__Introduction__

Testosterone is a hormone converted from cholesterol that is produced in the gonads and is secreted from the Leydig cells in the testes and is integral for sex differentiation, spermatogenesis, and fertility. Rats were selected for subjects as they have similar anatomy to humans (Demeter, Sarter, & Lusting, 2008). Testosterones effect was determined by measuring changes in percent composition of the heart, kidneys, liver, seminal vesicles, and the right gastrocnemius muscle (Bagatto, 2018). Testosterone is a primary hormone in males as it plays a direct role in certain aspects of the body as it has been seen that a decrease in testosterone can cause a reduction of bone mass, muscle mass, strength, physical function, and the production of sperm (Horstman, Dillon, Urban, & Sheffield-Moore, 2012). Testosterone is also an integral part of the immune response as it is associated with a decrease in cytokine responses, which creates an immuno-modulatory function (Trumble et al., 2016).

Testosterone therapy is given to men who have low testosterone levels. This lack of testosterone can cause a lack of sexual development and sexual desires, fatigue, and depression. Therapy has the capacity to boost the quality of life, depression, libido, and erectile function (Elliot et al., 2017). Virtually, a source of exogenous testosterone causes an increase in total testosterone allows for those with this treatment to live a better and healthier lifestyle. Thus, experimentation with testosterone allows us to understand what effect it has mechanistically on our bodies.

For the experiment, 26 rats were placed into three different treatment groups. The first treatment was castration with a testosterone implant which had 11 rats. The second treatment was no castration with a testosterone implant which had five rats. The final treatment was castration with a sham implant which had ten rats. After a 3-week waiting period following the surgery, the rats were weighed for post-surgery mass, euthanized, and then dissected to weigh the different organs imperative for analysis. Statistical analysis tests were done to determine the statistically significant difference between the different treatment groups: CAST/SHAM, CAST/TEST, and INTACT/TEST. I hypothesize that the castration with a testosterone implant will have the highest percent increase in body mass and a higher mean percent composition for the wet and the dry kidneys, the wet and the dry heart, the wet and the dry liver, the wet and the dry seminal vesicles, and the wet and the dry right gastrocnemius muscle than the other two treatments.

__Methods & Materials__

Each rat was obtained and weighed individually and then placed into one of the three different treatments. The sample size for the experiment was initially 26 rats, but one was removed due to infection. First, a 0.05 mL subcutaneous injection of Buprenorphine was administered. Next, each rat was placed in an anesthetic induction chamber with 5% isoflurane and 100% oxygen. The level of anesthesia was adjusted based on the breathing level. The hair on the scrotum and a 2-cm square portion located on the back was shaved off. The surgical areas were prepared by rubbing betadine initially and then alcohol in a cycle for three times. Next, surgical scissors were used to snip a 1 cm long incision on the surface of the scrotum. From the incision, the tunica on one side was cut, and the testi was popped out and pulled until the spermatic cord was visible. The spermatic cord was squeezed and then tied off with a 2-0 silk thread to limit bleeding. The testi and epididymis were cut off from the knot. After the spermatic cord was placed back into the tunica, the testi and epididymis were removed and placed on a weigh boat. The process was then repeated to remove the other testi. Once the testes were removed, they were moved to balance, and their weights were recorded. The incision area was sutured together using square knots after castration of both testes and washed with sterile saline solution. Tissue glue is then placed on top of the incision to make sure that the wound is not reopened.

For the second part of the experiment, a 0.5 cm incision was made between the shoulder blades. A hemostat was again used to create a small space beneath the skin. Based on the treatment group which was predetermined by the instructor, a silicone implant containing either testosterone or a sham was placed inside the space. These implants were stored in BSA and then transferred to ethanol one hour before the surgery. If the implant was a sham, then the initial length was recorded as 0 on the data file. If the implant had the testosterone propionate inside, the initial length of the implant was measured. The wound is then closed off with square knots and then washed with a sterile solution to prevent infections. Tissue glue was used to make sure that the wounds do not open up. The next morning, TAs administer another 0.05 mL injection of Buprenorphine. The rats are then proceeded to be monitored for the next three weeks. When it was time for the dissection and analysis of specific organs of the lab, the rats were once again placed in the anesthesia induction chamber with 5% isoflurane and 100% oxygen. The rats were then given 0.5 mL of a fatal injection. The rat was then weighed to find the post-surgery body mass. Once pronounced dead, the rats are dissected, and the heart, liver, kidneys, seminal vesicles, and right gastrocnemius muscle are removed and then placed in metal trays. The implant was retrieved during dissection, and the final testosterone length is measured. The metal trays were initially weighed and recorded. The organs were then immediately weighed individually (wet weight) and again after 24 hours in an incubator (dry weight).

Statistical tests such as an ANOVA test were conducted to find if there was a significant difference between the treatment groups. If the p-value was greater than 0.05, then it was determined that the treatment groups are not statistically significant. If the p-value was less than 0.05, then it was determined that the treatment groups are statistically significant from one another then another statistical test, Tukey’s HSD’s test was performed to find which treatments are statistically different from each other. Additionally, a two-sample t-test was performed to find statistical significance between testosterone implant length change. An ANOVA test was not performed as using this test could cause a greater chance for error (Bagatto, 2018).

__Results__

To find exact calculations for percent composition in the body, refer to Appendix A. To find the ANOVA and Tukey’s HSD’s test results, refer to Appendix B. To find the two-sample t-test results, refer to Appendix C. One rat in the castration and testosterone implant group was not used due to an infection.

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*Figure 1:** Graph depicts the mean percent increase in body mass across the three treatment groups. The mean percent increase in body mass of the castration and sham implant is 4.55%. The mean percent increase in body mass of the castration and testosterone implant is 0.999%. The mean percent increase in body mass of the no castration and testosterone implant is 2.29%. The p-value for the ANOVA test found statistical significance with a p-value of 0.0042*.

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*Figure 2:** Graph depicts the mean percent composition of the dry heart in the body across the three treatment groups. The mean percent composition of the dry heart in the body of the castration and sham implant is 0.091%. The mean percent composition of the dry heart in the body of the castration and testosterone implant is 0.107%. The mean percent composition of the dry heart in the body of the no castration and testosterone implant is 0.106%. An ANOVA test found no statistical significance with a p-value of 0.3431.*

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*Figure 3:** Graph depicts the mean percent composition of the wet heart in the body across the three treatment groups. The mean percent composition of the wet heart in the body of the castration and sham implant is 0.327%. The mean percent composition of the wet heart in the body of the castration and testosterone implant is 0.363%. The mean percent composition of the wet heart in the body of the no castration and testosterone implant is 0.360%. An ANOVA test found no statistical significance with a p-value of 0.4272.*

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*Figure 4:** Graph depicts the mean percent composition of the wet kidneys in the body across the three treatment groups. The mean percent composition of the wet kidneys in the body of the castration and sham implant is 0.629%. The mean percent composition of the wet kidneys in the body of the castration and testosterone implant is 0.824%. The mean percent composition of the wet kidneys in the body of the no castration and testosterone implant is 0.898%. An ANOVA test found statistical significance with a p-value of 0.0023.*

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*Figure 5:** Graph depicts the mean percent composition of the dry kidneys in the body*

*across the three treatment groups. The mean percent composition of the dry kidneys in the body of the castration and sham implant is 0.181%. The mean percent composition of the dry kidneys in the body of the castration and testosterone implant is 0.256%. The mean percent composition of the dry kidneys in the body of the no castration and testosterone implant is 0.244%. An ANOVA test found statistical significance with a p-*

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*Figure 6:** Graph depicts the mean percent composition of the wet liver in the body across the three treatment groups. The mean percent composition of the wet liver in the body of the castration and sham implant is 3.62%. The mean percent composition of the wet liver in the body of the castration and testosterone implant is 3.88%. The mean percent composition of the wet liver in the body of the no castration and testosterone*

*implant is 4.11%. An ANOVA test found statistical significance with a p-value of 0.0337.*

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*Figure 7:** Graph depicts the mean percent composition of the dry liver in the body across the three treatment groups. The mean percent composition of the dry liver in the body of the castration and sham implant is 1.58%. The mean percent composition of the dry liver in the body of the castration and testosterone implant is 1.88%. The mean percent composition of the dry liver in the body of the no castration and testosterone implant is 1.93%. An ANOVA test found statistical significance with a p-value of 0.0042.*

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*Figure 8:** Graph depicts the mean percent composition of the wet seminal vesicles in the body across the three treatment groups. The mean percent composition of the wet seminal vesicles in the body of the castration and sham implant is 0.075%. The mean percent composition of the wet seminal vesicles in the body of the castration and testosterone implant is 0.357%. The mean percent composition of the wet seminal vesicles in the body of the no castration and testosterone implant is 0.264%. An ANOVA test found statistical significance with a p-value less than 0.0001.*

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*Figure 9:** Graph depicts the mean percent composition of the dry seminal vesicles in the body across the three treatment groups. The mean percent composition of the dry seminal vesicles in the body of the castration and sham implant is 0.025%. The mean percent composition of the dry seminal vesicles in the body of the castration and testosterone implant is 0.106%. The mean percent composition of the dry seminal vesicles in the body of the no castration and testosterone implant is 0.074%.* *An ANOVA test found statistical significance with a p-value less than 0.0001.*

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*Figure 10:** Graph depicts the mean percent composition of the wet right gastrocnemius muscle in the body across the three treatment groups. The mean percent composition of the wet right gastrocnemius muscle in the body of the castration and sham implant is 0.646%. The mean percent composition of the wet right gastrocnemius muscle in the body of the castration and testosterone implant is 0.638%. The mean percent composition of the wet right gastrocnemius muscle in the body of the no castration and testosterone implant is 0.686%. An ANOVA test found no statistical significance with a*

*p-value of 0.8976.*

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*Figure 11:** Graph depicts the mean percent composition of the dry right gastrocnemius muscle in the body across the three treatment groups. The mean percent composition of the dry right gastrocnemius muscle in the body of the castration and sham implant is 0.186%. The mean percent composition of the dry right gastrocnemius muscle in the body of the castration and testosterone implant is 0.205%. The mean percent composition of the dry right gastrocnemius muscle in the body of the no castration and testosterone implant is 0.19%. An ANOVA test found no statistical significance with a p-value of 0.6767.*

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*Figure 12**: Graph depicts the mean percent decrease of testosterone implant length in the body for the two treatment groups. The mean percent decrease of testosterone implant length of the castration and testosterone implant is 57.8%. The mean percent decrease of testosterone implant length of the no castration and testosterone implant is 70.4%. **A two-sample t-test was done and a p-value of 0.0827 which signified no statistical significance.*

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The percent change in total body mass was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 1. Error bars represent one standard error of each treatment. The cast/sham group had the highest mean percent change with 4.54±0.82%. Intact/test group had a lower mean percent change with 2.29±1.15%. Cast/test had the lowest mean percent change with 0.99±0.82%. An ANOVA test found statistical significance with a p-value of 0.0189. A Tukey’s HSD analysis further found that that cast/sham and cast/test was significantly significant with a p-value of 0.0149. Intact/test was not significantly different from cast/test with a p-value of .6400 and was not significantly different from cast/sham with a p-value of .2681.

The percent composition of the dry heart in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 2. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.107±0.008%. Intact/test group had a lower mean percent composition with 0.106±0.01%. Cast/sham had the lowest mean percent composition with 0.091±0.008%. An ANOVA test found no statistical significance with a p-value of 0.3431. A Tukey’s HSD analysis was not needed as the p-value was not less than 0.05.

The percent composition of the wet heart in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 3. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.363±0.02%. Intact/test group had a lower mean percent composition with 0.360±0.03%. Cast/sham had the lowest mean percent composition with 0.327±0.02%. An ANOVA test found no statistical significance with a p-value of 0.4272. A Tukey’s HSD analysis was not needed as the p-value was not less than 0.05.

The percent composition of the wet kidneys in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 4. Error bars represent one standard error of each treatment. The intact/test group had the highest mean percent composition with 0.898±0.062%. The cast/test group had a lower mean percent composition with 0.824±0.044%. The cast/sham had the lowest mean percent composition with 0.629±0.062%. An ANOVA test found statistical significance with a p-value of 0.0023. A Tukey’s HSD analysis was done and further showed that intact/test and cast/sham are statistically significant with a p-value of 0.0048 and that cast/test and cast/sham are statistically significant with a p-value of 0.0122. Intact/test and cast/test are not statistically significant with a p-value of 0.5978.

The percent composition of the dry kidneys in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 5. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.256±0.011%. The intact/test group had a lower mean percent composition with 0.244±0.015%. The cast/sham had the lowest mean percent composition with 0.181±0.011%. An ANOVA test found statistical significance with a p-value of 0.0001. A Tukey’s HSD analysis was done and further showed that intact/test and cast/sham are statistically significant with a p-value of 0.0066 and that cast/test and cast/sham are statistically significant with a p-value of 0.0002. Intact/test and cast/test are not statistically significant with a p-value of 0.7905.

The percent composition of the wet liver in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 6. Error bars represent one standard error of each treatment. The intact/test group had the highest mean percent composition with 4.11±0.149%. The cast/test group had a lower mean percent composition with 3.88±0.105%. The cast/sham had the lowest mean percent composition with 3.62±0.105%. An ANOVA test found statistical significance with a p-value of 0.0337. A Tukey’s HSD analysis was done and further showed that intact/test and cast/sham are statistically significant with a p-value of 0.0321. The cast/test and cast/sham are not statistically significant with a p-value of 0.1992 and the intact/test and cast/test are not statistically significant with a p-value of 0.4279.

The percent composition of the dry liver in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 7. Error bars represent one standard error of each treatment. The intact/test group had the highest mean percent composition with 1.93±0.093%. The cast/test group had a lower mean percent composition with 1.88±0.066%. The cast/sham had the lowest mean percent composition with 1.58±0.066%. An ANOVA test found statistical significance with a p-value of 0.0042. A Tukey’s HSD analysis was done and further showed that intact/test and cast/sham are statistically significant with a p-value of 0.0161 and that the cast/test and cast/sham are statistically significant with a p-value of 0.0095. The intact/test and cast/test are not statistically significant with a p-value of 0.9281.

The percent composition of the wet seminal vesicles in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 8. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.357±0.018%. The intact/test group had a lower mean percent composition with 0.264±0.025%. The cast/sham had the lowest mean percent composition with 0.075±0.018%. An ANOVA test found statistical significance with a p-value less than 0.0001. A Tukey’s HSD analysis was done and further showed that intact/test and cast/sham are statistically significant with a p-value less than 0.0001. The cast/test and cast/sham are statistically significant with a p-value less than 0.0001. The intact/test and cast/test are statistically significant with a p-value of 0.0149.

The percent composition of the dry seminal vesicles in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 9. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.106±0.0065%. The intact/test group had a lower mean percent composition with 0.074±0.0092%. The cast/sham had the lowest mean percent composition with 0.025±0.0065%. An ANOVA test found statistical significance with a p-value less than 0.0001. A Tukey’s HSD analysis was done and further showed that cast/test and cast/sham are statistically significant with a p-value less than 0.0001. The intact/test and cast/sham are statistically significant with a p-value of 0.0007. The intact/test and cast/test are statistically significant with a p-value of 0.0240.

The percent composition of the wet gastrocnemius muscle in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 10. Error bars represent one standard error of each treatment. The intact/test group had the highest mean percent composition with 0.686±0.086%. The cast/sham group had a lower mean percent composition with 0.646±0.061%. The cast/test had the lowest mean percent composition with 0.638±0.061%. An ANOVA test found no statistical significance with a p-value of 0.8976. A Tukey’s HSD analysis was not needed as the p-value was not less than 0.05.

The percent composition of the dry gastrocnemius muscle in the body was measured in each rat across all three treatments and averaged for each treatment and is displayed in figure 11. Error bars represent one standard error of each treatment. The cast/test group had the highest mean percent composition with 0.205±0.016%. The intact/test group had a lower mean percent composition with 0.190±0.022%. The cast/sham had the lowest mean percent composition with 0.186±0.016%. An ANOVA test found no statistical significance with a p-value of 0.6767. A Tukey’s HSD analysis was not needed as the p-value was not less than 0.05.

The percent decrease in testosterone implant length was measured in each rat between the two treatment groups that used the testosterone implant and averaged the treatments and is displayed in figure 12. Error bars represent one standard error of each treatment. The intact/test group had the higher mean percent decrease with 70.4±5.49%. The cast/test group had a lower mean percent decrease with 57.7±3.88%. A two-sample t-test was done and a p-value of 0.0827. Since the p-value is greater than 0.05, this showed that there is no difference between the implant length decrease in the two treatment groups. This shows that the testosterone absorbed by the rat is not significantly different by the two groups and that another variable accounts for the difference between the two treatment groups.

__Discussion__

Testosterone is a hormone that is very vital for male development. During the first six weeks of a fetus, the SRY gene causes the creation of the testicles, which contains the Sertoli and Leydig cells. The Sertoli cells create the production of the Mullerian-inhibiting substance which causes the repression of the oviducts and in turn support the differentiation of the Wolffian duct which causes the formation of the epididymis, vas deferens, and the seminal vesicles (Hill, Wyse, & Anderson, 2018). In the case of females, the SRY gene is not present causing the degeneration of the Wolffian duct and supports the development of the Mullerian duct (Hill, Wyse, & Anderson, 2018). During puberty in males, the hypothalamo-hypophyseal portal system is particularly active. The hypothalamus releases GnRH, which travels through this portal system to the anterior pituitary and causes the release of two tropic hormones: LH and FSH. These two hormones travel through the bloodstream and attach to receptors in the male reproductive system. LH stimulates Leydig cells to convert cholesterol into testosterone. Testosterone then travels through the bloodstream and binds to androgen receptors in several tissues. The release of testosterone stimulates the Sertoli cells and causes spermatogenesis. The levels of these two hormones and testosterone are controlled by negative feedback (Nassar, 2018).

Figure one graphs the percent body mass increase across the three treatment groups. The castration and sham implant treatment is statistically different from the castration and testosterone implant treatment, while the no castration and testosterone implant is not statistically different from the other two treatment groups. These experimental results are supported by the study done by researchers at the medical colleges at Dow University. The study found that there is a negative correlation between the amount of total testosterone and BMI, the study also mentioned multiple cohort studies that found this negative correlation to be true (Shamim, Khan, & Arshad, 2015). Studies done at Karolinska Institute in Sweden found that in rats, low levels of testosterone cause the improvement of lipolytic activity in both types of fat cells as opposed to humans as testosterone can have different effects on lipolytic activity (Arner, 2005). This increased level lipolysis can lead to an increased risk of obesity. When the amount of adipocyte cells increases, low levels of testosterone causes lipase activity, and this causes the broken-down triglyceride to be stored as adipocytes (Kelly & Jones, 2013). This increase in adipocytes limits the release of LH which decreases testosterone further increasing lipase activity (Kelly & Jones, 2013). The treatment group of castration and sham implant has a lack of testosterone in the bloodstream and causes a buildup in adipocytes which leads to an increase in body mass.

Figure two graphs the percent composition of the dry heart in the body. There was no statistically significant difference between the three treatment groups. The data was not supported by a multitude of studies, as these sources stated that the castration and testosterone implant treatment should have the highest percent composition. One of the studies done at the Houston Methodist Hospital found that testosterone is imperative to heart function, as testosterone binds to androgen receptors in cardiovascular cells, which in turn activates specific genes that alter these cells behavior (Goodale et al., 2017). Another study done by the University of Michigan found that higher levels of total testosterone were associated with higher Left Ventricular mass and volume (Kim et al., 2016). Testosterone causes an increase in intracellular levels of calcium and activates T cells and inhibits the GSK-3 beta, by phosphorylation, which is an anti-hypertrophic (enlargement of an organ) factor in heart cells (Herald et al., 2017). The treatment group of castration and testosterone implant has an increase of testosterone amount, as when testosterone binds to Androgen receptors on cardiac cells causing inhibition of GSK-3 beta and a hypertrophic effect on the heart.

Figure five graphs the percent composition of the dry kidneys in the body. There was a statistically significant difference between the no castration and testosterone implant treatment and the castration and sham implant treatment. There was also a statistically significant difference between the castration and testosterone implant treatment and the castration and sham implant treatment. There was no statistically significant difference between the castration and testosterone implant treatment and the no castration and testosterone implant treatment, which had the two highest means for the percent composition. The data is supported by studies, as CAST/TEST and INTACT/TEST should have the highest means. A study done by the University of Erlangen found that rats that were castrated and had an exogenous source of testosterone had a 100% increase in kidneys weight and rats that only had the exogenous source of testosterone had a 151% increase in kidneys weight (Schwarzlose and Heim, 1973). The increase in testosterone causes an increase in glutamate synthesis and causes an increased reservoir of amino acids which in turn leads to a growth of tissue in the kidneys (Schwarzlose and Heim, 1973). In the case of the wet kidney, there was no statistical significance between the two highest treatments of castration and testosterone implant and the no castration and testosterone implant. In regard to the kidneys, testosterone binds to alpha Androgen receptors on cells to increase the rate of release of norepinephrine (Liu & Ely, 2011). The norepinephrine then binds to adrenoceptors in the kidney to cause an increase in reabsorption of Na ions which ultimately leads to reabsorption of water (Liu & Ely, 2011).

Figure seven graphs the percent composition of the dry liver in the body. There was a statistically significant difference between the no castration and testosterone implant treatment and the castration and sham implant treatment. There was also a statistically significant difference between the castration and testosterone implant treatment and the castration and sham implant treatment for the dry liver. There was no statistically significant difference between the castration and testosterone implant treatment and the no castration and testosterone implant treatment, which had the two highest means for the percent composition. The data is supported by studies, as the castration and testosterone implant treatment should have the highest mean. A study done by the University of Siena found that the application of testosterone to castrated rats caused an increase in hepatocytes (Tanganelli et al., 1991). Conversely, the lack of testosterone can lead to the development of non-alcoholic fatty liver diseases (Mody et al. 2015). Another study found that testosterone causes an increase in glucose uptake in HepG2 cells and causes the upregulation of mitogen protein kinase (Kelly, Akhtar, Bowskill, Smallwood, & Jones, 2014). Once testosterone binds to these cells, there is an increase in glucose uptake and the activation of the mitogen protein kinases causes an increase in mitotic activity in the liver. The castration and testosterone implant treatment has an exogenous source of testosterone which produces a hypertrophic effect in the liver.

Figure nine graphs the percent composition of the dry seminal vesicles in the body. There was a statistically significant difference between the castration and testosterone implant treatment, the castration and sham implant treatment, and the no castration and testosterone implant treatment. The castration and testosterone implant had the highest mean out of all the treatment groups. The data is supported by a study done by a university in Peru which showed that an increase in testosterone increases the activity of the seminal vesicles and the weight of seminal vesicles (Gonzales, 2001). A study done in London found that castration with no exogenous source of testosterone causes a decrease in epithelial cells paired with a substantial decrease in RNA, and when there is an added source of exogenous testosterone, causes a proliferation in the epithelial cells with a massive production of RNA (Higgins, Burchell, & Mainwaring, 1976). This supports the idea that the castration and testosterone implant treatment, had the exogenous testosterone bind to the AR receptor on the seminal vesicles causing a total growth of epithelial cells thus increasing the size of the seminal vesicles.

Figure eleven graphs the percent composition of the dry right gastrocnemius muscle in the body. There was no statistically significant difference between the three treatment groups. The data is not supported by the studies as the castration and testosterone implant treatment should have the highest mean. Testosterone causes an increase in lean body mass, as it causes pluripotent mesenchymal cells to become into muscle cells thus increasing the muscle mass. Testosterone also causes the increasing of the motor neurons size (Herbst and Bhasin, 2004). Through these changes, it causes an increase in muscle strength (Herbst and Bhasin, 2004). Additionally, testosterone caused an increase in diameter on the type 1 fibers while also inducing protein synthesis in the gastrocnemius which can change the shape and size and cause a change in the appearance in the fibers (Ustünel, Akkoyunlu, & Demir, 2003). When testosterone binds to androgen receptors, an increase of satellite cells occurs, causing the formation of myoblasts and leads to larger myofibers (Herbst and Bhasin, 2004). The exogenous source of the testosterone in the castration and testosterone implant treatment causes an increase in muscle mass due to the conversion of pluripotent cells to muscle cells and when bonded to androgen receptors causes an increase in myofibers size through satellite cells.

During the experiment, there was a multitude of issues. The first was that there was not a long waiting period between the time of the surgery and the dissection of the rat. This lack of time causes a lack of accuracy on the data and could have caused the data discrepancies. Another issue was that there was not an even number of rats in each treatment group. There was ten CAST/TEST, ten CAST/SHAM, and only five INTACT/TEST. There was a larger standard error in each graph due to the limited number of rats in the INTACT/TEST treatment. There were many confounding variables such as food consumption and exercise that could have impacted many of the weights of the organs and changed the percent composition in the body. Before the experiment, I hypothesized that the castration and testosterone implant treatment will have the highest percent increase in body mass and a higher mean percent composition for the wet and the dry kidneys, the wet and the dry heart, the wet and the dry liver, the wet and the dry seminal vesicles, and the wet and the dry right gastrocnemius muscle than the other two treatments. After the experiment, the highest percent increase in body mass was in the castration and sham implant treatment, while the castration and testosterone implant treatment had the highest percent composition of the dry and the wet heart, the dry kidney, the wet and the dry seminal vesicles, and the dry right gastrocnemius muscle. The no castration and testosterone implant treatment had the highest percent composition of the wet kidney, the wet and the dry liver, and the wet right gastrocnemius muscle. Through this, the hypothesis is rejected as treatments did not have a significant difference in all the organs.

Works Cited

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Bagatto, B. (E.d.). (2018). Rat Surgery Protocol

Demeter, E., Sarter, M., & Lustig, C. (2008). Rats and humans paying attention: cross-species task development for translational research. *Neuropsychology*, *22*(6), 787-99.

Elliot, J., Kelly, S. E., Millar, A. C., Peterson, J., Chen, L., Johnston, A., . . . Wells, G. A. (2017). Testosterone therapy in hypogonadal men: A systematic review and network meta-analysis. *BMJ Open,7*, 1-10.

Gonzales, G. F. (2001, December 3). Function of seminal vesicles and their role on male fertility. Retrieved from http://www.asiaandro.com/archive/1008-682X/3/251.htm

Goodale, T., Sadhu, A., Petak, S., & Robbins, R. (2017). Testosterone and the Heart. *Methodist DeBakey cardiovascular journal, 13*(2), 68-72

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