Search PubMed⌕ Search

Biomedical subjects

T Iwaki

Publications and source records attributed to T Iwaki.

At least 109 records · Page 6Linked to original sources
PubMed1998

An exploratory study of effects of smoking on mental rotation and mental paper-folding task.

To demonstrate the positive effects of smoking on spatial-imagery processing, behavioral (hit ratio and reaction time) and physiological indices (EEGs and HR) were examined in 12 student volunteers. Subjects performed two spatial-imagery tasks, one mental rotation and the other mental paper-folding. The two tasks were performed before and after smoking and the results compared. Subjects participated in both control and smoking sessions. Reaction time decreased after smoking, while the hit ratio did not change. EEG contour maps derived from 12-channel records of the beta band showed activation of the frontal area during the spatial-imagery processing. After smoking, EEG laterality showed increased right-hemisphere dominance. These findings implied that smoking facilitated selective activation of the hemisphere and did not support Gilbert and Wesler's hypothesis of left-hemisphere priming. Psychophysiological mechanisms of the effects of smoking were discussed.

Adult↗
PubMed1998

[Clinical significance of electrically evoked auditory brainstem response].

Electrically evoked auditory brainstem responses (EABR) were recorded in 31 postlingually deafened adults, who had recently received cochlear implants (mini-system, Cochlear Ltd). The wave consisted of three distinct positive peaks labeled P1, P2, and P3 with latency of 1.35 (+/- 0.14), 2.17 (+/- 0.18) and 4.08 (+/- 0.31) ms, respectively. The P3 threshold (EABR-T) and slope (EABR-S) were 0.9 (+/- 0.47) mA and 0.6 (+/- 0.28) muv/mA, respectively. The relationships between the EABR parameters (EABR T and -S of the P3 wave) and age, duration of deafness, promontory test and subjective response (T and C-level) were investigated. The scattergram showed a strong negative linear relationship between EABR-S and subjective T-level. This finding suggests that EABR-S is good measure of postoperative perception.

Adult↗
PubMed1998

[Predictive factors for speech perception in patients with cochlear implant].

Cochlear implant therapy is an epoch-making advance in artificial sensory organ transplants, but the positive effects on speech perception vary. Quantification theory type I, a multivariate analysis, was used to determine predictive factors for speech perception in patients with cochlear implants. Fifty-one postlingual deaf adults (18 male and 33 female, mean age, 53.4, mean duration of deafness, 8.6 years) were tested for speech perception three or more months after a Nucleus 22 channels cochlear implant. The cause of deafness in nine patients was labyrinthitis, ototoxicity in five, meningitis in three and unknown in the remaining 34. Speech perception was measured by vowel, consonant and word recognition using a live voice, and monosyllable, word and sentence recognition using a videodisc. All tests were administered in a sound only condition. Results of the univariate analysis indicated that age at implantation was correlated with monosyllable recognition, and duration of deafness was correlated with live voice word recognition. Residual hearing and coding strategy were both correlated with all outcome measures. The multivariate analysis revealed that coding strategy, duration of deafness, residual hearing and the number of electrodes were significant predictors of live voice word recognition in that order.

Adolescent↗
PubMed1998

High density culture of immortalized liver endothelial cells in the radial-flow bioreactor in the development of an artificial liver.

Liver endothelial cells are important components of the tissue along the hepatic sinusoid. They are responsible for microcirculation in the liver and scavenger functions. It would therefore be important to include these cells in any hybrid type of artificial liver in addition to hepatocytes. However, it is difficult to culture these cells in vitro. The development of a liver endothelial cell line, which maintains the characteristics of the primary culture, would thus be of great benefit in the development of an artificial liver. In the present study we established immortalized liver endothelial cells from the liver of an H-2Kb-tsA58 transgenic mouse, which harbors the SV40 TAg gene. Hepatic sinusoidal cells isolated from H-2Kb-tsA58 mouse proliferated in the presence of gamma-interferon at 33 degrees C. Four clones were established, out of which clone M1 had the highest amounts of PGI2 production, as well as plasminogen activator activity and internalized acetylated low density lipoprotein. On culture dishes the M1 cells grew individually and spread. Sieve plates on the cell surface were not readily visible, but small pores were detected under electron microscopic observation. These results suggest that M1 clone cells originated from liver endothelial cells. Moreover it was possible to culture the immortalized liver endothelial cells in a radial-flow bioreactor for 5 days, with a maximum 6-keto prostaglandin F1alpha production of 25 microg per day. This suggests that immortalized liver endothelial cells and a radial-flow bioreactor can prove useful tools in the development an artificial liver.

Animals↗
PubMed1998

[An autopsy case of rhino-orbito-cerebral mucormycosis associated with multiple cranial nerve palsy and subsequent subarachnoid hemorrhage].

We report an autopsy case of 53-year-old male with poor controlled diabetes mellitus and hepatocellular carcinoma who developed rhino-orbito-cerebral mucormycosis. Initial complaints were epistaxis and headache followed by a sudden blindness, the 2nd through 7th cranial nerve palsy and diabetes inspidus. Laboratory data revealed that he had liver cirrhosis due to hepatitis C virus infection and diabetes mellitus. Head CT and MRI showed no significant findings. Eleven days after the onset, he died of subarachnoid hemorrhage. The postmortem examination revealed severe infiltration of numerous mucors in the sphenoid sinus, cavernous sinus and bilateral internal carotid arteries. Severe granulomatous vasculitis was seen in the cavernous portion of the bilateral internal carotid arteries. Thus, we considered that this case had been caused by the infiltration of mucors to the cavernous sinus, resulting in the obstruction of ophthalmic arteries. Rupture of the right internal carotid artery was seen at the branching portion of the ophthalmic artery, demonstrating the cause of his death. We would like to emphasize that rhino-orbito-cerebral mucormycosis should be ruled out if we examine a nondiagnostic case of diabetes mellitus or immunosuppressed disease associated with rapid multiple cranial nerve palsy following the orbital symptoms.

Abducens Nerve↗
PubMed1997

Identification and characterization of the gene encoding a new member of the alpha-crystallin/small hsp family, closely linked to the alphaB-crystallin gene in a head-to-head manner.

alphaB-Crystallin is a member of the alpha-crystallin/small heat shock protein (hsp) family and under various neuropathologic conditions accumulates in reactive astrocytes and degenerating neurons. In the 5'-flanking region of the alphaB-crystallin gene on human chromosome 11q22-q23, where a constitutive DNase I hypersensitive site is located, we identified a gene transcribed in the opposite direction. Analysis of its mRNA structure by RT-PCR and 5'/3'RACE revealed that this gene is composed of two exons and encodes a new member of the alpha-crystallin/small hsp family. This gene was designated the HSPB2 gene by the HMGW Nomenclature Committee. The complete genomic structure of the rat homologue was also determined. Northern blot analysis revealed that the HSPB2 gene is expressed preferentially in skeletal muscle and heart but not in the lens, while the neighboring alphaB-crystallin gene is highly expressed in all three tissues. The two related genes are arranged in a head-to-head manner with an intergenic sequence of less than 1 kb, raising a possibility of shared regulatory elements for their expression.

Amino Acid Sequence↗
PubMed1997

Immunohistochemical study on tissue transglutaminase and copper-zinc superoxide dismutase in human myocardium: its relevance to apoptosis detected by the nick end labelling method.

The influence of free radicals on apoptosis was studied in the human heart; 45 autopsy cases were examined by the nick end labelling method (NELM) that detects DNA fragmentation. Immunostaining for copper-zinc superoxide dismutase (CuZn-SOD) and tissue transglutaminase (tTG) induced frequently during apoptosis were also studied. Positive immunoreaction for tTG was detected in mucinous degeneration of myocardial cells; these same cells were also positive for CuZn-SOD but negative for NELM. Myocardial cells showing basophilic alterations after haematoxylin and eosin staining were also positive for CuZn-SOD but negative for the other markers examined. Positive nuclear reaction by NELM was only observed in myocardial cells showing contraction band necrosis or irregularly shaped nuclei surrounding recent or long-standing infarcted foci. In these the other two markers were negative. Since mucinous degeneration lacks the distinguishing morphological features of apoptosis, immunoreactive tTG in this lesion may not imply that the cells are undergoing apoptosis. tTG can be induced in non-apoptotic conditions and may not be involved in apoptosis induced by infarction. Histological disassociation between CuZn-SOD expression and apoptosis suggests the possibility of a cytoprotective role played by endogenous CuZn-SOD against free radical generation in the human heart.

Adolescent↗
PubMed1997

Detection of SV40 T antigen genome in human gliomas.

The monkey polyomavirus simian virus 40 (SV40) has been reported to be associated with tumorigenesis of human neoplasms, mainly brain tumors. However, it remains controversial whether the virus really exists in human neoplasms and how the virus transforms human cells in vivo. We investigated the presence of SV40 T antigen genome in 33 human glioma tissue specimens from Japanese patients with different histopathologies by means of the polymerase chain reaction (PCR) followed by Southern blotting. The SV40 T antigen genome was amplified in 4 of the 13 ependymomas (31%) and 3 of the 20 other histotypes of gliomas (15%), whereas in the 22 nontumoral brain tissue specimens, only one case was found to be positive. DNA sequencing confirmed the PCR products to be those of SV40 T antigen. The findings thus suggest that the SV40 genome appears to exist in a certain population of brain tumors from Japanese patients, and that it may also play a role in the oncogenicity or maintenance of the transformed state.

Adolescent↗
PubMed1997

Leser-Trélat sign with anaplastic ependymoma--an autopsy case.

A 36-year-old Japanese male, who 7 years previously had been diagnosed as having an ependymoma in the left parietal region, had received surgery, chemotherapy and radiotherapy. He later developed a rapid growth of multiple skin lesions on his back and extremities, which coincided with a regrowth of the tumor. Postmortem examination revealed that the ependymoma showed anaplastic transformation and necrosis; however, no malignancy was observed in the extracranial organs. The skin lesions were histologically diagnosed as seborrheic keratoses. We have, therefore, diagnosed the patient as having Leser-Trélat sign associated with anaplastic ependymoma.

Adult↗
PubMed1997

Expression of neurofibromatosis 2 protein in human brain tumors: an immunohistochemical study.

The neurofibromatosis 2 (NF2) gene-encoded protein, named merlin, may function as a molecular linkage connecting cytoskeleton and plasma membrane. Merlin is thought to play a crucial role as a tumor suppressor not only in hereditary NF2-related tumors, but also in sporadic tumors such as schwannomas, meningiomas and gliomas. Using a merlin-expression vector system, we raised specific antiserum against merlin. We observed the intracellular distribution of merlin in cultured glioma cells, and further investigated merlin expression in 116 human brain tumors. Immunofluorescence microscopy revealed that merlin was localized beneath the cell membrane and concentrated at cell-to-cell adhesion sites, where actin filaments are densely associated with plasma membrane. By immunohistochemistry, none of the schwannomas from either NF2 patients or sporadic cases showed any immunoreactivity, while normal Schwann cells of cranial nerves were immunopositive. In meningiomas, merlin expression was frequently seen in the meningothelial subtype (8/10, 80%), but no expression could be detected in either the fibrous or the transitional variant. Most normal astrocytes were negative; however, reactive astrocytes often expressed merlin. Glioblastomas and anaplastic astrocytomas were found to be strongly positive, and focal positive staining was observed in fibrillary and pilocytic astrocytomas. Thus, the loss of merlin appears to be integral to schwannoma formation and the differential pathogenesis of meningioma subtypes. However, merlin alterations do not appear to play a critical role in either the tumorigenesis or malignant transformation of neoplastic astrocytes.

Brain Neoplasms↗
PubMed1997

A comparative study of embedded nerve tissue in six NF2-associated schwannomas and 17 nonassociated NF2 schwannomas.

BACKGROUND: Neurofibromatosis-2 (NF2) is an autosomal dominant disorder in which patients typically show bilateral acoustic tumors, and they are usually diagnosed histopathologically as schwannomas. The nerve of origin of a schwannoma is often demonstrated on the periphery along the capsule but not penetrating the substance of the tumor. However, there is a possibility that NF2 schwannomas and solitary schwannomas differ from participation in nerve components. METHODS: In this study, the authors noted the relationship between the tumor and the original nerves. To detect whether there were embedded nerves in the tumor, immunohistologic staining using neurofilament and myelin basic protein antibodies was performed on 6 NF2 schwannomas and 17 non-NF2 schwannomas. RESULTS: Four of five NF2 schwannomas had embedded nerves and one of four, which was considered to be the early stage of the tumor occurrence, remarkably embedded original nerves. On the other hand, embedded nerves were not seen in non-NF2 schwannomas. CONCLUSIONS: The authors concluded that the NF2 schwannomas tend have original nerves embedded in the tumor substance, which may be based on the difference of the motility of tumor cells, and the authors believe that it is difficult to remove NF2 schwannomas while preserving the original nerve.

Adolescent↗
PubMed1997

Histopathological aspects of dural arteriovenous fistulas in the transverse-sigmoid sinus region in nine patients.

OBJECTIVE: In recent years, dural arteriovenous fistulas (DAVFs) have been primarily thought to be acquired lesions, formed after sinus thrombosis. The pathogenesis of DAVF, however, is still controversial. We have studied histopathological aspects of DAVFs in resected specimens obtained from nine patients, to obtain clues to the pathogenesis of DAVFs. METHODS: Histological comparison was made among nine DAVF cases and five control cases without venous sinus disease. In addition, the relationship between the clinical course and histological aspects was investigated. RESULTS: The essential abnormality found was a connection between the dural arteries and the dural veins within the venous sinus wall, through small vessels averaging approximately 30 microns in diameter. By using several staining methods, we confirmed that the vessels were part of the venous system; we named these dilated venules "crack-like vessels." CONCLUSIONS: The development of abnormal communications between dural arteries and dural veins (crack-like vessels) is regarded as the essential part of the pathogenesis of DAVFs, and sinus thrombus is not thought to be an essential lesion of DAVFs. It might be postulated that sinus hypertension caused by stenocclusive disease of the venous sinuses triggers the development of fistulous connections between arteries and veins in the dural wall, which may result in increasingly dilated venules and the formation of DAVFs.

Adult↗
PubMed1997

Changes in alpha band EEG activity in the frontal area after stimulation with music of different affective content.

This study investigated the stimulating effects of music. Twelve-channel EEGs( Fp1, Fp2, F7, F8, Fz, C3, C4, Pz, T5, T6, O1, O2) were recorded on 10 students during periods of baseline, premusic rest, music (stimulating or calming), and postmusic rest. The amplitude of the alpha-2 (9.6 to 11.4 Hz) band was lower during the rest session than that during the baseline session. In the music period the amplitude of alpha-2 band increased during both the stimulating and calm music. The frontal interhemispheric coherence values (F7-F8) of the alpha-2 band increased during the stimulating music session, while the coherence values did not change during the calm music. These findings implied close relationships between the interhemispheric transmission of information in the frontal areas and positive attention to stimulating music.

Acoustic Stimulation↗