Monday, 15 July 2013

Chimerism

Another Greek title.  Anyway, let's get this out of the way:

Click to tweet: http://clicktotweet.com/bhTQ9 . I've postponed today's planned video, which was going to be on cells, because we're boycotting Facebook today. I'll say something about that below.

No infringement of intellectual property is intended in this post and all trademarks remain the property of their respective owners.

In the meantime, the reason i'm boycotting FB is their continued banning of breastfeeding pics. This would be less hypocritical were it not for the fact that plenty of erotic pictures of breasts appear on Facebook without being challenged. Clearly breasts have more than one function, considered biologically, since it's true that they are very likely to be perceived as secondary sexual characteristics and therefore fetishised sexually, but it still makes sense to see their primary biological function as the production of milk for children. As such, this should be encouraged because of its immune system, bonding and nutritional functions, and the idea of breasts as sexual needs to be reduced. In fact, i strongly suspect that breasts are fetishised precisely because of the deprecation of breastfeeding.

The problem with boycotting, of course, is that it looks like a pointless gesture, and also hypocritical because of course, as of tomorrow i'll be going back to Facebook. This suggests that i care enough to boycott it for one day but not enough to achieve a difference by boycotting it until the problem is resolved. The answer to this is that i'm boycotting Facebook in order to express my opposition, not because i expect them to change, and that expression is an emotional thing and nothing to do with achieving a concrete result. I am under no illusions that they will ever listen or respond, and i'm making a big enough effort elsewhere by trying to get myself to lactate, which in the long run would make a bigger difference than Facebook changing that policy and in any case ultimately lead to that changing anyway.

Anyway, cells tomorrow!


So no, i haven't made the cells video yet because i realised there was no point until i got back onto FB, so instead here's a video about why i'm not on Facebook today.  In fact there might have been some point because it's possible i could've generated some interest elsewhere but i wouldn't hold my breath and if i can manage that by posting it there as well, it's better to combine the two.


It occurred to me yesterday that there was in fact a way in which someone could have two physical sexes which could apply to me but almost certainly doesn't:  chimerism.  No, not one of these:

(Image will be removed on request and is from here), nor one of these, taken by Linda Snook:

but one of these:

I've alluded to this before.

In genetics, a chimera is an individual organism containing material from two or more separate cell lines.  The diagram above indicates that during pregnancy, cells from the foetus enter the mother's body and vice versa.  Many people are in fact chimeras for various reasons.  Firstly, the mother's cells may enter the foetus, a situation which potentially applies to everyone alive today, so anyone can be, and possibly even is, a chimera (why am i writing this?  Ah, who cares, i am!).  Secondly, as illustrated above, the foetal cells can colonise the mother's body, which is potentially a good thing but may provoke autoimmune disease because they're foreign cells.  Thirdly, a missing twin situation may develop as a result of one embryo being absorbed by another.  Finally, and this is what i currently suspect although it's quite convoluted, there's a more complicated scenario where foetal cells enter the mother, the mother becomes pregnant again and a few of those foetal cells end up in the next foetus.  I think this might particularly be the case with something like a miscarriage or careless abortion because from the perspective of the genome of a miscarried embryo, recolonising a foetus maximises the probability of replication.  All this is of course way down the road from my initial thoughts.

So, it occurs to me that it is in fact possible for someone to be a chimera of both female and male tissues.  This happens sometimes, for instance there's a case of a child with a testicle on one side and a fallopian tube and ovary on the other side.  There are also people with eyes like this:

(guess who this is incidentally).  This woman is a chimera (snigger!  No, no, she's fine, she's just histologically interesting).  There is a hypothesis that some gender dysphoric people might be chimeras, and in fact this is a way in which there could be a biological basis for the situation although it depends rather heavily on evolutionary psychology in my opinion.

One of the interesting things about this is that it can be corroborated, theoretically, maybe even by myself.  If it was completely pervasive, or the right bits were affected, it would show up in a blood sample.  Female human cells have only one active X chromosome.  The other(s) become(s) a "Barr body", which is a small, shrivelled version of the X chromosome near the centromere.  These can be seen under a sufficiently powerful light microscope.  If a blood sample were taken, mixed with citric acid to prevent coagulation (which depends on calcium ions which would form calcium citrate in such a situation), centrifuged to separate the white cells and the white cells were then examined, a male chimera with female cells might be detectable, depending on the type of chimerism.  In other words, he would have partly female blood.  However, only corroboration is possible because if the bone marrow wasn't affected he would just have male blood, and the significant thing, supposedly, is the brain.  However, a male with a female brain would rarely or never get headaches because his brain would be smaller, and i'm thinking (presumably incorrectly because it doesn't work that way hormonally) that he would also have a patchy beard.

However, i do realise that i'm just looking for clues here and probably seeing patterns which aren't there.  Also, this is very biologically deterministic.

Tomorrow, cells (in a different way).