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Shinji Kamimura

Publications and source records attributed to Shinji Kamimura.

7 recordsLinked to original sources
PubMed2006

Ciliated cells differentiated from mouse embryonic stem cells.

In the present study, we demonstrated that the mouse embryonic stem cells were differentiated into ciliated epithelial cells, with characteristics of normal ciliated cells. These cells expressed ciliary marker proteins, such as beta-tubulin IV and hepatocyte nuclear factor-3/forkhead homolog 4 (HFH-4), and processed microtubules were arranged in the 9 + 2 structure, which is the same specific alignment observed in normal ciliary microtubules. The cilia of these cells were beating at a frequency of 17-20 Hz. The differentiated embryoid bodies (EBs) containing these ciliated cells expressed respiratory marker genes such as thyroid transcription factor-1 and surfactant protein-C. For the induction of ciliated cells, culture of EBs in serum-free medium during the initial 2 days of the attachment was indispensable. When EBs were treated with bone morphogenetic proteins, the expression of HFH-4 was decreased, and the ciliated cells were scarcely differentiated. Previous methods for inducing ciliated cells in vitro from embryonic or adult tissues involved an air-liquid interface. The system used in this study more closely mimics the normal development of ciliated cells; thus, an added advantage of the system is as a tool for studying the differentiation mechanism of normal ciliated epithelial cells.

Animals↗
PubMed2005

Increase in intracellular pH induces phosphorylation of axonemal proteins for activation of flagellar motility in starfish sperm.

Increased intracellular pH ([pH]i) activates dynein in sea urchin and mammalian sperm and induces activation of flagellar motility. It is thought that cAMP-dependent protein phosphorylation is associated with motility activation through increasing [pH]i, but little attention has been given to the cAMP-independent phosphorylation also induced by the [pH]i increase. The present study demonstrates that the increase in [pH]i in starfish sperm induces the phosphorylation of axonemal proteins and activation of flagellar motility independently of cAMP. Flagellar motility of intact sperm was activated when the [pH]i was raised by addition of NH4Cl. Histidine, which is known to activate motility of starfish sperm, also raised the [pH]i during the motility activation. In addition, motility of demembranated sperm flagella was activated in a pH-dependent manner without cAMP. These results indicate that in starfish sperm it is the increase in [pH]i that induces activation of flagellar motility. Moreover, phosphorylation of axonemal proteins (of molecular mass 25, 32 and 45 kDa) was observed during the pH-dependent and cAMP-independent motility activation of demembranated sperm. This suggests that the increase in [pH]i regulates flagellar motility via cAMP-independent phosphorylation of axonemal proteins.

Ammonium Chloride↗
PubMed2004

Diameter oscillation of axonemes in sea-urchin sperm flagella.

The 9 + 2 configuration of axonemes is one of the most conserved structures of eukaryotic organelles. Evidence so far has confirmed that bending of cilia and flagella is the result of active sliding of microtubules induced by dynein arms. If the conformational change of dynein motors, which would be a key step of force generation, is occurring in a three-dimensional manner, we can easily expect that the microtubule sliding should contain some transverse component, i.e., a motion in a direction at a right angle to the longitudinal axis of axonemes. Using a modified technique of atomic force microscopy, we found such transverse motion is actually occurring in an oscillatory manner when the axonemes of sea-urchin sperm flagella were adhered onto glass substrates. The motion was adenosine triphosphate-dependent and the observed frequency of oscillation was similar to that of oscillatory sliding of microtubules that had been shown to reflect the physiological activity of dynein arms (S. Kamimura and R. Kamiya. 1989. Nature: 340:476-478; 1992. J. Cell Biol. 116:1443-1454). Maximal amplitude of the diameter oscillation was around 10 nm, which was within a range of morphological change observed with electron microscopy (F. D. Warner. 1978. J. Cell Biol. 77:R19-R26; N. C. Zanetti, D. R. Mitchell, and F. D. Warner. 1979. J. Cell Biol. 80:573-588).

Adenosine Triphosphate↗
PubMed2003

Study on the development of sperm motility and social dominance of male mice.

It has been shown that sperm motility and other parameters related to the reproductive activity varied depending on the social status of male mice. In order to clarify whether such variation is derived from inborn difference or depends on any conditions during maturation, we investigated developmental change of sperm motility, reproductive organs, and body size of ddY male mice. We also investigated how the establishment of social dominance of male mice during maturation was correlated with sperm motility. It was found that sperm motility was significantly higher during puberty than in adulthood, although there already existed relatively large statistical variance. The correlation between sperm motility and the social status was revealed to start after 10 weeks of age. It was suggested that a certain inborn difference of sperm motility became enlarged due to environmental factors experienced by male mice during maturation.

Aggression↗
PubMed2003

Effects of vomeronasal organ removal on the sperm motility in male mice.

Odors play important roles in the communication of house mice. They release behaviors and prime changes of the physiological conditions of other individuals. In our previous study, we showed that sperm motility was lowered in the subordinate mice comparing with dominant mice. Our hypothesis is that the lowered sperm motility was due to some primer effects by odor substances derived from dominant mice. To test the hypothesis, we destroyed the vomeronasal organ (VNO) of male mice (VNX male) at 5 weeks of age and paired them with intact male mice (Experimental Group). As control group males, intact male mice were kept in pairs (Control Group). At 15 weeks of age, the sperm motility and weights of reproductive organs, and social dominance was analyzed. The subordinate VNX males were found to have high sperm motility comparable to the dominant males. It was suggested that there is male-to-male primer effects, mediated by VNO, that suppress sperm motility of the subordinate mice.

Analysis of Variance↗
PubMed2002

Imaging of the fluorescence spectrum of a single fluorescent molecule by prism-based spectroscopy.

We have devised a novel method to visualize the fluorescence spectrum of a single fluorescent molecule using prism-based spectroscopy. Equipping a total internal reflection microscope with a newly designed wedge prism, we obtained a spectral image of a single rhodamine red molecule attached to an essential light chain of myosin. We also obtained a spectral image of single-pair fluorescence resonance energy transfer between rhodamine red and Cy5 in a double-labeled myosin motor domain. This method could become a useful tool to investigate the dynamic processes of biomolecules at the single-molecule level.

Carbocyanines↗