Friday, October 19, 2012

Early environments, parental care, and the importance of touch

The conditions that we experience early in life can have profound effects on our future physiology. For example, during the winter of 1944 the Netherlands suffered a famine because the Germans blockaded food and fuel from reaching the country. Mothers who were pregnant during this time gave birth to babies that had thrifty metabolisms, which unfortunately led to a high rate of diabetes, obesity, and other problems for these "Dutch Hunger Winter" children. Because the prenatal environment was nutritionally lacking, it made sense to shift towards a thrifty metabolism, but when the environment changed a thrifty metabolism phenotype proved to be detrimental. But what the Dutch Hunger Winter children proved is that our physiology is plastic during early life, and that conditions during this time will influence our future physiology.

In addition to affecting metabolism, early life nutritional states can also influence other physiological parameters. Zebra finch chicks grow at a slower rate if their parents are inattentative and do not feed them often enough. If brood sizes are enlarged (which causes chicks to face increase competition for food), barn swallow chicks will have decreased immune responsivness as adults and male collared flycatchers will face decreased, future reproductive output. While these examples all show that adequate nutrition is important for young animals, they also show that the quality of parental care can play a large role in physiological development.

Touch is another component of parental care that has been shown to profoundly affect post-natal development in mammals. This was shown in a very crude experiment by Emperor Frederick the II of Sicily (reign 1220-1230). Frederick wanted to know what language was the "natural" language of humans, so he devised an experiment where he had some infants placed in isolated rooms where they would be unable to hear any human speech. Maids were hired to clean and nurse the babies, but the maids were not allowed to spend any more time than necessary with the infants in case they accidentally talked in the infants presence. Frederick believed that when the infants reached an age where they could talk, they would reveal the "natural" human language (most likely, he thought, Latin or Greek). What happened instead was that all the infants languished and died. And so we now know that if babies are deprived of touch, if they are denied love and affection, they will most surely die very young. (Here's a happier research example on the importance of touch; premature infants are often placed in fancy incubators because they need special respiratory equipment, protection from infectious diseases, etc. But even with this special care, many infants still fail to thrive or require longer recovery times than expected. However, by gently stroking an infant's legs and arms for just a few, short periods everyday, researchers found that growth rates increased by 50%!)

Researchers have also shown that touch is very important for the development of young rats. Rat pups that are not licked and groomed enough during the first week of life will develop hyperactive stress responses, meaning that these pups will have high corticosterone (CORT) levels in response to stressors. Additionally, these pups will have poor negative feedback, which means that it will take them longer to decrease their CORT levels after responding to a stressor. Overall, pups from low-licking and grooming mothers will be exposed to more total CORT during their lifetimes, which may make them more susceptible to stress-related pathologies. Which leads us to this question; how does low-licking and grooming cause pups to develop hyperactive stress responses?

A hyperactive stress response is characterized by high stress-induced CORT levels and poor negative feedback. Poor negative feedback is often due to low levels of CORT receptors (think about it this way; during a stressor an animal has a surge in CORT, but after the stressor passes they need to decrease CORT production. Parts of the brain know when to shut down CORT production based on how many CORT receptors are bound. So, if you have fewer receptors, it takes longer for enough CORT receptors to be bound so the brain "knows" when to shut off CORT production).

OK, so pups with hyperreactive stress responses must have lower levels of CORT receptors, and this is exactly what Liu et al. (1997) found. However, CORT receptors are not permanent fixtures- they are constantly being recycled all throughout the body, so how can an event early in life cause a permanent change in receptor expression levels? The answer is at the level of the gene; basically, conditions early in life can affect how accessible the CORT receptor gene is to transcription. Weaver et al. (1997) found that the promoter region of the CORT receptor gene was highly methylated in the hippocampus. DNA methlyation occurs when a cytosine is converted into 5-methlycytosine, and this conversion makes it more difficult for transcription factors to bind to the promoter region, thus inhibiting transcription.

Another interesting thing about pups from low-licking and grooming mothers is that they will grow up to be low-licking and grooming mothers themselves. An elegant experiment by Francis et al. (1999) showed that the low-licking and grooming trait is inherited through behavioral processes, not genetic processes. Basically, Francis et al. (1999) took pups from low-licking and grooming mothers and switched them with pups from high-licking and grooming mothers (this is called a "cross-fostering study"). When the pups grew up, their own licking and grooming frequency was determined by the licking and grooming behavior of their foster mother, not their birth mother. The low-licking and grooming trait is thought to pass behaviorally because it's been shown that increased levels of CRF (corticotropin releasing factor, an important stress hormone that stimulates release of ACTH which then causes increased secretion of CORT) inhibits maternal behavior.

For further reading: As always, I highly recommend the book "Why Zebras Don't Get Ulcers" by Robert Sapolsky (I shamelessly borrowed his examples of Emperor Frederick II, premature babies, and the Dutch Hunger Winter children). Some great, foundational papers on maternal effects on the development of the mammalian stress response include; Liu, D. et al. 1997. Maternal care, hippocampal glucocorticoid receptors, and hypothalamic-pituitary-adrenal responses to stress. Science 277:1659-1662. Francis, D. et al. (1999). Nongenomic transmission across generations of maternal behavior and stress responses in the rat. Science 286: 1155-1158. Weaver et al. Epigenetic programming by maternal behavior. Nature Neuroscience 7:847-854. 

Thursday, October 4, 2012

Degus eat money; all about grant proposals

(The first half of this post is a general introduction to what grants are and how I applied for them. The second half of this post is advice for students writing grant proposals.)

Scientific research requires thoughtful preparation, careful execution, and painstaking analysis. It takes a lot of time to design a good experiment, carry it out, analyze the data, and then finally communicate the results. But what many people don't realize is that scientists have to spend additional time and effort to just get the money to do their research. This money is typically in the form of grants, which can be from the government (like the National Science Foundation, National Institutes of Health, Department of Energy, etc) or independent organizations (scientific societies, conservation groups, etc).

Typically, the Principal Investigator (the head of the lab) is the person in charge of securing research funds, while the graduate students, post-doctorates (post-docs are researchers who already have their PhDs), and technicians are in charge of carrying out the research. If a graduate student or post-doc wants to pursue a research project that's unrelated to their adviser's current grants, then they usually have to find their own research funds. That's what happened in my case, so by working on other scientist's grants and applying for my own funds, I've been able to carry out my research in Chile.

During my first field season in Chile, my collaborator from the University of Tennessee at Chattanooga (Dr. Loren Hayes) funded my research through an International Research Experience for Students (IRES) grant from the National Science Foundation (NSF). After my first field season in Chile I knew that I wanted to return, so I started applying for other grants (the IRES grant can only fund each student one time).

The first big step was finding grants; through a series of internet searches I found about 11 grants that seemed likely to fund my research project. The first place I looked at was my own university, Tufts! The Tufts Graduate School has several grants-in-aid of research that they award every semester. While small (max. of $700), these grants are a great springboard and have a high funding rate. The Tufts Graduate School also has a list of grants on their website (, which helped me find a few more funding opportunities. 

My adviser and thesis committee also recommended a few grants to me, like the NSF Doctoral Dissertation Improvement Grant, the American Mammalogist Society grant-in-aid of research, and the Sigma Xi grant-in-aid of research. And by chatting with other students in my department, I found out about grants available from Graduate Women in Science and the American Philosophical Society. After more internet searching, I also found grants from the Explorer's Club, the National Geographic Society, the Animal Behavior Society, and the Society of Comparative and Integrative Biology (the reason I'm listing all of these grants is so that it might be useful for other students in my field).

Then, the next big step was actually writing the grants. Writing the first grant was the most difficult, and then it got a lot easier from there since I could reuse sections from my first grant. Here's an outline for a basic grant:

1) Introduction- The first few sentences should discuss the unique phenomenon that's related to your project. You want something that will immediately interest your audience and make them agree that your project is going to help explore an important scientific question. The introduction should then continue, with each sentence logically building on the last, until you find a good place to introduce your study system. And then the introduction should continue on, narrowing and narrowing until you finally get to your hypothesis, and then don't be afraid to state your hypothesis in bold letters, italics, or whichever way you think it will best stand out!

2) Methods- This section should be brief and to the point, avoid going into too much detail! You want to convince your audience that what you're doing is feasible, but you also don't want to spend a lot of time describing your techniques. Don't forget to include the important facts like place of work, time frame, and number of animals. Try to present your steps in chronological order- this makes the section more logical and easy to read.

3) Expected Results- State what you think you're going to find, don't be afraid to use different fonts to make parts of this section stand out. Depending on the length of the grant, this can also be a good section to discuss the broader impacts of your study. How will this study make a novel contribution to your field of research? Are you going to do any outreach activities? Are you going to mentor or collaborate with other people?

4) References- Grants usually have word or space limits and you almost always want to write more than you're allowed. So, for once, avoid parenthetical citations and opt for superscript numbers. You can also save space by limiting the number of citations you use- the reviewers want to know that your statements are backed up, but they're more interested in what you're planning to do in your project.

Here are some general tips for writing grants;

-Ask for your letters of recommendation well in advance.
-Double-check that you've followed ALL grant guidelines! Many organizations will toss out a grant if you forget a section, use the wrong format, etc.
-Give yourself a lot of time to write your first grant, then the next grants will take much less time.
-Ask other students in your department if you can read their funded grant proposals. This was probably the most helpful thing for me, I learned a lot by reading other people's grants!
-Ask your peers to read your grants over, it's good to get a first round of editing before you send your grant to your adviser.
-Try to submit your grant at least one day before the deadline. Sometimes there are problems with the website because of high traffic and you'll experience technical problems, don't cut it close!
-Spend a lot of time on your grant budget. There's usually no space limit for your budget justification, so go ahead and lay out every detail if you can. I usually make a list of costs, and then I write a few paragraphs explaining how I calculated each cost.
-Start writing grants early in your career, it's best to start when you're an undergraduate! The more practice you have, the better. Many universities have undergraduate research grants, and 1st/2nd year graduate students should definitely apply for the NSF graduate research fellowship.
-Because your first grants will most likely not be funded, apply BEFORE you really need research funds so you can get feedback and improve your grant writing skills.
-That being said, don't let grant writing get in the way of your research, try to write grants only when you need the money or when you have the time to write grants.
-Don't be discouraged by rejections. There's a lot of rejection in science, and the best scientists are those that don't brood over failed attempts and instead jump back up and try again. Be persistent. 

I hope this post was informative and helpful. Grant writing isn't the most exciting thing to write about, but I spend quite a bit of time writing grants and it's an important part of scientific research, so I felt that the topic was appropriate for my blog.

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