Effect of various vaccination procedures on shedding, latency, and reactivation of attenuated and virulent pseudorabies virus in swine.

Various procedures of vaccination for pseudorabies were compared for their effects on shedding, latency, and reactivation of attenuated and virulent pseudorabies virus. The study included 6 groups: group 1 (10 swine neither vaccinated nor challenge-exposed), group 2 (20 swine not vaccinated, but challenge-exposed), and groups 3 through 6 (10 swine/group, all vaccinated and challenge-exposed). Swine were vaccinated with killed virus IM (group 3) or intranasally (group 4), or with live virus IM (group 5) or intranasally (group 6). The chronologic order of treatments was as follows: vaccination (week 0), challenge of immunity by oronasal exposure to virulent virus (week 4), biopsy of tonsillar tissue (week 12), treatment with dexamethasone in an attempt to reactivate latent virus (week 15), and necropsy (week 21). Vaccination IM with killed or live virus and vaccination intranasally with live virus mitigated clinical signs and markedly reduced the magnitude and duration of virus shedding after challenge exposure. Abatement of signs and shedding was most pronounced for swine that had been vaccinated intranasally with live virus. All swine, except 4 from group 2 and 1 from group 4, survived challenge exposure. Only vaccination intranasally with live virus was effective in reducing the magnitude and duration of virus shedding after virus reactivation. Vaccination intranasally with killed virus was without measurable effect on immunity. Of the 55 swine that survived challenge exposure, 54 were shown subsequently to have latent infections by use of dexamethasone-induced virus reactivation, and 53 were shown to have latent infections by use of polymerase chain reaction (PCR) with trigeminal ganglia specimens collected at necropsy. Fewer swine were identified by PCR as having latent infections when other tissues were examined; 20 were identified by testing specimens of olfactory bulbs, 4 by testing tonsil specimens collected at necropsy, and 4 by testing tonsillar biopsy specimens. Eighteen of the 20 specimens of olfactory bulbs and 3 of the 4 tonsil specimens collected at necropsy in which virus was detected by PCR were from swine without detectable virus-neutralizing antibody at the time of challenge exposure. One pig that had been vaccinated intranasally with live virus shed vaccine virus from the nose and virulent virus from the pharynx concurrently after dexamethasone treatment. Evaluation of both viral populations for unique strain characteristics failed to provide evidence of virus recombination.     

Wood age and leaf area influence fruit size and mineral composition of apple fruit

Summary

The influence of wood age, fruiting position and leaf area within the tree canopy on fruit mineral content and quality for several apple (Malus domestica Borkh.) cultivars was investigated. Size and Ca, Mg and K content of individual fruit on one-year (lateral and terminal positions), two-year and older than three-year wood were compared for cvs Royal Gala, Braeburn, Granny Smith and Fuji. Fruit on two-year spurs and one-year terminals was generally larger at commercial harvest than that on one-year laterals and spurs older than three years. Flower receptacles at full bloom were larger and fruit growth rates were greater from 60 to 100 d after full bloom on two-year spurs than on one-year laterals. Fruit Ca and Mg concentrations and contents at commercial harvest were highest for terminal fruit, but there was no consistent difference between fruit from other positions. One-year terminals had the greatest primary and bourse leaf areas, two-year spurs were intermediate and one-year laterals had the lowest areas of both leaf types. Removal of 50% of primary leaves and/or removal of bourse shoots from clusters at bloom reduced fruit Ca content at commercial harvest for two-year spurs, one-year laterals and one-year terminals. Bourse shoot removal also reduced Mg content for all positions. However there was no effect of leaf removal on fruit size or K content. Ca content of individual fruit increased curvilinearly with increasing total spur leaf area for fruit on two-year spurs and one-year terminals but not for fruit on one-year lateral clusters. Terminal fruit with total spur leaf areas and fruit size similar to those on two-year spur fruit had higher Ca content.     

Forest Damages by the Storm ‘Lothar’ in Permanent Observation Plots in Switzerland: The Significance of Soil Acidification and Nitrogen Deposition

In a network of permanent observation plots in Switzerland,the storm ‘Lothar’ uprooted 18.7% of Fagussylvaticaand 14.8% of Picea abies. The percentage of uprootingwas significantly inversely correlated with actual soil basesaturation (NH₄Cl-extract). At a base saturation of≤40% (calculated as an average over 0–40cm depth) uprootingwas increased by a factor of 4.8 in beech and by a factor of3.6 in Norway spruce compared to less acidic soils. In beech,the percentage of uprooted trees was also significantlycorrelated with nitrogen concentration in the leaves(positively) and with coarse pore volume in the soil(negatively). There was neither a relation with seasonalozone dose nor a relation with crown transparency, stemdiameter, crown size, slenderness, social position andposition within the stand. The results suggest thatanthropogenic stress factors play an important role in theextent of the ‘Lothar’ damages in Switzerland.