Bachelor of Science, Wittenberg University, 2021, Biology

Insecticide use is steadily increasing in the United States. Of these, the insecticide Sevin™ has the active ingredient carbaryl, which is a xenobiotic. This is a reverse inhibitor of acetylcholinesterase, which prevents nerve excitation causing paralysis and death in insects. Though insects are the target species, carbaryl has many routes of exposure such as run-off, inhalation, and physical contact making it easy to encounter for non-target species like aquatic life and humans. Carbaryl has been studied within in vitro models to test its effects on zebrafish. The insecticide has already been shown to act on the acetylcholinesterase (AChE) pathway, but it also has potential to act on a second pathway: the aryl hydrocarbon receptor (AhR) pathway. Zebrafish genes and genetic pathways are homologous to humans, allowing for insight on how carbaryl could be affecting humans as well. This study set out to use an in vivo model to show how carbaryl is inducing cytochrome P450 or other AhR pathway gene expression. Gene expression of carbaryl treated embryos were compared to untreated embryos to examine this possible relationship. Cyp1a and cyp1b gene expression was increased with an increase in carbaryl concentration suggesting that carbaryl may be causing induction of the AhR pathway.

Committee: Michelle McWhorter (Advisor); Matthew Collier (Committee Member); Daniel Marous (Committee Member) Subjects: Agricultural Chemicals; Biochemistry; Biology; Developmental Biology; Environmental Science; Genetics; Molecular Biology; Toxicology

Doctor of Philosophy, Case Western Reserve University, 2008, Biology

The zebrafish pineal is a powerful system to dissect the regulation of circadian rhythms during development. It has all the elements of the circadian timing system. Under constant conditions, an endogenous pineal clock drives many rhythms including higher levels of circulating melatonin at night and lower levels during the day. Photoreceptors within the zebrafish pineal reset the endogenous circadian oscillator. It has been shown that light is partly required for higher levels of mRNA expression of two rhythmic pineal genes extra-ocular rhodopsin (exorh) and serotonin-N-acetyltransferase 2 (aanat2) that encodes for a putative photopigment and a major melatonin biosynthetic enzyme, respectively. Many candidate photopigments are expressed in the zebrafish pineal such as red opsin, blue opsin, and Exorh. To determine the role of Exorh protein, I used two non-overlapping antisense morpholino oligonucleotides (MOs) to deplete Exorh. I found a dramatic reduction in the levels of exorh mRNA in Exorh-deficient embryos. Together with my fellow graduate student Lain Pierce, I discovered significantly reduced levels of aanat2 mRNA in Exorh-deficient embryos. Since higher levels of exorh and aanat2 mRNAs are partly dependent on light, these results suggest that Exorh participates in a light-sensing pathway that ultimately causes the activation of pineal gene expression. This is the first evidence for Exorh function. In mammals, pineal rhythms are regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus. While a similar structure has been identified in teleost fish such as zebrafish, evidence for its function is lacking. To define the role of the zebrafish SCN, I analyzed pineal gene expression rhythms in cyclops (cyc) mutants. cyc mutants are missing the ventral brain including the SCN precursors. My fellow graduate student Po-Nien Lu and I showed that the rhythmic expression patterns of aanat2 and exorh are indistinguishable between wild type (WT) fish and cyc mu (open full item for complete abstract)

Committee: Jennifer O. Liang Ph.D. (Advisor); Mark A. Willis Ph.D. (Committee Chair); Radhika P. Atit Ph.D. (Committee Member); Ron A. Conlon Ph.D. (Committee Member); Stephen E. Haynesworth Ph.D. (Committee Member); Neal S. Peachey Ph.D. (Committee Member) Subjects: Biology