Modern equipment, patience and perseverance are often important prerequisites for gaining new insights. Young scientist Anja Günther has taken up this challenge.
The Roman philosopher Seneca already recognised that the path to success is arduous. A good 2000 years later, this still applies to many researchers. If you want to gain new insights, you often have to persevere, especially in experimental work.
Neurobiologist Dr Anja Günther also had to overcome a few hurdles to gain new knowledge. She is working on the question of how the sensory cells in the retina of birds are connected to each other. A detailed question that should help to solve the riddle of bird migration in the long term.
There is much to suggest that certain mechanisms in the retina enable birds to perceive the Earth's magnetic field and thus navigate across the globe. However, it took Günther several years to obtain the first detailed data on the structure of the bird's retina. "You have to develop a certain tolerance for frustration to stay on the ball," says the biologist with a laugh.
For her doctoral thesis in Prof Dr Henrik Mouritsen's neurosensory research group, she had to establish a completely new method to pursue her research question. This was painstaking, detailed work that took a lot of time. But with success - because for the first time, Günther and her colleagues have succeeded in taking a detailed look at the retina of chickens. The team, which also includes Oldenburg neuroscientist Prof Dr Karin Dedek, has published the results in the renowned "Journal of Neuroscience".
Several terabytes of data
Günther used a special electron microscope to obtain this precise view. "This technology is only available at a few locations worldwide and is still under development," explains the biologist. Thanks to a co-operation with the Center of Advanced European Studies and Research (caesar) in Bonn, she was able to use the microscope there.
What makes it special: In contrast to conventional electron microscopes, this technology does not work with a single electron beam, but with 91 such beams. Similar to light beams, but much finer, the electron beams make it possible to take detailed images of tissue. Due to the higher number of electron beams, it is possible to create large amounts of data much faster than before and to reconstruct a three-dimensional image from it.
However, the method is not without its pitfalls: All the tiny image sections created in this way add up to several terabytes of data. It takes a lot of time just for the computer to process this information. In addition, preparing a retinal sample for microscopy is time-consuming, emphasises Günther.
Light-sensitive cells with complex wiring
For example, parts of the tissue first have to be moulded in a resin and coated with heavy metals for the subsequent contrast. "The result then looks similar to amber with an inclusion," says the young researcher. The neurobiologist then used a diamond saw to create wafer-thin slices 40 nanometres thick.
Günther is satisfied with the result, even though it took her longer than she had expected at the beginning of her doctorate. For the first time, she was able to take a detailed look at the structure of the bird's retina. "Ten years ago, this would not have been possible to this extent," she says with pride. Thanks to this insight, she was not only able to recognise different cell types - the light-sensitive photoreceptors and the bipolar cells behind them in the retina, which act as an intermediate layer that transmits information from the photoreceptors to the nerve cells behind them. The results also show how the different nerve cells are connected to each other.
For example, some bipolar cells are apparently highly specifically connected to only one particular cell type of the photoreceptors. Others, however, are linked to several photoreceptor types. The fact that the photoreceptor cells of the retina are also interconnected in a very complex way was previously unknown, says Günther. The researchers working with Günther now want to find out exactly what this means - for the animals' vision and ultimately also for their sense of magnetism. The difficulties have not deterred the neurobiologist. She is now continuing her work and still has a desire for research.
