Visible Changes in the Nervous System

A research team from Julius-Maximilians-Universität Würzburg (JMU) discovered this a few years ago. However, it was previously unknown where in the ants’ brains the magnetic information is processed. This has now changed: In a new study published in the journal PNAS — Proceedings of the National Academy of Sciences, the team shows that information about the Earth’s magnetic field is primarily processed in the ants’ internal compass, the so-called central complex, and in the mushroom bodies, the animals’ learning and memory centers.

Professor Wolfgang Rössler, holder of the Chair of Behavioral Physiology and Sociobiology at the University of Würzburg, Dr. Pauline Fleischmann, former scientist at the Chair of Behavioral Physiology and Sociobiology and now a member of the Neurosensorics/ Animal Navigation working group at the University of Oldenburg, and Dr. Robin Grob, who has since moved from Rössler’s chair to the Norwegian University of Science and Technology in Trondheim, were responsible for this study.

First Exploratory Walks for Calibration

“Before an ant leaves its underground nest for the first time and goes in search of food, it has to calibrate its navigation system,” says Pauline Fleischmann, explaining the background to the work. During so-called learning walks, the animals then explore the immediate surroundings around the nest entrance and repeatedly pirouette around their own body axis with short stops in between. During these pauses, they always look exactly back in the direction of the nest entrance, even though they cannot see it — a tiny hole in the ground.

Thanks to their field studies in southern Greece, where Cataglyphis ants are native, Fleischmann and her colleagues were able to prove that desert ants orient themselves to the Earth’s magnetic field during the learning walk phase. Pauline Fleischmann and Robin Grob were once again on site in Greece. This time, however, they not only investigated the ants’ orientation behavior while the magnetic field was being manipulated, but also looked for changes in the nervous system of Cataglyphis as an expression of the newly acquired experience.

A Faulty Magnetic Field Disrupts the Learning Process

The zoologists concentrated on young workers that had not yet undertaken any learning walks. The animals were only allowed to set off as part of the precisely planned experiments — sometimes under natural conditions, sometimes in a permanently manipulated magnetic field that, for example, displayed chaotic directions or did not allow horizontal orientation. With this faulty directional information, it was not suitable as a reliable reference system for the ants’ behavior to look back to the nest entrance during the learning walks.

The result: “Our neuroanatomical brain analyses show that ants exposed to an altered magnetic field have a smaller volume and fewer synaptic complexes in an area of the brain responsible for the integration of visual information and learning, the so-called mushroom body,” explain Fleischmann and Grob. In the central complex, the region of the ant’s brain in which spatial orientation is anchored, the same findings were observed under certain conditions.

The Number of Synaptic Connections Increases

Desert ants that were allowed to make their first excursions under natural conditions were clearly different. Their sensory experiences, a combination of information about the magnetic field, the position of the sun and the visual environment, triggered a learning process that was accompanied by structural changes in the neurons and an increase in synaptic connections in the aforementioned brain regions.

According to the scientists, this leads to the conclusion that magnetic information not only serves as a compass for navigation, but also as a global reference system that is crucial for the formation of spatial memory.

In Search of the Sensory Organ

The results of their experiments prove “that ants need a functioning magnetic compass during their learning walks in order to calibrate their visual compass and at the same time store images of the nest environment in their long-term memory,” as Pauline Fleischmann and Robin Grob say. At the same time, their research extends far beyond the field of compass calibration in ants. Wolfgang Rössler emphasizes that “the results provide valuable information on how multisensory stimuli can influence neuronal plasticity of brain circuits for navigation in a critical phase of brain maturation.”

In a next step, the team now wants to investigate in which sensory organ the desert ant receives the magnetic information and via which sensory pathways it is transmitted and processed. This has not yet been achieved with any animal species that orients itself to the Earth’s magnetic field. Due to their manageable and relatively small nervous system, insects, to which Cataglyphis belongs, offer a unique opportunity to investigate the neuronal basis of magnetic orientation at all levels.

The new research published in the Journal of Physiology conducted by an interdisciplinary consortium of clinicians and researchers led by University of Birmingham and collaborators in Germany.

The team found that male sex hormones, such as testosterone, also called androgenic anabolic steroids (AAS), which are misused for muscle building particularly among in young men can increase the risk of atrial fibrillation in individuals genetically predisposed to heart diseases.

Dr Laura Sommerfeld, Postdoctoral Researcher at the UKE Hamburg, who completed her PhD at the Institute of Cardiovascular Sciences at the University of Birmingham focusing on this work is lead author of the study.

Dr Sommerfeld said: “Our study can significantly contribute to understanding the impact on the heart health of young men who misuse anabolic steroids to increase muscle mass. Recent reports have shown that young men in particular are being targeted on social media such as TikTok being sold testosterone products, but we have shown how the misuse of steroids carries a specific risk that many people will not be aware of.”

Professor Larissa Fabritz, Chair of Inherited Cardiac Conditions at UKE Hamburg and Honorary Chair in the Institute of Cardiovascular Sciences at the University of Birmingham added:

“Heart muscle diseases like ARVC affect young, athletic individuals and can lead to life-threatening heart rhythm disturbances. Atrial fibrillation is a common condition in the general population. Elevated testosterone levels can result in an earlier onset of these diseases.”

The scientists examined potential effects on a condition called arrhythmogenic right ventricular cardiomyopathy (ARVC), which is genetically determined and primarily attributed to disruptions in the formation of cell connections critical for heart muscle stability.

The scientists initially confirmed, based on clinical patient data from UHB and elsewhere, that ARVC occurs more frequently and severely in men than in women. In laboratory experiments, they discovered that six weeks of AAS intake, combined with impaired cell connections, could lead to reduced sodium channel function in heart tissue and a slowing of signal conduction within the atria.

Dr Andrew Holmes, co-author and Assistant Professor in the Institute of Clinical Sciences at the University of Birmingham said:

“This work implies that young male individuals with key inherited genetic changes have a greater risk of developing electrical problems in the heart in response to anabolic steroid abuse.”

Many of these altered immune genes are the same ones that increase an individual’s risk for Alzheimer’s. Northwestern scientists theorize the cause could be a previous viral infection, environmental pollutants or other lifestyle factors and behaviors.

“It is possible that these findings implicate the peripheral immune response in Alzheimer’s disease risk,” said lead investigator David Gate, assistant professor of neurology at Northwestern University Feinberg School of Medicine. “We haven’t yet untangled whether these changes are reflective of brain pathology or whether they precipitate the disease.”

The study was published Feb. 9 in Neuron.

Previous research showed that many of the mutated genes putting a person at higher risk for Alzheimer’s are in the immune system. But scientists primarily studied the central immune system in the brain because Alzheimer’s is a brain disease. They have largely ignored the immune system in the blood, also known as the peripheral immune system.

Gate decided to study the blood. He and colleagues discovered every immune cell type in Alzheimer’s patients has epigenetic changes, indicated by open chromatin. Chromatin is the packaging of the DNA within cells. When chromatin is open — or exposed — the cells’ genome is vulnerable to alterations.

Then, Gate examined which genes are more open in these immune cells. He discovered that a receptor — CXCR3 — on the T cells was more exposed. Gate believes CXCR3 functions like an antenna on T cells that allows the cells to enter the brain. T cells do not normally enter the brain because they can cause inflammation.

“The brain is emitting a signal that it is damaged, and the T cells are homing to that signal by their antenna, CXCR3,” Gate said.

“T cells can be very toxic in the brain, but we also don’t know if these cells might be attempting to repair the damage in the brain,” Gate said.

Gate also discovered epigenetic changes in inflammatory proteins in white blood cells called monocytes.

“Altogether, these findings indicate that immune function in Alzheimer’s patients is significantly altered,” Gate said. “It could be that environmental factors, like pollutants, or infections that a person has in their lifetime cause these epigenetic changes.”

The findings revealed several genes that may be therapeutic targets for manipulating the peripheral immune system. Next steps in the research are preclinical studies using in vitro culture systems and animal models to test these targets.

Other Northwestern authors include Abhirami Ramakrishnan, Natalie Piehl, Brooke Simonton, Milan Parikh, Ziyang Zhang, Victoria Teregulova and Lynn van Olst.

The title of the article is “Epigenetic dysregulation in Alzheimer’s disease peripheral immunity.”

The research is supported by National Institute of Neurological Disorders and Stroke grant NS112458 and National Institute on Aging grant AG078713, both of the National Institutes of Health, Bright Focus Foundation, Alzheimer’s Association and Cure Alzheimer’s Fund.

Palaeontologists from the NHMW found snail shells of the superfamily Cerithioidea in Burgenland, Austria. The snails lived there twelve million years ago on the shores of a tropical sea. Professor Mathias Harzhauser at NHMW, who was involved in the discovery, explains: “It was unclear whether the patterns of reddish colour were from the original shell or were formed by later processes in the sediment.” Researchers at Göttingen University’s Geoscience Center solved the mystery. They analysed the pigments using Raman spectroscopy. This involves irradiating samples with laser light. The scattered light reflected from the sample can be used to clearly identify chemical compounds. They detected pigments in the fossilised shells that belong to the polyene group of chemicals. These are organic compounds that include the well-known “carotenoids,” which are responsible for producing the vibrant red, orange and yellow colours seen in birds’ feathers, carrots and egg yolks, for instance.

Dr Klaus Wolkenstein, who led the study and has been researching the chemistry of fossil pigments at Göttingen University for many years, explains: “Normally, after such a long period of time, the best we can hope for is that there are traces of degradation products of these chemicals. If degraded, however, these compounds would be devoid of colour. So, it was really surprising to discover these pigments, preserved almost intact, in fossils that are twelve million years old.”

When light shines on a semiconductor, its energy is absorbed. As a result, negatively charged electrons and positively charged holes combine in the semiconductor to form pairs, known as excitons. In the most modern two-dimensional semiconductors, these excitons have an extraordinarily high binding energy. In their study, the researchers set themselves the challenge of investigating the hole of the exciton. As physicist and first author Jan Philipp Bange from the University of Göttingen explains: “In our laboratory, we use photoemission spectroscopy to investigate how the absorption of light in quantum materials leads to charge transfer processes. So far, we have concentrated on the electrons that are part of the electron-hole pair, which we can measure using an electron analyser. Up to now, we didn’t have any way to directly access the holes themselves. So, we were interested in the question of how we could characterise not just the electron of the exciton but also its hole.”

To answer this question, the researchers, led by Dr Marcel Reutzel and Professor Stefan Mathias at Göttingen University’s Faculty of Physics, used a special microscope for photoelectrons in combination with a high-intensity laser. In the process, the breaking up of an exciton leads to a loss of energy in the electron measured in the experiment. Reutzel explains: “This energy loss is characteristic for different excitons, depending on the environment in which the electron and the hole interact with each other.” In the current study, the researchers used a structure consisting of two different atomically thin semiconductors to show that the hole of the exciton transfers from one semiconductor layer to the other, similar to a solar cell. Professor Ermin Malic’s team at the University of Marburg was able to explain this charge transfer process with a model to describe what happens at a microscopic level.

Mathias summarises: “In the future, we want to use the spectroscopic signature of the interaction between electrons and holes to study novel phases in quantum materials at ultrashort time and length scales. Such studies can be the basis for the development of new technologies and we hope to contribute to this in the future.”

This research benefited from the German Research Foundation (DFG) funding for the Collaborative Research Centres “Atomic scale control of energy conversion” and “Mathematics of Experiment” in Göttingen and “Structure and Dynamics of Internal Interfaces” in Marburg.

According to a new study, these so-called “Snowball” Earth periods, in which the planet’s surface was covered in ice for thousands or even millions of years, could have been triggered abruptly by large asteroids that slammed into the Earth.

The findings, detailed in the journal Science Advances, may answer a question that has stumped scientists for decades about some of the most dramatic known climate shifts in Earth’s history. In addition to Yale, the study included researchers from the University of Chicago and the University of Vienna.

Climate modelers have known since the 1960s that if the Earth became sufficiently cold, the high reflectivity of its snow and ice could create a “runaway” feedback loop that would create more sea ice and colder temperatures until the planet was covered in ice. Such conditions occurred at least twice during Earth’s Neoproterozoic era, 720 to 635 million years ago.

Yet efforts to explain what initiated these periods of global glaciation, which have come to be known as “Snowball Earth” events, have been inconclusive. Most theories have centered on the notion that greenhouse gases in the atmosphere somehow declined to a point where “snowballing” began.

“We decided to explore an alternative possibility,” said lead author Minmin Fu, the Richard Foster Flint Postdoctoral Fellow in the Department of Earth and Planetary Sciences in Yale’s Faculty of Arts and Sciences. “What if an extraterrestrial impact caused this climate change transition very abruptly?”

For the study, the researchers used a sophisticated climate model that represents atmospheric and ocean circulation, as well as the formation of sea ice, under different conditions. It is the same type of climate model that is used to predict future climate scenarios.

In this instance, the researchers applied their model to the aftermath of a hypothetical asteroid strike in four distinct periods of the past: preindustrial (150 years ago), Last Glacial Maximum (21,000 years ago), Cretaceous (145 to 66 million years ago), and Neoproterozoic (1 billion to 542 million years ago).

For two of the warmer climate scenarios (Cretaceous and preindustrial), the researchers found that it was unlikely that an asteroid strike could trigger global glaciation. But for the Last Glacial Maximum and Neoproterozoic scenarios, when the Earth’s temperature may have been already cold enough to be considered an ice age — an asteroid strike could have tipped Earth into a “Snowball” state.

“What surprised me most in our results is that, given sufficiently cold initial climate conditions, a ‘Snowball’ state after an asteroid impact can develop over the global ocean in a matter of just one decade,” said co-author Alexey Fedorov, a professor of ocean and atmospheric sciences in Yale’s Faculty of Arts and Sciences. “By then the thickness of sea ice at the Equator would reach about 10 meters. This should be compared to a typical sea ice thickness of one to three meters in the modern Arctic.”

As for the chances of an asteroid-induced “Snowball Earth” period in the years to come, the researchers said it was unlikely — due in part to human-caused warming that has heated the planet — even though other impacts could be as devastating.

The research was supported by the Flint Postdoctoral Fellowship at Yale and the ARCHANGE project. Co-authors of the study are Dorian Abbot of the University of Chicago and Christian Koeberl of the University of Vienna.