PubMed Health⌕ Search

Biomedical subjects

F Magni

Publications and source records attributed to F Magni.

At least 73 records · Page 4Linked to original sources
PubMed1983

The afferent and preganglionic parasympathetic innervation of the rat liver, demonstrated by the retrograde transport of horseradish peroxidase.

The afferent and parasympathetic preganglionic innervations of the rat liver were investigated by the use of retrograde transport of horseradish peroxidase (HRP). Vagal nerve fibers reach the rat liver by way of the left and right hepatic nerves, which originate from the homonimous abdominal vagal trunks. Three different experimental protocols were used: (i) intraparenchymal HRP injections; (ii) retrograde HRP injection through the common bile duct; (iii) HRP application to the central end of the severed hepatic nerves. The technical problems inherent in these 3 methods were experimentally investigated, with regard to the possible leakage of HRP from the liver after retrograde injection. It is concluded that leakage of HRP occurs, but it is not sufficient to cause non-specific labeling. Neurons of the lower thoracic dorsal root ganglia (DRG) are bilaterally labeled following intraparenchymal and retrograde HRP injections. Bilateral labeling of the nodose ganglia (NGs) following retrograde injection is still observed after subdiaphragmatic section of the left abdominal vagus, whereas cervical transection prevents labeling of the ipsilateral NG. Labeling produced by exposure of the left hepatic nerve to HRP is prevented by subdiaphragmatic transection of the left abdominal vagus. Efferent neurons located bilaterally in the dorsal motor nucleus (DMN) and in the left nucleus ambiguus (NA) are labeled following retrograde HRP injection. Only ipsilateral labeling is observed after HRP application to the cut left hepatic nerve. HRP exposure of the left abdominal vagus yields bilateral labeling in both DMN and NA. It is concluded that: (i) the afferent innervation of the rat liver is provided by the lower thoracic DRG and by the NGs of both vagi, mostly by the left; partial crossing of vagal afferent fibers takes place at thoracic level; and (ii) the liver receives efferent fibers bilaterally from the DMN and from the left NA; the DMN neurons project to the liver via the homolateral hepatic nerves, and those of the NA via the left hepatic nerve.

Animals↗
PubMed1983

Identification of the motoneurons innervating the stapedius muscle in Gallus gallus: a horseradish peroxidase study.

The location of the stapedial motoneurons in Gallus gallus was investigated by means of the retrograde transport of HRP, injected into the stapedius muscle. The labeled neurons are located in both the ventral and dorsal divisions of the VII nerve nucleus, in a lateral and ventral position respectively, facing the superior olivary nucleus. The neurons are distributed in two size classes. The functional implications of these findings are discussed, in relation both to the absence of the acoustic stapedial reflex in birds and to the functional properties of the stapedius muscle.

Animals↗
PubMed1981

The afferent innervation of the liver: a horseradish peroxidase study in the rat.

Scattered injections of horseradish peroxidase (HRP) into the rat liver produced labeling of a small number of large neurons located only in the rostral pole of the left nodose ganglion. The same amount injected in a single lobe also produced labeling of a few cells in Th7-Th10 dorsal root ganglia. No retrograde marking followed subcapsular injections. HRP injections around the porta hepatis yielded labeling of large and small neurons in the left nodose ganglion only. This indicates that most of the afferent fibers are of vagal origin, and that different receptors are located in different parts of the liver.

Afferent Pathways↗
PubMed1981

Two bidirectional nerve cord systems converging with electrical and chemical synapses on the Retzius cells of the leech Hirudo Medicinalis.

Electrical stimulation of the ventral cord of H. medicinalis elicits in both Retzius' cells of each segmental ganglion an EPSP which is composed by an early and a late component. The early EPSP is electrical in nature, since it is unaffected by displacements of the membrane potential and by high Mg2+, whereas the late one is chemical, being reversed in sign by membrane depolarization and suppressed by high Mg2+. Latency measurements show that the electrical and chemical EPSP components are mediated by two different pathways characterized by conduction velocities of 0.5 and 0.3 m/sec respectively. Both pathways run in each of the lateral connectives and propagate impulses in anterior and posterior direction. Collision experiments show that ascending and descending impulses along the pathway mediating the electrical EPSP travel along the same fibres. Separate stimulation of the lateral connectives and selective inactivation of one Retzius' cell show that both pathways converge onto each Retzius' cell show that both pathways converge onto each Retzius cell. The possible functional significance of the two excitatory pathways is discussed.

Animals↗
PubMed1980

A direct connection between visual Wulst and Tectum opticum in the pigeon (Columba livia) demonstrated by horseradish peroxidase.

Labelled neurons were observed bilaterally in part of the visual Wulst (Hyperstriatum accessorium and Hyperstriatum intercalatum superior) following unilateral injection of the enzyme horseradish peroxidase into the Tectum opticum of pigeons. No labelling was observed in Hyperstriatum dorsale. Horseradish peroxidase positive fibres running through the Tractus septomensencephalicus and ending bilaterally in the Tectum opticum were found following injection of the enzyme into Hyperstriatum accessorium. Labelled fibres were also found to end in the Hyperstriatum ventrale ventro-ventrale. These findings provide evidence for a bilateral projection of the telencephalic station of the thalamofugal pathway onto the tectofugal system, as suggested by electrophysiological data. The functional organization of these projections is discussed.

Animals↗
PubMed1979

The activated face-bow: simple, safe, extraoral traction.

A simple and safe extraoral traction model is described. This consists of a face-bow with activated outer arms and a neck strap or headgear without any elastic force, such as rubber bands, elastic ribbons, coil springs, etc. The appliance cannot be withdrawn from the mouth by acident; therefore, the patient is protected from possible injuries.

Activator Appliances↗
PubMed1979

Interaction of optic tract and visual wulst impulses on single units of the pigeon's optic tectum.

The influences of visual wulst and optic tract (OTr) stimulation on units recorded from the pigeon's optic tectum (OT) were studied. 127 tectal units were excited with short latency by a single OTr volley. Excitation was followed by a long-lasting inhibition. On 54 of the OTr-excited units, single-shock visual wulst stimulation exerted a long-lasting inhibitory effect. On 34 units, the effect was purely excitatory and, on 28 units, excitation was followed by prolonged inhibition. No effect was exerted by wulst stimulation on 24 units. These results are discussed in terms of convergence of wulst and retinal input on OT neurons, and the role of the integration of visual information from both peripheral and central origins is suggested for the OT neurons.

Animals↗
PubMed1978

The role of the occlusal "simulator" in orthodontic treatment prior to surgical osteotomy.

The application of occlusal geometry in skeletal Class III cases, as related to the surgical relocation of one or both dental arches, is described. It has been established when and why it is helpful to relate the dental arches to each other before surgery, and an orthodontic method utilizing a simulator for jaw relocation is illustrated. The effectiveness of the method is clearly demonstrated through a clinically treated case.

Acrylic Resins↗
PubMed1978

Patterns of activity and the effects of activation of the fast conducting system on the behaviour of unrestrained leeches.

1. The neural activity of the nerve cord of Hirudo medicinalis has been recorded in unrestrained animals by means of chronically implanted electrodes. 2. The Fast Conducting System (FCS) is inactive both in motionless animals and during various kinds of active behaviour (creeping, swimming, ventilation). 3. Photic and tactile stimuli applied to a motionless animal elicit a FCS discharge, which may be followed by generalized shortening. 4. Photic and tactile stimuli applied during ventilation are followed by a reversible blockade of the ongoing activity only if they are able to elicit a FCS discharge. No such effect is observed on swimming. 5. An explanation of these findings in terms of the known connexions of leech neurones is offered and a role in the control of reafferent inputs is attributed to the rectifying synapses made by FCS and T cells on the L motor neurones.

Animals↗
PubMed1977

Visual wulst influences on the optic tectum of the pigeon.

The influence of the visual wulst on the optic tectum of Columba livia were studied. Analysis of the surface field potential evoked by optic nerve stimulation showed that it is composed of two presynaptic waves (pr1 and pr2) a negative monosynaptic wave (N) and a late, positive component (P) due to activation of deeply located neurons. Single shock visual wulst stimulation elicited a surface-positive field potential the depth profile of which showed that it is due to the activation of neurons of the deep tectal layers, probably different from those responsible for the P wave. Visual wulst stimulation depresses the positive component of the field potential elicited by optic nerve stimulation. It is suggested that this effect is mediated by intratectal inhibitory interneurons.

Animals↗
PubMed1975

The neuron of the fast conducting system in hirudo medicinalis: identification and synaptic connections with primary afferent neurons.

A single neuron, located in the center of each segmental ganglion of H. medicinalis is antidromically activated by electrical stimulation of the ventral cord anteriorly and posteriorly to the ganglion, at the same threshold as the fast conducting system (FCS) and with a latency equal to the FCS conduction time. This neuron is activated trans-synaptically by tactile and photic stimulation of the skin and by stimulation of high-threshold fibres running along the cord. A spike evoked by intracellular stimulation of this neuron propagates along the FCS. Intracellular staining shows that this neuron sends two axonal branches in the anterior and posterior median connectives. Direct electrical stimulation of touch cells (T cells), as well as mechanical stimulation of the skin, lowers the threshold of and may eventually fire, the FCS neurons, not only at the level of the ganglion to which they belong, but also at the level of the neighbouring ganglia. This effect is mediated by bilateral pathwasy located in the lateral connectives. It is concluded that the FCS consists of a chain of single neurons, located in each ganglion and electrotonically coupled to each other. Touch cells project with excitatory synapses on the FCS neurons.

Animals↗
PubMed1975

Apomorphine pecking in the pigeon.

Pecking activity elicited by apomorphine was studied quantitatively in intact and thalamic pigeons. While apomorphine pecking is easily observed in the intact pigeon, it is absent in the acute thalamic animal. I reappears, however, in the chronic preparation simultaneously with the recovery of spontaneous pecking. Apomorphine pecking is described by satiation and increased by fasting. Reticular stimulation produces reversible blockade of both apomorphine and spontaneous pecking with the same parameters, without increase in heart rate. Apomorphine pecking can be observed only in the presence of visual contrast, and is always aimed at the contrast points or edges. A decrease in contrast produces a decrease in the number of pecks delivered to the contrast points and an increase in those missing the target, while the total number of pecks delivered in a unit time is unaffected. A lowering of the background luminance is followed by a decrease in the total number of pecks, which is mostly due to a reduction of those aimed at the contrast points. All these findings are discussed and it is concluded that: i) apomorphine exerts an excitatory action (direct or indirect) on the hypothalamic feeding centers; hence apomorphine pecking can be considered as a pharmacologically motivated behavior; ii) visual contrast exerts a dual action on apomorphine pecking, namely it acts both as triggering stimulus and goal object; iii) the decrease in apomorphine pecking induced by lowering the ambient light intensity is probably due to a decrease in the level of the general arousal.

Animals↗