BioMed Central has gone beyond conventional scientific publishing and started including movie supplements to scientific papers. I saw this one in my e-mail box and couldn't resist.
After all, if you don't have access to a microscope, equipped with a digital video camera, how are you supposed to see these sorts of things?
I took a look at the article from Neural Development, from Zolessi, et. al. comparing the development of retinal ganglion cells in vitro and in vivo. In the movie, linked below, the first cell looks a bit like a child playing "Pin the tail on the Donkey." He/She (the child) would have a blindfold on and would extend his/her arm with a tail and wave the arm around until he/she finds the poster with the donkey picture. In the case of the retinal ganglion cells, grown In vitro (a cell culture dish), the neurites extend outward from the cells until two cells find each other and start to form an axon.
In the movie, this process looks kind of cool because one of the developmental genes is attached to a gene for Green Fluorescent Protein. When the cells make contact, Zing! They turn bright green.
[11/9/2006 Correction: oops! it turns out that the cells appear bright green at that instant because the light got turned on - see the comments for details]
Apparently, from the paper, the actions that we see in the culture dish are bit different than from the activities that take place inside the zebrafish, itself. In the fish, the cells are anchored by a membrane, and do not flail their neurites randomly about. The developing axon knows just where to go.
The authors conclude that there are signals in vivo (inside the fish), that tell the cells which way to grow, and that these signals are absent when the cells are grown in culture. When the cells are in a fish they don't have to search for directions.
Here's a link to the movie so you can see the cells searching about for yourself. If you want to look at more movies from the paper, I've included a link to the paper below in the reference section.
The only downside to these movies is that it can take a couple of minutes for the information to download and the movie to start playing. I ran out of patience before I watched all them. Still, watching the cells on the screen is something that I never would have been able to do before. It would take me quite a bit longer to find a lab and watch the cells in person.
1. Zolessi, F., Poggi, L., Wilkinson, C., Chien, C., and W. Harris. 2006. Polarization and orientation of retinal ganglon cells in vivo. Neural Development 1:2.