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Y Iwakura

Publications and source records attributed to Y Iwakura.

At least 127 records · Page 7Linked to original sources
PubMed1983

Comparison of polysaccharide synthesis between preimplantation stage mouse embryos and F9 embryonal carcinoma cells.

Polysaccharide synthesis was compared between preimplantation stage mouse embryos and F9 embryonal carcinoma cells. When cells were labelled with [3H]fucose, elution profiles of the pronase digest from a Sephacryl S-200 column were similar for the two cell types and both had characteristic large polysaccharides of the same size (Mr 20-500K), although embryos contained less large polysaccharide than F9 cells, and embryonic polysaccharides were less acidic, suggesting poor sialosylation. A significant proportion of [3H]mannose was incorporated into complex-type glycopeptides in F9 cells, whereas in the case of embryonic cells most glycopeptides remained as high mannose-type. The most striking difference was observed when cells were labelled with galactose. In the case of embryonic cells, 90% of the radioactivity was incorporated into glycogen, whereas only 0.1% of the incorporated galactose occurred in this molecule in F9 cells. These observations indicate that carbohydrate metabolism of morula-stage embryos is very different from that of F9 cells.

Animals↗
PubMed1983

A class of large polysaccharides contains the antigenic determinants for the cytotoxic antibodies in a conventional syngeneic anti-F9 serum as well as a monoclonal antibody prepared against F9 cells.

The molecular natures of the antigenic targets detected by cytotoxic antibodies in both a monoclonal antibody (ECMA-3) made against F9 cells and a conventional mouse anti-F9 serum were investigated. Both of the antibodies precipitated a class of high molecular weight polysaccharides from Nonidet P40 lysates of F9 cells. These molecules were labeled by radioactive galactose and fucose but only poorly by amino acids; in addition, they were fairly resistant to pronase and the digest still had a molecular weight of 70 K or more. Even after extensive pronase digestion the polysaccharides inhibited the cytotoxic activities of the antibodies, suggesting that the antigenic targets reside on the carbohydrate portion. This class of polysaccharides was shown to be a minor component of the characteristic large polysaccharides of F9 cells.

Animals↗
PubMed1978

Nonglycosylated mouse L cell interferon produced by the action of tunicamycin.

The effect of tunicamycin, a specific inhibitor of protein glycosylation, on interferon production by L cells induced by Newcastle disease virus was studied. The interferon yields in the presence of tunicamycin ranged from 20 to 100% of control in various experiments. The two molecular species of normal L cell interferon with 40,000 and 24,000 daltons were completely eliminated, and a new species of a smaller size (18,000 daltons) was produced. Radiolabeling of interferon with [35S]methionine and [3H]glucosamine added to the induced cultures, as studied by immunoprecipitation and polyacrylamide gel electrophoresis, indicated that the two species of control interferon were both glycoproteins but tunicamycin interferon contained little or no sugar. In support of this was the loss of binding to lectin from Wistaria floribunda. A change in physical property of the molecule due to the absence of sugar was found in decreased heat stability in the presence of sodium dodecyl sulfate, although in its absence no significant difference from control interferon was observed. These results indicate that tunicamycin is an effective agent in producing nonglycosylated but fully active interferon molecules; the sugar moiety appears to be unnecessary for the antiviral activity and for secretion from cells.

Glucosamine↗
PubMed1978

Purification of mouse L cell interferon. Essentially pure preparations with associated cell growth inhibitory activity.

Mouse L cell interferon induced by Newcastle disease virus was purified by a combination of salt precipitation, ion exchange chromatography, gel filtration, and affinity chromatography using anti-interferon anti-body. The preparation was labeled with 125I at a later step of purification, which served as an index of protein concentration. Two main species of interferon molecules differing in molecular weight were separated from each other, and the final preparations obtained were shown to be essentially pure by polyacrylamide gel electrophoresis in the absence as well as in the presence of sodium dodecyl sulfate. The highest specific activities obtained were 2.6 X 10(9) and 7.3 X 10(8) international units/mg of protein (determined by 125I radioactivity) for the 40,000- and 24,000-dalton species, respectively. The preparations at different steps of purification, including those of the highest purity, were tested for the anti-cell growth activity. Their activities were found to be indistinguishable from each other when compared at the same antiviral doses, indicating that the anti-cell growth activity is carried by the interferon molecules themselves.

Cell Division↗
PubMed1976

Mechanism of polyadenylate-polyuridylate synthesis by RNA polymerase holoenzyme II of Escherichia coli.

Poly(A)-poly(U) synthesis in the absence of template DNA is a unique reaction catalyzed by the RNA polymerase [EC 2.7:7.6] holoenzyme II of Escherichia coli. As one approach to investigating the physiological role of the enzyme, the molecular mechanism of poly(A)-poly(U) synthesis was studied. Streptolydigin, an inhibitor of the elongation of RNA chains, was shown to inhibit poly(A)-poly(U) synthesis, and the inhibition was released by a streptolydigin-resistant mutation on the beta subunit. These observations indicate that the active site for the reaction might be located on the beta subunit. Another antibiotic, rifampicin, which is known to be a specific inhibitor of the initiation of DNA-dependent RNA synthesis, effectively inhibited both initiation and elongation steps in poly(A)-poly(U) synthesis. This suggests that the enzyme conformation during the chain elongation reaction might be different in this case from that in DNA-dependent RNA synthesis. Analysis of the products formed during the initiation reaction indicated that the rate-determining reaction in poly(A)-poly(U) synthesis was the formation of primers of short chain length, and that holoenzyme I was unable to form the first phosphodiester bond in this reaction. Functional properties of holoenzyme II are discussed in connection with these observations.

Adenosine Triphosphate↗
PubMed1975

Biosynthesis of RNA polymerase in Escherichia coli. II. control of RNA polymerase synthesis during nutritional shift up and down.

As an effort to elucidate the control of quality and quantity of the DNA-dependent RNA polymerase in Escherichia coli, the rate of synthesis of the individual subunits was determined during shift-up and -down of nutrients. When the strain B/r grown in a succinate medium was imposed to a shift-up by adding a mixture of glucose and amino acids, rapid rise was observed of the differential rates of the synthesis of alpha, beta and beta' subunits, the constituents of core enzyme, leading to the increase of core polymerase concentration. The differential rates decreased thereafter to the level characteristic of the post-shift rate of cell growth. Compared to the strain B/r, the adaptation was slow in the strain K12 W3350. On the other hand, upon transfer of the strain B/r from a glucose-amino acids medium to a glucose medium lacking amino acids, the differential rate of core polymerase synthesis decreased rapidly and then regained the rate characteristic of the new growth rate. Similar control was also observed on the rate of ribosomal protein synthesis suggesting the coordinate expression of genes for the core polymerase subunits and ribosomal proteins. Thus, the intracellular concentration of RNA polymerase as well as of ribosomes might be one of the most important factors that affect the rate of bacterial growth. The rate of alpha subunit synthesis, however, exhibited little change during the shift-up but a considerable decrease was observed during the shift-down.

Amino Acids↗