There is a new twist on the question of how biological clocks work.
In recent years, scientists have discovered that biological clocks help organize a dizzying array of biochemical processes in the body. Despite a number of hypotheses, exactly how the microscopic pacemakers in every cell in the body exert such a widespread influence has remained a mystery.
Now, a new study provides direct evidence that biological clocks can influence the activity of a large number of different genes in an ingenious fashion, simply by causing chromosomes to coil more tightly during the day and to relax at night.
“The idea that the whole genome is oscillating is really cool,” enthuses Vanderbilt Professor of Biological Sciences Carl Johnson, who headed the research that was published online Nov. 13 in the Proceedings of the National Academy of Sciences. “The fact that oscillations can act as a regulatory mechanism is telling us something important about how DNA works: It is something DNA jockeys really need to think about.”
Johnson’s team, which consisted of Senior Lecturer Mark A Woelfle, Assistant Research Professor Yao Xu and graduate student Ximing Qin, performed the study with cyanobacteria (blue-green algae), the simplest organism known to possess a biological clock. The chromosomes in cyanobacteria are organized in circular molecules of DNA. In their relaxed state, they form a single loop. But, within the cell, they are usually “supercoiled” into a series of small helical loops. There are even two families of special enzymes, called gyrases and topoisomerases, whose function is coiling and uncoiling DNA.
The researchers focused on small, non-essential pieces of DNA in the cyanobacteria called plasmids that occur naturally in the cyanobacteria. Because a plasmid should behave in the same fashion as the larger and more unwieldy chromosome, the scientists consider it to be a good proxy of the behavior of the chromosome itself.
When the plasmid is relaxed, it is open and uncoiled and, when it is supercoiled, it is twisted into a smaller, more condensed state. So, the researchers used a standard method, called gel electrophoresis, to measure the extent of a plasmid’s supercoiling during different points in the day/night cycle.
The researchers found a distinct day/night cycle: The plasmid is smaller and more tightly wound during periods of light than they are during periods of darkness. They also found that this rhythmic condensation disappears when the cyanobacteria are kept in constant darkness.
“This is one of the first pieces of evidence that the biological clock exerts its effect on DNA structure through the coiling of the chromosome and that this, in turn, allows it to regulate all the genes in the organism,” says Woelfle.
Some cyanobacteria use their biological clocks to control two basic processes. During the day, they use photosynthesis to turn sunlight into chemical energy. During the night, they remove nitrogen from the atmosphere and incorporate it into a chemical compound that they can use to make proteins.
According to the Johnson lab’s “oscilloid model,” the genes that are involved in photosynthesis should be located in regions of the chromosome that are “turned on” by the tighter coiling in the DNA during the day and “turned off” during the night when the DNA is more relaxed. By the same token, the genes that are involved in nitrogen fixation should be located in regions of the chromosome that are “turned off” during the day when the DNA is tightly coiled and “turned on” during the night when it is more relaxed.
The researchers see no reason why the bioclocks in higher organisms, including humans, do not operate in a similar fashion. “This could be a universal theme that we are just starting to decipher,” says Woelfle.
The DNA in higher organisms is much larger than that in cyanobacteria and it is linear, not circular. Stretched end-to-end, the genome in a mammalian cell is about six feet long. In order to fit into a microscopic cell, the DNA must be tightly packed into a series of small coils, something like microscopic Slinkies.
Previous studies have shown that in higher organisms between 5 to 10 percent of genes in the genome are controlled by the bioclock, compared to 100 percent of genes in the cyanobacteria. In the case of the higher organisms, the bioclock’s control is likely to be local rather than the global situation in cyanobacteria.
With a circular chromosome (as in cyanobacteria), twisting it at any point affects the entire molecule. When you twist a linear chromosome at a certain point, however, the effect only extends for a limited distance in either direction because the ends are not connected. That fits neatly with the idea that the bioclock’s influence on linear chromosomes is limited to certain specific regions, regions where the specific genes that it regulates are located.
Wednesday, November 21, 2007
MIT: Thermoelectric materials are 1 key to energy savings
Breathing new life into an old idea, MIT Institute Professor Mildred S. Dresselhaus and co-workers are developing innovative materials for controlling temperatures that could lead to substantial energy savings by allowing more efficient car engines, photovoltaic cells and electronic devices.
Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air conditioning and energy costs.
The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.
Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She’ll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26, at the annual meeting of the Materials Research Society in Boston.
Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and especially well with semiconductors — the materials from which computer chips are made. But it always had one big drawback: it is very inefficient.
The fundamental problem in creating efficient thermoelectric materials is that they need to be very good at conducting electricity, but not heat. That way, one end of the apparatus can get hot while the other remains cold, instead of the material quickly equalizing the temperature. In most materials, electrical and thermal conductivity go hand in hand. So researchers had to find ways of modifying materials to separate the two properties.
The key to making it more practical, Dresselhaus explains, was in creating engineered semiconductor materials in which tiny patterns have been created to alter the materials’ behavior. This might include embedding nanoscale particles or wires in a matrix of another material. These nanoscale structures — just a few billionths of a meter across — interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.
She and her MIT collaborators started working on these developments in the 1990s, and soon drew interest from the US Navy because of the potential for making quieter submarines (power generation and air conditioning are some of the noisiest functions on existing subs). “From that research, we came up with a lot of new materials that nobody had looked into,” Dresselhaus says.
After some early work conducted with Ted Harman of MIT Lincoln Labs, Harman, Dresselhaus, and her student Lyndon Hicks published an experimental paper on the new materials in the mid 1990s. “People saw that paper and the field started,” she says. “Now there are conferences devoted to it.”
Her work in finding new thermoelectric materials, including a collaboration with MIT professor of Mechanical Engineering Gang Chen, invigorated the field, and now there are real applications like seat coolers in cars. Last year, a small company in California sold a million of the units worldwide.
OTHER POTENTIAL APPLICATIONS
The same principle can be used to design cooling systems that could be built right into microchips, reducing or eliminating the need for separate cooling systems and improving their efficiency.
The technology could also be used in cars to make the engines themselves more efficient. In conventional cars, about 80 percent of the fuel’s energy is wasted as heat. Thermoelectric systems could perhaps be used to generate electricity directly from this wasted heat. Because the amount of fuel used for transportation is such a huge part of the world’s energy use, even a small percentage improvement in efficiency can have a great impact, Dresselhaus explains. “It’s very practical,” she says, “and the car companies are getting interested.”
The same materials might also play a role in improving the efficiency of photovoltaic cells, harnessing some of the sun’s heat as well as its light to make electricity. The key will be finding materials that have the right properties but are not too expensive to produce.
Dresselhaus and colleagues are continuing to probe the thermoelectric properties of a variety of semiconductor materials and nanostructures such as superlattices and quantum dots. Her research on thermoelectric materials is presently sponsored by NASA.
Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air conditioning and energy costs.
The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.
Dresselhaus and colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She’ll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26, at the annual meeting of the Materials Research Society in Boston.
Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. Conversely, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and especially well with semiconductors — the materials from which computer chips are made. But it always had one big drawback: it is very inefficient.
The fundamental problem in creating efficient thermoelectric materials is that they need to be very good at conducting electricity, but not heat. That way, one end of the apparatus can get hot while the other remains cold, instead of the material quickly equalizing the temperature. In most materials, electrical and thermal conductivity go hand in hand. So researchers had to find ways of modifying materials to separate the two properties.
The key to making it more practical, Dresselhaus explains, was in creating engineered semiconductor materials in which tiny patterns have been created to alter the materials’ behavior. This might include embedding nanoscale particles or wires in a matrix of another material. These nanoscale structures — just a few billionths of a meter across — interfere with the flow of heat, while allowing electricity to flow freely. “Making a nanostructure allows you to independently control these qualities,” Dresselhaus says.
She and her MIT collaborators started working on these developments in the 1990s, and soon drew interest from the US Navy because of the potential for making quieter submarines (power generation and air conditioning are some of the noisiest functions on existing subs). “From that research, we came up with a lot of new materials that nobody had looked into,” Dresselhaus says.
After some early work conducted with Ted Harman of MIT Lincoln Labs, Harman, Dresselhaus, and her student Lyndon Hicks published an experimental paper on the new materials in the mid 1990s. “People saw that paper and the field started,” she says. “Now there are conferences devoted to it.”
Her work in finding new thermoelectric materials, including a collaboration with MIT professor of Mechanical Engineering Gang Chen, invigorated the field, and now there are real applications like seat coolers in cars. Last year, a small company in California sold a million of the units worldwide.
OTHER POTENTIAL APPLICATIONS
The same principle can be used to design cooling systems that could be built right into microchips, reducing or eliminating the need for separate cooling systems and improving their efficiency.
The technology could also be used in cars to make the engines themselves more efficient. In conventional cars, about 80 percent of the fuel’s energy is wasted as heat. Thermoelectric systems could perhaps be used to generate electricity directly from this wasted heat. Because the amount of fuel used for transportation is such a huge part of the world’s energy use, even a small percentage improvement in efficiency can have a great impact, Dresselhaus explains. “It’s very practical,” she says, “and the car companies are getting interested.”
The same materials might also play a role in improving the efficiency of photovoltaic cells, harnessing some of the sun’s heat as well as its light to make electricity. The key will be finding materials that have the right properties but are not too expensive to produce.
Dresselhaus and colleagues are continuing to probe the thermoelectric properties of a variety of semiconductor materials and nanostructures such as superlattices and quantum dots. Her research on thermoelectric materials is presently sponsored by NASA.
New research shows climate change triggers wars and population decline
Climate change may be one of the most significant threats facing humankind. A new study shows that long-term climate change may ultimately lead to wars and population decline.
The study, published November 19 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS), revealed that as temperatures decreased centuries ago during a period called the Little Ice Age, the number of wars increased, famine occurred and the population declined.
Data on past climates may help accurately predict and design strategies for future large and persistent climate changes, but acknowledging the historic social impact of these severe events is an important step toward that goal, according to the study’s authors.
“Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source,” said Peter Brecke, associate professor in the Georgia Institute of Technology’s Sam Nunn School of International Affairs and co-author of the study.
This new study expands previous work by David Zhang of the University of Hong Kong and lead author of the study.
“My previous research just focused on Eastern China. This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles,” said Zhang.
Brecke, Zhang and colleagues in Hong Kong, China and the United Kingdom perceived a possible connection between temperature change and wars because changes in climate affect water supplies, growing seasons and land fertility, prompting food shortages. These shortages could lead to conflict – local uprisings, government destabilization and invasions from neighboring regions – and population decline due to bloodshed during the wars and starvation.
To study whether changes in temperature affected the number of wars, the researchers examined the time period between 1400 and 1900. This period recorded the lowest average global temperatures around 1450, 1650 and 1820, each separated by slight warming intervals.The researchers collected war data from multiple sources, including a database of 4,500 wars worldwide that Brecke began developing in 1995 with funding from the U.S. Institute of Peace. They also used climate change records that paleoclimatologists reconstructed by consulting historical documents and examining indicators of temperature change like tree rings, as well as oxygen isotopes in ice cores and coral skeletons.
Results showed a cyclic pattern of turbulent periods when temperatures were low followed by tranquil ones when temperatures were higher. The number of wars per year worldwide during cold centuries was almost twice that of the mild 18th century.
The study also showed population declines following each high war peak, according to population data Brecke assembled. The population growth rate of the Northern Hemisphere was elevated from 1400-1600, despite a short cooling period beginning in the middle of the 15th century. However, during the colder 17th century, Europe and Asia experienced more wars of great magnitude and population declines.
In China, the population plummeted 43 percent between 1620 and 1650. Then, a dramatic increase in population occurred from 1650 until a cooling period beginning in 1800 caused a worldwide demographic shock.
The researchers examined whether these average temperature differences of less than one degree Celsius were enough to cause food shortages. By assuming that agricultural production decreases triggered price increases, they showed that when grain prices reached a certain level, wars erupted. The ecological stress on agricultural production triggered by climate change did in fact induce population shrinkages, according to Brecke.
Global temperatures are expected to rise in the future and the world’s growing population may be unable to adequately adapt to the ecological changes, according to Brecke.
“The warmer temperatures are probably good for a while, but beyond some level plants will be stressed,” explained Brecke. “With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water.”
The study, published November 19 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS), revealed that as temperatures decreased centuries ago during a period called the Little Ice Age, the number of wars increased, famine occurred and the population declined.
Data on past climates may help accurately predict and design strategies for future large and persistent climate changes, but acknowledging the historic social impact of these severe events is an important step toward that goal, according to the study’s authors.
“Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source,” said Peter Brecke, associate professor in the Georgia Institute of Technology’s Sam Nunn School of International Affairs and co-author of the study.
This new study expands previous work by David Zhang of the University of Hong Kong and lead author of the study.
“My previous research just focused on Eastern China. This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles,” said Zhang.
Brecke, Zhang and colleagues in Hong Kong, China and the United Kingdom perceived a possible connection between temperature change and wars because changes in climate affect water supplies, growing seasons and land fertility, prompting food shortages. These shortages could lead to conflict – local uprisings, government destabilization and invasions from neighboring regions – and population decline due to bloodshed during the wars and starvation.
To study whether changes in temperature affected the number of wars, the researchers examined the time period between 1400 and 1900. This period recorded the lowest average global temperatures around 1450, 1650 and 1820, each separated by slight warming intervals.The researchers collected war data from multiple sources, including a database of 4,500 wars worldwide that Brecke began developing in 1995 with funding from the U.S. Institute of Peace. They also used climate change records that paleoclimatologists reconstructed by consulting historical documents and examining indicators of temperature change like tree rings, as well as oxygen isotopes in ice cores and coral skeletons.
Results showed a cyclic pattern of turbulent periods when temperatures were low followed by tranquil ones when temperatures were higher. The number of wars per year worldwide during cold centuries was almost twice that of the mild 18th century.
The study also showed population declines following each high war peak, according to population data Brecke assembled. The population growth rate of the Northern Hemisphere was elevated from 1400-1600, despite a short cooling period beginning in the middle of the 15th century. However, during the colder 17th century, Europe and Asia experienced more wars of great magnitude and population declines.
In China, the population plummeted 43 percent between 1620 and 1650. Then, a dramatic increase in population occurred from 1650 until a cooling period beginning in 1800 caused a worldwide demographic shock.
The researchers examined whether these average temperature differences of less than one degree Celsius were enough to cause food shortages. By assuming that agricultural production decreases triggered price increases, they showed that when grain prices reached a certain level, wars erupted. The ecological stress on agricultural production triggered by climate change did in fact induce population shrinkages, according to Brecke.
Global temperatures are expected to rise in the future and the world’s growing population may be unable to adequately adapt to the ecological changes, according to Brecke.
“The warmer temperatures are probably good for a while, but beyond some level plants will be stressed,” explained Brecke. “With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water.”
Monday, November 19, 2007
Sunbathing tree frogs' future under a cloud
Animal conservationists in Manchester are turning to physics to investigate whether global warming is responsible for killing sun-loving South American tree frogs.
In a unique collaborative project, researchers in The Photon Science Institute (PSI) at The University of Manchester have joined forces with The Manchester Museum, which boasts an amazing collection of colourful tree frogs.
Physicist Dr Mark Dickinson, working with Andrew Gray, Curator of Herpetology at the museum, and Dr Richard Preziosi from The Faculty of Life Sciences, has started using a technique called Optical Coherence Tomography (OCT) to investigate the properties of the tree frogs’ skin.
This non-invasive technique, which does not cause harm or distress to the frogs, allows images to be obtained from within tissue – and the Manchester team believe this innovative application of OCT could hold the key to understanding the alarming global decline in amphibians.
When in their natural habitat, the Costa Rican tree frogs being studied in Manchester prefer to live on leaves and branches high above the ground.
They enjoy basking in the hot sun – which is unusual because frogs normally avoid prolonged exposure to high levels of light due to the risk of overheating and dehydration.
The Manchester team’s hypothesis is that global warming is leading to more cloud cover in the frogs’ natural habitat.
They believe this is denying them the opportunity to 'sunbathe' and kill off fatal Chytrid fungal infections, leading to many species dying out.
In their work so far, the team have observed that the skin of basking tree frogs sometimes undergoes a visible change and becomes almost metallic in texture. They think that when this happens, the level of absorption and reflection and the skin temperature also changes.
The Manchester team believe tree frogs are able to bask happily under a fierce sun because they have the ability to regulate their body temperature and prevent overheating through the unique structure and properties of their skin.
Gray, Dickinson and Preziosi are now seeking further funding to do more comprehensive research using the OCT technique – which is more commonly used to examine the human retina – and put their hypothesis to the test.
As part of their studies, they want to use OCT to compare structural changes in the skin of tree frogs with the structural changes in the skin of frogs that do not have the same high levels of infrared reflectance.
This reflectance is associated with a pigment called pterorhodin, and allows the tree frogs to camouflage themselves from predators by adjusting the infrared reflection of their skin to match the infrared reflection of the leaves they laze upon.
They team are hoping to work with and support the important work being carried by the eminent climatologist, Alan Pounds, who has theorised that global warming is a major factor in amphibian declines.
The team plan to travel out to Costa Rica next year and to apply spectral reflectance techniques to tree frogs living in their natural habitat.
Dr Mark Dickinson said: "This is a great example of an exciting interdisciplinary research project that draws on expertise right across the university. It is proof that interdisciplinary research is not just a fashionable expression we band around, but something we actually do."
Andrew Gray said: “With a third of the world’s amphibians currently under threat it’s vitally important we do our utmost to investigate the reasons why they are dying out at such an alarming rate.
"The imaging technique we use is completely non-invasive and does not harm the frogs in any way. As an animal conservationist, I simply would not allow any research that distressed these amazing creatures."
In a unique collaborative project, researchers in The Photon Science Institute (PSI) at The University of Manchester have joined forces with The Manchester Museum, which boasts an amazing collection of colourful tree frogs.
Physicist Dr Mark Dickinson, working with Andrew Gray, Curator of Herpetology at the museum, and Dr Richard Preziosi from The Faculty of Life Sciences, has started using a technique called Optical Coherence Tomography (OCT) to investigate the properties of the tree frogs’ skin.
This non-invasive technique, which does not cause harm or distress to the frogs, allows images to be obtained from within tissue – and the Manchester team believe this innovative application of OCT could hold the key to understanding the alarming global decline in amphibians.
When in their natural habitat, the Costa Rican tree frogs being studied in Manchester prefer to live on leaves and branches high above the ground.
They enjoy basking in the hot sun – which is unusual because frogs normally avoid prolonged exposure to high levels of light due to the risk of overheating and dehydration.
The Manchester team’s hypothesis is that global warming is leading to more cloud cover in the frogs’ natural habitat.
They believe this is denying them the opportunity to 'sunbathe' and kill off fatal Chytrid fungal infections, leading to many species dying out.
In their work so far, the team have observed that the skin of basking tree frogs sometimes undergoes a visible change and becomes almost metallic in texture. They think that when this happens, the level of absorption and reflection and the skin temperature also changes.
The Manchester team believe tree frogs are able to bask happily under a fierce sun because they have the ability to regulate their body temperature and prevent overheating through the unique structure and properties of their skin.
Gray, Dickinson and Preziosi are now seeking further funding to do more comprehensive research using the OCT technique – which is more commonly used to examine the human retina – and put their hypothesis to the test.
As part of their studies, they want to use OCT to compare structural changes in the skin of tree frogs with the structural changes in the skin of frogs that do not have the same high levels of infrared reflectance.
This reflectance is associated with a pigment called pterorhodin, and allows the tree frogs to camouflage themselves from predators by adjusting the infrared reflection of their skin to match the infrared reflection of the leaves they laze upon.
They team are hoping to work with and support the important work being carried by the eminent climatologist, Alan Pounds, who has theorised that global warming is a major factor in amphibian declines.
The team plan to travel out to Costa Rica next year and to apply spectral reflectance techniques to tree frogs living in their natural habitat.
Dr Mark Dickinson said: "This is a great example of an exciting interdisciplinary research project that draws on expertise right across the university. It is proof that interdisciplinary research is not just a fashionable expression we band around, but something we actually do."
Andrew Gray said: “With a third of the world’s amphibians currently under threat it’s vitally important we do our utmost to investigate the reasons why they are dying out at such an alarming rate.
"The imaging technique we use is completely non-invasive and does not harm the frogs in any way. As an animal conservationist, I simply would not allow any research that distressed these amazing creatures."
MIT: 'Micro' livers could aid drug screening
MIT researchers have devised a novel way to create tiny colonies of living human liver cells that model the full-sized organ. The work could allow better screening of new drugs that are potentially harmful to the liver and reduce the costs associated with their development.
Liver toxicity is one of the main reasons pharmaceutical companies pull drugs off the market. These dangerous drugs slip through approval processes due in part to the shortcomings of liver toxicity tests. Existing tests rely on liver cells from rats, which do not always respond to toxins the way human cells do. Or they rely on dying human cells that survive for only a few days in the lab.
The new technology arranges human liver cells into tiny colonies only 500 micrometers (millionths of a meter) in diameter that act much like a real liver and survive for up to six weeks.
Sangeeta Bhatia, associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and MIT's Department of Electrical Engineering and Computer Science, and HST postdoctoral associate Salman Khetani describe their model liver tissue and its behavior in the November 18 online issue of Nature Biotechnology.
To build these model livers, Khetani uses micropatterning technology—the same technology used to place tiny copper wires on computer chips—to precisely arrange human liver cells and other supporting cells on a plate. Khetani adapted this method from Bhatia’s early work as an HST graduate student building micropatterned co-cultures of rat liver cells and supporting cells.
Such precisely arranged cells results in what Bhatia calls a “high-fidelity tissue model” because it so closely mimics the behavior of a human liver. For example, each model “organ” secretes the blood protein albumin, synthesizes urea, and produces the enzymes necessary to break down drugs and toxins.
To predict how close their model tissue is to real liver tissue, which has over 500 different functions, they also evaluated its gene expression profiles, measures of the levels of gene activation in the tissues. They found that these profiles are very similar to those of fresh liver cells, “giving us confidence that other [liver] functions are preserved,” said Khetani.
For drug testing purposes, this affinity to the human liver allows each colony to provide a window into the human liver’s response to a drug without having to expose human patients to the drug in a clinical trial, said Bhatia.
Further, because the engineered tissue lives for so long, it has the potential to make new types of toxicity tests possible. For instance, it opens the door to testing the effects of long-term drug use akin to taking one pill a day over multiple weeks. It also will allow more extensive testing of drug-drug interactions.
In addition to being a good biological model, the engineered tissue is designed to be seamlessly integrated into an industrial pharmaceutical science setting.
To mass-produce plates of the miniature liver models, Khetani relies on a technique called soft lithography. This technique fashions a reusable micropatterned rubber stencil from a silicon master. Each stencil contains an array of 24 wells, and each well contains a matrix of 37 tiny holes. Khetani “peels and sticks” the stencil onto plates and places the liver cells into the holes, patterning over 888 miniature model livers across the microwells in a matter of minutes.
In tests of drugs with a range of well-known toxicity levels, assays (chemical detection tests) on the miniature liver models showed the expected levels of toxicity. “Our platform was able to predict the relative toxicity of these drugs as seen in the clinic,” said Khetani. For instance, troglitazone, a drug withdrawn from the market by the FDA due to liver toxicity, showed toxicity levels much higher than its FDA-approved analogues, Rosiglitazone and Pioglitazone.
The model uses a fraction of the costly human liver cells used in other test platforms and can be assembled using frozen cells. Moreover, the expanded toxicity testing capabilities have the potential to allow drug developers to identify toxicity earlier in the development process, thereby avoiding the expense of investing in formulas that are bound to fail.
A startup company called Hepregen has licensed the technology and is working to introduce it into the pharmaceutical marketplace.
“My hope is that this new model will make drugs safer, cheaper, and better labeled,” said Bhatia.
Liver toxicity is one of the main reasons pharmaceutical companies pull drugs off the market. These dangerous drugs slip through approval processes due in part to the shortcomings of liver toxicity tests. Existing tests rely on liver cells from rats, which do not always respond to toxins the way human cells do. Or they rely on dying human cells that survive for only a few days in the lab.
The new technology arranges human liver cells into tiny colonies only 500 micrometers (millionths of a meter) in diameter that act much like a real liver and survive for up to six weeks.
Sangeeta Bhatia, associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and MIT's Department of Electrical Engineering and Computer Science, and HST postdoctoral associate Salman Khetani describe their model liver tissue and its behavior in the November 18 online issue of Nature Biotechnology.
To build these model livers, Khetani uses micropatterning technology—the same technology used to place tiny copper wires on computer chips—to precisely arrange human liver cells and other supporting cells on a plate. Khetani adapted this method from Bhatia’s early work as an HST graduate student building micropatterned co-cultures of rat liver cells and supporting cells.
Such precisely arranged cells results in what Bhatia calls a “high-fidelity tissue model” because it so closely mimics the behavior of a human liver. For example, each model “organ” secretes the blood protein albumin, synthesizes urea, and produces the enzymes necessary to break down drugs and toxins.
To predict how close their model tissue is to real liver tissue, which has over 500 different functions, they also evaluated its gene expression profiles, measures of the levels of gene activation in the tissues. They found that these profiles are very similar to those of fresh liver cells, “giving us confidence that other [liver] functions are preserved,” said Khetani.
For drug testing purposes, this affinity to the human liver allows each colony to provide a window into the human liver’s response to a drug without having to expose human patients to the drug in a clinical trial, said Bhatia.
Further, because the engineered tissue lives for so long, it has the potential to make new types of toxicity tests possible. For instance, it opens the door to testing the effects of long-term drug use akin to taking one pill a day over multiple weeks. It also will allow more extensive testing of drug-drug interactions.
In addition to being a good biological model, the engineered tissue is designed to be seamlessly integrated into an industrial pharmaceutical science setting.
To mass-produce plates of the miniature liver models, Khetani relies on a technique called soft lithography. This technique fashions a reusable micropatterned rubber stencil from a silicon master. Each stencil contains an array of 24 wells, and each well contains a matrix of 37 tiny holes. Khetani “peels and sticks” the stencil onto plates and places the liver cells into the holes, patterning over 888 miniature model livers across the microwells in a matter of minutes.
In tests of drugs with a range of well-known toxicity levels, assays (chemical detection tests) on the miniature liver models showed the expected levels of toxicity. “Our platform was able to predict the relative toxicity of these drugs as seen in the clinic,” said Khetani. For instance, troglitazone, a drug withdrawn from the market by the FDA due to liver toxicity, showed toxicity levels much higher than its FDA-approved analogues, Rosiglitazone and Pioglitazone.
The model uses a fraction of the costly human liver cells used in other test platforms and can be assembled using frozen cells. Moreover, the expanded toxicity testing capabilities have the potential to allow drug developers to identify toxicity earlier in the development process, thereby avoiding the expense of investing in formulas that are bound to fail.
A startup company called Hepregen has licensed the technology and is working to introduce it into the pharmaceutical marketplace.
“My hope is that this new model will make drugs safer, cheaper, and better labeled,” said Bhatia.
Sunday, November 18, 2007
Mutation Fired Outbreak of Deadly Tropical Virus
What a difference a nucleotide makes. A simple change in the genetic sequence of the chikungunya virus may have triggered a massive outbreak of the deadly tropical disease on an island in the Indian Ocean in 2005 and 2006. The mutation made it easier for the virus to reproduce inside the mosquitoes that transmit it to humans, researchers report in the current issue of PLOS One.
Chikungunya kills about one in every 1000 infected people; in the rest, it can cause rash, fever, and crippling joint and muscle pains. The outbreak at La Réunion, a French island 700 kilometers east of Madagascar, sickened at least a third of the 800,000 inhabitants (ScienceNOW, 17 February 2006). "The scope and magnitude were really unprecedented," says Ann Powers, an expert in insect-borne viruses at the Centers for Disease Control and Prevention in Fort Collins, Colorado. The virus was spread mainly by the Asian tiger mosquito, Aedes albopictus, although it wasn't known at the time as a prominent chikungunya vector.
From sequencing the RNA genomes of viruses isolated from patients, researchers knew that chikungunya had undergone a mutation early on in the epidemic. The mutation led to a one-amino-acid change within E1, a protein sitting on the viral coat. About September 2005, most patients still had the amino acid alanine at a certain position within E1. But from about December on, when the outbreak really got going, more than 90% had valine at that same position. Researchers suspected that the change had facilitated spread, but this was mostly speculation.
Now they have proof. A group led by Anna-Bella Failloux of the Pasteur Institute in Paris bred populations of A. albopictus mosquitoes from La Réunion and nearby Mayotte and fed them a blood meal spiked with virus having one or the other version of E1. The scientists then ground up the insect bodies at different time intervals after the feeding and measured the amount of virus inside. In mosquitoes fed with the valine-substituted E1, the virus occurred in quantities almost 100 times higher than in those without. This mutated virus was also better able to pass the wall of a mosquito's midgut and make its way to the salivary glands, from where it could pass to a new victim with the insect's next bite. Apparently, the mutation made the virus a much better fit for La Réunion's Asian tiger mosquito population and thus made the epidemic soar, says Failloux.
"It's an elegant study," says Powers. "They did a very nice job of showing that there is a difference in what was occurring early in the outbreak and later on." That said, many other factors must have conspired to fuel the epidemic, Powers says, from zero immunity in the human population--La Réunion was virgin territory for chikungunya--to the fact that the mosquitoes were apparently thriving at the time.
Chikungunya kills about one in every 1000 infected people; in the rest, it can cause rash, fever, and crippling joint and muscle pains. The outbreak at La Réunion, a French island 700 kilometers east of Madagascar, sickened at least a third of the 800,000 inhabitants (ScienceNOW, 17 February 2006). "The scope and magnitude were really unprecedented," says Ann Powers, an expert in insect-borne viruses at the Centers for Disease Control and Prevention in Fort Collins, Colorado. The virus was spread mainly by the Asian tiger mosquito, Aedes albopictus, although it wasn't known at the time as a prominent chikungunya vector.
From sequencing the RNA genomes of viruses isolated from patients, researchers knew that chikungunya had undergone a mutation early on in the epidemic. The mutation led to a one-amino-acid change within E1, a protein sitting on the viral coat. About September 2005, most patients still had the amino acid alanine at a certain position within E1. But from about December on, when the outbreak really got going, more than 90% had valine at that same position. Researchers suspected that the change had facilitated spread, but this was mostly speculation.
Now they have proof. A group led by Anna-Bella Failloux of the Pasteur Institute in Paris bred populations of A. albopictus mosquitoes from La Réunion and nearby Mayotte and fed them a blood meal spiked with virus having one or the other version of E1. The scientists then ground up the insect bodies at different time intervals after the feeding and measured the amount of virus inside. In mosquitoes fed with the valine-substituted E1, the virus occurred in quantities almost 100 times higher than in those without. This mutated virus was also better able to pass the wall of a mosquito's midgut and make its way to the salivary glands, from where it could pass to a new victim with the insect's next bite. Apparently, the mutation made the virus a much better fit for La Réunion's Asian tiger mosquito population and thus made the epidemic soar, says Failloux.
"It's an elegant study," says Powers. "They did a very nice job of showing that there is a difference in what was occurring early in the outbreak and later on." That said, many other factors must have conspired to fuel the epidemic, Powers says, from zero immunity in the human population--La Réunion was virgin territory for chikungunya--to the fact that the mosquitoes were apparently thriving at the time.
Shrewd Snake Savors Deadly Meal
Your mother may have warned that you'd get a tummy ache if you scarfed down your food, but for one Australian snake, eating too fast could be deadly. The death adder dines on frogs, but some of them are poisonous. So the snake has learned patience: After striking a particular poisonous frog, it waits for its victim's toxin to degrade before it dines. The finding could help ecologists decipher how one species can outevolve another.
The death adder stabs unsuspecting frogs with its fangs, injecting venom to kill its supper. The frogs have fought back, however, evolving various defenses--longer legs for bigger jumps or chemical substances that taste nasty and can kill. Ecologists Ben Phillips and Richard Shine, both of the University of Sydney, Australia, decided to study the snake's general feeding behavior. And when they did, they stumbled upon a strange twist in this evolutionary arms race.
The team dropped frogs of various species in the snakes' glass pens and kept a video camera rolling to record the action as the snakes captured their prey. The snakes gobbled up nontoxic frogs right after injecting them with venom, but they took more time with two other species, the researchers report in the December issue of The American Naturalist. The snake waited 10 minutes before munching on the marbled frog, which produces a gluelike substance on its skin when irritated. (Mouth full of goo? No, thank you!) Further studies revealed that the gunk loses its stickiness after 10 minutes. The snakes waited even longer--40 minutes--before eating the deadly Dahl's aquatic frog. Shine says that by letting the frogs' chemical defenses break down, the snakes have found an unbeatable strategy. "Any predator eating prey whose defenses will terminate after death can simply wait around," Shine says.
The results reveal an unusual adaptation on the part of the snakes, says Wolfgang Wüster, a zoologist at Bangor University in the U.K. He says the frogs may find another strategy to continue the evolutionary battle: "It is hard to say, however, how it would happen easily."
The death adder stabs unsuspecting frogs with its fangs, injecting venom to kill its supper. The frogs have fought back, however, evolving various defenses--longer legs for bigger jumps or chemical substances that taste nasty and can kill. Ecologists Ben Phillips and Richard Shine, both of the University of Sydney, Australia, decided to study the snake's general feeding behavior. And when they did, they stumbled upon a strange twist in this evolutionary arms race.
The team dropped frogs of various species in the snakes' glass pens and kept a video camera rolling to record the action as the snakes captured their prey. The snakes gobbled up nontoxic frogs right after injecting them with venom, but they took more time with two other species, the researchers report in the December issue of The American Naturalist. The snake waited 10 minutes before munching on the marbled frog, which produces a gluelike substance on its skin when irritated. (Mouth full of goo? No, thank you!) Further studies revealed that the gunk loses its stickiness after 10 minutes. The snakes waited even longer--40 minutes--before eating the deadly Dahl's aquatic frog. Shine says that by letting the frogs' chemical defenses break down, the snakes have found an unbeatable strategy. "Any predator eating prey whose defenses will terminate after death can simply wait around," Shine says.
The results reveal an unusual adaptation on the part of the snakes, says Wolfgang Wüster, a zoologist at Bangor University in the U.K. He says the frogs may find another strategy to continue the evolutionary battle: "It is hard to say, however, how it would happen easily."
New Material Doubles Record for Holding Hydrogen
If the hoped-for hydrogen economy is ever to become a reality, researchers must devise efficient ways to produce and store the gas. That will require a series of breakthroughs that have been slow in coming. But researchers in the United States have hit upon a material for storing hydrogen that could be far better than the competition--just the sort of break hydrogen researchers are looking for.
Hydrogen has long been seen as a potentially green alternative to gasoline, which is produced from fossil fuels and gives off the greenhouse gas carbon dioxide when burned. When piped through a fuel cell, hydrogen molecules (H2) combine with oxygen, producing only electricity and water. At room temperature, however, hydrogen is a gas, which makes it difficult to store enough of it on board a car to drive long distances. The gas can be compressed in high-pressure tanks or cooled to a liquid at ultracold temperatures. But both of those strategies require large amounts of energy themselves.
As an alternative, researchers have been searching for materials that can hold large amounts of H2 and release it on demand. But so far the best performers, which are known as metal hydrides, hold only about 2% of their weight in hydrogen at room temperature, well below what is needed for a practical gas tank. Other materials can get up to 7% but require either high or low temperatures, and thus added energy and cost.
Last year, however, researchers led by Taner Yildirim at the National Institute of Standards and Technology in Gaithersburg, Maryland, calculated that a material made from certain metals, such as titanium, and a small hydrocarbon called ethylene should form a stable complex that could bind up to 14% of its weight in hydrogen. Adam Phillips, a physicist and postdoc in the lab of Bellave Shivaram at the University of Virginia, Charlottesville, decided to give the proposal a try.
Phillips used a laser to vaporize titanium in a gas of ethylene. The combined material settled out of the gas and on to a substrate to form a film. When Phillips added hydrogen at room temperature and weighed the result, he found the 14% added weight, just as predicted. After running a series of successful control studies, Phillips and Shivaram reported their new material on Monday at the International Symposium on Materials Issues in a Hydrogen Economy in Richmond, Virginia.
The new result is "extremely interesting," says Gholam-Abbas Nazri, a hydrogen storage expert at the General Motors Research and Development Center in Warren, Michigan. However, Nazri adds, "we have to be very cautious." There have been numerous false starts in the field before, he says. And researchers still must make the material in bulk, demonstrate that it works in that form, and show that it will release hydrogen as easily as it sops it up.
Even with those caveats, George Crabtree, a physicist at Argonne National Laboratory in Illinois, says the result "is one of the most promising developments of the last few years."
Hydrogen has long been seen as a potentially green alternative to gasoline, which is produced from fossil fuels and gives off the greenhouse gas carbon dioxide when burned. When piped through a fuel cell, hydrogen molecules (H2) combine with oxygen, producing only electricity and water. At room temperature, however, hydrogen is a gas, which makes it difficult to store enough of it on board a car to drive long distances. The gas can be compressed in high-pressure tanks or cooled to a liquid at ultracold temperatures. But both of those strategies require large amounts of energy themselves.
As an alternative, researchers have been searching for materials that can hold large amounts of H2 and release it on demand. But so far the best performers, which are known as metal hydrides, hold only about 2% of their weight in hydrogen at room temperature, well below what is needed for a practical gas tank. Other materials can get up to 7% but require either high or low temperatures, and thus added energy and cost.
Last year, however, researchers led by Taner Yildirim at the National Institute of Standards and Technology in Gaithersburg, Maryland, calculated that a material made from certain metals, such as titanium, and a small hydrocarbon called ethylene should form a stable complex that could bind up to 14% of its weight in hydrogen. Adam Phillips, a physicist and postdoc in the lab of Bellave Shivaram at the University of Virginia, Charlottesville, decided to give the proposal a try.
Phillips used a laser to vaporize titanium in a gas of ethylene. The combined material settled out of the gas and on to a substrate to form a film. When Phillips added hydrogen at room temperature and weighed the result, he found the 14% added weight, just as predicted. After running a series of successful control studies, Phillips and Shivaram reported their new material on Monday at the International Symposium on Materials Issues in a Hydrogen Economy in Richmond, Virginia.
The new result is "extremely interesting," says Gholam-Abbas Nazri, a hydrogen storage expert at the General Motors Research and Development Center in Warren, Michigan. However, Nazri adds, "we have to be very cautious." There have been numerous false starts in the field before, he says. And researchers still must make the material in bulk, demonstrate that it works in that form, and show that it will release hydrogen as easily as it sops it up.
Even with those caveats, George Crabtree, a physicist at Argonne National Laboratory in Illinois, says the result "is one of the most promising developments of the last few years."
Japan fleet sets off to hunt humpbacks
SHIMONOSEKI, Japan - A defiant Japan embarked on its largest whaling expedition in decades Sunday, targeting protected humpbacks for the first time since the 1960s despite international opposition. An anti-whaling protest boat awaited the fleBid farewell in a festive ceremony in the southern port of Shimonoseki, four ships headed for the waters off Antarctica, resuming a hunt that was cut short by a deadly fire last February that crippled the fleet's mother ship.
Families waved little flags emblazoned with smiling whales and the crew raised a toast with cans of beer, while a brass band played "Popeye the Sailor Man." Officials told the crowd that Japan should not give into militant activists and preserve its whale-eating culture.
"They're violent environmental terrorists," mission leader Hajime Ishikawa told the ceremony. "Their violence is unforgivable ... we must fight against their hypocrisy and lies."
The whalers plan to kill up to 50 humpbacks in what is believed to be the first large-scale hunt for the once nearly extinct species since a 1963 moratorium in the Southern Pacific put the giant marine mammals under international protection.
The mission also aims to take as many as 935 minke whales and up to 50 fin whales in what Japan's Fisheries Agency says is its largest-ever scientific whale hunt. The expedition lasts through April.
Japan says it needs to kill the animals in order to conduct research on their reproductive and feeding patterns.
While scientific whale hunts are allowed by the International Whaling Commission, or IWC, critics say Japan is simply using science as a cover for commercial whaling.
The anti-whaling group Greenpeace said its protest ship, Esperanza, was moored just outside Japan's territorial waters and would chase the fleet to the southern ocean. There was no immediate word Sunday of an offshore confrontation.
"We are going to do everything in our power to reduce their catch," Karli Thomas, expedition leader on the Esperanza, told The Associated Press by telephone. "Japan's research program is a sham. We demand that the Japanese government cancel it."
An IWC moratorium on commercial whaling took effect in 1986, but Japan — where coastal villages have hunted whales for hundreds of years — has killed almost 10,500 mostly minke and Brydes whales under research permits since then. Tokyo has argued unsuccessfully for years for the IWC to overturn the moratorium.
The Japanese hunt, which puts meat from the whales on the commercial market, is growing rapidly despite an increasingly vocal anti-whaling movement. This winter season's target of up to 1,035 whales is more than double the number the country hunted a decade ago.
Japan argues that it should have the right to hunt whales as long as they are not in danger of extinction.
The head of Japan's Fisheries Agency said Sunday the fruits of Tokyo's research would help prove that sustainable whaling is possible.
"The scientific research we carry out will pave the way to overturning the moratorium on commercial whaling, which will better help us to utilize whale resources," Shuji Yamada told the ceremony.
The focus on this year's hunt is the humpback, which was in serious danger of extinction just a few decades ago. They are now a favorite of whale-watchers for their playful antics at sea, where the beasts — which grow as large as 40 tons — throw themselves out of the water.
Humpbacks feed, mate and give birth near shore, making them easy prey for whalers, who by some estimates depleted the global population to just 1,200 before the 1963 moratorium. The southern moratorium was followed by a worldwide ban in 1966.
Since then, only Greenland and the Caribbean nation of Saint Vincent and the Grenadines have been allowed to catch humpbacks under an IWC aboriginal subsistence program. Each caught one humpback last year, according to the commission.
The American Cetacean Society estimates the humpback population has recovered to about 30,000-40,000 — about a third of the number before modern whaling. The species is listed as "vulnerable" by the World Conservation Union.
Japanese fisheries officials insist the population has returned to a sustainable level and that taking 50 of them will have no impact.et offshore.
Families waved little flags emblazoned with smiling whales and the crew raised a toast with cans of beer, while a brass band played "Popeye the Sailor Man." Officials told the crowd that Japan should not give into militant activists and preserve its whale-eating culture.
"They're violent environmental terrorists," mission leader Hajime Ishikawa told the ceremony. "Their violence is unforgivable ... we must fight against their hypocrisy and lies."
The whalers plan to kill up to 50 humpbacks in what is believed to be the first large-scale hunt for the once nearly extinct species since a 1963 moratorium in the Southern Pacific put the giant marine mammals under international protection.
The mission also aims to take as many as 935 minke whales and up to 50 fin whales in what Japan's Fisheries Agency says is its largest-ever scientific whale hunt. The expedition lasts through April.
Japan says it needs to kill the animals in order to conduct research on their reproductive and feeding patterns.
While scientific whale hunts are allowed by the International Whaling Commission, or IWC, critics say Japan is simply using science as a cover for commercial whaling.
The anti-whaling group Greenpeace said its protest ship, Esperanza, was moored just outside Japan's territorial waters and would chase the fleet to the southern ocean. There was no immediate word Sunday of an offshore confrontation.
"We are going to do everything in our power to reduce their catch," Karli Thomas, expedition leader on the Esperanza, told The Associated Press by telephone. "Japan's research program is a sham. We demand that the Japanese government cancel it."
An IWC moratorium on commercial whaling took effect in 1986, but Japan — where coastal villages have hunted whales for hundreds of years — has killed almost 10,500 mostly minke and Brydes whales under research permits since then. Tokyo has argued unsuccessfully for years for the IWC to overturn the moratorium.
The Japanese hunt, which puts meat from the whales on the commercial market, is growing rapidly despite an increasingly vocal anti-whaling movement. This winter season's target of up to 1,035 whales is more than double the number the country hunted a decade ago.
Japan argues that it should have the right to hunt whales as long as they are not in danger of extinction.
The head of Japan's Fisheries Agency said Sunday the fruits of Tokyo's research would help prove that sustainable whaling is possible.
"The scientific research we carry out will pave the way to overturning the moratorium on commercial whaling, which will better help us to utilize whale resources," Shuji Yamada told the ceremony.
The focus on this year's hunt is the humpback, which was in serious danger of extinction just a few decades ago. They are now a favorite of whale-watchers for their playful antics at sea, where the beasts — which grow as large as 40 tons — throw themselves out of the water.
Humpbacks feed, mate and give birth near shore, making them easy prey for whalers, who by some estimates depleted the global population to just 1,200 before the 1963 moratorium. The southern moratorium was followed by a worldwide ban in 1966.
Since then, only Greenland and the Caribbean nation of Saint Vincent and the Grenadines have been allowed to catch humpbacks under an IWC aboriginal subsistence program. Each caught one humpback last year, according to the commission.
The American Cetacean Society estimates the humpback population has recovered to about 30,000-40,000 — about a third of the number before modern whaling. The species is listed as "vulnerable" by the World Conservation Union.
Japanese fisheries officials insist the population has returned to a sustainable level and that taking 50 of them will have no impact.et offshore.
Diesel pollution clogs arteries, raises risk of heart disease
Diesel fumes interact with fatty acids found in LDL ("bad") cholesterol to raise the risk of heart disease, according to a study published in the online journal "Genome Biology."On their own, both diesel fumes and certain fatty acids contained in LDL cholesterol create free radicals in the body. These free radicals damage cells and tissue, leading to the inflammation that can cause cardiovascular disease. In the new study, researchers at the University of California-Los Angeles found that the combination of diesel and the fats was far more dangerous than either factor separately."Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone," said lead researcher André Nel.The researchers first combined diesel pollutants with the fatty acids and added them to a culture of cells from the inside of human blood vessels. They found that the mixture activated the genes that promote cellular inflammation. Then the researchers exposed mice with high cholesterol to diesel particles. In response, many of the same genes were activated in the mice's bodies.Researchers said that the exact mechanism by which pollution leads to heart disease is still unknown."We do know that these particles are coated with chemicals that damage tissue and cause inflammation of the nose and lungs," Nel said. "Vascular inflammation in turn leads to cholesterol deposits and clogged arteries, which can give rise to blood clots and trigger heart attack or stroke."According to Cathy Ross, a cardiac nurse at the British Heart Foundation, it has long been known that air pollution increases a person's risk of death from cardiovascular disease. "Anyone with chronic lung disease or coronary heart disease should avoid staying outside for long periods when pollution levels are high," she said.
Evolutionary Biology Research on Plant Shows Significance of Maternal Effects
When habitat changes, animals migrate. But how do immobile organisms like plants cope when faced with alterations to their environment? This is an increasingly important question in light of new environmental conditions brought on by global climate change.A University of Virginia study, published in the Nov. 16 issue of the journal Science, demonstrates that plants grown in the same setting as their maternal plant performed almost 3½ times better than those raised in a different environment — indicating that maternal plants give cues to their offspring that help them adapt to their environmental conditions.Evolutionary biologist Laura Galloway, an associate professor of biology at the University of Virginia, recently completed a study of the American bellflower, a native wildflower that commonly grows in both shaded areas and areas that receive full sunlight for at least part of the day. She focused on the transmission of environmental information between maternal plants and their offspring.Galloway planted some seeds in light conditions similar to their maternal plants and some in different light. She found that plants growing in the same setting as their maternal plant outperformed those planted in a different environment. The work was conducted in a natural habitat at the University of Virginia’s Mountain Lake Biological Station in Southwest Virginia.Since seeds typically fall close to their maternal plant, they grow in a similar environment. When seeds are dispersed to different environments, Galloway found that the plants may suffer for one generation, but as long as the seeds of those plants grow locally, their offspring will recover. “We found a temporary mechanism of adaptation to local environmental conditions,” says Galloway. Since plant adaptation is typically studied on a permanent, genetic level rather than in direct response to environmental conditions, Galloway’s insights are unique. Galloway was led to this line of inquiry by chance. She was surprised to observe a number of years ago that plants that had experienced drought had smaller seeds than those that had not. This highly visible physiological change within only one generation intrigued her. “Historically maternal effects have been viewed as a complicating factor — an inconvenience,” explains Galloway. “But we have found that they can dramatically influence the performance of an individual.”
Human ancestors: more gatherers than hunters?
Chimpanzees crave roots and tubers even when food is plentiful above ground, according to a new study that raises questions about the relative importance of meat for brain evolution.
Appearing online the week of Nov. 12 in the early edition of the Proceedings of the National Academy of Sciences, the study documents a novel use of tools by chimps to dig for tubers and roots in the savanna woodlands of western Tanzania.
The chimps’ eagerness for buried treats offers new insights in an ongoing debate about the role of meat versus potato-like foods in the diet of our hominid ancestors, said first author Adriana Hernandez-Aguilar, who collected the field data for her doctoral research at the University of Southern California.
The debate centers on the diet followed by early hominids as their brain and body size slowly increased towards a human level. Was it meat-and-potatoes, or potatoes-and-meat"
“Some researchers have suggested that what made us human was actually the tubers,” Hernandez-Aguilar said.
Anthropologists had speculated that roots and tubers were mere fallback foods for hominids trying to survive the harsh dry season in the savanna 3.5 million years ago and later (hominids are known to have consumed meat at least as early as 2.5 million years ago).
But the study found that modern chimps only dig for roots during the rainy season, when other food sources abound.
The finding suggests, but does not prove, that hominids behaved the same way. Researchers view modern chimps as proxies for hominids because of similarities in habitat, brain mass and body size.
“We look at chimps for the way that we could have behaved when our ancestors were chimp-like,” Hernandez-Aguilar said.
Corresponding author Travis Pickering, of the University of Wisconsin-Madison, said: “Savanna chimps, we would contend, are dealing with environmental constraints and problems – evolutionary pressures – that our earliest relatives would have dealt with as well.”
The tuber-digging chimps “suggest that underground resources were within reach of our ancestors,” added co-author James Moore of the University of California at San Diego.
The study was based on observation of 11 digging sites in the Ugalla savanna woodland of western Tanzania.
Chimpanzees were linked to the excavated tubers and roots through knuckle prints, feces, and spit-out wads of fibers from those underground foods.
Seven tools were found at three of the sites, with worn edges and dirt marking implying their use as digging implements.
Because chimpanzees in the area are not habituated to humans, Hernandez-Aguilar was unable to observe them directly. She plans to conduct further observations in the area and to advocate for greater protection for the savanna chimps.
“Chimpanzees in savannas have not been considered a priority in conservation plans because they live in low densities compared to chimps in forests,” she said.
“We hope that discoveries such as this will show the value of conserving the savanna populations.”
Hernandez-Aguilar conducted her thesis work under Craig Stanford, professor of anthropology at USC.
The research was funded by the LSB Leakey Foundation, the National Science Foundation, the Jane Goodall Center at the University of Southern California, the University of California Committee on Research, the Palaeontology Scientific Trust and the Ugalla Primate Lab from UCSD. James Moore is the coordinator of the Ugalla Primate Project.
Appearing online the week of Nov. 12 in the early edition of the Proceedings of the National Academy of Sciences, the study documents a novel use of tools by chimps to dig for tubers and roots in the savanna woodlands of western Tanzania.
The chimps’ eagerness for buried treats offers new insights in an ongoing debate about the role of meat versus potato-like foods in the diet of our hominid ancestors, said first author Adriana Hernandez-Aguilar, who collected the field data for her doctoral research at the University of Southern California.
The debate centers on the diet followed by early hominids as their brain and body size slowly increased towards a human level. Was it meat-and-potatoes, or potatoes-and-meat"
“Some researchers have suggested that what made us human was actually the tubers,” Hernandez-Aguilar said.
Anthropologists had speculated that roots and tubers were mere fallback foods for hominids trying to survive the harsh dry season in the savanna 3.5 million years ago and later (hominids are known to have consumed meat at least as early as 2.5 million years ago).
But the study found that modern chimps only dig for roots during the rainy season, when other food sources abound.
The finding suggests, but does not prove, that hominids behaved the same way. Researchers view modern chimps as proxies for hominids because of similarities in habitat, brain mass and body size.
“We look at chimps for the way that we could have behaved when our ancestors were chimp-like,” Hernandez-Aguilar said.
Corresponding author Travis Pickering, of the University of Wisconsin-Madison, said: “Savanna chimps, we would contend, are dealing with environmental constraints and problems – evolutionary pressures – that our earliest relatives would have dealt with as well.”
The tuber-digging chimps “suggest that underground resources were within reach of our ancestors,” added co-author James Moore of the University of California at San Diego.
The study was based on observation of 11 digging sites in the Ugalla savanna woodland of western Tanzania.
Chimpanzees were linked to the excavated tubers and roots through knuckle prints, feces, and spit-out wads of fibers from those underground foods.
Seven tools were found at three of the sites, with worn edges and dirt marking implying their use as digging implements.
Because chimpanzees in the area are not habituated to humans, Hernandez-Aguilar was unable to observe them directly. She plans to conduct further observations in the area and to advocate for greater protection for the savanna chimps.
“Chimpanzees in savannas have not been considered a priority in conservation plans because they live in low densities compared to chimps in forests,” she said.
“We hope that discoveries such as this will show the value of conserving the savanna populations.”
Hernandez-Aguilar conducted her thesis work under Craig Stanford, professor of anthropology at USC.
The research was funded by the LSB Leakey Foundation, the National Science Foundation, the Jane Goodall Center at the University of Southern California, the University of California Committee on Research, the Palaeontology Scientific Trust and the Ugalla Primate Lab from UCSD. James Moore is the coordinator of the Ugalla Primate Project.
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