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Biomedical subjects

Y Oshima

Publications and source records attributed to Y Oshima.

At least 73 records · Page 4Linked to original sources
PubMed2000

Paralytic shellfish toxins in the freshwater cyanobacterium Aphanizomenon flos-aquae, isolated from Montargil reservoir, Portugal.

Montargil reservoir, located in a dry flat area in the centre of Portugal, was filled in 1958 to fulfil agricultural, electric and industrial requirements. In May 1996, an intensive bloom of phytoplankton was detected. The algal community was strongly dominated by cyanobacteria with predominance of Aphanizomenon flos-aquae from May to June and Microcystis aeruginosa from July to August. Extracts of samples collected during the bloom period showed high toxicity by mouse bioassay. During the M. aeruginosa predominance period, the toxicity was ascribed to the presence of hepatotoxins, but clear symptoms of paralytic shellfish poison were observed when A. flos-aquae was the dominant species. In order to confirm the production of neurotoxins a strain of A. flos-aquae was isolated and established in culture. In this manuscript, we show the morphological characteristics and confirm paralytic shellfish toxins production by the strain isolated and maintained in culture. Identification of the saxitoxin analogs was achieved using high performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD) and liquid chromatographic mass spectrometry technique (LC-MS). The toxins found in the culture extract were GTX5 (64.5 mol%), neoSTX (23.0 mol%), dcSTX (6.1 mol%), STX (5.4 mol%) and GTX6 (1.1 mol%). This is, to our knowledge, the first report of unambiguous evidence of paralytic shellfish toxins produced by freshwater cyanobacteria in Portugal. The toxin profile is rather different from the previously reported PSP producing A. flos-aquae and demonstrates its diversity in terms of toxin production.

Animals↗
PubMed2000

Suppression of the secretion of atrial and brain natriuretic peptide after total cavopulmonary connection.

OBJECTIVES: Among the modifications of the Fontan operation currently being used, total cavopulmonary connection offers the greatest potential for optimizing early and long-term postoperative outcomes. Although studies have established that abrupt increases in right atrial pressure elevate the plasma atrial natriuretic peptide level after the Fontan procedure, changes in plasma natriuretic peptide levels after total cavopulmonary connection have not been clarified. Our hypothesis is that secretion of atrial natriuretic peptide may be suppressed in patients undergoing total cavopulmonary connection because the atrium continues to function at low pressure in those patients. In this study, we measured plasma levels of atrial and brain natriuretic peptide before and during the postoperative period in patients undergoing total cavopulmonary connection. METHODS: We evaluated 60 patients: 30 patients underwent total cavopulmonary connection and 30 patients underwent definitive repair for Fallot's tetralogy. Blood samples for measurement of atrial and brain natriuretic peptide were obtained before the operation and in the postoperative period. RESULTS: Plasma levels of atrial and brain natriuretic peptide were significantly lower during the early postoperative period in patients undergoing total cavopulmonary connection than in patients undergoing definitive repair for Fallot's tetralogy. No correlations were identified between the atrial natriuretic peptide levels and central venous pressure after total cavopulmonary connection. CONCLUSION: These results suggest that total cavopulmonary connection attenuates the secretion of atrial and brain natriuretic peptide in the early postoperative period. The suppressed release of atrial and brain natriuretic peptide after total cavopulmonary connection may have clinical importance.

Adolescent↗
PubMed2000

Simultaneous STM and UHV electron microscope observation of silicon nanowires extracted from Si(111) surface

A miniaturized scanning tunnelling microscope (STM) was fitted in a side-entry holder of an ultra-high vacuum electron microscope. The clean Si(111)7 x 7 surface was observed by both STM and reflection electron microscopy (REM) at atomic resolution. The tungsten tips were often rounded off upon tip-approach with a constant current, through a gentle touch with the sample surface. The apices of such rounded tips had radii of several tens of granometre with widths of about 3 x 3 nm. Atomically resolved STM of the Si(111)7 x 7 surface was obtainable when an atom or an atomic cluster sits on the tip surface. The rounded tips were used for fabrication of Si nanowires by the touch-and-away operation of the tip. The nanowires grew longer at higher substrate temperature and they reached as long as several tens of nanometre at 700 degrees C. The nanowire had many twins and the (111) twin lamellae were stacked in the direction of the wire axis. In another case, the twin planes were oblique to the wire axis so that the (112) direction was nearly parallel to the wire axis.

Journal Article↗
PubMed2000

Optical cross-sectional evaluation of successfully repaired idiopathic macular holes by retinal thickness analyzer.

PURPOSE: To describe optical cross-sectional images of successfully repaired idiopathic macular holes and to determine the influences of epiretinal membranes and retinal pigment epithelial (RPE) changes on foveal reconstruction and the correlation between retinal thickness and postoperative visual acuity. METHODS: In a prospective study, optical cross-sectional imaging and retinal thickness measurement of the macula using a retinal thickness analyzer were performed on 63 eyes of 63 patients who underwent successful macular hole surgery. RESULTS: Cross-sectional images of foveal reconstruction were morphologically categorized into four patterns: normal fovea (23 eyes [37%]), cavernous fovea (19 eyes [30%]), flat fovea (11 eyes [17%]), and irregular fovea (10 eyes [16%]). Epiretinal membranes were observed in the last two groups (55% and 40%) and RPE changes were observed only in the irregular fovea group (16%). The mean retinal thickness of the fovea in all eyes was 213 +/- 92 microm (mean +/- SD; range, 93-570 microm), which varied significantly (P < 0.001) among the four groups. Linear regression analysis showed a significant correlation between retinal thickness at the fovea and logarithmic converted visual acuity (R2 = 0.42, P < 0.001). CONCLUSIONS: Structural features of foveal reconstruction following successful macular hole surgery involved four patters: normal fovea, cavernous fovea, flat fovea, and irregular fovea. Retinal thickness of the fovea, which varied among the groups, correlated with postoperative visual acuity. Postoperative epiretinal membrane formation and RPE damage may disturb normal foveal reconstruction and visual recovery.

Aged↗
PubMed2000

Real time fixation point monitoring system for photocoagulation of juxtafoveal neovascularisation.

BACKGROUND/AIMS: A new real time monitoring system has been developed to locate the fixation point during juxtafoveal laser photocoagulation. METHOD: The red diode laser beam is combined coaxially with the illumination beam to image a cross in the focal plane of the slit lamp, which allows projection of a red cross onto the patient's fundus. 27 patients with juxtafoveal choroidal neovascularisation were treated by photocoagulation using this system. RESULTS: 13 (48%) patients whose visual acuity ranged from 20/200 to 20/40 answered that it was easier to keep the focus on the cross target image than on the aiming beam. The patient maintained stable fixation throughout the treatment. The laser treatment was completed without foveal damage near the fixation point in all patients. CONCLUSION: The real time fixation monitoring system should allow surgeons to treat juxtafoveal lesions with laser photocoagulation more safely and accurately.

Choroidal Neovascularization↗
PubMed2000

Effective arterial elastance of irregular beats during atrial fibrillation in canine left ventricle.

Effective arterial elastance (E(a)) was originally defined as the end-systolic pressure (ESP)/stroke volume (SV) ratio of the left ventricle (LV). E(a) combined with LV contractility (E(max)), E(a)/E(max), proved to be powerful in analyzing the ventriculo-arterial coupling of normal and failing hearts in regular beats. However, E(a) sensitively changes with LV E(max), preload, and afterload widely changing among irregular beats. This has discouraged the use of E(a) during arrhythmia. However, we hypothesized that E(a) could serve as the effective afterload (not always arterial) elastance against ventricular ejection under arrhythmia. We tested this hypothesis by analyzing beat-to-beat changes in E(a) of irregular beats during electrically induced atrial fibrillation (AF) in normal canine in situ hearts. We newly found that during AF in each heart: 1) E(a) changed widely among irregular beats and became markedly high in weak beats with small SVs; 2) E(a) and E(a)/E(max) distributed non-normally with large skewness but 1/E(a) distributed more normally; 3) 1/E(a) correlated closely with end-diastolic volume, E(max) and preceding beat intervals; and 4) the reciprocal of mean 1/E(a) closely correlated with mean ESP/mean SV. These results support our hypothesis that E(a) can serve as the effective afterload elastance against ventricular ejection on a per-beat basis during AF. E(a)/E(max) can also quantify the ventriculo-afterload (not arterial) coupling on a per-beat basis. This study, however, warns that mean E(a) and mean E(a)/E(max) of irregular beats cannot necessarily represent their averages during AF.

Animals↗
PubMed1999

Potentiation by febrifugine of host defense in mice against Plasmodium berghei NK65.

The effect of febrifugine, the main alkaloidal constituent of an antimalarial crude drug, Dichroa febrifuga Lour., on protective immunity in mice infected with erythrocytic stage Plasmodium berghei NK65 was investigated. Febrifugine was administered orally, at a dose of 1 mg/kg/day, to mice before and/or after they were infected intraperitoneally with 2 x 10(6) parasitized red blood cells. Then, mortality and the levels of parasitemia and plasma NO3- [a degradation product of nitric oxide (NO)] were monitored. Febrifugine significantly reduced the mortality and the level of parasitemia. The plasma NO3- concentration began to rise within 2 days after treatment with febrifugine and declined to normal in 2 days when the mice were treated orally with febrifugine once a day for 3 consecutive days before parasite infection. This antimalarial activity of febrifugine was reduced by both N(G)-monomethyl-L-arginine and aminoguanidine. These results indicate that the increased production of NO by febrifugine plays an important role in host defense against malaria infection in mice.

Animals↗
PubMed1999

Target gene transfer of tissue plasminogen activator to cornea by electric pulse inhibits intracameral fibrin formation and corneal cloudiness.

Intracameral fibrin formation, a complication of ocular inflammation and intraocular operations, sometimes results in glaucoma and/or corneal damage leading to permanent visual loss. We transferred a therapeutic gene to the corneal endothelium in order to use it as a therapeutic organ. A plasmid encoding tissue plasminogen activator (tPA) was injected into the anterior chamber of rats and electric pulses (EPs) were given subsequently, which transferred a plasmid gene to a highly selected area of corneal endothelium with no inflammation. The biologically active tPA was clearly present for 4 days after treatment. Fibrin formation induced by YAG laser-generated bleeding in the anterior chamber decreased significantly more in treated eyes than in control eyes. Corneal opacity was significantly lower in treated eyes than in control eyes and histological damage was not apparent in the treated eyes. This genetic modification allows us to use the corneal endothelium to treat various ocular diseases and could be a new and effective type of pharmacologic gene therapy.

Animals↗
PubMed1999

New type of febrifugine analogues, bearing a quinolizidine moiety, show potent antimalarial activity against Plasmodium malaria parasite.

Febrifugine (1) and isofebrifugine (2), isolated from the roots of Dichroa febrifuga Lour. (Chinese name: Cháng Shan), are active principles against malaria. Adducts of 1 and 2 with acetone, Df-1 (3) and Df-2 (4), respectively, were obtained using silica gel and acetone. They showed high activity against P. falciparum malaria in vitro. Compound 3 was found to be equally effective against P. berghei in vivo as the clinically used drug chloroquine, whereas 4 showed only 1/24 of the activity of 3. Metabolism studies of these compounds revealed that compound 4 is readily metabolized in mouse liver. Accordingly, the dose of 4 must be higher than that of 3 to attain blood levels sufficient for a favorable therapeutic effect.

Animals↗
PubMed1999

Stimulation of neurotrophic factor secretion from 1321N1 human astrocytoma cells by novel diterpenoids, scabronines A and G.

Glial cells release neurotrophic factors that maintain neurons functionally. When rat pheochromocytoma cells (PC-12) were cultivated with the conditioned medium of human astrocytoma cells (1321N1) incubated with the new diterpenoids, scabronines A and G, isolated from Sarcodon scabrosus, they changed their morphology and there was neurite outgrowth. The scabronines increased the expression of mRNA for nerve growth factor (NGF), and the secretion of NGF from 1321N1 cells in a concentration-dependent manner. However, the enhanced neurite outgrowth produced by the conditioned media was slightly inhibited by NGF neutralizing antibody, and the concentration of NGF released in response to the scabronines was insufficient to cause differentiation. These results suggest that scabronines cause the secretion of other factors together with NGF from 1321N1 cells. The diterpenoids are useful drugs to clarify the mechanism of synthesis and secretion of neurotrophic factors.

Animals↗
PubMed1999

Brevetoxin B4 isolated from greenshell mussels Perna canaliculus, the major toxin involved in neurotoxic shellfish poisoning in New Zealand.

A new brevetoxin B analog, brevetoxin B4 (BTXB4), was isolated as the major toxin in greenshell mussels, Perna canaliculus, collected in New Zealand at the time of the neurotoxic shellfish poisoning incident. The new analog accounted for nearly two-thirds of the mouse lethality of the shellfish and was determined to be a mixture of N-myristoyl-BTXB2 and N-palmitoyl-BTXB2.

Animals↗
PubMed1999

Confirmation of yessotoxin and 45,46,47-trinoryessotoxin production by Protoceratium reticulatum collected in Japan.

Two different strains of the dinoflagellate Protoceratium reticulatum collected at Harima Nada and Yamada Bay in Japan were cultured and analyzed by fluorometric HPLC for yessotoxin production. Only the Yamada Bay strain produced yessotoxin. The toxin together with its analog, 45,46,47-trinoryessotoxin, were isolated from larger scale culture and unambiguously confirmed by (1)H NMR and MS measurements. This is the first confirmation of the biogenetic origin of yessotoxin in Japan, where the toxin was first reported. The results also indicate that the production of yessotoxins by P. reticulatum differs from strain to strain, in a similar way to that observed in many other toxigenic dinoflagellates such as Dinophysis spp. and Alexandrium spp.

Animals↗
PubMed1999

A sensitive and specific determination method for azaspiracids by liquid chromatography mass spectrometry.

A liquid chromatography/mass spectrometry (LC/MS) method was developed for the sensitive and specific determination of azaspiracid and its two analogs, the causative toxins of azaspiracid poisoning that occurred in the Netherlands and Ireland. The LC/MS method provided a detection limit of 50 pg for azaspiracid. The sensitivity was approximately 8 x 10(4) times greater than the mouse bioassay. The method was used to confirm the presence of azaspiracids in toxic mussels collected at Arranmore Island, Ireland in 1997.

Animals↗
PubMed1999

Conversion of right atrioventricular to total cavopulmonary anastomosis in the management of post-Fontan arrhythmia: report of a case.

Both the original and modified Fontan procedures are associated with several late complications such as atrial arrhythmias, thromboembolism, and right pulmonary vein compression caused by a markedly enlarged right atrium. We describe herein the case of a patient who underwent conversion of right atrioventricular to total cavopulmonary anastomosis to control atrial arrhythmia that developed 12 years after a modified Fontan operation. The procedure proved successful in alleviating his symptoms immediately. He is now doing well with no recurrence of atrial arrhythmia 1 year after the operation.

Arrhythmias, Cardiac↗