Interaction of inhibitory and excitatory junctional potentials in the control of a myogenic myocardium: the ventricle ofBusycon canaliculatum

Résumé Les auteurs ont étudié, par microélectrode interne, l'interaction entre les potentiels postsynaptique inhibitoire et excitatif dans un myocarde myogénique. Ils ont observé la sommation de ces potentiels et leur action facilitant l'inhibition par hyperpolarization et l'excitation par depolarisation.

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Supported by a grant from the National Institutes of Health, USA (P.H.S. Grant No. 5-R01-NS-08352-03 PHY, from the National Institute of Neurological Diseases and Stroke.)     

Abnormal cerebellar development and axonal decussation due to mutations in AHI1 in Joubert syndrome

Joubert syndrome is a congenital brain malformation of the cerebellar vermis and brainstem with abnormalities of axonal decussation (crossing in the brain) affecting the corticospinal tract and superior cerebellar peduncles. Individuals with Joubert syndrome have motor and behavioral abnormalities, including an inability to walk due to severe clumsiness and 'mirror' movements, and cognitive and behavioral disturbances. Here we identified a locus associated with Joubert syndrome, JBTS3, on chromosome 6q23.2-q23.3 and found three deleterious mutations in AHI1, the first gene to be associated with Joubert syndrome. AHI1 is most highly expressed in brain, particularly in neurons that give rise to the crossing axons of the corticospinal tract and superior cerebellar peduncles. Comparative genetic analysis of AHI1 indicates that it has undergone positive evolutionary selection along the human lineage. Therefore, changes in AHI1 may have been important in the evolution of human-specific motor behaviors.     

Isometric length-tension diagram for maximal tetanic contractions of cardiac muscle from a gastropod,Busycon canaliculatum

Zusammenfassung Der Herzmuskel von Mollusken unterscheidet sich von der übrigen Molluskenmuskulatur entsprechend wie sich der Herzmuskel der Wirbeltiere von ihrer Skelettmuskulatur unterscheidet, insofern man die Beziehungen zwischen passiver und aktiver Kraft betrachtet. Im Herzmuskel der Mollusken lässt sich der maximale Tetanus für die Messung der aktiven Kraft verwenden.

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This work was supported by Grant No. GB5598 from the U.S. National Science Foundation.