May 14, 2020
University of Sheffield
Research has given new insight into the cause of mutations in pluripotent stem cells and potential ways of stopping these mutations from occurring.
Research from the University of Sheffield has given new insight into the cause of mutations in pluripotent stem cells and potential ways of stopping these mutations from occurring.
The findings, published in Stem Cell Reports, show that pluripotent stem cells are particularly susceptible to DNA damage and mutations compared to other cells, and this could cause genetic mutations.
Pluripotent stem cells are able to develop into any cell type in the body, and there is considerable interest in using them to produce cells to replace diseased or damaged tissues in applications referred to as regenerative medicine.
One concern for the safety of this is that these cells often acquire recurrent mutations which might lead to safety issues if used in patients.
The researchers have found that these mutations are more likely to occur in a certain point during their cell cycle and have suggested ways of growing the cells to dramatically reduce the susceptibility to DNA damage and potentially the mutations that arise.
Peter Andrews, Professor of Biomedical Science at the University of Sheffield, said: "Clinical trials of regenerative medicine using cells derived from pluripotent stem cells are now beginning around the world, but there are concerns that mutations in the pluripotent stem cells may risk patient safety. Our results may allow us to significantly reduce that risk.
- Jason A. Halliwell, Thomas J.R. Frith, Owen Laing, Christopher J. Price, Oliver J. Bower, Dylan Stavish, Paul J. Gokhale, Zoe Hewitt, Sherif F. El-Khamisy, Ivana Barbaric, Peter W. Andrews. Nucleosides Rescue Replication-Mediated Genome Instability of Human Pluripotent Stem Cells. Stem Cell Reports, 2020; DOI: 10.1016/j.stemcr.2020.04.004
Cite This Page:
University of Sheffield. "New research into stem cell mutations could improve regenerative medicine." ScienceDaily. ScienceDaily, 14 May 2020. <www.sciencedaily.com/releases/2020/05/200514143533.htm>.
The design could advance the development of small, portable AI devices
June 8, 2020
Massachusetts Institute of Technology
Engineers have designed a 'brain-on-a-chip,' smaller than a piece of confetti, that is made from tens of thousands of artificial brain synapses known as memristors -- silicon-based components that mimic the information-transmitting synapses in the human brain.
MIT engineers have designed a "brain-on-a-chip," smaller than a piece of confetti, that is made from tens of thousands of artificial brain synapses known as memristors -- silicon-based components that mimic the information-transmitting synapses in the human brain.
The researchers borrowed from principles of metallurgy to fabricate each memristor from alloys of silver and copper, along with silicon. When they ran the chip through several visual tasks, the chip was able to "remember" stored images and reproduce them many times over, in versions that were crisper and cleaner compared with existing memristor designs made with unalloyed elements.
Their results, published today in the journal Nature Nanotechnology, demonstrate a promising new memristor design for neuromorphic devices -- electronics that are based on a new type of circuit that processes information in a way that mimics the brain's neural architecture. Such brain-inspired circuits could be built into small, portable devices, and would carry out complex computational tasks that only today's supercomputers can handle.
"So far, artificial synapse networks exist as software. We're trying to build real neural network hardware for portable artificial intelligence systems," says Jeehwan Kim, associate professor of mechanical engineering at MIT. "Imagine connecting a neuromorphic device to a camera on your car, and having it recognize lights and objects and make a decision immediately, without having to connect to the internet. We hope to use energy-efficient memristors to do those tasks on-site, in real-time."
Memristors, or memory transistors, are an essential element in neuromorphic computing. In a neuromorphic device, a memristor would serve as the transistor in a circuit, though its workings would more closely resemble a brain synapse -- the junction between two neurons. The synapse receives signals from one neuron, in the form of ions, and sends a corresponding signal to the next neuron.
A transistor in a conventional circuit transmits information by switching between one of only two values, 0 and 1, and doing so only when the signal it receives, in the form of an electric current, is of a particular strength. In contrast, a memristor would work along a gradient, much like a synapse in the brain. The signal it produces would vary depending on the strength of the signal that it receives. This would enable a single memristor to have many values, and therefore carry out a far wider range of operations than binary transistors.
Like a brain synapse, a memristor would also be able to "remember" the value associated with a given current strength, and produce the exact same signal the next time it receives a similar current. This could ensure that the answer to a complex equation, or the visual classification of an object, is reliable -- a feat that normally involves multiple transistors and capacitors.
Ultimately, scientists envision that memristors would require far less chip real estate than conventional transistors, enabling powerful, portable computing devices that do not rely on supercomputers, or even connections to the Internet.
Existing memristor designs, however, are limited in their performance. A single memristor is made of a positive and negative electrode, separated by a "switching medium," or space between the electrodes. When a voltage is applied to one electrode, ions from that electrode flow through the medium, forming a "conduction channel" to the other electrode. The received ions make up the electrical signal that the memristor transmits through the circuit. The size of the ion channel (and the signal that the memristor ultimately produces) should be proportional to the strength of the stimulating voltage.
Kim says that existing memristor designs work pretty well in cases where voltage stimulates a large conduction channel, or a heavy flow of ions from one electrode to the other. But these designs are less reliable when memristors need to generate subtler signals, via thinner conduction channels.
The thinner a conduction channel, and the lighter the flow of ions from one electrode to the other, the harder it is for individual ions to stay together. Instead, they tend to wander from the group, disbanding within the medium. As a result, it's difficult for the receiving electrode to reliably capture the same number of ions, and therefore transmit the same signal, when stimulated with a certain low range of current.
Borrowing from metallurgy
Kim and his colleagues found a way around this limitation by borrowing a technique from metallurgy, the science of melding metals into alloys and studying their combined properties.
"Traditionally, metallurgists try to add different atoms into a bulk matrix to strengthen materials, and we thought, why not tweak the atomic interactions in our memristor, and add some alloying element to control the movement of ions in our medium," Kim says.
Engineers typically use silver as the material for a memristor's positive electrode. Kim's team looked through the literature to find an element that they could combine with silver to effectively hold silver ions together, while allowing them to flow quickly through to the other electrode.
The team landed on copper as the ideal alloying element, as it is able to bind both with silver, and with silicon.
"It acts as a sort of bridge, and stabilizes the silver-silicon interface," Kim says.
To make memristors using their new alloy, the group first fabricated a negative electrode out of silicon, then made a positive electrode by depositing a slight amount of copper, followed by a layer of silver. They sandwiched the two electrodes around an amorphous silicon medium. In this way, they patterned a millimeter-square silicon chip with tens of thousands of memristors.
As a first test of the chip, they recreated a gray-scale image of the Captain America shield. They equated each pixel in the image to a corresponding memristor in the chip. They then modulated the conductance of each memristor that was relative in strength to the color in the corresponding pixel.
The chip produced the same crisp image of the shield, and was able to "remember" the image and reproduce it many times, compared with chips made of other materials.
The team also ran the chip through an image processing task, programming the memristors to alter an image, in this case of MIT's Killian Court, in several specific ways, including sharpening and blurring the original image. Again, their design produced the reprogrammed images more reliably than existing memristor designs.
"We're using artificial synapses to do real inference tests," Kim says. "We would like to develop this technology further to have larger-scale arrays to do image recognition tasks. And some day, you might be able to carry around artificial brains to do these kinds of tasks, without connecting to supercomputers, the internet, or the cloud."
This research was funded, in part, by the MIT Research Support Committee funds, the MIT-IBM Watson AI Lab, Samsung Global Research Laboratory, and the National Science Foundation.
- Hanwool Yeon, Peng Lin, Chanyeol Choi, Scott H. Tan, Yongmo Park, Doyoon Lee, Jaeyong Lee, Feng Xu, Bin Gao, Huaqiang Wu, He Qian, Yifan Nie, Seyoung Kim, Jeehwan Kim. Alloying conducting channels for reliable neuromorphic computing. Nature Nanotechnology, 2020; DOI: 10.1038/s41565-020-0694-5
Although the Cryonics Institute maintains a friendly and cooperative attitude toward other organizations and groups in the wider cryonics community, interactions with a particular group or mention in our magazine or website do not constitute a partnership, endorsement or other formal relationship unless specifically stated as such. An example of an organization we officially partner with would be Suspended Animation Inc., which we have negotiated with to provide special Standby offers for our members.
It is worth noting there are only a handful of these formal partnerships, so please be aware that if you see the Cryonics Institute name or logo being used somewhere in a way that suggests partnership or endorsement it is most likely not approved usage and will need to be removed.
CRYONICS GROUPS & ORGANIZATIONS
We do not partner with nor endorse any local standby or local cryonics organization. The “Cryonics Groups” listed in our magazine are provided only as information for our members who are encouraged to research and judge those groups and their capabilities for themselves. Since these groups operate independently, we can advise them on best practices or provide other assistance, but cannot certify or oversee their operations, practices and procedures and therefore cannot accept the liabilities that would come with an official endorsement or partnership.
LOGOS AND BRANDING
Use of the Cryonics institute logo or other branded materials is only approved for media stories about the Cryonics Institute or for links or references to the Cryonics Institute, usually as part of a list of cryonics service providers. Groups, organizations and individuals, including CI Members, are not allowed to incorporate or otherwise use the Cryonics Institute name or logo as part of their own name, branding or website in a way that suggests a formal partnership, endorsement or other affiliation, apart from the aforementioned personal membership in the organization if one is a member.
Photographs are a special case, and in some instances CI will allow our photographs to be used for cryonics-related web sites or other materials as illustrations as long as they are clearly labelled “Provided Courtesy of the Cryonics Institute” and the content it appears in is approved by us. Please contact us for review and permission before using CI materials on an individual, group or organization website, blog or in other online or print media.
PROTECTING THE CI NAME
If, as a member, you do see the Cryonics Institute logo or name being used online or in print as part of another group’s name or otherwise suggesting the group is affiliated with CI (particularly on social media accounts, discussion groups and websites) please contact us so we can investigate and have it removed if needed. As stated earlier, CI has only a handful of official partnerships so anything you see online suggesting a formal partnership or endorsement is most likely a misrepresentation.
Also, as a member, please do not identify yourself with the Cryonics Institute on social media or through other media as anything more than a member of the organization. Do not position yourself as representing the views of CI or its membership as a whole, but rather that any statements you make are your own personal opinions and not being presented on behalf of or with the endorsement of CI.
We do appreciate people promoting and discussing the Cryonics Institute in various ways, but we also need to be careful not to create confusion or misrepresentation of our organization and its goals, policies and positions by individuals outside the Cryonics Institute’s Leadership Team. Cryonics as a whole remains under intense public scrutiny which makes it vital to insure our official messaging is clear, consistent and on point.
Ultimately, CI can’t say whether other groups are utilizing proper procedures or have adequate finances, management or trained personnel.
There are some groups using the term “Cryonics” who we know nothing about. Some have tried to suggest that they are affiliated with CI when we have no relationship of any kind with them.
If you are interested in Cryonics then you need to do your own due diligence in investigating any Cryonics organization with whom you are considering dealing.
Thank you for your cooperation and understanding regarding allowed usage of the Cryonics Institute name, logo and brand. If you have further questions or concerns, please feel free to contact us at firstname.lastname@example.org.
President - Cryonics Institute