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Biomedical subjects

H Seto

Publications and source records attributed to H Seto.

At least 109 records · Page 6Linked to original sources
PubMed1997

Quantitative evaluation of blood flow distribution to exercising and resting skeletal muscles in patients with cardiac dysfunction using whole-body thallium-201 scintigraphy.

BACKGROUND AND HYPOTHESIS: Decreased blood flow to working muscles makes an important contribution to exercise intolerance in patients with chronic heart failure. This study was undertaken to examine whether maldistribution of skeletal muscle blood flow is closely related to exercise intolerance in patients with cardiac dysfunction. METHODS: Whole-body thallium scintigraphy was performed during one-leg exercise in 11 patients with left ventricular (LV) dysfunction (LV ejection fraction < 45%). Blood flow distribution to the exercising and resting legs was quantified by expressing regional thallium counts as a percentage of the whole-body counts at rest, at the level of anaerobic threshold, and at peak exercise. RESULTS: At anaerobic threshold, the thallium activity of exercising muscle increased from 4.2 +/- 0.7 to 14.0 +/- 2.5% (p < 0.05) in the thigh and from 1.7 +/- 0.3 to 4.1 +/- 0.9% (p < 0.05) in the calf, compared with the resting value. Consequently, the ratio of thallium activity between exercising and resting legs increased to 2.7 +/- 0.7 (p < 0.05) in the thigh and to 2.3 +/- 0.7 (p < 0.05) in the calf. When plotted as a function of anaerobic threshold, thallium activity of the exercising thigh (r = 0.78, p < 0.05) and the thallium ratio between exercising and resting thigh (r = 0.69, p < 0.05) declined with the reduction of exercise tolerance. These correlations were not observed in calves. CONCLUSION: Whole-body thallium scintigraphy demonstrated a maldistribution of leg blood flow in patients with reduced aerobic exercise capacity, suggesting that this abnormality could play an important role in exercising intolerance in these patients.

Adult↗
PubMed1997

Initial and postoperative hyponatremia associated with pituitary adenoma: a case report.

This 67 year-old man experienced 3 episodes of symptomatic hyponatraemia. Radiological examination revealed a sellar lesion and the tumour was removed via the transsphenoidal route. Thereafter, he simultaneously developed intractable diabetes insipidus and serious hyponatraemia with persistent natriuresis. His level of atrial natriuretic peptide was not significantly elevated, however, his plasma aldosterone concentration was low. The oral administration of salt gradually improved his hyponatraemia as well as the coincident symptoms. By the administration of a mineralocorticoid, fludrocortisone acetate, we succeeded in maintaining his serum sodium level without salt replacement. We discuss the mechanism(s) and treatment of hyponatraemia associated with pituitary tumour.

Adenoma↗
PubMed1997

MRI of acute cerebral infarction: a comparison of FLAIR and T2-weighted fast spin-echo imaging.

Fluid-attenuated inversion-recovery (FLAIR) sequences have been reported to provide high sensitivity to a wide range of central nervous system diseases. To our knowledge, however, FLAIR sequences have not been used to study patients with acute cerebral infarcts. We evaluated the usefulness of FLAIR sequences in this context. FLAIR sequences were acquired on a 0.5 T superconducting unit within 8 h of the onset in 19 patients (aged 26-80 years) with a total of 23 ischaemic lesions. The images were reviewed retrospectively by three neuroradiologists, and the FLAIR images were compared with T2-weighted fast spin-echo images. All but one of the ischaemic lesions involving grey matter was clearly demonstrated on FLAIR images as increased signal intensity in cortical or central grey matter. FLAIR images were particularly useful for detecting the hyperacute cortical infarcts within 3 h of onset, which were not readily detected on the spin-echo images. In 9 of 11 patients with complete proximal occlusion, the distal portion of the cerebral artery was visible as an area of high signal intensity on FLAIR images.

Acute Disease↗
PubMed1997

Filling defect sign in CT diagnosis of ruptured aneurysm.

We have encountered a ruptured aneurysm as a filling defect in cisternal blood on CT in patients with acute subarachnoid haemorrhage (SAH), as high-attenuation blood can act as a contrast medium. We term this finding the "filling defect sign". To evaluate the usefulness of the sign in the diagnosis of a ruptured aneurysm, we retrospectively analysed CT with 10-mm-thick slices obtained within 2 days of onset of SAH in 100 consecutive patients. The sign was observed in 30 of the 100 patients, and in 13 (68%) of 19 patients with a ruptured aneurysm more than 10 mm in diameter. The filling defect sign is useful in predicting the site of rupture.

Acute Disease↗
PubMed1997

Evaluation of the prognosis of cancer patients with metastatic bone tumors based on serial bone scintigrams.

We counted the lesions at the time of detection of bone metastases and calculated the rate of increase in the number of bone metastases from changes in serial bone scintigrams, and investigated the usefulness of serial scintigrams as a prognostic indicator in patients with metastatic bone tumors. Subjects were 112 patients with bone metastases from four types of primary lesion: 21 with prostate cancer, 27 breast cancer, 39 lung cancer and 25 stomach cancer. Of these, 18 (prostate), 19 (breast), nine (lung) and eight (stomach) underwent serial bone scintigrams in which bone metastases were first detected and identified as progressing. The numbers of lesions at the time of detection of bone metastases for prostate and stomach cancers were significantly greater than those for lung cancer. The rate of increase in the number of bone metastases for stomach cancer was significantly higher than that for prostate or breast cancers. There was no correlation between the survival time after the detection of bone metastases and the number of lesions at the time of detection in the four types of cancer. However, in prostate cancer, a negative correlation existed between the survival time after the detection of bone metastases and the rate of increase in the number of bone metastases. Thus, in patients with bone metastases from prostate cancer, it appears that the rate of increase in the number of bone metastases, estimated from serial bone scintigrams, was indicative of prognosis.

Adult↗
PubMed1997

Sequential subtraction scintigraphy with 99Tcm-RBC for the early detection of gastrointestinal bleeding and the calculation of bleeding rates: phantom and animal studies.

To improve the detectability of gastrointestinal (GI) bleeding, we have developed a new method, 'sequential subtraction scintigraphy' (SSS) with 99Tcm-labelled red blood cells (RBC). Sequential subtraction scintigrams were obtained by subtracting 5 min interval images from each other using a digital gamma camera. With this method, we are able to detect the bleeding site and calculate the bleeding rate earlier because of the lower background activity. The results of the present study demonstrate that the minimum detectable bleeding rate was 0.05 ml min-1 in both a phantom and an animal model. The minimum detectable activity volumes within 10 min were 0.5 ml by SSS and more that 3 ml by conventional non-subtraction scintigraphy (CNS). The bleeding rates calculated with the subtraction method correlated well with the actual syringe pump rates. The detectability of GI bleeding by SSS and CNS in animal models was compared using the area under receiver operator characteristic (ROC) curves. The results showed that SSS significantly increased the area under the ROC curves from 0.55 +/- 0.05 to 0.79 +/- 0.04 for the 10 min image set and from 0.65 +/- 0.05 to 0.83 +/- 0.04 for the 30 min image set (Z = 5.45, P < 0.0001 and Z = 4.36, P < 0.0001, respectively). These results suggest that sequential subtraction scintigraphy with 99Tcm-RBC is an effective method for the early detection of GI bleeding when compared with the conventional non-subtraction method.

Adult↗
PubMed1997

The Arabidopsis deetiolated2 mutant is blocked early in brassinosteroid biosynthesis.

The Arabidopsis DEETIOLATED2 (DET2) gene has been cloned and shown to encode a protein that shares significant sequence identity with mammalian steroid 5 alpha-reductases. Loss of DET2 function causes many defects in Arabidopsis development that can be rescued by the application of brassinolide; therefore, we propose that DET2 encodes a reductase that acts at the first step of the proposed biosynthetic pathway--in the conversion of campesterol to campestanol. Here, we used biochemical measurements and biological assays to determine the precise biochemical defect in det2 mutants. We show that DET2 actually acts at the second step in brassinolide biosynthesis in the 5 alpha-reduction of (24R)-24-methylcholest-4-en-3-one, which is further modified to form campestanol. In feeding experiments using 2H6-labeled campesterol, no significant level of 2H6-labeled campestanol was detected in det2, whereas the wild type accumulated substantial levels. Using gas chromatography-selected ion monitoring analysis, we show that several presumed null alleles of det2 accumulated only 8 to 15% of the wild-type levels of campestanol. Moreover, in det2 mutants, the endogenous levels of (24R)-24-methylcholest-4-en-3-one increased by threefold, whereas the levels of all other measured brassinosteroids accumulated to < 10% of wild-type levels. Exogenously applied biosynthetic intermediates of brassinolide were found to rescue both the dark- and light-grown defects of det2 mutants. Together, these results refine the original proposed pathway for brassinolide and indicate that mutations in DET2 block the second step in brassinosteroid biosynthesis. These results reinforce the utility of combining genetic and biochemical analyses to studies of biosynthetic pathways and strengthen the argument that brassinosteroids play an essential role in Arabidopsis development.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1997

Subacute and chronic subarachnoid hemorrhage: diagnosis with fluid-attenuated inversion-recovery MR imaging.

PURPOSE: To evaluate fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging in the detection of subacute and chronic subarachnoid hemorrhage. MATERIALS AND METHODS: The authors performed 19 FLAIR MR imaging examinations at 0.5 T in 14 adult patients with subarachnoid hemorrhage 3-45 days after the ictus and 22 FLAIR examinations in 22 adult control subjects. The detection of subacute and chronic subarachnoid hemorrhage on FLAIR images was compared with the detection on conventional spin-echo MR and computed tomographic (CT) images. RESULTS: In the detection of subacute subarachnoid hemorrhage, FLAIR (100% detection) was significantly superior to T1-weighted imaging (36% detection, P < .01), T2-weighted imaging (0% detection, P < .02), and CT (45% detection, P < .02 [Fisher exact test]). Although FLAIR imaging (63% detection) was superior in chronic subarachnoid hemorrhage detection, there were no statistically significant differences between modalities. FLAIR imaging demonstrated all subarachnoid hemorrhage areas as high-signal-intensity areas within 18 days and up to a maximum of 45 days after the ictus. In a blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in patients. CONCLUSION: FLAIR diagnostic images are superior to conventional MR or CT images in patients with subacute subarachnoid hemorrhage.

Acute Disease↗
PubMed1997

Analysis of water sorption behavior of native and denatured proteins by solution thermodynamics.

Water sorption isotherms of native and denatured ovalbumin samples were measured, and their affinity for water was quantitatively analyzed by solution thermodynamics. The structural change of the proteins was evaluated by several methods. Water activity above 0.9 was measured by adding a specific amount of water to a sample, while that elbow 0.9 was measured with apparatus for water sorption isotherms. Thus, water sorption isotherms for native and denatured ovalbumin samples were obtained up to a water activity of 0.99. The water sorption behavior of ovalbumin was affected not by its hydrophobicity but by its prominent conformational change. It was confirmed that parameter delta Gs calculated by solution thermodynamics was more suitable for evaluating the affinity for water from water sorption isotherms than delta Gws calculated by conventional adsorption thermodynamics.

Adsorption↗
PubMed1997

Carquinostatin B, a new neuronal cell-protecting substance produced by Streptomyces exfoliatus.

Brain ischemia injury is elicited by the excitotoxicity of L-glutamate. Carquinostatin B was isolated from Streptomyces exfoliatus 2419-SVT2 as a potent neuroprotective substance which protests neuronal hybridoma N18-RE-105 cells from L-glutamate toxicity. The structure of carquinostatin B was established principally by NMR studies to be a carbazole derivative with an ortho quinone function.

Animals↗