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Biomedical subjects

N Tsujita

Publications and source records attributed to N Tsujita.

15 recordsLinked to original sources
PubMed1991

[Catecholamine fluorescent, acetylcholinesterase positive and peptide immunoreactive nerve fibers in the rat hepatic portal system].

Innervation of rat hepatic portal system consisting of stem (portal vein) and peripheral portions (superior mesenteric vein, inferior mesenteric vein, splenogastric vein) was investigated by catecholamine fluorescence, acetylcholinesterase and immunohistochemical methods. Catecholamine fluorescent and Neuropeptide Y (NPY) immunoreactive (ir) nerve fibers were distributed throughout the hepatic portal system. Greater density was demonstrated in the peripheral portions. Catecholamine fluorescent and NPY ir nerve fibers formed ground plexus around the hepatic portal system. Acetylcholinesterase positive and vasoactive intestinal polypeptide-ir nerve fibers were sparsely distributed and no significant difference in density was noticed in the stem and the peripheral portions. Density of substance P ir, neurokinin A ir and calcitonin gene-related peptide ir nerve fibers was greater in the peripheral than the stem portion. All these fibers reticular showed pattern.

Acetylcholinesterase↗
PubMed1990

Disorders of gaze during head rotation.

We investigated gaze functions during sinusoidal head rotation in patients with peripheral and central vestibular lesions. Various kinds of gaze disturbance appeared in relation to deficient compensation (labyrinthine lesions), inaccurate gain regulation (cerebellar lesions), impaired gaze-induced suppression (cerebellar lesions), and inadequate visual correction (brain stem lesions). Analysis of gaze during head rotation may help to understand the regulation system of the vestibulo-ocular reflex as well as to detect gaze disturbances in patients with vestibular disorders, which cannot be attained by conventional vestibular examinations.

Adult↗
PubMed1989

The effect of alcohol on the vestibulo-ocular reflex and gaze regulation.

To clarify the effect of the temporary decline in cerebellar function on the vestibulo-ocular reflex (VOR) and gaze functions, we examined 12 normal adults under passive rotations before and after they drank alcohol at dosages of 0.43 and 0.65 g/kg. Whereas spatial gaze fixation was maintained accurately with 0.65 g/kg administration (0.06% blood alcohol level), gaze fixation on a head-fixed target and smooth pursuit were impaired by the higher dosage of 0.43 g/kg (0.03% blood alcohol). The magnitude of the alteration in the VOR gain after drinking was correlated significantly with the VOR gain before drinking: while small values were enhanced by drinking, large values were suppressed. The present study indicates that the VOR in the dark is regulated by the balance between the amplifying and suppressing forces controlled by the cerebellum.

Adult↗
PubMed1988

Vestibulo-ocular reflex and gaze functions in a patient with congenital inner ear anomalies.

We report on the vestibulo-ocular reflex (VOR) and gaze functions during horizontal rotations as well as upright locomotions in a fisherman with congenital inner ear anomalies. The finding of a marked gaze disturbance due to low VOR gain during passive rotations resembled that found in early acquired lesions. There was an improvement during active rotations, suggesting an intensified cervico-ocular reflex. Although head oscillations in the horizontal plane were abnormally large during stepping and running, they were compensated for visually even at high frequencies. The absence of complaints of oscillopsia as well as his ability to achieve proper balance seemed to be accomplished by his optokinetic ability, regularly transformed head oscillations and modified perceptive mechanisms at higher cortical levels.

Adult↗
PubMed1988

Pursuit and saccadic eye movements in response to unpredictable constant velocity targets.

Pursuit eye movements in response to unpredictable reversals of constant velocity target motion at 20 degrees, 40 degrees and 60 degrees/s were analysed in 20 normal subjects. The gain in smooth pursuit was originally determined by the preceding target duration; the shorter the preceding movement, the longer was the acceleration of pursuit velocity inhibited. The ongoing target duration secondarily affected the gain at faster target velocities by restricting time for eye velocity acceleration. Whereas the saccadic reaction time was around 200 ms, the intersaccadic interval shortened as target velocity increased. The saccadic amplitude increased in direct proportion to an increase in target velocity. The present study showed that, even under irregular stimulations, pursuit eye movement is regulated in a feedforward manner by the perceptual analysis of the preceding target motion, and that corrective saccades in pursuit eye movement correspond to those observed in step displacements, except for the programming on the basis of the changing rate of position error.

Adult↗
PubMedDate not supplied

Evaluation of the vestibulo-ocular reflex by gaze function.

The relationship between the vestibulo-ocular reflex (VOR) and gaze fixation was investigated in normal adults, normal children, patients with cerebellar lesion and patients with labyrinthine dysfunction. Large VOR gains were found in patients with cerebellar lesion and normal children, both presenting poor suppression by gaze. Pathological decline in the VOR gain with labyrinthine lesion impaired spatial gaze fixation; however, it did not affect fixation-induced suppression. Gaze effect on the VOR, whether amplifying or suppressing, decreased linearly and rapidly at higher frequencies so that VOR seemed to be no more modified in the light at 2-3 Hz in any subject group. The present study suggested that VOR is controlled even in the dark by both mechanisms to obtain spatial gaze fixation and to gaze at a spatially moving target.

Adult↗
PubMedDate not supplied

Effect of labyrinthine dysfunction upon head oscillation and gaze during stepping and running.

Head oscillations and eye movements when stepping and running were studied in normal subjects and in patients with labyrinthine dysfunctions. In normal subjects, whereas linear head oscillations in the horizontal plane were very limited during both stepping and running, a marked increase in the vertical linear displacement induced pitching motions of the head during running. Patients with unilateral and bilateral lesions complaining of oscillopsia manifested lateral and diffuse oscillations, respectively, in the horizontal plane during stepping. The ratio of eye amplitude to head amplitude in the vertical plane showed larger values in subjects with labyrinthine lesions than in normals. The present results suggested that oscillopsia during upright locomotion is closely related to linear head oscillations with irregular and high-frequency components, in addition to dysfunction of the vestibulo-ocular reflex.

Adult↗
PubMedDate not supplied

Failure of gaze stabilization under high-frequency head oscillation.

Gaze functions under high-frequency head oscillations with large amplitudes were investigated in 12 normal subjects. Oscillation amplitude decreased as the frequency increased (31 degrees at 2 Hz to 11 degrees at 5 Hz on average). Maximum head velocity and acceleration were 170-200 degrees/s and 2,500-5,000 degrees/s2, respectively. At frequencies higher than 2 Hz, the mean ratio of eye amplitude to head amplitude reached high large values (1.2 at 2 Hz to 1.8 at 5 Hz, on average), whereas it dropped to extremely low values (0.5-0.6 at 3-5 Hz) in the 2 referred patients with bilateral labyrinthine loss. High ratio values, different from the previous reports, may result from a failure of compensation due to abnormally high-frequency and large head oscillations. The present study indicated that the frequency range of VOR influenced by gaze should correspond to that of daily-experienced oscillations, and that once head oscillations exceed the limit, compensation quickly deteriorates.

Adult↗