A comparison of acute and long-term effects of industrial multiwalled carbon nanotubes on human lung and immune cells in vitro

The close resemblance of carbon nanotubes to asbestos fibers regarding their high aspect ratio, biopersistence and reactivity increases public concerns on the widespread use of these materials. The purpose of this study was not only to address the acute adverse effects of industrially produced multiwalled carbon nanotubes (MWCNTs) on human lung and immune cells in vitro but also to further understand if their accumulation and biopersistence leads to long-term consequences or induces adaptive changes in these cells. In contrast to asbestos fibers, pristine MWCNTs did not induce overt cell death in A549 lung epithelial cells and Jurkat T lymphocytes after acute exposure to high doses of this material (up to 30 g/ml). Nevertheless, very high levels of reactive oxygen species (ROS) and decreased metabolic activity were observed which might affect long-term viability of these cells. However, the continuous presence of low amounts of MWCNTs (0.5 g/ml) for 6 months did not have major adverse long-term effects although large amounts of nanotubes accumulated at least in A549 cells. Moreover, MWCNTs did not appear to induce adaptive mechanisms against particle stress in long-term treated A549 cells. Our study demonstrates that despite the high potential for ROS formation, pristine MWCNTs can accumulate and persist within cells without having major long-term consequences or inducing adaptive mechanisms.

A 20-channel receive-only mouse array coil for a 3 T clinical MRI system

A 20-channel phased-array coil for MRI of mice has been designed, constructed, and validated with bench measurements and high-resolution accelerated imaging. The technical challenges of designing a small, high density array have been overcome using individual small-diameter coil elements arranged on a cylinder in a hexagonal overlapping design with adjacent low impedance preamplifiers to further decouple the array elements. Signal-to-noise ratio (SNR) and noise amplification in accelerated imaging were simulated and quantitatively evaluated in phantoms and in vivo mouse images. Comparison between the 20-channel mouse array and a length-matched quadrature driven small animal birdcage coil showed an SNR increase at the periphery and in the center of the phantom of 3- and 1.3-fold, respectively. Comparison with a shorter but SNR-optimized birdcage coil (aspect ratio 1:1 and only half mouse coverage) showed an SNR gain of twofold at the edge of the phantom and similar SNR in the center. G-factor measurements indicate that the coil is well suited to acquire highly accelerated images.

Anamorphic pixels for multi-channel superresolution

Superresolution from plenoptic cameras or camera arrays is usually treated similarly to superresolution from video streams. However, the transformation between the low-resolution views can be determined precisely from camera geometry and parallax. Furthermore, as each low-resolution image originates from a unique physical camera, its sampling properties can also be unique. We exploit this option with a custom design of either the optics or the sensor pixels. This design makes sure that the sampling matrix of the complete system is always well-formed, enabling robust and high-resolution image reconstruction. We show that simply changing the pixel aspect ratio from square to anamorphic is sufficient to achieve that goal, as long as each camera has a unique aspect ratio. We support this claim with theoretical analysis and image reconstruction of real images. We derive the optimal aspect ratios for sets of 2 or 4 cameras. Finally, we verify our solution with a camera system using an anamorphic lens.

The J-curve in HIV: low and moderate alcohol intake predicts mortality but not the occurrence of major cardiovascular events.

OBJECTIVES In HIV-negative populations light to moderate alcohol consumption is associated with a lower cardiovascular morbidity and mortality than alcohol abstention. Whether the same holds true for HIV-infected individuals has not been evaluated in detail. DESIGN Cohort study METHODS:: Adults on antiretroviral therapy in the Swiss HIV Cohort Study with follow-up after August 2005 were included. We categorized alcohol consumption into: abstention, low (1-9 g/d), moderate (10-29 g/d in females and 10-39g/d in men) and high alcohol intake. Cox proportional hazards models were used to describe the association between alcohol consumption and cardiovascular disease free survival (combined endpoint) as well as cardiovascular disease events (CADE) and overall survival. Baseline and time-updated risk factors for CADE were included in the models. RESULTS Among 9,741 individuals included, there were 788 events of major CADE or death during 46,719 years of follow-up, corresponding to an incidence of 1.69 events/100 person-years. Follow-up according to alcohol consumption level was 51% abstention, 20% low, 23% moderate and 6% high intake. As compared to abstention, low (hazard ratio 0.79, 95% confidence interval 0.63-0.98) and moderate alcohol intake (0.78, 0.64-0.95) were associated with a lower incidence of the combined endpoint. There was no significant association between alcohol consumption and CADE. CONCLUSIONS Compared to abstention, low and moderate alcohol intake were associated with a better CADE-free survival. However, this result was mainly driven by mortality and the specific impact of drinking patterns and type of alcoholic beverage on this outcome remains to be determined.

High-flow venous pouch aneurysm in the rabbit carotid artery: A model for large aneurysms.

BACKGROUND AND PURPOSE Currently one of the most widely used models for the development of endovascular techniques and coiling devices for treatment of aneurysm is the elastase-induced aneurysm model in the rabbit carotid artery. Microsurgical techniques for creating an aneurysm with a venous pouch have also been established, although both techniques usually result in aneurysms less than 1 cm in diameter. We investigated whether an increase in blood flow toward the neck would produce larger aneurysms in a microsurgical venous pouch model. MATERIALS AND METHODS Microsurgical operations were performed on 11 New Zealand white rabbits. Both carotid arteries and the right jugular vein were dissected, and the right carotid artery was temporarily clipped followed by an arteriotomy. The left carotid artery was also clipped proximally, ligated distally, and sutured onto the proximal half of the arteriotomy in the right carotid artery. The venous graft was sutured onto the distal half of the arteriotomy. Digital subtraction angiography was also performed. RESULTS Angiography showed patent anastomosed vessels and aneurysms in the seven surviving rabbits. Mean aneurysm measurements among surviving rabbits with patent vessels were: 13.9 mm length, 9.3 mm width, and neck diameter 4.7 mm. The resulting mean aspect ratio was 3.35 and the mean bottleneck ratio was 3.05. CONCLUSION A large venous graft and increased blood flow toward the base of the aneurysm seem to be key factors in the creation of large venous pouch aneurysms. These large aneurysms allow testing of endovascular devices designed for large and giant aneurysms.

From supramolecular sheets to fibers and back: establishing the critical parameters that govern the morphology of pyrene-based self-assembled materials

The precise arraying of functional entities in morphologically well-defined shapes remains one of the key challenges in the processing of organic molecules1. Among various π-conjugated species, pyrene exhibits a set of unique properties, which make it an attractive compound for the utilization in materials science2. In this contribution we report on properties of self-assembled structures prepared from amphiphilic pyrene trimers (Py3) consisting of phosphodiester-linked pyrenes. Depending on the geometry of a pyrene core substitution (1.6-, 1.8-, or 2.7- type, see Scheme), the thermally-controlled self-assembly allows the preparation of supramolecular architectures of different morphologies in a bottom-up approach: two-dimensional (2D) nanosheets3 are formed in case of 1.6- and 2.7-substitution4 whereas one-dimensional (1D) fibers are built from 1.8- substituted isomers. The morphologies of the assemblies are established by AFM and TEM, and the results are further correlated with spectroscopic and scattering data. Two-dimensional assemblies consist of an inner layer of hydrophobic pyrenes, sandwiched between a net of phosphates. Due to the repulsion of the negative charges, the 2D assemblies exist mostly as free-standing sheets. An internal alignment of pyrenes leads to strong exciton coupling with an unprecedented observation (simultaneous development of J- and H-bands from two different electronic transitions). Despite the similarity in spectroscopic properties, the structural parameters of the 2D aggregates drastically depend on the preparation procedure. Under certain conditions extra-large sheets (thickness of 2 nm, aspect ratio area/thickness ~107) in aqueous solution are formed4B. Finally, one-dimensional assemblies are formed as micrometer-long and nanometer-thick fibers. Both, planar and linear structures are intriguing objects for the creation of conductive nanowires that may find interest for applications in supramolecular electronics.

From supramolecular sheets to fibers and back: establishing the critical parameters that govern the morphology of pyrene-based self-assembled materials

The precise arraying of functional entities in morphologically well-defined shapes remains one of the key challenges in the processing of organic molecules1. Among various π-conjugated species, pyrene exhibits a set of unique properties, which make it an attractive compound for the utilization in materials science2. In this contribution we report on properties of self-assembled structures prepared from amphiphilic pyrene trimers (Py3) consisting of phosphodiester-linked pyrenes. Depending on the geometry of a pyrene core substitution (1.6-, 1.8-, or 2.7- type, see Scheme), the thermally-controlled self-assembly allows the preparation of supramolecular architectures of different morphologies in a bottom-up approach: two-dimensional (2D) nanosheets3 are formed in case of 1.6- and 2.7-substitution4 whereas one-dimensional (1D) fibers are built from 1.8- substituted isomers. The morphologies of the assemblies are established by AFM and TEM, and the results are further correlated with spectroscopic and scattering data. Two-dimensional assemblies consist of an inner layer of hydrophobic pyrenes, sandwiched between a net of phosphates. Due to the repulsion of the negative charges, the 2D assemblies exist mostly as free-standing sheets. An internal alignment of pyrenes leads to strong exciton coupling with an unprecedented observation (simultaneous development of J- and H-bands from two different electronic transitions). Despite the similarity in spectroscopic properties, the structural parameters of the 2D aggregates drastically depend on the preparation procedure. Under certain conditions extra-large sheets (thickness of 2 nm, aspect ratio area/thickness ~107) in aqueous solution are formed4B. Finally, one-dimensional assemblies are formed as micrometer-long and nanometer-thick fibers. Both, planar and linear structures are intriguing objects for the creation of conductive nanowires that may find interest for applications in supramolecular electronics.

8p23 beta-defensin copy number determination by single-locus pseudogene-based paralog ratio tests risk bias due to low-frequency sequence variations.

BACKGROUND The copy number variation (CNV) in beta-defensin genes (DEFB) on human chromosome 8p23 has been proposed to contribute to the phenotypic differences in inflammatory diseases. However, determination of exact DEFB CN is a major challenge in association studies. Quantitative real-time PCR (qPCR), paralog ratio tests (PRT) and multiplex ligation-dependent probe amplification (MLPA) have been extensively used to determine DEFB CN in different laboratories, but inter-method inconsistencies were observed frequently. In this study we asked which one is superior among the three methods for DEFB CN determination. RESULTS We developed a clustering approach for MLPA and PRT to statistically correlate data from a single experiment. Then we compared qPCR, a newly designed PRT and MLPA for DEFB CN determination in 285 DNA samples. We found MLPA had the best convergence and clustering results of the raw data and the highest call rate. In addition, the concordance rates between MLPA or PRT and qPCR (32.12% and 37.99%, respectively) were unacceptably low with underestimated CN by qPCR. Concordance rate between MLPA and PRT (90.52%) was high but PRT systematically underestimated CN by one in a subset of samples. In these samples a sequence variant which caused complete PCR dropout of the respective DEFB cluster copies was found in one primer binding site of one of the targeted paralogous pseudogenes. CONCLUSION MLPA is superior to PRT and even more to qPCR for DEFB CN determination. Although the applied PRT provides in most cases reliable results, such a test is particularly sensitive to low-frequency sequence variations preferably accumulating in loci like pseudogenes which are most likely not under selective pressure. In the light of the superior performance of multiplex assays, the drawbacks of such single PRTs could be overcome by combining more test markers.

Ventilation-perfusion ratio in perflubron during partial liquid ventilation

BACKGROUND: Functional magnetic resonance imaging (fMRI) of fluorine-19 allows for the mapping of oxygen partial pressure within perfluorocarbons in the alveolar space (Pao(2)). Theoretically, fMRI-detected Pao(2) can be combined with the Fick principle approach, i.e., a mass balance of oxygen uptake by ventilation and delivery by perfusion, to quantify the ventilation-perfusion ratio (Va/Q) of a lung region: The mixed venous blood and the inspiratory oxygen fraction, which are equal for all lung regions, are measured. In addition, the local expiratory oxygen fraction and the end capillary oxygen content, both of which may differ between the lung regions, are calculated using the fMRI-detected Pao(2). We investigated this approach by numerical simulations and applied it to quantify local Va/Q in the perfluorocarbons during partial liquid ventilation. METHODS: Numerical simulations were performed to analyze the sensitivity of the Va/Q calculation and to compare this approach with another one proposed by Rizi et al. in 2004 (Magn Reson Med 2004;52:65-72). Experimentally, the method was used during partial liquid ventilation in 7 anesthetized pigs. The Pao(2) distribution in intraalveolar perflubron was measured by fluorine-19 MRI. Respiratory gas fractions together with arterial and mixed venous blood samples were taken to quantify oxygen partial pressure and content. Using the Fick principle, the local Va/Q was estimated. The impact of gravity (nondependent versus dependent) of perflubron dose (10 vs 20 mL/kg body weight) and of inspired oxygen fraction (Fio(2)) (0.4-1.0) on Va/Q was examined. RESULTS: In numerical simulations, the Fick principle proved to be appropriate over the Va/Q range from 0.02 to 2.5. Va/Q values were in acceptable agreement with the method published by Rizi et al. In the experimental setting, low mean Va/Q values were found in perflubron (confidence interval [CI] 0.08-0.29 with 20 mL/kg perflubron). At this dose, Va/Q in the nondependent lung was higher (CI 0.18-0.39) than in the dependent lung regions (CI 0.06-0.16; P = 0.006; Student t test). Differences depending on Fio(2) or perflubron dose were, however, small. CONCLUSION: The results show that derivation of Va/Q from local Po(2) measurements using fMRI in perflubron is feasible. The low detected Va/Q suggests that oxygen transport into the perflubron-filled alveolar space is significantly restrained.

(234)U/(238)U activity ratio disequilibrium technique for studying uranium mobility in the Opalinus Clay at Mont Terri, Switzerland

Mobility of naturally occurring U-238 and U-234 radionuclides was studied in a low permeability, reducing claystone formation (Opalinus Clay) near its contact with an overlying oxidising aquifer (Dogger Limestones) at Mont Terri, Switzerland. Our data point to a limited redistribution of U in some of the studied samples. Observed centimetre-scale U mobility is explained by slow diffusive transport of U-234 in the pore waters of the Opalinus Clay driven by spatially variable in situ supply (by alpha-recoil) of U-234 from the rock matrix. Metre-scale mobility is interpreted as a result of infiltration of meteoric water into the overlying aquifer which developed gradients of U concentration across the two rock formations. This triggered a slow in-diffusion of U with (U-234/U-238) > 1 into the Opalinus Clay as attested by a clear-cut pattern of decreasing bulk rock (U-234/U-238) inwards the Opalinus Clay, away from the Dogger Limestones.

Mycobacterium tuberculosis transmission in a country with low tuberculosis incidence: role of immigration and HIV infection

Immigrants from high-burden countries and HIV-coinfected individuals are risk groups for tuberculosis (TB) in countries with low TB incidence. Therefore, we studied their role in transmission of Mycobacterium tuberculosis in Switzerland. We included all TB patients from the Swiss HIV Cohort and a sample of patients from the national TB registry. We identified molecular clusters by spoligotyping and mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) analysis and used weighted logistic regression adjusted for age and sex to identify risk factors for clustering, taking sampling proportions into account. In total, we analyzed 520 TB cases diagnosed between 2000 and 2008; 401 were foreign born, and 113 were HIV coinfected. The Euro-American M. tuberculosis lineage dominated throughout the study period (378 strains; 72.7%), with no evidence for another lineage, such as the Beijing genotype, emerging. We identified 35 molecular clusters with 90 patients, indicating recent transmission; 31 clusters involved foreign-born patients, and 15 involved HIV-infected patients. Birth origin was not associated with clustering (adjusted odds ratio [aOR], 1.58; 95% confidence interval [CI], 0.73 to 3.43; P = 0.25, comparing Swiss-born with foreign-born patients), but clustering was reduced in HIV-infected patients (aOR, 0.49; 95% CI, 0.26 to 0.93; P = 0.030). Cavitary disease, male sex, and younger age were all associated with molecular clustering. In conclusion, most TB patients in Switzerland were foreign born, but transmission of M. tuberculosis was not more common among immigrants and was reduced in HIV-infected patients followed up in the national HIV cohort study. Continued access to health services and clinical follow-up will be essential to control TB in this population.

Seasonal variation and sources of low molecular weight organic acids in precipitation in the rural area of Anshun

Low mol. wt. (LMW) org. acids are important and ubiquitous chem. constituents in the atm. A comprehensive study of the chem. compn. of pptn. was carried out from June 2007 to June 2008 at a rural site in Anshun, in the west of Guizhou Province, China. During this period, 118 rainwater samples were collected and the main LMW carboxylic acids were detd. using ion chromatog. The av. pH of rainwater was 4.89 which is a typical acidic value. The most abundant carboxylic acids were formic acid (vol. wt. mean concn.: 8.77 μmol L-1) and acetic acid (6.90 μmol L-1), followed by oxalic acid (2.05 μmol L-1). The seasonal variation of concns. and wet deposition fluxes of org. acids indicated that direct vegetation emissions were the main sources of the org. acids. Highest concns. were obsd. in winter and were ascribed to the low winter rainfall and the contribution of other air pollution sources northeast of the study area. The ratio of formic and acetic acids in the pptn. ([F/A]T) was proposed as an indicator of pollution source. This suggested that the pollution resulted from direct emissions from natural or anthropogenic sources. Comparison with acid pptn. in other urban and rural areas in Guizhou showed that there was a decreasing contribution of LMW org. acids to free acidity and all anions in rainwater from urban to remote rural areas. Consequently, it is necessary to control emissions of org. acids to reduce the frequency of acid rain, esp. in rural and remote areas. [on SciFinder(R)]

Inbreeding and selection on sex ratio in the bark beetle Xylosandrus germanus

Background Local Mate Competition (LMC) theory predicts a female should produce a more female-biased sex ratio if her sons compete with each other for mates. Because it provides quantitative predictions that can be experimentally tested, LMC is a textbook example of the predictive power of evolutionary theory. A limitation of many earlier studies in the field is that the population structure and mating system of the studied species are often estimated only indirectly. Here we use microsatellites to characterize the levels of inbreeding of the bark beetle Xylosandrus germanus, a species where the level of LMC is expected to be high. Results For three populations studied, genetic variation for our genetic markers was very low, indicative of an extremely high level of inbreeding (FIS = 0.88). There was also strong linkage disequilibrium between microsatellite loci and a very strong genetic differentiation between populations. The data suggest that matings among non-siblings are very rare (3%), although sex ratios from X. germanus in both the field and the laboratory have suggested more matings between non-sibs, and so less intense LMC. Conclusions Our results confirm that caution is needed when inferring mating systems from sex ratio data, especially when a lack of biological detail means the use of overly simple forms of the model of interest.

Pros and cons of low-field magnetic resonance imaging in veterinary practice

Low-field (LF) (0.2-0.4T) magnetic resonance (MR) imaging predominates in veterinary practice. Advantages of LF MR include reduced costs, better patient access, and greater safety. High quality examinations can be achieved using appropriate protocols and investing more scanning time than with high-field (HF) systems. The main disadvantage of LF MR is the reduced signal to noise ratio compared with HF systems. LF MR protocols for small animal brain and spine imaging are described.