Biomedical subjects

K Hashimoto

Publications and source records attributed to K Hashimoto.

At least 163 records · Page 9Linked to original sources

PubMed2000

mGluR1 in cerebellar Purkinje cells essential for long-term depression, synapse elimination, and motor coordination.

Targeted deletion of metabotropic glutamate receptor-subtype 1 (mGluR1) gene can cause defects in development and function in the cerebellum. We introduced the mGluR1alpha transgene into mGluR1-null mutant [mGluR1 (-/-)] mice with a Purkinje cell (PC)-specific promoter. mGluR1-rescue mice showed normal cerebellar long-term depression and regression of multiple climbing fiber innervation, events significantly impaired in mGluR1 (-/-) mice. The impaired motor coordination was rescued by this transgene, in a dose-dependent manner. We propose that mGluR1 in PCs is a key molecule for normal synapse formation, synaptic plasticity, and motor control in the cerebellum.

Animals↗

PubMed2000

Isolation and characterization of a novel zinc finger gene, ZNF219, and mapping to the human chromosome 14q11 region.

We have isolated and characterized a novel zinc finger gene by screening a human testis cDNA library. The isolated cDNA, termed ZNF219, contains an open reading frame of 2169 nucleotides encoding 723 amino acids. Sequence analysis revealed 9 sets of Kruppel-related zinc finger structures and proline-rich regions in several parts. ZNF219 exhibited ubiquitous expression in all fetal and adult tissues examined. The transcript size was 5.5 kb in adult tissues, while the main transcript size in the embryo stage was 3.5 kb. The transcript size is developmentally regulated. When the plasmid cloned with green fluorescent protein (GFP)-tagged ZNF219 was expressed in HeLa and COS7 cells, strong fluorescence intensities were observed only in the nucleus of both cells by fluorescence confocal microscopy. These data suggest that ZNF219 may be related to the regulation of transcription and developmental regulation. Genomic structure analysis mapped ZNF219 to chromosome 14q11 between markers D14S72 and D14S990, because a sequence tagged site mapped to the locus was found in the intron region of the ZNF219 gene.

Adult↗

PubMed2000

Primitive synteny of vertebrate major histocompatibility complex class I and class II genes.

Major histocompatibility complex (MHC) class I and class II molecules bind to and display peptidic antigens acquired from pathogens that are recognized by lymphocytes coordinating and executing adaptive immune responses. The two classes of MHC proteins have nearly identical tertiary structures and were derived from a common ancestor that probably existed not long before the emergence of the cartilaginous fish. Class I and class II genes are genetically linked in tetrapods but are not syntenic in teleost fish, a phylogenetic taxon derived from the oldest vertebrate ancestor examined to date. Cartilaginous fish (sharks, skates, and rays) are in the oldest taxon of extant jawed vertebrates; we have carried out segregation analyses in two families of nurse sharks and one family of the banded houndshark that revealed a close linkage of class IIalpha and beta genes both with each other and with the classical class I (class Ia) gene. These results strongly suggest that the primordial duplication giving rise to classical class I and class II occurred in cis, and the close linkage between these two classes of genes has been maintained for at least 460 million years in representatives of most vertebrate taxa.

Amino Acid Sequence↗

PubMed2000

Asymmetric synthesis of axially chiral biaryls via desymmetrization of 2,2',6,6'-tetrahydroxybiphenyl using 1,4-Di-O-benzyl-L-threitol as a chiral template

Sequential etherification of 2,2',6,6'-tetrahydroxybiphenyl (1) with 1,4-di-O-benzyl-L-threitol under Mitsunobu conditions gives desymmetrized biphenyldiol 9 of S-axial chirality exclusively. Cyclization of 9 with 1,omega-dibromoalkanes followed by removal of the chiral auxiliary yields (S)-2,2'-biphenyldiols 14 with alkylenedioxy bridges at the 6 and 6' positions. (S)-6,6'-Dialkyl- and -diphenyldiols 20 are obtained in an efficient manner via Pd(0)-catalyzed cross-coupling of bis(triflate) derivative 17 with organozinc reagents. Bis(triflate) 17 also serves as an intermediate for asymmetric synthesis of axially chiral biphenyldicarboxylic acid 23, terphenylcarboxylic acid 28, lactone 26, and lactam 30.

Journal Article↗

PubMed2000

An IP3-assisted form of Ca2+-induced Ca2+ release in neocortical neurons.

Calcium increases induced by single action potentials in rat visual cortex layer II/III pyramidal neurons were shown to be augmented by muscarinic acetylcholine receptor (mAchR) stimulation. This augmentation was drastically reduced by intracellular injection of heparin but not ruthenium red, therefore involving inositol-1,4,5-trisphosphate (IP3)-sensitive rather than ryanodine-sensitive calcium stores. Only the calcium increase induced by the second or later spike of a spike train, but not that induced by the first spike, was augmented, indicating the requirement of both spike-induced calcium increase and mAchR activation. The calcium store depletor thapsigargin abolished this augmentation use-dependently. These findings suggest a neocortical occurrence of calcium-induced calcium release from IP3-sensitive calcium stores that have been sensitized beforehand by IP3 through mAchR-mediated mechanisms.

Action Potentials↗

PubMed2000

Effect of atypical antipsychotics on phencyclidine-induced expression of arc in rat brain.

The effect of atypical antipsychotics on the immediate-early gene, arc (activity-regulated cytoskeleton-associated gene), expression was investigated in phencyclidine (PCP)-treated rats using RT-PCR. Administration of PCP (10 mg/kg) increased arc mRNA levels in the prefrontal cortex, nucleus accumbens and posterior cingulate cortex. Pretreatment with clozapine (20 mg/kg), olanzapine (10 mg/kg) and risperidone (2 mg/kg), but not haloperidol (2 mg/kg), prevented PCP-induced arc expression in the prefrontal cortex and nucleus accumbens. Pretreatment of haloperidol increased the striatal arc mRNA levels. Clozapine, olanzapine and haloperidol inhibited the PCP-induced arc expression in the posterior cingulate cortex. These results suggest that the effects of antipsychotic drugs on PCP-induced arc expression in the prefrontal cortex and nucleus accumbens are useful for distinguishing atypical antipsychotic properties of the drugs.

Animals↗

PubMed2000

Increased D-type cyclin expression together with decreased cdc2 activity confers megakaryocytic differentiation of a human thrombopoietin-dependent hematopoietic cell line.

At the late phase of megakaryocytopoiesis, megakaryocytes undergo endomitosis, which is characterized by DNA replication without cell division. Although a number of cell cycle regulatory molecules have been identified, the precise roles of these molecules in megakaryocytic endomitosis are largely unknown. In a human interleukin-3-dependent cell line transfected with the thrombopoietin (TPO) receptor c-mpl (F-36P-mpl), either treatment with TPO or the overexpression of activated ras (Ha-Ras(G12V)) induced megakaryocytic maturation with polyploid formation. We found that TPO stimulation or Ha-Ras(G12V) expression led to up-regulation of cyclin D1, cyclin D2, and cyclin D3 expression. In addition, expression levels of cyclin A and cyclin B were reduced during the total course of both TPO- and Ha-Ras(G12V)-induced megakaryocytic differentiation, thereby leading to decreased cdc2 kinase activity. Neither the induced expression of cyclin D1, cyclin D2, or cyclin D3 nor the expression of a dominant negative form of cdc2 alone could induce megakaryocytic differentiation of F-36P-mpl cells. In contrast, overexpression of dominant negative cdc2 together with cyclin D1, cyclin D2, or cyclin D3 facilitated megakaryocytic differentiation in the absence of TPO. These results suggest that both D-type cyclin expression and decreased cdc2 kinase activity may participate in megakaryocytic differentiation.

CDC2 Protein Kinase↗

PubMed2000

Epiregulin, a novel member of the epidermal growth factor family, is an autocrine growth factor in normal human keratinocytes.

Epiregulin is a new member of the epidermal growth factor (EGF) family purified from conditioned medium of NIH-3T3 clone T7. Some EGF family growth factors play essential roles in human keratinocytes in an autocrine manner. We show here that epiregulin is another autocrine growth factor for human keratinocytes. Epiregulin stimulated human keratinocyte proliferation under both subconfluent and confluent culture conditions in the absence of exogenous EGF family growth factors. Immunoprecipitation of [(35)S]methionine-labeled conditioned medium revealed a 5-kDa band corresponding to epiregulin. Northern blot analysis detected a 4. 8-kilobase transcript of epiregulin, and the addition of epiregulin up-regulated epiregulin mRNA synthesis. Furthermore, an anti-epiregulin blocking antibody reduced DNA synthesis by 25%. Epiregulin up-regulated the mRNA levels of heparin-binding EGF-like growth factor (HB-EGF), amphiregulin, and TGF-alpha. In turn, the addition of EGF, HB-EGF, amphiregulin, and TGF-alpha increased epiregulin mRNA levels. These results demonstrate that epiregulin acts as an autocrine growth factor in human epidermal keratinocytes and is part of auto- and cross-induction mechanisms involving HB-EGF, amphiregulin, and TGF-alpha. The mRNA expression profile resulting from induction of differentiation with high calcium and fetal calf serum revealed the differential expression of epiregulin, HB-EGF, amphiregulin, and TGF-alpha in keratinocytes. This indicates that these four growth factors have distinct, non-redundant biological functions.

Amphiregulin↗

PubMed2000

Dizocilpine-induced neuropathological changes in rat retrosplenial cortex are reversed by subsequent clozapine treatment.

In this study, we examined the effect of post-treatment with clozapine on the neuropathological changes in the rat retrosplenial cortex induced by the administration of non-competitive NMDA receptor antagonist dizocilpine ((+)-MK-801). The maximal increase in vacuolized neurons, which are representative of neuropathology, was observed 4 hours after a single injection of dizocilpine (0.5 mg/kg s.c.), with a complete reversal of the neuropathology after 16-24 hours. The administration of clozapine (10 mg/kg, i.p.,) 4 hours after the administration of dizocilpine significantly decreased the number of vacuolized neurons in the retrosplenial cortex 6, 8 or 10 hours after administration of dizocilpine, compared to vehicle-treated animals. Furthermore, the administration of clozapine (5, 10 or 20 mg/kg i.p.) 4 hours after the administration of dizocilpine produced a significant decrease in the number of vacuolized neurons in the retrosplenial cortex in a dose-dependent manner when measure 6 hours post-dizocilpine. These results show that neuropathological changes in the rat retrosplenial cortex produced by dizocilpine can be attenuated by post-treatment with clozapine.

Animals↗

PubMed2000

Effects of zatebradine and propranolol on canine ischemia and reperfusion-induced arrhythmias.

1,3,4,5-Tetrahydro-7,8-dimethoxy-3[3-[[2-(3, 4-dimethoxyphenyl)-ethyl]methylamino]propyl]-2H-3-benzazepin-2-one -hy drochloride (Zatebradine) is a specific bradycardiac agent, blocking the hyperpolarization-activated pacemaker current (I(f)), and thus has no negative inotropic effect. The purpose of this study was to examine whether zatebradine is effective against ischemia and reperfusion-induced arrhythmias in dogs compared to propranolol. Arrhythmia was induced by ligation of the left anterior descending coronary artery followed by reperfusion. Ischemia-induced biphasic arrhythmias were suppressed in both zatebradine and propranolol groups. During ischemia, fatal ventricular fibrillation occurred in four dogs in the control group, 0 in the zatebradine group, and two dogs in the propranolol group. Of the 31 dogs subjected to reperfusion, mortality rates in the zatebradine, propranolol, and control groups were 56%, 75%, and 86%, respectively, and there were no significant differences. In the heart beating 10 beats/min faster than the predrug heart rate by atrial pacing, both zatebradine and propranolol attenuated ischemia-induced arrhythmias but did not affect reperfusion arrhythmias. Our results suggest that I(f) and/or beta-adrenoceptors rather than the bradycardiac action might be related to the antiarrhythmic effects during ischemia, but that they do not play a role in the generation of the reperfusion-induced ventricular arrhythmias.

Adrenergic beta-Antagonists↗

PubMed2000

Key amino acids of vasopressin V1a receptor responsible for the species difference in the affinity of OPC-21268.

A non-peptide, vasopressin V1a receptor-selective antagonist, OPC-21268, exhibited a markedly higher affinity for the rat V1a receptor (Ki = 380 nM) than for the human V1a receptor (Ki = 140 microM). To delineate the region responsible for the high affinity binding of OPC-21268 for the rat V1a receptor, we have constructed a series of chimeric human and rat V1a receptors, and examined the chimeric and point-mutated receptors by competitive radioligand binding analysis. The results showed that the transmembrane domain (TMD) VI-VII of the vasopressin V1a receptor, in particular the amino acid residue Ala-342 in TMD VII, is the major component conferring the rat-selective binding of OPC-21268 to the V1a receptor.

Amino Acid Sequence↗

PubMed2000

Thyroid hormone-independent interaction between the thyroid hormone receptor beta2 amino terminus and coactivators.

Thyroid hormone receptors (TRs) mediate hormone action by binding to DNA response elements (TREs) and either activating or repressing gene expression in the presence of ligand, T(3). Coactivator recruitment to the AF-2 region of TR in the presence of T(3) is central to this process. The different TR isoforms, TR-beta1, TR-beta2, and TR-alpha1, share strong homology in their DNA- and ligand-binding domains but differ in their amino-terminal domains. Because TR-beta2 exhibits greater T(3)-independent activation on TREs than other TR isoforms, we wanted to determine whether coactivators bound to TR-beta2 in the absence of ligand. Our results show that TR-beta2, unlike TR-beta1 or TR-alpha1, is able to bind certain coactivators (CBP, SRC-1, and pCIP) in the absence of T(3) through a domain which maps to the amino-terminal half of its A/B domain. This interaction is specific for certain coactivators, as TR-beta2 does not interact with other co-factors (p120 or the CBP-associated factor (pCAF)) in the absence of T(3). The minimal TR-beta2 domain for coactivator binding is aa 21-50, although aa 1-50 are required for the full functional response. Thus, isoform-specific regulation by TRs may involve T(3)-independent coactivator recruitment to the transcription complex via the AF-1 domain.

Binding Sites↗

PubMed2000

Increased adrenocorticotropin responses to acute stress in Otsuka Long-Evans Tokushima Fatty (type 2 diabetic) rats.

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a new diabetic strain of rats whose disease closely resembles human type 2 diabetes. We measured plasma adrenocorticotropic hormone (ACTH) and corticostrone levels, and iodine-125-labeled ovine corticotropin-releasing factor ([125I]oCRF) binding in the anterior pituitary after ether-laparotomy stress in OLETF rats to examine the alteration of the hypothalamic-pituitary-adrenal (HPA) axis. In addition, we examined ACTH secretion following CRF administration in vivo and in vitro to characterize the mechanisms regulating the HPA axis in OLETF rats. Body weight, plasma glucose and insulin levels in OLETF rats were significantly higher than that in Long-Evans Tokushima Otsuka (LETO) rats. Basal plasma ACTH levels tended to be higher in OLETF rats than in LETO but it did not reach statistical significance. Ether-laparotomy stress dramatically increased plasma ACTH levels at 2 h after the stress both in either OLETF and LETO rats; the peak plasma ACTH level in OLETF rats following the stress was significantly greater than in LETO rats. Plasma ACTH levels following CRF (2 microg/kg, i.v.) in OLETF and LETO rats showed statistically significant increases at 10 and 30 min after CRF administration compared to ACTH levels at 0 min, however, the peak plasma ACTH level in OLETF rats at 10 min after CRF administration was significantly greater than in LETO rats. In contrast to ACTH levels, no significant differences in corticosterone levels between OLETF and LETO were observed at any of the time points. CRF (10 ng/ml) significantly increased ACTH secretion in pituitary cultures from OLETF compared to LETO rats. These data reveal a complex regulation of the endocrine system in this diabetic condition and suggest that HPA axis may be more stimulated during acute stress in diabetes mellitus than in unaffected subjects.

Acute Disease↗

PubMed2000

Hypoxia response element of the human vascular endothelial growth factor gene mediates transcriptional regulation by nitric oxide: control of hypoxia-inducible factor-1 activity by nitric oxide.

Nitric oxide (NO) regulates production of vascular endothelial growth factor (VEGF) by normal and transformed cells. We demonstrate that NO donors may up-regulate the activity of the human VEGF promoter in normoxic human glioblastoma and hepatoma cells independent of a cyclic guanosine monophosphate-mediated pathway. Deletion and mutation analysis of the VEGF promoter indicates that the NO-responsive cis-elements are the hypoxia-inducible factor-1 (HIF-1) binding site and an adjacent ancillary sequence that is located immediately downstream within the hypoxia-response element (HRE). This work demonstrates that the HRE of this promoter is the primary target of NO. In addition, VEGF gene regulation by NO, as well as by hypoxia, is potentiated by the AP-1 element of the gene. Our study also reveals that NO and hypoxia induce an increase in HIF-1 binding activity and HIF-1alpha protein levels, both in the nucleus and the whole cell. These results suggest that there are common features of the NO and hypoxic pathways of VEGF induction, while in part, NO mediates gene transcription by a mechanism distinct from hypoxia. This is demonstrated by a difference in sensitivity to guanylate cyclase inhibitors and a different pattern of HIF-1 binding. These results show that there is a primary role for NO in the control of VEGF synthesis and in cell adaptations to hypoxia. (Blood. 2000;95:189-197)

Base Sequence↗

PubMed2000

Measurement of adenylate cyclase activity in the right ventricular endomyocardial biopsy samples from patients with chronic congestive heart failure.

A highly sensitive fluorometric assay technique was adopted in order to examine the adenylate cyclase activity in the minute right ventricular endomyocardial biopsy samples from patients with chronic congestive heart failure (n = 10). Norepinephrine (10(-4) M) and adenosine (10(-3) M) were incubated for 30 min with 10 microl of membrane preparation (1-2 mg protein/mg) to analyze the extent of the receptor-coupled adenylate cyclase activity. Forskolin (10(-4) M) stimulation was used to estimate the maximum adenylate cyclase activity (pmol/mg protein/min, mean +/- SE). The new microanalytical cyclic AMP assay involves four steps: enzymatic destruction of noncyclic adenine nucleotides and phosphorylated metabolites, conversion of cyclic AMP to ATP, amplification of ATP by enzymatic cycling, and fluorometric measurement of NADPH, which is generated in proportion to initial cyclic AMP levels. Basal and forskolin-stimulated maximum adenylate cyclase activities were 75 +/- 8 and 123 +/- 15, respectively. Norepinephrine increased the adenylate cyclase activity to 107 +/- 14, while adenosine tended to decrease it to 65 +/- 7. In addition, elimination of adenosine by adenosine deaminase (10 U/ml) slightly increased the adenylate cyclase activity to 82 +/- 9. These results indicate that the adenylate cyclase activity can be measured in minute endomyocardial biopsy samples. Use of this new approach shows promise of becoming a new and potentially important way to predict the efficacy of pharmacological treatment.

Adenosine↗

PubMed2000

Characteristics of myocardial 18F-fluorodeoxyglucose positron emission computed tomography in dilated cardiomyopathy and ischemic cardiomyopathy.

Myocardial 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has been used to assess myocardial ischemia and viability, but few studies have conducted on FDG-PET for dilated cardiomyopathy (DCM). We investigated myocardial FDG uptake in patients with DCM in comparison with ischemic cardiomyopathy (ICM). Twenty-four patients with heart failure were included in this study. Fourteen of them were diagnosed as DCM and the other 10 were ICM. All of them underwent myocardial FDG-PET at fasting and after glucose loading the same day. FDG uptake was quantified by the ratio of the counts at the heart to those at the liver (H/L ratio). Left ventricular (LV) function was measured by echocardiography. We classified FDG distribution patterns in the myocardium in the fasting state into 3 types (faint uptake, regional uptake and diffuse uptake). In DCM patients, 5 had faint uptake, 7 had regional uptake, and the other 2 had diffuse uptake. On the other hand, all ICM patient had regional uptake (p < 0.05). In DCM, there were no significant relationships between the patterns and LV functions. On the other hand, there were close correlation between the H/L ratio after glucose loading and the left ventricular ejection fraction (r = 0.680, p < 0.01). The changes in PET images caused by glucose loading were classified into 2 types (non-reversing and reversing patterns). DCM significantly showed a non-reversing pattern (86%, 12 of 14 patients) whereas ICM showed mainly a reversing pattern (70%, 7 of 10 patients; p < 0.05). In conclusion, myocardial FDG uptake after glucose loading may indicate a myocardial viable mass although FDG uptake at fasting was not evidently related to LV function. The change in the pattern of the FDG image from fasting to glucose loading may be useful in differentiating DCM from ICM.

Adult↗

PubMed2000

Pulmonary atresia with intact ventricular septum, antegrade coronary-right ventricular sinusoidal communication, and Wolff-Parkinson-White syndrome.

A fenestrated Fontan operation was performed successfully in a patient with pulmonary atresia with intact ventricular septum, an antegrade sinusoidal communication, and Wolff-Parkinson-White syndrome. Unlike most cases, blood flow in the sinusoidal communication was antegrade, from the left anterior descending artery to the right ventricle. This is the first report of the combination of pulmonary atresia with intact ventricular septum and Wolff-Parkinson-White syndrome.

Child, Preschool↗

PubMed2000

N-methyl-1-deoxynojirimycin (MOR-14), an alpha-glucosidase inhibitor, markedly improves postischemic left ventricular dysfunction.

We examined whether pharmacological inhibition of glycogenolysis by N-methyl-1-deoxynojirimycin (MOR-14), a new compound which reduces the glycogenolytic rate by inhibiting the alpha-1,6-glucosidase activity of the glycogen-debranching enzyme, can protect the heart against postischemic left ventricular dysfunction. The hearts of male Sprague-Dawley rats were excised, and perfused on a Langendorff apparatus with Krebs-Henseleit solution with a gas mixture of 95% O2 and 5% CO2. The hearts were paced at 320 beats/min except during the ischemia. Left ventricular developed pressure (LVDP, mmHg), +/-dP/dt (mmHg/s), and coronary flow (ml/min) were continuously monitored. All hearts were perfused for a total of 120 min including a 30-min preischemic period followed by a 30-min episode of global ischemia and 60 min reperfusion. with or without 0.5 or 2 mM of MOR-14 during the 30-min preischemic period or the first 30 min of reperfusion. In another series of experiments, the myocardial content of glycogen and lactate was measured during the 30-min episode of ischemia in groups treated with and without 2mM of MOR-14. Preischemic but not postischemic treatment with MOR-14 significantly improved LVDP and +/-dP/dt without altering coronary flow during reperfusion in a dose-dependent manner. MOR-14 significantly preserved the glycogen content and significantly attenuated the lactate accumulation during the 30-min episode of ischemia. Preischemic treatment with MOR-14 is protective against postischemic left ventricular dysfunction through the inhibition of glycogenolysis in the isolated rat heart.

1-Deoxynojirimycin↗