There are many myths about the brain that may or may not be true. One myth is that humans only use about 10% of our brain. This myth was coined by Albert Einstein and since then has been scientifically proven to be false. His logic was that only one out of every 10 nerve cells are being used, thus we only use 10% of our brain. There is scientifical evidence which proves this to not be true: even if neurons are not firing action potentials, they could still be recieving signals from other neurons. The fact is if you look at a cognitive brain map, every part of the brain is used. There are many different parts of the brain which aid other parts of the brain in successfully equipping a human being. Also, there is no point in having that much space in the brain if we only use 10% of it. For an example, consider a patient who experiences a traumatic blow to the head. When they go to a doctor, the doctor tells them they have brain damage all around the brain. They don't say, "Oh, you only have brain damage in this part of your brain, but good thing that's not the 10% of your brain that you actually use." The whole brain is used in everyday life. Every part of the brain works together to form a working machine. Some say that this myth still continues due to popular media continuing to advocate this false myth.
http://www.time-etc.com/2007/06/ten-myths-about-brain.html
http://faculty.washington.edu/chudler/tenper.html
Wednesday, July 23, 2008
Medtronic Fidelis Pacemaker
Medtronic's Fidelis pacemaker was different from other pacemakers most notably because of its lead. The lead on this pacemaker was thinner than usual, which was intentional in the pacemaker's design, due to the greater ease surgeons would have routing and connecting it to the heart. However, what made the pacemaker easier to set up in patients introduced a gigantic problem for the pacemaker's operation.
The thinner lead was much more prone to fracturing. This, obviously, would disrupt electrical impulses being sent to a malfunctioning heart. It would also scramble signals from the heart back to the pacemaker, which is just as dangerous; one paient with a Fidelis pacemaker died because the pacemaker, receiving jumbled data through a fractured lead, misfired very rapidly based on the incorrect data, causing a heart attack. The pacemaker was recalled on October 15th, 2007; Medtronic announced upon recalling their device that there had been a 2.3% failure rate in paients within the first 30 months receiving the device. Though this may seem like a small percentage, there are around 235,000 people with the Fidelis pacemaker. This means that roughly 5,000 patients can expect to have fractures in the leads of their pacemakers.
Replacing leads is no easy or inexpensive task: many complications can arise from removing leads from hearts, and the operation costs $12,500. Medtronic now offers replacement leads for free, and up to $800 towards the cost of the operation, but only upon reccomendation on lead removal by a doctor; not all people are in good enough condition for such an operation. And even with $800 towards the operation, patients deemed suitable to replacement may still be barely able or unable to afford the $11,700.
The thinner lead was much more prone to fracturing. This, obviously, would disrupt electrical impulses being sent to a malfunctioning heart. It would also scramble signals from the heart back to the pacemaker, which is just as dangerous; one paient with a Fidelis pacemaker died because the pacemaker, receiving jumbled data through a fractured lead, misfired very rapidly based on the incorrect data, causing a heart attack. The pacemaker was recalled on October 15th, 2007; Medtronic announced upon recalling their device that there had been a 2.3% failure rate in paients within the first 30 months receiving the device. Though this may seem like a small percentage, there are around 235,000 people with the Fidelis pacemaker. This means that roughly 5,000 patients can expect to have fractures in the leads of their pacemakers.
Replacing leads is no easy or inexpensive task: many complications can arise from removing leads from hearts, and the operation costs $12,500. Medtronic now offers replacement leads for free, and up to $800 towards the cost of the operation, but only upon reccomendation on lead removal by a doctor; not all people are in good enough condition for such an operation. And even with $800 towards the operation, patients deemed suitable to replacement may still be barely able or unable to afford the $11,700.
Tuesday, July 22, 2008
Neurogenesis in the Human Brain
Nick Ciborowski
There is a common belief floating around amongst the people of our society today and it is that our brains do not recreate new brain cells throughout our lives. People believe that they have a set number of brain cells from when they are born and they will never regenerate over time. And while there has been no legitimate evidence (involving humans) to prove our bodies can produce new brain cells throughout our lives, there have been discoveries and theories recently, in the field of neurogenesis, that have been turning heads in the scientific community. Biologists like Michael Kaplan and Joseph Altman were among the first to explore the realm of possibility of neurogenesis in the brain.
Initially, it was discovered that neurogenesis occurred in the brains of birds and later on, mammals like monkeys. Experiments were performed on monkeys and they revealed that new neurons were formed in the cerebral cortex. The latter discovery made many scientists believe that neurogenesis could in fact occur in humans as well. Scientists believe that neurogenesis occurs more effectively under certain conditions. They think that exercise and an “enriched environment” encourage neurogenesis. However, there can be adverse effects on neurogenesis as well. High stress levels as well as aging are a few factors that can be detrimental to the neurogenesis process. So even though it is still an unclear what the future will hold in the field of neurogenesis, we do know that new discoveries are just beyond the horizon.
People Use Only 10% of Their Brains
There is a common saying that people only use 10% of their brains. This is a common misconception. It has been proven that every part of the brain has a known function. This misunderstanding arose sometime in the early 1900’s when researchers either discovered that only about 10% of the neurons in the brain are firing at any given time. Either that or only 10% of brain function was able to be mapped at that time in scientific history.
Another possible origin of this misconception is that only 10% of total brain cells are neurons. The rest of the cells in the brain are called glial cells, which do not function the same way neurons do. On a lighter note, Some New Age proponents propagate this belief by asserting that the "unused" ninety percent of the human brain is capable of exhibiting psychic powers and can be trained to perform psychokinesis and extra-sensory perception.
References:http://en.wikipedia.org/wiki/Human_brain#Common_misconceptions
Are You a Righty or a Lefty?
Alexis Gorin
Farah Laiwalla
Engineering Biomedical Systems (BI920-3B)
Tuesday, July 22, 2008
To start a conversation, a common icebreaker is "Are you right-brained or left-brained?" making the asker associate a few characteristics to your character in 5 seconds based on whichever two words you choose. While certain abilities , such as verbal language, can be associated to either the left or right side of the brain, the right brain has been shown to be able to carry out verbal language, though to a lesser extent. Other than the left brain's superior ability to carry out verbal language, both sides of the brain are similarly able to carry out each ability with only a small difference of either the right or left being the better processor (Two Brains for the Price of One).
Left and right brain interaction to control a mental ability is also necessary, to the point that one can only be unable to perform a mental ability if both sides of the brain are damaged (Two Brains for the Price of One). Using the language example from before, it has been found that while left brain controls grammar and pronunciation, the right controls the pitch of the voice, both producing the ability to verbally speak (Brain Mythology). So next time someone asks whether you are a righty or a lefty, say your both, or just show them how you write, whichever you prefer.
"Two Brains for the Price of One? ." PsyBlog. PsyBlog. 23 Jul 2008 http://www.spring.org.uk/2008/03/two-brains-for-price-of-one.php.
"Brain Mythology." Brain Fitness Channel. 2008. Posit Science Corporation. 23 Jul 2008 http://bfc.positscience.com/brain/brain_mythology.php.
Stryke three for the stryker artificial hip
Stryker industries was sent warning letters from the FDA pertaining to the quality of it's product, the stryker artificial hip. These problems resulted in the neccesity of more surgery to correct the problem caused by the device. The problems included too much residual components left on the device upon packaging, which I imagine would not be very biofriendly. Another problem, invovled the devices design itself, causing fractures and squeaking noises, though I imagine that most people getting hip replacements don't really realize the latter.
All in all I wouldn't call this product a very successful one. Such a thing can and did marr Stryker industries' reputation, as they lost considerable amounts of stock. This raises the question of, why such carelessness? Where in the design process or manufacturing process was there such a reckless abandon? Better yet, why didn't the FDA realize this problem before clearing it? I don't really have the answers as I don't posses open contact with Stryker industries, who would probably lie about how the problem developed, or the FDA, who would probably lie about how they let the problem slip during testing.
http://www.healthsquare.com/news/news-200039.htm
All in all I wouldn't call this product a very successful one. Such a thing can and did marr Stryker industries' reputation, as they lost considerable amounts of stock. This raises the question of, why such carelessness? Where in the design process or manufacturing process was there such a reckless abandon? Better yet, why didn't the FDA realize this problem before clearing it? I don't really have the answers as I don't posses open contact with Stryker industries, who would probably lie about how the problem developed, or the FDA, who would probably lie about how they let the problem slip during testing.
http://www.healthsquare.com/news/news-200039.htm
Myth: Sleepy After Thanksgiving Dinner
Sleepy After Thanksgiving Dinner
The drowsiness that many people experience after a Thanksgiving feast is not a result of the turkey alone. Instead, it is the carbohydrate rich meal that accompanies the turkey that causes people to feel sleepy. The amino acid tryptophan can be metabolized to produce serotonin, a neurotransmitter that causes a calming effect and regulates sleep. Tryptophan is found in high levels in protein rich foods, such as turkey. Yet the amount of the amino acid present in turkey is not nearly high enough to have immediate effects, and similar concentrations of tryptophan are found in other foods that do not cause any affects. Contrary to popular belief, it is the carbohydrates consumed during a meal that cause drowsiness.
Once the tryptophan is in the bloodstream, it is competing with many other amino acids to take the journey across the blood-brain barrier. When carbohydrates are consumed, the pancreas secretes insulin, which causes the competing amino acids to leave the bloodstream and enter the muscle cells. This increases the relative concentration of tryptophan in the bloodstream and allows more of it to reach the brain and become serotonin. Basically, any carbohydrate rich diet that has some protein in it can cause the familiar sleepy feeling after a meal.
http://chemistry.about.com/od/holidaysseasons/a/tiredturkey.htm
http://wiki.answers.com/Q/Why_does_eating_turkey_on_Thanksgiving_make_you_sleepy
Mozart Mania
Myth: Playing music such as Mozart to babies increases intelligence
Fact: Research has found that the “Mozart Effect” does not exist
The Mozart effect is defined as the “increase in brain development that occurs in children under age 3 when they listen to the music of Wolfgang Amadeus Mozart” (Skeptics’ Dictionary). The concept originated in 1993 when two physicists, Rauscher and Shaw, conducted an experiment. After a group of college students listened to Mozart, they exhibited a short-term spatial-temporal reasoning enhancement. However, despite multiple efforts, similar results were not replicated. Several years later in 1997, Rauscher and Shaw performed another experiment that uncovered the power of Mozart’s music to enhance children’s reasoning abilities:
“The experiment included three groups of preschoolers: one group received private piano/keyboard lessons and singing lessons; a second group received private computer lessons; and a third group received no training. Those children who received piano/keyboard training performed 34% higher on tests measuring spatial- temporal ability than the others. These findings indicate that music uniquely enhances higher brain functions required for mathematics, chess, science and engineering” (Neurological Research, February 1997).
The discovery of this experiment launched a new industry, especially in the media. The Mozart effect sparked books, tapes, CDs, and programs that were not backed by extensive scientific evidence. The research of one experiment published in a scientific journal became an automatic truth. The media jumped on the bandwagon while distorting and exaggerating the not-so-scientific findings.
The experiment conducted was only a fluke. While some kids did have high scores, others scored unusually low. Current research has not found any links to the Mozart effect. However, this does not mean music and the brain do no share a connection. With additional research and more controlled experiments the link between intelligence and music may be discovered.
Ego Development:
http://www.egodevelopment.com/10-debunked-myths-myths-about-our-brain/
The Skeptics' Dictionary:
http://www.skepdic.com/mozart.html
Fact: Research has found that the “Mozart Effect” does not exist
The Mozart effect is defined as the “increase in brain development that occurs in children under age 3 when they listen to the music of Wolfgang Amadeus Mozart” (Skeptics’ Dictionary). The concept originated in 1993 when two physicists, Rauscher and Shaw, conducted an experiment. After a group of college students listened to Mozart, they exhibited a short-term spatial-temporal reasoning enhancement. However, despite multiple efforts, similar results were not replicated. Several years later in 1997, Rauscher and Shaw performed another experiment that uncovered the power of Mozart’s music to enhance children’s reasoning abilities:
“The experiment included three groups of preschoolers: one group received private piano/keyboard lessons and singing lessons; a second group received private computer lessons; and a third group received no training. Those children who received piano/keyboard training performed 34% higher on tests measuring spatial- temporal ability than the others. These findings indicate that music uniquely enhances higher brain functions required for mathematics, chess, science and engineering” (Neurological Research, February 1997).
The discovery of this experiment launched a new industry, especially in the media. The Mozart effect sparked books, tapes, CDs, and programs that were not backed by extensive scientific evidence. The research of one experiment published in a scientific journal became an automatic truth. The media jumped on the bandwagon while distorting and exaggerating the not-so-scientific findings.
The experiment conducted was only a fluke. While some kids did have high scores, others scored unusually low. Current research has not found any links to the Mozart effect. However, this does not mean music and the brain do no share a connection. With additional research and more controlled experiments the link between intelligence and music may be discovered.
Ego Development:
http://www.egodevelopment.com/10-debunked-myths-myths-about-our-brain/
The Skeptics' Dictionary:
http://www.skepdic.com/mozart.html
Head Injuries and Brain Cell Loss
Can a blow to the head actually lead to brain cell loss? The fact that brain cells can be lost due to head injuries is often overlooked by many when the injury is not severe. A traumatic head injury, such as a major concussion, can lead to the disconnection of some brain cells, which in turn causes cell death. Similar to how the affects of an injury can vary the seriousness of a concussion also varies. The brain basically floats inside the skull while immersed in spinal fluid. Although the skull is able to protect the brain from external trauma, it cannot absorb the impact of the force. The brain could hit the inner wall of the skull following a blow to the head, leading to bruising in the brain.
A minor concussion, or a weaker blow to the head, can leave a person vulnerable for more serious injury. Athletes who play contact sports are often prone to concussions. The dangers of a minor concussion come from the athlete continuing play with an injury that has not fully healed. The chances of the injury becoming critical are increased enough that another blow can cause rapid swelling of the brain and death.
A hit to the head can cause microscopic damage that is not visible on a CT scan, but still contains some bruising and bleeding. Many neurologists have been concerned that repeated injuries may cause problems later in life. While the injuries may appear to have healed, there can be a loss of brain cells. The loss of some brain cells may lead to additional harm to other brain cells. When it comes to the head, a person can never be too careful. There is a reason why doctors stress that athletes take time off when a head injury is involved.
References:
http://www.sciencedaily.com/releases/2008/03/080303190628.htm
http://query.nytimes.com/gst/fullpage.html?res=9500E5DC123EF932A35756C0A96E958260 http://www.neurosurgerytoday.org/what/patient_e/concussion.asp
A minor concussion, or a weaker blow to the head, can leave a person vulnerable for more serious injury. Athletes who play contact sports are often prone to concussions. The dangers of a minor concussion come from the athlete continuing play with an injury that has not fully healed. The chances of the injury becoming critical are increased enough that another blow can cause rapid swelling of the brain and death.
A hit to the head can cause microscopic damage that is not visible on a CT scan, but still contains some bruising and bleeding. Many neurologists have been concerned that repeated injuries may cause problems later in life. While the injuries may appear to have healed, there can be a loss of brain cells. The loss of some brain cells may lead to additional harm to other brain cells. When it comes to the head, a person can never be too careful. There is a reason why doctors stress that athletes take time off when a head injury is involved.
References:
http://www.sciencedaily.com/releases/2008/03/080303190628.htm
http://query.nytimes.com/gst/fullpage.html?res=9500E5DC123EF932A35756C0A96E958260 http://www.neurosurgerytoday.org/what/patient_e/concussion.asp
Monday, July 21, 2008
Plants Make Vaccine for Treating Type of Cancer in Stanford Study
Plants could act as safe, speedy factories for growing antibodies for personalized treatments against a common form of cancer, according to new findings from the Stanford University School of Medicine. The findings came in the first human tests of an injectable vaccine grown in genetically engineered plants.
The treatments, which would vaccinate cancer patients against their malignant cells, could lead to earlier personalized therapy to tackle follicular B-cell lymphoma, an immune-system malignancy diagnosed in about 16,000 people each year.
Doctors regard follicular B-cell lymphoma as a chronic, incurable disease. The standard treatment, chemotherapy, has such severe side effects that patients often opt for watchful waiting in the early stages of illness. However, plant-grown vaccines, which lack side effects, could allow earlier, more aggressive management of the cancer.
"This would be a way to treat cancer without side effects," said Ronald Levy, MD, professor of oncology and the Robert K. and Helen K. Summy Professor in the School of Medicine, who is the study's senior author. "The idea is to marshal the body's own immune system to fight cancer."
The findings will appear July 21 in the advance online issue of the Proceedings of the National Academy of Science. The study was a phase-1 trial that showed plant-grown cancer vaccines were safe for patients and could be produced quickly and cheaply. Sixteen newly diagnosed lymphoma patients received the treatment; none experienced any side effects from plant-grown vaccines.
Future studies will test the vaccine's effectiveness.
The cancer vaccines rely on a biological quirk of follicular B-cell lymphoma, which is a type of non-Hodgkin's lymphoma. The cancer starts when a single immune cell multiplies uncontrollably, producing many identical clones of itself. The clones all carry the same antibody on their exterior, a marker that is unique to the cancer and is not found on any of the body's healthy cells. Levy's vaccination strategy is to inject many copies of the cancer-specific antibody into a newly diagnosed lymphoma patient, stimulating the patient's immune system to seek and destroy malignant cells.
Previous trials of this kind of vaccine, produced in animal cells and tested in mice and humans, have had mixed success, and the vaccines are not yet commercially available. Growing cancer vaccines in plants could circumvent some of the hurdles to turning the concept into a real treatment, Levy said.
Because each person's cancer antibody is unique, every patient needs a personalized vaccine. Growing personalized vaccines in animal cells takes months, costs thousands of dollars per patient and comes with the theoretical risk that a patient might inadvertently be infected with an animal virus that contaminated the cells used to grow the vaccine. Personalized vaccines could also be produced with genetically engineered bacteria, but bacteria-grown vaccines aren't ideal, either.
"The plant system has some advantages," said Levy, who is also a member of the Stanford Cancer Center and a Howard Hughes Medical Institute investigator.
The researchers chose tobacco plants that were genetically engineered to reproduce quantities of the vaccine. To make a tobacco plant churn out a human antibody, scientists isolate the antibody from the patient's tumor and put the antibody gene into a modified version of the tobacco mosaic virus. They infect a tobacco plant with the gene-carrying virus by scratching the virus on its leaves. The virus takes the gene into the plant's cells, which then churn out lots of antibody. After a few days, technicians snip off the plant's leaves, grind them up and purify the antibody. Only a few plants are needed to make enough vaccine for each patient.
"The new manufacturing system allows very rapid production of a vaccine," said Charles Arntzen, PhD, a professor of plant biology at the Arizona Biodesign Institute at Arizona State University, who was not involved in the research. "I think without the speed, it would be hard to convince a cancer patient to wait for a vaccine to be developed, rather than going on some other therapy."
"It's pretty cool technology," Levy said. "And it's really ironic that you would make a treatment for cancer out of tobacco. That appealed to me." None of the harmful chemicals found in cigarettes end up in the purified vaccines.
Not only is the technology fast, cheap and safe, but Levy said there's reason to expect that the plant-grown antibodies will generate a stronger immune response than those made in animal cells. Both plant and animal cells attach sugars to antibodies and other proteins during biochemical processing, but the plant and animal sugars are different. The difference might prompt a more robust immune response to plant-grown antibodies, Levy said.
The next research step is a phase-2 clinical trial to test the effectiveness of plant-grown vaccines in a larger group of lymphoma patients, Levy said. He's optimistic, adding, "We know that if you get the immune system revved up, it can attack and kill cancer."
The research team included scientists from Stanford, Touro University in Vallejo, Calif., and the biotechnology companies Large Scale Biology Corp., CBR International Corp., Bayer HealthCare, Integrated Biomolecule Corp., The Biologics Consulting Group Inc. and Holtz Biopharma Consulting.
The study was funded by a grant from the National Institutes of Health and by Large Scale Biology Corp.
The treatments, which would vaccinate cancer patients against their malignant cells, could lead to earlier personalized therapy to tackle follicular B-cell lymphoma, an immune-system malignancy diagnosed in about 16,000 people each year.
Doctors regard follicular B-cell lymphoma as a chronic, incurable disease. The standard treatment, chemotherapy, has such severe side effects that patients often opt for watchful waiting in the early stages of illness. However, plant-grown vaccines, which lack side effects, could allow earlier, more aggressive management of the cancer.
"This would be a way to treat cancer without side effects," said Ronald Levy, MD, professor of oncology and the Robert K. and Helen K. Summy Professor in the School of Medicine, who is the study's senior author. "The idea is to marshal the body's own immune system to fight cancer."
The findings will appear July 21 in the advance online issue of the Proceedings of the National Academy of Science. The study was a phase-1 trial that showed plant-grown cancer vaccines were safe for patients and could be produced quickly and cheaply. Sixteen newly diagnosed lymphoma patients received the treatment; none experienced any side effects from plant-grown vaccines.
Future studies will test the vaccine's effectiveness.
The cancer vaccines rely on a biological quirk of follicular B-cell lymphoma, which is a type of non-Hodgkin's lymphoma. The cancer starts when a single immune cell multiplies uncontrollably, producing many identical clones of itself. The clones all carry the same antibody on their exterior, a marker that is unique to the cancer and is not found on any of the body's healthy cells. Levy's vaccination strategy is to inject many copies of the cancer-specific antibody into a newly diagnosed lymphoma patient, stimulating the patient's immune system to seek and destroy malignant cells.
Previous trials of this kind of vaccine, produced in animal cells and tested in mice and humans, have had mixed success, and the vaccines are not yet commercially available. Growing cancer vaccines in plants could circumvent some of the hurdles to turning the concept into a real treatment, Levy said.
Because each person's cancer antibody is unique, every patient needs a personalized vaccine. Growing personalized vaccines in animal cells takes months, costs thousands of dollars per patient and comes with the theoretical risk that a patient might inadvertently be infected with an animal virus that contaminated the cells used to grow the vaccine. Personalized vaccines could also be produced with genetically engineered bacteria, but bacteria-grown vaccines aren't ideal, either.
"The plant system has some advantages," said Levy, who is also a member of the Stanford Cancer Center and a Howard Hughes Medical Institute investigator.
The researchers chose tobacco plants that were genetically engineered to reproduce quantities of the vaccine. To make a tobacco plant churn out a human antibody, scientists isolate the antibody from the patient's tumor and put the antibody gene into a modified version of the tobacco mosaic virus. They infect a tobacco plant with the gene-carrying virus by scratching the virus on its leaves. The virus takes the gene into the plant's cells, which then churn out lots of antibody. After a few days, technicians snip off the plant's leaves, grind them up and purify the antibody. Only a few plants are needed to make enough vaccine for each patient.
"The new manufacturing system allows very rapid production of a vaccine," said Charles Arntzen, PhD, a professor of plant biology at the Arizona Biodesign Institute at Arizona State University, who was not involved in the research. "I think without the speed, it would be hard to convince a cancer patient to wait for a vaccine to be developed, rather than going on some other therapy."
"It's pretty cool technology," Levy said. "And it's really ironic that you would make a treatment for cancer out of tobacco. That appealed to me." None of the harmful chemicals found in cigarettes end up in the purified vaccines.
Not only is the technology fast, cheap and safe, but Levy said there's reason to expect that the plant-grown antibodies will generate a stronger immune response than those made in animal cells. Both plant and animal cells attach sugars to antibodies and other proteins during biochemical processing, but the plant and animal sugars are different. The difference might prompt a more robust immune response to plant-grown antibodies, Levy said.
The next research step is a phase-2 clinical trial to test the effectiveness of plant-grown vaccines in a larger group of lymphoma patients, Levy said. He's optimistic, adding, "We know that if you get the immune system revved up, it can attack and kill cancer."
The research team included scientists from Stanford, Touro University in Vallejo, Calif., and the biotechnology companies Large Scale Biology Corp., CBR International Corp., Bayer HealthCare, Integrated Biomolecule Corp., The Biologics Consulting Group Inc. and Holtz Biopharma Consulting.
The study was funded by a grant from the National Institutes of Health and by Large Scale Biology Corp.
Sunday, July 20, 2008
Researchers Grow Human Blood Vessels In Mice From Adult Progenitor Cells
ScienceDaily (July 18, 2008) — For the first time, researchers have successfully grown functional human blood vessels in mice using cells from adult human donors — an important step in developing clinical strategies to grow tissue, researchers report in Circulation Research: Journal of the American Heart Association.
“What’s really significant about our study is that we are using human cells that can be obtained from blood or bone marrow rather than removing and using fully developed blood vessels,” said Joyce Bischoff, Ph.D., senior author of the study and associate professor at Harvard Medical School and Children’s Hospital Boston.
The researchers combined two different types of progenitor cells in a culture dish of nutrients and growth factors, then washed off the nutrients and implanted the cells into mice with weakened immune systems. Once implanted, the progenitor cell mixture grew and differentiated into a small ball of healthy blood vessels.
Progenitor cells are similar to stem cells but can only differentiate into specific cells, while stem cells can differentiate into practically any cell in the body.
In the study, researchers used two different kinds of progenitor cells to grow blood vessels: the endothelial progenitor cells (EPCs), which become cells that line the vessels, and mesenchymal progenitor cells (MPCs), which differentiate into the cells that surround the lining and provide stability.
The researchers used different combinations of the two types of progenitor cells. They found that a mixture of adult blood- and adult bone marrow-derived progenitor cells or a combination of umbilical cord blood-derived and adult bone marrow-derived cells resulted in the greatest density of new blood vessel formation.
The ability to rapidly grow two-layered blood vessels without using embryonic or umbilical cord blood stem cells could skirt many ethical concerns, Bischoff said. It would also solve a persistent problem in treating several medical conditions that result from ischemia — the inability of oxygen-rich blood to reach an organ or tissue — such as heart attacks, wound healing and many acute injuries.
“What we are most interested in right now is speeding up the vascularization (the formation of blood vessels),” Bischoff said. “We see very good and extensive vasculature in seven days and we’d like to see that in 24 or 48 hours. If you have an ischemic tissue, it’s dying tissue, so the faster you can establish blood flow the better.”
If researchers can develop ways to speed the growth of the vessels, non-surgical cardiac bypass procedures could potentially grow new vessels around those blocked by atherosclerosis.
Bischoff said other findings include:
* The cells created a vigorous network of vessels that connected to one another and to the vessels of the host mouse within seven days and continued to transport blood during the four-week study.
* Once combined and implanted, the two progenitor cells arranged themselves into vessels with minimal outside help, i.e., without any genetic alteration or manipulation to improve their growth. This is important because many growth-promoting genes are the same genes that become activated in cancer.
* Mixtures of EPCs and MPCs from adult donors were as effective at generating vessels as those made from a mixture of cord blood EPCs and adult bone marrow MPCs. That finding increases the likelihood of someday being able to easily find clinically useful amounts of progenitor cells. The research could also enhance tissue engineering — growing new organs for later implantation into patients, another medical research field that needs good sources of microvascularization to develop, Bischoff said.
Co-authors are Juan M. Melero-Martin, Ph.D., lead author; Maria E. De Obaldia, A.B.; Soo-Young Kang, Ph.D.; Zia A. Khan, Ph.D.; Lei Yuan, Ph.D.; and Peter Oettgen, M.D. Individual author disclosures can be found on the manuscript.
The U.S. Army funded the research.
[http://www.sciencedaily.com/releases/2008/07/080718180719.htm]
“What’s really significant about our study is that we are using human cells that can be obtained from blood or bone marrow rather than removing and using fully developed blood vessels,” said Joyce Bischoff, Ph.D., senior author of the study and associate professor at Harvard Medical School and Children’s Hospital Boston.
The researchers combined two different types of progenitor cells in a culture dish of nutrients and growth factors, then washed off the nutrients and implanted the cells into mice with weakened immune systems. Once implanted, the progenitor cell mixture grew and differentiated into a small ball of healthy blood vessels.
Progenitor cells are similar to stem cells but can only differentiate into specific cells, while stem cells can differentiate into practically any cell in the body.
In the study, researchers used two different kinds of progenitor cells to grow blood vessels: the endothelial progenitor cells (EPCs), which become cells that line the vessels, and mesenchymal progenitor cells (MPCs), which differentiate into the cells that surround the lining and provide stability.
The researchers used different combinations of the two types of progenitor cells. They found that a mixture of adult blood- and adult bone marrow-derived progenitor cells or a combination of umbilical cord blood-derived and adult bone marrow-derived cells resulted in the greatest density of new blood vessel formation.
The ability to rapidly grow two-layered blood vessels without using embryonic or umbilical cord blood stem cells could skirt many ethical concerns, Bischoff said. It would also solve a persistent problem in treating several medical conditions that result from ischemia — the inability of oxygen-rich blood to reach an organ or tissue — such as heart attacks, wound healing and many acute injuries.
“What we are most interested in right now is speeding up the vascularization (the formation of blood vessels),” Bischoff said. “We see very good and extensive vasculature in seven days and we’d like to see that in 24 or 48 hours. If you have an ischemic tissue, it’s dying tissue, so the faster you can establish blood flow the better.”
If researchers can develop ways to speed the growth of the vessels, non-surgical cardiac bypass procedures could potentially grow new vessels around those blocked by atherosclerosis.
Bischoff said other findings include:
* The cells created a vigorous network of vessels that connected to one another and to the vessels of the host mouse within seven days and continued to transport blood during the four-week study.
* Once combined and implanted, the two progenitor cells arranged themselves into vessels with minimal outside help, i.e., without any genetic alteration or manipulation to improve their growth. This is important because many growth-promoting genes are the same genes that become activated in cancer.
* Mixtures of EPCs and MPCs from adult donors were as effective at generating vessels as those made from a mixture of cord blood EPCs and adult bone marrow MPCs. That finding increases the likelihood of someday being able to easily find clinically useful amounts of progenitor cells. The research could also enhance tissue engineering — growing new organs for later implantation into patients, another medical research field that needs good sources of microvascularization to develop, Bischoff said.
Co-authors are Juan M. Melero-Martin, Ph.D., lead author; Maria E. De Obaldia, A.B.; Soo-Young Kang, Ph.D.; Zia A. Khan, Ph.D.; Lei Yuan, Ph.D.; and Peter Oettgen, M.D. Individual author disclosures can be found on the manuscript.
The U.S. Army funded the research.
[http://www.sciencedaily.com/releases/2008/07/080718180719.htm]
Friday, July 18, 2008
Types of Artificial Hearts
Types of Artificial Hearts
Artificial hearts are devices that try to mimic either all or a part of the heart’s function. They are generally used for people who are not eligible for heart transplants. There are mainly two broad types of artificial hearts. There are Cardiac (heart) assist devices [CAD] and Total Artificial Hearts (TAH). CAD’s help the heart; they don’t do all the work for it. CAD’s are usually composed of left, right, or a combination of ventricular assist devices. When these devices are used the heart is not removed from the body, but rather the device takes the place of the heart’s components.
TAH’s are a little more complex in their nature. When these are used the heart must be completely removed from the body, and these devices are put in. these are similar to getting a human donor heart. TAH’s have decent reliability and are widely used in current times.
William Kolff in the early 1900’s invented the first TAH and from then on newer models were developed. The most widely known type of artificial heart is the Jarvik 7. This was invented by Dr. Robert Jarvik in 1982, so until relatively recently we had no replacement for a heart. The first patient it was used on ended up dying in only 112 days. The pump itself worked fine it was just its meeting with the body that caused problems. Currently Dr. Jarvik is working on a new type of artificial heart that is the size of one’s thumb. He will be calling this the Jarvik 2000.
A third type of artificial heart that is not yet been tested through time but has engineers rigorously working on is the electric heart. Dr. Michael DeBarkey has been the first to use this new device, but the public still has yet to see if it works well.
http://inventors.about.com/library/inventors/blartificialheart.htm
http://en.wikipedia.org/wiki/Artifical_heart
http://www.texasheart.org/Research/Devices/j7tah.cfm
Artificial hearts are devices that try to mimic either all or a part of the heart’s function. They are generally used for people who are not eligible for heart transplants. There are mainly two broad types of artificial hearts. There are Cardiac (heart) assist devices [CAD] and Total Artificial Hearts (TAH). CAD’s help the heart; they don’t do all the work for it. CAD’s are usually composed of left, right, or a combination of ventricular assist devices. When these devices are used the heart is not removed from the body, but rather the device takes the place of the heart’s components.
TAH’s are a little more complex in their nature. When these are used the heart must be completely removed from the body, and these devices are put in. these are similar to getting a human donor heart. TAH’s have decent reliability and are widely used in current times.
William Kolff in the early 1900’s invented the first TAH and from then on newer models were developed. The most widely known type of artificial heart is the Jarvik 7. This was invented by Dr. Robert Jarvik in 1982, so until relatively recently we had no replacement for a heart. The first patient it was used on ended up dying in only 112 days. The pump itself worked fine it was just its meeting with the body that caused problems. Currently Dr. Jarvik is working on a new type of artificial heart that is the size of one’s thumb. He will be calling this the Jarvik 2000.
A third type of artificial heart that is not yet been tested through time but has engineers rigorously working on is the electric heart. Dr. Michael DeBarkey has been the first to use this new device, but the public still has yet to see if it works well.
http://inventors.about.com/library/inventors/blartificialheart.htm
http://en.wikipedia.org/wiki/Artifical_heart
http://www.texasheart.org/Research/Devices/j7tah.cfm
The Jarvik-7 Artificial Heart
The Jarvik-7 Artificial Heart Among the most controversial of medical ethical issues is the Jarvik-7 Aritificial Heart. Its controversial nature began with its first permanent implantation in patient Barney Clark. Clark was a dentist from Seattle who wished to help further the research in this particular area. The issue in its entirety deals with the ethics of implanting humans with these hearts in this experimental manner.
Aside from its controversial nature and the media's subsequent focus on many of the complications in the patients that followed, the Jarvik-7 is the most successful artificial heart of its kind to have ever been designed. Five patients were implanted with the Jarvik-7 as a permanent replacement for the heart. On average, these patients lived 10 months, each with complications along the way. William Schroeder was among these five, and he lived longest on the Jarvik-7, for a period of 620 days.
Because the the Jarvik-7 proved to be viable for extended periods of time but not for "forever" so to speak, it has become part of the bridge process for the transplantation of a new heart. Patients who obtain and must live on Jarvik-7's during this bridge process have lived for years after receiving their donor hearts. For example, one patient lived fourteen years after receiving his donor heart.
The Jarvik-7 consists of two pumps that function in like the heart itself. It has two ventricles in the shape of a shpere and made of polyurethane. The pumps in the Jarvik-7 are powered by air pumps (pneumatic) that push the blood through inlet and outlet valves. The artificial heart itself is attached to the natural atria of the heart by Dacron felt. The powersource for the pumps themselves are powered by drive lines attached to an "air-driven, external power system" (Jarvik-7). The power system is a console roughly the size and weight of a home refrigerator, and is portable with a backup baterry system in case of power failure.
Aside from its controversial nature and the media's subsequent focus on many of the complications in the patients that followed, the Jarvik-7 is the most successful artificial heart of its kind to have ever been designed. Five patients were implanted with the Jarvik-7 as a permanent replacement for the heart. On average, these patients lived 10 months, each with complications along the way. William Schroeder was among these five, and he lived longest on the Jarvik-7, for a period of 620 days.
Because the the Jarvik-7 proved to be viable for extended periods of time but not for "forever" so to speak, it has become part of the bridge process for the transplantation of a new heart. Patients who obtain and must live on Jarvik-7's during this bridge process have lived for years after receiving their donor hearts. For example, one patient lived fourteen years after receiving his donor heart.
The Jarvik-7 consists of two pumps that function in like the heart itself. It has two ventricles in the shape of a shpere and made of polyurethane. The pumps in the Jarvik-7 are powered by air pumps (pneumatic) that push the blood through inlet and outlet valves. The artificial heart itself is attached to the natural atria of the heart by Dacron felt. The powersource for the pumps themselves are powered by drive lines attached to an "air-driven, external power system" (Jarvik-7). The power system is a console roughly the size and weight of a home refrigerator, and is portable with a backup baterry system in case of power failure.
- Robert Jarvik on the Jarvik-7. Jarvik Heart. <http://www.jarvikheart.com/basic.asp?id=69>.
- The Jarvik-7 Total Artificial Heart. April 2006. Texas Heart Institute. <http://www.texasheart.org/Research/Devices/j7tah.cfm>.
VAD's
When looking for a VAD, there are two categories to examine: Durability and bio-friendliness. The first category is pretty much self explanitory, asking 'how long does the machine normaly last' and 'can I expect mechanical failure,' but the second is a little broader. It asks 'what kind of medication do I need to take,' 'how much medication do I need to take', and 'does it increase my chance of infection.' Depending on what country you're in, you may also have to examine legal issues, as a number of devices are only approved in certain countries.
Based purely on longevity of a singal user, the best choice for a VAD is the Jarvik 2000, a very compact system which was able to support a patient for 7.5 years. However, it is still waiting approval in the U.S and has not of yet been used on a large number of patients. The Novacor LVAD, however, has been used on over 1,700 patiens, has approval in the US, EU and Japan, and, "among these recipients, 45 have been supported for more than two years, 24 for more than three years, 11 for more than four years and 1 for more than six years. Only 1.4% of the pumps have needed replacement. No patient deaths have been attributed to Novacor® LVAS failure." Sadly, both require anticoagulation medicine, but so do nearly all other VADs on the market. The exception to this is the Heartmate, which uses a biologically friendly material called fibrin to prevent the immune system from attacking the device. However, this too has disadvantages, as it increased the chances of infection and is not a durable as either the Jarvik or Novacor.
http://www.thoratec.com/medical-professionals/vad-product-information/heartmate-xve-lvad.aspx
http://en.wikipedia.org/wiki/Ventricular_assist_device
http://www.worldheart.com/products/novacor_lvas.cfm
http://www.jarvikheart.com/basic.asp?id=26
Based purely on longevity of a singal user, the best choice for a VAD is the Jarvik 2000, a very compact system which was able to support a patient for 7.5 years. However, it is still waiting approval in the U.S and has not of yet been used on a large number of patients. The Novacor LVAD, however, has been used on over 1,700 patiens, has approval in the US, EU and Japan, and, "among these recipients, 45 have been supported for more than two years, 24 for more than three years, 11 for more than four years and 1 for more than six years. Only 1.4% of the pumps have needed replacement. No patient deaths have been attributed to Novacor® LVAS failure." Sadly, both require anticoagulation medicine, but so do nearly all other VADs on the market. The exception to this is the Heartmate, which uses a biologically friendly material called fibrin to prevent the immune system from attacking the device. However, this too has disadvantages, as it increased the chances of infection and is not a durable as either the Jarvik or Novacor.
http://www.thoratec.com/medical-professionals/vad-product-information/heartmate-xve-lvad.aspx
http://en.wikipedia.org/wiki/Ventricular_assist_device
http://www.worldheart.com/products/novacor_lvas.cfm
http://www.jarvikheart.com/basic.asp?id=26
Valve Replacements
· Ball and Cage - The caged ball design is one of the early mechanical heart valves that use a small ball that is held in place by a welded metal cage. The ball in cage design was modeled after ball valves used in industry to limit the flow of fluids to a single direction. Natural heart valves allow blood to flow straight through the center of the valve. This property is known as central flow, which keeps the amount of work done by the heart to a minimum. With non-central flow, the heart must work harder to compensate for the momentum lost to the change of direction of the fluid. Caged-ball valves completely block central flow, therefore the blood requires more energy to flow around the central ball. In addition, the ball is notorious for causing damage to blood cells due to collisions. Damaged blood cells release blood clotting ingredients; hence the patients are required to take lifelong prescriptions of anticoagulants.
· Sinlge Leaflet - tilting disc to better mimic the natural patterns of blood flow. The tilting-disc valves have a polymer disc held in place by two welded struts. The disc floats between the two struts in such a way, as to close when the blood begins to travel backward and then reopens when blood begins to travel forward again. The tilting-disc valves are vastly superior to the ball-cage design. The titling-disc valves open at an angle of 60° and close shut completely at a rate of 70 times/minute. This tilting pattern provides improved central flow while still preventing backflow. The tilting-disc valves reduce mechanical damage to blood cells. This improved flow pattern reduced blood clotting and infection. However, the only problem with this design is its tendency for the outlet struts to fracture as a result of fatigue from the repeated ramming of the struts by the disc.
· BiLeaflet - two semicircular leaflets that pivot on hinges. The carbon leaflets exhibit high strength and excellent biocompatibility. The leaflets swing open completely, parallel to the direction of the blood flow. They do not close completely, which allows some backflow. Since backflow is one of the properties of defective valves, the bileaflet valves are still not ideal valves. The bileaflet valve constitutes the majority of modern valve designs. These valves are distinguished mainly for providing the closest approximation to central flow achieved in a natural heart valve.
· Animal Tissue Valves (porcine/bovine) - Both the porcine and bovine pericardial valves are stented valves. The metal stent in these valves takes up room which could be available for blood flow. Stentless valves are made by removing the entire aortic root and adjacent aorta as a block, usually from a pig. The coronary arteries are tied off, and the entire section is trimmed and then implanted into the patient. The St. Jude Toronto Stentless Porcine Valve (SPV) is one such valve. It appears to have excellent hemodynamics, and a significant decrease in the thickness of the heart has been observed after the valve is implanted. However, the valve is extremely difficult to implant, and it is still too new to have any valid data accounting for durability. The most common cause of bioprosthesis failure is stiffening of the tissue due to the build up calcium. Calcification can cause a restriction of blood flow through the valve (stenosis) or cause tears in the valve leaflets. Since younger patients have a greater calcium metabolism, bioprostheses tend to last best in senior citizens.
· Homograft - a valve that is transplanted from a deceased person to a recipient. A recipient has minimal problems with valve rejection and they do not require immunosuppressive therapy. A homograft that has been donated must be cryopreserved in liquid nitrogen until it is needed. In cases where the valve implants fit the dimensions of the patient correctly, homografts tend to have good hemodynamics and good durability. However, it is not clear whether homografts have better hemodynamics or durability than animal tissue valves.
· Autograft – The dysfunctional aortic valve is removed and the patient's pulmonic valve is then transplanted to the aortic position. A homograft pulmonic valve is usually used to replace the patient’s pulmonic valve. The Ross procedure allows the patient the advantage of receiving a living valve in the aortic position.. The tissues of the patients’ pulmonary valve have not shown a tendency to calcify, degenerate, perforate, or develop leakage.
I think the Pulmonary Autograft is the most effective type of valve replacement. It seems to last the longest with the least complications. The long term survival and freedom from complications for patients with aortic valve disease are better with the Ross Procedure than any other type of valve replacement. After 20 years, only 15% of patients require additional valve procedures. In cases where a human pulmonary artery homograft is used to replace the patients’ pulmonary valve, freedom from failure has been 94% after 5 years time, and 83% at 20 years. This procedure proves at the moment to be very successful.
http://cape.uwaterloo.ca/che100projects/heart/files/testing.htm#mech1
· Sinlge Leaflet - tilting disc to better mimic the natural patterns of blood flow. The tilting-disc valves have a polymer disc held in place by two welded struts. The disc floats between the two struts in such a way, as to close when the blood begins to travel backward and then reopens when blood begins to travel forward again. The tilting-disc valves are vastly superior to the ball-cage design. The titling-disc valves open at an angle of 60° and close shut completely at a rate of 70 times/minute. This tilting pattern provides improved central flow while still preventing backflow. The tilting-disc valves reduce mechanical damage to blood cells. This improved flow pattern reduced blood clotting and infection. However, the only problem with this design is its tendency for the outlet struts to fracture as a result of fatigue from the repeated ramming of the struts by the disc.
· BiLeaflet - two semicircular leaflets that pivot on hinges. The carbon leaflets exhibit high strength and excellent biocompatibility. The leaflets swing open completely, parallel to the direction of the blood flow. They do not close completely, which allows some backflow. Since backflow is one of the properties of defective valves, the bileaflet valves are still not ideal valves. The bileaflet valve constitutes the majority of modern valve designs. These valves are distinguished mainly for providing the closest approximation to central flow achieved in a natural heart valve.
· Animal Tissue Valves (porcine/bovine) - Both the porcine and bovine pericardial valves are stented valves. The metal stent in these valves takes up room which could be available for blood flow. Stentless valves are made by removing the entire aortic root and adjacent aorta as a block, usually from a pig. The coronary arteries are tied off, and the entire section is trimmed and then implanted into the patient. The St. Jude Toronto Stentless Porcine Valve (SPV) is one such valve. It appears to have excellent hemodynamics, and a significant decrease in the thickness of the heart has been observed after the valve is implanted. However, the valve is extremely difficult to implant, and it is still too new to have any valid data accounting for durability. The most common cause of bioprosthesis failure is stiffening of the tissue due to the build up calcium. Calcification can cause a restriction of blood flow through the valve (stenosis) or cause tears in the valve leaflets. Since younger patients have a greater calcium metabolism, bioprostheses tend to last best in senior citizens.
· Homograft - a valve that is transplanted from a deceased person to a recipient. A recipient has minimal problems with valve rejection and they do not require immunosuppressive therapy. A homograft that has been donated must be cryopreserved in liquid nitrogen until it is needed. In cases where the valve implants fit the dimensions of the patient correctly, homografts tend to have good hemodynamics and good durability. However, it is not clear whether homografts have better hemodynamics or durability than animal tissue valves.
· Autograft – The dysfunctional aortic valve is removed and the patient's pulmonic valve is then transplanted to the aortic position. A homograft pulmonic valve is usually used to replace the patient’s pulmonic valve. The Ross procedure allows the patient the advantage of receiving a living valve in the aortic position.. The tissues of the patients’ pulmonary valve have not shown a tendency to calcify, degenerate, perforate, or develop leakage.
I think the Pulmonary Autograft is the most effective type of valve replacement. It seems to last the longest with the least complications. The long term survival and freedom from complications for patients with aortic valve disease are better with the Ross Procedure than any other type of valve replacement. After 20 years, only 15% of patients require additional valve procedures. In cases where a human pulmonary artery homograft is used to replace the patients’ pulmonary valve, freedom from failure has been 94% after 5 years time, and 83% at 20 years. This procedure proves at the moment to be very successful.
http://cape.uwaterloo.ca/che100projects/heart/files/testing.htm#mech1
Shanice
VADs can be used to take over the right ventricle, the left ventricle and in some cases it is used to take over both ventricles. There are two types of pumps used in a VAD. First there is a pulsatile pump, which pumps blood through the body with a normal pulsing action then there is are centrifugal pumps that just sent the blood throughout the body continuously without a pulse. The centrifugal pump is recognized as the second generation of pumps because they are simpler than the pulsatile pump and it is smaller and more reliable.
Bioprosthetic Valves
-Bioprosthetic Valves are heart valves taken from either a human or an animal and used as a prosthetic.
-Theses Bioprosthetic valves are much more advantageous than artificial valves not only because they eliminate the need for long-term anti-coagulants, but they also don't cause any harm to blood cells.
- The human valves are separated into two categories homografts, which replace a human's valve with another human's valve, and autographs, which simply repositions a valve which is already in the patients body.
-Homografts have little to no problems with another human being able to accept the foreign valve, have good hemodynamics, which is simply defined as how much resistance to blood flow the valve gives, and durability.
-The most common procedure that uses autographs is called the Ross Procedure which replaces the valve in the aortic valve with the one in the pulmonic valve. The Ross Procedure is so effective that after 20 years only 15 percent of patients needed another surgery.
-This chart shows how successful the Homograft surgeries have been. The Blue Bar is the Percent Survival Rate, the Purple bar is percent of patients without Endocarditis, the yellow bar shows percent without pulminary tissue failure, and the green bar shows the percent of people who didn't need another surgery.
Websites
Artificial Pacemakers
An Artificial Pacemaker is a device that helps control irregular heart rhythms. Irregular in this case meaning, a heart that beats too slow, too fast, or just doesn’t beat in a regular fashion. The pacemaker device is usually implanted in the chest or abdomen. The name for irregular heart rhythms is arrhythmia. There are also 4 different methods to pacing an abnormally beating heart.
1. Percussive Pacing
2. Transcutaneous Pacing
3. Transvenous Pacing
4. Permanent Pacing
Out of all of these methods of pacing only the fourth method is permanent. The rest of the pacemakers are simply there to provide a bridge to the Permanent Pacing. The first two methods are a short bridge to Permanent Pacing while the third, Transvenous Pacing can be removed later without the addition of Permanent Pacing if the heart recovers from its arrhythmia. The Permanent Pacing device is usually made out of titanium since it is relatively inert inside the human body. The battery is usually a Lithium battery that has to be replaced about every fifteen years or so. If I had to choose which Pacemaker is the best I would say Permanent Pacing is the best. The only reason is because the permanent option is the only option that will last for any considerable amount of time.
http://en.wikipedia.org/wiki/Pacemakers#Methods_of_pacing
http://www.nhlbi.nih.gov/health/dci/Diseases/pace/pace_whatis.html
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