PubMed Health⌕ Search

Biomedical subjects

Y Takagi

Publications and source records attributed to Y Takagi.

At least 775 records · Page 43Linked to original sources
PubMed1976

Specialized transduction of colicin E1 DNA in Escherichia coli K-12.

Genetic studies were made on E. coli K-12 TM96, which carries recombinant molecules constructed by in vitro combination of colicin E1 DNA and a DNA fragment of E. coli for guanine synthesis derived from transducing phage. The recombinant molecules existed as stable plasmids within the cell and contained genes for colicin E1 immunity and the guaA enzyme (xanthosine 5'-monophosphate aminase) together with a part of the lambda genome, R through J: (R-A-F-J)+. A block of the lambda genome, int through Q, was not detected in the recombinant molecule. Thus, this recombinant molecule was named ColEl-coslambda-guaA, and the specialized tranduction of the ColEl-coslambda-guA DNA into various E. coli K-12 cells by lambda phage was described. Lysates prepared by lytic infection of lambda phage onto TM96 or by induction of TM96(lambda) lysogens contained transducing particles which could transduce gua-deleted E. coli to stable guaA+ cells. These transductants were proved to have similar genetic properties as those of TM96. The frequency of transduction was not affected by the presence of an attachement site for lambda, prophage lambda, colicin E1 plasmids, or the recA property within gua-deleted recipient cells. Transducing particles were resistant to EDTA treatment and most of them had an average density of about 1.472. This value corresponds to that of lambda phage particles, which contain about 72% of the lenght of lambda DNA.

Colicins↗
PubMed1976

Plasma membrane ultrastructural differences between the exponential and stationary phases of Saccharomyces cerevisiae as revealed by freeze-etching.

Ultrastructural changes in the plasma membrane of Saccharomyces cerevisiae during the exponential and stationary growth phases were studied by freeze-etching. In the exponential phase, plasma membrane-intercalated particles were distributed randomly. In the stationary phase, several areas of the plasma membrane showed a hexagonal arrangement of particles; these areas appeared to increase with the age of the culture. The polarity of the particles also changed partially: the E-face of the plasma membrane was only sparsely embedded with particles in exponential phase cells, but relatively densely embedded in stationary phase cells. Invaginations of the plasma membrane on the P-face were devoid of particles during both growth phases. Invaginations of the E-face were sparsely embedded with particles in exponential phase cells, but densely embedded with particles in stationary phase cells.

Cell Membrane↗
PubMed1976

Skin lesions during intravenous hyperalimentation: zinc deficiency.

Of 54 patients who received prolonged intravenous hyperalimentation during the past 4 years, six developed progressive, characteristic skin lesions. These cutaneous manifestations frequently were accompained by abdominal symptoms resembling those of acrodermatitis enteropathica in many respects. In the first four of these six patients, skin eruptions disappeared promptly after the initiation of oral feeding, which led us to assume that these skin manifestations are due to some unknown nutrient deficiency. Our experience in the remaining two patients enabled us to presume the underlying pathology to be zinc deficiency.

Adult↗
PubMed1975

The active form of cytochrome P-450 from bovine adrenocortical mitochondria.

Cytochrome P-450 from bovine adrenocortical mitochondria exists in three forms of molecular weight: 850,000 (protein 16), of one-half (protein 8), and of one-quarter of this value (protein 4). The forms of the enzyme are named according to the number of subunits and all appear to be active in converting cholesterol to 3beta-hydroxy-5-pregnen-20-one (side chain cleavage) (Shikita, M., and Hall, P.F. (1973) J. Biol. Chem. 248, 5606). To determine whether all three forms are active at their characteristic molecular weights, the three cytochromes were each layered onto separate sucrose density gradients and centrifuged at 49,000 rpm for 60 min; the gradients contained all the factors necessary for side chain cleavage including one of the following substrates: cholesterol, 20S-hydroxycholesterol, and 20S,22R-dihydroxycholesterol. Regardless of the form of P-450 layered onto the gradient and regardless of the substrate, enzyme activity (side chain cleavage) was observed only in fractions corresponding to a sedimentation coefficient of 20 to 22 S which is that for protein 16. No activity was observed at S values corresponding to either protein 8 or protein 4. These findings indicate that the active form of cytochrome P-450 from adrenocortical mitochondria is that containing 16 subunits, i.e. the form in which the cytochrome is normally isolated from adrenal mitochondria. Forms consisting of eight and four subunits which can be prepared from protein 16 become active only by forming protein 16, at least in an aqueous medium in vitro.

Adrenal Cortex↗
PubMed1975

Effects of extracts of rat tissues on the action of bleomycin.

The cell sap (105 000 times g supernatant) of various tissues of rats caused DNA degradation in the presence of bleomycin. The activity was fractionated into two peaks by column chromatography on Sephadex G-25. The activity in Peak A (excluded fraction) appeared to be due to some proteinaceous entity, while that recovered in Peak B (retarded fraction), constituting about 90% of the total activity, seemed to be due to ascorbic acid, judging by results of further gel filtration and the effect of treatment with ascorbate oxidase. Incubation of bleomycin with Peak A or B caused loss of the ability of the antibiotic to degrade DNA. It is proposed that the action of bleomycin on DNA, and its inactivation by tissue extracts, depend, at least in part, on the presence of ascorbic acid.

Animals↗
PubMed1975

Effects of reducing and oxidizing agents on the action of bleomycin.

The effects of reducing agents, such as 2-mercaptoethanol, dithiothreitol, L-ascorbic acid, or sodium borohydride, and oxidizing agents, such as hydrogen peroxide or dehydroascorbic acid, on the in vitro action of bleomycin were investigated. After the incubation of DNA with a low concentration of bleomycin and a reducing or oxidizing agent, single strand breaks were mainly caused in the DNA molecules. The degradation of DNA was largely prevented by the removal of oxygen, or by the addition of divalent cations or of S-(2-aminoethyl)isothiuronium bromide hydrobromide, a radical scavenger, to the incubation mixture. Preincubation of bleomycin with these reducing or oxidizing agents reduced the DNA-degrading activity of the antibiotic. However, this reduction in activity was observed even in the absence of oxygen, or in preincubation mixture supplemented with radical scavenger.

Ascorbic Acid↗
PubMed1975

Induction of phage production in the lysogenic Escherichia coli by hydroxyurea.

1) Hydroxyurea, a reversible DNA synthesis inhibitor, was used to study the mechanism of prophage lambda induction in Escherichia coli K12. Induction of prophage was judged on two criteria: increase of phage-producing cells and loss of colony-forming ability of the cells. 2) Hydroxyurea induced an increase of phage-producing cells only in lysogenic strains known to be inducible with ultraviolet irradiation for prophage development and not in strains such as E. coli K12 (lambdaind-) or E. coli K12 recA (lambda+). 3) When protein synthesis was inhibited, hydroxyurea did not increase phage-producing cells of lysogenic strains; it showed a bacteriocidal effect on lysogenic recA+ strains, but not on nonlysogenic strains. 4) The sensitivity of E. coli K12 recA to hydroxyurea was independent of whether or not the cells were lysogenic. 5) From the results it is suggested that certain steps leading to loss of colony-forming ability (i.e. prophage induction) do not require de novo protein synthesis but require the presence of the host recA+ gene.

Bacterial Proteins↗
PubMed1975

In vitro construction of different oligomeric forms of lambdadv DNA and studies of their transforming activities.

Plasmid lambdadv1, which is in a dimeric form, was converted to a linear monomer duplex by the action of EcoRI restriction endonuclease that incises at a unique site in this plasmid genome. The resulting products were then joined by Escherichia coli DNA ligase to produce molecules with various oligomeric forms, and from these monomeric, dimeric, or trimeric circular molecules were purified. By transformation of cells with these DNAs, clones were obtained that carried lambdadv1 in a monomeric or dimeric form. The former type of clones have not been generated in vivo, except for one in a different host strain, and carriers of timeric or tetrameric lambdadv1's have not been obtained so far. It was observed that a considerable fraction of these oligomeric circular DNAs were converted to lower oligomers (e.g., from trimer to dimer) during transformation. The characteristics of the monomeric lambdadv1 carriers obtained were compared with those of dimeric lambdadv1 carriers. The stabilities of the plasmids of the two forms were the same. However, the monomeric plasmid carriers were less tolerant to lambdavir phage infection and perpetuated about 30% less plasmid genomes in monomer units. Furthermore, dimeric plasmid carriers appeared spontaneously and accumulated in cultures of the monomeric lambdadv1 carriers.

Coliphages↗
PubMed1975

Biochemical study of fibrosis in the rat liver in biliary obstruction.

In an attempt to study the collagen formation in the liver occurring in association with obstructive jaundice, the authors carried out an experiment with liver slices from common bile duct-ligated rats. Hepatic collagen was fractionated into the neutral soluble, acid soluble and insoluble fractions, and the hydroxyproline synthesis rate of each fraction was measured using 14C-proline. Determination was also made for hexosamine content in the same liver tissue. The hydroxyproline content of hepatic collagen increased as biliary obstruction was prolonged, particularly from the 4th week, which is the transitional period of liver histology into biliary cirrhosis. The hexosamine content of hepatic collagen showed a similar tendency. The neutral soluble, acid soluble and insoluble collagen fractions all increased as biliary obstruction was prolonged. The collagenosynthetic activity of the neutral soluble fraction, attained a peak in 1 to 2 weeks of biliary obstruction, which indicates that collagen fibers are formed actively in the early stage of jaundice, although there is only a slight increase in the absolute amount of fibers developed then. Serum monoamine oxidase level tended to be parallel to collagenosynthetic activity but not to collagen content.

Animals↗
PubMed1975

Metabolism of short chain fatty acid in rat liver in biliary obstruction.

In an attempt to clarify the hepatic insufficiency in obstructive jaundice, hepatic metabolic rate of n-butyric acid, ketogenesis and CO2 formation from butyric acid were investigated using liver slices obtained from rats subjected to choledochal ligation or carbon tetrachloride (CCl4) injection. The hepatic metabolic rate of n-butyric acid was reduced with the prolongation of biliary obstruction, and the reduction was presumed to be caused for the most part by the reduced ketogenesis and in part by the impairment of the citric acid cycle (TCA-cycle). In 3approximately4 weeks after biliary obstruction, the metabolic rate reduced to a level comparable to liver necrosis produced by CCl4. This reduction of the metabolic rate of n-butyric acid is postulated as one of the pathogenic factors for fatal liver insufficiency in many cases of obstructive jaundice. While the reduction is mild and mobile in the early stage of jaundice, it may be of significance for preventing fatal liver insufficiency to relieve the obstruction as early as possible.

Animals↗