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Biomedical subjects

Y Shibagaki

Publications and source records attributed to Y Shibagaki.

At least 19 recordsLinked to original sources
PubMed2006

Cardiovascular events following renal transplantation: role of traditional and transplant-specific risk factors.

Cardiovascular mortality is increased in transplant recipients. However, studies including non-fatal events are critical to assess the burden of disease and to identify novel risk factors. We described the incidence of fatal and non-fatal events, and explored associations and interactions among traditional and transplant-specific risk factors and cardiovascular events (CVE) in a cohort of 922 patients transplanted between 1993 and 1998. One hundred and seventy-six patients experienced 201 CVE (111 cardiac, 48 cerebrovascular, 42 peripheral-vascular). Most CVE were non-fatal. Factors associated with cardiac events were (adjusted hazard ratios) tobacco (3.53; P<0.001), obesity (2.92; P<0.001), diabetes (2.63; P<0.001), multiple rejections (2.19; P=0.008), prior CVE (2.0; P=0.004), dialysis >1 year (1.91; P=0.007), and overweight status (1.68; P=0.04); with cerebrovascular events: diabetes and peritoneal dialysis (11.95; P<0.001), age >45 (6.77; P<0.001), diabetes (4.87; P<0.001), prior CVE (3.73; P<0.001), creatinine >141 micromol/l (3.16; P=0.001), peritoneal dialysis (3.06; P=0.027), and obesity (0.32; P=0.046); with peripheral-vascular events: diabetes (8.48; P<0.001), tobacco and cytomegalovirus (3.88; P<0.001), age >45 (2.31; P=0.019), and prior CVE (2.25; P=0.016); with mortality: tobacco and deceased-donor (3.52; P<0.001), age >45 (1.81; P=0.002), diabetes (1.76; P=0.002), pulse pressure (1.64; P=0.029), prior CVE (1.52; P=0.04), and dialysis >1 year (1.47; P=0.04). The majority of CVE post-transplant were non-fatal. Previous CVE was strongly associated with CVE post-transplant. Interactions among transplant-specific and traditional risks impacted significantly the incidence of CVE. Modifiable factors such as duration of dialysis, deceased-donor transplantation, and acute rejection should be viewed as cardiovascular risks.

Adolescent↗
PubMed2005

Optimal initial dose of oral cyclosporine in relation to its toxicities for graft-versus-host disease prophylaxis following reduced-intensity stem cell transplantation in Japanese patients.

Since the introduction of reduced-intensity stem-cell transplantation (RIST), allogeneic stem-cell transplantation has become available for elderly patients. While pharmacokinetics of cyclosporine might differ according to age or other factors, cyclosporine is uniformly started at an oral dose of 6 mg/kg/day. We retrospectively reviewed medical records of 35 patients aged between 32 and 65 (median 52) years who had undergone RIST. Doses of cyclosporine were adjusted to the target blood trough level of 150-250 ng/ml. Cyclosporine dosages were changed in 33 patients (94%). Dose reduction was required in 32 patients because of high blood levels (n=25), renal dysfunction (n=3), hepatic dysfunction (n=2), and hypertension (n=2). Cyclosporine doses were increased in one because of the suboptimal level. The median of the achieved stable doses was 3.1 mg/kg/day (range, 1.0-7.4). Five patients sustained Grade III toxicities according to NCI-CTC version 2.0: renal dysfunction (n=4), hyperbilirubinemia (n=2), and hypertension (n=2). No patients developed grade IV toxicity. There was no statistically significant difference in the frequency and severity of cyclosporine toxicities between patients aged 50 years and above and those below 50 years. The initial oral cyclosporine dose of 6 mg/kg/day was unnecessarily high irrespective of age. The possible overdose of cyclosporine might have aggravated regimen-related toxicities.

Administration, Oral↗
PubMed1999

Involvement of a cellular glycolytic enzyme, phosphoglycerate kinase, in Sendai virus transcription.

In vitro mRNA synthesis of Sendai virus is almost entirely dependent on the addition of cellular proteins (host factors). Previous studies indicated that the host factor activity from bovine brain was resolved into at least two complementary fractions, one of which may be tubulin. In this study, the host factor activity that stimulates the transcription in the presence of tubulin was further purified from bovine brain. This fraction was found to contain at least two complementary factors, and one of them was purified to a single polypeptide chain with an apparent M(r) of 46,000 (p46). From the amino acid sequence, biochemical, and immunological analyses, p46 was identified as a glycolytic enzyme, phosphoglycerate kinase (PGK). Purified native PGK from rabbit and yeast, and a recombinant human PGK substituted for p46. Although, as previously suggested, tubulin was involved in the transcription initiation complex formation by being integrated into the complex, p46 and its complementary factor had little effect on the complex formation. On the other hand, when p46 and the complementary factor were added to the RNA chain elongation reaction from the isolated initiation complex formed with tubulin, mRNA synthesis was dramatically stimulated. The enzymatic activity per se of PGK did not seem to be required for its activity. West-Western blot analysis showed that PGK could directly interact with tubulin. These data suggest that PGK stimulates Sendai virus mRNA synthesis at the elongation step, probably through its interaction with tubulin in the initiation complex.

Amino Acid Sequence↗
PubMed1999

Gestational thyrotoxicosis with acute Wernicke encephalopathy: a case report.

A 35-year-old hyperthyroid woman who developed nausea, vomiting, tachycardia, nystagmus and mental disturbance, was referred to our hospital with a suspected diagnosis of thyroid storm. However, the thyroid gland was only slightly palpable, bruits were not audible, and exophthalmos was not present. Serum levels of thyroid hormone were increased, but TSH receptor antibodies were negative. Echography and color flow doppler ultrasonography revealed a slightly enlarged thyroid gland and a slightly increased blood flow, both of which were much less milder than those expected for severe hyperthyroid Graves' disease. Under the diagnosis of hyperthyroidism due to gestational thyrotoxicosis associated with Wernicke encephalopathy, vitamin B1 was administered on the first day of admission. Her consciousness became nearly normal on the second day except for slight amnesia. Her right abducent nerve palsy rapidly improved, but horizontal and vertical nystagmus, diminished deep tendon reflexes and gait ataxia improved only gradually. MRI findings of the brain were compatible with acute Wernicke encephalopathy. We concluded that history taking and physical findings are important to make a differential diagnosis of gestational thyrotoxicosis with acute Wernicke encephalopathy from Graves' thyroid storm, and that Wernicke encephalopathy should be treated as soon as possible to improve the prognosis.

Acute Disease↗
PubMed1999

[Two cases of spinal epidural lipomatosis].

Two cases of spinal epidural lipomatosis (SEL) were reported. Patient 1 was on oral corticosteroid and patient 2 was obese and had prostate cancer. Patient 1 was a 45-year-old man diagnosed as sarcoid myelopathy at C 5/6 vertebral body levels and had been placed on oral corticosteroid therapy for 14 months. He showed spastic paraplegia, hypesthesia below C 4 level with distal dominancy and dysesthesia below Th 6 level. MRI revealed epidural lipomatosis from Th 3 to Th 9 vertebral bodies, which presented high in T 1 weighted image (WI) and T 2 WI, and non-signal in STIR image. On axial image spinal cord was compressed by this mass. Patient 2 was a 73-year-old man with spastic paraplegia, and superficial and deep sensory disturbances below Th 6. He had been obese (BMI 26.1) upon admission. He was diagnosed as prostate cancer with bone metastasis. On MRI of the thoracic spine revealed epidural mass of high in T 1 WI and T 2 WI, and non-signal in STIR image. SEL is a rare condition known as hyperplasia of normal fat tissue in epidural space which sometimes compresses the spinal cord or spinal nerve roots resulting in neurologic deficit. SEL should be kept in mind as having possible neurologic complications in obese patients or ones on long term steroid therapy.

Aged↗
PubMed1998

Cloning and characterization of three human cDNAs encoding mRNA (guanine-7-)-methyltransferase, an mRNA cap methylase.

The mRNA cap structure is synthesized by a series of reactions catalyzed by capping enzyme and mRNA (guanine-7-)-methyltransferase. mRNA (guanine-7-)-methyltransferase catalyzes the methylation of GpppN- at the guanine N7 position, which is an essential step for gene expression in eukaryotic cells. Here we isolated three human cDNAs encoding mRNA (guanine-7-)-methyltransferase termed hCMT1a, hCMT1b and hCMT1c. hCMT1a and hCMT1b encode 476 and 504 amino acids, respectively, and differ only at the region coding for the C-terminal portion of the enzyme after amino acid residue 465. The third cDNA hCMT1c seems to encode the same polypeptide as hCMT1a, however, the 3'-noncoding region of hCMT1c contains sequences corresponding to part of the C-terminal coding and noncoding regions of hCMT1b thus consisting of a mosaic of hCMT1a and hCMT1b. RT-PCR showed that all 3 types of mRNAs were expressed in every tissue examined. Comparison of the deduced amino acid sequences with those of other viral and cellular enzymes showed the regions which are highly conserved among mRNA (guanine-7-)-methyltransferases. The recombinant hCMT1a expressed in E. coli exhibited mRNA (guanine-7-)-methyltransferase activity. On the other hand, neither mRNA (guanine-7-)-methyltransferase nor mRNA (nucleoside-2'-O-)-methyltransferase activity was detected with the recombinant hCMT1b protein. Although the biological significance of the expression of these three mRNA (guanine-7-)-methyltransferase mRNA species remains unknown at present, the nucleotide sequences suggest that they are produced by alternative RNA splicing.

Amino Acid Sequence↗
PubMed1998

Cloning and characterization of two human cDNAs encoding the mRNA capping enzyme.

Previous studies demonstrated that the mammalian mRNA capping enzyme is a bifunctional enzyme containing RNA 5'-triphosphatase and mRNA guanylyl-transferase activities in a single polypeptide. In yeast, both the above activities are separated into two different subunits, alpha and beta, the genes for which we have cloned recently. It is thus interesting to compare the structural and functional relationships between the mammalian and yeast capping enzymes. Here we isolated two human cDNAs encoding mRNA capping enzymes termed hCAP1a and hCAP1b which encode 597 and 541 amino acids, respectively. They are different only at the region coding for the C-terminal portion of the enzyme. Comparison of the deduced amino acid sequences with other cellular and viral capping enzymes showed that all the regions conserved among mRNA guanylyltransferases are observed in our clones except one conserved C-terminal region which was absent in the hCAP1b protein. The purified recombinant hCAP1a gene product, hCAP1a, exhibited both RNA 5'-triphosphatase and mRNA guanylyltransferase activities. Deletion mutant analysis of hCAP1a showed that the N-terminal 213 amino acid fragment containing a tyrosine specific protein phosphatase motif catalyzed the RNA 5'-triphosphatase activity and the C-terminal 369 amino acid fragment exhibited the mRNA guanylyltransferase activity. On the other hand, hCAP1b showed RNA 5'-triphosphatase activity, but neither enzyme-GMP covalent complex formation nor cap structure formation was detected.

Amino Acid Sequence↗
PubMed1998

Significant reduction of the large-vessel blood volume by food intake during hemodialysis.

Postprandial hypotension during hemodialysis is a serious problem. The reduction of the blood volume (BV) by ultrafiltration and the redistribution of the blood from the large vessels to the splanchnic organs are regarded to be the principle mechanisms of postprandial hypotension during hemodialysis. The hematocrit (Ht) of the large vessels is expected to increase by ultrafiltration and also by peripheral shift of the blood, because Ht of the peripheral vessels is much less than Ht of the large vessels. To analyze the effects of food intake during hemodialysis on BV of the large vessels quantitatively, we monitored Ht of the arteriovenous shunt blood continuously in the patients treated with hemodialysis regularly and estimated BV using the following equation, i.e., BV/initial BV = initial Ht/Ht. The rate of ultrafiltration was kept constant during the study. The reduction rate of BV was expressed as percentage of the initial BV per hour (delta BV). Ultrafiltration rate was expressed as percentage of the dry weight per hour (delta BV), delta BV was 3.24 +/- 0.57%/h (mean +/- SE) before the meal and increased to 13.99 +/- 0.91%/h almost instantaneously when the meal started in the supine position. The minimum value of BV was less than that estimated from the ultrafiltration rate by 2.65 +/- 0.26% of the initial BV. The effects of food intake disappeared in 43 +/- 3 minutes. When the meal was taken in the sitting position, delta BV was 28.21 +/- 2.14%/h, and the minimum value of BV was less than that estimated from the ultrafiltration rate by 4.69 +/- 0.70% of the initial BV. We conclude that food intake during hemodialysis decreases BV of the large vessels transiently but significantly. The effects of food intake on BV were more severe when the meal was taken in sitting position than those when the meal was taken in supine position.

Adult↗
PubMed1997

Isolation and characterization of the yeast mRNA capping enzyme beta subunit gene encoding RNA 5'-triphosphatase, which is essential for cell viability.

The yeast Saccharomyces cerevisiae mRNA capping enzyme is composed of two subunits of alpha (52 kDa, mRNA guanylyltransferase) and beta (80 kDa, RNA 5'-triphosphatase). We have isolated the alpha subunit gene (CEG1) by immunological screening. In this report, with the aid of partial amino acid sequences of purified yeast capping enzyme, we isolated the gene, designated CET1, encoding the S. cerevisiae capping enzyme beta subunit. Amino acid sequence analysis revealed that the gene encodes for 549 amino acids with a calculated M(r) of 61,800 which is unexpectedly smaller than the size estimated by SDS-PAGE. Gene disruption experiment showed that CET1 is essential for yeast cell growth. The purified recombinant CET1 gene product, Cet1, exhibited an RNA 5'-triphosphatase activity which specifically removed the gamma-phosphate from the triphosphate-terminated RNA substrate, but not from nucleoside triphosphates, confirming the identity of the gene. Interaction between the Cet1 and the Ceg1 was also studied by the West-Western procedure using recombinant Ceg1-[32P]GMP as probe.

3-Isopropylmalate Dehydrogenase↗
PubMed1997

Characterization of feline immunodeficiency virus integrase and analysis of functional domains.

The wild-type and mutant derivatives of the integrase protein of feline immunodeficiency virus (FIV) were cloned and expressed in Escherichia coli. The purified proteins were examined using various model DNA substrates for their catalytic activities: 3'-end processing, 3'-end joining, and disintegration. The reactions required the presence of either Mn2+ or Mg2+ as a divalent cation. The N-terminal and C-subterminal domains (residues 1-52 and 189-235, respectively) were necessary for 3'-end processing and joining reactions but not for disintegration. Substitution of asparagine for the highly conserved aspartic acid at position 118 resulted in a complete loss of all three activities, confirming that the catalytic domain resides in the central core region (residues 53-188) of the protein. Deletion of the C-terminus (residues 236-281) resulted in a FIV integrase mutant that had efficient 3'-end processing and disintegration activities but weak 3'-end joining activity, a finding that has not been reported previously with other retroviral integrases. The result suggests that the C-terminus is the primary binding site for target DNA. Attachment of a histidine-tag at the N-terminus of the wild-type and deletion derivatives increased the binding affinity to the DNA substrate, resulting in altered levels of catalytic activities and selection of integration sites. Similar to other retroviral integrases, certain pairs of mutant derivatives of FIV integrase could complement each other to restitute 3'-end processing and joining activities, suggesting that formation of functional multimers is a general feature of proteins in the integrase family.

Animals↗
PubMed1997

Central core domain of retroviral integrase is responsible for target site selection.

Integration of retroviral DNA can occur into many sites on target DNA with a wide variation in preference. One factor known to affect target site selection is integrase, the viral protein required for the integration reaction. In this study, assays that measure the distribution and frequency of retroviral DNA integration showed that purified integrases of human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV) had different patterns of target site usage. The integrase domain involved in target site selection was mapped by analyzing the integration pattern of chimeric proteins formed between HIV-1 and FIV integrases and of deletion variants of the two wild-type integrases. The results indicate that the domain responsible for target site selection resides in the central core region of integrase.

Amino Acid Sequence↗
PubMed1997

Human immunodeficiency virus type 1 Vpr interacts with HHR23A, a cellular protein implicated in nucleotide excision DNA repair.

The human immunodeficiency virus type 1 (HIV-1) vpr gene is an evolutionarily conserved gene among the primate lentiviruses HIV-1, HIV-2, and simian immunodeficiency viruses. One of the unique functions attributed to the vpr gene product is the arrest of cells in the G2 phase of the cell cycle. Here we demonstrate that Vpr interacts physically with HHR23A, one member of an evolutionarily conserved gene family involved in nucleotide excision repair. Interaction of Vpr with HHR23A was initially identified through a yeast two-hybrid screen and was confirmed by the demonstration of direct binding between bacterially expressed recombinant and transiently expressed or chemically synthesized protein products. Visualization of HHR23A and Vpr by indirect immunofluorescence and confocal microscopy indicates that the two proteins colocalize at or about the nuclear membrane. We also map the Vpr-binding domain in HHR23A to a C-terminal 45-amino-acid region of the protein previously shown to have homology to members of the ubiquitination pathway. Overexpression of HHR23A and a truncated derivative which includes the Vpr-binding domain results in a partial alleviation of the G2 arrest induced by Vpr, suggesting that the interaction between Vpr and HHR23A is critical for cell cycle arrest induced by Vpr. These results provide further support for the hypothesis that Vpr interferes with the normal function of a protein or proteins involved in the DNA repair process and, thus, in the transmission of signals that allow cells to transit from the G2 to the M phase of the cell cycle.

Amino Acid Sequence↗
PubMed1997

[A case of basilar artery occlusion associated with one-and-a-half syndrome, paralytic pontine exotropia and WEBINO-syndrome].

We report a 79-year-old woman with basilar artery occlusion. She had a sudden onset of tetraplegia and disturbed consciousness, and within four days from the onset she showed a varied, fluctuating eye symptoms. On admission, she showed ocular bobbing, skew deviation with the right eye lower-positioned, upward gaze palsy, one-and-a-half syndrome, and paralytic pontine exotropia (PPE). On the third day after the onset, she showed wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) syndrome, and on the fourth day, she showed one-and-a-half syndrome again. Her right-gaze palsy improved repeatedly, and on the 19th day from the onset, only right MLF syndrome remained. Her eye symptoms fluctuated probably according to the distal migration of emboli, there by the responsible lesion and the mechanism of these eye symptoms are considered to be closely inter-correlated. On the fourth day after onset, the magnetic resonance imaging revealed cerebral infarctions in bilateral middle pons, the left paramedian lower pons, and the right paramedian midbrain, and a hemorrhagic infarction in the right inferior cerebellar hemisphere. We believe that that the eye symptoms of this patient were caused by lesions in the paramedian midbrain or pons.

Aged↗
PubMed1995

Localization and in vitro mutagenesis of the active site in the Saccharomyces cerevisiae mRNA capping enzyme.

The yeast mRNA capping enzyme is composed of 52 (alpha) and 80 kDa (beta) polypeptides, which are responsible for its mRNA guanylyltransferase and RNA 5'-triphosphatase activities, respectively. We isolated the gene encoding the alpha subunit (CEG1) and showed that CEG1 is essential for yeast cell growth [Shibagaki et al., (1992) J. Biol. Chem. 267, 9521-9528]. In this study, CEG1 was expressed in Escherichia coli and the alpha subunit protein was purified to near homogeneity. A [32P]GMP-bound tryptic peptide derived from the recombinant enzyme-[32P]GMP covalent reaction intermediate was converted to a [32P]phosphoryl-peptide through periodate oxidation followed by beta-elimination. Hydrolysis of the [32P]phosphoryl-peptide with alkali resulted in [32P]N epsilon-phospholysine as the only phosphoamino acid, indicating that GMP in the enzyme-GMP complex is bound to a lysine residue via a phosphoamide linkage. Microsequencing of the [32P]GMP-peptide showed that the GMP binding site was located in the region between amino acids 60 and 75, which contained an internal trypsin-resistant lysine at position 70. CEG1 was subjected to site-directed mutagenesis and the mutant proteins were expressed in E. coli. Substitution of His or Ile for Lys70 entirely abolished the enzyme-GMP formation activity, and this mutation was lethal to yeast in vivo, supporting the notion that the active site in the alpha subunit is located at Lys70. Replacement of Lys70 with Arg reduced the ability to form the enzyme-GMP complex; however, yeast cells bearing this allele were not viable. A series of mutations, including 8 amino acid replacements and 3 insertions, near the active site (Lys70-Thr-Asp-Gly motif) were also introduced and the mutant polypeptides were examined for catalytic activity in vitro as well as yeast cell viability in vivo. There was a good correlation between the in vitro and in vivo functions of the mutant proteins, except when Asp72 was replaced with Glu, which allowed formation of the enzyme-GMP complex but failed to support cell growth. The results with Lys70 to Arg and Asp72 to Glu substitutions indicated that guanylyltransfer to RNA and/or additional roles besides cap formation per se are impaired in these mutant proteins.

Acid Anhydride Hydrolases↗
PubMed1994

[A case of cortical blindness confirmed by single photon emission computerized tomography and visual evoked potential].

We reported a rare case of cortical blindness in cerebral ischemia following post-anoxic state confirmed by single photon emission computerized tomography (SPECT) and visual evoked potential. A 45-year-old woman who had been suffering from bronchial asthma was admitted to our hospital because of sudden progressive dyspnea and depressed consciousness. When she arrived at the hospital by ambulance, she was in hypoxic state and fell into cardiac arrest. Her respiratory condition gradually improved with respirator assistance, and she recovered consciousness, but complained of bilateral visual loss. She had no history of any neurological or psychiatric illness, nor of drug abuse. On neurological examination, she was alert and oriented. Light reflex, optic fundi, extraocular movement and other neurological findings were all normal, with the exception of bilateral blindness. EEG showed generalized slow background activity, but cranial CT scan and MRI showed no abnormalities. 99mTc-HMPAO SPECT indicated hypoperfusion in prominent bilateral occipital and parietal lobes. Simultaneous recordings of pattern reversal visual evoked potential (VEP) and electroretinograms (ERG) using transient checkerboard pattern reversal in 15 min and 30 min checks were recorded. The results showed normal b waves but absent P100 in the bilateral eyes. From the patient's neurological symptoms and the results of SPECT and VEP, she was diagnosed as cortical blindness in post-anoxic state. On the 30th hospital day, her visual acuity and visual fields improved, but she was suspected of having visual agnosia. Eighty-five days after the onset of the neurological abnormalities, no traces of visual disturbances were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Blindness↗
PubMed1992

Characterization and site-directed mutagenesis of a low M(r) GTP-binding protein, ram p25, expressed in Escherichia coli.

The ram gene encodes a GTP-binding protein with a M(r) of 25,068 (Nagata, K., Satoh, T., Itoh, H., Kozasa, T., Okano, Y., Doi, T., Kaziro, Y., and Nozawa, Y. (1990) FEBS Lett. 275, 29-32). It has a putative effector domain very similar to that of yeast SEC4 protein, and shares 40% identity and 60% homology with it, respectively. In order to analyze the biochemical properties, ram cDNA was engineered and inserted into a bacterial expression vector; this allowed the production at a high level of soluble recombinant ram p25 in Escherichia coli. The purified ram p25 contained an equimolar amount of GDP. The purified protein bound approximately 1 mol of [35S]guanosine 5'-O-(thiotriphosphate) GTP gamma S)/mol of protein, with a Kd value of 120 nM. [35S]GTP gamma S binding to this protein was inhibited by GTP and GDP, but not by ATP and ADP. In the presence of 10 mM Mg2+, the dissociation of [8,5'-3H]GDP and [35S]GTP gamma S from ram p25 occurred with rates of 0.015 min-1 and 0.004 min-1, respectively, showing that the ram p25 has a higher affinity for GTP than GDP. The rate of release of Pi from [gamma-32P]GTP-bound ram p25 was calculated to be 0.011 min-1. The contribution of guanine nucleotide-binding and GTP-hydrolysis domains of the protein to its biochemical activities was investigated by site-directed mutagenesis. Substitution of Val for Gly at position 19 resulted in disappearance of [35S]GTP gamma S- and [3H]GDP-binding activity in spite of good expression of the protein. Mutations of Thr41 to Ser, Ala76 to Thr, and Asn133 to His slightly increased the rates of [35S] GTP gamma S binding and [3H]GDP dissociation, but had almost no effects on the manner of [gamma-32P]GTP hydrolysis. Replacement of Gln78 with Leu significantly increased the [3H]GDP dissociation rate (7-fold) and decreased GTP hydrolytic activity considerably.

Amino Acid Sequence↗