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The Scientific Method
What is it?
The scientific method is the experimental testing of a hypothesis formulated after the systematic, objective
collection of data. A scientist who studies our immune system phrased this idea very well:
I now appreciate how much I learn by being wrong. I can change my mind when confronted with a rational
argument, without the need to have the change appear to be purely semantic or to hope it will pass unnoticed.
What must it be like to be a priest, general, bureaucrat, lawyer, medicine person, or politician who is never
permitted to be wrong? No wonder they learn so slowly. I am grateful to be in a profession where the
realization of being wrong is equivalent to an increase in knowledge.
-Melvin Cohn. Annual Review of Immunology 12, 2 (1994)
The scientific method is often divided into steps. This is helpful for putting the method into context, but
keep in mind that the key element of the scientific method is testing the hypothesis. In other words, can you
prove that you are wrong?
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Observe the situation
Ask a question
Turn that question into a testable hypothesis
Predict the outcome of your experiment
Perform your experiment
Analyze the results
Evaluate your hypothesis
Evaluating science
Mistakes made in applying the scientific method to real-world problems can result in unsupported, or even
incorrect, conclusions. An example of a scientific conclusions based on insufficient scientific method
recently occurred in the field of breast cancer research.
Breast cancer is caused when normal cells change and produce a tumor. In
a study published in the New England Journal of Medicine (336, 1269
(1997)), scientists from Norway studied the incidence of breast cancer in
25,624 women.
Participants gave details about their height, weight, diets, and exercise
habits. The results showed an over all reduction of breast cancer by 37% for
women who exercise regularly. Women who are lean and exercise at least 4
hrs per week showed the lowest incidence.
Image courtesy of WebPath
Many newspapers picked up on the data with headlines stating that exercise prevents cancer, but an
editorial in the same journal by Dr. Anne McTiernan put the results in proper perspective (ibid. p. 1311).
She points out that women who exercise regularly have higher levels of education and income, smoke less,
drink less alcohol, and consume fewer calories and less fat. She states that establishing a casual pathway
between reduced breast cancer and physical activity will require exploration for biologic mechanisms and
confirmation with clinical experiments. Her final conclusion states the situation very well.
Should a woman exercise and will it prevent breast cancer? I recommend a resounding YES to the first
question. Regular physical activity in women reduces overall mortality and the incidence of coronary heart
disease, diabetes mellitus, stroke, osteoporosis, obesity, and disability, and it also lessens the impact of arthritis
and cognitive decline. With respect to whether exercise reduces the risk of breast cancer, too many questions
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remain for women and their doctors to make informed decisions on whether, how and how much to exercise.
-Dr. Anne McTiernan, New England Journal of Medicine (336, 1311 (1997))
This example illustrates many of the problems associated with the science of biology and medicine.
ACTIVITIES
1.- Study a serie of world maps and compare the differences between countries related with
some parameters relate with the health.
Write a short composition about it.
2.- We need a healthy food as the documentary “supersize Me” shows.
State or research what do the students in our High School eat during the brake.
Wonder around the playground during the braketime and write your observations, later,
state a report with your conclusions.
3.- Analysing the composition of foods.
4.- Calculating the daily energy requirements.
Page 91, 3 of Eso, Santillana.
5.- Evaluating your diet. “”
6.-Scandals about transplants, (Taken from the wipipedia).
(To debate about them)
In 2008, California transplant surgeon Hootan Roozrokh was charged with dependent adult
abuse for prescribing what prosecutors said were excessive doses of morphine and sedatives
to hasten the death of a man with adrenal leukodystrophy and irreversible brain damage, in
order to procure his organs for transplant.[45] The case brought against Roozrokh was the
first criminal case against a transplant surgeon in the US, and resulted in his acquittal.
At California's Emanuel Medical Center, neurologist Narges Pazouki, MD, said an organprocurement organization representative pressed her to declare a patient brain-dead before
the appropriate tests had been done.[40] She refused.
In September 1999, eBay blocked an auction for “one functional human kidney” which had
reached a highest bid of $5.7 million. Under United States federal laws, eBay was obligated
to dismiss the auction for the selling of human organs which is punishable by up to five
years in prison and a $50,000 fine.[46]
On June 27, 2008, Indonesian, Sulaiman Damanik, 26, pleaded guilty in Singapore court for sale of his
kidney to CK Tang's executive chair, Mr Tang Wee Sung, 55, for 150 million rupiah (S$ 22,200). The
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Transplant Ethics Committee must approve living donor kidney transplants. Organ trading is banned in
Singapore and in many other countries to prevent the exploitation of "poor and socially disadvantaged
donors who are unable to make informed choices and suffer potential medical risks." Toni, 27, the other
accused, donated a kidney to an Indonesian patient in March, alleging he was the patient's adopted son, and
was paid 186 million rupiah (20,200 US). Upon sentence, both would suffer each, 12 months in jail or
10,000 Singapore dollars (7,300 US) fine.[
7.- Activitie about Asthma:
Asthma is an inflammatory disease of the lungs in which the patient’s airways become temporarily constricted, making breathing
difficult. Although the condition was virtually unknown in the early 1900s, today it affects 20.3 million people in the United
States and kills 5,000 of them per year. From 1980 to 1994, the prevalence of asthma increased 75%. Asthma rates in children
under the age of 5 have increased more than 160% in the same time period. The exact reason for the increased prevalence of
asthma is not known, but the following observations offer clues:
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Asthma "attacks" can be triggered by the common cold, exercise, cold air, emotional stress, viral infections, aspirin,
industrial air pollutants, smoking, obesity, ozone, and nitrogen dioxide.
Having two parents with asthma increases a child's chances of having the disease. Approximately 40% of children who
have asthmatic parents also develop asthma.
The disease tends to cluster in England and English-speaking countries.
Exposure of children to dust mites, cats, cockroaches, molds, and mildews increases their chances of getting the disease.
Children who are exposed to common parasites seem to have a better-developed immune system than children not
exposed to parasites. These exposed children do not suffer asthma as frequently.
Exposure to occupational agents such as dyes may trigger the onset of adult asthma.
Poverty seems to be a substantial risk factor for the development of asthma.
Questions
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How have the factors that trigger an asthma attack changed since the 1900s? As a researcher, how would you put
together the clues given here to explain the emerging epidemic?
Why do you think Europeans—and especially the English—are most affected by asthma?
Assigments
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Research the relationship between asthma and allergies. Describe how various agents trigger asthma or an asthma
attack.
Find out where in the world asthma is least prevalent, and hypothesize why this is so.
Define the word "epidemiology." How do researchers use epidemiology to study a disease such as asthma?
Research the CDC (Centers for Disease Control and Prevention), which is the epidemiological institution in the United
States. Write a two-page paper on the
different health problems the organization studies. When might common citizens need to use information from the
CDC?
Visit the CDC website on asthma at http://www.cdc.gov/asthma/default.htm and research the National Asthma Control
Program. Find the name and address of agencies in your state that the CDC has funded to fight asthma. Contact one of
those agencies to see what is being done in your area.
References
Asher, M.I., et al. 1998. Worldwide variation in the prevalence of asthma symptoms: The international study of asthma and
allergies in childhood. European Respiratory Journal 12:315–35.
Doyle, Roger. 2000. Asthma worldwide. Scientific American, June, 30.
http://www.mayoclinic.com
http://www.aaaai.org
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8.- Activitie about Medical Benefits of marijuana.
In 2004, Montana became the eleventh state to approve the limited use of marijuana for medical purposes. Previously, voters in
Alaska, Arizona, California, Colorado, Hawaii, Maine, Maryland, Nevada, Oregon, Vermont, and Washington had also approved
the medical use of this drug . However, the use of marijuana as both a psychoactive substance and a medicine is not new.
Marijuana comes from the dried leaves and flowering tops of the hemp plant, Cannabis. As far back as the mid-1800s, both
French and English medical literature reported the use of marijuana for such ailments as "spastic conditions, headache, and labor
pains." Hashish, the concentrated resin from the flower of the hemp plant, was readily available in U.S. pharmacies until the
Harrison Act in 1914, which attempted to regulate the traffic of opium. Somehow, by implication, the use of marijuana also came
under regulation, although it is neither an opiate nor a narcotic. Virtually all use of the drug declined until the 1960s, when it
became a popular recreational drug for the generation known as the baby boomers.
The medical use of marijuana revived during the 1970s. In 1975, a small study at the Sidney Farber Cancer Institute published an
article revealing that tetrahydrocannabinol (THC), a substance found in marijuana, could effectively lessen the nausea and
vomiting associated with chemotherapy. Marinol, a pill form of synthetic THC, has been available in the United States since
1986. THC is also used to treat glaucoma, multiple sclerosis, and weight loss associated with AIDS. However, few wide-range,
controlled studies on humans have been reported.
In 1990, the first Cannabis receptor gene was cloned at the National Institute of Mental Health. The gene was found in rat brain
tissue. The amino acid sequence of the protein receptor was named CB-1. When THC binds to a CB-1 receptor, the drug's effects
are produced. Scientific studies show that this system of cannabinoid (marijuana) receptors is involved in the coordination of
movement, short-term memory, and regulation of mood and emotion.
In 1993, yet another receptor for THC was found at the MRC Laboratory of Molecular Biology. This receptor was named CB-2
because it was not found in rat brains but in macrophages from the spleen. CB-2 receptors have since been found on immune
cells as well.
Questions
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How would a "controlled" study be conducted in terms of human medical treatment? Why do you think few controlled
studies of the effects of THC on humans have been conducted?
Does marijuana work on the spleen as well as the brain? Does marijuana have an effect on the immune system?
Why might pharmaceutical companies want to make an artificial, oral form of THC available?
Do you think the U.S. government should relax current regulations on the growth of the marijuana plant? Why or why
not?
Assignments
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Define “cannabinoid,” and identify what type of organic molecule THC is. Can THC easily travel through membranes
to the interior of cells? Why or why not? Why do cannabinoids and THC require receptors to produce their effects?
Review the meaning of "cloning" as applied to the Cannabis receptor gene. How do scientists clone genes?
Investigate the advantages and disadvantages of inhaling marijuana smoke compared to taking THC in capsule form.
Write up an appeal for a Senate hearing defending the growth, sale, and use of marijuana based on its medical value.
Use the scientific evidence presented above to support your appeal. You are suspicious that the pharmaceutical
companies have used their vast lobbying machines to gain governmental support to keep marijuana use and growth
illegal. In other words, the drug companies would prefer to manufacture an artificial substance to sell for medical
purposes. What would pharmaceutical companies have to gain if the government did keep the growth, sale, and use of
marijuana illegal?
References
Friedman, Hermand, and Thomas W. Klein. 1999. Marijuana and immunity. Science & Medicine. March/April, pp. 12-21.
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Klein, Thomas W.; Cathy Newton; and Herman Friedman. Cannabinoid receptors and immunity. Immunology Today. Vol.
19:373-381.
Watson, Stanley J. Jr., and John A. Benson, Jr. 1999. Institute of Medicine Report on the Medical Use of Marijuana.
Washington, National Academy Press.
http://www.rxmarihuana.com
http://www.nap.edu/books/0309071550/html
http://www.ecureme.com/emyhealth/natural/n_marijuana.asp
http://www.drugpolicy.org/marijuana/medical/
http://www.time.com/time/covers/1101021104/tgood3.html
9.- Caffeine and the brain
Ashley is about to take the final exam for her general biology class. She’s spent many long hours studying, and feels a little tired.
On her way to class, she stops by the student center to grab a large cup of coffee. She hopes that the caffeine in the coffee will
help her do better on the exam.
Chemically, caffeine (C8H10N4O2) is a purine with two oxygens and three methyl groups attached. When ingested, it is rapidly
absorbed and soon reaches all cells of the body, including those of the brain, where it acts as a stimulant. Caffeine is found not
only in coffee, but also in tea, chocolate, and many soft drinks, including popular “energy drinks.” In addition, caffeine is present
in numerous over-the-counter medications, such as headache remedies, diet pills, diuretics, and alertness aids.
How much can Ashley count on coffee to help her on the exam? Without a doubt, caffeine does fight fatigue, so it will likely
help Ashley avoid dozing off during the exam (surely among a student’s worst nightmares). But will it help her recall the
information she has learned? Most likely it will, because Ashley will be more alert. On the other hand, taking in too much
caffeine could make her feel too “jittery” to think clearly.
The mental effects of caffeine can be unpredictable. The rate at which an individual metabolizes caffeine varies by age and sex,
and may be affected by the concurrent use of other drugs, such as alcohol and nicotine. Also, the amount of caffeine an
individual ingests in a cup of coffee can vary quite a bit depending on the size of the cup, the variety of coffee beans, and the
brewing method.
How does caffeine exert its effects on the brain? Much of caffeine’s stimulant action is thought to be due to its blockade of
adenosine receptors located in the membranes of the brain’s neurons. Adenosine is not considered a true neurotransmitter, such
as acetylcholine, dopamine, or serotonin, because it is not stored and released at chemical synapses. However, adenosine is an
important neuromodulator, a chemical that influences synaptic function. One of adenosine’s prominent roles in the central
nervous system (CNS) is to promote sleep. When caffeine reaches the CNS, it binds to and blocks adenosine receptors,
preventing adenosine from causing drowsiness.
In 1999, Menahem Segal and Eduard Korkotian of the Department of Neurobiology at the Weizmann Institute in Israel reported
an interesting discovery. They had removed the part of the brain called the hippocampus from rat embryos and kept the cells
alive, cultured on microscope slides. The researchers then applied caffeine to the hippocampal cells and observed them under a
microscope to see if there were any changes. Dosing the cells with caffeine caused a rise in cellular calcium levels—a
phenomenon known to be related to learning and memory. Even more interesting was the observation that repeated caffeine
exposure caused some of the spines on the neuronal dendrites to grow longer! Dendritic spines are protrusions that may be
important in influencing the number of synaptic connections a neuron can receive. Thus, caffeine may influence learning and
memory by inducing changes in the brain’s “wiring” at the microscopic level.
Questions
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Ashley is standing in line at the coffee counter in the student center. What advice would you offer regarding her
impending use of caffeine? Explain your answer.
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Track your caffeine intake for one day. Be aware that caffeine may be present in unexpected dietary sources, including
certain herbal supplements and teas. Check food, beverage, and medicine labels for caffeine content. Did you take in
more or less caffeine than you would have predicted?
Assignments
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Review how cells form adenosine. (Hint: What does “ATP” stand for?) Research recent work on adenosine and its role
in sleep. What regions of the brain are involved in sleep?
Review the role membrane receptors play at a chemical synapse. How do they produce their effects? What role do
dendrites play in transmission at chemical synapses?
Research caffeine’s effects on the body. What does it mean when we say that caffeine is a CNS stimulant drug? What
are some other CNS stimulant drugs besides caffeine? Are they equally accessible and socially acceptable? Why or why
not? Does caffeine affect other organ systems besides the nervous system? Consider the cardiovascular, respiratory, and
urinary systems in particular. Besides the “caffeine jitters,” are there any adverse effects associated with ingesting
caffeine? If so, what are they? Is there any evidence to support health benefits from the use of caffeine-containing
beverages such as coffee and tea? If so, what?
Find out how much caffeine is present in a typical cup of coffee. How does this compare to the amount in a cup of tea or
a can of cola?
Research the role of the hippocampus in learning and memory. Explain why Segal and Korkotian chose this part of the
brain for their study of the effects of caffeine.
References
http://web.sfn.org/content/Publications/BrainBriefings/adenosine.html
http://web.sfn.org/content/Publications/BrainFacts/index.html
http://web.sfn.org/content/Publications/BrainFacts/index.html
http://health.howstuffworks.com/caffeine.htm
http://health.howstuffworks.com/sleep.htm
http://my.webmd.com/content/article/46/1826_50681.htm
http://my.webmd.com/content/article/17/1671_52718.htm
http://my.webmd.com/content/article/11/1671_50418.htm
http://my.webmd.com/content/article/11/1671_50455.htm
http://www.weizmann.ac.il/neurobiology/labs/segal/segal.html
http://health.howstuffworks.com/framed.htm?parent=sleep.htm&url=http://www.sciencenews.org/sn_arc97/5_24_97/fob2.htm
Weinberg, B. A., and B. K. Bealer. 2001. The world of caffeine: The science and culture of the world’s most popular drug.
Routledge.
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