Senescent cells are one of the hallmarks of aging and their elimination is being pursued for therapeutic purposes. The idea that cellular senescence cannot be reverted has been stated multiple times. Here's a selection of papers that show up in Google Scholar, each of which having being cited over a hundred times. Judith Campisi (2001) Because telomerase, the enzyme that can synthesize telomeric DNA de novo, is not expressed by most human cells, telomeres shorten with each cell cycle. When the telomeres er…

Organs age at different rates as measured by epigenetic clocks. The heart is around 10 years younger than you (as measured by your blood). Looking at telomeres however they had a similar length in both. The extracellular matrix may matter more for aging than we thought Aging of the skin, a review Eosinophils, part of the immune system that I did not talk about at all in my immunosenescence review look like key players in inflammaging. The Red Team Challenge (paying to identify mistakes in a scientific pape…

Introduction This post reviews the changes that occur in the immune system with age, and why that might be. Usually I aim to provide more or less coherent, first-principles explanations that capture what is the state of the art in the relevant field, figuring out if something is a collection of heterogeneous findings, just noise, or a true simple fact hidden under imperfect study designs. I have not been able to do that here, as I found a lot of discrepancies in the underlying literature, some of which have…

What does it mean to understand something in biology? There are of course Tinbergen's four questions to understand systems in biology. Tinbergen separates explanations into: What's the function of X, evolutionarily speaking? How did X evolve? How does X work? How does X develop as an organism grows? So for vision, wikipedia gives the following example: Four ways of explaining visual perception: Function: To find food and avoid danger. Phylogeny: The vertebrate eye initially developed with a blind spot, …

Back in 1945, Vannevar Bush wrote Science The Endless Frontier. The monograph itself aims to justify the establishment of what would later become the NSF (altough it was not the first time such a thing had been proposed), and Bush even proposes the exact structure and budget it should have. But, despite the title, the essay does not talk at all, implicitly or explicitly as science being an endless frontier. There is talk of science being an open frontier ripe for exploration, but that's as close as it gets.…

George Selgin starts his series on the economic effects of the New Deal OpenAI releases GPT-3, their latest general purpose language model. It represents a vindication of those who argued that "just more weights and data" would lead to a step change in performance. Gwern has more on this. Still far from AGI, but it's substantial progress. There are some senescent cells -in the liver, in this case- the cleareance of which is bad for the organism Andrew Gelman on peer review And peer review is broke…