Biomedical subjects

T Arai

Publications and source records attributed to T Arai.

At least 289 records · Page 16Linked to original sources

PubMed1998

Lactosylceramide stimulates human neutrophils to upregulate Mac-1, adhere to endothelium, and generate reactive oxygen metabolites in vitro.

Glycosphingolipids (GSLs) and their metabolites play important roles in a variety of biological processes. We have previously reported that lactosylceramide (LacCer), a ubiquitous GSL, stimulates NADPH oxidase-dependent superoxide generation by aortic smooth muscle cells and their consequent proliferation. We postulated that LacCer may upregulate adhesion molecules on human polymorphonuclear leukocytes (hPMNs), perhaps also via NADPH oxidase-dependent reactive oxygen metabolite (ROM) generation. Incubation of hPMNs with LacCer upregulated CD11b/CD18 (Mac-1) and CD11c/CD18, as determined by fluorescence-automated cell sorting. LacCer also stimulated these hPMNs to generate superoxide via NADPH oxidase, as determined by lucigenin-enhanced chemiluminescence. However, the upregulation of Mac-1 by LacCer did not itself appear to be mediated by ROMs, since neither an antioxidant nor an NADPH oxidase inhibitor substantially inhibited the Mac-1 upregulation. However, this Mac-1 upregulation was significantly inhibited by two disparate phospholipase A2 (PLA2) inhibitors. Moreover, LacCer induced arachidonic acid metabolism, which was inhibited by the PLA2 inhibitors, but not by an NADPH oxidase inhibitor. To evaluate the effect of LacCer on hPMN adhesion to endothelium, hPMNs stimulated with LacCer were allowed to adhere to unstimulated human endothelial cell monolayers. LacCer stimulated hPMN adhesion to endothelial cells, which was blocked by anti-CD18 and by the PLA2 inhibitors. We conclude that LacCer stimulates both Mac-1 upregulation and superoxide generation in hPMNs but that ROMs are not the upstream signal for Mac-1 upregulation. This mechanism may well be relevant to acute endothelial injury in inflammation and other pathological conditions.

Antigens, CD↗

PubMed1998

Measurement of local cerebral blood flow by magnetic resonance imaging: in vivo autoradiographic strategy using 17O-labeled water.

Local cerebral blood flow (LCBF) was measured in cats by magnetic resonance imaging (MRI), using 17O-labeled water (H[2]17O) as a tracer. Cat brain images were obtained using a 256 x 240 matrix fast spin-echo sequence with a total acquisition time of 124 seconds per image. Intravenous injection of H(2)17O and sampling of arterial blood were simultaneously performed during the MRI scan. Injection of H(2)17O over 40 seconds caused a transient decrease in brain signal intensity, from which the changes in H(2)17O concentration of brain tissue were calculated. The concentration of H(2)17O in arterial blood was measured directly by 17O nuclear magnetic resonance (NMR) spectroscopy, and used as an input function for the calculation of LCBF. LCBF was successfully determined using an in vivo autoradiographic strategy in a total of three cats. In one, LCBF measurements were also performed under hypercapnic conditions, and LCBF maps of the cat brain during normocapnia and hypercapnia were constructed. These LCBF maps reflected well the changes in LCBF induced by hypercapnia, which indicated the validity of the used method.

Animals↗

PubMed1998

The inhibitory effect of novel triterpenoid compounds, fomitellic acids, on DNA polymerase beta.

We previously found new triterpenoid compounds, designated fomitellic acid A and B, which selectively inhibit the activities of mammalian DNA polymerase alpha and beta in vitro. On DNA polymerase beta, the fomitellic acids acted by competing with both the substrate and the template primer, but on DNA polymerase alpha, they acted non-competitively. At least on DNA polymerase beta, the evidence suggests that each of the fomitellic acids bind to the active region competing with the substrate and/or template primer, and subsequently inhibits the catalytic activity. We therefore further investigated the enzyme-binding properties by using DNA polymerase beta and its proteolytic fragments. The 39 kDa enzyme was proteolytically separated into two fragments of the template-primer-binding domain (8 kDa) and the catalytic domain (31 kDa). The fomitellic acids bound tightly to the 8 kDa fragment, but not to the 31 kDa fragment. The immuno-precipitation by antibodies against the enzyme or each of the fragments also proved the binding. These results suggest that the fomitellic acid molecule competes with the template-primer molecule on its 8 kDa binding site, binds to the site, and the fomitellic acid molecule simultaneously disturbs the substrate incorporation into the template primer.

Animals↗

PubMed1998

A syndrome of peripheral blood T-cell infection with Epstein-Barr virus (EBV) followed by EBV-positive T-cell lymphoma.

The role of Epstein-Barr virus (EBV) in the pathogenesis of severe, chronic active EBV infection and its complications is unclear. We investigated two Japanese patients diagnosed with severe, chronic active EBV infection who subsequently developed EBV-positive T-cell lymphoma. The patients displayed abnormally high antibody titers to EBV antigens, and had evidence of peripheral blood CD4(+) T-cell infection with EBV, 19 months and 3 months, respectively, before the diagnosis of EBV-positive T-cell lymphoma. The lymphomas were infected with monoclonal EBV and expressed the EBV latency genes EBNA-1, LMP-1, and LMP-2. Genetic studies showed that the virus detected in the T-cell lymphoma was indistinguishable, with respect to type and previously defined LMP-1 and EBNA-1 gene variations, from virus detected in the peripheral blood T cells 19 months earlier. These studies support an important pathogenetic role of T-cell infection with EBV in chronic active EBV infection and in the EBV-positive T-cell lymphoma that followed.

Antibodies, Viral↗

PubMed1998

Distribution of the antiseptic-resistance genes qacE and qacE delta 1 in gram-negative bacteria.

The distribution of the antiseptic-resistance genes qacE and qacE delta 1 was studied in a large number of Gram-negative bacteria by a method that included the polymerase chain reaction (PCR). A total of 117 strains of Gram-negative bacteria, isolated from clinical or environmental sources, was used in this analysis. We demonstrated the presence of these genes in 48 of 78 strains of Pseudomonas, in 20 of 26 strains of Vibrio, and in four of 13 strains of other species. These results indicate that the antiseptic-resistance genes are present in a broad range of species of Gram-negative bacteria.

Anti-Infective Agents, Local↗

PubMed1998

Neuroprotective effects of pterin-6-aldehyde in gerbil global brain ischemia: comparison with those of alpha-phenyl-N-tert-butyl nitrone.

The superoxide (O2.-) scavenging activity and the neuroprotective effects of pterin-6-aldehyde (P6A), a xanthine oxidase inhibitor, were examined and compared with those of alpha-phenyl-N-tert-butyl nitrone (PBN), a spin trapping agent. The scavenging activity of P6A was more potent than that of PBN by 150-fold in neutrophil/phorbol myristate acetate O2.- generating system. P6A attenuated the neuronal damage with a much smaller dose and a greater efficiency than PBN in global brain ischemia in gerbils. These findings suggest that P6A is a more potent neuroprotective agent than PBN and has possible therapeutic effects against various diseases in which O2.- is involved.

Animals↗

PubMed1998

Genomic structure of the human Smad3 gene and its infrequent alterations in colorectal cancers.

The Smad3 gene is a member of the Smad family, vertebrate homologues of Drosophila Mad, and its gene product is a cytoplasmic element in the TGF-beta signaling pathway. Smad2 and Smad4/DPC4, other members of the Smad family, are possibly tumor suppressor genes because alterations of these genes occurred in various carcinomas. We determined the genomic structure of human Smad3 which consists of nine exons. Then we examined whether or not Smad3 gene mutations exist in sporadic and hereditary non-polyposis colorectal cancers and found no mutations in the entire coding region in 50 cancers. Loss of heterozygosity of Smad3 was observed in two of the 17 (11.8%) informative cases using a polymorphism found in intron 2. These findings suggest that the Smad3 gene may not play an important role in the tumorigenesis of colorectal cancers.

Base Sequence↗

PubMed1998

Mixed Micellar Properties of Nonionic Saccharide and Anionic Fluorocarbon Surfactants in Aqueous Solution

Mixed micellar properties of nonionic saccharides (n-decyllactobionamide, C10Glu2; n-dodecyllactobionamide, C12Glu2) and anionic fluorocarbon surfactants (lithium perfluorooctanesulfonate, LiFOS) in aqueous solutions have been studied by means of surface tensiometry, NMR, and light scattering. The interaction parameters estimated from the modified regular solution theory are -5.0 for the C10Glu2/LiFOS system and -0.2 for the C12Glu2/LiFOS system. This difference could be due to the interaction of the surfactant tails. The average aggregation number is almost identical over a wide mole fraction of C12Glu2 for the C12Glu2/LiFOS system, while it shows a minimum at a C10Glu2 mole fraction of 0.4 for the C10Glu2/LiFOS system. It is also found from NMR measurements that the segmental motions of surfactants in the mixed micelles of C12Glu2 and LiFOS are not restricted, whereas they are restricted at a C10Glu2 mole fraction of 0.4 for the C10Glu2/LiFOS system. These motional changes as well as micellar composition reflect the solubilization of decafluorobiphenyl in the mixed micelles. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗

PubMed1998

Neurons induce the activation of microglial cells in vitro.

Although microglial cells are well known to become activated in the pathological brain, mechanisms underlying the microglial activation are not fully understood. In the present study, with an aim to elucidate whether neurons are involved in the microglial activation, we compared the morphology and the superoxide anion (O2-)-generating activity of rat microglial cells in pure culture with those of cells cocultured with rat primary cortical neurons. Microglial cells in pure culture in serum-free Eagle's minimum essential medium on poly-L-lysine-coated coverslips displayed ramified morphology and suppressed activity of O2- generation. In contrast, microglial cells in neuron-microglia coculture under the same conditions as those for the pure culture displayed ameboid shape and upregulated activity of O2- generation. Electron microscopic observation revealed that microglial cells in coculture were more abundant in Golgi apparatus and secretory granules than those in pure culture and that some of microglial cells in the vicinity of neurites exhibited membrane specialization reminiscent of a junctional apparatus with high electron density between a microglial soma and a neurite. Microglial cells in coculture tended to tie neurites in bundles by extending processes. Medium conditioned by neurons significantly enhanced O2- generation by microglia, but microglial cells in contact with or in close apposition to cocultured neurons were much more intensely activated than those remote from the neurons. Furthermore, the membrane fraction of cortical neurons activated microglial cells, and this effect was abolished by treating the neuronal membrane with trypsin or neuraminidase. In conclusion, neuronal-microglial contact may be necessary to mediate microglial activation. The present findings suggest that the contact of microglia with damaged neurons in the brain is a plausible cause to activate microglia in the neuropathological processes.

Animals↗

PubMed1998

A clinicopathological investigation on superficial early invasive carcinomas of the colon and rectum.

Due to recent advances in endoscopic surgical techniques, it has now become possible to perform endoscopic resection of most early invasive carcinomas of the colon and rectum (EIC) even if the lesions have invaded the submucosa. In the present study, we investigated the microscopic characteristics of superficial EIC compared with protruding-type EIC, focusing particular attention on histological type, the presence or absence of vascular invasion, the extent of submucosal invasion, and other adverse prognostic factors, to establish appropriate treatment strategies. Our findings led us to conclude that: (1) most cases of EIC can be cured by endoscopic resection if their gross aspects are classified as type IIc, superficial depressed, or type IIa, superficial elevated; (2) colorectal resection with lymph node dissection should be performed first for type IIa + IIc EIC because these lesions are apt to be associated with a large number of adverse prognostic factors; (3) subsequent colorectal resection should be performed after initial endoscopic treatment of EIC if there are adverse prognostic indicators of metastasis in the endoscopically resected specimen, such as moderately or poorly differentiated adenocarcinoma, lymphatic invasion, venous invasion, or extensive submucosal invasion.

Adenocarcinoma↗

PubMed1998

Astrocytic pathology in progressive supranuclear palsy: significance for neuropathological diagnosis.

Progressive supranuclear palsy (PSP) is known to have tau-positive cytoskeletal abnormalities in astrocytes and oligodendroglia as well as neurons. Astrocytic tau-positive structures (tuft-shaped astrocytes; Tu-SA) were studied to elucidate their proper significance in the neuropathological diagnosis of PSP. The distribution and incidence of Tu-SA were examined in 26 cases of PSP. The disease specificity of Tu-SA was demonstrated by comparison with diseases accompanied by neurofibrillary tangles (NFTs) and those with or without cytoskeletal abnormalities other than NFTs. In PSP, Tu-SA appeared prominently in the precentral and premotor cortex (areas 4 and 6) of the superior and middle frontal gyri, but were quite scare in the temporal lobe and limbic area. In the subcortical nuclei, they appeared preferentially in the putamen and were also scattered in other degenerating regions. In the cerebrum the Tu-SA and NFTs were distributed in quite different regions. The assessment of the incidence of Tu-SA in area 6 revealed that only 5 of 26 PSP cases lacked Tu-SA in the examined fields. In contrast, in the control diseases, Tu-SA were found only rarely in cases of corticobasal degeneration in the cerebral cortex among other frequent tau-positive structures. One case of Pick's disease showed occasional Tu-SA but only in the hippocampal region and not in the frontal lobe or putamen. In summary, although the absence of Tu-SA does not necessarily exclude the possibility of PSP, Tu-SA in the frontal lobe and putamen is highly suggestive for PSP. Thus, detection of Tu-SA and the ranking of the characteristic distribution of NFTs contribute to the neuropathological diagnosis of PSP.

Aged↗

PubMed1998

The fibrotic focus in advanced colorectal carcinoma: a hitherto unrecognized histological predictor for liver metastasis.

A fibrotic focus (FF) is a clearly defined area consisting of fibroblasts and/or collagen fibres arranged in irregular or storiform patterns within tumours. We looked to see whether FF in advanced colorectal carcinoma was associated with distant organ metastasis especially to the liver. The correlation between FF and the presence of synchronous or total (synchronous and/or metachronous) liver metastasis and tumour recurrence was assessed in 77 patients with Dukes B and C advanced colorectal carcinoma treated by resection. The median follow-up period was 21 months. In multivariate analysis, FF significantly increased the relative risk (RR) of synchronous liver metastasis (RR=4.9, P<0.05) and total liver metastasis (RR=4.6, P<0.05). FF also increased the RR of tumour recurrence (RR=2.4), but the increase was not statistically significant. FF is a newly recognized histological indicator of liver metastasis in advanced colorectal carcinoma.

Adenocarcinoma↗

PubMed1998

Human platelet activation by thrombolytic agents: effects of tissue-type plasminogen activator and urokinase on platelet surface P-selectin expression.

The mechanisms that underlie reocclusion during thrombolytic therapy have not yet been clarified. The purpose of this study was to investigate the activating effects of tissue-type plasminogen activator and urokinase and the inhibitory effects of acetylsalicylic acid by measuring platelet surface P-selectin as a marker of platelet activation. After addition of urokinase (final concentration 192 U/ml, 1920 U/ml, or 19,200 U/ml) or tissue-type plasminogen activator (final concentration 120 U/ml, 1200 U/ml, or 12,000 U/ml) to platelet-rich plasma from 12 healthy persons, platelet surface P-selectin expression was measured by means of flow cytometry with an anti-CD62 monoclonal antibody. The presence of urokinase and tissue-type plasminogen activator increased platelet surface P-selectin expression in a concentration-dependent manner. In the next step, either 160 mg/day (n = 6) or 660 mg/day (n = 6) acetylsalicylic acid was administered to the 12 healthy persons, and venous blood samples were collected after 7 days of treatment. Platelet surface P-selectin expression was measured with the method used earlier and after addition of tissue-type plasminogen activator or urokinase. Although the effect of acetylsalicylic acid at 160 mg/day on P-selectin expression was minimal, a dose of 660 mg/day suppressed platelet P-selectin expression and inhibited the platelet activating effects of tissue-type plasminogen activator and urokinase in a statistically significant way. Platelets were activated by tissue-type plasminogen activator or urokinase, and this platelet activation was suppressed with administration of acetylsalicylic acid at 660 mg/day.

Aspirin↗

PubMed1998

Ischemic preconditioning suppresses the noradrenaline turnover in the rat heart.

OBJECTIVE: The mechanism by which ischemic preconditioning protects the heart is presumed to be related to the reduction of energy consumption during a subsequent myocardial infarction. Since the sympathetic nervous system enhances cardiac function and energy consumption, we investigated the relation between ischemic preconditioning and the turnover rate of noradrenaline (NA) in the rat heart. METHODS: The effect of 3 cycles of 5-min occlusions of the rat left coronary artery on changes in arterial blood pressure and heart rate provoked by a subsequent 30 min of ischemia were examined until 60 min after reperfusion. The effect of 3 cycles of occlusions on the infarct size was also evaluated 60 min after reperfusion by comparing the infarcted area with the area at risk in these animals (6 per preconditioned and sham-operated group). The tissue concentration of NA during sustained ischemia was determined in the left ventricle, the intraventricular septum, and the right ventricle in the preconditioned and sham-operated groups. Changes in the turnover rate of NA after 3 cycles of occlusions were also evaluated by assessing the alpha-methyl-p-tyrosine-induced depletion of NA (n = 7 per group). RESULTS: A series of transient occlusions reduced the infarct size 60 min after a sustained ischemia for 30 min. Arterial pressure and heart rate were not affected. The concentration of NA was decreased in the left ventricle 60 min after the onset of sustained ischemia in both the preconditioned and sham-operated groups. The treatment with alpha-methyl-p-tyrosine decreased the NA concentration in all regions of the heart in the sham-operated group after 60 min. However, the treatment with alpha-methyl-p-tyrosine did not deplete the NA concentration in both the occluded and nonoccluded regions in the preconditioned group. CONCLUSIONS: Transient ischemia ameliorated the heart injury induced by a subsequent sustained ischemia, as assessed histologically. The activity of the sympathetic nervous system in all regions of the heart was reduced by transient ischemia in the left coronary vascular bed. These findings suggest that the inhibition of the sympathetic nervous system by the treatment of ischemic preconditioning takes part in the cardiac protection.

Animals↗

PubMed1998

Oxypurinol, a xanthine oxidase inhibitor and a superoxide scavenger, did not attenuate ischemic neuronal damage in gerbils.

The superoxide (O2.-) scavenging activity and neuroprotective effects of oxypurinol, a xanthine oxidase inhibitor, were compared with those of alpha-phenyl-N-tert-butyl nitrone (PBN). The rate constant for the reaction of oxypurinol with O2.- at pH 7.4 was 1.71 x 10(3) M(-1) s(-1) which was more than 100-fold that of PBN (1.65 x 10 M(-1) s(-1)). Oxypurinol inhibited the release of O2.- from stimulated neutrophils better than did PBN. However, oxypurinol did not attenuate the ischemic neuronal damage in gerbils, while PBN did. These results indicate that neither xanthine oxidase inhibiting activity nor O2.- scavenging activity correlates to the therapeutic efficacy of neuroprotective agents in ischemic-reperfusion injury.

Animals↗

PubMed1998

Androgen metabolism in cultured rat renal inner medullary collecting duct (IMCD) cells.

Although the stimulations of renal hypertrophy and renal erythropoietin production have been well-known androgen effects in the kidney, recent investigative progresses are further providing good evidences for androgen-regulated gene productions of key enzymes or local hormone substrates important to renal cell metabolisms and tubular functions in mouse or rat proximal tubules, respectively. It has been also reported that testosterone restores vasopressin receptors in medullary collecting ducts of the ageing rat and improves a urinary concentrating ability. Therefore in the present study we examined a metabolic pathway of androgens in cultured rat renal IMCD cells, which finally determine a urinary composition and volume. IMCD cells cultured from kidneys of male Wistar rats weighing about 200 g were incubated with serum-free culture media containing 4 nM [3H] testosterone or [3H] androstenedione for 2-48 h. Radioactive compounds in incubation media were then separated by reverse-phase high-pressure liquid chromatography (HPLC) and identified mainly on the basis of comparison of retention times of standard materials on HPLC. The main metabolites identified in testosterone or androstenedione incubation experiment were 5 alpha-dihydrotestosterone or 5 alpha-androstanedione, respectively. 5 alpha-Reductase inhibitor, MK 906, effectively inhibited the formations of these Ring A reduced metabolites. These results may suggest that rat renal IMCD cells possess 5 alpha-reductase activity, thereby converting androgens into their biologically active forms in vivo.

5-alpha Reductase Inhibitors↗

PubMed1998

The effects of 17beta-estradiol on ischemia-induced neuronal damage in the gerbil hippocampus.

The effects of 17beta-estradiol, a potent estrogen, on ischemia-induced neuronal damage, membrane depolarization and changes in intracellular Ca2+ concentration were studied in gerbil hippocampi. The histological outcome evaluated seven days after 3 min of transient forebrain ischemia in hippocampal CA1 pyramidal cells was improved by high doses of 17beta-estradiol (30 microg, i.c.v. and 4 mg/kg, i.p.), whereas low doses of 17beta-estradiol (3 and 10 microg, i.c.v.) showed no protective effect. Administration of 17beta-estradiol did not affect the changes in the direct current potential shift in ischemia in the hippocampal CA1 area at any dosage. A hypoxia-induced intracellular Ca2+ increase was evaluated by in vitro microfluorometry in gerbil hippocampal slices. Pretreatment of 17beta-estradiol (4 mg/kg, injected i.p. 1 h before decapitation) suppressed the increase in the intracellular concentration of Ca2+ due to the in vitro hypoxia, affecting both the onset of the increase and the extent. The in vitro hypoxia in the Ca2+-free condition induced an elevation of the intracellular concentration of Ca2+, although the increase was gradual. Pretreatment of 17beta-estradiol (4 mg/kg, i.p.) also inhibited this elevation. These findings imply that high doses of 17beta-estradiol protect the neurons from ischemia by inhibiting the release of Ca2+ from the intracellular Ca2+ stores, as well as by inhibiting the influx of Ca2+ from the extracellular space.

Action Potentials↗

PubMed1998

Comparison of glucokinase activities in the peripheral leukocytes between dogs and cats.

Activities of hexokinase (HK), glucokinase (GK) and pyruvate kinase (PK), were measured. The expression of GK mRNA was investigated using reverse transcription-polymerase chain reaction (RT-PCR) in leukocytes (WBC) of dogs and cats. No significant differences between dogs and cats were found in concentrations of blood glucose and plasma insulin. Dog WBC showed GK activities and the specific fragment with predicted size of 574 bp containing conserved region including glucose- and ATP-binding domains of GK as determined with RT-PCR. However, in cat WBC, the activities and specific fragment of GK were absent. After fasting, the activities and gene expression of GK decreased greatly in the dog WBC. The cat WBC had significantly higher activities of HK and PK than dog WBC.

Animals↗