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51.
Four Lake Column Simulators were filled with hypolimnetic water from Lake Ontario and inoculated with algae and fish. Various microbial processes were monitored before and after the addition of dredged spoils. Loading rates of dredged spoils of 0.33, 3.3 or 33 g day?1 were used for each of three columns and one column with no addition of dredged spoils was maintained as a control. The effects of dredged spoils on microbial activities were most pronounced at the highest loading rate. 32P-PO4 was rapidly removed from the control water but the presence of suspended particles from dredged material increased both biological assimilation and physical adsorption processes. The influence of dredged spoils on 32P-PO4 uptake was most pronounced immediately following loading. Dredged spoils also increased 14C-acetate mineralization in water and the effects were again more pronounced immediately following loading. A 3 fold increase in heterotrophic activity during a 1 h incubation at 20°C was observed following addition of a 33 g day?1 loading. Dredged spoils increased the levels of N2-fixation in the columns as indicated by the C2H2-reduction assay procedure. Suspended dredged material reduced light penetration and decreased primary production in the columns. The increased availability of dissolved and particulate organic and inorganic nutrients from continuous addition of dredged spoils was responsible for a general stimulation of microbial activities in the epilimnetic and hypolimnetic regions of the simulated lake columns. 相似文献
52.
Lead and zinc mine tailings from Guangdong, China were found to be toxic to two common species of the earthworm Pheretima, unless the spoil was diluted by at least 20% with an artificial uncontaminated soil. With different soil dilutions, there were significant differences in mortality, growth and Zn uptake between the two species. Zinc and arsenic were principally responsible for the toxicity of the tailings. LC50 values for Zn, Pb, Cu and As for Pheretima were similar to those reported in the literature for Eisenia fetida. Following inoculation with the earthworms, spoil pH, EC and available metals increased; available-Pb and -Zn concentrations increased by up to 48.2% and 24.8% respectively. The findings suggest that earthworms may play an important role in reclamation of mining spoils to achieve a healthy soil supporting sustainable vegetation. Potentially increased toxicity of metals to plants and animals, through increased bioavailability in the presence of earthworms, is discussed in the context of their role in modifying the efficiency of phytoremediation treatments. 相似文献
53.
54.
Conidia of Cochliobolus sativus and five other pigmented fungi lysed when incubated in natural soil. Lysis followed perforation of the spore wall by holes of varying dia. Three possible causes of perforation were investigated, namely autolysis, mechanical puncture by soil animals and enzymatic erosion by soil micro-organisms. Results indicated that soil micro-organisms were the likely causal agents although no micro-organism able to perforate conidia has yet been isolated. Colonization of conidia by the soil microflora was studied by electron microscopy. On the basis of these direct observations, possible perforation mechanisms are suggested. Reports of perforation of fungal, plant and bacterial cell walls are briefly summarized and the perforation phenomenon discussed in relation to the biodegradation of pigmented fungal propagules in soils. 相似文献
55.
Effect of pH on in vitro ruminal conversion of L-tryptophan to 3-methylindole and indole 总被引:1,自引:0,他引:1
A C Hammond L L Slyter J R Carlson L P Wong R G Breeze 《American journal of veterinary research》1984,45(11):2247-2250
Three in vitro experiments were conducted to determine the effects of pH on ruminal conversion of L-tryptophan (TRP) to 3-methylindole (3-MI) and indole (IND). Experiment 1 involved 2 closed-system incubations, each with triplicate replications of buffered ruminal fluid at initial pH of 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. Highest molar conversions of TRP to 3-MI were 61.5 +/- 2.7% and 64.3 +/- 0.8% at initial pH treatments of 7.5 and 7.0 (final pH 7.3 and 6.9) for the 2 incubations, respectively. Experiment 2 used duplicate continuous cultures at each of 4 pH treatments. Following a common 5-day pretreatment period, effluent pH averaged 5.6, 6.1, 6.5, and 6.9 for the respective treatments. Data for 4 subsequent 5-day time periods showed production of 3-MI was affected by pH treatment (P less than 0.01), time (P greater than 0.01), and treatment X time (P less than 0.01); conversion of TRP to 3-MI reached 78% at pH 6.9 and decreased to less than 1% at pH 5.6. Production of IND was not related to pH treatment (P greater than 0.10). Total moles of volatile fatty acid (VFA) carbon produced showed a pH treatment X time interaction (P less than 0.01) which reflected a trend toward decreasing VFA production at lower pH and increasing VFA production at higher pH. Experiment 3 consisted of 2 pH treatments with additional continuous culture fermenters.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
56.
P J Ihrke A Wong A A Stannard S L Vivrette 《American journal of veterinary research》1988,49(6):770-772
The fungal flora of the hair and underlying skin from 2 sites was examined qualitatively in 20 horses free of skin or ocular disease. Fungi were isolated from both the hair and the underlying skin of all 20 horses. Twenty-two genera regarded commonly as saprophytes were identified and an additional 2 fungi resembled the perfect state of the cutaneous pathogenic genera Microsporum and Trichophyton. Cladosporium spp, Penicillium spp, and Rhizopus spp were the most frequently isolated saprophytes. In general, similar fungi were isolated from the hair and underlying skin, and differences were not noted in isolates from the saddle and rump regions. 相似文献
57.
Wong HK 《Science (New York, N.Y.)》1966,151(3712):887-889
58.
Regula G Lo Fo Wong DM Ledergerber U Stephan R Danuser J Bissig-Choisat B Stärk KD 《Preventive veterinary medicine》2005,70(1-2):29-43
An ideal national resistance monitoring program should deliver a precise estimate of the resistance situation for a given combination of bacteria and antimicrobial at a low cost. To achieve this, decisions need to be made on the number of samples to be collected at each of different possible sampling points. Existing methods of sample size calculation can not be used to solve this problem, because sampling decisions do not only depend on the prevalence of resistance and sensitivity and specificity of resistance testing, but also on the prevalence of the bacteria, and test characteristics of isolation of these bacteria. Our aim was to develop a stochastic simulation model that optimized a national resistance monitoring program, taking multi-stage sampling, imperfect sensitivity and specificity of diagnostic tests, and cost-effectiveness considerations into account. The process of resistance testing of Campylobacter spp. isolated from cloacal swab samples from poultry was modeled using a Markov Chain Monte Carlo model. Different sampling scenarios on the number of flocks to be tested, the number of birds from each flock, and the number of campylobacter colonies submitted to susceptibility testing were evaluated regarding the precision of the resulting prevalence estimate. Precision of the prevalence estimate was defined as the absolute difference between apparent and true prevalence of resistance. A partial budget approach was utilized to find the most cost-effective combination of samples to obtain a defined precision of the prevalence estimate. For a sampling scenario testing 100 flocks, five birds per flock, and one campylobacter colony per sample, the median error of the prevalence estimate was 2.5%, and 95% of the simulations resulted in an error of 7% or less. When the total number of samples was kept constant, maximizing the number of flocks tested, and only testing one bird per flock resulted in the most precise prevalence estimate. Submitting more than one campylobacter colony to resistance testing did not improve the prevalence estimate. Partial budget analysis indicated that the most cost-effective strategy was testing of two birds per flock, and submitting one colony per sample to resistance testing. 相似文献
59.
The effects of a short-term dietary arginine supplementation after hatching on subsequent growth and the immune system were assessed in growing male Leghorn-type chickens. An arginine-deficient basal diet (67 g/kg) supplemented with 0 (control), 2.7 (LA) or 5.4 (HA) g L-arginine/kg, was offered ad libitum to 1-d-old male ISA Brown chicks for 4 weeks, then all birds were offered ad libitum a commercial pullet grower feed (8.9 g arginine/kg) for another 8 weeks. Supplemented birds had higher growth rates and feed intake than control birds during the 4-week supplementation period, but these effects did not persist into the subsequent periods. When the supplementation ceased at week 4, no differences in lymphoid organ weights relative to body weight (BW), primary serum antibody levels against sheep red blood cells (SRBC) or cutaneous reactivity of toe webs to phytohaemagglutinin (PHA) were detected. LA-fed birds had lower immunoglobulin (Ig) G levels against bovine serum albumin (BSA) than the control at week 4, but this effect did not persist at weeks 8 and 12. No difference in anti-BSA IgM levels was detected among birds at week 4; at week 12, however, the LA-fed birds had a significantly higher anti-BSA IgM level than the control. An increased anti-SRBC antibody level and a reduced relative bursa weight in HA-fed birds were evident at week 8, without any prior effects. It is concluded that short-term supplementary L-arginine had minimal effects on immunity, but some enhancement of SRBC antibody responses in later stages of growth was observed with previous L-arginine administration. 相似文献
60.
Herd-level risk factors for subclinical Salmonella infection in European finishing-pig herds 总被引:3,自引:0,他引:3
Lo Fo Wong DM Dahl J Stege H van der Wolf PJ Leontides L von Altrock A Thorberg BM 《Preventive veterinary medicine》2004,62(4):253-266
Our objective was to find herd factors associated with pigs testing seropositive for Salmonella. Data were collected from 359 finishing-pig herds in Germany, Denmark, Greece, The Netherlands and Sweden, between 1996 and 1998. Pigs fed non-pelleted feed (dry or wet) had 2- and 2.5-times lower odds of seropositivity, compared to pigs fed pelleted feed. The protective effect of non-pelleted feed over pelleted feed may be ascribed to the structure and composition. Also, pigs that were given whey (to drink or as the liquid part of the diet) had 2.6-times lower odds to test seropositive than pigs not getting whey. Pigs produced in batches in herds with hygienic-lock facilities had >3-times lower odds for testing seropositive compared to pigs in herds where only one or neither factor was present. In herds where the caretaker(s) washed hands consistently before tending to the animals, pigs had 1.5-times lower odds of seropositivity than pigs in herds where the caretaker did not. Pigs which were able to have snout contact with pigs in neighbouring pens (because pen separations were either open or too low) had 1.7-times higher odds to test seropositive compared to pigs for which such contact was prevented. Pigs in herds recruiting from more than three supplier herds had three-times higher odds to test seropositive than pigs in herds which breed their own replacement stock or recruit from a maximum of three supplier herds. 相似文献