A slot blot hybridization technique was applied for detection of bluetongue virus (BTV) in blood mononuclear cells (BMNC) obtained from cattle with experimentally induced infection. This technique lacked sensitivity to detect the viral nucleic acid directly in clinical specimens. When aliquots of mononuclear cells from these cattle were cultivated in vitro for 10 days to amplify virus titer, only 33.3% of the samples collected during viremia gave a positive signal in the slot blot hybridization format. By contrast, results for 34.3% of noncultured and 63.3% of cultured mononuclear cell samples collected during viremia were positive by immunofluorescence. The average number of infected cells, as detected by immunofluorescence in the noncultured mononuclear cell samples, was 1 to 5/300,000, and was usually > 10/300,000 in the cultured cell samples. Virus was isolated from all postinoculation blood samples obtained from 4 heifers that were seronegative at the time of inoculation, but was not isolated from any of the preinoculation samples, or from any of the postinoculation samples obtained from 2 heifers that were seropositive at the time of inoculation. When virus isolation was attempted from separated mononuclear cells in 2 heifers, 43.7% of the noncultured and 87.5% of the cultured samples had positive results. 相似文献
Large‐scale inoculation with arbuscular mycorrhizal fungi (AMF) is generally impractical in most regions and we have little understanding of the factors that determine inoculation success. Nevertheless, the ability to take full advantage of indigenous AMF for sustainable production needs to be developed within cropping systems. We used part of a long‐term field experiment to understand the influence of tillage and the preceding crop on AMF colonization over the growing season. Arbuscular mycorrhiza colonization rate was more affected by treatment (tillage or the combination of crop and preceding crop) than by the total number of AMF spores in the soil. Conventional tillage (CT) had a statistically significant negative effect (P ≤ 0.05) on spore numbers isolated from the soil, but only in the first year of study. However, the AMF colonization rate was significantly reduced by CT, and the roots of wheat, Triticum aestivum, L, cv. Coa after sunflower, Helianthus annuus L., were less well colonized than were those of triticale, X Triticosecale Wittmack, cv. Alter after wheat, but the affect of tillage was more pronounced than was the effect of crop combination. Under no‐till there was a significant increase in AMF colonization rate throughout the sampling period in both wheat and triticale, indicating that the extraradical mycelium previously produced acted as a source of inoculum. In general, triticale showed greater AMF colonization than wheat, despite the preceding crop being less mycotrophic. Under these experimental conditions, typical of Mediterranean agricultural systems, AMF colonization responded more strongly to tillage practices than to the combination of crop and preceding crop. 相似文献
The present field experiment was conducted during two consecutive cropping seasons in central Portugal to study the effects of simultaneous elevation of carbon dioxide concentration ([CO2]) (550 μmol mol?1) and air temperature (+2–3 °C) on japonica rice (Oryza sativa L. “Ariete”) yield, crop duration, and SPAD-values across the seasons compared with the open-field condition. Open-top chambers were used in the field to assess the effect of elevated air temperature alone or the combined effect of elevated air temperature and atmospheric [CO2]. Open-field condition was assessed with randomized plots under ambient air temperature and actual atmospheric [CO2] (average 382 μmol mol?1). Results obtained showed that the rice “Ariete” had a moderate high yielding under open-field condition, but was susceptible to air temperature rise of +2–3 °C under controlled conditions resulting in reduction of grain yield. The combined increase of atmospheric [CO2] with elevated air temperature compensated for the negative effect of temperature rise alone and crop yield was higher than in the open-field. SPAD-readings at reproductive stage explained by more than 60 % variation the straw dry matter, but this finding requires further studies for consolidation. It can be concluded that potential increase in air temperature may limit rice yield in the near future under Mediterranean areas where climate change scenario poses a serious threat, but long term field experiments are required. 相似文献
Oxidative stress represents a challenge during sperm manipulation. We have tested the effect of increasing hydrogen peroxide (H2O2) levels on red deer spermatozoa after cryopreservation, and the role of male‐to‐male variation in that response. In a first experiment, eight thawed samples were submitted to 0, 25, 50, 100 and 200 μm H2O2 for 2 h at 37°C. Intracellular reactive oxygen species (H2DCFDA‐CM) increased with H2O2 concentration, but we only detected a decrease in sperm function (motility by CASA and chromatin damage by sperm chromatin structure assay) with 200 μm . Lipoperoxidation assessed by the thiobarbituric acid reactive substance (TBARS) method increased slightly with 50 μm H2O2 and above. In a second experiment, samples from seven males were submitted to 0 and 200 μm H2O2 for 2 h, triplicating the experiment within each male. Males differed at thawing and regarding their response to incubation and H2O2 presence. We found that the kinematic parameters reflected male‐to‐male variability, whereas the response of the different males was similar for lipid peroxidation and viability. A multiparametric analysis showed that males grouped differently if samples were assessed after thawing, after incubation without H2O2 or after incubation with H2O2. Red deer spermatozoa are relatively resilient to H2O2 after thawing, but it seems to be a great male‐to‐male variability regarding the response to oxidative stress. The acknowledgement of this individual variability might improve the development of optimized sperm work protocols. 相似文献
Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) dominate many of the European forest stands. Also, mixtures of European beech and Scots pine more or less occur over all European countries, but have been scarcely investigated. The area occupied by each species is of high relevance, especially for growth evaluation and comparison of different species in mixed and monospecific stands. Thus, we studied different methods to describe species proportions and their definition as proportion by area. 25 triplets consisting of mixed and monospecific stands were established across Europe ranging from Lithuania to Spain in northern to southern direction and from Bulgaria to Belgium in eastern to western direction. On stand level, the conclusive method for estimating the species proportion as a fraction of the stand area relates the observed density (tree number or basal area) to its potential. This stand-level estimation makes use of the potential from comparable neighboring monospecific stands or from maximum density lines derived from other data, e.g. forest inventories or permanent observations plots. At tree level, the fraction of the stand area occupied by a species can be derived from the proportions of their crown projection area or of their leaf area. The estimates of the potentials obtained from neighboring monospecific stands, especially in older stands, were poorer than those from the maximum density line depending on the Martonne aridity index. Therefore, the stand-level method in combination with the Martonne aridity index for potential densities can be highly recommended. The species’ proportions estimated with this method are best approximated by the proportions of the species’ leaf areas. In forest practice, the most commonly applied method is an ocular estimation of the proportions by crown projection area. Even though the proportions of pine were calculated here by measuring crown projection areas in the field, we found this method to underestimate the proportion by 25% compared to the stand-level approach. 相似文献
A 24‐day‐old Friesian colt died suddenly and a physical examination the morning the foal died showed no abnormalities and serum IgG levels >8.0 g/l. Necropsy examination revealed haemopericardium and a 2 cm transverse tear at the root of the aorta. The foal was also found to have Chlamydophila spp. in the epithelium and Balantidium coli on the mucosal surface of the large colon. An aortic rupture is a novel finding in a foal, colonic Chlamydiosis has not been previously reported in horses and Balantidium coli has not been reported in equids in North America. 相似文献
A total of 178 Escherichia coli isolates from diarrheic and healthy rabbits in the S?o Paulo State (Brazil) were serobiotyped and investigated by PCR for the presence of virulence genes. Among the 90 (50.6%) isolates which possessed the eae gene, 74 were from diarrheic animals and all but one encoded intimin beta. Sixty five (72.2%) of the eae+ isolates had insertion of the locus of enterocyte effacement locus in the pheU locus, 11 (12.2%) in the selC and 14 (15.6%) did not insert in either of these loci. All isolates were negative for genes of the E. coli enterotoxins, Stx1, Stx2, CNF1, CNF2 and EHEC hemolysin. The O132:H2 serotype was dominant, being present in 63 isolates (70%) of the 90 eae+ isolates, and 57 of the 63 isolates of this serotype belonged to biotype 30. PCR detected the gene for AF/R2 fimbriae in 75 (83.3%) of the 90 eae+ isolates. Adherence to HeLa cells was best detected following 6h incubation and a positive fluorescence actin staining (FAS) test was given by 52 isolates. These data show that isolates of E. coli associated with diarrhea in rabbits in Brazil possess the genotype and phenotype typically associated with rabbit enteropathogenic E. coli (EPEC). We conclude that EPEC that possess the eae gene are a common cause of diarrhea in Brazilian rabbit farms and that the pathogenic eae+ AF/R2+ isolates of O132:H2:B30 serobiotype are especially predominant. 相似文献
Enzootic nasal tumor (ENT) is a contagious neoplasm associated with enzootic nasal tumor virus (ENTV), which may induce disease in sheep (ENTV-1) and goats (ENTV-2). This study aimed to describe the occurrence of ENT in two Texel sheep (Ovis aries) from a 75-sheep flock, located in the city of Gravataí, southern Brazil. Animals used to be purchased from different origins, and no specific tests for disease monitoring or quarantine procedure were performed. Affected animals presented respiratory distress, anorexia with severe weight loss, and mucopurulent unilateral nasal discharge. Necropsy was performed in both animals and nasal cavity masses were observed. Histopathological analysis demonstrated an epithelial neoplasm compatible with nasal adenocarcinoma. PCR using a protocol that amplifies a 591 bp sequence of 5’LTR-gag region of ENTV1 was performed followed by DNA sequencing. Both samples were positive, and the sequences obtained presented highest identity (97%) with ENTV strain TN28 (GenBank accession number MH899613) detected in a Texel sheep from Scotland. This is the first report of ENTV-1 leading to enzootic nasal tumor in sheep in Latin America, which confirms the presence of the retrovirus in sheep flocks in the Brazilian territory.