PubMed Health⌕ Search

Biomedical subjects

Hiroshi Maeda

Publications and source records attributed to Hiroshi Maeda.

At least 19 recordsLinked to original sources
PubMed2006

High-loading nanosized micelles of copoly(styrene-maleic acid)-zinc protoporphyrin for targeted delivery of a potent heme oxygenase inhibitor.

Amphiphilic styrene-maleic acid (SMA) copolymer efficiently formed micelles with a potent heme oxygenase inhibitor-zinc protoporphyrin (ZnPP). The micelles were constructed by subtle pH adjustments to form non-covalent interaction between the hydrophobic ZnPP and amphiphilic SMA. The micelles (SMA-ZnPP) thus formed were nanoparticles with narrow size distribution in water (mean diameter 176.5nm), having tunable loading (from 15% to 60% w/w of ZnPP) with remarkable aqueous solubility. SMA-ZnPP had an average molecular size of 144kDa as determined by size-exclusion chromatography (SEC), this size is a marked increase from the molecular weight of free ZnPP (626.03Da), suggesting the formation of micellar structure. The micelles showed a constant ZnPP release rate of about 0.5%/day in vitro at neutral pH. SMA-ZnPP micelles inhibited splenic microsomal HO-1 activity, in a competitive and dose-dependent manner, with an apparent inhibitory constant (K(i)) of 0.12mum, comparable to free ZnPP and also exhibited marked cytotoxic effect on KYSE-510 human esophageal cancer cells. The unique features of SMA-ZnPP micelles are that they are nanoparticles in aqueous solution having high water solubility and loading, yet macromolecular in nature, which can be beneficial in targeted release of a potent HO-1 inhibitor.

Biocompatible Materials↗
PubMed2006

Tocopherols play a crucial role in low-temperature adaptation and Phloem loading in Arabidopsis.

To test whether tocopherols (vitamin E) are essential in the protection against oxidative stress in plants, a series of Arabidopsis thaliana vitamin E (vte) biosynthetic mutants that accumulate different types and levels of tocopherols and pathway intermediates were analyzed under abiotic stress. Surprisingly subtle differences were observed between the tocopherol-deficient vte2 mutant and the wild type during high-light, salinity, and drought stresses. However, vte2, and to a lesser extent vte1, exhibited dramatic phenotypes under low temperature (i.e., increased anthocyanin levels and reduced growth and seed production). That these changes were independent of light level and occurred in the absence of photoinhibition or lipid peroxidation suggests that the mechanisms involved are independent of tocopherol functions in photoprotection. Compared with the wild type, vte1 and vte2 had reduced rates of photoassimilate export as early as 6 h into low-temperature treatment, increased soluble sugar levels by 60 h, and increased starch and reduced photosynthetic electron transport rate by 14 d. The rapid reduction in photoassimilate export in vte2 coincides with callose deposition exclusively in phloem parenchyma transfer cell walls adjacent to the companion cell/sieve element complex. Together, these results indicate that tocopherols have a more limited role in photoprotection than previously assumed but play crucial roles in low-temperature adaptation and phloem loading.

Adaptation, Physiological↗
PubMed2006

Hydrophobic interactions between the secondary structures on the molecular surface reinforce the alkaline stability of serine protease.

We employed random mutagenesis to determine the region of the initial unfolding of hyper-alkaline-sensitive subtilisin, ALP I, that precedes the denaturation of the entire protein under highly alkaline conditions. This region comprises two alpha-helices and a calcium-binding loop. Stabilization of the region caused the stabilization of the entire protein at a high alkaline pH 12. The alkaline stability of this region was most effectively improved by hydrophobic interactions, followed by ionic interactions with Arg residues. The effect of mutations on the improvement was different with regard to the alkaline stability and thermostability. This indicated that different strategies were necessary to improve the alkaline stability and thermostability of the protein.

Enzyme Stability↗
PubMed2006

Reversible micelle-vesicle conversion of oleyldimethylamine oxide by pH changes.

A preliminary study on the reversible micelle-vesicle conversion of oleyldimethylamine oxide [Kawasaki, H. et al. J. Phys. Chem. B. 2002, 106, 1524 ] is extended in the present study. In the presence of 0.01 M NaCl at a surfactant concentration of 0.05 M, a micelle-to-vesicle conversion with increasing degree of ionization alpha takes place in the following sequence: growth of fibrous micelle (alpha < 0.2), a fused network (alpha approximately 0.3), fibrous micelles + (perforated) vesicles (alpha = 0.4), and vesicles + lamellae (alpha = 0.5). Viscoelasticity correspondingly varies from the Maxwell-type behavior of the entangled network of fibrous micelles to the gel-like behavior of vesicle suspensions, via a fluid solution-like behavior of the fused network. This phase sequence is in contrast with the case of no added salt where no branching of micelles is observed, and long micelles and bilayers (vesicles + lamellae) coexist at alpha = 0.5. In water, a state of the lowest viscoelasticity occurs around alpha = 0.2 for both surfactant concentrations 0.05 and 0.15 M. Synergism between protonated and nonprotonated amine oxide headgroups is observed despite low ionic strengths. From the time course of the reversible micelle-vesicle conversion, vesicles seem to be formed from threadlike micelles within 25 h according to the shear moduli, while a longer conversion time is suggested by a flow property (viscosity). Shear thickening behavior is observed at alpha = 0.2 and 0.4 in 0.01 M NaCl but not in water.

Journal Article↗
PubMed2006

Charge-induced unilamellar vesicle formation and phase separation in solutions of Di-n-decylmethylamine oxide.

A double-tail amine oxide surfactant, di-n-decylmethylamine oxide (2C10MAO), was prepared, and the effects of protonation on aggregate structure were examined by small-angle neutron scattering (SANS), cryo-transmission electron microscopy (cryo-TEM), turbidity, electric conductivity, and solubilization of an oil-soluble dye at various degrees of neutralization, X, defined as the mole ratio of HCl/2C10MAO. The surfactant makes an L(2) phase in the nonprotonated state (X = 0) in water. The L(2) phase is in equilibrium with an aqueous L(1) phase. On protonation, unilamellar vesicles (ULVs) are formed over a wide range of compositions (0.05 < X< 0.4-0.5 at C = 10 mM) as observed by cryo-TEM. At X = 0.2, the ULV is stable over a wide concentration range (3 mM < or = C < 0.1 M), but an L(alpha) phase replaces the vesicle phase at C > 0.1 M. SANS results show that the mean radius of the ULV is about 25 nm and the bilayer thickness is about 2 nm, consistent with the extended configuration of the alkyl chains of the surfactant. An important contribution to the enhanced stability of the bilayer structures over the L(2) phase is suggested to be the translational entropy of the counterions. The enhanced stability of the bilayers diminishes as the counterion concentration increases either by an increase of X or by the addition of a salt. When the counterion concentration exceeds a critical value, the ULV solutions transform into the L(2) phase (or L(2)/L(1) two-phase system at low surfactant concentrations). The critical composition X is about 0.4-0.5 in water, but it is below 0.4 in D(2)O. The critical NaCl concentration is below 5 mM at X = 0.2. The stability of ULVs against multilamellar vesicles is ascribed partly to undulation forces and partly to the adjustable nature of the spontaneous curvature of amine oxide monolayers. The characteristics of the ULV of the surfactant remain the same within a temperature range 25-50 degrees C at X = 0.2. An iridescent lamellar phase and possibly an L(3) phase were observed in a very narrow X range (0 < X < 0.02) prior to the vesicle phase.

Cryoelectron Microscopy↗
PubMed2006

alpha-Tocopherol plays a role in photosynthesis and macronutrient homeostasis of the cyanobacterium Synechocystis sp. PCC 6803 that is independent of its antioxidant function.

alpha-Tocopherol is synthesized exclusively in oxygenic phototrophs and is known to function as a lipid-soluble antioxidant. Here, we report that alpha-tocopherol also has a novel function independent of its antioxidant properties in the cyanobacterium Synechocystis sp. PCC 6803. The photoautotrophic growth rates of wild type and mutants impaired in alpha-tocopherol biosynthesis are identical, but the mutants exhibit elevated photosynthetic activities and glycogen levels. When grown photomixotrophically with glucose (Glc), however, these mutants cease growth within 24 h and exhibit a global macronutrient starvation response associated with nitrogen, sulfur, and carbon, as shown by decreased phycobiliprotein content (35% of the wild-type level) and accumulation of the nblA1-nblA2, sbpA, sigB, sigE, and sigH transcripts. Photosystem II activity and carboxysome synthesis are lost in the tocopherol mutants within 24 h of photomixotrophic growth, and the abundance of carboxysome gene (rbcL, ccmK1, ccmL) and ndhF4 transcripts decreases to undetectable levels. These results suggest that alpha-tocopherol plays an important role in optimizing photosynthetic activity and macronutrient homeostasis in Synechocystis sp. PCC 6803. Several lines of evidence indicate that increased oxidative stress in the tocopherol mutants is unlikely to be the underlying cause of photosystem II inactivation and Glc-induced lethality. Interestingly, insertional inactivation of the pmgA gene, which encodes a putative serine-threonine kinase similar to RsbW and RsbT in Bacillus subtilis, results in a similar increase in glycogen and Glc-induced lethality. Based on these results, we propose that alpha-tocopherol plays a nonantioxidant regulatory role in photosynthesis and macronutrient homeostasis through a signal transduction pathway that also involves PmgA.

Antioxidants↗
PubMed2006

Exploiting the enhanced permeability and retention effect for tumor targeting.

Of the tumor targeting strategies, the enhanced permeability and retention (EPR) effect of macromolecules is a key mechanism for solid tumor targeting, and considered a gold standard for novel drug design. In this review, we discuss various endogenous factors that can positively impact the EPR effect in tumor tissues. Further, we discuss ways to augment the EPR effect by use of exogenous agents, as well as practical methods available in the clinical setting. Some innovative examples developed by researchers to combat cancer by the EPR mechanism are also discussed.

Animals↗
PubMed2006

Novel hydrophobic surface binding protein, HsbA, produced by Aspergillus oryzae.

Hydrophobic surface binding protein A (HsbA) is a secreted protein (14.5 kDa) isolated from the culture broth of Aspergillus oryzae RIB40 grown in a medium containing polybutylene succinate-co-adipate (PBSA) as a sole carbon source. We purified HsbA from the culture broth and determined its N-terminal amino acid sequence. We found a DNA sequence encoding a protein whose N terminus matched that of purified HsbA in the A. ozyzae genomic sequence. We cloned the hsbA genomic DNA and cDNA from A. oryzae and constructed a recombinant A. oryzae strain highly expressing hsbA. Orthologues of HsbA were present in animal pathogenic and entomopathogenic fungi. Heterologously synthesized HsbA was purified and biochemically characterized. Although the HsbA amino acid sequence suggests that HsbA may be hydrophilic, HsbA adsorbed to hydrophobic PBSA surfaces in the presence of NaCl or CaCl(2). When HsbA was adsorbed on the hydrophobic PBSA surfaces, it promoted PBSA degradation via the CutL1 polyesterase. CutL1 interacts directly with HsbA attached to the hydrophobic QCM electrode surface. These results suggest that when HsbA is adsorbed onto the PBSA surface, it recruits CutL1, and that when CutL1 is accumulated on the PBSA surface, it stimulates PBSA degradation. We previously reported that when the A. oryzae hydrophobin RolA is bound to PBSA surfaces, it too specifically recruits CutL1. Since HsbA is not a hydrophobin, A. oryzae may use several types of proteins to recruit lytic enzymes to the surface of hydrophobic solid materials and promote their degradation.

Adipates↗
PubMed2006

Combined effects of benidipine and diltiazem on cardiohemodynamics in anesthetized dogs.

We examined the combined effects of the calcium channel blockers 1,4-dihydropyridine (benidipine) and benzothiazepine (diltiazem) on cardiohemodynamics in anesthetized dogs. Benidipine (3 microg/kg) lowered blood pressure (BP) slightly and continuously increased coronary flow (CF). Diltiazem (300, 1000 microg/kg) decreased BP, heart rate (HR), and the maximum rate of rise of left ventricular pressure (LV dP/dt max) with the increase of doses. Diltiazem increased CF, though it was transient when compared to benidipine. A combination of benidipine (3 microg/kg) and diltiazem (300 microg/kg) showed continuous decreases in BP, HR, and LV dP/dt max, and an increase in CF that was similar to that recorded for the benidipine group. The level of double product (DP: systolic BPxHR, an index of myocardium energy consumption) in the combination group was significantly lower than that of the benidipine group. The plasma concentrations of benidipine and diltiazem in the combination group were similar to those of the groups receiving either drug. These results demonstrate that the combination of benidipine and diltiazem increases CF more continuously than diltiazem alone, and decreases DP more potently than benidipine alone, indicating that the combination therapy possesses favorable properties as a treatment for angina pectoris. Therefore, the combination of benidipine and diltiazem is suggested as a useful treatment for improving the clinical benefits of monotherapy for angina, compared with the use of diltiazem alone at higher doses.

Anesthesia↗
PubMed2006

Peak C-reactive protein concentration correlates with left ventricular thrombus formation diagnosed by contrast echocardiographic left ventricular opacification in patients with a first anterior acute myocardial infarction.

BACKGROUND: Wall motion abnormality in the apical legion of the left ventricle (LV) with stagnant flow alone is not sufficient to identify patients at high risk for LV thrombus formation among those with first anterior acute myocardial infarction (AMI). The aim of this study was to identify the determinants of LV thrombus formation using contrast echocardiography. METHODS AND RESULTS: In 75 patients with first anterior AMI, standard and contrast echocardiography was performed to detect LV thrombus. Although LV thrombus was found in 10 patients (13%) using standard echocardiography, it was found in 15 patients (20%) using contrast echocardiography. Apical stagnant flow was observed in 14 patients (93%) with LV thrombus. In addition, patients with LV thrombus had a higher peak C-reactive protein (CRP) concentration (18.2+/-4.3 vs 7.9+/-5.5 mg/dl, p<0.0001). In multivariate analysis, only peak CRP concentration was identified as an independent predictor of LV thrombus (p=0.02, odds ratio: 1.400, confidence interval: 1.040-1.884). The receiver-operating characteristics (ROC) analysis revealed the best cutoff value of a peak CRP concentration >10.7 mg/dl to identify patients with LV thrombus (sensivity 0.93, specificity 0.75, area under ROC curve 0.91). CONCLUSIONS: The peak CRP concentration is a useful marker of patients with first anterior AMI who are at high risk for LV thrombus.

Aged↗
PubMed2006

Echolucent carotid plaques as a feature in patients with acute coronary syndrome.

BACKGROUND: Carotid arterial ultrasound examination may be helpful for screening populations at high risk for acute coronary syndrome (ACS), so the present study was designed to identify the carotid arterial characteristics of patients with ACS. METHODS AND RESULTS: Carotid ultrasound examinations were performed in 172 patients with ACS, 166 patients with stable coronary artery disease (CAD), and 96 control subjects. Common carotid arterial structures were assessed by the intima - media thickness (IMT), interadventitial diameter (IAD), lumen diameter (LD), the IMT to LD ratio (IMT/LD), and the plaque burden based on the plaque score. Plaque morphology was assessed by the echogenecity based on the gray-scale median (GSM). IMT, IAD, IMT/LD, and plaque score did not differ between the ACS and stable CAD groups. The GSM in the ACS group was lower (47.5+/-25.3, p<0.001) than in the control (70.1+/-22.5) and stable CAD (73.7+/-23.4) groups. Multiple logistic regression analysis showed that the presence of carotid echolucent plaques (GSM <or=60) was an independent predictor of ACS. CONCLUSIONS: Echolucent carotid plaques were strongly associated with ACS and may be a surrogate marker of high-risk patients.

Aged↗
PubMed2006

[An evaluation of teaching objectives for seminars and clerkship of social medicine in medical schools in Japan].

OBJECTIVES: The purpose of this study was to evaluate the curriculum of seminars and clerkship for social medicine in medical schools in Japan, with special reference to teaching objectives. METHODS: A survey was conducted in December, 2002 by sending questionnaires to all the member departments of the Conference for Hygiene and Public Health Teaching in Medical Schools in Japan. Teaching objectives for seminars and clerkship of social medicine stated in their curricula were analyzed by frequencies of key words related to learner's "Knowledge, Attitude, and Behavior". Also, five professors of public health independently rated the stated teaching objectives using nine evaluation criteria divided into three levels and mean ratings were obtained. RESULTS: Although 80% of the schools described their General Instructional Objectives (GIOs), only 63% of the universities stated Specific Behavioral Objectives (SBOs). Evaluation of the contents of the descriptions revealed that, although many courses described the GIOs with the student as subjective, only a small number of courses mentioned "Attitude and Behavior" in SBO. Also, many courses did not make any apparent distinction between GIOs and SBOs. CONCLUSIONS: Practical training is a crucial component in medical education and seminars and clerkship play an important role in teaching social medicine to medical students. However, the present study revealed that many medical schools in Japan do not have adequately defined teaching objectives. Improvement of the curricula in courses of social medicine is required with particular reference to specific behavioral objectives and goals for seminars and clerkship.

Clinical Clerkship↗
PubMed2005

Genome sequencing and analysis of Aspergillus oryzae.

The genome of Aspergillus oryzae, a fungus important for the production of traditional fermented foods and beverages in Japan, has been sequenced. The ability to secrete large amounts of proteins and the development of a transformation system have facilitated the use of A. oryzae in modern biotechnology. Although both A. oryzae and Aspergillus flavus belong to the section Flavi of the subgenus Circumdati of Aspergillus, A. oryzae, unlike A. flavus, does not produce aflatoxin, and its long history of use in the food industry has proved its safety. Here we show that the 37-megabase (Mb) genome of A. oryzae contains 12,074 genes and is expanded by 7-9 Mb in comparison with the genomes of Aspergillus nidulans and Aspergillus fumigatus. Comparison of the three aspergilli species revealed the presence of syntenic blocks and A. oryzae-specific blocks (lacking synteny with A. nidulans and A. fumigatus) in a mosaic manner throughout the genome of A. oryzae. The blocks of A. oryzae-specific sequence are enriched for genes involved in metabolism, particularly those for the synthesis of secondary metabolites. Specific expansion of genes for secretory hydrolytic enzymes, amino acid metabolism and amino acid/sugar uptake transporters supports the idea that A. oryzae is an ideal microorganism for fermentation.

Aspartic Acid Endopeptidases↗
PubMed2005

Microscale preparation of even- and odd-numbered N-acetylheparosan oligosaccharides.

In order to prepare a series of N-acetylheparosan (NAH)-related oligosaccharides, bacterial NAH produced in Escherichia coli strain K5 was partially depolymerized with heparitinase I into a mixture of even-numbered NAH oligosaccharides, having an unsaturated uronic acid (DeltaUA) at the non-reducing end. A mixture of odd-numbered oligosaccharides was derived by removing this DeltaUA in the aforementioned mixture by a 'trimming' reaction using mercury(II) acetate. Each oligosaccharide mixture was subjected to gel-filtration chromatography to generate a series of size-uniform NAH oligosaccharides of satisfactory purity (assessed by analytical anion-exchange HPLC), and their structures were identified by MALDITOF-MS, ESIMS, and 1H NMR analysis. As a result, a microscale preparation of a series of both even- and odd-numbered NAH oligosaccharides was achieved for the first time. The developed procedure is simple and systematic, and thus, should be valuable for providing not only research tools for heparin/heparan sulfate-specific enzymes and their binding proteins, but also precursor substrates with medical applications.

Acetylglucosamine↗
PubMed2005

Cyclic mechanical stretch augments hyaluronan production in cultured human uterine cervical fibroblast cells.

Hyaluronan (HA) a glycosaminoglycan with high affinity for water molecules stimulates local inflammatory reactions. Parturition causes a dramatic increase in the amount of HA fragments in the uterine cervix, thereby contributing to a rapid softening as well as opening of the cervical canal, i.e. cervical ripening. The aim of this study was to investigate the possible involvement of cyclic distension caused by labour in the augmentation of HA production during cervical ripening. Immunohistochemistry and/or RT-PCR detected hyaluronan synthase (HAS)1, 2 and 3 in samples of human cervical tissue obtained from pregnant women. Labour-like cyclic mechanical stretch for 24, 36 and 48 h significantly enhanced the secretion of HA, from cultured human uterine cervical fibroblast (CxF) cells, 128.7, 151.4 and 173.2%, respectively, concomitant with a significant augmentation of HAS1 (36, 48 h), HAS2 (24, 36 and 48 h) and HAS3 (48 h) mRNA expression. Cyclic mechanical stretch for 12, 36 and 48 h increased molecular size of the HA secreted from CxF cells. In conclusion, cyclic mechanical stretch of the uterine cervix caused by the presenting part of the fetus in labour may contribute to the increase in the secretion of HA during the process of cervical ripening.

Cells, Cultured↗
PubMed2005

Hydrogen ion titration of alkyldimethylamine oxides by 13C and 1H NMR and conventional methods.

In the hydrogen ion titration of micelles, the degree of ionization of the micelle at a given pH has to be evaluated to obtain a pKa value of micelles (Ka being the proton dissociation constant) at the pH. We compared the degree of ionization obtained from 13C and 1H NMR spectra with that obtained from the stoichiometric method. We used dodecyldimethylamine oxide (C12DMAO) and hexyldimethylamine oxide (C6DMAO) to examine the titration behavior of micelles and monomers, respectively. We determined pKa values of amine oxides both in H2O and D2O. As to the monomer (C6DMAO), the degree of ionization from NMR, alpha(NMR), coincided with that from the conventional stoichiometric method alpha. The difference of pK1 of amine oxide monomer between D2O and H2O was about 0.5: pK1(D) approximately pK1(H) + 0.5. The difference was about the same as that for carboxylic acids. As to the C12DMAO micelle, alphaNMR did not coincide with alpha over a considerable range of alpha. The NMR chemical shift might be influenced by micellar structure changes induced by the ionization, such as the sphere-to-rod transition. The intrinsic logarithmic dissociation constants of the micelle were 5.9+/-0.1 for H2O, and 6.5+/-0.1 for D2O.

Carbon Isotopes↗
PubMed2005

A thermodynamic analysis of charged mixed micelles in water.

A thermodynamic analysis is presented for electrically charged mixed micelles in water on the basis of the Gibbs-Duhem relation proposed by Hall in combination with the information on the degree of counterion binding. The proposed analyses are shown to work well for both ionic/nonionic mixed micelles and those consisting of ionic surfactants of like charges. Conclusions for ionic/nonionic mixed micelles are as follows. (1) The contribution from counterions is significant. (2) In media of low ionic strengths, the counterion concentration varies with the micellar mole fraction of the ionic species x. The dependency of the activity coefficients and the excess free energy on x is significantly influenced by this effect, but it can be corrected to a large extent in terms of the Corrin-Harkins relation. (3) The regular solution theory (RST) is not always valid even when the excess free energy is described well with the RST expression unless the observed range of the micelle composition is wide enough. (4) The RST overestimates x and underestimates the activity coefficient of the ionic species when applied to the mixed micelles to which it is inapplicable. For the ionic mixed micelles consisting of surfactants of like charges, the Lange-Shinoda approach is shown to be consistent with the present analysis in terms of the Gibbs-Duhem relation, but Motomura's approach is found to be not exact but approximate.

Journal Article↗