PubMed Health⌕ Search

Biomedical subjects

P Valli

Publications and source records attributed to P Valli.

At least 55 records · Page 3Linked to original sources
PubMed1989

Tracheobronchial foreign bodies. A persistent problem in pediatric patients.

Extraction of a foreign body from the tracheobronchial tree was accomplished for 83 children. The mean age was 1 year 9 months for the 27 girls and 3 years 1 month for the 56 boys; 46 children (55%) were younger than 2 years of age. Sixteen (19%) of the foreign bodies were radiopaque, and 35 (42%) were either verified or suspected radiologically before endoscopy. Forty-one foreign bodies (49%) were situated in the right bronchial tree. Extraction was successful in 81 children (98%) and was performed on 50 children (60%) during the first 24 hours. Twenty-five (30%) of the foreign bodies were peanuts. Three children experienced a residual foreign body, without serious complications. We believe that an open tube bronchoscopy should be performed whenever abnormal stridor or cough is observed in a healthy child and when appropriate antibiotic therapy is unsuccessful.

Bronchi↗
PubMed1986

Functional organization of the peripheral efferent vestibular system in the frog.

The functional organization of the efferent vestibular system (EVS) was studied in the isolated frog labyrinth. To ascertain whether, besides the efferent branching fibres that innervate several end-organs, the EVS is also endowed with efferent non-branching axons which might control a given population of sensory units in each end-organ, the 8th nerve and one of its branchlets were electrically stimulated while recordings of the spontaneous activity arising from the different sensors were made by impaling single afferent axons in all the 8th nerve branchlets. The results demonstrated that the vast majority of the sensory units whose activity was modified by stimulating the whole 8th nerve was also affected by stimulating an 8th nerve branchlet. These findings therefore rule out the possibility that the EVS is endowed with projective fibres and strengthen the view that the EVS is a highly divergent system with collaterals arising from single parent axons that innervate several end-organs. These experiments have also shown that the percentage of sensory units which are actually controlled by the EVS varies amongst the different labyrinthine organs. It is maximal in the sacculus (ca. 90%), somewhat lower in canal organs (ca. 80%) and the utriculus (ca. 70%) and considerably lower in the lagena (ca. 50%). This EVS arrangement therefore might allow information arising from some organs to be modified more extensively than that from others.

Animals↗
PubMed1985

[Receptor current in ciliate cells of the frog sacculus].

The present study aims to provide further contribution towards identifying the ions which actually sustain the receptor current in labyrinthine sensory cells. The experiments were carried out on isolated sacculi of the frog. The macular epithelium of the sacculus was positioned in a two compartment chamber which allows the fluid bathing the inside and the outside of the sacculus to be replaced separately with solutions having different ionic composition. The potential across the epithelium was clamped to zero and both the receptor current and the postsynaptic potentials in response to mechanical stimuli were first recorded when the endolymphatic fluid had a normal ionic composition and then, at different time intervals, after replacing the endolymph with solutions deprived of K+ (replaced with Na+, Rb+, Cs+ and Ca++) and Na+ (replaced with choline and saccharose). The results have shown that both the receptor current and the postsynaptic potentials are abolished after replacing the endolymphatic K+ with Na+, Cs+ or Ca++, whereas are partially preserved when K+ is replaced with Rb+. These findings strongly suggest that the receptor current in labyrinthine sensory cells is carried almost exclusively by K+ and that this current flows across specific K-channels.

Action Potentials↗
PubMed1985

[Pre- and post-synaptic activity of glutamate on preparations of the frog semicircular canal].

Glutamate (Glu) has at least two sites of action in the frog semicircular canal: the hair cell (presynaptic) and the primary afferent nerve fibres (postsynaptic). Glu's action on the hair cell results in an increased release of the natural transmitter which is responsible for a substantial increase in the frequency of firing in primary afferents. Glu produces a long-lasting depolarization in the afferent nerve fibres which does not by itself elicit any afferent discharge of impulses when the release of the natural transmitter is prevented. The difficulty of reconciling some of the observations made of the effects of Glu in semicircular canals with its presumed role as an afferent transmitter in this organ is discussed.

Animals↗
PubMed1985

[Effects of changes in K+ in the perilymphatic fluid on the activity of vestibular receptors in the frog].

The effect of rapid changes in K+ concentration (from 0 up to 5 mM) in the perilymphatic fluid was tested on ampullar receptor activity in isolated semicircular canals of the frog. The effects of the different K-concentrations were evaluated by recording both the transepithelium potentials (Adc) and the postsynaptic potentials (EPSPs and spikes discharge) led off from the ampullar nerve. The results have clearly demonstrated that crista ampullaris sensory cells are extremely sensitive to K-changes (+/- 0.25 mM). In fact both transepithelial potentials and discharge activity (EPSPs and propagated spikes) of first order vestibular neurones may be decreased or increased by decreasing or increasing the K-concentration in the outer fluid. The possible mechanism of action of K+ on ampullar receptors is discussed.

Animals↗
PubMed1985

The effect of glutamate on the frog semicircular canal.

L-glutamate (Glu) has at least two sites of action in the frog semicircular canal: the hair cell (presynaptic) and the primary afferent nerve fibres (postsynaptic). Glu's action on the hair cell results in an increased release of the natural transmitter which is responsible for a substantial increase in the frequency of firing in primary afferents. The presynaptic action of Glu is antagonized by D-alpha-aminoadipate (D alpha AA). Glu produces a long-lasting depolarization on the afferent nerve fibres which does not by itself elicit any afferent discharge of impulses when the release of the natural transmitter is prevented. Glu-induced nerve depolarization is only partially antagonized by D alpha AA. The difficulty of reconciling some of the observations made of the effects of Glu in semicircular canals with its presumed role as an afferent transmitter in this organ is discussed, but this role is not definitely rejected.

2-Aminoadipic Acid↗
PubMed1984

[Effect of various vasoactive drugs on synaptic transmission in the orthosympathetic ganglia in man].

The effects of the following vasoactive drugs: Bencyclan fumarate, Cetiedil citrate, Cinepazide maleate, Dihydroergocristine methane sulphonate, Nafthydrofuril acid oxalate, Papaverine hydrochloride, Piribedil monomethane sulphonate, Raubasine, Thymoxamine hydrochloride and Xanthinol nicotinate, in concentrations ranging between 0.001 - 2 mM, were tested on the compound action potentials led off from human isolated sympathetic ganglions. The experiments, carried out on 50 isolated lumbar ganglion preparations removed from 23 subjects with arteriopathy of the limbs, indicated that all the drugs are able to impair the synaptic transmission, although at different concentrations. These findings are in favour of the hypothesis that the vasodilatatory effects observed after therapeutic treatment of patients with vasoactive drugs are partially produced by the vasodilatation following the depression of the sympathetic nervous transmission.

Action Potentials↗
PubMed1984

[Action of D-alpha aminoadipic acid on the sensory organs of the inner ear in the frog].

Following the suggestions in the literature that glutamate or aspartate may be the transmitter at the primary afferent synapses of acoustico-lateralis organs, we have employed the "selective" excitatory amino acid antagonist. D-alpha amino adipate (DAA) as a tool with which to shed further light on this problem in the labyrinthine organs of the frog. DAA produces a dose-responsive, reversible depression of spontaneous activity in the afferent nerves of the posterior semicircular canal, saccule and basilar papilla. These structures are examples of ampullar, otolithic and auditory organs, respectively. The drug effect seems qualitatively the same throughout the labyrinth. The most interesting finding was that of a presynaptic (hair cell) effect of DAA on the semicircular canal. The means of recording did not permit detection of a presynaptic effect in the other organs examined. All the observed effects of DAA could be explained by a presynaptic action to inhibit transmitter release. Therefore, the ability of DAA to reduce transmission at primary afferent synapses of the frog labyrinth must not necessarily be interpreted to imply that the transmitter is an excitatory amino acid. A presynaptic action to reduce the release of a transmitter (of unknown structure) could explain all our results.

2-Aminoadipic Acid↗
PubMed1983

[Effects of temperature on postsynaptic potentials at the cyto-neural junctions of the frog semicircular canal].

An analysis of the EPSPs recorded intracellularly from single fibres of the VIII nerve revealed that the resting release of chemical transmitter at the cyto-neural junctions in the sensory organ of frog semicircular canals displays a rather low temperature dependence. This provides evidence that, in labyrinthine receptors, the resting activity is actually "evoked" in nature. A comparison between the discharge of EPSPs and propagated spikes in the VIII nerve fibres has shown that the "encoders" of primary vestibular neurones are highly sensitive to temperature changes and irreversibly damaged at temperatures exceeding 28 degrees C.

Animals↗
PubMed1983

[Temperature dependence of electrical potentials in the frog semicircular canal].

The temperature dependence of conversion processes in the sensory organ of frog semicircular canals has been tested in the range 0-28 degrees C by recording the ampullar (Adc) and nerve (Ndc) slow potentials as well as the afferent discharge of impulses (Nfr) in the VIII nerve fibres. The results have shown that Adc is scarcely affected by temperature changes (Q10 less than 2) thus suggesting that stimulus conversion in labyrinthine cells does not imply chemical processes but mainly potassium conductance changes at their apical membrane. By converse, postsynaptic potentials and propagated spikes are markedly reduced at low temperatures (Q10 2.8 and 7 respectively) and only slightly increased between 20 and 28 degrees C. These observations are interpreted by considering the chemical nature of the processes which are involved. The temperature dependence in labyrinthine receptor activation is discussed in the view of its physiological meaning.

Animals↗
PubMed1983

Peripheral organization of the vestibular efferent system in the frog: an electrophysiological study.

The distribution and the properties of efferent fibers in vestibular nerve were studied in the isolated frog labyrinth. Electrical stimulation of the central stump of any vestibular nerve branchlet elicited compound action potentials in all the other eighth nerve branchlets, indicating the existence of neural links between the various vestibular organs. The same experimental paradigm, when repeated in frogs with chronic section of the eighth nerve roots, demonstrated that these pathways are efferent collaterals extending to all vestibular organs. There are more collaterals linking the 3 semicircular canals than the otolith organs and the otoliths with the canal organs. Efferent connections in the eighth nerve were preserved in full after ablation of the ipsilateral hemi-cerebellum, suggesting that the efferent pathways probably originate in the brainstem. Intracellular recordings from single afferent fibers of both canal and otolith organs revealed that efferent fiber activation could elicit either inhibition or facilitation of the receptor discharge. It was concluded that the frog efferent vestibular system is endowed with non-selective control channels which allow single neurons to influence the receptor activity of different labyrinthine organs.

Animals↗
PubMed1983

[Legal provisions regarding the repeal and annulment of disability pensions].

The rapporteur after hawing having illustrated the significance of the revocation and the annulment of the invalid pension legislative measures much are not of a discretional nature, but an obliged legislative power of the public administration--has underlined that they must be used when the qualifications which x caused the recognition of the state of invalidity no longer exists or when it has been ascertained that they have never existed. It is discussed the role which the improvement in the psyco-physical conditions, the fact of the re-occupation of the invalid, the moment of the arisal of the infirmities, and of the physical mental defects and the charged attitude of the worker in the different and new occupations can play in judging the revocation. During the course of the lawful revision, the criteria of the judgement of the legal doctor must be the same as those adopted at the moment of the concession of the invalidity, without the need to proceed in comparing with the previous situation.

Persons with Disabilities↗
PubMed1982

[Effects of veratridine on labyrinth receptors in the frog].

The action of the veratrum alkaloid veratridine has been tested on the sensory apparatus of the frog semicircular canals. Intracellular and extracellular recordings of the electrical responses evoked by sinusoidal mechanical stimulations of the ampullar organ could not reveal an action of the drug on the hair cells whereas the onset of the impulse discharge at the encoder of the afferent nerve fibres is largely facilitated by veratridine. The mechanism of the drug action is discussed.

Animals↗
PubMed1982

[Effects of increased temperature on the sensory transduction process induced by frog ampullar receptors].

The function of the sensory organ in semicircular canals of the frog has been tested, at increasing temperatures from 20 to 34 degrees C, by recording the ampullar (Adc) and nerve (Ndc) potentials together with the afferent discharge of impulses in the VIII nerve fibres. The amplitude of the receptor potential increases by increasing the temperature up to 30 degrees C. Postsynaptic potentials and propragated spikes, by converse, are only slightly modified between 20-28 degrees C and are drastically depressed over 28 degrees C. The results are discussed also in connection with the possible use of the enzimatic pretreatment of the preparations to facilitate the insertion of microelectrodes in labyrinthine cells.

Animals↗
PubMed1980

[Axonal organization of the peripheral efferent system in the frog labyrinth].

The purpose of the present work is to investigate the distribution of the nerve fibres subserving efferent control in frog labyrinth. Following electrical stimulation of a twig of the isolated VIII nerve compound action potentials could be picked up from the others nervous twigs. Denervation experiments suggest that these compound potentials are sustained by efferent fibres which branch in the VIII nerve providing collaterals to otolith and canal organs. This axonal organization, therefore, enables single efferent neurones to control the activity arising from different types of labyrinthine receptors.

Action Potentials↗