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T Kohchi

Publications and source records attributed to T Kohchi.

At least 37 records · Page 2Linked to original sources
PubMed1989

Identification of a novel nifH-like (frxC) protein in chloroplasts of the liverwort Marchantia polymorpha.

The frxC gene, one of the unidentified open reading frames present in liverwort chloroplast DNA, shows significant homology with the nifH genes coding for the Fe protein, a component of the nitrogenase complex (Ohyama et al., 1986, Nature 322: 572-574). A truncated form of the frxC gene was designed to be over-expressed in Escherichia coli and an antibody against this protein was prepared using the purified product as an antigen. This antibody reacted with a protein in the soluble fraction of liverwort chloroplasts, which had an apparent molecular weight of 31,000, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in good agreement with a putative molecular weight of 31,945 deduced from the DNA sequence of the frxC gene. In a competitive inhibition experiment, the antigenicity of this protein was indicated to be similar to that of the over-expressed protein in E. coli. Therefore, we concluded that the frxC gene was expressed in liverwort chloroplasts and that its product existed in a soluble form. The molecular weight of the frxC protein was approximately 67,000, as estimated by gel filtration chromatography, indicating that the frxC protein may exist as a dimer of two identical polypeptides analogous to the Fe protein of nitrogenase. The results obtained from affinity chromatography supported the possibility that the frxC protein, which possesses a ATP-binding sequence in its N-terminal region that is conserved among various other ATP-binding proteins, has the ability to bind ATP.

Adenosine Triphosphate↗
PubMed1988

A nicked group II intron and trans-splicing in liverwort, Marchantia polymorpha, chloroplasts.

The chloroplast gene rps12 for ribosomal protein S12 in a liverwort, Marchantia polymorpha, is split into three exons by two introns, one of which (intron 1) is discontinuous. Exon 1 of rps12 for the N-terminal portion of the S12 protein is far from exons 2 and 3 for the C-terminal portion on the opposite DNA strand. S1-nuclease protection analysis and Northern hybridization with RNA isolated from the liverwort chloroplasts showed that: (i) the exons 1 and 2-3 of the rps12 gene with the neighboring genes were transcribed separately, (ii) the trans-splicing of intron 1 occurred after the processing of two primary transcripts to two pre-mRNAs, and (iii) there was no particular order for the splicing of intron 1 (trans) and intron 2 (cis) in the rps12 gene. We propose a bimolecular interaction model for trans-splicing by assuming that intermolecular base pairings between two pre-mRNAs result in the formation of the structure typical of group II introns except for disruption in the loop III region. This structure could be constructed in intron 1 of tobacco rps12 gene.

Base Sequence↗
PubMed1988

Structure and organization of Marchantia polymorpha chloroplast genome. I. Cloning and gene identification.

We have determined the complete nucleotide sequence of chloroplast DNA from a liverwort, Marchantia polymorpha, using a clone bank of chloroplast DNA fragments. The circular genome consists of 121,024 base-pairs and includes two large inverted repeats (IRA and IRB, each 10,058 base-pairs), a large single-copy region (LSC, 81,095 base-pairs), and a small single-copy region (SSC, 19,813 base-pairs). The nucleotide sequence was analysed with a computer to deduce the entire gene organization, assuming the universal genetic code and the presence of introns in the coding sequences. We detected 136 possible genes. 103 gene products of which are related to known stable RNA or protein molecules. Stable RNA genes for four species of ribosomal RNA and 32 species of tRNA were located, although one of the tRNA genes may be defective. Twenty genes encoding polypeptides involved in photosynthesis and electron transport were identified by comparison with known chloroplast genes. Twenty-five open reading frames (ORFs) show structural similarities to Escherichia coli RNA polymerase subunits, 19 ribosomal proteins and two related proteins. Seven ORFs are comparable with human mitochondrial NADH dehydrogenase genes. A computer-aided homology search predicted possible chloroplast homologues of bacterial proteins; two ORFs for bacterial 4Fe-4S-type ferredoxin, two for distinct subunits of a protein-dependent transport system, one ORF for a component of nitrogenase, and one for an antenna protein of a light-harvesting complex. The other 33 ORFs, consisting of 29 to 2136 codons, remain to be identified, but some of them seem to be conserved in evolution. Detailed information on gene identification is presented in the accompanying papers. We postulated that there were 22 introns in 20 genes (8 tRNA genes and 12 ORFs), which may be classified into the groups I and II found in fungal mitochondrial genes. The structural gene for ribosomal protein S12 is trans-split on the opposite DNA strand. The universal genetic code was confirmed by the substitution pattern of simultaneous codons, and by possible codon recognition of the chloroplast-encoded tRNA molecules, assuming no importation of tRNA molecules from the cytoplasm. The nucleotide residue A or T is preferred at the third position of the codons (G+C, 11.9%) and in intergenic spacers (G+C, 19.5%), resulting in an overall G+C content that is low (28.8%) throughout the liverwort chloroplast genome. Possible gene expression signals such as promoters and terminators for transcription, predicted locations of gene products, and DNA replicative origins are discussed.

Base Sequence↗
PubMed1988

Structure and organization of Marchantia polymorpha chloroplast genome. II. Gene organization of the large single copy region from rps'12 to atpB.

The nucleotide sequence (56,410 base-pairs) of the large single-copy region of chloroplast DNA from the liverwort Marchantia polymorpha has been determined. The sequence starts from one end (JLA) of the large single-copy region and encompasses genes for 21 tRNAs, six ATPase subunits (atpA, atpB, atpE, atpF, atpH and atpI), two photosystem I polypeptides (psaA and psaB), four photosystem II polypeptides (psbA, psbC, psbD and psbG), five ribosomal proteins (rps2, rps4, rps7, rps'12 and rps14), and three RNA polymerase subunits (rpoB, rpoC1 and rpoC2). In addition, we detected 18 open reading frames ranging from 29 to 2136 amino acid residues long, four of which share significant amino acid sequence homology to those of an Escherichia coli malK protein (designated mbpX), human mitochondrial ND2 (ndh2) and ND3 (ndh3) of a respiratory chain NADH dehydrogenase, or a bacterial antenna protein of a light-harvesting complex (lhcA). Sequence analysis suggests that four tRNA genes and six protein genes might be split by introns; they are trnG(UCC), trnK(UUU), trnL(UAA), trnV(UAC), atpF, ndh2, rpoC1, rps'12, ORF135 and ORF167. In the large single-copy region described here, the gene organization deduced is highly conserved with respect to that of higher plants, but an inversion of some 30,000 base-pairs flanked by trnL(CAA) and trnD(GUC) was seen between the liverwort and tobacco chloroplast genomes.

Adenosine Triphosphatases↗
PubMed1988

Structure and organization of Marchantia polymorpha chloroplast genome. III. Gene organization of the large single copy region from rbcL to trnI(CAU).

The nucleotide sequence (25,320 base-pairs) of a part of the large single-copy region of chloroplast DNA from the liverwort Marchantia polymorpha was determined. This region encodes putative genes for four tRNAs, isoleucine tRNA(CAU), arginine tRNA(CCG), proline tRNA(UGG) and tryptophan tRNA(CCA); eight photosynthetic polypeptides, the large subunit of ribulose bisphosphate carboxylase/oxygenase (rbcL), 51,000 Mr photosystem II chlorophyll alpha apoprotein (psbB), apocytochrome b-559 polypeptides (psbE and psbF), 10,000 Mr phosphoprotein (psbH), cytochrome f preprotein (petA), cytochrome b6 polypeptide (petB), and cytochrome b6/f complex subunit 4 polypeptide (petD); 13 ribosomal proteins (L2, L14, L16, L20, L22, L23, L33, S3, S8, S11, S12, S18 and S19); initiation factor 1 (infA); ribosome-associating polypeptide (secX); and alpha subunit of RNA polymerase (rpoA). Functionally related genes were located in several clusters in this region of the genome. There were two ribosomal protein gene clusters: rpl23-rpl2-rps19-rpl22-rps3-rpl16-+ ++rpl14-rps8-infA-secX-rps11-rpoA, with a gene arrangement similar to that of the Escherichia coli S10-spc-alpha operons, and the rps12'-rpl20-rps18-rpl33 cluster. There were gene clusters encoding photosynthesis components such as the psbB-psbH-petB-petD and the psbE-psbF clusters. Thirteen open reading frames, ranging in length from 31 to 434 amino acid residues, remain to be identified.

Amino Acid Sequence↗
PubMed1988

Structure and organization of Marchantia polymorpha chloroplast genome. IV. Inverted repeat and small single copy regions.

We characterized the genes in the regions of large inverted repeats (IRA and IRB, 10,058 base-pairs each) and a small single copy (SSC 19,813 bp) of chloroplast DNA from Marchantia polymorpha. The inverted repeat (IR) regions contain genes for four ribosomal RNAs (16 S, 23 S, 4.5 S and 5 S rRNAs) and five transfer RNAs (valine tRNA(GAC), isoleucine tRNA(GAU), alanine tRNA(UGC), arginine tRNA(ACG) and asparagine tRNA(GUU)). The gene organization of the IR regions in the liverwort chloroplast genome is conserved, although the IR regions are smaller (10,058 base-pairs) than any reported in higher plant chloroplasts. The small single-copy region (19,813 base-pairs) encoded genes for 17 open reading frames, a leucine tRNA(UAG) and a proline tRNA(GGG)-like sequence. We identified 12 open reading frames by homology of their coding sequences to a 4Fe-4S-type ferredoxin protein, a bacterial nitrogenase reductase component (Fe-protein), five human mitochondrial components of NADH dehydrogenase (ND1, ND4, ND4L, ND5 and ND6), two Escherichia coli ribosomal proteins (S15 and L21), two putative proteins encoded in the kinetoplast maxicircle DNA of Leishmania tarentolae (LtORF 3 and LtORF 4), and a bacterial permease inner membrane component (encoded by malF in E. coli or hisQ in Salmonella typhimurium).

Amino Acid Sequence↗
PubMed1988

Divergent mRNA transcription in the chloroplast psbB operon.

The genes psbB, psbH, petB and petD for the components in photosystem II and the cytochrome b6/f complex are clustered and co-transcribed in liverwort Marchantia polymorpha chloroplasts. On the opposite DNA strand in the spacer region between the genes psbB and psbH, we deduced an open reading frame consisting of 43 sense codons, and designated it as the ORF43 gene. The ORF43 gene was actively transcribed in liverwort chloroplasts. The ORF43 transcripts were entirely complementary to a part of the primary transcripts of the psbB operon. Heterogeneous Northern hybridization showed that the mRNA transcripts for the ORF43 gene increased with greening in pea seedlings. This is the first demonstration of divergent overlapping transcription in chloroplasts.

Amino Acid Sequence↗
PubMed1988

Ordered processing and splicing in a polycistronic transcript in liverwort chloroplasts.

From the complete sequence of the chloroplast DNA in a liverwort, Marchantia polymorpha, an unidentified open reading frame, ORF203, was found between the psbB and rps12' (trans-split) genes. ORF203 was a split gene consisting of three exons and two group II introns. Multiple transcripts for ORF203 were detected on Northern blots of the chloroplast RNA preparation. The ORF203 locus was primarily co-transcribed with the downstream genes rps12' and rpl20, and then processed into a monomeric precursor. S1 nuclease mapping gave the transcription initiation site 52 nucleotides upstream from the coding sequence of ORF203. The spliced RNA molecules were identified, as predicted, by the use of synthetic oligodeoxyribonucleotide probes specific to ligated exon sequences. The splicing reaction proceeded successively from the 5' to 3' direction. These results indicate that ordered RNA processing occurs in the chloroplast of land plants. Trans-membrane analysis by a computer indicated that ORF203 gene product could be associated with a chloroplast membrane.

Amino Acid Sequence↗
PubMed1988

[Transfer of cefuzonam into female genital organs].

Cefuzonam (CZON) was given intravenously at a 1 gram dose to 24 patients prior to abdominal total hysterectomy for uterine myoma. Concentrations of CZON in the serum of cubital vein, uterine artery, and in tissues of uterus and adnexa uteri were measured by the bioassay method. Bilateral uterine arteries were clamped at 15 and 30 minutes and 1, 2, 4 and 6 hours after the administrations of the drug. Measurements were done on 4 patients at each sampling. Concentrations of CZON in the serum of cubital vein and uterine artery changed in a similar manner with respective half-lives of 52.0 minutes and 48.2 minutes. Peak concentrations in oviduct, ovary, endometrium, myometrium, cervix uteri and portio vaginalis were reached at 15 minutes after drug administration. The peak concentration in the ovary was as high as 37.5 micrograms/g, and those in other tissues varied between 17.6 and 25.5 micrograms/g. Tissue concentrations decreased gradually after their peaks in similar manners to those in serum, and their half-lives ranged between 37.4 and 53.7 minutes. From these results, it was found that CZON was transferred to female genital organs in high enough concentrations to inhibit growth of bacteria which were often isolated from the pelvic inflammatory diseases, and CZON seemed to be highly effective to clinical pelvic inflammatory diseases.

Adnexa Uteri↗
PubMed1986

Differences in the effects of hypercapnia and hypoxia on the swallowing reflex in cats.

The effects of changes in PaCO2 and PaO2 on the swallowing reflex were studied in anaesthetized, vagotomized, paralysed and artificially ventilated cats. The swallowing reflex was induced by electrical stimulation of the superior laryngeal nerve (SLN). This initially suppressed activity in the phrenic nerve (PN). The swallowing reflex was then identified by a characteristic brief burst of PN activity and a large amplitude burst of hypoglossal nerve (HN) activity. Steady-state responses to constant SLN stimulation for 60 s were measured at four carbon dioxide tensions (PaCO2 3.9, 5.1, 6.3 and 7.8 kPa) with hyperoxia (PaO2 greater than 51 kPa) and at four values of PaO2 (PaO2 56, 11.3, 6.9 and 4.8 kPa) at a fixed PaCO2 (PaCO2 4.2 kPa). Although both hypercapnia and hypoxia increased the spontaneous respiratory activity in PN and HN, the number of swallows elicited during SLN stimulation was not influenced by PaCO2, whereas a progressive decrease in the number of swallows with decreasing PaO2 was observed consistently. These results indicate that the swallowing reflex is independent of the background respiratory activity and that hypoxia depresses the swallowing reflex, whereas hypercapnia has no effect.

Animals↗
PubMed1986

[A study on the penetration of imipenem/cilastatin sodium into the female genital tissues].

A new carbapenem antibiotic, imipenem/cilastatin sodium (MK-0787/MK-0791), was administered by intravenous drip infusion at a dose level of 500 mg/500 mg to 30 patients who underwent total abdominal hysterectomy for uterine myomas with or without benign ovarian tumors. The uterine arteries were clamped bilaterally at 0.25, 0.5, 1, 2, 3, 4, 6 and 8 hours after administration, and plasma samples and uterine tissues were taken for measurements of MK-0787 by bioassay and MK-0791 by HPLC. The measured values were analyzed using a two-compartment open model. Maximum concentrations of MK-0787 at 0.5 hour after the start of intravenous drip infusion were 98.5 micrograms/ml in the antecubital vein, 100.1 micrograms/ml in the uterine artery, 26.5 micrograms/g in the oviduct, 21.2 micrograms/g in the ovary, 19.1 micrograms/g in the endometrium, 19.0 micrograms/g in the myometrium, 22.1 micrograms/g in the cervix uteri and 16.4 micrograms/g in the portio vaginalis. These results suggest that the penetration of MK-0787/MK-0791 into female genital tissues is good, and sufficient concentrations are obtained enough to inhibit organisms which are frequently isolated from patients with pelvic inflammatory disease.

Adnexa Uteri↗
PubMed1985

Effects of increasing depth of anaesthesia on phrenic nerve and hypoglossal nerve activity during the swallowing reflex in cats.

The effects of increasing depths of anaesthesia on phrenic nerve (PN) activity and hypoglossal nerve (HN) activity during the swallowing reflex elicited by stimulation of the superior laryngeal nerve (SLN) were investigated in 10 cats. Swallowing induced by SLN stimulation always coincided with a characteristic brief burst of PN activity and a large amplitude burst of HN activity. These characteristic responses of PN and HN activities were not influenced by either bilateral vagotomy or neuromuscular blockade, indicating that the characteristic responses of PN and HN activities can be used as indicators of the swallowing reflex in vagotomized and paralysed animals. The results obtained in such animals showed that increasing depth of anaesthesia depressed progressively the swallowing reflex. Detailed analysis of HN activity revealed also that SLN stimulation elicited three different responses of HN activity which had different sensitivities to anaesthesia. However, the characteristic response observed during the swallowing reflex was the most sensitive to increasing depth of anaesthesia.

Anesthesia, Inhalation↗
PubMed1985

Responses of recurrent laryngeal, hypoglossal, and phrenic nerves to increasing depths of anesthesia with halothane or enflurane in vagotomized cats.

In order to compare the responses to increasing depths of anesthesia with inhalational anesthetic agents of the phrenic nerve and cranial nerves supplying upper airway muscles, the effects of acute administration of halothane (2.5%) or enflurane (5.0%) on the activities of the hypoglossal nerve (HN), the recurrent laryngeal nerve (RLN), and the phrenic nerve (PN) were investigated in artificially ventilated, vagotomized cats. Following administration of halothane or enflurane, rhythmic inspiratory activities of all three nerves decreased progressively, but the decrease in HN activity was more pronounced than the decreases in HN and RLN activities. During the course of respiratory depression due to increasing depth of anesthesia with halothane or enflurane, rhythmic inspiratory activities of PN and RLN decreased linearly and approximately at the same rate, indicating that the response of RLN more closely resembles that of PN. However, at a relatively deep level of anesthesia, rhythmic inspiratory RLN activity was replaced by strong tonic RLN activity, while PN activity was completely abolished, causing quantitatively and qualitatively different responses of RLN and PN. These peculiar responses of RLN activity to increasing depth of anesthesia were examined in more detail with the use of single- or few-fiber preparations. Increasing depth of anesthesia depressed the inspiratory RLN units while recruiting other units, originally silent, indicating that there are two different groups of fibers in RLN whose response to increasing depth of anesthesia is exactly opposite to one another.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗