Yoshio Ebina

AN ESR STUDY OF DEFECTS IN IRRADIATED HYDROXYAPATITE

Abstract Radiation-induced defects in synthetic hydroxyapatite (HAp) of six different origins have been investigated by electron spin resonance (ESR), X-ray diffraction (XRD), Raman scattering and IR measurements. The orthorhombic CO2− radicals were detected in almost of all the samples examined, but the isotropic CO2− was produced only in water-containing HAp with low crystallinity. The doublet signal due to H0 was clearly detected in HAp with extreme calcium deficiency as compared to the stoichiometry. The results of ESR and FTIR suggest that water molecules in low crystalline HAp are not on the surface but embedded in the HAp crystalline lattice.

Relationship between resting cytosolic Ca2+ and responses induced byN-methyl-d-aspartate in hippocampal neurons

Cytosolic calcium concentrations ([Ca2+]i) in cultured hippocampal neurons from rat embryos were measured using fura-2. Neurons with higher resting [Ca2+]i showed greater [Ca2+]i responses to N-methyl-D-aspartate (NMDA) and K+ depolarization. There was a strong relationship between resting [Ca2+]i and the maximal changes in [Ca2+]i (delta[Ca2+]i), which fit the our proposed equation to describe this relationship.

Some properties of membrane current fluctuations induced by kainate, quisqualate, and NMDA in cultured septal neurons of rat

Ionic currents induced by glutamate, kainate, quisqualate, and N-methyl-D-aspartate (NMDA) in cultured septal neurons were analyzed by fluctuations analysis. The power spectrum (PWS) of NMDA current fluctuations always fitted a single Lorentzian. PWSs of the other agonists fitted the sum of two Lorentzians; however, the slopes of PWSs became larger and the PWSs became closer to single Lorentzians as the number of drug application increased. This may be explained in such a way that, in multiple conductance channels activated by these agonists, the high frequency component decreases the gating activity in later recordings, whereas the low frequency component keeps its gating kinetics.

Further characterization of the lipid-depleted bovine rhodopsin obtained by cholate-ammonium sulfate fractionation

The rhodopsin preparation obtained by the method of ammonium sulfate fractionation contained 3-6 mol phospholipid and about 18 mol cholate per mol rhodopsin. The purified rhodopsin had 74% helical structure and showed a visible CD spectrum different from that of rhodopsin in the membrane. The rhodopsin was stable below but denatured gradually above 20 degrees C. The lifetime of metarhodopsin I was long in this preparation. Regeneration capacity was low and only 30% of the original rhodopsin was regenerable by addition of 11-cis-retinal after bleaching. 50 mol of phosphatidylcholine were maximally bound to 1 mol rhodopsin when the purified rhodopsin was mixed with phosphatidylcholine in 0.5% cholate. The rhodopsin recombined with lipid has properties similar to those of the original rhodopsin in the membrane. Exchange of cholate for other detergents was easily performed by dialysis. The rhodopsin preparation in which cholate was exchanged for digitonin gave almost the same CD, thermal stability and regenerability as those of native rhodopsin in the membrane but metarhodopsin I still retained its long lifetime.

A method for motion compensation of a moving nematode Caenorhabditis elegans and its application to frequency analysis of pharyngeal pulsation

A new sequential image processing method for motion compensation of a moving object with stringy shape has been developed for estimating the pharyngeal pulsation of the nematode Caenorhabditis elegans under several environmental conditions. The method is based on the pixel data transfer on a new image frame while changing the boundary shape and the position but preserving the conformation of the inner structure of an object. All digitized image frames of C. elegans were first converted to motion-compensated images to arrange the pulsation site in the same region of the every transformed frame. The pulsation site was then automatically detected by determining the pixels where the temporal brightness variation was much larger than that of the other pixels. Finally, the pulsation frequency was determined by the Fourier analysis. The validity of our method has been confirmed by analyzing various test data, and the method has been applied for detecting the pharyngeal pulsation frequencies of C. elegans on some environmental conditions, i.e. feed bacteria-free/rich, doping of nerve inactivating ethyl-alcohol and nerve stimulant neurochemical substance of serotonin. The motion compensation method automatically provided reasonable pulsation frequencies which were found to be comparable to those obtained by manual counting. Thus the method is useful for systematic investigations on the variation of pharyngeal pulsation associated with the activity change of the nervous system in environments.

The dose-response relationship for N-methyl-d-aspartate currents in cultured rat septal neurons: effects of magnesium ions and 2-amino-5-phosphonovaleric acid

Dose-response relations of the peak ionic current induced by N-methyl-D-aspartate (NMDA) under Mg-free vs normal saline (1.2 mM Mg) conditions were obtained in cultured neurons dissociated from septa of fetal rat brains using the single electrode voltage clamp method. The effect of D,L-2-amino-5-phosphonovalerate (APV) on the dose-response relationship was also studied. In the Mg-free condition, the response to NMDA increased progressively with dose up to 0.2 mM, at which point the response saturated up to 1 mM NMDA (ED50 was about 70 microM). At larger doses (1-3 mM) the response increased sharply. In normal saline the response increased up to doses of 10 mM, and there was no apparent plateau. In a comparison between the depressant effects of APV and Mg ions on the peak current value, the depression caused by APV (10-30 microM) at higher NMDA concentrations was larger than that caused by Mg.

2018 Extraction of characteristic features of movement and behavior in C. elegans by computer

OSAMU NAKAGAWASAI, KOICHI TAN-NO, TAKESHI TADANO, KENSUKE KISARA To examine the relationship between brain opioids and forced walking stress immunohistochemical estimation of /I-endorphin distribution in mouse brain was determined by fluorescent intensity with two-dimensional microphotometry. The intensity of P-endorphin was increased 6 hr after the forced walking in Periaqueductal gray matter, hypothalamus and limbic system.

Power spectrum density equation of fluctuating membrane current based on a discrete-time Markov chain model : application to the analysis of ion channels with two and three states

The measured power spectrum density PWSEX of the fluctuating membrane current of neurons often differs from the well known Lorentz curve. Representing the frequency dependence in the high frequency (f) above the corner frequency as f−n, n is less than 2, which indicates that the slope is smaller than in the Lorentz curve f−2. The reason for the rise of the high-frequency side of PWSEX is the aliasing effect produced by application of the FFT to discrete data over a finite interval. In this study, the theoretical expression PWSTH for the power spectrum density obtained from a discrete-line Markov model is used in the analysis of the experimental data. In the practical analysis of experimental data, we assume that the number of states of a single kind of channel on the membrane of the neuron is two or three. Using the discrete-time Markov model, an expression for PWSTH is derived. When the sampling time approaches zero, this expression approximates the known expression for the power spectrum density under the continuous-time Markov model. The plot of PWSTH gave a good fit to the experimental data. The open time that we obtained agreed well with existing values. These results confirm the usefulness of this form of PWSTH when it is applied to processing discrete data sampled at finite intervals.