters was quantified using biological indicators of stress (cortisol, cortisone, indices of nitrogen, carbohydrate, lipid and mineral metabolism and activity of basic blood plasma enzymes) taken from blood plasma of stocked carp at the end of the winter seasons (when the photoperiod was 12 light:12 dark, respectively, 13L:10D). Moreover, condition (Fulton’s coefficient of condition and fat content in muscles) and mortality rate of that carp were measured after over-wintering and also after the subsequent vegetation period. The analysis of blood and tissue samples of experimental fish showed changes in nitrogen, carbohydrate and mineral metabolism as well as levels of hormones and fat reserves. Higher response to stress in metabolism of carp with lower intensity of disturbance by otter suggests that high level of disturbance can lead to metabolic adaptation of carp to stress. The effect of stress on the mortality rate of carp during the over-wintering is not clear. Nevertheless, the negative effect of stress on survival, condition and growth rate of carp in the subsequent vegetation period was not observed.     

Large-scale permafrost degradation as a primary factor in Larix sibirica forest dieback in the Khentii massif,northern Mongolia

The objective of this study is to investigate the potential causes of widespread Larix sibirica Ledeb.mortality observed in the Khentii massif of northern Mongolia.The ratio of deadwood to living trees in affected stands in the Goricho region,the southernmost study site situated close to the Gobi Desert,was as high as 3.6:1.Moisture fluctuations monitored over 2 years using electrical impedance spectrometry revealed that the Goricho study site had higher soil moisture levels than the two less affected sites Barun Bayan and Dzun Bayan.High soil moisture was recorded in an area characterized by highly skeletal soils,ones with more than 35%by volume of rock fragments,and comparatively shallow soil horizons,from valley to mountains.The layer of permafrost influencing hydrogeological processes is much deeper in the Goricho region compared to the undisturbed study sites.Redundancy analysis confirmed a significant number of dead L.sibirica on sites with developed soils.Live forest stands,however damaged,grow in this region on well-drained scree slopes or on rocky bastions.The mass mortality observed for L.sibirica may be directly linked to accelerated permafrost thaw in the area bordered by the Tuul and the Terelj Rivers.Our assumption is that L.sibirica root system necrosis occurred as a result of long-term waterlogging of developed soils with high spatial heterogeneity,normally able to absorb high quantities of groundwater.The areas unaffected were scree fields and rocky bastions characterized by adequate drainage.All of our findings support the primary stages of large-scale permafrost thaw,i.e.,correlating increases in soil moisture with increasing permafrost active layer thickness.     

New data on aetiology of nodular gill disease in rainbow trout, Oncorhynchus mykiss

We studied amoebae associated with nodular gill disease (NGD) outbreaks in rainbow trout Oncorhynchus mykiss (Walbaum) in fish farms in South-Western Germany. Gills of 12 diseased rainbow trout were examined in fresh, by isolation attempts, histologically and using in situ hybridisation (ISH). A total of nine amoeba strains of the genera Acanthamoeba (1), Hartmannella (2), Naegleria (1), Protacanthamoeba (1) and Vannella (4) were isolated and determined using light microscopical, ultrastructural and molecular methods. Specific molecular probes designed from the SSU rDNA sequences of individual amoeba strains were used for non-radioactive ISH in histological sections. Association of Naegleria sp. with NGD and a direct ISH proof of Naegleria trophozoites attached to hyperplastic gill epithelium are novel findings, expanding the number of possible agents of NGD and supporting the hypothesis on multicausal aetiology of this disease.     

Direct effect of fertilization on microbial carbon transformation in grassland soils in dependence on the substrate quality

Response of microbial metabolism (growth, substrate utilization, energetic metabolism) to fertilization by N and P and resulting changes in soil‐organic‐matter (SOM) decomposition (priming effect) were studied in grassland soils with relatively high organic‐matter content. Treatments with and without glucose addition were studied to simulate difference between rhizosphere and bulk soil. Our expectation was that fertilization would decrease soil respiration in both treatments due to an increased efficiency of microbial metabolism. At first, fertilization activated microbial metabolism in both treatments. In glucose‐nonamended soils, this was connected with a short‐term apparent priming effect but if glucose was available, the higher energetic demand was covered by its mineralization in preference against SOM, causing significant SOM savings as compared to unfertilized soils. After a relatively short period of 1–3 d, however, the phase of deprived microbial metabolism occurred in both treatments, which was characterized by lower soil respiration in fertilized than in unfertilized soils. Fertilization further decreased net microbial growth following glucose addition, shortened turnover time of microbial biomass and changed the partitioning of assimilated glucose within microbial biomass (decreased accumulation of storage compounds and increased the proportion of mineralized glucose). As a result, fertilization reduced soil respiration mainly due to a deprivation of microbial metabolism. The rate and range of microbial response to fertilization and also the amount of saved soil C were larger in the soil with higher SOM content, likely driven by the higher content of microbial biomass.     

The inability of tapeworm Hymenolepis diminuta and fluke Dicrocoelium dendriticum to metabolize praziquantel

Biotransformation enzymes can, to a certain extent, protect parasitic worms against the toxic effects of anthelmintics and can contribute to drug-resistance development. The objective of our work was (1) to find and identify phase I and II metabolites of the anthelmintic praziquantel (PZQ) formed by the lancet fluke (Dicrocoelium dendriticum) and the rat tapeworm (Hymenolepis diminuta) and (2) to compare PZQ metabolites in helminths with PZQ biotransformation in rat as host species. Ultra high performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS) was used for this purpose. During in vitro incubations, mitochondria-like and microsomes-like fractions (prepared from homogenates of adult worms or from rat liver homogenate) were incubated with 10 and 100 μM PZQ. Liquid/liquid extraction was used for samples during in vitro experiments. In the ex vivo study, living D. dendriticum and H. diminuta adults were incubated in RPMI-1640 medium in the presence of 50 nM or 100 nM PZQ for 24h. After incubation, the worms were removed from the medium and homogenized. Homogenates of worms, medium from the incubation of worms or rat hepatocytes and rat urine (collected during 24h after oral PZQ administration) were separately extracted using solid-phase extraction. The results showed that both D. dendriticum and H. diminuta enzymatic systems are not able to metabolize PZQ. On the other hand, thirty one different phase I and four phase II PZQ metabolites were detected in rat samples using UHPLC/MS/MS analyses. These results show that our experimental helminths, as the members of tapeworm and fluke groups of parasites, are not able to deactivate PZQ, and that the biotransformation enzymes of the studied helminths do not contribute to PZQ-resistance.     

Different immune response of pigs to Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis infection

Mycobacterium avium subsp. avium (MAA) and Mycobacterium avium subsp. hominissuis (MAH) are the most common mycobacterial species isolated from granulomatous lesions in swine in countries with controlled bovine tuberculosis. This study is focused on the immunological aspect of MAA and MAH infection in pigs. We detected induction of humoral and cell-mediated immunity in experimentally infected pigs. Specific antibodies were analyzed in serum by ELISA and the IFN-γ release assay was used for evaluation of cell-mediated immunity. While MAA induced a significant increase of both types of immune responses, MAH-infected pigs had an unvarying level of specific antibodies and showed low cell-mediated immunity with high individual variability. The subsequent in vitro experiment confirmed the lower immunogenicity of the MAH strain in comparison to MAA. MAH-infected porcine monocyte-derived macrophages showed a weaker induction of pro-inflammatory mediators in comparison to MAA, which included mRNA for IL-1β, TNF-α, IL-23p19, IL-18 and chemokines CCL-3, CCL-5, CXCL-8 and CXCL-10. Additionally, qualitative proteomic analysis revealed 28 proteins exclusively in MAA and 7 proteins unique to MAH. In conclusion, closely related M. avium subspecies MAA and MAH showed different capacities to stimulate the porcine immune system. From a diagnostic point of view, the IFN-γ release assay showed higher sensitivity than the detection of specific antibodies by ELISA and seems to be an effective tool for discrimination of MAA-infected pigs. In the case of MAH infection, the IFN-γ release assay could fail because of the low immunogenic capacity of the MAH strain.