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.

Violation of homogeneity by the vestibulo-ocular reflex of the goldfish.

The vestibulo-ocular reflex (VOR) allows animals to maintain stable gaze during head rotations by generating compensatory eye rotations. The VOR is typically tested using sinusoidal head rotation, and VOR gain is calculated as the ratio of the amplitude of eye to head rotational velocity. Through habituation, prolonged exposure to lower frequency sinusoidal head rotation in the dark decreases VOR gain. The VOR has been treated and modeled as a linear system. If it is linear, then the VOR must obey the principle of homogeneity: VOR gain at a particular frequency should be the same regardless of head velocity. We examined the habituated goldfish VOR for homogeneity. We found that it violated this basic principle of linear systems and is therefore non-linear.

Serotonin immunoreactivity in the central nervous system of the marine molluscs Pleurobranchaea californica and Tritonia diomedea.

The central nervous systems of the marine molluscs Pleurobranchaea californica (Opisthobranchia: Notaspidea) and Tritonia diomedea (Opisthobranchia: Nudibranchia) were examined for serotonin-immunoreactive (5-HT-IR) neurons and processes. Bilaterally paired clusters of 5-HT-IR neuron somata were distributed similarly in ganglia of the two species. In the cerebropleural ganglion complex, these were the metacerebral giant neurons (both species), a dorsal anterior cluster (Pleurobranchaea only), a dorsal medial cluster including identified neurons of the escape swimming network (both species), and a dorsal lateral cluster in the cerebropleural ganglion (Pleurobranchaea only). A ventral anterior cluster (both species) adjoined the metacerebral giant somata at the anterior ganglion edge. Pedal ganglia had the greatest number of 5-HT-IR somata, the majority located near the roots of the pedal commissure in both species. Most 5-HT-IR neurons were on the dorsal surface of the pedal ganglia in Pleurobranchaea and were ventral in Tritonia. Neither the buccal ganglion of both species nor the visceral ganglion of Pleurobranchaea had 5-HT-IR somata. Afew asymmetrical 5-HT-IR somata were found in cerebropleural and pedal ganglia in both species, always on the left side. The clustering of 5-HT-IR neurons, their diverse axon pathways, and the known physiologic properties of their identified members are consistent with a loosely organized arousal system of serotonergic neurons whose components can be generally or differentially active in expression of diverse behaviors.

Cyclic AMP levels, adenylyl cyclase activity, and their stimulation by serotonin quantified in intact neurons.

In molluscan central neurons that express cAMP-gated Na+ current (INa,cAMP), estimates of the cAMP binding affinity of the channels have suggested that effective native intracellular cAMP concentrations should be much higher than characteristic of most cells. Using neurons of the marine opisthobranch snail Pleurobranchaea californica, we applied theory and conventional voltage clamp techniques to use INa,cAMP to report basal levels of endogenous cAMP and adenylyl cyclase, and their stimulation by serotonin. Measurements were calibrated to iontophoretic cAMP injection currents to enable expression of the data in molar terms. In 30 neurons, serotonin stimulated on average a 23-fold increase in submembrane [cAMP], effected largely by an 18-fold increase in adenylyl cyclase activity. Serotonin stimulation of adenylyl cyclase and [cAMP] was inversely proportional to cells' resting adenylyl cyclase activity. Average cAMP concentration at the membrane rose from 3.6 to 27.6 microM, levels consistent with the expected cAMP dissociation constants of the INa,cAMP channels. These measures confirm the functional character of INa,cAMP in the context of high levels of native cAMP. Methods similar to those employed here might be used to establish critical characters of cyclic nucleotide metabolism in the many cells of invertebrates and vertebrates that are being found to express ion currents gated by direct binding of cyclic nucleotides.

Serotonin-immunoreactivity in peripheral tissues of the opisthobranch molluscs Pleurobranchaea californica and Tritonia diomedea.

The distribution of serotonin (5-HT)-immunoreactive elements in peripheral organs of the sea-slugs Pleurobranchaea californica and Tritonia diomedea was studied in cryostat sections. For Pleurobranchaea, 5-HT-immunoreactive (5-HT-IR) neuron cell bodies were found only in the central nervous system (CNS); 5-HT-IR cell bodies were not observed in foot, tentacles, rhinophores, oral veil, mouth, buccal mass, esophagus, gills, salivary glands, skin, reproductive system, and acidic glands, nor in peripheral tentacle and rhinophore ganglia. However, 5-HT-IR neuronal processes were widely distributed in these structures and the patterns of 5-HT-IR elements were characteristic for each particular peripheral tissue. 5-HT-IR elements were most dense in the sole of the foot and the reproductive system, followed by rhinophores, tentacles, oral veil, mouth, buccal mass, and esophagus. The sensory epithelium of rhinophores, tentacles, and mouth showed a highly structured glomerular organization of 5-HT-IR fibers, suggesting a role for 5-HT in sensory signaling. A much lower density of 5-HT-IR innervation was observed in gills, skin, salivary, and acidic glands. 5-HT-IR was observed in neuropil of tentacle and rhinophore ganglia with many transverse 5-HT-IR axons running to peripheral sensory areas. The distribution of 5-HT-IR elements in Tritonia was similar to that of Pleurobranchaea. A significant suggestion of the data is that central serotonergic neurons may modulate afferent pathways from sensory epithelia at the periphery.

Cyclic AMP-gated sodium current in neurons of the pedal ganglion of Pleurobranchaea californica is activated by serotonin.

1. We studied the roles of adenosine 3',5'-cyclic monophosphate (cAMP) and cAMP-gated Na+ current (INa,cAMP) in the serotonin (5-HT)-induced excitation of putatively serotonergic "G" neurons of the pedal ganglion of Pleurobranchaea californica. Currents were recorded under voltage clamp during 5-HT application and iontophoretic intracellular cAMP injections. INa,cAMP responses to pulsed injections of cAMP were occluded by 5-HT-induced inward current (I5-HT). Occlusion was qualitatively and quantitatively similar to that observed during steady-state activation of INa,cAMP by tonic iontophoretic injection of cAMP. 2. Those neurons exhibiting occlusion of INa,cAMP during 5-HT application also exhibited depolarization-induced (Ca(2+)-dependent) inactivation of both INa,cAMP and I5-HT. The magnitudes of the inactivation to depolarizing pulses of I5-HT or INa,cAMP were similar. Recoveries from inactivation for I5-HT and INa,cAMP followed similar exponentially decaying time courses. 3. The decay rate of the INa,cAMP response is affected by phosphodiesterase inhibitors and can be taken as a sensitive measure of the rate of cAMP degradation. As background steady-state INa,cAMP was increased by larger tonic cAMP injections, the decay rate of super-imposed INa,cAMP responses to pulsed injections of cAMP was slowed as would be expected from saturation of endogenous phosphodiesterase activity. The decay of INa,cAMP responses to pulsed cAMP injections superimposed on I5-HT were similarly slowed, suggesting that 5-HT action is mediated specifically by cAMP. 4. The decay rate constants for INa,cAMP responses to pulsed injections of cAMP superimposed on I5-HT did not differ from those of INa,cAMP responses superimposed on equivalent, background steady-state INa,cAMP induced by tonic injection of cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP-activated Na+ current of molluscan neurons is resistant to kinase inhibitors and is gated by cAMP in the isolated patch.

The cAMP-dependent Na+ current (INa,cAMP) modulates excitability in many molluscan neurons. Rapid activation of INa,cAMP by cyclic nucleotide, its ion dependence, and its blockade by divalent cations resemble cyclic nucleotide-activated cation currents in vertebrate photoreceptors and olfactory receptors, where activation has been found to be independent of kinase activity. We tested the phosphorylation dependence of INa,cAMP in neurons of the feeding and locomotory networks of the predatory marine snail Pleurobranchaea. Identified neurons of pedal and buccal ganglia were axotomized for recording the INa,cAMP response to iontophoretic injection of cAMP under two-electrode voltage clamp. Intracellular injections of specific peptide inhibitor of protein kinase A had no blocking effects on activation of INa,cAMP by iontophoretic injection of cAMP. Inward single-channel currents were activated in excised inside-out patches during exposure to cAMP in salines without added ATP. Sodium was the major current carrying ion. Two distinct types of INa,cAMP channel activity were observed, where opening probability and open times differed, but conductance was similar, 36.7 pS. These observations suggest that INa,cAMP activation occurs by direct binding of cAMP to a regulatory site at the channel, rather than by phosphorylation.