Slashdot Mirror
Prions Evolve Despite Having No DNA
An anonymous reader writes "Scientists from the Scripps Research Institute have shown for the first time that 'lifeless' organic substances with no genetic material — prions similar to those believed responsible for Mad Cow disease and similar, rare conditions in humans — are capable of evolving just like higher forms of life. The discovery could reshape the definition of life and have revolutionary impacts on how certain diseases are treated."
Here are the criteria for brain death. An in the case of children, they must be consistent with repeatedly flat EEGs throughout 48 or 72 hours depending on the place. Also, barbiturate and BZD intoxication must be ruled out.
* Unresponsiveness
o The patient is completely unresponsive to external visual, auditory, and tactile stimuli and is incapable of communication in any manner.
* Absence of cerebral and brain stem function
o Pupillary responses are absent, and eye movements cannot be elicited by the vestibulo-ocular reflex or by irrigating the ears with cold water.
o The corneal and gag reflex are absent, and there is no facial or tongue movement.
o The limbs are flaccid, and there is no movement, although primitive withdrawal movements in response to local painful stimuli, mediated at a spinal cord level, can occur.
o Apnea Test: An apnea test should be performed to ascertain that no respirations occur at a PCO2 level of at least 60 mmHg. The patient oxygenation should be maintained with giving 100% oxygen by a cannula inserted into endotracheal tube as the PCO2 rises. The inability to develop respiration is consistent with medullary failure.
* Nature of coma must be know
o Known structural disease or irreversible systemic metabolic cause that can explain the clinical picture.
* Some causes must be ruled out
o Body temperature must be above 32 C to rule out hypothermia
o No chance of drug intoxication or neuromuscular blockade
o Patient is not in shock
* Persistence of brain dysfunction
o Six hours with a confirmatory isoelectric EEG or electrocerebral silence, performed according to the technical standards of the American Electroencephalographic Society
o Twelve hours without a confirmatory EEG
o Twenty-four hours for anoxic brain injury without a confirmatory isoeletric EEG
* Confirmatory tests (are not necessary to diagnose brain death)
o EEG with no physiologic brain activity
o No cerebral circulation present on angiographic examination( is the principal legal sign in many European countries)
o Brain stem-evoked responses with absent function in vital brain stem structures
Any matter has one mission and one mission only: to find greater order. If matter without DNA or any prior form of order couldn't achieve more order, then life would not exist. Things want to be able to interact with their environment more efficiently, and must evolve to do so.
All things in the Universe try to minimise the amount of energy they have. In some special cases, like crystals for example, this means becoming more ordered: the energy of each atom/molecule depends on its distance from its neighbours, with each "preferring" the lowest energy distance. Getting as many neighbours as possible at this distance is effectively packing spheres with that distance as their radius, which turns out to be the most efficient with ordered arrangements like hexagonal close packing, so that's what's observed. In the general case, however, the amount of order goes down, see http://en.wikipedia.org/wiki/Entropy . In fact, in every situation which becomes more ordered over time, Thermodynamics says that somewhere else there must be a system becoming even more disordered (as an example, if a system is minimising its energy by becoming ordered then it's exothermic: the energy its losing will come out as heat. This heat is itself disordered, and can disrupt the order of whatever it comes into contact with (which is why so many Physics experiments are done as close to zero Kelvin as possible). Also, the total energy such systems manage to lose is restricted by the fact that they are becoming more ordered, there is an "entropic cost" when becoming more ordered, which means that it requires energy to do and therefore the system must keep hold of that much energy to do it.
For a simple example of how becoming more ordered takes energy, try stretching an elastic band. The polymers it's made of would, in a totally disordered system, take "random walks", which is very degenerate (there are LOADS of ways to randomly walk a certain distance starting at a point A and ending at a point B is the distance AB is much shorter than the distance you walk, ideally A and B are in the same place). That's the band's preferred state, and as such it isn't particularly long. By stretching it, the distance AB goes up, so there are fewer random walks of the same length which satisfy these new positions. In the extreme case the distance AB will be the same length as the walk, and there would only be one valid random walk between them (ie. going in a straight line). It takes energy to stretch the band because you're making it more ordered, which it doesn't want to be.
If matter's mission is to find greater order then a stretched elastic band would never snap back ;)