Tuesday, January 31, 2023
Mitochondrial Health

7 महीने तक मुर्दा रहने के बाद फिर से जिंदा हो जाता है ये मेंढक। (हिन्दी मे)



अलास्कन वुड फ्रॉग (Alaskan wood frog) : यह मेंढक भी अजर अमर है। अलास्का में जब तापमान – 20°c गिर जाता है तब इस मेढक का शरीर लगभग फ्रीज हो जाता है और यह सीतनिद्रा (hibernation) में सो जाता है। तब यह लगभग 80% तक बर्फ में जम जाता है। इस दौरान उसका सांस लेना भी बंद हो जाता है।
The wood frog, Rana sylvatica, is the best-studied of a small group of amphibian species that survive whole body freezing during the winter months. These frogs endure the freezing of 65–70% of their total body water in extracellular ice masses. They have implemented multiple adaptations that manage ice formation, deal with freeze-induced ischemia/reperfusion stress, limit cell volume reduction with the production of small molecule cryoprotectants (glucose, urea) and adjust a wide variety of metabolic pathways for prolonged life in a frozen state. All organs, tissues, cells and intracellular organelles are affected by freeze/thaw and its consequences. This article explores mitochondria in the frozen frog with a focus on both the consequences of freezing (e.g., anoxia/ischemia, cell volume reduction) and mitigating defenses (e.g., antioxidants, chaperone proteins, upregulation of mitochondria-encoded genes, enzyme regulation, etc.) in order to identify adaptive strategies that defend and adapt mitochondria in animals that can be frozen for six months or more every year. A particular focus is placed on freeze-responsive genes in wood frogs that are encoded on the mitochondrial genome including ATP6/8, ND4 and 16S RNA. These were strongly up-regulated during whole body freezing (24 h at −2.5 °C) in the liver and brain but showed opposing responses to two component stresses: strong upregulation in response to anoxia but no response to dehydration stress. This indicates that freeze-responsive upregulation of mitochondria-encoded genes is triggered by declining oxygen and likely has an adaptive function in supporting cellular energetics under indeterminate lengths of whole body freezing.
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#frozenfrog #alaskanwoodfrog #frog

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