If you've ever uttered the words, "I'm so hungry I could eat a horse," you know it's not literally possible to chow down on such a huge animal in one sitting. But have you ever considered what stops us from being able to do so (besides the scarcity of horsemeat on most menus)? Scientists say a number of hormones are at work in alerting us that we've had enough to eat. Now there's fresh evidence that one of those hormones—leptin—may alter brain structure in areas associated with craving and addiction in obese individuals born without a gene that produces leptin. The researchers looked at brain scans to see leptin activity in the brain before and after treatment. "There are very few people who have a genetic mutation, that they are just born without it…they tend to eat too much," explains Julio Licinio, a biobehavioral researcher at UCLA who, along with a team of UCLA scientists, studied the only three such people scientists have identified as lacking the leptin gene. Licinio gave them daily leptin replacement while his colleague, brain researcher Edythe London, used MRI brain scans to look at the volunteers' brain structure before they took leptin, and then at three and 18 months into the study. "We found dramatic results in brain structure," says London. "The actual composition of the brain changed, but it wasn't all over the brain. The composition of the brain changed only in regions known to be related to self control behaviors." © ScienCentral, 2000-2005.

Keyword: Obesity; Drug Abuse
Link ID: 7673 - Posted: 06.24.2010

By Jennifer Viegas, Discovery News — Individuals who cope well with stress after trauma usually are described as being "thick skinned," but new research reveals the thickness is in their brains, not in their skin. Scientists determined that resilient people tend to have a thick ventral medial prefrontal cortex (vmPFC), which is near the front of the brain. Conversely, this region tends to be thin for those who experience a lot of anxiety. The discovery will enable doctors to predict who is at risk for stress-related disorders, which could lead to better treatments and may even determine who is best suited for certain careers and activities. "For instance, an individual with a thin vmPFC might wish to avoid high risk professions such as policeman, firefighter or soldier," said Scott Rauch, co-author of the study, which recently appeared in the Proceedings of the National Academy of Sciences. Rauch, who is associate chief of psychiatry for neuroscience research at Massachusetts General Hospital, and his colleagues made the determination after testing 14 healthy volunteers. Volunteers looked at digital photographs of furnished rooms that contained lamps. Whenever the lamps lit up in colors, the test subjects would receive an electrical shock that each participant previously rated as "highly annoying but not painful." Copyright © 2005 Discovery Communications Inc.

Keyword: Stress
Link ID: 7672 - Posted: 06.24.2010

By Rossella Lorenzi, Discovery News — Birds fly south in search of warmer climates because they lack the brains to survive harsh winter conditions, according to a new study. Published in the journal Proceedings of the Royal Society, the research suggests that non-migrating species have bigger brains and are more creative at finding food in the hard winter months. Daniel Sol of the Independent University of Barcelona in Spain and colleagues reanalyzed previous observations of 134 songbird species breeding in the Western Palaearctic region, which includes Europe, North Africa, the Middle East and Central Asia. They divided the songbird species into three groups: long-distance migrants that winter south of Sahara; short-distance migrants that winter south of its breeding range but north of Sahara; and year-round residents. It emerged that species that stayed in one place were more creative in finding food. Copyright © 2005 Discovery Communications Inc.

Keyword: Intelligence; Animal Migration
Link ID: 7671 - Posted: 06.24.2010

All too often we hear of a parent arrested for abusing his or her child. Inevitably, someone asks, "how can this happen?" While the exact reasons for any human behavior are complicated, researchers now have evidence that sometimes such behavior may be passed on from one generation to the next. Because infant abuse is found in animals as well as humans, researchers have been able to study animals like Rhesus Monkeys to see if there are lessons that can be applied to humans. In a study published in the Proceedings of the National Academy of Sciences Dario Maestripieri of the University of Chicago reported that the infant's "early experience" being abused seems to be how the behavior is passed on, adding, "It doesn't seem to be genetically transmitted." He found this by swapping infants "at birth between [the] abusive and non-abusive mothers" eliminating the possibility of a genetic link between mother and any abusive traits the offspring might later show. When the infants grew up and became mothers, Maestripieri found that, "The individuals that had been reared by abusive mother had a high chance of becoming abusive mothers, themselves. Whereas, those that were born to abusive mothers, but were reared by control mothers did not become abusive parents." © ScienCentral, 2000-2005

Keyword: Aggression; Sexual Behavior
Link ID: 7670 - Posted: 06.24.2010

Like the rest of the 18 million people worldwide, everyday Lola Crosswhite strives to live a normal life while battling the effects of Alzheimer's disease. Today she fights the disease with the help of medications, notes and her daughter Diana Shaw. "We have a planner, we call it mom's paper brain," says Shaw. But she also tried fighting it with gene therapy. In 2002, Crosswhite was one of eight early-stage Alzheimer's patients who volunteered for a clinical trial to test the safety of the first gene therapy for the disease. Researchers led by University of California, San Diego Mark Tuszynski reported in the journal Nature Medicine that the safety trial showed promise. They took skin cells from patients, grew them up in a culture dish and genetically engineered them to make human nerve growth factor (NGF). The cells were then injected into the area of the brain where cells were dying due to Alzheimer's. In this way, the implanted cells act as biological pumps for the local delivery of the growth factors in the brain. "The growth factor released by these genetically engineered cells will bath the other cells in the growth factor, slow down the degeneration and thereby improve, or slow the decline in Alzheimer's disease," Tuszynski explains. "Establishing clearly that degenerating human cells can respond to growth factors." © ScienCentral, 2000-2005.

Keyword: Alzheimers
Link ID: 7669 - Posted: 06.24.2010

The odds of having a son or daughter aren't always even. Many kinds of animals will preferentially bear more males, or females, to increase the chances of passing on their genes. Female fruit flies, for example, bear more sons after mating with younger males than with older ones. Why? The reason, researchers have learned, is that the sons of young lovers are much more likely to turn out to be virile studs. To solve the puzzle, evolutionary biologists Tristan Long, now at the University of California in Santa Barbara, and Alison Pischedda, at Queen's University in Kingston, Canada, mated virgin female Drosophila to males of various ages. The team found that the sons of young (1-day old) males produced more offspring than sons of old (13-day old) males; whereas there was no difference in numbers of offspring produced by daughters of young and old males. This indicates that it pays to produce more sons when mated to a high quality (in this case, young) male, the researchers report online 20 July in Proceedings of the Royal Society B. Older males may give rise to poorer quality sons because they've accumulated harmful mutations during their lives, and these will have a bigger effect on sons than daughters because males experience more intense selection pressure when it comes to mating, the team speculates. But the researchers don't know how fruit flies skew their progeny's sex ratio towards sons or daughters. Copyright © 2005 by the American Association for the Advancement of Science.

Keyword: Sexual Behavior
Link ID: 7668 - Posted: 06.24.2010

CAMBRIDGE, Mass., –- Scientists working with salmon have found that gene expression in the brain can differ significantly among members of a species with different life histories. Their study indicates that roughly 15 percent of Atlantic salmon genes show differential expression in males who migrate from their freshwater birthplaces to mature in oceans versus those who do not leave the freshwater environment to mature. The researchers, at Harvard University, the University of Massachusetts and the US Geological Survey, report the finding in the current issue of Proceedings of the Royal Society B. They compared female salmon, male salmon that will eventually undertake the well-known journey from their river birthplaces to oceans –- and then migrate heroically back upstream one to three years later to spawn –- and males of the same age known as "sneakers" that mature at greatly reduced size without leaving freshwater. "The finding that hundreds of the nearly 3,000 genes we studied were expressed differently in the brains of sneakers and other male salmon came as a surprise," says Nadia Aubin-Horth, a postdoctoral researcher in the Bauer Center for Genomics Research in Harvard's Faculty of Arts and Sciences. "Since these males of the same species in the same wild environment differed only in their life history, we did not expect the expression of so many of their genes to differ." Aubin-Horth and her colleagues were also surprised by some of the 17 separate classes of genes demonstrating differing activity levels.

Keyword: Genes & Behavior; Sexual Behavior
Link ID: 7667 - Posted: 06.24.2010

By Jennifer Viegas, Discovery News — Humans attempt to do many things at the same time, such as driving and chatting on the phone, or working and listening to music, and now research suggests why such multitasking may be possible: the brain appears to have its own control center. Studies indicate that the physical "center" of the brain is located in the prefrontal cortex, on the left-hand front side, just above the temple. This is the first time that a "mastermind," which could control both visual and auditory activity, has been identified. Before the new research, most scientists thought the brain processed sight and sound in different areas. Now it is believed that sight and sound influence each other. "Many others have studied how matched audio-visual events, such as watching lips move and hearing speech sounds, are processed in the brain, but we wanted to draw attention to all of the audio-visual events humans are exposed to that are completely unrelated, like driving and talking on a cell phone or cleaning your apartment and listening to music," said Jennifer Johnson, lead author of the study and a researcher in the experimental psychology program at McGill University. Copyright © 2005 Discovery Communications Inc.

Keyword: Attention
Link ID: 7666 - Posted: 06.24.2010

Roxanne Khamsi A hormone that regulates appetite may also influence memory formation, researchers say. Recent findings, and the worldwide trend toward larger waistlines, have convinced them that we need to take a closer look at how obesity affects learning. In the past decade, a hormone known as leptin has received enormous attention for its role in regulating appetite and metabolism. Fat tissues produce significant quantities of this natural compound, which in turn reduces a person's desire to eat. At first, researchers were surprised to discover that obese individuals often over-express this hormone, as this would be expected to reduce their appetite. But many now believe that these people are simply desensitized to leptin. At the same time, studies have begun to link memory deficits with metabolic diseases such as obesity and diabetes. Jenni Harvey of the University of Dundee, UK, says patients with diabetes can experience "anything from short-term memory loss to Alzheimer's-like symptoms". And she says leptin is the key. An increasing number of reports show that abnormal levels of leptin can significantly alter brain cell function, Harvey told an audience at the annual meeting of the Biochemical Society in Glasgow, UK, this week. ©2005 Nature Publishing Group

Keyword: Learning & Memory; Obesity
Link ID: 7665 - Posted: 06.24.2010

New research suggests that accumulation of amyloid-â peptides in cerebral blood vessels, as opposed to the brain itself, may be a more important pathological mediator of Alzheimer's disease. Two independent yet related articles describe such findings in the August issue of The American Journal of Pathology. Both articles are highlighted on the Journal's cover. Alzheimer's disease, the most common form of progressive dementia, affects an estimated 4.5 million Americans according to the Alzheimer's Association. Amyloid-â (Aâ) deposition is a hallmark of Alzheimer's disease and other cerebral amyloid angiopathies. However, exactly how Aâ accumulates and causes damage is not fully understood. In the first article, "Cerebral microvascular Aâ deposition induces vascular degeneration and neuroinflammation in transgenic mice expressing human vasculotropic mutant AâPP," Miao et al. describe early-onset Aâ deposition in Tg-SwDI mice. These mice express Aâ protein with mutations that are found in human early-onset cerebral amyloid angiopathy, causing specific accumulation of Aâ in cerebral blood vessels. The Aâ peptides accumulated because they could not adequately cross the blood-brain barrier to be cleared from the brain. Over time, Aâ accumulation increased in the cerebral microvessels of the thalamus and subiculum of the brain. This resulted in degeneration of blood vessels as evidenced by reduced vessel density and increased apoptosis.

Keyword: Alzheimers
Link ID: 7664 - Posted: 07.21.2005

Cocaine may keep users from adapting to new situations by disrupting connections between key brain regions, suggests a new study in rats. The finding may shed light on the impulsive behaviour seen in cocaine addicts, researchers say. A team looked at the connections between two regions of the brain: one involved with learning, memory and processing information - the prefrontal cortex and hippocampus - and one involved with pleasure seeking, emotion and reward behaviour - the nucleus accumbens in the limbic system. Normally, these two regions are held in balance with connections between the two sending information in both directions and allowing “plasticity” of thought, so that behaviour can be modified and adapted to different situations. Neuroscientists Yuriori Goto and Anthony Grace at the University of Pittsburgh, US, believe that cocaine disrupts these connections and causes the limbic system to become over stimulated. “It may explain why cocaine addicts are oriented towards pleasure rather than other goals, and have an impaired ability to make decisions. It could be why addicts go back to taking more of the drug and ex-addicts often become addicted again faster than those who have never taken it,” says Grace. © Copyright Reed Business Information Ltd.

Keyword: Drug Abuse
Link ID: 7663 - Posted: 06.24.2010

Scientists who have discovered a gene linked to autism believe they can use the new knowledge to work out an individual's risk of the condition. The French team from IntegraGen SA hope to have a working risk assessment test on the market by the end of 2006. The gene sits on chromosome 16 and holds the DNA code for a protein that plays a central role in brain function. Experts said the Molecular Psychiatry study was promising but that it was premature to talk about an autism test. For their study, the French authors looked at 116 families where at least one member had autism. By analysing the DNA from these individuals they found a region on chromosome 16 - PRKCB1 - appeared to be linked with autism. PRKCB1 is expressed in granule cells in the cerebellum of the brain. Its associated protein is involved in transmitting signals from the granule cells to the Purkinje cells. Both these cells help relay messages in and out of the brain. Researchers have already found a decreased number of both granule and Purkinje cells in the brains of people with autism. Lead researcher Dr Jorg Hager said: "This is the first time that the protein PRKCB1, and the brain functions that it is involved with, have been associated with autism. The test they are devising will check for the presence of four genes, including PRKCB1, linked to autism. They envisage that families who already have a child with autism would be able to have their other children tested at an early age - around 18 months. If the cheek swab sample is positive, it means the infant is at increased risk of developing autism and early interventions such as behavioural educational programmes, can be started, said Dr Hager. Around 535,000 people in the UK have an autism spectrum disorder. (C)BBC

Keyword: Autism; Genes & Behavior
Link ID: 7662 - Posted: 07.20.2005

By GARDINER HARRIS WASHINGTON, - Top officials from three of the nation's premier public health agencies held an unusual news conference on Tuesday to say that childhood vaccines are life-saving medicines with no proven link to autism. "The science says very clearly that vaccines save lives and protect our children," said one of the officials, Dr. Julie L. Gerberding, director of the Centers for Disease Control and Prevention. To many, that declaration might have seemed akin to an announcement so basic as that high cholesterol readings are linked with heart disease. But the officials felt a need to make a forceful defense of vaccines because a growing number of parents contend that a mercury-containing vaccine preservative called thimerosal caused their children to become autistic. Indeed, several parents held a vigil outside the news conference, with one holding a large sign blaming vaccines for her child's disorder. Representative Dave Weldon, a Florida Republican who champions the notion that thimerosal has caused an explosion of autism cases around the world, attended the news conference and, after it ended, gave his own press briefing criticizing the public health officials. Copyright 2005 The New York Times Company

Keyword: Autism; Neurotoxins
Link ID: 7661 - Posted: 07.20.2005

Seeing is something most of us take for granted, so a loss of vision can be frightening. "I was going to my college reunion and I was watching television the night before the reunion started. And all of a sudden I couldn't see anything on the television," recalls New Yorker Robert Burch, 71, who lost his sight in his right eye ten years ago due to age-related macular degeneration, or AMD. "All of a sudden that eye was finished, and it happens like that. And it's the scariest thing in the world because now you're afraid, 'My God, what happens if the second eye goes?'" Sadly, AMD, the leading cause of untreatable vision loss and legal blindness in the U.S. for people over the age of 60, has robbed more than 10 million Americans of some or all of their vision. Treatments have helped to keep people like Burch seeing longer, but there is no cure. Now, a team of researchers looking for the genetic causes of AMD has found that when a commonly inherited gene mutation is triggered, most likely by an infection, it can result in AMD. But at the same time they saw that certain other mutations in that gene actually protect against the chance of developing AMD. "The results were quite amazing," says geneticist Rando Allikmets, Acquavella Associate Professor in opthamology and Research Director at the Edward S. Harkness Eye Institute at Columbia University Medical Center. "Genetically speaking, I never believed there was a major gene that was involved in AMD… however it is the case. Now we know that at least half of the entire disease is caused by variants, common variants in Factor H." © ScienCentral, 2000-2005.

Keyword: Vision; Genes & Behavior
Link ID: 7660 - Posted: 06.24.2010

The hormone that controls the body's hunger pangs may also boost the memory, according to Scottish scientists. Researchers at Dundee University have found a link between the hormone leptin and the brain's memory and learning process. Leptin controls food intake and body weight and staves off the urge to eat. The study was carried out by a team which specialises in the braincell processes that produce learning and memory. Jenni Harvey, one of the researchers, said: "The hormone leptin, which is known to control food intake and body weight, has been shown to exert a profound influence on learning and memory processes in a region of the brain called the hippocampus. "Leptin enhances the level of communication between brain cells in the hippocampus in a process known as long-term potentiation (LTP)." It has been shown previously that people suffering from obesity have defects in their leptin levels and in the LTP process. The group's findings could therefore shed light on how obesity affects learning and memory. Dr Harvey said: "Defects in either leptin or genes that regulate leptin result in obesity and also cause impairments in LTP." (C)BBC

Keyword: Obesity; Learning & Memory
Link ID: 7659 - Posted: 07.19.2005

By NICHOLAS BAKALAR In recent years, many anticonvulsant drugs have been widely prescribed not only for seizure disorders, but for various kinds of chronic pain and for several different psychiatric illnesses, even though few have been approved by the Food and Drug Administration for those purposes. Now researchers are reporting a case of brain swelling, or cerebral edema, after abrupt withdrawal from pregabalin (Lyrica), a new antiepileptic drug that will be available this fall. The report appears online and in the August issue of Annals of Neurology. The patient, an 80-year-old woman, was in a clinical trial testing the drug for the severe pain of shingles, or postherpetic neuralgia. About a day after abruptly discontinuing it, she suffered nausea, headache and loss of balance, which progressed to delirium and hallucinations a week later. An M.R.I. scan revealed swelling in the same part of the brain that is affected in some epileptic patients who suddenly stop their drugs. Dr. Anne Louise Oaklander, the lead author on the paper, acknowledged that a single case did not constitute proof. "Maybe it's completely coincidental that she had M.R.I. abnormalities and a neurological illness, and that she'd recently stopped the drug," she said. "But the more likely explanation is that these things are linked." Copyright 2005 The New York Times Company

Keyword: Epilepsy
Link ID: 7658 - Posted: 07.19.2005

By NICHOLAS WADE Biologists have been making considerable progress in identifying members of a special class of genes - those that shape an animal's behavior toward others of its species. These social behavior genes promise to yield deep insights into how brains are constructed for certain complex tasks. Some 30 such genes have come to light so far, mostly in laboratory animals like roundworms, flies, mice and voles. Researchers often expect results from these creatures to apply fairly directly to people when the genes cause diseases like cancer. They are much more hesitant to extrapolate in the case of behavioral genes. Still, understanding the genetic basis of social behavior in animals is expected to cast some light on human behavior. Last month researchers reported on the role of such genes in the sexual behavior of both voles and fruit flies. One gene was long known to promote faithful pair bonding and good parental behavior in the male prairie vole. Researchers discovered how the gene is naturally modulated in a population of voles so as to produce a spectrum of behaviors from monogamy to polygamy, each of which may be advantageous in different ecological circumstances. The second gene, much studied by fruit fly biologists, is known to be involved in the male's elaborate suite of courtship behaviors. New research has established that a special feature of the gene, one that works differently in males and females, is all that is needed to induce the male's complex behavior. Copyright 2005 The New York Times Company

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 7657 - Posted: 07.19.2005

The controversy over whether the herbicide atrazine affects sexual differentiation in frogs is hopping again. A study in this issue of ES&T (pp 5255–5261) reports that gonadal abnormalities—in particular the presence of immature female egg cells, or oocytes, in the testes of male frogs—are common in Xenopus laevis, the “lab rat” of amphibian species. The research, funded by atrazine manufacturer Syngenta, suggests that such abnormalities may be a normal part of development, according to the authors. But other amphibian experts describe the results as “amazing” or “surprising” and say that they have never seen such abnormalities in laboratory studies. Normal or not? Oocytes—immature female egg cells—have been found in the testes of male X. laevis frogs that lived in outdoor tanks in South Africa.Atrazine is one of the most commonly used herbicides in the world, although it is banned in the EU. In 2002, University of California, Berkeley, amphibian endocrinologist Tyrone Hayes reported that atrazine exposure as low as 0.1 parts per billion induced gonadal abnormalities—multiple gonads or multiple testes and ovaries—in male X. laevis (Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 5476–5480). The paper set off a heated and acrimonious debate between Hayes and Syngenta-funded scientists over atrazine’s effects on frogs. In October 2003, U.S. EPA experts and a special pesticide scientific advisory panel concluded that studies supporting and refuting the finding all suffered from confounding effects (Environ. Sci. Technol. 2004, 38, 107A–108A). Despite the controversy, atrazine was re-registered for another three years by EPA in October 2003. Copyright © 2005 American Chemical Society

Keyword: Sexual Behavior
Link ID: 7656 - Posted: 06.24.2010

Whether or not an animal can recognize itself in the mirror has long been used by scientists as a means of self-awareness. Apes pass the test, but monkeys have been thought to perceive a stranger in their reflection. The results of a new study suggest that what monkeys see is not so simple: although they don't recognize themselves, they also treat their mirror twins differently than they do real animals. Primatologist Frans B. M. de Waal and his colleagues at Emory University studied how 14 adult capuchin monkeys responded to their reflections. They exposed the animals to both familiar and unfamiliar monkeys of the same sex and to a large mirror. Adult females acted friendly toward the mirror and made eye contact more often with their reflection than they did with a stranger. Males, on the other hand, had both friendly and negative reactions to the mirror monkeys but still treated the reflection differently than they did a live animal. The animals' reactions to the three situations were consistent and specific enough that human observers unaware of the experimental set-ups correctly categorized the testing conditions. The results indicate that capuchins know almost immediately that a reflection is not a regular stranger. It's possible, the authors argue in a report in the Proceedings of the National Academy of Sciences, that the monkeys are in an intermediate stage of recognizing that the mirror image as themselves and seeing it as another animal. --Sarah Graham © 1996-2005 Scientific American, Inc.

Keyword: Miscellaneous
Link ID: 7655 - Posted: 06.24.2010

COLUMBUS , Ohio – The tongue's ability to differentiate between sweet and bitter tastes may reside in the same taste bud cells, a new study reports. The study explains the discovery of a chemical messenger called neuropeptide Y (NPY) in taste bud cells. Though researchers have long known that NPY is active in the brain and gut, this is the first study to show that it is also active in taste bud cells. That finding gives scientists a deeper understanding of how the human brain may distinguish between different types of tastes, said Scott Herness, the study's lead author and a professor of oral biology and neuroscience at Ohio State University . The current study builds on previous work by Herness and his colleagues. A few years ago, the team found that another chemical messenger, cholecystokinin (CCK), is active in some taste bud cells. They think that these two peptides – small proteins that let cells talk to one another – have different effects in the same cells. The researchers report their findings in this week's online edition of the Proceedings of the National Academy of Sciences. CK may send opposite signals to the brain, depending on what kind of substance is on the tongue. Given the current findings, Herness thinks that CCK tells the brain that something bitter is on the tongue, while NPY sends a message that something sweet is being eaten.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 7654 - Posted: 06.24.2010