Spectral Induced Polarization (SIP) signatures of clayey soils containing toluene

We performed laboratory experiments to investigate the sensitivity of the Spectral Induced Polarization (SIP) method to toluene contamination in clayey soils. We used mixtures of quartzitic sand and montmorillonite as soil samples, artificially contaminated with varying amounts of toluene. Care was taken to quantify the experimental uncertainty resulting from packing since such effects must be quantified if variations in SIP signatures between samples are to be reliably interpreted in terms of the effects of hydrocarbon concentration. The SIP response of all samples following addition of toluene was monitored for a period of 40 days following sample preparation. Stepwise regression was used to examine the statistical significance of correlations between (i) clay content and (ii) toluene concentration and SIP parameters. Both single-frequency real and imaginary conductivity measurements, along with the integral chargeability, normalized chargeability, DC conductivity and time constant obtained from a Debye decomposition fitting, were examined in this regression analysis. The SIP measurements show a clear time dependence following sample preparation, indicating that samples containing toluene may take significant time to reach an equilibrium electrical response. SIP measurements are significantly related to toluene content shortly after sample preparation, when the expected dependence of SIP on clay concentration is apparently suppressed. However, for the state of electrical equilibrium after 40 days (interpreted to indicate surface chemistry at equilibrium) there is no significant relation between SIP measurements and toluene content; instead SIP measurements are then significantly correlated with clay concentration. The total chargeability, normalized chargeability and relaxation time obtained from the Debye decomposition show no correlation with toluene content, indicating that this procedure, which likely integrates over multiple mechanisms, may not be suitable for understanding relationships between SIP and hydrocarbon contamination. We find only small low-frequency polarization signals observed in relation to toluene concentration (2 mrad at 0.01 Hz), which initially decreases the interfacial polarization. Unlike earlier works, our results do not support the use of the SIP method as a tool for monitoring toluene contamination in clay soils.

Endothelial dysfunction in the pulmonary artery induced by concentrated fine particulate matter exposure is associated with local but not systemic inflammation

Clinical evidence has identified the pulmonary circulation as an important target of air pollution. It was previously demonstrated that in vitro exposure to fine particulate matter (aerodynamic diameter <= 2.5 mu m, PM2.5) induces endothelial dysfunction in isolated pulmonary arteries. We aimed to investigate the effects of in vivo exposure to urban concentrated PM2.5 on rat pulmonary artery reactivity and the mechanisms involved. For this, adult Wistar rats were exposed to 2 weeks of concentrated Sao Paulo city air PM2.5 at an accumulated daily dose of approximately 600 mu g/m(3). Pulmonary arteries isolated from PM2.5-exposed animals exhibited impaired endothelium-dependent relaxation to acetylcholine without significant changes in nitric oxide donor response compared to control rats. PM2.5 caused vascular oxidative stress and enhanced protein expression of Cu/Zn- and Mn-superoxide dismutase in the pulmonary artery. Protein expression of endothelial nitric oxide synthase (eNOS) was reduced, while tumor necrosis factor (TNF)-alpha was enhanced by PM2.5 inhalation in pulmonary artery. There was a significant positive correlation between eNOS expression and maximal relaxation response (E-max) to acetylcholine. A negative correlation was found between vascular TNF-alpha expression and E-max to acetylcholine. Plasma cytokine levels, blood cells count and coagulation parameters were similar between control and PM2.5-exposed rats. The present findings showed that in vivo daily exposure to concentrated urban PM2.5 could decrease endothelium-dependent relaxation and eNOS expression on pulmonary arteries associated with local high TNF-alpha level but not systemic pro-inflammatory factors. Taken together, the present results elucidate the mechanisms underlying the trigger of cardiopulmonary diseases induced by urban ambient levels of PM2.5. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

Long-lasting Hypotensive Effect in Renal Hypertensive Rats Induced by Nitric Oxide Released From a Ruthenium Complex

In this study, we investigated the effect of the ruthenium complex [Ru(terpy)(bdq)NO+](3+) (TERPY) on the arterial pressure from renal hypertensive 2 kidney-1 clip (2K-1C) rats, which was compared with sodium nitroprusside (SNP). The most interesting finding was that the intravenous bolus injection of TERPY (2.5, 5.0, 7 mg/kg) had a dose-dependent hypotensive effect only in 2K-1C rats. On the other hand, SNP (35 and 70 mu g/kg) presented a similar hypotensive effect in both normotensive (2K) and 2K-1C although the effect of 70 mu g/kg was >35 mu g/kg. The injection of the nonselective NO-synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME) increased the arterial pressure in 2K and 2K-1C rats with a similar magnitude. After infusion of L-NAME, the hypotensive effect induced by TERPY and SNP was potentiated in both 2K and in 2K-1C rats. The administration of the superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl increased the hypotensive effect induced by TERPY or SNP in both 2K and 2K-1C rats. The hypotensive effect induced by TERPY was longer than that produced by SNP. Taken together, our results show that the TERPY has a long-lasting hypotensive effect, which has a dose dependence and higher magnitude in 2K-1C compared with in 2K rats. In comparison with SNP, TERPY is less potent in inducing arterial pressure fall, but it presents a much longer hypotensive effect.

A simple analysis of the influence of the solvent-induced electronic polarization on the N-15 magnetic shielding of pyridine in water

Electronic polarization induced by the interaction of a reference molecule with a liquid environment is expected to affect the magnetic shielding constants. Understanding this effect using realistic theoretical models is important for proper use of nuclear magnetic resonance in molecular characterization. In this work, we consider the pyridine molecule in water as a model system to briefly investigate this aspect. Thus, Monte Carlo simulations and quantum mechanics calculations based on the B3LYP/6-311++G (d,p) are used to analyze different aspects of the solvent effects on the N-15 magnetic shielding constant of pyridine in water. This includes in special the geometry relaxation and the electronic polarization of the solute by the solvent. The polarization effect is found to be very important, but, as expected for pyridine, the geometry relaxation contribution is essentially negligible. Using an average electrostatic model of the solvent, the magnetic shielding constant is calculated as -58.7 ppm, in good agreement with the experimental value of -56.3 ppm. The explicit inclusion of hydrogen-bonded water molecules embedded in the electrostatic field of the remaining solvent molecules gives the value of -61.8 ppm.

Low-dose Enalapril Reduces Angiotensin II and Attenuates Diabetic-induced Cardiac and Autonomic Dysfunctions

Activation of renin-angiotensin system has been linked to cardiovascular and autonomic dysfunctions in diabetes. Experiments were performed to investigate the effects of angiotensin-converting enzyme inhibitor (ACEI), enalapril, on cardiac and autonomic functions in diabetic rats. Diabetes was induced by streptozotocin (50 mg/kg), and rats were treated with enalapril (1 mg.kg(-1).d(-1)). After 30 days, evaluations were performed in control, diabetic, and enalapril-treated groups. Cardiac function was evaluated by echocardiography and through cannulation of the left ventricle (at baseline and in response to volume overload). Heart rate and systolic blood pressure variabilities were evaluated in the time and frequency domains. Streptozotocin rats had left ventricular systolic and diastolic dysfunctions, expressed by reduced ejection fraction and increased isovolumic relaxation time. The ACEI prevented these changes, improved diastolic cardiac responses to volume overload and total power of heart rate variability, reduced the ACE1 activity and protein expression and cardiac angiotensin (Ang) II levels, and increased angiotensin-converting enzyme 2 activity, despite unchanged blood pressure. Correlations were obtained between Ang II content with systolic and diastolic functions and heart rate variability. These findings provide evidence that the low-dose ACEI prevents autonomic and cardiac dysfunctions induced by diabetes without changing blood pressure and associated with reduced cardiac Ang II and increased angiotensin-converting enzyme 2 activity.

Atomically resolved study of the morphology change of InAs/GaAs quantum dot layers induced by rapid thermal annealing

The optoelectronic properties of InAs/GaAs quantum dots can be tuned by rapid thermal annealing. In this study, the morphology change of InAs/GaAs quantum dots layers induced by rapid thermal annealing was investigated at the atomic-scale by cross-sectional scanning tunneling microscopy. Finite elements calculations that model the outward relaxation of the cleaved surface were used to determine the indium composition profile of the wetting layer and the quantum dots prior and post rapid thermal annealing. The results show that the wetting layer is broadened upon annealing. This broadening could be modeled by assuming a random walk of indium atoms. Furthermore, we show that the stronger strain gradient at the location of the quantum dots enhances the intermixing. Photoluminescence measurements show a blueshift and narrowing of the photoluminescence peak. Temperature dependent photoluminescence measurements show a lower activation energy for the annealed sample. These results are in agreement with the observed change in morphology. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770371]

Parahydrogen induced polarization on a clinical MRI system : polarization transfer of two spin order

Hyperpolarization techniques enhance the nuclear spin polarization and thus allow for new nuclear magnetic resonance applications like in vivo metabolic imaging. One of these techniques is Parahydrogen Induced Polarization (PHIP). It leads to a hyperpolarized 1H spin state which can be transferred to a heteronucleus like 13C by a radiofrequency (RF) pulse sequence. In this work, timing of such a sequence was analyzed and optimized for the molecule hydroxyethyl propionate. The pulse sequence was adapted for the work on a clinical magnetic resonance imaging (MRI) system which is usually equipped only with a single RF transmit channel. Optimal control theory optimizations were performed to achieve an optimized polarization transfer. A drawback of hyperpolarization is its limited lifetime due to relaxation processes. The lifetime can be increased by storing the hyperpolarization in a spin singlet state. The second part of this work therefore addresses the spin singlet state of the Cs-symmetric molecule dimethyl maleate which needs to be converted to the spin triplet state to be detectable. This conversion was realized on a clinical MRI system, both by field cycling and by two RF pulse sequences which were adapted and optimized for this purpose. Using multiple conversions enables the determination of the lifetime of the singlet state as well as the conversion efficiency of the RF pulse sequence. Both, the hyperpolarized 13C spin state and the converted singlet state were utilized for MR imaging. Careful choice of the echo time was shown to be crucial for both molecules.

Quantitative magnetic resonance imaging of enzymatically induced degradation of the nucleus pulposus of intervertebral discs

STUDY DESIGN: The structural integrity of the nucleus pulposus (NP) of intervertebral discs was targeted by enzyme-specific degradations to correlate their effects to the magnetic resonance (MR) signal. OBJECTIVE: To develop quantitative MR imaging as an accurate and noninvasive diagnostic tool to better understand and treat disc degeneration. SUMMARY OF BACKGROUND DATA: Quantitative MR analysis has been previously shown to reflect not only the disc matrix composition, but also the structural integrity of the disc matrix. Further work is required to identify the contribution of the structural integrity versus the matrix composition to the MR signal. METHODS: The bovine coccygeal NPs were injected with either enzyme or buffer, incubated at 37 degrees C as static, unloaded and closed 3-disc segments, and analyzed by a 1.5-Tesla MR scanner to measure MR parameters. RESULTS: Collagenase degradation of the NP significantly decreased the relaxation times, slightly decreased the magnetization transfer ratio, and slightly increased the apparent diffusion coefficient. Targeting the proteoglycan and/or hyaluronan integrity by trypsin and hyaluronidase did not significantly affect the MR parameters, except for an increase in the apparent diffusion coefficient of the disc after trypsin treatment. CONCLUSIONS: Our results demonstrate that changes in the structural integrity of matrix proteins can be assessed by quantitative MR.

Clinical validation of electromyography and acceleromyography as sensors for muscle relaxation

BACKGROUND AND OBJECTIVE: The aim of this study was to determine which of two clinically applied methods, electromyography or acceleromyography, was less affected by external disturbances, had a higher sensitivity and which would provide the better input signal for closed loop control of muscle relaxation. METHODS: In 14 adult patients, anaesthesia was induced with intravenous opioids and propofol. The response of the thumb to ulnar nerve stimulation was recorded on the same arm. Mivacurium was used for neuromuscular blockade. Under stable conditions of relaxation, the infusion-rate was decreased and the effects of turning the hand were investigated. RESULTS: Electromyography and acceleromyography both reflected the change of the infusion rate (P = 0.015 and P < 0.001, respectively). Electromyography was significantly less affected by the hand-turn (P = 0.008) than acceleromyography. While zero counts were detected with acceleromyography, electromyography could still detect at least one count in 51.1%. CONCLUSIONS: Electromyography is more reliable for use in daily practice as it is less influenced by external disturbances than acceleromyography.

Inhibition of ErbB2/neuregulin signaling augments paclitaxel-induced cardiotoxicity in adult ventricular myocytes

Paclitaxel (Taxol) has been successfully combined with the monoclonal antibody trastuzumab (Herceptin) in the treatment of ErbB2 overexpressing cancers. However, this combination therapy showed an unexpected synergistic increase in cardiac dysfunction. We have studied the mechanisms of paclitaxel/anti-ErbB2 cardiotoxicity in adult rat ventricular myocytes (ARVM). Myofibrillar organization was assessed by immunofluorescence microscopy and cell viability was tested by the TUNEL-, LDH- and MTT-assay. Oxidative stress was measured by DCF-fluorescence and myocyte contractile function by video edge-detection and fura-2 fluorescence. Treatment of ARVM with paclitaxel or antibodies to ErbB2 caused a significant increase in myofilament degradation, similarly as observed with an inhibitor of MAPK-signaling, but not apoptosis, necrosis or changes in mitochondrial activity. Paclitaxel-treatment and anti-ErbB2 reduced Erk1/2 phosphorylation. Paclitaxel increased diastolic calcium, shortened relaxation time and reduced fractional shortening in combination with anti-ErbB2. A minor increase in oxidative stress by paclitaxel or anti-ErbB2 was found. We conclude, that concomitant inhibition of ErbB2 receptors and paclitaxel treatment has an additive worsening effect on adult cardiomyocytes, mainly discernible in changes of myofibrillar structure and function, but in the absence of cell death. A potential mechanism is the modulation of the MAPK/Erk1/2 signaling by both drugs.

{\it In vivo\/} magnetic resonance studies of experimental liver disease: Carbon tetrachloride hepatotoxicity and alcohol-induced fatty liver in rat

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) were used to non-invasively determine if cirrhosis induced by carbon tetrachloride (CCl$\sb4$) and phospholipase-D (PLD) could be distinguished from fatty infiltration in rat. MRS localization and water suppression methods were developed, implemented and evaluated in terms of their application to in vivo proton NMR studies of experimental liver disease. MRS studies were also performed to quantitate fatty infiltration resulting from carbon tetrachloride (CCl$\sb4$) or alcohol (ethanol) administration and the MRS results were confirmed using biochemical total lipid analysis and histology. $\rm T\sb1$ weighted MR images acquired weekly, 48 hours post administration, demonstrated only a slight increase in overall liver intensity with CCl$\sb4$ or alcohol administration, which is consistent with previously reported results. The MR images were able to detect nodules resulting from CCl$\sb4$+PLD induced cirrhosis as hypointense regions, also consistent with previous reports. Localized in vivo water and lipid proton $\rm T\sb1$ relaxation time measurements were performed and demonstrated no statistically significant trends for either agent. In vivo proton spectra were also acquired using stimulated echo techniques to quantitatively follow the changes in liver lipid content. The changes in liver lipid content observed using MRS were verified by total lipid analysis using the Folch technique and histology. The in vivo $\rm T\sb1$ and lipid quantification data str inconsistent with the previous hypothesis that the changes in $\rm T\sb1$ weighted images were the result of increased "free" water content and, therefore, increased water $\rm T\sb1$ relaxation times. These data indicate that the long term changes are more likely the result of changes in lipid content. The data are also shown to agree with the accepted hypothesis that the time course and mechanism of fatty infiltration are different for CCl$\sb4$ and alcohol. The hypothesis that the lipids resulting from either protocol are from the same lipid fraction(s), presumably triglycerides, is also supported. And lastly, on the basis of MR images and quantitative MRS lipid information, it was shown that cirrhosis could be distinguished from fatty infiltration. ^

A specialist root herbivore reduces plant resistance and uses an induced plant volatile to aggregate in a density-dependent manner

1.Leaf-herbivore attack often triggers induced resistance in plants. However, certain specialist herbivores can also take advantage of the induced metabolic changes. In some cases, they even manipulate plant resistance, leading to a phenomenon called induced susceptibility. Compared to above-ground plant-insect interactions, little is known about the prevalence and consequences of induced responses below-ground. 2.A recent study suggested that feeding by the specialist root herbivore Diabrotica virgifera virgifera makes maize roots more susceptible to conspecifics. To better understand this phenomenon, we conducted a series of experiments to study the behavioural responses and elucidate the underlying biochemical mechanisms. 3.We found that D. virgifera benefitted from feeding on a root system in groups of intermediate size (3–9 larvae/plant in the laboratory), whereas its performance was reduced in large groups (12 larvae/plant). Interestingly, the herbivore was able to select host plants with a suitable density of conspecifics by using the induced plant volatile (E)-β-caryophyllene in a dose-dependent manner. Using a split root experiment, we show that the plant-induced susceptibility is systemic and, therefore, plant mediated. Chemical analyses on plant resource reallocation and defences upon herbivory showed that the systemic induced-susceptibility is likely to stem from a combination of (i) increased free amino acid concentrations and (ii) relaxation of defence inducibility. 4.These findings show that herbivores can use induced plant volatiles in a density-dependent manner to aggregate on a host plant and change its metabolism to their own benefit. Our study furthermore helps to explain the remarkable ecological success of D. virgifera in maize fields around the world.

E2F1's role in ultraviolet-induced DNA damage response

The E2F1 transcription factor is a well-known regulator of cell proliferation and apoptosis, but its role in the DNA damage response is less clear. It has been shown that E2F1 becomes stabilized in response to DNA double strand breaks (DSBs) and accumulates at sites of DSBs. This process requires ATM kinase and serine 31 phosphorylation, which provides a binding site for TopBp1. However, the role of E2F1 at sites of DNA damage is not clear. We expanded the study of E2F1's role in the DNA damage response by exploring its functions in ultraviolet (UV) induced DNA damage, and identified that E2F1 promotes DNA repair and cell survival. To further investigate the mechanisms underlying our findings, we examined the possibility for direct involvement of E2F1 in DNA repair. We found that E2F1 localizes to sites of UV irradiation-induced DNA damage dependent on the ATR kinase and serine 31 of E2F1. E2F1 also associates with the GCN5 histone acetyltransferase in response to UV irradiation and recruits GCN5 to sites of DNA damage. This correlates with an increase in histone H3 lysine 9 (H3K9) acetylation and chromatin relaxation. In the absence of E2F1 or GCN5, nucleotide excision repair (NER) proteins do not efficiently localize to sites of UV damage and DNA repair is impaired. E2F1 mutants unable to bind DNA or activate transcription retain the ability to stimulate NER. These findings demonstrate a non-transcriptional role for E2F1 in DNA repair involving GCN5-mediated H3K9 acetylation and increased accessibility to the NER machinery. ^

X-Ray Diffraction, Calorimetric and Dielectric Relaxation Study of the Amorphous and Smectic States of a Main Chain Liquid Crystalline Polymer

Los polímeros cristales líquidos (LCP) son sistemas complejos que forman mesofases que presentan orden orientacional y polímeros amorfos. Con frecuencia, el estado amorfo isotrópico no puede ser estudiado debido a la rápida formación de mesofases. En este trabajo se ha sintetizado y estudiado un nuevo LCP: poli(trietilenglicol metil p, p '-bibenzoato), PTEMeB. Este polímero presenta una formación de mesofase bastante lenta haciendo posible estudiar de forma independiente tanto los estados amorfo y de cristal líquidos. La estructura y las transiciones de fase del PTEMeB han sido investigados por calorimetría (DSC), con MAXS / WAXS con temperatura variable que emplean radiación de sincrotrón y con difracción de rayos X. Estos estudios han mostrado la existencia de dos transiciones vítreas, relacionadas con las fases amorfa y cristal líquido. Se ha realizado un estudio de relajación dieléctrica en amplios intervalos de temperatura y presión. Se ha encontrado que la transición vítrea dinámica de la fase amorfa es más lenta que la del cristal líquido. El estudio de la relajación ? nos ha permitido seguir la formación isoterma de la mesofase a presión atmosférica. Además, con el estudio el comportamiento dinámico a alta presión se ha encontrado que se produce la formación rápida de la mesofase inducida por cambios bruscos de presión. Liquid crystalline polymers (LCPs) are complex systems that include features of both orientationally ordered mesophases and amorphous polymers. Frequently, the isotropic amorphous state cannot be studied due to the rapid mesophase formation. Here, a new main chain LCP, poly(triethyleneglycol methyl p,p'-bibenzoate), PTEMeB, has been synthesized. It shows a rather slow mesophase formation making possible to study independently both the amorphous and the liquid crystalline states. The structure and phase transitions of PTEMeB have been investigated by calorimetry, variable-temperature MAXS/WAXS employing synchrotron radiation, and X-ray diffraction in oriented fibers. These experiments have pointed out the presence of two glass transitions, related to the amorphous or to the liquid crystal phases. Additionally, the mesophase seems to be a coexistence of orthogonal and tilted smectic phases. A dielectric relaxation study of PTEMeB over broad ranges of temperature and pressure has been performed. The dynamic glass transition turns out to be slower for the amorphous state than for the liquid crystal. Monitoring of the α relaxation has allowed us to follow the isothermal mesophase formation at atmospheric pressure. Additionally, the dynamical behavior at high pressures has pointed out the fast formation of the mesophase induced by sudden pressure changes.

ΔpH-Dependent Photosystem II Fluorescence Quenching Induced by Saturating, Multiturnover Pulses in Red Algae1

We have previously shown that in the red alga Rhodella violacea, exposure to continuous low intensities of light 2 (green light) or near-saturating intensities of white light induces a ΔpH-dependent PSII fluorescence quenching. In this article we further characterize this fluorescence quenching by using white, saturating, multiturnover pulses. Even though the pulses are necessary to induce the ΔpH and the quenching, the development of the latter occurred in darkness and required several tens of seconds. In darkness or in the light in the presence of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, the dissipation of the quenching was very slow (more than 15 min) due to a low consumption of the ΔpH, which corresponds to an inactive ATP synthase. In contrast, under far-red illumination or in the presence of 3-(3,4-dichlorophenyl)-1,1′-dimethylurea (only in light), the fluorescence quenching relaxed in a few seconds. The presence of N,N′-dicyclohexyl carbodiimide hindered this relaxation. We propose that the quenching relaxation is related to the consumption of ΔpH by ATP synthase, which remains active under conditions favoring pseudolinear and cyclic electron transfer.