Modern equipment, patience and perseverance are often essential for new discoveries to emerge. Early-career researcher Anja Günther has taken up this challenge.
The Roman philosopher Seneca noted long ago that the path to success is arduous. A good 2,000 years later, this still holds true for many researchers. Anyone wishing to gain new insights must often persevere, particularly when conducting experimental work.
Neurobiologist Dr Anja Günther, too, had to overcome a number of hurdles to gain new insights. She is investigating how the sensory cells in the retina of birds are interconnected. This is a specific question that should, in the long term, help to solve the mystery of bird migration.
There is strong evidence 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 just 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, laughing.
For her PhD thesis in Prof. Dr Henrik Mouritsen’s Neurosensory Research Group, she had to, amongst other things, establish a completely new method to pursue her research question. It was painstaking, meticulous work that took a great deal of time. But it paid off – for the first time, Günther and her colleagues have succeeded in gaining a detailed insight into the retina of chickens. The team, which also includes the Oldenburg-based neuroscientist Prof. Dr Karin Dedek, has published the results in the renowned journal *Journal of Neuroscience*.
Several terabytes of data
To obtain this detailed view, Günther used a specialised electron microscope. “This technology is only available at a few locations worldwide; it is still under development,” explains the biologist. Thanks to a co-operation with the Centre of Advanced European Studies and Research (caesar) in Bonn, she was able to use the microscope there.
What makes it special is that, unlike conventional electron microscopes, this technology does not use a single electron beam, but 91 such beams. Much like beams of light, but far finer, the electron beams enable detailed images of tissue to be captured. The higher number of electron beams makes it possible to generate large amounts of data much more quickly than before and to reconstruct a three-dimensional representation from it.
However, the method is not without its pitfalls: all the tiny image sections produced in this way add up to several terabytes of data. Processing this information on a computer alone takes a great deal of time. Furthermore, Günther emphasises that preparing a retinal sample for microscopy is a labourious process.
Light-sensitive cells interconnected in a complex manner
To do this, parts of the tissue would first have to be embedded in resin and treated with heavy metals to provide contrast later on. “The result then looks rather like a piece of amber with an inclusion,” says the early-career researcher. Using a diamond saw, the neurobiologist then made wafer-thin sections, just 40 nanometres thick.
Günther is pleased with the result, even though it took her longer than she had anticipated at the start of her PhD. For the first time, she was able to gain a detailed insight into the structure of the avian retina. “Ten years ago, this would not have been possible to this extent,” she says, not without pride. Thanks to this insight, she was not only able to identify different cell types – the light-sensitive photoreceptors and the bipolar cells lying behind them in the retina, which act as an intermediate layer to relay information from the photoreceptors to the nerve cells further back. Rather, the results also reveal how the various nerve cells are interconnected.
It appears that some bipolar cells are connected in a highly specific manner to just one particular type of photoreceptor. Others, by contrast, are linked to several types of photoreceptor. The fact that the photoreceptor cells of the retina are also interconnected in a very complex manner was previously unknown, says Günther. Günther and her team of researchers now intend to investigate further exactly what this means – for the animals’ vision and, ultimately, for their sense of magnetism. For the neurobiologist, these difficulties have not deterred her. She is now carrying on and remains keen to pursue research.
