Waves of death
Scientists have calculated the rate of spread of death in the cell of the body
Anna Kerman, XX2 century, based on Stanford Medicine: In apoptosis, cell death spreads through perpetuating waves
Scientists have found that death spreads through the cell in continuous waves at a speed of 30 microns per minute. This means that, for example, a nerve cell whose body can reach 100 microns in diameter will take 3 minutes and 20 seconds to die.
It sounds creepy, of course, but it is these "waves of death" that keep us alive and well. Apoptosis – programmed cell death – is necessary to cleanse the body of unnecessary or even dangerous cells. The danger may come, for example, from cells infected with viruses.
Apoptosis is also necessary for the normal development of the fetus – it helps to separate the forming organs. There is another way of cell death, necrosis – it differs from apoptosis, representing an unplanned response to a traumatic event.
If apoptosis does not go as it should, the consequences can be very serious. For example, cancer cells, having avoided a sad fate, will begin to multiply rapidly and spread throughout the body.
"Sometimes cells die when we would not like it – for example, in neurodegenerative diseases. And sometimes they don't die, again, against our wishes - for example, with cancer," explains lead author Dr. James Ferrell, professor of biology and biochemistry at Stanford University. "And if we want to interfere with these processes, we need to know how apoptosis is regulated."
Sometimes apoptosis is called "cellular suicide" because, in fact, it is a process of self-destruction. The "suicide" begins with an external or internal signal indicating to the caspases, special enzymes inside the cell, that it's time to get to work. However, before the new work appeared, it was unclear how apoptosis – after launch – spreads through the cell.
To find out, Ferrell and his colleagues decided to observe the apoptosis of one of the largest known cells, the egg of Xenopus laevis, the African spur frog (also known by other names – smooth spur frog, sycamore). For the experiment, the liquid from the eggs was poured into thin tubes, and the peptides contained in it were labeled with a fluorescent substance. Thus, if a glow appeared in the tube, it means that the process of apoptosis was going on.
It turned out that the glow in such conditions propagates at a constant speed. If apoptosis was based on simple diffusion, the rate would fall closer to the final stage – but this was not observed. The researchers concluded that at the molecular level, apoptosis spreads with the help of "trigger waves", "like a fire in a field." Caspases, when activated, cause activation of other caspases, and those of the following ones, until the cell is completely destroyed.
At the next stage of the experiment, scientists already used a whole egg of a spur frog – it was necessary to observe apoptosis in conditions as close to natural as possible. It turned out that inside the egg, apoptosis spreads at the same rate, about 30 microns per minute.
According to Dr. Ferrell, "trigger waves" are present everywhere in wildlife. They trigger the processes of cell reproduction, transmission of nerve signals in the brain and even the spread of viruses from cell to cell. Now a group of scientists plans to find out exactly where and how the "trigger waves" are involved, and to study them further.
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