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Biomedical subjects

H Tokuda

Publications and source records attributed to H Tokuda.

At least 379 records · Page 21Linked to original sources
PubMed1978

Mode of action of colicin Ia: effect of colicin on the Escherichia coli proton electrochemical gradient.

By use of the technique of flow dialysis, the membrane potential (deltapsi) and pH gradient (deltapH) have been measured in colicin Ia-treated Escherichia coli K-12 cells and in membrane vesicles prepared from such cells. Although such cells and vesicles are able to generate a transmembrane deltapH at pH 5.5, they do not generate a transmembrane deltapsi. Glucose-6-phospate uptake by cells is shown to be stimulated at pH 5.5 and inhibited at pH 7.5 by colicin Ia treatment. On the other hand, proline uptake is demonstrated to be inhibited progressively at pH 5.5, 6.6, and 7.5 in colicin Ia-treated cells. These data provide strong evidence for a colicin Ia-induced membrane deplorization and indicate that the membrane becomes permeable to ion(s) other than protons after treatment with colicin Ia.

Acid-Base Equilibrium↗
PubMed1977

Sodium-dependent methyl 1-thio-beta-D-galactopyranoside transport in membrane vesicles isolated from Salmonella typhimurium.

Membrane vesicles isolated from Salmonella typhimurium G-30 grown in the presence of melibiose catalyze methyl 1-thio-beta-D-galactopyranoside (TMG) transport in the presence of sodium or lithium, as shown initially with intact cells by Stock and Roseman (Stock, J., and Roseman, S. (1971), Biochem. Biophys. Res. Commun. 44, 132). TMG-dependent sodium uptake is also observed, but only when a potassium diffusion potential (interior negative) is induced across the vesicle membrane. Cation-dependent TMG accumulation varies with the electrochemical gradient of protons generated as a result of D-lactate oxidation, and the vesicles catalyze D-lactate-dependent sodium efflux in a manner which is consistent with the operation of a proton-sodium exchange mechanism. Although the stoichiometry between sodium and TMG appears to be 1:1 when transport is induced by a potassium diffusion potential, evidence is presented which indicates that the relationship may exceed unity under certain conditions. The results are explained in terms of a model in which TMG-sodium (lithium) symport is driven by an electrochemical gradient of protons which functions to maintain a low intravesicular sodium or lithium concentration through proton--sodium (lithium) antiport.

Biological Transport, Active↗
PubMed1977

Energetics and molecular biology of active transport in bacterial membrane vesicles.

Bacterial membrane vesicles retain the same sidedness as the membrane in the intact cell and catalyze active transport of many solutes by a respiration-dependent mechanism that does not involve the generation of utilization of ATP or other high-energy phosphate compounds. In E. coli vesicles, most of these transport systems are coupled to an electrochemical gradient of protons (deltamuH+, interior negative and alkaline) generated primarily by the oxidation of D-lactate or reduced phenazine methosulfate via a membrane-bound respiratory chain. Oxygen or, under appropriate conditions, fumarate or nitrate can function as terminal electron acceptors, and the site at which deltamuH+ is generated is located before cytochrome b1 in the respiratory chain. Certain (N-dansyl)aminoalkyl-beta-D-galactopyranosides (Dns-gal) and N(2-nitro-4-azidophenyl)aminoalkyl 1-thio-beta-D-galactopyranosides (APG) are competitive inhibitors of lactose transport but are not transported themselves. Various fluorescence techniques, direct binding assays, and photoinactivation studies demonstrate that the great bulk of the lac carrier protein (ca. 95%) does not bind ligand in the absence of energy-coupling. Upon generation of a deltamuH+ (interior negative and alkaline), binding of Dns-gal and APG-dependent photoinactivation are observed. The data indicate that energy is coupled to the initial step in the transport process, and suggest that the lac carrier protein may be negatively charged.

Bacteria↗
PubMed1977

[Use of clindamycin-2-phosphate in ophthalmology (author's transl)].

Clindamycin-2-phosphate was studied to evaluate its possible use in ophthalmology. 1. Sensitivity of organisms isolated from human clinical materials: Of 44 staphylococcal strains in vitro studied 13 were highly sensitive to 0.1 mug/ml and 28 were resistant to 100 mug/ml or more of clindamycin-2-phosphate. 2. In experiments with rabbits, clindamycin-2-phosphate showed superior penetration into the ocular tissues after intravenous injection than after intramuscular injection. 3. Clindamycin-2-phosphate was administered intramuscularly at the dose of 300 mg to 6 healthy volunteers. The blood concentrations of 6 cases averaged 3.2 mug/ml after 1 hour, and 0.8 mug/ml after 6 hours. 4. Fourteen patients with extraocular infection were treated with daily intramuscular administration of 300 mg of clindamycin-2-phosphate. All of them improved by the treatment, and no side effect was observed.

Adult↗