Posted on 09/08/2003 4:58:18 PM PDT by bondserv
How the Eye Lens Stays Clear 08/28/2003
To act as a true lens that can focus light, the lens of the eye must remain transparent for a lifetime. Yet the eye lens is not a piece of glass, but a growing, living tissue made up of cells. How can such a tissue stay clear, when the cells must be nourished, and when they contain organelles and chromosomes that would tend to obscure light?
Actually, that is exactly the problem with cataracts, one of the leading causes of blindness, in which the lens becomes clouded. Scientists at Bassnet Labs at Washington University (St. Louis, Missouri) have been studying how the eye maintains transparency, and found an enzyme that, when it fails, leads to cataracts in mice. The job of this enzyme is to chop up and dispose of DNA in lens cells. In a normal eye, “Light can pass through the lens because the cells break down their internal structures during development,” reports Science Now. Nagata et al. at the lab found large amounts of an enzyme named DLAD in mouse lens cells that chops up DNA for disposal. Mice lacking this enzyme developed cataracts. Failures in this enzyme, or the gene that codes for it, are also probably implicated in cataract development in humans.
Their work, published in Nature Aug. 28, explains how lens cells develop: “The eye lens is composed of fibre cells, which develop from the epithelial cells on the anterior surface of the lens. Differentiation into a lens fibre cell is accompanied by changes in cell shape, the expression of crystallins and the degradation of cellular organelles.” Until now it was not known how the cell dismantled its organelles and DNA. The fibre cells have their nuclei removed during maturation, but the DNA remains. It is the job of DLAD to act like a chipper and degrade the long DNA molecules into fragments that can be expelled. Even if the other aspects of fibre-cell cleanup succeed, this study shows that DNA stragglers are enough to cause cataracts.
So normal eye operation depends on the successful cleanup and removal of construction equipment and blueprints: organelles and DNA. Science Now tells a little more about these remarkable lens cells: “Even so, these cells aren’t simply empty; they house a highly organized network of proteins called crystallins* that transmit and focus the light passing through. Any disruption in this sophisticated scaffolding can cloud the lens, causing cataracts.” (Emphasis added.)
Here is an electron micrograph from Birkbeck College, UK showing how the fibre cells in the lens are stacked in neat rows like lumber with hexagonal edges for close packing.
What an amazing thing a living, transparent lens is. Did you ever think about this process, that a sophisticated molecular machine had to be produced from the DNA library that could chop up DNA into fragments, so that they could be removed and not obstruct the light path? Undoubtedly this is not the only enzyme involved in the cleanup job. Each fibre cell needs organelles and DNA during development, but they must be cleared away at the right time, and in the right order before the lens is deployed into operation, or else the user is denied the wonder of sight. This is just one tiny aspect of dozens of complex systems that all must work for vision to work.
Think of an eagle, detecting from high in the air a fish below the water, and using its visual sensors to accurately gauge its approach velocity, pitch, yaw and roll in order for it to capture food for the young in the nest, whose eyes are just opening to the world. Muscles, nerves, specialized tissues, detectors, software, image processing, cleanup, maintenance, lubrication and systems integration are just a few subsystems that must be accurately designed and coordinated in this, just one of many such complex sensory organs in the body.
Evolution is a fake fur that gives warm fuzzies to people who think in glittering generalities. Those who put on lab coats and examine the details and try to fit them into an evolutionary history get cold shudders.*A National Library of Medicine paper describes one of these crystallin proteins: “alpha-Crystallin is a major lens protein, comprising up to 40% of total lens proteins, where its structural function is to assist in maintaining the proper refractive index in the lens. In addition to its structural role, it has been shown to function in a chaperone-like manner. The chaperone-like function of alpha-crystallin will help prevent the formation of large light-scattering aggregates and possibly cataract. ... Reconstructed images of alpha B-crystallin obtained with cryo-electron microscopy support the concept that alpha B-crystallin is an extremely dynamic molecule and demonstrated that it has a hollow interior. Interestingly, we present evidence that native alpha-crystallin is significantly more thermally stable than either alpha A- or alpha B-crystallin alone. In fact, our experiments suggest that a 3:1 ratio of alpha A to alpha B subunit composition in an alpha-crystallin molecule is optimal in terms of thermal stability. This fascinating result explains the stoichiometric ratios of alpha A- and alpha B-crystallin subunits in the mammalian lens.” (Emphasis added.)
The old man of the mountain is of the same class as the man in the moon. It is a mental construct not a physical object. Different cultures see the rabbit in the moon too. The imagination comes in accepting that random mutations in nucleic acids result in formation of eyes and not in their destruction.
False. Humans have resistance to numerous agents which they have never even encountered. This is achieved by a somewhat miraculous antibody system. We can also learn resistance from vaccines. There are numerous ways to resist intrusions and that does not mean evolution happens at all. In fact, antibiotic resistant organisms are still the same organisms. They have not become in any way more complex than the original. What evolution needs to be true is to show the development of new complex functions. It has never been able to show evidence of that and never will because complex functions require many, many changes, not single mutations to make them happen.
For those who don't have a religious horror of imagination, yes. That, and you forgot to mention the selection pressures.
Out for the night. Way past usual beddy-bye.
Nonsense. Selection does not create anything, it kills. Mutations which are favorable are one in a million. Unlike what evolutionists claim, no species would be able to withstand such destruction. In addition, a single mutation does not provide a new function. Therefore it cannot be selected for. A single new gene of average size consists of some 500 base pairs of DNA. Not very likely. Thousands of such in millions of species is impossible - no matter how much time you have and no billions of years is not enough, even trillions of years would not be enough.
It is not a double-standard. That is why you cannot respond to my question and I can respond to yours. I can answer why scientifically why abiogenesis is impossible. You cannot answer why scientifically abiogenesis is possible.
That, and the fact that you stole your line from me is pretty funny ;)
Don't recall you ever saying that knowledge is the antidote to evolution.
If you pull the other leg, it plays a little tune...
gore3000, one hour ago: "Giving a long list of true facts does not prove evolution."
gore3000, one week ago: "And yes, the scientific facts above, by themselves are a prima facie case."
Planets do not create perfect spheres. Planets do not create anything. Neither do rocks. Planets and matter are just the playthings of universal forces, they do not create anything.
The facts pretty much speak for themselves. As to the conclusion, you must wait for the following installments.
To be continued ...
Slavoj Hontela, a Czech physician, writes (Target Paper 55 at Karl Jaspers Forum -- http://www.douglashospital.qc.ca/fdg/kjf/), "How far this consciousness might be or should be considered as a 'mental state' or a simple nerve-reflect structure is not easy to decide.... Even in an Amoeba there are definitely signs of a memory presence. In regard that the memory is shown at the DNA molecule, in the process of 'repairing' it might be presumed [that] the memory proceeds the state of consciousness."
He then describes an experiment conducted on an Amoeba [emphasis added]:
"We can see there an Amoeba, of Proteus species, slowly moving by stretching out its pseudopodia, looking probably for food. We place now with a glass pipette close to her [a] few powdered pigments of a dried Chinese Ink. The amoeba stretches one of her pseudopodia to a pigment grain closest to her (evidence of a chemotaxic reaction or ability!) and involves the grain into her pushing it down to the nucleus where the digestive vacuoles are present. It is certainly interesting that the pigment transported through the pseudopodia towards the nucleus, doesn't yet touch the nucleus capsule when obviously the Amoeba recognized the undigestibility of the Chinese Ink pigment, the further transportation in the direction to the nucleus stops and the foreign body is quickly pushed back and finally eliminated from the Amoeba's body.
"From this observation it is possible to make already several conclusions:
"2) A. was able to mobilize her pseudopodia giving them the appropriate message to approach this pigment and engulf it.
"3) With a certain delay which was obviously necessary to process the information related to the characteristic of the foreign body and the realization that it is indigestible follows another set of messages and the pigment was eliminated.
"The second phase of the observation experiment was even more interesting because it brought to the evidence the proof of the presence of memory. We have removed the pigment from the underlying microscopic glass dip, we put there a new drop of clear water and again placed there another pigment grain of Chinese Ink. The Amoeba stretched the pseudopodium to the closest pigment but did not touch it and, in contrary pulled back from the pigment grain. Obviously it preserved the memory for the identification of the indigestible pigment!
"It would be an exaggeration to speak about the mind or thinking but the period of might be 30 seconds which were passed by between the pigment taking and eliminating it; evokes the impression that the Amoeba needed a certain time to process the obtained information, i.e., it was 'thinking.'"
Clearly, this is not a description of a state of full "awareness." But there is a very strong indication that some type of information processing was going on....
One note johny. Harping on the same nonsense. Show me wrong, show what parts in my first and second articles are not essential to life. You cannot. That is why you just keep talking garbage. What I addressed in my statement was a long list of verbiage that proved nothing. Evolution has to prove that complex systems can arise in a gradual manner. No one has been able to do that therefore evolution is not science.
What a coincidence - I was addressing exactly the same thing a week ago. We should compare notes ;)
If, Then programing. Amazing.
Some of the ideas and links on betty boops thread stretch the mind to the snapping point. Good stuff.
That is true, but has no bearing on my point. Hence, your "False" assertion is itself false.
This is achieved by a somewhat miraculous antibody system.
"Somewhat" miraculous?! Either it's miraculous, or its not. Each fetus generates some millions of antibodies, and those that recognize local cells presumably amount to autoimmune problems. These antibodies are destroyed. Some time after birth, the remaining antibodies are given authority to command immune response - presumably, if they didn't get set off during gestation but are set off now, it's because of an external threat.
We can also learn resistance from vaccines. There are numerous ways to resist intrusions and that does not mean evolution happens at all.
Well, if you want to say that growing a billion cells that are immune to each of a dozen poisons, even though the starting population is killed by all of them, isn't evolution, then you and I mean different things by the word and probably can't talk about it.
In fact, antibiotic resistant organisms are still the same organisms.
No, they are different individuals. The people who survived the Black Death are different people from those who perished during it.
They have not become in any way more complex than the original.
In some cases, you are wrong and they have: one type of resistance emerges from molecular pumps that pump out the antibiotic. Inasmuch as the regular organisms lack these pumps, the resistant strain is indeed more complicated.
What evolution needs to be true is to show the development of new complex functions. It has never been able to show evidence of that and never will because complex functions require many, many changes, not single mutations to make them happen.
1. "Never will" is a pretty strong statement. 2. Mutations don't only happen one at a time.
I raised this example because there is much more intelligence at work even now in this creation than a materialist worldview can explain without appealing to eyebrow-raising scenarios. IMHO, eyeness is another example.
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