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Masataka Murakami

Publications and source records attributed to Masataka Murakami.

14 recordsLinked to original sources
PubMed2006

Stress characterization of Si by near-field Raman microscope using resonant scattering.

We have developed a tapping-mode scanning near-field optical Raman microscope (SNORM) with a caved and pyramidical probe, using resonant Raman scattering, and have measured the stress distribution of Si. The peak frequency shifts to a lower frequency by 0-0.5 cm(-1) in the area covered by silicon dioxide, whereas it shifts to a higher frequency by 0-0.3 cm(-1) in the area uncovered by silicon dioxide, showing that the areas covered and uncovered by silicon dioxide are under tensile and compressive stresses, respectively. It has been found that compressive stresses of about 0.69 GPa/cm2 are concentrated on the corner of the area uncovered by silicon dioxide. The comparison of stress distributions measured with and without the cantilever shows that the SNORM we developed has a spatial resolution of at least less than 250 nm.

Elasticity↗
PubMed2004

Role of the special pair in the charge-separating event in photosynthesis.

We synthesized special-pair/electron-acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl-substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole pi system of the dimer. Time-resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special-pair arrangement for efficient charge separation in photosynthesis.

Electron Transport↗
PubMed2004

Dynamics and mechanisms of the multiphoton gated photochromic reaction of diarylethene derivatives.

The cycloreversion (ring-opening) process of one of the photochromic diarylethene derivatives, bis(2-methyl-5-phenylthiophen-3-yl)perfluorocyclopentene, was investigated by means of picosecond and femtosecond laser photolysis methods. The drastic enhancement of the reaction yield was observed only by the picosecond laser exposure. The excitation intensity effect of the reaction profiles revealed that the successive multiphoton absorption process leading to higher excited states opened the efficient cycloreversion process with a reaction yield of (50 +/- 10)%, while the one-photon absorption directly pumped to a higher excited state did not lead to the efficient cycloreversion reaction. These results indicate that not the energy of the excitation but the character of the electronic state takes an important role in the enhancement of the cycloreversion reaction.

Journal Article↗
PubMed2004

Sequence of forebrain activation induced by intraventricular injection of hypertonic NaCl detected by Mn2+ contrasted T1-weighted MRI.

In order to define the sequence of forebrain activation involved in osmoregulation, central activation in response to intracerebroventricular injection of NaCl solution (10 microl of 0.15, 0.5, or 1.5 M) was detected using manganese-contrasted magnetic resonance imaging (MRI) in anesthetized rats. Changes in renal sympathetic nerve activity (RNA) were also measured, and the time courses of forebrain activation and RNA changes compared. NaCl injection resulted in rapid activation of the subfornical organ (SFO), organum vasculosum lamina terminalis (OVLT), and periventricular regions and the lateral hypothalamic area (LHA), then of the paraventricular hypothalamic nucleus (PVN) and supraoptic nucleus (SON). The delay in activation in the PVN and SON showed a wide variation from 0 to 5.78 min, and the average delay in the PVN (2.88+/-0.34 min) and SON (2.90+/-0.39 min) was significantly greater than that in the SFO (0.40+/-0.10 min) and OVLT (0.74+/-0.13 min). NaCl (1.5 M) injection elicited a rapid, large increase in RNA, which consisted of two components, an early rapid increase at 99 s after injection (160+/-27%) and a slower increase at 9 min after injection (209+/-34%). These results suggest that the PVN and SON are activated not only by the afferent input from the SFO and OVLT but also by diffusion of the hypertonic stimulus to these regions and probably by their intrinsic osmosensitivity. The PVN might be responsible for the second slower component of the RNA response, but cannot be responsible for the first component.

Animals↗
PubMed2003

Regulation mode of evaporative cooling underlying a strategy of the heat-tolerant FOK rat for enduring ambient heat.

Compared with other rat strains, the inbred FOK rat is extremely heat tolerant. This increased heat tolerance is due largely to the animal's enhanced saliva spreading abilities. The aims of the present study were to 1) quantify the heat tolerance capacity of FOK rats and 2) determine the regulatory mode of the enhanced salivary cooling in these animals. Various strains of rats were acutely exposed to heat. In the heat-intolerant strains, saliva spreading was insufficient and the core temperature (Tc) rose rapidly. In contrast, FOK rats maintained an elevated Tc plateau (39.5 +/- 0.7 degrees C) for 5-6 h over a wide range of ambient temperatures (Ta) (37.5-42.5 degrees C). In hot environments the FOK rats secreted copious amounts of saliva and spread it over more than the entire ventral body surface. FOK rats had a low Tc threshold for salivation, and the salivation rate increased linearly in proportion to the Tc deviation from the threshold. No strain difference or temperature effect was observed in the saliva secretion rate from in vitro submandibular glands perfused by sufficient doses of ACh. These results suggest that 1) the ability of FOK rats to maintain a moderate steady-state hyperthermia (39.5 +/- 0.7 degrees C) over a wide Ta range is enabled by a lowered threshold Tc for salivation and functional negative-feedback control of saliva secretion and 2) strain differences in ability to endure heat stress are mainly attributable to changes in the thermoregulatory control system rather than altered secretory abilities of the salivary glands.

Adaptation, Physiological↗
PubMed2003

Synthesis of directly linked zinc(II) porphyrin-imide dyads and energy gap dependence of intramolecular electron transfer reactions.

A series of zinc(II) porphyrin-imide dyads (ZP-Im), in which an electron donating ZP moiety is directly connected to an electron accepting imide moiety in the meso position, have been prepared for the examination of energy gap dependence of intramolecular electron transfer reactions with large electronic coupling. The nearly perpendicular conformation of the imide moiety towards the porphyrin plane has been revealed by Xray crystal structures. The energy gap for charge separation, 1ZP* - Im --> ZP+ - Im-, is varied by changing the electron accepting imide moiety to cover a range of about 0.8 eV in DMF. Definitive evidence for electron transfer has been obtained in three solvents (toluene, THF, and DMF) through picosecond-femtosecond transient absorption studies, which have allowed us to determine the rates of photoinduced charge separation, 1ZP* - Im --> ZP+ - Im-, and subsequent thermal charge recombination ZP+ - Im- --> ZP - Im. The free-energy gap dependence (energy gap law) has been probed from the normal to the nearly top region for the charge separation rate alone, and only the inverted region for the charge recombination rate. Although both of the energy gap dependencies can be approximately reproduced by means of the simplified semiclassical equation, when we take into consideration the effect of the high frequency vibrations replaced by one mode of averaged frequency, many features, including the effects of solvent polarity and the electron tunneling matrix element on the energy gap law, differ considerably from those of the previously studied porphyrin-quinone systems, which have weaker interchromophore electronic interactions.

Journal Article↗
PubMed2003

Morphological and functional changes in cell junctions during secretory stimulation in the perfused rat submandibular gland.

To examine the influence of cholinergic and beta-adrenergic agents on paracellular transport, we applied confocal microscopy and freeze-fracture to the isolated, perfused submandibular gland of the rat. By confocal microscopy, perfusion of lucifer yellow through an arterial catheter, revealed a bright fluorescence in the basolateral spaces of acini, but not in the intercellular canaliculi. However, addition of isoproterenol on carbachol stimulation, induced lucifer yellow fluorescence in intercellular canaliculi. This finding indicates that isoproterenol is capable of opening the paracellular route. The tight junction strands surrounding intercellular canaliculi were visualized using freeze replicas. Fixation was carried out both by vascular perfusion with Karnovsky's solution and by metal contact rapid freezing with liquid helium. In the chemically-fixed specimens, the strand particles of tight junctions formed 2-5 lines at the P-face along most of the apical portion at rest. With carbachol/isoproterenol stimulation, the strand particles rearranged with free ends and terminal loops. In the rapidly frozen specimens, the strand particles were arranged more irregularly even in the resting state. The meshwork of strands became more disheveled and interrupted during carbachol/ isoproterenol stimulation. The present findings led us to conclude that: 1) the beta-adrenergic agent, isoproterenol, can open the paracellular transport. 2) in the rapidly frozen specimen, the tight junction strand particles are arranged roughly and become disheveled and interrupted during stimulation by carbachol/isoproterenol. These findings may be related to rearrangement of subcellular structures, especially of the actin filament network.

Adrenergic beta-Agonists↗
PubMed2002

Water permeability of capillaries in the subfornical organ of rats determined by Gd-DTPA(2-) enhanced 1H magnetic resonance imaging.

The water permeability of capillaries in the subfornical organ (SFO) of rat was measured by a (1)H nuclear magnetic resonance method in combination with a venous injection of a relaxation reagent, gadolinium-diethylene triamine-N,N,N',N",N"-pentaacetic acid (Gd-DTPA(2-)), which could not pass through the blood-brain barrier (BBB). Judging from results of Gd-DTPA(2-) dose dependency in the intact brain and the BBB-permeabilized brain, Gd-DTPA(2-) could not have leaked out from the capillaries in the cortex, thalamus or SFO, but it could have been extravasated in the posterior lobe of the pituitary gland. The longitudinal (T(1)) relaxation time of water in the SFO region was measured by inversion-recovery magnetic resonance imaging at 4.7 T. The T(1) relaxation rates (1/T(1)) before and after Gd-DTPA(2-) infusion were 0.70 +/- 0.02 s(-1) (mean +/- S.E.M., n = 9) and 1.53 +/- 0.11 s(-1) (n = 9), respectively. The rate constant for water influx to the capillaries was estimated to be 0.84 +/- 0.11 s(-1) (n = 9) which corresponds with a diffusive membrane permeability (P(d)) of 3.7 x 10(-3) cm s(-1). Compared with values found in the literature available on this subject, this P(d) value for the capillaries in the SFO was the same order of magnitude as that for transmembrane permeability of water for the vasa recta, and it may be 10-100 times larger than that of the blood-brain barrier in the cortex. Areas of the cortex and thalamus showed minimal changes in the T(1) relaxation rate (ca 0.09 s(-1)), but these values were not statistically significant and they corresponded to P(d) values much smaller than those found in the SFO. From these results, we conclude that the capillaries in the SFO have one of the highest water permeability values among all of the capillaries in the brain. It is also suggested that this magnetic resonance imaging, based on T(1) relaxation rate, is a useful method to detect local water permeability in situ.

Animals↗
PubMed2002

Cyclic AMP has distinct effects from Ca(2+) in evoking priming and fusion/exocytosis in parotid amylase secretion.

Rat parotid acinar cells were perfused in small quartz columns to examine the role of cAMP and Ca(2+) in the priming and fusion/exocytosis of amylase secretion. Carbachol (CCh) evoked a biphasic response of amylase secretion with an initial rapidly occurring large peak and a subsequent sustained plateau. Isoproterenol produced slowly increasing amylase secretion that reached the plateau greater than that induced by CCh. Combined stimulation with isoproterenol and CCh greatly potentiated amylase secretion. The rise and decay of amylase secretion induced by the combined stimulation was similar to those induced by CCh but not by isoproterenol, suggesting that the potentiation is caused by isoproterenol-induced modification of the CCh effect. Concentration-dependent responses of CCh-induced amylase secretion with and without isoproterenol showed that isoproterenol greatly enhances both the sensitivity and maximum effect of CCh. Similar potentiation was observed when the Ca(2+) effect was directly examined in cells permeabilized to Ca(2+) with ionomycin instead of CCh. In a Ca(2+)-free medium, CCh evoked an initial peak but did not produce a sustained plateau. Isoproterenol did not enhance the effect of CCh on [Ca(2+)](i). 2,4-Dintrophenol and carbonyl cyanide m-chlorophenyl hydrazone did not decrease the CCh-induced initial peak of amylase secretion but markedly decreased the sustained responses induced by isoproterenol and CCh. These results suggest that CCh, via Ca(2+), has two distinct effects on amylase secretion: triggering of fusion/exocytosis and the priming of secretory granules. Isoproterenol, via cyclic AMP, also has two distinct effects: direct stimulation of priming and enhancement of the sensitivity to the Ca(2+)effects. Thus, isoproterenol stimulates amylase secretion by increasing the primed pools of secretory granules, whereas CCh increases the flux of secretory granules into/from the primed pools, which is greatly enhanced by isoproterenol.

2,4-Dinitrophenol↗
PubMed2002

Detection of hypothalamic activation by manganese ion contrasted T(1)-weighted magnetic resonance imaging in rats.

To examine the usefulness of Mn(2+) contrasted magnetic resonance imaging (MRI) in hypothalamic imaging, images obtained using T(1)-weighted MRI were compared with Fos expression, which is known to increase after activation of voltage-dependent Ca(2+) channels. Intravenous infusion of MnCl(2) elicited a rapid increase in the T(1)-weighted MRI signal intensity in the vessels and ventricles, but not in the brain parenchyma, suggesting that Mn(2+) did not diffuse freely across the blood-brain barrier. When the blood-brain barrier was broken by right intracarotid arterial injection of 25% D-mannitol, an increased signal intensity was seen in the right brain. Intracarotid arterial injection of hypertonic NaCl elicited rapid and striking increases in signal intensity in the paraventricular hypothalamic nucleus, supraoptic nucleus, and preoptic area, which are thought to be involved in central osmotic regulation. These observations were consistent with the Fos expression results. These results indicate that Mn(2+) contrasted MRI is a useful technique for investigating the autonomic center in the hypothalamus.

Animals↗
PubMed2002

Efficient photocyclization of dithienylethene dimer, trimer, and tetramer: quantum yield and reaction dynamics.

Multi-dithienylethene arrays, in which two, three, or four 1,2-bis(2,4-dimethylthiophen-3-yl)perfluorocyclopentenes are ethynylene-bridged, were synthesized. Upon irradiation with ultraviolet light the hexane solutions of the arrays turned violet-blue and the color disappeared by irradiation with visible light. The quantum yields of photocyclization reactions successively increased from 0.21 to 0.40 by increasing the number of the dithienylethene moieties in the arrays from one to four. Picosecond laser photolysis as well as the fluorescence depolarization experiment confirmed that efficient excited energy migration in the arrays from the photochemically inactive parallel conformer to the photoactive antiparallel conformer resulted in the high quantum yields.

Journal Article↗
PubMed2002

Visualization of 'water secretion' by confocal microscopy in rat salivary glands: possible distinction of para- and transcellular pathway.

Visualization of water transport in cells, tissues and organs is an important, yet still difficult, task in morphological science. By using confocal microscopy and the fluid-phase fluorescent tracer technique, we visualized water secretion and estimated the routes of water transport across the acinar epithelia in rat parotid and submandibular glands. Confocal microscopy of whole glands perfused arterially with Lucifer yellow revealed a bright fluorescence at the basolateral space of acini. Luminal space was devoid of fluorescence, but revealed it after isoproterenol pretreatment, ductal infusion of fluorescent dextrans into the lumen, or tissue dissociation by collagenase. Under these conditions, stimulation of fluid secretion with carbachol caused a rapid decline of the luminal fluorescence intensity, indicating that the secreted water washed out the fluorescent probes in the acinar lumen. In the stimulated dissociated acini, the luminal fluorescence disappeared by 15 sec, but reappeared at 30-45 sec to maintain a low plateau level. By assuming that the tight junction was 'paralyzed' by the collagenase digestion and that the paracellular fluid transport could not influence the dilution of Lucifer yellow, we estimated that the initial water secretion by CCh occurs via the transcellular pathway, while later than 30-45 sec the additional water permeates through the paracellular pathway.

Algorithms↗
PubMed2002

[Effects of quantity of Japanese cedar pollen, air pollution and urbanization on allergic rhinitis morbidity in Ibaraki prefecture].

OBJECTIVES: It has been reported that morbidity from allergic rhinitis in the National Health Insurance records in Ibaraki Prefecture for May correlated with the quantity of Japan cedar pollen scattered in each year. The purpose of the present investigation was to clarify the Japanese cedar pollinosis contribution to morbidity, and also clarifying the influence of air pollution and medical resources on the crisis and symptoms of allergic rhinitis. METHODS: The charts in four otolaryngology facilities were used for analyzing the Japan cedar pollinosis content with reference to the allergic rhinitis during the pollen season. The age-adjusted morbidity of allergic rhinitis was annually compared employing data of National Health Insurance records for medical examinations made in May during the period between 1988 and 1996 in Ibaraki Prefecture. The quantity of Japanese cedar pollen was measured at seven area points in Ibaraki Prefecture during the three-year period from 1994 to 1996, and was compared with the degree of Japan cedar wood occupation in each municipality. Traffic volume according to municipalities in Ibaraki Prefecture was taken as a surrogate indicator of air pollution. The area otolaryngology facilities and doctors were taken as medical resources. Values were thus compared with allergic rhinitis morbidity. RESULTS: Sixty to eighty percent of the allergic rhinitis patients examined in May were found to be suffering from pollinosis. The quantities of Japanese cedar pollen scatter at the seven points in Ibaraki Prefecture varied in concert every year, the quantities correlating well with the area of Japanese cedar woods stands in each municipality in some but not in other years. The morbidity in the records of allergic rhinitis according to municipalities correlated negatively with the proportion of the population occupied in farming (r = -0.38) and with the area of Japanese cedar woods in each municipality (r = -0.40). The traffic volume calculated according to municipalities in Ibaraki Prefecture correlated significantly with the yearly average concentration of nitrogen dioxide (r = 0.63, P < 0.01) and with the morbidity of allergic rhinitis. In places among the northern mountains of the Prefecture, both the morbidity in the records and the distribution of otolaryngology facilities were low. CONCLUSIONS: More than 60% of the morbidity from allergic rhinitis in May appeared in the National Health Insurance records to be associated with Japanese cedar pollinosis. This was confirmed by the correlation between yearly variation in morbidity and that of the quantity of Japanese cedar pollen scatter. As local factors increasing the morbidity of allergic rhinitis in the records, air pollution, urbanization and a greater availability of medical resources were indicated.

Air Pollutants↗