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Nomura, Fumimasa; Honda, Makoto; Takeda, Susumu; Inaba, Takehiko; Takiguchi, K.; Itoh, Tomohiko J.; Ishijima, Akihiko; Umeda, Tamiki; Hotani, Hirokazu

doi:10.1023/a:1019971429702

Cited by 9 publications

(6 citation statements)

References 13 publications

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“…As previously discussed, a pseudopod-like structure can be extruded owing to a difference in osmotic pressure. 18,19 However, the reversible formation of the pseudopod-like structure in this study cannot be explained only in terms of osmotic pressure.…”

Section: Resultsmentioning

confidence: 68%

“…These decreases may be caused by the dissolution of oleic acid owing to diffusing NaOH 21 and by water permeation due to the osmotic pressure difference between the inside and outside of the vesicle. 18,19 However, the membrane area and water volume did not show a dramatic change in the time range corresponding to one extrusion and contraction cycle (Figure 6a-2). When 1 M NaCl was used, the elongated vesicle did not contract (Figure 6b-2).…”

Section: Resultsmentioning

confidence: 95%

“…The extrusion of the cylindrical structure and pearling instability were discussed based on an osmotic pressure difference across the membrane; this type of shape change attracts special interest, 18 and the dynamics are essentially a monotonic relaxation towards the local equilibrium. 18,19 However, to the best of the authors' knowledge, oscillatory shape changes comprised of extrusion and contraction have not been reported to date. In this study, the direction of the extrusion was controlled by the pH gradient.…”

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confidence: 99%

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Chemotactic Amoeboid-Like Shape Change of a Vesicle under a pH Gradient

Nawa

Yamamoto

Shioi

2015

Bulletin of the Chemical Society of Japan

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A vesicle that exhibited the extrusion and contraction of a pseudopod-like structure under a pH gradient was studied. The vesicle is composed of oleate and oleic acid, and transforms from a double-spherical shape to a disk-like shape after numerous cyclic shape changes, including the reversal and rotation of the double-spherical vesicle. A pseudopod-like structure is extruded from the vesicle toward a pH gradient, created by NaOH diffusion, and is then contracted. This reversible motion is repeated many times. Notably, NaCl diffusion produces a monotonic and irreversible extrusion. The difference between the two systems could be explained by the cation permeability across the membrane. A mathematical model that accounted for this characteristic reproduced the experimental results semi-quantitatively. Vesicles exhibiting amoeboid-like behaviors, which may be useful in the design of amphiphilic molecular assemblies with biomimetic characteristics, have rarely been reported and are poorly understood. The present study may provide significant insight into the design of such biomimetic vesicles.

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 99%

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Chemotactic Amoeboid-Like Shape Change of a Vesicle under a pH Gradient

Nawa

Yamamoto

Shioi

2015

Bulletin of the Chemical Society of Japan

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“…Upon heating vesicles containing tubulin and GTP to 37°C, tubulin polymerizes to form MTs. A mechanism that explains the formation of a single filament of MTs by alignment of individual filaments (and thus creating a single-membrane protrusion) has previously been outlined by Hotani and coworkers (17). Most of the experiments that we describe here incorporate the UV-excitable probe 6-(9-anthroyloxy)stearic acid (6-AS) into the lipid membrane.…”

Section: Resultsmentioning

confidence: 94%

A physical model of axonal damage due to oxidative stress

Counterman

D'Onofrio²,

Andrews³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Oxidative damage is implicated in the pathogenesis of neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's diseases, and in normal aging. Here, we model oxidative stress in neurons using photogenerated radicals in a simplified membrane-encapsulated microtubule system. Using fluorescence and differential interference contrast microscopies, we monitor photochemically induced microtubule breakdown on the supported region of membrane in encapsulating synthetic liposomes as a function of lipid composition and environment. Degradation of vesicle-encapsulated microtubules is caused by attack from free radicals formed upon UV excitation of the lipid-soluble fluorescent probe, 6-(9-anthroyloxy)stearic acid. Probe concentration was typically limited to a regime in which microtubule degradation was slow, and microtubule degradation was monitored by changes in the observed protrusion of the membrane surface. The kinetics of microtubule degradation are influenced by lipid saturation level, fluorescent probe concentration, and the presence of free-radical scavengers. This system is sufficient to reproduce some degenerative morphologies found in vivo.O xidative modifications to proteins in neurons have been implicated in a number of degenerative disorders and have become a controversial topic in elucidating the progression of Parkinson's, Huntington's, and Alzheimer's diseases (1-7). Microtubules (MTs) are key cytoskeletal proteins in nerve cell axons. These protein polymers are responsible for many disparate functions of cells, including structural support and imparting polarity, and they are involved in motility and transport of intracellular cargo (8). Fundamental studies of MTs in vivo are complicated by the presence of the full complement of biomolecules that are required for cell survival. Thus, a substantial effort has been devoted to characterizing MT dynamics in vitro, and these studies have led to increased understanding of issues such as dynamic instability (9) and the involvement of molecular motors in producing motility (10). To mimic the confinement of a bilayer, MT assemblies (asters) have previously been examined in rigid, microfabricated wells (11). The drawback of such studies is that interactions between MTs and components of the elastic lipid membrane are neglected. It is important to be able to isolate and to quantify specific factors that impact the structural integrity of the cytoskeleton, while maintaining a simplified cell-like environment.Toward this aim, we have developed a minimal physical system with which to investigate the effects of oxidative stress on the cytoskeleton. Previous studies have demonstrated that incorporating actin and tubulin into liposomes and inducing these proteins to polymerize results in a morphological change in the liposome; a protrusion of the membrane is observed at one or both ends of the protein polymer (12-15). The asymmetry occurs frequently, when the MT wraps around within the encapsulating liposome (16). Here, we employ the membrane as a...

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“…[1] GVs are not only used to study lipid heterogeneity [2][3][4][5][6] but also to examine the interaction of proteins with the membrane. [7][8][9][10][11] However, the incorporation of proteins in GVs is difficult. Thus far only stable (small) membrane proteins have been successfully incorporated in GVs in a functional form.…”

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confidence: 99%