Splanchnic metabolism of nutrients and hormones in steers fed alfalfa under conditions of increased absorption of ammonia and L-arginine supply across the portal-drained viscera

Effects of increased ammonia and/or arginine absorption on net splanchnic (portal-drained viscera [PDV] plus liver) metabolism of nonnitrogenous nutrients and hormones in cattle were examined. Six Hereford x Angus steers (501 +/- 1 kg BW) prepared with vascular catheters for measurements of net flux across the splanchnic bed were fed a 75% alfalfa:25% (as-fed basis) corn and soybean meal diet (0.523 MJ of ME/[kg BW(0.75.)d]) every 2 h without (27.0 g of N/kg of DM) and. with 20 g of urea/kg of DM (35.7 g of N/kg of DM) in a split-plot design. Net flux measurements were made immediately before and after a 72-h mesenteric vein infusion Of L-arginine (15 mmol/h). There were no treatment effects on PDV or hepatic 02 consumption. Dietary urea had no effect on splanchnic metabolism of glucose or L-lactate, but arginine infusion decreased net hepatic removal Of L-lactate when urea was fed (P < 0.01). Net PDV appearance of n-butyrate was increased by arginine infusion (P < 0.07), and both dietary urea (P < 0.09) and arginine infusion (P < 0.05) increased net hepatic removal of n-butyrate. Dietary urea also increased total splanchnic acetate output (P < 0.06), tended to increase arterial glucagon concentration (P < 0.11), and decreased arterial ST concentration (P < 0.03). Arginine infusion increased arterial concentration (P < 0.07) and net PDV release (P < 0.10) and tended to increase hepatic removal (P < 0.11) of insulin, as well as arterial concentration (P < 0.01) and total splanchnic output (P < 0.01) of glucagon. Despite changes in splanchnic N metabolism, increased ammonia and arginine absorption had little measurable effect on splanchnic metabolism of glucose and other nonnitrogenous components of splanchnic energy metabolism.

Net nutrient absorption and liver metabolism in lactating dairy cows fed supplemental dietary biotin

The effect of feeding supplemental biotin on net absorption and metabolism of nutrients by the portal-drained viscera (PDV; the gut, pancreas, spleen and associated fat) and liver of lactating dairy cows was measured. Three cows in early to mid-lactation catheterised for measurements of net nutrient absorption and metabolism by the PDV and liver were fed a total-mixed ration with or without supplemental biotin at 20 mg/day using a switch-back design (ABA v. BAB) with three 2-week periods. There were no effects of feeding biotin on dry matter intake (22.2 kg/day), milk yield (29.5 kg/day) or milk composition. There was also no effect of feeding biotin on net release of glucose by the liver, net liver removal of glucose precursors (propionate, alanine, lactate) or net liver release of p-hydroxybutyrate. Feeding biotin increased net PDV release of ammonia. Reasons for the response are not certain, but a numerical increase in net PDV release of acetate suggests that rumen or hindgut fermentation was altered. Results of the present study do not support the hypothesis that supplemental biotin increases liver glucose production in lactating dairy cows.

Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks

This toxicology update reviews research over the past four years since publication in 2004 of the first measurement of intact esters of p-hydroxybenzoic acid (parabens) in human breast cancer tissues, and the suggestion that their presence in the human body might originate from topical application of bodycare cosmetics. The presence of intact paraben esters in human body tissues has now been confirmed by independent measurements in human urine, and the ability of parabens to penetrate human skin intact without breakdown by esterases and to be absorbed systemically has been demonstrated through studies not only in vitro but also in vivo using healthy human subjects. Using a wide variety of assay systems in vitro and in vivo, the oestrogen agonist properties of parabens together with their common metabolite (p-hydroxybenzoic acid) have been extensively documented, and, in addition, the parabens have now also been shown to possess androgen antagonist activity, to act as inhibitors of sulfotransferase enzymes and to possess genotoxic activity. With the continued use of parabens in the majority of bodycare cosmetics, there is a need to carry out detailed evaluation of the potential for parabens, together with other oestrogenic and genotoxic co-formulants of bodycare cosmetics, to increase female breast cancer incidence, to interfere with male reproductive functions and to influence development of malignant melanoma which has also recently been shown to be influenced by oestrogenic stimulation. Copyright (C) 2008 John Wiley & Sons, Ltd.

The local adsorption geometry and electronic structure of alanine on Cu{110}

The adsorption of alanine on Cu {110} was studied by a combination of near edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Large chemical shifts in the C 1s, N 1s, and O 1s XP spectra were found between the alanine multilayer and the chemisorbed and pseudo-(3 x 2) alaninate layers. From C, N, and O K-shell NEXAFS spectra the tilt angles of the carboxylate group (approximate to 26 degrees in plane with respect to [1 (1) over bar0] and approximate to 45 degrees out of plane) and the C-N bond angle with respect to [1 (1) over bar0] could be determined for the pseudo-(3 x 2) overlayer. Using this information three adsorption geometries could be eliminated from five p(3 x 2) structures which lead to almost identical heats of adsorption in the DFT calculations between 1.40 and 1.47 eV/molecule. Due to the small energy difference between the remaining two structures it is not unlikely that these coexist on the surface at room temperature. (c) 2006 Elsevier B.V. All rights reserved.

Tuning of redox potential and visible absorption band of ruthenium(II) complexes of (benzimidazolyl) derivatives: synthesis, characterization, spectroscopic and redox properties, X-ray structures and DFT calculations

Six ruthenium(II) complexes have been prepared using the tridentate ligands 2,6-bis(benzimidazolyl) pyridine and bis(2-benzimidazolyl methyl) amine and having 2,2'-bipyridine, 2,2':6',2 ''-terpyridine, PPh3, MeCN and chloride as coligands. The crystal structures of three of the complexes trans-[Ru(bbpH(2))(PPh3)(2)(CH3CN)I(ClO4)(2) center dot 2H(2)O (2), [Ru(bbpH(2))(bpy)Cl]ClO4 (3) and [Ru(bbpH(2))(terpy)](ClO4)(2) (4) are also reported. The complexes show visible region absorption at 402-517 nm, indicating that it is possible to tune the visible region absorption by varying the ancillary ligand. Luminescence behavior of the complexes has been studied both at RT and at liquid nitrogen temperature (LNT). Luminescence of the complexes is found to be insensitive to the presence of dioxygen. Two of the complexes [Ru(bbpH(2))(bpy)Cl]ClO4 (3) and [Ru(bbpH(2))(terpy]ClO4)(2) (4) show RT emission in the NIR region, having lifetime, quantum yield and radiative constant values suitable for their application as NIR emitter in the solid state devices. The DFT calculations on these two complexes indicate that the metal t(2g) electrons are appreciably delocalized over the ligand backbone. (C) 2006 Elsevier B.V. All rights reserved.

Inelastic neutron scattering in spectroscopic studies of hydrogen on carbon-supported catalysts-experimental spectra and computed spectra of model systems

Inelastic neutron scattering spectroscopy has been used to observe and characterise hydrogen on the carbon component of a Pt/C catalyst. INS provides the complete vibration spectrum of coronene, regarded as a molecular model of a graphite layer. The vibrational modes are assigned with the aid of ab initio density functional theory calculations and the INS spectra by the a-CLIMAX program. A spectrum for which the H modes of coronene have been computationally suppressed, a carbon-only coronene spectrum, is a better representation of the spectrum of a graphite layer than is coronene itself. Dihydrogen dosing of a Pt/C catalyst caused amplification of the surface modes of carbon, an effect described as H riding on carbon. From the enhancement of the low energy carbon modes (100-600 cm(-1)) it is concluded that spillover hydrogen becomes attached to dangling bonds at the edges of graphitic regions of the carbon support. (C) 2003 Elsevier Science B.V. All rights reserved.

Experimental and theoretical study of the infrared spectra of BrHI- and BrDI-

Gas phase vibrational spectra of BrHI- and BrDI- have been measured from 6 to 17 mum (590-1666 cm-1) using tunable infrared radiation from the free electron laser for infrared experiments in order to characterize the strong hydrogen bond in these species. BrHI-.Ar and BrDI-.Ar complexes were produced and mass selected, and the depletion of their signal due to vibrational predissociation was monitored as a function of photon energy. Additionally, BrHI- and BrDI- were dissociated into HBr (DBr) and I- via resonant infrared multiphoton dissociation. The spectra show numerous transitions, which had not been observed by previous matrix studies. New ab initio calculations of the potential-energy surface and the dipole moment are presented and are used in variational ro-vibrational calculations to assign the spectral features. These calculations highlight the importance of basis set in the simulation of heavy atoms such as iodine. Further, they demonstrate extensive mode mixing between the bend and the H-atom stretch modes in BrHI- and BrDI- due to Fermi resonances. These interactions result in major deviations from simple harmonic estimates of the vibrational energies. As a result of this new analysis, previous matrix-isolation spectra assignments are reevaluated. (C) 2004 American Institute of Physics.

Chalcogenide-halides of niobium (V). 1. Gas-phase structures of NbOBr3, NbSBr3, and NbSCl3. 2. Matrix infrared spectra and vibrational force fields of NbOBr3, NbSBr3, NbSCl3, and NbOCl3

The molecular structures of NbOBr3, NbSCl3, and NbSBr3 have been determined by gas-phase electron diffraction (GED) at nozzle-tip temperatures of 250 degreesC, taking into account the possible presence of NbOCl3 as a contaminant in the NbSCl3 sample and NbOBr3 in the NbSBr3 sample. The experimental data are consistent with trigonal-pyramidal molecules having C-3v symmetry. Infrared spectra of molecules trapped in argon or nitrogen matrices were recorded and exhibit the characteristic fundamental stretching modes for C-3v species. Well resolved isotopic fine structure (Cl-35 and Cl-37) was observed for NbSCl3, and for NbOCl3 which occurred as an impurity in the NbSCl3 spectra. Quantum mechanical calculations of the structures and vibrational frequencies of the four YNbX3 molecules (Y = O, S; X = Cl, Br) were carried out at several levels of theory, most importantly B3LYP DFT with either the Stuttgart RSC ECP or Hay-Wadt (n + 1) ECP VDZ basis set for Nb and the 6-311 G* basis set for the nonmetal atoms. Theoretical values for the bond lengths are 0.01-0.04 Angstrom longer than the experimental ones of type r(a), in accord with general experience, but the bond angles with theoretical minus experimental differences of only 1.0-1.5degrees are notably accurate. Symmetrized force fields were also calculated. The experimental bond lengths (r(g)/Angstrom) and angles (angle(alpha)/deg) with estimated 2sigma uncertainties from GED are as follows. NbOBr3: r(Nb=O) = 1.694(7), r(Nb-Br) = 2.429(2), angle(O=Nb-Br) = 107.3(5), angle(Br-Nb-Br) = 111.5(5). NbSBr3: r(Nb=S) = 2.134(10), r(Nb-Br) = 2.408(4), angle(S=Nb-Br) = 106.6(7), angle(Br-Nb-Br) = 112.2(6). NbSCl3: Nb=S) = 2.120(10), r(Nb-Cl) = 2.271(6), angle(S=Nb-Cl) = 107.8(12), angle(Cl-Nb-Cl) = 111.1(11).

Ab initio prediction of the infrared-absorption spectrum of the C2Cl radical

The three lowest (1(2)A('), 2(2)A('), and 1(2)A(')) potential-energy surfaces of the C2Cl radical, correlating at linear geometries with (2)Sigma(+) and (2)Pi states, have been studied ab initio using a large basis set and multireference configuration-interaction techniques. The electronic ground state is confirmed to be bent with a very low barrier to linearity, due to the strong nonadiabatic electronic interactions taking place in this system. The rovibronic energy levels of the (CCCl)-C-12-C-12-Cl-35 isotopomer and the absolute absorption intensities at a temperature of 5 K have been calculated, to an upper limit of 2000 cm(-1), using diabatic potential-energy and dipole moment surfaces and a recently developed variational method. The resulting vibronic states arise from a strong mixture of all the three electronic components and their assignments are intrinsically ambiguous. (c) 2005 American Institute of Physics.

Ab initio prediction of the infrared absorption spectrum of the C2Br radical

The first three electronic states (1(2)A', 2(2)A', 1(2)A '') of the C2Br radical, correlating at linear geometries with (2)Sigma(+) and (2)Pi states, have been studied ab initio, using Multi Reference Configuration Interaction techniques. The electronic ground state is found to have a bent equilibrium geometry, R-CC = 1.2621 angstrom, R-CBr = 1.7967 angstrom, < CCBr 156.1 degrees, with a very low barrier to linearity. Similarly to the valence isoelectronic radicals C2F and C2Cl, this anomalous behaviour is attributed to a strong three-state non-adiabatic electronic interaction. The Sigma, Pi(1/2), Pi(3/2) vibronic energy levels and their absolute infrared absorption intensities at a temperature of 5K have been calculated for the (CCBr)-C-12-C-12-Br-79 isotopomer, to an upper limit of 2000 cm(-1), using ab initio diabatic potential energy and dipole moment surfaces and a recently developed variational method.

Redox chemistry and electronic properties of 2,3,5,6-tetrakis(2-pyridyl)pyrazine-bridged diruthenium complexes controlled by N,C,N '-biscyclometalated ligands

To investigate the consequences of cyclometalation for electronic communication in dinuclear ruthenium complexes, a series of 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) bridged diruthenium complexes was prepared and studied. These complexes have a central tppz ligand bridging via nitrogen-to-ruthenium coordination bonds, while each ruthenium atom also binds either a monoanionic, N,C,N'-terdentate 2,6-bis(2'-pyridyl)phenyl (R-N boolean AND C boolean AND N) ligand or a 2,2':6',2 ''-terpyridine (tpy) ligand. The N,C,N'-, that is, biscyclometalation, instead of the latter N,N', N ''-bonding motif significantly changes the electronic properties of the resulting complexes. Starting from well-known [{Ru(tpy)}(2)(mu-tppz)](4+) (tpy = 2,2':2 '',6-terpyridine) ([3](4+)) as a model compound, the complexes [{Ru(R-N boolean AND C boolean AND N)}(mu-tppz){Ru(tpy)}](3+) (R-N boolean AND C(H)boolean AND N = 4-R-1,3-dipyridylbenzene, R = H ([4a](3+)), CO2Me ([4b](3+))), and [{Ru(R-N boolean AND C boolean AND N)}(2)(mu-tppz)](2+), (R = H ([5a](2+)), CO2Me ([5b](2+))) were prepared with one or two N,C,N'-cyclometalated terminal ligands. The oxidation and reduction potentials of cyclometalated [4](3+) and [5](2+) are shifted negatively compared to non-cyclometalated [3](4+), the oxidation processes being affected more significantly. Compared to [3](4+), the electronic spectra of [5](2+) display large bathochromic shifts of the main MLCT transitions in the visible spectral region with low-energy absorptions tailing down to the NIR region. One-electron oxidation of [3](4+) and [5](2+) gives rise to low-energy absorption bands. The comproportionation constants and NIR band shape correspond to delocalized Robin-Day class III compounds. Complexes [4a](3+) (R = H) and [4b](3+) (R = CO2Me) also exhibit strong electronic communication, and notwithstanding the large redox-asymmetry the visible metal-to-ligand charge-transfer absorption is assigned to originate from both metal centers. The potential of the first, ruthenium-based, reversible oxidation process is strongly negatively shifted. On the contrary, the second oxidation is irreversible and cyclometalated ligand-based. Upon one-electron oxidation, a weak and low-energy absorption arises.

The absorption of vitamin E is influenced by the amount of fat in a meal and the food matrix

Vitamin E absorption requires the presence of fat; however, limited information exists on the influence of fat quantity on optimal absorption. In the present study we compared the absorption of stable-isotope-labelled vitamin E following meals of varying fat content and source. In a randomised four-way cross-over study, eight healthy individuals consumed a capsule containing 150 mg H-2-labelled RRR-alpha-tocopheryl acetate with a test meal of toast with butter (17.5 g fat), cereal with full-fat milk (17.5 g fat), cereal with semi-skimmed milk (2.7 g fat) and water (0g fat). Blood was taken at 0, 0.5, 1, 1.5, 2, 3, 6 and 9 h following ingestion, chylomicrons were isolated, and H-2-labelled alpha-tocopherol was analysed in the chylomicron and plasma samples. There was a significant time (P<0.001) and treatment effect (P<0.001) in H-2-labelled alpha-tocopherol concentration in both chylomicrons and plasma between the test meals. H-2-labelled alpha-tocopherol concentration was significantly greater with the higher-fat toast and butter meal compared with the low-fat cereal meal or water (P< 0.001), and a trend towards greater concentration compared with the high-fat cereal meal (P= 0.065). There was significantly greater H-2-labelled α-tocopherol concentration with the high-fat cereal meal compared with the low-fat cereal meal (P< 0.05). The H-2-labelled alpha-tocopherol concentration following either the low-fat cereal meal or water was low. These results demonstrate that both the amount of fat and the food matrix influence vitamin E absorption. These factors should be considered by consumers and for future vitamin E intervention studies.

Absorption, tissue distribution and excretion of pelargonidin and its metabolites following oral administration to rats

Recent reports have demonstrated various cardiovascular and neurological benefits associated with the consumption of foods rich in anthocyanidins. However, information regarding absorption, metabolism, and especially, tissue distribution are only beginning to accumulate. In the present study, we investigated the occurrence and the kinetics of various circulating pelargonidin metabolites, and we aimed at providing initial information with regard to tissue distribution. Based on HPLC and LC-MS analyses we demonstrate that pelargonidin is absorbed and present in plasma following oral gavage to rats. In addition, the main structurally related pelargonidin metabolite identified in plasma and urine was pelargonidin glucuronide. Furthermore, p-hydroxybenzoic acid, a ring fission product of pelargonidin, was detected in plasma and urine samples obtained at 2 and 18 h after ingestion. At 2 h post-gavage, pelargonidin glucuronide was the major metabolite detected in kidney and liver, with levels reaching 0.5 and 0.15 nmol pelargonidin equivalents/g tissue, respectively. Brain and lung tissues contained detectable levels of the aglycone, with the glucuronide also present in the lungs. Other tissues, including spleen and heart, did not contain detectable levels of pelargonidin or ensuing metabolites. At 18 h post-gavage, tissue analyses did not reveal detectable levels of the aglycone nor of pelargonidin glucuronides. Taken together, our results demonstrate that the overall uptake of the administered pelargonidin was 18 % after 2 h, with the majority of the detected levels located in the stomach. However, the amounts recovered dropped to 1.2 % only 18 h post-gavage, with the urine and faecal content constituting almost 90 % of the total recovered pelargonidin.

Absorption of isoflavones in humans: effects of food matrix and processing

If soy isoflavones are to be effective in preventing or treating a range of diseases, they must be bioavailable, and thus understanding factors which may alter their bioavailability needs to be elucidated. However, to date there is little information on whether the pharmacokinetic profile following ingestion of a defined dose is influenced by the food matrix in which the isoflavone is given or by the processing method used. Three different foods (cookies, chocolate bars and juice) were prepared, and their isoflavone contents were determined. We compared the urinary and serum concentrations of daidzein, genistein and equol following the consumption of three different foods, each of which contained 50 mg of isoflavones. After the technological processing of the different test foods, differences in aglycone levels were observed. The plasma levels of the isoflavone precursor daidzein were not altered by food matrix. Urinary daidzein recovery was similar for all three foods ingested with total urinary output of 33-34% of ingested dose. Peak genistein concentrations were attained in serum earlier following consumption of a liquid matrix rather than a solid matrix, although there was a lower total urinary recovery of genistein following ingestion of juice than that of the two other foods. (c) 2006 Elsevier Inc. All rights reserved.

Extra virgin olive oil phenolics: absorption, metabolism, and biological activities in the GI tract

Olive oil, a typical ingredient of the Mediterranean diet, possesses many beneficial health effects. The biological activities ascribed to olive oil consumption are associated in part to its phenolics constituents, and mainly linked to the direct or indirect antioxidant activity of olive oil phenolics and their metabolites, which are exerted more efficiently in the gastrointestinal (GI) tract, where dietary phenolics are more concentrated when compared to other organs. In this regard, we present a brief overview of the metabolism, biological activities, and anticancer properties of olive oil phenolics in the GI tract. Toxicology and Industrial Health 2009; 25: 285-293.