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91.
Assi Weber Marjut Karsisto Riika Leppänen Veronica Sundman J. Skujiņš 《Soil biology & biochemistry》1985,17(3):291-296
Mineralization of organic matter and microbial activities in an intensively cultivated acid, N-rich peat soil planted with Salix sp. cv. aquatica were examined for 3 yr. The soil was amended with wood ash or NPK fertilizers providing N as ammonium nitrate or urea. The wood ash amendment (10 tons ha?1) increased soil pH from 4.6 to 5.5 and increased markedly all microbial activities measured, resulting in increased mineralization and N availability, and in loss of 9% total soil N during the first year. The addition of ammonium nitrate caused a corresponding though less pronounced increase in N mineralization. Cellulose decomposition increased in all amended soils, reaching rates 53–86% higher than in non-amended soil. Potential N2 fixation (C2H2 reduction) by free-living organisms was increased by the ash-amendment. Potential denitrification rates were positively correlated (r = 0.98) with the presence of water-soluble organic-C, which was more abundant in ash-amended and non-amended soils than in the soils fertilized with N. 相似文献
92.
Jürgen Weber Jupp Kreutzmann Anita Plantikow Evelyn Claus Werner Manz Peter Heininger 《Journal of Soils and Sediments》2006,6(2):84-91
Goal, Scope and Background Numerous xenobiotics released into surface waters are transferred to suspended particulate matter and finally attached to
sediments. Aquatic organisms may be exposed to them by direct particle feeding, by physical contact with contaminated surfaces
as an exposure route, and by the uptake of dissolved contaminants after equilibration via the free water phase. In order to
assess potential sediment toxicity, each of these exposure routes has to be addressed. This paper presents a newly developed
particle contact assay that uses the fermentation performance of a specific Saccharomyces cerevisiae strain for the assessment
of toxic effects in sediments. The test procedure is based on the characteristic feature of growing yeast cells to attach
to sediment particles, which are also relevant for the accumulation of contaminants. The physical contact with lipophilic
contaminants mirrors an exposition pathway for the direct uptake into the cells. In order to quantitatively characterize the
toxic effects of particle attached pollutants on the fermentation performance, unpolluted native reference sediment was spiked
with representatives for widely distributed anthropogenic contaminants.
Methods Saccharomyces cerevisiae was established as sensitive eukaryotic microorganism for the ecotoxicological assessment of particle
attached anthropogenic contaminants in freshwater sediments. For this purpose, yeast cells were cultivated in sediment samples
and the resulting fermentation performance was continuously measured. Sediments artifically spiked with HCB, PCB, g-HCH, DDT,
and benzo(a)pyrene and solutions of each contaminant were comparatively investigated by means of their adverse effects on
yeast fermentation performance. Additionally, four native river sediments characterized by increasing levels of pollution
were assessed by the yeast particle contact assay, and simultaneously by standard aquatic tests with algae, daphniae, and
luminescent bacteria using pore water and elutriates. Results of the bioassays were related to specific sediment contamination
with respect to metals and organic priority pollutants.
Results and Discussion In sediments spiked with PCB and benzo(a)pyrene fermentation, performance was affected extensively below concentrations inhibiting
fermentation in contaminant solutions. This suggests a high efficiency of the exposure route by physical contact. The fermentation
performance was only slightly affected by single lipophilic pollutants, whereas mixtures of individually spiked sediments
caused critically reduced fermentation performance suggesting additive synergistic effects. Native river sediments modestly
to critically polluted by hazardous organic compounds lead to a slightly to dangerously reduced fermentation performance in
the yeast contact assay. These inhibitory effects were much less pronounced in the standard bioassays conducted with algae,
daphniae and luminescent bacteria, applying pore waters and elutriates as sample matrices. Using pore water, inhibition was
measured only in the most polluted sediment, elutriates lead to a slight inhibition of the algal growth in the undiluted sample
only. These results indicate an improved sensitivity of the yeast particle contact assay compared to the standard assays,
due to uptake and physical cell contact as additional routes of exposure.
Conclusion The yeast particle contact assay is a valuable tool for the assessment of ecotoxicological potential in freshwater sediments.
Since the assay addresses physical contact as an exposure route, it indicates bioavailability of lipophilic compounds in sediments.
Outlook The sensitive indication of bioavailable contaminants associated to sediment particles by the newly developed yeast particle
contact assay recommends it as a complementary microbial bioassay in a test battery for assessing major pathways of contaminants
in whole sediments. 相似文献
93.
14-3-3 protein down-regulates key enzyme activities of nitrate and carbohydrate metabolism in potato plants 总被引:1,自引:0,他引:1
The 14-3-3 protein is one of the best candidates for coordinating all plant metabolic pathways. To verify this suggestion transgenic potato plants with repression of one (J4 and J5 plants), two (G1 plants), and six (G3 plants) constitutive 14-3-3 protein isoforms as well as plants overexpressing the 14-3-3 protein were studied. Reduction in the 14-3-3 protein level in the J4 and J5 transformants, the G1 transformants, and the G3 transformants was close to 29, 41.5, 38, and 55%, respectively. In the case of the 14-3-3 overexpressing plants (J2), a 30% increase in protein content was detected. Changes in nitrate reductase (NR), sucrose phosphate synthase (SPS), and starch synthase (SS) activities in the transgenic plants perfectly reflect the overall 14-3-3 protein level. The highest increase in enzyme activities was observed for the G3 plants and the lowest for the J4 transformants. The same was detected for the measured metabolites. The highest increase in the protein, starch, and sucrose levels was detected in the tubers from the G3 transgenic plants. Because there was almost no change in the isoform ratio in the transgenic plants when compared to the control, it is suggested that it is the overall content of the 14-3-3 protein, rather than the content of particular isoforms, which plays a crucial role in the regulation of enzyme activities and thus in metabolite synthesis. The properties of the 14-3-3 overexpressing plants are very similar to those of the control ones, suggesting that the protein is in excess in the nontransformants and a further increase in its content is not recognized by cell metabolism. A considerable influence of the 14-3-3 protein level on potato plant metabolism was demonstrated. This effect was observed in key metabolic enzyme activities and metabolite content as well. A high variability between mean values, representing individual transgenes, with respect to nitrate reductase, sucrose phosphate synthase, and starch synthase activities in the examined genotypes was noted. These changes were closely correlated with metabolite levels, among them protein, starch, reducing sugars, and sucrose. The results obtained for the five types of transgenic potato plants in comparison with the control were statistically assessed using discriminate function and cluster analyses. 相似文献
94.
95.
96.
165 (93.7%) of 175 E. coli strains isolated from various materials of different animal species were correctly identified as E. coli with help of commercially available Bactident E. coli (E. Merck, D-6100 Darmstadt). Further 52 strains of the family of Enterobacteriaceae (2x Providencia sp., 2x Salmonella sp., 7 Citrobacter sp., 9 Proteus sp., 15 Klebsiella sp., 17 Enterobacter sp.) were correctly not identified as E. coli by this test. Bactident E. coli is a suitable test for rapid identification of E. coli in veterinary bacteriology. 相似文献
97.
98.
Four methods of predicting breeding values for carcass gain are compared: “regressed” least squares (RLSQ), mixed model (MM), mixed model with relationships among sires considered (MMR) and contemporary-comparison (CC). Very small changes in the ranking of the sires were observed from one method to another (rank correlations > 0.96). Consideration of the relationships among the sires or deleting the breed-group factor from the model did not lead to substantially different breeding values. The good correspondence of the predictors is mainly due to the well balanced distribution of the progeny over herds. 相似文献
99.
A F Weber J C Meiske E C Hooker D L Haggard A M Domagala D K Sorensen L C Buoen 《American journal of veterinary research》1987,48(6):899-903
In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number. 相似文献
100.