Honors Program Theses


Open Access Honors Program Thesis

First Advisor

Kavita R. Dhanwada


Atrazine is one of the most widely used herbicides in the United States. It is frequently used for general weed control on both industrial and agricultural land. However, atrazine has been associated with many harmful non-target effects in animals and humans. Due to its prevalence in the environment, the United States Environmental Protection Agency (USEP A) has set the maximal contaminant level of atrazine in drinking water at 3 ppb (USEP A, 2003 ). One of the non-target effects of atrazine is slowed growth of both normal and immortalized human cells. Previous work from our lab demonstrated that exposing normal human fibroblasts to 0.8 parts per billion (ppb) or 0.8 µg/L of atrazine for 72 hours caused a statistically significant decrease in cell growth compared to unexposed cells (Dhanwada et al., 2003) and it took 12.5 ppb atrazine to show a statistically significant decrease in immortalized human hepatoma HepG2 cell growth (Powell and Dhanwada, 2006).

To understand the observed slow down in cell growth after atrazine exposure, the current study attempted to determine if the expression of cell cycle proteins that regulate passage through the cell cycle is being altered in atrazine exposed cells compared to unexposed cells. Three cyclins were studied: A, B, and E. Cyclin expression in atrazine-exposed cells (50, 100, 300, 500ppb) compared to control (0 ppb) HepG2 cells was quantitated under three experimental conditions, 24-hour atrazine exposure, 48-hour atrazine exposure, and 24 hour cell synchronization followed by 24-hour atrazine exposure. After the indicated time, cells were harvested for nuclear proteins, and Western blot analysis was performed.

The results of the current study show that cyclin A, B, and E expression patterns are altered in atrazine-exposed cells compared to control depending on the time of atrazine exposure. Results suggested that either a G1 or a G2 block in the cell cycle was occurring upon atrazine exposure.

Year of Submission



Department of Biology

University Honors Designation

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


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Date Original


Object Description

1 PDF file (viii, 82 pages)