Biomedical subjects

H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 307 records · Page 17Linked to original sources

PubMed1989

Purification of GTP-binding proteins from bovine brain membranes. Identification of heterogeneity of the alpha-subunit of Go proteins.

Using high-resolution Mono Q column chromatography, we purified 6 distinct peaks of GTP-binding proteins from bovine brain membranes. Five of them consisted of 3 polypeptides with alpha beta gamma-subunits and served as the substrate of islet-activating protein (IAP), pertussis toxin. The other one was purified as alpha-subunit alone and was also ADP-ribosylated by IAP in the presence of beta gamma-subunits. When each alpha-subunit was characterized by immunoblot analysis using various antibodies with defined specificity, the two of them were identified as Gi-1 and Gi-2, and other 4 appeared to be Go or Go-like G proteins. The alpha-subunits of immunologically Go-like proteins were apparently distinguishable from one another on elution profiles from the Mono Q column. Thus, there was a heterogeneity of the alpha-subunit of Go in the brain membranes.

Animals↗

PubMed1989

Hypoxia-sensitive hyperexcitability of the intramuscular nerve axons in Isaacs' syndrome.

A case of Isaacs' syndrome with Trousseau's phenomenon is reported. Myokymia, pseudomyotonia (difficulty relaxing after forceful contraction), and ischemia-induced carpal spasm (Trousseau's phenomenon) were not abolished by nerve block distal to the cuff or by intravenous infusion of calcium. Inhalation of oxygen suppressed the pseudomyotonia and Trousseau's phenomenon, but myokymia persisted. Phenytoin abolished all types of abnormal discharges. The morphological abnormality in biopsied short peroneal muscle consisted of intraterminal and ultraterminal sprouting. We postulate that the trigger zone for abnormal discharge in our case is in the distal segment of the intramuscular nerve axon, including the nerve terminal. Hypoxia-sensitive hyperexcitability of the axon membrane might be responsible for the generation of pseudomyotonia and Trousseau's phenomenon, although the mechanism underlying myokymia remains unknown.

Adult↗

PubMed1989

Spectral properties of signal averaging and a novel technique for improving the signal-to-noise ratio.

Averaging is one well-known method for improving the signal-to-noise (S/N) ratio of data or a time series, in which small amplitude responses to regularly occurring stimuli are contaminated by noise. We have considered the spectral properties of that process and introduce a new method which further improves the S/N ratio. We also demonstrate that the signal recovered by normal averaging is identical to that recovered by the frequency extraction technique which we propose. A formula for the sums-of-squares of the recovered signal is derived. The success of the frequency extraction technique has been demonstrated on sinusoids, white noise, evoked potentials contaminated by a background EEG, and the EEG recorded with the subject's eyes closed.

Algorithms↗

PubMed1989

Prevalence of HTLV-I-associated myelopathy among HTLV-I carriers in Saga, Japan.

Surveying the disease by sending questionnaires to all physicians of the Saga Medical Association, we tabulated 19 definite cases of HTLV-I-associated myelopathy (7 males and 12 females) as of January 31, 1988. The population at risk of HTLV-I carriers was estimated by applying sex- and age-specific anti-HTLV-I antibody-positive rates among blood donors at the Saga Red Cross Blood Center in the fiscal year of 1986 to the population of Saga Prefecture in 1982. The crude prevalence rates among HTLV-I carriers from 20 to 69 years of age per 100,000 were 65.7 for males and 86.9 for females, respectively. The summary prevalence rates with 95% confidence intervals were 46.5 (14.3-97.3) for males and 74.9 (35.3-129.2) for females. There was no remarkable difference in the age-specific prevalence rates in either sex. The crude and summary rates among females were higher than those among males, but the difference was not statistically significant.

Adult↗

PubMed1989

Human neurolymphomatosis by adult T-cell leukemia.

We report a case of adult T-cell leukemia presenting with sensorimotor polyneuropathy with persistent severe pain. The patient died without treatment after 4 months. Autopsy showed infiltration of peripheral nerves by leukemia with no involvement of the CNS. This case closely resembles Marek's disease of fowls, a virus-induced T-cell lymphoma associated with neurolymphomatosis.

Humans↗

PubMed1989

Nerve conduction study of human tetrodotoxication.

We carried out serial nerve conduction studies in a patient with tetrodotoxication caused by ingesting pufferfish. Conduction velocities and amplitudes of muscle and sensory nerve action potentials were equally affected. Neither temporal dispersion nor focal conduction block occurred. The proximal (F wave) motor latencies were also prolonged. These abnormalities rapidly improved in parallel with clinical recovery and with the decrease in the urinary excretion of tetrodotoxin (TTX). These results indicate that TTX equally and reversibly affects myelinated nerve fibers throughout the entire length of the axon by lowering the conductance of sodium currents at nodes of Ranvier.

Action Potentials↗

PubMed1989

Evaluation of the signal-to-noise ratio for average evoked potentials: determination of interstimulus interval and averaging number.

Repetitive stimuli have to be presented to improve the signal-to-noise ratio for the identification of evoked potential of the brain. The averaging method has been widely used for the response to repetitive stimuli. It should be noted that if the stimulus frequency is synchronized with the rhythm of the background noise of an electroencephalogram, the colored noise can only poorly be eliminated by the averaging method. This paper discusses the interstimulus interval of the stimuli and the requisite averaging number from the viewpoint of the S/N ratio of averaging evoked potentials. First, using the a priori information of the evoked potential and background noise, we determine the interstimulus interval of the stimuli. Next, under presentation of the stimulus with the interstimulus interval thus determined, the data of the electrical activity are recorded, and the requisite averaging number is obtained such that the S/N ratio of the average evoked potential becomes larger than the required S/N ratio. The results were applied to the data of the photic evoked potential in response to light-flashes in a healthy male.

Adult↗

PubMed1989

[A case of stimulus-sensitive segmental spinal myoclonus].

A 37-year-old-man was admitted to our hospital because of periodic contraction of the right shoulder muscles of approximately one month's duration. He denied any significant history such as trauma or fever. General physical examination was unremarkable. Neurological examination was also unremarkable except for the periodic synchronous myoclonus involving the right sternocleidomastoid, trapezius, deltoid, rhomboid and serratus anterior muscles. X-ray fluoroscopy demonstrated a synchronized rhythmic contraction of the right diaphragm. The myoclonus was considered to be of spinal origin, because those muscles were innervated by the right fourth and fifth cervical spinal segments. Its frequency was approximately 1.2 Hz. The myoclonus disappeared during sleep. It was enhanced by a voluntary contraction of the corresponding muscles, but mental stress such as arithmetic induced no change in the myoclonus. CBC, serum laboratory data including viral antibody titer, and cerebrospinal fluid were all normal. Radiological examination including MRI showed no abnormal finding. EEG as well as somatosensory evoked potentials following median nerve stimulation were normal. Jerk-locked averaging triggered by the myoclonus of the right deltoid muscle showed no pre-myoclonus spike at the scalp electrodes. Clonazepam (1.5-6 mg/day) and phenytoin (200 mg/day) reduced the rhythmicity as well as frequency of the myoclonus, which then became stimulus-sensitive. The reflex myoclonus was induced by tapping anywhere on the body or by electric shock, but not by flash or sound. There was a refractory period of approximately 800 msec. Lack of the stimulus-sensitivity early in the clinical course could be due to this refractory period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

[A case of orthostatic tremor in parkinsonism].

A 79-year-old woman presenting with orthostatic tremor (OT) was reported. In addition to OT, neurological examination showed mild dementia, bradykinesia, rigidity of the neck and the upper limbs and positive Babinski reflex on the left. These clinical signs and CT as well as MRI findings suggested vascular parkinsonism as its pathological background. Upon standing with her feet together, she rapidly developed rhythmic repetitive contraction of all leg muscles. The shaking disappeared by walking, sitting, or lying down. The EMG recording revealed 4-Hz tremor which consisted of alternating contraction of anti-gravity muscles and their antagonists. The EMG bursts associated with the tremor were synchronous in corresponding muscles of both legs. OT could be bilaterally reset by unilateral voluntary or passive movement of leg. In the supine position, the tremor was not evoked by voluntary contraction of leg muscles against resistance. As the tremor was aggravated by the administration of haloperidol was suppressed by L-DOPA, it was thought to have the pharmacological basis common to the resting tremor of parkinsonism. Furthermore, we postulated that the postural tonus-regulating system, which is thought to set and maintain the tonus of antigravity muscles for standing upright, might be involved in the generation of the rhythmic discharge pattern (reciprocal bursts in a given leg and synchronized bursts in both legs) of OT.

Aged↗

PubMed1988

Antigenic difference of acetylcholine receptor between single and multiple form endplates of human extraocular muscle.

The acetylcholine receptor (AChR) of human extraocular muscle (EOM) has been studied by the immunological method using anti-AChR antibodies obtained from the sera of patients with myasthenia gravis (MG) of ocular type, whose symptoms have been restricted to EOM. Those antibodies could distinguish the AChR of multiple (en grappe) form endplates from that of single (en plaque) form endplates. This result indicates the antigenic difference of AChR between those two forms of endplates of human EOM.

Autoantibodies↗

PubMed1988

Central vs peripheral nerve conduction. Before and after treatment of subacute combined degeneration.

Central and peripheral nerve conduction was studied in two patients with subacute combined degeneration by using the short-latency somatosensory evoked potentials and the peripheral nerve conduction study during treatment with cyanocobalamin. Before the treatment, somatosensory evoked potentials with median nerve stimulation were normal, but those with peroneal nerve stimulation revealed prolonged central conduction indicating dysfunction within the posterior column. Peripheral sensory and motor nerve action potentials were reduced with normal or slightly reduced conduction velocity. After treatment, marked shortening of the central conduction time (by 24% and 31%, respectively) was observed with mild or no recovery of peripheral nerve action potentials. These physiologic findings suggest that the main pathologic changes in the central nervous system may be demyelination in the posterior column in addition to axonal degeneration in the peripheral nerve. The former was responsive to treatment but the latter was poorly responsive to treatment. Sensory symptom in subacute combined degeneration appears to be, at least partially, attributed to the spinal cord lesion.

Adolescent↗

PubMed1988

Recording of movement-related potentials from the human cortex.

A patient with intractable epilepsy secondary to a brain tumor was evaluated with a chronically implanted array of 64 stainless-steel subdural electrodes covering the perirolandic area. Cortical potentials associated with voluntary, self-paced middle-finger extension were recorded simultaneously from subdural and scalp electrodes using a computer-assisted method for averaging movement-related potential (MRP) in relation to electromyographic (EMG) onset. A high-amplitude negative potential, Bereitschaftspotential/negative slope (BP/NS'), preceding the onset of the EMG activity by more than 1 sec was recorded in an extremely localized fashion exclusively from electrodes placed in the precentral hand motor area as well as in the more medial part of the somatosensory hand area. These results suggest that the hand motor and sensory areas have an essential participation in the generation of MRPs and, therefore, also in the preparation of voluntary finger movements.

Adult↗

PubMed1988

AAEE minimonograph #30: electrophysiologic studies of myoclonus.

Definition as well as classification of myoclonus and electrophysiologic methods for investigating myoclonus were reviewed. Among the electrophysiologic techniques currently available in most laboratories, the EEG-EMG polygraph is the most essential one and can provide us with the most important information. Jerk-locked averaging and evoked potential studies are useful for further investigating the pathophysiology of myoclonus and can be performed by using the same recording electrodes as those used for the polygraph. Jerk-locked evoked potentials and double-stimulation evoked potentials can be employed only for further investigating how cerebral cortex is involved in the generation of certain myoclonia. All these techniques can be used in proper combinations depending on the clinical features of the myoclonus in question, the purpose of the study, and the facilities available in each laboratory. These techniques also will be useful for following the clinical course during the treatment with antimyoclonus agents.

Electroencephalography↗

PubMed1988

Clinical picture of HTLV-I associated myelopathy.

Clinical and electrophysiological findings in 16 consecutive cases of HTLV-I associated myelopathy are reported. Symmetric spastic paraparesis associated with only mild hyperreflexia in the arms, clinical and electrophysiological evidence of moderate posterior column involvement at the thoracic level, urinary frequency and urgency associated with the detrusor-urethral sphincter dyssynergia but without systemic autonomic involvement, and absence of the segmental grey matter involvement, all suggest the presence of diffuse lesions of the white matter predominantly involving the thoracic cord. We conclude that HTLV-I associated myelopathy is a chronic diffuse leukomyelitis predominantly involving the thoracic cord.

Adolescent↗

PubMed1988

Construction of an evoked potential model expressed by parallel second order components with time lags.

We propose an evoked potential model consisting of a parallel combination of second order systems with time lags. Using this evoked potential model, scalp-recorded photic evoked potentials (PEPs) of three healthy young subjects were analysed, and the PEP waveforms decomposed into five basic waveforms. Generator sources for four components commonly observed in all three subjects are discussed.

Adult↗

PubMed1988

Somatosensory and acoustic brain stem reflex myoclonus.

A patient with brain stem reflex myoclonus due to a massive midbrain infarct was studied electrophysiologically. Myoclonic jerks were elicited at variable latencies by tapping anywhere on the body or by acoustic stimuli, and mainly involved flexor muscles of upper extremities. The existence of convergence of somatosensory and acoustic inputs in the brain stem was suggested. This myoclonus seemed to be mediated by a mechanism similar to the spino-bulbo-spinal reflex.

Aged↗

PubMed1988

Multimodality evoked potentials in HTLV-I associated myelopathy.

Multimodality evoked potentials (EPs) consisting of somatosensory EPs (SEPs), visual EPs (VEPs) and brainstem auditory EPs (BAEPs) were studied in 16 cases with HTLV-I associated myelopathy (HAM). Median nerve SEPs were normal in all cases. In posterior tibial nerve SEPs, the potential recorded at the 12th thoracic spinal process was normal in every case but cortical components were significantly prolonged in 10 cases, although five of these showed no sensory impairment. BAEPs were normal in every case whose hearing was intact, but VEPs were abnormal in two cases whose visual acuities were normal. The present results in HAM indicate predominant lesion in the thoracic cord, and might also suggest some subclinical lesion in the visual pathway.

Adult↗

PubMed1988

Auditory long latency event-related potentials in Alzheimer's disease and multi-infarct dementia.

An auditory discrimination paradigm was employed to elicit event-related brain potentials in 13 patients with Alzheimer's disease and 14 patients with multi-infarct dementia. The P300 latency was significantly prolonged in 12 patients with dementia compared with age-matched controls and showed a significant negative correlation with the score of Wechsler Adult Intelligence Scale (WAIS), especially with that of Digit Span subtest. There was no disease specificity. After physostigmine treatment, P300 latency decreased and WAIS score increased in 6 among 10 cases.

Aged↗