Ablation of brainstem C1 neurons improves cardiac function in volume overload heart failure

Activation of the sympathetic nervous system is a hallmark of heart failure (HF) and is positively correlated with disease progression. Catecholaminergic (C1) neurons located in the rostral ventrolateral medulla (RVLM) are known to modulate sympathetic outflow and are hyperactivated in volume overload HF. However, there is no conclusive evidence showing a contribution of RVLM-C1 neurons to the development of cardiac dysfunction in the setting of HF. Therefore, the aim of this study was to determine the role of RVLM-C1 neurons in cardiac autonomic control and deterioration of cardiac function in HF rats. A surgical arteriovenous shunt was created in adult male Sprague-Dawley rats to induce HF. RVLM-C1 neurons were selectively ablated using cell-specific immunotoxin (dopamine-β hydroxylase saporin [DβH-SAP]) and measures of cardiac autonomic tone, function, and arrhythmia incidence were evaluated. Cardiac autonomic imbalance, arrhythmogenesis and cardiac dysfunction were present in HF rats and improved after DβH-SAP toxin treatment. Most importantly, the progressive decline in fractional shortening observed in HF rats was reduced by DβH-SAP toxin. Our results unveil a pivotal role played by RVLM-C1 neurons in cardiac autonomic imbalance, arrhythmogenesis and cardiac dysfunction in volume overload-induced HF.

Auditory Responses in the Barn Owl's Nucleus Laminaris to Clicks: Impulse Response and Signal Analysis of Neurophonic Potential

We used acoustic clicks to study the impulse response of the neurophonic potential in the barn owl's nucleus laminaris. Clicks evoked a complex oscillatory neural response with a component that reflected the best frequency measured with tonal stimuli. The envelope of this component was obtained from the analytic signal created using the Hilbert transform. The time courses of the envelope and carrier waveforms were characterized by fitting them with filters. The envelope was better fitted with a Gaussian than with the envelope of a gamma-tone function. The carrier was better fitted with a frequency glide than with a constant instantaneous frequency. The change of the instantaneous frequency with time was better fitted with a linear fit than with a saturating nonlinearity. Frequency glides had not been observed in the bird's auditory system before. The glides were similar to those observed in the mammalian auditory nerve. Response amplitude, group delay, frequency, and phase depended in a systematic way on click level. In most cases, response amplitude decreased linearly as stimulus level decreased, while group delay, phase, and frequency increased linearly as level decreased. Thus the impulse response of the neurophonic potential in the nucleus laminaris of barn owls reflects many characteristics also observed in responses of the basilar membrane and auditory nerve in mammals.

Tone Language Type Change in Africa and Asia

SUMMARY Tone languages can be characterized by the degree to which they realize one of two tone language prototypes defined in terms of tone function. Type A tone languages (usually Asian) employ tone lexically and in minor morphological patterns. Type B tone languages (usually African and Mesoamerican) employ tone to make major morphological distinctions in addition to performing type A functions. For communicative reasons, these functions are necessarily linked to other structural properties of the languages of each type. This paper discusses three tone languages which have undergone different degrees of tone language type change and, as a result, are genetically or areally atypical: !Xũ (Khoisan), Gokana (Niger-Congo), and Mpi (Tibeto-Burman). It is the claim of the author that the driving force behind tone language type change, as exemplified by these three languages, is a change in the role of segmental morphology. RÉSUMÉ On peut caractériser les langues tonales par le degré par lequel elles réalisent un des deux prototypes de langues tonales définis en terme de fonction tonale. Les langues tonales de type A (généralement asiatiques) emploient le ton pour des fonctions lexicales et des fonctions morphologiques mineures. Outre les fonctions de type A, les langues tonales de type B (généralement africaines et mésoaméricaines) emploient le ton pour des fonctions morphologiques majeures. La communication ayant ses exigences, ces fonctions sont inévitablement liées aux autres propriétés structurales de chaque type. Dans cette étude il s'agit de trois langues tonales qui ont subi différents degrés de changement de type tonal et qui sont, par conséquent, atypiques du point de vue génétique et régional: !Xũ (Khoisan), Gokana (Niger-Congo), et Mpi (Tibeto-Birman). Se fondant sur ces trois langues, l'auteur émet l'hypothèse que la causalité de l'évolution du ton se trouve dans un changement du rôle de la morphologie segmentate. ZUSAMMENFASSUNG Tonsprachen kônnen nach dem Grade, nach dem sie einem der beiden Pro-totypen folgen, charakterisiert werden, und zwar im Sinne ihrer Funktion: Typ A Tonsprachen (meistens asiatische) verwenden Ton lexikalisch und in we-niger wichtigen morphologischen Strukturen; Typ B Tonsprachen (zumeist afrikanische und mittelamerikanische) hingegen verwenden Ton, um wichtige morphologische Unterscheidungen zu treffen, wâhrend sie gleichzeitig auch Funktionen des Typ A wahrnehmen. Aus kommunikativen Griinden sind die Funktionen notwendigerweise mit anderen Struktureigenschaften der Sprachen des jeweiligen Typs verbunden. Der Aufsatz analysiert drei Tonsprachen, die zu verschiedenen Graden Ànderungen in ihrem Tonsystemtyp erfahren haben und daher als entweder genetisch oder areal gesehen atypisch sind: !Xu (Khoi-san), Gokana (Niger-Kongo) und Mpi (Tibeto-Burmesisch). Die Autorin ist der Auffassung, daB die treibende Kraft hinter diesem Tonsprachentypwandel, wie er in diesen drei Sprachen aufgezeigt wird, in der Verânderung in der Rolle der segmentalen Morphologie in diesen Sprachen zu suchen sei.