Sequestration of muscarinic acetylcholine receptor m2 subtypes. Facilitation by G protein-coupled receptor kinase (GRK2) and attenuation by a dominant-negative mutant of GRK2

Sequestration of m2 receptors (muscarinic acetylcholine receptor m2 subtypes), which was assessed as loss of N-[3H]methylscopolamine ([3H]NMS) binding activity from the cell surface, was examined in COS 7 and BHK-21 cells that had been transfected with expression vectors encoding the m2 receptor and, independently, vectors encoding a G protein-coupled receptor kinase (GRK2) (beta-adrenergic receptor kinase 1) or a GRK2 dominant-negative mutant (DN-GRK2). The sequestration of m2 receptors became apparent when the cells were treated with 10(-5) M or higher concentrations of carbamylcholine. In this case, approximately 40% or 20-25% of the [3H]NMS binding sites on COS 7 or BHK-21 cells, respectively, were sequestered with a half-life of 15-25 min. In cells in which GRK2 was also expressed, the sequestration became apparent in the presence of 10(-7) M carbamylcholine. Approximately 40% of the [3H]NMS binding sites on both COS 7 and BHK-21 cells were sequestered in the presence of 10(-6) M or higher concentrations of carbamylcholine. When DN-GRK2 was expressed in COS 7 cells, the proportion of [3H]NMS binding sites sequestered in the presence of 10(-5) M or higher concentrations of carbamylcholine was reduced to 20-30%. These results indicate that the phosphorylation of m2 receptors by GRK2 facilitates their sequestration. These results are in contrast with the absence of a correlation between sequestration and the phosphorylation of beta-adrenergic receptors by the GRK2 and suggests that the consequences of phosphorylation by GRK2 are different for different receptors.

Control of 4-aminopyridine-induced synchronous activity by adenosine A1 and mu-opioid receptor agonists in adult rat hippocampus

In the presence of 4-aminopyridine (4AP, 50 microM) two types of spontaneous field potentials can be recorded in the CA3 stratum radiatum of adult rat hippocampal slices. First, epileptiform interictal discharges (0.85 +/- 0.25 Hz) that are blocked by excitatory amino acid ionotropic receptor antagonists. Second, negative-going synchronous potentials (0.036 +/- 0.015 Hz) which are solely abolished by application of bicuculline methiodide (BMI). Bath application of the specific adenosine A1 receptor agonist, N6-(L-2-phenylisopropyl) adenosine (L-PIA), reduced the frequency of interictal discharges in a dose-dependent manner (IC50 = 8.75 microM; n = 9 slices) and this effect was reversed by the specific adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 microM; n = 3 slices). L-PIA did not affect the frequency of occurrence of the negative-going field potential during application of excitatory amino acid receptor antagonists. This BMI-sensitive event was depressed, however, by application of the mu-opioid receptor agonist [D-Ala2-N-Me-Phe4,Gly5(5)-ol]enkephalin (DAGO, 10 microM; 15.1 +/- 8.7% of rate in control; n = 6 slices), an effect that was antagonized by naloxone (20 microM). Our results indicate that L-PIA reduces the 4AP-induced epileptiform activity through the activation of adenosine A1 receptors. This procedure does not influence the BMI-sensitive field potential, which is abolished, however, by DAGO. Thus, our findings support the hypothesis that the BMI-sensitive potential is due to the presynaptic release of GABA from interneurons.

Potassium channel activators counteract anoxic hyperexcitability but not 4-aminopyridine-induced epileptiform activity in the rat hippocampal slice

The K+ channel activators diazoxide and cromakalim were investigated for effects on 4-aminopyridine (4AP)-induced epileptiform activity in adult rat hippocampal slices maintained in vitro. Under normal conditions of oxygenation, 4AP (50 microM) induced two types of field potentials in extracellular recordings from the CA3 stratum radiatum (apical dendritic region): epileptiform interictal discharge-like events occurring at a frequency of 0.75 +/- 0.36 Hz and long-lasting negative-going potentials mediated by GABA receptor activation that occurred at 0.03 +/- 0.01 Hz (n = 36 slices). Neither diazoxide (0.65-1.3 mM, n = 21 slices) nor cromakalim (50-200 microM, n = 6 slices) altered these two types of discharge. Brief periods of anoxia (4-6 min) reduced the frequency of the 4AP-induced interictal-like events (from 0.75 +/- 0.36 Hz to 0.19 +/- 0.15 Hz, n = 20 slices). In 45% of the experiments, the depressant effect of anoxia was preceded by a period of hyperexcitability consisting of a transient (36.1 +/- 12.9 sec) increase in the frequency of interictal-like events riding on a negative-going DC shift (n = 9 slices). Both responses to anoxia were reversible upon reoxygenation. In contrast, the rate of occurrence of the GABA-mediated potentials was unaffected by the anoxic episodes. Perfusion with cromakalim (n = 4 slices) or diazoxide (n = 5 slices) abolished the initial period of hyperexcitability produced by O2 deprivation but did not alter the subsequent depression of activity. Our experiments indicate that the K+ channel activators can prevent the initial hyperexcitability produced by anoxia, but do not influence 4AP-induced epileptiform activity in normoxic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in neuronal contribution to contractile responses of vas deferens of young and adult guinea pigs

The response characteristics of vas deferens to electrical hypogastric nerve stimulation at various frequencies was studied in guinea pigs of 2 to 15 weeks old. In 2-week-old guinea pigs the stimulation induced monophasic contraction, some of which remained after blocking alpha 1-adrenoceptor and desensitizing P2-purinoceptors with prazosin and alpha, beta-methylene ATP, respectively. In guinea pigs of 10 to 15 weeks old stimulation induced biphasic contraction, which was almost completely inhibited by both blockers. These results suggest that some unknown component other than ATP and norepinephrine is involved in the transmission at 2 weeks, and that its relative significance changes during development.

Binding of [3H](+)-PN200-110 to aortic membranes from normotensive and spontaneously hypertensive rats

We report here the quantitative evaluation of binding density (Bmax) of [3H](+)-PN200-110 in aortic membranes obtained from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. At both 4 and 13 weeks of age, there were no significant differences in Bmax and the dissociation constants (Kd) of [3H](+)-PN200-110 binding between SHR and WKY rat aortas. Irrespective of strain, the Kd increased and the Bmax decreased with age. These results suggest that the number of Ca2+ channels in aortas of SHR and WKY rats are not significantly different, even when hypertension is established in SHR.

Differential potentiation by depolarization of the effects of calcium antagonists on contraction and Ca2+ current in guinea-pig heart

1. The effects of elevation of extracellular K+ concentration ([K+]o) on the negative inotropic potencies of three representative calcium antagonists, diltiazem, verapamil and nifedipine, were investigated in guinea-pig papillary muscle preparations. 2. The negative inotropic effect of diltiazem was potentiated 110 fold when [K+]o was raised from 2.7 mM to 12.7 mM. The effect of verapamil was also potentiated to a lesser extent, but that of nifedipine was not affected. 3. Resting membrane potentials in ventricular muscles were about -80 mV and -60 mV in 2.7 mM K+ and 12.7 mM K+, respectively. 4. To clarify the mechanism responsible for the differential potentiation of the negative inotropic effects, the blocking actions of the three calcium antagonists on the L-type Ca2+ channel current (ICa(L)) were compared at the holding potentials of -80 mV and -60 mV by the whole-cell patch-clamp technique. 5. The use-dependent blocking effect of diltiazem on ICa(L) was enhanced markedly by the change in the holding potential from -80 mV to -60 mV. The effect of verapamil was also enhanced to a lesser extent but that of nifedipine was not affected in this range of depolarization. 6. The differential effects of the [K+]o elevation on the negative inotropic potencies of the three calcium antagonists are explained by the differences in voltage-dependency of their use-dependent blocking effects on ICa(L). 7. The properties of diltiazem and verapamil observed in this study may contribute to their protective effects on the ischaemic myocardium, without affecting the normal myocardium.

Auditory middle latency responses under different task conditions

We examined the relationship between the Na and Pa components of human MLRs and the performance of different tasks. We also investigated whether MLRs are reliable indices of activity in the central motor-sensory system. The click stimuli we used consistently evoked the Na and Pa components. At CZ, the Na and Pa components significantly decreased for all tasks other than pegging with right hand while at FZ, these components were significantly decreased for all tasks. The Na and Pa latencies were slightly increased during task performances. These results indicate that the Na and Pa components of human MLRs decreased when various tasks were performed, while subjects were concentrating. A general principle of evoked potentials is that latencies decrease as amplitudes increase in excitation due to neural activation. Thus, it would appear that, under the conditions of this study, the pathways from the reticular formation and the thalamus to the primary auditory cortex were inhibited. Since the thalamus is considered to be the relay region for poly-sensory inputs, it is thought that the attenuation of the MLRs and SEPs occurs at the level of cerebral cortex, including the reticular formation, the thalamus, and the primary auditory cortex. Accordingly, since it is inferred that central factors are responsible for the attenuation of the MLRs, Na and Pa components observed during the performance of tasks carried out in the present experiment, it may be concluded that MLRs are reliable indices of activity in the central-motor system.

Effects of TA-0910, an orally active TRH analog, on the spinal reflex in spinal rats

Effects of TA-0910 (1-methyl-(S)-4,5-dihydroorotyl-L-histidyl-L-prolinamide), a new thyrotropin releasing hormone (TRH) analog, on spinal reflex potentials and flexor reflexes were compared with those of TRH in C1-spinal rats. Intravenously administered TA-0910 and TRH produced dose-dependent increases in the amplitudes of mono- and polysynaptic reflex potentials and withdrawal flexor reflexes. TA-0910 was more potent and more long-lasting than TRH. The stimulating actions of TA-0910 and TRH on the monosynaptic reflex potential were not antagonized by pretreatment with atropine, cyproheptadine, haloperidol or prazosin, suggesting no involvement of the cholinergic, serotonergic, dopaminergic or noradrenergic system. Intraduodenally administered TA-0910 also produced a lasting potentiation of the withdrawal flexor reflex, but intraduodenally administered TRH showed no effect. These results suggest that TA-0910 may be a more useful drug than TRH for spinal functional disorders.

[Very low-intensity anticoagulant therapy in elderly cardioembolic stroke patients with nonvalvular atrial fibrillation]

Several investigations revealed the significant effect of anticoagulant therapy for stroke prevention in patients with atrial fibrillation. However, in the elderly population, the optimal therapeutic strategy of secondary prevention of cardioembolic stroke is still controversial. We prospectively evaluated the efficacy and safety of very low-intensity anticoagulant therapy (target range, Thrombotest = 20-30%: INR = 1.47-1.81) for elderly cardioembolic stroke patients due to nonvalvular atrial fibrillation. Twenty cardioembolic stroke patients (average age 80.0) with nonvalvular atrial fibrillation were included in our study. Anticoagulant therapy began 5 of 7 days after the embolic event. The incidental rate of ischemic stroke recurrence and bleeding complication were evaluated. During mean follow-up of 14.7 month, the annual recurrent rate of ischemic stroke was 8.2% (cardioembolic stroke = 4.1%/year, atherothrombotic stroke = 0%/year, lacunar stroke = 4.1%/year), whereas one non-fatal gastrointestinal bleeding was observed. Our study suggested that even in the elderly population, very low-intensity anticoagulant therapy may be effective, and safe with respect to prevention of bleeding complications, for secondary cardioembolic stroke prevention.

[An adult case of basal encephalomeningocele with recurrent meningitis]

A 35-year-old man developed meningitis for the first time at the age of 23. Thereafter, he repeatedly suffered from meningitis for six times before he was admitted to our clinic. Each meningitis was preceded by upper respiratory infection. Chronic infection in the head and neck, fracture of the skull base, liquorrhea, Mollaret meningitis, and acquired immunodeficiency were all ruled out. Nasal fiberscope examination revealed a palpating white tumor in the left olfactory cleavage. Coronal CT scanning demonstrated encephalomeningocele at the left ethmoidal cavity. The encephalomeningocele was surgically repaired and the patient has been free from further meningitis. The causal relationship between the encephalomeningocele and recurrent meningitis was discussed.

[A case of acute idiopathic pandysautonomia complicated with acute pancreatitis and liver injury]

A case of acute idiopathic pandysautonomia (AIPD) complicated with acute pancreatitis and liver injury was reported. A 43-year-old woman acutely developed abdominal pain, low grade fever, lymphoadenopathy and generalized erythema in May 1992. She was found to have autonomic dysfunctions, such as orthostatic hypotension, hypohidrosis, paralytic ileus and urinary retention. A systematic investigation of autonomic function revealed an impairment of both sympathetic and parasympathetic post-ganglionic nerves. Serum concentrations of amylase, lipase, elastase 1, and transaminase and amylase creatinine clearance ratio were elevated in the early stage of the disease. No significant serological findings for viral infections were detected to suggest any special etiology of the disease; the symptoms gradually improved, although incompletely, after several months from the onset. AIPD complicated with acute pancreatitis or liver injury is uncommon. A possible link between undetectable viral infection and AIPD was discussed.

Cloning and nucleotide sequence of cDNA encoding a lipase from Fusarium heterosporum

Fusarium heterosporum produces a solvent-tolerant lipase. A 1.3-kbp lipase cDNA was isolated from the cDNA library by colony hybridization with an oligonucleotide probe corresponding to the N-terminal amino acid sequence. Nucleotide sequence analysis showed an open reading frame of 999 bp, and the deduced amino acid sequence contained the N-terminal sequence determined by Edman degradation and the consensus pentapeptide (-Gly-X-Ser-X-Gly-), which is conserved in lipase, esterase, and serine protease. The mature lipase consisted of 301 amino acid residues with a molecular mass of 32.7 kDa, preceded by the putative signal peptide or preprosequence. The enzyme was homologous to lipases from Humicola lanuginosa (39% homology), Rhizomucor miehei (32%), Rhizopus delemar (32%), and Rhizopus niveus (32%), and to mono- and diacylglycerol lipase from Penicillium camembertii (38%). Comparison of this lipase with these homologous enzymes suggested that the catalytic triad was composed of Ser144, Asp198, and His256, and that the oxyanion hole was formed with Ser 82.

Binding of a catechol derivative of denopamine (T-0509) and N-tert-butylnoradrenaline (Colterol) to beta 1- and beta 2-adrenoceptors

The affinities for beta-adrenoceptors, the subtype-selectivity and the agonistic effectiveness of T-0509 (a catechol derivative of denopamine) and colterol (N-tert-butylnoradrenaline; Col) were compared with those of other beta-agonists using a binding assay method. Specific binding of [3H]dihydroalprenolol (3H-DHA) to guinea pig left ventricular and lung membranes was saturable, and Scatchard and Hill analyses suggested that 3H-DHA bound to both membranes with a single population of binding sites with no binding site cooperativity. Addition of 5'-guanylylimidodiphosphate (GppNHp, 30 microM) led to a rightward shift of the 3H-DHA binding displacement curves of T-0509 and Col in both membranes, and the degree of shift was similar to that of full agonists such as isoproterenol (Iso), adrenaline (Adr) and noradrenaline (NA). Both T-0509 and Col were thus considered to be full agonists at both beta 1- and beta 2-adrenoceptors, respectively, unlike denopamine and procaterol. T-0509 and Col showed considerably high affinity for both beta 1- and beta 2-adrenoceptors, and T-0509, like denopamine, was as selective for the beta 1-subtype as NA (4.5-fold compared with Iso as a non-selective agonist), whereas Col was more selective for the beta 2-subtype than Adr (4.5-fold compared with Iso).

[False positives and false negatives seen in anti-HIV-1 antibody tests]

From September 1986 to December 1993 31059 anti-HIV antibody tests were performed on the samples from our clinic, from 29 health centers and their branches of Osaka Prefecture, from a hospital and from high risk groups. Enzyme immune assay (EIA) was used up to 1988 and from 1989 particle agglutination (PA) has been employed. The indeterminates of Western blot (WB) were seen in 5 EIA positives and in 2 PA positives. False positive rate of EIA was 0.235% (11/467) and that of PA was 0.011% (2/17922). Two false negative cases of anti-HIV-1 antibody test due to window period were documented and the importance of co-use of antigen test at the time of confirmative antibody tests was discussed.

Immunocytochemical detection of bone marrow-invasive neuroblastoma cells

We evaluated the utility of an immunocytochemical technique employing the commercially available anti-CD56 monoclonal antibody, NKH 1. The utility and sensitivity of this technique in the detection of invasive neuroblastoma (NB) cells in the bone marrow were compared with those of Wright-Giemsa staining. The correlation coefficient for the percent NB cells detected using Wright-Giemsa staining with the percent NKH 1 immunoreactive cells was 0.78. In the analysis of specificity, this monoclonal antibody showed slight cross-reactivity with normal bone marrow cells, including macrophages, lymphocytes and osteoblasts. In the evaluation of the sensitivity of the NKH 1 immunocytochemical technique, SK-N-DZ and SK-N-SH NB cell lines were added to morphologically normal bone marrow mononuclear cells from patients without NB to the final NB cell line at concentrations of 2%, 1% and 0.1%. NB cells at the final concentration of 0.1% could be detected by the immunocytochemical technique. We conclude that the NKH 1 immunocytochemical staining technique is useful in the detection of metastatic NB cells in bone marrow.

Hemodynamic and coronary vasodilative properties of a selective and full beta 1-adrenoceptor agonist, T-0509, in comparison with isoproterenol in anesthesized dogs

Recently, the beta 1-adrenoceptor was shown to mediate direct coronary vasodilation independent of metabolic demand in canine arrested heart preparation. To investigate the beta 1-adrenoceptor-mediated direct vasodilation in a beating heart preparation, we compared coronary blood flow (CBF) and coronary sinus oxygen tension (PO2) in anesthetized open-chest dogs using a beta 1-selective agonist, T-0509. T-0509 (0.005-0.05 microgram/kg intravenously, i.v.) increased the maximal rate of increase in left ventricular pressure (LVdp/dtmax) and heart rate (HR) to an extent similar to that induced by isoproterenol (ISO) without decreasing diastolic blood pressure (DBP). A beta 1-adrenoceptor antagonist, (-)-bisoprolol (10 micrograms/kg), but not a beta 2-adrenoceptor antagonist, ICI 118,551 (30 micrograms/kg), inhibited the T-0509-induced increase in LVdp/dtmax and HR. Thus, T-0509 showed selective beta 1 stimulation at the doses used. T-0509 also caused beta 1-selective relaxation in isolated coronary arteries. ISO increased both CBF and PO2. The early phase of the increase in CBF and the concurrent increases in PO2 were inhibited by ICI 118,551, whereas the late phase of the increase in CBF was inhibited by (-)-bisoprolol. T-0509 increased CBF, and this increase was inhibited by (-)-bisoprolol. A slight but significant increase in PO2 induced by T-0509 was not altered by these doses of the antagonists. Our results indicate that the T-0509-induced increase in CBF is due mainly to an indirect effect on myocardial beta 1-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of DP-1904, a thromboxane A2 synthetase inhibitor, on crescentic nephritis in rats

The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane A2 synthetase inhibitor, was compared with that of OKY-046, using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Test drugs were given p.o. once daily from the day after the the development of glomerular alteration as well as the elevation of proteinuria and plasma cholesterol. On the other hand, OKY-046 (20 mg/kg per day), a thromboxane A2 synthetase inhibitor, significantly inhibited only deterioration in the glomeruli. DP-1904 and OKY-046 inhibited glomerular thromboxane B2 production and increased glomerular prostaglandin E2 and 6-keto prostaglandin F1 alpha production in normal and nephritic rats. Both drugs inhibited the increase in platelet aggregability, restored decreased renal tissue blood flow to a near-normal level and decreased the deposition of rat immunoglobulin G on glomerular basement membrane in nephritic rats. These results suggest that DP-1904 may be an effective agent for the treatment of proliferative glomerulonephritis.