A stereochemical examination of the equine metabolism of 17alpha-methyltestosterone

An investigation was conducted into the stereochemistry of the equine urinary metabolites of 17α-methyltestosterone observed after oral administration. Standards of the complete range of C3/C5/C16 stereoisomeric 17α-methylandrostane-3,17β-diols, 17α-methylandrostane-3,16,17β-triols and 17α-hydroxymethylandrostane-3,17β-diols were purchased or synthesised, and were used to unequivocally identify the absolute structures of the metabolites. Phase I metabolism was found to involve combinations of Δ⁴-3-ketone reduction with both 5α,3β- and 5β,3α-stereochemistry, hydroxylation at C16 with both 16α- and 16β-stereochemistry and hydroxylation of the 17α-methyl substituent. Phase II metabolism involved mainly sulfation with a lesser degree of β-glucuronidation.     

Time and frequency resolved dynamics of ArBr2

We report the first spectroscopic observation of and vibrational predissociation dynamics for ArBr(2). Measurements are reported for the linear and T-shaped isomers with time and frequency resolution near the Fourier limit of a 15 ps pulse. For the T-shaped isomer, the Ar-Br(2) bond energy D(0) for the B state, nu(')=19, is found to be 200 cm(-1), yielding a D(0)(X) value of 213 cm(-1). Product appearance rates are determined for nu(')=16-25 of the B state of ArBr(2). While the rate generally increases with increasing vibrational quantum number, the trend is not monotonic. Also, obtaining reproducible rates for any given vibrational level requires very careful control of the experimental conditions. The data suggest that ArBr(2) undergoes vibrational predissociation (VP) in the sparse intramolecular vibrational relaxation regime. These observations are consistent with theoretical calculations that show that T-shaped ArBr(2) undergoes VP in the sparse regime, such that lifetimes are strongly dependent on both the vibrational and rotational quantum numbers. As for ArI(2), a linear isomer of ArBr(2) is found to contribute a quasicontinuous background to the excitation spectra. Direct excitation of this continuum results in a very broad product vibrational distribution.     

Effect of rotating secondary principal axes in scattered-light photoelasticity

A set of equations is presented and the effect of rotation of the secondary principal stress axes is discussed. The equations, general and relatively simple, adequately describe observed results. In studying the equations, a better understanding of the rotational effect can be achieved, and a technique is suggested which can eliminate any error resulting from rotation. This technique and the concepts involved are substantiated with experimental evidence and reported in this paper.     

The detection of modafinil and its major metabolite in equine urine by liquid chromatography/mass spectrometry

A method has been developed for the detection of modafinil and its major metabolite, modafinil acid, in equine urine by solid-phase extraction and positive ion electrospray ionisation liquid chromatography/mass spectrometry. The method has been applied to the analysis of equine urine samples obtained after the oral administration of modafinil. Modafinil acid was the major component in the urine, and was detected up to 4 days post-administration. Unchanged modafinil was present at substantially lower concentrations, and was detected for only 24 hours.