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Biomedical subjects

Y Okajima

Publications and source records attributed to Y Okajima.

118 records · Page 7Linked to original sources
PubMedDate not supplied

Interactions of somatosensory evoked potentials: simultaneous stimulation of two nerves.

To analyse the mechanism by which sensory inputs are integrated, interactions of somatosensory evoked potentials (SEPs) in response to simultaneous stimulation of two nerves were examined in 12 healthy subjects. Right, left and bilateral median nerves were stimulated in random order so that a precise comparison could be made among the SEPs. The arithmetical sum of the independent right and left median nerve SEPs was almost equal within 40 msec of stimulus onset to that evoked by the simultaneous stimulation of bilateral median nerves. However, a difference emerged after 40 msec. The greatest difference was recorded after 100 msec. Sensory information from right and left median nerves may interact in the late phase of sensory processing. Left median, left ulnar, and both nerves together were stimulated. The sum of the SEPs of left median and ulnar nerves was not equal to that evoked by the simultaneous stimulation of the two nerves even at early latencies. Differences between them were first recorded at 14-18 msec and became greater after 30-40 msec. It is suggested that the neural interactions between impulses in the median and ulnar nerves begin below the thalamic level.

Adult↗
PubMedDate not supplied

Recovery functions of somatosensory vertex potentials in man: interaction of evoked responses from right and left fingers.

Somatosensory vertex potentials (SVPs) were examined in 12 healthy subjects in response to painful electrical stimulation of the finger. SVPs consisted of N1, P1, and N2. The average latencies of the 3 peaks were 150, 225, and 350 msec, respectively. The latency and amplitude of each potential were reproducible for each subject. Recovery functions of the SVPs were analyzed in 10 subjects. A pair of stimuli were delivered to the right or left finger with interstimulus intervals (ISIs) of 50, 100, 150, 200, 350, 500 and 650 msec. SVPs partially recovered with the shortest ISI (50 msec). Full recovery could not be obtained even with the longest ISI (650 msec). Differences in recoveries within 650 msec of ISI were not observed between right and left stimulations. To examine the interaction between SVPs evoked by right and left finger stimulation, recovery functions from prior contralateral finger stimulation were analyzed with the same ISIs. SVP recoveries for right after left or left after right patterns of stimulus delivery were nearly the same as those for ipsilateral ones. It is suggested that SVPs are generated at nearly the same site in the sensory pathway regardless of the side stimulated.

Adult↗
PubMedDate not supplied

Clinical and MRI findings in a case of D-2-hydroxyglutaric aciduria.

We report the 3rd case in the literature of a 3-year-old boy with D-2-hydroxyglutaric (D-2-HG) aciduria, who presented primarily generalized hypotonia and feeding difficulty during the neonatal period, with eventual development of generalized myoclonic seizures. Gas chromatographic analysis of urinary organic acids showed persistent excretion of D-2-HG. The clinical manifestations are quite similar to those of the 2nd reported case with D-2-HG aciduria. Serial MRI performed 1 year and 2 1/2 years after birth demonstrated bilateral symmetrical periventricular lesions in the parieto-occipital white matter, which might reflect the cortical blindness in our patient.

Amino Acid Metabolism, Inborn Errors↗
PubMedDate not supplied

Striped iron zoning of olivine induced by dislocation creep in deformed peridotites.

Deformation of solid materials affects not only their microstructures, but also their microchemistries. Although chemical unmixing of initially homogeneous multicomponent solids is known to occur during deformation by diffusion creep, there has been no report on their chemical zoning due to deformation by dislocation creep, in either natural samples or laboratory experiments. Here we report striped iron zoning of olivine ((Mg,Fe)2SiO4) in deformed peridotites, where the iron concentration increases at subgrain boundaries composed of edge dislocations. We infer that this zoning is probably formed by alignment of edge dislocations dragging a so-called Cottrell 'atmosphere' of solute atoms (iron in this case) into subgrain boundaries during deformation of the olivine by dislocation creep. We have found that the iron zoning does not develop in laboratory experiments of high strain rates where dislocations move too fast to drag the Cottrell atmosphere. This phenomenon might have important implications for the generation of deep-focus earthquakes, as transformation of olivine to high-pressure phases preferentially occurs in high-iron regions, and therefore along subgrain boundaries which would be preferentially aligned in plastically deformed mantle peridotites.

Journal Article↗
PubMedDate not supplied

Accelerometric evaluation of ataxic gait: therapeutic uses of weighting and elastic bandage.

Two-dimensional (fore-aft and vertical) acceleration of locomotion was measured in 10 normal subjects and 13 patients with idiopathic olivopontocerebellar atrophy who were ataxic but able to walk without any assistance. Accelerometers were tightly placed on the third lumbar vertebra. Asymmetry and unsmoothness indices of locomotion defined from the line spectra of the accelerometric data were computed. Reproducibility of the indices was checked in the normal subjects and patients. The index values were significantly correlated with visual rating of gait unsteadiness in the patients. The indices for vertical components were significantly increased when subjects walked slowly. Effects of weights and bandages on gait were analysed by the fore-aft components of the indices. They were attached to both lower extremities. Weighting or bandaging did not change, or even increased the index values in most of the normal subjects. The indices were also unchanged in the patients. However, some of the patients showed significant improvement with weights or bandages. Mechanisms of therapeutic effects of weighting and elastic bandages on ataxia are discussed.

Acceleration↗
PubMedDate not supplied

Age-related changes of water and fat content in muscles estimated by magnetic resonance (MR) imaging.

The pixel values in fat/water suppression magnetic resonance (MR) images were measured for the thigh muscles of 18 healthy volunteers to investigate age-related changes in muscle water and fat content. Prior to the human studies the reproducibility of the data was confirmed using phantoms. The standard deviations (SDs) of the pixel values for one of the phantoms examined five times were found to be within a relatively narrow range. Both the pixel values in the fat suppression images (PV1) and the pixel values in the water suppression images (PV2) of all muscles tended to be higher in the oldest group. The results indicate that the water and fat content of skeletal muscles is higher in aged persons. Moreover, the PV1 in the non-dominant limbs was found to be increased in the extensor muscles of the knee joints, while the PV2 in the non-dominant limbs did not show a significant difference, except for the rectus femoris.

Adipose Tissue↗
PubMedDate not supplied

Effects of visual and auditory stimuli on median nerve somatosensory evoked potentials in man.

To demonstrate electrophysiological evidence of neural connections of somatosensory with visual and auditory pathways, interactions of median nerve somatosensory evoked potentials (SEPs) with visual evoked potentials (VEPs) and auditory evoked potentials (AEPs) were analyzed in 12 healthy subjects. In Experiment I (SEP vs. VEP), three patterns of stimulation, namely, electric stimulation of left median nerve, binocular LED flash, and simultaneous electric and flash stimulation, were applied with random interstimulus intervals of 2-4 sec until more than 100 responses had been obtained and averaged for each pattern of stimulation. Simultaneous electric and visual responses were subtracted from arithmetical sums of SEPs and VEPs to show interactions between somatosensory and visual responses. In Experiment II (SEP vs. AEP), binaural short-duration tone bursis instead of LED flashes were used in the same manner as in Experiment I, and interactions between somatosensory and auditory responses were analyzed. Results indicated that the effects of both visual and auditory interaction on SEPs were significant around 120-130 msec of latency. In other words, cross-modal sensory interaction occurred in the late phase of sensory processing.

Acoustic Stimulation↗