Two-phase change in CO2, Antarctic temperature and global climate during Termination II

The end of the Last Glacial Maximum (Termination I), roughly 20 thousand years ago (ka), was marked by cooling in the Northern Hemisphere, a weakening of the Asian monsoon, a rise in atmospheric CO2 concentrations and warming over Antarctica. The sequence of events associated with the previous glacial–interglacial transition (Termination II), roughly 136 ka, is less well constrained. Here we present high-resolution records of atmospheric CO2 concentrations and isotopic composition of N2—an atmospheric temperature proxy—from air bubbles in the EPICA Dome C ice core that span Termination II. We find that atmospheric CO2 concentrations and Antarctic temperature started increasing in phase around 136 ka, but in a second phase of Termination II, from 130.5 to 129 ka, the rise in atmospheric CO2 concentrations lagged that of Antarctic temperature unequivocally. We suggest that during this second phase, the intensification of the low-latitude hydrological cycle resulted in the development of a CO2 sink, which counteracted the CO2 outgassing from the Southern Hemisphere oceans over this period.

THEODORE, a two-step heating system for the EC/OC determination of radiocarbon (14C) in the environment

Measurements of 14C in the organic carbon (OC) and elemental carbon (EC) fractions, respectively, of fine aerosol particles bear the potential to apportion anthropogenic and biogenic emission sources. For this purpose, the system THEODORE (two-step heating system for the EC/OC determination of radiocarbon in the environment) was developed. In this device, OC and EC are transformed into carbon dioxide in a stream of oxygen at 340 and 650 �C, respectively, and reduced to filamentous carbon. This is the target material for subsequent accelerator mass spectrometry (AMS) 14C measurements, which were performed on sub-milligram carbon samples at the PSI/ETH compact 500 kV AMS system. Quality assurance measurements of SRM 1649a, Urban Dust, yielded a fraction of modern fM in total carbon (TC) of 0.522 ±0.018 (n ¼ 5, 95% confidence level) in agreement with reported values. The results for OC and EC are 0.70± 0.05 (n ¼ 3) and 0.066 ± 0.020 (n ¼ 4), respectively.

Monitoring protein-protein interactions between the mammalian integral membrane transporters and PDZ-interacting partners using a modified split-ubiquitin membrane yeast two-hybrid system

PDZ-binding motifs are found in the C-terminal tails of numerous integral membrane proteins where they mediate specific protein-protein interactions by binding to PDZ-containing proteins. Conventional yeast two-hybrid screens have been used to probe protein-protein interactions of these soluble C termini. However, to date no in vivo technology has been available to study interactions between the full-length integral membrane proteins and their cognate PDZ-interacting partners. We previously developed a split-ubiquitin membrane yeast two-hybrid (MYTH) system to test interactions between such integral membrane proteins by using a transcriptional output based on cleavage of a transcription factor from the C terminus of membrane-inserted baits. Here we modified MYTH to permit detection of C-terminal PDZ domain interactions by redirecting the transcription factor moiety from the C to the N terminus of a given integral membrane protein thus liberating their native C termini. We successfully applied this "MYTH 2.0" system to five different mammalian full-length renal transporters and identified novel PDZ domain-containing partners of the phosphate (NaPi-IIa) and sulfate (NaS1) transporters that would have otherwise not been detectable. Furthermore this assay was applied to locate the PDZ-binding domain on the NaS1 protein. We showed that the PDZ-binding domain for PDZK1 on NaS1 is upstream of its C terminus, whereas the two interacting proteins, NHERF-1 and NHERF-2, bind at a location closer to the N terminus of NaS1. Moreover NHERF-1 and NHERF-2 increased functional sulfate uptake in Xenopus oocytes when co-expressed with NaS1. Finally we used MYTH 2.0 to demonstrate that the NaPi-IIa transporter homodimerizes via protein-protein interactions within the lipid bilayer. In summary, our study establishes the MYTH 2.0 system as a novel tool for interactive proteomics studies of membrane protein complexes.

Protein and lipid binding parameters in rainbow trout (Oncorhynchus mykiss) blood and liver fractions to extrapolate from an in vitro metabolic degradation assay to in vivo bioaccumulation potential of hydrophobic organic chemicals

Binding of hydrophobic chemicals to colloids such as proteins or lipids is difficult to measure using classical microdialysis methods due to low aqueous concentrations, adsorption to dialysis membranes and test vessels, and slow kinetics of equilibration. Here, we employed a three-phase partitioning system where silicone (polydimethylsiloxane, PDMS) serves as a third phase to determine partitioning between water and colloids and acts at the same time as a dosing device for hydrophobic chemicals. The applicability of this method was demonstrated with bovine serum albumin (BSA). Measured binding constants (K(BSAw)) for chlorpyrifos, methoxychlor, nonylphenol, and pyrene were in good agreement with an established quantitative structure-activity relationship (QSAR). A fifth compound, fluoxypyr-methyl-heptyl ester, was excluded from the analysis because of apparent abiotic degradation. The PDMS depletion method was then used to determine partition coefficients for test chemicals in rainbow trout (Oncorhynchus mykiss) liver S9 fractions (K(S9w)) and blood plasma (K(bloodw)). Measured K(S9w) and K(bloodw) values were consistent with predictions obtained using a mass-balance model that employs the octanol-water partition coefficient (K(ow)) as a surrogate for lipid partitioning and K(BSAw) to represent protein binding. For each compound, K(bloodw) was substantially greater than K(S9w), primarily because blood contains more lipid than liver S9 fractions (1.84% of wet weight vs 0.051%). Measured liver S9 and blood plasma binding parameters were subsequently implemented in an in vitro to in vivo extrapolation model to link the in vitro liver S9 metabolic degradation assay to in vivo metabolism in fish. Apparent volumes of distribution (V(d)) calculated from the experimental data were similar to literature estimates. However, the calculated binding ratios (f(u)) used to relate in vitro metabolic clearance to clearance by the intact liver were 10 to 100 times lower than values used in previous modeling efforts. Bioconcentration factors (BCF) predicted using the experimental binding data were substantially higher than the predicted values obtained in earlier studies and correlated poorly with measured BCF values in fish. One possible explanation for this finding is that chemicals bound to proteins can desorb rapidly and thus contribute to metabolic turnover of the chemicals. This hypothesis remains to be investigated in future studies, ideally with chemicals of higher hydrophobicity.

Minimizing the Threat of a Positive Majority Deficit in Two-tier Voting Systems with Equipopulous Units

The mean majority deficit in a two-tier voting system is a function of the partition of the population. We derive a new square-root rule: For odd-numbered population sizes and equipopulous units the mean majority deficit is maximal when the member size of the units in the partition is close to the square root of the population size. Furthermore, within the partitions into roughly equipopulous units, partitions with small even numbers of units or small even-sized units yield high mean majority deficits. We discuss the implications for the winner-takes-all system in the US Electoral College.

Diagenesis of a light, tight-oil chert reservoir at the Ediacaran/Cambrian boundary, Sultanate of Oman

The Al Shomou Silicilyte Member (Athel Formation) in the South Oman Salt Basin shares many of the characteristics of a light, tight-oil (LTO) reservoir: it is a prolifi c source rock mature for light oil, it produces light oil from a very tight matrix and reservoir, and hydraulic fracking technology is required to produce the oil. What is intriguing about the Al Shomou Silicilyte, and different from other LTO reservoirs, is its position related to the Precambrian/Cambrian Boundary (PCB) and the fact that it is a ‘laminated chert‘ rather than a shale. In an integrated diagenetic study we applied microstructural analyses (SEM, BSE) combined with state-of-the-art stable isotope and trace element analysis of the silicilyte matrix and fractures. Fluid inclusion microthermometry was applied to record the salinity and minimum trapping temperatures. The microstructural investigations reveal a fi ne lamination of the silicilyte matrix with a mean lamina thickness of ca. 20 μm consisting of predominantly organic matter-rich and fi nely crystalline quartz-rich layers, respectively. Authigenic, micron-sized idiomorphic quartz crystals are the main matrix components of the silicilyte. Other diagenetic phases are pyrite, apatite, dolomite, magnesite and barite cements. Porosity values based on neutron density logs and core plug data indicate porosity in the silicilyte ranges from less than 2% to almost to 40%. The majority of the pore space in the silicilyte is related to (primary) inter-crystalline pores, with locally important oversized secondary pores. Pore casts of the silica matrix show that pores are extremely irregular in three dimensions, and are generally interconnected by a complex web or meshwork of fi ne elongate pore throats. Mercury injection capillary data are in line with the microstructural observations suggesting two populations of pore throats, with an effective average modal diameter of 0.4 μm. The acquired geochemical data support the interpretation that the primary source of the silica is the ambient seawater rather than hydrothermal or biogenic. A maximum temperature of ca. 45°C for the formation of microcrystalline quartz in the silicilyte is good evidence that the lithifi cation and crystallization of quartz occurred in the fi rst 5 Ma after deposition. Several phases of brittle fracturing and mineralization occurred in response to salt tectonics during burial. The sequences of fracture-fi lling mineral phases (dolomite - layered chalcedony – quartz – apatite - magnesite I+II - barite – halite) indicates a complex fl uid evolution after silicilyte lithifi cation. Primary, all-liquid fl uid inclusions in the fracturefi lling quartz are good evidence of growth beginning at low temperatures, i.e. ≤ 50ºC. Continuous precipitation during increasing temperature and burial is documented by primary two-phase fl uid inclusions in quartz cements that show brines at 50°C and fi rst hydrocarbons at ca. 70°C. The absolute timing of each mineral phase can be constrained based on U-Pb geochronometry, and basin modelling. Secondary fl uid inclusions in quartz, magnesite and barite indicate reactivation of the fracture system after peak burial temperature during the major cooling event, i.e. uplift, between 450 and 310 Ma. A number of fi rst-order trends in porosity and reservoir-quality distribution are observed which are strongly related to the diagenetic and fl uid history of the reservoir: the early in-situ generation of hydrocarbons and overpressure development arrests diagenesis and preserves matrix porosity. Chemical compaction by pressure dissolution in the fl ank areas could be a valid hypothesis to explain the porosity variations in the silicilitye slabs resulting in lower porosity and poorer connectivity on the fl anks of the reservoir. Most of the hydrocarbon storage and production comes from intervals characterized by Amthor et al. 114488 preserved micropores, not hydrocarbon storage in a fracture system. The absence of oil expulsion results in present-day high oil saturations. The main diagenetic modifi cations of the silicilyte occurred and were completed relatively early in its history, i.e. before 300 Ma. An instrumental factor for preserving matrix porosity is the diffi culty for a given slab to evacuate all the fl uids (water and hydrocarbons), or in other words, the very good sealing capacity of the salt embedding the slab.

Time-lapse pressure tomography for characterizing CO2 plume evolution in a deep saline aquifer

A time-lapse pressure tomography inversion approach is applied to characterize the CO2 plume development in a virtual deep saline aquifer. Deep CO2 injection leads to flow properties of the mixed-phase, which vary depending on the CO2 saturation. Analogous to the crossed ray paths of a seismic tomographic experiment, pressure tomography creates streamline patterns by injecting brine prior to CO2 injection or by injecting small amounts of CO2 into the two-phase (brine and CO2) system at different depths. In a first step, the introduced pressure responses at observation locations are utilized for a computationally rapid and efficient eikonal equation based inversion to reconstruct the heterogeneity of the subsurface with diffusivity (D) tomograms. Information about the plume shape can be derived by comparing D-tomograms of the aquifer at different times. In a second step, the aquifer is subdivided into two zones of constant values of hydraulic conductivity (K) and specific storage (Ss) through a clustering approach. For the CO2 plume, mixed-phase K and Ss values are estimated by minimizing the difference between calculated and “true” pressure responses using a single-phase flow simulator to reduce the computing complexity. Finally, the estimated flow property is converted to gas saturation by a single-phase proxy, which represents an integrated value of the plume. This novel approach is tested first with a doublet well configuration, and it reveals a great potential of pressure tomography based concepts for characterizing and monitoring deep aquifers, as well as the evolution of a CO2 plume. Still, field-testing will be required for better assessing the applicability of this approach.

Determining gypsum growth temperatures using monophase fluid inclusions-Application to the giant gypsum crystals of Naica, Mexico

Determining the formation temperature of minerals using fluid inclusions is a crucial step in understanding rock-forming scenarios. Unfortunately, fluid inclusions in minerals formed at low temperature, such as gypsum, are commonly in a metastable monophase liquid state. To overcome this problem, ultra-short laser pulses can be used to induce vapor bubble nucleation, thus creating a stable two-phase fluid inclusion appropriate for subsequent measurements of the liquid-vapor homogenization temperature, T-h. In this study we evaluate the applicability of T-h data to accurately determine gypsum formation temperatures. We used fluid inclusions in synthetic gypsum crystals grown in the laboratory at different temperatures between 40 degrees C and 80 degrees C under atmospheric pressure conditions. We found an asymmetric distribution of the T-h values, which are systematically lower than the actual crystal growth temperatures, T-g; this is due to (1) the effect of surface tension on liquid-vapor homogenization, and (2) plastic deformation of the inclusion walls due to internal tensile stress occurring in the metastable state of the inclusions. Based on this understanding, we have determined growth temperatures of natural giant gypsum crystals from Naica (Mexico), yielding 47 +/- 1.5 degrees C for crystals grown in the Cave of Swords (120 m below surface) and 54.5 +/- 2 degrees C for giant crystals grown in the Cave of Crystals (290 m below surface). These results support the earlier hypothesis that the population and the size of the Naica crystals were controlled by temperature. In addition, this experimental method opens a door to determining the growth temperature of minerals forming in low-temperature environments.

Stereoselective biotransformation of ketamine in equine liver and lung microsomes

Stereoselectivity has to be considered for pharmacodynamic and pharmacokinetic features of ketamine. Stereoselective biotransformation of ketamine was investigated in equine microsomes in vitro. Concentration curves were constructed over time, and enzyme activity was determined for different substrate concentrations using equine liver and lung microsomes. The concentrations of R/S-ketamine and R/S-norketamine were determined by enantioselective capillary electrophoresis. A two-phase model based on Hill kinetics was used to analyze the biotransformation of R/S-ketamine into R/S-norketamine and, in a second step, into R/S-downstream metabolites. In liver and lung microsomes, levels of R-ketamine exceeded those of S-ketamine at all time points and S-norketamine exceeded R-norketamine at time points below the maximum concentration. In liver and lung microsomes, significant differences in the enzyme velocity (V(max)) were observed between S- and R-norketamine formation and between V(max) of S-norketamine formation when S-ketamine was compared to S-ketamine of the racemate. Our investigations in microsomal reactions in vitro suggest that stereoselective ketamine biotransformation in horses occurs in the liver and the lung with a slower elimination of S-ketamine in the presence of R-ketamine. Scaling of the in vitro parameters to liver and lung organ clearances provided an excellent fit with previously published in vivo data and confirmed a lung first-pass effect.

Concentration-dependent isoflurane effects on withdrawal reflexes in pigs and the role of the stimulation paradigm

In this prospective two-phase experimental trial, 10 pigs were anaesthetized twice with isoflurane only. In the first phase, the individual minimum alveolar concentration (MAC) was determined and in the second phase the effects on withdrawal reflexes of increasing end-tidal isoflurane concentrations (from 1.6% to 2.8%) were assessed. Single, 10 and 60 repeated electrical stimulations were used to evoke withdrawal reflexes which were recorded and quantified by electromyography. Recruitment curves for reflex amplitude for increasing stimulation intensities and isoflurane concentrations were constructed. Isoflurane MAC was 1.9+/-0.3%. Reflexes evoked by repeated stimulation were suppressed at isoflurane concentrations significantly higher than those which suppressed complex movements during MAC determination (P=0.014 and P=0.006 for 10 and 60 repeated stimuli respectively). Isoflurane up to 2.8% was still not able to abolish reflex activity evoked by repeated stimulations in all pigs. Single stimulation reflexes were suppressed at significantly lower concentrations than repeated stimulation reflexes (P=0.008 and P=0.004 for 10 and 60 repeated stimuli, respectively). Reflex amplitude was significantly correlated with isoflurane concentration (P<0.001, r=-0.85) independent of the individual MAC. The findings indicate that the level at which isoflurane suppresses withdrawal reflexes is dependent on the stimulation paradigm (single vs. repeated electrical stimulation), and there is limited value in expressing reflex withdrawal suppression in terms of MAC as purposeful and reflex movements are independently affected by isoflurane in individual animals.

Dual dispatch early defibrillation in out-of-hospital cardiac arrest in a mixed urban–rural population

Aims The effects of a system based on minimally trained first responders (FR) dispatched simultaneously with the emergency medical services (EMS) of the local hospital in a mixed urban and rural area in Northwestern Switzerland were examined. Methods and results In this prospective study 500 voluntary fire fighters received a 4-h training in basic-life-support using automated-external-defibrillation (AED). FR and EMS were simultaneously dispatched in a two-tier rescue system. During the years 2001–2008, response times, resuscitation interventions and outcomes were monitored. 1334 emergencies were included. The FR reached the patients (mean age 60.4 ± 19 years; 65% male) within 6 ± 3 min after emergency calls compared to 12 ± 5 min by the EMS (p < 0.0001). Seventy-six percent of the 297 OHCAs occurred at home. Only 3 emergencies with resuscitation attempts occurred at the main railway station equipped with an on-site AED. FR were on the scene before arrival of the EMS in 1166 (87.4%) cases. Of these, the FR used AED in 611 patients for monitoring or defibrillation. CPR was initiated by the FR in 164 (68.9% of 238 resuscitated patients). 124 patients were defibrillated, of whom 93 (75.0%) were defibrillated first by the FR. Eighteen patients (of whom 13 were defibrillated by the FR) were discharged from hospital in good neurological condition. Conclusions Minimally trained fire fighters integrated in an EMS as FR contributed substantially to an increase of the survival rate of OHCAs in a mixed urban and rural area.

Safety and tolerability of slow-release oral morphine versus methadone in the treatment of opioid dependence

Opioid substitution treatment (OST) for opioid dependence may be limited by adverse events (AEs). Increasing the range of therapeutic options optimizes outcomes and facilitates patient management. An international, multi-center, two-phase study investigated the efficacy and safety of slow-release oral morphine (SROM) versus methadone in patients receiving methadone therapy for opioid dependence. In phase 1 (two way cross-over, 11 weeks each period) patients were randomized to SROM or methadone oral solution. In phase 2 (25 weeks), patients continued treatment with SROM (group A) or switched from methadone to SROM (group B). In total, 211 out of 276 completed phase 1 and 198 entered phase 2 (n = 95 group A, n = 103 group B). Treatment with both SROM and methadone was well tolerated. However, the mean QTc-interval associated with methadone was significantly longer than that under SROM. Higher treatment satisfaction, fewer cravings for heroin, and lower mental stress were reported with SROM. This study adds a significant further weight of evidence that SROM is an effective and well tolerated long-term maintenance treatment for opioid dependence with a beneficial risk profile compared to methadone regarding cardiac effects and supports its clinical utility.

Adjuvant exemestane with ovarian suppression in premenopausal breast cancer.

BACKGROUND Adjuvant therapy with an aromatase inhibitor improves outcomes, as compared with tamoxifen, in postmenopausal women with hormone-receptor-positive breast cancer. METHODS In two phase 3 trials, we randomly assigned premenopausal women with hormone-receptor-positive early breast cancer to the aromatase inhibitor exemestane plus ovarian suppression or tamoxifen plus ovarian suppression for a period of 5 years. Suppression of ovarian estrogen production was achieved with the use of the gonadotropin-releasing-hormone agonist triptorelin, oophorectomy, or ovarian irradiation. The primary analysis combined data from 4690 patients in the two trials. RESULTS After a median follow-up of 68 months, disease-free survival at 5 years was 91.1% in the exemestane-ovarian suppression group and 87.3% in the tamoxifen-ovarian suppression group (hazard ratio for disease recurrence, second invasive cancer, or death, 0.72; 95% confidence interval [CI], 0.60 to 0.85; P<0.001). The rate of freedom from breast cancer at 5 years was 92.8% in the exemestane-ovarian suppression group, as compared with 88.8% in the tamoxifen-ovarian suppression group (hazard ratio for recurrence, 0.66; 95% CI, 0.55 to 0.80; P<0.001). With 194 deaths (4.1% of the patients), overall survival did not differ significantly between the two groups (hazard ratio for death in the exemestane-ovarian suppression group, 1.14; 95% CI, 0.86 to 1.51; P=0.37). Selected adverse events of grade 3 or 4 were reported for 30.6% of the patients in the exemestane-ovarian suppression group and 29.4% of those in the tamoxifen-ovarian suppression group, with profiles similar to those for postmenopausal women. CONCLUSIONS In premenopausal women with hormone-receptor-positive early breast cancer, adjuvant treatment with exemestane plus ovarian suppression, as compared with tamoxifen plus ovarian suppression, significantly reduced recurrence. (Funded by Pfizer and others; TEXT and SOFT ClinicalTrials.gov numbers, NCT00066703 and NCT00066690, respectively.).

Induction and detoxification of maize 1,4-benzoxazin-3-ones by insect herbivores

In monocotyledonous plants, 1,4-benzoxazin-3-ones, also referred to as benzoxazinoids or hydroxamic acids, are one of the most important chemical barriers against herbivores. However, knowledge about their behavior after attack, mode of action and potential detoxification by specialized insects remains limited. We chose an innovative analytical approach to understand the role of maize 1,4-benzoxazin-3-ones in plant–insect interactions. By combining unbiased metabolomics screening and simultaneous measurements of living and digested plant tissue, we created a quantitative dynamic map of 1,4-benzoxazin-3-ones at the plant–insect interface. Hypotheses derived from this map were tested by specifically developed in vitro assays using purified 1,4-benzoxazin-3-ones and active extracts from mutant plants lacking 1,4-benzoxazin-3-ones. Our data show that maize plants possess a two-step defensive system that effectively fends off both the generalist Spodoptera littoralis and the specialist Spodoptera frugiperda. In the first step, upon insect attack, large quantities of 2-β-d-glucopyranosyloxy-4,7-dimethoxy-1,4-benzoxazin-3-one (HDMBOA-Glc) are formed. In the second step, after tissue disruption by the herbivores, highly unstable 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one (HDMBOA) is released by plant-derived β-glucosidases. HDMBOA acts as a strong deterrent to both S. littoralis and S. frugiperda. Although constitutively produced 1,4-benzoxazin-3-ones such as 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) are detoxified via glycosylation by the insects, no conjugation of HDMBOA in the insect gut was found, which may explain why even the specialist S. frugiperda has not evolved immunity against this plant defense. Taken together, our results show the benefit of using a plant–insect interface approach to elucidate plant defensive processes and unravel a potent resistance mechanism in maize.