Molecular composition of nitrogenous compounds in sea water and recent marine sediments

Molecular composition of nitrogenous organic compounds in sea water and sediment

Biogeochemistry of stable carbon isotopes

Biochemistry and geochemistry of stable carbon istope

Carbon isotope fractionation in the system CO2/gas/-CO2/aqueous/-HCO3-/aqueous/

Carbon isotope fractionation between gaseous carbon dioxide and aqueous bicarbonat

Amino acids and amino sugars in calcified tissues of portunid crabs

Amino acid and amino sugar in calcified tissues of portunid crab

Late Pleistocene-Holocene chemical stratigraphy and paleolimnology of the Rift Valley lakes of central Africa

The interaction of climate and geology in Central Africa during Late Pleistocene and Holocene is examined. The study is based on sedimentological and limnological work on the main lakes of the Western Branch of the East African Rift Valley, particularly Lake Kivu, Changes in sediment chemistry, mineralogy and diatom assemblage provide a detailed histogram of lake level oscillations. Calculations indicate that the drop in lake level could be as high as 600 m for Tanganyika and 400 m for Kivu, Fluctuations in water levels.are the means for reconstruction of climatic events in tropical Africa of the last 15,000 years. Paleoclimatic comparison between tropical and temperate zones reveals that pluvial times coincide with the prominent interstadials in Europe, e.g. Bølling, Allerød, Climatic Optimum, and reversely, cool and dry periods in equatorial Africa with ice ages in the Northern Hemisphere. The African climatic sequence of pluvials and interpluvials is accompanied by corresponding periods of hydrothermal activity and quiescence. This may suggest that rain water exercises control on hydrothermal. activities.Prepared for the National Science Foundation under Grants GA-30641 and GA-35334

Blunted angiogenesis and hypertrophy are associated with increased fatigue resistance and unchanged aerobic capacity in old overloaded mouse muscle.

We hypothesize that the attenuated hypertrophic response in old mouse muscle is (1) partly due to a reduced capillarization and angiogenesis, which is (2) accompanied by a reduced oxidative capacity and fatigue resistance in old control and overloaded muscles, that (3) can be rescued by the antioxidant resveratrol. To investigate this, the hypertrophic response, capillarization, oxidative capacity, and fatigue resistance of m. plantaris were compared in 9- and 25-month-old non-treated and 25-month-old resveratrol-treated mice. Overload increased the local capillary-to-fiber ratio less in old (15 %) than in adult (59 %) muscle (P < 0.05). Although muscles of old mice had a higher succinate dehydrogenase (SDH) activity (P < 0.05) and a slower fiber type profile (P < 0.05), the isometric fatigue resistance was similar in 9- and 25-month-old mice. In both age groups, the fatigue resistance was increased to the same extent after overload (P < 0.01), without a significant change in SDH activity, but an increased capillary density (P < 0.05). Attenuated angiogenesis during overload may contribute to the attenuated hypertrophic response in old age. Neither was rescued by resveratrol supplementation. Changes in fatigue resistance with overload and aging were dissociated from changes in SDH activity, but paralleled those in capillarization. This suggests that capillarization plays a more important role in fatigue resistance than oxidative capacity

Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified

Muscle fatigue resistance during stimulated contractions is reduced in young male smokers.

Aim: To determine whether muscle function is compromised in healthy smokers in comparison with activity-matched non-smokers. Methods: Nine male smokers (aged 22.2 ± 2.5 years: mean ± SD) with a smoking history of 2.5 ± 3.1 pack years, and ten male control participants (25.4 ± 2.9 years) matched for physical activity level participated in this study. Knee extensor strength was measured using isometric maximal voluntary contractions. Voluntary activation of the quadriceps and co-activation of the biceps femoris were determined using interpolated twitches and surface electromyography respectively. The frequency-torque relationship and fatigue resistance were assessed with electrically evoked contractions. A fatigue index was determined as the ratio of final torque to initial torque during a series of isometric contractions (2 min; 30 Hz; 1 s contraction/1 s rest). Quadriceps anatomical cross sectional area was measured with MRI at 50% of femur length. Results: Maximal voluntary contraction torque, quadriceps anatomical cross sectional area, knee extensor torque/quadriceps cross sectional area, activation, co-activation and force-frequency relationship were similar, whereas the fatigue index was 17% lower in smokers than non-smokers. Conclusion: In young men smoking does not significantly affect quadriceps muscle mass and contractile properties, but does reduce fatigue resistance of the quadriceps muscle, which was not attributable to differences in physical activity. © 2007 The Authors

Comparative metagenomic, phylogenetic and physiological analyses of soil microbial communities across nitrogen gradients

Terrestrial ecosystems are receiving elevated inputs of nitrogen (N) from anthropogenic sources and understanding how these increases in N availability affect soil microbial communities is critical for predicting the associated effects on belowground ecosystems. We used a suite of approaches to analyze the structure and functional characteristics of soil microbial communities from replicated plots in two long-term N fertilization experiments located in contrasting systems. Pyrosequencing-based analyses of 16S rRNA genes revealed no significant effects of N fertilization on bacterial diversity, but significant effects on community composition at both sites; copiotrophic taxa (including members of the Proteobacteria and Bacteroidetes phyla) typically increased in relative abundance in the high N plots, with oligotrophic taxa (mainly Acidobacteria) exhibiting the opposite pattern. Consistent with the phylogenetic shifts under N fertilization, shotgun metagenomic sequencing revealed increases in the relative abundances of genes associated with DNA/RNA replication, electron transport and protein metabolism, increases that could be resolved even with the shallow shotgun metagenomic sequencing conducted here (average of 75 000 reads per sample). We also observed shifts in the catabolic capabilities of the communities across the N gradients that were significantly correlated with the phylogenetic and metagenomic responses, indicating possible linkages between the structure and functioning of soil microbial communities. Overall, our results suggest that N fertilization may, directly or indirectly, induce a shift in the predominant microbial life-history strategies, favoring a more active, copiotrophic microbial community, a pattern that parallels the often observed replacement of K-selected with r-selected plant species with elevated N

Regional differences in prediction models of lung function in Germany

<p>Abstract</p> <p>Background</p> <p>Little is known about the influencing potential of specific characteristics on lung function in different populations. The aim of this analysis was to determine whether lung function determinants differ between subpopulations within Germany and whether prediction equations developed for one subpopulation are also adequate for another subpopulation.</p> <p>Methods</p> <p>Within three studies (KORA C, SHIP-I, ECRHS-I) in different areas of Germany 4059 adults performed lung function tests. The available data consisted of forced expiratory volume in one second, forced vital capacity and peak expiratory flow rate. For each study multivariate regression models were developed to predict lung function and Bland-Altman plots were established to evaluate the agreement between predicted and measured values.</p> <p>Results</p> <p>The final regression equations for FEV₁and FVC showed adjusted r-square values between 0.65 and 0.75, and for PEF they were between 0.46 and 0.61. In all studies gender, age, height and pack-years were significant determinants, each with a similar effect size. Regarding other predictors there were some, although not statistically significant, differences between the studies. Bland-Altman plots indicated that the regression models for each individual study adequately predict medium (i.e. normal) but not extremely high or low lung function values in the whole study population.</p> <p>Conclusions</p> <p>Simple models with gender, age and height explain a substantial part of lung function variance whereas further determinants add less than 5% to the total explained r-squared, at least for FEV1 and FVC. Thus, for different adult subpopulations of Germany one simple model for each lung function measures is still sufficient.</p