Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Constant lighting may disrupt development of preemie’s biological clocks

22.08.2006
Keeping the lights on around the clock in neonatal intensive care units may interfere with the development of premature babies’ biological clocks.

That is the suggestion of a new study reported in the Aug. 21 issue of the journal Pediatric Research.

The study, which was headed by Douglas McMahon, professor of biological sciences at Vanderbilt University and an investigator at the Vanderbilt Kennedy Center for Research on Human Development, reports that exposing baby mice to constant light keeps the master biological clock in their brains from developing properly and this can have a lasting effect on their behavior.

“We are interested in the effects of light on biological clocks because they regulate our physiology extensively, and also have an important effect on our mood,” McMahon said. “This study suggests that cycling the lights in NICUs may be better than constant lighting for premature babies’ from the perspective of developing their internal clocks.”

Every year about 14 million low-weight babies are born worldwide and are exposed to artificial lighting in hospitals.

“Today, we realize that lighting is very important in nursing facilities, but our understanding of light’s effects on patients and staff is still very rudimentary,” said William F. Walsh, chief of nurseries at Vanderbilt’s Monroe Carrel Jr. Children’s Hospital. “We need to know more. That is why studies like this are very important.”

Although older facilities still use round-the-clock lighting, modern NICUs, like that at Vanderbilt, cycle their lighting in a day/night cycle and keep lighting levels as low as possible, Walsh said. Also, covers are kept over the isolets that hold the babies in an effort to duplicate the dark conditions of the womb.

The finding that exposure to constant light disrupts the developing biological clock in baby mice provides an underlying mechanism that helps explain the results of several previous clinical studies. One found that infants from neonatal units with cyclic lighting tend to begin sleeping through the night more quickly than those from units with constant lighting. Other studies have found that infants placed in units that maintain a day/night cycle gain weight faster than those in units with constant light.

The research is a follow-up from a study that the McMahon group published last year which found that long periods of constant light disrupt the synchronization of the biological clock in adult mice. In all mammals, including mice and humans, the master biological clock is located in an area of the brain called the suprachiasmatic nuclei (SCN). It influences the activity of a surprising number of organs, including the brain, heart, liver and lungs and regulates the daily activity cycles known as circadian rhythms.

The SCN is filled with special neurons that are wired in such a way that their activity varies on a regular cycle of roughly 24 hours. In a normal brain, the activity of these clock neurons is synchronized to a single cycle which is set by the 24-hour day/night cycle.

McMahon’s previous study found that the SCN neurons in adult mice begin drifting out of phase after a mouse is exposed to constant light for about five months and that this is accompanied by a breakdown in their ability to maintain their normal nocturnal cycle.

“After we got this result, my post-doctoral fellow, Hidenobu Ohta, who is now a pediatrician at Tohoku University Hospital in Japan, wanted to study the impact of constant light on newborn mice because he was interested in finding out whether the use of constant light in NICUs may be having a similar effect,” McMahon said.

Newborn mice provide a good model for premature human infants because baby mice are born at an earlier stage of development than humans, a stage closely equivalent to that of premature babies.

“We found that the newborn mice were even more vulnerable to the effects of constant light than the adults,” McMahon said.

The researchers took two groups of newborn mice. One group was exposed to a normal cycle of 12 hours of light and 12 hours of darkness for the first three weeks of life. The second group was exposed to constant light for the same period. They used a special transgenic strain of mouse with an artificial gene that produces a green fluorescent protein under the control of one of the genes associated with the biological clock. As a result, when the neurons are active they produce a bright glow.

This allowed the scientists to determine that the SCN neurons in the baby mice who were exposed to a normal light cycle quickly became synchronized. By contrast, the clock neurons in baby mice exposed to constant light were unable to maintain coherent rhythms. However, when the constant-light mice were exposed to a day/night light cycle, the clock neurons rapidly fell into lock-step.

To get an idea whether the constant light exposure had any lasting impact, the scientists also exposed some of the mice to constant light for an additional four weeks and monitored their behavior. They found that two-thirds of the mice initially exposed to constant light were unable to establish a regular activity cycle during this extended period as measured by their use of the exercise wheel.

“We know that infants are strongly influenced by the rhythms of their mothers,” said McMahon. “But, even though the mothers maintained a regular cycle during the constant light period, the stimulatory effect of the light was strong enough to overcome their influence.”

In a separate study, newborn mice who had spent their first three weeks in a day/night cycle were exposed to constant light for an extended period were able to maintain their circadian rhythm for three to five months before their activity patterns became disrupted.

“This is a new area of research,” said McMahon, “so there are a lot of unanswered questions. For example, could disruption of a baby’s biological clock increase their vulnerability to associated mood disorders like depression and seasonal affective disorder? Could it make it harder for someone to adjust to shift work or suffer more from jet lag? All this is speculative at this point. But, certainly the data would indicate that human infants benefit from the synchronizing effect of a normal light cycle.”

Vanderbilt undergraduate Amanda Mitchell contributed to the study.

The research was funded by a grant from the National Institutes of Health.

Melanie Moran | Vanderbilt University
Further information:
http://www.vanderbilt.edu/exploration/stories/constantlight.html

More articles from Studies and Analyses:

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

nachricht A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>