Biomedical Engineering Reference
In-Depth Information
Members of Class Ciliophora have a peculiar system of two nuclei: a small
nucleus that contains the full genome, and a larger nucleus that plays the
active role in cellular regulation. The larger nucleus is regenerated from the
smaller nucleus through a process of gene amplification and gene editing. This
produces a functional, but non-reproductive nucleus, with an enrichment of
genes that play a role in cell regulation, and a reduction of genes that are
involved in nuclear regeneration. It would seem that the members of Class
Ciliophora have attained a mechanism whereby the nucleus divides its labors
by creating a back-up nucleus that preserves a full set of genes, and a working
nucleus, with a gene ensemble selected for cellular functionality.
Ciliophora
Litostomatea
Vestibuliferida
Balantiididae
*Balantidium
There is only one species of Class Ciliophora that is infectious in humans:
Balantidium coli. Balantidiasis is a zoonosis, found in a variety of animals,
but the most important reservoir is the pig. In pigs, the organisms produce
no apparent clinical disease. The organisms live in the pig's colon, and are
passed into the feces. Human disease, which is rare, occurs when humans
ingest food that has been contaminated by pig feces, or, rarely, from the
feces of infected humans.
There are two forms of the organism: trophozoite and cyst. The tropho-
zoites are the active, growing form of the organisms. Trophozoites transform
into cysts under poor growth conditions. Encystation typically occurs in the
distal colon, where the feces are relatively dry, and unfavorable for growth.
The cysts are inactive, but can survive adverse conditions. Cysts are passed
in the feces and are the passively infective form of the organism. Once in the
intestine, cysts transform into trophozoites.
The trophozoites are capable of invading into the wall of the colon and
occasionally produce ulcers. The ulcers of balantidiasis have a peculiar
inverted-flask shape (i.e., a small opening on the lumen surface overlying
edges that extends laterally and ends sharply as a flat base, in the colon
wall). Most cases of human balantidiasis are mild (some diarrhea or consti-
pation) or asymptomatic. Cases of balantidiasis occur worldwide, but they
are rare in the USA. Balantidiasis is a common infection in the Philippines.
Infectious species:
Balantidium coli (balantidiasis)
