Optic atrophy 1 (OPA1) is a dynamin protein that mediates mitochondrial fusion at the inner membrane. OPA1 is also necessary for maintaining the cristae and thus essential for supporting cellular energetics. OPA1 exists as membrane-anchored long form (L-OPA1) and short form (S-OPA1) that lacks the transmembrane region and is generated by cleavage of L-OPA1. Mitochondrial dysfunction and cellular stresses activate the inner membrane–associated zinc metallopeptidase OMA1 that cleaves L-OPA1, causing S-OPA1 accumulation. The prevailing notion has been that L-OPA1 is the functional form, whereas S-OPA1 is an inactive cleavage product in mammals, and that stress-induced OPA1 cleavage causes mitochondrial fragmentation and sensitizes cells to death. However, S-OPA1 contains all functional domains of dynamin proteins, suggesting that it has a physiological role. Indeed, we recently demonstrated that S-OPA1 can maintain cristae and energetics through its GTPase activity, despite lacking fusion activity. Here, applying oxidant insult that induces OPA1 cleavage, we show that cells unable to generate S-OPA1 are more sensitive to this stress under obligatory respiratory conditions, leading to necrotic death. These findings indicate that L-OPA1 and S-OPA1 differ in maintaining mitochondrial function. Mechanistically, we found that cells that exclusively express L-OPA1 generate more superoxide and are more sensitive to Ca2+-induced mitochondrial permeability transition, suggesting that S-OPA1, and not L-OPA1, protects against cellular stress. Importantly, silencing of OMA1 expression increased oxidant-induced cell death, indicating that stress-induced OPA1 cleavage supports cell survival. Our findings suggest that S-OPA1 generation by OPA1 cleavage is a survival mechanism in stressed cells.

V. A. Sadovnichii, Ya. T. Sultanaev and A. M. Akhtyamov
Trans. Moscow Math. Soc. 80 (2020), 123-131.
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Get the latest cybersecurity news, opinion and advice.

Actually, they weren.t caught together at all their images were put together with software. The shadows cast by the stars. faces give it away: The sun is coming from two different directions on the same beach! More elaborate digital doctoring is detected with mathematics. Calculus, linear algebra, and statistics are especially useful in determining when a portion of one image has been copied to another or when part of an image has been replaced. Tampering with an image leaves statistical traces in the file. For example, if a person is removed from an image and replaced with part of the background, then two different parts of the resulting file will be identical. The difficulty with exposing this type of alteration is that both the location of the replacement and its size are unknown beforehand. One successful algorithm finds these repetitions by first sorting small regions according to their digital color similarity, and then moving to larger regions that contain similar small ones. The algorithm.s designer, a leading digital forensics expert, admits that image alterers generally stay a step ahead of detectors, but observes that forensic advances have made it much harder for them to escape notice. He adds that to catch fakers, At the end of the day you need math.(1) For More Information: Can Digital Photos be Trusted?, Steve Casimiro, Popular Science, October 2005. _______ 1 It May Look Authentic; Here.s How to Tell It Isn't, Nicholas Wade, The New York Times, January 24, 2006.

Alexander Kolpakov and Sinai Robins
Math. Comp. 89 (2019), 2031-2046.
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George C. Linderman and Stefan Steinerberger
Math. Comp. 89 (2020), 1933-1952.
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Mahbub Alam and Anish Ghosh
Trans. Amer. Math. Soc. 373 (2020), 3357-3374.
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A. Ilyin and A. Laptev
St. Petersburg Math. J. 31 (2020), 479-493.
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Daniel Carando, Santiago Muro and Daniela M. Vieira
Proc. Amer. Math. Soc. 148 (2020), 2447-2457.
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Naoya Hiramatsu and Ryo Takahashi
Proc. Amer. Math. Soc. 148 (2020), 2359-2369.
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Alexander J. Rasmussen
Proc. Amer. Math. Soc. 148 (2020), 2345-2357.
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The Immigration Department today reminded the public to stay vigilant against phone scammers claiming to be from the department.

The department said victims in recent cases received pre-recorded voice calls from scammers posing as immigration officers informing them that they would have immigration restrictions imposed on them.

Such calls were then transferred to another scammer posing as a non-local law enforcement officer who asked the call recipient to provide sensitive information such as personal particulars, bank account numbers and passwords.

The department stressed that it does not make any pre-recorded voice calls to the public, nor will it transfer calls to other non-local authorities or ask the call recipient to provide information such as bank account numbers and passwords.

It reminded people to verify the identity of a caller and not to disclose their personal information.

If people have any doubts about a call, they should immediately report it to Police.

Required reading for any academic is Philip Roth’s “The Human Stain.” In the first few pages an older, tenured professor is “forced to retire.” Why? There were two students who never were present when he called roll. Even after roll … Continue reading →

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