Two methyl ester derivatives of microcystins, cyclic heptapeptide hepatotoxins, isolated from Anabaena flos-aquae strain CYA 83/1.

Cultured cells of Anabaena flos-aquae strain CYA 83/1, isolated from Lake Edlandsvatn, Norway, produced two microcystin mono-methyl ester derivatives (1 and 2) at the D-Glu unit in addition to microcystin-LR (3), [D-Asp3]microcystin-LR (4), microcystin-RR (5), and [D-Asp3]microcystin-RR (6). Structures of these compounds were assigned based on their amino acid analysis with a Waters Pico Tag HPLC system plus fast atom bombardment mass spectrometry (FABMS), including tandem FABMS, analysis on the two new microcystins, [D-Glu(OCH3)6]microcystin-LR (1) and [D-Asp3, D-Glu(OCH3)6]microcystin-LR (2). Toxicity data were not obtained for 1 and 2 because of the small amounts isolated from the cells.     

The assessment of the static component in rhythmic exercise

A new approach has been devised to assess the “static component” of dynamic exercise. This technique involves the measurement of the isometric endurance of muscles which have just taken part in rhythmic exercise and depends on the repeatability of trained subjects in isometric effort. The premise is that isometric endurance will be inversely related to the static component of the preceding dynamic exercise. The subjects worked on a bicycle ergometer at known fractions of their maximal aerobic capacity (max \(\dot V_{O_2 } \) ). The rate of pedalling was varied from 30 to 90 rpm, so that for a given % max \(\dot V_{O_2 } \) , the belt tension varied inversely with the speed of cycling. At any one speed of cycling, isometric endurance decreased as the belt tension increased. Following exercise at 30 rpm, the isometric endurance was 25 to 50% lower than that found at the most advantageous speed of cycling for our subjects; at these faster rates of cycling two subjects showed least static component following exercise at 90 rpm while the remaining subject performed best after cycling at 50 rpm.     

Isometric fatigue induced by different levels of rhythmic exercise

Summary Three subjects were trained in leg extensor isometric contractions and in cycling. They then cycled for three consecutive bouts, each of 2.75 min at a constant level of , from 20 to 80% max. Fifteen seconds after each bout of cycling the subjects exerted an isometric contraction of the right leg at 40% of the maximum voluntary contraction. In each experiment, the duration of the three successive isometric contractions decreased as in hand-grip contractions. There was also a linear reduction in isometric endurance as the severity of the preceding rhythmic exercise increased. In other experiments, after three bouts of rhythmic exercise at 20% max (each followed by a fatiguing contraction at 40% MVC), further bouts of cycling at increasing levels of severity up to 60% max resulted in a linear fall in isometric endurance which could be reversed by interposing a lighter level of cycling. The heart rates during these experiments showed a steady increase during the isometric exercise, to about 150 beats·min⁻¹, as the bouts of preceding rhythmic exercise became progressively more severe. The isometric contractions had little influence on the heart rate during cycling. But the rhythmic cycling exercise markedly increased the heart rate achieved at the end of the isometric contractions while decreasing theincrement in heart rateduring the contraction. Supported by HEW Contract HSM 99-71-21, and U.S.N. Grant N00014-77-0640     

Microfilament and microtubule function in human monocytes

The functions of microfilaments and microtubules in human monocytes were examined by exposing peripheral blood monocytes to cytochalasin B, a microfilament inhibitor, and to colchicine, an antitubulin. Cytochalasin B, 10 microgram/ml, inhibited all monocyte functions tested: chemotaxis was reduced by 96% of control levels (p less than 0.01), random mobility by 88% (p less than 0.01), candidacidal activity by 57% (p less than 0.01), and phagocytosis by 34% (p less than 0.01). Monocyte adherence was also significantly reduced (by 65%). Colchicine, 10 microgram/ml, significantly reduced monocyte chemotaxis by 39% (p less than 0.01) and random mobility by 59% (p less than 0.01), but phagocytosis and candidacidal activity were not diminished at 0.1 to 100 microgram/ml. Monocyte adherence was modestly decreased (46%) by 10 microgram/ml of colchicine. Thus, cytochalasin B, a microfilament inhibitor, reduced all five functions tested. In contrast, colchicine, an antitubulin, inhibited only chemotaxis, random mobility, and adherence. These data suggest that in monocytes (1) microfilaments are the structural element of cell membrane and cytoplasm required for most cellular functions and (2) microtubules facilitate membrane surface interaction in chemotaxis, random mobility, and adherence.     

Evaluation of the chronic inhalation toxocity of a manganese oxide aerosol. II. Clinical observations, hematology, clinical chemistry and histopathology.

Monkeys and rats were exposed to 11.6, 112.5, or 1152 microgram Mn/m3 as an Mn3O4 aerosol twenty-four hours per day for nine months. Various serum biochemical, and hematologic evaluations were conducted on both specie. Body weight gain was accelerated in rats exposed to 1152 microgram Mn/m3. Hemoglobin concentrations were slightly elevated for both sexes and both specie exposed to 1152 microgram Mn/m3; however, the effect may not be directly related to Mn. Some evidence of hypophosphatemia was observed. No exposure related effects were demonstrated by organ weight or histopathologic observations.