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David J Cutler

Publications and source records attributed to David J Cutler.

21 records · Page 2Linked to original sources

Multiple pharmacokinetic parameter prediction for a series of cephalosporins.

The goal of quantitative structure-pharmacokinetic relationship analyses is to develop useful models that can predict one or more pharmacokinetic properties of a particular compound. In the present study, a multiple-output artificial neural network model was constructed to predict human half-life, renal and total body clearance, fraction excreted in urine, volume of distribution, and fraction bound to plasma proteins for a series of cephalosporins. Descriptors generated solely from drug structure were used as inputs for the model, and the six pharmacokinetic parameters were simultaneously predicted as outputs. The final 10 descriptor model contained sufficient information for successful predictions using both internal and external test compounds. Descriptors were found to contribute to individual pharmacokinetic parameters to differing extents, such that descriptor importance was independent of the relationships between pharmacokinetic parameters. This technique provides the advantage of simultaneous prediction of multiple parameters using information obtained by nonexperimental means, with the potential for use during the early stages of drug development.

Cephalosporins↗

The mouse VPAC2 receptor confers suprachiasmatic nuclei cellular rhythmicity and responsiveness to vasoactive intestinal polypeptide in vitro.

Expression of coherent and rhythmic circadian (approximately 24 h) variation of behaviour, metabolism and other physiological processes in mammals is governed by a dominant biological clock located in the hypothalamic suprachiasmatic nuclei (SCN). Photic entrainment of the SCN circadian clock is mediated, in part, by vasoactive intestinal polypeptide (VIP) acting through the VPAC2 receptor. Here we used mice lacking the VPAC2 receptor (Vipr2-/-) to examine the contribution of this receptor to the electrophysiological actions of VIP on SCN neurons, and to the generation of SCN electrical firing rate rhythms SCN in vitro. Compared with wild-type controls, fewer SCN cells from Vipr2-/- mice responded to VIP and the VPAC2 receptor-selective agonist Ro 25-1553. By contrast, similar proportions of Vipr2-/- and wild-type SCN cells responded to gastrin-releasing peptide, arginine vasopressin or N-methyl-D-aspartate. Moreover, VIP-evoked responses from control SCN neurons were attenuated by the selective VPAC2 receptor antagonist PG 99-465. In firing rate rhythm experiments, the midday peak in activity observed in control SCN cells was lost in Vipr2-/- mice. The loss of electrical activity rhythm in Vipr2-/- mice was mimicked in control SCN slices by chronic treatment with PG 99-465. These results demonstrate that the VPAC2 receptor is necessary for the major part of the electrophysiological actions of VIP on SCN cells in vitro, and is of fundamental importance for the rhythmic and coherent expression of circadian rhythms governed by the SCN clock. These findings suggest a novel role of VPAC2 receptor signalling, and of cell-to-cell communication in general, in the maintenance of core clock function in mammals, impacting on the cellular physiology of SCN neurons.

Animals↗

Haplotype inference in random population samples.

Contemporary genotyping and sequencing methods do not provide information on linkage phase in diploid organisms. The application of statistical methods to infer and reconstruct linkage phase in samples of diploid sequences is a potentially time- and labor-saving method. The Stephens-Smith-Donnelly (SSD) algorithm is one such method, which incorporates concepts from population genetics theory in a Markov chain-Monte Carlo technique. We applied a modified SSD method, as well as the expectation-maximization and partition-ligation algorithms, to sequence data from eight loci spanning >1 Mb on the human X chromosome. We demonstrate that the accuracy of the modified SSD method is better than that of the other algorithms and is superior in terms of the number of sites that may be processed. Also, we find phase reconstructions by the modified SSD method to be highly accurate over regions with high linkage disequilibrium (LD). If only polymorphisms with a minor allele frequency >0.2 are analyzed and scored according to the fraction of neighbor relations correctly called, reconstructions are 95.2% accurate over entire 100-kb stretches and are 98.6% accurate within blocks of high LD.

Algorithms↗