The isotropic and anisotropic hyperfine coupling constants and g-values of the nitroxide spin label (1-oxyl-2,2,5,5-tetramethylpyrroline-3-methyl)methanethiosulfonate (MTSSL) were determined from 9-GHz and 95-GHz electron paramagnetic resonance (EPR) measurements in various solvents with a large distribution in polarity and proticity. The parameters A iso , g iso , A zz , and g xx of MTSSL were found to be sensitive to changes in solvent properties, where A-values increased and g-values decreased due to increased solvent polarity or proticity. A linear correlation was found for the isotropic (g iso , A iso ) and anisotropic (g xx , A zz ) parameters, respectively. Furthermore, density functional theory (DFT) calculations of the same parameters were performed for a model spin label with the possibility to vary the dielectric constant ( ) of the medium and the number of hydrogen bonds formed with the nitroxide oxygen. From a qualitative analysis of experimental and calculated results, it was possible to specify the causes of the parameter shifts in more detail. In the "apolar region" ( < 25), the sensitivity of A iso and A zz to is large. However, in the "polar region" ( > 25), the sensitivity to is small, and the shifts in A iso and A zz are mainly determined by the proticity of the solvent. Methanol was found to form ∼1 and water ∼2 hydrogen bonds to the nitroxide on average. The DFT method determined the shifts in g iso and g xx due to hydrogen bonding more accurately compared with the restricted open-shell Hartree-Fock method. The anisotropic spin label-solvent data can be used in the interpretation of rigid-limit data from spin-labeled proteins to gain further insight in local environmental properties.

Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd(2)O(3)) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd(2)O(3) nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd(2)O(3) nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd(2)O(3). Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level.

The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd 2 O 3 ) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r 1 , r 2 ) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd 2 O 3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd 2 O 3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd 3+ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG-Gd 2 O 3 and PEG-silane-SPGO (Gd 2 O 3 , < 40 nm diameter). The small and narrow size distribution of US-Gd 2 O 3 was confirmed with TEM (∼3nm)andDLS.PEG-silane-US-Gd 2 O 3 relaxation parameters were twice as high as for Gd-DTPA and the r 2 /r 1 ratio was 1.4. PEG-silane-SPGO gave low r 1 relaxivities and high r 2 /r 1 ratios, less compatible with positive contrast agent requirements. Higher r 1 were obtained with PEG-silane in comparison to DEG-Gd 2 O 3 . Treatment of DEG-US-Gd 2 O 3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd 2 O 3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.

Background & aims Only a fraction of IBS patients show increased perceptual sensitivity to rectal distension, suggesting possible differences in processing and/or modulation of visceral afferent signals within this group. The aim was to identify brain mechanisms which may underlie these perceptual differences. Methods 44 women with IBS and 20 female healthy control subjects (HCs) were included. Symptom severity in IBS was determined by Severity Scoring System (IBS-SSS). Anxiety and depression symptoms were assessed using the Hospital anxiety & depression score (HAD). Blood oxygen level dependent (BOLD) signals were measured by functional Magnetic Resonance Imaging (fMRI) during expectation and delivery of high (45mmHg) and low (15mmHg) intensity rectal distensions. Perception thresholds to rectal distension were determined in the scanner. Brain imaging data from 18 normosensitive, 15 hypersensitive IBS patients and 18 HCs were compared. Results were reported significant if peak p-value ≤ 0.05 with family wise error correction in regions of interest. Results The two IBS subgroups were similar in age, symptom duration, psychological symptoms and IBS symptom severity. While brain responses to distension were similar in normosensitive patients and HCs, hypersensitive IBS demonstrated greater activation of insula and reduced deactivation in pregenual anterior cingulate cortex during noxious rectal distensions, compared to both HCs and normosensitive IBS. During expectation of rectal distension, normosensitive IBS had more activation in right hippocampus than HCs. Conclusions Despite similarities in symptoms, hyper- and normosensitive IBS patients differed substantially in cerebral response to standardized rectal distensions and their expectation, consistent with differences in ascending visceral afferent input.

The aim of this study was to present a model that uses multi-parametric quantitative MRI to estimate the presence of myelin and edema in the brain. The model relates simultaneous measurement of R1 and R2 relaxation rates and proton density to four partial volume compartments, consisting of myelin partial volume, cellular partial volume, free water partial volume, and excess parenchymal water partial volume. The model parameters were obtained using spatially normalized brain images of a group of 20 healthy controls. The pathological brain was modeled in terms of the reduction of myelin content and presence of excess parenchymal water, which indicates the degree of edema. The method was tested on spatially normalized brain images of a group of 20 age-matched multiple sclerosis (MS) patients. Clear differences were observed with respect to the healthy controls: the MS group had a 79 mL smaller brain volume (1069 vs. 1148 mL), a 38 mL smaller myelin volume (119 vs. 157 mL), and a 21 mL larger excess parenchymal water volume (78 vs. 57 mL). Template regions of interest of various brain structures indicated that the myelin partial volume in the MS group was 1.6 ± 1.5% lower for gray matter (GM) structures and 2.8 ± 1.0% lower for white matter (WM) structures. The excess parenchymal water partial volume was 9 ± 10% larger for GM and 5 ± 2% larger for WM. Manually placed ROIs indicated that the results using the template ROIs may have suffered from loss of anatomical detail due to the spatial normalization process. Examples of the application of the method on high-resolution images are provided for three individual subjects: a 45-year-old healthy subject, a 72-year-old healthy subject, and a 45-year-old MS patient. The observed results agreed with the expected behavior considering both age and disease. In conclusion, the proposed model may provide clinically important parameters, such as the total brain volume, degree of myelination, and degree of edema, based on a single qMRI acquisition with a clinically acceptable scan time.

The study indicates the possibility of obtaining at least doubled relaxivity compared to Gd-DTPA using Gd(2)O(3)-DEG nanocrystals as contrast agent. The high T (1) relaxation rate at low concentrations of Gd(2)O(3) nanoparticles is very promising for future studies of contrast agents based on gadolinium-containing nanocrystals.

Mast cells are found in tissues throughout the body where they play important roles in the regulation of inflammatory responses. One characteristic feature of mast cells is their longevity. Although it is well established that mast cell survival is dependent on stem cell factor (SCF), it has not been described how this process is regulated. Herein, we report that SCF promotes mast cell survival through inactivation of the Forkhead transcription factor FOXO3a (forkhead box, class O3A) and down-regulation and phosphorylation of its target Bim (Bcl- 2 IntroductionMast cells are long-lived multifunctional effector cells of the immune system originating from the hematopoietic CD34 ϩ stem cells found in the bone marrow. 1 From the bone marrow, mast cell precursors enter the circulation where they are recruited into peripheral tissues to mature and express their final phenotype under the influence of stem cell factor (SCF) and other locally produced cytokines. 2 Although best known for their role in allergic reactions, mast cells are now also recognized as cells of importance in both innate immunity and in the onset and severity of chronic inflammations. 3,4 The versatile effector mechanisms mast cells have been endowed with can be deduced from their capability to release a wide variety of inflammatory mediators such as histamine, proteases, and cytokines that are preformed and stored in granules and prostaglandins, leukotrienes, and cytokines that are secreted upon activation. 5 The number of tissue mast cells is normally relatively constant, but during an acute or chronic inflammation the number can increase substantially. 6 The regulation of mast cell numbers is most likely regulated by proliferation, migration, and apoptosis or survival. The mechanisms that regulate the viability of mature mast cells or promote mast cell apoptosis are poorly investigated. SCF is a cardinal growth factor in mast cell biology, regulating mast cell growth, differentiation, adhesion, migration, and survival. 7 The number of tissue mast cells is at least in part regulated by SCF produced by resident stromal cells. SCF rescues mast cells from spontaneous apoptosis in vitro, whereas inhibition of SCF synthesis in vivo leads to mast cell apoptosis. [8][9][10] Although it is accepted that SCF is a prosurvival factor for mast cells, it remains largely unclear how SCF promotes survival in these cells.The B-cell lymphoma-2 (Bcl-2) family, which contains both prosurvival and proapoptotic proteins, are essential regulators of cell survival and apoptosis. 11 The levels and interactions of prosurvival versus proapoptotic Bcl-2 family proteins determine whether a cell survives or will undergo apoptosis. During apoptosis induced by proapoptotic Bcl-2 family members, cytochrome c is released from the mitochondria and a caspase cascade is activated that induces DNA fragmentation. 12,13 The prosurvival Bcl-2 family members include Bcl-2, Bcl-X L , Bcl-w, Mcl-1 (myeloid cell For personal use only. on May 12, 2018. by guest www.bloodjournal.org From leuk...

Ultrasmall gadolinium oxide nanoparticles doped with terbium ions were synthesized by the polyol route and characterized as a potentially bifunctional material with both fluorescent and magnetic contrast agent properties. The structural, optical, and magnetic properties of the organic-acid-capped and PEGylated Gd 2 O 3 :Tb 3+ nanocrystals were studied by HR-TEM, XPS, EDX, IR, PL, and SQUID. The luminescent/fluorescent property of the particles is attributable to the Tb 3+ ion located on the crystal lattice of the Gd 2 O 3 host. The paramagnetic behavior of the particles is discussed. Pilot studies investigating the capability of the nanoparticles for fluorescent labeling of living cells and as a MRI contrast agent were also performed. Cells of two cell lines (THP-1 cells and fibroblasts) were incubated with the particles, and intracellular particle distribution was visualized by confocal microscopy. The MRI relaxivity of the PEGylated nanoparticles in water at low Gd concentration was assessed showing a higher T 1 relaxation rate compared to conventional Gd-DTPA chelates and comparable to that of undoped Gd 2 O 3 nanoparticles.