线虫全神经实时成像 z-bio 2021-01-20 281

　　Researchers have recently imaged all nerve cell activity in a living organism for the first time.

　　As early as 1986, scientists have drawn the connection diagram of all 302 nerve cells of the nematode-this is the first and has not been repeated in any other organisms.

　　 But this "circuit diagram" does not help scientists determine the nerve cell path leading to a particular behavior. Alipasha Vaziri, a neuroscientist at the University of Vienna in Austria, also pointed out that researchers cannot predict what the nematode will do at any point in time based on the connection diagram. And by providing a way to display the signal activity between nerve cells in a three-dimensional and real-time manner, this new technology will enable scientists to achieve the above two goals.

　　Vaziri and his colleagues then genetically modified the Caenorhabditis elegans so that when a nerve cell is activated and calcium ions cross its cell membrane, the entire nerve cell will be lit.

　　 To capture these signals, the researchers used a technique called light field deconvolution microscopy to image the entire nematode. This technology integrates images from a group of microlenses and uses an algorithm to analyze them to obtain a high-resolution three-dimensional image. The researchers took up to 50 images of the entire nematode every second, allowing them to observe the activity of nerve cells in the C. elegans brain, central nerve trunk, and tail. Next, the researchers used this technique to analyze transparent zebrafish (Danio rerio) larvae-as the zebrafish responded to the smell of chemicals pumped into the water, they imaged the entire brain of the small fish . With the help of this technology, researchers can capture the activity of about 5,000 nerve cells at the same time (the zebrafish has about 100,000 nerve cells in total). Misha Ahrens, a neurobiologist at the Howard Hughes Medical Institute's Zhenlia Farm Research Park in Oschborn, Virginia, said: "The circuit diagram and nerve cell activity are completely complementary. By observing one or the other nerve cell , You don’t understand the entire nervous system.” Using circuit diagrams to map how nerve signals travel between nerve cells will allow researchers to find out the role each individual nerve cell plays. Ahrens said: "There are no more hidden variables here."

　　 In 2013, Ahrens’ team used a microscope technique to image the activity of the entire zebrafish brain by passing a piece of light through an animal’s tissue. However, the new technology is much faster-it can increase the number of images taken by researchers 100 times per second.

　　 Edward Boyden, a neurobiologist at the Massachusetts Institute of Technology in Cambridge, a collaborator of this study, said that the researchers will next use this technology to determine how nerve cells respond to a certain stimulus and build a model. He also hopes to improve the speed and resolution of this technology in order to be able to image larger tissues, such as mammalian brains.

　　 Caenorhabditis elegans is a non-toxic and harmless nematode that can live independently. The individual is small, the adult is only 1.5mm long, and is hermaphroditic. Male individuals account for only 0.2% of the population and can be self-fertilized or bisexual. The average life history at 20°C is 3.5 days, and the average fecundity is 300 to 350; But if it mates with a male, it can produce more than 1,400 offspring. Since 1965, scientists have used nematodes as a model organism in the field of molecular biology and developmental biology.