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Biomedical subjects

T Okazaki

Publications and source records attributed to T Okazaki.

At least 487 records · Page 27Linked to original sources
PubMed1977

RNA-linked nascent DNA pieces in T7 phage-infected Escherichia coli cells. I. Role of gene 6 exonuclease in removal of the linked RNA.

The presence of RNA-linked nascent DNA pieces in T7 phage-infected Escherichia coli cells has been shown by the selective degradation of the 5'-hydroxyl-terminated nascent DNA, produced by alkali or RNase treatment, with spleen exonuclease. At 43 degrees C, the proportion of RNA-linked DNA pieces in nascent short dna is 50 to 60% in T7 ts136 (ts mutant of gene 6) phage-infected E. coli, whereas that in T7 wild-type phage-infected cells is less than 6%. Joining of the nascent pieces is greatly retarded in T7 ts136-infected E. coli temperature sensitive polA mutants at 43 degrees C. These results suggest that gene 6 exonuclease plays a role in removal of the linked RNA during the discontinuous replication of T7 DNA.

Animals↗
PubMed1977

Lysosomal phospholipase A activities of rat ovarian tissue.

1.1. Lysosome-enriched fractions were prepared by differential centrifugation of homogenates of luteinized rats ovaries. Acid phospholipase A activities were characterized with [U-14C]diacyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-[9,10-3H]- or [1-14C]oleoyl-sn-glycero-3-phosphocholine as substrates. Acid phospholipase A1 activity had properties similar to other hydrolases of lysosomal origin; subcellular distribution, latency and acidic pH optimum. Acid phospholipase A2 activity with similar characteristics was also tentatively identified. We were unable to exclude the possibility that the combined action of phospholipase A1 and lysophospholipase contributed to the release of acyl moieties from the 2-position of the synthetic substrates. 2. Lysophospholipase activity was present in the lysosome-enriched fractions. This activity had an alkaline pH optimum. 3. Phospholipase A1 and A2 activities solubilized from lysosome fractions by freeze-thawing were inhibited by Ca2+ and slightly activated by EDTA. A Ca2+- stimulated phospholipase A2 activity, with an alkaline pH optimum, remained in the particulate residue of freeze-thawed lysosome preparations. This activity is believed to represent mitochondrial contamination. 4. Activities of acid phospholipase A, as well as other acid hydrolases, increased approx. 1.5-fold between 1 and 4 days following induction of luteinizatin, suggesting a hormonal influence on lysosomal enzyme activities.

Animals↗
PubMed1977

Discontinuous replication of replicative form DNA from bacteriophage phiX174.

Bacteriophage phiX174 DNA has been labeled with short pulses of [3H]thymidine during synthesis of replicative form molecules in infected Escherichia coli HF4704 cells. The replicating phiX174 DNA was isolated and analyzed by sedimentation in an alkaline sucrose gradient. During a brief pulse (5 sec at 30 degrees), the radioactivity incorporated into the complementary strand was found in chains much shorter than one genome length. Of the radioactivity incorporated into the viral strand, two-thirds was in the short pieces and the rest was in chains of one genome length or longer. RNA attachment to the 5' end of both strand components of the nascent short pieces was shown by the appearance of spleen exonuclease-digestable nascent molecules after alkali treatment. These observations suggest that the viral as well as the complementary strand is synthesized by the discontinuous mechanism with RNA primers during replication of duplex phiX174 DNA.

Centrifugation, Density Gradient↗
PubMed1977

Optimal antibody-receptor ratio in anaphylactic-sensitization.

The antigen-induced release of histamine from guinea pig and monkey lung fragments sensitized in vitro with hyperimmune rabbit antibody and human reaginic serum, respectively, was studied. When the amounts of whole antiserum, gamma-globulin fraction, or purified antibody were increased over the optimum in passive anaphylactic sensitization, the subsequent histamine release was reduced in spite of the fact that proportionately greater amounts of antigen were added to the system. The observed inhibition by higher antibody concentrations might be due to a reduction in cell-stimulating capacity of the antigen-antibody-receptor complex caused by inappropriate ratios among any of these three components.

Animals↗
PubMed1977

Detoxified hymenoptera venoms: preliminary studies of in vitro cytotoxicity and antigenicity of Apis mellifera 'venomoid'.

The preparation of detoxified venom (venomoid) of Apis mellifera is described. The venomoid obtained by formaldehyde detoxification retained significant antigenicity. Radioallergosorbent test (RAST) inhibition studies indicated a loss of the affinity of the venomoid for the venom-specific human IgE antibody. In rabbits the venomoid was capable of producing precipitating antibodies which cross-reacted with the original venom. Cytotoxic activity of venomoid as measured by nonimmunological histamine release and hemolytic activity with human cells was not detectable in vitro. Further studies seem warranted for the establishment of a venomoid as a diagnostic and/or therapeutic agent in the management of the hypersensitivity reactions to venom.

Animals↗
PubMed1977

Structure of aplasmomycin.

A new antibiotic, aplasmomycin, was isolated from a broth cultivated with a marine isolate of actinomycete, and inhibits Gram-positive bacteria in vitro and Plasmodium berghei in vivo. It is a natural ionophore and the structure of the Ag-salt was solved by an X-ray crystallographic analysis. It has symmetric structure having boron in the centre of the molecule.

Anti-Bacterial Agents↗
PubMed1976

Interactions of concanavalin A with chick embryo fibroblasts transformed by Rous sarcoma virus. Study with an RSV mutant thermosensitive for transformation.

The interactions between concanavalin A and chick embryo fibroblasts, normal and infected with Rous sarcoma virus (RSV-BH) or its thermosensitive mutant RSV-BH-Ta, have been studied. Normal chick embryo cells and RSV-BH transformed cells showed at 4 and 25 degrees C a similar number of concanavalin A receptors per cell. Analysis of the binding data by the Scatchard relation showed that apparent changes in binding as a function of temperature are due to the thermodynamic properties of the process and not to endocytosis. The lectin receptors on the cell surface of normal and RSV-BH infected cells showed homogeneity in their binding properties. Chick cells infected with RSV-BH-Ta showed a lectin binding behavior that was dependent on the temperature at which the cells were grown. At the permissive temperature for transformation (37 degrees C), the binding process was similar to that observed for normal and RSV-BH infected cells. At the nonpermissive temperature (41 degrees C), the cells showed at least two sets of concanavalin A receptors. The new set of receptors on the cell surface had a lower lectin affinity than those observed in the same cells at 37 degrees C. Chick cells infected with RSV-BH showed an enhanced agglutinability by concanavalin A, as compared with normal cells. Cells infected with RSV-BH-Ta showed a reversal of the correlation between increased concanavalin A agglutinability and the transformed state. At the permissive temperature for transformation, the cells were not agglutinable, whereas at the nonpermissive temperature they presented agglutinability indexes as high as those observed with RSV-BH infected cells. This enhanced agglutinability observed with cells maintained at the nonpermissive temperature for transformation may be related to the new set of low affinity receptors present at 41 degrees C.

Agglutination Tests↗