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21.
Arno Lindner Raul Signorini Luciana Brero Eduardo Arn Rúben Mazzini Alejandro Enriquez 《Journal of Equine Veterinary Science》2012
Intensive short intervals of exercise are used to condition horses for racing. In this study, the effect of exercising horses one, two, or three times a week during 6 weeks using two intervals with near-maximal speed over 100 m on v4 (speed at which, under defined conditions, the blood lactate concentration reaches 4 mmol/L) and muscle thickness (MT) of supraspinatus and extensor carpi radialis was examined. Thoroughbreds (4-5 years of age) were exercised twice at near-maximal speed over 100 m, separated by a 10-minute period at walk, on dirt track during conditioning periods (CP) of 6-week duration. This exercise was undertaken once (six horses), twice (six horses), or thrice (five horses) a week during a CP. Before, every 2 weeks during, and 2 weeks after the CP, horses were subjected to a standardized exercise test to determine their v4. Before and after CP, the MT of the extensor carpi radialis and the supraspinatus was examined by ultrasonography. There was no differential effect of the number of weekly exercises on v4. Pooling the data of all horses, a decrease of v4 was found. The decrease became evident after the sixth week of conditioning. MT did not change. The results indicate that the examined exercise protocols could negatively impact racing performance of horses. 相似文献
22.
Effect of plant age at time of infection by tomato spotted wilt tospovirus on the yield of field-grown tomato 总被引：1，自引：0，他引：1
E. Moriones J. Aramburu J. Riudavets J. Arnó A. Laviña 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(3):295-300
Naturally infected tomato plants that expressed tomato spotted wilt virus symptoms at 24, 38, 45, 60, 67, and 74 days after transplanting were monitored for production in an experimental crop grown in the open from May to September in northeastern Spain. Plants were tagged, tested for tomato spotted wilt virus infection by enzyme-linked immunosorbent assay, and data on symptom expression and yield were individually recorded. Plants that developed symptoms at 24, 38, or 45 days after transplanting yielded significantly less and produced fewer and smaller tomatoes than those that developed symptoms at 60, 67, and 74 days after transplanting. These later infected plants showed similar patterns of production with maximum yields between 27 July and 17 August, when most fruit was harvested. Production components such as fruit number per plant, yield of mature fruit per plant, or fruit weight increased the older the plants were when first symptoms were exhibited. However, marketable fruit production was drastically decreased by tomato spotted wilt virus infection, due to abnormal ripening of mature fruit in infected plants. Little and no significantly different amounts of marketable fruit were produced, irrespectively of plant age at time of symptom expression. Implications for spotted wilt management in tomato are discussed. 相似文献
23.
B. Aasted K. Gori J. Dominguez A. Ezquerra R. Bullido S. Arn A. Bianchi R. Binns R. M. Chu W. C. Davis S. Denham K. Haverson K. T. Jensen Y. B. Kim A. Magyar K. R. Petersen A. Saalmü ller D. Sachs C. Schü tt M. Shimizu C. Stokes T. Whittall H. Yang F. Zuckermann 《Veterinary immunology and immunopathology》1998,60(3-4):229-236
24.
M. D. Pescovitz B. K. Book B. Aasted J. Dominguez R. Bullido I. Trebichavsky B. Novikov I. Valpotic M. Tomaskovic J. Nielsen S. Arn D. H. Sachs J. K. Lunney P. C. Boyd J. Walker R. Lee A. Saalmüller 《Veterinary immunology and immunopathology》1998,60(3-4):269-273
Among the 57 monoclonal antibodies analyzed within the T-cell group, three mAbs fell within cluster T13 including the CD5a standard b53b7 (No. 174). The two new mAbs 1H6/8 (No. 058) and BB6-9G12 (No. 166) both precipitated 55 and 60 kDa proteins that were of similar molecular weights as the standard. Staining patterns on the various cell types were similar. Both new antibodies inhibited the binding of the CD5a reference mAbs b53b7 to peripheral lymphocytes. These mAbs, therefore both react with the CD5a epitope bringing the number of anti-porcine CD5 mAbs to eight, all of which appear to recognize the same epitope. 相似文献
25.
Setting the optimal length to be scanned in rows of vines by using mobile terrestrial laser scanners
Mapping the leaf area index (LAI) by using mobile terrestrial laser scanners (MTLS) is of significance for viticulture. LAI is related to plant vigour and foliar development being an important parameter for many agricultural practices. Since it may present spatial variability within vineyards, it is very interesting monitoring it in an objective repeatable way. Considering the possibility of using on-the-go sensors such as MTLS within an agricultural plot, it is necessary to set a proper length of the row to be scanned at each sample point for a reliable operation of the scanner. Three different row length sections of 0.5, 1, and 2 m have been tested. Data analysis has shown that models required to estimate LAI differ significantly depending on the scanned length of the row; the model required to estimate LAI for short sections (0.5 m) is different from that required for longer sections (1 and 2 m). Of the two models obtained, we recommend using MTLS for scanning row length sections of 1 m because the practical use of the sensor in the field is simplified without compromising the results (there is little variation in the model when the row length section changes from 1 to 2 m). In addition, a sufficient number of sampling points is obtained to support a map of the LAI. Linear regression models using as explanatory variable the tree area index, obtained from the data provided by the scanner, are used to estimate the LAI. 相似文献
26.
Several studies suggest that the expression of F1 fimbriae could be involved in the virulence of Escherichia coli for chickens. F1 fimbriae display multivalent properties such as adhesion to epithelia or interaction with the immune system that imply specific interactions between the adhesin FimH and different cell receptors. We constructed a delta fimH mutant of the avian pathogenic E. coli MT78 and evaluated its in vivo colonization and pathogenicity, as compared to that of the parent strain. The generated mutant PA68 was unable to adhere in vitro to chicken epithelial pharyngeal or tracheal cells; mutant bacteria were mostly afimbriated although a minority of them displayed altered piliation phenotypes. Two inoculation routes were used to compare the ability of MT78 and PA68 to colonize the respiratory tract and to induce colibacillosis in chickens. In the first model, 2-wk-old axenic chickens were inoculated intratracheally with one or both E. coli strains, after primary infection with infectious bronchitis virus. In the second model, 3-wk-old specific-pathogen-free chickens were inoculated via the caudal thoracic air sac. After intratracheal inoculation, the delta fimH mutant was found to be a better colonizer than MT78 in the trachea of inoculated chickens. Furthermore, when both strains were inoculated simultaneously, the delta fimH mutant constituted 98% of the bacterial population in the trachea at day 7 postinoculation. Irrespective to the inoculation route, MT78 and PA68 showed similar abilities to induce macroscopic lesions in chickens, to provoke bacteremia, and to colonize the internal organs. However, 4 days after intra-air sac inoculation, bacterial counts of the mutant were lower in the spleen and liver than those of MT78. Our results show that FimH is not required for colonization of the trachea of axenic chickens by E. coli and that it is not a major determinant of bacterial pathogenicity. On the contrary, the lack of expression of FimH seems to favor the in vivo colonization of the trachea of chickens by E. coli. 相似文献
27.
Jaume Arnó Alexandre Escolà Josep M. Vallès Jordi Llorens Ricardo Sanz Joan Masip Jordi Palacín Joan R. Rosell-Polo 《Precision Agriculture》2013,14(3):290-306
Estimation of grapevine vigour using mobile proximal sensors can provide an indirect method for determining grape yield and quality. Of the various indexes related to the characteristics of grapevine foliage, the leaf area index (LAI) is probably the most widely used in viticulture. To assess the feasibility of using light detection and ranging (LiDAR) sensors for predicting the LAI, several field trials were performed using a tractor-mounted LiDAR system. This system measured the crop in a transverse direction along the rows of vines and geometric and structural parameters were computed. The parameters evaluated were the height of the vines (H), the cross-sectional area (A), the canopy volume (V) and the tree area index (TAI). This last parameter was formulated as the ratio of the crop estimated area per unit ground area, using a local Poisson distribution to approximate the laser beam transmission probability within vines. In order to compare the calculated indexes with the actual values of LAI, the scanned vines were defoliated to obtain LAI values for different row sections. Linear regression analysis showed a good correlation (R 2 = 0.81) between canopy volume and the measured values of LAI for 1 m long sections. Nevertheless, the best estimation of the LAI was given by the TAI (R 2 = 0.92) for the same length, confirming LiDAR sensors as an interesting option for foliage characterization of grapevines. However, current limitations exist related to the complexity of data process and to the need to accumulate a sufficient number of scans to adequately estimate the LAI. 相似文献
28.
During the last few years following the invasion of European tomato crops by the invasive South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), several indigenous larval parasitoid species were recorded as natural enemies of this pest. Necremnus cf. artynes (Walker) and to a lesser extent Stenomesius sp. nr. japonicus (Ashmead) (Hymenoptera: Eulophidae) have been frequently reported attacking T. absoluta in tomato greenhouses in Europe and they are considered as possible biocontrol agents. Few biological data are available on these two species, notably when they parasitize T. absoluta. Therefore, the present study documents their biology when parasitizing T. absoluta, and provides scientific bases for potential development of biological control programs relying on larval ectoparasitoids in invaded areas. We demonstrated the ability of the two parasitoid species to reproduce on T. absoluta as host on tomato plants. On average, N. cf. artynes female parasitized 28.5 larvae and killed 26.2 larvae during its life time whereas S. sp. nr. japonicus female was more long-lived and consequently more efficient; it parasitized 144.3 larvae and killed 90.1 larvae. In a second step, we also explored the effect of T. absoluta larvae instar on parasitism by S. sp. nr. japonicus and subsequent development of the parasitoid offspring. Best results were obtained with the third larvae instar with a higher number of offspring produced, bigger individuals and a higher proportion of females. Our results support the hypothesis that the two species are good candidates for biological control programs targeting T. absoluta in Europe. 相似文献
29.
Snorri Gunnarsson Albert K Imsland Jón Árnason Arnþór Gústavsson Ingólfur Arnarson Jón Kjartan Jónsson Atle Foss Sigurd Stefansson Helgi Thorarensen 《Aquaculture Research》2011,42(2):221-229
The effect of rearing temperature on the growth and maturation of Arctic charr (Salvelinus alpinus) was investigated. Arctic charr juveniles were reared for 6 months (phase I, October–April, size range 20–500 g) at constant temperatures of 9, 12 and 15 °C and according to two temperature‐step groups (Tstep) i.e. fish transferred from 15 to 12 °C or from 12 to 9 °C. All the previous treatments were then reared either at 7 °C or at 12 °C for an additional 4 months (phase II, size range 300–1000 g) and then slaughtered in August 2008. The overall growth rate was the highest at a constant temperature of 15 °C for the first 6 months of the trial, with the fish in this group being 44% and 78% heavier than the fish reared at a constant temperature of 12 or 9 °C respectively. Arctic charr showed a negative response in terms of the growth rate when transferred from higher to lower temperatures, especially for groups previously reared at 15 °C. There was a trend for higher gonadosomatic index values at the end of the experiment for groups of fish that were exposed to higher rearing temperatures during the juvenile phase i.e. 4.18% (±0.79) and 7.29% (±0.89), for the temperature groups of 12 and 15 °C, respectively, compared with 2.49% (±0.74) for the 9 °C group. Our results suggest that for the production of fish >1000 g, moderate or low temperatures (here 9 °C) should be applied during the juvenile phase in order to reduce the negative effects arising from maturation. Farmers with access to heat sources should accordingly choose more moderate rearing temperatures during the juvenile stage, especially if the fish is to be moved down in the temperature regime during the on‐growing period. 相似文献