PubMed Health⌕ Search

Biomedical subjects

T Shigeta

Publications and source records attributed to T Shigeta.

At least 19 recordsLinked to original sources
PubMed2000

Magnetic resonance angiography evaluation of basilar artery stenosis in patients with vertebrobasilar insufficiency.

To assess the usefulness of evaluating basilar arterial flow by magnetic resonance angiography (MRA), MRA results for patients with vertebrobasilar insufficiency (VBI) were compared with those for age-matched individuals with no vestibular disorders. The presence of stenosis in the basilar artery, its severity and the presence of complications associated with atherosclerosis in the two groups were statistically compared. Analyses revealed significant differences in the incidence of stenosis, its severity, and the incidence of complications between the two groups. These findings suggest that MRA is valuable for the estimation of vertebrobasilar hemodynamics. MRA evaluation of basilar artery stenosis appears to be suitable for identifying a high-risk group among VBI patients, since basilar artery stenosis can result in serious disabilities.

Aged↗
PubMed1999

Defective control of apoptosis and mitotic spindle checkpoint in heterozygous carriers of ATM mutations.

Ataxia telangiectasia (AT) carrier-derived lymphoblastoid cell lines (AT-LCLs/hetero) with suboptimal ATM protein expression were examined for the regulation of radiosensitivity, apoptosis, and mitotic spindle checkpoint in response to DNA-damaging agents. Although AT-LCLs/hetero showed intermediate radiation sensitivity, as determined by clonogenic assay, they were resistant to early-onset apoptosis, as much as AT patient-derived LCLs (AT-LCLs/homo). Furthermore, two of three AT-LCLs/hetero showed defective mitotic spindle checkpoint control in response to X-ray irradiation, which is a recently characterized biological feature in AT-LCLs/homo. Our findings indicate that carriers of ATM mutation have biological abnormalities due to haploinsufficiency of ATM protein or dominant-negative effect of mutant ATM protein. Thus, although it is still controversial whether ATM mutation carriers are at higher risk for cancer during adulthood, our findings based on in vitro biological indicators support the notion that at least some of such carriers are at a higher risk for cancer development than those without ATM mutation. Our findings may help to reevaluate epidemiological studies on cancer susceptibility in AT carriers.

Apoptosis↗
PubMed1999

DNA damage-associated cell cycle and cell death control is differentially modulated by caffeine in clones with p53 mutations.

Caffeine is known to potentiate the cytotoxic effects of DNA damaging agents and increases the sensitivity of p53-deficient cells to X-irradiation (X-IR). We have analyzed the cell cycle and cell death control after X-IR in the absence or presence of caffeine in hematological cell lines with various configurations of the p53 gene; EBV-immortalized lymphoblastoid cells with heterozygous p53 mutation (wt/mt), human leukemia cell lines HL60 and KOPM28 with no and mutant p53 expression, respectively. These cell lines display an impaired G0/G1 checkpoint and G2 delay following X-IR, and resistance to apoptosis, which are in accordance with findings previously reported. When irradiated in combination with caffeine, all these cell lines overrode the G2 delay and accumulated at G0/G1. The cell cycle modifications in these cell lines correlated with the increase in radiation-induced p34Cdc2 kinase activity by caffeine. These cell cycle control modifications by caffeine, however, were not associated with enhancement of radiation-induced apoptosis or reduction of clonogenic growth activity in these cell lines. These results suggest that the cytocidal effect of caffeine may need to be verified independently of its cell cycle regulatory activities at least in some cases with p53 mutation.

Amino Acid Substitution↗
PubMed1999

Interaction between fibronectin and eosinophils in the growth of nasal polyps.

OBJECTIVES: The aim of this study was to determine roles of fibronectin and eosinophils in the etiology of nasal polyposis. STUDY DESIGN: We designed a cohort study of cases with nasal polyposis. Sampled nasal polyps were differentiated by their histopathologic characteristics, and compared by size and computed tomography (CT) stage. METHODS: The size of nasal polyps was determined on the basis of the endoscopic findings, and the extent of sinusitis was evaluated by CT staging. Nasal polyp samples were taken from 82 patients during ethmoidectomy and differentiated by morphologic characteristics, infiltration cell types, or fibronectin positivity. Then their sizes and CT stages were compared. In addition, correlation among these histological characteristics was analyzed. RESULTS: Nasal polyps showing edematous morphology, eosinophil infiltration, or fibronectin expression were significantly large in size. Concerning CT stages, only the infiltration cell type showed a significant difference. Significant correlation among edematous morphology, eosinophil infiltration, and fibronectin expression was also recognized. CONCLUSIONS: These findings suggest that interaction between eosinophils and fibronectin may play a role in edema formation, which contributes to the growth of nasal polyps.

Adolescent↗
PubMed1998

Defective control of apoptosis, radiosensitivity, and spindle checkpoint in ataxia telangiectasia.

We examined the regulation of apoptosis, radiosensitivity, and spindle checkpoint in response to DNA-damaging agents in ataxia telangiectasia (AT)-derived lymphoblastoid cell lines (AT-LCLs), which lack AT mutated (ATM) protein expression. In addition to the previous findings that AT-LCLs are defective in regulation of cell cycle at the G1, S, and G2-M checkpoints in response to X-ray irradiation (X-IR) and are highly sensitive to X-IR (J. Biol. Chem., 271: 20486-20493, 1996), we showed for the first time that AT-LCLs were defective in X-IR-associated spindle checkpoint control. The cells were also resistant to early apoptosis as much as LCLs derived from patients with Li-Fraumeni syndrome (LFS-LCLs). Terminal deoxynucleotidyl transferase-mediated nick end labeling assay of LCLs, however, demonstrated a significant increase in apoptotic cells among AT-LCLs cultured over a longer period after X-IR. These findings were in contrast to those of LFS-LCL, which showed very little increase in terminal deoxynucleotidyl transferase-mediated nick end labeling-positive population, even in cells with hyperploidy. Thus, although early apoptosis and cell cycle controls in response to DNA damage are disrupted in both ATM and p53 mutations, cells from AT patients are much more susceptible to late-onset apoptosis than those of LFS. These differences may depend on the level of accumulation of DNA damage and/or threshold that triggers late-onset cell death in ATM or p53 mutations. Our findings allow a better understanding of the role of ATM in p53-dependent and independent signal transduction pathways in response to DNA damaging agents.

Apoptosis↗
PubMed1998

Clinical value of MRA analysis of the vertebrobasilar system in vertiginous patients.

Vertebrobasilar haemodynamics correlate closely with syndromal vertigo. The aim of this study is to examine the clinical value of MRA for evaluation of vertebrobasilar haemodynamics in vertiginous patients. We examined 40 individuals (20 with vertebrobasilar insufficiency and 20 diagnosed with other vestibular disorders). MRA results were quantified on the basis of the severity of vascular stenosis in the major arteries of the vertebrobasilar system and we analysed the relationship of these results with otoneurological diagnoses, eye-tracking tests (ETT) and optokinetic nystagmus (OKN). MRA results correlated well with otoneurological diagnoses and ETT results. Consequently, MRA can be used as a screening examination to evaluate vertebrobasilar haemodynamics and ETT may be a sensitive functional parameter of vertebrobasilar insufficiency.

Adult↗
PubMed1998

Evaluation of the vertebrobasilar artery system by magnetic resonance angiography in the diagnosis of vertebrobasilar insufficiency.

To evaluate the advantages of magnetic resonance angiography (MRA) in assessing the vertebrobasilar artery system for diagnosing vertebrobasilar insufficiency (VBI), we compared the MRA results of middle-aged and older VBI cases with those of age-matched peripheral disorder cases. There were no significant differences in the rate of complications associated with atherosclerosis between VBI cases and peripheral disorder cases. The MRA results were quantitatively assessed by scores determined on the basis of the severity of stenosis in the vertebral arteries and basilar artery. The MRA score was defined as the total score of these three arteries. The severity of stenosis and the MRA score of VBI cases were significantly higher than those of peripheral cases. MRA can therefore be of value as a screening examination for estimating vertebrobasilar blood flow and can provide helpful information for diagnosing VBI.

Aged↗
PubMed1998

Quantitative analysis of correlation between smooth pursuit and vertebrobasilar hemodynamics.

The cerebellar arterial system is derived from the vertebrobasilar system. However, the relation between cerebellar function and vertebrobasilar hemodynamics remains poorly understood. In this study on patients with vertebrobasilar insufficiency symptoms we examined the relation between magnetic resonance angiography (MRA) abnormalities in the vertebrobasilar system and smooth pursuit function, which is a sensitive parameter of cerebellar function. MRA abnormality was quantitatively assessed on the basis of the severity of stenosis in the vertebral arteries and basilar artery, and on the visualization of the superior cerebellar arteries. Smooth pursuit dysfunction was quantified by the combined amplitude of spikes on an electronystagmograph. A significant correlation was found between MRA abnormality and smooth pursuit dysfunction. This suggests that smooth pursuit dysfunction is closely related to static factors of dysregulation of vertebrobasilar blood flow. Therefore, smooth pursuit can be valued as a sensitive parameter to dysfunction of vertebrobasilar blood flow.

Aged↗
PubMed1998

Comparative assessment of cell proliferation and accumulation of extracellular matrix in nasal polyps.

In nasal polyps constantly associated with chronic inflammation, a dysregulation of epithelial cell proliferation has been described. Involvement of extracellular matrix accumulation is also suggested in the formation and growth of nasal polyps. In this study, we attempted to evaluate the activity of the proliferation of epithelial cells and fibroblasts and the relation between fibronectin accumulation and these cell proliferations in nasal polyps. The pathological specimens of 30 patients were examined which manifested proliferating cell nuclear antigen (PCNA) expression in epithelial cells and fibroblasts and in fibronectin expression. PCNA expression was quantified by calculating the index for each sample. No significant difference in PCNA index was found between epithelial cells and fibroblasts. However, a significant correlation was found between the epithelial and fibroblastic PCNA index. In addition, fibronectin immunopositivity was well correlated with the activity of proliferation of fibroblasts. Therefore, proliferation of fibroblasts is also an important factor in the growth of nasal polyps, and its relationship with fibronectin accumulation may play a role in the pathogenesis of nasal polyposis.

Adult↗
PubMed1990

[Assessment of lumbar trabecular bone density by means of single energy quantitative CT in hospital control children and bone metabolic disorders. 1].

We studied the 3rd lumbar vertebral trabecular bone mineral density in 59 cross-sectional pictures of quantitative computed tomography (QCT) with CaCO3 phantom for 28 hospital control children and 30 cases of suspected bone metabolic disorders. The QCT value of bone mineral density of control children showed neither age dependency nor sexual difference before puberty: for males was 221.8 +/- 30.2 mg CaCO3/cm3 (Mean +/- SD) under 4 years, 218.1 +/- 39.7 at 5-9 years and 217.2 +/- 30.9 at 10-15 years; and for females 220.9 +/- 18.3 under 4 years and 240.0 +/- 29.4 at 5-9 years. The QCT values of bone mineral density in bed-ridden patients, children receiving glucocorticoids and children receiving anticonvulsants were significantly lower than that in control children (p less than 0.005). The QCT value of bone mineral density of bed-ridden patients was significantly lower than that of children receiving glucocorticoids and of children receiving anticonvulsants (p less than 0.05, p less than 0.005 respectively). Our study confirmed that single energy quantitative CT was very useful in pediatric clinical application.

Adolescent↗
PubMed1990

[CT findings of the benign tracheobronchial lesions with calcification].

In the benign tracheobronchial lesions with calcification, tracheobronchopathia osteochondroplastica, relapsing polychondritis and tracheobronchial amyloidosis were considered. CT demonstrated small nodules with calcifications at the trachea with or without deformity of tracheal wall in the case of tracheobronchopathia osteochondroplastica, swelling of tracheal cartilage with diffuse and multiple calcifications in the case of relapsing polychondritis and calcifications in the deep parts of tracheobronchial amyloid nodules. CT findings were able to differentiate those benign lesions. High-resolution CT is more useful in the distribution of abnormal calcification of these diseases.

Aged↗
PubMed1985

[Digital perfusion images for evaluating patients with mitral valve replacement].

To determine whether the distribution of pulmonary perfusion can be applied as a noninvasive means of evaluating patients with mitral valve replacement (MVR), computerized Tc-99m MAA pulmonary perfusion images (digital perfusion images: DPI) were obtained for 32 patients in the preoperative, early postoperative and late postoperative (18 months mean) periods. DPI consisted of isocount areas, and a 100-70% area was defined as a hyperperfusion area. The distribution of pulmonary perfusion was evaluated using patterns of hyperperfusion area in anterior DPI. In 32 patients above-mentioned had the hyperperfusion areas in the upper lung fields preoperatively, the perfusion of the lung base was investigated. In 21 patients hyperperfusion area appeared in the lung base in the late follow-up period (group A), and all patients improved clinically. In 11 patients, the DPI improved to nearly normal patterns. In five patients, the DPI improved after one year postoperatively. In 11 patients, hyperperfusion areas did not appear in the lung base in the late follow-up period (group B). Six of the 11 patients did not improve clinically. There were no significant hemodynamic differences between groups A and B except for slight differences in the postoperative pulmonary vascular resistance. These results suggested significant correlations between the clinical improvement and the normalization of the DPI. The use of DPI patterns may facilitate quantitative and objective estimations of postoperative states. Since DPI are easy to perform noninvasively, DPI may comprise a useful graphic diagnostic method for evaluating patients with MVR.

Adolescent↗