Q&A: Oscar Mendez's Parasite Research is the Cat's Meow

Get to know Oscar Mendez, a Ph.D. candidate who is studying how the parasite common in cat feces affects neurons in the brain.

Feb. 20, 2020

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(Photo by Mari Cleven/RII) "Research can be difficult and a lot times there might not be someone to help you. You have to figure it out yourself," says Mendez. "It helps you develop self-reliance and intellectual independence."

Major: Neuroscience

Year: Ph.D. candidate

Career aspiration: Independent investigator and director of a diversity program for undergraduate and graduate students

Tell us about your research.

Toxoplasma gondii, the common "cat litter parasite," is estimated to chronically infect the central nervous system, or CNS, of up to one third of the world’s population. For the most part, if someone has a working immune system, this persistent brain infection does not cause problems. Problems can arise in those with weakened immune responses, such as AIDS patients or developing fetuses. For this reason, doctors counsel pregnant women to avoid any contact with cat feces, including litter box chores.


The ability to persist in the CNS without causing problems makes Toxoplasma a unique microbe, leading many labs to study how Toxoplasma might change behaviors and brain physiology. From these studies, we have learned that rodents infected with Toxoplasma have altered global brain activity, but no one knows what happens to the firing of individual neurons in the brains of infected mice. To answer this question, I took advantage of our novel mouse model that allows us to permanently mark and track which cells of the CNS are injected with Toxoplasma protein. Using this system, I established a semi-automated system for determining which brain regions show high levels of Toxoplasma-injected neurons, or TINs. Once I recognized that a certain brain region, the striatum, often has many TINs, I realized I could now ask if injection with Toxoplasma proteins changed the physiology of these neurons.

What problem do you hope to solve through this work?

Currently, we think of immune responses in the brain as affecting all of the neurons in the inflammatory environment. But my preliminary work suggests that this idea may not be correct. The neighboring “bystander” neurons—neurons that are a couple cell bodies away from a TIN—do not really change much even though there is a massive immune response in the area. These data suggest that the toxic effect of inflammation in the brain may be far more localized and targeted than we thought.

Can you tell us a little bit about the prestigious research award you recently won and what you’ll be using the funding to do?

I was awarded a Diversity Specialized Predoctoral to Postdoctoral Advancement in Neuroscience (D-SPAN, F99/K00) award fellowship from the National Institute of Neurological Disorders and Stroke (NINDS) which is part of the National Institutes of Health. This fellowship funds my last year of graduate school and includes funding for four years of a postdoctoral position. The award was set up to support students from backgrounds underrepresented in neuroscience research as they transition into later stages of their career. Recipients are also given funds to attend the annual Society for Neuroscience meeting, including a DSPAN pre-meeting with the other students across cohorts, which allows us to form peer mentor groups to support each other. This fellowship program started about three years ago and I am part of the third cohort. Since we are encouraged to advertise the program, the upcoming deadlines to apply are April 15 and Dec. 15.

Why did you pick the University of Arizona?

It felt easy to talk everyone here and there is a wide range of research labs to choose from.

What do you like about the process of doing research?

Research can be difficult and a lot times there might not be someone to help you. You have to figure it out yourself, and it helps you develop self-reliance and intellectual independence.

Who or what inspired you to go into this area of study?

When I first arrived at UArizona, I was hoping to rotate in a pain lab on campus and one focused on neurodevelopment. Unfortunately, those labs had left the university, so I met with a program coordinator and asked her for some suggestions. She steered me to Dr. Koshy. My first interaction with Anita—she prefers to go by Anita rather than Dr. Koshy—was for 30 minutes and I enjoyed the conversation. I was really interested in the neuroinflammation component of her work because my prior lab worked on how neuroinflammation blocked spinal cord recovery. I rotated in the lab and was hooked. Ironically, another student from my DSPAN cohort is from the lab I originally wanted to join.

We heard the culture in Anita's lab is pretty cool. Can you tell us about it?

The lab has a relaxed environment and everyone gets along with each other. At one point, we all decided to design a sweatshirt for Anita with the label “Boss Lady” on it with a cartoon Toxoplasma chasing after a donut. Donuts are extremely important in the lab. You cannot forget about Donut Tuesday, when someone brings in donuts for everyone. There are also days of appreciation. It got to a point where we were told to dial back the ridiculous desk decorating on those days, but we might have ignored that suggestion.

If you could have a dinner party with any three guests of your choosing (dead or alive), who would you invite?

  • Rita Levi-Montalcini, scientist who discovered nerve growth factor
  • Anthony Bourdain, chef and professional eater
  • James Baldwin, author and civil rights leader

What do you like to do outside of academics and research?

I really like going to the Loft Cinema and watching movies in general. I try to see live music once a week. Recently I got a typewriter and I'm having fun figuring out how it works. It's made me realize how much we use autocorrect. 

What’s been your best, most memorable moment at UArizona so far?

I would say recording a neuron and seeing it fire for the first time. It was also pretty cool to see us win the PAC-12 south for football. Sadly, they lost in the conference championship game.

What advice would you give to an incoming graduate student?

Do three rotations and talk as much as possible to the people from the lab and think about whether or not you want to interact with them for multiple years. My second piece of advice would be to listen to your advisor. They might know what they're talking about.

Is there anything else you’d like to add?

I would like to mention how welcoming the Neuroscience Graduate Interdisciplinary Programs, or GIDP, was when I first came here and acknowledge the continued support I have received from its faculty. I'd also like to give a shout-out to Kirsten Grabo, the Neuroscience GIDP senior program coordinator,  and our fearless leader and program chair, Dr. Konrad Zinsmaier.


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