Biomedical subjects

Tetsuya Matsuura

Publications and source records attributed to Tetsuya Matsuura.

13 recordsLinked to original sources

PubMed2005

Hamstring muscle function after tendon harvest for anterior cruciate ligament reconstruction: evaluation with T2 relaxation time of magnetic resonance imaging.

BACKGROUND: Regeneration of the semitendinosus and gracilis tendons after harvesting for anterior cruciate ligament reconstruction has been reported; however, muscle belly function after tendon regeneration has not been well documented. HYPOTHESIS: The semitendinosus and gracilis muscles are highly activated during knee flexion if their tendons are well regenerated after anterior cruciate ligament reconstruction. STUDY DESIGN: Descriptive laboratory study. METHODS: Hamstring muscle activation in 11 patients who had undergone anterior cruciate ligament reconstruction with semitendinosus and gracilis tendons was evaluated by measuring the increase of T2 relaxation time measured via magnetic resonance imaging after knee flexion exercise. Tendon regeneration was evaluated via magnetic resonance imaging. RESULTS: Both muscles increased T2 relaxation time after knee flexion exercise in the operated legs, and there was no significant difference in those values between the operated and nonoperated legs. All the semitendinosus tendons were regenerated at or below the joint line, but no gracilis tendons were observed beyond the joint line. The results indicated that both muscles were highly recruited during knee flexion, regardless of the degree of their tendon regeneration. CONCLUSION: The semitendinosus and gracilis muscles are able to restore or maintain their contractile capability after harvest of their tendons for anterior cruciate ligament reconstruction, regardless of the degree of regeneration.

Adolescent↗

PubMed2005

Chemotaxis of Caenorhabditis elegans during simultaneous presentation of two water-soluble attractants, l-lysine and chloride ions.

Lysine and chloride ions are water-soluble attractants for Caenorhabditis elegans. When chemotaxis behavior to either of these attractants was assayed separately, the radial concentration gradients of 3 M lysine and 0.1 M ammonium chloride had similar potencies for attracting worms. However, when the concentration gradients of lysine and ammonium chloride at these concentrations were presented simultaneously, worms preferred lysine to ammonium chloride more than expected from the results obtained in separate experiments, suggesting the presence of an interaction between these two sensory information pathways within the nervous system. Chemotaxis behavior toward the radial concentration gradient of one of these attractants superimposed on a uniform concentration of the other attractant showed that the chemotaxis was augmented or attenuated by the ammonium chloride background depending on the background concentration, and attenuated by the lysine background, further supporting the interaction between the two sensory information pathways.

Ammonium Chloride↗

PubMed2005

Response properties of wind-sensitive giant interneurons in the fourth-instar nymphs of the cricket, Gryllus bimaculatus.

The response properties of four wind-sensitive giant interneurons (GIs) 8-1, 9-1, 9-2 and 9-3 in the fourth-instar nymphs of the cricket Gryllus bimaculatus were investigated to clarify the differences and/or similarities of the escape eliciting neural system between nymphs and adults. Air current was presented to the animal from 12 different directions in the horizontal plane, and the intensity-response curves for each GI were obtained at each stimulus direction. The intensity-response curves showed that the response magnitudes of GI 8-1 in the fourth-instar crickets increased with stimulus velocity up to 300 mm/s regardless of the stimulus direction. The response magnitudes of GI 9-1 in the nymphs reached a plateau at a stimulus velocity of 30 mm/s in most stimulus directions. The response magnitudes of GIs 9-2 and 9-3 increased with stimulus velocity up to 300 mm/s regardless of the stimulus direction. The directional sensitivity curves plotted on the basis of threshold velocities revealed that the preferential directions of the GIs were the ipsilateral-side in GI 8-1, the ipsilateral-front and contralateral-rear in GI 9-1, the ipsilateral-rear in GI 9-2 and the ipsilateral-front in GI 9-3, designated with respect to the side of the ventral nerve cord containing the axons. Although the GIs in nymphs occasionally showed higher threshold velocities and larger response magnitudes, the directional sensitivities, i.e., the preferred directions, of the GIs were basically the same with those of adults.

Animals↗

PubMed2005

Interactions between Caenorhabditis elegans individuals during chemotactic response.

The chemotactic response of the nematode Caenorhabditis elegans is known to be affected by the population density on an assay plate, suggesting the existence of interactions between individual animals. To clarify the interactions between individuals during chemotaxis, we investigated the effect of population density at an attractant area on the chemotactic response to water-soluble sodium acetate and odorant diacetyl using wild-type N2 animals and daf-22 (m130) mutants, which have defective pheromone secretion but can sense pheromone. The chemotaxis index of N2 animals at 90 min of the assay negatively correlated with the number of animals on the assay plate regardless of the type of attractant used (p<0.01). On the other hand, there was no significant difference in the chemotaxis indices of daf-22 (m130) mutants for either of the attractants between the low-and high-population groups. When daf-22 (m130) mutants of a high population density were placed at the attractant location in advance, the chemotaxis index of N2 animals was almost the same as that in the control assay in which no animals were placed at the attractant location in advance. When N2 animals of a high population density were placed at the attractant location in advance, the chemotaxis indices of N2 animals and daf-22 (m130) mutants were significantly smaller than those obtained in the control assay (p<0.05). In the absence of an attractant, we observed a decline in the fraction of animals in the neighborhood of N2 animals of a high population density, although the nematodes were not influenced by daf-22 (m130) mutants of a high population density. These results suggest that the attraction of nematodes to chemicals is inhibited by an increase in the concentration of the pheromone generated by N2 animals at the attractant location.

Animals↗

PubMed2004

Stimulus frequency dependence of the linear relationship between local cerebral blood flow and field potential evoked by activation of rat somatosensory cortex.

We investigated the relationship between evoked local cerebral blood flow (LCBF) and the field potential induced by somatosensory activation. The specific aim of the present study was to examine the correlation between variations of evoked LCBF and field potential when the stimulus duration was changed, and the dependency of the correlation on stimulus frequency. Evoked LCBF was measured using laser-Doppler flowmetry and the field potential was observed using a tungsten electrode inserted into the cortex alpha-chloralose-anesthetized rats. The cortex was activated by electrical stimulation of the hind paw with a 1.5 mA pulse (0.1 ms) applied at frequencies of 0.5, 1, 5 and 10 Hz for durations of 2, 5, 8, 10 or 15s. We extended our previous finding [Neurosci. Res. 40 (2001) 281-290], that both the magnitude of evoked LCBF (integrated LCBF) and the summed field potential (SigmaFP) exhibited a maximum at a stimulus frequency of 5 Hz to five different stimulus durations. Moreover, although variations of integrated LCBF and SigmaFP induced by changes in the stimulus duration were linearly correlated, the slope of the regression line depended on the stimulus frequency. This stimulus frequency dependence of the integrated LCBF-SigmaFP linear relationship may be because the vessel response is frequency dependent.

Animals↗

PubMed2004

Effect of simultaneous presentation of multiple attractants on chemotactic response of the nematode Caenorhabditis elegans.

Chemotactic behaviors of the nematode, Caenorhabditis elegans in response to chemical attractants, such as water-soluble sodium acetate and an odorant diacetyl, which were sensed by different sensory neurons, were investigated using various concentrations of these chemical attractants. In the presence of only sodium acetate attractant, the fraction of animals that were roaming around the outside of the attractant and original locations correlated negatively with the chemotaxis index for sodium acetate (P < 0.01). In contrast, the fraction of animals that remained in the original location correlated negatively with the chemotaxis index in the presence of only diacetyl attractant (P < 0.05). These results indicate that the manner of chemotaxis responses differs between sodium acetate and diacetyl. In order to investigate the effect of multiple attractants on chemotactic behaviors, the chemotactic responses to simultaneous presentation of sodium acetate and diacetyl were examined. The fraction of animals that gathered at the 0.7 M sodium acetate location was greater than that at the 0.1% diacetyl location in the presence of both attractants (P < 0.05), although the chemotaxis indexes for 0.7 M sodium acetate and 0.1% diacetyl were similar in the presence of a single attractant. On the other hand, the fraction of animals that gathered at the 0.02% diacetyl location was greater than that at the 0.1M sodium acetate location in the presence of both attractants (P < 0.05), although the chemotaxis indexes for 0.02% diacetyl and 0.1M sodium acetate were similar in the presence of a single attractant. These results suggest the existence of excitatory and/or inhibitory connections in the neuronal circuit for attractant selection, and that the efficacy of these connections may change according to the concentrations of both attractants.

Animals↗

PubMed2004

Functional changes of cricket giant interneurons caused by chronic unilateral cercal ablation during postembryonic development.

One of a pair of cerci was ablated in the first-, fourth- and last-instar nymphs of the cricket, Gryllus bimaculatus. The insects were then reared until the final molt, after which the intensity-response (I-R) relationships for four giant interneurons (GIs) 8-1, 9-1, 9-2 and 9-3 with regard to a controlled air current stimulus were measured. In order to examine the functional changes during postembryonic development and the differences in the physiological plasticity of GIs between nymphs and adults, the obtained I-R curves for each GI were compared with those measured in intact and unilaterally cercus-ablated adult crickets. Each GI showed a distinctive change in response magnitudes after the long-term unilateral cercal ablation. In most cases, the I-R curves for each GI in the crickets ablated from nymphal periods were different from those in the adult crickets mentioned above. Moreover, the pattern of change in response magnitude was different from GI to GI. In contrast to these observations, it was reported that some important characteristics of the wind-evoked escape behavior such as relative occurrence and escape direction in unilaterally cercus-ablated crickets investigated after a long-term rearing were almost identical with those in intact crickets. Therefore, the results obtained in the present study suggest that functional changes occur not only in GIs but also in many other neural elements in the escape-eliciting system in order to maintain the features of wind-evoked escape behavior.

Animals↗

PubMed2003

Postembryonic changes in the response properties of wind-sensitive giant interneurons in cricket.

The intensity-response (I-R) relations for four wind-sensitive giant interneurons (GIs 8-1, 9-1, 9-2 and 9-3) in the fourth-, sixth- and last-instar nymphs of the cricket, Gryllus bimaculatus, were investigated using a unidirectional air current stimulus in order to explore the functional changes of GIs during postembryonic development. Contrary to our expectations, the response properties of GIs in nymphs were largely different from those in adults. The response magnitude of GI 8-1 in an intact cricket decreased during development, i.e. the GI in younger insects showed a larger response magnitude. Although the response magnitudes of GIs 9-1 and 9-2 were almost identical during the nymphal period, a significant decrease was observed after the imaginal ecdysis. During the nymphal period, the response magnitude of GI 9-3 increased according to the developmental stage. However, it decreased significantly after the imaginal ecdysis. We also investigated the response magnitudes of the GIs in nymphs after unilateral cercal ablation. From the results of ablation experiments, the changes in excitatory and/or inhibitory connections between filiform hairs and each GI during postembryonic development were revealed.

Action Potentials↗

PubMed2003

15O Radioactivity clearance is faster after intracarotid bolus injection of 15O-labeled oxyhemoglobin than after 15O-water injection.

The authors tested the hypothesis that the oxygen content of brain tissue is negligible by injecting an intracarotid bolus of 15O-labeled tracer into rats. Under the hypothesis, the clearance rates of 15O radioactivity from the brain after injections of both 15O-labeled water (H(2)15O) and 15O-labeled oxyhemoglobin (HbO15O) should be identical. However, the logarithmic slope of the 15O radioactivity curve after HbO15O injection (0.494 +/- 0.071 min-1) was steeper than that after H(2)15O injection (0.406 +/- 0.038 min-1) (P<0.001, n = 13), where the time range used in the comparison was between 60 and 120 seconds after the injection. A possible interpretation of this result is that nonmetabolized O15O may dwell in the brain tissue for a finite period of time before it is eventually metabolized or returned to the blood stream unaltered. These findings contradict assumptions made by models currently used to measure cerebral oxygen metabolism.

Animals↗

PubMed2002

Motor program initiation and selection in crickets, with special reference to swimming and flying behavior.

An air puff stimulus to the cerci of a cricket (Gryllus bimaculatus) evokes flying when it is suspended in air, while the same stimulus evokes swimming when it is placed on the water surface. After bilateral dissection of the connectives between the suboesophageal and the prothoracic ganglia or between the brain and the suboesophageal ganglion, the air puff stimulus evokes flying even when the operated cricket is placed on the water surface. A touch stimulus on the body surface of crickets placed on the water surface elicits only flying when the connectives between suboesophageal and prothoracic ganglia are dissected, while the same stimulus elicits either swimming or flying when the connectives between the brain and the suboesophageal ganglion are dissected. These results suggest that certain neurons running through the ventral nerve cords between the brain and the suboesophageal ganglion or between the suboesophageal and the prothoracic ganglia play important but different roles in the initiation and/or switching of swimming and flying. In the suboesophageal ganglion, we physiologically and morphologically identified four types of "swimming initiating neurons". Depolarization of any one of these neurons resulted in synchronized activities of paired legs with a similar temporal sequence to that observed during swimming.

Air Movements↗

PubMed2002

Effect of nitric oxide synthase inhibitor on the local cerebral blood flow evoked by rat somatosensory stimulation under hyperoxia.

Hyperoxia reduces the hemodynamic latency and enhances the response magnitude of the evoked local cerebral blood flow (LCBF). The objective of this study was to test the hypothesis that a change in the production of nitric oxide (NO) is involved in a unique change in evoked LCBF during hyperoxia. We measured LCBF in alpha-chloralose-anesthetized rats by laser-Doppler flowmetry. Systemic administration of the NO synthase inhibitor N(omega)-nitro-L-arginine (LNA) caused a decline in the baseline level of LCBF (P<0.01). The LNA intravenous injection during hyperoxia (hyperoxia with LNA) reduced the normalized evoked LCBF (normalization with respect to the baseline level of LCBF) in response to somatosensory stimulation by approximately 37% when compared under normal conditions (normoxia without LNA) (P<0.01), although that during normoxia (normoxia with LNA) did not cause a significant difference in the normalized evoked LCBF. The integrated neuronal activity under hyperoxia with LNA was approximately 11% lower than that under normoxia without LNA (P<0.05), although there was no significant difference in integrated neuronal activity between normoxia with LNA and normoxia without LNA. These results do not support our hypothesis and suggest the existence of another interaction mechanism involving oxygen for the enhancement of evoked LCBF under hyperoxia.

Animals↗

PubMedDate not supplied

Why is the humeral retroversion of throwing athletes greater in dominant shoulders than in nondominant shoulders?

A rotation angle of the proximal humerus relative to the elbow (bicipital-forearm angle) was measured by use of ultrasonography to determine the relationship between humeral retroversion and growth in dominant and nondominant shoulders of 66 elementary and junior high school baseball players. The subjects were aged 12 years on average. The bicipital-forearm angle was significantly smaller in dominant shoulders than in nondominant shoulders. This indicated that the retroversion angle was greater in dominant shoulders than in nondominant shoulders. Furthermore, there was a moderately positive correlation between age and the bicipital-forearm angle in both dominant and nondominant shoulders. From these data, we conclude that the humeral retroversion angle decreases with age, and the decrease is much smaller in dominant shoulders. We assume that the repetitive throwing motion does not increase the retroversion of the humeral head but rather restricts the physiologic derotation process of the humeral head during growth.

Adaptation, Physiological↗

PubMedDate not supplied

The most effective exercise for strengthening the supraspinatus muscle: evaluation by magnetic resonance imaging.

BACKGROUND: Electromyography has been used to determine the best exercise for strengthening the supraspinatus muscle, but conflicting results have been reported. Magnetic resonance imaging T2 relaxation time appears to be more accurate in determining muscle activation. PURPOSE: To determine the best exercises for strengthening the supraspinatus muscle. STUDY DESIGN: Criterion standard. METHODS: Six male volunteers performed three exercises: the empty can, the full can, and horizontal abduction. Immediately before and after each exercise, magnetic resonance imaging examinations were performed and changes in relaxation time for the subscapularis, supraspinatus, infraspinatus, teres minor, and deltoid muscles were recorded. RESULTS: The supraspinatus muscle had the greatest change among the studied muscles in relaxation time for the empty can (10.5 ms) and full can (10.5 ms) exercises. After the horizontal abduction exercise the change in relaxation time for the supraspinatus muscle (3.6 ms) was significantly smaller than that for the posterior deltoid muscle (11.5 ms) and not significantly different from that of the other muscles studied. CONCLUSION: The empty can and full can exercises were most effective in activating the supraspinatus muscle.

Adult↗