Naked diggers against the oxidative theory of aging
Darkness is a friend of naked diggersPyotr Smirnov, "Newspaper.
WIKIPEDIA:
The naked digger lives in dry savannas and semi-deserts of Kenya, Ethiopia and Somalia. They are secretive burrowing animals that feed on underground parts of plants, including succulent tubers and bulbs. Food is stored in underground storerooms. They do not drink water, the liquid is obtained together with food. In captivity, they eat a variety of fruits and vegetables.
Naked diggers live in underground colonies of 70-80 individuals, although colonies of up to 295 individuals have been observed. The total length of tunnels occupied by one colony can reach 3-5 km, and the annual emissions of earth during digging – 3-4 tons. The usual diameter of the tunnel is 4 cm; they pass at a depth of up to 2 m, connecting nesting chambers, latrines and feeding areas. The diggers usually do not come to the surface.
Tunnels are dug collectively; as a rule, they are expanded after rains, when the soil becomes softer. The working individual walking in front bites into the hard soil with incisors, which is then raked to the exit of the tunnels along a "live conveyor" – a chain of 5-6 animals. Periodically, the front worker is replaced by one of the rear ones.
Naked diggers are eusocial – the social structure of their colonies is similar to the structure of colonies of social insects. All individuals in the colony are related; they rarely move out. Inbreeding is common, which leads to a high degree of genetic similarity between colony members. At the head of the colony is a single female producer (queen), which mates only with 2-3 fertile males. All other diggers, both females and males, are working individuals. Physiologically, they are capable of reproduction, but they do not participate in it while they are in the colony (as a rule, all their lives). As with many social insects, if the uterus is removed from the colony, several female workers enter into a fierce struggle for the place of the queen. When a female becomes a queen, she noticeably increases in size; in adults, this is due to an increase in the distance between the vertebrae.
The functions performed by workers depend on their size. Small individuals support the tunnel system, help take care of the cubs and search for food. The largest sterile individuals are "soldiers", apparently protecting the colony from the main enemies of the diggers – snakes. Most of the year, in addition to the rainy season, they account for only 5% of the total work (with 25-40% of the population inside the colony). After the rainy season, they actively expand the tunnel network and partially settle, establishing new colonies. The behavior of medium-sized workers is intermediate in nature. The "castes" of naked diggers pass into one another with age, and there is no clear distinction between them, observed, for example, in ants. The female is exclusively engaged in childbearing, producing hundreds of cubs over the years of her life (in one case, about 900 cubs were documented over 12 years).
They have developed sound communication: naked diggers are able to produce at least 18 different types of sounds – more than any other rodents.
Fortunately, Asish Chaudhuri from the University of Texas and his colleagues-gerontologists did not go so "simple way" and found out that these toothy diggers are resistant to oxidative stress for unknown reasons, and their proteins, unlike us or mice, practically do not change throughout all 20-25 years of life.
Diggers living in the dry savannas and semi-deserts of Kenya, Ethiopia and Somalia, since their discovery in 1842, have amazed scientists with their phenomenal abilities, described due to the underground lifestyle and the difficulties of breeding in captivity only recently. Firstly, their way of life with the obligatory uterus, division of labor and social care for offspring is more like social insects than animals. Secondly, their skin is absolutely devoid of pain sensitivity, be it strong acids, cuts or burns.
But the most remarkable thing for physiologists is the unique metabolism: these tunnel dwellers are practically cold–blooded, the intensity of their metabolism is twice as low as that of other rodents, and the ratio of carbon dioxide and oxygen in cramped tunnels and "halls" is incompatible with life for most animals. Against this background, individuals who live up to 26 years in captivity, compared with 3 years for mice of the same size, do not even seem so strange.
This is what constantly attracts the attention of supporters of various theories of aging to them, of which the most popular today is associated with free radicals formed as a result of oxidation. According to her, oxidized molecules, primarily structural proteins and enzymes, gradually accumulate, causing disruption of cell and tissue functions. Accordingly, the more intense the oxidation processes, the fewer years of life.
Hence the numerous methods of breathing, which are reduced to increasing the level of carbon dioxide, and tips on taking antioxidants and vitamins that suppress the formation of active radicals in the body. However, attempts to confirm this in experiments on mice in which the activity of antioxidant systems was genetically enhanced failed. It also does not agree with the data obtained by detailing the physiology of long-lived birds and bats.
When Chaudhuri and co-authors of the publication in the Proceedings of the National Academy of Sciences tested this hypothesis on the example of naked diggers, comparing them with ordinary laboratory mice of the same size, the contradictions turned out to be even more obvious: the intensity of oxidation of liver proteins in the inhabitants of the labyrinths was even higher, but unlike mice, it did not change with age.
And this is despite the fact that the diggers' proteins are one and a half times richer in cysteine, an amino acid residue that is most often oxidized. As a result, by the end of life, mice "accumulated" almost three times more irreversibly altered proteins than their African relatives. In addition, the proteins of the latter turned out to be phenomenally resistant to "unwinding" and changes in spatial structure, usually caused by heating or changes in acidity.
The authors themselves associate the contradictions found with the imperfection, or rather, the "non-universality" of the oxidative theory of aging. And we intend to search for intracellular systems in the near future that support phenomenal stability or are responsible for the "accelerated" processing of altered proteins.
And although the "naked digger phenomenon" certainly refers to exceptions, it is such an extreme case that can help determine the specific contribution of various factors to the aging of the body, whether it is oxidative stress, dietary restriction, sexual abstinence, changes in chromosomes or nuclear pores.
Portal "Eternal youth" www.vechnayamolodost.ru18.02.2009