Reduced secretion of triacylglycerol in CaCo-2 cells transfected with intestinal fatty acid-binding protein

The fatty acid-binding proteins are hypothesized to be involved in cellular fatty acid transport and trafficking. We established CaCo-2 cells stably transfected with intestinal fatty acid-binding protein (I-FABP) and examined how the expression of this protein may influence fatty acid metabolism. I-FABP expression was detectable in I-FABP-transfected cells, whereas parent CaCo-2 cells as well as mock-transfected cells failed to express detectable levels of I-FABP mRNA or protein at any stage of differentiation. For studies of lipid metabolism, cells were incubated with [¹⁴C]oleic acid in taurocholate micelles containing monoolein, and distribution of labeled fatty acid in cellular and secreted lipids was examined. In one transfected cell clone, expressing the highest level of I-FABP, labeled cellular triacylglycerol increased approximately twofold as compared to control cells. The level of intracellular triacylglycerol in two other I-FABP-transfected clones resembled that of control cells. However, secretion of triacylglycerol was markedly reduced in all the I-FABP-expressing cell lines. Our data suggest that increased expression of I-FABP leads to reduced triacylglycerol secretion in intestinal cells.     

Coupled model for the nonlinear analysis of sections made of anisotropic materials, subjected to general 3D loading. Part 2: Implementation and validation

A numerical model for the coupled analysis of cross-sections made of anisotropic materials under general combined loading was formulated in an accompanying paper (1). In this paper, additional aspects concerning its implementation and the scheme for nonlinear analysis are discussed. The model is validated by analyzing several isotropic and anisotropic elastic problems; excellent accuracy was obtained compared to closed-form solutions. Further, the case of a RC section presenting crack-induced anisotropy is investigated. The capability of the model to capture interactions between tangent and normal forces is proved. The conclusion drawn is that the developed model is a suitable sectional constitutive equation for 3D beam elements for realistic structural analysis.     

Process of extrusion in the unit of special design

Extrusion of paste materials is a means of processing powder materials to a granulated form. A powder material is mixed with a liquid and transformed to the form of paste. The paste has to have the appropriate flow properties to be able to be extruded. This is very important especially in the area of reduction between the barrel and die. There is the place where the paste has to deform itself and to flow into the holes of die that have a smaller cross section than is in the barrel. It is the zone where the rheology properties of paste and its speed have the biggest influence on the extrusion pressure. It can even happen that the paste can be dewatered under the pressure gradient in this place. If the rotor with blades is situated in this zone it has a positive influence on the process of extrusion. This element has an influence on the rate of shear strain and decreasing of the apparent viscosity with a following drop in the extrusion pressure. This paper describes research of the process of extrusion in equipment with separated drives of the screw and a rotor that is placed in the input zone in the hole of matrix. First influence of the operating speeds of screw and rotor on extrusion pressure is studied here, then it is compared with the torque that is needed for the drive of the rotor. According to the results it is evident that the extrusion pressure increases with the accrual of the speed of flowing paste and decreases with the increase of the rotors operating speed. The influence of flowing paste on the torque is complicated. There is an interval where the torque goes up and then an interval in which the torque decreases. The results of experiments confirmed that the rotor has a positive influence on the process of extrusion.We would like to thank the Grant Agency of the Slovak Republic for supporting our research work performed in the frame of Grant Project No.1/8092/01.     

Metabolic disturbance of tryptophan-nicotinamide conversion pathway by putative endocrine disruptors, bisphenol A and styrene monomer

Bisphenol A, a monomer of polycarbonate plastics, disturbed the conversion pathway of the amino acid tryptophan to the vitamin nicotinamide. The conversion ratio of tryptophan to nicotinamide was reduced to 1/15 by feeding a diet containing 1% bisphenol A. A putative disturbing reaction is kynurenine-->3-hydroxykynurenine, which is catalyzed by kynurenine monohydroxylase. This is an FAD-enzyme and requires NADPH as a coenzyme. Styrene monomer (1% addition to a normal diet) did not affect the food intake or the body weight, but slightly reduced the conversion ratio of tryptophan-nicotinamide.     

Polyalkylphosphazenes as solid proton conducting electrolytes

Several polydialkylphosphazenes, [P(RR) = N] _n , R and R = Me, Et, Pr; Bu, hexyl, were considered for the fabrication of solid proton conducting electrolytes due to their capacity to be protonated at the chain N atom. Protonated polydipropylphosphazene (PDPrP·nH⁺) was found the most suitable to this purpose. The solid state proton conducting properties and structural stability of PDPrP·nH⁺at 1H₃PO₄/N mole ratio in composite materials with polyphenylensulfide (Ryton® were studied by conductivity measurements in the 29–79°C temperature (T) and 0–33% relative humidity (RH) ranges, and by thermal analysis and NMR spectroscopy. The conductivity was found to increase upon increasing T and RH. Conductivity at 33% RH was in the same range of values reported for other polymers containing sulphonic or phosphonic acid groups. Conductivity in the dry state was in the range of values reported for polymers containing imidazole rings. NMR and conductivity data showed that upon aging in the above experimental conditions the polymer undergoes structural changes and exhibits higher conductivity.     

Design of bandstop filters by reactance transformation

The usual method for designing bandstop filters is the reactance transformation from a lowpass prototype. When the filter specifications do not satisfy geometrical symmetry, the choice of stopband central frequency constitutes an interesting problem. This letter shows that the mean square of the stopband edges is the stopband central frequency that leads to the lowest selectivity parameter of the prototype.     

Three-component competitive adsorption model for flow-through PAC systems. 1. Model development and verification with a PAC/membrane system

Natural organic matter (NOM) interferes with the adsorption of trace organic compounds on porous adsorbents such as powdered activated carbon (PAC) by pore blockage and direct competition for adsorption sites. The competitive effect of NOM in flow-through systems in which the retention time of the PAC is greater than the hydraulic retention time of the system can be magnified because NOM from the influent water can continue to adsorb on the PAC retained in the system. As a result, the adsorption capacity and the diffusion coefficient of trace compounds can decrease as NOM from the influent water accumulates. In this study, a dynamic three-component adsorption model was developed to quantitatively describe the removal of a trace compound from water in flow-through PAC processes. The system was simplified by using p-dichlorobenzene (p-DCB) to represent the NOM fraction that competes directly with the target trace organic atrazine for adsorption sites and by using poly(styrene sulfonate) (PSS-1.8k) to represent large, pore-blocking NOM. The model was based on the homogeneous surface diffusion assumption with the adsorption capacity of atrazine being gradually adjusted using a simplified version of the ideal adsorbed solution theory model developed in this study. The surface diffusion coefficients of atrazine and p-DCB were modeled as a function of the surface concentration of the pore-blocking compound, PSS-1.8k. The model was verified experimentally with a PAC/microfiltration (MF) system. The use of single-solute adsorption parameters obtained from batch isotherm and kinetic tests resulted in good model predictions for the adsorption of atrazine and the two model compounds under operating conditions typical of PAC/MF systems. The model will be applied to study various operating conditions and other system parameters of PAC/membrane systems in part 2 of this study.     

Ultra violet resonance Raman spectroscopy in lignin analysis: determination of characteristic vibrations of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures

Raman spectroscopy of wood and lignin samples is preferably carried out in the near-infrared region because lignin produces an intense laser-induced fluorescence background at visible excitation wavelengths. However, excitation of aromatic and conjugated lignin structures with deep ultra violet (UV) light gives resonance-enhanced Raman signals while the overlapping fluorescence is eliminated. In this study, ultra violet resonance Raman (UVRR) spectroscopy was used to define characteristic vibration bands of model compounds of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures at three excitation wavelengths (229, 244, and 257 nm). The intensities of each band, relative to the intensity of the aromatic vibration band at 1600 cm-1, were defined and the most suitable excitation wavelength was suggested for each structure. p-Hydroxyphenyl structures showed intensive characteristic bands at 1217-1214 and 1179-1167 cm-1 with excitation at 244 nm, whereas the bands of guaiacyl structures were more intensive with 257 nm excitation. Most intensive characteristic bands of guaiacyl structures were found at 1289-1279, 1187-1185, 1158-1155, and 791-704 cm-1. Syringyl structures had almost identical spectra with 244 and 257 nm excitations with characteristic bands at 1514-1506, 1333-1330, and 981-962 cm-1. The characteristic bands of the three structural units were also found from the compression wood, softwood, and hardwood samples, indicating that UVRR spectroscopy can be applied for the determination of chemical structures of lignin.