The phase-resetting response of a model of spontaneously active cardiac Purkinje fiber is investigated. The effect on the interbeat interval of injecting a 20-ms duration depolarizing current pulse is studied as a function of the phase in the cycle at which the pulse is delivered. At low current amplitudes, a triphasic response is recorded as the pulse is advanced through the cycle. At intermed...

Activity-dependent specification of neuronal architecture during early postnatal life is essential for refining the precision of communication between neurons. In the spinal cord under normal circumstances, the AMPA receptor subunit GluR1 is expressed at high levels by motor neurons and surrounding interneurons during this critical developmental period, although the role it plays in circuit for...

Animal communication theory holds that many signals have evolved from nonsignal precursors. This field and laboratory study of California ground squirrels (Spermophilus beecheyi) provides evidence for the coexistence of such a precursor with its derived display. The precursor is an ancient, endogenously sequenced (syntactic) pattern of cephalocaudal grooming movements (CCGs) shared by all roden...

This report describes the clinical course of a patient with bradycardia and tachycardia-dependent atrioventricular block. Bradycardia dependent A-V block (phase 4 block) was transient and precipitated by spontaneous slowing of the sinus rate, atrial and ventricular extrasystoles; The degree of slowing (critical RP interval) required to induce A-V block increased progressively over a three-day p...

Paraffin oil droplets containing Oil Red 0 and coated with Escherichia co/i lipopolysaccharide were ingested rapidly by human peripheral blood phagocytes only if they were pretreated with normal serum. This property formed the basis of a screening test in which lipopolysaccharide-coated particles were opsonized with patients’ serums and then were added to autologous leukocytes suspended in two ...

Relational governance works well in relatively small communities, which may be too small to allow perfect competition. This paper explores this idea using two models. In a spatial model with monopolistic competition, relational governance constrains the size of firms and can lead to inefficiently excessive entry. In a model where high quality is self-enforcing because its providers get a suffic...