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A heart muscle cell shows bundles of actin filaments and bands of myosin.

For the first time, scientists recreate cell division—outside a cell

Every living thing moves—prey from predators, ants to crumbs, leaves toward sunlight. But at the most fundamental level, scientists are still struggling to grasp the physics behind how our own cells build, move, transport and divide.

“The mechanisms that allow organisms to move and change shape are inherent to life, and they are all underlaid by physics,” said Margaret Gardel, professor of physics at the University of Chicago. “But despite how central they are for our understanding of biology, a great deal of these remain poorly understood.”

Gardel led an innovative new study, which for the first time recreates the mechanism of cell division—outside a cell. The experiment, led by postdoctoral fellow Kim Weirich and published May 21 in the Proceedings of the National Academy of Sciences, helps scientists understand the physics by which cells carry out their everyday activities, and could one day lead to medical breakthroughs, ideas for new kinds of materials or even artificial cells.

“How cells divide is one of the most basic aspects of trying to create life, and it’s something we’ve been trying to understand for hundreds of years,” said study senior author Gardel, who combines physics and biology to study the ways by which cells transform themselves.

Cells move through the body, but some of the most complex motion takes place inside the cell, as it ships ingredients and supplies from place to place, flattens or expands, and divides to recreate itself. One of the key players in this dance is actin, a protein that assembles itself into rods and structures.

IT’S SOMETHING WE’VE BEEN TRYING TO UNDERSTAND FOR HUNDREDS OF YEARS.”—Prof. Margaret Gardel on cell division Click To Tweet

Gardel’s team wanted to understand the physics behind the actions of actin. So Weirich turned to one of the main ways that scientists have for this question: take the ingredients and try to build with them outside the cell.

Weirich separated out actin proteins, and watched as they formed droplets that took on an almond shape. When Weirich added myosin (“motor” proteins common in muscles), they spontaneously found the center between the two ends of the droplet and pinched off the droplet into two.

They were totally shocked to see the process, Gardel said. “There’s no precedent for this. It looks exactly like the spindles that drive cell division.”

Working with fellow UChicago physicist Thomas Witten and chemist Suriyanarayanan Vaikuntanathan, postdoctoral fellow Kinjal Disbaswas modeled the physics at play.

When in a droplet, the rod-like actin molecules like to align themselves in parallel to minimize conflict, forming the almond shape. The longer myosin molecules prefer to gather in the center so that they can still stay parallel to the actin. But as more myosins gather, they begin to stick together, forming clusters that favor tilting rather than staying parallel—so it pinches off into two. It’s the first such detailed look at how a cell might accomplish this task.

           

Myosin molecules (white) gather in the center of the rod-like actin molecules (red). (Courtesy of Weinrich et al)

Watching this process—how living things exploit the structure of a droplet to form more life—is not only fascinating but useful, Gardel said. Though the types of proteins are different in cell division, the underlying principles are likely similar. “This is the kind of thing you need to know to imagine building things like artificial tissue for a wound,” she said.

“Ultimately, a great deal of problems in biology are about how ensembles of molecules work together,” she said, “and because these are often materials with chemical reactions going on inside, they’re very hard to model. These kinds of studies allow us the opportunity to explore the basic principles of the forces at play.”

Materials provided by University of Chicago

brain cells analysis

For the first time, researchers restore cellular functions in brains of dead pigs

Scientists have been able to partially revive some of the functions in the brains of dead pigs, hours after they were killed in the slaughterhouse.

The team of researchers at the Yale University maintained that the brains did not regain the kind of electrical signals which are normally equated with being conscious. But they have been successful to preserve certain amount of cellular functions. The findings were reported in the Nature journal.

The research work has created confusion in the world of ethics, as it blurs the separation between the living being and the dead ones. Nita Farahany, faculty of ethics at Duke Law School said that she was quite astonished by the implications of the work as it changes a lot of the current understanding about neuroscience and the irreversible nature of loss of brain functioning due to oxygen deprivation.

It is known that the human brain is very sensitive to the lack of oxygen and it shuts off pretty quickly due to the absence of oxygen. But it is also known for a long time to the researchers that viable cells can be separated from the postmortem brain after its death. The main problem here is that it disturbs the 3D organisation and structure of the brain.

So scientists have been working on the technique to study about the brain cells in the organ itself, though they were not sure whether it would be successful or not. They named the technology as BrainEx, in which they did a fully detailed study on 32 pig heads.

The brains from the pigs’ heads were cleared out of the residual blood and the tissues were cooled down. Then they were placed in a chamber, where some vital blood vessels were tied to a device which pumped specially prepared chemicals for almost six hours.

The brains looked much different than the ones which were left to rot in the slaughterhouse Some of the molecular functions were restored and cell death was reduced. This has been described by scientists as a breakthrough achievement in brain study, as it converges the gap between neuroscience and clinical research.

But the researchers were worried about restoring consciousness in the brains. They constantly monitored the electrical activity in the brains and if they had seen any evidence of consciousness, they would have used anesthesia to cool it down.

The special solution used for testing in the brain cells consisted of an anti-seizure drug, lambotrigine which dampens the neuronal activity. Scientists are finding ways to tackle the ethical and legal issues related to the experiment and also on organ donation from the ones who have been declared brain dead.