Ragweed – An allergy risk in Sweden?

Ragweed pollen, which is a major cause of allergic rhinitis in North America and during the last decades, also in parts of the European continent, has not been regarded as a risk in Sweden, since occurrences of Ambrosia have been rare and with two exceptions, ephemeral. During the last four years, however, long-distance transported pollen has been registered in South Sweden. Moreover, seeds are dispersed by man with birdseed and reports on ragweed plants growing at birdtables are becoming more and more common. In warm years, the fruits of these plants mature and are germinative. We argue that there is a risk that ragweed pollen may be a problem in the future in Sweden. Long-distance transport from the continent is likely to be increasingly more common, and in larger amounts, as ragweed is rapidly spreading in Europe. Among the plants now appearing within Sweden, selection is likely to favour phenotypes which are able to fulfil their life-cycle during the indigenous vegetation period, especially in a scenario of global warming.     

Vegetation development in abandoned gravel pits: effects of surrounding vegetation,substrate and regionality

Abstract. Vegetation development in 68 abandoned gravel pits and their surroundings in five regions in Sweden is described by means of classification and ordination. Most pits were less than 10 yr old, but some pits in central Sweden were up to 100 yr old. For 26 pits in central Sweden the results of mechanical and chemical soil analyses are presented. Vegetation in young pits is more homogeneous than the vegetation in the surroundings. The surrounding vegetation type strongly affects pit vegetation. There are regional differences in pit vegetation between pits in coniferous forests in different parts of Sweden. Old gravel pits are clearly distinguished from young ones and show more resemblance to the surrounding vegetation. Tree layer cover and nitrogen content increase, whereas C/N ratio and pH decrease with age. Species richness of the gravel pits was not related to their size.     

Predicting the intensity of the birch pollen season

We present a model for the prediction of the magnitude ofBetula flowering and pollen dispersal which may be used in the management of birch pollinosis and in the planning of clinical trials. The pollen sum during the flowering season is regressed on the temperature sum from May 1st to July 20th during the initiation year, the pollen sum of the initiation year, and the temperature sum during the main pollen season in the flowering year. We suggest that the fluctuating flowering pattern inBetula alba-species is primarily determined by the availability of assimilation products during inflorescence initiation and development during the spring one year before anthesis. When inflorescences, which are initiated during the previous year, elongate in the beginning of anthesis, they act as strong sinks to stored carbohydrates, and thus compete with developing leaves and shoots. The result is an initially reduced photosynthetic capacity in years with intense flowering, and a limited potential for the initiation of new inflorescences for the following year. The ambient temperature during catkin initiation affects assimilation efficiency and is a determinant of about equal importance to flowering intensity as is the magnitude of the flowering in the initiation year. The amount of pollen dispersed is also dependent on the weather during anthesis, which is not possible to predict until about one month in advance. The two other independent variables are available during the previous summer, making it possible to give a sufficiently valid prediction to allergologists about the magnitude of the next birch pollen season, according to its botanical determinants. We suggest that the varying reproductive output inBetula alba should not be described as true masting. A more parsimonious explanation to the flowering pattern is that an individual continually maximizes reproductive effort, according to what is possible, but that reproduction is often constrained by the environment.     

Remnant habitats for grassland species in an abandoned Swedish agricultural landscape

Questions: Which factors influence the persistence of vascular grassland plants in long‐abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration? Location: Forested highlands of Kilsbergen, south central Sweden. Methods: The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition. Results: Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species. Conclusion: After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands.     

Primary succession over sixty years on hundred-year old islets in Lake Hjälmaren,Sweden

New islands were created as a result of an artificial lowering of the water table of Lake Hjälmaren in 1882–1886 and the floras of 40 such islands have been monitored ever since plant colonization started in 1886. Data used in this paper are from belt-transects across ten of these islands which were analysed in 1927–29 and reanalysed in 1986. During this 60-year period shading by trees has increased and shading and litter accumulation have affected the ground flora. Succession includes aspects of both convergence and divergence. Species of dry, open sites and shore species have been excluded from the island interiors, making these parts of the islands more similar, but there has simultaneously been an increased variability of vegetation types of shaded, mesic habitats. There have been no consistent trends in beta-diversity between the two surveys. Differences in successional patterns between island interiors and shore habitats are attributed to an outward migration of plant species and to differences in disturbance regimes.     

Predicting the intensity of the birch pollen season

We present a model for the prediction of the magnitude ofBetula flowering and pollen dispersal which may be used in the management of birch pollinosis and in the planning of clinical trials. The pollen sum during the flowering season is regressed on the temperature sum from May 1st to July 20th during the initiation year, the pollen sum of the initiation year, and the temperature sum during the main pollen season in the flowering year. We suggest that the fluctuating flowering pattern inBetula alba-species is primarily determined by the availability of assimilation products during inflorescence initiation and development during the spring one year before anthesis. When inflorescences, which are initiated during the previous year, elongate in the beginning of anthesis, they act as strong sinks to stored carbohydrates, and thus compete with developing leaves and shoots. The result is an initially reduced photosynthetic capacity in years with intense flowering, and a limited potential for the initiation of new inflorescences for the following year. The ambient temperature during catkin initiation affects assimilation efficiency and is a determinant of about equal importance to flowering intensity as is the magnitude of the flowering in the initiation year. The amount of pollen dispersed is also dependent on the weather during anthesis, which is not possible to predict until about one month in advance. The two other independent variables are available during the previous summer, making it possible to give a sufficiently valid prediction to allergologists about the magnitude of the next birch pollen season, according to its botanical determinants. We suggest that the varying reproductive output inBetula alba should not be described as true masting. A more parsimonious explanation to the flowering pattern is that an individual continually maximizes reproductive effort, according to what is possible, but that reproduction is often constrained by the environment.     

Second Generation γ-Secretase Modulators Exhibit Different Modulation of Notch β and Aβ Production

The γ-secretase complex is an appealing drug target when the therapeutic strategy is to alter amyloid-β peptide (Aβ) aggregation in Alzheimer disease. γ-Secretase is directly involved in Aβ formation and determines the pathogenic potential of Aβ by generating the aggregation-prone Aβ42 peptide. Because γ-secretase mediates cleavage of many substrates involved in cell signaling, such as the Notch receptor, it is crucial to sustain these pathways while altering the Aβ secretion. A way of avoiding interference with the physiological function of γ-secretase is to use γ-secretase modulators (GSMs) instead of inhibitors of the enzyme. GSMs modify the Aβ formation from producing the amyloid-prone Aβ42 variant to shorter and less amyloidogenic Aβ species. The modes of action of GSMs are not fully understood, and even though the pharmacology of GSMs has been thoroughly studied regarding Aβ generation, knowledge is lacking about their effects on other substrates, such as Notch. Here, using immunoprecipitation followed by MALDI-TOF MS analysis, we found that two novel, second generation GSMs modulate both Notch β and Aβ production. Moreover, by correlating S3-specific Val-1744 cleavage of Notch intracellular domain (Notch intracellular domain) to total Notch intracellular domain levels using immunocytochemistry, we also demonstrated that Notch intracellular domain is not modulated by the compounds. Interestingly, two well characterized, nonsteroidal anti-inflammatory drugs (nonsteroidal anti-inflammatory drug), R-flurbiprofen and sulindac sulfide, affect only Aβ and not Notch β formation, indicating that second generation GSMs and nonsteroidal anti-inflammatory drug-based GSMs have different modes of action regarding Notch processing.