Tuesday, August 14, 2018
Scientists have clocked the speed of a form of cellular suicide called apoptosis
Scientists now know how long it takes for a cell to tell itself it’s time to die.
Signals triggering a type of cell suicide called apoptosis move through a cell like a wave, traveling at a rate of 30 micrometers per minute, Stanford University systems biologists Xianrui Cheng and James Ferrell Jr. report in the Aug. 10 Science.
These findings resolve a debate over whether these death signals spread by diffusion, with signaling molecules working their own way across a cell, or as self-regenerating trigger waves, like toppling dominoes. The apoptosis process starts with damage that causes the release of death signal chemicals. One example is cytochrome c leaking from damaged mitochondria, the cell’s power plant. Once cytochrome c concentrations get high enough, the chemicals signal proteins called caspases to go to work. Caspases trigger other proteins to poke holes in neighboring mitochondria, releasing more cytochrome c and moving the death wave across the cell. That chain reaction happens more quickly than diffusion can, Ferrell says. In an African clawed frog egg, a trigger wave takes about a half-hour to spread across the 1.2 millimeter cell, whereas diffusion would take five hours, he says.
Like forest fires, trigger waves will keep going as long as there is fuel to feed them — in this case, the death signal chemicals and proteins, Ferrell says. He predicts that many other biological signals may move as trigger waves.
“We biologists are just waking to this idea that trigger waves are a recurring theme in biological communication,” Ferrell says.
Discovering that apoptosis travels as trigger waves in cells may give scientists clues about how to persuade cancer cells to kill themselves (SN: 1/21/17, p. 10). Or researchers may learn how to prevent cells from dying in conditions such as Alzheimer’s disease or muscular dystrophy.
Monday, August 13, 2018
Sunday, August 12, 2018
Mensagem recebida de nosso primo José Antônio Brenner, agraciado com justa homenagem dos Centros de Cultura Alemã.
Por generosidade de amigos, indicação do Avenida Tênis Clube e pela escolha dos instituidores - Comissão das Comemorações da Imigração Alemã no Rio Grande do Sul, Federação dos Centros de Cultura Alemã no Brasil – FECAB e Centro Cultural 25 de Julho de Porto Alegre, fui agraciado com o prêmio "Distinção Imigração Alemã-2018".
Muito honrado, comunico a homenagem aos amigos e às amigas.