Isoprenaline stimulation of perfused rabbit hearts was associated with simultaneous phosphorylation of proteins in the myofilaments and phospholamban in the sarcoplasmic reticulum (SR). Hearts were perfused with Krebs-Henseleit buffer containing [32P]Pi, freeze-clamped in a control condition or at the peak of the inotropic response to isoprenaline, and myofibrils and SR were prepared from the same hearts. Stimulation of 32P incorporation in troponin I (TnI) and C-protein by isoprenaline was associated with a decrease in Ca2+-sensitivity of the myofibrillar Mg2+-dependent ATPase activity. Stimulation of 32P incorporation in SR by isoprenaline was associated with an increase in the initial rates of oxalate-facilitated Ca2+ transport, assayed with SR vesicles in either microsomal fractions or homogenates from the perfused hearts. These findings provide evidence that phosphorylation of TnI, C-protein and phospholamban in the intact cell is associated with functional alterations of the myofibrils and SR which may be responsible in part for the effects of catecholamines on the mammalian myocardium.
Bacterial meningitis is a common cause of morbidity and mortality in children. The oxidative stress in bacterial meningitis is barely determined. Forty children with bacterial meningitis were studied for their oxidants and antioxidants status in serum and cerebrospinal fluid. Fever (95%) was commonest presentation followed by seizure and vomiting. Neck rigidity and Kernig's sign were present in 37.5% and 27.5% cases, respectively. Plasma and cerebrospinal fluid malondialdehyde, protein carbonyl and nitrite levels were significantly raised in cases (p < 0.001). Plasma and cerebrospinal fluid ascorbic acid, glutathione and superoxide dismutase levels were significantly decreased in children with septic meningitis (p < 0.001). Significantly elevated malondialdehyde, nitrite and protein carbonyl levels reflect increased oxidative stress, whereas decreased concentrations of glutathione, ascorbic acid and superoxide dismutase indicates utilization of the antioxidants in septic meningitis. Thus, changes in oxidants and antioxidants observed suggest production of reactive oxygen species and their possible role in pathogenesis of septic meningitis.
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