Podcast Transcript

Stem Cells Muscle In

Scientists have shown that, contrary to prevailing wisdom, muscles contain stem cells that can repair, replace and strengthen injured tissue.  Writing in Nature Stanford researcher Helen Blau and her colleagues have identified a collection of chemical markers that can be used to identify a population of muscle stem cells. 

Dubbed "satellite cells" because these small round bodies usually loiter at the edges of muscles, when injected into an injured muscle they can rapidly begin to divide, producing more stem cells and new muscle tissue.

The team made the discovery by genetically labelling the cells with a coloured marker protein before injecting them into mice with damaged leg muscles.  This technique enabled the researchers to follow the progress of the same mouse over a period of time by using a sensitive camera that could pick up the increasing intensity of the coloured stem cells as they grew.

"We were able to show that the injected cells increased their own numbers, contributed to existing muscle and also produced entirely new muscle in these mice," points out Blau.  The results are very exciting because now researchers are able to readily identify the muscle stem cells they can turn their attention to discovering ways to activate them in people with muscle-wasting diseases, or use them to repair muscles in trauma patients.

"That's the next step," says Blau.

21st Sep 2008

‘Baby’ Fat may Beat Obesity

It’s something that many of us struggle with – fat.  But where does it come from?  Researchers in Dallas have finally tracked down the location of immature fat cells, which hide out waiting for the extra calories that turn them into flab.

For a while, researchers have suspected that immature fat cells, known as progenitors, were hiding in or around the blood vessels that feed fatty tissues, but their precise location wasn’t known.  Working with mice, the researchers engineered fat progenitor cells with a gene that makes them glow green, so they could be followed in the body. They discovered that the progenitor cells are embedded in the walls of blood vessels that run through fatty tissues, and are an integral part if the vessel wall.

The researchers think that the cells are there because it enables them to sense the levels of nutrients in the blood.  When they get a whiff of excess calories, they can drift out of the blood vessels and mature into big fat cells.

The green label also meant that researchers could separate the immature fat cells from other cells, and grow them in the lab for further study.  The team hopes that they will understand more about the mechanisms behind fat growth, which could lead to ways to cut obesity and metabolic diseases such as diabetes in the future.  

As well as potentially helping people who struggle with their figure, the research could also point to ways to reactivate immature fat cells –for example, to fill in damaged tissues such as after injury or breast cancer surgery.

White Fat Progenitor Cells Reside in the Adipose Vasculature
Wei Tang, Daniel Zeve, Jaemyoung Suh, Darko Bosnakovski, Michael Kyba, Bob Hammer, Michelle D. Tallquist, and Jonathan M. Graff
Published online September 18 2008

21st Sep 2008

Fungi are world's fastest fliers

Scientists have discovered the fastest fliers in nature and, somewhat surprisingly, they're fungi!

Ohio-based researcher Nicholas Money and his colleagues at Miami University made the discovery by using ultra-fast cameras capable of taking 250,000 frames per second.  Down the lens they were studying members of two fungal families - the ascomycetes and the zygomycetes - that do the essential but unsalubrious job of breaking down animal dung.  These fungi rely on their spores passing harmlessly through the guts of grazing animals so that they land, quite literally, in the remains of their lunch.  But animals generally avoid grazing in areas where another animal has defaecated, leaving fungi like these with a problem.  Their solution is to have evolved the mycological equivalent of a "super-soaker" squirt gun - they fire their spores from tiny fluid-filled fruiting bodies so that they land in patches of uncontaminated grass ready for the next browsing ruminant.  But although scientists realised that the fungal launchpad must be incredibly powerful, it was too fast and too small to surrender its secrets, at least until now.

Writing in this weeks PLoS ONE the team have successfully made fungal ballistic measurements of spore trajectories to reveal that these organisms are firing their microscopic projectiles, which measure just a fraction of a millimetre across, at speeds exceeding 25 metres per second and at rates corresponding to 180,000 times the acceleration due to gravity.  This is sufficient to propel the spores up to 2.5 metres away from the parent dung pile.

The team were also able to get a handle on how the organisms achieve their fungal feat.  A concentrated mixture of sugars, alcohols and other metabolites inside the fungus and its fruiting body pulls in water by osmosis, priming the gun at a pressure about four times that of the atmosphere.  At the right moment the structure ruptures and the pressure drives out the spores.  According to the researchers the images of these fungal ejaculations are so pretty that they've set them to music and plan to post them on YouTube!