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Biomedical subjects

T Osa

Publications and source records attributed to T Osa.

85 records · Page 5Linked to original sources
PubMed1970

Electrophysiological studies of the antrum muscle fibers of the guinea pig stomach.

The membrane potentials of single smooth muscle fibers of various regions of the stomach were measured, and do not differ from those measured in intestinal muscle. Spontaneous slow waves with superimposed spikes could be recorded from the longitudinal and circular muscle of the antrum. The development of tension was preceded by spikes but often tension appeared only when the slow waves were generated. Contracture in high K solution developed at a critical membrane potential of -42 mv. MnCl(2) blocked the spike generation, then lowered the amplitude of the slow wave. On the other hand, withdrawal of Na(+), or addition of atropine and tetrodotoxin inhibited the generation of most of the slow waves but a spike could still be elicited by electrical stimulation. Prostigmine enhanced and prolonged the slow wave; acetylcholine depolarized the membrane without change in the frequency of the slow waves. Chronaxie for the spike generation in the longitudinal muscle of the antrum was 30 msec and conduction velocity was 1.2 cm/sec. The time constant of the foot of the propagated spike was 28 msec. The space constants measured from the longitudinal and circular muscles of the antrum were 1.1 mm and 1.4 mm, respectively.

Acetylcholine↗
PubMed1967

Membrane properties of the smooth muscle of guinea-pig ureter.

1. The membrane properties of the guinea-pig ureter were studied in physiological Krebs solution by intra- and extracellular stimulating methods.2. The mean membrane potential was 50 mV. Action potentials triggered by external stimulation were composed of repetitive spikes and a plateau phase.3. The effects of intracellular polarization on the membrane activity elicited by extracellular stimulation were observed. Anodal polarization enhanced the amplitude and the maximum rate of rise of the spike while cathodal polarization reduced them. The number of the spikes, the duration and amplitude of the plateau phase were not changed by polarization of any direction.4. The spikes triggered by intracellular stimulation were mostly graded, but repetitive spikes sometimes continued even after cessation of the stimulation. The effective membrane resistance was 15-23 MOmega and the time constant was 2-3 msec.5. Conduction velocity (V), chronaxie, time constant (tau) and space constant (lambda) of the tissue were measured by extracellular stimulation. These values were as follows: V, 3-6 cm/sec; chronaxie, 20-40 msec; tau, 200-300 msec; lambda, 2.5-3 mm. The conduction of excitation might be related to the cable properties of the tissue.6. The relative refractory period measured by extracellular stimulation was as long as 30 sec. During the relative refractory period dissociation of the slow depolarization and the spikes was observed by successive stimuli.7. The plateau phase was prolonged and the frequency of the spontaneous discharges was increased by treatment with Ba(2+). Tetrodotoxin had no effect on spike activity nor on the plateau phase, but Mn(2+) blocked the membrane activity.

Action Potentials↗
PubMed1967

Electrophysiological study of the intestinal smooth muscle of the guinea-pig.

The membrane properties of single cells of intestinal smooth muscle of duodenum, jejunum, ileum, caecum and rectum of guinea-pig have been studied.1. The membrane potentials of longitudinal muscles of the duodenum, jejunum, ileum, caecum and rectum varied from 54 to 56 mV and those of circular muscles of jejunum, ileum, caecum and rectum varied from 57 to 60 mV. The ablated longitudinal muscle had a slightly lower value (50 mV) than the intact one.2. The longitudinal muscle generated spontaneous discharges but these were rare in the circular muscles of the intestine except for the caecum. Overshoot potentials could be observed in all regions of the intestine. The maximum rate of rise of the spontaneously discharging longitudinal muscles varied from 11 to 18 V/sec.3. Not all of the slow potential changes (but at least some) were generated by the nervous elements distributed between the muscle layers and in them.4. The conduction velocities measured from the longitudinal muscles of jejunum and rectum in the presence of tetrodotoxin were 2.1 cm/sec and 4.0 cm/sec respectively.5. Chronaxies of the longitudinal muscles of jejunum and rectum were 2-5 msec and 5-18 msec respectively.6. Intracellular stimulation of the single cells of the duodenum and caecum could trigger a spike, similar to that observed in the taenia coli. The spikes were mostly graded ones; a spike of full size was rarely elicited. When the spikes were triggered, the after-hyperpolarization appeared consistently presumably caused by the increased potassium conductance.7. The effective membrane resistance and the time constant were measured for the longitudinal muscles of the jejunum and rectum. When spikes were generated by intracellular stimulation the observed values were 40-50 MOmega and 3-5 msec in both tissues. These values were the same as those observed in the taenia coli.8. When the time constant of the membrane was measured by the extracellular polarizing method, the longitudinal muscles of the jejunum especially and the rectum had smaller time constants than the taenia coli.9. The differences of conduction velocity and chronaxie of the different regions of the intestine are discussed in relation to the cable properties of the tissues which are directly influenced by the morphological arrangements of the tissues.

Action Potentials↗
PubMed1967

Nervous factors influencing the membrane activity of intestinal smooth muscle.

The effects of various chemical agents on the spontaneous membrane activities and those electrically elicited in the smooth muscles of small intestine were investigated.1. The effects of various chemicals on the spontaneously active membrane might be summarized as follows. (a) Cholinergic agents; atropine slightly hyperpolarized the membrane and reduced the amplitude of slow potential changes even in aged preparations. Prostigmine depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. Atropine prevented the actions of prostigmine on the membrane. (b) Ba(2+) depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. The spike frequency was initially increased, then reduced. Atropine and tetrodotoxin partially prevented the action of Ba(2+) on the membrane activities.2. Effects of chemical agents on the membrane activity elicited by electrical stimulation might be summarized as follows. (a) Short pulse stimulation (0.5-1 msec) generated the spike as a direct response of the muscle cell membrane, then it was followed by slow depolarization, delayed hyperpolarization, i.e. the ;inhibitory potential', and post-inhibitory rebound successively. (b) The slow depolarization and the post-inhibitory rebound were reduced in amplitude by treatment with atropine, and enhanced by treatments with prostigmine and Ba(2+). Tetrodotoxin blocked all activities except the spike.3. When repetitive stimulation (20 c/s) was applied to the membrane, the membrane hyperpolarized; then, after 3-5 sec, it gradually depolarized even if the stimulation was continued, and triggered spikes. The hyperpolarization always preceded depolarization. The duration and the amplitude of the delayed depolarization was proportionally increased by the increased intensity and duration of stimulation. Atropine and tetrodotoxin blocked the generation of the post-inhibitory rebound.4. Effects of repetitive stimulation on the stored tissues were observed. The responses to repetitive stimulation of the membrane of muscles which had been stored 50 hr at 4 degrees C, were the same as those observed in the fresh tissue. The response of the tissue which had been stored 100 hr was the same as that observed in the fresh tissue treated with tetrodotoxin, i.e. all activities except the spikes were blocked.

Animals↗
PubMed1967

The action of 5-hydroxytryptamine on Mytilus smooth muscle.

1. In the nerve-muscle preparation, where catch was characteristically minimal, 5-hydroxytryptamine (5-HT) had no effect on resting membrane potential, junction potentials, spikes or contraction.2. In muscle bundles, where catch was prominent, 5-HT did not change membrane potentials, but prolonged junction potentials and lowered the threshold for spike discharge and contraction.3. In muscle bundles, exposed to high concentrations of 5-HT, depolarization evoked repetitive spikes, while in low 5-HT, spikes were seldom fired even with much greater depolarization.4. In muscle bundles, the effective membrane resistance, R(eff.), decreased from 45-60 to 23-35 MOmega as 5-HT concentration was increased.5. It is suggested that 5-HT may facilitate spike discharge by lowering the internal free Ca(2+) concentration.

Animals↗
PubMedDate not supplied

Potentiometric response of lipid modified ISFET.

The gate surface of an ion-sensitive field effect transistor (ISFET) was modified with Langmuir-Blodgett (LB) film composed of fatty acid or crown ether amphiphiles to examine their potentiometric response to H+ and K+ ions. The results demonstrate the possible use of the lipid films for preparing ISFET ion sensors.

Biosensing Techniques↗
PubMedDate not supplied

Fluorescence and energy transfer of polypeptides containing naphthyl groups in their side chains.

Energy transfer in the singlet state was studied in solution at 25 degrees C for poly(beta-1-naphthylmethyl L-aspartate) and copolymers of beta-1-naphthylmethyl L-aspartate and gamma-benzyl L-glutamate. Transfer efficiencies, migration coefficients, migration lengths, and interaction radii were determined from the quenching studies using biacetyl as a quencher. The migration coefficient increases with increasing naphthyl groups in the copolymers. This means that singlet energy migrates among more naphthyl groups with increasing naphthyl groups in the polymer chain. Interaction radius for the fluorescence quenching by biacetyl was estimated to be in the range of 5.8 to 8.9 A irrespective of whether energy donor is monomer or excimer. Moreover, it was shown that energy migration via excimer does not take place and energy of the excimer is localized.

Aspartic Acid↗