Categories
Biomedical Research

The Role of Twin Studies in Medicine

By Michelle Li

Published 4:09 EST, Mon November 15th, 2021

Introduction

“Nature or nurture” is a long standing question in the sciences; are people more influenced by biological or environmental factors when maturing? Twin studies attempt to answer that question, and although it has not been fully answered, these studies begin to provide an understanding of which aspects of human beings can be attributed to specific factors, whether those are genes or the environment in which people have grown up. Twin studies were first introduced to the scientific world in the 1870s by Sir Francis Galton. Galton attempted to answer this question of “nature or nurture” (Twin studies, 2007). In a number of published articles, he ultimately argued that nature was the more influential factor after studying the results of a questionnaire that focused on how similar or different twins turned out to be after aging, regardless of growing up together or separately. Although Galton’s conclusion was an early argument to a question that has still not been fully answered, it revealed the potential of studying twins in terms of gaining knowledge of the different genetic and environmental influences in human lives, and, eventually, how that knowledge relates to biomedical research relating to diseases.

Overview

Twins studies are valuable to biomedical research in that the unique cases of twins allow researchers to separate genetic and environmental influences. Twin cases are separated into two types: Dizygotic and Monozygotic. Dizygotic, or fraternal, twins are not genetically identical but are raised in the same settings from birth. These twins are conceived through two separate, fertilized eggs. They develop in the womb and are born at the same time, but they do not share the same genetics. Monozygotic, or identical, twins—on the other hand—do have the same genetic predispositions, as they have developed from the same fertilized egg. The single fertilized egg splits into two, allowing for two embryos to develop and explaining the identical genetic material (Brogan, 2020). Twin studies also offer the opportunity to control for the factors of age and gender, but the genetic similarity between identical twins is ultimately key to twin research.

When raised in separate environments, identical twins are not influenced by environmental factors, allowing for researchers to study only the biological influences. Similarities in behavior or predispositions to diseases that both twins possess would indicate a biological basis, as environmental influences have been controlled (Brogan, 2020). Conversely, studying identical twins raised in the same environments also have the potential to identify environmental triggers that are connected to diseases. When the genetics and environment of identical twins are the same, similar reactions or onsets to diseases after exposures from the environment can be identified, possibly linking environmental triggers to different conditions.

One twin study conducted by Chirag Lakhani that utilizes insurance claims data from the insurance company Aetna analyzed more than 56,000 twins. The insurance records allowed researchers to study the health of the twins while looking for a connection with some of the 560  diseases that the study focused on. Diseases that occur more often in identical twins in the study were believed to have a genetic influence, and the diseases that occurred in siblings regardless of their twin status were believed to have an environmental influence. Ultimately, the study found that of the 560 diseases that researchers focused on, 40% had a genetic component, while 25% had an environmental component (“Nature or nurture twins study”).

Twin Registries

Twin registries are collections of data on twins that are used for future studies. Many countries have established their own twin registries, and they may be overseen by universities or other nongovernmental organizations. Twin registries allow researchers to analyze existing twin data that has been archived, study data related to the development of twins, and pursue twins overtime for longitudinal data for studies completed over longer time frames (Brogan, 2020).

Advantages and Disadvantages

The major advantage of twin studies is that the unique situation of twins allows researchers to begin to calculate and separate the genetic and environmental influences on characteristics of people. Factors, specifically genetics or environment as well as age and gender, can be controlled in order to focus on the impact of a specific factor (Brogan, 2020).

In addition, there are also disadvantages and limitations. Separated, identical twins can still have (and often do still have) similar living environments (although they will not be the same). Twins that become orphans are commonly raised by relatives that share similar socioeconomic situations, influencing housing, living conditions, and financial stability. Adopted twins may also be sent to similar families to avoid favoritism (Brogan, 2020). These situations lessen the ability to effectively separate genetic and environmental influences, which is what makes twin studies valuable.

Conclusion

Twin studies are valuable opportunities to study the genetic and environmental factors that influence a person’s characteristics. Looking through the scope of medicine, twin studies can be used to identify genetic and environmental components of diseases or conditions. While these components are still yet to be fully understood, twin studies have offered partial answers and have the potential to return more significant research that relates to disease onset or other areas of medicine.

Michelle Li, Youth Medical Journal 2021

References

Brogan, R. F. (2020). Twin studies. In Gale Science Online Collection. Gale. Retrieved September 20, 2021, fromhttps://link.gale.com/apps/doc/KEIGGJ810319895/SCIC?u=mlin_m_newtnsh&sid=bookmark-SCIC&xid=2c42af4e

“Nature or nurture twins study helps sort out genes role in disease.” (2019, January 14). Community Healthcare System. Retrieved September 24, 2021, from https://www.comhs.org/about-us/newsroom/health-library/2019/01/14/nature-or-nurture-twins-study-helps-sort-out-genes-role-in-disease

Twin studies. (2007). In World of Genetics. Gale. Retrieved September 20, 2021, fromhttps://link.gale.com/apps/doc/CV2433500512/SCIC?u=mlin_m_newtnsh&sid=bookmark-SCIC&xid=fa0ee4c8

Categories
Biomedical Research

The Role of Language in Addressing Vaccine Hesitancy

By Michelle Li

Published 1:20 EST, Thurs October 21st, 2021

Introduction

Vaccines have played a vital role in the almost complete eradication of several infectious diseases, such as measles, chickenpox, and polio. However, in recent years, the contributions of vaccines to public health have been threatened by the spread of anti-vaccination sentiment and vaccine hesitancy. As defined by the World Health Organization (WHO), vaccine hesitancy  is the “delay in acceptance or refusal of vaccines despite availability of vaccine services” (MacDonald, 2015). The recent anti-vaccine movement has led to increased vaccine hesitancy and decreased vaccine coverage. Its spread presents detrimental consequences for public health with the resurgence of diseases. Many factors have contributed to this rise in vaccine hesitancy, with mistrust in vaccines playing a crucial role. Different interventions, such as providing access to educational resources, have been suggested. One factor that may be overlooked when considering interventions is the language utilized by healthcare workers when interacting with vaccine hesitant parents, as the word choice of providers is connected to different rates of vaccine acceptance. Correspondingly, a change in the word choices of healthcare providers, if used effectively, may be utilized to increase rates of vaccine acceptance and coverage. 

Presumptive Compared to Participatory Approaches

An examination led by Opel et al. (2013) found that there is a relationship between the approach of healthcare workers, particularly their word choice or language, and the parents’ acknowledgment or opposition to vaccination. In the study, vaccine discussions between providers and parents—both vaccine-hesitant and non-vaccine hesitant—were videotaped and analyzed. The parents had children aged 1 to 19 months old, and the Parent Attitudes about Childhood Vaccinations Survey was used to categorize parents as vaccine-hesitant (score of greater than or equal to 50) or non-vaccine hesitant based on their score. The investigation compared the effect of providers using presumptive methodologies against those that used participatory approaches on parents’ immunization choices. Providers with presumptive approaches used statements similar to “We have to do some shots,” while providers with participatory approaches used statements similar to “What do you want to do about these shots?”. In 74% of cases, healthcare workers implemented the presumptive strategy. In 26% of those cases, parents voiced resistance to immunization suggestions (Opel et al., 2013). Of those that resisted, there were significantly more vaccine-hesitant parents than non-vaccine hesitant parents. 50% of providers responded to the resistance by repeating their original stance through statements similar to “He really needs these shots,” and 47% of parents, who initially resisted, accepted the vaccine recommendations (Opel et al., 2013). When providers took on a participatory approach (26% of cases), 83% of parents resisted (Opel et al., 2013). These outcomes suggest that the type of approach used by healthcare providers influences the decision-making of parents regarding vaccination. Providers that introduce vaccines as requirements or the optimal decision are less likely to face parent resistance compared to those that give parents more of a choice—26% compared to 83%, respectively (Opel et al., 2013). In addition, almost 50% of those that initially showed resistance from the presumptive approach acknowledged immunization suggestions when pressed again with the provider’s original stance. The presumptive methodology uses language that assumes that the patient will consent to the vaccination, depicting vaccination as a routine technique that the healthcare provider recommends. On the other hand, the participatory approach removes the healthcare provider’s confidence in the vaccine, opening the situation to vaccine hesitancy-related sentiments. Conveying and emphasizing a provider’s confidence in vaccination influences the vaccination results of patients, as they will be more likely to feel confident about the vaccine if the provider does as well.

One explanation for the influence of presumptive approaches is the trust in the relationship between the healthcare provider and the patient. Provider-patient relationships have proven to play a vital role in combating vaccine hesitancy, specifically in countering the mistrust of vaccines. A study conducted by Gilkey et al. (2014) sought to measure confidence about adolescent vaccination (ages 13 to 17) in different populations of parents. Randomly selected parents who completed the 2010 National Immunization Survey-Teen were a part of the study. Participants rated their agreement to 8 vaccination belief statements—0 being strongly disagree and 10 being strongly agree. The study categorized the statements into factors: benefits of vaccination, harms of vaccination, and trust in healthcare providers. Data on subgroups and demographics—such as sex, race/ethnicity, and mother’s education—was also collected. Across these subgroups and demographics, the mean agreement rating for statements that fell under trust in healthcare providers was 9.0, while the mean agreement rating for those under benefits of vaccination was 8.5 (Gilkey, 2014). This aspect of the study showcases that parent confidence in vaccines is high when the trust patients have in healthcare providers is high. Therefore, approaches that emphasize that trust in the provider-patient relationship, namely presumptive approaches, may push parents to accept the recommendations of providers, thereby supporting the findings of the study by Opel et al. (2013).

Conclusion

While the word choices of healthcare providers alone will not resolve the issues of vaccine hesitancy, it can still influence the vaccine rate acceptance, as it capitalizes on the trust held between providers and patients, which has been shown to correlate positively with vaccine acceptance. A change in the language used by healthcare providers, in conjunction with existing interventions, can maximize the chances of persuading vaccine-hesitant parents, increasing vaccine coverage and protecting public health. Therefore, the language used by healthcare providers must not be overlooked when considering interventions involving vaccine-hesitant patients.

Michelle Li, Youth Medical Journal 2021

References

Burke, C. W. (2021). Anti-vaccination (anti-vax). In Gale Health and Wellness Online Collection. Gale. https://link.gale.com/apps/doc/FOXFJH723466243/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=1b6ab02b

Gilkey, M. B., Magnus, B. E., Reiter, P. L., McRee, A. L., Dempsey, A. F., & Brewer, N. T. (2014). The Vaccination Confidence Scale: a brief measure of parents’ vaccination beliefs. Vaccine, 32(47), 6259–6265. https://doi.org/10.1016/j.vaccine.2014.09.007

Lerner, B. W. (2021). Vaccine hesitancy. In K. H. Nemeh & J. L. Longe (Eds.), The gale encyclopedia of science (6th ed., Vol. 8, pp. 4632-4634). Gale. https://link.gale.com/apps/doc/CX8124402558/SCIC?u=mlin_m_newtnsh&sid=bookmark-SCIC&xid=160f31c4

MacDonald, N. E., & SAGE Working Group on Vaccine Hesitancy (2015). Vaccine hesitancy: Definition, scope and determinants. Vaccine, 33(34), 4161–4164. https://doi.org/10.1016/j.vaccine.2015.04.036

Opel, D. J., Heritage, J., Taylor, J. A., Mangione-Smith, R., Salas, H. S., Devere, V., Zhou, C., & Robinson, J. D. (2013). The architecture of provider-parent vaccine discussions at health supervision visits. Pediatrics, 132(6), 1037–1046. https://doi.org/10.1542/peds.2013-2037

Categories
Health and Disease

Pediatric Cancers Compared to Adult Cancers

By Michelle Li

Published 11:04 EST, Mon September, 20th, 2021

Introduction

Pediatric cancers refer to cancers that affect children under the age of 18 years old, while adult cancers are those that occur in people over 18. However, age is not the only difference between pediatric and adult cancers. There are a number of other key differences in the onset, progression, and treatment between the two that need to be taken into consideration. 

Onset and Development of Pediatric and Adult Cancers

The most significant difference between pediatric and adult cancers is that it is more common for adults to be diagnosed with cancer compared to children. According to the American Cancer Society, approximately 10,500 new cancer cases in children (ages 0-14) and 5,090 cases in adolescents (ages 15-19) will be diagnosed in the United States in 2021; this amounts to a total of 15,590 estimated new pediatric cancer cases (“Cancer Facts & Figures”). An expected 1.9 million new cancer cases are expected to be diagnosed in the United States 2021 (“Cancer Facts & Figures”). Only a small fraction of those cases are pediatric patients with cancer while the vast majority are adult cases. While this can be partially attributed to the differences in population percentages, the causes of pediatric and adult cancers also provide a partial explanation. According to the World Cancer Research Fund, at least 18% of diagnosed cancer cases in the United States are connected to body fatness, lack of exercise, alcohol consumption, or lack of nutrition in diet (“Diet and Physical Activity: What’s the Cancer Connection?”). As all four are lifestyle or environmental factors, adults are more likely to have been exposed to these factors over longer periods of time, contributing to the higher diagnoses of cancer in adults. Pediatric cancers are usually unrelated to these lifestyle choices, as children have most likely not been exposed to certain factors due to their age (specifically in the case of alcohol or tobacco) or have been exposed for shorter periods of time (Vahey). 

Additionally, the connection to lifestyle or environmental factors may also partially explain the difference in common types of cancers for children and adults. The most common pediatric cancers are leukemia, brain and central nervous system cancers, lymphoma, bone cancer, and neuroblastoma, among others (Watson). Common cancers for adults, on the other hand, include lung, breast, colon, kidney cancer, etc (“Cancer Statistics”). As children are less exposed to the lifestyle and environmental factors found to be related to cancer diagnoses, they are also less likely to have cancers related to those factors; for instance, children who have not been exposed to cigarette smoke are less likely to develop lung cancer. The opposite is true for adults who may make the choice to smoke tobacco products and, as a result, become more exposed to cigarette smoke and experience higher rates of lung cancer. Interestingly, the common types of adult cancers begin in specific organs, while the common pediatric cancers don’t occur in the same pattern (Vahey).

Progression: How Pediatric and Adult Cancers Act

In terms of progression of pediatric and adult cancers, pediatric cancers are often more aggressive and progress faster than adult cancers (Vahey). Pediatric cancers are also more likely to have moved to other organs by the time of diagnosis. This may also be partially attributed to the lack of useful screening tests for pediatric cancers; a number of screening tests are available for adult cancers, which may result in earlier detection for adults and diagnoses before the cancer has spread to other parts of the body (Vahey). 

Treatment

Another difference between pediatric and adult cancers lies in their prognosis. In general, children have a better prognosis compared to adults, as two-thirds of pediatric cancer cases are cured (Vahey). However, survival rates vary greatly depending on the type of cancer.

Treatment also differs between pediatric and adult cancer patients. Children’s bodies react differently and experience different risks than adults, and this is still true for cancer treatments. Besides the different considerations based on age, treatment also varies based on the type of cancer, the affected tissues, and the spread of the cancer. Since pediatric cancers spread faster and have often moved to other parts of the body by the time of diagnoses, surgery is not as likely to cure a pediatric cancer patient (Vahey). However, children’s bodies respond more positively to chemotherapy. This may be explained by the fact that chemotherapy is effective against fast-growing cancers — which pediatric cancers tend to be (“Treating Children with Cancer”). Additionally, children’s bodies may also recover better compared to adults after high doses of chemotherapy, which would allow for more intense treatments with higher chances of effectively treating the cancer. The possibility of more short and long term effects is still present, though (“Treating Children with Cancer”). In contrast, children’s bodies do not respond better to radiation therapy. In fact, children experience more serious side effects than adults who have undergone radiation therapy (“Treating Children with Cancer”). Different factors must be considered when treating pediatric patients with cancer than when treating adults. In addition to the different options for treatment for certain cancers, healthcare professionals must also consider how a pediatric patient will respond to a treatment, even if it has proven to be effective in adults with cancer.

Conclusion

Pediatric and adult cancers vary greatly in their onset, progression, and treatment. The difference in patient ages translates to different common cancers by age group, different developments in progression, and different treatments. Ultimately, the fact that pediatric cancers diverge so much from adult cancers speaks to the importance of considering the differences between pediatric and adult patients in healthcare settings for not only cancer but other conditions as well. 

Michelle Li, Youth Medical Journal 2021

References

“Cancer Facts & Figures 2021.” National Cancer Society, http://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/cancer-facts-figures-2021.html. Accessed 28 July 2021.

“Cancer Statistics.” National Cancer Institute, http://www.cancer.gov/about-cancer/understanding/statistics. Accessed 29 July 2021.

“Diet and Physical Activity: What’s the Cancer Connection?” American Cancer Society, http://www.cancer.org/cancer/cancer-causes/diet-physical-activity/diet-and-physical-activity.html. Accessed 28 July 2021.

“Treating Children with Cancer.” National Cancer Society, http://www.cancer.org/cancer/cancer-in-children/how-are-childhood-cancers-treated.html. Accessed 26 July 2021.

Vahey, Marianne, and Cameron Howell. “Childhood Cancers.” The Gale Encyclopedia of Cancer: A Guide to Cancer and Its Treatments, edited by Deirdre S. Hiam, 5th ed., vol. 1, Gale, 2021, pp. 517-27. Gale Health and Wellness, link.gale.com/apps/doc/CX8067200154/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=ea00a342. Accessed 28 July 2021.

Watson, Stephanie. “Pediatric Cancer.” The Gale Encyclopedia of Cancer: A Guide to Cancer and Its Treatments, edited by Deirdre S. Hiam, 5th ed., vol. 3, Gale, 2021, pp. 1622-27. Gale Health and Wellness, link.gale.com/apps/doc/CX8067200495/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=5600b57e. Accessed 28 July 2021.

Categories
Health and Disease

The Plague in the Modern Day

By Michelle Li

Published 8:21 EST, Mon August 30, 2021

Introduction and History

The plague is a disease that is caused by the bacterium Yersinia Pestis. The Black Death, one of the most notable pandemics in history, was a result of the transmission of Y. pestis from rats and fleas to humans, making it a zoonotic disease (Frey, “Plague). This transmission often occurred through flea bites or contact with the body fluid of an infected animal. The plague takes on three different forms depending on the affected area of the body: bubonic (affecting lymph nodes), pneumonic (affecting the lungs), and septicemic (affecting the blood). The Black Death is characterized by both the swelling of lymph nodes, which turn black as a result of bubonic plague, and the blackening of skin, resulting from septicemic plague (Frey, “Plague). An estimated 75 to 200 million lives were lost before the end of the Black Death (Frey, “Bubonic Plague”). Today, the number of fatalities resulting from (and cases of)  the plague are not even remotely close to the numbers seen during the Black Death; the recorded numbers are not zero, however. 

Plague in the modern day

Cases of the plague, although much less frequent, still exist today. A majority of the present day cases of the plague occur in developing countries. In fact, the plague is still endemic to (regularly found in) Madagascar, Peru, and the Democratic Republic of the Congo (Frey, “Bubonic Plague). Madagascar reports more plague cases than any other single country, averaging 200 to 400 cases every year (Hardman).

A portion also occurs in the United States. The Centers for Disease Control and Prevention (CDC) reports between 1 to 17 cases of the plague each year in the United States (with an average of 7 reported cases per year). Plague in the United States occurs in western, rural areas; northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and western Nevadea are the most affected regions. 80% of these U.S. cases are in bubonic form (“Plague in the United States”). 

Figure 1: This figure shows a world map of plague cases reported to the World Health Organization (WHO) by country between 2000 and 2009 (Centers for Disease Control and Prevention)

There are about 5,000 cases of the plague reported to the World Health Organization (WHO) each year worldwide, and 95% of these cases occur in Africa. Interestingly, the only two continents that are plague-free are Australia and Antarctica (Frey, “Plague”). 

More “recent” plague outbreaks include an outbreak of pneumonic plague in Surat, India in 1994, where 876 cases of infections, including 52 deaths, were reported to the WHO (Frey, “Plague”). The most recent outbreak in Madagascar occurred in 2017 and resulted in 2,575 confirmed or probable cases of bubonic and pneumonic plague, including 221 deaths (World Health Organization 2017). Even more recently, the WHO began reporting on an ongoing outbreak of suspected pneumonic plague in the Dominican Republic of Congo in January of 2020. As of May 2021, there are a total of 564 suspected pneumonic plague cases, including 43 deaths (World Health Organization 2021).

Antibiotics

Today, the plague is treatable with antibiotics. 80% to 90% of patients with bubonic plague that received rapid diagnosis and appropriate treatment will survive; the survival rates for septicemic plague and pneumonic plague are lower in comparison at 75% and 50%, respectively (Frey, “Bubonic Plague”). If left untreated however, each form of the plague is still fatal a majority of the time. Bubonic plague has a mortality rate of 60% to 70% in untreated cases, while untreated septicemic and pneumonic plague both have a mortality rate of 100%. Pneumonic plague, specifically, is 100% fatal if left untreated for 48 hours (Frey, “Bubonic Plague”). 

Streptomycin, an antibiotic discovered in the 1940s, is one of the first-line treatments for plague (Hardman). Gentamicin, chloramphenicol, and tetracycline are alternatives that can also be administered. It is important that the administration of antibiotics is started as soon as possible (Cua). 

The Future

Some scientists have also considered the association between climate and plague. The conditions following warmer weather in the spring and wet weather in the summer are beneficial for fleas and bacteria, which play key parts in the spread of plague (Hardman). Additionally, outbreaks of plague among local animals (called epizootics) most commonly occur after wet winters and cool summers; these epizootics could also affect humans (Frey, “Plague”). In the case of the plague outbreak in Surat, India, rainfall also influenced the spread of plague, as flooding increased contact with drowned, infected animals that were not disposed of (Frey, “Plague”). Similarly to other climate sensitive and infectious diseases, the effects of global warming may increase the number of outbreaks of plague in animals and, in turn, in human populations (Hardman). 

Lastly, the animal reservoirs of the plague (the host animal populations that infectious diseases survive off of) make the disease impossible to eradicate (Frey, “Plague”). Rats play a large role in the spread of the plague. Controlling that spread—considering their sheer numbers and the scope of human capabilities—proves to be near impossible. Surveillance of animal populations and careful reporting of plague cases, however, is still important in preventing plague (Frey, “Plague”).

Conclusion

The plague is an infectious disease that is well known due to its connection to the Black Death, one of the most notable epidemics in history. While the occurrence of the plague has changed since medieval times, the high mortality rates of untreated plague cases have remained and are currently affecting different regions of the world. Considering its connections to climate change and recent developments, the plague is not a disease of the past, but rather, one that is still relevant to the modern world. 

Michelle Li, Youth Medical Journal 2021

References

Centers for Disease Control and Prevention. “World Plague Map – 2000 to 2009 – CDC.” Wikimedia Commons, commons.wikimedia.org/wiki/File:World_Plague_Map_-_2000_to_2009_-_CDC.jpg. Accessed 30 June 2021. Map.

Cua, Arnold, and Rebecca J. Frey. “Plague.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 7, Gale, 2020, pp. 4067-71. Gale Health and Wellness, link.gale.com/apps/doc/CX7986601475/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=851c3f42. Accessed 1 July 2021.

Frey, Rebecca J., PhD. “Bubonic Plague.” The Gale Encyclopedia of Emerging Diseases, edited by Deirdre S. Hiam, Gale, 2018, pp. 45-52. Gale Health and Wellness, link.gale.com/apps/doc/CX3664800021/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=0a3632e4. Accessed 1 July 2021.

—. “Plague.” The Gale Encyclopedia of Public Health, edited by Brigham Narins, 2nd ed., vol. 2, Gale, 2020, pp. 847-51. Gale Health and Wellness, link.gale.com/apps/doc/CX7947900220/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=d93f373c. Accessed 1 July 2021.

Hardman, Lizabeth. “Plague Today and Tomorrow.” Plague, Lucent Books, 2010, pp. 74-87. Diseases & Disorders. Gale Health and Wellness, link.gale.com/apps/doc/CX1334700011/HWRC?u=mlin_m_newtnsh&sid=bookmark-HWRC&xid=8b9c5d6d. Accessed 1 July 2021.

“Plague in the United States.” Centers for Disease Control and Prevention, http://www.cdc.gov/plague/maps/index.html. Accessed 30 June 2021.

World Health Organization. Weekly Bulletin on Outbreaks and Other Emergencies. 15 Dec. 2017. World Health Organization, apps.who.int/iris/bitstream/handle/10665/259709/OEW50-1015122017.pdf;jsessionid=9E1F0CC89024B909F1E30F0B1064B43A?sequence=1. Accessed 30 June 2021.

—. Weekly Bulletin on Outbreaks and Other Emergencies. 27 June 2021. World Health Organization, apps.who.int/iris/bitstream/handle/10665/342077/OEW26-2127062021.pdf. Accessed 30 June 2021.

Categories
Biomedical Research

Neonatal Immunology: Our Immune Systems in the Weeks After Birth

By Michelle Li

Published 12:08 AM EST, Sun July 4, 2021

Introduction

Neonates are newborn infants that are four weeks old or younger. These first four weeks of an infant’s life are when the infant is at highest risk of dying. At this stage in life, neonates do not have fully developed immune systems and are more susceptible to different infections. Of the 5 million infant deaths that occur each year, 1.5 million are due to infections, making it important to understand the developing immune system of neonates (Tregoning). 

Part of understanding the immune systems of neonates is first understanding the transition form the sterile womb to an unsterile environment during birth. The fetal immune system is suppressed in the womb in order to limit interference with the mother’s immune system. While this provides stability before birth, the arrangement changes the second after birth, when the newborn enters the unsterile environment of the world. In addition to the risks of being exposed  to bacteria, the fetal immune system after birth (which was previously suppressed) is antigenically inexperienced; it does not yet have experience responding to different pathogens, which increases the infants susceptibility to infections (“Development of the Immune System”). Therefore, after birth, neonates depend on “passive immunity” for protection, as their own immune systems develop.

Passive Immunity

Neonates depend on antibodies from the mother for protection from different antigens. This is called “passive immunity,” as antibodies from the mother are passed down to the baby passively through the placenta, rather than the antibodies being created by the infant themselves. Most of the antibodies produced by the mother’s immune system cross the placenta during the third trimester, which ensures that there are high levels of antibodies after birth. This also explains the low levels of antibodies in premature babies; the timing of the birth does not allow for the same amount of antibodies to be transferred, making premature newborns more vulnerable to infections compared to full-term newborns. Additionally, breastfeeding is another form of passive immunity that allows for the passing of antibodies to infants (“Development of the Immune System”). 

Passive immunity only provides short term protection for neonates. The antibodies transferred through the placenta or breast milk are generally immunoglobulin A or G (IgA or IgG). Some of these maternal antibodies protect against measles, mumps, rubella, etc (“Immunity: Active, Passive, and Delayed”). The antibodies transferred passively from the mother to the child either through the placenta or breast milk only protection for the first few months of the infant’s life. This allows the infant’s immune system to develop and start working while keeping the infant protected (“Development of the Immune System”).

The Immune System At This Time

Newborns have a limited quantity of phagocytic cells (types of white blood cells such as neutrophils and macrophages), which are important for innate immunity (the nonspecific immune response immediately after the appearance of an antigen). During an infection, the immune system’s response will be limited by the quantity of neutrophils and macrophages. As a result, the pathogen will commonly overtake the immune system, and the infant will require medical care (“Development of the Immune System”).

In addition, there is also adaptive immunity, which is the specific immune response that occurs after the innate immunity system fails; it is the system that protects the body by remembering and destroying pathogens. As the newborn’s immune system is inexperienced, every pathogen is new, resulting in the immune response taking a longer time to develop. The fact that every pathogen is new also means that there are no memory immune responses, which affects antibody production (“Development of the Immune System”). The process of producing antibodies is less efficient in newborns compared to adults. Some B cell (a type of white blood cell) responses require T cells to produce antibodies. The interactions between T cells, which attack specific antigens, and antigen-presenting cells, which present antigens for recognition, are less effective and stimulating in newborns. There are lower levels of cytokines (which regulate the immune response) produced by T cells. Furthermore, the levels of types of T cells are different in newborns than in adults. For instance, there are lower levels of cytotoxic T cells, which are responsible for killing virus infected cells. These factors influence the levels of antibody production. For B cell responses that don’t involve T cells, B cells recognize the repeating proteins on the surface of a pathogen; this response is also reduced in newborns, resulting in increased susceptibility to bacteria (“Development of the Immune System’).

Vaccines

The reduced immune response of newborns affects the efficacy of vaccines, as there is reduced recognition of vaccine antigens as foreign. Therefore, there are also fewer protective memory responses induced by vaccines, making vaccines themselves less effective in newborns compared to adults with developed immune systems (Tregoning). However, this does not mean that early vaccinations are ineffective. They still aid in protecting against diseases, and they become more effective over time as the newborn’s immune system develops (“Development of the Immune System”). 

In fact, as the protection from passive immunity fades over a number of months, vaccinations are required to maintain protection against different antigens. The fading of maternal antibodies is also why there are certain required vaccinations after set periods of times; for instance, the MMR vaccine is required after 1 year of life (“Immunity: Active, Passive, and Delayed”).

Conclusion

The immune systems of neonates are, unsurprisingly, different and less developed than those of adults. As a result, newborns depend on passive immunity (antibodies passed down through the placenta or breast feeding) for protection against infections. The processes in the immune system itself are also different in newborns, which affects the immune system’s capabilities. The increased susceptibility to infections in newborns makes it all the more important to understand the neonatal immune system.

Michelle Li, Youth Medical Journal 2021

References

“Development of the Immune System.” Children’s Hospital of Philadelphia, http://www.chop.edu/centers-programs/vaccine-education-center/human-immune-system/development-immune-system. Accessed 31 May 2021.

“Immunity: Active, Passive, and Delayed.” World of Microbiology and Immunology, edited by Brenda Wilmoth Lerner and K. Lee Lerner, Gale, 2007. Gale in Context: Science, link.gale.com/apps/doc/CV2644650228/SCIC?u=mlin_m_newtnsh&sid=bookmark-SCIC&xid=bd032b6a. Accessed 31 May 2021.

Tregoning, John. “Neonatal Immunology.” British Society for Immunology, http://www.immunology.org/public-information/bitesized-immunology/immune-development/neonatal-immunology. Accessed 31 May 2021.

Categories
Health and Disease

Dyslexia: The Reading Disability

By Michelle Li

Published 1:57 PM EST, Fri May 7, 2021

Introduction

Dyslexia is a learning disability that is characterized by difficulty in reading, writing, spelling, and other language skills. It was first discovered in 1887 when German physician Rudolf Berlin published a case study on a young boy who had normal intelligence but faced difficulties in reading and writing (Nelson). A few years later in 1896, the first English-language case study of dyslexia was published by the British doctor W. Pringle Morgan. Similarly to the 1887 case study, Morgan also detailed a 14 year-old boy who had normal intellectual capabilities but had not learned to read. Before the term “dyslexia” was put into widespread use, the condition was referred to by Morgan and others as “word-blindness”. It is still retained the key characteristic of difficulty reading (Nelson). 

It is believed to have a hereditary component and is most commonly identified in the early years through symptoms related to hardships in reading or other language skills. Following a diagnosis, options to treat dyslexia through special education also exist.

Causes

Dyslexia is believed to be a hereditary condition, as 40% of boys and 20% of girls with a dyslexic parent also develop the disorder. Four genes have been found to be connected to dyslexia, but no specific cause has been identified for the disorder (Nelson). Some studies involving positron emission tomography or functional magnetic resonance imaging have shown that there is lower activity in the left inferior parietal cortex, left inferior frontal gyrus, the left inferior parietal lobule, and the left middle temporal gyrus of the brain in dyslexic children when they are given reading or word tasks to complete, highlighting the connection between dyslexia and certain areas of the brain (Nelson). 

Symptoms and Diagnoses

The symptoms of dyslexia appear through the affected reading, writing, listening, and speaking abilities of individuals. Some symptoms include slow reading speed, difficulty reading and spelling words, omission of words while reading, poor reading comprehension, reversal of words or letters, confusion between similar letters, delayed speech, and transferrence of information across modes—such as reading out loud or writing thoughts or speech (Nelson; Frey). 

When these symptoms create problems in school or work settings, individuals are referred to testing for dyslexia. As instruction on reading begins in kindergarten or first grade in the U.S., it is rare for dyslexia to be diagnosed before the age of five or six (Frey). Children are generally diagnosed with dyslexia when they demonstrate that their reading level is greater than two levels below the expected average for their age or education (Nelson). Other visual, hearing, speech, intelligence, and word or letter recognition tests are also conducted to rule out disorders that could impair vision or hearing and measure a child’s capabilities; they are also evaluated psychologically to rule out depression or anxiety as a cause for the learning impairment (Nelson, Frey). Generally, reading problems must substantially interfere with school or daily life, as outlined by the APA’s diagnostic criteria for dyslexia (Frey).

Treatment

Appropriate and early intervention through special education has been proven effective in treating dyslexia. Under the Individuals with Disabilities Education Act, children with dyslexia are entitled to individualized education plans (IEP) that address the learning disability (Nelson; Frey). The IEP defines specific problems and the associated learning objectives. This is usually done through a cross-disciplinary approach. The three core principles of the successful approach developed by Samuel Torrey Orton in the 1920s have a sound/symbol based component, where words are broken down into letters and associated sounds; a multisensory component, where visual, auditory, and kinesthetic connections are strengthened; and a highly structure component, which involves working up from letters to words to sentences with repetitive practice (Nelson). There are also a number of techniques that reading specialists may test out to see which are most effective. Generally, dyslexia can be treated with appropriate intervention; the earlier the diagnosis and intervention, the greater the likelihood of improved reading abilities and less interference in education.

Conclusion

As the most common learning disability in the United States, dyslexia interferes in the education and lives of many individuals each year. While a clear cause has not been identified, a hereditary component and low activity in certain areas of the brain have been linked to the condition. Symptoms are related to impairments in reading, writing, spelling, and speech; evaluations of these impairments are used to diagnose dyslexia. Early treatment through specialized education plans have been proven successful in improving reading and related abilities, providing hope for dyslexic individuals.

Michelle Li, Youth Medical Journal 2021

References

Frey, Rebecca J., and Jack Lasky. “Developmental Reading Disorder.” The Gale Encyclopedia of Children’s Health: Infancy through Adolescence, edited by Jacqueline L. Longe, 4th ed., vol. 2, Gale, 2021, pp. 846-50. Gale Health and Wellness, link.gale.com/apps/doc/CX8067400255/HWRC?u=mlin_m_newtnsh&sid=HWRC&xid=fee6c3a7. Accessed 19 Apr. 2021.

Nelson, Katy, and Jack Lasky. “Dyslexia.” The Gale Encyclopedia of Children’s Health: Infancy through Adolescence, edited by Jacqueline L. Longe, 4th ed., vol. 2, Gale, 2021, pp. 901-04. Gale Health and Wellness, link.gale.com/apps/doc/CX8067400273/HWRC?u=mlin_m_newtnsh&sid=HWRC&xid=d2d05de7. Accessed 19 Apr. 2021.

Categories
Health and Disease

Sudden Infant Death Syndrome (SIDS): An Unexplainable Nightmare For New Parents

By Michelle Li

Published 7:42 PM EST, Tues April 13, 2021

Introduction

SIDS is the leading cause of death for infants who are 1 month to 12 months in age in the U.S (Marshall). As the name suggests, SIDS is the sudden and unexplained death of a seemingly healthy infant under the age of 1. This most commonly occurs overnight when the infant is sleeping, therefore it is also known as crib death or cot death. Some time after being put to sleep, the infant is discovered lifeless and limp despite showing no health concerns previously. An investigation is then conducted with no clear causes being identified, leading to a diagnosis of SIDS (Odle).

SIDS is responsible for the deaths of 2,500 to 7,000 infants a year. 80% of these deaths occur in infants younger than 5 months old, and, with 60-70% of cases being male deaths, it disproportionately affects boys more than girls (“Sudden Infant Death Syndrome”). SIDS deaths are more frequent during the winter and early spring. Interestingly, babies whose siblings died of SIDS are at a slightly higher risk of the same syndrome despite the fact that it is not contagious or hereditary (Odle). 

Classification/Diagnosis

SIDS falls under the even broader category of SUIDS, Sudden Unexpected Infant Death Syndrome. For cases labeled as SUIDS, however, the cause of death can generally be identified. It is usually an environmental factor such as high room temperature, being placed to sleep with a pillow, etc. Whereas with SIDS, the cause of death can not be identified even after thorough investigations, autopsies, examinations of death scenes, and reviews of clinical history. Diagnosis of SIDS is a process of exclusion where other causes of death need to be ruled out (Odle). 

SIDS only officially became known as a cause of death in 1979, but sudden deaths in babies with or without explanation have been reported for hundreds of years. In the 1700s and 1800s, SIDS deaths may have been blamed on mothers for rolling on babies while sleeping with them. In the 1900s, co-sleeping between infants and parents became more rare, and speculative reasoning behind the sudden deaths shifted to the dressing of babies in clothes that were too warm during the night (Marshall). This shows how the speculated causes of SIDS change over time.

Speculation About Causes and Current Understanding of SIDS

Many have speculated about the causes of SIDS, and while a number of possible factors have been pointed out, there is still no clearly defined cause of SIDS to this day. One theory is that a genetic defect in an enzyme causes the brain to be deprived of energy, resulting in a coma (Marshall). Another theory focuses on the connection between abnormalities in breathing patterns/heart rhythm and SIDS (Marshall; Odle). Others speculate that a combination of factors and conditions results in SIDS (Odle).

There are also factors that increase the risk of SIDS, including mothers smoking during pregnancy, using drugs or alcohol, being underweight, having children less than one year apart, having children in teen years, and being obese. Babies who are born prematurely, weigh less than 4 pounds, are not breastfed, or are part of a set of twins/triplets/quadruplets are also at an increased risk of SIDS (Odle).

Additionally, the infant’s sleeping positions seem to play a role in deaths diagnosed as SIDS. Studies have shown that placing a baby on its stomach or side to sleep increases the risk of SIDS, as they would re-breathe their own carbon dioxide and would not be able to turn to get more oxygen (“Sudden Infant Death Syndrome”; Odle). This risk is reduced by putting a baby on its back to sleep in the supine sleeping position. Another study also shows that the use of pacifiers may protect against SIDS, reducing the risk of SIDS by 90% (“Sudden Infant Death Syndrome”).

Awareness Campaigns

New Zealand, Australia, and Norway saw campaigns aimed at raising awareness and reducing the risk factors of SIDS. These campaigns resulted in a decrease of SIDS deaths by as much as 50% (Odle). The U.S. also saw a similar campaign, the “Safe to Sleep” campaign, that focused on encouraging parents to put babies on their back when sleeping, as recommended by the American Academy of Pediatrics. The “Safe to Sleep” campaign also saw significant results, reducing the number of SIDS deaths by 20 to 35% in the 1990s. Results from other countries have also shown that a 5 to 10% in babies sleeping on their stomachs results in SIDS deaths decreasing by 70 to 80% (Odle). Although the direct causes of SIDS are still unknown, it seems that sleeping positions are an important risk factor which can be countered by awareness campaigns. 

Disparities in SIDS Deaths

It is also important to note that there are racial/ethnic disparities in SIDS deaths. African American, Native American, and Alaska Native babies all are at a higher risk of SIDS deaths than caucasian babies. African American babies are twice as likely to die from SIDS, while Native American and Alaska Native babies are three times as likely (Odle). Like the causes of SIDS, these disparities are also unexplained. It may be a result of health disparities and cultural differences that make populations more prone to the risk factors of SIDS. Another explanation that is offered is that the efforts of awareness campaigns in different countries are not reaching certain communities.

Conclusion

Sudden Infant Death Syndrome (SIDS) is a cause for concern for many as the leading cause of death for infants who are 1 month to 12 months in age in the U.S. Its unexplained causes and unequal impact on different communities make it an even greater cause for concern. Thankfully, awareness campaigns fighting to reduce the risk factors of SIDS seem to be effective, and there is hope for measures to prevent SIDS in the future as more developments are made to understand SIDS.

Michelle Li, Youth Medical Journal 2021

References

Marshall, Liz. “Sudden Infant Death Syndrome (SIDS).” The Gale Encyclopedia of Science: S, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 7, Gale, 2021, pp. 4314-16. Gale in Context: Science, link.gale.com/apps/doc/CX8124402378/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=930fe12c. Accessed 28 Mar. 2021.

Odle, Teresa, and Rebecca J. Frey. “Sudden Infant Death Syndrome.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 8, Gale, 2020, pp. 4954-58. Gale in Context: Science, link.gale.com/apps/doc/CX7986601813/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=d899e172. Accessed 28 Mar. 2021.

“Sudden Infant Death Syndrome.” World of Health, Gale, 2007. Gale in Context: Science, link.gale.com/apps/doc/CV2191501243/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=e054a249. Accessed 28 Mar. 2021.

Categories
Health and Disease

Muscular Dystrophy (MD): About the Conditions Centered Around Muscle Weakness

By Michelle Li

Published 10:41 PM EST, Wed March 10, 2021

Introduction

Muscular dystrophy (MD) is a group of conditions that causes muscle weakness and degeneration. It is an inherited disorder in which symptoms gradually worsen over time (Quercia). Age of onset varies depending on the type of muscular dystrophy, ranging from childhood to the later stages of life. The severity, rate of progression, and pattern of affected muscles also vary with the type of MD. Many individuals with muscular dystrophy lose the ability to walk and, unfortunately, live shorter lives than average due to the condition (“Muscular Dystrophy: Hope in Research”). There are no cures for any forms of muscular dystrophy, but treatments such as physical therapy and braces aim to improve muscle function and slow deterioration.

The first reported case of muscular dystrophy in the 1830s was of two brothers that were experiencing progressive muscle weakness that began around age 10. They developed general weakness and muscle damage, and it was observed that the damaged muscle tissue was replaced with fat and connective tissue. At the time, it was mistakenly thought that these were symptoms of tuberculosis. In the years that followed, more cases of boys developing muscle weakness and dying at an early age were reported. As more cases were studied and observed, the different types of muscular dystrophy were classified, and its genetic link was discovered (“Muscular Dystrophy: Hope in Research”).

Types of Muscular Dystrophy

Duchenne muscular dystrophy (DMD) was named after Guillaume Duchenne, a French neurologist who gave a detailed account of 13 boys with the disorder in the 1860s (“Muscular Dystrophy: Hope in Research”). Duchene muscular dystrophy is the most common—accounting for 50% of MD cases—and the most severe type of muscular dystrophy. It affects one in every 3,500 males (Bosworth). It most commonly affects young boys and is much rarer for females. Symptoms begin to appear in the early toddler years and become apparent with difficulty walking, an affected gait, loss of reflexes, frequent falls, etc. Progressive muscle-weakening begins in the legs before spreading to the upper arms. This results in the loss of the ability to walk and often the use of a wheelchair by early adolescence. Those with DMD also experience muscle wasting, a decrease in muscle mass and strength due to lack of physical activity. Eventually, the cardiac muscles are weakened, which leads to breathing problems and fatal infections. The average life expectancy of individuals with DMD is the late teens or early twenties, but this has improved significantly with some living in their 30s and 40s (Bosworth).

Becker muscular dystrophy shares some similarities with Duchenne MD but is less severe. It affects one in every 30,000 males with most experiencing symptoms at 11 years old to as late as 25 years old (Bosworth). Similar to Duchenne muscular dystrophy, a symmetrical progression of muscle weakness is usually noticed in the upper arms, legs, and pelvis. The rate of progression is slower than that of DMD, so some retain the ability to walk until their mid-thirties or never need to use a wheelchair. Cardiac complications are also often fatal for those with Becker MD, although the average life expectancy is the mid-forties (Bosworth).

Emery-Dreifuss muscular dystrophy also develops in children, most commonly boys, at a young age. Compared to Duchenne muscular dystrophy, they experience slower and less severe muscle weakness in their arms and legs. Prior to significant muscle weakness, those with Emery-Dreifuss MD also experience contractures—tightening of muscles that prevent normal movement—in the spine, neck, elbows, knees, and ankles; this results in locked elbows or rigid spines (“Muscular Dystrophy: Hope in Research”).

Limb-girdle muscular dystrophy affects both males and females with symptoms appearing in late childhood to early adulthood. Individuals experience muscle weakness and wasting of the muscles around the hip and shoulder areas, known as the limb-girdle area; this spreads to the neck and legs. They may have difficulty rising from chairs or have an affected gait. Different types of Limb-girdle MD have also been identified with different rates of progression and severity, ranging from symptoms that develop slowly and interfere minimally with life to more severe muscle damage and inability to walk (“Muscular Dystrophy: Hope in Research”).

Facioscapulohumeral muscular dystrophy also develops in both males and females beginning in late childhood to early adulthood. It affects about one in every 20,000 people (Quercia). This type of muscular dystrophy causes asymmetric muscle weakness in the face, shoulders, and upper arms. Muscles around the eyes and ears are commonly weakened before the shoulders and upper arms. This can also affect an individual’s appearance through slanted shoulders, a crooked smile, flattened facial features, etc (“Muscular Dystrophy: Hope in Research”). 

Myotonic dystrophy, the most common form of muscular dystrophy in adults, causes muscle weakness in the face, feet, and hands for males and females. In addition to progressive weakness, people with myotonic dystrophy also experience an inability to relax muscles after a contraction. Symptoms can appear from birth to adulthood (“Muscular Dystrophy: Hope in Research”). 

Oculopharyngeal muscular dystrophy affects those in their forties or fifties. The first symptom is drooping eyelids and weakness around the muscles in the face and throat. Additionally, the tongue may also be affected. These symptoms result in issues with vision (such as double vision), difficulty swallowing, and changes in an individual’s voice (“Muscular Dystrophy: Hope in Research”). 

Distal muscular dystrophy is characterized by muscle weakness in the muscles of the forearms, hands, lower legs, and feet (distal muscles). While this group of dystrophies is less severe and progresses slowly, it results in difficulties in extending fingers and, similarly to other muscular dystrophies, walking (“Muscular Dystrophy: Hope in Research”).

Lastly, congenital muscular dystrophy is defined by muscle weakness at birth. Failure to meet motor function and muscle control landmarks are usually the first signs of this muscular dystrophy. Those with congenital muscular dystrophy have trouble sitting or standing without support and may never learn to walk (“Muscular Dystrophy: Hope in Research”).

Michelle Li, Youth Medical Journal 2021

References

Bosworth, Michelle Q., MS, and Rebecca J. Frey, PhD. “Duchenne and Becker Muscular Dystrophy.” The Gale Encyclopedia of Genetic Disorders, edited by Tracie Moy and Laura Avery, 4th ed., vol. 1, Gale, 2016, pp. 579-85. Gale Health and Wellness, link.gale.com/apps/doc/CX3630400165/HWRC?u=mlin_m_newtnsh&sid=HWRC&xid=14e7d476. Accessed 14 Feb. 2021.

“Muscular Dystrophy: Hope Through Research.” National Institute of Neurological Disorders and Stroke, ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Muscular-Dystrophy-Hope-Through-Research. Accessed 14 Feb. 2021.

Quercia, Nada, and Karl Finley. “Muscular Dystrophy.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 6, Gale, 2020, pp. 3510-18. Gale in Context: Science, link.gale.com/apps/doc/CX7986601264/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=5502bdc3. Accessed 14 Feb. 2021.

Categories
Biomedical Research

Mice in Biomedical Research

Introduction

Mice constantly appear on the headlines of news articles next to a new finding in biomedical research. Laboratory mice have allowed researchers to study cancer, genetic conditions, and all sorts of diseases. But why mice? Why is it that mice are so involved in medical research? What do these creatures that seemingly bear little connection with humans offer to researchers? 

The beginning of mouse genetics research started in 1902 when Lucien Cuénot experimented with coat colors of mice to show that Mendel’s laws of inheritance–which were proved using sweet peas–also applied to mammals. Mice were seen as a more ideal research animal after Clarence Little created the first fully inbred strain of mice, DBA. This provided for genetically identical laboratory mice for experimental use (“How did the lab mouse come to be?”). The mouse genome was sequenced in 2002, and allowed  for more research into the connection between mouse and human genes as well as  health and diseases (“2002: Mouse Genome Sequenced”). Today, the most common species of laboratory mice is the House Mouse or Mus musculus

Why Mice?

Mice serve as ideal animal models for genetics and biomedical research for a number of reasons. For one, they share similarities with humans in DNA. The protein-coding regions of mice and human DNA, which are important for function, are 85% identical. These genes are evolutionarily conserved and range from 60% identical to 99% identical (Parente). 

Additionally, the bodies of mice and humans undergo similar processes and react similarly to diseases. Since the genes that mice and humans share have similar functions, mice have the same organs namely, the  heart, brain, lungs, and kidneys. It also translates to similar bodily systems such as the circulatory, reproductive, digestive, hormonal, or nervous systems (“Why are mice considered excellent models for humans?”). As such mice are susceptible to a number of the  same diseases as humans. For instance, they naturally develop conditions such as diabetes, cancer, and high blood pressure and when linked to genetics, the DNA that mice and humans share provides opportunities to study those genetically-linked conditions. Although they are not perfect, these parallels allow researchers to gain insight into the development of both humans and diseases.

Lastly, mice are convenient animal models for researchers. They  reproduce quickly, sometimes reproducing after nine weeks. Mice are small mammals, and they produce larger numbers of offspring. These factors make them economical to maintain and study. In addition, every one mouse year is the equivalent of 30 human years; this means that the entire life cycle of humans can be replicated in a few mouse years, allowing researchers to study aging and diseases over time (Parente). 

The mouse genome can also be easily edited to study a specific gene or disease. Knockout or knock-in mice have been used to study the role of specific genes through gene manipulation. By using a process in DNA repair called homologous recombination, artificial pieces of DNA can be introduced into the cell nucleus of mouse embryonic stem cells (cells from young mouse embryos). The cells with the manipulated piece of DNA are then injected into a surrogate female mouse. This process allows a targeted gene to be neutralized, as the artificial piece of DNA replaces or “knocks out” the original. Genes or mutant genes can also be introduced to produce knock-in mice that have a desired gene (Parente). Researchers use these mice to study the effects of the loss of a specific gene or the introduction of a mutant gene. This also allows researchers to introduce genes that would make mice susceptible to a specific condition, creating opportunities to study a specific disease.

Xenografting is another type of mouse model in which immunodeficient mice (mice with defective immune systems) are transplanted with cells from another species. Human cancer cells or tumor tissues are often transplanted. This allows for the studying of the effect of an anticancer drug on the mice and tumors (Parente). Transgenic mice, on the other hand, are inserted with genes from another source, specifically humans; this allows for a human gene that does not naturally occur in mice to be expressed in mice. For instance, when the human growth hormone gene was inserted using this technique, it resulted in large mice. Transgenic research has resulted in a better understanding of genetic regulation and a number of other diseases (Parente).

Ethical Concerns

The role of mice in biomedical research raises ethical concerns over animal health and welfare. Lab mice should be housed in see-through plastic cages with bedding and fed a specific nutritional diet. It is also important to provide them with enrichment and to house them with other mice in groups or pairs, as they are social animals (“Mouse”). There are existing guidelines and policies regarding animal experimentation; most provide strict regulation of laboratory animals. One widely used principle is that of the 3Rs (Replacement, Reduction, and Refinement), which aims to provide a framework for more humane animal studies. When possible, technologies or approaches that can fully or partially replace animals in experiments should be used. The number of animals used per experiment should be minimised while still allowing for the study to be conducted. Lastly, methods that minimise the pain, suffering, distress, or harm of a research animal should be taken to avoid compromising the results (“The 3Rs”). Laboratory mice in biomedical research are stand-ins for humans when studying diseases. It is important that their welfare is ensured, as they play an important role in furthering scientific knowledge.

Conclusion

Mice may not seem like ideal test subjects in research studies, but they bear a surprising resemblance to humans in their physiology and DNA. In this way, mice provide researchers with a convenient window into human genetics and diseases. Despite the ethical concerns of animal experimentation, it is undeniable that mice play a central role in biomedical research that is vital to furthering our understanding of human health.

Michelle Li, Youth Medical Journal 2021

References

“The 3Rs.” National Center for the Replacement Reduction and Refinement of Animals in Research, nc3rs.org.uk/the-3rs. Accessed 31 Jan. 2021.

“How did the lab mouse come to be?” The Jackson Laboratory, http://www.jax.org/why-the-mouse/lab-mouse. Accessed 31 Jan. 2021.

“Mouse.” Understanding Animal Research, http://www.understandinganimalresearch.org.uk/animals/a-z-animals/mouse/. Accessed 31 Jan. 2021.

Parente, Matilde. “Mouse Model.” Genetics, 2nd ed., vol. 3, Gale, 2018, pp. 127-32. Gale in Context: Science, link.gale.com/apps/doc/CX2491300180/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=e28e17be. Accessed 31 Jan. 2021.

“2002: Mouse Genome Sequenced.” National Human Genome Research Institute, http://www.genome.gov/25520486/online-education-kit-2002-mouse-genome-sequenced. Accessed 31 Jan. 2021.”Why are mice considered excellent models for humans?” The Jackson Laboratory, http://www.jax.org/why-the-mouse/excellent-models. Accessed 31 Jan. 2021.

Categories
Biomedical Research

Color Blindness: Not Just Black and White

Introduction

Color blindness, also known as color vision deficiency, is the inability to differentiate between certain colors. It can range from mild to severe, and while some see only black, white, and shades of grey, most experience a more mild form of colorblindness in which they can see a limited range of hues (Fallon). Depending on the severity of a person’s color blindness, they may have difficulty distinguishing between the colors of a traffic light or determining the ripeness of fruit. It may also prevent them from having professions in which perceiving color is important to the job, such as being a pilot (“Color Blindness,” National Eye Institute). These impairments are not detrimental, however, and many have adapted around them. As there are different types and varying ranges of color blindness, color blind people don’t see the world in the exact same way as others and are each impacted differently. The passing down of genes is the main cause of color blindness. While there is no cure for color blindness, there are methods that diagnose and help colorblind individuals adapt to the condition.

Types of Color Blindness

Red-green color blindness is the most common type of color blindness. It affects 7% of the male population and 0.4% of the women population in the U.S. (Fallon). Those with red-green color blindness mainly have difficulty telling the difference between red and green. Deuteranomaly, which makes shades of green look more red, is the most common form of red-green color blindness. Another form, protanomaly, makes shades of red look more green. Both are mild forms of color blindness. Protanopia and deuteranopia, however, are more severe forms that result in the complete inability to differentiate between reds and greens (“Types of Color Blindness”). 

Blue-yellow color blindness is less common, occurring in fewer than 1 in 10,000 people around the world. Despite its name, people with blue-yellow color blindness confuse blue with green and yellow with red. Those with tritanomaly have difficulty distinguishing between the mentioned colors, while those with tritanopia cannot distinguish between the colors at all (“Types of Color Blindness”).

Figure 1: This figure shows how the views of individuals with different types of color blindness compare with that of normal color vision (Simulation of Different Color Deficiencies, Color Blindness).

Achromatopsia—when someone sees only black, white, and shades of grey—is the rarest type of color blindness, despite it being what some perceive color blindness as. It occurs in about 1 in 30,000 people. Those with achromatopsia cannot see or distinguish between any colors and only perceive black, white, and shades of grey (“Types of Color Blindness”).

Causes

The type of colorblindness is dependent on the affected photoreceptor cells in the eyes, which are each responsible for sensing wavelengths of light and distinguishing red, yellow, or blue light. When a certain type of photoreceptor cell, called cones, is absent or altered, a person’s perception of color is affected (Turbert). For instance, the absence of L cones, which are sensitive to red light, correlates to protanopia and results in the inability to perceive the color red. More mild forms of color blindness result when cones are faulty.

Figure 2: This diagram shows the effects of the absence of different cones on color vision (“Types of Colour Blindness”).

Color blindness is also linked to genetics and is passed down through genes. Mutations in certain genes cause the absence or alteration of cones, resulting in color blindness. This hereditary connection can also be seen through the disparity between men and women with red-green color blindness. The genes connected with red-green color blindness are on the X chromosome, which males have one of and females have two of. Only one X chromosome with the gene connected to red-green color blindness is needed for a male to be red-green colorblind. For females, both X chromosomes must have the gene (“Causes of Color Blindness”). This explains the drastic difference between the 7% of men and 0.4% of women in the U.S. that are red-green color blind and the hereditary nature of color blindness.

Color blindness can also be caused by diseases or injuries. Alzheimer’s disease, glaucoma, and leukemia are some chronic illnesses that may lead to color blindness. Damage to the retina of the eye or the brain can also result in acquired color blindness (Fallon). 

Diagnosis and Treatment

Specific tests exist to identify color blindness. One example is the Ishihara Test, which is made up of eight plates. Each plate contains colored dots, and in the center of the plate is a number made up of dots that are a different color than the background. Someone with normal color vision is able to identify the number in the center. An individual with red-green or blue-yellow color blindness will see a different number, as they will see the colors and numbers outlined by the dots differently. The Ishihara Test is one of the more well known of many color blindness tests, which distinguishes and helps diagnose those with color blindness (Fallon).

Figure 3: This figure shows how individuals with different types of color blindness may perceive a plate from the Ishihara Test.

There is no cure for color blindness, but many have adapted to their color blindness by using color cues and other details. Eyeglasses that correct color blindness have also been developed. These eyeglasses filter out wavelengths of light, preventing the overlap of wavelengths that causes colors to look similar or be hard to differentiate for color blind individuals (Fallon).

Conclusion

Despite the common misconception of color blind people seeing just black and white, the majority of those with color blindness have a different type of color deficiency with varying degrees of severity. Many have difficulty distinguishing between certain colors rather than a complete loss of color vision. The main cause of color blindness is the passing down of genes, and while there is no cure for the condition, many eventually adapt to their color blindness. Another option for those with color blindness may lie in color correcting eyeglasses. These eyeglasses serve as proof of the understanding that has been gained on color vision deficiency, one that is important to know and that will hopefully become widespread to counter misconceptions about color blindness.

Michelle Li, Youth Medical Journal 2021

References

“Causes of Color Blindness.” National Eye Institute, http://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness/causes-color-blindness. Accessed 27 Dec. 2020.

“Color Blindness.” National Eye Institute, http://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness. Accessed 27 Dec. 2020.

Fallon, L. Fleming, Jr., and Monique Laberge. “Color Blindness.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 2, Gale, 2020, pp. 1269-72. Gale Health and Wellness, link.gale.com/apps/doc/CX7986600452/HWRC?u=mlin_m_newtnsh&sid=HWRC&xid=96de35f1. Accessed 27 Dec. 2020.

Ishihara Test. Wikimedia Commons, commons.wikimedia.org/wiki/File:Ishihara_compare_1.jpg. Accessed 27 Dec. 2020.

Simulation of Different Color Deficiencies, Color Blindness. Wikimedia Commons, commons.wikimedia.org/wiki/File:Red_to_Green_Color_Blindness.png. Accessed 27 Dec. 2020.

Turbert, David. “What Is Color Blindness?” American Academy of Ophthalmology, 6 Sept. 2019, http://www.aao.org/eye-health/diseases/what-is-color-blindness. Accessed 27 Dec. 2020.

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