This study evaluated the application of stable isotopes of carbon as an alternative and more accurate method to determine gastrointestinal transit time (GTT) in fish by comparing it to the inert marker method. The stable isotope method detects alterations of the normal carbon flow in a biological system by analyzing naturally occurring isotopes of carbon, contrary to studies based on conventional techniques that apply external markers to the diet to determine GTT through visual observation of the color change in feces. Therefore, 320 pacu, Piaractus mesopotamicus juveniles were reared in 32 tanks under two different temperatures (25 and 29 C). The pacu juveniles received two different diets, one based on ingredients derived from C3 photosynthetic cycle plants and the other based on C4 plant ingredients, both containing titanium oxide (TiO2) as a marker. After 40 d, the isotopic signature of the diets was changed, and the marker was replaced by chromic oxide (Cr2O3). In the isotopic technique, the feces were analyzed to determine the exchange in the isotopic ratio of carbon δ13C. Both methods found that GTT was faster (nearly 6 h) in fish at 29 C when using the C4/C3 feeding strategy and slower in fish at 25 C using the C3/C4 strategy (15 h by inert marker and 18 h by the isotopic method). In conclusion, GTT determination in pacu juveniles using the stable isotope technique exhibits the same accuracy obtained with the inert marker method at temperatures suitable (nearly 29 C) for the metabolism of these animals. 相似文献
In this paper, a parasitological and serological study performed in three cows up to the fourth gestation is reported in order to clarify the extent of vertical propagation and, secondly, in which period of gestation the recrudescence of previous infection occurs. The cows selected for the study delivered healthy but congenitally infected calves in first pregnancy. The parasite was found, by biological tests in Swiss mice, in all the placentas of the three cows examined, during the three subsequent gestations, at calving. The parasite was found, at slaughtering, in the brains of all nine calves born clinically healthy from the three cows as well. The serological profile, performed at monthly intervals on serum of the cows, showed that IgG and IgM increased in the third trimester of gestation; this rise of antibodies was constantly observed during the three gestations and in all three cows. In the calves, the IgG titres increase after colostrum consumption and an IgM peak at birth, were indicative of a late infection. These findings, along with negative results obtained by a serological study conducted simultaneously on 38 cows housed in the same stable as the experimental animals and the negative results obtained in isolating parasite or antibodies from farm dogs, suggest that N. caninum infection can be maintained over several bovine generations and that recrudescing persistent infection, rather than a new infection, explains the Neospora infection of calves. 相似文献
In the present study we compared the immunological reactions between Rhipicephalus sanguineus tick-infested susceptible (dogs and mice) and tick-resistant hosts (guinea pigs), elucidating some of the components of efficient protective responses against ticks. We found that T-cells from guinea pigs infested with adult ticks proliferate vigorously in the presence of concanavalin A (ConA), whereas ConA-induced cell proliferation of tick-infested mice and dogs was significantly decreased at 43.1 and 94.0%, respectively, compared to non-infested controls. Moreover, cells from mice and dogs submitted to one or three successive infestations did not exhibit a T-cell proliferative response to tick antigens, whilst cells from thrice tick-infested guinea pigs, when cultured with either a tick extract or tick saliva, displayed a significant increase in cell proliferation. Also, we evaluated the response of tick-infested mice to a cutaneous hypersensitivity test induced by a tick extract. Tick-infested mice developed a significant immediate reaction, whereby a 29.9% increase in the footpad thickness was observed. No delayed-type hypersensitivity (DTH) reaction was detected. Finally, the differential cell count at the tick attachment site in repeatedly infested mice exhibited a 6.6- and 4.1-fold increase in the percentage of eosinophils and neutrophils, respectively, compared to non-infested animals, while a decrease of 77.0-40.9 in the percentage of mononuclear cells was observed. The results of the cutaneous hypersensitivity test and the cellular counts at the tick feeding site for mice support the view that tick-infested mice develop an immune response to R. sanguineus ticks very similar to dogs, the natural host of this species of tick, but very different from guinea pigs (resistant host), which develop a DTH reaction in addition to a basophil and mononuclear cell infiltration at the tick-attachment site. In conclusion, saliva introduced during tick infestations reduces the ability of a susceptible animal host to respond to tick antigens that could stimulate a protective immune response. As a consequence, the animals present a lack of DTH response and disturbed cellular migration to tick feeding site, which can represent a deficient response against ticks. 相似文献
The potential of landscapes to supply multiple benefits to society beyond commodities production has received increasing research and policy attention. Linking the concept of multifunctionality with the ecosystem services (ES) approach offers a promising avenue for producing scientific evidence to inform landscape planning, e.g., about the relative utility of land-sharing and land-sparing. However, the value for decision-making of ES-based multifunctionality assessments has been constrained by a significant conceptual and methodological dispersion. To contribute towards a cohesive framework for landscape multifunctionality, we analyse case studies of joint ES supply regarding ten criteria designed to ultimately answer four aspects: (i) the multifunctionality of what (e.g., landscapes), (ii) the type of multifunctionality (e.g., based on ES synergies), (iii) the procedure of multifunctionality assessments, and (iv) the purpose of multifunctionality. We constructed a typology of methodological approaches based on scores for criteria describing the evaluation method and the level of stakeholder participation in assessments of joint ES supply. Surveyed studies and underlying types of methodological approaches (spatial, socio-spatial, functional, spatio-functional) differed in most criteria. We illustrate the influence of methodological divergence on planning recommendations by comparing two studies employing contrasting approaches (spatial and functional) to assess the joint supply of wildlife habitat and agricultural production in the Argentine Chaco. We distinguish between a pattern-based and process-based multifunctionality, where the latter can only be detected through approaches considering the ecological processes (e.g., ES complementarities) supporting the supply of multiple ES (functional and spatio-functional). Finally, we propose an integrated approach for assessing a socially-relevant process-based multifunctionality. 相似文献
While floating near the sea surface plastic debris interacts with a number of external factors, including many different organisms. Seabirds have the most extensive documented history of interactions with plastics, through ingestion, entanglement, and nest construction.
In the present study, eight seabird species from the South Pacific Ocean were used as a proxy to determine potential patterns of removal of marine plastic debris, and three hypotheses were tested in relation to their feeding habits and nesting areas.
Plastics from abiotic compartments (Chilean continental coast, South Pacific Gyre, and Rapa Nui beaches) and biotic compartments (surface-feeding seabirds, diving seabirds, and nesting areas) were compared, according to their type, colour, shape, and density.
Continental beaches had a relatively wide range of colours and shapes, with many non-buoyant plastics. Samples from the South Pacific Gyre (SPG) and Rapa Nui (Easter Island) beaches comprised mainly hard, rounded, buoyant, and white/grey plastics.
These results indicate that the composition of floating plastics from terrestrial sources changes during transport with oceanic currents, reducing the proportion of prey-like plastics present in the subtropical gyres.
The stomach contents of surface-feeding and diving seabirds were dominated by hard, white/grey, and round plastic items, similar to plastics from the SPG, suggesting non-selective (accidental or secondary) ingestion.
Nesting areas had a more variable composition of brightly coloured plastics, suggesting a pattern of selective removal of plastics by seabirds, probably from oceanic sources.
The present study reveals extensive interactions of seabirds with plastics on a broader scale, which is highly relevant given that the impacts of plastics on seabirds are increasing worldwide, compromising their efficient conservation.
Hot-air pasteurization was investigated in the EU-funded project “Reducing Egg Susceptibility to Contaminations in Avian Production in Europe (RESCAPE)” as an innovative treatment for surface bacterial decontamination of table eggs. Possible side effects of the treatment on egg quality traits were also studied. The decontamination power of hot air was evaluated over 1 month on shell eggs that were experimentally inoculated with Salmonella enteritidis, Escherichia coli, or Listeria monocytogenes. The S. Enteritidis and L. monocytogenes populations on the surfaces of treated eggs showed a significant reduction compared with untreated eggs. No statistically significant results were obtained comparing E. coli loads on treated and untreated eggs. No detrimental effects on quality traits either immediately after treatment or after 28 days of storage at 20°C were recorded.
An Agrobacterium-mediated transformation procedure for soybean [Glycine max L. Merrill] proliferating somatic embryos is here described. The Agrobacterium tumefaciens LBA4404 strain harboring pTOK233, pCAMBIA1390-olp or pH7WG2Dwrky plasmids was used to mediate gene transfer into the plant genome. Prior to Agrobacterium inoculation, proliferative soybean embryogenic clusters were microwounded by DNA-free tungsten particle bombardment. Three
independent transformation experiments were performed. In Experiment I, 26 transgenic plants were obtained from a unique clone
of cv Bragg, while 580 plants were recovered from 105 clones of cv IAS5. In Experiment II, a single hygromycin-resistant clone
of cv BRSMG68 Vencedora was recovered and gave rise to five plants. In Experiment III, 19 plants of cv Bragg and 48 plants
of IAS5 were recovered, representing five and 14 independent transformation events, respectively. PCR and Southern analyses
confirmed the transgenes’ integration into plant genomes. Transgenic plants were fertile. They flowered, set pods and seeds.
Transgene segregation in two T1 progenies fits the Mendelian pattern (3:1 transgenic:non-transgenic plants). This is the first report of transgenic fertile
soybean plants obtained from somatic embryogenic tissues transformed by the system that combines DNA-free particle bombardment
and Agrobacterium. 相似文献
A collection of 55 Fusarium graminearum (Gibberella zeae) strains isolated between 1969 and 2009 in Belgium, Canada, Germany, Italy, Luxembourg, or the USA belonging to the three
known chemotypes (3-acetylated deoxynivalenol, 15-acetylated deoxynivalenol and nivalenol) were screened for their sensitivity
towards the fungicide trifloxystrobin using a liquid culture assay. None of the isolates was completely inhibited by trifloxystrobin
concentrations up to 3 mM. For comparison, prothioconazole completely inhibited fungal growth of a standard isolate at concentrations
as low as 0.007 mM. The maximum level of inhibition, which could be obtained by trifloxystrobin, ranged from 14 to 65% among
the strains tested and was not significantly affected by the country of origin or by the chemotype. The absence of significant
differences in resistance levels between the countries of origin and chemotypes as well as the fact that strains isolated
before the market introduction of strobilurins in 1996 also showed a high level of resistance is evidence that this is largely
a case of natural resistance and not primarily related to strobilurin use in agriculture. 相似文献
In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species. 相似文献
The tetracycline resistance (tet) gene patterns of 52 tetracycline resistant Salmonella enterica subsp. enterica (S.) serovar Typhimurium isolates collected from animals, food of animal origin, and humans in Italy, were investigated to evaluate whether the tet gene patterns could be used for strain differentiation in addition to phage typing and ribotyping. The detection of tet genes was performed by specific PCR assays. Ribotyping was performed automatically using PvuII as restriction enzyme. Ten different ribotyping patterns were detected. All isolates were positive for at least one of the tet genes studied and six different tet gene patterns were observed. Ribotyping and tet gene patterns showed discriminatory indices of 0.741 and 0.812, respectively. Multiple tet genes were commonly found among tetracycline resistant S. typhimurium isolates from various sources. The resulting tet gene patterns allowed further discrimination of strains which were otherwise indistinguishable by their phage type, ribotype and origin. Thus, the analysis of tet gene patterns might represent an additional tool for the differentiation of S. typhimurium isolates. 相似文献