We suppressed the B-cell development and antibody response in mink by using treatment with polyclonal anti-immunoglobulin M (anti-IgM) to study the effects of antiviral antibodies on development of Aleutian mink disease parvovirus (ADV)-induced disease in more detail. Newborn mink kits were injected intraperitoneally with 1 mg of either anti-IgM or a control preparation three times a week for 30 to 34 days. At 21 days after birth, groups of mink kits were infected with the highly virulent United isolate of ADV. At selected time points, i.e., postinfection days 9, 13, 29, and 200, randomly chosen mink kits were sacrificed, and blood and tissues were collected for analyses. The efficacy of immunosuppressive treatment was monitored by electrophoretic techniques and flow cytometry. Effects of treatment on viral replication, on viral mRNA levels, and on development of acute or chronic disease were determined by histopathological, immunoelectrophoretic, and molecular hybridization techniques. Several interesting findings emerged from these studies. First, antiviral antibodies decreased ADV mRNA levels more than DNA replication. Second, suppression of B-cell development and antibody response in mink kits infected at 21 days of age resulted in production of viral inclusion bodies in alveolar type II cells. Some of these kits showed mild clinical signs of respiratory disease, and one kit died of respiratory distress; however, clinical signs were seen only after release of immunosuppression,
A fast method for estimating the net short-wave radiation in high arctic mountainous areas is developed by combining Landsat-5 Thematic Mapper (TM) satellite data and a digital elevation model (DEM). Methods to: (1) correct remote sensing data for the atmospheric e V ect; (2) perform a thorough and extensive topographic correction via the DEM; and (3) model the irradiance from a radiation model are described. By combining the above-mentioned methods, a model with great applicability-e.g. creation of albedo maps, terrain modelled short wave radiation and correction of satellite images for both topographic and atmospheric e V ects, is developed. A great advantage of this model is that it combines atmospheric and topographic correction. Most models only correct for one of the two. Another great advantage is that it has a limited number of inputs. Beside the satellite data and the DEM, the only inputs are visibility, latitude, longitude, atmospheric pressure and time of day and day of year (DOY). Furthermore the model can be implemented in any image processing software. The model was tested and validated on satellite data from April to September in the period 1995 to 1998 with a total of nine TM-images. To validate the model, the results were compared with ground measurements. The result of the validation showed that: (1) the modelled results show very good agreement with the measured data; (2) atmospheric and topographic correction of images is possible without using expensive software; and (3) the topographic correction is of great importance. Even a small change in the topography has a greater e V ect on the net short wave radiation than a lack of atmospheric correction. The future use of the model is to produce input to other models that estimate snowmelt, energy balance, biomass production and CO 2 -uxes and to determine regional and seasonal variation.
The Landsat-5 Thematic Mapper (TM) has provided data for more than 17 years, making it one of the most successful missions so far. TM sensor degradation is well documented and although efforts are made to account for this degradation when calibrating the sensor, such calibrations are often done over high reflective and bright surfaces in combination with a high solar irradiance. These conditions are not found in high-latitude and dark areas, making the calibration coefficients inappropriate to use. In this study reflectances obtained from TM bands 1-4 over a high-arctic area from 1987-1998 are compared to reflectances obtained from the Landsat-7 Enhanced Thematic Mapper Plus (ETMz) over the same area in 1999-2000. From the reflectance comparison it was found that a correction of the calibration gain could be described by a power function using days since launch as the controlling variable. From the power function, updated and lifetime calibration coefficients for TM bands 1-4 applicable for high-latitude and dark areas were determined. Furthermore, the study showed a continuous decrease of the TM sensor response with band 1 being the most affected and band 4 the most stable. The study also showed the possibility of using ETMz to determine updated calibration coefficients for TM by a cross-calibration even though the ETMz and TM scenes are not coincident.
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