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Biomedical subjects

Y Nakata

Publications and source records attributed to Y Nakata.

At least 145 records · Page 8Linked to original sources
PubMed1998

Methylenetetrahydrofolate reductase gene polymorphism: relation to blood pressure and cerebrovascular disease.

Hyperhomocysteinemia is reported to be associated with an increase in the incidence of ischemic heart disease and cerebrovascular disease. Genetic aberrations in methylenetetrahydrofolate reductase (MTHFR) may account for reduced enzyme activity and elevated plasma homocysteine level. A recent report revealed that a common mutation (677C to T; Ala to Val) in the MTHFR gene is associated with decreased specific MTHFR activity and with increased risk for coronary artery disease in the homozygous state (Val/Val). In the present study, we investigated whether the MTHFR gene is a genetic risk factor for cerebrovascular disease (CVD). To undertake a case-control study, we selected the patients with cerebral infarction (n = 48) or cerebral hemorrhage (n = 35) and examined the association between MTHFR gene polymorphism and CVD. The genotype distribution of the MTHFR gene was not significantly different between cases and controls. Because the possibility of matching the morbidity of the effects of hypertension, the lack of association could not be excluded in the first study; however, we also examined whether the MTHFR mutation was associated with any clinical risk factor for CVD or with hypertension. It turned out that the subjects with the Val allele of the MTHFR gene had significantly lower blood pressure than the subjects with other genotypes in the general population (P = .02), and that the frequency of the Val/Val genotype in hypertensive subjects (n = 173) was significantly lower than in control subjects (n = 184) (P = .03). From these results, we conclude that the Val/Val homozygous state of the MTHFR gene increased the risk of thrombosis, but reduced the blood pressure, which resulted in the lack of increased risk for CVD.

Cerebrovascular Disorders↗
PubMed1998

Comparison of acceleromyography and electromyography in vecuronium-induced neuromuscular blockade with xenon or sevoflurane anesthesia.

STUDY OBJECTIVES: To compare acceleromyography (AMG) and electromyography (EMG) with xenon or sevoflurane anesthesia during vecuronium-induced neuromuscular blockade. DESIGN: Prospective randomized study. SETTING: University hospital. PATIENTS: 28 ASA physical status I and II adult patients presenting for elective surgery. INTERVENTIONS: Patients received vecuronium for neuromuscular blockade and either xenon (n = 11) or sevoflurane (n = 17) anesthesia. MEASUREMENTS AND MAIN RESULTS: The first twitch depression, which was expressed as a ratio of the first twitch to that obtained before the blocking drug was administered (T1/Tc), was measured simultaneously by AMG and EMG. T1/Tc as measured by AMG consistently demonstrated greater depression than that by EMG during recovery. The limits of agreement were unacceptably wide, suggesting that T1/Tc obtained by AMG is a poor predictor of T1/Tc as measured by EMG. Such relations were not affected by the anesthetic (xenon or sevoflurane) used. CONCLUSION: AMG and EMG-cannot be used interchangeably with either xenon or sevoflurane anesthesia.

Acceleration↗
PubMed1998

Serving the emperor without asking: critical care ethics in Japan.

This article is an attempt by Japanese physicians to introduce the practice patterns and moral justification of Japanese critical care to the world. Japanese health care is characterized by the fact that the fee schedule does not reward high technology medicine, such as surgery and critical care. In spite of the low reimbursement, our critical care practice pattern is characterized by continuing futile treatment for terminal patients in the intensive care unit (ICU). This apparently wasteful practice can be explained by fundamental Japanese cultural values, social factors in Japan, the availability of extensive insurance coverage, physicians' psychological factors, lack of cost-benefit considerations and the pragmatic approach the Japanese take to situations. We attempt to make some brief suggestions regarding the improvement of our critical care practices. Although we can not fully present quantitative data to support our argument, this article represents our real-world approaches to the ethical issues in the ICU in Japan.

Attitude of Health Personnel↗
PubMed1998

Vecuronium-induced neuromuscular block during xenon or sevoflurane anaesthesia in humans.

Twitch response using accelerometry and plasma concentrations, of vecuronium and its metabolite were studied in 27 surgical patients during xenon or sevoflurance anaesthesia after administration of vecuronium 0.05 mg kg-1. Anaesthesia was maintained using oxygen-xenon (MAC = 71%) or oxygen-sevoflurane (MAC = 2%) at an end-tidal concentration equal to 0.8 MAC (i.e. 57% xenon and 1.6% sevoflurane). Mean time from administration of vecuronium to 25% recovery of the first twitch of the train-of-four response was significantly shorter in the xenon group than in the sevoflurane group (12.9 (SD 2.5) min vs 19.4 (6.0) min, respectively). Plasma concentrations of vecuronium at 25% recovery were significantly higher during xenon than during sevoflurane anaesthesia (187 (49) ng ml-1 vs 136 (40) ng ml-1, respectively), while those of 3-desacetylvecuronium were similar in both groups.

Adult↗
PubMed1998

Relationship between end-tidal and arterial carbon dioxide partial pressure using a cuffed oropharyngeal airway and a tracheal tube.

We have compared the differences between end-tidal PE'CO2 and arterial PaCO2 carbon dioxide partial pressures during general anaesthesia using either a cuffed oropharyngeal airway (COPA) or a tracheal tube (TT) in spontaneously breathing adult patients. After induction of anaesthesia, a COPA was inserted in 20 patients who were allowed to breathe spontaneously. When steady state was reached, PE'CO2 and PaCO2 were recorded. The COPA was removed, the trachea intubated with a TT and spontaneous ventilation allowed to resume. After a stable PE'CO2 was reestablished, PaCO2 was measured again and PE'CO2 recorded. Mean difference between PaCO2 and PE'CO2 with the COPA was 0.72 (SD 0.45) kPa and with the TT 0.64 (0.40) kPa (ns; paired t test). Our results suggest that Pe'CO2 is a clinically acceptable indicator of PaCO2 in adults breathing spontaneously via a COPA.

Adult↗
PubMed1998

Loss of SDF-1 receptor expression during positive selection in the thymus.

SDF-1 is a member of the CXC chemokines. In contrast to other chemokines that are induced by inflammation, SDF-1 is constitutively produced by stromal cells. In order to investigate the physiological roles of SDF-1, we constructed a fusion protein, SDF-1-Cgamma1, composed from murine SDF-1alpha and the constant region of human IgG. SDF-1-Cgamma1 stained EL-4 T lymphoma cells and the staining was blocked by rhSDF-1beta. The expression levels of SDF-1R altered along with the T cell maturation. Most c-kit+ hematopoietic precursors in fetal liver in gestational day (GD) 14.5 embryo were SDF-1R-, while c-kit+ double-negative (DN) thymocytes in the embryo were positive for SDF-1R. The receptor expression increased along with T cell maturation up to double-positive (DP) cell stage. Interestingly, SDF-1R expression was down-modulated after positive selection; CD69+CD3hi DP and CD3hi single-positive thymocytes were SDF-1R-/lo. Northern blot analysis demonstrated that SDF-1 and CXCR4 mRNAs were abundantly expressed in the thymuses of embryo and adult mice. These results demonstrate that SDF-1R expression is involved in T cell development in the thymus, particularly in positive selection.

Animals↗
PubMed1998

The placement of the cuffed oropharyngeal airway with sevoflurane in adults: a comparison with the laryngeal mask airway.

UNLABELLED: We sought to determine the anesthetic duration of sevoflurane required to achieve good conditions for placement of a cuffed oropharyngeal airway (COPA) or a laryngeal mask airway (LMA). Forty adult ASA physical status I or II patients presenting for elective surgery received single-breath vital capacity inhaled induction with 5% sevoflurane via face mask; thereafter, ventilation was manually assisted. The patients were randomized to receive either a COPA or LMA placement. The time of anesthetic exposure was varied for consecutive patients using the staircase method. The mean (95% confidence interval) anesthetic time required for acceptable COPA placement (100 [55-145] s) was significantly shorter than that for LMA (160 [101-219] s). The 50% and 95% effective doses (from logistic analyses) for acceptable conditions associated with COPA or LMA placement were 90 s and 145 s or 164 s and 261 s, respectively. These findings suggest that COPA insertion is less stimulating than the LMA. IMPLICATIONS: The cuffed oropharyngeal airway is a new airway device that is similar to a laryngeal mask airway in many ways. However, it requires shorter anesthetic duration for successful placement, which suggests that it can be placed with less stimulation. It may be an alternative to a laryngeal mask airway.

Adult↗
PubMed1998

Pattern electroretinogram elicited by a dartboard pattern.

The receptive field size of retinal ganglion cells is closely related to their eccentricity from the fovea. To elicit larger pattern-reversal electroretinograms (P-ERGs), it may be useful to stimulate the retina with patterns having elements that parallel this change in receptive field size. We describe a dartboard pattern consisting of reversal elements that enlarge gradually from the central to the peripheral stimulus field. The utility of the dartboard pattern for eliciting P-ERG was investigated by comparing it with the conventional uniform checkerboard pattern, but with the other stimulus parameters remaining unchanged (96% contrast, 35.9 cd/m2 mean luminance, 3.3 rev/s temporal frequency, 15 degrees circular field). The dartboard pattern produced a significantly larger P50 amplitude than did the checkerboard pattern, while no difference in peak latency was found when 54 min of arc was used as a standard check size for the checkerboard pattern. The dartboard pattern for eliciting P-ERG should prove clinically useful.

Adult↗
PubMed1998

Transient left bundle branch block induced by left-sided cardiac catheterization in patients without pre-existing conduction abnormalities.

A traumatic left bundle branch block (LBBB) is uncommon in a patient with intact atrioventricular conduction. Three of our patients developed LBBB during a left-sided catheterization. Two patients suffered from angina pectoris and the other had an abdominal aneurysm. Two of them had a history of hypertension. None of the patients had ever shown any conduction abnormalities before the catheterization. The electrocardiogram just before the examination was normal in all 3 patients. LBBB was observed when a catheter was introduced into the left ventricle, and lasted 2--4 min without significant change in heart rates. Examination revealed no significant stenosis proximal to the first septal perforator and normal left ventricular contraction in all patients. One patient developed permanent LBBB 14 months later. Catheter-induced LBBB may occur easily with certain anatomical characteristics of the left bundle branch or the distal His bundle, with or without some concealed damage to the conduction system. It is important to keep this complication in mind and to pay adequate attention to patients' electrocardiograms as well as their angiographical findings, especially in those with pre-existing right bundle branch block.

Aged↗
PubMed1998

[How do antipsychotics exert their effects on dopamine receptor subtypes?].

There have been many efforts to develop novel antipsychotic drugs with improved clinical efficacy and reduced side effects such as extrapyramidal side effects and hyperprolactinemia. Recent evidences from studies on the effects of novel antipsychotic drugs such as clozapine on neurotransmitter receptors are prompting reconsideration of the dopaminergic hypothesis of schizophrenia. This paper gives an overview of the current understanding, including our data, of the effects of several antipsychotics on dopamine receptor subtypes. The recent cloning of dopamine receptors has revealed that multiple dopamine receptor subtypes are generated from at least five distinct dopamine receptor genes. Aripiprazole, a candidate for a novel antipsychotic, has an antagonistic activity against dopamine D2 receptors with a high affinity, but has a weaker potency to up-regulate D2 receptors than haloperidol in the striatum and inhibitory effects on D2-receptor binding activities and mRNA in the pituitary, when it is chronically administrated to rats. Thus the occupancy or influences in D2 receptors in the striatum are involved in the extrapyramidal side effects of typical antipsychotic drugs. These studies provide new leads to understand the pathophysiology and causes of schizophrenia and to develop more effective and safe methods of treatment.

Animals↗
PubMed1998

Idiopathic scoliosis in twins studied by DNA fingerprinting: the incidence and type of scoliosis.

We investigated 21 pairs of twins for zygosity and idiopathic scoliosis. DNA fingerprinting confirmed that 13 pairs were monozygotic and eight were dizygotic. There was concordance for idiopathic scoliosis in 92.3% of monozygotic and 62.5% of dizygotic twins. Of the 12 pairs of monozygotic twins concordant for idiopathic scoliosis, six showed discordant curve patterns but eight had differences in Cobb angle of less than 10 degrees. Seven of the ten pairs of monozygotic twins had similar back shapes. Our findings suggest that there is a genetic factor in the aetiology of idiopathic scoliosis; they also indicate that there is a genetic factor in both the severity of the curve and the general shape of the back.

Adolescent↗
PubMed1998

Hepatic and splenic sarcoidosis evaluated by multiple imaging modalities.

We present a case of hepatosplenic sarcoidosis. A 51-year-old Japanese male, who was diagnosed to have sarcoidosis 4 years previously, was presented to our hospital because of dry cough and anorexia with weight loss. He had tender hepatosplenomegaly. A dynamic abdominal computed tomography (CT) revealed multiple small low-density areas in both liver and spleen, as well as in magnetic resonance imaging (MRI). The laparoscopic photographs showed many small whitish nodules surfacing on the liver and several tumorous nodules on the spleen. Multiple imaging modalities including dynamic CT and MRI are valuable for detecting focal hepatic and splenic lesions of sarcoidosis.

Biopsy↗
PubMed1997

Suppression of TNF-alpha secretion by azelastine in a rat mast (RBL-2H3) cell line: evidence for differential regulation of TNF-alpha release, transcription, and degranulation.

The mast cell plays a pivotal role in initiating allergic inflammation by secreting several cytokines including TNF-alpha, in addition to granule mediators such as histamine. Anti-allergic drugs including azelastine prevent immediate-type hypersensitivity by inhibiting mast cell degranulation, as well as blocking histamine H1 receptors. However, their effects on cytokine release from mast cells remain unknown. In a rat mast RBL-2H3 cell line, azelastine inhibited Ag- and ionomycin-induced TNF-alpha release with IC50 values of 25.7 +/- 3.4 microM and 1.66 +/- 0.45 microM, respectively. These effects were observed at lower concentrations than needed for the inhibition of degranulation. In Ag-stimulated cells, azelastine also inhibited TNF-alpha mRNA expression, TNF-alpha protein synthesis and release, and, possibly related to these effects, Ca2+ influx. In ionomycin-stimulated cells, however, azelastine inhibited TNF-alpha release to a greater extent than mRNA expression/protein synthesis and Ca2+ influx, suggesting that azelastine inhibits the release process more potently than transcription or production of TNF-alpha by interfering with a signal other than Ca2+. Azelastine added 1 h after ionomycin stimulation also immediately blocked subsequent release of TNF-alpha, which had been produced in the cells, without affecting Ca2+ influx. Pretreatment with 1 microM azelastine inhibited ionomycin-induced, but not Ag-induced, protein kinase C translocation to the membranes. These results suggest that the release process of TNF-alpha in mast cells is regulated by a mechanism distinct from that of degranulation, and that in Ca2+-ionophore-stimulated cells, it is also different from that of transcription/production, and possibly involves protein kinase C activation.

Animals↗
PubMed1997

Aripiprazole, a novel antipsychotic drug, inhibits quinpirole-evoked GTPase activity but does not up-regulate dopamine D2 receptor following repeated treatment in the rat striatum.

Aripiprazole, a quinolinone derivative, is a new dopaminergic agent which has been recently developed and demonstrated to be clinically useful as an antipsychotic drug with reduced extrapyramidal motor side effects. Here, we found that aripiprazole competed [3H]spiperone binding with a 100-fold higher affinity than [3H]SCH23390 binding, and inhibited the quinpirole-induced facilitation of high-affinity GTPase activity in rat striatal membranes. The effects of chronic administration of aripiprazole and haloperidol on dopamine D2 receptor binding and mRNA level in rat striata were examined by a [3H]spiperone binding assay and a ribonuclease protection assay. Haloperidol induced a significant rise in Bmax of [3H]spiperone binding at 1 mg/kg and in the level of dopamine D2L receptor mRNA at 4 mg/kg. A high dose of aripiprazole (100 mg/kg) only tended to increase the Bmax of [3H]spiperone binding non-significantly, and had no effect on the level of dopamine D2L receptor mRNA. These results indicated that aripiprazole had an antagonistic activity to dopamine D2 receptors with a high affinity, but that the potency of aripiprazole to up-regulate dopamine D2 receptors in the striatum was much smaller than that of haloperidol. This small up-regulation may be related to the ability to aripiprazole to act without side effects including tardive dyskinesia.

Animals↗
PubMed1997

Inhibitory effect of ethanol on the 5-HT3 receptor-mediated tachycardia in isolated guinea-pig atrium.

The influence of ethanol on 5-hydroxytryptamine (5-HT)-induced tachycardia mediated by 5-HT3 receptor activation in the isolated guinea-pig atrium was studied. Ethanol at 200 mM significantly inhibited 5-HT - but not isoproterenol- or histamine-induced tachycardia in the isolated guinea-pig atrium. The same inhibitory effect was observed in response to 2-propanol and chloral hydrate application. Both 2-propanol at 100 mM and chloral hydrate at 1 mM exhibited inhibitory effects on 5-HT -induced tachycardia as potent as those of ethanol at 200 mM. These alcohols did not inhibit the tachycardia induced by isoproterenol or histamine. The inhibitory effects of the alcohols seemed to be specific for 5-HT and to increase according to their lipophilicity. Our results suggest that the inhibitory effects of ethanol on 5-HT3 receptor-mediated tachycardia are related to the direct effect of ethanol on 5-HT3 receptors in the atrium.

1-Propanol↗
PubMed1997

Hypercoagulable state in a hypobaric, hypoxic environment causes non-bacterial thrombotic endocarditis in rats.

High-altitude hypoxia causes polycythaemia and a hypercoagulable state in humans and animals. This study examines the effects of a hypobaric, hypoxic environment (HHE) on the blood coagulation system in rats. A total of 170 male Wistar rats were housed in a chamber at the equivalent of 5500 m in altitude for 1-12 weeks. After 2 weeks of exposure to HHE, platelet counts decreased significantly; after 4 weeks, the prothrombin and activated partial thromboplastin times were significantly prolonged, compared with those of control rats. In addition, individual coagulation factors (VII, IX, X, XI, and XII) were significantly decreased at 8 weeks (P < 0.05). Levels of anti-thrombin III and alpha 2-plasmin inhibitor also decreased (between 4 and 8 weeks). After 4-12 weeks of exposure to HHE, 30 of 56 rats (54 per cent) developed (i) non-bacterial thrombotic endocarditis (NBTE) or (ii) infarction of the myocardium or kidney, or both (i) and (ii). The incidence of NBTE increased from 33 per cent (5/15 rats) at 4 weeks to 100 per cent (7/7 rats) at 12 weeks. Electron microscopy showed detached endothelial cells in the mitral valves at 1 week; platelets adhered to the subendocardial matrix and platelet aggregation with thrombus formation was seen at 2 weeks of exposure. The results suggest that exposure to HHE induces a hypercoagulable state and causes an NBTE in rats that may result in consumption coagulopathy.

Altitude Sickness↗