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Biomedical subjects

H Takezoe

Publications and source records attributed to H Takezoe.

34 records · Page 2Linked to original sources
PubMed1999

A neurally enriched coronin-like protein, ClipinC, is a novel candidate for an actin cytoskeleton-cortical membrane-linking protein.

Brain-enriched human FC96 protein shows a close sequence similarity to the Dictyostelium actin-binding protein coronin, which has been implicated in cell motility, cytokinesis, and phagocytosis. A phylogenetic tree analysis revealed that FC96 and two other mammalian molecules (p57 and IR10) form a new protein family, the coronin-like protein (Clipin) family; thus hereafter we refer to FC96 as ClipinC. A WD domain and a succeeding alpha-helical region are conserved among coronin and Clipin family members. ClipinC is predominantly expressed in the brain, and discrete areas in the mouse brain were intensely labeled with anti-ClipinC antibodies. ClipinC was also shown to bind directly to F-actin in vitro. Immunocytochemical analysis revealed that ClipinC accumulated at focal adhesions as well as at neurite tips and stress fibers. Furthermore, ClipinC was associated with vinculin, which is a major component of focal contacts. These results indicate that ClipinC is also a component part of the cross-bridge between the actin cytoskeleton and the plasma membrane. These findings and the previously reported function of coronin suggest that ClipinC may play specific roles in the reorganization of neuronal actin structure, a change that has been implicated in both cell motility and growth cone advance.

Actins↗
PubMed1999

Spontaneous Enantiomeric Resolution in a Fluid Smectic Phase of a Racemate.

Right- and left-handed homochiral domains segregate in a fluid smectic phase of the racemic (R*,S*)-beta-Me-TFMHPOBC analogue shown. This CF(3)-containing liquid crystalline compound exhibits an electrooptic response in a homogeneous cell, although no macroscopic dipole is expected to exist. Moreover, the homeotropic cells of this material exhibit striped domains, which are associated with fine stripes having two opposite tilt senses with respect to the predominant stripes.

Journal Article↗
PubMed1981

Lateral diffusion of photopigments in photoreceptor disk membrane vesicles by the dynamic Kerr effect.

The lateral diffusion of photopigment molecules in the photoreceptor disk membranes, osmotically swollen into spherical vesicles, has been investigated by dynamic Kerr effect measurements. Upon application of a rapidly reversing bipolar electric field to dilute aqueous suspensions of bovine disk membrane vesicles, the birefringence transient shows a characteristic rise and a deep dip corresponding to the first and second pulses, respectively. The birefringence transient is ascribed to the slowly induced dipole moment caused by electric field induced displacement of the photopigment distribution on the vesicular surface. The lateral translational diffusion coefficient is estimated from the time constant of the slowly induced dipole as D = (3.3 +/- 1.2) X 10(-9) cm2 s-1. When spermine, a cationic tetraamine, is bound to the disk membrane vesicles, the relaxation time of the slowly induced dipole is shown to become longer, indicating that the birefringence mechanism is indeed due to the field-induced photopigment displacement.

Animals↗
PubMed1981

Dynamic kerr effect measurements on photoreceptor disk membrane vesicles.

Dynamic Kerr effect measurements were performed with dilute aqueous suspensions of monodisperse spherical vesicles (approximately 1 micron diameter), isolated from the rod outer segment of bovine retina. A large birefringence, amounting to the specific Kerr constant of 10(-3) esu, can be observed. When a sufficiently long duration pulse (1 s) is applied, the decay of birefringence can be represented by a single exponential profile, yielding a relaxation time of 100 +/- 20 ms in 1 mM imidazole buffer. This is consistent with the rotatory relaxation time of these spherical membrane vesicles. When a short duration is applied, the birefringence increases more steeply and the decay profile contains several components. The slowest (terminal) relaxation time is 86 +/- 15 ms is due to the same process as the one observed in the slow pulse case.

Animals↗
PubMed1981

Electric and optical anisotropy and their osmotically induced changes of photoreceptor disk membrane vesicles.

Electro-optical characterization of the photoreceptor disk membrane vesicle is performed by examining the electric field and concentration dependence of the study-state birefringence of aqueous suspensions of the vesicles. The electric polarizability anisotropy is found to be negative and of large magnitude: alpha 1 - alpha 2 = -(1-3) X 10 cm3. The optical anisotropy is determined to be also negative but of small magnitude: g 1 - g 2 = -1 X 10(-7). The specific Kerr constant deduced from the concentration dependence of the Kerr constant is found to be very large: Ksp = 7 X 10(-4) e.s.u. Upon deforming the vesicles osmotically from the spherical shell to the disk structure, the steady-state birefringence increases by an order of magnitude which is attributed solely to the increase in optical anisotropy attending the corresponding change in the geometric eccentricity of the vesicle. A plausible birefringence mechanism based on the known structural features of the vesicles is proposed, which would account for these findings.

Animals↗