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Biomedical subjects

K Mukuno

Publications and source records attributed to K Mukuno.

At least 19 recordsLinked to original sources
PubMed1992

Bilateral innervation of the musculus levator palpebrae superioris by single motoneurons in the monkey.

The location of motoneurons innervating the musculus levator palpebrae superioris (LPS) was studied in the monkey (Macaca irus) by using Fast blue (FB) and propidium iodide (PI) as retrograde neuronal tracers. In each monkey, FB was injected into the LPS of one eye and PI into the LPS of the other eye. Neuronal cell bodies labeled with FB and/or PI were seen intermixed bilaterally through the entire rostrocaudal extent of the central caudal nucleus. While single-labeled (70%) cell bodies predominated, many double-labeled (30%) cell bodies were also encountered. Each of the double-labeled neurons was concluded to supply the LPS on both sides by way of axon collaterals.

Animals↗
PubMed1992

Bilateral homonymous hemianopsia due to tentorial herniation, with sparing of central vision: case report.

Cases of complete bilateral homonymous hemianopsia with sparing of central vision that are caused by bilateral tentorial herniation are extremely rare. We describe one such case resulting from severe head trauma, the first to be reported in which magnetic resonance images showed clear evidence of the responsible lesion. The causes of bilateral homonymous hemianopsia with sparing of central vision and the possible mechanisms whereby macular sparing may arise are discussed.

Adolescent↗
PubMed1992

[Unusual pathological ocular movement caused by dysfunction of the saccade generation mechanism].

We describe a patient with abnormal ocular movement, probably due to dysfunction of saccade generation mechanism in the lower pons involving the omnipause neuron and a feed-back circuit. A 26-year-old man had fever, mild headache and sore throat for a few days and also noted unstable gait and diplopia. These symptoms subsided, but he noticed oscillopsia about 2 months later. On admission in our hospital, the neurological examination revealed no abnormalities except for abnormal eye movements, which were induced by voluntary or involuntary ocular movement and lasted for a few minutes. The abnormal ocular movement was irregular in direction, amplitude and rhythmicity, and the voluntary and involuntary ocular movements could not be elicited during the period of this abnormal ocular movement. The abnormal ocular movement completely disappeared for about 1 hour by intravenous injection of TRH. At this time bilateral mild abducens palsy was demonstrated by EOG examination. The abnormal ocular movement in this patient, which has nerve been reported in the literature, was considered to be due to a disinhibition of excitatory burst neuron (EBN) caused by the dysfunction of omnipause neuron, and possibly due to a delay of feed-back information of saccade to the EBN.

Abducens Nerve↗
PubMed1991

[Localization of motoneurons of the vertical yoke muscles in a brainstem of the cat--a double labeling study].

Motor neurons innervating the vertical yoke muscles in cats were investigated using fluorescent dyes by the double labeling method. In 4 cats, the right superior rectus muscle (SR) and left inferior oblique muscle (IO) were injected with 3% fast blue (FB) and 5% diamidino yellow dihydrochloride (DY), respectively, for observing motoneurons innervating yoke muscles involving upward gaze. In 4 other cats, the left inferior rectus muscle (IR) and right superior oblique muscle (SO) were injected with 3% FB and 5% DY, respectively, to observe motoneurons innervating yoke muscles involving downward gaze. After SR and SO injections labeled cells were found in the bilateral oculomotor nucleus and the bilateral trochlear nucleus, respectively, predominantly on the contralateral side. Following IR and IO injections labeled cells were found only in the ipsilateral oculomotor nucleus. No double labeled cell was observed in any labeled neurons, which indicates that each of the yoke muscles was innervated by independent individual motoneurons. According to the present observation and past reports on rats, cats and monkeys, motoneurons innervating SR and SO have developed from lower mammals such as the rat into predominantly contralateral innervation in the monkey, from a phylogenetic point of view. On the other hand, compared to contralateral innervation in lower mammals, motoneurons innervating IR and IO have developed into ipsilateral innervation in the monkey.

Amidines↗
PubMed1991

[A case of post-traumatic medial longitudinal fasciculus syndrome].

Medial longitudinal fasciculus (MLF) syndrome recognized 2 days after a head injury is described. The patient was a 48-year-old man who had fallen from a ladder about 3m high. On his admission, scalp contusion on the left occipital area was noticed. Neurological examination revealed no neurological abnormalities except slightly disturbed consciousness. Plain skull X-ray films demonstrated a lineal skull fracture of the left occipital bone. Computed tomographic (CT) scans showed a slight subarachnoid hemorrhage within the bilateral sylvian fissures, but no parenchymal contusion in the brain stem was observed. On the 2nd day, when the patient regained full consciousness, impairment of adduction of the right eye and a fine nystagmus of the left eye on left lateral gaze were recognized. Convergence was intact. Right side MLF syndrome was diagnosed. This syndrome gradually disappeared followed by the initial improvement of adduction of the right eye, and the patient had completely recovered about 20 days after the head injury. Three major mechanisms leading to MLF syndrome caused by head injury are reported in the literature. They are: (1) primary brain stem injury, (2) secondary brainstem injury by trans-tentorial herniation, and (3) circulatory disturbance of perforating branches of the vertebro-basilar artery due to shearing force. In our case, the slightly disturbed consciousness at the time of the head injury indicates that this syndrome was not brought on by primary or secondary brain stem injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Injuries↗
PubMed1989

[Morphological study of innervation of orbicularis oculi in the cat with respect to motoneurons, nerve fibers and muscle fibers].

It has been suggested that the orbicularis oculi muscle functions in different modes of action in the orbital portion and in the palpebral portion. To study the anatomical correlation between the localization of muscular division and the size of motoneurons in facial nucleus, the retrograde tracing method was used. A histochemical study on the type of muscle fibers was also performed. The relationship between the motoneurons, nerve fiber and muscle fiber was discussed in terms of the functional organization of the palpebral or orbital orbicularis oculi. We injected a tracer of 50% horseradish peroxidase (HRP) into the orbital and/or palpebral portion of the orbicularis oculi muscle and HRP-labelled motoneurons at the brainstem were studied. In the facial nucleus, four subnuclei have been described: the ventrolateral, ventromedial, dorsolateral and dorsomedial. HRP-labelled motoneurons which innervated both the orbital and palpebral portions were spindle shaped and were found ipsilaterally in the dorsolateral subnucleus, and were distributed rostrocaudally. The histogram of the average soma diameter traced by the injection in the orbital portion presented two peaks at 30 microns and 40 microns in contrast to one peak of palpebral portion. Secondly, a histochemical study using alkali (pH 10.4) preincubated ATPase and acid (pH4.3) preincubated ATPase and NADH stain was performed. It was found that the muscle fibers of the orbital part were composed predominantly of large and middle diameter group II B, while the palpebral part consisted mainly of small diameter group II A. By diameter analyses of the facial nerve fibers, it was found that the myelinated nerve fibers consisted of 3 peaks in terms of the magnitude of histogram.

Animals↗
PubMed1988

Orbital lipoma.

A patient who had a huge orbital lipoma with extension to the muscle cone is described. The lipoma was 42 x 34 x 32 mm in size, and there was no visual disturbance following removal of the tumor and iliac bone grafting. Diagnosis of orbital lipoma is difficult to make. This is particularly true of a lipoma with an obvious capsule, which cannot be easily differentiated from a dermoid cyst. However, computed tomography scanning is useful in ascertaining the location, size, and relationship with orbital contents. A review of the literature concerning orbital lipoma revealed only a few reports, and the features of the orbital lipoma are summarized. In addition, the possible mechanism of orbital enlargement and the approach to the muscle cone are described.

Adult↗
PubMed1988

Instability of eye position in the dark in cerebellar degeneration.

Fourteen cases of spinocerebellar degeneration were examined. While the patients attempted to keep their eyes in the primary position, horizontal eye movements were recorded for 1 min in total darkness by infrared reflection oculography. Instability of eye position in the dark was observed in 10 patients. The range of the eye position error was 3-6 degrees in 6 patients, 6-10 degrees in 3 patients and over 10 degrees in 1 patient. These results indicate that the cerebellum plays an important role in extraretinal (nonvisual) eye position control.

Adult↗
PubMed1987

Quantitative measurement of upper eyelid movements.

A simple and noncontact method for recording upper eyelid movement by means of a solid state image sensor has been developed. Physiological parameters of blink and lid movements during gaze change were studied in 30 normal subjects. Maximum velocity against lid displacement was analyzed. Electromyography (EMG) of the levator palpebrae as well as orbicularis oculi muscles was conducted and vertical eye movement was recorded by electrooculography (EOG). The maximum lid velocity both for upward and downward gaze change was measured; it was always faster in the downward than in the upward gaze. The duration of lid movement during upward gaze change was about 70 msec longer than that of the vertical saccadic eye movement. By EMG, a pulse-step discharge has been well known to occur in the superior rectus muscle but it was never seen in the levator palpebrae muscle in the present observation. The maximum lid velocity of downward spontaneous blink showed two-phase distributions: phase 1 with an initial flat phase in small displacement and phase 2 with a steep phase in large displacement. By EMG, only the pretarsal portion of the orbicularis muscle discharged at the initial phase; preseptal as well as pretarsal orbicular muscle discharges were noted in the second phase. The simplicity of this technique would permit its wide clinical application.

Adult↗
PubMed1986

The origin of square wave jerks: conditions of fixation and microsaccades.

The effects of various fixation stimuli on square waves of eye movements were studied in 16 normal subjects. Fixation eye movements were recorded by infrared reflection oculography under visual and nonvisual conditions. The target size was varied from 9 to 72 minutes of arc in four steps. The mean amplitude of the square wave was enlarged more than 0.5 degrees with the targets over 18 minutes of arc and in total darkness. The findings indicate that the square wave jerks are enhanced microsaccades and are closely related to the instability of the fixation eye movements.

Adolescent↗
PubMed1985

Hemispheric lateralization of spatial contrast sensitivity.

Visuospatial contrast sensitivity was determined by the Arden grating chart in 23 patients with cerebral infarctions involving the primary visual cortex or visual association cortex. Subjects were classified into three groups according to their lesions: I, 6 patients with unilateral medial occipital or occipitotemporal lesions; II, 6 patients with left lateral parieto-occipital lesions; and III, 11 patients with right lateral parieto-occipital lesions. Contrast sensitivity was markedly reduced in Group III, especially in patients having hemispatial agnosia. Group I patients with hemispatial agnosia showed almost normal contrast sensitivity. Spatial contrast sensitivity appears to be more affected when the lesion has an influence on the nondominant lateral parieto-occipital cortex.

Adult↗
PubMed1985

Electron-microscopic study of iris nerves and muscles in diabetes.

The ultrastructure of the iris muscles and innervating nerves in patients with diabetes mellitus and approximately age-matched controls was examined by electron-microscopy. The specimens were obtained during cataract surgery. There were definite histopathological alterations at the nerve terminal innervating the dilator muscle, e.g. the presence of mitochondrial abnormalities, dense bodies and lamellar structures. No change was noted at the nerve terminal to the sphincter muscle. Moderate involvement of the muscle, especially at the sphincter, was observed in the specimens of diabetics. The control specimens had no change at the nerve terminals, while moderate change was observed at the sphincter muscle. Therefore, the change in the sphincter seen in the specimens of diabetics seemed to be mainly the result of the aging process, though the existence of early sympathetic neuropathy was confirmed.

Aged↗