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S Orita

Publications and source records attributed to S Orita.

At least 19 recordsLinked to original sources
PubMed2001

A RHO GTPase-mediated pathway is required during P cell migration in Caenorhabditis elegans.

The Rho family of guanine triphosphate hydrolases controls various cellular processes, including cell migration. We describe here the demonstration of a role for a RhoA GTPase homologue during cell migration in Caenorhabditis elegans. We show that eliminating or reducing rho-1 gene function by using a dominant-negative transgene or dsRNA interference results in a severe defect in migration of hypodermal P cells to a ventral position. Biochemical and genetic data also suggest that unc-73, which encodes a Trio-like guanine nucleotide exchange factor, may act as an activator of rho-1 in the migration process. Mutations in let-502 ROCK, a homologue of a RhoA effector in mammals, also cause defects in P cell migration, suggesting that it may be one of several effectors acting downstream of rho-1 during P cell migration. Finally, we provide evidence to support the idea that other small Rac subfamily small GTPases act redundantly and in parallel to RHO-1 in this specific cell migration event.

Animals↗
PubMed2001

[Treatment for recurrent paradoxical brain embolism through the patent foramen ovale].

We report here two patients with recurrent paradoxical brain embolism through the patent foramen ovale(PFO). The TIAs, which occurred frequently under antiplatelet therapy, resolved soon after commencing the anticoagulation therapy. Case 1, a 57-year-old woman, was diagnosed as having lacunar brain infarction and was treated with ticlopidine hydrochloride. Eleven months later, she suffered from frequent TIAs. Anticoagulation therapy was started after the presence of PFO was documented on transesophageal echocardiography(TEE). Thereafter, her TIA disappeared. Case 2 was a 67-year-old man with a history of lacunar brain infarction. Although he was treated with aspirin for 9 months, he showed transient monoplegia in his right leg. His TEE study also revealed the presence of PFO. After the anticoagulation therapy reached the proper level(PT-NR = 2), he never experienced the recurrence of TIA. If the antiplatelet therapy failed to prevent the recurrence of TIA, it is recommended to find out the presence of PFO which is a potential source of paradoxical brain embolism. In such a case, anticoagulation therapy should be instituted.

Aged↗
PubMed2000

Enhancing effects of 2-amino-4,5-diphenylthiazole-induced polycystic kidneys on renal carcinogenesis in rats treated with dimethylnitrosamine.

The effects of the polycystic kidney environment on dimethylnitrosamine (DMN)-induced renal carcinogenesis were investigated in rats. In Experiment 1, male Wistar rats were given 25 or 10 ppm DMN in their drinking water and simultaneously administered 1% 2-amino-4,5-diphenylthiazole (DPT) in the diet for 30 weeks. DPT-induced polycystic kidney was associated with a significant increase in the number of renal cell tumors and incidence of mesenchymal tumors in the 25 ppm DMN + DPT group and the incidence of atypical tubules in the 10 ppm DMN + DPT group. PCNA labeling indices of cystic renal tubules in DPT-treated rats were significantly higher than for corresponding noncystic tubules. In Experiment 2, PCNA indices of renal tubules in 10 ppm + DPT rats and immunohistochemically CYP2E1-positive renal tubules in DPT-treated rats were demonstrated to be significantly increased on day 14. CYP2E1 mRNA expression in the kidneys of DPT-treated rats showed a fivefold increase over constitutive levels. The results thus indicate that DPT induction of polycystic kidneys enhances DMN-induced renal carcinogenesis in rats, with DPT-induced elevated cell proliferation and CYP2E1 expression in renal tubules as possible underlying mechanisms.

Animals↗
PubMed2000

Delayed neutrophil elastase inhibition prevents subsequent progression of acute lung injury induced by endotoxin inhalation in hamsters.

To define the role of neutrophil elastase (NE) in the progression of acute lung injury (ALI), we examined the effects of post-treatment with a specific NE inhibitor, sivelestat sodium hydrate (sivelestat), on ALI induced by endotoxin (ET) inhalation in hamsters. Inhalation of ET (300 microg/ml, 30 min) in conscious hamsters increased inflammatory cell count, protein concentration, and hemorrhage in bronchoalveolar lavage fluid (BALF) that peaked 24 h after ET inhalation. These changes were significant 2 h after ET inhalation and paralleled the increase in NE activity in BALF. When intravenously infused from 2 to 24 h post-ET inhalation, sivelestat (0.03 to 3 mg/kg/h) dose-dependently attenuated changes in these BALF parameters at 24 h post-ET inhalation in a manner dependent on the inhibition of NE activity in BALF. Histopathological analysis also indicated that sivelestat prevented the progression of lung inflammation such as alveolar neutrophil infiltration and hemorrhage. In contrast, dexamethasone (3 mg/kg, intravenously) was not effective in this model when administered 2 h after ET inhalation, although it was highly effective when applied before ET. We conclude that delayed inhibition of NE activity with sivelestat prevents subsequent progression of ALI in hamsters after ET inhalation. Thus NE may play an important role in the progression of ALI.

Animals↗
PubMed2000

Mechanism of relaxant response to papaverine on the smooth muscle of non-pregnant rat uterus.

In the present paper, we examined a mechanism of the papaverine induced relaxation in the smooth muscle of non-pregnant rat uterus. The hyperosmotic 65 mM KCl (H-65K+)-or oxytocin-induced contraction in the uterus was inhibited by an addition of papaverine in a concentration-dependent manner. Papaverine did not increase both cAMP and cGMP contents in the uterus in the presence of H-65K+ or oxytocin. In fura 2 loaded muscles, papaverine did not affect an increase of [Ca2+]i level by high K+ or oxytocin. In permeabilized muscles, papaverine had no effect on the Ca2+-induced contraction. H-65K+ and oxytocin increased the rate of oxygen consumption 1.8 and 1.5 times higher than that in the resting condition, respectively. The increase of oxygen consumption in the H-65K+ or oxytocin was significantly inhibited by papaverine (1-100 microM). These results suggested that papaverine inhibits smooth muscle contraction mainly by inhibition of mitochondrial respiration in rat uterus as well as guinea pig ileum, which shows a highly spontaneous activity and a highly metabolic dependency of a contraction.

Animals↗
PubMed1999

Doc2alpha is an activity-dependent modulator of excitatory synaptic transmission.

Doc2alpha is a synaptic vesicle-associated Ca2 + -binding protein. To study the role of Doc2alpha in synaptic transmission and modulation, we generated homozygous null Doc2alpha mutant mice. In the CA1 region of hippocampal slices in the mutant mice, excitatory synaptic responses evoked with prolonged 5 Hz stimulation showed a significantly larger frequency facilitation followed by a steeper depression than those in wild-type mice, whereas there was no difference in synaptic transmission at lower frequencies or in paired-pulse facilitation. These results suggest that Doc2alpha regulates synaptic transmission when high Ca2 + concentrations in the presynaptic terminal are sustained. Furthermore, the mutant mice showed impairment in long-term potentiation and passive avoidance task. Thus, Doc2alpha may regulate transmitter release during repetitive synaptic activation, thereby contributing to memory formation.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1998

Interaction of Doc2 with tctex-1, a light chain of cytoplasmic dynein. Implication in dynein-dependent vesicle transport.

Doc2 has one Munc13-interacting domain at the N-terminal region and two C2-like domains interacting with Ca2+ and phospholipid at the C-terminal region. Doc2 consists of two isoforms, Doc2alpha and -beta. Doc2alpha is specifically expressed in neuronal cells and implicated in Ca2+-dependent neurotransmitter release, whereas Doc2beta is ubiquitously expressed and its function is unknown. We show here that both Doc2alpha and -beta interact with rat tctex-1, a light chain of cytoplasmic dynein, in both cell-free and intact cell systems. Overexpression of the N-terminal fragment of Doc2 containing the tctex-1-interacting domain induces changes in the intracellular localization of cation-independent mannose 6-phosphate receptor and its ligand, cathepsin D, which are transported from trans-Golgi network to late endosomes. Overexpression of the C-terminal fragment containing two C2-like domains shows the similar effect, but to a lesser extent, whereas overexpression of full-length Doc2 or the C-terminal fragment of rabphilin3 containing two C2-like domains does not show this effect. Because dynein is a minus-end-directed microtubule-based motor protein, these results suggest that Doc2, especially Doc2beta, plays a role in dynein-dependent intracellular vesicle transport.

Amino Acid Sequence↗
PubMed1998

p53 gene mutations in rectal cancer associated with schistosomiasis japonica in Chinese patients.

Mutations in p53 tumor suppressor gene were examined in 44 Chinese patients with rectal cancer, including 22 cases with advanced schistosomiasis japonica and 22 cases without schistosomiasis. In schistosomal rectal cancer (SRC), 13 mutations were found in 10 cases, which included 11 base-pair substitutions and two deletions. Of 11 base substitutions, nine were transitions and two were transversions and seven of them were located at CpG dinucleotides. In non-schistosomal rectal cancer (NSRC), 13 mutations were found in nine cases, all of which were base-pair substitutions. Of 13 substitutions, 10 were transitions and three were transversions and three of them were located at CpG dinucleotides. The proportion of base-pair substitutions at CpG dinucleotides was higher in SRC patients than in NSRC patients, although this was not statistically significant (P = 0.054). Point mutation was frequent at codon 248 in SRC. A higher frequency of arginine missense mutations was observed in SRC than in NSRC. These observations suggest that the mutations in SRC are the result of genotoxic agents produced endogenously through the course of schistosomiasis japonica.

Aged↗
PubMed1998

Role of the Doc2 alpha-Munc13-1 interaction in the neurotransmitter release process.

Doc2alpha and Munc13-1 proteins are highly concentrated on synaptic vesicles and the presynaptic plasma membrane, respectively, and have been implicated in Ca2+-dependent neurotransmitter release. Doc2alpha interacts with Munc13-1 through the N-terminal region of Doc2alpha (the Mid domain; amino acid residues 13-37). Here we examine whether the interaction between Doc2alpha and Munc13-1 is required for Ca2+-dependent neurotransmitter release from intact neuron. A synthetic Mid peptide (the Mid peptide), but not a control mutated Mid peptide or a scrambled Mid peptide, inhibited the interaction between Doc2alpha and Munc13-1 in vitro. Introduction of the Mid peptide into presynaptic neurons of cholinergic synapses, formed between rat superior cervical ganglion neurons, reversibly inhibited synaptic transmission evoked by action potentials. In contrast, the control peptides did not inhibit synaptic transmission. This inhibitory effect depended on the presynaptic activity and was affected by extracellular Ca2+ concentrations. The onset of the Mid peptide effect was shortened when the neuron was stimulated at a higher frequency, and the inhibition was more potent at 1 mM Ca2+ than at 5.1 mM Ca2+. These results suggest that the Doc2alpha-Munc13-1 interaction plays a role in a step before the final fusion step of synaptic vesicles with the presynaptic plasma membrane in the evoked neurotransmitter release process.

Animals↗
PubMed1998

A novel brain-specific isoform of beta spectrin: isolation and its interaction with Munc13.

Munc13 is a component of the neurotransmitter release machinery which is specifically expressed in brain. Munc13 interacts with Doc2 and syntaxin which are also implicated in the neurotransmitter release process. Here we isolated another Munc13-interacting molecule from a rat brain cDNA library by use of the yeast two-hybrid system, identified it to be a novel type of beta spectrin, and named it beta SpIII sigma 1. beta SpIII sigma 1 was specifically expressed in brain, where it was enriched in the synaptic vesicle and plasma membrane fractions. Because spectrin has been shown to interact with the actin cytoskeleton which is involved in the exocytotic process, the present results suggest that the Munc13-beta SpIII sigma 1 interactions play a role in neurotransmitter release.

Amino Acid Sequence↗
PubMed1998

Relationship between CD44 expression and differentiation of human prostate adenocarcinomas.

It is well documented that CD44 plays an important role in tumor metastasis. We investigated whether there is a correlation between the expression of its isoforms in prostate cancer cells and patient prognosis using 72 cases with biopsy specimens. Immunohistochemistry demonstrated expression of CD44H (68.1%), v6 (36.1%) and v9 (68.1%) to be relatively more frequent than that of other isoforms. A positive correlation between CD44H expression and tumor differentiation was found but this did not extend to clinical staging or prognosis. Likewise, results for CD44v6 or v9 expression suggest that they may be useful markers for prostate adenocarcinoma differentiation but not prognosis.

Adenocarcinoma↗
PubMed1998

Caenorhabditis elegans SUR-5, a novel but conserved protein, negatively regulates LET-60 Ras activity during vulval induction.

The let-60 ras gene acts in a signal transduction pathway to control vulval differentiation in Caenorhabditis elegans. By screening suppressors of a dominant negative let-60 ras allele, we isolated three loss-of-function mutations in the sur-5 gene which appear to act as negative regulators of let-60 ras during vulval induction. sur-5 mutations do not cause an obvious mutant phenotype of their own, and they appear to specifically suppress only one of the two groups of let-60 ras dominant negative mutations, suggesting that the gene may be involved in a specific aspect of Ras activation. Consistent with its negative function, overexpressing sur-5 from an extragenic array partially suppresses the Multivulva phenotype of an activated let-60 ras mutation and causes synergistic phenotypes with a lin-45 raf mutation. We have cloned sur-5 and shown that it encodes a novel protein. We have also identified a potential mammalian SUR-5 homolog that is about 35% identical to the worm protein. SUR-5 also has some sequence similarity to acetyl coenzyme A synthetases and is predicted to contain ATP/GTP and AMP binding sites. Our results suggest that sur-5 gene function may be conserved through evolution.

Amino Acid Sequence↗
PubMed1997

Physical and functional interactions of Doc2 and Munc13 in Ca2+-dependent exocytotic machinery.

Doc2 has two C2 domains that interact with Ca2+ and phospholipid. Munc13 has two C2 domains and one C1 domain that interacts with phorbol ester or diacylglycerol (DAG) and phospholipid. Both Doc2 and Munc13 are implicated in Ca2+-dependent neurotransmitter release, but their modes of action still remain unclear. We show here that Doc2 interacts with Munc13 both in a cell-free system and in intact PC12 cells during the high K+-induced Ca2+-dependent exocytosis. The Doc2-Munc13 interactions are stimulated by phorbol ester through the C1 domain of Munc13. Overexpression of the Doc2-interacting domain of Munc13 reduces the Ca2+-dependent exocytosis from PC12 cells, and co-expression with Doc2 suppresses this reduction. These results, together with the earlier findings that secretagogues produce DAG and elevate cytoplasmic Ca2+, suggest that the DAG-induced Doc2-Munc13 interactions play an important role in Ca2+-dependent exocytotic machinery.

Animals↗
PubMed1997

Molecular cloning of mouse Doc2alpha and distribution of its mRNA in adult mouse brain.

We have previously isolated from a human brain cDNA library, a new protein having two C2-like domains which interact with Ca2+ and phospholipid, and named Doc2alpha. Doc2alpha is abundantly expressed in brain, where it is highly concentrated on the synaptic vesicle fraction, and is implicated in Ca2(+)-dependent exocytosis. We have isolated here a mouse Doc2alpha cDNA and determined the localization of its mRNA in adult mouse brain. The amino acid sequence of the mouse Doc2alpha cDNA is 92% identical with that of the human counterpart. Northern blot analysis and in situ hybridization on adult mouse brain sections have revealed that Doc2alpha is predominantly expressed in mouse brain, where it is expressed in neuronal cells, but not in non-neuronal cells. Doc2alpha is highly expressed in the olfactory bulb, cerebral cortex, hippocampus, amygdaloid complex, and ventromedial hypothalamus nucleus, but not in the cerebellum, caudate-putamen, or ventral thalamus. These results indicate that Doc2alpha is expressed heterogeneously in mouse brain, where it is predominantly expressed in neuronal cells, and suggest that Doc2alpha plays a specific role in the area where it is expressed.

Amino Acid Sequence↗