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Biomedical subjects

A Sakaguchi

Publications and source records attributed to A Sakaguchi.

At least 19 recordsLinked to original sources
PubMed2003

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV.

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6<cos((theta(c.m.)(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective-Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are thus far undiscovered.

Journal Article↗
PubMed2003

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Journal Article↗
PubMed2002

Sigma-nucleus potential in A=28.

We have studied the (pi(-),K+) reaction on a silicon target to investigate the sigma-nucleus potential. The inclusive spectrum was measured at a beam momentum of 1.2 GeV/c with an energy resolution of 3.3 MeV (FWHM) by employing the superconducting kaon spectrometer system. The spectrum was compared with theoretical calculations within the framework of the distorted-wave impulse approximation, which demonstrates that a strongly repulsive sigma-nucleus potential with a nonzero size of the imaginary part reproduces the observed spectrum.

Journal Article↗
PubMed2001

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c.

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.

Journal Article↗
PubMed2001

A distinct subnuclear localization of mammalian DNA topoisomerase IIbeta in yeast.

Mammalian topoisomerase II isoforms alpha and beta are diverged in their C-terminal domain (CTD), but both isoforms complement the yeast top2 mutation. In this study, mammalian topoisomerase IIalpha-CTD and IIbeta-CTD were tagged with yellow fluorescent protein (YFP), expressed in yeast cells, and their localization was examined. YFP tagged-topoisomerase IIalpha-CTD was distributed evenly throughout the nucleus, while YFP tagged-topoisomerase IIbeta-CTD was sequestered into a subnuclear compartment. Deletion analysis revealed that two regions (amino acids 1207-1234 and 1513-1573) of the topoisomerase IIbeta-CTD are essential for specific localization of the beta isoform: if either of the two regions is removed, the mutant topoisomerase IIbeta-CTD distributes evenly throughout the nucleus. The data suggest that yeast cells distinguish the nuclear and subnuclear localization signals associated with these two mammalian topoisomerase II isoforms.

Amino Acid Sequence↗
PubMed2001

Observation of spin-orbit splitting in lambda single-particle states.

The spin-orbit splitting of Lambda single-particle states in (13)(Lambda)C was measured. The 13C(K-,pi(-))(13)(Lambda)C reaction was used to excite both the 1/2(-) and 3/2(-) states simultaneously, which have predominantly 12C(0(+)) x p(Lambda) configuration. gamma rays from the states to the ground state were measured in coincidence with the pi(-)'s, by which ls splitting was found to be 152+/-54(stat)+/-36(syst) keV. The value is 20-30 times smaller than exhibited by the ls splitting in the nuclear shell model. This value gives us new insight into the YN interaction.

Journal Article↗
PubMed2000

Structure-activity relationships of a new antifungal imidazole, AFK-108, and related compounds.

Fungicidal activity of widely used imidazole antifungal drugs in topical applications is not so strong in spite of their fungistatic activities against dermatophytes and pathogenic yeasts. In order to improve fungicidal activity of imidazole antifungal agents, a series of novel imidazole derivatives having a hydrophobic substituent derived from isoprenoid were synthesized. The efficacy of these compounds was evaluated with respect to direct cell-membrane damaging activity, ergosterol biosynthesis inhibition, minimum growth-inhibitory concentration (MIC) and therapeutic effect for experimental dermatophytosis of guinea pigs. Among the newly synthesized compounds, the geranyl derivative named AFK-108 (2a) showed the highest in vivo fungicidal activity with both cell membrane damaging activity and ergosterol biosynthesis inhibition in vitro.

Animals↗
PubMed1997

Testicular histopathology in congenital lipoid adrenal hyperplasia: a light and electron microscopic study.

This paper describes the testicular histopathology in 2 male patients with congenital lipoid adrenal hyperplasia who underwent orchiectomy at age 7 (case 1) and 12 (case 2) years, respectively. In both cases, seminiferous tubules were normal in diameter (mean: case 1 88.7 microm; case 2 115.9 microm) and consisted of an age-appropriate number of type A spermatogonia (mean: case 1 1.7/tubule; case 2 4.0/tubule) and an increased number of Sertoli cells (mean: case 1 34.7/tubule; case 2 27.9/tubule). The interstitial space was abundant and contained normal to increased numbers of Leydig cells (mean: case 1 4.0/ tubule; case 2 6.1/tubule) that were filled with lipid droplets. We suspect that lipid accumulation in Leydig cells is consistent with defective conversion of cholesterol into pregnenolone and thus constitutes the characteristic feature of this disease, while the remaining findings appear to be common to disorders associated with hypergonadotropic hypogonadism.

Adrenal Hyperplasia, Congenital↗
PubMed1996

Delayed improvement in skeletal muscle metabolism and exercise capacity in patients with mitral stenosis following immediate hemodynamic amelioration by percutaneous transvenous mitral commissurotomy.

The abrupt improvement in hemodynamics after successful percutaneous transvenous mitral commissurotomy (PTMC) does not immediately enhance exercise capacity. Improved exercise capacity several months after PTMC has been reported. We hypothesized that the delayed improvement in exercise capacity is due partly to the slow improvement in the metabolism of skeletal muscle. This study examined the short- and long-term effects of PTMC on exercise capacity and skeletal muscle metabolism in patients with mitral stenosis. Treadmill exercise testing with respiratory gas analysis was performed in 11 patients with symptomatic mitral stenosis before and 3, 30, and 90 days after successful PTMC. On the same schedule, forearm metabolism of high-energy phosphates was measured by magnetic resonance spectroscopy during and after handgrip exercise. Ten healthy volunteers were examined. PTMC resulted in an immediate symptomatic improvement. However, exercise capacity and skeletal muscle metabolism remained unchanged 3 days after PTMC. At 30 days after PTMC, there were significant improvements in peak oxygen consumption (p <0.05), intracellular pH at end-exercise (p <0.05), and time constant for phosphocreatine recovery (mean +/- SD 88.9 +/- 11.3 vs 106.3 +/- 11.7 seconds, p <0.01) compared with these baseline values. These improvements remained even at 90 days after PTMC. Exercise capacity improved with some time delay after immediate hemodynamic amelioration by PTMC. Long-term improvement in exercise capacity depends partly on the slowly progressing improvement in skeletal muscle metabolism after long-standing mitral stenosis.

Adult↗
PubMed1994

[Relationship between insulin resistance and blood pressure].

A study designed to analyze the relationship between blood pressure and insulin resistance was conducted on 353 subjects who received medical health examinations, and who did not have obvious diabetes. Fasting plasma insulin (IRI), fasting plasma glucose (FPG), body mass index (BMI), waist hip ratio (WHR), body fat percentage, total cholesterol (TC), triglyceride, and urine sodium concentrations were measured or calculated. After analysis of the correlation's between each value, multiple regression analyses were performed. The results were as follows: 1) hypertensive subjects were significantly higher than non-hypertensives in with age, value of IRI, FPG, WHR, TC and BMI. 2) The values of IRI, WHR, and BMI were correlated each other. 3) After adjusted for age and sex by multiple regression analyses, IRI, WHR, and BMI were shown to have significant relationship to mean blood pressure. From this study, it is concluded that IRI is an indicator for insulin resistance and is related to blood pressure.

Adolescent↗
PubMed1993

[A case of bronchogenic cyst in the posterior mediastinum with high level of serum SCC antigen].

A 78-year-old man was picked up by chest X-ray findings. His CT scan film showed a posterior mediasinal tumor shadow. Serum level of SCC antigen was high and thoracotomy revealed bronchogenic cyst with high production of SCC antigen. After resection of the cyst, his serum level of SCC was within normal range. It is proposed that the elevated serum level of SCC is due to chronic inflammation or structural feature of the cystic wall.

Aged↗
PubMed1992

Inhibition by a novel azole antifungal agent with a geranyl group on lanosterol 14 alpha-demethylase of yeast.

AFK-108 (1-[2-(2,4-dichlorophenyl)-2-((2E)-3,7-dimethylocta-2,6- dienyloxy)ethyl]-1H-imidazole) is a new imidazole derivative characterized by a geranyl substituent showing strong antifungal activity. Azole antifungal agents are known to be potent inhibitors of lanosterol 14 alpha-demethylase (P450(14)DM) of fungi. The role of the geranyl group of AFK-108 on interaction of AFK-108 with the target was studied by using Saccharomyces cerevisiae P450(14)DM as the model enzyme. AFK-108 and some of its derivatives bound to oxidized P450(14)DM with one-to-one stoichiometry and inhibited the demethylase activity. AFK-108 derivatives having the longer farnesyl or the shorter prenyl group showed lower affinity than AFK-108 for the enzyme. AFK-108 caused 100% inhibition at the equivalent concentration to P450(14)DM in the reaction mixture (0.07 microM), while the farnesyl derivative inhibited the activity by 60% at the same concentration. AFK-108 interfered with the binding of CO to the ferrous P450(14)DM. However, the interfering effect of the prenyl derivative was lower than that of AFK-108. Another AFK-108 derivative having the saturated 3,7-dimethyloctyl group was also a weaker inhibitor than AFK-108. These experiments suggest that the geranyl group of AFK-108 interacts with the substrate binding site of P450(14)DM that recognises the side chain of the substrate. AFK-108 is the first example of an azole derivative interacting with the side chain recognising region of the substrate binding site of P450(14)DM.

Antifungal Agents↗