Search PubMed⌕ Search

Biomedical subjects

H Usui

Publications and source records attributed to H Usui.

At least 127 records · Page 7Linked to original sources
PubMed1990

Endothelium-dependent contraction induced by platelet-derived substances in canine basilar arteries.

The supernatant obtained from platelet-suspension incubated with thrombin caused contractions in both intact and endothelium-removed canine basilar arteries. Cyproheptadine (5 x 10(-7) M), which reduced the serotonin-induced contraction to about 20%, attenuated the supernatant-induced contraction to 51% in intact arteries and to 24% in endothelium-removed arteries. In both absence and presence of cyproheptadine, the supernatant-induced contraction of intact arteries was significantly larger than that of endothelium-removed arteries. The cyproheptadine-resistant contraction by the supernatant of intact arteries was attenuated by aspirin, OKY-046 (a thromboxane A2 synthetase inhibitor) and ONO-3708 (a thromboxane A2 antagonist), whereas such contraction of endothelium-removed arteries was not affected by these agents. The concentrations of serotonin, ATP and ADP in the supernatant used here were approximately 3, 67 and 44 micrograms/ml, respectively. The mixed solution of serotonin, ATP and ADP, at the same concentrations as the supernatant, also induced cyproheptadine-resistant, endothelium-dependent contractions in intact arteries. The contraction induced by the mixed solution in intact arteries was also attenuated by aspirin, OKY-046 and ONO-3708. The present experiments indicate that the supernatant causes endothelium-dependent contraction in canine cerebral arteries and that platelet-derived ATP and ADP contribute to this contraction.

Adenosine Diphosphate↗
PubMed1989

Vasorelaxing action of melatonin in rabbit basilar artery.

1. In rabbit basilar arteries, melatonin (10(-5)-10(-3) M) and nifedipine (10(-10)-10(-8) M) inhibited the responses to KCl and 5-hydroxytryptamine. 2. Melatonin or nifedipine inhibited the Ca2+-responses in a Ca2+-free medium containing KCl (40 mM) or 5-HT (10(-5) M). 3. A combined treatment with nifedipine and melatonin caused no further inhibition of the Ca2+ response in the presence of K+ as compared to a single treatment with melatonin. 4. However, the combined treatment caused a greater inhibition of the Ca2+-response in the presence of 5-HT than the single treatment with either agent. 5. These results suggest that melatonin and nifedipine inhibit the same Ca2+ channels activated by KCl. Further, 5-HT-activated Ca2+ channels which are inhibited by melatonin may be different from nifedipine-sensitive Ca2+ channels activated by 5-HT.

Animals↗
PubMed1989

Crystal and molecular structures of carbon-bridged pyrimidine cyclonucleosides. Substrate analogs of ribonuclease A.

The crystal and molecular structures of carbon-bridged 6,5'-cyclo-5'-deoxy-4-thiouridine (6,5'-Cs4U), 6,5'-cyclo-5'-deoxy-2',3'-O-isopropylideneuridine (6,5'-CiU) and 6,6'-cyclo-5',6'-dideoxy-allofuranosyluracil (6,6'-CU) have been determined by X-ray diffraction. The molecular conformations of 6,5'-Cs4U and 6,5'-CiU are very similar; the conformation about the glycosidic bond is anti (low region), the torsion angle O(4')-C(1')-N(1)-C(2) being -150.0 degrees for 6,5'-Cs4U and -145.5 degrees for 6,5'-CiU, and the sugar puckering being both O(4')-exo. On the other hand, 6,6'-CU takes the glycosidic torsion angle of -116.9(4) degrees (middle anti region) and the sugar conformation of C(4')-endo. The cyclization causes little alteration in the geometry of the base moiety. 6,5'-Cs4U and 6,5'-CiU exhibit the similar base-base interactions between adjacent molecules, although their molecular packings are quite different; the 4-thiouracil or uracil moiety interacts with adjacent base moieties through hydrogen bonding and stacking interactions. In 6,6'-CU, cyclonucleosides were connected by hydrogen bondings between the hydroxyl and sugar ring oxygen atoms and between the hydroxyl groups and the base nitrogen and oxygen atoms. As the 2',3'-cyclic phosphates of these carbon-bridged cyclonucleosides are hydrolyzed by ribonuclease A, it is suggested that the conformers found in these cyclonucleosides are recognized by the enzyme.

Chemical Phenomena↗
PubMed1989

Expression of the cholecystokinin gene in the neuron and paraneuron.

Cholecystokinin (CCK), the long known gut hormone has recently been found in the brain and suggested to be a neurotransmitter or neuromodulator. In order to clarify the structure of the CCK precursor, we cloned the cDNA to mRNA of rat brain. We determined the nucleotide sequence of the inserted cDNA and deduced the amino acid sequence and proteolytic cleavage sites of the CCK precursor. The availability of CCK cDNA probes allowed us to examine the levels of CCK mRNA in the brain and intestine. CCK mRNA was barely detectable in the fetal brain, but started to increase postnatally and attained a plateau after 20-30 days. The level of CCK mRNA was the highest in the frontal cortex, followed by those of the hippocampus and striatum. The cerebellum contained only negligible CCK mRNA. Furthermore, we succeeded in cloning the CCK gene and revealed its structure which contained three exons interrupted by two introns. The size of this gene spanned about 7 kbp. The transcription initiation sites were determined by using S1 nuclease mapping and a primer extension procedure, showing evidence for the existence of the major and minor start sites. To analyze the mechanism for CCK gene expression in the neuron and paraneuron, we tried to examine the transcription of the DNA fragments from CCK gene by an in vitro cell free system. These experiments confirmed the existence of two transcription start sites. From experiments with the deleted mutants of DNA fragments, we could deduce the promoter sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Vasorelaxing effects of prostaglandin I2 on the canine basilar and coronary arteries.

The effects of prostaglandin (PG) I2 on canine basilar and coronary arteries were studied. PGI2 caused a relaxation from the basal level more effectively in the endothelium-intact preparations of the coronary artery than in those of the basilar artery. The PGI2-induced relaxation in the basilar artery was enhanced by removal of the endothelium, and by treatment with indomethacin (10(-6) M), aspirin (5 X 10(-5) M), both cyclooxygenase inhibitors, OKY-046 (3 X 10(-5) M) and RS-5186 (10(-6) M), both thromboxane (TX) A2 synthetase inhibitors and ONO-3708 (10(-8) M), a TXA2 antagonist. The enhancing effects of removal of the endothelium and treatment with indomethacin and aspirin on the PGI2-induced relaxation were greater than those of treatment with OKY-046, RS-5186 and ONO-3708. The PGI2-induced relaxation in the coronary artery was not affected by removal of the endothelium, treatment with indomethacin (10(-6) M) or methylene blue (10(-6) M). In the endothelium-removed preparations precontracted with a TXA2 agonist, PGI2-induced relaxation was less in the basilar artery than in the coronary artery. The present experiments suggest that endothelium-derived factors (TXA2 and other cyclooxygenase products) counteract the vasorelaxing effect of PGI2 in the canine basilar artery, but not in the coronary artery.

Animals↗
PubMed1989

Endothelium-dependent contractions induced by angiotensin I and angiotensin II in canine cerebral artery.

Whether angiotensin I and angiotensin II caused endothelium-dependent contraction was examined in canine cerebral arteries. In endothelium-intact preparations, angiotensin I and angiotensin II at 10(-8) to 10(-6) M caused dose-dependent contractions, whereas both angiotensins caused much less contractions in endothelium-removed preparations. The contractions induced by angiotensin I and angiotensin II were strongly attenuated by aspirin (cyclooxygenase inhibitor) (5 x 10(-5) M), OKY-046 [thromboxane (TX) A2 synthetase inhibitor] (10(-5) M) and ONO-3708 (TX)A2 antagonist) (5 X 10(-9) M). Captopril (10(-6) M) significantly attenuated the contractions induced by angiotensin I but not those induced by angiotensin II. Angiotensin I- and angiotensin II- induced contractions were inhibited markedly by Sar1, Ala8-angiotensin II (10(-9) and 10(-8) M). The present experiments demonstrate that angiotensin I and angiotensin II produce endothelium-dependent contraction in canine cerebral artery via a factor which appears to be TXA2. Angiotensin I may be converted by endothelial cells to angiotensin II, which may activate the cells to produce TXA2 in canine cerebral artery.

Angiotensin I↗
PubMed1988

Three distinct forms of type 2A protein phosphatase in human erythrocyte cytosol.

Two type 2A protein phosphatases, phosphatases I (Mr = 180,000) and III (Mr = 177,000), were purified to near homogeneity from human erythrocyte cytosol. Phosphatase I was composed of alpha (34 kDa), beta (63 kDa), and delta (74 kDa) subunits in a ratio of 1:1:1. Phosphatase III comprised alpha, beta, and gamma (53 kDa) subunits in the same ratio. Heparin-Sepharose column chromatography converted most of phosphatase I and 20% of phosphatase III into alpha 1 beta 1 which were indistinguishable from phosphatase IV (Usui, H., Kinohara, N., Yoshikawa, K., Imazu, M., Imaoka, T., and Takeda, M. (1983) J. Biol. Chem. 258, 10455-10463). The catalytic subunit alpha and the beta subunit of phosphatases I, III, and IV displayed identical V8 and papain peptide maps, respectively, while the peptide maps of the alpha, beta, gamma, and delta subunits were clearly distinct. The molar ratio of phosphatases I, III, and IV in erythrocyte cytosol was estimated to be 6:1:14. Comparison of molecular activities of alpha, alpha 1 beta 1, alpha 1 beta 1 delta 1, and alpha 1 beta 1 gamma 1 revealed that beta suppressed phosphorylase and P-H2B histone phosphatase activities of alpha but stimulated the P-H1 histone phosphatase activity, and delta suppressed all the phosphatase activities of alpha 1 beta 1. The gamma subunit stimulated the P-histone phosphatase activity of alpha 1 beta 1 but inhibited the phosphorylase and P-spectrin phosphatase activities. The beta subunit increased the Mg2+ or Mn2+ requirement for P-H2B histone phosphatase activity of alpha, an effect which was counteracted by delta. The effects of heparin, H1 histone, protamine, and polylysine on the phosphorylase phosphatase activity of phosphatases I, III, IV, and alpha were described and discussed in connection with the functions of the subunits.

Cytosol↗
PubMed1988

Endothelium-dependent contraction induced by nicotine in isolated canine basilar artery--possible involvement of a thromboxane A2 (TXA2) like substance.

The present experiments were undertaken to determine whether the response to nicotine in the isolated canine cerebral artery is endothelium-dependent. Changes in the tension of arterial strips were recorded isometrically. Removal of the endothelium was carried out by gentle rubbing, and confirmed by scanning electron microscopy. Rubbing procedure did not affect the contractile response of the strips to serotonin. Treatment of unrubbed strips with nicotine (10(-4)M) caused a transient contraction. This response was abolished by removal of endothelium and attenuated by hexamethonium (5 x 10(-6)M) and atropine (10(-6)M). The nicotine-induced contraction was attenuated also by aspirin (5 x 10(-5)M), a cyclooxygenase inhibitor, OKY-046 (5 x 10(-5)M), a thromboxane A2 (TXA2) synthetase inhibitor and ONO-3708 (5 x 10(-9)M), a TXA2 antagonist. These results indicate that the nicotine-induced contraction in canine cerebral artery is endothelium-dependent, and suggest that the endothelium-derived contracting factor (EDCF) in the nicotine-induced response is a TXA2-like substance.

Animals↗
PubMed1988

Tyrosine protein kinases in membrane fractions from rat cerebral cortex.

Specific activities of tyrosine tubulin kinase in the particulate fractions from rat cerebellum, medulla oblongata, hypothalamus, striatum, midbrain, and cerebral cortex ranged within 30% of each other and more than 3 times higher than those in the soluble fractions. In the cerebral cortex, tyrosine protein kinase activity toward tubulin and tyrosine-glutamate (1:4) copolymers was mainly distributed in the plasma membrane and the microsome fractions. The kinase activity in cerebral cortex particulate fractions was quantitatively solubilized and separated into two peaks, kinase I and kinase II, by Sephacryl S-300 gel filtration in the presence of 0.2% Nonidet P-40 and 0.2 M NaCl. Kinases I and II were each resolved into 5 active peaks (I-1----5 and II-1----5) by casein-Sepharose column chromatography. The molecular weights of these kinases were estimated from the s20,w values to be 59,000-65,000. The Km values of II-1----5 for tubulin were nearly 10 times higher than those of I-1----5. However, the Km values of the two groups of kinases for tyrosine-glutamate copolymers were not so significantly different. About 60% of the copolymers kinase activity in I-3, I-4, II-3, and II-4 was immunoprecipitable with a saturating amount of monoclonal antibody against pp60c-src. Incubation of the immunoprecipitates with ATP resulted in the autophosphorylation of a 60 kDa protein in I-3 and I-4, and a 52 kDa protein in II-3 and II-4. Immunoblotting also indicated I-3 and I-4 as 60 kDa bands and II-3 and II-4 as 52 kDa bands on SDS-polyacrylamide gels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Developmental and regional changes of mRNA for a cerebellar protein (spot 35) in the rat brain.

Spot 35 protein is a cerebellar Ca-binding protein. Because Southern blot analysis showed evidence for the nucleotide sequence of spot 35 protein cDNA in the rat genome, we applied cDNA to quantitate the mRNA of rat spot 35 protein. The size of this mRNA was about 1,900 nucleotides in length, and that of mRNA from bovine cerebellum was larger. We also examined the developmental changes and regional distribution of spot 35 protein mRNA in rat brains by dot-blot analysis using cDNA as a probe. During postnatal days 1-20, a rapid increase of mRNA levels was observed. Further, the level of mRNA for spot 35 protein was found in the cerebellum and was negligible in the cerebral cortex, striatum, and hippocampus.

Animals↗
PubMed1988

Physiological effects of portal ligation on the longitudinal and circular muscles of the dog portal tree.

We studied physiological effects of portal vein ligation on the longitudinal and circular muscles of the dog portal tree. Portal venous blood pressure after portal ligation was higher in dogs that died than in those that survived. The portal veins isolated from dogs that died after portal ligation exhibited both lower rate of onset and decreased intensity of spontaneous activity, compared with those from dogs that survived. Responsiveness of longitudinal muscles of each of the four portal segments to noradrenaline, acetylcholine, histamine and KCl was markedly reduced in dogs that died, compared with those that survived, although the responsiveness of circular muscle was nearly equal in both groups of dogs. The longitudinal muscle of the truncal portal vein from dogs that died responded less strongly to electrical transmural stimulation than that from surviving dogs. The nonadrenergic, noncholinergic response was almost abolished in dogs that died rapidly. The degree of spontaneous activity or responsiveness to various stimulations in smooth muscles of the portal tree is considered to reflect muscular development. The degree of development of the longitudinal muscle of the portal tree may determine the survival of dogs after portal ligation.

Acetylcholine↗
PubMed1988

Antihypertensive effect of NKY-722, a new water-soluble 1,4-dihydropyridine derivative, on conscious spontaneously hypertensive rats.

3-(4-Allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine dicarboxylate dihydrochloride (NKY-722) produced a dose-dependent antihypertensive effect in conscious spontaneously hypertensive rats (SHR). In this respect NKY-722 was more potent and longer-acting than nicardipine. In canine isolated mesenteric arteries, exposed to a Ca2+-free medium containing high K+, NKY-722 inhibited Ca2+-induced contraction in concentration-dependent manner, suggesting the calcium antagonism as the mechanism of action.

Animals↗
PubMed1988

An endothelium-dependent contraction induced by A-23187, a Ca++ ionophore in canine basilar artery.

In most isolated canine basilar arteries tested, Ca++ ionophore A-23187 induced a small relaxation followed by a transient contraction. Both contraction and relaxation were abolished by removal of endothelium. The endothelium-dependent contraction induced by A-23187 was attenuated by a phospholipase A2 inhibitor (quinacrine), cyclooxygenase inhibitors (aspirin and indomethacin), a thromboxane A2 (TXA2) synthetase inhibitor (OKY-046) and a TXA2 antagonist (ONO-3708). The A-23187-induced contraction was abolished by lowering the Ca++ concentration of medium to 10%, whereas the contraction induced by 9,11-epithio-11,12-methano-TXA2 (STA2) was attenuated slightly by lowering [Ca++]. The A-23187-induced contraction was reduced markedly by nifedipine (10(-9) to 10(-7) M), but the STA2-induced contraction was only attenuated slightly by nifedipine. Bay K 8644 did not affect the A-23187- and STA2-induced contractions. The present experiments demonstrate that A-23187 induced an endothelium-dependent contraction in canine basilar artery, and suggest that Ca++ might play a key role in production of an endothelium-derived contracting factor (probably TXA2).

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Endothelium-dependent contraction and -independent relaxation induced by adenine nucleotides and nucleoside in the canine basilar artery.

ATP, ADP, AMP and adenosine at 10(-8) induced a slight relaxation, and at concentrations greater than 10(-7) M caused a biphasic response consisting of an initial relaxation followed, after a brief period, by a transient contraction in canine basilar artery. ATP (10(-6) and 10(-5) M) caused a triphasic response consisting of a rapid, small contraction, a relaxation and then a second, transient contraction. The order of agonist potency for contraction was ATP greater than ADP much greater than AMP = adenosine, but for producing relaxation the agonists were equipotent. Removal of the endothelium abolished the contraction after the relaxation, but had virtually no effect on the relaxation and the rapid contraction induced by ATP (10(-6) and 10(-5) M). Only the relaxation in response to ATP (10(-6) M) was attenuated by removal of the endothelium. Aspirin (a cyclooxygenase inhibitor) (5 X 10(-5) M), OKY-046 (a thromboxane A2 synthetase inhibitor) (10(-5) M) and ONO-3708 (a thromboxane A2 antagonist) (5 X 10(-9) M) attenuated markedly the endothelium-dependent contraction induced by ATP (10(-5) M) and ADP (10(-5) M), but did not affect the relaxation. Phentolamine (10(-6) M) and atropine (10(-6) M) did not affect either the contraction or the relaxation. The relaxations induced by both ATP and adenosine in both endothelium-intact preparations and endothelium-removed preparations were attenuated by 8-phenyltheophylline (P1 antagonist) (10(-6) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗