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Biomedical subjects

M Doi

Publications and source records attributed to M Doi.

At least 19 recordsLinked to original sources
PubMed2006

Modeling on debonding dynamics of pressure-sensitive adhesives.

We propose a simple mechanical model describing viscoelasticity and cavitation during the debonding process in pressure-sensitive adhesives (PSA). Our calculation qualitatively reproduces typical stress-strain curves in the probe-tack test, such as the steep stress maxima and the following plateau region. It is shown that in the thin-film geometry the stress-strain curve is essentially determined by the cavities created by the large negative pressure. Effects of pre-existent air bubbles due to surface roughness are also discussed.

Adhesiveness↗
PubMed2005

Structure and property of self-assemble valinyl bolaform amides having different chirality.

Bolaform amides were designed from N,N'-bis(carboethoxy-L-valinyl)-diaminoethane (1) by linking t-butyloxycarbonyl-valine through ethylenediamine (EDA) to enable spectroscopic and X-ray diffraction analyses. N,N'-Bis(Boc-L-valinyl)-diaminoethane (2) and N,N'-bis(Boc-D-valinyl)-diaminoethane (3) were composed of L-Val and D-Val, respectively. N-(Boc-L-valinyl)-N'-(Boc-D-valinyl)-diaminoethane (4) was composed of both L-Val and D-Val, and was achiral (meso-peptide). Peptide 5 was a 1:1 mixture of 2 and 3, and was also achiral (racemate). These peptides mediated gelation of corn oil at a concentration of approximately 1%. Within crystals, the peptides formed beta-sheet ribbons, but differences were observed in hydrogen-bonding patterns and side-chain arrangements. These differences were also deduced from temperature dependence of amide protons. Force-field calculations based on the crystal structures indicated that association of beta-sheet ribbons had energy benefits, and it was assumed that molecular aggregation progressed spontaneously. These structural studies indicated the chirality of amino acids affected for the properties of bolaform amides.

Amides↗
PubMed2004

A case study of radon-222 transport from continental North-East Asia to the Japanese islands in winter by numerical analysis.

A case study of the regional transport ( approximately 3000 km) of radon-222 ((222)Rn) from continental North-East Asia to the Japanese islands was performed by numerical analysis using five separate source areas (South, Middle and North China, Russia and Korea), while a seasonal northwest wind blew over the Japan Sea. The results for three periods (Term I: 16-18, Term II: 22-25 and Term III: 27-28 in December 1990) were compared with concentrations measured at the Kanazawa site (near the coast of the Japan Sea facing the seasonal wind) and the Nagoya site (overland and downwind on the shores of the Pacific Ocean). Most of the (222)Rn at the Kanazawa site was calculated to come from North China and Korea in Term I, Middle China, North China, and Korea in Term II, and Russia and Korea in Term III. The considerable differences in the origins of (222)Rn emanated from the continent were estimated between Terms I, II and III, even though the similar northwest wind was dominant over the Japan Sea. A contour line analysis indicated movement of (222)Rn emanated from Middle China in a northerly direction first and then a southeasterly direction, resulting from low pressure. The results suggest that the low-pressure systems play an important role in the transport of (222)Rn in North-East Asia.

Air Movements↗
PubMed2004

Recurrent isolation of an uncommon yeast, Candida pararugosa, from a sarcoma patient.

A yeast was repeatedly isolated from the saliva of a sarcoma patient. A relatively uncommon species, Candida maris, was identified based on the API 20C profile. The yeast species most frequently obtained from the patient's mother and from clinic staff was Candida albicans. A comparison of the yeast obtained from the patient with the type strain of C. maris strongly suggested that the former was not representative of C. maris. Analysis of partial ribosomal DNA sequences of the patient strain and from the type strain of C. maris showed that the two are phylogenetically not closely related. The patient strain was very close to Candida pararugosa, a relatively uncommon asporogenous yeast. DNA reassociation studies among C. pararugosa and patient isolates showed that they were conspecific. We could not determine the source of the yeast infection. This case will alert hospital staff to be aware of the possibility of unexpected environmental microorganisms as causes of infections, colonizations and persistent environmental contamination events in immunocompromised patients.

Animals↗
PubMed2002

Effects of gamma-ray and high energy carbon ion irradiation on swimming velocity of Euglena gracilis.

The effects of gamma-ray and high energy carbon ion irradiation on the swimming velocity of the photosynthetic flagellate Euglena gracilis strain Z were studied, focusing on a dose-effect relationship. Cells were exposed to 60Co gamma-rays at 6 doses of 10, 15, 20, 40, 100 and 200 Gy for water, and also to 290 MeV/amu carbon ions from the Heavy Ion Medical Accelerator in Chiba at 7 doses (5, 10, 15, 20, 50, 100 and 200 Gy for water). The swimming velocity was measured by a biomonitoring system, called ECOTOX. The swimming velocities of Euglena gracilis cells were significantly decreased by >40 Gy gamma-rays and >5 Gy carbon ions, respectively. The 50% effective doses for inhibition, 34 +/- 4 Gy (gamma-rays) and 13 +/- 1 Gy (290 MeV/amu carbon ions), were estimated from the best fit to data of the logistic model. The relative biological effectiveness (2.6 +/- 0.4) was calculated by the ratio of 50% effective doses. The inhibition of the swimming velocity of the cells irradiated with gamma-rays was still present after 3 days, while recovery of the swimming velocity was shown in the cells exposed to 290 MeV/amu carbon ions. It is suggested that ionizing radiation inhibits ATP production and/or increases frictional drag on beating of the flagellum, thus decreasing swimming velocity.

Adenosine Triphosphate↗
PubMed2002

Effect of asymmetric modification on the conformation of ascidiacyclamide analogs.

Ascidiacyclamide (ASC), cyclo(-Ile1-Oxz2-d-Val3-Thz4-)2 (Oxz=oxazoline and Thz=thiazole) has a C2-symmetric sequence, and the relationships between its conformation and symmetry have been studied. In a previous study, we performed asymmetric modifications in which an Ile residue was replaced by Gly, Leu or Phe to disturb the symmetry [Doi et al. (1999) Biopolymers49, 459-469]. In this study, the modifications were extended. The Ile1 residue was replaced by Gly, Ala, aminoisobutyric acid (Aib), Val, Leu, Phe or d-Ile, and the d-Val3 residue was replaced by Val. The structures of these analogs were analyzed by X-ray diffraction, 1H NMR and CD techniques. X-Ray diffraction analyses revealed that the [Ala1], [Aib1] and [Phe1]ASC analogs are folded, whereas [Val1]ASC has a square form. These structures are the first examples of folded structures for ASC analogs in the crystal state and are similar to the previously reported structures of [Gly1] and [Phe1]ASC in solution. The resonances of amide NH and Thz CH protons linearly shift with temperature changes; in particular, those of [Aib1], [d-Ile1] and [Val3]ASCs exhibited a large temperature dependence. DMSO titration caused nonlinear shifts of proton resonances for all analogs and largely affected [d-Ile1] and [Val3]ASCs. A similar tendency was observed upon the addition of acetone to peptide solutions. Regarding peptide concentration changes, amide NH and Thz CH protons of [Gly1]ASC showed a relatively large dependence. CD spectra of these analogs indicated approximately two patterns in MeCN solution, which were related to the crystal structures. However, all spectra showed a similar positive Cotton effect in TFE solution, except that of [Val3]ASC. In the cytotoxicity test using P388 cells, [Val1]ASC exhibited the strongest activity, whereas the epimers of ASC ([d-Ile1] and [Val3]ASCs), showed fairly moderate activities.

Amino Acid Substitution↗
PubMed2002

High-energy carbon ion irradiation and the inhibition of negative gravitaxis in Euglena gracilis Z.

PURPOSE: To study the effects of high-energy carbon ion irradiation on negative gravitaxis in the photosynthetic flagellate Euglena gracilis strain Z in a dose-response-dependent manner. MATERIALS AND METHODS: Cells were exposed to 290 MeV amu(-1) carbon ion from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at 12 doses (0, 1, 5, 7.5, 10, 15, 20, 50, 75, 100, 150, 200 Gy for water). r was used to quantify negative gravitaxis observed in a recently developed biomonitoring system. RESULTS: Negative gravitaxis of Euglena was significantly affected by irradiation at a dose >7.5 Gy, 28 h after irradiation. Negative gravitaxis recovered after a few days. The rising phase of r during the first 30 s of orientation was independent of irradiation dose. The recovery mechanism itself was damaged by 290 MeV amu(-1) carbon ions at a dose >50 Gy. CONCLUSIONS: The results indicate that negative gravitaxis in Euglena may be affected by the radiation experienced during a space experiment especially during the occurrence of solar flares. The analyses of time needed to reorient to the gravitational vector suggest that the steering control of the flagellar apparatus is affected by exposure to the 290 MeV amu(-1) carbon ion irradiation, resulting in an altered beating pattern of a flagellum and/or changes of the cell form during reorientation.

Animals↗
PubMed2002

Association of beta-fibrinogen and factor VII polymorphism with plasma fibrinogen and factor VII levels, and no association of PAI-1 polymorphism with plasma PAI-1 levels in hemodialysis patients.

AIMS: Recent studies have stressed the roles of genetic factors on the plasma levels of hemostatic markers and on cardiovascular complications. We investigated the association of DNA polymorphisms for beta-fibrinogen, factor VII, and PAI-1 with plasma levels of these factors and with ischemic heart disease (IHD) and cerebral infarction (CI) in patients undergoing hemodialysis (HD). METHODS: beta-fibrinogen G/A-455, factor VII R353Q and PAI-1 4G/5G polymorphisms were determined by PCR-RFLP in 149 HD patients and in 100 controls. The plasma levels of fibrinogen, factor VII and PAI-1 were also measured. RESULTS: The allele frequencies and the genotype frequencies of these 3 polymorphisms were not different between HD patients and controls. In HD patients, plasma fibrinogen levels were significantly lower in the GG genotype than in the GA genotype, and plasma factor VII activity was significantly higher in the RR genotype than in the RQ genotype. Multiple regression analysis disclosed that CRP and beta-fibrinogen polymorphism were the significant determinants of fibrinogen levels. Plasma PAI-1 levels were not different among the 3 genotypes. The frequency of the A-455 allele was significantly higher in HD patients with CI than in those without CI, and the genotype distribution for beta-fibrinogen differed significantly between the 2 groups. Between the same 2 groups, however, significant differences were found neither in the frequency of the 353Q or 4G allele nor in the genotype distribution for factor VII and PAI-1. No significant differences in the frequency of the G-455, 353Q or 4G alleles, or in the genotype distribution for beta-fibrinogen, factor VII and PAI-1 were observed between patients with IHD and those without IHD. Multiple logistic regression analysis demonstrated that neither polymorphism was associated with CI or IHD. CONCLUSIONS: In HD patients, beta-fibrinogen and factor VII polymorphisms affected plasma levels of fibrinogen and factor VII, respectively. Beta-fibrinogen polymorphism was not an independent but a possible risk factor for CI in HD patients. Further study will be needed to confirm the precise role of 5-fibrinogen polymorphisms in the pathogenesis of CI in HD patients.

Adult↗
PubMed2002

Gamma-irradiation effect: variation of photosynthetic activity of Euglena.

OBJECTIVE: To study the effects of gamma-ray irradiation on carbon fixation (Specific production rate: SPR), CO2 utilization efficiency (CUE) and electron transfer rate (ETR) in the photosynthetic flagellate Euglena gracilis strain Z in a dose-response dependent manner. METHODS: Euglena cells were cultured in an inorganic nutrient medium containing ammonium chloride or proteose peptone. Cells were exposed to gamma-ray at 5 doses (0, 100, 250, 350, 500 Gy for water). Five days after irradiation, three photosynthetic activities were measured. SPR, which is a carbon uptake rate per unit carbon mass, was determined by 13C tracer methodology. CUE was evaluated using a relation of carbon isotope fractionation in Calvin cycle. ETR in photosystem II (PS II) was measured by a chlorophyll fluorescence analysis. RESULTS: Even at a dose of 500 Gy, 80% of ETR of the non-irradiated control (0 Gy) was sustained, while SPR and CUE were about half the level in the non-irradiated control at 500 Gy. Furthermore, the dose response of ETR was considerably different from the others. CONCLUSION: Our findings suggest that not only PS II but also the Calvin cycle in the photosynthetic system is affected by gamma ray irradiation.

Animals↗
PubMed2001

Phot1 and phot2 mediate blue light regulation of stomatal opening.

The stomatal pores of higher plants allow for gaseous exchange into and out of leaves. Situated in the epidermis, they are surrounded by a pair of guard cells which control their opening in response to many environmental stimuli, including blue light. Opening of the pores is mediated by K(+) accumulation in guard cells through a K(+) channel and driven by an inside-negative electrical potential. Blue light causes phosphorylation and activation of the plasma membrane H(+)-ATPase that creates this potential. Thus far, no blue light receptor mediating stomatal opening has been identified, although the carotenoid, zeaxanthin, has been proposed. Arabidopsis mutants deficient in specific blue-light-mediated responses have identified four blue light receptors, cryptochrome 1 (cry1), cryptochrome 2 (cry2), phot1 and phot2. Here we show that in a double mutant of phot1 and phot2 stomata do not respond to blue light although single mutants are phenotypically normal. These results demonstrate that phot1 and phot2 act redundantly as blue light receptors mediating stomatal opening.

Arabidopsis↗
PubMed2001

KNI-272, a highly selective and potent peptidic HIV protease inhibitor.

Kynostatin [KNI-272; systematic name: 3-[3-benzyl-2-hydroxy-9-(isoquinolin-5-yloxy)-6-methylsulfanylmethyl-5,8-dioxo-4,7-diazanonanoyl]-N-tert-butyl-1,3-thiazolane-4-carboxamide], a highly selective and potent HIV protease inhibitor containing allophenylnorstatin [(2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], has been crystallized as the hydrate, C(33)H(41)N(5)O(6)S(2) x 0.803H(2)O, from aqueous hexylene glycol. The observed disorder of the phenyl group in the structure is related to the mode of hydration. The backbone conformation of the molecule is twisted and the overall conformation of the free inhibitor is similar to that observed in its complex with HIV protease.

Crystallography, X-Ray↗
PubMed2001

Antiparallel pleated beta-sheets observed in crystal structures of N,N-bis(trichloroacetyl) and N,N-bis(m-bromobenzoyl) gramicidin S.

Despite intensive efforts, the structures of gramicidin S (GS) [cyclo(-Val-Orn-Leu-d-Phe-Pro-)(2)] and its analogues have not been elucidated by the X-ray diffraction method, except for the GS-urea complex (Hull et al., Nature 275, 206-207, 1978; Tishchenko et al., Acta Cryst. D53, 151-159, 1997). We focused on the acetylation of GS to obtain suitable crystals for X-ray diffraction. The amino groups of Orn residues were capped with trichloroacetic and m-bromobenzoic acids. Both trichloroacetyl and m-bromobenzoyl GSs (TcGS and BzGS, respectively) are hydrophobic and their properties are similar to those of acetyl-GS (AcGS). Although it is well known that AcGS yields hexagonal crystals, TcGS and BzGS yield monoclinic and orthorhombic crystals in aqueous dimethylformamide solution, respectively. Their cell volumes were approximately one-fourth or one-eighth of the hexagonal cell volume. The crystal structures of TcGS and BzGS were determined as the first examples of acetylated GS analogues: TcGS, C(64)H(90)N(12)O(12)Cl(6). 3(C(3)H(7)NO), M(r) = 1651.47, monoclinic, P2(1), a = 15.4366(6) A, b = 18.5312(4) A, c = 16.4774(6) A, beta = 14.160(2) degrees, V = 4300.6(2) A(3), Z = 2; and BzGS, C(64)H(98)N(12)O(12)Br(2). 1.54(H(2)O), M(r) = 1535.21, orthorhombic, P2(1)2(1)2(1), a = 16.748(10) A, b = 18.834(5) A, c = 28.558(10) A, V = 9008(7) A(3), Z = 4. Both these peptide molecules formed an antiparallel pleated beta-sheet, and pseudo twofold symmetries existed in the repeated sequence. beta-Turns formed at the fragments of d-Phe-Pro were classified into type II' based on their characteristics. The peptide conformations of TcGS and BzGS were similar to each other, and these structural features agreed with those of structures proposed by the previous studies.

Bromobenzoates↗
PubMed2001

Deviations from dynamic dilution in the terminal relaxation of star polymers.

We present a "slip-link" model for relaxation of entangled star polymers that accounts for chain-end fluctuations and constraint release and that explains deviations from the "dynamic dilution" equation observed in recent dielectric and stress relaxation data. In the terminal regime where tube expansion fails to keep up with chain relaxation, relaxation is controlled by rare events in which newly created entanglements near the branch point draw the chain end towards the last remaining old entanglement, where a shallow fluctuation releases it.

Journal Article↗
PubMed2001

Light-induced phase-delay of the chicken pineal circadian clock is associated with the induction of cE4bp4, a potential transcriptional repressor of cPer2 gene.

The chicken pineal gland contains the autonomous circadian oscillator together with the photic-input pathway. We searched for chicken pineal genes that are induced by light in a time-of-day-dependent manner, and isolated chicken homolog of bZIP transcription factor E4bp4 (cE4bp4) showing high similarity to vrille, one of the Drosophila clock genes. cE4bp4 was expressed rhythmically in the pineal gland with a peak at very early (subjective) night under both 12-h light/12-h dark cycle and constant dark conditions, and the phase was nearly opposite to the expression rhythm of cPer2, a chicken pineal clock gene. Luciferase reporter gene assays showed that cE4BP4 represses cPer2 promoter through a E4BP4-recognition sequence present in the 5'-flanking region, indicating that cE4BP4 can down-regulate the chick pineal cPer2 expression. In vivo light-perturbation studies showed that the prolongation of the light period to early subjective night maintained the high level expression of the pineal cE4bp4, and presumably as a consequence delayed the onset of the induction of the pineal cPer2 expression in the next morning. These light-dependent changes in the mRNA levels of the pineal cE4bp4 and cPer2 were followed by a phase-delay of the subsequent cycles of cE4bp4/cPer2 expression, suggesting that cE4BP4 plays an important role in the phase-delaying process as a light-dependent suppressor of cPer2 gene.

Amino Acid Sequence↗
PubMed2001

A locus for female discrimination behavior causing sexual isolation in Drosophila.

The genetic basis of sexual isolation that contributes to speciation is one of the unsolved questions in evolutionary biology. Drosophila ananassae and Drosophila pallidosa are closely related, and postmating isolation has not developed between them. However, females of both species discriminate their mating partners, and this discrimination contributes to strong sexual isolation between them. By using surgical treatments, we demonstrate that male courtship songs play a dominant role in female mate discrimination. The absence of the song of D. pallidosa dramatically increased interspecies mating with D. ananassae females but reduced intraspecies mating with D. pallidosa females. Furthermore, genetic analysis and chromosomal introgression by repeated backcrosses to D. pallidosa males identified possible loci that control female discrimination in each species. These loci were mapped on distinct positions near the Delta locus on the middle of the left arm of the second chromosome. Because the mate discrimination we studied is well developed and is the only known mechanism that prevents gene flow between them, these loci may have played crucial roles in the evolution of reproductive isolation, and therefore, in the speciation process between these two species.

Animals↗
PubMed2001

A new ray-tracing program RIGTRACE for X-ray optical systems.

A new ray-tracing simulation program, RIGTRACE, has been developed specifically for the X-ray optics range. It traces consecutively each ray, following its path from the source to the observation plane, and treats diffraction by a monochromator crystal by adopting the Darwin-Prins theory so that it may be seen how rays of slightly different energies and incident angles reach the plane. It is also possible to treat the case of the laboratory system, in which the optical elements are disposed close to each other. Examples of the application are provided.

Journal Article↗
PubMed2001

Caged and clustered structures of endothelin inhibitor BQ123, cyclo(-D-Trp-D-Asp--Pro-D-Val-Leu-)-Na+, forming five and six coordination bonds between sodium ions and peptides.

BQ123 is a cyclic pentapeptide and a potent endothelin-1 inhibitor. The crystal structure of the BQ123 sodium salt was determined as the first example of an endothelin inhibitor. Four independent molecules and many solvent molecules were found in the asymmetric unit; the total weight was about 3000 Da. The precise structure including the solvent molecules was determined using high-resolution data collected on a synchrotron source. Sodium ions formed unique structures with five and six coordination bonds and their forms were distinguished into three classes. An ion was sandwiched by two BQ123 molecules. This peptide-sodium (2:1) complex showed a cage-like structure and octahedral coordination was observed. Sodium ions also formed a cluster composed of hydrated water molecules and peptides. Two sodium ions were contained in this cluster, making five coordination bonds. Despite having the same coordination numbers, these ions were distinguishable by differences in the polyhedra. One was trigonal bipyramidal (having six planes) and the other was square pyramidal (having five planes). Both shapes were very similar to each other, although the synchrotron data clearly revealed slight geometrical differences.

Endothelin Receptor Antagonists↗