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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 793 records · Page 44Linked to original sources
PubMed1984

Nucleotide sequences of three proline tRNAs from Salmonella typhimurium.

The nucleotide sequences of three proline tRNAs from Salmonella typhimurium were determined by post-labeling procedures. The three proline tRNAs had almost identical sequences in the D-arm and T psi C-arm, and all contained 1-methylguanosine next to the 3'-end of the anticodon. The anticodon sequences of tRNAPro1, tRNAPro2 and tRNAPro3 were 5'-CGG-3', 5'-GGG-3', and 5'-VGG-3', respectively. The nucleotide sequence homologies of tRNAPro2 to tRNAPro1 and tRNAPro3 were 68% and 78%, respectively.

Anticodon↗
PubMed1984

The E. coli divE mutation, which differentially inhibits synthesis of certain proteins, is in tRNASer1.

The temperature-sensitive divE mutant of Escherichia coli cannot synthesize certain membrane and cytoplasmic proteins at a non-permissive temperature. Growth of the mutant cells is arrested at a specific stage of the cell cycle when exposed to the non-permissive conditions, suggesting that the divE mutant possesses a defect in cell division control. From sequence determination of a cloned 1.35-kbp DNA fragment that complements the temperature-sensitive divE42 mutation, we characterized two genes in the segment ; one for tRNASer1 and the other for a 23 500 dalton protein. In parallel experiments we cloned the homologous 1.35-kbp DNA fragment from the divE42 mutant and determined its entire nucleotide sequence. Comparison of the two sequences showed that the mutation site is located not in the protein gene, but in the tRNA gene, where A10 is replaced by G10 in the D-stem. Lambda transducing phages carrying the subcloned tRNASer1 gene complemented the divE42 mutation, thereby confirming the conclusion obtained from sequence analyses of the fragments. This finding indicates that tRNASer1 is specifically involved in regulation of cell cycle-specific protein synthesis, coupled with an important step in the process of cell division, or that usage of serine tRNA is functionally specific for the biosynthesis of certain proteins.

Bacterial Proteins↗
PubMed1984

Queuosine modification in tRNA and expression of the nitrate reductase in Escherichia coli.

In eubacteria the modified nucleoside queuosine is present in tRNAAsn, tRNAAsp, tRNAHis and tRNATyr. A precursor of queuine, pre-queuine, is synthesized from GTP, inserted into the first position of the anticodon of the corresponding tRNAs by a specific tRNA-guanine transglycosylase and further modified to queuosine. Isogenic pairs of Escherichia coli, containing or lacking the tRNA-transglycosylase (JE 7335, tgt+ lacZ+ and JE 7337, tgt- lacZ+; JE 7334, tgt+ lacZ- and JE 7336, tgt- lacZ-), have been employed to study the function of queuosine in tRNA. Compared with the tgt+ strain (JE 7335), the tgt- mutant (JE 7337) grown under anaerobic conditions, is defective with respect to the nitrate respiration system, in which electrons are transported from D(-)-lactate via quinone and cytochrome bNO3-(556) to nitrate. Low temperature cytochrome spectra of the anaerobically grown tgt- mutant show a lowered amount of type b cytochromes involving the spectrum of cytochrome bNO3-(556). In the case of the anaerobically grown tgt- mutant three proteins are missing in the protein pattern of cytoplasmic membranes. Their mol. wts. correspond to those of the subunits of the nitrate reductase complex. In contrast to the tgt+ strains (JE 7334, JE 7335) both tgt- mutants (JE 7336, JE 7337) cannot grow on lactate under anaerobic conditions with nitrate offered as electron acceptor and NO3- is not reduced to NO2-. A possible link between Q-modification of tRNAs, the synthesis of proteins of the nitrate reductase complex and the synthesis of menaquinone or ubiquinone is discussed.

Aerobiosis↗
PubMed1984

Immunological activity of chitin and its derivatives.

The effect of chitin and its derivatives on the activation of peritoneal macrophages in vivo, on the suppression of tumour growth in syngeneic mice and on the protection of the host against bacterial infection was examined. Thirty percent deacetylated chitin (30% DA-chitin), 70% DA-chitin and carboxymethyl-chitin (CM-chitin) induced cytotoxic macrophages most effectively. Chitosan, hydroxyethyl-chitin, dihydroxypropyl-chitin (DHP-chitin) and DHP-chitosan had moderate activities. Phosphorylated-, sulphonated- or acetyl-chitin, however, were less effective. Both 70% DA-chitin and DHP-chitosan were most active on the suppression of Meth-A tumour growth in BALB/c mice, and 30% DA-chitin had a moderate effect. For the stimulation of non-specific host resistance against Escherichia coli infection, 30% and 70% DA-chitin were effective.

Adjuvants, Immunologic↗
PubMed1984

Molecular cloning and the total nucleotide sequence of the human c-Ha-ras-1 gene activated in a melanoma from a Japanese patient.

The transforming gene of malignant melanoma tissue obtained from a Japanese patient and maintained in nude mice has been cloned in its biologically active form and identified as the c-Ha-ras-1 gene, a homologue of the viral Ha-ras gene. Nucleotide sequence analysis revealed that the genetic alteration responsible for the transforming activity of the melanoma oncogene was localized to a single point mutation in the second exon. The transversion of adenine to thymine results in the substitution of leucine for glutamine as amino acid residue 61 of the predicted p21 protein. Other nucleotide sequences spanning a 2.9-kilobase segment including the entire exons and introns were found to be exactly the same as those in a proto-oncogene from a normal Caucasian reported previously, except for base alterations explained as polymorphic differences.

Base Sequence↗
PubMed1984

Defense mechanism of the cochlear aqueduct against infection. A morphological study in the guinea pig.

Guinea pigs were used in this study. Physiological saline, india ink, and Staphylococcus aureus were injected into the cisterna magna, and S. aureus was also injected into the scala tympani. Changes in the microstructure of the cochlear aqueduct were observed by light microscopy and also by scanning electron microscopy, mainly by means of fracture preparations. From these experimental results, it could be confirmed that the periotic duct tissue of the cochlear aqueduct reacted especially to bacterial infection.

Animals↗
PubMed1984

Operation of internal Na-dependent Ca influx mechanism associated with catecholamine secretion in the adrenal chromaffin cells.

The cat adrenal gland was retrogradely perfused with a medium lacking divalent cation, and the secretion of catecholamines was induced by Ca reintroduction with or without simultaneous removal of external Na. These responses were markedly reduced after prior exposure to a medium containing Mg (1 mM) or lacking Na. The inhibition caused by Mg was reversed by ouabain treatment. Reversing the concentration gradient for Na alone by replacing external Na with Tris, choline, or Li did not stimulate catecholamine secretion when Ca2+ (0.1 mM) was present in the external medium throughout the experiment. However, the treatment with ouabain reversed this inhibitory effect of Ca so that Na removal did induce marked secretion. Essentially similar results concerning secretion were obtained in the cultured bovine chromaffin cells. There was a reasonable correlation between secretion and 45Ca uptake in these cells under various experimental manipulations, and alterations of these parameters were well correlated with the level of internal Na. Furthermore, the rate constant of 22Na efflux was found to increase when Ca was reintroduced with the simultaneous removal of Na during exposure to a medium containing ouabain. These results are consistent with the view that the mechanism of internal Na-dependent Ca influx is activated to induce catecholamine secretion whenever internal Na is raised above a critical level. On the other hand, there were significant increases in the catecholamine secretion and 45Ca uptake which were induced by substitution of NaCl with sucrose, even when the operation of the internal Na-dependent Ca influx mechanism was markedly restricted by various experimental manipulations. This suggests that other secretory mechanisms are involved under these conditions. This would account for the largest secretory effect of sucrose substitution under the condition in which internal Na-dependent Ca influx is activated.

Adrenal Medulla↗
PubMed1984

Mechanism of calcium efflux from isolated bovine adrenal chromaffin cells.

Chromaffin cells isolated from bovine adrenals and maintained in culture were loaded with 45Ca, and the mechanism of 45Ca efflux from these cells was investigated. During exposure to a Ca-deficient, Mg (1 mM)-containing medium, replacement of NaCl with sucrose, choline Cl, or Tris Cl reduced the rate of 45Ca efflux by approx. 30-40%, showing the presence of a Na-dependent 45Ca efflux mechanism. In contrast to the previous findings, however, Li can partially replace Na in maintaining 45Ca efflux. Reintroduction of Ca to a Ca-deficient medium increased the rate of 45Ca efflux depending on the concentrations of Ca, showing the presence of a Ca-dependent Ca efflux mechanism. The marked but transient rise in the rate of 45Ca efflux in response to Ca reintroduction was observed under conditions in which the concentration of internal Na was raised either by inhibiting Na pumping activity (ouabain or K removal) or by removal of Mg from the medium. The increased 45Ca efflux was further potentiated by simultaneous Na removal and was markedly inhibited by Ca channel blockers, suggesting that the transiently increased Ca influx in exchange for internal Na facilitated the rate of 45Ca efflux. However, other conditions which evoke catecholamine secretion by stimulating Ca influx also increased the rate of 45Ca efflux, suggesting that the increased Ca influx via any route increases 45Ca efflux. These results thus confirmed the presence of both Na-dependent and Ca-dependent Ca efflux mechanisms in chromaffin cells.

Adrenal Medulla↗
PubMed1984

Transuncodiscal approach to dumbbell tumors of the cervical spinal canal.

A combined anterior and lateral approach to the anterior cervical spinal canal with fusion was performed on five patients with cervical dumbbell-shaped tumors. The procedure consists of anterior discectomy and ipsilateral uncectomy, and removal of the posterolateral corners and posterior transverse ridges of the upper and lower vertebral bodies at the level of the tumor. In the case of a large tumor in the spinal canal, additional removal of a limited segment from the lateral part of the vertebral body was performed. The bone defect was filled with a T-shaped iliac bone graft. Two vertebral bodies were fused in each case. The highest level of the operation was C-2 and the lowest was T-1. The authors believe that any cervical dumbbell-shaped tumor below the C-2 level can be removed via an anterolateral approach as long as no more than three levels of the spine are involved.

Adult↗
PubMed1984

Effect of queuine on protein biosynthesis in mammalian cells.

Administration of queuine into intact cells has an affected protein biosynthesis in vivo. In C3H2K mouse kidney cells, synthesis of a protein having a molecular weight of 45,000 was prevented by addition of queuine into the culture medium. In the case of SA-1 cells, which are variant cells of mouse mammary tumor cells, a protein whose molecular weight was 95,000 and located in the cytosol of its cells was changed to a more basic protein by administration of queuine.

Animals↗
PubMed1984

DNA damage induced by asbestos in the presence of hydrogen peroxide.

Treatment of calf thymus DNA with various types of asbestos fibers in the presence of hydrogen peroxide under physiological conditions (pH 7.4, 37 degrees) resulted in the hydroxylation of the C-8 position of guanine residues. DNA strand scission was also detected after these treatments.

Animals↗
PubMed1984

Formation of 8-hydroxyguanine residues in DNA by X-irradiation.

A new type of ionizing radiation-induced DNA base damage, 8-hydroxyguanine formation, was found in DNA that had been irradiated by X-rays in aqueous solution. The extent of this modification linearly increased with increase in the X-ray dose up to 40 krad. When an OH radical scavenger, ethanol, was added to the DNA solution, the hydroxylation was inhibited almost completely, suggesting that the reaction proceeds via the formation of OH radicals.

DNA↗
PubMed1984

[Comparative study of two-dimensional echocardiography and left ventriculography in detecting interventricular septal asynergy in myocardial infarction].

We investigated the reasons for discrepancies between two-dimensional echocardiography (2DE) and left ventriculography (LVG) in detecting interventricular septal asynergy in anterior or inferior myocardial infarction. Twenty-six patients with anterior infarctions due to proximal lesions of the left anterior descending artery and 20 patients with inferior infarctions due to proximal lesions of the right coronary artery were studied by 2DE and LVG. A 2DE long-axis view, a short-axis view at the papillary muscle level, an apical four-chamber view (AP-4CV), and right and left anterior oblique left ventriculograms (RAO-LVG and LAO-LVG) were recorded. The interventricular septum (IVS) on LAO 60 degree-LVG was divided into the basal and apical portions. 2DE and LVG were independently evaluated individually by the same readers, and the interventricular septal asynergy was classified as hypokinesis, akinesis and dyskinesis. Anterior infarction About 80% of the patients with akinesis of the apical third of the IVS in a long-axis view or of the apical half of the IVS in an AP-4CV were assessed as having akinesis of the entire septum by LAO-LVG. Inferior infarction Asynergy was echocardiographically detected in the posterior IVS in a short-axis view at the papillary muscle level. LAO-LVG showed asynergy in the apical third of the posterolateral segment (segment 7) in all cases and akinesis in the apical IVS in six of 20 patients (30%). In conclusion, the extent of asynergy of the IVS in anterior infarction is overestimated by LAO-LVG compared to 2DE, and asynergy of the apex assessed by LAO-LVG in inferior infarction will correspond to that of the inferior segment by 2DE. This discrepancy is attributed to the different planes between a long-axis view and an LVG projection. We conclude both LVG and 2DE are mandatory for estimating accurately the extent of asynergy in the infarcted IVS.

Echocardiography↗