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Biomedical subjects

Y Naito

Publications and source records attributed to Y Naito.

At least 145 records · Page 8Linked to original sources
PubMed1999

Activation of stress signaling pathways by the end product of lipid peroxidation. 4-hydroxy-2-nonenal is a potential inducer of intracellular peroxide production.

In the present study, we studied the signal transduction mechanism that is involved in the expression of c-Jun protein evident after exposure of rat liver epithelial RL34 cells to the major end product of oxidized fatty acid metabolism, 4-hydroxy-2-nonenal (HNE). HNE treatment of the cells resulted in depletion of intracellular glutathione (GSH) and in the formation of protein-bound HNE in plasma membrane. In addition, HNE strongly induced intracellular peroxide production, suggesting that HNE exerted oxidative stress on the cells. Potent expression of c-Jun occurred within 30 min of HNE treatment, which was accompanied by a time-dependent increase in activator protein-1 (AP-1) DNA binding activity. We found that HNE caused an immediate increase in tyrosine phosphorylation in RL34 cells. In addition, HNE strongly induced phosphorylation of c-Jun N-terminal kinases (JNK) and p38 mitogen-activated protein kinases and also moderately induced phosphorylation of extracellular signal-regulated kinases. The phosphorylation of JNK was accompanied by a rapid and transient increase in JNK and p38 activities, whereas changes in the activity of extracellular signal-regulated kinase were scarcely observed. GSH depletion by L-buthionine-S, R-sulfoximine, a specific inhibitor of GSH biosynthesis, only slightly enhanced peroxide production and JNK activation, suggesting that HNE exerted these effects independent of GSH depletion. This and the findings that (i) HNE strongly induced intracellular peroxide production, (ii) HNE-induced JNK activation was inhibited by pretreatment of the cells with a thiol antioxidant, N-acetylcysteine, and (iii) H2O2 significantly activated JNK support the hypothesis that pro-oxidants play a crucial role in the HNE-induced activation of stress signaling pathways. In addition, we found that, among the inhibitors of tyrosine kinases, cyclooxygenase, and Ca2+ influx, only quercetin exerted a significant inhibitory effect on HNE-induced JNK activation. In light of the JNK-dependent induction of c-jun transcription and the AP-1-induced transcription of xenobiotic-metabolizing enzymes, these data may show a potential critical role for JNK in the induction of a cellular defense program against toxic products generated from lipid peroxidation.

Aldehydes↗
PubMed1999

Pathological changes in the myocardium of hypocalcaemic parturient cows.

Three parturient cows in lateral recumbency which were moaning and had tachycardia, arrhythmia and dyspnoea were thoroughly examined. They were hypocalcaemic (0.70-1.27 mmol/litre) and were euthanized within four days, because they failed to respond to calcium treatment. By light microscopy the most characteristic pathological changes in the heart were necrotic changes scattered throughout the myocardium. Electron microscopy revealed abnormalities in the myocytes which were characterised by focal myofibrillar lysis, irregular splitting, streaming and spreading of the Z band and myofibrillar disarray.

Animals↗
PubMed1999

Simulation for internal energy deposition in sustained off-resonance irradiation collisional activation using a monte carlo method

This paper proposes a novel computational approach employing a Monte Carlo method, aimed at an improved understanding of the dynamics and energetics of activated ions in sustained off-resonance irradiation collisionally activated dissociation (SORI-CAD) experimental events of Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). In SORI-CAD events, internal energies of activated ions are complicatedly associated with their motion undergoing off-resonance excitation (i.e. alternate accelerations and decelerations) and inherently stochastic ion-neutral collisions. Several types of pseudo-random generators were adapted to probability density functions (PDFs) which characterize the ion-neutral collision process. Simulated ion trajectories involve the realistic feature of pressurized SORI-CAD events, such as a collisional damping and those which have not been illustrated in conventional analytical approaches. The proposed method can simulate the time-varying translational and internal energies of activated ions. The present result suggests that the internal energy of a SORI-activated ion should be inversely proportional to the cube of the SORI excitation frequency offset. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1999

Characteristics of the production of active oxygen species from adherent and non-adherent neutrophils.

Our objective was to evaluate the characteristics of the production of AOS from the neutrophils that had adhered to the endothelial cells, fibronectin or polystyrene, using the method of electron paramagnetic resonance (EPR) spin trapping. Neutrophils and endothelial cells were isolated from human venous blood and umbilical veins, respectively. AOS production from neutrophils was not elicited only by adhesion. The stimulation of adherent neutrophils with phorbol myristate acetate (PMA) induced the production of AOS. The production of AOS from adherent neutrophils to endothelial cells, but not to fibronectin or polystyrene, decreased with the interval time between the adhesion and the stimulation by PMA. The amount of AOS produced by the neutrophils adherent to fibronectin or polystyrene was maintained for one hour after stimulation with PMA, whereas that by suspended neutrophils gradually decreased with the time after stimulation. Results indicate that adherent and non-adherent neutrophils exhibit differing time course of AOS production.

Cell Adhesion↗
PubMed1999

Age-related changes in adenosine 5'-triphosphate-induced constriction of isolated, perfused mesenteric arteries of rats.

In isolated mesenteric arteries of rats, dose-dependent increase in perfusion pressure by adenosine 5'-triphosphate (ATP, 0.1 approximately 3000 nmole) diminished with age. ATP responses of both 4- and 32-week-old rats were enhanced by indomethacin (5 microM), and further by the combination of indomethacin and N(G)-nitro-L-arginine methyl ester (L-NAME, 5 microM). The enhancement with each of the treatments was less in 32-week-old rats than that in 4-week-old rats, and there was no enhancement in 75-week-old rats. The ATP response was enhanced by removing the endothelium only in 4-week-old rats. The constrictions in response to ATP (1000 nmole) in both 4- and 32-week-old rats were equally enhanced by reactive blue 2 (30 micromole) and were inhibited by pyridoxal-phosphate-6-azophenyl-2',4-disulphonic acid (PPADS, 30 microM) and alpha, beta-methylene ATP (alpha, beta-mATP, 100 nmole) to a similar extent. The increased tone which was produced by the perfusion with physiological solution containing 100 mM potassium chloride was greater in older animals. This age-related change in the vascular tone disappeared when the responses were potentiated by L-NAME. These results demonstrate that in rat mesenteric arteries, ATP-induced constriction decreases with age. The age-related decline of vasoconstriction is not likely to arise from the changes in the contractility of smooth muscle, from the counterbalancing regulation by the endothelium, or from the cooperation of P2 purinoceptor subtypes. The density of purinoceptors and some post-receptor signal transduction mechanisms in the vascular smooth muscle cells may change with age. The enhanced ATP response might have special physiological significance in rats during development.

Adenosine Triphosphate↗
PubMed1999

Correlation between rCBF and speech perception in cochlear implant users.

OBJECTIVE: Although cochlear implants (CIs) have provided the opportunity for bilaterally deaf individuals to recover their hearing abilities, the speech perception performances of the CI users varies considerably. To elucidate the cortical mechanisms of processing speech signals coded by CIs, we evaluated the correlation between the brain activity during speech activation and speech perception in CI users by PET. METHODS: Fourteen postlingually deaf CI users were examined. CI used in the patients was a 22-channel system and its speech-coding strategy was the Nucleus spectral peak (SPEAK) strategy. To evaluate the speech perception performances, we examined vowel perception, consonant perception and speech tracking performances in the Japanese language. Regional cerebral blood flow (rCBF) was measured during no sound stimulation and speech sound stimulation. PET data of the silent condition was subtracted from that of speech stimulation to determine changes in rCBF. In the search for changes in rCBF in the areas for auditory processing, three regions of interest (ROI) were selected; primary auditory area, auditory association area and Broca's area. The correlation between the rCBF changes in the ROIs and the speech perception performances was analyzed using Pearson's correlation coefficient. RESULTS: The patient's speech perception performances ranged widely. Although there were no significant correlations between the speech perception and the rCBF increases in the primary auditory area and Broca's area, there were positive correlations in the auditory association area. In the left auditory association area, the correlation coefficient of the vowel perception performance was 0.546 (P <0.05) and that of the speech-tracking test was 0.657 (P < 0.05). Regarding the consonant perception performance, the correlation coefficient was 0.743 (P < 0.01). There was a positive correlation only between the consonant perception performance and the rCBF increase (R = 0.576, P < 0.05) in the right auditory association area. These correlations are stronger in the left hemisphere than in the right hemisphere. CONCLUSIONS: It is suggested that the improvement of the auditory processing of speech in CI users with SPEAK strategy is accompanied by the recruitment of more neurons in the auditory association areas. The adult auditory cortices may still have plasticity or

Adult↗
PubMed1999

Cochlear implant in patients with residual hearing.

OBJECTIVE: The postoperative speech perception abilities of severely hearing-impaired patients with multi-channel cochlear implant were compared with preoperative speech perception performance with conventional hearing aids. METHODS: Cochlear implantation was performed in six severely to profoundly hearing-impaired patients. They had unaided pure-tone thresholds of 70-100-dB HL and aided thresholds of 35-90-dB HL in the better ear, but were not able to perceive speech sounds well with hearing aids. RESULTS: Postoperatively, all the patients had significantly improved speech perception performance, exceeded the average skills of profoundly deaf cochlear implant users, and were able to communicate without writing. CONCLUSION: These results imply that cochlear implant may be indicated for severely to profoundly deaf subjects, if they receive little or no benefit from conventional hearing aids.

Adult↗
PubMed1999

Intersexual differences in the diving behaviour of foraging subantarctic cormorant (Phalacrocorax albiventer) and Japanese cormorant (P. filamentosus).

Cormorants feed by feet-propelled diving. How cormorants optimize foraging is of a particular interest in relation to the understanding of the feeding strategies of diving birds, as well as within the debate about cormorants' impact on sustainable resources. Using microdata loggers that recorded diving depth, we investigated the foraging strategy of males and females of subantarctic cormorants, which inhabit cold regions, and of Japanese cormorants, which live in the northern temperate zone. For both species, males and females daily spent the same amount of time submerged, and apparently captured the same amount of fish. However, males dived deeper and longer, which could be explained by their 15-20% larger body mass and may minimize potential competition for food.

Animals↗
PubMed1999

A patient who was found to be pregnant unexpectedly during hysteromyomectomy.

We present a case of an unexpected pregnancy and an ultimately successful obstetric outcome. The patient underwent abdominal myomectomy under spinal anaesthesia for a uterine leiomyoma with menorrhagia and infertility. Later, she was found to have been in the 7th gestational day at the time of surgery. The blastocyst survived the surgical manipulation and anaesthesia, resulting in a successful pregnancy. The literature on the endocrinological stress response during anaesthesia and surgery suggests that spinal anaesthesia administered in this case was potentially helpful in maintaining progesterone levels and avoiding increased prolactin levels; increased prolactin levels might be deleterious to implantation of the blastocyst.

Journal Article↗
PubMed1999

Effect of vitamin E in gastric mucosal injury induced by ischaemia-reperfusion in nitric oxide-depleted rats.

BACKGROUND: Neutrophil infiltration and lipid peroxide accumulation are involved in reperfusion-induced gastric mucosal injury in nitric oxide-depleted rats. AIM: To assess the effect of vitamin E on this injury. METHODS: After ischaemia-reperfusion, the total area of erosions, lipid peroxide contents in gastric mucosa, and gastric neutrophil accumulation were compared between nitric oxide-depleted rats with deficient, normal, and increased vitamin E intake over 8 weeks. Thiobarbituric acid-reactive substances and tissue-associated myeloperoxidase activity were measured in gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. RESULTS: The total area of erosions was significantly increased in the vitamin E-deficient group compared with the sufficient-intake and vitamin-supplemented groups. Both thiobarbituric acid-reactive substances and myeloperoxidase activity also were significantly increased in the vitamin E-deficient group compared with others. The total area of erosions closely paralleled the increases in both thiobarbituric acid-reactive substances and myeloperoxidase activity. CONCLUSION: These results indicate that the inhibition of lipid peroxidation and interference with neutrophil infiltration by vitamin E may be responsible for its cytoprotective effect in ischaemia-reperfusion.

Animals↗
PubMed1999

Effect of shear stress and a stable prostaglandin I2 analogue on adhesive interactions of colon cancer cells and endothelial cells.

In the process of cancer metastasis, adhesion between cancer cells and endothelial cells is an important early step. In the present study, the effects of shear stress and the adhesion molecules responsible for cancer cell interactions with endothelial cells were investigated in a system similar to in vivo microcirculation. The effect of prostaglandin I2 (PGI2) also was determined. Human colon cancer cell line Colo 201 and human umbilical vein endothelial cells (HUVEC) were used. After HUVEC on a glass slide were incubated with IL-1beta for 4 h, cancer cells in suspension were perfused on HUVEC at wall shear stresses of 5-40 microN/cm2. Experiments were videotaped, and the number of adherent cells were counted. Additionally, the effects of anti-sialyl Lewis a (SLea) MoAb, anti-E-selectin MoAb, and a PGI2 analogue were investigated. Expression of adhesion molecules on cancer cells and HUVEC was assessed using flow cytometry and enzyme immunoassay, respectively. Few cancer cells adhered to HUVEC without IL-1beta; however, many cancer cells adhered to IL-1beta-stimulated HUVEC at low shear stress (5-20 microN/cm2). Cancer cells did not migrate beneath HUVEC. The increased adhesion was inhibited by anti-E-selectin MoAb, anti-SLea MoAb, and a PGI2 analogue. In addition, the PGI2 analogue decreased the surface expression of SLea on Colo 201 cells. These results suggest that Colo 201 cells adhere to IL-1beta-stimulated endothelial cells via SLea and E-selectin under low flow conditions; PGI2 analogues may protect against metastasis by inhibiting cancer cell-endothelial cell interactions.

Adult↗
PubMed1999

Iron dependence of tryptophan hydroxylase activity in RBL2H3 cells and its manipulation by chelators.

Tryptophan hydroxylase requires Fe2+ for in vitro enzyme activity. In this study, the intracellular activity of tryptophan hydroxylase was assessed by applying 3-hydroxybenzylhydrazine (NSD-1015), an inhibitor of aromatic l-amino acid decarboxylase, to monolayer cultures of RBL2H3 cells, a serotonin producing mast cell line. The effect of manipulating intracellular 'free' iron levels on enzyme activity was analyzed by administration of iron chelators. Desferrioxamine (DFO) suppressed the intracellular enzyme activity. Salicylaldehyde isonicotinoyl hydrazone (SIH) also suppressed enzyme activity, but stimulated it when administered in the Fe-bound form. Hemin also stimulated enzyme activity, which progressively increased over several hours to more than sixfold the initial level. DFO and SIH inhibited the hemin stimulatory effect when administered simultaneously with hemin. Both suppression and stimulation with these chelators took place without a significant decrease or increase in the amount of enzyme. These results indicate that there was an inadequate supply of Fe2+ in the cells to support full activity of tryptophan hydroxylase.

Animals↗
PubMed1999

Vestibulo-ocular reflex in patients with Meniere's disease between attacks.

In Meniere's disease, spontaneous nystagmus beating toward the affected ear (ipsilateral nystagmus) is frequently observed especially during vertiginous periods. VOR against horizontal rotation was recorded in 19 patients with Meniere's disease exhibiting ispilateral beating nystagmus, and the dynamic aspect of vestibular function during vertiginous periods was examined by determining VOR gain and directional preponderance (DP). The patients sat on a rotation chair and were passively rotated at about 0.3-0.6 Hz. The maximal head velocity ranged from 80 to 120 deg/s and the duration of rotation from 20 to 30 s. In most patients exhibiting ipsilateral nystagmus, VOR gain toward the affected side was higher than that toward the intact side, indicating that the peripheral vestibular system on the affected side could still respond to head movements and that its dynamic function was increased. This asymmetry disappeared along with disappearance of ipsilateral nystagmus. During the period with contralateral nystagmus, VOR gain toward the affected side became lower than that toward the intact side. These findings indicate that alterations in the dynamic property of the peripheral vestibular system may correlate with the directional change of spontaneous nystagmus. However, the degree of VOR DP (VOR DP%) did not correlate with the slow phase velocity of spontaneous nystagmus, indicating that observation of spontaneous nystagmus alone cannot determine with precision the degree of imbalance in the dynamic aspect of vestibular function.

Adult↗
PubMed1999

A new vestibulo-ocular reflex recording system designed for routine vestibular clinical use.

A new vestibulo-ocular reflex (VOR) recording system was developed, which consists of an infrared eye camera, a small velocity sensor and a frequency modulator. Using this system, the head velocity signal was frequency modulated and simultaneously recorded as a sound signal on the audio track of a Hi8 video recorder with eye images. This device enabled recording of the VOR response in routine vestibular clinical practice. The reliability and effectiveness of this system were estimated by recording and analysing the VOR response against manually controlled rotation in normal subjects (n = 22) and in patients with unilateral severe vestibular hypofunction (n = 11). VOR gain on clockwise rotation viewed from the top was defined as R gain, and counterclockwise rotation as L gain. Directional preponderance (DP%) was also calculated. VOR gain towards the diseased side was significantly lower than that towards the intact side, and also significantly lower than that of normal subjects. DP% of unilateral vestibular hypofunction cases was significantly larger than that of normal subjects. These findings indicate that this VOR recording system reliably detects severe unilateral vestibular hypofunction.

Adult↗