4: Environmental Influences

Virus

• Not a living cell (not a prokaryote or eukaryote)

• 1/1000 size of bacteria

• Some have carbohydrate-protein complexes called antigen spikes that are used to attach to host cell

  • Common cold and Coronaviruses have high mutation rate in antigens

  • Slightly different antigens look completely new to host immune system

• Vaccines used to prevent infection, but can’t be killed with antibiotics

• Ex: HIV, hepatitis, influenza, Covid, poliomyelitis, chicken pox, smallpox, herpes, measles, rabies, HPV, yellow fever, Zika, Ebola

Bacteria

• Prokaryotic cell (single-celled organism, no nucleus)

• Can be treated with antibiotics (breaks down cell wall)

• Ex: tuberculosis, bubonic plague, cholera, gonorrhea, E. coli, Lyme disease, tetanus, salmonella, leprosy, syphilis, pertussis (whooping cough)

Parasite

• Eukaryotic organism (eukaryotic cells have a nucleus and function together in a multicellular, eukaryotic organism)

• Fungi, amoeba, protozoa, insects

• Can be treated with antiparasitic drugs

• Ex: malaria, toxoplasmosis, pinworms, Chaga’s, yeast infection

Colonization by pathogenic microorganisms

We have a symbiotic relationship with several bacteria that do not cause infection (microbiota, “flora”)

Symptoms are the body’s overactive response to an unknown pathogen

• The immune system does not recognize the pathogen, so it launches a rapid, last-minute response

Each person’s immune system has been exposed to various pathogens throughout life

• Their symptoms may differ slightly because their immune system’s response differs

Pathology – study of disease development and effects on host

Etiology – study of the cause of a disease

Epidemiology – study of when and where diseases occur and how they are transmitted

Sporadic – occurs occasionally

Endemic – constantly present in population (ex: hepatitis)

Outbreak – sudden rise in infections

Epidemic – outbreak results in many people infected in short amount of time

Pandemic – worldwide epidemic

Acute – develops rapidly but only lasts a short amount of time

• Ex: common cold

Chronic – develops slowly, may have mild symptoms or signs, but is recurrent for a long time

• Ex: tuberculosis

Latent – agent remains inactive for long period of time, then activates to cause disease

• Ex: shingles (after chicken pox, virus lives in nerve tissue and activates later in life)

Sepsis – toxic inflammatory condition from spread of bacteria or toxins from infection site

Opportunistic pathogen – pathogen that does not normally cause infection now causes infection because the body’s environment is altered or the immune system is compromised

• Yeast infection – change in vaginal pH affects Lactobacillus bacteria that keep Candida albicans fungi from overgrowing

Anaphylactic shock – allergen circulates in blood, leading to body-wide inflammation, and decrease in blood pressure (shock)

Autoimmune – targets normal body cells

• Insulin-dependent diabetes mellitus (type 1) – attacks pancreatic cells

• Multiple sclerosis – attacks white matter of central nervous system

• Rheumatoid arthritis – attacks joints

• Graves disease – attacks thyroid

Blood contains erythrocytes, leukocytes, and other cells

• Transport oxygen, hormones, waste

Erythrocytes – red blood cells

• Antigens – protein markers on red blood cells; body recognizes its own cells (pathogens have different antigens)

Leukocytes – white blood cells

• Usually low in numbers, but increase during infection (inflammation)

• Antibodies – Y-shaped proteins that are excreted and attach to antigens on pathogens

Allergies – antibodies bind to the allergen

Lymphocytes – type of white blood cells created by the lymphatic system (lymph nodes, thymus, spleen, appendix, tonsils)

• Protection against pathogens and cancer cells

Bats are known to carry a heavy viral load

• When other animals experience extreme body temperature or heart rate increases, immune system usually responds 

• However, flying is stressful on the body, so bats’ immune system is less sensitive and doesn't react as easily to infections

Motion sickness?

• Conflicting information; body is stationary, but inner ear indicates movement

• Brain comes to conclusion that individual is hallucinating because of toxin – vomiting reflex

Fetal complications

• Are humans more prone to effects on fetus than other species?

• Placenta – passage of nutrients as well as toxins

Placenta connects to fetus through umbilical cord

Hemochorial placenta

• Maternal blood comes in direct contact with embryo (found in primates, rats, mice, rabbits, guinea pigs)

• Morning sickness and food preferences – immune system side effects

Placental barrier

• Placenta and fetus could be seen as pathogen, so the barrier prevents the immune system from invading

• Several layers of cells acting as a barrier; secretions and immune system repressor cells

• Certain drugs can cross the placental barrier and should not be taken during pregnancy

• Teratogen – agent that causes birth defects

Folate (vitamin B9) – broccoli, lentils, peas, nuts, fruits, leafy greens, chickpeas

• Need up to 10 times more folate during pregnancy

• Decreases birth defects

• Folate deficiency – birth defects

Teratogens

• Drugs, alcohol, tobacco, toxins

• Excess glucose in blood from diabetes

Medication used in 1950s (Europe, Australia, Japan, wasn’t approved in U.S.)

Anti-nausea, sleep aid, morning sickness

Effective treatment, but during pregnancy, can cause birth defects

• At the time, we did not realize that certain drugs could pass through the placental barrier

Chronic conditions can persist over a long period of time

Cannot be prevented by vaccination or cured by medicines, nor do they disappear

Infectious diseases that can’t be cured can become chronic (ex: hepatitis, HIV)

Examples:

• Heart disease

• Obesity

• Hypertension

• Type 2 diabetes

• Cancer

• Mood disorders

• Osteoporosis

• Osteoarthritis

• Cirrhosis

• Dental caries

• Respiratory illnesses (asthma, COPD)

• Dementia

• POTS

Organic compounds; obtained through diet because the organism cannot produce them

E. coli bacteria in the large intestine also helps us with synthesizing vitamin K, and other bacteria can help with B7 

Humans can synthesize:

• B3 (niacin)

• D (calciferol)

Humans cannot synthesize (or body does not produce enough):

• A (retinol)

• B1 (thiamine)

• B2 (riboflavin)

• B5 (pantothenic acid)

• B6 (pyridoxine)

• B7 (biotin)

• B9 (folate)

• B12 (cobalamin)

• C (ascorbic acid)

• E (tocopherol)

• K (phylloquinone)

Many species can synthesize vitamin C

Mammals that cannot:

• Bats

• Guinea pigs

• Anthropoid primates (monkeys, apes, humans)

Species that cannot synthesize it had mutation and lost the GLO gene that allows the body to synthesize vitamin C

However, those species have a vitamin C-rich diet, so not a big deal (evolutionarily speaking)

Scurvy – vitamin C deficiency from not eating enough fruits and vegetables

Accumulation of crystals, dislodged from kidneys into joints, capillaries, skin, and other tissues

• Gouty arthritis is a type of arthritis where crystals form in joints

• When crystals form in kidneys – kidney stones (renal calculi)

  • Renal – refers to the kidneys; Adrenal glands are located on top of the kidneys, and they produce hormones that affect metabolism, stress response, blood pressure, and immunity

• Consuming calcium-rich foods does not cause kidney stones…calcium deficiencies increase risk

Other animals:

• Enzyme breaks down urate (type of uric acid) to a less crystallized form; process requires a lot of water

• In humans, it is not broken down (likely an adaptation to hot environments)

5th century – Hippocrates linked gout to lifestyle (associated with wealth)

Increasing prevalence over time

Bioarchaeological evidence:

• Bone growths indicating lesions

• More likely to appear on hands and feet, and these bones are least likely to be found

Risk factors:

• Sedentary lifestyle

• Meat

• Fructose (sugars)

• Seafood

• Alcohol

• Genetics

X-rays can show evidence of kidney stones, blockages, and organ dysfunction.  (Pueblo Radiology Imaging): https://www.puebloradiology.com/imaging-services/x-ray/

Cell growth exceeds cell death

• DNA damage causes DNA repair gene to be inactivated

• Leads to mutations

• Oncogene is created, which inhibits cell death 

Seems to affect humans more often than other species?

Oncogenes – cells that cause tumors; act like on/off switch

Carcinogens – substance that promotes carcinogenesis (normal cells are transformed to cancerous cells)

• Benzene, coal, smoke, asbestos, alcohol, viruses, parasites

Risk factors:

• Genetics

• Carcinogens

• Pollution

• Radiation

Benzene

• Volcanoes, forest fires, crude oil, gasoline

• Used to make plastics, resins, lubricants, rubbers, dyes, detergents, drugs, and pesticides

• Cigarette smoke is major source of exposure

• Low levels in air – concern is more with enclosed spaces with unventilated fumes

• Limit time spent near idling car engines, avoid skin contact with gasoline

To what extent are people psychologically drawn to fire for warmth, protection, and cooking?

• Controlling fire was crucial to hominin survival during the Ice Age

• Some anthropologists suggest that those who use fire on a regular basis seem to be less fascinated with it than those who don’t acquire fire mastery at a young age

• "Fire learning” instincts common – people who haven’t mastered it have more of a feeling of curiosity and fascination with it

Children tend to have strong instincts to be curious around fire and predatory animals

• Advantageous to pay special attention to information obtained about them?

Primate grooming and medicinal behaviors

• Primates will consume plants and insects that may be toxic

• Seems to be medicinal – somewhat toxic but kills parasites, treats various illnesses, used as insecticide to prevent spread of disease through insects, etc.

• Some cultural and medicinal practices involve smoke