PROGRESS IN PROTOZOOLOGY

IN VITRO CULTIVATION OF PARASITIC PROTOZOA 231
of the organisms had rounded up and resembled amastigotes. When these
forms were placed in Schneider's medium and incubated at 24°C,
they reverted to promastigote forms. The axenically grown amastigotes
were slightly larger than those found within the host cell, but their
ultrastructure was identical. This source of extracellular amastigotes
has been useful for further studies on drug action and determination
of biochemical and metabolic properties of the promastigotes, axenically
cultivated and host cell-derived amastigotes. Results of preliminary investigations
of the infectivity of these stages of L. b. panamensis have
indicated the axenic and the tissue derived-amastigotes produced cutaneous
lesions in African white tailed rats at about the same time (10
days) postinoculation, but much sooner than the promastigotes.
One of the most significant areas to be studied will be the use of the
host cell-free amastigotes as antigen in the production of species specific
monoclonal antibodies.
Trypanosoma cruzi
This parasite causes Chagas' disease in man. The parasite is widely
distributed in Central and South America and extends into the southern
United States. The disease in man occurs where dwellings are infested
with bugs. Man may contract the disease from bugs which had fed previously
on an infected animal.
Dr. R o i t m a n described some of the methods most commonly used
to cultivate the different developmental stages of this parasite. The early
blood-containing media could support substantial yields of epimastigote
and occasional development of trypomastigote forms in cultures incubated
at 25-28°C (Taylor and Baker 1968).
Several semi-defined liquid media have been described. In the medium
of Citri and Grossowitz (1955) the blood was replaced
by haemin, crystalline serum albumin and a series of growth factors.
No change in the growth pattern or the yields of T. cruzi flagellates
occurred during prolonged cultivation in this medium. It was demonstrated
by Bon6 and Parent (1963) that the main function of serum
in their medium was as a source of stearic acid, essential for growth
of T. cruzi epimastigotes. These workers devised a heat-sterilizable medium,
composed of peptone and known compounds; it produced maximum
populations of 7 X 10 7 organisms/ml. A macromolecule-free medium,
containing in its defined part 3 salts, glucose, haemin, 21 amino
acids, 3 lipids and some undefined components obtained by dialysis of
liver infusion, was developed by Yoshida (1975) for cultivation of
T. cruzi at 28°C. The medium supported prolonged cultivation with
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