Objectives: The objectives of this laboratory exercise include understanding how
the important carbohydrate fuel is regulated in vertebrates during starvation, ...
Biology 310/Endocrinology
Endocrinology Laboratory Regulation of Glucose by Hormones You should read in your textbook about the regulation of blood glucose by pancreatic insulin
Objectives: The objectives of this laboratory exercise include understanding how the important carbohydrate fuel is regulated in vertebrates during starvation, feeding, and during exercise. Experimental Design: We will split the class into the following three groups 1) Fasting students 2) Fasting students + Exercise 3) Fasting students + 50 grams of ingested glucose Blood Sampling: a blood sample will be removed from each student prior to exercise or glucose ingestion and this sample will represent fasting blood glucose of a population of UAS students. A blood sample will be removed every 15 minutes for at least 1h post experimental start. Glucose measurement: We will use a Glucometer Elite system to measure glucose in circulating blood. Statistics: You will calculate the average ± standard deviation of each of the three groups and plot this using Microsoft Excel.
Glucose Tolerance Test The following may be useful information for the recognizing the importance of coordinated glucose regulation in mammals. Deficiencies in endocrine regulation is the primary cause of Type 1 and Type 2 Diabetes The purpose of the glucose tolerance test is to determine how a fasting individual responds to a glucose load. Information gathered from this test can serve as a diagnosis for diabetes mellitus. Normally, glucose levels are maintained within normal ranges through homeostatic mechanisms governed by the pancreas. Increased plasma glucose (hyperglycemia) will lead to the secretion of insulin from the β-cells of the Islets of Langerhans within the pancreas. Insulin will increase the cellular uptake of glucose; thus decreasing plasma glucose. Conversely, decreased plasma glucose (hypoglycemia) will stimulate the release of glucagon from α-cells of the Islets of Langerhans within the pancreas which will ultimately increase plasma glucose levels. In this way, plasma glucose levels are maintained within physiological normal ranges (70-110 mg/dl) even under conditions of exercise and fasting.
Biology 310/Endocrinology If a person suffers from diabetes mellitus, regulation of blood glucose is impaired, and a potentially fatal situation exists. There are 2 major pathologies associated with insulin action. Type I diabetes in which the pancreas no longer secretes sufficient insulin in response to increased plasma glucose and Type II diabetes in which the tissues no longer responds well to circulating insulin. Both types result in hyperglycemia. Other signs of diabetes mellitus include, glucosuria (glucose in the urine), accelerated lipid and protein metabolism, ketoacidosis, and increased urine output. Type II diabetes is the most common form of this disease and occurs later in life in association with obesity. Type II diabetes is also detected in pregnant woman (gestational diabetes) and can lead to large birth-weight babies. Type II diabetes is oftentimes managed through changes in lifestyle including diet and exercise. If left untreated, type II diabetes can lead to circulatory problems (gangrene), blindness, and death. The following simple oral glucose tolerance test (GTT) is administered to detect type II diabetes and will not be performed on any individual who suffers from Type I diabetes. Before taking this test, you must fast for at least 16 hours to insure baseline glucose levels. Eating or exercising prior to the test can result in erroneous plasma glucose values. Step 1. The fasting volunteer will first measure glucose in his/her blood using a glucometer. You will then be instructed to drink a concentrated glucose solution within 5 minutes (Diabetics are not allowed to volunteer for this exercise). This drink contains 50 grams of glucose in 100 mls of carbonated water. Blood glucose will be measured at intervals of 30, 60, 90, and 120 minutes. You may choose to analyze your blood at only the 90-minute time point if desired. No one will be forced to give blood. Precautions: only allow the instructor to handle your blood. Samples will be analyzed in one region of the room. Each analysis takes approximately 1 minute to determine blood glucose. She will wear gloves at all times Step 2: Collect all of the data from the class. There should also be some students (Kyle; or your professor that will serve as control subjects). Discuss among yourselves your graphing strategy. All data will need to be analyzed using Excel. If you have never performed any statistical tests on data using this software, please see me. Figure 1 shows the results of a normal and two abnormal glucose tolerance test. The patient C suffers from Type I diabetes and patient B suffers from Type II diabetes
Biology 310/Endocrinology Time
A
Glucose (mg/dl)
0 30 60 300 90 120 150 250
B
87 Glucose 139 155 110 75 83
C
135 Tolerance 210 198 190 185 179
122
Test 254 Sample 248 250 247 246
Patient A Patient B Patient C
200 150 100 50 0 0
30
60
90
120
150
Time (min)
Third: Examine endocrine tissues that are provided at the front of the room under the compound microscope. Make sure you examine the following slides a) testis b) ovaries c) thyroid glands d) adrenal gland e) pituitary gland
Biology 310/Endocrinology
Exercises for Endocrine Laboratory 1) What is the purpose of a glucose tolerance test? 2. Plot your data using appropriate software. Compare the data from your group as well as data provided to you by your instructor and determine if each has a normal response to the glucose tolerance test. State your conclusions. 3. In the data for the subject provided by your instructor Patient X, could you conclude from this test whether he suffers from Type I or Type II diabetes? Why or why not? 4. Define the following terms • • • • • • • •
Hyperglycemia Hypoglycemia Insulin Glucagon Glycogenolysis Gluconeogenesis Glycogenesis Diabetes mellitus
You will write up the section on the glucose tolerance test as a formal laboratory report (refer to handout on laboratory write-ups).
Biology 310/Endocrinology Laboratory Report This laboratory report is worth 100 points and will be subject to revision When in doubt, please refer to Pechenik, J. A. (1999) A short guide to writing about biology. This book will help you with correct verbiage. This book will also explain each of the following sections in greater detail. For full credit, lab reports must adhere to the format outlined below (include section headings): TITLE: This should be brief but informative; be sure to include the concepts addressed in the report as well as some reference to the organisms involved. Do not use a separate title page. (3 points) NAME: yours (0 points) ABSTRACT: This is a concise description of your project and will be limited to 250 words (10 points) INTRODUCTION: This section should provide an introduction to the general issues that will be discussed in the report (i.e. set the stage and provide the reader with a conceptual framework for understanding and appreciating the research). At the end of this section, students should clearly state research questions being addressed. (25 points) METHODS: This section should clearly and briefly describe all those methods used to address the questions or hypotheses under consideration. The main objective is to generate a verbal description of your methods that someone else could use if they chose to repeat this project. (25 points) RESULTS: This section should succinctly report your findings (i.e. tell the reader about the data you collected, analyzed, and presented in table and/or figure form). Avoid speculating as to what your results mean; just tell the reader what you found without interjecting your interpretations. Also, don't discuss anything that was not first mentioned in the Methods section. (10 points) DISCUSSION: In this section, you should 1) briefly summarize your findings, being sure to emphasize your research questions or hypotheses; 2) elaborate on the strengths and weaknesses of your methods and results (Have you provided a rigorous test of the hypotheses? Is your data convincing? Did the experiments or comparisons “work”? If not, how would you do things differently next time?); 3) discuss any natural history observations that help understand your study system or results; and 4) speculate about the meaning of your results (yes, now you can do this, but not earlier!). (25 points) REFERENCES: you should have at least four citations that support either your introduction or/and your results. Your textbook may be one of these. (2 points)
