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Biomedical subjects

T Shibata

Publications and source records attributed to T Shibata.

At least 397 records · Page 22Linked to original sources
PubMed1996

Applying very high resolution microfocus X-ray CT and 3-D reconstruction to the human auditory apparatus.

Conventional high-resolution X-ray computed tomography (XCT) is an important medical technique because it provides sectional images (tomograms) of internal structures without destroying the specimen. However, it is difficult to observe and to analyze fine structures less than a few cubic millimeters in size because of its low spatial resolution of 0.4 mm. Overcoming this problem would not only enable visualization of human anatomical structures in living subjects by means of computer images but would make it possible to obtain the equivalent of microscopic images by XCT without making microscopic sections of biopsy material, which would allow the examination of the entire body and detection of focal lesions at an early stage. Bonse et al. and Kinney et al. studied absorption contrast microtomography by using synchrotron radiation and achieved 8-microns spatial resolution in human cancellous bone. Recently, Momose et al. reported examining the soft tissue of cancerous rabbit liver by a modification of the phase-contrast technique using synchrotron radiation with a spatial resolution of 30 microns (ref. 4). However, the equipment for synchrotron radiation requires a great deal of space and is very expensive. Aoki et al., on a different tack, reported microtomography of frog embryos by using a conventional laboratory microfocus X-ray source with a spot size of about 2 microns (ref. 5). As no human tomographic studies by superresolution microfocus XCT (MFXCT) using a normal open-type X-ray source have been reported, we tried using MFXCT with a maximum experimental spatial resolution of 2.5 microns, especially designed for industrial use, on the auditory ossicles of a human fetus, the smallest and lightest bones in the skeletal system. No XCT studies of fetal auditory ossicles have been reported to date. The fine tomograms with three-dimensional reconstructions obtained showed the existence of an apparently previously undescribed joint between the tympanic ring and the anterior process of the malleus. We hope the early development of this MFXCT for clinical use will make a great contribution to medicine.

Auditory Pathways↗
PubMed1996

Homologous recognition by RecA protein using non-equivalent three DNA-strand-binding sites.

A key step in homologous recombination is the formation of a heteroduplex joint between double-stranded DNA and single-stranded DNA by the homologous pairing and strand-exchange, and this step is also important in recombinational repair of damaged DNA in various organisms. The homologous pairing and the strand-exchange are promoted in vivo and in vitro by RecA protein of Escherichia coli or its homologues of bacteria, virus, and lower and higher eukaryotes. A central question on the mechanism of homologous recombination is how RecA protein (and its homologues) recognizes homologous sequences between single-stranded DNA and double-stranded DNA. Recent studies suggest that RecA protein promotes homologous recognition between these DNA molecules by the formation of a transient and additional pairing of identical sequences via non-Watson-Crick interactions to the Watson-Crick-type duplex DNA, and that RecA protein uses three non-equivalent DNA-strand-binding sites in this reaction.

Animals↗
PubMed1996

Endothelial pores in the rat soleus muscle capillaries after experimental limb immobilization.

Structural changes of capillaries were reexamined in the rat soleus muscle 12 weeks after limb immobilization. Most capillaries were of the continuous type, while capillaries with fenestrations were often observed around degenerated muscle fibers. In some of these fenestrated capillaries, the endothelial cell was partially disrupted and formed a small pore at its fenestrated portion. These findings suggest that the occurrence of capillaries with both diaphragmed fenestrae and pores represent degenerative changes in the long-term immobilized muscle.

Animals↗
PubMed1996

Comparison of in vivo efficacy of hypoxic cytotoxin tirapazamine and hypoxic cell radiosensitizer KU-2285 in combination with single and fractionated irradiation.

Development of strategies to eradicate radioresistant hypoxic cells would be of great benefit for clinical radiotherapy. In the present study, the in vivo effects of a promising hypoxic cytotoxin, tirapazamine (3-amino-1,2,4-benzotriazine 1,4-di-N-oxide), were examined in comparison with those of KU-2285, one of the best hypoxic cell radiosensitizers, in combination with both single and fractionated irradiation. The tumor response was assessed by the standard in vivo-in vitro clonogenic assay using SCCVII tumors in C3H mice and EMT-6/KU tumors in Balb/c mice with different characteristics of tumor hypoxia. With single-dose irradiation (18 Gy), both tirapazamine and KU-2285 showed significant enhancement of cell killing in a dose-dependent manner, but tirapazamine was more effective for SCCVII tumors with acutely hypoxic cells, while KU-2285 was more effective for EMT-6/KU tumors predominantly with chronically hypoxic cells. In fractionated irradiation regimens (4 fractions of 5 Gy at 12 h intervals), tirapazamine showed more marked combined effects at 10 and 20 mg/kg than KU2285 at 100-200 mg/kg in both SCCVII and EMT-6/KU tumors. We concluded that the effectiveness of KU-2285 and tirapazamine was correlated with the nature of tumor hypoxia with single-dose irradiation, whereas tirapazamine appeared more potent than KU-2285 with fractionated irradiation. These findings suggest the potential usefulness of tirapazamine in clinical fractionated radiotherapy.

Animals↗
PubMed1996

High acid secretion may protect the gastric mucosa from injury caused by ammonia produced by Helicobacter pylori in duodenal ulcer patients.

The aim of the present study was to investigate the mechanism by which gastric atrophy does not tend to occur in patients with duodenal ulcer despite frequent Helicobacter pylori infection. This investigation was performed in 60 patients with duodenal ulcer and 63 age-matched gastritis patients. Endoscopic findings in the antrum and corpus were classified as normal, atrophic and superficial changes. Biopsy specimens were taken from the antrum and corpus. Ninety per cent of patients with duodenal ulcer and 63.5% of patients with gastritis had H. pylori infection (P < 0.01). The incidence of normal findings in duodenal patients was 30% in antral regions and 50% in the corpus (P < 0.05). Atrophic change was observed in 21.7% of patients in the antrum and 3.3% of patients in the corpus (P < 0.01). The grade of inflammation in duodenal ulcer specimens was significantly higher in the antrum than in the corpus (P < 0.01). H. pylori density was significantly higher in the antrum than in the corpus in ulcer patients (P < 0.01). No significant difference in endoscopic findings, H. pylori density or the grade of inflammation was found between the antrum and corpus in patients with gastritis. The mean intragastric ammonia concentration was 10.3 mg/dL in duodenal ulcer patients and 6.2 mg/dL in gastritis patients (P < 0.01). The mean pH was 3.5 and 4.6 in ulcer and gastritis specimens, respectively (P < 0.01). Our data suggest that gastric mucosa injury is less frequently associated with duodenal ulcers than with gastritis due to the low H. pylori density in the corpus and to the higher acid output that neutralizes the ammonia produced by H. pylori.

Adult↗
PubMed1996

Biased VH family usage in primary gastric B cell lymphoma of mucosa-associated lymphoid tissue-type and the selected V beta expression of T cells infiltrating into the lymphoma cells.

Seven cases of primary gastric low-grade B cell lymphoma of mucosa-associated lymphoid tissue (MALT) type, two cases of high-grade B cell lymphoma with a low-grade component and three cases of pure high-grade lymphoma were selected for the current study. The Ig VH gene use of lymphoma cells and the V beta repertoires of infiltrating T cells were investigated. The VH gene analysis showed multiple VH family usage in 12 cases, but the MALT-type lymphoma cell usage was found to be biased for the families that have a low number of VH genes (VHIV and V). Another analysis of lymphoma-infiltrating T cells showed restricted expressions of the V beta repertoire in all seven low-grade cases and three high-grade cases. In those 10 cases, a considerable number of CD4-positive T cells infiltrated into lymphoma cells and RAG-1 was also prominently expressed. Based on these findings, it was thus assumed that the normal counterpart of gastric B cell lymphoma of MALT type is different from the conventional B cell lymphoma, and the restricted expression of V beta repertoires is therefore considered to be a characteristic finding in low-grade B cell lymphomas of MALT type as well as in a proportion of high-grade lymphomas (the so called 'high-grade lymphoma of MALT type').

Adult↗
PubMed1996

Metanephric adenoma of the kidney: ultrastructural, immunohistochemical and lectin histochemical studies.

A case of metanephric adenoma, a rare benign tumor of the kidney is reported, and the results of ultrastructural, immunohistochemical, and lectin histochemical studies are presented. The patient was a 47 year old Japanese man presenting with a left renal tumor by ultrasonography. The nephrectomy material revealed a well-demarcated tumor with medullary appearance, and on histological examination the tumor was composed of cuboidal cells forming regular small tubules with hyalinous stroma. Incomplete glomeruloid structures were formed in a few elongated tubules composed of columnar cells. Metanephric blastema was not observed in the tumor or in the normal kidney. By electron microscope, the tumor cells were observed to be immature cells with microvilli at the apical surfaces. The neoplastic tubules were surrounded by basal lamina. The tumor cells were immunoreactive for Leu 7, epithelial membrane antigen, vimentin, and low molecular weight cytokeratin, and were weakly immunoreactive for S-100 protein. Peanut agglutinin, soybean agglutinin, and Dolichos biflorus agglutinin were bound to the apical surfaces of the tumor cells.

Adenoma↗
PubMed1996

Enhancing effects of epidermal growth factor on human squamous cell carcinoma motility and matrix degradation but not growth.

In order to ascertain the effects of epidermal growth factor (EGF) on human cancer invasion abilities, three cell lines of human oral squamous cell carcinoma were studied using a phagokinetic track assay and zymography. EGF (1-100 ng/ml) was found to inhibit the growth but enhance the random motility of all three cell lines in a concentration-dependent fashion. Exposure to EGF, dose-dependently, led to an increased production of urokinase-type plasminogen activator and M(r) 92 kD matrix metalloproteinase by the same cells. These results strongly suggest that EGF may promote human squamous cell carcinoma invasion and metastasis.

Carcinoma, Squamous Cell↗
PubMed1996

Role of gamma-tubulin in mitosis-specific microtubule nucleation from the Schizosaccharomyces pombe spindle pole body.

The ability of the Schizosacchromyces pombe spindle pole body to nucleate microtubules is activated at the onset of mitosis for forming a mitotic spindle, but it is inactivated during interphase. We have previously developed an in vitro assay for studying the molecular mechanism of spindle pole body activation using permeabilized interphase S. pombe cells and Xenopus mitotic extracts. We have shown that the interphase spindle pole body is activated indirectly by p34cdc2 protein kinase in Xenopus mitotic extracts. In this study we examined the role of gamma-tubulin, a component of both interphase and mitotic spindle pole body, in formation of the microtubule nucleating complex at the mitotic spindle pole body. A polyclonal antibody specific to S. pombe gamma-tubulin inhibited both activation of the interphase spindle pole body and microtubule nucleation from the mitotic spindle pole body. Addition of bacterially expressed S. pombe gamma-tubulin or its amino-terminal fragments to Xenopus mitotic extracts inhibited spindle pole body activation. Affinity chromatography of partially fractionated Xenopus mitotic extracts with the amino-terminal fragment of S. pombe gamma-tubulin showed that fractions bound to the fragment supported the activation. The fractions did not contain Xenopus gamma-tubulin, showing that activation of the spindle pole body is not due to recruitment of Xenopus gamma-tubulin to the spindle pole body. The spindle pole body activation occurred in extracts depleted of p34cdc2 protein kinase or MAP kinase. The activity of the fractions bound to the fragment was inhibited by a protein kinase inhibitor, staurosporine. These results suggest that S. pombe gamma-tubulin is a component of the microtubule nucleating complex, and that the function of proteins that interact with gamma-tubulin is required for activation of the spindle pole body. We present possible models for the activation that convert the immature microtubule nucleating complex at interphase into the mature microtubule nucleating complex at mitosis.

Amino Acid Sequence↗
PubMed1996

Vasospastic angina in a patient with Fabry's disease who showed normal coronary angiographic findings.

It has been reported that coronary diseases in patients with Fabry's disease are induced by deposits in endothelial cells and coronary smooth muscle cells. Most of those are ischemia due to stenosis. This report describes a case of patient with Fabry's disease who showed severe vasospasms without coronary artery stenosis during acetylcholine loaded coronary angiography. In this case, a myocardial biopsy revealed that the deposits in the endothelial cells of the myocardial capillaries were lamellated appearance. Recently, it is reported that endothelial cell damage could be an important cause of coronary vasospasm. This case suggests that the some sort of functional disorder was induced by glyco-sphingolipid deposits in the coronary endothelial cells, and that this might have led to coronary artery spasms without the organic stenosis of coronary arteries.

Adult↗
PubMed1996

Exposure to magnetic field (5 mT at 60 Hz) does not affect cell growth and c-myc gene expression.

We designed and manufactured equipment for long-term and low-density (0 to 9 mT) exposures of cultured cells to extremely low frequency magnetic fields (ELF-MF), and examined the effects of ELF-MF on cell growth and c-myc mRNA expression in Chinese hamster ovary (CHO) cells. The ELF-MF equipment consists of a CO2 incubator with a built-in magnet generator using Helmholtz coils being 250 mm in inner diameter, 160 mm in distance and 128 turns, a slide regulator and a thermocontroller. No significant difference in the growth rate and the c-myc expression of CHO cells was observed with 5 mT ELF-MF exposure, sham-exposure and incubation in a conventional incubator.

Actins↗
PubMed1996

A new technique of extracapsular restoration with a tie made of ethylene tetrafluoroethylene (ETFE) for rupture of the cranial cruciate ligament in dogs.

A new extracapsular technique for repair of canine cranial cruciate ligament rupture using an ethylene tetrafluoroethylene (ETFE) tie was presented. Eighteen dogs (body weight: 6.0-46 kg) with this problem were used for this study. The advantages of this method were 1) the operation was easily performed. 2) Joint could be stabilized by proper fixation with microadjustment during operation. 3) This method presented less surgical invasion than the intracapsular one, since wide incision was not conducted over peripheral tissue of the stifle joint.

Animals↗
PubMed1996

Eosinophilic gastroenteritis with ileus and ascites.

We report a case of eosinophilic gastroenteritis, which has features of the predominant subserosal type presented as an ileus and ascites. A 48-year-old Japanese woman was admitted to our hospital because of epigastralgia, lower abdominal pain and vomiting. She had a past history of allergic disorders. The computed tomographic scan revealed ascites, and marked wall thickening and dilatation of the intestine. This patient showed eosinophilic ascites without marked peripheral eosinophilia. Histologic examination demonstrated eosinophilic infiltrates did not predominate in the gastrointestinal tract. Conservative treatment of intravenous infusion of antibiotics and Ringer's solution was effective in this case.

Ascites↗
PubMed1996

Exercise-induced change in beta-adrenergic receptor number in lymphocytes from trained and untrained men.

This study was undertaken to clarify whether beta-adrenergic receptor (beta-AR) translocation from intracellular sites to the cell surface contributes to an increase in the number of beta-AR in lymphocytes from trained and untrained men after exercise. Nine trained and 9 untrained subjects performed exercise on a bicycle ergometer until exhaustion. The number of beta-AR in the cell surface (beta-AR(surface)) and intracellular sites (beta-AR(intra)) was determined at rest and after maximal exercise by measuring the binding of the radioligand 125I-iodocyanopindolol in the presence or absence of hydrophilic (CGP-12177A) or lipophilic (propranolol) unlabeled ligands. The number of beta-AR(surface) increased after exercise from 1,524.4 +/- 321.4 to 3,432.6 +/- 503.3 sites/cell (p < 0.01), whereas that of beta-AR(intra) decreased from 356.2 +/- 85.7 to 190.3 +/- 60.2 sites/cell (p < 0.05). The isoproterenol-stimulated cAMP production per 1 x 10(6) lymphocytes after exercise was significantly higher than that at rest. However, the cAMP production per single beta-AR(surface) tended to be lower after exercise. No differences between the trained and untrained subjects were found in beta-AR numbers or intracellular cAMP levels. These findings demonstrate that maximal exercise induces the translocation of beta-AR from intracellular sites to the cell surface in human lymphocytes. However, this translocation accounts for only 10% of the increase in total cellular beta-AR, suggesting that other mechanisms are predominant and contribute substantially to the increase in beta-AR(surface).

Adult↗
PubMed1996

Posterior fusion for odontoid fracture in an infant--case report.

A 2-year-3-month-old girl presented with a rare displaced odontoid fracture. She was managed nonoperatively by manipulation followed by 3-month extracorporeal fixation with a halo brace. However, lateral radiography revealed recurrent dislocation at the base of the odontoid process. Magnetic resonance imaging demonstrated a "synchondrotic slip." She therefore underwent posterior wiring with iliac bone grafting to prevent pseudoarthrosis. The odontoid process had fused to the axis at 4 months postoperatively. Surgical management should be considered as a treatment method for pediatric odontoid fracture because of the difficulties in maintaining long-term immobilization and confirming the union.

Child, Preschool↗