PubMed Health⌕ Search

Biomedical subjects

K Asakura

Publications and source records attributed to K Asakura.

At least 37 records · Page 2Linked to original sources
PubMed2000

Mercury emissions from a coal-fired power plant in Japan

The emissions study for mercury was conducted at a 700 MW coal-fired plant for the combustion of three types of coal with mercury concentrations of 0.0063, 0.0367 and 0.065 mg/kg. The power plant is equipped with a cold-side electrostatic precipitator and wet type flue gas desulfurization system. During full load operation of the boilers, samples of the input and output streams such as coal, coal ash, ESP ash and post-ESP particulates and flue gas were collected. The Hg concentrations in solid were measured by cold-vapor atomic absorption spectrometry (AAS) after appropriate preparation and acid digestion. Gaseous Hg was collected using a mixed solution of potassium permanganate and sulfuric acid and the Hg concentrations in the samples were measured using cold-vapor AAS. The results were used to examine: (1) overall mass balances; (2) relative distribution in the power plant; (3) equilibrium of Hg species using MALT-2 calculation program; and (4) Hg concentrations in stack emissions. The mass balances estimated in this study were 100, 138 and 89%, respectively, for the coals. Total Hg concentrations in stack gas were 1.113, 0.422 and 0.712 microg(m3N), respectively, for the coals. More than 99.5% of the Hg in the stack emissions were in gaseous form and the proportion in particulate form was extremely low. The relative distribution of Hg in ESP, FGD and Stack ranged from 8.3 to 55.2%, 13.3 to 69.2% and 12.2% to 44.4%, respectively. The results indicated that factors other than the Hg concentration of coals and efficiency of pollution control devices might affect Hg emissions from coal-fired plant. The calculated equilibrium of the distribution of Hg species using the MALT2 program suggest that it is necessary to consider condensation mechanism to interpret the affect of Hg species on the variations of the removal efficiencies of Hg in the ESP.

Journal Article↗
PubMed2000

Neurotrophin-4/5 promotes proliferation of oligodendrocyte-type-2 astrocytes (O-2A).

In this study, the ability of neurotrophin-5 (NT-4/5) to promote the proliferation of oligodendrocyte precursor (O-2A) cells has been examined. This has been accomplished by the addition of exogenous NT-4/5 to purified cultures of O-2A cells maintained in an undifferentiated state by the addition of the mitogens platelet derived growth factor (PDGF-AA) and basic fibroblast growth factor (bFGF). Counts of cells incorporating bromodeoxyuridine (BrdU) showed that the addition of NT-4/5 for 24 h increased O-2A cell proliferation by 1.8-fold above that seen in PDGF-AA and bFGF alone. These data demonstrate a previously unidentified role for the neurotrophin NT-4/5 in oligodendrocyte biology.

Animals↗
PubMed2000

alpha-eudesmol, a P/Q-type Ca(2+) channel blocker, inhibits neurogenic vasodilation and extravasation following electrical stimulation of trigeminal ganglion.

In this study, we investigated the effect of alpha-eudesmol, which potently inhibits the presynaptic omega-agatoxin IVA-sensitive (P/Q-type) Ca(2+) channel, on neurogenic inflammation following electrical stimulation of rat trigeminal ganglion. Treatment with alpha-eudesmol (0.1-1 mg/kg. i.v.) dose-dependently attenuated neurogenic vasodilation in facial skin monitored by a laser Doppler flowmetry. In addition, alpha-eudesmol (1 mg/kg. i.v.) significantly decreased dural plasma extravasation in analysis using Evans blue as a plasma marker. On the other hand, alpha-eudesmol (1 mg/kg, i.v.) did not affect mean arterial blood pressure in rats. The calcitonin gene-related peptide (CGRP) and substance P (SP) released from activated sensory nerves have recently been suggested to be associated with the neurogenic inflammation. In this study, we also showed that alpha-eudesmol (0.45-45 microM) concentration-dependently inhibits the depolarization-evoked CGRP and SP release from sensory nerve terminals in spinal cord slices. These results indicate that the anti-neurogenic inflammation action of alpha-eudesmol, which does not affect the cardiovascular system, may be due to its presynaptic inhibition of the neuropeptide release from perivascular trigeminal terminals. We also suggest that the omega-agatoxin IVA-sensitive Ca(2+) channel blocker, alpha-eudesmol, may become useful for the treatment of the neurogenic inflammation in the trigemino-vascular system such as migraine.

Animals↗
PubMed2000

Human monoclonal antibodies reactive to oligodendrocytes promote remyelination in a model of multiple sclerosis.

Promoting remyelination, a major goal of an effective treatment for demyelinating diseases, has the potential to protect vulnerable axons, increase conduction velocity, and improve neurologic deficits. Strategies to promote remyelination have focused on transplanting oligodendrocytes (OLs) or recruiting endogenous myelinating cells with trophic factors. Ig-based therapies, routinely used to treat a variety of neurological and autoimmune diseases, underlie our approach to enhance remyelination. We isolated two human mAbs directed against OL surface antigens that promoted significant remyelination in a virus-mediated model of multiple sclerosis. Four additional OL-binding human mAbs did not promote remyelination. Both human mAbs were as effective as human i.v. Ig, a treatment shown to have efficacy in multiple sclerosis, and bound to the surface of human OLs suggesting a direct effect of the mAbs on the cells responsible for myelination. Alternatively, targeting human mAbs to areas of central nervous system (CNS) pathology may facilitate the opsonization of myelin debris, allowing repair to proceed. Human mAbs were isolated from the sera of individuals with a form of monoclonal gammopathy. These individuals carry a high level of monoclonal protein in their blood without detriment, lending support to the belief that administration of these mAbs as a therapy would be safe. Our results are (i) consistent with the hypothesis that CNS-reactive mAbs, part of the normal Ig repertoire in humans, may help repair and protect the CNS from pathogenic immune injury, and (ii) further challenge the premise that Abs that bind OLs are necessarily pathogenic.

Antibodies, Monoclonal↗
PubMed2000

omega-agatoxin IVA-sensitive Ca(2+) channel blocker, alpha-eudesmol, protects against brain injury after focal ischemia in rats.

omega-Agatoxin IVA-sensitive Ca(2+) channels have been thought to be involved in physiological excitatory amino acid glutamate release and these channels may also contribute to the development of ischemic brain injury. Recently, we demonstrated that alpha-eudesmol from Juniperus virginiana Linn. (Cupressaceae) inhibits potently the presynaptic omega-agatoxin IVA-sensitive Ca(2+) channels. In the present study, we investigated the effects of alpha-eudesmol on brain edema formation and infarct size determined after 24 h of reperfusion following 1 h of middle cerebral artery occlusion in rats. We first found that alpha-eudesmol concentration-dependently inhibited glutamate release from rat brain synaptosomes and that its inhibitory effect was Ca(2+)-dependent. In the middle cerebral artery occlusion study, intracerebroventricular (i.c.v.) treatment with alpha-eudesmol significantly attenuated the post-ischemic increase in brain water content. alpha-Eudesmol also significantly reduced the size of the infarct area determined by triphenyltetrazolium chloride staining after 24 h of reperfusion. Using a microdialysis technique, we further demonstrated that alpha-eudesmol inhibits the elevation of the extracellular concentration of glutamate during ischemia. From these results, we suggest that alpha-eudesmol displays an ability to inhibit exocytotic glutamate release and to attenuate post-ischemic brain injury.

Animals↗
PubMed2000

Accelerated radiotherapy for T1, 2 glottic carcinoma: analysis of results with KI-67 index.

PURPOSE: Hyperfractionated and accelerated radiotherapy without a split was performed to improve the local control probability of early glottic carcinomas. We analyzed the results of this regimen by using the Ki-67 index. METHODS AND MATERIALS: Over a 12-year period, 85 T1N0M0 glottic cancers and 50 T2N0M0 glottic cancers were treated with conventional fractionation (CF) from 1984 to 1989 and with accelerated fractionation (AF) since 1990. The CF program consisted of five daily fractions of 2 Gy per week, for a total of 64 Gy. The AF program consisted of 1.72 Gy per fraction, two fractions per day, 5 days a week, for a total of 55 or 58 Gy. The specimens, taken before radiotherapy, were immunohistochemically stained with anti-Ki-67 antibody. RESULTS: The 5-year local control probability for T1 tumors was 79.6 +/- 6.9% with CF treatment, whereas with AF it was 86.9 +/- 5.6%. For T2 tumors it was 62.7 +/- 12.2% with CF, whereas it was 74.7 +/- 7.8% with AF. The difference between CF and AF did not reach the point of statistical significance. However, when T1 tumors had a Ki-67 index lower than 50%, the local control rate achieved with AF was significantly better than that with CF (p = 0.018). When the tumors had a Ki-67 index that was 50% or more, there was no difference in the local control rate between CF and AF, whether they were T1 or T2. The peak mucosal reactions at the larynx and/or hypopharynx were much more severe and appeared at smaller doses and earlier in AF than in CF. The patients with AF showed no severe late complications. CONCLUSIONS: AF could not obtain statistically significant improvement in local control probability of T1 or T2 glottic carcinomas.

Adult↗
PubMed2000

Preferential expression of myelencephalon-specific protease by oligodendrocytes of the adult rat spinal cord white matter.

Myelencephalon-specific protease (MSP) is a novel serine protease that is expressed predominantly in the nervous system. In the adult rat spinal cord, MSP mRNA expression was dramatically upregulated, in both the white and gray matter, after systemic exposure to the glutamate receptor agonist, kainic acid (KA) (Scarisbrick et al. J Neurosci 17: 8156-8168, 1997b). To determine the cell-specific expression patterns of MSP, we generated MSP-specific monoclonal antibodies. These have been used in immunohistochemical and in situ hybridization colocalization studies, to demonstrate that MSP mRNA and protein are produced predominantly by CNP-immunoreactive oligodendroglia, but not by GFAP-immunoreactive astrocytes, in the white matter of the normal adult cord. In vitro, the soma of oligodendrocytes were also densely MSP immunoreactive, as were their growth tips, while astrocytes were associated with lower levels. These findings suggest that the enzymatic activity of MSP is likely to be important in the biology of oligodendrocytes and/or in the maintenance of the nerve fiber tracts of the adult spinal cord.

Animals↗
PubMed2000

Development of an X-ray photoemission electron microscopy system with multi-probes, and its application to surface imaging at static and dynamic states.

We have developed a new X-ray photoemission electron microscopy system combined with low energy electron microscopy, photoemission electron microscopy, mirror electron microscopy (MEM), secondary electron emission microscopy (SEEM) and Auger electron emission microscopy, which provides multi-angle information on the distribution and change of element, chemical state, structure, etc. at solid surfaces under the working conditions such as high temperature and gas atmosphere. The performance of each microscopical method was examined and typical images are presented. The dynamic behaviour of fabricated surfaces has been imaged in real time by SEEM and MEM.

Journal Article↗
PubMed2000

Relationship between infiltrating cells and adhesion molecules in the nasal mucosa of patients with allergic rhinitis.

Antigen-induced changes of cell adhesion molecules and their relationships to infiltrating cells were investigated immunohistochemically in nasal mucosa of perennial allergic rhinitis patients. An increased expression of E-selectin and VCAM-1 was noted on the vascular endothelium of the nasal mucosa 15-25 h after the topical antigen challenge. Although there was no increased expression of ICAM-1, we noted a positive correlation between the expression of E-selectin and ICAM-1. The expression of E-selectin and VCAM-1 as well as ICAM-1 was revealed to be correlated with the number of EG2-positive cells and CD4-positive cells, but not with elastase-positive cells. These findings suggest that all these adhesion molecules play a role in the topical influxes of eosinophils and CD4-positive cells in allergic nasal mucosa.

Adolescent↗
PubMed2000

Effects of anti-VLA-4 monoclonal antibody treatment in murine model of allergic rhinitis.

In order to study the role of VLA-4 in allergic rhinitis, the effects of anti-mouse VLA-4 monoclonal antibody (mAb) were evaluated in a murine model. BALB/c mice were sensitized first by i.p. injections (general sensitization) and then by daily nasal dripping of antigen (local sensitization) before performing a nasal antigen challenge. The mAb was applied either before the antigen challenge (BC group), before the local sensitization (BL group) or before the general sensitization (BS group). The effects were evaluated in terms of antigen-induced early-phase nasal symptoms (sneezing), late-phase nasal eosinophilia and the serum level of antigen-specific IgE. Antigen-induced nasal eosinophilia was significantly (p = 0.009) reduced in the BL group but not in the BC group (number of eosinophils = 114 +/- 15.1, 244 +/- 52.8 and 347 +/- 50.5 in the BL, BC and control groups, respectively). The serum level of the specific IgE was also significantly (p = 0.038) reduced in the BL group but not in the BC group (optical density = 1.18 +/- 0.07, 1.28 +/- 0.13 and 1.58 +/- 0.14 in the BL, BC and control groups, respectively). The suppressive effect on sneezing was not significant in either the BL or BC groups. In the BS group, suppressive effects on antigen-induced nasal responses and the specific IgE level were not statistically significant. These findings suggest that VLA-4 plays an important role in the topical booster or priming effects during repeated nasal antigen exposures in pre-sensitized animals.

Animals↗
PubMed2000

Effect of CT digital image compression on detection of coronary artery calcification.

PURPOSE: To test the effect of digital compression of CT images on the detection of small linear or spotted high attenuation lesions such as coronary artery calcification (CAC). MATERIAL AND METHODS: Fifty cases with and 50 without CAC were randomly selected from a population that had undergone spiral CT of the thorax for screening lung cancer. CT image data were compressed using JPEG (Joint Photographic Experts Group) or wavelet algorithms at ratios of 10:1, 20:1 or 40:1. Five radiologists reviewed the uncompressed and compressed images on a cathode-ray-tube. Observer performance was evaluated with receiver operating characteristic analysis. RESULTS: CT images compressed at a ratio as high as 20:1 were acceptable for primary diagnosis of CAC. There was no significant difference in the detection accuracy for CAC between JPEG and wavelet algorithms at the compression ratios up to 20:1. CT images were more vulnerable to image blurring on the wavelet compression at relatively lower ratios, and "blocking" artifacts occurred on the JPEG compression at relatively higher ratios. CONCLUSION: JPEG and wavelet algorithms allow compression of CT images without compromising their diagnostic value at ratios up to 20:1 in detecting small linear or spotted high attenuation lesions such as CAC, and there was no difference between the two algorithms in diagnostic accuracy.

Adult↗
PubMed2000

Repeat intervention for in-stent restenosis: re-expansion of the initial stent is a predictor of recurrence of restenosis.

BACKGROUND: In-stent restenosis has become a significant clinical problem as use of stents has increased. The optimal strategy for dealing with in-stent restenosis needs to be evaluated. OBJECTIVE: To compare the acute and late results of interventions for in-stent restenosis according to the device used, and to analyze the clinical and procedural variables of the lesions treated and identify the determinants of recurrence of restenosis and target lesion revascularization (TLR). METHODS: Procedural and late outcomes for 58 lesions in 50 patients who underwent repeat intervention for in-stent restenosis were analyzed. The results of interventions according to the device employed were compared. The predictors of recurrence of restenosis and TLR within 6 months were analyzed. The ratio of balloon diameter in repeat intervention to minimal lumen diameter after initial stenting (MLD0) was used as an index of re-expansion of stents. Serial intravascular ultrasound imaging was performed before and after repeat intervention for 33 lesions, and re-expansion of the initial stent was evaluated. RESULTS: Repeat intervention was successful in treating all lesions. Angiographic follow-up was possible for 49 lesions (84%). The overall incidences of recurrence of restenosis and TLR were 40.1 and 27.6%, respectively. Despite the immediate results having been good, the late results of stenting for in-stent restenosis were not favorable. Diffuse-type in-stent restenosis, early in-stent restenosis, and balloon diameter:MLD0 ratio > 1.25 are independent predictors of poor late results. Intravascular ultrasound findings have shown that expansion of the initial stent leads to recurrence of restenosis and TLR. CONCLUSIONS: Re-expansion of the initial stent can cause further vascular injury and there is a risk of recurrence of restenosis. Alternative therapeutic strategies that work without dilating the initial stent may be necessary for treating lesions with high risk of recurrence of restenosis.

Aged↗
PubMed2000

Determining appropriate small vessels for stenting by intravascular ultrasound.

To re-evaluate outcomes of stenting in small vessels, we studied 176 patients successfully treated with several types of stent by way of intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA). These lesions were divided into 3 subgroups according to reference diameter (RD) by QCA, and vessel diameter (VD) by IVUS (group I: pre-RD 2.5 mm; group II: pre-RD < 2.5 mm and pre-VD 4.0 mm; group III: pre-RD < 2.5 mm and pre-VD < 4.0 mm). Post-procedure percent diameter stenosis (4 +/- 3%), post-procedure percent plaque area (42 +/- 3%), and loss index (39 +/- 11%) in group II were not significantly different from those in group I (7 +/- 2%, 37 +/- 2%, 45 +/- 5%, respectively). The rates of restenosis and target lesion revascularization in group II (24.0% and 16.0%, respectively) were not different from those in group I (25.9% and 21. 2%, respectively), and were significantly favorable compared to group III (66.7% and 39.4%, respectively; p < 0.05). By the use of IVUS, we not only identified those vessels which would normally go unstented when only using QCA, but also documented excellent long-term outcome in these patients.

Aged↗
PubMed2000

Antibody-mediated remyelination: relevance to multiple sclerosis.

Intravenous immunoglobulin (IVIG) is widely used for treatment of autoimmune neurological disorders and is currently in clinical trials as a therapy for multiple sclerosis. We have previously demonstrated that certain mouse monoclonal antibodies of the IgM isotype, promote significant remyelination when administered to mice with chronic Theiler's murine encephalomyelitis virus-induced demyelinating disease. These IgM antibodies bind to antigens expressed on oligodendrocytes. We now demonstrate that polyclonal human IgG (IVIG) and polyclonal human IgM also promote remyelination in this system. Although both polyclonal human IgG and IgM promote remyelination, IgM is more potent. Polyclonal human IgM also differs from human IgG in its ability to bind strongly to antigens expressed in the CNS and by oligodendrocytes. We propose that polyclonal IgG and polyclonal IgM may function to promote remyelination by different mechanisms. IVIG may function based on its immunomodulatory activity, while the activity of IgM is critically dependent upon its reactivity with CNS antigens. This possibility has clear relevance to the use of antibodies as a therapy for multiple sclerosis, suggesting that combined treatment with antibodies exerting immunomodulatory activity, in concert with antibodies that function through direct binding to CNS antigens, may synergize to enhance the efficacy of the therapy.

Animals↗
PubMed1999

Evaluation of scaffolding effects of five different types of stents by intravascular ultrasound analysis.

The acute elastic recoil of 5 types of stents immediately after deployment by intravascular ultrasound and quantitative coronary angiography measurements was analyzed. Successfully implanted stents were: Palmaz-Schatz in 104 lesions, Gianturco-Roubin in 65, Wiktor in 45, gfx in 22, and Multi-Link stents in 22. Before and after stenting, the cross section of the smallest luminal area and vessel area was measured with intravascular ultrasound. The postdilatation balloon area was calculated by quantitative coronary angiography. Percent recoil was calculated as: [1-(preluminal area)/balloon area)] x 100. The ratio of balloon area-to-vessel area was also compared. Although preluminal areas in Gianturco-Roubin and Palmaz-Schatz stents were similar (2.4 +/- 0.1 vs 2.5 +/- 0.1 mm2, p = NS), postluminal area in the Gianturco-Roubin was significantly smaller than the area in the Palmaz-Schatz (6.3 +/- 0.2 vs 8.3 +/- 0.3 mm2, p <0.05). Although both the balloon area/vessel area (0.68 +/- 0.05, 0.80 +/- 0.08 vs 0.83 +/- 0.02, p <0.05) and the preluminal area (2.1 +/- 0.4, 1.6 +/- 0.2 vs 2.5 +/- 0.1 mm2, p <0.05) were smaller in gfx and Multi-Link than in the Palmaz-Schatz, postluminal area was comparable to the area in the Palmaz-Schatz (7.8 +/- 0.4, 7.4 +/- 0.4 vs 8.3 +/- 0.3 mm2, p = NS). Percent recoil in the Gianturco-Roubin was poorest among these 5 groups. More favorable initial gain can be obtained with Palmaz-Schatz, Wiktor, gfx, and Multi-Link stents than with the Gianturco-Roubin stent.

Aged↗
PubMed1999

The nonpeptide alpha-eudexp6l from Juniperus virginiana Linn. (Cupressaceae) inhibits omega-agatoxin IVA-sensitive Ca2+ currents and synaptosomal 45Ca2+ uptake.

Recently, the omega-agatoxin IVA (omega-Aga-IVA)-sensitive Ca2+ channel has been demonstrated to play an important role in the physiological neurotransmitter release in mammalian nerve terminals. In this study, we demonstrate that alpha-eudesmol from Juniperus virginiana Linn. (Cupressaceae) inhibits omega-Aga-IVA-sensitive Ca2+ channels in rat brain synaptosomes and cerebellar Purkinje cells. Thirty millimolar KCl-induced 45Ca2+ uptake into the synaptosomes was inhibited by omega-Aga-IVA but insensitive to omega-conotoxin GVIA (omega-CTX-GVIA, N-type Ca2+ channel blocker) and nicardipine (L-type Ca2+ channel blocker). We found that alpha-eudesmol concentration-dependently inhibited the above synaptosomal 45Ca2+ uptake with an IC50 value of 2.6 microM. Co-treatment with alpha-eudesmol and omega-Aga-IVA did not cause any additive inhibitory effect against the synaptosomal 45Ca2+ uptake. Using the whole-cell patch clamp electrophysiological technique, we further demonstrated that alpha-eudesmol concentration-dependently inhibited omega-Aga-IVA-sensitive Ca2+ channel currents recorded from Purkinje cells with an IC50 value of 3.6 microM. The current-voltage relationship of the omega-Aga-IVA-sensitive Ca2+ channel currents was not changed by alpha-eudesmol. On the other hand, alpha-eudesmol also displayed an inhibitory effect on N-type Ca2+ channel currents recorded from differentiated NG108-15 cells with an IC50 value of 6.6 microM. However, alpha-eudesmol had little inhibitory effect on L-type Ca2+ channel currents. Thus, the present data indicated that alpha-eudesmol is a potent nonpeptidergic compound which blocks the presynaptic omega-Aga-IVA-sensitive Ca2+ channel with relative selectivity.

Animals↗
PubMed1999

Prognostic factors of nasopharynx tumors investigated by MR imaging and the value of MR imaging in the newly published TNM staging.

PURPOSE: To examine the usefulness of MR imaging for predicting local control of nasopharyngeal carcinoma (NPC) and the value of MR imaging in the newly published fifth edition of the TNM classification. METHODS AND MATERIALS: We studied 29 patients with NPC with MR imaging and CT before and after treatment. Staging was done according to the fourth and newly published fifth editions of the International Union Against Cancer (UICC) staging system. The radiotherapy protocol was designed to deliver 66 to 68 Gy to the primary tumor and clinically involved nodes. RESULTS: MR proved better than CT at identifying obliteration of the pharyngobasilar fascia, invasion of the sinus of Morgagni, through which the cartilaginous portion of the eustachian tube and the levator veli palatini muscle pass, invasion of the skull base, and metastases to lymph nodes in the carotid and retropharyngeal spaces. All seven patients without invasion of the pharyngobasilar fascia had local control. The local control rates of patients with invasion of the skull base were not good (60 to 73%). There was no apparent relationship between tumor volume determined by T1-weighted MR images and local control when the tumor volume was more than 20 cc. The newly published N staging system appears to successfully identify the high-risk group for distant metastasis as N3. In our series, four of five patients with N3 disease developed distant metastases. CONCLUSION: Deep infiltration of the tumor is a more important prognostic factor in NPC than tumor volume. Since the newly published T staging system requires a search for tumor invasion into soft tissue such as parapharyngeal space and bony structures, MR imaging may be indispensable for the newly published NPC staging system.

Adolescent↗