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Tsutomu Hamada

Publications and source records attributed to Tsutomu Hamada.

8 recordsLinked to original sources
PubMed2006

Spontaneous transfer of phospholipid-coated oil-in-oil and water-in-oil micro-droplets through an oil/water interface.

We studied the evolution of oil-in-oil (O/O) and water-in-oil (W/O) phospholipid-coated micro-droplets at an oil/water interface. We found that, in both cases, micro-droplets spontaneously transferred from the oil phase to the water phase. O/O micro-droplets transformed into oil-in-water micro-droplets, while W/O micro-droplets led to the formation of liposomes.

Chemical Phenomena↗
PubMed2005

Reversible photoswitching in a cell-sized vesicle.

A photosensitive amphiphilic molecule can switch the shape of an assembled vesicle as determined by microscopic observation. Photoisomerization induces a change in membrane fluctuation behavior or a morphological transition between ellipsoid and bud shapes, depending on the asymmetrical degree of the initial shape. The mechanism of this reversible photoswitching in the vesicle morphology is interpreted in terms of a change in the effective cross-sectional area of the photosensitive molecule.

Azo Compounds↗
PubMed2005

Folding transition into a loosely collapsed state in plasmid DNA as revealed by single-molecule observation.

The conformational transition of a plasmid DNA, pGEG.GL3 (12.5 kbp, circular), induced by spermine(4+) was studied through the observation of individual DNA by fluorescence microscopy. We deduced the change in the hydrodynamic radius R(H) from an analysis of the Brownian motion of single DNA molecules. R(H) decreases in a continuous manner with an increase in spermine(4+), in contrast to the large discrete on/off change for long linear DNA. Just after the transition to the collapsed state, a small number of DNA molecules tend to form an assembly, which disperses in the bulk solution without precipitation.

DNA↗
PubMed2005

Self-running droplet: emergence of regular motion from nonequilibrium noise.

Spontaneous motion of an oil droplet driven by nonequilibrium chemical conditions is reported. It is shown that the droplet undergoes regular rhythmic motion under appropriately designed boundary conditions, whereas it exhibits random motion in an isotropic environment. This study is a novel manifestation on the direct energy transformation of chemical energy into regular spatial motion under isothermal conditions. A simple mathematical equation including noise reproduces the essential feature of the transition from irregularity into periodic regular motion. Our results will inspire the theoretical study on the mechanism of molecular motors in living matter, working under significant influence of thermal fluctuation.

Journal Article↗
PubMed2003

Gene expression within cell-sized lipid vesicles.

Functional protein synthesis was observed in cell-sized lipid vesicles following encapsulation of a gene-expression system. Expression of rsGFP (red-shifted green fluorescent protein) within individual vesicles was observed by fluorescence microscopy. Interestingly, at the early stage of the reaction, the expression efficiency inside the vesicle was remarkably higher than that in the solution outside. The synthesized rsGFP in individual vesicles is safe from attack by proteinase K added to the external aqueous solution. Studies on cell-sized vesicles expressing protein should contribute to a fundamental understanding of certain aspects of living systems and will be useful for practical applications, such as the construction of microreactors.

Endopeptidase K↗
PubMed2002

Improvement of reflux symptoms 3 years after cure of Helicobacter pylori infection: a case-controlled study in the Japanese population.

BACKGROUND: Development of reflux esophagitis is one of the adverse effects that cause concern in relation to curative treatment of Helicobacter pylori infection. However, recent studies present a rather negative association between curative treatment and development of reflux esophagitis or reflux symptoms. Therefore, this issue has remained controversial. Accordingly, we investigated the long-term adverse effects of H. pylori eradication treatment in special reference to development of reflux symptoms. PATIENTS AND METHODS: We conducted a case controlled study by mailing structured questionnaires on past (before curative treatment or 3 years previously) and current status. A case was an endoscopically confirmed peptic ulcer patient with confirmed cure of the infection after eradication treatment 3 years previously and a control was one who had not undergone the eradication treatment during the same period. We studied 241 pairs who matched for age, gender, and type of ulcer disease (GU, DU or GDU). Of these pairs, 81.3% were male and the mean age was 52.6 +/- 9.6 year (range 23-76). RESULTS: The rates of patients with improved reflux symptoms in the case and control groups were 65.4% and 30.4%, respectively, with the rate being significantly greater in the case group. On the contrary, the rates of those with worsened reflux symptoms were similar (5.1% and 7.6%). Regarding general events, the rate of patients with decreased frequency of hospital visits and of those who regularly used antiacid medications were significantly decreased in the case group. Furthermore, the case group experienced significantly fewer hospital admissions for various diseases in this 3-year period. However, a significantly greater number of case group patients than control subjects gained weight. CONCLUSION: Reflux symptoms as well as general well-being were significantly improved after cure of H. pylori infection.

Adult↗