Sunday, August 31, 2008
Memory Trick Shows Brain Organization
A simple memory trick has helped show UC Davis researchers how an area of the brain called the perirhinal cortex can contribute to forming memories. The finding expands our understanding of how those brain areas that form memories are organized.
The brain puts together different items -- the what, who, where and when -- to form a complete memory. It was previously thought that this association process occurred entirely in the brain structure called the hippocampus, but this appears not to be the case, said Charan Ranganath, a professor at the UC Davis Center for Neuroscience and the Department of Psychology who led the research.
"We want to know how the brain areas that encode memory are organized," Ranganath said. "If your memory is affected by aging or Alzheimer's disease, is there a way to learn that can capitalize on the brain structures that may still be working well?"
The researchers used functional magnetic resonance imaging (fMRI) to see which parts of the brain were active when volunteers memorized pairs of words such as "motor/bear" or "liver/tree." In this experiment, the volunteers either learned the pairs as separate words that could be fitted into a sentence, or as a new compound word, for example "motorbear," defined as a motorized stuffed toy.
"It's a sort of memory trick," Ranganath said.
When volunteers memorized word pairs as a compound word, the perirhinal cortex lit up, and this activity predicted whether the volunteers would be able to successfully remember the pairs in the future. The results suggest that the perirhinal cortex probably can form simple associations, such as between the parts of a complex object. This information is probably passed up to the hippocampus, which may create more complex memories, such as the place and time a specific object was seen.
Perirhinal Cortex Supports Encoding and Familiarity-Based Recognition of Novel Associations
Andrew Logan Haskins et al
Neuron Vol 59, 554-560, 28 August 2008
Link to Neuron abstract
Tradnl hmbking ingrdints
Browsing Tesco supermarket's online store, Diane Brown did a search for baking powder. She found it under a submenu entitled "Tradnl Hmbking Ingrdints", which she assumed meant "Traditional Home-baking Ingredients". This alerted her to the knotty problem of classification faced by large supermarkets.
Moving on to the Tesco world of "Bakery and Cakes", she discovered a submenu enticingly entitled "World and Speciality Bread" - but when she got down to the sub-submenu, all it showed was a choice of "Irish or Speciality". What, she wondered, sets Irish bread apart from the other breads of the world, such as naan, pitta or ciabatta? The answer, it turned out, is that pitta and naan are "Rolls, Bagels and Wraps", while ciabatta is a "Speciality", not a "Bread of the World". As for French baguettes, she failed to find any except the garlicked variety.
Questions kept occurring to her. Since Tesco was so picky about where bread-related products originate from, why was there a submenu dedicated to "Croissants and Crumpets" - two breakfast items from distinctly opposite sides of the English Channel? Interestingly, "Croissants and Crumpets" could be further subdivided into "Continental, Croissant" and "Crumpets, Pancakes and Muffins". This, she thought, was counter-intuitive. Who would expect to find pancakes under "Croissants and Crumpets"?
To round off the confusion, she next found "Wholemeal Baps" under "White Rolls", and "White Sub Rolls" under "Brown Rolls".
"I'm sure other areas of grocery are just as convoluted in their classification system," Brown says, "but I'm rather losing the will to live at this point. Thank goodness I have my own bread-maker, and only have to worry about flour and yeast. Now, what, I wonder, is yeast? Is it a tradnl hmbking ingrdint?"
And didn’t spellcheck have fun with that!
Saturday, August 30, 2008
Science Daily (Aug. 30, 2008)
Researchers at UT Southwestern Medical Center have discovered in mice that the brain must create new nerve cells for either exercise or antidepressants to reduce depression-like behavior. In addition, the researchers found that antidepressants and exercise use the same biochemical pathway to exert their effects.
These results might help explain some unknown mechanisms of antidepressants and provide a new direction for developing drugs to treat depression, said Dr. Luis Parada, chairman of developmental biology and senior author of the study published in the August 14 issue of the journal Neuron.
In animals, it was already known that long-term treatment with antidepressants causes new nerve cells to be generated in a part of the brain called the dentate gyrus. Exercise, which can also relieve the symptoms of depression, stimulates the generation of new nerve cells in the same area.
"We would never claim that what we study in mice directly relates to how antidepressants work in humans, but there are interesting features in parallel," Dr. Parada said. "The study unifies different observations that point to the brain's dentate gyrus region and to creation of nerve cells as being important in depression."
Antidepressants act very quickly to increase levels of natural compounds, called neurotransmitters, which nerve cells use to communicate. It takes several weeks to several months, however, for the patients who respond to such treatments to feel less depressed. Dr. Parada said this implies that some other long-term mechanism is also at work.
The researchers focused on a molecule called TrkB, or Track-B, which is found on the surface of nerve cells and responds to several growth factors to cause new nerves to grow in the dentate gyrus.
They genetically engineered mice to lack TrkB specifically in the stem cells that give rise to new neurons, then gave them antidepressants for several weeks or allowed them to run on wheels. When the mice were tested for depressive behavior, the tests revealed that neither the antidepressants nor the exercise had helped them, and the animals also had not grown new nerve cells in the dentate gyrus.
"At least in mice, this result directly links antidepressants and voluntary exercise with TrkB-mediated creation of nerve cells," Dr. Parada said.
The results also showed that antidepressants required TrkB to stimulate the growth of new nerve cells.
Matching the timeframe for medicated patients to feel less depressed, it takes several weeks for new nerve cells to grow, Dr. Parada said. This parallel effect, he said, may mean that antidepressants need to stimulate growth of new cells in the dentate gyrus in order to achieve their full effect.
"We can get biochemical, physiological, behavioral and anatomical results in animal models," Dr. Parada said. "These all resonate with the human condition, so perhaps you have a physiological relevancy.
TrkB Regulates Hippocampal Neurogenesis and Governs Sensitivity to Antidepressive Treatment
Yun Li et al
Neuron, Vol 59, 399-412, 14 August 2008
Link to Neuron abstract
Events of the past year in HIV vaccine research have led some to question whether an effective HIV vaccine will ever be developed. In the August 28 edition of the New England Journal of Medicine, officials from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, examine the extraordinarily challenging properties of the virus that have made a vaccine elusive and outline the scientific questions that, if answered, could lead to an effective HIV vaccine.
In recent years, the most extensively studied HIV vaccines have aimed to mobilize immune cells called T cells, write Anthony S. Fauci, M.D., NIAID director, and Margaret I. Johnston, Ph.D., director of the Vaccine Research Program in NIAID's Division of AIDS.
T-cell vaccines are not expected to prevent HIV infection. Rather, they could potentially reduce the level of virus (but not eliminate it) following infection, limit the number of immune cells that HIV destroys, and thus delay the progression to AIDS. There is no evidence yet that T-cell HIV vaccines work in humans, however.
If the vaccines ultimately do, their effectiveness may vary greatly depending on the genetic make-up of each individual, given that T-cell immunity is dependent on genetic factors. Furthermore, because the virus would persist in the blood of vaccinated individuals, T-cell vaccines would likely generate only transient "herd immunity"--that is, population-wide protection from disease conferred by vaccination of a percentage of the community.
In response to the failure last September of a T-cell vaccine for which many people had high hopes, the HIV vaccine field has undergone a self-reexamination and has determined that the balance between fundamental discovery research and product development should shift toward discovery. In particular, future research must intensify the study of broadly neutralizing antibodies to HIV, why most HIV-infected people do not make them, and the design of novel strategies to induce them with a vaccine.
Also, studying the earliest stages of HIV infection may shed light on ways to manipulate innate and mucosal immune responses to widen the window of opportunity for viral eradication, to prevent the virus from advancing to gut-associated lymphoid tissue, or both.
The authors conclude with cautious optimism that an effective HIV vaccine will be developed, but will depend on the significant growth of scientific understanding of HIV disease and human responses to the virus.
An HIV vaccine--challenges and prospects.
Margaret I. Johnston, Ph.D., and Anthony S. Fauci, M.D.
New England Journal of Medicine, 2008; DOI: 10.1056/NEJMp0806162
Link to NEJM abstract
Friday, August 29, 2008
There is a “hidden epidemic” of HIV amongst African migrants living in the United States, according to researchers writing in the September 12th edition of Journal of Acquired Immune Deficiency Syndromes(JAIDS). They found that African-born individuals in the US had a disproportionately high prevalence of HIV – although they comprised only 0.6% of the study population, almost 4% of HIV diagnoses were amongst African-born individuals. Furthermore, the investigators found that in one health area approximately 50% of HIV infections amongst black people were amongst individuals originating in Africa.
Because current US surveillance data do not routinely include information on individuals’ country of origin, it may be that a significant number of HIV infections currently classified as being amongst African-Americans are likely to involve recent migrants from Africa.
Failure to acknowledge the scale of the HIV epidemic amongst African-born individuals, could, the investigators argue, mean that the HIV prevention and care needs of African-born US residents are being neglected.
In 2005, almost two-thirds of the world’s HIV infections were located in sub-Saharan Africa. It is estimated that 25% or more of total HIV infections in western Europe are amongst migrants from southern Africa. Although the total number of African migrants in the US increased by 130% between 1990 and 2000, there is little information about the number of HIV infections amongst this community, and few HIV prevention or care services are targeted at individuals in this group.
US immigration law requires that all persons applying to become lawful permanent residents in the country have an HIV test. Infection with HIV is normally a bar to even temporary entry to the US (although this may change), but this prohibition is waived for refugees and in other special cases.
The study contacted health authorities in nine areas where African-born individuals comprised 0.5% or more of the total population. Six states (California, Georgia, Ohio, Massachusetts, Minnesota and Ohio) were included in the study, as were Washington DC, New York City and King County, Washington State.
The health authorities in these areas provided information on the total number of HIV infections within their district in 2003-04, as well as the place of birth of individuals diagnosed with HIV, and the HIV risk activity of these individuals.
A total of 459,000 African-born individuals were resident in the eight areas included in the study – some 47% of all African-born individuals living in the US according to figures from the US census. Although African migrants comprised just 0.6% of the total population of the districts participating in the study, they accounted for 4% of all HIV diagnoses..
The researchers believe their study has a number of implications:
- The failure of HIV surveillance methods to record the place of birth of individuals means that the needs of foreign-born individuals are being neglected.
- US surveillance data are currently being misinterpreted. For example, the increase in HIV infections amongst black people in King County, Washington, was originally thought to be due to new HIV infections amongst American-born black people. This could mean that prevention efforts are misdirected.
- By failing to properly estimate the full contribution of African-born individuals to the US HIV epidemic, current surveillance data may be underestimating the importance of heterosexual transmission to the ongoing epidemiology of HIV in the country.
The investigators call on US federal, state and local authorities and health departments to develop resources targeted at African-born individuals that provide information about the availability of HIV testing and care. The authors also note that there are unanswered questions about the “societal commitment to noncitizens residing in the United States”, particularly “to what extent will HIV-infected residents be eligible for medical care and how will testing HIV-positive affect their residency?”
HIV among African-born persons in the United States: a hidden epidemic.
Roxanne P Kerani, PhD;et al.
Journal of Acquired Immune Deficiency Syndromes(JAIDS) 49: 102 – 106, 2008.
Link to JAIDS abstract
Spanking has been, and still is, a common method of child discipline used by American parents.
But mothers who report that they or their partner spanked their child in the past year are nearly three times more likely to state that they also used harsher forms of punishment than those who say their child was not spanked, according to a new study led by the Injury Prevention Research Center at the University of North Carolina at Chapel Hill.
Such punishments included behaviors considered physically abusive by the researchers, such as beating, burning, kicking, hitting with an object somewhere other than the buttocks, or shaking a child less than 2 years old.
“In addition, increases in the frequency of spanking are associated with increased odds of abuse, and mothers who report spanking on the buttocks with an object – such as a belt or a switch – are nine times more likely to report abuse, compared to mothers who report no spanking with an object,” said Adam J. Zolotor, M.D., the study’s lead author and an assistant professor in the department of family medicine in the UNC School of Medicine.
The study will be published on the Web site of the American Journal of Preventive Medicine on and is scheduled for publication in the print version of the journal on September 17.
Although some surveys show evidence of a modest decline in spanking over the last 30 years, recent surveys show that up to 90 percent of children between the ages of 3 and 5 years are spanked by their parents at least occasionally.
Zolotor and his co-authors conducted an anonymous telephone survey on parenting of a probability sample of 1,435 mothers in North Carolina and South Carolina in 2002.
Forty-five percent of the mothers reported that they or their partner had spanked their child in the previous 12 months and 25 percent reported spanking with an object on the buttocks. Four percent reported using harsher forms of punishment that met the study’s definition of physical abuse.
Statistical analyses of the survey data found that while any spanking was associated with increased risk of abuse, spanking with an object was strongly associated with abuse. Only 2 percent of the mothers who reported no spanking reported use of physically abusive punishment. In comparison, 6 percent of mothers who reported spanking and 12 percent of mothers who reported spanking with an object also reported abusive punishment.
“This study demonstrated for the first time that parents who report spanking children with an object and parents who frequently spank children are much more likely to report other harsh punishment acts consistent with physical abuse,” Zolotor said.
The American Academy of Pediatrics states that “striking a child with an object is unacceptable and may be dangerous.” Zolotor said the study supports this policy statement by underscoring that while spanking increases the likelihood of physical abuse, frequent spanking and spanking with an object are far more likely to lead to abuse. He said this may be due to the limited effectiveness of discipline when parents have few other tools for discipline (such as positive reinforcement and time out).
The University of North Carolina site includes a video interview with Dr. Zolotor
Link to UNC study
Thursday, August 28, 2008
HIV Is Spreading in New York City at Three Times the National Rate, a Study Finds
HIV is spreading in New York City at three times the national rate — an incidence of 72 new infections for every 100,000 people, compared with 23 per 100,000 nationally — according to a study released on Wednesday by the city’s Department of Health and Mental Hygiene.
The findings, based on a new formula developed by the CDC estimated that 4,762 New Yorkers contracted H.I.V. in 2006, the most precise estimate the city had ever offered.
Blacks, and men who have sex with other men, are the groups at greatest risk of contracting H.I.V., the study found. A summary of the new data:
· Men accounted for 76 percent of new H.I.V. infections and women for 25 percent. (The figures exceed 100 percent because of rounding.)
· Blacks made up 46 percent of the newly infected; Hispanics, 32 percent; and whites, 21 percent. (Figures for other racial or ethnic groups were not provided.)
· Those under age 20 made up 4 percent of the newly infected; those 20 to 29 years old, 24 percent; those 30 to 39 years old, 29 percent; those 40 to 49 years old, 29 percent; and those 50 and older, 15 percent.
· Sex between men was the main cause in 50 percent of new infections; high-risk heterosexual sex in 22 percent; intravenous drug use in 8 percent; and unknown or uncertain causes in 18 percent.
As the health department has repeatedly noted, gay minority men were particularly at risk. For example, of new H.I.V. infections among men under age 30 who have sex with men, 77 percent were in black or Hispanic men, as were 59 percent of new H.I.V. infections among men ages 30 to 50 who have sex with men.
Over all, the study found some interesting differences between national and local rates of new H.I.V. infections. Nearly two-thirds of the city’s new infections occurred in people 30 to 50 years old. Nationally, people under 30 accounted for 41 percent of new infections, compared with 28 percent in New York City.
Also, within New York City, whites were infected at four times the national rate, Hispanics at three times the national rate, and blacks at almost twice the national rate.
Most college students understand how they can prevent the transmission of HIV but are less knowledgeable about HIV testing, according to a new University of Georgia study that appears in the July issue of the Journal of the National Medical Association
Su-I Hou, associate professor in the UGA College of Public Health, surveyed more than 500 students and found that they scored higher on general questions related to HIV and AIDS (82 percent correct) than items specifically related to HIV testing (72 percent correct).
A lack of knowledge about HIV testing can be dangerous, Hou said. She explained that most HIV tests do not measure or detect the virus itself but instead look for body’s reaction to the virus - the presence of antibodies to HIV. Antibodies generally appear within three months after HIV infection, but it may take up to six months in some people. During this “window period” an infected person may test negative yet still transmit the virus to others.
Because people may be reluctant to discuss sensitive information, Hou used an online survey. She recruited the students using flyers, classroom announcements, e-mail and even the social networking site Facebook.
While the study found that there were no significant differences between groups in scores related to general or testing-specific knowledge of HIV, it did reveal that African Americans rated significantly higher on their perceived knowledge of HIV. The study also found that black students were nearly seven times more likely to be tested for HIV.
Using an Online Survey to Assess Knowledge of HIV in General and Testing Specifically among Black and White College Students
Su-I Hou, DrPH, RN, CHES
Journal of the National Medical Association vol. 100, no. 7, July 2008: 826
Link to JNMA article [pdf]
Opt-Out Testing for Human Immunodeficiency Virus in the United States
Explores the Centers for Disease Control and Prevention (CDC) recommendation for HIV testing for all persons aged 13 to 64 years in all health care settings. Signed consent would not be required and counseling with referral would be managed as it is for other serious conditions.
Concerns about the change include laws in some states that mandate signed consent and counseling, a perception that counseling is an effective prevention strategy, variability in payment coverage for the test, concerns about the stigma and discrimination that may accompany the HIV diagnosis, and the possibility that other testing policies would be more effective.
Some states have changed legislation to reduce barriers to testing. 35 of 74 national professional societies have endorsed the new recommendations, and multiple demonstration projects have shown feasibility.
Opt-Out Testing for Human Immunodeficiency Virus in the United States: Progress and Challenges
John G. Bartlett et al
Link to JAMA abstract
Blood viral load predicts HIV transmission better than semen viral load in small study among MSM
A small US study among men who have sex with men has added new information to the debate around the links between HIV transmission and viral load levels in semen. The study, published in the August 20th issue of AIDS, found that blood viral load correlated better with transmission than seminal viral load. The study also investigated the role of infection with herpes simplex virus-2, finding an increased risk of HIV transmission, but only when the HIV source partner carried the virus.
Sexual transmission of HIV is affected by virological, biological and behavioral factors, such as viral load, mucosal inflammation and type of sexual intercourse. The complex interactions between these factors and the ways in which they might be modified to reduce the risk of transmitting the virus have been the subject of debate, but there are limited solid empirical data.
The debate over the impact of viral load on HIV transmission was brought into the open earlier this year when the Swiss Federal AIDS Commission released a statement arguing that under very specific conditions the risk of someone with an undetectable viral load transmitting HIV falls to the point of being negligible.
Amid this uncertainty that investigators at the University of California, San Diego established a case-controlled study of men who have sex with men (MSM) to assess the impact of two factors on HIV transmission: viral load (in blood and in semen) and HSV-2 infection.
The study identified 47 pairs of men in which one partner was HIV-positive and there had been the potential for transmission through sexual exposure. Blood and semen samples were collected from the HIV-positive partner and the time between exposure and sample was estimated. Exposure date was identified as either the known date of sexual intercourse or as 14 days prior to screening, based on participants being told to recruit sexual partners from only the previous two weeks. The presence of HSV-2 was tested, and treatment with aciclovir or valaciclovir was noted. Both partners were also tested and treated for the bacterial sexually transmitted infections gonorrhoea, chlamydia and syphilis.
Investigators evaluated the link between viral load in blood and semen, and transmission.
Upon multivariate analysis, blood viral load was significantly associated with transmission; semen viral load was not. The range of blood viral loads among transmitters had a higher maximum and narrower range of values than the non-transmitting group. However, the range of semen viral loads for transmitters fell completely within the range of semen viral loads for non-transmitters.
The association in this study between sexual transmission and blood viral load, but not seminal viral load, was puzzling, given that sexual transmission involves seminal virus not blood-borne virus. The investigators hypothesize that “this may well be artifactual owing to the lag between sexual exposures and specimen collections.” They state that future studies must do better to collect viral load specimens more closely to time of transmission, as semen viral loads have been shown to vary over time and over a broader range than matched blood viral loads.
Herpes simplex virus 2 serostatus and viral loads of HIV-1 in blood and semen as risk factors for HIV transmission among men who have sex with men.
David M Butler et al
AIDS 22:1667 – 1671, 2008.
Link to AIDS abstract
Link to Aidsmap article [with links to the articles & statements cited]
Wednesday, August 27, 2008
A man transmitted HIV to his regular male partner despite taking antiretroviral treatment and having an undetectable viral load in his blood, German doctors report in the journal Antiviral Therapy. The authors believe that this is the first recorded instance of an individual with an undetectable viral load infecting a sexual partner with HIV.
In an editorial accompanying the case report, two of the authors of what has come to be known as the “Swiss Statement”, whilst acknowledging a “very low” risk of transmission from individuals taking antiretroviral therapy with an undetectable viral load, highlight what they believe to be some weaknesses in the documentation of this case. Furthermore, they point out that in their own experience “all suspected cases of transmission during antiretroviral therapy turned out to have another source.”
And a separately published study looks likely to further fuel the already fierce debate about the infectiousness (or otherwise) of patients being treated with antiretroviral drugs. French investigators report in the August 20th edition of AIDS that 5% of antiretroviral-treated men with an undetectable viral load in their blood had detectable HIV in their semen. None of these men had a sexually transmitted infection.
In January this year, senior HIV doctors in Switzerland issued a statement saying that HIV-positive patients treated with antiretroviral drugs with good adherence to their treatment, a viral load below 40 copies/ml for at least six months, and no sexually transmitted infections should not be considered capable of transmitting HIV sexually. The statement has proved controversial and there was a lively debate about the infectiousness of patients taking successful antiretroviral therapy at the recent International AIDS Conference in Mexico City.
The conference was also told that the lowest blood viral load in a documented case of HIV transmission was approximately 300 copies/ml. But now doctors in Germany have reported a case of transmission when a patient taking antiretroviral therapy had a sustained undetectable viral load in his blood.
“We feel confident”, write the report’s authors, “that the present case report suggests that transmission can occur despite undetectable plasma viral load. Therefore, we cannot support any recommendations that abandon the use of safer-sex practices in this context without mentioning the possibility of HIV transmission.”
But the authors of the editorial accompanying the case report believe that even a well-documented case report of sexual transmission of HIV involving a patient taking anti-HIV drugs with an undetectable viral load would “not indicate that this practice is associated with a risk of sufficient magnitude to have public health implications.” They draw an analogy with oral sex, where individual cases of HIV transmission have been reported.
A separate French study has found that 5% of 145 HIV-positive men enrolled in an assisted conception study had detectable viral load in their semen, despite having an undetectable viral load in their blood.
Is transmission of HIV-1 in non-viraemic serodiscordant couples possible?
Martin Sturmer et al
Antiviral Therapy 13: 729 – 732, 2008.
Link to AT abstract
HIV transmission hunting – the chase for low risk events.
Pietro L Vernazza and Bernard Hirschel
Antiviral Therapy 13: 641 - 642, 2008.
Link to AT article [no abstract – subscription required]
Detection of HIV-1 RNA in seminal plasma samples from treated patients with undetectable HIV-1 RNA in blood plasma.
Anne-Genevieve Marcelin et al
AIDS 22: 1677 – 79, 2008.
Link to AIDS abstract
Link to Aidsmap article [also includes more links and details of cases cited]
A new study from researchers at the University of Pittsburgh and Carnegie Mellon University sheds light on why smokers' intentions to quit “cold turkey” often fizzle out within days or even hours.
If a smoker isn't yearning for a cigarette when he makes the decision to kick the habit-and most aren't-he isn't able to foresee how he will feel when he's in need of a nicotine buzz. The new study bolsters the theory that smokers not in a state of craving a cigarette will underestimate and underpredict the intensity of their future urge to smoke.
“We have observed previously that the idea of smoking a cigarette becomes increasingly attractive to smokers while they are craving,” said the study's lead investigator and University of Pittsburgh professor of psychology Michael Sayette. “This study suggests that when smokers are not craving, they fail to appreciate just how powerful their cravings will be. This lack of insight while not craving may lead them to make decisions-such as choosing to attend a party where there will be lots of smoking-that they may come to regret.”
The study looked at the cold-to-hot empathy gap-that is, the tendency for people in a “cold” state (not influenced by such visceral factors as hunger, fatigue) to mispredict their own behavior when in a “hot” state (hungry, fatigued), in part because they can't remember the intensity of their past cravings.
“These findings suggest that smokers are likely to underpredict their own future desire to smoke when they're not craving a cigarette,” said study coauthor George Loewenstein, the Herbert A. Simon Professor of Economics and Psychology at Carnegie Mellon.
“The research not only has implications for helping smokers quit, but it also enlightens us on how nonsmokers may pick up the habit. If smokers can't appreciate the intensity of their need to smoke when they aren't currently craving, what's the likelihood that people who have never smoked can do so,” said Loewenstein.
Exploring the Cold-to-Hot Empathy Gap in Smokers.
Psychological Science, September 2008
Polar Bears Found Swimming Miles From Alaskan Coast
An aerial survey by government scientists in Alaska’s Chukchi Sea recently found at least nine polar bears swimming in open water – with one at least 60 miles from shore – raising concern among wildlife experts about their survival.
Geoff York, the polar bear coordinator for WWF's Arctic Programme, said that when polar bears swim so far from land, they could have difficulty making it safely to shore and are at risk of drowning, particularly if a storm arises.
“To find so many polar bears at sea at one time is extremely worrisome because it could be an indication that as the sea ice on which they live and hunt continues to melt, many more bears may be out there facing similar risk,” he said.
“As climate change continues to dramatically disrupt the Arctic, polar bears and their cubs are being forced to swim longer distances to find food and habitat.”
Scientists say the Arctic is changing more rapidly and acutely than anywhere on the planet, noting that 2007 witnessed the lowest sea ice coverage in recorded history.
Satellite images indicate that ice was absent in most of the region where the bears were found on August 16, 2008, and some experts predict this year’s sea ice loss could meet or exceed the record set last year.
Tuesday, August 26, 2008
With long distance love, it's never as simple as boy meets girl.
Gavin is an ordinary boy from Billericay, Essex in southeast England.
Stacey is an ordinary girl from Barry Island, south Wales . . . .
Troubled Children Hurt Peers' Test Scores, Behavior
Troubled children hurt their classmates' math and reading scores and worsen their behavior, according to new research by economists at the University of California, Davis, and University of Pittsburgh.
Scott Carrell, an assistant professor of economics at UC Davis, and co-author Mark Hoekstra, an assistant professor of economics at the University of Pittsburgh, cross-referenced standardized test results and school disciplinary records with court restraining order petitions filed in domestic violence cases for more than 40,000 students enrolled in public elementary schools in Florida's Alachua County for the years 1995 through 2003.
Not only did children from troubled homes suffer, however: Test scores fell and behavior problems increased for their classmates as well. Troubled boys caused the bulk of the disruption, and the largest effects were on other boys. Indeed, Carrell and Hoekstra estimate that adding just one troubled boy to a class of 20 children reduces the standardized reading and math scores of other boys in the room by nearly two percentile points. And adding just one troubled boy to a class of 20 students increases the likelihood that another boy in the class will commit a disciplinary infraction by 17 percent.
Troubled girls, in contrast, had only a small and statistically insignificant impact on the test scores or behavior of their classmates. The study did not investigate the reasons for the gender differences.
"Our findings have important implications for both education and social policy," they write. "First, they suggest that policies that change a child's exposure to classmates from troubled families will have important consequences for his or her education outcomes. In addition, the results also help provide a more complete measure of the social costs of family conflict."
The research does not suggest that all disruptive schoolchildren come from families that experience domestic violence, nor are all children from domestic violence disruptive, Carrell emphasized.
Externalities in the Classroom: How Children Exposed to Domestic Violence Affect Everyone's Kids.
Scott E. Carrell & Mark L. Hoekstra
National Bureau of Economic Research Working Paper No. 14246, August 2008
Longevity: Independent, Even in Old Age
The flip side of a longer life expectancy might be a much greater public health burden in caring for the very old and extremely disabled. But that is not the case, according to a new report published online in the Proceedings of the National Academy of Sciences. The study tracked all Danes born in 1905 for seven years beginning in 1998. Most had died by the end of the study, but as the researchers examined them with four assessments at ages 94, 96, 98 and 100, the percentage living independently decreased only slightly in the seven-year span, to 32.7 percent from 38.9 percent.
At the same time, the small number of people who survived to age 100 — 156 of the original 2,234 — showed a significant increase in disability, to 67.3 percent at 100 from 30.1 percent at 92. The explanation for the apparent paradox, the authors write, is the high level of mortality among dependent participants. The few who survived the longest were least likely to be dependent at the start of the study.
“Some worry that extreme old age leads to extreme levels of disability,” said Dr. Kaare Christensen, the lead author of the study and a professor of epidemiology at the University of Southern Denmark. “But our study shows that people are no more dependent at 100 than at 92.”
Exceptional longevity does not result in excessive levels of disability
Kaare Christensen et al
Proceedings of the National Academy of Sciences Published online before print August 18, 2008, doi: 10.1073/pnas.0804931105
A research analysis of prescription drug claims data in Ontario, Canada found that three regulatory warnings of serious adverse events slowed the growth of use of atypical antipsychotic drugs among elderly patients with dementia, but they did not reduce the overall prescription rate of these drugs, found
The rate of use of these drugs actually increased 20% from the month prior to the first warning in September 2002 to the end of the study period in February 2007. About 70% of people receiving antipsychotic drugs lived in nursing homes, and approximately 40% were aged 85 or older.
Three new atypical antipsychotic drugs approved for the treatment of schizophrenia and other related psychiatric conditions by Health Canada, however only one of them was approved for short term use to treat symptoms of aggression and psychosis in elderly patients with dementia. Between October 2002 and June 2005 Health Canada released three warning of increased risk of stroke or death in elderly patients with dementia taking these drugs.
Effect of regulatory warnings on antipsychotic prescription rates among elderly patients with dementia: a population-based time-series analysis.
Elmira Valiyeva, PhD et al
Canadian Medical Association Journal, 2008; 179 (5): 438 DOI: 10.1503/cmaj.071540
Greater access to free medicine has helped reduce AIDS-related deaths in Malawi by 75 percent in the past four years, Mary Shawa, the country's principal secretary for HIV and AIDS, said Monday. HIV and AIDS have been blamed for 59 percent of deaths there among people 15 to 59 years old. As of March this year, the government had put 159,111 people on free antiretroviral drugs, and 106,547 of them were still alive.
BBC News on line also covers the story in Drugs 'slash' Malawi Aids deaths
Monday, August 25, 2008
Low-cost System Thwarts Internet Eavesdropping
The growth of shared Wi-Fi and other wireless computer networks has increased the risk of eavesdropping on Internet communications, but researchers at Carnegie Mellon University's School of Computer Science and College of Engineering have devised a low-cost system that can thwart these "Man-in-the-Middle" (MitM) attacks.
The system, called Perspectives, also can protect against attacks related to a recently disclosed software flaw in the Domain Name System (DNS), the Internet phone book used to route messages between computers.
The researchers — David Andersen, assistant professor of computer science, Adrian Perrig, associate professor of electrical and computer engineering and public policy, and Dan Wendlandt, a Ph.D. student in computer science — have incorporated Perspectives into an extension for the popular Mozilla Firefox v3 browser than can be downloaded free of charge at the Carnegie Mellon site
Perspectives employs a set of friendly sites, or "notaries," that can aid in authenticating Web sites for financial services, online retailers and other transactions requiring secure communications. By independently querying the desired target site, the notaries can check whether each is receiving the same authentication information, called a digital certificate, in response. If one or more notaries report authentication information that is different than that received by the browser or other notaries, a computer user would have reason to suspect that an attacker has compromised the connection.
Certificate authorities, such as VeriSign, Comodo and GoDaddy, already help authenticate Web sites and reduce the risk of MitM attacks. The Perspectives system provides an extra measure of security in those cases but will be especially useful for the growing number of sites that do not use certificate authorities and instead use less expensive "self-signed" certificates.
"When Firefox users click on a Web site that uses a self-signed certificate, they get a security error message that leaves many people bewildered," Andersen said. Once Perspectives has been installed in the browser, however, it can automatically override the security error page without disturbing the user if the site appears legitimate.
The system also can detect if one of the certificate authorities may have been tricked into authenticating a bogus Web site and warn the Firefox user that the site is suspicious. "Perspectives provides an additional level of safety to browse the Internet," Perrig said. "To the security conscious user, that is a significant comfort."
Most Internet communications, such as to standard hypertext transfer protocol (HTTP) sites, are unsecured, but those involving encryption over a secured socket layer (SSL) and those using secure shell (SSH) protocol, which involves the use of a login and password, require that sites authenticate themselves with a digital certificate containing a so-called public key, which is used for encryption.
The exchange of this security information typically occurs without the computer user being aware of it. But when something isn't quite right, a dialogue box such as "Unable to verify the identity of XYZ.com as a trusted site" is displayed by the Web browser.
"Most users don't have a clue about what to do in those cases," Wendlandt said. "A lot of them just shrug and go ahead with the connection, potentially opening themselves up to attack."
A vulnerability disclosed in July in the DNS software poses a different problem for computer users, but one that also is addressed by Perspectives. The software flaw could enable an attack against an Internet Service Provider (ISP) that would cause the ISP to connect users with a malicious site instead of the legitimate site they were seeking. "With Perspectives, even if a client's ISP has fallen victim to the attack, the client will be able to detect that the public key received from the fake site is inconsistent with the results returned from the notaries," Wendlandt said.
Researchers at Rutgers University and The University of Texas at Austin have reported a discovery that could help scientists develop drugs to fight the much-feared bird flu and other virulent strains of influenza.
The researchers have determined the three-dimensional structure of a site on an influenza A virus protein that binds to one of its human protein targets, thereby suppressing a person's natural defenses to the infection and paving the way for the virus to replicate efficiently. This so-called NS1 virus protein is shared by all influenza A viruses isolated from humans – including avian influenza, or bird flu, and the 1918 pandemic influenza virus.
A paper detailing this breakthrough discovery appears in the PNAS (Proceedings of the National Academy of Sciences) Early Edition and will be published in an upcoming issue of the PNAS print edition.