cAMP, Ca2+, pHi, and NO Regulate H-like Cation Channels That Underlie Feeding and Locomotion in the Predatory Sea Slug Pleurobranchaea californica

A systems approach to regulation of neuronal excitation in the mollusc Pleurobranchaea has described novel interactions of cyclic AMP-gated cation current (INa,cAMP), Ca2+, pHi, and NO. INa,cAMP appears in many neurons of feeding and locomotor neuronal networks. It is likely one of the family of hyperpolarization-activated, cyclic-nucleotide-gated currents (h-current) of vertebrate and invertebrate pacemaker networks. There are two isoforms. Ca2+ regulates both voltage dependence and depolarization-sensitive inactivation in both isoforms. The Type 1 INa,cAMP of the feeding network is enhanced by intracellular acidification. A direct dependence of INa,cAMP on cAMP allows the current to be used as a reporter on cAMP concentrations in the cell, and from there to the intrinsic activities of the synthetic adenyl cyclase and the degradative phosphodiesterase. Type 2 INa,cAMP of the locomotor system is activated by serotonergic inputs, while Type 1 of the feeding network is thought to be regulated peptidergically. NO synthase activity is high in the CNS, where it differs from standard neuronal NO synthase in not being Ca2+ sensitive. NO acidifies pHi, potentiating Type 1, and may act to open proton channels. A cGMP pathway does not mediate NO effects as in other systems. Rather, nitrosylation likely mediates its actions. An integrated model of the action of cAMP, Ca2+, pHi, and NO in the feeding network postulates that NO regulates proton conductance to cause neuronal excitation in the cell body on the one hand, and relief of activity-induced hyperacidification in fine dendritic processes on the other.

A tabletop exercise to assess a hospital emergency blood management contingency plan in a simulated acute blood shortage

The objective was to assess both our local plan and the assumptions made in the national guidelines on how laboratories should prepare for an acute shortage of red cells. The Chief Medical Officer's National Blood Transfusion Committee for England and North Wales has issued guidance on how hospitals should prepare contingency plans to deal with a shortage of red cells for transfusion. This study has therefore assessed the practicalities of these proposals together with assessing how well local policies would deal with this situation. A tabletop exercise was carried out in which all requests over a 21-day period were assessed. The restrictions as suggested by the national blood transfusion committee were applied and the impact on the blood stocks during an acute blood shortage was assessed. The results show that application of the national guidelines on the restriction of the use of red cells during an acute blood shortage resulted in all transfusion requests for red cells being met. We also appear to have shown that the assumptions made by the national transfusion team are realistic. Carrying out a tabletop exercise is a useful method to assess local procedures for dealing with an acute reduction in the supply of red cells.