A guanine nucleotide regulatory protein controls polyphosphoinositide metabolism, Ca2+ mobilization, and cellular responses to chemoattractants in human monocytes

Previous studies demonstrated that oligopeptide chemoattractant receptors on PMN and macrophages exist in high and low affinity states which are interconvertible by guanosine di- and triphosphates. These observations suggest that guanine nucleotide regulatory (N) proteins play a role in phagocyte activation by chemotactic factors. The data presented here indicate that chemotactic factor receptors on monocytes utilize an N protein to activate phospholipase C and subsequent biologic responses by the cells. This conclusion is based on the findings that inactivation of an N protein of 41,000 m.w. by Bordetella pertussis toxin (PT) treatment abolishes monocyte responsiveness to chemoattractants but not to lectins, PMA, or the Ca2+ ionophore A23187. Treatment with PT inhibited IP3 production, Ca2+ mobilization, and cellular activation as assessed by chemotaxis and changes in forward light scattering in response to the chemoattractants by at least 80%. Therefore, a PT-sensitive N protein plays an important role in the activation of monocytes by chemoattractants.     

Purification and characterization of a type II phosphatidylinositol 4-kinase from rat spleen and comparison with a PtdIns 4-kinase from lymphocytes.

A PtdIns 4-kinase from rat spleen particulate fraction was purified to homogeneity and its molecular properties were compared with a PtdIns 4-kinase from splenic lymphocytes. The enzyme activity was solubilized from spleen particulate fraction with Triton X-100 and chromatographed sequentially on phosphocellulose, DEAE-sephacel, heparin acrylamide and hydroxyapatite columns. The purified enzyme preparation showed a 55 kDa band on SDS-PAGE with silver staining. Renaturation of the enzyme activity from SDS-PAGE showed that it comigrated with the 55 kDa protein. Characterization of the enzyme showed that it was a type II PtdIns 4-kinase. Polyclonal antibodies raised against PtdIns 4-kinase inhibited the enzyme activity in in vitro assays. Analysis of adult rat tissue particulate fractions on immunoblots showed restricted immunoreactivity among PtdIns 4-kinases. However, the immunoreactivity is conserved in lymphoid tissues from mouse to human, suggesting that lymphoid tissue has a distinct PtdIns 4-kinase. Activation of rat splenocytes with Con A showed two fold increase in PtdIns 4-kinase activity. Comparison of PtdIns 4-kinases from spleen and splenic lymphocytes showed identical chromatographic behaviour, molecular mass, immunoreactivity, K(m) values for PtdIns and inhibition by adenosine.     

Metabolic acidosis and fatal myocardial failure after propofol infusion in children: five case reports.

OBJECTIVE--To examine the possible contribution of sedation with propofol in the deaths of children who were intubated and required intensive care. DESIGN--Case note review. SETTING--Three intensive care units. SUBJECTS--Five children with upper respiratory tract infections aged between 4 weeks and 6 years. RESULTS--Four patients had laryngotracheo-bronchitis and one had bronchiolitis. All were sedated with propofol. The clinical course in all five cases was remarkably similar: an increasing metabolic acidosis was associated with brady-arrhythmia and progressive myocardial failure, which did not respond to resuscitative measures. All children developed lipaemic serum after starting propofol. These features are not usually associated with respiratory tract infections. No evidence was found of viral myocarditis, which was considered as a possible cause of death. CONCLUSION--Although the exact cause of death in these children could not be defined, propofol may have been a contributing factor.