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Biomedical subjects

V Honrubia

Publications and source records attributed to V Honrubia.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Implications of Ewald's second law for diagnosis of unilateral labyrinthine paralysis.

The feasibility of replacement of the caloric test with sinusoidal rotatory stimulations of differing frequencies was investigated in ten normal subjects and seven patients with unilateral labyrinthine paralysis. Testing was performed at frequencies ranging from 0.0125 to 0.2 Hz at 60 degrees/sec and at 0.05 Hz at peak velocities of 30 degrees/sec to 180 degrees/sec. Gain, phase, and asymmetry of the nystagmic responses were measured in these groups. Results indicated that the rotatory test was not reliable enough to be used as the sole measure for identifying patients with unilateral labyrinthine lesions.

Analog-Digital Conversion↗
PubMedDate not supplied

Ewald's second law re-evaluated.

Patients and experimental animals (cats) with one functioning horizontal semicircular canal were tested with precise rotatory stimuli. Nystagmus responses were quantified with EOG and a laboratory digital computer. After large-magnitude stimuli there was a statistically significant difference between the maximum slow component velocity of nystagmus induced by ampullopetal endolymph flow and that induced by ampullofugal endolymph flow in all patients and cats.

Animals↗
PubMedDate not supplied

Voluntary control of the human vestibulo-ocular reflex.

The ability of normal subjects to increase their vestibulo-ocular reflex (VOR) gain with an imagined stationary frame of reference was dependent on their strategy and the test conditions. With large amplitude sinusoidal rotation (greater than 50 degrees) subjects could not increase their VOR gain regardless of the strategy used. With small amplitude excursions (less than 50 degrees) they could significantly increase their VOR gain if they used a 'single stripe' strategy. Accompanying this increase in VOR gain was an increase in the phase lead of VOR slow phase velocity relative to head velocity. Apparently the signal used to augment the VOR gain with an imagined stationary surround had phase characteristics similar to those of primary vestibular afferent neurons.

Eye Movements↗
PubMedDate not supplied

Differential effect of ischemia on spontaneous and sinusoidal-evoked activity in semicircular canal afferents in the bullfrog.

Spontaneous and sinusoidal-evoked nerve activity in semicircular canal afferent fibers of the bullfrog was evaluated prior to and following the production of ischemia of the labyrinthine arterial supply by mechanical occlusion of the vestibular artery. Neuronal spontaneous firing rates were observed to diminish by up to 100% within 10 min following the onset of ischemia. In most neurons there was a substantial increase in firing rate during the first few minutes. The sensitivity of the fibers to natural stimulation as determined by the gain in their responses to sinusoidal motion also diminished by as much as 75% over the same period. No detectable changes in the membrane potentials of the neurons were observed. The changes in excitability were closely correlated with the changes in spontaneous firing rate, but not all the neurons whose responses changed showed changes in spontaneous activity. Likewise, the relative magnitude of change varied from neuron to neuron.

Action Potentials↗
PubMedDate not supplied

The impulsive test in man.

The impulsive test is brief and comfortable to the patient. The SVM is the best discriminator of the variables examined. By using percent differences between CW and CCW responses in the same subject at the same stimulus magnitude, we can define a range for the normal population and indicate patients outside that normal range. The impulsive test gives directional information in patients with unilateral lesions. In patients with severe bilateral loss of vestibular function, measurable responses are still obtainable; while in patients with primary cerebellar disease, responses are increased. The test may also be useful in giving anatomic information about posterior fossa lesions.

Brain Neoplasms↗
PubMedDate not supplied

[A neuroanatomical study of the vestibular efferent system, III: the origin and pathway of the axons].

We have studied the vestibular efferent fibers pathway, after scratching the peripheral vestibular receptors and horseradish peroxidase injection, and TMB or DAB processing. We have proved the existence of a differentiated bundle in the main vestibular pathway, this bundle crosses the areas where the efferent somas have been situated, some of this fibers have been seen crossing the midline. It has not been possible to connect the efferent somas with the fibers.

Animals↗
PubMedDate not supplied

[Neuroanatomic study of the efferent vestibular system I: distribution of the somas in the brain stem. A qualitative study].

EVN are studied in the chinchilla by means of HRP tract tracer, using TMB and DAB as chromagen. Three groups of EVN somas have been identified within the brainstem; located in the proximity of the vestibular nuclei (I), the facial nerve genu (II) and the abducens nucleus (III). The extension, localization and anatomical relations have been determined.

Animals↗
PubMedDate not supplied

[Neuroanatomical study of the efferent vestibular system. II. Distribution of the somas in the brain stem. A morphological and quantitative study].

EVNs are studied in the chinchilla by means of HRP tract tracer. Morphological and quantitative analysis have been made noting that the contralateral groups outnumber the ipsilateral ones. Group I has the biggest number of somas. Round somas predominate over oval and polygonal shapes. In relation with size 10-15 microns, somas predominate.

Animals↗
PubMedDate not supplied

Aging and the human vestibular nucleus.

Degenerative changes during aging have been identified in the inner ear and in the vestibular nerve, but not in the human vestibular nuclear complex (VNC). Therefore, the purpose of this study was to document quantitative morphometric changes within the VNC in humans as a function of age. The VNC of normal human subjects was examined for age-related changes using computer-based microscopy. Neuronal counts, nuclear volume, neuronal density, and nuclear length of the 4 vestibular nuclei were determined in 15 normal people, age 40 to 93 years. Based on a linear model, there was approximately a 3% neuronal loss per decade from age forty to ninety. VNC volume and neuronal density also decreased significantly with age, although to a lesser degree than did the number of neurons. Neuronal loss as a percentage of the total number of neurons was greatest in the superior vestibular nucleus and least in the medial vestibular nucleus. Despite the overall loss of neurons, the number of giant neurons (> 500 microns2) increased in older people. This increase in giant neurons could be traced to the accumulation of lipofuscin deposits in the cell somata. The overall rate of neuronal loss with aging in the VNC is comparable to that previously observed in hair cells, primary vestibular neurons, and cerebellar Purkinje cells, but is in contrast to prior reports of no age-related loss of neurons in other brain stem nuclei.

Adult↗