Intracranial hypertension is a severe complication of acute liver failure (ALF) secondary to brain edema. The pathogenesis of cerebral edema in ALF is not clear, but seems to be related to energy metabolism in which lactate may have an important role. The aim of this study was to follow the synthesis of brain lactate using a novel in vivo metabolic technology in a rat model of ALF. Time-resolved 13C MRS of hyperpolarized 13C1-pyruvate was used to quantitatively follow the in vivo conversion of pyruvate to its substrates in a model of devascularized ALF in rats. Rats with ALF showed a significant increase in the lactate to pyruvate ratio from 36% to 69% during the progression of liver disease relative to rats with portocaval anastomosis. Rats with ALF also showed a significant increase in the alanine to pyruvate ratio from 72% to 95%. More interestingly, these increases were detectable at very early stages, just 6 h after ALF when animals had no evident disease signs in their behavior (without loss of righting or corneal reflexes). This study shows the dynamic consequences of cerebral in vivo13C metabolism at real time in rats with ALF. The early detection of the de novo synthesis of lactate suggests that brain lactate is involved in the physiopathology of ALF.
In her oral presentation “Enantiodifferentiation throgh frequency-selective pure shift 1H NMR” Laura explained that pure shift NMR experiments, by simplifying the typical JHH multiplicity pattern of 1H signals to singlets, allow an improved analysis of complex and overcrowded spectra, and that such approach can be used to determine the enantiomers molar ratio in the presence of chiral solvating agents.
Laura has been working as a Ph.D. candidate at the Department of Chemistry and SeRMN under the co-direction of Dr. Albert Virgili and Dr. Teodor Parella since Sept 2012, when she enrolled in the Department of Chemistry doctoral program at Universitat Autònoma de Barcelona with a fellowship from UAB. She is currently in her third year and expects to defend the doctoral thesis on 2015. You can read about her work on this blog.
“A new ex vivo method to evaluate the performance of candidate MRI contrast agents: a proof-of-concept study” by Candiota AP, Acosta M, Simões RV, Delgado-Goñi T, Lope-Piedrafita S, Irure A, Marradi M, Bomati-Miguel O, Miguel-Sancho N, Abasolo I, Schwartz S Jr, Santamaria J, Penadés S, Arús C, J Nanobiotechnology 2014 12:12. DOI: 10.1186/1477-3155-12-12.
A new method has been developed for selecting MRI contrast agents with better expected in vivo performance. This method requires only a very small amount of contrast agent (e.g. 5 nmols/animal, 800 times less than the quantity necessary for in vivo administration) and allows to carry out a more rationally informed candidate selection, avoiding unnecessary in vivo and toxicology tests for the ex vivo poorly performing substances, consequently reducing animal needs, material consumption and overall costs. For validation, novel paramagnetic gadolinium-based gold nanoparticles (Gd-GNPs) as well as superparamagnetic iron oxide nanoparticles (SPIONs) were tested.
Shoots and roots are autotrophic and heterotrophic organs of plants with different physiological functions. Do they have different metabolomes? Do their metabolisms respond differently to environmental changes such as drought? We used metabolomics and elemental analyses to answer these questions.
First, we show that shoots and roots have different metabolomes and nutrient and elemental stoichiometries. Second, we show that the shoot metabolome is much more variable among species and seasons than is the root metabolome. Third, we show that the metabolic response of shoots to drought contrasts with that of roots; shoots decrease their growth metabolism (lower concentrations of sugars, amino acids, nucleosides, N, P, and K), and roots increase it in a mirrored response. Shoots are metabolically deactivated during drought to reduce the consumption of water and nutrients, whereas roots are metabolically activated to enhance the uptake of water and nutrients, together buffering the effects of drought, at least at the short term.
Changes in plant chemical defenses after invasion could have consequences on the invaded ecosystems by modifying the interactions between plants and herbivores and facilitating invasion success. However, no comprehensive biogeographical studies have yet determined the phenotypic levels of plant chemical defenses, as consumed by local herbivores, covering large distributional areas of a species. Senecio pterophorus is a perennial shrub native to Eastern South Africa, expanded into Western South Africa and introduced into Australia and Europe. As other Asteraceae, S. pterophorus contains pyrrolizidine alkaloids (PAs) toxic to vertebrate and invertebrate herbivores. Here we analyzed S. pterophorus PAs by LC–MS/MS and NMR spectroscopy. Plants from different origins diverged in their PA absolute and relative concentrations. Rosmarinine was the most abundant compound in Australia and South Africa, but it was nearly absent in Europe. We characterized three plant chemotypes: retrorsine– senkirkine chemotype in Eastern South Africa, rosmarinine chemotype in Australia and Western South Africa, and acetylseneciphylline chemotype in Europe. PA absolute concentrations were highest in Australia. The increased absolute and relative concentrations of retronecine PAs from Australia and Europe, respectively, indicate that S. pterophorus is potentially more toxic in the invasive range than in the native range.
The amplitude and the phase of cross peaks in conventional 2D HSQC experiments are modulated by both proton–proton, JHH, and proton–carbon, 1JCH, coupling constants. It is shown by spectral simulation and experimentally that JHH interferences are suppressed in a novel perfect-HSQC pulse scheme that incorporates perfect-echo INEPT periods. The improved 2D spectra afford pure in-phase cross peaks with respect to 1JCH and JHH, irrespective of the experiment delay optimization. In addition, peak volumes are not attenuated by the influence of JHH, rendering practical issues such as phase correction, multiplet analysis, and signal integration more appropriate.
Organized by the SeRMN of the Autonomous University of Barcelona (UAB).
This course combines a comprehensive series of lectures on the technology of Magnetic resonance spectroscopy and imaging (MRS/MRI) with hands-on laboratory sessions to provide practical demonstrations of key concepts and procedures for preclinical studies.
Whether you are considering MRI as a research tool in your lab or just would like to learn more about MRI, this workshop addresses practical aspects of experimental MRI with laboratory animals and provide valuable hands-on experience on a 7 Tesla Bruker BioSpec spectrometer.
Number of participants will be limited to 4.
For the registration, please fill theRegistration Form and email it to firstname.lastname@example.org (registration deadline ends November 10th)
Some of our last research work will be presented next week at the VI Ibero-American NMR – VII GERMN Bienal – IV Iberian NMR joint meeting that will take place in Alcalá de Henares, Madrid (Spain) from 22nd to 25th September. Find below a summary of our contributions.
Laura Castañar presents an oral communication and a poster entitled “Enantiodifferentiation throgh frequency-selective pure shift 1H NMR”. NMR-aided discrimination of enantiomers using chiral solvating agents (CSAs) is a well established method to carry out enantiodifferentiation studies. The analysis is traditionally performed by observing chemical shift differences (ΔΔδ) in 1H signals by conventional 1D 1H NMR spectra. However signals overlapping caused by low ΔΔδ values and homonuclear scalar couplings (JHH) lead to the lack of spectral signal dispersion that preclude a straightforward analysis. Recently, pure shift NMR spectroscopy has emerged as a promising tool to simplify the typical JHH multiplicity pattern of 1H signals to singlets. This affords a general improvement on signal dispersion that allows an improved analysis of complex and overcrowded resonances. Based on the full-sensitive 1H-HOBS experiment, frequency-selective technique for the fast and simple discrimination of ΔΔδ in overlapped signals and for the determination of the R/S molar ratio in the presence of CSAs is here proposed.
Pure In-Phase Heteronuclear Correlation NMR Experiments; Laura Castañar, Josep Saurí, R. Thomas Williamson, Albert Virgili and Teodor Parella.
A general pulse scheme to provide pure in-phase (PIP) multiplets in heteronuclear correlation NMR experiments is presented. The implementation of a zero-quantum filter efficiently suppresses any unwanted anti-phase contributions that usually distort the multiplet pattern of cross-peaks and can hamper their analysis. The clean in-phase pattern obtained in PIP-HSQC and PIP-HSQMBC experiments is suitable for a direct extraction of coupling constants in resolved signals, for a peak-fitting process from a reference signal, or for the application of the IPAP technique in non-resolved multiplets.
Fast and efficient enantiodifferentiation through pure shift NMR;Laura Castañar, Míriam Pérez-Trujillo, Eva Monteagudo, Lars T. Kuhn, Pau Nolis, Albert Virgili, R. Thomas Williamson and Teodor Parella.
Several NMR enantiodifferentiation studies by using new pure shift (PS) NMR methods will be discussed. First, a frequency-selective 1D HOmodecoupled Band-Selective (HOBS) experiment is proposed for the fast 1H chemical shift discrimination of overlapped signals. On the other hand, the concepts of spectral aliasing (SA) and PS NMR are combined into a novel and robust 2D SAPS-HSQC experiment which provides simultaneous 1H and 13C enantiodifferentiated data with high digital resolution and excellent signal dispersion for both broadband-decoupled 1H and 13C nuclei.
Perfect-HSQC: Suppression of phase and amplitude JHH modulation; Laura Castañar, Eduard Sistaré, Albert Virgili, R. Thomas Williamson and Teodor Parella.
The amplitude and the phase of cross-peaks in conventional 2D HSQC experiments are modulated by both proton-proton, JHH, and proton-carbon, 1JCH, coupling constants. In this work we shown by spectral simulation and experimentally that JHH interferences can be efficiently suppressed in a novel perfect-HSQC pulse scheme that incorporates JHH-compensated INEPT periods. The improved 2D spectra afford pure in-phase cross-peaks with respect to 1JCH and JCH, irrespective to the experiment delay optimization. In addition, peak volumes are not attenuated by the influence of JHH, rendering practical issues such as phase correction, signal integration and multiplet analysis more accurate.
Simultaneous measurement of the magnitude and the sign of multiple heteronuclear coupling constants in 19F- or 31P-containing molecules; Josep Saurí, Pau Nolis and Teodor Parella.
A suite of selHSQMBC experiments are presented for the simultaneous measurement of multiple homo- and/or heteronuclear coupling constants from a single 2D cross-peak. A time-shared version allows such determinations for 13C and 15N at the same time and the incorporation of a TOCSY transfer extents its applicability for an entire spin system. The use of non-uniform linear sampling (NUS) and/or the signal detection under homodecoupling conditions will be also evaluated and illustrated with examples.
NMR-aided discrimination of enantiomers using chiral solvating agents (CSAs) is a well established method of enantiodifferentiation and measurement of enantiomeric ratios (er). The analysis is traditionally performed by observing chemical shift differences (ΔΔδ) in 1H signals by conventional 1D 1H NMR spectra. However, low ΔΔδ values and signal overlap caused by complex multiplets lead to the lack of spectral signal dispersion that preclude a straightforward analysis. The alternative of using 13C NMR spectroscopy can be more advantageous, because singlet signals are analyzed, but its routine use is limited by its low sensitivity.The combination of spectral aliasing and pure shift HSQC in SAPS-HSQC experiments represents an excellent routine tool for NMR enantiodifferentiation studies, yielding simultaneous 1H and 13C enantiodifferentiated data in short times and with high digital resolution and signal dispersion for both nuclei. Its use increases significantly the probability to detect an enantiodifferentiated nucleus, overlapping problems of common 1D 1H experiments are overcome, and poor enantiodifferentiation in 1D experiments can now be detected. The method is compatible with other heteronuclei, with the use of other chiral auxiliaries, and it can be of special interest for enantiodifferentiation experiments of complex mixtures.