April 2013 Archives

Today in lab, we made a mixture consisting of Dawn soap, water, and glycerine in order to play with bubbles. Although this was fun, it actually has some application to developmental biology. In fact, many biologists have written books about the math behind soap bubble forms that can be related to cellular architectures (i.e. epithelial sheet or a blastula).

Although it was a lot harder to manipulate the bubbles than I thought, I was able to make some pretty cool formations. The first bubble formation that I was able to make is similar to the blastoderm with the blastocoel and blastoderm layer (see image). Although I was only able to make a few bubbles line up, you can still see how the bubbles attach to the end of another bubble in order to form a lining around the center. However, this is also some asymmetry with the bubbles which was hard to avoid. photo.JPGblsatoderm.jpg

The second bubble formation that I was able to make is a little harder to describe in relation to biology. This bubble formation kind of resembles the gastrulation of the blastula to form the gastrula where the outside layer folds into the center. However, you can see the differences in the last image below of the gastrula. Gastrulation is the process that forms the three germ layers known as the ectoderm, endoderm, and mesoderm. After this stage, the organs will being to develop during organogenesis.
photo (2).JPGBlastula.png

In class today, we discussed the article "Evo-Devo and Brain Scaling: Candidate Developmental Mechanisms for Variation and Constancy in Vertebrate Brain Evolution" by Christine J. Charvet, Georg F. Striedter, and Barbara L. Finlay (2011). One of the most interesting concepts was how the delay in neurogenesis can impact development and the function of an animal.

Specifically, neurogenesis in the retina and the isocortex was explored amongst various animals. When looking at the retina, the nocturnal owl monkey and the diurnal capuchin monkey was compared. During development, the highest amount of neurogenesis is delayed in the owl monkey in comparison to the capuchin monkey. This is significant due to the time when rods and cones are developed. Early in development, cones are the focus, while later development consists of rod creation. Therefore, the neurogenesis in the owl monkey is delayed which results in larger amount of rod production. Rods are specialized for light and cones are specialized for color. The owl monkey, with a higher concentration of rods, is better able to see in the dark and be nocturnal.

Next, the paper discussed the differences in isocortex development among primates and rodents. The isocortex is made up of six layers (I-VI), which all grow during different times (i.e. layer VI develops before layer I). The neurogenesis of the isocortex is delayed in primates in comparison to rats. Therefore, the later layers (II-III) are disproportionately enlarged relative to the other layers in the primates due to a delay in neurogenesis.

It is interesting how the onset or offset of neurogenesis can have such significant impacts on the development and function of certain parts of organisms.capuchin-monkey-wallpaper--1080x960.jpgowlmonkey.jpg

Week Fourteen: Drosophila Mating Behavior

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nrg1101-879a-f1.gifAfter much struggle, we are finally done with the drosophila development lab. Our assignment was to pick something interesting during drosophila development (i.e. mating to pupae hatching) and record it using a Leica Wild M3C Scope and a PixieLINK camera. My lab partner and I put two flies (male and female) into a small petri dish with a damp KIMTECH wipe around the sides. Although this proved to be troublesome during recording, it allowed a moist environment for the flies to thrive.

During drosophila mating, males exhibit a unique courtship behavior in order to engage the female. Initially, the male circled the female in order to orient himself to her. Unless male flies are desperate, they will only engage in copulation with a virgin female fly. After orienting himself to the female, he began to flicker his wings at her. Then, the male chased the female around the petri dish, which was hard to follow in order to capture the video. The male, then, began to tap the female when he got close enough to her. It appeared as though the male also engaged in some other mating behaviors but it was hard to tell. The male attempted to copulate with the female but there was no clear copulation seen.

An interesting note: our female displayed mutant (white) eyes and very short wings. We were not sure if her wings were short because she was young or if she also displayed a mutant wing type, as well.

After many hours attempting to get perfect timing for certain development behaviors of fruit flies, we finally succeeded! Attached below are three videos that demonstrate our results as described above. Enjoy!

Fruit Fly Mating Behavior 1: iPhone Capture

Fruit Fly Mating Behavior 2

Fruit Fly Mating Behavior 3

Fruit Fly Mating Behavior

Week Thirteen: Maternal and Zygotic

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egg.jpgToday in class, we reviewed drosophila development and continued with vertebrate development. One of the most interesting concepts that we discussed was the role of maternal and zygotic sources for development. Although we often think that vertebrates (especially mammals and humans) are more 'nurturing' and 'motherly' than invertebrates, such as the fruit fly, our preconceived notions may be false in some manners.

During development, drosophila embryos have pre-patterning from their mothers that determines much of their development and organization. So many components of the fruit fly are fixed before any fertilization or division. Although this may seem odd, it serves much evolutionary purpose in saving time in order to exploit limited food sources.

In comparison, vertebrates, especially mammals, have much less pre-patterning from their mothers that determines the organization in development. In fact, maternal influences are minimal until after the organism is born. Due to the complexity of vertebral development, it takes much longer for the embryo to grow into a full-term fetus. Therefore, it would not be evolutionarily advantageous if a human baby developed in 8 months versus 9 months so there is nothing to drive this type of evolution. However, it is very advantageous for fruit flies to develop faster in order to survive.

Week Twelve: Why is this beautiful?

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butterfly.jpgIn class today, we continued to discuss Endless Forms Most Beautiful by Sean B. Carroll. Specifically, we dove into chapters 8 and 9 which pertain to butterfly wing spots and zebra stripes. Although Carroll has received much criticism for focusing so much on these two topics, we discussed why this information might be important and, more importantly to some, why it might be beautiful.

When applying for research funds, many organizations ask you to provide an explanation of why your research is important and how it can be applied to the well-being of humans. Although this may seem sort of ignorant to some, it is the main focus of much of society. In Carroll's book, butterfly wing spots and zebra stripes may seem unimportant, we discussed many reasons as to why it is important and applicable to the human population. For example, the main idea behind the unique patterns of animals is the ability of genetic switches to control expression in different body parts. While this may result in a spot on a butterfly wing, it could also apply to male baldness patterns or even more compelling mutations.

Although it is necessary to describe the importance in order to satisfy research funding organizations and much of society, many others are far more baffled with the idea that biologists like to research such things. So, a better question for these folks to answer would be, why is this beautiful? Despite the incredible patterns that zebra stripes and butterfly spots can display, there are many more intriguing aspects of such research. For example, when looking at two butterflies, they may display nearly the same pattern. However, they may be completely separate species of butterflies. So, how did they develop this patterning and what is it's significance? Only research will tell us.

As a biologist, it is oftentimes hard to explain to people why something can be equally important and intriguing if it does not have a direct connection to the human species. In order to continue research in peace or fuel motivation for research, it might be useful to think about why is this important? and why is this beautiful? Or sometimes, in the words of a wise student, it might be useful to respond by saying, 'In the future, we might want to learn how to become pigmented in patterns like the butterfly,' and that will probably be enough.

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