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.     

Mass Coral Reef Bleaching: A Recent Outcome of Increased El Niño Activity?

Coral reefs are generally considered to be the most biologically productive of all marine ecosystems, but in recent times these vulnerable aquatic resources have been subject to unusual degradation. The general decline in reefs has been greatly accelerated by mass bleaching in which corals whiten en masse and often fail to recover. Empirical evidence indicates a coral reef bleaching cycle in which major bleaching episodes are synchronized with El Niño events that occur every 3–4 years on average. By heating vast areas of the Pacific Ocean, and affecting the Indian and Atlantic Oceans as well, El Niño causes widespread damage to reefs largely because corals are very sensitive to temperature changes. However, mass bleaching events were rarely observed before the 1970s and their abrupt appearance two decades ago remains an enigma. Here we propose a new explanation for the sudden occurrence of mass bleaching and show that it may be a response to the relative increase in El Niño experienced over the last two decades.     

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.     

Perinatal anti-androgen treatment and genotype affect the mesotelencephalic dopamine system and behavior in mice

Sex and strain differences in tyrosine hydroxylase activity (TH) of brain dopamine systems have been reported for mice. To investigate if there might be a causal relationship between perinatal androgen secretion and regional mesotelencephalic TH activity, BALB/cJ and C57BL/6ByJ male mice were treated perinatally with cyproterone, a steroidal anti-androgen (or vehicle), and orchiectomized at 1 month of age. Two-way analysis of variance indicated significant treatment and strain effects in the mesencephalon and tuber olfactorium: perinatal cyproterone treatment lowered TH activity, and BALB/cJ had higher regional TH activities than those of C57BL/6ByJ. The most prominent behavioral effects of cyproterone treatment were found in the expression of scratching, which was considerably increased in both strains. Possible implications of these results are discussed.     

Chromosome-damaging effects of heraclenin in human lymphocytes in vitro

Heraclenin, a furocoumarin with an epoxide group in its side chain, was analyzed to see if it induced structural chromosome aberrations and sister-chromatid exchanges (SCEs) in human lymphocytes in vitro. The results were compared directly with those of imperatorin, which differs from heraclenin only in lacking an epoxide group. An equally strong clastogenic effect was found for both heraclenin and imperatorin: the number of metaphases with breaks was increased in both cases by approximately a factor of 6. Heraclenin produced a considerable dose-dependent increase in the SCE rate, i.e., by about 60 induced SCEs/metaphase, whereas imperatorin induced only about 4 SCEs/metaphase. The results are discussed with respect to the occurrence of structural aberrations, which are primarily due to the basic furocoumarin structure itself, whereas the large increase in the SCE rate produced by heraclenin is most probably significantly influenced by its epoxide group.