Perched on a gurney at dawn, Kricket Jerná Nimmons, 40, kicked her feet giddily, like a girl on the edge of a pool, preparing to take a plunge. She wore a hospital gown and purple socks with paw prints. Her face was clean-scrubbed — “no lash, no makeup, just me” — and she looked at peace.
“So, this is it,” she said, exhaling theatrically, which is her way.
Females are better at discriminating among colors, researchers say, while males excel at tracking fast-moving objects and discerning detail from a distance—evolutionary adaptations possibly linked to our hunter-gatherer past.
The study, led by Brooklyn College psychology professor Israel Abramov, put young adults with normal vision through a battery of tests.
In color experiments the men and women tended to ascribe different shades to the same objects. The researchers think they know why.
"Across most of the visible spectrum males require a slightly longer wavelength than do females in order to experience the same hue," the team concludes in the latest issue of the journal Biology of Sex Differences.
Since longer wavelengths are associated with "warmer" colors, an orange, for example, may appear redder to a man than to a woman. Likewise, the grass is almost always greener to women than to men, to whom verdant objects appear a bit yellower.
The study also found that men are less adept at distinguishing among shades in the center of the color spectrum: blues, greens, and yellows.
Where the men shone was in detecting quick-changing details from afar, particularly by better tracking the thinner, faster-flashing bars within a bank of blinking lights.
The team puts this advantage down to neuron development in the visual cortex, which is boosted by masculine hormones. Since males are flush with testosterone, in particular, they're born with 25 percent more neurons in this brain region than females, the team noted.
The vision findings support the so-called hunter-gatherer hypothesis, which argues that the sexes evolved distinct psychological abilities to fit their prehistoric roles, the team says. (See "Sex-Based Roles Gave Modern Humans an Edge, Study Says.")
Noting that men in the study showed "significantly greater sensitivity for fine detail and for rapidly moving stimuli," the researchers write that their hunter forebears "would have to detect possible predators or prey from afar and also identify and categorize these objects more easily."
Meanwhile, the vision of female "gatherers" may have become better adapted recognizing close-at-hand, static objects such as wild berries.
John Barbur, professor of optics and visual science at City University London, noted that females are often "worse off in terms of absolute chromatic [color] sensitivity than males."
But when it comes to noticing subtle differences among shades of a color, women do tend to come out on top, as they did in Abramov's experiments, said Barbur, who wasn't part of the new study.
"If you're not dealing with the absolute sensitivity for color detection but the way in which colors are judged—such as the ability to describe a color, or what that color means, and so on," he said, "I'd say that females are definitely much better than males."
Within a year, maybe in just a few months, a young soldier with a horrific injury from a bomb blast in Afghanistan will have an operation that has never been performed in the United States: a penis transplant.
The organ will come from a deceased donor, and the surgeons, from Johns Hopkins University School of Medicine in Baltimore, say they expect it to start working in a matter of months, developing urinary function, sensation and, eventually, the ability to have sex.
From 2001 to 2013, 1,367 men in military service suffered wounds to the genitals in Iraq or Afghanistan, according to the Department of Defense Trauma Registry. Nearly all were under 35 and were hurt by homemade bombs, commonly called improvised explosive devices, or I.E.D.s. Some lost all or part of their penises or testicles — what doctors call genitourinary injuries.
Missing limbs have become a well-known symbol of these wars, but genital damage is a hidden wound — and, to many, a far worse one — cloaked in shame, stigma and embarrassment.
“These genitourinary injuries are not things we hear about or read about very often,” said Dr. W. P. Andrew Lee, the chairman of plastic and reconstructive surgery at Johns Hopkins. “I think one would agree it is as devastating as anything that our wounded warriors suffer, for a young man to come home in his early 20s with the pelvic area completely destroyed.”
Only two other penis transplants have been reported in medical journals: a failed one in China in 2006 and a successful one in South Africa last year. The surgery is considered experimental, and Johns Hopkins has given the doctors permission to perform 60 transplants. The university will monitor the results and decide whether to make the operation a standard treatment. The risks, like those of any major transplant operation, include bleeding, infection and the possibility that the medicine needed to preventtransplant rejection will increase the odds of cancer.
Dr. Lee cautioned that patients should be realistic and not “think they can regain it all.” But doctors can give the recipients a range of what to expect.
Surgeons are preparing to perform the first penis transplant in the United States.
RECIPIENT
DONATION
An organ donor who has recently died will have his penis removed, with the permission of his family.
CONNECTION
Major blood vessels and nerves will be connected to the recipient and stitched together under a microscope.
FUNCTION
If the operation is successful, doctors hope that sexual function will be possible once the recipient’s nerves grow into the transplant, a process that could take several months.
Urethra
Arteries
Veins
Nerves
DONOR
PENIS
“Some hope to father children,” Dr. Lee said. “I think that is a realistic goal.”
Just the penis will be transplanted, not the testes, where sperm are produced. So if a transplant recipient does become a father, the child will be his own genetically, not the offspring of the donor. Men who have lost testicles completely may still be able to have penis transplants, but they will not be able to have biological children.
In the 2006 case in China, the recipient asked that the transplant be removed a few weeks after the operation because of “apparent psychological rejection,” the Johns Hopkins doctors said, adding that in photographs the transplant had patches of dead and peeling skin, possibly from inadequate blood flow.
But the South African recipient, a young man whose penis had been amputated because of a botched circumcision, recently became a father, said Dr. Gerald Brandacher, the scientific director of the reconstructive transplantation program at Johns Hopkins.
Doctors who treat young men wounded in combat say that no matter how bad their other injuries are, the first thing the men ask about when they wake up from surgery is whether their genitals are intact.
“Our young male patients would rather lose both legs and an arm than have a urogenital injury,” said Scott E. Skiles, the polytrauma social work supervisor at the Veterans Affairs Palo Alto Health Care System.
Sgt. First Class Aaron Causey, who lost both legs, one testicle and part of the other from an I.E.D. while in Afghanistan with the Army in 2011, said the testicular damage was the most troubling of his injuries.
“I don’t care who you are — military, civilian, anything — you have an injury like this, it’s more than just a physical injury,” Sergeant Causey said.
Some doctors have criticized the idea of penis transplants, saying they are not needed to save the patient’s life. But Dr. Richard J. Redett, director of pediatric plastic and reconstructive surgery at Johns Hopkins, said, “If you meet these people, you see how important it is.”
“To be missing the penis and parts of the scrotum is devastating,” Dr. Redett said. “That part of the body is so strongly associated with your sense of self and identify as a male. These guys have given everything they have.”
Jeffrey Kahn, a bioethicist at Johns Hopkins, said that at a conferenceconvened last year by the Bob Woodruff Foundation, which aids injured veterans, wives said that genitourinary injuries had eroded their husbands’ sense of manhood and identity. Most telling, Dr. Kahn said, was that the men themselves attended the conference but did not speak about their wounds.
Although surgeons can create a penis from tissue taken from other parts of a patient’s own body — an operation being done more and more on transgender men — erections are not possible without an implant, and the implants too often shift position, cause infection or come out, Dr. Redett said. For that reason, he said, the Johns Hopkins team thinks transplants are the best solution when the penis cannot be repaired or reconstructed. If the transplant fails, he said, it will be removed, leaving the recipient no worse off than before the surgery.
But can men — and their partners — get used to the idea that their most intimate part came from another man’s body?
The best analogy is hand transplants, Dr. Brandacher said, because hands are personal and distinctive — a transplant that the recipient can see, unlike a kidney or liver.
“I can tell you from all the patients — and I’ve been involved since 1998 — every single one, after surgery, look at the graft, try to move it and they immediately call it ‘my hand,’ ” Dr. Brandacher said. “They immediately incorporate it as part of their body. I would assume, extrapolating, that this is going to be the same for this kind of transplant.”
Dr. Kahn said it was essential that the families of organ donors be asked specifically for permission to use the penis, just as special permission was required for face and hand transplants. It is not assumed that people willing to donate kidneys or livers will also consent to having their loved one’s genitals removed. The surgeons want a relatively young donor to increase the odds that the transplanted organ will function sexually.
For now, the operation is being offered only to men injured in combat, Dr. Lee said. It is not available to transgender people, though that may change in the future.
“Once this becomes public and there’s some sense that this is successful and a good therapy, there will be all sorts of questions about whether you will do it for gender reassignment,” Dr. Kahn said. “What do you say to the donor? A 23-year-old wounded in the line of duty has a very different sound than somebody who is seeking gender reassignment.”
For a transplant to be possible, certain nerves and blood vessels have to be intact in the recipient, as does the urethra, the tube that carries urine out of the body. The screening process, as for any organ transplant, also involves making sure that the candidate is psychologically ready, understands the risks and benefits, can stick to the regimen of anti-rejection medicine and has a family support network.
A few initial candidates are being evaluated. “We have one that we’re moving forward with, and we’re very far in the process,” Dr. Redett said, adding that he expected the patient to be put on the transplant waiting list soon. “That means you are really only waiting for a donor.”
Comparing the surgery to hand transplants performed at Johns Hopkins, he estimated the cost at $200,000 to $400,000 per operation. He said the Department of Veterans Affairs would pay for the drug that the men will need to prevent transplant rejection.
The project has been years in the making, the doctors said, with extensive research and practice surgery on cadavers. Some of the work involved injecting brightly colored food dyes into the cadavers to map out thecirculatory system in the penis. Dr. Lee said the research had found previously unknown aspects of its blood supply, which will be critical to the transplant’s success.
The operation should take about 12 hours, Dr. Lee said. The surgeons will connect two to six nerves, and six or seven veins and arteries, stitching them together under a microscope.
For the first few weeks after the surgery, a catheter will be left in place to drain urine. Sexual function will take longer to develop — probably a few months, Dr. Lee said. He said nerves would grow from the recipient into the transplant at a rate of about one inch per month, so the timing will depend in part on the extent of the recipient’s injuries and how far the nerves need to go.
After the transplant, the men will begin taking anti-rejection medication and will need it for the rest of their lives. Such drugs work by suppressing the immune system and can increase the odds of infections and cancer.
To minimize the risks, the Johns Hopkins team has found a way to use just one drug, rather than the three usually needed for other transplants. At the time of the penis transplant, they will treat the recipient with a medication that reduces immune system cells. About two weeks later, he will receive an infusion of stem cells from the donor. The infusion dials back the tendency of the recipient’s immune system to attack the transplant, and just one anti-rejection drug, tacrolimus, is then enough to keep it in check. Doctors have used this technique successfully in patients who have had hand transplants.
Ultimately, the goal is to restore function, not just form or appearance, Dr. Brandacher emphasized. That is what the recipients want most.
“They say, ‘I want to feel whole again,’ ” Dr. Brandacher said. “It’s very hard to imagine what it means if you don’t feel whole. There are very subtle things that we take for granted that this transplant is able to give back.”
Scientists are investigating the epigenetics of fatherhood: how a man’s experiences can alter his sperm, and whether those changes in turn may alter his children.CreditDann Tardif/LWA, via Corbis
In 2013, an obese man went to Hvidovre Hospital in Denmark to have his stomach stapled. All in all, it was ordinary bariatric surgery — with one big exception.
A week before the operation, the man provided a sperm sample to Danish scientists. A week after the procedure, he did so again. A year later, he donated a third sample.
Scientists were investigating a tantalizing but controversial hypothesis: that a man’s experiences can alter his sperm, and that those changes in turn may alter his children.
That idea runs counter to standard thinking about heredity: that parents pass down only genes to their children. People inherit genes that predispose them to obesity, or stress, or cancer — or they don’t. Whether one’s parents actually were obese or constantly anxious doesn’t rewrite those genes.
Yet a number of animal experiments in recent years have challenged conventional thinking on heredity, suggesting that something more is at work.
In 2010, for example, Dr. Romain Barres of the University of Copenhagen and his colleagues fed male rats a high-fat diet and then mated them with females. Compared with male rats fed a regular diet, those on the high-fat diet fathered offspring that tended to gain more weight, develop more fat and have more trouble regulating insulin levels.
Eating high-fat food is just one of several experiences a father can have that can change his offspring. Stress is another. Male rats exposed to stressful experiences — like smelling the odor of a fox — will father pups that have a dampened response to stress.
To find the link between a father’s experiences and his offspring’s biology, scientists have taken a close look at sperm. A sperm cell delivers DNA to an egg, of course. But those genes are regulated by swarms of molecules, so-called epigenetic factors.
These molecules can respond to environmental influences by silencing some genes and activating others as needed. Some studies suggest the changes in epigenetic factors can be handed down to offspring via sperm.
When Dr. Tracy L. Bale, a neuroscientist at the University of Pennsylvania, and her colleagues looked at the sperm of stressed male rats, for example, they found unusual levels of epigenetic molecules called microRNAs.
They created a cocktail of microRNAs and injected them into embryos from mellow fathers. As Dr. Bale and her colleagues reported recently, the embryos developed into rats with altered stress responses.
The notion that environmental responses might influence human health in similar ways has huge implications. But scientists have only started to investigate the epigenetics of fatherhood. As is often the case when scientists turn from animal experiments to humans, the results have been provocative but hardly clear-cut.
Are changes like these actually caused by men’s obesity? Dr. Barres and his colleagues set out to investigate that potential link in two ways.
First, they collected sperm from 10 obese Danish men and 13 lean ones. They found numerous epigenetic differences. One type of epigenetic factor they looked at involved molecular caps that are placed on DNA in a process called methylation. Dr. Barres and his colleagues found more than 9,000 genes in which the methylation pattern differed between lean and obese men.
Then the scientists recruited six obese men getting bariatric surgery to see how losing weight changed these methylation patterns. In a report published on Thursday in the journal Cell Metabolism, Dr. Barres and his colleagues identified more than 3,900 genes that were methylated differently a year after surgery.
Among the genes that are epigenetically altered are those that affect such behaviors as appetite control. But the new study does not show whether those changes have any effect on a father’s children, Dr. Barres said.
“I don’t want to speculate whether it’s positive or negative in the following generation,” he said.
Dr. Barres and his colleagues are now expanding on the study by comparing epigenetic patterns in the sperm of obese fathers with the patterns in the blood cells of their offspring. “We’re going to try to see if there’s something transmitted all the way down,” Dr. Barres said.
Other scientists had mixed views about the study. On one hand, they agreed that the researchers used sophisticated methods to survey epigenetic differences in the sperm. But they were wary of drawing broad conclusions.
Dr. John M. Greally, an epigenetics expert at the Albert Einstein College of Medicine, said it was possible that genetic differences between the men were mostly to blame for the differences seen in their sperm.
He also shared a concern with Dr. Bale and Dr. Soubry that the study involved too few men. The differences in such a small sample might have occurred randomly.
“Honestly, I think a lot of what they have is noise,” Dr. Greally said.
That doesn’t mean that Dr. Greally thinks the Danish scientists are wrong, but rather that pinning down the epigenetic effects that fathers pass to their children will take much more work.
“I’d say, let’s do a study of hundreds of people,” Dr. Greally said. “It’s doable. It just requires that we’re bold about doing these things.
