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Meet a Few of Our Postdoctoral Fellows
Christal Bowman
Modelling allergic responses to food
Nick Radio
Protecting children's nervous systems
Terry Green
Investigating our risks from air pollution
John Wambaugh
Perfecting the computer models that keep us safe
David Reif
Pinpointing the causes of childhood asthma
Christal Bowman
Modelling allergic responses to food
What makes one person allergic to eggs, while her sister can eat omelets to her heart's content? What makes one person allergic to shellfish, and another allergic to peanuts? What, in essence, makes a food an allergen?
EPA postdoc Christal Bowman, left, examines protein bands in a polyacrylamide gel with mentor MaryJane Selgrade.
EPA postdoc Christal Bowman is researching just that question. Working with mentor MaryJane Selgrade of the National Health and Environmental Effects Research Laboratory, Bowman is developing models of food allergens to better understand how certain food proteins cause allergies. Her research will help ensure the safety of genetically modified food crops that produce their own protein-based pesticides.
"Allergies to food arise spontaneously, and no one knows why," Bowman explained. "We define something as an allergen when we observe it causing an allergic reaction, but no one knows for sure why some proteins cause reactions and others don't."
Bowman's goal is to create a model that could help predict whether a protein could be an allergen before any allergic response is observed. Her research has uncovered two important findings: Although the immune system's normal response to food is to ignore it rather than attacking it as a threat, the requirements for such tolerance are different for different foods; additionally, the harder a protein is to digest, the more likely it is to cause allergic reaction in the model.
Bowman's findings could improve current models and help identify potential allergens more accurately. Her work also could help doctors better treat people with food allergies.
Bowman has found the collaborative environment at EPA helpful for conducting her research and expanding her training.
"There's a really broad range of experts here, and they're completely accessible," she said. "You can find anybody who knows how to do anything in these buildings. And we're not competing with one another: You can talk to anyone here, and they're in a position to help you."
Nick Radio
Protecting children's nervous systems
Nick Radio's young son is in the exploring stage: He's always crawling around on the floor, picking something up, and putting it in his mouth. For Radio, that's just another validation for his chemical research at the Environmental Protection Agency.
Radio holds a postdoctoral position with the National Health and Environmental Effects Research Laboratory. He helps create streamlined, cellular-based laboratory tests to evaluate chemicals' effects on developing nervous systems; that is, young, growing nervous systems, like his son's.
EPA postdoc Nick Radio, left, examines data from a high-throughput screening assay with his mentor, Bill Mundy, standing.
"There are many new chemicals being used in our environment, and we don't have the time or the money to evaluate every chemical with conventional lab tests," Radio explained. "So we're developing high-throughput screening techniques."
Cellular high-throughput techniques involve placing small amounts of chemicals into a large plate of sample wells; each well also contains a small cell sample. An automated microscope then analyzes the samples in large batches, significantly cutting analysis time.
Radio spent more than a year honing the technique. Now he is using the method to screen larger volumes of chemicals. He recently began work on a joint project with the National Center for Computational Toxicology, evaluating 320 pesticides to determine their effects on developing nervous systems.
"One of the main reasons I decided to take this postdoc was the team-based research approach here in the lab," Radio said. "It's really great for a young scientist like me to be exposed to so many different viewpoints, because that helps me approach problems with more tools."
Multiple viewpoints serve well when tackling the real-world issues under investigation in Radio's lab, he said. Ultimately, Radio hopes that his work at EPA will help protect children like his son from harm.
Terry Green
Investigating our risks from air pollution
EPA scientists found that when they exposed a particular gene - the Ki-Ras gene - to high levels of air pollution, the gene mutated. Some of the mutations eventually caused tumors to form. But the high doses of hydrocarbons used in the laboratory experiment were much higher than the day-to-day levels found in our environment. How do we figure out our real risk at these lower levels of exposure?
EPA postdoc Terry Green and his mentor, Jeffrey Ross, load samples into a thermal cycler for analysis. The thermal cycler will create millions of copies of the Ki-ras gene, which Green will examine for mutations.
EPA postdoc Terry Green has been working on this issue for a year and a half. Applying his training in biochemistry and molecular biology to a new field - toxicology - Green investigates the mutations that occur when mammals are exposed to lower, more realistic levels of airborne pollutants.
"I'm trying to determine if there is a low-dose risk, and whether or not our current model of risk is accurate at these low doses," Green explained.
To examine these mutations, Green amplifies - or copies - the gene using a technique called polymerase chain reaction, generating millions or more copies.
"There could be one mutation in a million copies of the gene, and a mutation doesn't necessarily mean a tumor will form," Green said. "I'm trying to figure out the mechanism for the mutation: what, exactly, causes this gene to mutate under these conditions?"
Green's work is part of a larger effort to better understand how low-level exposure can lead to tumors. His research not only will help him hone his scientific skills and gain new expertise; ultimately, it will help protect us from unsafe levels of air pollution.
John Wambaugh
Perfecting the computer models that keep us safe
The significance of laboratory results can be tricky to pin down: scientists ask, did chemical X really cause this outcome, or were unknown variables also affecting the results? Uncertainty can increase when scientists must then use these results to predict chemicals' effects on humans.
That's where EPA postdoc John Wambaugh comes in. Working with mentors at the EPA's National Center for Computational Toxicology, Wambaugh helps reduce this uncertainty by applying the number crunching ability of computers to mathematical models designed to predict the effects of chemicals on humans.
Using data from laboratory experiments, Wambaugh looks for uncertainty within the models' equations and parameters.
EPA post doc John Wambaugh consults with mentor Woody Setzer about a statistical analysis problem.
"My job is to figure out what we don't know, in order to figure out how accurate these models are," Wambaugh explained. "You could be 90 percent sure that chemical X has a toxic effect; if you then extrapolate that to 300 million Americans, that 10 percent of uncertainty suddenly becomes a much bigger deal."
Wambaugh's experimental physics background comes in handy when sorting through the models' dense mathematical equations. When he gets stuck, he can turn to his mentors - biologist Hugh Barton and statistician Woody Setzer - for advice.
A full-time federal employee, Wambaugh appreciates the ways that his postdoc position is stretching his knowledge and experience.
"I'm learning all sorts of new things: a little of what Hugh knows, a little of what Woody knows," said Wambaugh. "Plus, I'm getting to learn how the government works. With the government funding so much of the research in academia, getting a feel for how a large government agency makes decisions and reaches conclusions is very valuable."
David Reif
Pinpointing the causes of childhood asthma
Asthma afflicts up to one in four urban children in the United States. It causes wheezing, coughing, shortness of breath and tightness of the chest. But scientists do not fully understand how a person's genes and environment interact to cause asthma. Doctors need this information to better treat patients, and people need to know how they could avoid risk factors.
EPA postdoc David Reif works at the forefront of asthma research in his position with the National Center for Computational Toxicology. Using computational methods to analyze data, Reif is helping pinpoint the causes of childhood asthma, be they genetic, environmental or both.
EPA postdoc David Reif consults with mentor Elaine Cohen Hubal on data from a study of pesticide exposure in residential settings. Cohen Hubal is an expert on environmental exposure and helps Reif apply his analytical skills to exposure science.
"My graduate work focused on genetic risk factors for complex diseases," Reif said. "Here, I'm bringing the genetic perspective and adding an environmental context, asking, 'Why do people's bodies react differently to the same environmental stimuli, such as mold or air pollution?'"
Reif analyzes genetic, environmental exposure and clinical data gathered from Detroit children as part of the EPA's Mechanistic Indicators of Childhood Asthma (MICA) study. A major goal of the study is to identify whether subtypes of asthma exist beyond the normal clinical diagnosis: perhaps one type of asthma is caused by a particular set of genes, while another is caused by mold, while yet another is caused by both, Reif explained.
Identifying asthma's causes will help with treatment. Scientists could develop therapies targeting a genetic cause, or doctors could recommend lifestyle changes if the cause is environmental.
Reif appreciates that his research skills can make a difference at the EPA.
"EPA's mission is to protect human health and the environment, so our research focuses on that goal," he said. "What we do here could make a difference in the near term, because our research is goal-oriented."
Links to More Postdoctoral Fellows