Sciencism 2013/03/03

In this weeks episode of Sciencism Ross, Dan and Andrew discus bone marrow niches, evidence for dark matter, discovering extra terrestrial planets, brain to brain rat interfaces, and discovery of a new Van Allen belt. We also discuss the merits of human space travel, science or fiction and last week in the past.

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Distinct niches in Bone Marrow1,2

All tissues in the body are derived from stem cells, ranging from pluripotent embryonic stem cells in the developing foetus which are capable of becoming any type of cell in the body to multipotent stem cells which can become a number of a limited range of cells. The blood system is in fact a tissue, one of the largest by volume in the body, and a type of stem cell called haematopoietic cells are responsible for growing new types of red blood cells known as erythrocytes and white blood cells known as leukocytes, which are critical to the body’s immune system.

Daniel link and his team from the Washington university school of Medicine investigated the niche, the environment in which cells mature, in which the haematopoietic stem cells develop in mice. By deactivating a gene called CXCL 12 which has previously been demonstrated to have an important role for keeping the blood stem cells healthy,  in different specific support cell types the team found that unlike previous thinking in which it was believed that a microniche existed where all blood cells matured, in fact there are separate niches for stem cells which become one of any type of blood cells and another separate niche for the T and B cells known as lymphocytes, the type of cell that is responsible for long term immunity.

This new discovery suggest that future investigations of treatment for leukaemias could focus on altering the environment of the specific niche for the cell type you are looking to treat. Chemotherapy currently has an extremely toxic effect on all blood cell populations which decreases the patient’s ability to fight infection and many tumour cells find a safe haven in bone marrow where the drug is less able to penetrate. If you could learn how to manipulate a specific niche you could force the target cells into the blood stream where the chemo therapy would be much more effective. At the other end of the scale if certain cell types are deficient a drug that boosts a specific niche could be used alongside established drugs such as G-CSF to target a more specific cell type rather than the shotgun growth increase which G-CSF currently causes.

More evidence about dark matter

There’s a problem with cosmology, most of you are probably already aware of it. There’s just too much gravity in the universe. The visible matter, that is the matter that emits detectable amounts of radiation just cannot account for what we see in galaxy clusters and other large objects in the universe. This can mean only two things, our theory of gravity isn’t completely correct, or there’s a lot more mass in the universe that we are unable as yet to detect. The evidence that we have suggests the latter is true, that the answer is Dark Matter, however dark matter still hasn’t been detected and the evidence doesn’t all point in this direction, just this week evidence for and against has been published.

In one corner a team from Tokyo examined the spectra (the properties of light) emitted from a cosmic event PS1-10afx. This event was 10 to 20 times brighter than a type 1a supernova, the type that results when a white dwarf syphons material from its binary pair then reaches critical mass and explodes. This extra brightness is extreme and hard to explain. It was thought that this constituted a new type of stellar event however the team from Tokyo’s data suggest that apart from the massive luminosity the spectra are consistent with a normal type 1a super nova.

They suggest that the extra brightness is caused by gravitational lensing. Gravitational lensing is when the gravity from a large object literally bends space time, light travelling through this space time is also bent which creates a lensing effect when we observe the light on earth. There is no visible dwarf galaxy in between us and the super nova which highly suggests that a substantial amount of “Dark Matter” is responsible.

Dark Matter isn’t completely accepted by the physics community though, not least because there is no direct evidence for its existence. The popular alternative is MOND, Modified Newtonian Dynamics which theories that gravity is not constant and that objects may feel a stronger pull in weaker gravitational fields.

Mordehai Milgrom was initially responsible for the MOND theory and recently used the formula in a computer model to predict the speeds of stars orbiting 17 dwarf spheroidal galaxies around Andromeda. The computer model was a very close match to the independently measured real life data which is strong support towards the theory, the team also plan predicted the speeds of stars in ten faint dwarf galaxies which have not yet been empirically measured success there too would be an even stronger win for the MOND theory.

An announcement from the AAAS this week however suggests that results from the Alpha Magnetic Spectrometer which is mounted to the outside of the International Space Station may yet provide the most comprehensive evidence yet for Dark Matter.

Science or Fiction

  • Virus discovered with “immune system”
  • Dust from Africa affects snowfall in California
  • E.Coli engineered to replace beta-cells in the pancreas


In 2007 it was discovered that bacteria and archea as well as vertebrates have an adaptive immune system. Bacteria store the DNA of viruses that attack them in a library called CRISPRs, next time they are attacked by a virus they recognise the DNA as new cas proteins to break down the viral DNA preventing infection. New research has discovered that the bacteriophage ICP1 which infects the pathogen responsible for cholera Vibrio cholerae stole part of the bacterias genome that codes for the cas proteins and had its own CRISPRs some of the genes involved in the bacterias immune system. When the team deleted those genes in the virus it was no longer able to infect it suggesting it destroys parts of the bacteria’s DNA responsible for its immune system in order to infect the cell.

Dust and Snow

In a paper published in Science this week the team tracked particles from California and traced them all the way back to the Sahara via China and Mongolia across the Pacific ocean, unlike previous studies which suggest that migrating particulates may decrease rainfall in northern California, the new study suggest these particles stimulate rain and snow, finding a correlation between increased particle density and rain or snow fall.

E.coli produce fatty acids from plant waste

Post doc duo Xiujun Zhang and Mai Li screened hundreds of E.coli strains and used genetic engineering to combine those with the with the best ability to convert sugars into fatty acids to reach a yield of 80-90%. The fatty acids can be used by refineries to create hydrocarbon based fuels and lubricants. The team say they will be working over the next few years to increase the yield and make sure the process will be robust enough to be used in an industrial setting.

1              Ding, L. & Morrison, S. J. Haematopoietic stem cells and early lymphoid progenitors occupy distinct bone marrow niches. Nature advance online publication, doi: (2013).

2              Greenbaum, A. et al. CXCL12 in early mesenchymal progenitors is required for haematopoietic stem-cell maintenance. Nature advance online publication, doi: (2013).


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