Bad Fish: A Case on Nervous Tissue

Your favorite uncle Mr. Marshall Westwood is in Indonesia on a busines trip.  One evening he sat down to eat a meal of puffer fish and rice. Within an hour of returning to his hotel room, Mr. Westwood felt numbness in his lips and tongue, which quickly spread to his face and neck. Before he could call the front desk, he began to feel pains in his stomach and throat, which produced feelings of nausea and eventually severe vomiting.

Fearing that he had eaten some “bad fish” for dinner, Mr. Westwood called a local hospital to describe his condition.  The numbness in his lips and face made it almost impossible for him to communicate, but the hospital staff managed to at least understand the address he gave them and they sent an ambulance. As Mr. Westwood was rushed to the hospital, his breathing became increasingly labored.

The patient presented in the ED with diaphoresis, motor dysfunction, paresthesias, nausea, and an ascending paralysis that started in his legs and spread to the upper body, arms, face, and head. The patient was cyanotic and hypoventilating. Within 30 minutes of presenting in the ED, Mr. Westwood developed bradycardia with a BP of 90/50 mmHg. Atropine was administered in response to the bradycardia. Intravenous hydration, gastric lavage, and activated charcoal followed a presumptive diagnosis of tetrodotoxin poisoning that was based on the clinical presentation in the ED. Five hours after treatment, the following vital signs were noted:

• BP 125/79 mmHg
• HR 78 bpm
• Oxygen saturation: 97% on room air

After discussing his case with his physician, he learned that he had probably been the victim of puffer fish poisoning. The active toxin in the tissues of this fish is a chemical called tetrodotoxin (TTX). Tetrodotoxin is in a class of chemicals known as neurotoxins because it exerts its effects on neurons. The specific action of tetrodotoxin is that it blocks voltage-gated sodium ion channels.

——————————————————————————————————————————-

Your aunt back home in US is very concerned about her husband’s condition and turns to you for answers.  Write a letter to your aunt explaining the mechanism behind food poisoning.  Your letter should address the following components of the nervous system in detail:

• Define the following phrases and terms associated with the signs and symptoms of Mr. Westwood’s TTX poisoning:  diaphoresis,motor dysfunction, paresthesias,cyanotic, hypoventilating, bradycardia, gastric lavage, oxygen saturation.
• As mentioned in the case description, tetrodotoxin is a molecule that blocks voltage-gated sodium ion channels. What is a voltage-gated sodium ion channel and what is its function?
• When nerve cells are at rest, there is an unequal amount of positive and negative charges on either side of a nerve cell membrane. This charge difference creates an electrical potential. Describe how the resting membrane potential (resting potential) is generated.
• What is happening to the electrical potential of a neuron when it generates an action potential? What is the function of the action potential in neurons?
• Describe the role of sodium ions and sodium channels in generating an action potential.
• What would happen to a neuron if it was exposed to tetrodotoxin? Be specific regarding its effect on the ability of a neuron to communicate.
• Now that you have addressed some of the basic biology of this case, explain why Dr. Westwood experienced numbness after eating the puffer fish meal.
• Paralysis is a term used to describe the loss of muscle function. If tetrodotoxin’s effect is on neurons, why did Dr. Westwood experience paralysis?

Final Applied Lab Project (1 credit Lab Component)

Addresses course outcomes 1-4:

• recognize and explain how the scientific method is used to solve problems
• make observations and discriminate between scientific and pseudoscientific explanations
• weigh evidence and make decisions based on strengths and limitations of scientific knowledge and the scientific method
• use knowledge of biological principles, the scientific method, and appropriate technologies to ask relevant questions, develop hypotheses, design and conduct experiments, interpret results, and draw conclusions

This is the culminating lab assessment in BIOL 103. It is designed to assess your ability to apply the principles of the scientific method.

The Effect of low pH on Enzyme Activity

Design an experiment in which you will test the effect of an acidic fluid on enzymatic activity. Recall: enzymes are proteins! To complete this project, it may be useful for you to first review the Scientific Method Tutorial, the OLI module about pH and enzymes, Lab 1 (Introduction to Science) and Lab 4 (Enzymes).  As you review Lab 4, you will be reminded that there are several factors that impact enzymatic activity: pH, temperature, and amount of reagent. It is OK to use the same enzyme/substrate/method as you did in lab 4 (but modify the treatment), or you can search on-line to find a different enzyme/substrate/method for measuring enzyme activity for your project (include all references).

As you design your experiment for this project, please remember that you are trying to examine how an acidic fluid will modify the outcome of an enzymatic reaction.  To successfully complete this project, you will need to identify the question(s) being asked in your experiment and the hypothesis that you are testing.  In your experimental design, you must clearly explain what you are doing. That means that you will need to identify the enzyme, the substrate, the acidic fluid used as treatment, the control treatment and the method of measuring enzyme activity, as well as explain your experimental protocol.  You must also thoroughly explain how the acidic fluid impacted enzyme activity based on the results from your own experiment as well as knowledge of enzymes and pH from the OLI modules, lab manual and potentially additional information sources.

Hint: Keep in mind that the acid will change the environmental conditions of the experiment (for example, a low pH value could change the shape of the active site on the enzyme protein), without directly participating in the reaction.

Lab Materials

You may need all or some of the following, depending on your experimental design:

Materials from your lab kit:

• pH paper
• hydrogen peroxide solution (you can purchase this at a pharmacy if you have used up the bottle that came with the lab kit)
• plastic beakers or cups
• vinegar
• yeast (can be purchased at grocery store if more is needed)
• balloons
• plastic bottle
• marker for labeling of beakers
• Cell phone/digital camera – pictures required

You may choose to use additional materials (different acidic fluids and/or different organisms and/or different substrate if you chose an enzyme other than catalase).

Outline:

Include the following in your outline:

• Name of enzyme you will use
• Name of organism (if applicable)
• The substrate
• Method for measuring enzyme activity
• Treatment: acidic fluid(s), pH, length of exposure, how you will treat your samples
• The control(s) in the experiment
• Sample size
• Hypothesis
• How you will present your data (table and/or type of graph)
• Anything else you would like to get feedback on before you start your experiment

Write a lab report that includes the following:

1. Title page: descriptive title, your name, course name, semester

2. Introduction: general background information about enzymes and specific information about your chosen enzyme, the question(s) that you are asking and a clear hypothesis for your experiment (20 points).

3. Design an experiment. Provide a detailed description of the materials and methods used to conduct the experiment. Identify control and experimental samples, as well as independent and dependent variables. Also include the methods used for data collection and analysis (20 points).

4. Conduct the experiment and record your results. Take picture of results. What did you observe? Present your data in table and/or graph format. Remember to label everything and include the unit of measure with all numbers (20 points)

5. Use your knowledge of enzymes and pH to interpret and discuss your results. It may be necessary for you to refer to the OLI course modules, lab manual and/or use additional information resources. What effect does the acidic treatment have on enzyme activity? Did you get the expected results? Explain. (20 points)

6. State a specific and accurate conclusion. Is your hypothesis supported by the results? Looking back, how could you have improved your experiment? (10 points)

7. Include a list of references to all information sources used in APA format (5 points).