Author Archive | American Physiological Society

Obesity creates wimpy rats

Obesity appears to impair normal muscle function in rats, an observation that could have significant implications for humans, according to Penn State researchers.
“Our findings demonstrate that obesity involves more than accumulating excess fat an…

The science behind the cape

Bethesda, Md. (Mar. 8, 2011) — What do you have when you line up a martial artist, acrobatic gymnast, police officer, firefighter, NASCAR driver, and NFL running back? “Watson,” the IBM super-computer that recently routed humanity’s best on …

Hyperoxia may slow formation of wrinkles

Bethesda, Md. (June 29, 2010) — It’s no secret that UVB radiation from the sun causes wrinkles. However, a Japanese study published in the American Journal of Physiology — Regulatory, Integrative and Comparative Physiology (http://ajpregu.physiology.org/)
indicates that oxygen may help combat the formation of wrinkles by lessening tissue damage done by UVB rays.

In the study, mice who were placed in an oxygen chamber after exposure to UVB radiation developed fewer wrinkles and showed fewer signs of tissue damage than mice who were exposed to UVB radiation alone.

UVB and Skin Damage

The readily visible hallmarks of skin damage are wrinkles and a thickening in the outer layer of skin, the epidermis. Together they make skin look and feel leathery.

The “sun-weathered” look is merely evidence of what is happening on a molecular level beneath the skin’s surface, however. When skin is repeatedly exposed to UVB radiation, new blood vessels form from existing blood vessels in the skin in a process called cutaneous angiogenesis. Several transcription factors — proteins that bind to specific DNA sequences — play a role in angiogenesis, including hypoxia inducible factor (HIF-1) and its subunit HIF-1 α and vascular endothelial growth factor (VEGF).

The Study

In the study, the researchers assigned 24 hairless mice into three groups. The control group, the UVB group, and the UVB+HO group. The control group was not exposed to UVB radiation. Both the UVB and the UVB+HO groups were exposed to UVB radiation by a special fluorescent lamp three times per week for five weeks, but the UVB+HO mice were placed in an oxygen chamber for two hours after each irradiation.

Over the five weeks, the mice in the UVB and UVB+HO groups developed wrinkles, but the wrinkles were more pronounced in the UVB group. Likewise, both the UVB and UVB+HO group experienced increased epidermal thickness, but again, this result was more pronounced in the UVB group.

There were differences between the UVB and UVB+HO groups on a molecular level, as well. The level of HIF-1α increased significantly in the UVB group compared to the control group, whereas there was no significant increase in the UVB+HO group. VEGF levels increased in both the UVB and the UVB+HO groups, but the UVB+HO group experienced a smaller increase. This implies that oxygen and the excess amount of oxygen in body tissue, or hyperoxia, that it provides can lessen skin damage and wrinkling caused by UVB radiation.

A Surprising Result

The study had one surprising result, as well, one involving molecules called matrix metalloproteinases (MMPs). Like HIF-1 α and VEGF, they play a role in angiogenesis. Two MMPs in particular, MMP-2 and MMP-9, are thought to accelerate wrinkling by degrading the outer components of cells. However, in this study, MMP-2 levels tended to decrease with exposure to UVB radiation and MMP-9 levels remained the same, even in mice who did not receive oxygen. According to the researchers, this implies that MMP-2 and MMP-9 are not main factors in wrinkle formation and angiogenesis, at least in the early stages of skin damage caused by UVB radiation.

The implications for humans remain to be seen, and the researchers note that further studies are required. In the meantime, the best way to avoid wrinkles caused by UVB radiation is to wear sunscreen.

Shigeo Kawada, Masaru Ohtani, and Naokata Ishii, all of the University of Tokyo, conducted the study. The study is entitled “Increased oxygen tension attenuates acute ultraviolet-B-induced skin angiogenesis and wrinkle formation” (doi:10.1152/ajpregu.00199.2010).

Editor’s Note: To arrange an interview with a member of the study team, or to receive a copy of the study, please contact Donna Krupa at (301) 634-7209 or dkrupa@the-aps.org.

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS) has been an integral part of this scientific discovery process since it was established in 1887.

Marmots can teach us about obesity

A nutrient that’s common to all living things can make hibernating marmots hungry – a breakthrough that could help scientists understand human obesity and eating disorders, according to a new study by a Colorado State University biologist.

The study appears in the current issue of the Journal of Experimental Biology. The full paper is available at http://jeb.biologists.org/cgi/reprint/213/12/2031.

Professor Greg Florant discovered he could slowly release a molecule called AICAR into yellow-bellied marmots that activates a neurological pathway driving food intake and stimulates appetite. The pathway, which shuts down during hibernation, relies on an important balance between two energy molecules — ATP and AMP. The lower the ratio between the two cellular molecules, the lower the energy in the cell and the more the appetite is stimulated.

Without this artificial stimulation, awake, hibernating marmots do not eat – even when researchers place food in front of them.

“The experimental group started to feed because they thought they had this energy deficit,” Florant said. “Then when the pumps dispensing the molecule finally stopped, the animals went right back into hibernation. That suggests to us that the animals are still sensing energy levels within cells during the hibernation period.”

Tissue samples taken from marmots in Florant’s lab allow researchers to identify biochemical processes and genes that are active during hibernation – as opposed to genes that are active when they’re feeding or engaging in other behaviors.

The American Physiological Society has called hibernators such as marmots, bears, woodchucks, hedgehogs and lemurs “medical marvels” because they can turn off their appetites and slow their breathing to a point that would be lethal to other animals.

Marmots typically hibernate for as many as six or seven months.

“You can’t eat if you’re asleep,” Florant said. “We’ve discovered that perhaps nutrients within the brain, such as fatty acids, can alter the food intake pathway, which normally shuts down when marmots hibernate. The perceived drop in energy nutrients (i.e. low ATP) makes the animals think they’ve got an energy deficit and want to eat.”

Florant said he’ll conduct additional research this summer to determine whether the reverse is true: Can he stop the animals from eating when they’re not hibernating?

His team will also identify neurons in the particular areas of the hypothalamus that are involved in food intake in animals. The hypothalamus is one of the master regulator areas of the brain and controls such activities as food intake, sex and temperature regulation.

“We know which neurons are driving this process,” he said. “We’re just trying to identify them within the marmot and distinguish what’s different about the neurons in a marmot compared to a rat or other animal that does not go into hibernation.”

Natural S-Equol suggested as critical component in SE5-OH for reducing menopausal hot flushes

Anaheim, Calif. (April 30, 2010) — Natural S-equol, a novel soy germ-based compound, is very likely the primary ingredient for reducing hot flushes in the dietary supplement SE5-OH, which is under development for reduction of menopause symptoms, according to pre-clinical efficacy data from studies using an animal model presented at the Experimental Biology (EB) 2010 annual meeting.

Exercise can forestall osteoporosis

AUGUSTA, Ga. — The stage for osteoporosis is set well before menopause — but exercise can help rewrite the script, according to Medical College of Georgia researchers.

Math used as a tool to heal toughest of wounds

COLUMBUS, Ohio — Scientists expect a new mathematical model of chronic wound healing could replace intuition with clear guidance on how to test treatment strategies in tackling a major public-health problem.

The story of the development of noninvasive heart care

BETHESDA, Md. (September 14, 2009) — Fifty-one years ago the average American home cost $30,000, Elvis Presley wooed listeners with Hard Headed Woman, and the hula hoop was introduced. That same year, 1958, a team comprised of a groundbreaking engineer — Dean Franklin — in concert with two exceptional physicians — Drs.

Estrogen can reduce stroke damage by inactivating protein

AUGUSTA, Ga. — Estrogen can halt stroke damage by inactivating a tumor-suppressing protein known to prevent many cancers, Medical College of Georgia researchers say.

“Our research suggests that estrogen suppresses p53 after stroke, which stops the damage,” says Limor Raz, a fourth-year Ph.D. student in the MCG School of Graduate Studies.