Studies on the chromatographic fractionation of metabolites of benzo[a]pyrene in faeces and urine from germfree and conventional rats

Rats, germfree and conventional, were dosed with 14C-labelled benzo[a]pyrene. Faeces and urine were collected. Metabolites in faeces were effectively extracted with a new method using a combination of solvents and solid sorbents. Metabolites in urine were extracted with octadecylsilane-bonded silica. The metabolites were fractionated into groups by chromatography on a cation exchanger (SP-LH-20 or SP-Sephadex C-25) and an anion exchanger (TEAP-LH-20). Some of the groups were further purified by column chromatography and analysed by HPLC and TLC. The analyses show a complex pattern of metabolism. A large part of the metabolites (9-24% depending on animal type and route of excretion) had amphoteric properties, e.g. like glutathione and cysteine conjugates. The abundance of conjugates sensitive to beta-glucuronidase and sulphatase was low. The relative amount of acidic conjugates in faeces was much higher in the germfree than in the conventional rats indicating the influence of the intestinal flora on the metabolism. The results support the view that the mercapturic acid pathway is a quantitatively important metabolic route for benzo[a]pyrene in rats. The methods of extraction and group fractionation were designed to be generally applicable to the analysis of lipophilic xenobiotics and their metabolites.     

Structure-activity relationships for apomorphine congeners. Conformational energies vs. biological activities

Summary A series of apomorphine congeners has been studied with respect to their ability to mimic the structural requirements of the dopamine pharmacophore in the potent and stereoselective dopamine receptor agonist (R)-apomorphine. Conformational energies of the mimicking structures calculated by molecular mechanics (MMP2) correlate well with the observed biological activities.     

Towards a Nonlinear Eddy-Viscosity Model Based on Elliptic Relaxation

A phenomenological method has been used to derive a nonlinear constitutive relationship that can be used in conjunction with any eddy-viscosity model utilizing the elliptic relaxation method. While retaining the merits of the elliptic relaxation to model near-wall turbulence, the new model also enables the turbulence anisotropy to be faithfully predicted in wall-bounded flows.     

Studies in the decay of103Ru

The decay of¹⁰³Ru to¹⁰³Rh has been studied using a double-focussing spectrometer for the electron and negaton spectra and a Ge(Li) detector for gamma-ray measurements. TheL-conversion groups of the 40, 53, and 497 keV transitions were resolved at high resolution and unambigous multipolarity assignments were obtained for these transitions. The level scheme proposed resembles in principle that suggested by previous investigators. One essential difference is the doublet character of the state around 0.65 MeV. Tentative spin-parity values have been assigned to all levels from the deduced multipolarities and logft values.     

Adsorption of polar solutes in reversed-phase liquid-liquid chromatography

Summary The properties of chloroform as a liquid stationary phase in reversed-phase liquid chromatography have been investigated. Stable systems and complete pore filling of the support were obtained. Uncharged acids were slightly adsorbed by the support. Amines in the cationic form showed tailing, which can be attributed to adsorption on the support material. The influence of several reversed-phase supports on retention and peak symmetry has been studied. Little difference was found for uncharged acids, but retention and peak shape of the cations was dependent on the specific support. Also on the poly(styrene-divinylbenzene) copolymer PRP-1 cations gave tailing peaks. The results indicate that the surface of reversed-phase supports is heterogeneous. From this and other studies it can be concluded that only certain reversed-phase silicas, such as -Bondapak, are suitable supports for cationic solutes. In liquid-liquid chromatography polar solutes only obey a liquid-liquid distribution model if the liquid stationary phase molecules contains a hydrophobic group, as well as a polar function.Presented in part at the 7th and 9th International Symposiums on Column Liquid Chromatography, Baden-Baden, FRG, May 1983, and Edinburgh, UK, July 1985, respectively.     

An internal conversion study of the decay of193Au

The internal conversion spectrum following the decay of¹⁹³Au has been studied in the electron energy region 0.8 to 700 keV, with the use of high-resolution magnetic beta-ray spectrometers. Several not previously reported transitions have been estabblished. Multipolarities and mixing ratios have been deduced fromK/L and subshell intensity ratios, and the majority of the transitions were found to be ofM1 and/orE2 characters. A revised level scheme for¹⁹³Pt, which consistently accomodates most transitions, has been constructed. Tentative spin-parity values have been assigned to all levels.     

Numerical Approximation for a White Noise Driven SPDE with Locally Bounded Drift

A numerical scheme for a stochastic partial differential equation of heat equation type is considered where the drift is locally bounded and the dispersion may be state dependent. Uniform convergence in probability is obtained. Roger Pettersson: Partially supported by the EU grant ref. ERBF MRX CT96 0057A.