Some Recent Advances in Our Understanding of Parasitic Protozoa*†

Abstract

SYNOPSIS. Striking progress in our understanding of parasitic protoroa has been achieved thru the employment of advanced electronmicroscopic, biochemical, immunologic, and cultivation methods. Some recent information gathered by means of these methods on trichomonad and trypanosomalid flagellates as well a s on eimeriidian and plnsmotliid haemosporiidian Sporozoa is discussed. It is empha-T is evident from the recent reports published in a variety I of journals, review articles, and books that the most striking progress in our understanding of parasitic protozoa has been achieved thru the employment of advanced electronmicroscopic, biochemical, immunologic, and cultivation methods. Among the organisms about which much information has been accumulated by {these methods are the trypanosomatid and trichomonad flagellates and the plasmodiid haemosporidians. For this reason, and also because of my relatively greater familiarity with them, the following discussion will deal largely with these assemblages. The elimination of many other groups of parasitic protozoa from the present consideration must not be construed as reflecting lack of activity in their studies, but merely less activity and also poorer knowledge of them on my part.Several recent publications reviewing the parasitic protozoa (21,23,31,36,82,98) indicate (that data pertaining to biochemistry are based to a very significant degree upon studies of organisms grown in culture. Indeed, in many instances, analytic methods could not have been used without large yields of organisms achievable only through cultivation on nonliving media. The observations I propose to make concerning cultivation are relevant almost exclusively to extracellular species. Maintenance of intracellular forms in the presence of host cells or cell cultures, or even free of all such cells(for references see 36), has contributed much to our understanding of leishrnanias, and particularly of malarial parasites. These methods of cultivation involve somewhat different problems, which will not be considered here.

THE ULTRASTRUCTURE OF TRICHOMONAS VAGINALIS DONNÉ BEFORE AND AFTER TRANSFER FROM VAGINAL SECRETION TO DIAMONDS MEDIUM

“…The glycogen content of extracellular parasitic protozoa usually drops when cells are transferred from the natural infection to artificial culture media. The growth rate of freshly isolated cells also changes and is usually increased when cells are maintained in uitro for some time (7,10). The present study demonstrates both types of changes in T. vag.…”

“…In cells of the in uivo material the chromatic granules (CG, Figs. 7,9) usually were surrounded by glycogen granules (GL, Figs. 7,9) and only by scattered clusters of ribosomes (RI, Figs.…”

Ultrastructural cytochemical identification of peroxisomes as organelles of terminal oxidation in amitochondrial trichomonad flagellates

“…The suggestion that PAG-PCG represent pools of precursor material for construction of the striated fiber and microtubule elements in these cells has been advanced (Mattern et al, 1967;Honigberg, 1968). More commonly, these organelles have been inferred to be mitochondrial analogues (Niel sen et al, 1966;Anderson and Beams, 1959;Akashi et al, 1961;Smith and Stewart, 1966), while other vesicular cytoplasmic structures have been assigned this role by others (Anderson, 1955;Chakraborty et al, 1961).…”