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Y Seki

Publications and source records attributed to Y Seki.

At least 55 records · Page 3Linked to original sources
PubMed1999

A multiparametric analysis of occlusal and periodontal jaw reflex characteristics in adult skeletal mandibular protrusion before and after orthognathic surgery.

Periodontal jaw reflex, duration of percussion sounds, tooth mobility, and time-moment analysis of occlusal contacts by the T-scan system were recorded in seven pre-orthognathic surgery patients and six post-orthognathic surgery patients over a 2-year period. The results showed that: (i) reflex response to the pressure applied to the upper right central incisor in the lingolabial direction varied, depending on the background jaw-clenching force (BCF) of the same-sided first molar. The BCF level required to elicit excitatory reflexes was only 0 kgf, and inhibitory reflexes were clearly elicited with a BCF of 1 kgf and beyond before orthognathic surgery. After orthognathic surgery BCF levels required to elicit excitatory reflexes were 0-4 kgf, and inhibitory reflexes were elicited with a BCF of 6 kgf and above; (ii) duration of percussion sounds determined via an occlusal sound analyser decreased in both the upper right central incisor and upper right first molar while tooth mobility measured by 'Periotest(R)' increased in the upper right central incisor, but did not change in the same-sided first molar after orthognathic surgery; (iii) the time moments of occlusal contacts were symmetrical toward the midsagittal axis of the occlusal plane after orthognathic surgery. The centre of the anterioposterior occlusal contacts did not differ between pre- and post-orthognathic surgery groups.

Adolescent↗
PubMed1999

A study on the relative breakthrough time (RBT) of a respirator cartridge for forty-six kinds of organic solvent vapors.

The breakthrough time of a commercially available respirator cartridge was measured for 46 kinds of organic solvents. The condition of the test air flow was set according to the Japanese government standard for the National Approval Test: at 300 ppm of an organic solvent vapor concentration, a temperature of 20 degrees C, a relative humidity of 50 percent, and a flow rate of 30 L/min. The interval between the start of passing the test flow through a cartridge and the time when the concentration of organic solvent vapors at the downstream of the cartridge reached 5 ppm was measured. The ratios of breakthrough times of organic solvents to that of cyclohexane which is designated as the standard test vapor in Japan, were calculated to obtain the relative breakthrough times (RBTs). Nine of the 46 organic solvents had breakthrough times shorter than that of cyclohexane, and these organic solvents with shorter RBTs were characterized by low boiling points and small molecular weights. The RBTs of 34 organic solvents were compared with the breakthrough times reported by Nelson et al. The relationship between the RBTs of this experiment and those reported by Nelson correlated well (correlation coefficient: 0.861).

Cyclohexanes↗
PubMed1999

The compact and expanded denatured conformations of apomyoglobin in the methanol-water solvent.

We have performed a detailed study of methanol-induced conformational transitions of horse heart apomyoglobin (apoMb) to investigate the existence of the compact and expanded denatured states. A combination of far- and near-ultraviolet circular dichroism, NMR spectroscopy, and small-angle X-ray scattering (SAXS) was used, allowing a phase diagram to be constructed as a function of pH and the methanol concentration. The phase diagram contains four conformational states, the native (N), acid-denatured (U(A)), compact denatured (I(M)), and expanded helical denatured (H) states, and indicates that the compact denatured state (I(M)) is stable under relatively mild denaturing conditions, whereas the expanded denatured states (U(A) and H) are realized under extreme conditions of pH (strong electric repulsion) or alcohol concentration (weak hydrophobic interaction). The results of this study, together with many previous studies in the literature, indicate the general existence of the compact denatured states not only in the salt-pH plane but also in the alcohol-pH plane. Furthermore, to determine the general feature of the H conformation we used several proteins including ubiquitin, ribonuclease A, alpha-lactalbumin, beta-lactoglobulin, and Streptomyces subtilisin inhibitor (SSI) in addition to apoMb. SAXS studies of these proteins in 60% methanol showed that the H states of these all proteins have expanded and nonglobular conformations. The qualitative agreement of the experimental data with computer-simulated Kratky profiles also supports this structural feature of the H state.

Apoproteins↗
PubMed1999

Suppression of STAT5 functions in liver, mammary glands, and T cells in cytokine-inducible SH2-containing protein 1 transgenic mice.

Various cytokines utilize Janus kinase (JAK) and the STAT (signal transducers and activators of transcription) family of transcription factors to carry out their biological functions. Among STATs, two highly related proteins, STAT5a and STAT5b, are activated by various cytokines, including prolactin, growth hormone, erythropoietin, interleukin 2 (IL-2), and IL-3. We have cloned a STAT5-dependent immediate-early cytokine-responsive gene, CIS1 (encoding cytokine-inducible SH2-containing protein 1). In this study, we created CIS1 transgenic mice under the control of a beta-actin promoter. The transgenic mice developed normally; however, their body weight was lower than that of the wild-type mice, suggesting a defect in growth hormone signaling. Female transgenic mice failed to lactate after parturition because of a failure in terminal differentiation of the mammary glands, suggesting a defect in prolactin signaling. The IL-2-dependent upregulation of the IL-2 receptor alpha chain and proliferation were partially suppressed in the T cells of transgenic mice. These phenotypes remarkably resembled those found in STAT5a and/or STAT5b knockout mice. Indeed, STAT5 tyrosine phosphorylation was suppressed in mammary glands and the liver. Furthermore, the IL-2-induced activation of STAT5 was markedly inhibited in T cells in transgenic mice, while leukemia inhibitory factor-induced STAT3 phosphorylation was not affected. We also found that the numbers of gamma delta T cells, as well as those of natural killer (NK) cells and NKT cells, were dramatically decreased and that Th1/Th2 differentiation was altered in transgenic mice. These data suggest that CIS1 functions as a specific negative regulator of STAT5 in vivo and plays an important regulatory role in the liver, mammary glands, and T cells.

Animals↗
PubMed1999

Inhibition of ischemia-induced glutamate release in rat striatum by dihydrokinate and an anion channel blocker.

BACKGROUND AND PURPOSE: Increased activation of excitatory amino acid (EAA) receptors is considered a major cause of neuronal damage. Possible sources and mechanisms of ischemia-induced EAA release were investigated pharmacologically with microdialysis probes placed bilaterally in rat striatum. METHODS: Forebrain ischemia was induced by bilateral carotid artery occlusion and controlled hypotension in halothane-anesthetized rats. During 30 minutes of ischemia, microdialysate concentrations of glutamate and aspartate were measured in the presence of a nontransportable blocker of the astrocytic glutamate transporter GLT-1, dihydrokinate (DHK), or an anion channel blocker, 4,4'-dinitrostilben-2,2'-disulfonic acid (DNDS), administered separately or together through the dialysis probe. RESULTS: In control striata during ischemia, glutamate and aspartate concentrations increased 44+/-13 (mean+/-SEM) times and 19+/-5 times baseline, respectively, and returned to baseline values on reperfusion. DHK (1 mmol/L in perfusate; n=8) significantly attenuated EAA increases compared with control (glutamate peak, 9. 6+/-1.7 versus control, 15.4+/-2.6 pmol/ microL). EAA levels were similarly decreased by 10 mmol/L DHK. DNDS (1 mmol/L; n=5) also suppressed EAA peak increases (glutamate peak, 5.8+/-1.1 versus control, 10.1+/-0.7 pmol/ microL). At a higher concentration, DNDS (10 mmol/L; n=7) further reduced glutamate and aspartate release and also inhibited ischemia-induced taurine release. Together, 1 mmol/L DHK and 10 mmol/L DNDS (n=5) inhibited 83% of EAA release (glutamate peak, 2.7+/-0.7 versus control, 10.9+/-1.2 pmol/ microL). CONCLUSIONS: These findings support the hypothesis that both cell swelling-induced release of EAAs and reversal of the astrocytic glutamate transporter are contributors to the ischemia-induced increases of extracellular EAAs in the striatum as measured by microdialysis.

ATP-Binding Cassette Transporters↗
PubMed1999

Postoperative magnetic resonance imaging after acoustic neuroma surgery: influence of packing materials in the drilled internal auditory canal on assessment of residual tumor.

Serial magnetic resonance (MR) images taken after acoustic neuroma surgery were analyzed to evaluate the pattern and timing of postoperative contrast enhancement in 22 patients who underwent acoustic neuroma removal via the suboccipital transmeatal approach. The opened internal auditory canal (IAC) was covered with a muscle piece in nine patients and with fibrin glue in 13. A total of 56 MR imaging examinations were obtained between days 1 and 930 after surgery. MR imaging showed linear enhancement at the IAC within the first 2 days after surgery, and revealed nodular enhancement on day 3 or later in patients with a muscle piece. MR imaging tended to show linear enhancement at the IAC, irrespective of the timing of the examination in the patients with fibrin glue. Postoperative MR imaging on day 3 or later showed the incidence of nodular enhancement in patients with muscle was significantly higher than in patients with fibrin glue. The results illustrate the difficulty in differentiating nodular enhancement on a muscle piece from tumor by a single postoperative MR imaging study. Therefore, fibrin glue is generally advocated as a packing material of the IAC because it rarely shows masslike enhancement on postoperative MR imaging. When a muscle piece is used in patients at high risk for postoperative cerebrospinal fluid leaks, MR imaging should be obtained within the first 2 days after surgery, since benign enhancement of muscle will not occur and obscure the precise extent of tumor resection.

Female↗
PubMed1999

Pulmonary clearance and lesions in rats after a single inhalation of ultrafine metallic nickel at dose levels comparable to the threshold limit value.

This study aimed to (1) determine the deposition and clearance rates of ultrafine metallic nickel (Uf-Ni) in rats after a 5 hours single inhalation exposure, and (2) to histopathologically examine the pulmonary lesions induced at dose levels comparable to the Occupational Exposure Limit recommended in Japan (OEL). The exposure concentrations of Uf-Ni for the 3 groups were 0.15 (Low), 1.14 (Medium), and 2.54 (High) mg/m3. Five rats/group were sacrificed at 0 h and 1, 3, 7, 14, and 21 days post exposure. The amount of Ni in the lung accumulated dose-dependently. The half-times for Ni in the lung were estimated as 32 days on average, and were similar to each other regardless of the initial dosage. The histopathologically observed pulmonary lesions induced by a single inhalation of Uf-Ni were, (1) a significant increase in lung weight in the High and Medium groups with time, (2) accumulation of foamy alveolar macrophages (AM), (3) degenerated AM indicating alveolar lipoproteinosis which was aggravated for up to 4 weeks in the High group and (4) acute calcification of the degenerated AM was remarkable. The present results suggest that even a single inhalation of Uf-Ni induces potency of lung lesions at dose levels comparable to the OEL (1 mg/m3 as Ni), or the TWA of ACGIH (1.5 mg/m3 for elemental/metal).

Animals↗
PubMed1999

A new model rat with acute bronchiolitis and its application to research on the toxicology of inhaled particulate matter.

The aim of the present study was to establish a useful animal model that simulates humans sensitive to inhaled particulate matter (PM). We have developed a new rat model of acute bronchiolitis (Br) by exposing animals to NiCl2 (Ni) aerosols for five days. Three days following the Ni exposure, the animals developed signs of tachypnea, mucous hypersecretion, and bronchiolar inflammation which seemed to progress quickly during the fourth to fifth day. They recovered from lesions after four weeks in clean air. To assess the sensitivity of the Br rats to inhaled particles, two kinds of PM of respirable size were tested with doses similar to or a little higher to the recommended threshold limit values (TLVs) for the working environment in Japan. Titanium dioxide (TiO2 = Ti) was chosen as an inert and insoluble particles and vanadium pentoxide (V2O5 = V), as a representative soluble and toxic airborne material. The Br rats exposed to either Ti or V were compared the pathological changes in the lungs and the clearance of particles to those in normal control or Br rats kept in clean air. The following significant differences were observed in Br rats: 1. delayed recovery from pre-existing lesions or exacerbated inflammation, 2. reductions in deposition and clearance rate of inhaled particles with the progress of lesions. The present results suggest that Br rats are more susceptible to inhaled particles than control rats. Therefore, concentrations of particulate matter lower than the TLVs for Japan, which have no harmful effects on normal lungs, may not always be safe in the case of pre-existing lung inflammation.

Acute Disease↗
PubMed1999

[Lead].

Explore the source record for details and available documents.

Adult↗
PubMed1999

[Sense of coherence, stressful life events and psychological health].

Aaron Antonovsky's Sense of Coherence (SOC), as a stable disposition of personality that serves as a major coping resource for the preservation of health, has been widely used in many studies. However, few empirical studies are conducted on the concept of SOC. We examined the stability of SOC and the buffering effect of SOC on the psychological health in dealing with stressful life events. The subjects were 200 adults randomly selected in Tokyo, and follow-up survey was conducted one year after the first survey. Goldberg's General Health Questionnaire (GHQ) was used for assessing psychological health. Antonovsky's SOC scale was translated into Japanese (and reverse translated) in this study. The test-retest reliability of SOC scale was 0.78. Cronbach's alpha was 0.91. The factors related to the SOC supported previous findings and Antonovsky's theory about the positive correlation with educational and economic status. In the follow-up survey, the subjects were also asked about the experience of 56 stressful life events (SLE) composed of four aspects of life during the previous year: personal, family, work and environment. The SLE was assessed through the total number and the weighted score. Contrary to the theory, the results showed that the SOC score has no intra-individual stability. The mean score of SOC in 1998 was 131.1 +/- 23.9, significantly lower than that in the previous year. When the subjects were divided into two groups based on a median 1997 score, the effect of SLE negatively affected SOC scores after one year among those who had a low SOC, although this effect was not observed among those who had a high SOC. The effect of SLE on changes of SOC was stronger among men compared to women. Also, the results showed the SOC was positively related to psychological health, and the buffering effect of SOC on the psychological health in dealing with stressful life events was only observed among men. Findings in this study suggest that SOC is variable for those with weak SOC if they experienced stressful life events. Also, the stressful life events differentially affect the SOC among men and women. The buffering effect was not sufficiently proven in this study. Methodological issues to confirm Antonovsky's theory are also presented.

Adult↗
PubMed1998

Expression of proto-oncogenes and gene mutation of sarcomeric proteins in patients with hypertrophic cardiomyopathy.

Several mutations of cardiac beta-myosin heavy chain (beta-MHC) gene were reported in patients with hypertrophic cardiomyopathy (HCM). Involvement of proto-oncogenes has been shown in the mechanism of experimental cardiac hypertrophy. This study sought to examine the effects of c-H-ras and c-myc expression in the steady-state myocardium on hypertrophic changes and to evaluate the possible interaction between beta-MHC mutation and proto-oncogene expression in HCM. Endomyocardial biopsy was performed in 17 HCM patients (5 beta-MHC mutations and 1 troponin T mutation) and 7 control subjects (no mutation). Reverse transcription-polymerase chain reaction analysis revealed c-H-ras expression in all members of both groups. Cardiomyocyte size was correlated with the expression level of c-H-ras (P<0.001), and c-H-ras expression was upregulated in HCM patients (P<0.01). HCM patients with a beta-MHC mutation had the higher c-H-ras expression than did control subjects or patients without a mutation (P<0.01). c-myc mRNA was expressed in 7 of 17 HCM patients but not in control subjects. Myocyte size was greater in c-myc-positive HCM patients than in control subjects and c-myc-negative HCM patients (P<0.001 and P<0.05, respectively). The proto-oncogene expression did not affect clinical findings, myocardial fibrosis, or disarray. In conclusion, c-H-ras and c-myc expression in the steady-state myocardium may play a role in the hypertrophic mechanism in HCM. It is possible that ss-MHC gene mutation has some effect on the regulation of proto-oncogene expression in HCM.

Adolescent↗
PubMed1998

Myocardial DNA strand breaks are detected in biopsy tissues from patients with dilated cardiomyopathy.

BACKGROUND: Progressive damage of cardiomyocytes with interstitial and replacement fibrosis accompanied by less inflammatory cell infiltration is observed in patients with dilated cardiomyopathy (DCM), suggesting some other mechanisms rather than necrotic cell death. HYPOTHESIS: The aim of this study was to assess the possible involvement of apoptotic process in the pathogenesis of DCM and myocarditis. METHODS: Endomyocardial biopsy was performed in patients with DCM (n = 9), myocarditis (n = 4), or atypical chest pain syndrome (as controls; n = 5). The TUNEL method was used for in situ detection of oligonucleosomal DNA strand breaks. RESULTS: The TUNEL-positive cells were observed in three of nine patients with DCM and in all four with myocarditis, but in none of the controls. The TUNEL-positive nuclei were observed exclusively in cardiomyocytes in DCM, whereas in myocarditis they were detected mainly in interstitial cells and in a few myocytes. In DCM, interstitial fibrosis was greater in the TUNEL-positive than in TUNEL-negative patients (p < 0.05). In either DCM or myocarditis, electron microscopic examination could not reveal morphologic features of apoptosis of cardiomyocytes. CONCLUSION: The DNA strand breaks were detected in cardiomyocytes in patients with DCM and mainly in interstitial cells in myocarditis. It is possible that the DNA strand breaks can be involved in mechanisms of progressive loss of functional cardiac units in these myocardial diseases.

Adult↗
PubMed1998

Age-dependent changes in metallothionein levels in liver and kidney of the Japanese.

Samples of liver, renal cortex, and medulla were obtained from 55 forensic autopsies (0- to 95-yr-old Japanese). Metallothionein (MT) was determined by the Ag-hem or Cd-hem method. Zinc (Zn), copper (Cu), and cadmium (Cd) were determined by atomic absorption spectrophotometry. The mean levels of MT were 250 micrograms/g in the liver, and 394 micrograms/g (cortex) and 191 micrograms/g (medulla) in the kidney. Age-dependent changes were observed in both the liver and kidney. In the liver, MT level decreased during infancy and increased thereafter with age. Similar age-dependent changes in the levels of Zn and Cu were observed. In the kidney cortex, MT level increased with age, although no correlation was found after middle age. The levels of Cd and Zn also increased with age until middle age; however, they decreased thereafter. These results suggest that age-dependent changes in renal MT levels are associated with accumulation of Cd.

Adolescent↗
PubMed1998

Benign osteoblastoma of the odontoid process of the axis: a case report.

BACKGROUND: The majority of benign spinal osteoblastomas arise from the posterior elements of the spine; there have been no published reports of the tumor in the odontoid process of the axis. Accurate preoperative localization of the tumor is important for planning minimally invasive surgery on such benign tumors. However, the magnetic resonance imaging (MRI) findings may be misleading, because peritumoral changes may be confusing. CASE DESCRIPTION: We report the case of a 20-year-old man, who presented with a 4-year history of protracted left posterior neck pain. Preoperative computed tomography (CT) revealed a discrete mixed-density mass within the odontoid process. MRI showed diffusely abnormal signal intensity and enhancement both in the odontoid process and the body of the axis, including regions from which biopsy specimens were normal or had minimal inflammatory changes. Precise preoperative localization of the tumor margins using CT and biopsy allowed for successful resection of the tumor via a transoral approach with preservation of a part of the axis and the odontoid process. Consequently, stabilization of the spine was unnecessary, and the patient remained symptom-free for 3.5 years. CONCLUSION: We reported a rare case of benign osteoblastoma of the odontoid process of the axis. The tumor was successfully resected via a transoral approach, preserving a part of the axis and the odontoid process. We have emphasized an advantage of CT over MRI for accurate localization of the tumor.

Adult↗
PubMed1998

Peripheral blood levels of matrix metalloproteases-2 and -9 are elevated in patients with acute coronary syndromes.

OBJECTIVES: This study was sought to investigate whether peripheral blood levels of matrix metalloproteases (MMPs) are affected in patients with acute coronary syndromes (ACS). BACKGROUND: Synthesis of MMPs has been reported in coronary atherosclerotic lesions in patients with unstable angina (UA), suggesting a pathogenic role of MMPs in the development of ACS. METHODS: Using sandwich enzyme immunoassay, serum MMP-2 and plasma MMP-9 were measured in 33 patients with ACS (22 with acute myocardial infarction [AMI], 11 with UA), 17 with stable effort angina (EA) and 17 normal control subjects. RESULTS: Serum MMP-2 in patients with UA and AMI on day 0 was two times greater than that in control subjects, and patients with EA showed higher MMP-2 levels than those in control subjects. Plasma MMP-9 in patients with UA and AMI on day 0 was elevated by threefold and twofold versus that in control subjects, respectively. In patients with UA and AMI who underwent medical treatment (n = 11 and 13, respectively), MMP-2 elevation was sustained until day 7. In patients with UA, MMP-9 elevation on day 0 was followed by a gradual decrease toward the control range up to day 7. Some patients with AMI showed a transient MMP-9 elevation with a peak on day 3, whereas in others, MMP-9 levels were significantly elevated on day 0 and remained higher than those in control subjects up to day 3. CONCLUSIONS: Serial changes in serum MMP-2 and plasma MMP-9 were documented in patients with ACS. These findings provide an insight into the molecular mechanism of plaque destabilization.

Angina Pectoris↗
PubMed1998

Transmural myocardial infarction caused by thromboembolism associated with mitral insufficiency in a dog.

A 10-year-old dog, which had been treated for mitral insufficiency, died suddenly. Transmural myocardial infarction secondary to thromboembolic occlusion of the subsinuosal interventricular branch of the left circumflex artery was noted in the posterior lower half of the left ventricular wall, involving the interventricular septum and a part of right ventricular wall. The mitral valve leaflets were markedly thickened (valvular endocardiosis). These were a patchy area of jet lesion and several mural thrombi on the left-atrial endocardium. The embolus in the subsinuosal interventricular branch was composed of mostly platelets and fibrin, showing the same histologic features as those of the mural thrombi on the left-atrial endocardium. From these findings, it was concluded that dislodgement of part of the mural thrombi on the left-atrial endocardium caused thromboembolism of the subsinuosal interventricular branch.

Animals↗
PubMed1998

Islet cell tumor in von Hippel-Lindau disease.

We describe a 42-year-old man with von Hippel-Lindau disease and islet cell tumor of the pancreas. He had retinal and cerebellar hemangioblastomas. His sister had pheochromocytoma. A pancreatic tumor was detected by ultrasonography at his periodical medical checkup. Contrast enhanced computed tomography and abdominal angiography revealed a hypervascular tumor in the pancreatic head. Histological examination of the resected tumor revealed characteristics of islet cell tumor of the pancreas, which was positive for chromogranin-A, S-100 protein, and pancreatic polypeptide, but was negative for insulin, gastrin, glucagon, somatostatin, vasoactive intestinal peptide, serotonin, and adrenocorticotropic hormone.

Adenoma, Islet Cell↗