Search PubMed⌕ Search

Biomedical subjects

S Kurihara

Publications and source records attributed to S Kurihara.

At least 19 recordsLinked to original sources
PubMed1995

Effects of a new inotropic drug (DN-9693) on Ca2+ transients and contraction in ferret ventricular muscles.

We investigated the mechanisms of the effects of a newly synthesized cyclic AMP phosphodiesterase inhibitor (PDEI: 1,5-dihydro-7-(1-piperidinyl)imidazo[2,1-beta]quinazolin- 2(3H)-one dihydrochloride hydrate, DN-9693) on intracellular Ca2+ transients and tension in ferret papillary muscles. We used the aequorin method to measure Ca2+ transients in intact preparations. DN-9693 (1-100 microM) increased the peaks of both Ca2+ transients and tension. The potentiation of Ca2+ transients by DN-9693 was significant at lower concentrations (1-10 microM) but not at higher concentrations (50 and 100 microM). The peak of tension was significantly increased when the concentration of DN-9693 was increased (1-100 microM). In addition, the time to peak light was shortened at lower concentrations (1 and 5 microM). Other parameters of Ca2+ transients were not significantly altered. The time course of tension was not affected by DN-9693. In Triton X-100-treated skinned preparations, DN-9693 decreased the Ca2+ concentration required for half-maximal activation of the pCa-tension relation. These results suggest that the positive inotropic effect of DN-9693 is attributable to the alteration in Ca2+ handling of sarcoplasmic reticulum (SR) and Ca2+ sensitization of the myofilaments.

Animals↗
PubMed1995

Treatment of granuloma annulare with tranilast.

Three cases of granuloma annulare which did not exhibit a self-limited course were treated with tranilast at the dose of 300 mg/daily. The treatment resulted in the resolution of skin lesions within three months of administration. Although spontaneous resolution is often observed in granuloma annulare, tranilast may provide an alternative therapy for the treatment of cases resistant to spontaneous healing.

Adult↗
PubMed1995

Late-onset focal dermal elastosis: clinical and histological features.

We describe two patients with lesions clinically resembling pseudoxanthoma elasticum and histologically exhibiting focal elastosis, with normal-appearing elastic fibres in the mid- and deep dermis. We consider that these skin lesions represent a previously undescribed entity, whose pathogenesis appears to be related to the ageing process.

Aged↗
PubMed1995

Intravenous calcitriol can increase bone mass in hemodialysis patients with osteitis fibrosa.

Intravenous calcitriol administration (IVC) suppressed parathyroid hormone (PTH) secretion and improved osteitis fibrosa (OF) in long-term hemodialysis (HD) patients, although it did not increase the mineralized bone area or the mineral apposition rate. We observed the long-term effects of IVC on OF in 8 HD patients. Bone biopsy of 7 patients revealed increased bone turnover and decreased bone mass. One microgram of calcitriol was given intravenously three times weekly after each HD session for 12 months. The dose was adjusted to maintain the serum corrected calcium level at < 11.5 mg/dl. Dual-energy X-ray bone absorptiometry (DEXA), 3rd lumbar vertebra bone density by quantitative computed tomography (QCT), and biochemical data were taken before IVC, and after 6 and 12 months of IVC. Seven HD patients were given 0.5 microgram/day 1 alpha-cholecalcitriol as controls. The serum corrected calcium levels were 9.9 +/- 0.3 (mean +/- SE) and 11.1 +/- 0.2 mg/dl at 0 and 12 months, respectively (p = 0.06). The serum phosphate levels were 6.2 +/- 0.7 and 6.6 +/- 0.6 mg/day at 0 and 12 months, respectively (p = 0.56). The serum intact PTH levels were 928 +/- 281 and 617 +/- 192 (p = 0.016) at 0 and 12 months, respectively. The bone mass of the 3rd lumbar vertebra measured by QCT was 195 +/- 17 and 218 +/- 186 g/cm3 at 0 and 12 months, respectively (p = 0.156). The bone mass of the trunk measured by DEXA was 660 +/- 44 and 706 +/- 32 g and 0 and 12 months, respectively (p = 0.156). These parameters did not change in controls. Sequential bone biopsy in 3 cases also supported these changes. We conclude that IVC not only suppresses bone turnover, but that it also restores decreased bone mass in HD patients with OF.

Adult↗
PubMed1995

Effects of thapsigargin on aequorin-injected and skinned preparations of ferret ventricular muscles.

OBJECTIVE: We investigated the effects of thapsigargin (TG) (0.1-1 microM) on the relation between intracellular Ca2+ concentration and tension in ferret papillary muscles using aequorin-injected and skinned preparations. METHODS: Aequorin was injected into the superficial cells of ferret papillary muscles; the Ca2+ signals of aequorin and tension in twitch and those with the application of 15 mM caffeine were simultaneously measured. The alteration of Ca2+ sensitivity of the contractile elements was examined by measuring the pCa-tension relation in Triton-X-treated skinned preparations. RESULTS: TG decreased the peak of the Ca2+ signal accompanied by a prolonged decay time. However, the tension was scarcely altered even at 1 microM TG. TG inhibited the caffeine-induced Ca2+ signal. Prolongation of decay of the Ca2+ signal by TG in twitch was further enhanced by isoprenaline (10 nM). The pCa-tension relation of the skinned preparation was slightly but significantly shifted to the right by TG. CONCLUSIONS: The apparent dissociation of the effects of TG on the Ca2+ signal and tension in intact preparations is not a result of alteration of the Ca2+ sensitivity of the myofilaments. The effects of TG in multicellular preparations are probably limited to the outer layer of the preparation. The slower time course of the Ca2+ signal induced by TG is due to the inhibition of Ca2+ uptake by sarcoplasmic reticulum, which is more significantly observed when the intracellular Ca2+ transient is increased by isoprenaline.

Aequorin↗
PubMed1994

Effects of a newly synthesized dihydropyridine, NZ-105, on intracellular Ca transients and tension in ferret ventricular muscles.

We investigated the effects of a newly synthesized dihydropyridine (DHP) derivative (NZ-105) on intracellular Ca transients and contraction in ferret ventricular muscles, using the aequorin method. Low concentrations of NZ-105 (10(-9)-10(-7) M) showed no significant effects on the light signal of aequorin and tension in twitch. High concentrations of NZ-105 (10(-6)-10(-5) M) inhibited the peaks of the light signal and tension without altering their time courses. The relation between the peaks of the light signal and tension in twitch, measured in solutions with varying Ca2+ concentrations, was shifted to the left by NZ-105. The relation between [Ca2+]i and tension measured in tetanic contraction was also shifted to the left by NZ-105. These results suggest that the inhibitory effect of NZ-105 on contraction in mammalian cardiac muscle is curtailed by an increase in Ca sensitivity of the contractile elements.

Animals↗
PubMed1992

CD8+ cutaneous anaplastic large-cell lymphoma: report of two cases with immunophenotyping, T-cell-receptor gene rearrangement and electron microscopic studies.

Two cases are reported of cutaneous anaplastic large-cell lymphoma with the suppressor/cytotoxic (CD8) phenotype. In both cases there was a solitary skin tumour in which there was a dense infiltrate with large irregularly shaped cells which on immunophenotyping expressed CD8. DNA hybridization analysis showed rearrangements of the T-cell-receptor gene in both cases.

Aged↗
PubMed1992

Changes in the microvasculature after mechanical pressure on the hamster cheek pouch.

The reaction of the microvasculature in the periodontal ligament to mechanical pressure is considered a very important phenomenon with respect to the biological background to orthodontic tooth movement. For clarification of the microvascular reaction to mechanical pressure, an experimental model that incorporated a hamster cheek pouch was established. This in vivo model solves some of the problems of other experimental models of the microvasculature of the periodontal ligament. Blood plasma permeation in this model was examined by means of a blue dye (pontamine sky blue), and histological observation was performed by light and transmission electron microscopy. Increased vascular permeability was observed within 30 min after removal of the mechanical stimulation. The threshold weight resulting in dye leakage was between 1 and 5 g applied for 60 min. From the histological observations, some large gaps between the endothelial cells in venules were found, while most basement membranes remained undisturbed. These observations suggest that the plasma leakage was due to mild traumatic injury to the endothelial cells. Both leukocytes and platelets were observed in the gaps between the endothelial cells in the venule. These types of microvascular reactions to mechanical pressure could initiate tissue changes in the periodontal ligament during orthodontic tooth movement.

Animals↗
PubMed1991

Time-resolved synchrotron X-ray diffraction studies of a single frog skeletal muscle fiber. Time courses of intensity changes of the equatorial reflections and intracellular Ca2+ transients.

Time-resolved X-ray equatorial diffraction studies on a single frog skeletal muscle fiber were performed with a 10 ms time resolution using synchrotron radiation in order to compare the time courses of the molecular changes of contractile proteins and the intracellular Ca2+ transient during an isometric twitch contraction at 2.7 degrees C. Measurements of the Ca2+ transient using aequorin as an intracellular Ca2+ indicator were conducted separately just before and after the X-ray experiments under very similar experimental conditions. The results, which showed a similar time course of tension to that observed in the X-ray experiment, were compared with the aequorin light signal, tension and the intensity changes of the 1,0 and 1,1 equatorial reflections. No appreciable change in both reflection spacings indicated that the effect of internal shortening of the muscle was minimized during contraction. The intensity change of the equatorial reflections generally occurred after the aequorin light signal. In the rising phase, the time course of increase in the 1,1 intensity paralleled that of the rise of the light signal and the intensity peak occurred 20-30 ms after the peak of the light signal. The decrease in the 1,0 intensity showed a time course similar to that of tension and the intensity minimum roughly coincided with the tension peak, coming at 80-90 ms and about 60 ms after the peaks of the light signal and the 1,1 intensity change, respectively. In the relaxation phase, the 1,1 intensity seemed to fall rapidly just before the tension peak and then returned to the original level in parallel with the decay of tension. The 1,0 intensity returned more slowly than the tension relaxation. Thus, the change of the 1,1 intensity was faster than that of the 1,0 intensity in both the rising and relaxation phases. When the measured aequorin light signal was corrected for the kinetic delay of the aequorin reaction with a first-order rate constant of either 50 or 17 s-1, the peak of the corrected light signal preceded that of the measured one by approx. 30 ms. Thus, the peak of the Ca2+ transient appeared earlier than the peaks of the 1,1 and 1,0 intensity changes by 50-60 and 110-120 ms, respectively. The time lag between the extent of structural change and the Ca2+ transient is discussed in relation to the double-headed attachment of a cross-bridge to actin.

Aequorin↗
PubMed1991

Abnormal expression of blood group-related antigens in uterine endometrial cancers.

The expression of A, B, and H group antigens, Lewis group antigens (Lewis(a), Lewis(b), Lewis(x), and Lewis(y)), and Lc4 and nLc4 antigens, the precursor antigens of both groups, was examined immunohistochemically with monoclonal antibodies in 9 normal endometria, 6 endometrial hyperplasias, and 31 endometrial cancers. 1) A, B and/or H antigens were detected in endometrial cancers at an incidence of 51.6%, while no distinct localization of these antigens was observed in normal endometria. H antigen, the precursor of A and B antigens, was particularly frequently detected in endometrial cancers. 2) An increased rate of expression of Lewis group antigens, particularly Lewis(b) antigen, was observed in endometrial cancers compared with its expression in normal endometria. 3) Lc4 and nLc4 antigens were detected in endometrial cancers at rates of 41.9% and 38.7%, respectively, these expressions being increased compared with those in normal endometria. 4) These results suggest that a highly abnormal expression of blood group-related antigens in endometrial cancers occurs not only at the level of A, B, and H antigens and Lewis group antigens, but also at the level of their precursor Lc4 and nLc4 antigens. 5) Lewis(a), Lewis(b), and Lc4 antigens, built on the type-1 chain, are more specific to endometrial cancers than their respective positional isomers, Lewis(x), Lewis(y), and nLc4 antigens, built on the type-2 chain.

ABO Blood-Group System↗
PubMed1991

Cross-bridge movement in fast and slow skeletal muscles of the chick.

1. Fast (posterior latissimus dorsi, PLD) and slow (anterior latissimus dorsi, ALD) muscles of the chick were studied by time-resolved X-ray diffraction using a synchrotron radiation source. 2. In both muscles and at both 20 and 30 degrees C, intensities of the X-ray equatorial reflections changed faster than tension at the beginning of tetanus. When the intensity change was converted into the mass transfer from the thick to the thin filament, the difference between the half-rise times of the transfer and tension development at 20 degrees C was 140 ms in ALD and 37 ms in PLD. At 30 degrees C it was 110 ms and 10-20 ms for ALD and PLD respectively. 3. These results indicate that in the early stage of contraction, some of the myosin heads in the vicinity of the thin filament are developing little or no tension, and suggest that the fast and slow muscles differ in the transition rate of myosin heads from the state of attachment with low tension to that with high tension.

Actins↗
PubMed1991

Vitamin D3 metabolites increase [Ca2+]i in rabbit renal proximal straight tubule cells.

Vitamin D metabolites exert both acute and chronic influences on proximal tubule function. To further evaluate vitamin D action on the kidney, we examined the immediate effects of vitamin D metabolites on cytoplasmic calcium ion concentration [( Ca2+]i), using fura-2 and patch-clamp method in cultured proximal straight tubule cells of rabbit kidney. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] and 25-hydroxyvitamin D3 [25(OH)D3] evoked a transient rise in [Ca2+]i, and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] caused a sustained rise in [Ca2+]i; all effects were dose dependent. [Ca2+]i transient, evoked by 1,25(OH)2D3 alone, was abolished in Ca(2+)-free media. Pretreatment of cells in Ca(2+)-free media with caffeine (4 mM) or ryanodine (1 microM) to deplete Ca2+ store of endoplasmic reticulum or with TMB-8 (5 mM) to block Ca2+ release from storage blunted the effect of 25(OH)D3 on [Ca2+]i but not of 24,25(OH)2D3. Data were also supported by activities of Ca-dependent K channel and show that these three vitamin D metabolites in pharmacological doses increase [Ca2+]i of proximal tubule cells from different sources.

24,25-Dihydroxyvitamin D 3↗
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↗