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Big-hearted snakes: pythons help put the squeeze on heart disease.

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Students at the University of Alabama are used to seeing a 3-meter (10 foot)-long Burmese python slithering down the hallways of the biology department. Following close behind is physiologist Stephen Secor's lab team as they monitor the python's heart.

Secor got wrapped up in studying Burmese pythons after observing their amazing digestive feats. The snakes--which grow to lengths of 7 m (23 ft) and can weigh more than 100 kilograms (220 pounds)--can swallow an animal their own size whole, and then go months without eating. That's like a person eating 600 hamburger patties in one sitting!

Within two or three days after a meal, most of the python's internal organs double in size and its heart size increases 40 percent. "Their hearts grow because so much is being asked of them when snakes are digesting this meal," says Secor. "They're having to pump blood to these now extremely active organs."

Over the years, Secor's team has uncovered a lot about pythons' hearts. Even so, no one understood how the snakes' hearts got to be super size so quickly. Then Secor got a phone call from Leslie Leinwand, a molecular biologist at the University of Colorado. She wanted to tackle the mystery in the hope that the snakes' secrets would lead to treatments for human heart disease.

HEART OF THE MYSTERY

Leinwand thought that python cardiac hypertrophy--an increase in the size of heart cells--might help people. Human hearts can also undergo hypertrophy, either for good or for bad. After the heart's chambers fill with blood, the heart muscle contracts to pump the blood throughout the body (see Inside a Human Heart, p. 14). In harmful cardiac hypertrophy, the heart muscle thickens and the size of the chambers decreases, making the heart less efficient at pumping.

On the other hand, athletes experience beneficial cardiac hypertrophy, in which both the heart muscle and the chambers increase in size over a period of months because of exercise. Pythons somehow achieve the same thing, but quickly and without exercise. This type of healthy growth could benefit people with heart disease whose doctors have cautioned against exercise.

"We might be able to use this biology of the python to mimic an exercise state---a beneficial state," says Leinwand. But to do that, the scientists would first have to figure out what triggers a python's heart to swell.

SLITHERY CLUES

Unlike the researchers in Secor's lab group, Leinwand's team wasn't used to handling snakes, but they put aside their fears and looked for clues. They suspected that a mystery substance circulating throughout the python's body is what caused its organs to increase in size. "We figured that since most of the organs in the body get bigger, there probably was something in the blood that was promoting that growth," says Leinwand. Her team compared blood from fasting pythons with blood from pythons that had been fed and saw that after a meal, the snake's blood was so full of fats that it looked milky.

One team member proposed an experiment: Add blood from fed pythons to rat heart cells in a dish and see if the rat cells would grow. Leinwand didn't think that moving a substance directly from reptile to mammal would be effective.

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"I told her not to do the experiment because there was no chance it was going to work, and she ignored me, which was a very good thing on her part," says Leinwand with a laugh. The rat cells ballooned in size, confirming that the mystery substance was in the python's blood--and raising hopes that it would work in riving mammals, including people.

The team experimented to find out which blood components had the supersizing effect on rat heart cells. When they finally hit on the right combination of three fatty acids, they sent the recipe to Secor, who infused the mixture into fasting pythons. Their hearts quickly grew--as if they'd just gulped down a large meal. Leinwand's team then infused the mixture into live mice and observed the same effect.

The researchers had identified the mystery substance, but much work remains before there can be human medical applications. Secor wants to investigate pythons further because he suspects that some of their other fast-growing organs may also hold medical secrets.

Other snakes and lizards have already been useful in the development of medicines to treat human diseases (see Life-Saving Reptiles, right). Secor says, "There's so much discovery yet to be made in the natural world."

WHAT DO YOU THINK?

What other animal adaptations might be beneficial for treating disease in people?

INSIDE A HUMAN HEART

The heart pumps blood throughout the body. This large muscle about the size of a fist beats about 60 to 100 times per minute. Blood vessels called arteries carry blood away from the heart, and veins carry blood back to the heart. Chambers called atriums and ventricles contract to pump the blood, and valves control the flow.

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Life-saving reptiles

Pythons aren't the only reptiles that hold keys to treating human disease. Scientists have already developed life-saving medicines from the venom of these reptiles:

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REPTILE: Gila monster

MEDICINE: exenatide (Byetta)

USE: Alters blood-sugar levels in people with type 2 diabetes

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REPTILE: Brazilian arrowhead viper

MEDICINE: captoprii (Capote.)

USES: Treats high blood pressure and heart failure

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REPTILE: Southeastern pygmy rattlesnake

MEDICINE: eptifibatide (Integrilin)

USE: Lessens blood clotting in people with acute coronary syndrome, a condition caused by lack of blood flow to the heart

NATIONAL SCIENCE EDUCATION STANDARDS:

Grades 5-8: Regulation and behavior

Grades 9-12: Behavior of organisms

COMMON CORE STATE STANDARD: LITERACY IN SCIENCE: 2. Distinguish among facts, judgment based on research, and speculation.

OBJECTIVE

Learn how scientists are studying the biology of Burmese pythons to help find treatments for human heart disease.

BEFORE READING

* What do you know about pythons? (They are some of the world's largest snakes. They are constrictors that suffocate prey by squeezing it. They swallow their prey whole.)

* What do you know about the human heart? (It is a muscle. It pumps to circulate blood through the body. It has four chambers, etc.)

* How can you help keep your heart healthy? (Exercise regularly, avoid foods with unhealthy fats, don't smoke, etc.)

LESSON

1, Go to www.scholastic.corn/scienceworld. Open the digital edition to page 12 and have students do the same in their magazines. Call on a volunteer to read the headline and the large text below it. Ask students what they think the article is going to be about.

DIGITAL STICKY NOTES 2. As a class, read the first two sections aloud (up to "Slithery Clues"). Ask students why the scientists became interested in studying pythons. What question did scientists hope to answer? (Con learning about snake hearts' hypertrophy help humans?) Record students' answers on a digital sticky note.

3. Read the rest of the article together. Then refer to the question students wrote on the sticky note in the previous step. Were the researchers able to answer the question?

DIGITAL STICKY NOTES 4. Engage students in a discussion about how the scientists attempted to answer the question. On another sticky note, list the steps the scientists took during their research. Highlight the observations that advanced the research. What conclusions did the scientists make at the end? Ask students to predict the next steps in the research.

DISCUSSION

Turn to the sidebar "Life-Saving Reptiles" on page 14. Have students read about other animals whose venom inspired medicines for humans. Then read the text in the box labeled "What Do You Think?" on page 14: "What other animal adaptations might be beneficial for treating diseases in people?" Discuss other animal features that would be useful for humans.

ASSESSMENT

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After discussing the scientists' research, pass out the "Observation or Conclusion'?" work sheet from the "Skills Sheets" tab at www.scholastic.com/scienceworld. Use the work sheet to evaluate students' understanding of observations versus conclusions.

DON'T TEACH BIOLOGY?

Go to www.scholastic.com/scienceworld to download these assessment skills sheets from the "Skill Sheets" tab:

EARTH SCIENCE: INVADING SNAKES

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Pythons may be helping scientists learn about the heart in the lab, but they are causing big problems in the wild in Florida. Read this passage to learn about the environmental impact of pythons in the Everglades.

PHYSICS: UNDER PRESSURE

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One of the most important body measurements is blood pressure, the force your blood exerts on the walls of your blood vessels. Use this graphing activity to learn more about blood pressure in animals.

RESOURCES

* VIDEO EXTRA: Watch a video of a python killing and eating its prey at: www.scholastic,com/scienceworld

* See a python eat an alligator whole (Caution: This is gory. Review prior to showing): www.pbs.org/wnet/nature/episodes/ invasion-of-thegiant.pythons/video.alligator-vs-python/5541.

* Learn more about the circulatory system: http://kidshealth.org/teen/your_body/body_basics/heart.html.
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Title Annotation:BIOLOGY: HEALTH
Author:Adams, Jacqueline
Publication:Science World
Geographic Code:1USA
Date:Mar 26, 2012
Words:1491
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