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Y Imai

Publications and source records attributed to Y Imai.

At least 199 records · Page 11Linked to original sources
PubMed2000

Subcellular localization of Dna-initiation proteins of Bacillus subtilis: evidence that chromosome replication begins at either edge of the nucleoids.

We examined the intracellular distribution of Bacillus subtilis Dna-initiation proteins by immunofluorescence microscopy to visualize the initiation complex of replication in vivo. DnaA was distributed throughout the cytoplasm, but both DnaB and DnaI were always detected as foci during the cell-division cycle. Interaction of DnaI with the DnaC helicase by the yeast two-hybrid assay suggests that DnaI acts as a helicase loader. The number of DnaB and DnaI foci within the cell exceeded that of oriC. Although the foci were not always co-localized with oriC, they seemed to be localized near the outer or inner edges of the nucleoids at initiation of replication. When the replication cycle was synchronized in cells using a temperature-sensitive dnaA mutant, duplication of the oriC region was observed predominantly near an edge of the nucleoid. Before initiation occurred, each one of the DnaB and DnaI foci was frequently observed near there. Furthermore, DnaX-GFP (DnaX is a component of DNA polymerase III) foci were detected near either of the edges of the nucleoids at the onset of replication. These results suggest that the replisome is recruited into oriC near either edge of the nucleoids to initiate chromosome replication in B. subtilis.

Animals↗
PubMed2000

Cardiac infarcts increase sodium transporter transcripts (rBSC1) in the thick ascending limb of Henle.

BACKGROUND: Enhanced expression of the kidney-specific sodium transporter, rBSC1, in the thick ascending limb of Henle (TAL) and of the renal water channel, aquaporin-2 (AQP2), in collecting duct has been identified in rats with congestive heart failure (CHF) as a cause for enhanced sodium and water retention in this condition. However, the mechanism of impaired urinary sodium excretion observed even in rats with mild cardiac dysfunction remains unknown. METHODS: Male Sprague-Dawley rats with myocardial infarctions measuring 15 to 30% of the left ventricular circumference with no overt CHF were prepared. We measured the amount of rBSC1 or AQP2 mRNA using competitive polymerase chain reaction (PCR) by inducing a point mutation at the middle of the PCR product for rBSC1 or by deleting 180 bp from the 760 bp PCR product for AQP2, respectively. The results were confirmed by in situ hybridization. rBSC1 protein expression was examined by immunohistochemistry and Western blot analysis using a specific antibody against rBSC1. RESULTS: Although plasma renin activity was slightly elevated in rats with myocardial infarction (MI), no significant differences in lung weight or plasma concentrations for aldosterone and atrial natriuretic peptide were observed between control rats and MI rats. Competitive PCR showed a significant increase in rBSC1 mRNA in the renal outer medulla and cortex of MI rats, which was confirmed by in situ hybridization. However, the AQP2 mRNA of these rats remained unchanged throughout the kidney. Renin-angiotensin II blockade by oral captopril administration did not influence the alteration in rBSC1 mRNA induced by myocardial infarction. Immunohistochemistry and Western blots showed the enhanced expression of rBSC1 protein in TAL of rats with small to moderate cardiac infarcts. CONCLUSIONS: rBSC1 is up-regulated even in rats with small to moderate myocardial infarctions, which may enhance the sodium transport in the TAL in this pathophysiologic condition.

Animals↗
PubMed2000

Risk factors for recurring hepatocellular carcinoma differ according to infected hepatitis virus-an analysis of 236 consecutive patients with a single lesion.

Patients with hepatocellular carcinoma (HCC) frequently experience intrahepatic HCC recurrence even after complete ablation of primary lesions. Because the oncogenic process may be different for hepatitis B viral (B-viral) and hepatitis C viral (C-viral) HCC, the present study was conducted to elucidate the factors contributing to HCC recurrence with respect to the infected hepatitis virus. Two hundred thirty-six patients with a single HCC lesion who underwent complete ablation of the tumor by PEIT and/or PMCT or surgical resection at Tokyo University and its affiliated hospitals from 1993 to 1997 were enrolled. The patients were classified into 3 groups: the B-viral group, C-viral group, and NBNC group. After complete removal of tumors, the patients were followed for a mean period of 39 months. The factors contributing to HCC recurrence were analyzed by univariate and multivariate analysis using the Cox proportional hazard model. The rate of intrahepatic recurrence in enrolled patients at 1, 3, and 5 years was 19%, 50%, and 64%, respectively. The intrahepatic recurrence rate in C-viral and B-viral HCC was higher than that in the NBNC-related HCC. Fibrosis staging, pathological grading of HCC, and serum AFP levels were significantly linked to intrahepatic recurrence by univariate analysis, and fibrosis staging was strongest in the multivariate analysis for C-viral HCC (P = .004). In contrast, fibrosis staging did not affect the recurrence in B-viral (P = .51) and NBNC-related (P = .77) HCC. Risk factors for HCC recurrence differed according to the infected viral state.

Aged↗
PubMed2000

Superparamagnetic iron oxide-enhanced magnetic resonance images of hepatocellular carcinoma: correlation with histological grading.

Superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging has been used for the detection of hepatic tumors. However, little is known about this technique in relation to hepatocellular carcinoma (HCC). The aim of this study was to investigate whether SPIO-enhanced MR imaging can be useful in assessing histological grades of HCC. The authors studied histologically proven tumors including 31 HCCs and 6 dysplastic nodules. The ratio of the Kupffer-cell count in the tumorous tissue relative to that in the nontumorous tissue (Kupffer-cell-count ratio) decreased as HCCs became less well differentiated. The ratio of the intensity of the tumorous lesion to that of the nontumorous area on SPIO-enhanced MR images (SPIO intensity ratio) correlated inversely with Kupffer-cell-count ratio in HCCs and dysplastic nodules (r = -.826, P <.001) and increased as the degree of differentiation of HCCs decreased, indicating that the uptake of SPIO in HCCs decreased as the degree of differentiation of HCCs declined. All of the dysplastic nodules and some well-differentiated HCCs showed hypointense or isointense enhancement, relative to the surrounding liver parenchyma, indicating greater or similar uptake of SPIO in the tumor when compared with nontumorous areas. These results suggest that SPIO-enhanced MR imaging reflects Kupffer-cell numbers in HCCs and dysplastic nodules, and is useful for estimation of histological grading in HCCs, although uncertainties persist in differentiating dysplastic nodules from well-differentiated HCCs.

Aged↗
PubMed2000

Experience with freeze-dried PGLA/HA/rhBMP-2 as a bone graft substitute.

We investigated bone induction by recombinant human bone morphogenetic protein-2 in rodents. The purpose of this study was to evaluate the osteoinductive potential of a resorbable bone substitute fabricated from freeze-dried poly(glycolic acid-co-lactic acid) (PGLA) mixed with hydroxyapatite particles incorporated with bone morphogenetic protein-2 in skull defects of rats (FD-PGLA/HA/rhBMP-2). The FD-PGLA/HA/rhBMP-2 composite or as a control, the FD-PGLA/HA by itself were implanted in skull defects (psi 8 mm) of rats. The samples were harvested at 2 or 4 weeks postoperatively and were studied radiographically and histologically. Four weeks after implantation, the FD-PGLA/HA/rhBMP-2 discs were completely replaced by newly-formed bone possessing bone marrow. In contrast, the defects implanted with FD-PGLA/HA were filled only with fibrous connective tissue. The results suggest that the FD-PGLA/HA/rhBMP-2 composite could be an optimum bone substitute with osteoinductive potential and could function as an alternative bone graft material for autogenous bone in humans.

Absorbable Implants↗
PubMed2000

Visualization of the secretory process involved in Ca2+-activated fluid secretion from rat submandibular glands using the fluorescent dye, calcein.

The central feature of fluid and electrolyte secretion by salivary acinar cells is transepithelial Cl- movement as a driving force for the secretion. However, little is known about the membrane localization and regulation by agonists of various anion channels. To characterize the anion transport and fluid secretion, we visualized the secretory process induced by the cholinergic agonist, carbachol (CCh), using the anionic fluorescent dye, calcein, under a confocal laser scanning microscope. The fluorescence of calcein loaded into the isolated acini was spread diffusely throughout the cytoplasm and was less intense in the secretory vesicles which occupied the apical pole. Cytoplasmic calcein was released into intercellular canaliculi just after the addition of CCh, depending upon a rise in [Ca2+]i by Ca2+ release from intracellular stores. Thereafter, the formation of watery vacuoles connected with intercellular canaliculi was visualized in the calcein-loaded acini, depending upon external Ca2+. Both the calcein release and vacuole formation were inhibited by suppressing the Ca(2+)-activated K+ efflux. The calcein release was also affected by the external anion substitution, suggesting that calcein is released through an anion channel. In the isolated, perfused glands, CCh-induced fluid secretion was sustained in two phases, whereas the loaded calcein was initially and transiently released into the saliva. By revealing the [Ca2+]i dependence and sensitivities to channel blockers, our results suggest that the initial phase of CCh-induced fluid secretion was evoked in association with the release of the organic anion, calcein, and the late phase of fluid secretion, during which calcein is less permeable, was associated with the formation of watery vacuoles. Thus, the anion channels possessing the distinct property of anion permeation may be activated in the initial phase and late phase. These results indicate that the anionic fluorescent dye, calcein, is useful for visualizing the process of Ca(2+)-dependent fluid secretion, and for clarifying the relation between fluid secretion and anion transport.

Animals↗
PubMed2000

Analysis of chromosomal rearrangements induced by postmeiotic mutagenesis with ethylnitrosourea in zebrafish.

Mutations identified in zebrafish genetic screens allow the dissection of a wide array of problems in vertebrate biology. Most screens have examined mutations induced by treatment of spermatogonial (premeiotic) cells with the chemical mutagen N-ethyl-N-nitrosourea (ENU). Treatment of postmeiotic gametes with ENU induces specific-locus mutations at a higher rate than premeiotic regimens, suggesting that postmeiotic mutagenesis protocols could be useful in some screening strategies. Whereas there is extensive evidence that ENU induces point mutations in premeiotic cells, the range of mutations induced in postmeiotic zebrafish germ cells has been less thoroughly characterized. Here we report the identification and analysis of five mutations induced by postmeiotic ENU treatment. One mutation, snh(st1), is a translocation involving linkage group (LG) 11 and LG 14. The other four mutations, oep(st2), kny(st3), Df(LG 13)(st4), and cyc(st5), are deletions, ranging in size from less than 3 cM to greater than 20 cM. These results show that germ cell stage is an important determinant of the type of mutations induced. The induction of chromosomal rearrangements may account for the elevated frequency of specific-locus mutations observed after treatment of postmeiotic gametes with ENU.

Animals↗
PubMed2000

Involvement of cytokines in the skin-to-lymph node trafficking of cells of the monocyte-macrophage lineage expressing a C-type lectin.

The mechanism by which dermal cells expressing a macrophage calcium-type lectin (MGL) trafficked to regional lymph nodes was investigated. Conditioned medium prepared from organ cultures of mouse skin sensitized with a mixture of acetone and dibutylphthalate was shown to decrease the number of MGL(+) cells in the dermis in ex vivo organ culture assays. In in vitro culture of sensitized skin, the loss of MGL(+) cells was abrogated by the addition to the culture medium of mAb against IL-1ss, while addition of recombinant IL-1ss to the medium in which untreated skin was cultured induced loss of MGL(+) cells. Intradermal injection of recombinant IL-1ss also resulted in a transient increase of MGL(+) cells in the T cell area of draining lymph nodes in vivo, indicating that IL-1ss is central in the entire process of MGL(+) cell trafficking to the lymph nodes. Supporting this is that cells producing IL-1ss were detected in the epidermis of cultured skin even early after sensitization. The possibility that IL-1ss simply down-regulates MGL expression was eliminated by Western blotting experiments with isolated MGL(+) cells treated with or without IL-1ss. IL-1alpha and tumor necrosis factor (TNF)-alpha were also able to induce migration of MGL(+) cells in the ex vivo assay in a manner akin to IL-1ss, and antibodies against them abrogated this. Isolated MGL(+) cells from skin cultured in type I collagen matrix in vitro displayed morphological changes upon exposure to IL-1ss, IL-1alpha or TNF-alpha, indicating that these cytokines exert a direct effect on these cells. Thus, pro-inflammatory cytokines, particularly IL-1ss, are produced at the site of skin sensitization and are involved in at least initiating the trafficking of cells expressing MGL to the lymph nodes.

Acetone↗
PubMed2000

Unique heme environment at the putative distal region of hydrogen peroxide-dependent fatty acid alpha-hydroxylase from Sphingomonas paucimobilis (peroxygenase P450(SPalpha).

Fatty acid alpha-hydroxylase from Sphingomonas paucimobilis is a hydrogen peroxide-dependent cytochrome P450 (P450) enzyme (P450(SPalpha)). In this study, heme-ligand exchange reactions of P450(SPalpha) were investigated using the optical spectroscopic method and compared with those of various P450s. Alkylamines (C >/= 5) induced changes in the spectrum of ferric P450(SPalpha) to one typical of a nitrogenous ligand-bound low-spin form of ferric P450, although their affinities were lower than those for other P450s, and a substrate, laurate, did not interfere with the binding in contrast with in the cases of other P450s. Other compounds having a nitrogen donor atom to the heme iron of P450, including pyridine or 1-methylimidazole, induced no change in the spectrum of P450(SPalpha) in either the ferric or ferrous state. Practically no spectral change was observed on the addition of alkyl isocyanides to ferric P450s. On the other hand, cyanide induced a change in the spectrum of ferric P450(SPalpha) to one characteristic of cyanide-bound form of ferric P450. The affinity of cyanide increased when the substrate was added, in contrast with in the cases of other P450s. Ferrous P450(SPalpha) combined with CO and alkyl isocyanides, and the affinity for CO was of the same order of magnitude as in the cases of other P450s. These findings suggest a unique heme environment of P450(SPalpha), in which most compounds usually acting as external ligands of ferric P450s are prevented from gaining access to the heme iron of P450(SPalpha). The unique properties of the hydroxylase reaction catalyzed by P450(SPalpha), where an oxygen atom of hydrogen peroxide but not of molecular oxygen is utilized and incorporated into a fatty acid at its alpha position, is possibly related with such a specific heme environment of this P450. A possible mechanism for the peroxygenase reaction of P450(SPalpha) is proposed.

Amines↗
PubMed2000

Dentin bonding and sealing ability of a new root canal resin sealer.

The aims of this study were to find a dentin bonding system suitable for root canal treatment using a newly developed root canal resin sealer, and to examine its sealing ability. The sealer was composed of vinylidene fluoride/hexafluoropropylene copolymer, methyl methacrylate, zirconia, and tributylborane catalyst. The effects of dentin conditioners and primers on dentin bonding were studied by tensile bond strength testing and scanning electron microscopy. Apical and coronal leakage were evaluated at 1-, 4-, and 12-wk intervals by a dye penetration test using a methylene blue solution. Pulp Canal Sealer EWT and Sealapex were used as controls. Significantly high bond strength was obtained by treating dentin with EDTA, followed by application of a glutaraldehyde/2-hydroxyethyl methacrylate primer. The experimental resin sealer produced a significantly superior coronal seal at 12 wk when compared with the two control sealers (p < 0.05). Scanning electron microscopic examination revealed few gaps at the resin sealer-dentin interface.

Alkenes↗
PubMed2000

Prediction of stroke by ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population: the Ohasama study.

OBJECTIVE: To investigate the association between 24 h, daytime and night-time ambulatory blood pressures and first symptomatic stroke, to compare their predictive powers for stroke with that of casual (screening) blood pressure, and to compare the predictive power for stroke between daytime and night-time blood pressures, in a general population in Ohasama, Japan. DESIGN: A prospective cohort study. SUBJECTS AND METHODS: We obtained ambulatory blood pressure on 1,464 subjects aged > or = 40 years without history of symptomatic stroke, then followed-up their stroke-free survival. There were 74 first symptomatic stroke during the follow-up period (mean = 6.4 years). The prognostic significance of blood pressure for stroke risk was examined by a Cox proportional hazards regression model adjusted for possible confounding factors. RESULTS: The non-parametric and parametric analysis indicated that 24-h, daytime and night-time ambulatory blood pressures were linearly related with stroke risk. The likelihood ratio analysis demonstrated that these ambulatory blood pressures were significantly better related to stroke risk than did screening blood pressure, and that daytime blood pressure better predicted stroke risk than did night-time blood pressure. CONCLUSIONS: The present study which prospectively investigated the relation between ambulatory blood pressure and first symptomatic stroke risk in a general population demonstrated that (i) ambulatory blood pressure values were linearly related to stroke risk; (ii) ambulatory blood pressures had the stronger predictive power for stroke risk than did screening blood pressure; and (iii) daytime blood pressure better related to stroke risk than did night-time blood pressure.

Blood Pressure↗
PubMed2000

Japanese individuals do not harbor the T594M mutation but do have the P592S mutation in the C-terminus of the beta-subunit of the epithelial sodium channel: the Ohasama study.

OBJECTIVE: To assess the implications of polymorphisms of the amiloride-sensitive epithelial sodium channel in essential hypertension in the Japanese population by determining the incidence of the T594M mutation in the , subunit of the epithelial sodium channel, and by screening the C-terminus of the epithelial sodium channel. METHODS: Single-strand confirmational polymorphism (SSCP) analysis using two sets of primers which cover the last two-thirds of the last exon coding the B epithelial sodium channel and modification of a specific enzyme restriction site (NlaIII) for the T594M mutation were performed on 803 Japanese subjects. They were randomly selected from the study participants representative of a general population of Ohasama, Japan, who measured their home blood pressure. Polymerase chain reaction (PCR) products presenting a shift in SSCP gel, as well as controls, were directly sequenced by autoanalyser to identify the mutation. RESULTS: SSCP analysis identified altered migration in five subjects. Four SSCP variants found by sequencing were heterogeneous for the P592S (CCT to TCT) mutation conserving the PY motif, although it was not significantly associated with either home or casual blood pressure values. The resting polymorphism was at codon Thr 594, leading to no change in the amino acid sequence (ACG to ACA). None of the PCR products were modified by NlaIII, indicating the absence of the T594M mutation. CONCLUSIONS: The epithelial sodium channel variants at the C-terminus are not involved in the common form of essential hypertension in Japanese.

Adult↗
PubMed2000

Solitary aneurysm of the innominate vein.

Two cases of isolated saccular aneurysms of the innominate vein are presented that appeared as mediastinal masses. Contrast-enhanced computed tomography (CT) allowed for accurate diagnosis in one patient, while the second patient had atypical CT findings that led to thoracotomy for proper diagnosis. A diagnosis of innominate vein aneurysm should be considered when a uniform attenuation mediastinal mass is seen on CT so that unnecessary biopsy and surgery can be avoided.

Adult↗
PubMed2000

Treatment of hypoglossia-hypodactyly syndrome without extremeity anomalies.

Three cases of hypoglossia-hypodactyly syndrome without limb deformities are reported. All exhibited different degrees of tongue hypoplasia, micrognathia, retrognathia with a very narrow space between the left and right halves of the mandible, constricted isthmus, and only one lower incisor. Bone lengthening for the midline mandibular hypoplasia and orthodontic treatment were performed in the three cases with satisfactory results.

Bone Lengthening↗
PubMed2000

Upregulated expression of Iba1 molecules in the central nervous system of mice in response to neurovirulent influenza A virus infection.

The present study deals with the expression of Iba1 molecules, a novel EF-hand Ca2+-binding protein, in the brain after stereotaxic introduction of the neurovirulent WSN strain of influenza A virus into the olfactory bulb of C57BL/6 mice. The virus selectively targeted the paraventricular and anterior olfactory nuclei. Infected neurons appeared as early as at day 3 post infection and degenerated and vanished by day 12. The Iba1 molecule was normally expressed in resting microglia. The overexpression of the Iba1 in microglial cells was detected at day 3 post infection, culminating at day 7 with a morphological activation. Iba1-immunopositive macrophages outnumbered microglia in the paraventricular and anterior olfactory nuclei, where the infected neurons had degenerated. Macrophages totally disappeared by day 12, and the Iba1-expression in microglia was reduced to a normal level by day 35. Lack of perforin predisposed the mice to long-term virus infection of the brain, leading to the prolonged Iba1-overexpression. These results show that the Iba1 is upregulated in the mouse brain in response to influenza virus infection and may play significant roles in the regulation of some immunological and pathophysiological functions of microglia during virus infection.

Animals↗
PubMed2000

Characterization and identification of Borrelia isolates as Borrelia valaisiana in Taiwan and Kinmen Islands.

Eleven pure cultures of Borrelia from 3 species of wild rodents (Apodemus agrarius, Mus formosanus, Rattus losea) captured in Taichung, located in the center of Taiwan island, and on Kinmen Island were characterized. Five isolates showed restriction fragment length polymorphism (RFLP) patterns of 5S-23S rRNA gene intergenic spacer sequences identical to those of strains 5MT and 10MT, identified as Borrelia valaisiana, which were isolated in the southern tip of South Korea. Although the remaining six isolates showed novel RFLP patterns, these isolates showed more similarity to members of B. valaisiana from Korea, Japan and Europe based on 16S rRNA gene and flagellin gene sequences. This led us to speculate that transmission and proliferation of this type of borrelia occurred between Taiwan and the southern part of South Korea.

Animals↗
PubMed2000

Prognostic significance of blood pressure and heart rate variabilities: the Ohasama study.

To investigate the association between cardiovascular mortality and short-term variabilities in blood pressure and heart rate, we performed a long-term prospective study of ambulatory blood pressure monitoring in Ohasama, Japan, starting in 1987. We obtained ambulatory blood pressure and heart rate in 1542 subjects >/=40 years of age. Blood pressure and heart rate variabilities were estimated as a standard deviation measured every 30 minutes by ambulatory monitoring. There were 67 cardiovascular deaths during the follow-up period (mean=8.5 years). The Cox proportional hazards model, adjusted for possible confounding factors, demonstrated a significant increase in cardiovascular mortality, with an increase in daytime systolic ambulatory blood pressure variability. A similar trend was observed in daytime diastolic and nighttime ambulatory blood pressures. Cardiovascular mortality rate increased linearly, with a decrease in daytime heart rate variability. Subjects in whom the daytime systolic ambulatory blood pressure variability was larger than third quintile and the daytime heart rate variability was lower than the mean-SD were at extremely high risk of cardiovascular mortality. The blood pressure and heart rate variabilities obtained every 30 minutes by ambulatory blood pressure monitoring were independent predictors for cardiovascular mortality in the general population.

Aged↗