What’s happening in and around the Cave Nebula? To help find out, NASA’s
orbiting Spitzer Space
Telescope looked into this optically-dark star-forming
region in four colors of infrared light.
The Cave Nebula,
cataloged as Sh2-155, is quite bright in infrared, revealing details not
only of internal pillars of gas and dust, but of the illuminating star cluster
too – all near the top of
the image. The red glow around the Cave’s entrance is created by dust
heated by bright young stars. To the right isCepheus
B, a star cluster that formed previously from the same cloud of gas and
dust. Other interesting
stars of Cepheus come to light in infrared as well, including those
illuminating an even younger nebula toward the image bottom, and a runaway starpushing a bow shock,
tinged in red near the image center. This region spans about 50 light years and lies
about 2,500 light years toward the constellation of the King of Aethiopia (Cepheus).
Image & info via APOD: https://apod.nasa.gov/apod/astropix.html
Image Credit: NASA, JPL-Caltach, Spitzer Space
Telescope
Scientists once thought that neurons, or possibly heart cells, were the
oldest cells in the body. Now, Salk Institute researchers have discovered that
the mouse brain, liver and pancreas contain populations of cells and proteins
with extremely long lifespans — some as old as neurons. The findings,
demonstrating “age mosaicism,” were published in Cell Metabolism on
June 6, 2019. The team’s methods could be applied to nearly any tissue in the
body to provide valuable information about lifelong function of non-dividing
cells and how cells lose control over the quality and integrity of proteins and
important cell structures during aging.
“We were quite surprised to find cellular structures that are essentially
as old as the organism they reside in,” says Salk Vice President, Chief Science
Officer Martin Hetzer, senior author and professor. “This suggests even greater
cellular complexity than we previously imagined and has intriguing implications
for how we think about the aging of organs, such as the brain, heart and
pancreas.”
Most neurons in the brain do not divide during adulthood and thus
experience a long lifespan and age-related decline. Yet, largely due to
technical limitations, the lifespan of cells outside of the brain was difficult
to determine.
“Biologists have asked — how old are cells in an organism? There is this
general idea that neurons are old, while other cells in the body are relatively
young and regenerate throughout the organism’s lifetime,” says Rafael Arrojo e
Drigo, first author and Salk staff scientist. “We set out to see if it was
possible that certain organs also have cells that were as long-lived as neurons
in the brain.”
Since the researchers knew that most neurons are not replaced during the
lifespan, they used them as an “age baseline” to compare other non-dividing
cells. The team combined electron isotope labeling with a hybrid imaging method
(MIMS-EM) to visualize and quantify cell and protein age and turnover in the
brain, pancreas and liver in young and old rodent models.
To validate their method, the scientists first determined the age of the
neurons, and found that — as suspected — they were as old as the organism. Yet,
surprisingly, the cells that line blood vessels, called endothelial cells, were
also as old as neurons. This means that some non-neuronal cells do not
replicate or replace themselves throughout the lifespan.
The pancreas, an organ responsible for maintaining blood sugar levels and
secreting digestive enzymes, also showed cells of varying ages. A small portion
of the pancreas, known as the islets of Langerhans, appeared to the researchers
as a puzzle of interconnected young and old cells. Some beta cells, which
release insulin, replicated throughout the lifetime and were relatively young,
while some did not divide and were long-lived, similar to neurons. Yet another
type of cell, called delta cells, did not divide at all. The pancreas was a
striking example of age mosaicism, i.e., a population of identical cells that
are distinguished by their lifespans.
Prior studies have suggested that the liver has the capacity to regenerate
during adulthood, so the researchers selected this organ expecting to observe
relatively young liver cells. To their surprise, the vast majority of liver
cells in healthy adult mice were found to be as old as the animal, while cells
that line blood vessels, and stellate-like cells, another liver cell type, were
much shorter lived. Thus, unexpectedly, the liver also demonstrated age
mosaicism, which points to potential new paths of regenerative research for
this organ.
On a molecular scale, a selection of the observed long-lived cells contained
protein complexes displaying age mosaicism. For example, the primary cilia
(hair-like appendages on the outside of cells) of beta cells in the pancreas
and neurons contained protein regions of vastly different lifespans. In stark
contrast, the cells in the liver contained no long-lived proteins at all.
“Thanks to new visualizing technologies we are able to pinpoint the age of
cells and their supramolecular complexes more accurately than ever before. This
opens new doors for studying all cells, tissues and organs in normal and in
disease states,” says Mark Ellisman, Distinguished Professor of Neurosciences
at UC San Diego’s School of Medicine and co-leader of the study with Hetzer.
His laboratory, the National Center for Microscopy and Imaging Research, developed
and provided the new tissue imaging methods for correlated multi-scale and
multi-modal microscopy. These methods provided the key new and enabling
technologies that allowed this study to be carried out.
“Determining the age of cells and subcellular structures in adult organisms
will provide new insights into cell maintenance and repair mechanisms and the
impact of cumulative changes during adulthood on health and development of
disease,” adds Hetzer. “The ultimate goal is to utilize these mechanisms to
prevent or delay age-related decline of organs with limited cell renewal.”
Next, the authors plan to decipher the difference in lifespans for nucleic
acids and lipids. They also want to understand how age mosaicism relates to
health and diseases such as type 2 diabetes.
Source: https://www.salk.edu/news-release/how-old-are-your-organs-to-scientists-surprise-organs-are-a-mix-of-young-and-old-cells/
Journal article: https://www.sciencedirect.com/science/article/abs/pii/S1550413119302505?via%3Dihub
