February 25, 2009
February 17, 2009
People turn to poison quick as lager turns to piss
Sweethearts are physically sick every time they kiss
If deadly nightshade is your flower and manslaughter your meat
Spend a year in a couple of hours -- on Beasley Street.
In the cheap seats, where murder breeds someone runs out of breath
Sleep is something he don't need, a sneak preview of death
A sociologist's paradise: each day is a repeat
Uneasy, sleazy, greasy, queasy, beastly Beasley Street.
February 14, 2009
John Stuart Mill could text by the time he was two.
February 12, 2009
Today's logo from google.co.uk:
And from google.com:
I guess it doesn't play so well in Peoria.
[Update: Robin tells me it does after all. Or did. So, good for Peoria.]
The general tenor of tonight's special programme on unemployment was, to nobody's great surprise, profoundly depressing, but three cheers for telly psych Oliver James, who in his limp-wristed bleeding-heart fashion gave a sound and well-earned kicking to the glib neolib pols. Theresa May's gobsmacked lemon-sucking gawp was a sight to lift the most cynical viewer's heart.
[Fear not, dear foreign readers, you are not expected to understand this post.]
February 10, 2009
Science in Winter
It's not as if nothing's been happening -- au contraire -- I've just not got around to blogging it. My bad.
For example, I left unrecorded my little flare up after step last Tuesday; and indeed, that's probably for the best, since it was very much not my finest hour. In any case, it seems to be patched up now.
Among other consequences, I did not follow up that night with my first bouncing session in roughly two and a half years, as I had planned. Instead, that pleasure was deferred to tonight, and very nice it turned out to be. I am, of course, rather rusty -- and will doubtless be aching like crazy tomorrow -- but things did gradually start coming back to me, and it's nice to know I can still scrape together a somersault if required, albeit a rather untidy one.
Last week also brought the latest Ballets C de la B outing at Sadler's Wells, founder Alain Platel's characteristically wayward take on JSB's St Matthew Passion, pitié! This was pretty familiar territory for C de la B aficionados, the usual mix of chaos, shock tactics, athleticism, beautiful music, randomly-stripped taut bodies and suffering, but I still thoroughly enjoyed it. The singers were great, especially the countertenor Serge Kakudji, and if the whole thing dragged a bit in the middle it picked up again by the end.
It has also been, on and off, fucking freezing, which may be why I'm overusing the nice warm and sunny colour scheme around here. The heating system at college has been malfunctioning, so the last couple of days have involved quite a bit of shivering in the lab. We have discovered that at least some elements of our experimental setup dislike the cold almost as much as I do. The closed-loop feedback control on the SICM's piezo actuators, for example, seems to develop a nasty chatter that completely thwarts scanning. To be fair, that might not actually be down to the cold, but it is a suspicious coincidence.
Also, for the record, HEK cells don't like expressing NMDARs. You know, in case you were wondering. We were warned about this, in fact, but it still seemed like a good idea. And perhaps it is. But I do sometimes wish that some minor parts of this whole project would just bloody work. Just one, even. For the novelty value.
To cap it off, my little beambot power supply widget for chloriding electrodes stopped working. The issue turned out to be a trivial mechanical fault with an IC socket, but I couldn't find a way of replacing it without destroying the board it was attached to, so I'm having to rebuild that bit from scratch, which is kind of annoying. It'll be out of action for a few more days, I think.
Hopefully the same will not be so for me, although after the abuse my creaky old bones have taken this evening who can be sure?
February 3, 2009
The main excitatory neurotransmitter in the central nervous system is glutamate, an ionic form of one of the 20 primary amino acids. Glutamate is the major endogenous agonist for many different receptors, meaning that lots of cells are sensitive to it in different ways.
The ionotropic glutamate receptors -- that is, those that are ion channels as well as receptors, able to change membrane ion permeability directly rather than acting through secondary messaging pathways -- can be further divided into three main groups by their sensitivity to the more specific (but non-physiological) ligands α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), kainic acid or kainate (KA), and N-methyl-D-aspartate (NMDA). Functionally, the distinction between the NMDA-sensitive and non-NMDA-sensitive receptors is probably most important, and for this reason AMPA and kainate receptors are often grouped together rather indiscriminately.
Loosely speaking, NMDA receptors are slower than AMPA/KA receptors, and in at least some cases mediate longer-term effects. Although they are nominally non-selective cation channels, they exhibit a disproportionately high permeability to calcium ions. Extracellular calcium is always present at much lower concentrations than sodium, so the latter tends to dominate the current flow, but many intercellular processes -- notably those controlling neurotransmitter release and the distribution of receptors -- are extraordinarily sensitive to calcium, so the NMDA receptor permeability can have large functional consequences.
NMDA receptors are characteristically blocked by magnesium ions unless the membrane is relatively depolarised. Since magnesium is always present under physiological conditions, this means that NMDA receptors are very seldom effectively open unless an action potential is being fired. NMDA receptors are thus very important coincidence detectors, allowing ions to flow only when two different types of event occur simultaneously: ligand binding (typically as a result of release from the axon terminal of an upstream neuron) and action potential firing (in the receptor's own cell). For this reason, NMDA receptors are popular in models of associative learning: their dependence on two different inputs
Although mainly thought of as existing post-synaptically, transducing anterograde excitatory signals, there is also evidence of presynaptic NMDA receptor localisation in some neurons. It is the latter that we are interested in for this project.
1 Interestingly, some taste buds have glutamate receptors, giving rise to the so-called "fifth taste" umami. These receptors are what give the flavour enhancing food additive monosodium glutamate its power.
2 In fact, there are at least three necessary inputs, since NMDA receptors also require the binding of another amino acid ligand, glycine or serine. However, this is pretty much always present at saturating levels in the vicinity of central neurons, so it doesn't normally have an effect on response.
February 2, 2009
February 1, 2009