Vestibular nerve projection to the cerebral cortex of the rhesus monkey.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
J M Fredrickson
Publications and source records attributed to J M Fredrickson.
Thyroid mass.
In addition to the history given in this case the consultants ask for information regarding a family history of thyroid cancer or exposure to irradiation. An FNA is in order all the time (Dr. Fredrickson), only if there is no history of irradiation (Dr. Clark), and repeatedly if the mass is cystic (Dr. Harvey). All concur with thyroid suppression if the FNA and thyroid scan support a benign diagnosis. With an FNA report of a "follicular neoplasm" the consultants state that the pathologist should narrow down the histology further. But coupled with the cold nodule on thyroid scan, a lobectomy is in order. All would proceed with a lobectomy and rely on frozen section before going further. If the mass is malignant on frozen section a completion total thyroidectomy is in order. With a frozen section report of papillary follicular carcinoma all agree that a total thyroidectomy is in order. The management of the lymph nodes varies with removal of the ipsilateral lymph nodes (Dr. Clark), bilateral paratracheal lymph node dissection (Dr. Fredrickson), or a sampling of adjacent lymph nodes including those in the mediastinum (Dr. Harvey). A neck dissection is in order only if some of the lymph nodes are positive for tumor. Two experts (Drs. Clark and Harvey) are never comfortable losing a parathyroid gland. If one is found it should be autotransplanted into the sternocleidomastoid muscle (Dr. Clark) or the brachioradialis (Dr. Harvey). While every attempt should be made to identify and preserve all the parathyroid glands another expert believes that one parathyroid gland is probably enough to sustain normal hormone levels (Dr. Fredrickson).(ABSTRACT TRUNCATED AT 250 WORDS)
Adenoma↗
Implantable hearing aids: changes in the auditory-evoked potential of the monkey in response to increased loading of the stapes.
This study examines the effects on the hearing response in the monkey resulting from an increasing load on the stapes exerted by an implantable middle ear transducer. The transducer was placed on the distal end portion of the long process of the incus in monkeys and progressively advanced in small increments in the direction of the long axis of the stapes. Auditory-evoked potentials were recorded to assess the hearing response induced by the vibration of the transducer at each point. A decrease in response equivalent to a change in stimulus sound pressure level of approximately 20 dB occurred as the load on the stapes increased. Frequency response may also change. Our results imply that, to achieve maximum efficiency, the load placed on the ossicles by a vibrating transducer must be minimized.
Animals↗
Totally implantable hearing aids: the effects of skin thickness on microphone function.
With the advent of totally implantable hearing aids, the question of the impact of the choice of implantation site on microphone function has yet to be fully addressed. We investigated the effects of skin thickness on microphone function over a 2-week period in a porcine model. Sound attenuation was found to be directly proportional to skin thickness within the range of 0.5 to 3.0 mm. A decrease in resonant frequency of 500 Hz was noted after implantation under a skin thickness of 3.0 mm. The general shape of the frequency response curves was maintained across all thicknesses tested. Attenuation (dB loss) across the range of 500 to 8,000 Hz appeared to be linear over the various skin thicknesses measured, with a regression coefficient (r = .99 at 1 kHz and r = .99 at 3 kHz). To minimize attenuation and exploit the sound-collecting qualities of the external ear, the deep meatal skin appears to be a favorable position for implantation.
Animals↗
Free flap reconstruction of recalcitrant hypopharyngeal stricture.
A case report is presented of the use of a jejunal microvascular free flap for the reconstruction of a hypopharyngeal stricture caused by caustic ingestion. Although the airway was reestablished, there was aspiration and diplophonia. This case is discussed as an example of an effective treatment of a difficult problem, but one posing secondary problems arising from the use of jejunum.
Adolescent↗
Leiomyosarcoma of the cervical trachea. Report of a case with reconstruction using a latissimus dorsi island flap.
A case of leiomyosarcoma of the cervical trachea is described, detailing clinical presentation, pathologic diagnosis and surgical management. The rarity of this tumor in this location accounted for difficulties in clinical diagnosis and pathologic classification. Surgical treatment involved resection of two thirds of the circumference of the infracricoid trachea, with partial resection of the cricoid cartilage and thyroid gland. The defect was reconstructed using bilateral "butterfly" advancement flaps and a latissimus dorsi myocutaneous island flap. The technique and advantages of the latissimus dorsi flap are briefly described.
Adult↗
Human speech development for an implantable artificial larynx.
An electromagnetic artificial larynx was implanted in two volunteer laryngectomees. Both patients were able to communicate well, but the voice quality still needed improving. Therefore, in this investigation, listener judgments were obtained of 22 different sound sources with a view to incorporating the preferred speech sound in a new version of the device. Electroglottograms were used as sound sources in a speech synthesizer and sentences were produced with different voice qualities for judgmental tests. The results of the listening tests showed a distinct preference for waveforms corresponding to a long completely open phase, a very brief completely closed phase, and an abrupt closing gesture. The optimum acoustic characteristics for the device will be used by electrical engineers to manufacture a new version of the artificial larynx with an improved voice quality.
Electrodiagnosis↗
Radiation-induced carcinoma in a hemangioma.
A case of squamous cell carcinoma arising in repeatedly irradiated buccal hemangioma is reported, and the surgical techniques used in reconstructing the cheek and lips are described.
Adult↗
Convergence and interaction of vestibular and deep somatic afferents upon neurons in the vestibular nuclei of the cat.
Explore the source record for details and available documents.
Anesthesia↗
Projection of the vestibular nerve to the SI arm field in the cerebral cortex of the cat.
Evoked cortical focal potentials from electrical vestibular nerve stimulation were recorded in the Pcd-area in cats anaesthetized with Chloralose or Nembutal. For comparison, additional cortical projections were located for n. rad. superficialis and group Ia muscle afferents from n. rad. prof., n. fibularis prof., n. femuralis ramus muscularis and the motor nerve to the trapezoid muscle. Surface positive potentials, which reversed to negativity in middle cortical layers, were for vestibular nerve stimulation recorded in the S I forelimb field in a small area close to Pcd in the posterior medial part of the deep radial nerve projection field. The location of this field is compared with the vestibulo-cortical projections described earlier for rodents, squirrel monkey, and rhesus monkey. The histology shows that the field was within the cytoarchitectonic 3a area.
Animals↗
Fine structure of the medial and descending vestibular nuclei in normal rats and after unilateral transection of the vestibular nerve.
Cells and neuropil are of similar structure in the descending and medial vestibular nuclei. Two cell types were found: small neurons and larger cells. Three types of axon terminals have been defined: small and large terminals containing spherical vesicles (SV) and terminals with elongated vesicles (EV). Small SV terminals contact perikarya and dendrites, whereas large SV terminals contact fine dendritic branches. EV terminals contact neurons at perikarya and large as well as small dendritic profiles. SV terminals can be presynaptic to EV terminals. Vestibular nerve transection resulted in degeneration of small SV terminals which were found from the first to fifth postoperative day in the ipsilateral nuclei. Glycogen granules were found in various types of axon terminals bilaterally in the vestibular nuclei 3-5 days after right vestibular transection. They were not observed in normal animals or in degenerating vestibular afferent terminals.
Animals↗
Labyrinthine input to the vestibular nuclei of the awake cat.
The labyrinthine input to the vestibular nuclei was investigated in 24 awake cats. Stimulus consisted of electrical shocks given through bipolar silver wire electrodes, implanted in the utricular and lateral ampullar nerves. Throughout the vestibular nuclei, single units were recorded extracellularly with glass micropipettes filled with Fast Green. The tracts of the penetrating electrodes were identified histologically. In all four nuclei units responding to both labyrinths outnumbered unilaterally responding neurones with certain differences between the individual nuclei. Excitatory as well as inhibitory responses were observed, polysynaptic being more common than mono- or disynaptic ones. No monosynaptic contralateral responses were seen. The latency distribution of contralateral responses closely mirrored that of ipsilateral responses within each nucleus. Both excitatory and inhibitory responses fell into relatively segregated populations, based upon latency distribution. This implies separate pathways for labyrinthine input to the vestibular nuclei.
Animals↗
Labyrinthine and somatosensory convergence upon vestibulo-ocular units.
The vestibular nuclei were investigated in 18 adult cats. Vestibulo-oculo-motor neurons were identified by antidromic stimulation of the ascending medial longitudinal fasciculus (MLF). The neurons were subjected to various stimuli: vestibular, neck, forelimb and hindlimb nerve stimulation on both sides. The recording was extracellular with micropipettes containing Fast Green. Only the medial and the superior vestibular nuclei were found to project to the MLF. All projecting units had input from the labyrinths. Excitatory response latencies to ipsilateral labyrinth stimulation never exceeded 3 msec. Both excitatory and inhibitory response latencies could be distributed into different categories. The majority of the neurons did not receive a somatosensory input, and surprisingly few convergent units could be seen. Peripheral somatosensory information apparently plays a minor role in vestibulo-ocular relations.
Afferent Pathways↗
Labyrinthine and somatosensory convergence upon vestibulospinal neurons.
In awake cats cells forming the lateral (LVST) and medial (MVST) vestibulospinal tracts were identified by employing antidromic stimulation of the spinal cord. Neuronal responses to bilateral vestibular, forelimb, hindlimb, and neck electrical nerve stimulation were analysed. Extracellular recording in the vestibular nuclei was performed via a glass micropipette saturated with Fast Green, to aid in later histological tract identification. The number of cells projecting to cervical and lumbar regions in the dorsal and ventral division of Deiters' nucleus did not differ significantly. An unexpectedly large number of MVST units was found in the descending nucleus. Some MVST units projected to the lumbar cord but in both the medial and descending nuclei, projections to the cervical cord were in majority. Almost all spinal projecting vestibular neurons received labyrinthine input and more than half received somatosensory input. The units could be separated into several populations on basis of excitatory and inhibitory labyrinthine response latencies indicating multiple pathways. As regards labyrinthine-somatosensory integration the two tracts were found to be quite similar. The extent and complexity of labyrinthine-somatosensory convergence indicate the importance of feed-back mechanisms upon postural controls also at the level of the vestibular nuclei.
Action Potentials↗
Efferent vestibular neurons. Electrophysiological evidence for axon collateralization to cristae ampullares in the pigeon (Columba livia).
Extracellular spikes were recorded under general anaesthesia from the cell bodies of efferent vestibular neurons located in the caudal pontine reticular nucleus of the pigeon. Discrete electrical stimuli, applied directly to the three ampullary nerve branches in one labyrinth and to the anterior ramus of the vestibular nerve trunk in the other labyrinth, evoked antidromic spikes which served to identify efferent neurons. Most cells could be antidromically driven only by stimuli to the vestibular nerve trunk (anterior ramus). The majority of cells exhibiting direct axonal connections to one individual semicircular canal crista ampullaris showed axon collateralization to one or two other cristae as well. Sixty percent of the efferent neurons responded with antidromic spikes to ipsilateral labyrinthine stimuli, 34% to contralateral stimuli, and 6% to both. Synaptic activation was observed in a few efferent and adjacent unidentified neurons. It is concluded that efferent neurons often send collaterals to various cristae in one labyrinth, and less frequently, to both labyrinths. Such projections are incompatible with the assumption that vestibular efferents provide a simple control mechanism which is related to the direction of head movement.
Animals↗
Revascularized iliac bone graft for mandibular reconstruction.
Revascularized iliac bone has advantages over other revascularized bone grafts for the reconstruction of large mandibular defects. This is a detailed anatomical study of the blood supply to the iliac bone using microfil and Batson injection methods. It confirms and extends Taylor's study. Clinical results are reported for six cases of extensive mandibular defects which were reconstructed using this method.
Aged↗
Caring for children in adult settings.
Explore the source record for details and available documents.
Adult↗