The effect of astemizole on bronchial hyperresponsiveness and exercise-induced asthma in children

The ability of the new generation H1-receptor antagonist, astemizole, to prevent histamine-induced airway obstruction and exercise-induced asthma (EIA) was studied in 20 children with asthma. The study was a randomised clinically controlled trial of oral astemizole versus placebo in a cross-over study. In each of the two treatment periods the children were tested at days 0, 6, 15 and 22 of therapy. The two treatment periods were separated by a washout period of 50 days, and at each visit a bronchial challenge with increasing concentrations of histamine followed by an exercise test was performed, and peak flow and asthmatic symptom score were recorded daily. The children tolerated significantly higher mean concentrations of histamine when treated with astemizole compared with placebo (P less than 0.001). Astemizole postponed the response to exercise, but no change in the maximal response was found. No differences between the treatment periods were found regarding frequency of asthmatic symptoms or the daily recording of peak flow.

Posture-correlated responses to vestibular polarization in vermal versus intermediate posterior cerebellar cortex

Cerebellar lesion experiments have led to the concept that the medial longitudinal zone controls postural tone while the intermediate zone controls discrete movement. This study is a test of the hypothesis that, of the two zones, the medial zone is more closely linked to the resting discharge of vestibular afferent fibers, a prime source of neural tonus underlying the tonus of posture. Unilateral polarizations of the vestibular apparatus via the round window in awake, unrestrained guinea pigs caused step changes of postural attitude, the direction of which was polarity dependent. In anesthetized animals, these currents caused nonadapting step changes, or posture-correlated responses in the level of resting discharge in vestibular primary afferent fibers. In the medial and the intermediate cerebellar cortices of the posterior lobe, the proportion of step-like responses was similar, in contradiction to the hypothesis. This suggests that the cerebellar computations for controlling both postural tonus and discrete movements require information about vestibular tonus in terms of simple spike activity.

Vestibular nerve input to neck and shoulder regions of lateral cuneate nucleus

Axonal transport of tritiated leucine by the vestibular nerve was observed in regions of the ipsilateral lateral cuneate nucleus (LCN) that were determined electrophysiologically to receive somatosensory input from the neck and shoulder and to respond to electrical stimulation of the vestibular nerve. Regions of the LCN receiving input from more distal musculature did not receive vestibular input.

Survival of function in the deafferentated vestibular nerve

After it has been deafferentated, spontaneous spike activity in the vestibular nerve is not abolished, but is drastically reduced 1-3 months post-op. If the nerve stump is cut again in the compensated animal, similarly directed postural asymmetries are re-induced, although of milder intensity. Electrical stimulation of the vestibular nerve stump evokes monosynaptic excitation in the vestibular nuclei and a vestibulo-ocular reflex at normal thresholds despite partial degeneration in the nerve. Therefore, the deafferentated nerve is capable of exerting compensatory influences upon the central nervous system.

Eye-head coordination and lateral canal block in squirrel monkeys

Eye and head nystagmus during horizontal optokinetic stimulation was analyzed in squirrel monkeys. Slow phase speed of coupled head and eye nystagmus showed highly significant negative correlations in normal subjects; correlation coefficients were -0.81 at 60 degrees/sec and -0.72 at 100 degree/sec stimuli. Bilateral semicircular canal block resulted in a reduction of the negative correlation. The postoperative reduction of the correlation coefficient value ranged from 0.17-0.28 (significant at P less than 0.01 level) at 60 degrees/sec stimulus and 0.06-0.13 (non significant) of 100 degrees/sec stimulus. Gaze speed was calculated by summing slow phase speeds of coupled head and eye nystagmus. Mean error of gaze in normal subjects was 1.5% at 60 degrees/sec stimulus and 7.8% at 100 degrees/sec stimulus. Mean gaze speed showed an overshoot (8% at 60 degrees/sec stimulus and 6.5% at 100 degrees/sec stimulus) in the tree to four weeks postoperative period; however, this subsided two to three months after the operation. Measurement of head-turning performance (in yaw plane) in humans may provide a clinically useful index for the assessment of certain types of vestibular function.

Head and eye movements following vestibular stimulus in squirrel monkeys

Head and eye movements induced by vestibular stimuli (rotational velocity steps) were studied under several experimental conditions in squirrel monkeys. Monkeys showed prominent head nystagmus under a free head condition. Slow phase gaze velocity (SPGV) was calculated by summing the slow phase speed of coupled head and eye nystagmus. A statistical test showed no significant difference between slow phase eye velocities in a fixed head versus SPGV in a free head condition. This indicates that an accurate negative feedback control of eye movements is performed by the vestibular system when sensing active head movements. Bilateral lateral semicircular canal block eliminated these responses in subjects without amphetamine injection. However, in amphetamine-injected animals, 14-21% of preoperative response could be found even after this operation. Since the plane of rotation was not parallel to that of the lateral semicircular canals, the result was considered to be due to vertical semicircular canal stimulation.

Eye-head coordination during optokinetic stimulation in squirrel monkeys

Head and eye movements in the yaw plane were recorded during and after optokinetic stimulation in squirrel monkeys. 1) Phasic or tonic head deviations to the side of the ocular quick phase occurred in 94% of total recordings (n = 50) during the perstimulus period, and in 75% of recordings (n = 49) during the poststimulus period. Magnitude of mean head deviation was significantly different between perstimulus and poststimulus periods. 2) Head nystagmus associated with eye nystagmus was consistently observed in seven of nine squirrel monkeys during optokinetic stimulation. Squirrel monkeys are thereby less prone to display head nystagmus than either guinea pigs, pigeons or chickens. 3) Slow phase speeds of coupled head and eye nystagmus were subjected to statistical analysis. A highly significant negative correlation was found between slow phase head and eye speeds. The correlation coefficient was - 0.81 at 60 degrees / sec stimulus (n = 119) and -0.72 at 100 degrees / sec stimulus (n = 131). The gaze speed, calculated by summing the head and eye speeds, was 59.1 plus or minus 6.8 / sec at 60 degrees / sec and 92.2 plus or minus 11.4 at 100 degrees / sec stimulus. There was no significant difference between the gaze speed in a free head condition and the eye speed when the head was fixed.