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Biomedical subjects

S Maki

Publications and source records attributed to S Maki.

At least 19 recordsLinked to original sources
PubMed2006

Structural transitions of the mono-olein bicontinuous cubic phase induced by inclusion of protein lysozyme solutions.

Inclusion of protein lysozyme molecules in the lipidic mono-olein cubic phase induces a transition from a Pn3m structure to an Im3m one. The small-angle x-ray scattering method with high-intensity synchrotron radiation enabled us to follow closely the transition depending on the conditions of lysozyme solutions. We show that concentrated lysozyme solutions induced the appearance of the Im3m structure coexisting with the Pn3m structure. From the relation between the lattice parameters of these two structures it is shown that they are related by the Bonnet transformation of the underlying triply periodic minimal surfaces. We found that the transition also occurred at lower lysozyme concentration when NaCl induced an attraction between lysozyme molecules. The origin of the transition was considered as a frustration in the cubic phase where lysozyme molecules were highly confined. A simple estimation of the frustration was given, which took into account the translational entropy of lysozyme molecules. At the highest concentration of lysozyme and NaCl the Im3m structure was found to disappear and left only the Pn3m structure. This was probably either due to the crystallization or phase separation of lysozyme solutions ongoing microscopically, which absorbed lysozyme molecules from channels of the cubic phase and thus removed the frustration.

Journal Article↗
PubMed2005

Comparative in vitro metabolism of the suspected pro-oestrogenic compound, methoxychlor in precision-cut liver slices from male and female rats.

The in vitro metabolism of [14C]methoxychlor (MXC), a suspected pro-oestrogenic compound, by male and female Fischer rats (F344) was compared in precision-cut liver slices. The results demonstrated time-dependent metabolism of MXC with integrated phase I and II reactions, and the sex differences were detected in the metabolic profiles. In liver slices from male rats, MXC was metabolized to bis-demethylated MXC (bis-OH-MXC) by sequential O-demethylation followed by subsequent O-glucuronidation. The doubly conjugated metabolite, bis-OH-MXC 4-O-sulphate 4'-O-glucuronide was additionally produced. In the case of the female rat, the glucuronides of both mono- and bis-OH-MXC were formed as the main metabolites, and the mono-OH-MXC glucuronide appeared to be specific to the female rat. The ratios of bis-/mono-demethylated metabolite, which include the amounts of corresponding conjugates, were approximately 95/5 for the male rats and 40/60 for the female. These results imply that demethylation to the intermediate metabolite, (S)-mono-OH-MXC, is a key step for the sex-dependent metabolism of MXC in the rats. The phase I metabolites produced were extensively conjugated with D-glucuronic acid in both male and female rats.

Animals↗
PubMed2005

Comparative in vitro metabolism of methoxychlor in male and female rats: metabolism of demethylated methoxychlor metabolites by precision-cut rat liver slices.

The in vitro metabolism of demethylated methoxychlor (MXC) metabolites, mono-OH-MXC (including (R)- and (S)-isomers) and bis-OH-MXC (mono- and bis-demethylated MXC, respectively), was conducted using precision-cut liver slices to understand the sex-dependent metabolism of MXC in rats. In the study with bis-OH-MXC, the substrate underwent extensive conjugation producing its glucuronide and glucuronide/sulphate diconjugate, and no significant sex differences were found. On the contrary, the metabolism of mono-OH-MXC appeared to exhibit the sex differences in the metabolic profiles. The bis-OH-MXC glucuronide and glucuronide/sulphate diconjugate were major metabolites in male rat, whereas the mono- and bis-OH-MXC glucuronides predominated in the female. The per cent distribution of the demethylated products (sum of bis-OH-MXC derivatives) was approximately 90% for the male (for both isomers) and 81 (R-) to 56% (S-) for the female. The metabolic profiles in (S)-mono-OH-MXC, which is the predominant enantiomer preferentially produced in MXC metabolism in rats, showed a similar pattern to that of MXC compared with the (R)-isomer. The results indicate that the sex differences in oxidative demethylation of the intermediate, (S)-mono-OH-MXC, could be one of the probable reasons for the sex-dependent metabolism of MXC in rats, and the stereo-structural preference of the contributing demethylase enzymes appear to be involved.

Animals↗
PubMed2004

In vitro metabolism of [14C]methoxychlor in rat, mouse, Japanese quail and rainbow trout in precision-cut liver slices.

1. The in vitro metabolism of [14C]methoxychlor (MXC) has been studied using precision-cut liver slices from the Sprague-Dawley male rat, CD-1 male mouse, WE strain male Japanese quail and juvenile rainbow trout (Oncorhynchus mykiss). The results demonstrated integrated phase I and II metabolism of MXC and species differences in the metabolic profiles were observed. 2. In rat liver slice preparations, MXC was rapidly metabolized to bis-OH-MXC by sequential O-demethylation followed by subsequent O-glucuronidation forming bis-OH-MXC glucuronide. No mono-OH-MXC glucuronide was detected. The doubly conjugated metabolite, bis-OH-MXC 4-O-sulphate 4'-O-glucuronide, was also detected as a rat-specific metabolite. 3. Formation of mono-OH-MXC and its glucuronide was the main metabolic pathway in the mouse and Japanese quail. In contrast to the rat, only minor amounts of bis-OH-MXC glucuronide were detected. A reductively dehalogenated metabolite, dechlorinated mono-OH-MXC glucuronide, was observed only in mouse preparations. 4. In rainbow trout, comparative amounts of both mono- and bis-OH-MXC glucuronide were formed as the major metabolites. Unconjugated forms of these metabolites were detected only as minor products. 5. The different metabolic profiles of MXC observed in the four animal species are possibly due to substrate specificity of contributing CYP450 monooxgenase enzyme(s) in different animal species.

Animals↗
PubMed2002

Discrepancies in dietary intakes and plasma concentrations of fatty acids according to age among Japanese female dietitians.

OBJECTIVE: To clarify the influences of age on dietary intakes and plasma concentrations of fatty acids (FAs) in Japanese female dietitians. SUBJECTS AND METHODS: In autumn 1996, we estimated dietary FA intakes based on 7 day weighed diet records and analyzed plasma FA concentrations in 79 healthy Japanese female dietitians, and investigated their relationships with age, dividing into three age groups (young (32-42 y), middle-aged (43-50 y) and elderly (51-66 y)). RESULTS: Dietary intakes of total FA, saturated FAs, monounsaturated FAs, n-3 polyunsaturated FAs (PUFAs) and alpha-linolenic acid (18:3n-3) were significantly highest in the middle-aged group, and lowest in the elderly. Similar trends were observed for dietary intakes of n-6 PUFAs and linoleic acid (18:2n-6), but there were no differences with regard to eicosapentaenoic acid (EPA; 20:5n-3), docosahexaenoic acid (DHA; 22:6n-3) and n-3 highly unsaturated FAs (HUFAs=EPA+22:5n-3+DHA). On the other hand, plasma concentrations of all FAs except for arachidonic acid (20:4n-6) demonstrated positive correlations with age. Moreover, plasma concentrations of EPA in all age groups, DHA in the elderly and n-3 HUFAs in the middle-aged and the elderly were all positively correlated with dietary intakes. CONCLUSIONS: We should take into account the influence of age on dietary habit and lipid metabolism when interpreting associations between dietary FA intakes and plasma FA concentrations.

Adult↗
PubMed2001

New stable neutral radical with intramolecular hydrogen bonding: synthesis and characterization of 2,5,8-tri-tert-butyl-7-hydroxy-6-oxophenalenoxyl.

A new stable neutral radical with intramolecular hydrogen bonding, 2,5,8-tri-tert-butyl-7-hydroxy-6-oxophenalenoxyl, was synthesized from the corresponding dihydroxyphenalenone and isolated as a stable solid under air atmosphere at room temperature. The structure was unequivocally determined by means of IR spectra, ESR/ENDOR techniques, and DFT calculations.

Journal Article↗
PubMed2001

On the bioactive conformation of the rhodopsin chromophore: absolute sense of twist around the 6-s-cis bond.

Incubation of opsin with synthetic 6-s-locked retinoids 2a and 2b only led to pigment formation from the alpha-locked 2a, the CD spectrum of which was similar to that of native rhodopsin (Rh). This establishes that the 6-s-bond of the chromophore in rhodopsin is cis, and that its helicity is negative. Earlier cross-linking studies showed that the 11-cis to all-trans photoisomerization occurring in the batho-Rh to lumi-Rh conversion induces a flip over of the side carrying the ring moiety. The GTP-binding assay of pigment Rh-(2a), incorporating retinal analogue 2a, has shown that its activity is 80% that of the native pigment. That is, the overall conformation around the 6-s bond is retained in the steps leading to G-protein activation.

Animals↗
PubMed2001

Relative validity of a semi-quantitative food frequency questionnaire versus 28 day weighed diet records in Japanese female dietitians.

OBJECTIVE: To assess the relative validity of a semi-quantitative food frequency questionnaire (SQFFQ) against 28 day weighed diet records (WDRs). SUBJECTS AND METHODS: The SQFFQ was administered to 106 (21 male and 85 female) Japanese dietitians in Aichi Prefecture in autumn, 1996 and four-season consecutive 7 day WDRs were carried out during 1996-1997. We evaluated validity of intakes of 15 foods and 31 macro- and micro-nutrients based on the SQFFQ against those according to 28 day WDRs among 79 Japanese female dietitians. RESULTS: Mean daily intakes of selected foods and nutrients determined by the SQFFQ were generally equivalent to those measured by 28 day WDRs. Pearson's de-attenuated correlation coefficients (CCs) with log-transformation and energy-adjustment between intakes of selected foods and nutrients quantified by the SQFFQ and 28 day WDRs (minimum-median-maximum) ranged from 0.17 (beverages)-0.52 to 0.74 (rice), and Spearman's rank CCs with energy-adjustment ranged from 0.28 (confectionery)-0.42 to 0.68 (rice). Respective Pearson's CCs for intakes of nutrients were 0.28 (PUFAs)-0.51 to 0.73 (magnesium), and Spearman's rank CCs ranged from 0.23 (n-3 PUFAs)-0.45 to 0.71 (magnesium). Favorably higher agreement for intakes of foods/nutrients was achieved along with lower disagreement. CONCLUSIONS: Satisfactorily higher relative validity was attained in Japanese female dietitians with the SQFFQ. This calibrated questionnaire seems therefore appropriate for administration to Japanese dietitians to clarify associations between diet and health/disease. SPONSORSHIP: A grant-in-aid from the Ministry of Education, Science, Sports and Culture (06454242).

Adult↗
PubMed2000

The bacterial flagellar cap as the rotary promoter of flagellin self-assembly.

The growth of the bacterial flagellar filament occurs at its distal end by self-assembly of flagellin transported from the cytoplasm through the narrow central channel. The cap at the growing end is essential for its growth, remaining stably attached while permitting the flagellin insertion. In order to understand the assembly mechanism, we used electron microscopy to study the structures of the cap-filament complex and isolated cap dimer. Five leg-like anchor domains of the pentameric cap flexibly adjusted their conformations to keep just one flagellin binding site open, indicating a cap rotation mechanism to promote the flagellin self-assembly. This represents one of the most dynamic movements in protein structures.

Bacteria↗
PubMed2000

Synthesis, biological evaluation, and conformational analysis of A-ring diastereomers of 2-methyl-1,25-dihydroxyvitamin D(3) and their 20-epimers: unique activity profiles depending on the stereochemistry of the A-ring and at C-20.

All eight possible A-ring diastereomers of 2-methyl-1, 25-dihydroxyvitamin D(3) (2) and 2-methyl-20-epi-1, 25-dihydroxyvitamin D(3) (3) were convergently synthesized. The A-ring enyne synthons 19 were synthesized starting with methyl (S)-(+)- or (R)-(-)-3-hydroxy-2-methylpropionate (8). This was converted to the alcohol 14 as a 1:1 epimeric mixture in several steps. After having been separated by column chromatography, each isomer led to the requisite A-ring enyne synthons 19 again as 1:1 mixtures at C-1. Coupling of the resulting A-ring enynes 20a-h with the CD-ring portions 5a,b in the presence of a Pd catalyst afforded the 2-methyl analogues 2a-h and 3a-h in good yield. In this way, all possible A-ring diastereomers were synthesized. The synthesized analogues were biologically evaluated both in vitro and in vivo. The potency was highly dependent on the stereochemistry of each isomer. In particular, the alpha alpha beta-isomer 2g exhibited 4-fold higher potency than 1 alpha,25-dihydroxyvitamin D(3) (1) both in bovine thymus VDR binding and in elevation of rat serum calcium concentration and was twice as potent as the parent compound in HL-60 cell differentiation. Furthermore, its 20-epimer, that is, 20-epi-alpha alpha beta 3g, exhibited exceptionally high activities: 12-fold higher in VDR binding affinity, 7-fold higher in calcium mobilization, and 590-fold higher in HL-60 cell differentiation, as compared to 1 alpha,25-dihydroxyvitamin D(3) (1). Accordingly, the double modification of 2-methyl substitution and 20-epimerization resulted in unique activity profiles. Conformational analysis of the A-ring by (1)H NMR and an X-ray crystallographic analysis of the alpha alpha beta-isomer 2g are also described.

Animals↗
PubMed2000

Structure and function of the fourth subunit (Dpb4p) of DNA polymerase epsilon in Saccharomyces cerevisiae.

DNA polymerase epsilon (Polepsilon) of Saccharomyces cerevisiae is purified as a complex of four polypeptides with molecular masses of >250, 80, 34 (and 31) and 29 kDa as determined by SDS-PAGE. The genes POL2, DPB2 and DPB3, encoding the catalytic Pol2p, the second (Dpb2p) and the third largest subunits (Dpb3p) of the complex, respectively, were previously cloned and characterised. This paper reports the partial amino acid sequence of the fourth subunit (Dpb4p) of Polepsilon. This protein sequence matches parts of the predicted amino acid sequence from the YDR121w open reading frame on S.cerevisiae chromosome IV. Thus, YDR121w was renamed DPB4. A deletion mutant of DPB4 (Deltadpb4) is not lethal, but chromosomal DNA replication is slightly disturbed in this mutant. A double mutant haploid strain carrying the Deltadpb4 deletion and either pol2-11 or dpb11-1 is lethal at all temperatures tested. Furthermore, the restrictive temperature of double mutants carrying Deltadpb4 and dpb2-1, rad53-1 or rad53-21 is lower than in the corresponding single mutants. These results strongly suggest that Dpb4p plays an important role in maintaining the complex structure of Polepsilon in S.cerevisiae, even if it is not essential for cell growth. Structural homologues of DPB4 are present in other eukaryotic genomes, suggesting that the complex structure of S. cerevisiae Polepsilon is conserved in eukaryotes.

Amino Acid Motifs↗
PubMed2000

The process of amyloid-like fibril formation by methionine aminopeptidase from a hyperthermophile, Pyrococcus furiosus.

Amyloid is associated with serious diseases including Alzheimer's disease and senile-systemic amyloidosis due to misfolded proteins. In the course of study of the denaturation process of methionine aminopeptidase (MAP) from the hyperthermophile P. furiosus, we found that MAP forms amyloid-like fibrils, and we then investigated the mechanism of amyloid fibril formation. The kinetic experiments on denaturation monitored by CD at 222 nm indicated that MAP in the presence of 3.37 M GuHCl at pH 3.31 changed to a conformation containing a considerable content of beta-sheet structure after the destruction of the alpha-helical structure. MAP in this beta-rich conformation was highly associated, and its stability was remarkably high: the midpoint of the GuHCl denaturation curve was 4.82 M at pH 3.0, and a thermal transition was not observed up to 125 degrees C by calorimetry. The amyloid-like fibril formation of MAP was confirmed by Congo red staining with a typical peak at 542 nm in the difference spectrum, showing a cross-beta X-ray diffraction pattern with a clear sharp reflection at 4.7 A and a characteristic unbranched fibrillar appearance with a length of about 1000 A and a diameter of about 70 A in the electron micrographs. Present results indicate that the amyloid-like form of MAP appears just after the protein is almost completely denatured, and even highly stable proteins can also form amyloid-like conformation under conditions where the denatured state of the protein is abundantly populated.

Aminopeptidases↗
PubMed2000

Mapping of cDNA clones on contig of Chlorella chromosome I.

Complementary DNA (cDNA) clones specific to the smallest chromosome (chromosome I) of Chlorella vulgaris C-169 were selected from cDNA libraries with probes of chromosome I DNA fragments amplified by degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR). A total of 15 clones was obtained, which included gene homologs for alpha-tubulin, inosine-5'-monophosphate dehydrogenase, beta-1,4-mannase, a TTG-binding protein, a heat shock protein, thioredoxin/protein disulfide isomerase, transcription factor NF-E2, an oxidoreductase, and UDP-n-acetylglucosamine enolpyruvyltransferase. These clones were definitely localized at specific sites on the chromosome I physical map constructed on the basis of overlapping cosmid clones (the contig). They were predominantly distributed within the left two-thirds of the chromosome. This contrasts with the distribution of repetitive elements such as short interspersed elements (SINEs), which are rather abundant in the right two-thirds of chromosome I. The comparative simplicity of the gene arrangement of Chlorella chromosome I suggests that it may be able to serve as a prototypic system for deciphering the complexity of huge plant chromosomes.

Journal Article↗
PubMed2000

A multicenter trial of mizoribine compared with placebo in children with frequently relapsing nephrotic syndrome.

BACKGROUND: The use of corticosteroids or cytotoxic/immunosuppressive agents such as cyclophosphamide, chlorambucil, and cyclosporine for the treatment of frequently relapsing nephrotic syndrome (FRNS) is limited because of their adverse effects. This study was conducted to evaluate the efficacy and safety of mizoribine, a relatively new immunosuppressive drug developed in Japan, in children with FRNS. METHODS: A double-blind, placebo-controlled, multicenter trial was carried out in children, from 2 to 19 years old, with FRNS. At relapse, patients were treated with prednisolone. According to a dynamic allocation, mizoribine or a placebo was concurrently administered to each patient. Prednisolone was gradually tapered and discontinued within 12 weeks. The test drug was maintained for 48 weeks. The primary end point was the relapse rate (the total number of relapses/the total treatment days for all patients). Analyses were performed according to the intention-to-treat principle. RESULTS: The primary analysis was conducted on 99 mizoribine- and 98 placebo-treated patients. The relapse rate was lower in the mizoribine group than in the placebo group (0.0055 vs. 0.0067; ratio 0.81, 95% CI, 0.61 to 1.05, P = 0.12). The hazard ratio of the cumulative remission rate between the two groups was 0.79 (95% CI, 0. 57 to 1.08). In the subgroups consisting of patients 10 years old or younger, the relapse rate ratio between the mizoribine subgroup (54 patients) and the placebo subgroup (57 patients) was 0.66 (95% CI, 0. 44 to 0.94, P = 0.017). The hazard ratio of the cumulative remission rate between the two subgroups was 0.56 (95% CI, 0.37 to 0.85, P = 0. 007). Hyperuricemia was the most common adverse event with mizoribine (16%), but was transient. CONCLUSIONS: Compared with the placebo, mizoribine significantly decreased the relapse rate and prolonged the remission period in the subgroup consisting of patients 10 years old or younger. This drug may be useful in young children with FRNS who generally relapse more frequently than older children.

Adolescent↗
PubMed2000

Amyloid protofilament formation of hen egg lysozyme in highly concentrated ethanol solution.

Mutant human lysozymes (Ile56Thr & Asp67His) have been reported to form amyloid deposits in the viscera. From the standpoint of understanding the mechanism of amyloid formation, we searched for conditions of amyloid formation in vitro using hen egg lysozyme, which has been extensively studied from a physicochemical standpoint. It was found that the circular dichroism spectra in the far-ultraviolet region of the hen egg lysozyme changed to those characteristic of a beta-structure from the native alpha-helix rich spectrum in 90% ethanol solution. When the concentration of protein was increased to 10 mg/mL, the protein solution formed a gel in the presence of 90% ethanol, and precipitated on further addition of 10 mM NaCl. The precipitates were examined by electron microscopy, their ability to bind Congo red, and X-ray diffraction to determine whether amyloid fibrils were formed in the precipitates. Electron micrographs displayed unbranched protofilament with a diameter of approximately 70 A. The peak point of the difference spectrum for the Congo red binding assay was 541 nm, which is characteristic of amyloid fibrils. The X-ray diffraction pattern showed a sharp and intense diffraction ring at 4.7 A, a reflection that arises from the interstrand spacing in beta-sheets. These results indicate that the precipitates of hen egg lysozyme are amyloid protofilament, and that the amyloid protofilament formation of hen egg lysozyme closely follows upon the destruction of the helical and tertiary structures.

Amyloid↗
PubMed1999

Predictors of death from congestive heart failure in hypertrophic cardiomyopathy.

In 309 patients with hypertrophic cardiomyopathy during long-term follow-up (mean 9.4 years), independent predictors of death from congestive heart failure (n = 15) were smaller electrocardiographic SV1 + RV5 and smaller echocardiographic fractional shortening at the initial evaluation. Our data may contribute to the construction of therapeutic strategies for the prevention of heart failure death in patients with hypertrophic cardiomyopathy.

Adolescent↗
PubMed1999

Role of [corrected] nigrostriatal dopamine system in learning to perform sequential motor tasks in a predictive manner.

Neurons in the primate striatum and the substantia nigra pars compacta change their firing patterns during sensory-motor learning. To study the consequences of nigrostriatal dopamine depletion for learning and memory of motor sequences, we used a neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), to deplete dopamine unilaterally in the striatum of macaque monkeys either before or after training them on sequential push-button motor tasks. We compared the monkeys' performance with the arms ipsilateral and contralateral to dopamine depletion. During training and retraining on the tasks, we measured initial and serial movement times and reaction times for the push button movements, electromyographic patterns of arm and orofacial muscle activity during button pushing and reward licking, and saccadic eye movements during the button push sequences. With the arm ipsilateral to the side of dopamine depletion, each monkey showed progressive shortening of movement times and initial and serial reaction times, and each developed consistent strategies of hand-orofacial and hand-eye coordination in which single button push movements were linked efficiently to succeeding movements so that performance of the whole sequence became predictive. These patterns did not develop for contralateral arm performance in this monkey treated with MPTP before training. With the arm contralateral to dopamine depletion, the monkey showed significant quantitative deficits in all parameters measured except initial reaction times. Movement times and serial reaction times were longer than those for the ipsilateral arm; anticipatory saccadic eye movements were not well time-locked to individual button pushes made with the contralateral hand; and push and licking movements were not smoothly coordinated. This monkey further showed striking differences in performance when using the ipsilateral and contralateral arms in switch trial tests in which reward was delivered unexpectedly one button early. He continued to make movements to the previously rewarded button with the ipsilateral arm but showed no such automatic movements when he used his contralateral arm. For the monkey treated with MPTP after training, performance on the push-button task was skilled for both arms before dopamine depletion, but the unilateral dopamine depletion produced deficits in contralateral arm performance for all parameters measured, again excepting initial reaction times. With retraining, however, his performance with the contralateral arm improved. We conclude that the striatum and its nigrostriatal afferents function in the initial learning underlying performance of sequences of movements as single motor programs. The nigrostriatal system also operates during the retrieval of these programs once learning is accomplished, but lesions of the nigrostriatal system spare the ability to relearn the previously acquired programs.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗