Plant Roots Work as Wires in Self-Growing Circuits
Andrew Adamatzky, Arxiv.org
An experiment to direct plant roots through maze-like channels is a step toward incorporating plant "wires" into self-growing circuits.
Wikicommons, Associated Press
In Greek mythology, chimeras were vicious monsters feared by many. This fire-breathing animal had the head and body of a lioness, with a goat head protruding from her back and the tail of a snake. Today, “chimera” refers to an animal that has two or more different sets of genetically distinct cells working together. Remember the mouse with the ear on its back? The movie "Splice" showcases a chimera experiment gone horribly wrong: scientists create a human-animal hybrid that becomes evil and goes completely out of control. While the movie is obviously science fiction, chimera experiments with human cells are not, and real life scientists have been conducting them for decades. We take a look at a few that have been successful in the past and how they’re advancing medicine.
Journal of Cell Research
Rabbit Eggs with Human Cells
The first successful human-animal chimeras were reported in 2003. Chinese researchers at the Shanghai Second Medical University successfully fused human cells with rabbit eggs. They were allowed to develop the eggs for several days in a petri dish before the embryos were harvested for their stem cells. Their hope was that this process could one day be used to grow cells or tissues for transplantation.
University of Minnestoa Mayo Clinic, PBS, Ass
Pigs with Human Blood
A year after the successful Chinese chimera experiment, researchers at the Mayo Clinic in Minnesota announced they had created pigs with human blood pumping through their veins. What was startling about the animal is not only did the pig blood cells flow with human cells, but some of the cells merged together, creating pig-human cell hybrids. Scientists said this experiment can give them a better understanding of how viral infections can pass from animals to humans such as HIV and various others.
University of Nevada-Reno, National Institute
Sheep with Human Livers
One of the efforts behind creating chimeras is to generate animal specimens that could grow human organs to be farmed for transplantation. In 2007, scientists at the University of Nevada-Reno announced they could grow livers made up of 20 percent human cells in sheep. Dr. Esmail Zanjani injected either human adult stem cells derived from bone marrow, or human embryonic stem cells, into growing sheep fetuses. Zanjani said he uses sheep because the circulation systems of sheep and humans are similar.
Salk Institute for Biological Studies
How do you develop treatments for liver infections and diseases only humans can get? Salk Institute researchers came up with one solution in February 2010. Using a mouse that was having liver problems of its own, the researchers replaced its liver with one that was made up of 95 percent human cells to study treatments for Hepatitis. Shown here is a cluster of mouse liver cells that have been replaced with human cells (shown in green). Typically, small animals can't be infected with Hepatitis, only humans and chimps can, but this "humanized" mouse not only became infected, it successfully responded to drug treatments. Scientists believe this experiment could open doors to finding cures for other human liver infections such as malaria.
University of Minnesota, Newcastle University
Cow Eggs with Human Cells
British researchers were given approval to conduct human-animal hybrid research in 2008, a decision that researchers touted would give them the ability to possibly find a cure for Parkinson’s disease. Before, only human cells were allowed to be injected into human eggs, but the researchers argued that animal eggs are much more available. After given permission, researchers went to work using cow eggs. The nucleus of the cow egg -- the source of most DNA and shown here in blue -- was removed, and replaced with the nucleus of a human cell such as a skin cell. Once the egg was allowed to develop and multiply it would become a early-stage cloned embryo called a blastocyst. Scientists could then extract the stem cells from this blastocyst to use in disease treatments.
University of California, Getty Images
Cat-Human Hybrid Proteins
Allergic to cats? Then you’ll appreciate this experiment. The feline Fel d 1 protein found in cat saliva contains an allergen that affects humans. When cats lick themselves, the saliva on their fur dries and turns into dust. In April 2005, scientists at the University of California created a human-cat hybrid when they fused the Fel d 1 protein with a human protein known to suppress allergic reactions. The feline protein would bind to immune cells that would cause the reaction and the human protein would tell the immune cells to calm down. When tested in mice, the chimeric protein stifled the allergy, and researchers hope they can be used in the future to treat allergy sufferers.
Irving Weissman, Stanford University professor and cofounder of the biotech company StemCells Inc., was granted permission by Stanford to create a mouse-human hybrid in 2005. Weissman and his team transplanted human-brain stem cells into the brains of mice with the intention to study neurodegenerative diseases such as Parkinson's and Alzheimer's. In his initial experiment, the human cells only made up less than 1 percent of the mouse brain. Shown here is an isolated mouse brain cell. In 2010, Stanford researchers announced they transformed mouse skin cells into fully functional neurons in a laboratory dish for the first time. They also announced in May that they successfully used mouse stem cells to develop sensory hair cells, which could combat human hearing loss.
George Washington University, DCI
We share over 98 percent of our DNA with chimpanzees, so would it be possible to create a human-chimp hybrid: a "humanzee," also called a "chuman" or "chumanzee"? In the 1920s, a Soviet biologist Ilia Ivanov artificially inseminated female chimps with human sperm, but the pregnancies didn't take. A chimp named Oliver became famous in the 1970s after it was thought he could be a human-chimp hybrid, because he walked upright. However, genetic testing in the 90s proved he was a chimp. Several researchers and citizens see such experiments has highly immoral and there is no known evidence of a human-chimp hybrid.
Computer scientist Andrew Adamatzky of the University of West England did a series of tests with four-day-old lettuce seedlings. To create bio-wires, he bridged two electrodes made from conductive aluminum foil with a seedling that was placed onto the electrodes in drops of distilled water.
Next, he applied electrical potential between electrodes ranging from 2 to 12 volts, and calculated the seedling's so-called potential transfer function that shows output potential as a fraction of input potential — the amount of energy produced relative to energy put in. [Super-Intelligent Machines: 7 Robotic Futures]
He found that resistance of the seedling repetitively changed with time, or oscillated. He determined that, roughly, the output potential was 1.5-2 V less than the input potential, "so by applying 12 V potential we get 10 V output potential," he said.
This meant that the resistance showed aperiodic oscillations, and thus, the wire was "somewhat noisy." Such noise, he admits, is not ideal for creating sensors, because energy gets wasted. But once new methods are developed for reliable routing of the plant roots between living and silicon components, it may be possible to incorporate plant wires into bio-hybrid self-growing circuits.
For such a leap to happen, researchers will have to "find a way of navigating plant roots in labyrinths," Adamatzky writes in his paper, detailed in a pre-print published on the Arxiv website.
Humans and Slime Molds
Almost any living creature, including humans, can conduct electricity and therefore be used as "wires," Adamatzky said. The problem is, not all creatures can remain motionless and without degrading for a long period of time. [Magnificent Microphotography: 50 Tiny Wonders]
But plants can -- provided they get enough light, water and minerals.
Previously, Adamatzky and his team tried to use slime mold as a computing medium, but the resulting sensors and processor were "very fragile, highly dependent on environmental conditions and somewhat difficult to control and constrain."
So they searched for less shifty alternatives, deciding to go with plants, because they are "in general, more robust and resilient, less dependent on environmental conditions and can survive in a hostile environment of bio-hybrid electronic devices longer than slime molds do," Adamatzky said.
To create bio-wires, scientists bridged two electrodes made from conductive aluminum foil with a lettuce seedling that was placed onto the electrodes in drops of distilled water.Andrew Adamatzky, Arxiv.org
Although the lettuce-based prototype was a success, Adamatzky insists that talking about getting the bio-wires out of the lab and onto the market was at the moment premature; there are a lot of challenges to be overcome before the wires can become commercially viable, he said.
Physicist Viktor Erokhin at the University of Parma in Italy, who was not involved in the study, said Adamatzky's findings are important. "It is interesting that living beings without nervous systems sometimes reveal 'intelligent’ behavior,'" he said.
"In this respect, such 'wires' can provide connections that will depend on the state of the environmental conditions. Moreover, such objects can be considered as bio-actuators," Erokhin said.
Ultimately, Erokhin believes, this research could lead to the development of bio-robots -- where scientists stimulate the plant cells so that they follow a biological blueprint and grow into truly green machines.
The main challenge now is to understand the intelligent behavior of plants and slime mold, he added.
It is not the first time researchers have turned to biology to create electronic components.
In 2013, a team of U.K. and U.S. scientists led by Tom Clarke, a lecturer at the school of biological sciences at the University of East Anglia (UEA), studied how marine bacteria conduct electricity to develop a model of microscopic bio-batteries.
And bio-physicist Angela Belcher at the Massachusetts Institute of Technology has succeeded in creating solar cells, plastics and more efficient batteries with the help of viruses.
Finally, U.S. scientists at Virginia Tech very recently developed a sugar-powered bio-battery. They claim it stores 10 times more energy than the equivalent-size lithium-ion batteries found in mobile phones. Recharging these sweet batteries could be as simple as pouring in some sugar solution.
The leader of the research, Y. H. Percival Zhang, a professor of biological systems engineering at Virginia Tech, predicts this biological battery could be on the market within three years -- and it would be a cheaper, easily re-chargeable, and more environmentally friendly alternative to traditional batteries.
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