Global Toxicologic Pathology Training Program

The NIEHS Division of Translational Toxicology (DTT) values diversity as a strength and actively works to foster an inclusive environment. Robert Sills, D.V.M., Ph.D., DACVP; Darlene Dixon, D.V.M., Ph.D., DACVP; Ronald Herbert, D.V.M., Ph.D.; and Angela King-Herbert, D.V.M., are role models for outstanding achievements and leadership in the Toxicologic Pathology and Laboratory Animal Medicine communities. They are grateful to Tuskegee University for providing a solid foundation in veterinary medicine that has allowed for their contributions to public health.

Robert Sills, D.V.M., Ph.D.

Robert Sills, D.V.M., Ph.D.
(Photo courtesy of Steve McCaw / NIEHS)
  • In 2012, Robert Sills, D.V.M., Ph.D., DACVP, chief of the Comparative and Molecular Pathogenesis Branch, was elected president-elect of the Society of Toxicologic Pathology (STP). After a year as president-elect, Sills served as president of STP.
  • Sills is the first person of color to serve as STP president.
  • Sills is an advocate for the most inclusive team for studying the role of the environment in health and disease with the aim of preventing illnesses.
  • At both NIEHS and while serving as STP president, his passion was about building global partnerships and outreach.

Darlene Dixon, D.V.M., Ph.D.

Darlene Dixon, D.V.M., Ph.D.
(Photo courtesy of Steve McCaw / NIEHS)

Ronald Herbert, D.V.M., Ph.D.

Ronald Herbert, D.V.M., Ph.D.
(Photo courtesy of Steve McCaw / NIEHS)
  • Ronald Herbert, D.V.M., Ph.D., head of the Pathology Support Group within the Comparative and Molecular Pathogenesis Branch, is a fellow of the International Academy of Toxicologic Pathology.
  • Herbert is a member of the International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) project’s Global Editorial Steering Committee (GESC), which includes experts in rodent and non-rodent pathology from North America, Europe, and Japan. The GESC oversees the activities of the INHAND project, which aims to harmonize diagnostic nomenclature for laboratory animals.

Angela King-Herbert, D.V.M.

Angela King-Herbert, D.V.M.
(Photo courtesy of Steve McCaw / NIEHS)

Diversity, Equity, and Inclusion Interviews

The DTT is strongly committed to training the next generation of diverse and innovative scientists, and exemplifies this focus by working in inclusive, collaborative, and multi-disciplinary teams.

Current NIEHS staff (Robert Sills, Darlene Dixon, Dondrae Coble and Sheba Churchill) and previous Comparative and Molecular Pathogenesis Branch fellows (Deepa Rao, Eui Jae Sung, Georgette Hill, Sheba Churchill and Tanasa Osborne) participated in interviews to discuss their training; careers; mentors and influences; and advocacy for diversity, equity, and inclusion.

Where did you complete your education and training?

  • Darlene Dixon: "Tuskegee University (BS); Tuskegee University College of Veterinary Medicine (DVM); Michigan State University (PhD); Postdoctoral Fellow, Laboratory Animal Research Center, The Rockefeller University."
  • Deepa Rao: "Veterinary College, Bangalore, India; Oklahoma State University and University of Oklahoma Health Sciences Center, Oklahoma; University of Wisconsin-Madison, Wisconsin; NIEHS, North Carolina."
  • Dondrae Coble: "North Carolina Agricultural and Technical State University; Tuskegee University College of Veterinary Medicine; Emory University – residency; Yerkes National Primate Research Center – clinical training."
  • Eui Jae Sung: "Seoul National University (South Korea), DVM; Diplomate of the American College of Veterinary Pathology (ACVP), September 2021."
  • Georgette Hill: "Undergraduate (BA in Biology) – Hampton University; DVM – Tuskegee University; Anatomic Pathology Internship – Tuskegee University; Anatomic Pathology Residency – North Carolina State University; Post-doctoral Trainee – Chemical Industry Institute of Toxicology; PhD (Comparative Biomedical Sciences) – North Carolina State University; Pathology Fellow - NIEHS."
  • Robert Sills: "DVM – Tuskegee University; Residency, Anatomical Pathology – Michigan State University; PhD, Toxicologic Pathology – Michigan State University (MSU)."
  • Sheba Churchill: "North Carolina State University, BS in Zoology & Doctorate in Veterinary Medicine; Postdoctoral Fellowship at DTT/NIEHS."
  • Tanasa Osborne: "Tuskegee University College of Veterinary Medicine (Veterinary training); University of Illinois at Urbana-Champaign (Anatomic Pathology residency); National Cancer Institute, NIH in partnership with University of Illinois at Urbana-Champaign (PhD); National Toxicology Program, NIEHS (specialty training in Toxicologic Pathology)."

How and when did you first become interested in toxicologic pathology or laboratory animal medicine?

  • Darlene Dixon: "I was always interested in understanding disease processes and what happens within a cell or an organ that results in an abnormal state or disease. While in graduate school, I majored in pathology with a minor in environmental toxicology, which fostered my interest in not only understanding the pathogenesis of disease processes, but also trying to understand the role of the environment and environmental exposures on disease and human health. As a postdoctoral fellow I was involved in research projects that allowed me to explore science at a very basic molecular level that drew my interests towards trying to understand the molecular perturbations that occur in a cell or an organ that manifest in disease."
  • Deepa Rao: "It was a natural transition from training in toxicology."
  • Dondrae Coble: "Exposure to laboratory animal medicine during my undergraduate education."
  • Eui Jae Sung: "When I did basic research in the Signal Transduction Laboratory with Dr. Stephen Shears at NIEHS."
  • Georgette Hill: "I became interested in toxicologic pathology when I sat on a Pathology Working Group as an observer at NIEHS while in graduate school at NC State."
  • Robert Sills: "During my residency and PhD training program where I had the opportunity to study the role of the environmental chemical dioxin and how it causes cancer in animal models."
  • Sheba Churchill: "I always knew I wanted to be a veterinarian from a young age and was focused on small animal general practice. I was first exposed to lab animal during a middle school STEM Club tour of a medical college’s vivarium. That was when I first learned about lab animal medicine and decided on that focus."
  • Tanasa Osborne: "Through a summer internship at Tuskegee following my first year of vet school. Prior to veterinary school, I had the unique opportunity to volunteer on an ostrich ranch (as I was certain I was going to be a Zoo Animal Vet) where there was massive mortality of all of the ostrich chicks. While I was there, no one could figure out what was going on. Fast forward to my first summer internship in vet school- it was a project involving chick mortality on various ostrich farms across Alabama. I assumed, this would be a clinical project where I would get to observe and perform examinations on the ostriches. I was so was a pathology-based project which in this case meant I would be evaluating tissues on slides. What?! I was so disappointed but agreed to give it a chance. It was a good decision, since microscopic examination of various tissues revealed the cause for massive mortality in the ostrich chicks (it was vitamin E/selenium deficiency!). This sparked my interest in pathology. The next summer I was selected for a summer internship at Merck & Co. This was my first exposure to veterinarians working on a multidisciplinary team and contributing in a way that I felt was so impactful. I loved the idea of being able to work in such a setting as a veterinarian with the goal of helping to produce such powerful results for patients. I was hooked!"

Who were your biggest influences?

  • Darlene Dixon: "Dr. Robert Leader, Dr. Stuart Sleight, Dr. Harold Davis, and Dr. Robert Maronpot have all influenced my professional life immensely."
  • Deepa Rao: "Parents and amazing dedicated mentors every step of the way."
  • Dondrae Coble: "Dr. Tracy Hanner led the Laboratory Animal Science program at N.C. A&T State University. Dr. Hanner worked as an animal care technician at NIEHS before entering and graduating as the first African American graduate from North Carolina State University’s College of Veterinary Medicine in 1986."
  • Eui Jae Sung: "Many people influenced me, including Drs. Dave Malarkey, Greg Travlos, and Steve Shears (NIEHS)."
  • Georgette Hill: "Wow… a lot of people have been big influencers: my parents; my pathology instructors at Tuskegee; my Ph.D. mentor, Dr. Jeff Everitt; and the toxicologic pathologists during my time at NIEHS (Drs. Bob Maronpot, Rick Hailey, Robert Sills, Ron Herbert, Darlene Dixon, John Peckham, Abraham Nyska, and Gordon Flake)."
  • Robert Sills: "Dr. Al Dade who was my pathology instructor at Tuskegee University. I was fascinated about the pathology specialty, since the science was about understanding the causes of diseases, which would then provide opportunities for prevention, intervention and treatment."
  • Sheba Churchill: "Honestly, there have been so many positive influencers along my journey. My parents – they were always supportive of my aspirations & my teachers – they encouraged my interest. I have had many great mentors at each step of my career, undergrad, vet school, and postdoc training. I consider my bosses (current and past) some of my best mentors throughout my career."
  • Tanasa Osborne: "Drs. Adelekan Oyejide, Ramon Kemp, and Wanda Haschek-Hock."

Tell us about your career path and your current job?

  • Deepa Rao: "An amazing journey to doing what I love and enjoy today. The path from veterinary medicine to toxicology to pathology while holding on to my need to understand how the nervous system processes environmental stimuli has been a driving motivation. Today, I focus on evaluating the effects of drugs and chemicals through endpoints within neurotoxicology and neuropathology."
  • Dondrae Coble: "My career path has been a mixture of working in small animal medicine (dogs, cats, and exotic pets) and laboratory animal medicine. I worked as an emergency veterinary clinician for 3 years prior to pursuing residency training in laboratory animal medicine. My laboratory animal medicine experience has encompassed leadership roles in academia, pediatric hospitals and in the government."
  • Eui Jae Sung: "I started to work at Charles River Laboratories (Ashland, OH) as a clinical pathologist from Aug 2021. I started my professional career in the United States as a cell biologist (2013 PhD NCSU) and did research in calcium and inositol signal transduction (2013-2016 NIEHS). During my postdoctoral research, I became interested in pathophysiologic mechanism in the body and how it reflects the cytology, hematology, and chemistry levels when there is a molecular signal dysfunction. I really wanted to learn this and applied to several clinical pathology residency programs and ended up getting training in NTP/NIEHS with NCSU support. I was supposed to take the ACVP board exam last year but it was canceled because of COVID pandemic, so I had to wait another year and passed the exam this year."
  • Georgette Hill: "After I received my Ph.D., I started working in the Laboratory of Experimental Pathology at NIEHS where I learned a lot about toxicologic pathology. After leaving NIEHS in 2006, I became a toxicologic pathologist at Integrated Laboratory Systems (ILS), in Research Triangle Park, NC. I became Assistant Pathology Program Manager at ILS in 2008 and the Pathology Program Manager in 2019."
  • Robert Sills: "After completing my residency and Ph.D. at MSU, NIEHS was a perfect fit for me since it allowed me to build on my interests for understanding the role of the environment and diseases. In my PhD, I focused on one environmental chemical, dioxin, and then at NIEHS I had the opportunity to be involved in research involving hundreds of environment agents. I started at NIEHS as a toxicologic pathologist and then became a group leader of a molecular pathology group, following which I was provided an opportunity to serve as a Branch Chief for the Comparative and Molecular Pathogenesis Branch."
  • Sheba Churchill: "I started my career in small animal practice following veterinary school. From there, I joined the United States Department of Agriculture Food Safety and Inspection Service as a public health veterinarian. I knew lab animal was my goal, so when DTT’s Postdoctoral Fellowship open, I applied. I was fortunate to be accepted; I completed the program and achieved lab animal board certification. From there I joined Charles River Laboratories as a staff veterinarian. In my current role, I server as a contractor to DTT’s Comparative Medicine Group (CM). Alongside CM’s director, I oversee, direct, and manage the use of laboratory animal models for the DTT."
  • Tanasa Osborne: "My career path has essentially been my training followed by current position at Novartis. I am an Associate Director in preclinical safety. I can have various roles within a team setting. I may provide strategic and broad leadership on drug discovery and/or development projects throughout the drug’s lifecycle. Or my role may be more of a “subject matter expert” where I expand scientific or technical knowledge within one or more related areas of deep expertise. I also help assess impact, limitations, and added value of scientific activities in order to support the team’s objectives and/or advance projects.

What aspects of your career do you find the most rewarding?

  • Darlene Dixon: "Mentoring wonderful trainees from the US and from all over the world who have become great research scientists, physicians, physician scientists, pharmacists, pathologists, toxicologists, veterinarians, all contributing to making the world environmentally safe and healthier. Also, inspiring and motivating young, underrepresented minority students to consider pursuing a career in science and biomedical research. Sharing the joys of research and allowing junior scientists to be creative in asking great research questions and designing experiments to address those questions. I think being a mentor has been my greatest accomplishment."
  • Deepa Rao: "That the work we do impacts public health in real ways."
  • Dondrae Coble: The advancement of scientific discovery to improve human and animal quality of life.
  • Eui Jae Sung: "As a toxicologic clinical pathologist, I am proud of having participated in developing novel therapeutic agents and preclinical safety assessment."
  • Georgette Hill: "I absolutely love the collaborative work I do. I learn so much from other disciplines such as toxicology and laboratory animal medicine. I also learn a great deal through my interactions with other pathologists as we’ve all received different training and can provide invaluable information to each other."
  • Robert Sills: "The opportunity to work with many different scientists (team science) and provide opportunities for mentorship and career development of team members."
  • Sheba Churchill: "The fact that I am contributing to the health and well-being of both animals and humans is extremely rewarding. I feel fortunate to live out my childhood dream."
  • Tanasa Osborne: "While the primary goal is to make sure that the medicines we are developing are safe and effective, I love being part of multidisciplinary teams that are constantly discovering new ways to think about and approach medicine/disease. It’s incredibly rewarding when a drug you’ve worked on (in some way at some point) has made it to market and is improving and extending our patient’s lives."

As a person who is part of a historically underrepresented group in the US, have you faced any specific challenges in your career? How have you handled these challenges?

  • Deepa Rao: "There may have been some. I figured early on that the more energy I put into trying to sort it out, the more complicated and draining it became. So, in the end, I just decided to focus on doing what I love, no matter what.
  • Dondrae Coble: Approximately 2% of the U.S. veterinary workforce is composed of Black veterinarians according to a 2021 publication from the Journal of the American Veterinary Medical Association. Active recruitment, bias training, and removal of barriers to veterinary student applicants were challenges that were addressed in my previous role as the Chairperson of the Admissions Committee at The Ohio State College of Veterinary Medicine."
  • Eui Jae Sung: "Especially I have had difficulties regarding visa status. If you don’t have a proper visa, you will not even get a chance to work or develop your career in the US regardless how good you are. People around me (especially Drs. Malarkey and Travlos) helped me a lot and resolved the problem.

    Also, the language barrier is very challenging to me. I still work on overcoming this language barrier. At first, I struggled with forming questions to ask something, so I always tried to find the answer by myself, which helped to develop my deep thinking and troubleshooting ability. Resolving problems by communication and conversation is also huge, so being a good communicator is very important and now I am getting adjusted to it."
  • Georgette Hill: "Yes, I’ve faced challenges in my career as an African American female. I handled the challenges the best way I could at the time. Took the high road and used the experience as a learning lesson."
  • Robert Sills: "One challenge early in my career was being judged by others without getting to know me. Once there was an understanding of me as a person, and with my passion for actively building communications with others, this was less of a challenge."

What are the most important lessons you’ve learned through your career?

  • Deepa Rao: "Learning to be honest, self-introspection, and listening to my heart."
  • Dondrae Coble: "The importance of effective communication. The ability to be agile and innovative. The importance of being open minded and welcoming new ideas and information. The importance of active listening."
  • Eui Jae Sung: "Keep going and hanging there if you want to get it. Be nice to people and don’t burn down your bridge as all good chances and opportunities are coming from other people."
  • Georgette Hill: "The most important lessons I’ve learned: to be okay with not knowing something and to not beat myself up if I make a mistake. Everyone makes them."
  • Robert Sills: "Take time to listen and get to know each other and build relationships and it is OK to agree to disagree in a respectful way."
  • Sheba Churchill: "One of the most important lessons I learned was to seek mentorship. It’s extremely rare that people are not open to mentorship, whether formal or informal. That has made the most difference in my career. Also, as a younger vet, I didn’t appreciate that a career is not always linear. I’ve learned over time to enjoy and appreciate the detours."
  • Tanasa Osborne: "Perseverance and patience are key and so is having a support network. Your support network should provide a “safe space” for learning and asking questions."

What are some things that can be done, or specific things you have done, to advocate for diversity, equity, and inclusion?

  • Darlene Dixon: "Active member and co-lead of the NIEHS Environmental Health Disparities and Environmental Justice Faculty and member of the North Carolina Women of Color Research Network (NC WoCRN). Mentor in the NIEHS Scholars Connect Program (NSCP), which offers a year-long apprenticeship program to students from historically black colleges and universities, as well as other area academic institutions."
  • Deepa Rao: "Outreach as scientists within communities. Engage with local neighborhood children about science."
  • Dondrae Coble: "Having an open mind and the willingness to engage in uncomfortable dialogue are great starting points. I currently serve at the Chairperson of the American College of Laboratory Animal Medicine Equity and Inclusion Task Force. Before joining NIEHS, I served as the Chairperson of the Abigail Wexner Research Institute Workforce Diversity Working Group."
  • Eui Jae Sung: "Be nice to people. Do your work diligently and ethically."
  • Georgette Hill: "I’ve tried to make myself available to talk to individuals (especially from underrepresented populations), interested in science, veterinary medicine, and veterinary pathology. In my opinion, taking time to answer questions, share experiences, provide resources, etc. is priceless."
  • Robert Sills: "Outreach to underrepresented groups in undergraduate and professional training programs and proving opportunities for exposure of students to various scientific disciplines, and then to see the students apply to advanced degree programs, and then they were able to add to a diverse and inclusive workforce in government, academia, and industry for improving the lives of others."
  • Sheba Churchill: "There are others following in your footsteps and being available to help and encourage is a great way to support DEI. As a student and new veterinarian, it was important to see someone who looked like me and doing a role that I hoped to do one day. I try to make myself available to students and younger veterinarians in the field, especially those in underrepresented groups. I participate in organizations that champion DEI and mentorship such as the North Carolina Association of Minority Veterinarians."
  • Tanasa Osborne: "Reach out to underrepresented groups (with people who look like them) and tell them about the wide variety of opportunities available in veterinary medicine beyond clinical practice. In the past I have spoken to underrepresented groups ranging from elementary to high school during “Career Day” events. I am currently a member of the Diversity Inclusion and Belonging Task Force (DIBTF) in the Society of Toxicologic Pathology (STP)."

What advice do you have for students, residents, and/or new toxicologic pathologists or laboratory animal scientists?

  • Darlene Dixon: "Stay positive and never give up. Times may get tough, but know that you are working towards a greater good. In the end, all of the sacrifices will be well worth it."
  • Deepa Rao: "Do what you love and love what you do. If you are not, then find it and do it."
  • Dondrae Coble: "Students: do your best academically and obtain leadership roles in extracurricular activities. Residents: take advantage of the opportunities to engage and work with individuals internal and external to the residency program. New Laboratory Animal Scientists: Collaborate and become comfortable as an individual looked upon to make important decisions."
  • Eui Jae Sung: "I am also a very new toxicologic pathologist so this advice would apply to me. Be proud of what you are doing."
  • Georgette Hill: "Work hard and don’t be afraid to ask questions. Find a mentor that can help nurture your career. Embrace a healthy work-life balance."
  • Robert Sills: "Take advantage of summer programs and engage with mentors to learn about their career paths for understanding both successes and challenges. Share your projects/research with others through as many speaking engagements and publications as possible so that others can learn about your important contributions to the global scientific community."
  • Sheba Churchill: "Mentorship is key for developing the career you want. Identify and rely on mentors early in your career to help develop your talents. They may see hidden potential or have been in similar junctions during their career. Also, be open to mentors that are different from you as it can bring a whole new perspective and fresh guidance."
  • Tanasa Osborne: "If you’re interested in either of these fields (or think you might be) and know of someone who is a toxicologic pathologist or lab animal scientist, don’t be afraid to take the initiative and reach out. Introduce yourself and ask if you could have a quick chat about their career path. You never know what may develop from that interaction."

Is there an additional question you wish we had asked (and your response)?

  • Georgette Hill: "What changes do you feel should be made regarding veterinary medicine education? To put equal emphasis on a career in veterinary medicine as is made for other professional careers, especially in high schools in predominantly underrepresented communities and at HBCUs."

Meet the Interviewees

Darlene Dixon, D.V.M., Ph.D., D.A.C.V.P.
Darlene Dixon, D.V.M., Ph.D., D.A.C.V.P.
Acting Chief, Mechanistic Toxicology Branch
Tel 984-287-3848
[email protected]
Deepa Rao, B.V.Sc., M.S., Ph.D.
Deepa Rao, B.V.Sc., M.S., Ph.D.
Dondrae J. Coble, D.V.M.
Dondrae J. Coble, D.V.M.
Chief, Comparative Medicine Branch
Tel 984-287-3263
[email protected]
Eui Jae Sung, D.V.M., Ph.D.
Eui Jae Sung, D.V.M., Ph.D.
Georgette Hill, D.V.M., Ph.D.
Georgette Hill, D.V.M., Ph.D.
Robert C. Sills, D.V.M., Ph.D.
Robert C. Sills, D.V.M., Ph.D.
Chief, Comparative and Molecular Pathogenesis Branch
Tel 984-287-3839
[email protected]
Sheba R. Churchill, D.V.M.
Sheba R. Churchill, D.V.M.
Contractor - Laboratory Animal Veterinarian
Tel 984-287-3832
[email protected]
Tanasa Osborne, D.V.M., Ph.D.
Tanasa Osborne, D.V.M., Ph.D.