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 arent 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.)
You can't remember what Morton's Demon never lets in.
Indeed it does - it takes millions of tries each and every single year, during the time frame of billions of years. And with a selection process that is able to weed out ever so slightly less successful models.
Prov 11:14
Where no counsel is, the people fall: but in the multitude of counsellors there is safety.
What a help the word is! All glory goes to God!
Yeah, because just think about how lost God would be without "science".
We can imagine a lot of things, some clearly impossible, some plausible.
What is the "intelligence" in planets creating perfect spheres? It's the need of things to go downhill; when everything is as downhill as it can be, it's a sphere. What is the "intelligence" in turning moths dark brown when pollution goes up, and turning them white when it goes down? Nothing, unless birds eating only the bugs they can see constitutes "intelligence." The need is merely that the birds don't want to starve, and eat moths, which they locate by sight.
Are you tripping too hard over "imagine?" Should I have just said "think of?" You tell me you don't see how the Old Man of the Mountain could have formed or been destroyed without design. I can think of ways in which both could have happened without design.
But let's stay with "imagine." You say something can't happen without guidance. I imagine otherwise. I give you a scenario which is all physics and chemistry, no intelligent being stirring the pot. If it's on one of these threads, your next line is "What's the PROOF of that?"
ID-ers could just skip the whole first step, the attempted proof by failure to imagine, but then I guess guys like Behe would be out of business.
Yup, they do, and your point that they did was your inability to answer the following question:
So what parts can we have life without?
Post# 34.
The facts in those articles are all pretty essential to life. So yes, they could not have arisen piecemeal. As I have often stated there are quite a few essential life functions. They all have to be present for life to exist. They could not have arisen piecemeal.
You see the problem with evolutionists and why evolution is not science is that they think that the different functions of life are not related and thus you can build things up like a house of blocks. You cannot. You need numerous parts to have life be life.
Nothing you have the wit to value, and it was already gone.
Let's hope not.:-) This is still America as long as Americans stand for freedom and the pursuit of truth.
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