Substituted dipyridophenazine complexes of Cr(III): synthesis, enantiomeric resolution and binding interactions with calf thymus DNA.

[Cr(phen)(2)(X(2)dppz)](3+) {X = H, Me, or F} have been synthesised, characterised, and chromatographically resolved into their constituent Delta and Lambda enantiomers. The DNA-binding interactions of each of the racemic complexes were investigated, with the results of linear dichroism, thermal denaturation, and emission quenching studies indicative of intercalative binding to CT-DNA with a significant electrostatic contribution. UV/Vis absorption titrations suggest strong DNA binding by each of the racemic complexes, with the methylated analogue [Cr(phen)(2)(Me(2)dppz)](3+) exhibiting the largest equilibrium binding constant. Emission quenching and UV-Vis titrations of the enantiomers of [Cr(phen)(2)(dppz)](3+) imply similar binding affinities for the Delta and Lambda isomers, although significant differences between the circular dichroism spectra of the enantiomers in the presence of DNA connote differences in binding orientation and/or conformation between the two.

Anion directed assembly of a dinuclear double helicate.

The synthesis and structural characterisation of the diamino-bis-pyridine ligand L2 and its diammonium-bispyridinium salt [(H4L2Cl)2].6Cl.H2O 1, are reported; X-ray diffraction studies reveal that chloride coordination causes the latter to adopt a double-helicate structure in the solid-state.

The South African Defence Force physical training programme. Part I. Effect of 1 year's military training on endurance fitness.

The effect of the South African Defence Force's (SADF) military training on the endurance fitness of recruits was investigated. Pre-military training maximal O2 consumption (53,14 ml/kg/min) did not change significantly during the study. In contrast, lactate turnpoint (ml O2/kg/min) and treadmill performance time were moderately enhanced (7,5% and 8% respectively; P less than 0,05) by the initial 10-week basic training programme. Further analysis of the results showed this endurance-training effect to be limited to recruits of average and, in particular, below-average fitness. The salutary effect of basic training on fitness levels was, however, transient, the values on completion of 1 year's military training being unaltered from those before conscription. This preliminary assessment of the SADF physical training programme suggests a need for the introduction of changes during and, in particular, after basic training.

The South African Defence Force physical training programme. Part II. Effect of 1 year's military training on muscular strength, power, power-endurance, speed and flexibility.

The effect of the South African Defence Force (SADF) military training on recruits' muscular strength, power, power-endurance, speed and flexibility was investigated. In the entire study group, a significant enhancement by basic training was observed for the isokinetic muscular strength of the right elbow extensors alone (17% increase; P less than 0,05). Stratification of training responses on the basis of initial fitness levels revealed significant improvements with basic training for all measures of muscular strength, power, power-endurance and speed, but not flexibility, in the below-average fitness recruit. For all variables the training effect was transient and values documented on completion of 1 year's military training differed insignificantly from those recorded before conscription. In contrast, with the exception of elbow extensor muscular strength, fitness levels of the average and above-average recruits were not increased by basic training. While further research to assess physical requirements of various military work and emergency situations is needed to evaluate the desirability of this observed selective enhancement of recruit fitness levels during basic training, it is evident that greater emphasis should be placed on flexibility training, and physical conditioning after basic training.

Thermoregulatory responses to weight training.

Thermoregulatory responses of eight healthy males (age 25.5 +/- 4.5 yrs) were studied during weight training comprising 3 sets of 15 repetitions of 9 exercises performed at a work cadence of 15 repetitions.min-1 with 1-min recovery intervals. The load for each exercise was increased from 50% of the 15-repetition maximum for the first set to 75% and 100% for the second and third sets, respectively. The thermoregulatory response was characterized by only moderate sweat rates (0.69 +/- 0.18 l.h-1) and rectal temperature rises (1.3 degree +/- 0.4 degree C, P less than 0.001), suggesting that dehydration and hyperthermia are unlikely to complicate weight training of the format used in this study. Despite a considerable lactic acidosis, small elevations in serum levels of aspartate aminotransferase and lactate dehydrogenase occurred, the core temperature rise being inadequate for significant cellular damage to ensue. Serum electrolyte levels measured immediately and 24 h post-exercise indicated that electrolyte supplementation is unlikely to be of benefit. Weight training induced a marked reduction of plasma volume (11.8% +/- 3.7%, P less than 0.001) in the presence of a minor water deficit (0.8% +/- 0.23%) and an O2 consumption of 32% +/- 8% of the predetermined treadmill exercise maximal O2 consumption. This finding suggests that exercise intensity as assessed by percentage maximal voluntary contraction rather than percentage maximal O2 consumption might determine the degree of hemoconcentration encountered during exercise.

Effect of beta-adrenoceptor blockade on thermoregulation during prolonged exercise.

The effect of clinically used equipotent doses of nonselective (beta 1/beta 2; propranolol) and selective (beta 1; atenolol) beta-adrenoceptor blockers on thermoregulation was studied during prolonged exercise in the heat. Oral propranolol (160 mg/day), atenolol (100 mg/day) or matching placebo were taken for 6 days each by 11 healthy young adult caucasian males. Subjects participated in 2 h of block-stepping at a work rate of 54 W in an environmental chamber with a temperature of 33.2 +/- 0.3 degree C dry bulb and 31.7 /+- 0.3 degree C wet bulb, 2 h after ingestion of the final dose of each drug. Both active agents produced similar marked (P less than 0.001) increases in subjective perception of effort, the mechanism of which was not immediately evident from changes in serum electrolytes, blood glucose, blood lactate, or ventilatory parameters. Propranolol did, however, cause a greater rise in serum K+ than placebo (P less than 0.02) and atenolol (P = NS) after exercise. Although rectal and mean skin temperatures were insignificantly altered by beta-adrenoceptor blockade, an increased total sweat production was noted with propranolol (P less than 0.01 vs. placebo) and to a lesser degree atenolol (P = NS vs. placebo) therapy. Analysis of the time course of sweat production showed the propranolol-mediated enhancement of sweating to ensue largely during the initial hour of block-stepping and to be transient in nature. The scientific and clinical implications of this observation will be dependent upon the precise underlying mechanism, a factor not identified by the present study.

Improved exercise ventilatory responses after training in coronary heart disease during long-term beta-adrenergic blockade.

Exercise ventilatory responses of 7 men with well-documented myocardial infarction receiving long-term beta-adrenergic blockade were studied before and after 4 months of endurance training. Observations were obtained during graded levels of upright treadmill exercise continued until 85% of the predetermined symptom-limited heart rate (working heart frequency limit). This submaximal testing procedure revealed a significant slowing of the heart rate (p less than 0.005) together with an increased oxygen pulse (p less than 0.05) after training, for what was previously a maximal work load for the working heart frequency limit. In addition, all patients achieved an increased exercise duration and work load, accompanied by significant increases in maximal oxygen uptake (p less than 0.01), oxygen pulse (p less than 0.025), and respiratory exchange ratio, for their working heart frequency limit after exercise conditioning. These results show that prolonged physical training results in physiologic adaptations to cardiac rehabilitation in the presence of long-term beta-adrenergic blockade.

Effects of caffeine ingestion on thermoregulatory and myocardial function during endurance performance.

The effect of caffeine administration on thermoregulatory and myocardial function during endurance performance was studied. A caffeine solution (250 ml; 5 mg caffeine/kg body weight) ingested 1 hour prior to 2 hours of running by 5 subjects was shown to have no significant effect on sweat loss, water deficit, percentage change in plasma volume, final rectal temperature and serum electrolyte levels, as compared with a similar control group who were given a caffeine-free drink. The rectal temperatures in both groups did, however, reach levels known to be associated with heatstroke despite a recommended regimen of fluid replacement. No pathological electrocardiographic changes occurred in either group. It is therefore concluded that the use of caffeine for ergogenic purposes by young athletes is a relatively safe procedure.