The effect of lipids on taurocholate absorption from intestinal loops in the rat

The rates of uptake and serosal trans-fer of [¹⁴C]-labelled taurocholate (7.77 mM in bicarbonate buffer, pH 6.5) were determined in situ in ligated segments of rat intestine in the presence of lipids. Oleic acid, monoolein, lecithin, and lysolecithin enhanced taurocholate uptake and transfer in the jejunum, each lipid exhibiting and optimal concentration at which the bile acid fluxes were maximal. The maximal rates of bile acid uptake observed with the various lipids were close to four times the uptake rates found with the lipid-free taurocholate medium, whereas serosal transfer rates under optimal conditions were enhanced about six-fold. The optimal concentrations differed widely among the various lipids, being inversely related to the lipids’ polarity. Simultaneous measurement of taurocholate and [³H]-labelled oleic acid showed that under optimal conditions, when the molar concentration of oleic acid was about equal to that of the bile acid, the fatty aicd and bile acid also exhibited closely similar rates of absorption. At other fatty acid concentrations, the fractional rate of absorption of the bile acid was much lower than that of the fatty acid. The rates of uptake and serosal transfer of pure taurocholate by the ileum exceeded those of the jejunum by factors of about 7 and 15, respectively, but in the presence of lipids this difference in absorptive capacity for bile acid between the distal and proximal segment largely disappeared.     

Transformation of single drop breakup from binary to ternary and multiple in turbulent jet flows

By releasing liquid drops in turbulent jet flows,we investigated the transformation of single drop breakup from binary to ternary and multiple.Silicone oil and deionized water were the dispersed phase and con-tinuous phase,respectively.The probability of binary,ternary,and multiple breakup of oil drops in jet flows is a function of the jet Reynolds number.To address the underlying mechanisms of this transfor-mation of drop breakup,we performed two-dimensional particle image velocimetry(PIV)experiments of single-phase jet flows.With the combination of drop breakup phenomenon and two-dimensional PIV results in a single-phase flow field,these transformation conditions can be estimated:the capillary number ranges from 0.17 to 0.27,and the Weber number ranges from 55 to 111.     

A comparison of lycopene and canthaxanthin absorption: Using the rat to study the absorption of non-provitamin a carotenoids

The purpose of this study was to validate the use of the mesenteric lymph duct cannulated rat to study the absorption of carotenoids which do not have provitamin Activity. The absorption of two carotenoids, a hydrocarbon carotenoid (lycopene) and a xanthophyll carotenoid (canthaxanthin), were investigated. In the first experiment, lipid emulsions containing lycopene (LYC) or canthaxanthin (CTX) were continuously infused into the duodenum, and lymph was collected for analysis at 2-h intervals. The time course for absorption of carotenoids and triacylglycerol (TAG) was similar. Carotenoids and TAG reached steady-state concentrations in the lymph by 6 h. There was no evidence for a delayed release of either carotenoid from the intestine relative to TAG. During a second experiment, emulsions containing increasing concentrations of LYC or CTX (5, 10, 15, 20 μmol/L) were infused. The LYC and CTX in the lymph increased in a dose-dependent manner. The average efficiency of CTX absorption was 16% while the efficiency of LYC absorption averaged only 6%. Efficiency of carotenoid absorption was not related to concentration infused. Finally, to test whether LYC and CTX interact during absorption both were added to a lipid emulsion at equal concentrations (20 μmol/L) and infused. The carotenoids did not significantly affect each other's absorption. These results demonstrate the usefulness of the rat as an animal model to study the absorption of non-provitamin A carotenoids.     

Thermogelation of methylcellulose from solution in N,N‐dimethylformamide and characterization of the transparent gels

A transparent gel was prepared through the cooling of a methylcellulose (MC) solution in N,N‐dimethylformamide (DMF) at 80°C to a lower temperature. The temperature at which gelation occurred was dependent on the concentration of the solution. The gel temperature increased with an increase in the concentration of MC. The gelation of MC in DMF was studied by means of optical microscopy (OM), differential scanning calorimetry, and dynamic mechanical analysis (DMA). The OM studies revealed the presence of loosely bound beads of MC with DMF at a lower concentration. These beads became interconnected to rods, and subsequently, a continuous, thick gel was formed as the concentration increased. From DMA studies, it was observed that the loss modulus of the gel crossed over the storage modulus at two different frequencies. This indicated the presence of two types of network structures generated from the weak and strong associations of MC with the organic solvent DMF. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Density, viscosity, and surface tension of water+ethanol mixtures from 293 to 323K

Density, viscosity, and surface tension of liquids are important physicochemical properties which affect mass and heat transfer in solutions. The density, viscosity, and surface tension of binary mixture of water+ethanol at 293, 298, 303, 308, 313, 318, and 323 K are reported and compared with the available literature data. The findings of these comparisons show how the measured data are reproducible from different laboratories. The molar volume of water+ ethanol mixtures are also calculated using measured density values. The Jouyban-Acree model was used for mathematical correlation of the data. The relative deviation (RD) was used as an error criterion and the RD values for correlation of density, viscosity, surface tension and molar volume data at investigated temperatures are 0.1±0.1%, 10.4±9.5%, 4.2±3.6%, and 0.3±0.3%, respectively. The corresponding RDs for the predicted properties after training using the experimental data at 298 K are 0.2±0.2%, 14.1±15.8%, 5.4±4.6% and 0.4±0.3%, respectively, for density, viscosity, surface tension, and molar volume data. This study shows that the Jouyban-Acree model can correlate/predict physicochemical properties of the mixtures of solvents at different temperatures with acceptable error in calculation.     

Complex refractive index,single scattering albedo,and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors

Refractive index and optical properties of biogenic and anthropogenic secondary organic aerosol (SOA) particles were investigated. Aerosol precursors, namely longifolene, α-pinene, 1-methylnaphthalene, phenol, and toluene were oxidized in a Teflon chamber to produce SOA particles under different initial hydrocarbon concentrations and hydroxyl radical sources, reflecting exposures to different levels of nitrogen oxides (NO_x). The real and imaginary components (n and k, respectively) of the refractive index at 375?nm and 632?nm were determined by Mie theory calculations through an iterative process, using the χ² function to evaluate the fitness of the predicted optical parameters with the measured scattering, absorption, and extinction coefficients from a Photoacoustic Extinctiometer and Cavity Attenuated Phase Shift Spectrometer. Single scattering albedo (SSA) and bulk mass absorption coefficient (MAC) at 375?nm were calculated. SSA values of SOA particles from biogenic precursors (longifolene and α-pinene) were ～0.98–0.99 (～6.3% uncertainty), reflecting purely scattering aerosols regardless of the NO_x regime. However, SOA particles from aromatic precursors were more absorbing and displayed NO_x-dependent SSA values. For 1-methylnaphthalene SOA particles, SSA values of 0.92–0.95 and ～0.75–0.90 (～6.1% uncertainty) were observed under intermediate- and high-NO_x conditions, respectively, reflecting the absorbing effects of SOA particles and NO_x chemistry for this aromatic system. In mixtures of longifolene and phenol or longifolene and toluene SOA under intermediate- and high-NO_x conditions, k values of the aromatic-related component of the SOA mixture were higher than that of 1-methylnaphthalene SOA particles. With the increase in OH exposure, k_phenol decreased from 0.10 to 0.02 and 0.22 to 0.05 for intermediate- and high-NO_x conditions, respectively. A simple relative radiative forcing calculation for urban environments at λ?=?375?nm suggests the influence of absorbing SOA particles on relative radiative forcing at this wavelength is most significant for aerosol sizes greater than 0.4?µm.

Copyright © 2019 American Association for Aerosol Research     

Studies on the absorption and disposition of 3H-labelled talc in the rat,mouse, guinea-pig and rabbit

The absorption and disposition of talc was studied in rats, mice and guinea-pigs, following a single oral dose of ³H-labelled material. The translocation of talc in the rabbit urogenital tract was studied after single and multiple intravaginal applications. More than 95% of the dose of orally administered talc was excreted in the faeces within 3–4 days by all three species studied. Traces of radioactivity found in the urine probably reflected contamination of the samples by contact with the faeces and the presence of labile ³H associated with the ³H-labelled talc. No translocation of talc to the liver or kidneys was found. In the rabbit study, no translocation of talc into the ovaries was detected.     

The role of gastric lipolysis on fat absorption and bile acid metabolism in the rat

In vivo studies were carried out in young Sprague-Dawley rats to examine the role of gastric lipolysis on fat absorption and bile acid metabolism. When fed by gastric perfusion 5 times (corn oil, 4 g/day) their usual dietary intake of fat, rats deprived of lingual lipase by the creation of an esophageal fistula had a significant degree of fat and bile acid malabsorption as well as a shortened bile acid halflife when compared to animals with a gastrostomy. The % fat absorption, bile acid loss and bile acid pool were normal in 2 groups of esophageal fistula rats fed the same quantity of corn oil or twice (8 g/day) that amount as a fine emulsion. In view of a negligible gastric lipase activity in animals with an esophageal fistula and of decreased hydrolysis of a triglyceride test meal, these data suggest that gastric lipolysis is of physiological importance in situations where lipolytic mechanisms are stressed by a large fat intake. Its principal role is to potentiate intestinal lipolysis by facilitating the emulsification of dietary lipids through its formed products and, therefore, the contact of pancreatic lipase with its substrates.     

Assessment of applicability of carreau,ellis, and cross models to the viscosity data of resin solutions

In this study, three popular rheological models, which fit adequately well to viscosity data of polymeric materials, are chosen for making a comparative assessment of their applicability to practical data. The resulting nonlinear equations of the three models are solved by using Levenberg Marquardt's algorithm. The assessment of their applicability to practical viscosity data of 66 solutions of two resins in 11 solvent systems and reported data of other polymers has been analyzed. The Carreau and Ellis models have yielded unique global estimates for various rheological parameters, whereas the Cross model yielded local solutions. However, both Carreau and Cross models yielded parameter estimates with low overall residual error. The three models are found to have good applicability to viscosity data of resin solutions in good and moderate solvents; however, some deviation is observed when they are tested for solvents in which the resin has poor solubility. © 1993 John Wiley & Sons, Inc.     

Effect of plant sterols,fatty acids and lecithin on cholesterol absorption in vivo in the rat

The inhibitory effect of plant sterols, fatty acids and lecithin on cholesterol intestnal absorption was studied in the unanesthetized rat using a single pass perfusion technique. Bile was excluded from the perfused intestine. Cholesterol absorption did not change following the additions of cholestanol, cholestanone, lanosterol, stigmasterol and β-sitosterol. A 3-fold increase in the molarity of cholestanol and β-sitosterol or the separate additions of the saturated short and medium chain fatty acids, butyric and octanoic, also did not change cholesterol absorption. The unsaturated long chain fatty acids, oleic, linoleic, linolenic and arachidonic, inhibited cholesterol absorption. Lecithin additions at concentrations of 0.1–1.5 mM caused a progressive, dose-related inhibition of cholesterol absorption. The inhibitory effect of these agents on cholesterol absorption is likely to have been caused by changes in cholesterol solubility in the micelle and shifts in the partition coefficient of cholesterol away from the cell membrane to the micelle.     

The effect of the viscosity ratio of dispersed phase to matrix on the rheological,morphological, and mechanical properties of polymer blends containing a LCP

The effect of the viscosity ratio of the dispersed LCP phase to the polystyrene/poly(phenylene oxide) (PS/PPO) thermoplastic matrix on the rheological, morphological, and resultant mechanical properties of the LCP blends was investigated. The viscosity of PS/PPO is largely dependent on the blend composition, so that different levels of viscosity ratios of dispersed LCP phase to PS/PPO thermoplastic matrix are obtained by using PS/PPO premixtures of different blend ratios as a thermoplastic matrix. When the viscosity of the LCP dispersed phase is lower than that of the thermoplastic matrix, finely distributed fibril structure of LCP is obtained. Tensile modulus of injection molded specimens show a positive deviation from the additive rule when the viscosity ratio (η_LCP/η_matrix) is smaller than unity. These improvements in tensile modulus are attributed to the formation of finely distributed LCP fibrils. © 1996 John Wiley & Sons, Inc.     

Temperature-/Frequency-dependent complex viscosity and tensile modulus of polymer nanocomposites from the glassy state to the melting point

In this study, the temperature-/frequency-dependent viscosity and tensile modulus of polymer nanocomposites were evaluated using the combination of developed Arrhenius's equation and percolation theory. To involve the drastic effects of the polymer/particles interphase region and the aggregation/agglomeration of nanoparticles in the model, the Nielsen–Lewis model was developed and used to interpret the related parameters from heat conduction test results. The value of different state-to-state conversion degrees was calculated using the developed percolation theory whose validity was evaluated via comparative studies with theoretical results obtained from developed Arrhenius's equations. The simultaneous effects of the nanoparticles content and temperature/frequency on the viscosity and tensile modulus were also studied, which defined the role of some important phenomena such as the breakdown of the nanoparticle clusters, the increased cluster stability by polar surface modifiers, the increased thermal conductivity of the nanocomposite due to the presence of nanoparticles, etc. Different PA nanocomposites samples, containing 1–4 vol% of spherical silica nanoparticles, were prepared and subject to dynamical mechanical analysis, by temperature ramps and frequency sweep, and the results were used to evaluate the accuracy of the model. The surface of the nanoparticles was chemically modified with (3-aminopropyl)triethoxysilane to ensure their perfect compatibility with PA phase.     

Effect of peanut oil and randomized peanut oil on cholesterol and oleic acid absorption, transport, and distribution in the lymph of the rat

Peanut oil was shown to be atherogenic in cholesterol-fed rats, rabbits, and monkeys. However, after randomization, a process in which the fatty acids in peanut oil are randomly rearranged, its atherogenicity was significantly reduced in cholesterol-fed rabbits and monkeys. The mechanism for this effect remains unknown. This study was designed to investigate whether the absorption, transport and distribution of dietary cholesterol and oleic acid in the lymph were altered in the presence of peanut oil or randomized peanut oil. Previous investigators collected lymph through the mesenteric duct for 6 h and analyzed lymph for cholesterol. In the present study, lymph fluids were collected at timed intervals for up to 8 h and then at 24 h via the thoracic duct. Cholesterol and oleic acid (fatty acid) were estimated not only in the whole lymph but also in lymph lipoprotein fractions and in major lipid fractions. A 24-h lymph collection will enhance accuracy as short-term fluctuations in lipid absorption will not affect the results. Thoracic duct lymph collection is quantitative compared to mesenteric duct lymph collection, which provides only a fraction of the total lymph. Rats were given a lipid emulsion containing either peanut oil or randomized peanut oil. The emulsion also contained cholesterol, oleic acid, and sodium taurocholate in saline and was given through a duodenal catheter. Results show that absorption, transport, and distribution of cholesterol and oleic acid in the lymph fluids were similar in both dietary groups. These results suggest that the atherogenicity of peanut oil may be due to other events taking place subsequent to the release of cholesterol-containing chylomicrons and very low density lipoprotein by the small intestinal epithelial cells into the blood or may be due to the triglyceride structure itself.     

Kinetics of absorption,equilibration (or distribution), and excretion of orally and intraperitoneally administered cholesterol in the rat

Resorption and metabolism of cholesterol administered intraperitoneally and per os have been described in the rat utilizing a technique of double isotopic labeling. Depending upon the route of administration, these parameters vary to a large degree. Alimentary cholesterol is progressively resorbed over a period of 10 hr, while the maximal blood level of cholesterol is attained after the 6th hr following intraperitoneal injection. On the other hand, cholesterol administered per os is more rapidly utilized in biliary acid synthesis than cholesterol administered intraperitoneally. In the range of concentrations utilized in this work (10–300 μg and 0.2–300 μg, respectively, administered to the rat, orally and intraperitoneally), the rate of cholesterol resorption remained constant.     

Inhibition of cholesterol synthesis in mammary tissue,lung, and kidney following cholesterol feeding in the lactating rat

Pregnant rats were randomly allocated to one of 3 experimental dietary groups: Group 1–15.5% butter, 2% cholesterol, 0.78% sodium cholate purified diet; Group 2-standard rat diet with the addition of 10% lard and 2% cholesterol, and Group 3-standard rat diet. Plasma and milk cholesterol at 10 days postpartum were significantly elevated in dams fed exogenous cholesterol. The rat of incorporation of [1-¹⁴C] acetate into digitonin-precipitable sterols of mammary tissue slices from dams in Group 1 and Group 2 was eight-fold and two-fold, respectively, less than controls. Mammary tissue cholesterol was greater in dams fed dietary cholesterol. Thus, our data, for the first time, demonstrate that cholesterol synthesis in lactating rat mammary tissue is suppressed following cholesterol feeding. In a second experiment, the rate of incorporation of [1-¹⁴C] acetate into digitonin-precipitable sterols in kidney and lung tissue of Group 1 rats was suppressed; however, this response was not as marked as that observed in lactating mammary tissue. The concentration of cholesterol in kidney and lung was greater than controls. These results suggest that extrahepatic inhibition of cholesterol synthesis exists in the rat with a concomitant increase in tissue cholesterol.