Biomedical subjects

Kenji Itoh

Publications and source records attributed to Kenji Itoh.

42 records · Page 3Linked to original sources

PubMed2002

Ruthenium-catalyzed cycloaddition of 1,6-diynes with isothiocyanates and carbon disulfide: first transition-metal catalyzed [2 + 2 + 2] cocyclotrimerization involving C=S double bond.

In the presence of 10 mol % Cp*Ru(cod)Cl, 1,6-diynes with a tertiary center at 4-position reacted with various isothiocyanates at their C=S double bond to afford bicyclic (2H)-thiopyranimines in 35-88% yields. The (2H)-thiopyran structure was unequivocally determined by X-ray analysis. The cycloaddition of carbon disulfide with a diyne similarly gave the expected bicyclic dithiopyrone in 50% yield.

Journal Article↗

PubMed2002

No effect of gender on tonal and phonetic mismatch negativity in normal adults assessed by a high-resolution EEG recording.

The auditory mismatch negativity (MMN) of event-related potential components has been widely used to assess the ability of auditory automatic change discrimination of verbal and nonverbal stimuli in healthy individuals and patients with various illnesses. To clarify the role of gender differences in the MMN, we compared the amplitude, latency, and topography of tonal and phonetic MMN between healthy males and females, using a high-density (128 channel) electroencephalography montage. The MMN was evaluated in 18 right-handed male and ten age-matched female adults. The MMN in response to a duration change of pure tone and that in response to a phonetic change (Japanese vowel /a/ versus /o/ with 150-ms duration) were recorded. There were no significant differences in amplitude, latency, or laterality for either tonal or phonetic MMN between male and female subjects. This lack of evidence for effects of gender on MMN in response to duration change of tones or that in response to changes of phonemes with a short duration in normal adults may be of relevance to a growing number of researchers who are studying the MMN in healthy individuals and various clinical groups.

Acoustic Stimulation↗

PubMed2002

Do high or low doses of anxiolytics and hypnotics affect mismatch negativity in schizophrenic subjects? An EEG and MEG study.

OBJECTIVE: Many studies have demonstrated mismatch negativity (MMN) attenuation in schizophrenia. Recently, investigators have shown that GABAergic inhibitory neurons may regulate MMN generation. Considering that a substantial proportion of schizophrenic patients receive anxiolytics and hypnotics that have affinity to GABA(A) receptors to reduce their comorbid symptoms of anxiety and sleep disturbances, we need to assess whether anxiolytics/hypnotics might affect their MMN generation. The aim of this study is to assess the possibility that high or low doses of anxiolytics/hypnotics received by schizophrenic subjects affect their mismatch negativity (MMN), using event-related potentials (ERPs) and magnetoencephalography (MEG). METHODS: Twenty-three and 16 patients with schizophrenia participated in the ERP and MEG studies, respectively. Three types of MMN (MMN in response to a duration change of pure-tone stimuli, within-category vowel change (Japanese vowel /a/ with short versus long duration), and across-category vowel change (vowel /a/ versus /o/)) were recorded. RESULTS: High or low doses of benzodiazepine had no significant effects on MMN amplitude/magnetic MMN power, topography/laterality, or latency under any conditions of the ERP or MEG study. CONCLUSIONS: These results suggest that chronic administration of anxiolytics/hypnotics does not significantly affect MMN in schizophrenia.

Acoustic Stimulation↗

PubMed2002

Early components of event-related potentials related to semantic and syntactic processes in the Japanese language.

Brain activities were compared between semantic and syntactic processing in the Japanese language using event-related potentials with a 58-ch EEG system. We previously found that semantic violations elicited N400 and syntactic violations elicited P600 but not early left anterior negativity (ELAN) or left anterior negativity (LAN) using a relatively long stimulus presentation time (1 s). In the present study, we adopted a shorter stimulus presentation time (0.5 s), which might impose a heavier burden on the working memory system, to test the possible relevance of load on the working memory system to ELAN/LAN. A global field power analysis showed an increased potential field strength at the latency of 320 ms in either type, as well as those at the later latencies reflecting N400 (556 ms) and P600 (712 ms). Statistical analyses revealed a significant negative deflection in the right frontal region for the semantic type, whereas no significant deflection in either specified region was obtained for the syntactic type at the latency of 320 ms. The lack of ELAN/LAN suggested that it was not due to the deactivation of the working memory system. Moreover, scalp current density topographies implied that the processing of the verbal stimuli was mediated by distinct areas within the left temporal region, according to its semantic congruency with the preceding context at a latency as early as 320 ms. These findings are in line with the dual-route hypothesis of reading, which suggests that the reading of verbal stimuli semantically incongruent with the preceding context is dominated by phonological processes rather than lexico-semantic.

Adult↗

PubMed2002

Impaired cortical network for preattentive detection of change in speech sounds in schizophrenia: a high-resolution event-related potential study.

OBJECTIVE: Schizophrenia is associated with language-related dysfunction. At the most basic level, the dysfunction of schizophrenic patients in perceiving phoneme boundaries has been demonstrated in a behavioral task. The goal in this study was to obtain an electrophysiological index of preattentive detection of change in speech sounds by schizophrenic patients. METHOD: A high-density recording system was used to measure mismatch negativity, i.e., difference in electrophysiological responses between standard and deviant auditory stimuli. The amplitude of mismatch negativity was measured in 23 right-handed schizophrenic patients and in 28 healthy comparison subjects. Three types of mismatch negativity were recorded: change in duration of pure-tone stimuli, change in duration of the Japanese vowel /a/, and difference between vowels /a/ and /o/ (across-phoneme change). RESULTS: The schizophrenic patients had a lower amplitude of mismatch negativity for across-phoneme change than for change in duration of tone or vowel. For across-phoneme change, the schizophrenia group showed significantly lower bilateral amplitude of mismatch negativity than the comparison subjects. These findings coincide with those from the analysis of scalp current density, indicating that the schizophrenic patients had a significantly weaker left temporal combination of current sink (perpendicularly sinking into the scalp) and current source (arising out of the scalp) and a significantly weaker right frontal/temporal current sink than the comparison subjects. CONCLUSIONS: These results demonstrate impaired frontotemporal cortical networks for preattentive detection of change in speech sounds in schizophrenia. The language-related dysfunction in schizophrenia may be present at the early stage of auditory processing of relatively simple stimuli, such as phonemes, and not just at stages involving higher-order semantic processes.

Adult↗

PubMed1999

The Cp(2)TiPh-Mediated Reductive Radical Cyclization of Cyanoketones and Related Reactions. Efficient Trapping of Ketyl Radicals by Cp(2)TiPh-Coordinated Polar Multiple Bonds.

The reductive radical cyclization of cyanoketones was achieved using Cp(2)TiPh. The Ti(III) reagent was prepared by the sequential addition of i-PrMgCl and PhMgBr to commercial Cp(2)TiCl(2) in this order and used effectively without isolation. The cyclization of the gamma- and delta-cyanoketones was performed in toluene at ambient temperature for several hours to give alpha-hydroxycyclopentanones and hexanones in moderate to good yields, respectively. The titanium reagent independently coordinates to both the carbonyl and cyano termini. As a result of lowering the LUMO of the cyano group upon coordination of the Ti(III) species, the irreversible cyclization successfully proceeds without formation of the unstable iminyl radical intermediate. The ester group can also be activated by the coordination of Cp(2)TiPh, and aromatic ketones with an ester group at the gamma position are cyclized to give the corresponding alpha-hydroxyketones.

Journal Article↗