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Biomedical subjects

Y Tsuda

Publications and source records attributed to Y Tsuda.

At least 289 records · Page 16Linked to original sources
PubMed1981

Ultrasonic Doppler studies after superficial temporal-middle cerebral artery anastomosis.

The ultrasonic Doppler technique was applied to evaluate the effect of STA-MCA anastomosis. Not only the STA itself, but also ophthalmic and major aortocranial arteries were recorded by the Doppler technique in 12 patients who had undergone STA-MCA anastomosis for internal carotid artery occlusion or stenosis. The examination was performed before, and within a month after the operation. The blood flow pattern of the STA, which had had an external carotid flow pattern, was altered to an internal carotid flow pattern by the STA-MCA bypass operation. The findings of Doppler sonograms of the STA were exactly consistent with post-operative angiograms and precisely represented the bypass patency. Among 7 patients with reverse flow direction in the ophthalmic artery before the operation, the reverse flow had decreased in 5 patients post-operatively. But no remarkable change in the ophthalmic artery was detected in the remaining 2 patients. The blood flow velocity patterns of major aortocranial arteries showed no change post-operatively.

Blood Flow Velocity↗
PubMed1980

Cytological diagnosis of leiomyogenic tumors of the stomach.

The cytological findings in 7 cases of leiomyoma and 4 cases of leiomyosarcoma can be summarized as follows: For differential diagnosis of these lesions, in comparison with leiomyoma cells, leiomyosarcoma cells were found to have 1) increased minor axis diameters of the nuclei and nuclear anisokaryosis, 2) dark nuclear staining, 3) enlarged and darkly stained chromocenters, 4) dark staining and thickening of the nuclear rim, 5) enlargement of nuclear clear areas, 6) increased numbers of oval nuclei and greater pleomorphism, 7) an increase in size and number of the nucleoli, 8) a strong tendency for cell atypism, such as anisocytosis and pleomorphism. In the light of these findings, it is believed that differential diagnosis is indeed possible.

Cell Nucleus↗
PubMed1980

Ion migration and inactivation in the calcium channel.

1. Calcium conduction has been studied under voltage clamp in isolated nerve cell bodies of Helix aspersa. A suction pipette method was used to produce internal perfusion and low access resistance to the cell's interior. 2. Ca current does not obey the independence principle and saturates with increasing extracellular Ca concentration. The effect is voltage-dependent. 3. The unit conductance for the Ca channel is between 10(-12) and 10(-13) S, values consistent with impeded conduction. 4. Inactivation is partly dependent upon an increase of intracellular Ca activity due to Ca current. However, a component remains after the increase in [Ca]i has been prevented with EGTA. 5. The Ca channel may have two open states or there may be two sets of Ca channels.

Animals↗
PubMed1979

The nature of the initial positive inotropic effect of K depletion in bullfrog atrial muscle.

In frog atrium, K depletion exerts initial, and late positive inotropic effects. The initial effect on the membrane potential, current and tension components was studied using a double gap method under voltage clamped and unclamped conditions. In both cases, the presence of the initial effect was demonstrated. The effect was clearer in preparations in which a positive inotropic effect to toxic doses of ouabain (10(-6) M) had already been attained. This suggests that the initial phase is independent from Na-pump inhibition. Voltage clamp study revealed that the slow inward calcium current (ICa) was enhanced transiently after K depletion concomitant with an augmentation of ICa-dependent phasic tension. ICa-independent tonic tension was not altered at this initial phase. For the enhancement of ICa, two mechanisms appeared to be involved, one an enhancement of gCa and the other a faster and/or longer opening of the slow channel. These results indicated that an enhancement of ICa together with the well-known prolongation of action potential were the cause of the initial positive inotropic effect of K depletion.

Action Potentials↗
PubMed1978

Effect of low temperature on the membrane currents and tension components of bullfrog atrial muscle.

In order to clarify the nature of inotropic action of low temperature, the effects of cooling on the membrane currents and tension components were studied on the bullfrog atrial muscle under voltage clamped and unclamped conditions with double gap method. Cooling (in between 35 degrees-7 degrees C) produced an increase of overshoot and a prolongation of the action potential accompanied by a slight depolarization of the membrane, a decrease of basal tension and an increase of twitch contraction. Under voltage clamp, a marked augmentation of contraction also occurred despite a decrease of basal tension, suggesting that the inotropic effect of cooling is not merely dependent on the prolongation of action potential. When the components of membrane current and tension were isolated in modified Ringer solutions, it became clear that ICa and ICa -dependent tension markedly increased at low temperature, while all other currents (INaf, INas, IK1 Ix) and ICa-independent tension decreased. Leaky membrane current (I1) for hyperpolarizing pulses also diminished. Temperature coefficient (Q10) of the ICa-independent tension component was 1.2-1.5 between 7 degrees C and 17 degrees C, while that of ICa-dependent tension varied depending on depolarization voltages. These data were discussed in relation to possible alteration of Ca concentration at outer and inner layers of the membrane which may depend on temperature.

Action Potentials↗