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Biomedical subjects

Tetsuo Koyama

Publications and source records attributed to Tetsuo Koyama.

11 recordsLinked to original sources
PubMed2006

Lactotriaose-containing carbosilane dendrimers: syntheses and lectin-binding activities.

Carbosilane dendrimers periphery-functionalized with lactotriaose (GlcNAcbeta1-3Galbeta1-4Glc) with valencies of three, four, six, and twelve were prepared for use in a lectin-binding assay. A lactotriaose derivative was prepared from D-glucosamine and D-lactose derivatives. The N-Troc-protected glucosamine glycosyl donor and 3'-O-unprotected lactose glycosyl acceptor were condensed in the presence of silver trifluoromethanesulfonate and methylsulfenyl bromide to provide corresponding trisaccharide with new beta-1-3 linkages in 92% yield. The protection group of the trisaccharide was transformed into an acetyl group. The 4-pentenyl glycoside was prepared from the acetate via glycosyl bromide. The alkene was converted into acetyl sulfide by addition of thioacetic acid under radical conditions. The lactotriaose unit was linked with carbosilane dendrimers to afford acetyl-protected glycodendrimers. De-O-acetylation of the dendrimers was carried out in the presence of sodium methoxide and then aq NaOH to give the desired lactotriaose clusters using a carbosilane dendrimer backbone. Their biological activities toward WGA were evaluated by fluorescence methods. The binding constants of free lactotriaose and trivalent, tetravalent, hexavalent, and dodecavalent glycodendrimers to WGA were determined to be 1.1x10(3), 4.4x10(4), 5.1x10(4), 2.8x10(6), and 1.3x10(6) M-1, respectively. The hexavalent glycodendrimer showed a 2500-fold larger binding effect than that of free lactotriaose.

Dendrimers↗
PubMed2006

Relationships between independence level of single motor-FIM items and FIM-motor scores in patients with hemiplegia after stroke: an ordinal logistic modelling study.

OBJECTIVE: To assess the relationships between independence levels of single motor-related Functional Independence Measure (FIM) items and summed FIM-motor scores of patients with hemiplegia after stroke. DESIGN: For each patient FIM scores were assessed 4 times during hospitalization. Ordinal logistic analyses were performed on group data. SUBJECTS: Fifty patients with hemiplegia after stroke staying in a long-term rehabilitation facility. RESULTS: Analyses revealed that FIM-motor scores accounted for much of the variability of independence levels for most of the single FIM items, including dressing upper body, and transfers to bed/chair/wheelchair and to toilet. For these items, the independence levels were proportionally associated with FIM-motor scores. For eating, higher FIM-motor scores (>60) were associated with modified independence and lower FIM-motor scores (<40) correlated with attainment of supervision/set-up levels. For dressing lower body, greater independence was apparent when FIM-motor scores were higher (>60). CONCLUSION: For single FIM items, relative difficulty was comparable with results from previous literatures using Rasch analyses. Moreover, our results revealed that relative difficulty for single items varied greatly between independence levels. With regard to disability task targets, probability of independence evaluated from logistic modelling is an aid to efficient rehabilitation scheduling.

Activities of Daily Living↗
PubMed2006

Flow-injection determination of L-histidine with an immobilized histidine oxidase from Brevibacillus borstelensis KAIT-B-022 and chemiluminescence detection.

A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel.

Bacillus↗
PubMed2005

Syntheses of a series of lacto-N-neotetraose clusters using a carbosilane dendrimer scaffold.

4-Pentenyl (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-(3,6-di-O-acetyl-2-deoxy-2-phthalimido-beta-d-glucopyranosyl)-(1-->3)-(2,6-di-O-benzoyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-beta-d-glucopyranoside (4) was synthesized by regioselective glycosylation of 4-pentenyl (2,6,-di-O-benzoyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-beta-d-glucopyranoside and (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-3,6-di-O-acetyl-2-deoxy-2-phthalimido-beta-d-glucopyranosyl chloride. By conversion of the protecting groups followed by thioacetylation, 4 was transformed into the corresponding lacto-N-neotetraose derivative, 5-(acetylthio)pentenyl (2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-O-(3,6-di-O-acetyl-2-acetamido-2-deoxy-beta-d-glucopyranosyl)-(1-->3)-(2,4,6-di-O-acetyl-beta-d-galactopyranosyl)-(1-->4)-2,3,6-tri-O-acetyl-beta-d-glucopyranoside (6). The lacto-N-neotetraose derivative 6 was introduced into carbosilane dendrimer cores of three shapes, and three kinds of new carbosilane dendrimers peripherally functionalized by lacto-N-neotetraose were obtained.

Carbohydrate Conformation↗
PubMed2005

The subjective experience of pain: where expectations become reality.

Our subjective sensory experiences are thought to be heavily shaped by interactions between expectations and incoming sensory information. However, the neural mechanisms supporting these interactions remain poorly understood. By using combined psychophysical and functional MRI techniques, brain activation related to the intensity of expected pain and experienced pain was characterized. As the magnitude of expected pain increased, activation increased in the thalamus, insula, prefrontal cortex, anterior cingulate cortex (ACC) and other brain regions. Pain-intensity-related brain activation was identified in a widely distributed set of brain regions but overlapped partially with expectation-related activation in regions, including the anterior insula and ACC. When expected pain was manipulated, expectations of decreased pain powerfully reduced both the subjective experience of pain and activation of pain-related brain regions, such as the primary somatosensory cortex, insular cortex, and ACC. These results confirm that a mental representation of an impending sensory event can significantly shape neural processes that underlie the formulation of the actual sensory experience and provide insight as to how positive expectations diminish the severity of chronic disease states.

Adult↗
PubMed2005

A new method for predicting functional recovery of stroke patients with hemiplegia: logarithmic modelling.

OBJECTIVE: To examine the validity and applicability of logarithmic modelling for predicting functional recovery of stroke patients with hemiplegia. DESIGN: Longitudinal postal survey. SUBJECTS: Stroke patients with hemiplegia staying in a long-term rehabilitation facility, who had been referred from acute medical service 30-60 days after onset. METHODS: Functional Independence Measure (FIM) scores were periodically assessed during hospitalization. For each individual, a logarithmic formula that was scaled by an interval increase in FIM scores during the initial 2-6 weeks was used for predicting functional recovery. RESULTS: For the study, we recruited 18 patients who showed a wide variety of disability levels on admission (FIM scores 25-107). For each patient, the predicted FIM scores derived from the logarithmic formula matched the actual change in FIM scores. The changes predicted the recovery of motor rather than cognitive functions. Regression analysis showed a close fit between logarithmic modelling and actual FIM scores (across-subject R2 = 0.945). CONCLUSIONS: Provided with two initial time-point samplings, logarithmic modelling allows accurate prediction of functional recovery for individuals. Because the modelling is mathematically simple, it can be widely applied in daily clinical practice.

Adult↗
PubMed2004

Effects of stimulus duration on heat induced pain: the relationship between real-time and post-stimulus pain ratings.

Pain is a temporally dynamic experience. Yet, in most instances, pain ratings are acquired in a static fashion and frequently require subjects to retrospectively evaluate the pain experience that occurred in a preceding interval of time. In order to determine which components of the real-time experience of pain contribute to static pain ratings, we obtained real-time (dynamic) and post-stimulus (static) ratings using a visual analogue scale during various of durations (5-30 s) of noxious thermal stimulation (43-49 degrees C). For both pain-intensity and pain-unpleasantness, real-time ratings revealed that pain adapted when stimulus temperatures were low to moderate and summated when stimulus temperature was high. Regression analyses examining both pain-intensity and pain-unpleasantness revealed that the mean response and the peak response of real-time ratings significantly contributed to post-stimulus ratings, while temporal components such as perceived duration of pain contributed minimally. Additional regression analyses revealed that mean and peak responses of real-time intensity ratings accounted for much of the variability of post-stimulus unpleasantness ratings whereas real-time unpleasantness ratings accounted for somewhat less of the variability of post-stimulus intensity ratings. Taken together, the close relationship between real-time and post-stimulus ratings of pain across stimulus conditions evoking both adaptation and temporal summation further confirms that post-stimulus, retrospective ratings of pain are valid measures of the real-time experience of pain.

Adolescent↗
PubMed2003

The single-epoch fMRI design: validation of a simplified paradigm for the collection of subjective ratings.

One of the goals of human functional imaging studies is to interpret brain activation in the context of an individual's subjective experience. However, functional magnetic resonance imaging (fMRI) studies usually employ a block design that consists of multiple epochs of stimulation; this strategy does not readily allow subjective responses to be assessed on a stimulus-by-stimulus basis. To address this issue, we developed a "single-epoch" design, consisting of a single stimulation period presented between two baseline periods. This allows subjective ratings to be acquired after each stimulus, while minimizing rating-induced confounds. To evaluate its sensitivity and utility, we obtained fMRI data using single-epoch and block designs (five stimuli between six baselines) and assessed regional brain activations evoked by both visual (a checkerboard pattern) and painful (noxious heat to right calf) stimuli. For both types of stimulation, data collected using the single-epoch design displayed activation patterns that were generally similar to those detected with the block design. Furthermore, only one single-epoch acquisition series was sufficient to detect bilateral activation in the visual cortex during visual stimulation and activation in the primary somatosensory cortex, the anterior cingulate cortex, and other regions during painful stimulation. In addition, analyses of a series of single-epoch data from a single individual revealed a stimulus-by-stimulus decrease in the activation in the anterior cingulate cortex that paralleled the decrease in the subject's psychophysical responses. These findings confirm that the single-epoch design is sensitive to regional signal changes and serves as a viable alternative to the block design when the collection of subjective responses is of critical importance.

Adult↗
PubMed2002

Visual responses in the temporal cortex to moving objects with invariant contours.

We were interested in how the visual attributes of motion and shape are integrated in the temporal cortex of monkeys. We recorded neural activity in the middle portion of the superior temporal sulcus (STS) of monkeys during a sequential visual discrimination task while the animals maintained fixation. We used images of objects with invariant outlines rotating in 3D space either clockwise or counterclockwise as visual stimuli. In the sequential discrimination task, after the fixation pattern was presented for 1.0 s, the sample stimulus (S1) appeared at the center of the monitor screen for 0.8 s. After a delay period of 0.5-2.0 s, the same stimulus or a new response stimulus appeared on the screen for 0.8 s. In each block, the response stimulus was either a new direction of rotation or a new shape. Of 425 responding neurons isolated in the STS, 202 (48%) showed significant activity when S1 stimuli were presented. Of these visual neurons, 27 (13%) were categorized as motion and shape selective (MS), 69 (34%) as shape selective (S), and 6 (3%) as motion selective (M). Briefer than for MS or S neurons, the latency of the remaining non-selective neurons was 80 ms. Latencies of visual response (110 ms) of both MS and S neurons were similar. On the other hand, MS neurons started responding later (180 ms) to changes in direction. Our findings show that neurons in the STS, responding selectively to changes in shape, do respond to relatively simple motion and that variable contouring is not essential to elicit motion response. The results may also suggest the functional segregation of selective versus non-selective neurons and the later arrival of directional response to MS neurons in the STS.

Action Potentials↗