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G Zucca

Publications and source records attributed to G Zucca.

69 records · Page 4Linked to original sources
PubMedDate not supplied

Ionic composition of the endolymph and sensory transduction in labyrinthine organs.

The role of various ions in stimuli conversion has been investigated in isolated frog semicircular canals, by replacing the endolymph with solutions deprived in turn of Na+, K+, Cl- and Ca++. Mechanical and electrical stimuli were employed and slow ampullar and nerve potentials were recorded, together with the afferent discharge of impulses in the eighth nerve. The results support evidence that K+ is the carrier of the receptor current, as postulated in Davis' hypothesis, while Ca++ is essential in the processes which allow the current to be modulated during cupula deflections and therefore endon hair cells with mechanical sensitivity.

Acoustic Stimulation↗
PubMedDate not supplied

Ionic mechanisms sustaining activity in ampullar receptors of the frog.

Ionic mechanisms sustaining sensory transduction in crista ampullaris sensory cells have been investigated chiefly by replacing the endolymph with solutions with K+ and Ca++ chelators added. The effects of the modified solutions were evaluated by extracellular and intracellular recordings of both and the presynaptic and postsynaptic activity of ampullar receptors. The results strongly suggest that the receptor current in labyrinthine cells is carried exclusively by K+. Moreover evidence are reported indicating that the transducer membrane in ampullar receptors is provided with Ca++ sensitive potassium channels whose opening is depending on free Ca++ released from cupular structures during excitatory deflections.

Animals↗
PubMedDate not supplied

Local mechanisms in vestibular receptor control. Effects of curare on the EPSPs and spike discharge recorded from single afferent fibres of the posterior canal nerve of the frog.

In the frog, the afferent discharge of EPSPs and spikes has been recorded intracellularly from single fibres of the posterior ampullar nerve before and after administration of D-tubocurarine (5 X 10(-6) M) in the following experimental conditions: (a) in animals in which the labyrinth was merely exposed (intact frogs), (b) in isolated acute labyrinth preparations, (c) in isolated chronic labyrinth preparations after degeneration of the efferent fibres. In both (a) and (c), curare induced either facilitation or inhibition of the resting discharge in a large number of units. By contrast, after degeneration of the efferent fibres, the effects of the drug were almost completely suppressed. These results indicate the existence of peripheral mechanisms involving the efferent nerve terminals which can control the release of afferent transmitter even in the absence of any central influence.

Animals↗
PubMedDate not supplied

Experimental skeletal muscle revascularization by jejunal loop implant.

The possible onset of a vascular connection between the parietal network of a jejunal loop transposed into the crural region and the quadriceps muscle in hypoperfused condition has been experimentally studied. Ten dogs were included in this study. Sixty days after the operation the angiograms obtained by cannulating the artery of the implanted loop showed a rich neovascularity in the muscular area near the implant and the direct visualization of the venous outflow of the thigh. Histology of the specimens showed no substantial abnormalities of the muscular tissue. From these data the possible effective role of the skeletal muscle revascularization in the management of some severe ischemic conditions, after the failure of all the conventional reconstructive procedures, is suggested.

Animals↗
PubMedDate not supplied

Why do benign paroxysmal positional vertigo episodes recover spontaneously?

It is well known that most episodes of benign paroxysmal positional vertigo (BPPV), even in untreated, recover spontaneously in 2 to 6 weeks. In the present study, we put forward the hypothesis that this is mainly due to the fact that endolymph, owing to its low calcium content (20 microM) is able to dissolve otoconia. To support this, the fate of frog saccular otoconia immersed in normal endolymph (Ca2+ content 20 microM) and in Ca2+-rich endolymphatic fluids (up to 500 microM) was studied by observing the crystals at regular intervals for 3 weeks. The results demonstrated that normal endolymph can dissolve otoconia very rapidly (in about 20 hours). When the endolymphatic Ca2+ content was increased (50 to 200 microM) otoconia dissolution time was slowed down (about 100 to 130 hours, respectively) and completely stopped when the endolymphatic Ca2+ content was of 500 microM. The present results therefore suggest that the major process involved in the spontaneous recovery of BPPV episodes is the capability of the endolymph to dissolve dislodged otoconia.

Animals↗