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H Inokuchi

Publications and source records attributed to H Inokuchi.

At least 109 records · Page 6Linked to original sources
PubMed1992

Isolation and characterization of a light-sensitive mutant of Escherichia coli K-12 with a mutation in a gene that is required for the biosynthesis of ubiquinone.

Cells with a novel mutation that is lethal when the cells are exposed to visible light were isolated from Escherichia coli K-12. The mutation was mapped at 63 min on the linkage map of the E. coli chromosome, and the gene, designated visB, was cloned and sequenced. From its map position and the evidence that the gene product VisB exhibits homology with flavin monooxygenase of Pseudomonas fluorescens, the visB gene was deduced to be identical to the ubiH gene, which is a gene required for the biosynthesis of ubiquinone and is thought to be similar to the gene for flavin monooxygenase. The photosensitive phenotype appears to be due to the accumulation of the substrate for the reaction catalyzed by the visB (ubiH) gene product because other mutations that block earlier steps in the biosynthesis of ubiquinone can reverse the photosensitivity. The accumulated intermediates may produce active species of oxygen in the mutant bacteria upon illumination by visible light, and these active oxygen species may cause the death of the cells by a mechanism similar to that associated with mutations in visA (hemH).

Amino Acid Sequence↗
PubMed1992

Adrenergic receptors (alpha 1 and alpha 2) modulate different potassium conductances in sympathetic preganglionic neurons.

Intracellular recordings were made from 168 sympathetic preganglionic neurons in the slice of the second or third thoracic spinal-cord segment of the adult cat to study the actions of noradrenaline on these neurons. Noradrenaline, applied by superfusion (0.5-50 microM), produced membrane depolarization in 73 neurons and membrane hyperpolarization in 39 neurons. In 26 neurons noradrenaline produced a biphasic response (depolarization-hyperpolarization or vice versa). The depolarization was blocked by prazosin, while the hyperpolarization was blocked by yohimbine. The noradrenaline-induced depolarization was associated with an increase in neuron input resistance, while the noradrenaline-induced hyperpolarization was associated with a decrease in neuron input resistance. Both responses decreased in amplitude with membrane hyperpolarization and were nullified at around the potassium equilibrium potential EK. The null potential of both responses became more and less negative with a decrease and an increase, respectively, in the extracellular potassium concentration. When the membrane potential was made more negative than EK, the noradrenaline-induced hyperpolarization reversed to depolarization in all cases, whereas in only 4 of 12 cases did the noradrenaline-induced depolarization reverse to hyperpolarization. These data suggest that the noradrenaline-induced depolarization is a result of a decrease, while the noradrenaline-induced hyperpolarization is a result of an increase in K+ conductance. Cobalt (2 mM), low calcium--high magnesium, and intracellular EGTA markedly reduced or abolished the noradrenaline-induced depolarization but had no significant effect on the noradrenaline-induced hyperpolarization. Barium (2 mM) depressed both responses. Tetraethylammonium (10-30 mM), 4-aminopyridine (3 mM), and cesium (2 mM) had no effect on either response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Photosensitivity of a protoporphyrin-accumulating, light-sensitive mutant (visA) of Escherichia coli K-12.

Mutations in the visA gene of Escherichia coli cause the mutant bacteria to die upon illumination with visible light. We confirmed genetically that the visA gene is a structural gene for ferrochelatase (protoheme ferro-lyase, EC 4.99.1.1). Since other mutations in the genes involved in the biosynthesis of heme can cure the photosensitivity, the light-induced cell death appears to be brought about by the accumulation of protoporphyrin IX, one of the substrates of ferrochelatase. When cells are illuminated with visible light, protoporphyrin IX seems to produce an active species of oxygen (probably 1O2) that is harmful to the cells. This defect is the same as that associated with the human disease protoporphyria.

Anaerobiosis↗
PubMed1991

Isolation and characterization of visible light-sensitive mutants of Escherichia coli K12.

Six mutants of Escherichia coli K12 that are sensitive to visible light have been isolated. Five of them, including an amber mutant, are defective in a gene that maps near 11 minutes on the linkage map of the chromosome, and this gene has been designated visA. The sixth mutant, which was isolated from bacteria that carried the visA+/visA+ diploid allele, is defective in a gene that maps near 63 minutes on the linkage map, which has been designated visB. These mutant strains of bacteria are killed by illumination with visible light. The effective wavelength of the light is around 460 nm. The nucleotide sequence of the visA gene was determined. As a result of a search for homologous products, we found that visA may be identical to hemH, the structural gene for ferrochelatase which catalyzes a final step in the biosynthesis of heme. A possible mechanism for the killing of the visA mutant bacteria is discussed.

Amino Acid Sequence↗
PubMed1991

Precise mapping of the rnpB gene encoding the RNA component of RNase P in Escherichia coli K-12.

In Kohara's library derived from Escherichia coli K-12 W3110 (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987), multiple copies of chromosomal sequence are found at 68 and at 64 to 65 min (M. Umeda and E. Ohtsubo, J. Mol. Biol. 213:229-237, 1990). We have determined that the rnpB gene (previously mapped at 70 min [B. J. Bachmann, Microbiol. Rev. 54:130-197, 1990]) is located within these segments of repeated sequences as five separate copies, together with tdcA, B, C, and R (mapped at 68 min [Bachmann, 1990]) and six unidentified open reading frames. Since close linkage of rnpB and tdc is found in various strains of E. coli K-12, the rnpB gene should be mapped at 68 min rather than 70 min.

Base Sequence↗
PubMed1991

Synaptic responses of guinea pig and rat central amygdala neurons in vitro.

1. To investigate postsynaptic potentials (PSPs), we made intracellular recordings from neurons of the amygdaloid central nucleus in slices from the guinea pig and rat brains maintained in vitro. The results from guinea pigs and rats were very similar. 2. In the presence of bicuculline (20 microM), focal electrical stimulation of the amygdaloid basal nucleus with low intensities elicited short-latency excitatory PSPs (EPSPs) followed by long-latency EPSPs. The short-latency EPSP was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX; 10-20 microM). The long-latency EPSP was preferentially abolished by D,L-2-amino-5-phosphonovaleric acid (D,L-APV; 40 microM) and was augmented by removal of extracellular Mg2+. The compound EPSP reversed at -4 mV, which was close to -1 mV, the reversal potential for pressure-ejected glutamate (Glu). 3. When the intensity of the focal stimulation was increased in the presence of bicuculline (20 microM), CNQX (20 microM), and D,L-APV (50 microM), a second EPSP with a short latency and a prolonged duration could be evoked in approximately 65% of the neurons. The EPSPs were reversibly blocked by d-tubocurarine (50 microM) or hexamethonium (200 microM) but were unaffected by atropine (1 microM) or a 5-hydroxytryptamine type 3 receptor antagonist, ICS-205930 (5-10 microM). In these neurons, acetylcholine (ACh; 1-3 mM) caused a depolarization, associated with a decreased input resistance. 4. In the presence of CNQX (20 microM) and D,L-APV (50 microM), single focal stimulation of the dorsolateral subdivision in the central nucleus with low intensities elicited a depolarizing inhibitory PSP (IPSP). The IPSP was reversibly abolished by bicuculline (20-40 microM). The reversal potential (-63 mV) for the IPSP was similar to the reversal potential (-61 mV) for the response to gamma-aminobutyric acid (GABA) applied by pressure ejection. 5. In the presence of bicuculline (20-40 microM) and CNQX (20 microM), a repetitive focal stimulus with high intensities delivered to the dorsolateral subdivision produced a hyperpolarizing PSP followed by a slow depolarization in most neurons. Of putative inhibitory amino acid transmitters, glycine (Gly; 3 mM) produced only a hyperpolarization, associated with a decrease in input resistance. Strychnine (1-2 microM) reversibly blocked both the Gly hyperpolarization and the synaptically evoked hyperpolarization. The reversal potential of -81 mV for the hyperpolarizing PSP was close to -82 mV for the Gly hyperpolarization. The reversal potential for the Gly response was shifted to less negative values by increasing the external K+ concentration or decreasing the extracellular Cl- concentration.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1991

[Surgical infection and its backgrounds].

The backgrounds of surgical infection of esophageal cancer patients are studied for host factors (relation of nutrition and immune response) and parasite factors surgical parts which are easily contaminated, the differences of serum concentration with 3 methods of antibiotics administration, and the relations about the bacteria in mouth and upper esophagus in operation and bacteria which were found in the respiratory system after operation). The results are as follows. The preoperative nutritional support was effective to rapid recovery of cytological immune functions. But in the post-operative infected cases, immunological recovery delayed and they nutritionally needed BCAA, glutamine, and essential fatty acids. For the study of parasite factors, surgical wounds (neck, chest wall, abdominal wall) were more easily contaminated than other parts except digestive tract. Continuous administration of antibiotics, 1g/hr x 4 was most excessive in three methods. The bacteria in the mouth and upper esophagus in operation and those in airway after operation, were not correlated. Furthermore, antibiotics-resistant bacteria which were Pseudomonas, MRSA were found in the airway. These results indicate that nutritional support is important for the host defense system and antibiotics should be administered considering each operative process. And about the postoperative respiratory infection, protection of hospital infection is important.

Bacterial Infections↗
PubMed1990

Importance of the G27-A43 mismatch at the anticodon stem of Escherichia coli tRNA(Thr2).

The tRNA(Thr2) isoacceptor of E. coli has a G-A mismatch at positions 27-43. When the anticodon of this tRNA was converted to an amber anticodon (CUA), this tRNA showed suppressor activity in E. coli. Moreover, introduction of the base pair (G-C or U-A) at positions 27-43 of this suppressor tRNA reduced its suppressor activity. These results indicate that the G27-A43 mismatch is necessary for full function of tRNA(Thr2).

Anticodon↗
PubMed1990

Functional expression of the mutants of the chloroplast tRNA(Lys) gene from the liverwort, Marchantia polymorpha, in Escherichia coli.

The anticodon of the tRNA(Lys) gene (trnK) in the liverwort, Marchantia polymorpha, was artificially converted to an amber anticodon. This mutant tRNA(Lys) (CTA) gene carrying either the intron of the C27-C43 mismatch at the anticodon-stem is not functional in Escherichia coli, but without both of them, it does work as a tRNA(Lys) amber suppressor.

Base Composition↗
PubMed1990

Genomic organization and physical mapping of the transfer RNA genes in Escherichia coli K12.

By using a set of 476 ordered DNA clones (in lambda phage vector) that covers the entire chromosome of Escherichia coli K12, we have made an exhaustive survey of tRNA genes in the E. coli genome. Ultraviolet-irradiated bacteria were separately infected with each of the 476 clones and the RNA molecules produced upon infection were labeled with 32P. The labeled tRNAs were separated by gel electrophoresis and then characterized by fingerprinting analysis. Fifty-nine of the 476 clones produced tRNAs, including adjacent overlapping ones that share the same tRNA genes. The products of all the previously mapped tRNA genes (about 60, to date) were detected according to their expected positions, and 19 more tRNA genes were newly elucidated. These new tRNA genes were identified by sequencing the DNA from relevant regions of the clones; the DNA sequences were scanned for the stretches that could be folded into the familiar cloverleaf structure and the transcription units were deduced by predicting the promoters and terminators. The total complement of the tRNA genes in E. coli K12 was 78 for 45 tRNA (or 41 anticodon) species, distributed in 40 different transcription units throughout the chromosome. In addition, a gene for selenocysteine tRNA was detected by hybridization and mapped to a specific DNA segment. A comprehensive tRNA gene map of E. coli was constructed, including the selenocysteine tRNA gene. All the tRNA genes encode the 3' CCA, and in several cases the terminal 19 nucleotides (including the 3' CCA) of a tRNA gene is repeated several times. Finally, in the present study the sites for a long inversion (approx. 800 x 10(3) base-pairs, around the oriC region) in Kohara's library was determined to be within the 23 S-5 S regions in rrnD and rrnE, revealing the exchange of combinations of spacer and distal tRNA genes between these two ribosomal RNA operons.

Base Sequence↗