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Biomedical subjects

I Kato

Publications and source records attributed to I Kato.

At least 127 records · Page 7Linked to original sources
PubMed1999

Amelioration of vasospasm after subarachnoid hemorrhage in transgenic mice overexpressing CuZn-superoxide dismutase.

BACKGROUND AND PURPOSE: To clarify the effect of superoxide dismutase (SOD) on vasospasm after subarachnoid hemorrhage (SAH), we investigated sequential changes in arterial diameter after SAH in transgenic mice overexpressing CuZn-SOD (SOD-1). METHODS: SOD-transgenic mice and nontransgenic littermates (35 to 40 g) were subjected to SAH produced by endovascular perforation of left anterior cerebral artery. At 4 hours and 1, 3, 7, and 14 days after SAH, the mice were perfused with 10% formalin and consequently with a mixture of carbon black and 10% gelatin to cast all vessels. Vasospasm was evaluated by measuring the diameter of the left middle cerebral artery (MCA) with a microscope. RESULTS: In nontransgenic mice, the diameter of the MCA on day 3 after SAH (110.5+/-20.5 microm [mean+/-SD]; n=16) was significantly reduced compared with that without SAH (138.5+/-14.5 microm; n=12) (P<0.01). Moreover, on day 3 after SAH, the diameter of the MCA in SOD-transgenic mice (127. 9+/-20.2 microm; n=20) was significantly larger than that in nontransgenic mice (110.5+/-20.5 microm; n=16) (P<0.05). CONCLUSIONS: These results suggest that SOD is effective on the amelioration of vasospasm after SAH and that oxygen free radicals, particularly superoxide, play an important role in the pathogenesis of vasospasm after SAH.

Animals↗
PubMed1999

Prevalence of intracranial saccular aneurysms in a Japanese community based on a consecutive autopsy series during a 30-year observation period. The Hisayama study.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage is a life-threatening disease that occurs mostly because of the rupture of intracranial saccular aneurysms. However, little is known about the prevalence of ruptured and unruptured aneurysms in the general population. The aim of the present study was to examine the prevalence of intracranial aneurysms on the basis of a consecutive autopsy series over a 30-year observation period in a general Japanese population in Hisayama. METHODS: We evaluated 1230 consecutive autopsy cases with craniotomy among the total deaths of Hisayama residents during 1962 through 1991 (overall autopsy rate, 80.1%). RESULTS: A total of 73 intracranial saccular aneurysms were found in 57 cases (4.6%). The prevalence of aneurysms for women was 2.4 times higher than that for men (7.1% versus 2.9%). Among men, the prevalence of aneurysms remained unchanged across the range of age groups. In contrast, there were 2 peaks in the prevalence of aneurysms for women falling in the 40- to 49-year (14.3%) and 60- to 69-year age groups (14.5%). The most common site of the aneurysms was the middle cerebral artery (31.5%), followed by the anterior communicating artery (30.1%), anterior cerebral artery (15.1%), vertebrobasilar artery (12.3%), and internal carotid artery (11.0%). Among these 73 aneurysms, 29 (39.7%) were ruptured. Ruptured aneurysms were common in subjects <80 years of age, whereas unruptured aneurysms were prevalent in those >/=80 years of age. The frequency of ruptured aneurysms was highest in the vertebrobasilar system (66.7%) and lowest in the middle cerebral artery (13.0%). CONCLUSIONS: Our data suggest that intracranial aneurysms are more frequent in women in the general Japanese population. Aneurysms are more prevalent in the middle cerebral artery, but the risk of rupture is highest in the vertebrobasilar system.

Adolescent↗
PubMed1999

[An autopsy case of pulmonary embolism due to renal angiomyolipoma in an elderly woman].

An 86-year-old woman with a 13-year history of hypertension was admitted because of consciousness disturbance, hypotension, tachycardia, and cyanosis at her extremities. Enhanced computed tomography showed a thrombus in the truncus pulmonalis and right pulmonary artery, and also showed a left renal mass and a right renal cyst. Under a diagnosis of pulmonary embolism we started anticoagulant therapy, but the patient died five days after admission. At autopsy, a saddle-like thrombus was found in the truncus pulmonalis and bilateral trunks of pulmonary arteries. Microscopic examination showed smooth muscle cells in the thrombus. We could not find any other thrombus in the inferior vena cava, intrapelvic veins, nor in veins of lower extremities by milking. We also found tumors in both kidneys. Microscopically all tumors were diagnosed as angiomyolipoma. There were many fibrin thrombi in the sinuses of the tumors but there was no evidence of malignancy. We finally diagnosed pulmonary embolism due to renal angiomyolipoma because there was no other thrombus origin and microscopically the same smooth muscle cells were found both in the renal tumor and the pulmonary thrombus. There is only one case report concerning pulmonary embolism due to renal angiomyolipoma which happened during operative treatment. The treatment method of renal angiomyolipoma is determined by tumor size and symptoms, and usually intensive treatment is not performed in cases without symptoms. Our patient had no symptoms until the onset of severe complication of pulmonary embolism, suggesting that radical treatment is necessary for renal angiomyolipoma with a thrombus even when there are no symptoms.

Aged↗
PubMed1999

[Osteocalcin].

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Adolescent↗
PubMed1998

The unusually slow unfolding rate causes the high stability of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus: equilibrium and kinetic studies of guanidine hydrochloride-induced unfolding and refolding.

To elucidate the energetic features of the anomalously high-level stabilization of a hyperthermophile pyrrolidone carboxyl peptidase (PfPCP) from a hyperthermophilic archaeon, Pyrococcus furiosus, equilibrium and kinetic studies of the guanidine hydrochloride (GuHCl)-induced unfolding and refolding were carried out with CD measurements at 220 nm in comparison with those from the mesophile homologue (BaPCP) from Bacillus amyloliquefaciens. The mutant protein of PfPCP substituted with Ser at both Cys142 and Cys188 (PfC142/188S) was used. The GuHCl unfolding for PfC142/188S and BaPCP was reversible. It was difficult to obtain the equilibrated unfolding curve of the hyperthermophile proteins at temperatures below 50 degreesC and pH 7, because of the remarkably slow rate of the unfolding. The unfolding for PfC142/188S attained equilibrium after 7 days at 60 degreesC, resulting in the coincidence between the unfolding and refolding curves. The Gibbs energy change of unfolding, DeltaGH2O (56.6 kJ/mol), for PfC142/188S at 60 degreesC and pH 7 was dramatically higher than that (7.6 kJ/mol) for BaPCP at 40 degreesC and pH 7. The unfolding and refolding kinetics for PfC142/188S and BaPCP at both 25 and 60 degreesC at pH 7 were approximated as a single exponential. The rate constant in water (kuH2O) of the unfolding reaction for PfC142/188S (1.6 x 10(-)15 s-1) at 25 degreesC and pH 7 was drastically reduced by 7 orders of magnitude compared to that (1.5 x 10(-)8 s-1) for BaPCP, whereas the refolding rates (krH2O) in water for PfC142/188S (9.3 x 10(-)2 s-1) and BaPCP (3.6 x 10(-)1 s-1) at 25 degreesC and pH 7 were similar. These results indicate that the greater stability of the hyperthermophile PCP was characterized by the drastically slow unfolding rate.

Circular Dichroism↗
PubMed1998

Adhesion to fibronectin maintains regenerative capacity during ex vivo culture and transduction of human hematopoietic stem and progenitor cells.

Recent reports have indicated that there is poor engraftment from hematopoietic stem cells (HSC) that have traversed cell cycle ex vivo. However, inducing cells to cycle in culture is critical to the fields of ex vivo stem cell expansion and retroviral-mediated gene therapy. Through the use of a xenograft model, the current data shows that human hematopoietic stem and progenitor cells can traverse M phase ex vivo, integrate retroviral vectors, engraft, and sustain long-term hematopoiesis only if they have had the opportunity to engage their integrin receptors to fibronectin during the culture period. If cultured in suspension under the same conditions, transduction is undetectable and the long-term multilineage regenerative capacity of the primitive cells is severely diminished.

Animals↗
PubMed1998

Crystal structure of methionine aminopeptidase from hyperthermophile, Pyrococcus furiosus.

The structure of methionine aminopeptidase from hyperthermophile Pyrococcus furiosus (PfMAP) with an optimal growth temperature of 100 degreesC was determined by the multiple isomorphous replacement method and refined in three different crystal forms, one monoclinic and two hexagonal, at resolutions of 2.8, 2.9, and 3.5 A. The resolution of the monoclinic crystal form was extended to 1.75 A by water-mediated transformation to a low-humidity form, and the obtained diffraction data used for high-resolution structure refinement. This is the first description of a eukaryotic type methionine aminopeptidase structure. The PfMAP molecule is composed of two domains, a catalytic domain and an insertion domain, connected via two antiparallel beta-strands. The catalytic domain, which possesses an internal 2-fold symmetry and contains two cobalt ions in the active site, resembles the structure of a prokaryotic type MAP from Escherichia coli (EcMAP), while the structure of the insertion domain containing three helices has a novel fold and accounts for a major difference between the eukaryotic and prokaryotic types of methionine aminopeptidase. Analysis of the PfMAP structure in comparison with EcMAP and other mesophile proteins reveals several factors which may contribute to the hyperthermostability of PfMAP: (1) a significantly high number of hydrogen bonds and ion-pairs between side-chains of oppositely charged residues involved in the stabilization of helices; (2) an increased number of hydrogen bonds between the positively charged side-chain and neutral oxygen; (3) a larger number of buried water molecules involved in crosslinking the backbone atoms of sequentially separate segments; (4) stabilization of two antiparallel beta-strands connecting the two domains of the molecule by proline residues; (5) shortening of N and C-terminal tails and stabilization of the loop c3E by deletion of three residues.

Amino Acid Sequence↗
PubMed1998

VLA-5 is expressed by mouse and human long-term repopulating hematopoietic cells and mediates adhesion to extracellular matrix protein fibronectin.

Fibronectin (FN), an extracellular matrix protein, is involved in the adhesion and migration of hematopoietic cells and has been shown to enhance retroviral gene transfer into primitive hematopoietic cells by co-localization of target cells and retrovirus when used as a substrate in vitro. We have previously found that mouse hematopoietic stem cells could be transduced on a FN fragment that included the recognition sequence Arg-Gly-Asp (RGD), suggesting that stem cells may express the integrin very late antigen (VLA)-5. To address this, we investigated the binding of mouse and human hematopoietic cells to recombinant peptides that contained one or a combination of the three principle cell-binding domains of FN. These domains included the VLA-5- binding sequence RGD, the VLA-4-binding site CS1, and the high affinity heparin-binding domain. Here we show that mouse long-term in vivo repopulating stem cells, as well as primitive human NOD/SCID mouse repopulating cells, can bind extracellular matrix protein FN by using integrin VLA-5 in vitro. This binding is specific and can be inhibited by antibodies to VLA-5. In addition, preincubation of BM cells with peptide CH-296, which contains all three primary FN-binding domains, decreased the engraftment of cells in the bone marrow in vivo, while intravenous injection of the same peptide induced an increase of progenitor cells in the spleen. In summary, our data demonstrate that VLA-5 is expressed on primitive mouse and human hematopoietic cells and suggest that there may be significant cooperation between integrin receptors and proteoglycan molecules in the engraftment of bone marrow cells and hematopoietic cell adhesion in vivo.

Animals↗
PubMed1998

The structures of asparagine-linked oligosaccharides of rat liver cathepsin L reflect the substrate specificity of lysosomal alpha-mannosidase.

We have studied the structures of asparagine-linked oligosaccharides of cathepsin L purified from rat liver in detail. The oligosaccharides released from rat liver cathepsin L on glycopeptidase-F treatment were tagged with 2-aminopyridine at their reducing ends. The pyridylamino (PA) derivatives were separated into seven fractions according to molecular size by normal-phase HPLC. The structure of each oligosaccharide thus isolated was analyzed by reversed-phase HPLC and characterized by ion-spray mass spectrometry and high-resolution proton nuclear magnetic resonance (1H-NMR) spectroscopy. Our results indicate that the asparagine-linked oligosaccharides of rat liver cathepsin L are of the oligomannose type, having two to six mannose residues. Among them, the five major ones are Manalpha1-6Manbeta1-4-GlcNAcbeta1-4GlcNAc, Manalpha1 -6Manalpha1-6Manbeta1-4GIcNAcbeta1-4GlcNAc, Manalpha1-6(Manalpha1-3)-Manalpha1-6Manbeta1- 4GlcNAcbeta1-4GlcNAc, Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3) Manbeta1-4Glc-NAcbeta1-4GlcNAc, and Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-++ +2Manalpha1-3)Manbeta1-4GlcNAcbeta1-4Glc-NAc. Their structures are shown to be products of Man6GlcNAc2 hydrolysis with lysosomal alpha-mannosidase.

Animals↗
PubMed1998

Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients.

Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca2+ mobilization for insulin secretion by glucose in pancreatic beta cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD+ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P </= 0.05). Insulin secretion from pancreatic islets by glucose is significantly inhibited by the addition of the NIDDM sera with anti-CD38 antibodies (P </= 0.04-0.0001), and the inhibition of insulin secretion is abolished by the addition of recombinant CD38 (P </= 0.02). The increase of cADPR levels in pancreatic islets by glucose was also inhibited by the addition of the sera (P </= 0.05). These results strongly suggest that the presence of anti-CD38 autoantibodies in NIDDM patients can be one of the major causes of impaired glucose-induced insulin secretion in NIDDM.

ADP-ribosyl Cyclase↗
PubMed1998

Electrostatic stabilization in methionine aminopeptidase from hyperthermophile Pyrococcus furiosus.

The thermostability of methionine aminopeptidase from a hyperthermophile P. furiosus (PfMAP) was extremely high: the denaturation temperature was 106.2 degreesC at pH 10.2. To explore the contribution of electrostatic interaction to the superior thermostability of PfMAP, the thermostability of PfMAP was examined by differential scanning calorimetry (DSC) in various salt concentrations in the acidic region far from the isoelectric point of PfMAP. (1) In 20 mM glycine buffer, the DSC curve of PfMAP exhibited a single peak. Transition temperatures (Tm) were lowered with decreasing pH from 4 to 3. The heat denaturation of PfMAP was not reversible. (2) Denaturation enthalpy (DeltaH) measured at different pHs linearly correlated with Tm up to 102 degreesC, suggesting that the denaturation heat capacity (DeltaCp) for PfMAP is constant up to 100 degreesC. DeltaCp was estimated to be 0.82 J K-1 g-1. (3) In the presence of 10-100 mM KCl at pH 3.2, two peaks appeared on the DSC curves. The first peak shifted to lower temperatures with increasing concentration of KCl and, oppositely, the second one to higher temperatures. It was found that the first and second peaks originated from the heat denaturation of the native form of PfMAP and the melting of the non-native associated form having molten globule-like structure, respectively, judged from the CD spectra and ultracentrifugation analyses. This indicates the following: first, the attractive electrostatic interaction is an important factor in stabilizing the native form of PfMAP; second, the presence of KCl stimulates the formation of the molten globule-like state of PfMAP and stabilizes it. (4) In a comparison of the sequence and crystal structure of PfMAP, which has been recently determined (1xgs.pdb), with those of MAP from Escherichia coli (EcMAP), it was predicted that the extra four short-range ion pairs less than 3 A involved in PfMAP are crucial candidates as determinants for the superior thermostability of PfMAP.

Aminopeptidases↗
PubMed1998

Metabolic labeling of a subset of glial cells by UDP-galactose: implication for astrocyte lineage diversity.

Astrocytes are implicated in many aspects of brain function; however, it remains unclear whether astrocytes arise from a single cell lineage. It is therefore important to obtain new markers for the astrocyte cell lineage. We show that exogenously added UDP-galactose (UDP-Gal) can be used to metabolically label a subset of glial fibrillary acidic protein-positive (GFAP+) cells. UDP-Gal was incorporated into the cultured embryonic mouse brain slices in a time-dependent manner. Surprisingly, the transferred sugar moiety was no longer Gal but was mainly glucose. Most of the radioactivity was transferred to a polymer of glucose, most likely to be glycogen, and also to glucosyl ceramide. In the slice culture, the reaction products were distributed densely in the ventricular zone and also on process-like structures extending to the pial surface. In dissociation culture, UDP-Gal labeled some of the GFAP+ cells and some of the vimentin+ cells. Because radial glial cells (RGCs) contain glycogen and change from vimentin+ to GFAP+, it is strongly suggested that UDP-Gal labeled RGCs and their descendants. Only 27% of the GFAP+ cells were labeled with UDP-Gal, which suggests that only a subset of astrocytes are derived from RGCs and that there is a discrete group of GFAP+ cells that is not generated from RGCs.

Animals↗
PubMed1998

Transformation system for prototrophic industrial yeasts using the AUR1 gene as a dominant selection marker.

We show a new transformation system for prototrophic yeast strains including those of Saccharomyces cerevisiae, Kluyveromyces lactis, K. marxianus, and Candida glabrata. This system is composed of an antibiotic, aureobasidin A (AbA), and its resistance gene AUR1-C as a selection marker. Southern analysis of genomic DNAs of the transformants indicated that the copy number of the plasmid increased from one to more than four, depending on the concentration of AbA used for selection of the transformants. The AUR1-C gene was also effective as a selection marker for gene disruption, and was able to disrupt both copies of the gene on homologous chromosomes of diploid cells by a single round of transformation. This system has a broad application in the transformation and gene disruption of prototrophic strains of a variety of yeast species.

Aspergillus↗
PubMed1998

Enzymatic synthesis of a neoglycoconjugate by transglycosylation with Arthrobacter endo-beta-N-acetylglucosaminidase: a substrate for colorimetric detection of endo-beta-N-acetylglucosaminidase activity.

The transglycosylation activity of endo-beta-N-acetylglucosaminidase from Arthrobacter protophormiae was used for the enzymatic synthesis of a novel oligosaccharide, Man6GlcNAc-p-nitrophenyl-alpha-D-glucose (Man6GlcNAc-Glc-pNP). The reaction was efficiently induced in aqueous solution containing dimethyl sulfoxide. In the medium containing 20% (v/v) dimethyl sulfoxide with 0.1 M Glc-pNP as an acceptor, the transglycosylation attained yields of 75% by high-performance anion-exchange chromatography. The structure of Man6GlcNAc-Glc-pNP was confirmed by ion mass spectrometry and 400 MHz 1H NMR spectrometry. Various endo-beta-N-acetylglucosaminidases hydrolyzed this oligosaccharide and Man6GlcNAc and Glc-pNP were released from the oligosaccharide by endo-beta-N-acetylglucosaminidase digestion. We have established a new procedure for the colorimetric detection of endo-beta-N-acetylglucosaminidase activity using Man6Glc-NAc-Glc-pNP, which is simple as that for other exoglycosidase assays with pNP-glycosides as substrates.

Acetylglucosaminidase↗
PubMed1998

Differential display with carboxy-X-rhodamine-labeled primers and the selection of differentially amplified cDNA fragments without cloning.

Differential display (DD) has been used extensively to detect differentially expressed genes. However, the low reproducibility of displayed bands makes verification by Northern blot difficult and the technique is labor-intensive. This report describes a fluorescent DD with a ROX (carboxy-X-rhodamine)-labeled anchor primer and a revised RT-PCR, utilizing AMV reverse transcriptase, a more thermostable reverse transcriptase than Mu-MLV, and optimized concentrations of dNTPs and of MgCl2. Our technique yielded clear fingerprints with high reproducibility. Further, we have developed a method of rapid screening to select the cDNA fragments of interest in excised bands from a polyacrylamide gel without cloning. This method consists of electrophoresis with an agarose gel containing a base-specific DNA ligand to separate the equally sized fragments differing in base composition, and side-by-side comparison of the reamplified products from the experimental and control lane. Most of the cDNA fragments selected by this protocol provided readable sequences by direct sequencing and were confirmed to exhibit differential expression by Northern blot analysis or semiquantitative RT-PCR.

Base Sequence↗
PubMed1998

Role of left atrial appendage in left atrial reservoir function as evaluated by left atrial appendage clamping during cardiac surgery.

We evaluated the role of left atrial appendage (LAA) in the left atrial (LA) reservoir function by assessing the changes in LA flow dynamics after LAA clamping during cardiac surgery. The subjects were 8 patients who had undergone coronary artery bypass grafting (CABG) and 7 who had undergone mitral valvular surgery due to mitral regurgitation. We recorded transmitral, pulmonary venous and LAA flow velocity patterns by intraoperative transesophageal pulsed Doppler echocardiography, monitoring LA pressure before and 5 minutes after LAA clamping. The maximal LAA area was significantly greater, and the peak late diastolic LAA emptying flow velocity was significantly lower before LAA clamping in the mitral regurgitation group than in the CABG group. In both groups, the peak early and late diastolic transmitral and pulmonary venous flow velocities significantly increased, and the peak second systolic pulmonary flow velocity significantly decreased during LAA clamping. There were no significant changes in heart rate and systemic systolic blood pressure during LAA clamping, whereas mean LA pressure and maximal LA dimension significantly increased in both the groups. The LA pressure-volume relation during ventricular systole shifted upward and to the left during LAA clamping, and the slope was steeper in the MR group than in the CABG group. We conclude that the LAA is more compliant than the LA main chamber, and plays an important role in LA reservoir function in the presence of LA pressure and/or volume overload.

Aged↗
PubMed1998

Transgenic mice overexpressing type 2 nitric-oxide synthase in pancreatic beta cells develop insulin-dependent diabetes without insulitis.

We generated transgenic mice carrying the mouse type 2 nitric-oxide synthase (NOS2) cDNA under the control of the insulin promoter. Western and immunohistochemical analyses revealed that NOS2 was expressed abundantly in transgenic islets but not in control islets. When islets were isolated and cultured, high levels of nitrite were released from the transgenic islets. In transgenic mice, the beta cell mass was markedly reduced without the infiltration of macrophages or lymphocytes, and extensive DNA strand breaks were detected in the islets by in situ nick translation. All the transgenic mice developed hypoinsulinemic diabetes by 4 weeks of age, and treatment with an inhibitor of NOS2, aminoguanidine (200 mg/kg body weight every 12 h), prevented or delayed the development of diabetes. The present study shows that the production of nitric oxide by beta cell NOS2 plays an essential role in the beta cell degeneration.

Animals↗