Elevated CO2 Levels do not Affect the Shell Structure of the Bivalve Arctica islandica from the Western Baltic

Shells of the bivalve Arctica islandica are used to reconstruct paleo-environmental conditions (e.g. temperature) via biogeochemical proxies, i.e. biogenic components that are related closely to environmental parameters at the time of shell formation. Several studies have shown that proxies like element and isotope-ratios can be affected by shell growth and microstructure. Thus it is essential to evaluate the impact of changing environmental parameters such as high pCO₂ and consequent changes in carbonate chemistry on shell properties to validate these biogeochemical proxies for a wider range of environmental conditions. Growth experiments with Arctica islandica from the Western Baltic Sea kept under different pCO₂ levels (from 380 to 1120 µatm) indicate no affect of elevated pCO₂ on shell growth or crystal microstructure, indicating that A. islandica shows an adaptation to a wider range of pCO₂ levels than reported for other species. Accordingly, proxy information derived from A. islandica shells of this region contains no pCO₂ related bias.     

Predicting Effects of Water Regime Changes on Waterbirds: Insights from Staging Swans

Predicting the environmental impact of a proposed development is notoriously difficult, especially when future conditions fall outside the current range of conditions. Individual-based approaches have been developed and applied to predict the impact of environmental changes on wintering and staging coastal bird populations. How many birds make use of staging sites is mostly determined by food availability and accessibility, which in the case of many waterbirds in turn is affected by water level. Many water systems are regulated and water levels are maintained at target levels, set by management authorities. We used an individual-based modelling framework (MORPH) to analyse how different target water levels affect the number of migratory Bewick’s swans Cygnus columbianus bewickii staging at a shallow freshwater lake (Lauwersmeer, the Netherlands) in autumn. As an emerging property of the model, we found strong non-linear responses of swan usage to changes in water level, with a sudden drop in peak numbers as well as bird-days with a 0.20 m rise above the current target water level. Such strong non-linear responses are probably common and should be taken into account in environmental impact assessments.     

Mycolactone toxin induces an inflammatory response by targeting the IL-1β pathway: Mechanistic insight into Buruli ulcer pathophysiology

Mycolactone, a lipid-like toxin, is the major virulence factor of Mycobacterium ulcerans, the etiological agent of Buruli ulcer. Its involvement in lesion development has been widely described in early stages of the disease, through its cytotoxic and immunosuppressive activities, but less is known about later stages. Here, we revisit the role of mycolactone in disease outcome and provide the first demonstration of the pro-inflammatory potential of this toxin. We found that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory cytokine, in a TLR2-dependent manner, targeting NLRP3/1 inflammasomes. We show our data to be relevant in a physiological context. The in vivo injection of these mycolactone-containing vesicles induced a strong local inflammatory response and tissue damage, which were prevented by corticosteroids. Finally, several soluble pro-inflammatory factors, including IL-1β, were detected in infected tissues from mice and Buruli ulcer patients. Our results revisit Buruli ulcer pathophysiology by providing new insight, thus paving the way for the development of new therapeutic strategies taking the pro-inflammatory potential of mycolactone into account.     

Studies on the protolytic reactions coupled with water cleavage in photosystem II membrane fragments from spinach

The protolytic reactions of PSII membrane fragments were analyzed by measurements of absorption changes of the water soluble indicator dye bromocresol purple induced by a train of 10 s flashes in dark-adapted samples. It was found that: a) in the first flash a rapid H⁺-release takes place followed by a slower H⁺-uptake. The deprotonation is insensitive to DCMU but is completely eliminated by linolenic acid treatment of the samples; b) the extent of the H⁺-uptake in the first flash depends on the redox potential of the suspension. In this time domain no H⁺-uptake is observed in the subsequent flashes; c) the extent of the H⁺-release as a function of the flash number in the sequence exhibits a characteristic oscillation pattern. Multiphasic release kinetics are observed. The oscillation pattern can be satisfactorily described by a 1, 0, 1, 2 stoichiometry for the redox transitions S_i S_i+1 (i=0, 1, 2, 3) in the water oxidizing enzyme system Y. The H⁺-uptake after the first flash is assumed to be a consequence of the very fast reduction of oxidized Q₄₀₀(Fe³⁺) formed due to dark incubation with K₃[Fe(CN)₆]. The possible participation of component Z in the deprotonation reactions at the PSII donor side is discussed.Abbreviations A protonizable group at the PSII acceptor side - BCP Bromocresol Purple - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FWHM Full Width at Half Maximum - Q_A, Q_B primary and secondary plastoquinone at PSII acceptor side - Q₄₀₀ redox group at PSII-acceptor side (high spin Fe²⁺) - P680 Photoactive chlorophyll of PSII reaction center - S_i redox states of the catalytic site of water oxidation - Z redox component connecting the catalytic site of water oxidation with the reaction center     

Ribonuclease in plant vacuoles: purification and molecular properties of the enzyme from cultured tomato cells

A ribonuclease which was previously shown to be located in isolated vacuoles from suspension-cultured cells of tomato (Lycopersicon esculentum L.; Abel and Glund 1986, Physiol. Plant. 66, 79–86) has been purified to near homogeneity. Purification was up to 55000-fold with a yield of about 20%. The vacuolar origin of the protein was evidenced by comparing its electrophoretic mobility, isoelectric point, pH-optimum for activity and other properties with that of the RNA-degrading activity present in isolated vacuoles. The molecular weight of the native single polypeptide chain was estimated at 17500 and 20300 by gel filtration and sedimentation analysis, respectively. The enzyme hydrolyzed only single-stranded RNA with a mode of action that was endonucleolytic. The vacuolar ribonuclease had no requirement for divalent metal ions, and did not exhibit phosphomonoesterase (EC 3.1.3.1; EC 3.1.3.2) and phosphodiesterase (EC 3.1.15.1; EC 3.1.16.1) activity. The specificity of the enzyme has been studied by using homopolyribonucleotides as substrates. The end-products obtained were the respective nucleoside 2:3-cyclic monophosphates and, to minor extents, the corresponding nucleoside 3(2)-monophosphates. According to these observations, the vacuolar ribonuclease from tomato can be classified as ribonuclease I (EC 3.1.27.1).Abbreviations DEAE diethylaminoethyl - RNase ribonuclease - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis     

Effects of salinity on chloride cells in the euryhaline cyprinodontid fish Rivulus marmoratus

Summary The ultrastructure and density of chloride cells in the gill, opercular epithelium, and opercular skin of the euryhaline self-fertilizing fish Rivulus marmoratus (Cyprinodontidae) were studied with electron and fluorescence microscopy. R. marmoratus raised from birth in 1, 50, 100, and 200% seawater were compared. Chloride cells from fish raised in each of the four salinities exhibited an invaginated pit structure at the apical crypt. Multicellular complexes were present in the 1% seawater group and in those fish raised in higher salinities where elaborate interdigitations were seen between cells. Chloride cells from gills of fish raised in 200% seawater had a significantly higher percentage of their cytoplasmic volume composed of mitochondria than did those from fish raised in 1% seawater (69.9% vs 37.4%). The opercular skin and opercular epithelium had the same density of chloride cells (4.2×10⁴-4.5×10⁴ chloride cells/cm²), and this number did not vary significantly with increased salinity. The opercular skin thus appears far more responsive to environmental salinity than the opercular epithelium. Chloride cells from the opercular epithelium of fish raised in 200% seawater were found to be 39% larger than those from fish raised in 1% seawater, whereas the chloride cells from the opercular skin of the 200% seawater group were 107% larger than those from the 1% seawater group.     

Metallothionein induction by nonsteroidal antiinflammatory drugs

In the present study we report on the effects of commonly used nonsteroidal antiinflammatory drugs on metallothionein (MT) and MT-I mRNA levels. A single dose of chloroquine (100 mg/kg), diclofenac (100 mg/kg), indomethacin (10 mg/kg), or piroxicam (100 mg/kg) was administered ip to C57B1 mice. After 18 h, MT levels were determined with a Cd-saturation radioassay. MT-I mRNA levels were measured by Northern Blot analyses using a probe containing the mouse MT-I gene. All drugs tested caused an increase in the MT content of the liver but not of the kidneys and lung. The lowest and highest effects were observed with chloroquine (8 times the control value) and diclofenac (18 times), respectively. In accordance with the stimulation of MT synthesis, increased accumulation of hepatic MT-I mRNA could be demonstrated. These results indicate that elevated MT levels may contribute to the effectiveness of nonsteroidal antiinflammatory drugs in the treatment of rheumatoid arthritis (RA).     

Protein synthesis rates in rat brain regions and subcellular fractions during aging

In vivo protein synthesis rates in various brain regions (cerebral cortex, cerebellum, hippocampus, hypothalamus, and striatum) of 4-, 12-, and 24-month-old rats were examined after injection of a flooding dose of labeled valine. The incorporation of labeled valine into proteins of mitochondrial, microsomal, and cytosolic fractions from cerebral cortex and cerebellum was also measured. At all ages examined, the incorporation rate was 0.5% per hour in cerebral cortex, cerebellum, hippocampus, and hypothalamus and 0.4% per hour in striatum. Of the subcellular fractions examined, the microsomal proteins were synthesized at the highest rate, followed by cytosolic and mitochondrial proteins. The results obtained indicate that the average synthesis rate of proteins in the various brain regions and subcellular fractions examined is fairly constant and is not significantly altered in the 4 to 24-month period of life of rats.A preliminary report of these results was previously presented at: WFN-ESN Joint Meeting on: Cerebral Metabolism in Aging and Neurological Disorders, Baden, August 28–31, 1986.     

Ferritin enhances production of DNA strand breaks by 6-hydroxydopamine,ascorbic acid and H2O2 in CCC PM2 bacteriophage DNA

Damage of CCC PM2 DNA by 6-hydroxydopamine (6-OHDA) and ascorbic acid (AA), compounds that are both able to release iron from ferritin, was significantly enhanced in the presence of ferritin. H₂O₂, a product of 6-OHDA autoxidation, did not induce DNA strand breaks in the absence of ferritin and only to a minor extent in the presence of ferritin. DNA damage by 6-OHDA and AA could be reduced by the hydroxyl radical scavenger mannitol, the iron chelator desferrioxamine, and, partly, by a combination of superoxide dismutase and catalase. These inhibitory effects were clearly less pronounced in the presence of ferritin. Ferritin obviously played an important role as a source of iron in the pro-oxidative processes of 6-OHDA and AA. These features might be of importance in cancer therapy since many tumor cells contain elevated ferritin levels.