Biological Fountain of Youth

April 25, 2015 by

March 27, 2015

By Medical Discovery News

The Biological Fountain of Youth

Over 500 years ago, Ponce de Leon landed in Florida as part of his search for the fountain of youth – magical waters that reverse aging, prevent illness, and grant immortality. He never found it, and neither has anyone else. While immortality is still impossible, we have come a long way in understanding the aging process.

We do not know the precise mechanism of aging, but there are some fundamental processes in our bodies that begin to change and this can drive aging. There are several theories of aging under intense scientific investigation.

A widely accepted theory of aging today is called evolutionary senescence, which mainly hinges on the concept of mutation accumulation. As we age, our cells accumulate mutations in our genetic material or DNA, which affects the ability of our cells to replicate and our tissues to regenerate. Also, some of our genes are designed to enhance reproduction early in life, but can cause problems later. Since genes can only be passed on during reproduction, which generally occurs earlier in life, genes that have negative effects later in life are not removed from the population – we are stuck with them! A good example is a gene called p53, which controls the fate of damaged cells by preventing their replication or directing them to die. This is important in preventing cancer in young people, but it may negatively impact our ability to replace aging cells in tissues as we grow older.

Another widely discussed theory centers on the maintenance of our genomes. As we get older, we accumulate damage to our DNA, which affects cellular function and our ability to renew tissues in the body. In a sense, this is a high mileage effect. Take for example the production of free radical molecules. These highly reactive molecules are normally produced in mitochondria, which use oxygen to produce cellular energy, a process that creates free radical molecules as a by-product. These free radical molecules lead to oxidative damage of DNA and other cellular components.

There is also evidence the neuroendocrine system (hormones that affect neurological function) influences aging. For example, a reduction in hormone levels can lead to a lengthening of life, at least in experimental animals. We are beginning to suspect that the insulin-related hormonal pathway may play a significant role in aging, at least in mice. Mutations that reduce the amount of this circulating hormone extend life.

A relatively new model of aging involves the replication of chromosomes as cells divide. When cells replicate, specialized structures at the ends of chromosomes called telomeres are shortened. Shortened telomeres are linked to decreased viability and increased cancer risk. Cells whose telomeres reach a critical length can no longer divide and are described as senescent.

We are expanding our understanding of how aging occurs. The search for a modern-day fountain of youth will require a great deal of dedicated work by biomedical scientists to safely improve and extend human life.

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Down Syndrome in the Middle Ages

February 22, 2015 by

Jan. 30, 2015

By Medical Discovery News

Down syndrome is likely as old as humans themselves, but a recently discovered skeleton of a girl who died 1,500 years ago in France is the oldest confirmed case. The way she was buried seems to indicate that she was not scorned during her life and death in the Early Middle Ages.

Down syndrome, also called Trisomy 21, arises when a person is born with three rather than two copies of chromosome 21. It occurs in one out of 691 babies born in the U.S., making it the most common genetic disorder. Every person with Down syndrome is unique and has different levels of physical and intellectual abilities. The most common physical signs are upward slanting eyes, flattened facial features, ears that are small or unusually shaped, broad hands with short fingers, and a small head.

Other, more serious complications can include poor muscle tone, heart problems, problems swallowing, blockages in the intestines, cataracts or crossed eyes, hearing loss, increased susceptibility to infections, a less-active thyroid gland, and a higher risk of developing leukemia. People with Down syndrome develop dementia at a younger age than the general population. Their intelligence ranges, but with therapies, many Down syndrome children grow up to have jobs and live independently.

The chance of giving birth to a baby with Down Syndrome increases with the mother’s age, from 1 in 1,000 at age 30 to 1 in 100 at age 40. The American College of Obstetrics and Gynecology now recommends that all pregnant women be offered a prenatal screening test for Down syndrome, which is 99 percent accurate.

For centuries, people with Down syndrome have been part of art and literature. It wasn’t until the late 1800s that an English physician named John Langdon Down published the first accurate description, calling the condition “Mongolism.” The modern term Down syndrome became the accepted term in the early 1970s. The cause of Down syndrome, Trisomy 21, was discovered by French pediatrician and geneticist Jerome Lejeune, although Marthe Gautier, a retired pediatric cardiologist and scientist from Paris, now claims she did most of the experimental work that led to the discovery of Trisomy 21.

This newly discovered skeleton, which is the oldest case of Down syndrome found thus far, was unearthed near a church in a fifth- and sixth-century necropolis in Saône-et-Loire in eastern France. The five- to seven-year-old girl exhibited a short, broad skull, flattened skull base, and thin cranial bones, all features of Down syndrome. She was buried on her back with her head in a westerly direction, similar to the 94 others buried there. The archeologists believe that since she wasn’t treated any differently in death, it’s unlikely she was stigmatized when she was alive. But researchers must uncover further details about Down syndrome in the Middle Ages to know more about how she may have lived.

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What Makes a Male?

May 16, 2014 by

May 16, 2014

By Medical Discovery News

What makes a male?

Despite centuries of women being celebrated for siring sons, or scorned for failing to produce an heir, it is actually men who determine a baby’s gender. Women give each of their offspring an X chromosome, but the male can give an X or a Y chromosome to create a female (XX) or male (XY), respectively. But how much of the Y chromosome is required to make a male? It turns out only two genes are needed to create a male mouse, a species that determines gender the same as humans. 

Humans have 23 pairs of chromosomes, one of which is the sex chromosome. Chromosomes contain lots and lots of genes, all which carry instructions that tell different parts of the body what to do. In males, the Y chromosome carries a gene called SRY that encodes the Sex-determining region Y (also abbreviated SRY) protein. This protein, as its name suggests, will decide the sex of future offspring. Consequently, this one single gene, SRY, is all that’s required to produce an anatomically male mouse. However, these male mice are infertile because they lack some of the genes involved in sperm production.

That’s where another gene called Eif2s3y comes in. With this second gene, male mice can at least generate sperm cell precursors known as round spermatids, but not mature sperm. To fully develop sperm, the mice need both copies of this gene. One is toward the end of the Y chromosome and the other version is on the X chromosome.

So with only two genes from the Y chromosome, male mice are able to produce immature sperm. Scientists used an assisted in vitro fertilization technique to treat male infertility by injecting the round spermatids directly into the eggs of female mice. The round spermatids fertilized the eggs nine percent of the time. In comparison, sperm from natural-born male mice fertilized eggs 26 percent of the time. The offspring born from these efforts developed into normal, healthy, fertile adult mice. 

Even though only two genes from the Y chromosome are required to produce fertile adult mice, the Y chromosome is still important. More genes are required to produce fully mature, motile sperm capable of fertilizing an egg without intervention. The Eif2s3y gene may play a role in some forms of male infertility in humans. With this new data, therapies could be invented to encourage the development of functional sperm that could reproduce through in vitro methods. Injecting round spermatid into eggs is not currently an option for humans due to technical and safety issues, but this technique is likely to get better with additional research. 

The genetic information contained in the Y chromosome plays important roles in reproduction by controlling the development of sperm and normal fertilization and will continue to do so, negating suggestions that it is being eliminated by evolution or rendered useless by in vitro fertilization. For now at least, men remain indispensable.

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A Risk-Free Test for Down’s

April 18, 2014 by

April 18, 2014

By Medical Discovery News

Keep Calm, It's Only An Extra Chromosome

When it comes to chromosomes, extra copies are not a good thing. Every cell in the human body carries the same genetic information in two copies of 23 chromosomes. Having an extra copy of a chromosome is called trisomy, and an extra copy of chromosome number 21 is what causes Down syndrome.

Physical signs of Down syndrome include upward slanting of the eyes, flattened facial features, small and unusually shaped ears, small heads, and broad hands with short fingers. Down syndrome can also cause more serious conditions such as varying degrees of mental retardation, poor muscle tone, an increased risk of early onset dementia, and heart, stomach, and eye problems. No two cases of Down syndrome are the same, and with therapy and support people with Down syndrome can live long, productive lives.

The risk of Down syndrome increases with the mother’s age during pregnancy. The risk of having a baby with Down syndrome increases from one in 1,300 to one in 25 at ages 25 to 49.

Women who are pregnant with a child who might have Down syndrome typically undergo an ultrasound test and blood tests for markers such as pregnancy-associated plasma protein-A and a hormone known as human chorionic gonadotropin. Abnormal levels of these markers may indicate a problem with the baby. These tests are generally done during weeks 11-13 of pregnancy. The American College of Obstetrics and Gynecology now recommends that all women undergo prenatal testing for chromosomal abnormalities.

Until recently, Down syndrome could only be confirmed by invasive tests that collect cells from the amniotic fluid surrounding the fetus, the placenta, or the fetus itself. These tests can be risky, with a one percent chance of miscarriage. However, a new, noninvasive screening test called circulating cell-free fetal DNA analysis may reduce the need for invasive prenatal tests. Circulating cell-free DNA from the fetus makes up three to 13 percent of the DNA fragments circulating in the mother’s bloodstream during pregnancy.

First, DNA is isolated from the mother’s plasma, the liquid component of blood. Then, there are two ways to determine if there are any chromosomal abnormalities. Massive parallel DNA genomic sequencing can be used to quantify millions of DNA fragments in just a few days and can accurately detect trisomies. Another approach is called Digital Analysis of Selected Regions, which analyzes only the chromosomes in question to evaluate them for any abnormalities.    

These tests are 99 percent accurate, can be done as early as the 10th week of pregnancy, and are more reliable. They can also diagnose other trisomies, like the ones that affect chromosome 18 (Edwards syndrome) and chromosome 13 (Patau syndrome). At this stage, invasive testing is still required to confirm the diagnosis of a trisomy. But in the near future this new technology will reduce or eliminate the need for additional invasive tests that put the fetus at risk. This is only the beginning of the development of safer and more accurate genetic tests.

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