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What emotional memories are made of

Mouse experiments reveal ‘flight or fight’ hormone’s role

Contact: Nick Zagorski
nzagors1@jhmi.edu
443-287-2251
Johns Hopkins Medical Institutions

Both extensive psychological research and personal experiences confirm that events that happen during heightened states of emotion such as fear, anger and joy are far more memorable than less dramatic occurrences. In a report this week in Cell, Johns Hopkins researchers and their collaborators at Cold Spring Harbor and New York University have identified the likely biological basis for this: a hormone released during emotional arousal “primes” nerve cells to remember events by increasing their chemical sensitivity at sites where nerves rewire to form new memory circuits.

Describing the brain as a big circuit board in which each new experience creates a new circuit, Hopkins neuroscience professor Richard Huganir, Ph.D. says that he and his team found that during emotional peaks, the hormone norepinephrine dramatically sensitizes synapses – the site where nerve cells make an electro-chemical connection – to enhance the sculpting of a memory into the big board.

Image showing phosphorylated GluR1 receptors congregating around sites of neuronal synapses.

Norepinephrine, more widely known as a “fight or flight” hormone, energizes the process by adding phosphate molecules to a nerve cell receptor called GluR1. The phosphates help guide the receptors to insert themselves adjacent to a synapse. “Now when the brain needs to form a memory, the nerves have plenty of available receptors to quickly adjust the strength of the connection and lock that memory into place,” Huganir says.

Huganir and his team suspected that GluR1might be a target of norepinephrine since disruptions in this receptor cause spatial memory defects in mice. They tested the idea by either injecting healthy mice with adrenaline or exposing them to fox urine, both of which increase norepinephrine levels in brain. Analyzing brain slices of the mice, the researchers saw increased phosphates on the GluR1 receptors and an increased ability of these receptors to be recruited to synapses.

When the researchers put mice in a cage, gave a mild shock, took them out of that cage and put them back in it the next day, mice who had received adrenaline or fox urine tended to “freeze” in fear – an indicator they associated the cage as the site of a shock – more frequently, suggestive of enhanced memory.

However, in a similar experiment with mice genetically engineered to have a defective GluR1 receptor that phosphates cannot attach to, adrenaline injections had no effect on mouse memory, further evidence of the “priming” effect of the receptor in response to norepinephrine.

The researchers plan on continuing their work by going in the opposite direction and engineering another mouse strain that has a permanently phosphorylated or “primed” receptor. “We’re curious to see how these mice will behave,” Huganir says. “We suspect that they’ll be pretty smart, but at the same time constantly anxious.”

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The research was funded by the National Institutes of Health, Damon Runyon Postdoctoral Fellowship, NARSAD, and the Ale Davis and Maxine Harrison Foundation

Authors on the paper are Hailan Hu, Eleonore Real, and Roberto Malinow of Cold Spring Harbor Laboratory; Joe LeDoux of New York University; and Kogo Takamiya, Myoung-Goo Kang, and Huganir of Johns Hopkins

On the Web:
http://neuroscience.jhu.edu/RichardHuganir.php
http://www.cell.com

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October 5, 2007 Posted by | General Psychiatry, Global Health Vision, Global News, Johns Hopkins University, journal Cell, Medical Journals, New York University, Norepinephrine, Research, RSS Feed, Science, W. Garfield Weston Fellows, Washington DC City Feed | 1 Comment

Americans consider global warming an urgent threat, according to poll

Contact: Janet Rettig Emanuel
janet.emanuel@yale.edu
203-432-2157
Yale University

Links (in order of appearance in the text) to have active are: Anthony Leiserowitz Yale Project on Climate Change

New Haven, Conn. — A growing number of Americans consider global warming an important threat that calls for drastic action, and 40% say that a presidential candidate’s position on the issue will strongly influence how they vote, according to a national survey conducted by Yale University, Gallup and the ClearVision Institute.

“One of the most surprising findings was the growing sense of urgency,” said Anthony Leiserowitz, director of the Yale Project on Climate Change and the study’s principal investigator. “Nearly half of Americans now believe that global warming is either already having dangerous impacts on people around the world or will in the next 10 years—a 20-percentage-point increase since 2004. These results indicate a sea change in public opinion.”

The survey’s findings include:

Sixty-two percent of respondents believe that life on earth will continue without major disruptions only if society takes immediate and drastic action to reduce global warming.

Sixty-eight percent of Americans support a new international treaty requiring the United States to cut its emissions of carbon dioxide 90 percent by the year 2050. Yet, Leiserowitz notes, the United States has yet to sign the Kyoto Protocol, an international treaty that would require the United States to cut its emissions 7 percent by the year 2012.

A surprising 40 percent of respondents say a presidential candidate’s position on global warming will be either extremely important (16 percent) or very important (24 percent) when casting their ballots. “With the presidential primaries and general election near,” Leiserowitz said, “candidates should recognize that global warming has become an important issue for the electorate.”

Eight-five percent of those polled support requiring automakers to increase the fuel efficiency of cars, trucks and SUVs to 35 miles per gallon, even if it meant a new car would cost up to $500 more; and 82 percent support requiring electric utilities to produce at least 20 percent of their electricity from renewable energy sources, even if it cost the average household an extra $100 a year.

Majorities of Americans, however, continue to oppose carbon taxes as a way to address global warming — either in the form of gasoline (67 percent against) or electricity taxes (71 percent against). —.

Finally, 50 percent of respondents say they are personally worried —15 percent say a “great deal”— about global warming. “Many Americans, however, believe that global warming is a very serious threat to other species, people and places far away,” said Leiserowitz, “but not so serious of a threat to themselves, their own families or local communities. Nonetheless, they do strongly support a number of national and international policies to address this problem.”

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The survey was conducted July 23-26, 2007, using telephone interviews with 1,011 adults, aged 18-plus. Respondents came from Gallup’s household panel, which was originally recruited through random selection methods. The final sample is consideredto be representative of U.S. adults nationwide, with a margin of error of ±4 percentage points. Survey results are available online: http://environment.yale.edu/news/5305-american-opinions-on-global-warming/.

The Yale Project on Climate Change at the Yale School of Forestry & Environmental Studies supports public discourse and engagement with climate-change solutions.

Gallup, Inc., headquartered in Washington, D.C., is one of the world’s leading research companies focusing on studying human nature and behavior. The Gallup Poll has been monitoring U.S. public opinion since 1935, and Gallup now tracks public opinion in over 100 countries worldwide on an ongoing basis.

The ClearVision Institute is a nonprofit organization dedicated to applying entertainment education as a social-change strategy to address climate change through U.S. commercial television.

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October 1, 2007 Posted by | Global, Global Health Vision, Global News, RSS Feed, Science, Yale University | 2 Comments

Satellites witness lowest Arctic ice coverage in history

14 September 2007

The area covered by sea ice in the Arctic has shrunk to its lowest level this week since satellite measurements began nearly 30 years ago, opening up the Northwest Passage – a long-sought short cut between Europe and Asia that has been historically impassable.


2007 Envisat mosaic of Arctic Ocean

In the mosaic image above, created from nearly 200 images acquired in early September 2007 by the Advanced Synthetic Aperture Radar (ASAR) instrument aboard ESA’s Envisat satellite, the dark gray colour represents the ice-free areas while green represents areas with sea ice.

Leif Toudal Pedersen from the Danish National Space Centre said: “We have seen the ice-covered area drop to just around 3 million sq km which is about 1 million sq km less than the previous minima of 2005 and 2006. There has been a reduction of the ice cover over the last 10 years of about 100 000 sq km per year on average, so a drop of 1 million sq km in just one year is extreme.

“The strong reduction in just one year certainly raises flags that the ice (in summer) may disappear much sooner than expected and that we urgently need to understand better the processes involved.”

Arctic sea ice naturally extends its surface coverage each northern winter and recedes each northern summer, but the rate of overall loss since 1978 when satellite records began has accelerated.


Mosaics of Arctic Ocean for 2005, 2006, 2007

The most direct route of the Northwest Passage (highlighted in the top mosaic by an orange line) across northern Canada is shown fully navigable, while the Northeast Passage (blue line) along the Siberian coast remains only partially blocked. To date, the Northwest Passage has been predicted to remain closed even during reduced ice cover by multi-year ice pack – sea ice that survives one or more summers. However, according to Pedersen, this year’s extreme event has shown the passage may well open sooner than expected.

The previous record low was in 2005 when the Arctic area covered by sea ice was just 4 million sq km. Even then, the most direct Northwest Passage did not fully open.


A 2007 ice-free portion of the Northwest Passage

The Polar Regions are very sensitive indicators of climate change. The UN’s Intergovernmental Panel on Climate Change showed these regions are highly vulnerable to rising temperatures and predicted the Arctic would be virtually ice free by the summer of 2070. Still other scientists predict it could become ice free as early as 2040 due to rising temperatures and sea ice decline.

Because sea ice has a bright surface, the majority of solar energy that hits it is reflected back into space. When sea ice melts, the dark-coloured ocean surface is exposed. Solar energy is then absorbed rather than reflected, so the oceans get warmer and temperatures rise, making it difficult for new ice to form.

The Arctic is one of Earth’s most inaccessible areas, so obtaining measurements of sea ice was difficult before the advent of satellites. For more than 20 years, ESA has been providing satellite data to the cryosphere communities. Currently, ESA is contributing to the International Polar Year (IPY) – a large worldwide science programme focused on the Arctic and Antarctic.

Since 2006, ESA has supported Polar View, a satellite remote-sensing programme funded through the Earthwatch GMES Service Element (GSE) that focuses on the Arctic and the Antarctic.

In 2009, ESA will make another significant contribution to cryosphere research with the launch of CryoSat-2. The observations made over the three-year lifetime of the mission will provide conclusive evidence on the rates at which ice cover is diminishing.

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September 15, 2007 Posted by | Global Health Vision, Global News, RSS Feed, Science, Washington DC City Feed, Weather Anomolies, World Health Organisation, World News | Leave a comment

Revealing the workings of ‘Mother Nature’s blowtorch’

Sept. 13, 2007 ANN ARBOR, Mich.—Using atom-level imaging techniques, University of Michigan researchers have revealed important structural details of an enzyme system known as “Mother Nature’s blowtorch” for its role in helping the body efficiently break down many drugs and toxins.

The research has been detailed in a series of papers, the most recent published online this month in the journal BBA Biomembranes.

The system involves two proteins that work cooperatively. The first, cytochrome P450, does the actual work, but only when it gets a boost from the second protein, cytochrome b5. To complicate matters, the two proteins can interact only when both are bound to a cell membrane. That makes it difficult to use traditional techniques to discern the structural details that are crucial to the interaction, said Ayyalusamy Ramamoorthy, who leads the research group.

For instance, X-ray crystallography, often used to determine protein structures, requires separating the molecules from their membrane environment. Because part of cytochrome b5 sticks to the membrane, such separations involve breaking the molecule at the sticking point, which happens to be the part that controls its interaction with cytochrome P450. So while crystallography can offer some information on structure, it can’t provide insights into exactly what goes on between P450 and b5 during their cozy, membrane-bound encounters, Ramamoorthy said.

However, the technique his lab uses—solid state NMR spectroscopy—can produce detailed images of proteins in the membrane environment, not only revealing molecular structure but also showing how a particular protein nestles into the membrane. Cytochrome b5 presented a challenge even to that versatile method, though, because the molecule has three parts that all behave differently: the rigid, sticky portion that buries into the cell membrane, a highly mobile, water-soluble portion, and a less mobile “linker” that connects the other two parts.

But by tweaking their technique, the researchers were able to get high-resolution images of all three portions.

“The challenge was something like having a room full of people and trying to get good photos of every one of them,” said Ramamoorthy, an associate professor of chemistry and Biophysics. “With one picture, you probably can’t do it. But if you say, ‘Everyone over age 50 stand up,’ and you take one picture, and then you ask for another age group and take another picture, and so on, you have a better chance.”

By spinning their samples (or aligning the molecules in the magnetic field), the researchers were able to differentiate parts of the molecule based not on age group, as in the photo analogy, but by mobility. “With the techniques we designed, we were able to observe the rigid portion separately from the highly mobile and less mobile portions,” Ramamoorthy said.

In the first part of the work, published in the Journal of the American Chemical Society in May, the researchers described the membrane-spanning segment of cytochrome b5, revealing for the first time its helical shape and the way it tilts in relation to the membrane. In the new work published in BBA Biomembranes, they determined that once both molecules are bound in the membrane, cytochrome b5 modulates the motion and the structure of cytochrome P450. More work is in progress to determine the detailed high-resolution structures of these two proteins.

Ramamoorthy’s team also is studying other membrane-associated proteins, a group that includes many biologically important molecules.

“These proteins are involved in all major diseases, everywhere in the body, and are therefore primary targets for pharmaceutical applications,” Ramamoorthy said. “In my opinion, solving the structures of membrane proteins should be the highest priority for structural biologists in the coming years.”

Ramamoorthy collaborated on the most recent work with Lucy Waskell, a professor of anesthesiology and a physician at the Department of Veterans Affairs Medical Center.

A leader in this area of research, Ramamoorthy has organized several major international symposia on the field at the University of Michigan, edited a special issue in the journal BBA-Biomembranes, published a number of papers in leading journals, and brought out a book on NMR Spectroscopy of Biological Solids. Ramamoorthy said that this area of research will grow considerably at U-M from implementing plans to set up a high magnetic field solid-state NMR spectrometer facility and an NIH-funded program.

Related Links:

More information on Ramamoorthy

Contact: Nancy Ross-Flanigan
Phone: (734) 647-1853

Related Categories: Science.

See also: News, Health, University of Michigan, Global News

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September 14, 2007 Posted by | Cytochrome b5, Cytochrome P450, Global Health Vision, Global News, Health, journal BBA Biomembranes, News USA, RSS Feed, Science, University of Michigan | Leave a comment

Medication appears helpful for treatment of erectile dysfunction in men with spinal cord injuries

The drug tadalafil appears to improve erectile function in men with spinal cord injuries, according to an article posted online today that will appear in the November 2007 print issue of Archives of Neurology, one of the JAMA/Archives journals.

Between 10.4 and 83 individuals per million worldwide experience spinal cord injuries every year, according to background information in the article. “Throughout the world, spinal cord injury occurs most often in young men, resulting in negative physical, social and psychological consequences,” the authors write. “Erectile dysfunction, defined as the inability to attain and maintain penile erection sufficient for satisfactory sexual performance, is a common complication in men with spinal cord injury.” Only 25 percent of men with spinal cord injuries are able to have erections that are adequate for having intercourse.

Francois Giuliano, M.D., Ph.D., of the Raymond Poincare Hospital, Garches, France, and colleagues, conducted a randomized, double-blind study of tadalafil in 197 men with spinal cord injuries (average age 38). After a four-week period during which none of the men received treatment, 142 were randomly assigned to the tadalafil treatment group and 44 to the placebo group. During the 12-week treatment phase, the participants were instructed to take the medication as needed before the potential for sexual activity, with a maximum of one dose daily. Those assigned to take tadalafil were given a 10-milligram dose at first and were evaluated every four weeks, at which time patients were switched to a 20-milligram dose based on their response to the treatment.

At the beginning of the study, the men’s average score on the International Index of Erectile Function—a 15-item questionnaire on which a score of 25 or lower indicates erectile dysfunction—was 13.4. After 12 weeks of treatment, men taking tadalafil had an average score of 22.6 (indicating mild erectile dysfunction) and men taking placebo had an average score of 13.6 (indicating moderate erectile dysfunction). Men taking tadalafil were, on average, successful 75.4 percent of the times they attempted penetration and 47.6 percent of the times they attempted intercourse, compared with a 41.1 success rate for penetration and 16.8 percent for intercourse among men taking placebo.

“Tadalafil was safe and well tolerated with few treatment-emergent side effects,” the authors write. Fifty (35 percent) of patients in the tadalafil group and 15 (34 percent) of those in the placebo group experienced at least one adverse effect. Among those taking tadalafil, the most common side effects were headache (8.5 percent of patients) and urinary tract infection (7.7 percent of patients).

“As in other erectile dysfunction studies that include patients who were difficult to treat owing to pre-existing conditions (e.g., prostatectomy, diabetes mellitus), tadalafil was efficacious for the treatment of erectile dysfunction after a traumatic spinal cord injury,” the authors write. “On-demand treatment with tadalafil (10 milligrams or 20 milligrams) may help improve the sex lives of patients with erectile dysfunction and spinal cord injury and their partners.”

(Arch Neurol. 2007;64(11):(doi:10.1001/archneur.64.11.nct70001). Available pre-embargo to the media at http://www.jamamedia.org.)

Editor’s Note: Funding for this study was provided by Lilly ICOS LLC, Bothell, Wash., and Indianapolis, Ind. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Contact: Francois Giuliano, M.D., Ph.D.
giuliano@cyber-sante.org
JAMA and Archives Journals

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September 10, 2007 Posted by | Archives of Neurology, Global Health Vision, Global News, JAMA/Archives journals, RSS Feed, Science, Spinal Cord Injuries, UK, Washington DC City Feed | Leave a comment

USC researcher identifies stem cells in tendons that regenerate tissue in animal model

Finding promise new treatments for tendon injury and disease

Los Angeles, Sept. 7, 2007—Athletes know that damage to a tendon can signal an end to their professional careers. But a consortium of scientists, led in part by University of Southern California (USC) School of Dentistry researcher Songtao Shi, has identified unique cells within the adult tendon that have stem-cell characteristics—including the ability to proliferate and self-renew. The research team was able to isolate these cells and regenerate tendon-like tissue in the animal model. Their findings hold tremendous promise for the treatment of tendon injuries caused by overuse and trauma.

The results of their research will be published in the October 2007 issue of the journal Nature Medicine and will be available online at http://www.nature.com/nm on Sunday, September 9, 2007.

Tendons, the tough band of specialized tissues that connect bone to muscle, are comprised of strong collagen fibrils that transmit force allowing the body to move. Tendon injuries are a common clinical problem as damaged tendon tissue heals slowly and rarely regains the integrity or strength of a normal, undamaged tendon.

“Clinically, tendon injury is a difficult one to treat, not only for athletes but for patients who suffer from tendinopathy such as tendon rupture or ectopic ossification,” Shi says. “This research demonstrates that we can use stem cells to repair tendons. We now know how to collect them from tissue and how to control their formation into tendon cells.”

Prior to this research, little existed on the cellular makeup of tendons and their precursors. By looking at tendons at the molecular level, the research team identified a unique cell population—termed tendon stem/progenitor cells (TSPCs) in both mice and adult humans—that when guided by a certain molecular environment, form into tendon cells. The team included leading scientists from the National Institute of Dental and Craniofacial Research at the National Institutes of Health, Johns Hopkins University and the University of Maryland School of Medicine.

Songtao Shi, a researcher for USC’s Center for Craniofacial Molecular Biology, a Division within the USC School of Dentistry, has published numerous studies on the role of stem cells in regeneration. He was part of an international research team that successfully generated tooth root and supporting periodontal ligaments to restore tooth function in the animal model. Earlier this year, his research was published in the journal Stem Cells after he and his team discovered that mesenchymal stem cells are capable of regenerating facial bone and skin tissue in the mouse and swine models.

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Funding for the study came from the USC School of Dentistry and the National Institutes of Health.

Yanming Bi, Driss Ehirchiou, Tina M Kilts, Colette A Inkson, Mildred C Embree, Wataru Sonoyama, Li Li, Arabella I Leet, Byoung-Moo Seo, Li Zhang, Songtao Shi & Marian F Young. “Identification of tendon stem/progenitor cells and the role of the extracellular matrix in their niche.” Nature Medicine, http://www.nature.com/nm

USC’s Center for Craniofacial Molecular Biology

USC’s Center for Craniofacial Molecular Biology is a research laboratory located on the Health Sciences Campus of the University of Southern California in Los Angeles. Administratively, CCMB is part of the USC School of Dentistry. The laboratory is funded through multiple research grants, including several from the National Institutes of Health, under which research is conducted into development, biochemical and molecular biological aspects of human development, with a special emphasis on craniofacial structures in both health and disease. Current investigations include the molecular etiology of cleft palate, the molecular genetics of tooth development and lung development in the premature infant.

Contact: Angelica Urquijo
urquijo@usc.edu
213-740-6568
University of Southern California

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September 9, 2007 Posted by | Global Health Vision, Global News, Health, News, NIH, Science, Tendons, USC | 1 Comment

Embryonic stem cells used to grow cartilage

Rice method is first to yield cartilage-like cells, engineer human cartilage

HOUSTON, Sept. 6, 2007 – Rice University biomedical engineers have developed a new technique for growing cartilage from human embryonic stem cells, a method that could be used to grow replacement cartilage for the surgical repair of knee, jaw, hip, and other joints.

“Because native cartilage is unable to heal itself, researchers have long looked for ways to grow replacement cartilage in the lab that could be used to surgically repair injuries,” said lead researcher Kyriacos A. Athanasiou, the Karl F. Hasselmann Professor of Bioengineering. “This research offers a novel approach for producing cartilage-like cells from embryonic stem cells, and it also presents the first method to use such cells to engineer cartilage tissue with significant functional properties.”

The results are available online and slated to appear in the September issue of the journal Stem Cells. The study involved cells from an NIH-sanctioned stem cell line.

Using a series of stimuli, the researchers developed a method of converting the stem cells into cartilage cells. Building upon this work, the researchers then developed a process for using the cartilage cells to make cartilage tissue. The results show that cartilages can be generated that mimic the different types of cartilage found in the human body, such as hyaline articular cartilage — the type of cartilage found in all joints — and fibrocartilage — a type found in the knee meniscus and the jaw joint. Athanasiou said the results are exciting, as they suggest that similar methods may be used to convert the stem cell-derived cartilage cells into robust cartilage sections that can be of clinical usefulness.

Tissue engineers, like those in Athanasiou’s research group, are attempting to unlock the secrets of the human body’s regenerative system to find new ways of growing replacement tissues like muscle, skin, bone and cartilage. Athanasiou’s Musculoskeletal Bioengineering Laboratory at Rice University specializes in growing cartilage tissues.

The idea behind using stem cells for tissue engineering is that these primordial cells have the ability to become more than one type of cell. In all people, there are many types of “adult” stem cells at work. Adult stem cells can replace the blood, bone, skin and other tissues in the body. Stem cells become specific cells based upon a complex series of chemical and biomechanical cues, signals that scientists are just now starting to understand.

Unlike adult stem cells, which can become only a limited number of cell types, embryonic stem cells can theoretically become any type of cell in the human body.

Athanasiou’s group has been one of the most successful in the world at studying cartilage cells and, especially, engineering cartilage tissues. He said that for his research the primary advantage that embryonic stem cells have over adult stem cells is their ability to remain malleable.

“Identifying a readily available cell source has been a major obstacle in cartilage engineering,” Athanasiou said. “We know how to convert adult stem cells into cartilage-like cells. The more problematic issue comes in trying to maintain a ready stock of adult stem cells to work with. These cells have a strong tendency to convert from stem cells into a more specific type of cell, so the clock is always ticking when we work with them.”

By contrast, Athanasiou said his research group has found it easier to grow and maintain a stock of embryonic stem cells. Nonetheless, he is quick to point out that there is no clear choice about which type of stem cell works best for cartilage engineering.

“We don’t know the answer to that,” Athanasiou said. “It’s extremely important that we study all potential cell candidates, and then compare and contrast those studies to find out which works best and under what conditions. Keep in mind that these processes are very complicated, so it may well be that different types of cells work best in different situations.”

Athanasiou began studying embryonic stem cells in 2005. Since funding for the program was limited, he asked two new graduate students in his group if they were interested in pursuing the work as a secondary project to their primary research. Those students, Eugene Koay and Gwen Hoben, are co-authors of the newly published study. Both are enrolled in the Baylor College of Medicine Medical Scientist Training Program, a joint program that allows students to concurrently earn their medical degree from Baylor while undertaking Ph.D. studies at Rice.

“Eugene and Gwen are both outstanding students,” Athanasiou said. “Each earned their undergraduate degree from Rice and each worked in my laboratory as undergraduate students. They have chosen to do this research because they think this may represent the future of regenerative medicine.”

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The research was funded by Rice University.

Contact: Jade Boyd
jadeboyd@rice.edu
713-348-6778
Rice University

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September 7, 2007 Posted by | Global Health Vision, Global News, Health, Health Canada, HIV, Hospital Epidemiology, News UK, News USA, RSS, Science, Stem Cells | Leave a comment

Male deer are born to live fast, die young

Study of 123 ungulate species shows males are born with smaller molars, expecting shorter lives

In the September issue of The American Naturalist, Juan Carranza (Biology and Ethology Unit, University of Extremadura, Spain) and Javier Pérez-Barbería (Macaulay Institute, United Kingdom) offer a new explanation for why males of ungulate species subjected to intense competition are born with lower survival expectancies than females. The research reveals that male ungulates have smaller molars relative to their body size – and hence less durable teeth that will wear out sooner, which might contribute to their shorter lives compared with females.

Roaring male Iberian red deer with females
(photograph by Juan Carranza)

Natural selection favors reproduction rather than survival; the cost of reproduction compromises survival. Males of species subjected to intense male-male competition for access to females are known to have shorter life expectancies than females. Earlier aging in males might be related to higher reproductive costs, especially when lifetime reproductive success in males takes place within the few years when they can win contests and maintain their dominance.

By comparing body and dental size of males and females of 123 species of ungulates, the authors offer another compelling explanation for why male ungulates lead shorter lives. They estimated the pattern of change of these traits along the evolutionary development of the group and found that for species where a single male has many females and where the males and females are different sizes, the rate of increase of dental size was lower than that of body size. As a result, smaller teeth (in comparison to body size) are produced in males. It is possible that natural selection did not produce larger, more durable teeth because there was no reproductive return from it, since males in these species do not generally increase their success by living longer after prime age.

“These findings,” the authors state, “provide us with interesting insights into how natural and sexual selection design our bodies and their longevity.”

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Juan Carranza and F. Javier Pérez-Barbería, “Sexual selection and senescence: male size-dimorphic ungulates evolved relatively smaller molars than females”, The American Naturalist (2007) volume 170:370–380. DOI: 10.1086/519852

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August 31, 2007 Posted by | Biological Sciences, Global Health Vision, Global News, Nature, RSS, Science | Leave a comment

What causes St. Elmos fire?

As a retired advanced weather spotter for the National Weather Service in Pontiac Michigan, I have observed numerous weather phenomon. I have “ball lightning” on video.

St. Elmo’s Fire is an electrical weather phenomenon in which visible plasma is created by a coronal discharge originating from a grounded object in an atmospheric electric field (such as those generated by thunderstorms).

St. Elmo’s fire is named after Erasmus of Formiae (also called St. Elmo), the patron saint of sailors (who sometimes held its appearance to be auspicious). Alternatively, Peter Gonzalez is said to be the St. Elmo after whom St. Elmo’s fire has its name.

Ball lightning is often erroneously identified as St. Elmo’s Fire. They are separate and distinct meteorological phenomena.(Wikipedia)

Physically, St. Elmo’s Fire is a bright blue or violet glow, appearing like fire in some circumstances, from tall, sharply pointed structures such as lightning rods, masts, spires and chimneys, and on aircraft wings. St. Elmo’s Fire can also appear on leaves, grass, and even at the tips of cattle horns. Often accompanying the glow is a distinct hissing or buzzing sound.

Benjamin Franklin correctly observed in 1749 that it is electric in nature.

Scientific Explanation

Although referred to as “fire”, St. Elmo’s Fire is in fact plasma. The electric field around the object in question causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Approximately 1,000 – 30,000 volts per centimeter is required to induce St. Elmo’s Fire; however, this number is greatly dependant on the geometry of the object in question. Sharp points tend to require lower voltage levels to produce the same result because electric fields are more concentrated in areas of high curvature, thus discharges are more intense at the end of pointed object.

The nitrogen and oxygen in earth’s atmosphere causes St. Elmo’s Fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow.

Flying through Iraq thunderstorm

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August 31, 2007 Posted by | Global Health Vision, Global News, RSS, Science, St. Elmos Fire, US Army soldiers in Iraq, Weather Anomolies | Leave a comment

One species’ entire genome discovered inside another’s

Whole-genome transfer raises questions about evolution, sequencing

Scientists at the University of Rochester and the J. Craig Venter Institute have discovered a copy of the entire genome of a bacterial parasite residing inside the genome of its host species.

The finding, reported in today’s Science, suggests that lateral gene transfer—the movement of genes between unrelated species—may happen much more frequently between bacteria and multicellular organisms than scientists previously believed, posing dramatic implications for evolution.

Such large-scale heritable gene transfers may allow species to acquire new genes and functions extremely quickly, says Jack Werren, a principle investigator of the study.

Wolbachia in yellow with host cells in red.

The results also have serious repercussions for genome-sequencing projects. Bacterial DNA is routinely discarded when scientists are assembling invertebrate genomes, yet these genes may very well be part of the organism’s genome, and might even be responsible for functioning traits.

“This study establishes the widespread occurrence and high frequency of a process that we would have dismissed as science fiction until just a few years ago,” says W. Ford Doolittle, Canada Research Chair in Comparative Microbial Genomics at Dalhousie University, who is not connected to the study. “This is stunning evidence for increased frequency of gene transfer.”

Fruit fly ovaries showing wolbachia infection within.

“It didn’t seem possible at first,” says Werren, professor of biology at the University of Rochester and a world-leading authority on the parasite, called Wolbachia. “This parasite has implanted itself inside the cells of 70 percent of the world’s invertebrates, coevolving with them. And now, we’ve found at least one species where the parasite’s entire or nearly entire genome has been absorbed and integrated into the host’s. The host’s genes actually hold the coding information for a completely separate species.”

Wolbachia may be the most prolific parasite in the world—a “pandemic,” as Werren calls it. The bacterium invades a member of a species, most often an insect, and eventually makes its way into the host’s eggs or sperm. Once there, the Wolbachia is ensured passage to the next generation of its host, and any genetic exchanges between it and the host also are much more likely to be passed on.

Since Wolbachia typically live within the reproductive organs of their hosts, Werren reasoned that gene exchanges between the two would frequently pass on to subsequent generations. Based on this and an earlier discovery of a Wolbachia gene in a beetle by the Fukatsu team at the University of Tokyo, Japan, the researchers in Werren’s lab and collaborators at J. Craig Venter Institute (JCVI) decided to systematically screen invertebrates. Julie Dunning-Hotopp at JCVI found evidence that some of the Wolbachia genes seemed to be fused to the genes of the fruitfly, Drosophila ananassae, as if they were part of the same genome.

Michael Clark, a research associate at Rochester then brought a colony of ananassae into Werren’s lab to look into the mystery. To isolate the fly’s genome from the parasite’s, Clark fed the flies a simple antibiotic, killing the Wolbachia. To confirm the ananassae flies were indeed cured of the wolbachia, Clark tested a few samples of DNA for the presence of several Wolbachia genes.

To his dismay, he found them.

“For several months, I thought I was just failing,” says Clark. “I kept administering antibiotics, but every single Wolbachia gene I tested for was still there. I started thinking maybe the strain had grown antibiotic resistance. After months of this I finally went back and looked at the tissue again, and there was no Wolbachia there at all.”

Clark had cured the fly of the parasite, but a copy of the parasite’s genome was still present in the fly’s genome. Clark was able to see that Wolbachia genes were present on the second chromosome of the insect.

Clark confirmed that the Wolbachia genes are inherited like “normal” insect genes in the chromosomes, and Dunning-Hotopp showed that some of the genes are “transcribed” in uninfected flies, meaning that copies of the gene sequence are made in cells that could be used to make Wolbachia proteins.

Werren doesn’t believe that the Wolbachia “intentionally” insert their genes into the hosts. Rather, it is a consequence of cells routinely repairing their damaged DNA. As cells go about their regular business, they can accidentally absorb bits of DNA into their nuclei, often sewing those foreign genes into their own DNA. But integrating an entire genome was definitely an unexpected find.

Werren and Clark are now looking further into the huge insert found in the fruitfly, and whether it is providing a benefit. “The chance that a chunk of DNA of this magnitude is totally neutral, I think, is pretty small, so the implication is that it has imparted of some selective advantage to the host,” says Werren. “The question is, are these foreign genes providing new functions for the host” This is something we need to figure out.”

Evolutionary biologists will certainly take note of this discovery, but scientists conducting genome-sequencing projects around the world also may have to readjust their thinking.

Before this study, geneticists knew of examples where genes from a parasite had crossed into the host, but such an event was considered a rare anomaly except in very simple organisms. Bacterial DNA is very conspicuous in its structure, so if scientists sequencing a nematode genome, for example, come across bacterial DNA, they would likely discard it, reasonably assuming that it was merely contamination—perhaps a bit of bacteria in the gut of the animal, or on its skin.

But those genes may not be contamination. They may very well be in the host’s own genome. This is exactly what happened with the original sequencing of the genome of the anannassae fruitfly—the huge Wolbachia insert was discarded from the final assembly, despite the fact that it is part of the fly’s genome.

In the early days of the Human Genome Project, some studies appeared to show bacterial DNA residing in our own genome, but those were shown indeed to be caused by contamination. Wolbachia is not known to infect any vertebrates such as humans.

“Such transfers have happened before in the distant past” notes Werren. “In our very own cells and those of nearly all plants and animals are mitochondria, special structures responsible for generating most of our cells’ supply of chemical energy. These were once bacteria that lived inside cells, much like Wolbachia does today. Mitochondria still retain their own, albeit tiny, DNA, and most of the genes moved into the nucleus in the very distant past. Like wolbachia, they have passively exchanged DNA with their host cells. It’s possible wolbachia may follow in the path of mitochondria, eventually becoming a necessary and useful part of a cell.

“In a way, wolbachia could be the next mitochondria,” says Werren. “A hundred million years from now, everyone may have a wolbachia organelle.”

“Well, not us,” he laughs. “We’ll be long gone, but wolbachia will still be around.”

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This research was funded by the National Science Foundation.

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August 30, 2007 Posted by | Genome, Global Health Vision, Global News, Research, RSS, Science, University of Rochester | 1 Comment