Tuesday, December 10, 2019

birth of Chimera piglets ! ~ good to mankind or unethical ?


Schneider plays Marvin Mange, a man who is critically injured but unknown to him he is put back together by a mad scientist who transplants animal parts, resulting in strange permanent changes to his behavior. Days later, Marvin returns to his normal life with no memory of what had happened. Suddenly, he's full of life. He can outrun horses, mean dogs are now scared of him, and he does not need his asthma medicine. He thinks it is due to his late-night TV purchase of "Badger Milk", which is guaranteed in the ads to make him stronger.

A pig is any of the animals in the genus Sus, within the even-toed ungulate family Suidae. Pigs include domestic pigs and their ancestor, the common Eurasian wild boar (Sus scrofa), along with other species. Juvenile pigs are known as piglets. Pigs are highly social and intelligent animals.  The domestic pig is among the most populous large mammals in the world.  .. .. the birth of a piglet is the subject-matter of this post !  Piglet is a fictional character from A. A. Milne's Winnie the Pooh books. Piglet is Winnie the Pooh's closest friend amongst all the toys and animals featured in the stories. Although he is a "Very Small Animal" of a generally timid disposition, he tries to be brave and on occasion conquers his fears.

It is not the birth of any-other piglet - Two chimera piglets containing monkey DNA have been born in China.   The news that researchers want to create human-animal chimeras has generated controversy recently and may conjure up ideas about Frankenstein-ish experiments. But chimeras aren't always man-made—and there are a number of examples of human chimeras that already exist.  A chimera is essentially a single organism that's made up of cells from two or more "individuals"—that is, it contains two sets of DNA, with the code to make two separate organisms. One way that chimeras can happen naturally in humans is that a fetus can absorb its twin. This can occur with fraternal twins if one embryo dies very early in pregnancy, and some of its cells are "absorbed" by the other twin. The remaining fetus will have two sets of cells, its own original set, plus the one from its twin.

Animal chimeras are produced by the merger of multiple fertilized eggs.  Another way that chimerism can occur in animals is by organ transplantation, giving one individual tissue that developed from a different genome. For example, transplantation of bone marrow often determines the recipient's ensuing blood type. Pig-primate chimeras have been born live for the first time but died within a week. The two piglets, created by a team in China, looked normal although a small proportion of their cells were derived from cynomolgus monkeys. “This is the first report of full-term pig-monkey chimeras” said Tang Hai at the State Key Laboratory of Stem Cell and Reproductive Biology in Beijing. The ultimate aim of the work is to grow human organs in animals for transplantation. But the results show there is still a long way to go to achieve this, the team said.

Hai and his colleagues genetically modified cynomolgus monkey cells growing in culture to make them produce a fluorescent protein called GFP, enabling them to track these cells and their descendants. They then derived embryonic stem cells from these modified cells and injected them into pig embryos five days after fertilisation. More than 4000 embryos were implanted in sows. Ten piglets were born as a result, of which two were chimeras. All died within a week of birth. In the chimeric piglets, multiple tissues – including the heart, liver, spleen, lung and skin – partly consisted of monkey cells, but the proportion was low: between one in 1000 and one in 10,000.

It isn’t clear why the piglets died, says Hai, but because the non-chimeric pigs died as well, the team suspects it is to do with the IVF process rather than the chimerism. IVF doesn’t work nearly as well in pigs as it does in humans and some other animals. The team is now trying to create healthy animals with a higher proportion of monkey cells, says Hai. If that is successful, the next step would be to try to create pigs in which one organ is composed almost entirely of primate cells.  Something like this has already been achieved in rodents. In 2010, Hiromitsu Nakauchi, now at Stanford University in California, created mice with rat pancreases by genetically modifying the mice so their own cells couldn’t develop into a pancreas.
Given the extremely low chimeric efficiency and the deaths of all the animals, a key stemcell biologist sees it as a flop and feels that it may never be possible to grow organs suitable for transplantation by creating animal-human chimeras. However, it makes sense to continue researching this approach along with others such as tissue engineering, he says. Despite the research, some members of the scientific community have warned against creating chimeras due to ethical concerns.  One quipped - 'For us to start to manipulate life functions in this kind of way without fully knowing how to turn it off, or stop it if something goes awry really scares me.'

However, China shows no sign of stopping after proposing in July to create monkeys with partially human-derived brains in order to better study diseases like Alzheimer's. Yale University stem cell expert Alejandro De Los Angeles has written that the search for a better animal model to simulate human disease has been a 'holy grail' of biomedical research for decades. It is hoped the research could offer an alternative to organ donation.  Every day few people die on road accidents,  because replacement organs cannot be found.

Scientists have long pursued the idea of keeping people alive by using parts from animals – a process referred to as xenotransplantation. But it was long believed to be impossible; early experiments showed that the body takes about five minutes to reject an organ from another species. Xenotransplantation (Xenos- from the Greek meaning "foreign" or strange, or heterologous transplant is the transplantation of living cells, tissues or organs from one species to another.

The one at the start on Schneider playing Marvin Mange, a man who is critically injured but unknown to him he is put back together by a mad scientist who transplants animal parts, resulting in strange permanent changes to his behavior was the storyline of ‘The Animal’ released in 2001, directed by Luke Greenfield, starring Rob Schneider, Colleen Haskell and others. 

Interesting !

With regards – S. Sampathkumar
10th Dec 2019.
(news source :  https://www.newscientist.com)

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