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Human ageing

Cross-linking theory of aging

Old couples Image credit goes to Cellinsight Everything about human ageing and related diseases Cross-linking theory The cross-linking theory of aging was proposed in 1942 by Johan Bjorksten. According to this theory Collagen and other proteins undergoing structural changes due to molecular cross linkage (collagen is an important body proteins comprising 30℅ of body proteins) . In the presence of oxygen glucose molecules binding to to proteins and this cross-linked proteins causing damage to cells and tissues resulting in aging. This theory is also called as glycosylation theory of aging.  # Wrinkle and skin changes The cross-linked skin protein collagen  is responsible for wrinkles and skin changes during aging # Tendon stiffening An increased cross-linked collagen is the reason behind tendon stiffening, tendons are connective tissues which connect muscles to bones. a stiff tendon can pass more mechanical energy from muscles to bone but it lose it's elastic prop

Animals who defeated ageing.

Cellinsight Everything about human ageing and related diseases

Immortal animals

Nothing is forever in this world, death is certain, one day it will visit us. But there are some creatures that never die by natural aging process. Human cells are capable of dividing only 50 times, later the cells entered the senescence stage, and this is the exact reason for aging. Any animal which is not experiencing senescence can defeat ageing, today I am going to tell about such types of animals and how they live without the fear of ageing

1. Jelly fish (Turritopsis dohrnii) 

Animals who defeated ageing
Immortal jellyfish
(Image credit goes to Wikimedia

Jelly fishes are sea animals, included in the phylum coelenterata (cnideria). Turritopsis dohrnii is a species of jellyfish which is known as immortal jellyfish. Jellyfish reproduce both sexually and asexually.The life cycle consisted of three main stages, planulae,polyps and medusae. fertilized egg give birth to planula. The Planula is the larval stage, after few days it attached to any solid substrate under water and later transformed to polyp. Polyps later start to bud off another larva known as Ephira. These larvae
grown in to mature form of jellyfish, the medusae. When medusae injured or sick they revert back to polyp stage again within three days.

2. Lobsters

Animals who defeated ageing.

Lobster is a member of phylum Arthropoda and sub phylum  crustacea. Lobsters not experiencing senescence, they produced adequate amounts of telomerase enzyme. The length of telomere is constantly maintaining by this enzyme, so it's length not reduced after each cell division. Lobsters grow too big size for their shell. Unfortunately shell shedding and grow another exoskeleton cost very high amount of energy. Larger the lobster more energy required for moulting and rebuilding of shell. Shell collapse is one of the reason for their death. It also die because of diseases, predation etc.   

 3. Hydra                   
Animals who defeated ageing.

                   (Image credit goes to Wikimedia)

  Hydra is a fresh water animal living in ponds, lakes, rivers etc. Both jellyfish and hydra are the members of the same phylum the coelenterata (cnideria). Unlike the case of jellyfish there is no medusa_stage in the life cycle of Hydra, polyp is the mature stage. Hydra do not show any aging sign in their life. There are lot of stem cells in their body, these stem cells are capable of continuous self renewal. A special gene called FoxO (forkhead box O) is the secret behind this capability of the stem cells.



Many other living beings also showed anti ageing capabilities. Out of three above mentioned animals only Turriptosis dohrnii is widely accepted immortal animal. They have different stages in their life cycle, they are able to revert back from mature medusal stage to polyp stage. But the case of human is different, we don't have such life cycle, so we can't adapt such type of anti ageing mechanism. But the anti aging technic of Lobsters and Hydra are very hopeful for us. We need a thorough study about the mechanisms. Lobsters are producing enough telomerase enzyme, and constantly maitain the length of telomere, the result is no senescent cells in their body. Humans are also producing telomerase enzyme, but the production is limited to embryonic stage only, why this happening? What is obstructing to produce telomerase in elder stage?. In the case of Hydra a special gene called Fox O gene is the secret of it's immortality. But in the case of humans we have four foxO genes, foxO1, foxO3, foxO4 and foxO6, these genes are involved in apoptosis, metabolism, stress resistance, cell cycle arrest etc. why these genes are not helping our stem cells for self renewal? We don't know, or even we don't have much idea about the working of foxO gene in hydra but one thing is sure foxO gene is the secret behind the immortality of Hydra. We need more studies in this regard. 

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