Presentation on theme: "An End to Ulcers? A Case Study in the Scientific Method by"— Presentation transcript:
1An End to Ulcers? A Case Study in the Scientific Method by Kristi Hannam, State University of New York - GeneseoandRod Hagley, University of North Carolina - Wilmington
2CQ1: What do you think causes ulcers? A: Stress.B: Excessive stomach acids.C: Bacteria.D: A bad diet and alcohol use.E: Being overweight.
3History of the understanding of stomach function & ailments HIPPOCRATESWILLIAM BEAUMONT
4What Causes Ulcers?Design an experiment to test if the “excess acid hypothesis” is true.In your small groups, design the experiment. Remember, be specific about how you would treat your groups and what you would measure!
5CQ2: Which is a good way to test the “excess acid hypothesis”? A: Examine ulcer patients of a range of ages and measure their stomach acid levels.B: Have volunteers drink alcohol and measure their stomach acid levels.C: Lower stomach acid levels of some volunteers (using drugs/antacids), and measure numbers of ulcers in all volunteers.D: Examine patients of a range of ages and measure the number of ulcers in each person.E: Put volunteers through a stress test and then measure their stomach acid levels.
6CQ3: What step in the scientific method does this test represent? A: Making observations.B: Developing a hypothesis.C: Determining predictions.D: Testing a hypothesis.E: Assessing support for a hypothesis.
7A Possible Study Design Doctors divide patients into two groups:After 3 months, the number of ulcers per patient is assessed.Predict what the results would look like if the excess acid theory was supported.Group 1 received antacids and were instructed to take them 3x/dayGroup 2 received sugar pills and were instructed to take them 3x/day
8Draw this graph: Predict what the results would look like if the “excess acid theory” was supported by the results of this study:# Ulcers/ patientGroup 1 Group 2Treatment Group
9CQ4: Which graph most closely matches the results you predicted? B# Ulcers/ patient# Ulcers/ patientGroup 1 Group 2Treatment GroupGroup 1 Group 2Treatment GroupDC# Ulcers/ patient# Ulcers/ patientGroup 1 Group 2Treatment GroupGroup 1 Group 2Treatment Group
10Unfortunately, this type of controlled experiment was NOT conducted. BUT, patients who took antacids had decreased ulcer symptoms.If the patients stopped taking the antacids their ulcers returned.Image by: Midnightcomm
11Dr. J. Robin Warren: (pathologist) Examines stomach biopsies of patients with various stomach ailments.
12B: Only one cell at a time. C: Organelles within the cells. CQ5: The slides that Dr. Warren examined had smudges that were not clearly visible under low power, so he attached a high-power lens to his microscope. What do you think he was able to see then?A: Many cells at once.B: Only one cell at a time.C: Organelles within the cells.D: Bacteria.E: Viruses .LOWPOWER
13Dr. Warren thought he saw: Helicobacter pylori (a new species of bacteria)But no one else believed him!The black squiggly spots on the slideare bacteria that Dr. Warren observedIn his biopsy slides.
14CQ6: Dr. Warren’s colleagues did not believe there were bacteria in the stomach. Why do you think other pathologists did not believe bacteria were in the stomach biopsies?A: Bacteria are never found inside the human body.B: The pH of the stomach is too acidic for any bacteria to survive.C: No one else had reported seeing bacteria in their biopsy samples.D: Ulcers and stomach cancer are caused by age, stress and diet – bacteria have nothing to do with the problems the patients came to the hospital for.
15So, Dr. Warren:Used a special stain that highlights bacteria on his slides.This convinced his colleagues that the bacteria were there.
16Talk to your neighbor Dr. Warren thinks H. pylori causes ulcers. What is another hypothesis to explain why Dr. Warren was finding bacteria on his slides? (there are at least three alternative hypotheses...)
17Alternative explanations (hypotheses): 1. The biopsy specimens were contaminated AFTER samples were taken from the patients.2. The bacteria live in the stomach, but do no damage.3. The bacteria are an opportunistic species that arrives AFTER ulcers have already weakened the stomach’s defenses.
18Dr. Barry J. Marshall Joins Dr. Warren’s Research Hypothesis: Bacteria CAUSE stomach ulcers.If you were working with Drs. Warren & Marshall to design a study to determine whether the bacteria caused ulcers, how would you do it?
19Their First Survey Study: 100 stomach ulcer patients surveyed (biopsy taken).100% had H. pylori present.
20CQ7: The doctors treated ulcer patients with antibiotics to see if the disease stopped. What is missing from their study?A: An experimental treatment.B: A control group.C: An independent variable.D: A dependent variable.E: A hypothesis.
21Important Aspects of Experimental Design Testable hypothesis, i.e., a way to measure a response and a way to divide groups up into:Control and Treatment GroupsControl is group that does not get the hypothesized treatment.Treatment is group that does get the hypothesized treatment.
22The Importance of Controls Why do we need controls? Explain to your neighbor …
23If they set up their antibiotic study with a treatment group receiving antibiotics and a control group receiving a placebo (no antibiotics), what results would you expect if the original “excess acid hypothesis” was supported?Control ExperimentalNumber of ulcersafter 2 months
24CQ8: What results would you expect if the old “excess acid hypothesis” were supported? BANumber of ulcersafter 2 monthsNumber of ulcersafter 2 monthsCon ExptlCon ExptlDCNumber of ulcersafter 2 monthsNumber of ulcersafter 2 monthsCon ExptlCon Exptl
25What results would you expect if Drs What results would you expect if Drs. Warren and Marshall’s “bacteria cause ulcers” hypothesis is supported?Control ExperimentalNumber of ulcersafter 2 months
26CQ9: What results would you expect if the “bacteria cause ulcers hypothesis” were supported? Number of ulcersafter 2 monthsANumber of ulcersafter 2 monthsCon ExptlCon ExptlCDANumber of ulcersafter 2 monthsNumber of ulcersafter 2 monthsCon ExptlCon Exptl
27Actual Results of Warren & Marshall’s Study When treated with antibiotics, 80% of patients were permanently cured of their ulcers.To further demonstrate the cause and effect relationship, Dr. Marshall (who did NOT suffer from ulcers), swallowed a flask of H. pylori from the lab.Within a week he was suffering from symptoms of gastritis and had H. pylori populations in his stomach!He cured himself with an antibiotic treatment.
28CQ10: If your father was diagnosed with stomach ulcers, what do you think the recommended treatment would be?A: Lower stress levels.B: Change diet to eliminate spicy food.C: Take a course of antibiotics.D: Drink milk to lower stomach acid levels.E: Lose weight and exercise.
29CQ11: If you were shown the results of the Warren & Marshall antibiotic study, you would conclude: A: The excess acid hypothesis is supported and is the best explanation for the causation of ulcers.B: The bacteria cause ulcers hypothesis is supported and is the best explanation for the causation of ulcers.C: The excess acid hypothesis has not been overturned, but bacteria might have something to do with ulcers.D: This study supports the bacteria cause ulcers hypothesis, but I need more evidence.
31Medical doctors worldwide were NOT easily convinced Drs. Warren and Marshall had trouble getting their results published in scientific journals and presenting results at scientific meetings.It took over 15 years and many more studies from researchers all over the world, before the “bacteria cause ulcers” hypothesis was accepted by the medical community.
32Drs. Warren & Marshall win the 2005 Nobel Prize in Medicine & Physiology The Nobel Prize committee recognizedWarren & Marshall’s work changed pepticulcers from one of the world’s most common chronic, debilitating diseases to one easily cured with a simple drug regimen.Opened new avenues of research -microbial causes of other chronic inflammatory diseases.Also increased understanding of links between chronic infection, inflammation, and cancer.
33CQ12: If your father was diagnosed with stomach ulcers, what do you think the recommended treatment would be?A: Lower stress levels.B: Change diet to eliminate spicy food.C: Take a course of antibiotics.D: Drink milk to lower stomach acid levels.E: Lose weight and exercise.