Bibliothek

Notizen: 1. Shallow lake ecosystems are normally dominated by submerged and emergent plants. Biological stabilising mechanisms help preserve this dominance. The systems may switch to dominance by phytoplankton, however, with loss of submerged plants. This process usually takes place against a background of increasing nutrient loadings but also requires additional switch mechanisms, which damage the plants or interfere with their stabilising mechanisms.2. The extent to which the details or even major features of this general model may change with geographical location are not clear. Manipulation of the fish community (biomanipulation) has often been used to clear the water of algae and restore the aquatic plants in northerly locations, but it is again not clear whether this is equally appropriate at lower latitudes.3. Eleven parallel experiments (collectively the International Mesocosm Experiment, IME) were carried out in six lakes in Finland, Sweden, England, the Netherlands and Spain in 1998 and 1999 to investigate the between-year and large-scale spatial variation in relationships between nutrient loading and zooplanktivorous fish on submerged plant and plankton communities in shallow lakes.4. Comparability of experiments in different locations was achieved to a high degree. Cross-laboratory comparisons of chemical analyses revealed some systematic differences between laboratories. These are unlikely to lead to major misinterpretations.5. Nutrient addition, overall, had its greatest effect on water chemistry then substantial effects on phytoplankton and zooplankton. Fish addition had its major effect on zooplankton and did not systematically change the water chemistry. There was no trend in the relative importance of fish effects with latitude, but nutrient addition affected more variables with decreasing latitude.6. The relative importance of top-down and bottom-up influences on the plankton differed in different locations and between years at the same location. The outcome of the experiments in different years was more predictable with decreasing latitude and this was attributed to more variable weather at higher latitudes that created more variable starting conditions for the experiments.

Notizen: 1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol.2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location.3. The overall meta-analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable.4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards.5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing-season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions.6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de-emphasis of the importance of nutrient loading in the experiment.

Notizen: 1. The impacts of nutrients (phosphorus and nitrogen) and planktivorous fish on phytoplankton composition and biomass were studied in six shallow, macrophyte-dominated lakes across Europe using mesocosm experiments.2. Phytoplankton biomass was more influenced by nutrients than by densities of planktivorous fish. Nutrient addition resulted in increased algal biomass at all locations. In some experiments, a decrease was noted at the highest nutrient loadings, corresponding to added concentrations of 1 mg L−1 P and 10 mg L−1 N.3. Chlorophyll a was a more precise parameter to quantify phytoplankton biomass than algal biovolume, with lower within-treatment variability.4. Higher densities of planktivorous fish shifted phytoplankton composition toward smaller algae (GALD 〈 50 μm). High nutrient loadings selected in favour of chlorophytes and cyanobacteria, while biovolumes of diatoms and dinophytes decreased. High temperatures also may increase the contribution of cyanobacteria to total phytoplankton biovolume in shallow lakes.

Notizen: Trauma and infection activated a murine mucosal IL-6 response in different ways: the IL-6 response to bacteria was sensitive to Cyclosporin A (CsA); the IL-6 response to trauma was not. The aim of the present study was to identify possible activators of the CsA-insensitive IL-6 secretion at the epithelial cell level. Two human epithelial cell lines from the kidney (A498) and bladder (J82) were exposed to Escherichia coli Hu734, interleukin-lα (IL-lα) and tumour necrosis factor a (TNF-α). The E. coli strain had been used for the in vivo experiments which led to this study, and IL-lα and TNF-α were likely to be released during infections and trauma. The secretion of IL-6 into the supernatants was compared between cells stimulated in the presence or absence of CsA. E. coli Hu734, IL-lα and TNF-α stimulated an IL-6 response in the two epithelial cell lines. The IL-lα-induced IL-6 response was rapid, and the secreted IL-6 levels were significantly higher than those induced by E. coli Hu734 or TNF-α. The IL-6 response to IL- lα was insensitive to CsA. By contrast, the IL-6 response to E. coli Hu734 and TNF-α was inhibited by CsA. These results demonstrated that the inhibitory effect of CsA depends on the stimulus triggering the IL-6 response. IL-lα may play a role in the induction of trauma-associated CsA-insensitive IL-6 secretion.

Notizen: The aim of the present study was to examine whether inhibition of the microglial cell reaction around axotomized motoneurons affects the subsequent regeneration process of the injured axons. The microglial cell reaction in the hypoglossal nucleus of the rat was blocked by infusion of cytosine-arabinoside (ARA-C) into the ventricular system. Axon regeneration was evaluated by determining the number and size distribution of myelinated axons at a defined level distal to the crush site, the number of neurons which could be retrogradely labelled from the distal stump as well as the number of motor endplates in the tongue at various times following injury. No significant difference was observed for any of these parameters between ARA-C-treated and untreated animals. Therefore, it is concluded that the microglial cell reaction is not necessary for peripheral nerves to regenerate and restore target contact at a normal rate and to a normal extent.

Notizen: Aim:  To investigate the risk of adult hand eczema and possible influence on later working life in persons with childhood atopic dermatitis.Method:  After reviewing medical records from the school healthcare in Stockholm regarding individuals born 1960–69, 600 individuals where signs of atopic dermatitis were noted (“cases”) and 600 matched controls without eczema or allergic disease (“controls”) were identified. 405 cases and 378 controls answered a questionnaire regarding past and present skin disease, choice of job, exposure at work and possible change of job due to eczema.Results: Hand eczema was more than 3 times more common among cases, 42%, compared to controls, 13%(p 〈 0.001). Hand eczema during the past 12 months was reported by 24% of the cases and 9% of the controls (p 〈 0.001). The proportion of individuals working in jobs with high-risk for hand eczema was equal between the groups, as well as exposure to water, detergents, chemicals and hand washing. Among the cases 9% reported change of job due to eczema compared to 2% of controls (p 〈 0.001) and sick leave 10% compared to 2%(p 〈 0.001).Conclusions: Childhood atopic dermatitis is a risk factor for hand eczema. As the proportion of individuals in jobs with high-risk for hand eczema and the exposure was the same in cases and controls measures preventive measures are important to reduce consequences like sick leave and change of job.

Notizen: This study examined the role of P and type 1 fimbriae for neutrophil migration across Escherichia coli-infected uroepithelial cell layers in vitro and for neutrophil recruitment to the urinary tract in vivo. Recombinant E. coli K-12 strains differing in P or type 1 fimbrial expression were used to infect confluent epithelial layers on the underside of transwell inserts. Neutrophils were added to the upper well, and their passage across the epithelial cell layers was quantified. Infection with the P- and type 1-fimbriated recombinant E. coli strains stimulated neutrophil migration to the same extent as a fully virulent clinical E. coli isolate, but the isogenic non-fimbriated vector control strains had no stimulatory effect. The enhancement of neutrophil migration was adhesion dependent; it was inhibited by soluble receptor analogues blocking the binding of P fimbriae to the globoseries of glycosphingolipids or of type 1 fimbriae to mannosylated glycoprotein receptors. P- and type 1-fimbriated E. coli triggered higher interleukin (IL) 8 secretion and expression of functional IL-8 receptors than non-fimbriated controls, and the increase in neutrophil migration across infected cell layers was inhibited by anti-IL-8 antibodies. In a mouse infection model, P- or type 1-fimbriated E. coli stimulated higher chemokine (MIP-2) and neutrophil responses than the non-fimbriated vector controls. The results demonstrated that transformation with the pap or fim DNA sequences is sufficient to convert an E. coli K-12 strain to a host response inducer, and that fimbriation enhances neutrophil recruitment in vitro and in vivo. Epithelial chemokine production provides a molecular link between the fimbriated bacteria that adhere to epithelial cells and tissue inflammation.

Notizen: The aim of this study was to evaluate the efficacy, safety and preference of pre-school children with regard to two different devices for treatment of bronchial asthma with terbutaline. Turbuhaler, a powder inhaler preloaded with pure terbutaline for inhalation, was compared with a pressurized metered dose inhaler, attached to a Nebuhaler. The study had an open, cross-over randomized design. Each treatment period consisted of 2 weeks. Diary cards were filled in every morning and evening by the parents regarding PEF, asthma symptoms, extra inhalations of terbutaline, and side effects. Twenty-one children (mean age 3.9 years) were included in the study. A highly significant (P 〈 0.001) increase in peak expiratory flow (PEF) was obtained after inhalation with both devices. The PEF values in the mornings after inhalation of terbutaline with Turbuhaler were significantly higher (P= 0.046) than those with Nebuhaler. Further, the PEF baseline values in the evenings before inhalation were also significantly higher (P= 0.03) with Turbuhaler. No difference was found in asthma symptoms and extra medication between the two devices. Side effects were mild and few with both devices. The parents found Turbuhaler easier to handle and 19 of 21 preferred this device for future use.