The purpose of this study was to evaluate the effects of 6 weeks of low-intensity continuous exercise training (CE; 40 min at 50% VO2peak, 3 days/week) and high-intensity interval exercise training (IE: 10 x 2 min at VO2peak, 3 days/week) on the parameters of the power-endurance time relationship for cycle ergometry. The hyperbolic relationship between power and endurance time was linearized by expressing the power against the inverse of time, as described by Whipp et al. (22). This model consists of two parameters: theta f, a fatigue threshold reflecting the capability for sustained aerobic power, and W', a constant postulated to reflect a finite energy store (i.e., those factors comprising the O2 deficit: Phosphagen stores, anaerobic glycogenolysis, myoglobin O2 stores). Prior to training, test-retest reliability coefficients (r2) for theta f and W' were 0.92 and 0.62, respectively (P less than 0.01). Training resulted in significant (P less than 0.01) increases in theta f for both CE [27 +/- 3 W (13.4%) increase] and IE [33 +/- 5 W (15.0%) increase], with no difference between groups. Increases in theta f were not dependent upon improvements in VO2peak. W' was not changed significantly in either group after training. However, a significant negative correlation between the training-induced changes in theta f and W' (R = 0.76; P less than 0.01) was obtained. The minimum intensity threshold for exercise training necessary to elicit increases in theta f has yet to be identified, but is at least as low as 50% of VO2peak.

Kinetic and chemical analysis show that the haploid genome of Leishmania donovani has between 4.6 and 6.5 X 10(7) Kb pairs of DNA. Cot analysis shows that the genome contains 12% rapidly reassociating DNA, U3% middle repetitive DNA with an average reiteration frequency of 77 and 62% single copy DNA. Saturation hybridization experiments show that 0.82% of the nuclear DNA is occupied by rRNA coding sequences. The average repetition frequency of these sequences is determined to be 166. Sedimentation velocity studies indicate the two major rRNA species have sedimentation values of 26S and 16S, respectively. The arrangement of the rRNA genes and their spacer sequences on long strands of purified rDNA has been determined by the examination of the structure of rRNA:DNA hybrids prepared for electron microscopy by the gene 32-ethidium bromide technique. Long DNA strands are observed to contain several gene sets (16S + 26S). One repeat unit contains the following sequences in the order given: (a) A 16S gene of length 2.12 Kb, (b) An internal transcribed spacer (Spl) of length 1.23 Kb, which contains a short sequence that may code for a 5.8S rRNA, (C) 26S gene with a length of 4.31 Kb which contains an internal gap region of length 0.581 Ib, (d) An external spacer of average length 5.85 Kb.

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