Cross-Species Comparison of Genes Related to Nutrient Sensing Mechanisms Expressed along the Intestine

Introduction Intestinal chemosensory receptors and transporters are able to detect food-derived molecules and are involved in the modulation of gut hormone release. Gut hormones play an important role in the regulation of food intake and the control of gastrointestinal functioning. This mechanism is often referred to as “nutrient sensing”. Knowledge of the distribution of chemosensors along the intestinal tract is important to gain insight in nutrient detection and sensing, both pivotal processes for the regulation of food intake. However, most knowledge is derived from rodents, whereas studies in man and pig are limited, and cross-species comparisons are lacking. Aim To characterize and compare intestinal expression patterns of genes related to nutrient sensing in mice, pigs and humans. Methods Mucosal biopsy samples taken at six locations in human intestine (n = 40) were analyzed by qPCR. Intestinal scrapings from 14 locations in pigs (n = 6) and from 10 locations in mice (n = 4) were analyzed by qPCR and microarray, respectively. The gene expression of glucagon, cholecystokinin, peptide YY, glucagon-like peptide-1 receptor, taste receptor T1R3, sodium/glucose cotransporter, peptide transporter-1, GPR120, taste receptor T1R1, GPR119 and GPR93 was investigated. Partial least squares (PLS) modeling was used to compare the intestinal expression pattern between the three species. Results and conclusion The studied genes were found to display specific expression patterns along the intestinal tract. PLS analysis showed a high similarity between human, pig and mouse in the expression of genes related to nutrient sensing in the distal ileum, and between human and pig in the colon. The gene expression pattern was most deviating between the species in the proximal intestine. Our results give new insights in interspecies similarities and provide new leads for translational research and models aiming to modulate food intake processes in man

Ab initio study of isotropic and anisotropic hyperfine interactions in phosphoranyl and phosphorane anion radicals

A detailed ab initio study of isotropic and anisotropic hyperfine couplings (hfc) is presented for the ·PH4 (C2V, C3V), ·PF4 (C2V, C3V) and ·PF5- (C4V) radicals. Unrestricted Hartree—Fock (UHF), optionally with annihilation of the largest spin contaminant (UHF + AN), and restricted open-shell Hartree—Fock (ROHF) calculations are used to obtain electronic wave functions which describe doublet states. Throughout a 4-31G basis set is used and the influence of the implementation of d-type Gaussians on phosphorus is evaluated. All studied quantum chemical methods give good results for the isotropic hfc. Anisotropic hfcs are in good agreement with the experimental data only if the wave function describes a pure doublet state. The inclusion of d-functions leads to a serious decrease of the hyperfine interactions of the apical ligands in the C2V radicals and the equatorial ligands in the C3V radicals. The calculations clearly show that the fluorine dipolar hfc for the two ·PF4 isomers and the ·PF5- radical is not directed along the corresponding P—F linkage, but makes a pronounced angle (˜25°) with this bond

A novel approach to tracer-kinetic modeling for (macromolecular) dynamic contrast-enhanced MRI

\u3cp\u3ePurpose To develop a novel tracer-kinetic modeling approach for multi-agent dynamic contrast-enhanced MRI (DCE-MRI) that facilitates separate estimation of parameters characterizing blood flow and microvascular permeability within one individual. Methods Monte Carlo simulations were performed to investigate the performance of the constrained multi-agent model. Subsequently, multi-agent DCE-MRI was performed on tumor-bearing mice (n = 5) on a 7T Bruker scanner on three measurement days, in which two dendrimer-based contrast agents having high and intermediate molecular weight, respectively, along with gadoterate meglumine, were sequentially injected within one imaging session. Multi-agent data were simultaneously fit with the gamma capillary transit time model. Blood flow, mean capillary transit time, and bolus arrival time were constrained to be identical between the boluses, while extraction fractions and washout rate constants were separately determined for each agent. Results Simulations showed that constrained multi-agent model regressions led to less uncertainty and bias in estimated tracer-kinetic parameters compared with single-bolus modeling. The approach was successfully applied in vivo, and significant differences in the extraction fraction and washout rate constant between the agents, dependent on their molecular weight, were consistently observed. Conclusion A novel multi-agent tracer-kinetic modeling approach that enforces self-consistency of model parameters and can robustly characterize tumor vascular status was demonstrated.\u3c/p\u3

NMR nanoparticle diffusometry in hydrogels:enhancing sensitivity and selectivity

\u3cp\u3eFrom the diffusional behavior of nanoparticles in heterogeneous hydrogels, quantitative information about submicron structural features of the polymer matrix can be derived. Pulsed-gradient spin?echo NMR is often the method of choice because it measures diffusion of the whole ensemble of nanoparticles. However, in \u3csup\u3e1\u3c/sup\u3eH diffusion-ordered spectroscopy (DOSY), low-intensity nanoparticle signals have to be separated from a highly protonated background. To circumvent this, we prepared \u3csup\u3e19\u3c/sup\u3eF labeled, PEGylated, water-soluble dendritic nanoparticles with a \u3csup\u3e19\u3c/sup\u3eF loading of ∼% to enable background free \u3csup\u3e19\u3c/sup\u3eF DOSY experiments. \u3csup\u3e19\u3c/sup\u3eF nanoparticle diffusometry was benchmarked against \u3csup\u3e1\u3c/sup\u3eH diffusion-T\u3csub\u3e2\u3c/sub\u3e correlation spectroscopy (DRCOSY), which has a stronger signal separation potential than the commonly used \u3csup\u3e1\u3c/sup\u3eH DOSY experiment. We used bootstrap data resampling to estimate confidence intervals and stabilize 2D-Laplace inversion of DRCOSY data with high noise levels and artifacts, allowing quantitative diffusometry even at low magnetic field strengths (30 MHz). The employed methods offer significant advantages in terms of sensitivity and selectivity.\u3c/p\u3

Polymer bonding process for nanolithography

\u3cp\u3eWe have developed a lithography process which originates from imprint lithography and offers advantages over it. Unlike imprint lithography, not only the sample but also the mold is covered with a thermoplastic polymer. The mold and sample are brought into contact, pressed together and heated above the glass transition temperature of the thermoplast, causing the two polymer layers to become bonded (glued) together. A special treatment of the mold and sample surface causes the polymer film to stick only to the substrate after cooling. The bonding occurs at pressures and temperatures lower than those usually applied in imprint technology, and eliminates problems in conventional imprint technology that are related to lateral transport of the polymer.\u3c/p\u3

Stereochemical selection in phosphoranyl radical formation using ionization radiation

Recent electron spin resonance (ESR) experiments on phosphorus-centered radicals generated by ionizing radiation demonstrate that stereochemical aspects act strongly on the rate of radical formation and can be decisive in the selection between the possible resulting radical structures. This phenomenon was first established in a single crystal ESR study on radiogenic electron-capture phosphorus-centered radicals of the racemic and meso stereoisomers of 1.2-dimethyl-1,2-diphenyldiphosphine disulfide (1). The radiation process of the racemic form involves the formation of a symmetric species with a threeelectron bond in an overall low yield. The meso isomer, on the other hand, yields exclusively asymmetric radical configurations in which the unpaired electmn resides on one of the two phosphorus nuclei. The high intensity of the ESR spectra for the meso compound indicate a more efficient electron-capture process. A similar pronounced difference in radiosensitivity was observed for the Rp (1 and Sp (2) isomers of (4S,5R)-2-chloro-3,4-dimethyl-5-phenyl-1,3,2-Oxazaphospholidine 2-sulfide. Upon X irradiation, 1 readily results in an electron-capture phosphorus centered radical, whereas the concurrent process in 2 is almost completely absent. Since the geometric parameters of the atoms directly linked to phosphorus are very much alike for 1 and 2 il can be concluded that the efficiency of electron-capture at phosphorus strongly depends on the relative configuration of the distant chiral centers at C4 and C5

Efficient functionalization of additives at supramolecular material surfaces

Selective surface modification reactions can be performed on additives that are supramolecularly incorporated into supramolecular materials. Hereby, processing of the material, that regularly requires harsh processing conditions (i.e., the use of organic solvents and/or high temperatures), and functionalization can be decoupled. Moreover, high-resolution depth profiling by time-of-flight (ToF) secondary-ion mass spectrometry clearly shows distinct differences in surface and bulk material composition

Scaling behavior of dendritic nanoparticle mobility in semidilute polymer solutions

\u3cp\u3eIn our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly(ethylene glycol) (PEG, M\u3csub\u3ew\u3c/sub\u3e = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (d\u3csub\u3eh\u3c/sub\u3e = 3.4-11.0 nm) and with internal \u3csup\u3e19\u3c/sup\u3eF moieties allow for background-free \u3csup\u3e19\u3c/sup\u3eF NMR diffusion measurements. This way, we were able to assess the self-diffusion coefficients as a function of particle diameter and length scales (correlation length, tube diameter, polymer radius of gyration) with high resolution. Scaling arguments allowed us to visualize a clear crossover between particles probing a lower apparent viscosity to near macroviscosity when the nanoparticle size is comparable to the PEG polymer coil size. The same arguments are shown to correctly predict particle diffusion coefficients as a function of polymer concentration when the particles are smaller than the polymer coils.\u3c/p\u3

Improved evaluation of antivascular cancer therapy using constrained tracer-kinetic modeling for multiagent dynamic contrast-enhanced MRI

\u3cp\u3eDynamic contrast–enhanced MRI (DCE-MRI) is a promising technique for assessing the response of tumor vasculature to antivascular therapies. Multiagent DCE-MRI employs a combination of low and high molecular weight contrast agents, which potentially improves the accuracy of estimation of tumor hemodynamic and vascular permeability parameters. In this study, we used multiagent DCE-MRI to assess changes in tumor hemodynamics and vascular permeability after vascular-disrupting therapy. Multiagent DCE-MRI (sequential injection of G5 dendrimer, G2 dendrimer, and Gd-DOTA) was performed in tumor-bearing mice before, 2 and 24 hours after treatment with vascular disrupting agent DMXAA or placebo. Constrained DCE-MRI gamma capillary transit time modeling was used to estimate flow F, blood volume fraction v\u3csub\u3eb\u3c/sub\u3e, mean capillary transit time t\u3csub\u3ec\u3c/sub\u3e, bolus arrival time t\u3csub\u3ed\u3c/sub\u3e, extracellular extravascular fraction v\u3csub\u3ee\u3c/sub\u3e, vascular heterogeneity index a\u3csup\u3e1\u3c/sup\u3e (all identical between agents) and extraction fraction E (reflective of permeability), and transfer constant K\u3csup\u3etrans\u3c/sup\u3e (both agent-specific) in perfused pixels. F, v\u3csub\u3eb\u3c/sub\u3e, and a\u3csup\u3e1\u3c/sup\u3e decreased at both time points after DMXAA, whereas t\u3csub\u3ec\u3c/sub\u3e increased. E (G2 and G5) showed an initial increase, after which, both parameters restored. K\u3csup\u3etrans\u3c/sup\u3e (G2 and Gd-DOTA) decreased at both time points after treatment. In the control, placebo-treated animals, only F, t\u3csub\u3ec\u3c/sub\u3e, and K\u3csup\u3etrans\u3c/sup\u3e Gd-DOTA showed significant changes. Histologic perfused tumor fraction was significantly lower in DMXAA-treated versus control animals. Our results show how multiagent tracer-kinetic modeling can accurately determine the effects of vascular-disrupting therapy by separating simultaneous changes in tumor hemodynamics and vascular permeability. Significance: These findings describe a new approach to measure separately the effects of antivascular therapy on tumor hemodynamics and vascular permeability, which could help more rapidly and accurately assess the efficacy of experimental therapy of this class.\u3c/p\u3