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Biomedical subjects

N Yui

Publications and source records attributed to N Yui.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cytoplasmic calcium level and membrane fluidity of platelets contacting poly(acrylamide-co-methacrylic acid) particles with different surface properties.

Changes in cytoplasmic free calcium levels and membrane fluidity of platelets in contact with poly(acrylamide-co-methacrylic acid) (PAAmMAc) particles were examined to analyze the mechanistic aspect of regulating platelet function. Our previous studies demonstrated interesting features of PAAmMAc particles during interaction with platelets: (1) PAAmMAc particles induce no calcium increase but enhance membrane fluidity of platelets: (2) thrombin induces no calcium increase in platelets when the platelets were mixed previously with PAAmMAc particles; and (3) PAAmMAc particles induce a calcium increase in platelets when they were treated previously with sodium azide (NaN3). These results suggest the possibility that PAAmMAc surfaces may regulate the calcium level by influencing platelet metabolism. In this study, non-cross-linked PAAmMAc solution with the same chemical composition as the particles showed a suppressive effect on thrombin-induced calcium increase, but, no influence on membrane fluidity. This result indicates that aggregated macromolecular surface assemblies of PAAmMAc may dominate the increase in membrane fluidity of platelets although the calcium change is induced by discrete molecular level interaction between the PAAmMAc and platelet membranes. It was also revealed that the suppression of thrombin-induced calcium increase and the membrane fluidity increase in platelets by PAAmMAc particles were reduced by albumin-treatment of the particles. This result suggests that such phenomena may be due to a decrease in any physicochemical interaction of PAAmMAc surfaces with albumin, rather than platelet metabolic change. PAAmMAc particle surfaces with higher carboxyl groups exhibited a more suppressive effect on thrombin-induced calcium increase, whereas those with lower carboxyl groups derived a higher calcium increase when the platelets were treated previously with NaN3. These results suggest the importance of electrostatic and any other physicochemical interaction of PAAmMAc chains on regulating cytoplasmic calcium levels.

Acrylic Resins↗
PubMed1995

[A study on thallium-201 SPECT in brain metastases of lung cancer: with special reference to tumor size and tumor to normal brain thallium uptake ratio].

Thallium-201 brain SPECT was performed on 20 patients with brain metastases of lung cancer using a three-head rotating gamma camera and the effect of tumor size on tumor detectability and tumor to normal brain thallium uptake ratio (T/N ratio) was studied. Among 71 metastatic lesions, only 9 (22.5%) of 40 lesions of 13 mm diameter or below and 31 (100%) of 31 lesions of 14 mm diameter or above could be detected in this study. There was a significant correlation between T/N ratio and tumor size (r = 0.75, p < 0.001). The greater the metastatic lesion, the higher the T/N ratio. Even among the tumors in a single patient with multiple brain metastases, there was a significant linear correlation between tumor size and T/N ratio (r = 0.96, p < 0.01). In this patient, T/N ratio varied by the tumor size and these differences in T/N ratios were thought to be based on the partial volume effect. However, T/N.d which was a parameter corrected by tumor diameter (d) showed a constant value regardless of tumor size. The present results showed that T/N ratio, which was usually believed to quantitate the malignancy grade of brain tumor, was affected by tumor size and that more accurate parameter could be obtained by the correction of T/N ratio by tumor size.

Adenocarcinoma↗
PubMed1994

[Fat suppression failure artifacts at the susceptibility interface on frequency selective fat suppression MR imaging in the head and neck].

Fat suppression MR imaging is a valuable technique mainly used for the orbit, head and neck, and spine, where the high signal from fat can often obscure adjacent pathology. Fat suppression failure artifact manifested as a high signal area without geographic distortion. The purpose of this study was to investigate the frequency and common location of these artifacts in clinical MR imaging and to caution against their misinterpretation. Fat suppression MR imaging of the head and neck was performed in 30 consecutive patients. The artifact was found in the orbital floor (57%), the skull base (10%), and subcutaneous fat (10%), where the air-fat interface is parallel to the static magnetic field direction. The fat signal in the air-fat interface perpendicular to the static magnetic field was well suppressed. This artifact was independent of the duration of TE, frequency/phase encoding direction, and the strength of gradient amplitude, and appeared to be related to the amount of surrounding air. This may simulate pathology if fat suppression is only performed following Gd-DTPA administration. The radiologist should be aware of the presence of artifact by considering the geographic relation to the static magnetic field.

Adipose Tissue↗
PubMed1994

Postadsorptive behavior of plasma proteins on poly(propylene oxide)-segmented nylon-610 surfaces and its implication in preventing contact-induced activation of platelets on these surfaces.

The influence of adsorbed plasma proteins on preventing contact-induced activation of platelets on poly(propylene oxide) (PPO)-segmented nylon-610 surfaces was investigated by monitoring changes in cytoplasmic free Ca2+ concentrations in platelets and adsorption/desorption of albumin and fibrinogen on these copolymer surfaces. Direct measurement of cytoplasmic free Ca2+ concentration in platelets in contact with copolymer surfaces was achieved by monitoring spectral changes of a fluorescent indicator dye, Fura 2. These copolymers were characterized by a surface microstructure composed of coexisting crystalline and amorphous phases. An increase in cytoplasmic free Ca2+ concentration in platelets interacting with polymer surfaces was observed, and this increase was found to be strongly reduced both by the adsorption of plasma proteins into the polymer surface and by modifying the surface microstructure of the polymer itself. Transient changes in cytoplasmic free Ca2+ concentration were observed in platelets in contact with the surface of copolymer 61P3-25, which exhibited excellent nonthrombogenicity in our previous studies, depending on the residence time of plasma and plasma concentration. Additionally, adsorption/desorption of albumin and fibrinogen on copolymer surfaces was estimated using 125I-labeled proteins. Exchange of the adsorbed albumin with fibrinogen and minimum fibrinogen adsorption were observed particularly on the 61P3-25 surface. Exchange of adsorbed fibrinogen with plasma proteins and/or increased fibrinogen adsorption were also observed on all other polymer surfaces examined. Finally, we conclude that controlled formation of a defined protein adsorption layer on the 61P3-25 surface via the transient exchange of adsorbed albumin with fibrinogen from plasma, can be a dominant factor in preventing platelet adhesion and activation on this surface.

Adsorption↗
PubMed1994

[Clinical usefulness of thallium-201 chloride in the diagnosis of tumors (I)--Evaluation in brain tumors].

Forty-eight patients with suspected brain tumor were studied to evaluate the clinical efficacy of Thallium-201 (201Tl) SPECT. 201Tl scintigrams showed abnormal accumulation in 24/26 (92.3%) and 9/14 (64.3%) of patients with malignant and benign tumors, respectively. 201Tl tended to be retained more prominently in malignant brain tumors than in benign ones. The lesion-to-normal ratios (L/N ratios) of 201Tl demonstrated significant correlation with those of 18F-FDG (n = 5, r = 0.90, p = 0.044). L/N ratios were higher in patients with recurrent tumors than those with necrotic lesions (3.33 +/- 0.81 and 1.73 +/- 0.81, respectively, p = 0.0123). The positive predictive value of L/N ratios > or = 2.5 for diagnosing as recurrence and L/N ratios < 2.5 as necrosis were 83.3% and 100%, respectively. These results suggest that 201Tl scintigraphy may be useful to determine the malignancy of brain tumors and to differentiate recurrence from necrosis after therapeutic procedures.

Adolescent↗
PubMed1994

[Clinical usefulness of thallium-201 chloride in the diagnosis of tumor (II)--An evaluation in bone, soft tissue and mediastinal tumors].

The clinical usefulness of scintigraphy with thallium-201 (201Tl) chloride injection was evaluated in 79 patients with suspected bone, soft tissue or mediastinal tumors. No abnormal changes of subjective or objective signs and clinical test values were observed post injection. It is considered that 201Tl chloride is a safe radiopharmaceutical. In comparison with benign tumors, malignant tumors showed longer retention or more increased uptake of the 201Tl in the lesions on delayed images. The results suggested that the evaluation of changes of 201Tl uptake might be useful to some extent to differentiate malignant tumor from benign tumor. It is considered that 201Tl scintigraphy is useful for evaluating the location and extent of tumor and differentiating malignant from benign tumor.

Adolescent↗
PubMed1993

Prevention of changes in platelet cytoplasmic free calcium levels by interaction with 2-hydroxyethyl methacrylate/styrene block copolymer surfaces.

Changes in platelet cytoplasmic free calcium levels were investigated in contact with cast film surfaces of a block copolymer containing 2-hydroxyethyl methacrylate (HEMA) and styrene (St) (0.5 mole fraction HEMA). These copolymer surfaces demonstrate microdomain alternating lamellae structures composed of hydrophilic HEMA domains (5 nm width) and hydrophobic St domains (20 nm width). The results were compared with those obtained from platelets contacting a random copolymer of HEMA-St (0.5 mole fraction HEMA) and from homopolymers of polystyrene (PSt) and poly(2-hydroxyethyl methacrylate) (PHEMA). Cytoplasmic free calcium levels in platelets contacting the microdomain structured surfaces of the HEMA-St block copolymer remained relatively constant in contrast to the significant increases observed for the radically prepared HEMA-St copolymer, PSt, and PHEMA surfaces. Adhering platelets were stimulated by exogenously introduced thrombin and calcium ionophore A23187 20 min after platelet adherence to the polymer surfaces. Only platelets on the block copolymer surfaces showed active metabolic responses. These results suggest that adhering platelets on the microdomain structured surfaces maintain high sensitivities to external stimulation due to an intrinsic strong inhibition of platelet functional changes induced by surface contact.

Blood Platelets↗
PubMed1993

Optimization of Butterworth filter for brain SPECT imaging.

A method has been described to optimize the cutoff frequency of the Butterworth filter for brain SPECT imaging. Since a computer simulation study has demonstrated that separation between an object signal and the random noise in projection images in a spatial-frequency domain is influenced by the total number of counts, the cutoff frequency of the Butterworth filter should be optimized for individual subjects according to total counts in a study. To reveal the relationship between the optimal cutoff frequencies and total counts in brain SPECT study, we used a normal volunteer and 99mTc hexamethyl-propyleneamine oxime (HMPAO) to obtain projection sets with different total counts. High quality images were created from a projection set with an acquisition time of 300-seconds per projection. The filter was optimized by calculating mean square errors from high quality images visually inspecting filtered reconstructed images. Dependence between total counts and optimal cutoff frequencies was clearly demonstrated in a nonogram. Using this nomogram, the optimal cutoff frequency for each study can be estimated from total counts, maximizing visual image quality. The results suggest that the cutoff frequency of Butterworth filter should be determined by referring to total counts in each study.

Brain↗
PubMed1993

Visualization of nasopharyngeal carcinoma with Tl-201 chloride and a three-head rotating gamma camera SPECT system.

Tl-201 SPECT was performed on 12 patients with nasopharyngeal carcinoma (NPC) by means of a three-head rotating gamma camera to evaluate whether or not Tl-201 SPECT was useful and reliable for assessing the tumor viability of NPC. Tl-201 clearly accumulated in the tumor in 3 patients before radiation treatment and increased Tl-201 uptake by the lesion ceased after the treatment. Three of 9 patients who were followed up after radiotherapy developed apparent local recurrence and Tl-201 SPECT clearly visualized these recurrent lesions. Tl-201 SPECT was very useful for assessing the tumor response to irradiation and for detecting local recurrent tumor. A high resolution SPECT system employing Tl-201 chloride is a new reliable and accurate diagnostic tool for the assessment of NPC.

Adult↗
PubMed1993

Usefulness of bone SPECT of the cervical spine: with special reference to separate visualization of the trachea and thyroid cartilage.

We applied bone SPECT for the examination of the cervical spine. A three-head rotating gamma camera SPECT system was employed for this study. The SPECT image disclosed 42.7% of abnormal accumulations in the skeleton not seen with planar imagings. SPECT could separately visualize the trachea and thyroid cartilage and also provided interpretation of abnormality in the anterior part of the vertebral body being difficult with planar imagings only. The trachea cartilage was seen in 55.4% and the thyroid cartilage was seen in 47.3% of patients with anterior neck density in planar imagings. SPECT clarified that marked cervical curvature and diffuse high uptake by the skeleton might cause high intensity of the anterior neck in planar imagings in the case of non-pathological change. We concluded that bone SPECT is a useful diagnostic tool in detecting occult lesion in the skeleton and to rule out extraskeletal accumulations in examination of the cervical spine.

Adult↗
PubMed1993

Demonstration of abnormal perfusion in the pons with high resolution SPECT and technetium-99m HMPAO in a patient with acoustic neuroma.

We detected a regional defect in the pons with ipsilateral cerebellar hypoperfusion in a patient with acoustic neuroma by brain SPECT with 99mTc HMPAO. A high spatial resolution SPECT system with three detectors equipped with fan-beam collimators was employed. This is the first report of a defect in the brainstem being visualized by perfusion SPECT and this method could make it possible to clarify the cause of a remote effect on the cerebellar perfusion by injury to the brainstem.

Cerebellum↗
PubMed1993

Mechanism of cytoplasmic calcium changes in platelets in contact with polystyrene and poly(acrylamide-co-methacrylic acid) surfaces.

Changes in cytoplasmic free calcium levels ([Ca2+]i) in platelets in contact with polystyrene (PSt) and poly(acrylamide-co-methacrylic acid) (PAAmMAc) particles were evaluated and results were compared with those from two representative biological calcium agonists; thrombin and calcium ionophore A23187. PSt particles stimulated a steep increase in cytoplasmic calcium levels in platelets as much as thrombin and A23187. Serratia protease-treated platelets showed a steep increase in [Ca2+]i by PSt particles, suggesting that PSt surfaces can initiate platelet activation independent of a glycoprotein Ib (GPIb)-mediated pathway. By contrast, dibucaine-treated platelets showed little increase in [Ca2+]i by PSt particles, indicating that microfilament assembly, including binding of GPIb with actin binding protein, should be required for platelet activation in contact with PSt surfaces. PAAmMAc particles induced little increase in cytoplasmic calcium levels in platelets. However, PAAmMAc particle-treated platelets demonstrated little response to thrombin in terms of an increase in [Ca2+]i and ATP release, suggesting the possibility that PAAmMAc surfaces may regulate [Ca2+]i by influencing platelet metabolism. Furthermore, sodium azide-treated platelets showed an increase in [Ca2+]i in platelets when contacting PAAmMAc particles, supporting the suggestion that PAAmMAc surfaces could regulate platelet functions. Fluorescence polarization measurements using 1,6-diphenyl-1,3,5-hexatriene-loaded platelets revealed that PAAmMAc particles increased membrane fluidity in platelets, which may be due to physicochemical interaction with PAAmMAc surfaces.

Acrylic Resins↗
PubMed1992

[Assessment of skull base involvement of nasopharyngeal carcinoma by bone SPECT using three detectors system].

SPECT of the skull was performed on twelve patients with histologically proven nasopharyngeal carcinoma using newly developed three detectors SPECT system (Toshiba GCA 9300A) mounted with fan-beam collimators, for the purpose of early detection of skull base involvement of the disease. This SPECT system has extremely improved resolution with FWHM of 8 mm in the center, and it provides clear tomographic images of the skull which has anatomically complex structure. SPECT image was taken 3 hours after injection of 740 MBq (20 mCi) of 99mTc-MDP following whole body skeletal survey. In twelve patients with confirmed nasopharyngeal carcinoma, 8 patients showed positive findings on SPECT. Three of SPECT positive patients also showed destructive findings on CT. Other five positive patients did not show destructive findings on CT at their initial examinations, but in three of them CT findings turned to positive later. SPECT was superior to CT in early detection of skull base involvement. We believe that SPECT of the skull is a diagnostic tool for early detection of skull base involvement of nasopharyngeal carcinoma.

Adult↗
PubMed1991

Quantitative measurement of uptake of radiolabeled monoclonal antibody by means of planar data.

Data obtained from planar images were used to measure the uptake of monoclonal antibody in organs and tumors. Background counts included in the region of interest were eliminated, and the attenuation of the photons emitted by the radionuclide through the intervening tissues was compensated for. The background counts and the intensity of the attenuation were determined from the results of phantom studies and numerical integration with a personal computer. The quantitative uptake of 111In labeled anti-melanoma Monoclonal Antibody (ZME-018) in a melanoma lesion, the liver, and the bone marrow of a patient was measured by the planar method which we developed.

Antibodies, Monoclonal↗
PubMed1991

Performance of a multislice fan beam collimator for SPECT imaging of the head.

A multislice fan beam collimator was designed for a SPECT system with a rotating scintillation camera, and it was constructed by the lead casting method which was devised in recent years. The focal length from the surface of the detector side of the collimator is 75 cm. In order to reconstruct the SPECT images we modified the interpolation method which was developed for reconstruction of the X-ray CT and applied it. Primary photopeak data were obtained with a 20% energy window centered at 140 keV for 99mTc and 159 keV for 123I. The fan beam collimator reduces the field of view, and it would therefore be limited to use only for the head and neck region at present; however, both resolution and sensitivity were approximately 20% better than those of the parallel hole collimator. A fan beam collimator is a useful implement for the SPECT study.

Equipment Design↗
PubMed1991

[Diagnosis of pancreatic cancer using 201Tl-chloride and a three-head rotating gamma camera SPECT system].

201Tl SPECT was performed on 17 patients with pancreatic cancer or chronic pancreatitis using a three-head rotating gamma camera SPECT system. In 7 of 10 patients with pancreatic cancer, the lesions were clearly delineated by 201Tl SPECT. Whereas the lesion of 30 mm in diameter was visualized, a large tumor of 80 mm in diameter could not be visualized. Namely, it was thought that 201Tl uptake by pancreatic cancer might be well correlated with tumor blood flow and/or its histological subtype rather than with tumor size. In 5 of 7 patients with chronic pancreatitis, no uptake by the pancreas was shown. The sensitivity, specificity, and accuracy in diagnosing pancreatic cancer by 201Tl SPECT were 70%, 71%, and 71%, respectively. The present results obtained by 201Tl SPECT were thought satisfactory enough to evaluate pancreatic cancer under the present conditions where there was no useful imaging agent for visualizing pancreatic cancer by SPECT. 201Tl SPECT is expected to be a new diagnostic tool for investigation of pancreatic tumorous lesion.

Adenocarcinoma↗