Cancerevo: Evolution and cancer
Studying cancer as an evolutionary disease. News and reviews about research on cancer and evolution from a theoretician's perspective.
Is there anything models can't do?
Date:
Monday, 06 Apr il 2009 - 00:15 UTC
I have to admit that I was thinking about posting something about coffee (it is still early in the morning here) and an article in The Economist mentions how coffee is being used to power cars. Apparently the same energy that can power people can power cars too, no idea whether that would be a sign that cars are becoming more human-like. Still, reassuringly for me, what the cars would use is not directly double espressos but the leftover grounds which would mean I could potentially feed my espresso cravings and fuel my car right with the same effort and cost.
Still, the topic of the day (or week to be a bit more realistic) is, as it was the previous time, something I read in Jerry Coyne’s book Why Evolution is true. The book describes the use of mathematical biology by Dan-Eric Nilsson and Susanne Pelger in a paper entitled A pessimistic estimate of the time required for an eye to evolve. In their model, a patch of cells capable (at least initially) of sensing light is allowed to evolve in a way in which only those mutations that increase the survival advantage were allowed to spread. Their conclusion is that, even in the worst case scenario, vision would nature evolve in only a few hundreds of thousands of years. As most evolutionary processes (unlike cancer) take lengths of time that are difficult for the human mind to fully grasp, a mathematical model can be a very useful tool to explain the evolutionary origin of one of the most sophisticated and, deceptively, engineered-like biological features.
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Last updated: Monday, 06 Apr 2009 - 00:15 UTC
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क्लीनिकल trial

In response to my last post, I wondered what Chris Scott's analysis of clinicaltrials.gov would say if he looked for fetal stem cells. He just told me he did the relevant search, and came up with nothing. In fact, one trial by StemCells that does use fetally derived cells does not say so in its clinical trial description. (See his post and several interesting comments at the link above.) Christopher Scott directs the program on stem cells and society at Stanford.
Scott has told me before that he is concerned that, because of enthusiasm for stem-cell research, clinicians may be including the term “stem cell” in clinical trials even if what’s being transplanted are poorly purified and characterized mixtures likely to contain stem cells. When I asked him about his recent analysis, he said he couldn't prove whether or not stem cells had been carefully purified or characterized. "It's just that the words "stem cell therapy" sounds sexier than "cell therapy" which is more accurate because most studies transplant populations of cells "enriched" for stem cells."
I suppose similar PR reasoning can explain the dearth of "fetal stem cells" in the database. A more charitable explanation would be that, of course, fetal stem cells is as poor a descriptor as is adult stem cells, since fetuses have already formed all their major organs. All the trials I know of using fetal cells use fetal neural cells. (But see my last post for more on that.)

स्टेम cells

Now we have the technology that can make a cloned child” reads the headline of the most-read article in the Independent right now. But the article does not actually break any news, nor does it use the common method of cloning; rather it discusses a well-understood implication of that recent reprogramming breakthroughs might yield yet another weird way of making a baby.If a technician wanted to do this, here’s how it would work: First, cells would be gathered from an existing human, probably through a skin biopsy. Second, these cells would be reprogrammed to an embryonic like state. (Current techniques to do this require engineered viruses to insert copies of genes into the reprogrammed cells. This makes the cells’ behavior less predictable and more prone to form tumours, but many scientists believe that new reprogramming techniques will soon be available that don’t require genetic modification.) Next, the reprogrammed cells would be merged with an early stage embryo, created by sperm fusing with egg in a laboratory dish. The “chimeric” embryo would be cultured for a few days and then implanted into a woman. If a baby was born, he or she would contain cells from two genetic individuals: the embryo and the human who supplied the cells. The baby would have three parents: two who gave the gametes for the embryo, one who gave the cells from a biopsy. (Such an individual would not be a clone. However, it is feasible that the chimeric embryo could be manipulated such that the original embryo only forms placenta and the reprogrammed cells form the body. This has been accomplished with mixtures mouse embryonic stem cells and mouse embryos, but not with mixtures of reprogrammed mouse cells and mouse embryos. )The results of some quick internet research suggests that using human iPS cells this way would not be allowed: In the UK, creating or using embryos outside the body requires a special license from the government, so I’d guess that permission would need to happen proactively. The US lacks legislation on reproductive cloning, though some individual states ban it. Australia distinguishes between research embryos (created through technical manipulation or by mixing genes from three or more people) and reproductive embryos (created through fusion of sperm and egg) and allows only reproductive embryos to used to create an embryo. A document dated to 2004 from Japan banned, among other things, the creation of chimeric human-human embryos for research.
Continue reading "Cloning by reprogramming?"