Search PubMed⌕ Search

Biomedical subjects

K Niki

Publications and source records attributed to K Niki.

44 records · Page 3Linked to original sources
PubMed1982

Retardation of thyroxine-induced metamorphosis by Amphenone B in toad tadpoles.

The effect of Amphenone B, an inhibitor of corticoid synthesis, on thyroxine (T4)-induced metamorphosis was studied in toad tadpoles kept in thiourea. Amphenone injections retarded T4-induced tail resorption markedly. The effect of Amphenone was nullified by aldosterone and corticosterone added to the water in which tadpoles were kept. Steroidogenic cells of adrenals in Amphenone-injected animals were enlarged markedly as compared with those in the saline-injected tadpoles or the Amphenone-injected tadpoles which were supplemented with corticoids. The results strongly suggest that endogenous corticoids act together with thyroid hormone to accelerate metamorphosis.

Adrenal Cortex Hormones↗
PubMed1981

Electrocatalytic four-electron reduction of oxygen at the cytochrome c3-adsorbed electrode.

The electrocatalytic activity of cytochrome c3 for the reduction of molecular oxygen was characterized from the studies of the adsorption of cytochrome c3 and the co-adsorption of cytochrome cs with cytochrome c on the mercury electrode by the a.c. polarographic technique. The adsorption of cytochrome c3 on the mercury electrode is irreversible and is diffusion-controlled. The maximum amount of cytochrome c3 absorbed was 0.92 . 10(-11) mol . cm-2 at -0.90 V. The amount of cytochrome c3 in the mixed adsorbed layer with cytochrome c was determined from the differential capacitance measurement. It was shown that the fractional coverage of cytochrome c3 can be estimated from its bulk concentration and the diffusion coefficient (1.05 . 10(-6) cm2 . s-1). Cytochrome c3 catalyzes the electrochemical reduction of molecular oxygen from the two-electron pathways via hydrogen peroxide to the four-electron pathway at the mercury electrode in neutral phosphate buffer solution. The catalytic activity varies with the bulk concentration of cytochrome c3. The highest catalytic activity for the oxygen reduction (no hydrogen peroxide formation) is attained when one-half of the mercury electrode surface is covered by cytochrome c3. The addition of cytochrome c or bovine serum albumin to the cytochrome c3 solution inhibits the catalytic activity of cytochrome c3. The reversible polarographic behavior of cytochrome c3 through the mixed adsorbed layer of cytochrome c3 and cytochrome c was also investigated.

Adsorption↗
PubMed1976

Quantitative and qualitative determinations of the combined effect of tetracycline and oleandomycin. I. In vitro effect.

Growth inhibitory effect of combined treatment of tetracycline (TC) and oleandomycin (OM), at a ratio of 2:1, on certain species of pathogenic bacteria including drug-resistant ones was examined. By the crossed paper strip method, synergistic effects were demonstrated against 9 of the 16 strains of Staphylococcus aureus, and all of the 5 strains of Escherichia coli studied. Antagonism was observed with none of the strains and with 2 strains of Streptococcus pyogenes and 2 strains of Streptococcus pneumoniae tested in the present experiments. The MICs determined by the agar dilution method, also gave similar results, although synergism was not conclusively demonstrated by this method. With representative strains of S. aureus, synergism was evidenced by quantitative measurement of growth inhibition. In some strains, 1.0 mug of one drug per ml of medium inhibited the induction of resistance to the second drug. Such a small dose of one drug also inhibited the development of a mutant resistant to the second drug. These inhibitory actions were thought to be one of the important factors causing the synergistic effect of TC and OM on drug resistant bacteria.

Drug Combinations↗