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Biomedical subjects

A Yokota

Publications and source records attributed to A Yokota.

At least 37 records · Page 2Linked to original sources
PubMed2001

The Arabidopsis HY2 gene encodes phytochromobilin synthase, a ferredoxin-dependent biliverdin reductase.

Light perception by the plant photoreceptor phytochrome requires the tetrapyrrole chromophore phytochromobilin (P Phi B), which is covalently attached to a large apoprotein. Arabidopsis mutants hy1 and hy2, which are defective in P Phi B biosynthesis, display altered responses to light due to a deficiency in photoactive phytochrome. Here, we describe the isolation of the HY2 gene by map-based cloning. hy2 mutant alleles possess alterations within this locus, some of which affect the expression of the HY2 transcript. HY2 encodes a soluble protein precursor of 38 kD with a putative N-terminal plastid transit peptide. The HY2 transit peptide is sufficient to localize the reporter green fluorescent protein to plastids. Purified mature recombinant HY2 protein exhibits P Phi B synthase activity (i.e., ferredoxin-dependent reduction of biliverdin IX alpha to P Phi B), as confirmed by HPLC and by the ability of the bilin reaction products to combine with apophytochrome to yield photoactive holophytochrome. Database searches and hybridization studies suggest that HY2 is a unique gene in the Arabidopsis genome that is related to a family of proteins found in oxygenic photosynthetic bacteria.

Alleles↗
PubMed2001

Water-soluble antioxidants inhibit macrophage recognition of oxidized erythrocytes.

Effect of exogenously added water-soluble antioxidants on the mouse macrophage lectin-like receptor activity for oxidized erythrocytes was investigated. A monolayer of thioglycollate-induced mouse peritoneal macrophages was preincubated with each of the antioxidants at 37 degrees C for 1 h, and the binding for mouse erythrocytes oxidized with ADP-chelated Fe(III) was examined. The binding was decreased by preincubation of macrophages with ascorbic acid-related compounds including ascorbic acid, erythorbic acid and dehydroascorbic acid in a dose-dependent fashion at relatively high concentrations above 10 microM. The binding was similarly decreased by preincubation of macrophages with catechin compounds including epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin gallate in a dose-dependent fashion at 0.01-100 microM. The binding was more effectively decreased by preincubation of macrophages with thiol-related compounds including glutathione, oxidized glutathione, glutathione isopropyl ester and N-acetylcysteine in a dose dependent fashion at relatively low doses below 1 microM. These results showed that water-soluble antioxidants especially glutathione and its derivatives reduced the ability of macrophages to bind oxidized erythrocytes, suggesting that the activity of lectin-like receptors of macrophages for oxidized erythrocytes was regulated by oxidative mechanisms.

Animals↗
PubMed2001

Atlas hypoplasia manifesting as myelopathy in a child--case report.

A 14-year-old Japanese boy presented with myelopathy due to atlas hypoplasia with complete posterior arch. Decompressive laminectomy of the atlas produced good neurological recovery, and follow-up T2-weighted magnetic resonance imaging showed disappearance of spinal cord edema. Congenital atlas stenosis may be symptomatic even in children, with no accompanying cervical spondylotic change. Such cases have previously occurred only in Asian adults. A radiological study of the patient's brother showed median cleft formation of the posterior arch of atlas, indicative of a wide spectrum of atlas anomalies and a possible genetic relationship between these anomalies.

Adolescent↗
PubMed2001

Delayed, transient neurological deterioration after mild head injury--case report.

A 16-year-old boy presented with delayed, transient neurological deterioration 18 days after mild head injury. Left hemiparesis and left homonymous hemianopsia appeared after right frontal contusional and mild subdural hematomas subsided. Neuroimaging examinations including cerebral angiography, magnetic resonance imaging, and single photon emission computed tomography showed vasodilation and hyperemia in the right cerebral hemisphere. The present case is not typical of acute "juvenile head trauma syndrome," but may represent a possible pathophysiology of the delayed type of transient neurological deterioration after mild head injury.

Adolescent↗
PubMed2001

Volumetric analysis of the germinal matrix and lateral ventricles performed using MR images of postmortem fetuses.

BACKGROUND AND PURPOSE: The volumetric changes of the ventricular system and germinal matrix are important to understand brain maturation and the mechanism of subependymal hemorrhage. Our purpose was to show the 3D configuration of the brain, germinal matrix, and lateral ventricles and to discuss the volumetric changes of each structure with maturation by using high-resolution MR imaging. METHODS: Three-dimensional MR images of 13 formalin-fixed fetal brains ranging from 7 to 28 weeks' gestational age (GA) were obtained on a 4.7-T unit. Each 3D configuration of the brain surface, germinal matrix, and ventricles was rendered from the cross-sectional imaging data sets and its volume measured. RESULTS: The germinal matrix was detected on MR images at 9 weeks' GA. Its volume exponentially increased by 23 weeks' GA (maximum, 2346 mm3) and then sharply decreased at 28 weeks' GA. The volume of the lateral ventricles increased gradually and reached 2646 mm3 peak volume at 23 weeks' GA. Between 11 and 23 weeks' GA, total brain and germinal matrix volumes were exponentially increasing, but the volume ratio of germinal matrix to brain was stable at about 5%. On the other hand, the volume ratio of lateral ventricles to brain was large between 10 and 13 weeks' GA. This period corresponded to the lateral ventricle showing a "vesicular" aspect with a thin mantle, and the developing mantle thickness of the hemisphere resulted in the decreasing ratio. CONCLUSION: Volumetric information concerning the germinal matrix and lateral ventricles may be useful in the accurate interpretation of clinical echograms and MR images of the fetal brain in utero.

Brain↗
PubMed2001

[Unusual MR findings of Wernicke encephalopathy with cortical involvement].

We report a 48-year-old chronic alcoholic man, who developed consciousness disturbance, oculomotor paresis, and flaccid tetraplegia. His dietary habit was very poor since one month prior to the present admission and he was drinking alcoholic beverage. On admission on April 19, 1999, he showed disturbance of consciousness, tetraparesis without sensory disturbance, gaze paresis, and vertical nystagmus on downward gaze. His blood thiamine level was 12 ng/ml (normal range: 23.8-45.9). MRI demonstrated symmetric hyperintense lesions in the motor and premotor cortices bilaterally, in addition to other changes indicating Wernicke's encephalopathy. His motor weakness and oculomotor disturbance improved after treatment with intravenous thiamine. His cortical MRI also normalized. We believe that his cortical abnormality was responsible for his motor paresis and this is an unusual and unique finding for Wernicke's encephalopathy.

Alcoholism↗
PubMed2001

[Persistent primitive hypoglossal artery aneurysm--case report].

The aneurysm arising from a persistent primitive hypoglossal artery (PHA) is rare, and only 13 such cases have been reported in literature. We present a 62-year-old woman with an aneurysm of PHA at its junction with the basilar artery. The patient consulted our hospital for a transient loss of consciousness and headaches. No neurological deficit was found, but MRI and MRA showed an aneurysm of the vertebrobasilar junction. Cerebral angiogram after admission showed the aneurysm of PHA at its junction with the basilar artery. Perspective 3D-CTA and 3D-T2 weighted MR images were composed to simulate the condition and aneurysmal surgery via the transcondylar approach was carried out. The aneurysm was successfully clipped and the patient was discharged with no neurological deficits. Perspective 3 D-CTA and MRI simulation were very useful for this operation.

Cerebral Arteries↗
PubMed2001

[Transient nephrotic syndrome after allogeneic bone marrow transplantation for chronic myelogenous leukemia].

A 42-year-old man with chronic myelogenous leukemia underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) from an unrelated donor in January 1998. About 100 days later, he developed skin eruption and a diagnosis of chronic graft-versus-host disease (cGVHD) was made by skin biopsy. The eruption improved with steroid therapy, and the dose of steroid was gradually tapered. On day 151, the patient developed nephrotic syndrome with proteinuria up to 20 g/day. A renal biopsy carried out on day 160 showed minimal change in the glomeruli. The proteinuria disappeared 19 days after the onset of nephrotic syndrome without any additional therapy, and no recurrence was observed upon re-tapering of the steroid. In this case, cGVHD might have been related to development of the nephrotic syndrome. Nephrotic syndrome after allo-HSCT is a rare complication, and only ten cases have been reported. The histological findings were mainly membranous nephropathy, and immunosuppressive therapy was effective. As seen in this case, transient nephrotic syndrome with cGVHD may occur after allo-HSCT, and care is necessary to ensure that treatment of cGVHD is sufficient.

Adult↗
PubMed2001

Preferential and persistent activation of the STAT1 pathway in rheumatoid synovial fluid cells.

OBJECTIVE: Inflammatory cytokines such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor-alpha are produced in great quantities in inflamed rheumatoid joints. However, little is known about the pathogenic significance of each cytokine in the proliferative synovitis and destruction of bone and joint. We investigated the role of cytokine receptor signals transduced into cells at the foci of rheumatoid inflammation. METHODS: Synovial fluid (SF) cells from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were examined for the activation of a group of cytokine receptor signaling molecules, signal transducers and activators of transcription (STAT). RESULTS: DNA binding of STAT1 in SF cells was observed in 8 out of 14 patients with RA, but in none of the 10 patients with OA studied, and this was prevented by preincubation of these cells with neutralizing anti-IL-6 antibody. IL-6 activated both STAT1 and STAT3 in normal peripheral blood (PB) leukocytes, and preferentially STAT1 in rheumatoid SF cells. Moreover, STAT1 activation in rheumatoid SF cells appeared to be continuous, in contrast to the transient activation in normal PB leukocytes. CONCLUSION: STAT1 and STAT3 are differentially regulated in response to IL-6 in different cell types. The continuous STAT1 activation may be of pathogenic significance in the progression and persistence of RA.

Adult↗
PubMed2000

Immunoassay of the MRSA-related toxic protein, leukocidin, with scanning electrochemical microscopy.

Scanning electrochemical microscopy (SECM) was applied to the immunoassay of leukocidin, which is a toxic protein produced by methicillin-resistant Staphylococcus aureus (MRSA), with the intention of developing and early diagnostic for MRSA infection. An antibody-chip for leukocidin was prepared by self-assembling of anti-leukocidin on a protein A-coated glass substrate. A sample solution containing leukocidin was spotted onto the antibody-chip, followed by labeling with horseradish peroxidase (HRP) via a sandwich method. The reduction current of the oxidized form of ferrocenylmethanol generated by the HRP reaction was monitored to view SECM images of the spot of captured leukocidin. The amplitude of reduction current depended on the concentrations of sample solutions used for making spots. This SECM-based immunoassay detects as low as 5.25 pg mL(-1) leukocidin.

Electrochemistry↗
PubMed2000

Chloroplast development in Arabidopsis thaliana requires the nuclear-encoded transcription factor sigma B.

Development of plastids into chloroplasts, the organelles of photosynthesis, is triggered by light. However, little is known of the factors involved in the complex coordination of light-induced plastid gene expression, which must be directed by both nuclear and plastid genomes. We have isolated an Arabidopsis mutant, abc1, with impaired chloroplast development, which results in a pale green leaf phenotype. The mutated nuclear gene encodes a sigma factor, SigB, presumably for the eubacterial-like plastid RNA polymerase. Our results provide direct evidence that a nuclear-derived prokaryotic-like SigB protein, plays a critical role in the coordination of the two genomes for chloroplast development.

Arabidopsis↗
PubMed2000

Hexachlorophene-induced brain edema in rat observed by proton magnetic resonance.

Rat brain was examined with 4.7 T proton magnetic resonance (MR). On administering hexachlorophene (HCP) 30 mg/kg/day for 5 days, myelin-rich structures stood out in T2-weighted images. Apparent diffusion coefficient (ADC) was markedly suppressed in all regions examined except for cerebral cortex. Seven days after terminating the exposure to HCP, without enhancement in T2-weighted images, ADC was still decreased in corpus callosum, optic nerve and trigeminal nerve. Rat administered with HCP and followed with high magnetic field proton MR seems to provide a good model for cytotoxic brain edema, and it may also be useful to visualize heavily myelinated structures.

Animals↗
PubMed2000

Developmental changes in mitochondrial activity and energy metabolism in fetal and neonatal rat brain.

Experiments were undertaken to investigate mitochondrial activity and energy metabolism in the developing rat brain from the late fetal stage to the neonatal stage. Samples of cerebral cortical tissue were obtained from fetuses at 14, 16, 18, and 20 days of gestation, and from pups at 1 h, 1 day and 7 days after birth. Mitochondrial respiration was measured polarographically using homogenates. Fetal and neonatal brains were frozen in situ and fluorometric enzymatic techniques were used for the analysis of ATP, ADP, AMP, and lactate. In the fetal brain, there was a gradual increase in stimulated (+ADP) and uncoupled respiratory rates using glutamate and malate as substrates, from 14 days to 20 days of gestation, together with a moderate increase in ATP concentration and in the sum total of adenine nucleotides, and a significant decrease in lactate. Since non-stimulated (-ADP) respiratory rates did not change with increasing gestational age, the respiratory control ratio appeared to increase over the same period. An increase in mitochondrial activity was more pronounced immediately after birth, together with a marked increase in ATP concentration and in the sum total of adenine nucleotides. The highest rate of mitochondrial respiration was observed in 1-hour-old pups. These results indicate that, in the rat brain, there is maturation of oxidative metabolism in mitochondria that is initiated in late gestation. Acceleration in mitochondrial respiration occurs immediately after birth in order to maintain high-energy phosphate levels, and this may be crucial for the successful outcome of the newborn.

Adenosine Diphosphate↗
PubMed2000

The transition state in the folding-unfolding reaction of four species of three-disulfide variant of hen lysozyme: the role of each disulfide bridge.

The effects of lacking a specific disulfide bridge on the transition state in folding were examined in order to explore the folding-unfolding mechanism of lysozyme. Four species of three-disulfide variant of hen lysozyme (3SS-lysozyme) were prepared by replacing two Cys residues with Ala or Ser: C6S/C127A, C30A/C115A, C64A/C80A and C76A/C94A. The recombinant hen lysozyme was studied as the standard reference containing four authentic disulfide bridges and the extra N-terminal Met: the recombinant hen lysozyme containing the extra N-terminal. Folding rates were measured by monitoring the change in fluorescence intensity associated with tri-N-acetyl-d-glucosamine binding to the active site of refolded lysozyme. It was confirmed that the folding rate of the recombinant hen lysozyme containing the extra N-terminal was the same as that of wild-type lysozyme, and that the folding rate was little affected by the presence of tri-N-acetyl-d-glucosamine (triNAG). The folding rate of C64A/C80A was found to be the fastest and almost the same as that of the recombinant hen lysozyme containing the extra N-terminal, and that of C30A/C115A the second, and that of C6S/C127A the third. The folding rate of C76A/C94A was particularly slow. On the other hand, the unfolding rates which were measured in the presence of triNAG showed the dependence on the concentration of triNAG. The intrinsic unfolding rate in the absence of triNAG was determined by extrapolation. Also in the unfolding rate, C76A/C94A was markedly slower than the others. It was found from the analysis of binding constants of triNAG to C64A/C80A during the unfolding process that the active site of C64A/C80A partly unfolds already prior to the unfolding transition. On the basis of these kinetic data, we suggest that C64A/C80A folding transition can occur with leaving the loop region around SS3 (C64-C80) flexible, while cross-linking by SS4 (C76-C94) is important for the promotion of folding, because it is an indispensable constraint on the way towards the folding transition state.

Amino Acid Substitution↗
PubMed2000

Brain of rats intoxicated with acrylamide: observation with 4.7 tesla magnetic resonance.

When rats were injected intraperitoneally with acrylamide (50 mg/kg per day) for 8 days, all animals developed ataxia and weakness in the hindlimbs. On examining their brain with an ultrahigh-field (4.7 T) magnetic resonance (MR) spectrometer, the lateral ventricles on both sides and the third ventricle were dilated. The aqueduct and cisterns were also enlarged. The size of the cerebral cortex was quantified in three MR image slices covering the cerebrum. Compared with the images of the brain of body weight-matched controls, the cerebral cortex of rats intoxicated with acrylamide was found to be smaller in the primary motor area in all slices, and in the primary or secondary sensory area in two slices. Taken together with previous enzymatic analyses, rats intoxicated with acrylamide (50 mg/kg per day for 8 days) seem to represent an animal model of acrylamide encephalopathy not only biochemically but also structurally.

Acrylamide↗
PubMed2000

Translocation (5;9)(q22;q34) in a case of acute lymphoblastic leukemia with multiple bone involvement: effectiveness of donor lymphocyte infusion for relapse after allogeneic stem cell transplantation.

A case of acute lymphoblastic leukemia with a new translocation, t(5;9)(q22;q34) is reported with special reference to the clinical features and the response to treatment. This case exhibited several unique clinical features, including expression of the myeloid antigen on the early pre-B-cell phenotype, multiple bone involvement, and favorable response to donor lymphocyte infusion despite early relapse after allogeneic hematopoietic stem cell transplantation.

Adult↗
PubMed2000

Formate protects photosynthetic machinery from photoinhibition.

In plants, environmental adversity often leads to the formation of reactive oxygen species (ROS) because of excess light energy. We found that incubation of rice leaves under high light intensity together with CO2-depleted air seriously damaged photosynthesis; however, the application of potassium formate (2 mM) before the photoinhibitory treatment protected the photosynthesis of the plant from photoinhibition. Further analysis revealed that formate protects PSII, RuBisCO, and FBPase from photoinhibition. Formate is thought to be involved in endogenous radical scavenging and/or in the supply of CO2, derived from the formate, thereby reducing oxidative damage to the photosystems under photoinhibitory conditions.

Journal Article↗