(Press-News.org) Using an innovative method, EPFL scientists show that the brain is not as compact as we have thought all along.
To study the fine structure of the brain, including its connections between neurons, the synapses, scientists must use electron microscopes. However, the tissue must first be fixed to prepare it for this high magnification imaging method. This process causes the brain to shrink; as a result, microscope images can be distorted, e.g. showing neurons to be much closer than they actually are. EPFL scientists have now solved the problem by using a technique that rapidly freezes the brain, preserving its true structure. The work is published in eLife.
The shrinking brain
Recent years have seen an upsurge of brain imaging, with renewed interest in techniques like electron microscopy, which allows us to observe and study the architecture of the brain in unprecedented detail. But at the same time, they have also revived old problems associated with how this delicate tissue is prepared before images can be collected.
Typically, the brain is fixed with stabilizing agents, such as aldehydes, and then encased, or embedded, in a resin. However, it has been known since the mid-sixties that this preparation process causes the brain to shrink by at least 30 percent. This in turn, distorts our understanding of the brain's anatomy, e.g. the actual proximity of neurons, the structures of blood vessels etc.
The freezing brain
A study by Graham Knott at EPFL, led by Natalya Korogod and working with Carl Petersen, has successfully used an innovative method, called "cryofixation", to prevent brain shrinkage during the preparation for electron microscopy. The method, whose roots go back to 1965, uses jets of liquid nitrogen to "snap-freeze" brain tissue down to -90oC, within milliseconds. The brain tissue here was mouse cerebral cortex.
The rapid freezing method is able to prevent the water in the tissue from forming crystals, as it would do in a regular freezer, by also applying very high pressures. Water crystals can severely damage the tissue by rupturing its cells. But in this high-pressure freezing method, the water turns into a kind of glass, preserving the original structures and architecture of the tissue.
The next step is to embed the frozen tissue in resin. This requires removing the glass-water and replacing it first with acetone, which is still a liquid at the low temperatures of cryofixation, and then, over a period of days, with resin; allowing it to slowly and gently push out the glassified water from the brain.
The real brain
After the brain was cryofixed and embedded, it was observed and photographed in using 3D electron microscopy. The researchers then compared the cryofixed brain images to those taken from a brain fixed with an "only chemical" method.
The analysis showed that the chemically fixed brain was much smaller in volume, showing a significant loss of extracellular space - the space around neurons. In addition, supporting brain cells called "astrocytes", seemed to be less connected with neurons and even blood vessels in the brain. And finally, the connections between neurons, the synapses, seemed significantly weaker in the chemically-fixed brain compared to the cryofixed one.
The researchers then compared their measurements of the brain to those calculated in functional studies - studies that measure the time it takes for a molecule to travel across that brain region. To the researchers' surprise, the data matched, adding even more evidence that cryofixation preserves the real anatomy of the brain.
"All this shows us that high-pressure cryofixation is a very attractive method for brain imaging," says Graham Knott. "At the same time, it challenges previous imaging efforts, which we might have to re-examine in light of new evidence." His team is now aiming to use cryofixation on other parts of the brain and even other types of tissue.
INFORMATION:
This work was funded by the Swiss National Science Foundation.
Reference
Korogod N, Petersen C, Knott G. Ultrastructural analysis of adult mouse neocortex comparing aldehyde perfusion with cryo fixation. eLife 11 August 2015. DOI: http://dx.doi.org/10.7554/eLife.05793
1. Clinical scoring system suggests possibility of more precise colon cancer screening
Free abstract: http://www.annals.org/article.aspx?doi=10.7326/M14-1720
Editorial: http://www.annals.org/article.aspx?doi=10.7326/M15-1677
URLs go live when embargo lifts
A clinical scoring system for colon cancer risk could help physicians identify which average-risk patients could potentially skip a colonoscopy and instead be screened with a less-invasive method. The researchers suggest that this approach could increase the uptake and efficiency of colorectal cancer (CRC) ...
Hamilton, ON (Aug. 10, 2015) -McMaster University research, published online today by the Annals of Internal Medicine, has demonstrated the benefits of corticosteroid therapy for one of the most common serious medical conditions.
"Our study should lead to an important change in treatment for pneumonia," said lead author, Dr. Reed Siemieniuk, a physician and a graduate student at McMaster University. "Corticosteroids are inexpensive and readily available around the world. Millions of patients will benefit from this new evidence."
Lower respiratory infections are the ...
DALLAS, Aug. 10, 2015 -- If your dinner plate often includes fried chicken, gravy-smothered liver, buttered rolls and sweet tea -- your heart may not find it so tasty. Eating a Southern-style diet is associated with an increased risk of heart disease, according to research published in Circulation, an American Heart Association journal.
In a large-scale study that explored the relationship between dietary patterns and heart disease risk, researchers found that people who regularly ate traditional Southern fare -- which they characterized as fried foods, fatty foods, eggs, ...
DALLAS, Aug. 10, 2015 -- For the first time, experts urge early monitoring for heart and blood vessel disease among teens with major depression or bipolar disorder, according to an American Heart Association scientific statement.
"Major Depressive Disorder and Bipolar Disorder Predispose Youth to Accelerated Atherosclerosis and Early Cardiovascular Disease" is published in Circulation, a journal of the American Heart Association.
This statement makes recommendations to consider these mood disorders as independent, moderate risk factors for cardiovascular diseases ...
An international team of astronomers studying 200,000 galaxies has measured the energy generated within a large portion of space more precisely than ever before, discovering that it's only half what it was 2 billion years ago and fading - the Universe is slowly dying.
Researchers from the International Centre for Radio Astronomy Research (ICRAR) in Western Australia used seven of the world's most powerful telescopes to observe galaxies at 21 different wavelengths from the far ultraviolet to the far infrared.
Initial observations were conducted using the Anglo-Australian ...
An international team of astronomers studying more than 200 000 galaxies has measured the energy generated within a large portion of space more precisely than ever before. This represents the most comprehensive assessment of the energy output of the nearby Universe. They confirm that the energy produced in a section of the Universe today is only about half what it was two billion years ago and find that this fading is occurring across all wavelengths from the ultraviolet to the far infrared. The Universe is slowly dying.
The study involves many of the world's most powerful ...
Through identification of increased toxin production by epidemic forms of group A streptococcus (the "flesh-eating" bacterium), for the first time scientists are able to pinpoint the molecular events that contribute to large intercontinental epidemics of disease. The study was based on sequencing almost 5,000 group A streptococcus genomes collected over decades.
Researchers from Houston Methodist Research Institute, Houston Methodist Hospital, institutions in Finland and Iceland, and the U.S. National Institute of Allergy and Infectious Diseases report their discoveries ...
Fast Facts:
Study reveals simple things hospitals can do to improve a patient's experience, including ongoing rounds by nurses and hospital leadership.
Study findings outline the following core practices that high-ranking hospitals employ: a devotion to consistency, personal and focused interactions with patients, and a culture that demands involvement of all levels of caregivers and services.
Based on responses to questionnaires and letters sent to CEOs and medical personnel from a nationwide sample of 53 hospitals, Johns Hopkins investigators have identified ...
Athens, Ga. - The time since the introduction of a non-native marine species best explains its global range, according to new research by an international team of scientists led by University of Georgia ecologist James E. Byers. The study, published in the open access journal Nature Scientific Reports, also contains a warning: The vast majority of marine invaders have not yet finished spreading.
Invasion by non-native species is a worldwide problem that causes billions of dollars of damage annually--more than $120 billion in the U.S. alone, according to a 2005 study ...
Berkeley -- The effort to improve food safety by clearing wild vegetation surrounding crops is not helping, and in some cases may even backfire, according to a new study led by researchers at the University of California, Berkeley.
The findings, to be reported Monday, Aug. 10, in the journal Proceedings of the National Academy of Sciences, call into question the effectiveness of removing non-crop vegetation as a way to reduce field contamination of fresh produce by disease-causing pathogens. This practice led to extensive loss of habitat in a region that is globally ...
