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Biomedical subjects

H Toyama

Publications and source records attributed to H Toyama.

At least 181 records · Page 10Linked 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

Differentiation of mycobacterial species by investigation of petroleum ether-soluble sulfolipids using thin-layer chromatography after incubation with [35S]sulfate.

The method of detecting petroleum ether-soluble sulfolipids by thin-layer chromatography after incubation with [35S]sulfate is useful for differentiation between mycobacterial species. Rapidly growing mycobacteria, including two subspecies of Mycobacterium chelonei, were differentiated by this method. Most species of slowly growing mycobacteria were characterized by the pattern of distribution of radioactive sulfolipids in the thin-layer chromatograms. Mycobacterium nonchromogenicum was clearly differentiated from Mycobacterium terrae and Mycobacterium triviale by the presence of a sulfolipid. The latter two did not contain any significant amount of sulfolipids. Mycobacterium avium contained a large amount of sulfolipids, whereas Mycobacterium scrofulaceum did not contain any detectable sulfolipid. Rapidly growing, scotochromogenic mycobacteria, except for Mycobacterium flavescens, did not contain any remarkable amounts of sulfolipids.

Chromatography, Thin Layer↗
PubMed1984

Protoplast Fusion of Trichoderma reesei, Using Immature Conidia.

Protoplast fusion of strains derived from Trichoderma reesei QM9414 and QM9136 and the segregation of the resulting fusants were studied. Combinations of protoplasts prepared from young conidia with double amino acid requirements, one of which was a common requirement and the other uncommon, were fused in the presence of polyethylene glycol 6000. Fusants were selected as regenerant colonies requiring only the commonly deficient amino acid. The frequency of fusion was 0.9 x 10 to 4.0 x 10 for the starting conidia and 3.0 x 10 to 4.9 x 10 for the regenerated protoplasts, which was significantly higher than the expected reversion frequencies by mutation. Conidia generated on the fusant colonies showed diverse phenotypes, i.e., parental types (40 to 80%) and nonparental types (20 to 60%). Colonies developed from single conidia of the nonparental phenotype contained special spots called "knobs" that have a higher density of mycelia. The phenotype of the knobs was again varied among prototrophs, parental types, and recombinant types; and their traits were inherited stably. The phenotype of the mycelia in the nonknob part was essentially the same as that of the original conidia and again formed knobs in colonies upon transfer of a piece of mycelia to a fresh medium. The conidial DNA content of the knob clone was almost the same as that of the parents, but that of the fusants was 1.2 to 2.0 times higher than that of the parents. From these results, we conclude that knobs are the segregants from the fusants. One knob clone showed twice the carboxymethyl cellulose hydrolyzing activity of the parents, suggesting the possibility of breeding T. reesei cells by the protoplast fusion technique.

Journal Article↗
PubMed1984

Susceptibility of hepatitis B virus to disinfectants or heat.

Using direct chimpanzee inoculation as an assay method, we tested the abilities of the following chemical or physical treatments to inactivate hepatitis B virus in human plasma: 1% aqueous glutaraldehyde at 24 degrees C for 5 min, 0.1% aqueous glutaraldehyde at 24 degrees C for 5 min, 80% ethyl alcohol at 11 degrees C for 2 min, and heat at 98 degrees C for 2 min. All treatments were shown to be effective, indicating that the resistance level of the hepatitis B virus is not extreme.

Aldehydes↗
PubMed1983

A new method for quantitative analysis of thallium-201 myocardial image-"corrected" circumferential profile method.

A new method for computer-assisted quantitative analysis of a thallium (Tl)-201 myocardial image ("corrected" circumferential profile method) was described. Since the Tl-201 myocardial image of a normal subject is not homogeneous, an attempt was made to correct for this non-homogeneity. Three groups of subjects were studied, including 10 normal volunteers (group A, mean age of 27.5 years), 14 patients with atypical chest pain and normal coronary arteriogram (group B, mean age of 56.7 years) and 16 patients with first transmural myocardial infarction (group C, mean age of 71.0 years). The myocardial images were acquired at rest at anterior, left anterior oblique (30 degrees and 60 degrees) and left lateral projections. With a scintigram, the left ventricle was outlined and divided into 24 radial segments by radii drawn from the center of the left ventricle. Average radioactivity per pixel in normal subjects was obtained in each segment and normalized to the highest segment (= 100%). The ratio of 100% to the mean of normalized radioactivity in percent in each segment from 10 normal volunteers was calculated and designated as a correction factor for each segment. After the correction of average radioactivity per pixel in each segment using this correction factor and after relating it to the highest radioactive segment, the mean (= 100%) and standard deviation (SD) were calculated and (100-4SD)% was defined as the normal lower limit. In the scintigram of groups B and C, "corrected" circumferential profiles were obtained from the regional radioactivity multiplied by the correction factor, normalized to the highest segment (100%) and compared with the lower normal limit. The ratio (%) of the area of patient's circumferential profile curve below the normal limit to the total area below the normal limit was obtained at each view and the sum of them was called the total "corrected" defect score. Infarct size analyzed by the "corrected" circumferential profile method correlated well with that analyzed by visual interpretation, and was useful in differentiating group C from group B.

Adult↗
PubMed1983

Cloning of antibiotic-resistance genes in Streptomyces.

Antibiotic-resistance genes were shotgun cloned from antibiotic-producing Streptomyces sp. using pock-forming plasmids (pSF689 and pSF765), as cloning vectors. Streptomyces chartreusis SF1623 and S. lividans 66 were used as host strains. The ribostamycin (RSM) resistance gene was cloned from S. ribosidificus SF733 DNA (on a 2.3 Md PstI fragment) into both S. chartreusis SF1623 and S. lividans 66, using pSF689 as vector. Kanamycin (KM), novobiocin (NB), destomycin (DM) and racemomycin (RM) resistance genes were cloned from S. kanamyceticus M1164, S. spheroides M1469, S. rimofaciens M1470 and S. lavendulae A249 genomic DNA into S. lividans 66, using pSF765 as vector. Furthermore two types of KM resistance determinants derived from S. kanamyceticus M1164 were cloned using S. lividans 66, the pSF689 vector. The RSM resistance gene showed no homology to plasmid pSF733 of S. ribosidificus SF733, but hybridized to PstI or BclI digested total DNA of S. ribosidificus SF733.

Anti-Bacterial Agents↗
PubMed1983

Pock forming plasmids from antibiotic-producing Streptomyces.

Pock forming ability of fifteen plasmids isolated from antibiotic-producing Streptomyces was examined with polyethylene glycol mediated protoplast transformation. Four plasmids (pSF765, pSF689, pSF674 and pSF601) were found to have pock forming ability on Streptomyces lividans 66. Each putative transformants isolated from the center of pock regions harbored plasmids with same restriction enzyme cleavage sites as original plasmids. The plasmids from the transformants produced pock, which were morphologically identical to the original plasmids. Transformation frequency of S. lividans 66 with pSF689 from S. lividans 66 was at least 500-fold higher (5 x 10(5) transformants per 1 microgram DNA) than that with the plasmid isolated from the original strain (10(3) transformants per 1 microgram DNA). In case of pSF765 the transformation frequency was not changed (about 10(5) transformants per 1 microgram DNA) by replications in S. lividans 66. Expanded restriction enzyme maps for the four plasmids are reported.

Anti-Bacterial Agents↗