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E Tanaka

Publications and source records attributed to E Tanaka.

At least 577 records · Page 32Linked to original sources
PubMed1984

Convolutional image reconstruction for quantitative single photon emission computed tomography.

Two image reconstruction algorithms have been investigated. They are based on filtered backprojection, and are useful when the tissue attenuation is considered to be uniform in the object. The first method uses a weighted backprojection, the weighting factor being determined in such a way that the photon attenuation is compensated with low noise propagation. The parameters involved in the convolution kernel and the correction function were determined by a computer iteration program. The second method, which is a simplified version of the first, uses conventional backprojection, and takes a shorter computation time than the first method. The statistical noise of an image can be minimised by suitable positioning of the coordinate origin for the reconstruction. The theory of the two methods, their performance on statistical noise and some results of mathematical and experimental phantom studies are described.

Mathematics↗
PubMed1984

A method for estimation of hepatic drug-metabolizing capacity: determination of concentration of trimethadione and its metabolite in human serum.

There have been significant correlations between serum concentration ratios of 5,5-dimethyl-2,4-oxazolidinedione (Dimethadione, DMO)/trimethadione (TMO) after administration of TMO and hepatic microsomal cytochrome P-450 contents in rats with various treatments (CCl4 or phenobarbital). The pharmacokinetics of TMO and DMO, and the serum concentration ratio of DMO/TMO have been investigated in healthy volunteers after oral administration of 1 mg/kg (N = 4), 2 mg/kg (N = 6) and 4 mg/kg (N = 6) TMO, respectively. TMO and DMO concentrations in serum were determined by a gas-liquid chromatographic method. Serum disappearance of TMO was described by one compartment model. The T1/2, Kel, Vd and C1 of TMO and of DMO were shown to have almost the same values in 2 mg/kg or 4 mg/kg TMO administration. Correlation coefficient between DMO/TMO ratio in serum and time course after 1 mg/kg, 2 mg/kg and 4 mg/kg TMO administration was found to be r = 0.958, r = 0.924 and r = 0.938, respectively. These results indicate that the serum concentration ratio of DMO/TMO, especially at 2 or 4 h after 4 mg/kg TMO administration orally, may be an index of hepatic drug-metabolizing capacity in human serum as well as in rats.

Adult↗
PubMed1984

The protective effect of cysteine on chemical-induced liver injury in rats.

The possible protective effect of cysteine on chemical-induced liver injury was studied in rats in vivo and in vitro. There was no increase in the activity of serum glutamic oxaloacetic transaminase (GOT) of rats pretreated with cysteine (1.2 g/kg, p,o.) followed by 0.25 ml/kg carbon tetrachloride (CCl4), d-galactosamine (GalN) or alpha-naphthylisothiocyanate (ANIT). However, rats pretreated with cysteine followed by 0.5 ml/kg CCl4 were not protected. The content of cytochrome P-450, activity of aminopyrine N-demethylase or serum ratio of 5,5-dimethyl-2,4-oxazolidinedione (DMO) to trimethadione (TMO) (DMO/TMO ratio) after CCl4, GalN or ANIT were not altered by pretreatment with cysteine. However, pretreatment with cysteine prevented changes in the content of cytochrome P-450, activity of aminopyrine N-demethylase and DMO/TMO ratio in serum as well as the activities of serum GOT and GPT when the rats were treated with bromobenzene (BZ). The degree of lipid peroxidation from CCl4 was markedly reduced by the presence of 10(-4)M cysteine. These results suggest that cysteine has a protective effect on chemical-induced liver injury produced via epoxide metabolites.

Alanine Transaminase↗
PubMed1984

Effects of allyl alcohol and bromobenzene on trimethadione metabolism in the rat.

The relationship between the serum concentration ratio of 5,5-dimethyl-2,4-oxazolidinedione (DMO) to trimethadione (TMO) and the cytochrome P-450-dependent drug-oxidizing enzyme activity in rats pretreated with different dose levels of bromobenzene (BZ) and allyl alcohol (AA) was investigated. Pretreatment of rats with increasing dose levels of BZ and AA resulted in a prolongation of TMO half-life, an increase in the area under the curve (AUC), a decrease in clearance (Cl) and a decrease in the apparent volume of distribution (Vd). At each dose of BZ and AA used, there was a good correlation between DMO/TMO ratios in serum and activities of hepatic cytochrome P-450-dependent drug-oxidizing enzymes, such as cytochrome P-450 content, aminopyrine N-demethylase, TMO N-demethylase and aniline hydroxylase activities. However, the correlation between the serum DMO/TMO ratio and the alcohol dehydrogenase activity in AA treated rats was poor, whereas the activity of this enzyme was not changed in BZ treated rats. These results, together with the previous findings, indicate that determination of the serum levels of TMO and DMO may a useful index of drug-oxidizing capacity of rats with hepatic necrosis specified regions.

1-Propanol↗
PubMed1984

Effect of atrial pacing on phase analysis in patients with the Wolff-Parkinson-White syndrome.

Phase analysis of ECG-gated radionuclide ventriculography was performed during sinus rhythm and atrial pacing for 11 patients with the Wolff-Parkinson-White (WPW) syndrome. During sinus rhythm, phase analysis demonstrated abnormal early-emptying segments reflecting preexcitation in six of the 11 patients. In the remaining five patients, the precise site of abnormal early-emptying could not be detected. Atrial pacing increased the degree of pre-excitation, and abnormal early-emptying segments became clear in all patients. Our study demonstrated the utility of atrial pacing in performing phase analysis for patients with the WPW syndrome. Seven patients had abnormal early-emptying segments; four of them with ECG type A, in the left ventricle, and three of them with ECG type B, in the right ventricle. These results were consistent with results of the body surface and electrophysiologic mapping. In patients with posterior septal accessory pathways, phase analysis suggested probable laterality of the accessory pathway.

Adolescent↗
PubMed1983

A two-site sandwich radioimmunoassay of human fibroblast (beta-) interferon with monoclonal antibodies.

Monoclonal antibodies were produced against human fibroblast (beta-)interferon (IFN-beta). Four of them were directed to the determinant designated a, while the remaining 3 to another determinant named b. An IFN molecule was found to bear one each of a and b determinants arranged in such a manner that the occupation of a with the corresponding antibody did not interfere with the binding of b to its corresponding antibody, and vice versa. This allowed the development of a 2-site sandwich radioimmunoassay in which antibody to b was immobilized on wells of a microtiter plate and the bound antigen was detected by the radiolabeled antibody to a. The 2-site sandwich radioimmunoassay detected, with a high sensitivity, IFN-beta either induced from fibroblast or produced by Escherichia coli harboring the gene of IFN-beta.

Animals↗
PubMed1983

Ca2+, calmodulin-dependent phosphorylation of glycogen synthase by a brain protein kinase.

A Ca2+, calmodulin-dependent protein kinase from brain with a Mr of 640 000 is capable of phosphorylating glycogen synthase from skeletal muscle. The reaction was inhibited by the addition of 1 mM EGTA and 50 microM trifluoperazine, but not by protein kinase inhibitor and heparin. The amount of phosphate incorporated into glycogen synthase was 1.4 mol/mol subunit. The phosphorylation sites of glycogen synthase were cyanogen bromide-treated peptides CB-1 and CB-2 and only the seryl residue was phosphorylated.

Animals↗
PubMed1983

Quantitative image reconstruction with weighted backprojection for single photon emission computed tomography.

A new method of image reconstruction for single photon emission computed tomography is presented. The method is basically a filtered backprojection with some modifications. The algorithm consists of three steps: normalization of observed projections, modified convolution operation, and weighted backprojection. The weighting function for backprojection is determined to provide perfect attenuation compensation for a uniform attenuation medium and to keep the statistical noise in the reconstructed image low. The relative contributions of two conjugate projections to the image can be controlled by the reconstruction parameters, enabling improvement of the signal-to-noise ratio and spatial resolution at off-center area compared with the conventional averaging method of two conjugate projections. Simulation studies indicated that the method provides a satisfactory image for an extended source of 99mTc (mu = 0.15 cm-1) having a diameter of up to approximately 35 cm. A myocardium phantom is adequately reconstructed from a 180 approximately 225 degrees angle scan. The effect of nonuniform attenuation medium surrounding the source region can be corrected. This paper presents the mathematical basis of the procedure, the evaluation of the statistical noise, and some illustrative computer simulations.

Image Enhancement↗
PubMed1983

Ca2+- and calmodulin-dependent phosphorylation of microtubule-associated protein 2 and tau factor, and inhibition of microtubule assembly.

Microtubule-associated proteins (MAPs) were phosphorylated by a Ca2+- and calmodulin-dependent protein kinase from rat brain cytosol. The maximal amount of phosphate incorporated into MAPs was 25 nmol of phosphate/mg protein. A Ka value of the enzyme for calmodulin was 57.0 nM, with MAPs as substrates. Among MAPs, MAP2 and tau factor were phosphorylated in a Ca2+- and calmodulin-dependent manner. The phosphorylation of MAPs led to an inhibition of microtubule assembly in accordance with its degree. This reaction was dependent on addition of the enzyme, Ca2+, and calmodulin, and had a greater effect on the initial rate of microtubule assembly rather than on the final extent. The critical tubulin concentration for microtubule assembly was unchanged by the MAPs phosphorylation. Therefore assembly and disassembly of brain microtubule are regulated by the Ca2+- and calmodulin-dependent protein kinase that requires only a nanomolar concentration of calmodulin for activation.

Adenosine Triphosphate↗
PubMed1983

Relationship between trimethadione metabolism and hepatic drug-oxidizing enzyme activities in different animal species.

The purpose of this investigation is to correlate between trimethadione (TMO) metabolism and hepatic microsomal drug-oxidizing activities in different animal species (mouse, hamster, rat and rabbit). A good correlation was obtained between the plasma concentration ratio of 5,5-dimethyl-2,4-oxazolidinedione (DMO) to TMO and relative activities of aminopyrine (r = 0.999 at 1 h, p less than 0.01; r = 0.994 at 2 h, p less then 0.01) and TMO (r = 0.988 at 1 h, p less than 0.02; r = 0.975 at 2 h, p less than 0.05) N-demethylase, and aniline (r = 0.993 at 1 h, p less than 0.01; r = 0.979 at 2 h, p less than 0.01) hydroxylase. These results indicate that the values of plasma DMO/TMO ratio determined at an appropriate time period following its administration would be reflecting the degree of hepatic drug-oxidizing capacity in various experimental animal species. These findings thus suggest that in vivo TMO metabolism would be a useful drug for predicting hepatic drug-oxidizing capacity in humans.

Animals↗
PubMed1983

Optokinetic functions and optokinetic after-nystagmus-producing mechanism in the monkey.

Optokinetic nystagmus (OKN) and after-nystagmus (OKAN) were investigated in monkeys subjected to conventional and reversed optokinetic stimulation. The decreasing patterns of OKAN slow phase speed (SPS) changed from a straight to a catenary-like pattern with increased stimulus speed. The total duration, however, of the first and second phases remained unchanged. Immediately after a sudden reversal of the stimulus direction, neither OKAN nor OKN was induced; the slow rising portion of OKN SPS became 1.2-1.6 times longer than that of the usual OKN. Since OKN inhibition after stimulation reversal shared similar characteristics with the slow rise of OKN SPS in the light and with the decrease of OKAN SPS in the dark, all of these can be regarded as adaptive processes of the after-nystagmus-producing mechanism.

Animals↗
PubMed1982

Effect of correction function on image characteristics of Positologica: a positron CT device for the head.

The effects of correction function on image characteristics were studied experimentally for a positron CT device Positologica. Correction functions were obtained by smoothing the Shepp and Logan function by convolution of Gaussian functions. Signal-to-noise ratio (SNR) and spatial resolution were measured for phantoms and related to the magnitude of smoothing. The relation between SNR and spatial resolution is also discussed. Some suggestions are made to indicate how to select correction functions for clinical images. A flow of data processing for Positologica is described together with an outline of its hardware.

Computers↗
PubMed1982

Analytical study of the performance of a multilayer positron computed tomography scanner.

The image-forming performance of multilayer positron tomographs for extended sources is evaluated analytically. The analysis is simplified by "rotation transform," by which three-dimensional photon detection problems are solved by two-dimensional treatment. Event rates of singles, unscattered true coincidence, and a single- and double-scattered coincidence are formulated for a uniform cylinder phantom as functions of various design parameters. Angle factors for Compton scattering and other parameters used in the evaluation are presented. Scatter components in projections and their effect on the reconstructed images are also evaluated. The scatter component in the reconstructed image depends critically on the detector ring radius, phantom radius, method of attenuation correction, etc. When the director radius is relatively small (40 or approximately 45 cm in diameter), the scatter/true ratio at the image center of a 20 cm diameter phantom may be larger than the scatter/true ratio in the event rates. Comparison with experimental data obtained with a head positron tomograph, POSITOLOGICA, showed reasonable agreement both in the total coincidence rates and in the scatter components in the images for a cylindrical phantom of 20 cm in diameter.

Mathematics↗