Communication within DNA

In Nature v. 431, 9. Sept. 2004, p. 142, "An unexpected social servant" by Christine Le Roy and Jeffrey L. Wrana is another excellent example of complexity in living things. "Cells communicate through signals that must be propagated from cell surface to nucleus." Lots of processes in the body require different cells to do things at the same time, or in a certain order. They communicate by releasing special chemicals, but how do the chemicals get inside other cells and then deep inside to the DNA "brains" in the nucleus? A study starting on p. 205 "reveals a surprising partner in this process."

It was already known that the chemical signals "are interpreted in responding cells by networks of signal-transduction proteins that regulate the appropriate cellular response" and that "One major class of signals"... hang on a sec... doesn't that indicate that there are a number of major classes and a number of minor ones, each with at least one kind of signal chemical? Wow.

Anyway, this one kind that is found "in all animals" (more "evolutionary conservation") is known as TGF-[beta], actually a "superfamily of growth and differentiation factors..." The surprise in this study was that one of the molecules involved in getting TGF-beta into the nucleus is cytoplasmic promyeloctyic leukaemia protein (cPML)." Isn't that surprising?

Okay, it meant nothing to me, but the review article explains that PML "is involved in a range of biological functions" -- but it was mostly known for keeping cells from becoming cancerous (trip it up when it's trying to do its work, and you get the leukemia that it gets its name from), and it does this work in the nucleus. Scientists knew some of it floated around in the rest of the cell (the cytoplasm), but nobody knew what it was doing there. This new study shows that it is required for cells to snag and haul TGF-beta molecules floating around outside.

Ooh, but wait! cPML is just one part of a system involving a pathway of several other components! I love this description: "cPML is crucial in orchestrating the dance that goes on during a signalling event, coordinating the receptors, SARA, Smads, and the internalization process." That's 4 parts or steps right there, and that appears to be a bit simplified. There are two big receptor molecules that stick up out of the cell and can clamp onto TGF-beta molecules floating by, but they need the other molecules.

SARA is a protein that binds to the receptors and to the Smads, which are signalling proteins that do their thing down in the nucleus. SARA can bind to Smads directly (in the lab), but for some reason it needs cPML to work inside cells. cPML is also required to get the whole TGF-beta/twin receptors/SARA/Smads conglomerations to move into a sort of bubble called the Early endosome (there's another required part) that acts as a taxi or tow-truck, taking everything deeper into the cell. It could be that the endosome bubble provides a different environment from the cytoplasm, and that's what allows SARA-Smad binding.

And clearly "The results raise lots of interesting questions," so there is a lot more to be learned about this one signaling pathway!

Some may choose to believe that this and all the many other complex systems in living things just happened to happen as random changes were weeded out by the rigors of physical constraints, but as for me, I praise God, for his works are marvelous, and his ways past finding out.

Until Next Time,

David Bump
Philippians 3: 13 Brethren, I
count not myself to have
apprehended: but [this] one thing
[I do], forgetting those things
which are behind, and reaching
forth unto those things which are
before, 14 I press toward the
mark for the prize of the high
calling of God in Christ Jesus.

http://home.att.net/~david.bump

Sizing Up the Matter

In Nature v. 431, 9. Sept. 2004, p. 139 "Relative size in the mating game" by Malte Andersson and Johan Wallander discusses a report in Proceedings of the National Academy of Sciences 101, 12224-12227 (2004). I point to it as an example of my contention that while evolutionists claim to have worked out the broad stages of evolution, that evolution is so well-supported by data that it can be considered a fact, etc., they're actually still struggling to nail down some rather basic points that are perfectly compatible with creation science anyway.

In this case, the fuss is over "an intriguing rule" proposed "five decades ago" by "the German evolutionary biologist Bernhard Rensch." This rule states that the bigger the species, the bigger males are on average relative to the females. It seems to hold true in all sorts of animals, but "The causes behind the rule...have remained unclear." Of course, evolutionists don't say "They just evolved that way" any more than creationists should say "God just made them that way" as we are purported to do.

Not surprisingly, the rule seems to be related to sexual selection. By studying when the rule holds and when there are exceptions among shorebirds, the authors of this study found that "In species with strong male competition (polygyny) and non-agile display, males are larger than females. In species with agile aerial display, males are smaller than females.

When competition over mates is weaker in males and strong in females (polyandry), females are the larger sex."(Fig. 2, p. 141). So the "larger male" rule is simply a matter of males physically fighting over females, and the larger the type of animal, the more effective and important being a bit larger is in a fight. When the males compete by doing acrobatics, it helps to be small and agile, and if the females are fighting over the males, then the males don't have any advantage in being the largest.

So why'd it take some 50 years to figure that out?

Until Next Time,

David Bump
Philippians 3: 13 Brethren, I
count not myself to have
apprehended: but [this] one thing
[I do], forgetting those things
which are behind, and reaching
forth unto those things which are
before, 14 I press toward the
mark for the prize of the high
calling of God in Christ Jesus.

http://home.att.net/~david.bump

Blood Flow Feeds the Brain

Continuing to examine Nature v. 431, 9. Sept. 2004...
p. 137, "Feeding the brain" by Claire Peppliatt and David Attwell is a review of studies of the systems that support the brain cells that do our thinking on the physical level. They also show another aspect of the marvelously designed complexity of our bodies.

Our brains need energy to think just as computers need electricity. The simple sugar glucose is the fuel, and oxygen is required to metabolize it, and these are provided through blood flowing through arteries, arterioles, and capillaries. When we're not thinking so hard, our brains don't need as much energy, and too much fuel would be wasteful, if not harmful. So the blood flow is regulated according to need, "but exactly how the flow is increased is uncertain." A study on p. 195 casts some light on part of the system.

Actually, it somewhat muddies the waters (to switch metaphors in mid-stream), as "the new data contradict a previous suggestion" for how the system works. We do know that in addition to the "computationally active" neurons, there are support cells such as astrocytes. Some of the neurons also form "Dedicated neuronal networks" that "signal to the smooth muscle to constrict or dilate arterioles and thus decrease or increase blood flow."

Apparently, just "the neuronal activity associated with information processing increases local blood flow." This alone is not a simple matter, as it involves a series of steps, starting with "the transmitter glutamate" a chemical which "raises the intracellular concentration" of calcium ions (calcium atoms with, in this case, two electrons removed) in other neurons, setting off an enzyme that produces nitric oxide, which (finally) causes the arterioles to dilate (open up more) and allow more blood to flow.

That's just one regulatory pathway, and the simple one at that. An earlier study indicated that the glutamate transmitter also triggered astrocytes to cause the dilation. As noted, astrocytes support the neurons, wrapping around them, but "they also send out an extension, called an endfoot, close to blood vessels: thus, astrocyte anatomy is ideal for regulating blood flow..." However, the new data indicate the situation isn't so simple as the earlier data indicated. In this study, increasing calcium ions inside the astrocytes "produces a constriction of nearby arterioles."

The investigation showed that, in astrocytes, the ions didn't activate a nitric oxide release, and instead different enzymes go into action. It's suggested in the review that this part of the system can produce different effects at different times.

Until Next Time,

David Bump
Philippians 3: 13 Brethren, I
count not myself to have
apprehended: but [this] one thing
[I do], forgetting those things
which are behind, and reaching
forth unto those things which are
before, 14 I press toward the
mark for the prize of the high
calling of God in Christ Jesus.

http://home.att.net/~david.bump