Biomedical subjects

Chie Ohmizo

Publications and source records attributed to Chie Ohmizo.

3 recordsLinked to original sources

PubMed2004

Mode of action of novel polyamines increasing the permeability of bacterial outer membrane.

We have clarified how the polyamines naphthylacetylspermine and methoctramine (N,N'-bis[6-[[(2-methoxyphenyl)methyl]amino]hexyl]-1,8-octanediamine), originally developed as a synthetic analogue of joro spider toxin and a muscarinic receptor antagonist, respectively, can increase the permeability of the outer membrane of Escherichia coli. These polyamines were recently found to be outer membrane permeabilisers, based on investigations of the structure-activity relationship using ion-selective electrodes. In a standard microbiological assay examining membrane-permeabilising ability, these polyamines enhanced the action of hydrophobic antibiotics such as novobiocin and erythromycin, which ineffectively traverse the outer membrane of E. coli, to inhibit the growth of E. coli. This result substantiated the outer membrane-permeabilising ability of these polyamines demonstrated by using ion-selective electrodes. We observed the release of lipopolysaccharide from the outer membrane in the concentration range causing permeabilisation, showing that the action of the polyamines is attributable to disruption of the outer membrane structure.

Bacteria↗

PubMed2004

Bacterial cytoplasmic membrane permeability assay using ion-selective electrodes.

We used K(+) and tetraphenylphosphonium (TPP(+)) electrodes simultaneously to evaluate the ability of antimicrobial peptides to form channels (or more generally to increase permeability) and to abolish membrane potential in bacterial cytoplasmic membranes in situ. Such evaluations are usually made independently by colorimetric monitoring of the hydrolysis of a chromogenic substrate by a cytoplasmic enzyme or by fluorimetric determination of membrane depolarization using a membrane potential-sensitive dye. In the present study, the K(+) electrode was used to evaluate channel-forming ability by monitoring the efflux of K(+) originally present in the cytoplasm of bacteria, while the TPP(+) electrode was used to examine membrane depolarization causing the efflux of TPP(+) accumulated in the cytoplasm of bacteria dependent on membrane potential. Thus, the combination of these two electrodes enabled us to clarify how the peptide-induced formation of ion channels is involved in disrupting the energy-generating system in situ.

Anti-Bacterial Agents↗

PubMed2003

Potassium and tetraphenylphosphonium ion-selective electrodes for monitoring changes in the permeability of bacterial outer and cytoplasmic membranes.

A tetraphenylphosphonium ion (TPP(+))-selective electrode, originally developed as a membrane potential indicator, is useful for measuring increases in the permeability of bacterial outer membranes induced by antimicrobial agents. The combination of this electrode with a potassium ion-selective electrode enabled us to determine changes in the permeability of bacterial outer and cytoplasmic membranes simultaneously. Outer membrane permeabilization induced by antimicrobial agents, chlorhexidine and polyhexamethylene biguanide (PHMB), as monitored with the TPP(+) electrode, correlated closely with the ability of the agents to release lipopolysaccharide (LPS) from the outer membrane.

Biguanides↗