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695 results on '"Lydy, Michael J."'

4. The Use of Non-targeted Lipidomics and Histopathology to Characterize the Neurotoxicity of Bifenthrin to Juvenile Rainbow Trout (Oncorhynchus mykiss)

Author

Magnuson, Jason T, Caceres, Leslie, Sy, Nathan, Ji, Chenyang, Tanabe, Philip, Gan, Jay, Lydy, Michael J, and Schlenk, Daniel

Subjects
Medical Biochemistry and Metabolomics, Agricultural, Veterinary and Food Sciences, Biomedical and Clinical Sciences, Fisheries Sciences, Neurosciences, Animals, Lipidomics, Oncorhynchus mykiss, Pyrethrins, Water Pollutants, Chemical, pyrethroid, salmonid, neurotoxic, brain, histology, adverse outcome, Environmental Sciences
Abstract

Due to the detection frequencies and measured concentrations in surface water, the type I pyrethroid insecticide, bifenthrin, has been of particular concern within the Sacramento-San Joaquin Delta in California. Concentrations have been detected above levels previously reported to impair neuroendocrine function and induce neurotoxicity to several species of salmonids. Metabolomic and transcriptomic studies indicated impairment of cellular signaling within the brain of exposed animals and potential alteration of lipid metabolism. To better understand the potential impacts of bifenthrin on brain lipids, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to mean bifenthrin concentrations of 28 or 48 ng/L for 14 days, and non-targeted lipidomic profiling in the brain was conducted. Brain tissue sections were also assessed for histopathological insult following bifenthrin treatment. Bifenthrin-exposed trout had a concentration-dependent decrease in the relative abundance of triglycerides (TGs) with levels of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) significantly altered following 48 ng/L bifenthrin exposure. An increased incidence of histopathological lesions, such as focal hemorrhages and congestion of blood vessels, was noted in the brains of bifenthrin-treated animals, suggesting an association between altered lipid metabolism and neuronal cell structure and integrity.

Published
2022

6. Exposure to permethrin or chlorpyrifos causes differential dose- and time-dependent behavioral effects at early larval stages of an endangered teleost species

Author

Mundy, Paige C, Hartz, Kara E Huff, Fulton, Corie A, Lydy, Michael J, Brander, Susanne M, Hung, Tien-Chieh, Fangue, Nann A, and Connon, Richard E

Subjects
Environmental Sciences, Pollution and Contamination, Life on Land, Delta smelt, Hypomesus transpacificus, Behavioral toxicology, Pyrethroid, Organophosphate, Biological Sciences, Ecology, Biological sciences, Environmental sciences
Abstract

Pyrethroid and organophosphate pesticides are two of the most commonly used classes of insecticide worldwide. At sublethal concentrations, permethrin (a pyrethroid) and chlorpyrifos (an organophosphate) impact behavior in model fish species. We investigated behavioral effects of environmentally relevant concentrations of permethrin or chlorpyrifos on early larval delta smelt Hypomesus transpacificus, a Critically Endangered teleost species endemic to the San Francisco Bay Delta, California, USA. Using a photomotor behavioral assay of oscillating light and dark periods, we measured distance moved, turn angle, meander, angular velocity, rotations, thigmotaxis (time spent in the border versus center), and swim speed duration and frequency. The lowest concentrations of permethrin used in the tests (0.05 and 0.5 μg l-1) caused significant increases in distance moved at 72 and 96 h, respectively. At 48, 72, and 96 h of exposure, 5 μg l-1 of permethrin caused a hyperactive state in which the larvae significantly decreased thigmotaxis, quickly turning in short bouts of activity, characterized by significant increases in rotations and freezing events. Larvae exposed to 0.05 μg l-1 chlorpyrifos significantly increased thigmotaxis at 72 and 96 h. In response to 5 μg l-1 chlorpyrifos, larvae significantly increased velocity at 72 h exposure, and significantly increased freezing events at 96 h. Behavioral data on larval delta smelt exposed to contaminants present in their limited habitat have the potential to aid evaluations of the suitability of spawning and rearing habitats for this endangered species, thus improving conservation management strategies focused on this sensitive life stage.

Published
2021

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