Insights & Outcomes: Nanowire networks and a galactic collision
This month, Insights & Outcomes finds intriguing answers to scientific questions about underground nanowire networks, distant galaxies that lack dark matter, and the connection between psychiatric disorders and immune system disorders.
Get in line, galaxies
Over the past four years, Yale astronomer Pieter van Dokkum and his collaborators have identified a pair of galaxies, DF2 and DF4, that have little or no dark matter and are located in close proximity to each other.
This cosmic togetherness is no coincidence, according to a new study in Nature led by van Dokkum, the Sol Goldman Family Professor of Astronomy in Yale’s Faculty of Arts and Sciences. The researchers say DF2 and DF4 — along with a handful of other galaxies — formed in a line after a “bullet” collision of two original galaxies about eight billion years ago.
The researchers said the colliding galaxies’ dark matter — an invisible, theorized material that emits no light or energy — continued traveling through space, unimpeded. But star-making gas from the colliding galaxies reacted violently. As it cooled and contracted, the gas created a tidy row of up to 10 new galaxies.
“We’re seeing the entire aftermath of this collision, laid out in the sky,” van Dokkum said. “There are these new galaxies with almost no dark matter, and then there are two objects at the leading edge of the row that we think may be the remnants of dark matter from the original galaxies.”
Going forward, the findings present an opportunity to study whether dark matter can interact with itself. The findings also provide an explanation for the existence of galaxies lacking dark matter.
“Everything fits now,” van Dokkum said. “We see the mechanism.”
Co-authors of the study were Zili Shen, Michael Keim, Dhruba Dutta Chowdhury, and Daisuke Nagai, all from Yale, and former Yale researcher Shany Danieli.
A power grid powerhouse — under our feet
The ground beneath our feet and under the ocean floor is an electrically charged grid, the product of bacteria “exhaling” excess electrons through tiny nanowires in an environment lacking oxygen. Yale researchers have been studying ways to enhance this natural electrical conductivity — within nanowires 1/100,000th the width of a human hair — by identifying the mechanism of electron flow.
A Yale team led by graduate student Peter Dahl with Nikhil Malvankar, assistant professor of molecular biophysics and biochemistry in the Microbial Sciences Institute, and Victor Batista, professor of chemistry and faculty member of the Energy Sciences Institute, found that nanowires move 10 billion electrons per second without any energy loss. The research also explains the remarkable capacity of these bacteria to send electrons over long distances.
The team also found that cooling the environment around nanowires of Geobacter bacteria from room temperature to freezing increases conductivity 300-fold within the nanowires. This is very surprising, the researchers said, because cooling typically freezes electrons and slows them down in organic materials.
By combining experiments with theory, the researchers found the colder temperatures restructure hydrogen bonds and flatten heme proteins within nanowires that enhance the flow of electricity. Leveraging this naturally occurring electrical grid might one day lead to the development of living and self-repairing electrical circuits, new sources of electricity, and bioremediation strategies.
The research was published in the journal Science Advances. Other authors include Sophia Yi, Yangqi Gu, Catharine Shipps, Jens Neu, Patrick O’Brien, Dennis Vu, and Sibel Ebru Yalcin from the Malvankar Lab and Atanu Acharya, Uriel Morzan, and Subhajyoti Chaudhuri from the Batista Lab.
The psychiatric disorder-immune system connection
People with psychiatric disorders are more likely to suffer from immune system disorders than those without mental health problems, and vice versa.
Scientists have struggled to explain these intriguing associations but a new Yale study suggests genetics plays an important role. The Yale team conducted a genome-wide analysis of patients and identified shared genetic liability between 31 pairs of psychiatric and immune system disorders. Conversely, they also identified 13 other genetic signatures that seemed to lessen the chances of someone with an autoimmune disorder also having mental health problems and vice versa.
Positive genetic correlations were found between multiple psychiatric disorders when paired with asthma, Crohn’s disease, hypothyroidism, ulcerative colitis, and primary biliary cholangitis. Negative genetic correlations were seen when several psychiatric disorders were paired with allergic rhinitis, primary sclerosing cholangitis, and Type 1 diabetes.
The genome-wide data alone does not explain which condition may trigger the other. However, by using different analytical tools, the researchers found evidence that suggests genetic liability for major depression, schizophrenia, and a multi-disorder condition may directly affect the risk of asthma and inflammatory bowel disorders.
The relationship between mental health and immune disorders could have multiple environmental causes, the researchers stress. They say more study is needed.
The research team was headed by lead author Daniel Tylee, a psychiatry resident in the Yale Neuroscience Research Training Program (NRTP), and senior author Renato Polimanti, assistant professor of psychiatry. The study was published in the journal JAMA Psychiatry.
Collecting the data on ketamine
Patients with treatment-resistant depression who received injections of ketamine did not differ in response and outcomes from those who received federally approved nasal spray esketamine, based on the primary outcome measure of a retrospective clinical study, Yale researchers show. However, patients who received intravenous ketamine showed slightly better improvement of depressive symptoms on some secondary outcome measures than those who received esketamine, according to the study published in JAMA Psychiatry.
Researchers stressed the results were not based on a randomized controlled trial and more investigation needs to be done to determine if the findings were clinically meaningful.
“While both treatments resulted in notable improvement of symptoms in many patients, we may be seeing a signal for a possible difference here; but this is far from a conclusive finding,” said corresponding author Sina Nikayin, assistant professor of psychiatry at the Yale School of Medicine. “We still need to conduct a prospective, randomized trial before we can reach any firm conclusions.”
Two decades ago, a finding by Yale scientists that ketamine, a common anesthetic medication, could quickly alleviate symptoms of chronic, treatment-resistant major depression set off a flurry of studies into why an anesthetic medication used since the 1970s had such a beneficial effect in psychiatric disorders. Yale holds a share of the patents licensed to Janssen Pharmaceuticals related to the intranasal administration of ketamine for treatment-resistant depression and to reduce suicide risk.
Intranasal esketamine (Spravato) was approved for the treatment of chronic depression by the U.S. Food and Drug Administration in 2019, and for treatment of depression with suicidal ideation in 2020.
Intravenous ketamine is not currently approved for the treatment of depression; however, it is used off-label in many clinics to treat chronic depression.