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Biomedical subjects

Y Ishida

Publications and source records attributed to Y Ishida.

At least 91 records · Page 5Linked to original sources
PubMed2001

[Diagnostic imaging in osteoporosis (CT and MRI)].

Osteoporosis is a systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture risk. In the past decade, considerable progress has been made in the development of methods for assessing the skeleton non-invasively, so that osteoporosis can be managed more effectively. Recently, attention has been focused on deriving measures that provide information about not only bone mineral density but also microstructure. Magnetic resonance imaging (MRI) and computed tomography (CT) are such new techniques which potentially may provide information pertaining to bone density and structure as well as to occult fracture detection. For example, quantitative CT (QCT), peripheral QCT and quantitative MRI are promising tools for the measurements of the bone density. Micro-CT and magnetic resonance microscopy are potentially available tools to image and quantify the three-dimensional structure of trabecular bone. These potentially useful techniques for assessing osteoporosis and predicting fracture risk are reviewed in this paper.

English Abstract↗
PubMed2000

Phase-dependent responses of Per1 and Per2 genes to a light-stimulus in the suprachiasmatic nucleus of the rat.

Single brief and discrete light treatments are sufficient to reset the overt mammalian rhythms of nocturnal rodents. In the present study, we examined the phase-dependent response of the mammalian clock genes, Per1 and Per2, to a brief strong light-stimulus (1000 lux) in the circadian oscillator center, the suprachiasmatic nucleus (SCN) of rats. Light-induced elevation of Per1 mRNA was observed through the subjective night (CT16, CT20 and CT0 (=CT24)) with a marked peak at the subjective dawn (CT0). However, the light influence was very limited for the induction of Per2; only weak elevation of Per2 mRNA was detected at CT16. The effect of light-stimulus on the Per1 gene was transient, and the effect was restricted to ventrolateral SCN neurons in both CT0 and CT16 after light exposure. Since it is known that these rats show a light-induced behavioral phase-shift throughout the subjective night with being strongest at subjective dawn, the present results suggest that the transient induction of Per1 in ventrolateral SCN neurons is a critical step in the resetting of the biological clock to environmental light-dark schedule.

Animals↗
PubMed2000

Repeated administration of high dose levodopa enhances hydroxyl radical production in the rat striatum denervated with 6-hydroxydopamine.

We examined whether levodopa (L-DOPA) might increase production of hydroxyl radicals in intact and dopamine-denervated rat striatum. Salicylate trapping combined with in vivo microdialysis provided measurements of 2,3-dihydroxybenzoic acid (2,3-DHBA) as a marker of hydroxyl radical production. Acute administration of high-dose L-DOPA (200, 500 mg/kg, i.p.) did not alter 2,3-DHBA levels in intact striatum or in striatum denervated with 6-hydroxydopamine. On the other hand, L-DOPA administration (200 mg/kg, i.p.) transiently increased 2,3-DHBA in dopamine-denervated striatum of rats after repeated administration of L-DOPA (200 mg/kg, i.p., once daily for 16 days). The results indicated that repeated administration of high dose L-DOPA increased production of hydroxyl radicals in dopamine-denervated striatum.

Animals↗
PubMed2000

GABA(A) and GABA(B) receptors modulating basal and footshock-induced nitric oxide releases in rat prefrontal cortex.

Using an in vivo brain microdialysis technique, we measured extracellular levels of nitric oxide (NO) metabolites (NO(x)(-)) in the medial prefrontal cortex (mPFC) upon perfusion of gamma-aminobutyric acid (GABA) receptor antagonists as well as agonists, and also examined the effects of GABA receptor agonists on mild intermittent footshock-induced NO releases in the mPFC in conscious rats. Perfusion of either bicuculline methiodide, a GABA(A) receptor antagonist, or saclofen, a GABA(B) receptor antagonist, through a microdialysis probe resulted in dose-dependent increases in NO(x)(-) levels. Higher-dose perfusion of either muscimol (50 microM), a GABA(A) receptor agonist, or baclofen (250 microM), a GABA(B) receptor agonist resulted in a significant decrease in NO(x)(-) levels. The elevated levels of NO(x)(-) after mild intermittent footshock were attenuated by perfusion of either muscimol (10 microM) or baclofen (50 microM), either of which alone did not affect basal NO(x)(-) levels. These findings are likely to provide helpful clues to our understanding of the inhibitory modulation of basal and footshock-induced NO metabolites releases by GABA(A) and GABA(B) receptors in the mPFC.

Animals↗
PubMed2000

Changes in electrophysiological properties of axon terminals of locus coeruleus neurons with age in F344 rat.

Age-dependent changes in electrophysiological properties of locus coeruleus (LC) neurons were studied in urethane anesthetized male F344 rats aged 8, 17 and 22 months. These properties, such as spontaneous firing rate, conduction time, and threshold currents were measured for individual LC neurons antidromically activated from terminals in the frontal cortex. We found no change in the electrophysiological properties with age except for an increased number of low-threshold LC neurons in 22-month-old rats compared to that of 8-month-old rats. These results suggested that the electrophysiological properties of cortical axon terminals of LC neurons changed with age.

Action Potentials↗
PubMed2000

Genomic organization and transcriptional regulation of maize ZmRR1 and ZmRR2 encoding cytokinin-inducible response regulators.

Maize genomic clones encoding cytokinin-inducible response regulators, ZmRR1 and ZmRR2, have been isolated. In comparison with the corresponding cDNAs, ZmRR2 was found to be interrupted in the translated region by an intron whereas ZmRR1 was not. The 5'-flanking regions of the two genes shared conserved regions and putative cis-elements, which had been identified in maize or other plant species. The run-on transcription assay and the analysis of stable maize transformants of ZmRR1 promoter-beta-glucuronidase fusion gene revealed that the accumulation of the transcripts in response to cytokinins is, at least in parts, attributed by transcriptional activation.

Cytokinins↗
PubMed2000

Differential profiles of nitric oxide and norepinephrine releases in the paraventricular nucleus region in response to mild footshock in rats.

The purpose of this study was to determine whether the application of mild intermittent footshock stress can cause changes in the nitric oxide (NO) and norepinephrine (NE) releases in the hypothalamic paraventricular nucleus (PVN) region and medial prefrontal cortex (mPFC). Extracellular levels of NO metabolites and NE in the PVN region and mPFC were determined using an in vivo brain microdialysis technique in conscious rats. In the PVN region, we demonstrated that perfusion of N-methyl-D-aspartate through a microdialysis probe resulted in a dose-dependent increase in NO metabolite levels, whereas intraperitoneal administration of N(G)-nitro-L-arginine methyl ester produced a dose-dependent reduction in the levels of NO metabolites. The levels of NO metabolites in the PVN region increased after intraperitoneal administration of interleukin-1beta in a dose-dependent manner, as we previously reported. This increase in NO metabolite levels was abolished 60 min after systemic administration of N(G)-nitro-L-arginine methyl ester compared to the vehicle-treated control group. Twenty minutes of intermittent footshock induced NE release but did not induce NO release in the PVN region. On the contrary, in the mPFC, 20 min of intermittent footshock induced both NO and NE releases. The present results reveal different patterns and time courses in NO and NE releases between the PVN region and the mPFC in response to mild intermittent footshock stress. These findings are likely to have helpful suggestions for our understanding of the hypothalamic-pituitary-adrenal axis and the limbic forebrain system response to different kinds of stress.

Animals↗
PubMed2000

Granule exocytosis, and not the fas/fas ligand system, is the main pathway of cytotoxicity mediated by alloantigen-specific CD4(+) as well as CD8(+) cytotoxic T lymphocytes in humans.

We investigated the cytotoxicity mechanisms of alloantigen-specific human CD4(+) and CD8(+) cytotoxic T lymphocytes (CTLs) using cells from family members with the Fas gene mutation. Alloantigen-specific CD4(+) and CD8(+) CTL bulk lines and clones were generated from 2 individuals by stimulation of their peripheral blood lymphocytes with allogeneic Fas(-/-) or Fas(+/-) cell lines that were established from B-lymphocytes of a patient with Fas deficiency and her mother, respectively. Both CD4(+) and CD8(+) CTL bulk lines and clones directed against allogeneic HLA antigens exerted cytotoxicity against Fas(-/-) and Fas(+/-) cells to almost the same degree. The cytotoxicity of CD4(+) and CD8(+) CTLs appeared to be Ca(2+)-dependent and was completely inhibited by concanamycin A, an inhibitor of perforin-mediated cytotoxicity. Messenger RNAs for the major mediators of CTL cytotoxicity, Fas ligand, perforin, and granzyme B were all detected in these CD4(+) CTLs with the use of the reverse transcriptase polymerase chain reaction. The majority of CD4(+) CTL clones that showed Fas-independent cytotoxicity were T(H)0, as determined by their cytokine production profile. These data, obtained with the use of a novel experimental system, clearly show that the main pathway of cytotoxicity mediated by alloantigen-specific human CD4(+) as well as by CD8(+) CTLs is granule exocytosis, and not the Fas/Fas ligand system.

Anti-Bacterial Agents↗
PubMed2000

Variation among giant rice bodies: report of four cases and their clinicopathological features.

OBJECTIVE: To report four cases of rice bodies (RBs) showing remarkable size variations and discuss their pathogenesis. DESIGN AND PATIENTS: Based on analysis of the clinical data, we speculate on the pathogenesis of RBs using immunohistochemical and ultrastructural methods. The patients comprised three men and one woman, three with RBs in the subacromial bursae and one in the wrist synovial sheath, aged 28 (woman), 44, 50 and 81 (wrist) years, respectively. RESULTS: There were no particular differences in clinical data among the patients. T2-weighted MR imaging was very useful for diagnosis of the RBs, allowing their clear delineation from the bursal fluid. The RBs consisted of a layered protein- aceous substance with vague targetoid cut surfaces. Much fibrin and a lesser amount of collagen fibers were recognized together with various mononuclear cells, which were few in number and predominantly T cells. The bursae and synovial sheath had multiple fibrinoid spheroids at the luminal surface. CONCLUSION: Fibrinoid nodular deposits probably became detached, forming the nuclei of RBs and growing to a giant RB 65 mm in diameter.

Adult↗
PubMed2000

Use of ECG-gated SPET to assess the evolution of perfusion after acute myocardial infarction.

Serial improvement in myocardial perfusion images from the acute or subacute to the chronic stage of acute myocardial infarction (AMI) has been attributed to improved coronary microcirculation or cell function after acute ischaemia and reperfusion. However, conventionally used non-gated imaging cannot eliminate the effect of improved regional contraction. We studied the possibility that such scintigraphic improvement reflects the functional recovery by using ECG-gated myocardial perfusion imaging with technetium-99m sestamibi. Nineteen AMI patients who received acute reperfusion therapy underwent ECG-gated myocardial single-photon emission tomography (SPET) in the subacute and chronic stages. Serial changes in regional image count distributions were analysed on the non-gated, end-diastolic (ED) and end-systolic (ES) images by using segmental mean percent peak activity (MPA) and AMPA (MPA in chronic stage - MPA in subacute stage) on bull's-eye polar maps. These changes were compared with those in regional wall motion on biplane left ventriculography (LVG) from the acute (just after reperfusion) to the chronic stage. During the follow-up, regional wall motion remained the same in 42 (group A) but improved in 17 (group B) of the 59 ischaemically compromised segments. MPA showed no improvement in group A but significant improvement in group B on the non-gated and ES images (P<0.0001 and P<0.001, respectively). However, MPA on the ED images showed no improvement in either group. In the follow-up study of AMI, the scintigraphic improvement documented on the non-gated myocardial images appears to be mainly related to the recovery of wall thickening and not to a real improvement in myocardial perfusion. Therefore, ECG-gated myocardial imaging, which enables simultaneous assessment of changes in perfusion and contraction, is preferable to conventional non-gated imaging for follow-up of AMI.

Acute Disease↗
PubMed2000

Gastric carcinoma presenting with extensive extraluminal growth: report of a case.

We report a 48-year-old-man with gastric carcinoma presenting with an unusual extraluminal growth. The patient underwent a barium meal examination and gastrofiberscopy because of progressive anemia over 6 months. These examinations revealed a Borrmann type 3 advanced gastric carcinoma of the greater curvature of the antrum. Biopsies showed moderately differentiated tubular adenocarcinoma. The intraoperative findings showed gastric carcinoma associated with extensive extraluminal invasion into the adjacent organs, i.e., the transverse colon and mesocolon. A palliative distal gastrectomy with a partial resection of the transverse colon was performed because of peritoneal dissemination found in the mesocolon and rectovesical pouch. A histological examination of the specimen confirmed adenocarcinoma which had massively infiltrated the transverse colon and mesocolon. His postoperative course was uneventful. However, he died of peritonitis carcinomatosa 9 months later.

Adenocarcinoma↗
PubMed2000

Tuberculous peritonitis defying diagnosis: report of a case.

A case of tuberculous peritonitis, which has been scarcely encountered in clinical practice in recent years, is reported. A 32-year-old man was admitted to our hospital complaining of abdominal fullness, anorexia, and a 15 kg weight loss. His abdomen was distended. There was neither any previous history nor recent contact with tuberculosis. The laboratory data indicated increased C-reactive protein and erythrocyte sedimentation rate, but the white blood cell count was normal. A chest X-ray examination revealed no abnormalities. Abdominal X-ray showed scattered, small-intestinal gas shadows. Abdominal computed tomography scanning revealed a diffuse thickening of the dilated bowel wall, mainly adjacent to the mesentery. After a detailed examination a diagnosis of peritonitis carcinomatosa of unknown origin was suspected, and an exploratory laparotomy was done. Severe adhesions between the parietal peritoneum and the bowel were found. An excisional biopsy specimen was taken from the peritoneum, and a diagnosis of tuberculosis was thus made. Triple therapy with isoniazid, rifampicin, and kanamycin was started, and both the intestinal obstruction and anorexia were thus resolved.

Adult↗
PubMed2000

Double aneurysms of arch and descending aorta associated with right aortic arch.

We report a case of a 69-year-old man in whom double aortic aneurysms of the arch and descending aorta with a right aortic arch and mirror-image branching were diagnosed by three-dimensional computed tomography and aortography. These techniques are useful to assess the exact anatomy of the lesion and branches of the arch. The patient was successfully treated by a two-stage operation consisting of aortic arch replacement followed by descending aorta replacement.

Aged↗