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Cytometry and karyometry in Trypanosoma cruzi^*

Silvia Helena Rabenhorst^I; Roberto Sogayar^II; Romeu Cardoso Guimaräes^III

^IDepartamento de Genética, Instituto de Biociências, UNESP, 18618-000 Botucatu, SP, Brasil
^IIDepartamento de Parasitologia, Instituto de Biociências, UNESP, 18618-000 Botucatu, SP, Brasil
^IIIDepartamento de Biologia Geral, Instituto de Ciências Biológicas, UFMG, Caixa Postal 2486, Av. Antonio Carlos 6627, 31270-010 Belo Horizonte, MG, Brasil. Send correspondence to R.C.G.

ABSTRACT

A total of 991 Trypanasoma cruzi cells, from four laboratory stocks, including the three differentiation forms, had their cellular outlines, nuclei and kinetoplasts measured at 9000 x magnification. Data on the identifiable cell cycle stages were used to search for intraspecific and biological cycle heterogeneity.
Cellular areas (CA) in the interphasic differentiation forms produced ratios of 1.07 for culture epimastigotes (E), 1 for blood trypomastigotes (T), and 0.86 for tissue forms (A). Homogeneity in terms of nuclear (NA) and kinetoplast (KA) areas prevailed among the stocks, with differences of at most 6%, for modal NA of strains CL and Y. NA of T-form was larger than the basic NA of early G1 A-form. T-form kinetoplast volume was 3-fold that of A-form K-DNA nucleoids.
One of the two recently divided kinetoplasts in mitotic E-form did not correlate with CA, indicating that mitochondrial division was unequal. The KA of CL strain T-form did not correlate with NA, suggesting a mitochondrial disfunction in this thermosensitive strain.
The CL strain T-form was more heterogeneous than the Y strain for all characters, showing greater frequency of large values, even reaching the G2 levels. This heterogeneity was interpreted as functional, consequent to the thermosensitivity of the CL strain. Precocious bursting of CL strain host cells would lead to the polymorphic T-forms. Post-S phase trypomastigotes could start division soon after penetration of host cells.

Keywords: Cytometry; Karyometry; Trypanosoma cruzi.

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* Part of a thesis presented by S.H.R. to the Instituto de Biociências, UNESP, Botucatu, in partial fulfillment of requirements for the Master's degree.