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Biomedical subjects

S Kuroda

Publications and source records attributed to S Kuroda.

At least 235 records · Page 13Linked to original sources
PubMed1996

Identification of IQGAP as a putative target for the small GTPases, Cdc42 and Rac1.

Cdc42 and Rac1 have been implicated in the regulation of various cell functions such as cell morphology, polarity, and cell proliferation. We have partially purified a Cdc42- and Rac1-associated protein with molecular mass of about 170 kDa (p170) from bovine brain cytosol. This protein interacted with guanosine 5'-(3-O-thio)triphosphate (GTPgammaS).glutathione S-transferase (GST)-Cdc42 and GTPgammaS++.GST-Rac1 but not with the GDP.GST-Cdc42, GDP.GST-Rac1, or GTPgammaS.GST-RhoA). We identified p170 as an IQGAP, which is originally identified as a putative Ras GTPase-activating protein. Recombinant IQGAP specifically interacted with GTPgammaS.Cdc42 and GTPgammaS.Rac1. The C-terminal fragment of IQGAP was responsible for their interactions. IQGAP was specifically immunoprecipitated with dominant-active Cdc42(Val12) or Rac1(Val12) from the COS7 cells expressing Cdc42(Val12) or Rac1(Val12), respectively. Immunofluorescence analysis revealed that IQGAP was accumulated at insulin- or Rac1-induced membrane ruffling areas. This accumulation of IQGAP was blocked by the microinjection of the dominant-negative Rac1(Asn17) or Cdc42(Asn17). Moreover, IQGAP was accumulated at the cell-cell junction in MDCK cells, where alpha-catenin and ZO-1 were localized. These results suggest that IQGAP is a novel target molecule for Cdc42 and Rac1.

Actin Cytoskeleton↗
PubMed1996

Increased Gi alpha and Go alpha mRNAs in hippocampus after repeated methamphetamine administration.

Changes in transcription of Gs alpha, Gi2 alpha and Go alpha proteins after repeated methamphetamine administration were investigated using in situ hybridization. Rats received daily injections of methamphetamine (4 mg kg-1) for 14 days. Four hours after the last injection, Go alpha mRNA showed an increase of 16.6-31.6% in CA1, CA3 and dentate gyrus of the hippocampus. Gi alpha mRNA level increased by 24.2% in CA1, while Gs alpha mRNA remained unaffected. Go alpha and Gi alpha mRNA returned to basal levels after 48 h abstinence. The expression of these G alpha mRNA in other brain regions, including substantia nigra, ventral tegmentum area, striatum, accumbens and cortices, was unchanged. The increase in Go alpha and Gi alpha mRNAs restricted only to the hippocampus after repeated methamphetamine administration may be involved in the development of dependence rather than behavioral sensitization.

Animals↗
PubMed1996

Activation of RAC-protein kinase by heat shock and hyperosmolarity stress through a pathway independent of phosphatidylinositol 3-kinase.

RAC protein kinase (RAC-PK), a serine/threonine protein kinase containing a pleckstrin homology (PH) domain, was activated by cellular stress such as heat shock and hyperosmolarity. Wortmannin, which is known as a potent inhibitor of phosphatidylinositol 3-kinase and normally inhibits growth factor-induced activation of RAC-PK, did not suppress heat-shock induced activation of RAC-PK, indicating that this stress-induced activation of the kinase is not mediated by phosphatidylinositol 3-kinase. The PH domain was indispensable for stress-induced activation of RAC PK. In heat-treated cells, PKC delta, a member of the protein kinase C family, was found to associate with the PH domain of RAC-PK. This PKC subspecies was phosphorylated in vitro by RAC-PK. The results suggest that RAC-PK may play a role in the cellular response to stress through its PH domain.

3T3 Cells↗
PubMed1996

Unstimulated polymorphonuclear neutrophils regulate proximal coronary arterial tone.

Our objective is to clarify, by measuring the superoxide production as a marker of inactive state of polymorphonuclear neutrophils, whether unstimulated polymorphonuclear neutrophils would influence coronary arterial tone. We recorded the isometric tension of the porcine coronary arterial ring in a bath of oxygenated Krebs Ringer solution. Unstimulated porcine polymorphonuclear neutrophils that contained little superoxide were added to the bath. We also analyzed the prostaglandins produced in the bath. The isometric tension of arterial rings increased dose-dependently when polymorphonuclear neutrophils were added to the bath. The vasoconstriction induced by unstimulated polymorphonuclear neutrophils was inhibited by endothelial denudation, indomethacin, anti-CD11a/18-like antibody. Thromboxane A2 synthetase inhibitor and superoxide dismutase did not effect the vasoconstriction. Prostaglandin E2 predominated among the prostaglandins produced in the bath; its production was significantly inhibited by indomethacin (without vs. with indomethacin; 3898 +/- 1704 vs 1956 +/- 715 pg/ml, P < 0.05, n=6). Pretreatment of vascular rings with indomethacin blocked the interaction of the coronary artery with polymorphonuclear neutrophils. Results suggested that unstimulated polymorphonuclear neutrophils constrict the proximal coronary artery. Such vasoconstriction may be produced by cyclooxygenase products, especially prostaglandin E2 produced in the vascular wall via the interaction between the polymorphonuclear neutrophils and the endothelium. Polymorphonuclear neutrophils may regulate coronary arterial tone.

Animals↗
PubMed1996

Different effects of various phospholipids on Ki-Ras-, Ha-Ras-, and Rap1B-induced B-Raf activation.

We have recently purified a Ki-Ras- and Ha-Ras-dependent extracellular signal-regulated kinase kinase from bovine brain and identified it as B-Raf protein kinase complexed with 14-3-3 proteins (Yamamori, B., Kuroda, S., Shimizu, K., Fukui, K., Ohtsuka, T., and Takai, Y. (1995) J. Biol. Chem. 270, 11723-11726). Moreover, we found that Rap1B as well as Ki-Ras and Ha-Ras stimulate the B-Raf activity. Since B-Raf contains a cysteine-rich domain originally found in protein kinase C as a domain responsible for interaction with phosphatidylserine (PS) and diacylglycerol or 12-O-tetradecanoylphorbol-13-acetate, we have examined here the effect of these compounds on the Ki-Ras-, Ha-Ras-, and Rap1B-induced activation of bovine brain B-Raf. Bovine brain PS enhanced Ki-Ras-stimulated B-Raf activity. Phosphatidic acid was slightly active, but other phospholipids, such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol (PI), PI-4-monophosphate, PI-4,5-bisphosphate, and PI-3,4,5-trisphosphate, were inactive. However, none of the above phospholipids affected the Ha-Ras-stimulated B-Raf activity, whereas PI, PS, phosphatidylethanolamine, and phosphatidic acid inhibited the Rap1B-stimulated B-Raf activity. Phosphatidylcholine or PI-4-monophosphate did not show any effect on the Rap1B-stimulated B-Raf activity. Synthetic PS with two unsaturated fatty acids, such as 1,2-dioleoyl-PS or 1,2-dilinoleoyl-PS, showed the same effect toward the Ki-Ras- and Rap1B-stimulated B-Raf activities, but synthetic PS with two saturated fatty acids, such as 1, 2-distearoyl-PS, was inactive. 12-O-Tetradecanoylphorbol-13-acetate did not affect the stimulatory or inhibitory effect of PS on the Ki-Ras- and Rap1B-stimulated B-Raf activities, respectively. PS did not affect the Ki-Ras-, Ha-Ras-, or Rap1B-independent basal B-Raf activity or the mitogen-activated protein kinase kinase or extracellular signal-regulated kinase activity. These results indicate that various phospholipids differently affect Ki-Ras-, Ha-Ras, and Rap1B-induced B-Raf activation.

Animals↗
PubMed1996

[3H]YM-09151-2 (nemonapride), a potent radioligand for both sigma 1 and sigma 2 receptor subtypes.

Using K+ phosphate buffer with 25 nM spiperone, [3H]YM-09151-2 binding showed a high affinity for sigma receptors but no affinity for D2 dopamine or 5-HT1A receptors in rat brain. The order of pKi values of various sigma compounds at [3H]YM-09151-2 binding sites and stereoisomer selectivity were consistent with previous studies using other sigma ligands such as (+)-[3H]SKF-10047, [3H]DTG and (+)-[3H]3-PPP. Although Scatchard analysis fitted a one-site model, competition between [3H]YM-09151-2 and (+)-pentazocine revealed two sites, sigma 1 and sigma 2 receptors, at which the Ki values of YM-09151-2 were 8.4 nM and 9.6nM, respectively. Autoradiography using [3H]YM-09151-2 also showed a characteristic distribution of sigma receptors in rat brain. [3H]YM-09151-2 is, therefore, a potent and useful radioligand for sigma 1/sigma 2 receptor subtypes.

Animals↗
PubMed1996

sigma Receptor antagonists block the development of sensitization to cocaine.

The effects of putative sigma receptor antagonists, BMY-14802 (alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine), rimcazole and SR-31742A (cis-3-(hexahydroazepin-1-yl)1-(3-chloro-4- cyclohexylphenyl)propene-1), on the development of behavioral sensitization induced by repeated administration of cocaine were investigated. Acute intraperitoneal injection of 15 mg/kg cocaine in rats induced moderate hyperactivity which mainly consisted of sniffing and rearing. These acute effects of cocaine were hardly affected by co-administration of the sigma receptor antagonists, except that BMY-14802 enhanced, but not significantly cocaine-induced locomotion. While repeated cocaine administration induced a progressive increase in stereotyped behaviors and resulted in sensitization, every sigma receptor antagonists tested attenuated the development of sensitization to cocaine. These prophylactic effects of sigma receptor antagonists against cocaine-induced sensitization were confirmed by the challenge test with cocaine alone after an abstinence. These results were consistent with results of our previous study which revealed that BMY-14802 blocked the sensitization to methamphetamine, another psychostimulant. Therefore, sigma receptors play a crucial role in the development of the psychostimulant-induced sensitization phenomenon, which is a pharmacological model of schizophrenia.

Animals↗
PubMed1996

Activation of brain B-Raf protein kinase by Rap1B small GTP-binding protein.

Rap1 small GTP-binding protein has the same amino acid sequence at its effector domain as that of Ras. Rap1 has been shown to antagonize the Ras functions, such as the Ras-induced transformation of NIH 3T3 cells and the Ras-induced activation of the c-Raf-1 protein kinase-dependent mitogen-activated protein (MAP) kinase cascade in Rat-1 cells, whereas we have shown that Rap1 as well as Ras stimulates DNA synthesis in Swiss 3T3 cells. We have established a cell-free assay system in which Ras activates bovine brain B-Raf protein kinase. Here we have used this assay system and examined the effect of Rap1 on the B-Raf activity to phosphorylate recombinant MAP kinase kinase (MEK). Recombinant Rap1B stimulated the activity of B-Raf, which was partially purified from bovine brain and immunoprecipitated by an anti-B-Raf antibody. The GTP-bound form was active, but the GDP-bound form was inactive. The fully post-translationally lipid-modified form was active, but the unmodified form was nearly inactive. The maximum B-Raf activity stimulated by Rap1B was nearly the same as that stimulated by Ki-Ras. Rap1B enhanced the Ki-Ras-stimulated B-Raf activity in an additive manner. These results indicate that not only Ras but also Rap1 is involved in the activation of the B-Raf-dependent MAP kinase cascade.

3T3 Cells↗
PubMed1996

Identification of AF-6 and canoe as putative targets for Ras.

Ras (Ha-Ras, Ki-Ras, N-Ras) is implicated in the regulation of various cell functions such as gene expression and cell proliferation downstream from specific extracellular signals. Here, we partially purified a Ras-interacting protein with molecular mass of about 180 kDa (p180) from bovine brain membrane extract by glutathione S-transferase (GST)-Ha-Ras affinity column chromatography. This protein bound to the GTP gamma S (guanosine 5'-(3-O-thio)triphosphate, a nonhydrolyzable GTP analog).GST-Ha-Ras affinity column but not to those containing GDP.GST-Ha-Ras or GTP gamma S.GST-Ha-Ras with a mutation in the effector domain (Ha-RasA38). The amino acid sequences of the peptides derived from p180 were almost identical to those of human AF-6 that is identified as the fusion partner of the ALL-1 protein. The ALL-1/AF-6 chimeric protein is the critical product of the t (6:11) abnormality associated with some human leukemia. AF-6 has a GLGF/Dlg homology repeat (DHR) motif and shows a high degree of sequence similarity with Drosophila Canoe, which is assumed to function downstream from Notch in a common developmental pathway. The recombinant N-terminal domain of AF-6 and Canoe specifically interacted with GTP gamma S.GST-Ha-Ras. The known Ras target c-Raf-1 inhibited the interaction of AF-6 with GTP gamma S.GST-Ha-Ras. These results indicate that AF-6 and Canoe are putative targets for Ras.

Amino Acid Sequence↗
PubMed1996

Delayed treatment with alpha-phenyl-N-tert-butyl nitrone (PBN) attenuates secondary mitochondrial dysfunction after transient focal cerebral ischemia in the rat.

The present experiments were undertaken to explore the mechanisms of secondary brain damage in focal ischemia of long duration (2 h), followed by recirculation. Recirculation has previously been found to cause partial recovery and secondary deterioration of cellular bioenergetic state, the subsequent damage being ameliorated by a free radical spin trap, alpha-phenyl-N-tert-butyl nitrone (PBN), even when the drug was given 1 (or 3) h after the start of recirculation. Our objective was to assess whether the secondary deterioration of the cellular bioenergetic state is due to mitochondrial dysfunction and to study whether PBN acts by preventing secondary damage to mitochondria. Focal and perifocal ("penumbral") tissues were sampled after 2 h of ischemia and after 1, 2, and 4 h of recirculation; at the latter two times, vehicle- and PBN-injected animals were studied, PBN being given after 1 h of recirculation. Homogenates were prepared, and stimulated (+ADP), nonstimulated (-ADP), and uncoupled respiratory rates were measured polarographically. The results were similar in focus and penumbra, albeit more pronounced in the focus. Ischemia was associated with a decrease in ADP-stimulated and uncoupled respiration rates, with a marked fall in the respiratory control ratio, defined as ADP-stimulated divided by nonstimulated respiration. Recirculation (1 h) brought about partial recovery, but continued reflow (2 and 4 h) was associated with a secondary deterioration of respiratory functions. This deterioration was prevented by PBN, given 1 h after the start of recirculation. The results raise the question whether the secondary deterioration of the cellular bioenergetic state in focal ischemia-reperfusion is due to secondary mitochondrial dysfunction and whether the amelioration of the subsequent damage by PBN is partly or wholly due to the effect of the spin trap on the mitochondria.

Adenosine Diphosphate↗
PubMed1996

Cerebral hypoxia after hyperventilation causes "re-build-up" phenomenon and TIA in childhood moyamoya disease. A near-infrared spectroscopy study.

Near-infrared spectroscopy was used to monitor the sequential changes in the cerebral oxygenation state during and after hyperventilation in two children with moyamoya disease. Hyperventilation induced the build-up phenomenon and a decrease in the concentration of oxy-hemoglobin ([oxy-Hb]) and total hemoglobin ([t-Hb]). The termination of hyperventilation was followed by partial recovery of [oxy-Hb] and [t-Hb]. Subsequently, however, [oxy-Hb] and [t-Hb] decreased again and cytochrome oxidase was reduced. These impairments of the cerebral hemodynamics and oxygen metabolism were closely associated with the re-build-up phenomenon on EEG and with transient ischemic attacks (TIA). The present study implies that cerebral hypoxia after hyperventilation is closely related to the re-build-up phenomenon and ischemic attacks in children with moyamoya disease.

Anastomosis, Surgical↗
PubMed1996

Regional cerebral hemodynamics during re-build-up phenomenon in childhood moyamoya disease. An analysis using 99mTc-HMPAO SPECT.

We investigated the role of ischemic hypoxia in the appearance of re-build-up phenomenon on electroencephalography in childhood moyamoya disease using 99mTc-hexamethyl propyleneamine oxime and single photon emission computed tomography (99mTc-HMPAO SPECT). In the case reported on, critical reduction of regional cerebral blood flow (rCBF) was observed during re-build-up phenomenon in the bilateral parieto-occipital area where acetazolamide testing revealed severe impairment of the perfusion reserve. On electroencephalography, the re-build-up phenomenon originated in these areas. In addition, re-build-up phenomenon developed into the entire hemisphere 30 s later, even where the severe ischemia was not observed. These results suggest that rCBF reduction induced by hyperventilation plays a critical role in the appearance of the re-build-up phenomenon, but other factors such as ischemic hypoxia after hyperventilation are also important in the development of this phenomenon.

Brain↗
PubMed1996

Moyamoya disease with precocious puberty and pustular psoriasis.

An 8-year-old girl suffering from precocious puberty and pustular psoriasis with moyamoya disease is described. The possibilities of a causal relationship between precocious puberty and moyamoya disease are discussed. The relevance of the patient's earlier upper respiratory tract infections to the pustular psoriasis and moyamoya disease is also considered.

Child↗
PubMed1996

BMY-14802 reversed the sigma receptor agonist-induced neck dystonia in rats.

To clarify clinical roles of sigma receptor binding affinity of neuroleptics, neck dystonia induced by microinjection of sigma receptor ligands and neuroleptics into rat red nucleus was investigated. DTG and (+)-3-PPP, putative sigma receptor agonists, induced neck dystonia in dose-dependent and reversible manner. Haloperidol and perphenazine induced dystonia in the same way as sigma receptor agonists, whereas zotepine and (-)-sulpiride did not. The rank order of potency in induction of dystonia and sigma receptor affinity of these compounds showed positive correlation. Although BMY-14802 has a high affinity for sigma receptors, it never produced dystonia by itself. On the other hand, combined injection of BMY-14802 with DTG attenuated DTG-induced dystonia. Therefore, it is suggested that typical neuroleptics such as haloperidol act agonistic and atypical neuroleptics such as BMY-14802 act antagonistic at rubral sigma receptors in the induction of neck dystonia.

Animals↗
PubMed1996

Near-infrared monitoring of cerebral oxygenation state during carotid endarterectomy.

BACKGROUND: Recent studies have indicated that near-infrared spectroscopy (NIRS) could continuously and noninvasively observe the changes in cerebral oxygenation state during hypoxia and ischemia, using their optical properties. Its validity and usefulness during cerebrovascular surgery, however, still remain to be clarified. METHODS: Using NIRS, we continuously monitored the changes in the concentration of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin ([oxy-HB], [deoxy-Hb], and [total Hb], respectively) and redox state of cytochrome oxidase (cyt ox) during carotid endarterectomy for 22 patients, and we compared the NIRS responses with those of intraoperative somatosensory evoked potentials (SEP) and regional cerebral blood flow (rCBF). RESULTS: In 9 of 22 patients, cross-clamping of the carotid artery caused a continuous decrease [oxy-Hb] and [total Hb], and an increase in [deoxy-Hb]. Cyt ox was partially reduced during the clamping. These NIRS responses demonstrated the occurrence of severe hypoxia in the ipsilateral cerebral tissue. These patients showed a marked decrease in the N20 amplitude of SEP and rCBF. In contrast, the other 13 patients did not show a significant decrease in the cerebral oxygenation state, which showed no remarkable changes in either SEP or in rCBF. CONCLUSIONS: NIRS could successfully jude the cerebral oxygenation state noninvasively during carotid surgery and was more sensitive to ischemic crisis than other indirect methods.

Aged↗
PubMed1996

Ontogeny of striatal dopamine release in rats after acute administration of methamphetamine.

In the present study, we examined the effects of acute MAP administration on striatal extracellular levels of dopamine (DA) and its metabolites in groups of rats on postnatal days (PNDs) 14, 21, 28, and 56. A single injection of 4 mg/kg MAP (IP) induced increase in extracellular DA and decrease in extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatal perfusates of rats on all PNDs examined. The magnitude of increase in DA concentrations at 20 min after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56, whereas the magnitude of decrease in DOPAC concentrations after the MAP injection was significantly smaller on PND 14 than PNDs 21, 28, and 56. After the MAP injection, homovanillic acid levels decreased on PNDs 21, 28, and 56, but increased on PND 14. These results suggest that rats on PND 14 differ from those thereafter in MAP-induced DA release and changes in its metabolites, and that such developmental effect on MAP-induced DA release may be involved in the ontogeny of MAP-induced behavioral sensitization.

3,4-Dihydroxyphenylacetic Acid↗