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RNA tails and gene expression

Saturday, June 30, 2007

Only a few years ago – definitely less than ten years – gene expression was thought to be a fairly simple process. One gene coded for one protein. The gene was "transcribed" from DNA to messenger RNA (mRNA), and in turn the mRNA was used to direct the manufacture of proteins in structures called ribosomes.

But then there were a series of "complications". Genes could be turned "on" or "off" by means of transcription factors, which are separate proteins produced by separate genes, and which are capable of either promoting or suppressing the transcription of other genes. Further, genes are not straight uninterrupted segments of DNA that correspond directly (via mRNA) to proteins, because genes contain segments called introns that are edited out of finished mRNA and ignored. And what is more, coding segments of genes (called exons) can be spliced together in different ways to produced finished mRNA (discussed here). This makes it possible to obtain multiple distinct proteins from a single gene.

And then, outside of the RNA transcription process, it turns out that small bits of RNA, called microRNA (miRNA) and small interfering RNA (siRNA), and which are coded for in parts of the genome long thought to be "junk", can become attached to mRNA and inhibit (or perhaps at times promote) production of proteins from it. (See this.) Nor should we forget to mention ribozymes, which can also mess around with mRNA. And if all that weren't enough, there are also a variety of epigenetic factors which can turn on or off entire segments of a genome.

Is that all? No. There are probably a number of other mechanisms that modify, regulate, and control gene expression – mechanisms as yet undiscovered. After all, there's a lot of "junk" DNA, whose function we still have no clue about – except that a lot of it isn't truly "junk".

Here's an example that has just come to light: RNA "tails".

Yeast: The Key To Understanding How Cells Work
The major contribution to the collaborative study by Associate Professor Preiss' Lab was to measure the length of polyadenosine "tails" on the messenger RNA (mRNA) molecules that are generated from each gene to serve as a blueprint in making proteins - the building blocks of life.

"One might think that a tail does not matter much, but with mRNAs it has a big impact on how long they stay around in cells and how much protein is made from them. In this way it is a case of the tail wagging the dog. Since nearly every mRNA in every human cell has these tails, it is not surprising that controlling their length turns out to be quite important. It is known to be involved in embryonic development and during learning and memory in the brain, for instance. The mRNA tails also seem to be the target for recently discovered tiny cellular brakes called microRNAs. Failure of these brakes contributes to human diseases, such as heart defects and cancer.

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Origins Of Nervous System Found In Genes Of Sea Sponge

One of the things that's always fascinating (or inspiring, astonishing, awe-inspiring – take your pick) about what we learn from the evolutionary history of living critters is how much very different sorts of living things have in common. This even reaches down to the level of single cells, where very similar genes can be found in mammals and yeast, even bacteria.

We also find complex subsystems with substantial similarities. So much so that the nervous system of the roundworm Caenorhabditis elegans, which has all of 302 neurons in its whole nervous system (hermaphrodite version), is routinely used as an experimental model for the nervous systems of much more complex animals.

Perhaps even more astonishing than that, however, is that it now appears some genes important for modern nervous systems existed even before there were nervous systems – in sea sponges, which are just about the most primitive animals known.

Origins Of Nervous System Found In Genes Of Sea Sponge
Scientists at the University of California, Santa Barbara have discovered significant clues to the evolutionary origins of the nervous system by studying the genome of a sea sponge, a member of a group considered to be among the most ancient of all animals.

And not only are some of the genes there, but the proteins they represent may have interacted similarly to the way that corresponding proteins interact in modern synapses.
"It turns out that sponges, which lack nervous systems, have most of the genetic components of synapses," said Todd Oakley, co-author and assistant professor in the Department of Ecology, Evolution and Marine Biology at UC Santa Barbara.

"Even more surprising is that the sponge proteins have 'signatures' indicating they probably interact with each other in a similar way to the proteins in synapses of humans and mice," said Oakley. "This pushes back the origins of these genetic components of the nervous system to at or before the first animals ---- much earlier than scientists had previously suspected."

Other blog articles: here

Original research paper: here

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Philosophia Naturalis #11 has been published

Friday, June 29, 2007

And it may be the best one yet. If you blog about the physical sciences and you haven't submitted some of your writing for Philosophia Naturalis... well, what's holding you back? You could be in some pretty fine company.

Anyhow, for the latest edition, you'll find it here at Highly Allochthonous, courtesy of Chris Rowan. The layout and presentation is especially clever. Great job, Chris!

Supersymmetry and big bang nucleosynthesis

Wednesday, June 27, 2007

The general acceptance of big bang cosmology for the past four decades rests primarily on three solid lines of evidence. First, the observation of the general expansion of the universe (using distance measurements based on "standard candles" like supernovae), is very consistent with the Friedmann equations derived from general relativity. Second, very precise measurements of inhomogeneities in the cosmic microwave background are very consistent with what is to be expected of conditions present in the universe at the time photons decoupled from matter. Third, the abundances of several light nuclei are very close to what would be expected to be produced in the process of nucleosynthesis that should have occurred around five minutes after the big bang.

As good as the agreement between theory and observation has been where nucleosynthesis is concerned, there have been various discrepancies that required some creative thinking to resolve. One of these involves the abundance of helium-3. We discussed it here.

Another example involves lithium. Although both lithium-6 and lithium-7 are calculated to have been produced in very small amounts, there was definitely some. Yet some very old stars have been observed that seem to contain no lithium at all. Where did it go? The theory here is that such stars are the result of mergers between even older stars, in which all the lithium was destroyed in the cataclysmic merger. See this.

Now there is yet another anomaly involving lithium observed in certain very old stars. The interesting thing is that one theorist is viewing this as possible evidence for very heavy supersymmetric particles that may not have yet decayed out of existence at the time of primordial nucleosynthesis.

Catalyzing Primordial Nuclear Chemistry
But a remaining puzzle is the amount of primordial lithium; both Li-6 and Li-7 are unexpectedly abundant in metal-poor stars (those with very few heavier elements). For example, a much higher than expected level of Li-6 might be pointing to a primordial origin (that is, not made later in stellar cores or in supernovas), in which case the BBN model would need to be amended. Maxim Pospelov ... of the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, and University of Victoria, British Columbia suggests that the anomaly can be explained if early nucleosynthesis was aided---catalyzed---by the presence of charged heavy particles, which are common in many models of particle physics.

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Some causes of atherosclerosis

There is a certain sort of person who likes to find a single, simple cause behind diverse phenomena. For instance, regarding disease, such a person likes to view it as preponderantly the result of poor nutrition, pollution, pesticides, infections (bacterial, viral, or both), lack of antioxidants in the diet to quench "free radical cascades", negative thoughts, or whatever.

Sometimes, evidence even comes along that, surprisingly, fingers a favored disease mechanism that most observers had not suspected. For instance, stomach ulcers, long believed to be due to "stress" and "anxiety", have turned out actually to be caused by a bacterium, Helicobacter pylori.

Although such simplistic views of disease etiology tend to be wrong in general, new cases continue to turn up, as we learn more, where the simple theory does work. (Or, at least, it is a factor, since many if not most diseases can have multiple "causes".) Infection, by bacteria, viruses, or other parasites, is a frequent example.

Here are two recent instances, both involving atherosclerosis:

Cytomegalovirus exacerbates atherosclerosis through an autoimmune mechanism
A new study conducted by researchers from the University of Verona and the Institute G. Gaslini in Genova, Italy, confirms the pivotal role played by Cytomegalovirus infection in the pathogenesis of atherosclerosis.

Atherosclerosis is the main cause of morbidity and mortality worldwide. Classic risk factors including smoking, diabetes, hypertension and high cholesterol levels are known to play a pivotal role in the pathogenesis of the disease that also recognises a genetic influence. However, it is well known that acute cardiovascular events may happen without the presence of the mentioned common risk factors. Recently inflammation and infectious agents have been shown to play an important role in the onset of acute cardiovascular events.

Bacterial Infection May Contribute To Cardiovascular Disease
A new dissertation shows that Chlamydia pneumoniae can contribute to cardiovascular disease. Half of the population of Swedish twenty-year-olds are carriers of the bacterium Chlamydia pneumoniae, an ubiquitous pathogen previously known to cause acute respiratory disease. It now appears that this bacterium also contributes to cardiovascular disease, the single greatest killer disease in the western world.

In a new thesis in the field of pharmacology, Hanna Kälvegren demonstrates that the respiratory bacterium Chlamydia pneumoniae stimulates the process that leads to hardening of the arteries. This in turn causes heart attacks and stroke, by increasing the risk of thrombus, or blood clots.

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Rings of algebraic integers

Sunday, June 24, 2007

"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and rings

Well, that's not exactly what he said, but close enough.

In our last installment of the series on algebraic number theory, we reviewed a couple of very important elementary examples of rings, namely the integers ℤ and the finite "quotient rings" ℤ/nℤ for any integer n>1. Earlier (here) we provided the basic abstract algebraic definition of a ring. In this and subsequent installments we're going to tackle rings in earnest, as they provide the best way to formalize the bulk of concepts needed to discuss algebraic number theory seriously.

Recall that our original objective was to find solutions to polynomial equations f(x)=0, and usually more specifically where the coefficients of the polynomial are ordinary integers in ℤ. Even more specifically, we were interested in Diophantine equations, where we wanted solutions that are integers, or "nearly" so.

Abstractly, we know by the fundamental theorem of algebra that if n is the degree of f(x), then exactly (counting multiplicity) n solutions exist in the complex numbers ℂ. If the coefficients of f(x) were rational numbers (in ℚ), then these solutions are by definition algebraic numbers. We know, further, that in some sense Galois theory provides a good description (so far as one can be given) of the nature of solutions of one polynomial equation in one variable with rational coefficients.

What we might hope for is finding solutions of such equations in integer or rational numbers. But that's very hard, so pragmatically it is best to ease off a bit and look for solutions in a somewhat larger class that's easier to handle theoretically. The key to the whole enterprise is finding the right abstraction to work with. We need to seek solutions which are conceptually somewhere between integers and fully general algebraic numbers. If we can deal with some intermediate construct, hopefully we can (with care) manage to bridge the gap and cross the chasm.

So let's call the concept we are looking for algebraic integers, and try to figure out how this concept should be defined. We have an advantage over mathematicians of the 19th century who first thought about these issues. Namely, and as a direct result of their work, we now have a collection of abstract algebraic concepts that have proven very useful for organizing the theory. High in importance among these concepts is that of a ring. Since ℤ is a ring, if algebraic integers are to form a construct that generalizes ℤ, this construct had better be a ring if we dare call it a generalization.

The next point to consider is that what is to be treated as an algebraic integer depends very much on being relative to a specific finite extension F⊇ℚ. More explicitly, if F is a field which is a finite extension of ℚ (that is, has finite degree over ℚ), F is called a number field or algebraic number field, because all of its members are algebraic numbers as defined previously (roots of some polynomial f(x)∈ℚ[x]).

To give a name to that which we are looking to define, let OF (or OF/ℚ when we want to be explicit about the base field) be the set of all elements of F that are algebraic integers. In short, F is a field of algebraic numbers over ℚ, and OF is to be a ring that plays a role in F analogous to the role of ℤ in ℚ. So we need to have ℤ⊆ OF.

For a clue as to how to define OF, suppose F=ℚ. F could then be defined as the set of solutions of f(x)=0, where f(x) is a first degree polynomial with coefficients in ℤ. That is, f(x) has the form ax+b, for a,b∈ℤ and a≠0. In other words, F is just all fractions b/a with a,b∈ℤ and a≠0, namely ℚ.

In this trivial case, how are the integers defined? All we need to do is require that f(x) be a monic first degree polynomial with coefficients in ℤ, that is f(x) has the form x+a for a∈ℤ. This suggests defining OF as the set of elements of F that have a minimal polynomial f(x) which is monic and has coefficients in ℤ. Somewhat amazingly, this turns out to work nicely.

With this definition, ℤ⊆OF obviously. What isn't so obvious and needs to be shown is that OF is a ring. In particular, if a,b∈OF, then both a+b and ab are also in OF. That's a little work, but not hard. It can even be shown that F is the "field of fractions" of OF, namely the set of all quotients b/a with a,b∈OF and a≠0. Beyond that, there are a whole slew of other results that flow from this definition and justify it many times over.

So rings of integers as defined here are the natural generalization of the rational integers ℤ, which is a subring of any ring of algebraic integers. It is fair to say that the main concern of algebraic number theory is determining properties of such rings OF for algebraic number fields F. However, there are various properties ℤ has which general rings of integers do not have. For example, all ideals of ℤ are "principal" ideals, and all elements of ℤ factor uniquely as a product of primes. Most rings of algebraic integers have neither of these properties, but criteria can be given for when they are present.

For future reference, note that we can also talk about rings of integers of arbitrary algebraic extensions E⊇F, where the base field isn't necessarily ℚ. The definition of the integers of E/F, denoted by OE/F, is simply all elements of E having a minimal polynomial over F which is monic and has coefficients in OF. This is useful for the general theory, but harder to work with when developing the basic theory.

To conclude this installment, let's look at the simplest sort of extension of ℚ, a quadratic extension F=ℚ(√d), where d is a square-free integer, which may be either positive or negative. Now √d is an algebraic integer because it satisfies x2-d=0. So is, for any b∈ℤ, b√d, since it satisfies x2-db2=0.

However, the situation for a+b√d, a,b∈ℤ isn't quite as obvious, unless we use the general fact (that hasn't been proven here) that the algebraic integers of F⊇ℚ form a ring, so that sums of integers are integers. It would be clearer just to produce the equation a+b√d satisfies in order to see directly that it is an integer. Fortunately this is quite easy.

Let α=a+b√d. From Galois theory, we recall that the "conjugate" of α is α*=a-b√d, and we have (x-α)(x-α*)=0. Multiplying things out we have f(α)=0, where f(x)=x2-2ax+a2-db2. Clearly f(x) is monic with integer coefficients, so a+b√d is an algebraic integer in ℚ(√d).

You might be tempted to conclude that OF is {a+b√d | a,b∈ℤ}, no matter what d is. But that's not true either. For example, if d=5, you can easily check that α=(1+√5)/2 satisfies x2-x-1=0, so α is an algebraic integer of ℚ(√5).

What actually is true is that OF = {a+b√d | a,b∈ℤ} if d is square-free and d ≡ 2 or 3 (mod 4). However, if d ≡ 1 (mod 4), then OF is {(a+b√d)/2 | a,b∈ℤ}. The proof isn't hard, and we'll come back to it later.

In the next installment we'll look further into some of the ring theory relevant to rings of integers.

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Skip Buying Extra Stuff And Take A Vacation Instead

Saturday, June 23, 2007

Skip Buying Extra Stuff And Take A Vacation Instead
Shopping for that new high-definition television this summer? Skip it, and take a vacation instead, says a University of Colorado at Boulder psychologist who studies happiness.

Assistant Professor Leaf Van Boven has conducted numerous surveys and experiments spanning several years and has found that life experiences, such as vacations, generally make people from various walks of life happier than material possessions.

One reason for this is that experiences are more open to positive reinterpretation, or mental editing, than material possessions. And vacations are a perfect example of this, according to Van Boven.

Sorry, the title of this was so good, I just couldn't resist.

I cannot see exactly why this is "science", nor why one might need surveys or a professor of psychology to validate the accuracy of the advice. Many times, it seems to me, psychological research only corroborates the obvious. This is one of those times.

I'll just chime in with a little advice of my own. This applies especially if you're young. Don't put off until "some other time" a vacation or other adventure if you can possibly do it when the opportunity presents itself. Especially if it's something simple but perhaps a bit strenuous or requires you to go a bit outside your comfort zone. Like, say, a camping trip without a lot of fancy gear, to some place that doesn't have a lot of tourist amenities.

You may find you remember fondly even the less idyllic parts, like spending days or nights in a tent, while the rain never stops coming down, and you can't even enjoy your electronic toys like the iPod 'cuz the battery needs a charge. Maybe that'll be the time the only thing you can think of for fun is taking off all your clothes and playing outside in the rain and the mud. Maybe that's what you'll remember the rest of your life.

Just don't keep putting off that sort of thing. Once you have kids (and you very probably will), there will be too many options you just don't want to take the chance on. Or that are plainly out of the question.

And don't think you'll have the chance again later, once the kids are grown. Even if your health and strength remain good (as is likely, though hardly a sure thing), what you will find is that you just don't want to take the kind of chances you did when younger, or to give up some luxuries or comforts you "just can't do without" now. To say nothing of the chances that your companion will still feel a similar spirit of adventure in the future.

Oh, yeah, one other consideration. Barring major catastrophe, the world won't have fewer people on it in a few decades, either nearby or in pleasant, little-known remote places. The "good places" keep getting discovered and ruined by popularity. Enjoy them now, before the crowds and the developers find them. And with climate change a pretty sure thing, many lakes, snowfields, woodlands, meadows will be only memories much sooner than anyone expects.

Modular arithmetic

Sunday, June 17, 2007

After some hiatus, let's return to our discussion of algebraic number theory. Check here for previous articles.

We have already talked briefly about groups and rings (here), but because ring theory is so important to the whole subject, we need to go into it a lot deeper. As preparation for that, we'll look at some of the simplest examples, which will turn out to be greatly generalized in the sequel.

The simplest example of all is probably the ring ℤ of ("rational") integers. We'll assume the properties of ℤ are well enough known as to require no further comment.

The next simplest example is a construction based on ℤ – the ring of integers "modulo" some positive integer n>1. You can read about it in a little more detail here. Of course, if you've studied any elementary number theory, you probably need no further explanation. On the other hand, if your only exposure to it has been courtesy of some writer who talks down to his readers by referring to the topic as "clock arithmetic", the chances are fair to good you could use a less condescending refresher.

In any case, the construction is so important and pervasive in more advanced ring theory and algebraic number theory that it's worth looking at from several points of view. The basic idea could hardly be much simpler. It involves a slightly generalized notion of "equality", or "equivalence" as it's more often referred to.

To begin with, pick and fix an integer n. n is usually assumed positive, though that's not strictly necessary. n, however, does need to be other than 0 or ±1, for reasons which will become obvious. We then say that any other two integers x and y at all are "equivalent modulo n" just in case the difference x-y is divisible by n. (This is why we want n≠0, since division by 0 is meaningless, and also n≠±1, since in that case we would have all integers equivalent modulo ±1. Although that case is meaningful, it isn't very interesting.)

Symbolically, we write x≡y (mod n) if x and y are equivalent modulo n. This notation is chosen to emphasize how ≡ is just a slight variation of the notion of equality. From this point of view, we are still talking about perfectly ordinary rational integers, but using a different notion of when they are "equal". All of the usual facts from elementay number theory about modular arithmetic can be developed from this point of view and the given definition.

But there are other points of view. For example, ≡ (mod n) is just a special case of what is called an "equivalence relation" in set theory. Specifically, let S be any (non-empty) set at all. A relation on a set S is, formally, a mapping from the set of ordered pairs (x,y) of elements of S to the set {0,1} of two elements. If the relation in question is denoted by R, then this function R(x,y) has the value 1 if x and y are in the relation R (which might be, for example, parent and child if S is a set of people). In this case we write xRy, which is not necessarily the same as yRx. On the other hand R(x,y)=0 just in case x and y are not in the indicated relation.

Given all that, there is a special type of relation R on a set S which is technically known as an "equivalence relation". For R to be an equivalence relation, three conditions must be satisfied. First, it must be "reflexive" – xRx for all x∈S. Second, it must be "symmetric" – xRy if and only if yRx, for all x,y. And third, it must be "transitive" – if xRy and yRz then xRz, for all x, y, z.

The interesting thing about equivalence relations is that if R is one on any set S, it is not hard to show that it causes S to be partitioned into disjoint (i. e. non-overlapping) subsets, called "equivalence classes". The classes need not in general all be the same size (regardless of whether S is finite or infinite), but every element of S is in one and only one class, possibly all by itself.

This exercise in abstraction actually has a useful point. Namely, if S=ℤ and R is ≡ (mod n), then obviously we have an equivalence relation on ℤ. Consequently, ℤ is partitioned into equivalence classes. Because of the structure of ℤ and the nature of ≡ (mod n), it turns out that all the equivalence classes are the same size – countably infinite, just like ℤ

From this new point of view, we can give the equivalence classes themselves the structure of a ring. And this ring will be finite in size, having exactly n equivalence classes. We will use the notation ℤ/nℤ for this set of equivalence classes – the reason for the notation will gradually make more sense.

Use the notation [x] for the equivalence class of x∈ℤ. To make a ring out of these equivalence classes, we need to define addition and multiplication. This is easily done: let [x]+[y]=[x+y] and [x][y]=[xy]. There is something subtle that needs to be proved, namely that these definitions are "well-defined", and they do not depend on the choice of a representative element for each equivalence class. For example, suppose [x]=[x′] and [y]=[y′], meaning, if we return to the basic definitions, that x≡x′ (mod n) and y≡y′ (mod n). Then it has to be shown that [x′+y′]=[x+y] and [x′][y′]=[xy]. (This is an easy exercise of unwinding the definitions for the reader.)

Now we can change the point of view just one more time. Let nℤ denote the set of all multiples of integers by the number n. We will redefine x≡y (mod n) from x-y is divisible by n to x-y is a member of the set nℤ. Clearly this doesn't really change anything. The equivalence relation remains the same.

So what have we accomplished? Simply this: starting from the ring ℤ we have found a way to define a new, finite ring ℤ/nℤ, consisting of equivalence classes. In the next installment of this series we will see how to generalize this construction to any "ring of integers of an algebraic number field" in place of ℤ. In the generalization we will replace nℤ with a special type of subring, called an ideal, of the ring of integers.

We will see that the theory of algebraic numbers is largely about the properties of these "ideals". For example, it is not true that any integer of an algebraic number field can be written as a unique product of "prime" numbers. Nevertheless, it is true that any ideal can be written uniquely as a product of "prime" ideals, suitably defined. For many applications in number theory, this is sufficient.

This point of view will also open up many interesting questions. For example, prime ideals in one ring of integers may actually factor into products of distinct prime ideals in the ring of integers of an extension field. And a very central question concerns the rules that govern such factorizations.

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New Hope For Baldness Treatment: Hair Follicles Created For First Time In Mouse Study

Saturday, June 16, 2007

At last! Medical science addresses a problem of great concern to (some) men under 50.

New Hope For Baldness Treatment: Hair Follicles Created For First Time In Mouse Study
Researchers at the University of Pennsylvania School of Medicine have found that hair follicles in adult mice regenerate by re-awakening genes once active only in developing embryos. These findings provide unequivocal evidence for the first time that, like other animals such as newts and salamanders, mammals have the power to regenerate. A better understanding of this process could lead to novel treatments for hair loss, other skin and hair disorders, and wounds.

Though tested so far only in mice, it's intersting that the technique involves recruiting the body's own stem cells – but not cells that are direct precursors of hair follicles. This means that other components of skin might be regenerated as well:
In this study, researchers found that wound healing in a mouse model created an "embryonic window" of opportunity. Dormant embryonic molecular pathways were awakened, sending stem cells to the area of injury. Unexpectedly, the regenerated hair follicles originated from non-hair-follicle stem cells.

"We've found that we can influence wound healing with wnts or other proteins that allow the skin to heal in a way that has less scarring and includes all the normal structures of the skin, such as hair follicles and oil glands, rather than just a scar," explains Cotsarelis.

Even more interesting, the technique involves an important family of protein known as "Wnt":
By introducing more wnt proteins to the wound, the researchers found that they could take advantage of the embryonic genes to promote hair-follicle growth, thus making skin regenerate instead of just repair. Conversely by blocking wnt proteins, they also found that they could stop the production of hair follicles in healed skin.

For a lot more on the Wnt signaling pathway, see here.

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News dump: the Wnt signaling pathway

Here's one of the interesting things about biology: sometimes small number of genes, present in a large number of animal species, can affect a very diverse range of biological processes – including a number we'd like to have better control over.

In this case, we're concerned with a family of about 19 related genes, called Wnt. Genes of this family code for proteins that are important in embryonic development. They also play an important role in the regeneration of body parts, in those species where such regeneration has been known to be possible – and perhaps someday even in humans.

Here are some recent news releases on the topic, most recent first.

Rare Mutation Causes Early Heart Disease And Metabolic Syndrome (3/14/07)
A very rare mutation of the LRP6 gene, whose protein affects the Wnt signaling pathway, has been found to cause high rates of early-onset coronary artery disease in a family that carries the mutation. Family members having the mutation were also at greater risk for other components of metabolic syndrome, as well as osteoporosis.

How Does A Zebrafish Grow A New Tail? The Answer May Help Treat Human Injuries (12/28/06)
Signaling pathways involving various Wnt proteins and Beta-catenin have been shown to control the regeneration of the fins of zebrafish. Some Wnt/Beta-catenin signals promote fin regeneration. A different pathway involving Wnt5b inhibits regeneration so it doesn't get out of hand. But a mutant form of Wnt5b speeds up regeneration, while an excess of Wnt8 also increases cell proliferation.

Researchers Discover Initial Steps In Development Of Taste (12/6/06)
Researchers have shown that Wnt signaling pathways regulates the development of taste buds in mice. They have also determined that Wnt proteins are required for hooking up the wiring of taste signals to the brain.

Control Mechanism For Biological Pattern Formation Decoded (11/30/06)
Using a mathematical model based on protein reactions and diffusions, researchers have been able to explain the dynamics and parameters of hair formation in mice, based on Wnt signaling.

Scientists Regenerate Wing In Chick Embryo (11/19/06)
This research provides direct evidence that limb regeneration in (some) vertebrates is affected by the Wnt signaling system. By activating Wnt signaling scientists were able to stimulate wing regeneration in chick embryos (where it does not normally occur), and by deactivating Wnt signaling in frogs, zebrafish, and salamanders it was possible to prevent regeneration of missing legs and tails.

Adult Stem Cells May Be Just Remnants Of Evolution (11/2/05)
At least some adult stem cells could be the mere remnants of former embryonal differentiation processes. In this research mesenchymal stem cells of mice we stimulated by Wnt signaling, but their transformation into muscle cells was not complete.

Wnt Signaling Controls The Fate Of Stem Cells In Adult Brains (10/31/05)
The Wnt3 protein affects whether neural stem cells in mice, upon division, continue as stem cell, become neurons, or become support cells, such as astrocytes or oligodendrocytes.

Prostate Cancer Uses Wnt Signaling Proteins To Promote Growth Of Bone Tumors (9/7/05)
Some Wnt proteins play a central role in regulating normal skeletal development in an embryo, but they may also be hijacked by prostate cancer cells to spread the cancer into bone tissue.

Mice With Hyperactive Gene Eat All They Want, But Have Half The Body Fat Of Normal Mice (6/30/04)
When the protein Wnt10b is present in artificially high amounts in fat tissue of experimental mice, the mice appear to be able to eat as much as they like without an increase in body fat.

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You Snooze, You Lose? Not True

Thursday, June 7, 2007

You Snooze, You Lose? Not True

Tired after lunch or by mid-afternoon? You might think that you should go buy yourself some coffee. But according to UCSD researcher Sara Mednick, you’re better off taking a nap.

Mednick, a faculty member in the department of psychiatry at the School of Medicine, has been researching napping since graduate school and recently published a book, titled “Take a Nap! Change Your Life.”

I like it. This is really "news you can use."
Some of her most striking research looks at napping compared to drinking caffeine. In one study, Mednick had one group of subjects nap for 90 minutes, while another drank 200 mg of caffeine. She also set up a control group, who took a placebo. Then she tested her subjects on several tasks, including typing and spatial skills, such as remembering the layout of a room or a map. On both tasks, coffee drinkers performed much worse than the placebo group, Mednick said. “Of course, this is a bummer for Starbucks,” she added.

Think about it. What would you really prefer – being well-rested, or being a caffeine zombie?

Hubble Photographs Grand Design Spiral Galaxy M81

Sunday, June 3, 2007

Hubble Photographs Grand Design Spiral Galaxy M81
The sharpest image ever taken of the large "grand design" spiral galaxy M81 is being released today at the American Astronomical Society Meeting in Honolulu, Hawaii. A spiral-shaped system of stars, dust, and gas clouds, the galaxy's arms wind all the way down into the nucleus. Though the galaxy is located 11.6 million light-years away, the Hubble Space Telescope's view is so sharp that it can resolve individual stars, along with open star clusters, globular star clusters, and even glowing regions of fluorescent gas.

M81 – click for 1280×860 image

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