How Blasts Injure the Brain

According to some estimates, more than 300,000 United States troops have suffered a traumatic brain injury (TBI) in the current wars in Iraq and Afghanistan. Most of these injuries have resulted from blasts from roadside bombs and other explosives planted by insurgents. The lack of knowledge about how an explosive blast injures the brain has hampered efforts to treat these injuries. Now, two studies offer a potentially important insight, pointing to a mechanism that hadn’t been considered before.

 

Occupational hazard. A new study provides clues about the cellular mechanisms of traumatic brain injury, a signature injury of the wars in Iraq and Afghanistan.

The lead author of the studies, Harvard University bioengineer Kevin Kit Parker, says he had a vested interest in the research. Parker shifted his focus from cardiac to brain research after two tours in Afghanistan as a U.S. Army infantry officer. “I kept seeing buddies of mine get hit and thought, ‘All right, I’ll take a look at this and see if I can get an angle on it.’ ”

Back at Harvard, Parker and his lab devised a blast simulator for cells. In one study, published today in PLoS ONE, the researchers grew rat neurons in a culture dish and then attached them to a sheet of stretchy polymer. A high-precision motor gave a carefully calibrated tug to the sheet to subject the neurons to mechanical forces Parker calculated to be comparable to those produced by an explosion.

Through a microscope, the researchers saw that the “blast” caused swelling, breakage, and other signs of injuries to the neurons’ spindly axons and dendrites, which send and receive signals from other neurons. A series of biochemical experiments found that the mechanical force disrupted proteins called integrins that help anchor cells to the scaffold of protein that surrounds them. Integrins have roles in a wide range of biochemical signaling pathways, but Parker’s team identified one particular pathway that seems to play a role in injury to axons. A drug that blocks a component of this cascade called Rho kinase reduced the damage to axons.

That result is intriguing given recent findings of damage to the brain’s white matter, which is made up of axons, in Iraq war veterans injured in blasts, Parker says. All the same, he cautions that much more work will be needed to see whether these culture dish findings are relevant to what happens in the brain of a soldier exposed to a blast. “It would be inappropriate to extrapolate from a dish to some dude’s head,” Parker says.

A second paper from Parker’s group, published last week in the Proceedings of the National Academy of Sciences, suggests that the same integrin-signaling mechanism may contribute to vasospasm, another harmful process associated with TBI. In experiments with muscle cells from the lining of blood vessels, the researchers found that a sudden mechanical force flips a genetic switch in these cells, making them more likely to contract. This contraction would choke off the blood supply wherever it occurs in the brain and exacerbate an injury by starving brain tissue of oxygen, Parker says.

“They’ve duplicated in vitro a finding that has been baffling to clinicians,” says Jack Tsao, a neurologist and neuroscientist at the Uniformed Services University of the Health Sciences in Bethesda, Maryland. Vasospasm typically results after a blow to the head causes bleeding in the space between the brain and the thin tissues that surround it. But in many troops with TBI from blasts, clinicians see stroke-like symptoms indicative of vasospasm even when brain scans show no evidence of bleeding. The new findings provide a possible explanation of how that could occur, Tsao says.

“These are both very elegant papers,” says David Hovda, a neuroscientist and director of the Brain Injury Research Center at the University of California, Los Angeles. Most research on the mechanisms of TBI has focused on neurochemical changes at the site of injury, such as metabolic alterations and ion imbalances inside neurons, he says. But the new findings suggest a mechanism that hasn’t been considered. The idea that integrins might play a role makes a lot of sense and raises interesting possibilities for treating TBI or minimizing its effects with drugs given prophylactically, he says.

Hovda says he sees no reason why these mechanisms wouldn’t contribute to other types of brain injury too, from car accidents to shaken baby syndrome. “I don’t think it’s specific to blast.”

Brains Grow at Earth’s Poles

 

Underneath those horned helmets, Vikings may have sported big brains. Like other residents of the dark north, however, the Scandinavian pillagers would’ve needed the grandiose noggins to see, not to sack cities. Scientists have long known that polar days tend to be shorter and dimmer, on average, than their equatorial counterparts. Northern and southern peoples seem to compensate much like owls do, scientists report online today in the Proceedings of the Royal Society B. The researchers examined 55 skulls dating back to the 1800s and taken from various parts of the world. They discovered that humans living along the tropics tend to have smaller eye sockets than people dwelling at higher and lower latitudes. Since bigger eyes absorb more light, large polar orbs could make up for the twilight conditions there. In fact, high- and low-latitude natives seem to see just as well in low light as tropical people do in bright light, according to the study. Cerebral size seems to grow by a few milliliters with increasing and decreasing latitude, probably because the brain’s visual centers expand as peepers widen.

History of medicine : Part 1

Learning from the past

Primitive humans called upon supernatural spirits to heal their sick while modern medicine relies on science. DNA and research has replaced spirits and shaman.

Looking at the history of medicine shows how ideas have developed over the centuries. Medieval barbers were the fore-runners of today’s skilled surgeons and the ancient Greeks set the foundations for modern diagnostic techniques. Leonardo da Vinci was amongst the first to dissect the human body to learn how it works. Medical students still learn about anatomy in the same way.

Today’s medicine has evolved over thousands of years as each generation built on the knowledge of earlier times. This will continue to happen. Our understanding of the human genome will lead to fresh treatments and new discoveries may open the door to unimagined advances in medicine.

8000 BC: Prehistoric medicine

It is difficult to imagine anything other than modern medical treatments but for thousands of years humans have become ill and for the same amount of time people have tried to cure them. Our ideas about medicines in prehistoric times come from archaeologists who have excavated and explored ancient sites. Their findings reveal a very different world to the one we experience today.

 

Link to the spirit world

Cave paintings and symbolic artefacts found by archaeologists suggest the earliest humans believed in spirits and supernatural forces. Animals, the stars, the land in which they lived and dead ancestors all inhabited a spirit world that was connected to their everyday life. Special individuals, like Shamen, were thought to be able to contact the spirit world and seek their guidance when they entered mysterious trances. These men and women would call upon the spirits to bring good hunting or heal the sick and were possibly the first doctors.

Spirit healers would perform ceremonies and cast spells to treat the sick. We also believe that they dispensed the first medicines. Drinking the blood of a wild animal killed in the hunt would give hunters special powers or eating special plants known only to the shaman could treat sickness. It is possible that these treatments would sometimes have a beneficial effect and it is thought that drugs like digitalis and morphine were first discovered in this way.

 

Primitive Brain Surgery

One form of primitive surgery seems quite shocking. Ancient skulls have been found with a hole bored into them. This appears to have been a deliberate operation and carried out whilst the person was still alive. We can only speculate as to the reason for this operation, called trepanning, but it may have been to allow the evil spirits to leave a sick person. Skulls show that the wounds healed and bone grew back so amazingly it appears that patients often survived this radical brain surgery.

Western medicine is based on scientific observation and experimentation. We no longer live in the mystical spirit world of the ancients but that does not mean that beliefs no longer play a part in healing. Many people still visit faith healers or follow alternative therapies that claim to tap into invisible forces of nature. Indeed, Shamen still play an important part in certain Native American and African cultures.