Cuyamaca College Endocrine System Biology Lab

Cuyamaca College Endocrine System Biology Lab Cuyamaca College Endocrine System Biology Lab medium of exchange regulates the functioning of every cell, tissue, and organ in the body. It acts to maintain a stable internal body environment, regardless of changes occurring within or outside of the body. Endocrine cells have the ability to sense and respond to changes via the excretion of specific chemicals known as hormones. Hormones are carried in the blood, usually attached to specific plasma proteins, and circulate around the body. When the hormone-protein complex reaches a target cell (the cell at which a chemical message is aimed), the hormone detaches from the protein and enters the cell to induce a specific reaction. Hormones work in different ways, depending upon their chemical structures. For example, polypeptide hormones, composed of chains of amino acids, work by first attaching to a protein receptor in the cell membrane, initiating a series of reactions in the membrane resulting in cyclic adenosine monophosphate (cAMP) entering the cell. The entrance of this chemical into the cell induces the cell to work harder and faster. Steroid hormones and thyroxine (a hormone secreted by the thyroid, which we will be examining in detail shortly) enter the cell to attach to a cytoplasmic receptor. The hormone-receptor complex then enters the nucleus of the cell to attach to specific points on the DNA. Each attachment causes the production of a specific mRNA, which then moves to the cytoplasm to be translated into a specific protein. Most regulation of hormone levels in the body is conducted by negative feedback: if a particular hormone is needed, production of that hormone will be stimulated; if there is enough of a particular hormone present, production of that hormone will be inhibited. In a few very specific instances, hormonal output is controlled by positive feedback mechanisms. One such instance is the output of the posterior pituitary hormone oxytocin. This hormone causes the muscle layer of the uterus, the myometrium, to contract during childbirth. Contraction of the Endocrine System Physiology EXERCISE 4 OBJECTIVES 1. To define the following: hormones, target cell, negative feedback, metabolism, thyroxine, thyroid stimulating hormone (TSH), thyrotropin releasing hormone (TRH), hypothalamus, hypothalamic pituitary portal system, portal vein, hormone replacement therapy, diabetes type I, diabetes type II, glucose standard curve 2. To give examples of how negative feedback loops regulate hormone release 3. To explain the role of thyroxine in maintaining an animal’s metabolic rate 4. To explain the effects of thyroid stimulating hormone (TSH) on an animal’s metabolic rate 5. To understand the role of the hypothalamus in the regulation of thyroxine and TSH production 6. To understand how hypothalamic hormones reach the pituitary gland 7. To understand how estrogen affects bone density 8. To explain how hormone replacement therapy works 9. To explain how fasting plasma glucose is used to diagnose diabetes 10. To understand how levels of cortisol and ACTH can be used to diagnose endocrine diseases 41 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 41 42 Exercise 4 (a) FIGURE 4.1 Metabolism and the thyroid gland. (a) Opening screen of the Metabolism experiment. (b) The regulation of thyroid secretion. indicates stimulation of release, indicates inhibition of release, T3 triiodothyronine, T4 thyroxine, TRH thyrotropin-releasing hormone, TSH thyroid-stimulating hormone. Cuyamaca College Endocrine System Biology Lab Hypothalamus TRH TSH T3, T4 Thyroid gland (b) Pituitary gland (hypophysis) 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 42 myometrium causes additional oxytocin to be released to aid in the contraction, regardless of the amount of hormone already present. Studying the effects of hormones on the body is difficult to do in a wet lab, since experiments can often take days, weeks, or even months to complete, and are quite expensive. In addition, live animals may need to be sacrificed, and technically difficult surgical procedures are sometimes necessary. The PhysioEx simulations you will be using in this lab will allow you to study the effects of given hormones on the body by using “virtual” animals rather than live ones. You will be able to carry out delicate surgical techniques with the click of a button. You will also be able to complete experiments in a fraction of the time that it would take in an actual wet lab environment. Hormones and Metabolism Metabolism is the broad term used for all biochemical reactions occurring in the body. Metabolism involves catabolism, a process by which complex materials are broken down into simpler substances, usually with the aid of enzymes found in body cells. Metabolism also involves anabolism, in which the smaller materials are built up by enzymes into larger, more complex molecules. When bonds are broken in catabolism, energy that was stored in the bonds is released for use by the cell. When larger molecules are made, energy is stored in the various bonds formed. Some of the energy liberated may go to the formation of ATP, the energy-rich material used by the body to run itself. However, not all of the energy liberated goes into this pathway. Some of that energy is given off as body heat. Humans are homeothermic animals, meaning they have a fixed body temperature. Maintaining this temperature is very important to maintaining the metabolic pathways found in the body. The most important hormone in maintaining metabolism and body heat is thyroxine. Also known as tetraiodothyronine, or T4, thyroxine is secreted by the thyroid gland, located in the neck. However, production of thyroxine is really controlled by the pituitary gland, which secretes thyroid stimulating hormone (TSH). TSH is carried by the blood to the thyroid gland (its target tissue) and causes the thyroid to produce more thyroxine. It is also important to understand the role of the hypothalamus in thyroxine and TSH production. The hypothalamus, located in the brain, is a primary endocrine gland that secretes several hormones affecting the pituitary gland (also located in the brain.)Cuyamaca College Endocrine System Biology Lab Among these hormones is thyrotropin releasing hormone (TRH), which stimulates production of TSH in the pituitary gland. If the hypothalamus determines that there is not enough thyroxine circulating to maintain the body’s metabolism, it will secrete TRH to stimulate production of TSH by the pituitary gland, which in turn will stimulate production of thyroxine by the thyroid (a classic example of a negative feedback loop). TRH travels from the hypothalamus to the pituitary gland via the hypothalamic-pituitary portal system, a specialized arrangement of blood vessels consisting of a single portal vein that connects two capillary beds. The hypothalamic-pituitary portal system transports many other hormones from the hypothalamus to the pituitary gland. Primarily, the hormones secreted by the hypothalamus are tropic (or trophic) hormones, which are hormones that stimulate or inhibit the secretion of other hormones. TRH is an example of a tropic hormone, since it stimulates the release of TSH (which is itself a tropic hormone, since it stimulates the release of thyroxine). In the following experiments you will be investigating the effects of thyroxine and TSH on an animal’s metabolic rate. To begin, follow the instructions for starting PhysioEx in the Getting Started section at the front of this manual. From the drop-down menu, select Exercise 4: Endocrine System Physiology and click GO. Before you perform the activities watch the BMR Measurement video to see an experiment in which basal metabolic rate is meaasured. Then click Metabolism. The opening screen will appear in a few seconds (see Figure 4.1). Select Balloons On/Off from the Help menu for help identifying the equipment on-screen (you will see labels appear as you roll over each piece of equipment). Select Balloons On/Off to turn this feature off before you begin the experiments. Study the screen. You will see a jar-shaped chamber to the left, connected to a respirometer-manometer apparatus (consisting of a U-shaped tube, a syringe, and associated tubing). You will be placing animals—in this case, rats—in the chamber in order to gather information about how thyroxine and TSH affect their metabolic rates. Note that the chamber also includes a weight scale, and that next to the chamber is a timer for setting and timing the length of a given experiment. Under the timer is a weight display. Two tubes are connected to the top of the chamber. The left tube has a clamp on it that can be opened or closed. Leaving the clamp open will allow outside air into the chamber; closing the clamp will create a closed, airtight system. The other tube leads to a T-connector. One branch of the T leads to a fluid-containing U-shaped tube, called a manometer. As an animal uses up the air in the closed system, this fluid will rise in the left side of the U-shaped tube and fall in the right. The other branch of the T-connector leads to a syringe filled with air. Using the syringe to inject air into the tube, you will measure the amount of air that is needed to return the fluid columns to their original levels. This measurement will be equal to the amount of oxygen used by the animal during the elapsed time of the experiment. Soda lime, found at the bottom of the chamber, absorbs the carbon dioxide given off by the animal so that the amount of oxygen used can be measured easily. Cuyamaca College Endocrine System Biology Lab The amount of oxygen used by the animal, along with its weight, will be used to calculate the animal’s metabolic rate. Also on the screen are three white rats in their individual cages. These are the specimens you will use in the following experiments. One rat is normal; the second is thyroidectomized (abbreviated on the screen as Tx), meaning its thyroid has been removed; and the third is hypophysectomized (abbreviated on the screen as Hypox)—meaning its pituitary gland has been removed. The pituitary gland is also known as the hypophysis, and removal of this organ is called a hypophysectomy. To the top left of the screen are three syringes containing various chemicals: propylthiouracil, thyroid stimulating hormone (TSH), and thyroxine. TSH and thyroxine have been previously mentioned; propylthiouracil is a drug that inhibits the production of thyroxine by blocking the incorporation of iodine into the hormone. You will be performing four experiments on each animal: 1) you will determine its baseline metabolic rate, 2) you will determine its metabolic rate after it has been injected with thyroxine, 3) you will determine its metabolic rate after it Endocrine System Physiology 43 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 43 has been injected with TSH, and 4) you will determine its metabolic rate after it has been injected with propylthiouracil. You will be recording all of your data on Chart 1 (see p. 45). You may also record your data onscreen by using the equipment in the lower part of the screen, called the data collection unit. This equipment records and displays the data you accumulate during the experiments. The data set for Normal should be highlighted in the Data Sets window, since you will be experimenting with the normal rat first. The Record Data button lets you record data after an experimental trial. Clicking the Delete Line or Clear Data Set buttons erases any data you want to delete. ACTIVITY 1 Determining the Baseline Metabolic Rates First, you will determine the baseline metabolic rate for each rat. 1. Using the mouse, click and drag the normal rat into the chamber and place it on top of the scale. When the animal is in the chamber, release the mouse button. 2. Be sure the clamp on the left tube (on top of the chamber) is open, allowing air to enter the chamber. If the clamp is closed, click on it to open it. 3. Be sure the indicator next to the T-connector reads “Chamber and manometer connected.” If not, click on the T-connector knob. 4. Click on the Weigh button in the box to the right of the chamber to weigh the rat. Record this weight in the Baseline section of Chart 1 for “Weight.” 5. Click the () button on the Timer so that the Timer display reads 1.00. 6. Click on the clamp to close it. This will prevent any outside air from entering the chamber, and ensure that the only oxygen the rat is breathing is the oxygen inside the closed system. 7. Click Start on the Timer display. You will see the elapsed time appear in the “Elapsed Time” display. Watch what happens to the water levels in the U-shaped tube. 8. At the end of the 1-minute period, the timer will automatically stop. When it stops, click on the T-connector knob so that the indicator reads “Manometer and syringe connected.” 9. Click the clamp to open it so that the rat can once again breathe outside air. 10. Look at the difference between the level in the left and right arms of the U-tube and estimate the volume of O2 that will need to be injected by counting the divider lines on both sides. Then click the () button under the ml O2 until the display reads that number. Then click Inject and watch what happens to the fluid in the two arms. When the volume is equalized the word “Level” will appear and stay on the screen. If you are under, click the () and then Inject. If you are over the word “Level” will flash and then disappear. Cuyamaca College Endocrine System Biology Lab You will then have to click the Reset button and try a lower volume. (This is equivalent to the amount of oxygen that the rat used up during the 1 minute in the closed chamber.) Record this measurement in the Baseline section of Chart 1 for “ml O2 used in 1 minute.” 11. Determine the oxygen consumption per hour for the rat. Use the following formula: ml O2/hr Record this data in the Baseline section of Chart 1 for “ml O2 used per hour.” 12. Now that you have the amount of oxygen used per hour, determine the metabolic rate per kilogram of body weight by using the following formula (Note that you will need to convert the weight data from g to kg before you can use the formula): Metabolic rate ___________ ml O2/kg/hr Record this data in the Baseline section of Chart 1 for “Metabolic rate.” 13. Click Record Data. 14. Click and drag the rat from the chamber back to its cage. 15. Click the Reset button in the box labeled Apparatus. 16. Now repeat steps 1–15 for the thyroidectomized (“Tx”) and hypophysectomized (“Hypox”) rats. Record your data in the Baseline section of Chart 1 under the corresponding column for each rat. Be sure to highlight Tx under Data Sets (on the data collection box) before beginning the experiment on the thyroidectomized rat; likewise, highlight Hypox under Data Sets before beginning the experiment on the hypophysectomized rat. Which rat had the fastest baseline metabolic rate? Cuyamaca College Endocrine System Biology Lab________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why did the metabolic rates differ? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ If an animal has been thryoidectomized, what hormone(s) would be missing from its blood? ________________________________________________ ml O2/hr wt. in kg 60 minutes hr ml O2 consumed 1 minute 44 Exercise 4 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 44 As a result of the missing hormone(s), what would the overall effect on the body be? ________________________________________________ ________________________________________________ ________________________________________________ How could you treat a thyroidectomized animal so that it functioned like a “normal” animal? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Endocrine System Physiology 45 Chart 1 Normal Rat Thyroidectomized Rat Hypophysectomized Rat Baseline Weight _______ grams _______ grams _______ grams ml O2 used in 1 minute _______ ml _______ ml _______ ml ml O2 used per hour _______ ml _______ ml _______ ml Metabolic rate _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. With Thyroxine Weight _______ grams _______ grams _______ grams ml O2 used in 1 minute _______ ml _______ ml _______ ml ml O2 used per hour _______ ml _______ ml _______ ml Metabolic rate _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. With TSH Weight _______ grams _______ grams _______ grams ml O2 used in 1 minute _______ ml _______ ml _______ ml ml O2 used per hour _______ ml _______ ml _______ ml Metabolic rate _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. With Propylthiouracil Weight _______ grams _______ grams _______ grams ml O2 used in 1 minute _______ ml _______ ml _______ ml ml O2 used per hour _______ ml _______ ml _______ ml Metabolic rate _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. _______ ml O2 /Kg./Hr. 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 45 If an animal has been hypophysectomized, what effect would you expect to see in the hormone levels in its body? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ What would be the effect of a hypophysectomy on the metabolism of an animal? ________________________________________________ ________________________________________________ ________________________________________________ ______________________________________________? ACTIVITY 2 Determining the Effect of Thyroxine on Metabolic Rate Next you will investigate the effects of thyroxine injections on the metabolic rates of all three rats. Please note that in a wet lab environment you would normally need to inject thyroxine (or any other hormone) into a rat daily for at least 1–2 weeks in order for any response to be seen. However, in the following simulations you will only inject the rat once and will be able to witness the same results as if you had administered multiple injections over the course of several weeks. In addition, by clicking the Clean button while a rat is inside its cage, you can immediately remove all residue of any previously injected hormone from the rat and perform a new experiment on the same rat. In a real wet lab environment you would need to either wait weeks for hormonal residue to leave the rat’s system or use a different rat. 1. Choose a rat to test. Cuyamaca College Endocrine System Biology Lab. You will eventually test all three, and it doesn’t matter what order you test them in. Do not drag the rat to the chamber yet. Under Data Sets, the simulation will highlight Normal, Tx, or Hypox depending on which rat you select. 2. Click the Reset button in the box labeled Apparatus. 3. Click on the syringe labeled thyroxine and drag it over to the rat. Release the mouse button. This will cause thyroxine to be injected into the rat. 4. Click and drag the rat back into the chamber. Perform steps 1–12 of Activity 1 again, except that this time, record your data in the With Thyroxine section of Chart 1. 5. Click Record Data. 6. Click and drag the rat from the chamber back to its cage, and click Clean to cleanse it of all traces of thyroxine. 7. Now repeat steps 1–6 for the remaining rats. Record your data in the With Thyroxine section of Chart 1 under the corresponding column for each rat. What was the effect of thyroxine on the normal rat’s metabolic rate? How does it compare to the normal rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ What was the effect of thyroxine on the thyroidectomized rat’s metabolic rate? How does it compare to the thyroidectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ What was the effect of thyroxine on the hypophysectomized rat’s metabolic rate? How does it compare to the hypophysectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ______________________________________________? 46 Exercise 4 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 46 ACTIVITY 3 Determining the Effect of TSH on Metabolic Rate Next you will investigate the effects of TSH injections on the metabolic rates of the three rats. Select a rat to experiment on first, and then proceed. 1. Under Data Sets, highlight Normal, Tx, or Hypox, depending on which rat you are using. 2. Click the Reset button in the box labeled Apparatus. 3. Click and drag the syringe labeled TSH over to the rat and release the mouse button, injecting the rat. 4. Click and drag the rat into the chamber. Perform steps 1–12 of Activity 1 again. Record your data in the With TSH section of Chart 1. 5. Click Record Data. 6. Click and drag the rat from the chamber back to its cage, and click Clean to cleanse it of all traces of TSH. 7. Now repeat this activity for the remaining rats. Record your data in the With TSH section of Chart 1 under the corresponding column for each rat. What was the effect of TSH on the normal rat’s metabolic rate? How does it compare to the normal rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ What was the effect of TSH on the thyroidectomized rat’s metabolic rate? How does it compare to the thyroidectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ What was the effect of TSH on the hypophysectomized rat’s metabolic rate? How does it compare to the hypophysectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ______________________________________________? ACTIVITY 4 Determining the Effect of Propylthiouracil on Metabolic Rate Next you will investigate the effects of propylthiouracil injections on the metabolic rates of the three rats. Keep in mind that propylthiouracil is a drug that inhibits the production of thyroxine by blocking the attachment of iodine to tyrosine residues and interfering with the conversion of thyroxine with triiodothyronine. Select a rat to experiment on first, and then proceed. 1. Under Data Sets, the simulation will highlight Normal, Tx, or Hypox, depending on which rat you are using. 2. Click the Reset button in the box labeled Apparatus. 3. Click and drag the syringe labeled Propylthiouracil over to the rat and release the mouse button, injecting the rat. 4. Click and drag the rat into the chamber. Perform steps 1–12 of Activity 1 again, except this time record your data in the With Propylthiouracil section of Chart 1. 5. Click Record Data. 6. Click and drag the rat from the chamber back to its cage, and click Clean to cleanse it of all traces of propylthiouracil. 7. Now repeat this activity for the remaining rats. Record your data in the With Propylthiouracil section of Chart 1 under the corresponding column for each rat. 8. Click Tools ? Print Data to print your data. What was the effect of propylthiouracil on the normal rat’s metabolic rate? How does it compare to the normal rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Endocrine System Physiology 47 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 47 Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________Cuyamaca College Endocrine System Biology Lab. What was the effect of propylthiouracil on the thyroidectomized rat’s metabolic rate? How does it compare to the thyroidectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ________________________________________________ What was the effect of propylthiouracil on the hypophysectomized rat’s metabolic rate? How does it compare to the hypophysectomized rat’s baseline metabolic rate? ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Why was this effect seen? ________________________________________________ ________________________________________________ ______________________________________________? Hormone Replacement Therapy Follicle-stimulating hormone (FSH) stimulates ovarian follicle growth. While the follicles are developing, they produce the hormone estrogen. As the female enters menopause, the ovaries stop producing estrogen. One of the symptoms of menopause is loss of bone density, which can result in osteoporosis and bone fractures. Postmenopausal treatments to prevent osteoporosis include the administration of estrogen to increase bone density. Calcitonin is a hormone that inhibits osteoclast activity and stimulates calcium uptake for deposit in bone. In this experiment we will use three ovariectomized rats because they are no longer producing estrogen due to the removal of their ovaries. The three rats were chosen because each has a baseline T score of 2.6, indicating osteoporosis. T scores are interpreted as follows: normal 1 to 0.99; osteopenia (bone thinning) 1.0 to 2.49; osteoporosis 2.5 and below. You will administer either estrogen therapy or calcitonin therapy, two types of hormone replacement therapy.Cuyamaca College Endocrine System Biology Lab. The third rat will serve as an untreated control and receive daily injections of saline. The vertebral bone density (VBD) of each rat will be measured with dual X-ray absorptiometry (DXA) to obtain the T score. Start by selecting Hormone Replacement Therapy from the Experiment menu. A new screen will appear (Figure 4.2) with three ovariectomized rats in cages. (Note that if this were a wet lab, the ovariectomies would have been performed on the rats a month prior to the rest of the experiment in order to ensure that no residual hormones remained in the rats’ systems.) Also on screen are a bottle of saline, a bottle of estrogen, a bottle of calcitonin, a clock, and a dual X-ray absorptiometry bone density scanner. ACTIVITY 5 Hormone Replacement Therapy 1. Click on the syringe, drag it to the bottle of saline, and release the mouse button. The syringe will automatically fill with 1 ml of saline. 2. Click and hold the syringe and drag the syringe to the control rat and place the tip of the needle in the rat’s lower abdominal area. Injections into this area are considered intraperitoneal and will quickly be picked up by the abdominal blood vessels. Release the mouse button—the syringe will empty into the rat and automatically return to its holder. Click Clean on the syringe holder to clean the syringe of all residue. 3. Click on the syringe again, this time dragging it to the bottle of estrogen, and release the mouse button.Cuyamaca College Endocrine System Biology Lab The syringe will automatically fill with 1 ml of estrogen. 4. Click and hold the syringe, drag it to the estrogentreated rat, and place the tip of the needle in the rat’s lower abdominal area. Release the mouse button—the syringe will empty into the rat and automatically return to its holder. Click Clean on the syringe holder to clean the syringe of all residue. 5. Click on the syringe again, this time dragging it to the bottle of calcitonin, and release the mouse button. The syringe will automatically fill with 1 ml of calcitonin. 6. Click and hold the syringe, drag it to the calcitonintreated rat, and place the tip of the needle in the rat’s lower abdominal area. Release the mouse button—the syringe will empty into the rat and automatically return to its holder. Click Clean on the syringe holder to clean the syringe of all residue. 7. Click on the clock. You will notice the hands sweep the clock face twice, indicating that 24 hours have passed. 8. Repeat steps 1–7 until each rat has received a total of 7 injections over the course of 7 days (1 injection per day). Note that the # of injections displayed below each rat cage records how many injections the rat has received. The control rat should receive 7 injections of saline, the estrogen-treated 48 Exercise 4 04_041_062_PhyEx8_HP_Ch04 1/11/08 7:59 AM Page 48 rat should receive 7 injections of estrogen, and the calcitonintreated rat should receive 7 injections of calcitonin. 9. You are now ready to measure the effect of each of the solutions. First, predict the effect that each solution will have on the rat’s vertebral bone density. Saline injections ___________________________________ ___________________________________________________ Estrogen injections _________________________________ ___________________________________________________ Calcitonin injections ________________________________ ___________________________________________________ 10.Cuyamaca College Endocrine System Biology Lab. A gaseous anesthetic will be applied to immobilize the rats for imaging. Click on the Anesthesia button for the control rat to immobilize the rat. 11. Click on the control rat and drag it to the exam table. Release the mouse to release the rat. 12. Click the Scan button to activate the scanner. Record the T score. T score (control): _____________ 13. Click Record Data. 14. Click and drag the rat to return it to its cage. 15. Repeat steps 10–14 for the estrogen-treated rat. T score (estrogen): _____________ 16. Repeat steps 10–14 for the calcitonin-treated rat. T score (calcitonin): _____________ 17. Click Tools ? Print Data to print your recorded data for this experiment. Recall that the baseline value for all three rats was 2.6. T scores are interpreted as follows: normal 1 to 0.99; osteopenia (bone thinning) 1.0 to 2.49; osteo

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