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<jats:p>Glial cell line-derived neurotrophic factor (GDNF) supports growth and survival of dopaminergic (DA) neurons. A replication-defective adenoviral (Ad) vector encoding human GDNF injected near the rat substantia nigra was found to protect DA neurons from the progressive degeneration induced by the neurotoxin 6-hydroxydopamine (6-OHDA) injected into the striatum. Ad GDNF gene therapy reduced loss of DA neurons approximately threefold 6 weeks after 6-OHDA lesion, as compared with no treatment or injection of Ad lacZ or Ad mGDNF (encoding a biologically inactive deletion mutant GDNF). These results suggest that Ad vector-mediated GDNF gene therapy may slow the DA neuronal cell loss in humans with Parkinson's disease.</jats:p>

<jats:p>Generally, impulse propagation in cardiac tissue is assumed to be impaired by a reduction of intercellular electrical coupling or by the presence of structural discontinuities. Contrary to this notion, the spatially uniform reduction of electrical coupling induced successful conduction in discontinuous cardiac tissue structures exhibiting unidirectional conduction block. This seemingly paradoxical finding can be explained by a nonsymmetric effect of uncoupling on the current source and the current sink in the preparations used. It suggests that partial cellular uncoupling might prevent the initiation of cardiac arrhythmias that are dependent on the presence of unidirectional conduction block.</jats:p>

<jats:p> Calcium signals were recorded from glial cells in acutely isolated rat retina to determine whether Ca <jats:sup>2+</jats:sup> waves occur in glial cells of intact central nervous system tissue. Chemical (adenosine triphosphate), electrical, and mechanical stimulation of astrocytes initiated increases in the intracellular concentration of Ca <jats:sup>2+</jats:sup> that propagated at ∼23 micrometers per second through astrocytes and Müller cells as intercellular waves. The Ca <jats:sup>2+</jats:sup> waves persisted in the absence of extracellular Ca <jats:sup>2+</jats:sup> but were largely abolished by thapsigargin and intracellular heparin, indicating that Ca <jats:sup>2+</jats:sup> was released from intracellular stores. The waves did not evoke changes in cell membrane potential but traveled synchronously in astrocytes and Müller cells, suggesting a functional linkage between these two types of glial cells. Such glial Ca <jats:sup>2+</jats:sup> waves may constitute an extraneuronal signaling pathway in the central nervous system. </jats:p>

<jats:p> Self-splicing group I introns, like other large catalytic RNAs, contain structural domains. Although the crystal structure of one of these domains has been determined by x-ray analysis, its connection to the other major domain that contains the guanosine-binding site has not been known. Site-directed mutagenesis and kinetic analysis of RNA splicing were used to identify a base triple in the conserved core of both a cyanobacterial ( <jats:italic>Anabaena</jats:italic> ) and a eukaryotic ( <jats:italic>Tetrahymena</jats:italic> ) group I intron. This long-range interaction connects a sequence adjacent to the guanosine-binding site with the domain implicated in coordinating the 5′ splice site helix, and it thereby contributes to formation of the active site. The resulting five-strand junction, in which a short helix forms base triples with three separate strands in the <jats:italic>Tetrahymena</jats:italic> intron, reveals exceptionally dense packing of RNA. </jats:p>