Volume 0, Number 8
Neurobiology of music|
Telomeres and atherosclerosis
Reversing Alzheimer's brain damage
Early universe structure
Adult stem cells
Memory and aging
Language processing in the brain
Fine structure constant
Active galactic nuclei
Extrasolar planetary systems
Cancer and the immune system
The divergence was most pronounced in people who had received musical training at an early age, as well as individuals who have "perfect pitch". This would imply that the characteristic is at least partially acquired by training at an appropriate age, instead of being wholly innate. The broader implication is that parts of the brain which process spoken language also become involved with other sensory signal patterns if they receive training at the "right" time. Hence it may be entirely appropriate to regard music and other artistic productions as a form of language for individuals who have been properly prepared.
A recent study comparing individuals with severe coronary artery disease (CAD) to a control group reveals that, when matched for age and sex, the people in the CAD group have significantly shorter telomeres in their circulating white blood cells. The difference corresponds to an implied "age" of the cells in the CAD group that is 8.6 years more than expected. The implications of this correlation are unclear. It may be that the disease process has a side effect that causes more rapid cellular aging. On the other hand, it is also possible that some other factor is responsible for this more rapid aging, which in turn plays a role in the development of CAD.
A team of several researchers has discovered that when the chemical messenger known as "nerve growth factor" (NGF) is injected directly into appropriate areas of the brains of the experimental mice, the size and shape of neurons was not only restored, but even the reduction in number was reversed. It appears that, although NGF continues as usual to be manufactured in the brain, the disease somehow blocks its delivery to the areas of the brain that need it. Research is continuing to ascertain whether behavioral improvements result in the mice which receive this treatment.
The observations were made on the spectrum of light in the far ultraviolet from one quasar, HE2347-4342, which is located at a redshift of z=2.885. The object is thus seen as it was at about 1/4 of the present age of the universe, or about 10 billion years ago. Indications are that the distribution of matter at that time is consistent with theories that predict the distribution from density fluctuations left over from the big bang. Further, the degree of ionization of helium indicates a contribution from light originating in both starburst galaxies and an abundance of quasars.
SKPs are similar, but not identical, to other adult-derived stem cells, such as those from bone marrow. The McGill University team which discovered the SKPs has made preliminary investigations into whether an analogue may be derived from human skin, and concluded the possibility looks promising. If SKPs can indeed be derived from adult human skin, this would open up many possibilities of tissue transplantation or regeneration that would not risk rejection if derived from the patient's own skin.
The studies were conducted on prion-infected mouse cells. The drugs appeared to inhibit the conversion of normal prion protein into the disease-causing form. The method of action of the drugs was not clear. Although the effect of quinacrine was ten times as potent as that of chlorpromazine, the latter might be more useful as a practical treatment for human prion diseases because of its greater ability to penetrate the blood-brain barrier. Clinical trials of the drugs in humans are being designed.
In seprarate research it has been found that certain antibodies are also effective against prion diseases. (See , .) Normal prion protein is expressed throughout the body and is found on the surfaces of cells in a wide variety of tissue. There is an abnormal form of prion which is folded into a different shape. This variant form is affects normal prion by casusing it to assume the abnormal shape, thus becoming toxic to the cell. The antibody, called Fab D18, has been found to bind to normal prion in mouse cell cultures, thereby preventing the infectious variant prion from altering the normal protein.
The main problem with this approach in finding a therapeutic drug is that of delivery to the location of the infection in brain tissue. As with the other research study, crossing the blood-brain barrier is difficult. It is hoped that small-molecule drugs can be found that are easier to deliver but bind to normal prion (or possibly the infections variant) the same way that Fab D18 does.
The algorithmic problem of finding the original order of DNA fragments is similar to the problem of finding the shortest route through many cities which visits each exactly once. This is what's called the traveling salesman problem, and in graph theory it's called finding a hamiltonian path. The problem is thought to be NP-complete, which means that no exact solution is known except the prohibitively lengthy one of trying every possible solution. In practice, solutions can be found which are not guaranteed to be minimal, and in the case of sequencing DNA the result is that the proposed sequence may contain errors.
Now, Pavel Pevzner, of the University of California, San Diego, and some colleagues have proposed an alternative algorithm which is equivalent to visiting each city of a network as often as desired while traveling each route between cities only once and trying to minimize the total number of visits. This graph theory problem is called finding an eulerian path. Called informally the chinese postman problem, it is known to be less computational complex than the traveling salesman problem.
The researchers have produced computer code to apply the technique to DNA sequencing. Although in theory it is less complex than the previous approach, it is still unclear whether it will actually be more efficient with large genomes at some arbitrary (small) level of acceptable sequence errors.
The research report was authored by Denise Park, directory of the University of Michigan's Center for Aging and Cognition. Although the means by which declines in cognitive skills were actually measured aren't discussed in the press release, there are graphs illustrating the decline in function in the areas of working memory, short-term memory, long-term memory, and speed of processing. One capability that does not decline, however, but tends to increase up to the age of 70 is verbal knowledge. It is asserted that other similar learned skills and expertise are retained into the 70s as well.
ASCI stands for Accelerated Strategic Computing Initiative, a program of the U. S. Department of Energy to develop supercomputers that will support management and simulated testing of nuclear weapons. In terms of computer technology, ASCI White represents a major step in the development of the Terascale Facility that will provide 100 teraflop computing power by 2005, using off-the-shelf components.
The reason there is only one active copy of the IGF2R gene is that the copy of the gene coming from the father is switched off by a process called imprinting, so only the copy coming from the mother is still active. Anything which happens accidentally in the cloning process to impair the operation of the single active IGF2R gene will cause fetal overgrowth. But a team of researchers at Duke University has discovered that in humans (and other primates), this gene definitely is not switched off by imprinting, making it very likely that two active copies will be passed to the fertilized egg, and hence rendering one particular cloning mishap much less probable. (And, indeed, primates seem to have lost this imprinting 70 million years ago.)
The fact that one copy of IGF2R is disabled by imprinting in most mammals, but not humans, has other implications as well. In particular, cancer is more of a risk in animals with imprinted IGF2R. Since this includes mice and rats, the laboratory animals most often used in carcinogenicity studies, it is quite possible that many substances which have been "found to cause cancer in rats", including potentially valuable drug candidates, may be less dangerous to humans than assumed.
There were two surprising differences in brain activity patterns. One was that the right side of the brain was not as active during reading as during listening. This suggests qualitative differences in language comprehension between the two modes. The second surprise was that during listening there was more activation of a left hemisphere region -- the pars triangularis, a part of Broca's area -- that is usually active in language processing or maintaining information in verbal working memory.
The researchers were careful to point out that the findings don't indicate that one means of receiving verbal information is necessarily superior to the other. However, one may speculate on what accounts for the differences. For one thing, the brain is forced to do more processing in "real time" when listening, because it is not possible to reprocess the input, as can be done when reading. Another consideration is that the human brain has essentially no evolutionary experience with processing language information visually -- innate language abilities evolved entirely in connection with spoken language. It may be surprising that humans have become able to read language in a visual form as easily as they do.
By making very careful measurements of absorption lines in light from a number of distant quasars, the team claims that alpha may have been about one part in one hundred thousand smaller twelve billion years ago. The research team first suggested the fine structure constant might be changing in preliminary results reported in 1998. They have since then made many more observations which reduce the measurement errors and ruled out many types of systematic errors. Nevertheless, the effect is so small and the implications so far-reaching that many physicists are still skeptical of the finding.
If the finding is correct, it is extremely significant. Current physical theories have assumed that "constants" like alpha really are constant, but in most cases offer no fundamental reasons this should be so, let alone any principles which would allow computation of the constants directly. Current tentative theories which attempt to unify gravity with the other fundamental forces allow for vaiation in alpha and other constants. A precise determination of just how alpha changes with time (if it does) may help narrow down the range of such theories that fit the data.
In many such theories, fundamental constants are related to the size of one or more very small "hidden dimensions". If alpha is changing, then the size of one of these dimensions would also be changing. Alpha is also directly related to three other fundamental constants: the speed of light, the charge of an electron, and Planck's constant. If alpha is changing, one or more of these others -- perhaps even the speed of light -- must be changing also.
In particular, the observations confirm the existence of "nuclear bars" surrounding the central black holes. These bars seem to conduct matter into the region from the rest of the galaxy. In something of a surprise, there appear to be young, newly-formed starts in the central regions as well.
Now there is a new and much more detailed simulation which seems to resolve most of the difficulties, developed by planetary scientists Robin Canup and Erik Asphaug. It postulates that the other planet was roughly the size of Mars (a tenth the mass of Earth), and the impact occurred 4.5 billion years ago. The model accounts for such details as the spin rate of the Earth and the lack of iron in the Moon. Happily, it also assumes a scenario which is more likely than others which could have been necessary, such as one where more than a single impact occurred.
Even so, the precise sort of impact required would still have been a rare event. Yet many scientists believe the existence of a Moon such as Earth has was crucial to the eventual development of higher forms of life on Earth, since the Moon's gravity keeps the tilt of the Earth's axis in a stable position, preventing massive climate swings.
The photosystem complexes contains iron as a key element, so a low concentration of iron in the environment presents a problem. Researchers with the Photosynthesis Research Group in London have discovered that in low iron conditions cyanobacteria produce a protein related to proteins in PS II. However, surprisingly, this protein works not with PS II but with PS I of the cyanobacteria to form a light harvesting antenna of 18 chlorophyll molecules around the protein complex. This increases the light harvesting ability of the complex by approximately 72%.
The ability of this PS II-like protein to enhance the operation of PS I suggests that at some earlier evolutionary stage the two complexes may have had more in common.
The human genome contains a number of genes, known as tumor suppressor genes, whose function is specifically to prevent uncontrolled cell growth. The gradual failure of one such gene, known as p16/lnk4a seems to be a key step in the development of melanoma. A team of scientists lead by Rhonda Alani of Johns Hopkins University reports that overexpression of another gene, called ld1, seems to deactivate or otherwise interfere with the expression of p16/lnk4a at a certain stage of the progression that occurs when melanoma develops from precancerous skin moles.
The researchers found high levels of ld1 protein are absent from the precancerous moles but present in early stage melanoma. The high levels then disappear from later stage invasive melanoma and metastatic melanoma. This suggests that while overexpression of ld1 is implicated in the incipient failure of p16/lnk4a, further changes occur to deactivate p16/lnk4a without the help of ld1. Whatever the exact mechanism, it appears that the presence of high levels of ld1 protein is a useful diagnostic for bad things to come.
Normally, B cells produce antibodies, which are highly specific to particular molecules called antigens that occur on the surfaces of foreign organisms such as viruses and bacteria. The antibodies bind to the antigens and act as signals to attract other components of the immune system to destroy the invading organism. The new research suggests that the key to the effect of HIV on B cells is a protein called CD21 which normally occurs on the surface of B cells. CD21 allows B cells to respond to signals in the form of another immune system protein called complement. Previous research had shown that HIV attaches itself to B cells by means of the CD21 protein.
In the presence of HIV, it appears that B cells malfunction in certain ways. They may produce excessive amounts of nonessential antibodies, fail to respond properly to normal physiologic signals, and are at increased risk of becoming cancerous. Normal B cells in the process of fighting an infection transform into plasma cells which rapidly divide and generate antibodies. In becoming plasma cells, B cells change shape, lose their CD21, and cease responding to usual B cell stimuli. The researchers believe that HIV causes B cells to make an incomplete or faulty metamorphosis into plasma cells, which destroys their immune system function. B cells affected in this way have lost their CD21
The new planet has a mass at least 3/4 the mass of Jupiter, and joins a companion at least 2.5 times the mass of Jupiter. (Since the inclination of the orbital plane to our line of sight is unknown, only the minimum mass can be estimated.) The newly discovered planet is farther from its star than the first, but both have orbits smaller than Jupiter's. 47 Ursae Majoris itself is a sun-like star 51 light years from Earth.
The importance of orbital shape and size is that it is believed planets like Earth capable of supporting complex life forms need to occur in solar systems much like our own. In particular, the life-supporting planet needs to be close enough to the star that liquid water can exist at the surface. The planet's orbit must be stable for several billion years, which means larger planets cannot be too close or in orbits that are too eccentric. In addition, having one or more large planets in the same system of a mass comparable to Jupiter is considered important in order to sweep smaller asteroid-size objects away from trajectories which could cause deadly collisions. In the case of the 47 Ursae Majoris system, the two detected planets may be a little too close to the star to allow for an Earth-like planet in the habitable zone even closer to the star.
Nevertheless, the existence of another system this similar to ours out of a sample of only 100 or so nearby stars which have been carefully examined is encouraging -- considering that there are about 100 billion stars in the whole galaxy.
Copyright © 2001 by Charles Daney, All Rights Reserved