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Cancer Warrior
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Classroom Activity
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Objective
To determine the toxicity of salt to an intracellular liver process
using a dose response curve.
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copy of "What's the Right Dose?" student handout (HTML)
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dropper bottle of .17 fluid ounce (5 ml) of liver cell homogenate
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dropper bottle of .17 fluid ounce (5 ml) of 2 percent salt
solution
- test tube and test tube rack spot plate balloons
- watch showing seconds plastic pipette
- graduated cylinder (.34-.85 fluid ounces; 10-25 ml)
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1.0-1.35 fluid ounces (30-40 ml) of 3 percent hydrogen peroxide
- safety glasses
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Gather the materials listed above and in
Materials Preparation below.
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Organize students into teams of two and provide each team with a
copy of What's the Right Dose? activity page and a set of
materials.
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Explain to students that they will be determining how different
salt concentrations affect the liver's ability to break down
toxic hydrogen peroxide.
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Students will conduct the experiment three times. Discuss with
them why it is important to conduct more than one trial at each
dose and report the average. Remind students to note sources of
error as they conduct each trial. Assign one group to do the
experiment as the control group, i.e., the liver cells that get
no dosages of salt.
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Assign each team a number of drops to experiment with, from 0
(control group) to 12. Have students begin, allowing a full four
minutes for the salt to "act" upon the liver cells. When they
are ready, students can start their three trials using the
instructions on the student activity page.
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Once students have recorded their results, have them determine
the average of the three trials. Include each team's average on
a class data table indicating: Team, Dosage of Salt (# of
drops), and Average Response Time (# of seconds).
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Have students graph the data by putting Dosage of Salt (# of
drops) on the X-axis and Degree of Inhibition (# of seconds) on
the Y-axis. You can establish degree of inhibition values
together as a class or use the Sample Test Results values in the
Activity Answer.
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To complete the lesson, discuss with students the four phases of
clinical trials (see Activity Answer for
more information).
Materials Preparation
Liver cell homogenate: Blend 1/4 pound (113.4 g) of fresh beef liver
with 13.5 fluid ounces (400 ml) of water in a blender. If possible,
strain homogenate through a cheese cloth. Keep in refrigerator until
20 minutes prior to use. Put into dropper bottles for each team.
2 percent salt solution: Add .07 ounces (2 g) of table salt to 6.8
fluid ounces (200 ml) of tap water. This will yield an approximately
2 percent salt solution. Put into dropper bottles for each team.
3 percent hydrogen peroxide solution: This can be purchased in any
pharmacy. Do not use a higher percent hydrogen peroxide solution.
Make sure you check the expiration date. Provide 1.7 fluid ounces
(50 ml) available to each team.
Balloons: Choosing the right size is critical. If too small, the
balloons will fill up too fast; if too big, they will fill up too
slowly.
Clinical trials are used to determine the efficacy and safety of new
drugs or treatments. According to National Institutes of Health,
there are four phases in clinical trials:
Phase I: The drug is tested on humans for first time, usually
on between 20 and 80 people. Researchers begin to evaluate the
drug's overall safety, its safe dosage range, and any side effects
it produces.
Phase II: In this phase, the drug is further evaluated with
testing on a larger group of people (100 to 300).
Phase III: The drug is administered to large groups of people
(1,000 to 3,000) to confirm its effectiveness, monitor its side
effects, and compare it to commonly used treatments.
Phase IV: After the drug has been marketed, testing is
continued to monitor how the drug reacts in various populations and
determine the consequences of long-term use.
This activity models part of a Phase I clinical
trial—investigating safe dosages. Students plot and use a dose
response curve to determine the toxicity of salt on an intracellular
liver process. The role of healthy liver cells is to deactivate and
eliminate a wide variety of toxic molecules in the body, including
hydrogen peroxide—H2O2—which can
damage cells and tissues. Since hydrogen peroxide is broken down
into two harmless substances, water and oxygen, the rate at which
oxygen gas is produced can reveal whether liver cells are
functioning normally. Salt inhibits the ability of liver cells to
change hydrogen peroxide into water and oxygen.
Breaking down hydrogen peroxide into water and oxygen is a two-step
process. During this process, free radicals are formed, which have
the ability to create havoc within the cell. If the liver is unable
to deactivate and eliminate hydrogen peroxide, cells and body
tissues may be harmed or poisoned, and thus be unable to carry out
their vital cell processes.
Sample Test Results
Book
Cooke, Robert.
Dr. Folkman's War: Angiogenesis and the Struggle to Defeat
Cancer.
New York: Random House, 2001.
Provides an account of Folkman's work on angiogenesis, offering
readers insight into how medical research is conducted.
Article
Folkman, Judah. Fighting Cancer by Attacking Its Blood Supply.
Explains how angiogenesis provides one of the keys to tumor growth,
and how anti-angiogenic drugs could be successful in stopping cancer
from proliferating, perhaps in combination with traditional cancer
treatments.
Web Sites
NOVA Online—Cancer Warrior
http://www.pbs.org/nova/cancer/
Provides program-related articles, interviews, interactive
activities, resources, and more.
CancerTrials
http://www.cancer.gov/clinical_trials/
Includes information about clinical trials and features a section to
help users locate ongoing trials. A service of the National Cancer
Institute.
ClinicalTrials.gov
http://www.ClinicalTrials.gov/
Provides a primer on understanding clinical trials, as well as
searchable information about current clinical research studies being
conducted.
Understanding Angiogenesis
http://rex.nci.nih.gov/behindthenews/uangio/uangiocontents.htm
Briefly explains key concepts in tumor angiogenesis, such as
metastasis and angiogenesis inhibitors. Includes illustrations.
The "What's the Right Dose?" activity aligns with the following
National Science Education Standards.
Grades 5-8
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Science Standard A: Science as Inquiry
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Abilities necessary to do scientific inquiry
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Science Standard C: Life Science
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Structure and function in living systems
Grades 9-12
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Science Standard A: Science as Inquiry
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Abilities necessary to do scientific inquiry
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Science Standard C: Life Science
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The cell
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