Methylmercury poisoning in common marmosets--a study of selective vulnerability within the cerebral cortex.

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesis is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fissures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrificed early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fissures or sulci.

Circulatory disturbance of rat spinal cord induced by occluding ligation of the dorsal spinal vein.

Spinal cord infarction can be caused by venous disturbances due to trauma or cancer invasion. However, the precise mechanism of venous infarction is not fully understood. To characterize disorders associated with spinal venous occlusion, we performed time-kinetic pathological analyses of rat spinal cord infarction induced by transdural ligation of the dorsal spinal vein at the levels of the T10-T13 vertebrae. One day after ligation congestion, edema and hemorrhage were observed mainly in the dorsal funiculus. Axons were well preserved, but on the 3rd day axonal degeneration became evident. On the 7th day, the necrotic lesion was confined to the dorsal funiculus and was round in shape with foamy macrophage infiltration and astrocytic gliosis. On the 14th day, the involved cord became atrophic, and infiltration of foamy macrophages and astrocytosis became more prominent. After 21-28 days, the infarction focus decreased in size due to gliosis, and residual macrophages were observed. The main lesion was confined to the dorsal funiculus at all times. However, the severity of the softening varied among rats. Thus, we conclude that the disturbance of venous drainage actually results in spinal cord softening. The variability in the lesions is probably due to the presence of unexpected anastomoses of the spinal venous system.

Effects of CP-060S, a novel cardioprotective drug, in the methacholine-induced ECG change model in rats.

We compared the antianginal effect of CP-060S, a novel cardioprotective drug with Na+ and Ca2+ overload-preventing activity as well as Ca2+ channel antagonistic activity, with that of diltiazem, in an experimental model of vasospastic angina induced by methacholine in anaesthetized rats. Intra-aortic injection of methacholine at the coronary ostium provoked the ST-segment elevation of the electrocardiogram (ECG), indicating myocardial ischemia. CP-060S (3, 5 and 10 mg/kg, i.d.) significantly and dose-dependently suppressed the methacholine-induced ST-elevation, with the duration of action being at least 3 h at the highest dose. In addition, CP-060S at 3 mg/kg could inhibit the ST-elevation without producing significant changes in blood pressure, heart rate or rate-pressure product (RPP). In contrast, diltiazem (10 and 30 mg/kg, i.d.) significantly decreased the RPP, a significant suppression of the ST-elevation could only be achieved at the highest dose and its duration of action was about 2 h. Similar results were obtained with i.v. administration of the drugs, i.e. CP-060S given i.v. could inhibit the ST-elevation with less haemodynamic changes than diltiazem. In conclusion, CP-060S exerted a more potent and sustained protection against myocardial ischemia evoked by methacholine than diltiazem. The characteristics of the effects of CP-060S observed here suggest that this drug may be a desirable drug for the treatment of vasospastic angina.

[A case of asymptomatic urachal cyst in autopsy--histopathological study of urachal cyst and review of the literature of 99 cases during a 10 year period in Japan].

Disorders of urachal remnants are common. While urachal cysts are usually asymptomatic, infection may mimic a variety of acute abdomen. Here we report a very rare case of urachal cyst that protruded in the urinary bladder cavity and among 99 accumulated cases, only 4 cases have been reported similar to this case characterized by intravesical development from 1990 to 1999. An uninfected urachal cyst was found in a 79-year-old male who had died of bile duct carcinoma. The cyst showed ovoid protrusion into urinary bladder cavity from the dome (3.5 x 2.0 x 2.0 cm in size). Histopathologically, the cyst wall was thin and consisted of fibrous connective tissue with muscular tissue and peripheral nerve, and lined by cuboidal epithelium but no inflammatory cells could be seen. Urachal cysts occur in both sexes are affected with equal frequency, and frequently occur in a younger population. In clinical symptoms the umbilical manifestations are predominant in patients younger than 30 years old, while the bladder manifestations are predominant in those older than 30.

Double cancer consisting of adenosquamous and hepatocellular carcinomas of the liver.

A very rare case of a double cancer consisting of adenosquamous and hepatocellular carcinomas of the liver in a 65-year-old-man is discussed. The patient was hospitalized with epigastralgia in May 1997. Abdominal computed axial tomography revealed a tumor located in the left lobe of the liver and a left hepatic lobectomy was performed. The tumor recurred several months after surgery and the patient died on 4 June 1999. At autopsy, both a major tumor mass with extensive involvement, located in the surgical margin, and a small mass located in S7 were discovered. Microscopically, the major tumor was diagnosed as adenosquamous carcinoma and the small one in S7 as hepatocellular carcinoma. To our knowledge, this is the first case of a double cancer consisting of adenosquamous and hepatocellular carcinomas of the liver. The pathological findings support the hypothesis that this tumor developed as a squamous transformation of adenocarcinoma.

Nicorandil metabolism in rat myocardial mitochondria.

The in vitro study using rats was carried out to clarify the hypothesis that nicorandil is denitrated and then may produce nitric oxide (NO) in myocardial mitochondria. In the presence of a NADPH-generating system, [14C]nicorandil, which was incubated in mitochondrial and microsomal fractions of the lung, heart, or liver, was converted to its main denitrated metabolite, SG-86 and other metabolites. Apparent Km and Vmax for nicorandil in mitochondrial and microsomal fractions of the heart were considerably similar to those of the lung, but completely different from those of the liver. It seems that glutathione-S-transferases (GSTs) are not primarily involved in the conversion of nicorandil to SG-86, because a known GST inhibitor, indomethacin, did not affect the nicorandil degradation in the mitochondrial fraction. Nitrite, the stable metabolite of NO, was measured by the Griess reaction. In the presence of an NADPH-generating system, nicorandil significantly increased nitrite production in myocardial mitochondria, but SG-86 did not. These data strongly indicate that nicorandil is metabolized to SG-86 in myocardial mitochondria, then releasing NO, and that GSTs are not primarily responsible for the conversion of nicorandil to SG-86.

Hypotensive interaction of sildenafil and nicorandil in rats through the cGMP pathway but not by K(ATP) channel activation.

The possibility that sildenafil citrate can potentiate nicorandil-induced hypotension by increasing cGMP levels of vascular smooth muscle cells was examined using anesthetized rats and isolated aortas. In pentobarbital-anesthetized rats, more than 0.3 mg/kg of sildenafil (i.v.) potentiated intra-aortic (i.Ao.) administration of nitroglycerin-induced hypotension. Hypotension due to nicorandil (100 microg/kg, i.Ao.) was potentiated by sildenafil (1 mg/kg, i.v.), even after glibenclamide treatment, although pinacidil-induced hypotension was not reinforced. Hypotensive responses to neither nitroglycerin (3 microg/kg, i.v.) nor nicorandil (100 microg/kg, i.v.) were potentiated by sildenafil, however. Increases in femoral blood flow due to nitroglycerin (0.1-3 microg, i.a.) were potentiated significantly by sildenafil, but those due to nicorandil (1-30 microg, i.a.) were not. Isolated rat aortas precontracted with phenylephrine were dilated dose-dependently using nicorandil, nitroglycerin, pinacidil or sildenafil. The relaxant effect due to nicorandil and nitroglycerin was reinforced significantly by pretreatment with an ineffective concentration of sildenafil (10(-8) M), but pinacidil was not. After ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) completely blocked relaxation by nicorandil, sildenafil did not increase relaxation. These findings suggest that combination of sildenafil with nicorandil, as well as with nitroglycerin, potentiates the hypotensive response by augmentation of vasodilatation. Synergism of vasodilatation may be linked with NO action, but not with K(ATP) channel-activation.

Novel calcium antagonists with both calcium overload inhibition and antioxidant activity. 2. Structure-activity relationships of thiazolidinone derivatives.

CP-060 (1), 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-[3-[N-methyl-N-[2-[3, 4-(methylenedioxy)phenoxy]ethyl]amino]propyl]-1,3-thiazolidin-4-on e, is a novel type of Ca(2+) antagonist possessing both Ca(2+) overload inhibition and antioxidant activity. The structure-activity relationships for this series of compounds were studied by synthesizing the analogues and evaluating these three kinds of activity. Ca(2+) antagonistic activity was largely determined by the lipophilicity of the phenyl group at the 2-position and the length of the alkyl chains. As for the antioxidant activity, it was demonstrated that the phenolic hydroxyl group is an essential structural element. Compounds with potent activity were evaluated for their effect on the coronary blood flow in vivo. Among these compounds, compound 1 was shown to be the most potent. Furthermore, the enantiomers of 1 were resolved by high-performance liquid chromatography with a chiral column. Compound (-)-1 showed about 10 times higher Ca(2+) antagonistic activity than (+)-1, though both enantiomers had similar potency in Ca(2+) overload inhibition and antioxidant activity. An X-ray crystal structure determination of (-)-1 hydrogen fumarate identified (-)-1 as having S configuration at the 2-position.

Effects of nicorandil on experimentally induced gastric ulcers in rats: a possible role of K(ATP) channels.

The anti-ulcer effects of nicorandil [N-(2-hydroxyethyl)nicotinamide nitrate ester] were examined on water-immersion plus restraint stress-induced and aspirin-induced gastric ulcers in rats, compared with those of cimetidine. Nicorandil (3 and 10 mg/kg) given orally to rats dose-dependently inhibited the development of acid-related damage (water-immersion- and aspirin-induced gastric lesions) in the models. Cimetidine (50 mg/kg, p.o.) also had anti-ulcer effects in the same models. However, in the presence of glibenclamide (20 mg/kg, i.v.), an antagonist of K(ATP) channels, nicorandil did not inhibit the formation of gastric lesions. Nicorandil (10 mg/kg) given intraduodenally (i.d.), like cimetidine (50 mg/kg), significantly reduced the volume of the gastric content, total acidity and total acid output in the pylorus ligation model. Glibenclamide reversed the changes caused by i.d. nicorandil. I.v. infusion of nicorandil (20 microg/kg per min) significantly increased gastric mucosal blood flow, without affecting blood pressure and heart rate, but the increase in the blood flow was not observed after i.v. treatment with glibenclamide (20 mg/kg). These results indicate that nicorandil administered orally to rats produces the anti-ulcer effect by reducing the aggressive factors and by enhancing the defensive process in the mucosa through its K(ATP)-channel-opening property.

Effects of CP-060S, a novel cardioprotective drug, on cardiac function and myocardial oxygen consumption.

1. We examined the effects of CP-060S on cardiac function and myocardial oxygen consumption (MVO2) in anesthetized dogs. 2. CP-060S (10-300 microg/kg i.v.) decreased heart rate, increased aortic flow and decreased mean blood pressure in a dose-dependent manner. The PR interval was significantly prolonged by administration of CP-060S (300 microg/kg i.v.). 3. CP-060S (10-300 microg/kg i.v.) increased coronary blood flow in a dose-dependent manner. Left ventricular end-diastolic pressure and maximal first derivative of left ventricular pressure were not significantly affected. 4. CP-060S (10-300 microg/kg i.v.) increased coronary sinus blood flow and decreased arteriovenous oxygen difference and MVO2 in a dose-dependent manner. 5. The effects of CP-060S on cardiac function and MVO2 are qualitatively similar to those of diltiazem, a typical Ca2+ antagonist.

Novel calcium antagonists with both calcium overload inhibition and antioxidant activity. 1. 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-(aminopropyl)thiazolidinones.

A series of 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-(aminopropyl)thiazolidinones was synthesized in order to explore novel calcium antagonists with potent antiischemic activity. These compounds were designed to have, in addition to Ca2+ antagonistic activity, both Ca2+ overload prevention and antioxidant activity in one molecule. These three kinds of activity were evaluated by using a K+-depolarized rat aorta, a veratridine-induced Ca2+ overload model of rat cardiomyocytes, and a soybean lipoxygenase-induced lipid peroxidation model of rabbit low-density lipoprotein, respectively. In particular, 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-[3-[N-methyl-N-[2-[3, 4-(methylenedioxy)phenoxy]ethyl]amino]propyl]-1,3-thiazolidin-4-on e (7o) was found to be highly potent and possessed a well-balanced combination of these actions in vitro.

Role for adenosine A1 and A2 receptors in femoral vasodilatation induced by intra-arterial adenosine in rabbits.

The vasodilator effects of adenosine injected into the femoral artery (i.a.) of rabbits were analyzed. Single bolus i.a. doses of adenosine (0.3-10 microg) and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA) (0.03-1 microg), an adenosine A2-receptor agonist, produced dose-dependent increases in femoral blood flow and decreases in resistance, almost without affecting blood pressure, heart rate, left ventricular (LV) pressure, and LVd P/dt max, even though CPCA elicited slight decreases in arterial blood pressure and LV pressure. On the other hand, bolus i.a. injections of N6-cyclopentyladenosine (CPA) (1-30 microg), an adenosine A1 receptor agonist, caused a relatively weak increase in blood flow, but markedly affected cardiac parameters, especially heart rate and LVd P/dt max. I.v. treatment with 3,7-dimethyl-1-propargylxanthine (DMPX)(2 mg kg(-1)), an antagonist of adenosine A2 receptors, or 8-phenyltheophylline (1 mg kg(-1)), an antagonist of adenosine A1 receptors, significantly attenuated the vasodilator response to adenosine, but not that to acetylcholine. Decreases in blood pressure, heart rate, LV pressure, LVdP/dt max and femoral vascular resistance, and increases in the blood flow elicited by CPA were not significantly modified by the DMPX treatment, but when this was combined with 8-phenyltheophylline, the responses to CPA were completely abolished. The present results indicate that the adenosine-induced femoral vasodilatation in rabbits may be mediated throughout activation of both adenosine A1 and A2 receptors.

Interrelationship of cardiovascular effects, plasma levels of nicorandil, and vascular cGMP formation in conscious rats.

The relationship between the dual activity of nicorandil (KATP channel-opening activity and nitrate-like action), plasma levels, and changes in vascular cGMP levels and cardiovascular parameters was investigated in conscious rats. Nicorandil (3 mg kg(-1), p.o.) was rapidly absorbed and caused a significant reduction in blood pressure, lasting for at least 1 h, increases in heart rate and femoral blood flow, and decreases in femoral vascular resistance. These were entirely abolished by intravenous glibenclamide (20 mg kg(-1)). The plasma concentration of nicorandil reached a maximum 30 min after dosing. After administration of nicorandil, a correlation was observed between blood pressure and plasma nicorandil level or femoral vascular resistance. A significant increase (P < 0.05) in the cGMP content of the thoracic aorta occurred 15 min after administration of nicorandil, and persisted for at least 2 h. These results imply that nicorandil induces vasodilatation by opening KATP channels in peripheral resistance vessels, leading to overt reduction of blood pressure, but acts on conductance vessels mainly through nitrate-like activity.

Synergistic effect of calcitonin gene-related peptide on adenosine-induced vasodepression in rats.

The action of calcitonin gene-related peptide (CGRP) on the vasodepressor response to adenosine was investigated in anesthetized rats. I.v. bolus injections of adenosine (1-100 microg/kg), acetylcholine (0.05-0.4 microg/kg), isoproterenol (1-30 ng/kg), nitroglycerin (0.3-10 microg/kg) and diltiazem (10-300 microg/kg) produced dose-dependent decreases in blood pressure, accompanied by changes in heart rate. Only the vasodepressor response elicited by adenosine, among the agents tested, was significantly enhanced by i.v. infusion of either CGRP (1 ng/kg per min) or cromakalim (0.1 microg/kg per min), which possesses glibenclamide-sensitive K+ channel opening activity. After i.v. treatment with glibenclamide (20 mg/kg), the vasodepressor responses not only to adenosine but also to CGRP (0.5 microg/kg) and cromakalim (30 microg/kg) were significantly reduced, while those to acetylcholine and isoproterenol remained unchanged. The result indicates that the enhancement of the adenosine-induced vasodepression by CGRP, like that elicited by cromakalim, seems to be mediated at least partly through ATP-sensitive K+ channel activation.

The protective effects of CP-060S on ischaemia- and reperfusion- induced arrhythmias in anaesthetized rats.

1. CP-060S is a novel sodium and calcium overload inhibitor, and is also characterized as a calcium channel blocker. As these activities have each been shown independently to ameliorate ischaemia damage in the myocardium, the combination may synergistically exert cardioprotection. In this study, therefore, the protective effect of CP-060S against ischaemia- and reperfusion-induced arrhythmia was evaluated in anesthetized rats. 2. Rats were anaesthetized with pentobarbitone, and the left anterior descending coronary artery was occluded for either 5 min with subsequent reperfusion (a reperfusion-induced arrhythmia model) or 30 min without (an ischaemia-induced arrhythmia model). All drugs were intravenously administered 1 min before the onset of occlusion. 3. In the reperfusion-induced arrhythmia model, the animals in the vehicle-treated group exhibited ventricular tachycardia (VT) in 100%, ventricular fibrillation (VF) in 89%, and death caused by sustained VF in 56%. CP-060S (30-300 microg kg(-1)) dose-dependently suppressed the incidences of arrhythmias. Significant decreases occurred at 100 microg kg(-1) in VF (incidence: 42%) and mortality (8%), and at 300 microg kg(-1) in VT (50%), VF (33%) and mortality (8%). This protective effect of CP-060S was 10 times more potent than that of a pure calcium channel blocker, diltiazem (30-1000 microg kg(-1)) we tested, in terms of effective dose ranges. As both drugs decreased myocardial oxygen consumption estimated by rate-pressure product to a similar extent, the calcium channel blocking activity of CP-060S would not seem to be sufficient to explain its potency. 4. In the same model, co-administration of ineffective doses of diltiazem (300 microg kg(-1)) and a sodium and calcium overload inhibitor, R56865 (100 microg kg(-1)), produced significant suppression of VT (incidence: 62%), VF (46%) and mortality (8%). By contrast, co-administration of R56865 at the same dose with CP-060S (300 microg kg(-1)) did not add to the effect of a single treatment of CP-060S. 5. In the ischaemia-induced arrhythmia model, CP-060S (300 microg kg(-1)) significantly decreased the incidence of VF from 75% to 29%, whereas diltiazem (1 mg kg(-1)) was ineffective. 6. These results suggest that CP-060S inhibits both ischaemia- and reperfusion-induced arrhythmia. The combination of the calcium channel blocking effect and the calcium overload inhibition was hypothesized to contribute to these potently protective effects.

Differential effects of nicorandil on the vasodepressor responses to vasoactive polypeptides administered intravenously to rats.

The effects of nicorandil on vasodepressor responses to vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P have been examined in anaesthetized rats. Intravenous bolus injections of VIP (0.3 microg kg(-1)), CGRP (0.1 microg kg(-1)) and substance P (0.1 microg kg(-1)) induced reductions of blood pressure accompanied by slight increases (less than 5%) in heart rate. Nicorandil infused intravenously at 10 or 30 microg kg(-1) min(-1) significantly augmented the vasodepressor responses to VIP and CGRP but did not modify the responses to substance P and acetylcholine (0.1 microg kg(-1)). Intravenous treatment with glibenclamide (20 mg kg(-1)) [corrected] significantly attenuated not only the vasodepression caused by VIP and CGRP, but also the enhancement of the effects of the agents by nicorandil. These results indicate that nicorandil can enhance the action of VIP and CGRP, in rats, at least partly through ATP-sensitive K+-channel activation.

Vascular levels and cGMP-increasing effects of nicorandil administered orally to rats.

We examined a relation between cyclic guanosine monophosphate (cGMP) production in thoracic aorta, as an indicator probably reflecting the vascular response, and the vascular as well as plasma levels of nicorandil administered orally to rats. Nicorandil (3 mg/kg) given orally was rapidly absorbed, reaching the maximal plasma (approximately 2,600 ng/ml) and vascular concentrations (approximately 176 ng/g) at 15 min after the dosing and thereafter decreased rapidly. Even 2 h after the dosing, the level of the vascular cGMP formation in vivo remained significantly higher (approximately 1,000 fmol/mg increase from the control level) in the nicorandil-treated group, compared with the vehicle-treated one, and was enough to develop pronounced muscle relaxation in in vitro aortic preparations. However, it seems that the vascular cGMP increase in vivo was not always correlated to the plasma concentration of nicorandil, because the plasma concentration (approximately 750 ng/ml corresponding to 3.5 microM) at 2 h after the dosing, caused only relatively low cGMP production (300-400 fmol/mg increase from the control level), when tested in in vitro aortic preparations. Our study may indicate, therefore, that the vascular cGMP elevation in vivo is due to the content of nicorandil effectively remaining at its vascular targets of action as well as the plasma nicorandil concentration.

CP-060S, a novel cardioprotective drug, limits myocardial infarct size in anesthetized dogs.

The myocardial infarct size (IS)-limiting effect of CP-060S, a novel cardioprotective drug that prevents Na+-, Ca2+-overload and has Ca2+ channel-blocking activity, was compared with that of diltiazem, a pure Ca2+ antagonist, to determine whether the prevention of Na+-, Ca2+-overload contributes to this IS-limiting effect. Dogs were subjected to 90 min of left circumflex coronary artery (LCx) occlusion followed by 5 h of reperfusion. Either CP-060S (300 microg/kg) or diltiazem (600 microg/kg) was administered intravenously 20 min before the occlusion. CP-060S significantly limited IS compared with that of vehicle (percentage of the area at risk: vehicle, 50.64 +/- 6.08%; CP-060S, 21.13 +/- 3.75%; p < 0.01 vs. vehicle). Although diltiazem exerted a significant decrease in rate-pressure product (RPP; an index of myocardial oxygen consumption) during occlusion equal to that of CP-060S, diltiazem did not significantly reduce IS (33.90 +/- 4.30%). Regional myocardial blood flow (RBF) was not significantly different between any of the groups. Therefore the IS-limiting effect of CP-060S cannot be explained in terms of changes in RPP or RBF. Thus the IS limitation induced by CP-060S is probably the consequence of a direct cardioprotective effect on myocytes. The prevention of Na+-, Ca2+-overload may be the primary reason for this IS-limiting effect.

Chronic liver failure induced by long-term administration of tegafur: a case report.

A 55 year-old man was admitted with massive ascites. Although the laboratory data on admission were compatible with hepatic cirrhosis and remarkable esophageal varices were observed during endoscopy, the imaging findings such as computed tomography and ultrasonographic examination did not confirm hepatic cirrhosis. The patient had no history of alcohol abuse, blood transfusions or acute hepatitis. Serological markers related to viral and autoimmune hepatitis were all negative. Seven years ago, the patient had undergone an operation for colon cancer and has been taking tegafur since then for a total of 55 months. Tegafur was suspected as the causative agent for the liver dysfunction of this patient and the administration of tegafur was stopped. His laboratory data improved gradually and the ascites vanished. The first liver biopsy performed 6 months after discontinuation of tegafur still revealed chronic active hepatitis. However, at the liver biopsy performed 18 months after withdrawal of tegafur, inflammatory activity had subsided and the third liver biopsy, performed 34 months thereafter, revealed further improvement of the pathological changes that had occurred in the liver. We therefore conclude that the administration of tegafur may have caused chronic active liver injury with portal hypertension manifested as ascites and esophageal varices.