HLTH 103 Biological Determinants of Health PDF

HLTH 103 – Biological Determinants of Health Scientific Method Health Sciences Outline of Topics  Case: Childbed Fever  Germ Theory of Disease: Robert Koch  Scientific Method – steps & process  Hypothesis Testing & Proof  Scientific assumptions about nature  Principle features of science  B...

HLTH 103 – Biological Determinants of Health Scientific Method Health Sciences Outline of Topics  Case: Childbed Fever  Germ Theory of Disease: Robert Koch  Scientific Method – steps & process  Hypothesis Testing & Proof  Scientific assumptions about nature  Principle features of science  Broader applications of the scientific method  Other forms of knowledge Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever  In 1846 in Ignaz Semmelweis was the head of obstetrics in Vienna  459 women died from childbed fever  Goal: to determine the cause of this disease  Approach: studied death records of women  Hospital: 2-divisions  Division 1: Doctors and medical students delivered babies  Division 2: Midwives delivered babies Picture of the Allgemelnes Krankenhau (general hosptial) in Vienna. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever Maternal Births and Deaths by Hospital Division (i.e. clinic) from 1841-1846 Source: WHO South-East Asia Journal of Public Health 2012;1(4):477-484 Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever  Systematically, through trial and error, he removed various causes  When a colleague died of a massive infection, he was able to determine the cause of childbed fever  This colleague was stuck in the finger by a scalpel during an autopsy on a woman who died of childbed fever  Dr. Semmelweis noted that the autopsy of his colleague looked like childbed fever  He thought that the doctors, after performing autopsies, were bringing “cadaverous particles” Picture of a painting by Robert Tom from with them 1966 showing medical professionals washing their hands Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press VIDEO: Ignaz Semmelweis  Video Link:  https://www.youtube.com/watch?v=kFGAES-G3wA Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE : Childbed Fever Proper Hand- washing Procedure Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever Source: WHO South-East Asia Journal of Public Health 2012;1(4):477-484 Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Application to Childbed fever Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever ~ Life Application  Once hospitals instituted hygienic practices, mortality rates dropped dramatically  By the early 1900s, the germ theory took hold and modern hygienic and sterilization practices became the norm  Childbed fever is caused by the same bacterium that causes strep throat, scarlet fever, and rheumatic fever: Streptococcus pyogenes Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press CASE: Childbed Fever ~ Life Application Streptococcus species - produces hemolysin toxin (alpha, beta or gamma) - categorized based on cell-wall antigens (alpha. letters A-O) - common pathogenic groups: - Group A beta-hemolytic (aka Group A Strep; GAS) = S. pyogenes comple partial No RBC lysis te RBC RBC lysis lysis Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Life Application: Streptococcus species  Strep throat is caused by one type of S. pyogenes and can lead to rheumatic fever in 3% of cases  It is detected by swabbing the throat then dipping the swab in a test tube containing chemicals that will extract molecules from the bacteria if they are present  Next, an antibody that binds to molecules specific to S. pyogenes is added, along with a third substance that will change color if antibody binding occurs  The swab samples are added to culture medium; a culture grows if the bacterium is present  S. pyogenes is hemolytic, so if it is cultured on blood agar, the destroyed red blood cells can be detected Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Germ Theory of Disease Early discoveries: Robert Koch (1843–1910) German physician  Studied cause and effect of human diseases  Established Germ Theory of Disease and Koch’s Postulates  many diseases are caused by microbes  Founder of the scientific method in microbiology  applied his methods to numerous lethal diseases  also developed pure culture technique  Awarded the Nobel prize in 1905 the Germ Theory of Disease Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Germ Theory of Disease Robert Koch wanted to show, scientifically, that bacterium were the cause of disease  injected mice with slivers of wood that had blood from animals that died from anthrax  for a control, he injected another group of mice with blood from healthy animals  demonstrated that mice injected with blood from diseased animals became ill  also demonstrated the anthrax bacterium could produce spores  spores germinate to create new bacterial cells. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Germ Theory of Disease Koch’s Postulates Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press How Does Science Work?  Acquisition of knowledge about the natural world  Can be discipline specific, multidisciplinary or transdisciplinary or interdisciplinary.  Directed towards fundamental questions (basic science) or applications (applied science).  Science is based on evidence rather than on opinion or belief  Empirical evidence is information that one gets from direct observation, from experience, or from the results of experiments and other tests of hypotheses  Science has a commitment to testability:  a procedure for determining the evidence in support of a hypothesis  hypothesis must be falsifiable: a test that is able to be proven wrong  Although most investigations are narrow in scope, scientists are still interested in the generality of their work – how widely it applies to situations other than the oneFrom: Adapted being tested Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method  The scientific method is a set of procedures scientists use in their investigations  Scientific method begins with observations (what you can see, hear, etc.) and facts (things you know to be true) about the natural world  It continues with a hypothesis (a possible cause for what is being studied) and a prediction (educated speculation about what an outcome will be)  Finally, results are tested and Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press evaluated Scientific Method – Steps & Process Step 1: Observation Step 2: Ask a Question Step 3: Form a hypothesis Step 4: Make a predication Step 5: Test the prediction / do an experiment Step 6: Collect and analyze Results Step 7: Modify & Repeat Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Observe and Generalize  Inductive reasoning: make generalizations based on observations about the world  Example  Observation: “Every winter in the past was colder than the preceding summer.”  Generalization: “Winter will always be colder than summer.” Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Formulate a Hypothesis  A hypothesis is a tentative statement about the natural world.  It is a statement that can lead to testable deductions.  Example: Drug X would be an effective treatment for high blood pressure. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Make a Testable Prediction  Hypotheses should be tested under many different conditions  Testable predictions  Should be based on the hypothesis  Should employ deductive reasoning  Are often in the form of “if…then” statements  Should be specific in order to be testable  Example: If Drug X is an effective treatment for high blood pressure in humans, then 10 mg/day of Drug X will lower blood pressure in people with high blood Adapted From:pressure within Bozzone, Biology one month. for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Experiment and observe  Truth or falsehood of prediction is tested by observation and experimentation.  Experiment: a carefully planned and executed procedure that is designed to test a prediction based on a hypothesis. Modify the hypothesis as necessary and modify steps three (prediction) and four (experiment)  If the prediction is false, modify the hypothesis.  If the prediction is true, only one small part of the hypothesis has been tested. Further testing required.  Hypotheses cannot be proven true, only supported or disproved. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Variables  Independent variable: the component of the system that is intentionally manipulated or changed by the researcher. Also known as the manipulated variable.  Dependent variable: an observed change or response in the system that is caused by the manipulation of the independent variable. Also known as the responding variable. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process A large number of subjects with high blood pressure are divided randomly into two groups  Experimental group: receives Drug X  Control group: receives a placebo  All other variables that might affect outcome (age, gender, previous health problems, blood pressure) are equalized between the two groups.  The receipt of Drug X or the placebo is the independent variable.  Blood pressure (dependent variable) of all participants is measured after one month and compared to their blood pressure at the start. Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press  Scientific Method: Steps & Process Findings can be disseminated in:  Peer-reviewed journals  Experts must approve articles before publication  Results are assumed to be valid only for conditions under which experiment was done  Popular press  Electronic publications  Internet is less regulated than print and broadcast media Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Steps & Process Assessing the Quality of an Internet Source  Who authored the article or site?  Academic or professional credentials?  Is the author an expert or are they writing outside of their expertise?  What is the purpose of the website?  Provide information?  Promote an agenda or a product?  When was the information updated? Is it current?  Where is the information coming from? Are references provided? Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Method: Hypothesis Testing & Proof  Science is based on a type of logic known as inductive reasoning – the search for general truths from specific observations  Example: Our hypothesis is that the sun orbits the Earth once a day  This predicts that the sun will rise in the east and set in the west every day. It does, but our hypothesis is still false  We neglected to consider another hypothesis: The Earth rotates around its axis once a day Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientific Assumptions about Nature  Science assumes that the rules for cause and effect hold for all natural phenomena  Every event in nature has a cause, and since cause and effect are related, a scientist can learn about causes by observing the effects that occur  If a scientist sets up the correct causes (conditions), the effects (results) can be predicted in advance Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Science vs other Knowledge  Science has been very successful, but this does not mean that it is superior to other ways of knowing  Other areas attempt to address other types of questions using methods appropriate for their subject area From Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Science vs other Knowledge  Pseudoscience (fake science):  Example: Creationism is an example of pseudoscience. It is the idea that a divine being created all the species in a single event  While it may be a valid theological notion, it is not a scientific hypothesis  Science:  Example: Evolution predicts that species have changed over time, and the fossil record evidence from embryos and molecular studies confirm it Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Science vs other Knowledge cientific Evidence of Evolution Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur  Early theory of life: ‘Spontaneous Generation’  “Life arises spontaneously from non-living material”  Known as ‘abiogenesis’  Fact or fiction?  Theory had supporters and detractors  Key scientists: Francesco Redi, Lazzaro Spallanzani, Louis Pasteur & John Tyndall  Scientists supported ‘biogenesis’: ‘living things arise only from others living things of the same kind’  Louis Pasteur successfully disproved spontaneous generation  provided experimental evidence for abiogenesis  developed pasteurization technique Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur  1668: Francesco Redi filled jars with decaying meat Conditions Results Jars covered with fine net No maggots Open jars Maggots appeared Sealed jars No maggots From where did the maggots come? What was the purpose of the sealed jars? Spontaneous generation or biogenesis? Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur  1745: John Needham put boiled nutrient broth into covered flasks Conditions Results Nutrient broth heated, then placed Cell growth growth in sealed flask From where did the microbes come? Spontaneous generation or biogenesis? Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur  1765: Lazzaro Spallanzani boiled nutrient solutions in sealed flasks Conditions Results Nutrient broth placed in flask, No new cell growth heated, then sealed Spontaneous generation or biogenesis? Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Scientist Spotlight: Life & Louis Pasteur Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Check your Understanding In Louis Pasteur’s Spontaneous Generation Experiments, What is the purpose of the: Beef Broth: Bunsen Burner: Flask & S-neck: Air: Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Adapted From: Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press