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Biomedical subjects

N Fujiki

Publications and source records attributed to N Fujiki.

At least 37 records · Page 2Linked to original sources
PubMed2000

Functional differentiation of the auditory association area in prelingually deaf subjects.

BACKGROUND: it is believed that the number of neurons of the human cortex increases rapidly in the first postnatal year, and then decreases gradually towards adult level as their functions are revised up to 11 years of age ('synaptic revision'). It is also confirmed that regional cerebral blood flow (rCBF) at rest represents the density of the neurons and decreases in accordance with the synaptic revision in process. If synaptic revision does not occur, rCBF remains at high level. Thus, we can evaluate whether functional differentiation has occurred in the human cortex by measuring rCBF at resting state. OBJECTIVE: to examine functional differentiation of the auditory association area (A2) in prelingually deaf subjects. METHODS: six postlingually and six prelingually deaf subjects who had undergone cochlear implant (CI) were involved in the current study. All prelingually deaf subjects underwent CI over 8 years old. The rCBF in A2 was examined during resting and listening to speech sounds using positron emission tomography (PET) and H2(15)O intravenous injection. Twelve normal subjects' rCBFs were also measured as control. Furthermore, three prelingually deaf subjects underwent follow up PET studies in which cortical activities in A2 for listening and lipreading were examined. RESULTS: in the examination of rCBF at rest, rCBFs of prelingually deaf subjects in A2 showed significantly higher than those of either the postlingually deaf subjects or normal subjects. During listening, rCBFs in A2 increased in postlingually deaf subjects and normal subjects, while there was no significant rCBF increase in the prelingually deaf. High rCBF level in A2 at rest observed in prelingually deaf subjects implied a lack of synaptic revision, and it was suggested that the functional differentiation for auditory processing was little in the A2 of prelingually deaf subjects. In the follow up study for three prelingually deaf subjects, activation of A2 was observed during lipreading but not during listening in two cases, who had developed the skill of lipreading while speech recognition was not improved by CI. In contrast, the other case had not used any visual clues in daily communication prior to CI, and the hearing acuity was well improved by CI. This case demonstrated an activity in A2 during listening, while lipreading induced no activation. CONCLUSION: it is suggested that functional differentiation of A2 should differ according to which of visual and auditory clue is chiefly used during critical periods for speech acquisition. The findings are thought to be important for us to schedule the education and treatment for prelingually deaf children.

Adolescent↗
PubMed2000

Hepatoportal bumetanide-sensitive K(+)-sensor mechanism controls urinary K(+) excretion.

To determine whether a K(+)-sensor mechanism exists in the hepatoportal region, periarterial hepatic afferent nerve activity responses to intraportal injection of KCl were examined in anesthetized rats. Hepatic afferent nerve activity increased in response to intraportal injection in a K(+) concentration-dependent manner, and the increase was attenuated by inhibition of the Na(+)-K(+)-2Cl(-) cotransporter by bumetanide in a dose-dependent manner. These results suggest that a bumetanide-sensitive K(+)-sensor mechanism exists in the hepatoportal region. Stimulation of this mechanism by intraportal KCl infusion elicited an immediate and powerful kaliuresis with no significant change in the plasma K(+) concentration; this was significantly greater than the kaliuresis induced by intravenous KCl infusion and was attenuated by severing the periarterial hepatic nervous plexus. These results indicate that a hepatoportal bumetanide-sensitive K(+)-sensor mechanism senses the portal venous K(+) concentration and that stimulation of this sensor mechanism causes kaliuresis, which is mainly mediated by the periarterial hepatic nervous plexus.

Afferent Pathways↗
PubMed2000

[Factors influencing satisfaction of cochlear implant users--a questionnaire-based study].

We surveyed on cochlear implant (CI) users using a questionnaire to determine how they use their CIs in daily life and to what degree they are satisfied with them. We also studied the relationship between the degree of satisfaction and speech perception score, age at operation, and deafness duration. Subjects were 37, postlingually-deafened adult CI users were subjected to this study. Average CI use per day was 13.6 hours. Some 60% of subjects understood person-to-person conversation without lipreading, but most could not communicate on the telephone, in meetings, or in noisy places, for example. Most--about 80%--were satisfied with CI, but 20% were not. Those not satisfied tended to be unable to understand person-to-person conversation even with CI and lipreading, indicating that understanding person-to-person conversation is one of the most important reasons for satisfaction in CI users. Speech recognition scores improved in all cases after implantation. Most patients with high speech recognition score-->40% in consonant recognition--were satisfied with CI, but those with recognition scores < 40% in consonant recognition, the degree of satisfaction varied. These results indicate that the degree of satisfaction in CI users does not always correspond to the degree of improvement in speech recognition score. Two patients not satisfied with CI had undergone surgery after the age of 65 years and deafness duration exceeding 20 years. Advanced age and a long deafness duration may thus reduce satisfaction with CIs.

Adult↗
PubMed2000

Afferent mechanisms of acute responses of renal sympathetic nerve activity to microgravity.

Exposure to microgravity is thought to induce an alteration of autonomic function through several afferent pathways. First, a removal of all hydrostatic gradients, which results in a large cephalad fluid shift. The fluid shift may induce an increase in transmural pressure in the cardiopulmonary region, which stimulates cardiopulmonary mechanoreceptors and baroreceptors, and elicits neurogenic responses. Secondly, an alteration of the vestibular input may modify sympathetic output via the vestibulosympathetic reflex. However, there is a lack of direct evidence for the role of cardiopulmonary mechanoreceptors, baroreceptors, and vestibular system in autonomic responses to microgravity. Accordingly, responses of renal sympathetic nerve activity (RNA) to microgravity, produced by free drop, were examined in anesthetized rats. To examine the afferent pathways of the RNA responses, the same experiment was performed in rats that had undergone labyrinthectomy, sinoaortic baroreceptor denervation (SAD), vagotomy, or SAD plus vagotomy.

Afferent Pathways↗
PubMed1999

Functional evidence for involvement of bumetanide-sensitive Na+K+2CI- cotransport in the hepatoportal Na+ receptor of the Sprague-Dawley rat.

To investigate mechanisms involved in hepatoportal Na+ sensing, responses of hepatic afferent nerve activity (HANA) to intraportal hypertonic NaCl injection were measured before, and after, intraportal infusion of inhibitors of Na+ transport systems. HANA increased in response to the intraportal injection of 0.75 M NaCl in a dose-dependent manner. The HANA response was not affected by amiloride or 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS), but was suppressed in a dose-dependent manner by intraportal infusion of ouabain, furosemide, or bumetanide. These results indicate that the hepatoportal Na+ receptor senses the Na+ concentration via the bumetanide-sensitive Na+K+2Cl- cotransporter.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1999

Correlation between rCBF and speech perception in cochlear implant users.

OBJECTIVE: Although cochlear implants (CIs) have provided the opportunity for bilaterally deaf individuals to recover their hearing abilities, the speech perception performances of the CI users varies considerably. To elucidate the cortical mechanisms of processing speech signals coded by CIs, we evaluated the correlation between the brain activity during speech activation and speech perception in CI users by PET. METHODS: Fourteen postlingually deaf CI users were examined. CI used in the patients was a 22-channel system and its speech-coding strategy was the Nucleus spectral peak (SPEAK) strategy. To evaluate the speech perception performances, we examined vowel perception, consonant perception and speech tracking performances in the Japanese language. Regional cerebral blood flow (rCBF) was measured during no sound stimulation and speech sound stimulation. PET data of the silent condition was subtracted from that of speech stimulation to determine changes in rCBF. In the search for changes in rCBF in the areas for auditory processing, three regions of interest (ROI) were selected; primary auditory area, auditory association area and Broca's area. The correlation between the rCBF changes in the ROIs and the speech perception performances was analyzed using Pearson's correlation coefficient. RESULTS: The patient's speech perception performances ranged widely. Although there were no significant correlations between the speech perception and the rCBF increases in the primary auditory area and Broca's area, there were positive correlations in the auditory association area. In the left auditory association area, the correlation coefficient of the vowel perception performance was 0.546 (P <0.05) and that of the speech-tracking test was 0.657 (P < 0.05). Regarding the consonant perception performance, the correlation coefficient was 0.743 (P < 0.01). There was a positive correlation only between the consonant perception performance and the rCBF increase (R = 0.576, P < 0.05) in the right auditory association area. These correlations are stronger in the left hemisphere than in the right hemisphere. CONCLUSIONS: It is suggested that the improvement of the auditory processing of speech in CI users with SPEAK strategy is accompanied by the recruitment of more neurons in the auditory association areas. The adult auditory cortices may still have plasticity or

Adult↗
PubMed1999

Cochlear implant in patients with residual hearing.

OBJECTIVE: The postoperative speech perception abilities of severely hearing-impaired patients with multi-channel cochlear implant were compared with preoperative speech perception performance with conventional hearing aids. METHODS: Cochlear implantation was performed in six severely to profoundly hearing-impaired patients. They had unaided pure-tone thresholds of 70-100-dB HL and aided thresholds of 35-90-dB HL in the better ear, but were not able to perceive speech sounds well with hearing aids. RESULTS: Postoperatively, all the patients had significantly improved speech perception performance, exceeded the average skills of profoundly deaf cochlear implant users, and were able to communicate without writing. CONCLUSION: These results imply that cochlear implant may be indicated for severely to profoundly deaf subjects, if they receive little or no benefit from conventional hearing aids.

Adult↗
PubMed1999

Focal (segmental) dyshidrosis in syringomyelia.

The features or mechanisms of dyshidrosis have not been sufficiently clarified. Neither has the difference between hyperhidrosis and hypohidrosis. To clarify the features and mechanisms of dyshidrosis (hyperhidrosis and hypohidrosis) in syringomyelia, the clinical features focusing on hidrosis of 30 patients with syringomyelia and Chiari malformation located from a syringomyelia database were prospectively analysed. The patients were classified into three groups: eight patients (26.7%) had segmental hypohidrosis, 10 (33. 3%) had segmental hyperhidrosis, and 12 (40.0%) had normohidrosis. We found that the Karnofsky functional status for the hyperhydrosis and normohidrosis groups were significantly higher than for the hypohidrosis group (p=0.0012), with no significant differences between the hyperhidrosis and normohidrosis groups. The duration from the onset of syringomyelia to the current dyshidrosis was significantly longer in the hypohidrosis group than in the hyperhidrosis group (p=0.0027). A significant correlation was identified between the duration from the onset of syringomyelia to the time at study and the performance score (r=-0.599, p=0.0003). The results substantiate previous hypotheses that in its early stage syringomyelia causes segmental hyperactivity of the sympathetic preganglionic neurons, and hyperactivity of these gradually subsides as tissue damage progresses. Focal hyperhidrosis may be regarded as a hallmark of a relatively intact spinal cord, as well as normohidrosis.

Adolescent↗
PubMed1999

[A case of HTLV-I associated myelopathy presenting with cerebellar signs as initial and principal manifestations].

We reported a 75-year-old woman with HTLV-I associated myelopathy (HAM) presenting with cerebellar signs. She was admitted to our hospital because of walking unsteadiness, which initially appeared 3 years previously with gradual worsening. Neurological examination revealed limb and truncal ataxia, cerebellar type dysfunction of eye movement, pyramidal sign, diminished vibration sense and neurogenic bladder. Anti HTLV-I antibody titers in serum and CSF were markedly elevated. MRI revealed abnormal signals in cerebral white matter, mild cerebellar atrophy and thoracic cord atrophy. Cerebellar signs and symptoms were initial and main neurological manifestations in this patient, which were improved by steroid therapy. We considered this case was unique among HAM, because cerebellum was considered her main lesions.

Aged↗