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Volume 0, Number 8
August 20, 2001

Neurobiology of music
Telomeres and atherosclerosis
Reversing Alzheimer's brain damage
Early universe structure
Adult stem cells
Prion disease
Genomic algorithms
Memory and aging
Terascale computing
Cloning
Language processing in the brain
Fine structure constant
Galaxy clusters
Active galactic nuclei
Lunar origins
Photosynthesis
Melanoma
AIDS
Prions
Extrasolar planetary systems
Cancer and the immune system


Neurobiology of music

It is not uncommon to refer to music, painting, and other types of artistic expression as a form of language. Now there is evidence, at least in professional musicians, that this may be more than a metaphor. Magnetic resonance imaging suggests that, in the professionals, brain structures (the planum temporale) on the left side are activated when listening to music -- the same areas which process spoken language. However, in non-professionals, the corresponding structures on the right seem to be activated.

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.

References:

  1. August 13, 2001 - Left in music
Background


Telomeres and atherosclerosis

A telomere is a structure at one end of a chromosome consisting of repeated sequences of base pairs. The length of a chromosomal telomere shortens every time the cell containing the chromosome undergoes division (mitosis). Cells stop dividing when their telomeres become sufficiently short. The length of the telomere in human chromosomes is such that the average cell can divide only about 50 or 60 times. Telomere length thus provides a sort of clock measuring the "age" of a cell.

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.

References:

  1. August 13, 2001 - Telomere Shortening May Be Linked To Atherosclerosis
Background


Reversing Alzheimer's brain damage

There doesn't seem to be much doubt that the proximate cause of the symptoms of Alzheimer's disease is the death or disablement of cholinergic neurons in the hippocampus and basal forebrain, although the mechanism by which this happens is unclear. Now there is evidence, from studies in mice that have been genetically engineered to experience just this kind of neural degeneration, that a reversal of the neural "death" may be possible.

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.

References:

  1. August 13, 2001 - Alzheimer's researchers revive "dead" brain cells
Background


Early universe structure

Observations by NASA's Far Ultraviolet Spectroscopic Explorer satelite (FUSE) have been announced which provide information on two different aspects of the universe when it was about a quarter of its present size and age. The first is the distribution of ionized helium, which is a good marker for the distribution of matter in general. The second is the relative abundance of very bright compact objects at that time -- quasars and "starburst" galaxies (which are undergoing an intense period of star formation).

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.

References:

  1. August 10, 2001 - Ghostly Cobweb Of Helium Left Over From Big Bang
  2. August 13, 2001 - New View Of Primordial Helium Traces The Structure Of Early Universe - Original press release
  3. August 14, 2001 - Observations of Primordial Helium Illuminate Structure of Early Universe
Background


Adult stem cells

Embryonic stem cells, called "totipotent" for their ability to differentiate into any type of body cell, possess the most scientific interest and potential for applications. But increasingly, more accessible types of stem cells (called "pluripotent" or "multipotent") are being isolated from other types of tissue. The latest finding involves stem cells derived from the dermis layer of skin in juvenile and adult mice. These cells, called skin-derived precursors (SKPs) have been found capable of developing into a variety of cell types, including neurons, glia, muscle cells, and fat cells -- all of which are typically found in the vicinity of skin cells. (See [1], [2], [3].)

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.

References:

  1. August 13, 2001 - Adult stem cells found in skin
  2. August 14, 2001 - Study Identifies New Source Of Stem Cells
  3. August 14, 2001 - Researchers Find Adult Stem Cells in Skin
  4. August 16, 2001 - No stemming the tide
Background


Prion disease

Recent research from the laboratory of Stanley Prusiner -- the Nobel Prize winning discoverer of infections prion proteins -- shows that two drugs commonly used to treat completely different diseases are also effective in combatting fatal prion diseases such as Creutzfeldt-Jakob disease. (See [1] and [2].) The drugs are quinacrine (used for malaria and giardiasis) and chlorpromazine (used for psychotic illnesses like schizophrenia).

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 [4], [5].) 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.

References:

  1. August 14, 2001 - Old Drugs Show New Promise in Combating Prion Diseases
  2. August 15, 2001 - UCSF Study Finds Two Old Drugs May Help Fight Prion Diseases - Original press release
  3. August 16, 2001 - Prion and on
  4. August 16, 2001 - Antibody Stops The Entire Process Of Prion Disease
  5. August 17, 2001 - Thwarting the Prion Protein
Backround


Genomic algorithms

The way that any genome, including large ones like the human genome, is sequenced is to first break the DNA into small fragments. The sequence in these fragments is easy to determine, but the problem is then to figure out what the original order of the sequence was. It is made more difficult by the fact that there are a lot of repetitive sequences in large genomes, and hence many identical small fragments. It's like trying to do a jigsaw puzzle with many almost identical pieces.

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.

References:

  1. August 14, 2001 - New path lays DNA puzzles bare
Background


Memory and aging

Bertrand Russell remarked in his autobiography (written late in life) that he recognized the decline in his mental powers from the time of his early 20s. New research shows that his observation was right on target. Of course, this really isn't news to anyone past the 40th or 50th birthday. The decline in mental function, however, begins much earlier, and doesn't become apparent to younger adults because (supposedly) they have more cognitive capacity than required for normal functioning.

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.

References:

  1. August 13, 2001 - Studies show that memory starts to decline in our mid-20s (This is the original press release.)
  2. August 14, 2001 - Memory Starts To Decline In Our 20s, Researcher Finds
  3. August 14, 2001 - Memory Starts To Decline In Our Mid-20s
  4. August 15, 2001 - Research Suggests That Memory Decline Begins in Mid-20s
Background


Terascale computing

IBM's 12.3 teraflop (trillion operations per second) supercomputer known as ASCI White has been switched on at the Lawrence Livermore National Laboratory in California. The supercomputer, estimated to be more powerful than the next three fastest existing computers combined, consists of 8192 IBM Power3 microprocessors, 6 TB (terabytes) of main memory, and 160 TB of disk storage. The main memory alone is about as much as in 50,000 high-end desktop computers.

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.

References:

  1. August 15, 2001 - IBM Unleashes World's Fastest Supercomputer
  2. August 15, 2001 - World's fastest computer boots up
Background


Cloning

In spite of the increased complexity of the human genome compared to that of other mammals, it now appears that cloning humans may be easier in at least one respect. One problem that has arisen in cloning many species is known as fetal overgrowth -- a fetus grows too fast, resulting in cancer or other types of fetal abnormalities, which can kill the fetus, the mother, or both. The problem results from the fact that in most mammals there is only one active copy of a gene that codes for a protein called insulin-like growth factor 2 receptor (IGF2R). This protein counteracts the growth-stimulating properties of another protein, insulin-like growth factor 2 (IGF2).

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.

References:

  1. August 15, 2001 - Genetic Difference May Make Humans Easier to Clone Than Sheep
  2. August 15, 2001 - Humans May Be Easier To Clone Than Sheep And Mice Because Of A Single Genetic Difference
  3. August 15, 2001 - Human cloning "safer" than animal cloning
Background


Language processing in the brain

A non-invasive brain-mapping technique known as functional magnetic resonance imaging has been used by Carnegie Mellon University scientists to demonstrate differences in brain processing that occur when subjects proces the exact same text by listening and by reading. The differences occur in processing related to comprehension of the text, not just in how the sensory signals are decoded. This research bears on the classic questions about language comprehension -- whether the means of delivery through eyes or ears makes a difference.

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.

References:

  1. August 15, 2001 - The Medium And The Message: Eyes And Ears Understand Differently
Background


Fine structure constant

The fine structure constant is one of a handful of "fundamental contstants" of physics. Usually denoted by the greek letter alpha, it has a value of approximately 1/137 and plays a role in some of the most basic physical equations. In particular, the energy levels of electrons in an atom, and hence the spacing of spectral lines characteristic of the atom, depend on alpha. A team of physicists led by John Webb of the University of New South Wales, Australia, now claims that alpha isn't exactly constant.

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.

References:

  1. August 9, 2001 - A Constant that Isn't Constant
  2. August 14, 2001 - Fundamental constant swells
  3. August 14, 2001 - When is a constant not a constant?
  4. August 15, 2001 - Keck Telescope Reveals an Inconsistent Constant
  5. August 15, 2001 - Light may have slowed down
  6. August 15, 2001 - Are the Laws of Physics Changing?
  7. August 15, 2001 - Cosmic Laws Like Speed of Light Might Be Changing, a Study Finds
  8. August 20, 2001 - Is Alpha, like Pi, a Fundamental Constant?
Background


Galaxy clusters

References:
  1. August 14, 2001 - Galaxy Cluster Found Using Gravitational Distortion, Suggests Independent Test of Accelerating Universe
  2. September 29, 2001 - Gravity's lens: Finding a dim cluster
Background


Active galactic nuclei

A team of astronomers using the Very Large Telescope (VLT) of the European Southern Observatory has obtained good images in infrared light of the central regions of three active galaxies (NGC 1097, NGC 1808 and NGC 5728). These images provide information about the flow of matter in the region of the central supermassive black holes within these galaxies.

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.

References:

  1. August 15, 2001 - Watching Heavy Black Holes Feed On Their Surroundings
Background


Lunar origins

Development of a theory of the origin of Earth's Moon was a difficult task, particularly after discoveries of the Apollo missions ruled out various early theories. However, for the last 25 years, the most generally accepted theory has been that the Moon formed out of debris left over from a collision between the young Earth and another planet during the early history of the solar system. Unfortunately, the size of the other planet and the time of the event have been hard to specify, and consequently computer simulations of the hypothesized event have been difficult to reconcile with observations, such as the size and angular momentum of the Earth-Moon system.

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.

References:

  1. August 15, 2001 - New clues to birth of the Moon
  2. August 15, 2001 - How did Earth get its moon?
  3. August 16, 2001 - Astronomers Model the Collision That Spawned the Moon
  4. August 16, 2001 - Moon making made easy
  5. August 16, 2001 - Mars-sized object probably created the Moon
  6. August 20, 2001 - Was Moon Born From Planet's Crash Into Earth?
Background


Photosynthesis

Photosythesis -- the chemical process that captures energy in plants and produces oxygen as a byproduct -- is an involved process utilizing scores of different molecules and many separate steps. The very first step is the capture of light energy by complexes of many proteins and dozens of chlorophyll molecules. Cyanobacteria and the chloroplasts of eukaryotic plant cells have two distinct complexes, known as Photosystem I (PS I) and Photosystem II (PS II), which are sensitive to slightly different wavelengths of light. Other photosynthetic prokaryotes have only PS I. Whether these two complexes are evolutionarily related has been unclear. But some evidence of a relationship has now been found.

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.

References:

  1. August 16, 2001 - Photosynthetic Link May Have Made Humankind Possible
Background


Melanoma

All cancers are ultimately alike in that uncontrolled cell growth in certain tissues leads to the failure of organs containing those tissues. But there are many paths which can lead to uncontrolled cell growth. In metastatic melanoma, a particularly deadly form of cancer, new findings throw a little more light on one step in the process for one particular path.

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.

References:

  1. August 16, 2001 - How Precancerous Moles Progress To Deadly Melanomas
  2. August 16, 2001 - Genetic Mutation May Be Key To Onset Of Deadly Skin Cancer
Background


AIDS

B cells are one of the main elements of the human immume system. They are also, along with other important parts of the immune system, seriously impaired from performing their normal function in the presence of an HIV infection. New findings presented in a paper whose lead author is Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), help explain what happens.

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

References:

  1. August 15, 2001 - Unique Subset Of B Cells In People Infected With HIV
  2. August 16, 2001 - NIAID Researchers Identify HIV-Induced Changes In B Cells
Background


Prions

References:
  1. August 15, 2001 - Drugs counter mad cow agent in cells
Background


Extrasolar planetary systems

More than 70 planets have been discovered oribiting other stars, but until now they have been in orbits unlike those of our solar system -- with the planets in very elliptical orbits, very close to the star, or both. Now for the first time, a system has been discovered containing more than one planet which generally resembles our solar system. A team of astronomers have detected a second planet orbiting 47 Ursae Majoris, and both planets are in circular orbits at a respectable distance from their star.

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.

References:

  1. August 15, 2001 - Newly Found Planet Hints at Solar System Like Ours in Big Dipper
  2. August 16, 2001 - Jupiter-Size Planet Found Orbiting Star In Big Dipper - original press release - original press release
  3. August 16, 2001 - Solar System Like Earth's Discovered in Big Dipper
  4. August 16, 2001 - Planet System Is Discovered With Orbits Like Earth's
  5. August 16, 2001 - Solar system much like our own is found
  6. August 16, 2001 - Planet hunt pays off
  7. August 17, 2001 - Astronomers Spot Jupiter-Size Planet Orbiting a Nearby Star
  8. August 17, 2001 - Berkeley Astronomers Detect Planet Orbiting Nearby Star
  9. August 18, 2001 - Astronomers spy familiar planetary system
Background


Cancer and the immune system

References:
  1. August 17, 2001 - Immune system blamed for cancer
Background


Copyright © 2001 by Charles Daney, All Rights Reserved