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T Nashida

Publications and source records attributed to T Nashida.

18 recordsLinked to original sources
PubMed2001

mRNA expression of membrane-fusion-related proteins in rat parotid gland.

The soluble N-ethylmaleimide-sensitive fusion (NSF) attachment protein (SNAP) receptor (SNARE) hypothesis has been applied to exocytosis in salivary glands. The expression of SNARE proteins has not been well investigated in the parotid gland. In this study, the mRNA expression of SNAREs and membrane-fusion-related proteins were investigated in the rat parotid by reverse transcriptase-polymerase chain reaction (RT-PCR). All syntaxins except syntaxin 1, and the vesicle-associated membrane proteins (VAMP) except VAMP-7, NSF, SNAP-23 and alpha-SNAP, were expressed for the SNAREs in rat parotid. Synaptotagmins 3, 4 and 11, Munc18s (1, 2 and 3), syncollin, prenylated Rab acceptor (PRA1), zygin 1, pantophysin and cellugyrin, which are the other membrane-fusion-related proteins, were also detected, but neither Rim nor rabphilin 3A, which have high specificity of binding to Rab 3A, were found. mRNA expressions of many SNAREs and of the membrane-fusion-proteins suggest novel interactions for the regulation of salivary exocytosis.

Animals↗
PubMed2000

The effect of deviant stimulus probability on the human mismatch process.

The present study addresses the separate activities of frontal and temporal MMN generators which might be differentially affected by a change in the probability of standard stimuli. As the probability of standard stimuli was increased, the frontal MMN component significantly increased in amplitude, while the temporal one was not affected. Correspondingly, the scalp current density (SCD) maps showed that the temporal MMN generator was activated even at low probability of standard stimuli, suggesting that even the weak memory trace could start the automatic mismatch process, whereas the frontal MMN generator was activated only with increased probabilities of standard stimuli, suggesting that the stronger the memory trace is, the easier it might trigger the involuntary switching of attention to stimulus change.

Acoustic Stimulation↗
PubMed2000

Automatic auditory information processing in sleep.

STUDY OBJECTIVES: The mismatch negativity (MMN) component of the event-related potentials reflects the automatic detection of sound change. Only a few researchers have investigated the MMN elicitation during sleep in adult human and some of them reported that MMN amplitude was decreased in sleep compared to in waking. However, it is not clear that the decrease of MMN amplitude was due to increased drowsiness or long-term response decrement. Two experiments were conducted to clarify whether or not the MMN was elicited in each sleep stage. We presented auditory stimuli to subjects continuously from waking until sleep state (Experiment 1). Using the same experimental condition, we examined whether or not MMN amplitude was influenced by long-term stimulus presentation (80min.) and by vigilance level (Experiment 2). DESIGN: N/A SETTING: N/A PARTICIPANTS: N/A INTERVENTIONS: N/A MEASUREMENTS & RESULTS: Experiment 1: MMN was obtained in both drowsiness and REM sleep. MMN was significantly smaller in amplitude and shorter in latency in the both stages than in the waking state. However, MMN was not found in another sleep stage. Experiment 2: Amplitudes were no different among 0-20 min., 20-40 min., 60-80 min. But it was decreased in 40-60 min. and power value of alpha-wave was decreased in 40-60 min. CONCLUSIONS: To obtain the reliable data, by using the automatic spectral analysis, we confirmed that MMN was elicited in REM sleep. MMN was not influenced by long-term stimulation. The result suggested that auditory stimuli could be processed in the pre-attentive sensory memory even in REM sleep.

Adult↗
PubMed2000

Mismatch negativity (MMN) reveals sound grouping in the human brain.

To investigate a part of the structure of the memory trace, auditory event-related potentials (ERPs) were recorded from reading subjects while they were presented with two different stimulus-series simultaneously. A clear mismatch negativity (MMN) was obtained from each series, when the stimulus sequence consisted of a high-frequency series and a low-frequency series. Moreover, the MMN showed independent elicitation within each series. However, if the frequency range of one series overlapped with that of the other series, the amplitude of the MMN was prominently reduced, suggesting that the two processing functions indexed by MMN coexisted simultaneously in the preattentive acoustic system and were produced by the respective grouping of high-frequency tones and low-frequency tones.

Acoustic Stimulation↗
PubMed2000

Expression, characterization, and localization of Rab26, a low molecular weight GTP-binding protein, in the rat parotid gland.

We investigated the expression of the genes encoding Rab proteins, low molecular weight GTP-binding proteins, in the rat parotid gland by the use of reverse transcription-polymerase chain reaction, and detected cDNAs of Rab3D, Rab4, and Rab26. We further examined the characteristics and localization of Rab26 by western blotting and light and electron microscopic immunocytochemistry. Western blotting using an antibody against the Rab26-specific, C-terminal peptide detected the His-tagged Rab26 protein as a single 27-kDa band. This band also displayed binding to [alpha-32P]GTP. The fraction containing secretory granule membranes in an acinar cell homogenate was immunostained with the antibody. Supporting this, the immunocytochemical reaction for Rab26 was localized immediately around secretory granules in the acinar cells. The immunostaining disappeared from the acinar cells after treatment of rats with isoproterenol. These findings suggest that Rab26 participates in the regulated secretion of granules and functionally belongs to the Rab3 group.

Animals↗
PubMed2000

Regulation of ANP-stimulated guanylate cyclase in the presence of Mn2+ in rat lung membranes.

The catalytic activity of guanylate cyclase (GCase) coupled to atrial natriuretic peptide (ANP) receptor depends on the metal co-factor, Mn2+ or Mg2+. ATP synergistically stimulates the ANP-stimulated GCase in the presence of Mg2+. We have now shown the ATP regulation of the ANP-stimulated GCase in the presence of Mn2+ in rat lung membranes. ANP stimulated the GCase 2.1-fold compared to the control. ATP enhanced both the basal (basal-GCase) and the ANP-stimulated GCase maximally 1.7- and 2.3- fold compared to the control, respectively, at a concentration of 0.1 mM. The stimulation by ATP was smaller in the presence of Mn2+ than in the presence of Mg2+. The addition of inorganic phosphate to the reaction mixture altered the GCase activities in the presence of Mn2+ with or without ANP and/or ATP. In the presence of 10 mM phosphate, ATP dose-dependently stimulated the basal GCase 5-fold compared to the control at a concentration of 1 mM and augmented the ANP-stimulated GCase, which was 4.2-fold compared to the basal-GCase, 5.5-fold compared to the control at a concentration of 0.5 mM. Protein phosphatase inhibitors, okadaic acid (100 nM), H8 (1 microM) and staurosporin (1 microM), did not alter the activity. Orthovanadate (1 mM), an inorganic phosphate analogue, significantly stimulated both the basal-GCase and the ANP-stimulated GCase, which were inhibited by ATP. It was assumed that phosphate and orthovanadate might interact with the GCase to regulate the activity in the opposite manner. This was the first report that inorganic phosphate and orthovanadate affected the ATP-regulation of the ANP-stimulated GCase in the presence of Mn2+.

Adenosine Triphosphate↗
PubMed1999

Comparison of phosphodiesterase isozymes in rodent parotid glands.

We investigated phosphodiesterase (PDE) isozymes, which hydrolyze cAMP, in rodent parotid glands (mouse, hamster and guinea pig) in order to clarify the effects of cGMP and Ca/calmodulin on the regulation of cellular cAMP and compared them with those of the rat. More than 80% of the activities were in the supernatant fractions except for the hamster. The isozymes were fractionated using Mono Q ion-exchange column. The mouse parotid PDEs consisted of PDE1 (Ca/calmodulin-dependent), PDE2 (cGMP-stimulated), PDE3 (cGMP-inhibited) and PDE4 (cAMP-specific) similar to those of the rat. PDE3 was not detected in the hamster, and PDE4 was not detected in the guinea pig. PDE activities in the supernatant of the mouse and the hamster were stimulated by cGMP, and that of the guinea pig was stimulated by Ca/calmodulin. These results suggest that various PDE isozymes are present in the parotid gland of several species of order Rodentia. There seems to be differences among the species with regard to the PDE isozymes.

Animals↗
PubMed1996

Characterization of natriuretic peptide receptors in the rat parotid.

Competition studies between 125I-ANP and ANP (atrial natriuretic peptide) or the ring-deleted analog C-ANF4-23 (C-ANF) revealed the presence of the A-type natriuretic peptide receptor (GC-A receptor) and the ANP-clearance (ANP-C) receptor in the rat parotid membrane. The ratio of the GC-A and ANP-C receptors was about 3 to 1. Enhancement of the cGMP level by the C-type natriuretic peptide (CNP) revealed the presence of the B-type natriuretic peptide receptor (GC-B receptor) in the rat parotid gland. Based on the binding studies with ANP and C-ANF and cGMP analysis by ANP and CNP, the natriuretic peptide receptors in the rat parotid gland were demonstrated to have a rank order on the amount of GC-A receptor > GC-B receptor > ANP-C receptor.

Animals↗
PubMed1996

Expression of mRNA encoding cAMP-specific phosphodiesterase isoforms in rat parotid glands.

In previous reports, we have shown that cAMP-specific phosphodiesterase (PDE4) is the major PDE in the rat parotid gland, and that PDE4 is activated by phosphorylation. In this study, we investigated the expression of PDE4 isoform genes and alternative splicing variants of PDE4D in the rat parotid gland using reverse transcriptase-polymerase chain reaction (RT-PCR). PDE4A, PDE4B, PDE4C and PDE4D of PDE4 subfamily were expressed. PDE4D was found to be the dominant PDE4 isoform. A weak band of PDE4C was detectable. Three alternative splicing variants (PDE4D1, PDE4D2 and PDE4D3) derived from the rat PDE4D gene were expressed in the parotid gland. These data suggested that the intracellular cAMP level is regulated by multiple response mechanisms through the activations of the PDE by phosphorylation and gene expression in the rat parotid gland.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Effect of cyclic GMP produced by natriuretic peptides on osteoblast-like MC3T3-E1 cells.

The C-type natriuretic peptide (10(-7) M) and atrial natriuretic peptide (10(-7) M) enhanced cGMP accumulation by 418 and 83 times the control value, respectively, in osteoblast-like MC3T3-E1 cells. The natriuretic peptide B receptor was assumed to be the major natriuretic peptide receptor. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) activated alkaline phosphatase doubled the activity versus the control value on day 15. Phosphodiesterase activity was not stimulated by the addition of cGMP (1 MicroM). cGMP-dependent protein kinase (G kinase) activity of the supernatant fraction was 25.5 pmol/min/mg protein. The 42 kDa protein band was detected to be phosphorylated by G kinase on SDS-PAGE. These results supported the hypothesis that natriuretic peptides regulate the differentiation of MC3T3-E1 cells through a cGMP-dependent pathway.

Alkaline Phosphatase↗
PubMed1995

Characterization of cyclic AMP phosphodiesterase isozymes in rat parotid gland.

Cyclic AMP phosphodiesterase (PDE) isozymes were isolated and characterized from the soluble fraction of rat parotid gland. Four main peaks containing PDE activity were obtained by Q-Sepharose Fast Flow column chromatography. The four peaks were identified as PDEs I-IV by kinetic properties, molecular-weight analysis and their responses to effectors and inhibitors.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

Regulation of cAMP phosphodiesterases by cyclic nucleotides in rat parotid gland.

Approximately 88% of the total cAMP phosphodiesterase (PDE) activity was detected in the supernatant fraction of the rat parotid homogenate. Mono Q ion-exchange chromatography revealed five main peaks (PDE I, PDE II, PDE III, PDE IV and unknown). A high concentration of cGMP (> 1 microM) was necessary to activate PDE II, whereas PDE III was inhibited by cGMP at a concentration that was 1,000 times lower (100 pM). PDEs III and IV were activated by treatment with a catalytic subunit of cAMP-dependent protein kinase (A kinase), and H-8, a A kinase inhibitor, inhibited the activation. Treatment of parotid slices with 1 microM isoproterenol stimulated PDE activity by approximately 120%, and 10 microM propranolol inhibited the activation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

Effect of PT-treatment on ANP-mediated inhibition of adenylate cyclase and amylase release in rat parotid gland.

Effects of pertussis toxin (PT) treatment on atrial natriuretic peptide (ANP)-mediated inhibition of adenylate cyclase and amylase release were investigated in rat parotid gland. Adenylate cyclase activity stimulated by GTP gamma S in PT-treated membranes was much larger than that in normal membranes. ANP dose-dependently inhibited adenylate cyclase stimulated by GTP gamma S in control rat parotid membranes, however in membranes prepared from PT-injected (in vivo) rat parotid gland, ANP did not inhibit adenylate cyclase. ANP(10(-7)M) inhibited cAMP accumulation stimulated by forskolin (10(-6)M) in control rat parotid acinar cells by about 34%, however, in PT-treated cells, the inhibitory effect of ANP was attenuated completely. In control cells amylase release stimulated by isoproterenol (10(-6)M) and forskolin (10(-6)M) were also depressed by ANP (10(-7)M) by 27 and 30% respectively. The inhibitory response of ANP on amylase release was completely attenuated by PT-treatment. Gi was detected as a ADP-ribosylated 41-KDa protein by incubation of parotid membranes with PT and [alpha-32P]NAD. In rat parotid gland, these results suggested that ANP mediates adenylate cyclase/cAMP system and consequently reduces amylase release through ANP-C receptor coupled to Gi.

Adenosine Diphosphate Ribose↗
PubMed1994

Influence of atrial natriuretic peptide on cyclic nucleotides and amylase release in rat parotid salivary gland in vitro.

Atrial natriuretic peptide (ANP), sodium nitroprusside and hydroxylamine increased cGMP accumulation in rat parotid acinar cells both in the presence and absence of forskolin but in a different manner. On the other hand, ANP decreased forskolin-stimulated cAMP accumulation, although sodium nitroprusside and hydroxylamine had no effect on cAMP accumulation. Amylase release stimulated by forskolin, dibutyryl-cAMP or isoproterenol was depressed by ANP, whereas sodium nitroprusside and hydroxylamine did not evoke the inhibition of forskolin-stimulated amylase release. These results suggest that the inhibition of cAMP accumulation and of amylase release by ANP were not mediated via cGMP produced by guanylate cyclase-A.

Amylases↗