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Biomedical subjects

T Mizutani

Publications and source records attributed to T Mizutani.

At least 91 records · Page 5Linked to original sources
PubMed2000

Double blinded evaluation of the effects of pallidal and subthalamic nucleus stimulation on daytime activity in advanced Parkinson's disease.

The results of a double blinded evaluation of the effects of globus pallidus (GPi; n=7) and subthalamic nucleus (STN; n=11) stimulation in patients with advanced Parkinson's disease are summarized. The patients were evaluated at 6-8months after surgery. In order to determine the benefits afforded by the stimulation to the actual daily activities, the patients were maintained on-medication with optimal doses and schedules. The stimulation was turned off overnight for at least 12h. It was turned on in the morning (or maintained turned off), and the best and worst scores during daytime activity were recorded, as on-period and off-period scores, respectively. A reduction in total motor score on the Unified Parkinson's Disease Rating Scale was clearly elicited by GPi and STN stimulation at both the off-period (-57 and -29%, respectively) and the on-period (-36 and -25%, respectively). The difference in effects between GPi and STN stimulation appeared to be due largely to an unintended difference in the patients' preoperative symptoms. The benefits provided by stimulation to the actual daily activities appears to be limited in patients who have become unresponsive to a large dose of levodopa. Two advantages of GPi and STN stimulation were identified. Firstly, the stimulation can supplement a reduced action of levodopa during the off-period. It thus improves the patient's daily activities through attenuation of the motor fluctuations. Secondly, the stimulation can replace part of the action of levodopa during the on-period. It thus attenuates dopa-induced dyskinesia through a reduced dose of medication. More importantly, the stimulation improves the daily activities in dopa-intolerant patients who are being administered a small dose of levodopa because of unbearable side effects. In addition, GPi stimulation has its own inhibitory effect on dopa-induced dyskinesia. Clinically important improvement was observed in severe gait freezing in 2 patients following unilateral anterodorsal GPi stimulation on the right side alone.

Journal Article↗
PubMed2000

Identification of SWI.SNF complex subunit BAF60a as a determinant of the transactivation potential of Fos/Jun dimers.

Fos family proteins form stable heterodimers with Jun family proteins, and each heterodimer shows distinctive transactivating potential for regulating cellular growth, differentiation, and development via AP-1 binding sites. However, the molecular mechanism underlying dimer specificity and the molecules that facilitate transactivation remain undefined. Here, we show that BAF60a, a subunit of the SWI.SNF chromatin remodeling complex, is a determinant of the transactivation potential of Fos/Jun dimers. BAF60a binds to a specific subset of Fos/Jun heterodimers using two different interfaces for c-Fos and c-Jun, respectively. Only when the functional SWI.SNF complex is present, can c-Fos/c-Jun (high affinity to BAF60a) but not Fra-2/JunD (no affinity to BAF60a) induce the endogenous AP-1-regulated genes such as collagenase and c-met. These results indicate that a specific subset of Fos/Jun dimers recruits SWI.SNF complex via BAF60a to initiate transcription.

Dimerization↗
PubMed2000

Nascent synthesis of leader sequence-containing subgenomic mRNAs in coronavirus genome-length replicative intermediate RNA.

Infection with coronavirus results in the accumulation of genomic-sized mRNA and six to eight subgenomic mRNAs that make up a 3' coterminal nested-set structure. Genome-length negative-strand RNA and subgenomic-length negative-strand RNAs, each of which corresponds to each of the subgenomic mRNAs, also accumulate in infected cells. The present study examined whether the genome-length negative-strand RNA serves as a template for subgenomic mRNA synthesis. Genome-length replicative intermediate (RI) RNA was purified by two-dimensional gel electrophoresis of intracellular RNAs from cells infected with mouse hepatitis virus. RNase A treatment of the purified genome-length RI resulted in the production of the genome-length replicative form RNA, indicating that the genome-length RI included genome-length template RNA. RNase protection assays using the purified genome-length RI and two probes, which corresponded to the 5' 300-nt region of mRNA 6 and to the same region of mRNA 7, showed the presence of nascent leader sequence-containing subgenomic mRNAs in the genome-length RI. These data demonstrated that the genome-length negative-strand RNA serves as a template for subgenomic mRNA synthesis.

Animals↗
PubMed2000

Molecular recognition of amines and amino esters by zinc porphyrin receptors: binding mechanisms and solvent effects.

Zinc porphyrin receptors bearing 12 ester groups in the meso phenyl groups (1-3) were prepared, and binding of amines and alpha-amino esters was studied with emphasis on the binding mechanisms. The X-ray crystallographic analysis of 5,10,15,20-tetrakis(2, 6-bis(carbomethoxymethoxy)-4-carbomethoxyphenyl)porphyrin (free base of 1) showed that the receptor has a binding pocket above the porphyrin plane. UV-visible titration experiments revealed that the zinc porphyrin receptors bound amines and alpha-amino esters with binding constants (K(a)) ranging from 0.5 to 52 700 M(-1) in CH(2)Cl(2) at 25 degrees C. The ester functional groups of 1 assisted the binding of aromatic alpha-amino esters (K(a) = 8 000-23 000 M(-1) in CH(2)Cl(2) at 25 degrees C) and inhibited the binding of bulky aliphatic alpha-amino esters (K(a) = 460 M(-1) for Leu-OMe in CH(2)Cl(2) at 25 degrees C), indicating that CH-pi type interactions and steric repulsions control the selectivity. The binding of amines and alpha-amino esters was tight both in a nonpolar solvent (CH(2)Cl(2)) and in a polar solvent (water) but loose in a solvent of intermediate polarity (H(2)O-MeOH (1:1)), demonstrating that two competitive driving forces are operating: (1) attractive electrostatic forces between host and guest such as coordination of the amino group to the zinc atom, and (2) entropic forces stemming from desolvation as well as enthalpic forces due to the host-guest dispersion forces. The former forces drive the binding in CH(2)Cl(2) while the latter forces drive the binding in water. The enthalpy changes in the binding in CH(2)Cl(2) and those in water range from -50 to -30 kJ mol(-1) and from -35 to 0 kJ mol(-1), respectively. The entropy changes in CH(2)Cl(2) and those in water range from -120 to -60 J K(-1) mol(-1) and from -50 to +60 J K(-1) mol(-1), respectively. Thus the binding in CH(2)Cl(2) is characterized by large negative enthalpy changes, while that in water by less negative entropy changes. These thermodynamic parameters also indicate that host-guest polar interactions (enthalpic forces) drive the binding in CH(2)Cl(2) while both host-guest dispersion interactions (an enthalpic force) and desolvation (an entropic force) drive the binding in water. Enthalpy-entropy compensation observed for the binding in water indicates that the binding of amines and amino esters in water by zinc porphyrins is associated with conformational changes as well as a high degree of dehydration. In CH(2)Cl(2), no clear compensation was observed, consistent with the mechanism that neither desolvation processes nor conformational changes contribute significantly to the binding energetics.

Binding Sites↗
PubMed2000

Activin A stimulates type IV collagenase (matrix metalloproteinase-2) production in mouse peritoneal macrophages.

The role of activin, a dimer of inhibin beta subunit, in mouse peritoneal macrophages was evaluated. Activin activity in the cultured macrophages was augmented in response to activation by LPS. In Western blot analysis, immunoreactive activin A was detected in the culture medium only when the macrophages were stimulated by LPS. Although mRNA expression of betaA subunit was detected, that of alpha and betaB subunit was not found in macrophages by reverse RT-PCR. The activin betaA mRNA level was increased in macrophages by LPS, suggesting that the activin production augmented by LPS is regulated at the mRNA level of the betaA gene. The mRNAs of four activin receptors (ActRI, ActRIB, ActRII, and ActRIIB) were also detected in the peritoneal macrophages, and the mRNA levels, except for ActRIB, were decreased during the LPS treatment. Exogenous activin A stimulated the mRNA expression and gelatinolytic activity of matrix metalloproteinase-2 (MMP-2) in macrophages in both the presence and the absence of LPS. In contrast, activin did not affect the production of MMP-9 in macrophages. These results suggested that 1) mouse peritoneal macrophages produced activin A; 2) expression of activin A was enhanced with activation of the macrophages; 3) the macrophages also expressed activin receptors; and 4) exogenous activin A stimulated MMP-2 expression and activity, implicating activin A as an positive regulator of MMP-2 expression. Considering that MMP-2 constitutes the rate-limiting proteinase governing the degradation of basement membrane collagens, activin A may be involved in migration and infiltration of macrophages through the basement membrane in an inflammatory state.

Activin Receptors↗
PubMed2000

Characterization of mSelB, a novel mammalian elongation factor for selenoprotein translation.

Decoding of UGA selenocysteine codons in eubacteria is mediated by the specialized elongation factor SelB, which conveys the charged tRNA(Sec) to the A site of the ribosome, through binding to the SECIS mRNA hairpin. In an attempt to isolate the eukaryotic homolog of SelB, a database search in this work identified a mouse expressed sequence tag containing the complete cDNA encoding a novel protein of 583 amino acids, which we called mSelB. Several lines of evidence enabled us to establish that mSelB is the bona fide mammalian elongation factor for selenoprotein translation: it binds GTP, recognizes the Sec-tRNA(Sec) in vitro and in vivo, and is required for efficient selenoprotein translation in vivo. In contrast to the eubacterial SelB, the recombinant mSelB alone is unable to bind specifically the eukaryotic SECIS RNA hairpin. However, complementation with HeLa cell extracts led to the formation of a SECIS-dependent complex containing mSelB and at least another factor. Therefore, the role carried out by a single elongation factor in eubacterial selenoprotein translation is devoted to two or more specialized proteins in eukaryotes.

Amino Acid Sequence↗
PubMed2000

Transcriptional regulation of rat scavenger receptor class B type I gene.

The scavenger receptor class B type I (SR-BI) mediates the selective transport of lipids from high density lipoprotein to cells and plays an important role in the reverse uptake of cholesterol to the liver and in the delivery of substrates for steroidogenesis in steroidogenic organs. We report here on the isolation and characterization of the upstream promoter region of the rat SR-BI gene. The transcription start site for rat SR-BI was mapped, and DNA sequence analysis revealed the presence of binding sites for the Sp1 family in the proximal 5'-flanking region. Analysis of deletion mutants with different 5' lengths revealed that the region between -121 and -90 base pairs from the transcription start site is essential for the efficient transcription of SR-BI. Both Sp1 and Sp3 bind to three GC boxes in the region (-141 to -1 base pairs) in a sequence-specific manner. Mutations in any of the GC boxes decreased efficient transcription from this promoter in MA-10 mouse Leydig tumor cells. The overexpression of Sp1 or Sp3 protein enhanced the rat SR-BI promoter activity. These results indicate that Sp1 family members of transcription factors are essential for transcription of the rat SR-BI gene.

Animals↗
PubMed2000

Identification of the primary auditory field in archival human brain tissue via immunocytochemistry of parvalbumin.

Using parvalbumin (PV)-immunocytochemistry, we identified the human primary auditory field (PAF) for the first time. The first gyrus of the right Heschl was identified, and a serial perpendicular cut to the gyrus was made. PV-immunoreactive neuropils delineated four zones, as have been described in monkeys. Unlike with conventional staining, zone 1, characterized by intense immunostaining, corresponded to the koniocortex (PAF), while zone 2, characterized by moderate immunostaining around zone 1, to the parakoniocortex. PV-immunocytochemistry was a useful way to identify PAF in formaline-fixed archival human brain tissue.

Aged↗
PubMed2000

Anti-mutagenic structural modification by fluorine-substitution in highly mutagenic 4-methylquinoline derivatives.

We have previously shown that fluorine-substitution at position 3 of quinoline deprived this molecule of mutagenicity, possibly due to interference with the yield of its metabolically activated form, the 1,4-hydrated 2,3-epoxide (enamine epoxide), which is directly responsible for the mutagenic modification of DNA. To further explore the possibility of a method for anti-mutagenic modification of mutagens by fluorine-substitution, 4-methylquinoline (4-MeQ), the most mutagenic form of all the quinoline derivatives examined so far, was used as a target in the present study. Five mono- and di-fluorinated derivatives of 4-MeQ, 2-fluoro-4-methylquinoline (2-F-4-MeQ), 6-F-4-MeQ, 7-F-4-MeQ, 2,6-difluoro-4-methylquinoline (2, 6-diF-4-MeQ), and 2,7-diF-4-MeQ, were subjected to analysis of their structure-mutagenicity relationships. The 2-fluorinated derivatives (2-F-4-MeQ, 2,6-diF-4-MeQ, and 2,7-diF-4-MeQ) were all non-mutagenic in the Ames test. 7-F-4-MeQ was as highly mutagenic as, and 6-F-4-MeQ was less mutagenic than non-fluorinated 4-MeQ. Metabolic studies were also conducted with 4-MeQ, 2-F-4-MeQ, 6-F-4-MeQ, and 7-F-4-MeQ, using a liver microsomal enzyme fraction prepared from the 3-methylcholanthrene-treated rat. The HPLC analytical data showed that, although the metabolic patterns (hydroxylation at 4-methyl group as a main metabolic pathway and 3-hydroxylation as a minor pathway) of these four F-MeQs were similar to one another, only the 3-hydroxy metabolite of 2-F-4-MeQ was not produced under the present experimental conditions employed. These results suggest that fluorine-substitution at position 2 of 4-MeQ inhibited the formation of the enamine epoxide in the pyridine moiety and deprived this molecule of mutagenicity as in the case of quinoline.

Animals↗
PubMed2000

Eukaryotic selenocysteine tRNA has the 9/4 secondary structure.

There are two secondary structure models for the eukaryotic selenocysteine (Sec) tRNA(Sec). One model, the 9/4 structure, was experimentally tested and possesses acceptor and T-stems with 9 and 4 bp, respectively [Sturchler et al., 1993; Hubert et al., 1998]. The other one, the 7/5 secondary structure with a bulge in the T-stem, was derived from theoretical calculation [Ioudovitch and Steinberg, 19991. In this report, we show more experimental results supporting the 9/4 secondary structure. Several tRNA(Sec) mutants, whose secondary structure can adopt only the 9/4 structure, were active for serylation and selenylation. Some mutants that cannot base-pair between positions 26 and 44 to provide the 6 bp anticodon stem were still active, inconsistent with the model by Steinberg. We also show that the orientation of the V-arm directly or indirectly influences the selenylation activity, and that the rigid 6 bp D-stem is important. Finally, we conclude that all tRNA(Sec) possess the 13 bp domain II made by the stacking of the colinear AA and T-stems, whether they present the 9/4 structure in Eukarya and Archaea or the 8/5 structure in bacteria.

Base Sequence↗
PubMed2000

A first-order liquid-liquid phase transition in phosphorus

First-order structural phase transitions are common in crystalline solids, whereas first-order liquid-liquid phase transitions (that is, transitions between two distinct liquid forms with different density and entropy) are exceedingly rare in pure substances. But recent theoretical and experimental studies have shown evidence for such a transition in several materials, including supercooled water and liquid carbon. Here we report an in situ X-ray diffraction observation of a liquid-liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms. In addition to a known form of liquid phosphorus--a molecular liquid comprising tetrahedral P4 molecules--we have found a polymeric form at pressures above 1 GPa. Changing the pressure results in a reversible transformation from the low-pressure molecular form into the high-pressure polymeric form. The transformation is sharp and rapid, occurring within a few minutes over a pressure range of less than 0.02 GPa. During the transformation, the two forms of liquid coexist. These features are strongly suggestive of a first-order liquid-liquid phase transition.

Journal Article↗
PubMed2000

Aorto-bronchial fistula after implantation of a self-expanding bronchial stent in a patient with aortic dissection.

We report a case of aorto-bronchial fistula after implantation of a self-expanding stent into the left main bronchus compressed by a dissected descending aorta. A 66-year-old female, who underwent Stanford type-B aortic dissection two years previously, was admitted to our hospital for the treatment of a newly developed false lumen that originated from the ascending aorta and extended to the aortic bifurcation. She was unable to be weaned from the respirator after the graft replacement of the ascending aorta. Fiberoptic bronchoscopic examination revealed complete obstruction of the left main bronchus by extrinsic compression. A self-expanding nitinol stent was implanted in the left main bronchus five days after the operation. Her respiratory condition improved remarkably, allowing her to be successfully weaned from the respirator. Her clinical course was uneventful until she suddenly died from massive hemoptysis 20 days after stent implantation. A communication of 5 mm in diameter between the dissected descending aorta and the left main bronchus was seen at autopsy. Permanent application of a self-expanding nitinol stent to relieve extrinsic compression of a left main bronchus by a dissected descending aorta is not recommended because pressure necrosis might lead to fatal aorto-bronchial fistula.

Aged↗
PubMed2000

NACP/alpha-synuclein and tau constitute two distinctive subsets of filaments in the same neuronal inclusions in brains from a family of parkinsonism and dementia with Lewy bodies: double-immunolabeling fluorescence and electron microscopic studies.

The co-localization of NACP/alpha-synuclein and tau epitopes was examined in the brain stem and hippocampal formation in two patients from a family of autosomal dominant parkinsonism and dementia with Lewy bodies (LBs) without two reported missense mutations in the NACP gene. Double-labeling immunofluorescence study revealed that some brain stem LBs, cortical LBs, pale bodies, Lewy-related neurites, and neurofibrillary tangles expressed both NACP epitopes and the PHF tau AT8 epitope. Double-immunolabeling electron microscopy demonstrated that the NACP antibody selectively labeled 9- to 13-nm-thick straight filaments (LB filaments), whereas AT8 recognized twisted tubules with 80-to 100-nm-interval constrictions in the same neuronal inclusions. We show that NACP and tau aggregate into different filamentous components even if both proteins are incorporated into the same inclusions.

Adult↗
PubMed2000

In vitro antiviral activity of lactoferrin and ribavirin upon hantavirus.

Bovine lactoferrin (LF) and ribavirin (Rbv) were tested as antiviral agents against Seoul type hantavirus (SR-11 strain) in vitro. Hantaviral foci number in Vero E6 cells infected with SR-11 was reduced with LF treatment by 5 days post infection to obtain a 50% effective dose (ED50) of 2500 microg/ml, while pretreatment with LF was highly efficacious having an ED50 of 39 microg/ml. Conversely, 1 h pretreatment with Rbv revealed no inhibition of viral focus formation but could significantly reduce the number of viral foci (ED50: 10 microg/ml) when used from the time of viral infection. One hour pre-treatment of the cell monolayer with LF and subsequent addition of Rbv revealed a synergistic anti-hantaviral effect against SR-11, <20 FFU/ml as compared to 10(5) foci/ml in the control. One hour treatment of SR-11 with LF prior to cell inoculation gave an ED50 of 312.5 microg/ml. Whereas, washing the LF-pretreated cell monolayer with PBS demonstrated minimal focus reduction, suggesting LF lightly adheres to cells. These results indicate that LF has anti-hantaviral activity in vitro and inhibition of virus adsorption to cells which play an important role in revealing the anti-hantaviral activity of LF. This paper reports for the first time the anti-hantaviral effect of LF.

Animals↗
PubMed2000

Expression of steroidogenic acute regulatory protein (StAR) in rat granulosa cells.

Steroidogenic acute regulatory protein (StAR) is a vital mitochondrial protein that is indispensable for the synthesis of steroids. To study the mechanisms of regulation of StAR in rat granulosa cells, we used granulosa cells obtained from diethylstilbestrol-treated immature rats. Northern blot analysis revealed two major transcripts of about 3.6 kb and 1.6 kb of rat StAR mRNA. Rat StAR mRNA had strongly increased within 2 h due to the treatment of FSH or 8-Br-cAMP in this culture, a parallel increase of transcripts of both sizes was observed. Compared to the control, StAR mRNA levels increased in a dose-dependent manner in the presence of increasing concentrations of FSH (1-100 ng/ ml) and 8-Br-cAMP (0.25-5 mM). Although co-treatment of rat granulosa cells with FSH and TGF-beta did not change FSH-induced StAR mRNA levels, these levels in granulosa cells were markedly increased by pretreatment with TGF-beta before being acutely (2 h) stimulated with an effective dose of FSH. The stimulatory effect of TGF-beta was time- and concentration-dependent (1-30 ng/ml).

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Evidence for the involvement of N-methylthiourea, a ring cleavage metabolite, in the hepatotoxicity of methimazole in glutathione-depleted mice: structure-toxicity and metabolic studies.

In mice depleted of GSH by treatment with buthionine sulfoximine (BSO), methimazole (2-mercapto-1-methylimidazole, MMI) causes liver injury characterized by centrilobular necrosis of hepatocytes and an increase in serum alanine transaminase (SALT) activity. MMI requires metabolic activation by both P450 monooxygenase and flavin-containing monooxygenase (FMO) before it produces the hepatotoxicity. MMI and its analogues were examined for the ability to increase SALT activity in GSH-depleted mice. Saturation of the C-4,5 double bond in MMI resulted in a complete loss of hepatotoxicity. Similarly, ring fusion of a benzene nucleus to the C-4,5 double bond, forming 2-mercapto-1-methylbenzimidazole, abolished the toxic potency. As for MMI, 2-mercapto-1,4,5-trimethylimidazole, and 2-mercapto-1-methyl-4, 5-di-n-propylimidazole, the toxic potency decreased with the increasing bulk of the 4- and 5-alkyl substituents. Furthermore, methylation of the thiol group of MMI totally reduced its toxicity. These structural requirements and the known toxicity of thiono-sulfur compounds led us to the hypothesis that MMI would undergo epoxidation of the C-4,5 double bond by P450 enzymes and, after being hydrolyzed, the resulting epoxide would be then decomposed to form N-methylthiourea, a proximate toxicant. Before N-methylthiourea would produce toxicity, it would be further biotransformed to its S-oxidized metabolites mainly by FMO. Evidence for this hypothesis was provided by the facts that N-methylthiourea and glyoxal as the accompanying fragment were identified as urinary metabolites in mice treated with MMI and that N-methylthiourea caused a marked increase in SALT activity when administered to mice in combination with BSO.

Animals↗
PubMed2000

SBP, SECIS binding protein, binds to the RNA fragment upstream of the Sec UGA codon in glutathione peroxidase mRNA.

In mammals, most of the selenium contained in the body is present as an unusual amino acid, selenocysteine (Sec), whose codon is UGA. Because the UGA codon is typically recognized as a translation stop signal, it is intriguing how a cell recognizes and distinguishes a UGA Sec codon from a UGA stop codon. For eukaryotic selenoprotein mRNAs, it has been proposed that a conserved stem-loop structure designated the Sec insertion sequence (SECIS) in the 3'-untranslated (3'-UTR) region is required for recognition of UGA as a Sec codon. Some proteins which bind to SECIS (SBP) have been reported. However, it is not clear how the SECIS element in the 3'-UTR can mediate Sec insertion far at the in-frame UGA Sec codons. The idea that there must be a signal near the UGA Sec codon is still considered. Therefore, we searched for a protein which binds to an RNA sequence surrounding the UGA Sec codon on human glutathione peroxidase (GPx) mRNA. We found a protein which strongly bound to the RNA fragment upstream of the UGA Sec codon. However, this protein did not bind to the RNA sequence downstream of the UGA codon. This protein also bound to the SECIS sequence in the 3'-UTR of human GPx, and this binding to SECIS was competed with the RNA fragment upstream of the UGA Sec codon. Comparison of the RNA fragment with the SECIS fragment identified the conserved regions, which appeared in the region upstream of the in-frame UGA Sec codon of Se-protein mRNAs. Thus, this study proposes a novel model to understand the mechanisms of Sec incorporation at the UGA Sec codon, especially the regions upstream of the UGA codon of mRNAs of mammalian selenoproteins. This model explains that the stem-loop structure covering the UGA codon is recognized by SBP and how the UGA Sec codon escapes from attack by eRF of the peptide releasing factor.

3' Untranslated Regions↗