Human Exposure to Selamectin from Dogs Treated with Revolution™: Methodological Consideration for Selamectin Isolation

This study was undertaken to determine selamectin residue in dog\u27s blood and in gloves worn while petting dogs after Revolution™ application. Revolution™ contains the active ingredient selamectin (a semisynthetic avermectin), which controls endoparasites and ectoparasites, including adult fleas, flea eggs, ticks, heartworms, ear mites, and sarcoptic mange in dogs, for 30 days. Revolution™ was applied topically on a group of six adult house hold dogs (240 mg selamectin/dog). The gloves worn for 5 min while petting the dogs were collected in glass jars and the blood samples (5 mL/dog) were collected in EDTA tubes at 0 h, 24 h, and 72 h, and at 1, 2, 3, 4, and 5 weeks post-Revolution™ application for selamectin residue determination. At no time during the study did the dogs show any signs of toxicity, weight loss, or change in body temperature. Extracts of the blood and the gloves were analyzed for selamectin residue using RP-HPLC coupled with a UV detector (246 nm). Selamectin standard used for peak identification and quantitation was purified from Revolution™. Selamectin residue was detected in the blood (10.26 ± 1.06 ng/mL) only at 72 h post-Revolution™ application, probably due to its poor dermal absorption and rapid elimination from the circulation. In the glove extracts, the highest concentration of selamectin (518.90 ± 66.80 ppm) was detected 24 h after Revolution™ application. Transferable residue of selamectin in gloves from dog\u27s coat was detected at a lesser magnitude after 1 week of Revolution™ application, and that was followed by a further descending trend during the second, third, and fourth weeks. No selamectin residue was detected in the glove extracts after the fifth week. In spite of selamectin\u27s binding to the sebaceous glands of the skin, gloves contained significant transferable residue. Thus, these findings suggest that repeated exposure to selamectin can pose potential health risks, especially to veterinarians, veterinary technologists, dog trainers/handlers, and pet owners

The Laser-Induced Blue State of Bacteriorhodopsin: Mechanistic and Color Regulatory Roles of Protein−Protein Interactions, Protein−Lipid Interactions, and Metal Ions

In this paper we characterize the mechanistic roles of the crystalline purple membrane (PM) lattice, the earliest bacteriorhodopsin (BR) photocycle intermediates, and divalent cations in the conversion of PM to laser-induced blue membrane (LIBM; λmax = 605 nm) upon irradiation with intense 532 nm pulses by contrasting the photoconversion of PM with that of monomeric BR solubilized in reduced Triton X-100 detergent. Monomeric BR forms a previously unreported colorless monomer photoproduct which lacks a chromophore band in the visible region but manifests a new band centered near 360 nm similar to the 360 nm band in LIBM. The 360 nm band in both LIBM and colorless monomer originates from a Schiff base-reduced retinyl chromophore which remains covalently linked to bacterioopsin. Both the PM→LIBM and monomer→colorless monomer photoconversions are mediated by similar biphotonic mechanisms, indicating that the photochemistry is localized within single BR monomers and is not influenced by BR−BR interactions. The excessively large two-photon absorptivities (≥106 cm4 s molecule-1photon-1) of these photoconversions, the temporal and spectral characteristics of pulses which generate LIBM in high yield, and an action spectrum for the PM→LIBM photoconversion all indicate that the PM→LIBM and Mon→CMon photoconversions are both mediated by a sequential biphotonic mechanism in which is the intermediate which absorbs the second photon. The purple→blue color change results from subsequent conformational perturbations of the PM lattice which induce the removal of Ca2+ and Mg2+ ions from the PM surface