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Biomedical subjects

T Nagaoka

Publications and source records attributed to T Nagaoka.

At least 19 recordsLinked to original sources
PubMed2006

Ca channel currents inhibited by serum from select patients with Guillain-Barré syndrome.

We performed an electrophysiological study demonstrating inhibition of spontaneous muscle action potentials within a coculture of rat muscle and spinal cord by exposure to serum, as well as purified IgG, from patients with the acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome (GBS). However, exposure to serum from two patients with the acute inflammatory demyelinating polyneuropathy (AIDP) form of GBS had no effect. Using a whole-cell recording technique, we then investigated the effects of serum and purified IgG from patients with GBS on voltage-dependent calcium channel (VDCC) currents in nerve growth factor-differentiated PC12 cells. Serum from patients with GBS (AMAN) inhibited VDCC currents in PC12 cells, which was fully reversible by washing with the bath solution. Similarly, purified IgG from the serum of two patients with GBS (AMAN) also inhibited VDCC currents in PC12 cells. In contrast, sera from patients with AIDP and healthy volunteers did not affect VDCC currents in PC12 cells. These results suggest that muscle weakness in some patients with GBS might be induced by inhibition of Ca2+ channel currents within motor nerve terminals.

Action Potentials↗
PubMed2006

Effect of pH and hydration on the normal and lateral interaction forces between alumina surfaces.

Interaction forces between alumina surfaces were measured using an AFM-colloid probe method at different pHs. For an alpha-alumina-sapphire system at acidic pH, the force curve exhibited a well-defined repulsive barrier and an attractive minimum. At basic pH, the interactive force was repulsive at all separations with no primary minimum. Lateral force measurements under the same conditions showed that frictional forces were nearly an order of magnitude smaller at basic pH than those observed at acidic pH. This behavior was attributed to the hydration of the alumina surface. Normal and lateral force measurements with the strongly hydrated rho-alumina surfaces supported these findings.

Journal Article↗
PubMed2006

Choroidal blood flow in the foveal region in eyes with rhegmatogenous retinal detachment and scleral buckling procedures.

AIMS: To investigate changes in choroidal blood flow (ChBF) in the foveal region of the human eye with rhegmatogenous retinal detachment induced by scleral buckling. METHODS: ChBF was measured in the foveal region using laser Doppler flowmetry in patients with a rhegmatogenous retinal detachment and no macular involvement before and after scleral buckling. The ChBF ratio was evaluated (ChBF of the affected eye to ChBF of the fellow control eye) to minimise individual variations. RESULTS: Retinal reattachment was confirmed by 2 weeks after scleral buckling in all patients. The ChBF in the foveal region of the affected eyes did not differ from the fellow eyes before scleral buckling. The ChBF ratio significantly (p<0.05) decreased 2 and 4 weeks after scleral buckling compared with that before scleral buckling and returned to baseline 12 weeks after scleral buckling. CONCLUSIONS: The results suggest that ChBF in the foveal region transiently decreases after scleral buckling and recovers to the baseline level within 12 weeks in patients with a retinal detachment and no macular involvement.

Adult↗
PubMed2006

Diffusion tensor feature in vasogenic brain edema in cats.

We investigated the correlation between the changes in diffusion tensor magnetic resonance imaging, regional water content, and tissue ultrastructure after vasogenic brain edema induced by cortical cold lesioning. In this cat model, E3 in the white matter was dominantly increased while fractional anisotropy (FA) was significantly decreased 8 hours after cortical cold lesioning. This finding indicates that water diffusion in the cortical white matter mainly increased perpendicularly rather than parallel to the direction of the nerve fibers. Additionally, in the area where edema is mild or moderate (tissues with water content of 65% to 75%), FA in the chronic phase was significantly lower than that in the acute phase. Histological examination demonstrated disordered arrangement of nerve fibers, highly dissociated neuronal fibers due to extracellular accumulation of protein rich-fluid, and enlarged interfiber spaces in the acute phase.

Animals↗
PubMed2005

Serum prorenin levels and diabetic retinopathy in type 2 diabetes: new method to measure serum level of prorenin using antibody activating direct kinetic assay.

AIM: To investigate the serum levels of prorenin and its correlation with the severity of diabetic retinopathy (DR). METHODS: 248 patients with diabetes and 108 control subjects were divided into four groups: no-DR (n = 146), no proliferative diabetic retinopathy (no-PDR) (n = 78), PDR (n = 24), and controls (n = 108). Serum levels of prorenin from all subjects were measured using the new antibody activating direct kinetic (AAD-PR) assay. The serum prorenin levels were compared among the groups. RESULTS: The serum levels of prorenin in the control, no-DR, no-PDR, and PDR groups, respectively, were 109.1 (66.1), 194.6 (160.4), 271.5 (220.3), and 428.4 (358.4) pg/ml (mean (SD)). Prorenin in the PDR group was remarkably high compared with the control and no-DR groups (p<0.0001) and with the no-PDR group (p = 0.002). Serum levels of prorenin increased with increasingly severe retinopathy. No correlation was found between the prorenin level and the duration of disease or HbA(1c). CONCLUSIONS: The serum levels of prorenin in patients with PDR were found to be markedly high using the AAD-PR assay. Increased levels of prorenin in diabetes may have an important role in the pathogenesis of DR.

Antibodies↗
PubMed2004

Peroxynitrite decomposition catalyst, FP15, and poly(ADP-ribose) polymerase inhibitor, PJ34, inhibit leukocyte entrapment in the retinal microcirculation of diabetic rats.

PURPOSE: Oxidative and nitrosative stress and activation of poly(ADP ribose) polymerase (PARP) play a role in the pathogenesis of diabetic complications. We evaluated the effectiveness of the peroxynitrite decomposition catalyst, FP15, and the PARP inhibitor, PJ34, in the treatment of leukocyte entrapment in the retinal microcirculation of diabetic rats. METHODS: Diabetes was induced in rats by intraperitoneal injection of 60 mg/kg of streptozotocin. Rats were divided into four groups: controls; untreated diabetes; diabetes treated with FP15 (10 mg/kg oral gavage twice daily) and diabetes treated with PJ34 (10 mg/kg oral gavage twice daily). All experiments were performed 4 weeks after initiation of treatment. Leukocyte entrapment in the retinal microcirculation was quantitatively evaluated in vivo with acridine orange digital fluorography. RESULTS: The density of leukocytes trapped in the retinal microcirculation 30 minutes after dye injection was significantly greater in untreated diabetes (32.1 +/- 4.7 cells/mm2) than in controls (11.3 +/- 4.5 cells/mm2) (p < 0.05). Compared with untreated diabetes, the density of trapped leukocytes significantly decreased in diabetes treated with FP15 (14.5 +/- 5.1 cells/mm2) (p < 0.0001) and diabetes treated with PJ34 (24.1 +/- 4.2 cells/mm2) (p < 0.05). CONCLUSIONS: Treatment with FP15 and PJ34 decreased enhanced leukocyte entrapment in the retinal microcirculation during the early diabetic period. The current study suggests a role for peroxynitrite production and for PARP activation in the pathogenesis of retinal microvascular leukostasis in early diabetes.

Acridine Orange↗
PubMed2004

Isolation and characterization of psychrophilic yeasts producing cold-adapted pectinolytic enzymes.

AIMS: The present study was conducted to screen for psychrophilic yeasts that are able to degrade pectin compounds at low temperature, and to examine the cold-active pectinolytic enzymes produced by the isolated psychrophilic yeasts. METHODS AND RESULTS: Psychrophilic yeasts, which grow on pectin as a sole carbon source, pectinolytic-psychrophilic yeast (PPY) strains PPY-3, 4, 5 and 6, were isolated from soil from Abashiri (Hokkaido, Japan). The sequences of 28S rDNA D1/D2 of strains PPY-3 and 4 indicated a taxonomic affiliation to Cryptococcus cylindricus and Mrakia frigida, respectively, strains PPY-5 and 6 belonged to Cystofilobasidium capitatum. The isolated strains were able to grow on pectin at below 5 degrees C, and showed the activities of several cold-active pectinolytic enzymes. CONCLUSION: The findings of this study indicate the possibility that the isolated strains produce novel pectinolytic enzymes that are able to degrade pectin compounds at low temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: It is possible that the cold-active pectinolytic enzymes from the isolated strains can be applied to the food industry, e.g. the clarification of fruit juice below 5 degrees C.

Basidiomycota↗
PubMed2004

Alteration of choroidal circulation in the foveal region in patients with type 2 diabetes.

AIM: To investigate changes in choroidal blood flow (CBF) in the foveal region in patients with type 2 diabetes. METHODS: Laser Doppler flowmetry was used to determine the CBF in the foveal region in 70 patients with type 2 diabetes and 36 age and sex matched healthy subjects (control group). The patients were classified into three groups: 33 patients (33 eyes) with no diabetic retinopathy (NDR), 20 patients (20 eyes) with non-proliferative diabetic retinopathy and no macular oedema (NPDR/MO-), and 17 patients (17 eyes) with NPDR and MO (NPDR/MO+). Optical coherence tomography was also used to measure the foveal thickness. RESULTS: The group averaged CBF values were 13.5 (4.9), 9.4 (2.5), 10.8 (4.8), and 5.6 (2.0) (arbitrary units) in the control, NDR, NPDR/MO-, and NPDR/MO+ groups, respectively. The group averaged CBF values in the NDR group decreased (30.2%; p<0.01) compared with the control group. The average CBF value in the NPDR/MO+ group was also significantly lower (48.2%; p<0.01) compared with that in the NPDR/MO- group. CONCLUSION: The CBF in the foveal region significantly decreases in patients with diabetes, especially those with macular oedema.

Analysis of Variance↗
PubMed2004

Effect of haemodialysis on retinal circulation in patients with end stage renal disease.

AIMS: To investigate the effect of haemodialysis on retinal circulation in patients with end stage renal disease (ESRD). METHOD: Seventeen consecutive patients with ESRD were recruited into the study. The authors simultaneously measured changes in vessel diameter and blood velocity and calculated the retinal blood flow (RBF) in the retinal veins in patients with ESRD before and after haemodialysis using a laser Doppler velocimetry system. In addition, the relations between the changes in systemic and retinal circulatory parameters were examined. RESULTS: There was a group averaged increase in vessel diameter (p = 0.003) after haemodialysis. However, the blood velocity and RBF values obtained after haemodialysis were not significantly different from those before haemodialysis (p = 0.66 and p = 0.63, respectively). The changes in vessel diameter were negatively (r = -0.549, p = 0.02) correlated with the change in MABP, but the changes in blood velocity and RBF were positively correlated with the change in MABP (r = 0.683, p<0.002 and r = 0.589, p<0.01, respectively). The change in RBF was also inversely correlated with the increase in haematocrit (r = -0.693, p<0.002) and the amount of fluid removed (r = -0.597, p<0.01). CONCLUSION: The results indicate that haemodialysis and the associated changes in systemic circulatory parameters may affect the retinal circulation in patients with ESRD.

Adult↗
PubMed2003

PET neuroreceptor imaging as predictor of severe cerebral ischemic insult.

Measurement of the adenosine A1 receptor (A1-R) with positron emission tomography (PET) using a newly developed positron ligand, [1-methyl-11C]8-dicyclopropylmethyl-1-methyl-3-propylxanthine (MPDX). were performed in a cat middle cerebral artery (MCA) occlusion and reperfusion. Eighteen adult cats underwent PET measurement of; 1) cerebral blood flow (CBF). 2) A1-R, 3) central benzodiazepine receptor (BDZ-R) and 4) glucose metabolism with 15O labeled water, MPDX, 11C-flumazenil (FMZ) and 18F-fluorodeoxyglucose (FDG), respectively. The CBF, A1-R, BDZ-R and FDG uptake were serially measured after 60 min occlusion of MCA in this order. MPDX binding and FMZ binding, but not CBF and FDG uptake, were significantly reduced in the groups with severer ischemic insult than in the groups with no or milder insults. Of the two receptor ligands, the reduction rate of the MPDX binding to A1-Rs was larger in a group that caused fatal ischemic insult. The newly developed PET in vivo imaging technique using MPDX was suitable in evaluating the function of adenosine and A1-Rs in relation to cerebral ischemia.

Animals↗
PubMed2003

Recovery of apparent diffusion coefficient after embolic stroke does not signify complete salvage of post-ischemic neuronal tissue.

BACKGROUND AND PURPOSE: It has been shown in previous studies that recovery of apparent diffusion coefficient (ADC) of water is not necessarily associated with a reversal of tissue damage. We examined the relationships between temporal ADC change and histological outcome after embolic stroke in rat using an experimental MRI scanner. SUBJECTS AND METHODS: Male Wistar rats underwent embolization of the right middle cerebral artery with autologous clot. ADC and relative cerebral blood flow (rCBF) were measured consecutively for 3 hours after embolization. The brains were prepared for histological examination. RESULTS: Transient decline of ADC was observed during the initial 2 hours after embolization. In these areas, serial rCBF measurement revealed incomplete recovery. In some other areas, ADC decrease without rCBF recovery was observed during 3 hours postischemia. Histological examination revealed infarction in areas with persistent ADC decrease. Scattered neuronal death was noticeable in areas with a transient--in some areas less than 0.5 hour--ADC decrease. CONCLUSION: Consecutive MRI analysis demonstrated postischemic transient ADC decrease in an embolic stroke model of rat. The normalization of ADC does not signify normalization of postischemic tissue, since the areas often evolve postischemic neuronal death at a later time.

Animals↗
PubMed2003

Features of abnormal choroidal circulation in central serous chorioretinopathy.

AIMS: To evaluate abnormalities in the choroidal circulation in cases of central serous chorioretinopathy (CSC). METHODS: A complete clinical ophthalmological examination was performed using simultaneous fluorescein and indocyanine green (ICG) angiography with a confocal scanning laser ophthalmoscopy and the digital images analysed in 36 consecutive patients with acute CSC. To quantify the choroidal circulation, the foveal choroidal blood flow was measured in 11 patients using laser Doppler flowmetry. RESULTS: Fluorescein angiography showed focal leakage from the retinal pigment epithelium in all patients. ICG angiography revealed delays in arterial filling in 27 eyes (75%), and fluorescein angiography showed small hypofluorescent points around the leakage in 27 eyes (75%). Abnormal choroidal hyperfluorescence was observed in 30 eyes (83%). The choroidal blood flow in eyes with CSC was 45% lower than in fellow eyes (p<0.01). CONCLUSION: Decreased choroidal blood flow in CSC was demonstrated for the first time. The decreased choroidal blood flow might be correlated with the small, localised hypofluorescent areas, which may indicate non-perfused areas of the choriocapillaris that are frequently seen during ICG angiography.

Adult↗
PubMed2002

Inhibitory effect of losartan, an AT1 angiotensin II receptor antagonist, on increased leucocyte entrapment in retinal microcirculation of diabetic rats.

BACKGROUND: The effectiveness of losartan for the treatment of leucocyte entrapment in the retinal microcirculation of diabetic rats was evaluated quantitatively. METHODS: After diabetes was induced by injection of streptozotocin (STZ), the rats were divided into two subgroups. The first subgroup (n = 6), received no medications; the second subgroup (n = 6) was given fresh drinking water supplemented with losartan (5 mg/kg/day) for 4 weeks. Six rats that were not injected with STZ or given medications served as controls. 4 weeks after intervention, leucocyte dynamics in the retina were observed using acridine orange digital fluorography. Leucocyte entrapment in the retina was compared among the three groups. RESULTS: In the untreated diabetic rats, the number of trapped leucocytes (6.1 (SD 1.4) cells/mm(2)) increased significantly compared with control rats (2.8 (1.2) cells/mm(2); p = 0.005) and diabetic rats treated with losartan (3.1 (0.9) cells/mm(2); p = 0.0002). CONCLUSIONS: Losartan, an AT1 angiotensin II receptor antagonist, inhibited increased leucocyte entrapment in the diabetic retina. The authors demonstrated that losartan may have therapeutic efficacy in preventing development of diabetic retinopathy. Further clinical studies of the effect of the angiotensin receptor antagonist on preventing development of diabetic retinopathy are needed.

Acridine Orange↗
PubMed2001

Characteristic changes in T(2)-value, apparent diffusion coefficient, and ultrastructure of substantia nigra evolving exofocal postischemic neuronal death in rats.

To correlate the magnetic resonance (MR) imaging characteristics of exofocal postischemic neuronal death (EPND) in the substantia nigra (SN) with associated histologic changes, we occluded the left middle cerebral artery of rats for 1, 4, 7, or 12 days. Day 1 (post-occlusion) T(2)-weighted images revealed high signal intensity indicative of infarction in the ipsilateral caudate nucleus, putamen, and cortex but not the SN. Diffusion-weighted images (DWIs) on day 1 similarly failed to reveal any changes in the SN. However, on day 4, DWIs revealed high signal intensity in the ipsilateral SN, in which the apparent diffusion coefficient (ADC) transiently decreased (P<0.05) while the T(2)-value increased (P<0.05). These measures returned to and remained at control levels on days 7 and 12. Histologic examination on day 4 revealed dark-staining neurons, markedly swollen perivascular astrocytic end-feet, many swollen neurons with cytoplasmic microvacuoles that mainly originated in the rough endoplasmic reticulum, and strongly roughed neuropils. Reactive astrocytes and dark neurons most frequently appeared on days 7 and 12. The severity of cellular swelling paralleled the change in the ADC. These results demonstrate that a transient high-intensity signal on DWIs, indicative of a decrease in the ADC, is predictive of EPND in the SN.

Animals↗
PubMed2001

Enhanced production of CC-chemokines (RANTES, MCP-1, MIP-1alpha, MIP-1beta, and eotaxin) in patients with atopic dermatitis.

CC-chemokines are potent molecules that direct the migration of leukocytes to inflammatory foci. To determine their role in inflammation associated with atopic dermatitis (AD), we determined serum levels and spontaneous production of CC-chemokines by peripheral blood mononuclear cells (PBMC) in AD patients using an ELISA. Serum levels of RANTES, MCP-1, MIP-1beta, and eotaxin were increased in AD patients (n = 52) compared with normal controls (n = 22). Serum levels of RANTES, MCP-1, and MIP-1beta were increased in AD patients with severe disease (n = 19) compared with normal controls (n = 22). Spontaneous production of RANTES, MCP-1, MIP-1alpha and MIP-1beta by PBMC was augmented in AD patients (n = 39) and in patients with severe AD (n = 14) compared with normal controls (n = 20). Serum RANTES levels correlated with total serum IgE levels, eosinophil numbers, and serum lactate dehydrogenase levels. Our results suggest that augmented production of CC-chemokines correlates with inflammation associated with AD.

Adolescent↗