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Discernment

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Jenny
43541.  Fri Jan 06, 2006 11:29 am Reply with quote

I admit that the heading is a stretch to drag this into a D topic, but I couldn't resist this item from the Guardian:

http://lifeandhealth.guardian.co.uk/food/story/0,,1614469,00.html

A hundred years ago, scientists thought that nerve endings on the tongue could identify four primary tastes: sweet, sour, bitter and salty. Then Professor Kidunae Ikeda, a biochemist at Tokyo Imperial University, discovered, thanks to his wife's use of seaweed to flavour her tofu and vegetable soup, that there was another taste, which he called 'umami', the Japanese word for 'savoury' or 'deliciousness', depending on your choice of translation.

The substance he isolated in 1909 was a chemical called glutamic acid, an amino acid produced by the human body and present in many foodstuffs. When the protein containing glutamic acid is broken down - by cooking, fermentation or ripening - it becomes glutamate. When crystallised, it makes monosodium glutamate - soluble in water and easy to store. It was an instant success and made Ikeda rich. Today the world eats 1.5 million tons of MSG every year.

Glutamate is present in almost every food stuff, and so vital to our functioning that our own bodies produce 40 grams of it a day. In fact, human milk contains large amounts of glutamate (about 10 times the levels present in cow's milk). Babies have very basic taste buds: it's believed that mother's milk offers two taste enhancements - sugar (as lactose) and umami (as glutamate) to encourage the little buggers to feed. Who knew that mothers' milk and a packet of cheese'n'onion crisps had so much in common?

Other sources include parmesan cheese, ripe cheese, ripe tomatoes, cured meats, dried mushrooms, soy sauce, Bovril, Worcester sauce, nam pla, and particularly Marmite, which at 1750mg per 100g, contains more glutamate than any other manufactured product except pure crystallised MSG.

After one study in 1968 talked about 'Chinese restaurant syndrome', there were many health scares about MSG, but scientists seem to have now quietly dropped these ideas, and in fact it is now being touted by the manufacturers as a healthy alternative to salt. Popular opinion hasn't kept pace with scientific research though, and many people are convinced it will harm them - so food manufacturers avoid the issue by simply calling it something else, most cheekily 'natural flavours'.

 
mckeonj
43548.  Fri Jan 06, 2006 11:40 am Reply with quote

I have been calling MSG 'organic salt' for several years past as a reaction to my relatives' insistence that only 'organic' food should be purchased at premium prices, rather than 'bad' ordinary food. Useless to point out that there was no inorganic food, and anyway, my granny was right when she said, 'If it don't go bad, don't eat it.', and in her day, instant mashed potato and pot noodles hadn't been invented yet.

 
gerontius grumpus
43687.  Fri Jan 06, 2006 5:37 pm Reply with quote

Quite interestingly, the chemicals that organic gardeners describe as 'organic', meaning they can be used in organic growing, are generally inorganic chemicals and the real baddies, the truly harmful ones are organic chemicals.

Nomenclature doesn't travel well between contexts.

 
mckeonj
43751.  Sat Jan 07, 2006 5:18 am Reply with quote

gerontius grumpus wrote:
Quite interestingly, the chemicals that organic gardeners describe as 'organic', meaning they can be used in organic growing, are generally inorganic chemicals and the real baddies, the truly harmful ones are organic chemicals.

Nomenclature doesn't travel well between contexts.

The terms 'organic' and 'inorganic' were coined by chemists in C19 to distinguish between chemicals associated with life processes and those not, and created two distinct schools. Unfortunately, Nature does not recognise the distinction, with the following delightful result.
For many years, bio-chemists knew that nervous signals were conveyed by a carrier compound, but were unable to isolate and identify it. It was assumed to be some complex organic molecule. When it was finally identified, it turned out to be NO, nitrous oxide, (aka laughing gas, freezing gas, aerosol propellant), just about the simplest inorganic compound you can get.

 
Celebaelin
43773.  Sat Jan 07, 2006 7:11 am Reply with quote

mckeonj wrote:
For many years, bio-chemists knew that nervous signals were conveyed by a carrier compound, but were unable to isolate and identify it. It was assumed to be some complex organic molecule. When it was finally identified, it turned out to be NO, nitrous oxide, (aka laughing gas, freezing gas, aerosol propellant), just about the simplest inorganic compound you can get.


Whu? This is a new one on me. Within nerves the action potential is carried along by Na+/K+ exchange through channel proteins (which jumps from neurilemma to neurilemma) and at synapses by neurotransmitter compounds, in connection with which I have never heard NO being mentioned.

After looking around a bit I found

Quote:
b) Neuronal NO

NO is also generated in the neuron and the grial (sic) cell in central or peripheral nerve systems (44). NO made in the central nerve system has drawn the attention of many researchers because it may be closely related to neuronal plasticity(45). Such NO is released by neuronal NOS, another constitutive type that is soluble in cytosol(46,47). The NOS is also activated with an intracellular calcium increase through agonist-receptor interactions. In the hippocampus, induction of long term potenticution or depression(LTP or LTD) has been reported(45, 48-50). However, carbon monoxide may be the key mediator of the events(51,52), and the NO- generating system seems to have some interaction with CO generation(53). Thus, NO may play role. In the cerebellum, NO clearly is related to the formation of LTD (54,55). Cerebellum LTD can be induced by co-stimulation of the climbing fiber and the parallel fiber connected to the prukinje cell. If the bergman gria surrounding the neuron is intact, LT formation is regulated with NO. Shibuki et al.(56) hypothesized that the grial cell prohibited LT formation and NO unlocked the prohibition, while the direction of LT, so that LTP or LTD, was determined by the calcium concentration change in the prukinje cell. The participation of the grial cell must be considered to better understand the NO function in the nerve system.
NO also directly regulated the formation of ion channels or receptors. NO modulates the potassium channel(57-59) to regulate the neuronal transmission. Stamler et al. suggested that NO took back-regulation to the NMDA receptor through nitrosation in the redox regulatory site(10). Rao et al. indicated that intestinal ion transport got the tonic regulation by NO released from the non adrenergic noc cholinergic neuron (sic) (NANC neuron)(60). Okamoto et al. indicated that the response of the ionotropic glutamate receptor to AMPA is modulated by NO that is released with the stimulation of the metabotropic glutamate receptor in the cerebellum in chick embryo(61). However, the modulation of ion channels and receptors may be related not to the NO molecule but to the nitrosothiol structure.
In the peripheral nerve system, the mainfunction of NO is vasoregulation(62). The renal blood flow is suggested to be regulated indirectly with NO through the attenuation of sympathetic neuronal activity in addition to the direct action (63,64). Whether NO originates in the NANC neuron or in the central nervous system is unknown.


http://www.dojindo.com/newsletter/review.html#Bioactivity

I should say that this is a Japanese article and the words “grial” and “-gria” are presumably meant to be ‘glial’ and ‘-glia’. Similarly NANC neurons are nonadrenergic noncholinergic not non adrenergic noc cholinergic neuron ie

Quote:
An autonomic efferent neuron whose transmission is not blocked by blocking adrenergic and cholinergic transmission. Nitric oxide may be the transmitter in some cases.

http://www.biology-online.org/dictionary/nonadrenergic_noncholinergic_neuron

So, with appologies, my

Quote:
in connection with which I have never heard NO being mentioned.

should be tempered by the additional comment of

until now!

 
Jenny
43995.  Sat Jan 07, 2006 6:28 pm Reply with quote

I've just realised, of course, that I could have put this in the D series under 'deliciousness', which would be a far better heading as it's one of the translations of 'umami'.

So the question could be - what does mother's milk have in common with a packet of cheese'n'onion crisps?

 

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