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Biomedical subjects

H Yabu

Publications and source records attributed to H Yabu.

At least 55 records · Page 3Linked to original sources
PubMed1987

Ca2+-induced Ca2+ release in skinned single smooth muscle cells isolated from guinea-pig taenia caeci.

The Ca2+ release from intracellular Ca2+ storage sites of skinned single smooth muscle cells isolated from guinea-pig taenia caeci was studied. The Ca2+ release from intracellular Ca2+ storage sites of the skinned single cells was enhanced by the presence of submicromolar concentrations of Ca2+ in the solution. The Ca2+ release was enhanced by caffeine and adenine, and suppressed by Mg2+ and procaine. These results suggest that the Ca2+-induced Ca2+ release mechanism may play an important role in the release of Ca2+ from intracellular storage sites of guinea-pig taenia caeci smooth muscle cells.

Adenine↗
PubMed1985

Single Ca channel currents in mammalian visceral smooth muscle cells.

Recordings of single Ca channel currents in mammalian visceral smooth muscle cells were obtained using patch clamp techniques. Smooth muscle cells from guinea-pig taenia coli were prepared by enzymatic dispersion using 0.3% collagenase. The recordings were obtained from cell-attached membrane patches of isolated cells with a pipette filled with isotonic 50 mM Ba2+. When the membrane patch was depolarized, brief inward current pulses of unitary size and small amplitude were observed. The amplitude of these single channel currents decreased linearly with increasing depolarization in a voltage range from -20 mV to +50 mV about the resting potential. The slope conductance was estimated to be about 30 pS. The mean current reconstructed by averaging individual current responses showed kinetic behaviour with a rapid activation and a slower inactivation process similar to the macroscopic Ca2+ current observed in strips of guinea-pig taenia coli. The present study suggests that the inward current pulses of unitary size induced by voltage-clamp pulses were due to Ba ions passing through a single voltage dependent Ca channel.

Animals↗
PubMed1980

[ATP dependent calcium uptake activity in plasma membrane fraction of intestinal smooth muscle (author's transl)].

Ca2+ binding and ATP dependent Ca2+ uptake by plasma membrane fraction were studied and the effect of treating plasma membrane fraction with trypsin, phospholipase c and neuraminidase on both activities was observed. 1. Plasma membrane fraction possessed the ability to bind Ca2+. The Scatchard plot of Ca2+ binding showed that plasma membrane had at least two types of Ca2+ binding sites of high and low affinity. 2. The amount of Ca2+ uptake by plasma membrane fraction was 18.51 +/- 1.31 nmoles Ca2+/mg protein/30 min at 10(-5)M Ca2+. The Ca2+ concentration for half maximal activation in Ca2+ uptake was 3.7 x 10(-7)M. 3. The ATP dependent Ca2+ uptake by the microsome isolated from guinea pig intestine was clearly stimulated by 4 mM K2-oxalate whereas that of plasma membrane fraction was not. 4. Trypsin and phospholipase c treatment led to a 40--88% reduction in the ATP dependent Ca2+ uptake. The Ca2+ concentration for half maximal activation Ca2+ uptake shifted to a high concentration. On the other hand, neuraminidase treatment resulted in a 43--93% increase in ATP dependent Ca2+ uptake. But, the Ca2+ concentration for half maximal activation in Ca2+ uptake was not shifted by neuraminidase treatment. The results show that plasma membrane plays an important role in regulating the cytoplasmic Ca2+ concentration. The results also suggest that a glycoprotein linked with sialic acid is involved in the flux of Ca2+ across the plasma membrane.

Adenosine Triphosphate↗
PubMed1979

[Examination of plasma membrane-enriched fraction from guinea pig intestinal smooth muscle by means of some marker enzymes (author's transl)].

By means of a preparation technique based on the discontinuous sucrose density gradient, subcellular fractions were isolated from guinea pig intestinal smooth muscle cells. A fraction which distributed to a 33% sucrose layer showed relatively high activities of 5'-nucleotidase, Na+ . K+-ATPase and ouabain sensitive Na+ . K+-ATPase. The fraction had a low NaN3 sensitive Mg2+-ATPase activity. On the other hand, the high activity of glucose-6-phosphatase showed a broad distribution. Though the sucrose density gradient proceeded over a series of the fine layers, cross-contamination of microsome into the 33% sucrose fraction was not reduced. To reduce microsomal cross-contamination, another procedure was employed. The homogenization time of 77000 xg sediment to be layered on the top of the sucrose density gradients was prolonged. This procedure did not change the distribution of K+ activated p-nitrophenylphosphatase, K+ activated ouabain sensitive p-nitrophenylphosphatase and ouabain sensitive Na+ . K+-ATPase activities. The peak of NADH cytochrome c reductase activity was shifted to a 38% sucrose fraction from a 33% sucrose fraction and the activity of this marker enzyme in the 33% sucrose fraction decreased to 60% of that of the prior procedure.

Adenosine Triphosphatases↗
PubMed1978

Selective inhibition of potassium contracture in guinea pig taenia coli by ruthenium red.

Effects of ruthenium red on isotonic KCl induced contracture (K-contracture), cellular 45Ca uptake and 45 Ca binding to surface membranes were examined in the smooth muscle cells of guinea pig taenia coli. These results were compared with those using lanthanum (La3+). The tonic component of the K-contracture was selectively inhibited by 1 mM ruthenium red. In contrast, 1 mM La3+ inhibited the phasic component of the K-contracture to a large extent. Use of 1 mM ruthenium red selectively inhibited the tonic component of K-contracture and caused a marked decrease in cellular 45Ca uptake in that component of K-contracture. In contrast, 1 mM La3+ largely inhibited the phasic component and caused a significant decrease in cellular 45Ca in that component. According to Scatchard plot analysis, there are two kinds of Ca2+ binding sites of high and low affinity, respectively, on the surface membrane of the taenia coli. One mM ruthenium red suppressed those of low affinity more strongly than those of high affinity. In contrast, 1 mM La3+ suppressed high affinity sites more markedly than low affinity sites. Based on these results, it seems possible to conclude that ruthenium red mainly blocks the initial binding sites linked with Ca2+ influx which is related to the production of the tonic component while La3+ blocks those sites related to the phasic component of the K-contracture of guinea pig taenia coli.

Animals↗
PubMed1976

Ca binding of intestinal smooth muscle myosin B.

By means of both centrifugation and filtration techniques, the Ca binding activity of intestinal myosin B was studied. The binding capacity of myosin B was Ca dependent and was approximately linear when the concentration of Ca in the medium ranged from 10(-4) to 10(-7) M. The Ca sensitivity of ATPase activity in the same range of Ca concentration exhibited a sigmoid curve. The Scatchard plot of Ca binding showed that intestinal myosin B had at least two types of binding sites. One of these was defined as a high affinity site with an apparent affinity constant of 2.5 x 10(6) M-1. The other was supposed to be a low affinity site of Ca binding. Mild trypsin treatment reduced the Ca binding capacity of intestinal myosin B by 1.45-2.44 nmol/mg protein. These values are approximately the concentration of the high affinity Ca binding sites in the intestinal myosin B. A major concern regarding the effect of trypsin is that the reduction of Ca binding surely accompanied the elimination of Ca sensitivity of myosin B ATPase activity. From these results, it seems likely that the high affinity sites of Ca binding identified in this study are based on the troponin-like component included in intestinal myosin B.

Adenosine Triphosphatases↗
PubMed1975

Changes in contractility and calcium binding of guinea pig taenia coli by treatment with enzymes which hydrolyze sialic acid.

The effects of neuraminidase and phospholipase C on the contractility and the Ca++ -binding of guinea pig taenia coli were investigated. Potassium contracture or histamine-induced contracture of taenia coli was inhibited by treatment with neuraminidase, though acetylcholine-induced contracture was not. Treatment with phospholipase C markedly inhibited the contracture induced by isotonic potassium, histamine or acetylcholine. By treatment with neuraminidase for 4 hr, about 40 mumol/100 mg wer wt of sialic acid was released from taenia coli. This corresponded to two-fifths of total content of sialic acid. By treatment with phospholipase C for 2 hr, a similar amount of sialic acid to that produced by neuraminidase treatment was released. The Scarchard plot of Ca++-binding was a biphasic pattern indicating the presence of two types ofthe Ca++ -binding site with different affinity constants. Neuraminidase produced a 57% decrease in the amount of bound Ca++. The Scatchard plot of Ca++ -binding changed to a monophasic pattern indicating the disapperance of thel ow affinity Ca++ -binding site. Phospholipase C caused a 59% decrease of bound Ca++. The Scatchard plot also indicated the disappearance of the low affinity Ca++ -binding site. From these results, we speculated that sialicacid residue of surface membrane of the muscle cell was first site in the Ca++ -influx mechanism.

Acetylcholine↗