Complexing of 3d transition metal ions with 9-substituted purines. IV. The effect of base-stacking on the basicity and complexing-ability

A number of 9-methylpurines were equilibrated between carbon tetrachloride or chloroform and aqueous solutions containing either nickel(II) perchlorate or N⁶,N⁶-dimethyladenosine. The equilibrium constants for the complex formation with nickel(II) ion and association with N⁶,N⁶-dimethyladenosine were calculated on the basis of the distribution data. The results, together with those obtained in the presence of both nickel(II) perchlorate and N⁶,N⁶-dimethyladenosine, are interpreted to indicate that stacking-association with the latter compound reduces the complexing-ability of 9-methylpurines. The protonation of guanosine in the presence of caffeine was examined potentiostatically and its association with caffeine studied by phase-solubility measurements. Association with caffeine was shown to lower the basicity of guanosine.     

Site‐adapted admixed tree species reduce drought susceptibility of mature European beech

Some forest‐related studies on possible effects of climate change conclude that growth potential of European beech (Fagus sylvatica L.) might be impaired by the predicted increase in future serious drought events during the growing season. Other recent research suggests that not only multiyear increment rates but also growth resistance and recovery of beech during, respectively, after dry years may differ between pure and mixed stands. Thus, we combined dendrochronological investigations and wood stable isotope measurements to further investigate the impact of neighborhood diversity on long‐term performance, short‐term drought response and soil water availability of European beech in three major geographic regions of Germany. During the last four decades, target trees whose competitive neighborhood consisted of co‐occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close‐by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures what is in line with the results of the stable isotope analysis. Apparently, the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. Our investigation strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatica.     

Diversity of luciferase sequences and bioluminescence production in Baltic Sea Alexandrium ostenfeldii

The toxic dinoflagellate Alexandrium ostenfeldii is the only bioluminescent bloom-forming phytoplankton in coastal waters of the Baltic Sea. We analysed partial luciferase gene (lcf) sequences and bioluminescence production in Baltic A. ostenfeldii bloom populations to assess the distribution and consistency of the trait in the Baltic Sea, and to evaluate applications for early detection of toxic blooms. Lcf was consistently present in 61 Baltic Sea A. ostenfeldii strains isolated from six separate bloom sites. All Baltic Sea strains except one produced bioluminescence. In contrast, the presence of lcf and the ability to produce bioluminescence did vary among strains from other parts of Europe. In phylogenetic analyses, lcf sequences of Baltic Sea strains clustered separately from North Sea strains, but variation between Baltic Sea strains was not sufficient to distinguish between bloom populations. Clustering of the lcf marker was similar to internal transcribed spacer (ITS) sequences with differences being minor and limited to the lowest hierarchical clusters, indicating a similar rate of evolution of the two genes. In relation to monitoring, the consistent presence of lcf and close coupling of lcf with bioluminescence suggests that bioluminescence can be used to reliably monitor toxic bloom-forming A. ostenfeldii in the Baltic Sea.     

Longitudinal study of circulating oxidized LDL and HDL and fatty liver: the Cardiovascular Risk in Young Finns Study

Oxidative reactions are thought to play a role in the inflammatory condition called fatty liver. It is unclear whether oxidized lipoprotein lipids or proteins are associated with future fatty liver. In the Cardiovascular Risk in Young Finns Study, we determined the circulating levels of LDL and HDL oxidized lipids and studied their associations with fatty liver assessed by ultrasonography. There were 1286 middle-aged subjects with normal liver and 288 subjects with fatty liver. Analysis of oxidized lipids consisted of conjugated dienes in isolated HDL (oxHDLlipids) and LDL (oxLDLlipids). Oxidized LDL was also measured with a method based on antibodies against oxidized apolipoprotein B (oxLDLprot). After adjustment for age, sex, leisure-time physical activity, body mass index, alcohol intake, smoking, serum LDL and HDL cholesterol as well as particle concentrations, participants with elevated oxLDLlipids (odds ratio for 1-SD change in oxLDLlipids?=?1.27, p?=?0.011) had an increased risk for fatty liver. Similarly, a high oxidation score (oxLDLlipids?+?oxLDLprot) was directly associated with fatty liver (odds ratio=1.34, p?=?0.012). The strongest direct association was seen with a high oxLDLlipids/oxHDLlipids ratio (odds ratio=1.49, p?=?0.001). These data suggest that oxidized lipoprotein lipids are linked with the risk of fatty liver in middle-aged adults.     

Inter- and intraspecific variation in the resistance of winter-dormant birch (Betula spp.) against browsing by the mountain hare

The palatability of saplings of several different species, geographic origins and F₂-families of Betula spp. to the mountain hare was tested in feeding trials with captive and free-ranging animals. Significant variation in the palatability was detected among species and among conspecifics representing different origins and families. The results show that the combination of genetic and environmental factors determines the resistance of individual plants to mammals. Saplings that were stressed by severe competition from surrounding weeds were more resistant than saplings of the same age grown under optimal conditions. One-yr-old seedlings were more resistant than 7-yr-old saplings of the same origin. Some of the exotic species tested were extremely resistant, whereas others were highly palatable. The most resistant species and origins came from Asia and Alaska.     

Virus-Induced Cytoplasmic Membrane Structures Associated with Semliki Forest Virus Infection Studied by the Freeze-Etching Method

Intracellular membrane structures associated with the Semliki Forest virus replication process were studied from freeze-etch replicas. Cleaved membrane structures inside the CPV I type vacuoles lacked the typical membrane particles present on most other fractured membranes. CPV II type vacuoles present in thin sections were obscured in the freeze-etch replicas by the cytoplasmic ground substance.     

Widespread occurrence of calicin, a basic cytoskeletal protein of sperm cells, in diverse mammalian species

A novel cytoskeletal element consisting of dense webs of thin (3-14 nm) filaments surrounding the nucleus of the sperm head has recently been isolated and shown to be associated with certain major basic proteins. Using antibodies specific for calicin, a prominent Mr-60,000 cytoskeletal protein of the posterior calyx of bull sperm heads detected in immunoblotting on gel electrophoretically separated polypeptides as well as in immunofluorescence and immunoelectron microscopy, we show that the same--or an immunologically related--polypeptide occurs in sperm heads of other species with greatly different morphology, including human, boar, guinea pig, hamster, rat and mouse. The calicin localization in the various species is described and discussed in relation to the specific sperm morphology.     

Assessing Phytoplankton and Bacterioplankton Production During Early Spring in Lake Erken, Sweden

The spring development of both phytoplankton and bacterioplankton was investigated between 18 April and 7 May 1983 in mesotrophic Lake Erken, Sweden. By using the lake as a batch culture, our aim was to estimate, via different methods, the production of phytoplankton and bacterioplankton in the lake and to compare these production estimates with the actual increase in phytoplankton and bacterioplankton biomass. The average water temperature was 3.5°C. Of the phytoplankton biomass, >90% was the diatom Stephanodiscus hantzchii var. pusillus, by the peak of the bloom. The ¹⁴C and O₂ methods of estimating primary production gave equivalent results (r = 0.999) with a photosynthetic quotient of 1.63. The theoretical photosynthetic quotient predicted from the C/NO₃ N assimilation ratio was 1.57. The total integrated incorporation of [¹⁴C]bicarbonate into particulate material (>1 μm) was similar to the increase in phytoplankton carbon determined from cell counts. Bacterioplankton increased from 0.5 × 10⁹ to 1.52 × 10⁹ cells liter⁻¹ (~0.5 μg of C liter⁻¹ day⁻¹). Estimates of bacterioplankton production from rates of [³H]thymidine incorporation were ca. 1.2 to 1.7 μg of C liter⁻¹ day⁻¹. Bacterial respiration, measured by a high-precision Winkler technique, was estimated as 4.8 μg of C liter⁻¹ day⁻¹, indicating a bacterial growth yield of 25%. The bulk of the bacterioplankton production was accounted for by algal extracellular products. Gross bacterioplankton production (production plus respiration) was 20% of gross primary production, per square meter of surface area. We found no indication that bacterioplankton production was underestimated by the [³H]thymidine incorporation method.     

Epithelio-mesenchymal interface and fibronectin in the differentiation of the rat mesonephric and paramesonephric ducts

Abstract. The distribution of fibronectin and the morphological differentiation of the genital ducts was studied in rat fetuses at ages from 15 to 21 days. Fibronectin was localized with the peroxidase-antiperoxidase and avidin-biotin method at the electron- and light-microscope level. In 15-day-old male and female fetuses, fibronectin was localized as a continuous lamella around the mesonephric duct and as a discontinuous lamella around the paramesonephric duct. During the differentiation of the female paramesonephric duct, the fibronectin layer became continuous and remained so after the age of 16 days. The fibronectin layer of the male mesonephric duct remained continuous at all ages. The accumulation of mesenchymal cells on the outer surface of the female mesonephric duct and the concomitant detachment of the fibronectin layer around the duct suggests that mesenchymal regulation plays a role in the regression of the mesonephric duct. In the regressing male paramesonephric duct fibronectin was simultaneously lost in the condensed periductal mesenchyme, the places of epithelio-mesenchymal contact, and the epithelial cytoplasmic protrusions towards the mesenchyme. Ultrastructurally, fibronectin was localized in the basal laminae, on the cell membrane in contact with the extracellular material, and on the surface of the fibrillar and flocculent extracellular material. In addition to auto- and heterophagy, epithelio-mesenchymal interactions seem to play an important role in the regression of the genital ducts, although in different ways in males and females. The present results give additional support to the theory of the possible migration of epithelial cells into the surrounding mesenchyme during the regression of the paramesonephric duct.