PubMed Health⌕ Search

Biomedical subjects

M Yokoi

Publications and source records attributed to M Yokoi.

At least 19 recordsLinked to original sources
PubMed1999

Interaction of hHR23 with S5a. The ubiquitin-like domain of hHR23 mediates interaction with S5a subunit of 26 S proteasome.

hHR23B is one of two human homologs of the Saccharomyces cerevisiae nucleotide excision repair (NER) gene product RAD23 and a component of a protein complex that specifically complements the NER defect of xeroderma pigmentosum group C (XP-C) cell extracts in vitro. Although a small proportion of hHR23B is tightly complexed with the XP-C responsible gene product, XPC protein, a vast majority exists as an XPC-free form, indicating that hHR23B has additional functions other than NER in vivo. Here we demonstrate that the human NER factor hHR23B as well as another human homolog of RAD23, hHR23A, interact specifically with S5a, a subunit of the human 26 S proteasome using the yeast two-hybrid system. Furthermore, hHR23 proteins were detected with S5a at the position where 26 S proteasome sediments in glycerol gradient centrifugation of HeLa S100 extracts. Intriguingly, hHR23B showed the inhibitory effect on the degradation of (125)I-lysozyme in the rabbit reticulocyte lysate. hHR23 proteins thus appear to associate with 26 S proteasome in vivo. From co-precipitation experiments using several series of deletion mutants, we defined the domains in hHR23B and S5a that mediate this interaction. From these results, we propose that part of hHR23 proteins are involved in the proteolytic pathway in cells.

Amino Acid Sequence↗
PubMed1999

The XPV (xeroderma pigmentosum variant) gene encodes human DNA polymerase eta.

Xeroderma pigmentosum variant (XP-V) is an inherited disorder which is associated with increased incidence of sunlight-induced skin cancers. Unlike other xeroderma pigmentosum cells (belonging to groups XP-A to XP-G), XP-V cells carry out normal nucleotide-excision repair processes but are defective in their replication of ultraviolet-damaged DNA. It has been suspected for some time that the XPV gene encodes a protein that is involved in trans-lesion DNA synthesis, but the gene product has never been isolated. Using an improved cell-free assay for trans-lesion DNA synthesis, we have recently isolated a DNA polymerase from HeLa cells that continues replication on damaged DNA by bypassing ultraviolet-induced thymine dimers in XP-V cell extracts. Here we show that this polymerase is a human homologue of the yeast Rad30 protein, recently identified as DNA polymerase eta. This polymerase and yeast Rad30 are members of a family of damage-bypass replication proteins which comprises the Escherichia coli proteins UmuC and DinB and the yeast Rev1 protein. We found that all XP-V cells examined carry mutations in their DNA polymerase eta gene. Recombinant human DNA polymerase eta corrects the inability of XP-V cell extracts to carry out DNA replication by bypassing thymine dimers on damaged DNA. Together, these results indicate that DNA polymerase eta could be the XPV gene product.

Alleles↗
PubMed1999

Metabotropic glutamate receptor subtype 7 ablation causes deficit in fear response and conditioned taste aversion.

Metabotropic glutamate receptors (mGluRs) consist of eight different subtypes and exert their effects on second messengers and ion channels via G-proteins. The function of individual mGluR subtypes in the CNS, however, largely remains to be clarified. We examined the fear response of freezing after electric shock in wild-type and mGluR7(-/-) knockout littermates. Wild-type mice displayed freezing immediately after and 1 d after footshock. In comparison, mGluR7(-/-) knockout mice showed significantly reduced levels in both immediate postshock and delayed freezing responses. However, the knockout mice exhibited no abnormalities in pain sensitivity and locomotor activity. To further examine amygdala-dependent behavior, we performed conditioned taste aversion (CTA) experiments. In wild-type mice, the administration of saccharin followed by intraperitoneal injection of the malaise-inducing agent LiCl resulted in an association between saccharin and LiCl. This association caused strong CTA toward saccharin. In contrast, mGluR7(-/-) knockout mice failed to associate between the taste and the negative reinforcer in CTA experiments. Again, the knockout mice showed no abnormalities in taste preference and in the sensitivity to LiCl toxicity. These results indicate that mGluR7 deficiency causes an impairment of two distinct amygdala-dependent behavioral paradigms. Immunohistochemical and immunoelectron-microscopic analyses showed that mGluR7 is highly expressed in amygdala and preferentially localized at the presynaptic axon terminals of glutamatergic neurons. Together, these findings strongly suggest that mGluR7 is involved in neural processes subserving amygdala-dependent averse responses.

Animals↗
PubMed1999

Oxidative stress and haematological changes in immobilized rats.

Immobilization stress induces formation of reactive oxygen species (ROS) and leads to the oxidative injury in various tissues. In this study, the effects of immobilization stress on peripheral blood cells distribution, plasma level of thiobarbituric acid reactive substances (TBARS), and activities of antioxidant enzymes in erythrocytes were investigated in male Fischer rats. A significant increase in plasma TBARS was observed during and after the stress. Dramatic increases of neutrophils and monocytes imply that ROS formation resulted from their activation. Furthermore, the antioxidant activities of catalase and superoxide dismutase (SOD) in erythrocytes were dramatically increased during and after the stress, while a large fall in erythrocyte number was observed. These findings suggest that the activation of immune cells can be a source of the immobilization-induced ROS production, and that antioxidant enzymes in erythrocytes play an important role in preventing the ROS-induced injuries.

Animals↗
PubMed1999

Effect of positive end-expiratory pressure on left and right ventricular diastolic filling assessed by transoesophageal Doppler echocardiography.

The effect of positive end-expiratory pressure (PEEP) on left and right ventricular diastolic filling dynamics was assessed by transmitral and transtricuspid flow patterns. Using transoesophageal Doppler echocardiography in fourteen ASA physical status 1 female patients, the following measurements were performed at baseline (0 cm H2O PEEP) and at 5, 10, 15, and 20 cm H2O PEEP: 1. peak velocity of early filling (peak E velocity), 2. peak velocity of atrial contraction (peak A velocity), 3. the ratio of the peak E to A velocity (peak E/A velocity ratio), 4. isovolumic relaxation time (IRT), 5. acceleration half-time (AHT), 6. deceleration half-time (DHT) of early filling, and 7. end-diastolic and end-systolic areas of both ventricles. Increasing PEEP progressively deceased peak E velocity of both ventricles. In contrast, peak A velocity did not change and the peak E/A velocity ratio decreased significantly with PEEP. IRT and AHTs remained unchanged, but DHTs of both ventricles increased following PEEP. End-diastolic and end-systolic areas of both ventricles decreased gradually and significantly with PEEP. It is concluded that PEEP was associated with decreased preload as well as reduced compliance of both ventricles, which was considered to contribute to the changes in diastolic ventricular filling.

Adult↗
PubMed1999

Favorable life-style modification and attenuation of cardiovascular risk factors.

In order to develop an effective counseling system for prevention of cardiovascular diseases, the association of a favorably changed life-style with improved risk factors was examined. Participants were 7,321 office workers aged 30-69 years from in and around Nagoya city. The age-adjusted odds ratio (OR) and its 95% confidence interval (CI) were calculated to assess the likelihood of risk factor improvement by favorable life-style modifications during a 3-year period. Those who began to eat breakfast and increased their vegetable intake normalized their previously abnormal diastolic blood pressure with more than twice the likelihood (adjusted OR [95% CI] 2.89 [1.29-6.46] and 2.60 [1.18-5.75], respectively). 'Began to eat breakfast' was also significantly associated with normalized total cholesterol (TC) (1.84, [1.05-3.21]). 'Stopped eating till full' significantly normalized the body mass index (2.03; [1.25-3.28]), uric acid (1.65; [1.07-2.52]) and TC (1.43; [1.04-1.97]). Those who started regular exercise significantly normalized their high-density lipoprotein-cholesterol (HDL-C) abnormality with 1.69-times the likelihood (1.69; [1.24-2.29]) and those who began to walk briskly also improved their TC abnormality (1.85; [1.19-2.89]). HDL-C was normalized with 2.55-times the likelihood in those who quit smoking (2.55; [1.68-3.86]). Because favorable life-style modifications can attenuate abnormal cardiovascular risk factors, then proper advice on specific risk factors should be routinely given at each health check-up in order to prevent the onset of cardiovascular diseases in subsequent years.

Adult↗
PubMed1999

Preparation and application of anti-idiotypic antibody against anti-gibberellin A4 antibody.

A monoclonal anti-idiotypic antibody was raised against anti-gibberellin A4 (GA4) antibody, which recognizes biologically active gibberellins such as GA1 and GA4 specifically. Amino acid sequences of variable regions of both anti-GA4 and anti-idiotypic antibodies were analyzed. By using the property of the anti-idiotypic antibody to compete with GA1/4 in binding to the anti-GA4 antibody, we successfully applied the anti-idiotypic antibody to ELISA as a tracer for measuring GA1/4. The single-chain Fv (scFv) gene of the anti-idiotypic antibody was constructed, and scFv expressed in E. coli showed binding activity to anti-GA4 antibody. These results suggest the possible application of anti-idiotypic antibody as a handy and stable source of an enzymatic tracer for ELISA by production of fusion protein of the scFv and an appropriate enzyme.

Amino Acid Sequence↗
PubMed1998

Ablation of cerebellar Golgi cells disrupts synaptic integration involving GABA inhibition and NMDA receptor activation in motor coordination.

The role of inhibitory Golgi cells in cerebellar function was investigated by selectively ablating Golgi cells expressing human interleukin-2 receptor alpha subunit in transgenic mice, using the immunotoxin-mediated cell targeting technique. Golgi cell disruption caused severe acute motor disorders. These mice showed gradual recovery but retained a continuing inability to perform compound movements. Optical and electrical recordings combined with immunocytological analysis indicated that elimination of Golgi cells not only reduces GABA-mediated inhibition but also attenuates functional NMDA receptors in granule cells. These results demonstrate that synaptic integration involving both GABA inhibition and NMDA receptor activation is essential for compound motor coordination. Furthermore, this integration can adapt after Golgi cell elimination so as not to evoke overexcitation by the reduction of NMDA receptors.

Animals↗
PubMed1998

The second-largest subunit of the mouse DNA polymerase alpha-primase complex facilitates both production and nuclear translocation of the catalytic subunit of DNA polymerase alpha.

DNA polymerase alpha-primase is a replication enzyme necessary for DNA replication in all eukaryotes examined so far. Mouse DNA polymerase alpha is made up of four subunits, the largest of which is the catalytic subunit with a molecular mass of 180 kDa (p180). This subunit exists as a tight complex with the second-largest subunit (p68), whose physiological role has remained unclear up until now. We set out to characterize these subunits individually or in combination by using a cDNA expression system in cultured mammalian cells. Coexpression of p68 markedly increased the protein level of p180, with the result that ectopically generated DNA polymerase activity was dramatically increased. Immunofluorescence analysis showed that while either singly expressed p180 or p68 was localized in the cytoplasm, cotransfection of both subunits resulted in colocalization in the nucleus. We identified a putative nuclear localization signal for p180 (residues 1419 to 1437) and found that interaction with p68 is essential for p180 to translocate into the nucleus. These results indicate that association of p180 with p68 is important for both protein synthesis of p180 and translocation into the nucleus, implying that p68 plays a pivotal role in the newly synthesized DNA polymerase alpha complex.

3T3 Cells↗
PubMed1998

Newly developed diabetic retinopathy and its preceding changes in biological markers.

To disclose the chronological changes prior to the manifestation of diabetic retinopathy (DR), we analyzed the time course of biological markers among apparently healthy diabetic subjects in a case-control study of 21,579 adults who had undergone comprehensive health examinations for > or = 10 years. We identified 54 cases who had newly developed DR, and selected 108 adults without fundus abnormalities, matching them for sex, age, and fasting plasma glucose (FPG) at the onset of the patient group's retinopathy as a referent group from the same population. In a multivariate analysis, a high average FPG (> 175 mg/dl) and a final-year FPG reduction (< -3%) were significantly associated with a 5.4 (95% CI, 1.8-15.7)- and 5.0 (95% CI, 1.0-24.7)-fold increased risk of DR, respectively. Thus, we surmised that sustained hyperglycemia and a subsequent drop in FPG might promote retinopathy in non-insulin dependent diabetes mellitus.

Biomarkers↗
PubMed1997

Relation of electrocardiographic left ventricular hypertrophy with and without T-wave changes to systemic blood pressure, body mass, and serum lipids and blood glucose levels in Japanese men.

Left ventricular (LV) hypertrophy, especially combined with an abnormal ST-T, is considered 1 of many coronary risk factors. Seven hundred forty-nine Japanese men were selected according to their electrocardiographic findings, i.e., normal electrocardiogram, LV hypertrophy without an abnormal ST-T segment, LV hypertrophy with a flat T wave, and LV hypertrophy with a negative T wave. Coronary risk factors were compared among these 4 age-matched groups. Groups with LV hypertrophy with negative or flat T waves had larger body mass index (24.9 vs 22.9 kg/m2), higher mean systemic blood pressure (111 vs 95 mm Hg), larger LV mass (265 vs 157 g), higher blood glucose (110 vs 100 mg/dl), higher serum triglyceride (148 vs 122 mg/dl), higher total cholesterol (206 vs 198 mg/dl), and lower high-density lipoprotein cholesterol (47 vs 54 mg/dl) than the normal group or the group with LV hypertrophy without T-wave change. Among these risk factors, blood pressure and glucose remained higher even after the adjustment by body mass index or by body mass index and blood pressure. Electrocardiographic LV hypertrophy with a changed T wave signified higher risk of coronary artery disease in Japanese men.

Blood Glucose↗
PubMed1997

Molecular cloning of the cDNA for the catalytic subunit of plant DNA polymerase alpha and its cell-cycle dependent expression.

BACKGROUND: DNA polymerase alpha has been studied in considerable detail in yeast and animals. Genetic and biochemical analyses reveal that this enzyme is composed of a heterotetramer and is necessary for replicon initiation and primer synthesis in lagging strand synthesis. In spite of the fact that modes of DNA replication in plants seem to be similar to those in other eukaryotes, very little is known about the biochemical components that participate in DNA replication of plants, including DNA polymerases. RESULTS: Using a 561-base pair DNA fragment, obtained by polymerase chain reaction amplification from a rice cDNA library as a probe, we isolated and sequenced a cDNA homologous to the cDNA for the catalytic subunit of rice DNA polymerase alpha. The encoded polypeptide has extensive homology with the catalytic subunit of DNA polymerase alpha from several species. Furthermore, when the cDNA was expressed in eukaryotic transcription/translation systems, the protein products showed DNA polymerase activity which was inhibited by a monoclonal antibody specific for DNA polymerase alpha. Using RNA gel blot analysis, we found that the levels of mRNA of the catalytic subunit of this enzyme is regulated during the cell-cycle in plant cells. CONCLUSION: This is the first report which describes the cDNA cloning of plant DNA polymerase. We conclude that the principal features of the DNA polymerase alpha catalytic subunit are conserved in plants.

Amino Acid Sequence↗
PubMed1996

Impairment of hippocampal mossy fiber LTD in mice lacking mGluR2.

Subtype 2 of the metabotropic glutamate receptor (mGluR2) is expressed in the presynaptic elements of hippocampal mossy fiber-CA3 synapses. Knockout mice deficient in mGluR2 showed no histological changes and no alterations in basal synaptic transmission, paired-pulse facilitation, or tetanus-induced long-term potentiation (LTP) at the mossy fiber-CA3 synapses. Long-term depression (LTD) induced by low-frequency stimulation, however, was almost fully abolished. The mutant mice performed normally in water maze learning tasks. Thus, the presynaptic mGluR2 is essential for inducing LTD at the mossy fiber-CA3 synapses, but this hippocampal LTD does not seem to be required for spatial learning.

Animals↗
PubMed1996

Acylated pelargonidin 3-sambubioside-5-glucosides in Matthiola incana.

Ten acylated pelargonidin 3-sambubioside-5-glucosides were isolated from the red-purple flowers of Matthiola incana, and also pelargonidin 3-glucoside was isolated from the brownish-red flowers of this plant. FAB mass measurements of 10 acylated anthocyanins gave their molecular ions [M]+ at 903-1195 m/z, which were based on acylated pelargonidin 3-sambubioside-5-glucosides with malonic acid, sinapic acid, p-coumaric acid, caffeic acid and/or ferulic acid. This was confirmed by the analysis of NMR spectra and the experiments of acid and alkaline hydrolysis. By spectral and chemical methods, seven of the 10 pigments were determined to be pelargonidin 3-O-[2-O-(2-O-(acyl-I)-beta-D-xylopyranosyl)- 6-O-(acyl-II)-beta-D-glucopyranoside]-5-O-[6-O-(malonyl)-beta-D- glucopyranoside], in which acyl moieties varied between sinapic, ferulic, caffeic and p-coumaric acids. The occurrence of these pigments was examined in 10 red-purple, 10 salmon-pink, three apricot and three copper colour cultivars of M. incana by HPLC. The acylated pelargonidin 3-sambubioside-5-glucosides were present as the dominant pigments in the red-purple, salmon-pink and apricot colour cultivars. On the other hand, pelargonidin 3-glucoside was present as a dominant anthocyanin in the copper colour cultivars and also pelargonidin 3-sambubioside-5-glucoside was confirmed by HPLC as a minor pigment in the copper colour flowers.

Acylation↗
PubMed1996

Acylated pelargonidin glycosides in red-purple flowers of Ipomoea purpurea.

Four acylated pelargonidin glycosides were isolated from the red-purple flowers of Ipomoea purpurea. The acylated anthocyanins were all based on pelargonidin 3-sophoroside-5-glucoside, acylated with caffeic acid and/or glucosylcaffeic acids. Three novel anthocyanins were elucidated to be pelargonidin 3-O-[2-O-(6-O-(trans-3-O-(beta-D-glucopyranosyl)-caffeyl)- beta-D-glucopyranosyl)-6-O-(trans-4-O-(6-O-(trans-caffeyl)-beta-D- glucopyranosyl)-caffeyl)-beta-D-glucopyranoside]-5-O- [beta-D-glucopyranoside], pelargonidin 3-O-[2-O-(6-O-(trans-caffeyl)-beta-D-glucopyranosyl)-6-O- (trans-4-O-(6-O-(trans-caffeyl)-beta-D-glucospyranosyl)-ceffeyl )-beta-D- glucopyranoside]-5-O-[beta-D-glucopyranoside] and pelargonidin 3-O[2-O-(2-O-(6-O-(trans-caffeyl)-beta-D-glucopyranosyl)-6-O- (trans-caffeyl)-beta-D-glucopyranoside]-5-O-[beta-D-glucopyoside]. Another anthocyanin was pelargonidin 3-O-[2-O-(glucosylcaffeylglucosyl)-6-O-(caffeyl)-glucoside]-5-gluc oside, which was reported to be present in the red-purple flowers of Pharbitis nil. Apart from the second pigment cited, these are analogous pigments of the violet-blue Ipomoea anthocyanins which are composed of acylated cyanidin glycosides, instead of pelargonidin.

Acylation↗
PubMed1996

Identification of the nuclear localization signal of mouse DNA primase: nuclear transport of p46 subunit is facilitated by interaction with p54 subunit.

DNA polymerase alpha-primase is a replication enzyme necessary for DNA replication in all eukaryotes. Mouse DNA primase is composed of two subunits: a 46 kDa protein (p46), which is the catalytic subunit capable of RNA primer synthesis, and a 54 kDa protein (p54), whose physiological role is not clear. To understand the structure-function relationship of DNA primase, we set out to characterize these two subunits individually or in combination using a cDNA expression system in mammalian cultured cells, and determined the subcellular distribution of ectopically expressed DNA primase. The p54 expressed in COS-1 cells after transfection was predominantly localized in the nucleus, whereas p46 was retained in the cytoplasm as shown by indirect immunofluorescence analysis. Using several mutant proteins with deletions or substitutions as well as chimeric constructs, we identified the nuclear localization signal of p54 as RIRKKLR, encoded near the amino terminus (residues 6-12). Furthermore, co-expression of both p46 and p54 subunits markedly altered the subcellular distribution of p46; co-expressed p46 was transported into the nucleus as efficiently as p54. These results demonstrate that p54 has a nuclear localization signal and is able to be translocated into the nucleus independently of DNA polymerase alpha subunits. In contrast, p46 lacks a nuclear localization signal, and its nuclear translocation is facilitated by interaction with p54. We present here first evidence for a novel role of p54 in the nuclear translocation process, and a piggy-back binding transport mechanism of mouse DNA primase.

3T3 Cells↗