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Biomedical subjects

N Yamada

Publications and source records attributed to N Yamada.

At least 577 records · Page 32Linked to original sources
PubMed1992

Scintigraphic analysis of hemodynamics in a patient with a single large pulmonary arteriovenous fistula.

A pulmonary perfusion study was performed on a 54-year-old man with a single large pulmonary arteriovenous fistula (aneurysmal type) using Tc-99m MAA. On the static imaging, a defect corresponding to the location of the mass and right-to-left shunt was clearly documented. Decreased uptake of Tc-99m MAA in the lung field surrounding the lesion was observed and was thought to reflect a "steal" of blood flow by the fistula. One advantage of using radionuclide angiography with Tc-99m MAA rather than with Tc-99m pertechnetate was that it more easily provided a time-activity curve that added useful quantitative information about the altered pulmonary hemodynamics.

Arteriovenous Fistula↗
PubMed1992

Bone and gallium scintigraphy in sacral chordoma. Report of four cases.

Bone scintigraphy with Tc-99m HMDP and gallium scintigraphy were evaluated in four patients with a primary sacrococcygeal chordoma. All lesions showed a photon-deficient or cold lesion corresponding to the tumor on bone scintigraphy, with no abnormal accumulation clearly observed on gallium scintigraphy. These findings led the authors to conclude that a midline sacrococcygeal tumor showing reduced uptake or a cold lesion on bone scintigraphy and no increased accumulation on gallium scintigraphy could be a chordoma rather than the malignant neoplasm suspected in this region.

Adult↗
PubMed1992

Quantitative assessment of myocardial enhancement with iodinated contrast medium in patients with ischemic heart disease by using ultrafast x-ray computed tomography.

BACKGROUND AND RATIONALE: The authors report the quantitation of myocardial enhancement using iodinated contrast medium in patients with ischemic heart disease. Twenty-eight patients with chronic ischemic heart disease and 11 controls were examined by ultrafast computed tomography (CT) using 100-msecond scans. METHODS: The authors analyzed M/L (ratio of post-contrast incremental increases in the left ventricular myocardial and luminal CT number) in early and late phases after contrast injection. RESULTS: In controls, mean values of early and late M/L were 30% and 51%, respectively. In infarcted or severely ischemic segments, early M/Ls (19%, 16%) were significantly small (P less than .001), whereas late M/Ls (90%, 63%) were higher (P less than .001, .01) than controls. Segments with infarction or severe ischemia were differentiated from mild or nonsignificant ischemia by using this parameter (sensitivity, 99%; specificity, 88%). CONCLUSIONS: M/L is useful for detection of the ischemic myocardium.

Contrast Media↗
PubMed1992

Quantitative evaluation of sialograms.

RATIONALE AND OBJECTIVES: The authors developed and evaluated a quantitative analytic method for interpreting clinical sialograms. METHODS: Images were obtained by digital subtraction sialography and transformed into binary form. The duct width of the image was calculated and represented as a normalized histogram. The effects of the volume of contrast medium injected and of the inclination angle of the objects on the histogram were examined. RESULTS: In model studies, the normalized histogram was affected insignificantly by these factors. Clinical sialograms of 18 patients with normal results, 12 patients with parotitis, and 5 patients with Sjögren syndrome were preliminarily analyzed by the histogram method and four representative parameters of the histogram. Discriminant analysis showed a relatively high correct-predictive rate in the distinction between patients with normal and abnormal results. CONCLUSIONS: This method reduces the effect of observer variation in diagnosing sialograms, and improves diagnostic accuracy for assessing the presence of inflammatory diseases of the parotid gland.

Animals↗
PubMed1992

Clinical and experimental studies on the mechanism of abnormal accumulation in lung scanning with 123I-IMP.

To investigate the intrapulmonary kinetics of N-isopropyl-p-I-123-iodoamphetamine (123I-IMP), lung scanning with 123I-IMP was performed in patients with various lung disorders. Compared with the normal lung field, abnormal accumulation of 123I-IMP was detected in all patients in delayed imaging performed 24 h after 123I-IMP injection. These sites were within areas of absent or reduced perfusion observed by pulmonary perfusion scanning using 99Tcm-macroaggregated albumin (99Tcm-MAA). A similar phenomenon was seen in additional experiments in rabbits with regional pulmonary arterial hypoperfusion resulting from a balloon catheter-induced bronchial occlusion. 123I-IMP accumulation in areas where 99Tcm-MAA images are absent or decreased may be explained by the ability of 123I-IMP to penetrate significantly narrowed microvascular beds with reduced perfusion. Our clinical and experimental results indicate that pulmonary arterial perfusion, particularly hypoperfusion, influence the pulmonary kinetics of 123I-IMP. This compound is a potentially useful non-particulate agent for the assessment of pulmonary arterial perfusion.

Aged↗
PubMed1992

Altered kinetics of 123I-IMP in irradiated rabbit lungs.

Radiation-induced alteration of intrapulmonary kinetics of 123I-IMP was investigated in 11 rabbits receiving a 50 Gy dose of radiation to one lung. In all 13 examinations of these rabbits, 3-17 weeks following radiation, the delayed images of 123I-IMP lung scintigrams showed abnormal accumulation in the irradiated lungs. The time-activity curves of the irradiated lung following injection of 123I-IMP had shallower downslopes of both the initial fast phase and the following slow phase than those of the non-irradiated lung. Finally the radioactivity of the irradiated lung exceeded that of the normal lung. The altered intrapulmonary kinetics of 123I-IMP in the irradiated lung was clearly confirmed. 99Tcm-MAA lung perfusion scintigrams showed reduced uptake in the irradiated lungs; the uptake decreased with time following radiation. Pulmonary arterial perfusion was considered to influence the distribution and kinetics of 123I-IMP, however, those of 123I-IMP did not reflect only the pulmonary arterial perfusion observed by 99Tcm-MAA scintigrams. Chest radiography and histological studies revealed a relatively slight change or injury of the irradiated lung in these rabbits. These results indicate that this agent could be useful in detecting and assessing early lung injury induced by radiation, and will give us pathological information in addition to lung perfusion in the peripheral area where the large 99Tcm-MAA molecule cannot reach.

Amphetamines↗
PubMed1992

Altered regional clearance of 99Tcm-DTPA in radiation pneumonitis.

99Tcm-diethylene triaminepenta-acetic acid (99Tcm-DTPA) lung scintigrams were investigated in 11 patients with radiation pneumonitis to assess the alteration of clearance of this small solute. Thirty minutes after the injection of 99Tcm-DTPA, all 11 patients showed abnormal accumulation. This uptake was seen in the areas with reduced 99Tcm-macroaggregated albumin activity. The curves of the lung/heart ratios obtained after 1 min after injection of 99Tcm-DTPA in areas showing abnormal accumulation were of three types. Comparison of the slope for the initial 5 min of the lung/heart curves between the abnormal accumulation sites and the contralateral non-irradiated lung revealed a significant difference. The uptake ratio (the mean counts of the last frame divided by initial peak count) was related to the degree of abnormal accumulation in the radiation pneumonitis. Moreover, study of rabbits with radiation pneumonitis revealed similar behaviour by 99Tcm-DTPA as observed clinically. This simple and rapid method may be useful in detecting and monitoring the altered regional kinetics of 99Tcm-DTPA in radiation pneumonitis.

Adult↗
PubMed1992

Morphological changes associated with growth inhibition of Trichophyton mentagrophytes by amorolfine.

Amorolfine inhibited the in-vitro growth of Trichophyton mentagrophytes to some extent at a low drug concentration of 0.8 ng/ml. Corresponding to the growth inhibition, SEM studies revealed a slight modification of hyphal morphology, i.e. a waving of the hyphal surface. These morphological alterations were more extensive with increases in drug concentration and treatment period: collapsed and distorted hyphae and exfoliation of the surface of T. mentagrophytes occurred at 8 ng/ml and marked deformation and disruption of the hyphal structure at 80 ng/ml of amorolfine. TEM revealed thickening of the cell walls and the accumulation of electron-dense granular structures in both the wall and cytoplasm in thin-sectioned cells pretreated with 8 ng/ml or more of amorolfine, although the nuclear and mitochondrial architecture was not noticeably influenced. Cytoplasmic membranes and other membranous structures of organelles such as nuclei and mitochondria were disrupted or fused, thereby losing their essential physiological activity in hyphal cells pretreated with 80 ng/ml of amorolfine. The ultrastructural study thus supports the observation that morphological changes of T. mentagrophytes caused by amorolfine were associated with its growth-inhibitory and killing activity, which depended on the drug concentration and treatment time.

Antifungal Agents↗
PubMed1992

Apolipoprotein E prevents the progression of atherosclerosis in Watanabe heritable hyperlipidemic rabbits.

Apo E plays an important role in plasma lipoprotein metabolism through its high affinity binding to cell surface LDL receptor. In the present study, we studied the effects of apo E on the atherogenic process in Watanabe heritable hyperlipidemic rabbits which are deficient in LDL receptor and an animal model for familial hypercholesterolemia. We isolated apo E from plasma of 1% cholesterol-fed rabbits and administered 10 mg of purified apo E intravenously into five Watanabe heritable hyperlipidemic rabbits three times a week from their age of 2.5 months to 11 months for 8.5 months. After sustained administration to apo E, we found a significant reduction in the accumulation of cholesterol ester in aortae (1.55 +/- 0.07 mg/g tissue) as compared to control rabbits (4.32 +/- 0.61 mg/g tissue). Supporting this, the percentage of the surface area of the aorta with macroscopic plaque was remarkably decreased in apo E-treated animals (18.8 +/- 5.1% vs. 38.8 +/- 8.0% in control). Thus, apo E definitely prevented the progression of atherosclerosis in Watanabe heritable hyperlipidemic rabbits.

Animals↗
PubMed1992

Plasma lipoprotein metabolism in transgenic mice overexpressing apolipoprotein E. Accelerated clearance of lipoproteins containing apolipoprotein B.

We have reported that transgenic mice overexpressing rat apo E shows marked reduction of plasma cholesterol and triglyceride levels due to the disappearance of VLDL and LDL. In this study, we investigated the metabolism of plasma lipoproteins in transgenic mice. After intravenous injection, the rates of clearance of 125I-VLDL and 125I-LDL were 3.0- and 2.4-fold greater in transgenic mice than in controls, respectively. Furthermore, clearance of chylomicron remnants estimated by oral retinyl palmitate-loading test was markedly enhanced in transgenic mice. The hepatic expression of LDL receptors by immunoblot analysis was similar in both groups. These data suggest that elimination of lipoproteins containing apo B was due to enhanced clearance of these lipoproteins enriched with apo E through hepatic LDL receptors. When fed a high cholesterol diet, controls showed twofold elevation of plasma cholesterol levels with marked increases in VLDL and LDL cholesterol on gel filtration chromatography. In contrast, cholesterol-fed transgenic mice showed resistance against these increases. High cholesterol feeding decreased the activity of hepatic LDL receptors and had no effect on enhancement of chylomicron remnant clearance in transgenic mice. Thus, overexpression of apo E facilitates metabolism of lipoproteins containing apo B presumably primarily via the LDL receptor pathway and possibly through an interaction with the chylomicron remnant receptor.

Animals↗
PubMed1992

Faecal lipid excretion levels in normal Japanese females on an unrestricted diet and a fat-restricted diet measured by simultaneous analysis of faecal lipids.

Faecal lipid excretion was determined in 16 females on an unrestricted diet and on a fat-restricted diet using a chromatographic method for the simultaneous analysis of faecal lipids. The fat-restricted diet reduced the total quantity of faeces and the amounts of fatty acids, neutral sterols and bile acids excreted were almost halved compared with when on an unrestricted diet. This indicates that dietary fat, fibre and cholesterol affect the amount of faecal bile acid, neutral sterol and fatty acid excretion. The amount of cholesterol/animal sterols excreted and the percentage of primary bile acids were, however, similar for both the fat-restricted and unrestricted diets.

Adult↗
PubMed1992

The contribution of frontal tomography to the diagnosis of temporomandibular joint osteoarthritis.

The contribution of frontal tomography to the diagnosis of temporomandibular joint (TMJ) osteoarthritis has been investigated. Ninety-one patients with clinically defined TMJ disorders were examined by simultaneous lateral and frontal TMJ tomograms taken in the intercuspal position. Abnormal findings were observed on frontal tomograms in 31 joints and suspicious findings in 22 joints. On the other hand, there were 41 joints with abnormal findings and 22 joints with suspicious findings on the lateral tomograms. Suspicious or abnormal findings were found on frontal tomograms alone in 14 joints (7.7%) of 14 patients (15.4%). It is concluded that simultaneous lateral and frontal tomography produces a more accurate radiographic diagnosis of TMJ osteoarthritis.

Adult↗