Harmonies from noise

Discussion on technology and how it could be used to assist spiritual development and NOT enslave us. This includes technology that will help us live in harmony with Nature (e.g.: "Lifter" technologies that could replace the petrol driven engine). Also, discussion of past and current scientific thought so that gems are not buried in the sands of time, and spiritual progress through science is achieved.

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Harmonies from noise

Post: # 9656Post bomohwkl »

Harmonies from noise
Michael Springer and Johan Paulsson
Do random environments make for random responses to them?
Mathematical models suggest that this is not always the case — adding
noise could create synchronous oscillations in cell–cell signalling systems.

Noise in communication devices is a familiar nuisance. In most Hollywood war films, radio
static seems to botch up any attempt at coordinated action, to the frustration of the troops in the trenches. Cells face much the same problem: their signalling is garbled by chemical noise — random fluctuations in the concentrations of different molecular constituents — both inside and outside the cell. This noise could in turn compromise the cell’s ability to grow and reproduce — or so one might think. But two things here are worth considering more carefully. First, chemical fluctuations are
always to some degree correlated, so different
noise-afflicted cells may see the same random
ups and downs. Second, in nonlinear systems
(such as those underlying cell development,
the cell cycle and circadian oscillators) the
effects of the ups and downs do not cancel out;
this in turn can qualitatively change the
dynamics of the system. Writing in Physical
Review Letters, Zhou et al.1 propose a model
for how the combination of these two effects
can create regular and synchronized oscillations
in an otherwise non-oscillatory cell
system. This is an example of how noise in a
biological process can have counterintuitive
effects, even suppressing other noise or
generating new, coherent behaviours.
The investigations of Zhou et al. were
inspired by a communication system between
bacterial cells known as quorum sensing. Many
bacteria produce a small ‘autoinducer’ molecule
that, diffusing in and out of cells, promotes
its own synthesis wherever it goes. This
provides a population-wide positive-feedback
loop that allows individual cells to count their
neighbours and take synchronous action: when
the population reaches a high enough concentration,
the cells collectively switch from a lowproduction
state, with minimal autoinduction,
to a fully induced, high-production state.
The effect of changes in the design of
quorum-sensing networks has been explored
in several models. One proposal is to add
a negative-feedback loop through an ‘autoinhibitor’
molecule that, again diffusing in and
out of cells, inhibits its synthesis wherever it
goes. This additional loop creates a network
similar to a circadian oscillator, in which
concentrations go up and down in stable
temporal waves; communication between cells
by means of a diffusive autoinducer molecule
could then allow these oscillations to be
synchronized2. Zhou et al.1 analyse a simpler
negative-feedback model, changing the natural
autoinducer into an autoinhibitor that acts
with some time delay. The system did not
oscillate; instead, the level of autoinhibitor
remained at a single steady state. But when
enough random noise was added, stable and
synchronized oscillations appeared.
How can this happen? Picture a mobile
hanging from a baby’s stroller. Although each
pendulum of the mobile can swing back and
forth periodically, none will actually move
until a force is applied. The system is, however,
poised to oscillate, and even a few petulant hits
or a gust of wind can act as a trigger. If all the
pendulums are affected at the same time and
in the same way (in our analogy, if there is correlated
extracellular noise), they can oscillate
together. If the pendulums are connected by a
string (if the cells can communicate), this is
even easier to achieve: any pendulum that is
out of synchrony is then literally pulled into
phase by the others.
The analogy is not perfect: the combination
of negative feedback and time delays can,
under certain conditions, cause oscillations
even without any external forces. And noise
affects these conditions: even uncorrelated
fluctuations can change the average concentration
at which cell decisions are made, turn
discrete all-or-nothing switches into smooth,
continuous responses, or even sharpen continuous
responses into discrete switches3.
Uncorrelated noise could thus, in principle,
sufficiently change the characteristics of a
non-oscillating feedback system to produce
stable oscillations3,4.
This goes against our expectation that noise
blunts a signal. In fact, the combination of
noise and nonlinear kinetics is capable of
almost anything, even in the simplest systems.
To take an example from biochemistry, the rate
at which two identical protein monomers
dimerize to form an active enzyme depends on
the square of the monomer concentration.
Cells with higher than average monomer levels
thus contribute disproportionately to the average
rate of dimerization in the population. If
each cell had exactly one monomer, no enzyme
would be produced. But if fluctuations were
such that half of the cells had two monomers
and the other half none, some enzyme would
be made even though the average amount of
monomer is the same5. Because protein fluctuations
in turn respond very differently to the
rates at which the genes encoding them are
transcribed and translated6, changing both
rates simultaneously can have unexpected
effects on the average rate of enzyme production,
potentially even making it proportional to
the cube, rather than the square, of the average
monomer concentration.
Correlated fluctuations between different
components in the same cell can be even more
useful. Studies using two identically regulated
alleles (gene variants) that encode fluorescent
‘reporter’ proteins show that some protein
noise is correlated and shared between alleles,
but that other sources of protein noise are
uncorrelated and experienced separately7.
From the viewpoint of each gene individually,
there is little difference between the two types
of noise; crucially,however, shared noise can be
used to coordinate action between them. To
continue the biochemical example, consider
this time two different types of monomer that
combine to form an active enzyme complex:
if the noise in the expression of the two
monomers were correlated, randomly pushing
up both concentrations at the same time, cells
could form enzyme complexes more efficiently.
Zhou and colleagues’ work1 is just one example
of the growing body of research that shows
how cells can use noise to suppress other noise,
or to create oscillations, multi-stabilities and
many other coherent kinetic traits. Coupled
with the recognition that even simple, noisefree
mechanisms can generate ‘deterministic
chaos’ — acting to amplify infinitesimal environmental
perturbations into large variations
in physiological characteristics8 — this line of
research subverts the simplest picture of noise.
That is that cells exploit noise when they need
heterogeneity, and suppress it when they need
deterministic, coherent behaviours.
This sea change in our perception raises an
important and almost entirely unaddressed
question. We know that cells can create virtually
any type of noise; we also know that they
can create almost any type of nonlinearity.
What we rarely know, however, is which of the
available strategies cells actually use. Is there a
grander scheme that explains the choice
between deterministic and noise-driven solutions?
The only way to address this question
experimentally is to characterize the singlecell
dynamics of a large number of systems,
and to see which strategies tend to be used to
solve which problems. Given some reasonable
physical constraints — mechanistic, energetic,
evolutionary or otherwise — it may even be
possible to partially answer the question from
first principles. ■
Michael Springer and Johan Paulsson are
in the Department of Systems Biology, Harvard
Medical School, Boston, Massachusetts 02108,
USA. Johan Paulsson is also in the Department of
Applied Mathematics and Theoretical Physics,
University of Cambridge, Cambridge CB3 0WA, UK.
e-mail: johan_paulsson@hms.harvard.edu
1. Zhou, T., Chen, L. & Aihara, K. Phys. Rev. Lett. 95, 178103
2. McMillen, D., Kopell, N., Hasty, J. & Collins, J. J. Proc. Natl
Acad. Sci. USA 99, 679–684 (2002).
3. Horsthemke, W. & Lefever, R. Noise-Induced Transitions:
Theory and Applications in Physics, Chemistry, and Biology
(Springer, Berlin, 1984).
4. Vilar, J. M., Kueh, H. Y., Barkai, N. & Leibler, S. Proc. Natl
Acad. Sci. USA 99, 5988–5992 (2002).
5. Raleigh, E. A. & Kleckner, N. Proc. Natl Acad. Sci. USA 83,
1787–1791 (1986).
6. Ozbudak, E. M., Thattai, M., Kurtser, I., Grossman, A. D. &
van Oudenaarden, A. Nature Genet. 31, 69–73 (2002).
7. Elowitz, M. B. et al. Science 297, 1183–1186 (2002).
8. Strogatz, S. H. Nonlinear Dynamics and Chaos: With
Applications to Physics, Biology, Chemistry, and Engineering
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Post: # 9728Post alexH »

hmm i think thats a little bit too long :wink:
If a blind man leads another, they will both fall into a pit. -Jesus Christ

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Post: # 9749Post Rezo »

robanan you wouldn't by chance be alluding to MRET or ERT concepts involved in protecting human cells from EM radiation from cell phones, etc. would you? I suppose it would be relevant.

Personally I rarely use my cell phone, and by rarely I mean virtually never. But, if I have to, I want to know the best way to protect me from EM since, theres the issue of 'secondhand' radiation not only from other users, but things like microwave towers, tv or radio stations. Is it via 'noise' [mret method] or diminution of the signal [said to also decrease your own cells em signals?]

I remember feeling very agitated after driving by a very powerful [high frequency, major channel] tv station. Was it psychosomatic? Or a natural response to cellular stress? I had no thoughts politically at all at the time, and felt otherwise fine previously, if I remember right. It did happen over a year ago to be fair.

Ive a newfound interest in this topic now, actually. I mean, I'm on this forum lots which means lots of computer use, and for other things too - studying, games, news..I may not use a cellphone much but I suuuure like to use my computer!
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Re: Harmonies from noise

Post: # 10296Post Robanan »

eh... huh? :?
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Re: Harmonies from noise

Post: # 10297Post Rezo »

maybe i got the idea of the article wrong, I had thought it was about noise in devices around [outside] our bodies, that cause negative cellular changes...

is the scope of this article instead just limited to what 'noise' occurs inside somebody? In that case, my mistake... :oops: but I do think large towers and high powered transmission lines can sometimes be uncomfortable to be around. Like a cordless phone above 900 Mhz for example, is always transmitting at the same signal strength no matter how far away you are from it when inside your home.
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