Search PubMed⌕ Search

Biomedical subjects

H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 289 records · Page 16Linked to original sources
PubMed1991

Pain-related somatosensory evoked potentials in syringomyelia.

Pain-related somatosensory evoked potentials following CO2 laser stimulation (pain SEPs) and conventional electrically-stimulated SEPs (electric SEPs) were examined in 8 patients with syringomyelia who showed various forms of dissociated sensory loss. Unlike clinical examination using a pin or needle, pain SEP is considered to be an objective and quantitative test to investigate functions of peripheral and central sensory pathways responsible for pain-temperature sensation (A delta fibres and the spinothalamic tract). Pain SEPs were abnormal in all patients. The results were generally compatible with the degree of a clinical impairment of pain-temperature sensation. Subclinical abnormality was detected in 3 patients. Electric median nerve SEPs using the scalp reference (Fz) were normal in 6 out of 8 patients. However, anterior and posterior cervical responses using a noncephalic reference were absent or small in 7 patients. Electric SEPs following tibial nerve stimulation were normal in 7 patients. These findings suggest that the function of the ascending fibres through the dorsal columns is intact in most patients, whereas the dorsal horn, where a fixed cervical potential is generated, is impaired. Pain SEPs combined with electric SEPs therefore appear to be extremely useful for investigating physiological function in the sensory pathways in patients who show 'dissociated sensory loss' such as in syringomyelia.

Adult↗
PubMed1991

Effects of age, gender, and stimulus side on scalp topography of somatosensory evoked potentials following median nerve stimulation.

This is the first study to evaluate the effects of age, gender, and stimulus side on scalp topography of somatosensory evoked potentials (SEPs) following stimulation of the median nerve by using computerized bit-mapped color images. Seventy-four normal subjects whose ages ranged from 7 to 88 years were studied, and Student's t test was performed on averaged mean maps and their standard deviations of each recognizable component by using the significance probability mapping method. Topographic maps of most components in aged subjects were significantly different from those in young subjects, mainly because of higher amplitudes of the components in the aged group. This difference was particularly significant for later components with the peak latencies of longer than 40 ms. Gender and stimulus side caused no significant differences in amplitude and topography of the components. Therefore, for clinical application of topographic maps of median nerve SEPs, a difference of gender and stimulus side could be disregarded, but it is necessary to consider the age effect.

Adolescent↗
PubMed1991

Deterioration of average evoked potential waveform due to asynchronous averaging and its compensation.

In order to improve the signal-to-noise ratio of evoked potentials, the responses to repetitive stimuli are usually recorded, and the averaging method is applied to them. If each starting point of the averaging varies with respect to the response because of asynchronous sampling of the measurement data, the average waveform of the evoked potential signal is distorted by the averaging. We analyzed the asynchronous averaging in the frequency domain and derived a relationship between the fluctuating time and the degree of the deterioration. By using this relationship, a required sampling rate was derived to ensure the accuracy of the averaging. Furthermore, we also deduced a compensation procedure for the asynchronous averaging in case of coarse sampling.

Evoked Potentials↗
PubMed1991

Ophthalmic complications in patients with paranasal sinus mucopyoceles.

We examined 45 (23 male and 22 female) Japanese patients with paranasal sinus mucopyoceles associated with ophthalmic complications. The patients ranged in age from 31 to 87 years. The patient distribution by the affected sinus was as follows: maxillary sinus alone, 17 patients; ethmoidal sinus alone, 9 patients; frontoethmoidal sinuses, 9 patients; frontal sinus alone, 7 patients, and other multiple sinuses, 3 patients. Thirty-nine mucoceles and 6 pyoceles were identified. Ophthalmic signs and symptoms included lid swelling, ocular pain, pseudoptosis, proptosis, displacement of the eyeball, epiphora, slight blurring of vision, severely decreased visual acuity, visual field abnormality, diplopia, disk edema, retinoichoroidal folds and increased intraocular pressure. Of the 45 patients, 1 had a history of sinus trauma and 29 had a history of sinus surgery.

Adult↗
PubMed1991

Pigmented paravenous retinochoroidal atrophy in a 68-year-old man.

A 68-year-old man with patchy paravenous zones of retinal degeneration with bone spicule pigmentation OU was diagnosed as having pigmented paravenous retinochoroidal atrophy. We reviewed the literature and found 71 previously reported cases of this condition. Most of the affected individuals were young adults. By comparison, our patient was afflicted at a considerably older age.

Aged↗
PubMed1991

[A case of familial essential myoclonus--electrophysiological study].

A case of familial essential myoclonus was reported with electrophysiological studies. A 58-year-old female presented with involuntary movement (myoclonic jerk) since age 6 years. At the age over 50, she developed difficulty in writing and fine finger movements. Two years ago, the diagnosis of hyperthyroidism was made, but she did not take any anti-thyroid medication. She was admitted to our hospital for further evaluation of myoclonus. On family history, her grandson (4-years-old) had myoclonus. On general physical examination, she showed a diffuse goiter. On neurological examination, she showed spontaneous myoclonus in the face, neck, trunk and the proximal limb muscles, especially in the left upper and right lower extremities. The myoclonus was exacerbated with auditory stimulation and emotional tension, but there was no temporal relationship between each stimulus and myoclonus. There was no myoclonus during sleep. Finger-to-nose test showed coarse intention myoclonus. Laboratory examinations including lysosomal enzyme assay revealed no abnormalities except for the decrease in total cholesterol (118 mg/dl) and the increase in serum lactate (19.7 mg/dl). The serum concentration of thyroxin was 18.4 micrograms/dl, that of triiodothyronine 3.0 ng/ml, and that of thyroid stimulating hormone (TSH) 0.027 microIU/ml. Anti-thyroglobulin antibody and anti-microsomal antibody were positive (X100, X6400). Neurological laboratory tests were normal including cerebrospinal fluid, peripheral nerve conduction study, electromyogram (EMG), muscle biopsy, cranial computed tomography and magnetic resonance imaging, and positron emission tomography. Electron transport system of the biopsied muscle was normal. So, we made a diagnosis of familial essential myoclonus and hyperthyroidism. In the electrophysiological studies, the electroencephalogram (EEG) was within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)

Electroencephalography↗
PubMed1990

Reduction of nerve growth factor level in the brain of genetically ataxic mice (weaver, reeler).

By a highly sensitive enzyme immunoassay we measured the level of nerve growth factor (NGF) in the cerebellum and cerebrum of the neurologically mutant mice, weaver, reeler and Purkinje cell degeneration (PCD). A significant decrease in NGF level was observed in both cerebellum and cerebrum of weaver and reeler mutants of either sex. However, there was no such difference between normals and mutants in the case of the PCD mice. These results show that weaver and reeler mice have abnormalities of NGF synthesis and/or degradation not only in the cerebellum but also in the cerebrum.

Animals↗
PubMed1990

Purification and characterization of five different alpha subunits of guanine-nucleotide-binding proteins in bovine brain membranes. Their physiological properties concerning the activities of adenylate cyclase and atrial muscarinic K+ channels.

We have purified five different alpha subunits of guanine-nucleotide-binding proteins (G proteins) from bovine brain membranes as active forms bound to guanosine 5'-[gamma-thio]triphosphate (GTP[gamma S]). All the purified alpha subunits were interacted with beta gamma subunits and served as a substrate for pertussin-catalyzed ADP-ribosylation. Based on the findings of immunoblot analyses using specific antibodies raised against various alpha subunits of G proteins, three of them were identified as alpha i-1, alpha i-2 and alpha i-3, and the other two were classified into alpha o type. One of the alpha o-type proteins was the most abundant in the brain membranes (termed alpha o), and the other (alpha o2) appeared to differ from alpha o in its proteolytic digestion data. The physiological properties of these purified GTP[gamma S]-bound alpha subunits towards adenylate cyclase and atrial muscarinic K+ channels were studied. The nucleotide-bound forms of alpha i-1, alpha i-2, alpha i-3 and alpha o2 inhibited the adenylate cyclase activity of S49 cyc- membranes which had been reconstituted with GTP[gamma S]-treated Gs; this inhibition appeared to be mainly competitive with the activated Gs, alpha i-1 having the most potent inhibitory activity among them. GTP[gamma S]-bound alpha o, however, could not inhibit the Gs-stimulated activity at all. On the other hand, all the GTP[gamma S]-bound alpha subunits activated atrial muscarinic K+ channels, accompanied by a lag time, at picomolar concentrations. The beta gamma subunits resolved from G proteins also activated the K+ channels without a lag time at nanomolar concentration. The maximum activation by the beta gamma subunits appeared to be more potent than that by any of the alpha subunits. These results suggest that alpha and beta gamma subunits might activate the K+ channels by mechanisms different from each other.

Adenosine Diphosphate Ribose↗
PubMed1990

Characterization of four G0-type proteins purified from bovine brain membranes.

Recently we reported there were at least four types of G0 or G0-like proteins in bovine brain membranes based on their elution profiles from Mono Q columns and their immunological reactivities; one of the proteins was purified as an alpha-monomeric form, and the others as alpha beta gamma-trimers. The four proteins, of which alpha-subunits were confirmed to be a family of G0-type by an immunoblot analysis, were thus referred to as alpha (0)1, G(0)2, G(0)3 and G(0)4, respectively, in order of their elutions from the column. Immunostained peptide mappings arising from proteolytic digestions of the four alpha-subunits, together with their fragmentation patterns containing radiolabeled ADP-ribose that had been incorporated by pertussis toxin-catalyzed ADP-ribosylation, suggested that the four G0-alpha were classified into either of two groups such as alpha (0)1 and G(0)2-alpha, or G(0)3-alpha and G(0)4-alpha. The kinetic parameters of their GTPase activities, however, revealed that there were different properties between alpha (0)1 and G(0)2-alpha or G(0)3-alpha and G(0)4-alpha. Thus, the four G0-type proteins appeared to be different entities from one another.

Amino Acid Sequence↗
PubMed1990

Diurnal rhythm in the plasma concentration of cortisol in paediatric patients with orthostatic dysregulation.

A gas chromatographic/mass spectrometric method using stable isotopically labelled cortisol as an internal standard was employed to determine patterns of episodic secretion of cortisol in three normal subjects and four paediatric patients with orthostatic dysregulation. The measurement of the plasma cortisol level at frequent time intervals revealed how the daily secretory pattern of cortisol differs in these patients and normal subjects.

Adolescent↗
PubMed1990

Hereditary pressure-sensitive neuropathy: demonstration of "tomacula" in motor nerve fibers.

By studying intramuscular nerves in 2 patients from 2 families with hereditary pressure-sensitive neuropathy (HPSN), the occurrence of abnormal thickening of myelin sheaths ("tomacula") was for the first time demonstrated in motor nerve fibers. Furthermore, the tomacula were found to line up on certain axons instead of being randomly distributed. These results indicate that the recurrent mononeuropathies of HPSN arise from an underlying asymptomatic motor and sensory polyneuropathy. It is also suggested that some signals emanating from the axons might be related to the formation of tomacula on the basis of the genetically determined myelination disorder.

Adolescent↗
PubMed1990

Method for recording short latency evoked potentials using an EKG artifact elimination procedure.

This paper describes the application of an EKG elimination procedure, previously reported by the authors, to evoked potentials (EPs) recording using a non-cephalic reference. The method consists of three separate steps: data acquisition, EKG artifact elimination, and EP averaging. EKG artifacts are eliminated from the raw EEG by applying a four step procedure to the simultaneously recorded EEG, EKG and stimulus pulse. The steps are: synchronized partition of the raw EEG, EKG averaging, synchronized repetition, and synchronized subtraction of the EKG estimate from the raw EEG. Average EP values are then obtained by averaging the processed EEG using the stimulus pulse as a trigger. Somatosensory evoked potentials to a hand reference, averaged using the proposed method, were compared with those obtained by two conventional averaging methods, and were shown to be more clearly defined. The advantage of the proposed method for recording short latency EP values with a non-cephalic reference is that it requires fewer sweeps and thus takes less time than other methods. The proposed method may also be applicable to the recording of other EP values.

Adult↗
PubMed1990

A method for real-time processing to study recovery functions of evoked potentials.

A new method for evaluating the recovery function of evoked potential (EP) in real time was reported. To record the test response of paired stimulation, the responses to alternate presentation of unpaired stimulus and several kinds of paired stimuli with various interstimulus intervals were averaged respectively and subtraction was made in real time. The EP's to the test stimulus obtained by the proposed method were proved to be accurate even under the changing recording conditions. A formula for computing the recovery correlation factor was derived as a measure of the recovery function of the recorded EP, and the recovery curves for three subjects were obtained.

Adult↗
PubMed1990

Pain-related somatosensory evoked potentials in cortical reflex myoclonus.

To elucidate the sensitivity to pain stimuli in patients with cortical reflex myoclonus, pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation and conventional electrically-stimulated SEPs (electric SEPs) were compared in four patients with cortical reflex myoclonus. The P25 peak of electric SEPs was considerably enhanced but the P320 potential of pain SEPs was of normal amplitude in all patients. After medication, myoclonus was reduced and the amplitude of P25 was decreased, but P320 showed no change. In our previous study of the scalp distribution in normal subjects, a subcortical site, probably the thalamus, was considered to be the generator source of P320. Because most pain stimuli do not reach the cortex, patients with cortical reflex myoclonus are not sensitive to pain stimuli and P320 in pain SEPs is not enhanced.

Adolescent↗
PubMed1990

Cortical tremor: a variant of cortical reflex myoclonus.

Two patients with action tremor that was thought to originate in the cerebral cortex showed fine shivering-like finger twitching provoked mainly by action and posture. Surface EMG showed relatively rhythmic discharge at a rate of about 9 Hz, which resembled essential tremor. However, electrophysiologic studies revealed giant somatosensory evoked potentials (SEPs) with enhanced long-loop reflex and premovement cortical spike by the jerk-locked averaging method. Treatment with beta-blocker showed no effect, but anticonvulsants such as clonazepam, valproate, and primidone were effective to suppress the tremor and the amplitude of SEPs. We call this involuntary movement "cortical tremor," which is in fact a variant of cortical reflex myoclonus.

Aged↗
PubMed1990

Auditory brainstem responses before and after shunting in patients with suspected normal pressure hydrocephalus.

Auditory brainstem responses (ABRs) were studied in 15 adults with suspected normal pressure hydrocephalus (NPH) before and after shunting. The patients were divided into Groups A (shunt-ineffective) and B (shunt-effective). The pre- and postoperative ABRs of each patient were compared with those of 20 normal volunteers, and the relationships between ABRs and certain clinical findings were investigated. Preoperatively, nine patients (60%) showed prolonged central conduction time (CCT) (interpeak latency of wave I-V or neural-axonal conduction time) relative to the mean control value plus 2 SD. There was no significant difference between Groups A and B in the percentage of patients with abnormal CCT, and no specific ABR abnormalities that were predictive of the efficacy of shunting. However, a significantly higher percentage of Group B patients (p less than 0.05) showed a postoperative reduction in the CCT of more than 1 SD of the mean control value. In Group A, the CCT was positively correlated with preoperative clinical disability. These results suggest that brainstem dysfunction may be reversed by shunting, but is not correlated with clinical disability in patients in whom shunting is effective, that is, in those with NPH. It appears that measurement of ABRs is a useful technique for the clinical monitoring of shunted patients.

Aged↗