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Biomedical subjects

A Ikeda

Publications and source records attributed to A Ikeda.

At least 199 records · Page 11Linked to original sources
PubMed1997

Human second somatosensory area: subdural and magnetoencephalographic recording of somatosensory evoked responses.

OBJECTIVE: To investigate somesthetic functions of the perisylvian cortex. METHODS: Somatosensory evoked magnetic fields (SEFs) and somatosensory evoked potentials (SEPs) of the perisylvian cortex were recorded directly from subdural electrodes in a patient with a left frontal brain tumour. RESULTS: The most prominent SEP components after electrical stimulation of the right and left hands and the right foot were double peaked negativity recorded just above the sylvian fissure (latency 80 to 150 ms), respectively (N1a and N1b). Generator sources for the magnetoencephalographic counterparts of those peaks (N1a(m) and N1b(m)) were both localised at the upper bank of the sylvian fissure, and those of N1a(m) were more anteromedially located than those of N1b(m). CONCLUSIONS: These findings suggest the existence of at least two separate somatosensory areas within the human perisylvian cortex.

Adult↗
PubMed1997

Expression and cellular localization of inhibin alpha-subunit mRNA in equine fetal gonads.

The expression of inhibin alpha-subunit mRNA in equine fetal gonads during pregnancy (Days 90 to 300) was examined by means of Northern blot analysis. In all samples examined, a single species of transcript was detected at the size of 1.5 kb. A digoxigenin-labeled antisense cRNA probe specific to equine inhibin alpha-subunit was synthesized and in situ hybridization analysis to locate the inhibin alpha-subunit mRNA positive cells was performed using frozen tissue sections of equine fetal ovary (day 150 of pregnancy) and equine fetal testis (day 180 of pregnancy). In the fetal ovary, positive cells were seen throughout the interstitial area but did not show any particular localization. In the fetal testis, on the other hand, the antisense cRNA hybridized almost exclusively to the interstitial cells surrounding developing seminiferous cords and Sertoli cells within the cords. Positive signals were also detected in a limited number of the interstitial cells located away from the cords. These results suggest that in equine fetal gonads, inhibin and/or inhibin alpha-subunit related molecules such as the monomeric form are produced and these molecules may have a paracrine/autocrine role within the gonads.

Animals↗
PubMed1997

Molecular cloning of bovine CD14 gene.

Genomic DNA encoding bovine CD14 was isolated from a bovine (Holstein) genomic library. Utilizing PCR fragment of mouse CD14 gene as a probe, we screened 9 x 10(5) plaques and obtained 3 clones containing the bovine CD14 gene. DNA sequencing showed that bovine CD14 gene encodes 373 amino acids, and the coding sequence was separated by a 90 nt intron. The identity of the deduced amino acid sequence of bovine CD14 was 61-73% to those of mouse, rabbit and human. Northern blot analysis revealed that CD14 mRNA (1.5 kb) was expressed in the lung. Expression of CD14 mRNA was stimulated about 2-fold in bovine peripheral blood macrophage activated with LPS in vitro.

Amino Acid Sequence↗
PubMed1997

Pathogenesis of reduced egg production and soft-shelled eggs in laying hens associated with Leucocytozoon caulleryi infection.

The pathogenesis of reduced egg production with soft-shelled eggs in laying hens naturally infected with Leucocytozoon caulleryi was investigated. Many large schizonts of L. caulleryi schizonts were seen in the ovary and oviducts of chickens. Granulomatous and lymphocytic inflammation, edema, and pressure atrophy were associated with these schizonts. The uterine region that secretes the egg shell exhibited the most severe damage. These lesions in the reproductive organs may explain the mechanism for causing the reduced egg production and soft-shelled eggs in laying hens infected with L. caulleryi.

Animals↗
PubMed1997

Failure of germinal center formation and impairment of response to endotoxin in tumor necrosis factor alpha-deficient mice.

To study the pathophysiologic roles of TNF alpha, we produced TNF alpha gene-disrupted mice by gene targeting. TNF alpha-deficient mice develop normally without any alteration in the lymphocyte populations. However, in these mice, the germinal center formation in the peripheral lymphoid organs failed in response to the T cell-dependent antigens. TNF alpha-deficient mice are resistant to lethal doses of endotoxin and D-galactosamine without hepatocyte apoptosis, yet demonstrate thymus apoptosis. Our results indicated an important role for TNF alpha in germinal center formation and in the sepsis-induced hepatocyte apoptosis that precedes liver failure.

Animals↗
PubMed1997

[Use of jerk-locked back averaging for detecting the epileptiform discharge in a patient with supplementary motor seizure].

A 23-year-old, right handed women has suffered from supplementary motor seizures manifesting tonic followed by clonic contractions of the left foot, occasionally spreading to the left hand and trunk, since the age of 7 years. The mean frequency of seizures on admission was about 10 times per day. A brain MRI showed an abnormal intensity area about 3 cm in diameter in the right mesial frontal lobe involving the superior frontal and cingulate gyri. Six habitual seizures were recorded during long-term monitoring with digital EEG segments time-locked to the clonic contractions of the left foot, a negative spike was detected about 50 ms before the EMG onset at the midline fronto-central area slightly lateralized to the left. In the focal motor seizure arising from the mesial frontal lobe like in the present case, jerk-locked back averaging helps detecting the epileptiform activity which is otherwise undetectable.

Adult↗
PubMed1997

Molecular cloning of the gene encoding a 2Fe-2S ferredoxin from extremely halophilic archaeon Haloarcula japonica strain TR-1.

A ferredoxin was purified from extremely halophilic archaeon Haloarcula japonica strain TR-1, and then characterized. The Ha. japonica ferredoxin proved to contain a 2Fe-2S cluster. A part of the gene encoding the ferredoxin was amplified by PCR. Subsequently, the entire ferredoxin gene was cloned from chromosomal DNA of Ha. japonica using the PCR product as a probe. The structural gene consisted of an open reading frame of 387 nucleotides. The deduced amino acid sequence showed 89-98% identities with those of the ferredoxins from other extremely halophilic archaea.

Amino Acid Sequence↗
PubMed1997

Cerebral hemodynamics and histological changes following acute cerebral venous occlusion in cats.

Using an acute cerebral venous occlusion model prepared by injecting cyanoacrylate into the cerebral venous system, superior sagittal sinus pressure (SSSP) and regional cerebral blood flow (r-CBF) were measured. In the same model, changes in cerebral metabolism at the site of r-CBF measurement were observed using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). Cases were classified according to occlusion site: group SSS [occlusion of the superior sagittal sinus (SSS) only], group LS[occlusion of SSS plus lateral sinus (LS)] and group CV[SSS and LS plus cortical veins (CV)]. In groups SSS and LS, SSSP changed very little up to 6 hours after occlusion. In group LS, r-CBF decreased slightly, but the change was not significant. In contrast, an increase in SSSP and decrease in r-CBF were observed in group CV. Phosphorus MRS also demonstrated a decrease in phosphocreatinine (PCr) and adenosine triphosphate (ATP) and increase in inorganic phosphorus (Pi) following occlusion. Histopathological examination of group CV revealed dramatic changes, including the development of intracerebral hematoma and edema. Experimental application of the proposed model revealed that widespread occlusion of the sinuses can cause an increase in intravenous pressure with a concomitant decrease in r-CBF, resulting in metabolic complications such as a decrease in PCr and ATP and an increase in Pi.

Acute Disease↗
PubMed1996

Abnormal sensorimotor integration in writer's cramp: study of contingent negative variation.

To investigate the pathophysiology of idiopathic focal dystonia, we recorded contingent negative variation (CNV) as a physiological index of sensorimotor integration in 14 right-handed patients with writer's cramp and compared it with normative data. CNV was recorded in the S2 choice reaction time paradigm: Two kinds of auditory S2 (Go or No-Go) were given 2 s after the auditory S1, and the subject reacted only to the Go signal by extending the wrist. In normal subjects, the late CNV amplitude had no difference at Cz between left- and right-hand tasks and was symmetric without significant amplitude laterality irrespective of the side of hand movement. In patients with writer's cramp, the late CNV amplitude at Cz was relatively larger for the left-hand task than the right-hand task (p < 0.03), and a significant amplitude laterality of the late CNV (larger on the right) was present especially at the central area for the right-hand task (p < 0.03). Since the late CNV is known to be generated, at least in part, from primary and supplementary motor cortices, the significant laterality of the late CNV seen with the right-hand task in patients with writer's cramp might represent functional abnormality of motor cortices possibly as the result of basal ganglia function.

Adult↗
PubMed1996

Clinical trial of piracetam in patients with myoclonus: nationwide multiinstitution study in Japan. The Myoclonus/Piracetam Study Group.

Sixty patients with disabling myoclonus excluding mainly spinal myoclonus were treated by piracetam as an open-labeled study, and myoclonus score, neurological symptoms, functional disability, and intensity of myoclonus were scored before and after treatment, including a blinded video inspection. Electrophysiological correlation also was investigated before and after treatment. Piracetam was effective in myoclonus, especially that of cortical origin, in both monotherapy and polytherapy. Piracetam also had positive benefits on gait ataxia and convulsions but not on dysarthria, and feeding and hand writing improved much more significantly. Psychologically significant improvement was seen in decreased motivation, sleep disturbance, attention deficit, and depression, all of which might be possibly secondary benefits associated with improvement of myoclonus. There was no positive correlation between clinical and electrophysiological improvement. Tolerance was good, and side effects were transient. However, hematological abnormalities observed in at least two patients in the present study should be kept in mind when relatively large doses of piracetam are administered, especially in combination with other antimyoclonic drugs.

Administration, Oral↗
PubMed1996

Somatosensory evoked potentials following proprioceptive stimulation of finger in man.

Brisk passive flexion of the proximal interphalangeal joint of the middle finger, produced by using a newly devised instrument, elicited evoked potentials on the scalp. The present study carefully excluded the possible contribution of sensory modalities other than proprioception. The initial part of cortical response was a positive deflexion at the contralateral central area (P1 at 34.6 ms after the stimulus). This was followed by a midfrontal negative wave (N1 at 44.8 ms) and a clear positivity at the contralateral centroparietal area (P2 at 48.0 ms). The evoked responses persisted in spite of the abolition of cutaneous and joint afferents of the finger caused by ischemic anesthesia, but they were lost by ischemic anesthesia of the forearm. Thus, the cortical evoked responses obtained in this study most probably reflect muscle afferent inputs. The scalp distribution of P1 suggested that its cortical generator source was different from that of the N20-P20 components of evoked potentials to electrical median nerve stimulation. Brodmann areas 2 and 3a of human brain, which are known to receive deep receptor inputs, are the most plausible generator sites for the early components of the proprioception-related evoked responses. The amplitude of P2 was related to the velocity but not to the magnitude of movement. In conclusion, the present study established a method for recording the evoked responses to the brisk passive movement of the finger joint, which mainly reflect the dynamic aspects of proprioception mediated through muscle afferent.

Adult↗
PubMed1996

Pain-related and cognitive components of somatosensory evoked potentials following CO2 laser stimulation in man.

We recorded cortical potentials evoked by painful CO2 laser stimulation (pain SEP) employing an oddball paradigm in an effort to demonstrate event-related potentials (ERP) associated with pain. In 12 healthy subjects, frequent (standard) pain stimuli (probability 0.8) were delivered to one side of the dorsum of the left hand while rare (target) pain stimuli (probability 0.2) were delivered to the other side of the same hand. Subjects were instructed to perform either a mental count or button press in response to the target stimuli. Two early components (N2 and P2) of the pain SEP demonstrated a Cz maximal distribution, and showed no difference in latency, amplitude or scalp topography between the oddball conditions or between response tasks. In addition, another positive component (P3) following the P2 was recorded maximally at Pz only in response to the target stimuli with a peak latency of 593 msec for the count task and 560 msec for the button press task. Its scalp topography was the same as that for electric and auditory P3. The longer latency of pain P3 can be explained not only by its slower impulse conduction but also by the effects of task difficulty in the oddball paradigm employing the pain stimulus compared with electric and auditory stimulus paradigms. It is concluded that the P3 for the pain modality is mainly related to a cognitive process and corresponds to the P3 of electric and auditory evoked responses, whereas both N2 and P2 are mainly pain-related components.

Adult↗
PubMed1996

Clinical application of automatic integrative interpretation of awake background EEG: quantitative interpretation, report making, and detection of artifacts and reduced vigilance level.

Methods for the automatic detection of artifacts and vigilance level of the EEG record were developed for a preprocessing procedure for the automatic integrative interpretation of awake background EEG. All equations for the detection were derived such that they would conform to the procedure that an EEGer adopts for visual EEG inspection. The automatic EEG interpretation system was improved by adding the proposed preprocessing procedure and gave satisfactory interpretation results for the EEG data even contaminated with artifacts or in the drowsy state. The automatic EEG interpretation method proposed here is suggested for clinical use as an assistant tool for EEGers and physicians.

Arousal↗
PubMed1996

Subdural potentials at orbitofrontal and mesial prefrontal areas accompanying anticipation and decision making in humans: a comparison with Bereitschaftspotential.

Field potentials associated with the execution of a warned choice Go/No-Go reaction task were recorded from prefrontal supplementary (SMA) and primary motor cortex (MI) by using subdural electrodes in 5 epileptic patients during presurgical evaluation. The choice was between a Go and a No-Go imperative stimulus (S2) in the S1-S2 paradigm. Orbitofrontal and mesial prefrontal areas generated a slow preceding potential before S2 (most likely late CNV), and bilateral mesial prefrontal areas generated a transient potential, most likely related to decision making, upon S2 in both Go and No-Go conditions. In self-paced, repetitive movement, the Bereitschaftspotential was seen only at SMA and MI, but not in the prefrontal area. The present result, therefore, suggests that in humans orbitofrontal and mesial frontal areas play an important role in preparation for cognition and in decision making, whereas SMA and MI do so in motor preparation.

Adult↗
PubMed1996

Effects of preoperative radiation and chemotherapy on AgNOR counts in oral squamous cell carcinoma.

PURPOSE: This study evaluated the relationship between argyophilic nucleolar organizer regions (AgNORs) and the histologic effects of preoperative chemotherapy or external radiation on oral squamous cell carcinoma. PATIENTS AND METHODS: Thirty-three cases of oral squamous cell carcinoma that were treated with chemotherapy (pepleomycin or 5-FU) or 60Co external radiation were studied. Biopsies were done on the tumor sites before therapy and the number of AgNORs per nucleus was recorded. After therapy, the tumors were resected and the therapeutic effects were assessed histologically. RESULTS: The number of AgNORs per nucleus before therapy ranged from 4.7 to 12.45 (mean +/- SD, 8.71 +/- 2.26). As the number of AgNORs per nucleus increased, the histological effects of preoperative therapy were enhanced. It was 5.75 +/- 0.77 in cases with a poor histological effect of preoperative treatment, 8.03 +/- 1.85 in cases with a mild histological effect, 9.09 +/- 1.85 in the moderate histological effect group, and 10.46 +/- 1.56 in the excellent histological effect group. CONCLUSION: These results suggest that AgNORs could be used to predict the effects of preoperative radiation and chemotherapy on oral squamous cell carcinoma.

Biomarkers, Tumor↗