Prominent location of a K+ channel containing the alpha subunit Kv 1.2 in the basket cell nerve terminals of rat cerebellum.

A panel of monoclonal antibodies specific for a family of voltage-dependent, fast-activating K+ channels, raised against alpha-dendrotoxin acceptors purified from bovine brain, were used to probe the distribution of these important proteins in rat cerebellum. All the antibodies reacted with their antigens in the folial white matter, the granular cell layer and the basket cell nerve termini within the Purkinje cell layer. However, a very intense staining pattern was exhibited by only one monoclonal that reacts exclusively with Kv 1.2 alpha subunit, the predominant isoform present in alpha-dendrotoxin sensitive K+ channels. Double-labelling procedures with neuronal and glial markers were used to verify this discrete antibody staining of the basket cell terminals that synapse with the base of Purkinje cell bodies in a readily recognizable and characteristic fashion. This is the first direct demonstration, using a monoclonal antibody, of a presynaptic location for a voltage-activated K+ channel; its discrete distribution in the basket cell pinceau suggests that it could control release of the inhibitory transmitter GABA and, thereby, influence excitability of Purkinje cells in the cerebellum.

Late angiographic follow-up after successful coronary arterial thrombolysis and angioplasty during acute myocardial infarction.

Emergency percutaneous transluminal coronary angioplasty (PTCA) is accepted as an important reperfusion intervention for acute myocardial infarction (AMI). Although its primary success rate is well documented, the frequency of restenosis after this procedure is unclear. The frequency of restenosis was determined in patients undergoing emergency PTCA at least 6 months after PTCA was performed during AMI. Of 66 consecutive patients undergoing emergency PTCA, 25 had a second, elective catheterization at an average of 22 months after AMI and 6 underwent repeat catheterization because of recurrent chest pain. Restenosis of the PTCA site was found in 10 of the 31 patients (32%) restudied. Also, 14 (45%) of these 31 patients showed progression of narrowing in the non-infarct-related coronary arteries. In summary, patients in whom AMI is treated by PTCA are at risk for restenosis and for progressive narrowing of the non-infarct artery.

Ultrastructural localization of a voltage-gated K+ channel alpha subunit (KV 1.2) in the rat cerebellum.

A highly specific monoclonal antibody and pre-embedding immunocytochemistry were employed to examine the distribution of the K+ channel, alpha subunit K(V)1.2 in the rat cerebellum. At the light microscopic level, the heaviest immunoreactivity was seen in the basket cell pinceau at the base of Purkinje cells, with lighter staining of basket and Golgi cell bodies and a punctate pattern in the granule cell and molecular layers. Electron microscopy was performed to identify the ultrastructural location of K(V)1.2 alpha subunit in these labelled structures. This revealed that the labelling of the pinceau was confined to the preterminal axonal plexus, the area immediately around the Purkinje axon initial segment being relatively devoid of staining. Basket cell parent axons were not immunostained, but gave rise to heavily stained fine processes. Immunoreactivity was also seen in myelinated axons in the granule cell layer and in the medial cerebellar nucleus, the staining being most concentrated at the juxtaparanodal regions of the axons. An unusual pattern of staining was seen in some mossy fibre terminals, with staining restricted to fine protuberances of mossy fibre glomeruli. Structures contacted by these protuberances included adjoining glial processes. Immunostaining was absent from Purkinje cell bodies, dendrites, their axon initial segments and their terminals in the medial cerebellar nucleus. In this study, the alpha subunit K(V)1.2 was localized to a number of different cell types in the cerebellum. Each neuronal type displays a distinct subcellular distribution of the subunit.