The responses of hippocampal cell fields to stimulation of afferent pathways projecting from outside and within the hippocampus have been shown to exhibit a remarkable degree of plasticity. Subsequent to conditioning stimulation of either single shocks or trains of stimuli at high frequency, the relationship between afferent stimulus and postsynaptic response can be dramatically changed. The long-term potentiation (LTP) of responses generated by stimulus trains does not appear to involve whole-neurone excitability changes, but is the result of altered synaptic effectiveness and can be localized to the region of afferent fibre termination. In a series of acute experiments extracellular potentials generated by stimulation of the entorhinal projection to the dentate gyrus of the hippocampus in the rat, have been recorded in the dorsal hippocampus and quantified before and after conditioning stimulation. A simple computer model was developed to help explain the observed response plasticity. Synaptic field potential LTP after afferent tetanization was explained by increased synaptic current flow, and the altered spatial distribution of the potentials by suggesting that the electrotonic properties of the granule cell dendrites are changed by repeated synaptic activation: an increase in dendritic membrane resistance being a possible mechanism. Light-microscopic examination of the entorhinal fibres at the site of stimulation in the angular bundle after staining with solochrome cyanine, revealed heterogeneous myelination; the fibres lying dorsal and lateral to the subiculum being more heavily myelinated than those more ventro-medial. This histological inhomogeneity appeared to be confirmed by conduction velocity measurements, suggesting two functionally different groups of fibres. It has yet to be determined whether these two groups correspond to the lateral and medial perforant paths described by other workers.

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Motivation: In the last years more than 20 vertebrate genomes have been sequenced, and the rate at which genomic DNA information becomes available is rapidly accelerating. Gene duplication and gene loss events inherently limit the accuracy of orthology detection based on sequence similarity alone. Fully automated methods for orthology annotation do exist but often fail to identify individual members in cases of large gene families, or to distinguish missing data from traceable gene losses. This situation can be improved in many cases by including conserved synteny information. Results: Here we present the SynBlast pipeline that is designed to construct and evaluate local synteny information. SynBlast uses the genomic region around a focal reference gene to retrieve candidates for homologous regions from a collection of target genomes and ranks them in accord with the available evidence for homology. The pipeline is intended as a tool to aid high quality manual annotation in particular in those cases where automatic procedures fail. We demonstrate how SynBlast is applied to retrieving orthologous and paralogous clusters using the vertebrate Hox and ParaHox clusters as examples.

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Ryanodine receptors (RyRs) are intracellular homotetrameric Ca2+-release channels constituting a family of three different isoforms, named RyRl, RyR2 and RyR3. RyRl and RyR2 are highly expressed in skeletal and cardiac muscles respectively, where they localize in the terminal cisternae of the sarcoplasmic reticulum (SR). Although RyRl and RyR2 have been found to be expressed in several other tissues at much lower level than in striated muscles, their major functional role is related to Ca2+-release from the SR following electrical depolarization of the plasma membrane, a process referred to as excitation-contraction (e-c) coupling and known to regulate striated muscle contraction. The third isoform, RyR3, is characterized by a wide pattern of expression, without any specific association to a tissue or a cell-type. The finding that RyR3 is also expressed in mammalian skeletal muscles parallels the presence of two distinct isoforms, o- and P-RyR, in non-mammalian vertebrate skeletal muscles, and suggests that two functionally distinct RyRs may be involved in the regulation of skeletal muscle contraction. The expression of RyR3 was analyzed in murine skeletal muscle from late foetal stages to adult, throughout neonatal phases of development. RyR3 was expressed widely during skeletal muscle post-natal development, disappearing in all muscles analyzed except diaphragm and soleus. RyR3 knockout mice were generated, and contractile properties of skeletal muscles were analyzed. Skeletal muscle contraction in RyR3-/- mice was impaired during the neonatal phase of development. In skeletal muscles isolated from RyR3-1- mice, the twitch elicited by electrical stimulation was strongly depressed. A significant reduction of the contractile activity was also elicited after stimulation with caffeine, an activator of Ca2+-release through RyRs. In the adults, no differences were detected between wild-type and mutant mice. These results are the first demonstrations of a physiological role of RyR3 in excitation-contraction coupling mechanisms of skeletal muscle, and support the model of a two-channel system regulating skeletal muscle contraction. In order to further characterize the RyR3-1- mouse, [3H]ryanodine binding experiments were performed on diaphragm and total hindlimb skeletal muscles from RyR3+/+ and RyR3-1- mice. Preliminary results will be presented and discussed.

No description available.

Prosaurolophus maximus is a crested hadrosaurine known from numerous specimens from the Dinosaur Park Formation of Alberta. Therefore, it is an ideal taxon to reconstruct patterns of growth and variation in hadrosaurids, and improve our understanding of their evolutionary relationships. This study describes the cranial anatomy of P. maximus, quantitatively examines its range of variation, and provides the first ontogenetic series for this taxon. A second species, P. blackfeetensis, was named based on morphological differences in the characteristic nasal crest; however, morphometric results fail to quantitatively differentiate P. blackfeetensis from P. maximus. A species-level phylogenetic analysis of hadrosaurids recovers P. maximus and P. blackfeetensis as sister taxa. Based on both the morphometric and phylogenetic data, this study supports the previous hypothesis that P. blackfeetensis is a junior synonym of P. maximus thereby substantially increasing its temporal range, and suggests a long period of morphological stasis in this taxon.

Prosaurolophus maximus is a crested hadrosaurine known from numerous specimens from the Dinosaur Park Formation of Alberta. Therefore, it is an ideal taxon to reconstruct patterns of growth and variation in hadrosaurids, and improve our understanding of their evolutionary relationships. This study describes the cranial anatomy of P. maximus, quantitatively examines its range of variation, and provides the first ontogenetic series for this taxon. A second species, P. blackfeetensis, was named based on morphological differences in the characteristic nasal crest; however, morphometric results fail to quantitatively differentiate P. blackfeetensis from P. maximus. A species-level phylogenetic analysis of hadrosaurids recovers P. maximus and P. blackfeetensis as sister taxa. Based on both the morphometric and phylogenetic data, this study supports the previous hypothesis that P. blackfeetensis is a junior synonym of P. maximus thereby substantially increasing its temporal range, and suggests a long period of morphological stasis in this taxon.