章 2: LANGUAGE LEARNING MAY BE BEFORE BIRTH
LANGUAGE LEARNING MAY BE BEFORE BIRTH
Experiments with new-born babies show that babies become aware of their native language while in the womb, pointing out that language learning may begin before birth.
Judit Gervain from the University of Padua in Italy states that it has been known for some time that babies in the womb can hear towards the end of pregnancy. In fact, new-born babies can recognize their mother's voice. To investigate further, Gervain and his colleagues examined the brain activity of 49 babies of French-speaking mothers at ages 1 to 5 days. Each new-born was fitted with a small cap containing 10 electrodes placed near areas of the brain associated with speech perception. The team then played the recordings to the babies in different orders, starting with 5 minutes of silence and continuing with 7 minutes of English, French and Spanish pieces from the story of Goldilocks and the Three Bears, and then exposed the babies to silence for a while.
When the babies listened to the French recording, they showed an increase in a type of brain signal called long-range temporal connections, which are involved in perceiving and processing speech. As babies were exposed to other languages, these signals decreased. The team found that in a group of 17 infants who had last heard French, this increase in neural activity continued during the subsequent silence.
According to Gervaine, these findings may indicate that babies recognize their mothers' native language as the more important language. The team now plans to conduct experiments involving babies born to mothers who speak different languages, particularly Asian or African languages, to see how general their results are. She also wants to investigate how the development of speech perception in the womb might differ in babies with less prenatal experience, such as premature babies.
***
Our Cells from Other Family Members
In the 1990s, Diana Bianchi and her colleagues at Harvard University discovered that women who had given birth to a boy about 27 years ago still had cells from their sons circulating in their blood. Bianchi, who is now director of the National Institute of Child Health and Human Development in Maryland, says the finding really changed her thinking about pregnancy at the time and surprised her. Scientists now know that the cells and DNA from our mothers, siblings and other family members, which can be located in different organs and systems in our bodies, play a role in keeping us healthy and can even affect the way we think.
This condition, called microchimerism, is defined as a situation in which a small number of cells or DNA from one individual are found in another individual. Many studies have shown that there is a transfer of stem cells between the mother and the fetus during pregnancy. These cells or DNA can remain in the recipient's blood or tissues for decades, creating the physiological state of microchimerism.
It was previously thought that microchimerism could be the cause of many different diseases. However, the detection of microchimerism in healthy individuals with non-autoimmune diseases also showed that microchimerism may play a role in repairing tissue damage rather than causing disease.
Later, other research groups detected mothers' cells in the blood samples of the children they followed, even when they were adults. When these results were combined, it became clear that a small portion of our cells were passed on to our mothers while we were in the womb, and vice versa, and then circulated in the body for decades.
But that's not all! Because it is thought that we also harbor cells from our older siblings, uncles, aunts and grandmothers. A study published in the journal CHIMERISM in 2015 on 154 Danish girls aged 10 to 15 found that 14% of the girls had male cells circulating in their blood. Moreover, this was even more likely if they had an older brother. So what did these findings indicate? It turns out that this could happen if a mother were to take cells from her son while pregnant, and then pass them on to her daughter during her next pregnancy. Theoretically, if the daughter then passed her brother's cells on to her own child, that child would carry her uncle's cells. Such effects can be seen years later, when the mother has a miscarriage or has to have her pregnancy medically terminated.
Studies have found that people with certain autoimmune disorders have higher levels of these cells in their blood, and although a causal link has not yet been established, it is thought that these cells may trigger the immune system. Meanwhile, increasing evidence suggests that these cells play an important role in repairing tissue damage and fighting off disease.
Blanchi and her colleagues found some of their first clues when they studied biopsies taken from women with thyroid disease. Bianchi says that a piece of thyroid taken from a woman contained entirely male cells. Researchers think that these cells come from the woman's son while she is pregnant with him, and then help repair the damaged thyroid.
Similarly, Keelin O'Donoghue and Uzma Mahmood at University College Cork in Ireland have discovered cells from the baby in the C-section wounds of women who have given birth to boys, and have found signs that they aid in the healing process. Cells from female fetuses have the same healing properties, but it is easier to find male fetal cells in the mothers because they carry a distinctive Y chromosome.
Hina Chaudhry at the Icahn School of Medicine at Mount Sinai in New York and her colleagues found that when pregnant mice's hearts are damaged, cells from their fetuses travel to the damaged area and develop into healthy heart cells. Chaudhry says this could explain why some people with heart failure heal spontaneously while pregnant.
The other way the cells are passed, from mother to fetus, is also thought to be helpful. For example, J. Lee Nelson of the Fred Hutchinson Cancer Center in Seattle and colleagues found female insulin-producing cells in the pancreas of an 11-year-old boy whose body could not produce insulin on its own during an autopsy. The female cells appeared to have come from the boy's mother and were trying to help his failing pancreas regenerate.
These cells, left over from pregnancy, have been found in every organ examined. Some of the most intriguing discoveries are being made in the brain. Recently, there have been signs that fetal stem cells proliferate in parts of the brain responsible for emotion and behavior, and develop into neurons that make new connections with the mother's own brain cells. It's not clear what these cells do later, but researchers hypothesize that these structural changes may play a role in the mother's ability to love and care for her child.
***
Tardigrade Mystery Solved!
Tardigrades, also known as water bears, are eight-legged microscopic invertebrates found all over the world. In adverse conditions such as freezing cold or intense radiation, they shrink into a dry ball and enter a deep hibernation. In their study published in January in the journal PLoS One, scientists have solved the mystery behind their ability to withstand these extraordinarily harsh conditions: Tiny molecular sensors in their cells can detect when they produce too many harmful molecules called free radicals and trigger a dormant state.
Derrick Kolling from Marshall University in West Virginia and his colleagues exposed tardigrades to high levels of hydrogen peroxide, sugar, salt and temperatures of -80°C. In these harsh conditions, the tardigrades produce harmful, highly reactive molecules called oxygen free radicals. The free radicals then react with other molecules, says team member Leslie Hicks from the University of North Carolina at Chapel Hill. The team found that the free radicals oxidize an amino acid called cysteine, one of the building blocks of proteins in the body. These reactions cause the structure and function of proteins to change, signaling the onset of dormancy. In experiments where cysteine oxidation was blocked, the tardigrades were unable to enter dormancy. It is said that cysteine acts as a kind of regulatory sensor, allowing the tardigrades to sense their environment and respond to stress. When conditions improved, the team also found that cysteine was no longer oxidized, allowing the tardigrades to wake up. The researchers believe that whether this is a general protective mechanism and whether it is also found in different tardigrade species are important questions to answer, as the answers could provide new information that could shed light on the study of the aging process and long-term space travel.
週次パワーステータス
-- 推薦
ランキング 
-- 推薦
チケット