It’s hard for a sixth-grader to nail down exactly what she wants to do for the rest of her life, but that’s when the process started for Madison Green. After all, it isn’t the easiest of decisions.
With a wide range of possibilities, it can be hard for anyone to be truly sure of a decision that will shape the rest of their life.
For Green, a junior biology and public health dual major, her path shifted toward science when she joined Science Olympiad, a national nonprofit organization dedicated to improving the quality of K-12 science education.
Once a week, every week for seven years, Green met after school with her friends and mentors to learn and prepare for competitions. The organization gave her the opportunity to try out different areas of science such as chemistry, biology and physics. With events that range from building Rube Goldberg-like devices to others focused on microbes or designing experiments, the events and preparation run the gambit of science, medicine and engineering. Through the academic seasons, Green built on what she learned previously, expanded her knowledge of science and fell in love with research.
“Science Olympiad really helped me focus more on biology and it also helped me become an independent learner,” Green said. “For all the events at the national level, we really had to take charge and decide what we needed to learn and where we needed to strengthen our knowledge.”
After all of her years competing in Science Olympiad, Green knew she wanted to pursue science, but the question now was in what capacity.
Early on in her undergraduate career Green started looking for opportunities in research to supplement what she was learning in class. She remembers being drawn to Cheryl Rosenfeld’s lab in the Bond Life Sciences Center because of the opportunity to research behavior in mice models.
“I became very interested in public health in high school,” Green said. “When I got to college, I began exploring different careers in the health care field and public health really stuck out to me. I realized I wanted to work more one-on-one with patients.”
Being able to give back and help her community was a top factor in Green’s decision to add public health as a second major. She saw the opportunity to connect her interest in biology and public health through her research in Rosenfeld’s lab. Overall, public health’s ability to assess problems on a population level drew Green in.
“We’re looking at the maternal-fetal effects of oxycodone on mother mice. My research partner is looking more at behavior and I’m looking at the placenta,” Green said. “It’s definitely an interesting bridge for myself between my biology major and my public health major. As a public health major, we’ve looked into the opioid crisis and the effect’s it’s having across the nation and here in Missouri.”
In order to solidify her decision, Green also joined Beta Beta Beta, the biology honor society, and pre-med society. In both groups, Green has found support and guidance from her fellow peers and mentors. Ultimately, her involvement in pre-med society is what guided her toward applying to medical school post-graduation.
But now, the big decision lies in what branch of medicine to pursue.
“I’m hoping to figure that out when I get to medical school, but right now, I’m really focused on emergency medicine as a strong contender,” Green said. “I think there is a great opportunity to impact public health whether it be because of the opioid crisis or people whose symptoms have worsened over time because they didn’t have access to a family health practitioner.”
Green’s life has been composed of carefully calculated steps that will one day launch her into her career. From Science Olympiad, to Rosenfeld’s lab, science societies and one day medical school, Green wants to ensure she’s on the right track.
“#IAmScience because research gives me an avenue to explore my curiosity and possibly discover something groundbreaking.”
Research is all about discovering the answers to the unknown, pushing boundaries and exploring the depths of the field. As a junior biology major, Madison Ortega is already getting a taste of that.
Her freshman year, Ortega got a brochure for the Maximizing Access to Research Careers/Initiative for Maximizing Student Diversity (MARC/IMSD) program. This program encourages students to get involved with science even if they have had little exposure to it previously. Its ultimate goal is to provide a foundation of advanced science skills for minorities that can be applied to higher degrees within the field.
“I got to start exploring research right away through IMSD,” Ortega said. “It gave me the opportunity to look into various labs.”
Ortega landed on working in Cheryl Rosenfeld’s lab at Bond LSC because she felt she would have ample opportunities. That experience has led her to an individual project working on samples of spiny rats — an endangered species from Japan.
“The male doesn’t have a Y chromosome, so we’re trying to figure out how sexual differentiation occurs in the species without it,” Ortega said.
Through Bond LSC, she connected with Hokkaido University in Japan who donated the samples.
“They’re not fresh samples — they’re about 10 years old,” Ortega said. “But I showed interest in the project and ended up getting to work on it one-on-one with our lab mentor.”
In addition to her individual project, Ortega works with other undergraduates within her lab.
“We’re doing a variety of experiments that include social testing on mice,” Ortega said. “We do anxiety testing and also perform Barnes maze with the animals.”
These mazes and tests aim to see the impact of chemicals in the environment that mimic hormones like estrogen and impact animal growth and development.
“Basically, we’re trying to see how endocrine disruptors we feed the mice affect their offspring,” Ortega said. “We want to know how it affects them neurologically. In order to accomplish this, we are collaborating with various other groups in Bond LSC.”
Ultimately, they’re aiming to uncover if Bisphenol S (BPS) has any impact on the mice neurologically. These substances are similar to Bisphenol A (BPA), a chemical used as a hardener in production of plastics and in other manufacturing. As concern has raised over BPA, companies have replaced the chemical with BPS and others to allay public anxiety over its impact. But not much research has been done on BPS and its effect on animals.
“They may be found to have some neurological effects, so research is trying to uncover what exactly those are,” Ortega said. “The many tests we run will help us understand to the extent these chemicals are affecting us.”
After graduation, Ortega envisions herself continuing with research as a focal point of her career.
“I love research,” Ortega said. “My end goal is medical school, but I’m considering a program that combines a master’s degree with a Ph.D. in either dermatology or pediatrics.”
Regardless of her path, the lab work she does now leaves her prepared for the future.
“I spend a lot of time in the lab with my team and individually,” Ortega said. “It’s fun to have ownership of a project, and it’s also fun to work with other undergraduates and have camaraderie. I’m really fortunate.”
“#IAmScience because research allows me to challenge my understanding of the world around me and strive toward figuring out the unknown.”
Paul Caldo isn’t your typical undergraduate student. As a junior, Caldo is double majoring in Biology and Psychology, which gives him a unique perspective on science as a whole.
It is in the overlap between his majors, however, that most interests him.
“I am fascinated with development in both psychology and biology because the early stages of life lay the foundation for who and what you will become,” he said. “I have an appreciation for all spheres of academia, and it is becoming more evident to me that an interdisciplinary approach to research will lead to more and more breakthroughs in science.”
As a member of both Dr. Cheryl Rosenfeld’s biology lab in Bond LSC and Dr. Ashley Groh’s psychology lab in Noyes Hall, Caldo gets the best of both worlds while studying the fields he loves. In Rosenfeld’s lab, he’s currently analyzing how endocrine disruptors – which are found in everyday products like sunscreen – impact the development of reproductive organs in female mice.
“By understanding the underlying mechanisms that drive this interaction, our goal is to potentially reverse some of the harmful effects that result from heavy exposure to endocrine disruptors,” Caldo said.
His efforts have not gone unnoticed. Caldo was selected to join an ASH Scholars undergraduate team mentored by Dr. Grohl and collaborator Dr. Amanda Rose. The ASH Scholars program, which provides a $2000 scholarship, is sponsored by the Honors College and the Office of Undergraduate Research. He also received a $200 travel grant that will allow him to present his findings at the Developmental Origins of Health and Disease Conference in Detroit later this month.
“I’m really excited about the travel grant to Detroit,” Caldo said. “It will be my first time attending a national-level conference. I hope to benefit from presenting my work as well as learning from many great scientists from across the country. I think it will be a really enriching experience, and I hope to take away a lot from it.”
After graduation, Caldo hopes to attend graduate school to study developmental psychology using an interdisciplinary bio-behavioral approach to answer research questions. Ultimately, his plan is to earn a PhD in developmental psychology. Until then, though, he’s enjoying his time at Bond LSC learning as much as possible.
“The ambiance is great – working closely with some of the best researchers on campus is an amazing feeling,” Caldo said.
Scientific success largely hinges on research results, and four recent promotions at Bond Life Sciences Center celebrate that achievement.
Cheryl Rosenfeld, D Cornelison and Melissa Mitchum of Bond Life Sciences Center were promoted to full professor as of September 1, while Laurie Erb received a promotion as a non-tenure-track research professor. They are the first female full professors in Bond LSC’s 13-year history.
University of Missouri’s Assistant Vice Chancellor of the Division of Inclusion, Diversity and Equity, Noor Azizan-Gardner, said the promotions made her optimistic.
“Three women all going up to full professor – it’s phenomenal,” she said. “And the fact that they all have labs in Bond LSC makes me deliriously happy. Not just for us and them, but for the women who will be the next generation. The ripple effect is bigger than just the three of them.”
Promotion and tenure at MU follows rigorous guidelines that take teaching, research success and service into account to advance professors through three tiers — from assistant to associate to full professorship — over more than a decade.
But like many technical fields, science lags behind in its proportion of women to men. Growing that diversity is important to the breadth of scientific inquiry. As an advocate of collaboration, the promotion of three women to full professor at Bond LSC hopes to reinforce that diversity.
Cornelison and Mitchum were quick to stress their promotions had nothing to do with their gender, and everything to do with their science.
“It just doesn’t cross my mind,” Mitchum said. “I honestly don’t walk around thinking about gender. I just do the best I can and that’s all I can do.”
Similarly, Cornelison said, “I am not a female scientist. I am a scientist. Period. It should not be a part of the story.”
Rosenfeld, however, is concerned that administrators are not giving women the support necessary to flourish in their careers.
“I work seven days a week and I deserve respect and to be taken seriously on par with my male colleagues,” she said. “I am not doing this as a hobby. This is my passion, and, hopefully in the future, women like myself will be treated equally.”
A Pervasive Problem
A study conducted in 2015 by the Chancellor’s Status of Women Committee and the Status of Women Committee in the College of Arts and Science at MU found that with regard to gender equity on campus, there was no evidence of a systematic pay bias against female faculty. However, it did find that the average salary for female faculty is almost $16,000 (or 15 percent) below the average salary for male faculty and that the colleges with the highest average salaries were predominantly male.
Cornelison, Mitchum and Rosenfeld all believe that female scientists at MU face at least three significant hurdles on their path to full professor: the amount of time it takes compared to their male colleagues, the lack of mentorship, and the high ratio of male full professors compared to female full professors in several departments.
Mitchum stated that there are only two other female full professors — Jeanne Mihail and Michelle Warmund — in the plant sciences department compared to at least 17 males. Rosenfeld and Cornelison had similar ratios in their respective departments.
Recent controversies indicate gender equity is a persistent challenge in the field as a whole.
In 2015, a study published by the American Psychological Association found that when considering requests from prospective students seeking mentoring in the future, the science faculty at research-intensive universities were more likely to hire a male lab manager, mentor him, pay him more and rate him as more competent than a female candidate with the exact same resume. And this year, two senior female scientists sued the prestigious Salk Institute for Biological Studies, alleging pervasive gender discrimination and systematic sexism.
Although female scientists remain underrepresented in many countries, academic journal publisher Elsevier released a report in 2017 that shows improvement. It stated that women’s scholarly authorship increased overall from 30 percent in the late 1990s to 40 percent two decades later. In terms of raw proportions, the percentage of women scientists in the U.S. increased from 31 percent from 1996-2000 to 40 percent from 2011-2015.
Rosenfeld, Cornelison and Mitchum’s success in the departments of Biomedical Sciences, Biological Sciences and Plant Sciences, respectively, follow several decades of hard work and passion in their fields.
But their interest in science started in unique ways.
“In middle and high school I was always excited about science classes,” said Mitchum. “I liked physics. I liked chemistry. I was lucky to have a science teacher, Patty Gustin, who knew I had an interest in science, saw some potential and encouraged me. She was actually the first person to encourage me to go on to college in science.”
Mitchum went on to get an undergraduate degree in biology at the University of Puget Sound in Tacoma, Washington. She immediately continued her education and received her masters in plant pathology at the University of Nebraska, Lincoln and her Ph.D. in plant pathology and biotechnology at North Carolina State University in Raleigh.
Cheryl Rosenfeld’s high school biology teacher, Patricia Murphy, was also the first person to put her on the science track.
“I can still picture her to this day,” Rosenfeld said, smiling. “She gave me a C on my first lab assignment. My friend received a better grade and we did the same work, so I asked her why I got such a low grade. She told me that I was going to be a scientist, that she expected more of me, and to improve my grade she allowed me to help prep the lab experiments.”
Rosenfeld went on to receive a bachelor of science and DVM (Doctor of Veterinary Medicine) from the University of Illinois at Urbana-Champaign and a Ph.D. in Animal Sciences and Reproductive Biology from MU.
Cornelison’s path was a bit different. Like many undergraduate scientists, she initially thought she would go to medical school. But during an independent study, she was assigned to a lab doing behavior genetics in mice and fell in love with research.
“Unlike my experience in Chemistry classes, I was now in an environment where I was expected to go and do things nobody had ever done before,” Cornelison said. “And I got to tell people about it. And I got to decide what the next unknown thing I wanted to know was. After that, I had to decide whether to apply to medical school or graduate school because I only had enough money to take the GRE or the MCAT, so I took the GRE. And I am still incredibly grateful for the people who took me into their lab and taught me to science.”
Cornelison credits that experience with why she enjoys having undergraduates in her lab. To date, over 20 of them have graduated with departmental honors based on their independent research projects.
“If I can give students a taste of what that experience of discovery feels like, I’m happy. It changes your perspective on many things,” she said.
The concept of mentorship is something Rosenfeld, Cornelison and Mitchum all agree is critical for budding scientists, male or female.
Each shared stories about the vast amount of mentors that inspired them and students they still keep in contact with. Mitchum has an especially meaningful relationship with one of her mentors.
“While I was working in a lab as an undergraduate I had the opportunity to interact with a visiting scientist who would work in our lab, Donald Foard, an older gentleman at the time, and he became my mentor,” Mitchum said fondly. “I don’t think I would be where I am today without his mentorship. As an undergraduate, he encouraged me. He believed in me. He inspired me to go to graduate school. And we still keep in contact today. He is 86 years old now and we still write letters back and forth. I recently had the privilege of sending him my promotion letter. The sheer excitement of sharing that promotion with him was incredibly meaningful.”
“Without him believing in me I don’t think I would be sitting here talking to you about this promotion today,” she added. “He believed in me during a time when I didn’t believe in myself.”
Supporting Women in STEM
In an effort to promote mentorship and address female-specific concerns in the STEM fields, such as wage negotiation and salary differences, MU recently started its first Women in STEM group. The group was spearheaded by Rosenfeld and Azizan-Gardner, and had its first meeting in July.
“The issue of mentoring is something that you see everywhere, not just here,” said Azizan-Gardner. “It is a pervasive problem we need to address. And we can do that here at MU and do something that will really benefit everyone.”
Female mentorship is something that Rosenfeld believes is critical for female scientists and she makes an effort to mentor female undergraduate and graduate students.
“When you’re struggling, you often think that there is no way you can do this,” said Rosenfeld. “But if you see someone that looks like you that has succeeded and is teaching you, all the sudden your goal does not seem impossible.”
Mitchum is another strong proponent of mentorship and undergraduate research. She has mentored 26 undergraduate researchers in her lab, and 12 of them went on to graduate school, while many of the rest went to medical school.
“It’s so important for us as mentors, female or male, to believe in and encourage the younger generation,” she said. “I believe in many cases, you just need someone to believe in you and know you can accomplish things. It’s important to have quality in mentorship — investing in students and giving students your time and direct attention.”
Rosenfeld hopes that the Women in STEM group will empower female scientists to be more assertive. She said the first meeting was “eye opening” because many of the participants had similar experiences and it was powerful to hear their frustrations. About 20 women attended the first meeting, and Rosenfeld is confident that number will increase.
Azizan-Gardner believes that Bond LSC has the potential to be a leader in promoting, recruiting and retaining female scientists. And as a result, will encourage more women to go into STEM fields.
“I hope having a strong Women in STEM group will be great recruitment as well for other general faculty to come to MU,” said Azizan-Gardner. “At least that’s my goal, and that’s the area I’m responsible for. And on top of that, I think it will really entice other undergraduate women to go into STEM.”
Turtles could help determine how exposure to harmful chemicals during development affects male and female brains Jeff Sossamon | MU News
Bisphenol A (BPA) is a chemical used in many consumer products including water bottles, metal food storage products and certain resins. Often, aquatic environments such as rivers and streams become reservoirs for BPA, affecting turtle habitats. Last year, a team of researchers led by the University of Missouri determined that BPA can disrupt sexual function in painted turtles, causing males to develop female sex organs. Now, the team has shown that BPA also can induce behavioral changes in turtles, reprogramming male turtle brains to show behavior common in females. Researchers worry this could lead to population declines in painted turtles.
“Previously, our research team found that BPA and ethinyl estradiol (EE2), a hormone found in birth control pills, could ‘sex-reverse’ turtles from males to females,” said Cheryl Rosenfeld, an associate professor of biomedical sciences in the MU College of Veterinary Medicine and an investigator in the Bond Life Sciences Center. “Painted turtles and other reptiles lack sex chromosomes. The gender of painted turtles and other reptiles is determined by the incubation temperature of the egg during development. Studies have shown that exposure to endocrine-disrupting chemicals (EDCs), such as BPA, can override incubation temperature and switch the sex of males to females. In our latest study, we found that BPA also affects how the male brain is ‘wired,’ potentially inducing males to show female type behavioral patterns.”
Researchers applied a liquid form of BPA and ethinyl estradiol to painted turtle eggs and incubated the eggs at a temperature that typically results in males. Five months after hatching, turtles were tested with a spatial navigation test that included four food containers, only one of which was baited with food. Each turtle was randomly assigned one food container that did not change over the trial period.
Researchers predicted that male turtles exposed to BPA and EE2 would exhibit improved navigational ability — similar to behaviors observed in female turtles. Results showed that developmental exposure to BPA and EE2 improved spatial navigational learning and memory in males, as evidenced by increased number of times spent in the correct target zone and greater likelihood of solving the maze compared to control turtles, who were male based on the lower incubation temperature.
“Previous studies have found that female turtles are much more adept at spatial navigation — think of female sea turtles that return many years later to the same beaches where they hatched to lay their own eggs,” Rosenfeld said. “We found that developmental exposure to BPA essentially overrides the brain development of male turtles as indicated by the enhanced navigational ability of the turtles we studied. While improved spatial navigation might be considered a good thing, it also may suggest that when they reach adulthood male turtles will not exhibit courtship behaviors needed to attract a mate and reproduce, which could result in dramatic population declines.”
Rosenfeld notes that this is the first study to show that these harmful chemicals not only reverse the physical sex-characteristics but also affect the brain in a turtle species. Turtles are known as an “indicator species” because they can be used as a barometer for the health of the entire ecosystem. By understanding the possible effects EDCs have on turtles, researchers might be able to understand the possible effects the chemicals have on other wildlife species and humans, Rosenfeld said.
How unruly data led MU scientists to discover a new microbiome By Roger Meissen | MU Bond Life Sciences Center
It’s a strange place to call home, but seminal fluid offers the perfect environment for particular types of bacteria.
Researchers at MU’s Bond Life Sciences Center recently identified new bacteria that thrive here.
“It’s a new microbiome that hasn’t been looked at before,” said Cheryl Rosenfeld, a Bond LSC investigator and corresponding author on the study. “Resident bacteria can help us or be harmful, but one we found called P. acnes is a very important from the standpoint of men. It can cause chronic prostatitis that results in prostate cancer. We’re speculating that the seminal vesicles could be a reservoir for this bacteria and when it spreads it can cause disease.”
Experiments published in Scientific Reports — a journal published by Nature — indicate these bacteria may start disease leading to prostate cancer in mice and could pass from father to offspring.
A place to call home
From the gut to the skin and everywhere in between, bacterial colonies can both help and hurt the animals or humans they live in.
Seminal fluid offers an attractive microbiome — a niche environment where specific bacteria flourish and impact their hosts. Not only is this component of semen chockfull of sugars that bacteria eat, it offers a warm, protected atmosphere.
“Imagine a pond where bacteria live — it’s wet it’s warm and there’s food there — that’s what this is, except it’s inside your body,” said Rosenfeld. “Depending on where they live, these bacteria can influence our cells, produce hormones that replicate our own hormones, but can also consume our sugars and metabolize them or even cause disease.”
Rosenfeld’s team wasn’t trying to find the perfect vacation spot for a family of bacteria. They initially wanted to know what bacteria in seminal fluid might mean for offspring of the mice they studied.
“We were looking at the epigenetic effects — the impact the father has on the offspring’s disease risk — but what we saw in the data led us to focus more on the effects this bacterium, P. acnes, has on the male itself,” Rosenfeld said. “We were thinking more about effect on offspring and female reproduction — we weren’t even considering the effect the bacteria that live in this fluid could have on the male — but this could be one of the more fascinating findings.”
But, how do you figure out what might live in this unique ecosystem and whether it’s harmful?
First, her team found a way to extract seminal fluid without contamination from potential bacteria in the urinary tract.
“We gowned up just like for surgery and we had to extract the fluid directly from the seminal vesicles to avoid contamination,” said Angela Javurek, primary author on the study and recent MU graduate. “You only have a certain amount of time to collect the fluid because it hardens like glue.”
Once they obtained these samples, they turned to a DNA approach, sequencing it using MU’s Genomics Technology Core.
They compared it to bacteria in fecal samples of the same mice to see if bacteria in seminal fluid were unique. They also compared samples from normal mice and ones where estrogen receptor genes were removed.
The difference in the data
It sounds daunting to sort and compare millions of DNA sequences, right? But, the right approach can make all the difference.
“A lot of it looks pretty boring, but bioinformatics allow us to decipher large amounts of data that can otherwise be almost incomprehensible,” said Scott Givan, the associate director of the Informatics Research Core Facility (IRCF) that specializes in complicated analysis of data. “Here we compared seminal fluid bacterial DNA samples to publicly available databases that come from other large experiments and found a few sequences that no one else has discovered or at least characterized, so we’re in completely new territory.”
The seminal microbiome continued to stand out when compared to mouse poop, revealing 593 unique bacteria.
One of the most important was P. acnes, a bacteria known to cause chronic prostatitis that can lead to prostate cancer in man and mouse. It was abundant in the seminal fluid, and even more so when estrogen receptor genes were present.
“We’re essentially doing a lot of counting, especially across treatments to see if particular bacteria species are more common than others,” said Bill Spollen, a lead bioinformatics analyst at the IRCF. “The premise is that the more abundant a species is, the more often we’ll see its DNA sequence and we can start making some inferences to how it could be influencing its environment.”
Although this discovery excites Rosenfeld, much is unknown about how this new microbiome might affect males and their offspring.
“We do have this bacteria that can affect the male mouse’s health, that of his partner and his offspring,” Rosenfeld said. “But we’ve been studying microbiology for a long time and we still find bacteria within our own bodies that nobody has seen before. That blows my mind.”
Female rats struggle to find their way in BPA study from MU and the NCTR/FDA
Despite concerns about bisphenol A (BPA), academic and regulatory scientists have yet to reach a consensus on BPA’s safety.
The National Institute of Environmental Health Sciences (NIEHS), the National Toxicology Program (NTP), the Food and Drug Administration and independent university researchers are working together to change that.
“The idea of this Consortium is to examine the potential systems that have been previously suggested to be affected by BPA,” said Cheryl Rosenfeld, an associate professor of biomedical sciences at the University of Missouri and one of twelve researchers involved in the project.
Rosenfeld’s group looked at spatial navigation learning and memory. They found that prenatal exposure to BPA could potentially hinder the ability of female rats to learn to find their way through a maze. This effect was not seen in male rats.
Approved by the FDA in the early 1960s, BPA can be found in a wide variety of products, including plastic food and drink containers with recycle codes 3 or 7, water and baby bottles, toys, the linings of metal cans and water pipes, even patient blood and urine samples.
BPA has structural similarities to estrogen and can potentially act as a weak estrogen in the body.
In Rosenfeld’s experiment, researchers at the National Center for Toxicology Research gave pregnant rats a fixed dose of BPA every day: a low, medium, or high dose.
After the baby rats were born, researchers continued to dose the babies, both male and female, according to what their mothers had received.
When these rats reached three months old, they were tested in a circular maze with twenty possible exit holes, one of which was designated as the correct escape hole. Every day for seven days, researchers tested the rats’ abilities to solve the maze in five minutes and timed them as they ran.
Rats solve mazes in three ways, Rosenfeld said.
They can run through the labyrinth in a spiral pattern, hugging the outer walls, and work their way in until they find the correct exit hole in what is called a serial search strategy.
Or they might move aimlessly in the maze using an indirect search strategy, Rosenfeld said. “In this case, the rats seemingly find the correct escape hole by random chance.”
Lastly, they can travel directly from the center of the maze to the correct escape hole. The third strategy is considered the most efficient method because the rats find their way swiftly, Rosenfeld said.
Sarah Johnson, a graduate student and first author on the paper, assessed each rat’s performance in the maze using a three-point tracking program that recognizes the rat’s nose, body, and tail.
Using the program, Johnson measured their performances in terms of the total distance traveled, the speed at which the rat ran the maze, how long it took the rats to solve the maze (latency), and how often the rat sniffed at an incorrect hole.
The last two parameters are considered the best gauges of spatial navigation learning and memory.
“What you expect to see is that they should start learning where that correct escape hole is,” Rosenfeld said. “Thus, their latency and sniffing incorrect holes should decrease over time.”
Rosenfeld’s group found that female rats that had been exposed to the highest dose of BPA since fetal development were less likely to find the escape hole than rats that hadn’t been exposed to BPA.
As for how this study may translate to people, Rosenfeld said, “the same brain regions control identical behaviors in rodents and humans.”
She considers it a starting point for setting up future experiments that take into consideration sex differences in cognitive behaviors and neurological responses to BPA.
Immediate next steps for the Rosenfeld group include analyzing tissue collected from the brains of rats that had undergone maze testing. Rosenfeld’s team of researchers will measure DNA methylation and RNA expression in the brain to determine which genes might be involved in navigational learning and memory. Their overarching goal is to determine how changes in observed sex- and dose-dependent behaviors occur on the molecular level.
NIEHS grant U01 ES020929 supported this research. Additional coauthors include Mark Ellersieck and Angela Javurek of the University of Missouri, Thomas H. Welsh Jr. of Texas A&M University, and Sherry Ferguson, Sherry Lewis, and Michelle Vanlandingham of the National Center of Toxicological Research/Food and Drug Administration. Read the full study on the Hormones and Behavior website and browse the supplementary data for this work.
Endocrine disruptors impact physical activity and metabolism in mice
By Caleb O’Brien | MU Bond Life Sciences Center
Could your experiences in the womb make you lazy as an adult?
A recent study of California mice suggests that early exposure to environmental chemicals can later impact an animal’s metabolism and level of voluntary physical activity, according to new University of Missouri research.
“We found that if we developmentally exposed California mice to bisphenol A (BPA) or ethinyl estradiol (EE), the estrogen present in birth control pills, it caused later disruptions in voluntary physical activity,” said Cheryl Rosenfeld, a researcher in MU’s Bond Life Sciences Center and associate professor of biomedical sciences in the College of Veterinary Medicine. “What that means is they move around less in their home cage, they’re more likely to sleep, and they engage in less voluntary physical activity.”
Rosenfeld’s lab studies the ways that exposure to environmental chemicals such as BPA can affect other behaviors, including cognition and parenting. Endocrine-disrupting chemicals can accumulate in the environment and act like the hormones naturally produced by many organisms, including humans. To test the chemicals’ impact on metabolism and activity, the lab used California mice. This mouse model is a good model for metabolic diseases. And because these animals are initially derived from the wild, they may better replicate the genetic diversity of most human populations.
The researchers exposed the mice to BPA and EE in the womb and until weaning via the mom’s diet. A third group of mice whose mothers were placed on a phytoestrogen-free control diet was not exposed to either chemical. The scientists then placed all the mice on this same control diet and measured their energy expenditure, body composition and level of voluntary physical activity as adults.
To test those attributes, Rosenfeld’s lab relied on a variety of tools and techniques. They rigged bicycle computers to “hamster wheels” to track how far, fast and for how long the mice ran. Using a device called a “Promethion continuous measurement indirect calorimetry system” the researchers continuously monitored the mice’s energy expenditure by measuring oxygen consumption and carbon dioxide production and by using a three-beam system, tracked the rodents’ movements during the dark and light cycles.
Later, the researcher measured the animals’ body composition using an EchoMRI, a tiny MRI machine the size of a filing cabinet, and finally measured circulating concentrations of glucose and hormones that regulate metabolism.
Female mice exposed to BPA and EE were less active than control mice. They moved around their cages less at night (when the nocturnal California mouse is considered most active), moved more slowly, drank less water, and spent more time sleeping. In addition, BPA-exposed females burned more carbohydrates relative to fats, as compared to control mice. This is similar to the difference between obese and slender humans, and many researchers believe that burning more carbohydrates relative to fats can lead to fats gradually accumulating in the body.
“It’s worrisome that environmental chemicals we are exposed to in utero can override our genes and disrupt our neuro-circuitry,” said Sarah Johnson, a research specialist and graduate student in Rosenfeld’s lab and primary author on the study. “The net effect is that we can have behavioral disruptions into adulthood, including altered physical activity.”
The researchers are currently conducting follow-up studies to determine if the changes caused by exposure to BPA and EE predispose mice to obesity and other metabolic disorders. They also are interested in exploring if exposure could affect the children and grandchildren of these mice and examining the potential underlying neural mechanisms.
“Our findings are significant because decreased voluntary physical activity, or lack of exercise, can predispose animals or humans to cardiovascular diseases, metabolic disorders and even cancer,” Rosenfeld said.
Other authors on the study are Angela Javurek and Michele Painter (MU Biomedical Sciences), Mark Ellersieck (MU Agriculture Experimental Station- Statistics), Charles Wiedmeyer (MU Veterinary Medical Diagnostic Laboratory and Department of Veterinary Pathobiology) and John Thyfault (Kansas University Medical Center, Molecular and Integrative Physiology)
The study, “Sex-Dependent Effects of Developmental Exposure to Bisphenol A and Ethinyl Estradiol on Metabolic Parameters and Voluntary Physical Activity” was supported by NIH Grant 5R21ES023150 (to C.S.R.) and R01DK088940 (JPT) and was published in the Journal of Developmental Origins of Health and Disease.
Endocrine disruptors alter parent behavior in California mice
By Roger Meissen | MU Bond Life Sciences Center
What if a chemical changes the way an animal parents?
That could happen due to endocrine disruptors like bisphenol A (BPA).
A recent study of California mice exposed to BPA showed parents spend less time feeding, grooming and interacting with their babies, according to University of Missouri research. Even mother mice not exposed to the chemical parented differently if their male partner was exposed during development.
Most studies only use laboratory mice and rats — where the mother is the sole parental provider — so how early contact to BPA may affect the father and his partner remained a critical gap in existing research.
“The nature and extent of care received by an infant is important because it can affect social, emotional and cognitive development,” said Cheryl Rosenfeld, a researcher in MU’s Bond Life Sciences Center and associate professor of biomedical sciences in the College of Veterinary Medicine. “We found that females who were exposed early on to BPA spent less time nursing, so the pups likely did not receive the normal health benefits ascribed to nursing. Likewise, we found that developmental exposure of males and females resulted in them spending more time out of the nest and away from their pups, further suggesting that biparental care was reduced.”
BPA and other endocrine disrupting chemicals like ethinyl estradiol (EE) — found in birth control — concern scientists because they build up in the environment and mimic natural hormones produced by animals, including humans. Everyday exposure to these chemicals can impact offspring development and now have been found to alter adult behavior in test animals.
California mice have special significance for studying parental behavior. Unlike most lab mice, Californian mice pair up to mate and care for offspring. This monogamous behavior could give researchers insight into child rearing behavior found in most human societies and other biparental animals that would be impossible to measure in lab mice and rats.
MU graduate student and primary author Sarah Johnson worked with Rosenfeld to design the study to look at both sexes. Female and male mice were fed one of three diets — food supplemented with BPA or ethinyl estradiol or endocrine-free (control) food — two weeks before breeding. The mice were then randomly paired with the same mate for the entire study. The behavior of both sexes was then tracked for activities like time spent grooming pups, time spent in the nest and time mothers spent nursing.
But how do you measure the behavior of parents?
Rosenfeld’s team depended on hundreds of hours of video footage, taken at particular times of day and night for seven days, starting two days prior to birth. By using infrared cameras they tracked all 56 litters of mice, logging the number of and duration of activities mothers and fathers completed. During this time, the body weight and temperature of the F2 pups, who were not directly or fetally exposed to any chemicals, was logged to monitor their development.
While results showed reduced pup attention from BPA/EE exposed mother mice, the most intriguing result showed that unexposed moms mated with exposed fathers reduced the time they groomed and cared for offspring.
“These female mice have not been exposed here, but if you can see they are still reducing parental care when paired with the BPA/EE-exposed males,” Rosenfeld said. “And what’s even more interesting is that if a mother and father are both exposed, that parental care diminishes further, and becomes even more statistically significant.”
Researchers hope these results will spur others to look at long-term effects of endocrine disruptors on parenting behavior from generation to generation in animal models and, more importantly, in humans, to see if these chemicals can disrupt parental behavior of mothers and fathers, and if so, whether these effects can be transmitted to subsequent generations.
Scientists at the University of Missouri have teamed up to show how low levels of certain endocrine disruptors like BPA can cause males to possess female gonadal structures in newly-hatched turtles. This collaboration between MU, Westminster College, the U.S. Geological Survey (USGS) and the Saint Louis Zoo exposed turtle eggs to levels of BPA similar to those currently found in the environment.
“It’s important because this is one of the first times we’ve seen low doses of BPA causing disorganization or reorganization of the male gonad to resemble females,” said Dawn Holliday, adjunct assistant professor of pathology & anatomical sciences at MU’s School of Medicine and assistant professor of biology at Westminster College. “We’re not sure what this means in terms of population-level effects, but certainly it can cause some reproductive dysfunction for turtles.”
Endocrine disruptors leach into rivers and streams and concern scientists because of potential effects on animals and humans. While BPA is used as a hardening agent in plastics, it also is used to line cans and in manufacturing where more than 15 billion tons are produced each year.
In the case of painted turtles, these chemicals have potential to alter sex ratios, which are normally regulated by temperature during incubation. Eggs exposed to cooler temperatures normally produce males and those hatched at warmer temperatures produce females.
In this experiment, turtle eggs were incubated at temperatures known to rear males and dosed with low, medium and high levels of BPA. BPA-exposed turtles were compared to hatchlings not exposed to chemicals as well as a group exposed to high levels of ethinyl estradiol — an endocrine disruptor found in birth control — at the USGS Columbia Environmental Research Center.
These doses resulted in turtle sex organs that should have been male , but abnormally contained female gonadal elements. The low dose represented BPA concentrations found in fields where turtles can nest while the mid and high doses approximate BPA levels near contaminated sites like landfills.
“We exposed the eggs for a limited amount of time right when they were most vulnerable to the effects,” said Cheryl Rosenfeld, a researcher at MU’s Bond Life Sciences Center and an associate professor of biomedical sciences in the College of Veterinary Medicine. “We found that we got partial feminization in more than 30 percent of turtle eggs exposed to BPA despite being incubated at male-permissive temperatures.”
These results give the team a look into what real-world exposure levels might mean in the wild and a starting point for comparison.
“Turtles are the most endangered vertebrate taxa and they have all sorts of conservation issues coming at them from people harvesting them to disease, and endocrine disruptors are another potentially big whammy they have against their conservation status,” said Sharon Deem, director of the Saint Louis Zoo’s Institute for Conservation Medicine. “This research is a stepping stone, and we are hoping we can apply these results to populations of turtles throughout the state and use these results as a marker to look at endocrine disruptors in the wild.”
Future studies plan to look at the underlying mechanisms behind sexual disruption and will extend the study to animals including fish and mammals. Rosenfeld’s laboratory is in the process of examining how early exposure of turtles to endocrine disruptors might affect cognitive behaviors, including spatial navigation ability.
Fred vom Saal, Curators Professor of Biological Sciences in the College of Arts and Science at MU, Don Tillitt, an adjunct professor of biological sciences at MU and a research toxicologist with the USGS, Ramji Bhandari, an assistant research professor of biological sciences and a visiting scientist with the USGS at MU and Caitlin Jandegian, a senior research technician at MU, all collaborated on the study.
Funding was provided by Mizzou Advantage, an MU initiative that fosters interdisciplinary collaboration among faculty, staff, students and external partners to solve real-world problems in four areas of strength identified at the University of Missouri. These areas include Food for the Future, Sustainable Energy, Media for the Future and One Health/One Medicine.