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internal structures of giardia

Mark Siddall mes at zoo.toronto.edu
Thu Nov 3 09:15:12 EST 1994

>In Article <mbernhar-0111942104580001 at f180-082.net.wisc.edu>
>mbernhar at facstaff.wisc.edu (mat bernhardt) writes:
>>could someone please name all the possible internal structures of g.
>>lamblia that can be visualized using direct interference contrast (dic)
>>microscopy?  please include a brief description of each structure (what it
>>looks like etc.) 
In article <398i9a$p84 at martha.utk.edu> ctfaulkn at utkvx.utk.edu writes:
>	Is this a quiz ?  Off the top of my head..... flagellar bundle 
>(several folded strands of flagellum running longitudinally and 
>bisecting the cyst), parabasal bodies (2, comma-shaped features oriented 
>transverse to the flagella, nuclei (either 4 or 2, usually, depending
>on the developmental stage of the cyst).  Some say an axoneme is visable 
>but I've never seen it.

The bodies are "median bodies" not "parabasal bodies".  The former are incom-
pletely formed microtubular sheets, the latter are golgi apparati in 
trichomonads.  Also, the shape of the median bodies in Giardia varies
depending on the species.  Comma-shaped for G. lamblia, other shapes for
G. muris etc.
There is no axoneme in Giardia or other diplomonads.  This too is a tricho-
monad feature.

What you can expect to see depends on whether you're looking at trophs
or cysts.
In trophs: teardrop-shped organism with two nuclei at the fat end of the drop.
Two flagella draped over the fat end and trailing off the sides plus two
other pairs of flagella comingfrom the center out at about 3/4 the way
down the sides to the point of the drop plus another pair coming off the
end of the point.  The latter have a sinusoidal shape.

The fat part of the drop should appear to have a rigid circle making it's 
shape.  This is the "adhesive" disk made up by a sheet of microtubules.

The median bodies may not be obvious by DIC.  I believe they are usually seen
in stained preps.

The cyst:
Rugby-ball shaped.  If mature, will have 4 nuclei clustered at one end
of the cyst and will appear to have a slightly "S" shaped partition down the
long axis.  The partition is somewhat fribrilar in appearance.
The reason for the appearance is that following encystation, the organism
divides bilaterally and the microtubular structures and flagellar
apparati are agregated near the central plane of the cyst.

An atlas of human parasitology should provide suitable figures.  As will 
almost any intro parasitology text worth it's weight.

Happy hunting!


Mark E. Siddall                "I don't mind a parasite...
mes at vims.edu                    I object to a cut-rate one" 
Virginia Inst. Marine Sci.                     - Rick
Gloucester Point, VA, 23062

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