February 2013 Archives

Hello all,

I deeply apologize to anyone that has been diligently following my blog (which, in reality, in probably no one) as I have not posted in about 2 weeks not. However, my lack of an internet presence does not mean I have been neglecting my lab and classroom studies! I have indeed been researching more and more in the lab and practicing more with the microscope, further developing my skills. In lab, we had an assignment to find and investigate a structure that we found particularly interesting and document its development through a multiple image portfolio.

This assignment is 100% representative of why I enjoy this lab so much: no pointless busywork, just development of one's own skills and interests. One of the reasons I took this class in the first place is that it is an excellent compliment to other courses I've taken, both in the Psychology and Biology majors. For example, I love Biological Psychology, but this course tells a completely different story from the perspective of development, rather than the interaction of fully developed adult brain structures. Because of this inherent interest I possess in BioPsych, I felt that documenting the development of the spinal cord and surrounding neurological tissue (i.e. the ventral and dorsal spinal nerves) to be a fitting choice for my assignment.

Here are a few images I took in lab. I found the development of the spinal nerves and the increased organization of the cells in the spinal ganglia to be especially cool to observe!
Note that I have also spent some time annotating some of the images to make various structure more clear when comparing different developmental stages. Here are just a few of the images from my portfolio:

Here is an image of the spinal cord earlier in development before the spinal nerves have really developed. Scale Bar = 25µm:

Still early in development here, but a closer magnification. Isn't it cool how you can see the individual cells!?:

Later in development, spinal nerves much more visible now. Most structures more defined and organized:

This week's entry is inspired by the difficulties of the US postal service to deliver packages on time!

Let me back up... for my developmental biology course, we were assigned to read a book about the nature of development. This book does supposedly does an excellent job at capturing the wonder of embryonic development without sacrificing the science behind it. This text, Endless Forms Most Beautiful, by Sean B. Carroll is a great supplement to any textbook in a developmental class, resulting in a more well-rounded view of embryology.

Unfortunately, I ordered this book online, and the order has been delayed. Hopefully it will arrive soon, as we are having discussions in class in which I feel disadvantaged. However, not having the text in-hand is no reason to declare defeat! I thought it would be appropriate to write a blog entry examining the author of this book, so that when the book did arrive, I could read it with a little bit on context under my belt.

Dr. Carroll seems to be a man of many interests in Biology, while remaining rooted in fundamental "micro-scale" research. He is a professor of Molecular Biology, as well as Genetics at the University of Wisconsin, which is a refreshing fact considering that many non-environmental scientists often lack a novelistic literary sense (speaking generally of course).

Having written multiple texts for the classroom, Carroll seeks to truly integrate the ideas of evolution and development. At times it is easy to lose sight of the overall context when pouring over embryonic microscopy slides, or perhaps to forget about genetic regulation and expression when considering a common ancestor among humans and apes. Without the coupling of these fields (along with ecology, in my opinion) conclusions drawn from either field individually are rather stunted, and can have little implication. I can truly appreciate the value in a biological text that looks at the "big picture" while still harkening back to the smaller elements, such as transcription factors and intricate gene expression.

While I have not yet read any of his work, I am sure that I will very much enjoy Carroll's interpretation of developmental biology.

Here is a link to a web page about Dr. Carroll, detailing some of the more specific facets of his research, academic involvements, and literary contributions.

seanbcarroll.com

Week 3 already?! It's hard to believe my last semester is passing me by so quickly!

One of the in-class assignments for my developmental biology class this past week was to read an article on positional information and how that information is perceived by the cells in the developing embryo to result in polarity, directional migration, and differentiation. The article spoke about the "French Flag" model for morphogen (extracellular agents that help to determine cell development) gradient formation, described in detail by Lewis Wolpert. This model is important representation of how a gradient can differentiate developing cells, but it certainly cannot be the entire story behind cellular positional information, as the article goes on to discuss (intercellular communication and regulation must also be at play).

A few specific examples of morphogens were provided, along with their typically understood function as they act in the developing embryo. Among them was the well-know (at least to developmental biologists) Dpp molecule. Decapentaplegic, or Dpp, is a morphogen that plays central roles in the development of the fruit fly embryo, specifically helping to differentiate the various imaginal discs (for example, wing disc) of the embryo, which later develop to form organs and limbs. Because this molecule is so important within embryology and has such widespread effects, I was curious about the details of its functionality. While the Wolpert et al. article talked a lot about mechanisms other then morphogens, I was more intrigued by the sensitive intricacies of a small concentration extracellular gradient possessing such omnipotence!

In my search for more information, I ran across a recent article by Zhou et al. seeking to understand more (among other things) about Dpp gradient formation. The authors point out that this is a difficult task, considering that gradients are usually present at extremely low concentration magnitudes, which can elicit confounding results from otherwise sound experimental procedure.

Without delving too deeply into the results of the paper, the authors suggest that Dpp gradient formation occurs firstly by simply diffusion, followed by a more complex process of cellular uptake and degradation, which helps to regulate the sensitive levels of Dpp in the extracellular matrix. It is this uptake process that pervious studies have failed to fully grasp, skewing previously accepted results about gradient formation.

A last comment provided by the authors urges us to recall that even if we understand how one morphogen functions, embryo development is a delicate symphony composed of entire suites of molecules, all in varying amounts and conformations. Each of these has a specific function, which can be altered by the presence and concentration of other morphogens. Understanding embryology from a single gradient is synonymous to extrapolating a comprehensive knowledge of the entire human brain from a single region. Cellular/molecular interplay and complex feedback pathway mapping is the name of the game here folks! So don't worry, there's a lot more science to be done!

Here are the articles to which I was referring throughout my entry:

Wolpert and Kerszberg (Positional Information).pdf

Zhou et al. (Extracellular Diffusion).pdf

Note: I am not claiming any rights to these articles by posting them. All copyright information can be found in the articles for the appropriate authors and publishers.