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Biomedical subjects

R Itoh

Publications and source records attributed to R Itoh.

At least 109 records · Page 6Linked to original sources
PubMed2001

Accuracy for detection of simulated lesions: comparison of fluid-attenuated inversion-recovery, proton density--weighted, and T2-weighted synthetic brain MR imaging.

OBJECTIVE: The objective of our study was to determine the effects of MR sequence (fluid-attenuated inversion-recovery [FLAIR], proton density--weighted, and T2-weighted) and of lesion location on sensitivity and specificity of lesion detection. MATERIALS AND METHODS: We generated FLAIR, proton density-weighted, and T2-weighted brain images with 3-mm lesions using published parameters for acute multiple sclerosis plaques. Each image contained from zero to five lesions that were distributed among cortical-subcortical, periventricular, and deep white matter regions; on either side; and anterior or posterior in position. We presented images of 540 lesions, distributed among 2592 image regions, to six neuroradiologists. We constructed a contingency table for image regions with lesions and another for image regions without lesions (normal). Each table included the following: the reviewer's number (1--6); the MR sequence; the side, position, and region of the lesion; and the reviewer's response (lesion present or absent [normal]). We performed chi-square and log-linear analyses. RESULTS: The FLAIR sequence yielded the highest true-positive rates (p < 0.001) and the highest true-negative rates (p < 0.001). Regions also differed in reviewers' true-positive rates (p < 0.001) and true-negative rates (p = 0.002). The true-positive rate model generated by log-linear analysis contained an additional sequence-location interaction. The true-negative rate model generated by log-linear analysis confirmed these associations, but no higher order interactions were added. CONCLUSION: We developed software with which we can generate brain images of a wide range of pulse sequences and that allows us to specify the location, size, shape, and intrinsic characteristics of simulated lesions. We found that the use of FLAIR sequences increases detection accuracy for cortical-subcortical and periventricular lesions over that associated with proton density- and T2-weighted sequences.

Adult↗
PubMed2001

T2 relaxation measurements in X-linked adrenoleukodystrophy performed using dual-echo fast fluid-attenuated inversion recovery MR imaging.

SUMMARY: The purpose of this study was to determine whether dual-echo fast fluid-attenuated inversion recovery MR imaging and corresponding T2 brain maps can show different zones in the affected white matter of patients with cerebral X-linked adrenoleukodystrophy. Ten male patients with cerebral X-linked adrenoleukodystrophy underwent imaging performed using dual-echo fast fluid-attenuated inversion recovery and dual-echo conventional spin-echo MR sequences. Corresponding T2 relaxation maps of the brain were generated. On the basis of dual-echo fast fluid-attenuated inversion recovery images and T2 maps, the affected white matter could be divided into two distinct zones in four patients with cerebral X-linked adrenoleukodystrophy.

Adolescent↗
PubMed2001

Time-resolved contrast-enhanced carotid MR angiography using sensitivity encoding (SENSE).

We describe a time-resolved, contrast-enhanced carotid MR angiographic technique using a 3D gradient-echo sequence in combination with a sensitivity-encoding scheme. We delineate the steps involved in generating the dynamic MR angiographic images, discuss issues related to image quality, and outline differences between this technique and recently reported similar methods that implement multiple parallel receivers to reduce imaging time.

Adult↗
PubMed2001

MR imaging of the human brain at 1.5 T: regional variations in transverse relaxation rates in the cerebral cortex.

BACKGROUND AND PURPOSE: Heterogeneity in cortical signal intensity on T2-weighted MR images has been recently documented. Using a whole-brain, multiecho MR imaging technique, we sought to determine the T2 relaxation times of nine predefined regions in the cerebral cortex and one region in the deep gray matter. METHODS: Ten adult volunteers (nine men and one woman; age range, 18-40 y; average age, 30.8 y) underwent whole-brain imaging with an oblique coronal multiecho 3D Carr-Purcell-Meiboom-Gill MR sequence at 1000/25, 50, 75, 100, 125, and 150 (TR/TE). T2 measurements were obtained, with variably sized regions of interest, from the primary auditory cortex, primary visual cortex, caudate nucleus, superior frontal gyrus, inferior temporal gyrus, middle temporal gyrus, superior temporal gyrus, insula cortex, cingulate gyrus, and hippocampus. Repeated-measures analysis of variance was used to assess the existence of differences in T2 measurements among the anatomic locations. RESULTS: On the basis of T2 measurements, the gray matter structures examined could be divided into four statistically different groups. In ascending order of T2 measurements, the first group consisted of the primary auditory cortex and primary visual cortex; the second group, the caudate nucleus, superior frontal gyrus, inferior temporal gyrus, middle temporal gyrus, and superior temporal gyrus; the third group, the insula cortex; and the fourth group, the cingulate gyrus and hippocampus. CONCLUSION: Significant variation in T2 values among the cortical gray matter of the human brain exists.

Adolescent↗
PubMed2001

A chloroplast protein homologous to the eubacterial topological specificity factor minE plays a role in chloroplast division.

We report the identification of a nucleus-encoded minE gene, designated AtMinE1, of Arabidopsis. The encoded AtMinE1 protein possesses both N- and C-terminal extensions, relative to the eubacterial and algal chloroplast-encoded MinE proteins. The N-terminal extension functioned as a chloroplast-targeting transit peptide, as revealed by a transient expression assay using an N terminus:green fluorescent protein fusion. Histochemical beta-glucuronidase staining of transgenic Arabidopsis lines harboring an AtMinE1 promoter::uidA reporter fusion unveiled specific activation of the promoter in green tissues, especially at the shoot apex, which suggests a requirement for cell division-associated AtMinE1 expression for proplastid division in green tissues. In addition, we generated transgenic plants overexpressing a full-length AtMinE1 cDNA and examined the subcellular structures of those plants. Giant heteromorphic chloroplasts were observed in transgenic plants, with a reduced number per cell, whereas mitochondrial morphology remained similar to that of wild-type plants. Taken together, these observations suggest that MinE is the third conserved component involved in chloroplast division.

Amino Acid Sequence↗
PubMed2000

Isolation and characterization of a Ca(2+)-activated chloride channel from human corneal epithelium.

PURPOSE: Transparency of the cornea is maintained through the activity of secretory mechanisms in the epithelium and endothelium, which offset the tendency of the stroma to imbibe fluid and swell. These secretory mechanisms establish osmotic gradients thereby providing the osmotic driving forces for coupled fluid transport from the stroma into both the tears and the anterior chamber. To further characterize the mechanism of epithelial Cl secretion, we cloned a cDNA encoding a Ca(2+)-dependent chloride channel, an abundant mRNA in human corneal epithelium. We investigated the abundance of all known human chloride channels in corneal epithelium to identify those responsible for regulating chloride conductance in this tissue. METHODS: For the isolation of a full-length cDNA clone, a probe was selected from a set of expressed sequenced tag (EST) clones classified as unique to corneal epithelium (http://bodymap. ims.u-tokyo.ac.jp). The expression patterns of the corresponding gene encoding novel chloride channel gene in human cornea and other tissues were examined by reverse transcription-polymerase chain reaction (RT-PCR). Quantitative PCR was performed to clarify the expression level of the novel chloride channel gene in cornea relative to that in other human tissues. RESULTS: We cloned a new Ca(2+)-activated chloride channel, CLCA2, from corneal epithelium. The full length cDNA clone encoded 943 amino acids with 62% identity to bovine Ca(2+)-activated chloride channel. The CLCA2 gene mapped to human chromosome 1p32. Quantitative expression analysis by RT-PCR showed that it is the most abundant chloride channel in corneal epithelium. CONCLUSION: High and tissue specific expression of the CLCA2 gene in human corneal epithelium implies an important role in corneal transparency maintenance.

Amino Acid Sequence↗
PubMed2000

A defect in a single allele of the Mlh1 gene causes dissociation of the killing and tumorigenic actions of an alkylating carcinogen in methyltransferase-deficient mice.

Mice with mutations in both alleles of the Mgmt and the Mlh1 gene, the former encoding a DNA repair methyltransferase and the latter a protein functioning at an early step of mismatch repair, are as resistant to the killing action of alkylating agents as are wild-type mice. These mice yielded a large number of tumors when exposed to alkylating carcinogens, but this characteristic was subdued since they also showed a relatively high level of spontaneous tumorigenicity, as a consequence of the defect in mismatch repair. This complexity is now resolved by introducing the Mlh1(+/-) mutation, instead of Mlh1(-/-), in these methyltransferase-deficient mice. Mgmt(-/-) Mlh1(+/-) mice, with about half the amount of MLH1 protein as Mgmt(-/-) Mlh1(+/+) mice, were resistant to the killing action of N-methyl-N-nitrosourea (MNU), up to the level of 30 mg/kg body wt. Eight weeks after exposure to this dose of MNU, 40% of MNU-treated Mgmt(-/-) Mlh1(+/-) mice had thymic lymphomas and there were no tumors in those mice not given the treatment. It seems that the cellular content of MLH1 protein is a critical factor for determining if damaged cells enter into either one of the two pathways leading to mutation induction or to apototic cell death. Loss of Mlh1 expression was frequently observed in tumors of Mgmt(-/-) Mlh1(+/-) mice and this might be related to progression of the tumors.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Detection and investigation of Campylobacter jejuni by polymerase chain reaction-restriction fragment length polymorphism analysis.

A molecular typing approach for Campylobacter jejuni with restriction fragment length polymorphism (RFLP) analysis of the flagellin gene flaA in C. jejuni, was generated and studied. Using polymerase chain reaction (PCR)-RFLP with the restriction endonuclease Mbo I, it was demonstrated that C. jejuni could be divided into four types. Genotypic analysis of C. jejuni by PCR-RFLP is a valuable technique for epidemiological typing.

Animals↗
PubMed2000

Diffusion-tensor MR imaging of the human brain with gradient- and spin-echo readout: technical note.

Diffusion-tensor MR imaging of the brain is an objective method that can measure diffusion of water in tissue noninvasively. Five adult volunteers participated in this study that was performed to evaluate the potential of gradient- and spin-echo readout for diffusion-tensor imaging by comparing it with single-shot spin-echo echo-planar imaging. Gradient- and spin-echo readout provides comparable measures of water diffusion to single-shot spin-echo echo-planar readout with significantly less geometrical distortion at the expense of a longer imaging time.

Adult↗
PubMed1999

Multi-forms of human MTH1 polypeptides produced by alternative translation initiation and single nucleotide polymorphism.

The human MTH1 gene for 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase, produces seven types (types 1, 2A, 2B, 3A, 3B, 4A and 4B) of mRNAs. The B-type mRNAs with exon 2b-2c segments have three additional in-frame AUGs in their 5' regions. We report here that these transcripts produce three forms of MTH1 polypeptides (p22, p21 and p18) in in vitro translation reactions. Three polypeptides were also detected in extracts of human cells, using western blotting. B-type mRNAs with a polymorphic alteration (GU-->GC) at the beginning of exon 2c that converts an in-frame UGA to CGA yielding another in-frame AUG further upstream, produced an additional polypeptide (p26) in vitro. Substitution of each AUG abolished the production of each corresponding polypeptide. Cell lines from individuals with the GC allele contain more B-type mRNAs than do those of GT homozygotes, and the former produce all of four polypeptides but the latter lack p26. Amounts of each polypeptide reflected copy number of the GC allele in each cell line. There is an apparent linkage dis-equilibrium between the two polymorphic sites, GT/GC at exon 2c and Val83/Met83 at codon 83 for p18.

Base Sequence↗
PubMed1999

The peroxin Pex14p. cDNA cloning by functional complementation on a Chinese hamster ovary cell mutant, characterization, and functional analysis.

Rat cDNA encoding a 376-amino acid peroxin was isolated by functional complementation of a peroxisome-deficient Chinese hamster ovary cell mutant, ZP110, of complementation group 14 (CG14). The primary sequence showed 28 and 24% amino acid identity with the yeast Pex14p from Hansenula polymorpha and Saccharomyces cerevisiae, respectively; therefore, we termed this cDNA rat PEX14 (RnPEX14). Human and Chinese hamster Pex14p showed 96 and 94% identity to rat Pex14p, except that both Pex14p comprised 377 amino acids. Pex14p was characterized as an integral membrane protein of peroxisomes, exposing its N- and C-terminal parts to the cytosol. Pex14p interacts with both Pex5p and Pex7p, the receptors for peroxisome targeting signal type 1 (PTS1) and PTS2, respectively, together with the receptors' cargoes, PTS1 and PTS2 proteins. Mutation in PEX14 from ZP161, the same CG as ZP110, was determined by reverse transcription-PCR as follows. A 133-base pair deletion at nucleotide residues 37-169 in one allele created a termination codon at 40-42; in addition to this mutation, 103 base pairs were deleted at positions 385-487, resulting in the second termination immediately downstream the second deletion site in the other allele. Neither of these two mutant forms of Pex14p restored peroxisome biogenesis in ZP110 and ZP161, thereby demonstrating PEX14 to be responsible for peroxisome deficiency in CG14.

Amino Acid Sequence↗
PubMed1999

Genomic organization and chromosomal localization of the human cathepsin L2 gene.

Cathepsin L2 is a recently described cysteine proteinase with high sequence homology to cathepsin L and other members of the papain superfamily of cysteine proteinases. Its expression is regulated in a tissue-specific manner and is high in thymus, testis and cornea. In the present study, the entire gene sequence, including 5' and 3' flanking region, and chromosomal localization of human cathepsin L2 were determined. The gene spans approximately 6.4 kb and consists of eight exons and seven introns. Genomic organization was similar to human cathepsin L and more than 50% similarity was found between the first introns of cathepsin L and L2, suggesting that they diverged late in evolution. The transcription initiation site, determined by primer extension, was 198 nucleotides from the first ATG. The 5' flanking region lacks a TATA box but has one SP1 site. The gene was mapped to chromosome 9q21-22 by fluorescence in situ hybridization and the distance from cathepsin L was determined to be 15 cM by compiling radiation hybrid mapping results with a genetic map.

Base Sequence↗
PubMed1999

Isolation of dividing chloroplasts with intact plastid-dividing rings from a synchronous culture of the unicellular red alga cyanidioschyzon merolae

In order to obtain a three-dimensional view of the plastid-dividing ring (PD ring) and promote the biochemical study of plastid division, we developed a procedure to isolate structurally intact dividing chloroplasts (rhodoplasts) possessing PD rings from a highly synchronized culture of the unicellular red alga Cyanidioschyzon merolae. The procedure consists of five steps. (1) The chloroplast division cycle is synchronized by light/dark cycles and treatment with 5-fluorodeoxyuridine. (2) The synchronized cells are treated with hypotonic solution. (3) The swollen cells are lysed in a French Pressure Cell. (4) The lysate is treated with DNase I. (5) The intact chloroplasts are separated by density-gradient centrifugation. The PD ring was visualized by fluorescence microscopy, after labeling the surface proteins of isolated chloroplasts with N-hydroxy-sulfo-succinimidyl biotin and detecting them with fluorescein isothiocyanate avidin. Scanning electron microscopy (SEM) showed that the outer envelopes and PD rings were conserved on the isolated dividing chloroplasts. These are the first fluorescence microscopic and SEM images of the PD ring and they clearly show PD rings encircling isolated dividing chloroplasts in three dimensions.

Journal Article↗
PubMed1999

Two ftsH-family genes encoded in the nuclear and chloroplast genomes of the primitive red alga Cyanidioschyzon merolae.

The red algal chloroplast genome encodes an essential prokaryotic cell division gene, ftsH, which has never been found in the mitochondrial genome of any organism. To compare the conserved prokaryote-derived mechanism for mitochondrial division with that of chloroplasts, we cloned chloroplast- and nuclear-encoded ftsH genes from the primitive red alga Cyanidioschyzon merolae. The deduced amino-acid sequence of chloroplast ftsH (ftsHcp) consists of 603 amino acids and shows the highest similarity with algal-chloroplast and cyanobacterial FtsH. On the other hand, the nuclear-encoded ftsH (ftsH2) encodes a protein of 920 amino acids and has the highest similarity with two yeast mitochondrial FtsHs, Rca1p and Afg3p. Furthermore, the amino-terminal extension of FtsH2 appears to be an amphipathic alpha-helix, a characteristic mitochondrial targeting signal, suggesting that FtsH2 is a mitochondrial protein. Southern hybridization revealed that ftsH2 is a single gene located on chromosome III of the 17 C. merolae chromosomes. The level of expression of the 3.0 and 4.0 kb transcripts of this gene decreased in concert during the organelle division phase of a synchronized culture, indicating a cell-cycle-dependent manner of ftsH2 transcription, while northern hybridization did not detect ftsHcp transcripts. Nevertheless, reverse transcription-PCR and immunoblotting demonstrated for the first time that chloroplast-encoded ftsH is transcriptionally and translationally active. Overproduction of FtsHcp and FtsH2 in Escherichia coli disrupted cytokinesis and produced filamentous cells, but had no effect on the replication, segregation, or distribution of their nucleoids, as also occurs in ftsH-deficient E. coli. These observations suggest the possible involvement of both C. merolae FtsHs in organelle division.

ATP-Dependent Proteases↗
PubMed1999

Dietary sodium, an independent determinant for urinary deoxypyridinoline in elderly women. A cross-sectional study on the effect of dietary factors on deoxypyridinoline excretion in 24-h urine specimens from 763 free-living healthy Japanese.

OBJECTIVE: To investigate the effect of sodium, protein and calcium in habitual diets on bone resorption. DESIGN: A cross-sectional study. SETTING: A community-based study. SUBJECTS: Healthy free-living male (n=342) and female (n=421) volunteers aged 20-79 y recruited for a health and nutrition examination survey conducted by a local government. METHODS: Bone resorption was assessed by the measurement of free deoxypyridinoline in 24 h urine. Dietary assessment was by one-day dietary record method. Sodium and urea in 24 h urine were also measured for assessment of sodium and protein intake. The relationships between deoxypyridinoline excretion and the dietary factors were examined using correlation and multiple regression statistics. RESULTS: In women aged 50-79 y, protein intake was positively associated with deoxypyridinoline excretion (P<0.05); and the urinary deoxypyridinoline/creatinine ratio was positively associated with both the urinary calcium/creatinine ratio (P<0.01) and sodium/creatinine ratio (P<0.05). In the multiple regression model, the association of the deoxypyridinoline/creatinine ratio and sodium/creatinine ratio was still significant (P<0.05) after adjustment for possible confounders, in this sex and age group. CONCLUSION: In elderly women, habitual excess sodium in diets may result in bone loss through accelerated bone resorption.

Adult↗
PubMed1999

Tear film instability induced by rigid contact lenses.

PURPOSE: To evaluate rigid contact lens-associated epithelial damage, the relationship between the tear film and the ocular surface epithelium was evaluated at the perilimbal area around rigid contact lenses (RCLs). METHODS: Twenty RCL [six polymethylmethacrylate (PMMA) and 14 rigid gas-permeable lens (RGPL)] wearers and 20 non-CL wearers were enrolled in this study. By using a newly developed tear interferometer, the noninvasive tear film break-up time (NIBUT) on the conjunctiva at the 3- and 9-o'clock portions was measured, and its stability evaluated. Fluorescein and sulforhodamine B staining was used to observe ocular-surface epithelial damage, and rose bengal staining was used to evaluate the mucin layer distribution. RESULTS: The conjunctival NIBUT at the 3- or 9-o'clock portions or both was abnormally shortened in 15 (75%) of 20 RCL-wearer eyes. Conjunctival epithelial staining at the 3- or 9-o'clock portion was seen in six (30%) of 20 eyes by using sulforhodamine B, and in four (20%) of 20 eyes by rose bengal; all of these eyes also demonstrated an abnormal tear film breakup. Corneal epithelial damage was seen in two (10%) of 20 RCL-wearer eyes at the 3- or 9-o'clock portions or both, and in both of these cases, conjunctival epithelial damage also was noted. Neither tear-film instability nor epithelial staining was seen in the normal controls. CONCLUSIONS: This study indicates that RCL-induced tear-film instability is associated with damage to the ocular-surface epithelium and mucin layer.

Adult↗