“The intact brain of a large mammal retains a previously underappreciated capacity for restoration of circulation and certain molecular and cellular activities multiple hours after circulatory arrest,” said senior author Nenad Sestan, professor of neuroscience, comparative medicine, genetics, and psychiatry.

However, researchers also stressed that the treated brain lacked any recognizable global electrical signals associated with normal brain function.

“At no point did we observe the kind of organized electrical activity associated with perception, awareness, or consciousness,” said co-first author Zvonimir Vrselja, associate research scientist in neuroscience. “Clinically defined, this is not a living brain, but it is a cellularly active brain.”

Cellular death within the brain is usually considered to be a swift and irreversible process. Cut off from oxygen and a blood supply, the brain’s electrical activity and signs of awareness disappear within seconds, while energy stores are depleted within minutes. Current understanding maintains that a cascade of injury and death molecules are then activated leading to widespread, irreversible degeneration.

However, researchers in Sestan’s lab, whose research focuses on brain development and evolution, observed that the small tissue samples they worked with routinely showed signs of cellular viability, even when the tissue was harvested multiple hours postmortem. Intrigued, they obtained the brains of pigs processed for food production to study how widespread this postmortem viability might be in the intact brain. Four hours after the pig’s death, they connected the vasculature of the brain to circulate a uniquely formulated solution they developed to preserve brain tissue, utilizing a system they call BrainEx. They found neural cell integrity was preserved, and certain neuronal, glial, and vascular cell functionality was restored.

The new system can help solve a vexing problem — the inability to apply certain techniques to study the structure and function of the intact large mammalian brain — which hinders rigorous investigations into topics like the roots of brain disorders, as well as neuronal connectivity in both healthy and abnormal conditions.

“Previously, we have only been able to study cells in the large mammalian brain under static or largely two-dimensional conditions utilizing small tissue samples outside of their native environment,” said co-first author Stefano G. Daniele, an M.D./Ph.D. candidate. “For the first time, we are able to investigate the large brain in three dimensions, which increases our ability to study complex cellular interactions and connectivity.”

While the advance has no immediate clinical application, the new research platform may one day be able to help doctors find ways to help salvage brain function in stroke patients, or test the efficacy of novel therapies targeting cellular recovery after injury, the authors say.

The research was primarily funded by the National Institutes of Health’s (NIH) BRAIN Initiative.

“This line of research holds hope for advancing understanding and treatment of brain disorders and could lead to a whole new way of studying the postmortem human brain,” said Andrea Beckel-Mitchener, chief of functional neurogenomics at the NIH’s National Institute of Mental Health, which co-funded the research.

The researchers said that it is unclear whether this approach can be applied to a recently deceased human brain. The chemical solution used lacks many of the components natively found in human blood, such as the immune system and other blood cells, which makes the experimental system significantly different from normal living conditions. However, the researcher stressed any future study involving human tissue or possible revival of global electrical activity in postmortem animal tissue should be done under strict ethical oversight.

“Restoration of consciousness was never a goal of this research,” said co-author Stephen Latham, director of Yale’s Interdisciplinary Center for Bioethics. “The researchers were prepared to intervene with the use of anesthetics and temperature-reduction to stop organized global electrical activity if it were to emerge. Everyone agreed in advance that experiments involving revived global activity couldn’t go forward without clear ethical standards and institutional oversight mechanisms.”

There is an ethical imperative to use tools developed by the Brain Initiative to unravel mysteries of brain injuries and disease, said Christine Grady, chief of the Department of Bioethics at the NIH Clinical Center.

“It’s also our duty to work with researchers to thoughtfully and proactively navigate any potential ethical issues they may encounter as they open new frontiers in brain science,” she said.

• Contacts and sources:
  Bill Hathaway
  Yale University
• Citation: Restoration of brain circulation and cellular functions hours post-mortem.
  Vrselja, Z. et al. Nature, 2019 DOI: 10.1038/s41586-019-1099-1

Snow is positively charged and gives up electrons. Silicone — a synthetic rubber-like material that is composed of silicon atoms and oxygen atoms, combined with carbon, hydrogen and other elements — is negatively charged. When falling snow contacts the surface of silicone, that produces a charge that the device captures, creating electricity.

“Snow is already charged, so we thought, why not bring another material with the opposite charge and extract the charge to create electricity?” said co-author Maher El-Kady, a UCLA assistant researcher of chemistry and biochemistry.

Findings about the device are published in the journal Nano Energy.

The discovery of this Earth-sized world is nevertheless exciting, as it demonstrates TESS’ ability to pick out small planets around nearby stars. In the near future, the TESS team expects the probe should reveal even colder planets, with conditions more suitable for hosting life.

“For stars that are very close by and very bright, we expected to find up to a couple dozen Earth-sized planets,” says lead author and TESS member Diana Dragomir, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research. “And here we are — this would be our first one, and it’s a milestone for TESS. It sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable.”

TESS has been hunting for planets beyond our solar system since it launched on April 18, 2018. The satellite is a NASA Astrophysics Explorer mission that is led and operated by MIT, and is designed to observe nearly the entire sky, in overlapping, month-long patches, or “sectors,” as it orbits the Earth. As it circles our own planet, TESS focuses its four cameras outward to monitor the nearest, brightest stars in the sky, looking for any periodic dips in starlight that could indicate the presence of an exoplanet as it passes in front of its host star.

Over its two-year mission, TESS aims to identify for the astronomy community at least 50 small, rocky planets, along with estimates of their masses. To date, the mission has discovered 10 planets smaller than Neptune, four of their masses which have been estimated, including π Men b, a planet twice the size of Earth, with a six-day orbit around its star; LHS 3844b, a hot, rocky world that’s slightly bigger than Earth and circles its star in a blistering 11 hours; and TOI 125b and c — two “sub-Neptunes” that orbit the same star, both within about a week. All four of these planets were identified from data obtained during TESS’ first two observing sectors — a good indication, the team writes in its paper, that “many more are to be found.”

Dragomir picked out this newest, Earth-sized planet from the first four sectors of TESS observations. When these data became available, in the form of light curves, or intensities of starlight, she fed them into a software code to look for interesting, periodic signals. The code first identified a possible transit that the team later confirmed as the warm sub-Neptune they announced earlier this year.

As is usually the case with small planets, where there’s one, there are likely to be more, and Dragomir and her colleagues decided to comb through the same observations again to see if they could spot any other small worlds hiding in the data.

“We know these planets often come in families,” Dragomir says. “So we searched all the data again, and this small signal came up.”

The team identified a small dip in the light from HD 21749, that occurred every 7.8 days. Ultimately, the researchers identified 11 such periodic dips, or transits, and determined that the star’s light was being momentarily blocked by a planet about the size of the Earth.

While this is the first Earth-sized planet discovered by TESS, other Earth-sized exoplanets have been discovered in the past, mainly by NASA’s Kepler Space Telescope, a since-retired telescope that monitored more than 530,000 stars. In the end, the Kepler mission detected 2,662 planets, many of which were Earth-sized, and a handful of those were deemed to be within their star’s habitable zone — where a balance of conditions could be suitable for hosting life.

However, Kepler observed stars that are many leagues further away than those that are monitored by TESS. Therefore, Dragomir says that following up on any of Kepler’s far-flung, Earth-sized planets would be much harder than studying planets orbiting TESS’ much closer, brighter stars.

“Because TESS monitors stars that are much closer and brighter, we can measure the mass of this planet in the very near future, whereas for Kepler’s Earth-sized planets, that was out of the question,” Dragomir says. “So this new TESS discovery could lead to the first mass measurement of an Earth-sized planet. And we’re excited about what that mass could be. Will it be Earth’s mass? Or heavier? We don’t really know.”

Contacts and sources:

• Jennifer Chu
• MIT – Massachusetts Institute of Technology