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Biomedical subjects

S Chiba

Publications and source records attributed to S Chiba.

At least 19 recordsLinked to original sources
PubMed1992

Potent antagonistic action of OPC-31260, a vasopressin V2 receptor antagonist, on [Arg8]vasopressin-induced vasoconstriction in isolated simian femoral arteries.

Using a perfusion technique with isolated vessels, we investigated the effect of OPC-21268 (a selective V1 receptor antagonist) and OPC-31260 (a V2 receptor antagonist) on arginine vasopressin (AVP)- or norepinephrine (NE)-induced vasoconstrictions of isolated simian femoral arteries. The dose-response curve for AVP was shifted to the right in parallel by OPC-31260 but not by OPC-21268. Neither antagonist significantly modified the NE-induced vasoconstriction. On the basis of these results, there are functionally constrictory vasopressin V2 receptors but no V1 receptors in isolated simian femoral arteries.

Animals↗
PubMed1992

Cardiac electrical responses to catecholamines are differentially mediated by beta 2-adrenoceptors in anesthetized dogs.

We investigated the beta 2-adrenoceptor-mediated effects of atrial and ventricular effective refractory period (ERP), SA node pacemaker activity, and AV conductivity induced by sympathetic nerve stimulation or epinephrine infusion in anesthetized dogs. A beta 2-adrenoceptor antagonist, ICI 118,551 up to 100 micrograms/kg, i.v., inhibited the positive chronotropic and dromotropic responses to sympathetic stimulation but did not shorten the atrial or ventricular ERP, ICI 118,551 also attenuated the positive chronotropic and dromotropic responses and the shortening of atrial ERP in response to epinephrine but not the shortening of ventricular ERP. A selective beta 1-adrenoceptor antagonist, atenolol, inhibited each electrical cardiac response to sympathetic stimulation and epinephrine infusion in a similar manner. These results suggest that beta 2-adrenoceptor-mediated electrical cardiac responses to endogenous catecholamines also exist in addition to the predominant beta 1-adrenoceptor-mediated responses, and that the order of the proportion of beta 2-adrenoceptor-mediated cardiac effects was SA node pacemaker activity much greater than AV conductivity = atrial ERP much greater than ventricular ERP in the dog heart.

Anesthesia↗
PubMed1992

Effects of YM435, a novel dopamine D1 receptor agonist, on pancreatic exocrine secretion in anesthetized dogs.

The effects of YM435, a novel dopamine (DA) D1 receptor agonist, on pancreatic exocrine secretion were investigated in anesthetized dogs. Each drug was injected i.a. as a single bolus. Graded doses of YM435 (0.3-30 nmol) produced dose-dependent increases in the rate of secretion of pancreatic juice, with a maximum effect at approximately 10 nmol, and with a high concentration of bicarbonate and low concentration of protein. SCH23390 (3-30 nmol), a selective D1 receptor antagonist, caused a progressive parallel shift to the right of the dose-response curve for YM435-stimulated pancreatic secretion without changing the maximum response. Schild analysis of the data indicated that the inhibitory constant (Ki) value was 2.9 nmol, and that SCH23390 inhibited YM435-stimulated pancreatic secretion in a competitive manner. Both DA (0.01-3 mumol) and SKF38393 (0.3-30 mumol), a selective D1 receptor agonist, also increased the secretory rate and bicarbonate concentration, and decreased the protein concentration to the same extent as YM435. These results suggest that YM435 is a potent stimulant of pancreatic exocrine secretion by acting on DA D1 receptors of the pancreas in dogs.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1992

Interactions between recombinant human erythropoietin and serum factor(s) on murine megakaryocyte colony formation.

We investigated the interactions between human erythropoietin (hEpo) and serum factor(s) on murine megakaryocyte (MK) colony formation. Serum-free cultures supported the growth of a large number of murine MK colonies in the presence of murine interleukin-3 (mIL-3). The addition of fetal calf serum (FCS) to mIL-3-containing cultures resulted in only a minimal increase in the number of murine MK colonies. In contrast, hEpo alone had no murine MK colony-stimulating activities in serum-free cultures. hEpo required the presence of FCS, murine serum, or human serum in cultures to promote murine MK colony growth and synergized with these sera to stimulate murine MK colony formation. Furthermore, sera from patients with aplastic anemia showed higher synergistic activities with hEpo than sera from hematologically normal persons (normal human serum). When normal human serum was fractionated by gel-filtration chromatography, two peaks with the synergistic activity were observed in the eluent. However, serum did not show any synergistic effects with hEpo on the growth of murine GM colonies or murine colony-forming unit-erythroid-derived colonies. Although human serum synergized with hEpo to stimulate murine MK colony formation, human cytokines such as IL-3, IL-4, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) failed to induce murine MK colony formation in Epo-containing cultures. In cultures containing human IL-1 alpha + human IL-6 + hEpo as well as in cultures containing hEpo, human IL-3 and human GM-CSF failed to show stimulatory effects on murine MK colony formation. Moreover, the synergistic activity of human serum with hEpo could not be neutralized by antibodies such as antihuman IL-1 alpha, antihuman IL-3, antihuman IL-4, antihuman IL-6, antihuman G-CSF, and antihuman GM-CSF. Our data show that serum contains a growth factor(s) that synergizes with Epo to stimulate the proliferation and differentiation of MK precursors, and strongly suggest that this factor(s) is an unique growth factor(s) that is distinct from IL-1 alpha, IL-3, IL-4, IL-6, G-CSF, and GM-CSF.

Anemia, Aplastic↗
PubMed1992

Identification of a soluble GM-CSF binding protein in the supernatant of a human choriocarcinoma cell line.

We identified two forms of the receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) made by the human choriocarcinoma cell line JEG-3 using an affinity-labeling technique. The protein was identified in the detergent-extract was 78 kDa, very similar to that of the membrane-bound GM-CSF receptor alpha chain expressed in a wide variety of hematopoietic and nonhematopoietic cells, including JEG-3. In contrast, a 62-kDa GM-CSF binding protein, or the soluble GM-CSF receptor, was identified in the supernatant of JEG-3 cells. Utilizing the same affinity labeling technique, we did not detect the soluble GM-CSF binding protein in the supernatant of several hematopoietic cell lines, such as U-937 and KG-1, which express membrane bound alpha chain as well as beta chain. The 62-kDa soluble GM-CSF receptor is produced in abundant amounts by JEG-3, but in very small amounts, if any, by hematopoietic cell lines.

Choriocarcinoma↗
PubMed1992

Replication of human cytomegalovirus in the cells of the U937 monocytoid cell line.

Human cytomegalovirus (HCMV) infection in immunocompromized hosts sometimes occurs as a result of reactivation. Cells of the monocyte-macrophage linkage are suggested to be a site of latency and persistence for HCMV. The human monocytic cell line U937 was infected with the AD169 strain and a clinical isolate of HCMV. The expression of surface antigens on the cells was assessed by flow cytometry. The polymerase chain reaction (PCR) was used to detect viral DNA from infected cells. CMV immediate early antigen, early antigen, and late antigen (LA) were detected from both clinical isolate- and AD169-inoculated U937 cells by flow cytometry. CMV DNA which code major immediate early gene (US3) and LA gene (US14) were detected from the clinical isolate-inoculated U937 over a period of 31 days as tested by PCR. These U937 cells proliferated as well as uninfected U937 cell, but only a small number of AD169-inoculated U937 cells survived after 14 days of inoculation. Interleukin-2 activities were detected in the media on days 24-40 after inoculation with AD169. This chronic CMV infection model of U937 might be utilized to study the mechanisms of persistence and reactivation.

Antigens, Viral↗
PubMed1992

Pharmacological properties of alpha 1-adrenoceptor-mediated vasoconstrictions in dog and monkey lingual arteries: evidence for subtypes of alpha 1-adrenoceptors.

We examined whether alpha 1-adrenoceptor-mediated vasoconstrictions were due to extra- or intracellular Ca2+ movements, and whether they were subdivided into alpha 1-adrenoceptor subtypes in dog and monkey lingual arteries. The NE-induced vasoconstriction in dog lingual arteries was mostly dependent on Ca2+ influx from the extracellular space, since it was readily blocked by a Ca2+ entry blocker, diltiazem, and the NE-induced response was attenuated approximately 90% in Ca(2+)-free solution. On the other hand, in monkey lingual arteries, diltiazem failed to depress the NE-induced dose-response curve, and the response was attenuated only about 60% in Ca(2+)-free solution. The vasoconstrictor response to 10mg caffeine in normal KHS was almost the same as that to 1 micrograms NE in Ca(2+)-free solution in both kinds of arteries, suggesting that alpha 1-adrenoceptor-mediating vasoconstrictions require a different number of sources of Ca2+ in different blood vessels. Pretreatment of preparations with CEC (an alpha 1B-antagonist) significantly suppressed and shifted the dose-response curve for NE to the right in monkey lingual arteries, but it had no significant effect in dog lingual arteries. However, WB4101 (an alpha 1A-antagonist) showed almost the same potency in blocking vasoconstrictor responses as bunazosin in both kinds of arteries (the pA2 values were not significantly different). Moreover, responses to ME (an alpha 1A-agonist) were blocked by diltiazem as well as by bunazosin and WB4101, while CEC had no blocking effect on ME-induced responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1992

Pharmacological analysis of positive chronotropic and inotropic responses to etilefrine in isolated dog heart preparations.

Positive chronotropic and inotropic responses to etilefrine (alpha-[(ethylamino)methyl]-m-hydroxybenzyl alcohol), an orally active cardiovascular agent, were investigated in isolated dog right atrial and left ventricular preparations. Intravenous administration of etilefrine to a support dog increased heart rate and mean systemic blood pressure, and increased sinus rate and atrial contractile force in the isolated right atrium perfused with blood from the support dog. Etilefrine injected intra-arterially to isolated atria and ventricles induced dose-dependent positive chronotropic and inotropic effects. Etilefrine was about 100 times less potent than isoproterenol. The effects of etilefrine in isolated atria were significantly inhibited by treatment with atenolol, but were not significantly inhibited by ICI 118,551. The effects of etilefrine were partially inhibited by imipramine. These results indicate that etilefrine is a highly selective beta-1 adrenoceptor agonist and suggest a moderate catecholamine-releasing activity by tyramine-like action in the blood-perfused dog heart.

Adrenergic beta-Antagonists↗
PubMed1992

Delayed expression of dystrophin on regenerating muscle from two siblings with Becker muscular dystrophy.

We present here a unique expression of dystrophin on biopsied muscle from 2 siblings with Becker muscular dystrophy (BMD). They had neither muscle weakness nor atrophy. Clustered dystrophin-deficient fibers were constituted to regenerating basophilic fibers (mainly type 2C fiber) based on histochemical stainings. We speculate that the developmental delay in the expression of dystrophin is a characteristic finding in regenerating fibers from asymptomatic and young BMD patients, such as the siblings in this report.

Child↗
PubMed1992

A correlation study between blink reflex habituation and clinical state in patients with Parkinson's disease.

The neurologic states and activities of daily life of patients with Parkinson's disease were evaluated using a rating scale with subitems, and subsequently the neurologic disturbance scores and the daily activity impairment scores were obtained. Subjects consisted of 19 normal controls, and 55 ambulatory patients without marked dyskinesia who were on various anti-parkinsonian drugs. Blink reflex was elicited by paired electrical stimulation over the supraorbital nerve. The interval time between the conditioning stimulation and the test stimulation was set at 200 ms, and 5 serial ipsilateral maximal R2 amplitudes on the stimulated side were measured. The mean of the paired maximal R2 amplitude ratio (test/conditioning), expressed as a percentage, was defined as the habituation index. The habituation indices in normal controls and those with Parkinson's disease were 17.1 +/- 7.6 and 51.9 +/- 29.3, respectively (P less than 0.01). The degree of akinesia, rigidity, balance/gait and dysarthria was positively correlated with the habituation index (P less than 0.01), while tremor was not. On the whole the habituation index was found to have a significant correlation not only with the neurologic disturbance score but also with the daily activity impairment score (P less than 0.01).

Activities of Daily Living↗
PubMed1992

Effects of aminoglycoside antibiotics on the auditory brainstem response and post rotatory nystagmus in rats.

Effects of three aminoglycoside antibiotics, amikacin (AMK), tobramycin (TOB), and gentamicin (GM), on the auditory and vestibular functions were assessed in rats, the most frequently used species in toxicity studies. Chronic electrodes for auditory brainstem response (ABR) recording were implanted on the epidural surface, and those for post rotatory nystagmus (PRN) were implanted at the nictitating membrane and the outer canthus. AMK, TOB, and GM were given intramuscularly twice daily for 3-4 weeks at a daily dose of 350, 150, and 100 mg/kg, respectively. The amplitude of each wave of the ABR was decreased or disappeared in the groups treated with AMK, TOB, and GM. In the PRN, the duration of the nystagmus was decreased in the TOB group and completely lost in the GM group. No abnormality was observed in the PRN in the AMK group. These results were similar to those reported in the ototoxicity studies of these drugs in guinea pigs and indicate that ototoxicity can be evaluated in rats as successfully as in guinea pigs by this procedure.

Amikacin↗
PubMed1992

Identification of human and bovine rotavirus serotypes by polymerase chain reaction.

The use of the polymerase chain reaction (PCR) for identifying serotypes of human and bovine rotaviruses was examined. In the identification of 115 human rotavirus samples in stools, results with PCR showed excellent agreement with results of serotyping by an enzyme-linked immunosorbent assay (ELISA) using serotype-specific monoclonal antibodies. Furthermore, the PCR showed a much higher sensitivity (93%) than the ELISA test (82.6%). The PCR method could also be applied for identifying the serotype of bovine rotaviruses.

Animals↗
PubMed1992

Evidence for a single catalytic site of honeybee alpha-glucosidase I by chemical modification with diethylpyrocarbonate.

Honeybee alpha-glucosidase I was inactivated with diethylpyrocarbonate (DEPC). The inactivation followed pseudo-first-order kinetics. The rate of the loss of activity was decreased by the addition of a substrate, maltose. Since there was no spectral change in the tyrosine absorption region, it was recognized that DEPC did not react with this residue. The alpha-glucosidase had one free sulfhydryl group, which was not involved in the catalytic reaction, and was not modified by DEPC. On the other hand, the specific reaction of DEPC with a histidyl residue was spectrophotometrically confirmed by an increase in absorption near 240 nm, and the activity of the inactivated enzyme was restored by hydroxylamine. The modification rate of one histidyl residue by DEPC was almost equal to the rate of the activity loss. These results indicate that there is one histidyl residue at or near the catalytic site, and that honeybee alpha-glucosidase I has a single active site.

Animals↗
PubMed1992

Inhibition by glibenclamide of negative chronotropic and inotropic responses to pinacidil, acetylcholine, and adenosine in the isolated dog heart.

The blocking effects of glibenclamide on the chronotropic and inotropic responses to K+ channel openers pinacidil (ATP-sensitive) and acetylcholine (ACh) or adenosine (receptor-operated) were investigated in the isolated, blood-perfused canine atrium or ventricle. Glibenclamide (0.1-3 mumol) induced no significant cardiac effects. Cumulative administration of pinacidil (0.03-3 mumol) dose-dependently decreased sinus rate much less than the contractile force of the atrial and ventricular muscles. Glibenclamide similarly inhibited the negative chronotropic and inotropic responses to pinacidil in a dose-related manner. A high dose of glibenclamide (3 mumol) slightly but significantly attenuated the negative chronotropic and inotropic responses to ACh and adenosine but not to verapamil. These results demonstrate that glibenclamide inhibits the negative chronotropic and inotropic responses to the ATP-sensitive K+ channel opener pinacidil and the receptor-operated K+ channel openers ACh and adenosine but more selectively antagonizes the responses to pinacidil in the dog heart and suggest that in contrast to ACh and adenosine, an ATP-sensitive K+ channel opener has a greater effect on the ventricle than on the sinoatrial node.

Acetylcholine↗
PubMed1992

Cardiac effects of vecuronium and its interaction with autonomic nervous system in isolated perfused canine hearts.

The chronotropic and inotropic effects of vecuronium bromide and its interaction with the autonomic nervous system were investigated in the isolated, cross-circulated right atrial and left ventricular preparations of the dog. Vecuronium, injected into the external jugular vein of the support dog, induced dose-dependent decreases in heart rate and arterial blood pressure, and increased atrial contractile force with no change in sinus rate in isolated atrial preparations. Vecuronium (1-3,000 micrograms), injected into the sinus node artery of the isolated atrium, induced dose-dependent increases in atrial contractile force with small increases in sinus rate. Vecuronium also increased the ventricular contractile force in a dose-dependent manner. The positive inotropic effect was attenuated in part by propranolol, but not by either tetrodotoxin or imipramine. Vecuronium inhibited in a dose-related manner the negative chronotropic and inotropic responses to parasympathetic nerve stimulation and carbachol (CCh) and the negative followed by positive cardiac responses to nicotine, but did not attenuate the positive responses to sympathetic nerve stimulation. The ID50s for the responses to parasympathetic stimulation, CCh, and nicotine were not significantly different. Vecuronium enhanced the positive chronotropic and inotropic responses to sympathetic nerve stimulation, tyramine, norepinephrine, and isoproterenol. These results indicate that (a) vecuronium causes the positive inotropic responses mediated by nonadrenergic mechanisms and beta-adrenoceptors, (b) vecuronium blocks ganglionic and presynaptic nicotinic and postsynaptic muscarinic receptor-mediated responses similarly, and (c) vecuronium enhances beta-adrenoceptor-mediated responses in the dog heart.

Animals↗