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S Obara

Publications and source records attributed to S Obara.

At least 55 records · Page 3Linked to original sources
PubMed1991

Arginine-specific ADP-ribosyltransferase and its acceptor protein p33 in chicken polymorphonuclear cells: co-localization in the cell granules, partial characterization, and in situ mono(ADP-ribosyl)ation.

We have reported the purification and characterization of arginine-specific ADP-ribosyltransferase from hen liver nuclei [Tanigawa, Y. et al. (1984) J. Biol. Chem. 259, 2022-2029] and the DNA-dependent mono(ADP-ribosyl)ation of p33, an acceptor protein in the nuclei [Mishima, K. et al. (1989) Eur. J. Biochem. 179, 267-273]. In the present study, we obtained evidence that among various tissues and cells from chicken, polymorphonuclear cells, so-called heterophils, possess both the ADP-ribosyltransferase and p33 at high levels. Percoll density gradient centrifugation of the postnuclear fraction of the heterophils revealed the co-localization of ADP-ribosyltransferase with p33 in the granule fraction. The enzyme and p33 were purified approximately 219- and 3.77-fold, respectively, from postnuclear pellet fraction to apparent homogeneity. The properties of heterophil ADP-ribosyltransferase and p33 were compared with those of the liver enzyme and p33. The molecular mass of the heterophil enzyme was estimated by SDS-polyacrylamide gel electrophoresis to be 27.5 kDa. The enzyme activity was stimulated by a sulfhydryl agent and inhibited by lysolecithin, NaCl, and inorganic phosphate. The mono(ADP-ribosyl)ation of p33 was markedly enhanced by polyanion, such as DNA, RNA, or poly(L-glutamate). SDS-polyacrylamide gel electrophoretic analysis after limited trypsin proteolysis of p33s, purified from chicken heterophils and liver, showed much the same pattern. Thus, it appears that ADP-ribosyltransferase and p33 present in heterophils are identical to those in the liver, respectively. p33 is considered to be an in situ substrate for ADP-ribosyltransferase, since it was specifically mono(ADP-ribosyl)ated in permeabilized heterophils.(ABSTRACT TRUNCATED AT 250 WORDS)

ADP Ribose Transferases↗
PubMed1991

NIK-247 blocks voltage-dependent ionic currents in crayfish axon.

NIK-247 (9-amino-2,3,5,6,7,8-hexahydro-1H-cyclopenta[b]-quinoline hydrochloride hydrate), an acetylcholinesterase inhibitor, is structurally related to 4-aminopyridine (AP). Its effects on ionic currents were examined in the artificial node of the crayfish axon under voltage-clamp. When applied externally, NIK-247 reversibly suppressed both inward and outward currents. Effects on K currents were further studied in the presence of tetrodotoxin. NIK-247 suppressed the K current dose-dependently, but with an IC50 at of 10(-3) M. THA (9-amino-1,2,3,4-tetra-hydroacridine hydrochloride hydrate), a related inhibitor, similarly suppressed the K current with an IC50 of 5 x 10(-4) M, in comparison with 3-AP and 4-AP which had IC50's of 3 x 10(-5) M and at 10(-5) M, respectively. Furthermore, NIK-247 (and THA) suppressed the K current uniformly for the whole time course, whereas AP the AP's suppressed mainly the fast activating and inactivating K current with a voltage- and frequency-dependent recovery. Therefore, NIK-247 and THA seem to be neither potent nor very specific as ionic channel blockers. With respect to the K current, however, they clearly differ from the AP's in their mode of suppression.

4-Aminopyridine↗
PubMed1991

[The effect of surfactant therapy associated with high frequency jet ventilation on oxygenation in canine lavaged lungs].

The effects of exogenous surfactant (SF) replacement therapy associated with high frequency jet ventilation (HFJV) on blood gas changes, pulmonary and hemodynamic variables were studied in canine lavaged lungs. The lungs were lavaged repeatedly with physiological saline until PaO2 decreased to 100 mmHg under intravenous pentobarbital anesthesia with 100% oxygen. SF (50 mg.kg-1) in the experimental group (n = 12) and saline in the control group (n = 8) were administered to the trachea using HFJV with a duration of 10 min. HFJV was further continued for 1 hour to make surfactant distribute evenly. Then respiration was controlled by the conventional mechanical ventilator for 3 hrs. During the administration of SF (10 min). PaCO2 was not altered. In the surfactant group, PaO2 improved significantly (200 mmHg) at the end of HFJV and was maintained for the next 3 hrs at this level, but it did not improve in the saline group. Therefore, we suggest that HFJV can be used safely for the treatment of acute respiratory failure and is an effective method for the administration of the pulmonary surfactant into the alveoli.

Animals↗
PubMed1989

Arginine-specific ADP-ribosyltransferase from rabbit skeletal muscle sarcoplasmic reticulum is solubilized as the active form with trypsin: partial purification and characterization.

Arginine-specific ADP-ribosyltransferase from rabbit skeletal muscle sarcoplasmic reticulum was solubilized as the active form with trypsin. The enzyme was partially purified by subsequent chromatography, successively on DE-52, Con A-Sepharose and Sephadex G-75. An approximately 2,000-fold purification was achieved from the 105,000 x g supernatant of trypsin-treated membrane with a recovery of 2.8%. Dithiothreitol, which activates hen liver nuclear ADP-ribosyltransferase, inhibited the enzyme.

Animals↗
PubMed1989

DNA-regulated arginine-specific mono(ADP-ribosyl)ation and de-ADP-ribosylation of endogenous acceptor proteins in human neutrophils.

Arginine-specific mono(ADP-ribosyl)ation and de-ADP-ribosylation reactions of endogenous acceptor proteins were examined using human neutrophils. The cells contained arginine-specific ADP-ribosyltransferase, acceptor proteins and hydrolase catalyzing the release of ADP-ribose from the ADP-ribose/acceptor conjugate. One major acceptor protein with an apparent molecular mass of 27 kDa was detected in the neutrophils. The ADP-ribosylation of this protein was greatly enhanced when double-stranded DNA was added. The release of ADP-ribose from the ADP-ribosyl core-histones was suppressed. These findings provide clues as to the physiological function of neutrophil ADP-ribosyltransferase.

ADP Ribose Transferases↗
PubMed1989

Receptor Ca current and Ca-gated K current in tonic electroreceptors of the marine catfish Plotosus.

The tonic electroreceptors of the marine catfish Plotosus consist of a cluster of ampullae of sensory epithelia, each of which is an isolated receptor unit that is attached to the distant skin with only a long duct. The single-cell layered sensory epithelium has pear-shaped receptor cells interspersed with thin processes of supporting cells. The apical border of the receptor cells is joined to the supporting cells with junctional complexes. Single ampullae were excised and electrically isolated by an air gap. Receptor responses were recorded as epithelial current under voltage clamp, and postsynaptic potentials (PSP) were recorded externally from the afferent nerve in the presence of tetrodotoxin. The ampulla showed a DC potential of -19.2 +/- 6.5 mV (mean +/- SD, n = 18), and an input resistance of 697 +/- 263 K omega (n = 21). Positive voltage steps evoked inward currents with two peaks and a positive dip, associated with PSPs. The apical membrane proved to be inactive. The inward current was ascribed to Ca current, and the positive dip to Ca-gated transient K current, bot in the basal membrane of receptor cells. The Ca channels proved to have ionic selectivity in the order of Sr2+ greater than Ca2+ greater than Ba2+, and presumably they also passed outward current nonselectively. Double-pulse experiments further revealed a current-dependent inactivation for a part of the Ca current.

Animals↗
PubMed1988

Effects of bath-applied L-glutamate and related chemicals on the afferent synapse of the Plotosus electroreceptor.

Tonic electroreceptors of the marine catfish Plotosus were isolated, and effects of chemicals applied in the bath were examined in terms of firing rate (F) responses in single unit afferent nerve. L-Glutamate (L-Glu) and agonists caused marked F increase in the spontaneous discharge. Their potencies, estimated from concentrations for 50% of max F increase, were in the order of quisqualate (2 microM), kainate (7 microM), L-Glu (0.4 mM), L-homocysteate (0.4 mM), D-Glu (3 mM) and L-aspartate (L-Asp, greater than 10 mM). N-Methyl-D,L-aspartate (10 mM) had no effect. L-Glu induced F increase also in the receptors fully suppressed either by cathodal pulses or by high Mg (15 mM), which indicated the postsynaptic action. The synaptic responses were often affected differently in the fast and slow phases, here termed as the peak F and the adapted F, respectively. L-Asp potentiated only the adapted F. Kynurenic acid (Kyn) suppressed only the adapted F, but incompletely and rather dose-independently. Kyn, however, competitively antagonized the amino acid-induced responses. The present results suggest the presence of two distinct postsynaptic receptors, one a Kyn-sensitive Glu receptor that is responsible for part of the adapted F, and the other still undetermined that is responsible for most of the synaptic responses.

Action Potentials↗
PubMed1987

An auscultatory recording method for blood pressure measurement during exercise.

For inspective determination of blood pressure at rest and during exercise, simultaneous recordings of cuff pressure, Korotkov's sounds, and ECG by an electromagnetic oscillograph were necessary. We devised an apparatus in line with the requirement. Results obtained using this apparatus demonstrate that the auscultatory recording method is suitable to determine the blood pressure during submaximal bicycle exercise.

Auscultation↗
PubMed1985

Afferent facilitation induced by iontophoretic application of acidic amino acids in the ampullary electroreceptors of Plotosus.

In an attempt to identify the afferent transmitter in acousticolateralis receptors, effects of some acidic amino acids were examined in ampullary electroreceptors of the marine catfish Plotosus anguillaris, which have only afferent innervation. The ampulla (sensory epithelium) was first hyperpolarized in situ to suppress receptor-cell activity and release of transmitter, and hence resting afferent discharges completely. In the absence of transmitter, amino acids were applied to the ampulla by iontophoresis through three-barreled electrodes. Afferent impulses were recorded from the nerve trunk by a suction electrode, and single-unit responses were analyzed by their instantaneous frequency (F) records. L-Glutamate (Glu) induces single-unit responses postsynaptically at discrete spots over the ampulla. The F records showed graded and slow time courses, and F peaks increased sigmoidally against Glu doses with Hill coefficients of 2-3. Response maxima reached 120-210 Hz in doses of one log unit over the threshold. Glu response showed little desensitization. At the Glu-sensitive spots, kainate (KA) and quisqualate (QA) induced more persistent excitation and L-homocysteate (HCA) weaker excitation than did Glu, with similar latency. L-Aspartate (Asp) induced small slow responses with long latency in only one third of the tested Glu spots. D-Glutamate (D-Glu), D-aspartate (D-Asp), L-cysteate (CA), L-cysteine sulfinate (CSA), and N-methyl-DL-aspartate generally induced no response. Some aspartate analogues, L- and D-Asp, CA, and CSA induced persistent potentiation of Glu responses. Apparent affinity increase and change in response shape during potentiation indicated suppression of Glu uptake. However, apparent slope change in the log dose-response curves suggested that additional mechanisms were involved. In contrast, QA, KA, Glu, and HCA induced the excitation only. Comparable topical application of the transmitter was simulated by stimulating a few receptor cells at Glu spots to induce focal responses. Some aspects of the focal and Glu responses were compared. Pharmacological and neurochemical evidence so far available on this material is discussed with respect to the Glu hypothesis. Glu, even though a potent agonist in terms of afferent excitation, seems to act on extrasynaptic receptor sites in the nonmyelinated nerve terminals.

Afferent Pathways↗
PubMed1984

Damped oscillation in the ampullary electroreceptors of Plotosus involves Ca-activated transient K conductance in the basal membrane of receptor cells.

K-blockers suppressed damped oscillation of Plotosus electroreceptors in situ. Ca-blockers abolished V-dependent non-linear responses, as well, and shifted the DC level in the ampulla by ca. -1 mV. Thus, the in situ receptor is held depolarized with maintained Ca current in the basal membrane of receptor cells. The oscillation involves Ca-activated transient K current in the same membrane, which contributes to the initial sensory adaptation, and presumably also to stabilizing the sensitive receptors.

Animals↗
PubMed1984

Ionic currents in the sensory epithelium examined in isolated electroreceptors of Plotosus under simulated in situ conditions.

The hypothesis of steady epithelial current in an electrically biased sensory epithelium was examined in Plotosus electroreceptors. The in situ conditions were simulated reversibly by electronic shunting of isolated receptors. The epithelial current had an N-shaped property due to Ca current superimposed over passive bias current, with net current close to zero when unstimulated. The high-gain synaptic transfer proved to be the result of modulation of steady Ca component.

Animals↗
PubMed1984

Differential blocking effects of a spider toxin on synaptic and glutamate responses in the afferent synapse of the acoustico-lateralis receptors of Plotosus.

The hypothesis that glutamate is the afferent transmitter in the acoustico-lateralis receptors was examined in Plotosus electroreceptors. JSTX , a spider toxin known to specifically block glutamate receptors, irreversibly abolished afferent impulse discharges induced by iontophoretically applied glutamate, whereas those induced synaptically by focal stimulation of receptor cells were little affected. Such differential blocking effects by JSTX , complementary to other biochemical data, further provide pharmacological evidence against the glutamate hypothesis.

Animals↗
PubMed1983

An improved instantaneous frequency meter for use with a multi-trace CRO: re-examination of the principles involved.

The instantaneous frequency display of single unit discharges provides a useful measure of neuronal activities. Such a device must produce voltage outputs proportional to the reciprocal of each inter-spike interval by on-line computation of the hyperbola of V = a/t. Segment approximation of the required hyperbola can be made by a series of exponential functions which increase in time constants by a factor of m. Numerical analysis of a normalized function indicates possible error maxima of 3.4, 2.4 and 1.1% for m of 2, 1.8 and 1.5, respectively. This prediction is fully confirmed by the actual performance where m of 1.5 is adopted. The test circuit combines only readily available ICs and other components, to give a linear F-V conversion over a dynamic range of 4-600 Hz with error maxima of approximately 1%. The outputs are square pulses of approximately 1.5 ms in duration through the use of a flexible sample-hold circuit. Compared with that of earlier models, this display mode gives better photographic records with the base-line in simultaneous multi-trace display. Simple and systematic methods are described for designing a circuit to one's own specifications, and also for compensating for component variations.

Animals↗
PubMed1982

Chronotropic effects of succinylcholine and succinylmonocholine on the sinoatrial node.

The mechanism of bradycardia caused by the administration of succinylcholine has not been fully elucidated. Accordingly, the effects of succinylcholine and succinylmonocholine on the sinoatrial node were studied in 35 mongrel dogs. The sinus node artery was selectively perfused with autologous blood from a femoral artery at a constant pressure of 100 mmHg, and 30 to 1,000 micrograms of succinylcholine or succinylmonocholine was administered directly into the artery. Succinylcholine caused a transient (63-600 s) dose-related positive chronotropic effect. The heart rate was increased to 14.4 +/- 2.1% (mean +/- SE) above the control value after the administration of 1,000 micrograms of succinylcholine. This positive chronotropic effect was inhibited by pretreatment with pindolol or reserpine. By contrast, succinylmonocholine produced a transient (30-248 s) dose-related negative chronotropic effect. The heart rate was decreased to 17.5 +/- 1.4% below the control value after administration of 1,000 micrograms of succinylmonocholine. The negative chronotropic effect was blocked partially by atropine. It was concluded that the positive chronotropic effect of succinylcholine may be mediated through beta-adrenergic receptor stimulation by catecholamine released from the adrenergic nerve endings in the sinoatrial node, and that the negative chronotropic effect of succinylmonocholine may be the result of excitation of cholinergic receptors in the sinus node. However, a direct effect of succinylmonocholine on the sinus node could not be ruled out.

Animals↗