Chapter 7. Life-Span Development of the Brain and Behavior
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By ALEX STONE Last summer, in a failed attempt at humor, Clorox ran an online ad that declared, “Like dogs or other house pets, new dads are filled with good intentions but lacking the judgment and fine motor skills to execute well.” Although the company pulled the ad amid a flurry of scorn from the online commentariat, it nevertheless played to a remarkably widespread stereotype — that fathers are somehow unfit to raise children. In “Do Fathers Matter?” — spoiler alert: they do — the veteran science writer Paul Raeburn jumps to Dad’s defense, drawing on several decades of research and his own experience as a five-time father. What emerges is a thought-provoking field piece on the science of fatherhood, studded with insights on how to apply it in the real world. Historically, developmental psychologists have largely dismissed fathers as irrelevant. Nearly half the articles on child and adolescent psychology published in leading journals from 1997 to 2005, for example, make no mention of fathers; before 1970, when fathers weren’t even allowed in delivery rooms, less than a fifth of the research on parental bonding took them into account. This bias reflects a deeply ingrained assumption that fathers play a marginal role in how their children turn out, a belief enshrined in the theory of infant attachment, which grew out of the work of the British psychiatrist John Bowlby in the second half of the 20th century. “It focused exclusively on mothers,” Mr. Raeburn writes. “The role of the father, Bowlby believed, was to provide support for the mother. In the drama of childhood, he was merely a supporting actor.” This was more or less the established view until a few decades ago, when psychologists, motivated in part by the growing number of women entering the work force, finally started paying attention to fathers. © 2014 The New York Times Company
|By Maria Burke and ChemistryWorld The world needs to tackle head-on the market failures undermining dementia research and drug development, UK Prime Minister David Cameron told a summit of world health and finance leaders in London in June. He announced an investigation into how to get medicines to patients earlier, extend patents and facilitate research collaborations, to report this autumn. But just how much difference will these sorts of measures make when scientists are still grappling with exactly what causes different types of dementia? Added to these problems is that dementia has become a graveyard for a large number of promising drugs. A recent study looked at how 244 compounds in 413 clinical trials fared for Alzheimer's disease between 2002 and 2012. The researchers findings paint a gloomy picture. Of those 244 compounds, only one was approved. The researchers report that this gives Alzheimer's disease drug candidates one of the highest failures rates of any disease area – 99.6%, compared with 81% for cancer. ‘Dementia is a ticking bomb costing the global economy £350 billion and yet progress with research is achingly slow,’ warned the World Dementia Envoy, Dennis Gillings. Businesses need incentives to invest in research and bring in faster, cheaper clinical trials, or the world won’t meet the ambition to find a cure or disease-modifying therapy by 2025, he added. ‘We need to free up regulation so that we can test ground-breaking new drugs, and examine whether the period for market exclusivity could be extended.’ © 2014 Scientific American
Link ID: 19828 - Posted: 07.15.2014
By Fredrick Kunkle Sleep disturbances such as apnea may increase the risk of Alzheimer’s disease, while moderate exercise in middle age and mentally stimulating games, such as crossword puzzles, may prevent the onset of the dementia-causing disease, according to new research to be presented Monday. The findings — which are to be introduced during the six-day Alzheimer’s Association International Conference in Copenhagen — bolster previous studies that suggest sleep plays a critical role in the aging brain’s health, perhaps by allowing the body to cleanse itself of Alzheimer's-related compounds during down time. The studies also add to a growing body of literature that suggests keeping the brain busy keeps it healthy. The battle against Alzheimer’s disease has become more urgent for the United States and other developing nations as their populations turn increasingly gray. The disease is the leading cause of dementia in older people and afflicts more than 5 million Americans. At its current pace, the number is expected to soar to 16 million people by 2050. In 2012, the United States adopted a national plan to combat the disease and the G-8 nations last year adopted a goal of providing better treatment and prevention by 2025. Erin Heintz, a spokeswoman for the Alzheimer’s Association, said U.S. government funding to combat the disease now stands at about $500 million a year. To reach its 2025 goal, the United States should be spending $2 billion a year, she said.
One in three cases of Alzheimer's disease worldwide is preventable, according to research from the University of Cambridge. The main risk factors for the disease are a lack of exercise, smoking, depression and poor education, it says. Previous research from 2011 put the estimate at one in two cases, but this new study takes into account overlapping risk factors. Alzheimer's Research UK said age was still the biggest risk factor. Writing in The Lancet Neurology, the Cambridge team analysed population-based data to work out the main seven risk factors for Alzheimer's disease. These are: Diabetes Mid-life hypertension Mid-life obesity Physical inactivity Depression Smoking Low educational attainment They worked out that a third of Alzheimer's cases could be linked to lifestyle factors that could be modified, such as lack of exercise and smoking. The researchers then looked at how reducing these factors could affect the number of future Alzheimer's cases. They found that by reducing each risk factor by 10%, nearly nine million cases of the disease could be prevented by 2050. In the UK, a 10% reduction in risk factors would reduce cases by 8.8%, or 200,000, by 2050, they calculated. BBC © 2014
Link ID: 19824 - Posted: 07.14.2014
By Fredrick Kunkle A simple test of a person’s ability to identify odors and noninvasive eye exams might someday help doctors learn whether their patients are at risk of Alzheimer’s disease, according to research to be presented Sunday. With Alzheimer’s disease growing fast among the world’s aging population, researchers are increasingly focused on the search for new ways to detect and treat the brain-killing disease in its earliest stages. In two separate studies on the connection between dementia and sense of smell, teams of researchers found that a decreased ability to detect odors in older people, as determined by a common scratch-and-sniff test, could point to brain cell loss and the onset of dementia. In two other studies, researchers showed that noninvasive eye exams also might offer a way to identify Alzheimer’s in its early stages. The findings — which are to be presented at the Alzheimer’s Association International Conference in Copenhagen on Sunday — raise hopes that doctors could develop simple, inexpensive diagnostic tools that would hunt down reliable biomarkers of a disease that affects more than 5 million people in the United States. Alzheimer’s is a progressive and incurable disease that begins in areas of the brain associated with memory. It is the leading cause of dementia in older people, usually striking after the age of 65. It robs people of their cognitive abilities, speech and, ultimately, their identities. Eventually, it shuts down the most basic body functions, resulting in death.
Link ID: 19823 - Posted: 07.14.2014
by Helen Thomson You are what your grandmother ate, potentially, but maybe not what your great grandmother consumed. A study in mice shows that undernourishment during pregnancy increases the chances that the next two generations will develop obesity and diabetes. But by then the slate is wiped clean. If the same holds true for humans, it may mean that stressful events in our lives affect our grandchildren's health, but not great-grandchildren. Environmental stresses cause chemical changes to DNA that turn genes on and off. Many researchers believe that these changes can be passed down through sperm and eggs – a mechanism known as epigenetic inheritance. Low-calorie diet For example, studies have linked pregnant mothers that were undernourished during the second world war with gene changes in their children that put them at higher risk of becoming obese or getting cancer. But what happens to later generations is not clear. To model this effect, Anne Ferguson-Smith at the University of Cambridge and her colleagues fed pregnant mice a diet containing 50 per cent fewer calories than usual from the 12th day of gestation until the birth, which is normally after about 20 days. Offspring were smaller than average and developed diabetes when fed a healthy diet. When the male pups had offspring, they were also at higher risk of becoming diabetic. The team analysed the sperm of the offspring from the undernourished mothers to see how many genes had had their expression altered by the addition or removal of a methyl group – an epigenetic change. The team found a decrease in methylation in 111 regions of the DNA compared with sperm from mice born to mothers fed a healthy diet. © Copyright Reed Business Information Ltd
Erika Check Hayden Nearly 750,000 babies born each year in the United Kingdom are at risk of brain damage because of low oxygen during birth. Cooling babies who are at risk of brain damage provides long-lasting prevention of such injuries, researchers report today in the New England Journal of Medicine1. A team led by Denis Azzopardi, a neonatologist at King’s College London, lowered the body temperature of 145 full-term babies who were born after at least 36 weeks of gestation. All were at risk of brain damage because they had been deprived of oxygen during birth — a problem that is often caused by troubles with the placenta or umbilical cord, and affects nearly 750,000 babies a year in the United Kingdom. The researchers cooled the infants to between 33°C and 34°C for 72 hours, starting within 6 hours of birth. The technique is known to boost the chances that children avoid brain damage until they become toddlers2, but any longer-term benefits have remained unclear. The study finds treated babies had better mental and physical health than untreated infants through to ages 6 or 7: they were 60% more likely to have normal intelligence, hearing and vision. Those who survived to childhood also had fewer disabilities such as difficulty walking and seeing. "The bottom line is that this doubles a child’s chance of normal survival," says David Edwards, a neonatologist at King’s College London and an author of the study. Neonatologist David Rowitch from the University of California, San Francisco, who studies treatments for paediatric brain damage, says the new findings are important because they show sustained improvements. "This study is encouraging, adding to the weight of evidence showing both positive early indicators and also school-age benefits to hypothermia," Rowitch adds. © 2014 Nature Publishing Group,
Keyword: Development of the Brain
Link ID: 19814 - Posted: 07.10.2014
Thomas B. Edsall It’s been a key question of American politics since at least 1968: Why do so many poor, working-class and lower-middle-class whites — many of them dependent for survival on government programs — vote for Republicans? The debate over the motives of conservative low-income white voters remains unresolved, but two recent research papers suggest that the hurdles facing Democrats in carrying this segment of the electorate may prove difficult to overcome. In “Obedience to Traditional Authority: A heritable factor underlying authoritarianism, conservatism and religiousness,” published by the journal Personality and Individual Differences in 2013, three psychologists write that “authoritarianism, religiousness and conservatism,” which they call the “traditional moral values triad,” are “substantially influenced by genetic factors.” According to the authors — Steven Ludeke of Colgate, Thomas J. Bouchard of the University of Minnesota, and Wendy Johnson of the University of Edinburgh — all three traits are reflections of “a single, underlying tendency,” previously described in one word by Bouchard in a 2006 paper as “traditionalism.” Traditionalists in this sense are defined as “having strict moral standards and child-rearing practices, valuing conventional propriety and reputation, opposing rebelliousness and selfish disregard of others, and valuing religious institutions and practices.” Working along a parallel path, Amanda Friesen, a political scientist at Indiana University, and Aleksander Ksiazkiewicz, a graduate student in political science at Rice University, concluded from their study comparing identical and fraternal twins that “the correlation between religious importance and conservatism” is “driven primarily, but usually not exclusively, by genetic factors.” The substantial “genetic component in these relationships suggests that there may be a common underlying predisposition that leads individuals to adopt conservative bedrock social principles and political ideologies while simultaneously feeling the need for religious experiences.” © 2014 The New York Times Company
By Helen Briggs Health editor, BBC News website The same genes drive maths and reading ability, research suggests. Around half of the genes that influence a child's aptitude for reading also play a role in how easily they learn maths, say scientists. The study of 12-year-old British twins from 3,000 families, reported in Nature Communications, adds to the debate about the role of genes in education. An education expert said the work had little relevance for public policy as specific genes had not been identified. Past research suggests both nature and nurture have a similar impact on how children perform in exams. One study found genes explained almost 60% of the variation in GCSE exam results. However, little is known about which genes are involved and how they interact. The new research suggests a substantial overlap between the genetic variations that influence mathematics and reading, say scientists from UCL, the University of Oxford and King's College London. But non-genetic factors - such as parents, schools and teachers - are also important, said Prof Robert Plomin of King's College London, who worked on the study. "The study does not point to specific genes linked to literacy or numeracy, but rather suggests that genetic influence on complex traits, like learning abilities, and common disorders, like learning disabilities, is caused by many genes of very small-effect size," he said. BBC © 2014
by Helen Thomson A blood test for Alzheimer's might be just two years away. Abdul Hye at King's College London and his colleagues have identified 10 proteins in blood that can predict who will develop Alzheimer's disease a year after having mild memory problems. Its accuracy is almost 90 per cent. That could prove a huge boost for researchers seeking treatments. So far, trials of Alzheimer's drugs are thought to have failed because they have been given too late in the course of the disease to halt progression. The new blood test will initially be used to identify those people with mild cognitive impairment who are likely to get Alzheimer's disease and so might be good candidates for clinical trials to find drugs that halt disease progression. "Having a blood test is a really big step forward," says team member Ian Pike of Proteome Sciences in Cobham, UK. "The most important thing we can do is get the correct patients into clinical trials so we can tell, for example, whether it is a drug that is slowing the progression of the disease or the fact that we just happen to have a group of patients who have a slow progressing form of the disease." "This [blood test] is a technical tour de force," says Eric Karran, director of research at the Alzheimer's Research UK charity. However, he remains cautious about its use beyond clinical research. For every 10 people who take the test, one will get an incorrect result. "Alzheimer's is the most feared diagnosis, so we have to be careful, particularly in the absence of any treatment," he says. © Copyright Reed Business Information Ltd.
Link ID: 19802 - Posted: 07.08.2014
|By Jessica Wright and SFARI.org CHD8, a gene that regulates the structure of DNA, is the closest thing so far to an ‘autism gene,’ suggests a study published today in Cell. People with mutations in this gene all have the same cluster of symptoms, including a large head, constipation and characteristic facial features; nearly all also have have autism. Autism is notoriously heterogeneous, perhaps involving mutations in any of hundreds of genes. Typically, researchers begin by studying people with similar symptoms and working backward to identify what causes those symptoms. But that approach has not been particularly productive. “We’ve tried for so long to identify subtypes of autism based on behavior alone and we’ve done abysmally at that,” says lead researcher Raphael Bernier, associate professor of psychiatry at the University of Washington in Seattle. The reverse approach — that is, beginning with people who all have mutations in the same gene and characterizing their symptoms — may prove to be more useful for simplifying autism’s complexity. For example, identifying subtypes of autism may help researchers develop drugs tailored to that particular cause, says Evan Eichler, professor of genome sciences at the University of Washington, who spearheaded the genetics side of the study. “I think the most important realization is that not all autisms are created equal,” he says. © 2014 Scientific American,
By Helen Briggs Health editor, BBC News website More than 99% of drug trials for Alzheimer's disease during the past decade have failed, according to a study. There is an urgent need to increase the number of potential therapies being investigated, say US scientists. Only one new medicine has been approved since 2004, they report in the journal Alzheimer's Research & Therapy. The drug failure rate is troubling and higher than for other diseases such as cancer, says Alzheimer's Research UK. Dr Jeffrey Cummings, of the Cleveland Clinic Lou Ruvo Center for Brain Health, in Las Vegas, and colleagues, examined a public website that records clinical trials. Between 2002 and 2012, they found 99.6% of trials of drugs aimed at preventing, curing or improving the symptoms of Alzheimer's had failed or been discontinued. This compares with a failure rate of 81% for cancer drugs. The failure rate was "especially troubling" given the rising numbers of people with dementia, said Dr Simon Ridley, of Alzheimer's Research UK. "The authors of the study highlight a worrying decline in the number of clinical trials for Alzheimer's treatments in more recent years," he said. "There is a danger that the high failure rates of trials in the past will discourage pharmaceutical companies from investing in dementia research. BBC © 2014
Link ID: 19793 - Posted: 07.04.2014
By Smitha Mundasad Health reporter, BBC News Researchers have identified a gene that may put people at greater risk of strokes and heart attacks. Writing in PLOS ONE they say the gene fault may encourage the formation of blood clots - the ultimate cause of most heart attacks and strokes. Scientists hope gene tests may help doctors one day to pinpoint individuals more likely to suffer these conditions. But experts say lifestyle factors such as smoking and exercise have the greatest influence on risk. Around one in 10 people in the Caucasian population carries this variation of the gene, named PIA2. And researchers from King's College London reviewed more than 80 studies involving about 50,000 people - the largest analysis of this genetic fault to date. Threat to under-45s They found individuals with PIA2 were more likely to have a stroke - caused by a blood clot blocking blood supply to the brain - than those without the gene. Scientists calculate the gene increases a person's risk of having a stroke by 10-15%. But how significant this increase is depends on an individual's baseline risk - influenced by factors such as smoking, diet, weight and exercise, the scientists say. Heart attacks are caused by a blockage to the blood vessels that carry oxygen to the heart. More than 100,000 heart attacks are recorded in the UK each year And for people with two copies of the gene the risk rises by up to 70% from this baseline. In a second study published in the same journal, the scientists show PIA2 is also linked to an increased risk of heart attacks in people under 45. More research is needed to see whether this holds true for the whole population, they say. About 150,000 people have a stroke in the UK each year and more than 100,000 heart attacks are recorded annually. BBC © 2014
By GRETCHEN REYNOLDS Exercise may help to keep the brain robust in people who have an increased risk of developing Alzheimer’s disease, according to an inspiring new study. The findings suggests that even moderate amounts of physical activity may help to slow the progression of one of the most dreaded diseases of aging. For the new study, which was published in May in Frontiers in Aging Neuroscience, researchers at the Cleveland Clinic in Ohio recruited almost 100 older men and women, aged 65 to 89, many of whom had a family history of Alzheimer’s disease. Alzheimer’s disease, characterized by a gradual and then quickening loss of memory and cognitive functioning, can strike anyone. But scientists have discovered in recent years that people who harbor a specific variant of a gene, known as the APOE epsilon4 allele or the e4 gene for short, have a substantially increased risk of developing the disease. Genetic testing among the volunteers in the new study determined that about half of the group carried the e4 gene, although, at the start of the study, none showed signs of memory loss beyond what would be normal for their age. Then the scientists set out to more closely examine their volunteers’ brains. For some time, researchers have suspected that Alzheimer’s disease begins altering the structure and function of the brain years or even decades before the first symptoms appear. In particular, it’s been thought that the disease silently accelerates the atrophy of the hippocampus, a portion of the brain critical for memory processing. Brain scans of people who have Alzheimer’s show that their hippocampi are considerably more shrunken than those of people of the same age without the disease. There’s been less study, though, of possible shrinkage in the brains of cognitively normal people at risk for Alzheimer’s. One reason is that, until recently, few interventions, including drugs, had shown much promise in slowing or preventing the disease’s progression, so researchers – and patients – have been reluctant to identify markers of its potential onset. © 2014 The New York Times Company
Link ID: 19783 - Posted: 07.02.2014
Learning a second language benefits the brain in ways that can pay off later in life, suggests a deepening field of research that specializes in the relationship between bilingualism and cognition. In one large Scottish test, researchers discovered archival data on 835 native speakers of English who were born in Edinburgh in 1936. The participants had been given an intelligence test at age 11 as part of standard British educational policy and many were retested in their early 70s. Those who spoke two or more languages had significantly better cognitive abilities on certain tasks compared with what would be expected from their IQ test scores at age 11, Dr. Thomas Bak of the Centre for Cognitive Aging and Cognitive Epidemiology at the University of Edinburgh reported in the journal Annals of Neurology. "Our results suggest a protective effect of bilingualism against age-related cognitive decline," independently of IQ, Bak and his co-authors concluded. It was a watershed study in 1962 by Elizabeth Peal and Wallace Lambert at McGill University in Montreal that turned conventional thinking on bilingualism on its head and set the rationale for French immersion in Canada. Psychologists at York University in Toronto have also been studying the effect of bilingualism on the brain across the lifespan, including dementia. They’ve learned how people who speak a second language outperform those with just one on tasks that tap executive function such as attention, selection and inhibition. Those are the high-level cognitive processes we use to multitask as we drive on the highway and juggle remembering the exit and monitoring our speed without getting distracted by billboards. © CBC 2014
by Laura Sanders At the playground yesterday, Baby V commando-crawled through a tunnel with holes on the side. Every so often, I stuck my face in there with a loud “peekaboo.” She reached up longingly toward the bouncy duck. I picked her up and steadied her as she lurched back and forth. She scrambled up some low stairs and launched down a slide. I lurked near the bottom, ready to assist and yell “yay” when she didn’t face-plant. The one thing I didn’t do was sit back and leave her to her own devices, free from my helicopter-mom tendencies. But since I have the most ridiculous crush on that girl, it’s hard for me to leave her be. As a parent who works outside of the home, I treasure our time together. But as she becomes more capable and independent, I realize that I need to be more thoughtful about letting her carve out some space for herself. A recent research paper emphasized this point. The study, published June 17 in Frontiers in Psychology, finds that children who spend more time in unstructured activities may better master some important life skills. Researchers sorted kids’ activities into structured activities, which included child-initiated activities such as playing alone or with friends, singing, riding bikes and camping, and structured activities, including soccer practice, piano lessons, chores and homework. Six- and seven-year-olds who had more unstructured time scored higher on a measure of executive function, complex cognitive abilities such as seamlessly switching between tasks, resisting impulses and paying attention — all things that help people get along in this world. © Society for Science & the Public 2000 - 2013.
Keyword: Development of the Brain
Link ID: 19780 - Posted: 07.02.2014
By RICHARD A. FRIEDMAN ADOLESCENCE is practically synonymous in our culture with risk taking, emotional drama and all forms of outlandish behavior. Until very recently, the widely accepted explanation for adolescent angst has been psychological. Developmentally, teenagers face a number of social and emotional challenges, like starting to separate from their parents, getting accepted into a peer group and figuring out who they really are. It doesn’t take a psychoanalyst to realize that these are anxiety-provoking transitions. But there is a darker side to adolescence that, until now, was poorly understood: a surge during teenage years in anxiety and fearfulness. Largely because of a quirk of brain development, adolescents, on average, experience more anxiety and fear and have a harder time learning how not to be afraid than either children or adults. Different regions and circuits of the brain mature at very different rates. It turns out that the brain circuit for processing fear — the amygdala — is precocious and develops way ahead of the prefrontal cortex, the seat of reasoning and executive control. This means that adolescents have a brain that is wired with an enhanced capacity for fear and anxiety, but is relatively underdeveloped when it comes to calm reasoning. You may wonder why, if adolescents have such enhanced capacity for anxiety, they are such novelty seekers and risk takers. It would seem that the two traits are at odds. The answer, in part, is that the brain’s reward center, just like its fear circuit, matures earlier than the prefrontal cortex. That reward center drives much of teenagers’ risky behavior. This behavioral paradox also helps explain why adolescents are particularly prone to injury and trauma. The top three killers of teenagers are accidents, homicide and suicide. The brain-development lag has huge implications for how we think about anxiety and how we treat it. It suggests that anxious adolescents may not be very responsive to psychotherapy that attempts to teach them to be unafraid, like cognitive behavior therapy, which is zealously prescribed for teenagers. © 2014 The New York Times Company
Keyword: Development of the Brain
Link ID: 19775 - Posted: 07.01.2014
A toxic caffeine level was found in the system of a high school student who died unexpectedly, says a U.S. coroner who warns young people need to be educated about the dangers of taking the potent powder that is sold online. Logan Stiner, 18, was found dead at his family’s home in May. Steiner was an excellent student and a healthy young man who didn’t do drugs, Dr. Stephen Evans, a coroner in Lorain County, Ohio, said Monday. "We sent his blood out for levels, and [when] it came back it was a toxic level. Caffeine toxicity will do exactly what happened to him. It'll lead to things like cardiac arrhytmias and seizures," Evans said in an interview. Use of caffeine from coffee, tea and other beverages is so widespread that it is considered innocuous, but that’s not the case when it’s taken in an overdose amount. Powdered caffeine is sold in bulk over the internet. Problems can arise because adding a teaspoon of the caffeine powder to water is the equivalent of 30 cups of coffee. About one-sixteenth of a teaspoon of the powder is equal to about two cups of coffee. Evans said he recognizes that weightlifters will say Stiner should’ve taken the correct amount. "One-sixteenth of a teaspoon. You expect a kid to figure that out?" He suggested that regulators re-consider internet sales of a pound of powdered caffeine to young people. When Evans and his staff reviewed the pathology literature, they found 18 other cases of deaths in the U.S. from caffeine overdoses. Some were suicides and others were accidental, but he suspects the deaths are underreported since few pathologists investigating deaths from seizure and cardiac arrhytmia check caffeine levels. © CBC 2014
Emotional and behavioral problems show up even with low exposure to lead, and as blood lead levels increase in children, so do the problems, according to research funded by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. The results were published online June 30 in the journal JAMA Pediatrics. “This research focused on lower blood lead levels than most other studies and adds more evidence that there is no safe lead level,” explained NIEHS Health Scientist Administrator Kimberly Gray, Ph.D. “It is important to continue to study lead exposure in children around the world, and to fully understand short-term and long-term behavioral changes across developmental milestones. It is well-documented that lead exposure lowers the IQ of children.” Blood lead concentrations measured in more than 1,300 preschool children in China were associated with increased risk of behavioral and emotional problems, such as being anxious, depressed, or aggressive. The average blood lead level in the children was 6.4 micrograms per deciliter. While many studies to date have examined health effects at or above 10 micrograms per deciliter, this study focused on lower levels. The CDC now uses a reference level of 5 micrograms per deciliter, to identify children with blood lead levels that are much higher than normal, and recommends educating parents on reducing sources of lead in their environment and continued monitoring of blood lead levels.
|By Lisa Marshall Is Alzheimer's disease an acquired form of Down syndrome? When neurobiologist Huntington Potter first posed the question in 1991, Alzheimer's researchers were skeptical. They were just beginning to explore the causes of the memory-robbing neurological disease. Scientists already knew that by age 40, nearly 100 percent of patients with Down syndrome, who have an extra copy of chromosome 21, had brains full of beta-amyloid peptide—the neuron-strangling plaque that is a hallmark of Alzheimer's. They also knew that the gene that codes for that protein lives on chromosome 21, suggesting that people acquire more plaque because they get an extra dose of the peptide. Potter, though, suggested that if people with Down syndrome develop Alzheimer's because of an extra chromosome 21, healthy people may develop Alzheimer's for the same reason. A quarter of a century later mounting evidence supports the idea. “What we hypothesized in the 1990s and have begun to prove is that people with Alzheimer's begin to make molecular mistakes and generate cells with three copies of chromosome 21,” says Potter, who was recently appointed director of Alzheimer's disease research at the University of Colorado School of Medicine, with the express purpose of studying Alzheimer's through the lens of Down syndrome. He is no longer the only one exploring the link. In recent years dozens of studies have shown Alzheimer's patients possess an inordinate amount of Down syndrome–like cells. One 2009 study by Russian researchers found that up to 15 percent of the neurons in the brains of Alzheimer's patients contained an extra copy of chromosome 21. Others have shown Alzheimer's patients have 1.5 to two times as many skin and blood cells with the extra copy as healthy controls. Potter's own research in mice suggests a vicious cycle: when normal cells are exposed to the beta-amyloid peptide, they tend to make mistakes when dividing, producing more trisomy 21 cells, which, in turn, produce more plaque. In August, Potter and his team published a paper in the journal Neurobiology of Aging describing why those mistakes may occur: the inhibition of a specific enzyme. © 2014 Scientific American
Link ID: 19771 - Posted: 06.25.2014