New mathematical model explains patterns of human movement by considering the costs

ScienceDaily (Oct. 13, 2011) — Using previously published data on the time-stamped locations of 100,000 anonymous cell-phone users, a researcher from Duke University has identified three distinct patterns of human mobility for short, medium, and long distance trips. In 2008, a separate research team that was not involved in the current study published a paper in which they had plotted data on cell-phone users' movements, and then fitted the data with a single, downward-sloping curve. The curve captured an intuitive relationship: the longer a trip, the less likely it was to occur.

Nicola Scafetta, however, thought deeper patterns might be hidden by the simple curve. In the AIP's journal Chaos, Scafetta proposes a finer-resolution analysis of the cell-phone data. He divided the data set up into three separate sections, one each for short (from 1 to 10 km), medium (from 10 to 300 km), and long (above 300 km) distance trips. He then fit each chunk of data with a separate curve. Surprisingly, the exponents from the three separate curve fits were simple numbers -- 1, 2 and 3 -- that illustrated a different relationship between distance and trip frequency for each zone. For all three zones, the likelihood of a trip decreases with increased distance, but the rate of decrease is faster in the higher-numbered zones.

Scafetta offers a physical and statistical explanation for this pattern. In zone one, people are running short-distance errands within an urban area, and may just consider one cost mechanism, like the time or the fuel cost of the trips, when deciding where and when to go. In the more distant zone two people are, for example, taking day-trips to nearby towns of specific interest. These trips might require travelers to consider both time and fuel costs in their decisions. And in zone three, people take multi-day trips and may consider time and fuel costs, as well as additional overnight lodging costs.

The increase in the number of considered costs for each zone could help explain the increase in the curve-fit exponent for each zone. Scafetta also rescaled the model and found that it could be used to interpret data gathered on the movements of volunteers who walked to their destinations, either in zone one (within 200 m) or zone two (from 200 to 1000 m).

The critical benefit of the alternative fitting method, Scafetta writes, is that it suggests clear physical and geographical mechanisms to explain the observations. Accurate models of human displacement have applications in traffic forecasting, urban planning, and in the study of social networks and the spread of diseases.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Institute of Physics, via EurekAlert!, a service of AAAS.

Journal Reference:

Nicola Scafetta. Understanding the complexity of the Lévy-walk nature of human mobility with a multi-scale cost/benefit model. Chaos: An Interdisciplinary Journal of Nonlinear Science, 2011

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Synthetic collagen from maize has human properties

ScienceDaily (June 28, 2011) — Synthetic collagen has a wide range of applications in reconstructive and cosmetic surgery and in the food industry. For proper function in animals a certain number of prolines within the protein need to be hydroxylated. BioMed Central's open access journal BMC Biotechnology reports that for the first time the a1 chain of type 1 collagen has been produced in maize with similar levels of proline hydroxylation to human collagen.

Most collagen used is derived from animals but there are risks associated with this collagen containing infectious agents or being rejected by the body. To avoid this problem several laboratory-based systems have been developed using plants to produce collagen. Plant-derived recombinant proteins should have lower contamination and fewer infectious agents, but these systems are unable to make modifications to the protein essential for proper function in human cells.

Working in collaboration with industrial partners researchers added a gene, which codes for the a1 chain of human CI (hCI a1), to maize along with genes which make human prolyl 4-hydroxylase. This second protein was able to hydroxylate approximately the same percentage of prolines in the recombinant collagen a1 chain, produced in maize, as seen for human collagen made in human cells.

Dr Kan Wang from Iowa State University said, "Producing human collagen in maize seeds is an inexpensive alternative to using animal-derived collagen. The seeds are easy to grow, process, and store. Our transgenic plant system is also able to produce a protein with human-like modifications making it a better choice for a wide range of applications."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by BioMed Central, via EurekAlert!, a service of AAAS.

Journal Reference:

Xing Xu, Qinglei Gan, Richard C Clough, Kamesh M Pappu, John A Howard, Julio A Baez, Kan Wang. Hydroxylation of recombinant human collagen type I alpha 1 in transgenic maize co-expressed with a recombinant human prolyl 4-hydroxylase. BMC Biotechnology, 2011; 11 (1): 69 DOI: 10.1186/1472-6750-11-69

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New method for engineering human tissue regeneration

ScienceDaily (May 13, 2011) — If pending clinical trials prove successful, a new discovery published in The FASEB Journal could represent a major scientific leap toward human tissue regeneration and engineering. In a research report appearing online, Yale scientists provide evidence to support a major paradigm shift in this specialty area from the idea that cells added to a graft before implantation are the building blocks of tissue, to a new belief that engineered tissue constructs can actually induce or augment the body's own reparative mechanisms, including complex tissue regeneration.

"With the constant growing clinical demand for alternative vessels used for vascular reconstructive surgeries, a significant development for alternative grafts is currently the primary focus of many investigators worldwide," said Christopher K. Breuer, M.D., a researcher involved in the work from Yale University School of Medicine/Yale-New Haven Hospital in New Haven, CT. "We believe that through an understanding of human vascular biology, coupled with technologies such as tissue engineering, we can introduce biological grafts that mimic the functional properties of native vessels and that are capable of growing with the patients." Breuer also says that patients are currently being enrolled in a first-of-its-kind clinical trial at Yale University to evaluate the safety and growth potential of tissue-engineered vascular grafts in children undergoing surgery for congenital heart disease.

To make this discovery, Breuer and colleagues conducted a three-part study, starting with two groups of mice. The first group expressed a gene that made all of its cells fluorescent green and the second group was normal. Researchers extracted bone marrow cells from the "green" mice, added them to previously designed scaffolds, and implanted the grafts into the normal mice. The seeded bone marrow cells improved the performance of the graft; however, a rapid loss of green cells was noted and the cells that developed in the new vessel wall were not green, suggesting that the seeded cells promoted vessel development, but did not turn into vessel wall cells themselves.

These findings led to the second part of the study, which tested whether cells produced in the host's bone marrow might be a source for new cells. Scientists replaced the bone marrow cells of a female mouse with those of a male mouse before implanting the graft into female mice. The researchers found that the cells forming the new vessel were female, meaning they did not come from the male bone marrow cells. In the final experiment, researchers implanted a segment of male vessel attached to the scaffold into a female host. After analysis, the researchers found that the side of the graft next to the male segment developed with male vessel wall cells while the side of the graft attached to the female host's vessel formed from female cells, proving that the cells in the new vessel must have migrated from the adjacent normal vessel.

"There's a very good chance that this study will eventually have a major impact on many disorders that afflict humankind," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "These scientists have basically used the body's repair mechanisms to make new tissues through bioengineering. In years to come, starfish and salamanders will have nothing on us!"

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Federation of American Societies for Experimental Biology, via EurekAlert!, a service of AAAS.

Journal Reference:

Narutoshi Hibino, Gustavo Villalona, Nicholas Pietris, Daniel R. Duncan, Adam Schoffner, Jason D. Roh, Tai Yi, Lawrence W. Dobrucki, Dane Mejias, Rajendra Sawh-Martinez, Jamie K. Harrington, Albert Sinusas, Diane S. Krause, Themis Kyriakides, W. Mark Saltzman, Jordan S. Pober, Toshiharu Shin'oka, Christopher K. Breuer. Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel. FASEB Journal, 2011; DOI: 10.1096/fj.11-182246

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Scientists afflict computers with 'schizophrenia' to better understand the human brain

ScienceDaily (May 6, 2011) — Computer networks that can't forget fast enough can show symptoms of a kind of virtual schizophrenia, giving researchers further clues to the inner workings of schizophrenic brains, researchers at The University of Texas at Austin and Yale University have found.

The researchers used a virtual computer model, or "neural network," to simulate the excessive release of dopamine in the brain. They found that the network recalled memories in a distinctly schizophrenic-like fashion.

Their results were published in April in Biological Psychiatry.

"The hypothesis is that dopamine encodes the importance-the salience-of experience," says Uli Grasemann, a graduate student in the Department of Computer Science at The University of Texas at Austin. "When there's too much dopamine, it leads to exaggerated salience, and the brain ends up learning from things that it shouldn't be learning from."

The results bolster a hypothesis known in schizophrenia circles as the hyperlearning hypothesis, which posits that people suffering from schizophrenia have brains that lose the ability to forget or ignore as much as they normally would. Without forgetting, they lose the ability to extract what's meaningful out of the immensity of stimuli the brain encounters. They start making connections that aren't real, or drowning in a sea of so many connections they lose the ability to stitch together any kind of coherent story.

The neural network used by Grasemann and his adviser, Professor Risto Miikkulainen, is called DISCERN. Designed by Miikkulainen, DISCERN is able to learn natural language. In this study it was used to simulate what happens to language as the result of eight different types of neurological dysfunction. The results of the simulations were compared by Ralph Hoffman, professor of psychiatry at the Yale School of Medicine, to what he saw when studying human schizophrenics.

In order to model the process, Grasemann and Miikkulainen began by teaching a series of simple stories to DISCERN. The stories were assimilated into DISCERN's memory in much the way the human brain stores information-not as distinct units, but as statistical relationships of words, sentences, scripts and stories.

"With neural networks, you basically train them by showing them examples, over and over and over again," says Grasemann. "Every time you show it an example, you say, if this is the input, then this should be your output, and if this is the input, then that should be your output. You do it again and again thousands of times, and every time it adjusts a little bit more towards doing what you want. In the end, if you do it enough, the network has learned."

In order to model hyperlearning, Grasemann and Miikkulainen ran the system through its paces again, but with one key parameter altered. They simulated an excessive release of dopamine by increasing the system's learning rate-essentially telling it to stop forgetting so much.

"It's an important mechanism to be able to ignore things," says Grasemann. "What we found is that if you crank up the learning rate in DISCERN high enough, it produces language abnormalities that suggest schizophrenia."

After being re-trained with the elevated learning rate, DISCERN began putting itself at the center of fantastical, delusional stories that incorporated elements from other stories it had been told to recall. In one answer, for instance, DISCERN claimed responsibility for a terrorist bombing.

In another instance, DISCERN began showing evidence of "derailment"-replying to requests for a specific memory with a jumble of dissociated sentences, abrupt digressions and constant leaps from the first- to the third-person and back again.

"Information processing in neural networks tends to be like information processing in the human brain in many ways," says Grasemann. "So the hope was that it would also break down in similar ways. And it did."

The parallel between their modified neural network and human schizophrenia isn't absolute proof the hyperlearning hypothesis is correct, says Grasemann. It is, however, support for the hypothesis, and also evidence of how useful neural networks can be in understanding the human brain.

"We have so much more control over neural networks than we could ever have over human subjects," he says. "The hope is that this kind of modeling will help clinical research."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Texas at Austin.

Journal Reference:

Ralph E. Hoffman, Uli Grasemann, Ralitza Gueorguieva, Donald Quinlan, Douglas Lane, Risto Miikkulainen. Using Computational Patients to Evaluate Illness Mechanisms in Schizophrenia. Biological Psychiatry, 2011; DOI: 10.1016/j.biopsych.2010.12.036

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Scientists afflict computers with 'schizophrenia' to better understand the human brain

ScienceDaily (May 6, 2011) — Computer networks that can't forget fast enough can show symptoms of a kind of virtual schizophrenia, giving researchers further clues to the inner workings of schizophrenic brains, researchers at The University of Texas at Austin and Yale University have found.

The researchers used a virtual computer model, or "neural network," to simulate the excessive release of dopamine in the brain. They found that the network recalled memories in a distinctly schizophrenic-like fashion.

Their results were published in April in Biological Psychiatry.

"The hypothesis is that dopamine encodes the importance-the salience-of experience," says Uli Grasemann, a graduate student in the Department of Computer Science at The University of Texas at Austin. "When there's too much dopamine, it leads to exaggerated salience, and the brain ends up learning from things that it shouldn't be learning from."

The results bolster a hypothesis known in schizophrenia circles as the hyperlearning hypothesis, which posits that people suffering from schizophrenia have brains that lose the ability to forget or ignore as much as they normally would. Without forgetting, they lose the ability to extract what's meaningful out of the immensity of stimuli the brain encounters. They start making connections that aren't real, or drowning in a sea of so many connections they lose the ability to stitch together any kind of coherent story.

The neural network used by Grasemann and his adviser, Professor Risto Miikkulainen, is called DISCERN. Designed by Miikkulainen, DISCERN is able to learn natural language. In this study it was used to simulate what happens to language as the result of eight different types of neurological dysfunction. The results of the simulations were compared by Ralph Hoffman, professor of psychiatry at the Yale School of Medicine, to what he saw when studying human schizophrenics.

In order to model the process, Grasemann and Miikkulainen began by teaching a series of simple stories to DISCERN. The stories were assimilated into DISCERN's memory in much the way the human brain stores information-not as distinct units, but as statistical relationships of words, sentences, scripts and stories.

"With neural networks, you basically train them by showing them examples, over and over and over again," says Grasemann. "Every time you show it an example, you say, if this is the input, then this should be your output, and if this is the input, then that should be your output. You do it again and again thousands of times, and every time it adjusts a little bit more towards doing what you want. In the end, if you do it enough, the network has learned."

In order to model hyperlearning, Grasemann and Miikkulainen ran the system through its paces again, but with one key parameter altered. They simulated an excessive release of dopamine by increasing the system's learning rate-essentially telling it to stop forgetting so much.

"It's an important mechanism to be able to ignore things," says Grasemann. "What we found is that if you crank up the learning rate in DISCERN high enough, it produces language abnormalities that suggest schizophrenia."

After being re-trained with the elevated learning rate, DISCERN began putting itself at the center of fantastical, delusional stories that incorporated elements from other stories it had been told to recall. In one answer, for instance, DISCERN claimed responsibility for a terrorist bombing.

In another instance, DISCERN began showing evidence of "derailment"-replying to requests for a specific memory with a jumble of dissociated sentences, abrupt digressions and constant leaps from the first- to the third-person and back again.

"Information processing in neural networks tends to be like information processing in the human brain in many ways," says Grasemann. "So the hope was that it would also break down in similar ways. And it did."

The parallel between their modified neural network and human schizophrenia isn't absolute proof the hyperlearning hypothesis is correct, says Grasemann. It is, however, support for the hypothesis, and also evidence of how useful neural networks can be in understanding the human brain.

"We have so much more control over neural networks than we could ever have over human subjects," he says. "The hope is that this kind of modeling will help clinical research."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Texas at Austin.

Journal Reference:

Ralph E. Hoffman, Uli Grasemann, Ralitza Gueorguieva, Donald Quinlan, Douglas Lane, Risto Miikkulainen. Using Computational Patients to Evaluate Illness Mechanisms in Schizophrenia. Biological Psychiatry, 2011; DOI: 10.1016/j.biopsych.2010.12.036

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method for engineering human tissue regeneration

ScienceDaily (May 13, 2011) — If pending clinical trials prove successful, a new discovery published in The FASEB Journal could represent a major scientific leap toward human tissue regeneration and engineering. In a research report appearing online, Yale scientists provide evidence to support a major paradigm shift in this specialty area from the idea that cells added to a graft before implantation are the building blocks of tissue, to a new belief that engineered tissue constructs can actually induce or augment the body's own reparative mechanisms, including complex tissue regeneration.

"With the constant growing clinical demand for alternative vessels used for vascular reconstructive surgeries, a significant development for alternative grafts is currently the primary focus of many investigators worldwide," said Christopher K. Breuer, M.D., a researcher involved in the work from Yale University School of Medicine/Yale-New Haven Hospital in New Haven, CT. "We believe that through an understanding of human vascular biology, coupled with technologies such as tissue engineering, we can introduce biological grafts that mimic the functional properties of native vessels and that are capable of growing with the patients." Breuer also says that patients are currently being enrolled in a first-of-its-kind clinical trial at Yale University to evaluate the safety and growth potential of tissue-engineered vascular grafts in children undergoing surgery for congenital heart disease.

To make this discovery, Breuer and colleagues conducted a three-part study, starting with two groups of mice. The first group expressed a gene that made all of its cells fluorescent green and the second group was normal. Researchers extracted bone marrow cells from the "green" mice, added them to previously designed scaffolds, and implanted the grafts into the normal mice. The seeded bone marrow cells improved the performance of the graft; however, a rapid loss of green cells was noted and the cells that developed in the new vessel wall were not green, suggesting that the seeded cells promoted vessel development, but did not turn into vessel wall cells themselves.

These findings led to the second part of the study, which tested whether cells produced in the host's bone marrow might be a source for new cells. Scientists replaced the bone marrow cells of a female mouse with those of a male mouse before implanting the graft into female mice. The researchers found that the cells forming the new vessel were female, meaning they did not come from the male bone marrow cells. In the final experiment, researchers implanted a segment of male vessel attached to the scaffold into a female host. After analysis, the researchers found that the side of the graft next to the male segment developed with male vessel wall cells while the side of the graft attached to the female host's vessel formed from female cells, proving that the cells in the new vessel must have migrated from the adjacent normal vessel.

"There's a very good chance that this study will eventually have a major impact on many disorders that afflict humankind," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "These scientists have basically used the body's repair mechanisms to make new tissues through bioengineering. In years to come, starfish and salamanders will have nothing on us!"

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Federation of American Societies for Experimental Biology, via EurekAlert!, a service of AAAS.

Journal Reference:

Narutoshi Hibino, Gustavo Villalona, Nicholas Pietris, Daniel R. Duncan, Adam Schoffner, Jason D. Roh, Tai Yi, Lawrence W. Dobrucki, Dane Mejias, Rajendra Sawh-Martinez, Jamie K. Harrington, Albert Sinusas, Diane S. Krause, Themis Kyriakides, W. Mark Saltzman, Jordan S. Pober, Toshiharu Shin'oka, Christopher K. Breuer. Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel. FASEB Journal, 2011; DOI: 10.1096/fj.11-182246

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Pioneering animal diabetes treatment: Researchers adapt human continuous glucose monitors for pets

ScienceDaily (Apr. 25, 2011) — Studies show the incidence of diabetes in dogs has increased 200 percent over the past 30 years. Now, University of Missouri veterinarians have changed the way veterinarians treat diabetes in animals by adapting a device used to monitor glucose in humans.

Dogs are susceptible to type 1, insulin-dependent diabetes. Affected animals are unable to utilize sugar in their bloodstream because their bodies do not produce enough insulin, a hormone that helps cells turn sugar into energy. Veterinarians treat animals with this type of diabetes similarly to the way humans are treated, with insulin injections and a low-carbohydrate diet.

Amy DeClue, assistant professor of veterinary internal medicine, and Charles Wiedmeyer, assistant professor of veterinary clinical pathology, have been studying the use of a "continuous glucose monitor" (CGM) on animals since 2003. A CGM is a small flexible device that is inserted about an inch into the skin, to constantly monitor glucose concentrations.

"Continuous glucose monitoring is much more effective and accurate than previous glucose monitoring techniques and has revolutionized how veterinarians manage diabetes in dogs," said DeClue. "The CGM gives us a complete view of what is happening in the animal in their natural setting. For example, it can show us if a pet's blood glucose changes when an owner gives treats, when the animal exercises or in response to insulin therapy."

CGMs have become more commonly used in dogs with diabetes that are not responding well to conventional treatment. The monitor provides detailed data for glucose concentrations throughout the course of three days in a dog's usual environment, so veterinarians can make better treatment decisions. Previously, veterinarians would have created an insulin regimen based on a glucose curve by taking blood from the animal in the veterinary hospital every two hours over the course of a single day. The glucose curve was often inaccurate due to increased stress from the animals being in an unnatural environment.

Dogs show clinical signs of diabetes similar to humans. Clinical signs include increased urination, thirst, hunger and weight loss. Typically, no direct cause is found for diabetes in dogs, but genetic disposition and obesity are thought to play a role in causing diabetes, according to DeClue. Just like people, dogs suffering with diabetes must be medically managed or complications can arise.

"Typically, dogs that are treated properly for diabetes go on to live a long, full life," said Wiedmeyer. "Actually, dogs with diabetes are similar to young children with diabetes but somewhat easier to manage. Dogs will eat what their owners give them at the same time each day and they won't ask for a cupcake at a friend's birthday party. With tools like the continuous glucose monitor to assist with disease management, the outlook is very good for a dog with diabetes."

In the future Wiedmeyer projects that the device will become smaller and less invasive. In addition, he hopes device manufacturers develop a device that would monitor blood sugar levels remotely.

DeClue and Wiedmeyer's most recent article on methods for monitoring and treating diabetes in dogs was published in the journal Clinic in Laboratory Medicine.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Missouri-Columbia.

Journal Reference:

Charles E. Wiedmeyer, Amy E. DeClue. Glucose Monitoring in Diabetic Dogs and Cats: Adapting New Technology for Home and Hospital Care. Clinics in Laboratory Medicine, 2011; 31 (1): 41 DOI: 10.1016/j.cll.2010.10.010

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here