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Biomedical subjects

A Kubo

Publications and source records attributed to A Kubo.

At least 307 records · Page 17Linked to original sources
PubMed1987

Shufflon: multi-inversion of four contiguous DNA segments of plasmid R64 creates seven different open reading frames.

The IncI alpha plasmid R64 was found to bear a highly mobile DNA segment which was designated as a clustered inversion region (J. Bacteriol. 165, 94-100, 1986). The clustered inversion region consists of four DNA segments designated respectively as A, B, C and D which differ in molecular size and restriction sites. The four DNA segments invert independently or in groups resulting in a complex DNA rearrangement. We now show the nucleotide sequence of the clustered inversion region of R64. The present results suggest that the clustered inversion region is a biological switch to select one of seven open reading frames whose primary structures at the region proximal to N-termini are constant while those at the C-terminal region are variable. A name, "Shufflon" was proposed to call this kind of the clustered inversion region.

Base Sequence↗
PubMed1987

Candidacidal activity of monocyte-derived human macrophages: relationship between Candida killing and oxygen radical generation by human macrophages.

Freshly isolated human monocytes ingested and killed Candida albicans, and generated O2- H2O2 and .OH efficiently. When monocytes were cultured in vitro, these cells transformed into macrophages. Cultured monocytes retained their ingestive activity but lost their candidacidal activity almost completely after day 3. The release of O2- by monocytes decreased slightly with culture and that of .OH was markedly decreased on day 3 of culture. The activity of myeloperoxidase in the monocytes decreased with culture. These results suggested that the loss of candidacidal activity is due to the decrease of .OH generation and myeloperoxidase activity in cultured monocytes.

Blood Physiological Phenomena↗
PubMed1987

The bactericidal mechanisms of polymorphonuclear leukocytes against Bacteroides fragilis: significance of the oxygen-dependent system.

The mechanism by which polymorphonuclear leukocytes (PMNs) kill ingested Bacteroides fragilis was examined using PMNs from patients with chronic granulomatous disease (CGD) which is an inherited disease characterized by the defect of their PMNs in oxygen-radical generation. The phagocytosis of B. fragilis by PMNs from CGD patients was comparable to that by normal PMNs. Although CGD cells killed B. fragilis to some extent, they did so less effectively than the normal PMNS. B. fragilis was killed by a xanthine oxidase system that generates oxygen radicals. When PMNs were incubated with opsonized B. fragilis, B. fragilis triggered the release of O2- and H2O2 from normal PMNs. Thus, normal PMNs appear to kill B. fragilis by both oxygen-dependent and oxygen-independent mechanisms.

Bacteroides fragilis↗
PubMed1987

[Experimental considerations of myocardial single photon emission CT image with a cardiac phantom].

We studied the quantity of thallium-201 myocardial single photon emission CT (SPECT) image with a cardiac phantom. The myocardial SPECT image is influenced by several causes, i.e., the absorption of gamma rays, collimator aperture, statistical noise and limited angle of rotation in data acquisition. The attenuation correction under the assumption of uniform distribution is not sufficient, so we have to consider the actual distribution of absorption. The effects of the nonuniform attenuation are most prominently appeared when we evaluate the quantity by the integral method. The aperture characteristics of a collimator are decided by the distance between the rotational center of the gamma camera and the collimator surface. Simultaneously scattered gamma rays affect the reconstructed image in the low frequency component, so the effective attenuation coefficient varies gradually. The statistical noise intermixed in the projection data generate artifacts like as lump-shaped pattern. The noise are clearly appeared in the spatial frequency upper than 0.25 cycle, so the low-pass filter are required with that of cut-off frequency. Moreover to enhance the details of the radionuclide distribution of cardiac muscle, the Wiener filter should be applied. The scan area also affects the appearance of the artifact in the myocardial SPECT image. The 180-degree scan usually generates false defects just nearby the center of reconstructed cross section. And the positions are changed with the conditions of gamma ray absorber and its relative position to the myocardial area. The 360-degree scan should be used from the standpoint of reconstructing more quantitative image.

Gamma Rays↗
PubMed1987

Comparative study on biological activities of heterocyclic quinones and streptonigrin.

Thirteen heterocyclic quinones (5 quinoline quinones, 7 isoquinoline quinones, 1 indole quinone) were tested for their effects on avian myeloblastosis virus reverse transcriptase, growth of murine lymphoblastoma L5178Y cells, respiration of rat liver mitochondria and oxidation of NADH by Clostridium kluyveri diaphorase in comparison with those of streptonigrin, in which the quinoline quinone moiety is considered to play a crucial role. Most of the quinoline quinones and isoquinoline quinones inhibited reverse transcriptase to the same extent as streptonigrin with the ID50 values ranging between 1 and 5 micrograms/ml, whereas the ID50 value of the indole quinone derivative, 4,7-dihydro-2,3-dimethylindole-4,7-dione, was 80 micrograms/ml. The cytotoxicities of the quinones were much lower than that of streptonigrin; the ID50 values of the quinones were higher than 0.15 micrograms/ml. In particular, the ID50 value of the ortho-quinoline quinone derivative, 8-methoxy-7-methyl-5,6-dihydroquinoline-5,6-dione, was as high as 16 micrograms/ml, while the 50% inhibition of cell growth was seen in the presence of 0.0025 micrograms/ml streptonigrin. The membrane transport of the quinones was evaluated by comparing the effects on oxygen consumption by mitochondria and oxidation of NADH by bacterial diaphorase, being proven not to be responsible for their lower cytotoxicities.

Animals↗
PubMed1987

Oxygen radical generation by polymorphonuclear leucocytes of beige mice.

Oxygen radical generation was measured using peritoneal exudate polymorphonuclear leucocytes (PMN) from a strain of beige mice, an animal model of the Chediak-Higashi syndrome. These PMN have been shown to exhibit delayed microbial killing and impaired phagosome-lysosome fusion. The amount of superoxide anion released by the PMN of the beige mice was similar to that released by the PMN of the control mice. The PMN of beige mice generated slightly less hydrogen peroxide than the control. Hydroxyl radical (.OH) generation and luminol-dependent chemiluminescence were significantly lowered in beige PMN stimulated with opsonized zymosan (OZ) or phorbol myristate acetate (PMA). Cytochalasin B-treated beige PMN showed a decreased ability to degranulate myeloperoxidase in response to OZ or PMA. We demonstrated the significant decrease in .OH generation and chemiluminescence in beige PMN, which might be one of the reasons to explain delayed microbial killing.

Animals↗