Metabolic features of rats resistant to a high-fat diet.

OBJECTIVE: We assessed the metabolic characteristics of high-fat-diet-resistant (DR) rats. METHODS: Body weight, energy intake, locomotor activity, oxygen consumption, plasma leptin and lipid levels, size of visceral-fat adipocytes, and mRNA levels of genes related to lipid metabolism were measured in control rats fed standard chow and in obesity-prone (high-fat-diet-induced obesity, DIO) and DR rats fed a high-fat diet. Glucose tolerance and insulin tolerance tests were also performed. RESULTS: DIO rats gained weight more rapidly than did DR and control rats; DR rats gained less weight than did DIO rats despite similar energy intake. Energy expenditure did not differ among the three groups. The diameter of visceral-fat adipocytes was similar in DR and control rats. mRNA levels of genes involved in lipogenesis, such as fatty acid synthase and acetyl-CoA carboxylase, tended to be lower in DR than in control and DIO rats, whereas those of carnitine palmitoyltransferase 1a, which is involved in fatty acid ß-oxidation, were greater in DR rats than in the other groups. DIO rats showed hyperinsulinemia and glucose intolerance, whereas DR rats had high sensitivity to insulin. CONCLUSION: DR rats show suppression of lipogenesis and acceleration of fatty acid ß-oxidation in the visceral fat. These characteristics likely contribute to the anti-obesity phenotype of DR rats.

Effects of hydrodynamic interaction on the equivalent conductivity minimum of electrolyte solutions in solvents of low dielectric constant.

Brownian dynamics simulation on model electrolyte solutions in our previous work [T. Yamaguchi et al., J. Chem. Phys. 134, 244506 (2011)] is extended to include the hydrodynamic interaction between ions, in order to examine its effects on ionic mobility in solvents of low dielectric constant. The effects of the hydrodynamic interaction are rather small as a whole, and the equivalent conductivity minimum is observed in systems with the hydrodynamic interaction. The hydrodynamic interaction increases the self-diffusion coefficient while decreases the equivalent conductivity, thereby increases the deviation from the Nernst-Einstein relationship. Based on the analysis of the time-dependent ionic mobilities, these changes are elucidated in terms of the electrophoretic and relaxation effects. It is also demonstrated that the concentration dependence of the ionic mobilities with the hydrodynamic interaction is reproduced fairly well by a theoretical calculation.

Dynamic mechanism of equivalent conductivity minimum of electrolyte solution.

The theory on electric conductivity of electrolyte solutions we have developed [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys. 127, 064508 (2007)] is applied to a model electrolyte solution that shows a minimum of equivalent conductivity as the function of concentration [T. Yamaguchi, T. Akatsuka, and S. Koda, J. Chem. Phys. 134, 244506 (2011)]. The theory succeeds in reproducing the equivalent conductivity minimum, whereas the mode-coupling theory (MCT) underestimates the conductivity in the low-concentration regime. The theory can also reproduce the decrease in the relaxation time of conductivity with increasing the concentration we have demonstrated with a Brownian dynamics simulation. A detailed analysis shows that the relaxation of the conductivity occurs through two processes. The faster one corresponds to the collision between a cation and an anion, and the slower one does to the polarization of the ionic atmosphere. The increase in the equivalent conductivity with concentration is attributed to the decrease in the effect of the ionic atmosphere, which is in turn explained by the fact that the counter ion cannot penetrate into the repulsive core when the Debye screening length is compatible or smaller than the ionic diameter. The same mechanism is also observed in MCT calculation with static structure factor determined by mean-spherical approximation.

Brownian dynamics simulation of a model simple electrolyte in solvents of low dielectric constant.

Brownian dynamics simulations are performed to investigate the ionic transport of model simple electrolytes, in which ions are interacting with each other through the repulsive core and Coulombic interactions. The equivalent conductivity and self-diffusion coefficient show minima as the function of the number density of ions when the dielectric constant of the solvent is low. Although the minimum of the former is in harmony with various experiments, no experiment has ever been reported on that of the latter. The analysis of time-dependent transport coefficients reveals that the presence of the minima is ascribed to the slow dynamics, rather than to static association models. The inclusion of a model function that resembles the short-range part of the potential of mean force induced by solvent affects the transport coefficients qualitatively, which suggests the importance of solvent-induced potential of mean force in the conduction mechanism of electrolytes in solvents of low dielectric constant.

Roles of translational and reorientational modes in translational diffusion of high-pressure water: comparison with soft-core fluids.

The dynamics of two soft-core fluids that show the increase in diffusivity with isothermal compression is studied with the mode-coupling theory (MCT). The anomalous density dependence of the diffusivity of these fluids is reproduced by the theory, and it is ascribed to the decrease in the first peak of the structure factor. The mechanism is quite different from that of high-pressure water revealed by MCT on molecular liquids described by the interaction-site model [T. Yamaguchi, S.-H. Chong, and F. Hirata, J. Chem. Phys., 119, 1021 (2003)]. The structures used in that study, calculated by the reference interaction-site model integral equation theory, showed the increase in the height of the first peak of the structure factor between oxygen atoms, whereas the structure obtained by molecular dynamics (MD) simulations shows the decrease in the peak height. In this work, calculations with MCT are performed on the simple fluids whose structure factor is the same as that between oxygen atoms of water from MD simulation, in order to clarify the role of translational structure on the increase in diffusivity with compression. The conclusion is that both the translational and reorientational modes contribute to the increase in diffusivity, and the effect of the latter is indispensable for the anomaly alone at least above freezing temperature.

Mode-coupling theoretical analysis of transport and relaxation properties of liquid dimethylimidazolium chloride.

The mode-coupling theory for molecular liquids based on the interaction-site model is applied to a representative molecular ionic liquid, dimethylimidazolium chloride, and dynamic properties such as shear viscosity, self-diffusion coefficients, reorientational relaxation time, electric conductivity, and dielectric relaxation spectrum are analyzed. Molecular dynamics (MD) simulation is also performed on the same system for comparison. The theory captures the characteristics of the dynamics of the ionic liquid qualitatively, although theoretical relaxation times are several times larger than those from the MD simulation. Large relaxations are found in the 100 MHz region in the dispersion of the shear viscosity and the dielectric relaxation, in harmony with various experiments. The relaxations of the self-diffusion coefficients are also found in the same frequency region. The dielectric relaxation spectrum is divided into the contributions of the translational and reorientational modes, and it is demonstrated that the relaxation in the 100 MHz region mainly stems from the translational modes. The zero-frequency electric conductivity is close to the value predicted by the Nernst-Einstein equation in both MD simulation and theoretical calculation. However, the frequency dependence of the electric conductivity is different from those of self-diffusion coefficients in that the former is smaller than the latter in the gigahertz-terahertz region, which is compensated by the smaller dispersion of the former in the 100 MHz region. The analysis of the theoretical calculation shows that the difference in their frequency dependence is due to the different contribution of the short- and long-range liquid structures.

A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions. II. Effect of hydrodynamic interaction.

The theory on the frequency-dependent electric conductivity of electrolyte solutions proposed previously by Yamaguchi et al. [J. Chem. Phys. 127, 234501 (2007)] is extended to include the hydrodynamic interaction between ions. The theory is applied to the aqueous solution of NaCl and the concentration dependence of the conductivity agrees well with that determined by experiments. The effects of the hydrodynamic and relaxation effects are highly nonadditive in the concentrated solution, because the hydrodynamic interaction between ions affects the time-dependent response of the ionic atmosphere. The decrease in the electric conductivity is divided into the contributions of ion pair distribution at various distances. The long-range ionic atmosphere plays a major role at the concentration as low as 0.01 mol/kg, whereas the contribution of the contact ion pair region is important at 1 mol/kg. The magnitude of the contribution of the contact ion pair region is scarcely dependent on the presence of the hydrodynamic interaction. The transport number of cation is calculated to be a decreasing function of concentration as is observed in experiments.

Gene transfection into adherent cells using electroporation on a dendrimer-modified gold electrode.

Gene transfection into adherent cells from plasmid DNA (pDNA)-arrayed substrates known as gene transfection arrays appears to be a promising tool for the high-throughput analysis of gene functions and protein-protein interaction networks. We tested the ability of electric pulse-stimulated gene transfection from a substrate to overcome low expression efficiency and cross contamination between spots on arrays. We prepared the electrodes used for electric pulse-stimulated gene transfection by sequentially loading a gold thin layer, a self-assembled monolayer of a carboxylic acid-terminated alkanethiol (COOH-SAM), and poly(amidoamine) (PAMAM) dendrimers, either through electrostatic interactions or by covalent linkage to COOH-SAM and then to pDNA. When dendrimers were loaded onto the electrode using electrostatic interactions, the gene-expression efficiency of adherent cells increased as the generation numbers of the dendrimers that we used increased. Gene expression was rarely observed in adherent cells when dendrimers were covalently immobilized onto the electrode. Additionally, we successfully demonstrated site-specific gene transfer using a dendrimer-array electrode with no cross contamination between spots on the electrode.

A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions.

The theory on the ultrasonic absorption of electrolyte solutions we have proposed previously [T. Yamaguchi et al., J. Chem. Phys. 126, 144505 (2007)] is extended to calculate the frequency-dependent electric conductivity of the solution. The ionic contribution of the dielectric relaxation spectrum is obtained at the same time. The theory is able to handle the contributions of both the ion-pair dynamics and the relaxation of ionic atmosphere, as is the case of ultrasonic absorption. The effect of the barrier height between the contact and solvent-separated ion pairs is investigated in detail. It is clarified that the competition between the dissociation and reorientational relaxation rates of the contact ion pair is an important factor for the ion pair to be regarded as the ion pair in terms of ionic conductivity.

Theoretical study on the sound absorption of electrolytic solutions. II. Assignments of relaxations.

The theory on the ultrasonic absorption spectrum of electrolytic solutions recently proposed by us is applied to the model system that resembles to the aqueous solution of MgSO4. The charges on ions are reduced to +/-1.5e in order to obtain the equilibrium structure by the integral equation theory. The theory reproduces the existence of two relaxations around 100 kHz and 1 GHz. The physical origin of the relaxation is analyzed based on the theoretical expression. The slower relaxation is shown to originate in the formation of contact ion pair, in harmony with the conventional assignment. The amplitude of this relaxation agrees with the experimental one fairly well. The absorption cross section is a weakly increasing function of the concentration of the salt in theory, whereas it depends little on the concentration in experiment, which is ascribed to the weaker association of the pair in the theory. The deviation from the Debye relaxation is found for the faster process, and the concentration dependence is small. The analysis shows that this relaxation stems from the coupling between the pressure and the long-range concentration fluctuation, and the concentration independence and the non-Debye relaxation are explained based on the theoretical analysis. In particular, the theory demonstrates that this process has the t(-3/2) tail in the time domain, which is confirmed by numerical calculation. The deviation of the theoretical relaxation amplitude from the experimental one is elucidated in terms of the theoretical expression of the coefficient.

Theoretical study on the sound absorption of electrolytic solutions. I. Theoretical formulation.

A theory is formulated that describes the sound absorption of electrolytic solutions due to the relative motion of ions, including the formation of ion pairs. The theory is based on the Kubo-Green formula for the bulk viscosity. The time correlation function of the pressure is projected onto the bilinear product of the density modes of ions. The time development of the product of density modes is described by the diffusive limit of the generalized Langevin equation, and approximate expressions for the three- and four-body correlation functions required are given with the hypernetted-chain integral equation theory. Calculations on the aqueous solutions of model electrolytes are performed. It is demonstrated that the theory describes both the activated barrier crossing between contact and solvent-separated ion pairs and the Coulombic correlation between ions.

Acoustic analysis of bound rubber formed in silica/SBR compounds.

The compressibility of the bound rubber around the silica particle was evaluated by an acoustic technique. The density and the longitudinal wave velocity of a silica/SBR compound were measured as a function of the silica content. The density increased linearly with the filler content. The longitudinal wave velocity was almost constant within the experimental error. The mass ratio of the bound rubber to the silica in the silica/SBR compounds was 1.08+/-0.03 kg kg(-1) which was measured by a thermal gravimetric analysis (TGA). The partial specific adiabatic compressibility of the silica was estimated as (0.1+/-0.5) x 10(-10) Pa(-1) on the basis of a three states model. The adiabatic compressibility of the bound rubbers in the silica/SBR compounds was (4.6+/-0.5) x 10(-10) Pa(-1). The compressibility was almost the same as that of the SBR, and the value was twice larger than the compressibility of the bound rubber formed in a CB/SBR composite.

Solute dependence of mobility of solvent molecules in solvophobic solute solutions: Dielectric relaxation of nonpolar solute/alcohol mixtures.

The dielectric relaxation spectra of alcohol/nonpolar solute mixtures are measured at several temperatures (-15 degrees C < or = T < or = 25 degrees C) and for several molar fractions of solute (0 < or = X(s) < or = 0.114) in the frequency range of 200 MHz < or = nu < or = 20 GHz. The double-Debye-type function is used for fitting of the spectra of mixtures, and the mean dielectric relaxation times (tau(mean)) of alcohol molecules are determined. In the systems having strong interaction between alcohol and nonpolar solutes, tau(mean) becomes shorter with an increase in the concentration of the solutes. On the other hand, tau(mean) becomes longer in the system having weak interaction between alcohol and nonpolar solutes. These results contradict with our intuitive predictions, do not correspond to mixing enthalpy, and are not explained by the hydrodynamic theory. They are attributed to the mechanism of the coupling between long-range electrostatic interactions and concentration fluctuation caused by the addition of solutes, which is suggested by Yamaguchi et al. based on the mode-coupling theory (Yamaguchi, T.; Matsuoka, T.; Koda, S. J. Chem. Phys. 2004, 120, 7590).

Mode-coupling study on the dynamics of hydrophobic hydration II: Aqueous solutions of benzene and rare gases.

The dynamic properties of both the solute and solvent of the aqueous solution of benzene, xenon and neon are calculated by the mode-coupling theory for molecular liquids based on the interaction-site model. The B-coefficients of the reorientational relaxation and the translational diffusion of the solvent are evaluated from their dependence on the concentration of the solute, and the reorientational relaxation time of water within the hydration shell is estimated based on the two-state model. The reorientational relaxation times of water in the bulk and within the hydration shell, that of solute, and the translational diffusion coefficients of solute and solvent, are calculated at 0-30 degrees C. The temperature dependence of these dynamic properties is in qualitative agreement with that of NMR experiment reported by Nakahara et al. (M. Nakahara, C. Wakai, Y. Yoshimoto and N. Matubayasi, J. Phys. Chem., 1996, 100, 1345-1349, ref. 36), although the agreement of the absolute values is not so good. The B-coefficients of the reorientational relaxation times for benzene, xenon and neon solution are correlated with the hydration number and the partial molar volume of the solute. The proportionality with the latter is better than that with the former. These results support the mechanism that the retardation of the mobility of water is caused by the cavity formation of the solute, as previously suggested by us (T. Yamaguchi, T. Matsuoka and S. Koda, J. Chem. Phys., 2004, 120, 7590-7601, ref. 34), rather than the conventional one that the rigid hydration structure formed around the hydrophobic solute reduces the mobility of water.

Generalized Langevin theory on the dynamics of simple fluids under external fields.

A theory on the time development of the density and current fields of simple fluids under an external field is formulated through the generalized Langevin formalism. The theory is applied to the linear solvation dynamics of a fixed solute regarding the solute as the external field on the solvent. The solute-solvent-solvent three-body correlation function is taken into account through the hypernetted-chain integral equation theory, and the time correlation function of the random force is approximated by that in the absence of the solute. The theoretical results are compared with those of molecular-dynamics (MD) simulation and the surrogate theory. As for the transient response of the density field, our theory is shown to be free from the artifact of the surrogate theory that the solvent can penetrate into the repulsive core of the solute during the relaxation. We have also found a large quantitative improvement of the solvation correlation function compared with the surrogate theory. In particular, the short-time part of the solvation correlation function is in almost perfect agreement with that from the MD simulation, reflecting that the short-time expansion of the theoretical solvation correlation function is exact up to t(2) with the exact three-body correlation function. A quantitative improvement is found in the long-time region, too. Our theory is also applied to the force-force time correlation function of a fixed solute, and similar improvement is obtained, which suggests that our present theory can be a basis to improve the mode-coupling theory on the solute diffusion.

Molecular dynamics simulation study on the transient response of solvation structure during the translational diffusion of solute.

The transient response function of the density profile of the solvent around a solute during the translational diffusion of the solute is formulated based on the generalized Langevin formalism. The resultant theory is applied to both neat Lennard-Jones fluids and cations in liquid water, and the response functions are obtained from the analysis of the molecular dynamics simulations. In the case of the self-diffusion of Lennard-Jones fluids, the responses of the solvation structures are in harmony with conventional pictures based on the mode-coupling theory, that is, the binary collision in the low-density fluids, the backflow effect from medium to high density fluids, and the backscatter effect in the liquids near the triple point. In the case of cations in water, the qualitative behavior is strongly dependent on the size of cations. The pictures similar to simple dense liquids are obtained for the large ion and the neutral molecule, while the solvent waters within the first solvation shell of small ions show an oscillatory response in the short-time region. In particular, the oscillation is remarkably underdumped for lithium ion. The origin of the oscillation is discussed in relation to the theoretical treatment of the translational diffusion of ions in water.

Development of porous ceramics with well-controlled porosities and pore sizes from apatite fibers and their evaluations.

Porous hydroxyapatite (HAp) ceramics possessing well-controlled porosities and pore sizes were developed by firing apatite-fiber compacts mixed with carbon beads and agar. The total porosities could be controlled in the range from 40 to 85% by varying compaction pressure (20-40 MPa), firing temperature (1000-1300 degrees C) and carbon/HAp ratio (0/10-10/10 (w/w)). Most of the pores were regarded as open pores. The pore sizes were mainly affected by the carbon-bead diameter (5, 20 or 150 microm) and partly by the compaction pressure and the firing temperature. The pore sizes of the porous HAp ceramics derived from the carbon beads of 150 microm in diameter were distributed in the two separate ranges of several micrometers and more than 100 microm.

Mode-coupling study on the dynamics of hydrophobic hydration.

The molecular motion of water in water-hydrophobic solute mixtures was investigated by the mode-coupling theory for molecular liquids based on the interaction-site description. When the model Lennard-Jones solute was mixed with water, both the translational and reorientational motions of solvent water become slower, in harmony with various experiments and molecular dynamics simulations. We compared the mechanism of the slowing down with that of the pressure dependence of the molecular motion of neat water [T. Yamaguchi, S.-H. Chong, and F. Hirata, J. Chem. Phys. 119, 1021 (2003)]. We found that the decrease in the solvent mobility caused by the solute can essentially be elucidated by the same mechanism: That is, the fluctuation of the number density of solvent due to the cavity formation by the solute strengthens the friction on the collective polarization through the dielectric friction mechanism: We also employed the solute molecule that is the same as solvent water except for the amount of partial charges, in order to alter the strength of the solute-solvent interaction continuously. The mobility of the solvent water was reduced both by the hydrophobic and strongly hydrophilic solutes, but it was enhanced in the intermediate case. Such a behavior was discussed in connection with the concept of positive and negative hydrations.

Effect of particle addition on sonochemical reaction.

Enhancement of chemical reaction with a photocatalyst of titanium dioxide (TiO(2)) by ultrasonic irradiation is studied through the absorbance measurements for liberation of iodine from a KI aqueous solution as an index of oxidation reaction. It is well known as a synergetic effect that the addition of TiO(2) fine particles under UV has an ability to enhance the yield in chemical reaction with OH-radical from hot spot at violent collapse of cavitation bubbles with intense ultrasound. In this study, the absorbance is measured after simultaneous irradiation of ultrasound and UV with the addition of TiO(2) much less than the usual concentration by two orders of content. It is shown that, even in case of quite a little TiO(2) addition where the photocatalytic effect is less, the yield is enhanced obviously in comparison with the summation in yield of independent procedure of ultrasound without TiO(2) and UV with TiO(2). The absorbance-peak deviation to the shorter wavelength implies the generation of titanium peroxide (TiO(3)). The effect of particle addition is due to the chemically activated particle surface on the TiO(2) and probably to the increase in the cavitation bubbles that results in promoting a transfer of OH-radical and other oxidants to bulk liquid region at the collapse.

Polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in serum samples of workers at intermittently burning municipal waste incinerators in Japan.

OBJECTIVES: To find whether or not incinerator workers employed at intermittently burning municipal incineration plants are exposed to high concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). METHODS: 20 Workers employed at three municipal waste incineration plants (incinerator workers) and 20 controls were studied. The previous job, dietary, smoking, and body weight and height were obtained from a questionnaire survey. Concentrations of PCDDs and PCDFs were measured in serum samples of the workers and the deposited dust of the plants. The influence of occupational exposure on concentrations of PCDDs and PCDFs in serum samples was examined by multiple regression analysis. RESULTS: Dust analysis showed that dominant constituents were octachlorodibenzo-p-dioxin (OCDD) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) among the PCDDs, and 1,2,3,4,6,7,8-heptachlorodibenzofuran (HpCDF) and octachlorodibenzofuran (OCDF) among the PCDFs. The toxicity equivalents (TEQs) of summed PCDDs and PCDFs in the deposited dust were 0.91, 33, and 11 ng TEQ/g, respectively, for plants I, II, and III. The means of TEQ in serum samples of summed PCDDs and PCDFs in the incinerator workers and controls were 22.8 and 16.4 pg TEQ/g lipid for area I, 29.4 and 19.3 pg TEQ/g lipid for area II, and 22.8 and 24.9 pg TEQ/g lipid for area III, which were almost the same as for the general population of Japan. No significant differences in the TEQ of PCDDs and TEQ of PCDDs and PCDDs were found between the incinerator workers and the controls. However, the TEQ of PCDFs was significantly higher among the incinerator workers in areas I and II, and the 1,2,3,4,6,7,8-HpCDF concentration was also significantly higher for all three areas. When the occupational exposure index for each constituent of PCDDs and PCDFs was defined as the product of the duration of employment at the incineration plant and the concentration of the constituent in the deposited dust, multiple regression analysis showed that the concentrations of HxCDF, HpCDF, and TEQ of PCDFs in serum samples increased with the occupational exposure index. The multiple regression analysis also suggested that significant factors affecting the concentrations in serum samples were area for HxCDD, age for TCDD, PeCDD, PeCDF, TEQ of PCDDs, TEQ of PCDFs, and TEQ of summed PCDDs and PCDFs, and BMI for HxCDD, HpCDD, and OCDD. CONCLUSION: This study showed that incinerator workers employed at intermittently burning incineration plants were not necessarily exposed to high concentrations of PCDDs and PCDFs. However, the increases in the concentrations in serum of HxCDF, HpCDF and TEQ of PCDFs with the occupational exposure index suggest that the incinerator workers had inhaled dust containing PCDDs and PCDFs during their work.