Name: Anonymous 2019-04-20 18:45
The naked mole-rat is also of interest because it is extraordinarily long-lived for a rodent of its size (up to 32 years[15][35]) and holds the record for the longest living rodent.[36] The mortality rate of the species does not increase with age, and thus does not conform to that of most mammals (as frequently defined by the Gompertz-Makeham law of mortality).[37] Naked mole-rats are highly resistant to cancer[38] and maintain healthy vascular function longer in their lifespan than shorter-living rats.[39] The reason for their longevity is debated, but is thought to be related to their ability to substantially reduce their metabolism during hard times, and so prevent aging-induced damage from oxidative stress. This has been referred to as "living their life in pulses".[40] Their longevity has also been attributed to "protein stability".[41] Because of their extraordinary longevity, an international effort was put into place to sequence the genome of the naked mole-rat.[42] A draft genome was made available in 2011[43][44][45] with an improved version released in 2014.[46] ts karyotype has 2n = 60.[5] Further transcriptome sequencing revealed genes related to mitochondria and oxidation reduction processes to have high expression levels in the naked mole-rat when compared to mice, which may contribute to their longevity.[47]
The DNA repair transcriptomes of the liver of humans, naked mole rats and mice were compared.[48] The maximum lifespans of humans, naked mole rats, and mice are respectively c. 120, 30 and 3 years. The longer-lived species, humans and naked mole rats, expressed DNA repair genes, including core genes in several DNA repair pathways, at a higher level than did mice. In addition, several DNA repair pathways in humans and naked mole rats were up-regulated compared with mice. These findings suggest that increased DNA repair facilitates greater longevity, and also are consistent with the DNA damage theory of aging.[49]
The naked mole-rat is the first mammal discovered to exhibit eusociality. This eusocial structure is similar to that found in ants, termites, and some bees and wasps.[54][55] Only one female (the queen) and one to three males reproduce, while the rest of the members of the colony function as workers.[56] The queen and breeding males are able to breed at one year of age. Workers are sterile,[55] with the smaller focusing on gathering food and maintaining the nest, while larger workers are more reactive in case of attack. The non-reproducing females appear to be reproductively suppressed, meaning the ovaries do not fully mature, and do not have the same levels of certain hormones as the reproducing females. On the other hand, there is little difference of hormone concentration between reproducing and non-reproducing males. In experiments where the reproductive female was removed or died, one of the non-reproducing females would take over and become sexually active. Non-reproducing members of the colony are involved in cooperative care of the pups produced by the reproducing female. This occurs through the workers keeping the pups from straying, foraging for food, grooming, contributing to extension of tunnels, and keeping them warm.[51
The DNA repair transcriptomes of the liver of humans, naked mole rats and mice were compared.[48] The maximum lifespans of humans, naked mole rats, and mice are respectively c. 120, 30 and 3 years. The longer-lived species, humans and naked mole rats, expressed DNA repair genes, including core genes in several DNA repair pathways, at a higher level than did mice. In addition, several DNA repair pathways in humans and naked mole rats were up-regulated compared with mice. These findings suggest that increased DNA repair facilitates greater longevity, and also are consistent with the DNA damage theory of aging.[49]
The naked mole-rat is the first mammal discovered to exhibit eusociality. This eusocial structure is similar to that found in ants, termites, and some bees and wasps.[54][55] Only one female (the queen) and one to three males reproduce, while the rest of the members of the colony function as workers.[56] The queen and breeding males are able to breed at one year of age. Workers are sterile,[55] with the smaller focusing on gathering food and maintaining the nest, while larger workers are more reactive in case of attack. The non-reproducing females appear to be reproductively suppressed, meaning the ovaries do not fully mature, and do not have the same levels of certain hormones as the reproducing females. On the other hand, there is little difference of hormone concentration between reproducing and non-reproducing males. In experiments where the reproductive female was removed or died, one of the non-reproducing females would take over and become sexually active. Non-reproducing members of the colony are involved in cooperative care of the pups produced by the reproducing female. This occurs through the workers keeping the pups from straying, foraging for food, grooming, contributing to extension of tunnels, and keeping them warm.[51