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H Tokuda

Publications and source records attributed to H Tokuda.

At least 361 records · Page 20Linked to original sources
PubMed1982

Roles of Na+ and K+ in alpha-aminoisobutyric acid transport by the marine bacterium Vibrio alginolyticus.

Effects of monovalent cations on alpha-aminoisobutyric acid (AIB) transport were examined in the marine bacterium Vibrio alginolyticus. In K+-containing cells, AIB was actively accumulated only in the presence of Na+, and the addition of K+ had essentially no effect. On the other hand, K+-depleted and Na+-loaded cells required K+ as well as Na+ for the accumulation of AIB against its concentration gradient. The characterization of the roles of Na+ and K+ in AIB transport was performed by manipulation of intra- and extracellular cation compositions. K+ concentration gradient (K+in greater than K+out) was not essential for the Na+-dependent AIB uptake. Na+ extrusion against its concentration gradient in Na+-loaded cells occurred only in the presence of K+(Rb+). Half-maximal stimulations of the Na+ extrusion and AIB uptake by K+ were observed at K+ concentration near apparent Km for K+ transport. Finally, in the presence of the Na+ electrochemical gradient (toward the inside), K+ was not necessary for AIB uptake. From these results, it was concluded that the Na+-dependent AIB uptake is driven by the Na+ electrochemical gradient across the membrane and that K+ is required for AIB uptake only for the generation of the Na+ electrochemical gradient.

Aminoisobutyric Acids↗
PubMed1982

Therapeutic effect of an aromatic retinoic acid analog on rats with bladder carcinoma upon administration alone or in combination with mitomycin C.

An aromatic retinoic acid analog (Ro 10-9359) was given orally in combination with intraperitoneal administration of mitomycin C (MMC), in an attempt to reduce the toxicity and enhance the therapeutic effect. Male ACI/N rats were inoculated subcutaneously with BC50-TC cells, an established bladder carcinoma cell line of ACI/N rats. The chemotherapy was initiated at 16 days after the inoculation and continued for 4 weeks thereafter. Tumor growth was significantly inhibited in the rats given 100 mg/kg/week Ro 10-9359 or 0.3 mg/kg/twice a week MMC. Neither additive nor synergistic effect was apparent when these two drugs were given simultaneously. No effect was seen when 0.1 mg/kg/twice a week MMC was given alone or in combination with Ro 10-9359. MMC may suppress Ro 10-9359 activity directly or indirectly by affecting the responding cells. Therefore care should be taken when prescribing retinoids with MMC or possibly with other cytotoxic agents.

Animals↗
PubMed1981

Potassium ion is required for the generation of pH-dependent membrane potential and delta pH by the marine bacterium Vibrio alginolyticus.

The electrochemical potential gradient of protons in the marine bacterium Vibrio alginolyticus was measured as a function of external pH. In K+-containing cells, the membrane potential (delta psi) and delta pH vary with external pH as reported in other bacteria. On the other hand, K+-depleted cells show little pH dependence in the magnitude of delta psi from pH 6.0 to 8.5. The cytoplasmic pH in these cells varies depending on external pH, resulting in the generation of a small delta pH at acidic pH. Addition of K+ to K+-depleted cells leads to partial dissipation of delta psi and concomitant generation of delta pH. Strikingly, this effect of K+ is dependent on external pH. Collapse of delta psi and generation of delta pH by the addition of K+ decrease with increasing external pH. Thus, the delta psi and delta pH obtained after addition of K+ are essentially the same as those determined in K+-containing cells, and cytoplasmic pH becomes less dependent on external pH. The results suggest that the variation of delta psi and delta pH with external pH is controlled by K+ transport.

Cell Membrane↗
PubMed1981

Cellular retinoic acid-binding protein in virus-induced Shope papillomas of rabbit skin.

Cellular retinoic acid-binding protein (cRABP) was detected in the cytosol of virus-induced papilloma (Shope) of rabbit skin. The Shope papilloma cRABP showed the same ligand specificity and sedimentation value (2S) as was found in other animal species. The level of cRABP in the papillomatous tissue was significantly higher than that in the normal rabbit skin and increased in accordance with the growth and development of the tumor, reaching a peak about 40 days after the inoculation of the Shope papilloma virus. Although this binding capacity was about 15 times greater than in the normal skin, the level of cRABP in the transplantable carcinomas Vx2 and Vx7, both originating from the virus-induced papillomas over 20 years ago, was much the same as in normal rabbit skin.

Animals↗
PubMed1979

Effect of colicins Ia and E1 on ion permeability of liposomes.

Colicins Ia and E1 are shown to inhibit the formation and bring about the collapse of a potassium diffusion potential imposed across the membrane of liposomes prepared from soybean or Escherichia coli phospholipids. Such depolarization results from a colicin-induced increase in membrane ion permeability. Colicins E2 and E3 do not depolarize such membranes. In addition to the colicin Ia-induced rapid efflux of preloaded rubidium, sodium, phosphate, or choline from liposomes, a slower efflux of preloaded sucrose or glucose 6-phosphate occurs. However, treated liposomes do not leak inulin or dextran, demonstrating that the effects of E1 and Ia are not due to a general disruption of membrane structure. The fact that colicin-induced ion efflux is observed in the complete absence of a membrane potential shows that the action of these colicins on liposomes is not voltage dependent. These results provide strong evidence that the depolarization of E. coli cells by colicins Ia and E1 results from a colicin-induced increase in membrane permeability to ions. It is proposed that this is brought about by the direct interaction of the colicin molecules with the bacterial cytoplasmic membrane.

Cell Membrane Permeability↗
PubMed1979

Mode of action of colicins Ia, E1 and K.

Addition of colicins Ia, E1 or K to sensitive Escherichia coli leads to inhibition of macromolecular synthesis and an uncoupling of electron transport from active transport. Recent results indicate that these colicins affect energy metabolism by interacting directly with the cytoplasmic membrane. This results in a transmembrane flow of ions leading to membrane depolarization. It is proposed that the function of the outer membrane colicin receptor is to mediate access of the colicin molecule to the cytoplasmic membrane.

Biological Transport, Active↗
PubMed1978

In vitro depolarization of Escherichia coli membrane vesicles by colicin Ia.

Conditions are reported under which membrane vesicles prepared from Escherichia coli K12 are depolarized by colicin Ia. Although incubation of membrane vesicles with active colicin Ia affects neither transport activity nor the ability of such vesicles to generate a deltapH or deltapsi, a single freeze-thaw cycle of such vesicles in the presence of colicin Ia leads to 1) retention of the colicin by the vesicles, 2) inactivation of transport activity, and 3) membrane depolarization, with a concomitant increase in the transmembrane deltapH. These effects are dependent upon the presence of active colicin Ia during the freeze-thaw cycle. These findings are consistent with our previous results showing that Ia-treated whole cells or membrane vesicles prepared from such cells are defective in their ability to generate a deltapsi, yet generate an increased deltapH (Tokuda, H., and Konisky, J. (1978) Proc. Natl. Acad. Sci. U. S. A., 75, 2579--2583). In addition to its effect on vesicles prepared from sensitive cells, we show that vesicles prepared from both colicin Ia-resistant and -tolerant cells are depolarized by colicin treatment with a concomitant increase in deltapH. It is concluded that the final target of colicin Ia is the cytoplasmic membrane. A model for the mechanism of colicin Ia action is presented in which colicin Ia binds to the specific colicin Ia outer membrane receptor and is subsequently translocated to the cytoplasmic membrane where its integration leads to the formation of ion channels.

Biological Transport↗