Paleontologists Discover Pterosaur Fossils In Sahara
Posted: Monday, December 22, 2003
Source: University Of Wisconsin-Madison
MADISON - When introduced to the world in 1998, human embryonic stem cells were considered heralds of a new age of transplant medicine. The prospect of an unlimited supply of cells and tissue of all kinds to treat disease captured public imagination and enthusiasm.
But lost in the glitz of the cells' potential to treat an array of devastating and sometimes fatal diseases was another quality that, when all is said and done, could match even the prospect of remaking transplant technology.
"Much of the excitement surrounding embryonic stem cell research focuses on their potential for transplantation to repair diseased organs," according to Thaddeus G. Golos, a University of Wisconsin-Madison professor of obstetrics and gynecology. "The cells are also a valuable model for beginning to understand the puzzles of early human development."
Indeed, a team led by Golos and colleagues at the Wisconsin National Primate Research Center has now taken some of the first critical steps to putting stem cells to use to understand early development and maternal and fetal health. Writing in the December online editions of the journal Endocrinology, the team led by Golos reports the development of a stem cell model that mimics the formation of the placenta during the earliest stages of human development.
The lab feat is important because prior to the advent of human embryonic stem cells, science's primary window to early development was through studies of mice and other animal models. Human embryonic stem cells and the work of Golos' team has now brought the very first stages of human development, as an embryo implants itself in the uterus, within reach of science. The work could one day help clinicians better understand and treat diseases of pregnancy such as preeclampsia, a disorder that occurs only during pregnancy and the postpartum period and that, by conservative estimates, kills at least 76,000 women and infants each year.
A key aspect of the work by the Wisconsin team was the creation of embryoid bodies, clumps of cells that arise when undifferentiated stem cells are removed from flat culture plates and grown in a suspended culture of proteins and hormones.
"Embryoid bodies are not embryos, but are spherical structures that form when embryonic stem cell colonies are released from the culture surface and grown in suspension," Golos explains.
In that environment, the team subsequently observed the development of trophoblast cells from the embryoid bodies. These specialized cells are the building blocks that lead to the formation of the placenta, which orchestrates a maternal environment that protects and nurtures a fetus during pregnancy.
Golos said that when the embryoid bodies were transferred into an artificial matrix that mimics the network of proteins that surrounds all of the cells in our bodies, his group observed a dramatic increase in trophoblasts' secretion of hormones associated with pregnancy.
"Moreover, the cell outgrowths that we observed from the embryoid bodies resembled aspects of the process by which placenta formation occurs as the embryo implants into the womb," Golos explains. "The opportunity to model these processes with embryonic stem cells is important because the earliest stages of placental function and how its development is controlled cannot be studied in human embryos or early human pregnancy."
By using embryonic stem cells to create a window to these very early stages of human development, scientists now can gain access to the cellular and chemical secrets of how such critical features as extraembryonic membranes, especially the placenta, grow and develop during pregnancy.
"These steps are essential for the establishment and maintenance of pregnancy," says Golos. "The establishment of mammalian pregnancy requires that the early embryo make a timely decision to begin to form the placenta, the first functional fetal organ."
The big picture, according to Golos, is that a better basic understanding of the events that occur during human pregnancy will ultimately lead to advances in maternal and fetal health. Down the road, such knowledge may lead to fewer birth defects, a lower incidence of miscarriage, and improved health for women and infants.
Co-authors of the new Endocrinology paper include Behzad Gerami-Naini, Oksana V. Dovzhenko, Maureen Durning and Frederick H. Wegner of the Wisconsin National Primate Research Center, and James A. Thomson of the Wisconsin National Primate Research Center and the UW-Madison Medical School's Department of Anatomy.
The March of Dimes Foundation and the National Institutes of Health supported the work of the Wisconsin team.
Send page by E-Mail The Evolution Of The Star Formation Rate
Posted: Monday, December 22, 2003
Source: European Southern Observatory (ESO)
The Color Of The Young Universe: VLT Study Gives Insight On The Evolution Of The Star Formation Rate
An international team of astronomers  has determined the colour of the Universe when it was very young. While the Universe is now kind of beige, it was much bluer in the distant past, at a time when it was only 2,500 million years old.
This is the outcome of an extensive and thorough analysis of more than 300 galaxies seen within a small southern sky area, the so-called Hubble Deep Field South. The main goal of this advanced study was to understand how the stellar content of the Universe was assembled and has changed over time.
Dutch astronomer Marijn Franx, a team member from the Leiden Observatory (The Netherlands), explains: "The blue colour of the early Universe is caused by the predominantly blue light from young stars in the galaxies. The redder colour of the Universe today is caused by the relatively larger number of older, redder stars."
The team leader, Gregory Rudnick from the Max-Planck Institut für Astrophysics (Garching, Germany) adds: "Since the total amount of light in the Universe in the past was about the same as today and a young blue star emits much more light than an old red star, there must have been significantly fewer stars in the young Universe than there is now. Our new findings imply that the majority of stars in the Universe were formed comparatively late, not so long before our Sun was born, at a moment when the Universe was around 7,000 million years old."
These new results are based on unique data collected during more than 100 hours of observations with the ISAAC multi-mode instrument at ESO's Very Large Telescope (VLT), as part of a major research project, the Faint InfraRed Extragalactic Survey (FIRES). The distances to the galaxies were estimated from their brightness in different optical near-infrared wavelength bands.
The full text of ESO PR 34/03, with one photo and all weblinks, is available at:
Observing the early Universe
It is now well known that the Sun was formed some 4.5 billion years ago. But when did most of the other stars in our home Galaxy form? And what about stars in other galaxies? These are some of the key questions in present-day astronomy, but they can only be answered by means of observations with the world's largest telescopes.
One way to address these issues is to observe the very young Universe directly - by looking back in time. For this, astronomers take advantage of the fact that light emitted by very distant galaxies travels a long time before reaching us. Thus, when astronomers look at such remote objects, they see them as they appeared long ago.
Those remote galaxies are extremely faint, however, and these observations are therefore technically difficult. Another complication is that, due to the expansion of the Universe, light from those galaxies is shifted towards longer wavelengths , out of the optical wavelength range and into the infrared region.
In order to study those early galaxies in some detail, astronomers must therefore use the largest ground-based telescopes, collecting their faint light during very long exposures. In addition they must use infrared-sensitive detectors.
Telescopes as giant eyes
The "Hubble Deep Field South (HDF-S)" is a very small portion of the sky in the southern constellation Tucanae ("the Toucan"). It was selected for very detailed studies with the Hubble Space Telescope (HST) and other powerful telescopes. Optical images of this field obtained by the HST represent a total exposure time of 140 hours. Many ground-based telescopes have also obtained images and spectra of objects in this sky area, in particular the ESO telescopes in Chile.
A sky area of 2.5 x 2.5 arcmin2 in the direction of HDF-S was observed in the context of a thorough study (the Faint InfraRed Extragalactic Survey; FIRES, see ESO PR 23/02). It is slightly larger than the field covered by the WFPC2 camera on the HST, but still 100 times smaller than the area subtended by the full moon.
Whenever this field was visible from the ESO Paranal Observatory and the atmospheric conditions were optimal, ESO astronomers pointed the 8.2-m VLT ANTU telescope in this direction, taking near-infrared images with the ISAAC multi-mode instrument. Altogether, the field was observed for more than 100 hours and the resulting images (see ESO PR 23/02), are the deepest ground-based views in the near-infrared Js- and H-bands. The Ks-band image is the deepest ever obtained of any sky field in this spectral band, whether from the ground or from space.
These unique data provide an exceptional view and have now allowed unprecedented studies of the galaxy population in the young Universe. Indeed, because of the exceptional seeing conditions at Paranal, the data obtained with the VLT have an excellent image sharpness (a "seeing" of 0.48 arcsec) and can be combined with the HST optical data with almost no loss of quality.
A bluer colour
The astronomers were able to detect unambiguously about 300 galaxies on these images. For each of them, they measured the distance by determining the redshift . This was done by means of a newly improved method that is based on the comparison of the brightness of each object in all the individual spectral bands with that of a set of nearby galaxies.
In this way, galaxies were found in the field with redshifts as high as z = 3.2, corresponding to distances around 11,500 million light-years. In other words, the astronomers were seeing the light of these very remote galaxies as they were when the Universe was only about 2.2 billion year old.
The astronomers next determined the amount of light emitted by each galaxy in such a way that the effects of the redshift were "removed". That is, they measured the amount of light at different wavelengths (colours) as it would have been recorded by an observer near that galaxy. This, of course, only refers to the light from stars that are not heavily obscured by dust.
Summing up the light emitted at different wavelengths by all galaxies at a given cosmic epoch, the astronomers could then also determine the average colour of the Universe (the "cosmic colour") at that epoch. Moreover, they were able to measure how that colour has changed, as the Universe became older.
They conclude that the cosmic colour is getting redder with time. In particular, it was much bluer in the past; now, at the age of nearly 14,000 million years, the Universe has a kind of beige colour.
When did stars form?
The change of the cosmic colour with time may be interesting in itself, but it is also an essential tool for determining how rapidly stars were assembled in the Universe.
Indeed, while the star-formation in individual galaxies may have complicated histories, sometimes accelerating into true "star-bursts", the new observations - now based on many galaxies - show that the "average history" of star-formation in the Universe is much simpler. This is evident by the observed, smooth change of the cosmic colour as the Universe became older.
Using the cosmic colour the astronomers were also able to determine how the mean age of relatively unobscured stars in the Universe changed with time. Since the Universe was much bluer in the past than it is now, they concluded that the Universe is not producing as many blue (high mass, short-lived) stars now as it was earlier, while at the same time the red (low mass, long-lived) stars from earlier generations of star formation are still present. Blue, massive stars die more quickly than red, low-mass stars, and therefore as the age of a group of stars increases, the blue short-lived stars die and the average colour of the group becomes redder. So did the Universe as a whole.
This behaviour bears some resemblance with the ageing trend in modern Western countries where less babies are born than in the past and people live longer than in the past, with the total effect that the mean age of the population is rising.
The astronomers determined how many stars had already formed when the Universe was only about 3,000 million years old. Young stars (of blue colour) emit more light than older (redder) stars. However, since there was just about as much light in the young Universe as there is today - although the galaxies are now much redder - this implies that there were fewer stars in the early Universe than today. The present study inidcates that there were ten times fewer stars at that early time than there is now.
Finally, the astronomers found that roughly half of the stars in the observed galaxies have been formed after the time when the Universe was about half as old (7,000 million years after the Big Bang) as it is today (14,000 million years).
Although this result was derived from a study of a very small sky field, and therefore may not be completely representative of the Universe as a whole, the present result has been shown to hold in other sky fields.
The research described in this Press Release will appear in the December 20 issue of the Astrophysical Journal ("The rest frame optical luminosity density, color, and stellar mass density of the Universe from z=0 to 3" by Gregory Rudnick et al.)
: Members of the team include Gregory Rudnick (MPA Garching, Germany), Hans-Walter Rix and Ignacio Trujillo (MPIA Heidelberg, Germany), Marijn Franx, Ivo Labbe, Natascha Foerster Schreiber, Arjen van de Wel, Paul van der Werf and Lottie van Starkenburg (Leiden Observatory, The Netherlands), Michael Blanton (New York University, USA), Emmanuele Daddi (ESO, Germany) and Pieter van Dokkum (Yale University, USA).
: In astronomy, the "redshift" denotes the factor by which the lines in the spectrum of an object are shifted towards longer wavelengths. Since the redshift of a cosmological object increases with distance, the observed redshift of a remote galaxy also provides an estimate of its distance.
The original news release can be found here.
Send page by E-Mail Science's Breakthrough Of The Year
Posted: Saturday, December 20, 2003
Source: American Association For The Advancement Of Science
Science's Breakthrough Of The Year: Illumination Of The Dark, Expanding Universe
In 2003, new evidence cemented the bizarre idea that the universe is made mostly of mysterious "dark matter," being stretched apart by an unknown force called "dark energy." This set of discoveries claims top honors as the Breakthrough of the Year, named by Science and its publisher, AAAS, the nonprofit science society.
These insights into our "dark" universe plus nine other research advances make up Science's top ten scientific developments in 2003, chosen for their profound implications for society and the advancement of science. The Top Ten list appears in the journal's 19 December issue.
This year, information from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite and the Sloan Digital Sky Survey (SDSS) telescopes confirmed some of cosmologists' strangest proposals about the fate of the universe.
"The implications of these discoveries about the universe are truly stunning. Cosmologists have been trying for years to confirm the hypothesis of a dark universe. Science is glad to recognize their success in this effort as the Breakthrough of the Year for 2003," said Don Kennedy, Editor-in-Chief of Science.
Those proposals entered the spotlight five years earlier, when Science's 1998 Breakthrough of the Year honored the discovery that the universe was expanding. Such an expansion would likely be driven by a "dark energy" that counters the effects of gravity. At the time, however, many cosmologists were wary of this strange idea.
Their doubts were dispelled in 2003. WMAP took the most detailed picture ever of the cosmic microwave background -- the light emitted by the universe during the first instant of its existence. By analyzing patterns in this light, researchers concluded that the universe is only 4 percent ordinary matter. Twenty-three percent is dark matter, which astrophysicists believe is made up of a currently unknown particle. The remainder, 73 percent, is dark energy.
WMAP also nailed down other basic properties of the universe, including its age (13.7 billion years old), expansion rate and density.
The SDSS, an effort to map out a million galaxies, also made major contribution to our understanding of the universe this year. By analyzing how galaxies are spread out through space, the researchers can see if the galaxies are being pulled apart by dark energy or pushed together by gravity.
In October, the SDSS team reported its analysis of the first quarter-million galaxies. Its conclusion was the same as WMAP's: the universe is dominated by dark energy.
Science also salutes nine other scientific achievements of 2003. Except for the first runner up, the others are in no particular order.
Cracking Mental Illness: Researchers identified particular genes that reliably increase one's risk of inherited disorders, such as schizophrenia, depression and bipolar disorder. Scientists are now working to understand how these genes can distort the brain's information processing and prod someone into mental illness. Researchers hope to understand brain biases underlying mental illnesses well enough to design drugs to repair them.
Climate Change Impacts: Global warming was no longer an abstract concept in 2003. Scientists reported melting ice, droughts, decreased plant productivity, and altered plant and animal behavior.
RNA Advances: In 2003, Scientists explored how small RNAs, Science's breakthrough of 2002, impact a cell's behavior, from early development to gene expression. Harnessing the power of "small interfering RNAs" may help researchers combat diseases such as HIV and hepatitis by controlling specific protein production.
Zooming in on Single Molecules: New collaborations between biologists and physicists captured the activities of individual molecules inside cells. Research this year offered a look at molecular motors, colored nanocrystal tags attached to cell receptors and a single enzyme digesting DNA.
Starbursts and Gamma Rays: Scientists improved our understanding of the most energetic explosions in the universe: tremendous blasts of energy called gamma ray bursts. Astronomers confirmed the connection between gamma ray bursts and supernovas--explosions of massive stars--when they spotted the unmistakable fingerprint of a supernova in the glow of a bright gamma ray burst. NASA's Swift satellite set for launch in mid-2004 should catch gamma ray bursts at five times the rate of any previous mission.
Spontaneous Sperm and Egg Cells: The surprising discovery that mouse embryonic stem cells can develop into both sperm and eggs may help scientists learn how these sex cells develop and why some kinds of infertility arise. The possibility that human embryonic stem cells might someday become a source for human eggs also raised serious ethical questions.
Left-Handed Materials: After two years of debate, several research teams confirmed that certain high-tech materials can bend light and other electromagnetic radiation in the "wrong" direction. Scientists used this new class of materials to produce an inverse Doppler Effect and are also working to craft better lenses.
The Self-Reliant Y Chromosome: In 2003, the genetic sequence of the human male Y chromosome revealed why this loner chromosome doesn't need a partner. It has duplicate genes, arranged as mirror-image "palindromes." Thus, when mutations arise and a new gene copy is needed, a twin copy is on-hand.
Breakthrough Cancer Therapies?: In June of 2003, researchers announced that an antiangiogenesis drug, given with conventional chemotherapy drugs in a large clinical trial, prolonged the lives of patients with advanced colon cancer. Antiangiogenesis drugs starve tumors by preventing blood vessel growth. With around 60 different antiangiogenesis drugs currently in clinical trials against a wide variety of cancers, researchers and patients now appear poised to reap the benefits of angiogenesis research.
Special SARS Section: Severe acute respiratory syndrome (SARS) clamored onto the world stage in March 2003 after first appearing in November 2002. SARS served as a reminder that new infectious diseases can emerge at any time--and that they don't have to sicken a lot of people to choke national economies. Thanks to worldwide collaboration, scientists definitively nailed the agent, a member of the coronavirus family, only five weeks after the World Health Organization sounded a global alarm. In the end, low-tech public health measures, such as strict isolation of patients, eventually cornered the virus after more than 8,400 reported cases and more than 916 deaths.
Science's Breakdown of the Year emerged on 1 February 2003, when the space shuttle Columbia disintegrated as it re-entered the atmosphere after a science mission. The tragedy left seven dead, the shuttle fleet grounded and NASA's future in question. Much of 2004 could be dedicated to a reexamination of NASA's civil space program.
Where Researchers Might Soar in 2004: As in previous years, Science highlighted areas to watch in 2004. This year, their choices include three planned Mars landings, microbiology and genomics for biodefense, more insights into the human genome, open access scientific journals, soils' impact on climate change and sustainable agriculture, the debate over the costs and benefits of tighter security and anti-terror measures in the realm of science, and studies of the heavy "bottom" quark.
Founded in 1848, AAAS has worked to advance science for human well-being through its projects, programs, and publications, in the areas of science policy, science education and international scientific cooperation. AAAS and its journal, Science, report nearly 140,000 individual and institutional subscribers, plus 272 affiliated organizations in more than 130 countries, serving a total of 10 million individuals. Thus, AAAS is the world's largest general federation of scientists. Science is an editorially independent, multidisciplinary, peer-reviewed weekly that ranks among the world's most prestigious scientific journals. AAAS administers EurekAlert! (http://www.eurekalert.org), the online news service, featuring the latest discoveries in science and technology.
"Dark Energy" Dominates The Universe
Galaxy Cluster Surveys May Help Explain "Dark Energy"
Chandra Probes Nature Of Dark Matter
Send page by E-Mail Proof of Our Exploding Universe
Posted: Friday, December 19, 2003
Science breakthrough of the year: proof of our exploding universe
Tim Radford, science editor
Friday December 19, 2003
Welcome to the dark side. Around 73% of the universe is made not of matter or radiation but of a mysterious force called dark energy, a kind of gravity in reverse. Dark energy is listed as the breakthrough of the year in the US journal Science today.
The discovery - in fact a systematic confirmation of a puzzling observation first made five years ago - paints an even more puzzling picture of an already mysterious universe. Around 200bn galaxies, each containing 200bn stars, are detectable by telescopes. But these add up to only 4% of the whole cosmos.
Now, on the evidence of a recent space-based probe and a meticulous survey of a million galaxies, astronomers have filled in at least some of the picture.
Around 23% of the universe is made up of another substance, called "dark matter". Nobody knows what this undetected stuff could be, but it massively outweighs all the atoms in all the stars in all the galaxies across the whole detectable range of space. The remaining 73% is the new discovery: dark energy. This bizarre force seems to be pushing the universe apart at an accelerating rate, when gravitational pull should be making it slow down or contract.
"The implications for these discoveries about the universe are truly stunning," said Don Kennedy, the editor of Science. "Cosmologists have been trying for years to confirm the hypothesis of a dark universe."
Sir Martin Rees, Britain's astronomer royal, called it a "discovery of the first magnitude".
The findings were made by an orbiting observatory called the Wilkinson Microwave Anisotropy Probe (WMAP). This measured tiny fluctuations in the cosmic microwave background, in effect the dying echoes of the Big Bang that launched time, space and matter in a tiny universal fireball.
These painstaking measurements were then backed up by the telescopes of the Sloan Digital Sky Survey, which mapped a million galaxies to see how they clumped together or spread out. Both confirmed that dark energy must exist.
The findings settle a number of arguments about the universe, its age, its expansion rate, and its composition, all at once. Thanks to the two studies, astronomers now believe the age of the universe is 13.7bn years, plus or minus a few hundred thousand. And its rate of expansion is a bewildering 71km per second per megaparsec. One megaparsec is an astronomical measure, totting up to 3.26m light years. Something latent in space itself is acting as a form of antigravity, exerting a push on the universe, rather than a pull.
Dark matter was proposed more than 20 years ago when it became clear that all the galaxies behaved as if they were far more massive than they seemed to be. All sorts of explanations - black holes, brown dwarfs and undetectable particles that are very different from atoms - have been suggested. None has been confirmed.
But dark matter exists, all the same. The dark energy story began in 1998 when astronomers reported that the most distant galaxies seemed to be receding far faster than calculations predicted. A study of a certain kind of supernova confirmed that they had not been misled: the universe was indeed expanding ever faster, rather than decelerating.
The discovery that some unexpected and undetectable force was pushing the fabric of space apart seemed to confirm a famous observation decades ago by the British scientist JBS Haldane: "The universe is not only queerer than we suppose. It is queerer than we can suppose." It once again raised profound questions about the nature of the universe: about space, and time, and energy, and matter. And it set the theorists on the hunt first for an explanation, and then for an experiment that would confirm their hypothesis.
So they turned once again to the original evidence for the Big Bang, the cosmic microwave background radiation. This is the original blaze of creation, cooled to minus 270 C - just about 3 C above absolute zero. Several lines of research, including experiments in the Antarctic and from high-flying balloons, began to provide a clearer picture: the universe simply had to consist of something more than just atoms and so-called dark matter.
"But WMAP, with superbly precise data beamed back from a little spacecraft a million miles away, has made the evidence more precise," said Sir Martin, of the Institute of Astronomy at Cambridge.
"The dark energy is spread uniformly through the universe, latent in empty space. Its nature is a mystery. Whereas there's a real chance of learning what the dark matter is within the next five to 10 years, I'd hold out less hope of understanding the dark energy unless or until there's a unified theory that takes us closer to the 'bedrock' of space and time."
Send page by E-Mail The Earliest Known Relative Of Marsupial Mammals
Posted: Thursday, December 11, 2003
Source: Carnegie Museum Of Natural History
Researchers Discover The Earliest Known Relative Of Marsupial Mammals
Pittsburgh -- An International team, including scientists from Carnegie Museum of Natural History, have discovered the most primitive and oldest know relative of all marsupial mammals.
In an article published today in Science, the team of American and Chinese scientists describe a 125 million year old fossilized skeleton of Sinodelphys szalayi, ([Sino] - Latin for China, [delphys] - Greek term used for basal marsupial species; [szalayi] - in honor of Professor F.S. Szalay, a leading expert on mammalian skeletal evolution.).
"This mammal could be the great grand aunt or uncle, or it could be the great grandparent of all marsupial mammals," said Dr. Zhe-Xi Luo, curator of Vertebrate Paleontology at Carnegie Museum of Natural History and the lead author of the paper.
Modern marsupials and their extinct relatives make up an important mammalian lineage, known as metatherians, consisting of mammals that are more closely related to modern marsupial mammals (such as opossum, kangaroos and koala) than to placentals (such as humans, rodents and whales). Modern marsupials are a significant part of the larger metatherian mammal group, and are the descendants of the extinct metatherians that lived during the age of dinosaurs, known as the Mesozoic.
With over 270 species, marsupials are the second most diverse mammal group (after placentals with over 4300 species). Marsupials and placentals are both therians mammals characterized by live-birth fetuses, yet they have different reproductive strategies.
Placentals produce better-developed fetuses after longer gestation. In contrast, marsupials give birth the less mature fetuses, and then nurse them for longer periods of time, often in the mother's "marsupial" pouch.
Today marsupials are present mostly in Australia, New Zealand and New Guinea, and in South America. One species, the Virginia opossum, is present in North America. However, in the age of dinosaurs, fossil relatives of marsupials evolved in Asia and North America, before marsupials spread to the rest of the world after the dinosaur extinction.
Prior to the discovery of Sinodelphys, the previously earliest metatherian fossils were some isolated teeth from the 110 million year old sediments of North America. The oldest jaw fragments of metatherians were from deposits of Uzbekistan 90 million years in age. The previously oldest skeletal fossil is from Mongolia and is 75 million years in age.
"The newly discovered Sinodelphys extends the duration for the marsupial lineage by 15 million years, and the earliest record of metatherian skeleton by 50 million years," said Dr. Luo. "This new fossil provided precious, new information about the skeletal anatomy, function, and habits of the earliest metatherians, and sheds light on the evolution of all marsupial mammals."
"The earliest fossils of metatherians are extremely important for scientific studies on the origins of all marsupial mammals, said Dr. John Wible, curator of Mammals at Carnegie Museum of Natural History and a co-author of the paper. "Because marsupials and placentals are close to each other and they dominated the world after the extinction of dinosaurs, the earliest metatherian fossils are also relevant for the understanding the divergence of marsupials and placentals, an important event in the history of vertebrate life."
A nearly complete skeleton of Sinodelphys, preserved on a shale slab, was found in the Mesozoic Yixian Formation in western Liaoning Province of China. The fossil is estimated to be 125 million years in geological age. Around the skeleton are well-preserved impressions of fur and some carbonized soft-tissues.
The mouse-sized animal was about 15 cm (about 6 inches) long and weighed 25 to 30 grams (one ounce). Marsupial-like features can be found in the wrist, anklebones, and in the anterior teeth. The dental features indicate that Sinodelphys ate insects and worms, much like modern-day small mammals.
As with modern tree-dwelling animals, Sinodelphys' shoulder, limbs and feet suggest that it was quite capable of climbing. It was adapted to climbing lower branches of trees and bushes. It lived in woods or shrubs on the lakeshore or riverbank and scurried on uneven surfaces on the ground.
Co-existing with Sinodelphys were the feathered theropod dinosaurs and giant sauropods. There were also pterosaurs, primitive birds, amphibians, reptiles, fish, insects, and diverse plants. Sinodelphys was one of several mammals in the Yixian biota, including: the earliest-known placental-relative Eomaia, the symmetrodonts Zhangheotherium and Maotherium, the eutriconodonts Jeholodens and Repenomamus, and the multituberculate Sinobaatar.
"Interestingly, the more primitive mammals of the Yixian feathered dinosaur fauna were adapted to terrestrial or ground dwelling living," said Dr. Wible. "But only the derived eutherian Eomaia and metatherian Sinodelphys were scansorial or climbing mammals. This suggests that scansorial adaptations were important in the earliest divergence of the modern marsupials and placentals."
A collaborative team of Chinese and American scientists accomplished the discovery and research on Sinodelphys. The Chinese research team was led by Dr. Qiang Ji of Nanjing University and the Chinese Academy of Geological Sciences. The American research team includes Dr. Zhe-Xi Luo and Dr. John Wible of the Carnegie Museum of Natural History.
This research was supported by funding from the Ministry of Land Resources and Ministry of Science and Technology of People's Republic of China (to Prof. Q. Ji), the National Science Foundation of USA (to Z.-X. Luo and J. R. Wible), the National Geographic Society (to Z.-X. Luo), and the funding from Carnegie Museum.
The original news release can be found here.
Send page by E-Mail Trail Of Black Holes and Neutron Stars
Posted: Tuesday, December 9, 2003
Source: NASA/Marshall Space Flight Center
Trail Of Black Holes and Neutron Stars Points To Ancient Collision
An image of an elliptical galaxy by NASA's Chandra X-ray Observatory has revealed a trail of black holes and neutron stars stretching more than fifty thousand light years across space. The trail of intense X-ray sources is evidence that this apparently sedate galaxy collided with another galaxy a few billion years ago.
"This discovery shows that X-ray observations may be the best way to identify the ancient remains of mergers between galaxies," said Lars Hernquist of the Harvard-Smithsonian Center for Astrophysics in Cambridge (CfA), Massachusetts, and a coauthor on an article on the galaxy NGC 4261 in an upcoming issue of The Astrophysical Journal Letters. "It could be a significant tool for probing the origin of elliptical galaxies."
"From the optical and radio images, we knew something unusual was going on in the nucleus of this galaxy, but the real surprise turned out to be on the outer edges of the galaxy," said Andreas Zezas, also of CfA, and lead-author of the paper on NGC 4261. "Dozens of black holes and neutron stars were strung out across space like beads on a necklace."
The spectacular structure is thought to represent the aftermath of the destruction of a smaller galaxy that was pulled apart by gravitational tidal forces as it fell into NGC 4261. As the doomed galaxy fell into the larger one, large streams of gas were pulled out into long tidal tails.
Shock waves generated as these tidal tails fell into the larger galaxy triggered the formation of large numbers of massive stars which over the course of a few million years evolved into neutron stars or black holes.
The origin of elliptical galaxies has long been a subject of intense debate among astronomers. The currently favored view is that they are produced by collisions between spiral galaxies. Computer simulations of galaxy collisions support this idea, and optical evidence of tails, shells, ripples, arcs and other structures have been interpreted as evidence for this theory. However the optical evidence rather quickly fades into the starry background of the galaxy, whereas the NGC 4261 X-ray observations show that the X-ray signature may linger for hundreds of millions of years.
NGC 4261 is approximately 100 million light years away from Earth. The data for these results were taken from the Chandra archive. NGC 4261 was originally observed with the Advanced CCD Imaging Spectrometer on May 6, 2000. Other members of the research team were Pepi Fabbiano and Jon Miller, both from the CfA.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.
Additional information and images are available at: http://chandra.harvard.edu/ and http://chandra.nasa.gov/
Send page by E-Mail Left Side Of Brain Activates Speech From Birth
Posted: Thursday, December 4, 2003
Source: University Of California - Los Angeles
For the first time, researchers have used functional magnectic resonance imaging (fMRI) to investigate infantbrain activity in response to speech. They found that, almost from birth, the brain's left hemisphere plays the leading role in processing most language functions. Presented Dec. 2 at the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), these preliminary findings challenge the previously held belief that left-hemisphere dominance doesn't develop fully until puberty.
"Language lateralization seems to be established almost from birth," said Shantanu Sinha, associate professor of radiology at the David Geffen School of Medicine at UCLA, where the study is ongoing.
Lateralization is the activation of a function, such as speech, from the right or left side of the brain.
"To the best of our knowledge, this is the first time fMRI has been used to study infants," Sinha said. "Using fMRI, we can non-invasively study the neuronal response of newborns to stimulation of different kinds, without any ionizing radiation or pharmaceutical injenctions."
As part of a larger, longitudinal study monitoring the cognitive development of infants with brain injury from birth to age 2, the researchers performed fMRI exams on 42 infants with documented brain injury. The fMRI analysis included cases only where both sides of the brain were equally capable of developing, and excluded children with brain trauma evident on the MR images.
The infants were asleep but not sedated during the procedure. During fMRI, the infants listened through headphones to tapes consisting of scanner noise, nonsense speech and "motherese" speech. The experiments were not sensitive enough to establish whether the infant brains were able to distinguish between the two types of speech. However, definite left-hemisphere-dominant activation patterns appeared during the portions of the tapes containing speech, as opposed to during the portions containing scanner noise.
These early findings challenge the conventional theory that lateralization of language to the left hemisphere is progressive until puberty, starting from an initial state in which neither hemisphere dominates.
"Detailed knowledge about the neural mechanisms associated with increasing levels of speech should prove useful in the study of developmental language disorders, which are the single largest handicapping condition of childhood," Sinha said. "The mapping of specific brain-language relationships should foster understanding of the mental process underlying language itself."
Sinha's co-authors, all from UCLA, included Susan Bookheimer, Meena Garg, Lina Badr and John Grinstead. The National Institutes of Health funded the research.
RSNA is an association of more than 35,000 radiologists, radiation oncologists and related scientists committed to promoting excellence in radiology through education and by fostering research, with the ultimate goal of improving patient care.
The original news release can be found here.
Send page by E-Mail A Window On Africa's "Missing Years"
Posted: Wednesday, December 3, 2003
Source: National Science Foundation
New Fossils From Ethiopia Open A Window On Africa's "Missing Years"
ARLINGTON, Va. -- An international team of researchers has announced the discovery of new fossils from the highlands of Ethiopia. The fossils fill a long-standing gap in scientists' understanding of the evolution of African mammals. The results are reported in this week's issue of the journal Nature.
The team is composed of researchers from several U.S. universities, including the University of Texas, Washington University, and the University of Michigan, as well as Addis Ababa University and the National Museum, both in Ethiopia. The project is supported by the National Science Foundation (NSF), the National Geographic Society, the Leakey Foundation, and the Ethiopian Ministry of Culture.
"The work of this team continues to reveal the extremely rich fossil record encased in East Africa's rocks," says Rich Lane, program director in NSF's division of earth sciences, which funded the research. "It also sheds light on the role pre-modern animals played in establishing the worldwide distribution of mammals today."
The dynamics of animal populations from 24 million to 32 million years ago has long stood as one of the most poorly known for all of Africa and Arabian, says John Kappelman, a paleontologist at the University of Texas and the project's leader.
During that time period, today's Red Sea had not yet begun to rift open and Africa and Arabia were still joined as a single continent that was isolated from the other landmasses by surrounding oceans and seas.
"These are the 'missing years' for Afro-Arabia," Kappelman adds, "and what, exactly, happened to mammals during this 8-million-year period has long remained a mystery to science."
Unlike well-publicized paleontological work reported from much younger rocks in Ethiopia's fossil-rich Rift Valley, this project is based in the highlands of the northwestern part of the country. The rugged terrain is some 2,000 meters in elevation and consists of massive flows of basalt lava that poured out of the Earth about 30 million years ago. The sediments that contain the fossils were deposited on top of these basalts and are now exposed among agricultural fields in stream and gully cuts.
"Geologists have known about the sediments in this region for nearly 100 years," says scientist Mulugeta Feseha of Addis Ababa University, "but it wasn't until we began our study that fossil mammals were discovered."
The international team relied on high-resolution satellite imagery to find sedimentary rocks located far from the nearest roads and then recorded the position of the fossils with GPS technology. Peter Copeland, of the University of Houston, determined the ages of the volcanic rocks found with the sediments to be 27 million years old.
Several of the newly discovered fossil mammals mark the earliest evidence for some of today's African mammals, while others represent the last holdouts of species thought to be extinct long before. The team was surprised for example, to find several species of primitive proboscideans—very distant cousins of today's elephants that were thought to be long extinct. Even more surprising, they were found living side by side with more advanced species that are the ancestors of today's elephants.
"The story of elephant evolution is one that we have long suspected to have occurred entirely in Africa," says scientist William Sanders of the University of Michigan, "but these new fossils provide the evidence that we needed to lock down this story. These more advanced elephants were much smaller than today's African elephants," he continued, "but at nearly 1,000 kg—about that of a medium-sized Texas longhorn—they were still a bit too big to keep in your backyard."
Some of the other fossil mammals are even more bizarre. Perhaps the most unusual of these is the arsinoithere, an animal larger than today's rhino with a pair of massive bony horns on its snout. This species is also a holdover from much earlier times, but the new discoveries show that it too survived through the period of the missing years.
"If this animal was still alive today it would be the central attraction at the zoo," says paleontologist Tab Rasmussen of Washington University.
The new discoveries from Ethiopia show that mammals of Afro-Arabia continued to evolve and produce new species on this isolated continent during the missing years, but the clock was ticking for many of the more primitive forms.
"At about 24 million years ago the continent of Afro-Arabian began to dock with Europe and Asia," says Kappelman, "and we believe that event set into motion both the eventual extinction of the more primitive species as well as the modernization of the rest of the African fauna."
The arsinoitheres and more primitive proboscideans became extinct, perhaps being out- competed by the invading species, while the ancestors of today's elephants flourished in spite of the new immigrants and managed to carry their adaptations out of Afro-Arabia to successfully colonize the rest of the world.
"More fossil localities closer in age to this major event are needed to fully evaluate the competing hypotheses," says Kappelman, "and we are now convinced that the fossils are out there waiting to be found."
The original news release can be found here.
Send page by E-Mail Chromosomes Are 'Nibbled' Before They Fuse
Posted: Wednesday, December 3, 2003
Source: Johns Hopkins Medical Institutions
Chromosomes Are 'Nibbled' Before They Fuse, Researchers Report
Overturning 60 years of scientific presumption, new evidence from Johns Hopkins scientists shows that enzymes nibble away at chromosomes when the chromosomes' protective tips, called telomeres, get too short.
Much like the plastic tips on shoelaces, telomeres protect the ends of chromosomes. When telomeres get too short, cells usually die. If they don't, the unprotected ends drag the chromosomes through an ugly assortment of fusions that lead to rearrangements, deletions and insertions that scramble the cell's genetic material and can lead to cancer. Until now, scientists had presumed that the fusions were the first thing to happen when telomeres stop protecting the chromosomes.
"We have always thought that if we can understand how shortened telomeres create genomic instability, we might be able to find targets in that process to push abnormal cells toward death and away from trying to repair themselves," says Carol Greider, Ph.D., professor and director of molecular biology and genetics at the Johns Hopkins School of Medicine. "Now it turns out that what we've always thought was the first step in the process is not the first step at all."
Writing in the December issue of Molecular and Cellular Biology, Greider and Hopkins graduate student Jennifer Hackett describe experiments with yeast which revealed that instead of just sticking, or fusing, end-to-end, chromosomes whose telomeres are too short are first nibbled by enzymes that normally clean up broken chromosomes.
"The fusion pathway was our favorite model of what goes wrong first when telomeres get too short. All the papers use that model to describe how loss of telomere function causes genomic instability," says Greider. "But just because we see a lot of something, doesn't mean it's the first thing that happens. We were quite surprised to find that fusion isn't the first effect of short telomeres."
In the traditional fusion scenario, officially called the "breakage-fusion-bridge" pathway, a cell interprets chromosomes with short telomeres as being broken, and sets in motion machinery to "fix" the break by fusing it to another exposed end. The unintended consequence of this fix is the connection of two chromosomes. If the fused chromosomes are pulled to opposite sides of a dividing cell, they form a bridge that breaks randomly as the cell divides, and the process begins again.
To test whether this was the correct or only scenario, Hackett inserted genetic markers into a yeast chromosome to reveal where genetic damage most often occurs when telomeres got too short. Instead of random damage, she discovered that the marker at the very end of the chromosome was most likely to be lost, and the marker closest to the chromosome's center the least likely.
"If fusion and breakage was the primary mechanism of gene loss, the pattern of loss would have been random -- each marker would have been just as likely as the others to be lost," explains Greider. "The marker loss we saw was not at all random, so we knew some other mechanism was at work."
Then, Hackett studied the engineered chromosomes in yeast missing an enzyme called exonuclease that normally recognizes and chews up broken chromosomes one strand of DNA at a time. Without the enzyme there were fewer chromosome rearrangements, offering strong evidence that this enzyme is doing the damage.
"Fusion happens, but it's not the primary mechanism that triggers gene loss after telomeres get too short," says Greider. "Instead, exonuclease activity causes the bulk of immediate gene loss."
To prove that fusion does indeed result in a random pattern of marker loss, Hackett made an artificial fused, or di-centric, chromosome, complete with genetic markers to identify which segments were destroyed. Since Hackett engineered it, this fused chromosome could not already have been "nibbled" by an exonuclease.
"We demonstrated that fused chromosomes do break randomly, at which point exonucleases attack the exposed ends," says Greider. "Fusion is a big part of what leads to major genomic instability when telomeres aren't working, but it's not the initial problem. Our discovery should spark researchers in the field to think along new lines."
Greider cautions that they still need to verify that the same mechanism is to blame for genomic instability in mammalian cells as in yeast. If so, identifying other proteins that work with exonucleases may offer a target to block the process and push cells in cancer toward death instead of genomic instability.
Hackett is now a postdoctoral fellow at Harvard Medical School. Hackett was funded by the Johns Hopkins Predoctoral Training Program in Human Genetics and Molecular Biology and the National Science Foundation. The studies were funded by the National Institute of General Medical Sciences, part of the National Institutes of Health.
On the Web: http://mcb.asm.org/
The original news release can be found here.
Send page by E-Mail New Drug To Treat Enlarged Prostate
Posted: Monday, December 1, 2003
Source: University College London
New Drug To Treat Enlarged Prostate Developed At University College London
Millions of men stand to benefit from a discovery by UCL scientists that could provide a breakthrough in the treatment of enlargement of the prostate (BPH). The UCL team has developed a new drug, Rho-kinase inhibitor that, in preliminary tests, has been found to treat the condition by both relaxing the prostate and stopping the growth of cells within it. Their findings are set out in the current issue of the Journal of Urology.
BPH affects approximately 85% of men over the age of 50 and causes frequent urination and irritation due to the obstruction of urine flow. The drugs currently available for treatment of BPH aim to either relax the prostrate or to reduce its size as two separate actions, and also have undesired hormonal effects. These effects, along with the need to take two separate treatments, often lead to problems of patient compliance. The discovery by the UCL scientists is novel in that this new drug can both relax the prostate and stop it from growing, with virtually no hormonal side effects.
Dr Selim Cellek, who led the investigation as a collaborative work between UCL's Wolfson Institute for Biomedical Research and its Institute of Urology and Nephrology, said: "We are very excited by this discovery, as it is a medical breakthrough which represents a major advance in treating a condition that affects such a large proportion of the population. We are still at the development stages and more research will be required before the new treatment becomes available. The next step will be to develop links with investors interested in developing this drug for the treatment of BPH.
"Research has shown that this type of compound can also be used to treat erectile dysfunction (impotence). The future for this line of research is therefore promising since men with an enlarged prostate often suffer from impotence. "
Malcolm Grant, UCL Provost, said: "The conversion of scientific results into new medicines is one of the main aims of the Wolfson Institute for Biomedical Research, and the early success of this project underlines the importance of collaborative research between academics and clinicians in achieving this goal. The practical application of UCL research is one of this University's great strengths."
News release issued by University College London.
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