NMDA receptor stimulation and brain-derived neurotrophic factor upregulate homer 1a mRNA via the mitogen-activated protein kinase cascade in cultured cerebellar granule cells

In three alternative splice variants of Homer 1 transcripts, Homer 1a mRNA has been shown to be upregulated selectively and rapidly by neural stimulation and represents a member of the immediate early gene (IEG) family. We investigated the mechanism underlying Homer 1a mRNA induction in cerebellar granule cell culture. All Homer 1 variants were expressed in cultured granule cells as analyzed by RNA blotting and immunochemical characterization. Glutamate stimulation of granule cells selectively upregulated Homer 1a mRNA via NMDA receptor-mediated influx of extracellular calcium. The induction of Homer 1a mRNA was much slower (peaked at 4 hr) and sustained longer than that of the typical IEG c-fos mRNA. Actinomycin D and cycloheximide experiments have revealed that, despite the presence of the mRNA-destabilizing AU-rich motif, transcriptional activation is a main determinant for selective Homer 1a mRNA induction. Inhibitor analysis as well as immunochemical characterization has indicated that the MEK (MAPK/ERK kinase)-ERK (extracellular signal-regulated kinase) cascade plays an indispensable role in glutamate-stimulated induction of Homer 1a mRNA. Consistent with this observation, brain-derived neurotrophic factor, which is known to activate the ERK cascade, similarly upregulated Homer 1a mRNA. These results demonstrate that MAPK (mitogen-activated protein kinase) is a key mediator that links distinct extracellular stimuli to the transcriptional activation of Homer 1a mRNA.

A key role of starburst amacrine cells in originating retinal directional selectivity and optokinetic eye movement

The directional selectivity of retinal ganglion cell responses represents a primitive pattern recognition that operates within a retinal neural circuit. The cellular origin and mechanism of directional selectivity were investigated by selectively eliminating retinal starburst amacrine cells, using immunotoxin-mediated cell targeting techniques. Starburst cell ablation in the adult retina abolished not only directional selectivity of ganglion cell responses but also an optokinetic eye reflex derived by stimulus movement. Starburst cells therefore serve as the key element that discriminates the direction of stimulus movement through integrative synaptic transmission and play a pivotal role in information processing that stabilizes image motion.

RP-1776, a novel cyclic peptide produced by Streptomyces sp., inhibits the binding of PDGF to the extracellular domain of its receptor

RP-1776, a novel cyclic peptide, was isolated from the culture broth of Streptomyces sp. KY11784. RP-1776 selectively inhibited the binding of PDGF BB to the extracellular domain of the PDGF beta-receptor with an IC50 value of 11 +/- 6 microM. Detailed binding experiments suggested that RP-1776 directly interacts with PDGF BB. RP-1776 inhibited the phosphorylation of the PDGF beta-receptor induced by PDGF BB. These results suggested that RP-1776 antagonizes the signaling of PDGF BB probably through the inhibition of PDGF BB binding to the PDGF beta-receptor.

Synthesis, SARs, and pharmacological characterization of 2-amino-3 or 6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid derivatives as potent, selective, and orally active group II metabotropic glutamate receptor agonists

(+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (4, LY354740), a highly selective and orally active group II metabotropic glutamate receptor (mGluR) agonist, has increased interest in the study of group II mGluRs. Our interest focused on a conformationally constrained form of compound 4, because it appeared that the rigid form resulted in not only selectivity for group II mGluR but was orally active. Therefore, we introduced a fluorine atom to compound 4, based on the molecular size (close resemblance to hydrogen atom) and electronegativity (effects on the electron distribution in the molecule) of this atom and carbon-fluorine bond energy. Compound (+)-7 (MGS0008), the best compound among 3-fluoro derivatives 7-10, retained the agonist activity of compound 4 for mGluR2 and mGluR3 ((+)-7: EC(50) = 29.4 +/- 3.3 nM and 45.4 +/- 8.4 nM for mGluR2 and mGluR3, respectively; 4: EC(50) = 18.3 +/- 1.6 nM and 62.8 +/- 12 nM for mGluR2 and mGluR3, respectively) and increased the oral activity of compound 4 ((+)-7: ED(50) = 5.1 mg/kg and 0.26 mg/kg for phencyclidine (PCP)-induced hyperactivity and PCP-induced head-weaving behavior, respectively; 4: ED(50) = >100 mg/kg and 3.0 mg/kg for PCP-induced hyperactivity and PCP-induced head-weaving behavior, respectively). In addition, a compound [(3)H]-(+)-7 binding study using mGluR2 or 3 expressed in CHO cells was successful ((+)-7: K(i) = 47.7 +/- 17 nM and 65.9 +/- 7.1 nM for mGluR2 and mGluR3, respectively; 4: K(i) = 23.4 +/- 7.1 nM and 53.5 +/- 13 nM for mGluR2 and mGluR3, respectively). On the basis of a successful result of compound 7, we focused on the introduction of a fluorine atom on the C6 position of compound 4. (1R,2S,5R, 6R)-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid ((-)-11) exhibited a high degree of agonist activity for group II mGluRs equal to that of compound 4 or 7 ((-)-11: K(i) = 16.6 +/- 5.6 and 80.9 +/- 31 nM for mGluR2 and mGluR3, respectively). Our interest shifted to modification on CH(2) at C4 position of compound 11, since replacement of the CH(2) group with either an oxygen atom or sulfur atom yielded compound 5 or 6, resulting in increased agonist activity. We selected a carbonyl group instead of CH(2) at the C4 position of compound 11. The carbonyl group might slightly change the relative conformation of three functional groups, the amino group and two carboxylic acids, which have important roles in mediating the interaction between group II mGluRs and their ligand, compared with the CH(2) group of 4, oxygen atom of 5, and sulfur atom of 6. (1R,2S,5S,6S)-2-Amino-6-fluoro-4-oxobicyclo[3.1. 0]hexane-2,6-dicarboxylic acid monohydrate ((+)-14, MGS0028) exhibited a remarkably high degree of agonist activity for mGluR2 (K(i) = 0.570 +/- 0.10 nM) and mGluR3 (K(i) = 2.07 +/- 0.40 nM) expressed in CHO cells but not mGluR4, 6, 7, 1a, or 5 expressed in CHO cells (K(i) = >100 000 nM). Furthermore, compound (+)-14 strongly inhibited phencyclidine (PCP)-induced head-weaving behavior (ED(50) = 0.090 microg/kg) and hyperactivity (ED(50) = 0.30 mg/kg) in rats. Thus, (+)-7 and (+)-14 are potent, selective, and orally active group II mGluR agonists and might be useful not only for exploring the functions of mGluRs but in the treatment of schizophrenia.

G protein-coupled receptor kinase-mediated desensitization of metabotropic glutamate receptor 1A protects against cell death

Metabotropic glutamate receptors (mGluRs) constitute a unique subclass of G protein-coupled receptors (GPCRs) that bear little sequence homology to other members of the GPCR superfamily. The mGluR subtypes that are coupled to the hydrolysis of phosphoinositide contribute to both synaptic plasticity and glutamate-mediated excitotoxicity in neurons. In the present study, the expression of mGluR1a in HEK 293 cells led to agonist-independent cell death. Since G protein-coupled receptor kinases (GRKs) desensitize a diverse variety of GPCRs, we explored whether GRKs contributed to the regulation of both constitutive and agonist-stimulated mGluR1a activity and thereby may prevent mGluR1a-mediated excitotoxicity associated with mGluR1a overactivation. We find that the co-expression of mGluR1a with GRK2 and GRK5, but not GRK4 and GRK6, reduced both constitutive and agonist-stimulated mGluR1a activity. Agonist-stimulated mGluR1a phosphorylation was enhanced by the co-expression of GRK2 and was blocked by two different GRK2 dominant-negative mutants. Furthermore, GRK2-dependent mGluR1a desensitization protected against mGluR1a-mediated cell death, at least in part by blocking mGluR1a-stimulated apoptosis. Our data indicate that as with other members of the GPCR superfamily, a member of the structurally distinct mGluR family (mGluR1a) serves as a substrate for GRK-mediated phosphorylation and that GRK-dependent "feedback" modulation of mGluR1a responsiveness protects against pathophysiological mGluR1a signaling.

Age-related reduction of [11C]MDL100,907 binding to central 5-HT(2A) receptors: PET study in the conscious monkey brain

Age-related alterations of serotonin (5-hydroxytryptamine; 5-HT) type 2A receptors (5-HT(2A)) in the living brains of young (6.0+/-1. 3 years old) and aged (19.2+/-3.0 years old) monkeys (Macaca mulatta) were evaluated with [11C]MDL100,907 in the conscious state using high-resolution positron emission tomography (PET). For quantitative analysis of 5-HT(2A) binding in vivo, PET scan of [11C]MDL100,907 was performed with arterial blood sampling in each animal, and the metabolic-corrected arterial input function was used for Logan graphical analysis. Higher cerebral binding of [11C]MDL100, 907 was observed in the hippocampus, cingulate gyrus, frontal, temporal and occipital cortices, regions known to contain high densities of 5-HT(2A), by in vitro assay. Binding was intermediate in the striatum and thalamus, and lower in the pons and cerebellum in both young and aged monkeys. The age-related decrease in [11C]MDL100,907 binding to 5-HT(2A) receptors was prominent in the hippocampus, cingulate gyrus, frontal, temporal and occipital cortices, but not in the striatum, thalamus and pons. These observation demonstrated the usefulness of [11C]MDL100,907 as an labeled compound for assessment of the aging process of the cortical 5-HT(2A) measured by PET.

Roles of GABAergic inhibition and NMDA receptor subunits in the spatio-temporal integration in the cerebellar cortex of mice

The cerebellar cortex consists of relatively small numbers of identified neuronal types, which form simple and well-defined layers. However, a direct high-resolution demonstration of spatio-temporal pattern of information transmission there has been lacking. Using an optical recording technique with a membrane-potential sensitive dye, we studied the spatio-temporal pattern of excitation propagation induced by white matter stimulation in the slice preparations. We focused on physiological roles of inhibitory synapses and N-methyl-D-aspartate (NMDA) receptors. White matter stimulation induced postsynaptic long-lasting depolarization in the granular layer and transient depolarization in the molecular layer, respectively. Inhibitory synapses modestly suppressed the amplitude of slow depolarization in the granular layer, whereas they exerted powerful lateral inhibition in the molecular layer. Using mutant mice deficient in NMDA receptor subunits NR2A and/or NR2C, we also demonstrated that the NR2A and NR2C subunits expressed in granule neurons contribute to the early and late components of slow depolarization respectively, and that both subunits cooperatively support the temporal summation of depolarization. Taking into account the anatomical organization of the cerebellar cortex, these results might suggest that the granular layer is specialized more in the temporal integration of input signals and the molecular layer in the spatial integration.

Structural basis of glutamate recognition by a dimeric metabotropic glutamate receptor

The metabotropic glutamate receptors (mGluRs) are key receptors in the modulation of excitatory synaptic transmission in the central nervous system. Here we have determined three different crystal structures of the extracellular ligand-binding region of mGluR1--in a complex with glutamate and in two unliganded forms. They all showed disulphide-linked homodimers, whose 'active' and 'resting' conformations are modulated through the dimeric interface by a packed alpha-helical structure. The bi-lobed protomer architectures flexibly change their domain arrangements to form an 'open' or 'closed' conformation. The structures imply that glutamate binding stabilizes both the 'active' dimer and the 'closed' protomer in dynamic equilibrium. Movements of the four domains in the dimer are likely to affect the separation of the transmembrane and intracellular regions, and thereby activate the receptor. This scheme in the initial receptor activation could be applied generally to G-protein-coupled neurotransmitter receptors that possess extracellular ligand-binding sites.

Mammalian achaete-scute and atonal homologs regulate neuronal versus glial fate determination in the central nervous system

Whereas vertebrate achaete-scute complex (as-c) and atonal (ato) homologs are required for neurogenesis, their neuronal determination activities in the central nervous system (CNS) are not yet supported by loss-of-function studies, probably because of genetic redundancy. Here, to address this problem, we generated mice double mutant for the as-c homolog Mash1 and the ato homolog Math3. Whereas in Mash1 or Math3 single mutants neurogenesis is only weakly affected, in the double mutants tectal neurons, two longitudinal columns of hindbrain neurons and retinal bipolar cells were missing and, instead, those cells that normally differentiate into neurons adopted the glial fate. These results indicated that Mash1 and Math3 direct neuronal versus glial fate determination in the CNS and raised the possibility that downregulation of these bHLH genes is one of the mechanisms to initiate gliogenesis.

Induction of midbrain dopaminergic neurons from ES cells by stromal cell-derived inducing activity

We have identified a stromal cell-derived inducing activity (SDIA) that promotes neural differentiation of mouse ES cells. SDIA accumulates on the surface of PA6 stromal cells and induces efficient neuronal differentiation of cocultured ES cells in serum-free conditions without use of either retinoic acid or embryoid bodies. BMP4, which acts as an antineuralizing morphogen in Xenopus, suppresses SDIA-induced neuralization and promotes epidermal differentiation. A high proportion of tyrosine hydroxylase-positive neurons producing dopamine are obtained from SDIA-treated ES cells. When transplanted, SDIA-induced dopaminergic neurons integrate into the mouse striatum and remain positive for tyrosine hydroxylase expression. Neural induction by SDIA provides a new powerful tool for both basic neuroscience research and therapeutic applications.

PICK1 interacts with and regulates PKC phosphorylation of mGLUR7

The G-protein-coupled metabotropic glutamate receptor subtype 7a (mGluR7a) is a member of group III metabotropic glutamate receptors that plays an important role as a presynaptic receptor in regulating transmitter release at glutamatergic synapses. Here we report that the protein interacting with C-kinase (PICK1) binds to the C terminus (ct) of mGluR7a. In the yeast two-hybrid system, the extreme ct of mGluR7a was shown to interact with the PSD-95/Discs large/ZO-1 (PDZ) domain of PICK1. Pull-down assays indicated that PICK1 was retained by a glutathione S-transferase fusion of ct-mGluR7a. Furthermore, recombinant and native PICK1/mGluR7a complexes were coimmunoprecipitated from COS-7 cells and rat brain tissue, respectively. Confocal microscopy showed that both PICK1 and mGluR7a displayed synaptic colocalization in cultured hippocampal neurons. PICK1 has previously been shown to bind protein kinase C alpha-subunit (PKCalpha), and mGluR7a is known to be phosphorylated by PKC. We show a relationship between these three proteins using recombinant PICK1, mGluR7, and PKCalpha, where they were co-immunoprecipitated as a complex from COS-7 cells. In addition, PICK1 caused a reduction in PKCalpha-evoked phosphorylation of mGluR7a in in vitro phosphorylation assays. These results suggest a role for PICK1 in modulating PKCalpha-evoked phosphorylation of mGluR7a.

Cryptic dimer interface and domain organization of the extracellular region of metabotropic glutamate receptor subtype 1

Previously, we produced the whole extracellular region of metabotropic glutamate receptor subtype 1 (mGluR1) in a soluble form. The soluble receptor retained a ligand affinity comparable with that of the full-length membrane-bound receptor and formed a disulfide-linked dimer. Here, we have identified a cysteine residue responsible for the intermolecular disulfide bond and determined domain organization of the extracellular region of mGluR1. A mutant, C140A, was a monomer under nonreduced conditions by SDS-polyacrylamide gel electrophoresis; however, C140A was eluted at the position similar to that of mGluR113, the wild type soluble receptor, by size exclusion column chromatography. Furthermore, C140A bound a ligand, [(3)H]quisqualate, with an affinity similar to that obtained by mGluR113. Oocytes injected with RNA for full-length mGluR1 containing C140A mutation showed responses to ligands at magnitudes similar to those with wild type full-length RNA. Thus, elimination of the disulfide linkage did not perturb the dimer formation and ligand signaling, suggesting that cryptic dimer interface(s) possibly exist in mGluR1. Limited proteolysis of the whole extracellular fragment (residue 33-592) revealed two trypsin-sensitive sites, after the residues Arg(139) and Arg(521). A 15-kDa NH(2)-terminal proteolytic fragment (residue 33-139) was associated with the downstream part after the digestion. Arg(521) was located before a cysteine-rich stretch preceding the transmembrane region. A new shorter soluble receptor (residue 33-522) lacking the cysteine-rich region was designed based on the protease-sensitive boundary. The purified receptor protein gave a K(d) value of 58.1 +/- 0.84 nm, which is compatible to a reported value of the full-length receptor. The B(max) value was 7.06 +/- 0. 82 nmol/mg of protein. These results indicated that the ligand-binding specificity of mGluR1 is confined to the NH(2)-terminal 490-amino acid region of the mature protein.

Impaired behavioral suppression by light in metabotropic glutamate receptor subtype 6-deficient mice

The metabotropic glutamate receptor subtype 6 is localized on the dendrites of ON bipolar cells in mammalian retina, and is responsible for synaptic transmission from photoreceptors to ON bipolar cells. We have previously provided electrophysiological evidence that metabotropic glutmate receptor subtype 6-deficient mice have an impairment in the ON visual pathway. In this study, we compared, between metabotropic glutamate receptor subtype 6-deficient (n=9) and wild-type mice (n=7), their daily wheel-running activity in constant dark and light-dark cycle environments. There was no difference in their free-running rhythmicity in a constant dark environment nor in their ability to entrain their active/rest phase to the phase-shifted light-dark cycle environment, indicating that the circadian system in mutant mice was functioning normally. However, the wheel-running activity was suppressed immediately after light onset of the light-dark cycle in wild-type mice (suppressive effect), whereas that of mutant mice was prolonged for several hours in spite of light onset (very weak suppressive effect). The suppression of activity in wild-type mice is a "masking effect" of the endogenous circadian rhythm in response to light stimuli. The results indicate that the failure of mutant mice to suppress their activity upon light onset is not due to abnormality in their circadian system, but to their lack of response to light stimuli. This study clearly demonstrates that the dysfunction of the ON visual pathway in metabotropic glutamate receptor subtype 6-deficient mice impairs their behavioral responsiveness to light and yet preserves their circadian system.

[Cost analysis on stomach cancer treatment in Japanese hospitals]

BACKGROUND

In an effort to further the discussion of DRG/PPS, we performed a coat analysis on stomach cancer cases in Japanese hospitals. We analyzed individual in-patient data (both clinical and financial) to research the amount of variation in treatment and costs.

METHODS

The data was taken from two hospitals. In order to compare the daily cost/revenue of each episode of operation/hospitalization, we analyzed the data that was stored for reimbursement purposes by using patient ID numbers. We also simulated the cost/revenue in cases where the length of stay could be shortened with clinical pathways created by Japanese hospitals.

RESULTS

(1) There is a common pattern for the operation/hospitalization of stomach cancer cases if the patient's condition, like severity, is well controlled. However, there is still a noticeable difference in the length of stay for patients both before and after the operation. (2) Hospitals are currently losing money by having extended patients' lengths of stay. Simulation results indicate that hospitals can reduce losses, even become profitable, by shortening the patient's length of stay.

CONCLUSIONS

The potentiality of implementing a standard treatment process and/or a fixed payment system, like DRG/PPS, is high, because there is a common a pattern among the treatment process. More research must be completed in this area, specifically on the significant variations in lengths of stay and the methodology for standardization of treatment. Furthermore, clinical outcomes research must also be done.

Synaptic integration mediated by striatal cholinergic interneurons in basal ganglia function

The physiological role of striatal cholinergic interneurons was investigated with immunotoxin-mediated cell targeting (IMCT). Unilateral cholinergic cell ablation caused an acute abnormal turning behavior. These mice showed gradual recovery but displayed abnormal turning by both excess stimulation and inhibition of dopamine actions. In the acute phase, basal ganglia function was shifted to a hyperactive state by stimulation and suppression of striatonigral and striatopallidal neurons, respectively. D1 and D2 dopamine receptors were then down-regulated, relieving dopamine-predominant synaptic perturbation but leaving a defect in controlling dopamine responses. The acetylcholine-dopamine interaction is concertedly and adaptively regulated for basal ganglia synaptic integration.

Lack of effect of LY314582 (a group 2 metabotropic glutamate receptor agonist) on phencyclidine-induced locomotor activity in metabotropic glutamate receptor 2 knockout mice

In metabotropic glutamate receptor 2 (mGlu(2)) knockout mice, the group 2 metabotropic glutamate receptor agonist LY314582 (20 mg/kg, i.p.), a racemate of LY354740, inhibits neither spontaneous nor phencyclidine (PCP)-induced (2.5 mg/kg, s.c.) locomotor activity. Since LY314582 attenuated spontaneous and PCP-induced locomotor activity in wild-type control mice, these data indicate that the effects of LY314582 are mediated via the mGlu(2) receptor and not via the mGlu(3) receptor.

Xenopus kielin: A dorsalizing factor containing multiple chordin-type repeats secreted from the embryonic midline

The midline tissues are important inductive centers of early vertebrate embryos. By signal peptide selection screening, we isolated a secreted factor, Kielin, which contains multiple cys-rich repeats similar to those in chordin (Chd). Expression of Kielin starts at midgastrula stages in the notochord and is detected in the floor plate of neurula embryos. Kielin is induced in mesoderm and in ectoderm by nodal-related genes. Chd is sufficient to activate Kielin expression in mesoderm whereas Shh or HNF-3beta in addition to Chd is required for induction in ectoderm. Kielin has a distinct biological activity from that of Chd. Injection of Kielin mRNA causes dorsalization of ventral marginal zone explants and expansion of MyoD expression in neurula embryos. Unlike Chd, Kielin does not efficiently induce neural differentiation of animal cap ectoderm, suggesting that the activity of Kielin is not simply caused by BMP4 blockade. Kielin is a signaling molecule that mediates inductive activities of the embryonic midline.

Xenopus Xenf: an early endodermal nuclear factor that is regulated in a pathway distinct from Sox17 and Mix-related gene pathways

We report a novel zygotic gene encoding a Xenopus endodermal nuclear factor, Xenf. Expression of Xenf starts at the late blastula stages and is decreased after gastrulation. Xenf shows no structural homology to any known proteins. When GFP-tagged Xenf is overexpressed in Xenopus cells, Xenf protein is localized to the nucleus, associating closely with the chromosomes. In animal cap assays, Xenf expression is strongly activated by mRNA injection of Vg1 and VegT, maternal vegetal genes that can induce endodermal differentiation. In contrast, Xenf is not induced by endoderm-inducing zygotic transcription factors such as Sox17 and Mix-related genes. In turn, Xenf does not activate expression of Sox17, Mixer or Milk. Thus, Xenf is regulated by maternal vegetal positional information in a parallel manner to Sox17 and Mix-related gene pathways.

Requirement of Sox2-mediated signaling for differentiation of early Xenopus neuroectoderm

From early stages of development, Sox2-class transcription factors (Sox1, Sox2 and Sox3) are expressed in neural tissues and sensory epithelia. In this report, we show that Sox2 function is required for neural differentiation of early Xenopus ectoderm. Microinjection of dominant-negative forms of Sox2 (dnSox2) mRNA inhibits neural differentiation of animal caps caused by attenuation of BMP signals. Expression of dnSox2 in developing embryos suppresses expression of N-CAM and regional neural markers. We have analyzed temporal requirement of Sox2-mediated signaling by using an inducible dnSox2 construct fused to the ligand-binding domain of the glucocorticoid receptor. Attenuation of Sox2 function both from the late blastula stage and from the late gastrula stage onwards causes an inhibition of neural differentiation in animal caps and in whole embryos. Additionally, dnSox2-injected cells that fail to differentiate into neural tissues are not able to adopt epidermal cell fate. These data suggest that Sox2-class genes are essential for early neuroectoderm cells to consolidate their neural identity during secondary steps of neural differentiation.

Reduced early diastolic inflow velocities in the antero-posterior transverse direction in the left ventricle of patients with dilated cardiomyopathy

In patients with dilated cardiomyopathy (DCM), the left ventricular (LV) inflow jet is narrow and has a high pressure gradient. A pulsed Doppler restrictive transmitral flow pattern is a characteristic feature of severe left ventricular disease. However, Doppler flow analysis is limited by the angle between the blood flow jet and the ultrasonic beam. In this study we used gated magnetic resonance imaging (MRI) to investigate the inflow velocity in the LV transverse directions during early diastole in patients with DCM.

METHODS

We studied 10 patients with DCM (mean age: 47 y). Ten age-matched healthy volunteers were also examined. Gradient echo images of the LV were obtained. Left ventricular short axis phase contrast images were obtained at the level of the mitral valve tip and 1 cm inside the LV. Long axis images were also obtained. Through-plane peak velocities at peak early diastolic filling were measured along the LV long axis, antero-posterior short axis, and right-left short axis. Blood velocity was measured in 50 ms blocks.

RESULTS

Early diastolic inflow velocity along the long axis, especially at the center of the LV, was well preserved in DCM. However, the inflow velocity in the antero-posterior transverse direction of the LV (i.e., in the direction of mitral valve excursion) was significantly reduced in DCM.

CONCLUSIONS

Early diastolic inflow velocity in the antero-posterior transverse direction of the LV is reduced in patients with DCM indicating that the vector component of the forces acting in the antero-posterior transverse direction of the LV may be decreased in patients with DCM during early diastolic filling.

Isoflurane anesthesia enhances the inhibitory effects of cocaine and GBR12909 on dopamine transporter: PET studies in combination with microdialysis in the monkey brain

The effects of the dopamine transporter (DAT) inhibitors cocaine and GBR12909 on DAT and dopamine D(2) receptors were evaluated in the brains under awake and isoflurane-anesthetized monkeys using high-resolution positron emission tomography (PET) in combination with microdialysis. The striatal DAT availability and dopamine D(2) receptor binding were assayed with [11C]beta-CFT (WIN35,428) and [11C]raclopride, respectively. Cocaine or GBR12909 at a dose of 2 mg/kg was administered intravenously 30 min prior to the injection of labeled compounds. In the awake state, the in vivo binding of [11C]beta-CFT to DAT was significantly decreased by administration of cocaine or GBR12909 at a dose of 2 mg/kg. In contrast, [11C]raclopride binding to dopamine D(2) receptors was decreased only by GBR12909. Under isoflurane anesthesia, dopamine concentration in the striatal extracellular fluid (ECF), as measured by microdialysis, was markedly increased by cocaine or GBR12909 compared to the awake state. Isoflurane anesthesia more markedly enhanced the binding of [11C]beta-CFT in the saline-injected animals, and the degrees of reduction by cocaine and GBR12909 were more marked than those observed in the awake state. Under isoflurane anesthesia, the binding of [11C]raclopride was reduced not only by GBR12909 but also by cocaine which did not affect the binding in the awake state. Taken together, these observations indicated that isoflurane anesthesia enhanced not only the direct inhibitory effects of cocaine and GBR12909 on DAT, but also their indirect effects on dopamine D(2) receptors.

Involvement of protein tyrosine phosphatases in activation of the trimeric G protein Gq/11

A variety of receptors coupled to the heterotrimeric guanine nucleotide-binding protein Gq/11 stimulate intracellular Ca2+ release through inositol (1,4,5)-trisphosphate (IP3) formation. We previously reported that tyrosine phosphorylation of the alpha subunit of the Gq/11 protein by protein tyrosine kinases (PTKs) regulates the activation of Gq/11 protein. Here we show that protein tyrosine phosphatases (PTPs) are also essential for Gq/11 protein activation. We find that Gq/11 protein-coupled receptor-mediated formation of IP3 is blocked by PTP inhibitors as well as PTK inhibitors. These inhibitors act prior to Gq/11 protein activation. Tyrosine phosphorylation of the alpha subunit of Gq/11 appears to inhibit its interaction with receptors. Thus, PTP is required for controlling the level of tyrosine phosphorylation of the alpha subunit of Gq/11 to promote its interaction with receptors. Therefore, we conclude that PTKs and PTPs co-operate to proceed activation cycle of the Gq/11 protein through tyrosine phosphorylation and de-phosphorylation of the alpha subunit of Gq/11.

Structural organization of the mouse metabotropic glutamate receptor subtype 3 gene and its regulation by growth factors in cultured cortical astrocytes

Metabotropic glutamate receptors (mGluRs) belong to the class of G protein-coupled receptors and consist of eight different subtypes. We have characterized the structural organization of the mouse mGluR3 gene by genomic cloning in combination with rapid amplification of 5'- and 3'-cDNA ends and examined regulatory expression of mGluR3 mRNA in cultured cortical astrocytes. The mGluR3 gene consists of six exons and spans over 95 kb. Exon 1 and its preceding putative promoter are located distantly from the following protein-coding region. In the mGluR family, mGluR3 and mGluR5 are both expressed in neuronal and glial cells and are upregulated during the early postnatal period. They are, however, coupled to two distinct signaling cascades and have been shown to exert opposite influences on some functions of cultured astrocytes. In cultured astrocytes, mGluR3 and mGluR5 mRNA levels were significantly increased by exposure to epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), or transforming growth factor-alpha; and EGF was more efficacious than bFGF in producing this increase. Hence, mGluR3 and mGluR5 mRNAs are concertedly upregulated in cultured astrocytes by specific growth factors. This finding suggests that the two mGluR subtypes may play an important role in maintaining the proper balance of astrocyte functions via two distinct signal transduction mechanisms.

Production of functional human alpha 1-antitrypsin by plant cell culture

Recombinant human alpha 1-antitrypsin (rAAT) was expressed and secreted from transgenic rice cell suspension cultures in its biologically active form. This was accomplished by transforming rice callus tissues with an expression vector, p3D-AAT, containing the cDNA for mature human AAT protein. Regulated expression and secretion of rAAT from this vector was achieved using the promoter, signal peptide, and terminator from a rice alpha-amylase gene Amy3D. The Amy3D gene of rice is tightly controlled by simple sugars such as sucrose. It was possible, therefore, to induce the expression of the rAAT by removing sucrose from the cultured media or by allowing the rice suspension cells to deplete sucrose catabolically. Although transgenic rice cell produced a heterogeneous population of the rAAT molecules, they had the same N-terminal amino acids as those found in serum-derived (native) AAT from humans. This result indicates that the rice signal peptidase recognizes and cleaves the novel sequence between the Amy3D signal peptide and the first amino acid of the mature human AAT. The highest molecular weight band seen on Western blots (AAT top band) was found to have the correct C-terminal amino acid sequence and normal elastase binding activity. Staining with biotin-concanavalin A and avidin horseradish peroxidase confirmed the glycosylation of the rAAT, albeit to a lesser extent than that observed with native AAT. The rAAT, purified by immunoaffinity chromatography, had the same association rate constant for porcine pancreatic elastase as the native AAT. Thermostability studies revealed that the rAAT and native AAT decayed at the same rate, suggesting that the rAAT is correctly folded. The productivity of rice suspension cells expressing rAAT was 4.6-5.7 mg/g dry cell. Taken together, these results support the use of rice cell culture as a promising new expression system for production of biologically active recombinant proteins.