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Biomedical subjects

A Maeda

Publications and source records attributed to A Maeda.

At least 451 records · Page 25Linked to original sources
PubMed1966

Interaction of colicins with bacterial cells. I. Studies with radioactive colicins.

Maeda, Akio (Department of Genetics, University of Wisconsin, Madison), and Masayasu Nomura. Interaction of colicins with bacterial cells. I. Studies with radioactive colicins. J. Bacteriol. 91:685-694. 1966.-By use of a preparation of radioactive colicin E2, the following conclusions, which had been obtained previously from indirect experiments, were tested directly: (i) colicin stays at the receptor site on the cell and acts from there; (ii) colicins E2 and E3 share the same receptor, although their mode of action is entirely different; (iii) colicinogenic cells adsorb homologous colicin, although they are resistant to that colicin. Our experimental results confirmed the above conclusions. When sensitive cells of Escherichia coli K-12 pretreated with radioactive E2 were disrupted with a French pressure cell, and fractionated by differential centrifugation, it was found that most of the radioactivity stayed with the cell envelope fraction. Trypsin removed a major part of radioactivity from cells pretreated with radioactive E2, as was expected from the previous experiments on trypsin reversal of colicin action. Furthermore, it was shown that the trypsin treatment causes a recovery of the capacity of E2-pretreated cells to adsorb further colicin E2. When cells were first treated with various amounts of nonradioactive E3, and then treated with radioactive E2, the amount of radioactive E2 adsorbed was found to be inversely related to the amount of nonradioactive E3 adsorbed first. It was also shown that E2-colicinogenic cells adsorb radioactive E2, and yet are resistant to this colicin.

Adsorption↗
PubMedDate not supplied

Possible mechanisms of positive inotropic action of synthetic human calcitonin gene-related peptide in isolated rat atrium.

The effect of synthetic human calcitonin gene-related peptide (hCGRP) on the isolated and electrically driven left atria of rats were investigated. The peptide at concentrations of 3 X 10(-9)-3 X 10(-7) M produced positive inotropic effects on the left atria in a dose-dependent manner. Verapamil (10(-5) M) and adenosine (10(-4) M) reduced the positive inotropic effect of hCGRP at concentrations of 3 X 10(-9) and 3 X 10(-8) M, but not at that of 3 X 10(-7) M. Ouabain (5 X 10(-5) M) inhibited the effect of hCGRP in concentrations of 3 X 10(-7) and 3 X 10(-8) M, but not in that of 3 X 10(-9) M. Simultaneous pretreatment with verapamil (10(-5) M) and ouabain (5 X 10(-5) M) suppressed the positive inotropy by hCGRP at all concentrations tested. On the other hand, tetrodotoxin (10(-6) M) potentiated only the positive inotropic effect of 3 X 10(-7) M hCGRP. Metoprolol (10(-7) M) and theophilline (10(-3) M) did not affect the inotropic effect of hCGRP. These results suggest that the positive inotropic effect of hCGRP is not mediated by beta-adrenoceptors but by two distinct mechanisms of action, which was inhibited by verapamil but not by ouabain (facilitation of Ca++ influx in lower concentrations of hCGRP) and which was blocked by ouabain but not by verapamil and potentiated by tetrodotoxin (inhibition of Na+/Ca++ exchange mechanism at higher concentrations of hCGRP).

Adenosine↗
PubMedDate not supplied

Changes in structure of the chromophore in the photochemical process of bovine rhodopsin as revealed by FTIR spectroscopy for hydrogen out-of-plane vibrations.

The hydrogen out-of-plane bending (HOOP) vibrations were studied in the difference Fourier transform infrared spectra of lumirhodopsin and metarhodopsin I by use of a series of specifically deuterated retinal derivatives of bovine rod outer segments. The 947 cm-1 band of lumirhodopsin and the 950 cm-1 band of metarhodopsin I were assigned to the mode composed of both 11-HOOP and 12-HOOP vibrations. This result suggests that the perturbation near C12-H of the retinal in the earlier intermediate, bathorhodopsin (Palings, van den Berg, Lugtenburg and Mathies, Biochemistry, 28 (1989) 1498-1507), is extinguished in lumirhodopsin and metarhodopsin I. Unphotolyzed rhodopsin and metarhodopsin I exhibited the 14-HOOP bands in the 12-D derivatives at 901 and 886 cm-1, respectively. Lumirhodopsin, however, did not show the 14-HOOP in the 12-D derivatives. The result suggests a change in geometrical alignment of the C14-H bond in lumirhodopsin with respect to the N-H bond of the Schiff base.

Animals↗
PubMedDate not supplied

Correlation between the sialylation of cell surface Thomsen-Friedenreich antigen and the metastatic potential of colon carcinoma cells in a mouse model.

The cell surface glycosylation profiles of a liver metastatic colon carcinoma variant cell line, SL4 cells previously selected from colon 38 cells in vivo for liver colonization were investigated. Flowcytometric analysis was performed with 7 plant lectins and 10 carbohydrate specific monoclonal antibodies. The results showed that peanut agglutinin (PNA), Sambucus nigra agglutinin, Ulex europeus agglutinin-I, anti-LeX, anti-LeY, and anti-Le(b) antibodies bound to the parental colon 38 cells but not to SL4 cells. Another variant cell line was selected in vitro for the paucity of cell surface PNA-binding sites using a magnetic cell sorter and was designated as 38-N4 cells. The binding profiles of plant lectins and carbohydrate-specific antibodies to 38-N4 cells were very similar to those of SL4 cells. After intrasplenic injections, metastatic ability of 38-N4 cells was higher than that of colon 38 cells. PNA binding to SL4 cells and 38-N4 cells was detected after sialidase treatment of these cells, indicating increased sialylation of Thomsen-Friedenreich antigen in these cells. The mRNA levels of sialyltransferases, ST3Gal I, ST3Gal II, ST6GalNAc I, and ST6GalNAc II, were compared. The level of ST3Gal II mRNA was elevated in both SL4 cells and 38-N4 cells, whereas the level of ST6GalNAc II mRNA was elevated in 38-N4 cells compared with colon 38 cells. According to the expression array analysis, there are other glycosyltransferase genes differentially expressed between SL4 and colon 38 cells, yet their involvement in the altered glycosylation in these cells is unclear.

Animals↗