End-tidal CO(2). An important parameter for a correct interpretation in functional brain studies using speech tasks

The aim was to investigate the effect of different speech tasks, i.e. recitation of prose (PR), alliteration (AR) and hexameter (HR) verses and a control task (mental arithmetic (MA) with voicing of the result on end-tidal CO2 (PETCO2), cerebral hemodynamics and oxygenation. CO2 levels in the blood are known to strongly affect cerebral blood flow. Speech changes breathing pattern and may affect CO2 levels. Measurements were performed on 24 healthy adult volunteers during the performance of the 4 tasks. Tissue oxygen saturation (StO2) and absolute concentrations of oxyhemoglobin ([O2Hb]), deoxyhemoglobin ([HHb]) and total hemoglobin ([tHb]) were measured by functional near-infrared spectroscopy (fNIRS) and PETCO2 by a gas analyzer. Statistical analysis was applied to the difference between baseline before the task, 2 recitation and 5 baseline periods after the task. The 2 brain hemispheres and 4 tasks were tested separately. A significant decrease in PETCO2 was found during all 4 tasks with the smallest decrease during the MA task. During the recitation tasks (PR, AR and HR) a statistically significant (p < 0.05) decrease occurred for StO2 during PR and AR in the right prefrontal cortex (PFC) and during AR and HR in the left PFC. [O2Hb] decreased significantly during PR, AR and HR in both hemispheres. [HHb] increased significantly during the AR task in the right PFC. [tHb] decreased significantly during HR in the right PFC and during PR, AR and HR in the left PFC. During the MA task, StO2 increased and [HHb] decreased significantly during the MA task. We conclude that changes in breathing (hyperventilation) during the tasks led to lower CO2 pressure in the blood (hypocapnia), predominantly responsible for the measured changes in cerebral hemodynamics and oxygenation. In conclusion, our findings demonstrate that PETCO2 should be monitored during functional brain studies investigating speech using neuroimaging modalities, such as fNIRS, fMRI to ensure a correct interpretation of changes in hemodynamics and oxygenation.

Comparison of Fluid Types for Resuscitation in Acute Hemorrhagic Shock and Evaluation of Gastric Luminal and Transcutaneous P co 2 in Leghorn Chickens

The objective of this study was to compare the effects of 3 different fluid types for resuscitation after experimentally induced hemorrhagic shock in anesthetized chickens and to evaluate partial pressures of carbon dioxide measured in arterial blood (Paco2), with a transcutaneous monitor (TcPco2), with a gastric intraluminal monitor (GiPco2), and by end tidal measurements (Etco2) under stable conditions and after induced hemorrhagic shock. Hemorrhagic shock was induced in 40 white leghorn chickens by removing 50% of blood volume by phlebotomy under general anesthesia. Birds were divided into 4 groups: untreated (control group) and treated with intravenous hetastarch (haes group), with a hemoglobin-based oxygen carrier (hemospan group), or by autotransfusion (blood group). Respiratory rates, heart rates, and systolic arterial blood pressure (SAP) were compared at 8 time points (baseline [T0]; at the loss of 10% [T10%], 20% [T20%], 30% [T30%], 40% [T40%], and 50% [T50%] of blood volume; at the end of resuscitation [RES]; and at the end of anesthesia [END]). Packed cell volume (PCV) and blood hemoglobin content were compared at 6 time points (T0, T50%, RES, and 1, 3, and 7 days after induced hemorrhagic shock). Measurements of Paco2, TcPco2, GiPco2, and Etco2 were evaluated at 2 time points (T0 and T50%), and venous lactic acid concentrations were evaluated at 3 time points (T0, T50%, and END). No significant differences were found in mortality, respiratory rate, heart rate, PCV, or hemoglobin values among the 4 groups. Birds given fluid resuscitation had significantly higher SAPs after fluid administration than did birds in the control group. In all groups, PCV and hemoglobin concentrations began to rise by day 3 after phlebotomy, and baseline values were reached 7 days after blood removal. At T0, TcPco2 did not differ significantly from Paco2, but GiPco2 and Etco2 differed significantly from Paco2. After hemorrhagic shock, GiPco2 and TcPco2 differed significantly from Paco2. The TcPco2 or GiPco2 values did not differ significantly at any time point in birds that survived or died in any of the groups and across all groups. These results showed no difference in mortality in leghorn chickens treated with fluid resuscitation after hemorrhagic shock and that the PCV and hemoglobin concentrations increased by 3 days after acute hemorrhage with or without treatment. The different CO2 measurements document changes in CO2-values consistent with poor perfusion and may prove useful for serial evaluation of responses to shock and shock treatment.

Net CO 2 surface emissions at Bern, Switzerland inferred from ambient observations of CO 2 , δ(O 2 /N 2 ), and 222 Rn using a customized radon tracer inversion

The 222Radon tracer method is a powerful tool to estimate local and regional surface emissions of, e.g., greenhouse gases. In this paper we demonstrate that in practice, the method as it is commonly used, produces inaccurate results in case of nonhomogeneously spread emission sources, and we propose a different approach to account for this. We have applied the new methodology to ambient observations of CO2 and 222Radon to estimate CO2 surface emissions for the city of Bern, Switzerland. Furthermore, by utilizing combined measurements of CO2 and δ(O2/N2) we obtain valuable information about the spatial and temporal variability of the main emission sources. Mean net CO2 emissions based on 2 years of observations are estimated at (11.2 ± 2.9) kt km−2 a−1. Oxidative ratios indicate a significant influence from the regional biosphere in summer/spring and fossil fuel combustion processes in winter/autumn. Our data indicate that the emissions from fossil fuels are, to a large degree, related to the combustion of natural gas which is used for heating purposes.

Central European hardwood trees in a high-CO 2 future: synthesis of an 8-year forest canopy CO 2 enrichment project

Rapidly increasing atmospheric CO2 is not only changing the climate system but may also affect the biosphere directly through stimulation of plant growth and ecosystem carbon and nutrient cycling. Although forest ecosystems play a critical role in the global carbon cycle, experimental information on forest responses to rising CO2 is scarce, due to the sheer size of trees. Here, we present a synthesis of the only study world-wide where a diverse set of mature broadleaved trees growing in a natural forest has been exposed to future atmospheric CO2 levels (c. 550ppm) by free-air CO2 enrichment (FACE). We show that litter production, leaf traits and radial growth across the studied hardwood species remained unaffected by elevated CO2 over 8years. CO2 enrichment reduced tree water consumption resulting in detectable soil moisture savings. Soil air CO2 and dissolved inorganic carbon both increased suggesting enhanced below-ground activity. Carbon release to the rhizosphere and/or higher soil moisture primed nitrification and nitrate leaching under elevated CO2; however, the export of dissolved organic carbon remained unaltered.Synthesis. Our findings provide no evidence for carbon-limitation in five central European hardwood trees at current ambient CO2 concentrations. The results of this long-term study challenge the idea of a universal CO2 fertilization effect on forests, as commonly assumed in climate-carbon cycle models.

Monitoring the Chemical State of Catalysts for CO 2 Electroreduction: An In Operando Study

A major concern of electrocatalysis research is to assess the structural and chemical changes that a catalyst may itself undergo in the course of the catalyzed process. These changes can influence not only the activity of the studied catalyst but also its selectivity toward the formation of a certain product. An illustrative example is the electroreduction of carbon dioxide on tin oxide nanoparticles, where under the operating conditions of the electrolysis (that is, at cathodic potentials), the catalyst undergoes structural changes which, in an extreme case, involve its reduction to metallic tin. This results in a decreased Faradaic efficiency (FE) for the production of formate (HCOO–) that is otherwise the main product of CO2 reduction on SnOx surfaces. In this study, we utilized potential- and time-dependent in operando Raman spectroscopy in order to monitor the oxidation state changes of SnO2 that accompany CO2 reduction. Investigations were carried out at different alkaline pH levels, and a strong correlation between the oxidation state of the surface and the FE of HCOO– formation was found. At moderately cathodic potentials, SnO2 exhibits a high FE for the production of formate, while at very negative potentials the oxide is reduced to metallic Sn, and the efficiency of formate production is significantly decreased. Interestingly, the highest FE of formate production is measured at potentials where SnO2 is thermodynamically unstable; however, its reduction is kinetically hindered.

T cell interaction with ICAM-1-deficient endothelium in vitro: essential role for ICAM-1 and ICAM-2 in transendothelial migration of T cells

Transendothelial migration is a crucial step in the complex process of lymphocyte extravasation during lymphocyte homing, immunosurveillance and inflammation. However, little is known about the precise role of cell adhesion molecules (CAM) involved in this particular event. To define the CAM involved in T cell adhesion versus transendothelial migration, we have previously established an in vitro transendothelial migration system using mouse T cells and mouse endothelioma cells. We demonstrate here that, using ICAM-1-deficient endothelioma cells derived from ICAM-1 mutant mice, transendothelial migration of T cells was inhibited to a much greater extent when compared to migration across wild-type cells treated with a blocking anti-ICAM-1 monoclonal antibody. This unexpected result was confirmed by a rescue experiment using retroviral transfer of wild-type ICAM-1 into ICAM-1-deficient endothelial cells. Additional experiments showed that, in the absence of functional ICAM-1, only ICAM-2 was involved in transendothelial migration, but not PECAM-1, VCAM-1, or E-selectin. Taking this novel approach, we show that ICAM-1 and ICAM-2 are essential for transendothelial migration of T cells.

Allgemeiner Zugang zu Polyaminen mit Ethan-1,2-diamin-Einheiten: Synthese von nicht natürlich vorkommenden homologen und isomerenN1,4-Di(4-cumaroyl)sperminen

The synthesis of the three N,N′-di(4-coumaroyl)tetramines, i.e., of (E,E)-N-{3-[(2-aminoethyl)amino]propyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] (1a), (E,E)-N-{4-[(2-aminoethyl)amino]butyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] (1b), and (E,E)-N-{6-[(2-aminoethyl)amino]hexyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] (1c), is described. It proceeds through stepwise construction of the symmetric polyamine backbone including protection and deprotection steps of the amino functions. Their behavior on TLC in comparison with that of 1,4-di(4-coumaroyl)spermine (=(E,E)-N-{4-[(3-aminopropyl)amino]butyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(propane-1,3-diyl)bis[prop-2-enamide]; 2) is discussed.

Bicyclo[3.2.1]amide-DNA: a chiral, non-chiroselective base-pairing system

The design, synthesis and base-pairing properties of bicyclo[3.2.1]amide-(bca)DNA, a novel phosphodiester based DNA analogue, is reported. This analogue consists of a conformationally constrained backbone entity which emulates a B-DNA geometry, to which the nucleobases were attached via an extended, acyclic amide linker. Homobasic adenine-containing bca-decamers form duplexes with complementary oligonucleotides containing the bca-, the DNA the RNA and, surprisingly, also the L-RNA backbone. UV- and CD-spectroscopic investigations revealed the duplexes with D- or L-complement to be of similar stability and enantiomorphic in structure. Bca-oligonucleotides containing all four bases form strictly antiparallel, left-handed complementary duplexes with itself and complementary DNA but not with RNA. Base-mismatch discrimination is comparable to that of DNA while the overall thermal stabilities of bca-oligonucleotide duplexes are inferior relative to that of DNA or RNA. A detailed molecular modeling study of left- and right-handed bca-DNA containing duplexes showed only minor changes in the backbone structure and revealed a structural switch around the base-linker unit to be responsible for the generation of enantiomorphic duplex structures. The obtained data are discussed with respect to the structural and energetic role of the ribofuranose entities in DNA and RNA association

Synthesis of (5' S )-5'- C -Alkyl-2'-deoxynucleosides

We describe the synthesis of (5 S )-5- C -butylthymidine ( 5a ), of the (5 S )-5- C -butyl- and the (5 S )-5- C -isopentyl derivatives 16a and 16b of 2-deoxy-5-methylcytidine, as well as of the corresponding cyanoethyl phosphoramidites 9a , b and 14a , b , respectively. Starting from thymidin-5-al 1 , the alkyl chain at C(5) is introduced via Wittig chemistry to selectively yield the ( Z )-olefin derivatives 3a and 3b ( Scheme 2 ). The secondary OH function at C(5) is then introduced by epoxidation followed by regioselective reduction of the epoxy derivatives 4a and 4b with diisobutylaluminium hydride. In the latter step, a kinetic resolution of the diastereoisomer mixture 4a and 4b occurs, yielding the alkylated nucleoside 2a and 2b , respectively, with (5 S )-configuration in high diastereoisomer purity (de=94%). The corresponding 2-deoxy-5-methylcytidine derivatives are obtained from the protected 5-alkylated thymidine derivatives 7a and 7b via known base interconversion processes in excellent yields ( Scheme 3 ). Application of the same strategy to the purine nucleoside 2-deoxyadenine to obtain 5- C -butyl-2-deoxyadenosine 25 proved to be difficult due to the sensitivity of the purine base to hydride-based reducing agents ( Scheme 4 ).

Central European vegetation response to abrupt climate change at 8.2 ka

Oxygen isotope records show a major climatic reversal at 8.2 ka in Greenland and Europe. Annually laminated sediments from two lakes in Switzerland and Germany were sampled contiguously to assess the response of European vegetation to climate change ca. 8.2 ka with time resolution and precision comparable to those of the Greenland ice cores. The pollen assemblages show pronounced and immediate responses (0–20 yr) of terrestrial vegetation to the climatic change at 8.2 ka. A sudden collapse of Corylus avellana (hazel) was accompanied by the rapid expansion of Pinus (pine), Betula (birch), and Tilia (linden), and by the invasion of Fagus silvatica (beech) and Abies alba (fir). Vegetational changes suggest that climatic cooling reduced drought stress, allowing more drought-sensitive and taller growing species to out-compete Corylus avellana by forming denser forest canopies. Climate cooling at 8.2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies. On the basis of our data we conclude that the early Holocene high abundance of C. avellana in Europe was climatically caused, and we question the conventional opinion that postglacial expansions of F. silvatica and A. alba were controlled by low migration rates rather than by climate. The close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses, expansions, and invasions of tree species.