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Biomedical subjects

K Matsunami

Publications and source records attributed to K Matsunami.

At least 73 records · Page 4Linked to original sources
PubMed1996

Application of the minimum jerk model to formation of the trajectory of the centre of mass during multijoint limb movements.

Smoothness of movement is an inherent characteristic of the motor repertoire of primates. According to the minimum hand jerk model, a major feature of motor coordination in two-joint upper limb movements by humans in the horizontal plane is the production of the smoothest possible movement of the end effector, the hand ('hand version'). In the present study, this model was extended to the formation of the trajectory of the centre of mass (CMt) of the whole arm system ('CMt version'), and its importance for the shaping of multijoint movements was tested against the classical 'hand version'. During point-to-point movements between many pairs of targets in the work space, the movements of the CMt showed lower changes of torque than in movements of the hand on a straight path. Furthermore, the CMt version of the minimum jerk model reproduced the curved hand trajectory that can be observed in actual human performance. Under the assumption that the smoothness criterion is induced by a high-level motor coordination, our results suggest that CMt-based planning can be an alternative strategy for joint coordination. It offers the advantage of the simplified scaling of joint torques which are suitable for execution of planned movements.

Computer Simulation↗
PubMed1995

GABAB receptor antagonist CGP 35348 shortens transcallosal response latency of pyramidal tract neurons.

The effects of a specific GABAB receptor antagonist, p-(3-aminopropyl)-p-diethoxymethyl-phosphonic acid (CGP 35348), on pyramidal tract neuron responses to transcallosal stimulation were investigated in the cat motor cortex in vivo. Iontophoretic application of CGP 35348 significantly increased the number of spikes from 10.3 +/- 4.4 (control; n = 27; mean +/- S.D.) to 16.7 +/- 7.2 (CGP 35348) for 20 transcallosal stimulation trials, while the latency of neuronal activity was significantly shortened from 4.4 +/- 2.1 ms (control; n = 27; mean +/- S.D.) to 3.8 +/- 1.7 ms (CGP 35348). In conclusion, CGP 35348 facilitated transcallosal synaptic transmission between pyramidal tract neurons by removal of GABAB inhibition.

Action Potentials↗
PubMed1995

Radioactive 2-DG incorporation patterns in the mesial frontal cortex of task-performing monkeys.

The pattern of radioactive 2-deoxy-D-glucose (2-DG) uptake in the rostral mesial cortex was investigated in seven hemispheres of four task-performing monkeys (a delayed-response task performed with a forelimb). A two-dimensional 2-DG map was constructed from frontal sections. Blob-like 2-DG incorporation sites (2-DG active sites) were observed in single frontal sections, e.g., in the anterior cingulate gyrus (CiG) and supplementary and primary motor cortices in the mesial surface, and around the superior precentral sulcus in the premotor area. Blob-like 2-DG incorporation sites were also observed in the medial part of the dorsal frontal cortex near the midline. However, most of these blob-like 2-DG active sites were revealed in fact not to be blobs. They formed rostrocaudally continuous streaks when they were constructed in a two-dimensional map. Streaks fused with one another in some areas, and gave off branches in other areas. These 2-DG uptake patterns were similar between the paired left and right hemispheres of three brains. It is highly probable that these 2-DG active streaks (or blobs) reflected neuronal activity related to somatomotor and/or eye movements, because the 2-DG-labeled areas included motor, premotor, supplementary motor, and possibly part of the supplementary eye fields. It is also probable that this 2-DG incorporation was related to cognitive or memory functions, because neuronal activity related to performance of a delayed-response was reported in the rostral mesial cortex and in the CiG.

Animals↗
PubMed1994

Cardiovascular responses to KC-135 hyper-gravity.

The present study was designed with two intentions; Are the effects of angular velocity detectable in the cardiovascular responses during the hyper-G? Another is object to examine how the otolith signal could modify the cardiovascular responses provoked by the exposure to the hyper-G. NASA/KC-135 hyper-gravity flight was used to generate high gravito-inertial forces to exclude a possible effect of angular velocity. Six healthy subjects was indicated to make dorsal flexion of the neck to reduce the otolith input. An exposure to +l.8Gz stress resulted in a remarkable increase of systolic and diastolic blood pressure, thereby pulse pressure became a little bit narrower. R-R interval revealed a tachycardia during the hyper-G except one subject. The present experiment bore the similar cardiovascular responses as those observed in the previous studies with a short rotating radius, suggesting that almost no effect of angular velocity acts on their responses. A weaker otolith input could possibly work on them. However a systematical observation can not recognize among the subjects for the vestibular effect on the cardiovascular responses. This fact of vestibular qualification leads us to speculate that it would depend on the subjects or other factors.

Adult↗
PubMed1994

Topography of commissural fibers in the corpus callosum of the cat: a study using WGA-HRP method.

The topography of the commissural fibers in the corpus callosum (CC) of the cat was systematically investigated using the WGA-HRP method. WGA-HRP was injected into various parts of the cerebral cortex and locations of WGA-HRP-stained commissural fibers in the CC were examined. Commissural fibers were arranged in a topological fashion in the CC. Cortical areas rostral to the cruciate sulcus (CrS), corresponding to motor or premotor cortices, projected fibers into the genu of the CC, while fibers from the cortex caudal to the CrS passed through the CC slightly caudal to the genu. When WGA-HRP was injected into the lateral gyrus (LG), it was observed that fibers from the anterior LG passed through the anterior one-third of the CC, whereas those from the posterior LG passed through or near the splenium, and fibers from the middle LG passed between those from the anterior and posterior LG. Similarly, the suprasylvian gyrus (SSG) projected commissural fibers in the CC in a rostrocaudal topological manner. Fibers from the anterior SSG passed through the anterior one-third of the CC, and those from the middle SSG through the middle one-third of the CC and upper part of the splenium. Injection into the most posterior part of the middle SSG revealed fibers passing through the caudal end of the splenium. Callosal fibers from the anterior SSG were focused on in this study, because this area (area 2v) is considered one of the vestibular projection cortices and is an area of special interest to the authors. Callosal fibers from the anterior SSG were observed to pass through the anterior one-third of the body of the CC. When WGA-HRP was injected into auditory areas, fibers from the anterior and middle ectosylvian gyri (ESG) were observed to pass through the posterior one-third of the body of the CC or through the splenium, while fibers from the posterior ESG passed through the splenium. WGA-HRP was also injected into the cingulate gyrus (CiG). Fibers from the anterior CiG (area 24) passed through the anterior portion of the CC while those from the posterior CiG (area 23) passed through the posterior portion of the CC.

Animals↗
PubMed1994

Relationship between force and electromyographic activity during rapid isometric contraction in power grip.

Force response and surface electromyographic (EMG) activity of extrinsic extensors and flexors of the hand were measured under 6 target force conditions during rapid pulse isometric contractions (power grip) targeted using an oscilloscope display of exerted and target forces. For target forces ranging from 16.7% to 50% of maximum voluntary contraction (MVC), the rate of force rise increased with the peak force, while the time to peak force remained almost constant. However, at target forces between 66.7% and 100.0% MVC, the rate of force rise leveled off and the time to peak force was prolonged. In association with these changes in force trajectories, modulation of the EMG activity of the flexor digitorum superficialis muscle was observed. At the lowest target force (16.7 MVC), the EMG of this muscle showed a single initial activity; the activity increased linearly up to the 50% MVC target force, while the duration was relatively constant. However, at target forces above 50% MVC, no further increase of the initial activity was observed, while the amplitude and duration of an additional activity progressively increased. These results indicate that the neural control of rapid isometric contraction at target forces at and below 50% MVC differs from that operating at larger target force levels.

Adolescent↗
PubMed1994

Marine natural products. XXXIV. Trisindoline, a new antibiotic indole trimer, produced by a bacterium of Vibrio sp. separated from the marine sponge Hyrtios altum.

A new antibiotic indole trimer named trisindoline (1) was isolated, together with a known dioxopiperazine brevianamide F (2), from the culture of a bacterium of Vibrio sp., which was separated from the Okinawan marine sponge Hyrtios altum. The structure of trisindoline (1) has been determined on the bases of physicochemical evidence and chemical synthesis.

Animals↗
PubMed1994

Intracranial blood flow measured with single photon emission computer tomography (SPECT) during transient -6 degrees head-down tilt.

Regional cerebral blood flow (CBF) during a transient head-down tilt of -6 degrees (-6 degrees HDT) was measured with single photon emission computer tomography (SPECT). CBF was measured and averaged for both sides of the brain areas; e.g., the bilateral anterior cerebral artery (bACA) area, the middle cerebral artery (bMCA) area, the posterior cerebral artery (bPCA) area, bilateral basal ganglia, and the cerebellum. Among these areas, a significant increase in CBF was observed in the basal ganglia and the cerebellum during -6 degrees HDT compared to pre-HDT. When CBF was measured separately in the left or right brain area, these significances disappeared, although a trend of increase or decrease was still observable. A trend of increase was observed in the left anterior cerebral artery (IACA) area, the right middle cerebral artery (rMCA) area, the right posterior cerebral artery (rPCA) area, the left and right basal ganglia, and the cerebellum. In rACA, IMCA and IPCA areas, a slight decrease in CBF was observed. At the same time, cardiac parameters were measured. Heart rate (HR), stroke volume (SV) and cardiac output (CO) did not change significantly, although SV slightly increased and HR slightly decreased during -6 degrees HDT.

Adult↗
PubMed1993

Neuronal responses to vestibular and callosal stimulation in the anterior suprasylvian gyrus of the cat.

Neuronal responses to electrical stimulation at the horizontal ampulla (HA), vestibular nerve (at the windows) and corpus callosum (CC) were investigated in neurons in the anterior suprasylvian gyrus of the cat. The field potentials to HA stimulation had short latency: 2.9 +/- 0.3 (mean +/- SD) ms from the stimulus to the onset and 5.6 +/- 1.9 ms to the peak. The focus of the evoked potentials was located in the anterior suprasylvian (ASS) gyrus or near the ASS sulcus. HA stimulation activated 6 neurons out of 674 examined, with the mean latency of 4.3 +/- 1.1 ms. Of these 6, four neurons also responded to window stimulation. Fifty-six neurons responded to window stimulation with the mean latency of 6.1 +/- 2.4 ms. The mean latency for CC stimulation was 1.9 +/- 0.9 ms (n = 76). Four neurons responded to CC stimulation antidromically (mean = 0.9 +/- 0.3 ms) and one of them also responded orthodromically. The convergence of CC inputs in relation to HA or window stimulation was examined. One (17%) of the 6 HA-activated cells responded to CC stimulation, compared with 8 (14%) of the 56 neurons activated by window stimulation. The other 612 neurons did not respond to either HA or window stimulation, and 80 (13%) of the 612 responded to CC stimulation. Therefore, it is concluded that neurons in the ASS gyrus received callosal input equally irrespective of the presence or absence of responses to ampulla or window stimulation. WGA-HRP was injected in the ASS gyrus to identify the passing callosal fibers in the CC. Fibers from the ASS area passed at the rostral third of the CC. The present results indicate that the ASS area received vestibular projection with short latency, but responses of this projection did not seem to be very strong, at least from the present unit study, to HA stimulation. Discussion was made on the poor neuronal responses to electrical HA stimulation in comparison with previous studies. Also consideration was made on neuronal activity to CC stimulation.

Animals↗
PubMed1993

Prolactin binds to human endometrial fibroblasts and inhibits mitogenicity of an endometrial carcinoma extract.

Uterine endometrial carcinoma has been reported to synthesize and secrete a putative peptide mitogen that elicits a potent proliferative response in endometrial fibroblasts. The extract from endometrial carcinoma stimulated [3H]thymidine incorporation into human endometrial fibroblasts in a dose-dependent manner. Concomitant exposure of the fibroblasts to prolactin (PRL) led to a remarkable inhibition of the extract-stimulated mitogenic activity of the fibroblasts. This inhibition was dependent on PRL dose, and maximal effect occurred at 1 microM of PRL. PRL (10 nM) suppressed an apparent maximal activity of the extract by 50%, and the half-maximal stimulated effect of the extract on thymidine incorporation was observed at the same concentration in the absence or presence of PRL. This noncompetitive manner may imply that PRL acts at a stage after the interaction of the mitogen in the extract with the specific receptor for mitogen. When the fibroblasts were first exposed to the extract for 12 hr and then to PRL, PRL suppressed the mitogenic activity with no lag. The rapid growth-inhibitory effect of PRL was mimicked by prostaglandin E1, but the combination of both types of ligand was not additive in the inhibitory action on growth. PRL and prostaglandin E1 may inhibit a similar mitogenic signaling cascade. Specific receptor sites for PRL were detected in the endometrial fibroblasts, showing high binding affinity (Kd = 16.1 nM) and low binding capacity (Bmax = 1.59 pmol/mg protein). Treatment of the fibroblasts with the endometrial carcinoma extract induced no changes in the level of PRL receptor, excluding the possibility that PRL competes for the binding sites with the mitogen. These findings would suggest that PRL may block the mitogenic activity of the fibroblasts stimulated by the endometrial carcinoma-derived mitogen via a PRL receptor-mediated mechanism, perhaps prostaglandin production.

Binding Sites↗
PubMed1992

Evidence of a role for phosphatidylinositol synthesis in human amnion cell proliferation.

Phosphatidylinositol (PtdIns) is the key precursor of phosphoinositide-derived intracellular mediators. The effects of changing the rate of PtdIns synthesis on mitogenic activity of human amnion-derived WISH cells were investigated. Incubation of the cells with [3H]inositol caused a time- and dose-dependent PtdIns labeling. Exogenous Ca2+ inhibited [3H]inositol incorporation in a dose-dependent fashion; half-maximal inhibition occurred with 0.3-1.0 mM Ca2+. In contrast, removal of cytosolic Ca2+ by ionophore A23187 and 1 mM EGTA induced enhancement of the PtdIns labeling as a function of A23187 concentration, perhaps through release of inhibitory effects of endogenous Ca2+. The A23187-stimulated PtdIns labeling with [3H]inositol was not abolished by additional unlabeled inositol, suggesting that [3H]inositol labeling of PtdIns occurred mainly through de novo synthesis catalyzed by PtdIns synthase (EC 2.7.8.11). In cells with PtdIns synthase activity decreased by exogenous Ca2+, [3H]thymidine incorporation was also inhibited, while A23187 caused dose-dependent enhancement of thymidine incorporation. The changes in PtdIns synthase activity occurred in parallel with changes in mitogenic activity caused by increasing the dose of exogenous Ca2+ or A23187. A similar lowering of mitogenic activity was observed upon suppression of PtdIns synthase by pemirolast potassium (9-methyl-3-1H-tetrazol-5yl-4H-pyrido[1,2-a]pyridin-4-one potassium) via a Ca(2+)-independent mechanism. These data demonstrate that changes in PtdIns synthase activity by some agents acting via different mechanisms are associated with parallel changes in thymidine incorporation, and suggest that PtdIns production is tightly coupled to cell proliferation in human amnion cells.

Amnion↗
PubMed1992

Enhancement of growth-promoting activity in extract from uterine cancers by protein kinase C in human endometrial fibroblasts.

Uterine cervical and corpus cancers have been reported to synthesize and secrete a putative peptide mitogen, which elicits a potent proliferative response in fibroblasts by a mechanism independent of phosphoinositide turnover. The extract from human uterine cervical cancer stimulated [3H]thymidine incorporation into human endometrial fibroblasts in a dose-dependent manner. Concomitant exposure of the fibroblasts to thrombin or fibroblast growth factor (FGF) led to synergistic enhancement of the extract-stimulated [3H]thymidine incorporation into fibroblasts. An apparent maximal activity of the extract in the presence of thrombin or FGF was 2-fold higher than that in the absence of them, implying that thrombin or FGF acted at a stage after the interaction of the mitogen in the extract with its specific receptor. Insulin or epidermal growth factor failed to augment the growth-promoting activity in the extract. The stimulatory action of thrombin or FGF was mimicked by protein kinase C activators, phorbol-12-myristate-13-acetate (PMA) or 1-oleoyl-2-acetyl glycerol, but not by Ca2+ ionophore A23187. When the fibroblasts were first exposed to the extract for 4 h and then to PMA, PMA succeeded to augment the mitogenic activity in the same manner. The identical effects of protein kinase C activators with thrombin or FGF suggested that both types of ligand share a similar signaling cascade of action, activation of protein kinase C. These results demonstrated that the growth-promoting activity in uterine cancer extract could be enhanced by the agents which promote phosphoinositide metabolism through activation of protein kinase C. These findings could give a new insight into pathophysiology of the interaction between malignant cells and their stromal cells, fibroblasts.

Endometrium↗
PubMed1991

ECG analysis of golden hamsters exposed to long-term -Gz conditions: ordinary and pathological findings.

Changes of ECG due to long and intense -Gz acceleration was investigated in anesthetized Syrian golden hamsters. The R-R interval decreased (heart rate increased) slightly at the very initial phase of steady -Gz load. However, the R-R interval increased during the rest of the whole steady -Gz period. The P-R interval increased with a smaller -Gz load (-4 and -6 Gz), but it decreased with a larger -Gz (-8 and -10 Gz). The size of the QRS complex was measured as R amplitude. It decreased in all -Gz conditions. Effects were a little different for smaller and larger -Gz, as was observed in the case of P-R changes. Pathological ECGs were frequently observed. They were: (1) Arrhythmia of heart rate with or without atrio-ventricular blocks. (2) Abnormal P wave; e.g., splitting, flattening, or abolition of P wave. (3) Alteration of the QRS complex in amplitude or contour. (4) Changes in ST-T components. In spite of all these changes, however, it should be noted that several Syrian golden hamsters could tolerate up to -10 Gz for as long as 1,000 s.

Acceleration↗
PubMed1991

The vestibulo-autonomic function viewed from cardiac responses in centrifuged monkeys.

Vestibulo-autonomic function was examined as the change of cardiac parameters (HR and SV) to +Gz and -Gx accelerations for 1,000 s in intact and bilaterally labyrinthectomized monkeys. Under anesthetized conditions, HR and SV slightly changed to +2Gz acceleration in both monkeys. In +3Gz acceleration, changes were remarkable and significant. HR increased in intact monkeys by as much as 30% while it decreased in labyrinthectomized monkeys, although a moderate initial increase was observed. SV decreased in intact as well as labyrinthectomized monkeys, but the reduction was significant and larger for the latter. This implies that vestibular input could modulate autonomic function. For larger +Gz, both intact and labyrinthectomized monkeys could tolerate no more due to severe cardiac dysfunction (rapid HR and SV decrease) which appeared soon after +4Gz application. In case of -Gx application, HR increased, although slightly, in proportion to the amplitude of applied -Gx in both monkeys, with less changes in labyrinthectomized ones. SV hardly changed in smaller -Gx, while it increased in larger -Gx. Difference between intact and labyrinthectomized monkeys was observed in -6Gx and -8Gx conditions.

Acceleration↗
PubMed1991

Suppression of growth-promoting activity in extract from human uterine cancer by cyclic AMP-mediated mechanism.

Uterine cervical and corpus cancers have been reported to synthesize and secrete the putative peptide mitogen, which elicits a potent proliferative response in the fibroblasts [Res. Commun. Chem. Pathol. Pharmacol. 66, 477-480 (1989)]. The extract from human cervical cancers stimulated [H]thymidine incorporation into human endometrial fibroblasts in a dose-dependent manner. Concomitant exposure of the fibroblasts to dibutyryl cyclic AMP (cAMP) of forskolin, the mitogenic activity of the extract was suppressed by 60%. A higher concentration of the extract did not overcome the inhibitory effects of them, implying that they acted at a stage after the mitogen in extract and specific receptor interaction. These results demonstrated that the growth-promoting activity in cervical cancer extract could be under negative control through cAMP-dependent mechanism.

Bucladesine↗
PubMed1991

Development of skill of children in the performance of the family computer game "Super Mario Brothers".

The development of skill of children in the performance of a family computer game (Super Mario Brothers) was investigated among three groups of different age: kindergarten children (6 years old) and primary school children (9 and 12 years old). The skill to perform the game with either hand was evaluated by the mean scores gained by the children. In the normal (right and dominant) situation, the mean score improved significantly with advancement of age. Similar was true in the reversed (left hand dominant) situation, but more distinctly. The mean scores were significantly higher in the normal than in the reversed situations. The experienced children were superior to the inexperienced children in playing the game. The correlation between the reaction time and the game score was also investigated with the same subjects for the 9- and 12-year-old school children. Almost no correlation could be elucidated.

Age Factors↗