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Biomedical subjects

Y Uchida

Publications and source records attributed to Y Uchida.

At least 343 records · Page 19Linked to original sources
PubMed1995

[Increased production of nitric oxide in the immediate and late asthmatic responses in models of guinea pig experimental asthma].

Nitric oxide is produced in mammalian airways by constitutive and inducible nitric oxide synthase, and endogenous nitric oxide can be detected as exhaled gas. Patients with asthma have large numbers of airway epithelial cells and inflammatory cells that contain nitric oxide synthase, and nitric oxide levels in exhaled air are high during immediate asthmatic responses. To examine the dynamics of nitric oxide synthase in the tracheas of guinea pigs, cumulative dose-response studies of 5-HT were done on tracheal strips, in the presence or absence of arginine and its analogues. This assay indicated that relative the activity of nitric oxide synthase was greater 6 hr after the challenge than immediately after, which suggests that nitric oxide is involved in the pathogenesis of bronchial asthma attacks.

Animals↗
PubMed1994

IL-1 beta regulates the expression of the Gi2 alpha gene via lipid mediators in guinea pig tracheal muscle.

When isolated guinea pig muscle preparations were incubated with human recombinant IL-1 beta, mRNA level of Gi2 alpha but not of Gs alpha increased in a time and dose dependent manner. The increase was partially blocked by inhibitors of lipoxygenase (NDGA) and cyclooxygenase (indomethacin) and PAF antagonist (SC47014A), while U46619 (thromboxane A2 mimetic), LTD4, 15-HETE and PAF partially mimicked it. The IL-1 beta induced Gi2 alpha expression was almost completely inhibited by anti-phospholipase A2 antiserum, whereas preimmune serum had no apparent effects. From these observations, we suggest that IL-1 beta first induces the synthesis and release of Type II inflammatory phospholipase A2, which in turn stimulates the expression of Gi2 alpha gene via production of various lipid mediators.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Possible involvement of L-arginine-nitric oxide pathway in modulating regional blood flow to brown adipose tissue of rats.

To evaluate whether the L-arginine-nitric oxide (NO) pathway is involved in the regulation of regional blood flow to brown adipose tissue (BAT), the effects of two specific NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA), on the blood flow to interscapular brown adipose tissue (IBAT) were studied in urethane-anesthetized rats. Regional blood flow in IBAT was measured with laser-Doppler flowmetry. An intravenous injection of L-NAME and L-NMMA, but not of either D-enantiomer, caused a transient and dose-dependent increase in IBAT blood flow. Dose-response curves for these NO synthase inhibitors showed that L-NAME was more potent than L-NMMA in increasing IBAT blood flow. We also observed a concomitant pressor effect accompanied by a slight decrease in heart rate following intravenous injection of L-NAME and L-NMMA. An elevation of IBAT blood flow and blood pressure induced by both L-NAME and L-NMMA was reversed by L-arginine in an enantiomerically specific manner. The increase in IBAT blood flow induced by NO synthase inhibitors was of shorter duration and less sensitive to L-arginine than the increase in blood pressure. Our results show that the IBAT blood flow is increased by inhibition of NO synthase and that the response of IBAT vasculature to NO synthase inhibitors is different from that of the resistance vessels which regulate blood pressure. The involvement of L-arginine-NO pathways in modulating microcirculation in IBAT is suggested.

Adipose Tissue, Brown↗
PubMed1994

Possible role of nitric oxide in 5-hydroxytryptamine-induced increase in vascular permeability in mouse skin.

In order to test the hypothesis that a 5-hydroxytryptamine (5-HT)-induced increase in vascular permeability results from a cascade triggered by activation of the synthesis of nitric oxide (NO), the vascular permeability was investigated using the Pontamine sky blue leakage method in male mice. Subcutaneous injection of 5-HT induced a dose-related increase of vascular permeability at the injection site. The vascular permeability induced by 5-HT was inhibited by pretreatment with intraperitoneal injection of ketanserin (5-HT2A antagonist) and methysergide (5-HT1/2A antagonist), less efficiently by 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl] piperazine (NAN-190) (5-HT1A antagonist), but not by granisetron (5-HT3 antagonist). Increase in vascular permeability induced by 5-HT was inhibited by concurrent intravenous administration of NO synthase inhibitors NG-nitro-L-arginine methyl ester (L-NAME) and methylene blue but not by the inactive enantiomer NG-nitro-D-arginine methyl ester (D-NAME). These results suggest that 5-HT increases vascular permeability by activating the 5-HT receptors and that endogenous NO is involved in this effect of 5-HT.

Amino Acid Oxidoreductases↗
PubMed1994

Sterol composition in polyene antibiotic-sensitive and resistant strains of Malassezia pachydermatis.

The membrane sterol compositions of ten strains of Malassezia pachydermatis were analysed by gas-liquid chromatography. Six of these were wild-type strains from clinical sources that were sensitive to polyene antibiotics, whereas the other four strains were resistant mutants that had arisen after treatment with N-methyl-N'-nitrosoguanidine or UV radiation. The wild-type strains contained 838.8 to 1291.7 micrograms of sterol per gram of freeze-dried mycelium. The sterols were composed of 79% ergosterol, 19% fecosterol and 2% lichesterol. The mutant strains contained 277.1 to 348.8 micrograms/g of sterols composed of 76% ergosterol and 24% fecosterol.

Chromatography, Thin Layer↗
PubMed1994

Involvement of endogenous nitric oxide in non-adrenergic, non-cholinergic contraction elicited by [Met5]-enkephalin in rat isolated duodenum.

To investigate the possible neuromodulatory role of nitric oxide (NO) in the gastrointestinal tract, an examination was made of the effects of NG-nitro-L-arginine (L-NOARG), an inhibitor of NO synthase, on the intestinal response to [Met5]-enkephalin (ENK) by recording the mechanical activity of the isolated duodenum from rats. [Met5]-enkephalin elicited a biphasic response of the duodenum, i.e. transient relaxation followed by contraction. The relaxation induced by ENK was blocked by naloxone, an opioid receptor antagonist, but not by tetrodotoxin (TTX). The contractile response of the duodenum to ENK was blocked by TTX but not by naloxone. The contractile response was not affected by hyoscine, a muscarinic antagonist, or guanethidine, an adrenergic neuron blocking agent, indicating mediation by non-adrenergic, non-cholinergic (NANC) nerves. The contractile but not the relaxant response to ENK was blocked by L- but not D-NOARG. The contractile response was also inhibited by methylene blue, an inhibitor of both NO synthase and guanylate cyclase, and by indomethacin, a cyclooxygenase inhibitor. Thus, endogenous NO and prostaglandins are involved in the contractile response to ENK. Endogenous NO may modulate the release of excitatory NANC transmitters via a prejunctional mechanism.

Amino Acid Oxidoreductases↗
PubMed1994

Naloxone attenuates drinking behavior in psychiatric patients displaying self-induced water intoxication.

1. The present study was performed to examine the effect of naloxone on drinking behavior in three schizophrenic inpatients with psychosis, intermittent hyponatremia, and polydipsia. 2. Their body weight were checked five times daily and the maximum weight gain during a day was chosen as an index of their polydipsia. 3. After control recording for six weeks, a daily naloxone (0.6 mg) injection series was performed once every two weeks for three series (six weeks). Withdrawal of this drug for six weeks resulted in weight gain recovering to control level. 4. The present study showed that naloxone seems to be a potential treatment for psychiatric patients displaying self-induced water intoxication and that endogenous opioid systems are involved in the compulsive drinking behavior of this syndrome.

Drinking Behavior↗
PubMed1994

Lower incidence of K-ras codon 12 mutation in flat colorectal adenomas than in polypoid adenomas.

In order to clarify genetic changes in flat adenomas, K-ras codon 12 point mutations were examined in 56 flat adenomas, 81 polypoid adenomas and 42 cancers of colon and rectum. The mutation frequency in flat adenomas was 23% (13/56), significantly lower than that in polypoid adenomas (67%: 54/81) and cancers (76%: 32/42). Even mildly dysplastic adenomas or small (less than 5 mm) adenomas showed higher mutation incidence in polypoid type (62%, 57%) than in flat type (23%, 19%). Among flat adenomas, flat elevated lesions exhibited relatively higher mutation frequency than completely flat or depressed ones. As for cancers, 14 tumors (33%) contained mutations only in a minor tumor cell population, indicating that these mutations occur at a late stage of tumorigenesis. These results suggest that the adenoma-carcinoma sequence through flat adenomas may be different from that through polypoid adenomas, and genetic changes may be heterogeneous in colorectal carcinogenesis.

Adenoma↗
PubMed1994

Antithrombin and thrombolytic effects of a new antithrombin agent: angioscopic and angiographic comparison with heparin or batroxobin.

The antithrombotic effect of three different types of antithrombotic agents (antithrombin:argatroban, heparin, defibrinogenating agent:batroxobin) were evaluated in canine coronary and iliac arteries. An occlusive thrombus was produced by balloon injury. One of the three agents was infused intravenously at 1 hour after thrombus formation (heparin 250 U/kg, argatroban 0.5 mg/kg, batroxobin 0.5 U/kg) and the effect of thrombus size reduction was evaluated. On the contralateral side of the iliac artery, the preventive effect of these agents on thrombus formation was evaluated after balloon injury. In the iliac artery, angioscopic percent area obstruction by the thrombus before and 60 minutes after treatment reduced from 69% to 32% in the argatroban group, and from 64% to 51% in the batroxobin group (P < 0.0001 and P < 0.05, respectively). No significant change was observed in the heparin group. Angiography demonstrated the same trend. The percent area stenosis with thrombus at 60 minutes following balloon injury was 0.75% in the argatroban group, 18.9% in the heparin group (P < 0.05 vs argatroban), and 12.9% in the batroxobin group. Thrombus size at the treated site was smaller than that at the control site in all three groups (P < 0.05 vs control). In the coronary artery, angioscopic percent area obstruction by the thrombus before and 60 minutes after treatment reduced from 84% to 53% in the argatroban group, and from 86% to 68% in the batroxobin group (P < 0.0001 and P < 0.05, respectively). No significant change was observed in the heparin group. Angiography also demonstrated the same trend. The activated partial thromboplastin time (APTT) was prolonged to 189% of the control value with argatroban and to 1253% of the value with heparin (P < 0.0001). Fibrinogen was markedly reduced with batroxobin. These results showed that both the antithrombin agent and the defibrinogenating agent have a preventive effect on thrombus formation and the effect on thrombus size reduction, without marked prolongation of the APTT.

Angiography↗
PubMed1994

Virulence of Rhodococcus equi isolates from patients with and without AIDS.

Rhodococcus equi is an emerging opportunistic pathogen of human immunodeficiency virus-infected patients. Thirty-nine isolates of R. equi from immunocompromised patients with and without AIDS were analyzed for the presence of virulence plasmid DNA, expression of 15- to 17-kDa antigens, and their pathogenicities in mice. Of the human isolates, eight contained an 85-kb virulence plasmid, expressed 15- to 17-kDa antigens, and were virulent in mice. Nineteen isolates carried cryptic plasmids of various sizes, and the remaining 12 isolates did not contain any plasmids. These 31 isolates did not express virulence-associated antigens and were not virulent in mice. The results suggested that opportunistic infections in immunocompromised patients could be caused by both virulent and avirulent R. equi strains and that the pathogenesis of R. equi infection in immunocompromised patients appears to be different from that which occurs in foals.

AIDS-Related Opportunistic Infections↗
PubMed1994

Exposure of workers to a mixture of toluene and xylenes. I. Metabolism.

The urinary excretion of hippuric acid and methylhippuric acid was studied in workers (233 subjects; 122 men and 111 women) exposed to toluene and xylenes in combination and in non-exposed controls (281 subjects; 141 men and 140 women) recruited from the same factories or factories of the same regions. Smoking and drinking habits of the subjects were obtained by medical interviews. From each worker, one urine sample was collected at the end of a shift and analysed for hippuric and methylhippuric acids by high performance liquid chromatography. Air samples for the estimation of toluene and xylenes were collected with diffusive personal samplers. There was a linear correlation between the time weighted average exposure either to toluene or xylene isomers and the concentrations of hippuric acid or methylhippuric acid isomers in urine. Essentially no difference was found in the correlation between quantitative exposure and excretion in the three xylene isomers. Comparison of the slopes of regression lines indicated the absence of metabolic interaction between toluene and xylenes at the measured concentrations. The metabolism of toluene and xylenes was significantly reduced among smokers or drinkers compared with non-smokers and non-drinkers.

Adult↗
PubMed1994

Exposure of workers to a mixture of toluene and xylenes. II. Effects.

The health effects of exposure to a mixture of toluene and xylene isomers was studied on the fourth or fifth days of a working week in factories in China. The study population comprised 233 subjects (122 men and 111 women), who were exposed to the time weighted geometric mean (maximum) concentrations of toluene (3 (203) ppm) and xylenes (4 (103) ppm). For comparison, 241 non-exposed controls (116 men and 125 women) were recruited from the same regions. The prevalence of some subjective symptoms significantly increased in the exposed population, and the symptom profiles were similar to those found after exposure to toluene or xylenes alone. Haematology and serum biochemistry did not show notable changes. It seems reasonable to conclude that the effects of the toxicities of toluene and xylenes in combination are additive.

Adult↗
PubMed1994

The effects of dobutamine, propranolol and nitroglycerin on an experimental canine model of congestive heart failure.

A new experimental model of acute congestive heart failure was established in open-chest dogs, and it was employed to examine the effects of dobutamine, propranolol and nitroglycerin. The model was induced by intracoronary administration of saponin, volume loading and intravenous infusion of methoxamine. Left ventricular end-diastolic pressure (LVEDP) increased from 7.9 +/- 0.6 to 24.2 +/- 1.4 mmHg, and aortic blood flow (AoF) decreased from 0.89 +/- 0.06 to 0.53 +/- 0.04 l/min. Systemic vascular resistance (SVR) increased from 9618 +/- 585 to 16492 +/- 1213 dynes.sec/cm5 and right atrial pressure (RAP) increased from 2.5 +/- 0.2 to 4.2 +/- 0.4 mmHg. Furthermore, Vmax decreased from 71.6 +/- 5.1 to 45.8 +/- 2.9 1/sec, and the time constant of left ventricular pressure decay (T) increased from 40.0 +/- 2.6 to 90.2 +/- 7.9 msec. These hemodynamic changes were stable for up to 80 min. Dobutamine improved cardiac function by increasing Vmax and by decreasing T. Consequently, dobutamine increased AoF and decreased LVEDP, while there was no change in SVR. Nitroglycerin reduced LVEDP, SVR and T; increased AoF; and did not change Vmax. Propranolol produced no improvement in the hemodynamics or cardiac function. These results indicate that the present congestive heart failure model is characterized by global left ventricular dysfunction with lowered cardiac output and increased peripheral vascular tone, and it is beneficial for evaluating the pharmacological properties of drugs for acute congestive heart failure.

Analysis of Variance↗