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Y Okada

Publications and source records attributed to Y Okada.

At least 361 records · Page 20Linked to original sources
PubMed1999

Excitatory effects of adenosine are not mediated by inhibition of GABAergic system in slices of superior colliculus and hippocampus from guinea pig.

Neurotransmission in the superior colliculus (SC) and the hippocampus is enhanced by application of adenosine. To investigate the possible involvement of disinhibition by adenosine on gamma-aminobutyric acid (GABA) -ergic action, the effects of adenosine and picrotoxin, a GABA antagonist, were studied using slices of SC and hippocampus of the guinea pig. Application of adenosine on SC slices (concentration at 100 microM) and hippocampus (concentration at 0.1 microM) enhanced the amplitude of population spikes (PS) in the superficial gray layer (SGL) of SC and in the granule cell layer of dentate gyrus of hippocampus. The application of picrotoxin at 100 microM increased the amplitude of both slices even after previous treatment with adenosine which once increased the amplitude. This was also true for adenosine with the previous treatment of picrotoxin. In SC slices, the increased amplitude by adenosine was reduced to the original amplitude after application of 3-[1-[3-(Dimetylamino) propyl]-1 H-indol-3-yl-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione (GF109203X) a protein kinase C inhibitor, the previous treatment by the drug counteracted the excitatory action of adenosine. However GF109203X failed to counteract the excitatory effects of picrotoxin. These results indicate that the excitatory mechanism of adenosine is different from that of picrotoxin and is not mediated by disinhibition of the GABAergic system through inhibitory action of adenosine on GABAergic interneurons.

Action Potentials↗
PubMed1999

Experimental implication of celiac ganglionotropic invasion of pancreatic-cancer cells bearing c-ret proto-oncogene with reference to glial-cell-line-derived neurotrophic factor (GDNF).

Perineural invasion is a prominent clinical feature of pancreatic cancer which causes difficulty in curative resection. In the present study, the human pancreatic cancer cell lines, PaCa-2, AsPC-1, SW1990 and Capan-2, were all found to express abundant c-ret proto-oncogene mRNA and RET protein, a member of the receptor-tyrosine-kinase superfamily, identified as being a receptor for glial-cell-line-derived neurotrophic factor (GDNF). In an invasion assay, the migration of pancreatic cancer cells was markedly induced by co-cultivation with human glioma cells, T98G or A172, capable of producing and secreting GDNF. Anti-GDNF antibody in conditioned media of glioma cells suppressed much of the migratory activity. Checkerboard analysis of the migration showed both chemotactic and chemokinetic activity of GDNF. There was no detectable expression of another GDNF receptor component, a glycosyl-phosphatidylinositol-linked receptor (GFR alpha-1), in pancreatic-cancer cell lines, suggesting that the neural invasion of pancreatic-cancer cells spreads along a concentration gradient of GDNF produced from peripheral ganglions through direct interaction of GDNF with its receptor, the c-ret proto-oncogene product. Immunochemical localization of GDNF in human celiac ganglionic tissue supported this contention.

Cell Movement↗
PubMed1999

Historical overview of research on the tobacco mosaic virus genome: genome organization, infectivity and gene manipulation.

Early in the development of molecular biology, TMV RNA was widely used as a mRNA [corrected] that could be purified easily, and it contributed much to research on protein synthesis. Also, in the early stages of elucidation of the genetic code, artificially produced TMV mutants were widely used and provided the first proof that the genetic code was non-overlapping. In 1982, Goelet et al. determined the complete TMV RNA base sequence of 6395 nucleotides. The four genes (130K, 180K, 30K and coat protein) could then be mapped at precise locations in the TMV genome. Furthermore it had become clear, a little earlier, that genes located internally in the genome were expressed via subgenomic mRNAs. The initiation site for assembly of TMV particles was also determined. However, although TMV contributed so much at the beginning of the development of molecular biology, its influence was replaced by that of Escherichia coli and its phages in the next phase. As recombinant DNA technology developed in the 1980s, RNA virus research became more detached from the frontier of molecular biology. To recover from this setback, a gene-manipulation system was needed for RNA viruses. In 1986, two such systems were developed for TMV, using full-length cDNA clones, by Dawson's group and by Okada's group. Thus, reverse genetics could be used to elucidate the basic functions of all proteins encoded by the TMV genome. Identification of the function of the 30K protein was especially important because it was the first evidence that a plant virus possesses a cell-to-cell movement function. Many other plant viruses have since been found to encode comparable 'movement proteins'. TMV thus became the first plant virus for which structures and functions were known for all its genes. At the birth of molecular plant pathology, TMV became a leader again. TMV has also played pioneering roles in many other fields. TMV was the first virus for which the amino acid sequence of the coat protein was determined and first virus for which cotranslational disassembly was demonstrated both in vivo and in vitro. It was the first virus for which activation of a resistance gene in a host plant was related to the molecular specificity of a product of a viral gene. Also, in the field of plant biotechnology, TMV vectors are among the most promising. Thus, for the 100 years since Beijerinck's work, TMV research has consistently played a leading role in opening up new areas of study, not only in plant pathology, but also in virology, biochemistry, molecular biology, RNA genetics and biotechnology.

Capsid↗
PubMed1999

Antithrombin III treatment improves parameters of acute inflammation in a highly histoincompatible model of rat lung allograft rejection.

BACKGROUND: Antithrombin III (AT-III) is an antithrombotic agent with known anti-inflammatory properties that is also known to attenuate acute inflammation, prevent ischemia-reperfusion injury, and disseminated intravascular coagulation (DIC) associated with sepsis and endotoxemia. Here, we examined the ability of AT-III to modify parameters of acute inflammation in a highly histoincompatible model of rat lung allograft rejection (AR). METHODS: After left single lung transplantations (BN-->Lew), recipient animals were treated i.v. with 50 U/kg of human AT-III (low dose group), 500 U/kg of human AT-III (high dose group), or normal saline (control group) on days 2 and 4 posttransplant. All animals were sacrificed on day 6, and several pathological categories of acute inflammation related to AR were scored (0-4). The effect of AT-III on concanavalin A (Con A)-stimulated rat spleen cell proliferation was also examined. RESULTS: The stage of AR, and the degrees of edema, hemorrhage, and necrosis were significantly reduced in the high dose group compared with the control group. AT-III significantly inhibited rat spleen cell proliferation in response to Con A, in a dose-dependent manner. Maximal inhibition was seen at 15 U/ml in culture. Identical inhibition of Con-A-stimulated cultures occurred in both serum free and serum-containing media, indicating that AT-III inhibition of Con-A-stimulated rat spleen cell proliferation is independent of its actions on thrombin. CONCLUSIONS: 1) AT-III treatment significantly improves parameters of acute inflammation seen in a highly histoincompatible model of rat lung AR. 2) AT-III inhibits in vitro T cell proliferation to the potent mitogen Con A, suggesting that protease inhibition may inhibit T cell activation in vitro. 3). The beneficial effects of AT-III on parameters of lung AR relate to the anti-coagulant, anti-inflammatory, and possibly immunoregulatory actions of AT-III.

Acute Disease↗
PubMed1999

A processive single-headed motor: kinesin superfamily protein KIF1A.

A single kinesin molecule can move "processively" along a microtubule for more than 1 micrometer before detaching from it. The prevailing explanation for this processive movement is the "walking model," which envisions that each of two motor domains (heads) of the kinesin molecule binds coordinately to the microtubule. This implies that each kinesin molecule must have two heads to "walk" and that a single-headed kinesin could not move processively. Here, a motor-domain construct of KIF1A, a single-headed kinesin superfamily protein, was shown to move processively along the microtubule for more than 1 micrometer. The movement along the microtubules was stochastic and fitted a biased Brownian-movement model.

Adenosine Triphosphate↗
PubMed1999

Enhanced production and activation of progelatinase A mediated by membrane-type 1 matrix metalloproteinase in human papillary thyroid carcinomas.

Matrix metalloproteinases (MMPs) are believed to be involved in the invasion and metastasis of various human carcinomas. In the present study, the production levels of seven different MMPs (MMP-1, -2, -3, -7, -8, -9, and -13), the activation of the zymogen of MMP-2 (proMMP-2), the expression of membrane-type MMPs (MT1-, MT2-, and MT3-MMPs), and the tissue localization of the activated enzyme were examined in human invasive papillary thyroid carcinomas. Sandwich enzyme immunoassays revealed that among the MMPs examined, only the MMP-2 production level is significantly enhanced in the carcinoma tissues compared with the follicular adenoma and normal control thyroid tissues. Gelatin zymography indicated that the proMMP-2 activation ratio is considerably higher in carcinomas with lymph node metastasis than it is in those without metastasis, follicular adenomas, or normal controls (P < 0.01). Northern blot analysis of the expression of MT1-, MT2-, and MT3-MMPs, which are known to activate proMMP-2 in vitro, demonstrated the predominant expression of MT1-MMP mRNA in the carcinoma tissues (15 of 15 cases), whereas MT2-MMP expression was confined to 26% of the cases (4 of 15 cases), and no consistent expression of MT3-MMP was observed. MTI-MMP mRNA expression levels correlated with the proMMP-2 activation ratio (r = 0.692; P < 0.01), but such a correlation was not obtained with MT2-MMP. There was also a direct correlation between MT1-MMP expression and lymph node metastasis (P < 0.05). In situ hybridization indicated that both carcinoma and stromal cells express MT1-MMP transcripts (five of six cases). MT1-MMP was also immunolocalized to carcinoma and stromal cells in all of the carcinoma samples (26 of 26 cases), which were positive for MMP-2. In situ zymography indicated definite gelatinolytic activity in the carcinoma cell nests, which was abolished by incubation of the carcinoma samples with a synthetic MMP inhibitor before the reaction. These results suggest for the first time that among seven different MMPs, the production of proMMP-2 and its MT1-MMP-mediated activation in the carcinoma cell nests play an important role in the lymph node metastasis of human invasive papillary thyroid carcinomas.

Adult↗
PubMed1999

Development of plasma kallikrein selective inhibitors.

During the course of the development of active center-directed plasmin inhibitors, it was found that N-(trans-4-aminomethylcyclohexanecarbonyl)-lysine-4-methoxycarb onylanilide inhibited plasma kallikrein more potently than other enzymes such as plasmin, urokinase, and thrombin, although the inhibitory activity was not as potent and enzyme selectivity not as high. Based on studies of structure-activity relationship, we designed and synthesized the plasma kallikrein selective inhibitor, N-(trans-4-aminomethylcyclohexanecarbonyl)-phenylalanine-4-carboxy methyl- anilide (Tra-Phe-APAA). Tra-Phe-APAA inhibited plasma kallikrein with a Ki value of 0.81 microM, while it inhibited glandular kallikrein, plasmin, urokinase, tissue plasminogen activator, factor Xa, factor XIIa, and thrombin with Ki values of > 500, 390, 200, > 500, > 500 > 500, and > 500 microM, respectively. We designated Tra-Phe-APAA as PKSI-527. Using PKSI-527 as an affinity ligand, we synthesized a new affinity gel (PKSI-Toyopearl) and employed it for the rapid purification of plasma kallikrein from human plasma. Human plasma activated with kaolin after acid treatment was applied to a PKSI-527-Toyopearl column. Adsorbed protein was eluted with 50 mM glycinehydrochloric acid buffer (pH 3.0). Plasma kallikrein was purified 181-fold with a yield of 85% from the kaolin-activated plasma.

Binding Sites↗
PubMed1999

Pressurization of bioactive bone cement in vitro.

We have developed a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW glass-ceramic powder), silica glass powder as an inorganic filler, and bisphenol-a-glycidyl methacrylate (bis-GMA) based resin as an organic matrix. The efficacy of this bioactive bone cement was investigated by evaluating its pressurization in a 5-mm hole and small pores using a simulated acetabular cavity. Two types of acetabular components were used (flanged and unflanged sockets) and a commercially available polymethylmethacrylate (PMMA) bone cement (CMW 1 Radiopaque Bone Cement) was selected as a comparative control. Bioactive bone cement exerted greater intrusion volume in 5-mm holes than PMMA bone cement in both the flanged and unflanged sockets 10 minutes after pressurization (p < 0.05). In the small pores the bioactive and PMMA bone cements exerted almost identical intrusion volumes in flanged and unflanged sockets 10 min after pressurization. The intrusion volume in the flanged socket 10 minutes after pressurization was greater than that in the unflanged socket in all groups (p < 0.05). These results show that bioactive bone cement intrudes deeper into anchor holes than PMMA bone cement.

Biocompatible Materials↗
PubMed1999

In vitro analysis of the stimulation of bone formation by highly bioactive apatite- and wollastonite-containing glass-ceramic: released calcium ions promote osteogenic differentiation in osteoblastic ROS17/2.8 cells.

We analyzed the mechanisms of the efficient bone formation on the osteoconductive surface of apatite- and wollastonite-containing glass-ceramic (AW) by using an in vitro system. AW releases Ca ions and bonds to bone via a submicron-thick hydroxycarbonate apatite (HCA) layer. AW disks were conditioned with simulated body fluid (SBF) to grow HCA layers, and the amount of released Ca ion was regulated by modulating the conditioning time from 24 to 240 h. Surface-transformed AW disks increased alkaline phosphatase (AP) activity in osteoblastic ROS17/2.8 cells by 1.5- to threefold over unconditioned disks. AW disks conditioned for 24 h [AW(24)], which had a homogeneous, submicron-thick apatite layer and increased extracellular ionized Ca concentration ([Ca(2+)](e)) in the culture medium to the greatest extent, enhanced the AP activity the most. High [Ca(2+)](e) promoted osteogenic differentiation in ROS17/2.8 cells: It increased AP activity in a dose-dependent manner by up to 1.6-fold, and up-regulated the expression of AP, osteocalcin (OC), and transforming growth factor-beta1 mRNAs in dose- and time-dependent manners. AW(24) enhanced AP activity in ROS17/2.8 cells as much as AW disks conditioned with SBF containing serum to exhibit in vivo surface-structure changes. AW(24) increased AP activity in ROS17/2.8 cells by 1.6-fold and enhanced the expression of AP and OC mRNAs significantly, compared with sintered hydroxyapatite (HA). After implantation of AW and HA in the distal metaphyses of rabbit femurs, thin, newly formed bone lined with cuboidal, osteoblast-like cells was characteristically observed adjacent to the AW surface within 8 days. These results provide evidence for the hypothesis that AW stimulates bone formation on its surface by increasing [Ca(2+)](e) to promote the HCA layer formation and the differentiation of osteogenic cells.

Animals↗
PubMed1999

Argatroban, an attractive anticoagulant, for left heart bypass with centrifugal pump for repair of traumatic aortic rupture.

Systemic heparinization often increases the risk of fatal bleeding from other injured organs in surgical repair of the aorta using extracorporeal circulation in patients with traumatic aortic rupture associated with multisystem injuries. We used an antithrombin agent, argatroban, as an alternative anticoagulant in left heart bypass with the Bio-Medicus centrifugal pump in 7 of 9 recent patients who underwent aortic repair using left heart bypass. All these patients survived without obvious evidence of systemic thromboembolization. Surgical treatments for other organ injuries were carried out in 3 patients concomitantly or immediately after aortic repairs without undue blood loss. Argatroban may have a complementary effect for preventing thrombus formation without aggravating bleeding tendency because of its monotarget specificity to thrombin. We believe intravenous administration (0.5 to 2 micrograms/kg/min) of argatroban is a safe anticoagulant for left heart bypass in repairs of traumatic aortic rupture associated with multiple organ injuries.

Adolescent↗
PubMed1999

A magnetic resonance abnormality correlating with permeability of the blood-brain barrier in a child with chemical meningitis during central nervous system prophylaxis for acute leukemia.

Chemical meningitis developed in a boy with acute lymphoblastic leukemia during central nervous system (CNS) prophylaxis. Cerebrospinal fluid examination showed pleocytosis and a high protein level. There were no malignant cytological findings. Calculated permeability of albumin across the blood-brain barrier (BBB) was more elevated than that of immunoglobulin or alfa2-macroglobulin. Magnetic resonance imaging (MRI) revealed diffuse pachymeningeal enhancement without any intracerebral lesion. Subsequent CNS prophylaxis was postponed. CSF findings and BBB permeability returned to normal, correlating well with the decrease of MRI abnormality.

Albumins↗
PubMed1999

Expression and tissue localization of membrane-type 1, 2, and 3 matrix metalloproteinases in human astrocytic tumors.

Three different membrane-type matrix metalloproteinases (MT1-, MT2-, and MT3-MMPs) are known to activate in vitro the zymogen of MMP-2 (pro-MMP-2, progelatinase A), which is one of the key MMPs in invasion and metastasis of various cancers. In the present study, we have examined production and activation of pro-MMP-2, expression of MT1-, MT2-, and MT3-MMPs and their correlation with pro-MMP-2 activation, and localization of MMP-2, MT1-MMP, and MT2-MMP in human astrocytic tumors. The sandwich enzyme immunoassay demonstrates that the production levels of pro-MMP-2 in the anaplastic astrocytomas and glioblastomas are significantly higher than that in the low-grade astrocytomas (P<0.05 and P<0.01, respectively), metastatic brain tumors (P<0.05), or normal brains (P<0.01). Gelatin zymography indicates that the pro-MMP-2 activation ratio is significantly higher in the glioblastomas than in other astrocytic tumors (P<0.01), metastatic brain tumors (P<0.01), and normal brains (P<0.01). The quantitative reverse transcription polymerase chain reaction analyses demonstrate that MT1-MMP and MT2-MMP are expressed predominantly in glioblastoma tissues (17/17 and 12/17 cases, respectively), and their expression levels increase significantly as tumor grade increases. MT3-MMP is detectable in both astrocytic tumor and normal brain tissues, but the mean expression level is approximately 50-fold lower compared with that of MT1-MMP and MT2-MMP in the glioblastomas. The activation ratio of pro-MMP-2 correlates directly with the expression levels of MT1-MMP and MT2-MMP but not MT3-MMP. In situ hybridization indicates that neoplastic astrocytes express MT1-MMP and MT2-MMP in the glioblastoma tissues (5/5 cases and 5/5 cases, respectively). Immunohistochemically, MT1-MMP and MT2-MMP are localized to the neoplastic astrocytes in glioblastoma samples (17/17 cases and 12/17 cases, respectively), which are also positive for MMP-2. In situ zymography shows gelatinolytic activity in the glioblastoma tissues but not in the normal brain tissues. These results suggest that both MT1-MMP and MT2-MMP play a key role in the activation of pro-MMP-2 in the human malignant astrocytic tumors and that the gelatinolytic activity is involved in the astrocytic tumor invasion.

Adenocarcinoma↗
PubMed1999

Comparison of MEG and EEG on the basis of somatic evoked responses elicited by stimulation of the snout in the juvenile swine.

OBJECTIVE: Some basic characteristics of magnetoencephalographic (MEG) and electroencephalographic (EEG) signals were studied by comparing somatic evoked fields (SEFs) and potentials (SEPs) elicited by electrical stimulations of different areas of the snout in piglets. METHODS: SEFs were measured with and without an intact skull, whereas SEPs were measured on the skull and cortex (Electrocorticograms - ECoG) and within the cortex of the same animal. RESULTS: The SEFs above the skull and dura were very similar to each other in temporal waveform and spatial topography, indicating small effects of the skull. They both revealed very similar somatotopic projections of the snout. The SEPs on the skull and cortex were, in contrast, clearly different in their amplitudes as well as temporal and spatial morphologies, indicating significant effects of the skull. However, an early component of the SEP on the skull revealed a somatotopic representation of the snout, indicating that EEG can be also useful for inferring cortical projection areas. Discrepancies in their maps were due to predominance of the potentials produced by currents in the gyral cortex. The projection sites inferred from SEFs were quite accurate in comparison to those inferred from ECoGs and intracortical SEPs. CONCLUSION: The similarities and differences clearly point out the complementary nature of MEG and EEG.

Animals↗
PubMed1999

Peter Paul Rickham Prize--1998. Neutrophil dysfunction the cellular mechanism of impaired immunity during total parenteral nutrition in infancy.

BACKGROUND: Studies have shown that total parenteral nutrition (TPN) in infancy is associated with impaired immunity. The causes of this acquired immunodeficiency are poorly understood. Bacterial infection is a major complication of TPN suggesting neutrophils may be affected by this feeding modality. PURPOSE: The aim of this study was to test the hypothesis that TPN-related impaired bactericidal activity is related to impairment of neutrophil function, particularly intracellular killing. METHODS: Studies were performed in five infants (age <2 months) who received long-term TPN (>10 days), five control infants who received a normal enteral diet, and five healthy adults. Patients on long-term TPN were clinically stable with no evidence of sepsis. The experimental study used an in vitro whole-blood model of septicaemia. Coagulase-negative staphylococci were the bacterial challenge. Whole-blood killing of coagulase-negative staphylococci was measured after 45 minutes using the Miles-Misra technique. Neutrophils were separated from whole blood after 15, 30, 45, and 60 minutes of bacterial challenge. The survival rate of the bacteria within the neutrophils was analysed by flow cytometry and the percentage of the bacteria killed by neutrophil intracellular killing assessed at each time-point. RESULTS: Whole-blood killing was significantly lower (P = .05) in infants who received long-term TPN (33.3%) compared with control infants (69.7%) and adults (67.7%). In all subjects studied, neutrophil intracellular killing increased with incubation time. At each time point the intracellular killing in infants on long-term TPN was significantly lower (P < .05) than in normal control infants and adults. CONCLUSION: Future strategies to prevent TPN-related infection should aim to minimise this acquired neutrophil dysfunction.

Adult↗
PubMed1999

Total parenteral nutrition directly impairs cytokine production after bacterial challenge.

BACKGROUND/PURPOSE: Previous studies have shown that total parenteral nutrition (TPN) influences host immunity, but the mechanism is unclear. This study explored the effect of TPN solution on neutrophil phagocytosis and whole-blood cytokine production in response to coagulase-negative staphylococci in vitro challenge. METHODS: Blood samples were taken from five enterally fed infants (age <6 months) and six healthy adults. Samples were incubated for 45 minutes with four isovolemic solutions: (A) control (saline), (B) TPN (0.1 microL/mL of blood), (C) TPN (1 microL/mL), (D) TPN (10 microL/mL). Solution C (1 microL/mL) corresponded to TPN-blood ratio used in clinical practice. After incubation, blood was challenged with coagulase-negative staphylococci. Neutrophil phagocytosis was measured by flow cytometry after 40 minutes of bacterial challenge, and tumour necrosis factor alpha (TNF-alpha) was measured by enzyme-linked immunosorbent assay (ELISA) after 2 hours of bacterial challenge. RESULTS: In infant blood, TNF-alpha production after coagulase-negative staphylococci challenge was impaired after the addition of a "physiological" dose of TPN solution (1 microL/mL of blood) as well as "supranormal" doses (10 microL/mL of blood). In adult blood, a similar effect was observed only after the addition of a supranormal dose of TPN. In both the infant and adult blood, there was no direct effect of TPN solution on neutrophil phagocytosis. CONCLUSIONS: These results suggest that infants are more susceptible than adults to TPN-related depression of cytokine production. The level of proinflammatory cytokines may be important in the host defence against bacterial infection.

Adult↗
PubMed1999

Traumatic dissection of the common carotid artery after blunt injury to the neck.

BACKGROUND: Occlusive lesions of the common carotid artery (CCA) resulting from blunt injury are extremely rare, and their clinicopathologic and therapeutic features have not yet been clarified. OBJECTIVES AND RESULTS: Five patients with occlusive lesions of the CCA developed neurologic deficits at 1.5 hours to 10 years after blunt neck injury. Lesions included two complete occlusions, one severe stenosis, and two segmental intimal dissections of the CCA. In the two patients with CCA occlusion, bypass surgery was performed using a Dacron graft between the ipsilateral subclavian artery and the carotid bifurcation. In the remaining three patients, the involved segments were replaced with a Dacron graft. Surgical specimens from the early posttraumatic period revealed intimal tears with mural thrombosis and/or subintimal hematomas and those from the later period showed myointimal hyperplasia or fibrotic organization. CONCLUSION: Traumatic occlusive lesions of the CCA tend to evolve from intimal dissections to severe stenoses or occlusion, compromising cerebral circulation. The involved CCA can be diagnosed early by B-mode Doppler sonography and successfully reconstructed using a Dacron graft.

Adult↗