Jump to content

User:Asingh7115/sandbox

From Wikipedia, the free encyclopedia

Communication[edit]

Naked mole rates live in colonies in which members have specialized roles. Because these rodents are blind, they must find an alternative ways of communicating. One method is the secretion of hormones by the queen of the colony and fertile males. These members produce chemical signals that keep other members sterile.[1] Once the sterile naked mole rats are removed from these habitats, they become fertile once again.[1] In another form of communication, if one member of the colony is threatened by a predator, it can release a foul odor that calls other members of the colony to the location of the breach, where a combined population can produce a defense.[2] The secretion of hormones seems to be the prevalent form of communication within the species.

Fertility[edit]

Naked mole rats do not suffer from age-related infertility.[3] Breeding females mate and give birth until death.[3] The oldest male naked mole rat surviving in captivity was observed mating in the last year of his life.[3]

Naked mole rats, which are unique in being the only eutherian rodents, exhibit characteristics of both R and K selection. In unpredictable environments, species evolve to use R-selection, which is characterized by large numbers of offspring, lack of parental care, and rapid growth and attainment of sexual maturity.[3] However, in more stable environments where predation is a relative non-issue, K-selective is more prevalent.[4] K-selection is characterized by a small number of young and greater parental care and protection as well as longer gestation periods and slower growth.[4] K-selection is usually characteristic of large animals, but naked mole rats, which remain underground for most of their lives in nearly unchanging conditions, reproduce by this strategy for the most part.[3] They commit greater energy to maintaining their cells rather than growth and reproduction.[3] Sterile workers take care of young and only a few members of the population invest energy into reproduction. However, the reproductive habits of the naked mole rat also show some traits of the R-selection reproduction type.[3] Naked mole rats give birth to a relatively large number of offspring and there is a high mortality rate of young among the species.[3] In addition, naked mole rats have short telomeres in their somatic cells.[3]

Longevity[edit]

Tolerance of hypoxia[edit]

Naked mole rats live in underground tunnels that are protected from predators, however, this habitat is oxygen-deficient enough to cause severe hypoxia and death in many similar-sized rodents.[5] The naked mole rat has defenses against hypoxia that allow it to thrive in this predator-free environment. Hypoxic conditions cause the levels of free calcium ions in the brain to increase.[5] Free calcium ions in the brain are a cause of cell death.[5] Naked mole rats show a higher resistance to free calcium ion production than other rodents at all ages.[5] Though the propensity for producing free calcium ions increases with age, naked mole rats retain a high degree of resistance throughout their lives.[5] This tolerance to calcium build-up in the brain of the naked mole rat results in its ability to withstand lower oxygen levels.[5] Naked mole rats accumulate such little calcium in their brains because they retain high levels of the hormoneGluN2D, which stops calcium ions from forming in the brain.[4] This defense is usually found in newborn mammals, but the naked mole rat maintains it to shield against calcium accumulation even in advanced years.[4]

Protein resilience as a defense against oxidative stress[edit]

In low oxygen environments, naked mole rats must fulfill some of their oxygen needs with reactive oxygen species (ROS), which have the unfortunate side effect of causing oxidative stress.[6] Oxidative stress involves the increased production of oxidizing agents within cells and is negatively linked to heart disease.[6] Naked mole rats are protected from the harmful effects of oxidative stress because of the presence of proteins that are resistant to unfolding and ubiquitination (a type of protein modification).[7] Cysteine is one such protein that is highly resistant to degradation of oxidative stress.[7] It exists in the naked mole rat in high quantities and at consistent levels throughout the life of the organism.[7] However, because of the widespread nature of the damage that oxidative stress is able to do, for example to lipids, DNA, and cell signalling pathways, it is likely that other proteins with similar defenses exist in the naked mole rat.[7]

Low metabolic rate[edit]

The naked mole rat is already considered to have a low metabolism for a mammal of its size.[8] Naked mole rats have lower resting body temperatures, lower fasting blood glucose levels, and lower hormone levels.[3] When oxygen levels are decreased under a constant temperature, metabolism rates for the naked mole rat decrease further.[8] This decrease in metabolic speed places the naked mole rat in a stasis, causing it to devote a greater margin of its energy towards cell maintenance, homeostasis, and protection of important processes within the cell rather than the rapid growth of the organism and sexual and reproductive maturation.[8]

Resistance to cancer[edit]

There are different mechanisms that promote tolerance to the growth of tumors and cancer resistance in the naked mole rat.

The cells of a naked mole rat have a naturally higher level of contact inhibition than most other animals.[9] Greater levels of contact inhibition prevents the cells of naked mole rat from growing out of control and creating tumors.[10] These cells also react less strongly to carcinogens, or cancer causing agents.[10] When exposed to carcinogens, naked mole rats cells go into crisis instead of forming tumors: they divide to form nonfunctional cells that have lower than normal rates of mitosis and harmful structural problems.[9] Cells that go into crisis eventually all die rather than form tumors.[9]

Naked mole rats have a larger number of tumor suppressors in their genes then do humans.[11] For example, humans have the p27 suppressor, which promotes contact inhibition.[11] The naked mole rat also has the p27 suppressor, but it has another suppressor as well called p16, which blocks cell division at an earlier stage than p27.[11] These multiple tumor suppressors combine to give the naked mole rat a greater tolerance for uncontrolled cell growth.[11]

References[edit]

  1. ^ a b Faulkes, C. G.; Abbott, D. H. (1 September 1993). "Evidence that primer pheromones do not cause social suppression of reproduction in male and female naked mole-rats (Heterocephalus glaber)". Reproduction. 99 (1): 225–230. doi:10.1530/jrf.0.0990225. PMID 8283442. S2CID 29471780.
  2. ^ Edrey, Yael H.; Park, Thomas J.; Kang, Hyesin; Biney, Adriana; Buffenstein, Rochelle (1 February 2011). "Endocrine function and neurobiology of the longest-living rodent, the naked mole-rat". Experimental Gerontology. 46 (2–3): 116–123. doi:10.1016/j.exger.2010.09.005. PMID 20888895. S2CID 25701763.
  3. ^ a b c d e f g h i j Mele, J.; Edrey, Y. H.; Lewis, K. N.; Buffenstein, R. (5 September 2010). "Mechanisms of aging in the naked mole-rat: The case for programmed aging". Russian Journal of General Chemistry. 80 (7): 1455–1464. doi:10.1134/S1070363210070418. S2CID 98541322.
  4. ^ a b c d Peterson, Bethany L.; Park, Thomas J.; Larson, John (1 January 2012). "Adult naked mole-rat brain retains the NMDA receptor subunit GluN2D associated with hypoxia tolerance in neonatal mammals". Neuroscience Letters. 506 (2): 342–345. doi:10.1016/j.neulet.2011.11.042. PMID 22155615. S2CID 14738515.
  5. ^ a b c d e f Peterson, Bethany L.; Larson, John; Buffenstein, Rochelle; Park, Thomas J.; Fall, Christopher P. (21 February 2012). "Blunted Neuronal Calcium Response to Hypoxia in Naked Mole-Rat Hippocampus". PLOS ONE. 7 (2): e31568. doi:10.1371/journal.pone.0031568. PMC 3283646. PMID 22363676.
  6. ^ a b Grimes, K. M.; Lindsey, M. L.; Gelfond, J. A. L.; Buffenstein, R. (24 February 2012). "Getting to the Heart of the Matter: Age-related Changes in Diastolic Heart Function in the Longest-lived Rodent, the Naked Mole Rat". The Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 67A (4): 384–394. doi:10.1093/gerona/glr222. PMC 3309875. PMID 22367435.
  7. ^ a b c d Pérez, Viviana I.; Buffenstein, Rochelle; Masamsetti, Venkata; Leonard, Shanique; Salmon, Adam B.; Mele, James; Andziak, Blazej; Yang, Ting; Edrey, Yael; Friguet, Bertrand; Ward, Walter; Richardson, Arlan; Chaudhuri, Asish (17 February 2009). "Protein stability and resistance to oxidative stress are determinants of longevity in the longest-living rodent, the naked mole-rat". Proceedings of the National Academy of Sciences. 106 (9): 3059–3064. doi:10.1073/pnas.0809620106. PMC 2651236. PMID 19223593.
  8. ^ a b c Nathaniel, Thomas I.; Otukonyong, Effiong; Abdellatif, Ahmed; Soyinka, Julius O. (1 October 2012). "Effect of hypoxia on metabolic rate, core body temperature, and c-fos expression in the naked mole rat". International Journal of Developmental Neuroscience. 30 (6): 539–544. doi:10.1016/j.ijdevneu.2012.04.004. PMID 22633996. S2CID 205242522.
  9. ^ a b c Seluanov, A. (26 October 2009). "Cozzarelli Prize Winner@;DELIM@;From the Cover: Hypersensitivity to contact inhibition provides a clue to cancer resistance of naked mole-rat". Proceedings of the National Academy of Sciences. 106 (46): 19352–19357. doi:10.1073/pnas.0905252106. PMID 19858485. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ a b Liang, Sitai; Mele, James; Wu, Yuehong; Buffenstein, Rochelle; Hornsby, Peter J. (23 April 2010). "Resistance to experimental tumorigenesis in cells of a long-lived mammal, the naked mole-rat (Heterocephalus glaber)". Aging Cell. 9 (4): 626–635. doi:10.1111/j.1474-9726.2010.00588.x. PMID 20550519. S2CID 205634187.
  11. ^ a b c d Kim, Eun Bae; et al. (12 October 2011). "Genome sequencing reveals insights into physiology and longevity of the naked mole rat". Nature. 479 (7372): 223–227. doi:10.1038/nature10533. PMC 3319411. PMID 21993625.
Retrieved from "https://en.wikipedia.org/w/index.php?title=User:Asingh7115/sandbox&oldid=1168303094"