Short report: a major genotype of Japanese encephalitis virus currently circulating in Japan

A 240-nucleotide sequence of the capsid/premembrane gene region of 23 Japanese encephalitis virus (JEV) strains isolated in Tokyo and Oita, Japan was determined and phylogenetic analyses were performed. All the strains clustered into two distinct genotypes (III and I). All strains isolated before 1991 belonged to genotype III, while those isolated after 1994 belonged to genotype I. In addition, the strains of the genotype I isolated in Japan showed a close genetic relationship with those from Korea and Malaysia.     

Efflux transport of N-monodesethylamiodarone by the human intestinal cell-line Caco-2 cells

Amiodarone (AMD) is a benzofurane derivative with class III antiarrhythmic activity that is effective in controlling intractable cardiac arrhythmias. One of the most common and serious drug interactions in clinical practice is the interaction between digoxin and an antiarrhythmic agent. It has been reported that AMD and N-monodesethylamiodarone (DEA), the active metabolite of AMD, inhibit the P-glycoprotein (P-gp/MDR1)-mediated digoxin transport. However, the intestinal transport processes of AMD and DEA have not been fully revealed. In this study, we focused on the intestinal transport mechanism of DEA and characterized the intestinal transport of DEA using Caco-2 cells. Basal-to-apical transport of DEA by Caco-2 cells was greater than apical-to-basal transport. The relationship between concentration and basal-to-apical flux rate appeared to approach saturation. The uptake of DEA by Caco-2 cells was increased in the presence of typical ATP-depletion compounds and thyroid hormones. On the other hand, substrates for P-gp, multidrug resistance-associated proteins (MRPs/ABCCs) and breast cancer resistance protein (BCRP/ABCG2) had no effect on the efflux of DEA. These results suggest that an ATP-binding cassette (ABC) transporter, which is different from P-gp, MRPs and BCRP, mediates the efflux of DEA across the apical membrane in Caco-2 cells and that thyroid hormone inhibits this transporter.     

Central administration of p-hydroxyamphetamine produces a behavioral stimulant effect in rodents: evidence for the involvement of dopaminergic systems

Rationale and objectives

It is well-known that amphetamine induces increased locomotor activity in rodents. We previously found that intracerebroventricular (i.c.v.) administration of p-hydroxyamphetamine (p-OHA), an amphetamine metabolite, increases synaptic dopamine (DA) levels in the striatum. In the present study, we investigated the effect of p-OHA on locomotor activity in rodents.

Results

In mice, i.c.v. administration of p-OHA significantly increased locomotor activity in a dose-dependent manner. p-Hydroxynorephedrine, another amphetamine metabolite, did not increase locomotor activity. This effect of p-OHA was inhibited by pretreatment with nomifensine, a dopamine-uptake inhibitor, but not by fluoxetine, a serotonin-uptake inhibitor, or diethyldithiocarbamate, a dopamine-β-hydroxylase inhibitor. Furthermore, we tested the effects of microinjections of p-OHA into the rat nucleus accumbens (NAc) on locomotor activity. Local infusion of p-OHA into the NAc significantly increased locomotor activity. As in mice, the increased locomotor activity induced by p-OHA microinjection into the NAc in rats was inhibited by nomifensine.

Conclusions

These data suggest that dopaminergic systems in the NAc may play important roles in p-OHA-induced locomotor activity in rodents.     

Alterations in cognitive function in prepubertal mice with protein malnutrition: relationship to changes in choline acetyltransferase

We have found that protein malnutrition (PM) causes a significant impairment of memory-related behavior on the 15th and 20th day after the start of PM (5% casein) feeding in prepubertal mice but not in postpubertal mice, as measured by a passive-avoidance task. This impairment was almost completely reversed by merely switching to a standard protein (20% casein) diet on the 10th day after the start of PM. However, the reversal was not observed when the switching to a standard protein regimen was done on the 15th day of the PM diet. Interestingly, the impairment of memory-related behavior on the 20th day was improved by the chronic administration of physostigmine (0.1 mg/kg/day x last 10 days, i.p.), a cholinesterase inhibitor. To correlate brain cholinergic neuron function with the memory-related behavior impairment induced by PM, microphotometry was used to determine the histological distribution of the imunofluorescence intensity for choline acetyltransferase (ChAT), a functional marker of presynapse in cholinergic neurons. The change in the intensity of fluorescence indicated that ChAT protein was decreased in the hippocampus (CA1, CA3 and dentate gyrus) on the 20th day after PM feeding in comparison with controls. These results suggest the possibility that the memory-related behavior deficits observed in prepubertal mice with PM are caused by a dysfunction of the cholinergic neurons in the hippocampus.     

A case of chorea-acanthocytosis with dilated cardiomyopathy and myopathy]

We report a patient of chorea-acanthocytosis (CA), presenting with dilated cardiomyopathy and myopathy. The patient, 40-year-old male, was seen in our clinic because of progressive gait disturbance. Neurologically, he had chorea, tic, dystonia, diminished tendon reflexes and mild muscular atrophy and weakness. Serum creatine kinase level was elevated to 5.514 IU/l, MRI study showed atrophy of the putamen and caudate nucleus. Peripheral nerve involvement was confirmed pathologically and electrophysiologically. Acanthocytosis was found after repeated blood examinations. Furthermore, he had dilated cardiomyopathy on echocardiogram and cardiac muscle biopsy, and his muscle biopsy taken from gastrocnemius indicated myopathic changes with fiber necrosis. From these clinical and laboratory data, he was suspected to have McLeod syndrome (McS). However, he had normal expression of Kell antigens, and direct sequence of XK gene from genomic DNA sample showed no mutations. Accordingly, he was diagnosed as having CA. As CA shares the similar clinical and laboratory features with McS except Kell antigens, the evaluation of Kell blood system is crucial for differential diagnosis. As seen in our patient, blood sampling should be repeated for identification of acanthocytosis, because the finding is not always clearly present.     

Pathophysiological roles of endogenous endothelin-1 in dogs with chronic heart failure produced by rapid right ventricular pacing.

This study was designed to analyze the pathophysiological role of the endogenous endothelin (ET) system and the therapeutic approach to congestive heart failure (CHF) with ET(A)/ET(B) receptor antagonists in a canine CHF model. After 3 weeks of rapid right ventricular pacing (240 beats/min), concentrations of immunoreactive ET-1 in dogs increased approximately 2-fold in plasma and in the left and right ventricles but not in the lung. There were no meaningful changes in the density and affinity of total ET receptors, or in the ratio of ET(A) to ET(B) receptors. To clarify the functional role of endogenous ET, we examined the effects of acute injection of J-104132 (1 and 3 mg/kg i.v.), an ET(A)/ET(B) receptor antagonist, on cardiovascular and renal function in dogs with CHF. Compared with vehicle, J-104132 at both doses significantly decreased pulmonary artery pressure (PAP), pulmonary capillary wedge pressure (PCWP), and mean arterial pressure (MAP), and increased cardiac output (CO) and renal blood flow. J-104132 had no effects on heart rate and cardiac contractility. In addition, we examined whether J-104132 has an additive effect in the presence of enalaprilat. J-104132 (1 mg/kg i.v.) administered after enalaprilat (0.05 mg/kg i.v.) induced further decreases in MAP, PCWP and PAP, and further increases in CO, resulting in further decreases in total peripheral resistance. These results indicate that the endogenous ET system is exaggerated in CHF and has a detrimental effect on cardiac function. Therefore, J-104132 given alone or as combination therapy may play a beneficial role in the treatment of CHF in humans.     

Intrathecally administered big dynorphin,a prodynorphin-derived peptide,produces nociceptive behavior through an N-methyl-D-aspartate receptor mechanism

Intrathecal (i.t.) administration of big dynorphin (1-10 fmol), a prodynorphin-derived peptide consisting of dynorphin A and dynorphin B, to mice produced a characteristic behavioral response, the biting and/or licking of the hindpaw and the tail along with slight hindlimb scratching directed toward the flank, which peaked at 5-15 min after an injection. Dynorphin A produced a similar response, though the doses required were higher (0.1-30 pmol) whereas dynorphin B was practically inactive even at 1000 pmol. The behavior induced by big dynorphin (3 fmol) was dose-dependently inhibited by intraperitoneal injection of morphine (0.125-2 mg/kg) and also dose-dependently, by i.t. co-administration of D(-)-2-amino-5-phosphonovaleric acid (D-APV) (1-4 nmol), a competitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (0.25-4 nmol), an NMDA ion-channel blocker, and ifenprodil (2-8 pmol), an inhibitor of the NMDA receptor ion-channel complex interacting with the NR2B subunit and the polyamine recognition site. On the other hand, naloxone, an opioid receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA glutamate receptor antagonist, 7-chlorokynurenic acid, a competitive antagonist of the glycine recognition site on the NMDA receptor ion-channel complex, [D-Phe(7),D-His(9)]-substance P(6-11), a specific antagonist for substance P (NK1) receptors, and MEN-10376, a tachykinin NK2 receptor antagonist, had no effect. These results suggest that big dynorphin-induced nociceptive behavior is mediated through the activation of the NMDA receptor ion-channel complex by acting on the NR2B subunit and/or the polyamine recognition site but not on the glycine recognition site, and does not involve opioid, non-NMDA glutamate receptor mechanisms or tachykinin receptors in the mouse spinal cord.