Your mother *is* always with you

Mother and child, microchimeras

When you’re in utero, you’re protected from the outside world, connected to it only via the placenta, which is supposed to keep you and your mother separated. Separation is generally a good thing because you are foreign to your mother, and she is foreign to you. In spite of the generally good defenses, however, a little bit of you and a little bit of her cross the barrier. Scientists have recently found that when that happens, you often end up toting a bit of mom around for decades, maybe for life.

The presence of cells from someone else in another individual is called microchimerism. A chimera in mythology was a beast consisting of the parts of many animals, including lion, goat, and snake. In genetics, a chimera carries the genes of some other individual along with its own, perhaps even the genes of another species. In microchimerism, we carry a few cells from someone else around with us. Most women who have been pregnant have not only their own cells but some cells from their offspring, as well. I’m probably carrying around cells from each of my children.

Risks and benefits of sharing

Microchimerism can be useful but also carries risks. Researchers have identified maternal cells in the hearts of infants who died from infantile lupus and determined that the babies had died from heart block, partially from these maternal cells that had differentiated into excess heart muscle. On the other hand, in children with type 1 diabetes, maternal cells found in the pancreatic islets appear to be responding to damage and working to fix it.

The same good/bad outcomes exist for mothers who carry cells from their children. There has long been an association between past pregnancy and a reduced risk of breast cancer, but why has been unclear. Researchers studying microchimerism in women who had been pregnant found that those without breast cancer had fetal microchimerism at a rate three times that of women who with the cancer.

Microchimerism and autoimmunity

Autoimmune diseases develop when the body attacks itself, and several researchers have turned to microchimerism as one mechanism for this process. One fact that led them to investigate fetal microchimerism is the heavily female bias in autoimmune illness, suggesting a female-based event, like pregnancy. On the one hand, pregnancy appears to reduce the effects of rheumatoid arthritis, an autoimmune disorder affecting the joints and connective tissues. On the other hand, women who have been pregnant are more likely to develop an autoimmune disorder of the skin and organs called scleroderma (“hard skin”) that involves excess collagen deposition. There is also a suspected association between microchimerism and pre-eclampsia, a condition in pregnancy that can lead to dangerously high blood pressure and other complications that threaten the lives of mother and baby.

Human leukocyte antigen (HLA)

The autoimmune response may be based on a similarity between mother and child of HLA, immune-related proteins encoded on chromosome 6. This similarity may play a role in the immune imbalances that lead to autoimmune diseases; possibly because the HLAs of the mother and child are so similar, the body clicks out of balance with a possible HLA excess. If they were more different, the mother’s immune system might simply attack and destroy fetal HLAs, but with the strong similarity, fetal HLAs may be like an unexpected guest that behaves like one of the family.

Understanding the links between microchimerism and disease is the initial step in exploiting that knowledge for therapies or preventative approaches. Researchers have already used this information to predict the development of a complication in stem cell transplant called “graft-versus-host disease” (GVH). In stem cell transplants, female donors with previous pregnancies are more associated with development of GVH because they are microchimeric. Researchers have exploited this fact to try to predict whether or not there will be an early rejection of a transplant in kidney and pancreas organ transplants.

(Photo courtesy of Wikimedia Commons and photographer Ferdinand Reus).

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Placoderms had the "fun kind" of sex

Dunkleosteus, a Devonian placoderm. Pencil drawing, digital coloring, Nobu Tamura, http://www.palaeocritti.com. Obtained from Wikimedia Commons.

Timeline, 2008: From about 420 to 350 million years ago, the rulers of Earth’s seas were an unattractive-looking armored fish known today as the placoderms. This group, consisting of many species, were the bulldogs of the fish world, heavy-bodied with big ugly mouths full of protruding, potentially dangerous bony plates. Some of them were quite small, but a few species grew as large as 20 feet in length. They were the dominant vertebrate worldwide for about 70 million years.

Conventional scientific wisdom would say that these ancient fish reproduced the way modern representatives of ancient lineages do: external fertilization, the sperm fertilizing the egg with a little help from water. The wisdom was so conventional, in fact, that experts placed the rise of internal fertilization—delivery of the sperm into the female via an act of copulation—a good 200 million years after the placoderms swam the seas.

A catastrophe on the reef

In what is now Western Australia, something terrible happened about 380 million years ago in the shallow seas covering a coral reef: the oxygen that fed the reef suddenly plummeted, leaving the coral starved and unable to support the food web built around it. The outcome was a rapid, catastrophic loss of all of the species on the reef, including the placoderms. Thanks to stable plate tectonics and some good sediment coverage, these hapless animals remained preserved for the subsequent millions of years until a team of fossil hunters uncovered them. They now populate one of the most famous fossil finds in the world, the Gogo fossil sites, which are packed with perfect specimens of long-lost species.

The role of Sir David Attenborough, the world’s coolest naturalist

Among those perfect specimens—so perfect, in fact, that three-dimensional samples are available—is a species that now has the name Materpiscis attenboroughi. The name means “Attenborough’s mother fish” and requires a bit of explanation. Back in the late 1970s, Sir David Attenborough produced a wonderful nature and science series called Life on Earth. In the series, he highlighted the Gogo sites, and his interest led researchers to name the fish after him. But the first part of the name, the genus name Materpiscis, means “Mother fish.” Why? Because when this 10-inch fish died during that catastrophic reef loss, she died just before becoming a mother.

We know this because a couple of researchers working on her fossilized remains decided at the last minute to expose the fossil to one more round of acid treatment. They had pretty much decided to write her up as she was, which would have been plenty because of the preserved 3D perfection of her remains. But they agreed to that last treatment, which gently etches away layers of the fossil to reveal what lies beneath. They are glad they did, because what that last treatment exposed, inside of the adult fish, is a tiny, fossilized fish embryo, about a quarter of the size of its mother.

Eureka! Again, and again, and again

Anyone looking at that embryo, inside of that fish, might have had any number of “Eureka” thoughts in that moment. Eureka! It’s a fish embryo, 380 million years old! There aren’t that many of those lying around. But even more important, Eureka! It’s a fish embryo inside of the mother. That means that the egg was fertilized inside of the mother, where the embryo grew, nourished in her body, just as mammals do it. The embryo was even attached by a tiny, fossilized umbilical cord. A final Eureka! just might be that we can confirm the sex of this fish just based on the fact that she was pregnant when she died.

This just in: Sex is fun

The presence of an internally developing embryo in this placoderm sets the assumed evolutionary timing of internal fertilization back about 200 million years. No one would have guessed that these ancient, armored bulldog-like fish would represent the earliest-known internal fertilization. And the fact that fertilization was internal means that these animals must have copulated, the standard mechanism for getting sperm into the female to meet the egg. That recognition led one of the embryo’s discoverers to remark that this animal represents the earliest example a species engaging in “sex that was fun.”

Bisphenol A: multisystem effects

These bottles were produced without BPA in response to concerns about the chemical. Photo via Creative Commons, attributed to Alicia Vorhees, thesoftlanding

Are endocrine disruptors stealing our future?

Endocrine-disrupting compounds are chemicals in the environment—usually compounds that we have introduced—that can alter normal hormone signaling processes. Often, exposure to these compounds has little immediate effect in adult animals, but it can have big effects on organisms during sensitive developmental periods, like embryogenesis. During embryonic development in vertebrates, steroid hormones govern many processes, and the fetal hormone environment is usually carefully calibrated to ensure that these processes go forward normally.

Tiny amounts, big changes

But many compounds disrupt these processes, knocking them off track and resulting in development that is unusual or abnormal. For example, male alligators exposed in the egg to these compounds—which often persist in fatty tissues or yolk—emerge with serious penile abnormalities that can affect their ability to reproduce. The banned pesticide DDT is probably one of the best-known of these compounds, and exposure to it or its metabolites has been shown to disrupt hormone signaling to the point of altering sex development completely.

When we think of hormones, we often think of puberty, the time when hormones seem to govern our every move. When we think of estrogen, we probably think “female” because estrogen has historically been considered the “female” hormone. What you might not know is that estrogen, which is made in the ovaries, is also made in our brains during embryonic development. In mammals, appropriate male development appears to require neural estrogen synthesis. When estrogen synthesis in embryonic mammals is blocked, the males that develop do not exhibit typical male behaviors when they reach reproductive maturity.

Bisphenol A: ubiquitous chemical

Among the compounds that have been identified as endocrine disruptors is bisphenol A (BPA). In the United States, we produce about 2 billion pounds of BPA a year. Previous studies have demonstrated that BPA can disrupt thyroid signaling to the point of affecting the thyroid’s role in appropriate brain development. In addition, BPA has been linked to feminization of reptiles. Some scientists were aware of BPA’s hormone-activity potential as far back as the early twentieth century.

But because no one took that knowledge or its potential seriously—the field of endocrine disruptors is relatively young—BPA has found its way into almost every aspect of our lives. It is in the dental sealants we put on our teeth to keep the cavities at bay. It is in the lining that coats the insides of food cans to keep the metal from rusting. It is in the hard plastic that we use for baby bottles and teething rings. And it can leach from these products into the food that we eat. BPA is found at high levels in some pregnant women, and it appears to accumulate in higher concentrations around the umbilical cord and in the fetal amniotic fluid.

BPA and effects on the developing brain

Work from Yale and from researchers in Japan also points to some potentially serious effects on the brain. Part of the role of estrogen in brain development is facilitating synaptic connections in a crucial brain area called the hippocampus. The hippocampus is the center where neurons organize that will later be activated to produce sex-appropriate activity in vertebrates. It is also the area of the brain involved in the formation and retention of memory.

The researchers found that small doses of BPA—doses that fall within EPA-approved levels for exposure—can inhibit hippocampal synaptic formation in rats, counteracting the effect of estrogen. That BPA is an estrogen inhibitor could be serious for our brains if the results translate into human effects. As we age and our endogenous estrogen levels decrease, for example, the hippocampus suffers and our memory does, too. If BPA sets this process in motion even earlier, hippocampal—and thus, memory—decline may occur even earlier.

Rodents, monkeys, and people–oh, my

A recent report in Environmental Health Perspectives concludes that rodents, rhesus monkeys, and people all exhibit similar pharmacokinetics with BPA and that exposures may be far greater than previously calculated. Other recent studies suggest effects on sugar metabolism related to diabetes, an association with polycystic ovarian syndrome in rats, and a relationship to the development of asthma in a mouse model.

A gal for George, the world's loneliest tortoise?

Long-lived, lonely: The tragic fate of Lonesome George

George has seen a lot in his life. He was born sometime between 80 and 200 years ago, so what exactly he’s seen remains speculative. What we do know is that in 1971, some goat herders spotted George on the island of Pinta in the Galapagos, and George’s life changed significantly. Researchers rushed to the site to find the tortoise. The reason for the rush? They thought George was the very last of his subspecies, the lone denizen of Pinta, a survivor of the combined adverse effects of whalers and goats in the Galapagos.

George’s people+goats problem

Probably within George’s memory—if he could form such memories—whalers arrived at the Galapagos islands and decimated tortoise populations by eating the animals, whose abundant meat proved irresistible to the protein-starved mariners. With the people came the goats, and the goats proceeded to eat their way through everything on Pinta that the tortoises like to eat, too, destroying all of the tortoise’s nesting sites in the process. By the 1970s, biologists were pretty sure that there were no longer any Geochelone nigra abingdonii, George’s subspecies, living on the island. Then George popped up his wrinkled head just as the goatherders were walking by.

George elicits some bizarre human behavior, ignores tortoise females

The people took George to a tortoise sanctuary, where they attempted to introduce him to the joys of female companionship. Because George was alone, species-wise, they selected a couple of females from a closely related subspecies, Geochelone nigra becki, who hailed from Wolf Island, part of the Galapagos island chain. There, George lived with the females for 30 years with nary a leering glance at them, much less successful mating. One frustrated researcher went so far as to join George in his pen, where she covered herself in eau d’ female tortoise, excretions from the female that presumably carried male-attracting pheromones. During her time with George, the male tortoise appeared to have a sort of sexual awakening, showing a bit of interest and exhibiting signs of sexual activity. The researcher even confirmed that George was indeed male and that everything appeared to be functioning normally.

Then, her research period at the sanctuary ended, and George lost his trainer in the romantic arts. Bachelor and celibate, his claim to fame remained that he was the world’s loneliest animal. He even made it into the Guinness Book of World Records as the rarest creature on Earth. His sobriquet became Lonesome George, and thousands of people came to view him at his island sanctuary. Over time, he has had his trials: a caretaker who let him eat too much, periodic overindulgence in cactus—a tortoise delicacy—that led to constipation, and a fall that almost killed him. But still, no mating.

Will George find his Ms. Right?

Then, a group of researchers tackled the job of drawing blood from tortoises on the nearby island of Isabela, where a different subspecies of tortoise lives. They performed microsatellite DNA analysis on the blood, a type of analysis that produces a DNA fingerprint that can be used to characterize a species. To their surprise, they found a tortoise among their samples who appeared to be half-George. The male tortoise had a microsatellite DNA pattern that was a 50% match for George, meaning that somewhere on the island of Isabela, a possibly-female G. n. abindonii lurked and, apparently, mated.

Now the search is on for the individual who may blow George’s place in the record books but also be the last hope for their mutual species to persist on the planet. If the tortoise is female, researchers hope to introduce her to George, possibly awakening his long-dormant libido. Meanwhile, George’s former island home of Pinta could be a tortoise Eden for the pair: the goats are gone and much of the vegetation has returned to its original ecological state. If they can find George a mate, he may very well cease to be Lonesome George and become his species’ Adam, partner to the as-yet-unidentified Eve.

Batty bigamy and worse

Normally, inbreeding isn’t such a good thing

The idea that three generations of related females might share the same mate is, frankly, abhorrent and strange to us humans, but among bats, this tactic may be a fairly common phenomenon.

Generally, animals avoid inbreeding with one another because doing so results in the development of “inbreeding depression” in a population. This depression refers to falling rates of reproduction and survival that result when relatives interbreed. An example of what happens with inbreeding can be found among the royal houses of Europe in previous centuries. The members of these families would often receive papal dispensations to ignore the rules about consanguinity—close relatedness—to be allowed to marry another royal personage. There just weren’t that many eligible royal folk wandering around Europe and inbreeding was the ultimate result.

Hidden disorders emerge

Because of this inbreeding, often with third or second cousins marrying through several generations, the royal families would manifest disorders that normally would remain hidden. Some of these disorders required the inheritance of two alleles, both carrying mutations, for them to manifest. If the royal families had not constantly been intermarrying, the two recessive alleles would have been much less likely to come together in a single person. As it was, many royal households had children who were sickly, who could not reproduce successfully, or who manifested mental illness or retardation. One particularly notable trait that arose through several families was the “Hapsburg jaw,” a severe underbite and jutting jawbone that traced its way through the European royal chessboard. One potentate had a jaw deformity so severe that he could not chew his food.

Horseshoe bats don’t care

But the greater horseshoe bat appears to be untroubled by such issues of consanguinity, at least in the sense that related females from several generations will mate with the same male. In the world of the horseshoe bat, it pays to be a male bat who attracts a female. If the male attracts the daughter, he has a good chance of also mating with the mother and the grandmother, too. And he may be set for his relatively long bat-life; greater horseshoe bats can live up to 30 years, and females will consistently select the same male for the annual bat mating ritual, which results in a single offspring per female each year.

In spite of this inbreeding and polygyny, in which several females mate with the same male, the females apparently are quite adept at avoiding mating with their own fathers. A female will only mate with her mother’s partner if her mother has switched partners and is no longer mating with the daughter’s father.

Beat that, Belgium

This complex mating web results in a bat family tree that is more confusing than that of all the royal houses of Europe combined. It is possible for a female bat and her maternal half-aunt to be half-sisters on their father’s side.

How did researchers unravel this remarkable complexity? They identified a colony of female bats—who spend most of the year living in single-sex groups—in an old mansion in Great Britain. DNA analysis showed that the several hundred females lived in about 20 groups of related females who shared mates. The females met up with the males, who lived in a permanent stag party condition in a nearby cave, only once a year. Researchers speculate that females use smell to avoid mating with their fathers.

What benefit this interbreeding?

Why risk interbreeding in the first place? Actually, many species exhibit tactics that lead to closer kinship among individuals. Researchers speculate that closer kinships result in better teamwork to protect the genetic investment. In the world of team-playing ants, for example, female siblings can be 75% related, rather than the 50% most sexually producing species share genetically with their siblings. Experts believe that this extra genetic relatedness enhances the teamwork atmosphere of an ant colony. In much the same way, the related groups of female bats work together to raise the young. Researchers believe that this horseshoe bat tactic may extend beyond the greater horseshoe to other bat species.

Sad update: Baby red panda has died

This update on the baby red panda from a news release via the National Zoo:

An animal keeper at the Smithsonian’s National Zoo discovered a recently born red panda cub lifeless yesterday during evening animal rounds. The 21-day-old cub was immediately transported to the veterinary hospital where a veterinary team confirmed his death. Born June 16, this male was the first cub for parents Shama and Tate and the first cub born at the Zoo in 15 years.

Zoo keepers had closely observed the cub since his birth. First-time mother Shama had moved the cub around the outdoor exhibit instead of keeping the cub in a nest box, as would be expected. As a result of Shama’s behavior, the exhibit was roped off to the public in order to provide her with peace and quiet. Animal care staff weighed the cub regularly, observed and reviewed the behavior of the cub and parents at least twice daily and volunteers monitored the behavior in-person and via camera several hours each day.

Due to the recent extreme heat, keepers were extra vigilant maintaining the animals’ cooling centers (chilled spaces within the exhibit). Nonetheless, there is a 50 percent mortality rate for red panda cubs born in captivity. Pathologists performed the necropsy last evening but the definite cause of death was not evident. Additional testing, including histopathology, is underway and should provide additional information.

The National Zoo has been breeding red pandas successfully for 48 years. Since 1962, 184 cubs have been born at both the Zoo and the Smithsonian Conservation Biology Institute in Front Royal, Va., with a mortality rate of about 40 percent, below the national average. Currently there is one cub at the Front Royal facility.

“This is an enigmatic and important species,” said Dennis Kelly, director of the National Zoological Park. “We’re deeply disappointed to lose this cub but there are inherent risks in the conservation of rare species. Our cumulative breeding and research success has positioned the Smithsonian’s National Zoo as one of the leaders in the field of red panda conservation. We’ll stay the course until this animal is no longer listed as vulnerable.”

Red pandas breed once a year and animal care staff anticipate that they will breed again next year.

Awww. Baby red panda

It was love at first sight for Shama and Tate, the red pandas at the Smithsonian’s National Zoo, and now, nearly 1½ years after they were introduced, the pair has a cub as evidence of their strong bond. On Wednesday, June 16, Shama gave birth to a single cub—the first for both of the Zoo’s red pandas (Ailurus fulgens) and the first red panda cub born at the National Zoo in Washington, D.C., in 15 years.

Red pandas have a baby. It’s very cute.

The National Zoo is celebrating its first birth of a red panda in 15 years. The history of the red panda–at least, of its classification–is complicated. More on that in a mo. What’s significant here is its current situation. Thanks to habitat loss, the species has declined in the wild to fewer than 2500 individuals, and it is endangered. So a birth–especially between an apparently happy couple with a strong mutual attraction–is a success for the zoo and for red panda conservation, too.

The proud mother was born at the Smithsonian Conservation Biology Institute in Front Royal, Va., and more than 100 surviving cubs have been born at both this research facility and the Washington, D.C., campuses since 1962.

Panda or raccoon?

Taxonomists–the folks who classify organisms by relatedness–have had a conundrum on their hands with the red panda. You’d think that the name says it all: it’s a panda, right?

Well, no. Nothing’s ever that easy in taxonomy. For some time, arguments that it was a relative of the raccoon held weight. But the animal has some strong panda-like traits, including an affinity for bamboo and similar habitats to the giant panda. But they differ in their far more diverse diet and greater habitat distribution.

The panda’s thumb

The giant panda has a faux thumb that’s really just a bone extension of the wrist bones. It’s not an opposable thumb like the one primates have, but the giant panda uses it in a thumb-like way. The red panda happens to share this odd trait. They also share many similarities in their DNA, which ended in the red panda briefly joining the bear family.

So, is it a panda or a raccoon?

The species also has some commonalities with the raccoon, including the ringed tail and more diverse diet compared to the giant panda, one that includes a taste for bird eggs. For these reasons, it also has been classified into the raccoon family. So, which family is it?

It’s neither. While the red panda has now been classified as a distant relative of the giant panda–the bamboo! the “thumb”!–it falls into its very own family, the Ailuridae, of which the red panda, or Ailurus fulgens, is the sole member. Unlike bears, this species arose in Asia and never made the trek to the “new world.”

Interesting note, the snow leopard–another severely endangered species–is their sole wild predator.

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