Kinetoplast DNA from normal and dyskinetoplastic strains of Trypanosoma equiperdum

Isolated kinetoplast DNA (kDNA) from a normal kinetoplastic strain of Trypanosoma equiperdum exists as a high molecular weight, covalently closed network composed of catenated minicircles and maxicircles. Analytical cesium chloride ultracentrifugation shows the kDNA (rho = 1.692 g/cm3) to be retained in normal amounts and of normal base composition in two dyskinetoplastic strains of T. equiperdum. Kinetoplast DNA isolated from these mutant cells by CsCl-DAPI (4,6diamino-2-phenylindole) equilibrium ultracentrifugation lacks the complex networks found in the normal strain and no minicircles are detectable. Large circular molecules, approximately 5 micrometer in contour length, are present in isolated kDNA from both dyskinetoplastic strains. These molecules probably correspond to the maxicircles in the normal kDNA networks. We conclude that the presence of a complex kDNA network is not essential to the bloodstream trypanosome and that the kDNA network of the normal strain of T. equiperdum is structurally dependent on the presence of catenated minicircles.

Free plasma amino acid profiles of normal and Trypanosoma vivax infected sheep

The free amino acids in the plasma of normal and Trypanosoma vivax infected sheep and also in the trypanosome organism per se were determined. Threonine, asparagine, methionine, tyrosine, citrulline, ornithine, histidine, arginine and urea were significantly decreased in the plasma of infected sheep. Alanine was significantly elevated in plasma of infected sheep. Valine, isoleucine, leucine values were also elevated in the plasma of infected sheep, although not at significant level. Taurine was present among the amino acid profile of T. vivax organisms and also in the plasma of normal and infected sheep. The significance of the amino acid changes in terms of host and T. vivax metabolism is discussed.

Polysaccharides of crithidia fasciculata. Identification and partial characterization of a cell surface constituent

A carbohydrate-containing fraction was extracted from the trypanosomatid Crithidia fasciculata by a phenol-water procedure. Ion-exchange chromatography separated this fraction into three components: a polysaccharide which was not retained on the column; RNA which eluted upon addition of salt; and, another polysaccharide which eluted upon addition of detergent. The unretained fraction was shown to be composed solely of D-mannose. The mannan, which was heterodisperse on Sephadex G-100, had an average molecular weight of approx. 14 000 as based on analysis of reducing groups. The detergent-eluted material yielded arabinose and galactose upon acid hydrolysis. The arabinogalactan was excluded from Sephadex G-100 and Sephacryl S-200 molecular sieve columns, suggesting a molecular weight greater than or equal to 200 000. Cell fractionation studies showed the bulk of extractable polysaccharide was associated with a particulate fraction. Further determination of the cellular localization of the polysaccharide was accomplished by employing a specific antiserum prepared from rabbits immunized with the polysaccharide extract. The cell surface localization of the arabinogalactan was demonstrated by cell agglutination studies as well as immunocytochemical techniques using fluorescein and ferritin conjugated antibodies.

Polyamines in trypanosomatids

Polyamines were determined by n-butanol extraction and thin-layer chromatography in four trypanosomatids: Trypanosoma brucei (rat infection) and cultures of Crithidia fasciculata, Leptomonas sp., and Trypanosoma mega. All had putrescine and spermidine but no detectable spermine. Putrescine and spermidine levels were quantitated for extracts of leptomonas during the normal growth cycle. Spermidine values peaked 18 h before peak cell populations. Spermidine-putrescine ratios for all organisms were related to the presumed phylogeny of the group.

The structure of kinetoplast DNA. 1. The mini-circles of Crithidia lucilae are heterogeneous in base sequence

We have analysed limit digests of mini-circles from kinetoplast DNA of Crithidia luciliae by gel electrophoresis. Endonucleases HapII and AluI cut the circles into at least 37 and 21 fragments, respectively, and leave no circles intact. In both cases the added molecular weights of the fragments, estimated from mobility in gels, exceeds 18 X 10(6), i.e. more than 12 times the molecular weight of the mini-circle DNA. Endonucleases HindII + III, EcoRI and HpaI cut only part of the circles. These results show that the mini-circles are heterogeneous in base sequence. Different sequence classes are present in different amounts. DNA-DNA renaturation analysis of mini-circle DNA yields a complexity of about 3 X 10(6), i.e. twice the molecular weight on one mini-circle. The delta tm of native and renatured duplexes is about 1 degree C, showing that the sequence heterogeneity is a micro-heterogeneity. Electron microscopy, gel electrophoresis and sedimentation analysis show that the circles that are not cut by endonucleases HindII + III remain catenated in very large associations. These associations lack the 'rosette' structures and the long edge loops characteristic of intact kinetoplast DNA. This suggests that the mini-circle classes cut by endonucleases HindII + III are present throughout the network and that the maxi-circle component of the network (see accompanying paper) is not essential to hold the network together. Prolonged electrophoresis on 1.5% or 2% agarose gels resolves the open mini-circles into three and linearized mini-circles into four bands, present in different amounts. We conclude that the mini-circles are also heterogeneous in size, the difference in size between the two extreme size classes being 4% of the contour length. Digestion with endonuclease HapII shows that at least three out of these four bands differ in sequence. Possible mechanisms that could account for the micro-heterogeneity in sequence of mini-circles are discussed.

The structure of kinetoplast DNA. 2. Characterization of a novel component of high complexity present in the kinetoplast DNA network of Crithidia luciliae

1. Degradation of highly purified kinetoplast DNA (kDNA) networks with restriction endonucleases yields "extra" bands in agarose gels that are absent from digests of mini-circles. Each of the five endonucleases tested, i.e. AluI, HapII, EcoRI, Hsu and HindII + III, yields a unique set of "extra" bands. The "extra" bands consist of linear DNA; they are not mini-circle oligomers and their added molecular weight, calculated from mobility in gels, are around 2 X 10(7). Double digests with two restriction endonucleases yield a new set of "extra" bands, showing that the "extra" bands obtained with different enzymes are all derived from the same complex component of kDNA. In digests of 32P-labelled kDNA an average of 2.3% of the radioactivity is recovered in the "extra" bands. 2. Treatment of kDNA networks with the single-strand-specific S1 nuclease of Aspergillus oryzae preferentially releases a linear DNA with a molecular weight of 26 X 10(6), calculated from mobility in gels. We present evidence that the 'extra' bands obtained with restriction endonucleases are derived from this component. 3. DNA-DNA renaturation analysis of fragmented kDNA shows the presence of a minor complex component with a complexity of about 3 X 10(7), making up less than 10% of the total kDNA. 4. From these results we conclude that 3--5% of the kDNA consists of a homogeneous class of maxi-circles catenated in the mini-circle network. The molecular weight of these maxi-circles is about 26 X 10(6) and they contain a unique, non-repetitive, non-mini-circle nucleotide sequence. This component is a prime candidate for the true mitochondrial DNA of trypanosomes.

O2'-Methylinosine, a constituent of the ribosomal RNA of Crithidia fasciculata

A novel nucleoside, O2'-methylinosine (Im), has been identified as a constituent of the ribosomal RNA of Crithidia fasciculata, a hemoflaggelate protozoan. The nucleoside is released as part of an alkali-stable dinucleotide, Im-Up, by alkaline hydrolysis of Crithidia rRNA, and as a 5'-nucleotide, pIm, by snake venom hydrolysis of the same RNA. The Im-containing derivatives isolated from Crithidia rRNA were characterized by comparison with marker compounds prepared by chemical deamination of the corresponding adenosine analogues. O2'-Methylinosine prepared from either natural Im-Up or natural pIm had the same ultraviolet absorption spectra and chromatographic properties as marker Im. Characterization of the base and sugar components of Im as hypoxanthine and 2-O-methylribose, respectively, provided final confimration of structure. Control experiments have eliminated the possibility that Im arises from O2'-methyladenosine (Am), a known constituent of ribosomal RNA, by chemical or enzymatic deamination during hydrolysis of Crithidia rRNA.

Trypanosoma lewisi, Trypanosoma rhodesiense: mitotic activity in normal and folic acid deficient rats

Ten experiments were performed to compare mitotic activity in livers of rats infected with Trypanosoma rhodesiense and Trypanosoma lewisi. The host dietary groups were: (1) complete of full complement; (2) folic acid deficient, and (3) pair-fed or calorically restricted. Liver mitotic counts of T. lewisi-infected rats fed complete and pair-fed control diets showed a high degree of significance over that of control rats. From days 35 to 55, liver mitotic counts of T. lewisi-infected rats deficient in folic acid showed an average of 16 +/- 2 mitotic phases as compared to 9 +/- 2 for livers of uninfected animals. Liver mitotic counts of T. rhodesiense-infected and non-infected rats fed complete and pair-fed control diets showed that there were essentially no differences in the mitotic counts from that seen in liver from control, uninfected animals. On day 25 (day 5 of infection), folic acid-deficient infected rats showed a significantly higher number of dividing cells than the controls. Folate was measured in isolated, washed T. lewisi and T. rhodesiense cells. T. lewisi and T. rhodesiense contained 9.6 ng folate per 10(8) cells and 6.2 ng of folate per 10(8) cells respectively. Metabolic products of T. lewisi contained an average of 0.51 ng of folate per 10(8) trypanosomes. T. rhodesiense metabolic products contained 0.3 ng of folate per 10(8) trypanosomes.

Cell volume and DNA content of Trypanosoma lewisi and T. mega in vitro

Two species of trypanosomes were harvested at a comparable stage in vitro development, just as cell division was ceasing and cell length had become maximal and its variability minimal. At this stage, T. mega displayed both a larger cell volume than T. lewisi (27.5 vs. 14.3 mu-2) and a greater DNA content (0.23 vs. 0.048 pg/cell).