c0nc0rdance: Here's your Friday Science🧪 Motivation💪: Today, roughly 10 MILLION of your cells will die and be replaced. In fact, the mass of cells that die each year is close to your body weight. Make this a great last day for them! Fond farewell, Neuron #189547! Bon voyage!

Here's your Friday Science🧪 Motivation💪: Today, roughly 10 MILLION of your cells will die and be replaced. In fact, the mass of cells that die each year is close to your body weight. Make this a great last day for them! Fond farewell, Neuron #189547! Bon voyage!

You're off by a few orders of magnitude. It's around 300 billion (yes, with a 'b') per day. That's about 80g/day, mostly blood cells: www.nature.com/articles/s41...

The distribution of cellular turnover in the human body - Nature Medicinewww.nature.com A comprehensive census of the dynamics of death and regeneration of cells and tissues provides an estimation of the distribution of cellular turnover in the human body.

Oof! Big mistake, and not even sure where 10 million even came from. I see numbers from 50 billion to 300 billion. Thanks for the correction!

Question: Why don’t red blood cells have a nucleus?

The standard explanation is "more room for hemoglobin", but there's a tantalizing possibility that it has more to do with managing redox state and the cumulative oxidative stress. A fascinating question is : Why do nucleated RBC persist in other species?

Red blood cell extrudes nucleus and mitochondria against oxidative stress - PubMedpubmed.ncbi.nlm.nih.gov Mammal red blood cells (erythrocytes) contain neither nucleus nor mitochondria. Traditional theory suggests that the presence of a nucleus would prevent big nucleated erythrocytes to squeeze through t...

Also, it's *mammalian* red blood cells that lack a nucleus—those of other vertebrates have them. IlRC, there are some birds that have both rbc with and without nuclei

According to wikipedia, it's the gentoo penguin species who can have a mix

Gonna be honest, it being just one bird is even weirder than all of them.

I think gentoo penguins are the fastest birds in the water, and can dive deep and for a long time, so their aerobic capacity must be very specially adapted? digitalcommons.usf.edu/cgi/viewcont...

digitalcommons.usf.edu

Recent support too: pubmed.ncbi.nlm.nih.gov/37808769/

Ancient genomic linkage couples metabolism with erythroid development - PubMedpubmed.ncbi.nlm.nih.gov Generation of mature cells from progenitors requires tight coupling of differentiation and metabolism. During erythropoiesis, erythroblasts are required to massively upregulate globin synthesis then c...

Ohhhhh that’s super interesting, thank you! And also, no mitochondria either?! RBC are so weird… I might return with more questions about this!

Some species have nucleated blood cells (birds, lizards). But probably the nucleus is ejected to maximize hemoglobin carrying capacity as it's no longer needed. wi.mit.edu/news/how-red....

How red blood cells nuke their nucleiwi.mit.edu In the first mechanistic study of how a red blood cell loses its nucleus, the research sheds light on one of the most essential steps in mammalian evolution.

They do during prenatal (human) life, by the way. And can be found in low quantities in the maternal circulation, potentially favoring non-invasive prenatal genetic diagnoses.

Thorough review: www.ncbi.nlm.nih.gov/pmc/articles...

Erythropoiesis: Development and Differentiationwww.ncbi.nlm.nih.gov Through their oxygen delivery function, red blood cells are pivotal to the healthy existence of all vertebrate organisms. These cells are required during all stages of life—embryonic, fetal, neonatal,...

But not your corneal endothelial cells, so take good care of your eyes! 👀

"Make this a great last day for them!"

Post