ADAPTED FROM:
From stem cell to any cell
The search is on for ways to use stem cells to treat injuries and cure diseases.
BY EMILY SOHN 12:00AM, OCTOBER 11, 2005
For maybe a day, about 9 months before you were born, you were just one cell.
Then you were two identical cells. Then you were four. Then eight.
Since then, you've grown into a complicated organism with many trillions of cells
grouped into specialized tissues and organs. The cells in your brain do the
thinking. The cells in your heart pump blood. The cells in your tongue let you
taste food. And so on.
In recent years, scientists have made an amazing discovery. Even though most cells
have specific jobs, some primitive cells — called stem cells — exist in everyone's
body. Stem cells are unspecialized cells that can develop into nearly any type of
body Embryos — babies in the earliest stages of growth before they are born — have
stem cells. Certain tissues in adults also contain stem cells, although the range of
cells into which they can develop is limited.
In 1998, scientists at the University of Wisconsin–Madison figured out how to
collect human embryonic stem cells and make them grow. Since then, researchers
have learned to mix stem cells with combinations of proteins called growth
factors to make the cells grow into different types of cells. Now, the search is on
for ways to use stem cells to treat injuries and cure diseases.
For example, stem cells could be extracted, turned into new bone cells, and then
injected into weak or broken bones. Or, they could become nerve cells that could
heal spinal cord injuries, skin cells that could replace badly burnt skin, or brain
cells that could help people who have suffered brain damage. The possibilities are
endless.
"At this point, the ability to create all the different cells in the body has been
pretty much proven to be real," says Gary Friedman. He's director of the Center
for Regenerative Medicine in Morristown, N.J. "All the focus now is on getting
new cells to behave the way we want them to and to go where we want them to
go."
Living better
Treating heart disease is one promising area of research. In dishes in the
laboratory, scientists have already turned stem cells into heart cells, which gather
into a group and throb in synch with one another, just like cells do in your heart.
At the University of Texas Health Science Center in Houston, researchers are
now taking stem cells from a patient's own body and injecting them into the
heart to rebuild heart tissue and combat heart disease.
Elsewhere, scientists are working to battle spinal cord injuries, diabetes, cancer,
and more. But stem cells can't cure all our ills. Some health problems are proving
harder to treat this way than others.
Hearts, nerves, and livers are simple, Friedman says. Kidneys and lungs, on the
other hand, are organs are tougher to repair. In kidneys, for example, stem cells
have to not only specialize but also move into appropriate positions.
The goal of stem cell research is to help people live better, Friedman says.
"If kids are looking at their grandparents, maybe they see somebody who can't
walk well or somebody who is partly paralyzed because of a stroke," he says.
"If you could take an older person and give that person cells to regenerate heart
muscle or part of the brain that died during a stroke, or inject cells into joints to
take away arthritis, all of a sudden you're going to have a pretty vibrant person
there," Friedman says.
"This will help society," he says. "People will be more functional instead of being
in a weakened state and having to be cared for."
More than science
As promising as the research may seem, discussions about stem cells often
involve more than just science. Ethics is also involved, along with politics and
religion, especially when it comes to stem cells taken from embryos.
So far, embryonic stem cells appear to be more useful than stem cells that come
from adults. Because an embryo's cells are still dividing and specializing anyway, its
stem cells can still become almost anything. By the time we grow up, however,
our stem cells have a more limited ability to diversify.
To repair heart muscle in a mouse, researchers inject adult stem cells into the
muscle of the damaged wall of a mouse heart.
National Institutes of Health
The problem with embryonic stem cells, for some people, is that they originally
come from destroyed embryos. Many scientists argue that stem cells are our best
hope for curing a huge number of diseases. They also argue that fertility clinics
end up with a surplus of embryos that are never born anyway.
Nevertheless, critics think its wrong to use cells from dead embryos. It's a very
complicated issue that involves basic beliefs about when life begins, and these are
the types of beliefs about which people tend to feel passionate.
Some recent research may help put an end to the debate, Friedman says.
A new technique called "somatic cell nuclear transfer" has given scientists the
ability to create embryonic-like stem cells out of a person's own cells. This
strategy is especially appealing to doctors, because it's always better to use a
person's own cells for transplants and injections. Our bodies often reject cells
that come from someone else, even if that someone else is an unborn embryo.
Scientists have also found embryonic-like stem cells in umbilical cord blood.
About 100 million babies are born each year, and every one of them has an
umbilical cord that connects it to its mother. If umbilical cords prove to be a
reliable source, the supply of stem cells could be enormous and controversy-free.
All this may sound a bit confusing, but it's worth learning more. Stem cells are big
news in medicine right now. "I don't think a day goes by when there aren't articles
or something on the Web about it," Friedman says.
As you get older, you're bound to hear more and more about stem cells.
Name: _________________________________
Date: ______________
Life Science
Period: _____________
From Stem Cell to Any Cell
By Amy Sohn
ScienceNewsforKids.org
Answer the following questions in complete sentences. You will be graded according to the
distributed Weekly Science Article rubric.
1. What are stem cells? Where are they found? _________________________________
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2. What are three important uses for stem cells? __________________________________
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3. Identify two organs that are easy to repair using stem cells, and two organs that are
difficult to repair using stem cells.
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4. Why are embryonic stem cells more useful than other stem cells?
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5. What makes the new technique called “somatic cell nuclear transfer” appealing to
doctors?
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6. How are scientists trying to get around ethical concerns about the use of embryonic stem
cells in research and medicine?
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7. The use of stem cells is a highly controversial ethical issue that has recently been used
as one of the major points on which a political platform is built during election season. Do
you support or oppose stem cell research? State your opinion and your reasoning in a
minimum of four complete sentences in a cohesive paragraph.
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www.ShellysScienceSpot.com
ADAPTED FROM:
A Change in Leaf Color
By Emily Sohn / September 18, 2006
Every autumn, traffic creeps along New England’s roads as visitors look
everywhere but at the road. These tourists flock to the region as soon as leaves
begin to change color from a summery green to spectacular shades of red,
orange, yellow, and purple.
New England’s brilliant fall colors attract many visitors.
“Being in the Northeast during autumn is just about as good as it gets in this
country,” says David Lee. He’s a botanist at Florida International University in
Miami.
Lee studies leaf color, so he’s biased. But plenty of other people share his
admiration. Areas of the United States with especially colorful fall displays attract
thousands of leaf peepers.
Even as they “ooh” and “aah,” few people know what makes many plants blush in
the autumn. Research has shown that leaves change color when their foodmaking processes shut off. The chemical chlorophyll, which gives leaves their
green color, breaks down. This allows other leaf pigments—yellow and orange—
to become visible.
No one knows exactly how global warming will alter forests and affect fall colors.
But “there’s still a lot we don’t know about this,” Lee says.
It isn’t clear, for example, why different species of plants turn different colors. Or
why some trees become redder than others, even when they’re standing right
next to each other. And no one knows exactly how global warming will alter
forests and affect leaf-peeping season.
Food factory
In summer, when a plant is green, its leaves contain the pigment chlorophyll, which
absorbs all colors of sunlight except green. We see the reflected green light.
The plant uses the energy it absorbs from the sun to turn carbon dioxide and
water into sugars (food) and oxygen (waste). The process is called
photosynthesis.
When chlorophyll breaks down, yellow pigments in leaves become visible.
As days get shorter and colder in the autumn, chlorophyll molecules break down.
Leaves quickly lose their green color. Some leaves begin to look yellow or orange
because they still contain pigments called carotenoids. One such pigment,
carotene, gives carrots their bright-orange color.
But red is special. This brilliant color appears only because the leaves of some
plants, including maples, actually produce new pigments, called anthocyanins.
That’s a strange thing for a plant to do without a reason, says Bill Hoch of the
University of Wisconsin in Madison. Why? Because it takes a lot of energy to
make anthocyanins.
Why red?
To figure out the purpose of the red pigment, Hoch and his coworkers bred
mutant plants that can’t make anthocyanins and compared them with plants that
do make anthocyanins. They found that plants that can make red pigments
continue to absorb nutrients from their leaves long after the mutant plants have
stopped.
Red leaves get their color from a pigment called anthocyanin.
This study and others suggest that anthocyanins work like a sunscreen. When
chlorophyll breaks down, a plant’s leaves become vulnerable to the sun’s harsh
rays. By turning red, plants protect themselves from sun damage. They can
continue to take nutrients out of their dying leaves. These reserves help the
plants stay healthy through the winter.
The more anthocyanins a plant produces, the redder its leaves become. This
explains why colors vary from year to year, and even from tree to tree. Stressful
conditions, such as drought and disease, often make a season redder.
Now, Hoch is breeding plants for a new set of experiments. He wants to find out
whether turning red helps plants survive cold weather.
“There’s a clear correlation between environments that get colder in the fall and
the amount of red produced,” he says. “Red maples turn bright red in Wisconsin.
In Florida, they don’t turn nearly as bright.”
More protection
Elsewhere, scientists are looking at anthocyanins in other ways. A recent study in
Greece, for instance, found that as leaves grow redder, insects eat them less. On
the basis of this observation, some scientists argue that red pigments defend a
plant against bugs.
Leaves may turn red in the autumn to protect themselves from the sun’s
ultraviolet rays.
J. Miller
Hoch rejects that theory, but Lee thinks that it might make sense. He points out
that red leaves contain less nitrogen than green ones do. “It may actually be that
insects avoid red leaves because they’re less nutritious,” Lee says.
However, “it’s pretty confusing at this point,” Lee admits. “People debate back and
forth.”
To settle the debate, scientists will need to look at more species under more
conditions, Lee says. So, he’s now researching leafy plants rather than trees. He’s
especially interested in tropical plants, whose leaves turn red when they’re young
rather than old.
You can do your own leafy experiments. Observe the trees in your neighborhood
and keep track of weather conditions. When autumn begins, write down when
the leaves change, which species change first, and how rich the colors are.You can
even see anthocyanins under a simple microscope. After several years, you might
start to notice some patterns.
Name: ________________________________
Date: ____________
Life Science
Period: __________
A Change in Leaf Color
By Emily Sohn
www.ScienceNewsForKids.org
Read the article “A Change in Leaf Color” and answer the following questions in complete
sentences. You will be graded according to the previously distributed rubric.
1. Why do leaves change color in the fall?
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2. What is chlorophyll? How does it work to make our eyes view plants as being
green?
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3. What happens during photosynthesis?
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4. Aside from chlorophyll, what pigments are present in plant leaves? What colors do
they provide our eyes with?
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www.ShellysScienceSpot.com
5. Identify three reasons why tree leaves turn red.
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6. How are the colors of leaves affected by weather conditions?
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7. Many of us find leaves of different colors to be beautiful. Science offers explanations
for this beauty. Do you think it’s important to understand the reasons why something
is beautiful to enjoy it fully? In a minimum of four complete sentences in a cohesive
paragraph, explain your thoughts on the topic.
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www.ShellysScienceSpot.com
ADAPTED FROM:
Catching Some Rays
By Sarah Webb / July 2, 2007
Harnessing the power of the sun is nothing new. People have had solar-powered
calculators and buildings with solar panels for decades. But plants are the real
experts: They’ve been using sunlight as an energy source for billions of years.
Cells in the green leaves of plants work like tiny factories to convert sunlight,
carbon dioxide, and water into sugars and starches—stored energy that the
plants can use. This conversion process is called photosynthesis. Unfortunately,
unless you’re a plant, it’s difficult and expensive to convert sunlight into storable
energy. That’s why scientists are taking a closer look at exactly how plants do it.
Plants such as this sunflower efficiently convert the sun’s light into energy that
they can use.
In a world with increasing energy needs, researchers are always looking for new
ways to power everything from cars to computers without putting more stress
on the environment. That’s another reason why scientists are so interested in
solar power—it doesn’t pollute the air, water, or land. And since the sun lights and
warms the entire planet, the ability to harness its energy could provide a clean
energy source for everyone.
Focusing on fuel
The main sources of energy that people use today are called fossil fuels, such as
natural gas, oil, and coal. Unfortunately, the supply of fossil fuel is limited. Once we
use all the coal and oil in the Earth, they’re gone for good. The sun, on the other
hand, is a renewable energy source. No matter how we tap it for energy, the sun
will be around—at least for the next few billion years.
There’s another problem with burning fossil fuels—pollution. The ideal energy
sources of the future will be "clean": they won’t produce carbon dioxide and
other gases that pollute the environment as fossil fuels do.
Hydrogen is one alternative to fossil fuels that interests many researchers today.
Hydrogen burns clean—it produces only water, not carbon dioxide. Researchers
are trying to come up with ways to make large quantities of hydrogen cheaply
and cleanly, and one way involves using plants or plant-like organisms, such as
algae.
Putting plants to work
Some scientists are trying to get plants, or biological cells that act like plants, to
work as miniature photosynthetic power stations. For example, Maria Ghirardi of
the National Renewable Energy Laboratory in Golden, Colo., is working with
green algae. She’s trying to trick them into producing hydrogen instead of sugars
when they perform photosynthesis. Once the researchers can get the algae
working efficiently, the hydrogen that they produce could be used to power fuel
cells in cars or to generate electricity.
During photosynthesis, plants normally make sugars or starches. "But under
certain conditions, a lot of algae are able to use the sunlight energy not to store
starch, but to make hydrogen." Ghirardi says. For example, algae will produce
hydrogen in an airfree environment. It’s the oxygen in the air that prevents algae
from making hydrogen most of the time.
Working in an airfree environment, however, is difficult. It’s not a practical way to
produce cheap energy. But Ghirardi and her colleagues have discovered that by
removing a chemical called sulfate from the environment that the algae grow in,
they will make hydrogen instead of sugars, even when air is present.
Unfortunately, removing the sulfate also makes the algae’s cells work very slowly,
and not much hydrogen is produced. Still, the researchers see this as a first step
in their goal to produce hydrogen efficiently from algae. With more work, they
may be able to speed the cells’ activity and produce larger quantities of The researchers hope that algae will one day be an easy-to-use fuel source. The
organisms are cheap to get and to feed, Ghirardi says, and they can grow almost
anywhere: "You can grow them in a reactor, in a pond.You can grow them in the
ocean. There’s a lot of flexibility in how you can use these organisms."
Making sun catchers from scratch
Other scientists interested in alternate fuel sources are also focusing on plants.
But these researchers want to re-create what plants do without actually using
them.
Plants have molecules that catch and store solar energy. Scientists want to create
molecules that mimic what plant molecules do.
Plants have specific molecules that catch the energy of sunlight during
photosynthesis. Some biochemists have used special techniques to take a
snapshot of these molecules inside a cell. "We finally know what the little factory
looks like," says Daniel Nocera, a professor of chemistry at the Massachusetts
Institute of Technology (MIT).
Chemists in Nocera’s lab have an ambitious plan to capture the sun’s energy.
Instead of tweaking the sun-catching molecules found naturally in plants and algae,
these researchers want to build artificial sun-catching molecules from scratch.
"We’re all busily working away to try to figure out how to make [photosynthesis]
happen outside of the leaf," Nocera says.
Their goal—even though it is still many years away—is to have the artificial
molecules produce hydrogen for everyday use.
Sunlight is already Earth’s chief energy source. If humans can learn to harness
solar energy more efficiently, sunlight will provide even more energy than it does
now.
Finding solutions to our energy problems is one of the great scientific challenges
of our time, Nocera says. But it’s the challenge of the unanswered questions that
keeps him excited about his work. "It’s like we need to paint a picture," he says.
"At some points, we don’t even have the paints yet."
Name: ________________________________
Date: ____________
Life Science
Period: __________
Catching Some Rays
by Sarah Web
www.ScienceNewsForKids.org
Read the article “Catching Some Rays” and answer the following questions in complete
sentences. You will be graded according to the previously distributed rubric.
1. Photosynthesis is the process by which plants produce energy that they can store
and then use. What materials do plants require to perform photosynthesis? Where in
the plant does photosynthesis occur?
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2. Why does solar power appeal to researchers who are looking for new ways to power
our lifestyles?
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3. From what source do we currently get most of our energy? What are two problems
associated with this power source?
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4. Why is hydrogen a desirable alternative to our current fuel source?
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5. The article states that scientist Maria Ghirardi is “trying to trick them (algae) into
producing hydrogen instead of sugars when they perform photosynthesis”. Explain
the two ways in which she is trying to “trick” the algae.
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6. How is Professor Daniel Nocera attempting to use energy from the sun to provide us
with an alternative fuel source?
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7. This article mentions various ways of making alternative energy. In a minimum of
four complete sentences in a cohesive paragraph, identify which method you think is
most likely to solve the world’s energy problem while providing support to your opinion
with facts from the article or elsewhere.
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