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Biomedical subjects

H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 253 records · Page 14Linked to original sources
PubMed1993

[The classification of myoclonus].

The term "myoclonus" was originally used to indicate brief jerky involuntary movements. But, nowadays the meaning of myoclonus has expanded so much that its definition and classification have been considerably obscured. In this view, the definition of myoclonus is described and the characteristic clinical features are discussed. The classification of myoclonus is presented based on the pathophysiological observations. Myoclonus is divided into two large groups, cortical myoclonus directly associated with the activity of the motor cortex, and subcortical myoclonus which comprises various types of myoclonus (including spinal myoclonus). Furthermore, the electrophysiological aspects of myoclonus and its pathogenesis are briefly discussed.

Diagnosis, Differential↗
PubMed1992

Stable isotope dilution mass spectrometry for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in plasma.

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in human plasma is described. [1,1,19,19,19-2H5]Cortisol, [1,1,19,19,19-2H5]cortisone, [1,19,19,19-2H4]prednisolone and [1,19,19,19-2H4]prednisone were used as internal standards. Formation of the bismethylenedioxy-3-heptafluoro-n-butyryl (BMD-HFB) derivatives made possible the separation of the four corticosteroids with good gas chromatographic behaviour. The new double derivatization has been demonstrated to be of value for sensitive and selective quantification by this technique. Detection was performed by monitoring the molecular ion (M+) of the BMD-HFB derivatives for cortisone and prednisolone, the [M - 18]+ ion for cortisol, and the [M - 30]+ ion for prednisone. The method requires no complex corrections for contributions and provides good accuracy and precision.

Cortisone↗
PubMed1992

Reversible stepwise mechanism involving a carbanion intermediate in the elimination of ammonia from L-histidine catalyzed by histidine ammonia-lyase.

L-Histidine labeled with deuterium at the C-5' position of the imidazole ring, L-[5'-2H]histidine (His-5'-D), was used as a probe for investigating a stepwise reversible mechanism via a carbanion intermediate in the elimination of ammonia catalyzed by histidine ammonia-lyase (EC 4.3.1.3). The labeled L-histidine (His-5'-D) (2.45 mM) was incubated with histidine ammonia-lyase (200 units) from Pseudomonas fluorescens at pH 7.0 or 9.0 at 25.0 degrees C for 24 h. The time course of the reaction was examined to determine the rates of enzyme-catalyzed hydrogen exchange at C-5' of L-histidine and urocanic acid. The finding of the enzyme-catalyzed hydrogen exchange at C-5' of both L-histidine and urocanic acid in the presence of L-histidine provided a rational explanation for a stepwise reversible mechanism via a carbanion intermediate in the elimination reaction. The rate of increase in the concentration of urocanic acid exchanged with hydrogen (UA-5'-H) did not depend on the formation rate of urocanic acid and UA-5'-H was continuously formed at a constant rate (25.6 microM/h) even after the completion of urocanic acid formation. These observations suggested the presence of the reversible reaction of urocanic acid and a carbanion intermediate. Since there was only a minor contribution for the formation of UA-5'-H from L-histidine exchanged with solvent hydrogen (His-5'-H), the main pathway in the enzymatic reaction of His-5'-D must be the formation of UA-5'-D via a carbanion intermediate (carbanion-D). Regeneration of the carbanion-D from UA-5'-D by its reverse reaction and subsequent hydrogen incorporation at C-5' would contribute to a large extent for the formation of UA-5'-H. The stability of carbanion was also demonstrated to be approximately three times higher at pH 7.0 than at pH 9.0.

Ammonia↗
PubMed1992

Simultaneous determination of stable isotopically labelled L-histidine and urocanic acid in human plasma by stable isotope dilution mass spectrometry.

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of stable isotopically labelled L-histidine (L-[3,3-2H2,1',3'-15N2]histidine, L-His-[M + 4]) and urocanic acid ([3-2H,1',3'-15N2]urocanic acid, UA-[M + 3]) in human plasma was developed using DL-[2,3,3,5'-2H4,2'-13C,1',3'-15N2]histidine (DL-His-[M + 7]) and [2,3,5'-2H3,2'-13C,1',3'-15N2]urocanic acid (UA-[M + 6]) as internal standards. L-Histidine and urocanic acid were derivatized to alpha N-(trifluoroacetyl)-imN-(ethoxycarbonyl)-L-histidine n-butyl ester and imN-(ethoxycarbonyl)urocanic acid n-butyl ester. Quantification was carried out by selected ion monitoring of the molecular ions of the respective derivatives of L-His-[M + 4], DL-His-[M + 7], UA-[M + 3] and UA-[M + 6]. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring plasma concentrations of L-His-[M + 4] and UA-[M + 3] following administration of trace amounts of L-His-[M + 4] to humans.

Gas Chromatography-Mass Spectrometry↗
PubMed1992

Simultaneous determination of cortisol and cortisone in human plasma by stable-isotope dilution mass spectrometry.

A method for the simultaneous determination of cortisol and cortisone in human plasma was developed using capillary gas chromatography-mass spectrometry-selected ion monitoring. [2H5]Cortisol and [2H5]cortisone were used as internal standards. Cortisol and cortisone in plasma were determined from the peak-height ratios of the [M-31] fragment ions of the methoxime-trimethylsilyl derivatives of cortisol and [2H5]cortisol (m/z 605 and 610) and of cortisone and [2H5]cortisone (m/z 531 and 536). Sensitivity, specificity, precision, accuracy and reproducibility of the method were demonstrated to be satisfactory for measuring the circulating concentrations of cortisol and cortisone.

Cortisone↗
PubMed1992

Automatic EEG interpretation: a new computer-assisted system for the automatic integrative interpretation of awake background EEG.

A new computer-assisted system for automatic interpretation of the awake electroencephalogram (EEG) was developed. First, all the items necessary for EEG interpretation were determined in accordance with the procedure that a qualified electroencephalographer (EEGer) goes through for the visual inspection of the background EEG activity, and then each item was defined quantitatively. For the automatic interpretation, specific EEG parameters were determined for each item so that they could fit the graded judgement of the item by the qualified EEGer as closely as possible. These specific EEG parameters were actually calculated from periodograms obtained from the time series of EEG records of 14 patients with various neurological diseases. The automatic EEG interpretation system thus established was applied to the EEG data of these 14 subjects and to 3 additional EEGs, and the results were compared with those obtained through the visual interpretation by the EEGer. This automatic EEG interpretation was found to be in good agreement with the visual interpretation by the EEGer in most EEG records. In contrast with the previous automatic analyses of EEG which were focussed on certain aspects of EEG such as the dominant rhythm, the present system is unique in its capability of providing an integrative interpretation of the spontaneous awake EEG by taking into account all its features except for paroxysmal abnormalities.

Adult↗
PubMed1992

Physiological study of the spinothalamic tract conduction in multiple sclerosis.

This is the first paper to study the physiological function of the spinothalamic tract in multiple sclerosis (MS) using pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation. Among 12 patients with MS, hand- and foot-stimulated pain SEPs were significantly delayed or absent in 3 and 7, respectively. These results were totally consistent with clinical impairment of pain-temperature sensation. In contrast, the results of conventional electrically-stimulated SEPs were compatible with impairment of vibration sensation. Therefore, the examination of both pain and electric SEPs is very useful to evaluate the physiological function of the ascending spinal tract in patients with MS.

Adult↗
PubMed1992

Preparation of multiply deuterium-labeled cortisol.

Cortisol labeled with four deuterium atoms at chemically stable sites ([9,11,12,12-(2)H4]cortisol, cortisol-d4) was prepared by hydrogen-deuterium exchange and reductive deuteration reactions. After protecting the C-17 dihydroxyacetone side chain of cortisone (cortisone-BMD), hydrogen-deuterium exchange was carried out with 6.5% NaOD in MeOD, which was followed by protection of the C-3 carbonyl as the semicarbazone. Subsequent reductive deuteration at C-11 with NaBD4 followed by removal of exchangeable deuterium under the same exchange-reaction conditions in a medium of 6.5% NaOH in MeOH and deprotection afforded the desired cortisol-d4 with high isotopic content (d3, 21.2%; d4, 78.1%; d5, 0.74%). The method was applied to the synthesis of cortisol labeled with nine deuterium atoms [( 1,1,9,11,12,12,19,19,19-(2)H9]cortisol, cortisol-d9) starting from [1,1,19,19,19-(2)H5]cortisone (cortisone-d5).

Cortisone↗
PubMed1992

Movement-related potentials recorded from supplementary motor area and primary motor area. Role of supplementary motor area in voluntary movements.

Movement-related potentials (MRPs) were recorded from subdural electrodes chronically implanted in the interhemispheric fissure in two patients being evaluated for epilepsy surgery. Different types of movements (finger, foot, tongue and vocalization) were executed. Foot movements elicited a clearly defined, well-localized slow negativity or positivity (Bereitschaftspotential, BP) preceding electromyogram (EMG) onset. These BPs were seen from the contralateral primary motor foot area and also from bilateral supplementary motor areas (SMAs) with equivalent amplitudes and temporal evolutions. A steeper potential [negative slope (NS')] occurred about 300 ms before EMG onset and the motor potential (MP) started 100 ms before EMG onset. Negative slopes and MPs also arose from the contralateral primary motor area as well as from the bilateral SMAs. Finger movements elicited well-localized BPs and NS' which were generated from the bilateral SMAs, but were of higher amplitude on the contralateral SMA. Motor potentials started 50 ms prior to EMG onset and arose exclusively from the contralateral SMA. Tongue protrusions and vocalizations also elicited BP, NS' and MP which were seen in the bilateral SMAs. Movement-related potentials for different types of movements had a somatotopic distribution in the SMA, which was consistent with the SMA somatotopic organization defined by electrical simulation. Movement-related potentials for tongue movements and vocalization had a similar distribution and waveform. It was concluded that bilateral SMAs generate well-defined MRPs consistent with the assumption that the SMA plays a significant role in the organization of voluntary movements. However, the MRPs from the bilateral SMAs do not have characteristics which are different from those of the primary motor area. This suggests the hypothesis of 'supplementary' function for SMA, and does not support the hypothesis of 'supramotor' function.

Adolescent↗
PubMed1992

Event-related potential studies in infants and children.

The current status of event-related potentials (ERPs) in infants and children is discussed based on a review of the relevant literature. Although the N100-P200 component evoked by tone stimuli is clearly detected using an odd-ball paradigm in children over approximately 6 years of age, that component evoked by speech stimuli is not clearly detected until at least 10 years of age. In contrast to the adult N100-P200 component evoked by speech stimuli, infants and young children show a positivity at a latency of about 85-120 ms and a negativity at about 200-240 ms. The definition of P300 in children has not yet been established. P300 latency evoked by both auditory and visual stimuli decreases throughout childhood and reaches the mature value by puberty or young adulthood. However, P300s elicited by auditory and visual stimuli show different developmental time courses from each other, suggesting that they may originate from different neural generators. The Nc component is elicited by a variety of attention-getting events in infants and children. Interestingly, the developmental change in the Nc amplitude parallels the maturational course of synaptogenesis in the frontal cortex, and the Nc latency reaches the mature value at the time when myelinogenesis is complete in the nonspecific thalamic radiation.

Arousal↗
PubMed1992

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

This is the first thorough study to evaluate the effects of age, gender, and stimulus side on the scalp topographies of somatosensory evoked potentials (SEPs) following stimulation of the posterior tibial nerve by using computerized bit-mapped color images and the significance probability mapping method. Seventy-four normal subjects whose ages ranged from 7 to 88 years were studied. Topographic mappings 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. However, scalp distribution of each component did not show a large difference among different age groups. There was a tendency that amplitudes in women were larger than those in men, and the gender differences of some components were significantly larger for some age groups. Stimulus side and handedness caused no significant difference in amplitudes and topographies of the components. These results were very similar to our previous results of the scalp topographies of SEPs following median nerve stimulation.

Adolescent↗
PubMed1992

Invasive recording of movement-related cortical potentials in humans.

Movement-related cortical potentials (MRCPs), especially the premovement components seen only in association with voluntary movements, may represent the higher brain functions related to preparation for voluntary movements. Recent advances in many aspects (single unit and field potential recordings in animals, intracranial recording of MRCPs in epileptic patients, magnetoencephalography, and positron emission tomography) have provided new information about the physiological significance of MRCPs. In contrast to the findings on scalp recordings, in which the early potentials prior to movement onset are seen more widely, the main cortical generators appear to be discretely localized in bilateral primary and supplementary motor areas with a contralateral predominance. This review outlines the findings in scalp-recorded MRCPs and compares them with the results of invasive recordings, paying special attention to their physiological significance.

Animals↗
PubMed1992

Dying back type axonal degeneration of sensory nerve terminals in muscle spindles of the gracile axonal dystrophy (GAD) mutant mouse.

A disorder of the gracile axonal dystrophy (GAD) mutant mouse is characterized by a neuromuscular disease with sensory ataxia (detectable 30 days after birth) and paresis of the hindlimbs (detectable at 80 days). In the sensory ataxia stage, histological study of the primary sensory system shows that, in addition to the lesions in the central nervous system, peripherally projecting axons have also started to degenerate at their distal ends in muscle spindles. Although the structure of Ia fibre endings appear normal until 15 days after birth, initial changes in the annulo-spiral structure are detected around the 20th day by a degeneration of the terminal axons. Degeneration then progressed proximally and the secondary endings also start to degenerate. Neuron cell bodies located in the dorsal root ganglia are morphologically intact until the later stages. Chronological studies indicate that, although axonal degeneration progresses throughout life, it is accentuated during the rapid somatic growth period. Around 50 days of age, transient regeneration takes place at axonal endings when somatic growth has attained a plateau. Such primary sensory endings tend to be restored by fine, multiple axons which gain access to the intrafusal fibres through the original endoneurial tubes. Ultrastructural observations at the fully affected stage show intrafusal muscle fibres lying scattered within spindles due to loss of the fine network of inner capsule layers and an almost complete loss of sensory endings from the surface of intrafusal muscle fibres. These results indicate that this mutant mouse is a useful model for naturally occurring 'dying back' type axonal degeneration or 'central and peripheral distal axonopathies', and would provide significant information about the complete evolution of the pathological processes involved.

Animals↗
PubMed1992

Pain-related somatosensory evoked potentials following CO2 laser stimulation in peripheral neuropathies.

Pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation were examined in 30 patients with peripheral neuropathies, and the results were compared with clinical sensory findings. Pain SEP findings showed a significant correlation with the clinical impairment of pain sensation, but not with the impairment of deep sensations. In contrast, conventional electrically-stimulated SEPs (electric SEPs) showed a significant correlation with deep sensations, but not with the impairment of pain sensation. Examinations of both pain SEPs and electric SEPs, therefore, are considered to be very useful to evaluate physiological functions of sensory nerves in patients with peripheral neuropathies.

Adult↗
PubMed1992

Mechanisms of pain relief by vibration and movement.

Mechanisms of pain relief induced by vibration and movement were investigated. A CO2 laser beam, which is useful for pure nociceptive stimulation, was used for recording pain-related somatosensory evoked potentials (pain SEPs) and for measuring pain threshold and reaction time (RT). Concurrently applied vibratory stimuli to and active movements of the fingers significantly reduced and prolonged pain SEPs, increased pain threshold, and prolonged RT, indicating that an increase in the inhibitory mechanisms of painful feeling was induced by the concurrently adopted sensory inputs mediated by large myelinated fibres. In contrast, continuous cooling enhanced pain SEPs and decreased pain threshold, probably due to the spatial summation of two kinds of nociceptive impulses mediated by the same pathways. The results of this investigation throw light on the mechanisms of the alleviation of pain by vibration and movement.

Adult↗
PubMed1992

Superficial punctate keratopathy and bacterial growth in patients with unilateral aphakia using extended-wear soft contact lenses.

We prospectively examined corneal conditions and bacterial growth in 77 individuals with unilateral aphakia who were using extended-wear soft contact lenses. The ratios of positive bacterial growth (70.6-79.4%) from 34 patients with superficial punctate keratopathy were significantly higher than those (41.9-46.5%) from the 43 subjects with normal corneas. Bacterial growth was found frequently in patients with superficial punctate keratopathy who were older than 80 years and in those using soft contact lenses for more than 22 days. Several kinds of bacteria grew from the specimens. Among the most common were Staphylococcus epidermidis and Corynebacterium species. Pseudomonas aeruginosa grew from patients with superficial punctate keratopathy who were using extended-wear soft contact lenses.

Aged↗