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Who is Maria Mayorga?
Maria Mayorga was born in San Antonio, Texas, on October
30, 1952. While growing up, she attended an all-girls school
in San Antonio. Maria's love for biology began through her science
studies at school. She remembers that her biology teacher was
very dynamic. "She didn't just teach from the textbook.
She always brought in articles and tied in current events. We
did laboratories to illustrate the science concepts we were learning.
She made science exciting and fun, not just something in a textbook."
Maria was inspired by her teacher and decided she wanted to become
a physician, but she also decided that she always wanted to keep
doing some type of research because she loved exploring and making
discoveries.
Finishing Her Education Despite a Difficult
Path
At the age of 16, Maria married her high school sweetheart. By
the time she finished high school, their first child was born.
Nevertheless, she enrolled immediately as a freshman at St. Mary's
University in San Antonio. Soon after, she went to see the undergraduate
counselor about her courses, but he was far from encouraging.
At the time, she had a 3-month-old infant and was pregnant with
her second child. The counselor barely listened to Maria. He
thought she would never finish her undergraduate degree. She
was determined and said, "You watch me!" With help
from her husband and family, she continued to take undergraduate
courses and work several part-time jobs. Maria completed her
bachelor's degree with a major in biology and a minor in chemistry
in four years.
Maria wanted to go on to medical school. Unfortunately, her
husband did not support her goals. Soon after, they divorced.
Maria then entered medical school at the University of Texas-San
Antonio; she chose the school so she could be close to her family.
They were very supportive of Maria's studies and took care of
her two children while she was in class. In 1978, she earned
her M.D. and, over the next seven years, she completed an internship
and residency in internal medicine and a fellowship in pulmonary
medicine.
Joining the Army
During her internship, Maria met and married another physician,
Dr. Al Wehrle, who was an officer in the U.S. Army. Al, Maria,
and her two children, Raquel and Emiliano, became a family. Soon
after, Al was scheduled to move his new family to Germany. Maria
decided to join the Army as well, since that would allow her
to continue her medical practice while in Germany, something
she could not do as a private citizen. Throughout her medical
practice, she kept involved in medical research activities. She
felt it would provide her with greater career flexibility for
the future.
After returning from Germany in 1989, Maria decided to pursue
her research interests further. She applied for and received
a Medical Research Fellowship to work and study at the Walter
Reed Army Institute of Research (WRAIR) in Washington, DC. There,
she was able to learn additional research techniques that allowed
her to pursue her medical research interests more intensively.
She became a member of the Department of Respiratory Research
at WRAIR. One year later, she became chief of the department
and was promoted to lieutenant colonel (LTC).
Protecting Workers
The research in LTC Mayorga's department contributes to ensuring
the safety of people who work in a variety of very dangerous
situations. Her department is especially interested in two areas
-- the shock waves that accompany explosions and the effects
of potentially toxic gases.
In LTC Mayorga's first area of research, her department is
developing computer models to depict how shock waves affect the
body's organs. Whenever a firefighter or petroleum worker is
exposed to a fire or explosion, or a soldier fires a weapon,
toxic gases are released and the body is subjected to pressure,
including sound waves, from the explosion. Those organs that
normally contain air or have open spaces, such as the heart,
lungs, stomach, and intestines, are especially susceptible to
damage. This research will be used to modify safety equipment
for firefighters and petroleum workers, and weapons for soldiers,
to minimize the impact of blast pressure on the body.
LTC Mayorga's second area of research is on the toxic gases
released during explosions, including carbon dioxide and nitrogen
dioxide. How much of these gases is produced? How do they affect
the respiratory system? How can we minimize the production of
the gas and, more importantly, its effects on nearby persons?
LTC Mayorga's department is working on a computer model that
will predict these effects. Since these same gases are produced
during home and forest fires and during fires in petroleum wells,
such as in off-shore drilling, the research is important for
people in a variety of occupations.
LTC Mayorga continues to enjoy balancing her involvement in
research with her medical practice. She says, "Research
is always interesting. You answer one question and there is always
another question waiting for someone to discover the answer.
I take pleasure from knowing that what I do contributes to world
health and to the world's scientific progress."
A Busy Home Life
LTC Mayorga also places a high priority on spending plenty of
time with her family. She and her husband and their three children,
John Paul, 14, Elizabeth, 9, and Michael, 7, live in a wooded
area in rural Maryland outside of Washington, DC. Raquel and
Emiliano, now adults, are frequent visitors to their home. Organization
is LTC Mayorga's key to managing her busy household. She also
sets aside some time for herself. After taking her children to
school, LTC Mayorga uses her half-hour drive to work to have
her morning coffee and work on voice lessons and language tapes.
Her favorite hobbies are gardening and taking care of the family's
dogs. She also is interested in national and international politics,
enjoys watching the news, and reads historical fiction and self-improvement
books. Music has a special place in LTC Mayorga's life too; she
sings in a choir and takes voice and piano lessons.
What Is LTC Mayorga's Advice for Students?
LTC Mayorga encourages students to "...love and be good
to yourself. Develop a positive self-image. Whatever goals you
set for yourself, give yourself time to accomplish them. Don't
allow others to dissuade you from your goals. Finally, be sure
to develop outside friendships and cultivate them. They provide
both support and perspective."
ACTIVITY #1: Exploring Diffusion
The Problem
You ordered two vials of fluid from a chemical company to
use in a future experiment. One vial contains a protein solution
(protein and water) and the other contains a starch solution
(cornstarch and water).
The salesperson who sent you the fluids told you over the
telephone which code number referred to the protein solution
and which referred to the starch solution. She also told you
that one of the solutions was contaminated by a sugar (D-glucose).
For the experiment you want to do later, you need these solutions
"cleaned up" -- with most of the sugar removed. Although
you knew you should have entered this information into your laboratory
notebook, instead you wrote it down on a scrap of paper...and
lost it!
Now you don't know which code number refers to protein and
which refers to starch or which solution was contaminated with
sugar!
Your Missions
1. Use the chart and procedures on the following page to determine
which solution contains protein, which contains starch, and which
contains sugar.
2. Use what you know about diffusion and osmosis to show how
you can reduce the amount of sugar in the contaminated sample
without losing the protein or starch.
Mission #1: Identifying Unknown Solution
Testing Procedures for Unknown Solutions
(Be sure to use separate eyedroppers for each substance!)
1. To test for the presence of protein in the unknown solutions.
Place 3 drops of protein solution into a small test tube. Add
3 drops of Biuret reagent.
Do you see any changes in the solution?
Place 3 drops of unknown solution #1 into a small test tube.
Add 3 drops of Biuret reagent.
Did you get the same response as you did with the protein solution?
Place 3 drops of unknown solution #2 into a small test tube.
Add 3 drops of Biuret reagent.
Did you get the same response as you did with the protein solution?
2. To test for the presence of starch in the unknown solutions.
Place 3 drops of starch solution into a small test tube. Add
1 drop of iodine reagent.
Do you see any changes in the solution?
Place 3 drops of unknown solution #1 into a small test tube.
Add 1 drop of iodine reagent.
Did you get the same response as you did with the starch solution?
Place 3 drops of unknown solution #2 into a small test tube.
Add 1 drop of iodine reagent.
Did you get the same response as you did with the starch solution?
3. To test for the presence of glucose (a sugar) in the unknown
solutions.
Cut 0.5 in. piece of glucose test paper. Place 1 drop of glucose
solution on paper.
Wait the amount of time given on the paper directions. Did the
paper change color?
Does this indicate the presence of glucose?
Cut another 0.5 in. piece of glucose test paper.
Place 1 drop of unknown solution #1 on paper.
Wait the amount of time given on the paper directions. Did the
paper change color?
Does this indicate the presence of glucose?
Cut a third 0.5 in. piece of glucose test paper.
Place 1 drop of unknown solution #2 on paper.
Wait the amount of time given on the paper directions. Did the
paper change color?
Does this indicate the presence of glucose?
What did you conclude was in each of your samples?
Unknown #1: _______________________________
Unknown #2: _______________________________
NOTE: Before you continue to "Mission #2," confirm
your findings with your instructor!
Mission #2: Reducing Contamination
Now that you know which solution is contaminated, how will
you "clean it up," that is, remove some of the sugar?
Fortunately, you have some dialysis tubing handy. Dialysis tubing
is a clear tubing, made of cellulose (from plants). The tubing
has tiny holes in it, just large enough to let smaller molecules
pass through, but holding most larger molecules inside. How can
you make use of this characteristic to help reduce the amount
of sugar in your sample? (See the Instructions, "Using Dialysis
Tubing," below.)
Devise a plan for completing mission #2. Use what you know
about diffusion and osmosis to complete this mission. Show how
you can reduce the amount of sugar in the contaminated sample
without losing the protein or starch.
INSTRUCTIONS: Using Dialysis Tubing
1. Cut a piece of tubing about 15-18 cm (6-7 in.) long.
2. Wet the tubing with water.
3. Fold up one end of the tubing and tie it tightly with string.
4. Partly fill the tube with whatever solution you choose.
5. Tie off the top end of the tube by tying a piece of string
tightly around it.
6. Rinse off the tube under running water.
7. Place the tube into a 500-ml beaker half filled with whatever
fluid you choose (for example, water or protein solution). Be
sure the tube is covered with the solution.
8. Gently stir the solution around the dialysis bag every minute
or so, being careful to not poke a hole in the bag.
9. Take samples every 10-15 minutes to check for the presence
of sugar, protein, etc. From which solution do you want to take
samples...inside the bag or outside?
Plan for Completing Mission #2
Write your plan below. Be sure to show your plan to your
instructor before you execute it!
Experimental Design
Problem:
Hypothesis:
Materials:
Methods:
Results (What evidence do you have that you are succeeding
in removing the sugar?):
Conclusions:
For future experiments, how could you speed up this process?
SUGGESTIONS FOR TEACHERS
ACTIVITY #1: Exploring Diffusion
Purpose
To provide students with an opportunity to apply their basic
understanding of diffusion to problems involving the separation
of solutes by molecular weight.
Objectives
1) To improve students' skills in experimental design.
2) To learn how to test solutions for protein, starch, and sugar
unknowns.
3) To gain skills in using dialysis as a tool for purifying solutions.
Materials
For each student working individually or for each group of
two to three students
- 1 envelope of gelatin (e.g., Knox)
- 5 g D-glucose (dextrose)
- 1 tablespoon cornstarch
- 15- to 18-cm piece of cellulose dialysis tubing
- several drops of Biuret reagent
- 3-4 glucose test strips (available at any pharmacy)
- Lugol's iodine or tincture of iodine
- 9 eyedroppers or disposable pipettes
- 500-ml beaker or clear plastic cup
- 3 vials for unknown solutions
- 6 small test tubes (plastic or glass)
- glass rod or straw for stirring
- string or tubing clamps (white embroidery floss works well;
use 2 single 15-cm strands)
- scissors
Before You Begin
1) Purchase Biuret solution, Lugol's iodine or tincture of
iodine, and glucose test strips (see "References and Resources"
below).
2) Prepare protein solution. Dissolve gelatin in warm water.
Use 1 teaspoon per 100 ml warm water. Stir frequently.
3) Prepare starch solution. Dissolve 1 tablespoon of cornstarch
in 100 ml cold water. Stir frequently. Not all of the cornstarch
will dissolve.
4) Divide protein and starch solutions into two beakers each.
Add D-glucose (1 g per 100 ml solution) to one beaker of each
solution.
5) Prepare unknown vials of protein solution and starch solution
for each pair of students (10 ml each). Code each vial so that
you can identify its contents; for example, even-numbered vials
could be protein and odd-numbered vials could be starch. Be sure
you can identify which vials contain sugar.
6) Cut dialysis tubing into 15- to 18-cm (6-7 in.) lengths. Wet
tubing with water before use.
Safety Considerations
- Biuret solution and iodine solutions are toxic and should
not come in contact with the eyes or mouth. Students should wear
safety goggles and laboratory coats or aprons.
- Students should wash their hands following the experiment.
- Both of these solutions can stain clothing.
Questions to Ask
- How do you know that your solution is becoming "cleaner,"
that is, contains less sugar?
What is your evidence for this?
- How can you tell when your solution is "clean,"
that is, free of sugar?
- Do molecules move through the membrane both ways? How can
you tell?
- Which is larger, sugar or protein? sugar or starch? What
is your evidence for this?
- How could you speed up the dialysis process (e.g., stirring,
using fresh dialysis solution to keep the concentration gradient
high)?
- In this activity, we used molecular weight to separate different
substances. What other characteristics of a substance might you
use to separate them (e.g., solubility, positive or negative
charge, etc.)?
Where to Go From Here
- Do Activity #2, "Diagnosing the Damaged Lung."
- Interview a biomedical researcher to learn how dialysis is
used in research. This is a very common research technique, used
to reduce the amount of salt, sugar, or water in a mixture of
substances.
- Conduct a study of red blood cell permeability and hemolysis,
such as the one developed by Cusker (1991).
- Try the activity, Membrane Permeability with Beets by P.
Vavala (see "References and Resources" section).
Ideas for Assessment
- Students' initial experimental design and laboratory reports
can serve as one assessment tool.
- Teams of students also can provide verbal reports as they
are working on their conclusions or prepare research posters
showing their results.
References and Resources
Cusker, J. (1991). Hemolysis of red blood cells: A study of
cell permeability. In: D.S. Sheldon, &
J. E. Penick (Eds.). Favorite Labs from Outstanding Biology
Teachers. Reston, VA: National Association of Biology Teachers.
Daniel, A. B. (1994). I'm passing through! In: Y. S. George,
A. B. Daniel, V. L. Worthington, &
S. M. Malcom (Eds.). The AAAS Black Church Health Connection
Project: Hands-on Life Sciences Activities. Washington, DC:
American Association for the Advancement of Science.
Membrane Transport Kit. (1993). Chippewa Falls, WI:
Hubbard Scientific, Inc.
Vavala, P. (1995). Membrane permeability with beets.
On the Access Excellence Home Page at http//www/gene.com:80/ae/.
For science supplies:
Carolina Biological Supply Company, 2700 York Road, Burlington,
NC 27215, (800) 334-5551.
Fisher Scientific, Educational Division, 485 South Frontage Road,
Burr Ridge, IL 60521, (800) 955-1177.
Flinn Scientific, P.O. Box 219, Batavia, IL 60510, (630) 761-8518.
WARD'S, 5100 West Henrietta Road, P.O. Box 92912, Rochester,
NY 14692-9012, (800) 962-2660.
Photo credit:
Photos on pages 51 and 54 courtesy of Maria Mayorga, Walter
Reed Army Institute of Research, Washington, DC.
ACTIVITY #2: Diagnosing the Damaged Lung
The Problem
Workers at a manufacturing plant have been accidentally exposed
to small amounts of a particular gas and considerable dust over
a period of several weeks. Although the gas is not known to be
poisonous in small amounts, some workers have complained of coughing
and irritation in their throats and chests.
You suspect that the gas has caused some damage to the lung
tissue _ actually creating tiny tears in the tissue. Normal lung
tissue would regulate the substances coming into and out of the
blood and tissue, but damaged areas would be unable to do so.
Therefore, tissues would lose important materials (such as proteins,
carbohydrates, and salts) and would be exposed to damaging materials
(such as toxins, bacteria, and viruses).
Your Mission
You have obtained samples of lung tissue from patients who
were exposed to the gas and from patients who were not exposed.
Under the microscope, you think you can see damage to the tissue,
but you want more proof.
Use what you have learned about diffusion to design and perform
an experiment to prove or disprove that the samples from the
damaged lungs are "leaking" larger molecules (such
as protein or starch) that the undamaged lungs do not.
Procedure
1. Rather than use actual lung tissue, we will use dialysis
tubing as a model for the cell membranes that separate the lung
tissue from the air spaces in the lung. The inside of the tubing
can represent the space inside the lung and the area surrounding
the dialysis tubing can be the lung tissue itself _ or vice versa.
Be sure to indicate in your final report which space you used
to represent the lung tissue and which represented the space
inside the lung.
2. Brainstorm with your partner or group about possible ways
to determine whether or not the damaged tubing will "leak"
larger molecules such as protein and starch.
3. Design a "Plan for Completing Your Mission" on page
67. Be sure to write out your purpose and hypothesis, what your
procedures will be, what materials you will need, and what your
dependent and independent variable(s) are. Develop a data chart
where you can write down your findings. Be sure your experimental
design takes into account the "Questions to Answer"
on page 67.
4. BEFORE you do the experiment, review your experimental design
with your teacher.
5. Perform the experiment and record your findings.
6. Prepare a report on your experimental design and your findings.
Be sure to include the following: purpose, hypothesis, materials,
procedures (including description of dependent and independent
variables and controls), results, conclusions, and further research
needed.
Materials
- dialysis tubing (keep it wet, please)
- protein solution
- Biuret solution (protein detector)
- starch solution
- Lugol's iodine (starch detector)
- 50-ml beakers or small cups
- string (white embroidery floss) or dialysis clamps
- scissors
- eyedroppers
- small test tubes or small cups
- glass rod or straw for stirring
Plan for Completing Your Mission
Be sure to show your plan to your instructor before you execute
it!
Experimental Design
Problem:
Hypothesis:
Materials:
Methods:
Results (draw a chart for your data):
Conclusions:
Questions To Answer
1. Does protein leak through the damaged lung tissue? through
the normal tissue?
2. Do complex carbohydrates such as starch leak through the damaged
and normal lung tissues?
3. What is your "control" in this experiment?
4. What conclusions can you draw from your findings?
5. What other experiments would you want to do to explore this
further?
SUGGESTIONS FOR TEACHERS
ACTIVITY #2: Diagnosing the Damaged Lung
Purpose
To strengthen students' skills in developing hypotheses, designing
experiments, and analyzing results.
Objectives
1) To design and conduct an experiment that will distinguish
between damaged and normal "lung tissue."
2) To use dialysis tubing as a model and to employ principles
of diffusion.
Materials
For each group of two to three students
- 2 pieces of dialysis tubing, one "damaged" (see
below) and the other undamaged
- 10 ml protein solution (see below)
- several drops of Biuret solution (protein detector)
- 10 ml starch solution (see below)
- several drops of Lugol's iodine or tincture of iodine (starch
detector)
- 500-ml beakers or small cups
- string or tubing clamps (white embroidery floss works well;
use 2 single 15-cm strands)
- scissors
- several eyedroppers
- 4-8 small test tubes or small cups (such as souffle cups)
- 2-3 glass rods or straws for stirring
Before You Begin
1) Cut dialysis tubing into 15- to 18-cm (6-7 in.) pieces.
Soak tubing in water before use. Divide the pieces into two groups,
damaged and normal. For the damaged pieces, use the tip of a
sharp needle to poke small holes through each piece of tubing;
be sure to make holes all the way through each piece but don't
make the holes large and conspicuous.
2) Prepare the protein solution by dissolving gelatin (such as
Knox) in warm water. Use approximately 1 teaspoon per 100 ml
warm water. Stir frequently.
3) Prepare the starch solution by dissolving 1 tablespoon of
cornstarch in 100 ml cold water. Stir frequently. Not all of
the cornstarch will dissolve.
4) Purchase Biuret solution and Lugol's iodine or tincture of
iodine (see the section, "References and Resources").
Use in a well-ventilated area.
Safety Considerations
- Biuret solution and iodine solutions are toxic and should
not come in contact with the eyes or mouth. Students should wear
safety goggles and laboratory coats or aprons.
- Students should wash their hands following the experiment.
- Both of these solutions can stain clothing.
Questions to Ask
- Does protein leak through the damaged lung tissue? through
the normal tissue? What is your evidence for this?
- Do complex carbohydrates such as starch leak through the
damaged and normal lung tissues? What is your evidence for this?
- What is your "control" in this experiment?
- What conclusions can you draw from your findings?
- Now that you have done your experiment, can you think of
ways to improve your experimental design?
- What other experiments would you want to do to explore this
further?
- What types of things come into your lungs that normal tissue
would prevent from getting into your system (e.g., bacteria,
viruses, certain gases, etc.)?
Where to Go From Here
Teams of students could explore and develop a poster or presentation
on different respiratory diseases: What causes them? How do they
affect the respiratory system at the tissue or cellular level?
What are the symptoms? How can they be prevented? How can they
be treated? Who is most at risk for developing this disease?
Good possibilities include emphysema, "walking" pneumonia,
tuberculosis, cystic fibrosis, lung cancer, asthma, chronic obstructive
pulmonary disease (COPD), or sarcoidosis. Your local American
Lung Association and public library health section are good sources
of information.
Ideas for Assessment
Students' initial experimental design and laboratory reports
can serve as one assessment tool. Teams of students also can
provide verbal reports as they are working on their conclusions.
References and Resources
See listing at end of Activity #1, "Suggestions for Teachers." |
