Rapid sequential injections of hyperpolarized [1-C]pyruvate in vivo using a sub-kelvin,multi-sample DNP polarizer

The development of hyperpolarized technology utilizing dynamic nuclear polarization (DNP) has enabled the rapid measurement of ¹³C metabolism in vivo with very high SNR. However, with traditional DNP equipment, consecutive injections of a hyperpolarized compound in an animal have been subject to a practical minimum time between injections governed by the polarization build-up time, which is on the order of an hour for [1-¹³C]pyruvate. This has precluded the monitoring of metabolic changes occurring on a faster time scale. In this study, we demonstrated the ability to acquire in vivo dynamic magnetic resonance spectroscopy (MRS) and 3D magnetic resonance spectroscopic imaging (MRSI) data in normal rats with a 5 min interval between injections of hyperpolarized [1-¹³C]pyruvate using a prototype, sub-Kelvin dynamic nuclear polarizer with the capability to simultaneously polarize up to 4 samples and dissolve them in rapid succession. There were minimal perturbations in the hyperpolarized spectra as a result of the multiple injections, suggesting that such an approach would not confound the investigation of metabolism occurring on this time scale. As an initial demonstration of the application of this technology and approach for monitoring rapid changes in metabolism as a result of a physiological intervention, we investigated the pharmacodynamics of the anti-cancer agent dichloroacetate (DCA), collecting hyperpolarized data before administration of DCA, 1 min after administration, and 6 min after administration. Dramatic increases in ¹³C-bicarbonate were detected just 1 min (as well as 6 min) after DCA administration.     

Absolute configuration of eldanolide,the wing gland pheromone of the male African sugar cane borer,Eldana saccharina (Wlk.) syntheses of its (+) and (−) enantiomers.

Eldanolide $\text{1}$, a novel terpenoid lactone pheromone, was shown to have (3S,4R) configuration by synthesis of both enantiomers and comparison of their CD with the natural pheromone.     

Microstubs resonators integrated to bent Y-branch waveguide

We report numerical simulations, based on a finite difference time domain (FDTD) method, of light propagation in two-dimensional semiconductor micro-optical waveguides coupled to one or several lateral stubs. It is shown that when the stub is covered with a perfectly metallic thin layer, the transmission spectrum contains several narrow dips. Such simulation of the metallic coating can be used in the far infrared frequency domain, far from the optical regime. We propose a selective filtering device based on the interaction between several stubs. Inserting an appropriate defect stub between a set of periodical stubs leads to a tunnelling transmission, with a narrow peak inside the gap. This filtering phenomenon is used to propose a demultiplexer based on a Y-shaped waveguide for separating signals with different frequencies. Finally, we show that the filtering effect of a stub can also be reproduced when the metal is described in the frame of a Drude model instead of being perfect, which makes plausible the realization of the above devices in the near optical regime.     

Physicochemical evaluation of PLA nanoparticles stabilized by water-soluble MPEO-PLA block copolymers

Different water-soluble MPEO-PLA diblock copolymers with various alpha-methoxy-omega-hydroxyl polyethylene (MPEO) and poly(lactic acid) (PLA) block lengths have been synthesized. Their surface-active properties were evidenced by surface tension (water/air) measurements. In each case the surface tension leveled down above a critical polymer concentration, which was attributed to the formation of a dense polymer layer at the liquid-air interface. The applicability of copolymers as emulsion stabilizers in the preparation of PLA nanospheres by an o/w emulsion/evaporation technique was then investigated. Four copolymers presenting sufficient water solubility and good surfactive properties were used to prepare PLA nanospheres with MPEO chains firmly anchored at the particle surface. The effect of polymer concentration in emulsion on particle size and surface coverage was examined. Whatever the copolymer characteristics, it was found that the optimal concentration to obtain a large amount of MPEO at the particle surface was similar (around 2 g/l). The effect of the copolymer composition on MPEO layer characteristics and on colloidal stability was also evaluated. The conformation of MPEO blocks at the PLA particle surface is discussed in relation to the layer thickness and the surface area occupied per molecule.     

Configurations absolues des methylbenzhydryl,isopropylbenzhydryl et isopropylbenzylcarbinols

The absolute configurations of methylbenzhydryl, isopropylbenzhydryl and isopropylbenzylcarbinols have been determined unequivocally by chemical correlations.     

La methode mathematique de Ruch et Ugi. Application au dedoublement partiel selon horeau

The Ruch and Ugi mathematical treatment is discussed from a critical point of view. It is not valid for the kinetic resolution of α-phenylbutyric acid by chiral secondary alcohols.     

High-resolution intracranial MRA at 7T using autocalibrating parallel imaging: initial experience in vascular disease patients

Purpose

Greater spatial resolution in intracranial three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) is possible at higher field strengths, due to the increased contrast-to-noise ratio (CNR) from the higher signal-to-noise ratio and the improved background suppression. However, at very high fields, spatial resolution is limited in practice by the acquisition time required for sequential phase encoding. In this study, we applied parallel imaging to 7T TOF MRA studies of normal volunteers and patients with vascular disease, in order to obtain very high resolution (0.12 mm³) images within a reasonable scan time.

Materials and Methods

Custom parallel imaging acquisition and reconstruction methods were developed for 7T MRA, based on generalized autocalibrating partially parallel acquisition (GRAPPA). The techniques were compared and applied to studies of seven normal volunteers and three patients with cerebrovascular disease.

Results

The technique produced high resolution studies free from discernible reconstruction artifacts in all subjects and provided excellent depiction of vascular pathology in patients.

Conclusions

7T TOF MRA with parallel imaging is a valuable noninvasive angiographic technique that can attain very high spatial resolution.     

Feasibility of using hyperpolarized [1-13C]lactate as a substrate for in vivo metabolic 13C MRSI studies

The development of dynamic nuclear polarization in solution has enabled in vivo 13C MR studies at high signal-to-noise ratio following injection of prepolarized 13C substrates. While prior studies have demonstrated the ability to observe metabolism following injection of hyperpolarized 13C pyruvate, the goal of this study was to develop and test a new hyperpolarized agent for investigating in vivo metabolism, [1-13C]lactate. A preparation for prepolarized 13C lactate and the requisite dissolution media were developed to investigate the feasibility for in vivo 13C MRS/MRSI studies following injection of this hyperpolarized agent. This study demonstrated, for the first time, not only the ability to detect hyperpolarized [1-13C]lactate in vivo but also the metabolic products 13C pyruvate, 13C alanine and 13C bicarbonate following injection in normal rats. The use of 13C lactate as a substrate provided the opportunity to study the conversion of lactate to pyruvate in vivo and to detect the secondary conversions to alanine and bicarbonate through pyruvate. This study also demonstrated the potential value of this hyperpolarized agent to investigate in vivo lactate uptake and metabolism in preclinical animal models.