This could potentially be relevant to sorting out issues of whether or not new human species are actually species? Some, I hear, have contested the status of the humanoid found in Flores... Could there be any stable isotope tools to probe this question?
Hi Mike,
This is is a good question and the answer is yes? The only way to do is to identified t a particlar organic compound of interest, and compare the CSIA.
well sure, Trisomy 21 (Down syndrome) is a chromosomal abnormality.
Comparing for example, stable isotopes between cancer patients cells and cells holy confirms a significant difference and discrimination can be explained by well indistinct metabolic pathways.
I am not so sure. Which kind of compounds not influenced by other parameters (diet, etc.) we could analyzed?.
I think this is issue is not so easy.
Unless one can identify a particular metabolic / enzymatic / biochemical step or turn-over rate that is significantly reduced or increased due to trisomy 21 I would rate the chances as pretty slim to correlate let alone link Down-Syndrome to a change in stable isotopic composition of a particular compound (or tissue). The main reason why cancer can result in changes of stable isotope composition of key metabolites is their increased rate of growth and thus increased rate of metabolism. If the rate constant k of a particular biochemical reaction changes so does the corresponding isotopic fractionation factor alpha. Like k, alpha is reaction specific. If reaction conditions change, so will k and alpha.
For stable C isotopes, if we take into account the wide range of delta13C values (see attached figure) exhibited by the different natural compounds (eg. C3 and C4 plant groups) and the possible dietary differences between specimens of the same animal species, as well as the fact that "the stable carbon isotope composition of animal tissues represents the weighted sum of the variety of food sources eaten (Codron et al. 2011. Can J Zool 89(6), 453-465)", it seems that it would be quite difficult to see statistically significant isotopic differences in tissues of those affected by down-syndrome (or even between tissues from two separate animal species) without a total control of the ingested food in order to eliminate the isotopic variability introduced with the diet. Or maybe your question about "physiological differences that could lead to stable isotope differences in tissues of those affected by down-syndrome?" is related to the possibility of any internal difference between different tissues within a single individual?
http://www.science.uottawa.ca/eih/ch5/Image137.gif
Yes, you would need a baseline. Either from other tissues or from other animals. For which you would have to infer similar behaviours/food sources. The question is too complicated to addres without having a few more specimens at the very least. I think it would be most useful to perhaps establish any differences in tissues within an individual first. ZINC isotopes for example have a tell tale sign for Alzheimer's if you look at bone vs soft tissue. Something f. Moynier talked about at AGU. So maybe the best approach would be similar.
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