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Viruses
 

Viruses

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Notes - Viruses

Notes - Viruses

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    Viruses Viruses Presentation Transcript

    • Viruses The word virus means “poison” in Latin.
    • Introduction
      • Influenza pandemic of 1918
      • Smallpox in the 18 th and 19 th century.
      • AIDS statistics…
    • Viral Diseases
      • Common Cold
      • Flu (influenza)
      • Mumps
      • Measles
      • Smallpox
      • Chicken Pox
      • Hepatitis
      • Warts
    • More Viral Diseases…
      • Cold Sores
      • Polio
      • AIDS
      • Bronchitis
      • Viral Pneumonia
      • Mononucleosis
      • West Nile Virus
      • Rabies
    • How are viral illnesses treated?
      • Some have a vaccine to protect you.
      • Rest, plenty of fluids and time…
      • Sometimes an antibiotic is given to prevent a secondary infection.
    • Germs are everywhere. How can you avoid being infected?
      • Wash your hands !!!
      • The 3 most common places to get germs:
        • #3 Door knob
        • #2 Computer mouse
        • #1 Shopping cart handles
        • http://www.youtube.com/watch?v=MWQ86R-aT-I
        • http://www.youtube.com/watch?v=RHqNk8_rOHk&feature=related
    • History of Vaccines
      • 1796 – Edward Jenner (England)
        • Took infected matter from a sore on the hand of local milkmaid who had cowpox .
        • He rubbed it into small incisions on the arm of an 8 year old boy named Edward Phipps.
        • The boy developed a cowpox sore on his arm.
    • 6 weeks later:
      • Jenner took some infected matter from a victim of smallpox and rubbed it into incisions made in Phipp’s arm again.
      • The boy remained healthy!
        • Jenner produced a vaccine for smallpox .
    •  
    • Louis Pasteur - 1884
      • Produced a weakened infective material from rabid dogs that was used as a rabies vaccine .
      • First used on a young boy who had been bitten by a rabid dog.
    • Rabies symptoms
      • After a symptom-free incubation period that ranges from 10 days to a year or longer (the average is 30 to 50 days), the patient complains of malaise, loss of appetite, fatigue , headache , and fever . Over half of all patients have pain (sometimes itching) or numbness at the site of exposure. They may complain of insomnia or depression .
      • Two to 10 days later, signs of nervous system damage appear, hyperactivity and hypersensitivity, disorientation , hallucinations, seizures, and paralysis . Death may be sudden, due to cardiac or respiratory arrest, or follow a period of coma that can last for months with the aid of life-support measures .
    •  
    • Jonas Salk - 1953
      • Created a polio vaccine .
      • He actually killed the active form of the virus and used it as a vaccine.
        • 1952 – 57,000 cases of polio.
        • 1957 – virtually no cases.
    •  
    • Albert Sabin - 1960
      • Treated the polio virus to weaken it.
      • Produced a longer lasting immunity to polio than the Salk vaccine .
    • Vaccinations : artificial immunity
      • 1. Inject a dead or weakened form of the virus (called an antigen .)
      • 2. Your body produces antibodies .
      • 3. The antibodies recognize the protein coat of the virus and hold it as it enters the body.
      • 4. Macrophage (a type of white blood cell) surround and digest the virus.
      • 5. You are now immune to this virus.
    •  
    • macrophage engulfs antigen by phagocytosis.
    • Definitions:
      • Antigen – A substance that stimulates the production of antibodies.
      • Antibodies – A substance produced by plasma cells (in the blood) in response to specific antigens. They “hold” the antigen until white blood cells (phagocytes) surround and destroy it.
    • Definitions cont…..
      • Vaccines – a commercially produced antigen of a particular disease.
      • It is not as “strong” as the actual disease itself.
      • Passive immunity – Babies receive antibodies from their mother.
      • It is temporary: it usually lasts for only 6-12 months.
    • More definitions…
      • Pathogen – an agent that causes disease.
    • Discovery of a Virus - 1933
      • Read pages 455-456 in textbook.
    • Size of a virus
      • Much smaller than any cell.
        • Smallest is 17 nm (.000000017 meter) or 17 billionth of a meter! (nm = 10 -9 meter)
        • The largest is 100 nm (.0000001 nm) or 1 ten millionth of a meter.
        • Barely visible in an electron microscope.
        • http://www.cellsalive.com/howbig.htm
    • Composition of a Virus
      • A strand of nucleic acid (DNA or RNA) surrounded by a protein coat known as a capsid.
      • It may also have an outer “envelope” that it has taken from a host cell.
      • It is the shape of the capsid or outer envelope that our immune system recognizes.
    • Is a virus a living organism?
      • Living things vs. Virus
      • Made of cells Not a cell
      • Metabolism No metabolism
      • Use energy No cell respiration
      • Grow/develop No growth or development
      • Definite life span Life span?
      • Reproduce Need host cell to reproduce
      • Respond to stimuli “Inert” (inactive)
    • Bacteriophage - “bacteria eater”
      • See page 457 in textbook.
    • Lytic Cycle – 5 steps
      • Step 1 – Attachment – Virus attaches to a specific receptor site on a cell.
      • Step 2 – Penetration – Virus enters the host cell
      • Step 3 – Replication – Viral DNA and protein is copied.
      • Step 4 – Assembly - DNA and protein is assembled into a virus.
      • Step 5 – Release – Viruses rupture the cell membrane and are released to infect other cells.
      • http://biology.about.com/gi/dynamic/offsite.htm?site=http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/adlyt.html
    • Lysogenic Cycle
      • Same as the lytic cycle but the viral DNA becomes incorporated into the host cell’s DNA.
      • It lies “dormant” until a later date.
      • http://student.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/lysolc.html#si
    • Viral Subunit Reassortment
      • Two strains of a virus infect a cell at the same time.
      • The nucleic acid (DNA or RNA) mix to create new combinations .
      • New viruses are produced.
      • *It is believed this happens with cold and flu viruses commonly.
      • http://www.hhmi.org/biointeractive/animations/subunit/sub_middle_frames.htm
    • Gene Therapy – A useful purpose of a virus
      • The harmful DNA is removed from a virus.
      • A “helpful” strand of DNA is inserted in its place.
      • Allow virus to deliver the genes to their target cells.
      • http://www.edu365.cat/aulanet/comsoc/Lab_bio/simulacions/GeneTherapy/GeneTherapy.htm
    • Problems with gene therapy:
      • Locating the correct cells.
      • Genes accidentally spliced in the wrong place.
      • May trigger a nearby oncogene (cancer causing gene.)
      • May cause too much of something to be produced.
      • May cause a severe immune response.
    • Current Research with gene therapy:
      • What diseases could be treated with gene therapy? ( From AMA website.)
      • About 4,000 diseases have been traced to gene disorders. Current and possible candidates for gene therapy include cancer , AIDS , cystic fibrosis , Parkinson’s and Alzheimer’s diseases , amyotrophic lateral sclerosis ( Lou Gehrig's disease ), cardiovascular disease and arthritis .