Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Isolated female rats subjected to a 30-minute stressor heal faster than males

28.02.2006


’Staggeringly stronger’ immune response may be why socially isolated women seem to be less susceptible to illness and death than isolated men. Gender difference in immune inflammatory response may be related to demands of motherhood.



Socially isolated female rats that experience stress generate a "staggeringly stronger" response to an immune challenge than similarly isolated and stressed males, according to a new study.

The difference in the female rats’ responses may stem from the demands of motherhood, researchers speculate in the study "Social isolation and the inflammatory response: sex differences in the enduring effects of a prior stressor" by Gretchen L. Hermes, Anthony Montag and Martha K. McClintock of the University of Chicago, and Louis Rosenthal of the University of Wisconsin, Madison. The study appears in the February issue of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, published by the American Physiological Society.


The study reinforces a growing body of evidence on health disparities between men and women and may shed light on why socially isolated men are more vulnerable to disease and death than isolated women, Hermes said.

Previous studies have established a link between stress and immune function, Hermes said. But this study looked at the long-lasting effect that three months of isolation (the equivalent of chronic social stress) and one 30-minute episode of acute physical stress had on the inflammatory response, the body’s innate immune response to bacteria, viruses, and parasites. The authors found that a full two to three weeks after being subjected to isolation and the acute physical stress, male rats showed a markedly slower healing response when injected with a foreign body compared to female rats, Hermes said.

This finding potentially has great clinical significance because the inflammatory response is an important immune response involved in many diseases, including heart disease, cancer, and infectious disease, said senior author Martha McClintock, director of the Institute for Mind and Biology at the University of Chicago.

Results show ’real life’ complexity; evolutionary benefits of motherhood? The experiment involved Norway rats, a particularly social species of rats that lives in large colonies of closely spaced burrows with cooperative grooming, feeding and rearing of offspring. "They are not just any old animal, but are gregarious, particularly the females," Hermes noted. "Removing them from their social context produces a profound effect."

The study covered three months, a significant portion of the rat’s life span, and showed the lasting effects of an acute stressor superimposed on the chronic social condition of isolation, Hermes said. Other studies have examined the cumulative effect of repeated stressors, with researchers measuring the immune response immediately after the stressful event. But in this study, the individual experiences a stressful event and sometime much later experiences an immune challenge. "This study is more like real life," she said.

This research dovetails with studies which have found that in times of stress, rats are more likely to give birth to female offspring than male offspring, McClintock said, suggesting that male offspring are less likely to survive under stressful circumstances. The study also fits with human studies, which found that socially isolated men are more likely to become ill and die sooner than similarly isolated women.

It is not clear why females heal more quickly than males under stress, but the authors said it may be a protection that evolved in the context of females protecting their offspring.

"While lactating, maternal rats become highly aggressive toward intruders and predators and are at high risk for wounding, particularly from neck bites that puncture the skin where the foreign substance was induced," the paper noted. "Stress-induced facilitation of the inflammatory response in threatened maternal rats would promote their healing and survival, with obvious benefit to her dependent offspring."

Females may have a different physiological response to stress that evolved differently from males because of motherhood. "For example, oxytocin, a hormone secreted by females in social contexts, may function as part of an alternative stress regulatory system that facilitates wound healing," the authors wrote.

Another possibility is that male and females experience stress differently, the study said. If females perceive the restraint as more traumatic, they may react more strongly to the stress associated with the induction of the foreign substance and have a stronger immune reaction.

Stressor simulates collapsed burrow The 120 rats in the study, 60 males and 60 females, were weaned 28 days after birth, and assigned to one of two groups: those that lived in their own cages (isolated) and those that lived in same-sex groups of five (non-isolated). The isolated and non-isolated groups had an equal number of males and females.

When the rats were 100 days old, the researchers subdivided the two groups. They placed half the isolated rats into the stressed group and half into the non-stressed group. They divided the non-isolated rats in the same way. The four resultant groups -- isolated and stressed, isolated and non-stressed, non-isolated and stressed, and non-isolated and non-stressed -- each had 15 females and 15 males.

The researchers then injected the two non-stressed groups, (isolated and non-isolated), with carrageenin (seaweed), a substance that doesn’t harm the rats but does challenge their immune systems. The immune system responds by walling off the carrageenin with scar tissue, then neutralizing and reabsorbing it, Hermes explained.

The rats in the stressed groups, both isolated and non-isolated, however, weren’t injected with the carrageenin at the 100-day mark. Instead, each was placed for 30 minutes in a restraint tube (the acute stressor). The restraint tube inhibits the rat from moving and simulates a collapsed burrow. The stressed animals were injected with carrageenin 14 days after they experienced the stress of the restraint tube.

When the researchers compared the two groups that were not stressed (isolated, non-stressed versus non-isolated, non-stressed), they found that the isolated female and male rats healed more slowly than the non-isolated female and male rats, Hermes said. In addition, the researchers found no significant differences in healing rates between the male and female rats within the isolated, non-stressed group. That is, healing was a function of whether the rat was isolated, not its gender.

But when rats experienced chronic social isolation and an acute stressor, the responses were the opposite for males and females: the stressor actually stimulated the healing response in females and delayed it in males, with stressed males generating a much weaker immune response to the carrageenin than the females, Hermes explained.

In fact, the females that experienced an acute restraint stress healed more rapidly than the female rats both isolated and non-isolated, that had not been stressed. "For whatever reason, a history of an acute stressor was immuno-enhancing for females of this species," Hermes said.

"This is striking, because it shows that, in effect, ’stress’ is not ’stress,’" McClintock added. "For females, the long-term social stressor and the brief physical stressor had opposite effects on immune function."

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

More articles from Studies and Analyses:

nachricht Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT

nachricht Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont

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: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>