Salamanders can regrow entire limbs and regenerate parts of major organs, an ability that relies on their immune systems, research now shows. 

A study of the axolotl, an aquatic salamander, reveals that immune cells called macrophages are critical in the early stages of regenerating lost limbs. Wiping out these cells permanently prevented regeneration and led to tissue scarring. The findings hint at possible strategies for tissue repair in humans.

"We can look to salamanders as a template of what perfect regeneration looks like," lead study author James Godwin said in a statement.

"We need to know exactly what salamanders do and how they do it well, so we can reverse-engineer that into human therapies," added Goodwin, of the Australian Regenerative Medicine Institute (ARMI) at Monash University in Melbourne. 

In mammals, macrophage cells play an important role in the immune system  response to injury, arriving at a wound within two to four days. There, they engulf and digest pathogens, or infectious particles, and generate both inflammatory and anti-inflammatory signals for healing. 

Now, Godwin and his colleagues have shown that macrophages are essential for salamanders' superherolike ability to sprout new limbs. The researchers studied the biochemical processes that occurred in salamanders at the site of a limb amputation. They then wiped out some or all of the macrophage cells to determine whether these cells were essential for regrowing the limbs.

Signals of inflammation  were detected at the wound sites within one day of the amputations. Unexpectedly, anti-inflammatory signals, which normally arrive later in mammals recovering from injury, were also present at that time. Along with these signals, the researchers detected macrophages at the wound, peaking in number around four to six days after the injury.

To investigate the role of macrophages in salamander limb regeneration, the researchers injected the animals with a chemical substance that destroys or "depletes" these cells. The macrophage levels were either partially or fully depleted.

Salamanders that had all their macrophages removed failed to generate new limbs and showed substantial scar-tissue buildup. Salamanders that had only some of their macrophages could still regenerate their limbs, but more slowly than normal.

Once the salamanders replenished their macrophage levels, the researchers re-amputated the animals' limb stumps, which then fully regenerated at the normal rate. Collectively, these findings suggest macrophages are essential to the salamanders' remarkable wound-healing abilities.

Studying the regenerative abilities of salamanders could offer insight into treating spinal cord and brain injuries in humans, the researchers say. Furthermore, the knowledge might lead to new treatments for heart and liver diseases or recovery from surgery, by preventing harmful scarring.

Macrophages are already known to play a vital role in organ and tissue development in mouse embryos. They produce small signaling molecules that activate other types of cells that promote the growth of new limbs and the healing of wounds.

Many animals may have a capability for tissue regeneration that has been turned off as the result of evolution, but it might be possible to reactivate the process, Godwin said.

The findings were detailed today (May 20) in the journal Proceedings of the National Academy of Sciences.

Original article on  LiveScience.com.

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There's really no other way to put this: During a Pilates stretching exercise, a 59-year-old woman said her body "swallowed" one of her breast implants. Sounds like something we just made up, but the woman's case is the subject of an unbelievable report, just published online in the latest New England Journal of Medicine. 

The woman was a breast cancer survivor who'd had a double mastectomy, and afterward had gotten breast implants. During a Pilates routine, she was doing a Valsalva maneuver, a breathing technique in which a person takes a deep breath and holds it while bearing down. (In other words, you're going through the motions of exhaling forcibly, but without letting any air escaping through the mouth or nose.)

Doing a Valsalva maneuver increases pressure inside your chest cavity. In this lady's case, enough pressure built to essentially send her right implant through the thin tissue between her ribs and into the space in between the lungs. This left her more perplexed than anything -- where did it go?! Fortunately (and incredibly), she said upon arriving in the the emergency department of the Johns Hopkins Hospital in Baltimore that she wasn't experiencing any chest pain or shortness of breath. 

"I can picture how this could happen in a freak occurrence," says Dr. Anthony Youn, a Michigan-based cosmetic surgeon and frequent contributor to msnbc.com, who didn't treat this patient but gave us his professional opinion on what the heck happened here.

Note that Youn called this a "freak occurrence" -- this is not exactly going to happen to your average Pilates lover, as this woman's case had some extra complications. She'd recently undergone a surgery to repair her heart's mitral valve, a procedure that typically involves some separating of the muscles that run between the ribs. 

"What likely happened in this instance is that the breast implant was placed under the chest muscle and on top of the ribs, an extremely common practice in breast reconstruction," Youn says. "When the patient Valsalva'd, the pectoralis (chest) muscle likely contracted and pushed the implant through the space between her ribs," which was particularly fragile after the valve surgery.

"The weakened scar tissue was easily torn, and the strength of the pectoralis muscle pushed the implant deep into her chest," Youn explains. 

The woman was treated at Johns Hopkins, where surgeons retrieved the implant from within her chest and put it back where it belonged. 

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The joke sounds like a mordant New Yorker cartoon, or a crack from Dennis Leary’s stand-up routine: A pizza delivery guy lies dead from a gunshot just steps from his destination. The waiting customers find the pizza and one asks “How much do we think we should tip him?”

But this really happened to a real pizza delivery guy and a group of hospital doctors who ordered the pizza, leading one of those doctors to ask Northwestern University bioethicist Katie Watson a question: “Was it wrong to make the joke?”

Watson, writing in a report for the Hastings Center, a bioethics think tank in Garrison, New York, answers no. “To me, the butt of the doctors’ tip joke is not the patient. It’s death,” she writes in the report.

Gallows humor is a time-honored coping mechanism. Soldiers, emergency room doctors and nurses, reporters, cops, even families facing the imminent death of a loved one engage in gallows humor, much of it utterly unprintable here. One of the funniest people I know worked as a “death counselor” for the terminally ill and tragically injured, and it was amazing what she could do with material like stab wounds and brain cancer.

In the case of the doctors, when they found the pizza man, they struggled to save his life and failed. Yet they had a shift to work at the hospital and more patients to help. Cracking a joke, as crass as it may seem upon reflection, helped them do that.

“Doctors are not robotic systems for healthcare delivery,” Watson said in an interview. “They are human beings. Yet they are expected to behave as if vomit doesn’t smell, and death is not scary.”

Some of what Watson calls “backstage” humor -- jokes and stories told among doctors, or teachers in a teachers’ lounge, or war reporters in a bar -- is a way to relieve tension and excise demons.

Which is not to say it’s always OK. Watson believes doctors, or anybody else, should be guided by the thought of harm. Who will a joke hurt? Is the humor making somebody a punching bag when a doctor’s real anger is toward, say, his or her boss? Could future patients be harmed in any way?

Of course not all doctors, or reporters, or school teachers, or firefighters, want to publicize the fact that they make cracks behind closed doors at all. One surgeon, Watson said, “was upset with me for discussing it outside the healthcare profession. She worried it would make patients trust doctors less.”

To which we say -- nyuk, nyuk, nyuk – give us the doctor who laughs.

Follow msnbc.com contributor Brian Alexander on Twitter.

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