90 Uptake of putrescine by Trypanosoma granulosum
School of Life Sciences, Kingston University, Kingston-upon-Thames.Biochemical Society Transactions (Impact Factor: 3.19). 12/1998; 26(4):S376. DOI: 10.1042/bst026s376
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ABSTRACT: Concentrations of free polyamines were investigated in Trypanosoma granulosum cultured in a semidefined medium containing traces of polyamines. Spermidine content peaked in early logarithmic growth while putrescine was not detectable. Unlike African trypanosomes and Leishmania, spermine was measured at equivalent amounts to spermidine in mid to late logarithmic stage cells. Addition of d,l-alpha-difluoromethylornithine to cultures did not decrease polyamine content nor was ornithine decarboxylase activity detected. In contrast, incubation of parasites with tritiated putrescine showed rapid uptake and subsequent conversion to spermidine and spermine. At late logarithmic growth, parasites contained glutathione (77% of total sulphydryl groups) and ovothiol A as major low molecular mass thiols with glutathionylpolyamine conjugates undetectable. However, the addition of exogenous putrescine elevated trypanothione and glutathionylspermidine content to 48% of total sulphydryl groups. Correspondingly, the addition of exogenous cadaverine increased homotrypanothione content. This first report of polyamines and low molecular mass thiols in Trypanosoma granulosum indicates intriguing similarities with the metabolism of the human pathogen Trypanosoma cruzi.
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ABSTRACT: Polyamines are important in the growth, division and differentiation of many cell types, including trypanosomes. The ultrastructure of culture forms of Trypanosoma granulosum was examined following growth in a modified semidefined medium (controls) and in the same medium with added polyamine biosynthesis inhibitors (DFMO, MGBG and Berenil). Untreated trypanosomes had ultrastructural features in common with other cultured flagellates. Those treated with DFMO were generally more rounded in contour. Cytoplasmic vacuoles and swollen mitochondrial membranes suggested osmotic imbalance, perhaps resulting from compromised membrane integrity. An anticlockwise arm dividing subtubule B of the peripheral doublets of the flagellum was noted in some trypanosomes treated with 20 mm DFMO. Vacuolation was also induced by MGBG and flagellar division occurred more frequently at 0.2 mm than in controls. With 1 mm MGBG, mitochondria were difficult to discern and kinetoplasts were disrupted. With 0.2 mm Berenil, vacuoles, swollen mitochondria, membranous whorls, additional microtubules underlying subpellicular tubules and disaggregated kinetoplasts were noted. With 1 mm Berenil, much of the cell structure was destroyed, although the pellicle, flagellum and paraxial rod remained intact. The present study illustrates the importance of functional polyamine synthetic pathways for the integrity of membranes, mitochondria, kinetoplasts and possibly microtubules in cultured T. granulosum.