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Research Roundup

How Do Otters Remain Sleek and Warm?

Unlike many other mammals that spend a considerable amount of time in the water–polar bears, seals, dolphins, and whales–river otters do not have a thick layer of body fat to keep warm. Instead, they rely on their fur and the densely packed layer of specially adapted underhairs.

Using scanning electron microscopy and polarizing light microscopy, Dr. John W. Weisel,professor of cell and developmental biology in the School of Medicine, and colleagues, examined the structure of these hairs for clues to their exceptional insulation abilities. They found that the cuticle surface structure of the underhairs and base of the less-abundant guard hairs are distinctively shaped to interlock, with wedge-shaped fins or petals fitting into wedge-shaped grooves between fins of adjacent hairs. Dr. Weisel and colleagues reported their findings in the Canadian Journal of Zoology.

Dr. Weisel and research specialist Chandrasekaran Nagaswami, also in the department of cell and developmental biology, usually work on defining the physical properties of blood clots and applying this knowledge to find better treatments for heart disease.

“Most hair from animals has a distinctive pattern, which is how we can distinguish one species from another,” says Dr. Weisel. The fins of one hair loosely insert into the grooves between fins of an adjacent hair, thus permitting the hairs to form a web-like pattern that keeps water from the otter’s skin and decreases heat loss. Also, the grooves between fins trap air bubbles, which help increase the thermal insulation of the otter’s coat. Indeed, biologists have observed otters actively blowing air bubbles into their fur while grooming, and their energetic rolling catches air in their fur. “The air insulates like a down jacket,” explains Dr. Weisel.

A common otter behavior is their constant grooming. This behavior is another important aspect of an otter’s heat-sparing abilities. In addition to the interlocking structure of the underhairs, these hairs are coated with a thin layer of body oil from the otter’s sebaceous glands, thus providing another barrier to water. The fins of the underhairs are also aligned away from the body, which is consistent with the direction in which otters run their paws through their hair during this self-grooming, thereby ensuring that their claws do not get caught on the fin-like projections.

Impact of Bupropion in Smoking Cessation Treatment

A study by researchers at the Transdisciplinary Tobacco Use Research Center (TTURC) at the School of Medicine indicates that a smoker’s genetic make-up may affect whether they quit or not while using either bupropion (Zyban®) or nicotine replacement therapies (NRTs) such as the nicotine patch or nasal spray. The results appear in the August issue of Neuropsychopharmacology.

“This study provides new evidence that genetic differences in the brain-reward pathways of smokers may reveal whether they would benefit more from Zyban® or nicotine replacement therapy as an aid to quitting smoking,” said lead author Dr. Caryn Lerman, director of the TTURC and associate director for Cancer Control Population Sciences at the Abramson Cancer Center.   

Dr. Lerman led a research team that completed two randomized clinical trials each with a six-month follow-up period: a double blind placebo-controlled trial of bupropion and an open-label trial of transdermal nicotine patch versus nicotine nasal spray. Both trials examined the roles of functional genetic variation in the dopamine D2 Receptor (DRD2) gene called DRD2–141C. At this location in the DRD2 gene, people carry one of two different variants, a Del C variant or an Ins C variant (Del is for deletion and Ins is for Insertion). The research team found that smokers with two copies of the DRD2–141 Ins C variant were significantly more likely to be abstinent at the six-month follow-up if they used Zyban®, as compared to smokers carrying the Del C variant. By contrast, smokers carrying the Del C variant had significantly higher quit rates if they used NRTs as compared to those with the Ins C variant.

This research may have important implications for the delivery of quit-smoking medications that are targeted to individual smokers’ needs. “Although these results require confirmation in a larger study prior to translation to practice,” said Dr. Lerman, “they do suggest that genetic information may be useful in selecting the type of nicotine dependence treatment that will be most beneficial for a particular smoker.”

Implantable Pump Device to Treat Heart Disease

Cardiothoracic surgeons at HUP are helping to pave the way for new implantable pump devices to treat end-stage heart disease. As part of a nationwide clinical trial, HUP cardiothoracic surgeons have become the first in the region to implant a HeartMate II Left Ventricular Assist System into a patient for ongoing, permanent support for late-stage heart failure, otherwise known as Destination Therapy. The adult male is now recovering after the procedure done on July 14.

“Before this procedure, this patient was dying of end-stage heart failure. He reported that his quality-of-life was seriously diminished and his clinical condition suggested that he had only a few more weeks to live,” said Dr. Michael Acker, chief of cardiothoracic surgery at HUP. “What makes this particular device so unique is that rather than mimicking the actual pumping motion of the heart, it works to put out a continuous flow of blood. And it’s only about the size of your thumb. It will require less surgical trauma than other current devices and it can be used in smaller people like women and children.”

The HeartMate II device is powered by a rotary pumping mechanism, with one moving part, and weighs only about 14 ounces. It is much smaller and quieter than other currently approved devices. The device is implanted alongside a patient’s heart and takes over the job of moving along the blood of the weakened heart’s left ventricle. An external controller regulates pump speed and a power cable connects the device to a small monitor and power base unit. It’s about 1.8 inches in diameter and 3.2 inches long. It pumps blood from the heart throughout the body at up to 10 liters per minute, the full output of a healthy heart. It’s designed for reliable long-term support to improve outcomes and quality of life.

Dr. Rohinton Morris, surgical director of the Heart Transplant Program at HUP added, “The axial flow device is a significant addition to the various surgical methods of treating end-stage heart failure. It is a major advance in treatment, and holds high promise for the future.”

Thoratec, the maker of the HeartMate II Left Ventricular Assist System, says it’s designed to address the need for smaller, long lasting devices in Destination Therapy for patients requiring long-term cardiac support. The clinical study is being held at 27 centers across the nation, including HUP.

DNA-Based Sensors for Nano-Tongues and Nano-Noses

Nano-sized carbon tubes coated with strands of DNA can create tiny sensors with abilities to detect odors and tastes, according to researchers at Penn and Monell Chemical Sciences Center. Their findings are published in the September issue of the journal Nano Letters, a publication of the American Chemical Society.

According to the researchers, arrays of these nanosensors could detect molecules on the order of one part per million, akin to finding a one-second play amid 278 hours of baseball footage or a single person in Times Square on New Years’ Eve. In the report, the researchers tested the nanosensors on five different chemical odorants, including methanol and dinitrotoluene, or DNT, a common chemical that is also frequently a component of military-grade explosives.  The nanosensors could sniff molecules out of the air or taste them in a liquid, suggesting applications ranging from domestic security to medical detectors.  

“What we have here is a hybrid of two molecules that are extremely sensitive to outside signals:  single stranded DNA, which serves as the ‘detector,’ and a carbon nanotube, which functions as ‘transmitter,’” said Dr. A. T. Charlie Johnson, associate professor of physics and astronomy.  “Put the two together and they become an extremely versatile type of sensor, capable of finding tiny amounts of a specific molecule.”               

Given the size of such sensors, each carbon nanotube is about a billionth of a meter wide. Dr. Johnson and his colleagues believe arrays of these sensors could serve as passive detection systems in almost any location.  The sensor surface is also self-regenerating, with each sensor lasting for more than 50 exposures to the targeted substances, which means they would not need to be replaced frequently.

The specificity of single-stranded DNA is what makes these sensors so capable.  These biomolecules can be engineered, in a process called directed evolution, to recognize a wide variety of targets, including small molecules and specific proteins.    

Likewise, the nanotubes are ideal for signalling when the DNA has captured a target molecule. Single-walled nanotubes are formed from a single sheet of carbon molecules connected together and then rolled. It is a unique material in which every atom is on both the surface and the interior.  Although nanotubes have many applications, they are extremely sensitive to electrostatic variations in their environment, whether the nanotube is in a liquid or in air.

According to Dr. Johnson, an array of 100 sensors with different response characteristics and an appropriate pattern recognition program would be able to identify a weak known odor in the face of a strong and variable background.

“There are few limits as to what we could build these sensors to detect, whether it is a molecule wafting off an explosive device or the protein byproduct of a cancerous growth,” Dr. Johnson said.  

Researchers involved in the project include Cristian Staii, a graduate student in physics and astronomy; Michelle Chen, a graduate student in material science and engineering; and Dr. Alan Gelperin of Monell.

 

 



 
  Almanac, Vol. 52, No. 6, October 4, 2005

ISSUE HIGHLIGHTS:

Tuesday,
October 4, 2005
Volume 52 Number 6
www.upenn.edu/almanac

 

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