Honors Program Theses


Open Access Honors Program Thesis

First Advisor

Kavita R. Dhanwada


Atrazine is the most frequently used triazine herbicide in the United States. Studies have shown an association between herbicide exposure and increased levels of DNA damage, reproductive and endocrine problems, and an increased risk for certain cancers. The United States Environmental Protection Agency (USEP A) has set a maximum allowable limit at 3 parts per billion (ppb ). Previous work from our lab has shown decreased cell proliferation of normal human fibroblasts after low-level atrazine exposure for 72 hours at 0.8-100 ppb without a corresponding increase in apoptosis or necrosis.

The objective of the current study is to determine a mechanism for the observed decrease in cell number after atrazine exposure. We used flow cytometric analysis to see if treated cells progressed through the cell cycle differently than control cells and resulted in fewer cells after exposure. We hypothesized treated cells would take longer to cycle, so fewer cells would be present after a specific amount of time. Synchronized and unsynchronized normal human fibroblasts were exposed to increasing concentrations of atrazine (0-300 ppb) for 24, 32, or 48 hours and flow cytometric analysis was performed.

Results suggest a G 1 block in atrazine-treated cells after 24, 32, and 48 hour exposure in both synchronized and unsynchronized cells. This block would increase the length of the cell cycle, thus supporting our hypothesis. Additionally, the number of apoptotic cells after treatment was comparable to control, again supporting previous growth study results.

Year of Submission



Department of Biology

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors


If you are the rightful copyright holder of this thesis and wish to have it removed from the Open Access Collection, please submit a request to scholarworks@uni.edu and include clear identification of the work, preferably with URL.

Date Original


Object Description

1 PDF file (vi, 33 pages)