Biomedical subjects
Publications and source records attributed to H Inokuchi.
It has been discovered that expression of promoter activity can be inhibited by visible light when specific fragments of E. coli DNA are inserted in a vector system designed to assay for promoter activity. These fragments have been located on regions of the E. coli chromosome to which no gene has been assigned to date. The effective wavelength of light that produces this phenomenon has been determined.
UGA-specific nonsense suppressors from Escherichia coli K-12 were isolated and characterized. One of them (Su+UGA-11) was identified as a mutant of the prfB gene for the peptide releasing factor RF2. It appears that in this strain, while peptide release at sites of UGA mutations is retarded, the UGA stop codon is read through even in the absence of a tRNA suppressor, exhibiting a novel type of passive nonsense suppression. Three suppressors (Su+UGA-12, -16 and -34) were capable of restoring the streptomycin sensitive phenotype in resistant bacteria (strAr). Because of their drug-related phenotype, these are possibly mutations in the components of the ribosomal machinery, particularly those concerned with peptide release at UGA nonsense codons. A tRNA suppressor was also obtained which was derived from the tRNA(Trp) gene. In this strain, a long region between rrnC (84.5 min) and rrnB (89.5 min) was duplicated and one of the duplicated genes of tRNA(Trp) was mutated to the suppressor. The mechanism of UGA-suppression is discussed in terms of translation termination at the nonsense codon in both active and passive fashions.
The serum Lp(a) lipoprotein concentration in 103 healthy control subjects was determined by ELISA (TintElise Lp(a) kit, Biopool, Umea, Sweden). The distribution of Lp(a) in the controls was highly skewed (mean 132, S.D. 109, median 99 mg/liter), which is similar to the results previously reported. Serum Lp(a) level in 104 subjects who underwent coronary angiography was also measured. These subjects were divided into two groups: 59 cases of stenosis(-) and 45 of stenosis(+) groups. Lp(a) level of the stenosis(+) group (mean 235, S.D. 197, median 159 mg/liter) was significantly higher than that of the stenosis(-) group (mean 156, S.D. 133, median 123 mg/liter) and of the controls (Wilcoxon test, p less than 0.05 and p less than 0.01, respectively). Further, stenosis(+) group was divided into three subgroups: 20 with single vessel disease, 13 with double vessel disease and 12 with triple vessel disease subgroups. Lp(a) level was correlated with the number of stenotic coronary vessels (Spearman's rank correlation coefficient, p less than 0.05). These results suggest that Lp(a) may play an important part as a risk factor for coronary heart disease.
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Effects of an anti-ulcer drug, 2'-carboxymethoxy-4,4'-bis(3-methyl-2-butenyloxy) chalcone (sofalcone), on the generative cells and kinetics of superficial epithelial cells in mouse gastric mucosa, including the effect of hydrocortisone on them, were investigated by the use of 3H-thymidine autoradiography. The labeling indices and the width of the generative cell zone in the fundic mucosa were significantly decreased by administration of hydrocortisone. The decrease in the labeling indices and the width of the generative cell zone induced by administration of hydrocortisone were not inhibited by sofalcone. Hydrocortisone had no significant influence on the labeling indices of the generative cell zone in the pyloric mucosa, but decreased the width of it. The decrease in the width of the generative cell zone induced by hydrocortisone was inhibited by sofalcone. Concerning the influence on the kinetics of superficial epithelial cells, hydrocortisone inhibited the increase in the labeling indices of the superficial epithelial cells after continuous administration of 3H-thymidine in both the fundic mucosa and pyloric mucosa. In the fundic mucosa, sofalcone showed no influence on the inhibition by hydrocortisone, but in the pyloric mucosa, the effect of hydrocortisone was abolished by sofalcone. These results suggest that sofalcone inhibits the reduction of the cell production and the prolongation of the life span of superficial epithelial cells caused by hydrocortisone in the pyloric mucosa.
Transposon Tn3 was inserted into a tRNA operon of the amber suppressor Su+2 on a transducing phage (lambda hcI857nin5pSu+2) by selecting phages with ampicillin resistance and Su- phenotypes. In a strain thus obtained, Tn3 was inserted between the promoter and the first tRNA gene of the operon, which was determined by DNA sequencing. The Su+2 tRNA operon on the transducing phage consisted of two tRNA genes for tRNA(Met) and Su+2 tRNA(2Gln), which was a deletion derivative of the supB-E tRNA operon of E. coli containing seven tRNA genes in the order of promoter-Met-Leu-Gln1-Gln1-Met-Gln2-Gln2. Proliferating the lambda hcI857nin5pSu+2::Tn3 in E. coli cells, a number of phages which had lost Tn3 were isolated, and their tRNA gene compositions as well as the DNA structures of the tRNA operon were analyzed. In many cases the tRNA genes which had been deleted from the original transducing phage were regained from the chromosomal supB-E operon. Thus the loss of Tn3 from the phages was not due to excision of the transposon but due to the replacement of a portion of the tRNA operon, including Tn3, with the host homologous region that did not contain Tn3. This type of replacement takes place rather efficiently as a consequence of Tn3 insertion, owing to the general recombination occurring between homologous tRNA genes of phage and host chromosomes in the presence of either host recA or phage red. No such enhanced recombination in a similar cross between phage and host chromosomes was observed with the Tn3 present in the trans position on an independent plasmid. We conclude that inserting Tn3 in cis promotes general recombination in the neighboring regions. Possible mechanisms for this new type of genetic effect of Tn3 are discussed. During the course of this study, a natural defective mutation (T11) was also detected in one of the duplicated tRNA(2Gln) genes in an E. coli K12 strain we used.
The effects of chemical sympathectomy on the differentiation of the generative cells, superficial epithelial cells and gastrin cells of the gastric mucosa of hamster were examined by 3H-thymidine autoradiography. The labeling indices of the generative cell zone in the gastric mucosa and antral gastrin cells showed a transient significant decrease after chemical sympathectomy, and then they were gradually restore with time. After 4 weeks onward, the labeling indices of the generative cells showed a slightly low value compared with those in controls. The renewal of superficial epithelial cells and gastrin cells was examined in the hamster sympathectomized for 4 weeks. The time required for the differentiation to PAS positive superficial epithelial cells or gastrin cells had a tendency to elogate after chemical sympathectomy. These results suggest that chemical sympathectomy played an inhibitive action on the proliferation and the differentiation of gastric mucosa.
Intracellular recordings were made from 79 neurones in the mesencephalic nucleus of fifth nerve (MNV) contained within rat brain stem slice preparation in vitro. The electrical membrane characteristics of 20 neurones among them were measured. The resting membrane potential, input resistance and membrane time constant of MNV neurones were -60.3 +/- 5.6 mV, 10.5 +/- 5.4M omega and 1.3 +/- 0.5 ms respectively. No action potential occurred spontaneously at resting membrane potential. The action potential was elicited by application of a depolarizing rectangular pulse to the neuron. The data of 32 MNV neurones action potentials showed that the threshold potentials ranged from -50 mV to -55 mV, the duration of the spike was 0.8 +/- 0.2 ms and the amplitude of the spike was 69.5 +/- 6.1 mV with an overshoot of 11.9 +/- 3.6 mV. The action potential disappeared reversibly by perfusion of Na-free solution or TTX (0.3 mumol/L) added in Krebs solution. The repetitive discharge was elicited by a long lasting depolarizing rectangular pulse applied to the neuron, its frequency was 200-250 Hz at the beginning of the pulse and disappeared before the ending of the pulse. The repetitive discharge usually consists of 2-15 spikes. The halfway disappearance of the repetitive discharge was prevented by TEA or 4-AP. The subthreshold potential oscillation followed the action potential at membrane potential -60(-)-55 mV, and this potential oscillation was not affected by TTX, but it was abolished by perfusion of Ca-free solution. However, its amplitude was increased by TEA or 4-AP. When the resting membrane potential was depolarized, the outward rectification in 40 among 45 MNV neurones was seen, which was inhibited by TEA, 4-AP or Ca-free perfusion. On the other hand, the inward rectification was seen when the resting membrane potential was hyperpolarized, which was inhibited by Cs ion or Na-free perfusion. When the blockers of K channels were added into Krebs solution, the steady state I-V relationship of the neurones was changed correspondingly. It is suggested that the IDR, IA, IK(Ca), and IQ are related to the resting membrane conductances.
It is well known that gastrin immunoreactive cells are observed in the fetal and postnatal rat pancreas. The role of the gastrin cells is unknown, however, it has been suspected that pancreatic gastrin may influence the development of pancreas and the gastrointestinal tract. The present study shows the localization of pancreatic gastrin cells and the ability of auto-proliferation of them in development. Gastrin cells were seen in 0-d to 2-wk-old rats in islet and in 0-d to 4-wk-old rats among exocrine cells. The ratio of gastrin cells to islet cells decreased in neonatal development and in rats older than 14-d gastrin cells were never observed in islet. Labeling indices of pancreatic gastrin cells after one injection of tritiated thymidine were 2.6% to 4.6% for 10 days after birth. It was suggested that gastrin cells have the ability of autoproliferation for 10 days after birth.
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.
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.
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).
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