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61.
Human activity has increased the amount of N entering terrestrial ecosystems from atmospheric NO3− deposition. High levels of inorganic N are known to suppress the expression of phenol oxidase, an important lignin-degrading enzyme produced by white-rot fungi. We hypothesized that chronic NO3− additions would decrease the flow of C through the heterotrophic soil food web by inhibiting phenol oxidase and the depolymerization of lignocellulose. This would likely reduce the availability of C from lignocellulose for metabolism by the microbial community. We tested this hypothesis in a mature northern hardwood forest in northern Michigan, which has received experimental atmospheric N deposition (30 kg NO3−-N ha−1 y−1) for nine years. In a laboratory study, we amended soils with 13C-labeled vanillin, a monophenolic product of lignin depolymerization, and 13C-labeled cellobiose, a disaccharide product of cellulose degradation. We then traced the flow of 13C through the microbial community and into soil organic carbon (SOC), dissolved organic carbon (DOC), and microbial respiration. We simultaneously measured the activity of enzymes responsible for lignin (phenol oxidase and peroxidase) and cellobiose (β-glucosidase) degradation. Nitrogen deposition reduced phenol oxidase activity by 83% and peroxidase activity by 74% when compared to control soils. In addition, soil C increased by 76%, whereas microbial biomass decreased by 68% in NO3− amended soils. 13C cellobiose in bacterial or fungal PLFAs was unaffected by NO3− deposition; however, the incorporation of 13C vanillin in fungal PLFAs extracted from NO3− amended soil was 82% higher than in the control treatment. The recovery of 13C vanillin and 13C cellobiose in SOC, DOC, microbial biomass, and respiration was not different between control and NO3− amended treatments. Chronic NO3− deposition has stemmed the flow of C through the heterotrophic soil food web by inhibiting the activity of ligninolytic enzymes, but it increased the assimilation of vanillin into fungal PLFAs. 相似文献
62.
Courtin CM Gys W Gebruers K Delcour JA 《Journal of agricultural and food chemistry》2005,53(19):7623-7629
The relationship between syruping in refrigerated doughs upon prolonged storage and different aspects of arabinoxylan (AX) hydrolysis was investigated using Triticum aestivum xylanase inhibitor (TAXI) and different xylanases in the dough formula. Dough characteristics were evaluated with strong emphasis on the AX population and its fate as a function of storage time. Selective reduction of part of the flour endogenous xylanase activity in dough by added TAXI reduced dough syruping after 12 and 20 days of storage by 50%, providing straightforward evidence for the involvement of xylanases and, thus, AX in the syruping phenomenon. Addition of xylanases with different inhibitor sensitivities [an inhibition-sensitive Bacillus subtilis xylanase (XBS(i)) as well as a noninhibited mutant (XBS(ni)) thereof] to dough confirmed the importance of xylanases in dough syruping, on one hand, and the power of wheat flour TAXI to constitute a significant barrier against xylanase-mediated dough syruping, on the other hand. Use of xylanases with different substrate selectivities [an Aspergillus aculeatusxylanase (XAA) versus XBS(ni)] showed degradation of water-extractable AX (WE-AX) and solubilized AX to low molecular weight molecules rather than the conversion of water-unextractable AX (WU-AX) to high molecular weight water extractable components to be the main factor influencing dough syruping. 相似文献
63.
An extensive literature survey on metazoan parasites from rainbow trout Oncorhynchus mykiss has been conducted. The taxa Monogenea, Cestoda, Digenea, Nematoda, Acanthocephala, Crustacea and Hirudinea are covered. A total of 169 taxonomic entities are recorded in rainbow trout worldwide although few of these may prove synonyms in future analyses of the parasite specimens. These records include Monogenea (15), Cestoda (27), Digenea (37), Nematoda (39), Acanthocephala (23), Crustacea (17), Mollusca (6) and Hirudinea (5). The large number of parasites in this salmonid reflects its cosmopolitan distribution. 相似文献
64.
Mechanical transmission of porcine reproductive and respiratory syndrome virus throughout a coordinated sequence of events during cold weather 总被引:1,自引:1,他引:0
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Scott Dee John Deen Kurt Rossow Carrie Wiese Satoshi Otake Han Soo Joo Carlos Pijoan 《Canadian journal of veterinary research》2002,66(4):232-239
Using a field-based model, mechanical transmission of porcine reproductive and respiratory syndrome virus (PRRSV) was assessed throughout a coordinated sequence of events that replicated common farm worker behavior during cold weather (< 0°C). The model involved fomites (boots and containers), vehicle sanitation, transport, and the movement of personnel. A field strain of PRRSV was inoculated into carriers consisting of snow and water, and carriers were adhered to the undercarriage of a vehicle. The vehicle was driven approximately 50 km to a commercial truck washing facility where the driver's boots contacted the carriers during washing, introducing the virus to the vehicle interior. The vehicle was then driven 50 km to a simulated farm site, and the driver's boots mechanically spread virus into the farm anteroom. Types of containers frequently employed in swine farms (styrofoam semen cooler, metal toolbox, plastic lunch pail, and cardboard animal health product shipping parcel) contacted drippings from footwear on the anteroom floor. The truck wash floor, vehicle cab floor mats, boot soles, anteroom floor, and the ventral surface of containers were sampled to track the virus throughout the model. Ten replicates were conducted, along with sham-inoculated controls. At multiple sampling points PRRSV nucleic acid was detected in 8 of 10 replicates. In each of the 8 PCR-positive replicates, infectious PRRSV was detected on the surfaces of containers by virus isolation or swine bioassay. All sham-inoculated controls were negative. These results indicate that mechanical transmission of PRRSV can occur during coordinated sequence of events in cold weather. 相似文献
65.
Evaluation of mosquitoes, Aedes vexans, as biological vectors of porcine reproductive and respiratory syndrome virus 总被引:1,自引:0,他引:1
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Satoshi Otake Scott A. Dee Roger D. Moon Kurt D. Rossow Carlos Trincado Carlos Pijoan 《Canadian journal of veterinary research》2003,67(4):265-270
The objective of this study was to determine whether mosquitoes, Aedes vexans (Meigen), could serve as biological vectors of porcine reproductive and respiratory syndrome virus (PRRSV). Specifically, the study assessed the duration of viability and the site of PRRSV within mosquitoes, and evaluated whether PRRSV could be transmitted to a susceptible pig by mosquitoes following a 7- to 14-day incubation period after feeding on an infected pig. For the first experiment, a total of 100 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV (day 7 post-inoculation) and were then maintained alive under laboratory conditions. A set of 10 mosquitoes were collected at 0 hour (h), 6 h, 12 h, 24 h, 48 h, 72 h, 5 days (d), 7 d, 10 d, and 14 d post-feeding (pf). Samples of exterior surface washes, salivary glands, thorax carcasses, and gut homogenates were collected from each set of mosquitoes, and tested for PRRSV. Infectious PRRSV was detected by polymerase chain reaction and swine bioassay only from the gut homogenates of mosquitoes collected at 0 h and 6 h pf. For the second experiment, a total of 30 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV and the mosquitoes were then maintained under laboratory conditions. On each of day 7, 10, and 14 pf, a set of 10 mosquitoes were allowed to feed on a susceptible pig. Transmission of PRRSV to susceptible pigs did not occur, and PRRSV was not detected from the mosquitoes. These findings indicate that mosquitoes are not likely to serve as biological vectors of PRRSV. 相似文献
66.
Trout fry were experimentally infected with endoparasites (Anisakis sp.) and/or ectoparasites (Gyrodactylus derjavini). During the following 3 weeks the infection level of G. derjavini was significantly lowered in fish infected with live anisakids compared to fish injected with physiological saline, a corresponding amount of Anisakis protein sonicate or to untreated fish. Subsequent scanning electron microscopy (SEM) of recovered nematodes from the trout showed an extensive colonization of the worms with host macrophages. It is indicated that the activation of the fish immune system by infection with live anisakids influences the skin response of the host with a subsequent negative effect on the ectoparasites G. derjavini. 相似文献
67.
Kurt Boek Werner Schuphan 《Plant foods for human nutrition (Dordrecht, Netherlands)》1959,5(3):199-208
Zusammenfassung Zur Prüfung der für die menschliche Ernährung wichtigen Frage des in gesundheitlicher Beziehung nicht ganz unbedenklichen Nitratgehaltes von Gemüse wurden an der Bundesanstalt für Qualitätsforschung in Geisenheim/Rheingau umfangreiche Untersuchungen durchgeführt. Die Nitratbestimmungen ergaben verschieden hohe Gehalte je nach botanisch-systematischer Zugehörigkeit der einzelnen Gemüsearten. Typische Nitratspeicherer unter den häufiger genossenen Gemüsepflanzen sind der Spinat, die Rote Rübe und die Kohlarten. Die einzelnen Pflanzenorgane führten Nitrat in unter-schiedlicher Höhe.Einen entscheidenden Einfluß auf die Menge des gespeicherten Nitrats hat die Art und Höhe der Stickstoffdüngung. Verabfolgung von Jauche führte, ebenso wie Salpeterdüngung zu höheren Nitratgehalten als eine Düngung mit ammoniumhaltigen Mineraldüngern. Je höher die Stickstoffgaben waren, desto höher stieg im allgemeinen auch der Nitratgehalt des untersuchten Pflanzenmaterials. Auch die Lichtintensität erwies sich als mitbestimmender Faktor auf die Höhe des Nitratgehaltes, wie Klimakammerversuche bei abgestufter künstlicher Beleuchtung mit Spinat zeigten (hohe Licht-Intensität = niedriger, geringe L.I. = hoher Nitratgehalt). Standortversuche, ebenfalls mit Spinat, an klimatisch differenten Orten ergaben, daß die Nitratgehalte bei sonnigen warmen Witterungsbedingungen (Geisenheim/Rhein) niedrig, bei kühlen niederschlagsreichen, also lichtärmeren (Kiel), hoch waren.Mit diesem im Nitratgehalt unterschiedlichen Spinat wurden (nach Dosenkonservierung) Ernährungsversuche mit Säuglingen in der Universitätskinderklinik Kiel (Direktor: Prof. Dr. med.W. Catel) durch Dr. med.W. Kübler durchgeführt, die in seiner nachfolgenden Arbeit beschrieben werden (16).
Mit 5 Tabellen und 2 Fig.
Gemeinschaftsversuche der BAQ mit der Universitätskinderklinik Kiel (Direktor: Prof. Dr. med.W. Catel) vgl. auch S. 297. 相似文献
Summary Experiments have been carried out at the Bundesanstalt für Qualitätsforschung pflanzlicher Erzeugnisse in Geisenheim/Rhine on vegetables to determine the amount of nitrates, to be looked upon as somewhat detrimental for human health. Determinations of nitrate showed contents, different according to systematic relationships of vegetables. Those vegetables, as spinach, beet roots, cabbages and kale are typical plants storing nitrates. Plant organs differ in the amount of nitrates stored.Nitrogen-fertilizers influence the amount of accumulated nitrates depending on N-fertilizers and amount of Nitrogen. Liquid manure and nitrate supply gave rise to higher contents of nitrate as ammoniac fertilizers.The higher the amount of nitrogen, the higher raised the contents of nitrate in plant material investigated. Different light intensities, mesured in climate chambers, have been proved to be a determining factor regarding amount of nitrates in plants. High light intensity show low contents of nitrate, low one a high amount of NO3. Environmental experiments with spinach on places, different in climatic conditions, resulted in contents of nitrates which were low when sunny warm weather conditions (Geisenheim/Rh.) prevailed and vice versa (Kiel).After canning, this spinach differing in nitrate-contents has been administered babies in nutritional trials by Dr. med.W. Kübler in the Univ. Klinik Kiel (Director Prof. Dr. med.W. Catel). The results are given in the following paper by Dr.Kübler (16).
Mit 5 Tabellen und 2 Fig.
Gemeinschaftsversuche der BAQ mit der Universitätskinderklinik Kiel (Direktor: Prof. Dr. med.W. Catel) vgl. auch S. 297. 相似文献
68.
George Holan Wynona M. P. Johnson Kurt Rihs Christopher T. Virgona 《Pest management science》1984,15(4):361-368
Several new series of insecticidally active oxime O-ethers are reported, and compared structurally and biologically with known oxime O-ether insecticides. These compounds can exist in two geometric forms. Biological results demonstrate that the configuration of the active isomer and the effect of substituents around the C-N double bond vary between series. A detailed structure-activity examination is presented. 相似文献
69.
In a short time feeding experiment it was shown that the liver weight of cod was significantly reduced in prawn-fed cod compared to sand-eel-fed cod. The dry weight and the protein content of the muscle were not significantly reduced. It is concluded that short time energy deprivation of cod primarily affects the liver. The results futher support the view that the food type and ration of cod can produce anomalous effects in field studies of e.g. parasite induced liver weight decrease in cod. 相似文献
70.