Magnifying the microscopic

During the “Mouse Door Opener Day” on October 3, 2019, children visited the Life Imaging Center (LIC) at the University of Freiburg. They were able to see water fleas and tadpoles, zebrafish and human cells under modern light microscopes, which they were also allowed to operate themselves. The interest was great, and so was the effort.

Doctoral student Zazie Pfeiffer shows Frederik how to take a photo of cells.
Photo: Patrick Seeger

“I can see stars,” says Elisabeth, giving Frederik a turn at the microscope. “Me too!” he cries, “pretty big ones at that!” Frederik and Elisabeth are both eight years old. They are wearing white lab coats, appropriate for a lab setting. In front of them stands a classic stereo microscope that magnifies objects by a maximum of ten times. Under the objective there is a ten cent coin. "To practice, we first took something that can't run away," explains Tobias Dürr. Frederik turns a black knob on the side of the microscope until he can very clearly see some of the stars surrounding the Brandenburg Gate on the coin.

Tobias Dürr is pursuing his doctoral thesis in bioorganic chemistry, but for today he is an assistant at the "Mouse Door Opener Day", showing what can be done with the many microscopes of the LIC. At the "Door Opener Day", fans of the "Sendung mit der Maus" can take a look behind the scenes across Germany that are otherwise closed and get to know, for example, artisan businesses and theaters, farms and city halls - as well as scientific laboratories such as the Freiburg LIC.

Water fleas as a quality guarantee

A small bowl with pond water is sitting beneath the microscope. It comes from the University’s Botanical Garden, which is just outside the laboratory windows. “Looks like dust particles, but I can't see it properly,” says Frederik, turning the knobs to adjust focus and magnification. The dots move back and forth. Now it looks as if they have legs, says Frederik. Tobias Dürr explains that they are water fleas. “You can tell from them that the water quality is good,” he says.

The LIC is part of the Center for Biosystems Analysis and is a central institution at the University of Freiburg. “We offer the entire spectrum of light microscopy,” explains LIC head Dr. Roland Nitschke. The Center mainly investigates animal, plant and human cells. The Life Imaging Center is open to all scientists at the University: “Most of them come from the Faculties of Biology and Medicine and the University Medical Center, but also from the Faculties of Engineering, Chemistry and Environmental Sciences.” When the LIC was founded in 2001, it was only the third central light microscopy facility in Germany.

“We train young scientists, carry out experimental pilot projects and also help with publications,” says Nitschke. One focus is on the scientific evaluation of images taken with high-tech microscopes, using special software. Nitschke estimates the total value of the equipment in his institution at eight to ten million euros. In 2016, Nitschke founded the Microscopy and Image Analysis Platform (MIAP), a network of light and electron microscopy facilities in Freiburg, Basel, Mulhouse and Strasbourg funded by the German Research Foundation (DFG).

Elisabeth and Roland Nitschke observe a zebrafish beneath the microscope.
Photo: Patrick Seeger

Fish in gelatine

Now Nitschke stands in front of a wide-field microscope and shows Elisabeth a zebra fish. She stands on a red plastic stool and looks into the lenses. “The knob located at six o'clock is the head,” says Nitschke. Then he presses a switch and, thanks to the camera built into the microscope, the fish appears in front of them on a computer screen. It is actually only about two millimeters in size and transparent, but now its image fills almost the entire monitor.

The small fish is alive, but it is lying in a drop of a kind of gelatine so that it cannot swim away. Using a control lever, Nitschke can slowly move the slide with the zebrafish back and forth under the microscope, thereby selecting the section he is looking at on the screen with Elisabeth. “What moves relatively quickly here is the heart,” he explains and changes the magnification, now only part of the tail is visible: “The line here is a blood vessel, and the points that move within are the individual blood cells.”

The interest in the Door Opener Day was huge, Nitschke later explains. Six groups of his colleagues lead the day through the LIC, eight children each, so that everyone can also use the devices. The parents receive a guided tour through the LIC during their one-hour visit. “The 48 places were already fully booked four weeks in advance,” says Nitschke. “We could have gotten 100 registrations.” He is pleased that the LIC can present its work to the public.

However, the effort was also huge, not only because volunteers had to be found for the action on the holiday. The safety classifications also created some extra work. “Actually, all our laboratories are in level S2; this means that access is restricted". Together with the University and the Regional Council in Tübingen, which is responsible for biological safety, a way was found to downgrade individual rooms to S1. "However, we had to agree on exactly what we would do and make sure that the children would all put on a lab coat.”

Green mesh on the monitor

While Elisabeth is looking at the zebrafish, Frederik is working on another microscope next to it. The microscope slide is surrounded by a small box made of plexiglass that can be used to keep living cells or microorganisms warm. Frederik has just taken a closer look at a tadpole, but now human cells are lying under the microscope. Zazie Pfeiffer, who is pursuing her doctoral thesis in medicine, shows him how to take a photo of the cells, which then appears on the computer screen. “Where exactly are the cameras on the microscope," he asks. Pfeiffer shows them to him, and also which paths the light in the device takes. The cells were previously stained in order to make various components more visible. The monitor shows a green mesh. “If you click here with the mouse, individual colors can be switched on and off,” she says. Only blue dots are visible: “These are the cell nuclei.”

Later, Frederik's parents tell us that they used to live near the LIC and have often wondered what people do there. The Mouse Door Opener Day came just at the right time. In previous years, Frederik was already with the fire brigade in Bad Krozingen and in the solar observatory on the Schauinsland, he says, that wasn't bad either. “But I had never seen real cells before.”

Thomas Goebel