Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Seals protect brain, conserve oxygen by turning off shivering response on icy dives

11.10.2006
Seals shiver when exposed to cold air but not when diving in chilly water, a finding that researchers believe allows the diving seal to conserve oxygen and minimize brain damage that could result from long dives.

The researchers presented the study at The American Physiological Society's conference "Comparative Physiology 2006: Integrating Diversity," in Virginia Beach, Va., October 8-11. The researchers, Arnoldus Schytte Blix, Petter H. Kvadsheim and Lars P. Folkow hail from the University of Tromsø, located above the Arctic Circle in Tromsø, Norway.

The research provides insight into how seals allow their bodies to cool (become hypothermic) during a dive, presumably to better cope with a lack of oxygen (hypoxia). Research into hypothermia and hypoxia is important because they are problems that affect people under a variety of circumstances. Doctors often are called upon to treat people who have suffered accidental hypothermia, for example, as a result of falling into the ocean or becoming lost during the winter. In addition, several hundred thousand people die or are irreversibly injured each year following cardiac arrest, stroke or respiratory disorders which cause inadequate oxygen supply to the brain, Folkow explained.

Folkow will present a second study on hypoxia, involving diving birds, at the conference. The study "Neuronal hypoxic tolerance in diving birds and mammals," examines how diving birds and seals preserve brain cell function in the face of oxygen deficits. The study is by Folkow, Stian Ludvigsen and Blix, of the University of Tromsø and Jan-Marino Ramirez of the University of Chicago.

Shivers produce warmth

Shivering is an involuntary response that consists of muscle contractions which produce warmth. Mammals and birds are physiologically programmed to shiver when body temperature drops below a certain "set-point."

While breathing air, seals shiver just like other animals. But when they dive below the surface in frigid water, shivering is switched off, the study found.

By shutting down the shivering response, a seal allows its body temperature to drop and achieves the benefits of hypothermia: a slower metabolism and lowered oxygen requirements which extends the dive time, Folkow said.

Taking the plunge

The seal experiment took place in a tank in which the seals took a series of experimental dives into cold water of 2-3° C. The researchers recorded shivering, heart rate, brain temperature and rectal temperature while the seals were on the surface and while they were diving.

The seals shivered on the surface but stopped or nearly stopped shivering when they dove, even though their bodies continued to cool. Their heart rates and temperatures dropped while they dove, but when they returned to the surface they restarted their shivering nearly immediately.

Seals have a remarkable capacity to store oxygen in their blood and muscles – four times as much as humans – to which they add this oxygen-conserving step of not shivering, Folkow said. By allowing body temperatures to drop, they slow metabolism and reduce oxygen demand. In addition, since shivering itself requires oxygen, there is an oxygen-conserving advantage to not shivering when diving.

In addition to slowing metabolism and generally reducing the need for oxygen, the researchers found that the seal's brain may cool about 3° C during the dives. The cooler brain requires less energy and oxygen and reduces the chance of damage caused by hypoxia, Folkow explained.

Achieved while remaining active

Seals have this physiological adaptation available just in case. This study found the seals can dive to more than 1,000 meters and for more than an hour. However, they usually take dives much shorter than their maximum capacity, and only occasionally perform very long dives. By limiting dive duration, seals maintain aerobic metabolism, avoid lactate buildup that occurs in the face of insufficient oxygen and require little time to recover, Folkow explained. Seals often spend 80-90% of their time at sea underwater, he said.

Seals in the wild occasionally dive for so long that they use nearly all their oxygen, but they can recover with these special adaptations. Humans cannot tolerate oxygen levels nearly so low as a seal can.

"Somehow they tolerate hypoxia better, we don't know why," Folkow said. The study of how seals handle this lack of oxygen may someday give us knowledge that is useful in treating people who have suffered severe hypoxia, although those advances are likely years in the future, he added.

Christine Guilfoy | EurekAlert!
Further information:
http://www.the-aps.org

More articles from Health and Medicine:

nachricht New antibody analysis accelerates rational vaccine design
09.08.2018 | Scripps Research Institute

nachricht Distrust of power influences choice of medical procedures
01.08.2018 | Johannes Gutenberg-Universität Mainz

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

Im Focus: A molecular switch may serve as new target point for cancer and diabetes therapies

If certain signaling cascades are misregulated, diseases like cancer, obesity and diabetes may occur. A mechanism recently discovered by scientists at the Leibniz- Forschungsinstitut für Molekulare Pharmakologie (FMP) in Berlin and at the University of Geneva has a crucial influence on such signaling cascades and may be an important key for the future development of therapies against these diseases. The results of the study have just been published in the prestigious scientific journal 'Molecular Cell'.

Cell growth and cell differentiation as well as the release and efficacy of hormones such as insulin depend on the presence of lipids. Lipids are small...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

NRL's sun imaging telescopes fly on NASA Parker Solar Probe

13.08.2018 | Physics and Astronomy

UT-ORNL team makes first particle accelerator beam measurement in six dimensions

13.08.2018 | Physics and Astronomy

ASU astrophysicist helps discover that ultrahot planets have starlike atmospheres

13.08.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>