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Biomedical subjects

N Shiga

Publications and source records attributed to N Shiga.

At least 19 recordsLinked to original sources
PubMed2006

Microfabricated surface-electrode ion trap for scalable quantum information processing.

Individual laser-cooled 24Mg+ ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 microm above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.

Journal Article↗
PubMed2003

Thermally excited modes in a pure electron plasma.

Thermally excited plasma modes are observed in near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05<kT<5 eV. The measured thermal emission spectra together with a plasma-antenna coupling calibration uniquely determine the temperature. This calibration is obtained from the spectra themselves when absorption of the receiver-generated noise is significant, or from kinetic theory. This nondestructive temperature diagnostic agrees well with standard diagnostics and may be useful for expensive species such as antimatter.

Journal Article↗
PubMed2001

Iridium complex-catalyzed allylic amination of allylic esters.

Iridium complex-catalyzed allylic amination of allylic carbonates was studied. The solvent strongly affected the catalytic activity. The use of a polar solvent such as EtOH is essential for obtaining the products in high yield. The reaction of (E)-3-substituted-2-propenyl carbonate and 1-substituted-2-propenyl carbonate with pyrrolidine in the presence of a catalytic amount of [Ir(COD)Cl](2) and P(OPh)(3) (P/Ir = 2) gave a branch amine with up to 99% selectivity. Both secondary and primary amines could be used for this reaction. When a primary amine was used, selective monoallylation occurred. No diallylation product was obtained. The reaction of 1,1-disubstituted-2-propenyl acetate with amines exclusively gave an alpha,alpha-disubstituted allylic amine. This reaction provides an alternative route to the addition of an organometallic reagent to ketimines for the preparation of such amines. The reaction of (Z)-3-substituted-2-propenyl carbonate with amines gave (Z)-linear amines with up to 100% selectivity. In all cases, no (E)-linear amine was obtained. The selectivities described here have not been achieved in similar palladium complex-catalyzed reactions.

Journal Article↗
PubMed2001

Frequency and clinical characteristics of dilated cardiomyopathy caused by desmin gene mutation in a Japanese population.

AIMS: Dilated cardiomyopathy is partly caused by a mutation of some cytoskeletal or nuclear envelope proteins. It has been confirmed recently that a missense mutation of the gene encoding desmin, a cytoskeletal protein, can cause dilated cardiomyopathy. This study was aimed at elucidating the frequency and clinical characteristics of dilated cardiomyopathy caused by desmin mutation. METHODS AND RESULTS: We examined 265 Japanese patients with dilated cardiomyopathy (217 sporadic cases and 48 probands of familial dilated cardiomyopathy). The exon 8 of the desmin gene, the critical region for the pathogenesis of dilated cardiomyopathy, was analysed by polymerase chain reaction, single-strand conformation polymorphism and sequencing. The same missense mutation (Ile451Met) as reported previously was detected in three patients (1.1%). All these patients were male and sporadic, and more likely to be accompanied by characteristics such as younger age at diagnosis, lower fractional shortening and ejection fraction than each mean value of sporadic cases. The chronological changes in cardiac function were inconsistent in the three patients. CONCLUSION: The missense mutation (Ile451Met) of the desmin gene can be the genetic cause of dilated cardiomyopathy, although with very low frequency. The ages at diagnosis were younger and the cardiac function had deteriorated further than general cases of sporadic dilated cardiomyopathy.

Adult↗
PubMed2000

Non-homologous recombination between Alu and LINE-1 repeats caused a 430-kb deletion in the dystrophin gene: a novel source of genomic instability.

Although large deletions in the dystrophin gene have been identified in more than two-thirds of Duchenne and Becker muscular dystrophy patients, the molecular mechanisms that lead to the generation of these deletions are largely unknown. Here, Alu and LINE-1 (L1) repetitive elements were shown to be present at one or other of the two ends, respectively, of a 430-kb deletion in the dystrophin gene. The breakpoint of the deletion, which stretches from exons 2 to 7, was defined more precisely by polymerase chain reaction (PCR) walking on introns 1 and 7. Finally, the region containing the breakpoint was amplified as a fragment of more than 10kb. Sequencing of the deletion endpoint revealed the presence of an Alu sequence in intron 1, 25 kb downstream from the 3' end of exon 1 that was joined directly to an L1 sequence in intron 7, 4.5kb downstream from the 3' end of exon 7. The deletion was calculated to be 430kb. To our knowledge, this is a novel recombination event joining non-homologous Alu and L1 repeats, and is the largest known intrachromosomal deletion that is thought to involve repetitive genetic elements. Sequence characteristics around the breakpoint are discussed.

Alu Elements↗
PubMed2000

Carvedilol improves endothelium-dependent dilatation in patients with coronary artery disease.

OBJECTIVE: Flow-mediated, endothelium-dependent dilatation (FMD) of the coronary and peripheral circulation is impaired by increased oxidative stress in patients with coronary artery disease (CAD). Carvedilol is a novel beta-blocker that also shows an antioxidant effect in vitro. However, the effect of carvedilol on endothelial dysfunction associated with established coronary atherosclerosis has not been examined in the clinical setting. METHODS: We studied 29 patients with CAD, including 17 with recent myocardial infarction and 12 with stable effort angina pectoris. Nineteen patients received carvedilol (10 with infarction and 9 with angina), and 10 were treated with placebo (7 with infarction and 3 with angina). We also studied 13 age- and sex-matched control subjects. Brachial FMD during reactive hyperemia and nitroglycerin-induced, endothelium-independent dilatation were assessed by high-resolution ultrasound. RESULTS: FMD was smaller in patients with CAD compared with controls, although nitroglycerin-induced dilatation was similar. Carvedilol significantly improved FMD after long-term treatment (5. 1% +/- 0.4% at baseline to 7.8% +/- 0.3% after 4 months; P <.01) but not after short-term treatment (5.1% +/- 0.4% at baseline to 5.0% +/- 0.7% after 2 hours). Placebo therapy had no effect on endothelial dysfunction. Neither carvedilol nor placebo had an effect on nitroglycerin-induced dilatation after short- and long-term treatment. Long-term carvedilol therapy also significantly decreased the plasma level of thiobarbituric acid-reactive substances compared with placebo (carvedilol, 5.8 +/- 0.4 nmol/mL to 4.6 +/- 0.3 nmol/mL, P <.01; placebo, 5.9 +/- 0.4 nmol/mL to 5.8 +/- 0.4 nmol/mL, P = not significant). CONCLUSION: These findings suggest that the improvement of endothelial function by carvedilol may be caused by its antioxidant activity.

Adrenergic beta-Antagonists↗
PubMed2000

[Mutations of the dystrophin gene in dilated cardiomyopathy].

X-linked dilated cardiomyopathy(XLDCM) is caused by mutations of the dystrophin gene, which was originally cloned as the responsible gene for Duchenne muscular dystrophy and Becker muscular dystrophy. Mutations due to XLDCM are centered on 5' end of the gene, especially M-promoter and the adjacent region. However, other mutations are dispersed and cannot be characterized. Three mechanisms have been proposed by which the involvement of cardiac muscle is so severe in spite of the lack of skeletal muscle symptoms; 1) up-regulation of B- and P-dystrophin in merely skeletal muscle compensating for the defect of M-dystrophin, 2) dysfunction of some parts of dystrophin specifically essential to cardiac muscle, 3) different expression patterns of mutant mRNA between cardiac and skeletal muscle.

Cardiomyopathy, Dilated↗
PubMed1999

Systemic endothelial function is preserved in men with both active and inactive variant angina pectoris.

To test the hypothesis that coronary spasm could be a coronary manifestation of systemic endothelial dysfunction and that the activity of coronary spasm could influence systemic endothelial function, we examined brachial flow-mediated, endothelium-dependent vasodilation and nitroglycerin-induced endothelium-independent vasodilation with high-resolution ultrasound in 11 men with variant angina pectoris (6 active and 5 inactive) without established coronary atherosclerosis. Endothelium-dependent vasodilation in peripheral circulation was preserved in men with active and inactive variant angina pectoris, suggesting that systemic endothelial dysfunction is not involved in either the pathogenesis or the activity of coronary spasm.

Aged↗
PubMed1999

Mutational analysis of the cardiac actin gene in familial and sporadic dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) results in part from genetic disorders. Recently, missense mutations of the cardiac actin gene have been reported to cause DCM. We studied 136 Japanese DCM cases to elucidate how frequently the gene mutations are involved in its pathogenesis. Genomic DNA samples were obtained from 136 DCM cases (107 males, 29 females), containing 30 familial DCM (5 confirmed and 25 suspected). All six exons of the cardiac actin gene were analyzed by polymerase chain reaction, single-strand conformation polymorphism, and sequencing. We detected no mutations of the disease causation previously reported (G867A or A1014G) but two silent mutations (G979C and C1018T) in exon 6 and one point mutation (T1080A) in the 3'-untranslated region. As a result of screening 128 healthy subjects, these novel silent mutations were found to be mere genetic polymorphisms, not responsible for the disease. Although some genetic polymorphisms exist in the cardiac actin gene, mutations of the gene are rarely responsible for DCM, at least in the Japanese patients.

3' Untranslated Regions↗
PubMed1997

Disruption of the splicing enhancer sequence within exon 27 of the dystrophin gene by a nonsense mutation induces partial skipping of the exon and is responsible for Becker muscular dystrophy.

The mechanism of exon skipping induced by nonsense mutations has not been well elucidated. We now report results of in vitro splicing studies which disclosed that a particular example of exon skipping is due to disruption of a splicing enhancer sequence located within the exon. A nonsense mutation (E1211X) due to a G to T transversion at the 28th nucleotide of exon 27 (G3839T) was identified in the dystrophin gene of a Japanese Becker muscular dystrophy case. Partial skipping of the exon resulted in the production of truncated dystrophin mRNA, although the consensus sequences for splicing at both ends of exon 27 were unaltered. To determine how E1211X induced exon 27 skipping, the splicing enhancer activity of purine-rich region within exon 27 was examined in an in vitro splicing system using chimeric doublesex gene pre-mRNA. The mutant sequence containing G3839T abolished splicing enhancer activity of the wild-type purine-rich sequence for the upstream intron in this chimeric pre-mRNA. An artificial polypurine oligonucleotide mimicking the purine-rich sequence of exon 27 also showed enhancer activity that was suppressed by the introduction of a T nucleotide. Furthermore, the splicing enhancer activity was more markedly inhibited when a nonsense codon was created by the inserted T residue. This is the first evidence that partial skipping of an exon harboring a nonsense mutation is due to disruption of a splicing enhancer sequence.

Adult↗
PubMed1996

Effects of ethanol on meal-stimulated secretion of pancreatic polypeptide and cholecystokinin: comparison of healthy volunteers, heavy drinkers, and patients with chronic pancreatitis.

Tiscornia and Dreiling (Physiopathogenic Hypothesis of Alcoholic Pancreatitis: Supranormal Ecbolic Stimulation of the "Pancreon" Units Secondary to the Loss of the Negative Component of Pancreas Innervation. Pancreas 1987;2:604-612.) proposed that hypertonicity of intrapancreatic cholinergic neurons provoked by chronic alcoholism may contribute to the pathogenesis of chronic pancreatitis (CP). In the present study, the validity of this hypothesis was investigated in humans by studying the effects of atropine, cisapride, and ethanol on the meal-stimulated secretion of pancreatic polypeptide (PP) and cholecystokinin (CCK) in healthy volunteers, heavy drinkers, and CP patients. In healthy volunteers, the early phase PP response (0-40 min) to a test meal was completely blocked by atropine, whereas it was augmented by cisapride, an enhancer of acetylcholine release from cholinergic nerves. The early phase PP response to a test meal was inhibited by ethanol in healthy volunteers, whereas, in heavy drinkers, the response was augmented and the inhibition by ethanol was abrogated. In CP patients, ethanol tended to enhance the early phase PP response. Ethanol did not affect the early phase CCK response to a test meal in any group, but it significantly enhanced the late phase CCK response (40-120 min) in CP patients. These results suggest that: (i) oral ethanol may inhibit the postprandial activation of the cholinergic neural pathway to the pancreas in healthy subjects, (ii) in heavy drinkers, postprandial cholinergic tone may be augmented and become resistant to the inhibition by ethanol, and (iii) the ethanol-induced increase in the postprandial CCK response in CP patients may play some role in the pathophysiology of this disease.

Adult↗
PubMed1996

Vestibular dark cells contain the Na+/H+ exchanger NHE-1 in the basolateral membrane.

Vestibular dark cells and strial marginal cells transport K+ by similar mechanisms. We have shown that K+ transport in vestibular dark cells is sensitive to the cytosolic pH (pHi) (Wangemann et al. (1995a): J. Membrane Biol. 147: 255-262). The present study addresses pharmacologically the questions whether vestibular dark cells and strial marginal cells from the gerbil contain a Na+/H+ exchanger (NHE) and in which membrane, apical or basolateral, NHE is located. Further, the study addresses the question which NHE subtype is present in vestibular dark cells. pHi was measured micro-fluorometrically with the pH-sensitive dye 2',7'-bicarboxyethyl-5(6)-carboxyfluorescein (BCECF), cell volume which is a measure of the net balance between ion influx and efflux was monitored as cell height (CH) and the equivalent short circuit current (Isc) which is a measure of transepithelial K+ secretion was calculated from measurements of the transepithelial voltage (Vt) and the transepithelial resistance (Rt). Changes in pHi were induced by 20 or 40 mM propionate. In the presence of propionate a transient acidification of pHi was observed in vestibular dark cells as well as a subsequent alkalinization to pHi values exceeding those under control conditions. The alkalinization of pHi in the presence of propionate was inhibited by the NHE blockers amiloride and EIPA. Propionate-induced swelling of vestibular dark cells was inhibited by amiloride. The NHE blocker amiloride caused in vestibular dark cells an acidification of pHi and a decrease in CH. Amiloride caused in both vestibular dark cells and strial marginal cells a transient stimulation of Isc when added to the basolateral side but not added to the apical side. Similar effects and pHi were observed in vestibular dark cells with the amiloride analog ethyl-isopropyl-amiloride (EIPA) and similar effects on Isc were observed with EIPA and the NHE blocker HOE694 when applied to the basolateral side of vestibular dark cell epithelium. The IC50 for these basolateral effects of EIPA, HOE694 and amiloride on Isc in vestibular dark cells were 2 x 10(-7) M, 8 x 10(-7) M and 4 x 10(-5) M. These observation suggest that vestibular dark cells and strial marginal cells contain NHE in their basolateral membrane, that K+ transport in strial marginal cells in pHi sensitive similar to K+ transport in vestibular dark cells and that NHE in vestibular dark cells consists of the subtype NHE-1.

Amiloride↗
PubMed1996

A rare case of severe acute pancreatitis complicated with pancreatic pseudocysts, obstructive jaundice and intraperitoneal hemorrhage.

A 58-year-old man visited our hospital because of back pain. Blood examinations revealed the presence of acute inflammation and an increase of pancreatic enzymes. Abdominal computed tomography indicated pseudocysts in the pancreas. The patient was diagnosed as having acute pancreatitis with pseudocysts formation. During the course of the disease, a newly formed pseudocyst in the pancreatic head compressed the common bile duct, leading to the obstructive jaundice. In addition, the rupture of a pseudocyst in the pancreatic tail caused intraperitoneal hemorrhage. This is an interesting case of acute pancreatitis with pseudocysts in which two rare complications developed.

Acute Disease↗
PubMed1996

[Mechanism of volume regulation of vestibular dark cells of the gerbil].

The volume response of vestibular dark cells of the gerbil to a hyposmotic challenge was investigated. Tissues including dark cells were perfused in preparations in which the perfusate had access to both sides of the epithelium and the height of the dark cell layer was measured as an indicator of its volume. We found that dark cells showed a fast and strong regulatory volume decrease (RVD) and prevented cell swelling in hypotonic media. This mechanism was dependent upon extracellular [K+] and [Cl-]. Ion selectivity of this mechanism was K+ = Rb+ > Cs+ > Na+ = NMDG+ (N-methyl-D-glucamine) for cations and Cl- = SCN- = NO3- > > gluconate- for anions. RVD of dark cells was inhibited by K(+)- channel blockers barium, quinidine and lidocaine, by Cl(-)-channel blockers 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, by an Na(+)-K+ ATPase inhibitor ouabain and by low temperature, but was not inhibited by a loop diuretic bumetanide, by carbonic anhydrase inhibitors acetazolamide and ethoxyzolamide, by a K(+)-channel blocker tetraethylammonium, by a Cl(-)-channel blocker 5-nitro-2 (3-phenylpropylamino)-benzoic acid or by an inhibitor of the Na(+)-H+ exchanger amiloride. These data suggest that the RVD of dark cells occurs via separate K+ and Cl- channels which are different from those active under isosmotic condition, and is presumably activated by a hyposmotic stimulus.

Animals↗
PubMed1996

[Analysis of processes of elevating calcaneum bone stiffness in young women--from the view point of their life-style].

Calcaneum bone stiffness in 222 young women was investigated by using an ultra-sound bone densitometer (Achilles). Their exercise experiences, amounts of dairy products (including foods which contain a lot of calcium) consumed and 24 questions on their eating attitudes were also analysed. Stiffness showed a significant (p < 0.05) positive correlation with age, BMI and the onset of menarche by polynomial (2) regressions. Using these three variables, expected stiffness was calculated by multiple regression, and according to the differences between the real and expected stiffness, the subjects were divided into three subgroups. Group H which showed higher stiffness, showed significantly (p < 0.05) higher exercise experiences and had the habit of consuming more dairy products and small fish than the other two groups. In all of the subjects, the most important variable which increased the stiffness was the exercise experience at junior high school and the next was the habit of eating small fish. The subjects who customarily ate their meals with their families were more likely to eat small fish. These findings suggest that family eating habits should be noticed not only in post-menopausal women, but also in young girls.

Adolescent↗