In 1905, a French surgeon tried to transplant a rabbit kidney transplant to a patient with renal failure. Although this patient only survived for two weeks, the doctor’s attempt provided the world with a new idea for organ transplantation. . In addition to allogeneic transplantation, xenotransplantation first appeared in people’s sight.
However, subsequent studies have continued to show that organ transplantation between heterogeneous species will produce strong immune rejection, ranging from organ damage to loss of organ function and causing death. It was not until 2002 that the biggest problem known as xenotransplantation was declared to be solved. The American “Science” magazine published 100 major scientific discoveries that year, among which the world’s first genetically modified pig turned out to be quite eye-catching.
Cultivate “genetically modified” pig
Japanese scientists hope that stem cells will be injected into the human animal embryos to create “chimeric embryos” implanted in the uterus of animals, when the animals grew, the stem cells can grow into functional healthy human organs such as the liver or kidneys. This means that when the animal is fully grown, researchers can extract organs from the animal and implant it into the human body that needs an organ transplant.
Scientists expect to breed pigs with human pancreas first. Creating the kidney and human heart is much more complicated, but it is still feasible. The actual use of these cultivated organs may take another five years.
Scientists use a series of genetic modification methods to knock out the most critical genes in pigs that can cause rejection, and then add some human genes. After such “genetic modification” of pigs, they will become The “universal donor” that will produce immune rejection.
The so-called xenotransplantation refers to the transplantation of animal tissues and organs to humans to replace unhealthy tissues and organs to perform functions. Compared with homologous transplantation, the advantage of xenotransplantation is that the source of organs is not restricted, but the immune rejection reaction between xenogenes is much stronger than that between the same species, which is the biggest problem.
For pigs, the main cause of rejection is that the endothelial cells of pigs contain a sugar molecule that humans don’t have. When pig organs are implanted into the human body, the body’s immune system will recognize this sugar molecule as a foreign substance. Attack, the transplanted organ can be destroyed within minutes. To solve this problem, it is necessary to “knock out” the gene responsible for the production of this sugar molecule in pig cells, and then use this modified cell to clone, so that the cultivated pig organs will not be produced after being transferred into the human body. Rejected.
At present, scientists plan to build an “ultra-clean pig farm” to breed 5000-10000 pigs of this kind. Researchers will select healthy sows and use their uterus to breed “genetically modified pigs”. The principle is like cloned sheep. . Then after a caesarean section, the piglets that were born were separated from their mothers immediately and reared artificially in a sterile environment. In order to make the pigs cleaner and lower the adverse effects on the human body, the third generation of pigs can be provided to people. organ.
This pig can provide humans with cornea, skin transplantation, pancreatic islets, transitional liver, and even permanent heart, kidney, and liver.
Will humans behave like pigs after transplanting pig organs?
In reality, it is not uncommon to see reports of major changes in temperament due to organ transplantation. People suspect that it is because the transplanted organ brings the character of the organ donor to the body of the transplanted person. So, if pig organs are transplanted, will humans behave like pigs?
Australia has a case of hand transplantation. There was a patient who had no hands, so the doctor transplanted two-handed donors to him. The patient sees his hands every day and feels that they are not his own hands, and often thinks that they are the hands of a dead person. It’s getting lower and lower. In the end, he was unwilling to continue taking anti-immune drugs because he could not bear the pain. As a result, his hands had a rejection reaction, and the doctor had to remove the hands.
However, for people who really need a donor to save their lives, life is the most important thing. As long as they can save lives, they can’t control the psychological effects or unforeseen “adverse reactions”. For example, there is no problem with kidney, liver, heart, and lung transplantation between people. The reason is that firstly, these donors are used to save lives, and secondly, these donors are transplanted into the body and cannot be seen. Therefore, whether pig organs can be accepted as a donor depends entirely on the actual situation of the patient. As for whether organs have memory function, the current world level of science and technology cannot explain it. There is no scientific research to prove that after the organs of pigs are replaced, what changes will happen to human temperament? These are still uncharted territory.
Why should genetically modify pigs instead of chickens, sheep, fish, etc.?
According to a latest report, chickens seem to be smarter than previously expected. They have better computing and spatial perception capabilities than young children. Researchers from the University of Manchester in the United Kingdom were studying orangutans in Indonesia and found that apes were on trees. Construct complex nests, using a series of different specially selected materials; flies can remember their destination, even if there are certain disturbances and obstacles on the road; researchers have found that fish can be trained to associate a sound with eating Time is connected, and it can be remembered even after being released into the wild; an early study showed that goldfish only have three seconds of memory. This conclusion was finally found to be unfounded-goldfish can learn to suppress Some things can even be recalled months later; the sheep are actually smarter than previously thought. In a series of tests conducted by researchers at the University of Cambridge in the United Kingdom involving how to obtain food from different colored baskets and recognize different shapes, sheep performed as well as monkeys, and even better than rodents. Sheep can also recognize and remember the faces of 50 individual shepherd dogs, as well as human faces.
After a series of studies, the high intelligence of pigs has become more and more widely recognized. In 2009, a study published by Cambridge University researchers found that pigs can use a mirror to find a hidden bowl of food. After we understand all this, can we still use animals without restriction?
Animals have played a very important role in the survival and evolution of mankind. They are the main food source for mankind. Scientists have discovered that humans were carnivores 1.5 million years ago; they have also served as vehicles for humans in the long history of mankind. 5000 years ago, humans drove horse-drawn carriages; before the invention of machinery, humans relied on cattle to grow food; until modern times, dogs still take care of the work of nursing homes; cats are also good helpers for rodent control. Modern medicine relies on animals as guinea pigs to advance. Of course, each region, each ethnic group, and the relationship with various animals are different. But it is undeniable that humans cannot do without animals. However, “planting” organs in animals for human use is still groundbreaking research. We cannot stop the advancement of history, but we must also consider the harm that animals have suffered in this matter and make what is most beneficial to nature. select.
A carrier pigeon, even if you take it to a strange place thousands of miles away, it can take the letter home. Wind a few turns of coils on the top of the pigeon’s head and neck, powered by a small battery, and the pigeon’s head will generate a uniform additional magnetic field, which interferes with its reception of the geomagnetic field. When the current flows in a clockwise direction, the pigeons that are released on a cloudy day will fly in all directions. This shows that pigeons rely on geomagnetic navigation, so how do pigeons rely on geomagnetic navigation? Someone has put forward the view that the pigeon is regarded as a semiconductor with a resistance of 1000 ohms. When it flaps its wings in the earth’s magnetic field, the wings cut the magnetic lines of induction and move, thus generating an induced voltage between the two wings. The pigeon flies in different directions, because the cutting magnetic induction lines are in different directions, so the magnitude of the induced voltage generated is different, and the direction can be distinguished. But experiments show that when flying on a sunny day, the additional magnetic field does not affect its flight, which shows that geomagnetism is not its only compass. It turns out that pigeons can detect polarized light. On a sunny day, it can choose the direction of flight according to the position of the sun, and the body clock can correct the movement of the sun accordingly. In addition, when the current flows counterclockwise, it can fly home whether it is sunny or cloudy.