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M Maeda

Publications and source records attributed to M Maeda.

At least 505 records · Page 28Linked to original sources
PubMed1996

Molecular design of inhibitors of in vitro oriC DNA replication based on the potential to block the ATP binding of DnaA protein.

DnaA protein, the initiation factor for chromosomal DNA replication in Escherichia coli, is activated by binding to ATP. We earlier reported that 3-acetoxy-2,2'-bi-1H-indol inhibited the ATP binding to DnaA protein (Sasaki, S., Mizushima, T., Hashimoto, T., Maeda, M., and Sekimizu, K. (1994) Bioorg. Med. Chem. Lett. 4, 1771-1774). In the present study, derivatives of 3-acetoxy-2,2'-bi-1H-indol with different lengths of aliphatic chains at the 3-O position were synthesized, and their potential to inhibit the ATP binding to DnaA protein was examined. Elongation of the aliphatic chain resulted in inhibition of the ATP binding to DnaA protein at lower concentrations. Among the derivatives, 3-[N-(11-carboxyundecyl)]carbamoylmethoxy-2,2'-bi-1H-indol (structure 7 (3-CUCM-BI)) exhibited the most potent inhibition with an IC50 value of 7 microM. The mode of the inhibition was competitive. We further demonstrated that structure 7 (3-CUCM-BI) inhibited DNA replication of the oriC plasmid in a system reconstituted from purified proteins. This inhibition was specific for the initiation of DNA replication rather than for the elongation. The inhibition was overcome by preincubation of DnaA protein with ATP. Furthermore, structure 7 (3-CUCM-BI) showed little inhibition on DNA synthesis in the ABC primosome system. We propose that structure 7 (3-CUCM-BI) functions in the in vitro oriC DNA replication by inhibiting the ATP binding to DnaA protein.

Adenosine Triphosphate↗
PubMed1996

Association study between schizophrenia and dopamine D3 receptor gene polymorphism.

Crocq et al. [1992: J Med Genet 29:858-860] reported the existence of an association between schizophrenia and homozygosity of a BalI polymorphism in the first exon of the dopamine D3 receptor (DRD3) gene. In response to this report, further studies were conducted; however, these studies yielded conflicting results. In the present study, we examined 100 unrelated Japanese schizophrenics and 100 normal controls to determine any association between this polymorphism and schizophrenia. Results suggest that neither allele nor genotype frequencies of the DRD3 gene in the schizophrenics as a whole are significantly different from those of the controls. Further, we found no association between any allele or genotype and any clinical subtype based on family history of schizophrenia and age-at-onset. A significantly high frequency of homozygosity of a dopamine D3 receptor gene allele was not observed in the schizophrenics as a whole, or in clinical subtypes. Our results suggest that an association between the dopamine D3 receptor gene and schizophrenia is unlikely to exist.

Adolescent↗
PubMed1996

Transmembrane topology of Escherichia coli H(+)-ATPase (ATP synthase) subunit a.

Escherichia coli H(+)-ATPase subunit a is a hydrophobic F0 subunit. To investigate the topology of the subunit in the membrane, we prepared site-specific polyclonal antibodies against amino-terminal (Ser-3 to Leu-16), middle loop (Lys-167 to Gln-181), and carboxyl-terminal (Thr-259 to His-271) peptide segments. Enzyme-linked immunosorbent assay revealed that these antibodies specifically reacted with subunit a of inside-out membrane vesicles, but not with that of right-side-out spheroplasts. Full reactivity appeared when spheroplasts were disrupted with Triton X-100 (0.5%) or by sonication. These results suggest that at least parts of the three peptide segments of subunit a face the cytoplasm. Based on these observations, we propose a novel transmembrane topology of subunit a.

Amino Acid Sequence↗
PubMed1996

Transmembrane segment 10 is important for substrate recognition in Ga12 and Hxt2 sugar transporters in the yeast Saccharomyces cerevisiae.

A systematic series of chimeras between Ga12 galactose transporter and Hxt2 glucose transporter in yeast was produced to delineate the essential domain for substrate recognition. A domain of 101 amino acids close to the COOH-terminus that has been previously identified as the critical substrate recognition region was further divided into four subdomains, by introducing five restriction enzyme sites at exactly corresponding locations of both genes without changing coding amino acids. When each of all possible 16 modified genes was expressed, all the galactose transport-active chimeras were found to possess Ga12-derived transmembrane segment (TM) 10. Of the 35 amino acids in the TM1O region, only 12 differ between Ga12 and Hxt2, indicating that these 12 amino acids include the critical residue(s) responsible for the differential recognition of galactose and glucose in these transporters.

Amino Acid Sequence↗
PubMed1996

The human OX40/gp34 system directly mediates adhesion of activated T cells to vascular endothelial cells.

Fresh leukemic cells from patients with adult T cell leukemia (ATL) and some ATL-derived T cell lines show adhesion to human umbilical vein endothelial cells (HUVECs) mainly through E-selectin, but a proportion of this binding remains unaffected by the addition of combinations of antibodies against known adhesion molecules. By immunizing mice with one of such cell lines, we established monoclonal antibodies (mAbs), termed 131 and 315, that recognize a single cell surface antigen (Ag) and inhibit the remaining pathway of the adhesion. These mAbs did not react with normal resting peripheral blood mononuclear cells (PBMC) or most of the cell lines tested except for two other human T cell leukemia virus type I (HTLV-I)-infected T cell lines. After stimulation with phytohemagglutinin (PHA), PBMC expressed Ag 131/315 transiently, indicating that these mAbs define a T cell activation Ag. Western blotting and immunoprecipitation revealed that Ag 131/315 has an apparent molecular mass of 50 kD. Expression cloning was done by transient expression in COS-7 cells and immunological selection to isolate a cDNA clone encoding Ag 131/315. Sequence analysis of the cDNA indicated that it is identical to human OX40, a member of the tumor necrosis factor/nerve growth factor receptor family. We then found that gp34, the ligand of OX40, was expressed on HUVECs and other types of vascular endothelial cells. Furthermore, it was shown that the adhesion of CD4+ cells of PHA-stimulated PBMC to unstimulated HUVECs was considerably inhibited by either 131 or 315. Finally, OX40 transfectants of Kit 225, a human interleukin 2-dependent T cell line, were bound specifically to gp34 transfectants of MMCE, a mouse epithelial cell line, and this binding was blocked by either 315 or 5A8, an anti-gp34 mAb. These results indicate that the OX40/gp34 system directly mediates adhesion of activated T cells or OX40+-transformed T cells to vascular endothelial cells.

Animals↗
PubMed1996

Doc2 enhances Ca2+-dependent exocytosis from PC12 cells.

We previously isolated a new protein having two C2-like domains which interacted with Ca2+ and phospholipid and named Doc2 (Double C2). Because Doc2 was abundantly expressed in brain where it was highly concentrated on the synaptic vesicle fraction, we have examined here whether Doc2 is involved in Ca2+-dependent exocytosis from cultured PC12 cells. For this purpose, we took advantage of the growth hormone (GH) co-expression assay system of PC12 cells in which GH is stored in dense core vesicles and released in response to high K+ in an extracellular Ca2+-dependent manner. Northern and Western blot analyses indicated that Doc2 is present in PC12 cells. Overexpression of hemagglutinin-tagged Doc2 stimulated the Ca2+-dependent, high K+-induced release of co-expressed GH without affecting the basal release. In the PC12 cells transfected with a plasmid with the coding sequence of Doc2 in the antisense orientation, the high K+-induced release of co-expressed GH was inversely inhibited. The Doc2 mutant expressing an N-terminal fragment or a C-terminal fragment containing two C2-like domains inhibited the high K+-induced release of co-expressed GH. These results indicate that Doc2 enhances Ca2+-dependent exocytosis of dense core vesicles from PC12 cells.

Amino Acid Sequence↗
PubMed1996

Seven helix chemoattractant receptors transiently stimulate mitogen-activated protein kinase in Dictyostelium. Role of heterotrimeric G proteins.

Mitogen-activated protein (MAP) kinases are involved in controlling a cell's responses to a variety of stimuli and can be activated by both protein tyrosine kinase and G protein-coupled receptors. It was shown previously that Dictyostelium MAP kinase ERK2 is required for normal activation of adenylyl cyclase and erk2 null cells are aggregation-deficient. In this manuscript, we show that the Dictyostelium MAP kinase ERK2 is rapidly and transiently activated in response to the chemoattractant cAMP. This response requires cAMP receptors, but is independent of the coupled G alpha2 subunit and the only known G beta subunit. These data indicate that ligand-mediated receptor activation of adenylyl cyclase requires two receptor-dependent pathways, one of which requires heterotrimeric G proteins, including G alpha2 and the only known G beta subunit, and the second of which requires ERK2. Our results suggest that ERK2 may be activated by a novel receptor-mediated pathway.

Adenylyl Cyclases↗
PubMed1996

Involvement of rabphilin-3A in Ca2+-dependent exocytosis from PC12 cells.

Rabphilin-3A, a putative target molecule of Rab3A small GTP-binding protein implicated in Ca2+-dependent exocytosis, consists of two functionally different domains: the N-terminal Rab3A-binding domain and the C-terminal two C2-like domains (C2A and C2B domains) interacting with Ca2+ and phospholipid. Here, we used the growth hormone (GH) co-expression assay system of PC12 cells in which expressed GH is released in response to high K+. Reduction of endogenous rabphilin-3A inhibited the Ca2+-dependent, high K+-induced GH release. Various rabphilin-3A mutants expressing an N-terminal, C-terminal, or C2B fragment, but not the rabphilin-3A mutant expressing a C2A fragment, inhibited the high K+-induced GH release. These results indicate that rabphilin-3A is involved at least in Ca2+-dependent exocytosis from PC12 cells and that the C2A and C2B domains have different functions.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Analysis of single-strand DNA conformation polymorphism by capillary electrophoresis.

Analysis of single-strand conformation polymorphism (SSCP) by capillary electrophoresis (CE) was developed. The conformational change of single-strand DNA is caused by a mutation in a DNA fragment. The change is detected as mobility shift in CE. The effects of acrylamide gel concentration, running temperature and fragment size amplified by the polymerase chain reaction (PCR) were studied to develop the separation of SSCP. The model DNA used was the divE 42 gene carrying wild- and mutant-type (G-->A point mutation at the 141 site). The results show that two single-strand DNA fragments that differ in one nucleotide can be separated by CE within minutes. This method was also applied to the separation of SSCP for N-ras gene including four kinds of mutations. All mutations tested in this study could be distinguished. CE is well suited for clinical analysis of SSCP because it is rapid and reproducible, allows on-line detection and is easy.

Base Sequence↗
PubMed1996

A new technique for quantitative imaging of cerebrovascular reserve capacity using a double injection method with N-isopropyl-p-[123I]iodoamphetamine.

Estimation of local cerebrovascular reserve capacity is an important aspect of the management of patients with cerebrovascular occlusive disease. Regional normal values of cerebrovascular reserve capacity have not yet been established. Recently, Mori et al. (1994) introduced a method to quantitatively measure cerebral blood flow twice in 30 min after a double injection of N-isopropyl-p-[123I]iodoamphetamine using a background subtraction method. We utilized this double injection method in tandem with acetazolamide (20 mg/kg, intravenous injection) in 10 normal volunteers to produce a map of quantitative cerebrovascular reserve capacity using single photon emission computed tomography. The normal regional cerebrovascular reserve capacity was: frontal lobe, 51.0 +/- 19.8%; temporal lobe, 53.6 +/- 12.4%; parietal lobe, 69.3 +/- 31.8%; basal ganglia, 85.1 +/- 42.7%; cerebellum, 49.6 +/- 17.9% (mean +/- SD). One-way analysis of variance showed that the cerebrovascular reserve capacity did not differ significantly among structures. This new imaging technique and normal values of regional cerebrovascular reserve capacity may provide information about the pathophysiology and surgical indication in patient with occlusive cerebrovascular disease.

Adult↗
PubMed1996

Expression and regulation of the dystrophin Purkinje promoter in human skeletal muscle, heart, and brain.

Dystrophin mRNA transcripts from the P (Purkinje) promoter were shown to be differentially expressed in human skeletal muscle, heart, and brain. The expression pattern was characteristic of tissue type and developmental stage. Polymerase chain reaction (PCR) analysis of the P promoter transcripts in adult skeletal muscle and adult brain identified two alternatively spliced sequences, one that encodes a full-length dystrophin mRNA and a second that transcribes a termination codon 27 nucleotides (8 amino acids) after the ATG initiation site. Alternative splicing of this truncated coding transcript was developmentally regulated, and it was expressed as the major form in adult cortical brain and adult heart. The biological significance of this peptide remains unclear. The full-length transcript was the major form in fetal cortical brain and adult skeletal muscle. Ribonuclease protection assay demonstrated that as much as 20% of dystrophin transcription in normal adult skeletal muscle was derived from the full-length transcript from the P promoter. In contrast, adult heart did not express significant levels of P promoter derived transcripts. Thus, transcripts from the P promoter were found to be developmentally regulated in the brain, and its activity was differentially expressed in skeletal versus cardiac muscle tissues. These data show that the P promoter transcript displays a broader scope of expression, regulation, and complexity than previously appreciated.

Adult↗
PubMed1996

Cerebral blood flow decreases following microinjection of sodium nitroprusside into the nucleus tractus solitarii of anesthetized rats.

The present study was undertaken to examine the effects of microinjection of sodium nitroprusside (SNP), which releases nitric oxide (NO) spontaneously, into the nucleus tractus solitarii (NTS) on cerebral circulation. Cerebral blood flow (CBF) was measured in urethane-anesthetized (1.5 g middle dotkg-1, i.p.), paralysed and artificially ventilated rats using labeled microspheres or laser Doppler flowmetry. The CBF was significantly decreased by microinjection of SNP (5 nmol, n=10, microsphere technique; 0.5 nmol, n=6, laser Doppler flowmetry) into the unilateral NTS. Microinjection of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of the formation of NO, prevented cerebral vasoconstrictor responses induced by microinjection of L-glutamate into the NTS (n=10). Microinjection of NG-monomethyl-D-arginine (D-NMMA) had no effect on the cerebral vasoconstrictor responses induced by L-glutamate (n=11). Unilateral microinjections of L-NMMA into the NTS (n=9), of SNP into the area adjacent to the NTS (n=9), of vehicle solution into the NTS (n=10), and of light-inactivated SNP into the NTS (n=6) had no effect on cerebral circulation. Cerebral autoregulation was well maintained in our protocols (n=9). These results indicate that microinjection of SNP, an NO donor, into the NTS decreases CBF.

Animals↗
PubMed1996

Management of malignant tracheobronchial stenosis with metal stents and Dumon stents.

BACKGROUND: Tracheobronchial stenosis caused by malignancy is a life- threatening problem. Stenting is one of the treatment modalities and recently has been used widely for the management of such stenosis, but we do not have a clear guide as to which stent should be selected. METHODS: We evaluated 25 patients (19 men, 6 women; mean age, 60.7 years; range, 34 to 77 years) received 24 metal stents (four covered with silicone rubber) and three Dumon stents. All 25 patients had severe dyspnea because of airway stenosis caused by malignant tumors. RESULTS: Among the 25 patients, airway obstruction due to extrinsic compression by tumor developed in 11 and was treated with a bare metal stent. The airway remained patent in 10 patients. In 16 patients with intraluminal tumor invasion, nine lesions were treated with a bare metal stent, four lesions with a covered metal stent, and the remaining three lesions with a Dumon stent. Recurrent stenosis did not occur in any patient with a covered metal stent or a Dumon stent. However, restenosis occurred in 4 patients with a bare metal stent, all of whom received laser therapy. In all patients, stenting immediately relieved dyspnea. Six patients lived for 32 days to 53 months after stenting, and 19 patients died of primary malignancies with a mean survival of 131.9 days. CONCLUSIONS: Metal stents are effective in treating malignant extrinsic tracheobronchial compression. The use of covered metal stents or Dumon stents is preferable for intraluminal stenosis due to malignant growth.

Adult↗
PubMed1996

Spinal cord lactate concentration during chemical stimulation of the nucleus tractus solitarii in anesthetized rats.

This study was conducted to determine the mechanism of spinal cord blood flow (SCBF) decrease following the nucleus tractus solitarii (NTS) activation. In urethane-anesthetized, paralyzed and artificially ventilated rats, neurons in the NTS were chemically stimulated by microinjection of L-glutamate (1.7 nmol; 50 nl) and the lactate concentration, one of indicators of local neuronal metabolism, in the spinal cord was monitored in real time using an enzyme electrode. Before the chemical stimulation study, the responses of the enzyme electrode and its specificity were tested in vitro and in vivo. The electrode responded to step changes in lactate concentration and a calibration plot and regression line were obtained in vitro. The lactate concentration was significantly (P < 0.01) increased during induced apnea in vivo (n = 8). The lactate concentration in the spinal cord was not significantly changed by chemical stimulation of the NTS when arterial blood pressure (ABP) remained above the lower limit of spinal cord autoregulation (n = 21). When chemical stimulation of the NTS decreased ABP to below the lower limit of autoregulation (n = 18), the lactate concentration in the spinal cord was significantly (P < 0.01) increased. This may only be due to hypotensive effects because the lactate concentration was also significantly (P < 0.01) increased when the ABP was passively decreased below the lower limit of autoregulation by controlled hemorrhage in intact (n = 11) and sinoaortic denervated rats (n = 10). Intravenous lactate injection produced no significant increase in the current from the enzyme electrode in the spinal cord (n = 4). Using the electrode with inactivated enzyme solution, the current from the electrode did not change with the increase in lactate in the spinal cord. These findings indicate that the enzyme electrode can detect rapid changes of lactate, a product of anaerobic metabolism. These results also indicate that the spinal cord vasoconstrictor response elicited by chemical stimulation of the NTS, which was performed above the lower limit of spinal cord autoregulation in our previous study, may be due to neurogenic regulatory mechanism, but not to the secondary effects of changes in metabolism.

Anesthesia↗
PubMed1996

Spinal cord blood flow decreases following microinjection of sodium nitroprusside into the nucleus tractus solitarii of anesthetized rats.

This study was undertaken to examine whether or not nitric oxide (NO) is involved in synaptic transmission in the nucleus tractus solitarius (NTS) during control of the spinal cord circulation. Employing urethane-anesthetized, paralyzed and artificially ventilated rats, sodium nitroprusside (SNP), which produces NO, was microinjected unilaterally into the NTS and the spinal cord blood flow (SCBF) was determined using labeled microspheres. Arterial blood pressure (ABP) was decreased by unilateral microinjection of SNP into the NTS, but its value was kept within the normotensive range by blood transfusion, in order to measure SCBF at normotension. After microinjection of SNP into the NTS, the SCBFs of the cervical, thoracic and lumbar cords decreased significantly from 63 +/- 8 (mean +/- S.E.M.) to 49 +/- 7 (P < 0.05), from 54 +/- 7 to 37 +/- 7 (P < 0.05), and from 77 +/- 9 to 58 +/- 8 (P < 0.05) ml/min/(100 g), respectively (n = 10). Prior microinjection of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of the formation of NO from L-arginine, into the NTS blocked the spinal cord vasoconstrictor response produced by microinjection of L-glutamate into the NTS (n = 10). Prior microinjection of NG-monomethyl-D-arginine (D-NMMA), which does not inhibit the formation of NO from L-arginine, did not block the spinal cord vasoconstrictor response elicited by microinjection of L-glutamate (n = 11). Unilateral microinjection of L-NMMA into the NTS exerted no effect on the spinal cord circulation (n = 9). These findings suggest that NO may be involved in the control of the spinal cord circulation in the NTS.

Animals↗
PubMed1996

Vasodilatation and enhanced oxidative metabolism of the cerebral cortex provoked by the periaqueductal gray matter in anaesthetized rats.

The aim of the present study was to evaluate the possible contribution of the cerebral cortical oxidative metabolism to the cortical vasodilator action of the periaqueductal gray. In 70 rats with cervical cordotomy, we found that unilateral stimulation of the caudal third of the lateral longitudinal column of the periaqueductal gray with N-methyl-D-aspartate bilaterally provoked the greatest increase in cortical blood flow (laser-Doppler flowmetry and/or microsphere flowmetry). The response was widespread over the entire neocortical regions, elicited in a dose-dependent manner, with little change in arterial blood pressure. The flow was increased effectively by a submaximal dose of the amino acid (1 mM, 100 nl), attaining a peak increase by 99 +/- 41% of the baseline level (mean +/- S.D., n = 30), and was associated with an enhancement of the cortical metabolic rate for oxygen by 51 +/- 26%. We then compared the flow increase with that induced by cold exposure (by 52 +/- 29%, n = 27), the latter response being tightly coupled to an enhanced metabolic rate for oxygen (by 41 +/- 23%). It was thus found that the increase in cortical blood flow provoked by the subdivision was dependent on the cerebrovasodilator mechanism that may be coupled to the cortical oxidative metabolism to the extent of one-half, and on certain other mechanisms for the remaining half. In view of the fact that this particular region serves to generate vigorous defence reactions that involve flight behaviour, the region should also help to meet the urgent demand for an increased cortical blood flow, so as to prepare for the possible generation of cortical hyperactivity in coping vigorously with a threatening emergency.

Anesthesia↗
PubMed1996

Plasma levels of molecular markers of blood coagulation and fibrinolysis in progressive systemic sclerosis (PSS).

Seventy-four patients with PSS were evaluated with regard to plasma concentration of blood coagulation and fibrinolysis factors: fibrinogen (Fbg), prothrombin time (PT), active partial thromboplastin time (APTT), protein C, thrombin-antithrombin III complex (TAT), antithrombin-III (AT-III), factor XIII (XIII) fibrinopeptide A (FPA), alpha 1-antitrypsin (alpha 1-AT), plasminogen (Pmg), alpha 2-plasmin inhibitor plasmin complex (PIC), alpha 2-plasmin inhibitor (alpha 2-PI), alpha 2-macroglobulin (alpha 2-MG), fibrinopeptide B beta 15-42 (FPB beta-15-42) and soluble fibrin monomer complex (SFMC), FDP (fibrin degradation product) and D-dimer. They were also evaluated with regard to platelet-derived proteins: beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), thromboxane B2 and 6-keto-prostaglandin F1 alpha (6KF). In the coagulation/fibrinolysis systems high plasma levels of TAT, AT-III, FPA, alpha 2-MG and FPB beta 15-42 could be demonstrated in more than 50% of total PSS patients. There was no statistical correlation between those of TAT and AT-III. Plasma levels of PIC, D-dimer, FDP and SFMC were not always high. There was no statistical correlation between those of TAT and PIC. These data lead us to consider that alpha 2-MG may play an important role for inhibiting PIC, which accelerates the conversion from fibrin into FDP. Subsequently, there were high plasma levels of FPB beta 15-42 converted from fibrin monomer. These data seem to be indicative of an involvement of coagulation and platelet disorder in PSS. These platelet-vessel system disorders might be closely related to the pathophysiology of PSS.

Adult↗