Category Archives: New Scientist
Hybrid Hearts: Stem Cell Transplants 2.0
“Can we use stem cells to make a new heart/eye/lung/liver etc?”
This is the predictable and perennial question that comes up from at least one student when we are looking at stem cells, genetic engineering, cell differentiation and transplanting. Until now, the answer has (perhaps in an oversimplified way) been ‘no’.
We can use stem cell transplants to treat lymphoma. Recently a young woman had a trachea transplant based on stem cell technology. Skin grafts from a patient’s own cultured cells are also possible, as are stem cell-based bladders. However, these are all rather simple technologies.
To treat lymphoma, bone marrow cells are replaced, and are all the same. The trachea transplant was a pre-existing trachea simply coated in the patient’s stem cells to prevent immune rejection. Skin transplants are basically sheets of epidermis that cover a wound, yet do not have the intricate functions of original skin: temperature regulation, secretion, senses. The bladder is a bag.
The challenge with using stem cells to transplant a more complex organ, such as a heart, is that it is not a simple sheet made of one type of cell. It is complex 3D structure, with a range of cells performing specific tasks within the organ. These cells have differentiated to perform their functions: cardiomyocytes (beating cells), vascular endothelial cells (smooth internal surfaces) and smooth muscle cells (blood vessel walls).
How can we get the stem cells to become the right type of cell, in the right position?
The answer to this question could be the key to opening up new doors in the search for viable transplantable organs in medicine, and bears much in common with the trachea case. It also marks a return to form for the NewScientist YouTube channel, who have this short clip of the new hearts in action:
A full article to accompany the footage is here.
In a nutshell:
Decellularised pig heart: the scaffold (NewScientist)
1. Find a suitable transplant organ, such as a pig’s heart.
2. Strip of all cells and DNA, using a detergent. Only the collagen ‘scaffold’ remains, as in the image of the decellularised heart to the right.
3. Coat the scaffold with the recipient’s stem cells.
4. Ensure that the blood supply is adequate and will provide the right signals for differentiation.
What is amazing in this case is how the cells ‘knew’ what specialised cells to become. The leader of the research group, Dr. Doris Taylor, puts it down to the mechanical stimulus of the pressure of the blood in the vessels and chambers and chemical signals from growth factors and peptides that remained on the stripped heart structure.
They even went as far as replacing a healthy rat’s heart with one of these new hybrid hearts. The rat survived for the trial, but she says they need to focus on producing more muscular hearts in order to ensure long-term survival of transplant recipients.
Food for thought:
Read the whole article and some of the links within it. Discuss these questions:
1. What are the potential uses for this kind of transplant technology?
2. What are the current limitations of this method and how might they be overcome?
3. What are the ethical issues related to using hybrid (pig-human) organs in medical transplants? How would you feel if you were the patient?
4. Who are the various stakeholders in this technology and what are their viewpoints?
Useful Sources:
Dr Doris Taylor’s research page from the University of Minnesota
NewScientist Article: Hybrid hearts could solve transplant problem
BioAlive stem cells links and resources
Can stem cells repair a damaged heart? from the NIH
Research reveals how stem cells build a heart, from Harvard news.
Facebook gives you cancer and infantilises the population. Ahem.
“There is no evidence because it would be hard to prove…” Aduh.
BadScience hero Ben Goldacre and Jeremy Paxman take on Baroness Greenfield, The Daily Mail (always a good target) and Aric Sigman in this interview from Newsnight. For a bit of background this is all a response to this story from the Daily Mail: http://www.dailymail.co.uk/health/article-1149207/How-using-Facebook-raise-risk-cancer.html
If you’re in my class, the page you need to comment on is here.
The Daily Mail reports Sigman is claiming (without any real evidence) that time on the computer takes you away from real people. This makes you isolated and lonely and means you are not producing the right hormones and your genes will act up – potentially leading to cancer, immune problems and impaired mental function. That’s a far reach for a newspaper article to be making, but these kind of shock headlines sell papers, or get more traffic on their website.
In this debate we see the importance of peer-reviewed research before making public claims. We see that correlation does not necessarily imply causality and we see that poor reporting of sensitive issues can lead to gross misunderstandings. If we remember, the Daily Mail was central in the reporting of the MMR vaccine scare.
When you watch this interview and read the article, can you think of responses to these questions?
– Are there parts of Sigman and Greenfield’s claims that might sound plausible?
– What kind of evidence would you want to see to support these claims?
– What is the significance of Goldacre’s comment “… you can make anything look dangerous if you are selective in which evidence you quote” ?
– Sigman makes a comment “The paper weas supposed to be a one-sided provocative feature article for The Biologist to make people think more carefully about where society is going.” How does he feel about the media attention that his words have attracted outside this publication?
– Central to Sigman’s claims were that internet use increases social isolation. He had no peer-reviewed work after 1998 to support this, yet Goldacre pointed out all these references that suggest otherwise.
– Sigman tries to re-state ‘social networking’ as a phrase meant for real-life interactions between people rather than internet-based interactions. How has his interpretation of the term led to confusion in the wider public? Who do you think is responsible for this confusion and how could it be rectified?
– Sigman tries to distance himself from the headlines and the conjectures of Greenfield and returns to his concern that internet use is having a direct and negative impact ont the lives of children. Take this opportunity to discuss the benefits and potential negative impacts of the internet with regard to childhood use.
– Goldacre makes a comment that it woudl be bad for research to prioritse what research is done based on the headlines in the newspapers. Do you agree/ disagree? Why?
– How do you think the precautionary principle might relate to the decisions parents make based on this issue?
How would you like to see this story develop? What further research would convince you of the harms or otherwise this debate?
Nature’s YouTube Channel (and some others)
On the heels of the NewScientist YouTube channel we have the offering from Nature. Where NewScientist provides a news-style clip of current Science headlines, Nature’s YouTube channel takes the approach of a video background to articles published in their journal. So far they have ten videos, though they provide useful background to articles such as the Antikythera mechanism, whale evolution and this one on sequencing the platypus genome:
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It’s an encouraging trend to see these journals reach out into internet video publishing – cheap, easy and a great starting place for students getting involved in science. Let’s hope Nature can keep their channel going longer than ScientificAmerican, who started strongly but seem to have given up.
Of course, the bees knees of YouTube channels so far are NationalGeographic, with 847 videos to date. Here’s a gratuitous Great White clip:
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JoVE
Another great channel (though not on YouTube) is the Journal of Visualised Experiments – actually publishing scientific research papers as videos. A good idea, and some really effective videos – especially for letting us see what is going on in the experiment or operation. Unfortunately, their videos can’t be embedded, so get yourself on over there and have a look.
Now comes the question of citing online videos in your work – and here is the answer! (pdf)
Other ‘tube’ resources worth a look are DNAtube and TeacherTube.
Parthenogenesis – Virgin Births in Nature
Happy (belated) Christmas!
How do you really reproduce without sexual reproduction? Asexual reproduction, of course. Simple, really… but not for the females of some species.
There are loads of links in this post, so click on them to learn more.
Parthenogenesis
Some plants, insects, shark and lizard species are known to reproduce by parthenogenesis – embryo development is carried out without fertilisation by a male -so called ‘virgin creations.’
Parthenogenesis can take a range of pathways :
- The egg can be fertilised by a polar body (a ‘leftover’ of egg production), making the chromosome number diploid and triggering embryo development. Here is a simple explanatory animation from amateurmicrography.net.
- Chromosomes in the egg can self-replicate, making up the diploid number and the embryo develops from there.
Other methods include suppression of male genotypes (technically still sexual reproduction?), or eggs cells dividing by meiosis.
The resulting offspring are going to be all the same gender. In some species, the XY system determines gender and parthenogenesis produces all females. In other, the ZW system dictates that they will all be male.
Parthenogenesis is a reproductive strategy that sacrifices the genetic variation (a driving force of evolution) of sexual reproduction for the simple ability to reproduce. Small invertebrates, such as aphids, can use it to produce large numbers of females very quickly.
Komodo Dragons
Larger organisms, such as Komodo dragons (Indonesia link!), have been known to use parthenogenesis in the absence of males, producing an all-male clutch of eggs. It is thought that this might allow them to set up new populations on isolated islands, using just a single female. Here’s a quick video of a Komodo dragon parthenogen hatching:
Some interesting Komodo readers here from Richard Dawkins and Not Exactly Rocket Science.
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Parthenogenesis in sharks
Parthenogenesis has also been observed in captive sharks – the female had no access to males, yet gave birth to live young (though only one, where the normal litter would be larger). Genetic tests confirmed parthenogenesis, rather than the alternative hypothesis of superfecundation (storing sperm for a long period of time). Read the full paper here, and another on hammerheads here. BBC audio explanation here.
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So can it work in us?
Let’s let House MD explain:
In short, no. Not naturally.
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Generally, we use mitosis to replace and repair damaged cells and tissues and for growth and development – filling in the gaps with copied cells. Along the way, our cells differentiate to their function and we end up with a body full of specialised cells – each cell’s structure and biochemistry reflect its function.
We don’t use mitosis for reproduction, as it narrows genetic variation – one of the driving forces of evolution. Instead, when sperm and eggs are produced, meiosis is used – producing daughter cells with half a set of chromosomes. During meiosis, crossing over occurs, giving some recombinants – or ‘mixed up’ chromosomes – leading to some varation. The greatest variation comes from the process of sexual reproduction itself – the gametes – sperm and egg – meet in fertilisation, combining their chromosomes to make a new blastocyst, which becomes an embryo, then a fetus and out pops a baby.
All the offspring of organisms that reproduce sexually carry two copies of each chromosome – one from each parent – and each chromosome carries different alleles – ‘versions’ of each gene. This leads to a great deal of variation and this genetic diversity keeps the the population going.
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What about uses in technology?
Funny you should ask that…
Induced parthenogenesis is being pursued as a method for obtaining embryonic stem cells. Read this New Scientist article to learn more.
The disgraced Korean scientist Hwang Woo-Suk, who shot to infamy after faking stem cell results, was actually and inadvertently pivotal in the use of parthenogenesis as a method to produce human embryonic stem cell lines:
Normally these parthenogenic embryos die after a few days, yet researchers are able to harvest them for stem cells for research. Ethically, these are considered engineered eggs, rather than human embryos. How do you feel about that?
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Questions to think about:
1. How does parthenogenesis differ from binary fission in bacteria, or vegetative reproduction in some plants?
2. How do the XY and ZW gender systems work?
3. How does sexual reproduction lead to genetic variation?
4. What are the costs of parthenogenesis in terms of evolution or resistance to disease?
5. How would the genetic fingerprint of a parthenogen differ from its parent?
6. How would researchers use genetic fingerprinting to determine whether the offspring were parthenogens or were the product of sexual reproduction?
7. What are the ethical considerations of using parthenogenic human ambryonic stem cells?
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References:
Chapman et al. Parthenogenesis in a large-bodied requiem shark, the blacktip <i>Carcharhinus limbatus</i>. Journal of Fish Biology, 2008; 73 (6): 1473 DOI: 10.1111/j.1095-8649.2008.02018.x
Chapman et al. Virgin birth in a hammerhead sharkBiol Lett. 2007 August 22; 3(4): 425–427. Published online 2007 May 22. doi: 10.1098/rsbl.2007.0189.
2000 year-old Greek “computer” recreated
A British curator has recreated an ancient proto-computer, the Antikythera device, based on 2000 year-old salvaged parts, X-ray tomography and huge patience – and got it to work!
As you can see in the NewScientist video, it was an example of a mechanical computer – designed to pr
edict the relative positions of the planets, chart astrology and count down to the Olympics.It shows us just how advanced Greek science was, and makes us wonder – what would have happened if this technology had not been lost? Would the Greeks have been playing Spore in 200AD?
Some questions to think about:
– What makes this a computer?
– What sets it apart from an old alarm clock?
– Where do you think we would be now if this knowledge hadn’t been lost?
Total Eclipse of the Sun – 1st August 2008
Viewers in Chine were treated to a cracking eclipse of the Sun last Friday and NewScientist were on hand to film it:
There is a great explanation and animation of how solar eclipses happen on the BBC website.
Exploratorium have a full-length clip on their webcast page, as well as a nice animation of how eclipses occur. (I’ll give Exploratorium its own post very soon).
Javanese White Rhino Filmed!
Yay!
Ujung Kulon national park – a reserve on the western tip of Java, home to a lot of protected wildlife and just a few hours from Bandung – has some young white rhinos! Thought to be on the verge of extinction, they are a sign of hope for the future.
My favourite part was the camera-smackdown at the end.
And whiie we’re on the subject of hope in the Indonesian environment, here’s news of a great success in re-introducing native species to cleared land, up in Borneo.
It makes me feel all warm and fuzzy.
Just to balance it with a bit of doom and gloom:
This recent story tells of the clearance of tropical forests to make way for palm oil. Boo!
And this one investigates the effects of Indonesia’s paper industry.
How can we make positive changes in our lives to create real, measurable improvements in the local and global environment?
Gene Therapy ‘Reverses Hereditary Blindness’
Awesome. And just in time for the Grade 11 Genetics unit!
Here’s the NewScientist article. And here’s an old one about gene therapy treating deafness.
Here is an article from the Guardian’s Science section that sums it up nicely.
Learn.Genetics @ Utah has loads of gene therapy interactives to learn more.
And for the hard-of-researching, here is the gene therapy wikipedia page.
Exciting times we live in.
Obama vs Clinton – Who will be better for Science? (via NewScientist)
This is from the NewScientist channel and is an interesting conversation starter. Last week at the American Association for the Advancement of Science (AAAS) meeting in Boston, representatives from Clinton and Obama’s teams were on hand to outline their positions on Science and Technology.
What kind of impact on voting do scientific policies really have in the US elections?
Is Science one of those promises that is all too easy to forget about once the candidate is in place?
What could the UK do to boost its Science departments and improve the quality of graduates (and retain a skilled scientific workforce)?
The idea of Science Debate 2008 is an interesting one – but will they be bothered to turn up?
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Here are the candidates’ Sci-Tech policies:
Obama: energy and environment, technology, higher education, healthcare.
Clinton: energy and environment, innovation, education, healthcare.
McCain: energy and environment, education, healthcare. *
* it’s interesting to see that McCain has no section on his site relating to science and technology, nor did he send anyone to the AAAS meeting.
It all reminds me a bit of the South Park episodes where the military and FBI were deriding the professors by sneering “Mister Scientist” at them at every given opportunity.
There’s a funny South Park style Mac vs PC ad after the jump:
The New Scientists playing with food
Two experiments from the New Scientist book ‘How to Fossilise Your Hamster‘.
In the first, we find out how to extract iron from breakfast cereal (perhaps we could use it to make a hammer to deal with the presenter):
In the second, we see how to extract casein (as an example of a polymer) from milk, using just vinegar and a stove. They keep saying ‘plastic’ here, but I’m pretty sure it’s not a plastic. Plastics are polymers, but casein is a protein (though still a polymer). Correct me if I’m wrong. Either way, it might be a good trick to introduce the proteins topics in DP Bio.
i-Biology 
