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A Muraki

Publications and source records attributed to A Muraki.

13 recordsLinked to original sources
PubMed1996

Sequence analysis of the genome of the unicellular cyanobacterium Synechocystis sp. strain PCC6803. II. Sequence determination of the entire genome and assignment of potential protein-coding regions.

The sequence determination of the entire genome of the Synechocystis sp. strain PCC6803 was completed. The total length of the genome finally confirmed was 3,573,470 bp, including the previously reported sequence of 1,003,450 bp from map position 64% to 92% of the genome. The entire sequence was assembled from the sequences of the physical map-based contigs of cosmid clones and of lambda clones and long PCR products which were used for gap-filling. The accuracy of the sequence was guaranteed by analysis of both strands of DNA through the entire genome. The authenticity of the assembled sequence was supported by restriction analysis of long PCR products, which were directly amplified from the genomic DNA using the assembled sequence data. To predict the potential protein-coding regions, analysis of open reading frames (ORFs), analysis by the GeneMark program and similarity search to databases were performed. As a result, a total of 3,168 potential protein genes were assigned on the genome, in which 145 (4.6%) were identical to reported genes and 1,257 (39.6%) and 340 (10.8%) showed similarity to reported and hypothetical genes, respectively. The remaining 1,426 (45.0%) had no apparent similarity to any genes in databases. Among the potential protein genes assigned, 128 were related to the genes participating in photosynthetic reactions. The sum of the sequences coding for potential protein genes occupies 87% of the genome length. By adding rRNA and tRNA genes, therefore, the genome has a very compact arrangement of protein- and RNA-coding regions. A notable feature on the gene organization of the genome was that 99 ORFs, which showed similarity to transposase genes and could be classified into 6 groups, were found spread all over the genome, and at least 26 of them appeared to remain intact. The result implies that rearrangement of the genome occurred frequently during and after establishment of this species.

Bacterial Proteins↗
PubMed1994

Competitive and noncompetitive NMDA antagonists block sensitization to methamphetamine.

The present study examined the effects of both competitive (D-CPP-ene) and noncompetitive (MK-801) NMDA antagonists on behavioral sensitization to methamphetamine (MA). Behavioral effects of repeated administration of NMDA antagonists were also examined. Rats treated with MA according to an escalating dose schedule (2.5, 5, 7.5, and 10.0 mg/kg, SC, twice a day on days 1, 3, 5, and 7, respectively) indicated behavioral supersensitivity. Pretreatment with either MK-801 (0.5 mg/kg, IP) or D-CPP-ene (20 mg/kg, IP) prior to MA administration prevented the development of the supersensitivity. Rats treated with MK-801 showed a decrease in the motor activity when subsequently challenged with MK-801 compared with saline-treated rats. Likewise, rats administered with D-CPP-ene showed decreased motor activity when challenged with D-CPP-ene. There was no cross-sensitization nor tolerance between MA and MK-801 or D-CPP-ene. These results suggest that both competitive and noncompetitive NMDA antagonists block sensitization to MA and that repeated administration with NMDA antagonists results in behavioral tolerance.

Animals↗
PubMed1993

Competitive and noncompetitive N-methyl-D-aspartate antagonists protect dopaminergic and serotonergic neurotoxicity produced by methamphetamine in various brain regions.

Protective effects of NMDA antagonists on dopaminergic and serotonergic neurotoxicity produced by methamphetamine (MA) were examined. Four injections of MA (7.5 mg/kg, s.c., at 2 h intervals) caused significant decrements (40-60% of control values) in levels of dopamine (DA) and its metabolites in the rat striatum and levels of serotonin (5-HT) and its metabolite in the medial prefrontal cortex, nucleus accumbens, striatum, anterior hypothalamus, amygdala and hippocampus. These decreases in DA, 5-HT and their metabolites were prevented by pretreatment with MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) antagonist, or D-CPP-ene (SDZ EAA 494), a competitive NMDA antagonist. The results suggest that NMDA receptors play a role for MA-induced serotonergic damage in various brain regions as well as dopaminergic damage in the striatum.

Animals↗
PubMed1993

Effects of single and repeated immobilization stress on corticotropin-releasing factor concentrations in discrete rat brain regions.

1. Corticotropin-releasing factor (CRF) has been suggested to regulate many responses to stress. The authors investigated the effect of single and repeated stress on brain CRF immunoreactivity (CRF-ir) and plasma corticosterone levels in rats, using radioimmunoassay. 2. Single immobilization stress significantly increased plasma corticosterone levels but did not change CRF-ir in the discrete brain regions at all. Repeated immobilization stress (a 180 min session, once a day for 10 days) did not affect plasma corticosterone levels at 24 hr poststress. However, it increased CRF-ir in the median eminence (ME) though not in the other brain regions. 3. The increased level of CRF in the ME after chronic intermittent stress suggests that repeated stimulation by stress may increase the storage pool of CRF in the ME.

Animals↗
PubMed1993

Iododeoxyuridine uptake and retention as a measure of tumor growth.

Iodine-131-iododeoxyuridine (IUdR) uptake and retention was measured in two C6 glioma cell lines (C6m and C6a) with different growth characteristics. Animals with intracerebral (i.c.) C6a tumors had a mean survival of 16 days, whereas only 1 of 20 animals with i.c. C6m tumors died during an 8-wk period of observation. The growth of i.c. C6m tumors could be described by the Gompertz equation; tumor doubling time increased from 1.9 to 5.2 days between Days 8 and 16 after tumor inoculation. Corresponding measurements of 131I-IUdR uptake and retention (24 hr after IUdR administration) by i.c. C6m tumors were also time-dependent and decreased from 0.075 to 0.027 to 0.011 %dose/g in 8-, 10- and 16-day-old tumors, respectively. Iodine-131-IUdR uptake in "rapidly growing" i.c. C6a tumors was substantially higher (0.30 %dose/g at 24 hr) than that in "slowly growing" i.c. C6m tumors and corresponded with differences in the survival data. Subcutaneous C6a tumors had comparable high uptake values (0.49 %dose/g at 24 hr), and 93% of total tumor radioactivity was recovered in DNA 24 hr after IUdR administration. Clearance of radioactivity was rapid in nonproliferative tissues; more than 80% of plasma radioactivity was cleared in 24 hr. Tumor-to-cortex radioactivity ratios ranged from 100/1 to 120/1 and 150/1 between 24, 48 and 96 hr after IUdR injection respectively. A "washout strategy," which reduces tissue background activity and increases specificity for PET and SPECT imaging of IUdR-DNA incorporation, is possible with longer-lived radioisotopes of iodine.

Animals↗
PubMed1993

[Effects of antagonists of NMDA receptor on methamphetamine-induced decrease in the dopamine uptake sites in the rat striatum and on the behavioral sensitization].

In humans, repeated use of methamphetamine produces hypersensitivity to the psychotogenic effects of methamphetamine that persists for months to years after the discontinuation of methamphetamine administration. Methamphetamine-induced psychosis has been thought to be a useful experimental model for schizophrenia. A possible involvement of the glutamate system in the hypersensitivity including behavioral sensitization or reverse tolerance is recognized in an animal model for methamphetamine psychosis. We investigated the effects of antagonists of N-methyl-D-aspartate (NMDA) receptor on methamphetamine-induced decrease in dopamine (DA) uptake sites in the rat striatum and on the behavioral sensitization. Repeated administrations of escalating doses of methamphetamine (2.5, 5, 7.5, 10mg/kg s. c. x 2, every other day for a week) decreased DA uptake sites to about 75% of the control in the striatum assayed by binding with [3H]GBR 12935. Co-administration of MK-801, a non-competitive antagonist of NMDA receptor, and methamphetamine significantly prevented the methamphetamine-induced decrease in striatal [3H]GBR 12935 binding in a dose dependent manner. Administration of MK-801 alone did not affect the [3H]GBR 12935 binding. Furthermore, co-administration of SDZ EAA494, a competitive antagonist of NMDA receptor, and methamphetamine also prevented the methamphetamine-induced decrease in the striatal [3H]GBR 12935 binding in a dose dependent manner. In methamphetamine-pretreated rats, the methamphetamine challenge (2.5mg/kg) after a 7-day-drug-free period produced an initial elevation in locomotion lasting for 10-30 min which was followed by a precipitous drop in the locomotion activity to very low levels for approximately 50-70 min. During the period of reduced locomotor activity, methamphetamine-pretreated rats showed intense focused stereotyped behavior. In contrast, animals treated with both MK-801 and methamphetamine showed neither the progressive enhancement of the locomotor activity nor the stereotyped behavior induced by the drug. Pretreatment with MK-801 blocked the development of the methamphetamine-induced behavioral sensitization. These results suggest an involvement of excitatory amino acids in neurochemical effects of methamphetamine on the dopamine system in the striatum.

Animals↗
PubMed1992

MK-801, a non-competitive antagonist of NMDA receptor, prevents methamphetamine-induced decrease of striatal dopamine uptake sites in the rat striatum.

We investigated the effects of MK-801, a non-competitive antagonist of NMDA receptor, on methamphetamine-induced decrease in dopamine (DA) uptake sites in the rat striatum. Repeated administrations of an escalating dose of methamphetamine (2.5, 5, 7.5, 10 mg/kg s.c. x2, every other day for a week) produced decreased DA uptake sites assayed by binding with [3H]GBR 12935 in the striatum. Co-administration of MK-801 and methamphetamine significantly prevented the methamphetamine-induced decrease in striatal [3H]GBR 12935 binding. Administration of MK-801 alone did not affect [3H]GBR 12935 binding. These results suggest that some neurochemical effects of methamphetamine may be mediated via mechanism involving excitatory amino acids.

Animals↗
PubMed1990

MRI characterization of 9L-glioma in rat brain at 4.7 Tesla.

In vivo estimation of intracranial tumor progression is important in tumor treatment response studies in animal models. High resolution MR images at 4.7 T of 9L-gliomas stereotactically implanted in Fisher-344 rat brains were obtained. Due to elongation of T1 at higher fields, tissue contrast is diminished in T1-weighted images. However, normal anatomy and vasogenic edema are clearly discerned in T2-weighted images (echo times of greater than 50 ms and recycle times of greater than 2 sec). Tumor tissue is not always clearly delineated. Images obtained after administration of contrast agents (Gadolinium DTPA), with short TR (0.6 sec) selectively enhanced the tumorous tissue, with little effect upon normal tissue and edema. Good correlation of enhanced tumor lesions has been observed with histological examination of formalin fixed brains. Relaxation times (T1 and T2) of tumor and normal tissues were measured using stimulated-echo and multi-echo sequences, respectively. Serial images corresponding to tumor growth were recorded, from which tumor volume progression was monitored.

Animals↗
PubMed1986

Syringomyelia in a man with sarcoidosis.

Sarcoidosis, generally a systemic ailment, uncommonly affects the central nervous system. It only rarely affects the spinal cord alone or in combination with other areas. Syringomyelia has never been associated with sarcoidosis. We report the case of a 32-year-old man with sarcoidosis who presented with surgically verified syringomyelia. The pertinent literature is reviewed. The mechanisms by which sarcoidosis could cause a syrinx are discussed.

Adult↗