Biomedical subjects

R Yoshimoto

Publications and source records attributed to R Yoshimoto.

At least 19 recordsLinked to original sources

PubMed2001

Antithrombotic activity of AT-1015, a potent 5-HT(2A) receptor antagonist, in rat arterial thrombosis model and its effect on bleeding time.

The antithrombotic activity of N-[2-(4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)piperidino)ethyl]-1-formyl-4-piperidinecarboxamide monohydrochloride monohydrate (AT-1015; a 5-HT(2A) receptor antagonist) was studied in a photochemically induced arterial thrombosis (PIT) model in the rat femoral artery, and in the tail transection bleeding time test. Ticlopidine (an antiplatelet agent) and sarpogrelate (a selective 5-HT(2A) receptor antagonist) were studied as reference compounds. Pretreatment with AT-1015 (1 mg/kg, p.o.) significantly prolonged the time required to occlusion of the artery with thrombus, and the effect (3 mg/kg, p.o.) persisted for 24 h with significant inhibition of 5-HT-induced vascular contraction. Ticlopidine and sarpogrelate also significantly prolonged the time to occlusion at 100 mg/kg, p.o. Sarpogrelate (300 mg/kg, p.o.) showed the similar antithrombotic efficacy to AT-1015 (3 mg/kg, p.o.), while the effect disappeared within 6 h. No significant bleeding time prolongation was observed at 10 mg/kg of AT-1015, which is 10 times higher than the antithrombotic effective dose; whereas ticlopidine significantly prolonged bleeding time at the same dose as the antithrombotic effective dose. These results suggested that AT-1015 is a potent and long-acting oral antithrombotic agent in this model, which may be elucidated by its potent and long-acting inhibition of vasoconstriction through 5-HT(2A) receptor.

Animals↗

PubMed2001

Chronic effect of doxorubicin on vascular endothelium assessed by organ culture study.

We have attempted to determine the chronic effects of doxorubicin, a commonly used anticancer agent, on vascular endothelium using an organ culture system. In rabbit mesenteric arteries treated with 0.3 microM doxorubicin for 7 days, rounding and concentrated nuclei and TUNEL-positive staining were observed in endothelial cells, indicating DNA damage and the induction of apoptosis. However, the endothelium-dependent relaxation induced by substance P and the expression of mRNA encoding endothelial NO synthase (eNOS) did not differ from those in control arteries. In arteries treated with a higher concentration (1 microM) of doxorubicin, apoptosis and damage to nuclei occurred in the endothelial cells at the third day of treatment, and the detachment and excoriation of endothelium from the tunica interna of the vascular wall were also observed. The impairment of endothelium-dependent relaxation was observed at the fifth day of the treatment with 1 microM doxorubicin. Additionally, apoptotic change in the smooth muscle layer was observed at this concentration of doxorubicin. Apoptotic phenomena were further confirmed by DNA fragmentation using isolated bovine aortic endothelial cells (BAECs) and A7r5 vascular smooth muscle cells, and it was revealed that BAECs are more sensitive than A7r5 to the apoptotic effect of doxorubicin. These results suggest that chronic treatment with doxorubicin at therapeutic concentrations induces apoptosis and excoriation of endothelial cells, which diminishes endothelium-dependent relaxation.

Analysis of Variance↗

PubMed2001

Anti-human vWF monoclonal antibody, AJvW-2 Fab, inhibits repetitive coronary artery thrombosis without bleeding time prolongation in dogs.

The antithrombotic and antihaemostatic effects of the monoclonal antibody against human vWF (AJvW-2 Fab) were investigated in comparison with those of the monoclonal antibody against platelet GPIIb/IIIa (abciximab) in dogs. The ex vivo platelet aggregation and template bleeding time were measured before, 5, 90, 210 min and 24 h after injection of either AJvW-2 Fab or abciximab in anesthetized beagle dogs. Plasma concentration, vWF occupancy and plasma vWF antigen level were also measured by ELISA. In addition, the antithrombotic effect was evaluated in a canine model of repetitive coronary thrombosis (Folts model). AJvW-2 Fab significantly inhibited the ex vivo botrocetin-induced platelet aggregation at 0.18 mg/kg (53% plasma vWF occupancy) and also inhibited cyclic flow reductions (CFRs) at 0.06 mg/kg (31% occupancy). A significant prolongation of the bleeding time was observed at 1.8 mg/kg (95% occupancy), which was 30 times as high as the antithrombotic effective dose. Whereas, abciximab significantly inhibited both the ex vivo ADP-induced platelet aggregation and CFRs at 0.8 mg/kg, which was the minimally effective dose, also resulting in a significant prolongation of the bleeding time. These results suggest that blockade of the GPIb-vWF axis with AJvW-2 Fab leads to the inhibition of thrombus formation in the stenosed coronary arteries without less bleeding time prolongation than the GPIIb/IIIa blockade with abciximab.

Animals↗

PubMed2001

Effects of a dual L/N-type Ca(2+) channel blocker cilnidipine on neurally mediated chronotropic response in anesthetized dogs.

We investigated the effects of an L-type and N-type Ca(2+) channel blocker, cilnidipine, on neurally mediated chronotropic responses to clarify the anti-autonomic profile of cilnidipine in anesthetized dogs. Pretreatment with cilnidipine (0.3, 1.0 and 3.0 microg/kg, i.v.), which decreased mean blood pressure by 5 to 31 mm Hg, inhibited the changes in heart rate and plasma norepinephrine concentration induced by bilateral carotid artery occlusion, whereas it had no effect on vagal nerve stimulation-induced bradycardia. These results suggest that antihypertensive and antisympathetic doses of cilnidipine fail to influence chronotropic responses mediated by parasympathetic nerve activation in the in vivo canine heart.

Anesthesia, General↗

PubMed2001

Cardiovascular action of a cardioselective Ca(2+)channel blocker AH-1058 in conscious dogs assessed by telemetry.

AH-1058, 4-(5H-Dibenzo[a,d]cyclohepten-5-ylidene)-1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-propenyl]piperidine hydrochloride, is a novel Ca(2+)channel blocker exerting cardioselective action in isolated or anesthetized canine heart preparations. To clarify the cardiac and hemodynamic action of AH-1058 in conscious dogs, we assessed the effects of the drug on the hemodynamic parameters continuously recorded by telemetry in conscious unrestrained beagle dogs, and its cardiovascular effects were compared with those of verapamil, disopyramide and atenolol. Oral administration of AH-1058 (0.15, 0.3 and 0.6 mg/kg) reduced the systolic blood pressure and maximal upstroke velocity of the left ventricular pressure (LVdP/dt(max)), increased heart rate and prolonged the QA interval in a dose-dependent manner whereas the drug did not affect diastolic blood pressure. Verapamil at 10 mg/kg reduced systolic and diastolic blood pressure with little effect on heart rate, LVdP/dt(max) and QA interval. Disopyramide at 20 mg/kg increased systolic and diastolic blood pressure, decreased LVdP/dt(max) and prolonged the QA interval with little changes in heart rate. Atenolol at 10 mg/kg decreased LVdP/dt(max) and prolonged the QA interval with little changes in systolic blood pressure, diastolic blood pressure and heart rate. The time course of the cardiohemodynamic action of AH-1058 was longer than those of the other drugs. These results suggest that AH-1058 is a long-acting cardiodepressive drug, and its hemodynamic profile is obviously different from that of disopyramide and atenolol. This unique cardiovascular profile may be beneficial for the treatment of certain pathological processes in which selective inhibition of the ventricular Ca(2+)channels would be the target of drug therapy.

Animals↗

PubMed2001

AH-1058: a novel cardioselective Ca2+ channel blocker.

The pharmacologic profile of a cyproheptadine-related compound, 4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)-1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-propenyl]piperidine hydrochloride (AH-1058), was assessed in various in vivo and in vitro models. In guinea pig cardiomyocytes, AH-1058 effectively suppressed L-type Ca2+ channel currents without affecting other ion channel or ion exchange currents. In rat cerebral cortical membranes AH-1058 appears to bind preferentially to L-type Ca2+ channels at phenylalkylamine- and benzothiazepine-binding sites. In canine isolated, blood-perfused heart preparations, AH-1058 exerted negative inotropic, dromotropic, and chronotropic and weak coronary vasodilator effects. In halothane-anesthetized dogs, AH-1058 suppressed ventricular contractility and decreased blood pressure and cardiac output. Total peripheral vascular resistance was hardly affected by the drug, suggesting that in vivo AH-1058 can selectively suppress cardiac, as compared to peripheral vascular, function. In conscious dogs, by intravenous administration AH-1058 reduced systolic blood pressure and maximal upstroke velocity of the left ventricular pressure, while it increased heart rate in a dose-dependent manner. The drug did not affect diastolic blood pressure, which is quite different from cardiovascular properties of well-known Ca2+ channel blockers, verapamil and diltiazem. This unique cardiovascular profile of AH-1058 is expected to be useful in the treatment of certain pathological processes such as the obstructive hypertrophic cardiomyopathy, vasovagal syncope, dissecting aortic aneurysm, and ventricular arrhythmias, in which selective inhibition of the ventricular Ca2+ channels is essential for drug therapy.

Animals↗

PubMed2001

Utilization of telemetry system to assess the cardiovascular profile of AH-1058, a new cardioselective Ca2+ channel blocker, in conscious dogs.

Cardiovascular effects of a new Ca2+ channel blocker AH-1058, 4-(5H-dibenzo[a,d]cyclo-hepten-5-ylidene)-1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-propenyl]piperidine hydrochloride, were assessed in conscious dogs using a new telemetry system. AH-1058 (0.03, 0.1 and 0.3 mg/kg, i.v.) reduced systolic blood pressure and the maximal upstroke velocity of the left ventricular pressure and increased the heart rate in a dose-dependent manner without affecting the diastolic blood pressure; each of these responses lasted for several hours. These results support the previous knowledge that AH-1058 is a long-lasting cardiodepressive drug. The telemetry system provided important information for predicting favorable clinical effects of AH-1058.

Animals↗

PubMed2001

In vivo antiarrhythmic profile of AP-792 assessed in different canine arrhythmia models.

The antiarrhythmic effects of a novel antiarrhythmic drug AP-792, 4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)-1-[4-cyclohexylbutyl]piperidine hydrochloride, were analyzed using the epinephrine-, digitalis- and two-stage coronary ligation-induced canine ventricular arrhythmia models. Intravenous administration of AP-792 (0.3 or 1.0 mg/kg) effectively suppressed each of the ventricular arrhythmias, an action that resembles that of a typical cardioselective Ca2+ channel blocker, AH-1058. The antiarrhythmic action of AP-792 was slow in onset and longer-lasting than those in our previous studies using more than 50 antiarrhythmic drugs, including Na+ and Ca2+ channel blockers. These results suggest that AP-792 can become a unique long-acting antiarrhythmic drug.

Animals↗

PubMed2000

Regulation of shortening velocity by calponin in intact contracting smooth muscles.

To elucidate the function of calponin in intact contracting smooth muscle cells in vivo, we generated mice with a mutated basic calponin (h1) locus (Yoshikawa et al., Genes Cells 3, 685-695, 1998). Crossbridge cycling rates were estimated in aortic smooth muscle by the force redevelopment following an isometric step shortening as a function of time after K(+) depolarization. Evidence is presented that calponin is involved in the inhibition of shortening velocity in the tonic phase of contraction. The phosphorylation levels of myosin regulatory light chain and cytosolic calcium concentrations were not significantly different in paired comparisons between calponin-deficient (-/-) and wild-type (+/+) muscles at any time point after stimulation. The force-velocity relationships in vas deferens smooth muscle showed that the maximum shortening velocity of -/- muscle was significantly faster than that of +/+ muscle. There was no change in the length-force relationships in both -/- and +/+ muscles of aorta and vas deferens. The results suggest that calponin plays a role in regulation of the crossbridge cycling and that it may be responsible for reduced shortening velocity during a maintained contraction of mammalian smooth muscle.

Animals↗

PubMed2000

Antiarrhythmic and cardiohemodynamic effects of a novel Ca(2+) channel blocker, AH-1058, assessed in canine arrhythmia models.

The antiarrhythmic profile and cardiohemodynamic effect of a novel Ca(2+) channel blocker, 4-(5H-Dibenzo[a, d]cyclohepten-5-ylidene)-1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-p ropeny l]piperidine hydrochloride (AH-1058), were analyzed using the epinephrine-, digitalis- and two-stage coronary ligation-induced canine ventricular arrhythmia models. Intravenous administration of AH-1058 (100 microg/kg) effectively suppressed each of the ventricular arrhythmias accompanied by weak hypotensive effects. The results contrast well with those of a typical Ca(2+) channel blocker, verapamil, which suppresses only the epinephrine-induced ventricular arrhythmia with severe hypotension. These results indicate that AH-1058 may possess a more selective inhibitory action on Ca(2+) channels in the heart than on those in the vessels. Furthermore, the antiarrhythmic actions of AH-1058 were slower in onset and longer-lasting, than those in our previous studies using other antiarrhythmic drugs, including Na(+) and Ca(2+) channel blockers. The antiarrhythmic effects of AH-1058 did not correlate with its plasma concentrations when administered either intravenously or orally. These results suggest that AH-1058 can become a long-acting Ca(2+) channel blocker with unique antiarrhythmic properties, and that AH-1058 may be used in certain pathological processes, for which selective inhibition of the cardiac Ca(2+) channels is essential.

Animals↗

PubMed2000

Proteolysis of acidic calponin by mu-calpain.

Acidic calponin is an actin binding protein expressed in smooth muscle and brain. Although the role of smooth muscle calponin (basic calponin) has been well studied, few studies have been performed on acidic calponin. In the present study, we demonstrated that acidic calponin binds to filamentous actin, but not monomeric actin. A co-sedimentation assay indicated that acidic calponin binds to actin with an apparent binding constant of 4 x 10(5) M(-1). In the presence of an excess amount of calmodulin, the binding of acidic calponin to actin was inhibited. The binding of acidic calponin to calmodulin was Ca(2+)-dependent with K(d) of 31 microM. We next investigated whether or not acidic calponin could be a substrate for mu-calpain in vitro, since it has been shown that basic calponin is cleaved by mu-calpain. The results showed that acidic calponin was also cleaved by mu-calpain. Neither the proteolytic pattern nor velocity of acidic calponin was different in the absence or presence of calmodulin. When acidic calponin had bound to actin, however, the susceptibility of the acidic calponin to mu-calpain was significantly reduced, which was reversed by the addition of calmodulin. Our results suggest that acidic calponin might be involved in the mu-calpain-regulated actin cytoskeleton.

Animals↗

PubMed2000

AT-1015, a novel serotonin (5-HT)2 receptor antagonist, blocks vascular and platelet 5-HT2A receptors and prevents the laurate-induced peripheral vascular lesion in rats.

The serotonin (5-HT2A) antagonistic activities and the protective effect on laurate-induced peripheral vascular lesions of AT-1015, a novel 5-HT2 receptor antagonist, were investigated. In platelet aggregation, AT-1015 selectively inhibited in vitro 5-HT2A receptor-mediated aggregation, and the activity was almost equivalent to that of ketanserin (5-HT2A/2C receptor antagonist) and 100 times more potent than sarpogrelate (5-HT2A receptor antagonist). AT-1015 also inhibited 5-HT2A receptor-mediated aggregation by oral administration in rat, and the dose required for inhibition was equivalent to ketanserin. In a 5-HT-induced vasoconstriction study in rat, AT-1015 slightly reduced maximal contraction and caused a rightward shift of the concentration-response curve (pKB value, 9.5), which was unlike competitive inhibitors such as ketanserin and sarpogrelate (pA2 value, 9.3 and 8.7, respectively). Moreover, the ex vivo inhibitory activity significantly remained after oral administration (1 mg/kg). In the rat peripheral vascular lesion model, AT-1015 (1 mg/kg, p.o.) effectively prevented progression of peripheral lesions, and it was more potent compared with ketanserin, sarpogrelate, and cilostazol. These results suggest that AT-1015 is a potent 5-HT2A receptor antagonist, and its insurmountable antagonism may be relevant to its therapeutic potential in peripheral vascular disease.

Animals↗

PubMed2000

Comparison of cardiovascular effects of a new calcium channel blocker AH-1058 with those of verapamil assessed in blood-perfused canine heart preparations.

The cardiovascular effects of AH-1058, a novel calcium channel blocker, were examined in comparison with those of verapamil using canine isolated, blood-perfused papillary muscle, atrioventricular node, and sinoatrial node preparations. Intravenous administration of AH-1058 (20, 50, and 100 microg/kg) or verapamil (20, 50, and 100 microg/kg) to the blood-donor dog induced negative inotropic, dromotropic, and chronotropic effects and a coronary vasodilator action in cross-circulated isolated heart preparations, simultaneously inducing the same cardiac effects in the blood-donor dog. The order of potency of the effects of AH-1058 was ventricular contraction > coronary blood flow >> atrioventricular conduction > sinoatrial automaticity, whereas that of verapamil was coronary blood flow >> atrioventricular conduction >> sinoatrial automaticity > ventricular contraction. The cardiosuppressive effects of AH-1058, especially on ventricular contraction, were slower in onset and longer lasting than those of verapamil. These results suggest that this unique cardiovascular profile of AH-1058 may become beneficial for the treatment of certain pathologic processes, in which selective inhibition of ventricular calcium channels would be essential for drug therapy.

Animals↗

PubMed2000

Anti-human von willebrand factor monoclonal antibody AJvW-2 prevents thrombus deposition and neointima formation after balloon injury in guinea pigs.

Immediately after angioplasty, platelet adhesion to the injured arterial wall and subsequent release of various mitogens may contribute to neointima formation. The purpose of this study was to evaluate the inhibitory effect of AJvW-2, a monoclonal antibody against human von Willebrand factor (vWF), on neointima formation in a guinea pig model. The carotid artery was injured with a balloon catheter, and AJvW-2 was administered by a single bolus injection. AJvW-2 dose-dependently prevented neointima formation 14 days after injury. Significant inhibition was observed at 1.8 mg/kg, at which dose significant inhibition of platelet aggregation was achieved for 2 days. By elastic-Masson staining, organized thrombi were observed in the neointimal lesion on day 14. The thrombus area was significantly correlated with neointimal thickness. Furthermore, thrombus deposition, immunostained for vWF and fibrin(ogen), was observed on the media immediately after balloon injury. AJvW-2 significantly reduced the deposition of both adhesive proteins and reduced the incidence of organized thrombus formation, which might affect subsequent neointima formation. However, the proliferation of cultured smooth muscle cells was not affected by AJvW-2. These results suggest that AJvW-2 prevents neointima formation by inhibition of initial platelet-mediated thrombus formation rather than by direct inhibition of smooth muscle cell proliferation.

Angioplasty, Balloon↗

PubMed2000

Inhibitory effects of a newly synthesized 5-HT2 receptor antagonist, AT-1015 (N-[2-[4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)piperidino]-ethyl]-1-for myl-4-piperidinecarboxamide monohydrochloride monohydrate), on contraction and relaxation of pig coronary arteries induced by 5-HT and alpha-methylserotonin: comparison with ketanserin.

Inhibitory effects of a newly synthesized 5-HT2 receptor antagonist, AT-1015 (N-[2-[4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)piperidinolethyl ]-1-formyl-4-piperidinecarboxamide monohydrochloride monohydrate) on contraction and relaxation of coronary arteries of pig hearts mediated by 5-HT2 subtypes were evaluated and these results were compared with those of ketanserin. Contraction and relaxation were determined by adding 5-HT or alpha-methylserotonin (alpha-Me-5-HT) as agonists. Although ketanserin induced rightward shifts of contraction, AT-1015 inhibited the maximal response. In addition, ketanserin inhibited relaxation induced by high concentration of agonists, but there were no inhibitory effects of AT-1015 on relaxation. Thus, these results suggest that AT-1015 is a strong non-competitive 5-HT2 antagonist in porcine coronary arteries and that this drug clearly exhibited different effects on the contraction and relaxation of coronary arteries of pig hearts from those of ketanserin.

Animals↗

PubMed2000

Electrophysiological and cardiohemodynamic effects of AH-1058, a new type calcium channel blocker, assessed by the in vivo canine model.

AH-1058 (4-(5H-dibenzo[a, d]cyclohepten-5-ylidene)- 1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-propenyl]piperidine hydrochloride) is a novel calcium channel blocker whose chemical structure is quite different from those of typical calcium channel blockers. In this study, electrophysiological and hemodynamic effects of AH-1058 were assessed in the halothane-anesthetized, closed-chest canine model. Intravenous administration of a canine antiarrhythmic dose of 100 microg/kg of AH-1058 (n = 6) did not affect the cardiovascular variables, except that the cardiac output was decreased at 30 min after the drug administration. Additional administration of 200 microg/kg of AH-1058 (n = 6) suppressed the sinus nodal automaticity, AV nodal conduction and ventricular contraction and decreased the mean blood pressure, cardiac output and double product. The effects gradually appeared, while no change was detected in the intraventricular conduction, ventricular repolarization period, ventricular effective refractory period, preload to the left ventricle and total peripheral vascular resistance during the observation period of 30 min. The cardiosuppressive effects of AH-1058 can be explained by its calcium channel blocking action demonstrated in a previous in vitro experiment, while the lack of the effect on the vascular resistance would suggest that AH-1058 may become a slow-acting cardioselective calcium channel blocker.

Animals↗

PubMed2000

Ca2+-Sensitization of contraction in the h1 calponin-deficient smooth muscle.

Role of h1 calponin on Ca2+-sensitivity of smooth muscle contraction was investigated using h1 calponin gene-deficient mice (CP -/-) and wild type mice (CP +/+). PGF2. induced a comparable force in intact aorta of CP +/+ and CP -/-. DPB showed similar effects to PGF2alpha. In membrane-permeabilized ileal smooth muscle, PDBu enhanced Ca2+-sensitivity of contraction comparably in CP +/+ and CP -/-. GTPgamma-S showed similar effects. Our results suggest that h1 calponin does not regulate Ca2+-sensitivity in the contractile mechanism of smooth muscle.

Animals↗

PubMed1999

Selectivity of dihydropyridines for cardiac L-type and sympathetic N-type Ca2+ channels.

The blocking effects of cilnidipine and other dihydropyridines on L-type cardiac Ca2+ channels (I(Ca,L)) and N-type sympathetic Ca2+ channel currents (I(Ca,N)) were studied using a whole-cell patch-clamp technique. At -80 mV, cilnidipine had little inhibitory effect below concentrations of 1 microM on I(Ca,L) (IC50 value; 17 microM). However, 1 microM cilnidipine strongly shifted the steady-state inactivation curve of I(Ca,L) toward negative potentials without changing the current-voltage relationship. Each action of cilnidipine was characterized by a high affinity for the inactivated channel in preference to the resting channel. The IC50 values of dihydropyridines for I(Ca,L) were in the range between 0.01 and 10 microM, and those for I(Ca,N) were between 3 and 30 microM. Cilnidipine had the strongest affinity for I(Ca,N) among the dihydropyridines tested. These results suggest that cilnidipine did not cause hypotension-evoked tachycardia deficiency by depression of cardiac L-type channels but by sympathetic N-type channels blockade.

Animals↗