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various microbial eukaryotes
- i. Fungi
- ii. Protozoa
- iii. Helminths
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types of non-living infectious agents (all are different)
- i. viruses
- ii. viriods
- iii. prions
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Fungal General Characteristics
- eukaryotic cells
- (all fungi )reproduce sexualy and nonsexually)
- nonmotile
- heterotrophic (use organic compounds a carbon source; they can’t make their own sugars(FOOD); no photosynthesis)
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Fungi facultative anaerobes example
Yeast
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Fungi saprophytes - obtain nutrients by
decomposing dead & decaying matter important in ecosystems as decomposers
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Fungi structure
- hyphae can be coenocytic NO SEPERATION NO CROSS WALL (undivided network of branching tubes) or have SEPTA (cross walls).
- CAN BE MULTI AND UNICELLULAR ARE ROD SHAPE
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Fungus have cell wal;s composed of
- •cellulose, chitin (contains nitrogen - also found in the
- exoskeletons of insects, crayfish, etc.), or a combination of the two.
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Fungi asexual reproduction
- Occurs by elongation of hyphae, budding, or asexual spore production
- Only contain one genome
- Budding is one cell copying its genome and seppararing (like yeast)
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(Fungi) Asexual Spores are products of a type of cell division called
mitosis (one cell divides to form 2 daughter cells that are identical to one another and to the original parent cell).
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Types of asexual spores
- sporangiospores
- conidiospores
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Fungi Sexual Reproduction Occurs by
producing sexual spores, which form following sexual fusion of gametes (similar to sperm & eggs)
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Types of sexual reproducing fungi
- zygospore
- ascospores
- basidiospores
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Underground one filament fungi are known as
hyphi
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Duramycota fungi
- Imperfect fungi, group not known much about only that they reproduce asexual and are temporary grouping
- untill more info is known
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Yeasts vs. Molds
- •Yeast are nonfilamentous and unicellular
- •Molds are filamentous and multicellular
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Fungi key points
- •Fungi are eukaryotes
- •Fungi are heterotrophs
- •Can reproduce via asexual and/or sexual reproduction
- •Can cause human diseases
- •Many different types of fungi
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Mycoses
- •Humans usually acquire fungal disease from nature; they are not highly contagious.
- •Fungi are a leading cause of nosocomial infections (hospital aquire infections)
- Fungal infections are a major problem in immune suppressed people.
- Fungal infections are often mistaken for bacterial infections, with fatal consequences.
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Mycoses fungi
- •Superficial
- •Cutaneous
- •Subcutaneous
- •Systemic (most dangerous)
- •Opportunistic (most dangerous)
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Superficial mycoses infection of outerlayer of skin
- Pityriasis versicolor--pigmented lesions on torso
- Tinea nigra--gray to black macular lesions often on palms
- Black piedra--dark gritty deposits on hair
- White piedra--soft whitish granules along hair shaft
- All are diagnosed by microscopy and are easily treated by topical preparations
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Three genera of dermatophytes:
- Microsporum
- Trichophyton
- Epidermophyton
- -cause infections of skin and its appendages
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Systemic fungal disease is most often associated with four organisms
- 1.Coccidioides immitis
- 2. Histoplasma capsulatum
- 3.Blastomyces dermatitidis
- 4.Paracoccidioides brasiliensis (S. America)
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Infection caused by inhalation of spores
•Coccidiodes immitis is considered to be the most virulent of fungal pathogens.
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Opportunistic Mycoses
- •Fungal infections that do not normally cause disease in
- healthy people, but do cause disease in people with weakened immune defenses (immunocompromised people).
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prime importance in the occurrence of vaginal candidiasis
Local factors such as pH and glucose concentration (under hormonal control)
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Protozoa General Characteristics:
- Unicellular eukaryotes.
- Animal-like
- Limited to a moist environment because they lack a cell wall
- Heterotrophs
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Fungi reproduce asexually by
- 1.fission (one cell divides to form 2 identical daughter cells and budding
- 2.schizogony (multiple fission).
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Sexual reproduction occurs by
- 1.conjugation: the fusion of vegetative cells
- 2.fusion of specialized gametes called gametocytes.
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Life cycle
- Some have complex life cycles
- Requiring multiple hosts and changing their morphology
- Plasmodium uses the mosquito as an intermediate host
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Trophozoite
- active, motile, feeding stage of protozoans; parasitic stage
- that causes the disease in the host
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Cyst
resistant, inactive stage; how diseases are usually transmitted by the fecal-oral route; usually more useful than trophozoites for lab identification
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Classification based on mode of
locomotion or motility
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Sarcodina
- Move by means of pseudopodia or "false feet"
- Temporary extensions of the cell body caused by protein filaments of the cytoskeletonpushing on the cell membrane)
- Feed on algae, bacteria, and other protozoans by phagocytosis.
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Mastigophora or Zoomastigophora
- Move by means of flagella
- Some can also have pseudopodia
- Many are disease-causing species
- Some are parasites
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Ciliophora
- Move by means of cilia
- Cilia are short, hairlike projections of cytoplasm composed of pairs of microtubules surrounded by cell membrane.
- Multinucleate organisms
- Macronucleus controls cell functions and asexual reproduction.
- Micronucleus is also involved with sexual reproduction.
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Apicomplexa or Sporozoa
- Basically nonmotile.
- All have an infectious, sporelike stage (sporozoite) that is often transmitted to new hosts by an insect vector.
- All are parasitic (obligate parasites - cannot live apart from the host).
- Some have elaborate life cycles, changing body form (trophozoite, sporozoite, merozoite)
- Life cycle includes schizogony (multiple fission).
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Protozoan Diseases
Several serious human diseases:
- Ameobiasis
- Chaga’s disease
- Malaria
- African sleeping sickness
- Leishmaniasis
- Taxoplasmosis.
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Trypanosoma
(African sleeping sickness)
- Flagellated protozoans
- TseTse fly carries
- Stages:
- --Systemic: multiplies in blood
- --Progresses to neurological stage, infects central nervous system → meningoencephalitis
- --Loss of consciousness. Hence, the SLEEP part.
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Malaria caarried by the
- Anopheles Mosquito
- ----Plasmodium. falciparum– most virulent and prevalent
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Define Vectors
(insects) that convey a parasite from host to host
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Protozoas are unicellular
Heterotrophs
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Helminths
- Multicellular
- Eukaryotes
- Heterotrophs
- Reside in humans, but do not usually replicate there
- Not intracellular
- Most infected individuals carry few, immune system not heavily engaged, level of immunity generated is often poor
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Define Cephalization
Concentration of sensory receptors toward the anterior end
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Flatworm sexual reproduction
Most are monoecious (Male & Female) both reproductive organs in same animal
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Sexual reproduction in roundworms
Dioceious (Seperate Sexes)
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Types of Helminths
Flat and round worms
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Describe Platyhelminthes
- Flatworms
- Most are free living
- Marine and Freshwater
- Predator, Scavengers, or Parasitic
- Some have regenerative capabilities
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Trematodes + Cestodes =
Flatworms = Platyhelminthes
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Trematoda (Flukes)
- All parasitic of vertebrates
- Have complex life cycles that include sexual and asexual phases
- They require at least 2 kinds of organisms to complete the cycle
- They reach sexual maturity in a primary or definitive host (always a vertebrate), their larval stages develop or become encysted in an intermediate host (usually an invertebrate).
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Cestoda (Tapeworms)
- Intestinal parasites of vertebrates
- No digestive system like in trematodes & nematodes
- They absorb nutrients through their tegument!
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Tapeworm Morphology
- Scolex (head) with suckers and/or hooks (for attachment)
- Proglottids (body units - each one has male and female reproductive organs)
- 1.immature proglottids (closest to the scolex)
- 2.mature proglottids (next closest to the scolex)
- 3.gravid proglottids (furthest from the scolex - in these proglottids, the uterus is filled with eggs).
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Life cycle
- The gravid proglottids break off and are passed in the definitive host's feces
- Larval forms hatch when the eggs are ingested by the intermediate host
- Larvae then encyst in the intermediate host (called a cysticercus or bladder worm)
- Adult worms usually develop in the definitive host when raw or poorly cooked infected meat is eaten.
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larvae encyst in the intermediate host (called a
cysticercus or bladder worm
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What part of the body may harbor cysticerci.
Every organ in the body
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When a cysticercus dies, it releases
toxins and usually causes a severe allergic reaction, which is sometimes fatal.
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Nematoda Characteristics
- Nematodes are everywhere!!!!
- They are freeliving in soil, fresh & salt water, & are parasitic in plants and animals.
- Dioecious (separate sexes).
- •Possess
- a nonliving cuticle, which is secreted by the epidermis and is resistant to the
- digestive enzymes of the hosts.
- More highly developed than flatworms.
- Adults do not latch onto the host like the tapeworms
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Ascaris
roundworms in the small intestine
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Schistosoma
trematode worm causing debilitating infection
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Taenia
Tapeworm of cattle and pigs
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Trichinella
roundworm of pigs causing Trichinosis
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Schistosomiasis
3 major species:
- –S. mansoni (intestinal mesenteric veins)
- –S. japonicum (intestinal mesenteric veins)
- –S. haematobium (urinary bladder veins
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Snails release 300-3000
cercariae (free swimming larvae)
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Cercariae secrete digestive
digestive enzymes and bore into skin
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Schistosomiasis Symptoms
- •½ the eggs can remain: invade intestinal wall, liver, or bladder → hemorrhage
- Unexcreted eggs induce
- cell-mediated delayed type hypersensitvity. Large granulomas are formed and walled off by fibrous tissue
- Granulomas often obstruct venous blood flow to the liver or bladder.
- Survive for up to 20 years evading attack of localized cellular buildup of immune andinflammatory cells
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Taenia solium
- (Pork Tapeworm)
- Humans can be infected with the adults by consuming rare pork containing cysticerci larvae
- Larvae then develop into adults in digestive tract of the human.
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Ascaris lumbricoides
- Largest intestinal nematode (round worm) in humans.
- Disease is called ascariasis
- Eggs can remain viable even in preservative!
- Females are longer; males are shorter & have a hooked posterior end
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Helminths are
Multicellular eukaryotes
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Two types of helminths (worm-like parasites):
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Most common route of infection caused by Helminths is by
Eating uncooked meat
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Viruses
- General characteristics
- Life cycle
- Growing virus
- Viral infections
- Other acellular organisms
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Virus Characteristics
- Obligate intracellular parasites (can reproduce/replicate only inside a host cell)
- Not cells
- Consist of nucleic acids (DNA or RNA) in a protein coat, called a capsid (no cell membrane)
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Virus insert themselves into a host
host cell & direct the host cell's metabolic machinery to make more virus
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Viruses can attack
all cellular organisms
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Characteristics of living things:
- 1. reproduction
- 2. metabolism
- 3. organized as cells, contain all organic molecules (lipids, enzymes, nucleic acids, carbs)
- 4. evolution & adaptation to changing environments.
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What characteristics do viruses have
- They can evolve
- They contain some macromolecules
- They direct their own reproduction
- However, they are not cells - they do not have cytoplasm, a cell membrane, organelles, ribosomes, or a nucleus.
- They have DNA or RNA, unlike prokaryotic and eukaryotic cells, which have both.
- In addition, they lack a metabolism of their own (they cannot produce ATP, etc.) - raw materials and driving force (ATP & reducing power) are supplied by the host cell.
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Viruses are classified by
- Size
- Structure
- Host range
- Life cycles
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Basic structure of a virus is a
nucleic acid surrounded by a protein capsid
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Describe a virion
- A complete viral particle (= capsid + nucleic acid + envelope if it is present)
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Viruses store their genetic info in the
Nucleic Acid
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Viruses protein coat that surrounds the nucleic acid is called
Capsids
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the constituent protein molecules making up the capsids are called
Capsomeres
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3 basic shapes based on how the capsomeres are arranged
- Helical
- Polyhedral
- Complex
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Helical
proteins fit together as a spiral to form a rod-shaped structure
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Polyhedral
- proteins are arranged in equilateral triangles that fit together to form a geodesic dome-shaped structure; some appear almost spherical; you may have seen
- architectural structures that have this shape
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Complex
combination viruses with a helical portion (tail) attached to a polyhedral portion (head); ex. many bacteriophages; may also have a tail sheath (participates in injecting the viral nucleic acid into the host cell), plate, pins, & tail fibers (help virus attach to host cell).
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Viruses that lack envelopes are called
Naked Viruses
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Envelopes also help viruses infect new cells by
Fusion of the envelope with the host's cell membrane
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Viral specificity is determined by whether or not a virus can
- Attach to a cell
- Attachment depends on the presence specific receptor sites
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Examples of receptor sites are
Proteins, LPS’s, glycolipids, or glycoproteins.
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Lytic Cycle: Replication
- a. Adsorption - the virion attaches itself to a
- specific receptor site on the surface of the host cell.
- b. Penetration - the viral nucleic acid penetrates the host cell
- c. Uncoating - removing the capsid & envelope
- d. Viral Synthesis (Latent Period) (also
- called biosynthesis) - more viral components
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Virus remains latent for many cellular generations by becoming
integrated into a host cell's chromosome (the integrated viral DNA is called a prophage
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Produce population of bacteria infected with the prophage occurs by
Cell division
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Cultivating Animal Viruses is done more economical & efficient by
Embryonated chicken eggs
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measles virus causes the membranes of neighboring cells to
fuse, creating giant, multinucleated cells. (Infection that can be seen under the microscope
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large group of RNA viruses; includes
- HIV
- (Human Immunodeficiency Virus) which causes AIDS (acquired immune deficiency syndrome); infects T cells (type of white blood cell).
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Retroviruses
Retro means "backward." This virus uses the enzyme
enzyme reverse transcriptase to make DNA from its RNA. This DNA can be integrated into the host cell's chromosome
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AZT (azidothymidine), which is used against
HIV, helps stop reverse transcription by targeting the enzyme reverse transcriptase
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Tumors
uncontrolled growth of tissue (cells are dividing out of control); most are benign (non-life threatening); some are malignant (they spread or metastasize to surrounding tissues).
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Cancer
malignant tumors that metastasize to surrounding tissues
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Tumors and Cancer Causes
Most human cancers arise form genetic mutations or cellular damage caused by environmental factors (chemicals - nicotine, pesticides; radiation - UV, X-rays, etc.; diet). About 15% are attributed to viral infections.
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Viruses and Cancer Examples:
- Human T-cell leukemia (blood cancer),
- Epstein-Barr virus causes Burkitt's lymphoma
- Hepatitis B virus causes hepatocellular carcinoma (liver cancer)
- Human papillomavirus causes skin & cervical cancers.
- Kaposi’s sarcoma – thought to be associated with herpesvirus
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infectious particle
- Viroids: circular molecule, dont produce proteins, cause plant disease
- Prions: Infectious agent composed only of protein, affect CNS,
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Fungi are
eukaryotes that can cause mycoses
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Protozoa are
unicellular animal-like eukaryotes
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Helminths are
are multicellular parasites
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Viruses, viroids and prions are
are acellular infectious agents
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