Category: Science

Study Measures Pleasure Response from Chocolate from Signals in the Eyes

Chocolate brownies were the food stimulus in Nasser’s study. (Photo by jeffreyw, CC-BY-2.0, via Wikimedia Commons)

Originally posted on DrexelNow.

The brain’s pleasure response to tasting food can be measured through the eyes using a common, low-cost ophthalmological tool, according to a study just published in the journal Obesity. If validated, this method could be useful for research and clinical applications in food addiction and obesity prevention.

Dr. Jennifer Nasser, an associate professor in the department of Nutrition Sciences in Drexel University’s College of Nursing and Health Professions, led the study testing the use of electroretinography (ERG) to indicate increases in the neurotransmitter dopamine in the retina.

Dopamine is associated with a variety of pleasure-related effects in the brain, including the expectation of reward. In the eye’s retina, dopamine is released when the optical nerve activates in response to light exposure.

Nasser and her colleagues found that electrical signals in the retina spiked high in response to a flash of light when a food stimulus (a small piece of chocolate brownie) was placed in participants’ mouths. The increase was as great as that seen when participants had received the stimulant drug methylphenidate to induce a strong dopamine response. These responses in the presence of food and drug stimuli were each significantly greater than the response to light when participants ingested a control substance, water.

“What makes this so exciting is that the eye’s dopamine system was considered separate from the rest of the brain’s dopamine system,” Nasser said. “So most people– and indeed many retinography experts told me this– would say that tasting a food that stimulates the brain’s dopamine system wouldn’t have an effect on the eye’s dopamine system.”

This study was a small-scale demonstration of the concept, with only nine participants. Most participants were overweight but none had eating disorders. All fasted for four hours before testing with the food stimulus.

If this technique is validated through additional and larger studies, Nasser said she and other researchers can use ERG for studies of food addiction and food science.

“My research takes a pharmacology approach to the brain’s response to food,” Nasser said. “Food is both a nutrient delivery system and a pleasure delivery system, and a ‘side effect’ is excess calories. I want to maximize the pleasure and nutritional value of food but minimize the side effects. We need more user-friendly tools to do that.”

The low cost and ease of performing electroretinography make it an appealing method, according to Nasser. The Medicare reimbursement cost for clinical use of ERG is about $150 per session, and each session generates 200 scans in just two minutes. Procedures to measure dopamine responses directly from the brain are more expensive and invasive. For example, PET scanning costs about $2,000 per session and takes more than an hour to generate a scan.

Nasser performed the study with colleagues at St. Luke’s-Roosevelt Hospital Center, New York Obesity Nutrition Research Center, in New York City.

– See more at: http://drexel.edu/now/archive/2013/June/Pleasure-Response-from-Chocolate-Measured-Through-Eyes/

Science and the Senses at the Museum: Academy of Natural Sciences Gets More Autism-Friendly

Drexel News Blog Dinosaur Hall at the Academy of Natural Sciences of Drexel University. Credit: Will Klein From the iconic T-Rex at the entrance to the active fossil prep lab tucked away in the back corner, Dinosaur Hall at the Academy of Natural Sciences of … Continue reading Science and the Senses at the Museum: Academy of Natural Sciences Gets More Autism-Friendly

Dusting for Prints from a Fossil Fish to Understand Evolutionary Change

Drexel News Blog Dorsal view of the dermal armor of the newly identified fossil fish species, Phyllolepis thomsoni. Credit: Academy of Natural Sciences of Drexel University. In 370 million-year-old red sandstone deposits in a highway roadcut, scientists have discovered a new species of armored fish … Continue reading Dusting for Prints from a Fossil Fish to Understand Evolutionary Change

New Fossil from a Fish-Eat-Fish World Driving the Evolution of Limbed Animals

Originally posted on DrexelNow.

“We call it a ‘fish-eat-fish world,’ an ecosystem where you really needed to escape predation,” said Dr. Ted Daeschler, describing life in the Devonian period in what is now far-northern Canada.

This was the environment where the famous fossil fish species Tiktaalik roseae lived 375 million years ago. This lobe-finned fish, co-discovered by Daeschler, an associate professor at Drexel University in the Department of Biodiversity, Earth and Environmental Science, and associate curator and vice president of the Academy of Natural Sciences of Drexel University, and his colleagues Dr. Neil Shubin and Dr. Farish A. Jenkins, Jr., was first described in Nature in 2006.This species received scientific and popular acclaim for providing some of the clearest evidence of the evolutionary transition from lobe-finned fish to limbed animals, or tetrapods.

Excavating Devonian fossils in the Canadian Arctic. Credit: Academy of Natural Sciences of Drexel University

Excavating Devonian fossils in the Canadian Arctic. Credit: Academy of Natural Sciences of Drexel University

Daeschler and his colleagues from the Tiktaalik research, including Academy research associate Dr. Jason Downs, have now described another new lobe-finned fish species from the same time and place in the Canadian Arctic. They describe the new species, Holoptychius bergmanni, in the latest issue of the Proceedings of the Academy of Natural Sciences of Philadelphia.

“We’re fleshing out our knowledge of the community of vertebrates that lived at this important location,” said Downs, who was lead author of the paper. He said describing species from this important time and place will help the scientific community understand the transition from finned vertebrates to limbed vertebrates that occurred in this ecosystem.

“It was a tough world back there in the Devonian. There were a lot of big predatory fish with big teeth and heavy armor of interlocking scales on their bodies,” said Daeschler.

Daeschler said Holoptychius and Tiktaalik were both large predatory fishes adapted to life in stream environments. The two species may have competed with one another for similar prey, although it is possible they specialized in slightly different niches; Tiktaalik’s tetrapod-like skeletal features made it especially well suited to living in the shallowest waters.

The fossil specimens of Holoptychis bergmanni that researchers used to characterize this new species come from multiple individuals and include lower jaws with teeth, skull pieces including the skull roof and braincase, and parts of the shoulder girdles. The complete fish would have been 2 to 3 feet long when it was alive.

“The three-dimensional preservation of this material is spectacular,” Daeschler said. “For something as old as this, we’ll really be able to collect some good information about the anatomy of these animals.”

Portions of the skull (left and center) and lower jaw (right) of Holoptychius bergmanni. Credit: Academy of Natural Sciences of Drexel University, with drawings by Scott Rawlins.

Above: Portions of the skull (left and center) and lower jaw (right) of Holoptychius bergmanni. Credit: Academy of Natural Sciences of Drexel University, with drawings by Scott Rawlins.

The research on Holoptychius bergmanni was led by Downs, a former post-doctoral fellow working with Daeschler who also teaches at Swarthmore College. Other co-authors of the paper with Downs and Daeschler are Dr. Neil Shubin of the University of Chicago, and the late Dr. Farish Jenkins, Jr. of Harvard University, who passed away in 2012.

Honoring a Modern Arctic Explorer and Supporter of Science

Field research team excavating Devonian fossils at the site in the Canadian Arctic where they found Tiktaalik roseae. Credit: Academy of Natural Sciences of Drexel University

Field research team excavating Devonian fossils at the site in the Canadian Arctic where they found Tiktaalik roseae. Credit: Academy of Natural Sciences of Drexel University

The researchers named the new fossil fish species Holoptychius bergmanni in honor of the late Martin Bergmann, former director of the Polar Continental Shelf Program (PCSP), Natural Resources Canada, the organization that provided logistical support during the team’s Arctic research expeditions spanning more than a decade. Bergmann was killed in a plane crash in 2011 shortly after the team’s most recent field season in Nunavut.

“We decided to choose Martin Bergmann to honor him, not ever having met him, but with the understanding that his work with PCSP made great strides in opening the Arctic to researchers,” said Downs. “It’s an invaluable project happening in the Canadian Arctic that’s enabling this type of work to happen.”

Bergmann’s organization assisted the research team with many aspects of expedition logistics including difficult flight operations to carry supplies and research personnel to remote research sites on Ellesemere Island. Daeschler described the pilots as capable of landing a Twin Otter aircraft almost anywhere, as long as the ground was solid – a condition they tested by briefly touching down the airplane and circling back to see if the tires left a deep mark in the mud.

Daeschler and colleagues intend to return to Ellesemere Island for another field expedition in the summer of 2013 to search for fossils in older rocks at a more northerly field site than the one where they discovered T. roseae and H. bergmanni.

A Deeper Look at the Devonian

Daeschler and a different co-author described another new species of Devonian fish in addition to H. bergmanni, in the same issue of the Proceedings of the Academy of Natural Sciences. More information about this new placoderm from Pennsylvania is available at the Drexel News Blog.

– See more at: http://drexel.edu/now/archive/2013/March/Fossil-Species-from-Fish-Eat-Fish-World/

Researchers Describe the Physical Forces Underlying Sickle Cell Disease

An oxygenated red blood cell (left) is disc-shaped and flexible. A red blood cell in a sickle disease patient, when not carrying oxygen, forms a larger, rigid sickle shape (right).

Originally posted on DrexelNow.

Researchers at Drexel University have identified the physical forces in red blood cells and blood vessels underlying the painful symptoms of sickle cell disease. Their experiment, the first to answer a scientific question about sickle cell disease using microfluidics engineering methods, may help future researchers better determine who is at greatest risk of harm from the disease. They report their findings in Cell Press’s Biophysical Journal today.

Capillary Blockage Conundrum

Like many scientific questions, this discovery began with a mystery. Normal, healthy red blood cells are extremely flexible, squeezing and slipping through blood vessels with ease, even passing through the smallest capillaries that are narrower than the red blood cells themselves. But in sickle cell disease, red blood cells are prone to deforming and turning rigid while flowing through the body. A seemingly logical explanation for sickle cell disease was that its symptoms – painful episodes and organ damage caused by oxygen deprivation – resulted from the rigid sickle cells forming inside narrow capillaries and then getting stuck there.

In fact, sickle cells do not get stuck inside capillaries. The symptoms of sickle cell disease come from partial obstructions in slightly wider blood vessels farther downstream—vessels wide enough that sickle cells should be wide enough to flow through. The mystery, then, was why? How do wide, rigid cells regularly pass through the narrowest channels without getting stuck?

To find out, the Drexel researchers developed an experimental setup to test flow through a model blood vessel.

“We created a channel, using microfluidic methods, that would be comparable in size to a human capillary,” explained Dr. Frank Ferrone, a professor of physics in Drexel’s College of Arts and Sciences and senior associate vice provost for Research, who was the study’s senior author.

Ferrone and colleagues took advantage of the fact that, for as long as they are carrying oxygen, red blood cells in sickle disease patients remain as squishy as healthy red blood cells. “They are the functional equivalent of a beanbag,” Ferrone said.

It is only after delivering their cargo to the body that hemoglobin molecules become prone to an internal reaction that turns the squishy “beanbag” cells rigid.

To test why the rigid cells do not get stuck in narrow capillaries, the researchers parked a red blood cell from a sickle patient at the center of their artificial narrow channel while the cell was still in its flexible state. Then, using a laser method, they induced the cell’s hemoglobin to begin the polymerization reaction that leads to sickling. Then they gradually raised the pressure at one end of the channel. They repeated this experiment multiple times with multiple different red blood cells. The amount of pressure required to dislodge the cells reached its maximum near 100 pascal.

“On the scale of pressures between arteries and veins, that’s not a whole lot,” Ferrone said. The pressure required to dislodge a rigid cell from inside a capillary is within the range of typical pressures in these blood vessels.

Uncooked Spaghetti in the Beanbag

Based on this experiment, Ferrone said, “we understand these processes in fundamental physical terms – we know how the stiffness of sickle cell arises, in other words – and so we have a more complete picture.”

That picture, Ferrone explained, describes what happens inside sickling cells as they turn from beanbag-like flexibility while carrying oxygen to rigid inflexibility.

Inside sickle cells, hemoglobin molecules remain separate when carrying oxygen (left). The molecules combine to form long, rigid polymer chains (right) when not carrying oxygen.
Inside sickle cells, hemoglobin molecules remain separate when carrying oxygen (left). The molecules combine to form long, rigid polymer chains (right) when not carrying oxygen.

Once the hemoglobin releases its oxygen, in sickle disease there is an ensuing molecular chain reaction between hemoglobin molecules to form long polymer chains that are rigid – a bit like uncooked spaghetti, according to Ferrone. As the spaghetti chains begin to grow inside the beanbag, the cell becomes less and less flexible.

However, if the cell is restrained inside a narrow channel when this reaction begins, its shape is physically restrained from growing outward. The rigid-spaghetti polymer chains inside the cell are blocked from growing beyond a certain length across its radial axis. They exert pressure outward on the cell membrane, thereby causing resistance. As observed in the experiment, that slight resistance requires a small amount of external pressure to dislodge cells from the capillary.

The researchers also found a relationship in their experiment that bolsters this explanation: the higher the concentration of hemoglobin in the cell, the greater the pressure required to dislodge the cell. This makes sense, Ferrone explained, because more hemoglobin would create more polymer chains pushing outward on the cell membrane.

Danger at Intermediate Speeds

Ferrone said these findings also indicate that the timing of polymerization inside sickle cells may be important to understanding patients’ susceptibility to symptoms.

The researchers described three potential scenarios for red blood cells turning rigid as they circulate in the bodies of sickle disease patients.

In the best-case scenario, the polymerization reaction is so slow that red blood cells remain flexible until they return to the lungs to pick up more oxygen.

The next-best scenario, which Ferrone said was somewhat surprising, is for hemoglobin to polymerize relatively quickly. If the cells begin to grow rigid while in a narrow capillary – the real-life equivalent of their experimental setup – then they will be forced into a skinny sausage shape. After passing through the capillary, rigid cells in that relatively thin shape can continue slipping through narrower spaces in wider vessels where partial obstructions have begun to form.

But intermediate-speed sickling is potentially most dangerous, according to the research team. If red blood cells flow past capillaries while still flexible, but later begin to grow rigid in a wider space, they are more likely to become both rigid when larger in size – making them susceptible to getting trapped in a vessel where previous sickle cells have already caused partial obstructions.

Ferrone suggested that this intermediate-speed danger may be a pitfall that investigators should avoid when developing therapies aimed at slowing the cell-sickling process.

Other authors of the paper with Ferrone were Dr. Alexey Aprelev, an assistant teaching professor of physics in Drexel’s College of Arts and Sciences, William Stephenson, a recent Drexel graduate who conducted work on this project for his undergraduate senior project in physics, Hongseok (Moses) Noh, an associate professor in the College of Engineering and Maureen Meier, a nurse at St. Christopher’s Hospital for Children.

– See more at: http://drexel.edu/now/archive/2012/October/Physics-of-Sickle-Cell-Disease/

Driver’s Side Mirror with No Blind Spot Receives U.S. Patent

Originally posted on DrexelNow.

A side mirror that eliminates the dangerous “blind spot” for drivers has now received a U.S. patent. The subtly curved mirror, invented by Drexel University mathematics professor Dr. R. Andrew Hicks, dramatically increases the field of view with minimal distortion.

Traditional flat mirrors on the driver’s side of a vehicle give drivers an accurate sense of the distance of cars behind them but have a very narrow field of view. As a result, there is a region of space behind the car, known as the blind spot, that drivers can’t see via either the side or rear-view mirror. It’s not hard to make a curved mirror that gives a wider field of view – no blind spot – but at the cost of visual distortion and making objects appear smaller and farther away.

Hicks’s driver’s side mirror has a field of view of about 45 degrees, compared to 15 to 17 degrees of view in a flat driver’s side mirror. Unlike in simple curved mirrors that can squash the perceived shape of objects and make straight lines appear curved, in Hicks’s mirror the visual distortions of shapes and straight lines are barely detectable.

Hicks, a professor in Drexel’s College of Arts and Sciences, designed his mirror using a mathematical algorithm that precisely controls the angle of light bouncing off of the curving mirror.

“Imagine that the mirror’s surface is made of many smaller mirrors turned to different angles, like a disco ball,” Hicks said. “The algorithm is a set of calculations to manipulate the direction of each face of the metaphorical disco ball so that each ray of light bouncing off the mirror shows the driver a wide, but not-too-distorted, picture of the scene behind him.”

Hicks noted that, in reality, the mirror does not look like a disco ball up close. There are tens of thousands of such calculations to produce a mirror that has a smooth, nonuniform curve.

Hicks first described the method used to develop this mirror in Optics Letters in 2008.

In the United States, regulations dictate that cars coming off of the assembly line must have a flat mirror on the driver’s side. Curved mirrors are allowed for cars’ passenger-side mirrors only if they include the phrase “Objects in mirror are closer than they appear.”

Because of these regulations, Hicks’s mirrors will not be installed on new cars sold in the U.S. any time soon. The mirror may be manufactured and sold as an aftermarket product that drivers and mechanics can install on cars after purchase. Some countries in Europe and Asia do allow slightly curved mirrors on new cars. Hicks has received interest from investors and manufacturers who may pursue opportunities to license and produce the mirror.

The U.S. patent, “Wide angle substantially non-distorting mirror” (United States Patent 8180606) was awarded to Drexel University on May 15, 2012.

– See more at: http://drexel.edu/now/archive/2012/June/Drivers-Side-Mirror-With-No-Blind-Spot-Receives-US-Patent/