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Human Parasitology > Protozoa - Amoebae > Flashcards

Protozoa - Amoebae Flashcards

1
Q

Name the basic groups of traditional parasites.

A
  1. helminths 2. protozoa
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2
Q

How do Helminths & Protozoa differ?

A

helminths - multicellular, platyhelminths, nematoda vs. protozoa - unicellular

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3
Q

What are some characteristics of the protozoa?

A
  1. diversity 2. unicellular eukaryotes w/ membrane bound nucleus (chrs) & organelles 3. heterotrophs: ~45,000 spp identified in all environment, very significant in their health impact on humans
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4
Q

What is one characteristic common to all the members of the Phylum Sarcomastigophora?

A
  1. subphylum sarcodina is characterized by having pseudopodia 2.subphylum mastigophora is characterized by presence of flagella
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5
Q

What is one characteristic common to all the members of the Phylum Ciliophora?

A

presence of cilia

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6
Q

What is one characteristic common to all the members of the Phylum Apicomplexa?

A

presence of apical complex

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7
Q

What are the 4 genera in the order Amoebida?

A
  1. Entamoeba
  2. Endolimax
  3. Idoamoeba
  4. Acanthamoeba
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8
Q

Naegleria is classified in which order?

A

Schizopyrenida

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9
Q

Name the three orders in which members posses a flagellum.

A
  1. Diplomonadida (Giardia lamblia)
  2. Trichomonadida (Trichomonas vaginalis)
  3. Kinetoplastida (Trypanosoma + Leishmania)
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10
Q

Which genera are found in the phylum Apicomplexa?

A

Plasmodium + toxoplasma

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11
Q

Describe flagella

A

mastigophora
trophozoite stage - one or more flagella extending from it
swim - can be in a liquid medium
cytoplasmic extension surrounded by plasma membrane
axoneme - embedded in flagellum provides support
basal body (aka blepharoplast, kinetosome) anchors flagellum

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12
Q

Describe pseudopodia

A

amoebae
used for locomotion & food acquisition
temporary extensions of cytoplasm & plasma membrane
depend on actin & myosin
requires substrate

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13
Q

Describe cilia

A

smaller & more numerous than flagella

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14
Q

Do all protozoa have mitochondria?

A 
no
present in some species:
cristae - tubular shape
muticellular eukaryotes have 1 amellar (flat) cristae
absent in some species:
anaerobia metabolism
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15
Q

Where do organisms in the order Amoebida live?

A

most are free living

some in vertebrate or invertebrate intestinal tracts

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16
Q

How do Amoebida reproduce?

A

binary fission - asexual

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17
Q

What types of symbiotic relationships with humans are possible?

A

most are commenals (+/0): amoeba benefits, no effect on humans
few are pathogenic

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18
Q

Which genera of Amoebida are associated with humans?

A
  1. entamoeba
  2. endolimax
  3. lodamoeba
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19
Q

How are the 3 genera of Amoebida assoicated with humans differentiated?

A

differ in size & nucleus structure - major features used to identify species

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20
Q

In the nucleus of organisms in the genus Entamoeba, how can the chromatin be distributed?

A

varies among species

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21
Q

What is an endosome and how is it useful in identification?

A

in nucleus
similar to nucleolus - contains RNA & genes for ribosome synthesis
size & position of endosome in the nucleus are important features in making identification
size: small vs. large
location: centric (middle) vs. eccentric (off to side)

22
Q

What two stages occur in the life cycle of Entamoeba?

A 
1. trophozoic - feeding stage
stage found inside the host
2. cyst
survives external environment
infective stage/transmission stage
23
Q

What are chromatoidal bars and in which stage of Entamoeba are they found?

A

deposits of nucleic acids
morphology varies
in most species - only found in young cysts
in old cysts - disappears & disintegrates
presence or absence - gives age

24
Q

How many people worldwide are affected by Entamoeba histolytica?

A

~500 million infected

~110,000 deaths / year

25
Q

What is the size of a trophozoite?

A

~25mm in diameter

26
Q

Describe the morphology of the nucleus of Entamoeba histolytica.

A

endosome - small & centric

PC - fine, evenly distributed

27
Q

How do the trophozoites reproduce?

A

binary fission
daughter cells move away from each other
~1/3 of dividing cells can’t break apart

28
Q

What happens if the two daughter cells can’t break apart?

A

release chemoattractant - attracts a midwife cell

midwife cell ruptures cleavage furrow

29
Q

What stimulates encystment?

A

drying out to encyst

30
Q

What is a precyst?

A

lots of glycogen - energy

secretes - cyst wall

31
Q

How many times does the nucleus undergo division in the cyst

A

2 divisions.

1-2-4

32
Q

What does the chromatoidal bar look like?

A

long with rounded ends

33
Q

What is a mechanical vector and how is it relevant in this life cycle of Entamoeba histolytica?

A

fecal oral route uses mechanical vector
vector actively moves parasite but no parasite development
ex: flies & cockroaches

34
Q

What happens when the cyst is ingested by a human?

A

resistant to gastric acids
encysts in SI - trypsin helps break down cyst wall
cytoplasm & nuclei divide - 8 metacystic trophozoites
move to LI

35
Q

Noninvasive intestinal disease is caused by which stage of Entamoeba histolytica?

A

cyst stage

36
Q

Why are asymptomatic individuals the main source of infection in Entamoeba histolytica?

A

carrier are the same source of infection - ovivirulent

37
Q

What is a secretagogue?

A

substance that stimulates secretion of another substance
stimulates increased mucus secretion by host
body secretes so much it runs out of mucus

38
Q

What is stimulated by the E. histolytica secretagogue?

A

mucus secretion

39
Q

What is a lectin?

A

protein which has a high binding specificity for a particular CH2O

40
Q

How is the Gal/GalNAc lectin of E. histolytica involved in invasion?

A

trophs binds surface of host cell (cytoadherence)

41
Q

What is an amebapore?

A

small peptides that come together to form hexamers

hallow structure

42
Q

How does amebapore peptide affect the host cell membrane?

A

inserts itself into host plasma membrane, bores a hole
host cytoplasm leaks out
host cell dies

43
Q

How do E. histolytica cysteine proteases affect the host?

A

cleave the host cells & cause tissue damage

44
Q

What happens if the E. histolytica trophozoites advance into the submucosa?

A

ulcer deepens & spreads laterally

forms flask-shaped ulcer

45
Q

What are the symptoms of E. histolytica infections?

A

diarrhea, dysentery, cramps, flatulence, nausea
circulation becomes inadequate: sheets of epithelial cells slough off, bleeding, loss of electrotytes
10-20 stools/day
fever
deydration - big problem in children

46
Q

What is acute necrotizing colitis?

A

severe form of E. histolytica infection
blood diarrhea, fever, pain
most of mucus depleted
mortality exceeds 50%

47
Q

What is an ameboma?

A

inflammatory thickening of intestinal wall around ulcer
painful
can by confused with tumors

48
Q

How can perianal ulcers form in an E. histolytica infection?

A

trophs invade skin around anus

49
Q

How are infections with E. histolytica diagnosed and treated?

A 
diagnosis: fecal -cysts only useful for luminal amebiasis (non-invasive)
ELISA - antibodies
treatment:
metronidazole - inhibit NA synthesis
surgery
antibodies
50
Q

How can this parasite be controlled?

A

sanitation:
removing pathogens from drinking water
sand filtration - water goes through sand, large particles like cysts are trapped in the sand

Human Parasitology (22 decks)

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