Posts Tagged ‘magnetism’

Researchers at Ludwing Maximilliams Universitat Muchen have for the first time mapped the distribution of magnetic particles in the human brain. The study reveals that the particles are primarily located in the cerebellum and the brainstem, which are the more ancient parts of the brain.

Many living organisms, such as migratory birds, are thought to possess a magnetotactic sense, which enables them to respond to the Earth’s magnetic field. Whether or not humans are capable of sensing magnetism is the subject of debate. However, several studies have already shown that one of the preconditions required for such a magnetic sensory system is indeed met: magnetic particles exist in the human brain. Now a team led by Stuart A. Gilder (a professor at LMU‘s Department of Earth and Environmental Sciences) and Christoph Schmitz (a professor at LMU’s Department of Neuroanatomy) has systematically mapped the distribution of magnetic particles in human post mortem brains. Their findings were published in the journal Scientific Reports (Nature Publishing Group)

In their study, the LMU researchers confirmed the presence of magnetic particles in human brains. The particles were found primarily in the cerebellum and the brainstem, and there was striking asymmetry in the distribution between the left and right hemispheres of the brain. “The human brain exploits asymmetries in sensory responses for spatial orientation, and also for sound-source localization,” Schmitz explains. The asymmetric distribution of the magnetic particles is therefore compatible with the idea that humans might have a magnetic sensor. But in all probability, this sensor is much too insensitive to serve any useful biological function, he adds. Furthermore, the chemical nature of the magnetic particles remains unknown. “We assume that they are all made of magnetite (Fe3O4), but it is not yet possible to be sure,” says Gilder.

The study was funded by the Volkswagen Foundation’s “Experiment!” program, which is designed specifically to get daring new research projects, whose ultimate outcome is uncertain, off the ground. This is in contrast to traditional NIH-style support, which largely supports research that has already been conducted and for which the outcome is almost certain. The data were obtained from seven human post mortem brains, which had been donated for use in medical research. In all, a total of 822 tissue samples were subjected to magnetometry. The measurements were performed under the supervision of Stuart Gilder in a magnetically shielded laboratory located in a forest 80 km from Munich which is largely free from pervasive magnetic pollution that is characteristic of urban settings nowadays.

In further experiments, the LMU team plans to characterize the properties of the magnetic particles found in human brains. In collaboration with Professor Patrick R. Hof (Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York), they also hope to perform analogous localization studies on far larger mammals – whales. These huge marine mammals are known to migrate between feeding and breeding grounds across great distances in the world’s oceans. “We want determine whether we can detect magnetic particles in the brains of whales, and if so whether they are also asymmetrically distributed“ says Schmitz. “It goes without saying that such studies will be carried out on animals that have died of natural causes.”

https://www.en.uni-muenchen.de/news/newsarchiv/2018/schmitz_magnetite.html

Distribution of magnetic remanence carriers in the human brain
Stuart A. Gilder, Michael Wack, Leon Kaub, Sophie C. Roud, Nikolai Petersen, Helmut Heinsen, Peter Hillenbrand, Stefan Milz & Christoph Schmitz
Scientific Reportsvolume 8, Article number: 11363 (2018)

Advertisements

On the heels of one failed drug trial after another, a recent study suggests people with early Alzheimer’s disease could reap modest benefits from a device that uses magnetic fields to produce small electric currents in the brain.

Alzheimer’s is a degenerative brain disorder that afflicts more than 46 million people worldwide. At present there are no treatments that stop or slow its progression, although several approved drugs offer temporary relief from memory loss and other cognitive symptoms by preventing the breakdown of chemical messengers among nerve cells.

The new study tested a regimen that combines computerized cognitive training with a procedure known as repetitive transcranial magnetic stimulation (rTMS). The U.S. Food and Drug Administration has cleared rTMS devices for some migraine sufferers as well as for people with depression who have not responded to antidepressant medications.

Israel-based Neuronix reported results of a phase III clinical trial of its therapy system, known as neuroAD, in Alzheimer’s patients. More than 99 percent of Alzheimer’s drug trials have failed. The last time a phase III trial for a wholly new treatment succeeded (not just a combination of two already approved drugs) was about 15 years ago. The recent study did not test a drug but rather a device, which usually has an easier time gaining FDA clearance. NeuroAD has been approved for use in Europe and the U.K., where six weeks of therapy costs about $6,700. The system is not commercially available in the U.S., but based on the latest results the company submitted an application for FDA clearance last fall.

The neuroAD setup resembles a dental chair fitted with a touch screen and flexible arms, which generate magnetic fields from metal coils positioned near the person’s scalp. The magnetic fields produce electric currents within the brain that influence the activity of neurons. The procedure can reportedly speed up learning by strengthening synaptic connections between neurons while the person performs tasks that engage those particular brain cells. In the cognitive training that accompanies rTMS, when study participants see a picture of a strawberry and touch the screen to identify it as “fruit” or “furniture,” for instance, the system stimulates Wernicke’s area, the brain region responsible for language comprehension.

For its latest rTMS trial, the company enrolled about 130 people with mild to moderate Alzheimer’s at 10 sites—nine in the U.S. and one in Israel. Four out of five participants were already taking symptom-relieving therapies. At the start of the trial, each person took a cognitive battery—a 30-minute paper-and-pencil test commonly used to gauge mental function in Alzheimer’s studies—and was randomly assigned to receive the rTMS-cognitive therapy or a sham treatment for six weeks. The sessions lasted about an hour each day, five days per week.

A week after the six-week regimen, and again five weeks later, participants retook the paper-and-pencil test to see if their cognition improved. Despite the elaborate protocol, study adherence was high. More than 90 percent of participants completed at least 90 percent of their visits, says Babak Tousi, who heads the Clinical Trials Program at Cleveland Clinic Lou Ruvo Center for Brain Health and reported the trial’s results at the Vienna meeting.

Based on past studies of the neuroAD system in smaller groups (none had more than 30 participants), the company expected to see a cognitive benefit after six weeks of treatment. Curiously, though, the recent study revealed no significant difference in test scores between active and sham groups at the seven-week time point. (The sham group sat in the chair and saw pictures on the screen but received no cognitive training or exposure to magnetic fields.) At week 12—six weeks after the therapy ended—the active group did show an 1.8-point test score advantage over the sham group. “That is a pretty small effect,” says Lon Schneider, who directs the State of California Alzheimer’s Disease Center at the University of Southern California in Los Angeles and heard the study results presented in Vienna. By comparison, he says, drugs currently approved to treat Alzheimer’s symptoms have shown a 2.5- to 3-point improvement in six-month clinical trials. And in a study reported last fall, a leading pharmaceutical candidate tested in more than 2,100 people seemed to work about as well (a roughly 1.5-point improvement) but failed to achieve statistical significance.

Plus, the modest effect seen with the new rTMS trial only turned up in participants with mild Alzheimer’s, Tousi reported. People with more advanced cases did not improve on the therapy. “We’ve got that typical problem of a small study that does seem to give outcomes, but the outcomes are either unclear or not fully evaluable,” Schneider says, adding it is unclear, for instance, if the test scores improved because of the cognitive training or resulted from possible mood-enhancing effects of the rTMS, because some Alzheimer’s patients have depression or other psychiatric symptoms.

John-Paul Taylor, a neuropsychiatrist at Newcastle University in England who was not involved with the study and researches TMS’s prospects for treating visual hallucinations in dementia, agrees that it is hard to tell if the cognitive improvement was indeed “a real TMS effect.” He says, however, this technology is “ripe for more investigation.”

Taylor is working with colleagues who are trying to use computational modeling to get a better idea how rTMS works. “That’s where it’s going to get really interesting,” he says. “I suspect you’ll have to tailor the stimulation to individual patients.” Consistent with that idea, earlier this year researchers reported using brain imaging to identify different types of depression—and patients in one of those subgroups responded especially well to rTMS.

With the computational modeling, one could imagine feeding in a person’s brain scan “and the computer would say, you need to be in this position at this stimulation intensity to equal what another person would receive,” Taylor says. “That’s not that far off.” Ultimately, though, “we want a therapeutic that still works across everybody to some degree,” he says. “There’s a hint of that in this trial. I’m cautiously optimistic.”

https://www.scientificamerican.com/article/could-magnetic-brain-stimulation-help-people-with-alzheimer-rsquo-s/

Quick – can you tell where north is? Animals as diverse as sea turtles, birds, worms, butterflies and wolves can, thanks to sensing Earth’s magnetic field.

But the magnet-sensing structures inside their cells that allow them to do this have evaded scientists – until now.

A team led by Can Xie’s at Peking University in China has now found a protein in fruit flies, butterflies and pigeons that they believe to be responsible for this magnetic sense.

“It’s provocative and potentially groundbreaking,” says neurobiologist Steven Reppert of the University of Massachusetts who was not involved in the work. “It took my breath away.”

There used to be two competing theories about magnetic sense: some thought it came from iron-binding molecules, others thought it came from a protein called cryptochrome, which senses light and has been linked to magnetic sense in birds.

Xie’s group was the first to guess these two were part of the same system, and has now figured out how they fit together.

“This was a very creative approach,” says Reppert. “Everyone thought they were two separate systems.”

Xie’s team first screened the fruit fly genome for a protein that would fit a very specific bill.

The molecule had to bind iron, it had to be expressed inside a cell instead of on the cell membrane and do so in the animal’s head – where animals tend to sense magnetic fields – and it also had to interact with cryptochrome.

“We found one [gene] fit all of our predictions,” says Xie. They called it MagR and then used techniques including electron microscopy and computer modelling to figure out the protein’s structure.

They found that MagR and cryptochrome proteins formed a cylinder, with an inside filling of 20 MagR molecules surrounded by 10 cryptochromes.

The researchers then identified and isolated this protein complex from pigeons and monarch butterflies.

In the lab, the proteins snapped into alignment in response to a magnetic field. They were so strongly magnetic that they flew up and stuck to the researchers’ tools, which contained iron. So the team had to use custom tools made of plastic.

The team hasn’t yet tried to remove the MagR protein from an animal like a fruit fly to see if it loses its magnetic sense, but Xie believes the proteins work the same way in a living animal.

Although this protein complex seems to form the basis of magnetic sense, the exact mechanism is still to be figured out.

One idea is that when an animal changes direction, the proteins may swing around to point north, “just like a compass needle,” says Xie. Perhaps the proteins’ movement could trigger a connected molecule, which would send a signal to the nervous system.

Journal reference: Nature Materials, DOI: 10.1038/nmat4484

https://www.newscientist.com/article/dn28494-animal-magnetic-sense-comes-from-protein-that-acts-as-a-compass

Thanks to Kebmodee for bringing this to the It’s Interesting community.

Since the 1930s scientists have been searching for particles that are simultaneously matter and antimatter. Now physicists have found strong evidence for one such entity inside a superconducting material. The discovery could represent the first so-called Majorana particle, and may help researchers encode information for quantum computers.

Physicists think that every particle of matter has an antimatter counterpart with equal mass but opposite charge. When matter meets its antimatter equivalent, the two annihilate one another. But some particles might be their own antimatter partners, according to a 1937 prediction by Italian physicist Ettore Majorana. For the first time researchers say they have imaged one of these Majorana particles, and report their findings in the October 3 Science.

The new Majorana particle showed up inside a superconductor, a material in which the free movement of electrons allows electricity to flow without resistance. The research team, led by Ali Yazdani of Princeton University, placed a long chain of iron atoms, which are magnetic, on top of a superconductor made of lead. Normally, magnetism disrupts superconductors, which depend on a lack of magnetic fields for their electrons to flow unimpeded. But in this case the magnetic chain turned into a special type of superconductor in which electrons next to one another in the chain coordinated their spins to simultaneously satisfy the requirements of magnetism and superconductivity. Each of these pairs can be thought of as an electron and an antielectron, with a negative and a positive charge, respectively. That arrangement, however, leaves one electron at each end of the chain without a neighbor to pair with, causing them to take on the properties of both electrons and antielectrons—in other words, Majorana particles.

As opposed to particles found in a vacuum, unattached to other matter, these Majoranas are what’s called “emergent particles.” They emerge from the collective properties of the surrounding matter and could not exist outside the superconductor.

The new study shows a convincing signature of Majorana particles, says Leo Kouwenhoven of the Delft University of Technology in the Netherlands who was not involved in the research but previously found signs of Majorana particles in a different superconductor arrangement. “But to really speak of full proof, unambiguous evidence, I think you have to do a DNA test.” Such a test, he says, must show the particles do not obey the normal laws of the two known classes of particles in nature—fermions (protons, electrons and most other particles we are familiar with) and bosons (photons and other force-carrying particles, including the Higgs boson). “The great thing about Majoranas is that they are potentially a new class of particle,” Kouwenhoven adds. “If you find a new class of particles, that really would add a new chapter to physics.”

Physicist Jason Alicea of California Institute of Technology, who also did not participate in the research, said the study offers “compelling evidence” for Majorana particles but that “we should keep in mind possible alternative explanations—even if there are no immediately obvious candidates.” He praised the experimental setup for its apparent ability to easily produce the elusive Majoranas. “One of the great virtues of their platform relative to earlier works is that it allowed the researchers to apply a new type of microscope to probe the detailed anatomy of the physics.”

The discovery could have implications for searches for free Majorana particles outside of superconducting materials. Many physicists suspect neutrinos—very lightweight particles with the strange ability to alter their identities, or flavors—are Majorana particles, and experiments are ongoing to investigate whether this is the case. Now that we know Majorana particles can exist inside superconductors, it might not be surprising to find them in nature, Yazdani says. “Once you find the concept to be correct, it’s very likely that it shows up in another layer of physics. That’s what’s exciting.”

The finding could also be useful for constructing quantum computers that harness the laws of quantum mechanics to make calculations many times faster than conventional computers. One of the main issues in building a quantum computer is the susceptibility of quantum properties such as entanglement (a connection between two particles such that an action on one affects the other) to collapse due to outside interference. A particle chain with Majoranas capping each end would be somewhat immune to this danger, because damage would have to be done to both ends simultaneously to destroy any information encoded there. “You could build a quantum bit based on these Majoranas,” Yazdani says. ”The idea is that such a bit would be much more robust to the environment than the types of bits people have tried to make so far.”

http://www.scientificamerican.com/article/majorana-particle-matter-and-antimatter/