Protozoa - Amoebae Flashcards
Name the basic groups of traditional parasites.
- helminths 2. protozoa
How do Helminths & Protozoa differ?
helminths - multicellular, platyhelminths, nematoda vs. protozoa - unicellular
What are some characteristics of the protozoa?
- 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
What is one characteristic common to all the members of the Phylum Sarcomastigophora?
- subphylum sarcodina is characterized by having pseudopodia 2.subphylum mastigophora is characterized by presence of flagella
What is one characteristic common to all the members of the Phylum Ciliophora?
presence of cilia
What is one characteristic common to all the members of the Phylum Apicomplexa?
presence of apical complex
What are the 4 genera in the order Amoebida?
- Entamoeba
- Endolimax
- Idoamoeba
- Acanthamoeba
Naegleria is classified in which order?
Schizopyrenida
Name the three orders in which members posses a flagellum.
- Diplomonadida (Giardia lamblia)
- Trichomonadida (Trichomonas vaginalis)
- Kinetoplastida (Trypanosoma + Leishmania)
Which genera are found in the phylum Apicomplexa?
Plasmodium + toxoplasma
Describe flagella
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
Describe pseudopodia
amoebae
used for locomotion & food acquisition
temporary extensions of cytoplasm & plasma membrane
depend on actin & myosin
requires substrate
Describe cilia
smaller & more numerous than flagella
Do all protozoa have mitochondria?
no present in some species: cristae - tubular shape muticellular eukaryotes have 1 amellar (flat) cristae absent in some species: anaerobia metabolism
Where do organisms in the order Amoebida live?
most are free living
some in vertebrate or invertebrate intestinal tracts
How do Amoebida reproduce?
binary fission - asexual
What types of symbiotic relationships with humans are possible?
most are commenals (+/0): amoeba benefits, no effect on humans
few are pathogenic
Which genera of Amoebida are associated with humans?
- entamoeba
- endolimax
- lodamoeba
How are the 3 genera of Amoebida assoicated with humans differentiated?
differ in size & nucleus structure - major features used to identify species
In the nucleus of organisms in the genus Entamoeba, how can the chromatin be distributed?
varies among species
What is an endosome and how is it useful in identification?
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)
What two stages occur in the life cycle of Entamoeba?
1. trophozoic - feeding stage stage found inside the host 2. cyst survives external environment infective stage/transmission stage
What are chromatoidal bars and in which stage of Entamoeba are they found?
deposits of nucleic acids
morphology varies
in most species - only found in young cysts
in old cysts - disappears & disintegrates
presence or absence - gives age
How many people worldwide are affected by Entamoeba histolytica?
~500 million infected
~110,000 deaths / year
What is the size of a trophozoite?
~25mm in diameter
Describe the morphology of the nucleus of Entamoeba histolytica.
endosome - small & centric
PC - fine, evenly distributed
How do the trophozoites reproduce?
binary fission
daughter cells move away from each other
~1/3 of dividing cells can’t break apart
What happens if the two daughter cells can’t break apart?
release chemoattractant - attracts a midwife cell
midwife cell ruptures cleavage furrow
What stimulates encystment?
drying out to encyst
What is a precyst?
lots of glycogen - energy
secretes - cyst wall
How many times does the nucleus undergo division in the cyst
2 divisions.
1-2-4
What does the chromatoidal bar look like?
long with rounded ends
What is a mechanical vector and how is it relevant in this life cycle of Entamoeba histolytica?
fecal oral route uses mechanical vector
vector actively moves parasite but no parasite development
ex: flies & cockroaches
What happens when the cyst is ingested by a human?
resistant to gastric acids
encysts in SI - trypsin helps break down cyst wall
cytoplasm & nuclei divide - 8 metacystic trophozoites
move to LI
Noninvasive intestinal disease is caused by which stage of Entamoeba histolytica?
cyst stage
Why are asymptomatic individuals the main source of infection in Entamoeba histolytica?
carrier are the same source of infection - ovivirulent
What is a secretagogue?
substance that stimulates secretion of another substance
stimulates increased mucus secretion by host
body secretes so much it runs out of mucus
What is stimulated by the E. histolytica secretagogue?
mucus secretion
What is a lectin?
protein which has a high binding specificity for a particular CH2O
How is the Gal/GalNAc lectin of E. histolytica involved in invasion?
trophs binds surface of host cell (cytoadherence)
What is an amebapore?
small peptides that come together to form hexamers
hallow structure
How does amebapore peptide affect the host cell membrane?
inserts itself into host plasma membrane, bores a hole
host cytoplasm leaks out
host cell dies
How do E. histolytica cysteine proteases affect the host?
cleave the host cells & cause tissue damage
What happens if the E. histolytica trophozoites advance into the submucosa?
ulcer deepens & spreads laterally
forms flask-shaped ulcer
What are the symptoms of E. histolytica infections?
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
What is acute necrotizing colitis?
severe form of E. histolytica infection
blood diarrhea, fever, pain
most of mucus depleted
mortality exceeds 50%
What is an ameboma?
inflammatory thickening of intestinal wall around ulcer
painful
can by confused with tumors
How can perianal ulcers form in an E. histolytica infection?
trophs invade skin around anus
How are infections with E. histolytica diagnosed and treated?
diagnosis: fecal -cysts only useful for luminal amebiasis (non-invasive) ELISA - antibodies treatment: metronidazole - inhibit NA synthesis surgery antibodies
How can this parasite be controlled?
sanitation:
removing pathogens from drinking water
sand filtration - water goes through sand, large particles like cysts are trapped in the sand
