Benefits Of Multiple Mates?
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Thought others would find this one interesting. Feel free to share your thoughts/ideas.

Research Sheds Light On Benefits Of Multiple Mates

New research could explain why females of many species have multiple partners. Published on November 21, 2008 in the journal Science, the study was carried out by a team from the Universities of Exeter (UK), Okayama (Japan) and Liverpool (UK).

Females of most species, including many mammals, mate with multiple partners. The driving forces for this practice, known as 'polyandry', have been a mystery for evolutionary biologists for decades. This research suggests that polyandry could be the result of females adapting to avoid producing offspring carrying selfish genetic elements that reduce male fertility.

The research team based the study on the fruitfly Drosophila pseudoobscura, which they bred over ten generations. Some males of this species carry a 'selfish gene' on their X chromosome that causes sperm carrying the Y-chromosome to fail. This means that males carrying this gene can only produce daughters, all of which carry the sperm damaging gene.

In this study females evolved to mate with more partners when they were exposed to males carrying this selfish gene. There was no way for the females to tell whether or not a potential mate carried the gene, but they evolved to re-mate more quickly. After ten generations, they re-mated after an average of 2.75 days, compared with 3.25 days among the original population. By mating more frequently, females ensure sperm from different males compete. This competition favours males without the sperm-damaging selfish genes, allowing females to bias paternity against these males.

Corresponding author Dr Nina Wedell of the University of Exeter said: "Multiple mating by females has puzzled biologists for decades. It's more risky and costs precious time and energy for females. Our study suggests that these significant costs are worthwhile because the female increases her chances of producing healthy offspring of both sexes that do not carry the selfish gene."

Selfish genes occur at random as a result of mutations. They spread quickly through populations because they subvert normal patterns of inheritance, increasing their presence in the next generation.

The researchers believe the findings have relevance for a range of species with polyandrous females, including some primates. Dr Nina Wedell explains: "Selfish genetic elements exist in all living organisms and many compromise male fertility. Our study could provide a new explanation for why polyandry is so remarkably widespread."

At this stage the researchers do not know what implications these findings might have for understanding human reproduction. However, it is possible that some types of male fertility disorder are caused by the manipulation of selfish genes.

This study was funded by the Natural Environment Research Council.
Adapted from materials provided by University of Exeter, via EurekAlert!, a service of AAAS.

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Did Mars Had Massive Oceans?
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Gamma-Ray Evidence Suggests Ancient Mars Had Massive Oceans

An international team of scientists who analyzed data from the Gamma Ray Spectrometer onboard NASA's Mars Odyssey reports new evidence for the controversial idea that oceans once covered about a third of ancient Mars.

"We compared Gamma Ray Spectrometer data on potassium, thorium and iron above and below a shoreline believed to mark an ancient ocean that covered a third of Mars' surface, and an inner shoreline believed to mark a younger, smaller ocean," said University of Arizona planetary geologist James M. Dohm, who led the international investigation.

"Our investigation posed the question, Might we see a greater concentration of these elements within the ancient shorelines because water and rock containing the elements moved from the highlands to the lowlands, where they eventually ponded as large water bodies?" Dohm said.

Mars Odyssey's GRS, or Gamma Ray Spectrometer, led by William Boynton of UA's Lunar and Planetary Laboratory, has the unique ability to detect elements buried as much as 1/3 meter, or 13 inches, below the surface by the gamma rays they emit. That capability led to GRS' dramatic 2002 discovery of water-ice near the surface throughout much of high-latitude Mars.

Results from Mars Odyssey and other spacecraft suggest that past watery conditions likely leached, transported and concentrated such elements as potassium, thorium and iron, Dohm said. "The regions below and above the two shoreline boundaries are like cookie cutouts that can be compared to the regions above the boundaries, as well as the total region."

The younger, inner shoreline is evidence that an ocean about 10 times the size of the Mediterranean Sea, or about the size of North America, existed on the northern plains of Mars a few billion years ago. The larger, more ancient shoreline that covered a third of Mars held an ocean about 20 times the size of the Mediterranean, the researchers estimate.

The potassium-thorium-iron enriched areas occur below the older and younger paleo-ocean boundaries with respect to the entire region, they said. The scientists used data from Mars Global Surveyor's laser altimeter for topographic maps of the regions in their study.

They are reporting their findings in the article, "GRS Evidence and the Possibility of Paleo-oceans on Mars." The article will be published in a special edition of Planetary and Space Science, which stems from a June 2007 workshop on Mars and its Earth analogs held in Trento, Italy. UA Regents' Professor Victor Baker and Boynton, and other scientists from the United States, Italy, Spain, South Korea and Canada are co-authors.

Scientific debate on the possible existence of ancient Martian oceans marked by shorelines was sparked by several studies almost 20 years ago. One such study, by Baker and colleagues at the UA Lunar and Planetary Laboratory, proposed that a few billion years ago, erupting magma unleashed floods far greater than Brazil's Amazon River. The floods ponded in the northern lowlands of Mars, forming seas and lakes that triggered relatively warmer and wetter conditions that lasted tens of thousands of years.

Scientists are driven to understand how and when water existed on Mars because water is critical to life.

Spacecraft images going back to Mariner 9 in the early 1970s and the Viking orbiters and landers later in the 1970s showed widespread evidence for a watery past for Mars. Images and other information from a flotilla of U.S. and European Mars orbiters have sharpened the details in the past decade, they added. Results from Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter highlight a water-and-ice-sculpted Martian landscape.

Scientists studying spacecraft images have a hard time confirming "shoreline" landforms, the researchers said, because Mars shorelines would look different from Earth's shorelines. Earth's coastal shorelines are largely a direct result of powerful tides caused by gravitational interaction between Earth and the moon, but Mars lacks a sizable moon. Another difference is that lakes or seas on Mars could have formed largely from giant debris flows and liquefied sediments. Still another difference is that Mars oceans may have been ice-covered, which would prevent wave action.

"The GRS adds key information to the long-standing oceans-on-Mars controversy," Dohm said. "But the debate is likely to continue well into the future, perhaps even when scientists can finally walk the Martian surface with instruments in hand, with a network of smarter spaceborne, airborne and ground-based robotic systems in their midst."
Adapted from materials provided by University of Arizona.



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Can We Mutate Viruses To Death?
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Forced Evolution: Can We Mutate Viruses To Death?

It sounds like a science fiction movie: A killer contagion threatens the Earth, but scientists save the day with a designer drug that forces the virus to mutate itself out of existence. The killer disease? Still a fiction. The drug? It could become a reality thanks to a new study by Rice University bioengineers.

The study, which is available online and slated for publication in the journal Physical Review E, offers the most comprehensive mathematical analysis to date of the mechanisms that drive evolution in viruses and bacteria. Rather than focusing solely on random genetic mutations, as past analyses have, the study predicts exactly how evolution is affected by the exchange of entire genes and sets of genes.

"We wanted to focus more attention on the roles that recombination and horizontal gene transfer play in the evolution of viruses and bacteria," said bioengineer Michael Deem, the study's lead researcher. "So, we incorporated both into the leading models that are used to describe bacterial and viral evolution, and we derived exact solutions to the models."

The upshot is a newer, composite formula that more accurately captures what happens in real world evolution. Deem's co-authors on the study include Rice graduate student Enrique Muñoz and longtime collaborator Jeong-Man Park, a physicist at the Catholic University of Korea in Bucheon.

In describing the new model, Deem drew an analogy to thermodynamics and discussed how a geneticist or drug designer could use the new formula in much the same way that an engineer might use thermodynamics formulas.

"Some of the properties that describe water are density, pressure and temperature," said Deem. "If you know any two of them, then you can predict any other one using thermodynamics.

"That's what we're doing here," he said. "If you know the recombination rate, mutation rate and fitness function, our formula can analytically predict the properties of the system. So, if you have recombination at a certain frequency, I can say exactly how much that helps or hurts the fitness of the population."

Deem, Rice's John W. Cox Professor in Biochemical and Genetic Engineering and professor of physics and astronomy, said the new model helps to better describe the evolutionary processes that occur in the real world, and it could be useful for doctors, drug designers and others who study how diseases evolve and how our immune systems react to that evolution.

One idea that was proposed about five years ago is "lethal mutagenesis." In a nutshell, the idea is to design drugs that speed up the mutation rates of viruses and push them beyond a threshold called a "phase transition." The thermodynamic analogy for this transition is the freezing or melting of water -- which amounts to a physical transition between water's liquid and solid phases.

"Water goes from a liquid to a solid at zero degrees Celsius under standard pressure, and you can represent that mathematically using thermodynamics," Deem said. "In our model, there's also a phase transition. If the mutation, recombination or horizontal gene transfer rates are too high, the system delocalizes and gets spread all over sequence space."

Deem said the new results predict which parameter values will lead to this delocalization.

A competing theory is that a mutagenesis drug may eradicate a virus or bacterial population by reducing the fitness to negative values. The new mathematical results allow calculation of this mechanism when the fitness function and the mutation, recombination and horizontal gene transfer rates are known.

Without theoretical tools like the new model, drug designers looking to create pills to induce lethal mutagenesis couldn't say for certain under what parameter ranges the drugs really worked. Deem said the new formula should provide experimental drug testers with a clear picture of whether the drugs -- or something else -- causes mutagenesis.

The research is supported by the Defense Advanced Research Projects Agency and the Korea Research Foundation.
Adapted from materials provided by Rice University.


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DNA Chunks, Chimps And Humans
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DNA Chunks, Chimps And Humans: Marks Of Differences Between Human And Chimp Genomes


ScienceDaily (Nov. 6, 2008) — Researchers have carried out the largest study of differences between human and chimpanzee genomes, identifying regions that have been duplicated or lost during evolution of the two lineages. The study, published in Genome Research, is the first to compare many human and chimpanzee genomes in the same fashion.

The team show that particular types of genes - such as those involved in the inflammatory response and in control of cell proliferation - are more commonly involved in gain or loss. They also provide new evidence for a gene that has been associated with susceptibility to infection by HIV.

"This is the first study of this scale, comparing directly the genomes of many humans and chimpanzees," says Dr Richard Redon, from the Wellcome Trust Sanger Institute, a leading author of the study. "By looking at only one 'reference' sequence for human or chimpanzee, as has been done previously, it is not possible to tell which differences occur only among individual chimpanzees or humans and which are differences between the two species.

"This is our first view of those two important legacies of evolution."

Rather than examining single-letter differences in the genomes (so-called SNPs), the researchers looked at copy number variation (CNV) - the gain or loss of regions of DNA. CNVs can affect many genes at once and their significance has only been fully appreciated within the last two years. The team looked at genomes of 30 chimpanzees and 30 humans: a direct comparison of this scale or type has not been carried out before.

The comparison uncovered CNVs that are present in both species as well as copy number differences (CNDs) between the two species. CNDs are likely to include genes that have influenced evolution of each species since humans and chimpanzees diverged some six million years ago.

"Broadly, the two genomes have similar patterns and levels of CNVs - around 70-80 in each individual - of which nearly half occur in the same regions of the two species' genomes," continues Dr Redon. "But beyond that similarity we were able to find intriguing evidence for key sets of genes that differ between us and our nearest relative."

One of the genes affected by CNVs is CCL3L1, for which lower copy numbers in humans have been associated with increased susceptibility to HIV infection. Remarkably, the study of 60 human and chimpanzee genomes found no evidence for fixed CNDs between human and chimp and no within-chimp CNV. Rather, they found that a nearby gene called TBC1D3 was reduced in number in chimpanzee compared to human: typically, there were eight copies in human, but apparently only one in all chimpanzees.

The authors suggest that it might be evolutionary selection of CNDs in TBC1D3 that have driven the population differences. Consistent with this novel observation, TBC1D3 is involved in cell proliferation (favoured category) and is on a core region for duplication - a focal point for large regions of duplication in human genome.

"It is evident that there has been striking turnover in gene content between humans and chimpanzees, and some of these changes may have resulted from exceptional selection pressures," explains Dr George Perry from Arizona State University and Brigham and Women's Hospital, another leading author of the study. "For example, a surprisingly high number of genes involved in the inflammatory response - APOL1, APOL4, CARD18, IL1F7, IL1F8 - are completely deleted from chimp genome. In humans, APOL1 is involved in resistance to the parasite that causes sleeping sickness, while IL1F7 and CARD18 play a role in regulating inflammation: therefore, there must be different regulations of these processes in chimpanzees.

"We already know that inactivation of an immune system gene from the human genome is being positively selected: now we have an example of similar consequences in the chimpanzee."

CNVs in humans and chimpanzees often occur in equivalent genomic locations: most lie in regions of the genomes, called segmental duplications, that are particularly 'fragile'. However, one in four of the 355 CNDs that the team found do not overlap with CNVs within either species - suggesting that they are variants that are 'fixed' in each species and might mark significant differences between human and chimpanzee genomes.

DNA Samples and analysis

The project used DNA samples from 30 chimpanzees (29 from W Africa, one from E Africa): the chimpanzee reference was produced using DNA from Clint, the chimpanzee whose DNA was used for the genome sequence.

Human DNA samples were obtained from following participants: ten Yoruba (Ibadan, Nigeria), ten Biaka rainforest hunter-gatherers (Central African Republic) and ten Mbuti rainforest hunter-gatherers (Democratic Republic of Congo). The human reference is a European-American male from the HapMap Project (NA10852).

CNVs and CNDs were detected using a whole-genome tilepath of DNA clones spanning the human genome used previously to map human CNVs: this platform can reveal structural variants greater than around 10,000 base-pairs in size.

This work was funded by the Wellcome Trust, the LSB Leakey Foundation, the Wenner-Gren Foundation for Anthropological Research, the National Institutes of Health, The University of Louisiana at Lafayette-New Iberia Research Center and the Howard Hughes Medical Institute.

The authors thank the Human Genome Diversity Project, the Coriell Institute for Medical Research, the Integrated Primate Biomaterials and Information Resource, New Iberia Research Center, and the Primate Foundation of Arizona for samples.


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Journal references:

1. The Chimpanzee Sequencing and Analysis Consortium. Initial sequence of the chimpanzee genome and comparison with the human genome. Nature, 2005; 437 (7055): 69 DOI: 10.1038/nature04072
2. Perry et al. Copy number variation and evolution in humans and chimpanzees. Genome Research, 2008; 18 (11): 1698 DOI: 10.1101/gr.082016.108

Adapted from materials provided by Wellcome Trust Sanger Institute.

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African Middle Stone Age

New Classification Of African Middle Stone Age

ScienceDaily (Nov. 3, 2008) — The Cologne archaeologist Dr. Ralf Vogelsang from the Africa Research Centre of the Institute of Prehistoric Archaeology and a team of international researchers have succeeded in dating layers in South Africa that provide information about stone tool innovation on the Middle Stone Age.

This archaeological epoch began at the same time as the earliest appearances of humans (homo sapiens sapiens), about 200,000 years ago, in Africa and differs from the European Middle Stone Age chronologically. It is categorized as an era of change and marked by the development of regional stone tool traditions, the appearance of many innovations and the emergence of significant new behaviour such as the production of art and jewellery.

It seems to be apparent that this surge in innovation is linked to the appearance of this new human form of anatomically more modern humans, who spread from Africa to Europe and superseded the Neanderthals. However, the chronological classification of the stone tool industry has always been very difficult.

With the help of the OSL method (Optically Stimulated Luminescence Dating) and under the direction of Dr. Zenobia Jacobs and Professor Richard Roberts from University of Wollongong (Australia), scientists have been able to date layers from new sites at the stone tool industries of Still bay and Howieson's Poort. The OSL method measured when grains of quartz were last irradiated by sunlight at these sites.

According to the results, both industries operated between 60,000 and 80,000 years ago, were short-lived and did not coexist. The reasons for the rise and fall of these two cultural groups has been unclear until now, however, climate change does not seem to have played a significant role.

Interestingly, the dispersion of modern man from Africa, which ultimately resulted in the in the supersession and extinction of the Neanderthals in Europe, occurred at the same time.

Journal reference:

1. Jacobs et al. Ages for the Middle Stone Age of Southern Africa: Implications for Human Behavior and Dispersal. Science, 2008; 322 (5902): 733 DOI: 10.1126/science.1162219

Adapted from materials provided by University of cologne, Universitaet zu Koeln.

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Marijuana and Liver Transplants?

Should Hepatitis C Patients Who Smoke Marijuana Be Eligible For Liver Transplants?

ScienceDaily (Oct. 24, 2008) — The pain is debilitating. The only option: smoking medical marijuana. That's the reality for many hepatitis C patients whose road to health includes a liver transplant. Although Canadian transplant centres are more willing than those in the United States, not everyone says yes to liver patients who smoke marijuana, and a University of Alberta researcher says that decision-making process is unacceptable.

Karen Kroeker, along with three other students at various universities, sent out surveys to a number of transplant clinics across the United States and Canada. Results found that the difference between the two countries were obvious in some patient groups: around 60 per cent of Canadian centres would either do the surgery or consider it for a liver transplant patient who smoked marijuana, while 70 per cent of U.S. transplant programs said absolutely not. Kroeker also found that patients in both countries, who have no social support—meaning they have no family, friends or a social worker—aren't likely to receive the organ they need.

The problem Kroeker has with these results: the lack of literature to support the surgeons' decision. As a result of her findings, which will be published in the November issue of Liver International, Kroeker says physicians need to determine eligibility criteria for liver-transplant patients that pertains directly to the likelihood of a patient rejecting the organ and is based only on empirical medical evidence.

When a patient is being reviewed for eligibility, whether they smoke marijuana shouldn't be a factor, she says. "If we have evidence to say the patients don't do well, then I think that's a reason to exclude people," Kroeker said.

She cites alcohol use as an example. When transplants first began to be performed, those who drank alcohol weren't eligible for a new liver. Kroeker's study found, however, that surgeons conducted studies on the topic of abstinence and liver health and, as a result of that research, transplant rules changed. If the patient has been sober for six months, 94 per cent of the clinics in North America will now consider transplantation.

The same goes for HIV-positive patients. "When they first started transplanting, HIV was an absolute contraindication. No one even considered transplantation because the disease was a death sentence at that time." Kroeker adds that's no longer the case and that there is research being conducted on post-transplant HIV-patients that will help determine the viability of transplants in HIV-positive patients.

In reference to her findings, Kroeker said, "I think there should be a large-scale study," because too-little research is available on post-transplant patients whose eligibility may currently be in question.

"Unless you actually perform transplants for those people, how would you know how they do?"
Adapted from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

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New Hope For Multiple Sclerosis Sufferers

A drug which was developed in Cambridge and initially designed to treat a form of leukaemia has also proven effective against combating the debilitating neurological disease multiple sclerosis (MS).


The study, led by researchers from the University of Cambridge, has found that alemtuzumab not only stops MS from advancing in patients with early stage active relapsing-remitting multiple sclerosis (RRMS) but may also restore lost function caused by the disease. The findings were recently published in the New England Journal of Medicine.

Alemtuzumab has a long connection with Cambridge, England. In 1984, Cambridge scientist Cesar Milstein was awarded the Nobel Prize for Physiology or Medicine, jointly with George Kohler, for inventing the technology to make large quantities of a desired type of monoclonal antibody. Further work in Cambridge, by Herman Waldmann and Greg Winter, led to the production of the first humanised monoclonal antibody for use as a medicine, Campath-1H, now known as alemtuzumab. It has been licensed for the treatment of chronic lymphocytic leukaemia, and has also been tested in several diseases where the immune system is overactive, such as multiple sclerosis.

The new study, which was funded by Genzyme and Bayer Schering Pharma AG, Germany , found that alemtuzumab reduces the number of attacks experienced by people with relapsing-remitting multiple sclerosis by 74 per cent over and above that achieved with interferon beta-1a, one of the most effective licensed therapies for similar cases of MS. More importantly, alemtuzumab also reduced the risk of sustained accumulation of disability by 71 per cent compared to interferon beta-1a.

Additionally, the investigators showed that many individuals in the trial who received alemtuzumab recovered some of their lost functions and so were less disabled after three years than at the beginning of the study, in contrast to worsening disability in the interferon beta-1a treated patients. These findings suggest that alemtuzumab may allow damaged brain tissue to repair, enabling the recovery of neurologic functions lost following poor recovery from previous MS attacks.

The new research shows that alemtuzumab is a much more effective treatment for early-stage RRMS than the currently approved drug interferon beta-1a. However, as the study was a Phase 2 clinical trial, additional research will need to be conducted before the drug is considered for approval in the treatment of MS.

"Alemtuzumab is the most promising experimental drug for the treatment of multiple sclerosis, and we are hopeful that the Phase 3 trials will confirm that it can both stabilize and allow some recovery of what had previously been assumed to be irreversible disabilities," says the principal investigator Alastair Compston, Professor of Neurology and the Head of the Department of Clinical Neurosciences at the University of Cambridge.

Multiple sclerosis is an autoimmune disease which is caused by the body's immune system attacking nerve fibres and their protective insulation, the myelin sheath, in the central nervous system. This damage prevents the nerves from 'firing' properly, and then leads to their destruction, resulting in physical and intellectual disabilities. Alemtuzumab works by destroying one population of white blood cell (lymphocytes) and, by shutting down the immune system, inhibits the damage to brain tissue that occurs in MS.

"The ability of an MS drug to promote brain repair is unprecedented. We are witnessing a drug which, if given early enough, might effectively stop the advancement of the disease and also restore lost function by promoting repair of the damaged brain tissue," says Dr Alasdair Coles, University Lecturer at the Department of Clinical Neurosciences, University of Cambridge who coordinated many aspects of the study.

The main side effect of treatment is, paradoxically, that people can develop other autoimmune diseases as the immune system gradually recovers following exposure to alemtuzumab. During the trial, 20% of people treated with alemtuzumab developed an over- or under-active thyroid gland. Rarely (3%) people developed a low platelet count and were vulnerable to bleeding. This complication led to one fatality during the trial. Although potentially very serious, this complication can be easily treated if recognised early.

The Phase 2 clinical study involved 334 patients who had been diagnosed with early-stage RRMS but had not previously been treated. Patients either received alemtuzumab (one of two dose levels intravenously for five days initially and three days of re-treatment 12 months later) or interferon beta-1a (given by injection three times per week). The patients were followed for three years to determine the efficacy of the treatments as well as the effect on the patients' disabilities.

MS affects almost 100,000 people in the United Kingdom, 400,000 in the United States and several million worldwide. Symptoms of the disease can include loss of physical skills, sensation, vision, bladder control, and intellectual abilities.

Background

History of alemtuzumab and Cambridge: Alemtuzumab (previously known as Campath-1H) was first created by academics at Cambridge University in the late 1970s. The drug was shown to be useful in treating leukemia by killing the cancerous white cells of the immune system. It was also used experimentally to treat autoimmune diseases, where the white cells of the immune system are not cancerous but are targeting and damaging normal parts of the body. It was believed that a 'short sharp shock' to the immune system by alemtuzumab would re-educate' the immune system and stop it from fighting the healthy tissues in the body.

Since 1991, Professor Alastair Compston, principal investigator of this study, has been exploring the use of alemtuzumab as an experimental treatment of multiple sclerosis. Dr Alasdair Coles joined the team in 1994 and has since had primary responsibility for most practical aspects of the work. The scientists initially treated individuals with severe forms of the disease in whom disability was already well advanced. Although alemtuzumab successfully stopped new attacks of multiple sclerosis in these people, their disability continued to get worse.

The doctors realized that once the immune system has attacked the insulating covering to the nerves in the brain (the myelin sheath), the consequent secondary damage to the underlying nerves continues unabated, even if the immune attack has been turned off by alemtuzumab. It was at this stage that they decided to treat people with much earlier multiple sclerosis, before there was too much permanent damage in the brain and spinal cord.

The clinical trial was sponsored by Genzyme, who own the rights to develop Campath® and have strongly supported the MS programme. Genzyme and Bayer Schering Pharma AG, Germany are co-developing alemtuzumab in oncology, multiple sclerosis and other indications. Bayer Schering Pharma AG, Germany holds exclusive worldwide marketing and distribution rights to alemtuzumab.

Relapsing-remitting multiple sclerosis (RRMS) is the most common form of MS. It is often followed by secondary-progressive MS (SPMS) which is a more disabling form of the disease.

Journal reference:

1. . Alemtuzumab versus Interferon beta-1a in Early, Relapsing-Remitting Multiple Sclerosis. New England Journal of Medicine, 23 October 2008

Adapted from materials provided by University of Cambridge.

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Stephen Hawking Stepping Down

Stephen Hawking Stepping Down From Academic Post


CAMBRIDGE, England — Cosmologist Stephen Hawking will retire from his prestigious post at Cambridge University next year, but intends to continue his exploration of time and space.

Hawking, 66, is Lucasian Professor of Mathematics, a title once held by the great 18th century physicist Isaac Newton.

The university said Friday that he would step down at the end of the academic year in September, but would continue working as Emeritus Lucasian Professor of Mathematics.

"We look forward to him continuing his academic work at the Department of Applied Mathematics and Theoretical Physics, playing a leading role in research in cosmology and gravitation," said Professor Peter Haynes, who heads the department.



Hawking became a scientific celebrity through his theories on black holes and the nature of time, work that he carried on despite becoming paralyzed by motor neurone disease.

University policy is that officeholders must retire at the end of the academic year in which they become 67. Hawking will reach that milestone on Jan. 8.

The Lucasian professorship post was founded in 1663 by Henry Lucas, who left his 4,000 books and land expected to yield 100 pounds a year to the university. King Charles II officially established the position in 1664.

Sir Isaac Newton was the second to hold the post. Paul Dirac, a specialist in quantum mechanics who predicted the existence of positron particles, had the title from 1932 to 1969.

Hawking was appointed to the chair in 1979.

His 1988 book, "A Brief History of Time," was an international best-seller; "A Briefer History of Time," intended to be more accessible, followed in 2005.

"George's Secret Key to the Universe," co-authored with Hawking's daughter Lucy, was published last year for the children's market.

Hawking first earned prominence for his theoretical work on black holes. Disproving the belief that black holes are so dense that nothing could escape their gravitational pull, he showed that black holes leak a tiny bit of light and other types of radiation, now known as "Hawking radiation."

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Moths Mimic Sounds To Survive
Current mood: amused

The research was conducted by Jesse Barber, a doctoral student in biology at Wake Forest. William E. Conner, professor of biology at Wake Forest, co-authored the study.

This is the first study to definitively show how an animal species uses acoustic mimicry as a defensive strategy.

The research was conducted by Jesse Barber, a doctoral student in biology at Wake Forest. William E. Conner, professor of biology at Wake Forest, co-authored the study.

In response to the sonar that bats use to locate prey, the tiger moths make ultrasonic clicks of their own. They broadcast the clicks from a paired set of structures called "tymbals." Many species of tiger moth use the tymbals to make specific sounds that warn the bat of their bad taste. Other species make sounds that closely mimic those high-frequency sounds.

"We found that the bats do not eat the good-tasting moths that make the similar sounds," said Barber, who has worked on this research for four years.

In the study, other types of moths that were similar in size to the sound-emitting moths, but did not make sounds, were gobbled up by the bats.
The researcher trained free-flying bats to hunt moths in view of two high-speed infrared video cameras to record predator-prey interactions that occur in fractions of a second. He also recorded the sounds emitted from each moth, as well as the sounds made by the bats.

All the bats quickly learned to avoid the noxious moths first offered to them, associating the warning sounds with bad taste. They then avoided a second sound-producing species even though it was not chemically protected. This is similar to the way birds avoid butterflies that look like the bad-tasting Monarch.

The two species of bats used were big brown bats and red bats. Barber raised the bats in the lab so behavior learned in the wild would not influence the results of the experiment.

Barber said anecdotal observations have suggested that animals such as snakes, owls and bees use acoustic mimicry. This study takes the next step and provides the definitive experimental evidence for how mimicking sounds helps an animal survive.

This research is to be published in the May 29 issue of the Proceedings of the National Academy of Sciences.

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When Under Attack, Plants Can Signal Microbial Friends For Help

Researchers at the University of Delaware have discovered that when the leaf of a plant is under attack by a pathogen, it can send out an S.O.S. to the roots for help, and the roots will respond by secreting an acid that brings beneficial bacteria to the rescue.

The finding quashes the misperception that plants are "sitting ducks"--at the mercy of passing pathogens--and sheds new light on a sophisticated signaling system inside plants that rivals the nervous system in humans and animals.

The research was led by Harsh Bais, assistant professor of plant and soil sciences at UD, former postdoctoral researcher Thimmaraju Rudrappa, who is now a research scientist at the DuPont Co., Kirk Czymmek, associate professor of biological sciences and director of UD's Bio-Imaging Center, and Paul Paré, a biochemist at Texas Tech University.

The study is reported in the November issue of Plant Physiology and also is featured on the journal's cover. Rudrappa is the lead author of the research paper.

"Plants are a lot smarter than we give them credit for," says Bais from his laboratory at the Delaware Biotechnology Institute.

"People think that plants, rooted in the ground, are just sitting ducks when it comes to attack by harmful fungi or bacteria, but we've found that plants have ways of seeking external help," he notes.

In a series of laboratory experiments, the scientists infected the leaves of the small flowering plant Arabidopsis thaliana with a pathogenic bacterium, Pseudomonas syringae. Within a few days, the leaves of the infected plants began yellowing and showing other symptoms of disease.

However, the infected plants whose roots had been inoculated with the beneficial microbe Bacillus subtilis were perfectly healthy.

Farmers often add B. subtilis to the soil to boost plant immunity. It forms a protective biofilm around plant roots and also has antimicrobial properties, according to Bais.

Using molecular biological tools, the scientists detected the transmission of a long-distance signal, a "call for help," from the leaves to the roots in the plants that had Bacillus in the soil. The roots responded by secreting a carbon-rich chemical--malic acid.

All plants biosynthesize malic acid, Bais explains, but only under specific conditions and for a specific purpose--in this case, the chemical was actively secreted to attract Bacillus. Magnified images of the roots and leaves showed the ratcheted-up defense response provided by the beneficial microorganisms.

Czymmek captured the definitive proof using a state-of-the-art LSM 510 DUO laser scanning confocal microscope in UD's Bio-Imaging Center. UD is among only a few universities that own one of these million-dollar instruments.

"A plant is a challenge to image because at least half of it is below ground in the form of roots," Czymmek notes. "Here at UD, we use modern technologies including hydroponic growth systems with see-through chambers and sophisticated optical techniques that will enhance the image clarity when visualizing plants and the pathogens attacking them."

Bais and his colleagues are now working to determine what the aerial signal is from the infected leaf to the root using different pathogen-associated molecular markers (PAMPs).

The research not only sheds light on the remarkable signaling system in plants, but also is important to understand how invasive plants conquer new territory with the aid of plant microbes.

"Plants can't move from where they are, so the only way they can accrue good neighbors is through chemistry," Bais notes.

The research was funded by the National Science Foundation's Division of Integrative Organismal Systems, the University of Delaware Research Foundation and the Delaware Experimental Program to Stimulate Competitive Research (EPSCoR).
Adapted from materials provided by University of Delaware. Original article written by Tracey Bryant.

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