Theses and Dissertations

Issuing Body

Mississippi State University


Chambers, Janice E.

Committee Member

Crow, John Allen

Committee Member

Willeford, Kenneth O.

Committee Member

Carr, Russell L.

Committee Member

Shan, Xueyan

Date of Degree


Original embargo terms


Document Type

Dissertation - Open Access


Environmental Toxicology

Degree Name

Doctor of Philosophy


College of Veterinary Medicine


Environmental Toxicology Program


Organophosphates (OPs) are used in agriculture via pesticides, and warfare and terrorism via nerve agents. OPs can inhibit acetylcholinesterase (AChE) activity in the nervous system, leading to the buildup of acetylcholine (ACh), and overstimulation of the nervous system and eventual asphyxiation and death. The development of novel blood-brain barrier () penetrating pyridinium oxime reactivators have previously demonstrated efficacy towards treatment of OP poisoning after exposure of rats to a sarin or a VX surrogate, nitrophenyl isopropyl methylphosphonate (NIMP) and nitrophenyl ethyl methylphosphonate (NEMP), respectively. An effective oxime antidote capable of penetrating the and restoring nervous system activity after exposure to a cyclosarin surrogate, nitrophenyl cyclohexyl methylphosphonate (NCMP), has yet to be determined. In Chapter 2, in vitro testing of the efficacy of 17 total novel oxime candidates to utilize against NCMP was conducted with a modified Ellman’s AChE assay. Pools of naïve adult male rat brains were utilized as the AChE source. The first variable investigated was the measurement of AChE activity after inhibition with NCMP and subsequent reactivation with one of the oximes. The second variable investigated restoration of AChE activity after simultaneous oxime and NCMP incubation. The final variable investigated the restoration of AChE activity after simultaneous 2-PAM, oxime and NCMP incubation. A thorough kinetic analysis of our best oximes has yet to be accomplished. In Chapter 3, the best oxime antidotes for NEMP and NIMP were used for kinetic analysis with a modified 96-well plate Ellman’s AChE assay. Protein concentrations were analyzed with a modified Lowry protein tube assay to ensure consistent analytical concentrations. The sources of AChE included pooled rat brain and skeletal muscle, and rat and human erythrocytes and plasma. Butyrylcholinesterase (BChE) activity was also measured in the rat and human plasma samples. The results of these studies strengthen the argument that our oxime antidotes can be used as potential therapeutic drugs for OP poisoning. The kinetic data provided critical information to help propose, for Chapter 4, a dynamic pharmacokinetic based model to predict human AChE or BChE activity after exposure to nerve agent surrogates (NEMP and NIMP) and the oximes (44.08 and 44.25).



sarin||organophosphates||VX||weapons of mass destruction