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Biomedical subjects

K Yasui

Publications and source records attributed to K Yasui.

369 records · Page 21Linked to original sources

Recirculation-type Amplatz clot macerator: determination of particle size and distribution.

PURPOSE: A high-speed mechanical clot macerator was tested in vitro, and the distributions and sizes of residual particles produced by this device were determined. MATERIALS AND METHODS: Human thrombi aged for 4 days and 10 days were macerated using a recirculation-type Amplatz thrombectomy device with an 8-F, high-speed screw propeller. The device was activated for 15, 30, and 60 seconds. Two different methods of particle measurement were used to determine overall particle distribution and to determine the size and number of large particles. RESULTS: The recirculation device liquefied 99.2% of 4-day-old and 98.8% of 10-day-old thrombi, producing particles ranging in size from 13 to 1,000 microns; all particles were smaller than 1,000 microns. Particle size and distribution results were identical for the 30-second and 60-second activation times. CONCLUSION: The recirculation-type thrombectomy device appears to perform well as a method of macerating human thrombi. Clinical trials need to be conducted to test the device further and to determine if it can be used safely on venous as well as arterial occlusions.

Humans↗

In vitro and in vivo experimental evaluation of a new vena caval filter.

PURPOSE: A new stainless steel (MP35N alloy) vena cava filter without a central stasis point was evaluated in vitro and in vivo. MATERIALS AND METHODS: The clot-trapping efficiency and hemodynamic flow pattern of the filter were assessed in a flow model and were compared with those of currently available commercial filters including the Vena Tech-LGM, Simon nitinol, Greenfield, and Bird's Nest filters. The new filter was placed in the inferior vena cava (IVC) of 31 dogs; 21 of the 31 dogs were followed up with cavography for up to 3 months. At the termination of the study, the filters and IVCs were examined grossly and histologically. An in vivo clot-trapping test was carried out in five dogs. RESULTS: The least turbulence was noted with the new filter and the titanium Greenfield filter. The stainless steel Greenfield and Simon nitinol filters caused major flow disturbances. Migration within 5 cm of initial placement occurred in two animals (9.5%). There were no IVC thromboses, perforations, or filter embolizations. An in vivo clot-trapping study showed an 80% efficiency for small thrombi (3 x 20 mm) and 100% efficiency for large thrombi (6 x 20 mm) with the new filter. The Simon and the new filter had the best clot-trapping capabilities. The Vena Tech-LGM and Bird's Nest filters were slightly inferior and the Greenfield filter demonstrated by far the lowest trapping capacity. CONCLUSION: The new vena cava filter is easily introduced percutaneously through a 12-F sheath and appears to be very promising due to its high filtering capability, low turbulence, nonmagnetic properties, good mechanical stability, and hypothrombogenicity. Clinical trials are warranted.

Alloys↗

Evaluation of crossing vessels in patients with ureteropelvic junction obstruction by means of helical CT.

Helical computed tomography (CT) was used to demonstrate the distribution of crossing vessels in patients with ureteropelvic junction (UPJ) obstruction for planning surgical management. Twenty patients with symptomatic UPJ obstruction were evaluated with dual-phase contrast material-enhanced helical CT. In addition to axial images, coronal, sagittal, and curved paracoronal images along the crossing vessels or the UPJ were obtained by means of multiplanar reconstruction. Crossing vessels were evaluated according to type, position, and association with UPJ obstruction. Fifteen vessels in 12 of the 20 patients were found to cross the UPJ at helical CT. Nine vessels were arteries and six were veins; seven vessels crossed anteriorly and eight crossed posteriorly. In 11 patients, crossing vessels were thought to be associated with UPJ obstruction at helical CT; retroperitoneoscopic repair was performed, and the diagnosis was found to have been accurate in all except one. In the eight patients in whom no significant vessels were seen and the one patient in whom the crossing vessel was not associated with UPJ obstruction at helical CT, endopyelotomy was performed and UPJ obstruction was relieved, with no complications. Helical CT is useful for evaluation of vessels crossing the UPJ and for planning surgical management.

Adolescent↗

Lipopolysaccharide in combination with serum potentiates the stimulated activity of phospholipase D in human neutrophils via CD14.

The addition of fMet-Leu-Phe or phorbol 12-myristate 13-acetate to human neutrophils stimulates phospholipase D activity as evidenced by the release of phosphatidic acid and the generation of diacylglycerol, and in the presence of ethanol the formation of phosphatidyl ethanol. The activation of phospholipase D by either the chemotactic factor or active phorbol ester is inhibited by the tyrosine kinase inhibitor erbstatin. The fMet-Leu-Phe-induced stimulation of this enzyme is greatly potentiated in cells which have been preincubated with low concentrations of lipopolysaccharide and serum. The presence of serum is essential for the potentiation by low concentrations of lipopolysaccharide. Moreover, the monoclonal antibody MY4(IgG2b) against CD14 inhibits the potentiation by the low concentration of lipopolysaccharide. These data suggest three important points. First, a tyrosine kinase step is necessary for the activation of phospholipase D. This suggests that the phospholipase D enzyme needs to be phosphorylated on tyrosine residues to be activated. Second, low concentrations of lipopolysaccharide, in the presence of serum, can potentiate the stimulated activity of this enzyme. Third, the priming action of the lipopolysaccharide-serum complex is mediated by CD14.

Adult↗

CT and MR findings of splenic angiosarcoma.

A surgically confirmed primary splenic angiosarcoma is described. Although angiography showed most of the characteristic findings of the present patient, MR imaging provided a useful information as a supplemental tool. The tumor demonstrated low-signal intensity on both T1- and T2-weighted images, which might differ from hemangioma findings. Subacute hemorrhage within the tumor was revealed by MR imaging, suggesting the way in which the tumor grew during a short period of time. This finding was different from reported angiosarcoma MR findings of siderotic nodules within the tumor. After the administration of Gd-DTPA, MR images clearly demonstrated heterogeneous enhancement within the tumor, which corresponded to the pathologic findings of solid parenchyma with necrotic tissues.

Contrast Media↗

Attenuation changes in periportal region during triple-phasic contrast-enhanced CT.

OBJECTIVE: To evaluate attenuation changes in the periportal regions of the liver during triphasic contrast CT. MATERIALS AND METHODS: The study group consisted of 93 patients, all of whom underwent triphasic contrast-enhanced CT with a helical scanner for survey of liver disease. The three phases included the arterial phase, portal venous phase, and equilibrium phase. Attenuation changes in the periportal area in each phase were evaluated in every patient. Factors surmised to be related with periportal low attenuation, including elevation of venous pressure, presence of ascites, cardiac enlargement, and lymphadenopathy of the porta hepatis and lesser omental region, were also evaluated. RESULTS: Periportal low attenuation was seen in 65 patients (69.8%) in the portal venous phase where the liver parenchyma showed the largest attenuation value. Among them, periportal low attenuation was continuously observed in every phase in 13 patients (13.9%), while it was confirmed only in the portal venous phase in 28 patients (30.1%), and in 24 patients (32.2%) in the portal venous phase plus either the arterial or equilibrium phase. None of the factors that were investigated could be related to the appearance of periportal low attenuation. CONCLUSION: Periportal low attenuation was a relatively common finding in the portal venous phase of triphasic contrast CT, whereas it was less usual in the arterial or equilibrium phase.

Adult↗

Cavernous hemangioma with arterioportal and arterio-hepatic vein shunts coexisting with hepatocellular carcinoma.

A patient with hepatocellular carcinoma (HCC) and coexisting hepatic cavernous hemangiomas with arterioportal and arterio-hepatic vein shunts is reported. Antegrade and retrograde opacifications of portal vein radicles and filling of a branch of the right hepatic vein verging on cavernous hemangiomas were observed in the late arterial phase of hepatic arteriography in addition to HCC. Unenhanced CT scans performed eight days after the arterial infusion of Lipiodol showed clearly the location of the tumors and the shunting vessels. To the authors' knowledge, this is the first reported case of cavernous hemangioma with arterioportal and arterio-hepatic vein shunts accompanied by hepatocellular carcinoma.

Angiography↗