Even single neurons have a big impact on behavior, studies show
By E.J. Mundell
Posted 12/19/07
WEDNESDAY, Dec. 19 (HealthDay News) -- The human brain constantly sorts through its 1 trillion cells, looking for perhaps only one or a handful of neurons to carry out a particular action, a trio of new studies says.
The research, conducted with rodents and published in the Dec. 20 issue of Nature, could rewrite the textbooks on just how important individual brain cells or cell clusters are to the working mind.
Before these insights, "The thinking was that very large ensembles of neurons [brain cells] had to be activated at some point for the animal to feel or perceive" a stimulus, explained the senior researcher of two of the studies, Karel Svoboda, a group leader at the Howard Hughes Medical Institute in Ashburn, Va.
"But it turns out that a remarkably small number -- on the order of 50 or so activated neurons -- is sufficient to drive reliable behaviors," said Svoboda, who is also associated with the Cold Spring Harbor Laboratory, in New York.
Another study, this one conducted by scientists at Humboldt University Berlin and Erasmus Medical Center in Rotterdam, the Netherlands, found that stimulating just one out of the estimated 100 million neurons in a rat's brain was enough to cause the rodent to act differently.
"The fact that a single cell can influence behavior in the cortex is fascinating," said neuroscientist Paul Sanberg, director of the Center for Excellence for Aging and Brain Repair at the University of South Florida, Tampa. The new findings are "allowing us to answer questions about how the brain controls behavior at the cellular level," added Sanberg, who was not involved in the studies.
In one of the studies, Svoboda and his colleagues genetically engineered a select few brain cells in active mice so that the cells would react to a light stimulus.
Then they exposed a part of the rodent's brain and placed a small light-emitting diode over the area. The experiment "was essentially a trick to stimulate [only] these cells," Svoboda explained.
Finally, they adjusted the amount of light downward until they found the lowest number of brain cells needed to evoke a measurable response in the mice. That number turned out to be less than 50 -- much fewer than the wide-flung networks of cellular activation neuroscientists had previously assumed would be necessary, Svoboda said.
The mouse brain's ability to tap into a mere 50 cells is even more remarkable when you consider that the activity of this cluster of cells takes place amid a background roar of other neurological "noise" from millions of cells, he said.
"At the same time, the functional brain area just chatters along and produces perhaps a hundred thousand spontaneous action potentials [electrical signals]," he noted. "So, the brain can actually distinguish the tiny, tiny number of action potentials from that huge background."
According to Svoboda, the experiment strongly supports a theory of brain function called "sparse coding," in which "neurons that listen to the neurons that we have activated have to be able to pull out very sparse subsets of activity."
In another study, Svoboda and co-researcher Christopher Harvey, also of the HHMI and Cold Spring Harbor Laboratory, focused on the synapse -- the microscopic gap separating individual neurons. Messages are passed neuron-to-neuron across the synapse by a complex mechanism of electrochemical signaling.
"Scientists had shown that synapses behave rather independently," Svoboda said, so that long-term electrical activation ("potentiation") of one synapse didn't directly affect a neighboring synapse. Long-term potentiation is, in essence, the key cellular step in how the brain lays down memory.
However, computer models had suggested that activation at one synapse might more subtly strengthen the synapses around it. In their experiments, Svoboda and Harvey found this to be true.
They report that "neighborhoods" of 10 or 20 synapses "influence each other cooperatively," strengthening discrete groups of synapses.
What's more, this type of synaptic teamwork happens within a specific time-frame -- about 10 minutes, a perfect amount of time for laying down the kinds of memories that can lead to learning, Svoboda said.
"That's a very behavioral timescale for learning and memory," he said. For example, a mouse can be placed in a chamber, explore it for a few minutes, then be removed from the chamber and yet retain a working memory of that chamber once it has been reintroduced to it.
That's probably due to the fact that the mouse's brain formed synaptic clusters (i.e., memory) specific to the new chamber while it was exploring it, Svoboda explained.
"In this way, they can be dissociated [from the stimulus] over several minutes but still lead to learning," he said.
While many of these experiments were done in mice, the human brain should work similarly, albeit on a much larger scale, Svoboda said. While the mouse brain contains about 100 million neurons, human brains top out at a trillion such cells, he said.
And even though the research looked at healthy brain function, it may have implications for research into aging or diseased brains, as well.
"You need to understand the fundamental mechanisms. Then you can gain better insight into what might go wrong during neurodevelopmental and neurodegenerative disorders," Svoboda said.
Sanberg agreed.
"This work clearly shows us that all cells are important, and we should try and maintain and keep as many brain cells as possible," he said. "But the number is always flexible and, as you can see, even one cell can influence a number of others."
More information
Learn more about the human brain at The Franklin Institute.
Copyright © 2007 ScoutNews, LLC. All rights reserved.
Saturday, December 22, 2007
FDA renews alert on painkiller patch
The drug, which the agency says has been misused and wrongly prescribed, is a suspect in 3,500 deaths. Heat can increase the absorption rate.
By Ricardo Alonso-Zaldivar, Los Angeles Times Staff Writer December 22, 2007
WASHINGTON -- The government issued a new safety warning Friday for a skin patch containing a potent painkiller that has been implicated in hundreds of deaths, saying the patch poses unique risks that doctors and patients often fail to understand.The Food and Drug Administration said the widely used fentanyl patch was being wrongly prescribed by doctors and being misused by patients unaware that something as routine as taking a hot shower while wearing the patch could trigger a potentially fatal overdose.A study published in a medical journal last summer identified fentanyl, a narcotic up to 100 times more powerful than morphine, as the suspect drug in more than 3,500 accidental deaths reported to the FDA from 1998 to 2005.
Safety advocates said the agency's latest warning, which echoes an alert issued in 2005, was too little, too late.The patch was developed for cancer patients who suffer severe chronic pain and in some cases have trouble swallowing pills. But Dr. Bob Rappaport, head of the FDA division that oversees painkillers, said some doctors had been prescribing the patch to patients who didn't need such a powerful narcotic -- and in at least one case, even used it to treat headaches.
Patches can be more convenient than pills; the fentanyl patch is designed to deliver the drug at a steady rate for as long as three days, so patients don't have to take medication several times a day. But there are also drawbacks: A single patch contains a substantially larger quantity of the medication than individual pills; heat and exercise can increase the rate at which the drug is absorbed through the skin.Rappaport said the FDA had not found such serious problems with other methods of delivering fentanyl, including by injection. "It's a unique problem with patches because of . . . the way that the drug is delivered to the body and the way that it's metabolized," he said. "It's complicated by the patch formulation.
"The FDA said doctors should not prescribe the patch for patients whose pain was expected to go away, such as those recovering from an operation. The patch should be used only by patients who are in chronic pain and are already safely taking opioid-type drugs.The agency warned patients to call their doctors if they have trouble breathing, because fentanyl can shut down the respiratory system. It said patients wearing the patch should avoid hot showers and heating pads.Rappaport said the situation was "very concerning" because such patch-related deaths could easily be prevented.And adult patients are not the only ones at risk: At least one child has died after applying a parent's patch.
Not only is the fentanyl patch strong medicine, it is also widely used. About 4.7 million prescriptions were filled in 2006, according to Verispan, a market analysis firm. The patch was introduced in 1990 under the brand name Duragesic by Johnson & Johnson, but generic versions by Mylan Inc. and other manufacturers now dominate the market.Friday's advisory reinforced an FDA alert in 2005, which all sides acknowledge did not do enough to reduce the risk to patients. This time, the agency is directing drug makers to issue brochures that explain the dangers in plain language.That was not enough to satisfy safety advocates who have been tracking problems with the patch for years."I think there is more that needs to be done, or else we're just going to see this [warning] happen again another two years from now," said Michael Cohen, president of the Institute for Safe Medication Practices. "The deaths are going to continue." The Pennsylvania group advises hospitals and doctors on how to prevent medication errors.Cohen has called on the FDA to limit the number of doctors allowed to prescribe the drug.
That could be done by requiring physicians to take special instruction in assuring safety.But the FDA's Rappaport said such restrictions could prevent some patients who need the medication from getting prescriptions. About 60 million Americans suffer from chronic pain, he said, but only several thousand doctors in the country are certified pain specialists.Nonetheless, Cohen said, he is worried the FDA's latest warning won't register with busy doctors, particularly those who don't regularly deal with powerful narcotics. He recommended that hospitals, which usually have pain experts on staff, require their specialists to review all prescriptions for the fentanyl patch.
Several deaths reported to his group involved patients inappropriately prescribed the patch for pain relief after surgery.Last summer, a study named fentanyl as the second-deadliest drug in accidental deaths, behind painkiller oxycodone. Analyzing reports to the FDA from 1998 to 2005, researchers identified 3,545 deaths linked to fentanyl. The study looked at all forms of fentanyl, but "the patch was by far the largest contributor," lead author Thomas J. Moore said in an interview.
By comparison, the paper found that Vioxx -- the painkiller whose 2004 withdrawal was the catalyst for safety reforms at the FDA -- was a suspect in 932 deaths.Rappaport said the FDA did not have a definitive count of deaths caused by the patch and was working to develop one. He suggested the number could be smaller than reported because many patients using the patch were severely ill and could have died from underlying diseases.Spokesmen for Ortho-McNeil Inc., the subsidiary that makes Duragesic, and for Mylan said the manufacturers supported the FDA's action.Greg Panico of Ortho-McNeil said the company's research indicated that the safety warnings might be working. Reports of unapproved uses of Duragesic have declined significantly since the summer of 2006, he said.
By Ricardo Alonso-Zaldivar, Los Angeles Times Staff Writer December 22, 2007
WASHINGTON -- The government issued a new safety warning Friday for a skin patch containing a potent painkiller that has been implicated in hundreds of deaths, saying the patch poses unique risks that doctors and patients often fail to understand.The Food and Drug Administration said the widely used fentanyl patch was being wrongly prescribed by doctors and being misused by patients unaware that something as routine as taking a hot shower while wearing the patch could trigger a potentially fatal overdose.A study published in a medical journal last summer identified fentanyl, a narcotic up to 100 times more powerful than morphine, as the suspect drug in more than 3,500 accidental deaths reported to the FDA from 1998 to 2005.
Safety advocates said the agency's latest warning, which echoes an alert issued in 2005, was too little, too late.The patch was developed for cancer patients who suffer severe chronic pain and in some cases have trouble swallowing pills. But Dr. Bob Rappaport, head of the FDA division that oversees painkillers, said some doctors had been prescribing the patch to patients who didn't need such a powerful narcotic -- and in at least one case, even used it to treat headaches.
Patches can be more convenient than pills; the fentanyl patch is designed to deliver the drug at a steady rate for as long as three days, so patients don't have to take medication several times a day. But there are also drawbacks: A single patch contains a substantially larger quantity of the medication than individual pills; heat and exercise can increase the rate at which the drug is absorbed through the skin.Rappaport said the FDA had not found such serious problems with other methods of delivering fentanyl, including by injection. "It's a unique problem with patches because of . . . the way that the drug is delivered to the body and the way that it's metabolized," he said. "It's complicated by the patch formulation.
"The FDA said doctors should not prescribe the patch for patients whose pain was expected to go away, such as those recovering from an operation. The patch should be used only by patients who are in chronic pain and are already safely taking opioid-type drugs.The agency warned patients to call their doctors if they have trouble breathing, because fentanyl can shut down the respiratory system. It said patients wearing the patch should avoid hot showers and heating pads.Rappaport said the situation was "very concerning" because such patch-related deaths could easily be prevented.And adult patients are not the only ones at risk: At least one child has died after applying a parent's patch.
Not only is the fentanyl patch strong medicine, it is also widely used. About 4.7 million prescriptions were filled in 2006, according to Verispan, a market analysis firm. The patch was introduced in 1990 under the brand name Duragesic by Johnson & Johnson, but generic versions by Mylan Inc. and other manufacturers now dominate the market.Friday's advisory reinforced an FDA alert in 2005, which all sides acknowledge did not do enough to reduce the risk to patients. This time, the agency is directing drug makers to issue brochures that explain the dangers in plain language.That was not enough to satisfy safety advocates who have been tracking problems with the patch for years."I think there is more that needs to be done, or else we're just going to see this [warning] happen again another two years from now," said Michael Cohen, president of the Institute for Safe Medication Practices. "The deaths are going to continue." The Pennsylvania group advises hospitals and doctors on how to prevent medication errors.Cohen has called on the FDA to limit the number of doctors allowed to prescribe the drug.
That could be done by requiring physicians to take special instruction in assuring safety.But the FDA's Rappaport said such restrictions could prevent some patients who need the medication from getting prescriptions. About 60 million Americans suffer from chronic pain, he said, but only several thousand doctors in the country are certified pain specialists.Nonetheless, Cohen said, he is worried the FDA's latest warning won't register with busy doctors, particularly those who don't regularly deal with powerful narcotics. He recommended that hospitals, which usually have pain experts on staff, require their specialists to review all prescriptions for the fentanyl patch.
Several deaths reported to his group involved patients inappropriately prescribed the patch for pain relief after surgery.Last summer, a study named fentanyl as the second-deadliest drug in accidental deaths, behind painkiller oxycodone. Analyzing reports to the FDA from 1998 to 2005, researchers identified 3,545 deaths linked to fentanyl. The study looked at all forms of fentanyl, but "the patch was by far the largest contributor," lead author Thomas J. Moore said in an interview.
By comparison, the paper found that Vioxx -- the painkiller whose 2004 withdrawal was the catalyst for safety reforms at the FDA -- was a suspect in 932 deaths.Rappaport said the FDA did not have a definitive count of deaths caused by the patch and was working to develop one. He suggested the number could be smaller than reported because many patients using the patch were severely ill and could have died from underlying diseases.Spokesmen for Ortho-McNeil Inc., the subsidiary that makes Duragesic, and for Mylan said the manufacturers supported the FDA's action.Greg Panico of Ortho-McNeil said the company's research indicated that the safety warnings might be working. Reports of unapproved uses of Duragesic have declined significantly since the summer of 2006, he said.
Monday, May 28, 2007
What is high cholesterol?
Cholesterol is a type of fat. Your body needs it for many things, such as making new cells. But too much cholesterol in your blood increases your chances of having a heart attack and stroke.
You get cholesterol from the foods you eat and from your liver. Your liver makes most of the cholesterol your body needs.
Desirable cholesterol is less than 200 milligrams per deciliter (mg/dL).
Borderline-high cholesterol is 200 to 239.
High cholesterol is 240 or higher.
What are the different kinds of cholesterol?
Cholesterol travels through your blood attached to a protein. This cholesterol-protein package is called a lipoprotein. Lipoproteins are either high-density or low-density, based on how much protein and fat they have.
Low-density lipoproteins (LDL) are mostly fat with only a small amount of protein. LDL is the bad kind of cholesterol because it can clog your arteries. If you have high cholesterol, your doctor will want you to lower your LDL.
LDL levels:
Best LDL is less than 100 mg/dL.
Near best LDL is 100 to 129.
Borderline-high LDL is 130 to 159.
High LDL is 160 to 189.
Very high LDL is 190 and above.
See an illustration of a clogged artery (atherosclerosis).
High-density lipoproteins (HDL) help clear the bad cholesterol from your blood and keep it from clogging your arteries. HDL is the good kind of cholesterol. High levels of HDL (60 or above) can protect you from a heart attack.
HDL levels:
Desirable or high HDL is 60 mg/dL or above.
Undesirable or low HDL is less than 40.
Triglycerides are another type of fat in your blood. If you have high triglycerides and high LDL, your chances of having a heart attack are higher.
Triglyceride levels:
Borderline high is 150 to 199 mg/dL.
High is 200 or above.
Very high is 500 or higher.
What causes high cholesterol?
High cholesterol may run in your family. The foods you eat also may cause high cholesterol.
Causes include:
Your diet. Eating too much saturated fat and cholesterol can cause high cholesterol. Saturated fat and cholesterol come from animal foods such as beef, pork, veal, milk, eggs, butter, and cheese. Many packaged foods contain saturated fat such as coconut oil, palm oil, or cocoa butter. You will also find saturated fat in stick margarine and vegetable shortening. Cookies, crackers, chips, and other snacks usually contain partially hydrogenated vegetable oil or trans fat, which can raise cholesterol.
Your weight. Being overweight may raise triglycerides and lower HDL.
Your activity level. Not exercising may raise LDL and lower HDL.
Your overall health. Having diseases such as low thyroid can raise cholesterol. Cigarette smoking may lower HDL.
Your age. After you reach age 20, your cholesterol starts to rise. In men, cholesterol levels usually level off after age 50. In women, cholesterol levels stay fairly low until menopause. After that, they rise to about the same level as in men.
Your family. A disease called a lipid disorder can also cause high cholesterol. This rare problem is inherited from family members, and it changes how your body handles cholesterol. If you have a lipid disorder, your cholesterol may be well over 250 mg/dL. It may be harder to treat.
What are the symptoms?
High cholesterol doesn't make you feel sick. But if cholesterol builds up in your arteries, it can block blood flow to your heart or brain and cause a heart attack or stroke.
In some people, cholesterol deposits called xanthomas may form under the skin. They look like small bumps.
How is high cholesterol diagnosed?
Your doctor will use a blood test to check your cholesterol.
A lipoprotein analysis is the most complete test. It measures your total cholesterol: HDL, LDL, and triglycerides. You cannot have food for 12 hours before this test.
A simple cholesterol test can measure your total cholesterol and HDL. You can eat before this test. Sometimes doctors do this test first and then order a lipoprotein analysis if you have high cholesterol or low HDL.
How is it treated?
You and your doctor may decide first to treat your high cholesterol without medicine. Changes to your lifestyle and diet may be all you need. These changes include eating foods low in saturated fat, being more active, losing weight if you need to, and quitting smoking if needed.
If you cannot lower your cholesterol enough after trying lifestyle changes for a few months, you may need to take a medicine called a statin.
If you have high blood pressure, diabetes, or coronary artery disease (CAD), your doctor may want you to take a statin right away. This is because your chance of having a heart attack is higher.
Use this Interactive Tool: Are You at Risk for a Heart Attack?
Research shows that people who have a high risk for heart attack could benefit from taking higher doses of statins to lower their LDL cholesterol as much as possible. The more these people can lower their LDL, the less likely they are to have a heart attack. 1
Things that increase your risk for heart attack include:
Having high blood pressure.
Smoking.
Having low HDL (good) cholesterol.
Having peripheral arterial disease, which is narrowing of the arteries that supply blood to the legs, abdomen, pelvis, arms, or neck.
Having diabetes.
Having a family history of heart disease.
Being age 45 or older if you are a man, and age 55 or older if you are a woman.
You get cholesterol from the foods you eat and from your liver. Your liver makes most of the cholesterol your body needs.
Desirable cholesterol is less than 200 milligrams per deciliter (mg/dL).
Borderline-high cholesterol is 200 to 239.
High cholesterol is 240 or higher.
What are the different kinds of cholesterol?
Cholesterol travels through your blood attached to a protein. This cholesterol-protein package is called a lipoprotein. Lipoproteins are either high-density or low-density, based on how much protein and fat they have.
Low-density lipoproteins (LDL) are mostly fat with only a small amount of protein. LDL is the bad kind of cholesterol because it can clog your arteries. If you have high cholesterol, your doctor will want you to lower your LDL.
LDL levels:
Best LDL is less than 100 mg/dL.
Near best LDL is 100 to 129.
Borderline-high LDL is 130 to 159.
High LDL is 160 to 189.
Very high LDL is 190 and above.
See an illustration of a clogged artery (atherosclerosis).
High-density lipoproteins (HDL) help clear the bad cholesterol from your blood and keep it from clogging your arteries. HDL is the good kind of cholesterol. High levels of HDL (60 or above) can protect you from a heart attack.
HDL levels:
Desirable or high HDL is 60 mg/dL or above.
Undesirable or low HDL is less than 40.
Triglycerides are another type of fat in your blood. If you have high triglycerides and high LDL, your chances of having a heart attack are higher.
Triglyceride levels:
Borderline high is 150 to 199 mg/dL.
High is 200 or above.
Very high is 500 or higher.
What causes high cholesterol?
High cholesterol may run in your family. The foods you eat also may cause high cholesterol.
Causes include:
Your diet. Eating too much saturated fat and cholesterol can cause high cholesterol. Saturated fat and cholesterol come from animal foods such as beef, pork, veal, milk, eggs, butter, and cheese. Many packaged foods contain saturated fat such as coconut oil, palm oil, or cocoa butter. You will also find saturated fat in stick margarine and vegetable shortening. Cookies, crackers, chips, and other snacks usually contain partially hydrogenated vegetable oil or trans fat, which can raise cholesterol.
Your weight. Being overweight may raise triglycerides and lower HDL.
Your activity level. Not exercising may raise LDL and lower HDL.
Your overall health. Having diseases such as low thyroid can raise cholesterol. Cigarette smoking may lower HDL.
Your age. After you reach age 20, your cholesterol starts to rise. In men, cholesterol levels usually level off after age 50. In women, cholesterol levels stay fairly low until menopause. After that, they rise to about the same level as in men.
Your family. A disease called a lipid disorder can also cause high cholesterol. This rare problem is inherited from family members, and it changes how your body handles cholesterol. If you have a lipid disorder, your cholesterol may be well over 250 mg/dL. It may be harder to treat.
What are the symptoms?
High cholesterol doesn't make you feel sick. But if cholesterol builds up in your arteries, it can block blood flow to your heart or brain and cause a heart attack or stroke.
In some people, cholesterol deposits called xanthomas may form under the skin. They look like small bumps.
How is high cholesterol diagnosed?
Your doctor will use a blood test to check your cholesterol.
A lipoprotein analysis is the most complete test. It measures your total cholesterol: HDL, LDL, and triglycerides. You cannot have food for 12 hours before this test.
A simple cholesterol test can measure your total cholesterol and HDL. You can eat before this test. Sometimes doctors do this test first and then order a lipoprotein analysis if you have high cholesterol or low HDL.
How is it treated?
You and your doctor may decide first to treat your high cholesterol without medicine. Changes to your lifestyle and diet may be all you need. These changes include eating foods low in saturated fat, being more active, losing weight if you need to, and quitting smoking if needed.
If you cannot lower your cholesterol enough after trying lifestyle changes for a few months, you may need to take a medicine called a statin.
If you have high blood pressure, diabetes, or coronary artery disease (CAD), your doctor may want you to take a statin right away. This is because your chance of having a heart attack is higher.
Use this Interactive Tool: Are You at Risk for a Heart Attack?
Research shows that people who have a high risk for heart attack could benefit from taking higher doses of statins to lower their LDL cholesterol as much as possible. The more these people can lower their LDL, the less likely they are to have a heart attack. 1
Things that increase your risk for heart attack include:
Having high blood pressure.
Smoking.
Having low HDL (good) cholesterol.
Having peripheral arterial disease, which is narrowing of the arteries that supply blood to the legs, abdomen, pelvis, arms, or neck.
Having diabetes.
Having a family history of heart disease.
Being age 45 or older if you are a man, and age 55 or older if you are a woman.
Four more breast cancer genes found
Monday, 28 May 2007. www.abc.net.au
Four more genes that play a role in breast cancer have been uncovered by an international team of scientists.But women who have mutated versions of these genes have a relatively low risk of developing breast cancer, which scientists say makes it unlikely that individual screening tests for these mutations will be developed.
Researchers, including those from Australia, publish their results today in the journals Nature and Nature Genetics.Genetic causes account for between 5-10% of breast cancer cases, with lifestyle factors such as smoking and environmental factors accounting for the rest.But until now, only about 25% of the genes that are suspected to cause inherited breast cancer have been identified. The new culprits - flawed versions of genes called FGFR2, TNRC9, MAP3K1 and LSP1 - are believed to account for an additional 4%. The researchers found them after sifting through the DNA of nearly 50,000 women, half of them healthy and half of them patients with breast cancer. While flawed versions of the four genes are common in the general population, the good news is that the genes are considered a relatively low hazard.This means that women who have them run a comparatively small risk of developing cancer.
By contrast, the breast cancer genes BRCA1 and BRCA2 are relatively rare in the population but women who have them run a high risk of the disease. Because the four newly-identified genes are so common yet relatively low-risk, individual tests for them may be unsuitable, according to Cancer Research UK, whose scientists led the investigation."[But] as more of these 'low-risk' genes are found it may be possible to design tests for a combination of genes," it says."This could help doctors make decisions about prevention, diagnosis and treatment for women who inherit faults in one or more of these genes."
There could be as many as 200 genes that influence someone's chance of developing breast cancer (Image: iStockphoto)Dr Georgia Chevenix-Trench, from the Queensland Institute of Medical Research, contributed data from Australian patients to the study."This is probably the most important paper on breast cancer genetics since the cloning of BRCA2 in 1995," she says.She adds that there are probably 100-200 similar genes that contribute to breast cancer risk and that these studies will give researchers a good idea of where to look for them.Much remains to be learnt about the four genes, especially whether they react with each other or with lifestyle factors in a way that boosts the risk for some women, the scientists add.Most previously identified breast cancer genes are involved in DNA repair. But these latest genes seem to be more related to the control of cell growth or to cell signalling.
Of the four genes identified, only FGFR2 was known to be associated with breast cancer.And scientists say it may be a logical candidate for a breast cancer gene. It encodes a receptor, a kind of molecular doorway, for a compound called tyrosine kinase that is involved in several cancers.One of the studies found there were four common mutations in the gene that were associated with sporadic breast cancer in postmenopausal women, women who developed cancer without known risk factors for it.
The mutations raised the risk of breast cancer risk by 20% if a woman carried one copy of the gene and by 60% if she carried two copies. And close to 60% of the women studied carried at least one copy.But the findings do not yet have any real relevance for women, says author Professor David Hunter of Harvard University."It is premature to recommend screening women for these gene variants, at least until the scientific community has further combed through the genome-wide findings and found all the variants that are associated with increased risk," he says.More evidence for TNRC9 In the third study, researchers found genetic variants on chromosomes 2 and 16, both increasing the risk of oestrogen receptor-positive breast cancer.One of these variants is near to the gene TNRC9, one of the genes found in another of the other studies released today.
Four more genes that play a role in breast cancer have been uncovered by an international team of scientists.But women who have mutated versions of these genes have a relatively low risk of developing breast cancer, which scientists say makes it unlikely that individual screening tests for these mutations will be developed.
Researchers, including those from Australia, publish their results today in the journals Nature and Nature Genetics.Genetic causes account for between 5-10% of breast cancer cases, with lifestyle factors such as smoking and environmental factors accounting for the rest.But until now, only about 25% of the genes that are suspected to cause inherited breast cancer have been identified. The new culprits - flawed versions of genes called FGFR2, TNRC9, MAP3K1 and LSP1 - are believed to account for an additional 4%. The researchers found them after sifting through the DNA of nearly 50,000 women, half of them healthy and half of them patients with breast cancer. While flawed versions of the four genes are common in the general population, the good news is that the genes are considered a relatively low hazard.This means that women who have them run a comparatively small risk of developing cancer.
By contrast, the breast cancer genes BRCA1 and BRCA2 are relatively rare in the population but women who have them run a high risk of the disease. Because the four newly-identified genes are so common yet relatively low-risk, individual tests for them may be unsuitable, according to Cancer Research UK, whose scientists led the investigation."[But] as more of these 'low-risk' genes are found it may be possible to design tests for a combination of genes," it says."This could help doctors make decisions about prevention, diagnosis and treatment for women who inherit faults in one or more of these genes."
There could be as many as 200 genes that influence someone's chance of developing breast cancer (Image: iStockphoto)Dr Georgia Chevenix-Trench, from the Queensland Institute of Medical Research, contributed data from Australian patients to the study."This is probably the most important paper on breast cancer genetics since the cloning of BRCA2 in 1995," she says.She adds that there are probably 100-200 similar genes that contribute to breast cancer risk and that these studies will give researchers a good idea of where to look for them.Much remains to be learnt about the four genes, especially whether they react with each other or with lifestyle factors in a way that boosts the risk for some women, the scientists add.Most previously identified breast cancer genes are involved in DNA repair. But these latest genes seem to be more related to the control of cell growth or to cell signalling.
Of the four genes identified, only FGFR2 was known to be associated with breast cancer.And scientists say it may be a logical candidate for a breast cancer gene. It encodes a receptor, a kind of molecular doorway, for a compound called tyrosine kinase that is involved in several cancers.One of the studies found there were four common mutations in the gene that were associated with sporadic breast cancer in postmenopausal women, women who developed cancer without known risk factors for it.
The mutations raised the risk of breast cancer risk by 20% if a woman carried one copy of the gene and by 60% if she carried two copies. And close to 60% of the women studied carried at least one copy.But the findings do not yet have any real relevance for women, says author Professor David Hunter of Harvard University."It is premature to recommend screening women for these gene variants, at least until the scientific community has further combed through the genome-wide findings and found all the variants that are associated with increased risk," he says.More evidence for TNRC9 In the third study, researchers found genetic variants on chromosomes 2 and 16, both increasing the risk of oestrogen receptor-positive breast cancer.One of these variants is near to the gene TNRC9, one of the genes found in another of the other studies released today.
Wednesday, May 23, 2007
What causes high Cholestrol ?
Cause
High cholesterol may run in your family. The foods you eat may also cause high cholesterol.
Causes include:
What you eat. Eating too much saturated fat can cause high cholesterol. You will find this
unhealthy fat in foods that come from animals. Beef, pork, veal, milk, eggs, butter, and cheese contain saturated fat. Packaged foods that contain coconut oil, palm oil, or cocoa butter may have a lot of saturated fat. You will also find saturated fat in stick margarine, vegetable shortening, and most cookies, crackers, chips, and other snacks.
Your weight. Being overweight may increase triglycerides and decrease HDL.
Your activity level. Lack of physical activity, which may increase LDL and decrease HDL.
Your age and gender. After you reach age 20, your cholesterol levels naturally begin to rise. In men, cholesterol levels generally level off after age 50. In women, cholesterol levels stay fairly low until menopause, after which they rise to about the same level as in men.
Your overall health. Having certain diseases, such as diabetes or hypothyroidism, may cause high cholesterol.
Your family history. If family members have high cholesterol, you may also.
Cigarette smoking. Smoking can lower your good cholesterol.
In rare cases, high cholesterol is caused by an inherited problem called a lipid disorder that changes the way the body handles cholesterol. People with lipid disorders may have total cholesterol levels well over 250 milligrams per deciliter. Certain types of inherited lipid disorders may be more difficult to treat
High cholesterol may run in your family. The foods you eat may also cause high cholesterol.
Causes include:
What you eat. Eating too much saturated fat can cause high cholesterol. You will find this
unhealthy fat in foods that come from animals. Beef, pork, veal, milk, eggs, butter, and cheese contain saturated fat. Packaged foods that contain coconut oil, palm oil, or cocoa butter may have a lot of saturated fat. You will also find saturated fat in stick margarine, vegetable shortening, and most cookies, crackers, chips, and other snacks.
Your weight. Being overweight may increase triglycerides and decrease HDL.
Your activity level. Lack of physical activity, which may increase LDL and decrease HDL.
Your age and gender. After you reach age 20, your cholesterol levels naturally begin to rise. In men, cholesterol levels generally level off after age 50. In women, cholesterol levels stay fairly low until menopause, after which they rise to about the same level as in men.
Your overall health. Having certain diseases, such as diabetes or hypothyroidism, may cause high cholesterol.
Your family history. If family members have high cholesterol, you may also.
Cigarette smoking. Smoking can lower your good cholesterol.
In rare cases, high cholesterol is caused by an inherited problem called a lipid disorder that changes the way the body handles cholesterol. People with lipid disorders may have total cholesterol levels well over 250 milligrams per deciliter. Certain types of inherited lipid disorders may be more difficult to treat
Sunday, May 20, 2007
Mental Development Similar Among Boys, Girls
FRIDAY, May 18 (HealthDay News) -- U.S. scientists are getting the first comprehensive look at how children's brains and behaviors change over time, and it's yielding some surprises.
It turns out that much-touted differences in the mental evolution of boys and girls aren't so pronounced after all.
On the other hand, the amount of money a child's family makes may have a big impact on his or her intellectual ability, with IQs rising alongside incomes.
Those are just the highlights of preliminary findings from a team of psychologists and psychiatrists at the U.S. National Institutes of Health. Their project, the National Institutes of Health MRI Study of Normal Brain Health, is assessing the neurological and behavioral development of 450 American children carefully selected to be free of problems and representing the diversity of the country's population.
"This is being done to learn more about the structural and functional development of the normal brain," explained Deborah P. Waber, associate professor of psychology at Children's Hospital Boston, lead author of the report. "The data will be used as baseline for all kinds of disorders of childhood brain development."
The first findings from the project were published Friday in the online edition of the Journal of the International Neuropsychological Society.
They include:
Mental performance differs little by gender. "We found a few significant differences that we would have suspected," Waber said. "For example, boys are better at visual and spatial tasks, and girls are better at motor speed, but there are no differences in many other paths, like memory."
Family income matters. Kids from more affluent homes do better than those from lower-income families, with average IQs of 105, 110 and 115, respectively, for children classified as low-, middle- and high-income. "But when we limit the groups to healthy children, the differences are not as great," Waber said. "That suggests that the difference has more to do with disparity in health care related to income."
Young children make the biggest gains. Mental performance climbed steadily from age 6, leveled off for most tests between age 10 and 12, and then improved only very slightly or not at all during adolescence, challenging the idea of a growth spurt in learning during the early teens.
In addition to undergoing three rounds of performance and behavioral tests as they aged, the children also underwent MRI and other scans of their brains to study the growth of different brain structures and the formation of neural connections. The scans also tracked changes in brain chemistry. Those images, and the information gleaned from them, will be made available to clinicians and scientists who study brain development.
There will be further reports, but "I don't think we are going to follow these children any further," Waber said. "This has been a very labor-intensive study at six sites across the country. It represents pretty much the limit of what our resources allow us to do."
No comparable study of normal cognitive development has ever been done, noted Judy Rumsey, the project officer who spearheaded the U.S. National Institute of Mental Health's participation in the project.
"This information will help determine what the developmental trajectories are and whether gender differences appear or disappear in the development of typically developing children up to 18 years of age -- children with no neurological disease, developmental disorder or psychiatric disorder," Rumsey said. "There has been nothing as comprehensive as this. It goes down to a very young age, with a sampling designed to insure diversity and representation for different social groups."
It is not possible to say just when the full range of images and information will be made available to professionals, Rumsey said. She said there still are some major issues to be settled, notably that of preserving the privacy of the young people who took part in the project.
More information
The project is described in detail by the U.S. National Institutes of Health.
It turns out that much-touted differences in the mental evolution of boys and girls aren't so pronounced after all.
On the other hand, the amount of money a child's family makes may have a big impact on his or her intellectual ability, with IQs rising alongside incomes.
Those are just the highlights of preliminary findings from a team of psychologists and psychiatrists at the U.S. National Institutes of Health. Their project, the National Institutes of Health MRI Study of Normal Brain Health, is assessing the neurological and behavioral development of 450 American children carefully selected to be free of problems and representing the diversity of the country's population.
"This is being done to learn more about the structural and functional development of the normal brain," explained Deborah P. Waber, associate professor of psychology at Children's Hospital Boston, lead author of the report. "The data will be used as baseline for all kinds of disorders of childhood brain development."
The first findings from the project were published Friday in the online edition of the Journal of the International Neuropsychological Society.
They include:
Mental performance differs little by gender. "We found a few significant differences that we would have suspected," Waber said. "For example, boys are better at visual and spatial tasks, and girls are better at motor speed, but there are no differences in many other paths, like memory."
Family income matters. Kids from more affluent homes do better than those from lower-income families, with average IQs of 105, 110 and 115, respectively, for children classified as low-, middle- and high-income. "But when we limit the groups to healthy children, the differences are not as great," Waber said. "That suggests that the difference has more to do with disparity in health care related to income."
Young children make the biggest gains. Mental performance climbed steadily from age 6, leveled off for most tests between age 10 and 12, and then improved only very slightly or not at all during adolescence, challenging the idea of a growth spurt in learning during the early teens.
In addition to undergoing three rounds of performance and behavioral tests as they aged, the children also underwent MRI and other scans of their brains to study the growth of different brain structures and the formation of neural connections. The scans also tracked changes in brain chemistry. Those images, and the information gleaned from them, will be made available to clinicians and scientists who study brain development.
There will be further reports, but "I don't think we are going to follow these children any further," Waber said. "This has been a very labor-intensive study at six sites across the country. It represents pretty much the limit of what our resources allow us to do."
No comparable study of normal cognitive development has ever been done, noted Judy Rumsey, the project officer who spearheaded the U.S. National Institute of Mental Health's participation in the project.
"This information will help determine what the developmental trajectories are and whether gender differences appear or disappear in the development of typically developing children up to 18 years of age -- children with no neurological disease, developmental disorder or psychiatric disorder," Rumsey said. "There has been nothing as comprehensive as this. It goes down to a very young age, with a sampling designed to insure diversity and representation for different social groups."
It is not possible to say just when the full range of images and information will be made available to professionals, Rumsey said. She said there still are some major issues to be settled, notably that of preserving the privacy of the young people who took part in the project.
More information
The project is described in detail by the U.S. National Institutes of Health.
Wednesday, May 16, 2007
Heat Waves and Breathing problems
Posted by Franklin Adkinson, M.D. on Thu, May 10, 2007, 8:19 am PDT
You may remember last summer's sweltering heat wave and the many tragic heat-related deaths. As we approach the warmer months this year, it's important to remember how asthma can be triggered by protracted heat.
It's not so much the heat itself that aggravates asthma but the air inversions that result from heat waves. These inversions, in which a layer of warm air is trapped by cooler air above, can increase the amount of toxic air pollutants by more than tenfold.
The increase in harmful oxidants and particles present during heat waves makes breathing even harder for persons with asthma and other chronic respiratory conditions.
These breathing difficulties are not caused by the extra allergens in the air but because they increase the twitchiness of the airways, making the lungs more vulnerable to the allergens we are always exposed to, like Grandma's cat, dust mites, or molds.
If you have asthma and are caught in a heat wave and your start to wonder when it's all going to end, stay in air-conditioned comfort as much as possible and get your exercise in the swimming pool or at an air-conditioned gym. Your local weather channel's air-pollution alert can give you daily updates about the quality of the air you can expect in your region.
Hot weather deserves healthy respect, especially from people with heart and lung diseases. Stay ahead of the game by drinking lots of fluids.
You may remember last summer's sweltering heat wave and the many tragic heat-related deaths. As we approach the warmer months this year, it's important to remember how asthma can be triggered by protracted heat.
It's not so much the heat itself that aggravates asthma but the air inversions that result from heat waves. These inversions, in which a layer of warm air is trapped by cooler air above, can increase the amount of toxic air pollutants by more than tenfold.
The increase in harmful oxidants and particles present during heat waves makes breathing even harder for persons with asthma and other chronic respiratory conditions.
These breathing difficulties are not caused by the extra allergens in the air but because they increase the twitchiness of the airways, making the lungs more vulnerable to the allergens we are always exposed to, like Grandma's cat, dust mites, or molds.
If you have asthma and are caught in a heat wave and your start to wonder when it's all going to end, stay in air-conditioned comfort as much as possible and get your exercise in the swimming pool or at an air-conditioned gym. Your local weather channel's air-pollution alert can give you daily updates about the quality of the air you can expect in your region.
Hot weather deserves healthy respect, especially from people with heart and lung diseases. Stay ahead of the game by drinking lots of fluids.
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