Effects of autoclaving and charcoal on root-promoting substances present in water extracts made from gelling agents

The root-promoting ability of water extracts made from gelling agents (agar and Gelrite) was investigated using the mungbean rooting bioassay. Autoclaving these water extracts decreased the number of roots in mungbean cuttings compared to the controls. The addition of activated charcoal to the water extracts from Agar Bacteriological and Agar Commercial Gel had no effect on their root-promoting ability. Extracts with exogenous indole-3-butyric acid (IBA) which were treated by autoclaving or via a freeze-thaw cycle, significantly increased rooting. However, incorporation of activated charcoal to similar IBA-containing extracts reduced rooting. Our results indicate that more attention should be given to the choice of gelling agent and its interaction with other additives in the media used during tissue culture.

Exercise promotes a subcellular redistribution of calcium-stimulated protease activity in striated muscle

The aims of this study were (i) to investigate whether the contractile activity associated with running increases calcium-stimulated, calpastatin-inhibited protease activity (calpain-like) in a time-dependent manner and (ii) to determine whether the changes, if any, are proportionately distributed between soluble (cytosolic) and particulate (bound) fractions of striated muscle in vivo. Calcium-dependent, calpastatin-inhibited caseinolysis (i.e., calpain-like activity) was measured in control and exercised rats (25 m/min, 0% grade) at 2, 5, 15, 30, and 60 min. Total calpain-like activity in skeletal muscle increased by 26% (13.2 +/- 1.3 vs. 17.9 +/- 2.2 U/g wet wt.) (p < 0.05) after running (60 min), accompanied by an increased activity in the particulate fraction. In cardiac muscle, exercise (60 min) increased total calpain-like activity by 33% (p < 0.05), which was attributable to increases in both the cytosolic and particulate fractions. Both tissues responded with an early (2-5 min) activation of total calpain-like activity (p < 0.05), supported by early increases for particulate fractions from skeletal muscle; whereas for cardiac muscle, a noticeable early drop (p < 0.05) occurred in the particulate fraction. Minimal changes were observed for total, cytosolic, and particulate fractions of noncontracting tissue (i.e., liver). The results of this study support the hypothesis that the total calpain-like activity increases associated with level running occur early on with exercise and that the increases are accompanied by changes in the redistribution of soluble to particulate fractions. The changes would set the stage for enhanced rates of protein degradation known to occur in striated muscle with exercise.

A calcium stimulated cysteine protease involved in isoproterenol induced cardiac hypertrophy

The purpose of this study was to test the relationship between biochemical and functional changes accompanying beta-agonist induced cardiac hypertrophy and the activation of a calcium stimulated cysteine protease. Because the ultrastructural and ionic changes accompanying beta-agonist induced cardiac hypertrophy are reminiscent of the actions of the calcium activated neutral protease, calpain, it was hypothesized that lowering calpain activity (by the use of an exogenous inhibitor(s)) would reduce the extent of hypertrophy. Rats (275-300 g) were randomly assigned to either a control, beta-agonist (iso) or cysteine protease inhibitor (E64c) group. Isoproterenol administration (1 mg/kg) resulted in changes for ventricular weight to body weight ratio (increases 19%), ventricular [RNA] (increases 105.6%), rate of pressure development (increases 22% for +dP/dt) and maximum developed left ventricular pressure (increases 19%) (p < 0.05) after 3 days. Calpain-like activity (assessed by microplate method) increased by 45% (p < 0.05), while [cAMP] returned to control levels (following a transient rise at 1 day; 606.03 +/- 124.1 pmol/g/wet/wt to 937.9 +/- 225 (p < 0.05)). E64c (administered 1 h prior to iso) reduced the extent of hypertrophy, from 19 to 12%, and prevented the increases in; total [RNA], left ventricular function, the initial [cAMP] increase and calpain-like activity. It is concluded that a calcium stimulated cysteine protease(s), such as calpain, may be involved in the biochemical and functional changes associated with isoproterenol induced cardiac hypertrophy.

Heart, liver, and skeletal muscle myeloperoxidase activity during exercise

The purpose of this study was to determine whether contractile activity associated with running exercise was a prerequisite for neutrophil infiltration into rat tissues. H2O2-dependent myeloperoxidase (MPO) activity for rat (n = 8) liver, heart, and gastrocnemius muscles was assayed after 58 +/- 11 min of running to voluntary exhaustion (25 m/min; 0% grade). MPO activity values measured with 0.6 mM H2O2 were 0.988 +/- 0.331 (SD) U/g (skeletal muscle), 1.563 +/- 0.303 U/g (heart), and 1.652 +/- 0.510 U/g (liver) for control samples, compared with 1.690 +/- 0.321, 3.128 +/- 1.221, and 2.752 +/- 0.437 U/g, respectively, for the exercise group (P < or = 0.05). Kinetic analysis revealed that maximum velocity for all tissues increased as a result of the exercise (P < 0.05). The Michaelis constant (Km) values at rest for all tissues were similar (range 0.53-0.57 mM H2O2; P > or = 0.05). Exercise did not alter the Km values for cardiac and liver samples; however, for skeletal muscle, the Km was 28% lower than control (P < or = 0.05). The results of this study show that, with prolonged running, MPO activity is elevated in most rat tissues and not exclusively in skeletal muscle. Moreover, the metabolic status of the tissues may be an important factor for neutrophil infiltration with exercise and not exclusively the type of muscle contraction, as previously hypothesized.