[Pharmacology of the 21st century and the Japanese Pharmacological Society (discussion)].
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Drug Design↗
Biomedical subjects
C Tanaka
Publications and source records attributed to C Tanaka.
Suppression of nerve growth factor-induced neuronal differentiation of PC12 cells. N-acetylcysteine uncouples the signal transduction from ras to the mitogen-activated protein kinase cascade.
The cellular redox state is thought to play an important role in a wide variety cellular signaling pathways. Here, we investigated the involvement of redox regulation in the nerve growth factor (NGF) signaling pathway and neuronal differentiation in PC12 cells. N-acetyl-L-cysteine (NAC), which acts as a reductant in cells both by its direct reducing activity and by increasing the synthesis of the cellular antioxidant glutathione, inhibited neuronal differentiation induced by NGF or by the expression of oncogenic ras in PC12 cells. NAC suppressed NGF-induced c-fos gene expression and AP-1 activation. These results suggest that neuronal differentiation and NGF signaling are subject to regulation by the cellular redox state. NAC also suppressed the NGF-induced activation of mitogen-activated protein kinases (MAPKs) and decreased the amount of tyrosine phosphorylation of MAPKs. The suppression of MAPK by NAC was independent of glutathione synthesis. In parallel with the suppression of MAPK, the activation of MAPK kinase kinase activity was also suppressed in the presence of NAC. In contrast, NGF-induced activation of Ras was not inhibited by NAC. The inhibitory effect of NAC on the MAPK cascade was independent of transcription and translation. Thus, NAC suppresses NGF-induced neuronal differentiation by uncoupling the signal transduction from Ras to the MAP kinase cascade in PC12 cells.
Acetylcysteine↗
Phencyclidine alters regional concentrations of neuropeptide Y and peptide YY in rat brain.
The psychotomimetic effects of Phencyclidine (PCP) often have a delayed onset and extend far from the time plasma drug levels reach their peak. PCP at a low dose is considered selective for actions on the N-methyl-D-aspartate-PCP receptor. We evaluated effects of PCP (2 and 10 mg/kg, IP) on regional content of neuropeptide Y (NPY)-like immunoreactivity (LI) and peptide YY (PYY)-LI, in the rat brain. Thirty minutes after administration of PCP, NPY-LI levels were significantly elevated in some limbic structures following both doses. A significant, widespread increase in NPY-LI levels was induced 2 hours after administration of the higher dose of PCP. On the contrary, NPY-LI was significantly decreased in a number of the regions 24 hours after PCP. The extent of reduction was less following the higher dose of PCP than following the lower dose. PCP did not cause a consistent effect on PYY-LI. The findings suggest that effects of PCP on brain NPY content might depend on the dose and the interval between administration of the drug and sacrifice.
Animals↗
Regulation of glutamate release via NMDA and 5-HT1A receptors in guinea pig dentate gyrus.
The regulation by 5-HT1A and N-methyl-D-aspartate (NMDA) receptors on the endogenous glutamate release was investigated in slices of guinea pig dentate gyrus. The release of glutamate was increased dose-dependently by the 5-HT1A receptor antagonist, NAN-190 at 0.01 to 300 nM, but was not affected by the 5-HT1A receptor agonist, 8-OH-DPAT even at 100 nM. The release of glutamate evoked by 0.1 microM NAN-190 was Ca(2+)-dependent, tetrodotoxin-sensitive and inhibited significantly by 8-OH-DPAT at 1, 10 and 100 nM. These results suggest that the 5-HT1A receptor, which is located postsynaptically on glutamatergic neurons, is involved in the inhibitory regulation of glutamate release. The release of glutamate evoked by 200 microM NMDA from dentate gyrus was inhibited significantly by pretreatment with 8-OH-DPAT at 1, 10 and 100 nM. The release of glutamate evoked by 0.1 microM NAN-190 was inhibited significantly by pretreatment with MK-801 at 1 and 10 microM, a selective non-competitive NMDA receptor antagonist. The release of glutamate evoked by NMDA at 25 and 75 microM from dentate gyrus was augmented by the concurrent application of 1 nM NAN-190. We propose that the glutamate release from guinea pig dentate gyrus is regulated both by the postsynaptic 5-HT1A receptor in an inhibitory manner and by the NMDA receptor in a stimulatory manner.
8-Hydroxy-2-(di-n-propylamino)tetralin↗
NMDA receptor activation induces glutamate release through nitric oxide synthesis in guinea pig dentate gyrus.
We tested the hypothesis that the release of glutamate following activation of N-methyl-D-aspartate (NMDA) receptors is mediated by nitric oxide (NO) production, using slices of the guinea pig hippocampus. The NMDA-induced glutamate release from slices of dentate gyrus or CA1, which was both concentration-dependent and Ca(2+)-dependent, was also Mg(2+)-sensitive and abolished by MK-801, a selective non-competitive NMDA receptor antagonist. In dentate gyrus, the NMDA-induced glutamate release was inhibited non-significantly by tetrodotoxin, whereas the NO synthase (NOS) inhibitor NG-nitro-L-arginine (L-NNA) blocked the NMDA-induced release of glutamate in a concentration-dependent manner, but not a high K(+)-evoked release of glutamate. In addition, the L-NNA blockade of NMDA-induced release of glutamate was recovered by pretreatment with L-arginine, the normal substrate for NOS. These results suggest that activation of NMDA receptors in dentate gyrus, as well as subsequent Ca2+ fluxes, is required for the neuronal glutamate release mediated by NO production. On the other hand, the NMDA-evoked glutamate release from CA1 region was tetrodotoxin-sensitive and was not inhibited by L-NNA, thereby suggesting that activation of NMDA receptors in CA1 results in increased glutamate release in an NO-independent manner. Taken together, the NMDA receptor-mediated neuronal release of glutamate from the guinea pig dentate gyrus likely involves the recruitment of NOS activity.
Analysis of Variance↗
Nerve growth factor and forskolin prevent H2O2-induced apoptosis in PC12 cells by glutathione independent mechanism.
PC12 cells died by apoptosis at relatively low concentrations of H2O2, of which cytotoxicity was effectively suppressed by nerve growth factor (NGF), forskolin, and dbt-cAMP. Treatment with NGF or forskolin for 24 h increased the level of cellular antioxidant glutathione (GSH) by 1.6-2.0-fold. However, both NGF and forskolin protected cells against H2O2-stress even when cellular GSH was depleted by treatment with L-buthionine-(S,R)-sulfoximine (BSO). The GSH-independent protection effects of NGF and forskolin did not require new protein or RNA synthesis. Exogenous expression of an oncogenic ras suppressed apoptosis caused by H2O2 indicating that Ras protein also plays a role in suppressing apoptosis caused by oxidative radical stress.
Animals↗
Expression of apolipoprotein E mRNA in rat microglia.
Apolipoprotein E (apoE) is a major risk factor for Alzheimer disease (AD), which is the most common cause of progressive dementing illness. ApoE has been postulated to be synthesized by astrocytes and taken up by microglia and neuronal cells. However, it remains unknown whether apoE is also produced by microglia in the brain. We analyzed apoE mRNA expression of microglia using a rat primary culture system. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed expression of apoE mRNA in cultured rat microglia. By RT-in situ-PCR, microglia showed positive staining for the PCR product of apoE mRNA. These results indicated that apoE was biosynthesized in rat microglia. We suggest that microglia might be one of the sources of apoE in the brain, and that apoE synthesized in microglia might be closely related to the pathogenesis of AD.
Animals↗
Presynaptic and Ca(2+)-independent PKC subspecies modulates NMDAR1 current.
We have studied the properties of the protein kinase C (PKC) subspecies that modulates the NMDA receptor (NMDAR1). The current through homomeric NMDAR1 expressed in Xenopus oocytes was increased by 200-500% by phorbol ester and also by activation of a metabotropic glutamate receptor (mGluR1) expressed in the same oocytes. This potentiation of the NMDAR1 current was not inhibited by the intracellular injection of EGTA. Intracellular injection of epsilon-PKC, a presynaptic PKC subspecies, potentiated the NMDAR1 current more efficiently that did the Ca(2+)-dependent gamma-PKC, a postsynaptic subspecies of the enzyme. Our findings suggested that the presynaptic NMDA receptor could be potentiated in a Ca(2+)-independent manner by the activation of presynaptic PKC subspecies.
Animals↗
Stump pressure as a guide to the safety of permanent occlusion of the internal carotid artery.
Does the absolute value of the stump pressure (post-occlusion back pressure) become a useful index of a good collateral circulation? The authors continuously monitored the mean arterial pressure before, during and after 20-minute balloon test occlusion in 24 patients. The stump pressure was then compared with the results of 99mTc-hexa-methyl propyleneamine (99mTc-HMPAO) single photon emission computed tomography (SPECT) performed after 20 minutes of test occlusion. Patients who failed to tolerate even brief periods of carotid occlusion and showed asymmetric decreases in cerebral blood flow (CBF) on SPECT were divided into high and moderate risk groups. Those with no significant change in CBF on the occluded side formed the minimum risk group. Mean stump pressure was over 50 mmHg in three of a total of 13 patients in the high and moderate risk groups, and below 50 mmHg in two of the 11 patients in the minimum risk group. The ratios of the initial mean stump pressure to the pre-occlusion mean arterial pressure (%) and of the final mean stump pressure at the end of occlusion to the post-opening mean arterial pressure (%) did not exceed 58% in any patient in the high and moderate risk groups, and were at least 60% in all patients of the minimum risk group. Maintenance of a mean stump pressure of 60% or more of the mean systemic pressure during test occlusion may be a more useful index of a good collateral circulation than the absolute value of mean stump pressure.
Adult↗
Neuronal and glial localization of two GABA transporters (GAT1 and GAT3) in the rat cerebellum.
The localization of GABA transporters (GAT1 and GAT3) was examined immunocytochemically in the rat cerebellum at both light and electron microscopic levels using antibodies specific for each subtype. Immunoblot analysis showed that the antibodies against GAT1 and GAT3 specifically recognized their respective antigens in the cerebellum. Both GAT1 and GAT3 were found in the neuropil but not in neuronal somata or glial cell bodies. GAT1 immunoreactivity was seen throughout all layers of the cerebellar cortex with the highest immunoreactivity in the molecular layer, but little immunoreactivity was found in the deep cerebellar nuclei. GAT1 immunoreactivity was seen in the pinceau area of the Purkinje cell layer and in the mossy fiber glomeruli in addition to the neuropil of the molecular layer. Weak GAT3 immunoreactivity was found in the granular layer of the cerebellar cortex, and intense immunoreactivity was observed around the unstained large neurons in the deep cerebellar nuclei. Electron microscopic analysis of the cerebellum revealed that GAT1 immunoreactivity was predominantly localized in the presynaptic terminals, while GAT3 immunoreactivity was localized in the glial processes. These results suggested that GABAergic transmission at synapses is terminated by three GABA uptake systems, (1) only neuronal uptake through GAT1, (2) only glial uptake through GAT3, and (3) both neuronal and glial uptake through GAT1 and GAT3 respectively, and also that the GABA uptake system is different in each type of GABAergic neuron.
Animals↗
Determination of alpha 1-adrenoceptor antagonists in plasma by radioreceptor assay.
A simple, rapid and sensitive radioreceptor assay (RRA) for the quantification of alpha 1-adrenoceptor antagonists such as prazosin in plasma is described. The method involves the use of an RRA based on [3H]prazosin displacement in rat cerebral cortical membranes. The method is reliable, with intra-assay and inter-assay RSDs ranging from 5.9 to 9.2%. The limit of detection is 0.2 (prazosin hydrochloride), 0.05 (tamsulosin hydrochloride) and 0.3 (bunazosin hydrochloride) pmol per assay. Using this method the plasma levels of prazosin hydrochloride were determined in beagle dogs administered orally 2.39 mumol kg-1 of this drug. The plasma levels of prazosin in beagle dogs are in good agreement with those obtained using a high-performance liquid chromatography (HPLC). This RRA proved to be applicable to the monitoring of plasma prazosin levels in patients with essential hypertension and/or benign prostatic hypertrophy receiving therapy with this drug with the therapeutic dosage schedule. Thus, the concentrations of alpha 1-adrenoceptor antagonists in plasma can be adequately monitored by RRA as well as by HPLC.
Adrenergic alpha-1 Receptor Antagonists↗
Stability of a metabolizable ester bond in radioimmunoconjugates.
Ester bonds have been used as metabolizable linkages to reduce radioactivity levels in non-target tissues following the administration of antibodies labeled with metallic radionuclides. In this radiochemical design of antibodies, while the ester bonds should be cleaved rapidly in non-target tissues, high stability of the ester bonds in plasma is also required to preserve target radioactivity levels. To assess the structural requirements to stabilize the ester bond, a new benzyl-EDTA-derived bifunctional chelating agent with an ester bond, (1-[4-[4-(2- maleimidoethoxy)succinamido]benzyl]ethylenediamine-N,N,N',N' -tetraacetic acid; MESS-Bz-EDTA), was developed. MESS-Bz-EDTA was coupled with a thiolated monoclonal antibody (OST7, IgG1) prepared by reducing its disulfide bonds to introduce the ester bond close and proximal to the antibody molecule. For comparison, 1-[4-(5- maleimidopentyl)aminobenzyl]ethylenediamine-N,N,N',N'-tetraacetic acid (EMCS-Bz-EDTA) and meleimidoethyl 3-[131I]iodohippurate (MIH) was coupled to OST7 under the same conjunction chemistry. When incubated in 50% murine plasma or a buffered-solution of neutral pH, OST7-MESS-Bz-EDTA-111In rapidly released the radioactivity, and more than 95% of the initial radioactivity was liberated after a 24 h incubation in both solutions, due to a cleavage of the ester bond. On the other hand, only about 20% of the radioactivity was released from OST7-MIH-131I in both solutions during the same incubation period. In mice biodistribution studies, while a slightly faster radioactivity clearance from the blood with less radioactivity levels in the liver and kidneys was observed with OST7-MIH-131I than with OST7-EMCS-Bz-EDTA-111In, OST7-MESS-Bz-EDTA-111In indicated radioactivity clearance from the blood much faster than and almost comparable to that of OST7-MIH-131I and succinamidobenzyl-EDTA-111In, respectively. These findings as well as previous findings on radiolabeled antibodies with ester bonds suggested that while an introduction of an ester bond close to an antibody molecule stabilized the ester bond against esterase access, chemical structures of the linkages and radiolabels attached to the ester bonds play a significant role in the chemical stability of the ester bond. This may explain the different stability of the ester bonds in radioimmunoconjugates so far reported.
Animals↗
Discrimination of brain abscess from necrotic or cystic tumors by diffusion-weighted echo planar imaging.
Diagnostic difficulties in discriminating brain abscess from necrotic or cystic tumors using conventional CT and MRI have been reported. In this article, we examine the diagnostic ability of diffusion-weighted imaging to discriminate brain abscess from necrotic or cystic tumors. In previous reports, necrotic or cystic tumors show low signal intensity in diffusion-weighted imaging, indicating a high apparent diffusion coefficient (ADC). In contrast, in our study, high signal intensity was observed in the abscess fluid, associated with low ADC.
Brain Abscess↗
Electrophysiological and pharmacological characteristics of ionotropic glutamate receptors in medial vestibular nucleus neurons: a whole cell patch clamp study in acutely dissociated neurons.
A patch clamp study was performed to determine which subtype of ionotropic glutamate receptors is involved in the glutamate-induced excitation of the medial vestibular nucleus (MVN) neurons. Whole cell recording was performed on MVN neurons that were acutely dissociated by enzymatic and mechanical treatments. Application of glutamate at a concentration of 100 microM produced a current with a reversal potential of approximately 0 mV. The glutamate-induced current was completely blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM), a non-N-methyl-D-aspartate (NMDA)-receptor antagonist. Application of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) and kainic acid (KA), non-NMDA-receptor agonists, at concentrations of 30 and 100 microM produced a concentration-dependent depolarization concomitantly with an increase in firing rates during current clamp recording. During voltage clamp recording, glutamate, AMPA and KA elicited a concentration-dependent current with an equilibrium potential of approximately 0 mV. To clarify whether NMDA receptors are present in MVN neurons, the effects of glycine on the glutamate- and NMDA-induced current were examined. Two types of NMDA receptor-mediated current (types 1 and 2) were obtained in terms of the difference in sensitivity to both magnesium ion and MK-801, which act on the NMDA-receptor channel. In the type 1 neurons, the NMDA-induced current was not apparently blocked by magnesium ion or MK-801, although a larger current was obtained in the absence of magnesium ion. In the type 2 neurons, marked blockade of the NMDA-induced current was seen in the presence of magnesium ion and MK-801, as previously reported in other neurons of the central nervous system. These findings indicate the presence of both non-NMDA and NMDA receptors, which are involved in primary afferent transmission, in the MVN neuron, and two distinct types of NMDA receptors.
6-Cyano-7-nitroquinoxaline-2,3-dione↗
Absence of mutations at codon 768 of the RET proto-oncogene in sporadic and hereditary pheochromocytomas.
Sixteen sporadic pheochromocytomas, 3 pheochromocytomas in neurofibromatosis 1, and 4 pheochromocytomas in multiple endocrine neoplasia (MEN) 2A or 2B were screened for mutations at codon 768 of the RET proto-oncogene by AluI digestion of polymerase chain reaction PCR products and mutations in exon 13 by PCR-single strand conformation polymorphism (SSCP) analysis. Although mutations at codon 768 (GAG --> GAC; Glu --> Asp) of the RET proto-oncogene were recently reported to be found in 40% of sporadic medullary thyroid carcinomas (MTCs), the absence of missense mutations at codon 768 was confirmed both with PCR-restriction fragment length polymorphism (RFLP) and PCR-SSCP analysis in all examined cases of pheochromocytomas. These results suggest that mutations at codon 768 of the RET proto-oncogene do not represent a frequent mechanism of tumorigenesis for both sporadic and hereditary pheochromocytomas.
Adrenal Gland Neoplasms↗
Obvious mRNA and protein expression but absence of mutations of the RET proto-oncogene in parathyroid tumors.
The study on the expression of the RET proto-oncogene in parathyroid tumors disclosed obvious mRNA expression by the reverse transcription (RT)-polymerase chain reaction (PCR) method and protein expression by Western blotting. To find out whether mutations in the cysteine-rich regions or tyrosine kinase domain of the RET proto-oncogene are etiological for parathyroid tumorigenesis, sporadic parathyroid adenomas and carcinomas, parathyroid tumors from multiple endocrine neoplasia 1, familial isolated hyperparathyroidism or hereditary hyperparathyroidism-jaw tumor syndrome were screened by PCR-single strand conformation polymorphism and PCR restriction fragment length polymorphism. Missense mutations in the cysteine-rich region, or codons 768 or 918 in the tyrosine kinase domain of the RET proto-oncogene, were not detected in any of the examined cases of parathyroid tumors. These results suggest that mutations of the RET proto-oncogene do not represent a frequent mechanism of tumorigenesis for parathyroid tumors.
Adult↗
[Clinical application of functional mapping; the present state of the art and its future prospects: (series 1) functional MRI: signal mechanism of fMRI and quantification of brain function by echo planar imaging].
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Brain↗
Identification of putative 5-hydroxytryptamine(4) (5-HT4) receptors in guinea pig stomach: The effect of TKS159, a novel agonist, on gastric motility and acetylcholine release.
We investigated the existence and the function of 5-hydroxytryptamine(4) (5-HT4) receptors and the effect of TKS159, a novel agonist of 5-HT4 receptor, on guinea pig stomach. The mechanical activity and the release of [3H]ACh were measured using preparations of muscle layers attached to intramural plexus from guinea pig stomach. 5-HT in the presence of 1 microM methysergide, 1 microM ketanserin and 1 microM granisetron, 5-methoxytryptamine or TKS159 enhanced the electrical transmural stimulation-evoked contraction and [3H]ACh release in strips of the stomach in a concentration-dependent manner. This enhancement by 5-HT, 5-methoxytryptamine or TKS159 was antagonized by SDZ 205-557 or atropine. Cisapride, metoclopramide and TKS159 enhanced the electrical transmural stimulation-evoked contraction and release of [3H]ACh in a concentration-dependent manner. We conclude that the pharmacological characteristics of the receptor, which mediates contraction of the guinea pig stomach by the activation of cholinergic nerves, are consistent with its being of the putative 5-HT4 receptor type and that TKS159 is an agonist at 5-HT4 receptors.
4-Aminobenzoic Acid↗