Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.     

The effect of metabolic acid-base changes on the ventilatory changes at the end of heavy exercise

The purpose of this study was to determine the effect of altered metabolic acid-base status on the changes in ventilation in the transition from heavy exercise above anaerobic threshold to rest. Seven subjects ingested, in a randomized and blind manner, either NaHCO3 or CaCO3 (placebo) at a dose of 300 mg.kg-1 body mass and ran on a treadmill for five minutes (90% VO2max and above anaerobic threshold) on ten different occasions. Changes in minute ventilation in the exercise transitions were studied by starting and stopping the treadmill abruptly with a remote switch. The fast increase in ventilation at the start of exercise was not accompanied by a corresponding fast drop in ventilation at the end of exercise (P less than or equal to 0.001) and the effects of chemicals on these changes were not significantly different (P greater than 0.05). A single-component exponential model, without a time delay, was used to determine the time constants of off-transitional decay in ventilation for the two chemicals in each subject. Parametric and non-parametric statistical tests revealed that the time constants were not as significantly different as the venous pH measurements which were significantly higher with NaHCO3 (P less than or equal to 0.001). The results indicate that the absence of fast change in ventilation at the end of heavy exercise is not due to lactic acidosis and the consequent slow ventilatory changes in the off-transition of heavy exercise are at least partly mediated by non-humoral factors such as a central neural reverberatory mechanism.