Search PubMed⌕ Search

Biomedical subjects

Y Katayama

Publications and source records attributed to Y Katayama.

At least 127 records · Page 7Linked to original sources
PubMed2000

Hemorrhagic transformation after fibrinolytic therapy with tissue plasminogen activator in a rat thromboembolic model of stroke.

In this study, the effects of early vs. delayed tPA treatment on the development of hemorrhagic transformation was compared in a rat thromboembolic model of stroke. Fibrinolysis was performed by administering tPA intravenously at 2 or 6 h after ischemic onset. Twenty-four hours later, confluent hemorrhagic infarction was observed only in rats treated with tPA at 6 h at the rate of 50%. In this delayed treatment group, significantly increased numbers of polymorphonuclear leukocytes (PMNL) were observed to accumulate inside microvessels within the ischemic core. PMNL accumulation may be related to the induction of hemorrhagic infarction after delayed tPA treatment.

Animals↗
PubMed2000

A first-order liquid-liquid phase transition in phosphorus

First-order structural phase transitions are common in crystalline solids, whereas first-order liquid-liquid phase transitions (that is, transitions between two distinct liquid forms with different density and entropy) are exceedingly rare in pure substances. But recent theoretical and experimental studies have shown evidence for such a transition in several materials, including supercooled water and liquid carbon. Here we report an in situ X-ray diffraction observation of a liquid-liquid transition in phosphorus, involving an abrupt, pressure-induced structural change between two distinct liquid forms. In addition to a known form of liquid phosphorus--a molecular liquid comprising tetrahedral P4 molecules--we have found a polymeric form at pressures above 1 GPa. Changing the pressure results in a reversible transformation from the low-pressure molecular form into the high-pressure polymeric form. The transformation is sharp and rapid, occurring within a few minutes over a pressure range of less than 0.02 GPa. During the transformation, the two forms of liquid coexist. These features are strongly suggestive of a first-order liquid-liquid phase transition.

Journal Article↗
PubMed2000

Effects of external acidosis on HERG current expressed in Xenopus oocytes.

We investigated effects of external acidosis on HERG current expressed in Xenopus oocytes. HERG current was rapidly and reversibly suppressed by external acidosis in a voltage-independent manner. The slope conductance was decreased from 143 +/- 11 to 93.4 +/- 6.8 microS by changing external pH (pH(o)) from 7.6 to 6.0 (P<0.05). Steady-state activation was shifted by about 20 mV in a depolarized direction with a change from pH(o) 7.6 to 6.0, while steady-state inactivation was not significantly changed. Activation time constants were increased, deactivation and recovery time constants were decreased, while those of inactivation showed no significant change. When external K(+) concentration ([K(+)](o)) was increased from 2 mM to 10 mM, a ratio of slope conductance at pH(o) 6.0 to pH(o) 7.6 was significantly smaller in 2 mM (pH(o) 6.0/pH(o) 7.6 = 0.65 +/- 0.04) than in 10 mM[K(+)](o) (0.83 +/- 0.06, P<0.05). The changes in activation, deactivation and recovery from inactivation were not affected by change in [K(+)](o). The results indicated that external acidosis suppressed HERG current mainly by shifting the voltage-dependence of the activation and deactivation kinetics, and partly by decreasing slope conductance. Moreover, the reduction of HERG current could be partly antagonized with increasing [K(+)](o).

Animals↗
PubMed2000

Heterogeneous mechanisms of early edema formation in cerebral contusion: diffusion MRI and ADC mapping study.

Severe cerebral contusion is sometimes associated with early edema formation within 24-48 hours post-trauma, and this frequently results in progressive ICP elevation and clinical deterioration. To investigate the underlying mechanisms of such severe contusion edema, diffusion imaging and ADC mapping were performed in 20 patients with cerebral contusion, employing 1.5 T echo planar MRI. Within 24 hours post-trauma, the diffusion images demonstrated a low intensity core in the central area and a high intensity rim in the peripheral area of contusion. The ADC value increased in the central area (ADC ratio (contusion/normal brain) = 1.13 +/- 0.13) and decreased in the peripheral area (ADC ratio = 0.83 +/- 0.13). This suggested that intra- and extracellular components underwent disintegration and homogenization within the central area, whereas cellular swelling was predominant in the peripheral area. A crescent-shaped zone of very high ADC value (ADC ratio = 1.38-1.61) was observed at the border between these two areas during the period of 24-48 hours post-trauma in some cases, apparently indicating that edema fluid was accumulated within a space formed by homogenization. The ADC values in the peripheral area shifted to an increase after 48-72 hours post-trauma. These findings imply that multiple mechanisms operate in early edema formation in cerebral contusion. It appears that the capacity for edema fluid accumulation increases in the central area and resistance for edema fluid propagation is elevated by cellular swelling in the peripheral area. We suggest that a combination of such events facilitates edema fluid accumulation in the central area and contributes, together with the cellular swelling in the peripheral area, to the mass effect of contusion edema. Diffusion MRI and ADC mapping represent powerful tools for investigating spatially as well as temporally heterogeneous mechanisms of contusion edema.

Brain↗
PubMed2000

Clinicopathological study of vascular endothelial growth factor (VEGF), p53, and proliferative potential in familial von Hippel-Lindau disease and sporadic hemangioblastomas.

We examined the clinical characteristics and prognosis in six patients with familial von Hippel-Lindau (VHL) disease and seven with sporadic hemangioblastomas. The expression of vascular endothelial growth factor (VEGF), p53 protein, and proliferative potential with Ki67 monoclonal antibody (MIB-1) was compared using immunohistochemical methods between sporadic and VHL disease-associated hemangioblastomas. Patients with sporadic CNS hemangioblastomas were treated by total removal of the tumors, and they had a good long-term prognosis without neurological deficits on recurrence. However, patients with familial VHL disease often had multiple hemangioblastomas in the CNS and visceral tumors. Even if total removal of CNS hemangioblastomas in patients with VHL disease was performed initially, small multiple hemangioblastomas recurred during long-term follow-up in areas remote from the primary region resected by surgery. All of the hemangioblastomas displayed extensive overexpression of VEGF protein, with moderate to marked proliferation of blood vessels. The MIB-1 indices showed low values of 0.8% as the mean, with a range of 0.03%-2.1% for all the hemangioblastomas. None of the hemangioblastomas expressed p53 protein. The hemangioblastomas in patients with VHL disease were multiple in the CNS and were combined with visceral tumors. Patients with VHL disease had a poor long-term prognosis, in contrast to those with sporadic hemangioblastomas. The immunohistochemical findings for VEGF protein, p53 protein, and MIB-1 did not differ significantly between the sporadic and VHL disease-associated hemangioblastomas.

Adolescent↗
PubMed2000

Intrasubject correlation between static scan and distribution volume images for [11C]flumazenil PET.

Accumulation of [11C]flumazenil (FMZ) reflects central nervous system benzodiazepine receptor (BZR). We searched for the optimal time for a static PET scan with FMZ as semi-quantitative imaging of BZR distribution. In 10 normal subjects, a dynamic series of decay-corrected PET scans was performed for 60 minutes, and the arterial blood was sampled during the scan to measure radioactivity and labeled metabolites. We generated 13 kinds of "static scan" images from the dynamic scan in each subject, and analyzed the pixel correlation for these images versus distribution volume (DV) images. We also analyzed the time for the [11C]FMZ in plasma and tissue to reach the equilibrium. The intra-subject pixel correlation demonstrated that the "static scan" images for the period centering around 30 minutes post-injection had the strongest linear correlation with the DV image. The ratio of radioactivity in the cortex to that in the plasma reached a peak at 40 minutes after injection. Considering the physical decay and patient burden, we conclude that the decay corrected static scan for [11C]FMZ PET as semi-quantitative imaging of BZR distribution is to be optimally acquired from 20 to 40 minutes after injection.

Adult↗
PubMed2000

Aorto-bronchial fistula after implantation of a self-expanding bronchial stent in a patient with aortic dissection.

We report a case of aorto-bronchial fistula after implantation of a self-expanding stent into the left main bronchus compressed by a dissected descending aorta. A 66-year-old female, who underwent Stanford type-B aortic dissection two years previously, was admitted to our hospital for the treatment of a newly developed false lumen that originated from the ascending aorta and extended to the aortic bifurcation. She was unable to be weaned from the respirator after the graft replacement of the ascending aorta. Fiberoptic bronchoscopic examination revealed complete obstruction of the left main bronchus by extrinsic compression. A self-expanding nitinol stent was implanted in the left main bronchus five days after the operation. Her respiratory condition improved remarkably, allowing her to be successfully weaned from the respirator. Her clinical course was uneventful until she suddenly died from massive hemoptysis 20 days after stent implantation. A communication of 5 mm in diameter between the dissected descending aorta and the left main bronchus was seen at autopsy. Permanent application of a self-expanding nitinol stent to relieve extrinsic compression of a left main bronchus by a dissected descending aorta is not recommended because pressure necrosis might lead to fatal aorto-bronchial fistula.

Aged↗
PubMed2000

The relationship between risk of hypoglycemia and use of cibenzoline and disopyramide.

OBJECTIVE: A case-control study was carried out to compare the risks of hypoglycemia caused by disopyramide and cibenzoline. METHODS: We selected 91 subjects with hypoglycemia from among 14,156 outpatients who consulted the National Cardiovascular Center (NCVC) and received drug therapy between September 1997 and February 1998. We used the fasting blood sugar (FBS) level of 75 mg/dl or less as the cut-off level to screen for hypoglycemia. For each case, five controls matched for gender and age were selected from the clinical division consulted by relevant subjects. RESULTS: Ninety-one cases and 455 controls were enrolled in this study. Of 91 cases with hypoglycemia, 8 (8.8%) were treated with cibenzoline and 3 (3.3%) with disopyramide. The percentage of cases treated with cibenzoline was greater than that in the controls (1.5%), and the prescription frequency of cibenzoline during the study period was 2%. With adjustment for potential confounding factors using conditional logistic regression, hypoglycemia was significantly correlated with the use of cibenzoline [OR 8.0 (95% CI 1.7-36.8)], insulin [OR 48.4 (95% CI 8.8-267.2)], and thyroid agents [OR 13.0 (95% CI 1.1-160.4)]. An increased risk of hypoglycemia associated with the use of sulfonylureas was not detected. In additional logistic regression analysis, including the variables with individual sulfonylureas, glibenclamide but not gliclazide significantly increased the risk of hypoglycemia. The use of disopyramide did not affect the risk of hypoglycemia. In separate analyses for diabetic and non-diabetic patients, the risks of hypoglycemia associated with the use of drugs other than beta-blocking agents in non-diabetic patients were estimated to be lower than those in diabetic patients. CONCLUSION: The use of cibenzoline was significantly correlated with an increased risk of hypoglycemia.

Adult↗
PubMed2000

Nonenzymatic elimination of ascorbic acid in clinical samples.

OBJECTIVES: Ascorbic acid interferes significantly in the oxidative reaction of chromogenic reagents by peroxidase and hydrogen peroxide. Currently, ascorbate oxidase is commonly utilized for eliminating the interference of ascorbic acid in the oxidative colorimetric reaction. This enzyme, however, displays several disadvantages, such as high cost, variation from lot to lot, and low stability. We applied a series of commercially available and stable radicals (ascorbic acid quenchers [AAQs]) for nonenzymatic quenching of ascorbic acid in the uricase-based uric acid determination in serum and urine. DESIGN AND METHODS: In order to evaluate the quenching activity of AAQs, a commercially available uric acid detection kit was used. TBA-80FR.NEO biochemical analyzer was utilized for the assay. RESULTS: 4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical (AAQ-2) was the most effective ascorbic acid quencher among the four stable radicals, and the uric acid assay suffered no interference by AAQ-2. The ascorbic acid quenching ability of 2 mmol/L of AAQ-2 in reagent solution (reagent-I) was > or = 2 U/ml ascorbate oxidase in reagent solution. CONCLUSIONS: AAQ-2 was proven to be a suitable quencher of ascorbic acid in clinical samples.

Ascorbate Oxidase↗
PubMed2000

Deletion 7p in gastric MALT lymphoma.

Deletion of the long arm of chromosome 7 has been related to loss of tumor suppressor genes which may constitute a primary step of carcinogenesis in many kinds of malignancies, including low-grade B-cell lymphoma. However, deletion of the short arm of chromosome 7, del(7p), in low-grade B-cell lymphoma has not been reported. Here, we report a case of gastric MALT lymphoma with the chromosome aberration del(7p) which progressed in spite of eradication of Helicobactor pylori. Deletion 7p may represent a new karyotypic change that is possibly related to autonomous growth of MALT lymphoma.

Chromosome Deletion↗
PubMed2000

Ikaros expression in human hematopoietic lineages.

The Ikaros gene has been implicated in lymphoid development and proliferation from the results of gene targeting studies in mice. Recently we reported that the Ikaros gene may be involved in the disease progression of chronic myelogenous leukemia (CML). In this report, we investigated Ikaros isoforms in human non-lymphoid leukemia cell lines and normal granulocyte/macrophage (CFU-GM) and erythroid (BFU-E)-derived colonies. We evaluated Ikaros gene expression by RT-PCR, Southern blotting, sequencing analysis, Northern blotting, and immunoblotting.Ikaros isoforms Ik-1 and Ik-2, 3 were predominantly expressed in human non-lymphoid leukemia cell lines. Ik-4 and Ik-8 were also detectable as a minor population. In contrast to the previous report in mice, multiple Ikaros isoforms were expressed in human CFU-GM and BFU-E-derived colonies, and the dominant-negative isoform Ik-6 was not detectable. We also showed that human Ikaros isoforms contained an additional coding sequence in the N-terminal region, which was highly homologous to the sequence reported in mice. These observations suggest that the Ikaros gene may play some role in the development of human non-lymphoid lineage hematopoiesis. Moreover, the finding that the dominant-negative isoform Ik-6, which was overexpressed in patients with blast crisis of CML, was rarely detectable in non-lymphoid lineages supports its pathogenetic role in human hematologic malignancies.

Animals↗
PubMed2000

Mechanosensitive chloride channels on the growth cones of cultured rat dorsal root ganglion neurons.

We developed an experimental system to investigate mechanosensitivity of a single neuron, using cultured rat dorsal root ganglion cells. Highly precise mechanical stimulation was applied to various sites of the cells, using a piezo-driven glass microcapillary whose movement was computer-controlled, while whole-cell patch-clamp recordings were made from the cell bodies. When the growth cones and lamillipodia from the cell soma were mechanically stimulated, inward currents were recorded at the holding potential of -60mV. Filopodia were most sensitive to mechanical stimulation. However, when neurites or soma of dorsal root ganglion cells were stimulated in the same way, electrical responses were hardly recorded. Two types of currents varying in time-course were observed: fast type of 100-200ms and slow type of several seconds in duration. When the membrane potential was held at around 0mV, both types of currents were almost abolished or even reversed, and the reversal potential was estimated to be about -2. 2mV. Replacement of extracellular sodium by tetraethylammonium did not significantly change the reversal potential. In the low-chloride solution ([Cl(-)](o)=11.7mM), the reversal potential was about +60mV, as expected from the Nernst equation for chloride. These inward currents were almost completely inhibited by extracellular application of chloride channel blocker, 5-nitro-2-(3-phenylpropylamino) benzoic acid (100microM). These results indicate that the inward currents are due to activation of mechanosensitive chloride channels, preferentially located on the growth cones of cultured dorsal root ganglion neurons.

Animals↗
PubMed2000

Ubiquinone systems in fungi. V. Distribution and taxonomic implications of ubiquinones in Eurotiales, Onygenales and the related plectomycete genera, except for Aspergillus, Paecilomyces, Penicillium, and their related teleomorphs.

The ubiquinone (coenzyme Q) systems were determined for 176 teleomorphic isolates, 14 anamorphic isolates, and three samples of fruit-bodies of Dendrosphaera eberhardtii, which belonged to Eurotiales, Onygenales, and related taxa. In Eurotiales, Ascosphaera had Q-9, whereas Bettsia had Q-10. All isolates of Monascaceae had the Q-10 system, whereas those of four genera of Pseudeurotiaceae had the Q-10(H2) system. The Q-10(H2) system was found in genera of Trichocomaceae, except for Aspergillus, Penicillium, Paecilomyces, and their related taxa. However, Thermoascus had the Q-9 system. In Onygenales, members of Arthrodermataceae had Q-9, and those of Gymnoascaceae had Q-10(H2). Isolates of Myxotrichaceae were characterized by Q-10(H2) with few exceptions, which had Q-10. The quinones of Onygenaceae belonged to complex systems, i.e., Q-9, 0-10 and 0-10(H2), and a combination of two systems. Families Onygenaceae and Trichocomaceae are likely a phylogenetic heterogeneity. Ubiquinone analysis provides a very useful criterion of great promise for classifying eurotialean taxa and also for identifying their isolates.

Ascomycota↗
PubMed2000

Crossed cerebellocerebral diaschisis in patients with cerebellar stroke.

OBJECTIVES: We performed single-photon emission computed tomography (SPECT) to investigate crossed cerebellocerebral diaschisis (CCCD) in patients with cerebellar stroke. MATERIAL AND METHODS: Fifteen patients with unilateral cerebellar stroke underwent SPECT of the brain with N-isopropyl-p-[123I] iodoamphetamine (123I-IMP). Regional cerebral blood flow (rCBF) was measured by the autoradiographic method. Regions of interest were defined in the cerebral cortex, striatum, thalamus and cerebellum to compare structures (contralateral to the cerebellar lesion) with counterparts ipsilateral to the stroke. RESULTS: In the frontal and parietal cortices, especially the posterior superior frontal, anterior midfrontal, precentral, postcentral, and supramarginal areas, rCBF contralateral to the lesion was significantly lower than on the side of the lesion (showing CCCD). CONCLUSION: This CCCD phenomenon is important to be aware of in clinical reading of images.

Aged↗
PubMed2000

Neurological and neuroradiological progression in hereditary spastic paraplegia with a thin corpus callosum.

We followed-up a Japanese man suffering from hereditary spastic paraplegia with a thin corpus callosum (HSP-TCC) by single photon emission computed tomography (SPECT) using 123IN-isopropyl-piodoamphetamine (123I-IMP) over 4 years (25 to 29 years old). Besides the initial symptoms of lower limb spasticity, mental deterioration slightly progressed and upper limb spasticity and slight cerebellar ataxia were developed, during the period. Cranial magnetic resonance imaging (MRI) revealed an extremely thin corpus callosum and medial frontal atrophy, which remained essentially unchanged during the period. 123I-IMP SPECT demonstrated that cerebral blood flow was decreased in the thalamus and the medial frontal, temporal and parietal cortices at the first examination, and that the thalamus showed further reduction but the other involved regions presented essentially no progression during the follow-up period. This is the first report referring to the longitudinal clinical and neuroradiological changes in HSP-TCC.

Adult↗
PubMed2000

A fluorescent-labeled oligopeptide for monitoring PKA-mediated phosphorylation.

A fluorescent-labeled oligopeptide (DACM-CLRRASLK-fluorescein), containing a consensus amino acid sequence (RRXSL) of cyclic AMP (cAMP) dependent protein kinase A (PKA) substrate-proteins, was designed. The fluorescent peptide was a good substrate of PKA, and the phosphorylation of its serin residue caused an intensive change in fluorescent intensity. We expect that the peptide will be useful as a fluorescent indicator for monitoring PKA activity in living cells.

Cyclic AMP-Dependent Protein Kinases↗