Let sleeping animals sleep!!!!!
Why are animals sleeping? Why are people "wasting" sleeping a third time of their lives? For all organisms with a nervous system, including invertebrates such as flies, worms, and even jellyfish, sleep has remained universal and essential throughout evolution. But the reason animals sleep-despite the ongoing threat of predators remains a mystery, and is considered one of life science's biggest unanswered questions.
Researchers at Bar-Ilan University in Israel reveal a novel and unexpected sleep function in a new study published today in the journal Nature Communications that they believe could explain how sleep and sleep disturbances affect brain performance, aging and various brain disorders. The researchers were able to define sleep in a single chromosome resolution using 3D time-lapse imaging techniques in live zebrafish and show, for the first time, that single neurons need sleep to perform nuclear maintenance.
Many processes such as radiation, oxidative stress, and even neuronal activity can cause DNA damage. Within each cell, DNA repair systems correct this damage. The current work shows that DNA damage accumulates consistently during wakefulness, when chromosome dynamics are low, and can reach unsafe levels. Sleep's role is to increase the dynamics of the chromosome and to normalize the levels of DNA damage in each neuron. Apparently, during the online wakefulness period, this DNA maintenance process is not sufficiently efficient and requires an offline sleep period with reduced brain input to occur.
"It's like potholes on the road," says Prof. Lior Appelbaum of Mina at Bar-Ilan University and Gonda (Goldschmied) Multidisciplinary Brain Research Center, who led the study. "Roads accumulate wear and tear, particularly during daytime rush hours, and it is most convenient and efficient to fix them at night when there is light traffic." Appelbaum calls the accumulation of DNA a "wakefulness price." He and his doctoral student David Zada, the study's first author, as well as co-authors, Dr. Tali Lerer-Goldshtein, Dr. Irina Bronshtein, and Prof. Yuval Garini, respectively.
Within individual neurons, and this theory will be confirmed. Due to the characteristics of the zebrafish model, their discovery was achieved. With their absolute transparency and a human-like brain, zebrafish are a perfect organism for studying single cells under physiological conditions within a living animal. The movement of DNA and nuclear proteins within the cell-within the fish-can be observed while the fish are awake and asleep using a high-resolution microscope. The researchers were particularly surprised to find that at night, when the body rests, chromosomes are more active, but this increased activity allows DNA damage to be repaired effectively.
The results identify chromosome dynamics as a potential marker for defining single sleeping cells and suggest that nuclear maintenance is the restorative function of sleep. "We found a causal connection between sleep, chromosome dynamics, neuronal activity, and DNA damage and repair with direct physiological relevance to the whole organism," says Professor Appelbaum. "Sleep provides an opportunity to reduce DNA damage accumulated in the brain during wakefulness." "Despite the risk of reduced environmental awareness, animals — ranging from jellyfish to zebrafish to humans— have to sleep to enable their neurons to perform effective DNA maintenance, and this may be the reason why.
