Unit 2: Keeping Healthy
B2.1 What are the causes of disease?
The relationship between Health and Disease
Health and disease exist on a continuum.
Individuals can move between states of health and disease and sometimes experience overlapping conditions.
Factors that promote health can reduce the risk of disease, and conversely, factors that increase disease risk can undermine health.
The body's ability to maintain health involves complex mechanisms that defend against disease.
Types of Diseases
Communicable Diseases (Infectious Diseases): diseases that are caused by pathogens (microorganisms) such as bacteria, viruses, fungi, or parasites.
They can spread from person to person or from animals to people.
Transmission can occur through:
Direct contact (e.g., touching, kissing)
Airborne transmission (e.g., coughing, sneezing)
Contaminated food or water
Vector-borne transmission (e.g., mosquito bites)
Bodily fluids
Non-Communicable Diseases (NCDs): diseases that are not caused by infectious agents and cannot be spread from person to person.
They are often chronic conditions that develop over a long period.
Risk factors include:
Genetics
Lifestyle choices (e.g., unhealthy diet, lack of exercise, tobacco use)
Environmental factors
Other ways to categorize diseases:
Genetic Diseases: Are caused by abnormalities in genes or chromosomes.
Examples: Cystic fibrosis, Down syndrome, sickle cell anemia.
Autoimmune Diseases: Occur when the immune system mistakenly attacks the body's own tissues.
Examples: Rheumatoid arthritis, lupus, multiple sclerosis.
Mental Disorders: Affect mood, thinking, and behavior.
Examples: Depression, anxiety disorders, schizophrenia.
Deficiency Diseases: Caused by a lack of essential nutrients.
Examples: Scurvy (vitamin C deficiency), anemia (iron deficiency).
Common Human Infection
Viral Infections
Influenza (the flu): Caused by influenza viruses.
Symptoms: Fever, chills, cough, sore throat, muscle aches, fatigue.
Transmission: Airborne droplets, direct contact.
Prevention: Annual flu vaccination, good hygiene.
HIV/AIDS: Caused by the human immunodeficiency virus (HIV).
Attacks the immune system, leading to acquired immunodeficiency syndrome (AIDS).
Transmission: Through bodily fluids (blood, semen, vaginal fluids, breast milk).
Prevention: Safe sex practices, avoiding sharing needles, antiretroviral therapy (ART).
Bacterial Infections
Salmonellosis (Salmonella): Caused by Salmonella bacteria.
Symptoms: Diarrhea, fever, abdominal cramps.
Transmission: Contaminated food or water.
Prevention: Proper food handling and cooking, good hygiene.
Sexually transmitted infections such as:
Chlamydia
Gonorrhea
Syphilis
Fungal Infections
Athlete's foot: Caused by various fungi (dermatophytes).
Symptoms: Itching, scaling, cracking of the skin on the feet.
Transmission: Contact with contaminated surfaces (e.g., floors, shoes).
Prevention: Keeping feet clean and dry, wearing appropriate footwear.
Parasitic Infections (Protist)
Malaria: Caused by Plasmodium parasites.
Symptoms: Fever, chills, sweating, headache, muscle aches.
Transmission: Mosquito bites.
Prevention: Mosquito nets, insect repellent, antimalarial medications.
Plant Diseases
Tobacco Mosaic Virus (TMV) (Viral)
Cause: TMV is a single-stranded RNA virus that infects a wide range of plants, particularly tobacco and other members of the Solanaceae family (tomatoes, peppers, etc.).
Symptoms: Characterized by a distinctive "mosaic" pattern of light and dark green areas on leaves.
Other symptoms include leaf distortion, curling, and stunted growth.
Infected plants may also exhibit yellowing and reduced fruit production.
Transmission: Spread through mechanical transmission, such as by contaminated tools or hands.
It can also persist in plant debris and soil.
Impact: TMV can significantly reduce crop yields and quality.
Ash Dieback (Fungal)
Cause: Caused by the ascomycete fungus Hymenoscyphus fraxineus.
Symptoms: Leaf lesions, dieback of twigs and branches, and eventual death of the tree.
Diamond-shaped lesions may appear on the bark.
The crown of the tree thins, and shoots may develop from the trunk.
Transmission: Spores are spread by wind.
It also spreads through the movement of infected plant material.
Impact: Ash dieback has caused widespread devastation of ash tree populations across Europe.
Crown Gall Disease (Bacterial)
Cause: Caused by the bacterium Agrobacterium tumefaciens.
Symptoms: Characterized by the formation of tumor-like growths (galls) on the roots, crown, and stems of plants.
These galls disrupt the plant's vascular system, hindering water and nutrient uptake.
Transmission: The bacterium enters plants through wounds.
It can persist in soil and be spread through contaminated tools and water.
Impact: Crown gall can weaken and kill plants, particularly fruit trees and ornamental plants.
B2.2 How do organisms protect themselves against pathogens?
Non-specific (Innate) Defence Systems of the Human Body against Pathogens
These defenses are present from birth and do not require prior exposure to a specific pathogen. They act as the body's first line of defense.
Physical Barriers
Skin: The skin is the body's largest organ and acts as a physical barrier, preventing most pathogens from entering.
Its outer layer, the epidermis, is tough and contains keratin, a protein that makes it difficult for pathogens to penetrate.
Skin also produces oils and sweat, which contain antimicrobial substances.
Mucous Membranes: These line the respiratory, digestive, and urogenital tracts.
They secrete mucus, a sticky substance that traps pathogens.
In the respiratory tract, cilia (tiny hair-like projections) sweep mucus and trapped pathogens out of the body.
Chemical Barriers
Enzymes: Lysozyme, found in tears, saliva, and sweat, breaks down the cell walls of certain bacteria.
Stomach acid: The highly acidic environment of the stomach kills most ingested pathogens.
Body fluids: sebum, produced by skin glands, contains chemicals that inhibit bacterial growth.
Antimicrobial proteins
Interferons: these proteins are produced by cells that have been infected by viruses. They signal to other cells to increase their viral defenses.
Complement system: This is a system of proteins that enhance the ability of antibodies and phagocytic cells to clear microbes and damaged cells, promote inflammation, and attack the pathogen's plasma membrane.
Microbial Barriers
Normal Flora (Microbiota): The body hosts a vast community of beneficial microorganisms, particularly in the gut and on the skin.
These normal flora compete with pathogens for resources and space, preventing them from establishing infections.
They also contribute to the bodies defenses by producing substances that are harmful to pathogenic bacteria.
Platelets
known as thrombocytes, are tiny, irregularly shaped cell fragments circulating in the blood.
Plays a crucial role in hemostasis, the process that stops bleeding.
Adaptations of Platelets for Hemostasis
Small Size and Irregular Shape: Their small size allows them to easily navigate through blood vessels, reaching sites of injury quickly.
Their irregular shape, with numerous projections, increases their surface area, enhancing their ability to adhere to damaged vessel walls and interact with other platelets.
Lack of a Nucleus: Platelets are cell fragments, not complete cells, and therefore lack a nucleus.
This allows them to be small and efficient, carrying essential clotting factors without the overhead of cellular reproduction.
Presence of Granules: Platelets contain granules filled with various substances essential for clotting:
Clotting factors: These proteins initiate and propagate the coagulation cascade, leading to fibrin formation.
Growth factors: These stimulate vessel repair.
Chemical messengers (e.g., ADP, thromboxane A2): These attract more platelets to the site of injury and promote platelet aggregation (clumping).
Surface Receptors: Platelets possess specific surface receptors that enable them to:
Adhere to collagen, a protein exposed when blood vessel walls are damaged.
Bind to fibrinogen, a protein that forms the meshwork of a blood clot.
Bind to other platelets.
Ability to Change Shape: When activated, platelets undergo a dramatic shape change, extending numerous pseudopodia (temporary projections).
This shape change increases their surface area and facilitates their aggregation, forming a platelet plug.
Membrane Phospholipids: The platelet membrane contains phospholipids that play a vital role in the coagulation cascade.
These phospholipids act as a surface where clotting factors can bind and react, accelerating clot formation.
Plant Defence Systems
Leaf Cuticle: The leaf cuticle is a waxy, water-repellent layer that covers the epidermal cells of leaves, stems, and fruits.
Function: It acts as a barrier, preventing water loss, which is essential for plant survival.
Prevents the entry of many pathogens, such as fungi and bacteria, by creating a hydrophobic surface that they struggle to penetrate.
It can also provide some level of protection against herbivore attack, making the leaf surface less palatable or accessible.
The plant’s first line of defense against the outside world.
Cell Wall: Plant cells are surrounded by a rigid cell wall, primarily composed of cellulose.
Function: Provides structural support to the plant, maintaining cell shape and preventing excessive water uptake.
Acts as a significant physical barrier against pathogen invasion.
When a plant is under attack, the cell wall can be reinforced with additional materials like lignin, making it even more difficult for pathogens to penetrate.
The cell wall is also involved in signaling pathways that activate other plant defenses.
A strong rigid barrier that many pathogens have difficulty breaching.
The Human Immune System
A complex network of cells, tissues, and organs that work together to defend the body against harmful invaders, known as pathogens (bacteria, viruses, fungi, and parasites).
Key Functions
Recognition: The immune system's primary task is to distinguish between "self" (the body's own cells) and "non-self" (foreign invaders).
It does this by recognizing specific molecules called antigens on the surface of pathogens.
Defense: Once a pathogen is identified, the immune system launches an attack to neutralize and eliminate it. This involves a variety of mechanisms, including:
Producing antibodies that bind to antigens, marking pathogens for destruction.
Activating specialized cells that directly kill infected cells.
Releasing chemical signals that coordinate the immune response.
Memory: A remarkable feature of the immune system is its ability to "remember" past encounters with pathogens.
This immunological memory allows for a faster and more effective response upon subsequent exposure to the same pathogen, providing long-term immunity.
The basis of how vaccines work.
Homeostasis: The immune system also plays a role in maintaining homeostasis by removing damaged or dead cells from the body.
It also can work to destroy cancerous cells.
Components and Processes:
Innate Immunity: This is the body's first line of defense, providing rapid, non-specific protection against a wide range of pathogens.
It includes physical barriers (skin, mucous membranes), chemical barriers (enzymes, acids), and specialized cells (phagocytes, natural killer cells).
Adaptive Immunity: This is a more specific and targeted response that develops after exposure to a particular pathogen.
It involves specialized cells called lymphocytes (B cells and T cells), which produce antibodies and mount cell-mediated immune responses.
White Blood Cells
(or leukocytes) are essential components of the immune system, playing a crucial role in defending the body against pathogens and other threats.
General Adaptations
Mobility: Unlike red blood cells, white blood cells can move out of blood vessels and into tissues, allowing them to reach sites of infection or inflammation.
They achieve this through a process called diapedesis or extravasation, where they squeeze through the capillary walls.
Chemotaxis: White blood cells are attracted to chemical signals released by damaged tissues or pathogens.
This chemotaxis allows them to migrate towards the source of infection or injury.
Phagocytosis: Many white blood cells, particularly neutrophils and macrophages, are capable of phagocytosis, the process of engulfing and destroying pathogens or cellular debris.
Specific White Blood Cell Types and Adaptations
Neutrophils
Function: They are the most abundant type of white blood cell and are the first responders to bacterial infections.
They are highly phagocytic, engulfing and destroying bacteria.
Adaptations: They have a multi-lobed nucleus, which allows them to squeeze through narrow capillary walls.
They contain granules filled with enzymes and antimicrobial substances that kill pathogens.
Macrophages
Function: They are large phagocytic cells that engulf pathogens, cellular debris, and dead cells.
They also play a role in presenting antigens to T cells, initiating the adaptive immune response.
Adaptations: They are highly mobile and can migrate throughout the body's tissues.
They have a large number of lysosomes, which contain enzymes for digesting engulfed material.
Lymphocytes (B cells and T cells)
B cells
Function: They produce antibodies, proteins that bind to specific antigens on pathogens, neutralizing them or marking them for destruction.
Adaptations: They have surface receptors that allow them to recognize specific antigens.
They can differentiate into plasma cells, which are specialized for antibody production.
T cells
Function: They play a crucial role in cell-mediated immunity, directly killing infected cells or releasing cytokines that regulate the immune response.
Adaptations: They have T cell receptors that recognize specific antigens presented by infected cells.
Cytotoxic T cells directly kill infected cells. Helper T cells release cytokines that activate other immune cells.
Eosinophils
Function: They defend against parasitic infections and play a role in allergic reactions.
Adaptations: They contain granules filled with enzymes that are effective against parasites.
Basophils
Function: They release histamine and other inflammatory mediators, contributing to allergic reactions and inflammation.
Adaptations: They contain granules filled with histamine and other chemicals.
Chemical Plant Defense Responses
Chemical defenses are particularly crucial for protecting plants against a wide array of threats, including pathogens and herbivores.
Antimicrobial Substances
Plants produce a diverse range of antimicrobial compounds to combat pathogens like bacteria and fungi. These substances can:
Inhibit pathogen growth.
Disrupt pathogen cell membranes.
Interfere with pathogen metabolism.
Examples
Phytoalexins: These are antimicrobial compounds synthesized de novo (newly) in response to pathogen attack. They are a broad group of low molecular weight antimicrobial compounds.
Pathogenesis-related (PR) proteins: These proteins have various antimicrobial activities, including chitinases (which break down fungal cell walls) and glucanases.
Terpenoids: These are a large and diverse group of organic compounds that often have antimicrobial properties.
Phenolic compounds: These include tannins and salicylic acid, which can act as antioxidants and antimicrobial agents.
Alkaloids: These are nitrogen-containing compounds that can be toxic to pathogens and herbivores.
Other Chemical Defense Mechanisms
Defense Signaling: Plants use signaling molecules like salicylic acid, jasmonic acid, and ethylene to coordinate defense responses.
These signals can trigger the production of antimicrobial compounds and activate systemic acquired resistance (SAR), a long-lasting defense response throughout the plant.
Herbivore Deterrents: Plants produce a variety of chemicals to deter herbivores, including:
Toxins: These can cause illness or death in herbivores.
Repellents: These can make plants taste or smell unpalatable.
Volatile Organic Compounds (VOCs): Plants release VOCs that can:
Attract natural enemies of herbivores.
Warn neighboring plants of impending attack.
Directly inhibit pathogen growth.
Key Concepts
Systemic Acquired Resistance (SAR): This is a "whole-plant" resistance response that occurs after an initial localized infection.
It provides long-lasting protection against a broad range of pathogens.
Induced Systemic Resistance (ISR): This is a similar defense response triggered by beneficial microbes, rather than pathogens.
Chemical Priming: This is where plants, after being exposed to certain chemical signals, have a heightened defense response when later being attacked by pathogens.
B2.3 How can we prevent the spread of infections?
The spread of communicable diseases poses significant challenges to human, animal, and plant health. Effective prevention strategies are crucial to minimize their impact.
To reduce or prevent the spread of these diseases
Hygiene and Sanitation: This is fundamental in preventing the spread of many diseases.
Proper handwashing, disinfection of surfaces, and maintaining clean environments are essential.
Isolation and Quarantine: Separating infected individuals (or organisms) from healthy ones can prevent further transmission.
Vaccination: Vaccines stimulate the immune system to develop resistance to specific pathogens, providing crucial protection.
Vector Control: Many diseases are transmitted by vectors (e.g., mosquitoes, ticks). Controlling these vectors can significantly reduce disease spread.
Biosecurity: This involves implementing measures to prevent the introduction and spread of pathogens.
Vaccines
are a cornerstone of modern public health, playing a crucial role in preventing infectious diseases.
Function
Stimulating the Immune System: Vaccines introduce a safe form of a pathogen (a disease-causing organism) to the body. This "safe form" can be:
A weakened (attenuated) live virus.
An inactivated (killed) virus or bacteria.
A part of the pathogen (subunit vaccine).
a toxoid(a toxin made by the germ that has been inactivated.)
mRNA that codes for a part of the pathogen.
Creating Immunity: If the body encounters the actual pathogen in the future, the memory cells quickly mobilize, producing antibodies to neutralize the threat before it can cause illness.
This process creates immunity, which can be long-lasting or even lifelong for some diseases.
B2.4 How can we identify the cause of an infection?
Disease Detection and Identification (Lab and Field)
Plant Diseases
Field Observations
Visual Inspection: Observing symptoms like leaf spots, wilting, stunted growth, discoloration, or abnormal growths (galls).
Distribution Patterns: Noting if the disease is clustered, random, or following a specific pattern in the field.
Environmental Factors: Considering weather conditions, soil type, and other environmental factors that may contribute to disease development.
Laboratory Techniques
Microscopy: Examining plant tissue under a light microscope to identify fungal spores, bacterial cells, or other pathogens.
Culturing: Growing the pathogen on a nutrient medium to isolate and identify it. This is frequently used for bacterial and fungal pathogens.
PCR (Polymerase Chain Reaction): Detecting specific DNA sequences of pathogens, allowing for highly sensitive and accurate identification. This is very useful for identifying viral and bacterial pathogens.
ELISA (Enzyme-Linked Immunosorbent Assay): Using antibodies to detect specific pathogen proteins, providing a rapid and specific identification.
Serological Tests: Similar to ELISA, these tests use antibodies to identify pathogens based on their reactions.
Molecular Analysis: Sequencing of DNA or RNA to identify the pathogen.
Human Diseases
Field/Clinical Observations
Symptom Assessment: Evaluating patient symptoms to narrow down potential causes.
Physical Examination: Directly observing signs of illness.
Patient history: Gathering information about the patients previous health, and possible exposures.
Laboratory Techniques
Microscopy: Examining blood, urine, or tissue samples to identify bacteria, fungi, parasites, or abnormal cells.
Culturing: Growing microorganisms from patient samples to identify the causative agent.
PCR: Detecting specific DNA or RNA sequences of pathogens.
ELISA: Detecting antibodies or antigens related to specific diseases.
Blood Tests: Measuring levels of various components in the blood to identify infections or other abnormalities.
Imaging (X-rays, CT scans, MRIs): Visualizing internal structures to detect abnormalities caused by diseases.
Using a Light Microscope to Observe Microorganisms
Preparation
Prepare a wet mount or a stained slide of the sample containing the microorganisms.
Wet mounts are used for observing live microorganisms, while stained slides are used for fixed specimens.
Setting Up the Microscope: Place the slide on the microscope stage and secure it with the stage clips.
Start with the lowest magnification objective lens (e.g., 4x or 10x).
Turn on the light source.
Focusing: Use the coarse adjustment knob to bring the objective lens close to the slide.
Looking through the eyepiece, slowly turn the coarse adjustment knob in the opposite direction to bring the specimen into rough focus.
Use the fine adjustment knob for precise focusing.
Increasing Magnification: Once the specimen is in focus, you can switch to a higher magnification objective lens (e.g., 40x or 100x).
Use only the fine adjustment knob when using higher magnification lenses.
When using the 100x objective lens, immersion oil must be used.
Observation: Observe the microorganisms, noting their size, shape, and movement (if alive).
Adjust the light intensity using the diaphragm or condenser to improve visibility.
Recording Observations: Draw or photograph the microorganisms and record your observations.
Note the total magnification, which is the objective lens magnification multiplied by the eyepiece magnification.
Aseptic Techniques
a set of practices used in microbiology and other laboratory settings to prevent contamination of cultures with unwanted microorganisms that is crucial for obtaining accurate and reliable results.
Core Principles
Sterilization: Involves completely eliminating all living microorganisms, including bacteria, fungi, viruses, and spores, from equipment, media, and work surfaces. Common sterilization methods are:
Autoclaving: Using high-pressure steam to kill microorganisms.
Dry heat sterilization: Using a oven to apply very high temperatures.
Filtration: Using membrane filters to physically remove microorganisms from liquids.
Flaming/Incineration: Using a flame to destroy microorganisms on loops and needles.
Disinfection: Reduces the number of viable microorganisms but doesn't necessarily eliminate all of them, especially spores. Common disinfectants are:
Alcohol (e.g., 70% ethanol)
Bleach solutions
Other chemical disinfectants
Preventing Airborne Contamination: Microorganisms are present in the air, so it's essential to minimize their entry into cultures. Techniques include:
Working near a Bunsen burner flame, which creates an upward flow of hot air, preventing airborne particles from settling.
Limiting air currents by closing windows and doors.
Working in laminar flow hoods, which provide a sterile airflow.
Limiting the amount of time that sterile items are exposed to the open air.
Specific Techniques
Handwashing: Thorough handwashing with antimicrobial soap is the first line of defense against contamination.
Sterile Work Area: Disinfecting work surfaces with appropriate disinfectants before and after culturing.
Sterile Equipment: Using sterilized pipettes, loops, needles, and other instruments.
Flaming Loops and Needles: Passing inoculating loops and needles through a Bunsen burner flame until they glow red to sterilize them.
Flaming Tube Necks: Briefly passing the necks of test tubes and flasks through a flame after opening and before closing them to create a sterile environment.
Proper Handling of Culture Plates: Minimizing the time culture plates are open to the air and keeping them partially covered.
Inverting plates during incubation to prevent condensation from dripping onto the culture.
Using Sterile Media: Ensuring that all culture media is properly sterilized before use.
Importance
Obtaining pure cultures.
Preventing contamination in experiments.
Ensuring the accuracy of results.
Limiting the risk of spreading harmful microorganisms.
Calculate Cross-Sectional Areas of Bacterial Cultures
Formula
π (pi) is a mathematical constant approximately equal to 3.14159.
r is the radius of the circular area.
r2 means the radius squared (radius multiplied by itself).
The formula πr 2 gives you the area of a circle.
Calculating the Cross-Sectional Area of a Bacterial Culture (Assuming a Circular Growth Pattern): Sometimes, bacterial growth on an agar plate can appear as a relatively circular colony.
Measurements: Use a ruler or calipers to measure the diameter of the bacterial growth.
Divide the diameter by 2 to get the radius (r).
Calculation: Plug the radius value into the formula: Area = πr 2 .
Calculate the area.
Example: If the diameter of a bacterial colony is 4 cm, the radius is 2 cm.
Area = π(2 cm) 2 =π(4 cm 2 )≈12.57 cm 2 .
Calculating the Area of Clear Zones (Zones of Inhibition) Around Antibiotic
Discs: When an antibiotic disc is placed on an agar plate with bacterial growth, a clear zone (zone of inhibition) may appear around the disc, indicating that the antibiotic has inhibited bacterial growth.
Measurements: Measure the diameter of the clear zone, including the antibiotic disc.
Divide the diameter by 2 to obtain the radius.
Calculation: Plug the radius value into the formula: Area = πr 2.
Calculate the area.
Example: If the diameter of a clear zone is 3 cm, the radius is 1.5 cm.
Area = π(1.5 cm) 2 =π(2.25 cm 2 )≈7.07 cm 2.
Monoclonal Antibodies
are highly specific antibodies that are identical because they are produced by a single clone of cells. Their production involves a sophisticated process, primarily using hybridoma technology.
Steps of Production
Antigen Injection into an Animal: The process begins by injecting a specific antigen (the substance that triggers an immune response) into an animal, typically a mouse.
This stimulates the animal's immune system to produce antibodies against that particular antigen.
The animal's B-lymphocytes (a type of white blood cell) begin to produce a mixture of antibodies, known as polyclonal antibodies, which recognize different epitopes (binding sites) on the antigen.
Antibody-Producing Cells Taken from Animal: Once the animal's immune system has produced a sufficient amount of antibodies, antibody-producing cells, specifically B-lymphocytes, are collected from the animal's spleen.
These B-lymphocytes are responsible for producing the desired antibodies.
Cells Producing the Correct Antibody Selected Then Cultured:
Hybridoma Formation: The collected B-lymphocytes are then fused with myeloma cells (cancerous cells that can divide indefinitely) to create hybridoma cells.
This fusion is typically achieved using polyethylene glycol (PEG).
The resulting hybridoma cells possess the antibody-producing capability of the B-lymphocytes and the immortality of the myeloma cells.
Selection: The hybridoma cells are then cultured in a selective medium, such as HAT (hypoxanthine-aminopterin-thymidine) medium.
This medium allows only the hybridoma cells to survive, while unfused B-lymphocytes and myeloma cells die.
The surviving hybridoma cells are then screened to identify those that produce the desired antibody.
Cloning and Culture: The hybridoma cells that produce the correct antibody are then cloned, meaning that individual cells are isolated and allowed to multiply.
This ensures that all the resulting cells produce identical monoclonal antibodies.
These cloned hybridoma cells are then cultured in large quantities to produce a substantial amount of the desired monoclonal antibodies.
Antibody Purification: Finally, the monoclonal antibodies are purified from the culture medium to obtain a pure antibody product.
B2.5 How can lifestyle, genes and the environment affect health?
Interaction of Genetic and Lifestyle Factors in Non-Communicable Diseases
Non-communicable diseases (NCDs) are a significant global health burden.
They're often complex, resulting from the interaction of genetic predisposition and lifestyle choices.
Genetic Factors
Genes can increase susceptibility to certain diseases.
For example, specific gene variants can increase the risk of developing familial hypercholesterolemia (high cholesterol), a major risk factor for cardiovascular disease.
Some genes influence how the body metabolizes nutrients, affecting the risk of type 2 diabetes.
Genes can also affect the body's ability to repair DNA damage, influencing cancer risk.
However, genes alone do not always determine disease outcome. Many people with high-risk genes never develop the disease, while others with low-risk genes do.
Lifestyle Factors
Diet: A diet high in saturated and trans fats, salt, and processed foods increases the risk of cardiovascular disease, type 2 diabetes, and some cancers. Conversely, a diet rich in fruits, vegetables, and whole grains can be protective.
Physical Activity: Lack of exercise increases the risk of obesity, cardiovascular disease, type 2 diabetes, and some cancers. Regular physical activity can reduce these risks.
Tobacco Use: Smoking is a major risk factor for cardiovascular disease, lung cancer, and other respiratory diseases.
Alcohol Consumption: Excessive alcohol intake can lead to liver disease, cardiovascular disease, and some cancers.
Stress: Chronic stress can contribute to cardiovascular disease and other health problems.
Environmental Factors: Exposure to pollutants and toxins can increase the risk of cancer and respiratory diseases.
Interaction: Lifestyle factors can modify the expression of genes.
For example, a person with a genetic predisposition to type 2 diabetes may avoid developing the disease by maintaining a healthy weight and exercising regularly.
Conversely, unhealthy lifestyle choices can exacerbate the effects of high-risk genes. A person with a genetic predisposition to cardiovascular disease who smokes and eats a high-fat diet has a significantly increased risk.
Examples
Cardiovascular Diseases: Genetic predisposition to high cholesterol combined with a high-fat diet and sedentary lifestyle significantly increases the risk of heart disease.
Type 2 Diabetes: Genetic factors influencing insulin sensitivity coupled with obesity and a sedentary lifestyle greatly increases the risk.
Cancer: Genetic mutations that affect DNA repair combined with exposure to carcinogens (e.g., tobacco smoke, UV radiation) increases cancer risk.
Liver Diseases: Genetic conditions that affect liver function combined with excessive alcohol consumption greatly increases the risk of liver damage.
Lung diseases: Genetic conditions that effect lung function, combined with smoking, or exposure to air pollution, greatly increase the risk of lung disease.
Practical Investigation of Exercise on Pulse Rate and Recovery Rate
An example of practical experiment to investigate how exercise affects pulse rate and recovery rate.
Materials
Stopwatch or timer
A method to record pulse rate (e.g., manual palpation of radial or carotid artery, fitness tracker)
A way to record data (paper and pen or a spreadsheet)
A safe space for exercise
Procedure
Baseline Measurement: Have the subject sit or lie down quietly for 5 minutes.
Measure and record their resting pulse rate (beats per minute).
Exercise: Choose a simple exercise, such as jumping jacks, running in place, or step-ups.
Perform the exercise for a set duration (e.g., 2 minutes).
Immediate Post-Exercise Measurement: Immediately after the exercise, measure and record the subject's pulse rate.
Recovery Measurements: Measure and record the subject's pulse rate every minute for 5 minutes (or until their pulse returns to near-resting levels).
Data Analysis: Calculate the change in pulse rate from resting to post-exercise.
Calculate the recovery rate (the time it takes for the pulse to return to near-resting levels).
Graph the pulse rate over time to visualize the recovery process.
Repeat: Repeat the experiment with different exercise intensities or durations to see how they affect pulse rate and recovery rate.
Repeat the experiment on multiple subjects to gather more data.
Variables
Independent Variable: Exercise intensity or duration.
Dependent Variable: Pulse rate and recovery rate.
Controlled Variables: The type of exercise, the environment, and the method of measuring pulse rate.
Expected Results: Pulse rate will increase significantly during exercise.
Recovery rate will vary depending on the intensity and duration of exercise and the individual's fitness level.
Fitter individuals will generally have a faster recovery rate.
Safety Considerations: Ensure the exercise is appropriate for the subject's fitness level.
Monitor the subject for any signs of discomfort or distress.
If the subject has any underlying health conditions, consult with a healthcare professional before conducting the experiment.
Incidence of non-communicable diseases at local, national and global levels
Global Level
Dominant Impact: NCDs are the leading cause of death worldwide, accounting for a significant majority of deaths. The World Health Organization (WHO) highlights that cardiovascular diseases, cancers, chronic respiratory diseases, and diabetes are the primary NCDs.
Key lifestyle factors driving this global burden
Unhealthy Diets: Increased consumption of processed foods, high salt, sugar, and unhealthy fats.
Physical Inactivity: Sedentary lifestyles due to urbanization and changes in work patterns.
Tobacco Use: A major risk factor for various cancers, cardiovascular, and respiratory diseases.
Harmful Use of Alcohol: Contributing to liver diseases, cardiovascular diseases, and some cancers.
Disparities: Low- and middle-income countries bear a disproportionate burden of NCDs, with a higher percentage of premature deaths. This is often due to limited access to healthcare, increased exposure to risk factors, and weaker public health systems.
National Level
Variations: NCD incidence varies significantly between countries, influenced by cultural, economic, and policy factors.
For example, countries with high rates of tobacco use will see higher rates of lung cancer and respiratory diseases.
National dietary habits, such as high consumption of processed foods or red meat, will impact cardiovascular disease and cancer rates.
National healthcare systems, and the availability of preventative care, and treatments, greatly effect the outcomes of NCD's.
Policy Impact: National policies play a crucial role in mitigating NCDs. Examples are:
Tobacco control measures (taxes, advertising bans)
Food labeling and regulations to promote healthy diets
Public health campaigns to encourage physical activity
Alcohol control policies
Local Level
Community Factors
Local environments and community factors significantly influence individual lifestyle choices.
Access to healthy food options, safe spaces for physical activity, and exposure to environmental pollutants vary greatly between communities.
Socioeconomic disparities within cities or regions can lead to unequal exposure to risk factors.
Local cultural norms, and social behaviors will greatly influence the populations lifestyle choices.
Targeted Interventions: Local interventions can be highly effective in addressing specific NCD risk factors. Examples are:
Community-based exercise programs.
Nutrition education initiatives in schools and workplaces.
Local policies to create smoke-free environments.
Key Lifestyle Factors and Their Impact
Exercise: Regular physical activity reduces the risk of cardiovascular diseases, type 2 diabetes, and some cancers.
Lack of exercise contributes to obesity, a major risk factor for many NCDs.
Diet: Unhealthy diets high in processed foods, saturated fats, and sugar increase the risk of cardiovascular diseases, type 2 diabetes, and some cancers.
Healthy diets rich in fruits, vegetables, and whole grains are protective.
Alcohol: Excessive alcohol consumption contributes to liver diseases, cardiovascular diseases, and some cancers.
Smoking: Smoking is a major risk factor for lung cancer, cardiovascular diseases, and respiratory diseases.
Data related to the causes, spread, effects and treatment of disease
Translating Information Between Graphical and Numerical Forms
Numerical to Graphical: Imagine you have a table showing the number of new COVID-19 cases reported each day for a week. You can translate this into a line graph to visualize the trend over time, or a bar chart to compare daily case numbers.
Or, you may have the percentage of people with a disease who respond to a specific treatment. That numerical data can be shown as a pie chart, showing the percentage of responders and non-responders.
Graphical to Numerical: If you have a bar chart showing the prevalence of different types of cancer in a population, you can extract the numerical values (e.g., the exact number or percentage for each cancer type) from the bar heights.
From a line graph showing the change in blood glucose levels after insulin injection, you can read the numerical values of glucose at specific time points.
Example: a pie chart depicts the percentage of people with different blood types. You can extract the percentage of each blood type, and if you know the total population number, calculate the number of people with each blood type.
Constructing and Interpreting Frequency Tables and Diagrams, Bar Charts, and Histograms
Frequency Tables: These tables organize data by showing how often each value or range of values occurs. For example, a frequency table could show the number of patients with different blood pressure ranges.
Bar Charts: Bar charts are used to compare categorical data. For example, you could use a bar chart to show the number of cases of different infectious diseases in a region.
Histograms: Histograms are used to display the distribution of continuous data. For example, a histogram could show the distribution of patient ages in a clinical trial.
Interpretation
Look for trends, patterns, and outliers in the data.
Identify the most frequent values (mode) or the average value (mean).
Assess the spread of the data (range, standard deviation).
Understanding the Principles of Sampling as Applied to Scientific Data
Sampling: In disease studies, it's often impossible to collect data from the entire population. Therefore, researchers use sampling to select a representative subset.
Principles
Random Sampling: Every individual in the population has an equal chance of being selected, minimizing bias.
Stratified Sampling: The population is divided into subgroups (strata), and samples are taken from each stratum, ensuring representation of all groups.
Sample Size: A larger sample size generally leads to more accurate and reliable results.
Representative Sample: The sample should accurately reflect the characteristics of the population being studied.
Bias: Understanding and mitigating potential sources of bias is critical in ensuring the validity of study findings.
Using a Scatter Diagram to Identify a Correlation Between Two Variables
Scatter Diagrams: Display the relationship between two continuous variables.
For example, you could use a scatter diagram to explore the relationship between smoking and lung cancer incidence.
Correlation
Positive Correlation: As one variable increases, the other also tends to increase (points slope upwards).
Negative Correlation: As one variable increases, the other tends to decrease (points slope downwards).
No Correlation: There is no apparent relationship between the variables (points are scattered randomly).
Correlation Strength: The closer the points are to a straight line, the stronger the correlation.
Causation vs. Correlation: It's crucial to remember that correlation does not imply causation. Just because two variables are correlated doesn't mean one causes the other.
Interactions between Different Types of Disease
Comorbidity: Refers to the presence of two or more chronic diseases or conditions in a patient.
Examples
Diabetes and cardiovascular disease: Diabetes increases the risk of heart disease and stroke.
HIV/AIDS and tuberculosis: HIV weakens the immune system, making individuals more susceptible to tuberculosis.
Mental health disorders and chronic pain: These conditions often coexist and can exacerbate each other.
Impact: Comorbidity can complicate diagnosis, treatment, and management of individual diseases. It can also increase healthcare costs and reduce quality of life.
Increased Susceptibility: One disease can weaken the immune system, making an individual more vulnerable to other infections.
Examples
Influenza and bacterial pneumonia: A viral influenza infection can damage the respiratory system, creating an opportunity for bacterial pneumonia to develop.
Cancer and opportunistic infections: Cancer treatments, such as chemotherapy, can suppress the immune system, increasing the risk of opportunistic infections.
Malnutrition, and infectious diseases: Malnutrition weakens the immune system, making individuals more susceptible to infectious diseases like malaria, or diarrheal diseases.
Disease Interactions Through Shared Risk Factors: Certain lifestyle factors or environmental exposures can increase the risk of multiple diseases.
Examples
Smoking: Increases the risk of lung cancer, cardiovascular disease, and chronic obstructive pulmonary disease (COPD).
Obesity: Increases the risk of type 2 diabetes, cardiovascular disease, and some cancers.
Poor sanitation: Increases the risk of multiple infectious diseases.
Impact: Addressing shared risk factors can have a broad impact on preventing multiple diseases.
Disease Interactions Through Treatment: Treatments for one disease can increase the risk of developing another.
Examples
Long-term use of corticosteroids: Can increase the risk of osteoporosis and diabetes.
Certain cancer treatments: Can increase the risk of heart disease or secondary cancers.
Antibiotic overuse: Can lead to the rise of antibiotic resistant bacteria, which can cause other difficult to treat infections.
Synergistic Effects: In some cases, the combined effect of two diseases can be greater than the sum of their individual effects.
Examples
HIV and hepatitis C: The combination can accelerate liver damage.
COPD and sleep apnea: each condition on its own effects the bodies ability to take in oxygen, the combination of the two conditions can be very dangerous.
Disease Interactions through Inflammation: Chronic inflammation is now understood to be a major contributor to many diseases. Therefore, diseases that cause chronic inflammation can increase the risk of other diseases that are also related to chronic inflammation.
Examples
Rheumatoid arthritis, and cardiovascular disease: Rheumatoid arthritis causes chronic inflammation, which increases the risk of cardiovascular disease.
Periodontal disease, and diabetes: Periodontal disease causes chronic inflammation, which can make it harder to control blood sugar in people with diabetes.
B2.6 How can we treat disease?
Use of Medicines
Medicines: play a crucial role in modern healthcare, and antibiotics are a very important subset of those medicines.
General Use of Medicines
Treatment of Symptoms: Many medicines focus on alleviating the symptoms of a disease, even if they don't cure the underlying cause.
For example, pain relievers like ibuprofen or acetaminophen reduce fever and pain.
Other medicines might reduce inflammation, or reduce nausea.
Treatment of Underlying Causes: Some medicines target the root cause of a disease.
For example, antiviral medications work to inhibit the reproduction of viruses.
Hormone replacement therapies replace hormones that the body is no longer producing adequetly.
Prevention of Disease: Vaccines are a prime example of medicines used for prevention.
They stimulate the immune system to develop antibodies against specific pathogens, providing immunity.
Other preventative medicine can include things like statins, which help to prevent cardiovascular disease.
Management of Chronic Conditions: Many medicines are used to manage chronic diseases, allowing individuals to live healthier lives.
Examples include insulin for diabetes, and medications for high blood pressure.
Antibiotics
Targeting Bacterial Infections: Antibiotics are specifically designed to combat bacterial infections.
They work by either killing bacteria (bactericidal) or inhibiting their growth (bacteriostatic).
They are effective against a wide range of bacterial infections, including:
Strep throat
Urinary tract infections
Pneumonia (some forms)
Skin infections
Treatments for Cardiovascular Disease
Cardiovascular disease (CVD): a broad term encompassing various conditions affecting the heart and blood vessels.
Effective management often requires a multifaceted approach, combining lifestyle adjustments, medications, and, in some cases, surgical interventions.
Lifestyle Changes
Dietary Modifications: Emphasis on a heart-healthy diet: Rich in fruits, vegetables, whole grains, lean proteins, and low in saturated and trans fats, cholesterol, and sodium.
Benefits: Can lower cholesterol, blood pressure, and weight, reducing CVD risk.
Evaluation: Highly effective for prevention and management, with minimal side effects. Requires long-term commitment.
Regular Physical Activity: Aim for at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic exercise per week.
Benefits: Improves cardiovascular fitness, lowers blood pressure, and helps maintain a healthy weight.
Evaluation: Crucial for overall heart health. Requires consistent effort.
Smoking Cessation: Quitting smoking is one of the most significant steps to improve heart health.
Benefits: Reduces the risk of heart attack, stroke, and other CVD complications.
Evaluation: Essential for all smokers with or at risk of CVD.
Weight Management: Maintaining a healthy weight reduces strain on the heart.
Benefits: lowers blood pressure, cholesterol, and diabetes risk.
Evaluation: very effective, and can be achieved through diet, and exercise.
Stress Management: Chronic stress contributes to CVD risk. Techniques like yoga, meditation, and deep breathing can help.
Benefits: Lowers blood pressure and heart rate.
Evaluation: a great supporting method for overall health.
Limiting Alcohol consumption: Excessive alcohol consumption can increase blood pressure, and contribute to heart failure.
Benefits: lowers blood pressure, and risk of heart failure.
Evaluation: very effective for those who consume excessive alcohol.
Medicines
Statins: Lower cholesterol levels.
Benefits: Reduce the risk of heart attack and stroke.
Evaluation: Highly effective, but may have side effects like muscle aches.
Blood Pressure Medications: Include ACE inhibitors, beta-blockers, and diuretics.
Benefits: Lower blood pressure, reducing the risk of stroke and heart failure.
Evaluation: Effective, but may have side effects like dizziness or fatigue.
Antiplatelet Drugs (e.g., Aspirin): Prevent blood clots.
Benefits: Reduce the risk of heart attack and stroke.
Evaluation: Effective, but increase the risk of bleeding.
Nitrates: These widen blood vessels.
Benefits: help to relieve chest pain.
Evaluation: very helpful for those with angina.
Surgery and Procedures
Angioplasty and Stenting: Opens blocked coronary arteries.
Benefits: Improves blood flow to the heart.
Evaluation: Effective for relieving angina and improving quality of life.
Coronary Artery Bypass Grafting (CABG): Bypasses blocked coronary arteries using grafts from other blood vessels.
Benefits: Improves blood flow and reduces angina.
Evaluation: Major surgery, but highly effective for severe coronary artery disease.
Pacemaker Implantation: Regulates heart rhythm.
Benefits: Treats arrhythmias.
Evaluation: very effective for those with heart rhythm problems.
Heart Valve Surgery: Repairs or replaces damaged heart valves.
Benefits: Improves heart function.
Evaluation: Major surgery, but necessary for severe valve disease.
Process of Discovery and Development of Potential New Medicines
I. Discovery Phase (Pre-Discovery)
Target Identification: Researchers identify a specific biological target (e.g., a protein, enzyme, or gene) believed to be involved in a disease.
This target should be "druggable," meaning it can be affected by a small molecule or biological agent.
Lead Discovery: Scientists screen libraries of chemical compounds or biological substances to find "lead compounds" that interact with the target.
High-throughput screening (HTS) allows for rapid testing of thousands of compounds.
Computational chemistry and bioinformatics play a crucial role in predicting and designing potential drug candidates.
Lead Optimization: The lead compound is modified to improve its potency, selectivity, and pharmacokinetic properties (absorption, distribution, metabolism, and excretion - ADME).
This involves iterative cycles of chemical synthesis and biological testing.
II. Preclinical Testing
In Vitro Studies: Testing is conducted in cells or tissues in a laboratory setting to assess the compound's activity and toxicity.
This helps to understand the mechanism of action and identify potential safety concerns.
In Vivo Studies (Animal Studies): The compound is tested in animal models to evaluate its efficacy and safety in a living organism.
These studies provide crucial information about pharmacokinetics, pharmacodynamics, and potential side effects.
Adherence to ethical guidelines and animal welfare is paramount.
Toxicity Studies: Extensive studies are conducted to assess the compound's potential toxicity, including acute, subchronic, and chronic toxicity.
These studies determine the highest dose that can be given without causing significant adverse effects.
Pharmacokinetics and Pharmacodynamics (PK/PD): PK studies determine how the drug is absorbed, distributed, metabolized, and eliminated by the body.
PD studies examine the drug's effects on the body.
III. Clinical Testing (Human Studies)
Phase 1: Small group of healthy volunteers (20-100) are given the drug to assess its safety, tolerability, and pharmacokinetics.
Researchers determine the maximum tolerated dose (MTD).
Phase 2: Larger group of patients (100-300) with the target disease are given the drug to evaluate its efficacy and identify optimal dosing.
This phase provides preliminary evidence of whether the drug works.
Phase 3: Large-scale, randomized, controlled trials (RCTs) involving thousands of patients are conducted to confirm efficacy and monitor for long-term safety.
These studies are designed to provide definitive evidence for regulatory approval.
These studies often compare the new medication to the current standard of care, or to a placebo.
Phase 4 (Post-Marketing Surveillance):
After the drug is approved and available to the public, ongoing monitoring is conducted to detect rare or long-term side effects.
This phase provides valuable information about the drug's safety and effectiveness in real-world settings.
This stage can also lead to the discovery of new uses for the medication.
IV. Regulatory Approval
Pharmaceutical companies submit a New Drug Application (NDA) or Biologics License Application (BLA) to regulatory agencies (e.g., FDA in the United States, EMA in Europe).
The application includes all preclinical and clinical data, manufacturing information, and labeling.
Regulatory agencies review the data and decide whether to approve the drug for marketing.
Monoclonal Antibodies as Cancer Treatment
Monoclonal antibodies (mAbs): represent a targeted approach to cancer treatment, leveraging the immune system's specificity to attack cancer cells.
I. Producing Monoclonal Antibodies Specific to a Cancer Cell Antigen
Antigen Identification: Cancer cells often display unique antigens (proteins or other molecules) on their surface that are not present or are present in much lower quantities on normal cells.
Researchers identify these cancer-specific antigens as targets for mAb therapy.
Immunization: An animal (typically a mouse) is injected with the cancer cell antigen.
The animal's immune system responds by producing antibodies specific to that antigen.
Hybridoma Production: Spleen cells from the immunized animal, which contain the antibody-producing B cells, are fused with myeloma cells (cancer cells that can divide indefinitely).
This fusion creates hybridoma cells, which can both produce the desired antibodies and divide continuously.
Selection and Cloning: Hybridoma cells are screened to identify those that produce the specific antibody targeting the cancer antigen.
These selected hybridoma cells are then cloned to create a pure population of cells, all producing the same (monoclonal) antibody.
Antibody Production: The hybridoma cells are cultured in large quantities to produce the desired monoclonal antibodies.
II. Injecting the Antibodies into the Blood
The produced mAbs are purified and formulated into a pharmaceutical preparation.
These mAbs are then administered to the patient, usually by intravenous injection.
III. The Antibodies Bind to Cancer Cells, Tagging Them for Attack by White Blood Cells
Targeted Binding: The injected mAbs circulate in the bloodstream and specifically bind to the cancer cell antigens.
Opsonization: By binding to the cancer cells, the mAbs act as "tags," marking the cancer cells for destruction by the patient's immune system.
Antibody-Dependent Cellular Cytotoxicity (ADCC): White blood cells, such as natural killer (NK) cells, have receptors that recognize the bound mAbs.
This triggers the white blood cells to attack and destroy the cancer cells.
Complement-Dependent Cytotoxicity (CDC): In some cases, the binding of mAbs to cancer cells can activate the complement system, a part of the immune system that leads to the lysis (rupturing) of the cancer cells.
IV. The Antibodies can also be Attached to a Radioactive or Toxic Substance to Deliver It to Cancer Cells
Conjugated Monoclonal Antibodies: mAbs can be chemically linked (conjugated) to radioactive isotopes (radioimmunotherapy) or cytotoxic drugs (antibody-drug conjugates, ADCs).
Targeted Delivery: The mAb acts as a delivery system, specifically targeting the radioactive or toxic substance to the cancer cells, minimizing damage to healthy tissues.
Radioimmunotherapy: Radioactive isotopes attached to the mAb emit radiation that kills the cancer cells.
Antibody-Drug Conjugates (ADCs): Cytotoxic drugs attached to the mAb are internalized by the cancer cells, leading to their death.
Advantages of Monoclonal Antibody Therapy
High Specificity: mAbs target cancer cells with high precision, minimizing damage to healthy tissues.
Reduced Side Effects: Compared to traditional chemotherapy, mAbs generally have fewer side effects.
Enhanced Immune Response: mAbs can stimulate the patient's own immune system to fight cancer.
Limitations
Target Antigen Availability: Effective mAbs require the identification of suitable cancer-specific antigens.
Resistance: Cancer cells can develop resistance to mAb therapy.
Cost: mAb therapy can be expensive.
"Humanizing" Antibodies: Mouse-produced antibodies can cause immune reactions in humans.
To combat this, the antibodies are often "Humanized" or are fully human, to reduce the immune response.