The active site cysteine of the proapoptotic protein glyceraldehyde-3-phosphate dehydrogenase is essential in oxidative stress-induced aggregation and cell death.

Recent studies have revealed that the redox-sensitive glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), is involved in neuronal cell death that is triggered by oxidative stress. GAPDH is locally deposited in disulfide-bonded aggregates at lesion sites in certain neurodegenerative diseases. In this study, we investigated the molecular mechanism that underlies oxidative stress-induced aggregation of GAPDH and the relationship between structural abnormalities in GAPDH and cell death.

A minor role for Ca2+ sensitization in sustained contraction through activation of muscarinic receptor in circular muscle of rat distal colon.

We previously demonstrated that Ca(2+) sensitization has an essential role for carbachol-induced contraction in the longitudinal muscle of the rat distal colon. In the present study, we extended these studies to clarify the role of Ca(2+) sensitization in contraction induced by the activation of muscarinic receptors in the circular muscle of the rat distal colon. Carbachol induced a rapid phasic contraction followed by a sustained contraction that was significantly lower than the phasic and was superimposed with the rhythmic contractions.

Orexin A affects ascending contraction depending on downstream cholinergic neurons and descending relaxation through independent pathways in mouse jejunum.

The involvement of orexin in neural pathways for peristalsis was examined in mouse jejunal segments. Localized distension of the segments using a small balloon resulted in ascending contraction and descending relaxation. Ascending contraction was abolished by atropine and tetrodotoxin.

Inhibitory effects of alendronate on cholinergic responses in rat lower esophageal sphincter.

Alendronate is a potent inhibitor of osteoclast-mediated bone resorption, but its use results in serious esophageal damage. In order to clarify the latter, we examined the effects of alendronate on electrical field stimulation-induced responses in the rat lower esophageal sphincter. Electrical field stimulation induced atropine-sensitive contraction.

Roles of PACAP and PHI as inhibitory neurotransmitters in the circular muscle of mouse antrum.

Mediators of neurogenic responses of the gastric antrum were studied in wild-type and pituitary adenylate cyclase-activating polypeptide (PACAP) -knockout (KO) mice. Electrical field stimulation (EFS) to the circular muscle strips of the wild-type mouse antrum induced a triphasic response; rapid transient relaxation and contraction, and sustained relaxation that was prolonged for an extended period after the end of EFS. The transient relaxation and contraction were completely inhibited by L-nitroarginine and atropine, respectively.

PACAP- and PHI-mediated sustained relaxation in circular muscle of gastric fundus: findings obtained in PACAP knockout mice.

Mediators of neurogenic responses of the gastric fundus were studied in wild type and pituitary adenylate cyclase activating peptide (PACAP) knockout mice. Electrical field stimulation (EFS) to the circular muscle strips of the wild type mouse fundus induced a tri-phasic response, rapid transient contraction and relaxation, and sustained relaxation that was prolonged for an extended period after the end of EFS. The transient relaxation and contraction were completely inhibited by N(G)-nitro-L-arginine and atropine, respectively.

Ascending contraction and descending relaxation in the distal colon of mice lacking interstitial cells of Cajal.

Recently an essential role of interstitial cells of Cajal (ICC) within myenteric plexus (ICC-MY) was suggested in ascending contraction and descending relaxation in the mouse ileum. The role of ICC in these neural reflexes was examined in the distal colonic segments prepared from the wild type and c-kit mutant, W/W(V) mice, in the present study. Localized distension of the segments from the wild type mice by using a small balloon resulted in ascending contraction and descending relaxation.

Examination of the role of cholinergic myenteric neurons with the impairment of neural reflexes in the ileum of c-kit mutant mice.

Our previous study showed that impairment of ascending and descending neural reflexes in the ileum of the c-kit mutant, W/W(V), mice is due to a loss of interstitial cells of Cajal present at the myenteric plexus region (ICC-MY) in the mutant. In the present study, cholinergic interneurons were thought to be involved in these pathways, since hexamethonium, an antagonist of the nicotinic ACh receptor, significantly inhibited both neural reflexes in wild type mice. Therefore, we examined whether the loss of ICC-MY affects cholinergic interneurons involved in these pathways.

Participation of ATP in nonadrenergic, noncholinergic relaxation of longitudinal muscle of wistar rat jejunum.

A role of ATP in nonadrenergic, noncholinergic (NANC) relaxations was examined in the Wistar rat jejunum. Electrical field stimulation (EFS) induced NANC relaxation of longitudinal muscle of the jejunal segments in a frequency-dependent manner. A purinoceptor antagonist, adenosine 3'-phosphate 5'-phosphosulfate (A3P5PS, 100 muM) inhibited the relaxation: relaxations induced by EFS at lower or higher frequencies were either completely or partially inhibited, respectively.

Role of the interstitial cells distributed in the myenteric plexus in neural reflexes in the mouse ileum.

We examined the role of interstitial cells of Cajal (ICC) in the ascending and descending neural reflexes in the ileal segments prepared from wild type mice and c-kit mutant W/WV mice. Localized distension of the ileal segments from wild type mice with a small balloon caused contraction or relaxation of the circular muscle on the oral or anal side of the distended region, respectively. However, these intestinal reflexes were not induced in the ileal segments from the mutant mice.

Roles of M2 and M4 muscarinic receptors in regulating acetylcholine release from myenteric neurons of mouse ileum.

We investigated the subtype of presynaptic muscarinic receptors associated with inhibition of acetylcholine (ACh) release in the mouse small intestine. We measured endogenous ACh released from longitudinal muscle with myenteric plexus (LMMP) preparations obtained from M1-M5 receptor knockout (KO) mice. Electrical field stimulation (EFS) increased ACh release in all LMMP preparations obtained from M1-M5 receptor single KO mice.

Mechanisms involved in carbachol-induced Ca(2+) sensitization of contractile elements in rat proximal and distal colon.

1. Mechanisms involved in Ca(2+) sensitization of contractile elements induced by the activation of muscarinic receptors in membrane-permeabilized preparations of the rat proximal and distal colon were studied. 2.

Essential role of the interstitial cells of Cajal in nitric oxide-mediated relaxation of longitudinal muscle of the mouse ileum.

The role of interstitial cells of Cajal (ICC) in electrical field stimulation (EFS)-induced neurogenic responses in ileum was studied by using the ICC-deficient mutant (SLC-W/W(V)) mouse and its wild type. In the immunohistochemical study with anti-c-Kit antibody, ICC was observed in the myenteric plexus (MY) and deep muscular plexus (DMP) region in the wild type. In the mutant, ICC-MY were lost, only ICC-DMP were present.

[Roles of interstitial cells of Cajal in regulation of motility of the mouse intestine].

The role of interstitial cells of Cajal (ICC) in contractile activity of the gastrointestinal tract has been intensely studied. Among ICC present within various regions of the gastrointestinal tissue, ICC within the myenteric plexus (ICC-MY) and within the submuscular plexus (ICC-SMP) are regarded as the pacemaker. Action potentials initiated in ICC were suggested to propagate to adjacent smooth muscle cells and to induce the spontaneous activity.

Changes in mechanism of PACAP-induced relaxation in longitudinal muscle of the distal colon of Wistar rats with age.

Mechanisms of relaxation of longitudinal muscle of the distal colon induced by exogenously added pituitary adenylate cyclase activating peptide (PACAP) were studied in 2- to 30-week-old Wistar rats. Exogenous PACAP induced very significant relaxation of the longitudinal muscle in 2-week-old rats, but this effect decreased significantly with age. The cyclic AMP-cyclic AMP-dependent protein kinase (PKA) pathway and the tyrosine kinase-small conductance Ca2+-activated K+ channel (SK channel) pathway were found to be involved in the mechanism of PACAP-induced relaxation.

Origin of ATP for Ca2+-induced contraction in the guinea-pig femoral artery.

Previously, we have described differences between the rat proximal colon and femoral artery with respect to the role of ATP newly synthesized by creatine kinase. In the present study the role of newly synthesized ATP was studied in the guinea-pig femoral artery to examine species differences. In the alpha-toxin-permeabilized preparation of the guinea-pig femoral artery, the rapid Ca(2+)-induced contraction was suppressed when creatine kinase activity was inhibited.

Dependence of Ca2+-induced contraction on ATP in alpha-toxin-permeabilized preparations of rat femoral artery.

Effects of various concentrations of ATP on Ca(2+)-induced contraction were studied in alpha-toxin-permeabilized preparations obtained from the rat femoral artery. The contractile magnitude was highest in the presence of 1 mM ATP and decreased with both increasing and decreasing the concentration, suggesting the presence of an optimum ATP concentration in inducing contraction. The magnitude of the contractions in various concentrations of ATP correlated with the extent of the phosphorylated myosin light chain (MLC).

Essential role of ATP synthesized by creatine kinase in contraction of alpha-toxin permeabilized preparations of tonic type smooth muscle.

The role of ATP newly synthesized from ADP and phosphocreatine (PC) by creatine kinase (CK) in the contraction of tonic type smooth muscle, rat femoral artery was studied, since its necessity for phasic type smooth muscle was previously shown. In alpha-toxin-permeabilized preparations obtained from rat femoral artery, Ca(2+) induced a tonic type contraction in the presence of ATP and PC. Omission of PC inhibited significantly the contraction.

Expression of the small conductance Ca2+-activated K+ channel, SK3, in the olfactory ensheathing glial cells of rat brain.

Olfactory sensory neurons are wrapped by ensheathing glial cells in the olfactory nerve layer (ONL). Neither functional roles nor electrical properties of ensheathing glial cells have been, as yet, fully clarified. Four subunits (SK1-4) of small conductance Ca2+-activated K+ (SK) channels have been cloned.

Localization of Ca2+-activated K+ channel, SK3, in fibroblast-like cells forming gap junctions with smooth muscle cells in the mouse small intestine.

In the present study, we examined the expression and the localization of apamin-sensitive small conductance Ca(2+)-activated K(+) channels (SK channels) in the mouse intestine. SK3-immunoreactivity (IR) was detected in both ileum and colon. Double staining experiments showed that SK3-IR was colocalized with prolyl 4-hydroxylase (PH(alpha))-IR, but not with c-Kit-IR which are markers of fibroblast cells and the interstitial cells of Cajal (ICC), respectively.

The site where newly synthesized ATP is necessary for tension development in alpha-toxin permeabilized preparations of rat proximal colon.

Since it was suggested in our previous study that ATP newly synthesized from ADP and phosphocreatine (PCr) by creatine kinase had an important role in Ca2+-induced phasic contraction in alpha-toxin permeabilized smooth muscle of rat proximal colon, we studied the role of newly synthesized ATP on myosin ATPase activity, by assessing a rate of force development as an index of myosin ATPase activity. The alpha-toxin-permeabilized preparations were thiophosphorylated by treatment with ATPgammaS. After the thiophosphorylation, the contraction induced by ATP plus PCr in the absence of Ca2+ reached the maximum at 30 s.

PAC1 receptor-mediated relaxation of longitudinal muscle of the mouse proximal colon.

Since pituitary adenylate cyclase-activating polypeptide (PACAP) was shown to partially mediate nonadrenergic, noncholinergic (NANC) relaxation of longitudinal muscle of the proximal colon of ICR mice, we further studied the receptor subtype activated by PACAP by using a mutant mouse whose PAC1 receptors are markedly reduced. In wild-type mice, the PACAP-mediated component of NANC relaxation was 33%, but it was absent in the mutant mice. The potency of exogenous PACAP in inducing relaxation in the mutant mice was one hundredth of that in wild-type mice.

A possible role of neurotensin in NANC relaxation of longitudinal muscle of the jejunum and ileum of Wistar rats.

The mediators of nonadrenergic, noncholinergic (NANC) relaxation in longitudinal muscle of the jejunum and ileum of Wistar rats were examined in vitro. Treatment of the jejunal and ileal segments with alpha-chymotrypsin resulted in decreases in the NANC relaxations induced by electrical field stimulation (EFS) by about one half. The NANC relaxations were also decreased by about one half after the segments had been desensitized to neurotensin.

Specific localization of an inwardly rectifying K(+) channel, Kir4.1, at the apical membrane of rat gastric parietal cells; its possible involvement in K(+) recycling for the H(+)-K(+)-pump.

Hydrochloric acid (HCl) is produced in parietal cells of gastric epithelium by a H(+)-K(+) pump. Protons are secreted into the gastric lumen in exchange for K(+) by the action of the H(+)-K(+)-ATPase. Luminal K(+) is essential for the operation of the pump and is thought to be supplied by unidentified K(+) channels localized at the apical membrane of parietal cells.