Selective up-regulation of an NMDA receptor subunit mRNA in cultured cerebellar granule cells by K(+)-induced depolarization and NMDA treatment

High KCI or NMDA treatment promotes the survival of cultured neonatal cerebellar granule cells, and these cells become sensitive to NMDA toxicity after prolonged K+ depolarization. Following both treatments, the NMDA receptor increases, as assessed by fura-2 fluorescence analysis of NMDA receptor-mediated intracellular Ca2+ increase. Northern analysis indicates that both treatments specifically up-regulate NMDAR2A subunit mRNA through an increase in resting intracellular Ca2+ concentration. Antisense oligonucleotide analysis further indicates that NMDAR2A mRNA up-regulation is responsible for NMDA receptor induction. Our results demonstrate that regulation of a specific NMDA receptor subunit mRNA governs NMDA receptor induction, which is thought to play an important role in granule cell survival and death.

Molecular diversity of glutamate receptors and their physiological functions

Glutamate receptors play an important role in many integrative brain functions and in neuronal development. We report the molecular diversity of NMDA receptors and metabotropic glutamate receptors on the basis of our studies of molecular cloning and characterization of the diverse members of these receptors. The NMDA receptors consist of two distinct types of subunits. NMDAR1 possesses all properties characteristic of the NMDA receptor-channel complex, whereas the four NMDAR2 subunits, termed NMDAR2A-2D, show no channel activity but potentiate the NMDAR1 activity and confer functional variability by different heteromeric formations. The NMDA receptor subunits are considerably divergent from the other ligand-gated ion channels, and the structural architecture of these subunits remains elusive. The mGluRs form a family of at least seven different subtypes termed mGluR1-mGluR7. These receptor subtypes have, seven transmembrane segments and possess a large extracellular domain at their N-terminal regions. The seven mGluR subtypes are classified into three subgroups according to their sequence similarities, signal transduction mechanisms and agonist selectivities: mGluR1/mGluR5, mGluR2/mGluR3 and mGluR4/mGluR6/mGluR7. On the basis of our knowledge of the molecular diversity of the NMDA receptors and mGluRs, we have studied the physiological roles of individual receptor subunits or subtypes. We have shown that K(+)-induced depolarization or NMDA treatment in primary cultures of neonatal cerebellar granule cells induces the functional NMDA receptor and specifically up-regulates NMDAR2A mRNA among the multiple NMDA receptor subunits through the increase in resting intracellular Ca2+ concentrations. Our study demonstrates that the regulation of the specific NMDA receptor subunit mRNA governs the NMDA receptor induction that is thought to play an important role in granule cell survival and death. Analysis of an agonist selectivity and an expression pattern of mGluR6 has indicated that mGluR6 is responsible for synaptic neurotransmission from photoreceptor cells to ON-bipolar cells in the visual system. We have also investigated the function of mGluR2 in granule cells of the accessory olfactory bulb by combining immunoelectron-microscopic analysis with slice-patch recordings on the basis of the identification of a new agonist selective for this receptor subtype. Our results demonstrate that mGluR2 is present at the presynaptic site of granule cells and modulates inhibitory GABA transmission from granule cells to mitral cells. This finding indicates that the mGluR2 activation relieves excited mitral cells from GABA inhibition but maintains the lateral inhibition of unexcited mitral cells, thus resulting in enhancement of the signal-to-noise ratio between the excited mitral cells and their neighboring unexcited mitral cells.

Substance P receptor-immunoreactive neurons in the rat neostriatum are segregated into somatostatinergic and cholinergic aspiny neurons

Immunochemical characteristics of neostriatal neurons producing substance P receptor (SPR) were examined in adult rats by double- and triple-immunofluorescence methods. In the neostriatum, SPR immunoreactivity was detected in large and medium-sized aspiny neurons. Virtually all SPR-immunoreactive neurons in the neostriatum contained somatostatin (SS) or choline acetyltransferase (ChAT), but not parvalbumin. All SS- and ChAT-immunoreactive neurons in the neostriatum showed SPR immunoreactivity. The co-existence of SS and ChAT was, however, not found in single neurons expressing SPR immunoreactivity. The present results indicate that neostriatal neurons immunoreactive for SPR are segregated into 2 groups: (1) medium-sized, spiny somatostatinergic, and (2) large, aspiny cholinergic neurons.

Role of a metabotropic glutamate receptor in synaptic modulation in the accessory olfactory bulb

Various functions of glutamate transmission are mediated by both ionotropic and metabotropic glutamate receptors. The metabotropic glutamate receptors (mGluRs) consists of at least six different subtypes that are classified into three subgroups, mGluR1/mGluR5, mGluR2/mGluR3, and mGluR4/mGluR6 (refs 1-5), but their physiological roles are largely unknown. Here we report the identification of a very potent agonist for mGluR2/mGluR3, DCG-IV, and the specific localization of mGluR2 in granule cell dendrites that form dendrodendritic synapses with mitral cells in the accessory olfactory bulb. Using the DCG-IV agonist for mGluR2 in combination with slice patch-recording, we demonstrate that the granule cell mGluR2 presynaptically suppresses inhibitory GABA (gamma-aminobutyrate) transmission to the mitral cell. Our results indicate that mGluR2 in granule cells plays an important role in the persistent excitation of olfactory sensory transmission in the accessory olfactory bulb by relieving mitral cells from the GABA inhibition.

Inhibition of histamine secretion by wortmannin through the blockade of phosphatidylinositol 3-kinase in RBL-2H3 cells

The surface engagement of high affinity immunoglobulin E receptor (Fc epsilon RI) of rat basophilic leukemia 2H3 (RBL-2H3) cells induced histamine secretion and leukotriene release following activation of the tyrosine kinase Lyn together with phosphatidylinositol 3-kinase (PI3-kinase). Wortmannin inhibited the activity of partially purified PI3-kinase from calf thymus, as well as the PI3-kinase activity in anti-PI3-kinase p85 immunoprecipitates from RBL-2H3 cells, at a concentration as low as 1.0 nM and with IC50 values of 3.0 nM, but did not inhibit PI4-kinase activity. The inhibition of PI3-kinase by wortmannin was irreversible. Wortmannin inhibited both Fc epsilon RI-mediated histamine secretion and leukotriene release up to 80% with IC50 values of 2.0 and 3.0 nM, respectively. Wortmannin inhibited PI3-kinase activity in intact cells up to 80% with an IC50 value of 2.0 nM, which is almost equal to those for PI3-kinase in vitro and for histamine secretion and leukotriene release. With anti-wortmannin antibody, we have shown that wortmannin binds to the 110-kDa protein, but not to PI3-kinase 85-kDa regulatory subunit both in vitro and in whole cells. Furthermore, there was a positive correlation between the potencies of wortmannin derivatives as inhibitors of PI3-kinase and as inhibitors of histamine secretion. Wortmannin had no effect on the activation of the tyrosine kinase Lyn. These results suggest that PI3-kinase is involved in the signal transduction pathway responsible for histamine secretion following stimulation of Fc epsilon RI and that wortmannin blocks these responses through direct interaction with the catalytic subunit of this enzyme.

MS-347a, a new inhibitor of myosin light chain kinase from Aspergillus sp. KY52178

MS-347a was isolated from the culture broths of Aspergillus sp. KY52178 as an inhibitor of smooth muscle myosin light chain kinase (MLCK). MS-347a inhibited the activity of chicken gizzard MLCK with an IC50 value of 9.2 microM. The inhibition was dependent on time of preincubation of MS-347a with the enzyme, suggesting irreversible inhibition. It is likely that the inhibitor binds to the catalytic domain of MLCK, since the compound inhibited not only calmodulin-dependent but also calmodulin-independent activity of MLCK. Calmodulin-dependent cyclic nucleotide phosphodiesterase, cAMP-dependent protein kinase and cGMP-dependent protein kinase were not inhibited by 150 microM MS-347a at all, although the compound inhibited protein kinase C with an IC50 value of 16 microM. MS-347b, a minor component was also isolated from the same culture broths. This minor component at 150 microM did not inhibit the activity of MLCK.

Two types of left ventricular wall motion abnormalities with distinct clinical features in patients with hypertrophic cardiomyopathy

During the long-term follow-up of patients with hypertrophic cardiomyopathy (HCM), some patients develop left ventricular (LV) wall motion abnormalities in the absence of fixed coronary artery disease. The purpose of this study is to clarify which clinical features in patients with HCM seem to influence gradual development of LV wall motion abnormalities over an extended period of time. The study investigates the incidence, mechanism and predictors of these abnormalities. In this retrospective study of 162 patients with HCM, followed-up for an average of 13.3 years, we focused our attention on 16 patients who gradually developed two different forms of LV wall motion abnormality. In 11 of these 16 patients, apical segmental dysfunction with midzone obstruction was recognized; the remaining five patients showed generalized hypokinesis, as seen in dilated cardiomyopathy. The 11 patients with apical segmental dysfunction presented with extensive apical hypertrophy reaching the midventricular level at first examination. The five patients with generalized hypokinesis showed a slight decrease in LV contractility and reduced localized antero-apical wall motion even at initial examination. None of the patients in either group developed the other group's features during their clinical course. These two groups had different initial manifestations and pursued different clinical courses, suggesting that the underlying mechanisms causing wall motion abnormalities are different.

Immunohistochemical localization of a metabotropic glutamate receptor, mGluR5, in the rat brain

A trpE-fusion protein containing a C-terminal sequence of a rat metabotropic glutamate receptor, mGluR5, was used to produce an antibody. On immunoblot, the antibody specifically reacted with mGluR5 expressed in mammalian cells and rat brain. Immunohistochemical analysis revealed intense mGluR5-like immunoreactivity (LI) in the olfactory bulb, anterior olfactory nuclei, olfactory tubercle, cerebral cortex, hippocampus, lateral septum, striatum, nucleus accumbens, inferior colliculus, and spinal trigeminal nuclei. The distribution pattern of mGluR5-LI corresponds very well with that of mGluR5 mRNA. Electron microscope analysis of the striatum revealed dense accumulation of immunoreaction products in dendrites which were often provided with asymmetrical synapses. These results suggest that mGluR5 is predominantly located in postsynaptic elements.

Direct effects of cutaneous neuropeptides on adenylyl cyclase activity and proliferation in a keratinocyte cell line: stimulation of cyclic AMP formation by CGRP and VIP/PHM, and inhibition by NPY through G protein-coupled receptors

Many neuropeptides are present in the peripheral nerves of human skin and are distributed from the intraepidermis to subcutaneous appendages, and those peptides are considered to be involved in the pathogenesis of various inflammatory dermatoses. In this investigation, we determined the effects of various neuropeptides on intracellular cyclic adenosine-5'-monophosphate (AMP) formation in cultured human keratinocytes. Among the many peptides tested, calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), peptide histidine-methionine (PHM), and growth hormone releasing factor (GRF) stimulated a rapid and marked formation of intracellular cyclic AMP in keratinocytes in a dose-dependent manner. The direct association of the receptors for CGRP and VIP with adenylyl cyclase in keratinocytes was confirmed by the findings that CGRP and VIP stimulated the enzyme activity in membrane preparations derived from cultured keratinocytes in the presence of guanosine triphosphate (GTP). On the other hand, neuropeptide Y (NPY) showed an inhibitory effect on forskolin-induced cyclic AMP accumulation in keratinocytes. This inhibitory effect of NPY was completely eliminated by glucocorticoid pretreatment of cultured keratinocytes. Furthermore, the presence of peptides that substantially increase intracellular cyclic AMP accumulation also stimulated DNA synthesis and proliferation in a human keratinocyte cell line in a dose-dependent manner. These results suggest that neuropeptides work directly as biologic modulators of keratinocytes through the cyclic AMP cascade.

[Circulating immune complexes and anti-mite specific IgG antibody in status asthmatics--effects of methylprednisolone and analysis of an anti-complementary factor]

Serial changes of circulating immune complexes and anti-mite specific IgG antibody in the peripheral blood were measured eight times in six status asthmatics treated with high doses of methylprednisolone (MPS). Circulating immune complexes decreased to normal levels three hours after MPS administration. By contrast, anti-mite specific IgG antibody increased to beyond the normal range 14 days after MPS administration. Serum levels of IgE and allergen specific IgG4 antibody did not show any significant changes. In vitro experiments, circulating immune complexes in the sampled sera were decreased by an absorption test with anti-mite specific IgG antibody, and increased by reaction with an adequate volume of mite allergen. These facts indicate that circulating immune complexes are an anti-complementary factor working on the complement system, as previously reported, and that mite allergen and anti-mite IgG antibody relate to their conformation in status asthmatics. Clinically, MPS might possess an inhibitory effects on the formation of immune complexes and/or accelerate complement-dependent solubilization of antigen-antibody complexes, so that anti-mite specific IgG antibody increased markedly in the peripheral blood.

Localization of endothelin receptor messenger ribonucleic acid in the rat ovary and fallopian tube by in situ hybridization

Rat mRNAs encoding two subtypes of the endothelin (ET) receptor (ET(A) and ETB) were studied in the rat ovary and fallopian tube by means of Northern blotting and in situ hybridization. The mRNA transcripts for the endothelin-1-specific type receptor (ET(A)) in pooled RNA from the ovary and fallopian tube were 4.2 and 5.2 kilonucleotides, and that for the nonselective type receptor (ETB) was 4.7 kilonucleotides; these were similar to transcripts for endothelin receptors from other tissues. ET(A) mRNA expression was abundant in the muscle cell layer of the fallopian tube, but low in the ovary. On the other hand, ETB mRNA was abundant in the granulosa cells in the developing follicles, but low in atretic follicles and absent in the fallopian tube. These results demonstrated that the mRNAs for the two subtypes of the rat endothelin receptor have different expression profiles in the ovary and fallopian tube. ETs may mainly affect the granulosa cells in the dominant follicles as well as the muscle cells of the fallopian tube through ETB and ET(A), respectively.

Role of the large extracellular domain of metabotropic glutamate receptors in agonist selectivity determination

Metabotropic glutamate receptors consist of at least six different subtypes termed mGluR1-mGluR6. They belong to the family of G protein-coupled receptors and commonly possess an unusually large extracellular domain preceding the seven transmembrane segments. mGluR1 and mGluR2 show similar affinities for L-glutamate but distinct patterns in their responsiveness to quisqualate and trans-1-amino-1,3-cyclopentane-dicarboxylate (tACPD). To assign structural determinants for the different agonist selectivities, we constructed a series of chimeric receptors at the extracellular domains of mGluR1 and mGluR2 and determined their agonist selectivities by measuring their electrophysiological responses to L-glutamate, quisqualate, and tACPD in Xenopus oocytes. Replacement of the extracellular domain up to about one-half of the amino-terminal extracellular domain of mGluR1 with the corresponding portion of mGluR2 generated a pattern of the agonist selectivity characteristic of mGluR2. The acquirement of this property in agonist selectivity was further indicated by the selective responses of these chimeric receptors to an mGluR2-specific agonist, (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine. This investigation demonstrates that the extracellular domain of mGluR is critical in determining agonist selectivity and that the mode of determination of agonist selectivity of mGluR is different from that of other G protein-coupled receptors for small molecule transmitters.

Distribution of the mRNA for a metabotropic glutamate receptor (mGluR3) in the rat brain: an in situ hybridization study

Distribution of the mRNA for a metabotropic glutamate receptor, mGluR3, which is coupled to the inhibitory cAMP cascade, was examined in the central nervous system of the adult albino rat by in situ hybridization. The hybridization signals of mGluR3 were detected not only on neuronal cells but also on many glial cells throughout the brain and spinal cord. In the neuronal cells, prominent expression of mGluR3 mRNA was seen in the thalamic reticular nucleus. Moderately labeled neurons were seen in the anterior olfactory nucleus, cerebral neo- and mesocortical regions, lateral amygdaloid nucleus, ventral part of the basolateral amygdaloid nucleus, dorsal endopiriform nucleus, supraoptic nucleus, superficial layers of the superior colliculus, inferior colliculus, interpeduncular nucleus, superior olivary nuclei, and Golgi cells in the cerebellar cortex. Weakly labeled neurons were observed in the striatum, nucleus accumbens, ventral pallidum, globus pallidus, entopeduncular nucleus, lateral hypothalamic area, hypothalamic paraventricular nucleus, medial habenular nucleus, anterior pretectal nucleus, Barrington's nucleus, Nucleus O, paragenual nucleus, trigeminal sensory complex, cochlear nuclei, dorsal motor nucleus of the trigeminal nerve, dorsal cap of the inferior olive, spinal dorsal horn, and lamina X of the spinal cord. The stellate cells in the cerebellar cortex, and neurons in the deep cerebellar nuclei were also labeled weakly. The granule cell layer of the dentate gyrus, as a whole, appeared to be labeled intensely, but each of the granule cells was labeled only weakly. No significant labeling was detected in the mitral and tufted cells in the olfactory bulb, hippocampal pyramidal cells, Purkinje and granule cells in the cerebellar cortex, or somatic motoneurons. The distribution of mGluR3 mRNA in particular neurons and glial cells indicates specific roles of mGluR3 in the glutamatergic system of the central nervous system.

Pharmacological characteristics of tachykinin receptors mediating acetylcholine release from neonatal rat spinal cord

The pharmacological profiles of tachykinin receptors mediating the release of acetylcholine were examined in the isolated spinal cord of the neonatal rat. The acetylcholine release evoked by neurokinin A or acetyl-[Arg6,Pro9]substance P-(6-11) was depressed by the tachykinin antagonists, spantide and GR71251 at 10 microM, whereas the release evoked by substance P (0.3 microM) or neurokinin B (0.3 microM) was not affected by these tachykinin antagonists. Polymerase chain reaction amplification of rat spinal cord cDNA and sequence analysis revealed the presence of a substantial amount of fragments having sequences identical to that of the NK1 or NK3 receptor, but only a few having a sequence identical to that of the NK2 receptor. These results suggest that in the neonatal rat spinal cord a novel subtype of tachykinin receptor similar but not identical to the classical NK1 receptor is involved in tachykinin-evoked acetylcholine release.

Long-term prognosis in 990 medically treated Japanese patients with coronary artery disease

We performed a retrospective analysis of the fate of 990 medically treated Japanese patients with coronary artery disease. Patients were enrolled in this study between September 1973 and February 1984. They were confirmed to have significant coronary artery disease by coronary angiography. There were 924 males and 66 females with a mean age of 54.4 years. The mean duration of follow-up was 9.4 years with a range of 6.5 to 17.0 years. The 5-year and 10-year survival rates for the entire population were 92.1% and 84.4%. The 5-year and 10-year survival rates in patients with single- (SVD), double- (DVD), and triple-vessel disease (TVD) and left main trunk (LMT) disease were as follows: 96.0% and 91.9% for SVD, 93.8% and 87.5% for DVD, 83.2% and 68.3% for TVD, and 89.3% and 84.6% for LMT disease. This was the first large follow-up study of coronary artery disease in Japan. Its results suggest that the prognosis of Japanese patients with coronary artery disease is more favorable than that of patients in Western countries. In addition, the findings should provide a control data base for future studies in Japan and the West.