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S Kurihara

Publications and source records attributed to S Kurihara.

At least 109 records · Page 6Linked to original sources
PubMed1991

Intracellular calcium signals measured with fura-2 and aequorin in frog skeletal muscle fibers.

Intracellular Ca(2+)-related optical signals during and after contraction (twitch and tetanus) were measured in single frog skeletal muscle fibers with fura-2 and aequorin. In twitch response, the peaks of [Ca2+]i estimated from the in vitro calibrations of fura-2 and aequorin were significantly different (0.5 microM for fura-2 and 5 microM for aequorin). Even 30s after twitch response, the fura-2 fluorescence ratio (F340/F380) signal did not recover to the resting level before stimulation. When the stimulation frequency was increased, an increase in the resting fura-2 ratio signal became obvious and after the cessation of stimulation this increase gradually recovered to the level before stimulation. After tetanus (50 Hz for 1 s), a higher fura-2 ratio signal than that before stimulation was sustained longer than 90 s. These results indicate that the dissociation of the released Ca2+ from the intracellular Ca2+ binding sites probably takes longer time than that previously reported. The present results, therefore, demonstrate that fura-2 is advantageous for qualitative monitoring of a slight change in the resting level of [Ca2+]i, which is not easily detectable with aequorin. In addition, the problems encountered in quantitative estimation of [Ca2+]i with fura-2 are also discussed.

Aequorin↗
PubMed1991

[Flow cytometric DNA analysis of uterine endometrial carcinoma].

The DNA content in individual cells from 40 cases of histopathologically normal endometria, 15 of endometrial hyperplasia and 68 of endometrial adenocarcinoma was measured by flow cytometry. An aneuploid cell population was found in 50% of malignant endometria, but in the remaining endometrial carcinomas, the flow cytometrical findings showed no difference from those of benign tissue. Aneuploidy was more common (77.8%) in poorly differentiated tumors than in highly differentiated tumors (35.5%). Two and more aneuploid cell populations were found in 8 cases of 34. The DNA indices of aneuploid tumors were classified into 3 groups: hyperdiploidy, low hyperdiploidy (DNA index range: 1.04-1.2) and high hyperdiploidy (DNA index range: More than 1.2). The proportion of tumors with a high DNA index tended to increase as tumors became less differentiated. In normal endometria the fraction of cells with DNA content corresponding to the s-phase (s-fraction) was 8 +/- 3% on average in the proliferative phase. In well differentiated diploid tumors the s-fraction was 12 +/- 6%, but in moderately and poorly differentiated tumors it was higher (16.0% and 19.0%).

Adenocarcinoma↗
PubMed1990

Modulation of Ca2+ transients and contractile properties by beta-adrenoceptor stimulation in ferret ventricular muscles.

1. The mechanism of modulation of Ca2+ transients and contraction by beta-adrenoceptor stimulation was studied in ferret ventricular muscles using aequorin to measure intracellular Ca2+. 2. Peaks of tension and light transients were increased by isoprenaline (10(-9) - 5 x 10(-7) M) which also abbreviated their time courses. 3. Time-to-peak tension was significantly shortened by 5 x 10(-9) M-isoprenaline and time-to-peak light was abbreviated by 10(-9) M-isoprenaline. 4. The time for the light to decay was shortened at 10(-9) M-isoprenaline. However, a higher concentration of isoprenaline (10(-8) M) was required for significant shortening of the half-relaxation time (TR50). 5. When isoprenaline was removed and beta-blocker (bupranolol, 1 microM) was applied, the time course of the light transients recovered but the time course of relaxation did not recover. 6. The relationship between [Ca2+]i and tension in tetanic contraction produced in the presence of ryanodine (5 microM) was shifted to the right by isoprenaline (10(-8) M). This was recovered by the replacement of isoprenaline with bupranolol (1 microM). 7. Isoprenaline (10(-7) M) added to the solution containing 20 mM [Ca2+]O and Bay K 8644 (1 microM), which produced maximal tension, caused a large light signal and enhancement of the initial phasic tension in tetanic contraction. However, the replacement of isoprenaline with bupranolol after immersing the preparation in 20 mM [Ca2+]O solution with Bay K 8644 and isoprenaline, did not significantly change the tension level, although the light signal decreased. Similar results were obtained in the ventricular muscle of young rats. 8. These results suggest that the dose dependence of modulation of the contractile element and sarcoplasmic reticulum (SR) by beta-adrenoceptor stimulation differs, and that additional factors, other than the faster Ca2+ uptake by SR and the decrease in Ca2+ sensitivity of the contractile element, might be involved in the shortening of the half-relaxation time by beta-adrenoceptor stimulation. In addition, beta-adrenoceptor stimulation does not produce a marked change in the maximal tension level.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

[Ca2+]i rises via G protein during regulatory volume decrease in rabbit proximal tubule cells.

Although animal cells swell in hypotonic medium, their volume is subsequently regulated by a net loss of KCl via Ca2(+)-dependent channels. A rise in intracellular free calcium ([Ca2+]i) thus appears to be an initial event in the adaptation of external tonicity, although details of this mechanism are not known. To investigate cell volume regulation, we measured [Ca2+]i (by use of fura-2) and cell diameters in single cells of cultured renal proximal convoluted tubule. We found that a rapid rise in [Ca2+]i occurred after cells were exposed to hypotonic solution (250 mosM) from 95.8 +/- 3.8 to 468.2 +/- 24 nM (n = 16). The rise in [Ca2+]i was not observed in cells exposed to Ca2(+)-free medium, and exposure to isotonic high-K or low-Na medium did not elicit a rise in [Ca2+]i, suggesting that this rise was a result of Ca2+ influx and not via voltage-dependent Ca2+ influx or decrease of Ca2+ efflux via Na(+)-Ca2+ pump. Pretreatment of cells with pertussis toxin dose dependently blocked the rise in [Ca2+]i. The hypotonic solution enhanced accumulations of inositol tris- and tetra-phosphate after a 1-min exposure. Studies that measured cell diameters suggest that recovery of cell volume may include the rise in [Ca2+]i. These data suggest that the regulatory volume decrease of proximal tubule cells involves a pertussis toxin-sensitive guanine nucleotide binding protein-operated Ca2+ influx.

Animals↗
PubMed1990

Effects of isoprothiolane and phytosterol on lipogenesis and lipolysis in adipocytes from rats of dietary fat necrosis.

To study effects of isoprothiolane and phytosterol on dietary fat necrosis, 3 groups of rats were fed hardened-tallow (HT) diet. Two groups of rats received either isoprothiolane (50 mg/kg) or phytosterol (20 mg/kg) orally once a day consecutively for 10 weeks. One group of rats received standard diet (CE-2) as a control. Fat necrotic lesions were observed in epididymal and perirenal adipose tissues from all rats in the 3 groups fed HT diet. Rats with fat necrosis were characterized by visceral type obesity and saturation in fatty acid composition of triglyceride in adipose tissue. The highest glucose conversion to total lipids was seen in adipocytes from the rats given phytosterol. There was no lipolytic response to epinephrine stimulation (1-100 microM) in adipocytes from the rats given only HT diet, while similar response of adipocytes from the 2 groups treated with either drug to those from the rats fed standard diet was observed. The levels of total saturated fatty acids of phospholipid in adipose tissue from the rats given either drug were lower than that of the rats given only HT diet. These data suggest that either drug alters fatty acid composition of phospholipid in fat cell membrane and enhances lipolysis of the cells.

Adipose Tissue↗
PubMed1990

Effects of length change on intracellular Ca2+ transients in ferret ventricular muscle treated with 2,3-butanedione monoxime (BDM).

Quick release of the right ventricular papillary muscle of ferrets, injected with aequorin, from Lmax (initial length) to 92% Lmax during twitch response produced an extra-light signal of aequorin. 2,3-Butanedione monoxime (BDM) at 10 mM decreased the peak tension to less than 10% of that in control and the light signal to 70%. In the BDM-treated muscle, the extra-light in response to the quick release did not occur. A quick stretch from Lmax to 103% Lmax, in the presence and absence of BDM, did not cause any changes in the light signal. The results indicate that the extra-light signal in the quick release is tension dependent. The tension reduction by the quick release decreases the affinity of troponin-C (Tn-C) for Ca2+ without affecting Ca2+ handling system in intact cardiac muscle.

Aequorin↗
PubMed1990

[Matrix vesicles in membranous ossification].

Calcification process in membranous ossification was examined histologically by light and electron microscopies in comparison with that in enchondral ossification. The following results were obtained: 1) In the rat tibial articular cartilage, the extracellular matrix proceeding from the transitional to the hypertrophic zone consisted of the following three layers from the proximal: the first layer in which ruthenium red positive granules were densely populated and thin collagen fibrils diffusely arranged but few matrix vesicles were observed; the second one containing numerous matrix vesicles and slightly thick collagen fibrils; and the last one in which the thick collagen fibrils were observed while matrix vesicles and ruthenium red positive granules were few. 2) In the calcified regions in the extracellular matrix of MC3T3-E1 cells, the regions of alveolar new bone formation due to orthodontic tooth movement and the calcified regions in the interparietal suture expanded mechanically in vitro, the number of matrix vesicles was less than those in the regions of enchondral ossification. 3) Ruthenium red positive granules were fewer in the regions of alveolar new bone formation after the orthodontic tooth movement than in the calcified regions of cartilage. 4) The observation on MC3T3-E1 cells revealed the two different possibilities of the processes of calcification: the calcification induced by matrix vesicles as an initiator and that directly related to mineral deposit on the collagen fibrils.

Alveolar Process↗
PubMed1990

[Long-term follow-up study of I-131 therapy for Graves' disease--index associated with late-onset hypothyroidism].

We have studied the follow-up of thyroid function in the patients with late-onset hypothyroidism and euthyroidism after I-131 therapy of hyperthyroidism. Thirty three patients who did not need the thyroid treatment until ten years after I-131 therapy were classified as euthyroid group. And eleven patients who needed the thyroid supplement of thyroid hormone for late-onset hypothyroidism were classified as hypothyroid group. Patients in both groups who required only a single dose of I-131 for successful treatment of hyperthyroidism had similar age, gland size, 24 hour I-131 uptake, pretreatment serum T3 uptake level and T4 concentration, and I-131 treatment dose. Subclinical hypothyroidism occurred in 28.6% of euthyroid group and 66.7% of hypothyroid group four months after I-131 therapy. The levels of T3 were recovered to higher than normal range at 6 months in euthyroid group, while the levels of T3 were kept within the normal range in the seventy percent of hypothyroid group. Patients who were still lower in the level of T3 uptake than normal range at 6 months had a higher incidence of late-onset hypothyroidism. Our observation showed no significant difference in the course of follow-up studies after I-131 therapy between the patients with late-onset hypothyroidism and euthyroidism.

Adult↗
PubMed1989

Binding of murine monoclonal antibodies to the active and inactive configurations of aequorin.

Murine monoclonal IgG1 antibodies (MAb), designated Aq-11 and Aq-12, were prepared against the photoprotein aequorin from jelly fish. Aequorin is a calcium-sensitive photoprotein which consists of a single polypeptide chain, apoaequorin, and a functional chromophore, coelenterazine. Native aequorin consists of two species with molecular masses of 25 and 23.5 kDa. MAb Aq-12 was found by immunoblot analysis to bind specifically to the 25 kDa species, while MAb Aq-11 reacted with the 23.5 kDa protein. Activation of apoaequorin with coelenterazine was associated with a shift of the 23.5 kDa molecule to the 25 kDa species. In contrast, treatment with calcium ions induced a shift back to the 23.5 kDa form. These changes between the active and inactive forms were identified by reactivity with MAbs Aq-11 and Aq-12. The results thus indicate that these MAbs should be useful in monitoring activation of this photoprotein.

Aequorin↗
PubMed1989

Affinity labeling of cofactor-binding region of human placental estradiol 17 beta-dehydrogenase by periodate-oxidized NADP+ (o-NADP+).

Periodate-oxidized NADP+ (o-NADP+), an analogue of the cofactors, is a reversible inhibitor of estradiol 17 beta-dehydrogenase in human placenta. Mode of the inhibition by o-NADP+ appeared to be competitive type (Ki = 0.84 microM) against NAD+ and non-competitive type (Ki = 1.13 microM) against estradiol, respectively. Treatment of the estradiol 17 beta-dehydrogenase with o-NADP+ resulted in time-dependent loss of the enzyme activity. The inactivation exhibited pseudo-first order kinetics (t1/2 = 15 min) and was protected by NAD+ and NADP+. On the other hand, periodate-oxidized ATP inactivated slightly the estradiol 17 beta-dehydrogenase. These results indicate that the residue(s) of lysines is located near the cofactor-binding region of estradiol 17 beta-dehydrogenase of human placenta.

17-Hydroxysteroid Dehydrogenases↗
PubMed1989

Effect of coenzyme Q10 on hemodynamic response to ocular timolol.

Coenzyme Q10 (CoQ10) is an essential component of the mitochondrial membrane and plays an important role in the maintenance of normal cardiac function. To evaluate the effects of ocular timolol on the cardiovascular system and determine the protective effect of CoQ10, 16 patients with glaucoma were studied using impedance cardiography. Following instillation of 1 mg timolol maleate in each eye, heart rate (HR) and stroke index (SI) decreased, and total peripheral resistance index (TPRI) increased significantly. Reexamination was performed after 6 weeks of 90 mg oral CoQ10. Despite decreases in HR, percent changes in HR were significantly less after CoQ10 at 120 min. Stroke index showed an initial increase which was not observed without CoQ10. These data suggest that CoQ10 delayed the appearance of inotropic blockade of timolol and hastened the disappearance of chronotropic blockade. Additional study of six normal volunteers with 6 weeks of oral CoQ10 showed a similar decrease of intraocular pressure after timolol instillation as compared to those without CoQ10. Thus, administration of oral CoQ10 in patients receiving ocular timolol may be useful in mitigating cardiovascular side effects without affecting intraocular pressure in the treatment of glaucoma.

Administration, Oral↗
PubMed1989

Heterogeneous response of cytoplasmic free Ca2+ in proximal convoluted and straight tubule cells in primary culture.

Cytoplasmic free calcium [( Ca2+]c) plays an important role in cellular signal transduction in response to hormones. The development of microfluorometric digital image analysis makes it possible to obtain an image of a calcium-indicator dye, fura-2, in a single living cell. Subconfluent primary cultured cells from isolated proximal convoluted and straight tubules were analyzed for [Ca2+]c. The basal level of [Ca2+]c was 92.0 +/- 0.82 nM in convoluted and 75.0 +/- 4.7 nM in straight tubule cells. Exposure of convoluted tubule cells to parathyroid hormone (10(-7) M) elicited a 1.4-fold transient rise in [Ca2+]c. Treatment of straight tubule cells with calcitonin (0.1 U/ml), on the other hand, evoked a 1.6-fold transient increase in [Ca2+]c. [Ca2+]c in proximal straight tubule cells did not respond to parathyroid hormone, nor did that in convoluted tubule cells to calcitonin. [Ca2+]c peaks were diminished in straight tubule cells by repeated additions of calcitonin at 5-min intervals. These hormonal responses were abolished by perfusing the cells with calcium-free solution and were not mimicked by perfusion with adenosine 3',5'-cyclic monophosphate (10(-4) M) or with forskolin (5 X 10(-5) M). The results suggest that the [Ca2+]c response to the selected peptide hormones is different in proximal convoluted and straight tubule cells in primary culture.

Animals↗
PubMed1989

Value of vectorcardiography in predicting progress in dilated cardiomyopathy.

Sixteen of 75 patients with dilated cardiomyopathy (DCM) died during a mean follow-up period of 39.7 months. In non-survivors, the cardiothoracic ratio and the left ventricular end-diastolic dimensions were greater, the left ventricular end-diastolic pressures were more elevated, and the cardiac index was lower than in the survivors at the time of initial diagnosis. There were no significant differences between survivors and non-survivors in the magnitude of the maximum QRS and T vectors or in the maximum T angle. In the non-survivors, the maximum QRS vector was directed more posteriorly and the width/length ratio of the loop in the horizontal plane was smaller than in survivors. The QRS loop in the horizontal plane was often distorted in non-survivors or showed a bizarre figure-of-eight configuration. It appears that in DCM a marked posterior displacement of a QRS loop that is narrow and distorted or is in a bizarre figure-of-eight configuration in the horizontal plane indicates an unfavorable prognosis.

Adult↗